ABSTRACT
Recent studies have demonstrated that repeated short-term nutrient withdrawal (i.e. fasting) has pleiotropic actions to promote organismal health and longevity. Despite this, the molecular physiological mechanisms by which fasting is protective against metabolic disease are largely unknown. Here, we show that, metabolic control, particularly systemic and liver lipid metabolism, is aberrantly regulated in the fasted state in mouse models of metabolic dysfunction. Liver transcript assays between lean/healthy and obese/diabetic mice in fasted and fed states uncovered "growth arrest and DNA damage-inducible" GADD45ß as a dysregulated gene transcript during fasting in several models of metabolic dysfunction including ageing, obesity/pre-diabetes and type 2 diabetes, in both mice and humans. Using whole-body knockout mice as well as liver/hepatocyte-specific gain- and loss-of-function strategies, we revealed a role for liver GADD45ß in the coordination of liver fatty acid uptake, through cytoplasmic retention of FABP1, ultimately impacting obesity-driven hyperglycaemia. In summary, fasting stress-induced GADD45ß represents a liver-specific molecular event promoting adaptive metabolic function.
Subject(s)
Cell Cycle Proteins/metabolism , Fasting , Fatty Acids/metabolism , Liver/metabolism , Nuclear Proteins/metabolism , Animals , Fatty Acid-Binding Proteins/metabolism , Mice , Mice, KnockoutABSTRACT
Transformed cancer cells have an altered metabolism, characterized by a shift towards aerobic glycolysis, referred to as 'the Warburg phenotype'. A change in flux through mitochondrial OXPHOS and cytosolic pathways for ATP production and a gain of capacity for biomass production in order to sustain the needs for altered growth and morphodynamics are typically involved in this global rewiring of cancer cell metabolism. Characteristically, these changes in metabolism are accompanied by enhanced uptake of nutrients like glucose and glutamine. Here we focus on the relationship between cell metabolism and cell dynamics, in particular the formation and function of invadopodia, specialized structures for focal degradation of the extracellular matrix. Since we recently found presence of enzymes that are active in glycolysis and associated pathways in invadopodia, we hypothesize that metabolic adaptation and invadopodia formation are linked processes. We give an overview on the background for this idea and show for the first time that extracellular matrix degradation by invadopodia can be differentially manipulated, without effects on cell proliferation, by use of metabolic inhibitors or changes in nutrient composition of cell culture media. We conclude that cell metabolism and carbohydrate availability, especially pyruvate, are involved in fuelling of invadopodia formation and activity.
Subject(s)
Extracellular Matrix/metabolism , Neoplasms/metabolism , Pseudopodia/metabolism , Cell Growth Processes/physiology , Cell Line, Tumor , Humans , Oxidative Phosphorylation , Signal Transduction , Tumor Cells, CulturedABSTRACT
BACKGROUND: In diabetes mellitus, increased formation of reactive oxygen species due to high level of glucose in both blood plasma and tissues creates oxidative stress and damages the tissues. Antioxidants together with the antioxidant enzymes are very important in order to protect the cells against oxidative damage. METHODS: Differential expressions of both mRNA and proteins of major antioxidant enzymes in streptozotocin-induced diabetic rat kidneys were measured with the help of real-time polymerase chain reaction and western blot analysis, respectively. Furthermore, effects of two strong antioxidants α-lipoic acid, vitamin C and their combination on the regulation of both expressions and the activities of antioxidant enzymes were also studied. RESULTS: In diabetic rat kidney tissue, both catalase and glutathione peroxidase activities were reduced (although mRNA expression for both was greatly increased) when compared with controls. No significant change was observed in superoxide dismutase (SOD) activity. Alpha-lipoic acid increased catalase activity towards the control values. Combined administration of alpha-lipoic acid and vitamin C increased the activities of both catalase and SOD, demonstrating a posttranslational effect. Glutathione concentrations were decreased in diabetic kidney; alpha-lipoic acid treatment partially restored the glutathione levels. CONCLUSIONS: All data showed the importance of post-transcriptional and translational regulation of the antioxidant enzyme activities against oxidative stress that is associated with diabetes.
