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Skeletal muscle PGC-1? modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice.

ABSTRACT: Ketone bodies (KBs) are crucial energy substrates during states of low carbohydrate availability. However, an aberrant regulation of KB homeostasis can lead to complications such as diabetic ketoacidosis. Exercise and diabetes affect systemic KB homeostasis, but the regulation of KB metabolism is still enigmatic. In our study in mice with either knockout or overexpression of the peroxisome proliferator-activated receptor-? coactivator (PGC)-1? in skeletal muscle, PGC-1? regulated ketolytic gene transcription in muscle. Furthermore, KB homeostasis of these mice was investigated during withholding of food, exercise, and ketogenic diet feeding, and after streptozotocin injection. In response to these ketogenic stimuli, modulation of PGC-1? levels in muscle affected systemic KB homeostasis. Moreover, the data demonstrate that skeletal muscle PGC-1? is necessary for the enhanced ketolytic capacity in response to exercise training and overexpression of PGC-1? in muscle enhances systemic ketolytic capacity and is sufficient to ameliorate diabetic hyperketonemia in mice. In cultured myotubes, the transcription factor estrogen-related receptor-? was a partner of PGC-1? in the regulation of ketolytic gene transcription. These results demonstrate a central role of skeletal muscle PGC-1? in the transcriptional regulation of systemic ketolytic capacity.-Svensson, K., Albert, V., Cardel, B., Salatino, S., Handschin, C. Skeletal muscle PGC-1? modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice.

SUBMITTER: Svensson K

PROVIDER: S-EPMC4970654 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Skeletal muscle PGC-1α modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice.

Svensson Kristoffer K Albert Verena V Cardel Bettina B Salatino Silvia S Handschin Christoph C

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20160205 5

Ketone bodies (KBs) are crucial energy substrates during states of low carbohydrate availability. However, an aberrant regulation of KB homeostasis can lead to complications such as diabetic ketoacidosis. Exercise and diabetes affect systemic KB homeostasis, but the regulation of KB metabolism is still enigmatic. In our study in mice with either knockout or overexpression of the peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α in skeletal muscle, PGC-1α regulated ketolytic gene ...[more]

PMID: 26849960

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Project description:Aim/hypothesisThe peroxisome proliferator-activated receptor-γ coactivator α (PGC-1α) plays a critical role in the maintenance of glucose, lipid and energy homeostasis by orchestrating metabolic programs in multiple tissues in response to environmental cues. In skeletal muscles, PGC-1α dysregulation has been associated with insulin resistance and type 2 diabetes but the underlying mechanisms have remained elusive. This research aims to understand the role of TET3, a member of the ten-eleven translocation (TET) family dioxygenases, in PGC-1α dysregulation in skeletal muscles in obesity and diabetes.MethodsTET expression levels in skeletal muscles were analysed in humans with or without type 2 diabetes, as well as in mouse models of high-fat diet (HFD)-induced or genetically induced (ob/ob) obesity/diabetes. Muscle-specific Tet3 knockout (mKD) mice were generated to study TET3's role in muscle insulin sensitivity. Genome-wide expression profiling (RNA-seq) of muscle tissues from wild-type (WT) and mKD mice was performed to mine deeper insights into TET3-mediated regulation of muscle insulin sensitivity. The correlation between PGC-1α and TET3 expression levels was investigated using muscle tissues and in vitro-derived myotubes. PGC-1α phosphorylation and degradation were analysed using in vitro assays.ResultsTET3 expression was elevated in skeletal muscles of humans with type 2 diabetes and in HFD-fed and ob/ob mice compared with healthy controls. mKD mice exhibited enhanced glucose tolerance, insulin sensitivity and resilience to HFD-induced insulin resistance. Pathway analysis of RNA-seq identified 'Mitochondrial Function' and 'PPARα Pathway' to be among the top biological processes regulated by TET3. We observed higher PGC-1α levels (~25%) in muscles of mKD mice vs WT mice, and lower PGC-1α protein levels (~25-60%) in HFD-fed or ob/ob mice compared with their control counterparts. In human and murine myotubes, increased PGC-1α levels following TET3 knockdown contributed to improved mitochondrial respiration and insulin sensitivity. TET3 formed a complex with PGC-1α and interfered with its phosphorylation, leading to its destabilisation.Conclusions/interpretationOur results demonstrate an essential role for TET3 in the regulation of skeletal muscle insulin sensitivity and suggest that TET3 may be used as a potential therapeutic target for the metabolic syndrome.Data availabilitySequences are available from the Gene Expression Omnibus ( https://www.ncbi.nlm.nih.gov/geo/ ) with accession number of GSE224042.

Project description:Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1α (PGC-1α) is a coactivator of various nuclear receptors and other transcription factors whose expression increases in the skeletal muscle during exercise. We have previously made transgenic mice overexpressing PGC-1α in the skeletal muscle (PGC-1α-Tg mice). PGC-1α upregulates the expression of genes associated with red fibers, mitochondrial function, fatty acid oxidation, and branched chain amino acid (BCAA) degradation. However, global analyses of the actual metabolic products have not been investigated. In this study, we conducted metabolomic analysis of the skeletal muscle in PGC-1α-Tg mice by capillary electrophoresis with electrospray ionization time-of-flight mass spectrometry. Principal component analysis and hierarchical cluster analysis showed clearly distinguishable changes in the metabolites between PGC-1α-Tg and wild-type control mice. Changes were observed in metabolite levels of various metabolic pathways such as the TCA cycle, pentose phosphate pathway, nucleotide synthesis, purine nucleotide cycle, and amino acid metabolism, including BCAA and β-alanine. Namely, metabolic products of the TCA cycle increased in PGC-1α-Tg mice, with increased levels of citrate (2.3-fold), succinate (2.2-fold), fumarate (2.8-fold), and malate (2.3-fold) observed. Metabolic products associated with the pentose phosphate pathway and nucleotide biosynthesis also increased in PGC-1α-Tg mice. Meanwhile, BCAA levels decreased (Val, 0.7-fold; Leu, 0.8-fold; and Ile, 0.7-fold), and Glu (3.1-fold) and Asp (2.2-fold) levels increased. Levels of β-alanine and related metabolites were markedly decreased in PGC-1α-Tg mice. Coordinated regulation of the TCA cycle and amino acid metabolism, including BCAA, suggests that PGC-1α plays important roles in energy metabolism. Moreover, our metabolomics data showing the activation of the purine nucleotide pathway, malate-aspartate shuttle, as well as creatine metabolism, which are known to be active during exercise, further suggests that PGC-1α regulates metabolism in exercise. Thus, we demonstrated the roles of PGC-1α in the skeletal muscle at the metabolite level.

Project description:ObjectiveThe aim of this study was to eluc\idate the preventive and therapeutic effects and the underlying mechanisms of Huoxue Huatan Decoction (HXHT) on myocardial ischemia/reperfusion (I/R) injury in hyperlipidemic rats.MethodsAn I/R model was established in hyperlipidemic Wistar rats. After 4-8 weeks of HXHT treatment, the physical signs of rats were observed. Lipid metabolism, myocardial enzyme spectrum, cardiac function, myocardial histomorphology, and mitochondrial biosynthesis were investigated by a biochemical method, ultrasonography, electron microscopy, pathological examination, real-time PCR, and Western blot.ResultsHXHT can affect lipid metabolism at different time points and significantly reduce the levels of cholesterol (CHO), triglyceride (TG), high-density lipid-cholesterol (HDL-C), and low-density lipid-cholesterol (LDL-C) in hyperlipidemic rats (P < 0.05 or P < 0.01); it can significantly reduce the levels of creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH), reduce the myocardial infarct size and myocardial ischemic area, and improve cardiac function. The results of myocardial histomorphology showed that HXHT could protect myocardial cells, relieve swelling, reduce the number of cardiac lipid droplets, and improve myocardial mitochondrial function. HXHT could significantly increase the levels of total superoxide dismutase (T-SOD) and succinate dehydrogenase (SDH) (P < 0.05 or P < 0.01), increase CuZn-superoxide dismutase (CuZn-SOD) and glutathione-peroxidase (GSH-Px) levels, and decrease the levels of malondialdehyde (MDA) (P < 0.05); it could increase the mRNA and protein expression levels of peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α), peroxisome proliferator-activated receptor alpha (PPARα), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (mtTFA) (P < 0.05 or P < 0.01), and increase the synthesis of mitochondrial DNA (mtDNA) (P < 0.01).ConclusionHXHT can reduce myocardial I/R injury in hyperlipidemic rats. The protective mechanisms may involve a reduction in blood lipids, enhancement of PGC-1α-PPARα pathway activity, and, subsequently, an increase in fatty acid β-oxidation, which may provide the required input for mitochondrial energy metabolism. HXHT can additionally enhance PGC-1α-NRF1-mtTFA pathway activity and, subsequently, increase the antioxidant capacity, promote mtDNA synthesis, and reduce mitochondrial damage. The two pathways use PGC-1α as the intersection point to protect mitochondrial structure and function, reduce I/R-induced injury, and improve cardiac function.

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Skeletal muscle PGC-1? modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice.

Publications

Skeletal muscle PGC-1α modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice.

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