Metformin Protects H9C2 Cardiomyocytes from High-Glucose and Hypoxia/Reoxygenation Injury via Inhibition of Reactive Oxygen Species Generation and Inflammatory Responses: Role of AMPK and JNK

Abstract

Metformin is a first-line drug for the management of type 2 diabetes. Recent studies suggested cardioprotective effects of metformin against ischemia/reperfusion injury. However, it remains elusive whether metformin provides direct protection against hypoxia/reoxygenation (H/R) injury in cardiomyocytes under normal or hyperglycemic conditions. This study in H9C2 rat cardiomyoblasts was designed to determine cell viability under H/R and high-glucose (HG, 33 mM) conditions and the effects of cotreatment with various concentrations of metformin (0, 1, 5, and 10 mM). We further elucidated molecular mechanisms underlying metformin-induced cytoprotection, especially the possible involvement of AMP-activated protein kinase (AMPK) and Jun NH(2)-terminal kinase (JNK). Results indicated that 5 mM metformin improved cell viability, mitochondrial integrity, and respiratory chain activity under HG and/or H/R (P < 0.05). The beneficial effects were associated with reduced levels of reactive oxygen species generation and proinflammatory cytokines (TNF-α, IL-1α, and IL-6) (P < 0.05). Metformin enhanced phosphorylation level of AMPK and suppressed HG + H/R induced JNK activation. Inhibitor of AMPK (compound C) or activator of JNK (anisomycin) abolished the cytoprotective effects of metformin. In conclusion, our study demonstrated for the first time that metformin possessed direct cytoprotective effects against HG and H/R injury in cardiac cells via signaling mechanisms involving activation of AMPK and concomitant inhibition of JNK.

Glibenclamide Mimics Metabolic Effects of Metformin in H9c2 Cells

“…Clinical trials and registries have consistently shown that metformin does not increase cardiovascular morbidity and mortality of diabetic patients; in fact, a favourable effect of metformin on diabetes-related cardiovascular risk has been reported [5]. Consistently, most experimental studies have demonstrated that metformin prevents ischemic cardiac damage, this protection being ascribed to various pathways, not necessarily downstream of the reduction in complex I activity, such as activation of AMPK and phosphoinositide 3-kinase/ AKT, enhanced intramyocardial availability of adenosine, blunting of oxidative stress, and inhibition of mitochondrial permeability transition pore opening [24,31]. By contrast, therapy with glibenclamide has been associated with negative cardiovascular outcomes in epidemiological analysis [2,3] and glibenclamide has been shown to worsen ischemic injury of cardiomyocytes in cell and animal models [31].…”

“…Metformin and glibenclamide are very different molecules with different mechanism of action. Similarly to metformin [23,24] glibenclamide increases AMPK phosphorylation and mitochondrial dysfunction.…”

“…24 h later, the cell medium was removed, cells were washed twice with PBS and were incubated either in regular medium or in starvation medium. 24 h later cells were treated or not with metformin, glibenclamide or gliclazide.…”

The Effects of Metformin on Obesity-Induced Dysfunctional Retinas

“…7 The effectiveness of metformin as an antihyperglycemic agent is based on its ability to suppress gluconeogenesis in the liver. 5,8 In addition, metformin has been identified as an activator of the AMP-activated protein kinase (AMPK) pathway in numerous cell types including hepatocytes, 9 endothelial cells, 10 cardiomyocytes, 11 cancer cells, 12 and adipose tissue. 13 In addition to its use as an antihyperglycemic agent, one beneficial effect from metformin is mild weight loss.…”

Metformin; a mini-review to its antioxidative and anti-inflammatory properties

“…AMPK activation suppresses protein synthesis in heart tissue and post-MI hypertrophy (18). Hu et al have shown, for the first time, that metformin could protect cardiomyocytes against high-glucose (HG) and hypoxia/reoxygenation (H/R) injury by suppressing Jun NH(2)-terminal kinase (JNK) activation and raising AMPK activation (19). Metformin also impresses gastrointestinal tract by reducing inflammation.…”