The effects of selenium on GPX4-mediated lipid peroxidation and apoptosis in germ cells.

Emerging evidence suggests that selenium plays an essential role in sperm maturation. However, the specific signaling pathway by which selenium exerts effect has not been elucidated. To evaluate the effect of selenium on GPX4-mediated lipid peroxidation and apoptosis in germ cells, selenium deficiency was modeled by culturing GC2-spd cells in serum-free medium. Treatment with 0.5-µM sodium selenite (NaSe) or 5.0-µM selenomethionine (SeMet) significantly improved the proliferation rate and GPX4 protein expression after selenium deficiency. Moreover, NaSe and SeMet decreased the MDA content and lipid peroxidation. When adenovirus was used to knockdown the expression of the GPX4 gene (shRNA-GPX4), the early apoptosis rate of the shRNA-GPX4 cells was significantly higher than that of the EGFP cells. Increased expression of Caspase3 and Bax, as well as MDA content were observed in the shRNA-GPX4 cells compared with EGFP cells. In further, overexpression of the GPX4 gene (ORF-GPX4) cells exhibited increased cell proliferation and decreased MDA content. However, there was no significant difference in 12/15-lox expression both in ORF-GPX4 cells and shRNA-GPX4 cells. Conclusively, GPX4 was involved in the regulation of lipid peroxidation and apoptosis in GC2-spd cells. Selenium played a role in promoting cell proliferation by mediating GPX4. The regulation of GPX4 may occur independently of 12/15-Lox. These findings confirmed the effect of selenium on spermatogenesis and offered a potential target for treating abnormal semen quality in men.

DEHP induces obesity and hypothyroidism through both central and peripheral pathways in C3H/He mice.

OBJECTIVE: Di(2-ethylhexyl) phthalate (DEHP) is reported to cause obesity and hypothyroidism in both humans and rodents, but the underlying mechanisms were largely unknown. This study was designed to clarify the effects and the mechanisms of DEHP on the pathogenesis of obesity and hypothyroidism and to discover the relationship between them. METHODS: Male C3H/He mice were treated with DEHP for 5 weeks, and the body weight, food intake, and body temperature were recorded during the exposure. After exposure, key organs and serum were analyzed by Q-PCR, Western blot, and ELISA. RESULTS: DEHP induced significant body weight gain and adipogenesis in all exposure groups except for 0.05 mg/kg. Marked hyperphagia and daytime hypothermia were also observed, which were accompanied by disturbed hypothalamic neuropeptide expression and reduced BAT UCP1 expression. In addition, WAT lipid metabolism was significantly deceased at low dose (0.5 mg/kg) and increased at high dose (50 and 200 mg/kg). DEHP also induced hypothyroidism, which was probably attributed to the combined effects of hepatic CAR activation and hypothalamic TRH inhibition induced by hypothalamic leptin resistance. CONCLUSIONS: Chronic DEHP exposure could induce obesity by interrupting energy homeostasis, which is probably due to the synergistic effects of hypothyroidism and hypothalamic leptin resistance.

Central prolactin receptors (PRLRs) regulate hepatic insulin sensitivity in mice via signal transducer and activator of transcription 5 (STAT5) and the vagus nerve.

AIMS/HYPOTHESIS: Recent studies have revealed the crucial role of the central nervous system (CNS), especially the hypothalamus, in the regulation of insulin sensitivity in peripheral tissues. The aim of our current study was to investigate the possible involvement of hypothalamic prolactin receptors (PRLRs) in the regulation of hepatic insulin sensitivity. METHODS: We employed overexpression of PRLRs in mouse hypothalamus via intracerebroventricular injection of adenovirus expressing PRLR and inhibition of PRLRs via adenovirus expressing short-hairpin RNA (shRNA) specific for PRLRs in vivo. Selective hepatic vagotomy was employed to verify the important role of the vagus nerve in mediating signals from the brain to peripheral organs. In addition, a genetic insulin-resistant animal model, the db/db mouse, was used in our study to investigate the role of hypothalamic PRLRs in regulating whole-body insulin sensitivity. RESULTS: Overexpression of PRLRs in the hypothalamus improved hepatic insulin sensitivity in mice and inhibition of hypothalamic PRLRs had the opposite effect. In addition, we demonstrated that hypothalamic PRLR-improved insulin sensitivity was significantly attenuated by inhibiting the activity of signal transducer and activator of transcription 5 (STAT5) in the CNS and by selective hepatic vagotomy. Finally, overexpression of PRLRs significantly ameliorated insulin resistance in db/db mice. CONCLUSIONS/INTERPRETATION: Our study identifies a novel central pathway involved in the regulation of hepatic insulin sensitivity, mediated by hypothalamic PRLR/STAT5 signalling and the vagus nerve, thus demonstrating an important role for hypothalamic PRLRs under conditions of insulin resistance.

Central activating transcription factor 4 (ATF4) regulates hepatic insulin resistance in mice via S6K1 signaling and the vagus nerve.

Recent studies have revealed that the central nervous system, particularly the hypothalamus, is critical for regulating insulin sensitivity in peripheral tissues. The aim of our current study is to investigate the possible involvement of hypothalamic activating transcription factor 4 (ATF4) in the regulation of insulin sensitivity in the liver. Here, we show that overexpression of ATF4 in the hypothalamus resulting from intracerebroventricular injection of adenovirus expressing ATF4 induces hepatic insulin resistance in mice and that inhibition of hypothalamic ATF4 by intracerebroventricular adenovirus expressing a dominant-negative ATF4 variant has the opposite effect. We also show that hypothalamic ATF4-induced insulin resistance is significantly blocked by selective hepatic vagotomy or by inhibiting activity of the mammalian target of rapamycin (mTOR) downstream target S6K1. Finally, we show that inhibition of hypothalamic ATF4 reverses hepatic insulin resistance induced by acute brain endoplasmic reticulum (ER) stress. Taken together, our study describes a novel central pathway regulating hepatic insulin sensitivity that is mediated by hypothalamic ATF4/mTOR/S6K1 signaling and the vagus nerve and demonstrates an important role for hypothalamic ATF4 in brain ER stress-induced hepatic insulin resistance. These results may lead to the identification of novel therapeutic targets for treating insulin resistance and associated metabolic diseases.