Glucagon-like Peptide-1 Acts as Signaling Mediator to Modulate Human Sperm Performance via Targeting Akt, JNK and IRS-1 Cell Signaling Cascades: Novel Insights into Sperm Physiopathology

Sitagliptin exhibits protective effects against methotrexate-induced testicular toxicity: The involvement of oxidative stress-related factors

Methotrexate (MTX) is widely prescribed to treat different malignancies as well as autoimmune diseases. However, it causes a range of side effects in different organs such as testis. This study aims to clarify the role of dipeptidyl peptidase 4 (DPP4) in MTX-induced testicular damage via pathways involved in oxidative stress and evaluates the protective effects of sitagliptin as a DPP4 inhibitor. Twenty-four animals randomly allocated into four groups including: (I) control, (II) MTX (20 mg/kg, i.p.), (III) sitagliptin (20 mg/kg, i.p., for four consecutive days), and MTX + sitagliptin in which received chemicals resembling group II and III. Histopathological examinations conducted to assess the structural changes in testes of different experimental groups. Also, ELISA method employed to investigate the levels of DPP4, AKT, p-AKT, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1). In addition, the total malondialdehyde (MDA) content and the activity of superoxide dismutase (SOD) were assessed. The results indicated that MTX administration was accompanied with testicular damage, which reversed by sitagliptin treatment. The biochemical observations demonstrated that MTX markedly increased the levels of DPP4, decreased p-AKT/AKT ratio followed by a marked decrement in Nrf2 and HO-1 levels. Also, it was observed that MTX decreased the activity of SOD and increased total MDA content in testicular specimen. However, sitagliptin treatment diminished mentioned alterations effectively. Altogether, our findings supported the possible role of DPP4 in MTX-induced testicular toxicity along with the potential protective features of sitagliptin via suppressing of the histopathological and biochemical alterations induced by MTX.

Obesity and male fertility disorders

Often associated with obesity, male infertility represents a widespread condition that challenges the wellbeing of the couple. In this article, we provide a comprehensive and critical analysis of studies exploring the association between obesity and male reproductive function, to evaluate the frequency of this association, and establish the effects of increased body weight on conventional and biofunctional sperm parameters and infertility. In an attempt to find possible molecular markers of infertility in obese male patients, the numerous mechanisms responsible for infertility in overweight/obese patients are reviewed in depth. These include obesity-related functional hypogonadism, insulin resistance, hyperinsulinemia, chronic inflammation, adipokines, irisin, gut hormones, gut microbiome, and sperm transcriptome. According to meta-analytic evidence, excessive body weight negatively influences male reproductive health. This can occurr through a broad array of molecular mechanisms. Some of these are not yet fully understood and need to be further elucidated in the future. A better understanding of the effects of metabolic disorders on spermatogenesis and sperm fertilizing capacity is very useful for identifying new diagnostic markers and designing therapeutic strategies for better clinical management of male infertility.

Phosphorylation Codes in IRS-1 and IRS-2 Are Associated with the Activation/Inhibition of Insulin Canonical Signaling Pathways

Insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) are signaling adaptor proteins that participate in canonical pathways, where insulin cascade activation occurs, as well as in non-canonical pathways, in which phosphorylation of substrates is carried out by a diverse array of receptors including integrins, cytokines, steroid hormones, and others. IRS proteins are subject to a spectrum of post-translational modifications essential for their activation, encompassing phosphorylation events in distinct tyrosine, serine, and threonine residues. Tyrosine residue phosphorylation is intricately linked to the activation of the insulin receptor cascade and its interaction with SH2 domains within a spectrum of proteins, including PI3K. Conversely, serine residue phosphorylation assumes a different function, serving to attenuate the effects of insulin. In this review, we have identified over 50 serine residues within IRS-1 that have been reported to undergo phosphorylation orchestrated by a spectrum of kinases, thereby engendering the activation or inhibition of different signaling pathways. Furthermore, we delineate the phosphorylation of over 10 distinct tyrosine residues at IRS-1 or IRS-2 in response to insulin, a process essential for signal transduction and the subsequent activation of PI3K.