Microalbuminuria, a predictor for overt nephropathy and early cardiovascular mortality, is always associated with hypertension, hyperglycemia, and dyslipidemia (1). In the study of Tai et al. (2), performed in Taiwanese type 2 diabetic patients, albumin excretion rate was significantly associated with hypertension but not with glycemic control. To further examine the association between lipid profile and microalbuminuria in Taiwanese type 2 diabetic subjects, a total of 260 nonsmoking patients (117 men, 143 women; mean age ± SD, 60.7 ± 11.0 years) with normal renal function and not using antihypertensive or lipid-lowering agents were cross-sectionally recruited. Normoalbuminuria (n = 152) and microalbuminuria (n = 108) were defined as urinary albumin-to-creatinine ratios (ACRs) <30 and 30–299 μg/mg, respectively. Lipid parameters included serum total cholesterol, triglycerides, HDL and LDL cholesterol, apolipoprotein A1, and apolipoprotein B (ApoB). Potential confounders (age, sex, BMI, duration of diabetes, insulin therapy, systolic and diastolic blood pressure, and HbA1c) were adjusted for in multivariate analyses. Mann-Whitney U test, Spearman correlation coefficients, and logistic regression were used.
The results showed that among the lipid profile, only total cholesterol and ApoB were significantly (P < 0.05) different between patients with microalbuminuria and those with normoalbuminuria (208.5 ± 40.9 vs. 197.5 ± 38.6 mg/dl for total cholesterol and 123.1 ± 37.9 vs. 106.4 ± 29.0 mg/dl for ApoB). For correlation coefficients, only ApoB was significantly correlated with ACR (γ = 0.166); total cholesterol showed borderline significance (γ = 0.113, 0.05 < P < 0.1). Multivariate-adjusted odds ratios (ORs) (95% CI) for microalbuminuria were significant only for ApoB (1.016 [1.007–1.024]) and total cholesterol (1.007 [1.000–1.014]), but total cholesterol was nonsignificant with additional adjustment for ApoB. While the lipid parameters were treated as binary variables with cut points at medians and using the lower halves as reference groups, only ApoB (cut point: 108 mg/dl) showed significant multivariate-adjusted OR for microalbuminuria (2.209 [1.303–3.746]).
Atherogenic lipoproteins can infiltrate into the glomerular endothelium and mesangial cells, initiating a cascade of events similar to atherosclerosis (3). Samuelsson et al. (4) reported that ApoB was associated with a declining glomerular filtration rate in patients with chronic renal disease and that renal dyslipidemia was predominantly associated with the accumulation of ApoB-containing lipoproteins in both sclerotic and nonsclerotic glomeruli (5). The observation of the present study in Taiwanese type 2 diabetic patients suggests that ApoB-containing lipoproteins could also initiate early glomerular injury leading to incipient diabetic nephropathy with microalbuminuria.
