No abstract

The potential inhibitory effect of the antidiabetic and anti‐inflammatory drug, metformin on thioacetamide (TAA)‐induced hepatotoxicity associated with the inhibition of mammalian target of rapamycin (mTOR)–hypoxia‐inducible factor‐1α (HIF‐1α) axis has not been investigated before. Therefore, we tested whether metformin can protect against liver injuries including fibrosis induced by TAA possibly via the downregulation of mTOR–HIF‐1α axis and profibrogenic and inflammatory biomarkers. Rats either injected with TAA (200 mg/kg; twice a week for 8 weeks) before being killed after 10 weeks (model group) or were pretreated with metformin (200 mg/kg) daily for 2 weeks before TAA injections and continued receiving both agents until the end of the experiment, at Week 10 (protective group). Using light and electron microscopy examinations, we observed in the model group substantial damage to the hepatocytes and liver tissue such as collagen deposition, infiltration of inflammatory cells, and degenerative cellular changes with ballooned mitochondria that were substantially ameliorated by metformin. Metformin also significantly ( p < 0.05) inhibited TAA‐induced HIF‐1α, mTOR, the profibrogenic biomarker α‐smooth muscle actin, tissue inhibitor of metalloproteinases‐1, tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), alanine aminotransferase (ALT) and aspartate aminotransferase in harvested liver homogenates and blood samples. In addition, a significant ( p < 0.01) positive correlation between hypoxia scoring (HIF‐1α) and the serum levels of TNF‐α ( r = 0.797), IL‐6 ( r = 0.859), and ALT ( r = 0.760) was observed. We conclude that metformin protects against TAA‐induced hepatic injuries in rats, which is associated with the inhibition of mTOR–HIF‐1α axis and profibrogenic and inflammatory biomarkers; thus, may offer therapeutic potential in humans.

Bone marrow derived mesenchymal stem cells (BM-MSCs) have demonstrated potential in treating diabetic cardiomyopathy. However, diabetic patients are on multiple drugs and there is lack of understanding on how transplanted stem cells would respond in presence of such drugs. Metformin is an AMP Kinase (AMPK) activator, the widest used anti-diabetic drug. In this study, we investigated the effect of metformin on the efficacy of stem cell therapy in a diabetic cardiomyopathy animal model using streptozotocin (STZ) in male Wistar rats. To comprehend the effect of metformin on the efficacy of BM-MSCs, we transplanted BM-MSCs (1 million cells/rat) with or without metformin. Our data demonstrate that transplantation of BM-MSCs prevented cardiac fibrosis and promoted angiogenesis in diabetic hearts. However, metformin supplementation downregulated BM-MSCs mediated cardioprotection. Interestingly, both BM-MSCs and metformin treatment individually, improved cardiac function with no synergistic effect of metformin supplementation along with BM-MSCs. Investigating the mechanisms of loss of efficacy of BM-MSCs in the presence of metformin, we found that metformin treatment impairs homing of implanted BM-MSCs in the heart and leads to poor survival of transplanted cells. Furthermore, our data demonstrate that metformin mediated activation of AMPK is responsible for poor homing and survival of BM-MSCs in the diabetic heart. Hence, current study confirms that a conflict arises between metformin and BM-MSCs for treating diabetic cardiomyopathy. Approximately 10% of the world population is diabetic to which metformin is prescribed very commonly. Hence, future cell replacement therapies in combination with AMPK inhibitors may be more effective for diabetic patients.

No abstract

Wnt/β‐catenin signaling pathway plays a crucial role in diabetic cardiomyopathy (DCM), thus we aimed at investigating the effect of one therapeutic approach with resveratrol (RSV) given systemically and combined treatment of RSV with mesenchymal stem cells (MSCs) that was either RSV‐preconditioned or not on Wnt/β‐catenin signaling pathway in streptozotocin‐induced DCM, and to evaluate effects of RSV preconditioning on MSCs therapeutic potential. The rats were divided into control (C, n = 8), diabetic (DM, n = 8), diabetic treated with systemic RSV (DM‐RSV, n = 8), diabetic treated with RSV and nonconditioned MSCs (DM‐RSV‐MSCs, n = 8), diabetic treated with RSV and RSV‐incubated with MSCs (DM‐RSV‐MSCc, n = 8) and diabetic treated with RSV‐conditioned MSCs (DM‐MSCc, n = 8). Echocardiography (Echo) showed significant improvement of cardiac functions in all groups treated with RSV either systemic or added in culture media. Data of ejection fraction (EF%) of DM‐RSV‐MSCc (81.50; interquartile range [IQR], 80.00–83.00) was comparable to both DM‐RSV‐MSCs (77.50; IQR, 71.50–79.00), and DM‐MSCc (71.50; IQR, 70.00–74.50). Histological examination of the left ventricles was performed for all groups. DM group revealed significant myocardial hypertrophy, apoptosis, interstitial fibrosis, and microvascular affection. All treated groups were associated, in variable degrees, with attenuation of cardiac hypertrophy and fibrosis, decreased area% for cardiac immunostaining of secreted frizzled‐related protein (sFRP2) and Wnt/β‐catenin and improvement of the microvasculature. In conclusion, MSCs pretreated with resveratrol for 7 days showed increased 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, and combined use of RSV (systemically and in culture media) significantly could improve cardiac remodeling capacity of MSCs via attenuation of sFRP2‐mediated fibrosis and the downstream Wnt/β‐catenin pathway.