Interrelationships between Fasting Insulin, Insulin Resistance, and Pancreatic β-Cell Function in Type 2 Diabetes Patients
Michael Ukpang Ajen
*
Department of Biochemistry, Faculty of Basic Medical Sciences, University of Calabar, Nigeria.
Anthony Obi Ewa
Department of Family Medicine, University of Calabar Teaching Hospital, Calabar, Cross River State, Nigeria.
Godwin Ekpo Okon
Department of Biochemistry, Faculty of Basic Medical Sciences, University of Calabar, Nigeria.
Victor Orok Ironbar
Department of Medicine and Surgery, Faculty of Clinical Sciences, University of Calabar, Nigeria.
Temidayo Olamide Adigun
Department of Life Sciences, Faculty of Science and Computing, Abdulrasaq Abubakar Toyin University, Ganmo, Nigeria.
Amarachukwu Obiezu Joyce
General Hospital, New Karu, Nasarawa, Nigeria.
Felix Uchenna Ekenjoku
General Practice, Fairfield General Hospital, Bury, Greater Manchester.
Veronica Ubache Akeke
Department of Nursing Services, Cross River State Ministry of Health, Nigeria.
Amina Balarabe Shehu
National Agricultural Extension and Research Liaison Services (NAERLS), ABU, Zaria, Kaduna State, Nigeria.
Gbadebo Moses Adetoyi
Department of Medical Biochemistry, Faculty of Basic Medical Sciences, College of Health Sciences, University of Ilorin, Kwara State, Nigeria and Department of Chemical Pathology and Immunology, Faculty of Basic Clinical Sciences, College of Health Sciences, University of Ilorin, Ilorin, Nigeria.
Walter Agbor Ogar
Department of Surgery, University of Calabar Teaching Hospital, Calabar, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background: Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and Homeostatic Model Assessment for β-cell function (HOMA-β) are validated surrogate indices used to evaluate insulin sensitivity and pancreatic β-cell function. However, evidence describing the interrelationships among fasting insulin, HOMA-derived indices, and glycated haemoglobin (HbA1c) in Nigerian adults remains limited.
Objective: This study investigated the relationships between fasting insulin concentration, insulin resistance, pancreatic β-cell function, and glycaemic control among adults with T2DM and apparently healthy non-diabetic individuals in Calabar, Nigeria.
Methods: A hospital-based comparative cross-sectional study was conducted. Fasting plasma glucose (FPG), fasting serum insulin, and glycated haemoglobin (HbA1c) were determined using standardised biochemical methods. HOMA-IR and HOMA-β were calculated using the original Matthews equations. Pearson's correlation analysis was used to evaluate relationships among HbA1c, fasting insulin, HOMA-IR, and HOMA-β, with statistical significance set at p < 0.05.
Results: Fasting insulin demonstrated a very strong positive correlation with HOMA-IR (r = 0.9721, p < 0.05) and a strong positive correlation with HOMA-β (r = 0.8745, p < 0.05) among diabetic participants, while HOMA-IR was strongly correlated with HOMA-β (r = 0.7640, p < 0.05). In contrast, HbA1c exhibited weak, non-significant positive correlations with fasting insulin, HOMA-IR, and HOMA-β. Conversely, among non-diabetic participants, fasting insulin correlated strongly with HOMA-IR (r = 0.9642, p < 0.05) and HOMA-β (r = 0.9084, p < 0.05), while HOMA-IR showed a strong positive correlation with HOMA-β (r = 0.8778, p < 0.05). HbA1c demonstrated weak, non-significant negative correlations with fasting insulin, HOMA-IR, and HOMA-β.
Conclusion: Fasting insulin, HOMA-IR, and HOMA-β exhibited strong interrelationships in both diabetic and non-diabetic participants, highlighting their complementary roles in evaluating insulin sensitivity and pancreatic β-cell function. Conversely, HbA1c showed no significant association with these metabolic indices, suggesting that long-term glycaemic control reflects broader physiological influences beyond fasting insulin dynamics and β-cell function.
Keywords: Type 2 diabetes mellitus, insulin resistance, fasting insulin, glycated haemoglobin, HbA1c, pancreatic β-cell function