Adipose Tissue Macrophage Polarisation and Its Role in Insulin Signalling Disruption in a Murine Obesity Model: Mechanistic Evidence for Dietary Intervention Strategies Relevant to South West Nigeria

Background: Adipose tissue macrophage polarisation toward the pro-inflammatory M1 phenotype is a central mechanism linking obesity-associated adipose inflammation to insulin signalling disruption and type 2 diabetes development. Dietary interventions using indigenous Nigerian plant-derived bioactives with anti-inflammatory properties, including moringa leaf and bitter leaf extracts, may modulate macrophage polarisation and restore insulin sensitivity. The mechanistic physiological evidence supporting these dietary strategies is lacking. Objectives: This study aims to characterise adipose tissue macrophage polarisation dynamics and their downstream effects on insulin receptor substrate-1 phosphorylation and AKT-GLUT4 pathway signalling in a diet-induced obese murine model, and to evaluate the mechanistic effects of standardised moringa and bitter leaf extract supplementation on these pathways. Methods: Sixty male C57BL/6 mice will be divided into standard chow, high-fat diet, high-fat diet plus moringa extract, high-fat diet plus bitter leaf extract, and high-fat diet plus combined extract groups for 16 weeks. Stromal vascular fraction of epididymal adipose will be analysed by flow cytometry for M1 (CD11c+) and M2 (CD206+) macrophage proportions. Insulin signalling will be assessed by western blot of phosphorylated insulin receptor substrate-1, phosphorylated AKT, and GLUT4 translocation. Interleukin-6, tumour necrosis factor-alpha, and interleukin-10 will be measured by ELISA in adipose explant supernatants. One-way ANOVA with Tukey post-hoc tests will be applied. Expected Outcomes: Moringa and combined extracts are hypothesised to shift adipose macrophage balance toward M2 predominance, restore insulin receptor substrate-1 phosphorylation, and reduce pro-inflammatory cytokine secretion relative to untreated obese controls. Conclusion: This study will provide original mechanistic evidence supporting indigenous dietary bioactives as insulin-sensitising interventions relevant to obesity management in South West Nigeria. Keywords: adipose macrophage polarisation, insulin signalling, obesity, moringa, dietary bioactives.