Proinsulin is sensitive to reflect glucose intolerance

AIMS/INTRODUCTION: We investigated associations between glucose tolerance and β‐cell function using a series of estimation methods in a population‐based study. MATERIALS AND METHODS: Data from the Dynamics of Lifestyle and Neighborhood Community on Health Study were analyzed. A total of 489 participants (263 women) were divided into three groups: normal glucose tolerance (NGT), prediabetes (PDM) and diabetes group. We estimated β‐cell function by the homeostasis model assessment of β‐cell function, proinsulin level (PI), C‐peptide index, proinsulin‐to‐C‐peptide ratio (PI/CPR) and proinsulin‐to‐insulin ratio. Because data on all five parameters of β‐cell function showed skewed distributions, the values of these parameters were normalized by natural logarithmic (ln) transformation. Next, the association between glucose tolerance and β‐cell function among participants without diabetes was examined. In this analysis, glucose tolerance was assessed based on glycated hemoglobin levels. RESULTS: In the crude analysis, ln(PI) and ln(PI/CPR) were significantly higher in the diabetes group than those in the PDM and NGT groups, and these parameters were significantly higher in the PDM group than in the NGT group. Only ln(PI) in the PDM group was significantly higher compared with that in the NGT group after adjustment for age, sex and body mass index (ln[PI]: PDM group 2.38 pmol/L, 95% confidence interval 2.29–2.47 pmol/L; NGT group 2.17 pmol/L, 95% confidence interval 2.12–2.22 pmol/L; P < 0.05). In addition, ln(PI) levels were significantly and positively correlated with glycated hemoglobin quartile in participants without diabetes. CONCLUSIONS: Our results showed that PI was the most sensitive to reflect glucose intolerance.