Prophylactic Antidiabetic Effect of Turmeric (Curcuma longa L.) in a High-Fat High-Sugar Diet and Alloxan-Induced Type 2 Diabetic Rat Model – Biochemical and Histopathological Evaluation

Abstract

Introduction

Diabetes mellitus represents a rapidly expanding global health challenge, characterised by insulin resistance and progressive pancreatic β-cell dysfunction driven by metabolic and oxidative stress. The present study evaluated the prophylactic efficacy of turmeric co-administered with black pepper (TBP) in a combined high-fat high-sugar (HFHS) diet and alloxan-induced diabetic rat model.

Methods

Forty-eight male Sprague-Dawley rats were randomised into six groups: three controls; [normal (NC), control (DC), and metformin (MC)] groups, and three prophylactic TBP [high-dose extract (PTBP-H), low-dose extract (PTBP-L), and whole powder without extraction (PTBP-W)] groups. Diabetes was induced by HFHS diet and alloxan. Prophylactic TBP treatment was given throughout the study, whereas metformin was initiated only after induction. Body weight and fasting blood glucose (FBG) were monitored weekly. Fasting serum insulin (FSI), glycated haemoglobin (HbA1c), oral glucose tolerance (OGTT), and pancreatic histopathology were assessed. Data were analysed by one-way ANOVA followed by Tukey's post-hoc test.

Results

Prophylactic TBP significantly improved glycaemic control compared with the DC group (p<0.001). High-dose extract (PTBP-H) demonstrated the strongest effect, reducing FBG to 114.67±9.22 mg/dL and HbA1c to 4.45±0.45%, while maintaining higher FSI levels (p<0.001). All PTBP formulations markedly improved oral glucose tolerance and reduced the area under the curve. PTBP treatment significantly reduced pancreatic islet necrosis, inflammation, and atrophy, with the high-dose group exhibiting the best preservation of islet architecture, comparable to DC group.

Conclusion

Prophylactic turmeric with black pepper protects pancreatic islet structure and function and improves glycaemic parameters, suggesting potential to delay diabetes progression.