PT  - JOURNAL ARTICLE
AU  - Abigail S. Jackson
AU  - Dinesh Shrikrishna
AU  - Julia L. Kelly
AU  - Nicholas Hart
AU  - John Moxham
AU  - Michael I. Polkey
AU  - Paul Kemp
AU  - Nicholas S. Hopkinson
TI  - Vitamin D and skeletal muscle strength and endurance in COPD
AID  - 10.1183/09031936.00043112
DP  - 2013 Feb 01
TA  - European Respiratory Journal
PG  - 309--316
VI  - 41
IP  - 2
4099  - http://erj.ersjournals.com/content/41/2/309.short
4100  - http://erj.ersjournals.com/content/41/2/309.full
SO  - Eur Respir J2013 Feb 01; 41
AB  - 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)2D) 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 (r2=0.5, p=0.01) and a positive relationship between mrf4 and MHCIIa expression (r2=0.5, p=0.009), and myogenic regulatory factor myf5 and MHCI expression (r2=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.