Long noncoding RNA MIR22HG promotes Leydig cell apoptosis by acting as a competing endogenous RNA for microRNA-125a-5p that targets N-Myc downstream-regulated gene 2 in late-onset hypogonadism.

Leydig cells (LCs) apoptosis is responsible for the deficiency of serum testosterone in Late-onset hypogonadism (LOH), while its specific mechanism is still unknown. This study focuses on the role of long noncoding RNA (lncRNA) MIR22HG in LC apoptosis and aims to elaborate its regulatory mechanism. MIR22HG was up-regulated in the testicular tissues of mice with LOH and H2O2-treated TM3 cells (mouse Leydig cell line). Interference of MIR22HG ameliorated cell apoptosis and upregulated miR-125a-5p expression in H2O2-treated TM3 cells. Then, the interaction between MIR22HG and miR-125a-5p was confirmed with RIP and RNA pull-down assay. Further study showed that miR-125a-5p downregulated N-Myc downstream-regulated gene 2 (NDRG2) expression by targeting its 3'-UTR of mRNA. What's more, MIR22HG overexpression aggravated cell apoptosis and reduced testosterone production in TM3 cells via miR-125a-5p/NDRG2 pathway. MIR22HG knockdown elevated testosterone levels in LOH mice. In conclusion, MIR22HG up-regulated NDRG2 expression through targeting miR-125a-5p, thus promoting LC apoptosis in LOH.

Melanocortin 4 Receptor Activation Attenuates Mitochondrial Dysfunction in Skeletal Muscle of Diabetic Rats.

A previous study has confirmed that the central melanocortin system was able to mediate skeletal muscle AMP-activated protein kinase (AMPK) activation in mice fed a high-fat diet, while activation of the AMPK signaling pathway significantly induced mitochondrial biogenesis. Our hypothesis was that melanocortin 4 receptor (MC4R) was involved in the development of skeletal muscle injury in diabetic rats. In this study, we treated diabetic rats intracerebroventricularly with MC4R agonist R027-3225 or antagonist SHU9119, respectively. Then, we measured the production of reactive oxygen species (ROS), the levels of malondialdehyde (MDA) and glutathione (GSH), the mitochondrial DNA (mtDNA) content and mitochondrial biogenesis, and the protein levels of p-AMPK, AMPK, peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), sirtuin 1 (SIRT1), and manganese superoxide dismutase (MnSOD) in the skeletal muscle of diabetic rats. The results showed that there was significant skeletal muscle injury in the diabetic rats along with serious oxidative stress and decreased mitochondrial biogenesis. Treatment with R027-3225 reduced oxidative stress and induced mitochondrial biogenesis in skeletal muscle, and also activated the AMPK-SIRT1-PGC-1α signaling pathway. However, diabetic rats injected with MC4R antagonist SHU9119 showed an aggravated oxidative stress and mitochondrial dysfunction in skeletal muscle. In conclusion, our results revealed that MC4R activation was able to attenuate oxidative stress and mitochondrial dysfunction in skeletal muscle induced by diabetes partially through activating the AMPK-SIRT1-PGC-1α signaling pathway. J. Cell. Biochem. 118: 4072-4079, 2017. © 2017 Wiley Periodicals, Inc.

[Study on five point mutations in mitochondrial DNA in patients with Leber's hereditary optic neuropathy].

OBJECTIVE: To analyze the relationship between the primary mutation at np11778 and the secondary mutations at np9804, np13708, np13730, np15257 in three Chinese pedigrees with Leber's hereditary optic neuropathy (LHON) and to detect the effects of the mutations on LHON. METHODS: Thirty-seven maternal individuals from three LHON pedigrees and forty-seven normal controls were involved in this study. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing were used to detect the mutations in mitochondrial DNA (mtDNA). RESULTS: All patients and their maternal relatives had the np11778 mtDNA primary mutation. None had the secondary mutations at np9804, np13708 and np13730 and np15257. DNA sequencing of the PCR fragment revealed six new point mutations at np13759, np13928, np13942, np15301, np15323 and np15326. CONCLUSION: All three Chinese pedigrees with LHON had the mtDNA11778 primary mutation. The frequency of mutation at np13759 in Chinese patients with LHON is higher than that in normal Chinese controls. These findings indicate that np13759 is a new secondary mutation of LHON in Chinese.

SIRT1 overexpression in skeletal muscle in vivo induces increased insulin sensitivity and enhanced complex I but not complex II-V functions in individual subsarcolemmal and intermyofibrillar mitochondria.

SIRT1 is known to improve insulin resistance (IR), but whether this effect is direct or not is still unclear, and this question has not been addressed in vivo in the skeletal muscle. Therefore, we sought to test if acute overexpression of SIRT1 in skeletal muscle of high-fat diet (HFD) rats in vivo would affect subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondrial complexes I-V activities and antioxidant enzymes thereby improving insulin action. In vivo electrotransfer was used to overexpress SIRT1 in the skeletal muscle of rats fed HFD for 12 weeks. Skeletal muscle insulin sensitivity and downstream effects of SIRT1 on AMPK, SIRT3, and mitochondrial biogenesis were studied. Citrate synthase (CS), complexes I-V, oxidative stress, and antioxidant levels were assessed in SS and IMF mitochondria. HFD rats showed skeletal muscle IR as well as decreased SIRT1 and SIRT3 expressions, mitochondrial DNA (mtDNA), and mitochondrial biogenesis (p < 0.05). SS and IMF mitochondria displayed lower CS, complexes I-V, and antioxidant enzyme activities (p < 0.05). By contrast, moderate (~2.5 folds) SIRT1 overexpression attenuated HFD-induced skeletal muscle IR. This improvement was associated with increased AMPK, PGC-1α, SIRT3, and mtDNA expressions as well as SS and IMF mitochondrial CS and complexes I-V activities. Importantly, SIRT1 overexpression largely restored antioxidant enzyme activities and enhanced complex I but not complexes II-V functions in individual SS and IMF mitochondria. This study suggests that SIRT1 overexpression improved IR at least partly by targeting complex I functions of SS and IMF mitochondria through the activation of SIRT1 and SIRT3.