Clinical Significance of the Maximum Body Mass Index Before Onset of Type 2 Diabetes for Predicting Beta-Cell Function

OBJECTIVE: This study aimed to clarify the clinical significance of the maximum body mass index (BMI) before the onset of type 2 diabetes (MBBO) for predicting pancreatic beta-cell function. METHODS: This was a cross-sectional observational study. Of 1304 consecutively admitted patients with type 2 diabetes, we enrolled 410 patients satisfying the criteria in this study. The correlations between the C-peptide index (CPI), which is one of the parameters that reflects beta-cell function, and various clinical parameters, including MBBO and duration of diabetes, were analyzed in multiple linear regression analyses. RESULTS: The analyses revealed that MBBO was correlated with CPI independently after adjustment for age, sex, HbA1c, and duration of diabetes. When we divided the subjects into three subgroups by MBBO (MBBO < 25 kg/m(2); 25 kg/m(2) ≤ MBBO < 30 kg/m(2); MBBO ≥ 30 kg/m(2)), CPI was negatively correlated with duration of diabetes in each subgroup, while the rates of CPI based on the duration of diabetes were not different among the three MBBO subgroups. In contrast, the declining rates of CPI were higher in the BMI ≥ 25 kg/m(2) group on admission than in the BMI < 25 kg/m(2) group on admission. CONCLUSIONS: MBBO may be an independent factor correlating with beta-cell function and may predict insulin secretion capacity at diagnosis, but it does not seem to affect the rate of decline in insulin secretion capacity after diagnosis. It is important to preserve beta-cell function by decreasing a patient’s BMI during treatment after diagnosis regardless of MBBO.