Growth Hormone Improves Adipose Tissue Browning and Muscle Wasting in Mice with Chronic Kidney Disease-Associated Cachexia

Common mouse models of chronic kidney disease are not associated with cachexia

The 5/6 nephrectomy and adenine-induced nephropathy mouse models have been extensively used to study Chronic Kidney Disease (CKD)-related cachexia. One common caveat of these CKD models is the cross-sectional nature of comparisons made versus controls. We here performed a comprehensive longitudinal assessment of body composition and energy metabolism in both models. The most striking finding is that weight loss is largely driven by reduced food intake which promotes rapid loss of lean and fat mass. However, in both models, mice catch up weight and lean mass a few days after the surgery or when they are switched back to standard chow diet. Muscle force and mass are fully recovered and no sign of cachexia is observed. Our data demonstrate that the time-course of kidney failure and weight loss are unrelated in these common CKD models. These data highlight the need to reconsider the relative contribution of direct and indirect mechanisms to muscle wasting observed in CKD.

Metabolic underpinnings of cancer-related fatigue

Cancer-related fatigue (CRF) is one of the most prevalent and detrimental complications of cancer. Emerging evidence suggests that obesity and insulin resistance are associated with CRF occurrence and severity in cancer patients and survivors. In this narrative review, we analyzed recent studies including both preclinical and clinical research on the relationship between obesity and/or insulin resistance and CRF. We also describe potential mechanisms for these relationships, though with the caveat that because the mechanisms underlying CRF are incompletely understood, the mechanisms mediating the association between obesity/insulin resistance and CRF are similarly incompletely delineated. The data suggest that, in addition to their effects to worsen CRF by directly promoting tumor growth and metastasis, obesity and insulin resistance may also contribute to CRF by inducing chronic inflammation, neuroendocrinological disturbance, and metabolic alterations. Furthermore, studies suggest that patients with obesity and insulin resistance experience more cancer-induced pain and are at more risk of emotional and behavioral disruptions correlated with CRF. However, other studies implied a potentially paradoxical impact of obesity and insulin resistance to reduce CRF symptoms. Despite the need for further investigation utilizing interventions to directly elucidate the mechanisms of cancer-related fatigue, current evidence demonstrates a correlation between obesity and/or insulin resistance and CRF, and suggests potential therapeutics for CRF by targeting obesity and/or obesity-related mediators.

Evaluation of Antioxidant Effects of Pumpkin (Cucurbita pepo L.) Seed Extract on Aging- and Menopause-Related Diseases Using Saos-2 Cells and Ovariectomized Rats

Aging and menopause are associated with oxidative stress and inflammation. Here, we evaluated the antioxidant properties of pumpkin (Cucurbita pepo L.) seed extract and assessed its ameliorative effects on aging- and menopause-related diseases using Saos-2 cells and ovariectomized rats. The seed extract had bioactive components that exhibited antioxidant activity. The extract increased the alkaline phosphatase (ALP) activity of Saos-2 cells. The oral administration of the extract to ovariectomized rats for 12 weeks decreased their body weight, fat weight, and cardiac risk indices. It also contributed to reductions in the levels of reactive oxygen species, oxidative stress, and inflammation, as assessed by measuring the serum levels of malondialdehyde and analyzing gene expression in rats. Furthermore, the administration of the extract also promoted an enhancement of the transcription of nuclear factor erythroid 2-related factor (Nrf2), heme oxygenase-1 (Ho-1), and catalase (Cat), involved in antioxidant activity; endothelial nitric oxide synthase (eNos), involved in vasculoprotective activity; and PR/SET domain 16 (Prdm16) and peroxisome proliferator-activated receptor-gamma coactivator (Pgc1α), involved in brown adipogenesis and thermogenesis. Our results using ovariectomized rats show that pumpkin seed extract may have ameliorative effects on menopause-related diseases by increasing ALP activity, evaluating the antioxidant system, ameliorating oxidative stress and thermogenesis, and enhancing lipid profiles.

Indoxyl sulfate inhibits muscle cell differentiation via Myf6/MRF4 and MYH2 downregulation

BACKGROUND

Chronic kidney disease (CKD) is associated with a significant decrease in muscle strength and mass, possibly related to muscle cell damage by uremic toxins. Here, we studied in vitro and in vivo the effect of indoxyl sulfate (IS), an indolic uremic toxin, on myoblast proliferation, differentiation and expression of myogenic regulatory factors (MRF)-myoblast determination protein 1 (MyoD1), myogenin (Myog), Myogenic Factor 5 (Myf5) and myogenic regulatory factor 4 (Myf6/MRF4)-and expression of myosin heavy chain, Myh2.

METHODS

C2C12 myoblasts were cultured in vitro and differentiated in myotubes for 7 days in the presence of IS at a uremic concentration of 200 µM. Myocytes morphology and differentiation was analyzed after hematoxylin-eosin staining. MRF genes' expression was studied using reverse transcription polymerase chain reaction in myocytes and 5/6th nephrectomized mice muscle. Myf6/MRF4 protein expression was studied using enzyme-linked immunosorbent assay; MYH2 protein expression was studied using western blotting. The role of Aryl Hydrocarbon Receptor (AHR)-the cell receptor of IS-was studied by adding an AHR inhibitor into the cell culture milieu.

RESULTS

In the presence of IS, the myotubes obtained were narrower and had fewer nuclei than control myotubes. The presence of IS during differentiation did not modify the gene expression of the MRFs Myf5, MyoD1 and Myog, but induced a decrease in expression of Myf6/MRF4 and MYH2 at the mRNA and the protein level. AHR inhibition by CH223191 did not reverse the decrease in Myf6/MRF4 mRNA expression induced by IS, which rules out the implication of the ARH genomic pathway. In 5/6th nephrectomized mice, the Myf6/MRF4 gene was down-regulated in striated muscles.

CONCLUSION

In conclusion, IS inhibits Myf6/MRF4 and MYH2 expression during differentiation of muscle cells, which could lead to a defect in myotube structure. Through these new mechanisms, IS could participate in muscle atrophy observed in CKD.

Chronic Kidney Disease: Underlying Molecular Mechanisms-A Special Issue Overview

Chronic kidney disease (CKD) is an epidemic health issue that requires global attention [...].

Redox Signaling in Chronic Kidney Disease-Associated Cachexia

Redox signaling alterations contribute to chronic kidney disease (CKD)-associated cachexia. This review aims to summarize studies about redox pathophysiology in CKD-associated cachexia and muscle wasting and to discuss potential therapeutic approaches based on antioxidant and anti-inflammatory molecules to restore redox homeostasis. Enzymatic and non-enzymatic systems of antioxidant molecules have been studied in experimental models of kidney diseases and patients with CKD. Oxidative stress is increased by several factors present in CKD, including uremic toxins, inflammation, and metabolic and hormone alterations, leading to muscle wasting. Rehabilitative nutritional and physical exercises have shown beneficial effects for CKD-associated cachexia. Anti-inflammatory molecules have also been tested in experimental models of CKD. The importance of oxidative stress has been shown by experimental studies in which antioxidant therapies ameliorated CKD and its associated complications in the 5/6 nephrectomy model. Treatment of CKD-associated cachexia is a challenge and further studies are necessary to investigate potential therapies involving antioxidant therapy.

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.

Is There a Need to "Modernize" and "Simplify" the Diagnostic Criteria of Protein-Energy Wasting?

Protein energy wasting(PEW) is a term that most nephrologists used to define nutritional disorders in patients with acute kidney injury and chronic kidney disease. Although this nomenclature is well implemented in the field of nephrology, the use of other terms such as cachexia or malnutritionin the majority of chronic diseases can induce confusion regarding the definition and interpretation of these terms. There is ample evidence in the literature that the pathways involved in cachexia/malnutrition and PEW are common. However, in kidney diseases, there are pathophysiological conditions such as accumulation of uremic toxins, and the use of dialysis, which may induce a phenotypic specificity justifying the original term PEW. In light of the latest epidemiologic studies, the criteria for PEW used in 2008 probably need to be updated. The objective of this review is to summarize the main mechanisms involved in cachexia/malnutrition and PEW. We discuss the need to modernize and simplify the current definition and diagnostic criteria of PEW. We consider the interest of proposing a specific nomenclature of PEW for children and elderly patients with kidney diseases.

Metabolic and histomorphological changes of adipose tissue in cachexia

PURPOSE OF REVIEW

To describe the role of the main changes occurring in adipose tissue during cachexia and how these affects patient's outcomes, with a specific focus on cancer.

RECENT FINDINGS

In cachexia, the changes within the adipose tissue have been recently described as the presence of inflammatory infiltration (T-lymphocytes and macrophages), enhanced fibrosis, and the occurrence of beige adipocytes (i.e., browning). The latter one is a process driving cachexia enhancing thermogenesis, primarily via modulation of uncoupling protein 1. Also, increased lipolysis of white adipose tissue, especially in cancer, via higher expression of hormone sensible and adipose tissue triglyceride lipases, was detected in experimental models and in human adipose tissue. Other systemic metabolic alterations occur in association with changes in adiposity, including insulin resistance and increased inflammation, all conditions associated with a worse outcome. Moreover, these profound metabolic alterations were shown to be implicated in several consequences, including extreme and progressive unvoluntary body weight loss.

SUMMARY

Alterations in adiposity occur early during cachexia. Adipose tissue atrophy, as well as metabolic changes of white adipose tissues were observed to be pivotal in cachexia, and to be implicated in several clinical complications and poor prognosis.Further research is necessary to clarify the mechanisms underlying the loss of adiposity and therefore to identify novel therapeutic options to counteract this phenomenon in cachexia.