Inhibition of Diabetes Mellitus-Induced Knee Joint Injury in Rats by a Combination of Metformin and Captopril

Osteoarthritis (OA) is an inflammatory disease that damages the joints and affects millions of people worldwide. The potential inhibitory effects of the antidiabetic drug metformin combined with captopril, the angiotensin-converting enzyme inhibitor, on diabetes-induced damage to the knee joint articular cartilage associated with the inhibition of glycemia, dyslipidemia, and inflammation has not been investigated before. Therefore, we induced diabetes in rats using high carbohydrate and fat diets and a single injection of streptozotocin (50 mg/kg). The protective group of rats was pre-treated with combined daily doses of metformin (Met; 200 mg/kg body weight) and captopril (Cap; 150 mg/kg body weight) for 14 days before diabetic induction and continued on metformin and resveratrol until the end of the experiment at week 12. Harvested tissues obtained from knee joints were prepared for basic histology staining with haematoxylin and eosin (H&E) and examined under light microscopy. Representative H&E images showed that OA was developed in the diabetic rats as demonstrated by a profound damage to the knee joints such as irregular eroded and a sharp decrease in the thickness of the articular cartilage surface and abnormal remodeling of the subchondral bone that were substantially ameliorated by Met+Cap. Met+Cap also significantly (p< 0.05) reduced blood levels of glucose, glycated hemoglobin (HbA1c), dyslipidemia, and the inflammatory biomarkers, high sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α) induced by diabetes. In addition, a significant (p≤ 0.0014) correlation between the articular cartilage thickness and the blood levels of glucose, HbA1c, triglyceride (TG), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein- cholesterol (HDL-C), and hs-CRP were observed. Thus, we demonstrate that Met+Cap effectively protect the knee joint against injuries induced secondary to diabetes in rats, possibly due to the inhibition of glycemia, dyslipidemia, and biomarkers of inflammation.