CAPE TOWN, South Africa—Researchers at the University of Cape Town explored the interactions between dietary fat intake and the tumor necrosis factor-alpha (TNFA) -308 G/A polymorphism on obesity, insulin resistance and serum lipid concentrations in urbanized black South African women in a study published in the Journal of Nutrition (2010;140(5):901-07). One of TNFA’s primary roles is regulating immune cells. It also plays a role in insulin resistance.
A total of 105 normal-weight women and 118 obese women underwent measurements of body composition, fat distribution, fasting serum lipids, glucose and insulin concentrations, and dietary intake. Participants were genotyped for the functional TNFA -308 G/A polymorphism. The genotype or allele frequency of the TNFA -308 G/A polymorphism did not differ between the body mass index (BMI) groups. However, when dietary fat intake was 30 percent of total energy intake, the odds of being obese with the TNFA GA+AA genotype was only 12 percent of that with GG, but increasing intake of dietary fat was associated with a significantly faster rate of increase in obesity risk in women with the TNFA GA+AA genotype compared with those with the GG genotype (P=0.036). There were significant diet-gene interactions between alpha-linolenic acid (ALA) and the total cholesterol:high-density lipoprotein (HDL) ratio (P=0.036), and polyunsaturated fatty acid (PUFA) and low-density lipoprotein (LDL) cholesterol levels (P=0.026), with participants with the A allele being more responsive to changes in relative fat intake. The TNFA -308 G/A polymorphism modified the relationship between dietary fat intake, obesity risk and serum lipid concentrations in black South African women.
