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The AMPK activator R419 improves exercise capacity and skeletal muscle insulin sensitivity in obese mice.

Marcinko K, Bujak AL, Lally JS, Ford RJ, Wong TH, Smith BK, Kemp BE, Jenkins Y, Li W, Kinsella TM, Hitoshi Y, Steinberg GR - Mol Metab (2015)

Bottom Line: In WT, but not AMPK-MKO mice, R419 improved treadmill running capacity.Treatment with R419 increased muscle electron transport chain content and activity in WT mice; effects which were blunted in AMPK-MKO mice.R419 also increases exercise capacity and improves mitochondrial function in obese WT mice; effects that are diminished in the absence of skeletal muscle AMPK.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario L8N 3Z5, Canada.

ABSTRACT

Objective: Skeletal muscle AMP-activated protein kinase (AMPK) is important for regulating glucose homeostasis, mitochondrial content and exercise capacity. R419 is a mitochondrial complex-I inhibitor that has recently been shown to acutely activate AMPK in myotubes. Our main objective was to examine whether R419 treatment improves insulin sensitivity and exercise capacity in obese insulin resistant mice and whether skeletal muscle AMPK was important for mediating potential effects.

Methods: Glucose homeostasis, insulin sensitivity, exercise capacity, and electron transport chain content/activity were examined in wildtype (WT) and AMPK β1β2 muscle-specific (AMPK-MKO) mice fed a high-fat diet (HFD) with or without R419 supplementation.

Results: There was no change in weight gain, adiposity, glucose tolerance or insulin sensitivity between HFD-fed WT and AMPK-MKO mice. In both HFD-fed WT and AMPK-MKO mice, R419 enhanced insulin tolerance, insulin-stimulated glucose disposal, skeletal muscle 2-deoxyglucose uptake, Akt phosphorylation and glucose transporter 4 (GLUT4) content independently of alterations in body mass. In WT, but not AMPK-MKO mice, R419 improved treadmill running capacity. Treatment with R419 increased muscle electron transport chain content and activity in WT mice; effects which were blunted in AMPK-MKO mice.

Conclusions: Treatment of obese mice with R419 improved skeletal muscle insulin sensitivity through a mechanism that is independent of skeletal muscle AMPK. R419 also increases exercise capacity and improves mitochondrial function in obese WT mice; effects that are diminished in the absence of skeletal muscle AMPK. These findings suggest that R419 may be a promising therapy for improving whole-body glucose homeostasis and exercise capacity.

No MeSH data available.


Related in: MedlinePlus

R419 improves insulin sensitivity and insulin-stimulated glucose disposal in skeletal muscle. (A) 12 h fasting blood glucose. (B) 12 h fasting serum insulin. (C) Glucose tolerance test (GTT) and GTT AUC. (D) Insulin tolerance test (ITT) and ITT AUC. (E) Glucose infusion rate (GIR) curve and clamped GIR. (F) Blood glucose concentration curve during clamp. (G) Glucose disposal rate (GDR). (H) 2-[14C]DG uptake in TA, EDL, and quadriceps (quad) muscle in WT and AMPK-MKO mice treated with or without R419. (I) Representative western blots of pAkt Ser473, pAkt Ser308, total Akt, GLUT4, and GAPDH. (J) Protein expression of pAkt Ser473 relative to Akt (from separate gels). (K) Protein expression pAkt Thr308 relative to Akt (from separate gels). (L) Protein expression of GLUT4 relative to GAPDH. Numbers within bars represent number of mice per group. Data are expressed as means ± SEM, †p < 0.05, ††p < 0.01, †††p < 0.001 for difference from HFD control vs HFD + R419, as determined by two-way ANOVA and Bonferroni post hoc test; ‡p < 0.05, ‡‡p < 0.01, ‡‡‡p < 0.001 for difference between HFD WT and HFD + R419 WT, and ¶p < 0.05, ¶¶¶p < 0.001 for difference between HFD AMPK-MKO and HFD + R419 MKO, as determined by two-way repeated measures ANOVA and Bonferroni post hoc test (C,D,E,F).
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fig2: R419 improves insulin sensitivity and insulin-stimulated glucose disposal in skeletal muscle. (A) 12 h fasting blood glucose. (B) 12 h fasting serum insulin. (C) Glucose tolerance test (GTT) and GTT AUC. (D) Insulin tolerance test (ITT) and ITT AUC. (E) Glucose infusion rate (GIR) curve and clamped GIR. (F) Blood glucose concentration curve during clamp. (G) Glucose disposal rate (GDR). (H) 2-[14C]DG uptake in TA, EDL, and quadriceps (quad) muscle in WT and AMPK-MKO mice treated with or without R419. (I) Representative western blots of pAkt Ser473, pAkt Ser308, total Akt, GLUT4, and GAPDH. (J) Protein expression of pAkt Ser473 relative to Akt (from separate gels). (K) Protein expression pAkt Thr308 relative to Akt (from separate gels). (L) Protein expression of GLUT4 relative to GAPDH. Numbers within bars represent number of mice per group. Data are expressed as means ± SEM, †p < 0.05, ††p < 0.01, †††p < 0.001 for difference from HFD control vs HFD + R419, as determined by two-way ANOVA and Bonferroni post hoc test; ‡p < 0.05, ‡‡p < 0.01, ‡‡‡p < 0.001 for difference between HFD WT and HFD + R419 WT, and ¶p < 0.05, ¶¶¶p < 0.001 for difference between HFD AMPK-MKO and HFD + R419 MKO, as determined by two-way repeated measures ANOVA and Bonferroni post hoc test (C,D,E,F).

Mentions: HFD AMPK-MKO mice had comparable fasting blood glucose and insulin levels compared to WT littermates irrespective of R419 treatment (Figure 2A,B). AMPK-MKO mice had higher fasting serum NEFA (Table 1). Glucose and insulin tolerance and corresponding areas under the curve (AUC) were also similar between AMPK-MKO and WT littermates fed a HFD (Figure 2C,D), indicating that a lack of AMPK does not promote the dysregulation of glucose homeostasis. Of note, the degree of glucose and insulin intolerance achieved in the HFD-fed mice of this study was comparable to many previous studies from our laboratory in which normal chow diet fed controls were also examined in parallel [33,38].


The AMPK activator R419 improves exercise capacity and skeletal muscle insulin sensitivity in obese mice.

Marcinko K, Bujak AL, Lally JS, Ford RJ, Wong TH, Smith BK, Kemp BE, Jenkins Y, Li W, Kinsella TM, Hitoshi Y, Steinberg GR - Mol Metab (2015)

R419 improves insulin sensitivity and insulin-stimulated glucose disposal in skeletal muscle. (A) 12 h fasting blood glucose. (B) 12 h fasting serum insulin. (C) Glucose tolerance test (GTT) and GTT AUC. (D) Insulin tolerance test (ITT) and ITT AUC. (E) Glucose infusion rate (GIR) curve and clamped GIR. (F) Blood glucose concentration curve during clamp. (G) Glucose disposal rate (GDR). (H) 2-[14C]DG uptake in TA, EDL, and quadriceps (quad) muscle in WT and AMPK-MKO mice treated with or without R419. (I) Representative western blots of pAkt Ser473, pAkt Ser308, total Akt, GLUT4, and GAPDH. (J) Protein expression of pAkt Ser473 relative to Akt (from separate gels). (K) Protein expression pAkt Thr308 relative to Akt (from separate gels). (L) Protein expression of GLUT4 relative to GAPDH. Numbers within bars represent number of mice per group. Data are expressed as means ± SEM, †p < 0.05, ††p < 0.01, †††p < 0.001 for difference from HFD control vs HFD + R419, as determined by two-way ANOVA and Bonferroni post hoc test; ‡p < 0.05, ‡‡p < 0.01, ‡‡‡p < 0.001 for difference between HFD WT and HFD + R419 WT, and ¶p < 0.05, ¶¶¶p < 0.001 for difference between HFD AMPK-MKO and HFD + R419 MKO, as determined by two-way repeated measures ANOVA and Bonferroni post hoc test (C,D,E,F).
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fig2: R419 improves insulin sensitivity and insulin-stimulated glucose disposal in skeletal muscle. (A) 12 h fasting blood glucose. (B) 12 h fasting serum insulin. (C) Glucose tolerance test (GTT) and GTT AUC. (D) Insulin tolerance test (ITT) and ITT AUC. (E) Glucose infusion rate (GIR) curve and clamped GIR. (F) Blood glucose concentration curve during clamp. (G) Glucose disposal rate (GDR). (H) 2-[14C]DG uptake in TA, EDL, and quadriceps (quad) muscle in WT and AMPK-MKO mice treated with or without R419. (I) Representative western blots of pAkt Ser473, pAkt Ser308, total Akt, GLUT4, and GAPDH. (J) Protein expression of pAkt Ser473 relative to Akt (from separate gels). (K) Protein expression pAkt Thr308 relative to Akt (from separate gels). (L) Protein expression of GLUT4 relative to GAPDH. Numbers within bars represent number of mice per group. Data are expressed as means ± SEM, †p < 0.05, ††p < 0.01, †††p < 0.001 for difference from HFD control vs HFD + R419, as determined by two-way ANOVA and Bonferroni post hoc test; ‡p < 0.05, ‡‡p < 0.01, ‡‡‡p < 0.001 for difference between HFD WT and HFD + R419 WT, and ¶p < 0.05, ¶¶¶p < 0.001 for difference between HFD AMPK-MKO and HFD + R419 MKO, as determined by two-way repeated measures ANOVA and Bonferroni post hoc test (C,D,E,F).
Mentions: HFD AMPK-MKO mice had comparable fasting blood glucose and insulin levels compared to WT littermates irrespective of R419 treatment (Figure 2A,B). AMPK-MKO mice had higher fasting serum NEFA (Table 1). Glucose and insulin tolerance and corresponding areas under the curve (AUC) were also similar between AMPK-MKO and WT littermates fed a HFD (Figure 2C,D), indicating that a lack of AMPK does not promote the dysregulation of glucose homeostasis. Of note, the degree of glucose and insulin intolerance achieved in the HFD-fed mice of this study was comparable to many previous studies from our laboratory in which normal chow diet fed controls were also examined in parallel [33,38].

Bottom Line: In WT, but not AMPK-MKO mice, R419 improved treadmill running capacity.Treatment with R419 increased muscle electron transport chain content and activity in WT mice; effects which were blunted in AMPK-MKO mice.R419 also increases exercise capacity and improves mitochondrial function in obese WT mice; effects that are diminished in the absence of skeletal muscle AMPK.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, 1280 Main St. W., Hamilton, Ontario L8N 3Z5, Canada.

ABSTRACT

Objective: Skeletal muscle AMP-activated protein kinase (AMPK) is important for regulating glucose homeostasis, mitochondrial content and exercise capacity. R419 is a mitochondrial complex-I inhibitor that has recently been shown to acutely activate AMPK in myotubes. Our main objective was to examine whether R419 treatment improves insulin sensitivity and exercise capacity in obese insulin resistant mice and whether skeletal muscle AMPK was important for mediating potential effects.

Methods: Glucose homeostasis, insulin sensitivity, exercise capacity, and electron transport chain content/activity were examined in wildtype (WT) and AMPK β1β2 muscle-specific (AMPK-MKO) mice fed a high-fat diet (HFD) with or without R419 supplementation.

Results: There was no change in weight gain, adiposity, glucose tolerance or insulin sensitivity between HFD-fed WT and AMPK-MKO mice. In both HFD-fed WT and AMPK-MKO mice, R419 enhanced insulin tolerance, insulin-stimulated glucose disposal, skeletal muscle 2-deoxyglucose uptake, Akt phosphorylation and glucose transporter 4 (GLUT4) content independently of alterations in body mass. In WT, but not AMPK-MKO mice, R419 improved treadmill running capacity. Treatment with R419 increased muscle electron transport chain content and activity in WT mice; effects which were blunted in AMPK-MKO mice.

Conclusions: Treatment of obese mice with R419 improved skeletal muscle insulin sensitivity through a mechanism that is independent of skeletal muscle AMPK. R419 also increases exercise capacity and improves mitochondrial function in obese WT mice; effects that are diminished in the absence of skeletal muscle AMPK. These findings suggest that R419 may be a promising therapy for improving whole-body glucose homeostasis and exercise capacity.

No MeSH data available.


Related in: MedlinePlus