Rheumatoid cachexia: metabolic abnormalities, mechanisms and interventions.

We have previously identified the phrase 'rheumatoid cachexia' to describe the loss of body cell mass (BCM) that may occur among patients with rheumatoid arthritis (RA). Specifically, rheumatoid cachexia is characterized by altered energy and protein metabolism (reduced total energy expenditure, increased resting energy expenditure and increased whole-body protein catabolism) and increased inflammatory cytokine production (interleukin-1beta and tumour necrosis factor-alpha). Patients with rheumatoid cachexia consistently have a diet that appears adequate in protein and calories (based on US Dietary Reference Intakes), but with reduced physical activity. These phenomena are similar to some of the metabolic abnormalities that occur with normal ageing, but the aetiology appears to be different in RA. This review will focus on describing the metabolic abnormalities observed in rheumatoid cachexia, identifying potential mechanisms for loss of BCM and discussing strategies for intervention.