A renal-cerebral-peripheral sympathetic reflex mediates insulin resistance in chronic kidney disease

Chronic kidney disease combined with metabolic syndrome is a non-negligible risk factor

Metabolic syndrome (MetS) is a group of conditions characterized by hypertension (HTN), hyperglycaemia or insulin resistance (IR), hyperlipidaemia, and abdominal obesity. MetS is associated with a high incidence of cardiovascular events and mortality and is an independent risk factor for chronic kidney disease (CKD). MetS can cause CKD or accelerate the progression of kidney disease. Recent studies have found that MetS and kidney disease have a cause-and-effect relationship. Patients with CKD, those undergoing kidney transplantation, or kidney donors have a significantly higher risk of developing MetS than normal people. The present study reviewed the possible mechanisms of MetS in patients with CKD, including the disorders of glucose and fat metabolism after kidney injury, IR, HTN and the administration of glucocorticoid and calcineurin inhibitors. In addition, this study reviewed the effect of MetS in patients with CKD on important target organs such as the kidney, heart, brain and blood vessels, and the treatment and prevention of CKD combined with MetS. The study aims to provide strategies for the diagnosis, treatment and prevention of CKD in patients with MetS.

Comparison of the effects of renal denervation at early or advanced stages of hypertension on cardiac, renal, and adipose tissue pathology in Dahl salt-sensitive rats

Renal denervation (RDN) has emerged as a novel therapy for drug-resistant hypertension. We here examined the effects of RDN at early versus advanced stages of hypertension on blood pressure and organ pathology in rats with salt-sensitive hypertension. Dahl salt-sensitive (DahlS) rats fed an 8% NaCl diet from 6 weeks of age were subjected to RDN (surgical ablation and application of 10% phenol in ethanol) or sham surgery at 7 (early stage) or 9 (advanced stage) weeks and were studied at 12 weeks. RDN at early or advanced stages resulted in a moderate lowering of blood pressure. Although RDN at neither stage affected left ventricular (LV) and cardiomyocyte hypertrophy, it ameliorated LV diastolic dysfunction, fibrosis, and inflammation at both stages. Intervention at both stages also attenuated renal injury as well as downregulated the expression of angiotensinogen and angiotensin-converting enzyme (ACE) genes and angiotensin II type 1 receptor protein in the kidney. Furthermore, RDN at both stages inhibited proinflammatory gene expression in adipose tissue. The early intervention reduced both visceral fat mass and adipocyte size in association with downregulation of angiotensinogen and ACE gene expression. In contrast, the late intervention increased fat mass without affecting adipocyte size as well as attenuated angiotensinogen and ACE gene expression. Our results thus indicate that RDN at early or late stages after salt loading moderately alleviated hypertension and substantially ameliorated cardiac and renal injury and adipose tissue inflammation in DahlS rats. They also suggest that cross talk among the kidney, cardiovascular system, and adipose tissue may contribute to salt-sensitive hypertension. Supposed mechanism for the beneficial effects of RDN on hypertension and target organ damage in DahlS rats. RDN at early or late stages after salt loading moderately alleviated hypertension and substantially ameliorated renal injury in DahlS rats. Cross talk among the kidney, cardiovascular system, and adipose tissue possibly mediated by circulating RAS may contribute to salt-sensitive hypertension. LV; left ventricular, NE; norepinephrine, RAS; renin-angiotensin system, RDN; renal denervation.

Dapagliflozin attenuates renal fibrosis by suppressing angiotensin II/TGFβ signaling in diabetic mice

AIMS

Diabetic nephropathy (DN) complicates diabetes Mellitus and intimately relates to intrarenal renin-angiotensin system (RAS) activity. Dapagliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), has been validated to improve renal outcomes in diabetic patients from clinical research by elusive mechanisms. This study explored the presumption that the eagerness activity of intrarenal RAS in DN generated oxidative stress to promote renal fibrosis, and the process can be interrupted by dapagliflozin.

METHODS

A streptozotocin-induced DN model was established in male C57BL/6J mice. Mice were treated with dapagliflozin or losartan for 14 weeks. Biochemical data, renal fibrosis, oxidative stress, and RAS were measured.

RESULTS

DN mice were characterized by overtly low body weight, high levels of blood glucose, and renal injury. Interrupting SGLT2 and RAS significantly improved renal dysfunction and pathological lesions in DN mice. Consistent with these favorable effects, dapagliflozin revoked the local RAS/oxidative stress and the succeeding transforming growth factor beta (TGFβ) signaling.

CONCLUSIONS

This research clarifies that intrarenal RAS activity triggers renal injury in DN, and dapagliflozin attenuates renal fibrosis by suppressing Angiotensin II/TGFβ signaling. It unravels a novel insight into the role of prevention and treatment of SGLT2 inhibitors to DN.

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.

Environmental level bisphenol A accelerates alterations of the reno-cardiac axis by the MAPK cascades in male diabetic rats: An analysis based on transcriptomic profiling and bioinformatics

In humans and animal models, the kidneys and cardiovascular systems are negatively affected by BPA from the environment. It is considered that BPA have some potential estrogen-like and non-hormone-like properties. In this study, RNA-sequencing and its-related bioinformatics was used as the basic strategy to clarify the characteristic mechanisms of kidney-heart axis remodeling and dysfunction in diabetic male rats under BPA exposure. We found that continuous BPA exposure in diabetic rats aggravated renal impairment, and caused hemodynamic disorders and dysfunctions. There were 655 and 125 differentially expressed genes in the kidney and heart, respectively. For the kidneys, functional annotation and enrichment, and gene set enrichment analyses identified bile acid secretion related to lipid synthesis and transport, and MAPK cascade pathways. For the heart, these bioinformatics analyses clearly pointed to MAPKs pathways. A total of 12 genes and another total of 6 genes were identified from the kidney tissue and heart tissue, respectively. Western blotting showed that exposure to BPA activated MAPK cascades in both organs. In this study, the exacerbated remodeling of diabetic kidney-heart axis under BPA exposure and diabetes might occur through hemodynamics, metabolism disorders, and the immune-inflammatory response, as well as continuous estrogen-like stimulation, with focus on the MAPK cascades.

Organ-differential Roles of Akt/FoxOs Axis as a Key Metabolic Modulator during Aging

FoxOs and their post-translational modification by phosphorylation, acetylation, and methylation can affect epigenetic modifications and promote the expression of downstream target genes. Therefore, they ultimately affect cellular and biological functions during aging or occurrence of age-related diseases including cancer, diabetes, and kidney diseases. As known for its key role in aging, FoxOs play various biological roles in the aging process by regulating reactive oxygen species, lipid accumulation, and inflammation. FoxOs regulated by PI3K/Akt pathway modulate the expression of various target genes encoding MnSOD, catalases, PPARγ, and IL-1β during aging, which are associated with age-related diseases. This review highlights the age-dependent differential regulatory mechanism of Akt/FoxOs axis in metabolic and non-metabolic organs. We demonstrated that age-dependent suppression of Akt increases the activity of FoxOs (Akt/FoxOs axis upregulation) in metabolic organs such as liver and muscle. This Akt/FoxOs axis could be modulated and reversed by antiaging paradigm calorie restriction (CR). In contrast, hyperinsulinemia-mediated PI3K/Akt activation inhibited FoxOs activity (Akt/FoxOs axis downregulation) leading to decrease of antioxidant genes expression in non-metabolic organs such as kidneys and lungs during aging. These phenomena are reversed by CR. The results of studies on the process of aging and CR indicate that the Akt/FoxOs axis plays a critical role in regulating metabolic homeostasis, redox stress, and inflammation in various organs during aging process. The benefical actions of CR on the Akt/FoxOs axis in metabolic and non-metabolic organs provide further insights into the molecular mechanisms of organ-differential roles of Akt/FoxOs axis during aging.

Targeting mitochondria-inflammation circle by renal denervation reduces atheroprone endothelial phenotypes and atherosclerosis

OBJECTIVE

The disruption of mitochondrial redox homeostasis in endothelial cells (ECs) can cause chronic inflammation, a substantial contributor to the development of atherosclerosis. Chronic sympathetic hyperactivity can enhance oxidative stress to induce endothelial dysfunction. We determined if renal denervation (RDN), the strategy reducing sympathetic tone, can protect ECs by ameliorating mitochondrial reactive oxygen species (ROS)-induced inflammation to reduce atherosclerosis.

METHODS AND RESULTS

ApoE deficient (ApoE^-/-) mice were conducted RDN or sham operation before 20-week high-fat diet feeding. Atherosclerosis, EC phenotype and mitochondrial morphology were determined. In vitro, human arterial ECs were treated with norepinephrine to determine the mechanisms for RDN-inhibited endothelial inflammation. RDN reduced atherosclerosis, EC mitochondrial oxidative stress and inflammation. Mechanistically, the chronic sympathetic hyperactivity increased circulating norepinephrine and mitochondrial monoamine oxidase A (MAO-A) activity. MAO-A activation-impaired mitochondrial homeostasis resulted in ROS accumulation and NF-κB activation, thereby enhancing expression of atherogenic and proinflammatory molecules in ECs. It also suppressed mitochondrial function regulator PGC-1α, with involvement of NF-κB and oxidative stress. Inactivation of MAO-A by RDN disrupted the positive-feedback regulation between mitochondrial dysfunction and inflammation, thereby inhibiting EC atheroprone phenotypic alterations and atherosclerosis.

CONCLUSIONS

The interplay between MAO-A-induced mitochondrial oxidative stress and inflammation in ECs is a key driver in atherogenesis, and it can be reduced by RDN.

Association of heart rate and diabetes among 0.5 million adults in the China Kadoorie biobank: Results from observational and Mendelian randomization analyses

BACKGROUND AND AIMS

Observational studies have associated resting heart rate with incident diabetes. Whether the associations are causal remains unclear. We aimed to examine the shape and strength of the associations and assessed the causal relevance of such associations in Chinese adults.

METHODS AND RESULTS

The China Kadoorie Biobank enrolled 512,891 adults in China. Cox proportional hazard regression models was conducted to estimate hazard ratios (HRs) for the associations of resting heart rate with type 2 diabetes and total diabetes. Among 92,724 participants, 36 single-nucleotide polymorphisms (SNPs) related to resting heart rate were used to construct genetic risk score. We used Mendelian randomization analyses to make the causal inferences. During a median follow-up of 9 years, 7872 incident type 2 diabetes and 13,349 incident total diabetes were documented. After regression dilution bias adjustment, each 10 bpm higher heart rate was associated with about a 26% higher risk of type 2 diabetes (HR, 1.26 [95% CI, 1.23, 1.29]) and 23% higher risk of total diabetes (HR, 1.23 [95% CI, 1.20, 1.26]). Instrumental variable analyses showed participants at top quintile compared with those at bottom quintile had 30% higher risk for type 2 diabetes (HR, 1.30 [95% CI, 1.17, 1.43]), and 10% higher risk for total diabetes (HR, 1.10 [95% CI, 1.02, 1.20]).

CONCLUSIONS

This study provides evidence that resting heart rate is an important risk factor for diabetes risk. The results suggest that novel treatment approaches targeting reduction of high heart rate for incidence of diabetes may be worth further investigation.

Metabolic effects two years after renal denervation in insulin resistant hypertensive patients. The Re-Shape CV-risk study

BACKGROUND & AIMS

Denervation of renal sympathetic nerves (RDN) is an invasive endovascular procedure introduced as an antihypertensive treatment with a potential beneficial effect on insulin resistance (IR). We have previously demonstrated a reduction in blood pressure (BP) six months after RDN, but severe hepatic and peripheral IR, assessed by glucose tracer and two step hyperinsulinemic-euglycemic clamp (HEC), did not improve. The aim of the current study was to evaluate IR and adipokines profiles in relation to BP and arterial stiffness changes two years after RDN.

METHODS

In 20 non-diabetic patients with true treatment-resistant hypertension, ambulatory and office BP were measured after witnessed intake of medications prior to, six and 24 months after RDN. Arterial stiffness index (AASI) was calculated from ambulatory BP. Insulin sensitivity (IS) was assessed using an oral glucose tolerance test (OGTT), the Homeostasis Model Assessment (HOMA-IR), HOMA-Adiponectin Model Assessment (HOMA-AD), the Quantitative Insulin Sensitivity Check Index (QUICKI), the Triglyceride and Glucose Index (TyG) and the Leptin-to-Adiponectin Ratio (LAR). These surrogate indices of IS were compared with tracer/HEC measurements to identify which best correlated in this group of patients.

RESULTS

All measured metabolic variables and IS surrogate indices remained essentially unchanged two years after RDN apart from a significant increase in HOMA-AD. OGTT peak at 30 min correlated best with reduction in endogenous glucose release (EGR) during low insulin HEC (r = -0.6, p = 0.01), whereas HOMA-IR correlated best with whole-body glucose disposal (WGD) (r = -0.6, p = 0.01) and glucose infusion rate (r = -0.6, p = 0.01) during high insulin HEC. BP response was unrelated to IS prior to RDN. Nocturnal systolic BP and arterial stiffness before RDN correlated positively with a progression in hepatic IR at six-month follow-up.

CONCLUSION

IR, adiponectin and leptin did not improve two years after RDN. There was no correlation between baseline IS and BP response. Our study does not support the notion of a beneficial metabolic effect of RDN in patients with treatment resistant hypertension.

Taxifolin improves disorders of glucose metabolism and water-salt metabolism in kidney via PI3K/AKT signaling pathway in metabolic syndrome rats

AIMS

Our study was designed to explore the function and mechanism of taxifolin on glucose metabolism and water-salt metabolism in kidney with metabolic syndrome (MS) rats.

MAIN METHODS

Spontaneous hypertensive rats were induced by fructose to establish MS model. Systolic blood pressure (SBP) and homeostasis model assessment of insulin resistance (HOMA-IR) were measured after 7 weeks of continuous administration with taxifolin. Kidney injury indices and histopathological evaluation were done. The apoptosis rate of primary kidney cells was detected by flow cytometry. Insulin signaling pathway related proteins and renal glucose transport-related proteins were detected by western blotting. We assessed the effects of taxifolin on sodium water retention and renin-angiotensin-aldosterone system (RAAS) in MS rats. We examined not only changes in urine volume, osmotic pressure, urinary sodium and urinary chloride excretion, but also the effects on NA⁺/K⁺-ATPase and RAAS indicators. We also detected changes in inflammatory factors by immunohistochemical staining and immunofluorescence. In vitro experiment, high glucose and salt stimulated NRK-52E cells. By adding the PI3K inhibitor (wortmannin) to inhibit the PI3K, the effects of inhibiting the PI3K/AKT signaling pathway on glucose metabolism, water-sodium retention and inflammatory response were discussed.

KEY FINDINGS

Taxifolin effectively reversed SBP, HOMA-IR, the kidney indices and abnormal histopathological changes induced by MS. Besides, taxifolin called back the protein associated with the downstream glucose metabolism pathway of PI3K/AKT. It also inhibited overactivation of RAAS and inflammatory response. In vitro experiments have demonstrated that the PI3K/AKT signaling pathway plays an important role in this process.

SIGNIFICANCE

Taxifolin can improve homeostasis of glucose, inhibit overactivation of RAAS and reduce inflammatory response by PI3K/AKT signaling pathway.

Alleviation of salt-induced exacerbation of cardiac, renal, and visceral fat pathology in rats with metabolic syndrome by surgical removal of subcutaneous fat

OBJECTIVES

Evidence suggests that visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) should be considered as distinct types of white fat. Although VAT plays a key role in metabolic syndrome (MetS), the role of subcutaneous adipose tissue (SAT) has been unclear. DahlS.Z-Lepr^fa/Lepr^fa (DS/obese) rats, an animal model of MetS, develop adipocyte hypertrophy and inflammation to similar extents in SAT and VAT. We have now investigated the effects of salt loading and SAT removal on cardiac, renal, and VAT pathology in DS/obese rats.

METHODS

DS/obese rats were subjected to surgical removal of inguinal SAT or sham surgery at 8 weeks of age. They were provided with a 0.3% NaCl solution as drinking water or water alone for 4 weeks from 9 weeks of age.

RESULTS

Salt loading exacerbated hypertension, insulin resistance, as well as left ventricular (LV) hypertrophy, inflammation, fibrosis, and diastolic dysfunction in DS/obese rats. It also reduced both SAT and VAT mass but aggravated inflammation only in VAT. Although SAT removal did not affect LV hypertrophy in salt-loaded DS/obese rats, it attenuated hypertension, insulin resistance, and LV injury as well as restored fat mass and alleviated inflammation and the downregulation of adiponectin gene expression in VAT. In addition, whereas salt loading worsened renal injury as well as upregulated the expression of renin-angiotensin-aldosterone system-related genes in the kidney, these effects were suppressed by removal of SAT.

CONCLUSIONS

SAT removal attenuated salt-induced exacerbation of MetS and LV and renal pathology in DS/obese rats. These beneficial effects of SAT removal are likely attributable, at least in part, to inhibition of both VAT and systemic inflammation.

Sympathetic Overactivity in CKD Disrupts Buffering of Neurotransmission by Endothelium-Derived Hyperpolarizing Factor and Enhances Vasoconstriction

BACKGROUND

Hypertension commonly complicates CKD. Vascular smooth muscle cells (VSMCs) of resistance arteries receive signals from the sympathetic nervous system that induce an endothelial cell (EC)-dependent anticontractile response that moderates vasoconstriction. However, the specific role of this pathway in the enhanced vasoconstriction in CKD is unknown.

METHODS

A mouse model of CKD hypertension generated with 5/6-nephrectomy (5/6Nx) was used to investigate the hypothesis that an impaired anticontractile mechanism enhances sympathetic vasoconstriction. In vivo, ex vivo (isolated mesenteric resistance arteries), and in vitro (VSMC and EC coculture) models demonstrated neurovascular transmission and its contribution to vascular resistance.

RESULTS

By 4 weeks, 5/6Nx mice (versus sham) had augmented increases in mesenteric vascular resistance and mean arterial pressure with carotid artery occlusion, accompanied by decreased connexin 43 (Cx43) expression at myoendothelial junctions (MEJs), impaired gap junction function, decreased EC-dependent hyperpolarization (EDH), and enhanced contractions. Exposure of VSMCs to NE for 24 hours in a vascular cell coculture decreased MEJ Cx43 expression and MEJ gap junction function. These changes preceded vascular structural changes evident only at week 8. Inhibition of central sympathetic outflow or transfection of Cx43 normalized neurovascular transmission and vasoconstriction in 5/6Nx mice.

CONCLUSIONS

5/6Nx mice have enhanced neurovascular transmission and vasoconstriction from an impaired EDH anticontractile component before vascular structural changes. These neurovascular changes depend on an enhanced sympathetic discharge that impairs the expression of Cx43 in gap junctions at MEJs, thereby interrupting EDH responses that normally moderate vascular tone. Dysregulation of neurovascular transmission may contribute to the development of hypertension in CKD.

Metabolic and cardiovascular risk factors in Klinefelter syndrome

Klinefelter syndrome (KS), which normally presents with a 47,XXY karyotype, is the most common sex chromosome disorder in males. It is also the most common genetic cause of male infertility. KS subjects are typically tall, with small and firm testes, gynecomastia, broad hips, and sparse body hair, although a less evident presentation is also possible. KS is also characterized by a high prevalence of hypogonadism, metabolic syndrome (MetS) and cardiovascular disease. The aim of this article is to systematically review metabolic and the cardiovascular risk factors in KS patients. Hypogonadism has an important role in the pathogenesis of the changes in body composition (particularly visceral obesity) and hence of insulin resistance and MetS, but the association between KS and MetS may go beyond hypogonadism alone. From childhood, KS patients may show an increase in visceral fat with a reduction in lean body mass and an increase in glucose and impaired fat metabolism. Their increased incidence of congenital anomalies, epicardial adipose tissue, and thromboembolic disease suggests they have a higher risk of cardiovascular disease. There is conflicting evidence on the effects of testosterone therapy on body composition and metabolism.

Renal Nerve Deafferentation Attenuates the Fall in GFR during Intravenous Infusion of Furosemide in Anesthetized Rats

INTRODUCTION

Furosemide reduces the glomerular filtration rate (GFR) and increases the renal vascular resistance (RVR) despite inhibiting tubuloglomerular feedback but increases proximal tubule pressure, renin release, and renal nerve activity.

OBJECTIVE

This study tested the hypothesis that the fall in GFR with furosemide is due to volume depletion or activation of angiotensin type 1 (AT1) receptors or renal nerves.

METHODS

Furosemide was infused for 60 min at 1.0 mg·kg-1·h-1 in groups of 5-8 anesthetized rats. Additional groups received intravenous volume replacement to prevent fluid and Na+ losses or volume replacement plus losartan or plus sham denervation or plus renal denervation or renal nerve deafferentation.

RESULTS

At 60 min of infusion, furosemide alone reduced the GFR (-37 ± 4%; p < 0.01). This fall was not prevented by volume replacement or pretreatment with losartan, although losartan moderated the increase in RVR with furosemide (+44 ± 3 vs. +82 ± 7%; p < 0.01). Whereas the GFR fell after furosemide in rats after sham procedure (-31 ± 2%), it was not changed significantly after prior renal deafferentation. Proximal tubule pressure increased significantly but returned towards baseline over 60 min of furosemide, while urine output remained elevated, and GFR and renal blood flow depressed.

CONCLUSIONS

The fall in GFR over 60 min of furosemide infusion is independent of volume depletion or activation of AT1 receptors but is largely dependent on renal afferent nerves.

Biochanin A protects against angiotensin II-induced damage of dopaminergic neurons in rats associated with the increased endophilin A2 expression

The brain renin-angiotensin system plays a vital role in the modulation of the neuroinflammatory responses and the progression of dopaminergic (DA) degeneration. Angiotensin II (Ang II) induces microglia activation via angiotensin II type 1 receptor (AT1R), which in turn affects the function of DA neurons. Endophilin A2 (EPA2) is involved in fast endophilin-mediated endocytosis and quickly endocytoses several G-protein-coupled receptor (GPCR), while AT1R belongs to GPCR family. Therefore, we speculated that EPA2 may modulate microglia activation via endocytosing AT1R. Biochanin A is an O-methylated isoflavone, classified as a kind of phytoestrogen due to its chemical structure that is similar to mammalian estrogens. In this study, we investigated the protective effects of biochanin A on Ang II-induced DA neurons damage in vivo, and molecular mechanisms. The results showed that biochanin A treatment for 7 days attenuated the behavioral dysfunction, inhibited the microglial activation, and prevented DA neuron damage in Ang II-induced rats. Furthermore, biochanin A increased EPA2 expression and decreased the expression of AT1R, gp91phox, p22 phox, NLRP3, ASC, Caspase-1, IL-1β, IL-6, IL-18, and TNF-α. In summary, these results suggest that biochanin A exerts protective effects in Ang II-induced model rats, and the mechanisms may involve inhibition of inflammatory responses, an increase in EPA2 expression and a decrease in AT1R expression.

Adipocytes initiate an adipose-cerebral-peripheral sympathetic reflex to induce insulin resistance during high-fat feeding

The underlying mechanism by which amassing of white adipose tissue in obesity regulates sympathetic nerve system (SNS) drive to the tissues responsible for glucose disposal, and causes insulin resistance (IR), remains unknown. We tested the hypothesis that high-fat (HF) feeding increases afferent impulses from white adipose tissue that reflexively elevate efferent nerve activity to skeletal muscle (SM) and adipose tissue to impair their local glucose uptake. We also investigated how salt-intake can enhance IR. HF-fed rats received a normal salt (0.4%) or high salt (4%) diet for 3 weeks. High-salt intake in HF fed rats decreased insulin-stimulated 2-deoxyglucose uptake by over 30% in white adipose tissue and SM, exacerbated inflammation, and impaired their insulin signaling and glucose transporter 4 (Glut4) trafficking. Dietary salt in HF fed rats also increased the activity of the adipose-cerebral-muscle renin-angiotensin system (RAS) axes, SNS, and reactive oxygen species (ROS). Insulin sensitivity was reduced by 32% in HF rats during high-salt intake, but was improved by over 62% by interruption of central RAS and SNS drive, and by over 45% by denervation or deafferentation of epididymal fat (all P<0.05). Our study suggest that a HF diet engages a sympathetic reflex from the white adipose tissue that activates adipose-cerebral-muscle RAS/ROS axes and coordinates a reduction in peripheral glucose uptake. These are all enhanced by salt-loading. These findings provide new insight into the role of a reflex initiated in adipose tissue in the regulation of glucose homeostasis during HF feeding that could lead to new therapeutic approaches to IR.

The regulation effect of WNT-RAS signaling in hypothalamic paraventricular nucleus on renal fibrosis

Background

Abnormal activation of wnt/β-catenin signaling and renin-angiotensin system is known to play a vital role in the development and progression of CKD. We hypothesized that abnormal expression of central wnt/β-catenin signaling and renin-angiotensin system (WNT-RAS signaling) was tightly involved in CKD.

Methods

We established sham-operated and 5/6 nephrectomized (5/6 NX) rat model and blocked the central wnt signaling by intracerebroventricular injection of adeno-associated virus vector which can overexpress target gene DKK1. The central and renal expression level of wnt/β-catenin signaling and RAS and renal injury were assessed.

Results

The expression levels of the main wnt/β-catenin signaling components in both brain and kidney of 5/6NX rats, such as wnt3a and active-β-catenin, were elevated obviously and the up-regulation were inhibited by central blockade of the wnt signaling. Furthermore, the expression of the major components of RAS in both brain and kidney in 5/6NX rats, such as angiotensinogen (AGT), angiotensin converting enzyme (ACE-1), angiotensin II AT1-receptor (AT1R), was significantly up-regulated and the up-regulated expression was inhibited by central blockade of the wnt singling. Notably, central blockade of the wnt signaling improved renal function as indicated by decreased serum creatinine and 24 h urinary protein, and attenuated interstitial fibrosis as indicated by reduced Sirius red staining and expression of Fibronectin, Collagen-I and α-SMA.

Conclusion

These data suggest that the central WNT-RAS signaling plays a significant role in the development and progression of CKD.