Journal of molecular endocrinology最新文献

In the endoplasmic reticulum (ER) lumen, glucose-6-phosphatase catalytic subunit 1 and 2 (G6PC1; G6PC2) hydrolyze glucose-6-phosphate (G6P) to glucose and inorganic phosphate whereas hexose-6-phosphate dehydrogenase (H6PD) hydrolyzes G6P to 6-phosphogluconate (6PG) in a reaction that generates NADPH. 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1) utilizes this NADPH to convert inactive cortisone to cortisol. HSD11B1 inhibitors improve insulin sensitivity whereas G6PC inhibitors are predicted to lower fasting blood glucose (FBG). This study investigated whether G6PC1 and G6PC2 influence G6P flux through H6PD and vice versa. Using a novel transcriptional assay that utilizes separate fusion genes to quantitate glucocorticoid and glucose signaling, we show that overexpression of H6PD and HSD11B1 in the islet-derived 832/13 cell line activated glucocorticoid-stimulated fusion gene expression. Overexpression of HSD11B1 blunted glucose-stimulated fusion gene expression independently of altered G6P flux. While overexpression of G6PC1 and G6PC2 blunted glucose-stimulated fusion gene expression, it had minimal effect on glucocorticoid-stimulated fusion gene expression. In the liver-derived HepG2 cell line, overexpression of H6PD and HSD11B1 activated glucocorticoid-stimulated fusion gene expression but overexpression of G6PC1 and G6PC2 had no effect. In rodents, HSD11B1 converts 11-dehydrocorticosterone (11-DHC) to corticosterone. Studies in wild-type and G6pc2 knockout mice treated with 11-DHC for 5 weeks reveal metabolic changes unaffected by the absence of G6PC2. These data suggest that HSD11B1 activity is not significantly affected by the presence or absence of G6PC1 or G6PC2. As such, G6PC1 and G6PC2 inhibitors are predicted to have beneficial effects by reducing FBG without causing a deleterious increase in glucocorticoid signaling.

Several studies provide evidence that erythropoietin (EPO) could play an important role in the recovery of the heart subjected to ischemia-reperfusion. In this regard, it has been suggested that EPO could be involved in protein kinase B (Akt) activation as a cell survival protein. The aim of the present study was to investigate the effects of EPO on the Akt/glycogen synthase kinase 3 beta (GSK-3β) pathway in the presence or absence of wortmannin (W, Akt inhibitor) and its relationship with mitochondrial morphology and function preservation in ischemic-reperfused rat hearts. EPO improved the functional recovery of the heart subjected to ischemia-reperfusion, reduced the release of CK and the infarct size, and promoted preservation of the mitochondrial structure. Moreover, it reduced tissue lactate content and preserved glycogen in order to prevent ischemia. The results showed greater Akt activation, accompanied by preservation of swelling and mitochondrial calcium retention capacity, as well as an increase in ATP synthesis capacity. These results were accompanied by an inhibition of GSK-3β, suggesting regulation of Akt on the opening of the mitochondrial permeability transition pore. All these beneficial effects exerted by acute treatment with EPO were prevented by W. The present study provided novel evidence that EPO not only enhances intrinsic activation of Akt during myocardial ischemia-reperfusion but also promotes GSK-3β inhibition, contributing to mitochondrial structure and function preservation.

Metabolic syndrome is a group of risk factors that increase the risk of developing metabolic and cardiovascular disease (CVD) and include obesity, dyslipidemia, insulin resistance, atherosclerosis, hypertension, coronary artery disease, and heart failure. Recent research indicates that excessive production of aldosterone and associated activation of mineralocorticoid receptors (MR) impair insulin metabolic signaling, promote insulin resistance, and increase the risk of developing metabolic syndrome and CVD. Moreover, activation of specific epithelial sodium channels (ENaC) in endothelial cells (EnNaC), which are downstream targets of endothelial-specific MR (ECMR) signaling, are also believed to play a crucial role in the development of metabolic syndrome and CVD. These adverse effects of ECMR/EnNaC activation are mediated by increased oxidative stress, inflammation, and lipid metabolic disorders. It is worth noting that ECMR/EnNaC activation and the pathophysiology underlying metabolic syndrome and CVD appears to exhibit sexual dimorphism. Targeting ECMR/EnNaC signaling may have a beneficial effect in preventing insulin resistance, diabetes, metabolic syndrome, and related CVD. This review aims to examine our current understanding of the relationship between MR activation and increased metabolic syndrome and CVD, with particular emphasis placed on the role for endothelial-specific ECMR/EnNaC signaling in these pathological processes.

Placenta synthesizes hormones that play a vital role in adapting maternal physiology and supporting fetal growth. This study aimed to explore the link between progesterone, a key steroid hormone produced by placenta, and mitochondrial fission and protein kinase R through the use of chemical inhibition in trophoblasts subjected to endotoxin lipopolysaccharide and double-stranded RNA analog polyinosinic:polycytidylic acid stress. Expressions of protein kinase R, dynamin-related protein 1, mitochondrial fission protein 1, and heat shock protein 60 were determined by applying lipopolysaccharide and polyinosinic:polycytidylic acid to BeWo trophoblast cells. Next, cells were treated with protein kinase R inhibitor 2-aminopurine and mitochondrial division inhibitor 1 to examine changes in progesterone levels and expression levels of proteins and mRNAs involved in progesterone biosynthesis. Last, effect of 2-aminopurine on mitochondrial fission was determined by immunoblotting and quantitative PCR (qPCR). Mitochondrial structural changes were also examined by transmission electron microscopy. Lipopolysaccharide and polyinosinic:polycytidylic acid stimulation induced mitochondrial fission and activated protein kinase R but decreased heat shock protein 60 levels and progesterone synthesis. Chemical inhibition of mitochondrial fission elevated progesterone synthesis and protein and mRNA levels of genes involved in progesterone biosynthesis. Inhibition of protein kinase R with 2-aminopurine prevented lipopolysaccharide and polyinosinic:polycytidylic acid induced mitochondrial fission and increased progesterone biosynthesis. Use of chemical inhibitors to treat placental stress caused by pathogens has potential to stabilize the production of progesterone. The study reveals that inhibiting mitochondrial fragmentation and reducing activity of stress kinase protein kinase R in syncytiotrophoblasts leads to an increase in progesterone synthesis when exposed to lipopolysaccharide and polyinosinic:polycytidylic acid.

Maternal obesity predisposes offspring to obesity in adulthood. Since the perinatal period is a critical window for adipose organogenesis, we evaluated if maternal obesity affects the perinatal offspring adipogenesis. Female mice were fed a standard diet (eutrophic dam, ED) or a high-fat diet supplemented with condensed milk (obese dam, OD) for 6 weeks before mating, and the diets were maintained until the end of the protocol. Inguinal adipose tissue of offspring at gestational day 16.5 (E16.5), postnatal day 0 (P0), and P2 was collected to analyze morphological and molecular features. In OD offspring, the number of preadipocytes increased at E16.5 and P0 compared to ED offspring. The cell cycle-related elements Ccnd1 and Ki67 were also upregulated in these groups. In parallel, lipid accumulation started at E16.5 in OD offspring, while ED offspring preadipocytes only accumulated lipids after P0. Peroxisome proliferator-activated receptor gamma (PPARγ) levels and activity were decreased in OD offspring due to impaired nuclear migration. Increased Hdac1 expression, which negatively regulates PPAR-responsive elements in the genome, was also detected. At P2, OD adipocytes presented abnormal features, including a clustered distribution and decreased expression of PPARγ target genes and Adbr3 and Slc2a4, which are highly expressed in mature functional adipocytes. The abnormal adipose tissue is one of the major factors promoting metabolic abnormalities in adulthood. This study demonstrates for the first time the morphological and molecular alterations induced by maternal obesity in vivo in the perinatal adipogenesis in murine inguinal adipose tissue.

Arylalkylamine N-acetyltransferase (AANAT), a rate-limiting enzyme in melatonin synthesis, is present in extra-pineal tissues such as the hippocampus. The hippocampal AANAT activity in amyloid β (Aβ) neurotoxicity has not been exactly defined. Adult male rats received bilateral intra-CA1 Aβ administration. The hippocampus tissue sampling was performed 2, 12, and 24 h after Aβ injection in the morning and night. The inflammation was monitored using tumor necrosis factor-alpha (TNF-α) immunohistochemistry. The AANAT enzyme activity and melatonin levels were measured using western blotting and high-performance liquid chromatography. The sampling in the morning vs night showed no significant differences in the AANAT activity. The Aβ increased the area of TNF-α positive staining 24 h after injection, which indicated the induction of an inflammatory context. It was accompanied by a significant reduction in AANAT activity and hippocampal melatonin. A reverse correlation was also detected between TNF-α and AANAT activity in the 24-h group. The TNF-α positive area was significantly increased in the 24-h group as compared to the 12-h group. Data showed that inflammatory processes began 12 h after the Aβ injection and augmented 24 h later. In the second experiment, the impact of Aβ injection on hippocampus AANAT activity was examined in the pinealectomized (PIN×) animals. The PIN× per se did not affect the hippocampal AANAT and melatonin levels. However, there was a significant decrease in hippocampal melatonin in the PIN×+Aβ group. The findings suggest the accompanying hippocampal inflammatory context and AANAT enzyme activity reduction in early stages after Aβ administration. Understanding the underlying mechanism of the decreased AANAT activity may suggest new treatment strategies.

Excessive hepatic gluconeogenesis partially accounts for the occurrence of type 2 diabetes mellitus. Serum- and glucocorticoid inducible-kinase 1 (SGK1) is linked to the development of metabolic syndrome, such as obesity, hypertension, and hyperglycemia. However, the regulatory role of SGK1 in glucose metabolism of liver remains uncertain. Our microarray analysis showed that SGK1 expression was strongly induced by 8-Br-cAMP and suppressed by metformin in primary mouse hepatocytes. Hepatic SGK1 expression was markedly increased in obese and diabetic mice. Metformin treatment decreased hepatic SGK1 expression levels in db/db mice. Inhibition or knockdown of SGK1 suppressed gluconeogenesis in primary mouse hepatocytes, with decreased expressions of key gluconeogenic genes. Furthermore, SGK1 silencing in liver decreased hepatic glucose production in C57BL/6 mice. Knockdown of SGK1 had no impact on CREB phosphorylation level but increased AKT and FoxO1 phosphorylation levels with decreased expressions of transcription factors including FoxO1 and hepatocyte nuclear factors. Adenovirus-mediated expression of dominant-negative AMPK antagonized metformin-suppressed SGK1 expression induced by 8-Br-cAMP. These findings demonstrate that hepatic specific silence of SGK1 might be a potential therapeutic strategy for type 2 diabetes.

Melatonin, a pineal hormone, has potential role on steroidogenesis, growth and maturation of sperm and ovum during gametogenesis. The possible use of this indolamine as an antioxidant in the production of good quality gametes opens up a new area of current research. Nowadays, a large number of reproductive dysfunctions like infertility and failure in fertilization due to gametic malformations are major concern worldwide. So, understanding molecular mechanisms including interacting genes and their action is a prerequisite to the therapeutic approach against these issues. The aim of present bioinformatic study is the detection of molecular network concerning therapeutic potential of melatonin in gametogenesis. It includes target genes identification, gene ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, network analysis, prediction of signalling pathways and molecular docking. We obtained common top 52 targets of melatonin in the process of gametogenesis. They are involved in biological processes related to the development of gonads and primary sexual characteristics and sex differentiation. We took top 10 pathways out of total 190 enriched pathways for further analysis. Subsequently, principal component analysis also revealed that among top ten hub targets (TP53, CASP3, MAPK1, JUN, ESR1, CDK1, CDK2, TNF, GNRH1 and CDKN1A), only TP53, JUN and ESR1were significantly interacted with melatonin on the basis of squared cosine value. So, present in silico investigation provides considerable information on the interactive network between therapeutic targets of melatonin along with the involvement of intracellular signalling cascade regulating biological processes associated with the gametogenesis. This novel approach may be pertinent in improving modern research on reproductive dysfunctions associated abnormalities.

Liver sinusoidal endothelial cells (LSECs) are highly specialised endothelial cells that form the liver microvasculature. LSECs maintain liver homeostasis, scavenging bloodborne molecules, regulating immune response, and actively promoting hepatic stellate cell quiescence. These diverse functions are underpinned by a suite of unique phenotypical attributes distinct from other blood vessels. In recent years, studies have begun to reveal the specific contributions of LSECs to liver metabolic homeostasis and how LSEC dysfunction associates with disease aetiology. This has been particularly evident in the context of non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of metabolic syndrome, which is associated with the loss of key LSEC phenotypical characteristics and molecular identity. Comparative transcriptome studies of LSECs and other endothelial cells, together with rodent knockout models, have revealed that loss of LSEC identity through disruption of core transcription factor activity leads to impaired metabolic homeostasis and to hallmarks of liver disease. This review explores the current knowledge of LSEC transcription factors, covering their roles in LSEC development and maintenance of key phenotypic features, which, when disturbed, lead to loss of liver metabolic homeostasis and promote features of chronic liver diseases, such as non-alcoholic liver disease.

Liver transthyretin (TTR) synthesis and release are exacerbated in insulin-resistant states but are decreased by exercise training, in relation to the insulin-sensitizing effects of exercise. We hypothesized that TTR knockdown (TTR-KD) may mimic this exercise-induced metabolic improvement and skeletal muscle remodeling. Adeno-associated virus-mediated TTR-KD and control mice were trained for 8 weeks on treadmills. Their metabolism status and exercise capacity were investigated and then compared with sedentary controls. After treadmill training, the mice showed improved glucose and insulin tolerance, hepatic steatosis, and exercise endurance. Sedentary TTR-KD mice displayed metabolic improvements comparable to the improvements in trained mice. Both exercise training and TTR-KD promoted the oxidative myofiber compositions of MyHC I and MyHC IIa in the quadriceps and gastrocnemius skeletal muscles. Furthermore, training and TTR-KD had an additive effect on running performance, accompanied by substantial increases in oxidative myofiber composition, Ca2+-dependent Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, and the downstream expression of PGC1α as well as the unfolded protein response (UPR) segment of PERK-p-eIF2a pathway activity. Consistent with these findings, electrical pulse stimulation of an in vitro model of chronic exercise (with differentiated C2C12 myoblasts) showed that exogenous TTR protein was internalized and localized in the endoplasmic reticulum, where it disrupted Ca2+ dynamics; this led to decreases in intracellular Ca2+ concentration and downstream pathway activity. TTR-KD may function as an exercise/Ca2+-dependent CaMKII-PGC1α-UPR regulator that upregulates the oxidative myofiber composition of fast-type muscles; it appears to mimic the effect of exercise training on insulin sensitivity-related metabolic improvement and endurance capacity.