Pancreatic Beta-Cell Reserve and Insulin Secretion Dynamics in Newly Diagnosed Type 2 Diabetes Mellitus in Kano: A Characterisation Using Oral Glucose Tolerance Testing and Modelling

The extent of beta-cell dysfunction at the time of type 2 diabetes diagnosis has critical prognostic implications for disease trajectory and therapeutic strategy, yet this has not been characterised using dynamic modelling approaches in a Nigerian diabetic population. This study characterised pancreatic beta-cell reserve and insulin secretion dynamics in newly diagnosed type 2 diabetes patients in Kano, North West Nigeria, using oral glucose tolerance testing combined with mathematical modelling of insulin secretion kinetics. A cross-sectional observational design enrolled 80 patients within three months of diagnosis and 40 age-matched normal glucose-tolerant controls. Extended 3-hour oral glucose tolerance tests with blood sampling at 0, 30, 60, 90, 120, and 180 minutes assessed glucose, insulin, and C-peptide profiles. Beta-cell function was characterised using the oral minimal model to derive beta-cell responsivity indices and hepatic insulin extraction. Disposition index was calculated as the product of insulin secretion and sensitivity. Cluster analysis identified beta-cell dysfunction subtypes. Results revealed markedly heterogeneous beta-cell dysfunction patterns: 40 percent showed predominant first-phase secretion deficiency, 35 percent showed hepatic insulin hypersecretion with extraction deficit, and 25 percent showed pan-secretory impairment. Disposition index was reduced in all subtypes relative to controls. This study provides the first minimal model-based beta-cell characterisation in newly diagnosed Nigerian type 2 diabetes, identifying physiologically distinct subgroups with different therapeutic implications. Subtype-specific pharmacological targeting is proposed for precision diabetes management. Keywords: beta-cell function, oral glucose tolerance, insulin secretion, minimal model, Kano.