Apple polyphenols reduce inflammation response of the kidneys in unilateral ureteral obstruction rats

Redox signaling pathways in unilateral ureteral obstruction (UUO)-induced renal fibrosis

Unilateral ureteral obstruction (UUO) is an experimental rodent model that mimics renal fibrosis associated with obstructive nephropathy in an accelerated manner. After UUO, the activation of the renin-angiotensin system (RAS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and mitochondrial dysfunction lead to reactive oxygen species (ROS) overproduction in the kidney. ROS are secondary messengers able to induce post-translational modifications (PTMs) in redox-sensitive proteins, which activate or deactivate signaling pathways. Therefore, in UUO, it has been proposed that ROS overproduction causes changes in said pathways promoting inflammation, oxidative stress, and apoptosis that contribute to fibrosis development. Furthermore, mitochondrial metabolism impairment has been associated with UUO, contributing to renal damage in this model. Although ROS production and oxidative stress have been studied in UUO, the development of renal fibrosis associated with redox signaling pathways has not been addressed. This review focuses on the current information about the activation and deactivation of signaling pathways sensitive to a redox state and their effect on mitochondrial metabolism in the fibrosis development in the UUO model.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

Dietary apple polyphenols promote fat browning in high-fat diet-induced obese mice through activation of adenosine monophosphate-activated protein kinase α

BACKGROUND

Promoting brown and beige adipogenesis contributes to adaptive thermogenesis, which provides a defense against obesity and related disorders. Apple polyphenols (APs) play a significant role in treating variety of metabolic diseases. This study was conducted to determine the effects of APs on the development of brown and beige adipocytes and thermogenesis and investigate whether these effects are mediated by adenosine monophosphate-activated protein kinase (AMPK). High-fat diet (HFD)-induced obese mice and differentiated 3T3-L1 adipocytes were subjected to APs treatment. The thermogenic program and associated regulatory factors, and the involvement of AMPKα was assessed.

RESULTS

Dietary APs supplementation reduced adiposity and improved insulin sensitivity in HFD-induced obese mice. Moreover, APs increased the oxygen consumption and heat production and decreased respiratory exchange ratio, which were accompanied by the upregulation of thermogenic genes expression and the activation of AMPKα in brown fat and inguinal white fat. Further, APs treatment directly increased expression of brown adipogenic markers and induced phosphorylation of AMPKα in differentiated 3T3-L1 adipocytes, whereas the beneficial effects of APs were reversed by AMPK inhibition.

CONCLUSION

Our results provide new insights into the function of APs in regulating brown/beige adipogenesis and adaptive thermogenesis and suggest the potential application of APs in the prevention and therapeutics of obesity and associated metabolic diseases. © 2020 Society of Chemical Industry.

Protective effects of hydroalcoholic extracts from an ancient apple variety 'Mela Rosa dei Monti Sibillini' against renal ischemia/reperfusion injury in rats

The purpose of this work was to investigate the effect of hydroalcoholic extracts from the peel (APE) and pulp (APP) of a traditional apple variety of central Italy, the 'Mela Rosa dei Monti Sibillini', on the damage caused by renal ischemia/reperfusion injury (IRI) in rats. Thirty mg per kg b.w. of the extracts were administered intraperitoneally to male adult Wistar rats 3 days before the induction of IRI by pedicle clamping. A significant decrease in the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNFα), interleukin 1 beta (IL-1β) and nuclear factor-κB (NF-κB) was observed in the groups pre-treated with APE when compared with IRI rats. The chemical composition of APE was determined by HPLC-DAD-MSⁿ highlighting a significant amount of proanthocyanidins (52.9 mg g^-1), flavonols (42.27 mg g^-1) and dihydrochalcones (11.75 mg g^-1). These findings indicated that this ancient apple variety is a promising source of nutraceuticals and functional foods helpful to manage complications of renal disorders.

Unilateral Ureteral Obstruction as a Model to Investigate Fibrosis-Attenuating Treatments

Renal fibrosis is the common pathway for most forms of progressive renal disease. The Unilateral Ureteral Obstruction (UUO) model is used to cause renal fibrosis, where the primary feature of UUO is tubular injury as a result of obstructed urine flow. Furthermore, experimental UUO in rodents is believed to mimic human chronic obstructive nephropathy in an accelerated manner. Renal fibrosis is the common pathway for most forms of progressive renal disease. Removing the obstruction may not be sufficient to reverse fibrosis, so an accompanying treatment may be of benefit. In this review, we have done a revision on treatments shown to ameliorate fibrosis in the context of the UUO experimental model. The treatments inhibit the production of fibrotic and inflammatory proteins such as Transforming Growth Factor β1 (TGF-β₁), Tumor Necrosis Factor α (TNF-α), collagen and fibronectin, Heat Shock Protein 47 (HSP47), suppress the proliferation of fibroblasts, prevent epithelial-to-mesenchymal transition, reduce oxidative stress, inhibit the action of the Nuclear Factor κB (NF-κB), reduce the phosphorylation of mothers against decapentaplegic homolog (SMAD) family members 2 and 3 (Smad2/3) or Mitogen-Activated Protein Kinases (MAPKs), inhibit the activation of the renin-angiotensin system. Summaries of the UUO experimental methods and alterations observed in the UUO experiments are included.

Kidney Tissue Targeted Metabolic Profiling of Unilateral Ureteral Obstruction Rats by NMR

Renal interstitial fibrosis is a common pathological process in the progression of kidney disease. A nuclear magnetic resonance (NMR) based metabolomic approach was used to analyze the kidney tissues of rats with renal interstitial fibrosis (RIF), induced by unilateral ureteral obstruction (UUO). The combination of a variety of statistical methods were used to screen out 14 significantly changed potential metabolites, which are related with multiple biochemical processes including amino acid metabolism, adenine metabolism, energy metabolism, osmolyte change and induced oxidative stress. The exploration of the contralateral kidneys enhanced the understanding of the disease, which was also supported by serum biochemistry and kidney histopathology results. In addition, the pathological parameters (clinical chemistry, histological and immunohistochemistry results) were correlated with the significantly changed differential metabolites related with RIF. This study showed that targeted tissue metabolomic analysis can be used as a useful tool to understand the mechanism of the disease and provide a novel insight in the pathogenesis of RIF.