Comparative and combined effects of oat and hawthorn on glucose homeostasis, zinc status, and oxidative stress in zinc-deficient diabetic rats

Oat (Avena sativa L.) and hawthorn (Crataegus azarolus L.) are rich in polyphenols and trace elements, including zinc, which play important roles in glucose metabolism and redox regulation. This study evaluated the effects of oat, hawthorn, and their combination on glucose homeostasis, zinc status, and oxidative stress in a zinc-deficient diabetic rat model. Methanolic extracts were characterized by HPLC-PDA. Forty-eight male Wistar rats were divided into six groups: non-diabetic control, zinc-sufficient diabetic, zinc-deficient diabetic, and zinc-deficient diabetic treated with oat (10% diet), hawthorn (150 mg/kg/day), or their combination. Assessments included oral glucose tolerance test, serum biochemical parameters, tissue zinc concentrations, oxidative stress markers, and pancreatic histopathology. Zinc deficiency aggravated hyperglycemia, dyslipidemia, oxidative stress, and pancreatic damage. Oat or hawthorn alone partially improved metabolic and antioxidant parameters and zinc status. The combined treatment showed stronger effects, significantly improving glucose tolerance, restoring tissue zinc levels, reducing lipid peroxidation, and preserving pancreatic islet architecture. These findings suggest synergistic protective effects of oat and hawthorn against zinc deficiency–exacerbated diabetic alterations, likely through modulation of phenolic compounds, zinc bioavailability, and redox balance.