Context Aging is a primary risk factor for most chronic diseases, including type 2 diabetes. Both exercise and hypoxia regulate pathways that ameliorate age-associated metabolic muscle dysfunction. Objective We hypothesized that the combination of hypoxia and exercise would be more effective in improving glucose metabolism than normoxia exercise. Design and Participants We randomized 29 older sedentary individuals (62 ± 6 years; 14 women, 15 men) to bicycle exercise under normobaric hypoxia (fraction of inspired oxygen = 15%) or normoxia (fraction of inspired oxygen = 21%). Intervention Participants trained thrice weekly for 30 to 40 minutes over 8 weeks at a heart rate corresponding to 60% to 70% of peak oxygen update. Main Outcome Measures Insulin sensitivity measured by hyperinsulinemic-euglycemic glucose clamp and muscle protein expression before and after hyperinsulinemic-euglycemic glucose clamp. Results Heart rate and perceived exertion during training were similar between groups, with lower oxygen saturation when exercising under hypoxia (88.7 ± 1.5 vs 96.2 ± 1.2%, P < 0.01). Glucose infusion rate after 8 weeks increased in both the hypoxia (5.7 ± 1.1 to 6.7 ± 1.3 mg/min/kg; P < 0.01) and the normoxia group (6.2 ± 2.1 to 6.8 ± 2.1 mg/min/kg; P = 0.04), with a mean difference between groups of –0.44 mg/min/kg; 95% CI, –1.22 to 0.34; (P = 0.25). Markers of mitochondrial content and oxidative capacity in skeletal muscle were similar after training in both groups. Changes in Akt phosphorylation and glucose transporter 4 under fasting and insulin-stimulated conditions were not different between groups over time. Conclusions Eight weeks of hypoxia endurance training led to similar changes in insulin sensitivity and markers of oxidative metabolism compared with normoxia training. Normobaric hypoxia exercise did not enhance metabolic effects in sedentary older women and men beyond exercise alone.

Both nutrition and exercise are known to affect metabolic regulation in humans. Sirtuins are essential regulators of cellular energy metabolism; SIRT1, SIRT3, and SIRT4 have a direct effect on glycolysis, oxidative phosphorylation, and fatty acid oxidation. This cross-sectional study investigates the effect of different diets on exercise-induced regulation of sirtuins. SIRT1 and SIRT3–SIRT5 were measured in blood from omnivorous, lacto-ovo vegetarian, and vegan recreational runners (21–25 subjects, respectively) before and after exercise at the transcript, protein, and enzymatic levels. SIRT1, SIRT3, and SIRT5 enzyme activities increased during exercise in omnivores and lacto-ovo vegetarians, commensurate with increased energy demand. However, activities decreased in vegans. Malondialdehyde as a surrogate marker of oxidative stress inversely correlated with sirtuin activities and was elevated in vegans after exercise compared to both other groups. A significant negative correlation of all sirtuins with the intake of the antioxidative substances, ascorbate and tocopherol, was found. In vegan participants, increased oxidative stress despite higher amounts of the antioxidative substances in the diet was observed after exercise.

BackgroundSirtuins are NAD+ dependent deacetylases, which regulate mitochondrial energy metabolism as well as cellular response to stress. The NAD/NADH-system plays a crucial role in oxidative phosphorylation linking sirtuins and the mitochondrial respiratory chain. Furthermore, sirtuins are able to directly deacetylate and activate different complexes of the respiratory chain. This prompted us to analyse sirtuin levels in skin fibroblasts from patients with cytochrome c-oxidase (COX) deficiency and to test the impact of different pharmaceutical activators of sirtuins (SRT1720, paeonol) to modulate sirtuins and possibly respiratory chain enzymes in patient cells in vitro.MethodsWe assayed intracellular levels of sirtuin 1 and the mitochondrial sirtuins SIRT3 and SIRT4 in human fibroblasts from patients with COX- deficiency. Furthermore, sirtuins were measured after inhibiting complex IV in healthy control fibroblasts by cyanide and after incubation with activators SRT1720 and paeonol. To determine the effect of sirtuin inhibition at the cellular level we measured total cellular acetylation (control and patient cells, with and without treatment) by Western blot.ResultsWe observed a significant decrease in cellular levels of all three sirtuins at the activity, protein and transcriptional level (by 15% to 50%) in COX-deficient cells. Additionally, the intracellular concentration of NAD+ was reduced in patient cells. We mimicked the biochemical phenotype of COX- deficiency by incubating healthy fibroblasts with cyanide and observed reduced sirtuin levels. A pharmacological activation of sirtuins resulted in normalized sirtuin levels in patient cells. Hyper acetylation was also reversible after treatment with sirtuin activators. Pharmacological modulation of sirtuins resulted in altered respiratory chain complex activities.ConclusionsWe found inhibition of situins 1, 3 and 4 at activity, protein and transcriptional levels in fibroblasts from patient with COX-deficiency. Pharmacological activators were able to restore reduced sirtuin levels and thereby modulate respiratory chain activities.

Background: Sirtuins (SIRT) are NAD+-dependent deacetylases that are involved in stress response, antioxidative defense, and longevity via posttranslational modifications. SIRT1 directly activates nitric oxide synthase (NOS). Aging is associated with a reduced sirtuin function and reduction of the cofactor NAD+. Age-related atherosclerosis and vascular diseases are linked to a compromised sirtuin function. Vascular events like stroke and cardiac infarction result in acute hypoxia, which can additionally impact sirtuins and thus the vascular function. This prompted us to study sirtuins in intact HUVECs, under acute, short-term hypoxic conditions. Methods: We measured intracellular sirtuin and NAD+ levels in HUVECs exposed to hypoxia (2% O₂) for 10–120 min, compared to normoxic controls. SIRT1, SIRT3, and SIRT4 were measured at the protein (Western Blot) and the transcript level (qRT-PCR), SIRT1 and SIRT3 at the enzyme level (fluorometrically), and NAD+ levels were measured spectrophotometrically. Results: We observed a reduction of SIRT1 and SIRT4 at the protein level, a downregulation of SIRT1 at the transcript level and increased NAD+ levels under hypoxia. SIRT3 was not affected by hypoxia. Conclusions: Downregulation of SIRT1 under hypoxia might reduce production of the reactive oxygen species (ROS) via the respiratory chain and inhibit the mitochondrial ATP-synthase, resulting in energy conservation. NOS might be impaired if SIRT1 is decreased. Increased NAD+ levels might compensate these effects. Hypoxic downregulation of SIRT4 might lead to mitochondrial uncoupling, hence endothelial dysfunction, and ADP/ATP-translocase 2 (ANT2)-inhibition. NAD+ upregulation might partly compensate this effect.

Background: Gestational diabetes (GDM) has long-term consequences for the offspring. Sirtuins (SIRTs) are associated with vascular and metabolic functions. We studied the impact of GDM on SIRT activity and expression in fetal endothelial colony-forming cells (ECFCs) and human umbilical vein endothelial cells (HUVECs) from pregnancies complicated by GDM. Methods: ECFCs and HUVECs were isolated from cord and cord blood of 10 uncomplicated pregnancies (NPs) and 10 GDM pregnancies. Nicotinamidadenindinukleotid (NAD + ) concentration, SIRT1 and SIRT3 activity, transcription levels of SIRT1, SIRT3, and SIRT4, and protein levels of SIRT1, SIRT3, and SIRT4 were determined in vitro with or without SIRT activators resveratrol (RSV) and paeonol. results: Fetal ECFCs from GDM pregnancies showed a decreased NAD + concentration, reduced SIRT1 and SIRT3 activity, and lower transcription levels of SIRT1, SIRT3, and SIRT4. HUVECs from GDM pregnancies had decreased NAD + concentrations and transcription levels of SIRT1 and SIRT4. RSV markedly enhanced the expression and activity of SIRTs in ECFCs and HUVECs, while paeonol was active only in ECFCs. conclusion: A reduction of SIRT activity and expression in fetal endothelial cells provides potential mechanistic insights into the pathophysiology of long-term cardiovascular complications observed in the offspring of GDM pregnancies. SIRT activators can increase SIRT activity in ECFCs, which opens perspectives for new therapeutic targets. a dverse events during fetal life have been implicated to induce fetal programming, which can result in chronic diseases (1). Especially gestational diabetes (GDM) of the mother has been associated with cardiovascular disease, metabolic syndrome, and obesity during later life in the offspring (2,3). The pathophysiological processes responsible for these late complications are largely unknown.Sirtuins (SIRTs) are important regulators of aging and metabolic diseases (4,5). Mammalian SIRTs belong to the histone deacetylase class III family comprising seven members (SIRT1-7), which require Nicotinamidadenindinukleotid (NAD + ) for their enzymatic activity (6). SIRT1 downregulation has been observed in peripheral blood mononuclear cells of individuals with impaired glucose tolerance (7,8). SIRT1 is known to regulate vascular endothelial cell functions (9). Furthermore, in vitro and in vivo studies demonstrated that a reduction in the number of endothelial progenitor cells (EPCs) under hyperglycemia is associated with reduced SIRT1 levels and activity (8,10). Endothelial cells regulate vascular tone and are the first fetal cells exposed to maternal hyperglycemia.In recent years, it has become evident that SIRT1 is a key player of EPC dysfunction in insulin resistance and metabolic syndrome (7,10,11). Overexpression of endothelium-specific SIRT1 protects against endothelial dysfunction induced by a high-fat diet and hyperglycemia (12,13). Recently, resveratrol (RSV) and paeonol (2′-Hydroxy-4′-methoxyacetophenone) have been shown to activate SIRTs and thus c...

The hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome is frequently observed in mothers whose offspring have long-chain fatty acid oxidation defects. We previously found that fatty acid oxidation is compromised not only in these inborn errors of metabolism but also in human umbilical vein endothelial cells (HUVECs) from all pregnancies complicated by the HELLP syndrome. Sirtuins are oxidized nicotinamide adenine dinucleotide (NAD)dependent deacetylases linked to the metabolic status of the cell. SIRT 4 is known to have regulatory functions in fatty acid oxidation. The HELLP syndrome is often associated with short-term hypoxia. We studied sirtuins (SIRT 1, SIRT 3, and SIRT 4) in HUVECs from pregnancies complicated by the HELLP syndrome and uncomplicated pregnancies exposed to hypoxia (n = 7 controls, 7 HELLP; 0, 10, 60, or 120 minutes of 2% O). Protein levels of SIRT 4 were significantly higher in HUVECs from HELLP compared to control after 60 and 120 minutes of hypoxia. The NAD levels increased in a time-dependent manner.