Effect of metformin on testicular expression and localization of leptin receptor and levels of leptin in the diabetic mice

Abstract

Diabetes mellitus impairs testicular activity and leads to infertility. Leptin is one of the endogenous regulators of the male reproductive functions, but the role of leptin and its receptor (LEPR/Ob-R) in the control of testosterone production and testicular proliferation has not been investigated so far, especially in the Type 1 diabetes mellitus (DM1). Metformin is an anti-hyperglycemic drug which is beneficial for treating the both DM2 and DM1. The aim of this work was to study the possible role of leptin and Ob-R in the regulation of steroidogenesis and proliferation in the testes of mice with streptozotocin-induced DM1 (75 mg/kg/day, 4 days) and to estimate the restoring effect of metformin treatment (500 mg/kg, 2 weeks) on the diabetic testes. In the diabetic testes, the plasma and intratesticular leptin levels and plasma testosterone levels were reduced and completely restored by metformin treatment. Metformin also restored the expression of the steroidogenic transport protein steroidogenic acute regulatory protein reduced in DM1. In the diabetic testes, the expression of Ob-R was downregulated and the immunolocalization of Ob-R showed weak staining in the Leydig cells, the primary spermatocytes and the round spermatids. The germ cell proliferation was also reduced in DM1, as noticed with proliferating cell nuclear antigen (PCNA) expression. Metformin increased the Ob-R expression and immunostaining in the different cell types and improved the PCNA expression. Thus, DM1 impairs the testicular steroidogenesis and proliferation by inhibiting the leptin signaling, causing a decrease in leptin levels and Ob-R expression in the testes of diabetic mice, while metformin improves the leptin signaling and restores testosterone production and testicular proliferation. K E Y W O R D S diabetes mellitus, leptin, metformin, Ob-R, testes, testosterone 1 | INTRODUCTION The Types 1 and 2 diabetes mellitus (DM1 and DM2) are widespread metabolic diseases. The DM1 is characterized by insulin deficiency and severe hyperglycemia, while the DM2 is characterized by insulin resistance and impaired glucose tolerance (American Diabetes Association, 2013). In DM, the prolonged hyperglycemia, the pathological changes in energy metabolism and

The effect of metformin treatment on the basal and gonadotropin‐stimulated steroidogenesis in male rats with type 2 diabetes mellitus

“…The dynamics of stimulating hCG effect on blood T levels in control and MF-treated diabetic rats was similar, and differed from untreated diabetic animals ( Figure 3). Among the mechanisms of MF effect on steroidogenesis can be both restoration of intratesticular LH receptor expression, which improves LH signalling, and normalisation of intratesticular leptin level, which improves leptin signalling and AMPK activity in the testes (Annie et al, 2020;Bertoldo et al, 2015;Hoffmann et al, 2016;Nguyen et al, 2019;Shpakov et al, 2018). This is evidenced by our data that basal and hCG-stimulated levels of leptin and its receptor in the testes of control and MF-treated diabetic rats were similar (Figure 4).…”

“…As shown by us earlier, two-week treatment of mice with DM1 using MF (500 mg kg −1 day −1 ) restored blood T levels, intratesticular content of leptin and its receptors and Star gene expression, all reduced in DM1, and normalised proliferation of testicular cells (Annie et al, 2020).…”

“…However, clinical data on the ability of MF therapy to restore steroidogenesis in patients with DM2 are not currently available. There are experimental works demonstrating the improving MF effect on steroidogenesis and spermatogenesis in rodents with both diet-induced obesity and high-dose STZ-induced DM1 (Annie et al, 2020;Nna et al, 2018Nna et al, , 2019Yan et al, 2015). MF treatment (100 mg kg −1 day −1 , 8 weeks) of obese male Sprague-Dawley rats restored the plasma levels of insulin, leptin and T, and improved sperm quality and testes morphology (Yan et al, 2015).…”

“…However, the data on MF effect on the content of leptin and leptin receptor in the testes of animals with DM2 are currently not available. Earlier we showed the normalisation of intratesticular levels of leptin and leptin receptors in mice with streptozotocin-induced type 1 diabetes mellitus (DM1), but the origin of leptin signalling impairment in DM1 and DM2 is very different (Annie et al, 2020).…”

“…The patients and experimental animals with DM2, along with insulin resistance, have increased plasma leptin levels and leptin resistance in the target tissues, including the testes, which is believed to make a significant contribution to weakening the testicular functions (Elfassy et al, 2018;Shpakov et al, 2018). This is due to the fact that leptin and its signalling system play an important role in the regulation of steroidogenesis and spermatogenesis (Annie et al, 2020;Elfassy et al, 2018;Roumaud & Martin, 2015;Syriou, Papanikolaou, Kozyraki, & Goulis, 2018). However, the data on MF effect on the content of leptin and leptin receptor in the testes of animals with DM2 are currently not available.…”