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

Evaluations of secondary hypertension and laboratory data in the elderly population

Secondary hypertension in the elderly poses many challenges and requires a comprehensive diagnostic and management approach. This review explores the prevalence, diagnostic strategies, and treatment modalities for secondary hypertension in elderly patients, focusing on etiologies including primary aldosteronism, renal vascular disease, renal parenchymal disease, obstructive sleep apnea, thyroid disorders, Cushing's syndrome, pheochromocytomas and paragangliomas, and drug-induced hypertension. Key considerations include age-related changes in physiology and atypical presentations of underlying conditions necessitating thorough screening with a combination of clinical evaluation, laboratory tests, and imaging studies. Collaboration among healthcare providers is essential to ensure a timely diagnosis and personalized management tailored to the unique needs of elderly patients. Further research is needed to address knowledge gaps and optimize clinical strategies for managing secondary hypertension in this population.

The Role of Collagen VIII in the Aging Mouse Kidney

The gradual loss of kidney function due to increasing age is accompanied by structural changes such as fibrosis of the tissue. The underlying molecular mechanisms are complex, but not yet fully understood. Non-fibrillar collagen type VIII (COL8) could be a potential factor in the fibrosis processes of the aging kidney. A pathophysiological significance of COL8 has already been demonstrated in the context of diabetic kidney disease, with studies showing that it directly influences both the development and progression of renal fibrosis occurring. The aim of this study was to investigate whether COL8 impacts age-related micro-anatomical and functional changes in a mouse model. The kidneys of wild-type (Col8-wt) and COL8-knockout (Col8-ko) mice of different age and sex were characterized with regard to the expression of molecular fibrosis markers, the development of nephrosclerosis and renal function. The age-dependent regulation of COL8 mRNA expression in the wild-type revealed sex-dependent effects that were not observed with collagen IV (COL4). Histochemical staining and protein analysis of profibrotic cytokines TGF-β1 (transforming growth factor) and CTGF (connective tissue growth factor) in mouse kidneys showed significant age effects as well as interactions of the factors age, sex and Col8 genotype. There were also significant age and Col8 genotype effects in the renal function data analyzed by urinary cystatin C. In summary, the present study shows, for the first time, that COL8 is regulated in an age- and sex-dependent manner in the mouse kidney and that the expression of COL8 influences the severity of age-induced renal fibrosis and function.

A high level of thyroid-stimulating hormone is a risk factor for the development of chronic kidney disease in men: a 10-year cohort study

Hypothyroidism has been reported to be associated with chronic kidney disease (CKD). However, the impact of thyroid-stimulating hormone (TSH) on new onset of CKD and its gender dependence remain undetermined. We investigated the association of serum TSH level and the development of CKD defined by estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 or positive for urine protein in 28,990 Japanese subjects who received annual health examinations. After excluding subjects with no data for serum TSH, urinalysis and eGFR and those with CKD at baseline, a total of 10,392 subjects (men/women: 6802/3590, mean age: 48 years) were recruited. During a 10-year follow-up, 1185 men (6.7%) and 578 women (2.9%) newly developed CKD. Multivariable Cox proportional hazard models after adjustment of age, body mass index, smoking habit, hypertension, diabetes mellitus, dyslipidemia, ischemic heart disease and eGFR (≥ 90 mL/min/1.73 m2) showed that the hazard ratio (HR) for the development of CKD in the high TSH (> 4.2 mU/L) group was significantly higher than that in the low TSH (≤ 4.2 mU/L) group in men (HR [95% confidence interval]: 1.41 [1.09-1.83]) but not in women (1.08 [0.77-1.51]). There was a significant interaction between sex and the category of TSH level for the development of CKD (p = 0.02). The adjusted HR with a restricted cubic spline increased with a higher level of TSH in men but not in women. In conclusion, a high level of TSH is associated with an increased risk for the development of CKD in men but not in women.

Contrast-Associated Acute Kidney Injury: Definitions, Epidemiology, Pathophysiology, and Implications

Acute kidney injury (AKI) is a common occurrence after contrast media administration. Hemodynamic changes, direct tubular injury, and reactive oxygen species are the proposed mechanisms involved in AKI. However, in most scenarios, it is not possible to establish causality despite extensive clinical evaluation, therefore, contrast-associated AKI (CA-AKI) has become a widely accepted term to define AKI postcontrast. CA-AKI is associated with worse clinical outcomes including cardiovascular events and mortality; however, discussions are ongoing whether CA-AKI is a marker of an increased risk of adverse outcomes or a mediator of such outcomes.

Long-term effects of primary hyperparathyroidism and parathyroidectomy on kidney function

IMPORTANCE

Limited evidence supports kidney dysfunction as an indication for parathyroidectomy in asymptomatic primary hyperparathyroidism (PHPT).

OBJECTIVE

To investigate the natural history of kidney function in PHPT and whether parathyroidectomy alters renal outcomes.

DESIGN

Matched control study.

SETTING

A vertically integrated health care system serving 4.6 million patients in Southern California.

PARTICIPANTS

6058 subjects with PHPT and 16 388 matched controls, studied from 2000 to 2016.

EXPOSURES

Biochemically confirmed PHPT with varying serum calcium levels.

MAIN OUTCOMES

Estimated glomerular filtration rate (eGFR) trajectories were compared over 10 years, with cases subdivided by severity of hypercalcemia: serum calcium 2.62-2.74 mmol/L (10.5-11 mg/dL), 2.75-2.87 (11.1-11.5), 2.88-2.99 (11.6-12), and >2.99 (>12). Interrupted time series analysis was conducted among propensity-score-matched PHPT patients with and without parathyroidectomy to compare eGFR trajectories postoperatively.

RESULTS

Modest rates of eGFR decline were observed in PHPT patients with serum calcium 2.62-2.74 mmol/L (−1.0 mL/min/1.73 m2/year) and 2.75-2.87 mmol/L (−1.1 mL/min/1.73 m2/year), comprising 56% and 28% of cases, respectively. Compared with the control rate of −1.0 mL/min/1.73 m2/year, accelerated rates of eGFR decline were observed in patients with serum calcium 2.88-2.99 mmol/L (−1.5 mL/min/1.73 m2/year, P < .001) and >2.99 mmol/L (−2.1 mL/min/1.73 m2/year, P < .001), comprising 9% and 7% of cases, respectively. In the propensity score–matched population, patients with serum calcium >2.87 mmol/L exhibited mitigation of eGFR decline after parathyroidectomy (−2.0 [95% CI: −2.6 to −1.5] to −0.9 [95% CI: −1.5 to 0.4] mL/min/1.73 m2/year).

CONCLUSIONS AND RELEVANCE

Compared with matched controls, accelerated eGFR decline was observed in the minority of PHPT patients with serum calcium >2.87 mmol/L (11.5 mg/dL). Parathyroidectomy was associated with mitigation of eGFR decline in patients with serum calcium >2.87 mmol/L.

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.

Arginine Dysregulation and Myocardial Dysfunction in a Mouse Model and Children with Chronic Kidney Disease

Cardiovascular disease is the leading cause of death in chronic kidney disease (CKD). Arginine, the endogenous precursor for nitric oxide synthesis, is produced in the kidneys. Arginine bioavailability contributes to endothelial and myocardial dysfunction in CKD. Plasma from 129X1/SvJ mice with and without CKD (5/6th nephrectomy), and banked plasma from children with and without CKD were analyzed for amino acids involved in arginine metabolism, ADMA, and arginase activity. Echocardiographic measures of myocardial function were compared with plasma analytes. In a separate experiment, a non-specific arginase inhibitor was administered to mice with and without CKD. Plasma citrulline and glutamine concentrations correlated with multiple measures of myocardial dysfunction. Plasma arginase activity was significantly increased in CKD mice at 16 weeks vs. 8 weeks (p = 0.002) and ventricular strain improved after arginase inhibition in mice with CKD (p = 0.03). In children on dialysis, arginase activity was significantly increased vs. healthy controls (p = 0.04). Increasing ADMA correlated with increasing RWT in children with CKD (r = 0.54; p = 0.003). In a mouse model, and children, with CKD, arginine dysregulation correlates with myocardial dysfunction.

RAGE is a critical factor of sex-based differences in age-induced kidney damage

Introduction: Advanced glycation end products (AGEs) are a heterogeneous group of molecules with potential pathophysiological effects on the kidneys. Fibrosis together with the accumulation of AGEs has been investigated for its contribution to age-related decline in renal function. AGEs mediate their effects in large parts through their interactions with the receptor for AGEs (RAGE). RAGE is a transmembrane protein that belongs to the immunoglobulin superfamily and has the ability to interact with multiple pro-inflammatory/pro-oxidative ligands. The role of RAGE in aging kidneys has not been fully characterized, especially for sex-based differences.

Methods: Therefore, we analyzed constitutive RAGE knockout (KO) mice in an age- and sex-dependent manner. Paraffin-embedded kidney sections were used for histological analysis and protein expression of fibrosis and damage markers. RNA expression analysis from the kidney cortex was done by qPCR for AGE receptors, kidney damage, and early inflammation/fibrosis factors. FACS analysis was used for immune cell profiling of the kidneys.

Results: Histological analysis revealed enhanced infiltration of immune cells (positive for B220) in aged (&gt;70 weeks old) KO mice in both sexes. FACS analysis revealed a similar pattern of enhanced B-1a cells in aged KO mice. There was an age-based increase in pro-fibrotic and pro-inflammatory markers (IL-6, TNF, TGF-β1, and SNAIL1) in KO male mice that presumably contributed to renal fibrosis and renal damage (glomerular and tubular). In fact, in KO mice, there was an age-dependent increase in renal damage (assessed by NGAL and KIM1) that was accompanied by increased fibrosis (assessed by CTGF). This effect was more pronounced in male KO mice than in the female KO mice. In contrast to the KO animals, no significant increase in damage markers was detectable in wild-type animals at the age examined (&gt;70 weeks old). Moreover, there is an age-based increase in AGEs and scavenger receptor MSR-A2 in the kidneys.

Discussion: Our data suggest that the loss of the clearance receptor RAGE in male animals further accelerates age-dependent renal damage; this could be in part due to an increase in AGEs load during aging and the absence of protective female hormones. By contrast, in females, RAGE expression seems to play only a minor role when compared to tissue pathology.

Glomerular filtration in the aging population

In the last decades, improvements in the average life expectancy in the world population have been associated with a significant increase in the proportion of elderly people, in parallel with a higher prevalence of non-communicable diseases, such as hypertension and diabetes. As the kidney is a common target organ of a variety of diseases, an adequate evaluation of renal function in the approach of this population is of special relevance. It is also known that the kidneys undergo aging-related changes expressed by a decline in the glomerular filtration rate (GFR), reflecting the loss of kidney function, either by a natural senescence process associated with healthy aging or by the length of exposure to diseases with potential kidney damage. Accurate assessment of renal function in the older population is of particular importance to evaluate the degree of kidney function loss, enabling tailored therapeutic interventions. The present review addresses a relevant topic, which is the effects of aging on renal function. In order to do that, we analyze and discuss age-related structural and functional changes. The text also examines the different options for evaluating GFR, from the use of direct methods to the implementation of several estimating equations. Finally, this manuscript supports clinicians in the interpretation of GFR changes associated with age and the management of the older patients with decreased kidney function.

Increased LDL cholesterol level is associated with deterioration of renal function in males

Background

Relationships between levels of serum lipid fractions and the time course of renal function are discrepant in the literature. Here we examined this issue by analyses of healthy subjects in a cohort.

Methods

Of all subjects who received health examinations at Keijinkai Maruyama Clinic, Sapporo in 2006, subjects with hypertension, diabetes mellitus or chronic kidney disease (CKD) and those taking medication for dyslipidemia were excluded, and a total of 5,586 subjects (male/female: 3,563/2,023, mean age: 43 ± 8 years) were followed for 10 years.

Results

Linear mixed effect models showed that baseline low-density lipoprotein (LDL)-cholesterol level was negatively associated with estimated glomerular filtration rate (eGFR) during the 10-year follow-up period after adjustment of confounders. Interactions between the follow-up year and baseline level of LDL-cholesterol or high-density lipoprotein (HDL)-cholesterol for eGFR values during the follow-up period were significant in males but not in females. There were no significant interactions for eGFR between the follow-up year and baseline levels of total cholesterol, triglycerides, or HDL-cholesterol/triglycerides ratio. During the follow-up period, 346 males and 223 females developed CKD. When male subjects were divided into subgroups according to tertiles of baseline levels of LDL-cholesterol, the adjusted risk for CKD in the third tertial group was significantly higher than that in the first tertile group as a reference (hazard ratio [95% confidence interval]: 1.39 [1.02-1.90], p = 0.035). Such a difference was not observed for LDL-cholesterol tertiles in females or HDL-cholesterol tertiles in both sexes.

Conclusions

A high LDL-cholesterol level may be a risk factor of new-onset CKD in apparently healthy males.

The Other Way Around: Living With Chronic Kidney Disease From the Perspective of Men

A wealth of evidence has suggested sex (biological) and gender (sociocultural) differences in the prevalence, progression, and outcomes of persons with chronic kidney disease. Much of this evidence tends to emphasize differences in which women are disadvantaged, and less attention is paid to findings in which women are better off or similar to men. However, gender medicine recognizes that men and women have different disease determinants, presentation, and attitudes, and it pertains to both sexes. In this review, we revisit chronic kidney disease through the perspective of men, and illustrate a population segment at need of stringent preventative and management strategies.

Podocyte Aging: Why and How Getting Old Matters

The effects of healthy aging on the kidney, and how these effects intersect with superimposed diseases, are highly relevant in the context of the population's increasing longevity. Age-associated changes to podocytes, which are terminally differentiated glomerular epithelial cells, adversely affect kidney health. This review discusses the molecular and cellular mechanisms underlying podocyte aging, how these mechanisms might be augmented by disease in the aged kidney, and approaches to mitigate progressive damage to podocytes. Furthermore, we address how biologic pathways such as those associated with cellular growth confound aging in humans and rodents.

Physiological factors characterizing heat-vulnerable older adults: A narrative review

More frequent and intense periods of extreme heat (heatwaves) represent the most direct challenge to human health posed by climate change. Older adults are particularly vulnerable, especially those with common age-associated chronic health conditions (e.g., cardiovascular disease, hypertension, obesity, type 2 diabetes, chronic kidney disease). In parallel, the global population is aging and age-associated disease rates are on the rise. Impairments in the physiological responses tasked with maintaining homeostasis during heat exposure have long been thought to contribute to increased risk of health disorders in older adults during heatwaves. As such, a comprehensive overview of the provisional links between age-related physiological dysfunction and elevated risk of heat-related injury in older adults would be of great value to healthcare officials and policy makers concerned with protecting heat-vulnerable sectors of the population from the adverse health impacts of heatwaves. In this narrative review, we therefore summarize our current understanding of the physiological mechanisms by which aging impairs the regulation of body temperature, hemodynamic stability and hydration status. We then examine how these impairments may contribute to acute pathophysiological events common during heatwaves (e.g., heatstroke, major adverse cardiovascular events, acute kidney injury) and discuss how age-associated chronic health conditions may exacerbate those impairments. Finally, we briefly consider the importance of physiological research in the development of climate-health programs aimed at protecting heat-vulnerable individuals.

Elevated Serum Uric Acid is Associated with Rapid Decline in Kidney Function: A 10-Year Follow-Up Study

Purpose

The long-term impact of changes in serum uric acid (SUA) concentration on the estimated glomerular filtration rate (eGFR) among the general population remains unclear. We investigated the longitudinal associations between changes in SUA and eGFR over 10 years in 1222 participants with baseline eGFR ≥60 mL/min/1.73 m².

Methods

This was a 10-year retrospective cohort study conducted from 2007 to 2017. Rapid eGFR decline (defined as the highest quartile of change in eGFR between 2007 and 2017) and new-onset kidney disease (defined as an eGFR <60 mL/min/1.73 m² at a 10-year follow-up) were examined using multiple logistic regression analysis, adjusted for sex, age, body mass index, systolic blood pressure, SUA, fasting plasma glucose, serum total cholesterol, and triglyceride at baseline.

Results

SUA was inversely correlated with eGFR, and the slopes of the SUA-eGFR regression lines were consistently steeper in females than males. A significant inverse correlation was also observed between 10-year changes in SUA and eGFR in both sexes. Multivariate analysis showed that every 1 mg/dL increase in SUA from baseline was associated with higher risk of rapid eGFR decline and new-onset kidney disease (OR 1.25; 95% CI 1.14–1.33 and OR 1.40; 95% CI 1.26–1.49, respectively). Furthermore, the subjects in the highest SUA quartile (>6.0 mg/dL) had a 2.45 times higher risk of rapid eGFR decline (95% CI 1.51–3.42) compared to those in the lowest SUA quartile (<3.9 mg/dL).

Conclusion

Elevated baseline SUA is an independent risk factor for rapid eGFR decline and new-onset kidney disease in the general population.

The Healthy, Aging, and Diseased Kidney: Relationship with Cardiovascular Disease

The cardiovascular and renal systems share an intimate physiological relationship, wherein a perturbance in one system may have an adverse effect on the other. Since the burden of renal disease increases with age, there is a considerable interest in the pathophysiology of kidney disease in the geriatric patient population. This review will explore the physiological dynamics behind the increased susceptibility to kidney disease in this population. A better understanding of these pathophysiological changes may lead to improved prevention and management strategies.

Detecting Ordinal Subcascades

Ordinal classifier cascades are constrained by a hypothesised order of the semantic class labels of a dataset. This order determines the overall structure of the decision regions in feature space. Assuming the correct order on these class labels will allow a high generalisation performance, while an incorrect one will lead to diminished results. In this way ordinal classifier systems can facilitate explorative data analysis allowing to screen for potential candidate orders of the class labels. Previously, we have shown that screening is possible for total orders of all class labels. However, as datasets might comprise samples of ordinal as well as non-ordinal classes, the assumption of a total ordering might be not appropriate. An analysis of subsets of classes is required to detect such hidden ordinal substructures. In this work, we devise a novel screening procedure for exhaustive evaluations of all order permutations of all subsets of classes by bounding the number of enumerations we have to examine. Experiments with multi-class data from diverse applications revealed ordinal substructures that generate new and support known relations.

Pathophysiology of Contrast-Induced Acute Kidney Injury

Passing contrast media through the renal vascular bed leads to vasoconstriction. The perfusion decrease leads to ischemia of tubular cells. Through ischemia and direct toxicity to renal tubular cells, reactive oxygen species formation is increased, enhancing the effect of vasoconstrictive mediators and decreasing the bioavailability of vasodilative mediators. Reactive oxygen species formation leads to oxidative damage to tubular cells. These interacting pathways lead to tubular necrosis. In the pathophysiology of contrast-induced acute kidney injury, low osmolar and iso-osmolar agents have theoretic advantages and disadvantages; however, clinically the difference in incidence of contrast-induced acute kidney injury has not changed.

Nitride oxide synthase 3 and klotho gene polymorphisms in the pathogenesis of chronic kidney disease and age-related cognitive impairment: a systematic review and meta-analysis

Background: While it has been known that the development of chronic kidney disease (CKD) and age-related cognitive impairment involves several mediators, the evidence in clinical practice only reveals nitride oxide synthase (NOS) and klotho. However, the evidence for this topic is conflicted. The aim of this study was to assess the role of NOS and klotho single nucleotide polymorphisms (SNPs) in the pathogenesis of CKD and age-related cognitive impairment. Methods: We performed a meta-analysis during October to December 2019. Paper collection was performed in major scientific websites, and we extracted information of interest from each paper. Data were analyzed using a Z-test with either random or fixed effect model. Results: Our initial assessment identified NOS3 G894T, NOS3 T786C, NOS3 4b/4a, klotho ( KL) G395A, and KL C1818T as the gene candidate for our meta-analysis. Our pooled calculation revealed that NOS3 G894T was associated with the risk of both age-related cognitive impairment and CKD. Increased susceptibility to age-related cognitive impairment was observed in the GG genotype, and increased risk of CKD was found in patients with a single T allele and TT genotype for NOS3 nucleotide 894. For NOS3 4b/4a, increased risk of CKD was only found in 4a4a genotype. For NOS3 T786C, we failed to show the association with both CKD and age-related cognitive impairment. Subsequently, for KL G395A, A allele and GA genotype were found to correlate with increased susceptibility to CKD, while its correlation to age-related cognitive impairment was failed to clarify. For KL C1818T, our analysis failed to find the correlation with the risk of CKD. Conclusions: Our results reveal that the NOS3 G894T gene polymorphism has a crucial role in the pathogenesis of both CKD and age-related cognitive impairment.

Nitride oxide synthase 3 and klotho gene polymorphisms in the pathogenesis of chronic kidney disease and age-related cognitive impairment: a systematic review and meta-analysis

Background: While it has been known that the development of chronic kidney disease (CKD) and age-related cognitive impairment involves several mediators, the evidence in clinical practice only reveals nitride oxide synthase (NOS) and klotho. However, the evidence for this topic is conflicted. The aim of this study was to assess the role of NOS and klotho single nucleotide polymorphisms (SNPs) in the pathogenesis of CKD and age-related cognitive impairment. Methods: We performed a meta-analysis during October to December 2019. Paper collection was performed in major scientific websites, and we extracted information of interest from each paper. Data were analyzed using a Z-test with either random or fixed effect model. Results: Our initial assessment identified NOS3 G894T, NOS3 T786C, NOS3 4b/4a, klotho ( KL) G395A, and KL C1818T as the gene candidate for our meta-analysis. Our pooled calculation revealed that NOS3 G894T was associated with the risk of both age-related cognitive impairment and CKD. Increased susceptibility to age-related cognitive impairment was observed in the GG genotype, and increased risk of CKD was found in patients with a single T allele and TT genotype for NOS3 nucleotide 894. For NOS3 4b/4a, increased risk of CKD was only found in 4a4a genotype. For NOS3 T786C, we failed to show the association with both CKD and age-related cognitive impairment. Subsequently, for KL G395A, A allele and GA genotype were found to correlate with increased susceptibility to CKD, while its correlation to age-related cognitive impairment was failed to clarify. For KL C1818T, our analysis failed to find the correlation with the risk of CKD. Conclusions: Our results reveal that the NOS3 G894T gene polymorphism has a crucial role in the pathogenesis of both CKD and age-related cognitive impairment.

Contrast-Induced Acute Kidney Injury: Review and Practical Update

Contrast-induced acute kidney injury (CI-AKI) is an important consideration in patients undergoing cardiac catheterization. There has been a continuous strive to decrease morbidity and improve procedural safety. This review will address the pathophysiology, predictors, and clinical management of CI-AKI with a concise overview of the pathophysiology and a suggested association with left atrial appendage closure. Minimizing contrast administration and intravenous fluid hydration are the cornerstones of an effective preventive strategy. A few adjunctive pharmacotherapies hold promise, but there are no consensus recommendations on prophylactic therapies.

Sex hormones and their influence on chronic kidney disease

PURPOSE OF REVIEW

The majority of end-stage renal disease including dialysis and kidney transplant patients are men. In contrast, the incidence of chronic kidney disease (CKD) is higher in women compared with men. In this review, we dissect the sex hormone levels and its effects on experimental models and patients with CKD.

RECENT FINDINGS

Sex hormones are clearly involved in CKD progression to end-stage renal disease (ESRD). A significant reduction in lipid peroxidation as a mechanism of renoprotection has been observed in kidneys of streptozotocin (STZ)-diabetic ovariectomized rats after estradiol administration. Furthermore, a G-protein-coupled estrogen receptor inhibits podocyte oxidative stress maintaining the integrity of the mitochondrial membrane. Sex hormone depletion has been shown to modulate RAS system and protect against kidney injury in the male STZ-diabetic model. In human primary proximal tubular epithelial cells, a proteomic study showed that dihydrotestosterone dysregulated metabolic, suggesting that the deleterious effect of androgens within the kidney maybe related to altered energy metabolism in renal tubules.

SUMMARY

Male gender is associated with worse CKD progression and this fact may be ascribed to sex hormone. Although male hormones exert a deleterious effect in terms of increasing oxidative stress, activating RAS system, and worsening fibrosis within the damaged kidney, female hormones exert a renoprotective effect.

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

CONTEXT

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

DESIGN AND METHODS

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

RESULTS

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

CONCLUSION

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

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.

Prolonged prenatal hypoxia selectively disrupts collecting duct patterning and postnatal function in male mouse offspring

KEY POINTS

In the present study, we investigated whether hypoxia during late pregnancy impairs kidney development in mouse offspring, and also whether this has long-lasting consequences affecting kidney function in adulthood. Hypoxia disrupted growth of the kidney, particularly the collecting duct network, in juvenile male offspring. By mid-late adulthood, these mice developed early signs of kidney disease, notably a compromised response to water deprivation. Female offspring showed no obvious signs of impaired kidney development and did not develop kidney disease, suggesting an underlying protection mechanism from the hypoxia insult. These results help us better understand the long-lasting impact of gestational hypoxia on kidney development and the increased risk of chronic kidney disease.

ABSTRACT

Prenatal hypoxia is a common perturbation to arise during pregnancy, and can lead to adverse health outcomes in later life. The long-lasting impact of prenatal hypoxia on postnatal kidney development and maturation of the renal tubules, particularly the collecting duct system, is relatively unknown. In the present study, we used a model of moderate chronic maternal hypoxia throughout late gestation (12% O₂ exposure from embryonic day 14.5 until birth). Histological analyses revealed marked changes in the tubular architecture of male hypoxia-exposed neonates as early as postnatal day 7, with disrupted medullary development and altered expression of Ctnnb1 and Crabp2 (encoding a retinoic acid binding protein). Kidneys of the RARElacZ line offspring exposed to hypoxia showed reduced β-galactosidase activity, indicating reduced retinoic acid-directed transcriptional activation. Wild-type male mice exposed to hypoxia had an early decline in urine concentrating capacity, evident at 4 months of age. At 12 months of age, hypoxia-exposed male mice displayed a compromised response to a water deprivation challenge, which was was correlated with an altered cellular composition of the collecting duct and diminished expression of aquaporin 2. There were no differences in the tubular structures or urine concentrating capacity between the control and hypoxia-exposed female offspring at any age. The findings of the present study suggest that prenatal hypoxia selectively disrupts collecting duct patterning through altered Wnt/β-catenin and retinoic acid signalling and this results in impaired function in male mouse offspring in later life.

Age-, Gender-, and in Vivo Different Doses of Isoproterenol Modify in Vitro Aortic Vasoreactivity and Circulating VCAM-1

Different human-like cardiomyopathies associated to β-adrenergic stimulation are experimentally modeled in animals through variations in dose, route, and duration of administration of different cardiotoxic drugs. However, associated changes in the vasculature and their relation to systemic inflammation, and the influence of cardiovascular diseases risk factors (gender and age) upon them are seldom analyzed. Here we studied the effect of age and gender on the vasoreactivity of aortas from mice subjected to in vivo repeated β-adrenergic stimulation with different doses of isoproterenol (ISO) in association with circulating inflammatory cytokines. Young (2 months) and old (18 months) male and female mice received 0 (control), 5, 40, 80 or 160 μg/g/d of ISO (7 days, s.c.). IL-1α, IL-4 and vascular cell adhesion molecule-1 (VCAM-1) were quantified in plasma. In vitro, norepinephrine-induced vasoconstriction and acetylcholine-induced relaxation were measured in aortas. No differences in contraction, relaxation, IL-1α, and IL-4 were found between control young males and females. Age decreased contraction in males and relaxation was lower in females and abolished in males. VCAM-1 was higher in young males than in females and increased in old mice. Vasoconstriction in ISO-treated mice results as a bell-shaped curve on contraction in young and old males, with lower values in the latter. In females, ISO-160 increased contraction in young females but decreased it in old females. Vasorelaxation was reduced in ISO-treated young males and females. ISO-80 and 160 reduced vasorelaxation in old females, and intermediate doses relaxed aortas from old males. VCAM-1 was higher in young and old males with ISO-80 and 160; while VCAM-1 was higher only with ISO-160 in old females. Our results demonstrate that repeated β-adrenergic stimulation modifies vascular reactivity depending on gender, age, and dose. Females were less sensitive to alterations in vasoreactivity, and young females required a higher amount of the adrenergic stimuli than old females to show vascular alterations. Changes were independent of IL-1α and IL-4. VCAM-1 only changed in old females stimulated with ISO 160. Our results highlight the relevance of considering and comparing in the same study females and aged organisms to improve the accuracy of applications to clinical studies.

Sex and gender disparities in the epidemiology and outcomes of chronic kidney disease

Improved understanding of sex and gender-specific differences in the aetiology, mechanisms and epidemiology of chronic kidney disease (CKD) could help nephrologists better address the needs of their patients. Population-based studies indicate that CKD epidemiology differs by sex, affecting more women than men, especially with regard to stage G3 CKD. The effects of longer life expectancy on the natural decline of glomerular filtration rate (GFR) with age, as well as potential overdiagnosis of CKD through the inappropriate use of GFR equations, might be in part responsible for the greater prevalence of CKD in women. Somewhat paradoxically, there seems to be a preponderance of men among patients starting renal replacement therapy (RRT); the protective effects of oestrogens in women and/or the damaging effects of testosterone, together with unhealthier lifestyles, might cause kidney function to decline faster in men than in women. Additionally, elderly women seem to be more inclined to choose conservative care instead of RRT. Dissimilarities between the sexes are also apparent in the outcomes of CKD. In patients with predialysis CKD, mortality is higher in men than women; however, this difference disappears for patients on RRT. Although access to living donor kidneys among men and women seems equal, women have reduced access to deceased donor transplantation. Lastly, health-related quality of life while on RRT is poorer in women than men, and women report a higher burden of symptoms. These findings provide insights into differences in the underlying pathophysiology of disease as well as societal factors that can be addressed to reduce disparities in access to care and outcomes for patients with CKD.

Sex and gender disparities in the epidemiology and outcomes of chronic kidney disease

Improved understanding of sex and gender-specific differences in the aetiology, mechanisms and epidemiology of chronic kidney disease (CKD) could help nephrologists better address the needs of their patients. Population-based studies indicate that CKD epidemiology differs by sex, affecting more women than men, especially with regard to stage G3 CKD. The effects of longer life expectancy on the natural decline of glomerular filtration rate (GFR) with age, as well as potential overdiagnosis of CKD through the inappropriate use of GFR equations, might be in part responsible for the greater prevalence of CKD in women. Somewhat paradoxically, there seems to be a preponderance of men among patients starting renal replacement therapy (RRT); the protective effects of oestrogens in women and/or the damaging effects of testosterone, together with unhealthier lifestyles, might cause kidney function to decline faster in men than in women. Additionally, elderly women seem to be more inclined to choose conservative care instead of RRT. Dissimilarities between the sexes are also apparent in the outcomes of CKD. In patients with predialysis CKD, mortality is higher in men than women; however, this difference disappears for patients on RRT. Although access to living donor kidneys among men and women seems equal, women have reduced access to deceased donor transplantation. Lastly, health-related quality of life while on RRT is poorer in women than men, and women report a higher burden of symptoms. These findings provide insights into differences in the underlying pathophysiology of disease as well as societal factors that can be addressed to reduce disparities in access to care and outcomes for patients with CKD.

Sexual Dimorphic Pattern of Renal Transporters and Electrolyte Homeostasis

Compared with males, females have lower BP before age 60, blunted hypertensive response to angiotensin II, and a leftward shift in pressure natriuresis. This study tested the concept that this female advantage associates with a distinct sexual dimorphic pattern of transporters along the nephron. We applied quantitative immunoblotting to generate profiles of transporters, channels, claudins, and selected regulators in both sexes and assessed the physiologic consequences of the differences. In rats, females excreted a saline load more rapidly than males did. Compared with the proximal tubule of males, the proximal tubule of females had greater phosphorylation of Na+/H+ exchanger isoform 3 (NHE3), distribution of NHE3 at the base of the microvilli, and less abundant expression of Na+/Pi cotransporter 2, claudin-2, and aquaporin 1. These changes associated with less bicarbonate reabsorption and higher lithium clearance in females. The distal nephrons of females had a higher abundance of total and phosphorylated Na+/Cl- cotransporter (NCC), claudin-7, and cleaved forms of epithelial Na+ channel (ENaC) α and γ subunits, which associated with a lower baseline plasma K+ concentration. A K+-rich meal increased the urinary K+ concentration and decreased the level of renal phosphorylated NCC in females. Notably, we observed similar abundance profiles in female versus male C57BL/6 mice. These results define sexual dimorphic phenotypes along the nephron and suggest that lower proximal reabsorption in female rats expedites excretion of a saline load and enhances NCC and ENaC abundance and activation, which may facilitate K+ secretion and set plasma K+ at a lower level.

Mitochondrial cyclophilin D ablation is associated with the activation of Akt/p70S6K pathway in the mouse kidney

The mitochondrial matrix protein cyclophilin D (CypD) is an essential component of the mitochondrial permeability transition pore (MPTP). Here we characterized the effects of CypD ablation on bioenergetics in the kidney. CypD loss triggers a metabolic shift in Ppif-/- male and female mouse kidneys towards glycolysis and Krebs cycle activity. The shift is accompanied by increased glucose consumption and a transcriptional upregulation of effectors of glucose metabolism in the kidney. These included activation of Akt, AMPK (only in males) and p70S6K kinases. Gender specific differences between the Ppif-/- male and female mouse kidneys were observed including activation of pro-surviving ERK1/2 kinase and inhibited expression of pro-apoptotic and pro-fibrotic JNK and TGFβ1 proteins in Ppif-/- females. They also showed the highest expression of phosphorylated-ERK1/2 and Akt S473 proteins of all four investigated animal groups. Furthermore, Ppif-/- females showed higher lactate concentrations and ATP/ADP-ratios in the kidney than males. These metabolic and transcriptional modifications could provide an additional level of protection to Ppif-/- females. In summary, loss of mitochondrial CypD results in a shift in bioenergetics and in activation of glucose-metabolism regulating Akt/AMPK/p70S6 kinase pathways that is expected to affect the capability of Ppif-/- mice kidneys to react to stimuli and injury.

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

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

Sex-specific computational models of the spontaneously hypertensive rat kidneys: factors affecting nitric oxide bioavailability

The goals of this study were to 1) develop a computational model of solute transport and oxygenation in the kidney of the female spontaneously hypertensive rat (SHR), and 2) apply that model to investigate sex differences in nitric oxide (NO) levels in SHR and their effects on medullary oxygenation and oxidative stress. To accomplish these goals, we first measured NO synthase (NOS) 1 and NOS3 protein expression levels in total renal microvessels of male and female SHR. We found that the expression of both NOS1 and NOS3 is higher in the renal vasculature of females compared with males. To predict the implications of that finding on medullary oxygenation and oxidative stress levels, we developed a detailed computational model of the female SHR kidney. The model was based on a published male kidney model and represents solute transport and the biochemical reactions among O₂, NO, and superoxide ([Formula: see text]) in the renal medulla. Model simulations conducted using both male and female SHR kidney models predicted significant radial gradients in interstitial fluid oxygen tension (Po₂) and NO and [Formula: see text] concentration in the outer medulla and upper inner medulla. The models also predicted that increases in endothelial NO-generating capacity, even when limited to specific vascular segments, may substantially raise medullary NO and Po₂ levels. Other potential sex differences in SHR, including [Formula: see text] production rate, are predicted to significantly impact oxidative stress levels, but effects on NO concentration and Po₂ are limited.

Does 2 L Polyethylene Glycol Plus Ascorbic Acid Increase the Risk of Renal Impairment Compared to 4 L Polyethylene Glycol?

BACKGROUND

The use of polyethylene glycol (PEG)-based solutions is the gold standard for bowel preparation. However, PEG use might be associated with the risk of acute kidney injury.

AIMS

We aimed to compare the safety of 2 L PEG plus ascorbic acid (AA) versus 4 L PEG.

METHODS

Health examinees that underwent colonoscopy and blood tests on the same day at our center were included in this retrospective study. All subjects were prescribed either 2 L PEG plus AA or 4 L PEG for the bowel preparation prior to the colonoscopy. The incidences of electrolyte imbalance and renal impairment after colonic preparation were investigated. Renal impairment was determined if the subject's estimated glomerular filtration rate was measured less than 60 mL/min/1.73 m².

RESULTS

Of the 29,789 cases, 14,790 received 2 L PEG plus AA (group A) and 14,999 received 4 L PEG (group B) for colonic preparation. Renal impairment occurred more commonly in group A (n = 467, 3.2 %) than in group B (n = 189, 1.3 %). Electrolyte changes such as hypernatremia and hyperkalemia were more common in group A than group B, whereas hyponatremia, hypokalemia, and hypophosphatemia were more common in group B than group A. Old age, male sex, and the use of 2 L PEG plus AA were independent risk factors for renal impairment.

CONCLUSIONS

The evidence strongly suggests that acute kidney injury is more likely to occur when 2 L PEG plus AA is used for the bowel preparation than when 4 L PEG is used.

CLINICAL TRIAL REGISTRATION NUMBER

KCT0001703.

Sex Differences in Renal Proximal Tubular Cell Homeostasis

Studies in human patients and animals have revealed sex-specific differences in susceptibility to renal diseases. Because actions of female sex hormones on normal renal tissue might protect against damage, we searched for potential influences of the female hormone cycle on basic renal functions by studying excretion of urinary marker proteins in healthy human probands. We collected second morning spot urine samples of unmedicated naturally ovulating women, postmenopausal women, and men daily and determined urinary excretion of the renal tubular enzymes fructose-1,6-bisphosphatase and glutathione-S-transferase-α Additionally, we quantified urinary excretion of blood plasma proteins α1-microglobulin, albumin, and IgG. Naturally cycling women showed prominent peaks in the temporal pattern of urinary fructose-1,6-bisphosphatase and glutathione-S-transferase-α release exclusively within 7 days after ovulation or onset of menses. In contrast, postmenopausal women and men showed consistently low levels of urinary fructose-1,6-bisphosphatase excretion over comparable periods. We did not detect changes in urinary α1-microglobulin, albumin, or IgG excretion. Results of this study indicate that proximal tubular tissue architecture, representing a nonreproductive organ-derived epithelium, undergoes periodical adaptations phased by the female reproductive hormone cycle. The temporally delimited higher rate of enzymuria in ovulating women might be a sign of recurring increases of tubular cell turnover that potentially provide enhanced repair capacity and thus, higher resistance to renal damage.

The Role of Gender in Chronic Kidney Disease

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

The protective role of G protein-coupled estrogen receptor 1 (GPER-1) on methotrexate-induced nephrotoxicity in human renal epithelium cells

Nephrotoxicity is an important problem during methotrexate (MTX) treatment, which has been widely used for the treatment of several cancer types. Females are less susceptible to kidney diseases; however, the reason for this condition has not to be fully clarified. But sex hormones such as estrogen may have a protective effect on the kidney. We aimed to evaluate the possible protective role of estrogen on the MTX-induced renal epithelial cell death. Primary renal proximal tubular epithelial cells (RPTEC) were incubated with MTX (1, 10 and 100 μM), either alone or in combination with the 17β-estradiol, G protein-coupled estrogen receptor 1 (GPER1) agonist G-1, estrogen receptor alpha agonist propyl pyrazole triol (PPT), estrogen receptor beta agonist diarylpropionitrile (DPN). Cell viability was determined by MTT assays. Interleukin (IL)-1β, IL-6, superoxide dismutase (SOD) and malondialdehyde (MDA) levels were determined in RPTEC. Approximately half of the cell death was observed with 10 μM MTX incubation for 48 h. The cell death was prevented by co-incubating with17β-estradiol, PPT and G-1. MTX was significantly induced IL-1β and IL-6.17β-estradiol, PPT and G-1 significantly decreased effects of MTX. SOD activity was significantly decreased treatment with MTX compared to control group. SOD activity was increased with co-incubation with 17β-estradioland G-1 compared to treatment with MTX. MDA levels significantly increased in treatment with MTX compared with the control group. Increased MDA levels by MTX-induced was decreased significantly by the treatment with 17β-estradiol and G-1. These data indicate that especially 17β-estradiol and G-1 may be useful in preventing undesirable effects of MTX in renal failure.

Antioxidant diet and sex interact to regulate NOS isoform expression and glomerular mesangium proliferation in Zucker diabetic rat kidney

Oxidative stress contributes substantially to the pathophysiology of diabetic nephropathy (DN). Consumption of an antioxidant-fortified (AO) diet from an early age prevents or delays later development of DN in the Zucker rat female with type 2 diabetes. We hypothesize this is due to effects on mesangial matrix and renal nitric oxide synthase (NOS) distribution and to sex-specific differences in NOS responses in the diabetic kidney. Total glomerular tuft area (GTA) and PAS-positive tuft area (PTA), endothelial (e), neuronal (n) and inducible (i) NOS were quantified in males and females on AO or regular (REG) diet at 6 and 20 weeks of age. eNOS was observed in glomeruli and tubules. nNOS predominantly localized to tubular epithelium in both cortex and medulla. iNOS was expressed in proximal and distal tubules and collecting ducts. Sex, diabetes duration and AO diet affected the distribution of the three isoforms. GTA and PTA increased with duration of hyperglycemia and showed a negative correlation with renal levels of all NOS isoforms. AO diet in both genders was associated with less PAS-positive staining and less mesangial expansion than the REG diet, an early increase in cortical iNOS in males, and sex-specific changes in cortical eNOS at 20 weeks. These effects of AO diet may contribute to sex-specific preservation of renal function in females.

Does a Reduction in the Glomerular Filtration Rate Increase the Overall Severity of Coronary Artery Stenosis?

OBJECTIVE

Chronic kidney disease is a risk factor of coronary events, however, its impact on coronary artery stenosis has not yet been clarified with the use of a large database. We examined the association between a reduced glomerular filtration rate (GFR) and the overall severity of coronary stenosis.

METHODS

We enrolled 1,150 patients [mean age, 68±12 (SD) years; 66.6% men] who consecutively underwent coronary angiography for suspected stable angina pectoris. The overall severity of stenosis in the coronary arteries was assessed by the Gensini score (GS), and its logarithmic values (log-GS) were used for statistical analyses since the GS does not follow a normal distribution.

RESULTS

The log-GS was significantly larger in men than in women (2.5±1.5 vs. 1.9±1.7), while the estimated GFR (eGFR) and comorbidities were comparable between both sexes. A multivariate regression analysis indicated that age, smoking, eGFR, HDL-cholesterol and HbA1c were independent explanatory variables of the log-GS in men, although the eGFR explained only 1.2% of the log-GS variation. In women, the eGFR was not included in the significant explanatory variables shown by the multivariate analysis. However, the sex difference in the regression for the eGFR-log-GS relationship was not statistically significant.

CONCLUSION

A reduced eGFR is a significant, but minor, determinant of the overall severity of coronary artery stenosis in men and potentially women.

Accelerated age-related decline in renal and vascular function in female rats following early-life growth restriction

Many studies report sexual dimorphism in the fetal programming of adult disease. We hypothesized that there would be differences in the age-related decline in renal function between male and female intrauterine growth-restricted rats. Early-life growth restriction was induced in rat offspring by administering a low-protein diet (LPD; 8.7% casein) to dams during pregnancy and lactation. Control dams were fed a normal-protein diet (NPD; 20% casein). Mean arterial pressure (MAP) and renal structure and function were assessed in 32- and 100-wk-old offspring. Mesenteric artery function was examined at 100 wk using myography. At 3 days of age, body weight was ∼24% lower ( P < 0.0001) in LPD offspring; this difference was still apparent at 32 wk but not at 100 wk of age. MAP was not different between the male NPD and LPD groups at either age. However, MAP was greater in LPD females compared with NPD females at 100 wk of age (∼10 mmHg; P < 0.001). Glomerular filtration rate declined with age in the NPD male, LPD male and LPD female offspring (∼45%, all P < 0.05), but not in NPD female offspring. Mesenteric arteries in the aged LPD females had reduced sensitivity to nitric oxide donors compared with their NPD counterparts, suggesting that vascular dysfunction may contribute to the increased risk of disease in aged females. In conclusion, females growth-restricted in early life were no longer protected from an age-related decline in renal and arterial function, and this was associated with increased arterial pressure without evidence of renal structural damage.

Development of progressive albuminuria in male Munich Wistar Frömter rats is androgen dependent

Munich Wistar Frömter (MWF) rats develop spontaneous albuminuria that is linked to autosomal genetic loci and inherit a nephron deficit in both female and male animals, respectively. However, albuminuria and kidney damage are clearly more pronounced in males. Here we tested whether androgens and the androgen receptor influence albuminuria in male MWF. We first demonstrated in a pilot study that orchiectomy (Ox) of male MWF led to a significant suppression of urinary albumin excretion (UAE), while continuous testosterone supplementation in MWF Ox led to UAE levels similar to sham-operated (Sham) MWF rats. Subsequently, we performed a comparative main study between male MWF and normal Wistar rats to evaluate the effect of the androgen receptor on UAE development in adult animals up to the age of 18 wk. MWF Sham developed a marked increase in UAE compared with Wistar Sham (48.30 ± 6.16 vs. 0.42 ± 0.08 mg/24 h, P < 0.0001). UAE was significantly lower in MWF Ox compared with MWF Sham (-55%, P < 0.0001). In MWF Ox animals supplemented with testosterone and treated with the androgen receptor antagonist flutamide (OxTF) UAE at 18 wk was even lower compared with MWF Ox (-71%, P < 0.01) and similar to age-matched female MWF. The mRNA expression of renal tubular injury markers Kim1 and NGAL was increased in MWF Sham compared with Wistar Sham (P < 0.0008, respectively) and expression decreased significantly in MWF OxTF (P < 0.0004, respectively). Thus, the sexual dimorphism in albuminuria development in MWF can be attributed to testosterone and the androgen receptor in male rats.

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

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

The impact of elevation of serum uric acid level on the natural history of glomerular filtration rate (GFR) and its sex difference

BACKGROUND

The impact of elevation of the serum uric acid level (SUA) on the natural history of glomerular filtration rate (GFR) remains controversial.

METHODS

If elevation of SUA is a result, rather than a cause, of a decline in GFR, the relationship between SUA and GFR should be the same in the same population over years except for shifts by age-dependent reduction of GFR. We tested this hypothesis using data from two cohorts and a group of allopurinol-treated patients.

RESULTS

In Cohort 1 consisting of urban residents aged 40.6 ± 9.0 years (n = 3 446), SUA was inversely correlated with estimated GFR (eGFR) in both men and women, and the slope of the SUA-eGFR relationship was steeper in women than in men. The slopes of the regression lines became significantly steeper after a 6-year interval in both sexes, and the change in the slope was larger in women. A similar sex difference in the SUA-eGFR relationship and 6-year change in the slope were observed in Cohort 2 consisting of rural town residents aged 61.7 ± 12.2 years (n = 404). Multiple regression analyses showed that explanatory factors of eGFR after a 6-year interval were age and SUA at baseline in both cohorts, and partial regression coefficients of SUA were more negative in women than in men. The SUA-eGFR relationship in allopurinol-treated patients (n = 346, 63.5 ± 13.3 years old) was similar to that in Cohort 2.

CONCLUSIONS

The results indicate that elevation of SUA accelerates the yearly decline in eGFR and that women are more susceptible to urate-induced decline in eGFR.

Mitigation of lead-induced neurotoxicity by the naringin: erythrocytes as neurons substitute markers

This study aimed to investigate the effect of lead (Pb) on neuronal nitric oxide synthase (nNOS) activity using erythrocytes as neurons surrogate markers. Moreover, the protective effect of naringin (NAR) against lead acetate (PbAc)-induced neurotoxicity was investigated. Human erythrocytes were incubated with L-arginine (L-Arg), Nω-nitro-L-Arginine methyl ester ( L-NAME), NAR, PbAc, PbAc+L-Arg, PbAc+NAR, or PbAc+L-Arg+NAR. The present results revealed that incubation of erythrocytes with PbAc inhibited NOS activity and decreased nitrite levels as an index for nitric oxide (NO) production to values similar that of L-NAME as known NOS inhibitor. Likewise, PbAc induced a significant decrease in activities of ATPases and acetylcholinesterase compared to control cells. Furthermore, PbAc exposure significantly increased protein carbonyl content (PCC) and malondialdehyde (MDA) levels while significantly decrease the levels of reduced glutathione (GSH). On the contrary, incubation of erythrocytes with PbAc in the presence of L-Arg+NAR synergistically ameliorated the investigated parameters compared to erythrocytes incubated with PbAc alone. These data suggest that NAR can restore NO bioavailability in a situation of Pb-induced cellular damage. This attributed to antioxidant activity and restoration NOS activity.

Tissue-specific changes in pregnancy associated plasma protein-A expression with age in mice

Pregnancy-associated plasma protein-A (PAPP-A) is a novel zinc metalloproteinase that functions in many systems outside of pregnancy. Data in both humans and mice suggest a role for PAPP-A in aging and age-related diseases. However, our knowledge of tissue-specific PAPP-A expression and possible changes in this expression with age is limited. Thus, the aim of this study was to determine PAPP-A mRNA expression in multiple tissues with age in both male and female mice using real-time PCR. These included the heart, liver, kidney, bone, fat, skeletal muscle, gonads, brain, thymus and spleen. In young mice, PAPP-A mRNA was expressed at relatively high levels in all tissues examined except for liver. The only difference in expression between males and females was seen in the kidney, subcutaneous fat and gonads. The highest PAPP-A mRNA expression levels were found in visceral fat and these were 10-fold higher than in subcutaneous fat. PAPP-A expression significantly increased with age in kidney, brain and gonads. PAPP-A expression significantly deceased with age in bone and skeletal muscle. In the thymus, PAPP-A mRNA showed a biphasic response with age. There were no age-related changes in PAPP-A expression seen in any of the other tissues examined. Expression of IGFBP-5 mRNA, a marker of insulin-like growth factor-I (IGF-I) bioactivity known to be regulated by PAPP-A, paralleled the changes in PAPP-A expression with age in kidney, bone, skeletal muscle and thymus. Thus, tissue-specific PAPP-A expression in mice is differentially affected during aging, and may regulate local IGF-I bioactivity in certain tissues.