Changes in β-Cell Function in Offspring of Type-2 Diabetic Patients, as per Fasting and Two-Hour Plasma Glucose Levels

Background The changes in β-cell function in high-risk populations who are apparently in the normal glucose tolerant stage are still under investigation for designing earlier prevention strategies. This study analyzes changes in β-cell function and insulin sensitivity across fasting and two-hour glucose categories spanning normal glucose tolerance (NGT) to impaired glucose tolerance (IGT), in offspring of subjects with type-2 diabetes mellitus (T2DM) compared to the controls without a known family history of T2DM. Methods Offspring of T2DM patients (cases) and individuals without a family history of T2DM (controls) were the subjects for this cross-sectional study. All participants underwent a 75 g oral glucose tolerance test and blood samples were collected for plasma glucose, insulin, C-peptide and proinsulin, at zero, 30, 60, and 120 minutes. Results A total of 358 cases (age 23.0 ± 10.8 years, 54% males) and 287 controls (age 28.4 ± 8.10 years, 65% males) were the subjects of this study. Cases and controls were divided into subgroups based on fasting and two-hour glucose categories spanning NGT to IGT. Compared to the reference category of controls (< 80 mg/dL for fasting glucose and < 84 mg/dL for two-hour glucose), cases with IGT had ~60% decline in both β-cell compensation (as measured as disposition index {0-120}) and insulin sensitivity (as measured as whole-body insulin sensitivity index {0-120}); adjusted for age, gender, and body mass index. From lower to higher fasting and two-hour glucose categories, there was a continuous and significant decline in β-cell compensation in both cases and controls. Significant reduction in first-phase insulin secretion, as measured as insulinogenic (0-30) index, was only observed among two-hour glucose categories, not among the fasting glucose categories. In the transition from late NGT cases to IGT cases, there was a significant decline in β-cell compensation, first-phase insulin secretion (more prominent than a decline in overall β-cell secretion) and the changes in whole-body insulin sensitivity were not statistically significant. Conclusions The decline in β-cell compensation was continuous and significant in offspring of subjects with type-2 diabetes and controls without a known family history of diabetes from early normal glucose tolerant ranges to impaired glucose tolerant ranges. Compared to the strictest glucose controlled category of controls, approximately 60% decline was observed in β-cell compensation and insulin sensitivity, in impaired glucose tolerant offspring of subjects with type-2 diabetes mellitus.