Hypogonadotropic hypogonadism in nephrotic rats: increased sensitivity to negative feedback effects of testosterone

A Novel Model for Nephrotic Syndrome Reveals Associated Dysbiosis of the Gut Microbiome and Extramedullary Hematopoiesis

Glomerular kidney disease causing nephrotic syndrome is a complex systemic disorder and is associated with significant morbidity in affected patient populations. Despite its clinical relevance, well-established models are largely missing to further elucidate the implications of uncontrolled urinary protein loss. To overcome this limitation, we generated a novel, inducible, podocyte-specific transgenic mouse model (Epb41l5^fl/fl*Nphs1-rtTA-3G*tetOCre), developing nephrotic syndrome in adult mice. Animals were comprehensively characterized, including microbiome analysis and multiplexed immunofluorescence imaging. Induced knockout mice developed a phenotype consistent with focal segmental glomerular sclerosis (FSGS). Although these mice showed hallmark features of severe nephrotic syndrome (including proteinuria, hypoalbuminemia and dyslipidemia), they did not exhibit overt chronic kidney disease (CKD) phenotypes. Analysis of the gut microbiome demonstrated distinct dysbiosis and highly significant enrichment of the Alistipes genus. Moreover, Epb41l5-deficient mice developed marked organ pathologies, including extramedullary hematopoiesis of the spleen. Multiplex immunofluorescence imaging demonstrated red pulp macrophage proliferation and mTOR activation as driving factors of hematopoietic niche expansion. Thus, this novel mouse model for adult-onset nephrotic syndrome reveals the significant impact of proteinuria on extra-renal manifestations, demonstrating the versatility of this model for nephrotic syndrome-related research.

Bioavailable Testosterone Is Positively Associated With Bone Mineral Density in Male Kidney Transplantation Candidates

Introduction

Low levels of sex hormones are common in patients with chronic kidney disease (CKD) and may be a contributing factor to bone fragility. We investigated associations between levels of sex hormones and bone mineral density (BMD) in adult kidney transplantation candidates.

Methods

Volumetric BMD of spine and hip were measured by computed tomography. Parathyroid hormone (PTH), testosterone (T), estradiol (E), and sex hormone–binding globulin were measured from fasting morning blood samples. Bioavailable (Bio) T and E were calculated based on constants for protein binding.

Results

A total of 146 patients (102 men and 44 women) were included in the analyses. The median age was 54 years (range, 32−72 years); 32% were diabetic; and 36% received maintenance dialysis therapy. In men, Bio T was positively associated with BMD at the lumbar spine (β = 5.02, P = 0.002), total hip (β = 6.35, P = 0.001), and femoral neck (β = 13.9, P = 0.002), independently of age, body mass index, dialysis, diabetes type 1 and 2, parathyroid hormone, and steroid exposure. Bio E was positively associated with BMD at the lumbar spine (β = 0.23, P = 0.03) and femoral neck (β = 0.61, P = 0.04) using the same fully adjusted model. In postmenopausal women, Bio T was positively correlated with lumbar spine BMD (r = 0.46, P = 0.02).

Conclusion

High endogenous levels of sex hormones are associated with greater BMD in male kidney transplantation candidates. Disturbances in the gonadal axis may contribute to skeletal fragility in men with late-stage CKD.

[Andrologic consequences of chronic renal failure: State of the art for the yearly scientific report of the French National Association of Urology]

OBJECTIVE

To describe the state of the art of current knowledge regarding gonadal consequences of end-stage chronic kidney disease (CKD) and renal transplantation.

MATERIAL AND METHOD

A systematic review of the literature search was performed from the databases Medline (NLM, Pubmed) and Embase, focused on the following keywords: "chronic kidney disease"; "chronic renal failure"; "hypogonadism"; "kidney transplantation"; "testicular dysfunction"; "testosterone". Publications obtained were selected based on methodology, language, date of publication (last 10 years) and relevance. Prospective and retrospective studies, in English or French, review articles; meta-analysis and guidelines were selected and analyzed. This search found 383 articles. After reading titles and abstracts, 51 were included in the text, based on their relevance.

RESULTS

The prevalence of hypogonadism in CKD is reported between 24 % and 66 %, and decreases partially after renal transplantation. This is a hypogonadotropic hypogonadism whose pathophysiology is multifactorial, involving mainly a primitive testicular deficit, a hypothalamic-pituitary dysregulation, and an hyperprolactinemia. The consequences of this hypogonadism are not only sexual but also contribute to anemia, sarcopenia, atherosclerosis, and potentially in the progression of CKD. Hypogonadism is an independent risk factor for mortality in CKD patients.

CONCLUSIONS

CKD is frequently associated with an hypogonadism whose correction is validated only in the setting of erectile dysfunction treatment. The other benefits of the correction of hypogonadism in the CKD patients, including overall survival, needs to be evaluated.

The vulnerable man: impact of testosterone deficiency on the uraemic phenotype

Testosterone deficiency or hypogonadism is a common finding in men undergoing dialysis, to a great extent a consequence of the failing kidney per se. Testosterone restoration in hypogonadism is common practice among endocrinologists. However, there is currently little awareness of this condition among both uremic patients and nephrologists, and in many cases, testosterone deficiency remains unscreened and untreated. This review article summarizes our current understanding of the role of testosterone deficiency at the crossroad of cardiometabolic complications of patients with chronic kidney disease. Pathways discussed include, among others, the plausible role of testosterone deficiency in the development of anaemia and ESA hyporesponsiveness, muscle catabolism, endothelial dysfunction, cognitive dysfunction, decreased libido, cardiovascular disease and mortality. As there are limited sources to guide decision-making, we also review existing testosterone replacement therapy studies in the context of CKD as well as considerations for side and adverse effects. This review makes a case for consideration of screening and better management of hypogonadism in men undergoing dialysis.

Evaluation of the pituitary-testicular function during experimental nephrosis

To investigate the pituitary-testicular function in nephrotic rats, a sequence of experiments was undertaken in adult male rats after a single dose of puromycin aminonucleoside (PAN). Endocrine modifications were evaluated chronologically throughout the experimental disease in order to determine the appearance of hormone alterations which lead to the axis dysfunction. Serum concentration of LH, FSH, androstenedione, total and free testosterone, estradiol as well as urine testosterone were measured by specific RIAs on days 3, 7 and 10 after treatment on nephrotic and control groups. Prolactin was also evaluated on day 10. Likewise, total weight of various androgen responsive tissues from both groups was recorded, and the number of androgen receptor (AR) binding sites were determined. To know the functional status of the hipophyseal-testicular unit, groups of nephrotic and control rats were stimulated with LHRH (300 ng/100 g b.w.) or with one or four doses of hCG (8 UI), respectively. Additionally, the relative in vitro biological activity of FSH from nephrotic and control rats before and after LHRH stimulus was determined. The results from the hormonal profile revealed clear endocrine disorders characterized by a progressive diminution of all serum hormones except prolactin and urine testosterone, which remained unmodified. The weight of the main androgen responsive tissues, the ventral prostate and the seminal vesicle, decreased parallelly to androgen diminution. The binding analysis of AR shows a significant elevation of the available androgen sites in all analyzed tissues except kidney and hypothalamus. The secretion of LH and FSH from nephrotic animals after LHRH administration was lower than that from intact animals at the registered times. Interestingly, the biological activity of FSH from nephrotic rats was not detectable at both, before and after LHRH administration. Testicular response to hCG stimuli, in terms of testosterone synthesis was not significantly different in the two groups analyzed with respect to the intact animals. By contrast, no response was observed in terms of estradiol production at either one or four doses of hCG. On the whole, the results presented herein allow us to conclude that experimental nephrosis has a harmful effect on the pituitary-testicular axis, and strongly suggests that the endocrine dysfunction is initiated at the hypophyseal level; even though a specific testicular damage is also present.

Transient alteration of the reproductive function in nephrotic rats

The reproductive function of male and female rats with induced nephrotic syndrome was examined by assessing hormonal levels, the estrous cycle pattern and fertility. Measurements were carried out on day 10 (nephrotic stage) and on day 30 (remission stage) after treatment (a single s.c. dose of puromycin aminonucleoside 15 mg/100 g body wt.). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone (P4) from both sexes as well as 17beta-estradiol (E2) in females and total testosterone (tT) in males were assayed at both phases of the illness by specific radioimmunoassays; free and urine testosterone (fT, uT) was also determined in male rats on day 10. The estrous cycle was followed alongside the study through vaginal smears, while fertility was estimated by the rate of pregnancies (females) or pregnancy induction (males), and by the litter size. The results showed that most serum hormone levels, except FSH in females, were significantly reduced at the nephrotic stage of the illness, returning to their normal values after 30 days. Besides, on day 10, fT was found reduced in nephrotic males, while uT concentrations remained unmodified. The ovulatory cycle of nephrotic rats was disrupted on day 3 and not restored until day 23; nevertheless, the reproductive function, measured as a fertility index, was fully reinstalled at the remission stage. Interestingly, the capacity of fertilization of the nephrotic males was not entirely abolished during the acute phase, since 37% of the animals were fertile. Moreover, on day 30 the reproductive function in nephrotic males was totally recovered. The data from this study show the existence of reversible endocrine disorders in rats bearing nephrotic syndrome; such changes are manifested during the acute phase of the illness as a temporary cessation of the reproductive processes.