The association between musculoskeletal pain and circulating ornithine: A population-based study

Abstract

Objective. Based on several previous clinical studies, we hypothesized that ornithine levels are different among subjects with persistent musculoskeletal pain compared with other subjects in the population. Design. The study sample consisted of 221 adults with nonpersistent pain, 76 with persistent pain, and 61 with no pain. Concentrations of glutamic acid, ornithine, citrulline, arginine, proline, and spermidine were analyzed using a mass spectrometer. Setting. Lapinlahti municipality in Finland. Results. For the subjects with no pain, nonpersistent pain, and persistent pain, the ornithine concentrations for men were 85.3 mmol/L (S=528.9 mmol/L), 98.9 mmol/L (S=537.8 mmol/L), and 102.1 mmol/L (S=537.1 mmol/L; P=0.033), respectively. The corresponding concentrations for women were 82.8 mmol/L (S=525.2 mmol/L), 83.7 mmol/L (S=527.8 mmol/L), and 103.2 mmol/L (S=534.9 mmol/L; P=0.0031). There were no significant differences between the pain groups for any of the other investigated amino acids. Relative sex-specific ornithine concentration adjusted for age, glomerular filtration rate, smoking, body mass index, physical activity, and depressive symptoms was associated with pain (P=0.025), the ornithine level being higher in the persistent pain group than in the no pain (P=0.006) and nonpersistent pain (P=0.032) groups. Conclusion. Ornithine levels are elevated in general population subjects with persistent pain.