Influence of early diabetic nephropathy on very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and low density lipoprotein (LDL) composition

The procedure of discontinuous gradient ultracentrifugation (DGU) was used to characterize the influence of early diabetic nephropathy on the composition of very low density lipoprotein (VLDL, flotation density 60-400 Svedberg (Sf) units), low density lipoprotein (LDL, flotation density 0-12 Sf) and subfractions of intermediate density lipoprotein (IDL₁ and IDL₂, 20-60 and 12-20 Sf, respectively). Forty-six subjects with type 1 (insulin-dependent) diabetes and serum creatinine, < 140 μmol/l were studied, of whom 23 consistently had normal rates of albumin excretion (AER < 15 μg/min), and 23 had persistent albuminuria (AER 20.0-960.6 μg/min). The two groups were similar with respect to total serum lipids, glycaemic control, age and body mass. The composition (lipid, protein and phospholipid) and mass of VLDL, LDL and IDL₂ was not appreciably altered by early nephropathy, but free and total cholesterol concentration in IDL₁ (Sf 20-60) was increased (total cholesterol 0.68 (0.09) (mean (SE)) vs. 0.47 (0.07) mmol/1, and free cholesterol 0.27 (0.04) vs. 0.17 (0.03) mmol/l, both P < 0.05). The explanation of these findings was probably an accumulation in the circulation of the remnants of chylomicron metabolism and/or intermediates in the conversion from VLDL to IDL₁. In addition, there was a decrease in serum high density lipoprotein (HDL) cholesterol in early nephropathy (1.27 (0.06) vs. 1.38 (0.10) mmol/l, P < 0.05), due to a decrease in the HDL₂ cholesterol subfraction (P < 0.05). These findings may in part explain the increased risk of premature atherosclerosis associated with the development of albuminuria.