Sex and the kidneys: current understanding and research opportunities

Adenine-induced animal model of chronic kidney disease: current applications and future perspectives

Chronic kidney disease (CKD) with high morbidity and mortality all over the world is characterized by decreased kidney function, a condition which can result from numerous risk factors, including diabetes, hypertension and obesity. Despite significant advances in our understanding of the pathogenesis of CKD, there are still no treatments that can effectively combat CKD, which underscores the urgent need for further study into the pathological mechanisms underlying this condition. In this regard, animal models of CKD are indispensable. This article reviews a widely used animal model of CKD, which is induced by adenine. While a physiologic dose of adenine is beneficial in terms of biological activity, a high dose of adenine is known to induce renal disease in the organism. Following a brief description of the procedure for disease induction by adenine, major mechanisms of adenine-induced CKD are then reviewed, including inflammation, oxidative stress, programmed cell death, metabolic disorders, and fibrillation. Finally, the application and future perspective of this adenine-induced CKD model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given the simplicity and reproducibility of this animal model, it remains a valuable tool for studying the pathological mechanisms of CKD and identifying therapeutic targets to fight CKD.

Sex-related similarities and differences in responses to heart failure therapies

Although sex-related differences in the epidemiology, risk factors, clinical characteristics and outcomes of heart failure are well known, investigations in the past decade have shed light on an often overlooked aspect of heart failure: the influence of sex on treatment response. Sex-related differences in anatomy, physiology, pharmacokinetics, pharmacodynamics and psychosocial factors might influence the response to pharmacological agents, device therapy and cardiac rehabilitation in patients with heart failure. In this Review, we discuss the similarities between men and women in their response to heart failure therapies, as well as the sex-related differences in treatment benefits, dose-response relationships, and tolerability and safety of guideline-directed medical therapy, device therapy and cardiac rehabilitation. We provide insights into the unique challenges faced by men and women with heart failure, highlight potential avenues for tailored therapeutic approaches and call for sex-specific evaluation of treatment efficacy and safety in future research.

Differences in excess mortality by recipient sex after heart transplant: An individual patient data meta-analysis

BACKGROUND

Identification of differences in mortality risk between female and male heart transplant recipients may prompt sex-specific management strategies. Because worldwide, males of all ages have higher absolute mortality rates than females, we aimed to compare the excess risk of mortality (risk above the general population) in female vs male heart transplant recipients.

METHODS

We used relative survival models conducted separately in SRTR and CTS cohorts from 1988-2019, and subsequently combined using 2-stage individual patient data meta-analysis, to compare the excess risk of mortality in female vs male first heart transplant recipients, accounting for the modifying effects of donor sex and recipient current age.

RESULTS

We analyzed 108,918 patients. When the donor was male, female recipients 0-12 years (Relative excess risk (RER) 1.13, 95% CI 1.00-1.26), 13-44 years (RER 1.17, 95% CI 1.10-1.25), and ≥45 years (RER 1.14, 95% CI 1.02-1.27) showed higher excess mortality risks than male recipients of the same age. When the donor was female, only female recipients 13-44 years showed higher excess risks of mortality than males (RER 1.09, 95% CI 1.00-1.20), though not significantly (p = 0.05).

CONCLUSIONS

In the setting of a male donor, female recipients of all ages had significantly higher excess mortality than males. When the donor was female, female recipients of reproductive age had higher excess risks of mortality than male recipients of the same age, though this was not statistically significant. Further investigation is required to determine the reasons underlying these differences.

Sex-Dimorphic Kidney-Brain Connectivity Map of Mice

The kidneys are essential organs that help maintain homeostasis, and their function is regulated by the neural system. Despite the anatomical multi-synaptic connection between the central autonomic nuclei and the kidneys, it remains unclear whether there are any variations in neural connections between the nervous systems and the renal cortex and medulla in male and female mice. Here, we used the pseudorabies virus to map the central innervation network of the renal cortex and medulla in both sexes. The data revealed that specific brain regions displayed either a contralateral-bias or ipsilateral-bias pattern while kidney-innervating neurons distributed symmetrically in the midbrain and hindbrain. Sex differences were observed in the distribution of neurons connected to the left kidney, as well as those connected to the renal cortex and medulla. Our findings provide a comprehensive understanding of the brain-kidney network in both males and females and may help shed light on gender differences in kidney function and disease susceptibility in humans.

Association of Postoperative Serum Lactate Levels with Acute Kidney Injury in Mexican Patients Undergoing Cardiac Surgery

Acute kidney injury (AKI) is a highly prevalent and a critical complication of cardiac surgery (CS). Serum lactate (sLac) levels have consistently shown an association with morbimortality after CS. We performed a cross-sectional study including 264 adult patients that had a cardiac surgery between January and December 2020. Logistic regression analysis was performed to determine factors associated with AKI development. We measured the postoperative levels of sLac for all participants immediately after CS (T0) and at 4 h (T4) after the surgical intervention. A linear regression model was used to identify the factors influencing both sLac metrics. We identified four risk predictors of AKI; one was preoperative (atrial fibrillation), one intraoperative (cardiopulmonary bypass time), and two were postoperative (length of hospital stay and postoperative sLac). T0 and T4 sLac levels were higher among CS-AKI patients than in Non-CS-AKI patients. Postoperative sLac levels were significant independent predictors of CSA-AKI, and sLac levels are influenced by length of hospital stay, the number of transfused packed red blood cells, and the use of furosemide in CS-AKI patients. These findings may facilitate the earlier identification of patients susceptible to AKI after CS.

Podocytes from hypertensive and obese mice acquire an inflammatory, senescent, and aged phenotype

Patients with hypertension or obesity can develop glomerular dysfunction characterized by injury and depletion of podocytes. To better understand the molecular processes involved, young mice were treated with either deoxycorticosterone acetate (DOCA) or fed a high-fat diet (HFD) to induce hypertension or obesity, respectively. The transcriptional changes associated with these phenotypes were measured by unbiased bulk mRNA sequencing of isolated podocytes from experimental models and their respective controls. Key findings were validated by immunostaining. In addition to a decrease in canonical proteins and reduced podocyte number, podocytes from both hypertensive and obese mice exhibited a sterile inflammatory phenotype characterized by increases in NLR family pyrin domain containing 3 (NLRP3) inflammasome, protein cell death-1, and Toll-like receptor pathways. Finally, although the mice were young, podocytes in both models exhibited increased expression of senescence and aging genes, including genes consistent with a senescence-associated secretory phenotype. However, there were differences between the hypertension- and obesity-associated senescence phenotypes. Both show stress-induced podocyte senescence characterized by increased p21 and p53. Moreover, in hypertensive mice, this is superimposed upon age-associated podocyte senescence characterized by increased p16 and p19. These results suggest that senescence, aging, and inflammation are critical aspects of the podocyte phenotype in experimental hypertension and obesity in mice.NEW & NOTEWORTHY Hypertension and obesity can lead to glomerular dysfunction in patients, causing podocyte injury and depletion. Here, young mice given deoxycorticosterone acetate or a high-fat diet to induce hypertension or obesity, respectively. mRNA sequencing of isolated podocytes showed transcriptional changes consistent with senescence, a senescent-associated secretory phenotype, and aging, which was confirmed by immunostaining. Ongoing studies are determining the mechanistic roles of the accelerated aging podocyte phenotype in experimental hypertension and obesity.

Finerenone cardiovascular and kidney outcomes by age and sex: FIDELITY post hoc analysis of two phase 3, multicentre, double-blind trials

OBJECTIVES

This study aimed to evaluate the efficacy and safety of finerenone, a selective, non-steroidal mineralocorticoid receptor antagonist, on cardiovascular and kidney outcomes by age and/or sex.

DESIGN

FIDELITY post hoc analysis; median follow-up of 3 years.

SETTING

FIDELITY: a prespecified analysis of the FIDELIO-DKD and FIGARO-DKD trials.

PARTICIPANTS

Adults with type 2 diabetes and chronic kidney disease receiving optimised renin-angiotensin system inhibitors (N=13 026).

INTERVENTIONS

Randomised 1:1; finerenone or placebo.

PRIMARY AND SECONDARY OUTCOME MEASURES

Cardiovascular (cardiovascular death, non-fatal myocardial infarction, non-fatal stroke or hospitalisation for heart failure (HHF)) and kidney (kidney failure, sustained ≥57% estimated glomerular filtration rate (eGFR) decline or renal death) composite outcomes.

RESULTS

Mean age was 64.8 years; 45.2%, 40.1% and 14.7% were aged <65, 65-74 and ≥75 years, respectively; 69.8% were male. Cardiovascular benefits of finerenone versus placebo were consistent across age (HR 0.94 (95% CI 0.81 to 1.10) (<65 years), HR 0.84 (95% CI 0.73 to 0.98) (65-74 years), HR 0.80 (95% CI 0.65 to 0.99) (≥75 years); Pinteraction=0.42) and sex categories (HR 0.86 (95% CI 0.77 to 0.96) (male), HR 0.89 (95% CI 0.35 to 2.27) (premenopausal female), HR 0.87 (95% CI 0.73 to 1.05) (postmenopausal female); Pinteraction=0.99). Effects on HHF reduction were not modified by age (Pinteraction=0.70) but appeared more pronounced in males (Pinteraction=0.02). Kidney events were reduced with finerenone versus placebo in age groups <65 and 65-74 but not ≥75; no heterogeneity in treatment effect was observed (Pinteraction=0.51). In sex subgroups, finerenone consistently reduced kidney events (Pinteraction=0.85). Finerenone reduced albuminuria and eGFR decline regardless of age and sex. Hyperkalaemia increased with finerenone, but discontinuation rates were <3% across subgroups. Gynaecomastia in males was uncommon across age subgroups and identical between treatment groups.

CONCLUSIONS

Finerenone improved cardiovascular and kidney composite outcomes with no significant heterogeneity between age and sex subgroups; however, the effect on HHF appeared more pronounced in males. Finerenone demonstrated a similar safety profile across age and sex subgroups.

TRIAL REGISTRATION NUMBERS

NCT02540993, NCT02545049.

Advances in pediatric acute kidney injury pathobiology: a report from the 26th Acute Disease Quality Initiative (ADQI) conference

BACKGROUND

In the past decade, there have been substantial advances in our understanding of the pathobiology of pediatric acute kidney injury (AKI). In particular, animal models and studies focused on the relationship between kidney development, nephron number, and kidney health have identified a number of heterogeneous pathophysiologies underlying AKI. Despite this progress, gaps remain in our understanding of the pathobiology of pediatric AKI.

METHODS

During the 26th Acute Disease Quality Initiative (ADQI) Consensus conference, a multidisciplinary group of experts discussed the evidence and used a modified Delphi process to achieve consensus on recommendations for opportunities to advance translational research in pediatric AKI. The current state of research understanding as well as gaps and opportunities for advancement in research was discussed, and recommendations were summarized.

RESULTS

Consensus was reached that to improve translational pediatric AKI advancements, diverse teams spanning pre-clinical to epidemiological scientists must work in concert together and that results must be shared with the community we serve with patient involvement. Public and private research support and meaningful partnerships with adult research efforts are required. Particular focus is warranted to investigate the pediatric nuances of AKI, including the effect of development as a biological variable on AKI incidence, severity, and outcomes.

CONCLUSIONS

Although AKI is common and associated with significant morbidity, the biologic basis of the disease spectrum throughout varying nephron developmental stages remains poorly understood. An incomplete understanding of factors contributing to kidney health, the diverse pathobiologies underlying AKI in children, and the historically siloed approach to research limit advances in the field. The recommendations outlined herein identify gaps and outline a strategic approach to advance the field of pediatric AKI via multidisciplinary translational research.

Predictors of oliguria in post-traumatic acute kidney injury

BACKGROUND

Acute kidney injury is classified by urine output into non-oliguric and oliguric variants. Non-oliguric acute kidney injury has lower morbidity and mortality and accounts for up to 64% of acute kidney injury in hospitalized patients. However, the incidence of non-oliguric acute kidney injury in the trauma population and whether the 2 variants of acute kidney injury share the same risk factors is unknown. We hypothesized that oliguria would be present in the majority of acute kidney injury in severely injured trauma patients and that unique risk factors would predispose patients to the development of oliguria.

METHODS

Patients admitted to the trauma intensive care unit and diagnosed with an acute kidney injury between 2016 to 2021 were identified. Cases were categorized based on urine output into oliguric (<400 mL per day) and non-oliguric (>400 mL per day) disease. Risk factors, management, and outcomes were compared. Logistic regression was used to identify risk factors associated with oliguria.

RESULTS

A total of 227 patients met inclusion criteria. Non-oliguric acute kidney injury accounted for 74% of all cases and was associated with greater survival (78% vs 35.6%, P < .001). Using logistic regression, female sex, vasopressor use, and a greater net fluid balance at 48 hours were all predictive of oliguria (while controlling for age, race, shock index, massive transfusion, operative intervention, cardiac arrest, and nephrotoxic medication exposure).

CONCLUSION

Non-oliguria accounts for the majority of post-traumatic acute kidney injury and is associated with improved survival. Specific risk factors for the development of oliguric acute kidney injury include female sex, vasopressor use, and a higher net fluid balance at 48 hours.

Current perspective on circadian function of the kidney

Behavior and function of living systems are synchronized by the 24-h rotation of the Earth that guides physiology according to time of day. However, when behavior becomes misaligned from the light-dark cycle, such as in rotating shift work, jet lag, and even unusual eating patterns, adverse health consequences such as cardiovascular or cardiometabolic disease can arise. The discovery of cell-autonomous molecular clocks expanded interest in regulatory systems that control circadian physiology including within the kidney, where function varies along a 24-h cycle. Our understanding of the mechanisms for circadian control of physiology is in the early stages, and so the present review provides an overview of what is known and the many gaps in our current understanding. We include a particular focus on the impact of eating behaviors, especially meal timing. A better understanding of the mechanisms guiding circadian function of the kidney is expected to reveal new insights into causes and consequences of a wide range of disorders involving the kidney, including hypertension, obesity, and chronic kidney disease.

Nicotinamide riboside activates renal metabolism and protects the kidney in a model of Alport syndrome

Chronic kidney disease (CKD) is associated with renal metabolic disturbances, including impaired fatty acid oxidation (FAO). Nicotinamide adenine dinucleotide (NAD + ) is a small molecule that participates in hundreds of metabolism-related reactions. NAD + levels are decreased in CKD, and NAD + supplementation is protective. However, both the mechanism of how NAD + supplementation protects from CKD, as well as the cell types most responsible, are poorly understood. Using a mouse model of Alport syndrome, we show that nicotinamide riboside (NR), an NAD + precursor, stimulates renal peroxisome proliferator-activated receptor α signaling and restores FAO in the proximal tubules, thereby protecting from CKD in both sexes. Bulk RNA-sequencing shows that renal metabolic pathways are impaired in Alport mice and dramatically activated by NR in both sexes. These transcriptional changes are confirmed by orthogonal imaging techniques and biochemical assays. Single nuclei RNA-sequencing and spatial transcriptomics, both the first of their kind from Alport mice, show that NAD + supplementation restores FAO in the proximal tubules with minimal effects on the podocytes. Finally, we also report, for the first time, sex differences at the transcriptional level in this Alport model. Male Alport mice had more severe inflammation and fibrosis than female mice at the transcriptional level. In summary, the data herein identify both the protective mechanism and location of NAD + supplementation in this model of CKD.

Furosemide Responsiveness Predicts Acute Kidney Injury Progression After Cardiac Surgery

BACKGROUND

As patients with acute kidney injury (AKI) progress to a higher stage, the risk for poor outcomes dramatically rises. Early identification of patients at high risk for AKI progression remains a major challenge. This study aimed to evaluate the value of furosemide responsiveness (FR) for predicting AKI progression in patients with initial mild and moderate AKI after cardiac surgery.

METHODS

We performed 2 separate exploratory analyses. The Zhongshan cohort was a single-center, prospective, observational cohort, whereas the Beth Israel Deaconess Medical Center cohort was a single-center, retrospective cohort. We calculated 2 FR parameters for each patient, namely the FR index and modified FR index, defined as 2-hour urine output divided by furosemide dose (FR index, mL/mg/2 h) and by furosemide dose and body weight (modified FR index, mL/[mg·kg]/2 h), respectively. The primary outcome was AKI progression within 7 days.

RESULTS

AKI progression occurred in 80 (16.0%) and 359 (11.3%) patients in the Zhongshan and Beth Israel Deaconess Medical Center cohorts, respectively. All FR parameters (considered continuously or in quartiles) were inversely associated with risk of AKI progression in both cohorts (all adjusted P < .01). The addition of FR parameters significantly improved prediction for AKI progression based on baseline clinical models involving C-index, net reclassification improvement, and integrated discrimination improvement index in both cohorts (all P < .01).

CONCLUSIONS

FR parameters were inversely associated with risk of AKI progression in patients with mild and moderate AKI after cardiac surgery. The addition of FR parameters significantly improved prediction for AKI progression based on baseline clinical models.

Exploring Hematological and Biochemical Disparities in Same-Sex and Opposite-Sex Females: A Cross-Sectional Twin Study in a Ghanaian Population

There are sex-dependent differences in hematological and biochemical variables in adulthood attributed to the predominant effects of testosterone in males and estrogen in females. The Twin Testosterone Transfer (TTT) hypothesis proposes that opposite-sex females may develop male-typical traits due to exposure to relatively higher levels of prenatal testosterone than same-sex females. Additionally, prenatal testosterone exposure has been suggested as a correlate of current circulating testosterone levels. Consequently, opposite-sex females might exhibit male-typical patterns in their hematological and biochemical variables. Despite this hypothesis, routine laboratory investigations assign the same reference range to all females. Our cross-sectional study, conducted in Tamale from January to September 2022, included 40 twins, comprising 10 opposite-sex (OS) males (25%), 10 OS females (25%), and 20 same-sex (SS) females (50%), all aged between 18 and 27 years. Fasting venous blood samples were collected and analyzed using automated hematology and biochemistry laboratory analyzers. Results indicated that levels of hemoglobin, serum creatinine, gamma-glutamyl transferase, total protein, globulins, and total testosterone were significantly higher in OS males than OS females. Conversely, total cholesterol and low-density lipoprotein cholesterol were significantly higher in OS females than OS males. Unexpectedly, levels of low-density lipoprotein cholesterol and total testosterone were significantly higher in SS females than OS females. Contrary to expectations, opposite-sex females did not exhibit male-typical patterns in their hematological and biochemical variables. This suggests that the TTT effect may not occur or may not be strong enough to markedly affect hematological and biochemical variables in OS females.

Sex differences in renal transporters: assessment and functional consequences

Mammalian kidneys are specialized to maintain fluid and electrolyte homeostasis. The epithelial transport processes along the renal tubule that match output to input have long been the subject of experimental and theoretical study. However, emerging data have identified a new dimension of investigation: sex. Like most tissues, the structure and function of the kidney is regulated by sex hormones and chromosomes. Available data demonstrate sex differences in the abundance of kidney solute and electrolyte transporters, establishing that renal tubular organization and operation are distinctly different in females and males. Newer studies have provided insights into the physiological consequences of these sex differences. Computational simulations predict that sex differences in transporter abundance are likely driven to optimize reproduction, enabling adaptive responses to the nutritional requirements of serial pregnancies and lactation - normal life-cycle changes that challenge the ability of renal transporters to maintain fluid and electrolyte homeostasis. Later in life, females may also undergo menopause, which is associated with changes in disease risk. Although numerous knowledge gaps remain, ongoing studies will provide further insights into the sex-specific mechanisms of sodium, potassium, acid-base and volume physiology throughout the life cycle, which may lead to therapeutic opportunities.

Are Differences in Living Kidney Donation Rates a Sex or a Gender Disparity?

Sex-disaggregated data reveal significant disparities in living kidney donation, with more female than male living kidney donors in most countries and proportions over 60% in some countries. We summarize the present state of knowledge with respect to the potential drivers of this disparity and argue that it is primarily driven by gender-related factors. First, we present the differences between sex and gender and then proceed to summarize the potential medical reasons that have been proposed to explain why males are less likely to be living kidney donors than females, such as the higher prevalence of kidney failure in males. We then present counterarguments as to why biological sex differences are not enough to explain lower living kidney donation among males, such as a higher prevalence of chronic kidney disease among females, which could affect donation rates. We argue that gender differences likely provide a better explanation as to why there are more women than men living kidney donors and explore the role of economic and social factors, as well as gender roles and expectations, in affecting living kidney donation among both men and women. We conclude with the need for a gender analysis to explain this complex psychosocial phenomenon in living kidney donation.

Aromatase enzyme: Paving the way for exploring aromatization for cardio-renal protection

Documented male-female differences in the risk of cardiovascular and chronic kidney diseases have been largely attributed to estrogens. The cardiovascular and renal protective effects of estrogens are mediated via the activation of estrogen receptors (ERα and ERβ) and G protein-coupled estrogen receptor, and involve interactions with the renin-angiotensin-aldosterone system. Aromatase, also called estrogen synthase, is a cytochrome P-450 enzyme that plays a pivotal role in the conversion of androgens into estrogens. Estrogens are biosynthesized in gonadal and extra-gonadal sites by the action of aromatase. Evidence suggests that aromatase inhibitors, which are used to treat high estrogen-related pathologies, are associated with the development of cardiovascular events. We review the potential role of aromatization in providing cardio-renal protection and highlight several meta-analysis studies on cardiovascular events associated with aromatase inhibitors. Overall, we present the potential of aromatase enzyme as a fundamental contributor to cardio-renal protection.

Why do we keep ignoring sex in kidney disease?

Throughout the history of nephrology, little attention has been paid to the sex and gender differences in kidney disease. This lack of awareness prevents optimal diagnosis and management of kidney disease. In today's world of precision medicine, it is imperative to appreciate the differential factors regarding gender and kidney disease. This editorial summarizes the up-to-date literature regarding sex and gender differences in kidney disease and considers areas where knowledge is incomplete and where further research is needed. We address sex-specific effects on chronic kidney disease epidemiology; risks of dialysis underdosing and medication overdosing in women; unexplained loss of female sex advantage in life expectancy during dialysis, and impact of sex on diagnosis and management of genetic kidney disease. We also aim to highlight the impact of gender on kidney health and raise awareness of disparities that may be faced by women, and transgender and gender-diverse persons when a male-model approach is used by healthcare systems. By understanding the link between sex and kidney disease, kidney specialists can improve the care and outcomes of their patients. In addition, research on this topic can inform the development of targeted prevention and intervention strategies that address the specific needs and risk factors of different populations.

Estrogen-induced signalling and the renal contribution to salt and water homeostasis

The kidney is considered to be one of the most estrogen-responsive, not reproductive organs in the body. Different estrogen receptors (ERs) show sex-specific differences in expression along the nephron and the expression of different ERs also changes with the estrous cycle of the female. The kidney becomes more estrogen-sensitive when estradiol levels are at their highest, just prior to ovulation. This review discusses the different mechanisms by which estradiol can modify the salt and water conservation processes of the kidney through transporter regulation to support the fluid and electrolyte homeostasis changes required in mammalian reproduction. The kidney plays a critical role in regulating blood pressure by controlling fluid homeostasis, and so protects the female cardiovascular system from dramatic changes in whole body fluid volume that occur at critical points in the human menstrual cycle and in pregnancy. This is augmented by the direct actions of estradiol on the cardiovascular system, for example through the direct stimulation of endothelial nitric oxide (NO) synthase, which releases NO to promote vasodilation. This and other mechanisms are less evident in the male and give women a degree of cardiovascular protection up until menopause, when the risks of cardiovascular disease and chronic kidney disease begin to match the risks experienced by males.

Sex Differences in Cardiovascular and All-Cause Mortality in Adults with and without CKD: NHANES 1999-2018

Women with CKD had a lower cardiovascular disease mortality risk than men. Kidney function markers (i.e. , eGFR and urinary albumin-to-creatinine ratio) may influence mortality risk in women with CKD, but not in men.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Gender-based research underscores sex differences in biological processes, clinical disorders and pharmacological interventions

Earlier research has presumed that the male and female biology is similar in most organs except the reproductive system, leading to major misconceptions in research interpretations and clinical implications, with serious disorders being overlooked or misdiagnosed. Careful research has now identified sex differences in the cardiovascular, renal, endocrine, gastrointestinal, immune, nervous, and musculoskeletal systems. Also, several cardiovascular, immunological, and neurological disorders have shown differences in prevalence and severity between males and females. Genetic variations in the sex chromosomes have been implicated in several disorders at young age and before puberty. The levels of the gonadal hormones estrogen, progesterone and testosterone and their receptors play a role in the sex differences between adult males and premenopausal women. Hormonal deficiencies and cell senescence have been implicated in differences between postmenopausal and premenopausal women. Specifically, cardiovascular disorders are more common in adult men vs premenopausal women, but the trend is reversed with age with the incidence being greater in postmenopausal women than age-matched men. Gender-specific disorders in females such as polycystic ovary syndrome, hypertension-in-pregnancy and gestational diabetes have attained further research recognition. Other gender-related research areas include menopausal hormone therapy, the "Estrogen Paradox" in pulmonary arterial hypertension being more predominant but less severe in young females, and how testosterone may cause deleterious effects in the kidney while having vasodilator effects in the coronary circulation. This has prompted the National Institutes of Health (NIH) initiative to consider sex as a biological variable in research. The NIH and other funding agencies have provided resources to establish state-of-the-art centers for women health and sex differences in biology and disease in several academic institutions. Scientific societies and journals have taken similar steps to organize specialized conferences and publish special issues on gender-based research. These combined efforts should promote research to enhance our understanding of the sex differences in biological systems beyond just the reproductive system, and provide better guidance and pharmacological tools for the management of various clinical disorders in a gender-specific manner.

Gender differences in comorbidities of patients with COVID-19: An Italian local register-based analysis

In the current COVID-19 pandemic scenario, it is still necessary to understand if differences exist between genders in terms of patients' characteristics and clinical outcomes. For this reason, we retrospectively analyzed data obtained from a local register-based dataset of all SARS-CoV-2 positive patients diagnosed in the province of Catania (Italy). The main aim of this analysis was to understand any differences between genders in the distribution of previous medical conditions, and to evaluate which of them posed individuals at higher risk of death. With this purpose, we analyzed data from 1424 patients with at least one underlying medical condition, who were tested positive for SARS-CoV-2 infection from February 2020 to December 2021. Overall, males were 59.5% of the total population and significantly younger than females (median ages: 68 years vs. 72 years; p = 0.011). The age distribution of cases by gender confirms that individuals from 70 to 79 years were the most affected in both genders. The comparison of underlying comorbidities by gender shows significant differences for diabetes (p < 0.001), other metabolic diseases (p = 0.006), and obesity (p = 0.019). Accordingly, multivariable logistic regression analysis confirmed that diabetes was more likely to be present in males than in females (p = 0.001), while other metabolic diseases and obesity were less likely to be present (p = 0.003 and p = 0.005, respectively). Although no difference in mortality was evident between genders (p = 0.141), both male and female COVID-19 patients had a significantly higher risk of death if they had comorbidities such as CVDs, kidney diseases, or chronic neurological diseases. Moreover, diabetes and chronic respiratory diseases were significant risk factors for COVID-19 mortality among men, whereas cancer was a significant contributor among women. Our findings confirm gender-differences in pre-existing medical conditions of COVID-19 patients, which may influence the risk of death. Further studies, however, are needed to understand physiological and pathological mechanisms underpinning these differences.

Female cardiovascular biology and resilience in the setting of physiological and pathological stress

For years, females were thought of as smaller men with complex hormonal cycles; as a result, females have been largely excluded from preclinical and clinical research. However, in the last ten years, with the increased focus on sex as a biological variable, it has become clear that this is not the case, and in fact, male and female cardiovascular biology and cardiac stress responses differ substantially. Premenopausal women are protected from cardiovascular diseases, such as myocardial infarction and resultant heart failure, having preserved cardiac function, reduced adverse remodeling, and increased survival. Many underlying biological processes that contribute to ventricular remodeling differ between the sexes, such as cellular metabolism; immune cell responses; cardiac fibrosis and extracellular matrix remodeling; cardiomyocyte dysfunction; and endothelial biology; however, it is unclear how these changes afford protection to the female heart. Although many of these changes are dependent on protection provided by female sex hormones, several of these changes occur independent of sex hormones, suggesting that the nature of these changes is more complex than initially thought. This may be why studies focused on the cardiovascular benefits of hormone replacement therapy in post-menopausal women have provided mixed results. Some of the complexity likely stems from the fact that the cellular composition of the heart is sexually dimorphic and that in the setting of MI, different subpopulations of these cell types are apparent. Despite the documented sex-differences in cardiovascular (patho)physiology, the underlying mechanisms that contribute are largely unknown due to inconsistent findings amongst investigators and, in some cases, lack of rigor in reporting and consideration of sex-dependent variables. Therefore, this review aims to describe current understanding of the sex-dependent differences in the myocardium in response to physiological and pathological stressors, with a focus on the sex-dependent differences that contribute to post-infarction remodeling and resultant functional decline.

A multinational cohort study uncovered sex differences in excess mortality after kidney transplant

Worldwide and at all ages, males have a higher mortality risk than females. This mortality bias should be preserved in kidney transplant recipients unless there are sex differences in the effects of transplantation. Here we compared the excess risk of mortality (risk above the general population) in female versus male recipients of all ages recorded in three large transplant databases. This included first deceased donor kidney transplant recipients and accounted for the modifying effects of donor sex and recipient age. After harmonization of variables across cohorts, relative survival models were fitted in each cohort separately and results were combined using individual patient data meta-analysis among 466,892 individuals (1988-2019). When the donor was male, female recipients 0-12 years (Relative Excess Risk 1.54, 95% Confidence Interval 1.20-1.99), 13-24 years (1.17, 1.01-1.34), 25-44 years (1.11, 1.05-1.18) and 60 years and older (1.05, 1.02-1.08) showed higher excess mortality risks than male recipients of the same age. When the donor was female, the Relative Excess Risk for those over 12 years were similar to those when the donor was male. There is a higher excess mortality risk in female than male recipients with differences larger at younger than older ages and only statistically significant when the donor was male. While these findings may be partly explained by the known sex differences in graft loss risks, sex differences in the risks of death with graft function may also contribute. Thus, higher risks in females than males suggest that management needs to be modified to optimize transplant outcomes among females.

The G protein-coupled oestrogen receptor GPER in health and disease: an update

Oestrogens and their receptors contribute broadly to physiology and diseases. In premenopausal women, endogenous oestrogens protect against cardiovascular, metabolic and neurological diseases and are involved in hormone-sensitive cancers such as breast cancer. Oestrogens and oestrogen mimetics mediate their effects via the cytosolic and nuclear receptors oestrogen receptor-α (ERα) and oestrogen receptor-β (ERβ) and membrane subpopulations as well as the 7-transmembrane G protein-coupled oestrogen receptor (GPER). GPER, which dates back more than 450 million years in evolution, mediates both rapid signalling and transcriptional regulation. Oestrogen mimetics (such as phytooestrogens and xenooestrogens including endocrine disruptors) and licensed drugs such as selective oestrogen receptor modulators (SERMs) and downregulators (SERDs) also modulate oestrogen receptor activity in both health and disease. Following up on our previous Review of 2011, we herein summarize the progress made in the field of GPER research over the past decade. We will review molecular, cellular and pharmacological aspects of GPER signalling and function, its contribution to physiology, health and disease, and the potential of GPER to serve as a therapeutic target and prognostic indicator of numerous diseases. We also discuss the first clinical trial evaluating a GPER-selective drug and the opportunity of repurposing licensed drugs for the targeting of GPER in clinical medicine.

Multiomics Analyses Reveal Sex Differences in Mouse Renal Proximal Subsegments

SIGNIFICANCE STATEMENT

Sex-dependent differences in kidney function are recognized but the underlying molecular mechanisms are largely unexplored. Advances in genomics and proteomic technologies now allow extensive characterization of differences between the same cell types of males and females. Multiomics integrating RNA-seq, ATAC-seq, and proteomics data to investigate differences in gene expression, chromatin accessibility, and protein expression in proximal tubules of male and female mice identified many sex-biased genes and proteins associated with kidney functions, including metabolic and transport processes. Sex differences may also arise from variations of the interaction between transcription factors and accessible chromatin regions. A comprehensive web resource is provided to advance understanding of sex differences in cells of the proximal tubule.

BACKGROUND

Sex differences have been increasingly recognized as important in kidney physiology and pathophysiology, but limited resources are available for comprehensive interrogation of sex differences.

METHODS

RNA-seq and ATAC-seq of microdissected mouse proximal tubules and protein mass spectrometry of homogenized perfused mouse kidneys reveal differences in proximal tubule cells of males and females.

RESULTS

The transcriptomic data indicated that the major differences in the proximal tubules between the sexes were in the S2/S3 segments, and most of the sex-biased transcripts mapped to autosomes rather than to the sex chromosomes. Many of the transcripts exhibiting sex-biased expression are involved in monocarboxylic acid metabolic processes, organic anion transport, and organic acid transport. The ATAC-seq method on microdissected tubules captured chromatin accessibility. Many of the more than 7000 differentially accessible DNA regions identified were in distal regions. Motif analyses revealed a lack of direct involvement of estrogen receptors or the androgen receptor (absence of canonical hormone response elements), suggesting an indirect regulatory role of sex hormones. Instead, analyses identified several transcription factors (TFs) ( Tead1 , Nfia/b , and Pou3f3 ) whose interplay with proximal tubule-specific TFs ( e.g. , Hnf1b , Hnf4a ) may contribute to sex differences. Finally, the whole-kidney proteome was correlated with the transcriptome, and many sex-biased proteins ( e.g. , Cyp2e1, Acsm2/3) were identified.

CONCLUSIONS

Sex-dependent cis-regulatory elements interact with TFs in ways that lead to sex-biased gene expression in proximal tubule cells. These data are provided as a user-friendly web page at https://esbl.nhlbi.nih.gov/MRECA/PT/ .

Sex Modulates Response to Renal-Tubule-Targeted Insulin Receptor Deletion in Mice

Insulin facilitates renal sodium reabsorption and attenuates gluconeogenesis. Sex differences in this regulation have not been well characterized. Using tetracycline-inducible Cre-lox recombination, we knocked out (KO) the insulin receptor (InsR) from the renal tubule in adult male (M) and female (F) mice (C57Bl6 background) with a paired box 8 (PAX8) promoter. Body weights were not affected by the KO, but mean kidney weights were reduced in the KO mice (13 and 3%, in M and F, respectively, relative to wild-type (WT) mice). A microscopic analysis revealed 25 and 19% reductions in the proximal tubule (PT) and cortical collecting duct cell heights, respectively, in KOMs relative to WTMs. The reductions were 5 and 11% for KOFs. Western blotting of renal cortex homogenates showed decreased protein levels for the β and γ subunits of the epithelial sodium channel (ENaC) and the sodium-potassium-2-chloride cotransporter type 2 (NKCC2) in both sexes of KO mice; however, α-ENaC was upregulated in KOMs and downregulated in KOFs. Both sexes of KO mice cleared exogenously administered glucose faster than the WT mice and had lower semi-fasted, anesthetized blood glucose levels. However, KOMs (but not KOFs) demonstrated evidence of enhanced renal gluconeogenesis, including higher levels of renal glucose-6-phosphatase, the PT's production of glucose, post-prandial blood glucose, and plasma insulin, whereas KOFs exhibited downregulation of renal high-capacity sodium glucose cotransporter (SGLT2) and upregulation of SGLT1; these changes appeared to be absent in the KOM. Overall, these findings suggest a sex-differential reliance on intact renal tubular InsR signaling which may be translationally important in type 2 diabetes, obesity, or insulin resistance when renal insulin signaling is reduced.

Immune checkpoint inhibitor-associated acute kidney injury in patients with cancer: a systematic review and meta-analysis of risk factors

BACKGROUND

As a novel antineoplastic drug, immune checkpoint inhibitors (ICIs) are associated with a spectrum of autoimmune-related side effects, including acute kidney injury (AKI). Understanding the risk factors for immune-associated acute kidney injury will inform future symptom management measures to reduce this risk. This study aims to identify the risk factors for ICIs-AKI in cancer patients through a systematic review and meta-analysis.

METHODS

The systematic search was conducted in The Cochrane Library, Pubmed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang Data, and VIP Database. The related studies published since the establishment of the database to Aug 22, 2022, were screened, data was extracted following the inclusion and exclusion criteria, and the quality of the selected studies was assessed by Newcastle-Ottawa Scale (NOS). The above was performed independently by the two reviewers. The estimated pooled odds ratios (ORs) for risk factors of developing ICIs-AKI were conducted by random-effects meta-analysis.

RESULTS

A total of 8 publications, including 5267 patients, were included. Meta-analysis results showed that extrarenal immune-related adverse events (irAEs), therapy with the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), male, hypertension, pre-existent use of a diuretic, and a proton pump inhibitor (PPI) were significantly correlated to ICIs-AKI.

CONCLUSIONS

We identified extrarenal irAEs, CTLA-4 treatments, males, hypertension, previous use of diuretics, and PPIs are essential predictors of ICIs-AKI. These findings are helpful for healthcare providers to monitor ICIs-AKI for management and timely interventions.

Circadian gene expression in mouse renal proximal tubule

Circadian variability in kidney function is well recognized but is often ignored as a potential confounding variable in physiological experiments. Here, we have created a data resource consisting of expression levels for mRNA transcripts in microdissected proximal tubule segments from mice as a function of the time of day. Small-sample RNA sequencing was applied to microdissected S1 proximal convoluted tubules and S2 proximal straight tubules. After stringent filtering, the data were analyzed using JTK-Cycle to detect periodicity. The data set is provided as a user-friendly webpage at https://esbl.nhlbi.nih.gov/Databases/Circadian-Prox2/. In proximal convoluted tubules, 234 transcripts varied in a circadian manner (4.0% of the total). In proximal straight tubules, 334 transcripts varied in a circadian manner (5.3%). Transcripts previously known to be associated with corticosteroid action and with increased flow were found to be overrepresented among circadian transcripts peaking during the "dark" portion of the day [zeitgeber time (ZT)14-22], corresponding to peak levels of corticosterone and glomerular filtration rate in mice. To ask whether there is a time-of-day dependence of protein abundances in the kidney, we carried out LC-MS/MS-based proteomics in whole mouse kidneys at ZT12 and ZT0. The full data set (n = 6,546 proteins) is available at https://esbl.nhlbi.nih.gov/Databases/Circadian-Proteome/. Overall, 293 proteins were differentially expressed between ZT12 and ZT0 (197 proteins greater at ZT12 and 96 proteins greater at ZT0). Among the regulated proteins, only nine proteins were found to be periodic in the RNA-sequencing analysis, suggesting a high level of posttranscriptional regulation of protein abundances.NEW & NOTEWORTHY Circadian variation in gene expression can be an important determinant in the regulation of kidney function. The authors used RNA-sequencing transcriptomics and LC-MS/MS-based proteomics to identify gene products expressed in a periodic manner. The data were used to construct user-friendly web resources.

Allometric body shape indices, type 2 diabetes and kidney function: A two-sample Mendelian randomization study

AIM

To examine the association between body mass index (BMI)-independent allometric body shape indices and kidney function.

MATERIALS AND METHODS

We performed a two-sample Mendelian randomization (MR) analysis, using summary statistics from UK Biobank, CKDGen and DIAGRAM. BMI-independent allometric body shape indices were: A Body Shape Index (ABSI), Waist-Hip Index (WHI) and Hip Index (HI). Kidney function outcomes were: urinary albumin-to-creatinine ratio (UACR), estimated glomerular filtration rate and blood urea nitrogen. Furthermore, we investigated type 2 diabetes (T2D) as a potential mediator on the pathway to albuminuria. The main analysis was inverse variance-weighted random-effects MR in participants of European ancestry. We also performed several sensitivity MR analyses.

RESULTS

A 1-standard deviation (SD) increase in genetically predicted ABSI and WHI levels was associated with higher UACR (β = 0.039 [95% confidence interval: 0.016, 0.063] log [UACR], P = 0.001 for ABSI, and β = 0.028 [0.012, 0.044] log [UACR], P = 6 x 10^-4 for WHI) in women, but not in men. Meanwhile, a 1-SD increase in genetically predicted HI was associated with lower UACR in women (β = -0.021 [-0.041, 0.000] log [UACR], P = 0.05) and in men (β = -0.026 [-0.058, 0.005] log [UACR], P = 0.10). Corresponding estimates in individuals with diabetes were substantially augmented. Risk of T2D increased for genetically high ABSI and WHI in women (P < 6 x 10^-19 ) only, but decreased for genetically high HI in both sexes (P < 9 x 10^-3 ). No other associations were observed.

CONCLUSIONS

Genetically high HI was associated with decreased risk of albuminuria, mediated through decreased T2D risk in both sexes. Opposite associations applied to genetically high ABSI and WHI in women only.

Sex-Associated Differences in Short-Term Outcomes in Patients with Deep Sternal Wound Infection after Open-Heart Surgery

Deep sternal wound infection (DSWI) is a feared complication after cardiac surgery. The impact of sex-related differences on wound infection prevalence is poorly understood. Our aim was to evaluate the effect of sex on short-term outcomes in patients with DSWI after open-heart surgery. The study was a retrospective cohort study. A total of 217 patients with DSWI were identified and retrospectively analyzed using our institutional database. Patients were divided into two groups: males (n = 150) and females (n = 67). This study also includes a propensity score based matching (PSM) analysis (male group (n = 62) and female group (n = 62)) to examine the unequal groups. Mean age (p = 0.088) and mean body mass index (BMI) (p = 0.905) did not significantly differ between both groups. Vacuum assisted closure (VAC) therapy was performed among most patients (82.3% (male group) vs. 83.9% (female group), p = 0.432). The most commonly isolated bacteria from the wounds were Staphylococcus epidermidis and Staphylococcus aureus in both groups. Acute renal failure was significantly higher (p = 0.010) in the male group compared to the female group. However, dialysis rate did not significantly differ (p = 0.491) between male and female groups. Further secondary outcomes showed no major differences between the groups. Likewise, in-hospital mortality rate did not differ significantly (p = 0.680) between both groups. Based on our data, sex has no impact on deep wound infection prevalence after cardiac surgery.

Sex differences in resilience to ferroptosis underlie sexual dimorphism in kidney injury and repair

In both humans and mice, repair of acute kidney injury is worse in males than in females. Here, we provide evidence that this sexual dimorphism results from sex differences in ferroptosis, an iron-dependent, lipid-peroxidation-driven regulated cell death. Using genetic and single-cell transcriptomic approaches in mice, we report that female sex confers striking protection against ferroptosis, which was experimentally induced in proximal tubular (PT) cells by deleting glutathione peroxidase 4 (Gpx4). Single-cell transcriptomic analyses further identify the NFE2-related factor 2 (NRF2) antioxidant protective pathway as a female resilience mechanism against ferroptosis. Genetic inhibition and pharmacological activation studies show that NRF2 controls PT cell fate and plasticity by regulating ferroptosis. Importantly, pharmacological NRF2 activation protects male PT cells from ferroptosis and improves cellular plasticity as in females. Our data highlight NRF2 as a potential therapeutic target to prevent failed renal repair after acute kidney injury in both sexes by modulating cellular plasticity.

Does sex interact with the 2D:4D ratio or adult circulating hormones on the estimated glomerular filtration rate? A cross-sectional study in Ghana

The 2D:4D ratio is the putative marker of prenatal hormone exposure and has been suggested as a correlate of adult circulating testosterone and estrogen. The study aimed to determine whether sexual dimorphism in the estimated glomerular filtration rate (eGFR) can be partly explained by the 2D:4D ratio or adult circulating testosterone or estrogen. The study was cross-sectional from June to December 2021 at the University for Development Studies. The study involved 206 healthy adults (Female = 93, Male = 113) between 18 and 30 years. The 2D:4D ratio was measured using computer-assisted analysis. Venous blood samples were collected and analyzed for testosterone, estradiol and creatinine using the ELISA technique and routine biochemical analysis. The adjusted eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation (2021). The eGFR and the testosterone-to-estradiol ratio (TT:E2 ) were significantly higher in males than in females (p < 0.001). There was a significant interaction between sex and the TT:E2 on the eGFR (p < 0.001). Although the relationship between the eGFR and the TT:E2 was negative in both males and females, a unit change in the TT:E2 had a greater impact on the eGFR in females (B = -1.38) than in males (B = -0.01). Sexual dimorphism in the eGFR is influenced by both testosterone and estradiol. Although the sex difference in the eGFR may be influenced by the TT:E2 , estrogen seems to account for more variability in the eGFR than testosterone.

Identification of Potential Megalin/Cubilin Substrates Using Extensive Proteomics Quantification from Kidney Megalin-Knockdown Mice

Megalin and cubilin, endocytic proteins present in the proximal tubule of the kidney, are responsible for reabsorbing filtered proteins from urine. Our hypothesis was that potential substrates of megalin/cubilin could be identified by examining urinary protein differences between control (WT) mice and kidney-specific megalin knockdown (KD) mice. Using the IonStar proteomics approach, 877 potential megalin/cubilin substrates were discovered, with 23 of these compounds representing known megalin/cubilin substrates. Some of the proteins with the largest fold changes in the urine between KD and WT included the known megalin substrates retinol-binding protein and vitamin D-binding protein. Of the total proteins identified as novel substrates, about three-quarters of compounds had molecular weights (MWs) below 69 kDa, the MW of albumin, and the remaining had higher MWs, with about 5% of the proteins having MWs greater than 150 kDa. Sex differences in the number of identified substrates occurred, but this may be due to differences in kidney megalin expression between both male and female megalin KD and WT animals, with the ratio of megalin between WT and KD being 2.76 and 2.14 for female and male mice, respectively. The top three ingenuity canonical pathways based on the urinary proteins in both female and male KD mice were acute phase response signaling, liver X receptor/retinoid X receptor activation, and intrinsic prothrombin activation pathways. In conclusion, analysis of urine samples from kidney-specific megalin KD and WT mice was found to be useful for the identification of potential endogenous substrates for megalin and cubilin.

Consensus-Based Recommendations on Priority Activities to Address Acute Kidney Injury in Children: A Modified Delphi Consensus Statement

IMPORTANCE

Increasing evidence indicates that acute kidney injury (AKI) occurs frequently in children and young adults and is associated with poor short-term and long-term outcomes. Guidance is required to focus efforts related to expansion of pediatric AKI knowledge.

OBJECTIVE

To develop expert-driven pediatric specific recommendations on needed AKI research, education, practice, and advocacy.

EVIDENCE REVIEW

At the 26th Acute Disease Quality Initiative meeting conducted in November 2021 by 47 multiprofessional international experts in general pediatrics, nephrology, and critical care, the panel focused on 6 areas: (1) epidemiology; (2) diagnostics; (3) fluid overload; (4) kidney support therapies; (5) biology, pharmacology, and nutrition; and (6) education and advocacy. An objective scientific review and distillation of literature through September 2021 was performed of (1) epidemiology, (2) risk assessment and diagnosis, (3) fluid assessment, (4) kidney support and extracorporeal therapies, (5) pathobiology, nutrition, and pharmacology, and (6) education and advocacy. Using an established modified Delphi process based on existing data, workgroups derived consensus statements with recommendations.

FINDINGS

The meeting developed 12 consensus statements and 29 research recommendations. Principal suggestions were to address gaps of knowledge by including data from varying socioeconomic groups, broadening definition of AKI phenotypes, adjudicating fluid balance by disease severity, integrating biopathology of child growth and development, and partnering with families and communities in AKI advocacy.

CONCLUSIONS AND RELEVANCE

Existing evidence across observational study supports further efforts to increase knowledge related to AKI in childhood. Significant gaps of knowledge may be addressed by focused efforts.

Comorbidity, life-style factors and healthcare utilization in incident chronic kidney disease: sex-specific analyses of claims data

BACKGROUND

Chronic kidney disease (CKD) is common in aging men and women. In contrast to other European countries, Germany lacks CKD registries. The aim of this study was to determine the incidence of CKD stages 2-5 in men and women in Germany. Furthermore, differences between the sexes in terms of comorbidities, potentially inappropriate medications (PIM), and healthcare utilization were examined.

METHODS

In this retrospective observational study, claims data from members of a statutory health insurance fund aged 18 years or older with incident CKD between 2011 and 2018 were analyzed. Incident CKD was defined as having two confirmed diagnoses of CKD stages 2-5 from outpatient care or one primary or secondary diagnosis from inpatient care.

RESULTS

The age- and sex-standardized incidence of all CKD stages was 945/100 000 persons between 2011 and 2018. Incident CKD, especially stages 3 and 4, occurred more frequently in women, while the incidence of stages 2 and 5 was higher in men. While women visited their GP more frequently and were prescribed PIMs more often, men were more likely to visit a nephrologist and were more often hospitalized after the incident CKD diagnosis.

CONCLUSION

More awareness needs to be raised towards the early detection of CKD and the use of PIMs, especially in women. Improved care coordination is needed to avoid an overprovision of patients with uncomplicated incident stages and ensure that patients with advanced CKD stages get timely access to specialist care.

Proximity to petrochemical industrial parks and risk of chronic glomerulonephritis

This study determined whether individuals residing near petrochemical industrial parks (PIPs) have a higher risk of chronic glomerulonephritis (CGN). We performed population-based 1:4 case-control study by using Taiwan's National Health Insurance Research Database from 2000 to 2016. The subjects were aged 20-65 years, residing in western Taiwan, and did not have a history of any renal or urinary system disease in 2000. The case cohort included those who had at least three outpatient visits or one hospitalization between 2001 and 2016 with codes for CGN as per International Classification of Diseases (ICD)-Ninth and Tenth Revisions. Controls were randomly sampled age-, sex-, and urbanization-matched individuals without renal and urinary system diseases. Petrochemical exposure was evaluated by the distance to the nearest PIP of the residential township, and petrochemical exposure probability was examined considering the monthly prevailing wind direction. Conditional logistic regression was used to determine the association between petrochemical exposure and CGN risk. A total of 320,935 subjects were included in the final analysis (64,187 cases and 256,748 controls). After adjustment for potential confounders, living in townships within a 3-km radius of PIPs was associated with a higher risk of CGN (adjusted odds ratio [aOR] = 1.32, 95% confidence interval [CI] = 1.28-1.37). Compared with townships more than 20 km away from PIPs, those within 10 km of PIPs were associated with significantly increased risks of CGN in a dose-dependent manner. When prevailing wind was considered, townships with high exposure probability were associated with a significantly increased risk of CGN. We found that those residing near PIPs or with high petrochemical exposure probability had a higher risk of CGN. These findings highlight the need for monitoring environmental nephrotoxic substances and the renal health of residents living near PIPs.

A Reproducible Mouse Model of Moderate CKD With Early Manifestations of Osteoblastic Transition of Cardiovascular System

Chronic kidney disease (CKD) is a significant public health challenge with a substantial associated risk of mortality, morbidity, and health care expenditure. Culprits that lead to development and progression of CKD are multifaceted and heterogenous in nature. This notion underscores the need for diversification of animal models to investigate its pathophysiology, related complications, and to subsequently enable discovery of novel therapeutics. Importantly, animal models that could recapitulate complications of CKD in both genders are desperately needed. Cardiovascular disease is the most common cause of death in CKD patients that may be due in part to high prevalence of vascular calcification (VC). Using DBA/2 mice that are susceptible to development of VC, we sought to investigate the feasibility and reproducibility of a unilateral ischemia-reperfusion model followed by contralateral nephrectomy (UIRI/Nx) to induce CKD and its related complications in female and male mice. Our results demonstrate that irrespective of gender, mice faithfully displayed complications of moderate CKD following UIRI/Nx as evidenced by significant rise in serum creatinine, albuminuria, higher degree of collagen deposition, elevated expression of classic fibrotic markers, higher circulating levels of FGF-23, PTH and hepcidin. Moreover, we corroborate the osteoblastic transition of aortic smooth muscle cells and cardiomyocytes based on higher levels of osteoblastic markers namely, Cbfa-1, osteopontin, osteocalcin, and osterix. Our data confirms a viable, and consistent model of moderate CKD and its associated complications in both male and female mice. Furthermore, early evidence of osteoblastic transition of cardiovascular system in this model confirms its suitability for studying and implementing potential preventive and/or therapeutic approaches that are urgently needed in this field.

Intact mitochondrial substrate efflux is essential for prevention of tubular injury in a sex-dependent manner

The importance of healthy mitochondrial function is implicated in the prevention of chronic kidney disease (CKD) and diabetic kidney disease (DKD). Sex differences also play important roles in DKD. Our previous studies revealed that mitochondrial substrate overload (modeled by homozygous deletion of carnitine acetyl-transferase [CrAT]) in proximal tubules causes renal injury. Here, we demonstrate the importance of intact mitochondrial substrate efflux by titrating the amount of overload through the generation of a heterozygous CrAT-KO model (PT-CrATHET mouse). Intriguingly, these animals developed renal injury similarly to their homozygous counterparts. Mitochondria were structurally and functionally impaired in both sexes. Transcriptomic analyses, however, revealed striking sex differences. Male mice shut down fatty acid oxidation and several other metabolism-related pathways. Female mice had a significantly weaker transcriptional response in metabolism, but activation of inflammatory pathways was prominent. Proximal tubular cells from PT-CrATHET mice of both sexes exhibited a shift toward a more glycolytic phenotype, but female mice were still able to oxidize fatty acid-based substrates. Our results demonstrate that maintaining mitochondrial substrate metabolism balance is crucial to satisfying proximal tubular energy demand. Our findings have potentially broad implications, as both the glycolytic shift and the sexual dimorphisms discovered herein offer potentially new modalities for future interventions for treating kidney disease.

Epidemiology of chronic kidney disease: an update 2022

Chronic kidney disease is a progressive condition that affects >10% of the general population worldwide, amounting to >800 million individuals. Chronic kidney disease is more prevalent in older individuals, women, racial minorities, and in people experiencing diabetes mellitus and hypertension. Chronic kidney disease represents an especially large burden in low- and middle-income countries, which are least equipped to deal with its consequences. Chronic kidney disease has emerged as one of the leading causes of mortality worldwide, and it is one of a small number of non-communicable diseases that have shown an increase in associated deaths over the past 2 decades. The high number of affected individuals and the significant adverse impact of chronic kidney disease should prompt enhanced efforts for better prevention and treatment.

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.

Sex and Gender in Glomerular Disease

There is increasing understanding that a multifaceted interplay of sex-dependent genetic and immune dysregulation underpins the development of glomerular disorders. Regional and ethnic variations in glomerular disease incidence make delineating the effects of sex and gender on disease pathophysiology more complex, but there is a marked paucity of research in this area. This review article presents a summary of the current understanding of sex and gender in glomerular disease, highlighting the broader effects of sex and gender on autoimmunity, clinical presentations, and pathophysiology of individual glomerular diseases, as well as exploring sex, gender, and glomerular disease within a wider socioenvironmental context. It is important to specifically consider the effects of sex and gender when presenting and analyzing clinical and scientific studies on glomerular disease. Failure to do so risks promoting disparities within health care provision, neglecting opportunities to identify sex-specific biomarkers, and potentially hindering the development of sex-specific therapies.

Chronic Kidney Disease in the Transgender, Nonbinary, or Gender Diverse Person

Nephrologists are increasingly providing care to transgender, nonbinary, and gender diverse (TNBGD) individuals with chronic kidney disease. This narrative review discusses the care of TNBGD individuals from a nephrology perspective. TNBGD individuals are under-represented in the nephrology literature. TNBGD individuals are at an increased risk of adverse outcomes compared with the cisgender population including mental health, cardiovascular disease, malignancy, sexually transmitted infections, and mortality. Gender-affirming hormone therapy (GAHT) with estradiol in transfeminine individuals potentially increases the risk of venous thromboembolism and cardiovascular disease. GAHT with testosterone in transmasculine individuals potentially increases the risk of erythrocytosis and requires careful monitoring. GAHT modifies body composition and lean muscle mass, which in turn influence creatinine generation and excretion, which may impact the performance of estimated glomerular filtration rate (GFR) equations and the estimation of 24-hour urine values from spot urine albumin/protein to creatinine ratios. There are limited studies regarding TNBGD individuals with chronic kidney disease. Additional research is needed to evaluate the effects of GAHT on GFR and biomarkers of kidney function and the performance of the estimated GFR equation in TNBGD populations.

Spatially Resolved Transcriptomic Analysis of Acute Kidney Injury in a Female Murine Model

BACKGROUND

Single-cell sequencing technologies have advanced our understanding of kidney biology and disease, but the loss of spatial information in these datasets hinders our interpretation of intercellular communication networks and regional gene expression patterns. New spatial transcriptomic sequencing platforms make it possible to measure the topography of gene expression at genome depth.

METHODS

We optimized and validated a female bilateral ischemia-reperfusion injury model. Using the 10× Genomics Visium Spatial Gene Expression solution, we generated spatial maps of gene expression across the injury and repair time course, and applied two open-source computational tools, Giotto and SPOTlight, to increase resolution and measure cell-cell interaction dynamics.

RESULTS

An ischemia time of 34 minutes in a female murine model resulted in comparable injury to 22 minutes for males. We report a total of 16,856 unique genes mapped across our injury and repair time course. Giotto, a computational toolbox for spatial data analysis, enabled increased resolution mapping of genes and cell types. Using a seeded nonnegative matrix regression (SPOTlight) to deconvolute the dynamic landscape of cell-cell interactions, we found that injured proximal tubule cells were characterized by increasing macrophage and lymphocyte interactions even 6 weeks after injury, potentially reflecting the AKI to CKD transition.

CONCLUSIONS

In this transcriptomic atlas, we defined region-specific and injury-induced loss of differentiation markers and their re-expression during repair, as well as region-specific injury and repair transcriptional responses. Lastly, we created an interactive data visualization application for the scientific community to explore these results (http://humphreyslab.com/SingleCell/).

Interaction of sex and HIV infection on renal impairment: baseline evidence from the CHART cohort

OBJECTIVE

Females are more vulnerable to renal impairment (RI) in people living with HIV (PLWH), but few studies have examined sex disparity in the association of HIV serostatus with RI.

METHODS

In total, 2,101 PLWH on antiretroviral treatment (ART) and 4,202 HIV-negative people were selected and frequency matched in 1:2 ratio by sex and age categories. RI was defined as estimated glomerular filtration rate (eGFR) <90 mL/min/1.73 m². The interaction effect of sex with HIV serostatus and correlates of RI were assessed by logistic regression models.

RESULTS

In total, 78.2% of participants were males with median age 43.7 (IQR: 32.5-54.4) years. The prevalence of RI was comparable for PLWH and HIV-negative people overall (30.4% vs 30.1%) but significantly higher for HIV-positive females (37.1%) than HIV-negative females (30.1%). Multiple logistic regression identified an interaction between sex and HIV serostatus on RI (adjusted odds ratio [aOR] of the interaction term: 1.66, 95% CI: 1.23-2.26). HIV infection was significantly associated with RI in females (aOR: 1.55, 95% CI: 1.17-2.06) but not in males. Central obesity and nadir CD4 count were significantly associated with RI in HIV-infected females but not in HIV-infected males.

CONCLUSIONS

Sex seems to modify the association between HIV infection and RI, suggesting a sex-specific mechanistic pathogenesis of RI in PLWH, which warrants further investigation and intervention.

Kidney Function, Kidney Replacement Therapy, and Mortality in Men and Women

Introduction

Women are more likely to have chronic kidney disease (CKD), compared with men, yet they are less likely to receive dialysis. Whether this sex disparity, which has predominantly been observed in nephrology-referred or CKD-specific cohorts so far, has a biological root cause remains unclear.

Methods

We extracted general population data from the Stockholm CREAtinine Measurements project (SCREAM) (N = 496,097 participants, 45.5% men, 54.5% women). We used Cox regression to model male-to-female cause-specific hazard ratios (csHRs) for the competing events kidney replacement therapy (KRT, by dialysis or transplantation) and pre-KRT death, adjusted for baseline age, baseline kidney function (assessed via estimated glomerular filtration rate [eGFR] and eGFR slope), and comorbidities. Furthermore, we modeled sex-specific all-cause mortality by eGFR, again adjusted for age, eGFR slope, and comorbidities at baseline.

Results

Compared with women, men were significantly more likely to receive KRT (fully adjusted male-to-female csHR for KRT 1.41 [95% CI 1.13–1.76]) but also more likely to experience pre-KRT death (csHR 1.36 [95% CI 1.33–1.38]). Differences between men and women regarding all-cause mortality by eGFR indicated a higher mortality in men at low eGFR values.

Conclusion

Our data show that sex differences in CKD outcomes persist even after controlling for important comorbidities and kidney function at baseline. While future studies with a wider range of biological factors are warranted, these data suggest that nonbiological factors may be more important in explaining existing sex disparities in CKD progression and therapy.