Obesity causes renal mitochondrial dysfunction and energy imbalance and accelerates chronic kidney disease in mice

Involvement of the vagus nerve and hepatic gene expression in serum adiponectin concentrations in mice

Several humoral factors, such as adiponectin and urate, have been suggested to affect metabolic syndromes. Previously, we reported a reduction in blood adiponectin concentrations after a high-fructose diet partially via the vagus nerve in rats. Although a lithogenic diet (LD), i.e., supplementation of a normal control diet (CT) with 0.6% cholesterol and 0.2% sodium cholate, reduced blood adiponectin concentrations, the involvement of the vagus nerve in this mechanism remains unclear. To estimate the involvement of the vagus nerve in the regulation of blood adiponectin concentrations using an LD, male imprinting control region mice that had been vagotomized (HVx) or only laparotomized (Sham) were administered a CT or an LD for 10 weeks. Serum adiponectin concentrations in the Sham-LD, HVx-CT, and HVx-LD groups were reduced by half compared with the Sham-CT group. The hepatic mRNA levels of fibroblast growth factor 21 (Fgf21), which reportedly stimulates adiponectin secretion from white adipose tissue, were lower in the LD groups compared with the CT groups. HepG2 hepatoma cells showed that various bile acids reduced the mRNA expression of FGF21. Moreover, the LD increased serum urate concentrations and reduced hepatic expressions of the acyl-CoA oxidase 1 (Acox1) mRNA and glucokinase, suggesting insufficient regeneration of ATP from AMP. In conclusion, serum adiponectin concentration may be regulated via the vagus nerve in normal mice, whereas a reduction of hepatic Fgf21 mRNA by bile acids may also lower serum adiponectin levels. Moreover, the LD may promote hepatic AMP accumulation and subsequently increase the serum urate concentration in mice.

Skeletal muscle atrophy in clinical and preclinical models of chronic kidney disease: A systematic review and meta-analysis

Patients with chronic kidney disease (CKD) are often regarded as experiencing wasting of muscle mass and declining muscle strength and function, collectively termed sarcopenia. The extent of skeletal muscle wasting in clinical and preclinical CKD populations is unclear. We evaluated skeletal muscle atrophy in preclinical and clinical models of CKD, with multiple sub-analyses for muscle mass assessment methods, CKD severity, sex and across the different preclinical models of CKD. We performed a systematic literature review of clinical and preclinical studies that measured muscle mass/size using the following databases: Ovid Medline, Embase and Scopus. A random effects meta-analysis was utilized to determine standard mean difference (SMD; Hedges' g) between healthy and CKD. Heterogeneity was evaluated using the I2 statistic. Preclinical study quality was assessed via the Systematic Review Centre for Laboratory Animal Experimentation and clinical studies quality was assessed via the Newcastle-Ottawa Scale. This study was registered in PROSPERO (CRD42020180737) prior to initiation of the search. A total of 111 studies were included in this analysis using the following subgroups: 106 studies in the primary CKD analysis, 18 studies that accounted for diabetes and 7 kidney transplant studies. Significant atrophy was demonstrated in 78% of the preclinical studies and 49% of the clinical studies. The random effects model demonstrated a medium overall SMD (SMD = 0.58, 95% CI = 0.52-0.64) when combining clinical and preclinical studies, a medium SMD for the clinical population (SMD = 0.48, 95% CI = 0.42-0.55; all stages) and a large SMD for preclinical CKD (SMD = 0.95, 95% CI = 0.76-1.14). Further sub-analyses were performed based upon assessment methods, disease status and animal model. Muscle atrophy was reported in 49% of the clinical studies, paired with small mean differences. Preclinical studies reported significant atrophy in 78% of studies, with large mean differences. Across multiple clinical sub-analyses such as severity of CKD, dialysis modality and diabetes, a medium mean difference was found. Sub-analyses in both clinical and preclinical studies found a large mean difference for males and medium for females suggesting sex-specific implications. Muscle atrophy differences varied based upon assessment method for clinical and preclinical studies. Limitations in study design prevented conclusions to be made about the extent of muscle loss with disease progression, or the impact of dialysis. Future work would benefit from the use of standardized measurement methods and consistent clinical staging to improve our understanding of atrophy changes in CKD progression, and analysis of biological sex differences.

Kidney Fibrosis and Oxidative Stress: From Molecular Pathways to New Pharmacological Opportunities

Kidney fibrosis, diffused into the interstitium, vessels, and glomerulus, is the main pathologic feature associated with loss of renal function and chronic kidney disease (CKD). Fibrosis may be triggered in kidney diseases by different genetic and molecular insults. However, several studies have shown that fibrosis can be linked to oxidative stress and mitochondrial dysfunction in CKD. In this review, we will focus on three pathways that link oxidative stress and kidney fibrosis, namely: (i) hyperglycemia and mitochondrial energy imbalance, (ii) the mineralocorticoid signaling pathway, and (iii) the hypoxia-inducible factor (HIF) pathway. We selected these pathways because they are targeted by available medications capable of reducing kidney fibrosis, such as sodium-glucose cotransporter-2 (SGLT2) inhibitors, non-steroidal mineralocorticoid receptor antagonists (MRAs), and HIF-1alpha-prolyl hydroxylase inhibitors. These drugs have shown a reduction in oxidative stress in the kidney and a reduced collagen deposition across different CKD subtypes. However, there is still a long and winding road to a clear understanding of the anti-fibrotic effects of these compounds in humans, due to the inherent practical and ethical difficulties in obtaining sequential kidney biopsies and the lack of specific fibrosis biomarkers measurable in easily accessible matrices like urine. In this narrative review, we will describe these three pathways, their interconnections, and their link to and activity in oxidative stress and kidney fibrosis.

Determination of mitochondrial functions and damage in kidney in female LeeSung minipigs with a high-fat diet-induced obesity

The purpose of this study was to investigate the nexus between mitochondrial function and kidney injury by using a dietary-induced obese minipig model. Female Lee-Sung minipigs feeding a high-fat diet (HFD) for 6 months exhibited obesity, hyperglycaemia and dyslipidemia. HFD elevated the levels of plasma biomarkers related to renal injury, including symmetric dimethylarginine, creatinine and urea nitrogen. An extensive structural change in tubules and glomeruli was observed in HFD-fed pigs. A great amount of triacylglycerol was accumulated in HFD kidney compared to control kidney, whereas a reduction of ATP level and antioxidant capacity were exhibited in HFD kidney. Moreover, HFD altered the expressions of mitochondrial-related protein in renal cortex. To conclude, long-term HFD feeding to Lee-Sung minipigs induced obesity and kidney injury accompanied by abnormal mitochondrial functions in the renal cortex, suggesting an interrelationship with renal disease progression.

Mitochondrial disorders as a mechanism for the development of obese Sarcopenia

Obese sarcopenia is a severe and prevalent disease in an aging society. Compared to sarcopenia alone, the development and advanced stage of obesity sarcopenia is faster and more severe. Diagnosis of the cause of adipocyte accumulation is also more complicated; however, no effective pharmacological treatment is available. Chronic inflammation is one of the causes of sarcopenia, and obese patients, who are more likely to develop chronic inflammation, may simultaneously suffer from obesity and sarcopenia. Mitochondrial metabolic disorders have been more easily observed in the tissue cells of patients with obesity and sarcopenia. Mitochondrial metabolic disorders include abnormal mtDNA release, mitochondrial autophagy, and dynamic mitochondrial disorders. Therefore, this review will reveal the mechanism of development of obesity myasthenia gravis from the perspective of mitochondria and discuss the currently existing small-molecule drugs.

Metabolic and Hepatic Effects of Empagliflozin on Nonalcoholic Fatty Liver Mice

Purpose

Among chronic liver diseases, non-alcoholic fatty liver disease (NAFLD) is one of the commonest. Although empagliflozin has several therapeutic uses in treating cardiovascular and renal disorders, its impacts and mechanisms on NAFLD are poorly understood. This research aimed to examine the metabolic regulatory mechanism through which empagliflozin protects against NAFLD.

Methods

Equal grouping of twenty-seven male C57BL/6J mice into those fed a normal diet (NCD), those fed a high-fat diet (HFD), and those fed an HFD with empagliflozin (Empa) was approached. HE, oil red O staining, and Masson staining were utilized for evaluating the pathological damage to the liver and the mice's liver and body weights. Lipids, blood glucose, and inflammation index were compared across the three groups. Liquid chromatography/mass spectrometry (LC-MS) has been employed for identifying liver metabolomics.

Results

The findings suggested that empagliflozin mitigated the inflammatory and oxidative stress response associated with the buildup of lipids caused by HFD. Differentially expressed metabolites (DEMs) were identified by metabonomics analysis as present in both the HFD/NCD and Empa/HFD groups. These DEMs were primarily found in lipids and organic acids like lysophosphatidylcholine (lysoPC), lecithin (PC), triglyceride (TG), palmitic acid, and L-isoleucine. Among the enriched pathways that were shown to be important were those involved in the metabolism of histidine, arachidonic acid, the control of lipolysis in adipocytes, and insulin resistance. There was a strong correlation between inflammation and oxidative stress in most of the metabolites. The inflammation and oxidative stress unbalance were ameliorated by empagliflozin.

Conclusion

NAFLD mice model showed considerable improvement in metabolic abnormalities and liver protection after treatment with empagliflozin. The process may include the overexpression of L-isoleucine and the downregulation of lysoPC, PC, TG, and palmitic acid to reduce liver harm caused by lipotoxicity.

Mitochondrial dysfunction: roles in skeletal muscle atrophy

Mitochondria play important roles in maintaining cellular homeostasis and skeletal muscle health, and damage to mitochondria can lead to a series of pathophysiological changes. Mitochondrial dysfunction can lead to skeletal muscle atrophy, and its molecular mechanism leading to skeletal muscle atrophy is complex. Understanding the pathogenesis of mitochondrial dysfunction is useful for the prevention and treatment of skeletal muscle atrophy, and finding drugs and methods to target and modulate mitochondrial function are urgent tasks in the prevention and treatment of skeletal muscle atrophy. In this review, we first discussed the roles of normal mitochondria in skeletal muscle. Importantly, we described the effect of mitochondrial dysfunction on skeletal muscle atrophy and the molecular mechanisms involved. Furthermore, the regulatory roles of different signaling pathways (AMPK-SIRT1-PGC-1α, IGF-1-PI3K-Akt-mTOR, FoxOs, JAK-STAT3, TGF-β-Smad2/3 and NF-κB pathways, etc.) and the roles of mitochondrial factors were investigated in mitochondrial dysfunction. Next, we analyzed the manifestations of mitochondrial dysfunction in muscle atrophy caused by different diseases. Finally, we summarized the preventive and therapeutic effects of targeted regulation of mitochondrial function on skeletal muscle atrophy, including drug therapy, exercise and diet, gene therapy, stem cell therapy and physical therapy. This review is of great significance for the holistic understanding of the important role of mitochondria in skeletal muscle, which is helpful for researchers to further understanding the molecular regulatory mechanism of skeletal muscle atrophy, and has an important inspiring role for the development of therapeutic strategies for muscle atrophy targeting mitochondria in the future.

High Fructose Corn Syrup Accelerates Kidney Disease and Mortality in Obese Mice with Metabolic Syndrome

The presence of obesity and metabolic syndrome is strongly linked with chronic kidney disease (CKD), but the mechanisms responsible for the association are poorly understood. Here, we tested the hypothesis that mice with obesity and metabolic syndrome might have increased susceptibility to CKD from liquid high fructose corn syrup (HFCS) by favoring the absorption and utilization of fructose. We evaluated the pound mouse model of metabolic syndrome to determine if it showed baseline differences in fructose transport and metabolism and whether it was more susceptible to chronic kidney disease when administered HFCS. Pound mice have increased expression of fructose transporter (Glut5) and fructokinase (the limiting enzyme driving fructose metabolism) associated with enhanced fructose absorption. Pound mice receiving HFCS rapidly develop CKD with increased mortality rates associated with intrarenal mitochondria loss and oxidative stress. In pound mice lacking fructokinase, the effect of HFCS to cause CKD and early mortality was aborted, associated with reductions in oxidative stress and fewer mitochondria loss. Obesity and metabolic syndrome show increased susceptibility to fructose-containing sugars and increased risk for CKD and mortality. Lowering added sugar intake may be beneficial in reducing the risk for CKD in subjects with metabolic syndrome.

Saturated fatty acids increase LPI to reduce FUNDC1 dimerization and stability and mitochondrial function

Ectopic lipid deposition and mitochondrial dysfunction are common etiologies of obesity and metabolic disorders. Excessive dietary uptake of saturated fatty acids (SFAs) causes mitochondrial dysfunction and metabolic disorders, while unsaturated fatty acids (UFAs) counterbalance these detrimental effects. It remains elusive how SFAs and UFAs differentially signal toward mitochondria for mitochondrial performance. We report here that saturated dietary fatty acids such as palmitic acid (PA), but not unsaturated oleic acid (OA), increase lysophosphatidylinositol (LPI) production to impact on the stability of the mitophagy receptor FUNDC1 and on mitochondrial quality. Mechanistically, PA shifts FUNDC1 from dimer to monomer via enhanced production of LPI. Monomeric FUNDC1 shows increased acetylation at K104 due to dissociation of HDAC3 and increased interaction with Tip60. Acetylated FUNDC1 can be further ubiquitinated by MARCH5 for proteasomal degradation. Conversely, OA antagonizes PA-induced accumulation of LPI, and FUNDC1 monomerization and degradation. A fructose-, palmitate-, and cholesterol-enriched (FPC) diet also affects FUNDC1 dimerization and promotes its degradation in a non-alcoholic steatohepatitis (NASH) mouse model. We thus uncover a signaling pathway that orchestrates lipid metabolism with mitochondrial quality.

High fat diet is protective against kidney injury in hypertensive-diabetic mice, but leads to liver injury

Chronic kidney disease (CKD) is a worldwide health burden with increases risk of end-stage renal function if left untreated. CKD induced in the context of metabolic syndrome (MS) increases risks of hypertension, hyperglycemia, excess body fat and dyslipidemia. To test if combining a high-fat diet (HFD) regimen onto the hypertensive/ diabetic phenotype would mimic features of MS induced-CKD in mice, hyperglycemia was induced in genetically hypertensive mice (Lin), followed by HFD regimen. For that, 8-week-old male were subjected to streptozotocin (STZ) intraperitoneal (i.p.) injections (50 mg/kg, 5 days consecutive). LinSTZ were fed a 60% kCal HFD for 8 weeks. Lin mice treated with STZ developed polydipsia, became hypertensive and hyperglycemic. HFD induced weight gain, protected against glomerular hypertrophy, scarring, and albuminuria at endpoint compared to regular diet fed LinSTZ. On the other hand, HFD induced steatosis, liver fibrosis, inflammation, and increase in AST/ALT ratio, characteristics of non-alcoholic liver disease. Taken together, our results show that LinSTZ mice fed a HFD did not lead to a more robust model of MS-induced CKD, protected against kidney injury, but inducing liver damage. More studies are necessary to understand the kidney protective mechanisms of HFD when superimposed with hypertension and type 1 diabetes.

Oxidative Stress and Mitochondrial Dysfunction in Chronic Kidney Disease

The kidney contains many mitochondria that generate ATP to provide energy for cellular processes. Oxidative stress injury can be caused by impaired mitochondria with excessive levels of reactive oxygen species. Accumulating evidence has indicated a relationship between oxidative stress and kidney diseases, and revealed new insights into mitochondria-targeted therapeutics for renal injury. Improving mitochondrial homeostasis, increasing mitochondrial biogenesis, and balancing mitochondrial turnover has the potential to protect renal function against oxidative stress. Although there are some reviews that addressed this issue, the articles summarizing the relationship between mitochondria-targeted effects and the risk factors of renal failure are still few. In this review, we integrate recent studies on oxidative stress and mitochondrial function in kidney diseases, especially chronic kidney disease. We organized the causes and risk factors of oxidative stress in the kidneys based in their mitochondria-targeted effects. This review also listed the possible candidates for clinical therapeutics of kidney diseases by modulating mitochondrial function.

Metabolomics Provides Insights into Renoprotective Effects of Semaglutide in Obese Mice

PURPOSE

Semaglutide, a new long-acting glucagon-like peptide-1 analogue, has shown benefits for renal diseases, but its direct role on kidney metabolism under obesity remains unclear. The study aims to elucidate the protective effect and metabolic modulation mechanism of semaglutide on obesity-related kidney injury.

METHODS

Male C57BL/6J mice were divided into control and obesity groups. Mice in the obesity group had a high-fat diet and were treated with or without semaglutide (30nmol/kg/day). The study assayed blood biochemistry and then evaluated renal pathological injury through Periodic Acid-Schiff staining and electron microscopy. Metabolomics was utilized to analyze obesity-related metabolites in kidney samples.

RESULTS

Semaglutide significantly improved glucose homeostasis, insulin resistance, and kidney injury in obese mice. We successfully identified 377 altered metabolites (P<0.05). It was suggested that semaglutide directly improved oxidative stress and inflammation-related metabolites such as nicotinamide adenine dinucleotide (NAD+) and adenosine in the kidney of obese mice, which have not been documented in obesity-related kidney injury. Relevant enriched pathways were included phospholipids and lysophospholipids metabolism, purine metabolism, NAD+ metabolism, and insulin resistance-related metabolism. They could serve as potential targets for intervention of obesity-related kidney injury.

CONCLUSION

Our study revealed the metabolomics-based renoprotective mechanism of semaglutide in obese mice for the first time. The innovation lied in the identified metabolites such as NAD+ and adenosine targeted by semaglutide, which have not been documented in obesity-related kidney injury. Semaglutide may be a promising therapy for obesity-related kidney diseases.

Dynapenic-abdominal obesity as an independent risk factor for chronic kidney disease in postmenopausal women: a population-based cohort study

OBJECTIVE

Low muscle strength and obesity lead to a higher risk of chronic kidney disease (CKD). Perimenopause is associated with a natural decline in muscle strength and an increase in visceral adiposity. Dynapenic obesity, which is the coexistence of low muscle strength and obesity, is expected to synergistically increase the prevalence of CKD in postmenopausal women. The aim of this study was to determine combined associations of dynapenia and obesity with CKD in postmenopausal women.

METHODS

This study used data from the Korean National Health and Nutrition Examination Survey, 2016 to 2019. The study included 4,525 postmenopausal women aged 42 to 80 years that were classified into four groups based on waist circumference (≥85 cm) and hand grip strength (<18 kg): normal, dynapenic, obese, or dynapenic-obese. According to the Kidney Disease: Improving Global Outcomes, we defined CKD as an estimated glomerular filtration rate <60 mL/min per 1.73 m2. Complex sample logistic regression models were conducted to determine the relationships among coexistence of dynapenia, abdominal obesity, and the risk of CKD.

RESULTS

Dynapenic-abdominal obese group displayed lower estimated glomerular filtration rate levels than other groups (P < 0.05 for all data). The prevalence rates of CKD were 15.5%, 7.8%, 6.2%, and 2.4% in the dynapenic-abdominal obese, dynapenic, abdominal obese, and normal groups, respectively (P < 0.001). Complex sample logistic regression analyses, after adjusting for age, height, health behaviors, and comorbidities, showed that the odds ratio for CKD with respect to dynapenic-abdominal obesity was 1.82 (95% confidence interval, 1.19-2.79) and to abdominal obesity was 1.54 (95% confidence interval, 1.07-2.22) than in the normal group.

CONCLUSIONS

This study demonstrated that dynapenic-abdominal obesity, as determined by low handgrip strength and high waist circumference values, was associated with increased risk of CKD in postmenopausal women.

Mediation Effect of Platelet Traits on Associations of Central Obesity with Aging Biomarkers in Rural Adults of Henan, China

Background: To assess the associations of platelet traits and obesity indices with aging biomarkers (telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN)). Methods: A cross-sectional study was performed among 5091 rural Chinese adults. Obesity indices (waist circumference (WC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR)) and platelet traits (plateletcrit (PCT), platelet large cell ratio (P-LCR), mean platelet volume (MPV) and platelet distribution width (PDW)) were collected by physical examination. The aging biomarkers were determined by quantitative real-time polymerase chain reaction. Generalized linear regression models and mediation analysis were applied to explore the relationships between platelet traits, obesity indices, and aging biomarkers. Results: The mean age of the participants was 56 years (range: 18–79). Each one-unit increment in WC, WHR and WHtR were related to a 0.316 (95% confidence interval (CI): −0.437, −0.196), 0.323 (95% CI: −0.513, −0.134) and 0.277 (95% CI: −0.400, −0.153) decrease in relative TL; or a 0.102 (95% CI: −0.197, −0.007), 0.109 (95% CI: −0.258, −0.041) and 0.101 (95% CI: −0.199, −0.004) decrease in relative mtDNA-CN. The proportions of obesity indices with aging biomarkers mediated by platelet indices ranged from 2.85% to 10.10%. Conclusions: Increased central obesity indices in relation to shortened relative TL or decreased mtDNA-CN were mediated by platelet traits, indicating that obesity in association with the accelerated aging process may be partially attributable to abnormal platelet activity.

Obesity-Related Chronic Kidney Disease: Principal Mechanisms and New Approaches in Nutritional Management

Obesity is the epidemic of our era and its incidence is supposed to increase by more than 30% by 2030. It is commonly defined as a chronic and metabolic disease with an excessive accumulation of body fat in relation to fat-free mass, both in terms of quantity and distribution at specific points on the body. The effects of obesity have an important impact on different clinical areas, particularly endocrinology, cardiology, and nephrology. Indeed, increased rates of obesity have been associated with increased risk of cardiovascular disease (CVD), cancer, type 2 diabetes (T2D), dyslipidemia, hypertension, renal diseases, and neurocognitive impairment. Obesity-related chronic kidney disease (CKD) has been ascribed to intrarenal fat accumulation along the proximal tubule, glomeruli, renal sinus, and around the kidney capsule, and to hemodynamic changes with hyperfiltration, albuminuria, and impaired glomerular filtration rate. In addition, hypertension, dyslipidemia, and diabetes, which arise as a consequence of overweight, contribute to amplifying renal dysfunction in both the native and transplanted kidney. Overall, several mechanisms are closely related to the onset and progression of CKD in the general population, including changes in renal hemodynamics, neurohumoral pathways, renal adiposity, local and systemic inflammation, dysbiosis of microbiota, insulin resistance, and fibrotic process. Unfortunately, there are no clinical practice guidelines for the management of patients with obesity-related CKD. Therefore, dietary management is based on the clinical practice guidelines for the nutritional care of adults with CKD, developed and published by the National Kidney Foundation, Kidney Disease Outcome Quality Initiative and common recommendations for the healthy population. Optimal nutritional management of these patients should follow the guidelines of the Mediterranean diet, which is known to be associated with a lower incidence of CVD and beneficial effects on chronic diseases such as diabetes, obesity, and cognitive health. Mediterranean-style diets are often unsuccessful in promoting efficient weight loss, especially in patients with altered glucose metabolism. For this purpose, this review also discusses the use of non-classical weight loss approaches in CKD, including intermittent fasting and ketogenic diet to contrast the onset and progression of obesity-related CKD.

Renal mitochondrial injury in the pathogenesis of CKD: mtDNA and mitomiRs

Chronic kidney disease (CKD) is a public health concern that affects over 200 million people worldwide and is associated with a tremendous economic burden. Therefore, deciphering the mechanisms underpinning CKD is crucial to decelerate its progression towards end-stage renal disease (ESRD). Renal tubular cells are populated with a high number of mitochondria, which produce cellular energy and modulate several important cellular processes, including generation of reactive oxygen species (ROS), calcium homeostasis, proliferation, and apoptosis. Over the past few years, increasing evidence has implicated renal mitochondrial damage in the pathogenesis of common etiologies of CKD, such as diabetes, hypertension, metabolic syndrome (MetS), chronic renal ischemia, and polycystic kidney disease (PKD). However, most compelling evidence is based on preclinical studies because renal biopsies are not routinely performed in many patients with CKD. Previous studies have shown that urinary mitochondrial DNA (mtDNA) copy numbers may serve as non-invasive biomarkers of renal mitochondrial dysfunction. Emerging data also suggest that CKD is associated with altered expression of mitochondria-related microRNAs (mitomiRs), which localize in mitochondria and regulate the expression of mtDNA and nucleus-encoded mitochondrial genes. This review summarizes relevant evidence regarding the involvement of renal mitochondrial injury and dysfunction in frequent forms of CKD. We further provide an overview of non-invasive biomarkers and potential mechanisms of renal mitochondrial damage, especially focusing on mtDNA and mitomiRs.

Thyroid-Stimulating Hormone Inhibits Insulin Receptor Substrate-1 Expression and Tyrosyl Phosphorylation in 3T3-L1 Adipocytes by Increasing NF-κB DNA-Binding Activity

Background. Abundant evidence indicates that thyroid-stimulating hormone (TSH) levels are associated with insulin resistance in adipocytes. However, the potential mechanism of the association remains uncertain. The objective of this study was to determine the potential role of TSH in the suppression of insulin receptor substrate-1 (IRS-1) expression and IRS-1 tyrosyl phosphorylation, which might contribute to insulin resistance. Methods. Mouse 3T3-L1 preadipocytes were differentiated into adipocytes. After treatment with 0.01, 0.1, and 1.0 mIU/ml bovine TSH, the TNF-α concentration in the medium was determined by enzyme-linked immunosorbent assay (ELISA). Nuclear factor-kappa B (NF-κB) DNA-binding activity was quantified by electrophoretic mobility shift assay (EMSA). IRS-1 levels in adipocytes were quantified by Western blotting, and tyrosine phosphorylation was measured by immunoprecipitation. Results. TSH induced TNF-α secretion in a dose-dependent manner. There was a significant positive correlation between NF-κB DNA-binding activity and TNF-α secretion. This effect and correlation were weakened by BAY 11-7082 (a nuclear NF-κB inhibitor) and H89 (an inhibitor of cyclic adenosine monophosphate- (cAMP-) dependent protein kinase A (PKA)). Treatment of cultured adipocytes with TSH inhibited insulin-stimulated IRS-1 tyrosyl phosphorylation but promoted TSH-dependent secretion of TNF-α and activation of NF-κB DNA-binding activity. The effects of TSH were significantly inhibited by BAY 11-7082 and H89 and were completely blocked by the TNF-α antagonist WP9QY. Conclusion. TSH inhibited IRS-1 protein expression and tyrosyl phosphorylation in 3T3-L1 adipocytes by stimulating TNF-α production via promotion of NF-κB DNA-binding activity. TSH might play a pivotal role in the development of insulin resistance.

Chicoric Acid Attenuated Renal Tubular Injury in HFD-Induced Chronic Kidney Disease Mice through the Promotion of Mitophagy via the Nrf2/PINK/Parkin Pathway

As the main factor in the pathogenesis of chronic kidney disease (CKD), the excessive apoptosis of renal tubular epithelial cells (RTECs) and its underlying mechanism of action are worth further investigation. Chicoric acid (CA), a major active constituent of the Uyghur folk medicine chicory, was recorded to possess a renal protective effect. The precise effect of CA on renal tubular injury in obesity-related CKD remains unknown. In the current study, CA was proven to ameliorate metabolic disorders including overweight, hyperglycemia, hyperlipidemia, and hyperuricemia in high fat diet (HFD)-fed mice. Furthermore, the reverse effect of CA on renal histological changes and functional damage was confirmed. In vitro, the alleviation of lipid accumulation and cell apoptosis was observed in palmitic acid (PA)-exposed HK2 cells. Treatment with CA reduced mitochondrial damage and oxidative stress in the renal tubule of HFD-fed mice and PA-treated HK2 cells. Finally, CA was observed to activate the Nrf2 pathway; increase PINK and Parkin expression; and regulate LC3, SQSTM1, Mfn2, and FIS1 expression; therefore, it would improve mitochondrial dynamics and mitophagy to alleviate mitochondrial damage in RTECs of obesity-related CKD. These results may provide fresh insights into the promotion of mitophagy in the prevention and alleviation of obesity-related CKD.

Metabolic syndrome severity score and the progression of CKD

BACKGROUND

Metabolic syndrome severity, expressed by the continuous metabolic syndrome risk score (MetS score), has been demonstrated to be able to predict future health conditions. However, little is known about the association between MetS score and renal function.

METHODS

A total of 22,719 participants with normal renal function abstracted from the Kailuan Study were followed from 2006 to 2016. The new onset of chronic kidney disease (CKD) was defined as eGFR <60 ml/min per 1.73 m² and/or proteinuria >300 mg/dl. Progressive decline in renal function was defined as an annual change rate of eGFR below the 10th percentile of the whole population.

RESULTS

In the multivariate-adjusted model, we found that the risk of progressive decline in renal function increased consistently with the MetS score, with an odds ratio of 1.49 (95% CI, 1.28, 1.73) for those subjects>75th percentile compared with those <25th percentile. Additionally, a high MetS score was found to be associated with an increased risk of CKD, with a hazard ratio of 1.53 (95% CI, 1.33, 1.78) for subjects >75th percentile compared with those <25th percentile.

CONCLUSIONS

Our findings suggested that the MetS score was associated with an increased risk of a progressive decline in renal function and was also a strong and independent risk factor for the development of CKD. These findings provide evidence of the potential clinical utility of the MetS score for assessing metabolic syndrome severity to detect the risk of decreased renal function and CKD.

IκB kinase promotes Nrf2 ubiquitination and degradation by phosphorylating cylindromatosis, aggravating oxidative stress injury in obesity-related nephropathy

BACKGROUND

Obesity-related nephropathy (ORN) has become one of the leading causes of end-stage renal disease and has tripled over the past decade. Previous studies have demonstrated that decreased reactive oxygen species production may contribute to improving ORN by ameliorating oxidative stress injury. Here, IκB kinase (IKK) was hypothesized to inactivate the deubiquitination activity of cylindromatosis (CYLD) by activating the phosphorylation of CYLD, thus promoting the ubiquitination of NF-E2-related factor 2 (Nrf2) and further aggravating oxidative stress injury of the kidney in ORN. This study was aimed to confirm this hypothesis.

METHODS

Haematoxylin and eosin (HE), periodic acid-Schiff (PAS) and Oil Red O staining were performed to assess histopathology. Dihydroethidium (DHE) staining and MDA, SOD, CAT, and GSH-PX assessments were performed to measure reactive oxygen species (ROS) production. Immunohistochemical (IHC) staining, qRT-PCR and/or western blotting were performed to assess the expression of related genes. JC-1 assays were used to measure the mitochondrial membrane potential (ΔΨm) of treated HK-2 cells. Co-immunoprecipitation experiments (Co-IP) were used to analyse the interaction between CYLD and Nrf2 in ORN.

RESULTS

ORN in vivo and in vitro models were successfully constructed, and oxidative stress injury was detected in the model tissues and cells. Compared with the control groups, the phosphorylation level of CYLD increased while Nrf2 levels decreased in ORN model cells. An IKK inhibitor reduced lipid deposition, ROS production, CYLD phosphorylation levels and ΔΨm in vitro, which were reversed by knockdown of CYLD. Nrf2 directly bound to CYLD and was ubiquitinated in ORN cells. The proteasome inhibitor MG132 activated the Nrf2/ARE signalling pathway, thereby reversing the promoting effect of CYLD knockdown on oxidative stress.

CONCLUSION

IKK inactivates the deubiquitination activity of CYLD by activating the phosphorylation of CYLD, thus promoting the ubiquitination of Nrf2 and further aggravating oxidative stress injury of the kidney in ORN. This observation provided a feasible basis for the treatment of kidney damage caused by ORN.

Puerarin attenuates cadmium-induced hepatic lipid metabolism disorder by inhibiting oxidative stress and inflammation in mice

Cadmium (Cd) is a common environmental pollutant with known toxic effects on the liver. Puerarin (PU), a natural flavonoid, has been shown to exert protective effect in numerous pathological processes. However, whether PU affords protection in Cd-induced liver damage is still equivocal. Therefore, 40 mice were treated with Cd and/or PU by gavage for 9 weeks, then the serum and liver samples were collected to verify this issue. In this study, Cd exposure triggered hepatic lipid metabolism disorders and resultant liver damage as evidenced by Oil Red O staining and total cholesterol (TC) and triglyceride (TG) levels in serum and liver, aspartate transaminase (AST) and alanine transaminase (ALT) levels in serum, and histopathology, which were significantly improved by PU. Moreover, PU also normalized the expression of Cd-disturbed lipid metabolism-related proteins to improve lipid accumulation, contributing to the alleviation of liver injury. Moreover, Cd-decreased antioxidative indices superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) as well as glutathione (GSH) in hepatic tissues were significantly attenuated by PU administration, while Cd-elevated hepatic malondialdehyde (MDA) and reactive oxygen species (ROS) levels were markedly down-regulated by PU treatment, demonstrating the antioxidant effect of PU against Cd exposure. In addition, PU supplementation increased the anti-inflammatory potential, and normalized the levels of proinflammatory cytokines during Cd exposure. In conclusion, these observations demonstrate that PU treatment decreases oxidative stress and inflammation response, which may contribute to prevent Cd-induced lipid metabolism disorder and consequent liver damage.

Peri-renal adipose inflammation contributes to renal dysfunction in a non-obese prediabetic rat model: Role of anti-diabetic drugs

Diabetic nephropathy is a major health challenge with considerable economic burden and significant impact on patients' quality of life. Despite recent advances in diabetic patient care, current clinical practice guidelines fall short of halting the progression of diabetic nephropathy to end-stage renal disease. Moreover, prior literature reported manifestations of renal dysfunction in early stages of metabolic impairment prior to the development of hyperglycemia indicating the involvement of alternative pathological mechanisms apart from those typically triggered by high blood glucose. Here, we extend our prior research work implicating localized inflammation in specific adipose depots in initiating cardiovascular dysfunction in early stages of metabolic impairment. Non-obese prediabetic rats showed elevated glomerular filtration rates and mild proteinuria in absence of hyperglycemia, hypertension, and signs of systemic inflammation. Isolated perfused kidneys from these rats showed impaired renovascular endothelial feedback in response to vasopressors and increased flow. While endothelium dependent dilation remained functional, renovascular relaxation in prediabetic rats was not mediated by nitric oxide and prostaglandins as in control tissues, but rather an upregulation of the function of epoxy eicosatrienoic acids was observed. This was coupled with signs of peri-renal adipose tissue (PRAT) inflammation and renal structural damage. A two-week treatment with non-hypoglycemic doses of metformin or pioglitazone, shown previously to ameliorate adipose inflammation, not only reversed PRAT inflammation in prediabetic rats, but also reversed the observed functional, renovascular, and structural renal abnormalities. The present results suggest that peri-renal adipose inflammation triggers renal dysfunction early in the course of metabolic disease.

Child-to-adult body mass index trajectories and the risk of subclinical renal damage in middle age

BACKGROUND

Although it is well established that obesity is a risk factor for chronic kidney disease, the impact of distinct long-term body mass index (BMI) developmental patterns on renal function in later life is poorly understood.

METHODS

This study utilized data derived from the Hanzhong Adolescent Hypertension Cohort, a prospective cohort followed over 30 years. We used latent class growth mixture modeling method to identify the BMI trajectories of participants who had received BMI measurements at least three times from childhood (age: 6-15 years) to adulthood (age: 36-45 years). The modified Poisson regression model was used to identify potential associations between BMI trajectories and subclinical renal damage (SRD) in midlife.

RESULTS

Within a total of 2162 individuals, we identified four distinct long-term BMI trajectories: stable normal (54.72%), moderately increasing overweight (32.42%), resolving (10.27%), and progressively increasing obese (2.59%). By the latest follow-up in 2017, a total of 257 (13.1%) individuals were diagnosed with SRD. Compared with the stable normal group, the moderately increasing overweight group and the progressively increasing obese group exhibited significantly a higher urinary albumin-to-creatinine ratio and a higher odd of existing SRD in 2017 (risk ratio [RR], 1.70 [95% confidence interval (CI), 1.33-2.19] and 4.35 [95% CI, 3.00-6.30], respectively). However, individuals who resolved their elevated BMI in early life had a similar risk for SRD as those who had never been obese or overweight (RR, 1.17 [95% CI, 0.77-1.79]).

CONCLUSIONS

Child-to-adult BMI trajectories that worsen or persist at high levels were associated with an increased risk for SRD in midlife. Maintaining a normal BMI or reversing an elevated BMI in early life may be beneficial to renal function over the long term.

Liraglutide improves obesity-induced renal injury by alleviating uncoupling of the glomerular VEGF-NO axis in obese mice

Obesity-related kidney disease is associated with generalized endothelial dysfunction. Liraglutide, a glucagon-like peptide-1 agonist, has cardiovascular-renal protective effects in patients with diabetes. In this study, the ability of liraglutide to reduce urinary albumin excretion by alleviating glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis uncoupling was assessed in high fat diet-induced obese mice. C57BL/6J mice were divided into control and obesity groups, treated with or without liraglutide (200 μg/kg/day). Blood biochemistry and urinary albumin excretion were measured. Glomerular VEGF and the AMPK-endothelial nitric oxide synthase (eNOS) pathway were assayed by western blotting. Glomerular NO, renal haeme oxygenase-1 activity, and malondialdehyde levels were also measured. Treatment of obese mice with liraglutide led to significant reductions in body weight gain (46 ± 1 g vs 55 ± 1 g, P < .0001), visceral fat (8.9 ± 0.6 g vs 14.5 ± 0.6 g, P < .0001), perirenal fat (2.9 ± 0.2 g vs 5.4 ± 0.3 g, P < .0001), and free fatty acid (1.71 ± 0.12 mmol/L vs 1.02 ± 0.08 mmol/L, P < .0001). Liraglutide significantly improved glucose homeostasis, which was impaired in obese mice. Liraglutide reduced urinary albumin excretion and glomerular hypertrophy in obese mice. Additionally, liraglutide significantly decreased VEGF and increased glomerular NO production in glomeruli, indicating restoration of the glomerular VEGF-NO axis. Furthermore, liraglutide activated the glomerular AMPK-eNOS pathway in obese mice, upregulated renal haeme oxygenase-1 activity, and reduced the renal malondialdehyde levels in obese mice. In conclusion, liraglutide reduced microalbuminuria and ameliorated renal injury by alleviating the uncoupling of the glomerular VEGF-NO axis.

Uremic Sarcopenia: Clinical Evidence and Basic Experimental Approach

Sustained physical activity extends healthy life years while a lower activity due to sarcopenia can reduce them. Sarcopenia is defined as a decrease in skeletal muscle mass and strength due not only to aging, but also from a variety of debilitating chronic illnesses such as cancer and heart failure. Patients with chronic kidney disease (CKD), who tend to be cachexic and in frail health, may develop uremic sarcopenia or uremic myopathy due to an imbalance between muscle protein synthesis and catabolism. Here, we review clinical evidence indicating reduced physical activity as renal function deteriorates and explore evidence-supported therapeutic options focusing on nutrition and physical training. In addition, although sarcopenia is a clinical concept and difficult to recapitulate in basic research, several in vivo approaches have been attempted, such as rodent subtotal nephrectomy representing both renal dysfunction and muscle weakness. This review highlights molecular mechanisms and promising interventions for uremic sarcopenia that were revealed through basic research. Extensive study is still needed to cast light on the many aspects of locomotive organ impairments in CKD and explore the ways that diet and exercise therapies can improve both outcomes and quality of life at every level.

Genomic and Non-Genomic Mechanisms of Action of Thyroid Hormones and Their Catabolite 3,5-Diiodo-L-Thyronine in Mammals

Since the realization that the cellular homologs of a gene found in the retrovirus that contributes to erythroblastosis in birds (v-erbA), i.e. the proto-oncogene c-erbA encodes the nuclear receptors for thyroid hormones (THs), most of the interest for THs focalized on their ability to control gene transcription. It was found, indeed, that, by regulating gene expression in many tissues, these hormones could mediate critical events both in development and in adult organisms. Among their effects, much attention was given to their ability to increase energy expenditure, and they were early proposed as anti-obesity drugs. However, their clinical use has been strongly challenged by the concomitant onset of toxic effects, especially on the heart. Notably, it has been clearly demonstrated that, besides their direct action on transcription (genomic effects), THs also have non-genomic effects, mediated by cell membrane and/or mitochondrial binding sites, and sometimes triggered by their endogenous catabolites. Among these latter molecules, 3,5-diiodo-L-thyronine (3,5-T2) has been attracting increasing interest because some of its metabolic effects are similar to those induced by T3, but it seems to be safer. The main target of 3,5-T2 appears to be the mitochondria, and it has been hypothesized that, by acting mainly on mitochondrial function and oxidative stress, 3,5-T2 might prevent and revert tissue damages and hepatic steatosis induced by a hyper-lipid diet, while concomitantly reducing the circulating levels of low density lipoproteins (LDL) and triglycerides. Besides a summary concerning general metabolism of THs, as well as their genomic and non-genomic effects, herein we will discuss resistance to THs and the possible mechanisms of action of 3,5-T2, also in relation to its possible clinical use as a drug.

Inhibition of Inflammatory Cytokine Expression Prevents High-Fat Diet-Induced Kidney Injury: Role of Lingonberry Supplementation

Chronic low-grade inflammation is a major stimulus for progression of chronic kidney disease (CKD) in individuals consuming high-fat diet. Currently, there are limited treatment options for CKD other than controlling the progression rate and its associated complications. Lingonberry (Vaccinium vitis-idaea L.) is rich in anthocyanins with demonstrated anti-inflammatory effect. In the current study, we investigated the potential renal protective effect of lingonberry and its anthocyanin (cyanidin-3-glucoside) in high-fat diet fed obese mice and in human proximal tubular cells. Prolonged consumption of high-fat diets is strongly associated with obesity, abnormal lipid and glucose metabolism. Mice (C57BL/6J) fed a high-fat diet (62% kcal fat) for 12 weeks developed renal injury as indicated by an elevation of blood urea nitrogen (BUN) level as well as an increase in renal kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and renin expression. Those mice displayed an activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and increased expression of inflammatory cytokines-monocyte chemoattractant-1 (MCP-1), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) in the kidneys. Mice fed a high-fat diet also had a significant elevation of inflammatory cytokine levels in the plasma. Dietary supplementation of lingonberry for 12 weeks not only attenuated high-fat diet-induced renal inflammatory response but also reduced kidney injury. Such a treatment improved plasma lipid and glucose profiles, reduced plasma inflammatory cytokine levels but did not affect body weight gain induced by high-fat diet feeding. Lingonberry extract or its active component cyanidin-3-glucoside effectively inhibited palmitic acid-induced NF-κB activation and inflammatory cytokine expression in proximal tubular cells. These results suggest that lingonberry supplementation can reduce inflammatory response and prevent chronic kidney injury. Such a renal protective effect by lingonberry and its active component may be mediated, in part, through NF-κB signaling pathway.