title: Vitamin D and skeletal muscle strength and endurance in COPD.
abstract: It is not known whether vitamin D levels make a significant contribution to muscle dysfunction in chronic obstructive pulmonary disease (COPD). In 104 COPD patients (mean±sd forced expiratory volume in 1 s 44±22 % predicted) and 100 age- and sex-matched controls, serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)(2)D) and parathyroid hormone (PTH) levels were measured and related to quadriceps strength and endurance. In a subset of 26 patients and 13 controls, quadriceps biopsy was performed and mRNA expression of myogenic regulatory factors (mrf) and fibre-specific myosin heavy chains (MHC) was determined. COPD patients were weaker and less physically active than controls. 25(OH)D levels were similar in both groups (48.5±25.5 nmol·L(-1) COPD versus 55.4±28.3 nmol·L(-1) control, p=0.07) but PTH levels were significantly higher in patients (5.2±2.3 pmol·mL(-1) versus 4.4±2.0 pmol·L(-1), p=0.01). 1,25(OH)D was significantly correlated with strength in controls, but not in COPD patients and not with quadriceps endurance assessed using repetitive magnetic stimulation in COPD (n=35) or control (n=35) subjects. In controls, but not COPD patients, muscle biopsy analysis showed a negative relationship between 25(OH)D and MHCIIa expression (r(2)=0.5, p=0.01) and a positive relationship between mrf4 and MHCIIa expression (r(2)=0.5, p=0.009), and myogenic regulatory factor myf5 and MHCI expression (r(2)=0.72, p=0.004). In contrast with healthy controls, muscle strength is not associated with vitamin D levels in COPD, which may represent vitamin D resistance.
authors.affiliation: National Institute for Health Research Respiratory Disease Biomedical Research Unit at the Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: Abigail S
authors.initials: AS
authors.lastname: Jackson
authors.forename: Dinesh
authors.initials: D
authors.lastname: Shrikrishna
authors.forename: Julia L
authors.initials: JL
authors.lastname: Kelly
authors.forename: Samuel V
authors.initials: SV
authors.lastname: Kemp
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hart
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.forename: Paul
authors.initials: P
authors.lastname: Kemp
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
mesh_terms: D000368:Aged; D000465:Algorithms; D001706:Biopsy; D002112:Calcifediol / Q000097:blood*; D002117:Calcitriol / Q000097:blood*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010281:Parathyroid Hormone / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000378:metabolism
chemical_list: D010281:Parathyroid Hormone; D018995:Myosin Heavy Chains; D002117:Calcitriol; D002112:Calcifediol