The Impact of Testosterone on Metformin Action on Hypothalamic‐Pituitary‐Thyroid Axis Activity in Men: A Pilot Study

Selenium protects against nesfatin-1 modulation of the hypothalamic-pituitary-testicular axis during hypothyroidism in male rats

Normal gonadal function can be disrupted by hypothyroidism. Hypothyroidism disturbs testicular function directly and centrally by affecting the hypothalamic-pituitary-testicular axis with unclear mechanism. As nesfatin-1 neurons co-localized with TRH and GnRH neurons in the hypothalamus, it could play a role in centrally hypothyroidism induced testicular dysfunction. Selenium (Se), by affecting thyroid iodide supply, could relieve these disturbances. So, we aim to identify the role of nesfatin-1 as a link between testicular dysfunction and hypothyroidism through modulating the MAPK/ERK pathway while discussing the possible role of Se in alleviating hypothyroidism and associated testicular damage. Forty male rats were divided equally into: Control: distilled water, Se: Se orally, Propylthiouracil (PTU): PTU orally, PTU + Se: Se with PTU orally. Serum thyroid function, gonadal hormones, nesfatin-1, testicular redox status, sperm analysis, brain tissue GnRH, nucleobindin 2-derived polypeptide, pMAPK/ERK gene expression, histological changes and immunohistochemical expression of testicular proliferating cell antigen (PCNA) were done. PTU induced hypothyroidism and reduction of gonadal hormones which both were correlated with reduced nesfatin-1. There was testicular stress with reduced GnRH, NUCB2, pMAPK/ERK gene expression, and PCNA immunopositive cells. These parameters were reversed by Se. Nesfatin-1 could be the central link between hypothyroidism and disturbances of the hypothalamic pituitary testicular axis.

Thymoquinone protects the testes of hypothyroid rats by suppressing pro-inflammatory cytokines and oxidative stress and promoting SIRT1 testicular expression

Background: Hypothyroidism has been linked to many testicular structural and dysfunctional changes in males. Thymoquinone (TQ) has shown a potent testicular protective effect through its antioxidant, anti-inflammatory, antiapoptotic, fertility-enhancing, and endocrine modulatory activities. Objectives: This study aimed to investigate the efficacy of TQ in preserving the testicular structure of a model of experimentally induced hypothyroidism in rats and identify the mechanism behind this effect. Materials and methods: Propylthiouracil (PTU) was used to induce hypothyroidism in adult male Wistar rats, who were then treated with TQ (50 mg/kg/body weight) for 4 weeks and compared to the untreated rats. Thyroid hormonal profile, oxidants/antioxidants profile, and serum testosterone levels were assessed. Gene expression and immune expression of SIRT1 and pro-inflammatory cytokines TNF-α and NF-κB were also assessed in the testicular tissue. Results: TQ administration successfully improved PTU-induced disturbance in the thyroid hormonal profile (T3, T4, and TSH), serum testosterone level, and pancreatic antioxidants compared to the untreated hypothyroid group. TQ significantly downregulated (p = 0.001, p ˂ 0.001) TNF-α and NF-κB transcription, while it significantly upregulated (p = 0.01) SIRT1 transcription in the testes of hypothyroid rats. TQ markedly relieved the histopathological testicular changes induced by PTU and significantly increased (p = 0.002, p = 0.01) the sectional area of seminiferous tubules and germinal epithelial height, respectively. TUNEL-positive apoptotic germinal cells were significantly decreased (p ˂ 0.001), while PCNA-positive proliferating germinal cells and androgen receptor expression were significantly increased (p ˂ 0.001) in the testes of TQ-treated hypothyroid rats. Conclusion: Thymoquinone could limit the hypothyroidism-induced structural changes in the testis, mostly through the upregulation of SIRT1 expression, which seems to mediate its promising antioxidant, anti-inflammatory and antiapoptotic effects that were evident in this study. Therefore, TQ is recommended as an adjuvant safe supplement in managing hypothyroidism, especially in males.

Pituitary effects of metformin in men with early-onset androgenic alopecia

Males with early-onset androgenic alopecia are characterized by elevated androgen levels. The aim of the present study was to investigate whether the presence of this condition modulates the impact of metformin on pituitary hormone production. This study compared two groups of young men with prediabetes, matched for age, blood pressure and insulin sensitivity: 23 subjects with early-onset male-pattern baldness (group 1) and 25 individuals with normal hair growth (group 2). Throughout the study, both groups were treated with metformin for six months. Circulating levels of glucose, insulin, glycated hemoglobin, gonadotropins, thyrotropin, prolactin, ACTH, insulin-like growth factor-1 and androgens were determined at the beginning of the study and six months later. At entry, LH, the LH/FSH ratio, total testosterone, bioavailable testosterone, ACTH and DHEA-S were higher in group 1 than in group 2. The effect of metformin on fasting glucose, insulin sensitivity and glycated hemoglobin was more pronounced in group 2 than in group 1. Only in group 1, metformin reduced LH levels and the LH/FSH ratio. Metformin did not affect plasma levels of the remaining hormones. In untreated men with androgenic alopecia (group 3, n = 22), glucose homeostasis markers and hormone levels remained at a similar level throughout the study period. The obtained results suggest that the impact of metformin on gonadotroph secretory function is stronger in men with early-onset androgenic alopecia than in men with normal hair growth. Metformin treatment may protect men with early-onset androgenic alopecia against the development of gonadotroph hyperplasia and/or of focal testicular changes. This article is protected by copyright. All rights reserved.

Metformin and primary bone cancer risk in Taiwanese patients with type 2 diabetes mellitus

BACKGROUND

The effect of metformin on primary bone cancer risk has not been researched. This retrospective cohort study investigated the risk of primary bone cancer between metformin initiators and non-metformin initiators in patients with type 2 diabetes mellitus.

METHODS

A total of 673,532 patients with newly diagnosed type 2 diabetes mellitus and had been prescribed antidiabetic drugs for 2 or more times during 1999-2009 were enrolled from Taiwan's National Health Insurance. Metformin initiators and non-metformin initiators were defined according to the prescriptions of antidiabetic drugs within the initial 12 months. The patients were then followed up until December 31, 2011 for the incidence of primary bone cancer. Cox regression incorporated with the inverse probability of treatment-weighting using propensity scores was used to estimate hazard ratios in intention-to-treat and per-protocol analyses.

RESULTS

In the intention-to-treat analysis, the respective incidence rates were 10.56 and 12.90 per 100,000 person-years in 453,532 metformin initiators and 220,000 non-metformin initiators and the hazard ratio for initiators versus non-initiators was 0.830 (95% confidence interval 0.686-1.004, P-value = 0.0551). In the per-protocol analysis, the incidence rates were 7.58 and 11.77 per 100,000 person-years, respectively, and the hazard ratio was 0.615 (95% confidence interval 0.468-0.808, P-value = 0.0005). Subgroup analyses with regards to sex and age (<60 and ≥60 years) showed that the significantly lower risk associated with metformin use was only observed in men aged ≥60 years in the per-protocol analysis.

CONCLUSIONS

A significantly lower risk of primary bone cancer can be observed in patients with type 2 diabetes mellitus who adhere to metformin treatment. This benefit can only be observed in men aged ≥60 years.

Hypothalamic-pituitary-gonadal axis and sexual functioning in metformin-treated men after discontinuation of testosterone replacement therapy: A pilot study

WHAT IS KNOWN AND OBJECTIVE

Metformin was found to reduce elevated gonadotropin levels. The aim of the present study was to determine whether metformin modulates the impact of discontinuation of testosterone therapy on hypothalamic-pituitary-gonadal axis activity and sexual function in men with low testosterone levels.

METHODS

The study included 28 men with late-onset hypogonadism (defined according to the criteria of the European Male Aging Study group) receiving testosterone undecanoate (120 mg in three equal doses), 12 of whom had been treated with oral metformin (1.7-3 g daily). Both testosterone and metformin had been administered for at least six months before enrolment. In all patients, testosterone replacement required to be discontinued. The control group included 16 testosterone- and metformin-treated men with late-onset hypogonadism who during the entire study period continued their treatment. Glucose homeostasis markers, as well as plasma levels of insulin, gonadotropins, testosterone, calculated bioavailable testosterone, dehydroepiandrosterone-sulphate, oestradiol, thyrotropin, free thyroxine, prolactin, insulin-growth factor-1 and cortisol were measured at the beginning of the study and four months later. Moreover, at the beginning and the end of the study, all enrolled patients completed a questionnaire assessing their sexual functioning (IIEF-15).

RESULTS AND DISCUSSION

Discontinuation of testosterone therapy resulted in a decrease in total testosterone and bioavailable testosterone (by 42% and 45% in metformin-treated patients, and by 52% and 54% in metformin-naïve patients), as well as impaired all aspects of male sexual function. Changes in bioavailable testosterone, as well as in erectile function, orgasmic function and sexual desire were less pronounced if subjects received metformin. Only in metformin-naïve men, follow-up FSH and LH levels were higher than at baseline (by 75% and 62%). Moreover, discontinuation of testosterone therapy in metformin-naïve men increased glycated haemoglobin, as well as worsened insulin sensitivity. There were no differences between baseline and follow-up levels of the remaining hormones. In metformin-naïve subjects, the increase in gonadotropin levels correlated with the changes in testosterone levels and insulin sensitivity. No effect on glucose homeostasis markers, hormone levels and sexual functioning was observed in the control group.

WHAT IS NEW AND CONCLUSION

The obtained results suggest that metformin treatment mitigates the unfavourable effect of discontinuation of testosterone treatment on hypothalamic-pituitary-testicular axis activity and sexual function in men with late-onset hypogonadism.

Metformin and cognition from the perspectives of sex, age, and disease

Metformin is the safest and the most widely prescribed first-line therapy for managing hyperglycemia due to different underlying causes, primarily type 2 diabetes mellitus. In addition to its euglycemic properties, metformin has stimulated a wave of clinical trials to investigate benefits on aging-related diseases and longevity. Such an impact on the lifespan extension would undoubtedly expand the therapeutic utility of metformin regardless of glycemic status. However, there is a scarcity of studies evaluating whether metformin has differential cognitive effects across age, sex, glycemic status, metformin dose, and duration of metformin treatment and associated pathological conditions. By scrutinizing the available literature on animal and human studies for metformin and brain function, we expect to shed light on the potential impact of metformin on cognition across age, sex, and pathological conditions. This review aims to provide readers with a broader insight of (a) how metformin differentially affects cognition and (b) why there is a need for more translational and clinical studies examining multifactorial interactions. The outcomes of such comprehensive studies will streamline precision medicine practices, avoiding "fit for all" approach, and optimizing metformin use for longevity benefit irrespective of hyperglycemia.