Postmenopausal hormone replacement improves proteinuria and impaired creatinine clearance in type 2 diabetes mellitus and hypertension

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.

Role of sex hormones in diabetic nephropathy

Diabetic nephropathy (DN) is the most common microvascular complication in diabetes and one of the leading causes of end-stage renal disease. The standard treatments for patients with classic DN focus on blood glucose and blood pressure control, but these treatments can only slow the progression of DN instead of stopping or reversing the disease. In recent years, new drugs targeting the pathological mechanisms of DN (e.g., blocking oxidative stress or inflammation) have emerged, and new therapeutic strategies targeting pathological mechanisms are gaining increasing attention. A growing number of epidemiological and clinical studies suggest that sex hormones play an important role in the onset and progression of DN. Testosterone is the main sex hormone in males and is thought to accelerate the occurrence and progression of DN. Estrogen is the main sex hormone in females and is thought to have renoprotective effects. However, the underlying molecular mechanism by which sex hormones regulate DN has not been fully elucidated and summarized. This review aims to summarize the correlation between sex hormones and DN and evaluate the value of hormonotherapy in DN.

Bidirectional causal associations between type 2 diabetes and COVID-19

Observational studies have reported high comorbidity between type 2 diabetes (T2D) and severe COVID-19. However, the causality between T2D and COVID-19 has yet to be validated. We performed genetic correlation and Mendelian randomization (MR) analyses to assess genetic relationships and potential causal associations between T2D and three COVID-19 outcomes (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] infection, COVID-19 hospitalization, and critical COVID-19). Molecular pathways connecting SARS-CoV-2 and COVID-19 were reconstructed to extract insights into the potential mechanisms underlying the connection. We identified a high genetic overlap between T2D and each COVID-19 outcome (genetic correlations 0.21-0.28). The MR analyses indicated that genetic liability to T2D confers a causal effect on hospitalized COVID-19 (odds ratio 1.08, 95% confidence interval [CI] 1.04-1.12) and critical COVID-19 (1.09, 1.03-1.16), while genetic liability to SARS-CoV-2 infection exerts a causal effect on T2D (1.25, 1.00-1.56). There was suggestive evidence that T2D was associated with an increased risk for SARS-CoV-2 infection (1.02, 1.00-1.03), while critical COVID-19 (1.06, 1.00-1.13) and hospitalized COVID-19 (1.09, 0.99-1.19) were associated with an increased risk for T2D. Pathway analysis identified a panel of immunity-related genes that may mediate the links between T2D and COVID-19 at the molecular level. Our study provides robust support for the bidirectional causal associations between T2D and COVID-19. T2D may contribute to amplifying the severity of COVID-19, while the liability to COVID-19 may increase the risk for T2D.

Hormonal Regulation of Renal Fibrosis

Fibrosis is a severe complication of many acute and chronic kidney pathologies. According to current concepts, an imbalance in the synthesis and degradation of the extracellular matrix by fibroblasts is considered the key cause of the induction and progression of fibrosis. Nevertheless, inflammation associated with the damage of tissue cells is among the factors promoting this pathological process. Most of the mechanisms accompanying fibrosis development are controlled by various hormones, which makes humoral regulation an attractive target for therapeutic intervention. In this vein, it is particularly interesting that the kidney is the source of many hormones, while other hormones regulate renal functions. The normal kidney physiology and pathogenesis of many kidney diseases are sex-dependent and thus modulated by sex hormones. Therefore, when choosing therapy, it is necessary to focus on the sex-associated characteristics of kidney functioning. In this review, we considered renal fibrosis from the point of view of vasoactive and reproductive hormone imbalance. The hormonal therapy possibilities for the treatment or prevention of kidney fibrosis are also discussed.

Comparison of the Surgical Resection and Infarct 5/6 Nephrectomy Rat Models of Chronic Kidney Disease

The 5/6 nephrectomy rat remnant kidney model is commonly employed to study chronic kidney disease (CKD). This model requires removal of one whole kidney and two-thirds of the other. The two most common ways of producing the remnant kidney are surgical resection of poles, known as the polectomy (Pol) model, or ligation of upper and lower renal arterial branches, resulting in pole infarction (Inf). These models have much in common, but also major phenotypic differences, and thus respectively model unique aspects of human CKD. The purpose of this review is to summarize phenotypic similarities and differences between these two models and their relation to human CKD, while emphasizing their vascular phenotype. In this article we review studies that have evaluated arterial blood pressure, the renin-angiotensin-aldosterone-system (RAAS), autoregulation, nitric oxide, single nephron physiology, angiogenic and anti-angiogenic factors, and capillary rarefaction in these two models. Phenotypic similarities: both models spontaneously develop hallmarks of human CKD including uremia, fibrosis, capillary rarefaction, and progressive renal function decline. They both undergo whole-organ hypertrophy, hyperfiltration of functional nephrons, reduced renal expression of angiogenic factor VEGF, increased renal expression of the anti-angiogenic thrombospondin-1, impaired renal autoregulation, and abnormal vascular nitric oxide physiology. Key phenotypic differences: the Inf model develops rapid-onset, moderate-to-severe systemic hypertension, and the Pol model early normotension followed by mild-to-moderate hypertension. The Inf rat has a markedly more active renin-angiotensin-aldosterone-system. Comparison of these two models facilitates understanding of how they can be utilized for studying CKD pathophysiology (e.g., RAAS dependent or independent pathology).

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.

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.

Medroxyprogesterone opposes estradiol-induced renal damage in midlife ovariectomized Long Evans rats

OBJECTIVE

Our laboratory previously published that long-term administration of estradiol (E2) was detrimental to the kidneys of midlife ovariectomized Long Evans rats, contrasting clinical studies in showing that menopausal hormone therapy is associated with decreased albuminuria. However, it is unknown whether this renal benefit was due to estrogen and/or the combination with progestogen. Therefore, the objective of the current study was to determine the impact of medroxyprogesterone (MPA) on E2-mediated renal damage using a rodent model.

METHODS

Female Long Evans retired breeders underwent ovariectomy at 11 months of age and were treated for 40 days with subcutaneous E2, E2+MPA or vehicle at doses mimicking that of menopausal hormone therapy (N = 5-7 per group). Systolic blood pressure was measured along with indices of renal damage and function to investigate the impact of MPA on E2-mediated renal outcomes. Renal estrogen receptor alpha and G protein-coupled estrogen receptor transcript copy numbers were measured in all treatment groups through droplet digital PCR.

RESULTS

Middle-aged female Long Evans rats displayed spontaneous hypertension with similar systolic blood pressures and heart weights between groups. Even though blood pressure was comparable, E2 reduced glomerular filtration rate and increased proteinuria indicating pressure-independent renal damage. Coadministration with MPA prevented E2-induced glomerular filtration rate impairment and proteinuria by promoting renal hypertrophy and preventing renal interstitial fibrosis. Both E2 and E2+MPA reduced renal estrogen receptor alpha (ERα) and increased renal G protein-coupled estrogen receptor mRNA, but neither ERα nor ERß protein was different between groups.

CONCLUSION

MPA was protective against E2-induced renal damage and dysfunction in middle-aged female Long Evans rats. Assessing the impact of hormone therapy on renal outcomes may be an important clinical factor when considering treatment options for postmenopausal women.

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.

Sex Differences in Biopsy-Confirmed Diabetic Kidney Disease

BACKGROUND

To investigate the association between sex differences and end-stage kidney disease (ESKD) in patients with biopsy-confirmed diabetic kidney disease (DKD).

METHOD

We performed a retrospective cohort study. A total of 336 patients with biopsy-confirmed DKD who were followed up for at least 12 months were enrolled. Baseline clinical and pathological data at the time of biopsy were collected. ESKD was defined by an estimated glomerular filtration rate of <15 ml/min/1.73 m² or initiation of renal replacement therapy. The association between sex differences and ESKD was assessed using the log-rank test and Cox regression.

RESULT

There were 239 (71%) male and 97 (29%) female patients in our cohort. Female patients had higher systolic blood pressure, total cholesterol and low-density lipoprotein cholesterol levels compared with male. There were a lower proportion of female patients in the very high risk grade according to the chronic kidney disease categories (37% of female vs. 44% of male). During a median follow-up time of 20 months, 101 (57.7%) male and 43 (44.3%) female entered into ESKD, with no significant difference by the log-rank test (P >0.05). Univariate [male: hazard ratio (HR) [95% confidence interval (CI)], 1.005, (0.702-1.439)] and multivariable ([male: HR (95%CI), 1.164, (0.675-2.007)]. Cox regression further showed that sex difference was not significantly associated with ESKD.

CONCLUSION

Female patients had the higher systolic blood pressure, total cholesterol, LDL-C, compared with male patients. However, there was no significant association observed between sex difference and ESKD in our study.

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.

Kidney Transplantation in Transgender Patients

PURPOSE OF REVIEW

Kidney transplantation and gender affirmation treatments are becoming increasingly more prevalent due to advances in technology. However, there is a paucity of data regarding kidney transplantation in transgender patients. Interesting considerations must be made in this patient population, since there are many hormonal interactions with kidney function and the transplantation process.

RECENT FINDINGS

The diagnosis of estimated glomerular filtration rate (eGFR), preoperative assessment/counseling, decreased testosterone levels in a transgender male to female patient, increased estrogen/progesterone in a female to male patient, and drug side effects all have important and unique implications for kidney transplant recipients. Kidney transplantation can be safely and effectively managed in transgender patients with special considerations in eGFR calculations, mental health/lifestyle counseling, and drug interactions.

Transgender women on oral HIV pre-exposure prophylaxis have significantly lower tenofovir and emtricitabine concentrations when also taking oestrogen when compared to cisgender men

INTRODUCTION

Oral HIV Pre-Exposure Prophylaxis (PrEP) with tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC) is highly effective. Transgender women (TGW) have increased HIV risk, but have been underrepresented in trials. For TGW on oestrogens for gender-affirming hormone treatment (GAHT), TDF/FTC-oestrogen interactions may negatively affect HIV prevention or gender-affirming goals. Our aim was to evaluate any pharmacokinetic drug-drug interaction between GAHT and TDF/FTC.

METHODS

We performed a pharmacokinetic study, in an urban outpatient setting in 2016 to 2018, of the effects of GAHT on TFV, FTC and the active forms TFV diphosphate (TFV-DP) and FTC triphosphate (FTC-TP) in eight TGW and eight cisgender men (CGM). At screening, participants were HIV negative. TGW were to maintain their GAHT regimens and have plasma oestradiol concentrations >100 pg/mL. Under direct observation, participants took oral TDF/FTC daily for seven days. At the last dose, blood was collected pre-dose, one, two, four, six, eight and twenty-four hours, and colon biopsies were collected at 24 hours to measure drug concentration. TGW versus CGM concentration comparisons used non-parametric tests. Blood and colon tissue were also obtained to assess kinase expression.

RESULTS

Plasma TFV and FTC C24 (trough) concentrations in TGW were lower by 32% (p = 0.010) and 32% (p = 0.038) respectively, when compared to CGM. Plasma TFV and FTC 24-hr area under the concentration-time curve in TGW trended toward and was significantly lower by 27% (p = 0.065) and 24% (p = 0.028) respectively. Peak plasma TFV and FTC concentrations, as well as all other pharmacokinetic measures, were not statistically significant when comparing TGW to CGM. Oestradiol concentrations were not different comparing before and after TDF/FTC dosing. Plasma oestrogen concentration, renal function (estimated creatinine clearance and glomerular filtration rate), and TFV and FTC plasma concentrations (trough and area under the concentration-time curve) were all correlated.

CONCLUSIONS

GAHT modestly reduces both TFV and FTC plasma concentrations. In TGW taking GAHT, it is unknown if this reduction will impact the HIV protective efficacy of a daily PrEP regimen. However, the combination of an on demand (2 + 1 + 1) PrEP regimen and GAHT may result in concentrations too low for reliable prevention of HIV infection.

Effect of age at menarche on microvascular complications among women with Type 1 diabetes

AIM

To test the hypothesis that delayed menarche is associated with an increased microvascular complication risk among women with Type 1 diabetes.

METHODS

We studied the female participants of an ongoing prospective study of childhood-onset Type 1 diabetes diagnosed during the period 1950-1980. Of 325 women, we included data from 315 who had reached menarche by the study baseline (1986-1988) and who self-reported their age at menarche. Both cross-sectional and prospective analyses over the 25-year follow-up were used to assess the relationship of age at menarche with the prevalence, incidence and cumulative incidence of microvascular complications, comprising overt nephropathy, proliferative retinopathy and confirmed distal symmetric polyneuropathy.

RESULTS

In cross-sectional analyses at baseline, the odds of overt nephropathy increased 1.24 times (P=0.02) with each annual increase in age at menarche, and 3.2 times (P=0.009) in those with delayed menarche compared with women with normal menarche onset, after adjustment. Similarly, the cumulative incidence of overt nephropathy increased 1.16 times (P=0.01) with each older year of menarche and women with delayed menarche were at twofold increased risk of overt nephropathy (hazard ratio 2.30, P=0.001) compared with women with normal menarche onset. However, age at menarche was not significantly associated with either proliferative retinopathy or confirmed distal symmetric polyneuropathy after adjusting for covariates.

CONCLUSIONS

Age at menarche was significantly associated with the prevalence and cumulative incidence of overt nephropathy, but not with proliferative retinopathy or confirmed distal symmetric polyneuropathy in Type 1 diabetes. Women with delayed menarche may therefore be targeted for early screening and timely interventions to prevent the development of nephropathy.

Hormone therapy and urine protein excretion: a multiracial cohort study, systematic review, and meta-analysis

OBJECTIVE

Experimental models suggest estrogen has a renoprotective effect, but human studies show variable results. Our objective was to study the association of hormone therapy (HT) and albuminuria in postmenopausal women and to synthesize the results with outcomes from prior studies.

METHODS

We analyzed data from postmenopausal women who participated in the second study visit (2000-2004) of the Genetic Epidemiology Network of Arteriopathy (GENOA) study. The exposure was self-reported HT use and the outcome was albuminuria (urine albumin-to-creatinine ratio >25 mg/g creatinine). We also conducted a systematic review and meta-analysis on the association of HT and urine protein in postmenopausal women. Continuous and dichotomous measures of protein excretion were converted to a standardized mean difference (SMD) for each study.

RESULTS

In the GENOA cohort (n = 2,217), there were fewer women with albuminuria among HT users than nonusers (9% vs 19%, P < 0.001). HT use was associated with decreased odds of albuminuria (odds ratio 0.65, 95% confidence interval (CI), 0.45-0.95), after adjusting for significant differences in age, race, education, comorbidities, and the age at and cause of menopause. The SMD of the effect of HT on urine proteinuria/albuminuria in the randomized control trials (n = 3) was 0.02 (95% CI, -0.29 to 0.33) and -0.13 (95% CI, -0.31 to 0.05) in the observational studies (n = 9). There was significantly less albuminuria among HT users (SMD -0.15, 95% CI, -0.27 to -0.04) in the 9 studies that only reported albuminuria as an outcome and in the 10 studies with a comparator arm (SMD -0.15, 95% CI, -0.26 to -0.04).

CONCLUSIONS

HT is associated with decreased odds of albuminuria, but some of the observed benefits may be related to reported outcomes, the presence of a comparator arm, and the type of study design.

Sex Hormones and Measures of Kidney Function in the Diabetes Prevention Program Outcomes Study

CONTEXT

Despite sex differences in chronic kidney disease (CKD) onset and progression, it is unclear whether endogenous sex hormones are associated with kidney function in persons without CKD.

DESIGN AND METHODS

We conducted a secondary analysis of the Diabetes Prevention Program (DPP) and its follow-up observational study, the DPP Outcomes Study, over 11 years. Participants included overweight and glucose-intolerant men (n = 889) and pre- and postmenopausal women (n = 1281) not using exogenous sex hormones and whose urine albumin-to-creatinine ratio (ACR) was <30 mg/g and normal estimated glomerular filtration ratio (eGFR) was ≥60 mL/min/1.73 m2 at randomization. We examined the association between sex hormone levels and incidence of low eGFR and/or ACR ≥30 mg/g on at least one measurement.

RESULTS

At randomization, the mean (SD) eGFR was 94 (15) mL/min/1.73 m2; the median ACR (interquartile range) was 4.5 (3.3 to 7.6) mg/g. During follow-up, 187 men (24.6%) and 263 women (24.2%) had incident albuminuria and 136 men (17.9%) and 123 women (11.3%) had incident low eGFR. Among men, higher baseline sex hormone-binding globulin (SHBG) level was associated with reduced low eGFR risk (hazard ratio per SD, 0.80; 95% CI, 0.57 to 0.90) in adjusted analyses. No significant associations were observed among women. There were significant interactions between sex steroid levels and low eGFR by randomization arm.

CONCLUSION

Sex steroids were not associated with development of low eGFR or albuminuria. Among men, higher SHBG level was associated with reduced risk of low eGFR on at least one measurement.

Hormone therapy and clinical and surrogate cardiovascular endpoints in women with chronic kidney disease: a systematic review and meta-analysis

OBJECTIVE

Women with chronic kidney disease (CKD) experience kidney dysfunction-mediated premature menopause. The role of postmenopausal hormone therapy (HT) in this population is unclear. We sought to summarize current knowledge regarding use of postmenopausal HT and cardiovascular (CV) outcomes, and established surrogate measures of CV risk in women with CKD.

METHODS

This is a systematic review and meta-analysis of adult women with CKD. We searched electronic bibliographic databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials) (inception to 2014 December), relevant conference proceedings, tables of contents of journals, and review articles. Randomized controlled trials and observational studies examining postmenopausal HT compared with either placebo or untreated control groups were included. The intervention of interest was postmenopausal HT, and the outcome measures were all-cause and CV mortality, nonfatal CV event (myocardial infarction, stroke), and surrogate measures of CV risk (serum lipids, blood pressure).

RESULTS

Of 12,482 references retrieved, four randomized controlled trials and two cohort studies (N = 1,666 participants) were identified. No studies reported on CV outcomes or mortality. Compared with placebo, postmenopausal HT was associated with decreased low-density lipoprotein cholesterol (-13.2 mg/dL [95% CI, -23.32 to -3.00 mg/dL]), and increased high-density lipoprotein (8.73 mg/dL [95% CI, 4.72-12.73 mg/dL]) and total cholesterol (7.96 mg/dL [95% CI, 0.07-15.84 mg/dL]). No associations were observed between postmenopausal HT triglyceride levels and blood pressure.

CONCLUSIONS

Studies examining the effect of postmenopausal HT on CV outcomes in women with CKD are lacking. Further prospective study of the role of postmenopausal HT in this high-risk group is required.

Sex and gender differences in chronic kidney disease: progression to end-stage renal disease and haemodialysis

Sex and gender differences are of fundamental importance in most diseases, including chronic kidney disease (CKD). Men and women with CKD differ with regard to the underlying pathophysiology of the disease and its complications, present different symptoms and signs, respond differently to therapy and tolerate/cope with the disease differently. Yet an approach using gender in the prevention and treatment of CKD, implementation of clinical practice guidelines and in research has been largely neglected. The present review highlights some sex- and gender-specific evidence in the field of CKD, starting with a critical appraisal of the lack of inclusion of women in randomized clinical trials in nephrology, and thereafter revisits sex/gender differences in kidney pathophysiology, kidney disease progression, outcomes and management of haemodialysis care. In each case we critically consider whether apparent discrepancies are likely to be explained by biological or psycho-socioeconomic factors. In some cases (a few), these findings have resulted in the discovery of disease pathways and/or therapeutic opportunities for improvement. In most cases, they have been reported as merely anecdotal findings. The aim of the present review is to expose some of the stimulating hypotheses arising from these observations as a preamble for stricter approaches using gender for the prevention and treatment of CKD and its complications.

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

Diabetes is manifested predominantly in males in experimental models, and compelling evidence suggests that 17β-estradiol (E2) supplementation improves hyperglycemia in humans. We previously generated a severely diabetic transgenic (Tg) mouse model by β-cell–specific overexpression of inducible cAMP early repressor (ICER) and found that male but not female ICER-Tg mice exhibit sustained hyperglycemia and develop major clinical and pathologic features of human diabetic nephropathy (DN). Thus, we hypothesized that differences in circulating hormone levels have a key role in determining susceptibility to diabetes. Here, we examined whether DN in male ICER-Tg mice is rescued by adjusting the androgen-to-E2 ratio to approximate that in normoglycemic female ICER-Tg mice. We treated hyperglycemic male ICER-Tg mice with orchiectomy (ORX), E2 pellet implantation, or both. E2 pellet implantation at an early stage of DN with or without ORX caused a rapid drop in blood glucose and a dramatic increase in β-cell number, and it markedly inhibited DN progression [namely, E2 reduced glomerulosclerosis, collagen 4 deposition and albuminuria, and prevented hyperfiltration]. Furthermore, E2 pellet implantation was more effective than ORX alone and induced a remarkable improvement, even when initiated at advanced-stage DN. In contrast, induction of normoglycemia by islet transplant in ICER-Tg mice eliminated albuminuria but was less effective than E2 + ORX in reducing glomerulosclerosis, collagen 4 deposition, and hyperfiltration. These findings indicate that E2 treatment is effective, even after establishment of DN, whereas glucose normalization alone does not improve sclerotic lesions. We propose that E2 intervention is a potential therapeutic option for DN.

Diseases and Aging: Gender Matters

At first glance, biological differences between male and female sex seem obvious, but, in fact, they affect a vast number of deeper levels apart from reproductive function and related physiological features. Such differences affect all organizational levels including features of cell physiology and even functioning of separate organelles, which, among other things, account for such global processes as resistance to diseases and aging. Understanding of mechanisms underlying resistance of one of the sexes to pathological processes and aging will allow taking into consideration gender differences while developing drugs and therapeutic approaches, and it will provide an opportunity to reproduce and enhance such resistance in the more vulnerable gender. Here we review physiological as well as cellular and biological features of disease course including aging that are affected by gender and discuss potential mechanisms behind these processes. Such mechanisms include features of oxidative metabolism and mitochondrial functioning.

The Role of Gender in Chronic Kidney Disease

Chronic kidney disease (CKD) is a common disease worldwide and is associated with high rates of morbidity and mortality. This review discusses several aspects of the relationship between gender and CKD. While the prevalence of CKD tends to be higher in women, the disease is more severe in men, who also have a higher prevalence of end-stage renal disease. Most of the evidence in the current literature suggests a higher progression rate and mortality risk of CKD in men compared with women, except in post-menopausal women and diabetic patients. However, the decrease in glomerular filtration rate and the increase in the level of albuminuria are more prominent mortality risk factors among women. Sex hormones are thought to play a major role in the biological mechanisms associated with variability in CKD prevalence and characteristics between men and women. Animal studies have demonstrated the harmful influence of testosterone and protective influence of oestrogen on several biological processes that are involved in kidney injury. However, the role of sex hormones in explaining gender-related differences in CKD in humans has not yet been established. In summary, gender has an important influence on several aspects of CKD. Further research is needed to find additional gender-related characteristics in CKD and to identify the mechanisms of sexual dimorphism in CKD.

RAS and sex differences in diabetic nephropathy

The incidence and progression of kidney diseases are influenced by sex. The renin-angiotensin system (RAS) is an important regulator of cardiovascular and renal function. Sex differences in the renal response to RAS blockade have been demonstrated. Circulating and renal RAS has been shown to be altered in type 1 and type 2 diabetes; this enzymatic cascade plays a critical role in the development of diabetic nephropathy (DN). Angiotensin converting enzyme (ACE) and ACE2 are differentially regulated depending on its localization within the diabetic kidney. Furthermore, clinical and experimental studies have shown that circulating levels of sex hormones are clearly modulated in the context of diabetes, suggesting that sex-dependent RAS regulation may be also be affected in these individuals. The effect of sex hormones on circulating and renal RAS may be involved in the sex differences observed in DN progression. In this paper we will review the influence of sex hormones on RAS expression and its relation to diabetic kidney disease. A better understanding of the sex dimorphism on RAS might provide a new approach for diabetic kidney disease treatment.

Non-proteinuric pathways in loss of renal function in patients with type 2 diabetes

Largely on the basis of data from patients with type 1 diabetes, the natural history of diabetic renal disease has been classified as a sequence of three stages: normoalbuminuria, microalbuminuria, and macroalbuminuria. Progressive decline of glomerular filtration rate (GFR) was thought to parallel the onset of macroalbuminuria (overt nephropathy), whereas glomerular hyperfiltration was deemed a hallmark of early disease. However, researchers have since shown that albuminuria is a continuum and that GFR can start to decline before progression to overt nephropathy. In addition to proteinuria, other risk factors might contribute to GFR deterioration including female sex, obesity, dyslipidaemia (in particular hypertriglyceridaemia), hypertension, and glomerular hyperfiltration, at least in a subgroup of patients. This phenomenon could explain why patients with type 2 diabetes can have renal insufficiency even before the onset of overt nephropathy, and might also suggest why the heterogeneous phenotype of type 2 diabetic renal disease does not necessarily associate with typical histological lesions of diabetic renal disease, unlike in type 1 diabetic renal disease. Patients with renal insufficiency but without albuminuria are usually excluded from randomised clinical trials in overt nephropathy, thus optimum treatment for this group of patients is unknown. The wide inter-patient variability of the disease probably needs individually tailored intervention.

Worse renal disease in postmenopausal F2[Dahl S x R]-intercross rats: detection of novel QTLs affecting hypertensive kidney disease

The prevalence of hypertension increases after menopause with 75% of postmenopausal women developing hypertension in the United States, along with hypertensive end organ diseases. While human and animal model studies have indicated a protective role for estrogen against cardiovascular disease and glomerulosclerosis, clinical studies of hormone replacement therapy in postmenopausal women have shown polar results with some improvement in hypertension but worsening of hypertensive kidney disease, or no effect at all. These observations suggest that the pathogenesis of postmenopausal hypertension and its target organ complications is more complex than projected, and that loss of endogenous estrogens induces epigenetic changes that alter genetic susceptibility to end-organ complications per se resulting in pathogenetic mechanisms beyond correction by hormone replacement. We studied postmenopausal-induced changes in renal disease and performed a total genome scan for quantitative trait loci (QTLs) affecting kidney disease in postmenopausal 16m-old F2[Dahl S x R]-intercross female rats. We used glomerular injury score (GIS) as quantitative trait. We compared QTLs amongst premenopausal, ovariectomized and postmenopausal F2[Dahl S x R]-intercross rats using identical phenotype characterization. Postmenopausal F2[Dahl S x R]-intercross rats exhibited increased hypertensive glomerulosclerosis (P<0.01) and equivalent levels of kidney disease when compared to premenopausal and ovariectomized F2[Dahl S x R]-intercross rats respectively. We detected three significant to highly significant GIS-QTLs (GIS-pm1 on chromosome 4, LOD 3.54; GIS-pm2 on chromosome 3, LOD 2.72; GIS-pm3 on chromosome 5, LOD 2.37) and two suggestive GIS-QTLs (GIS-pm4 on chromosome 2, LOD 1.70; GIS-pm5 on chromosome 7, LOD 1.28), all of which were unique to this postmenopausal population. Detection of increased renal disease phenotype in postmenopausal and ovariectomized subjects suggests a protective role of ovarian hormones. Furthermore, the detection of distinct GIS-QTLs in postmenopausal intercross female rats suggests that distinct genetic mechanisms underlie hypertensive glomerulosclerosis in premenopausal and postmenopausal states.

A cross-sectional and 10-year prospective study of postmenopausal estrogen therapy and blood pressure, renal function, and albuminuria: the Rancho Bernardo Study

OBJECTIVE

Blood pressure, urine albumin-to-creatinine ratio, and estimated glomerular filtration rate (GFR) are highly correlated conditions. The longitudinal effect of exposure to postmenopausal estrogen therapy on these traits studied together has not been reported.

METHODS

This was a cross-sectional study of 1,044 older postmenopausal community-dwelling women from the Rancho Bernardo Study (1992-1996); 443 women were reevaluated ∼ 10 years later (2002-2005). We determined the cross-sectional and prospective association of baseline postmenopausal estrogen therapy and blood pressure, urine albumin-to-creatinine ratio, GFR, and the odds of categorical hypertension (physician diagnosis, medication, or blood pressure ≥ 140/≥ 90 mm Hg), chronic kidney disease (GFR ≤ 60 mL/min per 1.73 m2), and albuminuria (urine albumin-to-creatinine ratio ≥ 25 mg/g).

RESULTS

At baseline, the mean age was 68.3 years for current estrogen users, 75.4 years for past users, and 74.3 years for never users. In the cross-sectional analyses, current users had lower diastolic blood pressure and lower odds of having chronic kidney disease, independent of covariates. In the ∼ 10-year follow-up, comparisons between never, past, and current estrogen use (91% continuous use since baseline), the mean diastolic blood pressure declined over time in current users, whereas systolic blood pressure increased among never users. Urine albumin-to-creatinine ratio also increased in never users and decreased in current users; GFR did not differ by estrogen use.

CONCLUSIONS

In cross-sectional analyses, estrogen users had better GFR and blood pressure than nonusers did, but the 10-year follow-up showed improved blood pressure and decreased urine albumin-to-creatinine ratio among mostly long-term current users, without differences in GFR by estrogen use. This study suggests no association of GFR with 10 years of continuous estrogen use and an inverse association with albuminuria.

Chronic kidney disease in postmenopausal women

Menopause is derived from the Greek words men (month) and pauses (cessation) and means permanent cessation of menstruation after the loss of ovarian activity. Chronic kidney disease (CKD) has recently been associated with cardiovascular events in several studies. CKD patients have a heavy burden of traditional cardiovascular risk factors in addition to a range of nontraditional risk factors such as inflammation and abnormal metabolism of calcium and phosphate. In this review, the association of CKD and cardiovascular disease (CVD), as well as of osteoporosis in postmenopausal women is discussed. CKD mineral and bone disorder, characterized by disturbances of calcium/phosphate/parathyroid hormone, bone abnormalities and vascular and soft tissue calcification, is highly prevalent in CKD and is a strong, independent predictor of bone fracture, CVD and death. Estrogen has been shown to: (a) decrease the expression of angiotensin type 1 receptors in vasculature and kidneys; (b) reduce the expression and activity of angiotensin-converting enzyme, and (c) cause the release of angiotensinogen substrate from the liver. However, the degree of activation or suppression of the renin-angiotensin-aldosterone system by estrogen has not been clearly established. Clinical data on the effects of estrogen therapy on bone mineral densities are extremely limited in the ESRD population. CVD is the most common cause of death in postmenopausal women with CKD and many contributing factors have been explored. Future research for prevention of CVD in postmenopausal women with CKD would focus on the biology of vascular calcification as well as bone loss.

Raloxifene, a selective estrogen receptor modulator, is renoprotective: a post-hoc analysis

Estrogens have a protective effect on kidney fibrosis in several animal models. Here, we tested the effect of raloxifene, an estrogen receptor modulator, on the change in serum creatinine or estimated glomerular filtration rate (eGFR) and incident kidney-related adverse events. We performed a post-hoc analysis of the multiple outcomes of raloxifene evaluation trial, a double-masked, placebo-controlled randomized clinical trial encompassing 7705 post-menopausal women (aged 31-80 years) with osteoporosis. Participants were randomized to either of two doses of raloxifene, 60 or 120 mg/day, or placebo. Serum creatinine was measured at a central laboratory at baseline and annually. Adverse events were assessed every 6 months and uniformly categorized. Compared with those in the placebo group, participants on raloxifene had a slower yearly rate of increase in creatinine (significant at the low dose) and a significantly slower yearly rate of decrease in eGFR for both doses over 3 years of follow-up. Raloxifene was associated with significantly fewer kidney-related adverse events compared with placebo. Thus, treatment with raloxifene was safe and renoprotective. Clinical trials of raloxifene in post-menopausal women with kidney disease designed to look at kidney outcomes are needed to confirm these findings.

The effects of polymicrobial sepsis with diabetes mellitus on kidney tissues in ovariectomized rats

OBJECTIVES

Sepsis model was used to understand the role of sustained hyperglycemia and ovariectomy, either separately or concomitantly, on the response of the activity of the nuclear factor kappa B (NF-kappaB) and the oxidative response in kidney.

SUBJECTS

Polymicrobial sepsis was induced by cecal ligation and puncture (CLP). Diabetes was induced in female rats using administration of alloxan. The rats were divided into five groups: sham control (group 1), ovariectomy (group 2), ovariectomy + sepsis (group 3), ovariectomy + diabetes (group 4), and ovariectomy + diabetic + sepsis (group 5).

RESULTS

In kidney tissues, the levels of lipid peroxidation (LPO) and glutathione (GSH) and the activity of catalase (CAT) were higher for groups 3, 4, 5 than the control groups. Superoxide dismutase (SOD) activity was lower for groups 3, 4, 5 than the control groups. We determined that CLP produced injury evident in the kidneys of rats when compared to the control group, whereas the severity of the injury was higher in the diabetes + ovariectomy + CLP group when compared to the CLP group. In immunohistochemical staining, we determined that CLP operation increased NF-kappaB activation. In the ovariectomized, septic, and diabetic group, NF-kappaB activation was significantly higher than other groups.

CONCLUSIONS

Hyperglycemia and ovariectomy severely increased NF-kappaB activation and oxidant levels with the stages of our sepsis model. Ovariectomy resulted in general changes in metabolism, which are seen in the kidney with diabetes under sepsis conditions.

Effects of hormone replacement therapy with vitamin C and E supplementation on plasma thyroid hormone levels in postmenopausal women with Type 2 diabetes

Recent studies have shown that hormone replacement therapy (HRT) can exert regulatory affects on lipid and glucose homeostasis. It has been demonstrated that hyperglycemia also involving the formation of lipid peroxides, exert several biological effects that may contribute to the onset and progression of thyroid and kidney abnormalities of postmenopausal women Type 2 diabetes. Therefore, the aim of our study was to evaluate the effect of HRT, vitamin C and E (VCE) treatments on some plasma biochemical and hematological parameters and plasma thyroid hormone levels in postmenopausal women with or without diabetes. Oral HRT and VCE supplementation were compared with no HRT treatment in 40 non-diabetic postmenopausal women and 40 postmenopausal women with Type 2 diabetes mellitus, in a 6-week randomized prospective study. In the 20 women with diabetes who received oral HRT and the 20 women with diabetes who received HRT plus VCE, there was a significant fall in urea, uric acid, creatinine, total bilirubin, conjugated bilirubin, AST, ALT, LDH values. There was no significant change in red blood cell counts, total protein, albumin, sodium, potassium, hematocrit, hemoglobin and free thyrotoxine and triiodothyronine values in postmenopausal women with diabetes or treated with oral HRT and VCE. In conclusion, daily VCE and HRT administrations seem to produce significant improvement on biochemical parameters in the blood of postmenopausal women with Type 2 diabetes. The HRT and VCE supplementations may strengthen the antioxidant defense system and they may play a role in preventing kidney and liver diseases of postmenopausal women with Type 2 diabetes.

Sexual dimorphism in the aging kidney: differences in the nitric oxide system

Females-both rats and women-are substantially protected against the age-dependent decrease in renal function that occurs in males of the species. In part, this finding reflects the cardioprotective and renoprotective effects of estrogens, but estrogen has multiple actions, not all of which are beneficial. In addition, the low androgen level in women might be protective against a decline in renal function, but animal and clinical data on possible adverse effects of androgens are controversial. Androgens also have multiple actions, one of which-aromatization to estrogen-is likely to be protective. Sex steroids clearly have many complex actions, which explains the conflicting information on their relative benefits and dangers. Endothelial nitric oxide (NO) deficiency contributes importantly to cardiovascular risk and intrarenal NO deficiency is clearly linked to chronic kidney disease progression in animal models. Endothelial dysfunction develops with increasing age but is delayed in females, correlating with a delayed rise in asymmetric dimethylarginine level. There is no clear link between aging and arginine (the NO synthase substrate) deficiency. Animal data suggest that the aging kidney develops NO deficiency as a result of changes in neuronal NO synthase. The increased oxidative stress that occurs with aging affects multiple stages of the NO biosynthetic pathway and results in decreased production and/or action of NO. NO production is better preserved in females than in males, partly as a result of the actions of estrogens.

17 beta-estradiol and tamoxifen upregulate estrogen receptor beta expression and control podocyte signaling pathways in a model of type 2 diabetes

Diabetic nephropathy remains one of the most important causes of end-stage renal disease. This is particularly true for women from racial/ethnic minorities. Although administration of 17beta-estradiol to diabetic animals has been shown to reduce extracellular matrix deposition in glomeruli and mesangial cells, effects on podocytes are lacking. Given that podocyte injury has been implicated as a factor leading to the progression of proteinuria and diabetic nephropathy, we treated db/db mice, a model of type 2 diabetic glomerulosclerosis, with 17beta-estradiol or tamoxifen to determine whether these treatments reduce podocyte injury and decrease glomerulosclerosis. We found that albumin excretion, glomerular volume, and extracellular matrix accumulation were decreased in these mice compared to placebo treatment. Podocytes isolated from all treatment groups were immortalized and these cell lines were found to express the podocyte markers WT-1, nephrin, and the TRPC6 cation channel. Tamoxifen and 17beta-estradiol treatment decreased podocyte transforming growth factor-beta mRNA expression but increased that of the estrogen receptor subtype beta protein. 17beta-estradiol, but not tamoxifen, treatment decreased extracellular-regulated kinase phosphorylation. These data, combined with improved albumin excretion, reduced glomerular size, and decreased matrix accumulation, suggest that both 17beta-estradiol and tamoxifen may protect podocytes against injury and therefore ameliorate diabetic nephropathy.

Sex, diabetes and the kidney

The incidence and the rate of progression of nondiabetic renal disease is generally greater in men compared with age-matched women, suggesting that the female sex is protective and/or that the male sex is a risk factor for the development and progression of nondiabetic renal disease. In diabetes, even though the male sex still appears to be a risk factor, this relationship is not as strong as it is in nondiabetic renal disease. Experimental evidence suggests that both estrogens and androgens play an important role in the pathophysiology of renal disease. Thus one of the potential mechanisms for the absence of a clear sex difference in the setting of diabetes may be alterations in sex hormone levels. Indeed, studies suggest that diabetes is a state of an imbalance in sex hormone levels; however, whether these changes correlate with the decline in renal function associated with diabetes is unclear. Furthermore, diabetic renal disease rarely develops before puberty, and the onset of puberty accelerates microalbuminuria, supporting the idea of the involvement of sex hormones in the development and progression of the disease. However, other than a handful of experimental studies indicating that treatment with or removal of sex hormones alters the course of diabetic renal disease, very few studies have actually directly examined the correlation between sex hormones and the disease development and progression. Further studies are necessary to determine the precise contribution of sex hormones in the pathophysiology of diabetic renal disease to develop novel and potentially sex-specific therapeutic treatments.

The effects of hormone replacement therapy on renal function

This Practice Point commentary discusses a study by Ahmed et al. that evaluated the effects of hormone replacement therapy (conjugated estrogen alone, progestin alone or a combination of progestin and conjugated estrogen) on renal function in elderly community-dwelling postmenopausal women. The authors found that oral estrogen therapy in this population was associated with accelerated decline in kidney function over a 2-year period. In addition, the cumulative amount of estrogen intake was dose-dependently associated with the rate of renal functional decline. This commentary highlights the human and experimental evidence suggesting that endogenous and exogenous estrogen affect renal function, and discusses the possible beneficial or detrimental effects of hormone supplementation on kidney function.

Estrogens and the diabetic kidney

BACKGROUND

Across all ages, the incidence and rate of progression of most nondiabetic renal diseases are markedly higher in men compared with age-matched women. These observations suggest that female sex may be renoprotective. In the setting of diabetes, however, this female protection against the development and progression of renal disease is diminished.

OBJECTIVE

This review aimed to summarize our current understanding of sex differences in the development and progression of diabetic renal disease, and of the contribution of sex hormones, particularly estrogens, to the pathophysiology of this disease. We also attempted to answer why female sex does not protect the diabetic kidney.

METHODS

Using terms such as gender, sex, diabetes, diabetic nephropathy, estrogens, and sex hormones, the PubMed database was searched for English-language articles; targeted searches were conducted using terms such as gender/sex differences in diabetic renal disease. No restrictions were imposed on publication dates.

RESULTS

Although the existing data regarding the sex differences in the incidence and progression of diabetic renal disease are inconclusive, the undisputed fact is that women with either type 1 or type 2 diabetes mellitus exhibit a much higher incidence of renal disease compared with nondiabetic women. It is conceivable that the loss of female sex as a renoprotective factor in diabetes may be related to the abnormal regulation of sex hormone concentrations. Both clinical and experimental data suggest that diabetes may be associated with an imbalance in estradiol concentrations. Supplementation with 17beta-estradiol or administration of selective estrogen receptor modulators reduces the incidence of diabetes and attenuates the progression of diabetic renal disease.

CONCLUSIONS

Serum concentrations of ovarian hormones may provide a new means for predicting future risk of renal complications in diabetes. Exogenous steroid hormones may be an effective treatment for attenuating the progression of diabetic nephropathy.

Mechanisms underlying sex differences in progressive renal disease

Men with nondiabetic renal disease exhibit a faster rate of decline in renal function compared with women. To investigate this sex difference in renal disease progression, our research group has been studying the renal wrap (RW) model of hypertension in rats. Compared with RW female rats, the glomerulosclerosis index, mean glomerular volume, and proteinuria were greater (3.1-, 1.7-, and 1.8-fold, respectively) in RW males under conditions in which no differences in the degree of hypertension were detected, suggesting that sex differences may exist in the mechanisms underlying renal injury, independent of blood pressure. Gonadal steroids contribute to these sex differences, because orchidectomy attenuated and ovariectomy exacerbated the severity of renal injury, whereas dihydrotestosterone and 17beta-estradiol (E(2)) replacement prevented these respective effects. Chronic renal disease is associated with impairment in nitric oxide (NO) signaling and elevated levels of superoxide. Sex differences were observed in RW-induced changes in renal nitric oxide synthesis (NOS) protein abundance. Whereas RW had no effect on NOS in the female kidney, endothelial NOS was elevated and neuronal NOS was decreased in the male kidney, suggesting that renal injury may cause dysfunction in NO metabolism in the male. Sex differences in superoxide signaling were also observed. Renal cortical nicotinamide adenine dinucleotide phosphate oxidase activity was 1.3-fold higher in RW males than in RW females, and ovariectomy increased enzyme activity 1.4-fold, whereas E(2) replacement prevented this effect. These changes in enzyme activity were mirrored by changes in protein abundance of the p22(phox) regulatory subunit. Our findings suggest that E(2) may protect the female kidney from hypertension-associated renal disease by attenuating injury-induced superoxide production.

Oral estrogen therapy in postmenopausal women is associated with loss of kidney function

Women are generally protected against progressive loss of kidney function; however, this advantage seems to diminish with menopause. Because of conflicting reports on the association between use of hormone therapy and kidney function we studied 5845 women (1459 on hormone therapy and 4386 non-users) who were over 66 years of age and had at least 2 serum creatinine measurements during the 2 year study period. After adjustment for covariates, hormone use (estrogen-only, progestin-only, or both) was associated with a significant loss of estimated GFR as the primary outcome along with an increased risk of rapid loss of kidney function as the secondary outcome compared to non-users. This increased rate of loss was associated with oral but not transvaginal estrogen use. An increased cumulative dose of estrogen was also associated with a greater decline in estimated GFR. Our study shows an independent association in a dose-dependent manner of estrogen use and loss of kidney function in this elderly population.

17beta-Estradiol attenuates diabetic kidney disease by regulating extracellular matrix and transforming growth factor-beta protein expression and signaling

We previously showed that supplementation with 17beta-estradiol (E2) from the onset of diabetes attenuates the development of diabetic renal disease. The aim of the present study was to examine whether E2 can also attenuate the disease process once it has developed. The present study was performed in nondiabetic and streptozotocin-induced diabetic Sprague-Dawley rats. E2 supplementation began after 9 wk of diabetes and continued for 8 wk. Diabetes was associated with an increase in urine albumin excretion, glomerulosclerosis, tubulointerstitial fibrosis, renal cortical collagen type I and IV, laminin, plasminogen activator inhibitor-1, tissue inhibitors of metalloproteinase-1 and -2, transforming growth factor (TGF)-beta, TGF-beta receptor type I and II, Smad2/3, phosphorylated Smad2/3, and Smad4 protein expression, and CD68-positive cell abundance. Decreases in matrix metalloproteinase (MMP)-2 protein expression and activity and decreases in Smad6 and Smad7 protein expression were also associated with diabetes. E2 supplementation completely or partially attenuated all these changes, except Smad4 and fibronectin, on which E2 supplementation had no effect. These data suggest that E2 attenuates the progression of diabetic renal disease once it has developed by regulating extracellular matrix, TGF-beta, and expression of its downstream regulatory proteins. These findings support the notion that sex hormones in general, and E2 in particular, are important regulators of renal function and may be novel targets for the treatment and prevention of diabetic renal disease.

Effect of raloxifene -- a selective oestrogen receptor modulator -- on kidney function in post-menopausal women with Type 2 diabetes: results from a randomized, placebo-controlled pilot trial

AIMS

Epidemiological and experimental data suggest that activation of the oestrogen receptor pathway limits the incidence and the progression of diabetic nephropathy. We tested the hypothesis that raloxifene protects against increasing urinary albumin excretion in post-menopausal women with Type 2 diabetes in a randomized pilot clinical trial.

METHODS

We included 39 post-menopausal women with Type 2 diabetes and micro- or macro-albuminuria in a 6-month, double-blind, placebo-controlled trial: 20 received placebo and 19 received 60 mg raloxifene per day. The albumin : creatinine ratio (ACR) in urine was determined on three consecutive days during the week before randomization and during the week before the final visit.

RESULTS

One patient in each group dropped out in the first 3 weeks, leaving 37 patients for the analysis (19 on placebo and 18 on raloxifene). From randomization to the final visit, mean ACR was unchanged in the placebo group {277 microg/mg (67; 651) [median (interquartile range)] vs. 284 microg/mg (79; 1508)} but decreased slightly in the raloxifene group [376 microg/mg (67; 615) vs. 243 microg/mg (103; 549)]. This corresponds to a change of +24 (-37; +517) for the placebo group vs. -10 microg/mg (-36; +16) for the raloxifene group (P = 0.11). In multivariate analysis, raloxifene treatment (P(adjusted) = 0.013), baseline low-density lipoprotein (LDL) cholesterol (P(adjusted) = 0.023) and change in LDL cholesterol (P(adjusted) = 0.008) were related to the absolute change in ACR. Adverse effects were similar in the two groups.

CONCLUSIONS

These results suggest that raloxifene may limit the progression of albuminuria in post-menopausal women with diabetes; further studies in a larger population are warranted.

Female protection in progressive renal disease is associated with estradiol attenuation of superoxide production

BACKGROUND

Several types of renal disease progress at a faster rate in men compared with women, but the reasons for this sex difference are not well understood. Chronic renal disease is associated with elevated levels of toxic reactive oxygen species (ROS). Superoxide, the major ROS in the kidney, is generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase.

OBJECTIVE

To determine if female protection from renal disease progression is consistent with 17beta-estradiol (E2) attenuation of superoxide production, this study was conducted to assess superoxide production in the renal cortex of male and female control and renal wrap (RW) rats, as well as in ovariectomized rats treated with vehicle or E2.

METHODS

Sprague-Dawley rats were divided into 2 sham operation male (Sham-M) and female (Sham-F) control groups, and 4 RW hypertensive groups: RW-M; RW-F; RW ovariectomized females treated with vehicle (RW-OVX); and RW ovariectomized females treated with E2, supplied as a 0.24 mg/60-day release pellet (RW-OVX+E2). All groups were maintained on a high-sodium (4% NaCl) diet for 6 weeks.

RESULTS

Mean (SEM) markers of renal injury and oxidative stress, including urinary protein (mg/24 h: RW-M, 298 [31] vs RW-F, 169 [22]; P < 0.001), microalbuminuria (RW/Sham arbitrary units [AU]/24 h: M, 8.78 [0.58] vs F, 4.31 [1.0]; P < 0.005), and malondialdehyde (nmol/24 h: RW-M, 167 [23] vs RW-F, 117 [8.5]; P < 0.05) levels, as well as mean glomerular volume (microm3 x 10(6): RW-M, 2.25 [0.16] vs RW-F, 1.25 [0.04]; P < 0.001) and the glomerulosclerotic index (AU: RW-M, 2.64 [0.19] vs RW-F, 1.10 [0.09]; P < 0.001) were greater in both control and RW males compared with females in the same treatment groups. Though RW surgery increased mean arterial pressure in both male and female rats, no sex difference was observed. Under these conditions, mean (SEM) renal cortical NADPH oxidase activity was 1.3-fold higher in RW males compared with RW females (relative light units [RLU]/180 sec: RW-M, 4080 [240] vs RW-F, 3200 [260]; P < 0.05). Ovariectomy increased NADPH oxidase activity by 1.4-fold (RLU/180 sec: RW-OVX, 4520 [184]; P < 0.01) under conditions in which the mean glomerular volume and glomerulosclerotic index were both increased by 1.5-fold, whereas E2 replacement (RLU/180 sec: RW-OVX+E2, 2745 [440]) prevented these effects. Furthermore, the effects on NADPH oxidase activity were mirrored by changes in the protein abundance of NADPH oxidase subunit p22P(phox).

CONCLUSION

These results suggest that E2 protects the female kidney in part by attenuating injury-induced increases in renal superoxide production.

Diabetes mellitus and dementia

Alzheimer's disease (AD) and diabetes mellitus (DM) are two of the most common and devastating health problems in the elderly. They share a number of common features amongst which high prevalence after 65 years, important impact of patient's quality of life, substantial health care costs. Reviews on the epidemiological studies on cognitive impairment in patients with DM found evidence of cross-sectional and prospective associations between type 2 DM and moderate cognitive impairment, on memory and executive functions. There is also evidence for an elevated risk of both vascular dementia and AD in patients with type 2 DM, albeit with strong interaction of other factors such as hypertension, dyslipidaemia and ApoE genotype. DM is an independent predictor of post-stroke dementia. DM being an atherogenic risk factor, it may increase the risk of dementia through associations with stroke, causing vascular dementia. In addition, vascular reactivity may be adversely affected by advanced glycosylation end products resulting in more subtle perfusion abnormalities. Cerebrovascular disease may exacerbate AD through direct interactions between the two pathological processes or through cognitive impairment secondary to cerebrovascular disease "unmasking" AD at an earlier stage than it would otherwise become apparent. The increased risk of AD may also be mediated by the exacerbation of B-amyloid neurotoxicity by advanced glycosylation end products identified in the matrix of neurofibrillary tangles and amyloid plaques in AD brains, or associations with insulin functions. Decreased cholinergic transport across the blood-brain barrier observed in diabetic animals may exacerbate cognitive impairment in AD. Many interventions could reduce the cognitive decline associated with DM, yet not enough are taken into account so far.

17beta-Estradiol supplementation reduces tubulointerstitial fibrosis by increasing MMP activity in the diabetic kidney

We previously reported that supplementation with 17beta-estradiol (E2) attenuates albuminuria, glomerulosclerosis, and tubulointerstitial fibrosis in diabetic nephropathy. The present study examined the mechanisms by which E2 regulates extracellular matrix (ECM) metabolism, a process that contributes to the development of glomerulosclerosis and tubulointerstitial fibrosis. The study was performed in female nondiabetic (ND), streptozotocin-induced diabetic (D), and diabetic with E2 supplementation (D+E2) Sprague-Dawley rats for 12 wk. Diabetes was associated with an increase in the renal expression of collagen alpha type IV [ND, 0.22 +/- 0.02; D, 0.99 +/- 0.09 relative optical density (ROD); P < 0.05] and fibronectin protein (ND, 0.36 +/- 0.08; D, 1.47 +/- 0.08 ROD; P < 0.05), as measured by Western blot analysis. E2 supplementation partially attenuated this increase in collagen alpha type IV (D+E2, 0.47 +/- 0.10 ROD) and fibronectin (D+E2, 0.71 +/- 0.16 ROD) protein expression associated with D. Diabetes was also associated with a decrease in the expression of matrix metalloproteinase (MMP) isoform MMP-2 (ND, 0.79 +/- 0.01; D, 0.62 +/- 0.06 ROD; P < 0.05) and MMP-9 protein (ND, 0.49 +/- 0.02; D, 0.33 +/- 0.03 ROD; P < 0.05). E2 supplementation restored MMP-2 and MMP-9 protein to levels similar or even greater than in the ND kidneys (MMP-2, 0.75 +/- 0.06; MMP-9, 0.73 +/- 0.01 ROD). The activities of MMP-2 (ND, 7.88 +/- 0.44; D, 5.60 +/- 0.54 ROD; P < 0.05) and MMP-9 (ND, 29.9 +/- 1.8; D, 12.9 +/- 2.3 ROD; P < 0.05), as measured by zymography, were also decreased with D. E2 supplementation restored MMP-2 and MMP-9 activity to levels similar to that in ND kidneys (MMP-2, 7.66 +/- 0.35; MMP-9, 21.4 +/- 2.9 ROD). We conclude that E2 supplementation is renoprotective by attenuating glomerulosclerosis and tubulointerstitial fibrosis by reducing ECM synthesis and increasing ECM degradation.