High density lipoprotein subfractions in insulin-dependent diabetic and normal subjects.

Serum lipoproteins have been separated by preparative ultracentrifugation in randomly selected groups of insulin-dependent diabetics and in age- and sex-matched non-diabetic controls. The major high density lipoprotein (HDL) subclass; HDL2 (density (d) 1.063-1.125 kg X m-3) and HDL3 (d greater than 1.125) and the further fractions of HDL2:HDL2b (d 1.063-1.100) and HDL2a (d 1.100-1.125) were also separated and their cholesterol (C) concentrations determined. These diabetic men and women were relatively normolipaemic and the major difference from controls was a significantly raised total HDL-C in men which was confirmed by a separate chemical precipitation method. This increase was associated with a significant rise in HDL2a-C and in total HDL2-C concentration. The non-significant increase in diabetic women compared to men was associated with poorer metabolic control. Among factors influencing serum HDL2-C concentration, the most important was the negative association with the level of very low density lipoprotein-triglycerides. Although insulin-dependent diabetics have an increased risk of atherosclerotic coronary heart disease (CHD), this is not reflected in their HDL subfraction-C distribution which, if present in non-diabetics, would be expected to confer protection from CHD.