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Muscle-specific IRS-1 Ser->Ala transgenic mice are protected from fat-induced insulin resistance in skeletal muscle.

Morino K, Neschen S, Bilz S, Sono S, Tsirigotis D, Reznick RM, Moore I, Nagai Y, Samuel V, Sebastian D, White M, Philbrick W, Shulman GI - Diabetes (2008)

Bottom Line: Tg IRS-1 Ser-->Ala mice were protected from fat-induced insulin resistance, as reflected by lower plasma glucose concentrations during a glucose tolerance test and increased insulin-stimulated muscle glucose uptake during a hyperinsulinemic-euglycemic clamp.Furthermore, Tg IRS-1 Ser-->Ala mice displayed a significant increase in insulin-stimulated IRS-1-associated phosphatidylinositol 3-kinase activity and Akt phosphorylation in skeletal muscle in vivo compared with WT control littermates.These data demonstrate that serine phosphorylation of IRS-1 plays an important role in mediating fat-induced insulin resistance in skeletal muscle in vivo.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA.

ABSTRACT

Objective: Insulin resistance in skeletal muscle plays a critical role in the pathogenesis of type 2 diabetes, yet the cellular mechanisms responsible for insulin resistance are poorly understood. In this study, we examine the role of serine phosphorylation of insulin receptor substrate (IRS)-1 in mediating fat-induced insulin resistance in skeletal muscle in vivo.

Research design and methods: To directly assess the role of serine phosphorylation in mediating fat-induced insulin resistance in skeletal muscle, we generated muscle-specific IRS-1 Ser(302), Ser(307), and Ser(612) mutated to alanine (Tg IRS-1 Ser-->Ala) and IRS-1 wild-type (Tg IRS-1 WT) transgenic mice and examined insulin signaling and insulin action in skeletal muscle in vivo.

Results: Tg IRS-1 Ser-->Ala mice were protected from fat-induced insulin resistance, as reflected by lower plasma glucose concentrations during a glucose tolerance test and increased insulin-stimulated muscle glucose uptake during a hyperinsulinemic-euglycemic clamp. In contrast, Tg IRS-1 WT mice exhibited no improvement in glucose tolerance after high-fat feeding. Furthermore, Tg IRS-1 Ser-->Ala mice displayed a significant increase in insulin-stimulated IRS-1-associated phosphatidylinositol 3-kinase activity and Akt phosphorylation in skeletal muscle in vivo compared with WT control littermates.

Conclusions: These data demonstrate that serine phosphorylation of IRS-1 plays an important role in mediating fat-induced insulin resistance in skeletal muscle in vivo.

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Related in: MedlinePlus

Generation of Tg IRS-1 Ser→Ala mice. A: Serine phosphorylation of IRS-1 protein in skeletal muscle. Serine phosphorylation of IRS-1 and protein expression of IRS-1 were analyzed by Western blotting. All mice were killed at age 16 weeks. The high-fat diet group was fed for 8 weeks. B: Vector construct of the mutated IRS-1 gene (Ser302, Ser307, and Ser612 to Ala mutant) for Tg IRS-1 Ser→Ala and WT IRS-1 gene for Tg IRS-1 WT. C: Comparison of IRS-1 expression in different insulin-targeting tissues. Protein expression of total IRS-1 and actin were analyzed by Western blotting. D: Comparison of IRS-1 expression between Tg IRS-1 Ser→Ala and Tg IRS-1 WT mice. Each graph was expressed as fold difference to their littermates. GAS, Musculus gastrocnemius; QD, Musclus quadriceps; TA, Musculus tibialis anterior; WAT, white adipose tissue.
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f1: Generation of Tg IRS-1 Ser→Ala mice. A: Serine phosphorylation of IRS-1 protein in skeletal muscle. Serine phosphorylation of IRS-1 and protein expression of IRS-1 were analyzed by Western blotting. All mice were killed at age 16 weeks. The high-fat diet group was fed for 8 weeks. B: Vector construct of the mutated IRS-1 gene (Ser302, Ser307, and Ser612 to Ala mutant) for Tg IRS-1 Ser→Ala and WT IRS-1 gene for Tg IRS-1 WT. C: Comparison of IRS-1 expression in different insulin-targeting tissues. Protein expression of total IRS-1 and actin were analyzed by Western blotting. D: Comparison of IRS-1 expression between Tg IRS-1 Ser→Ala and Tg IRS-1 WT mice. Each graph was expressed as fold difference to their littermates. GAS, Musculus gastrocnemius; QD, Musclus quadriceps; TA, Musculus tibialis anterior; WAT, white adipose tissue.

Mentions: To evaluate previous reports regarding increased serine phosphorylation on IRS-1 in skeletal muscle, we tested Ser307 and Ser612 residues using high-fat–fed mice and ob/ob mice. We found slight increases on Ser307 and Ser612 but decreased total IRS-1 protein in ob/ob mice (Fig. 1A).


Muscle-specific IRS-1 Ser->Ala transgenic mice are protected from fat-induced insulin resistance in skeletal muscle.

Morino K, Neschen S, Bilz S, Sono S, Tsirigotis D, Reznick RM, Moore I, Nagai Y, Samuel V, Sebastian D, White M, Philbrick W, Shulman GI - Diabetes (2008)

Generation of Tg IRS-1 Ser→Ala mice. A: Serine phosphorylation of IRS-1 protein in skeletal muscle. Serine phosphorylation of IRS-1 and protein expression of IRS-1 were analyzed by Western blotting. All mice were killed at age 16 weeks. The high-fat diet group was fed for 8 weeks. B: Vector construct of the mutated IRS-1 gene (Ser302, Ser307, and Ser612 to Ala mutant) for Tg IRS-1 Ser→Ala and WT IRS-1 gene for Tg IRS-1 WT. C: Comparison of IRS-1 expression in different insulin-targeting tissues. Protein expression of total IRS-1 and actin were analyzed by Western blotting. D: Comparison of IRS-1 expression between Tg IRS-1 Ser→Ala and Tg IRS-1 WT mice. Each graph was expressed as fold difference to their littermates. GAS, Musculus gastrocnemius; QD, Musclus quadriceps; TA, Musculus tibialis anterior; WAT, white adipose tissue.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2551673&req=5

f1: Generation of Tg IRS-1 Ser→Ala mice. A: Serine phosphorylation of IRS-1 protein in skeletal muscle. Serine phosphorylation of IRS-1 and protein expression of IRS-1 were analyzed by Western blotting. All mice were killed at age 16 weeks. The high-fat diet group was fed for 8 weeks. B: Vector construct of the mutated IRS-1 gene (Ser302, Ser307, and Ser612 to Ala mutant) for Tg IRS-1 Ser→Ala and WT IRS-1 gene for Tg IRS-1 WT. C: Comparison of IRS-1 expression in different insulin-targeting tissues. Protein expression of total IRS-1 and actin were analyzed by Western blotting. D: Comparison of IRS-1 expression between Tg IRS-1 Ser→Ala and Tg IRS-1 WT mice. Each graph was expressed as fold difference to their littermates. GAS, Musculus gastrocnemius; QD, Musclus quadriceps; TA, Musculus tibialis anterior; WAT, white adipose tissue.
Mentions: To evaluate previous reports regarding increased serine phosphorylation on IRS-1 in skeletal muscle, we tested Ser307 and Ser612 residues using high-fat–fed mice and ob/ob mice. We found slight increases on Ser307 and Ser612 but decreased total IRS-1 protein in ob/ob mice (Fig. 1A).

Bottom Line: Tg IRS-1 Ser-->Ala mice were protected from fat-induced insulin resistance, as reflected by lower plasma glucose concentrations during a glucose tolerance test and increased insulin-stimulated muscle glucose uptake during a hyperinsulinemic-euglycemic clamp.Furthermore, Tg IRS-1 Ser-->Ala mice displayed a significant increase in insulin-stimulated IRS-1-associated phosphatidylinositol 3-kinase activity and Akt phosphorylation in skeletal muscle in vivo compared with WT control littermates.These data demonstrate that serine phosphorylation of IRS-1 plays an important role in mediating fat-induced insulin resistance in skeletal muscle in vivo.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA.

ABSTRACT

Objective: Insulin resistance in skeletal muscle plays a critical role in the pathogenesis of type 2 diabetes, yet the cellular mechanisms responsible for insulin resistance are poorly understood. In this study, we examine the role of serine phosphorylation of insulin receptor substrate (IRS)-1 in mediating fat-induced insulin resistance in skeletal muscle in vivo.

Research design and methods: To directly assess the role of serine phosphorylation in mediating fat-induced insulin resistance in skeletal muscle, we generated muscle-specific IRS-1 Ser(302), Ser(307), and Ser(612) mutated to alanine (Tg IRS-1 Ser-->Ala) and IRS-1 wild-type (Tg IRS-1 WT) transgenic mice and examined insulin signaling and insulin action in skeletal muscle in vivo.

Results: Tg IRS-1 Ser-->Ala mice were protected from fat-induced insulin resistance, as reflected by lower plasma glucose concentrations during a glucose tolerance test and increased insulin-stimulated muscle glucose uptake during a hyperinsulinemic-euglycemic clamp. In contrast, Tg IRS-1 WT mice exhibited no improvement in glucose tolerance after high-fat feeding. Furthermore, Tg IRS-1 Ser-->Ala mice displayed a significant increase in insulin-stimulated IRS-1-associated phosphatidylinositol 3-kinase activity and Akt phosphorylation in skeletal muscle in vivo compared with WT control littermates.

Conclusions: These data demonstrate that serine phosphorylation of IRS-1 plays an important role in mediating fat-induced insulin resistance in skeletal muscle in vivo.

Show MeSH
Related in: MedlinePlus