Citations
Citations
Citations
Citations
Metformin, a well-known anti-diabetic drug, has gained interest due to its association with the reduction of the prevalence of cancer in patients with type 2 diabetes and the anti-proliferative effect of metformin in several cancer cells. Here, we investigated the anti-proliferative effect of metformin with respect to apoptosis and autophagy in H4IIE hepatocellular carcinoma cells.
H4IIE rat cells were treated with metformin in glucose-free medium for 24 hours and were then subjected to experiments examining the onset of apoptosis and/or autophagy as well as the related signaling pathways.
When H4IIE cells were incubated in glucose-free media for 24 hours, metformin and 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) reduced the viability of cells. Inhibition of AMP-activated protein kinase (AMPK) by compound C significantly blocked cell death induced by metformin or AICAR. Pro-apoptotic events (nuclear condensation, hydrolysis of intact poly ADP ribose polymerase and caspase-3) were stimulated by metformin and then suppressed by compound C. Interestingly, the formation of acidic intracellular vesicles, a marker of autophagy, was stimulated by compound C. Although the deprivation of amino acids in culture media also induced apoptosis, neither metformin nor compound C affected cell viability. The expression levels of all of the autophagy-related proteins examined decreased with metformin, and two proteins (light chain 3 and beclin-1) were sensitive to compound C. Among the tested inhibitors against MAP kinases and phosphatidylinositol-3-kinase/mammalian target of rapamycin, SB202190 (against p38MAP kinase) significantly interrupted the effects of metformin.
Our data suggest that metformin induces apoptosis, but suppresses autophagy, in hepatocellular carcinoma cells via signaling pathways, including AMPK and p38 mitogen-activated protein kinase.
Citations
Metformin Induces Autophagy via the AMPK-mTOR Signaling Pathway in Human Hepatocellular Carcinoma Cells
Diabetic nephropathy is a leading cause of end stage renal disease and its occurance is increasing worldwide. The most effective treatment strategy for the condition is intensive treatment to strictly control glycemia and blood pressure using renin-angiotensin system inhibitors. However, a fraction of patients still go on to reach end stage renal disease even under such intensive care. New therapeutic targets for diabetic nephropathy are, therefore, urgently needed. Autophagy is a major catabolic pathway by which mammalian cells degrade macromolecules and organelles to maintain intracellular homeostasis. The accumulation of damaged proteins and organelles is associated with the pathogenesis of diabetic nephropathy. Autophagy in the kidney is activated under some stress conditions, such as oxidative stress and hypoxia in proximal tubular cells, and occurs even under normal conditions in podocytes. These and other accumulating findings have led to a hypothesis that autophagy is involved in the pathogenesis of diabetic nephropathy. Here, we review recent findings underpinning this hypothesis and discuss the advantages of targeting autophagy for the treatment of diabetic nephropathy.
Citations
Salvianolic Acid B Improves Chronic Mild Stress-Induced Depressive Behaviors in Rats: Involvement of AMPK/SIRT1 Signaling Pathway
Numerous studies have established a link between autophagy and aging; however, the relationship has not been clearly defined. Aging is a very complex process caused by the accumulation of various factors due to the gradual failure of cellular maintenance. Recent studies have shown that autophagy reduces the stress responses induced by starvation, reactive oxygen species, and the accumulation of intracellular proteins and organelles through cytoprotection, clearance of damaged mitochondria, and lysosomal degradation. Here, we summarize our current understanding of the relationship between autophagy and the aging process.
Citations
Autophagy is necessary for the degradation of long-lasting proteins and nonfunctional organelles, and is activated to promote cellular survival. However, overactivation of autophagy may deplete essential molecules and organelles responsible for cellular survival. Lifelong calorie restriction by 40% has been shown to increase the cardiac expression of autophagic markers, which suggests that it may have a cardioprotective effect by decreasing oxidative damage brought on by aging and cardiovascular diseases. Although cardiac autophagy is critical to regulating protein quality and maintaining cellular function and survival, increased or excessive autophagy may have deleterious effects on the heart under some circumstances, including pressure overload-induced heart failure. The importance of autophagy has been shown in nutrient supply and preservation of energy in times of limitation, such as ischemia. Some studies have suggested that a transition from obesity to metabolic syndrome may involve progressive changes in myocardial inflammation, mitochondrial dysfunction, fibrosis, apoptosis, and myocardial autophagy.
Citations