Plasma HDL-cholesterol and triglycerides, but not LDL-cholesterol, are associated with insulin secretion in non-diabetic subjects

Objective Experimental data support the notion that lipoproteins might directly affect beta cell function, however clinical data are sparse and inconsistent. We aimed at verifying whether, independently of major confounders, serum lipids are associated with alterations in insulin secretion or clearance non-diabetic subjects. Methods Cross sectional and observational prospective (3.5 yrs), multicentre study in which 1016 non-diabetic volunteers aged 30–60 yrs. and with a wide range of BMI (20.0–39.9 kg/m2) were recruited in a setting of University hospital ambulatory care (RISC study). Main outcome measures: baseline fasting lipids, fasting and OGTT-induced insulin secretion and clearance (measured by glucose and C-peptide modeling), peripheral insulin sensitivity (by the euglycemic clamp). Lipids and OGTT were repeated in 980 subjects after 3.5 years. Results LDL-cholesterol did not show independent associations with fasting or stimulated insulin secretion or clearance. After accounting for potential confounders, HDL-cholesterol displayed negative and triglycerides positive independent associations with fasting and OGTT insulin secretion; neither with insulin clearance. Low HDL-cholesterol and high triglycerides were associated with an increase in glucose-dependent and a decrease in non-glucose-dependent insulin secretion. Over 3.5 years both an HDL-cholesterol decline and a triglycerides rise were associated with an increase in fasting insulin secretion independent of changes in body weight or plasma glucose. Conclusions LDL-cholesterol does not seem to influence any major determinant of insulin bioavailability while low HDL-cholesterol and high triglycerides might contribute to sustain the abnormalities in insulin secretion that characterize the pre-diabetic state.