Relative and combined effects of ethanol and protein deficiency on gonadal function and histology

The chronic alcohol consumption influences the gonadal axis in men: Results from a meta-analysis

BACKGROUND

Low testosterone concentrations affect 2-13% of adult males, with a direct association between reduction in testosterone (T) concentrations and cardiovascular events. Lifestyle habits have been linked to visceral fat accumulation and endocrine disorders like secondary hypogonadism. Alcohol intake has also been a topic of debate, with studies showing a detrimental effect on sperm production and underlying mechanisms. This meta-analysis aims to comprehensively evaluate the effect of alcohol consumption on T serum concentrations in adult men.

METHODS

The literature search included only controlled clinical trials comparing men who drink alcohol to men who do not, or who assumed placebo or nonalcoholic beverages. The primary outcome was the comparison of total testosterone serum concentrations between the study and control groups. The publications were examined for publication bias using Egger's test.

RESULTS

Twenty-one studies were included in the analysis for a total of 30 trials that examined the effects of alcohol consumption on testosterone level in 10,199 subjects. The meta-analysis showed that alcohol consumption overall is related to significant reduction in circulating concentrations of total testosterone (mean difference [MD] = -4.02; 95% CI -6.30, -1.73), free T (MD = -0.17; 95% CI -0.23, -0.12), sex hormone binding globulin (SHBG) (MD = -1.94; 95% CI -3.37, -0.48), an increase in estradiol (E2) (MD = 7.65; 95% CI 1.06, 14.23) and neutral effect on luteinizing hormone (LH) (MD = -0.15; 95% CI -0.36, 0.06), independently by age, body mass index (BMI), E2, and LH serum concentrations and alcohol intake. However, these results are evident only in healthy men exposed to chronic alcohol consumption and not in those with a recognized diagnosis of alcohol use disorder or after acute alcohol intake.

CONCLUSION

This study suggests how chronic alcohol consumption may inhibit the gonadal axis in healthy men, although the exact pathophysiological mechanisms connecting alcohol exposure and steroidogenesis are still not completely clarified.

The effect of dietary protein intake on factors associated with male infertility: A systematic literature review and meta-analysis of animal clinical trials in rats

BACKGROUND

Studies have shown that the amount of protein in the diet affects the hypothalamic-pituitary-testis axis and sub-optimal quantity reduces male fertility potential in both animals and humans. However, individual research reports on the factors associated with male infertility are collectively uncharacterized.

AIM

We systematically reviewed, and meta-analysed animal (rats) studies on the effect of low protein diet on factors associated with male infertility.

METHODS

PubMed Central, EMBASE and Scopus databases were searched from inception to 30 March 2019 for the study concepts and related keywords in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Data on the outcome measures were extracted and pooled across trials using random-effects model and expressed as mean differences (MD) at a 95% confidence interval (CI).

RESULTS

Twelve trials identified from 3327 studies, met our inclusion criteria in the comparison of a low protein diet (2-10% protein) vs control protein diet (17-23% protein). The results showed that a low protein diet caused a significant reduction in the body weight (P = 0.0001) testis weight (P = 0.0001), seminal vesicle weight (P = 0.0003), epididymis weight P = 0.02), serum testosterone (P = 0.001) and follicle-stimulating hormone (FSH) concentrations (P = 0.04) compared with the control treatments. No effect on luteinizing hormone (LH) plasma concentration (P = 0.13) was observed.

CONCLUSION

This study revealed that low protein diet caused significant reductions in body weight, testis, epididymis and seminal vesicle weights, serum testosterone and FSH concentration in rats. We infer that sub-optimal protein consumption reduces the gonadal and endocrine function, and consequently male infertility.

Fluoxetine-induced androgenic failure impairs the seminiferous tubules integrity and increases ubiquitin carboxyl-terminal hydrolase L1 (UCHL1): Possible androgenic control of UCHL1 in germ cell death?

The selective serotonin reuptake inhibitor fluoxetine has been used for the treatment of depression. Although sexual disorders have been reported in male patients, few studies have demonstrated the fluoxetine effect on the reproductive histophysiology, and the target of this antidepressant in testes is unknown. We evaluated the impact of short-term treatment with fluoxetine on the adult rat testes, focusing on steroidogenesis by Leydig cells (LC) and androgen-dependent testicular parameters, including Sertoli cells (SC) and peritubular myoid cells (PMC). Since UCHL1 (ubiquitincarboxyl-terminal hydrolase L1) seems to control spermatogenesis, the immunoexpression of this hydrolase was also analyzed. Adult male rats received 20 mg/kg BW of fluoxetine (FG) or saline (CG) for eleven days. In historesin-embedded testis sections, the seminiferous tubule (ST) and epithelial (Ep) areas, and the LC nuclear diameter (LCnu) were measured. The number of abnormal ST, androgen-dependent ST, SC and PMC was quantified. Testicular β-tubulin levels and peritubular actin immunofluorescence were evaluated. Serum testosterone levels (STL) and steroidogenesis by 17β-HSD6 immunofluorescence were analyzed, and either UCHL1-immunolabeled or TUNEL-positive germ cells were quantified. In FG, abnormal ST frequency increased whereas ST and Ep areas, androgen-dependent ST number, LCnu, 17β-HSD6 activity and STL reduced significantly. TUNEL-positive PMC and SC was related to decreased number of these cells and reduction in peritubular actin and β-tubulin levels. In FG, uncommon UCHL1-immunoexpression was found in spermatocytes and spermatids, and the number of UCHL1-immunolabeled and TUNEL-positive germ cells increased in this group. These findings indicate that LC may be a fluoxetine target in testes, impairing PMC-SC integrity and disturbing spermatogenesis. The increase of UCHL1 in the damaged tubules associated with high incidence of cell death confirms that this hydrolase regulates germ cell death and may be controlled by androgens. The fertility in association with the androgenic status of patients treated with fluoxetine should be carefully evaluated.

Relative and combined effects of ethanol and protein deficiency on bone histology and mineral metabolism

This study was performed to analyze the relative and combined effects of ethanol and protein deficiency on bone histology and mineral metabolism in 4 groups of 7 animals each which were pair-fed during 8 weeks with 1) a nutritionally adequate diet; 2) a 36% (as energy) ethanol containing isocaloric diet; 3) a 2% protein, isocaloric diet; and 4) a 36% ethanol 2% protein isocaloric diet, respectively, following the Lieber-DeCarli model. Another group of five rats were fed ad libitum the control diet. The first and second lumbar vertebrae were removed after sacrifice, and processed for histomorphometrical analysis of undecalcified bone samples. Blood and 24-h urine were also collected. Protein malnutrition, but not ethanol, leads to osteoporosis and reduced osteoid synthesis, whereas ethanol and protein malnutrition both lead to impaired bone mineral apposition and increased urinary hydroxyproline excretion. These changes are accompanied by an increase in serum parathormone and serum 1,25 dihydroxy vitamin D3, a slight hypomagnesemia, hypercalciuria and hyperphosphaturia; protein deficiency plays an independent role in these alterations, whereas both ethanol and protein deficiency exert independent effects on decreasing serum testosterone levels; this last alteration may contribute to the bone changes mentioned before.

Effect of alcohol on the proestrous surge of luteinizing hormone (LH) and the activation of LH-releasing hormone (LHRH) neurons in the female rat

Reproduction is adversely affected by alcohol abuse in humans and laboratory animals. In rats, alcohol exposure suppresses both luteinizing hormone (LH) and sex steroid secretion, although consensus is lacking as to which level of the hypothalamic-pituitary-gonadal (HPG) axis is primarily affected. We tested the hypothesis that acute alcohol treatment inhibits the HPG axis by blunting release of LH-releasing hormone (LHRH) in female rats, by examining the effect of this drug on the central reproductive endocrine event; i.e., the proestrous surge of gonadotropins, which triggers ovulation. In a first series of experiments, we injected alcohol at 8 A.M. and 12 P.M. on proestrus and measured plasma levels of LH, estradiol (E2), and progesterone during the afternoons of proestrus and estrus. Alcohol administration blocked the proestrous surge of LH and ovulation. In subsequent experiments, alcohol inhibited the surge of LHRH (measured by push-pull cannulation) and LHRH neuronal activation (measured by Fos labeling in LHRH neurons). Because alcohol also decreased E2 levels, we reasoned that it might have prevented positive feedback; however, alcohol retained its ability to inhibit the LH surge evoked by E2 implantation in ovariectomized females, disproving this hypothesis. Additionally, alcohol does not act via increased corticosteroid secretion, because alcohol also blocked the proestrous surge in adrenalectomized females. Last, exogenous administration of LHRH to alcohol-blocked animals evoked LH secretion and ovulation, indicating that pituitary and/or ovarian function could be restored by mimicking the hypothalamic signal. Collectively, these data indicate that in female rats, alcohol inhibits the gonadotropin surge primarily by decreasing LHRH secretion.

Sustained effects of a single injection of ethanol on the hypothalamic-pituitary-gonadal axis in the male rat

The hormones responsible for regulating the hypothalamic-pituitary-gonadal axis are essential for proper reproductive function. Ethanol (EtOH) has been shown to exert its effect at all three levels of this axis. The present study defines striking differences in the time course of recovery of luteinizing hormone (LH) in gonadally intact, compared with, castrated male rats after acute EtOH administration. Serum levels of LH and testosterone were measured at various time points up to 2 weeks (1.5, 3, 24, 48, 72, 96, 168, and 336 hr) after a single intraperitoneal injection of either saline or 3 g/kg of EtOH in intact adult male rats. One EtOH injection significantly suppressed testosterone levels as low as 20% (p < 0.01) of saline-injected intact rats. This occurred as early as 1.5 hr after EtOH administration (the first measured time point), and statistically significant suppression was sustained for 96 hr. Similarly, LH levels showed a significant decrease. However, this significant fall in LH did not begin until 3 hr (p < 0.05) and continued up to 96 hr (p < 0.01), with a gradual return to control levels at 168 and 336 hr after treatment. Despite the significant and prolonged fall in testosterone levels in the EtOH-treated intact rats, beta-LH mRNA levels were inappropriately not elevated, as would be expected in the context of low circulating testosterone. However, at 168 and 336 hr, steady-state levels of beta-LH mRNA were significantly higher than seen in saline-injected controls (p < 0.05 and p < 0.01, respectively), temporally correlating with the return of serum LH to control. LH levels in the castrated animals were significantly suppressed at 1.5 hr (p < 0.05) and 3 hr (p < 0.01) after EtOH treatment, compared with controls, yet they returned much more quickly by 24 hr after treatment. beta-LH mRNA levels of castrated animals also showed a significant depression at 1.5 and 3 hr, and returned to control levels by 24 hr. In these rats, the hypothalamic LH-releasing hormone mRNA levels were not altered by a single EtOH injection at any time point. However, in the intact animals, there was a transient increase in LH-releasing hormone mRNA at 72 and 96 hr (p < 0.01 and p < 0.05, respectively) that may lead to the upregulation of beta-LH mRNA expression. These studies indicate that EtOH causes prolonged decreases in important serum hormones that are essential to the reproductive axis of the adult male rat.