Aging impairs insulin-stimulated glucose uptake in rat skeletal muscle via suppressing AMPKalpha.
Insufficient intracellular fat oxidation is an important contributor to aging-related insulin resistance, while the precise mechanism underlying is unclear. AMP-activated protein kinase (AMPK) is an important regulator of intracellular fat oxidation and was evidenced to play a key role in high-glucose and high-fat induced glucose intolerance. In the present study, we investigated whether altered AMPK expression or activity was also involved in aging-related insulin resistance. Insulin sensitivity of rats' skeletal muscles was evaluated using in-vitro glucose uptake assay. Activity of alpha subunit of AMPK (AMPKalpha) was evaluated by measuring the phosphorylation of both AMPKalpha (P-AMPKalpha) and acetyl-CoA carboxylase (P-ACC), while expression of AMPKalpha was assessed by determining the mRNA levels of AMPKalpha1 and AMPKalpha2, and protein contents of AMPKalpha. Compared with 4-month old rats, 24-month old rats exhibited obviously impaired insulin sensitivity. At the same time, AMPKalpha activity significantly decreased, while AMPKalpha expression did not alter during aging. Glucose transporter 4 expression also decreased in old rats. Compared with 24-month old rats, administration of the specific activator of AMPK, 5-aminoimidazole-4-carboxamide riboside (AICAR), significantly elevated AMPKalpha activity and GluT4 expression. Also, aging-related insulin resistance was significantly ameliorated by AICAR treatment. In conclusion, aging-related insulin resistance is associated with impaired AMPKalpha activity and could be ameliorated by AICAR, thus indicating a possible role of AMPK in aging-induced insulin resistance.
Qiang
Wan
W
Department of Internal Medicine, Shandong Provincial Hospital Shandong University, Jinan 250021, China.
Weiqiang
Kang
K
Qing
Zhu
Z
Pengju
Zhang
Z
Yi
Liu
L
D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000375:Aging / Q000502:physiology*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D008297:Male; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012265:Ribonucleotides / Q000494:pharmacology
D051275:Glucose Transporter Type 4; D007328:Insulin; D009097:Multienzyme Complexes; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase; C031143:AICA ribonucleotide; D005947:Glucose