Interleukin-6 gene polymorphisms, dietary fat intake, obesity and serum lipid concentrations in black and white South African women.

Yael Joffe,Estelle Lambert,Alison September,Malcolm Collins,Lize Van Der Merwe,Julia Goedecke,Juliet Evans

doi:10.3390/nu6062436

Abstract

This study investigated interactions between dietary fat intake and IL-6 polymorphisms on obesity and serum lipids in black and white South African (SA) women. Normal-weight and obese, black and white women underwent measurements of body composition, serum lipids and dietary fat intake, and were genotyped for the IL-6 −174 G>C, IVS3 +281 G>T and IVS4 +869 A>G polymorphisms. In black women the IVS4 +869 G allele was associated with greater adiposity, and with increasing dietary fat intake adiposity increased in the IVS3 +281 GT+GG and IVS4 +869 AA or AG genotypes. In white women, with increasing omega-3 (n-3) intake and decreasing n-6:n-3 ratio, body mass index (BMI) decreased in those with the −174 C allele, IVS3 +281 T allele and IVS4 +869 AG genotype. In the white women, those with the IVS3 +281 T allele had lower triglycerides. Further, with increasing n-3 polyunsaturated fatty acid (PUFA); triglyceride and total cholesterol:high-density lipoprotein cholesterol (T-C:HDL-C) ratio decreased in those with the −174 C allele. In black women, with increasing total fat intake, triglycerides and T-C:HDL-C ratio increased in those with the IVS4 +869 G allele. This study is the first to show that dietary fat intake modulates the relationship between the IL-6 −174 G>C, IVS3 +281 G>T and IVS4 +869 A>G polymorphisms on obesity and serum lipids in black and white SA women.

Highlights

The cytokine interleukin 6 (IL-6) is known to regulate inflammation [1]
All genotype frequencies reported in this study were similar to European and African populations reported in the Ensembl database, none of the African populations reported in the Ensembl database were representative of populations from
To improve the validity of the dietary intake data we used a validated FFQ developed for the South African (SA) population, and included only adequate reporters in the analyses. No lifestyle factors such as physical activity and socioeconomic factors were included, that may impact the obese phenotype. This novel study showed that dietary fat intake, and the quality of the dietary fatty acids consumed, were associated with obesity risk and serum lipids differently, depending on the IL-6 genotype

Summary

Introduction

The cytokine interleukin 6 (IL-6) is known to regulate inflammation [1]. Higher circulating concentrations of IL-6 have been associated with obesity and visceral adipose tissue (VAT)deposition [2,3,4], lipid metabolism [1] and increased risk for cardiovascular disease (CVD) [5]. There is a growing body of evidence linking polymorphisms within the IL-6 gene to increased risk of obesity and dyslipidaemia [1,6,7,8,9]. Within the IL-6 gene, the most frequently studied polymorphism is the IL-6 −174 G>C polymorphism (rs1800795). This polymorphism is functional, with most studies showing the C allele to be associated with raised IL-6 and the acute phase protein, C-reactive protein (CRP) concentrations [5,10,11,12,13]. Association studies between this IL-6 gene polymorphism, obesity and dyslipidaemia have yielded conflicting results. A recent large meta-analysis by Yu et al [10,14] found the −174 G>C polymorphism to be associated with obesity [13]

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