Abnormal cholesterol distribution among lipoprotein fractions in normolipidemic patients with mild NIDDM

This study was carried out to identify and define lipoprotein abnormalities in patients with noninsulin-dependent diabetes mellitus (NIDDM) who do not have clinical elevations of cholesterol or triglycerides. Thirty-four male patients with mild NIDDM and normolipidemia (plasma cholesterol ≤ 240 mg/dl and triglycerides ≤ 250 mg/dl) were compared with 35 healthy male normolipidemic subjects. The two groups had similar age and body mass index. Measurements in the two groups included concentrations and chemical composition of lipoproteins and sizing of low-density lipoprotein (LDL) particles. The patients with NIDDM, compared to control subjects, had two distinct lipoprotein abnormalities: first, a significantly reduced level of high-density lipoprotein (HDL) cholesterol (mean ± S.D., 35 ± 8 mg/dl vs. 41 ± 10 mg/dl, respectively; P = 0.006); and second, a high cholesterol-to-apolipoprotein (apo) B ratio both in very low density lipoprotein (VLDL) + intermediate density lipoprotein (IDL) fraction (mean ± S.D.; 3.2 ± 0.8 vs. 2.8 ± 0.9, respectively; P = 0.02) and in LDL fraction (mean ± S.D.; 1.61 ± 0.11 vs. 1.52 ± 0.13, respectively; P = 0.003). Increased cholesterol content in LDL was mainly due to free cholesterol. No differences were detected between the two groups in the frequency of LDL pattern A (major LDL peak > 255 Å) and pattern B (major LDL peak ≤ 255 Å). However, a higher frequency of LDL pattern B was found in NIDDM patients with low plasma total triglycerides concentrations (< 150 mg/dl) compared to the control subjects (45% vs. 7%, P = 0.02). Thus in normolipidemic patients with mild NIDDM, the major lipoprotein abnormalities were a low level of HDL cholesterol and compositional changes in LDL and VLDL + IDL fractions. Compositional abnormalities included enrichment of apo B-containing lipoproteins with cholesterol. These lipoprotein abnormalities could have atherogenic potential in patients with mild NIDDM and normolipidemia.