Serum homocysteine level and protein intake are related to risk of microalbuminuria: The Hoorn study

Background. Microalbuminuria (MA) is a strong predictor of cardiovascular disease, but its causes are incompletely understood. Hyperhomocysteinemia is a recently recognized risk factor for cardiovascular disease independent of established risk factors. It is not known whether hyperhomocysteinemia is associated with MA, and thus could be a possible cause of microalbuminuria. Methods. We studied an age-, sex- and glucose- tolerance-stratified random sample of a 50- to 75-year-old general Caucasian population (N = 680). The urinary albumin-to-creatinine ratio (ACR) was measured in an early morning spot urine sample. MA was defined as an ACR > 3.0 mg/mmol. Results. The prevalence of MA was 4.3% (13 of 304) in subjects with normal glucose tolerance, 9.2% (1.7 of 185) in impaired glucose tolerance and 18.3% (30 of 164) in non-insulin-dependent diabetes mellitus (NIDDM); it was 3.7% (15 of 402) in subjects without hypertension and 17.9% (45 of 251) in those with hypertension. After adjusting for age, sex, glucose tolerance category, hypertension, dyslipidemia and smoking, the odds ratio [OR; 95% confidence interval (95%CI)] for MA per 5 μmol/liter total homocysteine increment was 1.33 (1.08 to 1.63). Additional adjustment for HbA(1c), waist-hip ratio, protein intake and serum creatinine did not attenuate the association between MA and total homocysteine. A 0.1 g/kg · day increment of protein intake was also associated with an increased risk for MA after adjustment for age, sex, classical risk factors and serum total homocysteine [OR (95% CI); 1.20 (1.08 to 1.32)]. Conclusion. Both hyperhomocysteinemia and protein intake are related to microalbuminuria independent of NIDDM and hypertension. Hyperhomocysteinemia may partly explain the link between MA and increased risk of cardiovascular disease.