Apolipoprotein(a) in insulin-dependent diabetic patients with and without diabetic nephropathy

Abstract

Insulin-dependent diabetic patients with diabetic nephropathy have a highly increased morbidity and mortality from cardiovascular diseases. To determine whether altered levels of apolipoprotein(a) (apo(a)), the glycoprotein of the potentially atherogenic lipoprotein(a) (Lp(a)), contribute to the increased risk of ischaemic heart disease, apo(a) was determined in 50 insulin-dependent diabetic patients with diabetic nephropathy (group 1), in 50 insulin-dependent diabetic patients with microalbuminuria (group 2), in 50 insulin-dependent diabetic patients with normoalbuminuria (group 3), and in 50 healthy subjects (group 4). The groups were matched with regard to sex, age and body mass index. The diabetic groups were also matched with regard to diabetes duration. The level of apo(a) was approximately the same in the four groups, being: 122 (×//4.2) U 1⁻¹, 63 (×//.4) U 1^−l, 128 (×//3.5) U 1⁻¹ and 126 (×//3.7) U 1⁻¹ (geometric mean (×//antilog SD)) in group 1, 2, 3 and 4, respectively. 1 U 1⁻¹ apo(a) approximates 0.7 mg 1⁻¹ Lp(a). The serum concentration of the following apolipoproteins and lipids was higher in patients with nephropathy as compared to the three other groups (group 1 vs group 3): apolipoprotein B 1.36 ± 0.38 vs 1.11 ± 0.30 g 1⁻¹ (mean ± SD) (p < 0.01), total-cholesterol 6.0 ± 1.6 vs 5.3 ± 1.1 mmol 1⁻¹ (p < 0.05), low-density lipoprotein (LDL)-cholesterol 3.85 ± 1.35 vs 3.22 ± 1.09 mmol 1⁻¹ (p < 0.01) and triglyceride 1.28 (×//1.7) vs 0.85 (×//1.6 mmol 1⁻¹ (p < 0.01). High-density lipoprotein (HDL)-cholesterol was lower in patients with nephropathy as compared to patients with micro-and normoalbuminuria (group 1 vs group 3): 1.42 ± 0.42 vs 1.61 ± 0.41 mmol 1⁻¹ (p < 0.05). Our case-control study has revealed that insulin-dependent diabetic patients with diabetic nephropathy have hyperlipidaemia but a serum concentration of apo(a) comparable to healthy subjects.

Key Words:

• apolipoprotein(a)
• apolipoproteins
• diabetic nephropathy
• incipient diabetic nephropathy
• lipid metabolism