Gut microbiota in cardiovascular disease and heart failure

Accumulating evidence supports a relationship between the complexity and diversity of the gut microbiota and host diseases. In addition to alterations in the gut microbial composition, the metabolic potential of gut microbiota has been identified as a contributing factor in the development of diseases. Recent technological developments of molecular and biochemical analyses enable us to detect and characterize the gut microbiota via assessment and classification of its genomes and corresponding metabolites. These advances have provided emerging data supporting the role of gut microbiota in various physiological activities including host metabolism, neurological development, energy homeostasis, and immune regulation. Although few human studies have looked into the causative associations and underlying pathophysiology of the gut microbiota and host disease, a growing body of preclinical and clinical evidence supports the theory that the gut microbiota and its metabolites have the potential to be a novel therapeutic and preventative target for cardiovascular and metabolic diseases. In this review, we highlight the interplay between the gut microbiota and its metabolites, and the development and progression of hypertension, heart failure, and chronic kidney disease.

Coagulation, thrombophilia and patency of arteriovenous fistula in children undergoing haemodialysis compared with healthy volunteers: a prospective analysis

This study aimed to assess whether markers of coagulation, fibrinolysis or thrombophilia are increased in children on haemodialysis compared with controls and whether measurement of any of these factors could help to identify patients at an increased risk of arteriovenous fistula (AVF) occlusion. Blood samples were taken from 55 children immediately before a session of haemodialysis and from 20 healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, plasmin-antiplasmin (PAP) and anticardiolipin immunoglobulin G (ACA-Ig G) were measured by ELISA. Factor V Leiden mutation (G1691A) was determined by gene polymorphism [restriction fragment length polymorphism (RFLP)]. Determination of the patency of the AVF was prospectively followed up for a minimum of 4 years or until the AVF was nonfunctioning. Fifty-five patients were studied with a median follow-up of 659 days (range 30-1670 days). A significant increase was found in the levels of D-dimer, PAP and ACA-Ig G in haemodialysis patients with thrombosed and nonthrombosed native AVFs vs.

CONTROLS

There was a significant difference between both chronic haemodialysis patients with thrombosed and nonthrombosed native AVF with regard to ACA-IgG levels. At 1 year follow-up, primary patency was 61.4% (27 patients). In multivariate analysis, D-dimer was inversely associated with secondary patency.Thrombophilia may predispose children with end stage renal disease to access failure. The promising finding is that in children on haemodialysis, D-dimer levels were increased and inversely correlated with secondary patency. Further evaluation is required into the possible role of D-dimer as a biomarker of AVF occlusion.

Assessment of nutritional status in children with chronic kidney disease and on dialysis

Protein-energy wasting (PEW) is defined as a state of decreased body protein mass and fuel reserves (body protein and fat mass) and is a common complication of chronic kidney disease (CKD). It is multifactorial: the main causative factors are hormonal imbalances and a low nutrient intake, but low residual renal function, inadequate dialysis dose, chronic inflammation and metabolic acidosis are other important contributory factors. Adult PEW has been defined, but there is no accepted definition of pediatric PEW and consequently no precise diagnostic criteria. Assessing nutritional status in children is also complicated by the absence of a gold standard, specific abnormalities in body composition, and the slowly progressive course of the disease. The evaluation of PEW should take into account all of its pathogenetic aspects, which include dietary assessment, clinical and anthropometric assessment (based on weight, height, and body mass index), a panel of biochemical parameters, and a normalized protein catabolic rate (in the case of adolescents on hemodialysis). Bioimpedance indices can be used in individual patients on a regular basis in centers with expertise. The longitudinal follow-up data relating to the above parameters are valuable for comparing patient and normative data. Given the complex nature of PEW, only a multidisciplinary approach can provide an accurate assessment of nutritional status and its derangements in children with CKD and on dialysis.

A pegylated leptin antagonist ameliorates CKD-associated cachexia in mice

Elevated serum leptin levels correlate with inflammation and predict changes in lean body mass in patients with CKD, and activation of the melanocortin system by leptin signaling mediates the pathophysiology of CKD-associated cachexia. We tested whether treatment with a pegylated leptin receptor antagonist (PLA) attenuates cachexia in mice with CKD. CKD and Sham mice received vehicle or PLA (2 or 7 mg/kg per day). At these doses, PLA did not influence serum leptin levels in mice. Treatment with 7 mg/kg per day PLA stimulated appetite and weight gain, improved lean mass and muscle function, reduced energy expenditure, and normalized the levels of hepatic TNF-α and IL-6 mRNA in mice with CKD. Furthermore, treatment with 7 mg/kg per day PLA attenuated the CKD-associated increase in the transcriptional and protein abundance of uncoupling proteins that mediates thermogenesis, and it normalized the molecular signatures of processes associated with muscle wasting in CKD, including proteolysis, myogenesis and muscle regeneration, and expression of proinflammatory muscle cytokines, such as IL-1α, -1β, and -6 and TNF-α. Our results suggest that leptin antagonism may represent a viable therapeutic strategy for cachexia in CKD.

Leptin/adiponectin ratio is an independent predictor of mortality in nondiabetic peritoneal dialysis patients

BACKGROUND

The leptin/adiponectin (L/A) ratio has been suggested to be an atherosclerotic index for diabetic patients and a useful marker of insulin resistance in patients with and without diabetes. Even though end-stage renal disease (ESRD) patients on peritoneal dialysis (PD) are well characterized by abnormal adipocytokine metabolism, the significance of alterations in the L/A ratio is largely unexplored in these patients. In this prospective study, we investigated the associations of leptin, adiponectin, and the L/A ratio with clinical outcomes in nondiabetic PD patients.

METHODS

The study included 131 stable nondiabetic ESRD patients who had been on PD for more than 3 months. Serum leptin and adiponectin levels were determined at baseline. Mortality was evaluated over a 5-year follow-up period.

RESULTS

During the follow-up period, 22 patients died (16.8%), including 10 (45.5%) as a result of cardiovascular disease. The L/A ratio showed a significant positive correlation with body mass index [BMI (r = 0.47, p < 0.001)], high-sensitivity C-reactive protein (r = 0.32, p < 0.001), and triglycerides (r = 0.43, p < 0.001). In addition, we observed significant inverse correlations between the L/A ratio and percentage lean body mass (r = -0.30, p = 0.001) and high-density lipoprotein cholesterol (r = -0.31, p = 0.001). In contrast to individual leptin and adiponectin levels, the L/A ratio was found to be independently associated with an increased mortality risk (relative risk: 1.15; 95% confidence interval: 1.05 to 1.27; p = 0.003) even after adjustments for age and BMI.

CONCLUSIONS

The L/A ratio might be better related to patient outcomes than adipocytokines are individually in nondiabetic patients undergoing PD.

Leptin in anorexia and cachexia syndrome

Leptin is a product of the obese (OB) gene secreted by adipocytes in proportion to fat mass. It decreases food intake and increases energy expenditure by affecting the balance between orexigenic and anorexigenic hypothalamic pathways. Low leptin levels are responsible for the compensatory increase in appetite and body weight and decreased energy expenditure (EE) following caloric deprivation. The anorexia-cachexia syndrome is a complication of many chronic conditions including cancer, chronic obstructive pulmonary disease, congestive heart failure, chronic kidney disease, and aging, where the decrease in body weight and food intake is not followed by a compensatory increase in appetite or decreased EE. Crosstalk between leptin and inflammatory signaling known to be activated in these conditions may be responsible for this paradox. This manuscript will review the evidence and potential mechanisms mediating changes in the leptin pathway in the setting of anorexia and cachexia associated with chronic diseases.

Nontraditional risk factors and biomarkers for cardiovascular disease: mechanistic, research, and clinical considerations for youth: a scientific statement from the American Heart Association

The rapid increase in the prevalence and severity of obesity in children is likely to lower the age of onset and increase the incidence of cardiovascular disease worldwide. Understanding the pathophysiology and improving the clinical management of cardiovascular disease involve a knowledge of novel risk factors and biomarkers. The clinical and mechanistic roles of these novel biological factors during childhood are currently being investigated. The goals of this scientific statement are to present the existing knowledge and theoretical framework of nontraditional risk factors for cardiovascular disease as they relate to children and adolescents, to describe the relevance and weight of available experimental and clinical evidence and the therapeutic implications pertaining to nontraditional risk factors in the pediatric population, and to stimulate further research with a goal of developing valid and reliable approaches to identify and validate novel risk factors that will aid in the clinical evaluation and perhaps prediction of cardiovascular disease in the pediatric population. Although several biomarkers are promising, substantial research is required before nontraditional risk factors can be used to identify and reduce cardiovascular disease risk in children and adolescents.

Upregulation of surrogate markers of inflammation and thrombogenesis in patients with ESRD: pathophysiologic and therapeutic implications

Patients with end-stage renal disease (ESRD) undergoing regular hemodialysis have high annual mortality rate of around 15%. The most predominant cause of death is cardiovascular, which is not entirely explainable with conventional cardiac risk factors present in these patients. It has been postulated that ESRD is a chronic inflammatory and hypercoagulable condition with marked elevation of several markers that may explain this high mortality. In the current study, patients with ESRD on a stable regimen of hemodialysis were studied for the inflammatory and thrombogenesis markers to explain this phenomenon. The parameters studied were of thrombogenesis-thrombin-antithrombin III complex (TAT), prothrombin fragment (F1.2), D-dimer, and fibrinopeptide A (FPA) and inflammation-CD40 ligand, myeloperoxidase (MPO), tumor necrosis factor α (TNF-α), monocyte chemotactic protein-1 (MCP-1), and nitric oxide (NO), and compared to control group comprised of 100 healthy volunteers. Our study shows that ESRD patients exhibit activation of the coagulation and inflammatory processes.

Ghrelin and its potential in the treatment of eating/wasting disorders and cachexia

The gastrointestinal "hunger" hormone ghrelin is the only known circulating peripheral molecule with the ability to decrease body fat utilization and to increase body weight gain. Accordingly, due to ghrelin's effects to promote food intake while decreasing energy expenditure ghrelin may offer potential as a drug for treatment of eating/wasting disorders and cachexia. Therapeutic potential of ghrelin and ghrelin analogues to promote food intake and body weight gain was recently indicated in several clinical studies. The recent discovery of the ghrelin O-acyltransferase as the key enzyme responsible for ghrelin acylation has further deepened our understanding of ghrelin activation, thereby paving the way for more efficient targeting of the ghrelin pathway. Here, we summarize the current knowledge pertaining to the potential of the endogenous ghrelin system as a drug target for the treatment of eating/wasting disorders and cachexia.

Ghrelin improves disturbed myocardial energy metabolism in rats with heart failure induced by isoproterenol

To explore the effects of ghrelin on disturbed myocardial energy metabolism during chronic heart failure (CHF). Rats were subcutaneously injected with isoproterenol (ISO) for 10 days with or without ghrelin for another 10 days. Enzyme immunoassay was to measure ghrelin concentrations. Compared with the control group, ISO-treated rats showed suppressed cardiac function with high ghrelin/GHS-R expressions. These rats also showed the decreases in food consumption and weight. The decreased levels of plasma glucose and myocardial glucogen, but the high lactate in blood and myocardium showed myocardial metabolic disturbance. Compared with the group given ISO alone, the rats with ghrelin (20 and 100 microg/kg/day) improved cardiac dysfunction and increased food intake by 13.5 and 14.2% (both P < 0.01), and rate of weight gain by 95% (P < 0.05) and 1.71-fold (P < 0.01), respectively. The plasma glucose were increased by 49.7 and 50.8% (both P < 0.01), and myocardial glucogen, by 40.5 and 51.7% (both P < 0.01), but blood lactate decreased by 1.56- and 1.96-fold (both P < 0.01), and myocardial lactate by 32.1 and 48.7% (both P < 0.05), respectively. Their MCT1 mRNA and protein expressions increased. The myocardial ghrelin/GHS-R pathway can be upregulated during CHF. The ghrelin can attenuate cardiac dysfunction and energy metabolic disturbance in CHF rats.

Inflammation and cachexia in chronic kidney disease

Chronic inflammation is associated with cachexia and increased mortality risk in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Inflammation suppresses appetite and causes the loss of protein stores. In CKD patients, increased serum levels of pro-inflammatory cytokines may be caused by reduced renal function, volume overload, oxidative or carbonyl stress, decreased levels of antioxidants, increased susceptibility to infection in uremia, and the presence of comorbid conditions. Cachexia is brought about by the synergistic combination of a dramatic decrease in appetite and an increase in the catabolism of fat and lean body mass. Pro-inflammatory cytokines act on the central nervous system to alter appetite and energy metabolism and to provide a signal-through the nuclear factor-kappaB and ATP-ubiquitin-dependent proteolytic pathways-that causes muscle wasting. Further research into the molecular pathways leading to inflammation and cachexia may lead to novel therapeutic therapies for this devastating and potentially fatal complication of chronic disease.

Ghrelin and obestatin levels in end-stage renal disease

Malnutrition is fairly common in end-stage renal disease (ESRD) patients, persistent lack of appetite being a major symptom. Ghrelin and obestatin are two hormones that are involved in appetite and energy homeostasis. The present study examined ghrelin and obestatin levels in 24 ESRD patients undergoing haemodialysis and 24 age-matched healthy controls. Serum and saliva ghrelin and obestatin levels in the ESRD patients were significantly higher compared with controls, while saliva ghrelin and obestatin levels in all study participants were significantly higher than serum levels. Saliva ghrelin correlated with serum ghrelin and saliva obestatin correlated with serum obestatin in all study participants, although there was no correlation between ghrelin and obestatin levels. In conclusion, the results suggest that the kidneys may have a role in the metabolism and/or clearance of obestatin, as they do for ghrelin. Further studies are needed to determine if elevated levels of these hormones in ESRD patients contribute to the malnutrition that is common in these patients.