Microproteinuria in Type 2 Diabetes Mellitus from Diagnosis

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Abstract
Glomerular and tubular microproteinuria precede the development of overt nephropathy in Type 1 diabetes mellitus. However, in Type 2 diabetes urinary protein excretion and its relationship to diabetic nephropathy has not been clearly characterized. Twenty consecutive, newly diagnosed patients with Type 2 diabetes, whose urine was Albustix‐negative and sterile on culture, were studied. Two timed overnight urine samples were collected at diagnosis, and after 2 months and 2 years, and excretion rates of albumin, α‐1‐microglobulin and N‐acetyl‐ß‐D‐glucosaminidase were calculated. HbA1c fell from 12.1 ± 2.4 % at diagnosis to 9.5 ± 1.5 % at 2 months and 9.6 ± 2.2 % at 2 years. Albumin excretion rate fell marginally from 6.5 (2.1–242.5) μg min−1 at diagnosis to 5.5 (1.7–274.0) μg min−1 at 2 months (p < 0.05) rising again to 6.1 (1.9–201.7) μg min−1 at 2 years. α‐1‐Microglobulin excretion rate fell from 13.5 (3.6–59.9) μg min−1 at diagnosis to 8.4 (2.9–16.1) μg min−1 2 months and 8.8 (1.8–54.1) μg min−1 at 2 years (both p < 0.05). Albumin excretion rate was found to correlate significantly with creatinine clearance at diagnosis (rs=0.61, p < 0.005), though not subsequently. In contrast, excretion rates of α‐1‐microglobulin and N‐acetyl‐ß‐D‐glucosaminidase correlated with HbA1c (rs = 0.68 and 0.66, respectively, p < 0.005 at diagnosis and rs = 0.57 and 0.53, p < 0.05 subsequently in both cases). After 24 months of treatment, all but two of the eight patients with abnormal albumin excretion rate at diagnosis had values within the normal range. The results suggest that in patients with Type 2 diabetes, raised albumin excretion rate at diagnosis is not indicative of persistent proteinuria.