Effects of four weeks intermittent hypoxia intervention on glucose homeostasis, insulin sensitivity, GLUT4 translocation, insulin receptor phosphorylation, and Akt activity in skeletal muscle of obese mice with type 2 diabetes

Abstract Aims/hypothesis Increased levels of branched-chain amino acids (BCAAs) are associated with type 2 diabetes pathogenesis. However, most metabolomic studies are limited to an analysis of plasma metabolites under fasting conditions, rather than the dynamic shift in response to a metabolic challenge. Moreover, metabolomic profiles of peripheral tissues involved in glucose homeostasis are scarce and the transcriptomic regulation of genes involved in BCAA catabolism is partially unknown. This study aimed to identify differences in circulating and skeletal muscle BCAA levels in response to an OGTT in individuals with normal glucose tolerance (NGT) or type 2 diabetes. Additionally, transcription factors involved in the regulation of the BCAA gene set were identified. Methods Plasma and vastus lateralis muscle biopsies were obtained from individuals with NGT or type 2 diabetes before and after an OGTT. Plasma and quadriceps muscles were harvested from skeletal muscle-specific Ppargc1a knockout and transgenic mice. BCAA-related metabolites and genes were assessed by LC-MS/MS and quantitative RT-PCR, respectively. Small interfering RNA and adenovirus-mediated overexpression techniques were used in primary human skeletal muscle cells to study the role of PPARGC1A and ESRRA in the expression of the BCAA gene set. Radiolabelled leucine was used to analyse the impact of oestrogen-related receptor α (ERRα) knockdown on leucine oxidation. Results Impairments in BCAA catabolism in people with type 2 diabetes under fasting conditions were exacerbated after a glucose load. Branched-chain keto acids were reduced 37–56% after an OGTT in the NGT group, whereas no changes were detected in individuals with type 2 diabetes. These changes were concomitant with a stronger correlation with glucose homeostasis biomarkers and downregulated expression of branched-chain amino acid transaminase 2, branched-chain keto acid dehydrogenase complex subunits and 69% of downstream BCAA-related genes in skeletal muscle. In primary human myotubes overexpressing peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α, encoded by PPARGC1A), 61% of the analysed BCAA genes were upregulated, while 67% were downregulated in the quadriceps of skeletal muscle-specific Ppargc1a knockout mice. ESRRA (encoding ERRα) silencing completely abrogated the PGC-1α-induced upregulation of BCAA-related genes in primary human myotubes. Conclusions/interpretation Metabolic inflexibility in type 2 diabetes impacts BCAA homeostasis and attenuates the decrease in circulating and skeletal muscle BCAA-related metabolites after a glucose challenge. Transcriptional regulation of BCAA genes in primary human myotubes via PGC-1α is ERRα-dependent. Graphical abstract

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Down-Regulation of Insulin Receptor Substrates (IRS)-1 and IRS-2 and Src Homologous and Collagen-Like Protein Shc Gene Expression by Insulin in Skeletal Muscle Is Not Associated with Insulin Resistance or Type 2 Diabetes

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem.87.1.8144 ◽

2002 ◽

Vol 87 (1) ◽

pp. 255-259 ◽

Cited By ~ 10

Author(s):

Xudong Huang ◽

Allan Vaag ◽

Mona Hansson ◽

Leif Groop

Keyword(s):

Gene Expression ◽

Insulin Resistance ◽

Type 2 Diabetes ◽

Skeletal Muscle ◽

Insulin Receptor ◽

Down Regulation ◽

Insulin Receptor Substrates

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Adipocyte PU.1 knockout promotes insulin sensitivity in HFD-fed obese mice

Scientific Reports ◽

10.1038/s41598-019-51196-8 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Denise E. Lackey ◽

Felipe C. G. Reis ◽

Roi Isaac ◽

Rizaldy C. Zapata ◽

Dalila El Ouarrat ◽

...

Keyword(s):

Gene Expression ◽

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Sensitivity ◽

Glucose Tolerance ◽

Target Genes ◽

Obese Mice ◽

Tissue Macrophage

Abstract Insulin resistance is a key feature of obesity and type 2 diabetes. PU.1 is a master transcription factor predominantly expressed in macrophages but after HFD feeding PU.1 expression is also significantly increased in adipocytes. We generated adipocyte specific PU.1 knockout mice using adiponectin cre to investigate the role of PU.1 in adipocyte biology, insulin and glucose homeostasis. In HFD-fed obese mice systemic glucose tolerance and insulin sensitivity were improved in PU.1 AKO mice and clamp studies indicated improvements in both adipose and liver insulin sensitivity. At the level of adipose tissue, macrophage infiltration and inflammation was decreased and glucose uptake was increased in PU.1 AKO mice compared with controls. While PU.1 deletion in adipocytes did not affect the gene expression of PPARg itself, we observed increased expression of PPARg target genes in eWAT from HFD fed PU.1 AKO mice compared with controls. Furthermore, we observed decreased phosphorylation at serine 273 in PU.1 AKO mice compared with fl/fl controls, indicating that PPARg is more active when PU.1 expression is reduced in adipocytes. Therefore, in obesity the increased expression of PU.1 in adipocytes modifies the adipocyte PPARg cistrome resulting in impaired glucose tolerance and insulin sensitivity.

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Effects of one‐legged high‐intensity interval training on insulin‐mediated skeletal muscle glucose homeostasis in patients with type 2 diabetes

Acta Physiologica ◽

10.1111/apha.13245 ◽

2019 ◽

Vol 226 (2) ◽

pp. e13245 ◽

Cited By ~ 7

Author(s):

Flemming Dela ◽

Arthur Ingersen ◽

Nynne B. Andersen ◽

Maria B. Nielsen ◽

Helga H. H. Petersen ◽

...

Keyword(s):

Type 2 Diabetes ◽

Skeletal Muscle ◽

Glucose Homeostasis ◽

High Intensity ◽

Interval Training ◽

High Intensity Interval Training ◽

High Intensity Interval

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Human skeletal muscle mitochondrial dynamics in relation to oxidative capacity and insulin sensitivity

Diabetologia ◽

10.1007/s00125-020-05335-w ◽

2020 ◽

Author(s):

Alexandre Houzelle ◽

Johanna A. Jörgensen ◽

Gert Schaart ◽

Sabine Daemen ◽

Nynke van Polanen ◽

...

Keyword(s):

Type 2 Diabetes ◽

Skeletal Muscle ◽

Quality Control ◽

Insulin Sensitivity ◽

Aerobic Capacity ◽

Mitochondrial Dynamics ◽

Oxidative Capacity ◽

Protein Balance ◽

Diabetes Patients

Abstract Aims/hypothesis Mitochondria operate in networks, adapting to external stresses and changes in cellular metabolic demand and are subject to various quality control mechanisms. On the basis of these traits, we here hypothesise that the regulation of mitochondrial networks in skeletal muscle is hampered in humans with compromised oxidative capacity and insulin sensitivity. Methods In a cross-sectional design, we compared four groups of participants (selected from previous studies) ranging in aerobic capacity and insulin sensitivity, i.e. participants with type 2 diabetes (n = 11), obese participants without diabetes (n = 12), lean individuals (n = 10) and endurance-trained athletes (n = 12); basal, overnight fasted muscle biopsies were newly analysed for the current study and we compared the levels of essential mitochondrial dynamics and quality control regulatory proteins in skeletal muscle tissue. Results Type 2 diabetes patients and obese participants were older than lean participants and athletes (58.6 ± 4.0 and 56.7 ± 7.2 vs 21.8 ± 2.5 and 25.1 ± 4.3 years, p < 0.001, respectively) and displayed a higher BMI (32.4 ± 3.7 and 31.0 ± 3.7 vs 22.1 ± 1.8 and 21.0 ± 1.5 kg/m2, p < 0.001, respectively) than lean individuals and endurance-trained athletes. Fission protein 1 (FIS1) and optic atrophy protein 1 (OPA1) protein content was highest in muscle from athletes and lowest in participants with type 2 diabetes and obesity, respectively (FIS1: 1.86 ± 0.79 vs 0.79 ± 0.51 AU, p = 0.002; and OPA1: 1.55 ± 0.64 vs 0.76 ± 0.52 AU, p = 0.014), which coincided with mitochondrial network fragmentation in individuals with type 2 diabetes, as assessed by confocal microscopy in a subset of type 2 diabetes patients vs endurance-trained athletes (n = 6). Furthermore, lean individuals and athletes displayed a mitonuclear protein balance that was different from obese participants and those with type 2 diabetes. Mitonuclear protein balance also associated with heat shock protein 60 (HSP60) protein levels, which were higher in athletes when compared with participants with obesity (p = 0.048) and type 2 diabetes (p = 0.002), indicative for activation of the mitochondrial unfolded protein response. Finally, OPA1, FIS1 and HSP60 correlated positively with aerobic capacity (r = 0.48, p = 0.0001; r = 0.55, p < 0.001 and r = 0.61, p < 0.0001, respectively) and insulin sensitivity (r = 0.40, p = 0.008; r = 0.44, p = 0.003 and r = 0.48, p = 0.001, respectively). Conclusions/interpretation Collectively, our data suggest that mitochondrial dynamics and quality control in skeletal muscle are linked to oxidative capacity in humans, which may play a role in the maintenance of muscle insulin sensitivity. Clinical Trial registry numbers NCT00943059, NCT01298375 and NL1888

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Changes in dietary sodium consumption modulate GLUT4 gene expression and early steps of insulin signaling

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00396.2003 ◽

2004 ◽

Vol 286 (4) ◽

pp. R779-R785 ◽

Cited By ~ 15

Author(s):

Maristela Mitiko Okamoto ◽

Dóris Hissako Sumida ◽

Carla Roberta Oliveira Carvalho ◽

Alessandra Martins Vargas ◽

Joel Cláudio Heimann ◽

...

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Adipose Tissue ◽

Insulin Sensitivity ◽

Insulin Receptor ◽

Tyrosine Phosphorylation ◽

Insulin Signaling ◽

Dietary Sodium ◽

Glut4 Translocation ◽

Glut4 Gene Expression

Previous studies have shown that chronic salt overload increases insulin sensitivity, while chronic salt restriction decreases it. In the present study we investigated the influence of dietary sodium on 1) GLUT4 gene expression, by Northern and Western blotting analysis; 2) in vivo GLUT4 protein translocation, by measuring the GLUT4 protein in plasma membrane and microsome, before and after insulin injection; and 3) insulin signaling, by analyzing basal and insulin-stimulated tyrosine phosphorylation of insulin receptor (IR)-β, insulin receptor substrate (IRS)-1, and IRS-2. Wistar rats were fed normal-sodium (NS-0.5%), low-sodium (LS-0.06%), or high-sodium diets (HS-3.12%) for 9 wk and were killed under pentobarbital anesthesia. Compared with NS rats, HS rats increased ( P < 0.05) the GLUT4 protein in adipose tissue and skeletal muscle, whereas GLUT4 mRNA was increased only in adipose tissue. GLUT4 expression was unchanged in LS rats compared with NS rats. The GLUT4 translocation in HS rats was higher ( P < 0.05) both in basal and insulin-stimulated conditions. On the other hand, LS rats did not increase the GLUT4 translocation after insulin stimulus. Compared with NS rats, LS rats showed reduced ( P < 0.01) basal and insulin-stimulated tyrosine phosphorylation of IRS-1 in skeletal muscle and IRS-2 in liver, whereas HS rats showed enhanced basal tyrosine phosphorylation of IRS-1 in skeletal muscle ( P < 0.05) and of IRS-2 in liver. In summary, increased insulin sensitivity in HS rats is related to increased GLUT4 gene expression, enhanced insulin signaling, and GLUT4 translocation, whereas decreased insulin sensitivity of LS rats does not involve changes in GLUT4 gene expression but is related to impaired insulin signaling.

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Loss of HIF-1α impairs GLUT4 translocation and glucose uptake by the skeletal muscle cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00597.2012 ◽

2014 ◽

Vol 306 (9) ◽

pp. E1065-E1076 ◽

Cited By ~ 31

Author(s):

Hidemitsu Sakagami ◽

Yuichi Makino ◽

Katsutoshi Mizumoto ◽

Tsubasa Isoe ◽

Yasutaka Takeda ◽

...

Keyword(s):

Type 2 Diabetes ◽

Skeletal Muscle ◽

Protein Kinase ◽

Glucose Metabolism ◽

Glucose Uptake ◽

Intracellular Signaling ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Glut4 Translocation

Defects in glucose uptake by the skeletal muscle cause diseases linked to metabolic disturbance such as type 2 diabetes. The molecular mechanism determining glucose disposal in the skeletal muscle in response to cellular stimuli including insulin, however, remains largely unknown. The hypoxia-inducible factor-1α (HIF-1α) is a transcription factor operating in the cellular adaptive response to hypoxic conditions. Recent studies have uncovered pleiotropic actions of HIF-1α in the homeostatic response to various cellular stimuli, including insulin under normoxic conditions. Thus we hypothesized HIF-1α is involved in the regulation of glucose metabolism stimulated by insulin in the skeletal muscle. To this end, we generated C2C12myocytes in which HIF-1α is knocked down by short-hairpin RNA and examined the intracellular signaling cascade and glucose uptake subsequent to insulin stimulation. Knockdown of HIF-1α expression in the skeletal muscle cells resulted in abrogation of insulin-stimulated glucose uptake associated with impaired mobilization of glucose transporter 4 (GLUT4) to the plasma membrane. Such defect seemed to be caused by reduced phosphorylation of the protein kinase B substrate of 160 kDa (AS160). AS160 phosphorylation and GLUT4 translocation by AMP-activated protein kinase activation were abrogated as well. In addition, expression of the constitutively active mutant of HIF-1α (CA-HIF-1α) or upregulation of endogenous HIF-1α in C2C12cells shows AS160 phosphorylation comparable to the insulin-stimulated level even in the absence of insulin. Accordingly GLUT4 translocation was increased in the cells expressing CA-HIF1α. Taken together, HIF-1α is a determinant for GLUT4-mediated glucose uptake in the skeletal muscle cells thus as a possible target to alleviate impaired glucose metabolism in, e.g., type 2 diabetes.

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