LDL size and subclass pattern in Mexico City residents and San Antonio Mexican Americans.

Recent studies suggest that a relative abundance of small dense LDL is a risk factor for coronary heart disease. We compared LDL size in Mexico City residents (n = 191) and San Antonio Mexican Americans (n = 282), two genetically similar populations that differ markedly in dietary behaviors: in Mexico City approximately 62% of calories are from carbohydrate and approximately 19% from fat, and in San Antonio approximately 40% of calories are from carbohydrate and approximately 40% from fat. Mean LDL size in Mexico City was 258.6 +/- 0.9 A, and in San Antonio, 255.9 +/- 0.6 A (P = .013). After adjustment for the higher triglyceride and lower HDL cholesterol levels (the two most important predictors of LDL size) in Mexico City, LDL size was significantly lower in San Antonio than in Mexico City by -8.33 +/- 0.84 A (P < .001). Our data suggest that the higher triglyceride concentrations in Mexico City residents that are associated with a higher carbohydrate diet may not be associated with atherogenic changes in LDL.

LDL size and subclass pattern in a biethnic population.

Recently, the presence of small, dense low-density lipoprotein (LDL) has been recognized as a risk factor for coronary heart disease. There has been little work on correlates of LDL size in population-based studies and none in Mexican Americans. We examined the relationship of LDL size and pattern to anthropometric and metabolic variables in 466 Mexican Americans and non-Hispanic whites in the San Antonio Heart Study. LDL size in Angstrom units was significantly lower in Mexican Americans (255.8 +/- 0.6) than in non-Hispanic whites (257.9 +/- 0.7) (P = 0.041) after adjustment for gender and age. The percentage of subjects with pattern B tended to be higher in Mexican Americans than in non-Hispanic whites (40.0% versus 34.4%, respectively), although this difference did not reach statistical significance. In univariate analysis, LDL size was significantly associated with glucose (r = -.20), insulin (r = -.19), male gender (r = -.20), total cholesterol (r = -.22), high-density lipoprotein cholesterol (HDL-C) (r = .53), and triglyceride concentrations (r = -.63). In multivariate analyses, higher triglyceride, insulin, and glucose concentrations, lower HDL-C, and male gender were independent correlates of smaller, denser LDL. Correlates of LDL size were similar in Mexican Americans and non-Hispanic whites. Our results confirm previous reports that triglyceride and HDL-C concentrations are the most important variables associated with LDL size. The additional findings of independent effects of male gender, glucose, and insulin concentrations suggest that sex hormones and the insulin resistance syndrome may also play an important role.(ABSTRACT TRUNCATED AT 250 WORDS)

Studied of very low density lipoprotein triglyceride metabolism in an obese population with low plasma lipids: lack of influence of body weight or plasma insulin.

Pima Indians have a high prevalence of hyperinsulinemia, obesity, and diabetes, but they have low plasma cholesterol levels, reduced low density lipoprotein synthesis, and little arteriosclerotic heart disease. To investigate lipoprotein metabolism further in this group, very low density lipoprotein (VLDL) metabolism was studied, using [3H]glycerol as an endogenous precursor of triglyceride (TG) synthesis, in 15 obese Pima nondiabetic males and compared to that of 10 obese and 13 normal weight, normolipidemic, nondiabetic Caucasian males. The resultant kinetic data were analyzed using a multicompartmental model which includes two pathways for VLDL-TG synthesis and a process of stepwise delipidation for VLDL catabolism. As compared to obese Caucasians, the obese Pimas had a lower rate of VLDL-TG synthesis, and a lower proportion of slow pathway for synthesis. The fractional catabolic rate in the Pimas was higher than in either Caucasian group, a larger proportion of VLDL-TG was delipidized at each step, and particle residence time was shorter. When the relation between VLDL-TG metabolism and plasma insulin was examined, plasma insulin levels in the Pima were not correlated with VLDL-TG synthetic rates, catabolic rates, or plasma pools. On the other hand VLDL-TG synthetic rates were correlated with plasma free fatty acid levels. Thus, in this population with low plasma lipids and reduced arteriosclerotic heart disease, VLDL-TG synthesis is low, VLDL-TG catabolism is accelerated, and VLDL pools appear to be insensitive to the influence of body weight and hyperinsulinemia.