Increased Urinary Excretions of Immunoglobulin G, Ceruloplasmin, and Transferrin Predict Development of Microalbuminuria in Patients With Type 2 Diabetes
- From the Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University School of Medicine, Akita, Japan
- Address correspondence and reprint requests to Takuma Narita, The Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University School of Medicine, Hondo, Akita 010-8543, Japan. E-mail:
Microalbuminuria is generally considered as the best available noninvasive predictor of diabetic nephropathy. However, several studies have shown that increases in certain urinary proteins (immunoglobin G [IgG] [1–3], transferrin [Tf] [4–7], and ceruloplasmin [CRL] [3,8]) were found in normoalbuminuric diabetic patients. Recently, we reported that in normoalbuminuric diabetic patients, there was a strong linear correlation among these urinary proteins (9). To assess whether increased urinary excretions of IgG, CRL, and Tf can predict development of microalbuminuria, we conducted a 5-year follow-up study of type 2 diabetic patients with normoalbuminuria at baseline.
RESEARCH DESIGN AND METHODS
In 1998 and 1999, we recruited 140 type 2 diabetic patients with normoalbuminuria from outpatients. Normoalbuminuria was defined as a urinary albumin-to-creatinine ratio <30 mg/gCr in all of three serial spot urine samples. No subjects had a history of disease other than diabetes, hypertension, or dyslipidemia.
Since urinary IgG, CRL, and Tf can be easily affected by meal protein (10,11), timed overnight urine samples were collected on three different days within 2 or 3 months for analyses of these urinary proteins and N-acetylglucosaminidase (NAG) (3,8–13). Geometric means of the results expressed as protein-to-creatinine (Cr) ratios including albumin (U-Alb/Cr, U-IgG/Cr, U-CRL/Cr, U-Tf/Cr, and U-NAG/Cr, respectively) were calculated. Increases in these parameters …