FNDC5 and chronic obstructive pulmonary disease: To strengthen this result, we also find, only in COPD patients, a significant inverse correlation between both haptoglobin and total adiponectin with irisin, also normalized for the muscle mass, leading to the concept that in this cohort of patients, irisin may be counteracted by the pro-inflammatory adipocytokines, adiponectin and haptoglobin, that sustain the inflammatory state in COPD patients.