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      Size Matters: Body Composition and Outcomes in Maintenance Hemodialysis Patients

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          In hemodialysis patients a low body mass index (BMI) is correlated with an unfavorable clinical outcome, a phenomenon known as ‘reverse epidemiology’. Mechanisms underlying this observation are unclear. We propose the following: uremic toxin generation occurs predominantly in visceral organs and the mass of key uremiogenic viscera (gut, liver) relative to body weight is higher in small people. Consequently, the rate of uremic toxin generation per unit of BMI is higher in patients with a low BMI. Body water, mainly determined by muscle mass, serves as a dilution compartment for uremic toxins. Therefore, the concentration of uremic toxins is higher in small subjects. Uremic toxins are taken up by adipose and muscle tissues, subsequently metabolized and stored. Thus, the larger the ratio of fat and muscle mass to visceral mass, the lower the concentration of uremic toxins and the better the survival. To test this hypothesis, studies on uremic toxin kinetics in relation to body composition are needed.

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          Most cited references 12

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          Effects of body size and body composition on survival in hemodialysis patients.

          It is unclear whether increased muscle mass or body fat confer the survival advantage in hemodialysis patients with high body-mass index (BMI). Twenty-four-hour urinary creatinine (UCr) excretion was used as a measure of muscle mass. The outcomes of hemodialysis patients with high BMI and normal or high muscle mass (inferred low body fat) and high BMI and low muscle mass (inferred high body fat) were studied to study the effects of body composition on outcomes. In 70,028 patients who initiated hemodialysis in the United States from January 1995 to December 1999 with measured creatinine clearances reported in the Medical Evidence form, all-cause and cardiovascular mortality were examined in Cox and parametric survival models. When compared with normal BMI (18.5 to 24.9 kg/m(2)) group, patients with high BMI (> or = 25 kg/m(2)) had lower hazard of death (hazard ratio [HR], 0.85; P 25th percentile (0.55 g/d), high BMI patients with UCr >0.55 g/d had lower hazard of all-cause (HR, 0.85; P < 0.001) and cardiovascular death (HR, 0.89; P < 0.001), and high BMI patients with UCr < or =0.55 g/d had higher hazard of all-cause death (HR, 1.14; P<0.001) and cardiovascular death (HR, 1.19; P <0.001). Both BMI and body composition are strong predictors of death. The protective effect conferred by high BMI is limited to those patients with normal or high muscle mass. High BMI patients with inferred high body fat have increased and not decreased mortality.
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            Leptin, from fat to inflammation: old questions and new insights.

            Leptin is 16 kDa adipokine that links nutritional status with neuroendocrine and immune functions. Initially thought to be a satiety factor that regulates body weight by inhibiting food intake and stimulating energy expenditure, leptin is a pleiotropic hormone whose multiple effects include regulation of endocrine function, reproduction, and immunity. Leptin can be considered as a pro-inflammatory cytokine that belongs to the family of long-chain helical cytokines and has structural similarity with interleukin-6, prolactin, growth hormone, IL-12, IL-15, granulocyte colony-stimulating factor and oncostatin M. Because of its dual nature as a hormone and cytokine, leptin links the neuroendocrine and the immune system. The role of leptin in the modulation of immune response and inflammation has recently become increasingly evident. The increase in leptin production that occurs during infection and inflammation strongly suggests that leptin is a part of the cytokine network which governs the inflammatory-immune response and the host defense mechanisms. Leptin plays an important role in inflammatory processes involving T cells and has been reported to modulate T-helper cells activity in the cellular immune response. Several studies have implicated leptin in the pathogenesis of autoimmune inflammatory conditions, such as experimental autoimmune encephalomyelitis, type 1 diabetes, rheumatoid arthritis, and intestinal inflammation. Very recently, a key role for leptin in osteoarthritis has been demonstrated: leptin indeed exhibits, in concert with other pro-inflammatory cytokines, a detrimental effect on articular cartilage by promoting nitric oxide synthesis in chondrocytes. Here, we review the recent advances regarding leptin biology with a special focus on those actions relevant to the role of leptin in the pathophysiology of inflammatory processes and immune responses.
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              Secretory factors from human adipose tissue and their functional role.

               Hans Hauner (2005)
              Obesity is characterized by an expanded adipose tissue mass. Recent data suggest that adipose tissue is a multi-functional organ rather than simply a passive storage site for excess energy. It has been clearly demonstrated that human adipose tissue produces a variety of secretory factors that exert multiple effects at both the local and the systemic level. To date, >100 products, covering a broad range of protein families as well as many fatty acids and prostaglandins, have been reported to be secreted by adipose tissue. The source of these secreted factors is not only mature fat cells but also poorly-identified cells present in the stromal-vascular fraction including macrophages. Secreted factors of particular interest include many cytokines or chemokines, such as TNF-alpha, IL-6, IL-8, as well as plasminogen activator inhibitor-1, angiotensin-II, leptin, and adiponectin. In the obese state the expression and secretion of these factors is disturbed. With the exception of adiponectin, most circulating factors are elevated. From this perspective, obesity can be described as a pro-inflammatory condition. In addition, regional differences in adipose expression of many of these factors have been found. There is now growing evidence that many secretory factors play an important role in the pathophysiology of the metabolic and cardiovascular complications of obesity. The question arising from these observations is how the secretory pattern of adipose tissue can be modified by dietary and pharmacological measures to reduce the health risks of obesity.

                Author and article information

                Blood Purif
                Blood Purification
                S. Karger AG
                December 2006
                14 December 2006
                : 25
                : 1
                : 27-30
                aKrankenhaus der Barmherzigen Brüder, Graz, Austria; bRenal Research Institute, and cWeill Cornell Medical Center, New York-Presbyterian Hospital, New York, N.Y., USA
                96393 Blood Purif 2007;25:27–30
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 2, References: 19, Pages: 4
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/96393


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