Viviane O. Leal

Use of handgrip strength in the assessment of the muscle function of chronic kidney disease patients on dialysis: a systematic review

BACKGROUND Even though handgrip strength (HGS) is considered a simple and reliable method to evaluate muscle function and, indirectly, the nutritional status in clinical settings, there is still no consensus concerning its use in patients with chronic kidney disease (CKD) undergoing dialysis. This study presents a systematic review of the literature on the use of HGS as a parameter for nutritional assessment and a prognostic marker in patients on dialysis. METHODS The MEDLINE database (1966 to October 2009) was consulted for this systematic review by using the search terms hand strength or muscle strength dynamometer and dialysis. Eighteen articles were identified and included in the analysis. RESULTS Similar to the general population, HGS values were associated with age and gender. The analysed studies showed correlation between muscle function estimated by HGS and variables used in the assessment of muscle mass and nutritional status, as well as the prediction of clinical complications. CONCLUSIONS The analysis indicates that HGS is a useful tool for continuous and systematic assessment of muscle mass related to nutritional status in patients on dialysis. However, it is still necessary to standardize the techniques used for HGS, especially with respect to the position of measurement, the evaluation period, the choice of arm side and the diagnostic criterion.

Resistance exercise training does not affect plasma irisin levels of hemodialysis patients.

Irisin, a hormone secreted by myocytes induced in exercise, acts as a muscle-derived energy-expenditure signal that binds to undetermined receptors on the white adipose tissue surface, stimulating its browning and uncoupling protein 1 (UCP1) expression. The purpose of this study was to assess the effect of an intradialytic resistance exercise training program (RETP) on plasma irisin levels of hemodialysis (HD) patients and compare the baseline plasma irisin levels of HD patients to healthy subjects. This longitudinal study enrolled 26 patients undergoing HD (50% men, 44.8±14.1 years, body mass index (BMI) 23.5±3.9 kg/m²). The healthy subjects group consisted of 11 women and 7 men with mean age of 50.9±6.6 years and BMI, 24.2±2.7 kg/m². Anthropometric and biochemistry parameters (Irisin by Enzyme-Linked Immunosorbent Assay) were measured at the baseline and after 6 months of RETP (in both lower limbs). There was no difference regarding gender, age, and BMI between HD patients and healthy subjects. Plasma irisin levels in HD patients were lower than in healthy subjects (71.0±41.6 vs. 101.3±12.5 ng/ml, p<0.05). Although the muscle mass increased in consequence of exercise [evaluated by arm muscle area from 27.9 (24.1) to 33.1 (19.0) cm²], plasma irisin did not differ significantly after exercises (71.0±41.6 vs. 73.3±36.0 ng/ml). HD patients seem to have lower plasma irisin when compared to healthy subjects. Moreover, a resistance exercise training program was unable to augment plasma irisin despite increasing muscle mass.

Resveratrol: Why Is It a Promising Therapy for Chronic Kidney Disease Patients?

Resveratrol, a phenolic compound found in various plants, including grapes, berries, and peanuts, shows promise for the treatment of cancer, aging, type 2 diabetes, and cardiovascular diseases. Resveratrol can promote transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) activation, increase the expression level of SIRT-1, which is a sirtuin family protein, and reduce mTOR pathway signaling. This compound has anti-inflammatory properties in that it inhibits or antagonizes the nuclear factor-κB (NF-κB) activity, which is a redox-sensitive transcription factor that coordinates the inflammatory response. Inflammation and oxidative stress, which are common features in patients with chronic kidney disease (CKD), are interrelated and associated with cardiovascular disease and the progression of CKD itself. Because of the modulation of the mechanisms involved in the inflammatory-oxidative stress cycle, resveratrol could play an important role in controlling CKD-related metabolic derangements. Although resveratrol supplementation in theory is a promising therapy in this patient group, there are no studies evaluating its effects. Thus, the present review aims to describe the role of resveratrol in inflammation and oxidative stress modulation and its possible benefits to patients with CKD.

Is a body mass index of 23 kg/m2 a reliable marker of protein–energy wasting in hemodialysis patients?

OBJECTIVE To evaluate the body composition and inflammatory status in patients on hemodialysis (HD) according to the cutoff of 23 kg/m² for the body mass index (BMI). METHODS Forty-seven patients (30 men, 11 diabetics, 53.8 ± 12.2 y of age, 58.2 ± 50.9 mo on HD) were studied. Anthropometric data and handgrip strength were evaluated. C-reactive protein, tumor necrosis factor-α, leptin, and interleukin-6 were measured. Mortality was assessed after 24 mo of follow-up. RESULTS Nineteen patients (40.4%) presented BMI values lower than 23 kg/m² and leptin levels, midarm muscle area, and free-fat mass were significantly lower in these patients. The prevalence of functional muscle loss according to handgrip strength was not different between the BMI groups. The sum of skinfold thicknesses, the percentage of body fat, fat mass, the fat mass/free-fat mass ratio, and waist circumference were significantly lower in patients with a BMI lower than 23 kg/m², but the mean values did not indicate energy wasting. Patients with a BMI higher than 23 kg/m² presented a higher prevalence of inflammation and higher waist circumference and body fat values. The adiposity parameters were correlated with C-reactive protein and leptin. A Cox multivariate regression analysis demonstrated that C-reactive protein, tumor necrosis factor-α, and interleukin-6 predict cardiovascular mortality. CONCLUSION Patients on HD with a BMI lower than 23 kg/m² did not present signs of energy wasting, whereas those with a BMI higher than 23 kg/m² had more inflammation, probably because of a greater adiposity. Thus, the BMI value of 23 kg/m² does not seem to be a reliable marker of protein-energy wasting in patients on HD.

Is zinc-α2-glycoprotein a cardiovascular protective factor for patients undergoing hemodialysis?

BACKGROUND Zinc-α2-glycoprotein (ZAG) is a lipid mobilizing factor. Its anti-inflammatory action and expression pattern suggest that ZAG could act by protecting against the obesity-associated disorders. In hemodialysis (HD) patients, ZAG levels were described to be elevated but its effects on markers of inflammation and LDL oxidation are still unclear. We investigated the relationship between ZAG and markers of systemic inflammation and LDL atherogenic modification profile in HD patients. METHODS Forty-three patients regularly on HD were studied and compared to 20 healthy subjects. Plasma ZAG, adiponectin, electronegative LDL [LDL(-)], an atherosclerotic negatively charged LDL subfraction, and anti-LDL(-) autoantibodies levels were measured by ELISA. Markers of inflammation and atherogenic cell recruitment (TNF-α, interleukin-6, VCAM-1, ICAM-1, MCP-1 and PAI-1) were also determined. RESULTS Inflammatory markers and atherogenic cell recruitment were higher in HD patients when compared to healthy subjects. ZAG levels were also higher in HD patients (151.5 ± 50.1 mg/l vs 54.6 ± 23.0 mg/l; p<0.0001) and its levels were negatively correlated with TNF-α (r=-0.39; p=0.001) and VCAM-1 (r=-0.52; p<0.0001) and, positively correlated with anti-LDL(-) autoantibodies (r=0.38; p=0.016). On multivariate analyses, plasma ZAG levels were independently associated with VCAM-1 (p=0.01). CONCLUSION ZAG is inversely associated with markers of pro-atherogenic factors linked to systemic inflammation and oxidative stress. Thus, this adipokine may constitute a novel marker of a favorable metabolic profile regarding cardiovascular risk factors in HD population.

Underreporting of Energy Intake in Maintenance Hemodialysis Patients: A Cross-sectional Study

OBJECTIVE To analyze the reported energy intake (EI(rep)) in hemodialysis (HD) patients by total energy expenditure (TEE) measured by a dedicated device. DESIGN Cross-sectional study. SETTING RenalCor and RenalVida Clinics (Rio de Janeiro, Brazil). PATIENTS AND OTHERS PARTICIPANTS Forty-eight HD patients (51.4 ± 12.2 years, 62% men, body mass index [BMI], 23.8 ± 4.5 kg/m(2)) were studied. MAIN OUTCOME MEASURE EI(rep) was evaluated using a 3-day food record. TEE was measured over a 2-day period by SWA (SenseWear Pro2 Armband, BodyMedia Inc., Pittsburgh, PA). Subjects were identified as underreporters (URs), acceptable reporters (ARs), or overreporters (ORs) from their EI(rep)/TEE ratio. ARs were defined as having the EI(rep)/TEE ratio in the range of 0.76 to 1.24, URs as EI(rep)/TEE <0.76, ORs as EI(rep)/TEE >1.24 according to Goldberg index. RESULTS The mean TEE and EI(rep) were 34.7 ± 9.4 kcal/kg/day and 22.8 ± 10.6 kcal/kg/day, respectively, and 37.5% of patients presented overweight or obesity. Thirty-one patients (65%) were identified as URs, and the mean of Goldberg index was 0.54 ± 0.12 (0.23 to 0.75), versus 0.95 ± 0.12 (0.79 to 1.2) for ARs. There were no ORs among the patients studied. There were negative correlations between Goldberg index and BMI (r = -0.35, P < .01) and % body fat (r = -0.4, P < .01) and between EI(rep) and BMI (r = -0.58, P < .001). CONCLUSION These results confirm a high prevalence of underreporting of EI in HD patients, particularly in patients with high BMI.

Apelin: A Peptide Involved in Cardiovascular Risk in Hemodialysis Patients?

Inflammation, oxidative stress, and obesity are important features associated with pathogenesis of cardiovascular disease, a major contributor to the mortality of hemodialysis (HD) patients. Apelin is an adipokine involved in a variety of physiological functions; however, little is known about apelin in chronic kidney disease (CKD). Thus, the purpose of this study was to analyze apelin plasma levels in HD patients and verify whether there is any relationship with inflammation, oxidative markers, and obesity. Twenty-four HD patients [53.6 ± 14.4 years, 14 men, and body mass index (BMI) of 25.0 ± 4.2 kg/m2] were studied and compared with 15 healthy subjects (51.3 ± 13.5 years, 7 men, and BMI of 26.3 ± 3.7 kg/m2). Plasma apelin-12 and -36 were measured using the enzyme immunometric assay method. Plasma electronegative low-density lipoprotein [LDL(–)] levels were measured using ELISA method, and tumor necrosis factor-α, interleukin-6, leptin, and plasminogen activator inhibitor-1 levels were measured by a multiplex assay kit. C-Reactive protein (CRP) was determined by immunoturbidimetry. Anthropometric data were also evaluated. There was no difference between apelin-36 levels in HD patients (0.82 ± 0.60 ng/mL) and healthy subjects (0.83 ± 0.23 ng/mL). In contrast, apelin-12 levels were significantly higher in patients (0.34 ± 0.15 ng/mL vs. 0.24 ± 0.13 ng/mL in healthy subjects). TNF-α, CRP, and LDL(–) levels were higher in patients; however, there was no correlation among apelin-12 or -36 and inflammatory or oxidative markers. The adiposity parameters were also not associated with apelin-12 or -36. In conclusion, plasma apelin seems to be not associated with cardiovascular risk in HD patients.

Effect of Brazil Nut Supplementation on Plasma Levels of Selenium in Hemodialysis Patients: 12 Months of Follow-up

BACKGROUND Large amounts of reactive oxygen species are produced in hemodialysis (HD) patients, and, at higher concentrations, reactive oxygen species are thought to be involved in the pathogenesis of cardiovascular disease. It has been proposed that selenium (Se) may exert an antiatherogenic influence by reducing oxidative stress. The richest known food source of Se is the Brazil nut (Bertholletia excelsa, family Lecythidaceae), found in the Amazon region. OBJECTIVE The objective of this work was to determine if Se plasma levels in HD patients submitted to a program of supplementation during 3 months with 1 Brazil nut by day could be sustained after 12 months. METHODS A total of 21 HD patients (54.2 ± 15.2 years old; average time on dialysis, 82.3 ± 51.6 months; body mass index, 24.4 ± 3.8 kg/m(2)) from the RenalCor Clinic in Rio de Janeiro, Brazil, were followed up 12 months after the supplementation study ended. The Se plasma levels were determined by atomic absorption spectrophotometry with hydride generation. RESULTS The Se Plasma levels (17.3 ± 19.9 μg/L) were below the normal range (60 to 120 μg/L) before nut supplementation, and after 3 months of supplementation, the levels increased to 106.8 ± 50.3 μg/L (P < .0001). Twelve months after supplementation, the plasma Se levels decreased to 31.9 ± 14.8 μg/L (P < .0001). CONCLUSIONS The data showed that these patients were Se deficient and that the consumption of Brazil nut was effective to increase the Se parameters of nutritional status. Se levels 12 months after the supplementation period were not as low as presupplementation levels but yet significantly lower, and we needed to motivate patients to adopt different dietary intake patterns.

Relationship between zinc levels and plasma leptin in hemodialysis patients

UNLABELLED Recent evidences suggested a possible relationship between zinc deficiency and leptin levels in pathogenesis of anorexia in chronic kidney disease. The present study addressed the relationship between zinc and leptin in hemodialysis (HD) patients. METHODS Fifty HD patients (54.3±12.7years old, 62% men) were studied and compared to 21 healthy volunteers (50.7±15.7years old, 43% men). Biochemical data, serum zinc, plasma leptin, IL-6, TNF-α and C-Reactive Protein levels were determined. Anthropometric parameters, food intake and appetite score were also assessed. RESULTS The leptin levels were higher in HD patients (16.1μg/mL (0.21-118.25) vs 6.0μg/mL (0.50-23.10)) in healthy volunteers (p=0.04), whereas serum zinc levels were lower (54.5±16.3μg/dL) compared to healthy volunteers (78.4±9.4μg/dL) (p=0.0001). The plasma leptin was correlated negatively with plasma zinc (r=-0.33; p=0.007), energy (r=-0.38; p=0.002) and protein intake (r=-0.34; p=0.006) and, positively correlated with BMI (r=0.54; p=0.0001), % body fat (r=0.70; p=0.0001) and conicity index (r=0.46; p=0.001). Plasma zinc was associated with hemoglobin (r=0.30; p=0.04) and negatively associated with TNF-α (r=-0.37; p=0.002) and C-Reactive Protein (r=-0.37; p=0.004). There was no correlation among Zn, leptin and appetite score in these patients. CONCLUSION This study showed that low plasma zinc levels are negatively associated with high leptin levels in HD patients.

Acidose metabólica na doença renal crônica: abordagem nutricional

Metabolic acidosis is a common manifestation of chronic kidney disease and is associated with increased protein catabolism, decreased protein synthesis and negative nitrogen balance. Diet strongly influences acid generation, determining the level of acidosis in chronic kidney disease patients. Some researchers have observed that it is possible to estimate renal net acid excretion, and the analysis of the renal acid load of selected, frequently consumed foods may allow an appropriate prediction of the effects of diet on metabolic acidosis. This article discusses the physiological bases as well as the clinical implications of acidosis in patients with chronic kidney disease and the influence of the diet on the acid-base balance of these patients.