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Muscle-specific knockout of PKC-λ impairs glucose transport and induces metabolic and diabetic syndromes
Robert V. Farese, … , Ursula Braun, Michael Leitges
Robert V. Farese, … , Ursula Braun, Michael Leitges
Published August 1, 2007
Citation Information: J Clin Invest. 2007;117(8):2289-2301. https://doi.org/10.1172/JCI31408.
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Research Article Metabolism

Muscle-specific knockout of PKC-λ impairs glucose transport and induces metabolic and diabetic syndromes

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Abstract

Obesity, the metabolic syndrome, and type 2 diabetes mellitus (T2DM) are major global health problems. Insulin resistance is frequently present in these disorders, but the causes and effects of such resistance are unknown. Here, we generated mice with muscle-specific knockout of the major murine atypical PKC (aPKC), PKC-λ, a postulated mediator for insulin-stimulated glucose transport. Glucose transport and translocation of glucose transporter 4 (GLUT4) to the plasma membrane were diminished in muscles of both homozygous and heterozygous PKC-λ knockout mice and were accompanied by systemic insulin resistance; impaired glucose tolerance or diabetes; islet β cell hyperplasia; abdominal adiposity; hepatosteatosis; elevated serum triglycerides, FFAs, and LDL-cholesterol; and diminished HDL-cholesterol. In contrast to the defective activation of muscle aPKC, insulin signaling and actions were intact in muscle, liver, and adipocytes. These findings demonstrate the importance of aPKC in insulin-stimulated glucose transport in muscles of intact mice and show that insulin resistance and resultant hyperinsulinemia owing to a specific defect in muscle aPKC is sufficient to induce abdominal obesity and other lipid abnormalities of the metabolic syndrome and T2DM. These findings are particularly relevant because humans who have obesity, impaired glucose tolerance, and T2DM reportedly have defective activation and/or diminished levels of muscle aPKC.

Authors

Robert V. Farese, Mini P. Sajan, Hong Yang, Pengfei Li, Steven Mastorides, William R. Gower Jr., Sonali Nimal, Cheol Soo Choi, Sheene Kim, Gerald I. Shulman, C. Ronald Kahn, Ursula Braun, Michael Leitges

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Figure 1

Effects of homozygous and heterozygous muscle-specific KO of PKC-λ on basal and insulin-stimulated glucose transport in vivo (A–D), glucose transport in vitro (E), and plasma membrane (PM) GLUT4 levels (F).

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Effects of homozygous and heterozygous muscle-specific KO of PKC-λ on ba...
Equal numbers of 5-month-old male and female mice were grouped (results were indistinguishable and therefore pooled), and after an overnight fast, glucose transport and GLUT4 translocation were measured. Glucose uptake was measured in vastus lateralis (VL) and heart muscle during 10 minutes insulin or vehicle treatment (A–D). (E) Glucose transport was measured in isolated extensor digitorum longus (EDL) and soleus muscles obtained from male mice. (F) Vastus lateralis and gastrocnemius muscles were used to prepare plasma membranes. Values are mean ± SEM. n for each group is shown in parentheses. Insets show immunoreactive levels of total cellular aPKC (A, B, and E) or plasma membrane and internal membrane (IM) GLUT4 levels or IGF1 receptor (IGF1R) and insulin receptor (InsR) β subunit levels as markers to show equal plasma membrane loading (F) in WT (Cre–loxP–/–), heterozygous KO (Cre+loxP+/–; Het KO), and homozygous KO (Cre+loxP+/+; Homo KO) groups. aPKC levels in muscles of heterozygous control (Cre–loxP+/–; Het con) and Cre control (Cre+loxP–/–; Cre con) mice were the same as in WT mice (not shown). *P < 0.05; **P < 0.01; ***P < 0.001.

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ISSN: 0021-9738 (print), 1558-8238 (online)

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