Obesity Related Hypertension in Prevalent Hemodialysis Patients

Abstract

Due to its high worldwide prevalence, obesity is currently the most common metabolic disease in the world. The WHO estimates that more than one billion people are overweight and, of these, 300 million can be considered as obese, with a BMI above 30 kg/m² according its own BMI based classification of (Wu et al., 2002) Overweight and obesity are the fifth leading risk for global deaths. At least 2.8 million deaths die each year as a result of being overweight or obese, in addition, 44% of the diabetes burden, 23% of the ischemic heart disease burden and between 7% and 14% of the certain cancer burden are attributable to overweight and obesity (WHO, 2011). However, in some (but not all) studies into the survival of patients on haemodialysis (HD) the phenomenon of “paradoxical obesity” or reverse epidemiology occurs, whereas higher body mass index (BMI) is accompanied by better survival rates (Kamyar K Zadeh and Kopple, 2006). In this complex population some findings have suggested that the relation between adiposity and cardiovascular risk factors does not follow the same pattern as in the normal population. In fact, stage 5 CRF non-overweight patients frequently have dyslipaemia and inflammation (Kaysen et al., 2009). Adipose tissue is a complex organ, with pleiotropic functions beyond the mere storage of energy. It is related with the secretion of a number of proteins (adipokines), including leptin and adiponectin and also cytokines such as interleukin-6 (IL-6). Today, we know that adipose tissue plays an important role in the production of these molecules in the catabolic uraemic medium through its influence on systemic inflammation and uraemic anorexia (Axelsson and Stenvinkel, 2008). Among the inflammation markers, C-reactive protein (CRP) is, furthermore, a cardiovascular risk marker in the general population and in dialysis patients, as is the plasmatic level of some cytokines such as IL-6 (Hasuike et al., 2009). In our study we tried to find the pathogenetic relationship between obesity, as we consider the adipose tissue as an endocrine organ secreting different adipokines IL6 and CRP, and hypertension in patients on regular hemodialysis. The study was conducted on 80 ESRD patients on regular hemodialysis. GroupA:20 ESRD patients on regular hemodialysis, obese (BMI≥30) and hypertensives (BP≥140/90) (JNephrol.,2002).Group B:20 ESRD patients on regular hemodialysis with normal weight (BMI=18.5-24.9) and hypertensives (BP≥140/90).Group C :20 ESRD patients on regular hemodialysis, obese (BMI≥30) and normotensives (BP<140/90).GroupD:20 ESRD on regular hemodialysis with normal weight (BMI =18.5-24.9) and normal blood pressure (BP<140/90). All groups were subjected to:Written medical consent and informed consent was obtained from each participant, Full history taking and clinical examination with stress on body mass index, blood pressure (etiology, duration, antihypertensive medications) and of hemodialysis (cause of renal failure, duration, frequency and compliance of dialysis sessions), measurement of blood pressure which was estimated by mean postdialysis arterial blood pressure recordings during the month before the study, measurement of body mass index (BMI) of each patient was calculated by the following equation: BMI=Weight (in kg.)Postdialysis dry weight/Height (in meters) Squared. Laboratory tests for all patients and control group: Serum predialysis (Urea reduction percentage, Creatinine, Na, K, Ca, phosphorus and Albumin), measurement of serum IL-6, as an inflammatory marker, by ELISA on interdialytic day and measurement of serum hsCRP by ELISA. We found a strong relation between BMI and serum level of IL6 and CRP especially in obese groups and in hypertensive patients within these groups, and that hemodialysis process per se augment this effect.We also found that both CRP and IL6 have a significant difference with systolic and diastolic blood pressure blood pressure confirming the aim of our study which suggests that adipose tissue is an endocrine organ secreting cytokines result in development of chronic inflammation in patients with ESRD affecting blood vessels causing hypertension. We found that serum albumin was negatively correlated with both IL-6 and CRP values among all studied groups consistent with the inflammation-malnutrition complex theory. In conclusion, as regards to the results, our study suggests the endocrine nature of adipose tissue as a major source of inflammatory cytokines which already increased in hemodialysis patients due to different dialysis factors.These cytokines propably has a pathogenic effect on blood vessles causing hypertension in ESRD patients, that may increase the possibility of high morbidity and mortality in these patients. But unfortunately our study lacks the detailed history of accompanying morbid diseases, especially cardiovascular one, of our patients that should have been of great importance to our result interpretation demonstrating the effect of obesity and inflammation on the patient life quality and survival.