Non-insulin-dependent diabetes mellitus: dietary monounsaturated fatty acids and low-density lipoprotein composition and function

Alterations in low-density lipoprotein (LDL) composition in diabetes affectits function with respect to control of de novo cholesterol synthesis. Weexamined the effect of 4 weeks of an oleic-acid-rich diet on LDLcomposition and function in eight Type 2 diabetic and eight non- diabeticcontrol subjects. LDL (density 1.019-1.063 g/l) was isolated by sequentialultracentrifugation. LDL composition was measured and LDL fatty acids weredetermined by gas liquid chromatography. Cholesterol synthesis was measuredby [14C]-acetate incorporation into the freshly isolated mononuclearleucocytes. Fasting blood glucose fell from 9.3 +/- 2.0 to 8.2 +/- 1.2mmol/l (p < 0.05) and fasting serum insulin increased from 8.3 +/- 2.8to 10.4 +/- 5.0 mIU/l (p > 0.05) in the diabetic patients. LDL oleicacid increased in the diabetic patients from 18.8 +/- 1.8% to 22.5 +/- 1.9%(p < 0.01) and in the non-diabetic subjects from 19.9 +/- 1.8% to 23.3+/- 2.8% (p < 0.01). The LDL- esterified to free cholesterol ratios of3.0 +/- 0.6 and 2.7 +/- 0.2 for the diabetic and non-diabetic patients weresimilar, and decreased significantly (p < 0.01) to 2.4 +/- 0.5 and 2.2+/- 0.4, respectively. Baseline [14C]-acetate incorporation was similar inthe two groups, and decreased after diet from 437 +/- 239 to 249 +/- 144ng/g cell protein (p < 0.05) in the diabetic patients. There was anegative correlation between the LDL-esterified to free cholesterol ratioand the ratio of oleic to linoleic acid in the LDL (r = -0.39, p < 0.05)and a negative correlation between fasting blood glucose and LDL oleic acidin the diabetic patients (r = -0.51, p < 0.05). Enrichment of LDL witholeic acid appears to improve its ability to regulate endogenouscholesterol synthesis in both control and diabetic subjects. In thediabetic population, the diet had a favourable effect on glycaemic control.