Association between interleukin 6 -174 G/C promoter gene polymorphism and runners' responses to the dietary ingestion of antioxidant supplementation based on pequi (Caryocar brasiliense Camb.) oil: a before-after study

Abstract

Exercise is a double-edged sword: when practiced in moderation, it increases the expression of antioxidant enzymes, but when practiced strenuously it causes oxidative stress and cell damage. In this context, polymorphisms in the interleukin (IL)-6 gene should be investigated better because they can influence performance, at least in exercise that generates oxidative stress and leads to muscular injuries with consequent inflammation. In this work, we investigated the influence of IL-6 –174 G/C polymorphism on tissue damage and inflammation markers, lipid peroxidation, hemogram and lipid profile of runners before and after ingestion of 400 mg of pequi oil in capsules supplied daily for 14 consecutive days. The IL-6 genotypes were associated with significant differences in lipid peroxidation, with the CC mutant having lower values. There were also significant differences among these genotypes in the response to supplementation with pequi oil, exercise-induced damage and C-reactive protein (CRP) levels. The best protection against damage was observed with the heterozygous genotype. Although the CC genotype showed an increase in CRP levels after supplementation, the lack of a positive correlation between triglycerides and high-sensitivity CRP in this mutant genotype after supplementation indicated a protective effect of pequi. These findings deserve further investigation, particularly with regard to the quantification of circulating IL-6 concentrations.

Keywords
antioxidant supplementation; exercise-induced oxidative damage; inflammatory markers; nutrigenetics; nutrigenomics

Introduction

Regular physical activity, apart from enhancing the expression of antioxidant enzymes, also induces a systemic increase in many cytokines with anti-inflammatory properties that protect against chronic disorders associated with low-grade systemic inflammation (Gomez-Cabrera et al., 2008; Colombini et al., 2011; Miranda-Vilela, 2012). Similarly, micro-injuries to skeletal muscle, resulting from regular exercise, lead to the recruitment of cytokines such as interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) that initiate and regulate the repair process. The long-term anti-inflammatory effect of exercise is also mediated by muscle-derived interleukin 6 (IL-6) (Colombini et al., 2011), which is involved in immune function, muscle repair and hypertrophy following exercise-induced damage (Eynon et al., 2011a). IL-6 stimulates circulating anti-inflammatory IL-1Ra and IL-10 and inhibits the production of pro-inflammatory TNF-α (Colombini et al., 2011).

In contrast to regular exercise, strenuous exercise or training above habitual intensity can lead to oxidative stress through the enhanced formation of reactive oxygen and nitrogen species (RONS), causing muscle injuries and inflammation that can compromise performance and potentially increase the future risk of cardiovascular disease (CVD) in athletes (Miranda-Vilela, 2012; Miranda-Vilela et al., 2011a, 2012). Strenuous exercise not only induces lipid peroxidation, but also promotes inflammation, changes in the immune cell count and the release of acute phase proteins such as C-reactive protein (CRP) (Oleto et al., 2011; Miranda-Vilela et al., 2009a, 2012; Miranda-Vilela, 2012). The synthesis of CRP is, in turn, regulated by cytokines, mostly IL-6 (Moleres et al., 2009); chronically elevated levels of IL-6 are associated with vascular smooth muscle growth, increased production of acute phase protein and effects on lipid and lipoprotein metabolism, all of which can contribute to an increased risk of CVD (Shen et al., 2008; Gan et al., 2013). Furthermore, an increase in the circulating levels of cytosolic proteins such as aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatine kinase (CK) after exercise reflects cellular injury and can be used as markers for exercise-induced damage (Akimoto et al., 2010; Miranda-Vilela 2012; Miranda-Vilela et al., 2012).

Physical exercise is thus a double-edged sword: when regularly practiced in moderation, it increases the expression of antioxidant enzymes and should be considered an antioxidant, but when practiced strenuously it causes oxidative stress and cell damage (Gomez-Cabrera et al., 2008), possibly leading to overtraining syndrome (Miranda-Vilela et al., 2011a; Miranda-Vilela, 2012). These observations have led to research into whether antioxidant supplementation could prevent the damaging effects of enhanced production of RONS in response to exercise, thereby improving athletic performance (Miranda-Vilela et al., 2011a; Miranda-Vilela, 2012). In this context, pequi oil, a carotenoid-rich oil extracted from the pulp of pequi (Caryocar brasiliense Camb.), a typical fruit found in the Brazilian Cerrado, has been shown to have anti-inflammatory properties, besides reducing arterial pressure, exercise-induced anisocytosis and DNA and tissue damage (Miranda-Vilela et al., 2009a,b, 2010, 2011a,b).

In addition to its natural antioxidants, pequi oil is composed mainly of oleic (51.37-55.87%) and palmitic (35.17-46.79%) fatty acids that modulate the triglyceride (TG):cholesterol ratio in postprandial triglyceride-rich lipoprotein (TRL) (Miranda-Vilela et al., 2009a,c). Postprandial and intestinally produced TRLs play an important role in increasing the risk of atherogenesis (Bermúdez et al., 2008; Varela et al., 2013), while the dietary substitution of saturated fatty acids (SFA; mainly palmitic acid, 16:0) with monounsaturated fatty acids (MUFA; mainly oleic acid, 18:1 ω-9) influences protection against atherosclerosis by preventing excessive lipid accumulation in monocyte/macrophage cells (Varela et al., 2013). In our previous study, supplementation with pequi oil also reduced postprandial total cholesterol and low-density lipoprotein (LDL) in runners (particularly men) > 45 years old; LDL is considered an independent risk factor for CVD (Miranda-Vilela et al., 2009a). Since elevated plasma CRP and LDL have been associated with increased risk of CVD (Moleres et al., 2009), pequi oil has been suggested as a means of decreasing the risk of atherogenesis in these groups of more susceptible athletes (Miranda-Vilela et al., 2009a).

Despite these protective effects of pequi oil, some of the responses in runners are influenced by genetic polymorphisms related to oxidative stress and inflammatory markers (Miranda-Vilela et al., 2009b, 2010, 2011a,b; Ribeiro et al., 2013). Because some polymorphic genes are able to modify the risk of various diseases, and physical fitness has a genetic component, it would be interesting to study variations in genes that can influence athletic performance and pathogenic processes such as inflammatory responses (Colombini et al., 2011). In this regard, polymorphisms in the IL-6 gene need to be investigated better because they can influence performance, at least in those cases where the oxidative stress generated by strenuous exercise leads to muscle injuries and consequent inflammation.

The human IL-6 gene is located on the short arm of chromosome 7 (7p21) (Capurso et al., 2004) and has about 50 single-nucleotide polymorphisms (SNPs) in its promoter region (Pereira et al., 2011). Among these SNPs, a functional –174 G/C SNP (rs1800795) has been reported to affect the plasma levels of this cytokine, with the mutant C allele expressing lower levels of plasma IL-6 than the wild-type G allele (Fishman et al., 1998; Capurso et al., 2004). IL-6 regulates the immune response by acting on B and T cells, but also acts on hematopoietic stem cells, megakaryocytes and hepatocytes (e.g., mesangial cells), nerve cells, keratinocytes and plasmacytoma/myeloma cells (Hirano et al., 1990) such that changes in the expression of this cytokine can influence these cells. Indeed, a deficiency in IL-6 alters the balance between the proliferation and differentiation of progenitor cells of the granulocytic-monocytic, megakaryocytic and erythroid lineages into mature blood cells, leading to abnormal levels of committed progenitors in these lineages and to a slow recovery from hematopoietic ablation (Bernad et al., 1994).

Because the IL-6 –174 G/C polymorphism (SNP rs1800795) has been associated with exercise-related phenotypes (Eynon et al., 2011a,b), and since diet can affect an individual's genes and these can in turn affect the response to supplementation (Miranda-Vilela et al., 2011a; Miranda-Vilela, 2012; Ribeiro et al., 2013), in this work we investigated the influence of this IL-6 polymorphism on the levels of creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), acute phase proteins (C-reactive protein - CRP and high-sensitivity CRP – hs-CRP), lipid peroxidation (evaluated by the TBARS assay), complete hemogram, and lipid profile of runners before and after ingestion of 400 mg of pequi oil in capsules supplied daily for 14 consecutive days. Overall, we sought to evaluate how individual genetic differences in IL-6 –174 G/C affected each athletes response to antioxidant supplementation with pequi oil during oxidative stress while exercising, and how the diet with pequi oil interacted with an individual's IL-6 gene to influence the response to this supplementation.

Materials and Methods

Study design and participants

Initially, 139 trained street runners of both genders (53 females and 86 males) and different age groups were recruited based on previously reported criteria (Miranda-Vilela et al., 2009a,b, 2010, 2011a,b; Ribeiro et al., 2013). Briefly, the tests were done after two races in the same environment and under closely comparable conditions, according to the type, intensity and length of the athletes weekly training, before and after the ingestion of 400 mg of pequi oil in capsules supplied daily for 14 consecutive days. There were no significant changes in the daily routine, training or lifestyle of the runners between the first and second race, except for the ingestion of pequi oil capsules. The athletes could choose the distance that they would cover (4-21 km) based on the type, intensity and length of their weekly training so as to guarantee no additional physical stress beyond that which they were accustomed to. This approach avoided differences in the amount or intensity of training and consequent increase in oxidative stress. Only those athletes who followed the instructions correctly and participated in both races were enrolled in the study, which involved 125 athletes (49 females and 76 males), aged 15-67 years old.

This study was done according to the guidelines laid down in the Declaration of Helsinki, and the procedures were approved by the Ethics Committee of the University of Brasília and by the National Commission for Ethics in Research (CONEP). Written informed consent was obtained from all subjects.

Preparation of capsules

Pequi oil, the composition of which has previously been described (Miranda-Vilela et al., 2009a,b,c, 2010; Miranda-Vilela et al., 2011a,b; Ribeiro et al., 2013; Miranda-Vilela et al., 2014), was extracted by cold maceration using chloroform as a solvent (Miranda-Vilela et al., 2009c) and incorporated in Aerosil (colloidal silicon dioxide) q.s.p. (Miranda-Vilela et al., 2009a,b, 2010, 2011a,b). The capsule production was patented as number PI0601631-6 (National Institute of Industrial Property – INPI) and a voucher of the pequi specimen (C. brasiliense Camb.) was deposited in the herbarium of the University of Brasilia (UnB) by Professor Cassia Munhoz (PhD) (collection number 7402, registration number 165.857).

Procedures and measurements

Waist circumference (WC), hip circumference, waist-hip ratio and body mass index (BMI) were checked before the first race as previously reported (Miranda-Vilela et al., 2009a). Peripheral blood samples collected immediately after the two races in Vacutainer tubes containing EDTA were used to perform immune cell counting and genotyping, while serum samples were used to quantify CK, AST, ALT, acute phase proteins (CRP and hs-CRP), postprandial lipid profile and TBARS.

Hemogram and biochemical analyses

A complete blood count or hemogram was done in an automated analyzer (Cell-Dyn 3700, Abbott Diagnostics, Chicago, Illinois, US); serum ALT, AST, CK, CRP and postprandial lipid profile analyses were run on an automated chemistry analyzer ADVIA 1650 (Bayer Diagnostics, Greenburgh, NY, US) and serum hs-CRP was measured by an immunometric assay (Immulite 2000, DPC, Medlab) using the appropriate chemical reagents, controls and protocols of the manufacturers. The TBARS assay was done according to Wasowicz et al. (1993) and the fluorescence was measured with a Jasco FP-777 spectrofluorometer (excitation: 525 nm, emission: 547 nm).

Genotyping of the polymorphism

Genomic DNA was isolated from the buffy-coat layer using a Blood genomic Prep mini spin kit (GE Healthcare, Buckinghamshire, England). DNA samples were quantified in a Nanovue spectrophotometer (GE Healthcare), diluted in milli-Q water to a final concentration of 50 ng/μL and stored at -20°C until analysis. DNA samples were amplified in an MJ PTC-100 thermocycler (MJ Research Inc., Waltham, MA, USA). The IL-6 genotypes were determined by allele-specific amplification (Eynon et al., 2011b). The PCR products were separated by electrophoresis in 6% non-denaturing polyacrylamide gels and visualized by staining with silver nitrate.

Statistical analyses

The minimum sample size was estimated by power analysis based on the statistical analysis of quantitative data and a maximum tolerable sampling error (standard error or sampling error) of 0.05-0.20, depending on the population variability for the reference intervals of the laboratory tests and samples after stratification of the entire group (Ribeiro et al., 2013; Barbosa et al., 2014).

The genotype distributions were tested for Hardy-Weinberg equilibrium (HWE) by the Chi-square (χ²) test, using the Genepopweb statistical program, version 4.2 (http://genepop.curtin.edu.au). Values of p > 0.05 were indicative of HWE. The same program was used to calculate the allelic and genotypic frequencies of each locus, as well as genetic diversity parameters such as observed heterozygosity (Ho), expected heterozygosity (He) and inbreeding coefficient (FIS).

Statistical analysis was done using SPSS (Statistical Package for the Social Sciences) version 17.0. The data were expressed as the mean ± SD (standard deviation) and values of p < 0.05 were considered statistically significant. The continuous variables were tested for normal distribution with the Shapiro-Wilk test. For the parameters analyzed, possible differences between the sexes were evaluated by Students t-test or the Mann-Whitney U test (non-normalized data), while differences among age groups, distance covered and genotypes were evaluated by ANOVA or the Kruskal-Wallis test (data not normally distributed), followed, respectively, by the Tukey or Mann-Whitney U tests. Students paired t-test or the Wilcoxon matched pairs test (when the data were not normally distributed) was used to assess differences in before-after comparisons of supplementation with pequi oil.

The possible correlations between the parameters genetic polymorphisms/sex, genetic polymorphisms/age group and genetic polymorphisms/distance covered were analyzed using the Chi-square correlation test. As the correlations sex/age group, sex/distance covered, age group/distance covered have already been published (Miranda-Vilela et al., 2009a; Ribeiro et al., 2013), they will not be presented here. The Spearman correlation test was used to assess correlations between qualitative variables (genotypes) and laboratory tests, while correlations between quantitative variables were tested by the Pearson (normalized data) or Spearman (data not normally distributed) correlation tests (Barbosa et al., 2014).

The odds ratio (OR) with 95% confidence intervals (CI) was also calculated to estimate the relative chance of risk or protection for higher levels of CK, AST, ALT, CRP, hs-CRP and lipid peroxidation. To calculate the OR for the biochemical tests, the parameters > or < than the maximum reference limit were considered, and were: CK: 145 U/L (female) and 170 U/L (male) (Freire et al., 2008; Schumann and Klauke, 2003), AST: 31 U/L (female) and 37 U/L (male), ALT: 35 U/L (female) and 40 U/L (male) (Freire et al., 2008), and CRP and hs-CRP: 1.0 mg/L for both sexes, based on the low risk of having a heart attack as defined by the American Heart Association and the US Center for Diseases Control (Ridker, 2003), with women usually having lower values than men (Rifai and Ridker, 2003). For the TBARS assay the median was used, i.e., > 0.027 and < 0.027 nmol of MDA/mL for both sexes (Akimoto et al., 2010).

Results

The frequencies of the IL-6 –174 G/C (SNP rs1800795) genotypes were in Hardy-Weinberg equilibrium (p > 0.05) and the distribution of their allele and genotype frequencies, as well as the genetic diversity parameters and HWE data for the Chi-square (χ2) test are shown in Table 1. There were no significant differences in the distribution of IL-6 genotypes between the sexes (Table 2), among age groups (Table 3) or in relation to the distance covered (Table 4).

Table 1
Distribution of IL-6 –174 G/C (SNP rs1800795) allele frequencies, genetic diversity parameters, genotype frequencies and Hardy-Weinberg equilibrium (HWE) data for the Chi-square (χ²) test.

Genetic polymorphism	Chromosome location	Allele frequencies		Heterozygosity-observed (Ho)	Heterozygosity-expected (He)	FIS (Inbreeding coefficient)	Genotypes	Genotype frequencies	Number of observed individuals	Number of expected individuals	HWE test (p)
						IL-6 -174					7p15.3	G	0.68				GG	0.4720	59	57.6908
G/C		C	0.32	0.4160	0.4352	0.0481	GC	0.4160	52	54.6185	0.6806
							CC	0.1120	14	12.6908

• The p value was calculated using the statistical program Genepopweb version 4.2 (http://genepop.curtin.edu.au).

Table 2
Distribution of IL-6 –174 G/C (SNP rs1800795) genotypes in relation to the total number of subjects and gender. The results are expressed as a percentage (%) in relation to the total sample size of each group.

IL-6 genotypes	Total (%) [N=125]	Male (%) [N=76]	Female (%) [N=49]	p
GG	59 (47.2)	38 (50)	21 (42.9)
GC	52 (41.6)	29 (38.2)	23 (46.9)	0.569
CC	14 (11.2)	9 (11.8)	5 (10.2)

• The p value was calculated with the Mann-Whitney U test using SPSS (Statistical Package for the Social Sciences), version 17.0.

Table 3
Distribution of IL-6 –174 G/C (SNP rs1800795) genotypes in relation to age group (years old). The results are expressed as a percentage (%) in relation to the total sample size of each group.

IL-6 genotypes	15-19 (%) [N=20]	20-24 (%) [N=25]	25-29 (%) [N=25]	30-34 (%) [N=12]	35-39 (%) [N=16]	40-44 (%) [N=10]	> 45 (%) [N=17]	p
GG	10 (50)	10 (40)	14 (56)	4 (33.3)	9 (56.3)	4 (40)	8 (47.1)
GC	5 (25)	10 (40)	10 (40)	7 (58.3)	6 (37.5)	6 (60)	8 (47.1)	0.717
CC	5 (25)	5 (20)	1 (4)	1 (8.3)	1 (6.3)	0 (0)	1 (5.9)

• The p value was calculated with the Kruskal-Wallis test using SPSS (Statistical Package for the Social Sciences), version 17.0.

Table 4
Distribution of IL-6 –174 G/C (SNP rs1800795) genotypes relative to the distance covered (km). The results are expressed as a percentage (%) in relation to the total sample size of each group.

IL-6 genotypes	4-5 (%) [N=50]	6-7 (%) [N=38]	8-10 (%) [N=30]	16-21 (%) [N=7]	p
GG	23 (46)	21 (55.3)	11 (36.7)	4 (57.1)
GC	19 (38)	13 (34.2)	18 (60)	2 (28.6)	0.697
CC	8 (16)	4 (10.5)	1 (3.3)	1 (14.3)

• The p value was calculated with the Kruskal-Wallis test using SPSS (Statistical Package for the Social Sciences), version 17.0.

For the biochemical tests, there were significant differences in the TBARS values of the genotypes CC and GG (p=0.011) and CC and GC (p=0.028) before supplementation with pequi oil. After supplementation, these differences persisted between CC and GG (p=0.023) and appeared for GC and GG (p=0.041). In both cases, before and after pequi, the wild type (GG) genotype showed higher lipid peroxidation [higher MDA (malondialdehyde) values in the TBARS assay]. Significant differences in the before-after comparison were observed for the GC genotype in relation to the CK (p = 0.030) and AST (p = 0.030) values that were reduced after supplementation, and for the CC genotype in which CRP was significantly increased (p = 0.021) after supplementation with pequi, although still within the limits of the reference value (Ridker, 2003) (Table 5).

Table 5
Influence of IL-6 –174 G/C polymorphism (SNP rs1800795) on the CK, AST, ALT, CRP, hs-CRP and TBARS values before and after supplementation with pequi oil.

	CK (U/L)		AST (U/L)		ALT (U/L)		CRP (mg/dL)		hs-CRP (mg/dL)		TBARS (nmol of MDA/mL)
IL-6 genotypes	Before	After	Before	After	Before	After	Before	After	Before	After	Before	After
GG	327.84 ± 425.25	275.39 ± 295.09	29.98 ± 8.47	29.26 ± 7.55	23.60 ± 11.23	21.91 ± 8.96	0.37 ± 0.41	0.37 ± 0.32	1.95 ± 2.81	1.78 ± 1.93	0.0280 ± 0.008	0.0278 ± 0.006
GC	237.75 ± 217.36	186.08 ± 106.10#	30.04 ± 8.88	27.52 ± 6.49#	23.19 ± 11.52	21.94 ± 9.48	0.31 ± 0.23	0.33 ± 0.25	1.32 ± 1.54	1.29 ± 1.64	0.0264 ± 0.007	0.0257 ± 0.006a
CC	271.71 ± 307.44	260.64 ± 212.95	28.36 ± 9.88	26.43 ± 8.47	20.57 ± 11.92	19.14 ± 7.50	0.21 ± 0.18	0.52 ± 0.39#	1.06 ± 0.99	1.66 ± 1.91	0.0222 0.007a,b	0.0229 ± 0.007a
p	0.192	0.428	0.494	0.274	0.271	0.519	0.371	0.247	0.291	0.194	0.026	0.019

• The results are expressed as the mean ± SD. ALT – alanine aminotransferase, AST – aspartate aminotransferase; CK – creatine kinase, CRP – C-reactive protein, hs-CRP – high-sensitivity CRP, U/L – units per liter, mg/dL – milligrams per deciliter, nmol of MDA/mL – nanomoles of malondialdehyde per milliliter of serum. The p values were calculated using the Kruskal-Wallis test. The lowercase letters indicate significant differences detected by the Mann-Whitney U test between genotypes in 2 X 2 comparisons, where a and b indicate significance compared to the GG and GC genotypes, respectively. The symbol # indicates significant differences in the comparisons before and after supplementation with pequi oil as detected by the Wilcoxon test.

For the hemogram, supplementation with pequi resulted in a significant difference only for the platelet deviation weight (PDW) between the genotypes GC and GG (p = 0.045), with the heterozygous genotype having the higher values. However, in the before-after comparison, several responses to supplementation were observed among the IL-6 genotypes (Table 6).

Table 6
Influence of IL-6 –174 G/C polymorphism (SNP rs1800795) on erythrocytes (A), leukocytes (B) and platelets (C) before and after supplementation with pequi oil.

Erythrocytes
IL-6 genotypes	RBC (millions/mm3)		HGB (g/dL)		HCT (%)		MCV (fl)		MCH (pg)		MCHC (g/% ou g/dL)		RDW (%)
	Before	After	Before	After	Before	After	Before	After	Before	After	Before	After	Before	After
GG	5.20 ± 0.50	5.14 ± 0.50	14.82 ± 2.24	14.76 ± 2.25	44.47 ± 3.60	43.86 ± 3.65#	85.74 ± 4.19	85.73 ± 4.28	29.25 ± 1.59	29.57 ± 1.62#	34.13 ± 0.98	34.50 ± 0.58#	14.92 ± 1.09	14.28 ± 1.18#
GC	5.25 ± 0.53	5.17 ± 0.47#	14.40 ± 3.21	14.37 ± 3.26	45.41 ± 4.03	44.73 ± 3.62	86.58 ± 3.29	86.69 ± 3.09	29.53 ± 1.55	29.96 ± 1.40#	34.10 ± 1.08	34.55 ± 0.69#	14.86 ± 0.84	14.33 ± 0.96#
CC	5.26 ± 0.46	5.16 ± 0.54	13.37 ± 4.45	13.11 ± 4.45#	45.77 ± 3.33	44.84 ± 3.84#	87.12 ± 3.49	87.14 ± 4.13	30.06 ± 1.23a	30.09 ± 1.43	34.49 ± 0.72	34.57 ± 0.83	14.47 ± 1.11	13.89 ± 0.93#
p	0.859	0.953	0.917	0.717	0.320	0.415	0.310	0.315	0.098	0.251	0.555	0.557	0.321	0.386

Leukocytes
IL-6 genotypes	WBC (/mm3)		Lymphocytes (/mm3)		Segmented (/mm3)		Rods (/mm3)		Basophils (/mm3)		Eosinophils (/mm3)		Monocytes (/mm3)
	Before	After	Before	After	Before	After	Before	After	Before	After	Before	After	Before	After
GG	7479.63 ± 2265.44	7455.56 ± 1918.79	2595.07 ± 993.02	2519.36 ± 927.72	4099.18 ± 1712.91	4097.45 ± 1431.03	45.33 ± 114.77	36.22 ± 101.18	83.82 ± 49.08	95.64 ± 50.05	150.76 ± 115.62	159.96 ± 131.14	509.67 ± 248.69	550.20 ± 211.13
GC	7428.57 ± 2504.83	7508.16 ± 1916.90	2757.73 ± 967.59	2762.43 ± 965.14	3942.14 ± 1918.00	3851.43 ± 1427.28	9.81 ± 29.72	14.23 ± 56.91	86.67 ± 52.35	99.10 ± 43.88	148.24 ± 125.84	164.92 ± 132.83#	481.14 ± 198.17	557.20 ± 201.21#
CC	7371.43 ± 1219.35	7264.29 ± 2259.55	2666.36 ± 919.23	2552.79 ± 1367.59	3963.64 ± 1145.49	3938.43 ± 1629.83	7.57 ± 28.33	31.00 ± 90.22	87.64 ± 56.75	107.57 ± 46.38	122.79 ± 82.68	108.57 ± 63.06	503.29 ± 197.44	517.07 ± 216.85
p	0.842	0.843	0.603	0.451	0.536	0.711	0.223	0.557	0.947	0.695	0.763	0.384	0.850	0.728

Platelets
IL-6 genotypes	Platelets (thousand/mm3)		Platelets (%)		MPV (fl)		PDW (%)
	Before	After	Before	After	Before	After	Before	After
GG	337.54 ± 72.86	309.07 ± 61.22#	0.36 ± 0.10	0.31 ± 0.07#	10.42 ± 1.59#	10.03 ± 1.45	18.07 ± 1.16	17.86 ± 0.92
GC	336.92 ± 67.49	319.76 ± 69.30#	0.36 ± 0.09	0.35 ± 0.10	10.59 ± 1.68	10.67 ± 1.79	17.87 ± 1.08	18.35 ± 1.11#
CC	320.43 ± 61.78	297.93 ± 61.07	0.34 ± 0.06	0.32 ± 0.07	10.83 ± 1.62	10.75 ± 1.82	18.23 ± 1.47	18.29 ± 1.15
p	0.544	0.505	0.722	0.376	0.593	0.199	0.641	0.123

• The data are expressed as the mean ± SD. HCT – hematocrit, HGB – hemoglobin, MCV – mean corpuscular volume, MCH – mean corpuscular hemoglobin, MCHC – mean corpuscular hemoglobin concentration, MPV – mean platelet volume, PDW – platelet deviation weight, RBC – red blood cells, RDW – red cell distribution width, WBC – white blood cells, g/dL – gram per deciliter, fl – femtoliter, pg – picograms, g/% – gram per percentage. P values for RBC, HCT, RDW and basophils were calculated by ANOVA, while the other p values were calculated with the Kruskal-Wallis test. The lowercase letters indicate significant differences between genotypes in the 2 X 2 comparisons, where a and b indicate significance compared to the GG and GC genotypes, respectively. The symbol # indicates significant differences in the comparisons before and after supplementation with pequi oil detected by Students t-test (HCT, RBC, RDW) or the Wilcoxon test (other variables).

The postprandial lipid profile revealed significant differences after supplementation with pequi only between the LDL values of the CC and GG genotypes (p=0.012) and CC and GC (p=0.003), with the homozygous mutant genotype (CC) having lower values. No significant differences were observed in the before-after comparisons (Table 7).

Table 7
Influence of IL-6 –174 G/C polymorphism (SNP rs1800795) on the postprandial lipid profile before and after supplementation with pequi oil.

IL-6 genotypes	Total cholesterol (mg/dL)		Triglycerides (mg/dL)		HDL (mg/dL)		LDL (mg/dL)		VLDL (mg/dL)
	Before	After	Before	After	Before	After	Before	After	Before	After
GG	187.37 ± 37.43	186.04 ± 35.98	116.06 ± 66.43	116.72 ± 55.42	54.02 ± 13.90	53.07 ± 13.80	109.68 ± 28.56	108.85 ± 27.77	23.21 ± 13.29	23.34 ± 11.08
GC	193.22 ± 39.60	193.29 ± 33.71	111.35 ± 55.53	116.41 ± 46.27	55.14 ± 12.87	55.98 ± 13.32	116.19 ± 35.36	113.91 ± 29.26	22.27 ± 11.11	23.28 ± 9.25
CC	169.57 ± 35.67	170.21 ± 32.63	108.21 ± 58.52	130.86 ± 63.45	51.93 ± 12.99	54.50 ± 16.22	96.00 ± 26.19	89.54 ± 21.75a,b	21.64 ± 11.70	26.17 ± 12.69
p	0.126	0.086	0.945	0.747	0.368	0.313	0.149	0.012	0.945	0.747

• The data are expressed as the mean ± SD. HDL – high-density lipoprotein, LDL – low-density lipoprotein, VLDL – very-low-density lipoprotein, mg/dL= milligram per deciliter. P values for total cholesterol were calculated by ANOVA, while those for the other parameters were calculated by the Kruskal-Wallis test. The lowercase letters indicate significant differences detected between genotypes in the 2 X 2 comparisons, where a and b indicate significance compared to the GG and GC genotypes, respectively.

Several correlations among the serum levels of the biochemical parameters and postprandial lipid profile were observed in the group as a whole and in the IL-6 genotypes. In particular, there was a positive correlation between triglycerides before vs hs-CRP, which was particularly related to the CC genotype (Table 8).

Table 8
Correlation between total cholesterol and other serum lipids in the whole group and in relation to the IL-6 –174 G/C genotypes.

Group	Comparison	Correlation	p
		coefficient
Whole group	Total cholesterol before vs
	Triglycerides before	0.366	0.000
	HDL before	0.409	0.000
	LDL before	0.905	0.000
	VLDL before	0.366	0.000
	Total cholesterol after vs
	Triglycerides after	0.365	0.000
	HDL after	0.406	0.000
	LDL after	0.897	0.000
	VLDL after	0.365	0.000
	Triglycerides before vs
	VLDL before	1.000	0.000
	hs-CRP before	0.197	0.041
	Triglycerides after vs
	HDL after	-0.182	0.049
	VLDL after	1.000	0.000
IL-6 GG genotype	Total cholesterol before vs
	Triglycerides before	0.444	0.003
	LDL before	0.554	0.000
	VLDL before	0.463	0.002
	Total cholesterol after vs
	Triglycerides after	0.432	0.004
	HDL after	-0.304	0.045
	LDL after	0.451	0.002
	VLDL after	0.431	0.004
	Triglycerides before vs
	HDL before	-0.363	0.017
	VLDL before	1.000	0.000
	Triglycerides after vs
	HDL after	-0.426	0.004
	VLDL after	1.000	0.000
	HDL before vs
	VLDL before	-0.363	0.017
	HDL after vs
	VLDL after	-0.426	0.004
IL-6 GC genotype	Total cholesterol before vs
	Triglycerides before	0.318	0.031
	LDL before	0.544	0.000
	VLDL before	0.318	0.031
	Total cholesterol after vs
	LDL after	0.548	0.000
	Triglycerides before vs
	VLDL before	1.000	0.000
	Triglycerides after vs
	VLDL after	1.000	0.000
IL-6 CC genotype	Triglycerides before vs
	VLDL before	1.000	0.000
	hs-CRP before	0.843	0.001
	Total cholesterol after vs
	LDL after	0.756	0.018
	Triglycerides after vs
	VLDL after	1.000	0.000

The OR with 95% CI indicated that individuals carrying the wild type genotype (GG) were 2.9 times more likely to have MDA values (TBARS assay) > 0.027 nmol/mL, while the GC genotype decreased this risk. For females carrying the GG genotype, this risk was > 5.0, while for males, there was a decreased risk for the CC, but not for GC, genotype (Table 9).

Table 9
Odds ratios (OR) and 95% confidence intervals (CI).

		Comparisons	OR (95% CI)	p
Total group		IL-6 GG and TBARS after > 0.027 nmol of MDA/mL	2.917 (1.407-6.047)	0.004
		IL-6 GC and TBARS after > 0.027 nmol of MDA/mL	0.462 (0.222-0.961)	0.046
Gender	Male	IL-6 CC and TBARS before > 0.027 nmol of MDA/mL	0.129 (0.015-1.087)	0.031
	Female	IL-6 GG and TBARS after > 0.027 nmol of MDA/mL	5.278 (1.535-18.148)	0.007
		IL-6 GC and TBARS after > 0.027 nmol of MDA/mL	0.232 (0.070-0.770)	0.015

Discussion

The IL-6 –174 G/C polymorphism (SNP rs1800795) tends to be quite variable in Caucasians, but in Asians and Africans the frequency of the C allele is much lower than in Caucasians, tending to be almost monomorphic for the wild-type G allele (Gan et al., 2013). The Brazilian population is very mixed, primarily because of five centuries of interethnic crosses among Europeans (European colonizers, mainly represented by the Portuguese), Africans (slaves) and Amerindians (the indigenous population) (Parra et al., 2003; Hiragi et al., 2011; Lordelo et al., 2012; Barbosa et al., 2014); this miscegenation can strongly influence the distribution of certain polymorphisms (Lordelo et al., 2012; Barbosa et al., 2014). Moreover, Brazil's large geographic size and the fact that different population groups have moved to different parts of the country has resulted in considerable phylogeographical heterogeneity (Parra et al., 2003). As the population of Brasilia (the Federal Capital) is formed by migrants from all regions of Brazil, it tends to reflect the Brazilian population better than any other region (Miranda-Vilela et al., 2009d; Hiragi et al., 2011). In this regard, our results confirm a major influence of European ancestry in the IL-6 polymorphism studied here. Moreover, as there were no sex-, age- or distance-related differences in the distribution of the IL-6 genotypes, we have no reason to reject the hypothesis that the significant differences seen here reflected each individuals IL-6 response to antioxidant supplementation with pequi, and possibly also a direct interaction of pequi with the IL-6 gene to influence the response to this supplementation.

Although we did not examine the biomarkers before each race, most of the exercise-induced physiological and biochemical changes have already been well documented (Ji and Leichtweis, 1997; Kargotich et al., 1998; Kasapis and Thompson, 2005; Mattusch et al., 2000; Urso and Clarkson, 2003; Brancaccio et al., 2007; Cruzat et al., 2007; Ferreira et al., 2007; Mougios, 2007) and our study did not aim to evaluate such alterations. We undertook a controlled before-after study in which observations are made before and after the implementation of an intervention; in our case, before (first race) and after (second race) intervention with pequi oil. This type of study is validated in the scientific literature (Meads and Davenport, 2009) and, although it has some limitations compared to randomized placebo-controlled studies, we followed all of the recommended steps to guarantee quality control and the validity of our study (American College of Physicians, 1999; Meads and Davenport, 2009), as previously reported (Miranda-Vilela et al., 2009a,b, 2010, 2011a,b; Ribeiro et al., 2013). Our results support the proposed hypothesis since the values observed did not exceed the reference limits determined for clinical purposes (Ridker, 2003; Schumann and Klauke, 2003; Freire et al., 2008), and much less for athletes (Mougios, 2007).

In addition to increasing oxygen consumption and inducing oxidative stress, exercise can initiate an inflammatory process that is regulated by cytokines, mostly IL-6 (Moleres et al., 2009). Since the IL-6 –174 G/C polymorphism is associated with serum IL-6 and/or CRP levels (Szydlowski et al., 2013), our results demonstrated that pequi oil may remove the positive association between triglycerides and hs-CRP seen in the homozygous mutant IL-6 CC genotype before (but not after) pequi. Furthermore, pequi oil may promote a non-significant increase in triglycerides (Miranda-Vilela et al., 2009a) because of its natural triglyceride (TG) composition (Segall et al., 2006; Miranda-Vilela et al., 2009c). Since individuals genetically predisposed to higher IL-6 secretion may be at risk of dyslipidemia, especially during the postprandial phase, it has been suggested that the IL-6 –174 G/C polymorphism determines the difference in both fasting and postprandial TG metabolism and that this phenomenon could be responsible for the observed association of this genetic variant with a risk for CVD (Shen et al., 2008). C-reactive protein (CRP) is an acute phase reactant and indicator of inflammation that promotes lipid accumulation in the atherosclerotic plaque and exerts direct effects on endothelial cells, thereby contributing to endothelial dysfunction (Erbel et al., 2008). CRP and hs-CRP measure the same molecule in blood, but hs-CRP has been developed to detect CRP at lower levels and is therefore much more sensitive for diagnostic purposes (Rifai and Ridker, 2003). The levels of hs-CRP can be used to predict future cardiovascular disease in seemingly healthy middle-aged adults (Erbel et al., 2008), and the lack of correlation after pequi supplementation in the present study suggested a protective effect of pequi oil, primarily for the IL-6 CC genotype.

Pequi oil has a high concentration of monounsaturated oleic (MUFA) and saturated palmitic (SFA) fatty acids that are anti- and pro-atherogenic agents, respectively (Aguilar et al., 2012). This oil is also rich in natural antioxidants such as carotenoids (Azevedo-Meleiro and Rodriguez-Amaya, 2004; Oliveira et al., 2006; Lima et al., 2007) and vitamin E (α-tocopherol), both of which are encountered in cooked pulp (Cardoso et al., 2013). Thus, although pequi oil has been associated with atherogenic worsening of the lipid profile (Aguilar et al., 2012), it has also been reported to efficiently reduce exercise-induced inflammation (Miranda-Vilela et al., 2009a). This anti-inflammatory action may be associated not only with the antioxidant properties of the oil, but also with its MUFA oleic acid-to-SFA palmitic acid ratio.

The increase in O₂ consumption induced by physical exercise is associated with an increase in reactive oxygen species (ROS) production. These species induce oxidative stress, a term generally used to describe the damage caused by an imbalance between pro-oxidants and antioxidant defense mechanisms (Leal Junior et al., 2011). Endothelial oxidative stress is associated with impaired function and is a key feature in the onset and evolution of CVD (Conti et al., 2012). The increase in the MUFA oleic acid-to-SFA palmitic acid ratio in postprandial TRL has been linearly correlated with an increased down-regulation of the apolipoprotein B48 receptor (ApoB48R; a macrophage receptor that binds to apolipoprotein B48 of dietary TRL), with a consequent decrease in lipid accumulation (Varela et al., 2013). This receptor may provide essential lipids, lipid-soluble vitamins and other nutrients to reticuloendothelial cells. When overwhelmed with elevated plasma triglyceride levels, the apolipoprotein B48 receptor may contribute to foam cell formation, endothelial dysfunction and atherothrombogenesis (Brown et al., 2000). These responses agree with the suggestion regarding the importance of the MUFA oleic acid-to-SFA palmitic acid ratio indicated above.

High concentrations of ROS result in damage to DNA, proteins and lipids that can cause cell and tissue impairment (Conti et al., 2012). Biomarkers of lipid oxidation, such as malondialdehyde (MDA) measured as thiobarbituric acid reactive substances (TBARS), may be independent risk indicators for patients with stable coronary artery disease (CAD), independently of traditional risk factors and inflammatory markers (Walter et al., 2004). In the present study done in athletes, the wild type GG genotype showed significantly higher MDA values than the other IL-6 genotypes, a situation that was not improved by supplementation with pequi oil. In addition, the Odds ratio indicated an increased risk for higher MDA values among females. Women have a lower risk of CVD than men because endogenous estrogens during the fertile period of life delay the manifestation of atherosclerotic disease in women (Maas and Appelman, 2010). In the present study, only athletes in their fertile period were investigated, with the overall mean absolute level of TBARS being much lower than that reported for patients with stable coronary artery disease (1.49 ± 0.57 μM or ng/dL) (Walter et al., 2004). In addition, the absolute global CVD risk inspired by the Framingham Heart Study is calculated based on a combination of several key risk factors that include the patients history of cardiovascular disease, diabetes, smoking, blood pressure and blood lipid concentrations (Bitton and Gaziano, 2010). Pequi oil reportedly modulates postprandial lipemia and reduces exercise-induced inflammation and blood pressure in runners (Miranda-Vilela et al., 2009a).

Exercise induces transitory alterations in the serum/plasma cytokine profile that involve mainly an increase in serum levels of interleukin-6 (IL-6) (Oleto et al., 2011). Although we did not quantify circulating IL-6 levels, the significant reductions in CK and AST seen in individuals heterozygous for IL-6 and the non-significant reduction in these parameters observed for the other genotypes in the before-after comparison of pequi-oil suggested a better response to this antioxidant supplementation against exercise-induced damage in the GC genotype. The results of the platelet count corroborate our suggestion.

In conclusion, the IL-6 genotypes showed significant differences in lipid peroxidation, with the CC mutant showing lower values. There were also significant differences among the genotypes with respect to the response to antioxidant supplementation with pequi oil, mainly in relation to exercise-induced damage and CRP levels. The best response against muscle damage was seen in the heterozygous genotype, although the CC genotype showed an increase in CRP levels after supplementation; the lack of a positive correlation between triglycerides and hs-CRP for this mutant genotype after supplementation indicated a protective effect of pequi oil. Because pequi oil has been associated with an atherogenic effect, worsening the lipid profile and at the same time modulating posprandial lipemia and reducing exercise-induced inflammation and blood pressure of human runners, these findings deserve further investigations, in which evaluations of the IL-6 levels should also be performed.

Acknowledgments

The authors gratefully acknowledge the subjects who participated in this research, Sabin Institute/Sabin Laboratories and Farmacotécnica for technical support and the University of Brasília (UnB), the National Council for Technological and Scientific Development (CNPq) and the Scientific and Technological Enterprises Foundation (FINATEC) for financial support.

References

• Aguilar EC, Jascolka TL, Teixeira LG, Lages PC, Ribeiro AC, Vieira EL, Peluzio MC and Alvarez-Leite JI (2012) Paradoxical effect of a pequi oil-rich diet on the development of atherosclerosis: Balance between antioxidant and hyperlipidemic properties. Braz J Med Biol Res 45:601-609.
• Akimoto AK, Miranda-Vilela AL, Alves PC, Pereira LC, Lordelo GS, Hiragi CO, da Silva IC, Grisolia CK and Klautau-Guimarães MN (2010) Evaluation of gene polymorphisms in exercise-induced oxidative stress and damage. Free Radic Res 44:322-331.
• American College of Physicians (1999) A primer on before/after studies: Evaluating a report of a “successful intervention”. Eff Clin Pract 2:241-243.
• Azevedo-Meleiro CH and Rodriguez-Amaya DB (2004) Confirmation of the identity of the carotenoids of tropical fruits by HPLC-DAD and HPLC-MS J Food Comp Anal 17:385-396.
• Barbosa LCP, Miranda-Vilela AL, Hiragi CO, Ribeiro IF, Daldegan MB, Grisolia CK and Santos-Neto LL (2014) Haptoglobin and myeloperoxidase (-G463A) gene polymorphisms in Brazilian sickle cell patients with and without secondary iron overload Blood Cells Mol Dis 52:95-107.
• Bermúdez B, López S, Pacheco YM, Villar J, Muriana FJ, Hoheisel JD, Bauer A and Abia R (2008) Influence of postprandial triglyceride-rich lipoproteins on lipid-mediated gene expression in smooth muscle cells of the human coronary artery. Cardiovasc Res 79:294-303.
• Bernad A, Kopf M, Kulbacki R, Weich N, Koehler G and Gutierrez-Ramos JC (1994) Interleukin-6 is required in vivo for the regulation of stem cells and committed progenitors of the hematopoietic system. Immunity 1:725-731.
• Bitton A and Gaziano T (2010) The Framingham Heart Study's impact on global risk assessment. Prog Cardiovasc Dis 53:68-78.
• Brancaccio P, Maffulli N and Limongelli FM (2007) Creatine kinase monitoring in sport medicine. Br Med Bull 81-82:209-230.
• Brown ML, Ramprasad MP, Umeda PK, Tanaka A, Kobayashi Y, Watanabe T, Shimoyamada H, Kuo WL, Li R, Song R, et al (2000) A macrophage receptor for apolipoprotein B48: Cloning, expression, and atherosclerosis. Proc Natl Acad Sci U S A 97:7488-7493.
• Capurso C, Solfrizzi V, D'Introno A, Colacicco AM, Capurso SA, Capurso A and Panza F (2004) Interleukin 6-174 G/C promoter gene polymorphism and sporadic Alzheimer's disease: Geographic allele and genotype variations in Europe. Exp Gerontol 39:1567-1573.
• Cardoso LM, De Lazzari Reis B, Rossi Hamacek F and Pinheiro Sant'ana HM (2013) Chemical characteristics and bioactive compounds of cooked pequi fruits (Caryocar brasiliense Camb.) from the Brazilian savannah. Fruits 68:3-14.
• Colombini A, Lombardo G, Banfi G, Arpesella M and Pelissero G (2011) Athleticogenomics and elite athletes: A review of the state of the art and a possible relationship with inflammatory response. Ital J Public Health 8:275-285.
• Conti V, Corbi G, Russomanno G, Simeon V, Ferrara N, Filippelli W, Limongelli F, Canonico R, Grasso C, Stiuso P, et al (2012) Oxidative stress effects on endothelial cells treated with different athletes' sera. Med Sci Sports Exerc 44:39-49.
• Cruzat VF, Rogero MM, Borges MC and Tirapegui J (2007) Aspectos atuais sobre estresse oxidativo, exercícios físicos e suplementação. Rev Bras Med Esporte 13:336-342.
• Erbel R, Möhlenkamp S, Lehmann N, Schmermund A, Moebus S, Stang A, Grönemeyer D, Seibel R, Mann K, Volbracht L, et al (2008) Sex related cardiovascular risk stratification based on quantification of atherosclerosis and inflammation. Atherosclerosis 197:662-672.
• Eynon N, Ruiz JR, Meckel Y, Santiago C, Fiuza-Luces C, Gómez-Gallego F, Oliveira J and Lucia A (2011a) Is the -174 C/G polymorphism of the IL6 gene associated with elite power performance? A replication study with two different Caucasian cohorts. Exp Physiol 96:156-162.
• Eynon N, Morán M, Birk R and Lucia A (2011b) The champions' mitochondria: Is it genetically determined? A review on mitochondrial DNA and elite athletic performance. Physiol Genomics 43:789-798.
• Ferreira F, Ferreira R and Duarte J (2007) Stress oxidativo e dano oxidativo muscular esquelético: Influência do exercício agudo inabitual e do treino físico. Rev Port Cien Desp 7:257-275.
• Fishman D, Faulds G, Jeffery R, Mohamed-Ali V, Yudkin JS, Humphries S and Woo P (1998) The effect of novel polymorphisms in the interleukin-6 (IL-6) gene on IL-6 transcription and plasma IL-6 levels, and an association with systemic-onset juvenile chronic arthritis. J Clin Invest 102:1369-1376.
• Freire LMD, Sodré FL and Oliveira RA (2008) Controle de qualidade laboratorial pré-analítico: Avaliação de solicitações médicas de exames bioquímicos no Hospital de Clínicas da Universidade Estadual de Campinas, São Paulo, Brasil. Rev Bras Anál Clín 40:143-145.
• Gan G-G, Subramaniam R, Lian L-H and Nadarajan VS (2013) Ethnic variation in interleukin-6 –174 (G/C) polymorphism in the Malaysian population. Balkan J Med Genet 16:53-58.
• Gomez-Cabrera M-C, Domenech E and Viña J (2008) Moderate exercise is an antioxidant: Upregulation of antioxidant genes by training. Free Radic Biol Med 44:126-131.
• Hiragi CO, Miranda-Vilela AL, Rocha DM, Oliveira SF, Hatagima A and Klautau-Guimarães MN (2011) Superoxide dismutase, catalase, glutathione peroxidase and gluthatione S-transferases M1 and T1 gene polymorphisms in three Brazilian population groups. Genet Mol Biol 34:11-18.
• Hirano T, Taga T, Matsuda T, Hibi M, Suematsu S, Tang B, Murakami M and Kishimoto T (1990) Interleukin 6 and its receptor in the immune response and hematopoiesis. Int J Cell Cloning 8:155-167.
• Ji L and Leichtweis S (1997) Exercise and oxidative stress: Sources of free radicals and their impact on antioxidant systems. Age 20:91-106.
• Kargotich S, Goodman C, Keast D and Morton A (1998) The influence of exercise-induced plasma volume changes on the interpretation of biochemical parameters used for monitoring exercise, training and sport. Sports Med 26:101-117.
• Kasapis C and Thompson PD (2005) The effects of physical activity on serum C-reactive protein and inflammatory markers: A systematic review. J Am Coll Cardiol 45:1563-1569.
• Leal Junior ECP, Baroni BM, Rossi RP, de Godoi V, De Marchi T, Tomazoni SS, de Almeida P, Salvador M, Grosselli D, Generosi, et al (2011) Light emitting diode therapy (LEDT) applied pre-exercise inhibits lipid peroxidation in athletes after high-intensity exercise: A preliminary study. Rev Bras Med Esporte 17:8-12.
• Lima A, Silva AMO, Trindade RA, Torres RP and Mancini-Filho J (2007) Composição química e compostos bioativos presentes na polpa e na amêndoa do pequi (Caryocar brasiliense, Camb.). Rev Bras Frutic 29:695-698.
• Lordelo GS, Miranda-Vilela AL, Akimoto AK, Alves PC, Hiragi CO, Nonino A, Daldegan MB, Klautau-Guimarães MN and Grisolia CK (2012) Association between methylene tetrahydrofolate reductase and glutathione S-transferase M1 gene polymorphisms and chronic myeloid leukemia in a Brazilian population. Genet Mol Res 11:1013-1026.
• Maas AHEM and Appelman YEA (2010) Gender differences in coronary heart disease. Neth Heart J 18:598-603.
• Mattusch F, Dufaux B, Heine O, Mertens I and Rost R (2000) Reduction of the plasma concentration of C-reactive protein following nine months of endurance training. Int J Sports Med 21:21-24.
• Meads CA and Davenport CF (2009). Quality assessment of diagnostic before-after studies: Development of methodology in the context of a systematic review. BMC Med Res Methodol 9:e3.
• Miranda-Vilela AL, Pereira LC, Gonçalves CA and Grisolia CK (2009a) Pequi fruit (Caryocar brasiliense Camb.) pulp oil reduces exercise-induced inflammatory markers and blood pressure of male and female runners. Nutr Res 29:850-858.
• Miranda-Vilela AL, Akimoto AK, Alves PC, Pereira LC, Gonçalves CA, Klautau-Guimarães MN and Grisolia CK (2009b) Dietary carotenoid-rich pequi oil reduces plasma lipid peroxidation and DNA damage in runners and evidence for an association with MnSOD genetic variant -Val9Ala. Genet Mol Res 8:1481-1495.
• Miranda-Vilela AL, Grisolia CK, Resck IS and Mendonça MA (2009c) Characterization of the major nutritional components of Caryocar brasiliense fruit pulp by NMR spectroscopy. Quím Nova 32:2310-2313.
• Miranda-Vilela AL, Akimoto AK, Alves PCZ, Hiragi CO, Penalva GC, Oliveira SF, Grisolia CK and Klautau-Guimarães MN (2009d) Haptoglobin gene subtypes in three Brazilian population groups of different ethnicities. Genet Mol Biol 32:456-461.
• Miranda-Vilela AL, Akimoto AK, Alves PC, Pereira LC, Klautau-Guimarães MN and Grisolia CK (2010) Dietary carotenoid-rich oil supplementation improves exercise-induced anisocytosis in runners: Influences of haptoglobin, MnSOD (Val9Ala), CAT (21A/T) and GPX1 (Pro198Leu) gene polymorphisms in dilutional pseudoanemia (sports anemia). Genet Mol Biol 33:359-367.
• Miranda-Vilela AL, Lordelo GS, Akimoto AK, Alves PC, Pereira LC, Klautau-Guimarães MN and Grisolia CK (2011a) Genetic polymorphisms influence runners' responses to the dietary ingestion of antioxidant supplementation based on pequi oil (Caryocar brasiliense Camb.): A before-after study. Genes Nutr 6:369-395.
• Miranda-Vilela AL, Alves PCZ, Akimoto AK, Lordelo GS, Klautau-Guimarães MN and Grisolia CK (2011b) Under increased hydrogen peroxide conditions, the antioxidant effects of pequi oil (Caryocar brasiliense Camb.) to decrease DNA damage in runners are influenced by sex, age and oxidative stress-related genetic polymorphisms. Free Radic Antiox 1:27-39.
• Miranda-Vilela AL (2012) Exercise, injuries and athlete performance. In: Bastos JH and Silva AC (eds) Athlete Performance and Injuries. Nova Science Publishers, New York, pp 1-50.
• Miranda-Vilela A, Akimoto A, Lordelo G, Pereira LS, Grisolia C and Klautau-Guimarães MN (2012) Creatine kinase MM TaqI and methylenetetrahydrofolate reductase C677T and A1298C gene polymorphisms influence exercise-induced C-reactive protein levels. Eur J Appl Physiol 112:941-950.
• Miranda-Vilela AL, Grisolia CK, Longo JP, Peixoto RC, de Almeida MC, Barbosa LC, Roll MM, Portilho FA, Estevanato LL, Bocca AL, et al (2014) Oil rich in carotenoids instead of vitamins C and E as a better option to reduce doxorubicin-induced damage to normal cells of Ehrlich tumor-bearing mice: Hematological, toxicological and histopathological evaluations. J Nutr Biochem 25:1161-1176.
• Moleres A, Rendo-Urteaga T, Azcona C, Martínez JA, Gómez-Martínez S, Ruiz JR, Moreno LA, Marcos A, Marti A and the AVENA Group (2009) Il6 gene promoter polymorphism (-174G/C) influences the association between fat mass and cardiovascular risk factors. J Physiol Biochem 65:405-413.
• Mougios V (2007) Reference intervals for serum creatine kinase in athletes. Br J Sports Med 41:674-678.
• Oleto AF, Oleto AF, Sousa LP, Barreto TO, Cruz JS, Penaforte CL, Magalhães JC, Sousa-Franco J, Pinto KM, Campi-Azevedo AC, et al (2011) Plasma cytokine response, lipid peroxidation and NF-B activation in skeletal muscle following maximum progressive swimming. Braz J Med Biol Res 44:546-552.
• Oliveira MNS, Gusmão E, Lopes PSN, Simões MOM, Ribeiro LM and Dias BAS (2006) Estádio de maturação dos frutos e fatores relacionados aos aspectos nutritivos e de textura da polpa de pequi (Caryocar brasiliense Camb.). Rev Bras Frutic 28:380-386.
• Parra FC, Amado RC, Lambertucci JR, Rocha J, Antunes CM and Pena SDJ (2003) Color and genomic ancestry in Brazilians. Proc Natl Acad Sci U S A 100:177-182.
• Pereira DS, Garcia DM, Narciso FM, Santos ML, Dias JM, Queiroz BZ, Souza ER, Nóbrega OT and Pereira LS (2011) Effects of 174 G/C polymorphism in the promoter region of the interleukin-6 gene on plasma IL-6 levels and muscle strength in elderly women. Braz J Med Biol Res 44:123-129.
• Ribeiro IF, Miranda-Vilela AL, Klautau-Guimarães MN and Grisolia CK (2013) The influence of erythropoietin (EPO T → G) and α-actinin-3 (ACTN3 R577X) polymorphisms on runners' responses to the dietary ingestion of antioxidant supplementation based on pequi oil (Caryocar brasiliense Camb.): A before-after study. J Nutrigenet Nutrigenomics 6:283-304.
• Ridker PM (2003) C-reactive protein: A simple test to help predict risk of heart attack and stroke. Circulation 108:e81-e85.
• Rifai N and Ridker PM (2003) Population distributions of C-reactive protein in apparently healthy men and women in the United States: Implication for clinical interpretation. Clin Chem 49:666-669.
• Schumann G and Klauke R (2003) New IFCC reference procedures for the determination of catalytic activity concentrations of five enzymes in serum: Preliminary upper reference limits obtained in hospitalized subjects. Clin Chim Acta 327:69-79.
• Segall SD, Artz WE, Raslan DS, Ferraz VP and Takahashi JA (2006) Triacylglycerol analysis of pequi (Caryocar brasiliensis Camb.) oil by electrospray and tandem mass spectrometry. J Sci Food Agric 86:445-452.
• Shen J, Arnett DK, Pérez-Martínez P, Parnell LD, Lai CQ, Peacock JM, Hixson JE, Tsai MY, Straka RJ, Hopkins PN, et al (2008) The effect of IL6-174C/G polymorphism on postprandial triglyceride metabolism in the GOLDN studyboxs. J Lipid Res 49:1839-1845.
• Szydlowski L, Skierska A, Markiewicz-Loskot G, Mazurek B, Morka A and Undas A (2013) The role of interleukin-6, its -174 G > C polymorphism and C-reactive protein in idiopathic cardiac arrhythmias in children. Adv Med Sci 58:320-325.
• Urso ML and Clarkson PM (2003) Oxidative stress, exercise, and antioxidant supplementation. Toxicology 189:41-54.
• Varela LM, Ortega-Gomez A, Lopez S, Abia R, Muriana FJG and Bermudez B (2013) The effects of dietary fatty acids on the postprandial triglyceride-rich lipoprotein/apoB48 receptor axis in human monocyte/macrophage cells. J Nutr Biochem 24:2031-2039.
• Walter MF, Jacob RF, Jeffers B, Ghadanfar MM, Preston GM, Buch J and Mason RP (2004) Serum levels of thiobarbituric acid reactive substances predict cardiovascular events in patients with stable coronary artery disease: A longitudinal analysis of the PREVENT study. J Am Coll Cardiol 44:1996-2002.
• Wasowicz W, Nève J and Peretz A (1993) Optimized steps in fluorometric determination of thiobarbituric acid-reactive substances in serum: Importance of extraction pH and influence of sample preservation and storage. Clin Chem 39:2522-2526.

• Associate Editor: Daisy Maria Fávero Salvadori

Publication Dates

• Publication in this collection
  10 Oct 2016
• Date of issue
  Oct-Dec 2016

History

• Received
  17 Nov 2015
• Accepted
  16 Mar 2016