Higher percentages of fat tissue are associated with a better response to erythropoiesis-stimulating agents (ESAs) in hemodialysis (HD) patients, according to a recent study.

In a cross-sectional observational study, Almudena Vega, MD, PhD, of Hospital General Universitario Gregorio Marañón, Madrid, Spain, and colleagues analyzed erythropoietin resistance index (ERI) in relation to body composition in 218 HD and peritoneal dialysis (PD) patients.

They calculated ERI by dividing the weekly weight-adjusted dose of ESA by the hemoglobin (Hb) level. They also calculated the fat tissue index (FTI) and lean tissue index (LTI), defined, respectively, as fat tissue and lean tissue adjusted for body surface area. 

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The study, published online ahead of print in Renal Failure, revealed a direct linear correlation between BMI and FTI and a significant inverse correlation between ERI and BMI and FTI in HD patients, but not in PD patients. They observed no association between ERI and LTI. The authors said they assumed that the protective effects of BMI on ERI may be due to a higher percentage of fat tissue.

Although the data show an association between fat tissue and ESA response, the researchers acknowledged that they cannot offer a causal explanation.  They suggest, however, an association between the hydration state and fat tissue. “As fat tissue presents a lower percentage of water, it is possible that a decreased distribution volume of hemoglobin in patients with a higher percentage of fat may influence ESA response,” they wrote.

Alternatively, fat tissue may autonomously modulate ESA response via autocrine regulation, the researchers stated. They noted that leptin, which occurs at higher levels in overweight patients, has been shown to stimulate erythropoiesis.