High‐Protein Diet Exacerbates Insulin Resistance via the JNK / IKKβ ‐ IRS ‐1 Pathway

Objective To investigate the effects of a high‐protein (HP) diet on insulin resistance in a type 2 diabetes (T2D) mouse model. Methods A high‐fat diet combined with streptozotocin (STZ, 25 mg/kg) was used to induce a T2D model. Fasting blood glucose levels > 7 mmol/L were considered successful modelling. The models were further divided into three groups: the Normal‐Protein‐T2D (TN, n = 8), High‐Protein‐T2D (TH, n = 8), and High‐Fat‐T2D (TF, n = 8) groups. These groups were fed diets containing 20% protein, 60% protein, and 60% fat, respectively. Additionally, 24 Kunming (KM) mice, serving as non‐T2D controls, were divided into a Normal‐Protein‐Control (N, n = 8), a High‐Protein‐Control (H, n = 8), and a Low‐Protein‐Control (L, n = 8), fed 20% protein, 60% protein, and 5% protein diets, respectively. After 6 weeks of dietary intervention, FBG, serum biochemical markers, hepatic inflammatory factors and pathological changes, and pancreatic immunohistochemistry were assessed. Expression of IRS‐1, JNK, IKKβ, and their phosphorylated proteins were analysed. Results Mice in the H group exhibited significantly impaired glucose tolerance, exacerbated insulin resistance, and reduced liver function. In the T2D model, TH mice exhibited more severe hyperglycemia, insulin resistance, and β‐cell dysfunction than TN mice, accompanied by increased hepatic TNF‐α and IL‐6 expression, enhanced lipid accumulation, suppressed IRS‐1 phosphorylation, and enhanced JNK and IKKβ phosphorylation. Conclusion A HP diet induces insulin resistance in normal mice and further exacerbates glucose metabolism disorders in T2D models, suggesting that restricting HP intake may serve as a strategy for preventing T2D.