Antioxidant diet and sex interact to regulate NOS isoform expression and glomerular mesangium proliferation in Zucker diabetic rat kidney

SGLT2 inhibition leads to a restoration of hepatic and circulating metabolites involved in the folate cycle and pyrimidine biosynthesis

Inhibition of sodium-glucose cotransporter 2 (SGLT2) by empagliflozin (EMPA) and other "flozins" can improve glycemic control under conditions of diabetes and kidney disease. Though they act on the kidney, they also offer cardiovascular and liver protection. Previously, we found that EMPA decreased circulating triglycerides and hepatic lipid and cholesterol esters in male TallyHo mice fed a high-milk-fat diet (HMFD). The goal of this study was to determine whether the liver protection is associated with a change in metabolic function by characterizing the hepatic and circulating metabolic and lipidomic profiles using targeted LC-MS. In both male and female mice, HMFD feeding significantly altered the circulating and hepatic metabolome compared with low-fat diet (LFD). Addition of EMPA resulted in the restoration of circulating orotate (intermediate in pyrimidine biosynthesis) and hepatic dihydrofolate (intermediate in the folate and methionine cycles) levels in males and acylcarnitines in females. These changes were partially explained by altered expression of rate-limiting enzymes in these pathways. This metabolic signature was not detected when EMPA was incorporated into an LFD, suggesting that the restoration requires the metabolic shift that accompanies the HMFD. Notably, the HMFD increased expression of 18 of 20 circulating amino acids in males and 11 of 20 in females, and this pattern was reversed by EMPA. Finally, we confirmed that SGLT2 inhibition upregulates ketone bodies including β-hydroxybutyrate. Collectively, this study highlights the metabolic changes that occur with EMPA treatment, and sheds light on the possible mechanisms by which this drug offers liver and systemic protection.NEW & NOTEWORTHY Sodium-glucose cotransporter 2 (SGLT2) inhibitors, including empagliflozin, have emerged as a new treatment option for individuals with type 2 diabetes that have positive impacts on kidney and cardiovascular disease. However, less is known about their impact on other tissues, including the liver. Here, we report that empagliflozin reduces hepatic steatosis that is associated with restoring metabolic intermediates in the folate and pyrimidine biosynthesis pathways. These changes may lead to new approaches to treat nonalcoholic fatty liver disease.

Inonotus obliquus (Chaga) against HFD/STZ-induced glucolipid metabolism disorders and abnormal renal functions by regulating NOS-cGMP-PDE5 signaling pathway

Our prior investigations have established that Inonotus obliquus (Chaga) possesses hypoglycemic effects. Persistent hyperglycemia is known to precipitate renal function abnormalities. The functionality of the kidneys is intricately linked to the levels of cyclic guanosine-3',5'-monophosphate (cGMP), which are influenced by the activities of nitric oxide synthase (NOS) and phosphodiesterase (PDE). Enhanced cGMP levels can be achieved either through the upregulation of NOS activity or the downregulation of PDE activity. The objective of the current study is to elucidate the effects of Chaga on disorders of glucolipid metabolism and renal abnormalities in rats with type 2 diabetes mellitus (T2DM), while concurrently examining the NOS-cGMP-PDE5 signaling pathway. A model of T2DM was developed in rats using a high-fat diet (HFD) combined with streptozotocin (STZ) administration, followed by treatment with Chaga extracts at doses of 50 and 100 mg·kg-1 for eight weeks. The findings revealed that Chaga not only mitigated metabolic dysfunctions, evidenced by improvements in fasting blood glucose, total cholesterol, triglycerides, and insulin resistance, but also ameliorated renal function markers, including serum creatinine, urine creatinine (UCr), blood urea nitrogen, 24-h urinary protein, and estimated creatinine clearance. Additionally, enhancements in glomerular volume, GBM thickness, podocyte foot process width (FPW), and the mRNA and protein expressions of podocyte markers, such as nephrin and wilms tumor-1, were observed. Chaga was found to elevate cGMP levels in both serum and kidney tissues by increasing mRNA and protein expressions of renal endothelial NOS and neural NOS, while simultaneously reducing the expressions of renal inducible NOS and PDE5. In summary, Chaga counteracts HFD/STZ-induced glucolipid metabolism and renal function disturbances by modulating the NOS-cGMP-PDE5 signaling pathway. This research supports the potential application of Chaga in the clinical prevention and treatment of T2DM and diabetic nephropathy (DN), with cGMP serving as a potential therapeutic target.

Locus coeruleus tyrosine hydroxylase positive neurons mediated the peripheral and central therapeutic effects of transcutaneous auricular vagus nerve stimulation (taVNS) in MRL/lpr mice

OBJECTIVE

This study aims to investigate the effects of transcutaneous auricular vagus nerve stimulation (taVNS) on the development of systemic lupus erythematosus (SLE) in MRL/lpr mice.

METHODS

MRL/lpr mice were treated with taVNS for ten weeks. Locus coeruleus (LC) tyrosine hydroxylase positive (TH+) neurons were selectively lesioned by stereotactic injection of 6-hydroxydopamine (6-OHDA) or selectively activated by chemogenetic methods. Sympathetic denervation was conducted by intraperitoneal injection of 6-OHDA.

RESULTS

TaVNS activated the TH + neurons in LC. TaVNS produced central therapeutic effects by reducing the number of hippocampal microglia, and increasing the number of surviving LC TH+ neurons in MRL/lpr mice. TaVNS also retarded the development of lymphadenectasis and splenomegaly, decreased the proportion of double-negative T (DNT) cells, and alleviated nephritis in MRL/lpr mice. The lesion of LC TH+ neurons eliminated both these central and peripheral therapeutic effects of taVNS, while chemogenetic activation of LC TH+ neurons mimicked most central and peripheral protective effects of taVNS in MRL/lpr mice. Furthermore, taVNS regulated the autonomic nervous system in MRL/lpr mice.

CONCLUSION

This study provides direct evidence that taVNS can retard the development of peripheral and central symptoms of SLE, which is mediated by the LC TH+ neurons.

Oxidative Stress, Reductive Stress and Antioxidants in Vascular Pathogenesis and Aging

This review is focused on the mechanisms that regulate health, disease and aging redox status, the signal pathways that counteract oxidative and reductive stress, the role of food components and additives with antioxidant properties (curcumin, polyphenols, vitamins, carotenoids, flavonoids, etc.), and the role of the hormones irisin and melatonin in the redox homeostasis of animal and human cells. The correlations between the deviation from optimal redox conditions and inflammation, allergic, aging and autoimmune responses are discussed. Special attention is given to the vascular system, kidney, liver and brain oxidative stress processes. The role of hydrogen peroxide as an intracellular and paracrine signal molecule is also reviewed. The cyanotoxins β-N-methylamino-l-alanine (BMAA), cylindrospermopsin, microcystins and nodularins are introduced as potentially dangerous food and environment pro-oxidants.

Sex- and gender-differences in chronic long-term complications of type 1 and type 2 diabetes mellitus in Italy

AIMS

This review summarizes the contribution of Italian diabetologists devoted to a better understanding of the complex relationship linking sex/gender and long-term complications of type 1 (T1DM) and type 2 diabetes (T2DM) over the last fifteen years.

DATA SYNTHESIS

Microvascular and macrovascular complications of diabetes show sex- and gender-related differences, involving pathophysiological mechanisms, epidemiological features and clinical presentation, due to the interaction between biological and psychosocial factors. These differences greatly impact on the progression of diabetes and its long-term complications, especially in the cardiovascular, renal and liver districts.

CONCLUSION

A better knowledge of such sex- and gender-related characteristics is required for a more precise patient phenotypization, and for the choice of a personalized antihyperglycemic treatment. Despite such mounting evidence, current diabetes clinical guidelines do not as yet adequately consider sex/gender differences.

Nitric-Oxide-Mediated Signaling in Podocyte Pathophysiology

Nitric oxide (NO) is a potent signaling molecule involved in many physiological and pathophysiological processes in the kidney. NO plays a complex role in glomerular ultrafiltration, vasodilation, and inflammation. Changes in NO bioavailability in pathophysiological conditions such as hypertension or diabetes may lead to podocyte damage, proteinuria, and rapid development of chronic kidney disease (CKD). Despite the extensive data highlighting essential functions of NO in health and pathology, related signaling in glomerular cells, particularly podocytes, is understudied. Several reports indicate that NO bioavailability in glomerular cells is decreased during the development of renal pathology, while restoring NO level can be beneficial for glomerular function. At the same time, the compromised activity of nitric oxide synthase (NOS) may provoke the formation of peroxynitrite and has been linked to autoimmune diseases such as systemic lupus erythematosus. It is known that the changes in the distribution of NO sources due to shifts in NOS subunits expression or modifications of NADPH oxidases activity may be linked to or promote the development of pathology. However, there is a lack of information about the detailed mechanisms describing the production and release of NO in the glomerular cells. The interaction of NO and other reactive oxygen species in podocytes and how NO-calcium crosstalk regulates glomerular cells’ function is still largely unknown. Here, we discuss recent reports describing signaling, synthesis, and known pathophysiological mechanisms mediated by the changes in NO homeostasis in the podocyte. The understanding and further investigation of these essential mechanisms in glomerular cells will facilitate the design of novel strategies to prevent or manage health conditions that cause glomerular and kidney damage.

Sex and Gender Related Differences in Diabetic Kidney Disease

Diversity in sex and gender are important considerations in the pathogenesis, prognostication, research, and management of diabetic kidney disease (DKD). Sex and gender differences in the disease risk, disease-specific mechanisms, and outcomes in DKD may be attributed to biological differences between males and females at the cellular and tissue level, inconsistencies in the diagnostic and assessment tools used in chronic kidney disease and DKD, as well societal differences in the way men, women, and gender-diverse individuals self-manage and interact with health care systems. This review outlines key considerations related to the impact of sex on DKD, specifically elaborating on how they contribute to observed differences in disease epidemiology, pathogenesis, and treatment strategies. We also highlight the effect of gender on DKD progression and care.

Sex-related differences in diabetic kidney disease: A review on the mechanisms and potential therapeutic implications

Sexual dimorphism may play a key role in the pathogenesis of diabetic kidney disease (DKD) and explain differences observed in disease phenotypes, responses to interventions, and disease progression between men and women with diabetes. Therefore, omitting the consideration of sex as a biological factor may result in delayed diagnoses and suboptimal therapies. This review will summarize the effects of sexual dimorphism on putative metabolic and molecular mechanisms underlying DKD, and the potential implications of these differences on therapeutic interventions. To successfully implement precision medicine, we require a better understanding of sexual dimorphism in the pathophysiologic progression of DKD. Such insights can unveil sex-specific therapeutic targets that have the potential to maximize efficacy while minimizing adverse events.

Malignant fibrous histiocytoma amplified sequence 1 alleviates inflammation and renal fibrosis in diabetic nephropathy by inhibiting TLR4

BACKGROUND

Diabetic nephropathy (DN) is the most common complication of diabetes mellitus (DM). The signal pathway and molecular mechanism of renal fibrosis are not fully understood. In the present study, we aimed to explore the function of malignant fibrous histiocytoma amplified sequence 1 (MFHAS1) in DN.

METHOD

Mouse mesangial cells (MMCs) were treated with low glucose (LG) or high glucose (HG). TAK242 or short hairpin TLR4 (shTLR4) were employed to down-regulate Toll-like receptor 4 (TLR4). The effect of MFHAS1 knockdown or overexpression on fibrosis-related factors, inflammatory factors and TLR4 in MMCs were examined after transfecting with short hairpin RNA (shRNA) or MFHAS1 overexpressed plasmid, respectively. The expression levels of MFHAS1, inflammatory factors, fibrosis factors and TLR4 in db/db or streptozotocin (STZ) mice tissues and MMCs were examined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. The effect of MFHAS1 overexpression in vivo was also evaluated.

RESULTS

The expression of MFHAS1 in db/db or STZ mice and HG-treated MMCs were significantly increased compared with normal control mice and LG-treated MMCs. Overexpression of MFHAS1 inhibited the expression of inflammatory and fibrotic factors, while knockdown of MFHAS1 promoted them. MFHAS1 suppressed the activation of TLR4 pathway via inhibiting the expression of TLR4, and then alleviating inflammation and fibrosis in DN. MFHAS1 overexpression in vivo improved the symptoms of STZ-induced DN mice.

CONCLUSION

The current study demonstrated that MFHAS1 relieved inflammation and renal fibrosis in DN mice via inhibiting TLR4. The results revealed that the MFHAS1 may be a molecular target in DN therapy.

Sex Differences in Diabetic Kidney Disease

While the global prevalence of both type 1 and type 2 diabetes mellitus is similar in men and women, the consequences of diabetes on associated end-organ complications, including diabetic kidney disease appear to be more sex-specific. Particularly, women with diabetes have higher mortality rates for diabetes-related deaths, and higher prevalence of diabetic kidney disease risk factors such as hypertension, hyperglycemia, obesity, and dyslipidemia. However, the evidence for the impact of sex on diabetic kidney disease prevalence and disease progression is limited and inconsistent. Although most studies agree that the protective effect of the female sex against the development of kidney disease is diminished in the setting of diabetes, the reasons for this observation are unclear. Whether or not sex differences exist in the risk of diabetic kidney disease is also unclear, with studies reporting either higher risk in men, women, or no sex differences. Despite the remaining controversies, some of the factors that associate with sex differences in the risk of diabetic kidney disease are age at onset, and type and duration of diabetes. There is growing appreciation of the importance of sex hormones in the regulation of renal function, with estrogens generally considered to be renoprotective. Although some progress has been made towards better understanding of the mechanisms by which sex hormones play a role in the pathophysiology of diabetic kidney disease, the translational potential of this knowledge is still underappreciated. A better understanding of sex differences in diabetic kidney disease may provide basis for personalized and sex-specific treatment of diabetic kidney disease.

Dual inhibition of cannabinoid CB1 receptor and inducible NOS attenuates obesity-induced chronic kidney disease

Background and Purpose

Obesity, an important risk factor for developing chronic kidney disease (CKD), affects the kidneys by two main molecular signalling pathways: the endocannabinoid/CB₁ receptor system, whose activation in obesity promotes renal inflammation, fibrosis, and injury, and the inducible NOS (iNOS), which generates ROS resulting in oxidative stress. Hence, a compound that inhibits both peripheral CB₁ receptors and iNOS may serve as an effective therapeutic agent against obesity‐induced CKD.

Experimental Approach

Here, we describe the effect of a novel peripherally restricted, orally bioavailable dual CB₁ receptor/iNOS antagonist, MRI‐1867 (3 mg·kg⁻¹), in ameliorating obesity‐induced CKD, and compared its metabolic and renal efficacies to a stand‐alone peripheral CB₁ receptor antagonist (JD5037; 3 mg·kg⁻¹), iNOS antagonist (1400W; 10 mg·kg⁻¹), and pair feeding. Mice with high‐fat diet‐induced obesity were treated orally with these compounds or vehicle (Veh) for 28 days. Standard diet‐fed mice treated with Veh served as controls.

Key Results

Enhanced expression of CB₁ receptors and iNOS in renal tubules was found in human kidney patients with obesity and other CKDs. The hybrid inhibitor ameliorated obesity‐induced kidney morphological and functional changes via decreasing kidney inflammation, fibrosis, oxidative stress, and renal injury. Some of these features were independent of the improved metabolic profile mediated via inhibition of CB₁ receptors. An additional interesting finding is that these beneficial effects on the kidney were partially associated with modulating renal adiponectin signalling.

Conclusions and Implications

Collectively, our results highlight the therapeutic relevance of blocking CB₁ receptors and iNOS in ameliorating obesity‐induced CKD.

Sex differences in diabetes and kidney disease: mechanisms and consequences

Type 1 and type 2 diabetes, along with their accompanying hyperglycemia, are associated with a multitude of comorbidities including the development of diabetic kidney disease. Although the hallmarks of these metabolic disorders have been well characterized in population and animal studies, it is becoming increasingly apparent that diabetes manifests itself differently in men and women. This review summarizes the recent diabetic literature with a focus on known sex differences in clinical and preclinical studies. It explores the physiological differences of glucose handling and the development of diabetes between men and women. This review also uncovers potential mechanisms for these differences, honing in on the vital role that sex hormone signaling plays in the progression of diabetes and renal complications.

Mesenchymal stem cells-microvesicle-miR-451a ameliorate early diabetic kidney injury by negative regulation of P15 and P19

Microvesicles (MVs) from mesenchymal stem cells (MSCs) have been reported as a new communicated way between cells. This study evaluated the influence and underlying mechanism of MVs-shuttled miR-451a on renal fibrosis and epithelial mesenchymal transformation (EMT) in diabetic nephropathy (DN) with hyperuricemia. MVs were isolated from MSCs-cultured medium by gradient ultracentrifugation. The level of miR-451a in MSCs and MVs was analyzed by qPCR. The changes of miR-451a, E-cadherin, α-SMA, P15INK4b (P15), and P19INK4d (P19) were measured in hyperglycosis and hyperuricemia-induced cell (HK-2) and mouse models. The changes of cell cycle were analyzed by flow cytometry. The ability of proliferation and viability was measured by BrdU and CCK8, respectively. Dual-luciferase reporter assays were conducted to determine the target binding sites. The renal function and histological changes of mice were analyzed. MVs showed the same surface markers as MSCs but much higher miR-451a expression (4.87 ± 2.03 fold higher than MSCs). miR-451a was decreased to 26% ± 11% and 6.7% ± 0.82% in injured HK-2 cells and kidney, respectively. MV-miR-451a enhanced the HK2 cells proliferation and viability in vitro, and decreased the morphologic and functional injury of kidney in vivo. Moreover, infusion of MV-miR-451a reduced the level of α-SMA and raised E-cadherin expression. These effects were responsible for the improved arrested cell cycle and down-regulation of P15 and P19 via miR-451a targeting their 3′-UTR sites. This study demonstrated that MSC–MV-miR-451a could inhibit cell cycle inhibitors P15 and P19 to restart the blocked cell cycle and reverse EMT in vivo and in vitro, and thus miR-451a is potentially a new target for DN therapy.

Impact statement

The mechanism of MSCs repairing the injured kidney in diabetic nephropathy is not yet clear. In the research, MVs showed the same surface markers as MSCs but much higher MiR-451a expression. miR-451a was decreased in both injured HK-2 cells and kidneys. MV-miR-451a stimulated the cell proliferation and viability in vitro and promoted structural and functional improvements of injured kidney in vivo. Infusion of MV-miR-451a ameliorated EMT by reducing α-SMA and increasing E-cadherin. These effects relied on the improved cell cycle arrest and the down-regulation of P15 and P19 via miR-451a binding to their 3′-UTR region. This study demonstrated that MSC–MV-miR-451a could specifically inhibit cell cycle inhibitors to restart the blocked cell cycle and reverse EMT in vivo and in vitro. Therefore, miR-451a may be a new target for DN therapy.

Regulation of blood pressure is influenced by gender: A study in obese Zucker rats

AIM

The present study determined the role of renin-angiotensin system (RAS), endothelin system, and eicosanoid system in the blood pressure (BP) regulation in male and female Zucker rats, and whether the pressor response change similarly in lean and obese animals.

MATERIAL AND METHODS

In female (f) and male (m), lean (L) and obese (O) Zucker rats (ZR) at 22 weeks old, we evaluated the role of the 3 mentioned systems using the following treatments: 1) enalapril (angiotensin I converting enzyme inhibitor), 2) the ABT-627 (endothelin receptor A (ET_A) antagonist), and 3) the 1-aminobenzotriazol (1-ABT: eicosanoid synthesis inhibitor).

KEY FINDINGS

MAP by radiotelemetry was similar and significantly higher in mOZR (120 ± 2 mm Hg) and fOZR (116 ± 4 mm Hg) (p < 0.05 vs. m-, fLZR), than mLZR (105 ± 3 mm Hg) and fLZR (106 ± 1 mm Hg), that were also similar. Enalapril reduced MAP more in mOZR (23%) and mLZR (26%), than fLZR (20%, p < 0.905 vs. mLZR) or fOZR (9%; p < 0.05 vs. other groups). After 10 days of drug-free and recovery period, ABT-627 reduced MAP in fLZR and mLZR by similar amounts (102 ± 4 to 92 ± 3 mm Hg, n = 6; p < 0.05 and 105 ± 2 vs. 92 ± 3 mm Hg, n = 6; p < 0.05, respectively), but did not affect either fOZR or mOZR. After another 10 days of drug-free and recovery period, 1-ABT reduced MAP in fOZR (116 ± 4 to 95 ± 2, n = 6; p < 0.05), and did not affect all other groups.

SIGNIFICANCE

We show that the mechanisms responsible for elevated BP in male and female OZR and LZR are different, and suggest that obesity may cause an increase in BP via different mechanisms in men and women as well.

Evaluation of inducible nitric oxide synthase inhibition on kidney function and structure in high-fat diet-induced kidney disease

NEW FINDINGS

What is the central question of this study? The metabolic pathways regulating the effects of obesity on the kidney remain unknown. We sought to determine whether inducible nitric oxide synthase (iNOS) is involved in the underlying mechanisms of high-fat diet-induced kidney disease using a specific iNOS inhibitor, N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL). What is the main finding and its importance? We did not demonstrate an upregulation of iNOS renal expression after high caloric intake, suggesting that iNOS might not be a crucial player in the development of obesity-induced kidney disease. Although L-NIL treatment clearly ameliorated systemic metabolic parameters, the effect on loss of renal function, impairment of tubular integrity, oxidative stress and inflammation appeared to be more moderate. Central obesity is related to caloric excess, promoting deleterious cellular responses in targeted organs. Nitric oxide (NO) has been determined as a key player in the pathogenesis of metabolic diseases. Here, we investigated the implication of inducible NO synthase (iNOS) in the development of obesity-induced kidney disease. C57Bl/6 male mice were randomized to a low-fat diet (LFD) or a high-fat diet (HFD) and treated with N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL), a specific iNOS inhibitor, for 16 weeks. Mice fed an HFD exhibited a significant increase in body weight, fasting blood glucose and plasma concentrations of non-esterified fatty acids, triglyceride and insulin. Inhibition of iNOS prevented these changes in mice fed an HFD. Interestingly, the significant increase in albuminuria and mesangial matrix expansion were not ameliorated with L-NIL, whereas a significant decrease in proteinuria, N-acetyl-β-d-glucosaminidase excretion and renal triglyceride content were found, suggesting that iNOS inhibition is more suitable for tubular function than glomerular function. The urinary concentration of hydrogen peroxide, a stable product of reactive oxygen species production, that was found to be increased in mice fed an HFD, was significantly reduced with L-NIL. Finally, despite a moderate effect of L-NIL on inflammatory processes in the kidney, we demonstrated a positive impact of this treatment on adipocyte hypertrophy and on adipose tissue inflammation. These results suggest that inhibition of iNOS leads to a moderate beneficial effect on kidney function in mice fed an HFD. Further studies are needed for better understanding of the role of iNOS in obesity-induced kidney disease.