Adjusting the 17β-Estradiol-to-Androgen Ratio Ameliorates Diabetic Nephropathy

Persistence and expansion of hypoxia detected by pimonidazole adduct immunostaining during progression of diabetic nephropathy in diabetic mice

Hypoxia and oxidative stress are considered to be underlying factors in the deterioration of renal function and pathogenesis in acute kidney injury (AKI) and chronic kidney disease, including diabetic nephropathy (DN). However, the long-term role of hypoxia in DN is unknown. Here, we investigated the distribution, severity, and time course of hypoxia during DN development in our well-established severely diabetic transgenic (Tg) DN mouse model that mimics human DN up to 80 wk of age, using pimonidazole adduct immunohistochemistry. The relationship between pimonidazole adduct distribution and hypoxia-inducible factor (HIF) expression was also examined. We found 1) persistent pimonidazole immunostaining mainly in the outer zone of the outer medulla, extending into the inner zone, 2) significant expansion of area and intensity up to 40 wk of age, and 3) characteristic subcellular localization mainly at apical sites in vesicular form by laser scanning microscopy of thin slices. The distribution of pimonidazole adducts was different from that of HIF reported previously, indicating that hypoxia does not directly contribute to persistent abnormal HIF expression. These results suggest that pimonidazole adducts produced under low [Formula: see text] conditions are sustained by a mechanism distinct from direct ischemia. We propose that in the long course of DN development, persistent hyperfiltration and hyperexcretion of glucose, albumin, and water increase metabolism and energy expenditure in the tubules, and such chronic stimulation leads to relative ischemia and local hypoxia, which may contribute in part to the loss of nephrons.NEW & NOTEWORTHY This study provides new insights into hypoxia during the long course of diabetic nephropathy development. Hypoxia was persistently localized only in limited areas and its distribution differed significantly from that of hypoxia-inducible factors. These findings suggests that in the long course of diabetic nephropathy development, increased energy requirements and limited blood supply may lead to relative ischemia and induction of local and persistent hypoxia, which may contribute in part to the loss of nephrons.

The Role of Gender Differences and Menopause in Obesity-Related Renal Disease, Renal Inflammation and Lipotoxicity

The pathogenesis of obesity-related-renal disease is unknown. Menopause can promote renal disease in obese women, but this interaction is unclear. In a previous study, we observed that obese male and female mice developed albuminuria, hyperfiltration, and glomerulomegaly, and these changes were more severe in those obese ovariectomized females. In this study, we also evaluated renal inflammation and lipotoxicity in that animal model. For six months, 43 males and 36 females C57BL6/J mice were randomized to standard diet (SD) or high fat diet (HFD). A group of female animals on SD or HFD was ovariectomized to simulate menopause. We evaluated cytokines: NF-κβ p65, IL-1β, MCP-1, TNF-α, total lipid content, lipid classes, and fatty acid profile in total lipid and individual lipid classes in renal tissue and urine. We found that obese males and females showed higher NF-kβ p-65, TNF-α and MCP-1 in renal tissue, and obese females ovariectomized had higher IL-1β and TNF-α compared with not-ovariectomized. Also, obese animals showed lower proinflammatory and higher anti-inflammatory fatty acids in kidney total lipids, while obese females ovariectomized had a more exacerbated pattern. In brief, obesity induces inflammation and an unbalanced lipidic profile in renal tissue. This pattern seems to be enhanced in obesity after menopause.

Greb1 Transiently Accelerates Pancreatic β-Cell Proliferation in Diabetic Mice Exposed to Estradiol

Decrease of pancreatic β cells leads to diabetes. In an inducible cAMP early suppressor (ICER-Iγ) transgenic mouse model of severe type 2 diabetes with reduced insulin production and depleted β cells, supplementation with high concentrations of 17β-estradiol (E2) markedly enhances β-cell proliferation and normalizes glucose levels. The current study explored the underlying mechanisms leading to a dynamic increase of β cells and pathologic changes in diabetic mice exposed to E2. Gene expression profiling of pancreatic islets of 6-month-old ICER-transgenic mice recovering from diabetes due to elevated E2 levels identified growth regulation by estrogen in breast cancer 1 (Greb1) as a gene significantly up-regulated during the recovery phase. To substantiate this, β-cell-specific Greb1-deficient mice were generated, and Greb1 was shown to be essential for recovery of depleted β cells in diabetic mice. Graft growth and glucose lowering were observed in 50 islets with increased Greb1 expression transplanted adjacent to E2 pellets beneath the kidney capsule of streptozotocin-induced diabetic mice. Greb1 expression due to a drastic increase in exogenous or endogenous E2 was transient and closely correlated with changes in E2-related and some cell cycle-related genes. These findings provide new insights into in vivo proliferation of deficient β cells and suggest the possibility of new therapeutic approaches targeting pancreatic β cells that could revolutionize the concept of diabetes treatment, which has been considered difficult to cure completely.

Role of Sex Hormones in Prevalent Kidney Diseases

Chronic kidney disease (CKD) is a constantly growing global health burden, with more than 840 million people affected worldwide. CKD presents sex disparities in the pathophysiology of the disease, as well as in the epidemiology, clinical manifestations, and disease progression. Overall, while CKD is more frequent in females, males have a higher risk to progress to end-stage kidney disease. In recent years, numerous studies have highlighted the role of sex hormones in the health and diseases of several organs, including the kidney. In this review, we present a clinical overview of the sex-differences in CKD and a selection of prominent kidney diseases causing CKD: lupus nephritis, diabetic kidney disease, IgA nephropathy, and autosomal dominant polycystic kidney disease. We report clinical and experimental findings on the role of sex hormones in the development of the disease and its progression to end-stage kidney disease.

HNF1A binds and regulates the expression of SLC51B to facilitate the uptake of estrone sulfate in human renal proximal tubule epithelial cells

Renal defects in maturity onset diabetes of the young 3 (MODY3) patients and Hnf1a-/- mice suggest an involvement of HNF1A in kidney development and/or its function. Although numerous studies have leveraged on Hnf1α-/- mice to infer some transcriptional targets and function of HNF1A in mouse kidneys, species-specific differences obviate a straightforward extrapolation of findings to the human kidney. Additionally, genome-wide targets of HNF1A in human kidney cells have yet to be identified. Here, we leveraged on human in vitro kidney cell models to characterize the expression profile of HNF1A during renal differentiation and in adult kidney cells. We found HNF1A to be increasingly expressed during renal differentiation, with peak expression on day 28 in the proximal tubule cells. HNF1A ChIP-Sequencing (ChIP-Seq) performed on human pluripotent stem cell (hPSC)-derived kidney organoids identified its genome-wide putative targets. Together with a qPCR screen, we found HNF1A to activate the expression of SLC51B, CD24, and RNF186 genes. Importantly, HNF1A-depleted human renal proximal tubule epithelial cells (RPTECs) and MODY3 human induced pluripotent stem cell (hiPSC)-derived kidney organoids expressed lower levels of SLC51B. SLC51B-mediated estrone sulfate (E1S) uptake in proximal tubule cells was abrogated in these HNF1A-deficient cells. MODY3 patients also exhibit significantly higher excretion of urinary E1S. Overall, we report that SLC51B is a target of HNF1A responsible for E1S uptake in human proximal tubule cells. As E1S serves as the main storage form of nephroprotective estradiol in the human body, lowered E1S uptake and increased E1S excretion may reduce the availability of nephroprotective estradiol in the kidneys, contributing to the development of renal disease in MODY3 patients.

Identification and validation of immune-related biomarkers and potential regulators and therapeutic targets for diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is a major complication of diabetes and the leading cause of end-stage renal disease worldwide. Renal inflammation and infiltration of immune cells contribute to the development and progression of DKD. Thus, the aim of the present study was to identify and validate immune-related biomarkers and analyze potential regulators including transcription factors (TFs), microRNAs (miRNAs), and drugs for DKD.

METHODS

Immune-related genes from the ImmPort database and glomeruli samples from GSE1009 and GSE30528 were used to identify differentially expressed immune-related genes (DEIRGs) of DKD. The expression level and clinical correlation analyses of DEIRGs were verified in the Nephroseq database. Murine podocytes were cultured to construct the high glucose-induced podocyte injury model. The reliability of the bioinformatics analysis was experimentally validated by RT-qPCR in podocytes. Networks among DEIRGs, regulators, and drugs were constructed to predict potential regulatory mechanisms for DKD.

RESULTS

DKD-associated DEIRGs were identified. CCL19 and IL7R were significantly upregulated in the DKD group and negatively correlated with glomerular filtration rate (GFR). GHR, FGF1, FYN, VEGFA, F2R, TGFBR3, PTGDS, FGF9, and SEMA5A were significantly decreased in the DKD group and positively correlated with GFR. RT-qPCR showed that the relative mRNA expression levels of GHR, FGF1, FYN, TGFBR3, PTGDS, FGF9, and SEMA5A were significantly down-regulated in the high glucose-induced podocyte injury group. The enriched regulators for DEIRGs included 110 miRNAs and 8 TFs. The abnormal expression of DEIRGs could be regulated by 16 established drugs.

CONCLUSIONS

This study identified immune-related biomarkers, regulators, and drugs of DKD. The findings of the present study provide novel insights into immune-related diagnosis and treatment of DKD.

The Relevant of Sex Hormone Levels and Acne Grades in Patients with Acne Vulgaris: A Cross-Sectional Study in Beijing

Background

The tests of sex hormones play pivotal roles in the clinical diagnosis and treatment of acne vulgaris, but the majority of patients with acne vulgaris present regular sex hormone levels within the normal reference range.

Objective

To determine the correlation among levels of sex hormones, ratio of androgen to estrogen and acne grades in patients with acne vulgaris.

Methods

A cross-sectional study was applied to collect 693 patients with acne vulgaris. All samples were screened by cluster sampling among those who underwent tests of sex hormones at Beijing Jingcheng Skin Hospital from July 2021 to June 2022. A gender stratified analysis was performed to classify acne grades I–IV. Spearman correlation analysis was used to analyze the relationship between age, sex hormones, ratio of androgen to estrogen and acne grades, with multinomial logistic regression to analyze the association of sex hormones with acne grades in patients with acne.

Results

(1) The testosterone levels were mostly within normal reference values for both males and females with varying degrees of acne. For females, the serum follicle-stimulating hormone, estradiol, progesterone, testosterone, and ratio of androgen to estrogen were significantly different between acne grades. For males, there were significant differences in serum estradiol, testosterone, and ratio of androgen to estrogen across acne grades. (2) The acne grade was negatively correlated with estradiol and positively correlated with the ratio of androgen to estrogen; the female acne grade was also negatively correlated with age and progesterone, but positively correlated with follicle-stimulating hormone. (3) Multivariate logistic regression analysis indicated that the ratio of androgen to estrogen was independently correlated with the grade of acne and that acne grade worsened as the ratio increased.

Conclusion

The increase in the ratio of androgen to estrogen may aggravate the acne grade in patients with acne vulgaris.

Differences in long-term effects of standard rodent diets on blood glucose and body weight of offspring

Standard rodent diets are similar and contain well-balanced components, such as crude protein, fat, fiber, and ash. However, it is not clear whether there are differences in their long-term effects on metabolism. Here, we investigated the effects of long-term feeding of major standard diets, CRF-1, CE-2, and FR-1 to wild-type (WT) C57BL/6 mice on the blood glucose levels and body weight gain of their offspring, which were raised on the same diet and in the same environment as the mothers. The offspring have been influenced by the maternal diet during the fetal and neonatal stages, and were maintained on the same diet thereafter (until 60 weeks of age). In the CE-2 group, the offspring showed stable blood glucose levels and had the lowest body weight. The FR1 group showed the lowest blood glucose level, but body weight was increased significantly compared to the CE-2 group. In the CRF-1 group, higher blood glucose levels were seen from the neonatal stage and body weight increased more rapidly than in the other groups. Next, to determine the effects of blood glucose level and housing pattern on food and water consumption, severely diabetic (hyperglycemic) inducible cAMP early repressor (ICER) transgenic (Tg) mice and littermate WT mice (normoglycemic) were fed CE-2 diet and housed individually or in groups. Food and water consumption of WT mice was independent of housing pattern, whereas Tg mice showed significantly increased food and water consumption when housed individually, compared to group housing, and this did not change at different ages. Thus, the selection of standard diet and rearing method can have a marked impact on experimental outcomes in experiments using mice and presumably mouse cells, especially in studies of metabolism, diabetes, and obesity.

Amelioration of Murine Diabetic Nephropathy with a SGLT2 Inhibitor Is Associated with Suppressing Abnormal Expression of Hypoxia-Inducible Factors

Diabetic nephropathy (DN), once manifested, is unlikely to completely recover. Factors that influence DN progression were explored by investigating the process of glomerulosclerosis and interstitial fibrosis and chronological changes in glucose, albuminuria, hyperfiltration, and expressions of sodium-glucose cotransporter 2 (SGLT2) and hypoxia-inducible factors (HIFs) up to 50 weeks in inducible cAMP early repressor transgenic mice, a model of severe DN. Long-term intervention with the SGLT2 inhibitor canagliflozin or islet transplantation or heminephrectomy was used. Inducible cAMP early repressor transgenic mice exhibited progressive diabetic glomerulosclerosis and mild interstitial fibrosis, and expressed extensive HIF-1α and HIF-2α in glomerulus and tubules, with sustained hyperfiltration up to 50 weeks. Canagliflozin ameliorated glomerulosclerosis/interstitial fibrosis gradually and reduced HIF overexpression. Islet-transplanted mice exhibited no amelioration. None of the heminephrectomized diabetic mice survived the hyperfiltration overload, but all of the canagliflozin-treated mice survived with re-expressions of HIF-1α and HIF-2α. These results suggest that persistent glomerular hyperfiltration might initiate glomerular injury, and persistent overexpression of HIFs could promote the development of glomerulosclerosis and interstitial fibrosis. Canagliflozin attenuated both changes. Oxidative stress or hypoxia was undetectable in this model. The abnormal expression of HIF-1α and HIF-2α may be a potential therapeutic target for preventing glomerulosclerosis and interstitial fibrosis.

Icariin attenuates renal interstitial fibrosis through G protein-coupled estrogen receptor in a UUO murine model

BACKGROUND/AIMS

Icariin plays an antifibrotic role in the unilateral ureteral obstruction (UUO) model; however, its primary mechanism has not been elucidated. G protein-coupled estrogen receptor (GPER) has been shown to be associated with fibrosis and mitochondrial biogenesis. In this study, we aimed to investigate the impact of GPER on renal fibrosis and whether icariin attenuates renal fibrosis dependent on GPER.

METHODS

In the in vivo study, 10-week-old mice were subjected to the UUO model followed by UUO with icariin, G-15 (a GPER antagonist), and icariin + G-15. GPER expression, renal fibrosis levels, and mitochondrial alterations were measured and analyzed. In an in vitro study, we examined the antifibrotic effect of icariin on rat renal fibroblasts (NRK-49F) via GPER.

RESULTS

Consistent with a previous study, icariin significantly attenuated fibrotic markers and protected the kidneys against mitochondrial injuries in the UUO model. However, G-15 exacerbated renal fibrosis and abolished the protective effect of icariin in the UUO model. Furthermore, antagonizing or knocking down GPER in NRK-49F significantly increased fibrotic markers and eliminated the antifibrotic effect of icariin.

CONCLUSIONS

Our findings indicate that (1) GPER inhibition exacerbates renal fibrosis, and (2) icariin exerts antifibrotic effects against renal fibrosis through GPER.

Castrated autoimmune glomerulonephritis mouse model shows attenuated glomerular sclerosis with altered parietal epithelial cell phenotype

Sex hormones help in maintaining proper immunity as well as renal homeostasis in mammals, and these multi-functional properties characterize the onset of sex-dependent diseases. To clarify the contribution of sex hormones to autoimmune disease-related renal pathogenesis, BXSB/MpJ-Yaa was investigated as a murine autoimmune glomerulonephritis model. BXSB/MpJ-Yaa and its wild-type, BXSB/MpJ-Yaa+ were castrated or sham-operated at three weeks and examined until six months of age. Both castrated strains showed significantly lower serum testosterone levels and body weights than sham-operated mice. Castration did not change the disease phenotypes in BXSB/MpJ-Yaa+. At three months, both sham-operated and castrated BXSB/MpJ-Yaa manifested splenomegaly, autoantibody production, and glomerulonephritis, and castrated BXSB/MpJ-Yaa tended to show heavier spleen weights than the sham-operated group. At six months, both the treated BXSB/MpJ-Yaa showed equivalent autoimmune disease conditions; however, castrated mice clearly showed milder glomerular sclerotic lesions than the sham-operated groups. Urinary albumin excretion in castrated BXSB/MpJ-Yaa was significantly milder than in sham-operated mice at four months, but those of both the treated BXSB/MpJ-Yaa were comparable at six months. The examined renal histopathological indices in parietal epithelial cells were remarkably altered by castration. Briefly, castration decreased the height of parietal epithelial cells and total parietal epithelial cell number in BXSB/MpJ-Yaa at six months. For immunostaining, parietal epithelial cells facing the injured glomeruli of BXSB/MpJ-Yaa expressed CD44, an activated parietal epithelial cell marker, and CD44-positive parietal epithelial cells showed nuclear localization of the androgen receptor and proliferation marker Ki67. CD44- or Ki67-positive parietal epithelial cells were significantly fewer in castrated group than in sham-operated BXSB/MpJ-Yaa at six months. Further, quantitative indices for CD44-positive parietal epithelial cell number and frequency in renal corpuscles positively correlated with glomerular sclerotic severity in BXSB/MpJ-Yaa. In conclusion, androgen seemed to have an effect on both systemic immunity and renal morpho-function; however, the effect on the latter could be more clearly observed in BXSB/MpJ-Yaa, as parietal epithelial cell activation resulted in glomerular sclerosis.

Gender Differences in Diabetic Kidney Disease: Focus on Hormonal, Genetic and Clinical Factors

Diabetic kidney disease (DKD) is one of the most serious complications of both type 1 (T1DM) and type 2 diabetes mellitus (T2DM). Current guidelines recommend a personalized approach in order to reduce the burden of DM and its complications. Recognizing sex and gender- differences in medicine is considered one of the first steps toward personalized medicine, but the gender issue in DM has been scarcely explored so far. Gender differences have been reported in the incidence and the prevalence of DKD, in its phenotypes and clinical manifestations, as well as in several risk factors, with a different impact in the two genders. Hormonal factors, especially estrogen loss, play a significant role in explaining these differences. Additionally, the impact of sex chromosomes as well as the influence of gene-sex interactions with several susceptibility genes for DKD have been investigated. In spite of the increasing evidence that sex and gender should be included in the evaluation of DKD, several open issues remain uncovered, including the potentially different effects of newly recommended drugs, such as SGLT2i and GLP1Ras. This narrative review explored current evidence on sex/gender differences in DKD, taking into account hormonal, genetic and clinical factors.

Network Pharmacology-Based Prediction of Mechanism of Shenzhuo Formula for Application to DKD

Background

Shenzhuo formula (SZF) is a traditional Chinese medicine (TCM) prescription which has significant therapeutic effects on diabetic kidney disease (DKD). However, its mechanism remains unknown. Therefore, this study aimed to explore the underlying anti-DKD mechanism of SZF.

Methods

The active ingredients and targets of SZF were obtained by searching TCMSP, TCMID, SwissTargetPrediction, HIT, and literature. The DKD target was identified from TTD, DrugBank, and DisGeNet. The potential targets were obtained and PPI network were built after mapping SZF targets and DKD targets. The key targets were screened out by network topology and the “SZF-key targets-DKD” network was constructed by Cytoscape. GO analysis and KEGG pathway enrichment analysis were performed by using DAVID, and the results were visualized by Omicshare Tools.

Results

We obtained 182 potential targets and 30 key targets. Furthermore, a “SZF-key targets-DKD” network topological analysis showed that active ingredients like M51, M21, M5, M71, and M28 and targets like EGFR, MMP9, MAPK8, PIK3CA, and STAT3 might play important roles in the process of SZF treating in DKD. GO analysis results showed that targets were mainly involved in positive regulation of transcription from RNA polymerase II promoter, inflammatory response, lipopolysaccharide-mediated signaling pathway, and other biological processes. KEGG showed that DKD-related pathways like TNF signaling pathway and PI3K-Akt signaling pathway were at the top of the list.

Conclusion

This research reveals the potential pharmacological targets of SZF in the treatment of DKD through network pharmacology and lays a foundation for further studies.

Kidney hemodynamic function in men and postmenopausal women with type 2 diabetes and preserved kidney function

The progression of kidney disease may differ between sexes in type 2 diabetes (T2D), with previous studies reporting a slower decline in women. Glomerular hyperfiltration is a key factor driving the kidney function decline. The current study aimed to investigate the differences in kidney hemodynamic function between men and women with T2D. A cross-sectional analysis of pooled data from three studies compared kidney hemodynamic function between men and postmenopausal women with T2D without overt nephropathy. The outcome measures were glomerular filtration rate (GFR; inulin clearance), effective renal plasma flow (ERPF; p-aminohippurate clearance), filtration fraction (GFR/ERPF), and renal vascular resistance (RVR; mean arterial pressure/renal blood flow). Glomerular hydraulic pressure (P_GLO) as well as afferent and efferent vascular resistance were estimated by Gomez formulae. Sex differences were assessed with linear regression models adjusted for systolic blood pressure, glucose, use of renin-angiotensin system blockers, and body mass index. In total, 101 men [age: 63 (58-68) yr, body mass index: 31.5 ± 3.9 kg/m², GFR: 111 ± 18 mL/min, HbA_1c: 7.4 ± 0.7%] and 27 women [age: 66 (62-69) yr, body mass index: 30.9 ± 4.5 kg/m², GFR: 97 ± 11 mL/min, HbA_1c: 7.1 ± 0.5%] were included. GFR was higher in men versus women [11.0 mL/min (95% confidence interval: 3.6, 18.4)]. Although statistically nonsignificant, P_GLO trended higher in men [1.9 mmHg (95% confidence interval: -0.1, 4.0)], whereas RVR [-0.012 mmHg/L/min (95% confidence interval: -0.022, -0.002)] and afferent vascular resistance were lower [-361 dyn/s/cm⁵ (95% confidence interval: -801, 78)]. In conclusion, in adults without overt nephropathy, GFR was higher in men compared with women. P_GLO also trended to be higher in men. Both findings are possibly related to afferent vasodilation and suggest greater prevalence of hyperfiltration. This could contribute to accelerated GFR loss over time in men with T2D.NEW & NOTEWORTHY In adults with type 2 diabetes, men had higher markers of hyperfiltration, which could potentially explain the accelerated progression of diabetic kidney disease in men compared with women.

Proximal tubular epithelial insulin receptor mediates high-fat diet-induced kidney injury

The role of insulin receptor (IR) activated by hyperinsulinemia in obesity-induced kidney injury is not well understood. We hypothesized that activation of kidney proximal tubule epithelial IR contributes to obesity-induced kidney injury. We administered normal-fat diet (NFD) or high-fat diet (HFD) to control and kidney proximal tubule IR–knockout (KPTIRKO) mice for 4 months. Renal cortical IR expression was decreased by 60% in male and female KPTIRKO mice. Baseline serum glucose, serum creatinine, and the ratio of urinary albumin to creatinine (ACR) were similar in KPTIRKO mice compared to those of controls. On HFD, weight gain and increase in serum cholesterol were similar in control and KPTIRKO mice; blood glucose did not change. HFD increased the following parameters in the male control mice: renal cortical contents of phosphorylated IR and Akt, matrix proteins, urinary ACR, urinary kidney injury molecule-1–to-creatinine ratio, and systolic blood pressure. Renal cortical generation of hydrogen sulfide was reduced in HFD-fed male control mice. All of these parameters were ameliorated in male KPTIRKO mice. Interestingly, female mice were resistant to HFD-induced kidney injury in both genotypes. We conclude that HFD-induced kidney injury requires renal proximal tubule IR activation in male mice.

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.

Nuclear receptors in the kidney during health and disease

Over the last 30 years, nuclear receptors (NRs) have been increasingly recognized as key modulators of systemic homeostasis and as contributing factors in many diseases. In the kidney, NRs play numerous important roles in maintaining homeostasis-many of which continue to be unraveled. As "master regulators", these important transcription factors integrate and coordinate many renal processes such as circadian responses, lipid metabolism, fatty acid oxidation, glucose handling, and inflammatory responses. The use of recently-developed genetic tools and small molecule modulators have allowed for detailed studies of how renal NRs contribute to kidney homeostasis. Importantly, while NRs are intimately involved in proper kidney function, they are also implicated in a variety of renal diseases such as diabetes, acute kidney injury, and other conditions such as aging. In the last 10 years, our understanding of renal disease etiology and progression has been greatly shaped by knowledge regarding how NRs are dysregulated in these conditions. Importantly, NRs have also become attractive therapeutic targets for attenuation of renal diseases, and their modulation for this purpose has been the subject of intense investigation. Here, we review the role in health and disease of six key renal NRs including the peroxisome proliferator-activated receptors (PPAR), estrogen-related receptors (ERR), the farnesoid X receptors (FXR), estrogen receptors (ER), liver X receptors (LXR), and vitamin D receptors (VDR) with an emphasis on recent findings over the last decade. These NRs have generated a wealth of data over the last 10 years that demonstrate their crucial role in maintaining normal renal homeostasis as well as their capacity to modulate disease progression.

Evidence for G-Protein-Coupled Estrogen Receptor as a Pronatriuretic Factor

Background The novel estrogen receptor, G-protein-coupled estrogen receptor (GPER), is responsible for rapid estrogen signaling. GPER activation elicits cardiovascular and nephroprotective effects against salt-induced complications, yet there is no direct evidence for GPER control of renal Na+ handling. We hypothesized that GPER activation in the renal medulla facilitates Na+ excretion. Methods and Results Herein, we show that infusion of the GPER agonist, G1, to the renal medulla increased Na+ excretion in female Sprague Dawley rats, but not male rats. We found that GPER mRNA expression and protein abundance were markedly higher in outer medullary tissues from females relative to males. Blockade of GPER in the renal medulla attenuated Na+ excretion in females. Given that medullary endothelin 1 is a well-established natriuretic factor that is regulated by sex and sex steroids, we hypothesized that GPER activation promotes natriuresis via an endothelin 1-dependent pathway. To test this mechanism, we determined the effect of medullary infusion of G1 after blockade of endothelin receptors. Dual endothelin receptor subtype A and endothelin receptor subtype B antagonism attenuated G1-induced natriuresis in females. Unlike males, female mice with genetic deletion of GPER had reduced endothelin 1, endothelin receptor subtype A, and endothelin receptor subtype B mRNA expression compared with wild-type controls. More important, we found that systemic GPER activation ameliorates the increase in mean arterial pressure induced by ovariectomy. Conclusions Our data uncover a novel role for renal medullary GPER in promoting Na+ excretion via an endothelin 1-dependent pathway in female rats, but not in males. These results highlight GPER as a potential therapeutic target for salt-sensitive hypertension in postmenopausal women.

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.

Ameliorative effects of quercetin on the preimplantation embryos development in diabetic pregnant mice

AIM

Maternal diabetes adversely retards the development of preimplantation embryos. Quercetin is a flavonoid belonging to phytoestrogens family and may be useful in treatment of reproductive disorders. The aim of this study was investigation of the ameliorative effects of quercetin administration on preimplantation embryo development in diabetic pregnancy.

METHODS

Diabetic and healthy female mice were treated with 30 mg/kg/day quercetin 4 weeks before conception. Blastocysts were recovered at the 4th day of pregnancy for protein and mRNA expression changes. Plasma sex-steroid levels were also analyzed.

RESULTS

Quercetin significantly decreased blood glucose levels in diabetic mice. Embryos retrieved from diabetic mice exhibited a considerable delay in morphological development. In diabetic mice with quercetin treatment, morphological distribution was shifted considerably to the well-developed stages. Serum estradiol level reduced in diabetic mice but, treatment with quercetin significantly increased serum estradiol level. While IGF1R, integrin αvβ3, and Cox2 mRNA expression in the blastocyst of diabetic mice decreased significantly, quercetin treatment caused increasing expression levels of these genes. Expression of the Caspase3 gene increased dramatically in the collected blastocysts from diabetic mice and reduced following quercetin treatment. Besides, the inactive β-catenin protein level in the blastocysts of diabetic mice was higher than that in normal mice, while treatment with quercetin decreased the level of inactive β-catenin protein in the blastocyst of diabetic mice.

CONCLUSION

Quercetin protects preimplantation embryos from destructive effects of diabetes. The amelioration of sex hormones disturbance in early pregnancy may help to treat reproductive disorders in diabetic women. Quercetin can be considered as a novel solution to the improvement of reproductive disorders in the diabetic females.

Sex differences in progression of diabetic nephropathy in OVE26 type 1 diabetic mice

AIMS

OVE26 mice (FVB background), genetically overexpressing calmodulin in pancreatic beta cells, develop early onset type 1 diabetes, leading to progressive diabetic nephropathy (DN), with features of established human DN. The role of gender in characteristics of renal lesions has remained unexplored.

METHODS

Male and female OVE26 mice were compared to age and sex matched wild-type, nondiabetic FVB mice at ages of 4, 12, 24 and 36 weeks. Nephropathy was examined by measuring urine albumin-to-creatinine ratio, histopathology, expression of pathological markers and immunochemistry in the same cohort of mice.

RESULTS

Progression of diabetic kidney disease was evident first in the OVE26 glomerulus, initially as mesangial matrix expansion at 4 weeks followed by loss of podocytes, glomerular volume expansion and severe albuminuria at 12 weeks. Tubule dilation and initiation of interstitial fibrosis did not become significant until 24 weeks. T-lymphocyte infiltration into the renal parenchyma appeared at 36 weeks. OVE26 female mice developed more advanced DN than male OVE26 mice, such as more severe albuminuria, greater podocyte loss, additional fibrosis and significantly more inflammatory cell infiltration. The female OVE26 mice had lowest level of plasma estradiol in all 36 weeks old mice, as well as renal estrogen receptors.

CONCLUSIONS

This demonstration of the role of gender, combined with the detailed characterization of DN progression illustrates the value of OVE26 mice for understanding gender effects on DN and provides the basis for researchers to better select the age and sex of OVE26 mice in future studies of type 1 DN.

RESEARCH IN CONTEXT

What is already known about this subject? What is the key question? What are the new findings? How might this impact on clinical practice in the foreseeable future?

Sex and the kidneys: current understanding and research opportunities

Concerns regarding sex differences are increasingly pertinent in scientific and societal arenas. Although biological sex and socio-cultural gender are increasingly recognized as important modulators of renal function under physiological and pathophysiological conditions, gaps remain in our understanding of the mechanisms underlying sex differences in renal pathophysiology, disease development, progression and management. In this Perspectives article, we discuss specific opportunities for future research aimed at addressing these knowledge gaps. Such opportunities include the development of standardized core data elements and outcomes related to sex for use in clinical studies to establish a connection between sex hormones and renal disease development or progression, development of a knowledge portal to promote fundamental understanding of physiological differences between male and female kidneys in animal models and in humans, and the creation of new or the development of existing resources and datasets to make them more readily available for interrogation of sex differences. These ideas are intended to stimulate thought and interest among the renal research community as they consider sex as a biological variable in future research projects.

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

Estrogen has been implicated in the regulation of growth and immune function in the kidney, which expresses the full-length estrogen receptor-α (ERα66), its ERα splice variants, and estrogen receptor-β (ERβ). Thus, we hypothesized that these splice variants may inhibit the glomerular enlargement that occurs early in type 1 diabetes (T1D). T1D was induced by streptozotocin (STZ) injection in 8- to 12-wk-old female mice lacking ERα66 (ERα66KO) or all ERα variants (αERKO), and their wild-type (WT) littermates. Basal renal ERα36 protein expression was reduced in the ERα66KO model and was downregulated by T1D in WT mice. T1D did not alter ERα46 or ERβ in WT-STZ; however, ERα46 was decreased modestly in ERα66KO mice. Renal hypertrophy was evident in all diabetic mice. F4/80-positive immunostaining was reduced in ERα66KO compared with WT and αERKO mice but was higher in STZ than in Control mice across all genotypes. Glomerular area was greater in WT and αERKO than in ERα66KO mice, with T1D-induced glomerular enlargement apparent in WT-STZ and αERKO-STZ, but not in ERα66KO-STZ mice. Proteinuria and hyperfiltration were evident in ERα66KO-STZ and αERKO-STZ, but not in WT-STZ mice. These data indicate that ERα splice variants may exert an inhibitory influence on glomerular enlargement and macrophage infiltration during T1D; however, effects of splice variants are masked in the presence of the full-length ERα66, suggesting that ERα66 acts in opposition to its splice variants to influence these parameters. In contrast, hyperfiltration and proteinuria in T1D are attenuated via an ERα66-dependent mechanism that is unaffected by splice variant status.

Kidneys and women's health: key challenges and considerations

The theme of World Kidney Day 2018 is 'kidneys and women's health: include, value, empower'. To mark this event, Nature Reviews Nephrology asked four leading researchers to discuss key considerations related to women's kidney health, including specific risk factors, as well as the main challenges and barriers to care for women with kidney disease and how these might be overcome. They also discuss policies and systems that could be implemented to improve the kidney health of women and their offspring and the areas of research that are needed to improve the outcomes of kidney disease in women.

Transcriptional Profile of Kidney from Type 2 Diabetic db/db Mice

Diabetic nephropathy (DN), a common diabetic microvascular complication, is characterized by progressive glomerular sclerosis and tubulointerstitial fibrosis. However, the underlying mechanisms involved in DN remain to be elucidated. We explored changes in the transcriptional profile in spontaneous type 2 diabetic db/db mice by using the cDNA microarray. Compared with control db/m mice, the db/db mice exhibited marked increases in body weight, kidney weight, and urinary albumin excretion. Renal histological analysis revealed mesangial expansion and thickness of the basement membrane in the kidney of the db/db mice. A total of 355 differentially expressed genes (DEGs) were identified by microarray analysis. Pathway enrichment analysis suggested that biological oxidation, bile acid metabolism, and steroid hormone synthesis were the 3 major significant pathways. The top 10 hub genes were selected from the constructed PPI network of DEGs, including Ccnb2 and Nr1i2, which remained largely unclear in DN. We believe that our study can help elucidate the molecular mechanisms underlying DN.

Renal Protective Effects of 17β-Estradiol on Mice with Acute Aristolochic Acid Nephropathy

Aristolochic acid nephropathy (AAN) is a progressive kidney disease caused by a Chinese herb containing aristolochic acid. Excessive death of renal tubular epithelial cells (RTECs) characterized the acute phase of AAN. Therapies for acute AAN were limited, such as steroids and angiotensin-receptor blockers (ARBs)/angiotensin-converting enzyme inhibitors (ACEIs). It was interesting that, in acute AAN, female patients showed relative slower progression to renal failure than males. In a previous study, female hormone 17β-estradiol (E2) was found to attenuate renal ischemia-reperfusion injury. Thus, the aim of this study was to investigate the potential protective role of E2 in acute AAN. Compared with male C57BL/6 mice of acute AAN, lower serum creatinine (SCr) and less renal injury, together with RTEC apoptosis in females, were found. Treatment with E2 in male AAN mice reduced SCr levels and attenuated renal tubular injury and RTEC apoptosis. In the mice kidney tissue and human renal proximal tubule cells (HK-2 cells), E2 both attenuated AA-induced cell apoptosis and downregulated the expression of phosphor-p53 (Ser15), p53, and cleaved-caspase-3. This study highlights that E2 exhibited protective effects on the renal injury of acute AAN in male mice by reducing RTEC apoptosis, which might be related to inhibiting the p53 signaling pathway.