According to The National Health and Nutrition Examination Survey, African-Americans have more incidences of cardiovascular diseases compared to caucasians. However, previous studies have also found that African-Americans have less dyslipidemia compared to caucasians, wherein their HDL-cholesterol (HDL-C) levels are higher, and triglycerides (TG) lower. Other factors linked to cardiovascular diseases in African-Americans are insulin resistance, found to be higher, and visceral adipose tissue (VAT), which studies show is lower in African-Americans than whites. Current evidence strongly links cholesterol and insulin resistance with the risk of developing diabetes.
Liyun Wang from the Department of Nutrition, Harvard School of Public Health, USA and colleagues sought to compare African-American women with white women, in terms of influences of insulin resistance and VAT on the apoAI concentrations of two HDL subtypes – one that contains apoCIII, associated with increased risk of coronary heart disease (CHD), and one that does not have apoCIII, associated with decreased CHD. The researchers also aimed to compare racial differences with apoCIII concentrations of HDL and apoB lipoproteins, with the operating premise that ApoCIII is an important predictor of CHD risk, as it is associated with apoB lipoproteins, and enhances the atherogenicity of very low-density lipoproteins (VLDL) and low density lipoproteins (LDL).
The study entitled “Racial differences between African-American and white women in insulin resistance and visceral adiposity are associated with differences in apoCIII containing apoAI and apoB lipoproteins”, was recently published in the journal Nutrition & Metabolism.
The team of researchers compared 14 African-Americans and 18 white women, age-matched, with a mean BMI of 34 kg/m2 and 30kg/m2, respectively, based on levels of HDL and visceral adipose tissue. For 7 days, a diet containing 33% fat, 52% carbohydrate and 15% protein was given to both groups. Then, on day 7 the researchers gave the women a test meal containing 40% fat, 40% carbohydrate and 20% protein. The participants were then assessed for insulin sensitivity.
The researchers found that African-Americans had a higher apoAI level in HDL with apoCIII, compared to whites, and that this was associated with insulin sensitivity, whereas VAT was not associated with this HDL subspecies. Additionally, African-Americans were found to have lower apoCIII in apoB lipoproteins compared to whites, and that the lower levels were associated with insulin sensitivity, whereas VAT is associated with higher apoCIII in all apoB lipoproteins. Adjustment for VAT was found to reduce the difference in apoCIII between the groups.
These results indicate the importance of studying lipoproteins in response to food intake. The researchers hope to highlight the importance of insulin sensitivity and VAT as contributing factors to the differences in lipoprotein levels, associated with CHD risk, among African-American women and white women.