Background Aged skeletal muscle is characterized by an increased incidence of metabolic and functional disorders, which if allowed to proceed unchecked can lead to increased morbidity and mortality. The mechanism(s) underlying the development of these disorders in aging skeletal muscle are not well understood. Protein kinase B (Akt/PKB) is an important regulator of cellular metabolism and survival, but it is unclear if aged muscle exhibits alterations in Akt function. Here we report a novel dysfunction of Akt in aging muscle, which may relate to S-nitrosylation and can be prevented by acetaminophen intervention. Principal Findings Compared to 6- and 27-month rats, the phosphorylation of Akt (Ser473 and Thr308) was higher in soleus muscles of very aged rats (33-months). Paradoxically, these increases in Akt phosphorylation were associated with diminished mammalian target of rapamycin (mTOR) phosphorylation, along with decreased levels of insulin receptor beta (IR-β), phosphoinositide 3-kinase (PI3K), phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and phosphorylation of phosphoinositide-dependent kinase-1 (PDK1) (Ser241). In vitro Akt kinase measurements and ex vivo muscle incubation experiments demonstrated age-related impairments of Akt kinase activity, which were associated with increases in Akt S-nitrosylation and inducible nitric oxide synthase (iNOS). Impairments in Akt function occurred parallel to increases in myocyte apoptosis and decreases in myocyte size and the expression of myosin and actin. These age-related disorders were attenuated by treating aged (27-month) animals with acetaminophen (30 mg/kg body weight/day) for 6-months. Conclusions These data demonstrate that Akt dysfunction and increased S-nitrosylation of Akt may contribute to age-associated disorders in skeletal muscle and that acetaminophen may be efficacious for the treatment of age-related muscle dysfunction.
References
[1]
Jejurikar SS, Henkelman EA, Cederna PS, Marcelo CL, Urbanchek MG, et al. (2006) Aging increases the susceptibility of skeletal muscle derived satellite cells to apoptosis. Exp Gerontol 41: 828–836.
[2]
Balagopal P, Rooyackers OE, Adey DB, Ades PA, Nair KS (1997) Effects of aging on in vivo synthesis of skeletal muscle myosin heavy-chain and sarcoplasmic protein in humans. Am J Physiol 273: E790–800.
[3]
Brown M (1987) Change in fibre size, not number, in ageing skeletal muscle. Age Ageing 16: 244–248.
[4]
Faulkner JA, Larkin LM, Claflin DR, Brooks SV (2007) Age-related changes in the structure and function of skeletal muscles. Clin Exp Pharmacol Physiol 34: 1091–1096.
[5]
Gupte AA, Bomhoff GL, Geiger PC (2008) Age-related differences in skeletal muscle insulin signaling: the role of stress kinases and heat shock proteins. J Appl Physiol 105: 839–848.
[6]
Leger B, Derave W, De Bock K, Hespel P, Russell AP (2008) Human sarcopenia reveals an increase in SOCS-3 and myostatin and a reduced efficiency of Akt phosphorylation. Rejuvenation Res 11: 163–175B.
[7]
Bodine SC, Stitt TN, Gonzalez M, Kline WO, Stover GL, et al. (2001) Akt/mTOR pathway is a crucial regulator of skeletal muscle hypertrophy and can prevent muscle atrophy in vivo. Nat Cell Biol 3: 1014–1019.
[8]
Cross DA, Alessi DR, Cohen P, Andjelkovich M, Hemmings BA (1995) Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B. Nature 378: 785–789.
[9]
Nave BT, Ouwens M, Withers DJ, Alessi DR, Shepherd PR (1999) Mammalian target of rapamycin is a direct target for protein kinase B: identification of a convergence point for opposing effects of insulin and amino-acid deficiency on protein translation. Biochem J 344 Pt 2: 427–431.
[10]
Alessi DR, James SR, Downes CP, Holmes AB, Gaffney PR, et al. (1997) Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha. Curr Biol 7: 261–269.
[11]
Sarbassov DD, Guertin DA, Ali SM, Sabatini DM (2005) Phosphorylation and regulation of Akt/PKB by the rictor-mTOR complex. Science 307: 1098–1101.
[12]
Scheid MP, Marignani PA, Woodgett JR (2002) Multiple phosphoinositide 3-kinase-dependent steps in activation of protein kinase B. Mol Cell Biol 22: 6247–6260.
[13]
Ono H, Katagiri H, Funaki M, Anai M, Inukai K, et al. (2001) Regulation of phosphoinositide metabolism, Akt phosphorylation, and glucose transport by PTEN (phosphatase and tensin homolog deleted on chromosome 10) in 3T3-L1 adipocytes. Mol Endocrinol 15: 1411–1422.
[14]
Mahimainathan L, Das F, Venkatesan B, Choudhury GG (2006) Mesangial cell hypertrophy by high glucose is mediated by downregulation of the tumor suppressor PTEN. Diabetes 55: 2115–2125.
[15]
Yasukawa T, Tokunaga E, Ota H, Sugita H, Martyn JA, et al. (2005) S-nitrosylation-dependent inactivation of Akt/protein kinase B in insulin resistance. J Biol Chem 280: 7511–7518.
[16]
Carvalho-Filho MA, Ueno M, Hirabara SM, Seabra AB, Carvalheira JB, et al. (2005) S-nitrosation of the insulin receptor, insulin receptor substrate 1, and protein kinase B/Akt: a novel mechanism of insulin resistance. Diabetes 54: 959–967.
[17]
Lu XM, Lu M, Tompkins RG, Fischman AJ (2005) Site-specific detection of S-nitrosylated PKB alpha/Akt1 from rat soleus muscle using CapLC-Q-TOF(micro) mass spectrometry. J Mass Spectrom 40: 1140–1148.
[18]
Wu MD, Kimura M, Inafuku S, Ishigami H (1997) Effect of aging on the expression of iNOS and cell death in the mouse cochlear spiral ganglion. Okajimas Folia Anat Jpn 74: 155–165.
[19]
Fujimoto M, Shimizu N, Kunii K, Martyn JA, Ueki K, et al. (2005) A role for iNOS in fasting hyperglycemia and impaired insulin signaling in the liver of obese diabetic mice. Diabetes 54: 1340–1348.
[20]
Pacheco ME, Beltran A, Redondo J, Manso AM, Alonso MJ, et al. (2006) High glucose enhances inducible nitric oxide synthase expression. Role of protein kinase C-betaII. Eur J Pharmacol 538: 115–123.
[21]
Kurowski TG, Lin Y, Luo Z, Tsichlis PN, Buse MG, et al. (1999) Hyperglycemia inhibits insulin activation of Akt/protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle. Diabetes 48: 658–663.
[22]
Oku A, Nawano M, Ueta K, Fujita T, Umebayashi I, et al. (2001) Inhibitory effect of hyperglycemia on insulin-induced Akt/protein kinase B activation in skeletal muscle. Am J Physiol Endocrinol Metab 280: E816–824.
[23]
Wu M, Desai DH, Kakarla SK, Katta A, Paturi S, et al. (2009) Acetaminophen prevents aging-associated hyperglycemia in aged rats: effect of aging-associated hyperactivation of p38-MAPK and ERK1/2. Diabetes Metab Res Rev 25: 279–286.
[24]
Rice KM, Wu M, Blough ER (2008) Aortic Aging in the Fischer 344/NNiaHSd x Brown Norway/BiNia Rat. J Pharmacol Sci 108: 393–398.
[25]
Casamayor A, Morrice NA, Alessi DR (1999) Phosphorylation of Ser-241 is essential for the activity of 3-phosphoinositide-dependent protein kinase-1: identification of five sites of phosphorylation in vivo. Biochem J 342 (Pt 2): 287–292.
[26]
Caiozzo VJ, Baker MJ, Herrick RE, Tao M, Baldwin KM (1994) Effect of spaceflight on skeletal muscle: mechanical properties and myosin isoform content of a slow muscle. J Appl Physiol 76: 1764–1773.
[27]
Simon DI, Mullins ME, Jia L, Gaston B, Singel DJ, et al. (1996) Polynitrosylated proteins: characterization, bioactivity, and functional consequences. Proc Natl Acad Sci U S A 93: 4736–4741.
[28]
Ryu YS, Lee JH, Seok JH, Hong JH, Lee YS, et al. (2000) Acetaminophen inhibits iNOS gene expression in RAW 264.7 macrophages: differential regulation of NF-kappaB by acetaminophen and salicylates. Biochem Biophys Res Commun 272: 758–764.
[29]
Birle D, Bottini N, Williams S, Huynh H, deBelle I, et al. (2002) Negative feedback regulation of the tumor suppressor PTEN by phosphoinositide-induced serine phosphorylation. J Immunol 169: 286–291.
[30]
Crettaz M, Prentki M, Zaninetti D, Jeanrenaud B (1980) Insulin resistance in soleus muscle from obese Zucker rats. Involvement of several defective sites. Biochem J 186: 525–534.
[31]
Segal SS, Faulkner JA (1985) Temperature-dependent physiological stability of rat skeletal muscle in vitro. Am J Physiol 248: C265–270.
