Obesity and Renal Diseases

Dr. YAP Yat Hin Desmond - Council Member, HKOS

Obesity and chronic kidney disease (CKD) are growing clinical problems in developed countries including Hong Kong. The identification of obesity-related CKD is important as obesity is a potentially modifiable risk factor for CKD development and progression. The relationship between obesity and CKD is intriguing. While obesity can be linked to CKD via its association with hypertension, diabetes mellitus and metabolic syndrome, previous cross-sectional and observational studies have cornered obesity as an independent risk factor for CKD onset and progression after adjustment of these important confounding co-morbidities. The pathogensis of obesity-related kidney diseases is complex. In this context, possible pathogenic mechanisms include excessive activation of the renin-angiotensin and sympathtetic nervous systems, heightended insulin resistance, altered adipokines homeostasis, increased circulating endothelin-1 and plasminogen activator inhibitor-1 levels, reduced brain natriuretic peptides as well as phenotypic switch of infiltrating macrophages. Mounting evidence has also indicated that obesity per se can exert direct hemodynamic effects on the kidneys such as increased plasma flow, glomerular filtration and albumin excretion. Furthermore, both animal and human data have suggested that obesity is associated with structural changes which include increased kidney weight and glomerular planar surface, mesangial expansion and podocyte injury. These hemodynamic and structural changes contribute to pathological lesions such as glomerulomegaly, glomerulosclerosis and obesity-related glomerulopathy, which can manifest as proteinuria and progressive renal impairment. Other possible associations between obesity and the kidneys include escalated risk of renal cell carcinoma and kidney stones. While the pathogenesis of obesity-related kidney diseases remains elusive, further researches are warranted to delineate the impact of obesity on CKD and elucidate the underlying mechanims for such clinical observations. Given the potential reversibility of the deleterious effects of obesity on CKD progression and outcomes, proper weight management should be incorporated into the therapeutic strategies in obese individuals who suffer from or are at risk of CKD.