Retinoic acid-induced testosterone production and retinoylation reaction are concomitant and exhibit a positive correlation in Leydig (TM-3) cells

Dual effects of 9-cis retinoic acid on ACTH-dependent hyperplastic adrenal tissues

Retinoids play a pivotal role in adrenal development and differentiation. Recent clinical trials revealed therapeutic potential of both all-trans and 9-cis retinoic acid in patients with cortisol excess due to a pituitary ACTH-secreting adenoma and indicated that retinoids might act also on the adrenal. Aim of the present study was to evaluate the effect of 9-cis retinoic acid on adrenals from patients with ACTH-dependent Cushing’s syndrome. Adrenal specimens from six patients with Cushing’s disease were incubated with 10 nM–1 µM 9-cis retinoic acid with and without 10 nM ACTH. Cortisol secretion was measured by immunoassay and expression of genes involved in steroidogenesis as well as retinoic acid action were evaluated by real-time RT-PCR. Incubation with 10–100 nM 9-cis retinoic acid increased spontaneous cortisol secretion and expression of STAR and CYP17A. On the other hand, in wells treated with ACTH, 9-cis retinoic acid markedly diminished ACTH receptor upregulation and no stimulatory effect on cortisol secretion or steroidogenic enzyme synthesis was observed. ACTH itself increased ligand-induced retinoic acid receptor expression, possibly enhancing sensitivity to retinoic acid. Our findings indicate that the effect of 9-cis retinoic acid in presence of ACTH is distinct from unchallenged wells and support the hypothesis of a direct adrenal action in patients with Cushing’s disease.

How biological sex of the host shapes its gut microbiota

The gut microbiota is a complex system, consisting of a dynamic population of microorganisms, involved in the regulation of the host's homeostasis. A vast number of factors are driving the gut microbiota composition including diet, antibiotics, environment, and lifestyle. However, in the past decade, a growing number of studies also focused on the role of sex in relationship to changes in the gut microbiota composition in animal experiments as well as in human beings. Despite the progress in investigation techniques, still little is known about the mechanism behind the observed sex-related differences. In this review, we summarized current knowledge on the sex-dependent differences of the intestinal commensals and discuss the probable direct impact of sex hormones and more indirect effects such as dietary habits or antibiotics. While we have to conclude limited data on specific developmental stages, a clear role for sexual hormones and most probably for testosterone emerges.

Transcriptome Analysis Reveals that Vitamin A Metabolism in the Liver Affects Feed Efficiency in Pigs

Feed efficiency (FE) is essential for pig production. In this study, 300 significantly differentially expressed (DE) transcripts, including 232 annotated genes, 28 cis-natural antisense transcripts (cis-NATs), and 40 long noncoding RNAs (lncRNAs), were identified between the liver of Yorkshire pigs with extremely high and low FE. Among these transcripts, 25 DE lncRNAs were significantly correlated with 125 DE annotated genes at a transcriptional level. These DE genes were enriched primarily in vitamin A (VA), fatty acid, and steroid hormone metabolism. VA metabolism is regulated by energy status, and active derivatives of VA metabolism can regulate fatty acid and steroid hormones metabolism. The key genes of VA metabolism (CYP1A1, ALDH1A2, and RDH16), fatty acid biosynthesis (FASN, SCD, CYP2J2, and ANKRD23), and steroid hormone metabolism (CYP1A1, HSD17B2, and UGT2B4) were significantly upregulated in the liver of high-FE pigs. Previous study with the same samples indicated that the mitochondrial function and energy expenditure were reduced in the muscle tissue of high-FE pigs. In conclusion, VA metabolism in liver tissues plays important roles in the regulation of FE in pigs by affecting energy metabolism, which may mediate fatty acid biosynthesis and steroid hormone metabolism. Furthermore, our results identified novel transcripts, such as cis-NATs and lncRNAs, which are also involved in the regulation of FE in pigs.

Role of the steroidogenic acute regulatory protein in health and disease

Steroid hormones are an important class of regulatory molecules that are synthesized in steroidogenic cells of the adrenal, ovary, testis, placenta, brain, and skin, and influence a spectrum of developmental and physiological processes. The steroidogenic acute regulatory protein (STAR) predominantly mediates the rate-limiting step in steroid biosynthesis, i.e., the transport of the substrate of all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane. At the inner membrane, cytochrome P450 cholesterol side chain cleavage enzyme cleaves the cholesterol side chain to form the first steroid, pregnenolone, which is converted by a series of enzymes to various steroid hormones in specific tissues. Both basic and clinical evidence have demonstrated the crucial involvement of the STAR protein in the regulation of steroid biosynthesis. Multiple levels of regulation impinge on STAR action. Recent findings demonstrate that hormone-sensitive lipase, through its action on the hydrolysis of cholesteryl esters, plays an important role in regulating STAR expression and steroidogenesis which involve the liver X receptor pathway. Activation of the latter influences macrophage cholesterol efflux that is a key process in the prevention of atherosclerotic cardiovascular disease. Appropriate regulation of steroid hormones is vital for proper functioning of many important biological activities, which are also paramount for geriatric populations to live longer and healthier. This review summarizes the current level of understanding on tissue-specific and hormone-induced regulation of STAR expression and steroidogenesis, and provides insights into a number of cholesterol and/or steroid coupled physiological and pathophysiological consequences.

Anti-inflammatory potential of β-cryptoxanthin against LPS-induced inflammation in mouse Sertoli cells

β-cryptoxanthin (CX), a major carotenoid pigment, can inhibit inflammatory gene expression in mice with nonalcoholic steatohepatitis. In the present study, we examined the anti-inflammatory effects of CX on lipopolysaccharide (LPS)-induced inflammation in mouse primary Sertoli cells and the possible molecular mechanisms behind its effects. The results showed that CX significantly inhibited LPS-induced decreases in cell viability and in the percentage of apoptotic cells. Moreover, CX inhibited the LPS-induced up-regulation of tumor necrosis factor α (TNF-α), interleukin-10 (IL-10), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in Sertoli cells. In addition, CX significantly limited the LPS-induced down-regulation of AR, HSF2, CREB, FSHR, INHBB and ABP in Sertoli cells. Western blot analysis showed that CX significantly suppressed NF-κB (p65) activation as well as MAPK phosphorylation. All the results suggested that CX suppressed inflammation, possibly associated with the NF-κB activation and MAPK of phosphorylation. Thus, CX may possess therapeutic potential against inflammation-related diseases.

Nuclear MEK1 sequesters PPARγ and bisects MEK1/ERK signaling: a non-canonical pathway of retinoic acid inhibition of adipocyte differentiation

Uncontrolled adipogenesis and adipocyte proliferation have been connected to human comorbidities. Retinoic acid (RA) is known to inhibit adipocyte differentiation, however the underlying mechanisms have not been adequately understood. This study reports that RA acting as a ligand to RA receptors (RARs and RXRs) is not a sine qua non to the inhibition of adipogenesis. Our intriguing observation of a negative correlation between increased retinoylation and adipogenesis led us to explore retinoylated proteins in adipocytes. Exportin (CRM1) was found to be retinoylated, which in turn can affect the spatio-temporal regulation of the important signaling molecule mitogen-activated protein kinase kinase 1 (MEK1), likely by disrupting its export from the nucleus. Nuclear enrichment of MEK1 physically sequesters peroxisome proliferator-activated receptor gamma (PPARγ), the master regulator of adipogenesis, from its target genes and thus inhibits adipogenesis while also disrupting the MEK1-extracellular-signal regulated kinase (ERK) signaling cascade. This study is first to report the inhibition of adipocyte differentiation by retinoylation.

Synergistic activation of steroidogenic acute regulatory protein expression and steroid biosynthesis by retinoids: involvement of cAMP/PKA signaling

Both retinoic acid receptors (RARs) and retinoid X receptors (RXRs) mediate the action of retinoids that play important roles in reproductive development and function, as well as steroidogenesis. Regulation of steroid biosynthesis is principally mediated by the steroidogenic acute regulatory protein (StAR); however, the modes of action of retinoids in the regulation of steroidogenesis remain obscure. In this study we demonstrate that all-trans retinoic acid (atRA) enhances StAR expression, but not its phosphorylation (P-StAR), and progesterone production in MA-10 mouse Leydig cells. Activation of the protein kinase A (PKA) cascade, by dibutyrl-cAMP or type I/II PKA analogs, markedly increased retinoid-responsive StAR, P-StAR, and steroid levels. Targeted silencing of endogenous RARα and RXRα, with small interfering RNAs, resulted in decreases in 9-cis RA-stimulated StAR and progesterone levels. Truncation of and mutational alterations in the 5'-flanking region of the StAR gene demonstrated the importance of the -254/-1-bp region in retinoid responsiveness. An oligonucleotide probe encompassing an RXR/liver X receptor recognition motif, located within the -254/-1-bp region, specifically bound MA-10 nuclear proteins and in vitro transcribed/translated RXRα and RARα in EMSAs. Transcription of the StAR gene in response to atRA and dibutyrl-cAMP was influenced by several factors, its up-regulation being dependent on phosphorylation of cAMP response-element binding protein (CREB). Chromatin immunoprecipitation studies revealed the association of phosphorylation of CREB, CREB binding protein, RXRα, and RARα to the StAR promoter. Further studies elucidated that hormone-sensitive lipase plays an important role in atRA-mediated regulation of the steroidogenic response that involves liver X receptor signaling. These findings delineate the molecular events by which retinoids influence cAMP/PKA signaling and provide additional and novel insight into the regulation of StAR expression and steroidogenesis in mouse Leydig cells.

Effects of vitamin A on in vitro maturation of pre-pubertal mouse spermatogonial stem cells

Testicular tissue cryopreservation is the only potential option for fertility preservation in pre-pubertal boys exposed to gonadotoxic treatment. Completion of spermatogenesis after in vitro maturation is one of the future uses of harvested testicular tissue. The purpose of the current study was to evaluate the effects of vitamin A on in vitro maturation of fresh and frozen-thawed mouse pre-pubertal spermatogonial stem cells in an organ culture system. Pre-pubertal CD1 mouse fresh testes were cultured for 7 (D7), 9 (D9) and 11 (D11) days using an organ culture system. Basal medium was supplemented with different concentrations of retinol (Re) or retinoic acid (RA) alone or in combination. Seminiferous tubule morphology (tubule diameter, intra-tubular cell type), intra-tubular cell death and proliferation (PCNA antibody) and testosterone level were assessed at D7, D9 and D11. Pre-pubertal mouse testicular tissue were frozen after a soaking temperature performed at -7°C, -8°C or -9°C and after thawing, were cultured for 9 days, using the culture medium preserving the best fresh tissue functionality. Retinoic acid at 10^-6M and retinol at 3.3.10^-7M, as well as retinol 10^-6M are favourable for seminiferous tubule growth, maintenance of intra-tubular cell proliferation and germ cell differentiation of fresh pre-pubertal mouse spermatogonia. Structural and functional integrity of frozen-thawed testicular tissue appeared to be well-preserved after soaking temperature at -8°C, after 9 days of organotypic culture using 10^-6M retinol. RA and Re can control in vitro germ cell proliferation and differentiation. Re at a concentration of 10^-6M maintains intra-tubular cell proliferation and the ability of spermatogonia to initiate spermatogenesis in fresh and frozen pre-pubertal mouse testicular tissue using a soaking temperature at -8°C. Our data suggested a possible human application for in vitro maturation of cryopreserved pre-pubertal testicular tissue.

Fresh onion juice enhanced copulatory behavior in male rats with and without paroxetine-induced sexual dysfunction

Onion ( Allium cepa) is one of the most commonly cultivated species of the family Liliaceae, and has long been used in dietary and therapeutic applications. Treatment with fresh onion juice has been reported to promote testosterone production in male rats. Testosterone is the male sex hormone responsible for enhancing sexual libido and potency. This study aimed to investigate the effects of onion juice on copulatory behavior of sexually potent male rats and in male rats with paroxetine-induced sexual dysfunction. Sexually experienced male rats were divided into seven groups: a control group, three onion juice-treated groups, a paroxetine-treated group, and two groups treated with paroxetine plus different doses of onion juice. At the end of the treatments, sexual behavior parameters and testosterone levels were measured and compared among the groups. Administration of onion juice significantly reduced mount frequency and latency and increased the copulatory efficacy of potent male rats. In addition, administration of onion juice attenuated the prolonged ejaculatory latency period induced by paroxetine and increased the percentage of ejaculating rats. Serum testosterone levels increased significantly by onion juice administration. However, a significant reduction in testosterone because of paroxetine therapy was observed. This reduction was restored to normal levels by administration of onion juice. This study conclusively demonstrates that fresh onion juice improves copulatory behavior in sexually potent male rats and in those with paroxetine-induced sexual dysfunction by increasing serum testosterone levels.

Adrenal glands and testes as steroidogenic tissue are affected by retinoylation reaction

This study was undertaken to better understand the physiological role of the retinoylation process in steroidogenic tissues. In adrenal gland mitochondria, the retinoylation extent was found equal to that of testes mitochondria but without ATP in the incubation buffer. We pointed out that the endogenous mitochondrial ATP in adrenal glands is much higher than in testes, about 1.3 x 10(-2) M and 5.2 x 10(-8) M, respectively. In addition, less CoASH is required for the maximal acylation activity of the retinoyl moiety to protein(s) compared to testes. The fatty acid analysis revealed a different composition of mitochondrial membranes of these two tissues. Among the different values of fatty acids, it is important to note that adrenal glands contain a much higher amount of C18:0 and a much lower amount of C22:5 omega6 and C22:6 omega3 than testes in the mitochondrial membranes. In addition, there were also differences in arachidonic acid (ARA, C20:4 omega6) content between adrenal glands and testes mitochondria. These different values in the fatty acids composition should explain the different extent of the retinoylation process between the two organs.