Cited by 167Metabolism, Diabetes, and CancerMuscle Physiology and DisordersMuscle metabolism and nutrition

The role of skeletal muscle Akt in the regulation of muscle mass and glucose homeostasis

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Jaiswal, N., Gavin, M.G., Quinn, W.J., Luongo, T.S., Gelfer, R.G., Baur, J.A., Titchenell, P.M.·2019·Molecular Metabolism

Abstract

OBJECTIVE: Skeletal muscle insulin signaling is a major determinant of muscle growth and glucose homeostasis. Protein kinase B/Akt plays a prominent role in mediating many of the metabolic effects of insulin. Mice and humans harboring systemic loss-of-function mutations in Akt2, the most abundant Akt isoform in metabolic tissues, are glucose intolerant and insulin resistant. Since the skeletal muscle accounts for a significant amount of postprandial glucose disposal, a popular hypothesis in the diabetes field suggests that a reduction in Akt, specifically in skeletal muscle, leads to systemic glucose intolerance and insulin resistance. Despite this common belief, the specific role of skeletal muscle Akt in muscle growth and insulin sensitivity remains undefined. METHODS: We generated multiple mouse models of skeletal muscle Akt deficiency to evaluate the role of muscle Akt signaling in vivo. The effects of these genetic perturbations on muscle mass, glucose homeostasis and insulin sensitivity were assessed using both in vivo and ex vivo assays. RESULTS: Surprisingly, mice lacking Akt2 alone in skeletal muscle displayed normal skeletal muscle insulin signaling, glucose tolerance, and insulin sensitivity despite a dramatic reduction in phosphorylated Akt. In contrast, deletion of both Akt isoforms (M-AktDKO) prevented downstream signaling and resulted in muscle atrophy. Despite the absence of Akt signaling, in vivo and ex vivo insulin-stimulated glucose uptake were normal in M-AktDKO mice. Similar effects on insulin sensitivity were observed in mice with prolonged deletion (4 weeks) of both skeletal muscle Akt isoforms selectively in adulthood. Conversely, short term deletion (2 weeks) of skeletal muscle specific Akt in adult muscles impaired insulin tolerance paralleling the effect observed by acute pharmacological inhibition of Akt in vitro. Mechanistically, chronic ablation of Akt induced mitochondrial dysfunction and activation of AMPK, which was required for insulin-stimulated glucose uptake in the absence of Akt. CONCLUSIONS: Together, these data indicate that chronic reduction in Akt activity alone in skeletal muscle is not sufficient to induce insulin resistance or prevent glucose uptake in all conditions. Therefore, since insulin-stimulated glucose disposal in skeletal muscle is markedly impaired in insulin-resistant states, we hypothesize that alterations in signaling molecules in addition to skeletal muscle Akt are necessary to perturb glucose tolerance and insulin sensitivity in vivo.

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Crossref · 10.1016/j.molmet.2019.08.001

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  1. [68]Moller L.L.V. Jaurji M. Nielsen I.L. Joseph G.A. Kjobsted R. Knudsen J.R. The role of p-21 activated kinases (PAKs) in glucose homeostasis and skeletal muscle glucose uptake BioRxiv 2019

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Authors
Jaiswal, N., Gavin, M. G., Quinn, W. J., Luongo, T. S., Gelfer, R. G., Baur, J. A., & Titchenell, P. M.
Affiliations
University of Pennsylvania (US)
Corresponding author
Titchenell, P.M.
Venue
Molecular Metabolism
Publisher
Elsevier BV
Published
2019-10
Volume
28
Pages
1-13
ISSN
2212-8778 (ISSN-L)
OpenAlex
W2964701486
Cited by
167
References
81
Citations by year
2026: 10 · 2025: 28 · 2024: 27 · 2023: 20 · 2022: 40 · 2021: 23 · 2020: 18 · 2019: 1
FWCI
6.78
Type
journal article
Language
en
Open access
Locations
  • Molecular Metabolism (publishedVersion, cc-by-nc-nd)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • University of Pennsylvania
  • National Institutes of Health (P30 19525, K01 111715)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Metabolism, Diabetes, and Cancer
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
Keywords
AKT2, Akt isoforms, muscle mass, muscle atrophy, glucose homeostasis, insulin resistance, insulin sensitivity, insulin-stimulated glucose uptake, mitochondrial dysfunction, AMPK, skeletal muscle insulin signaling
MeSH terms
Animals, Glucose, Homeostasis, Humans, Male, Weight Gain, Muscle, Skeletal, Proto-Oncogene Proteins c-akt, Mice

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