OBJECTIVE -Because skeletal muscle is one of the target tissues for insulin, skeletal muscle mass might be associated with type 2 diabetes. Serum creatinine is a possible surrogate marker of skeletal muscle mass. The purpose of this study was to determine whether serum creatinine level is associated with type 2 diabetes. RESEARCH DESIGN AND METHODS -The study participants were nondiabetic Japanese men (n ϭ 8,570) aged 40 -55 years at entry. Type 2 diabetes was diagnosed if fasting plasma glucose was Ն126 mg/dl or if participants were taking oral hypoglycemic medication or insulin.RESULTS -During the 4-year follow-up period, 877 men developed type 2 diabetes. Lower serum creatinine was associated with an increased risk of type 2 diabetes. The multiple-adjusted odds ratio for those who had serum creatinine levels between 0.40 and 0.60 mg/dl was 1.91 (95% CI 1.44 -2.54) compared with those who had levels between 0.71 and 0.80 mg/dl. CONCLUSIONS -Lower serum creatinine increased the risk of type 2 diabetes. Diabetes Care 32:424-426, 2009A lthough skeletal muscle is one of the major target organs of insulin (1-3), to our knowledge, no prospective study has investigated the association between total skeletal muscle mass and type 2 diabetes. Serum creatinine is primarily a metabolite of creatine, almost all of which is located in skeletal muscle. Because the amount of creatine per unit of skeletal muscle mass is consistent and the breakdown rate of creatine is also consistent, plasma creatinine concentration is very stable and a direct reflection of skeletal muscle mass (4). If skeletal muscle mass is associated with type 2 diabetes, consequently, serum creatinine might also be associated with type 2 diabetes. Considering this hypothesis, we examined the prospective relationship between serum creatinine and type 2 diabetes in Japanese men. RESEARCH DESIGN AND METHODS -The Kansai HealthcareStudy is an ongoing cohort investigation designed to examine the risk factors for cardiometabolic diseases. The details of this study have been described previously (5). The protocol for this research was reviewed by the human subjects review committee at Osaka City University.For the current analysis, study participants consisted of 11,063 Japanese men aged 40 -55 years at entry who had fasting plasma glucose levels Ͻ126 mg/dl and serum creatinine levels Ͻ2.0 mg/dl and were not taking oral hypoglycemic medication or insulin. Follow-up examinations were conducted annually, and the follow-up period was 4 years. A total of 2,493 men were excluded because of loss to follow-up. The analytic cohort consisted of 8,570 men.Blood samples were drawn after an overnight 12-h fast. Serum creatinine was mainly measured by an enzymatic method using a Hitachi 7350 automatic chemistry analyzer (Hitachi, Tokyo, Japan). Serum creatinine was also measured by the Jaffe method in 1,770 participants. We recalibrated the Jaffe method to the enzymatic method using the following formula: serum creatinine (mg/dl, enzymatic method) ϭ 1.02 ϫ serum creatinine (mg...

OBJECTIVE -We prospectively assessed whether the combined measurements of fasting plasma glucose (FPG) and A1C were effective for predicting type 2 diabetes.RESEARCH DESIGN AND METHODS -Study participants included 6,736 nondiabetic Japanese men aged 40 -55 years. Type 2 diabetes was diagnosed in those who had an FPG Ն126 mg/dl or who were being treated with an oral antidiabetic agent or insulin. The models including FPG, A1C, and both were compared using the area under the receiver operating characteristic (AUROC) curves.RESULTS -During the 4-year follow-up period, we confirmed 659 diabetes cases. In multivariate analysis, both FPG and A1C were independently associated with the risk of type 2 diabetes. The model including both FPG and A1C had a greater AUROC curve than that including FPG alone (0.853 vs. 0.818; P Ͻ 0.001) or A1C alone (0.853 vs. 0.771; P Ͻ 0.001).CONCLUSIONS -The combined measurement of FPG and A1C was effective for predicting type 2 diabetes. Diabetes Care 32:644-646, 2009

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