Role of leptin and melanocortin signaling in uremia-associated cachexia

Leptin signalling altered in infantile nephropathic cystinosis-related bone disorder

BACKGROUND

The CTNS gene mutation causes infantile nephropathic cystinosis (INC). Patients with INC develop Fanconi syndrome and chronic kidney disease (CKD) with significant bone deformations. C57BL/6 Ctns-/- mice are an animal model for studying INC. Hyperleptinaemia results from the kidney's inability to eliminate the hormone leptin in CKD. Ctns-/- mice have elevated serum leptin concentrations. Leptin regulates bone metabolism through its receptor that signals further via the hypothalamic melanocortin 4 receptor (MC4R). Leptin signalling may affect bone health in Ctns-/- mice.

METHODS

We first defined the time course of bone abnormalities in Ctns-/- mice between 1 and 12 months of age. We used both genetic and pharmacological approaches to investigate leptin signalling in Ctns-/- mice. We generated Ctns-/-Mc4r-/- double knockout mice. Bone phenotype of Ctns-/-Mc4r-/- mice, Ctns-/- mice and wild type (WT) mice at 1, 4, and 9 months of age were compared. We then treated 12-month-old Ctns-/- mice and WT mice with a pegylated leptin receptor antagonist (PLA) (7 mg/kg/day, IP), a MC4R antagonist agouti-related peptide (AgRP) (2 nmol, intracranial infusion on days 0, 3, 6, 9, 12, 15, 18, 21, 24, and 27), or vehicle (normal saline), respectively, for 28 days. Whole-body (BMC/BMD, bone area) and femoral bone phenotype (BMC/BMD, bone area, length and failure load) of mice were measured by DXA and femoral shaft biochemical test. We also measured lean mass content by EchoMRI and muscle function (grip strength and rotarod activity) in mice. Femur protein content of JAK2 and STAT3 was measured by ELISA kits, respectively.

RESULTS

Bone defects are present in Ctns-/- mice throughout its first year of life. The deletion of the Mc4r gene attenuated bone disorder in Ctns-/- mice. Femoral BMD, bone area, length, and strength (failure load) were significantly increased in 9-month-old Ctns-/-Mc4r-/- mice than in age-matched Ctns-/- mice. PLA and AgRP treatment significantly increased femoral bone density (BMC/BMD) and mechanical strength in 12-month-old Ctns-/- mice. We adopted the pair-feeding approach for this study to show that the protective effects of PLA or AgRP on bone phenotype are independent of their potent orexigenic effect. Furthermore, an increase in lean mass and in vivo muscle function (grip strength and rotarod activity) are associated with improvements in bone phenotype (femoral BMC/BMD and mechanical strength) in Ctns-/- mice, suggesting a muscle-bone interplay. Decreased femur protein content of JAK2 and STAT3 was evident in Ctns-/- mice. PLA or AgRP treatment attenuated femur STAT3 content in Ctns-/- mice.

CONCLUSIONS

Our findings suggest a significant role for dysregulated leptin signalling in INC-related bone disorder, either directly or potentially involving a muscle-bone interplay. Leptin signalling blockade may represent a novel approach to treating bone disease as well as muscle wasting in INC.

Nutrition in Children With Chronic Kidney Disease: How to Thrive?

The nutritional status and management of children with chronic kidney disease (CKD) are complex and require a combined pediatric nephrology team work approach with physicians, nutritionists, nurses, and physical/occupational therapists. Prospective observational studies such as Children with CKD in the US, the 4C study in Europe and the International Pediatric Peritoneal Dialysis Network have advanced the field. However, most recommendations and guidelines from international task forces such as Kidney Diseases Improving Global Outcomes and Pediatric Renal Nutrition Taskforce are opinion-based rather than evidence-based. There is exciting ongoing research to improve nutrition in children with CKD to help them thrive.

The prevalence and clinical significance of loss of appetite in older patients with chronic kidney disease

PURPOSE

To determine predictors of loss of appetite among older adults with chronic kidney disease (CKD).

METHODS

Demographic and clinical data, and scores of comprehensive geriatric assessment parameters of patients who were ≥ 60 years old and have CKD according to an estimated glomerular filtration rate (eGFR) of < 60 mL/min/1.73 m2 were reviewed. Loss of appetite was defined as a score of ≤ 28 in The Council on Nutrition Appetite Questionnaire. Logistic regression analysis was performed to determine the predictors of loss of appetite.

RESULTS

Of the 398 patients included, 288 (72%) were female, and the mean age was 80 ± 7. Loss of appetite was present in 233 (59%) of patients. The frequency appeared to significantly increase with a decline in eGFR to < 45 mL/min/1.73 m2 (p < 0.05). Older age, female sex, the presence of frailty, and higher scores of Insomnia Severity Index and geriatric depression scale-15 were associated with a higher risk of loss of appetite, while longer time on education, higher levels of hemoglobin, eGFR, and serum potassium, and higher scores of handgrip strength, Tinetti gait and balance test, basic and instrumental activities of daily living, and Mini-Nutritional risk Assessment (MNA) were associated with a lower risk (p < 0.05). Associations between insomnia severity and geriatric depression remained significant after adjustment for all parameters including the MNA score.

CONCLUSION

Loss of appetite is quite common in older adults with CKD and may be a sign of poor health status in older people with CKD. There is a close relationship between loss of appetite and insomnia or depressive mood.

Cachexia: A systemic consequence of progressive, unresolved disease

Cachexia, a systemic wasting condition, is considered a late consequence of diseases, including cancer, organ failure, or infections, and contributes to significant morbidity and mortality. The induction process and mechanistic progression of cachexia are incompletely understood. Refocusing academic efforts away from advanced cachexia to the etiology of cachexia may enable discoveries of new therapeutic approaches. Here, we review drivers, mechanisms, organismal predispositions, evidence for multi-organ interaction, model systems, clinical research, trials, and care provision from early onset to late cachexia. Evidence is emerging that distinct inflammatory, metabolic, and neuro-modulatory drivers can initiate processes that ultimately converge on advanced cachexia.

Adipose tissue metabolic changes in chronic kidney disease

Adipose tissue is a complex organ whose functions go beyond being an energy reservoir to sustain proper body energy homeostasis. Functioning as an endocrine organ, the adipose tissue has an active role in the body's metabolic balance regulation through several secreted factors generally termed as adipokines. Thus, adipose tissue dysregulation in chronic kidney disease (CKD) can have a deep impact in the pathophysiology of diseases associated with metabolic dysregulation including metabolic syndrome, insulin resistance (IR), atherosclerosis, and even cachexia. CKD is a progressive disorder linked to increased morbidity and mortality. Despite being characterized by renal function loss, CKD is accompanied by metabolic disturbances such as dyslipidemia, protein energy wasting, chronic low-grade inflammation, IR, and lipid redistribution. Thus far, the mechanisms by which these changes occur and the role of adipose tissue in CKD development and progression are unclear. Further understanding of how these factors develop could have implications for the management of CKD by helping identify pharmacological targets to improve CKD outcomes.

Advanced Glycation End Products and Inflammatory Cytokine Profiles in Maintenance Hemodialysis Patients After the Ingestion of a Protein-Dense Meal

OBJECTIVE

The goal of this investigation was to evaluate circulating and skeletal muscle inflammatory biomarkers between maintenance hemodialysis (MHD) and demographic-matched control subjects (CON) before and after ingestion of a protein-rich meal.

DESIGN AND METHODS

CON (n = 8; 50 ± 2 years; 31 ± 1 kg/m2) and MHD patients (n = 8; 56 ± 5 years; 32 ± 2 kg/m2) underwent a basal blood draw and muscle biopsy and serial blood draws after the ingestion of a mixed meal on a nondialysis day. Plasma advanced glycation end products (AGEs) and markers of oxidation were assessed via liquid chromatography-tandem mass spectrometry before and after the meal (+240 min). Circulating inflammatory cytokines and soluble receptors for AGE (sRAGE) isoforms (endogenous secretory RAGEs and cleaved RAGEs) were determined before and after the meal (+240 min). Basal muscle was probed for inflammatory cytokines and protein expression of related signaling components (RAGE, Toll-like receptor 4, oligosaccharyltransferase subunit 48, TIR-domain-containing adapter-inducing interferon-β, total IκBα, and pIκBα).

RESULTS

Basal circulating AGEs were 7- to 343-fold higher (P < .001) in MHD than those in CON, but only MG-H1 increased in CON after the meal (P < .001). There was a group effect (MHD > CON) for total sRAGEs (P = .02) and endogenous secretory RAGEs (P < .001) and a trend for cleaved RAGEs (P=.09), with no meal effect. In addition, there was a group effect (MHD < CON; P < .05) for circulating fractalkine, interleukin (IL)10, IL17A, and IL1β and a trend (P < .10) for IL6 and macrophage inflammatory protein 1 alpha, whereas tumor necrosis factor alpha was higher in MHD (P < .001). In muscle, Toll-like receptor 4 (P = .03), TIR-domain-containing adapter-inducing interferon-β (P = .002), and oligosaccharyltransferase subunit 48 (P = .02) expression was lower in MHD than that in CON, whereas IL6 was higher (P = .01) and IL8 (P = .08) tended to be higher in MHD.

CONCLUSION

Overall, MHD exhibited an exaggerated, circulating, and skeletal muscle inflammatory biomarker environment, and the meal did not appreciably affect the inflammatory status.

Obesity-related kidney disease: Beyond hypertension and insulin-resistance

Chronic kidney disease (CKD) causes considerable morbidity, mortality, and health expenditures worldwide. Obesity is a significant risk factor for CKD development, partially explained by the high prevalence of diabetes mellitus and hypertension in obese patients. However, adipocytes also possess potent endocrine functions, secreting a myriad of cytokines and adipokines that contribute to insulin resistance and induce a chronic low-grade inflammatory state thereby damaging the kidney. CKD development itself is associated with various metabolic alterations that exacerbate adipose tissue dysfunction and insulin resistance. This adipose-renal axis is a major focus of current research, given the rising incidence of CKD and obesity. Cellular senescence is a biologic hallmark of aging, and age is another significant risk factor for obesity and CKD. An elevated senescent cell burden in adipose tissue predicts renal dysfunction in animal models, and senotherapies may alleviate these phenotypes. In this review, we discuss the direct mechanisms by which adipose tissue contributes to CKD development, emphasizing the potential clinical importance of such pathways in augmenting the care of CKD.

Expression of leptin mRNA as non-invasive biomarker in type 2 diabetes mellitus

CONTEXT

Leptin, an adipocyte-derived signalling molecule that plays important role in the regulation of energy balance, body weight and glucose metabolism.

OBJECTIVE

To evaluate leptin mRNA expression as a predictive biomarker in type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

To detect the expression patterns of leptin mRNA, a quantitative real-time polymerase chain reaction was performed on samples collected from 71 T2DM patients and 32 non-diabetic controls. The receiver operating characteristic curve (ROC) was utilised to assess the discriminatory power of leptin mRNA.

RESULTS

Leptin mRNA levels were reduced significantly in diabetic patients compared with non-diabetic controls (P ≤ .0001). The ROC curve analysis showed a significant association between leptin mRNA levels and T2DM (P ≤ .0001), with a high area under the ROC curve (AUC) of 0.95 (95% CI: 0.89-0.98). The analysis also showed that fasting blood glucose and glycosylated haemoglobin had high AUC values of 0.88 and 0.97 with (95% CI: 0.80-0.93 and 0.92-0.99), respectively.

CONCLUSION

This study shows that the reduced leptin mRNA expression level is significantly associated with T2DM and could be used as a predictive and diagnostic biomarker for T2DM.

Targeting interleukin-1 for reversing fat browning and muscle wasting in infantile nephropathic cystinosis

BACKGROUND

Ctns-/- mice, a mouse model of infantile nephropathic cystinosis, exhibit hypermetabolism with adipose tissue browning and profound muscle wasting. Inflammatory cytokines such as interleukin (IL)-1 trigger inflammatory cascades and may be an important cause for cachexia. We employed genetic and pharmacological approaches to investigate the effects of IL-1 blockade in Ctns-/- mice.

METHODS

We generated Ctns-/- Il1β-/- mice, and we treated Ctns-/- and wild-type control mice with IL-1 receptor antagonist, anakinra (2.5 mg/kg/day, IP) or saline as vehicle for 6 weeks. In each of these mouse lines, we characterized the cachexia phenotype consisting of anorexia, loss of weight, fat mass and lean mass, elevation of metabolic rate, and reduced in vivo muscle function (rotarod activity and grip strength). We quantitated energy homeostasis by measuring the protein content of uncoupling proteins (UCPs) and adenosine triphosphate in adipose tissue and skeletal muscle. We measured skeletal muscle fiber area and intramuscular fatty infiltration. We also studied expression of molecules regulating adipose tissue browning and muscle mass metabolism. Finally, we evaluated the impact of anakinra on the muscle transcriptome in Ctns-/- mice.

RESULTS

Skeletal muscle expression of IL-1β was significantly elevated in Ctns-/- mice relative to wild-type control mice. Cachexia was completely normalized in Ctns-/- Il1β-/- mice relative to Ctns-/- mice. We showed that anakinra attenuated the cachexia phenotype in Ctns-/- mice. Anakinra normalized UCPs and adenosine triphosphate content of adipose tissue and muscle in Ctns-/- mice. Anakinra attenuated aberrant expression of beige adipose cell biomarkers (UCP-1, CD137, Tmem26, and Tbx1) and molecules implicated in adipocyte tissue browning (Cox2/Pgf2α, Tlr2, Myd88, and Traf6) in inguinal white adipose tissue in Ctns-/- mice. Moreover, anakinra normalized gastrocnemius weight and fiber size and attenuated muscle fat infiltration in Ctns-/- mice. This was accompanied by correction of the increased muscle wasting signalling pathways (increased protein content of ERK1/2, JNK, p38 MAPK, and nuclear factor-κB p65 and mRNA expression of Atrogin-1 and Myostatin) and the decreased myogenesis process (decreased mRNA expression of MyoD and Myogenin) in the gastrocnemius muscle of Ctns-/- mice. Previously, we identified the top 20 differentially expressed skeletal muscle genes in Ctns-/- mice by RNAseq. Aberrant expression of these 20 genes have been implicated in muscle wasting, increased energy expenditure, and lipolysis. We showed that anakinra attenuated 12 of those top 20 differentially expressed muscle genes in Ctns-/- mice.

CONCLUSIONS

Anakinra may provide a targeted novel therapy for patients with infantile nephropathic cystinosis.

A Leptin Receptor Antagonist Attenuates Adipose Tissue Browning and Muscle Wasting in Infantile Nephropathic Cystinosis-Associated Cachexia

Mice lacking the functional cystinosin gene (Ctns-/-), a model of infantile nephropathic cystinosis (INC), exhibit the cachexia phenotype with adipose tissue browning and muscle wasting. Elevated leptin signaling is an important cause of chronic kidney disease-associated cachexia. The pegylated leptin receptor antagonist (PLA) binds to but does not activate the leptin receptor. We tested the efficacy of this PLA in Ctns-/- mice. We treated 12-month-old Ctns-/- mice and control mice with PLA (7 mg/kg/day, IP) or saline as a vehicle for 28 days. PLA normalized food intake and weight gain, increased fat and lean mass, decreased metabolic rate and improved muscle function. It also attenuated perturbations of energy homeostasis in adipose tissue and muscle in Ctns-/- mice. PLA attenuated adipose tissue browning in Ctns-/- mice. PLA increased gastrocnemius weight and fiber size as well as attenuated muscle fat infiltration in Ctns-/- mice. This was accompanied by correcting the increased expression of muscle wasting signaling while promoting the decreased expression of myogenesis in gastrocnemius of Ctns-/- mice. PLA attenuated aberrant expressed muscle genes that have been associated with muscle atrophy, increased energy expenditure and lipolysis in Ctns-/- mice. Leptin antagonism may represent a viable therapeutic strategy for adipose tissue browning and muscle wasting in INC.

The role of IL-1 in adipose browning and muscle wasting in CKD-associated cachexia

Cytokines such as IL-6, TNF-α and IL-1β trigger inflammatory cascades which may play a role in the pathogenesis of chronic kidney disease (CKD)-associated cachexia. CKD was induced by 5/6 nephrectomy in mice. We studied energy homeostasis in Il1β-/-/CKD, Il6-/-/CKD and Tnfα-/-/CKD mice and compared with wild type (WT)/CKD controls. Parameters of cachexia phenotype were completely normalized in Il1β-/-/CKD mice but were only partially rescued in Il6-/-/CKD and Tnfα-/-/CKD mice. We tested the effects of anakinra, an IL-1 receptor antagonist, on CKD-associated cachexia. WT/CKD mice were treated with anakinra (2.5 mg/kg/day, IP) or saline for 6 weeks and compared with WT/Sham controls. Anakinra normalized food intake and weight gain, fat and lean mass content, metabolic rate and muscle function, and also attenuated molecular perturbations of energy homeostasis in adipose tissue and muscle in WT/CKD mice. Anakinra decreased serum and muscle expression of IL-6, TNF-α and IL-1β in WT/CKD mice. Anakinra attenuated browning of white adipose tissue in WT/CKD mice. Moreover, anakinra normalized gastrocnemius weight and fiber size as well as attenuated muscle fat infiltration in WT/CKD mice. This was accompanied by correcting the increased muscle wasting signaling pathways while promoting the decreased myogenesis process in gastrocnemius of WT/CKD mice. We performed qPCR analysis for the top 20 differentially expressed muscle genes previously identified via RNAseq analysis in WT/CKD mice versus controls. Importantly, 17 differentially expressed muscle genes were attenuated in anakinra treated WT/CKD mice. In conclusion, IL-1 receptor antagonism may represent a novel targeted treatment for adipose tissue browning and muscle wasting in CKD.

Skeletal myopathy in CKD: a comparison of adenine-induced nephropathy and 5/6 nephrectomy models in mice

Preclinical animal models of chronic kidney disease (CKD) are critical to investigate the underlying mechanisms of disease and to evaluate the efficacy of novel therapeutics aimed to treat CKD-associated pathologies. The objective of the present study was to compare the adenine diet and 5/6 nephrectomy (Nx) CKD models in mice. Male and female 10-wk-old C57BL/6J mice (n = 5-9 mice/sex/group) were randomly allocated to CKD groups (0.2-0.15% adenine-supplemented diet or 5/6 Nx surgery) or the corresponding control groups (casein diet or sham surgery). Following the induction of CKD, the glomerular filtration rate was reduced to a similar level in both adenine and 5/6 Nx mice (adenine diet-fed male mice: 81.1 ± 41.9 µL/min vs. 5/6 Nx male mice: 160 ± 80.9 µL/min, P = 0.5875; adenine diet-fed female mice: 112.9 ± 32.4 µL/min vs. 5/6 Nx female mice: 107.0 ± 45.7 µL/min, P = 0.9995). Serum metabolomics analysis indicated that established uremic toxins were robustly elevated in both CKD models, although some differences were observed between CKD models (i.e., p-cresol sulfate). Dysregulated phosphate homeostasis was observed in the adenine model only, whereas Ca2+ homeostasis was disturbed in male mice with both CKD models. Compared with control mice, muscle mass and myofiber cross-sectional areas of the extensor digitorum longus and soleus muscles were ∼18-24% smaller in male CKD mice regardless of the model but were not different in female CKD mice (P > 0.05). Skeletal muscle mitochondrial respiratory function was significantly decreased (19-24%) in CKD mice in both models and sexes. These findings demonstrate that adenine diet and 5/6 Nx models of CKD have similar levels of renal dysfunction and skeletal myopathy. However, the adenine diet model demonstrated superior performance with regard to mortality (∼20-50% mortality for 5/6 Nx vs. 0% mortality for the adenine diet, P < 0.05 for both sexes) compared with the 5/6 Nx surgical model.NEW & NOTEWORTHY Numerous preclinical models of chronic kidney disease have been used to evaluate skeletal muscle pathology; however, direct comparisons of popular models are not available. In this study, we compared adenine-induced nephropathy and 5/6 nephrectomy models. Both models produced equivalent levels of muscle atrophy and mitochondrial impairment, but the adenine model exhibited lower mortality rates, higher consistency in uremic toxin levels, and dysregulated phosphate homeostasis compared with the 5/6 nephrectomy model.

Caloric Intake in Renal Patients: Repercussions on Mineral Metabolism

The aim of this paper is to review current knowledge about how calorie intake influences mineral metabolism focussing on four aspects of major interest for the renal patient: (a) phosphate (P) handling, (b) fibroblast growth factor 23 (FGF23) and calcitriol synthesis and secretion, (c) metabolic bone disease, and (d) vascular calcification (VC). Caloric intake has been shown to modulate P balance in experimental models: high caloric intake promotes P retention, while caloric restriction decreases plasma P concentrations. Synthesis and secretion of the phosphaturic hormone FGF23 is directly influenced by energy intake; a direct correlation between caloric intake and FGF23 plasma concentrations has been shown in animals and humans. Moreover, in vitro, energy availability has been demonstrated to regulate FGF23 synthesis through mechanisms in which the molecular target of rapamycin (mTOR) signalling pathway is involved. Plasma calcitriol concentrations are inversely proportional to caloric intake due to modulation by FGF23 of the enzymes implicated in vitamin D metabolism. The effect of caloric intake on bone is controversial. High caloric intake has been reported to increase bone mass, but the associated changes in adipokines and cytokines may as well be deleterious for bone. Low caloric intake tends to reduce bone mass but also may provide indirect (through modulation of inflammation and insulin regulation) beneficial effects on bone. Finally, while VC has been shown to be exacerbated by diets with high caloric content, the opposite has not been demonstrated with low calorie intake. In conclusion, although prospective studies in humans are needed, when planning caloric intake for a renal patient, it is important to take into consideration the associated changes in mineral metabolism.

Diverging metabolic programmes and behaviours during states of starvation, protein malnutrition, and cachexia

BACKGROUND

Our evolutionary history is defined, in part, by our ability to survive times of nutrient scarcity. The outcomes of the metabolic and behavioural adaptations during starvation are highly efficient macronutrient allocation, minimization of energy expenditure, and maximized odds of finding food. However, in different contexts, caloric deprivation is met with vastly different physiologic and behavioural responses, which challenge the primacy of energy homeostasis.

METHODS

We conducted a literature review of scientific studies in humans, laboratory animals, and non-laboratory animals that evaluated the physiologic, metabolic, and behavioural responses to fasting, starvation, protein-deficient or essential amino acid-deficient diets, and cachexia. Studies that investigated the changes in ingestive behaviour, locomotor activity, resting metabolic rate, and tissue catabolism were selected as the focus of discussion.

RESULTS

Whereas starvation responses prioritize energy balance, both protein malnutrition and cachexia present existential threats that induce unique adaptive programmes, which can exacerbate the caloric insufficiency of undernutrition. We compare and contrast the behavioural and metabolic responses and elucidate the mechanistic pathways that drive state-dependent alterations in energy seeking and partitioning.

CONCLUSIONS

The evolution of energetically inefficient metabolic and behavioural responses to protein malnutrition and cachexia reveal a hierarchy of metabolic priorities governed by discrete regulatory networks.

Inflammation and Skeletal Muscle Wasting During Cachexia

Cachexia is the involuntary loss of muscle and adipose tissue that strongly affects mortality and treatment efficacy in patients with cancer or chronic inflammatory disease. Currently, no specific treatments or interventions are available for patients developing this disorder. Given the well-documented involvement of pro-inflammatory cytokines in muscle and fat metabolism in physiological responses and in the pathophysiology of chronic inflammatory disease and cancer, considerable interest has revolved around their role in mediating cachexia. This has been supported by association studies that report increased levels of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in some, but not all, cancers and in chronic inflammatory diseases such as chronic obstructive pulmonary disease (COPD) and rheumatoid arthritis (RA). In addition, preclinical studies including animal disease models have provided a substantial body of evidence implicating a causal contribution of systemic inflammation to cachexia. The presence of inflammatory cytokines can affect skeletal muscle through several direct mechanisms, relying on activation of the corresponding receptor expressed by muscle, and resulting in inhibition of muscle protein synthesis (MPS), elevation of catabolic activity through the ubiquitin-proteasomal system (UPS) and autophagy, and impairment of myogenesis. Additionally, systemic inflammatory mediators indirectly contribute to muscle wasting through dysregulation of tissue and organ systems, including GCs via the hypothalamus-pituitary-adrenal (HPA) axis, the digestive system leading to anorexia-cachexia, and alterations in liver and adipocyte behavior, which subsequently impact on muscle. Finally, myokines secreted by skeletal muscle itself in response to inflammation have been implicated as autocrine and endocrine mediators of cachexia, as well as potential modulators of this debilitating condition. While inflammation has been shown to play a pivotal role in cachexia development, further understanding how these cytokines contribute to disease progression is required to reveal biomarkers or diagnostic tools to help identify at risk patients, or enable the design of targeted therapies to prevent or delay the progression of cachexia.

Adipokines and Gut Hormones in End-Stage Renal Disease

Cachexia is common in end-stage renal disease (ESRD) patients, and it is an important risk factor for poor quality of life and increased mortality and morbidity. Chronic inflammation is an important cause of cachexia in ESRD patients. In the present review, we examine recent evidence suggesting that adipokines or adipocytokines such as leptin, adiponectin, resistin, tumor necrosis factor α, interleukin-6, and interleukin-1β may play important roles in uremic cachexia. We also review the physiology and the potential roles of gut hormones, including ghrelin, peptide YY, and cholecystokinin in ESRD. Understanding the molecular pathophysiology of these novel hormones in ESRD may lead to novel therapeutic strategies.

Melanocortin-4 receptor antagonist TCMCB07 ameliorates cancer- and chronic kidney disease-associated cachexia

Cachexia, a devastating wasting syndrome characterized by severe weight loss with specific losses of muscle and adipose tissue, is driven by reduced food intake, increased energy expenditure, excess catabolism, and inflammation. Cachexia is associated with poor prognosis and high mortality and frequently occurs in patients with cancer, chronic kidney disease, infection, and many other illnesses. There is no effective treatment for this condition. Hypothalamic melanocortins have a potent and long-lasting inhibitory effect on feeding and anabolism, and pathophysiological processes increase melanocortin signaling tone, leading to anorexia, metabolic changes, and eventual cachexia. We used 3 rat models of anorexia and cachexia (LPS, methylcholanthrene sarcoma, and 5/6 subtotal nephrectomy) to evaluate efficacy of TCMCB07, a synthetic antagonist of the melanocortin-4 receptor. Our data show that peripheral treatment using TCMCB07 with intraperitoneal, subcutaneous, and oral administration increased food intake and body weight and preserved fat mass and lean mass during cachexia and LPS-induced anorexia. Furthermore, administration of TCMCB07 diminished hypothalamic inflammatory gene expression in cancer cachexia. These results suggest that peripheral TCMCB07 treatment effectively inhibits central melanocortin signaling and therefore stimulates appetite and enhances anabolism, indicating that TCMCB07 is a promising drug candidate for treating cachexia.

Vitamin D repletion ameliorates adipose tissue browning and muscle wasting in infantile nephropathic cystinosis-associated cachexia

BACKGROUND

Ctns-/- mice, a mouse model of infantile nephropathic cystinosis, exhibit hypermetabolism with adipose tissue browning and profound muscle wasting. Ctns-/- mice are 25(OH)D3 and 1,25(OH)2 D3 insufficient. We investigated whether vitamin D repletion could ameliorate adipose tissue browning and muscle wasting in Ctns-/- mice.

METHODS

Twelve-month-old Ctns-/- mice and wild-type controls were treated with 25(OH)D3 and 1,25(OH)2 D3 (75 μg/kg/day and 60 ng/kg/day, respectively) or an ethylene glycol vehicle for 6 weeks. Serum chemistry and parameters of energy homeostasis were measured. We quantitated total fat mass and studied expression of molecules regulating adipose tissue browning, energy metabolism, and inflammation. We measured lean mass content, skeletal muscle fibre size, in vivo muscle function (grip strength and rotarod activity), and expression of molecules regulating muscle metabolism. We also analysed the transcriptome of skeletal muscle in Ctns-/- mice using RNAseq.

RESULTS

Supplementation of 25(OH)D3 and 1,25(OH)2 D3 normalized serum concentration of 25(OH)D3 and 1,25(OH)2 D3 in Ctns-/- mice, respectively. Repletion of vitamin D partially or fully normalized food intake, weight gain, gain of fat, and lean mass, improved energy homeostasis, and attenuated perturbations of uncoupling proteins and adenosine triphosphate content in adipose tissue and muscle in Ctns-/- mice. Vitamin D repletion attenuated elevated expression of beige adipose cell biomarkers (UCP-1, CD137, Tmem26, and Tbx1) as well as aberrant expression of molecules implicated in adipose tissue browning (Cox2, Pgf2α, and NF-κB pathway) in inguinal white adipose tissue in Ctns-/- mice. Vitamin D repletion normalized skeletal muscle fibre size and improved in vivo muscle function in Ctns-/- mice. This was accompanied by correcting the increased muscle catabolic signalling (increased protein contents of IL-1β, IL-6, and TNF-α as well as an increased gene expression of Murf-2, atrogin-1, and myostatin) and promoting the decreased muscle regeneration and myogenesis process (decreased gene expression of Igf1, Pax7, and MyoD) in skeletal muscles of Ctns-/- mice. Muscle RNAseq analysis revealed aberrant gene expression profiles associated with reduced muscle and neuron regeneration, increased energy metabolism, and fibrosis in Ctns-/- mice. Importantly, repletion of 25(OH)D3 and 1,25(OH)2 D3 normalized the top 20 differentially expressed genes in Ctns-/- mice.

CONCLUSIONS

We report the novel findings that correction of 25(OH)D3 and 1,25(OH)2 D3 insufficiency reverses cachexia and may improve quality of life by restoring muscle function in an animal model of infantile nephropathic cystinosis. Mechanistically, vitamin D repletion attenuates adipose tissue browning and muscle wasting in Ctns-/- mice via multiple cellular and molecular mechanisms.

Oral ghrelin receptor agonist MK-0677 increases serum insulin-like growth factor 1 in hemodialysis patients: a randomized blinded study

Background

Protein-energy wasting (PEW) in end-stage renal disease (ESRD) patients is associated with increased morbidity and mortality, but options for treatment are limited. Growth hormone (GH) increases insulin-like growth factor 1 (IGF-1), with improved nutritional parameters, but must be given subcutaneously and does not provide normal GH secretion patterns. MK-0677, an oral ghrelin receptor agonist (GRA), maintains normal GH secretion and increases lean body mass in normal subjects; it has not been studied in dialysis patients, an essential step in assessing efficacy and safety prior to clinical trials.

Methods

We performed a randomized crossover double-blind study in assessing the effect of MK-0677 versus placebo on IGF-1 levels, the primary outcome, in hemodialysis patients. In total, 26 subjects enrolled and 22 completed the 3-month crossover study.

Results

The geometric mean IGF-1 was 1.07-fold greater [95% confidence interval (CI) 0.89-1.27; P = 0.718] after placebo. In patients receiving MK-0677, the geometric mean IGF-1 were 1.76-fold greater (95% CI 1.48-2.10; P < 0.001) following MK-0677. When the data were adjusted for preintervention IGF-1 concentration, the ratio of geometric means (MK-0677 relative to placebo) for the pre- versus postintervention change in the IGF-1 was 1.65 (95% CI 1.33-2.04; P < 0.001). These data demonstrate a 65% greater increase (95% CI 33-104%) in IGF-1 in MK-0677-dosed subjects compared with placebo. There were no serious adverse effects attributable to MK-0677.

Conclusions

MK-0677 increased serum IGF-1 levels with minimal adverse effects in hemodialysis subjects. Studies are needed to evaluate whether long-term therapy with MK-0677 improves PEW, lean body mass, physical strength, quality of life and survival in CKD/ESRD patients.

Interaction between galectin-3 and cystinosin uncovers a pathogenic role of inflammation in kidney involvement of cystinosis

Inflammation is involved in the pathogenesis of many disorders. However, the underlying mechanisms are often unknown. Here, we test whether cystinosin, the protein involved in cystinosis, is a critical regulator of galectin-3, a member of the β-galactosidase binding protein family, during inflammation. Cystinosis is a lysosomal storage disorder and, despite ubiquitous expression of cystinosin, the kidney is the primary organ impacted by the disease. Cystinosin was found to enhance lysosomal localization and degradation of galectin-3. In Ctns-/- mice, a mouse model of cystinosis, galectin-3 is overexpressed in the kidney. The absence of galectin-3 in cystinotic mice ameliorates pathologic renal function and structure and decreases macrophage/monocyte infiltration in the kidney of the Ctns-/-Gal3-/- mice compared to Ctns-/- mice. These data strongly suggest that galectin-3 mediates inflammation involved in kidney disease progression in cystinosis. Furthermore, galectin-3 was found to interact with the pro-inflammatory cytokine Monocyte Chemoattractant Protein-1, which stimulates the recruitment of monocytes/macrophages, and proved to be significantly increased in the serum of Ctns-/- mice and also patients with cystinosis. Thus, our findings highlight a new role for cystinosin and galectin-3 interaction in inflammation and provide an additional mechanistic explanation for the kidney disease of cystinosis. This may lead to the identification of new drug targets to delay cystinosis progression.

Chronic Kidney Disease: Treatment of Comorbidities I: (Nutrition, Growth, Neurocognitive Function, and Mineral Bone Disease)

PURPOSE OF REVIEW

This review discusses the complications of nutrition, growth, neurocognitive function and mineral and bone disorder in pediatric chronic kidney disease. We discuss the most recent evidence-based methods for evaluation and prevention of these complications in addition to treatment strategies to address the complications and mitigate adverse effects.

RECENT FINDINGS

Frequent nutritional assessment is important, particularly for infants and young children. Due to anorexia, oral aversion and dietary restrictions, weight gain may be difficult to achieve. Adequate nutrition is important for growth. Children with CKD tend to be short, which can impact quality of life and social achievements. Once nutrition is optimized, growth hormone is an effective, but underutilized strategy to improving terminal height. Mineral and bone disorder is a difficult but common complication of CKD which may present with and be driven by abnormalities in calcium, phosphorus and parathyroid hormone levels. Treatment strategies include dietary phosphorus restriction, phosphorus binders, and inactive vitamin D and active vitamin D sterols. Effective treatment may reduce the risk for bone deformities, growth abnormalities, fractures, cardiovascular disease and mortality. Children with CKD also suffer from cognitive difficulties. Control of anemia, aggressive childhood nutrition, and decreased exposure to heavy metals (via dialysate and dietary binding agents) has provided substantial improvement to the more profound neurocognitive sequelae observed prior to the 1990s. Current prevention of cognitive sequelae may best be directed at improved blood pressure control and augmented school support.

SUMMARY

Pediatric CKD has systemic ramifications and can impact all aspects of normal development, including nutrition, growth, bone and mineral metabolism and neurocognitive function. Regular evaluation for disease complications and prompt treatment can reduce the untoward effects of CKD thereby improving the quality and duration of life.

Abnormalities in Glucose Metabolism, Appetite-Related Peptide Release, and Pro-nflammatory Cytokines Play a Central Role in Appetite Disorders in Peritoneal Dialysis

Background: Appetite disorders are frequent and scantly studied in peritoneal dialysis (PD) patients and are associated with malnutrition and cardiovascular complications. Objective: We investigated the relationship between uremic insulin resistance, pro-inflammatory cytokines, and appetite-related peptides release (ARPr) with eating-behavior disorders in PD patients. Methods: We included 42 PD patients (12 suffering anorexia, 12 obese with high food-intake, and 18 asymptomatic) and 10 controls. We measured blood levels of ARPr including orexigens [neuropeptide-Y (NPY), ghrelin, and nitric-oxide], anorexigens [cholecystokinin, insulin, corticotropin-releasing factor, leptin, and adiponectin (Ad)], and cytokines (TNF-α, sTNFα-R2, and IL-6) both at baseline and after administering a standard-food stimulus (SFS). We also measured the expression of TNF-α, leptin and Ad-encoding mRNAs in abdominal adipose tissue. We compared these markers with eating motivation measured by a Visual Analog Scale (VAS). Results: Anorexics showed both little appetite, measured by a VAS, and low levels of orexigens that remained constant after SFS, coupled with high levels of anorexigens at baseline and after SFS. Obeses showed higher appetite, increased baseline levels of orexigens, lower baseline levels of anorexigens and cytokines and two peaks of NPY after SFS. The different patterns of ARPr and cytokines pointed to a close relationship with uremic insulin resistance. In fact, the euglycemic-hyperglycemic clamp reproduced these disorders. In anorexics, TNF-α fat expression was increased. In obese patients, leptin expression in fat tissue was down-regulated and showed correlation with the appetite. Conclusion: In PD, appetite is governed by substances that are altered at baseline and abnormally released. Such modulators are controlled by insulin metabolism and cytokines and, while anorexics display inflammatory predominance, obese patients predominantly display insulin resistance.

Energy-Dense Diets and Mineral Metabolism in the Context of Chronic Kidney Disease⁻Metabolic Bone Disease (CKD-MBD)

The aim of this paper is to review current knowledge about the interactions of energy-dense diets and mineral metabolism in the context of chronic kidney disease–metabolic bone disease (CKD-MBD). Energy dense-diets promote obesity and type II diabetes, two well-known causes of CKD. Conversely, these diets may help to prevent weight loss, which is associated with increased mortality in advanced CKD patients. Recent evidence indicates that, in addition to its nephrotoxic potential, energy-dense food promotes changes in mineral metabolism that are clearly detrimental in the context of CKD-MBD, such as phosphorus (P) retention, increased concentrations of fibroblast growth factor 23, decreased levels of renal klotho, and reduction in circulating concentrations of calcitriol. Moreover, in uremic animals, a high fat diet induces oxidative stress that potentiates high P-induced vascular calcification, and these extraskeletal calcifications can be ameliorated by oral supplementation of vitamin E. In conclusion, although energy-dense foods may have a role in preventing undernutrition and weight loss in a small section of the CKD population, in general, they should be discouraged in patients with renal disease, due to their impact on P load and oxidative stress.

Garlic (Allium sativum) exhibits a cardioprotective effect in experimental chronic renal failure rat model by reducing oxidative stress and controlling cardiac Na+/K+-ATPase activity and Ca2+ levels

Gentamicin (GNT)-induced nephrotoxicity culminates into renal failure with a possible cardiovascular impact. Garlic extract (GE) is a cardiovascular protectant with limited mechanistic data. Therefore, we assessed the disturbance in specific cardiac parameters and the potential protective effect of GE supplementation against them in a rat model of GNT-induced chronic renal failure (CRF). Adult male rats (n = 24) were randomly assigned into four groups (n = 6 each): normal controls (CON), garlic extract controls (GE; 250 mg kg-1, orally), GNT-induced CRF (GNT; 100 mg kg-1, i.p.), and GNT + GE (GNT and GE in the same previous doses) groups. GNT and GE were given daily for 3 weeks. Animals co-treated with GNT and GE exhibited improved renal functions, body weight (BW), and heart weight (HW)/BW ratio; declined blood pressure; lowered plasma levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), and total peroxides (TP); and elevated total antioxidant capacity (TAC) levels. Moreover, the heart tissue contained raised levels of TAC and Na+/K+-ATPase activity and lowered levels of TP and Ca2+. Findings provide evidence that administration of GE in experimental CRF model helped protect the heart through reducing oxidative stress and controlling cardiac Na+/K+-ATPase activity and Ca2+ levels.

Regulation of energy rheostasis by the melanocortin-3 receptor

Like most homeostatic systems, adiposity in mammals is defended between upper and lower boundary conditions. While leptin and melanocortin-4 receptor (MC4R) signaling are required for defending energy set point, mechanisms controlling upper and lower homeostatic boundaries are less well understood. In contrast to the MC4R, deletion of the MC3R does not produce measurable hyperphagia or hypometabolism under normal conditions. However, we demonstrate that MC3R is required bidirectionally for controlling responses to external homeostatic challenges, such as caloric restriction or calorie-rich diet. MC3R is also required for regulated excursion from set point, or rheostasis, during pregnancy. Further, we demonstrate a molecular mechanism: MC3R provides regulatory inputs to melanocortin signaling, acting presynaptically on agouti-related protein neurons to regulate γ-aminobutyric acid release onto anorexigenic MC4R neurons, exerting boundary control on the activity of MC4R neurons. Thus, the MC3R is a critical regulator of boundary controls on melanocortin signaling, providing rheostatic control on energy storage.

Muscle wasting in chronic kidney disease

Loss of lean body mass is a relevant component of the cachexia, or protein energy wasting (PEW), syndrome. Reduced muscle mass seems to be the most solid criterion for the presence of cachexia/PEW in patients with chronic kidney disease (CKD), and those with greater muscle mass loss have a higher risk of death. Children with CKD have many risk factors for lean mass and muscle wasting, including poor appetite, inflammation, growth hormone resistance, and metabolic acidosis. Mortality risks in patients with CKD increases as body mass index (BMI) and weight decreases. However, data regarding cachexia/PEW and muscle wasting in children with CKD is scarce due to lack of consensus in diagnostic criteria and an appropriate investigative methodology. Further research is urgently needed to address this important complication in the pediatric CKD setting, which may have fundamental impact on clinical outcomes.

Growth and Nutrition in Pediatric Chronic Kidney Disease

Children with chronic kidney disease (CKD) feature significant challenges to the maintenance of adequate nutrition and linear growth. Moreover, the impaired nutritional state contributes directly to poor growth. Therefore, it is necessary to consider nutritional status in the assessment of etiology and treatment of sub-optimal linear growth. The major causes of poor linear growth including dysregulation of the growth hormone/insulin-like growth factor-I (IGF-I) axis, nutritional deficiency, metabolic acidosis, anemia, renal osteodystrophy/bone mineral disease, and inflammation. This review summarizes the causes and assessment tools of growth and nutrition while providing a summary of state of the art therapies for these co-morbidities of pediatric CKD.

Anorexia-cachexia syndrome-like hypothalamic neuroendocrine dysfunction in a patient with a papillary craniopharyngioma

The craniopharyngiomas are solid cystic suprasellar tumors that can present extension to adjacent structures, conditioning pituitary and hypothalamic dysfunction. Within hypothalamic neuroendocrine dysfunction, we can find obesity, behavioral changes, disturbed circadian rhythm and sleep irregularities, imbalances in the regulation of body temperature, thirst, heart rate and/or blood pressure and alterations in dietary intake (like anorexia). We present a rare case of anorexia–cachexia syndrome like a manifestation of neuroendocrine dysfunction in a patient with a papillary craniopharyngioma. Anorexia–cachexia syndrome is a complex metabolic process associated with underlying illness and characterized by loss of muscle with or without loss of fat mass and can occur in a number of diseases like cancer neoplasm, non-cancer neoplasm, chronic disease or immunodeficiency states like HIV/AIDS. The role of cytokines and anorexigenic and orexigenic peptides are important in the etiology. The anorexia–cachexia syndrome is a clinical entity rarely described in the literature and it leads to important function limitation, comorbidities and worsening prognosis.

Inflammatory Cytokines as Uremic Toxins: "Ni Son Todos Los Que Estan, Ni Estan Todos Los Que Son"

Chronic kidney disease is among the fastest growing causes of death worldwide. An increased risk of all-cause and cardiovascular death is thought to depend on the accumulation of uremic toxins when glomerular filtration rate falls. In addition, the circulating levels of several markers of inflammation predict mortality in patients with chronic kidney disease. Indeed, a number of cytokines are listed in databases of uremic toxins and uremic retention solutes. They include inflammatory cytokines (IL-1β, IL-18, IL-6, TNFα), chemokines (IL-8), and adipokines (adiponectin, leptin and resistin), as well as anti-inflammatory cytokines (IL-10). We now critically review the cytokines that may be considered uremic toxins. We discuss the rationale to consider them uremic toxins (mechanisms underlying the increased serum levels and evidence supporting their contribution to CKD manifestations), identify gaps in knowledge, discuss potential therapeutic implications to be tested in clinical trials in order to make this knowledge useful for the practicing physician, and identify additional cytokines, cytokine receptors and chemokines that may fulfill the criteria to be considered uremic toxins, such as sIL-6R, sTNFR1, sTNFR2, IL-2, CXCL12, CX3CL1 and others. In addition, we suggest that IL-10, leptin, adiponectin and resistin should not be considered uremic toxins toxins based on insufficient or contradictory evidence of an association with adverse outcomes in humans or preclinical data not consistent with a causal association.

Possible prevention of uremic nausea by vitamin D receptor activators in non-dialysis patients with stage 5 chronic kidney disease

Background

Nausea is a major uremic symptom and a frequent indication for starting dialysis. However, preventive medication for uremic nausea has not yet been identified. Vitamin D receptor activators (VDRAs) may prevent uremic nausea via their pleiotropic actions. The objective of this study was to explore whether VDRA administration during the predialysis period is associated with a reduced prevalence of uremic nausea just prior to beginning dialysis.

Methods

A multicenter, retrospective, cross-sectional study was performed to identify a medication to prevent uremic nausea. Patients with stage 5 CKD who were followed-up over 3 months were included. The primary outcomes examined were the prevalence of uremic nausea, congestive heart failure (CHF), and intractable edema at dialysis commencement. The predictor variable was VDRA use during the predialysis period.

Results

One thousand five hundred and thirty six patients who had just begun dialysis in nine Japanese facilities between January 2006 and October 2013 were included. Two hundred and thirty (15.0%) patients had commenced dialysis because of uremic nausea, and three hundred and ninety two (25.5%) patients had been using VDRAs before initiating dialysis. Logistic regression analysis showed that, among the medications examined in this study, only VDRA use was independently associated with a lower frequency of uremic nausea (OR 0.512, 95% CI 0.347–0.738, P = 0.0003). On the other hand, CHF and intractable edema were not associated with VDRA administration.

Conclusion

Use of VDRAs during the predialysis period was the only factor associated with a lower prevalence of uremic nausea, suggesting that VDRAs may prevent uremic nausea in patients with advanced CKD.

Activation of the central melanocortin system chronically reduces body mass without the necessity of long-term caloric restriction

Melanotan II (MTII) is a potent appetite suppressor that rapidly reduces body mass. Given the rapid loss of anorexic response upon chronic MTII treatment, most investigations have focused on the initial physiological adaptations. However, other evidence supports MTII as a long-term modulator of energy balance that remains to be established. Therefore, we examined the chronic effects of MTII on energy homeostasis. MTII (high or low dose) or artificial cerebrospinal fluid (aCSF) was infused into the lateral ventricle of the brain of 6-month-old F344BN rats (6-7/group) over 40 days. MTII suppressed appetite in a dose-dependent manner (P < 0.05). Although food intake promptly rose back to control level, body mass was persistently reduced in both MTII groups (P < 0.01). At day 40, both MTII groups displayed lower adiposity than the aCSF animals (P < 0.01). These results show that MTII chronically reduces body mass without the requirement of long-term caloric restriction. Our study proposes that food restriction helps initiate mass loss; however, combined with a secondary pharmacological approach preserving a negative energy balance state over time may help combat obesity.

[Wasting in chronic kidney disease: Refeeding techniques and artificial nutrition practices]

Protein energy wasting (PEW) is an independent factor associated with morbi-mortality in chronic kidney disease. Wasting is particularly common in chronic diseases of organs such as kidney disease with a major impact at the stage of dialysis. It covers 20 to 70% of patients diagnosed with chronic kidney disease according to the degree of evolution of the disease and the diagnostic method used patients. Mechanisms of PEW are based mainly on anorexia and metabolic abnormalities caused by kidney disease. Nutritional treatment differs depending on the stage of the kidney disease acute or chronic treated whether or not by dialysis. Nutritional monitoring should be regular, individualized and collaborative to detect a risk of PEW or treat installed PEW. Refeeding techniques should allow all the nutritional needs. Their indications depend on the clinic, biochemical assessment and nutrient intake.

Correlation between serum leptin and bone mineral density in hemodialysis patients

Introduction: For diagnosing of specific types of bone lesions in hemodialysis (HD) patients, it is necessary to conduct a bone biopsy as the gold standard method. However, it is an invasive procedure. While different markers have been suggested as alternative methods, none of them has been selected. The frequency of hip fractures is 80 fold in HD patients who have two-fold mortality as compared with general population.

Objectives: Recently, serum leptin has been suggested as a bone density marker. This study tries to confirm this proposal.

Patients and Methods: In this study about 104 HD patients (53.8% male and 46.2% female) were enrolled. The average age was 38.28±7.89 years. Serum leptin, bone alkaline phosphatase, intact parathyroid hormone (iPTH), 25(OH)D, calcium, phosphorus and bone mineral density (BMD) (at the femoral neck and lumbar spine, as measured by dual-energy x-ray absorptiometry [DXA]) were assessed.

Results: Analysis by polynomial regression revealed no correlation between BMD Z-score at two points and serum leptin level. According to the thresholds of 25 ng/mL and 18-24 ng/mL in some studies, we detected 25 ng/mL as the threshold in our patients. Under this threshold, the leptin effect on bone mass was negative, and above the threshold of 25 ng/mL, we found leptin had positive effect on bone mass.

Conclusion: In this investigation, we found, leptin has a bimodal effect on bone mass. Cortical bones assessment may be a better option for assessment.

Mechanisms of metabolic dysfunction in cancer-associated cachexia

Metabolic dysfunction contributes to the clinical deterioration observed in advanced cancer patients and is characterized by weight loss, skeletal muscle wasting, and atrophy of the adipose tissue. This systemic syndrome, termed cancer-associated cachexia (CAC), is a major cause of morbidity and mortality. While once attributed solely to decreased food intake, the present description of cancer cachexia is a disorder of multiorgan energy imbalance. Here we review the molecules and pathways responsible for metabolic dysfunction in CAC and the ideas that led to the current understanding.

Inflammation and nutrition in children with chronic kidney disease

Chronic inflammation and nutritional imbalance are important comorbid conditions that correlate with poor clinical outcomes in children with chronic kidney disease (CKD). Nutritional disorders such as cachexia/protein energy wasting, obesity and growth retardation negatively impact the quality of life and disease progression in children with CKD. Inadequate nutrition has been associated with growth disturbances in children with CKD. On the other hand, over-nutrition and obesity are associated with poor outcomes in children with CKD. The exact mechanisms leading to these unfavorable conditions are not fully elucidated and are most likely multifactorial. In this review, we focus on the pathophysiology of nutrition disorders and inflammation and their impact on clinical outcomes in children with CKD.

Validating Appetite Assessment Tools Among Patients Receiving Hemodialysis

OBJECTIVE

To test the performance of appetite assessment tools among patients receiving hemodialysis (HD).

DESIGN

Cross-sectional.

SUBJECTS

Two hundred twenty-one patients receiving HD enrolled in seven dialysis facilities in Northern California.

INTERVENTION

We assessed 5 appetite assessment tools (self-assessment of appetite, subjective assessment of appetite, visual analog scale [VAS], Functional Assessment of Anorexia/Cachexia Therapy [FAACT] score, and the Anorexia Questionnaire [AQ]).

MAIN OUTCOME MEASURES

Reported food intake, normalized protein catabolic rate, and change in body weight were used as criterion measures, and we assessed associations among the appetite tools and biomarkers associated with nutrition and inflammation. Patients were asked to report their appetite and the percentage of food eaten (from 0% to 100%) during the last meal compared to usual intake.

RESULTS

Fifty-eight (26%) patients reported food intake ≤ 50% (defined as poor appetite). The prevalence of anorexia was 12% by self-assessment of appetite, 6% by subjective assessment of appetite, 24% by VAS, 17% by FAACT score, and 12% by AQ. All the tools were significantly associated with food intake ≤ 50% (P < .001), except self-assessment of appetite. The FAACT score and the VAS had the strongest association with food intake ≤ 50% (C-statistic 0.80 and 0.76). Patients with food intake ≤ 50% reported weight loss more frequently than patients without low intake (36% vs 22%) and weight gain less frequently (19% vs 35%; P = .03). Normalized protein catabolic rate was lower among anorexic patients based on the VAS (1.1 ± 0.3 vs 1.2 ± 0.3, P = .03). Ln interleukin-6 correlated inversely with food intake (P = .03), but neither interleukin-6 nor C-reactive protein correlated with any of the appetite tools. Furthermore, only the self-assessment of appetite was significantly associated with serum albumin (P = .02), prealbumin (P = .02) and adiponectin concentrations (P = .03).

CONCLUSIONS

Alternative appetite assessment tools yielded widely different estimates of the prevalence of anorexia in HD. When considering self-reported food intake as the criterion standard for anorexia, the FAACT score and VAS discriminated patients reasonably well.

Endotoxemia-induced muscle wasting is associated with the change of hypothalamic neuropeptides in rats

In critical patients, sepsis-induced muscle wasting is considered to be an important contributor to complications and mortality. Previous work mainly focuses on the peripheral molecular mechanism of muscle degradation, however little evidence exists for the role of central nervous system in the process. In the present study, we, for the first time, characterized the relationship between muscle wasting and central neuropeptide changes in a septic model. Thirty-six adult male Sprague-Dawley rats were intraperitoneally injected with lipopolysaccharide (LPS) or saline. Twelve, 24 and 48 hrs after injection, skeletal muscle and hypothalamus tissues were harvested. Muscle wasting was measured by the mRNA expression of two E3 ubiquitin ligases, muscle ring finger 1 (MuRF-1) and muscle atrophy F-box (MAFbx), as well as 3-methyl-histidine (3-MH) and tyrosine release. Hypothalamic neuropeptides and inflammatory marker expressions were also measured in three time points. LPS injection caused an increase expression of MuRF-1 and MAFbx, and a significant higher release of 3-MH and tyrosine. Hypothalamic neuropeptides, proopiomelanocortin (POMC), cocaine- and amphetamine-regulated transcript (CART), agouti-related protein (AgRP) and neuropeptide Y (NPY) presented a dynamic change after LPS injection. Also, hypothalamic inflammatory markers, interleukin-1 β (IL-1β) and tumor necrosis factor α (TNF-α) increased substantially after LPS administration. Importantly, the expressions of POMC, AgRP and CART were well correlated with muscle atrophy gene, MuRF-1 expression. These findings suggest hypothalamic peptides and inflammation may participate in the sepsis-induced muscle wasting, but the exact mechanism needs further study.

Leptin as an uremic toxin: Deleterious role of leptin in chronic kidney disease

White adipose tissue secretes a large variety of compounds named adipokines amongst which, leptin exhibits pleiotropic metabolic actions. Leptin is an anorexigenic hormone, secreted in proportion of fat mass, with additional effects on the regulation of inflammation, cardiovascular system, immunity, hematopoiesis and bone metabolism. Chronic kidney disease (CKD) is characterized by an increase of plasma leptin concentration that may be explained by a lack of renal clearance. Hyperleptinemia plays a key role in the pathogenesis of complications associated with CKD such as cachexia, protein energy wasting, chronic inflammation, insulin resistance, cardiovascular damages and bone complications. Leptin is also involved in the progression of renal disease through its pro-fibrotic and pro-hypertensive actions. Most of the adverse effects of leptin have been documented both experimentally and clinically. Leptin may therefore be considered as an uremic toxin in CKD. The aim of this review is to summarize the pathophysiological and clinical role of leptin in in vitro studies, experimental models, as well as in patients suffering from CKD.

Mechanisms of muscle wasting in chronic kidney disease

In patients with chronic kidney disease (CKD), loss of cellular proteins increases the risks of morbidity and mortality. Persistence of muscle protein catabolism in CKD results in striking losses of muscle proteins as whole-body protein turnover is great; even small but persistent imbalances between protein synthesis and degradation cause substantial protein loss. No reliable methods to prevent CKD-induced muscle wasting currently exist, but mechanisms that control cellular protein turnover have been identified, suggesting that therapeutic strategies will be developed to suppress or block protein loss. Catabolic pathways that cause protein wasting include activation of the ubiquitin-proteasome system (UPS), caspase-3, lysosomes and myostatin (a negative regulator of skeletal muscle growth). These pathways can be initiated by complications associated with CKD, such as metabolic acidosis, defective insulin signalling, inflammation, increased angiotensin II levels, abnormal appetite regulation and impaired microRNA responses. Inflammation stimulates cellular signalling pathways that activate myostatin, which accelerates UPS-mediated catabolism. Blocking this pathway can prevent loss of muscle proteins. Myostatin inhibition could yield new therapeutic directions for blocking muscle protein wasting in CKD or disorders associated with its complications.

Effect of hemodiafiltration with endogenous reinfusion on overt idiopathic chronic inflammation in maintenance hemodialysis patients: a multicenter longitudinal study

Chronic inflammation is widely diffuse in maintenance hemodialysis (MHD) patients and is associated with poor survival. Hemodiafiltration with endogenous reinfusion (HFR) is a dialysis technique, highly biocompatible, able to adsorb proinflammatory cytokines and to decrease amino acids and antioxidants loss. These features could be helpful in MHD patients affected by idiopathic chronic inflammation, but this issue remains to be elucidated. We performed a multicenter longitudinal study to assess the effect of the switching from bicarbonate HD to HFR in patients with serum C-reactive Protein (CRP) > 5 mg/L coupled with albumin <4.0 g/dL in the last 6 months. We enrolled 24/176 (14%) patients, of which 20 patients were assessed at 4 months and 18 completed the study. We excluded 11 patients with evident causes of inflammation. At baseline, serum levels of CRP (18.7[7.0-39.4] mg/L) and albumin (3.5[3.3-3.7] g/dL) were significantly correlated (r = -0.49; P = 0.028). The effect on CRP and albumin was almost evident in the first 4 months and remained stable until to eighth month. A strict correlation (R = -0.49; 0.040) between percentage change of CRP (-35%) and albumin (+14%) after 8 months of HFR. These effects were associated with the reduction of IL-6, IL-1β, and TNF-α and the increment of pre-albumin and leptin, whereas the serum levels of Branched Chain Amino Acid (BCAA) remained unchanged. In MHD patients affected by idiopathic chronic inflammation the switching from BHD to HFR is associated with improvement of inflammation. Whether these favorable effects may modify the outcomes of these high-risk patients needs to be confirmed by studies ad hoc.

MicroRNAs: a new therapeutic frontier for muscle wasting in chronic kidney disease

Multiple microRNAs (miRs) are implicated in muscle cell differentiation and muscle mass regulation. Pharmacological agents targeting miR-486 and other miRs, involved in muscle mass regulation, could potentially be developed into therapeutic agents for muscle wasting. Muscle wasting is prevalent among patients with chronic kidney disease (CKD). Xu et al. showed that miR-486 mimetic ameliorated muscle wasting in mice with CKD. miR mimetics may represent a new therapeutic frontier for muscle wasting in CKD.

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.

A systems biology preview of the relationships between mineral and metabolic complications in chronic kidney disease

There are emerging data that the skeleton is connected to systemic biological functions through the release of two osteoblast-/osteocyte-derived hormones, fibroblastic growth factor 23 (FGF23) and undercarboxylated osteocalcin (Ocn). FGF23 is important in the regulation of phosphate and vitamin D metabolism, whereas Ocn participates in endocrine networks, coordinating bone and fat mass, energy metabolism, and sex hormone production. Bone remodeling and mineralization per se, along with the hormones leptin, insulin, glucocorticoids, PTH, and 1,25(OH)2D, regulate the release of FGF23 and Ocn, leading to complex cross-talk and coordination between endocrine networks previously thought to be distinct. These pathways are particularly important in chronic kidney disease, in which both FGF23 and Ocn are increased. Although these hormones initially serve an adaptive role, with progressive loss of renal function they show maladaptive effects, particularly on the cardiovascular system, through multiple mechanisms, including possible cross-talk with the renin angiotensin system. The complex interconnections between the various endocrine networks in chronic kidney disease may account for the difficulty in treating the uremic state.

The adipose tissue as an endocrine organ

During the past 2 decades, results of both basic science and clinical studies have changed the physicians' views about adipocyte pathophysiology. Since leptin was discovered in 1994, white adipose tissue was recognized as an endocrine organ and an important source of biologically active substances with local and/or systemic action called adipokines. Inappropriate secretion of several adipokines by the excessive amount of white adipose tissue seems to participate in the pathogenesis of obesity-related pathologic processes including endothelial dysfunction, inflammation, atherosclerosis, diabetes mellitus, and chronic kidney disease. In this review endocrine action of selected adipokines (mainly leptin and adiponectin) in the context of kidney diseases is discussed. Specifically, the role of these adipokines in malnutrition, chronic kidney disease progression, and pathogenesis of cardiovascular complications is presented.

Inflammatory factors and exercise in chronic kidney disease

Patients with chronic kidney disease frequently present with chronic elevations in markers of inflammation, a condition that appears to be exacerbated by disease progression and onset of haemodialysis. Systemic inflammation is interlinked with malnutrition and muscle protein wasting and is implicated in a number of morbidities including cardiovascular disease: the most common cause of mortality in this population. Research in the general population and other chronic disease cohorts suggests that an increase in habitual activity levels over a prolonged period may help redress basal increases in systemic inflammation. Furthermore, those populations with the highest baseline levels of systemic inflammation appear to have the greatest improvements from training. On the whole, the activity levels of the chronic kidney disease population reflect a sedentary lifestyle, indicating the potential for increasing physical activity and observing health benefits. This review explores the current literature investigating exercise and inflammatory factors in the chronic kidney disease population and then attempts to explain the contradictory findings and suggests where future research is required.