Effect of lipoproteins on cholesterol synthesis in rat Sertoli cells

Dietary supplementation with barley sprouts and d-aspartic acid improves reproductive hormone concentrations, testicular histology, antioxidant status, and mRNA expressions of apoptosis-related genes in aged broiler breeder roosters

The objective was to determine effects of dietary supplementation of barley sprouts (BS) and/or d-aspartic acid (DA) on the reproductive potential of aged broiler roosters. Birds (n = 32, 50 wk old) were randomly allocated to receive dietary supplements of BS powder (2 % of basal diet), and DA (200 mg/kg BW), both, or neither, for 12 wk. Roosters were housed individually, with 14-h light/10-h dark, ad libitum feed and water, and euthanized after 12 wk. Mean (±SEM) total phenolic compounds and IC50 in methanol extract of sprouted barley were 302.8 ± 10.9 mg GAE/g and 600.8 ± 50.5 mg TE per 100 g, respectively. In weekly semen collections, sperm total and progressive motility, plasma membrane integrity, sperm concentration, and sperm production were higher (P < 0.05) in both the DA + BS and BS groups compared to the Control, but sperm abnormalities were unaffected. Feeding DA increased right, left, and combined testicular weights (P < 0.05, P < 0.05, and P < 0.01, respectively) and, the testicular index (P = 0.01). Feeding BS increased seminiferous tubule diameter (P < 0.01), whereas BS + DA increased seminiferous epithelium thickness (P < 0.01). There were more spermatogonia (P < 0.01) and Leydig cells (P < 0.05) in BS-fed roosters but Sertoli cells were highest in BS + DA (P < 0.01). Serum MDA concentrations were lowest in BS (P < 0.01), whereas serum testosterone and LH were highest in DA (P < 0.05) and BS + DA (P < 0.01), respectively. Feeding BS reduced serum total cholesterol (P < 0.05) and increased serum HDL-cholesterol (P < 0.01), with decreases in serum LDL (P < 0.01) and the LDL/HDL ratio (P < 0.01) for BS + DA compared to Control. Relative expression of glutathione peroxidase mRNA was increased by BS (P < 0.01) or DA (P < 0.05), whereas relative mRNA expression of SOD was highest in BA (P < 0.01). Control roosters were highest for both BAX (P < 0.01) and the relative expression of the BAX/BCL-2 ratio (P < 0.01), whereas BS + DA increased BCL-2 (P < 0.05). In conclusion, feeding BS, and/or DA significantly improved reproductive potential in aged broiler roosters.

PCSK9 Contributes to the Cholesterol, Glucose, and Insulin2 Homeostasis in Seminiferous Tubules and Maintenance of Immunotolerance in Testis

The PCSK9 contribution to cholesterol and immunotolerance homeostasis and response to glucose, and insulin in testis and hypophysis were studied using Pcsk9-deficient (-/-) and transgenic [Tg (PCSK9)] mice, and diabetic, obese ob/ob and db/db mice. The spermatids/spermatozoa acrosome, peritubular vessels, and epididymal adipocytes were PCSK9- and LDL-R-positive. The pro-PCSK9/PCSK9 ratio was high in interstitial tissue-fractions (ITf) and spermatozoa and low in seminiferous tubule-fractions (STf) in normal adult mice. This ratio decreased in ITf in ob/ob and db/db mice but increased in tubules in ob/ob mice. Deleting pcsk9 lowered cholesterol in serum but increased testicular cholesterol. Furthermore, HMGCoA-red, ACAT-2 and LDL-R turnover increased whereas SR-BI decreased in ITf; in tubules, ABCA1 decreased and 160 kDa LDL-R increased in Pcsk9 -/- mice. Excess testicular cholesterol could result from increased cholesterol synthesis and uptake with reduction in SR-BI-mediated efflux in ITf and from the overload of apoptotic cells, lowered ABCA1-mediated efflux and stimulated LDL-R protein synthesis in tubules in Pcsk9 -/- mice. Concomitantly with the cholesterol accumulation, tubules showed infiltrates of immune cells, elevated IL-17A and IL-17RA, and changes in the immunotolerance homeostasis. PCSK9 deficiency decreased glucose in tubules and spermatozoa while increasing insulin2 in ITf and tubules not serum. Moreover, IR-α, and IR-β augmented in tubules but decreased in the anterior pituitary; IR-α increased whereas IR-β decreased in ITf. The histology and cholesterol levels were normal in Tg (PCSK9) mouse testis. The excess cholesterol creates a milieu favorable to the action of high IL-17A and IL-17RA, the development of inflammatory conditions and self-tolerance breakdown in testis.

Adipokines in metabolic and reproductive functions in birds: An overview of current knowns and unknowns

Adipose tissue is now recognized as an active endocrine organ, which synthesizes and secretes numerous peptides factors called adipokines. In mammals, they exert pleiotropic effects affecting energy metabolism but also fertility. In mammals, secretion of adipokines is altered in adipose tissue dysfunctions and may participate to obesity-associated disorders. Thus, adipokines are promising candidates both for novel pharmacological treatment strategies and as diagnostic tools. As compared to mammals, birds exhibit several unique physiological features, which make them an interesting model for comparative studies on endocrine control of metabolism and adiposity and reproductive functions. Some adipokines such as leptin and visfatin may have different roles in avian species as compared to mammals. In addition, some of them found in mammals such as CCL2 (chemokine ligand 2), resistin, omentin and FGF21 (Fibroblast Growth factor 21) have not yet been mapped to the chicken genome model and among its annotated gene models. This brief review aims to summarize data (structure, metabolic and reproductive roles and molecular mechanisms involved) related to main avian adipokines (leptin, adiponectin, visfatin, and chemerin) and we will briefly discuss the adipokines that are still lacking in avian species.

Effects of dietary L-carnitine on puberty indices in the young breeder rooster

The aim of current study was to investigate the effect of dietary L-Carnitine (LC) in immature roosters on reproductive hormones, lipid profile and testicular histology at the time of maturity. Eighteen 12-wk-old breeder roosters (Ross 308) of similar weights were randomly allocated into 3 dietary treatments (LC-0: basic diet, LC-250: basic diet + 250 mg LC/kg of diet, LC-500: basic diet + 500 mg of LC/kg of diet) in 6 replicates. The feeding program and photoperiod regimen were performed based on ROSS 308 management handbook. Dietary LC supplementation markedly improved testicle weight and testicle index (p < 0.05). Comb height was also affected by LC supplementation (p < 0.05). The testicle weight and index, comb height, and shank lengths improved linearly with increasing levels of dietary LC (p < 0.05). The LC-250 and LC-500 diets significantly improved the number of sertoli cells (NSC), height epithelium seminiferous tubules (HEST), seminiferous tubules diameter (STD), spermiogenesis index (SI) and tubular differentiation index (TDI) of rooster's testis tissue (p < 0.05). The number of seminiferous tubules (NST) was affected by of the amount of LC (p < 0.05). The roosters on the LC-250 mg/kg diet had longer HEST compared to roosters that received the LC-500 mg/kg diet (p < 0.05). Testicular histology parameters increased in a linear and quadratic manner in response to increasing levels of LC (p < 0.05). Dietary LC significantly increased (p < 0.05) plasma concentrations of testosterone, GnRH, LH, FSH and High-Density Lipoprotein (HDL), but reduced the plasma concentration of Low-Density Lipoprotein (LDL). However, no significant differences were observed between LC-250 and LC-500 groups in these parameters. Plasma testosterone, GnRH, LH, LDL and HDL were affected in a linear and quadratic manner in response to increasing levels of LC (p < 0.05). Similarly, FSH increased linearly with increasing dietary LC (p < 0.05). Thus, adding up to 250g of LC per kg of the rooster chicken can improve reproductive hormones, blood lipids and testicular histology parameters at the time of maturity.

Cholesterol-enriched diet disrupts the blood-testis barrier in rabbits

About 15% of heterosexual couples in the USA suffer from infertility issues; male infertility accounts for ∼50% of all infertility cases and roughly 50% of male infertility is idiopathic. Increased levels of plasma cholesterol affect spermatogenesis and male fertility negatively, but by unclear mechanisms. Clearly, spermatogenesis occurs in immune-privileged seminiferous tubules that are protected by the blood-testis barrier (BTB), and BTB disruption results in sperm damage and male infertility. Accordingly, using rabbits fed a 2% cholesterol-enriched diet for 2, 4, and 6 wk to raise levels of plasma cholesterol, we tested the hypothesis that elevated levels of plasma cholesterol disrupt the BTB functionally and biochemically. The cholesterol-enriched diet increased lipid deposition dramatically and time-dependently in the seminiferous tubules and disrupted the BTB as evidenced by increased IgG staining within the seminiferous tubules. Total protein levels of the tight-junction proteins ZO-1 and occludin were increased in the seminiferous tubules of rabbits fed the cholesterol-enriched diet, and the distribution patterns of tight-junction proteins were markedly affected, including an increased accumulation of tight-junction proteins in endosomes. Disruption of the integrity of the BTB due to increased plasma levels of cholesterol might play a role in male infertility.

Characterization of chicken Sertoli cells in vitro

In the testis, Sertoli cells play a key physiological role in that they support, nourish, and protect germ cells. Because of the importance of Sertoli cells, several laboratories have established a culture system of Sertoli cells. These cultures have been well developed in mammalian species, but to our knowledge no purified avian Sertoli cells culture has been described. The aim of this study was to isolate avian Sertoli cells and to investigate their function using a chicken model in an in vitro test system. Immature chicken Sertoli cells in culture present morphology similar to that of mammalian cells and conserve expression of the specific Sertoli marker, anti-Müllerian hormone. Furthermore, in contrast to mammals, they express the 3β-hydroxysteroid dehydrogenase enzyme. Stimulation of Sertoli cells with ovine follicle-stimulating hormone rapidly activates the 3 main downstream signaling pathways of the follicle-stimulating hormone receptor: cyclic( )adenosine monophosphate/protein kinase A, phosphatidylinositol 3-kinase/Akt, and mitogen-activated protein kinase pathways. In vitro, Sertoli cells are able to secrete lactate and inhibin and have conserved the phagocytosis property. Finally, avian Sertoli cells present 3 interesting characteristics: they actively proliferate in vitro, can be passaged several times, and are suitable for freezing in nitrogen. A direct consequence of these properties is to use this cell culture test system as an alternative method to bird reprotoxicity studies.

Aging Men and Lipids

Many theories aim at explaining the mechanisms of aging and death in humans. Decreased levels of androgens, growth hormone, and insulin-like growth factor accompany natural aging in men. Androgens influence the growth and maturation of men in various stages of their life. The action of androgens is performed by binding or not binding to androgen receptors. However, various actions of androgens were clarified after the discovery and genotyping of the androgen receptor. The influence of androgens on the lipid profile was reported by several researchers. This negative influence of androgens in men and the positive influence of estrogens in women are responsible for the higher impact of atherogenesis in men compared with women. In aging men, this negative influence of androgens on the lipid profile is more pronounced. This review considers the influence of age on lipid metabolism in men.

The liver X receptor-{beta} is essential for maintaining cholesterol homeostasis in the testis

The liver X receptor (LXR)alpha and -beta has been found to play a central role in maintaining cellular cholesterol homeostasis. In this study we comprehensively investigated the effect of deleting LXRalpha and -beta on testicular morphology and function. In the absence of LXRbeta, excessive cholesterol accumulated in the Sertoli cells from 2.5 months, resulting in severe cellular disruption and dysregulation of spermatogenesis by 10 months of age. This correlated with gene expression analyses that clearly indicated that LXRbeta was the dominant transcript in the testis Although the LXRalpha(-/-) testis was normal, the LXRalpha(-/-)beta(-/-) testis presented with a more severe phenotype than the LXRbeta(-/-) mice, and males were infertile by 4 months of age, indicating LXRalpha may partially rescue the testicular phenotype. Although Leydig cells did not accumulate excessive cholesterol, declining serum and intratesticular androgen levels with age suggested that these cells were in fact less functional. Treatment of a Sertoli cell line with the LXR agonist T0901317 led to increased expression of known LXR target genes like ATP binding cassette-G1 and sterol regulatory binding protein-1c; similar results were observed in wild-type testis after in vivo administration, suggesting the LXR is functioning in the same way as in other tissues. Ordinarily increased levels of cholesterol activate intracellular sensors to decrease these levels; however, the increasing amount of cholesterol in the Sertoli cells indicates improper control of cholesterol metabolism when LXRbeta is absent. Although the precise molecular mechanism at this time remains unclear, our study highlights the crucial role for LXRbeta in retaining cholesterol homeostasis in Sertoli cells.

Expression, activity, and subcellular localization of testicular hormone-sensitive lipase during postnatal development in the guinea pig

The present work reports on testicular hormone-sensitive lipase (HSL), the biological significance of which has been documented in male fertility. The HSL protein levels and enzymatic activity were measured, respectively, by densitometry of immunoreactive bands in Western blots, performed with antibodies against recombinant rat HSL, and by spectrophotometry in seminiferous tubules (STf) and interstitial tissue (ITf) enriched fractions generated from neonatal, pubertal, and adult guinea pig testes. In addition, HSL was studied in subcellular fractions obtained from STf isolated from adult testes and in epididymal spermatozoa (Spz). A 104-kDa HSL protein was detected in STf and ITf, the expression and activity of which increased with testicular development. Three immunoreactive bands of 104, 110, and 120 kDa were detected in the lysosomal subfraction, and two bands of 104 and 120 kDa were detected in Spz. The HSL activity was positively correlated with free (FC) and esterified (EC) cholesterol ratios in STf and ITf, but not with triglyceride (TG) levels, during testicular development. Immunolabeling localized HSL to elongated spermatids and Sertoli cells, where its distribution was stage-dependent, and within the cells lining the excurrent ducts of the testis. The findings of the 104- and 120-kDa HSL immunoreactive bands and of HSL activity in Spz as well, as the detection of the 104-, 110-, and 120-kDa immunoreactive bands in lysosomes, suggest that part of HSL may originate from germ cells and be imported in Sertoli cells. The HSL protein levels and enzymatic activity in ITf and STf were positively correlated with serum testosterone levels during development. To the best of our knowledge, this study is the first to contribute insights regarding the impact of HSL on FC:EC cholesterol ratios and TG levels in the interstitial tissue and tubules in relation to serum testosterone levels during postnatal development, and regarding the immunolocalization of the enzyme in regions of the male gamete consistent with spermatozoa-oocyte interaction.

Rat Leydig cells use apolipoprotein E depleted high density lipoprotein to regulate testosterone production

Rat HDL are known to increase testosterone production by cultured Leydig cells either following gonadotropin stimulation or cholesteryl ester depletion. However, rat HDL contain apolipoprotein E and have a high affinity for the members of the low density receptor family such as LDL receptor, LDL receptor related protein and VLDL receptor. In contrast with the adrenal cells, the contribution of apo A-I and apo E pathways in HDL cholesterol uptake has not been yet evidenced in rat Leydig cells. Recent data provided evidence that hCG stimulates scavenger receptor BI expression in testes. In order to investigate if testosterone production can be stimulated by apo E depleted HDL, we compared the level of testosterone stimulation by HDL with or without apo E first, in presence of saturating dose of hCG (1 IU/ml) and second, after depletion of cholesterol synthesis by pravastatin, an inhibitor of HMG-CoA reductase. In presence of hCG, HDL with or without apo E increased testosterone production respectively by 37 and 25%. Pravastatin at 100 microg/ml inhibited the cholesterol synthesis and the testosterone production by 25% and decreased the cholesteryl content by 25%. The addition of HDL with or without apo E (50 microg protein HDL/ ml) completely overcame the depletion of cellular cholesteryl esters and the inhibition of testosterone production induced by pravastatin. In the presence of heparin, apo E depleted HDL overcame the testosterone production induced by pravastatin, indicating that uptake of HDL without apo E via a secretion of apo E by the cells themselves was not involved. Therefore, in absence of apo E, it is suggested that rat Leydig cells used HDL to regulate steroidogenesis via an apolipoprotein A-I pathway.

Transfer of cholesterol between high density lipoproteins and cultured rat Sertoli cells

In the testes, the Sertoli cells are separated from the blood capillaries by the basement membrane, thereby excluding the passage of low density lipoproteins (LDLs) but allowing the passage of high density lipoproteins (HDLs). The present study examines first the capacity of Sertoli cells to uptake cholesterol from HDL and secondly the role of apolipoproteins (apo) A-I and E in cholesterol flux between HDL and cultured rat Sertoli cells. In the presence of HDL in cultured medium, rat Sertoli cells accumulated few amounts of esterified cholesterol. Incubation of [14C] cholesterol-labelled Sertoli cells with [3H]cholesterol-labelled HDL showed that the amount of cholesterol influx slightly exceeded its efflux, thus resulting in a net uptake of cholesterol from HDL to rat Sertoli cells. The amount of HDL-cholesterol converted to steroids by Sertoli cells was about 32% of influx. Uptake of cholesterol by Sertoli cells was three times higher with phospholipid-apo A-I vesicles and seven times higher with phospholipid- apo E vesicles than that with phospholipid vesicles without apolipoprotein. Phospholipid- apo A-I vesicles promoted cholesterol efflux at the same rate as native HDL and twice as efficiently as phospholipid- apo E vesicles. Thus, this study shows that rat Sertoli cells have the capacity to take up HDL-cholesterol for membrane renewal and steroid production mainly by apo E dependent pathways.