5’-AMP-Activated Protein Kinase Regulates Goat Sperm Functions via Energy Metabolism In Vitro

Abstract

Background/Aims: ATP is essential for mammalian sperm to survive and maintain fertilizing capacity. AMP-activated protein kinase (AMPK) is a sensor of cellular energy status. The aims of the present study were to explore the localization of AMPK in goat sperm and to investigate whether and how AMPK regulates sperm functions in vitro. Methods: Sperm were treated with AMPK modulators (AICAR, metformin and Compound C) during incubation. Sperm motility was assessed with a computer-assisted spermatozoa analysis system (CASA). Membrane integrity, acrosome reaction and mitochondrial membrane potentials were detected by SYBR-14/PI, FITC-PNA and JC-1 staining, respectively. And the lactate content, ATP content, AMPK activity, activity of pyruvate kinase (PK) and lactate dehydrogenase (LDH) were also measured with the commercial assay kits. Immunofluorescence staining was used to analyze the distribution of PK, LDH, AMPK and phospho-Thr172-AMPK in sperm. The role of AMPK was further studied during induction of capacitation and acrosome reaction. Results: We found that AMPKα was localized in the entire acrosomal region, the midpiece and the flagellum, while the phospho-Thr172-AMPK was distributed in the head, the midpiece and flagellum. Activation of AMPK by AICAR and metformin significantly improved sperm motility, membrane integrity and acrosome reaction, largely maintained sperm mitochondrial membrane potentials, lactate content and ATP content, and enhanced the activity of AMPK, PK and LDH, whereas inhibition by Compound C triggered the converse effects. Moreover, PK was localized in the acrosomal area and the midpiece, while LDH was distributed in the tail. Induction of capacitation and acrosome reaction led to AMPK phosphorylation. AMPK phosphorylation regulated the activity of energetic enzymes. Conclusion: This study for the first time provides evidence that AMPK governs goat sperm functions through energy metabolism in vitro. This finding will help to improve assisted reproductive techniques in goats and the other species.

The Role of Resveratrol in Mammalian Reproduction

“…Related to these findings, supplementation of resveratrol increased AMPK activity and was beneficial for protection against cryopreservation-induced oxidative stress of human spermatozoa by improving DNA integrity and transcripts, which were used as markers of sperm quality [ 130 ]. Similar results were obtained in boar [ 131 ] and goat [ 132 ] spermatozoa. In both studies, the addition of resveratrol activated AMPK phosphorylation, allowing the reduction of ROS production, while enhancing the sperm antioxidative defense system such as GSH level and activities of glutathione peroxidase (GPx), SOD, and catalase ( Figure 3 ).…”

Melatonin Inhibits Formation of Mitochondrial Permeability Transition Pores and Improves Oxidative Phosphorylation of Frozen-Thawed Ram Sperm

“…Bioenergetic functions of sperm mitochondria modulate ATP formation through the mitochondrial ETC, leading to ATP synthesis through the OXPHOS pathway, critical to sustaining sperm viability and motility (23). In human (24) and animal (25,26) sperm, freezing causes damage, decreasing both motility and fertilizing potential. However, some protective effects of melatonin were reported at mitochondrial level (27).…”

In vitro exposure to metformin activates human spermatozoa at therapeutically relevant concentrations

“…In vivo studies have shown that metformin improves sperm concentration and motility of diabetic rodents, but reduces that of alloxan‐induced diabetic rabbits and healthy animals with normal blood glucose levels . In vitro studies using ejaculated spermatozoa from animal models have shown that metformin improved sperm motility, viability, and the acrosome reaction in chicken and goat models, but inhibited sperm motility in boar and mouse models. So far few studies have investigated the effects of metformin on male reproduction in humans.…”