title: The effects of osteoarthritis and age on skeletal muscle strength, Na+-K+-ATPase content, gene and isoform expression.
abstract: Knee osteoarthritis (OA) is a debilitating disorder prevalent in older populations that is accompanied by declines in muscle mass, strength, and physical activity. In skeletal muscle, the Na(+)-K(+) pump (NKA) is pivotal in ion homeostasis and excitability and is modulated by disuse and exercise training. This study examined the effects of OA and aging on muscle NKA in 36 older adults (range 55-81 yr), including 19 with OA (69.9 ± 6.5 yr, mean ± SD) and 17 asymptomatic controls (CON, 66.8 ± 6.4 yr). Participants completed knee extensor strength testing and a physical activity questionnaire. A vastus lateralis muscle biopsy was analyzed for NKA content ([(3)H]ouabain binding sites), α1-3- and β1-3-isoform protein abundance (immunoblotting), and mRNA (real-time RT-PCR). The association between age and NKA content was investigated within the OA and CON groups and in pooled data. The NKA content was also contrasted between subgroups below and above the median age of 68.5 yr. OA had lower strength (-40.8%, P = 0.005), but higher NKA α2- (∼34%, P = 0.006) and α3-protein (100%, P = 0.016) abundance than CON and performed more incidental physical activity (P = 0.035). No differences were found between groups for NKA content, abundance of other NKA isoforms, or gene expression. There was a negative correlation between age and NKA content within OA (r = -0.63, P = 0.03) and with both groups combined (r = -0.47, P = 0.038). The NKA content was 25.5% lower in the older (69-81 yr) than in the younger (55-68 yr) subgroup. Hence older age, but not knee OA, was related to lowered muscle NKA content in older adults.
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL Melbourne, Victoria, Australia;
authors.forename: Ben D
authors.initials: BD
authors.lastname: Perry
authors.forename: Pazit
authors.initials: P
authors.lastname: Levinger
authors.forename: Fabio R
authors.initials: FR
authors.lastname: Serpiello
authors.forename: Marissa K
authors.initials: MK
authors.lastname: Caldow
authors.forename: David
authors.initials: D
authors.lastname: Cameron-Smith
authors.forename: John R
authors.initials: JR
authors.lastname: Bartlett
authors.forename: Julian A
authors.initials: JA
authors.lastname: Feller
authors.forename: Neil R
authors.initials: NR
authors.lastname: Bergman
authors.forename: Itamar
authors.initials: I
authors.lastname: Levinger
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McKenna
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D016022:Case-Control Studies; D027682:Cation Transport Proteins / Q000378:metabolism; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D017079:Exercise Tolerance; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000201:enzymology* / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism; D012737:Sex Factors; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D011795:Surveys and Questionnaires
chemical_list: C488756:ATP1A3 protein, human; C503551:ATP1B1 protein, human; C504190:ATP1B2 protein, human; C519304:ATP1B3 protein, human; D027682:Cation Transport Proteins; D015816:Cell Adhesion Molecules, Neuronal; D007527:Isoenzymes; D012333:RNA, Messenger; C499076:ATP1A1 protein, human; C498531:ATP1A2 protein, human; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Na+-K+ pump; aging; excitability; exercise; osteoarthritis; physical activity