Blood levels of total homocysteine in patients with type 1 diabetes (with no complications, diabetic nephropathy and/or retinopathy) and in their non-diabetic relatives.

BACKGROUND AND AIM: It has been reported that plasma homocysteine (Hcy) levels in type 1 diabetes (T1DM) patients without renal involvement are higher, similar to or lower than those in healthy controls. METHODS AND RESULTS: We measured plasma Hcy in 60 controls, 79 type 1 diabetics (23 with retinopathy, 22 with nephropathy) and 73 non-diabetic relatives of 30 probands. The female controls had lower levels than their male counterparts: geometric mean 10.5 vs 13.6 mumol/L, p < 0.001. Among the controls, smokers (n = 20) and ex-smokers (n = 12) had higher Hcy levels than non-smokers (n = 28): 13.2 and 13.2 vs 10.9 mumol/L, p < 0.01. Among the diabetics, high plasma Hcy levels were associated with male gender: 11.9 vs 9.1 mumol/L in women, p < 0.01. The patients without complications had higher plasma glucose and hemoglobin A1c (HbA1c) levels (p < 0.001), and lower plasma Hcy (9.2 mumol/L vs 12.2, p < 0.01) and uric acid levels (p < 0.05) than the controls. The patients with nephropathy and higher levels of Hcy (13.0 mumol/L vs 9.0, p < 0.05), and different levels of creatinine (p < 0.01), uric acid (p < 0.01), fibrinogen (p < 0.05), and urinary albumin (p < 0.001) than those with retinopathy. There was no difference in Hcy levels between the patients' relatives and the controls: 11.9 mumol/L in siblings vs 11.6 mumol/L, 13.5 mumol/L in parents vs 12.1 mumol/L. In the control group, plasma Hcy levels were associated with age, gender and smoking; among the diabetics, they correlated with age, gender, smoking, and plasma creatinine and lipoprotein (a) levels. CONCLUSIONS: 1) male gender and smoking are associated with high Hcy levels in healthy people; 2) plasma Hcy levels are lower in T1DM patients than in healthy people (glomerular hyperfiltration and accelerated hepatic transsulfuration?); 3) high Hcy levels are associated with diabetic nephropathy and plasma creatinine levels; and 4) non-diabetic first-degree relatives of type 1 diabetics have normal plasma Hcy concentrations.