Uncoupling protein 2 expression affects androgen synthesis in polycystic ovary syndrome

Emerging role and the signaling pathways of uncoupling protein 2 in kidney diseases

OBJECTIVES

Uncoupling protein 2 (UCP2) was involved in the pathogenesis and development of kidney diseases. Many signaling pathways and factors regulate the expression of UCP2. We aimed to investigate the precise role of UCP2 and its signaling pathways in kidney diseases.

METHODS

We summarized the available evidence to yield a more detailed conclusion of the signal transduction pathways of UCP2 and its role in the development and progression of kidney diseases.

RESULTS

UCP2 could interact with 14.3.3 family proteins, mitochondrial phospholipase iPLA2γ, NMDAR, glucokinase, PPARγ2. There existed a signaling pathway between UCP2 and NMDAR, PPARγ. UCP2 can inhibit the ROS production, inflammatory response, and apoptosis, which may protect against renal injury, particularly AKI. Meanwhile UCP2 can decrease ATP production and inhibit the secretion of insulin, which may alleviate chronic renal damages, such as diabetic nephropathy and kidney fibrosis.

CONCLUSIONS

Homeostasis of UCP2 is helpful for kidney health. UCP2 may play different roles in different kinds of renal injury.

Polycystic ovarian syndrome: signs and feedback effects of hyperandrogenism and insulin resistance

Polycystic ovary syndrome (PCOS) is a disease whose diagnosis is based on the detection of hyperandrogenism (HA) and ovulatory dysfunction. Women with PCOS frequently develop insulin resistance (IR), which generates a metabolic condition that involves a decrease in the action of insulin at the cellular level and is linked to compensatory hyperinsulinemia (HI). In PCOS, the ovary remains sensitive to the action of insulin. Additionally, it has been observed that the main effect of insulin in the ovary is the stimulation of androgen synthesis, resulting in HA, one of the fundamental characteristics of the PCOS. In this sense, the excess of androgens favors the development of IR, thus perpetuating the cycle of IR-HI-HA, and therefore PCOS. Moreover, mitochondrial dysfunction is present in PCOS patients and is a common feature in both IR and HA. This review places electron transfer as a key element in HA and IR development, with emphasis on the relationship between androgen biosynthesis and mitochondrial function. Indeed, metformin has been involved in repair mitochondrial dysfunction, decrease of oxidative stress, reduction of androgens levels and the enhancing of insulin sensitivity. Therefore, we propose that treatment with metformin could decrease HI and consequently HA, restoring, at least in part, the metabolic and hormonal disorders of PCOS.

Vitamin D3 affects mitochondrial biogenesis through mitogen-activated protein kinase in polycystic ovary syndrome mouse model

Polycystic ovarian syndrome (PCOS) is a disorder characterized by oligomenorrhea, anovulation, and hyperandrogenism. Altered mitochondrial biogenesis can result in hyperandrogenism. The goal of this study was to examine the effect of vitamin D3 on mitochondrial biogenesis of the granulosa cells in the PCOS-induced mouse model. Vitamin D3 applies its effect via the mitogen-activated pathway kinase-extracellular signal-regulated kinases (MAPK-ERK1/2) pathway. The PCOS mouse model was induced by the injection of dehydroepiandrosterone (DHEA). Isolated granulosa cells were subsequently treated with vitamin D3, MAPK activator, and MAPK inhibitor. Gene expression levels were measured using real-time polymerase chain reaction. MAPK proteins were investigated by western blot analysis. We also determined reactive oxygen species (ROS) levels with 2', 7'-dichlorofluorescein diacetate. Mitochondrial membrane potential (mtMP) was also measured by TMJC1. Mitochondrial biogenesis (peroxisome proliferator-activated receptor gamma coactivator 1-α and nuclear respiratory factor), antioxidant (superoxide dismutase, glutathione peroxidase, and catalase), and antiapoptotic (B-cell lymphoma-2) genes were upregulated in the PCOS mice that treated with vitamin D3 compared with the PCOS mice without any treatment. Vitamin D3 and MAPK activator-treated groups also reduced ROS levels compared with the nontreated PCOS group. In summary, vitamin D3 and MAPK activator increased the levels of mitochondrial biogenesis, MAPK pathway, and mtMP markers, while concomitantly decreased ROS levels in granulosa cells of the PCOS-induced mice. This study suggests that vitamin D3 may improve mitochondrial biogenesis through stimulation of the MAPK pathway in cultured granulosa cells of DHEA-induced PCOS mice which yet to be investigated.

Mitochondrial Uncoupling Protein 2 in human cumulus cells is associated with regulating autophagy and apoptosis, maintaining gap junction integrity and progesterone synthesis

To explore the roles of mitochondrial Uncoupling Protein 2 (UCP2) in cumulus cells (CCs), human CCs were cultured in vitro, and the UCP2 was inhibited by treatment with Genipin, a special UCP inhibitor, or by RNA interference targeting UCP2. No significant differences in adenosine triphosphate levels and the ratio of ADP/ATP were observed after UCP2 inhibition. UCP2 inhibition caused a significant increase in cellular oxidative damage, which was reflected in alterations to several key parameters, including reactive oxygen species (ROS) and lipid peroxidation levels and the ratio of reduced GSH to GSSG. UCP2 blocking resulted in an obvious increase in active Caspase-3, accompanied by the decline of proactive Caspase-3 and a significant increase in the LC3-II/LC3-I ratio, suggesting that UCP2 inhibition triggered cellular apoptosis and autophagy. The mRNA and protein expression of connexin 43 (Cx43), a gap junction channel protein, were significantly reduced after treatment with Genipin or siRNA. The progesterone level in the culture medium was also significantly decreased after UCP2 inhibition. Our data indicated that UCP2 plays highly important roles in mediating ROS production and regulating apoptosis and autophagy, as well as maintaining gap junction integrity and progesterone synthesis, which suggests that UCP2 is involved in the regulation of follicle development and early embryo implantation and implies that it might serve as a potential biomarker for oocyte quality and competency.

Epigenetic regulation of an adverse metabolic phenotype in polycystic ovary syndrome: the impact of the leukocyte methylation of PPARGC1A promoter

OBJECTIVE

To investigate PPARGC1A promoter methylation and mitochondria DNA (mtDNA) content in the leukocytes of women with polycystic ovary syndrome (PCOS) and analyze the relationship between these indices and metabolic risk for women with PCOS.

DESIGN

Cross-sectional study.

SETTING

University hospital.

PATIENT(S)

A total of 175 women with PCOS and 127 healthy controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Women with and without PCOS classified using the typical metabolic risk criteria of the National Cholesterol Education Program's Adult Treatment Panel III report (ATPIII), methylation of PPARGC1A promoter tested by methylation-specific polymerase chain reaction, and mtDNA content confirmed by quantitative polymerase chain reaction (PCR).

RESULT(S)

PPARGC1A promoter methylation was specifically increased, but mtDNA content was specifically decreased in women with PCOS compared with the control women after adjustment for body mass index. Moreover, in women with PCOS who have increased metabolic risk, the differences in PPARGC1A promoter methylation and mitochondrial content were aggravated.

CONCLUSION(S)

In conclusion, PPARGC1A promoter methylation and mitochondrial content were found to be potential biomarkers for the prediction of metabolic risk in women with PCOS.

Genetics of PCOS: A systematic bioinformatics approach to unveil the proteins responsible for PCOS

Polycystic ovary syndrome (PCOS) is a hormonal imbalance in women, which causes problems during menstrual cycle and in pregnancy that sometimes results in fatality. Though the genetics of PCOS is not fully understood, early diagnosis and treatment can prevent long-term effects. In this study, we have studied the proteins involved in PCOS and the structural aspects of the proteins that are taken into consideration using computational tools. The proteins involved are modeled using Modeller 9v14 and Ab-initio programs. All the 43 proteins responsible for PCOS were subjected to phylogenetic analysis to identify the relatedness of the proteins. Further, microarray data analysis of PCOS datasets was analyzed that was downloaded from GEO datasets to find the significant protein-coding genes responsible for PCOS, which is an addition to the reported protein-coding genes. Various statistical analyses were done using R programming to get an insight into the structural aspects of PCOS that can be used as drug targets to treat PCOS and other related reproductive diseases.

Effects of Mitochondrial Uncoupling Protein 2 Inhibition by Genipin in Human Cumulus Cells

UCP2 plays a physiological role by regulating mitochondrial biogenesis, maintaining energy balance, ROS elimination, and regulating cellular autophagy in numerous tissues. But the exact roles of UCP2 in cumulus cells are still not clear. Genipin, a special UCP2 inhibitor, was added into the cultural medium to explore the roles of UCP2 in human cumulus cells. There were no significant differences in ATP and mitochondrial membrane potential levels in cumulus cells from UCP2 inhibiting groups as compared with the control. The levels of ROS and Mn-SOD were markedly elevated after UCP2 inhibited Genipin. However, the ratio of reduced GSH to GSSG significantly declined after treatment with Genipin. UCP2 inhibition by Genipin also resulted in obvious increase in the active caspase-3, which accompanied the decline of caspase-3 mRNA. The level of progesterone in culture medium declined obviously after Genipin treatment. But there was no significant difference in estradiol concentrations. This study indicated that UCP2 is expressed in human cumulus cells and plays important roles on mediate ROS production, apoptotic process, and steroidogenesis, suggesting UCP2 may be involved in regulation of follicle development and oocyte maturation and quality.