Urinary excretion of apolipoprotein(a) fragments in type 1 diabetes mellitus patients

High levels of plasma lipoprotein(a) [Lp(a)] represent an independent risk factor for cardiovascular morbidity; however, Lp(a) has not yet been identi fied as a risk factor for type 1 diabetic patients. Results from the limite d number of available studies on plasma Lp(a) levels in relation to renal f unction in type 1 diabetes mellitus are inconclusive. We hypothesized that only type 1 diabetes mellitus patients with impaired renal function show in creased plasma Lp(a) levels, due to decreased urinary apolipoprotein(a) [ap o(a)] excretion. We therefore measured urinary apo(a) levels in 52 type 1 d iabetes mellitus patients and 52 matched controls, and related the urinary apo(a) concentration to the plasma Lp(a) level, kidney function, and metabo lic control. Our findings indicate that patients with incipient diabetic ne phropathy as evidenced by microalbuminuria (20 to 200 mu g/min) exhibit sig nificantly higher plasma Lp(a) levels (median, 15.6 mg/dL) in comparison to normoalbuminuric patients (median, 10.3 mg/dL) and healthy controls (media n, 12.0 mg/dL). Urinary apo(a) normalized to creatinine excretion was signi ficantly elevated in both normoalbuminuric (median, 22.3 mu g/dL) and micro albuminuric type 1 diabetic patients (median, 29.1 mu g/dL) compared with h ealthy subjects (median, 16.0 mu g/dL) and correlated significantly with Lp (a) plasma levels in both patient and control groups (P < .003). No correla tion existed between the Lp(a) plasma level or urinary apo(a) concentration and metabolic control in type 1 diabetes mellitus patients. From these stu dies, we conclude that urinary apo(a) excretion is significantly increased in type 1 diabetic patients and correlates with plasma Lp(a) levels, and on ly type 1 diabetic patients with microalbuminuria have higher plasma levels of Lp(a) compared with patients with normoalbuminuria and healthy controls .