Background: This study sought to investigate the association between plasma homocysteine (HCY) levels and pancreatic islet beta-cell function in type 2 diabetes mellitus (T2DM) patients.
Methods: 430 hospitalized T2DM patients were enrolled in this cross-sectional study from December 2013 to December 2016. All participants were requested to complete a detailed questionnaire and undergo anthropometric measurements. Blood samples were collected from all participants. A 75-g oral glucose tolerance test (OGTT) was performed to diagnose T2DM in each individual, and an insulin releasing test (IRT) was used to calculate selected parameters for glucose, insulin, and C-peptide. Linear correlation and multivariate regression analyses were performed to assess the association between serum HCY concentration and these parameters.
Results: Patients were divided into the following subgroups based on quartiles of serum HCY levels: Group Q1: <17.03 µmol/L; Group Q2: 17.03-19.50 µmol/L; Group Q3: 19.5-24.7 µmol/L; and Group Q4: >24.7 µmol/L. The levels of fasting blood glucose (FBG), 2 h postprandial blood glucose (2hPBG), glycated hemoglobin A1c (HbA1c), fasting C-peptide and fasting insulin increased significantly as HCY levels increased (P<0.05). The area under the curves (AUCs) of serum glucose and insulin in IRT increased significantly and that of serum C-peptide decreased as HCY levels increased (P<0.05). The levels of Homeostasis Model Assessment-β (HOMA-β), Modified Beta-cell function Index (MBCI), Disposal Index (DI), C-peptide immunoreactivity (CPR), Insulinogenic Index 30 (IGI 30), and Secretory Units of Islets in Transplantation (SUIT) decreased as HCY levels increased. An inverse linear correlation was found between HOMA-β, MBCI, DI, CPR, IGI 30, SUIT 0 h, and HCY plasma concentration (R2, 0.539, 0.569, 0.500, 0.676, 0.579, and 0.588, respectively; P<0.001), and this association was independent of many confounders, such as age, gender, body mass index, glucose and insulin levels, and HbA1c.
Conclusions: Serum HCY levels were inversely related to the parameters for pancreatic islet beta-cell function. Thus, the insulin releasing function of beta cells in the pancreas can be well elucidated by plasma HCY concentration.
Keywords: Homeostasis Model Assessment-β (HOMA-β); Type 2 diabetes mellitus (T2DM); homocysteine; pancreatic islet β-cells function.