Jesper Olesen

PGC-1α-mediated adaptations in skeletal muscle

Lifestyle-related diseases are rapidly increasing at least in part due to less physical activity. The health beneficial effects of regular physical activity include metabolic adaptations in skeletal muscle, which are thought to be elicited by cumulative effects of transient gene responses to each single exercise, but how is this regulated? A potential candidate in this is the transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, which has been identified as a master regulator of mitochondrial biogenesis, but also been shown to regulate proteins involved in angiogenesis and the anti-oxidant defence as well as to affect expression of inflammatory markers. Exercise increases PGC-1α transcription and potentially PGC-1α activity through post-translational modifications, and concomitant PGC-1α-mediated gene regulation is suggested to be an underlying mechanism for adaptations in skeletal muscle, when exercise is repeated. The current review presents some of the key findings in PGC-1α-mediated regulation of metabolically related, anti-oxidant and inflammatory proteins in skeletal muscle in the basal state and in response to exercise training, and describes functional significance of PGC-1α-mediated effects in skeletal muscle. In addition, regulation of PGC-1α expression and activity in skeletal muscle is described. The impact of changes in PGC-1α expression in mouse skeletal muscle and the ability of PGC-1α to regulate multiple pathways and functions underline the potential importance of PGC-1α in skeletal muscle adaptations in humans. The absence of exercise-induced PGC-1α-mediated gene regulation during a physical inactive lifestyle is suggested to lead to reduced oxidative capacity of skeletal muscle and concomitant impaired metabolism.

Resveratrol blunts the positive effects of exercise training on cardiovascular health in aged men

•  In rodents, resveratrol has been shown to enhance training‐induced changes in cardiovascular function, exercise performance and the retardation of atherosclerosis. We examined the effect of 8 weeks of exercise training with and without concomitant resveratrol supplementation in aged men. •  Exercise training potently improved blood pressure, blood cholesterol, maximal oxygen uptake and the plasma lipid profile. •  Resveratrol supplementation reduced the positive effect of exercise training on blood pressure, blood cholesterol and maximal oxygen uptake and did not affect the retardation of atherosclerosis. •  Whereas exercise training improved formation of the vasodilator prostacyclin, concomitant resveratrol supplementation caused a shift in vasoactive systems favouring vasoconstriction. •  The present study is the first to demonstrate negative effects of resveratrol on training‐induced improvements in cardiovascular health parameters in humans and adds to the growing body of evidence questioning the positive effects of resveratrol supplementation in humans.

Exercise training, but not resveratrol, improves metabolic and inflammatory status in skeletal muscle of aged men

Ageing is associated with lifestyle‐related metabolic diseases, and exercise training has been suggested to counteract such metabolic deteriorations. The natural antioxidant resveratrol has been reported to exert ‘exercise‐like’ health beneficial metabolic and anti‐inflammatory effects in rodents, but little is known about the metabolic effects of resveratrol supplementation alone and in combination with exercise training in humans. The present findings showed that exercise training markedly improved muscle endurance, increased content and activity of oxidative proteins in skeletal muscle and reduced markers of oxidative stress and inflammation in skeletal muscle of aged men. Resveratrol alone did not elicit metabolic effects in healthy aged subjects, but even impaired the exercise training‐induced improvements in markers of oxidative stress and inflammation in skeletal muscle.

Effect of lifelong resveratrol supplementation and exercise training on skeletal muscle oxidative capacity in aging mice; impact of PGC-1α

BACKGROUND The present study tested the hypothesis that lifelong resveratrol (RSV) supplementation counteracts an age-associated decrease in skeletal muscle oxidative capacity through peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and that RSV combined with lifelong exercise training (EX) exerts additive effects through PGC-1α in mice. METHODS 3 month old PGC-1α whole body knockout (KO) and wild type (WT) littermate mice were placed in cages with or without running wheel and fed either standard chow or standard chow with RSV supplementation (4 g/kg food) for 12 months. Young (3 months of age), sedentary mice on standard chow served as young controls. A graded running performance test and a glucose tolerance test were performed 2 and 1 week, respectively, before euthanization where quadriceps and extensor digitorum longus (EDL) muscles were removed. RESULTS In PGC-1α KO mice, quadriceps citrate synthase (CS) activity, mitochondrial (mt)DNA content as well as pyruvate dehydrogenase (PDH)-E1α, cytochrome (Cyt) c and vascular endothelial growth factor (VEGF) protein content were 20-75% lower and, EDL capillary-to-fiber (C:F) ratio was 15-30% lower than in WT mice. RSV and/or EX had no effect on the C:F ratio in EDL. CS activity (P=0.063) and mtDNA content (P=0.013) decreased with age in WT mice, and CS activity, mtDNA content, PDH-E1α protein and VEGF protein increased ~1.5-1.8-fold with lifelong EX in WT, but not in PGC-1α KO mice, while RSV alone had no significant effect on these proteins. CONCLUSION Lifelong EX increased activity/content of oxidative proteins, mtDNA and angiogenic proteins in skeletal muscle through PGC-1α, while RSV supplementation alone had no effect. Combining lifelong EX and RSV supplementation had no additional effect on skeletal muscle oxidative and angiogenic proteins.

Exercise-induced liver chemokine CXCL-1 expression is linked to muscle-derived interleukin-6 expression

Non‐technical summary  Exercise is known to stimulate the production of various exercise factors including the well‐described muscle‐derived interleukin‐6 (IL‐6). We show that exercise causes a massive expression of the chemokine CXCL‐1 in serum, in skeletal muscle and especially in the liver. Furthermore we find that this exercise‐induced liver CXCL‐1 expression is regulated by IL‐6 and that muscle‐derived IL‐6 is capable of stimulating liver CXCL‐1 expression. Such knowledge of the regulation of exercise factors contributes to the understanding of how the liver and muscle communicate in response to exercise.

Skeletal muscle PGC-1α is required for maintaining an acute LPS-induced TNFα response.

Many lifestyle-related diseases are associated with low-grade inflammation and peroxisome proliferator activated receptor γ coactivator (PGC)-1α has been suggested to be protective against low-grade inflammation. However, whether these anti-inflammatory properties affect acute inflammation is not known. The aim of the present study was therefore to investigate the role of muscle PGC-1α in acute inflammation. Quadriceps muscles were removed from 10-week old whole body PGC-1α knockout (KO), muscle specific PGC-1α KO (MKO) and muscle-specific PGC-1α overexpression mice (TG), 2 hours after an intraperitoneal injection of either 0.8 µg LPS/g body weight or saline. Basal TNFα mRNA content was lower in skeletal muscle of whole body PGC-1α KO mice and in accordance TG mice showed increased TNFα mRNA and protein level relative to WT, indicating a possible PGC-1α mediated regulation of TNFα. Basal p65 phosphorylation was increased in TG mice possibly explaining the elevated TNFα expression in these mice. Systemically, TG mice had reduced basal plasma TNFα levels compared with WT suggesting a protective effect against systemic low-grade inflammation in these animals. While TG mice reached similar TNFα levels as WT and showed more marked induction in plasma TNFα than WT after LPS injection, MKO PGC-1α mice had a reduced plasma TNFα and skeletal muscle TNFα mRNA response to LPS. In conclusion, the present findings suggest that PGC-1α enhances basal TNFα expression in skeletal muscle and indicate that PGC-1α does not exert anti-inflammatory effects during acute inflammation. Lack of skeletal muscle PGC-1α seems however to impair the acute TNFα response, which may reflect a phenotype more susceptible to infections as also observed in type 2 diabetes patients.

Role of PGC-1α in exercise training- and resveratrol-induced prevention of age-associated inflammation

BACKGROUND/AIM Age-related metabolic diseases are often associated with low-grade inflammation. The aim of the present study was to investigate the role of the transcriptional co-activator PGC-1α in the potential beneficial effects of exercise training and/or resveratrol in the prevention of age-associated low-grade inflammation. To address this, a long-term voluntary exercise training and resveratrol supplementation study was conducted. EXPERIMENTAL SETUP Three month old whole body PGC-1α KO and WT mice were randomly assigned to four groups: untrained chow-fed, untrained chow-fed supplemented with resveratrol, chow-fed voluntarily exercise trained and chow-fed supplemented with resveratrol and voluntarily exercise trained. The intervention lasted 12 months and three month old untrained chow-fed mice served as young controls. RESULTS Voluntary exercise training prevented an age-associated increase (p<0.05) in systemic IL-6 and adiposity in WT mice. PGC-1α expression was required for a training-induced prevention of an age-associated increase (p<0.05) in skeletal muscle TNFα protein. Independently of PGC-1α, both exercise training and resveratrol prevented an age-associated increase (p<0.05) in skeletal muscle protein carbonylation. CONCLUSION The present findings highlight that exercise training is a more effective intervention than resveratrol supplementation in reducing age-associated inflammation and that PGC-1α in part is required for the exercise training-induced anti-inflammatory effects.

Effects of Exercise Training on Regulation of Skeletal Muscle Glucose Metabolism in Elderly Men

BACKGROUND The aim was to investigate the molecular mechanisms behind exercise training-induced improvements in glucose regulation in aged subjects. METHODS Twelve elderly male subjects completed 8 weeks of exercise training. Before and after the training period, the subjects completed an oral glucose tolerance test (OGTT) and a muscle biopsy was obtained from the vastus lateralis before and 45 minutes into the OGTT. Blood samples were collected before and up to 120 minutes after glucose intake. RESULTS Exercise training increased Hexokinase II, GLUT4, Akt2, glycogen synthase (GS), pyruvate dehydrogenase (PDH)-E1α, PDK2 protein, and glycogen content in skeletal muscle. Furthermore, in response to glucose, GS activity was increased and the dephosphorylation of GS site 2 + 2a and 3a was enhanced after the training intervention. The glucose-mediated insulin stimulation of TBC1D4 Thr(642) phosphorylation was increased after exercise training. In the trained state, the PDHa activity was reduced following glucose intake and without changes in phosphorylation level of PDH-E1α. CONCLUSIONS The present results suggest that exercise training improves glucose regulation in elderly subjects by enhancing the capacity and acute regulation of glucose uptake and by enhancing intracellular glucose removal to glycogen synthesis rather than glucose oxidation.

Resveratrol modulates the angiogenic response to exercise training in skeletal muscles of aged men

In animal studies, the polyphenol resveratrol has been shown to influence several pathways of importance for angiogenesis in skeletal muscle. The aim of the present study was to examine the angiogenic effect of resveratrol supplementation with parallel exercise training in aged men. Forty-three healthy physically inactive aged men (65 ± 1 yr) were divided into 1) a training group that conducted 8 wk of intense exercise training where half of the subjects received a daily intake of either 250 mg trans-resveratrol (n = 14) and the other half received placebo (n = 13) and 2) a nontraining group that received either 250 mg trans-resveratrol (n = 9) or placebo (n = 7). The group that trained with placebo showed a ~20% increase in the capillary-to-fiber ratio, an increase in muscle protein expression of VEGF, VEGF receptor-2, and tissue inhibitor of matrix metalloproteinase (TIMP-1) but unaltered thrombospodin-1 levels. Muscle interstitial VEGF and thrombospodin-1 protein levels were unchanged after the training period. The group that trained with resveratrol supplementation did not show an increase in the capillary-to-fiber ratio or an increase in muscle VEGF protein. Muscle TIMP-1 protein levels were lower in the training and resveratrol group than in the training and placebo group. Both training groups showed an increase in forkhead box O1 protein. In nontraining groups, TIMP-1 protein was lower in the resveratrol-treated group than the placebo-treated group after 8 wk. In conclusion, these data show that exercise training has a strong angiogenic effect, whereas resveratrol supplementation may limit basal and training-induced angiogenesis.

Exercise training protects against aging-induced mitochondrial fragmentation in mouse skeletal muscle in a PGC-1α dependent manner

Abstract Aging is associated with impaired mitochondrial function, whereas exercise training enhances mitochondrial content and function in part through activation of PGC‐1&agr;. Mitochondria form dynamic networks regulated by fission and fusion with profound effects on mitochondrial functions, yet the effects of aging and exercise training on mitochondrial network structure remain unclear. This study examined the effects of aging and exercise training on mitochondrial network structure using confocal microscopy on mitochondria‐specific stains in single muscle fibers from PGC‐1&agr; KO and WT mice. Hyperfragmentation of mitochondrial networks was observed in aged relative to young animals while exercise training normalized mitochondrial network structure in WT, but not in PGC‐1&agr; KO. Mitochondrial fission protein content (FIS1 and DRP1) relative to mitochondrial content was increased with aging in both WT and PGC‐1&agr; KO mice, while exercise training lowered mitochondrial fission protein content relative to mitochondrial content only in WT. Mitochondrial fusion protein content (MFN1/2 and OPA1) was unaffected by aging and lifelong exercise training in both PGC‐1&agr; KO and WT mice. The present results provide evidence that exercise training rescues aging‐induced mitochondrial fragmentation in skeletal muscle by suppressing mitochondrial fission protein expression in a PGC‐1&agr; dependent manner.