Abstract 125: Weight Loss Selectively Increases High-density Lipoprotein without apoC-III, a Subfraction with Protective Association Against Coronary Heart Disease.

Abstract

Human high-density lipoprotein (HDL) particles are highly heterogeneous in composition, and in relation to coronary heart disease (CHD). Specifically, HDL containing apoC-III predicts increased incidence of CHD, whereas HDL that does not contain apoC-III predicts decreased CHD incidence. Recently, we found that obese subjects had a higher concentration of HDL with apoC-III and a lower concentration of HDL without apoC-III than normal weight controls. However, the effects of weight loss on HDL with or without apoC-III are not known. We studied 39 obese participants (mean BMI of 34) in a weight-loss trial assigned to a high fat 40%/high protein 25%/low carbohydrate 35% diet for 2 years. We chose this diet group because HDL-cholesterol (-C) levels increased the most compared to the other diet groups with more carbohydrate and less fat. Participants with at least 8% loss of initial body weight at 2 years were assigned to the weight loss group (n=21), while those without a change in weight comprised the no-weight loss group (n=18). Subjects were matched by age (mean 51 years), gender, and race. HDL without apoC-III and HDL with apoC-III were separated from plasma by sequentially using anti-apoA-I and anti-apoC-III immunoaffinity chromatography. For both groups, the mean baseline HDL-C and total plasma apoA-I concentrations were 48 and 119mg/dL, respectively. Weight loss increased HDL-C concentration by an average of 25% (p<0.01 for changes between groups), and total apoA-I by 9% (p<0.02). In the weight-loss group, mean apoA-I concentrations of HDL without apoC-III increased by12% (from 99 to 111 mg/dL) compared to a decrease of 6% in the no-weight loss group (from 107 to 101mg/dL) (p<0.02). The apoA-I concentration of HDL with apoC-III, 15 mg/dL, remained unchanged. In conclusion , moderate weight loss selectively increased the concentration of HDL without apoC-III, the predominant HDL type that predicts reduced incidence of CHD. In contrast, weight loss did not affect HDL with apoC-III, an HDL type associated with increased CHD risk. This represents a partial normalization of HDL subtypes by moderate weight loss. This effect on HDL subpopulations defined by absence of apoC-III suggests a novel mechanism by which weight loss may reduce cardiovascular disease risk.