Assessment of Intact Proinsulin, C-peptide and Vitamin D as Markers of β-cell Dysfunction in Type 2 Diabetes Mellitus (T2DM) in Côte d’Ivoire

Background : Type 2 diabetes mellitus (T2DM) is associated with disturbances in insulin secretion and vitamin D metabolism; intact proinsulin and C-peptide are useful biomarkers of β-cell function, yet data on these markers remain scarce in Côte d’Ivoire. Aims : To evaluate intact proinsulin, C-peptide, and vitamin D status in patients with T2DM in Côte d’Ivoire in order to contribute to improved clinical management of the disease. Study Design : Case-control study. Methodology : A case-control study was conducted in the Department of Medical and Fundamental Biochemistry of the Pasteur Institute of Côte d’Ivoire, in collaboration with the Diabetes Clinic of the Treichville University Teaching Hospital, between November 2018 and July 2020. The study included 80 patients with T2DM and 80 controls aged 30–75 years. Concentrations of intact proinsulin and C-peptide were determined using an enzyme-linked immunosorbent assay (ELISA). Biochemical parameters were measured using a Roche Hitachi Cobas C311 analyser, and vitamin D levels were assayed using a Waters® (USA) high-performance liquid chromatography (HPLC) system. Results: The results showed a significant decrease in vitamin D concentration (p = 0.0013) and a significant increase in intact proinsulin concentration (p = 0.0011) in patients with diabetes compared with non-diabetic controls. Among patients with diabetes, 21.25% of men and 25% of women had intact proinsulin levels > 11 pmol/L ; vitamin D deficiency was observed in 33.75% of women and 32.5% of men. C-peptide levels below 0.5 ng/mL were observed among patients with diabetes, whereas levels above 3.2 ng/mL were found in 10% of patients. Correlations among intact proinsulin, C-peptide, and vitamin D were weak and not statistically significant. Conclusion : The study demonstrated elevated intact proinsulin levels, altered C-peptide levels, and reduced vitamin D levels in Ivorian patients with type 2 diabetes, findings consistent with pancreatic β-cell dysfunction and insulin resistance.