Sex differences in kidney gene expression during the life cycle of F344 rats

Multi-omic and spatial analysis of mouse kidneys highlights sex-specific differences in gene regulation across the lifespan

There is a sex bias in the incidence and progression of many kidney diseases. To better understand such sexual dimorphism, we integrated data from six platforms, characterizing 76 kidney samples from 68 mice at six developmental and adult time points, creating a molecular atlas of the mouse kidney across the lifespan for both sexes. We show that proximal tubules have the most sex-biased differentially expressed genes emerging after 3 weeks of age and are associated with hormonal regulations. We reveal potential mechanisms involving both direct and indirect regulation by androgens and estrogens. Spatial profiling identifies distinct sex-biased spatial patterns in the cortex and outer stripe of the outer medulla. Additionally, older mice exhibit more aging-related gene alterations in loops of Henle, proximal tubules and collecting ducts in a sex-dependent manner. Our results enhance the understanding of spatially resolved gene expression and hormone regulation underlying kidney sexual dimorphism across the lifespan.

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.

T-cells regulate albuminuria but not hypertension, renal histology, or the medullary transcriptome in the Dahl SSCD247+/+ rat

In the current study, we took advantage of the loss of protection from hypertension in SSCD247-/- rats to characterize the pathological effects of renal T-cells in isolation from the confounding effects of elevated renal perfusion pressure. Male SSCD247-/- and SSCD247+/+ littermates were fed 4.0% NaCl (high salt) diet to induce hypertension. Blood pressure was assessed continuously throughout the time course with radiotelemetry. Urine albumin and protein excretion were assessed on the final day of high salt. Renal injury and medullary transcriptome were assessed after completion of the high salt protocol. In contrast to previous studies, mean arterial pressure was not significantly different between SSCD247-/- and SSCD247+/+ rats. Despite this lack of pressure difference, urinary albumin was significantly lower in SSCD247-/- rats than their wild-type littermates. In the outer medulla, substantially more transcriptomic changes were found to correlate with endpoint blood pressure than with the absence of presence of renal T-cells. We also demonstrated that renal histological damage was driven by elevated renal perfusion pressure rather than the presence of renal T-cells. In conclusion, using the loss of protection from hypertension in SSCD247-/- rats, we demonstrated that renal perfusion pressure has more profound pathological effects on the kidney than renal T-cells. However, renal T-cells, independently of blood pressure, modulate the progression of albuminuria.NEW & NOTEWORTHY In vivo studies in a T-cell-deficient rat model of salt-sensitive hypertension (SSCD247-/- rats) were used to evaluate the role of T-cells on the development of hypertension and renal damage. Detailed physiological and transcriptomic analysis demonstrated no difference in blood pressure between rats with (SSCD247+/+) or without (SSCD247-/-) T-cells. Despite this, albuminuria was significantly lower in SSCD247-/- rats than SSCD247+/+ rats.

Direct androgen receptor control of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility, and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA sequencing (RNA-seq) data demonstrated that sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR)-mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation, whereas analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, disease, and metabolic linkage of sexually dimorphic gene activity.

Direct androgen receptor regulation of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA-seq data demonstrated sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR) mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation while analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, and disease and metabolic linkage, of sexually dimorphic gene activity.

Kidney transcriptome and cystic kidney disease genes in zebrafish

Introduction: Polycystic kidney disease (PKD) is a condition where fluid filled cysts form on the kidney which leads to overall renal failure. Zebrafish has been recently adapted to study polycystic kidney disease, because of its powerful embryology and genetics. However, there are concerns on the conservation of this lower vertebrate in modeling polycystic kidney disease. Methods: Here, we aim to assess the molecular conservation of zebrafish by searching homologues polycystic kidney disease genes and carrying transcriptome studies in this animal. Results and Discussion: We found that out of 82 human cystic kidney disease genes, 81 have corresponding zebrafish homologs. While 75 of the genes have a single homologue, only 6 of these genes have two homologs. Comparison of the expression level of the transcripts enabled us to identify one homolog over the other homolog with >70% predominance, which would be prioritized for future experimental studies. Prompted by sexual dimorphism in human and rodent kidneys, we studied transcriptome between different sexes and noted significant differences in male vs. female zebrafish, indicating that sex dimorphism also occurs in zebrafish. Comparison between zebrafish and mouse identified 10% shared genes and 38% shared signaling pathways. String analysis revealed a cluster of genes differentially expressed in male vs. female zebrafish kidneys. In summary, this report demonstrated remarkable molecular conservation, supporting zebrafish as a useful animal model for cystic kidney disease.

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/ .

Trefoil factor 3: New highlights in chronic kidney disease research

Trefoil factor 3 (TFF3, also known as intestinal trefoil factor) is a small-molecule peptide containing a typical trefoil structure. TFF3 has several biological effects, such as wound healing, immune regulation, neuroprotection, and cell migration and proliferation promotion. Although TFF3 binding sites were identified in rat kidneys more than a decade ago, the specific effects of this small-molecule peptide on kidneys remain unclear. Until recently, much of the research on TFF3 in the kidney field has focused exclusively on its role as a biomarker. Notably, a large prospective randomized study of patients with 29 common clinical diseases revealed that chronic kidney disease (CKD) was associated with the highest serum TFF3 levels, which were 3-fold higher than in acute gastroenteritis, which had the second-highest levels. Examination of each stage of CKD revealed that urine and serum TFF3 levels significantly increased with the progression of CKD. These results suggest that the role of TFF3 in CKD needs further research. The present review summarizes the renal physiological expression, biological functions, and downstream signaling of TFF3, as well as the upstream events that lead to high expression of TFF3 in CKD.

Persistent vascular congestion in male spontaneously hypertensive rats contributes to delayed recovery of renal function following ischemia-reperfusion compared to females

Acute kidney injury (AKI) is a serious and frequent clinical complication with mortality rates up to 80%. Vascular congestion in the renal outer medulla occurs early after ischemia reperfusion (IR) injury, and congestion has been linked to worsened outcomes following IR. There is evidence implicating both male sex and preexisting hypertension as risk factors for poor outcomes following IR. The present study tested the hypothesis that male spontaneously hypertensive rats (SHR) have greater vascular congestion and impaired renal recovery following renal IR vs. female SHR and normotensive male Sprague-Dawley rats (SD). 13 wk old male and female SHR and SD were subjected to sham surgery or 30 minutes of warm bilateral ischemia followed by reperfusion. Rats were euthanized 24 hours or 7 days post-IR. IR increased renal injury in all groups vs. sham controls at 24 hours. At 7 days post-IR, injury remained elevated only in male SHR. Histological examination of SD and SHR kidneys 24 hours post-IR showed vascular congestion in males and females. Vascular congestion was sustained only in male SHR 7 days post-IR. To assess the role of vascular congestion on impaired recovery following IR, additional male and female SHR were pretreated with heparin (200 U/kg) prior to IR. Heparin pre-treatment reduced IR-induced congestion and improved renal function in male SHR 7 days post-IR. Interestingly, preventing increases in BP in male SHR did not alter sustained vascular congestion. Our data demonstrate that IR-induced vascular congestion is a major driving factor for impaired renal recovery in male SHR.

Matters of the heart: Cellular sex differences

Nearly all cardiovascular diseases show sexual dimorphisms in prevalence, presentation, and outcomes. Until recently, most clinical trials were carried out in males, and many animal studies either failed to identify the sex of the animals or combined data obtained from males and females. Cellular sex in the heart is relatively understudied and many studies fail to report the sex of the cells used for in vitro experiments. Moreover, in the small number of studies in which sex is reported, most of those studies use male cells. The observation that cells from males and females are inherently different is becoming increasingly clear - either due to acquired differences from hormones and other factors or due to intrinsic differences in genotype (XX or XY). Because of the likely contribution of cellular sex differences in cardiac health and disease, here, we explore differences in mammalian male and female cells in the heart, including the less-studied non-myocyte cell populations. We discuss how the heart's microenvironment impacts male and female cellular phenotypes and vice versa, including how secretory profiles are dependent on cellular sex, and how hormones contribute to sexually dimorphic phenotypes and cellular functions. Intracellular mechanisms that contribute to sex differences, including gene expression and epigenetic remodeling, are also described. Recent single-cell sequencing studies have revealed unexpected sex differences in the composition of cell types in the heart which we discuss. Finally, future recommendations for considering cellular sex differences in the design of bioengineered in vitro disease models of the heart are provided.

S-Methyl-L-Ergothioneine to L-Ergothioneine Ratio in Urine Is a Marker of Cystine Lithiasis in a Cystinuria Mouse Model

Cystinuria, a rare inherited aminoaciduria condition, is characterized by the hyperexcretion of cystine, ornithine, lysine, and arginine. Its main clinical manifestation is cystine stone formation in the urinary tract, being responsible for 1–2% total and 6–8% pediatric lithiasis. Cystinuria patients suffer from recurrent lithiasic episodes that might end in surgical interventions, progressive renal functional deterioration, and kidney loss. Cystinuria is monitored for the presence of urinary cystine stones by crystalluria, imaging techniques or urinary cystine capacity; all with limited predicting capabilities. We analyzed blood and urine levels of the natural antioxidant L-ergothioneine in a Type B cystinuria mouse model, and urine levels of its metabolic product S-methyl-L-ergothioneine, in both male and female mice at two different ages and with different lithiasic phenotype. Urinary levels of S-methyl-L-ergothioneine showed differences related to age, gender and lithiasic phenotype. Once normalized by L-ergothioneine to account for interindividual differences, the S-methyl-L-ergothioneine to L-ergothioneine urinary ratio discriminated between cystine lithiasic phenotypes. Urine S-methyl-L-ergothioneine to L-ergothioneine ratio could be easily determined in urine and, as being capable of discriminating between cystine lithiasis phenotypes, it could be used as a lithiasis biomarker in cystinuria patient management.

Maternal obesity (MO) programs morphological changes in aged rat offspring small intestine in a sex dependent manner: Effects of maternal resveratrol supplementation

Maternal obesity (MO) leads to offspring metabolic problems. The mechanisms involved are multifactorial. The small intestine plays an important role in the absorption of nutrients and is modified as we age. Few studies have explored MO programming effects on offspring (F1) small intestine morphology. The aim of this study was to investigate MO effects on old adult F1 intestinal morphology, and whether any F1 intestinal changes due to MO were modified by maternal resveratrol supplementation. From weaning throughout pregnancy and lactation, female Wistar rats (F0) ate standard chow (controls, C: 5%-fat) or high-fat diet (MO: 25%-fat). One month before mating at postnatal day (PND) 120 through lactation half of each group received 20 mg/kg/day of resveratrol orally (Cres or MOres). After weaning F1 were fed with chow diet until the end of the study at PND 650. Body weight, percent of fat, glucose, cholesterol and triglyceride serum concentrations were determined. F1 small intestinal samples were collected for histological analysis. Male F1 body weight was higher in MO and MOres compared with C and Cres. Female F1 body weight and percent of fat was higher in MO than C and MOres. Triglyceride concentrations were higher in MO and MOres male F1 compared with C and Cres. There were no differences among groups in female triglyceride concentrations. Male F1 duodenal villus height was smaller in MO compared with MOres. Female F1 duodenal and jejunal crypt depth was smaller in MO compared with C and was greater compared with MOres. Female F1 villus height in jejunum was greater in MO compared with MOres. In conclusion, exposure to the developmental challenge of MO changed the aged F1 intestinal morphological and metabolic profiles. Maternal resveratrol supplementation ameliorated these effects in an F1 sex dependent manner.

The role of sex-differentiated variations in stress hormones, antioxidants, and neuroimmune responses in relation to social interaction impairment in a rodent model of autism

Males are more likely to develop autism as a neurodevelopmental disorder than females, but the mechanisms underlying male susceptibility are not fully understood. In this paper, we used a well-characterized propionic acid (PPA) rodent model of autism to study sex differences in stress hormones, antioxidants' status, and the neuroimmune response that may contribute to the preponderance of autism in males. Sprague Dawley rats of both sexes were divided into a saline-treated group as controls and PPA-treated groups, receiving 250 mg/kg of PPA per day for three days. Animals' social behavior was examined using the three-chamber social test. Hormones (ACTH, corticosterone, melatonin, and oxytocin), oxidative stress biomarkers (glutathione, glutathione-S-transferase, and ascorbic acid), and cytokines (IL-6, IL-1α, IL-10, and IFNγ) were measured in the brain tissue of all the animals. The results showed a sex dimorphic social response to PPA treatment, where males were more susceptible to the PPA treatment and exhibited a significant reduction in social behavior with no effects observed in females. Also, sex differences were observed in the levels of hormones, antioxidants, and cytokines. Female rats showed significantly higher corticosterone and lower oxytocin, antioxidants, and cytokine levels than males. The PPA treatment later modulated these baseline differences. Our study indicates that the behavioral manifestation of autism in PPA-treated males and not females could be linked to neural biochemical differences between the sexes at baseline, which might play a protective role in females. Our results can contribute to early intervention strategies and treatments used to control autism, an increasingly prevalent disorder.

Activation of G protein-coupled estrogen receptor 1 ameliorates proximal tubular injury and proteinuria in Dahl salt-sensitive female rats

Recent evidence indicates a crucial role for G protein-coupled estrogen receptor 1 (GPER1) in the maintenance of cardiovascular and kidney health in females. The current study tested whether GPER1 activation ameliorates hypertension and kidney damage in female Dahl salt-sensitive (SS) rats fed a high-salt (HS) diet. Adult female rats were implanted with telemetry transmitters for monitoring blood pressure and osmotic minipumps releasing G1 (selective GPER1 agonist, 400 μg/kg/day ip) or vehicle. Two weeks after pump implantation, rats were shifted from a normal-salt (NS) diet (0.4% NaCl) to a matched HS diet (4.0% NaCl) for 2 wk. Twenty-four hour urine samples were collected during both diet periods and urinary markers of kidney injury were assessed. Histological assessment of kidney injury was conducted after the 2-wk HS diet period. Compared with values during the NS diet, 24-h mean arterial pressure markedly increased in response to HS, reaching similar values in vehicle-treated and G1-treated rats. HS also significantly increased urinary excretion of protein, albumin, nephrin (podocyte damage marker), and KIM-1 (proximal tubule injury marker) in vehicle-treated rats. Importantly, G1 treatment prevented the HS-induced proteinuria, albuminuria, and increase in KIM-1 excretion but not nephrinuria. Histological analysis revealed that HS-induced glomerular damage did not differ between groups. However, G1 treatment preserved proximal tubule brush-border integrity in HS-fed rats. Collectively, our data suggest that GPER1 activation protects against HS-induced proteinuria and albuminuria in female Dahl SS rats by preserving proximal tubule brush-border integrity in a blood pressure-independent manner.

Time Course of Renal Transcriptomics after Subchronic Exposure to Ochratoxin A in Fisher Rats

The mycotoxin ochratoxin A (OTA) is a potent nephrocarcinogen, mainly in male rats. The aim of this study was to determine the time course of gene expression (GeneChip® Rat Gene 2.0 ST Array, Affymetrix) in kidney samples from male and female F344 rats, treated daily (p.o) with 0.50 mg/kg b.w. (body weight) of OTA for 7 or 21 days, and evaluate if there were differences between both sexes. After OTA treatment, there was an evolution of gene expression in the kidney over time, with more differentially expressed genes (DEG) at 21 days. The gene expression time course was different between sexes with respect to the number of DEG and the direction of expression (up or down): the female response was progressive and consistent over time, whereas males had a different early response with more DEG, most of them up-regulated. The statistically most significant DEG corresponded to metabolism enzymes (Akr1b7, Akr1c2, Adh6 down-regulated in females; Cyp2c11, Dhrs7, Cyp2d1, Cyp2d5 down-regulated in males) or transporters (Slc17a9 down-regulated in females; Slco1a1 (OATP-1) and Slc51b and Slc22a22 (OAT) down-regulated in males). Some of these genes had also a basal sex difference and were over-expressed in males or females with respect to the other sex.

Targeting the Renin-Angiotensin-Aldosterone System to Prevent Hypertension and Kidney Disease of Developmental Origins

The renin-angiotensin-aldosterone system (RAAS) is implicated in hypertension and kidney disease. The developing kidney can be programmed by various early-life insults by so-called renal programming, resulting in hypertension and kidney disease in adulthood. This theory is known as developmental origins of health and disease (DOHaD). Conversely, early RAAS-based interventions could reverse program processes to prevent a disease from occurring by so-called reprogramming. In the current review, we mainly summarize (1) the current knowledge on the RAAS implicated in renal programming; (2) current evidence supporting the connections between the aberrant RAAS and other mechanisms behind renal programming, such as oxidative stress, nitric oxide deficiency, epigenetic regulation, and gut microbiota dysbiosis; and (3) an overview of how RAAS-based reprogramming interventions may prevent hypertension and kidney disease of developmental origins. To accelerate the transition of RAAS-based interventions for prevention of hypertension and kidney disease, an extended comprehension of the RAAS implicated in renal programming is needed, as well as a greater focus on further clinical translation.

Estrogen and estrogen receptors in kidney diseases

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

Hepatic Transcript Profiles of Cytochrome P450 Genes Predict Sex Differences in Drug Metabolism

Safety assessments of new drug candidates are an important part of the drug development and approval process. Often, possible sex-associated susceptibilities are not adequately addressed, and better assessment tools are needed. We hypothesized that hepatic transcript profiles of cytochrome P450 (P450) enzymes can be used to predict sex-associated differences in drug metabolism and possible adverse events. Comprehensive hepatic transcript profiles were generated for F344 rats of both sexes at nine ages, from 2 weeks (preweaning) to 104 weeks (elderly). Large differences in the transcript profiles of 29 drug metabolizing enzymes and transporters were found between adult males and females (8-52 weeks). Using the PharmaPendium data base, 41 drugs were found to be metabolized by one or two P450 enzymes encoded by sexually dimorphic mRNAs and thus were candidates for evaluation of possible sexually dimorphic metabolism and/or toxicities. Suspension cultures of primary hepatocytes from three male and three female adult rats (10-13 weeks old) were used to evaluate the metabolism of 11 drugs predicted to have sexually dimorphic metabolism. The pharmacokinetics of the drug or its metabolite was analyzed by liquid chromatography/tandem mass spectrometry using multiple reaction monitoring. Of those drugs with adequate metabolism, the predicted significant sex-different metabolism was found for six of seven drugs, with half-lives 37%-400% longer in female hepatocytes than in male hepatocytes. Thus, in this rat model, transcript profiles may allow identification of potential sex-related differences in drug metabolism. SIGNIFICANCE STATEMENT: The present study showed that sex-different expression of genes coding for drug metabolizing enzymes, specifically cytochrome P450s, could be used to predict sex-different drug metabolism and, thus, provide a new tool for protecting susceptible subpopulations from possible adverse drug events.

Greater T Regulatory Cells in Females Attenuate DOCA-Salt-Induced Increases in Blood Pressure Versus Males

Hypertension is the most common risk factor for cardiovascular disease, causing over 18 million deaths a year. Although the mechanisms controlling blood pressure (BP) in either sex remain largely unknown, T cells play a critical role in the development of hypertension. Further evidence supports a role for the immune system in contributing to sex differences in hypertension. The goal of the current study was to first, determine the impact of sex on the renal T-cell profiles in DOCA-salt hypertensive males and females and second, test the hypothesis that greater numbers of T regulatory cells (Tregs) in females protect against DOCA-salt-induced increases in BP and kidney injury. Male rats displayed greater increases in BP than females following 3 weeks of DOCA-salt treatment, although increases in renal injury were comparable between the sexes. DOCA-salt treatment resulted in an increase in proinflammatory T cells in both sexes; however, females had more anti-inflammatory Tregs than males. Additional male and female DOCA-salt rats were treated with anti-CD25 to decrease Tregs. Decreasing Tregs significantly increased BP only in females, thereby abolishing the sex difference in the BP response to DOCA-salt. This data supports the hypothesis that Tregs protect against the development of hypertension and are particularly important for the control of BP in females.

Sexual dimorphism in glutathione metabolism and glutathione-dependent responses

Glutathione is the most abundant intracellular low molecular weight thiol in cells and tissues, and plays an essential role in numerous cellular processes, including antioxidant defenses, the regulation of protein function, protein localization and stability, DNA synthesis, gene expression, cell proliferation, and cell signaling. Sexual dimorphisms in glutathione biology, metabolism and glutathione-dependent signaling have been reported for a broad range of biological processes, spanning the human lifespan from early development to aging. Sex-depended differences with regard to glutathione and its biology have also been reported for a number of human pathologies and diseases such as neurodegeneration, cardiovascular diseases and metabolic disorders. Here we review the latest literature in this field and discuss the potential impact of these sexual dimorphisms in glutathione biology on human health and diseases.

Sex specific associations in genome wide association analysis of renal cell carcinoma

Renal cell carcinoma (RCC) has an undisputed genetic component and a stable 2:1 male to female sex ratio in its incidence across populations, suggesting possible sexual dimorphism in its genetic susceptibility. We conducted the first sex-specific genome-wide association analysis of RCC for men (3227 cases, 4916 controls) and women (1992 cases, 3095 controls) of European ancestry from two RCC genome-wide scans and replicated the top findings using an additional series of men (2261 cases, 5852 controls) and women (1399 cases, 1575 controls) from two independent cohorts of European origin. Our study confirmed sex-specific associations for two known RCC risk loci at 14q24.2 (DPF3) and 2p21(EPAS1). We also identified two additional suggestive male-specific loci at 6q24.3 (SAMD5, male odds ratio (ORmale) = 0.83 [95% CI = 0.78-0.89], Pmale = 1.71 × 10-8 compared with female odds ratio (ORfemale) = 0.98 [95% CI = 0.90-1.07], Pfemale = 0.68) and 12q23.3 (intergenic, ORmale = 0.75 [95% CI = 0.68-0.83], Pmale = 1.59 × 10-8 compared with ORfemale = 0.93 [95% CI = 0.82-1.06], Pfemale = 0.21) that attained genome-wide significance in the joint meta-analysis. Herein, we provide evidence of sex-specific associations in RCC genetic susceptibility and advocate the necessity of larger genetic and genomic studies to unravel the endogenous causes of sex bias in sexually dimorphic traits and diseases like RCC.

Increase of cortisol levels after temperature stress activates dmrt1a causing female-to-male sex reversal and reduced germ cell number in medaka

In vertebrates, there is accumulating evidence that environmental factors as triggers for sex determination and genetic sex determination are not two opposing alternatives but that a continuum of mechanisms bridge those extremes. One prominent example is the model fish species Oryzias latipes which has a stable XX/XY genetic sex determination system, but still responds to environmental cues, where high temperatures lead to female-to-male sex reversal. However, the mechanisms behind are still unknown. We show that high temperatures increase primordial germ cells (PGC) numbers before they reach the genital ridge, which, in turn, regulates the germ cell proliferation. Complete ablation of PGCs led to XX males with germ cell less testis, whereas experimentally increased PGC numbers did not reverse XY genotypes to female. For the underlying molecular mechanism, we provide support for the explanation that activation of the dmrt1a gene by cortisol during early development of XX embryos enables this autosomal gene to take over the role of the male determining Y-chromosomal dmrt1bY.

Regulation of Nitric Oxide Production in the Developmental Programming of Hypertension and Kidney Disease

Development of the kidney can be altered in response to adverse environments leading to renal programming and increased vulnerability to the development of hypertension and kidney disease in adulthood. By contrast, reprogramming is a strategy shifting therapeutic intervention from adulthood to early life to reverse the programming processes. Nitric oxide (NO) is a key mediator of renal physiology and blood pressure regulation. NO deficiency is a common mechanism underlying renal programming, while early-life NO-targeting interventions may serve as reprogramming strategies to prevent the development of hypertension and kidney disease. This review will first summarize the regulation of NO in the kidney. We also address human and animal data supporting the link between NO system and developmental programming of hypertension and kidney disease. This will be followed by the links between NO deficiency and the common mechanisms of renal programming, including the oxidative stress, renin–angiotensin system, nutrient-sensing signals, and sex differences. Recent data from animal studies have suggested that interventions targeting the NO pathway could be reprogramming strategies to prevent the development of hypertension and kidney disease. Further clinical studies are required to bridge the gap between animal models and clinical trials in order to develop ideal NO-targeting reprogramming strategies and to be able to have a lifelong impact, with profound savings in the global burden of hypertension and kidney disease.

Sex-biased gene expression in the frontal cortex of common marmosets (Callithrix jacchus) and potential behavioral correlates

INTRODUCTION

The common marmoset (Callithrix jacchus), a small New World monkey, has been widely used as a biological model in neuroscience to elucidate neural circuits involved in cognition and to understand brain dysfunction in neuropsychiatric disorders. In this regard, the availability of gene expression data derived from next-generation sequencing (NGS) technologies represents an opportunity for a molecular contextualization. Sexual dimorphism account for differences in diseases prevalence and prognosis. Here, we explore sex differences on frontal cortex of gene expression in common marmoset's adults.

METHODS

Gene expression profiles in six different tissues (cerebellum, frontal cortex, liver, heart, and kidney) were analyzed in male and female marmosets. To emphasize the translational value of this species for behavioral studies, we focused on sex-biased gene expression from the frontal cortex of male and female in common marmosets and compared to humans (Homo sapiens).

RESULTS

In this study, we found that frontal cortex genes whose expression is male-biased are conserved between marmosets and humans and enriched with "house-keeping" functions. On the other hand, female-biased genes are more related to neural plasticity functions involved in remodeling of synaptic circuits, stress cascades, and visual behavior. Additionally, we developed and made available an application-the CajaDB-to provide a friendly interface for genomic, expression, and alternative splicing data of marmosets together with a series of functionalities that allow the exploration of these data. CajaDB is available at cajadb.neuro.ufrn.br.

CONCLUSION

The data point to differences in gene expression of male and female common marmosets in all tissues analyzed. In frontal cortex, female-biased expression in synaptic plasticity, stress, and visual processing might be linked to biological and behavioral mechanisms of this sex. Due to the limited sample size, the data here analyzed are for exploratory purposes.

Sex-dependent gene expression after ochratoxin A insult in F344 rat kidney

Ochratoxin A (OTA) is a potent rodent nephrocarcinogen; being males more sensitive than females. The objective was to study the response between sexes at gene expression level (whole genome transcriptomics) in kidneys of F344 rats treated with 0.21 or 0.50 mg/kg bw OTA for 21 days. DNA methylation analysis of selected genes was also studied (MALDI-TOF mass spectrometry). OTA-induced response was dose-dependent in males and females, although clearer in males. Females showed a higher number of altered genes than males but functional analysis revealed a higher number of significantly enriched toxicity lists in 0.21 mg/kg treated males. OTA modulated damage, signaling and metabolism related lists, as well as inflammation, proliferation and oxidative stress in both sexes. Eleven toxicity lists (damage, fibrosis, cell signaling and metabolism) were exclusively altered in males while renal safety biomarker and biogenesis of mitochondria lists were exclusively enriched in females. A high number of lists (39) were significantly enriched in both sexes. However, they contained many sex-biased OTA-modulated genes, mainly phase I and II, transporters and nuclear receptors, but also others related to cell proliferation/apoptosis. No biologically relevant changes were observed in the methylation of selected genes.

Evaluating mice lacking serum carboxylesterase as a behavioral model for nerve agent intoxication

Mice and other rodents are typically utilized for chemical warfare nerve agent research. Rodents have large amounts of carboxylesterase in their blood, while humans do not. Carboxylesterase nonspecifically binds to and detoxifies nerve agent. The presence of this natural bioscavenger makes mice and other rodents poor models for studies identifying therapeutics to treat humans exposed to nerve agents. To obviate this problem, a serum carboxylesterase knockout (Es1 KO) mouse was created. In this study, Es1 KO and wild type (WT) mice were assessed for differences in gene expression, nerve agent (soman; GD) median lethal dose (MLD) values, and behavior prior to and following nerve agent exposure. No expression differences were detected between Es1 KO and WT mice in more than 34 000 mouse genes tested. There was a significant difference between Es1 KO and WT mice in MLD values, as the MLD for GD-exposed WT mice was significantly higher than the MLD for GD-exposed Es1 KO mice. Behavioral assessments of Es1 KO and WT mice included an open field test, a zero maze, a Barnes maze, and a sucrose preference test (SPT). While sex differences were observed in various measures of these tests, overall, Es1 KO mice behaved similarly to WT mice. The two genotypes also showed virtually identical neuropathological changes following GD exposure. Es1 KO mice appear to have an enhanced susceptibility to GD toxicity while retaining all other behavioral and physiological responses to this nerve agent, making the Es1 KO mouse a more human-like model for nerve agent research.

Sex differences in the excretion levels of traditional and novel urinary biomarkers of nephrotoxicity in rats

Urinary biomarkers have been used widely in preclinical toxicity studies to detect dysfunctions and injuries of the kidney caused by drugs under development. While they have been well studied for evaluating nephrotoxicity, knowledge of sex differences in excretion levels of urinary biomarkers remains inadequate. We conducted experiments focused on effects of endogenous sex hormones on urinary biomarkers using intact and castrated male and female rats. Comparisons of the urinary biomarker excretion levels between intact male and female rats at 5, 7, 9 and 12 weeks of age revealed higher excretion levels of leucine aminopeptidase (LAP), γ-glutamyl transpeptidase (γGTP), total protein, liver-type fatty acid-binding protein (L-FABP), cystatin C (Cys-C) and β2-microglobulin (β2-MG), and lower excretion level of kidney injury molecule 1 (Kim-1), in male rats as compared to female rats. Orchidectomized male rats showed lower urinary excretion levels of alkaline phosphatase (ALP), LAP, γGTP, N-acetyl-β-D-glucosaminidase (NAG), glucose, total protein, L-FABP, Cys-C, β2-MG and neutrophil gelatinase-associated lipocalin (NGAL), and higher urinary excretion levels of clusterin (CLU) and Kim-1, than sham-operated male rats. On the other hand, no significant differences in the urinary biomarker excretion levels excluding ALP were observed between ovariectomized and sham-operated female rats. In the present study, we demonstrated the existence of sex differences in excretion levels of urinary biomarkers that are universally used in preclinical toxicity studies, and also that these differences, especially in relation to the urinary excretions of ALP, LAP, γGTP, total protein, L-FABP, Cys-C, and β2-MG, may closely relate to the endogenous testosterone.

Developmental Origins of Chronic Kidney Disease: Should We Focus on Early Life?

Chronic kidney disease (CKD) is becoming a global burden, despite recent advances in management. CKD can begin in early life by so-called "developmental programming" or "developmental origins of health and disease" (DOHaD). Early-life insults cause structural and functional changes in the developing kidney, which is called renal programming. Epidemiological and experimental evidence supports the proposition that early-life adverse events lead to renal programming and make subjects vulnerable to developing CKD and its comorbidities in later life. In addition to low nephron endowment, several mechanisms have been proposed for renal programming. The DOHaD concept opens a new window to offset the programming process in early life to prevent the development of adult kidney disease, namely reprogramming. Here, we review the key themes on the developmental origins of CKD. We have particularly focused on the following areas: evidence from human studies support fetal programming of kidney disease; insight from animal models of renal programming; hypothetical mechanisms of renal programming; alterations of renal transcriptome in response to early-life insults; and the application of reprogramming interventions to prevent the programming of kidney disease.

Sex differences in renal transcriptome and programmed hypertension in offspring exposed to prenatal dexamethasone

Glucocorticoids, predominantly dexamethasone (DEX), are widely used to reduce the risk of prematurity-related chronic lung disease. However, prenatal DEX treatment links to adverse effects in later life, including hypertension. Given that sex differences exist in the blood pressure (BP) control, and that renal transcriptome is sex-specific, thus we intended to elucidate whether prenatal DEX-induced programmed hypertension is in a sex-specific manner and identify candidate genes and pathways using the whole-genome RNA next-generation sequencing (NGS) approach. Offspring were assigned to 4 groups (n=7-8/group): male control (MC), female control (FC), male DEX (MD), and female DEX (FD). Dexamethasone (0.1mg/kg body weight) or vehicle was intraperitoneally administered to pregnant SD rats from gestational day 16-22, to construct a DEX model. Rats were killed at 16weeks of age. Prenatal DEX induced sex-specific increase in BPs in male but not female adult offspring. Prenatal DEX elicited renal programming in a sex-specific fashion as demonstrated by 8 and 18 DEGs in male and female offspring, respectively. Among them, two genes, Hbb and Hba-a2, were shared. The resistance of female offspring to prenatal DEX-induced programmed hypertension is related to a lower Agt expression. Prenatal DEX induced programmed hypertension in adult male but not female offspring, which was related to renal programming affecting sex-biased genes and the RAS. Early identification of sex-specific underlying mechanisms could provide novel deprogramming strategy to reach maximal optimization in both sexes.

Gene expression kinetics of renal transporters induced by ochratoxin A in male and female F344 rats

Ochratoxin A (OTA) is a mycotoxin that contaminates foodstuffs. The most relevant concern is its high kidney carcinogenicity in male rats and its unclear mechanism of action. It has been hypothesized that variations in transport mechanisms in kidney cells may be the reason of different sex-dependent sensitivities towards OTA. The aim of this study was to analyze, by RT- qPCR, renal transporters expression in 15-week-old male (M) and female (F) F344 rats at basal level and after single oral OTA administration (0.50 mg/kg bw). Temporal profiles (24h, 48h, 72h, 96h, 1 and 2 months) were studied per sex and transporter. The reference gene for all comparisons was Ppia. At basal level, sex differences were confirmed for Oatp1, Bcrp (M>F) and Oat2 (F>M). OTA tended to inhibit the expression of almost all transporters in both sexes, but clearly induced the expression of Oat2 in males. Regarding time profiles, the highest sex differences involved Oat (Slc22) transporters: Oat2, Oat3 and Oat5 expression showed a significant increase in males (24h) while Oat1, Oat2 and Oat5 level decreased in females (48h). Overall, basal sex differences in F344 rats and the specific sex-dependent response to OTA of Oat2 might contribute to high kidney damage in male rats.

Aliskiren Administration during Early Postnatal Life Sex-Specifically Alleviates Hypertension Programmed by Maternal High Fructose Consumption

Key points summary

Maternal high-fructose (HF) induces programmed hypertension in adult offspring.

Early aliskiren administration prevents HF-induced hypertension in both sexes of adult offspring.

HF regulates RAS components in the offspring kidney in a sex-specific manner.

HF alters renal transcriptome, with female offspring being more sensitive.

Deprogramming strategy to prevent hypertension might be sex-specific.

Background: Maternal high fructose (HF) intake induced renal programming and hypertension in male adult offspring. We examined whether maternal HF intake causes programmed hypertension and whether aliskiren administration confers protection against the process in a sex-specific manner, with a focus on the transcriptome changes in the kidney using next-generation RNA sequencing (NGS) technology and renin-angiotensin system (RAS).

Methods: Pregnant Sprague—Dawley rats received regular chow or chow supplemented with 60% fructose throughout pregnancy and lactation. Offspring were assigned to six groups: male control, male HF (MHF), MHF+Aliskiren, female control, female HF (FHF), and FHF+Aliskiren. Oral aliskiren 10 mg/kg/day was administered via gastric gavage between 2 and 4 weeks of age. Rats were sacrificed at 12 weeks of age.

Results: Maternal HF intake induced programmed hypertension in 12-week-old offspring of both sexes. HF regulated renal transcriptome and RAS components in the offspring kidney in a sex-specific manner. Aliskiren administration prevented HF-induced programmed hypertension in both sexes of adult offspring. Aliskiren administration increased ACE2 and MAS protein levels in female kidneys exposed to maternal HF intake.

Conclusion: Maternal HF induced programmed hypertension in both sexes of adult offspring, which was sex-specifically mitigated by early aliskiren administration. Better understanding of the sex-dependent mechanisms that underlie maternal HF-induced renal programming will help develop a novel sex-specific strategy to prevent programmed hypertension.

The Food and Drug Administration Office of Women's Health: Impact of Science on Regulatory Policy: An Update

The U.S. Food and Drug Administration Office of Women's Health (FDA OWH) has supported women's health research for ∼20 years, funding more than 300 studies on women's health issues, including research on diseases/conditions that disproportionately affect women in addition to the evaluation of sex differences in the performance of and response to medical products. These important women's health issues are studied from a regulatory perspective, with a focus on improving and optimizing medical product development and the evaluation of product safety and efficacy in women. These findings have influenced industry direction, labeling, product discontinuation, safety notices, and clinical practice. In addition, OWH-funded research has addressed gaps in the knowledge about diseases and medical conditions that impact women across the life span such as cardiovascular disease, pregnancy, menopause, osteoporosis, and the safe use of numerous medical products.

Gender Specific Mutation Incidence and Survival Associations in Clear Cell Renal Cell Carcinoma (CCRCC)

Renal cell carcinoma (RCC) is diagnosed in >200,000 individuals worldwide each year, accounting for ~2% of all cancers, but the spread of this disease amongst genders is distinctly uneven. In the U.S. the male:female incidence ratio is approximately 2:1. A potential hypothesis is mutation spectra may differ between tumors dependent upon the gender of the patient, such as mutations of X chromosome encoded genes being more prevalent in male-derived tumors. Combined analysis of three recent large-scale clear cell renal cell carcinoma (CCRCC) mutation sequencing projects identified a significantly increased mutation frequency of PBRM1 and the X chromosome encoded KDM5C in tumors from male patients and BAP1 in tumors from female patients. Mutation of BAP1 had previously been significantly associated with poorer overall survival; however, when stratified by gender, mutation of BAP1 only significantly affected overall survival in female patients. Mutation of chromatin remodeling genes alters gene regulation, but the overall effect of these alterations may also be modified by the presence of other gender specific factors. Thus, the combination of gender and mutation of a specific gene, such as BAP1, may have implications not only for prognosis but also for understanding the role of chromatin remodeling gene mutations in kidney cancer progression.

We know very little about the subjective effects of drugs in females

Pharmaceutical companies assessing the nervous system effects of candidate therapeutics often use a behavioral assay in rodents that assesses the drug's subjective (internal stimulus) effects. Variants of this so-called "drug discrimination task" have also been widely used by basic scientist for more than 50 years to study the receptor actions of a host of ligands related to disease states and neuropathologies. Notably, most published research with this task has used male rats or mice. This situation is unfortunate and severely limits the utility of the research, given the well-documented differences between women and men on drug efficacy and safety, as well as known sex differences in the neural and behavioral effects of drugs. In this Viewpoint, we highlight the need for basic researchers, as well as pharmaceutical scientists, to include females in drug discrimination studies in a manner that allows detection and interpretation of potential sex differences.

Expression of drug transporters in human kidney: impact of sex, age, and ethnicity

Background

Differences in expression of drug transporters in human kidney contribute to changes in pharmacokinetics and toxicokinetics of a variety of drug compounds. The basal expression levels of genes involved in drug transport processes in the kidney introduces differences in bioavailability, distribution, and clearance of drugs, possibly influencing drug efficacy and adverse reactions. Sex differences in gene expression of transporters are a key cause of differences in sex-dependent pharmacokinetics, which may characterize many drugs and contribute to individual differences in drug efficacy and toxicity. Therefore, evaluating the expression of drug transporters in normal human kidneys is important to better understand differences in drug bioavailability, distribution, and clearance of drugs in humans. Other factors such as age and ethnicity may also contribute to individual differences in gene expression of drug transporters in the human kidney.

Methods

Quantitative real-time PCR (QRT-PCR) was performed to determine the gene expression of 30 drug transporters in 95 age-matched normal human kidney tissues. Multiple Student’s t-tests (Sidak-Bonferroni correction) and two-way ANOVA (Bonferroni correction) analyses were used to determine statistically significant differences.

Results

In the 30 transporter genes examined, sex, ethnicity, and age differences in gene expression were exhibited in normal human kidney tissue. These changes in expression were not found to be differentially significant. However, sex-age and sex-ethnicity interactions were found to be statistically significant. For sex-age interactions, SCL22A12 was found to be significantly higher expressed in females <50 years compared to males <50 years. Expression levels of SLC22A2, SLC22A12, SLC6A16, and ABCB6 were significantly higher in females <50 years compared to females ≥50 years. In sex-ethnicity interactions, expression levels of ATP7B and KCNJ8 were found to be significantly higher in African American females compared to European American females. Also, the expression of SLC31A2 was significantly higher in European American males compared to European American females.

Conclusions

Sex, age, and ethnic differences impacted the expression of drug transporters in normal human kidneys, which suggests that the analysis of gene expression of drug transporters will aid in improving the usage/dosage of drug therapies influencing personalized medicine and susceptibility to adverse drug reactions.

Age and sex differences in kidney microRNA expression during the life span of F344 rats

Background

Growing evidence suggests that epigenetic mechanisms of gene regulation may play a role in susceptibilities to specific toxicities and adverse drug reactions. MiRNAs in particular have been shown to be important regulators in cancer and other diseases and show promise as predictive biomarkers for diagnosis and prognosis. In this study, we characterized the global kidney miRNA expression profile in untreated male and female F344 rats throughout the life span. These findings were correlated with sex-specific susceptibilities to adverse renal events, such as male-biased renal fibrosis and inflammation in old age.

Methods

Kidney miRNA expression was examined in F344 rats at 2, 5, 6, 8, 15, 21, 78, and 104 weeks of age in both sexes using Agilent miRNA microarrays. Differential expression was determined using filtering criteria of ≥1.5 fold change and ANOVA or pairwise t-test (FDR <5%) to determine significant age and sex effects, respectively. Pathway analysis software was used to investigate the possible roles of these target genes in age- and sex-specific differences.

Results

Three hundred eleven miRNAs were found to be expressed in at least one age and sex. Filtering criteria revealed 174 differentially expressed miRNAs in the kidney; 173 and 34 miRNAs exhibiting age and sex effects, respectively. Principal component analysis revealed age effects predominated over sex effects, with 2-week miRNA expression being much different from other ages. No significant sexually dimorphic miRNA expression was observed from 5 to 8 weeks, while the most differential expression (13 miRNAs) was observed at 21 weeks. Potential target genes of these differentially expressed miRNAs were identified.

Conclusions

The expression of 56% of detected renal miRNAs was found to vary significantly with age and/or sex during the life span of F344 rats. Pathway analysis suggested that 2-week-expressed miRNAs may be related to organ and cellular development and proliferation pathways. Male-biased miRNA expression at older ages correlated with male-biased renal fibrosis and mononuclear cell infiltration. These miRNAs showed high representation in renal inflammation and nephritis pathways, and included miR-214, miR-130b, miR-150, miR-223, miR-142-5p, miR-185, and miR-296*. Analysis of kidney miRNA expression throughout the rat life span will improve the use of current and future renal biomarkers and inform our assessments of kidney injury and disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-014-0019-1) contains supplementary material, which is available to authorized users.

Sexual dimorphism in the expression of mitochondria-related genes in rat heart at different ages

Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Moreover, sex and age are considered major risk factors in the development of CVDs. Mitochondria are vital for normal cardiac function, and regulation of mitochondrial structure and function may impact susceptibility to CVD. To identify potential role of mitochondria in sex-related differences in susceptibility to CVD, we analyzed the basal expression levels of mitochondria-related genes in the hearts of male and female rats. Whole genome expression profiling was performed in the hearts of young (8-week), adult (21-week), and old (78-week) male and female Fischer 344 rats and the expression of 670 unique genes related to various mitochondrial functions was analyzed. A significant (p<0.05) sexual dimorphism in expression levels of 46, 114, and 41 genes was observed in young, adult and old rats, respectively. Gene Ontology analysis revealed the influence of sex on various biological pathways related to cardiac energy metabolism at different ages. The expression of genes involved in fatty acid metabolism was significantly different between the sexes in young and adult rat hearts. Adult male rats also showed higher expression of genes associated with the pyruvate dehydrogenase complex compared to females. In young and adult hearts, sexual dimorphism was not noted in genes encoding oxidative phosphorylation. In old rats, however, a majority of genes involved in oxidative phosphorylation had higher expression in females compared to males. Such basal differences between the sexes in cardiac expression of genes associated with energy metabolism may indicate a likely involvement of mitochondria in susceptibility to CVDs. In addition, female rats showed lower expression levels of apoptotic genes in hearts compared to males at all ages, which may have implications for better preservation of cardiac mass in females than in males.

Sexually dimorphic characteristics of the small intestine and colon of prepubescent C57BL/6 mice

BACKGROUND

There is increasing appreciation for sexually dimorphic effects, but the molecular mechanisms underlying these effects are only partially understood. In the present study, we explored transcriptomics and epigenetic differences in the small intestine and colon of prepubescent male and female mice. In addition, the microbiota composition of the colonic luminal content has been examined.

METHODS

At postnatal day 14, male and female C57BL/6 mice were sacrificed and the small intestine, colon and content of luminal colon were isolated. Gene expression of both segments of the intestine was analysed by microarray analysis. DNA methylation of the promoter regions of selected sexually dimorphic genes was examined by pyrosequencing. Composition of the microbiota was explored by deep sequencing.

RESULTS

Sexually dimorphic genes were observed in both segments of the intestine of 2-week-old mouse pups, with a stronger effect in the small intestine. Amongst the total of 349 genes displaying a sexually dimorphic effect in the small intestine and/or colon, several candidates exhibited a previously established function in the intestine (i.e. Nts, Nucb2, Alox5ap and Retnlγ). In addition, differential expression of genes linked to intestinal bowel disease (i.e. Ccr3, Ccl11 and Tnfr) and colorectal cancer development (i.e. Wt1 and Mmp25) was observed between males and females. Amongst the genes displaying significant sexually dimorphic expression, nine genes were histone-modifying enzymes, suggesting that epigenetic mechanisms might be a potential underlying regulatory mechanism. However, our results reveal no significant changes in DNA methylation of analysed CpGs within the selected differentially expressed genes. With respect to the bacterial community composition in the colon, a dominant effect of litter origin was found but no significant sex effect was detected. However, a sex effect on the dominance of specific taxa was observed.

CONCLUSIONS

This study reveals molecular dissimilarities between males and females in the small intestine and colon of prepubescent mice, which might underlie differences in physiological functioning and in disease predisposition in the two sexes.

Why are sex and gender important to basic physiology and translational and individualized medicine?

Sex refers to biological differences between men and women. Although sex is a fundamental aspect of human physiology that splits the population in two approximately equal halves, this essential biological variable is rarely considered in the design of basic physiological studies, in translating findings from basic science to clinical research, or in developing personalized medical strategies. Contrary to sex, gender refers to social and cultural factors related to being a man or a woman in a particular historical and cultural context. Unfortunately, gender is often used incorrectly by scientists and clinical investigators as synonymous with sex. This article clarifies the definition of sex and gender and reviews evidence showing how sex and gender interact with each other to influence etiology, presentation of disease, and treatment outcomes. In addition, strategies to improve the inclusion of female and male human beings in preclinical and clinical studies will be presented, and the importance of embedding concepts of sex and gender into postgraduate and medical curricula will be discussed. Also, provided is a list of resources for educators. In the history of medical concepts, physiologists have provided pivotal contributions to understanding health and disease processes. In the future, physiologists should provide the evidence for advancing personalized medicine and for reducing sex and gender disparities in health care.

Metzincins and related genes in experimental renal ageing: towards a unifying fibrosis classifier across species

BACKGROUND

We have previously described a transcriptomic classifier consisting of metzincins and related genes (MARGS) discriminating kidneys and other organs with or without fibrosis from human biopsies. We now apply our MARGS-based algorithm to a rat model of age-associated interstitial renal fibrosis.

METHODS

Untreated Fisher 344 rats (n = 76) were sacrificed between 2 to 104 weeks of age. For gene expression studies, we used single colour (Cy3) Agilent Whole Rat Genome 4 × 44k microarrays; 4-5 animals of each sex were profiled at each of the following ages: 2, 5, 6, 8, 15, 21, 78 and 104 weeks. Intensity data were subjected to variance stabilization (www.Partek.com). Data were analysed with ANOVA and other statistical methods.

RESULTS

Sixty MARGS were differentially expressed across age groups. More MARGS were differentially expressed in older males than in older females. Principal component analysis showed gene expression induced segregation of age groups by sex from 6 to 104 weeks of age. The expression level of MMP7 correlated best with fibrosis grade. Severity of fibrosis was determined in 20 animals at 78 and 104 weeks of age. Expression values of 15 of 19 genes of the original classifier present on the Agilent array, in conjunction with linear discriminant analysis, was sufficient to correctly classify these 20 samples into non-fibrosis and fibrosis. Overrepresentation of MMP2 protein and CD44 protein in fibrosis was confirmed by immunofluorescence.

CONCLUSIONS

Based on these results and our previous work, the MARGS classifier represents a cross-organ and cross-species classifier of fibrosis irrespective of aetiology. This finding provides evidence for a common pathway leading to fibrosis and will help to design a PCR-based clinical test.

Gender differences of B cell signature in healthy subjects underlie disparities in incidence and course of SLE related to estrogen

The aim of the present study was to investigate mechanism of the gender differences of B cells. The results showed that 358 differential gene expressions (DEGs) were displayed between healthy females and males. Compared with male, 226 and 132 genes were found to be up- and downregulated in the female. 116 genes displayed possible correlation with estrogen. Moreover, the upregulated DEGs (Cav1, CD200R1, TNFRSF17, and CXCR3) and downregulated DEGs (EIF1AY and DDX3Y) in healthy female may be involved in gender predominance of some immune diseases. Furthermore, signaling pathway analysis for estrogen-relevant DEGs showed that only 26 genes were downregulated in SLE female versus SLE male, of which expressions of 8 genes had significant difference between SLE females and SLE males but are having nonsignificant difference between healthy females and healthy males. Except for the 5 Y-chromosome-related genes or varients, only 3 DEGs (LTF, CAMP, and DEFA4) were selected and qRT-PCR confirmed that the expressions of LTF and CAMP decreased significantly in B cells from female SLE patients. These data indicated that the gender differences were existent in global gene expression of B cells and the difference may be related to estrogen.

Life cycle analysis of kidney gene expression in male F344 rats

Age is a predisposing condition for susceptibility to chronic kidney disease and progression as well as acute kidney injury that may arise due to the adverse effects of some drugs. Age-related differences in kidney biology, therefore, are a key concern in understanding drug safety and disease progression. We hypothesize that the underlying suite of genes expressed in the kidney at various life cycle stages will impact susceptibility to adverse drug reactions. Therefore, establishing changes in baseline expression data between these life stages is the first and necessary step in evaluating this hypothesis. Untreated male F344 rats were sacrificed at 2, 5, 6, 8, 15, 21, 78, and 104 weeks of age. Kidneys were collected for histology and gene expression analysis. Agilent whole-genome rat microarrays were used to query global expression profiles. An ANOVA (p<0.01) coupled with a fold-change>1.5 in relative mRNA expression, was used to identify 3,724 unique differentially expressed genes (DEGs). Principal component analyses of these DEGs revealed three major divisions in life-cycle renal gene expression. K-means cluster analysis identified several groups of genes that shared age-specific patterns of expression. Pathway analysis of these gene groups revealed age-specific gene networks and functions related to renal function and aging, including extracellular matrix turnover, immune cell response, and renal tubular injury. Large age-related changes in expression were also demonstrated for the genes that code for qualified renal injury biomarkers KIM-1, Clu, and Tff3. These results suggest specific groups of genes that may underlie age-specific susceptibilities to adverse drug reactions and disease. This analysis of the basal gene expression patterns of renal genes throughout the life cycle of the rat will improve the use of current and future renal biomarkers and inform our assessments of kidney injury and disease.