Adipose tissue in renal disease: clinical significance and prognostic implications

Obesity is not only associated with the development of diabetes and hypertension, but is also a known risk factor for chronic kidney disease (CKD) and is a risk factor for progressive renal function loss. Abdominal obesity is especially related to incident CKD and mortality. The decline in fat mass over time has also been related to mortality in this population. In patients on peritoneal dialysis, intra-abdominal fat accumulation has been related to cardiovascular morbidity and mortality. The body mass index is a simple method to estimate fat mass in dialysis patients. Maximum abdominal circumference, triceps and subscapular skinfolds, and arm circumference have been proposed as alternative methods in assessing subcutaneous adipose tissue to overcome the altered hydration status associated with dialysis. Waist-to-hip ratio, waist-to-height ratio and the conicity index are used to estimate abdominal fat deposits. Dual-energy X-ray absorptiometry, bioelectrical impedance analysis, computed tomography and magnetic resonance imaging are more precise and reliable methods to estimate body composition in dialysis patients. Adipose tissue is the source of a novel group of hormonally active substances known as adipokines. Patients with CKD exhibit an increase in serum concentration of most of these substances. Besides, the kidney plays an important role in the regulation of adipokines, and altered renal handling of these substances might contribute to an increase in the uraemia-associated increased risk of cardiovascular disease and mortality. In particular, pro-inflammatory adipokines, such as leptin, tumour necrosis factor-alpha and inteleukin-6, have been associated with an increased risk of mortality, whereas the link between adiponectin, an anti-atherogenic adipokine, and survival is controversial in patients with CKD.