Transendothelial lipoprotein exchange and microalbuminuria

OBJECTIVE: Microalbuminuria associates with increased risk of atherosclerosis in individuals without diabetes. We hypothesized that transendothelial lipoprotein exchange is elevated among such individuals, possibly explaining increased intimal lipoprotein accumulation and thus atherosclerosis.

METHODS: Using an in vivo isotope technique, transendothelial exchange of low density lipoprotein (LDL) was measured in 77 non-diabetic individuals. Autologous 131-iodinated LDL was reinjected intravenously, and the 1-h fractional escape rate was calculated as index of transendothelial exchange.

RESULTS: There was no difference in transendothelial LDL exchange between subjects with microalbuminuria versus normoalbuminuria (mean (95% confidence interval) 3.8%/h (3.3-4.3%/h) versus 4.2%/h (3.7-4.7%/h); P=0.33). In contrast, there was a positive correlation between transendothelial LDL exchange and (logarithmically transformed) plasma insulin: beta=0.6 (95% CI: 0.1-1.1); R=0.22; P<0.05. This correlation was independent of age, sex, blood pressure, plasma concentration of lipoproteins, LDL size, body mass index, plasma volume, and use of medicine, and it was unlikely caused by altered hepatic LDL receptor expression, or glycosylation of LDL.

CONCLUSION: In non-diabetic individuals, transendothelial LDL exchange is not associated with microalbuminuria, but possibly with hyperinsulinemia.