Renoprotective impact of estrogen receptor-α and its splice variants in female mice with type 1 diabetes

Sex differences in obesity-induced renal lipid accumulation revealed by lipidomics: a role of adiponectin/AMPK axis

BACKGROUND

Sex differences have been observed in the development of obesity-related complications in patients, as well as in animal models. Accumulating evidence suggests that sex-dependent regulation of lipid metabolism contributes to sex-specific physiopathology. Lipid accumulation in the renal tissue has been shown to play a major role in the pathogenesis of obesity-induced kidney injury. Unlike in males, the physiopathology of the disease has been poorly described in females, particularly regarding the lipid metabolism adaptation.

METHODS

Here, we compared the lipid profile changes in the kidneys of female and male mice fed a high-fat diet (HFD) or low-fat diet (LFD) by lipidomics and correlated them with pathophysiological changes.

RESULTS

We showed that HFD-fed female mice were protected from insulin resistance and hepatic steatosis compared to males, despite similar body weight gains. Females were particularly protected from renal dysfunction, oxidative stress, and tubular lipid accumulation. Both HFD-fed male and female mice presented dyslipidemia, but lipidomic analysis highlighted differential renal lipid profiles. While both sexes presented similar neutral lipid accumulation with obesity, only males showed increased levels of ceramides and phospholipids. Remarkably, protection against renal lipotoxicity in females was associated with enhanced renal adiponectin and AMP-activated protein kinase (AMPK) signaling. Circulating adiponectin and its renal receptor levels were significantly lower in obese males, but were maintained in females. This observation correlated with the maintained basal AMPK activity in obese female mice compared to males.

CONCLUSIONS

Collectively, our findings suggest that female mice are protected from obesity-induced renal dysfunction and lipotoxicity associated with enhanced adiponectin and AMPK signaling compared to males.

Naringenin and Phytoestrogen 8-Prenylnaringenin Protect against Islet Dysfunction and Inhibit Apoptotic Signaling in Insulin-Deficient Diabetic Mice

It has been shown that citrus flavanone naringenin and its prenyl derivative 8-prenylnaringenin (8-PN) possess various pharmacological activities in in vitro and in vivo models. Interestingly, it has been proposed that prenylation can enhance biological potentials, including the estrogen-like activities of flavonoids. The objective of this study was to investigate the anti-diabetic potential and molecular mechanism of 8-PN in streptozotocin (STZ)-induced insulin-deficient diabetic mice in comparison with naringenin reported to exhibit hypoglycemic effects. The oral administration of naringenin and 8-PN ameliorated impaired glucose homeostasis and islet dysfunction induced by STZ treatment. These protective effects were associated with the suppression of pancreatic β-cell apoptosis and inflammatory responses in mice. Moreover, both naringenin and 8-PN normalized STZ-induced insulin-signaling defects in skeletal muscles and apoptotic protein expression in the liver. Importantly, 8-PN increased the protein expression levels of estrogen receptor-α (ERα) in the pancreas and liver and of fibroblast growth factor 21 in the liver, suggesting that 8-PN could act as an ERα agonist in the regulation of glucose homeostasis. This study provides novel insights into the mechanisms underlying preventive effects of naringenin and 8-PN on the impairment of glucose homeostasis in insulin-deficient diabetic mice.

Splenocyte transfer from hypertensive donors eliminates premenopausal female protection from ANG II-induced hypertension

Premenopausal females are protected from angiotensin II (ANG II)-induced hypertension following the adoptive transfer of T cells from normotensive donors. For the present study, we hypothesized that the transfer of hypertensive T cells (HT) or splenocytes (HS) from hypertensive donors would eliminate premenopausal protection from hypertension. Premenopausal recombination-activating gene-1 (Rag-1)-/- females received either normotensive (NT) or hypertensive cells 3 wk before ANG II infusion (14 days, 490 ng/kg/min). Contrary to our hypothesis, no increase in ANG II-induced blood pressure was observed in the NT/ANG or HT/ANG groups. Flow cytometry demonstrated that renal FoxP3+ T regulatory cells were significantly decreased, and immunohistochemistry showed an increase in renal F4/80+ macrophages in the HT/ANG group, suggesting a shift in the renal inflammatory environment despite no change in blood pressure. Renal mRNA expression of macrophage chemoattractant protein-1 (MCP-1), endothelin-1 (ET-1), and G protein-coupled estrogen receptor-1 (GPER-1) was significantly decreased in the HT/ANG group. The adoptive transfer of hypertensive splenocytes before ANG II infusion (HS/ANG) eliminated premenopausal protection from hypertension and significantly decreased splenic FoxP3+ T regulatory cells compared with females that received normotensive splenocytes (NS/ANG). Expression of macrophage inflammatory protein 1α/chemokine (C-C motif) ligand 3 (MCP-1/CCL3), a potent macrophage chemokine, was elevated in the HS/ANG group; however, no increase in renal macrophage infiltration occurred. Together, these data show that in premenopausal females, T cells from hypertensive donors are not sufficient to induce robust ANG II-mediated hypertension; in contrast, transfer of hypertensive splenocytes (consisting of T/B lymphocytes, dendritic cells, and macrophages) is sufficient. Further work is needed to understand how innate and adaptive immune cells and estrogen signaling coordinate to cause differential hypertensive outcomes in premenopausal females.NEW & NOTEWORTHY Our study is the first to explore the role of hypertensive T cells versus hypertensive splenocytes in premenopausal protection from ANG II-induced hypertension. We show that the hypertensive status of T cell donors does not impact blood pressure in the recipient female. However, splenocytes, when transferred from hypertensive donors, significantly increased premenopausal recipient blood pressure following ANG II infusion, highlighting the importance of further investigation into estrogen signaling and immune cell activation in females.

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.

Loss of renal olfactory receptor 1393 leads to improved glucose homeostasis in a type 1 diabetic mouse model

Renal olfactory receptor 1393 (Olfr1393) is an understudied sensory receptor that contributes to glucose handling in the proximal tubule. Our previous studies have indicated that this receptor may serve as a regulator of the sodium glucose co-transporters (SGLTs) and contributes to the development of glucose intolerance and hyperfiltration in the setting of diet-induced obesity. We hypothesized that Olfr1393 may have a similar function in Type 1 Diabetes. Using Olfr1393 wildtype (WT) and knockout (KO) mice along with streptozotocin (STZ) to induce pancreatic β-cell depletion, we tracked the development and progression of diabetes over 12 weeks. Here we report that diabetic male Olfr1393 KO mice have a significant improvement in hyperglycemia and glucose tolerance, despite remaining susceptible to STZ. We also confirm that Olfr1393 localizes to the renal proximal tubule, and have uncovered additional expression within the glomerulus. Collectively, these data indicate that loss of renal Olfr1393 affords protection from STZ-induced type 1 diabetes and may be a general regulator of glucose handling in both health and disease.

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.

Estrogen and estrogen receptors in kidney diseases

Acute kidney injury (AKI) and chronic kidney disease (CKD) are posing great threats to global health within this century. Studies have suggested that estrogen and estrogen receptors (ERs) play important roles in many physiological processes in the kidney. For instance, they are crucial in maintaining mitochondrial homeostasis and modulating endothelin-1 (ET-1) system in the kidney. Estrogen takes part in the kidney repair and regeneration via its receptors. Estrogen also participates in the regulation of phosphorus homeostasis via its receptors in the proximal tubule. The ERα polymorphisms have been associated with the susceptibilities and outcomes of several renal diseases. As a consequence, the altered or dysregulated estrogen/ERs signaling pathways may contribute to a variety of kidney diseases, including various causes-induced AKI, diabetic kidney disease (DKD), lupus nephritis (LN), IgA nephropathy (IgAN), CKD complications, etc. Experimental and clinical studies have shown that targeting estrogen/ERs signaling pathways might have protective effects against certain renal disorders. However, many unsolved problems still exist in knowledge regarding the roles of estrogen and ERs in distinct kidney diseases. Further research is needed to shed light on this area and to enable the discovery of pathway-specific therapies for kidney diseases.

Trimetazidine Inhibits Renal Tubular Epithelial Cells to Mesenchymal Transition in Diabetic Rats via Upregulation of Sirt1

Trimetazidine (TMZ), as a metabolic regulator, is effective in treatment of coronary atherosclerotic heart disease with rare side effects in the clinic for long years. Interestingly, studies have shown that TMZ protects against several acute kidney injuries (AKI). However, the effect of TMZ on chronic kidney diseases (CKD) remains unknown. This study aimed to investigate the role of TMZ in diabetic nephropathy (DN) and its potential mechanisms. A rat model of DN was established in male Sprague-Dawley rats by streptozotocin (STZ) intraperitoneal injection. Experimental rats were separated into three groups: control, DN and DN + TMZ treatment. Metabolic parameters, pathological features and renal function markers were evaluated after 20 weeks of diabetes induction. In vitro experiments, the effect of TMZ on high fat and high glucose (HFG) induced or TGFβ1-induced epithelial-to-mesenchymal transition (EMT) was examined in HK-2 cells. Our results showed that TMZ could maintain renal function without affecting hemodynamic and plasma metabolic levels in diabetic rats. The effect was associated with a reversion of pathological progression of DN, especially for tubulointerstitial fibrosis. EMT is an important contributor to renal fibrosis. In this study, we investigated the role of TMZ in the process of EMT in DN. Mechanistically; TMZ attenuated HFG-induced EMT by relieving oxidative stress via deacetylation forkhead box O1 (FoxO1) in a Sirt1-dependent pathway. And it suppressed TGFβ1-induced EMT by deacetylating Smd4 in a Sirt1-dependent manner. Moreover, our study found that TMZ upregulated Sirt1 expression by increasing the expression of nicotinamide phosphoribosyl transferase (Nampt), which is a rate limiting enzyme for nicotinamide adenine dinucleotide (NAD⁺) generation by salvage pathway. And the increased NAD⁺ promoted Sirt1 expression. In conclusion, TMZ can prevent renal dysfunction and pathogenesis of tubulointerstitial fibrosis in DN, partly by inhibition of EMT via FoxO1/ROS pathway and TGFβ/Smad pathway in a Nampt/NAD⁺/Sirt1 dependent manner.

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.

Menopause and FOXP3+ Treg cell depletion eliminate female protection against T cell-mediated angiotensin II hypertension

Although it is known that the prevalence and severity of hypertension increases in women after menopause, the contribution of T cells to this process has not been explored. Although the immune system is both necessary and required for the development of angiotensin II (ANG II) hypertension in men, we have demonstrated that premenopausal women are protected from T cell-mediated hypertension. The goal of the current study was to test the hypotheses that 1) female protection against T cell-mediated ANG II hypertension is eliminated following progression into menopause and 2) T regulatory cells (Tregs) provide premenopausal protection against ANG II-induced hypertension. Menopause was induced in Rag-1^-/- mice (via 4-vinylcyclohexene diepoxide), and all mice received a 14-day ANG II infusion. Donor CD3⁺ T cells were adoptively transferred 3 wk before ANG II infusion. In the absence of T cells, systolic blood pressure responses to ANG II were similar to those seen in premenopausal mice (Δ12 mmHg). After adoptive transfer of T cells, ANG II significantly increased systolic blood pressure in postmenopausal females (Δ28 mmHg). A significant increase in F4/80 positive renal macrophages, an increase in renal inflammatory gene expression, along with a reduction in renal expression of mannose receptor C-type 1, a marker for M2 macrophages, accompanied the increase in systolic blood pressure (SBP). Flow cytometric analysis identified that Tregs were significantly decreased in the spleen and kidneys of Rag-1^-/- menopausal mice versus premenopausal females, following ANG II infusion. In a validation study, an anti-CD25 antibody was used to deplete Tregs in premenopausal mice, which induced a significant increase in SBP. These results demonstrate that premenopausal protection against T cell-mediated ANG II hypertension is eliminated once females enter menopause, suggesting that a change in hormonal status upregulates macrophage-induced proinflammatory and T cell-dependent responses. Furthermore, we are the first to report that the presence of Tregs are required to suppress ANG II hypertension in premenopausal females.NEW & NOTEWORTHY Whether progression into menopause eliminated female protection against T cell-mediated hypertension was examined. Menopausal mice without T cells remained protected against angiotensin II (ANG II) hypertension; however, in the presence of T cells, blood pressure responses to ANG II increased significantly in menopause. Underlying mechanisms examined were anti-inflammatory protection provided by T regulatory cells in premenopausal females and renal inflammatory processes involving macrophage infiltration and cytokine activation.