Glycogen Synthase Activity Research Articles

MicroRNA-425-5p promotes tau phosphorylation and cell apoptosis in Alzheimer's disease by targeting heat shock protein B8.

Alzheimer's disease (AD) is the most prevalent and age-related dementia accompanied by neurodegenerative disorder, memory loss, and abnormal behaviors. Recent studies have shown an increasing interest in studying the role of microRNAs (miRNAs) and their potential values in the early diagnostics of AD. MiR-425-5p has extensively expression within various tissues and organs, acting as an important regulator in many pathological procedures. The functions of miR-425-5p involved in AD were investigated in the present study. The results showed that miR-425-5p was upregulated in patients with AD and HEK293/tau cells. Transfections with miR-425-5p overexpression vector significantly enhanced cell apoptosis, activated glycogen synthase kinase-3β (GSK-3β), and increased tau phosphorylation in HEK293/tau cells. Heat shock protein B8 (HSPB8) was directly targeted by miR-425-5p. Upregulation of miR-425-5p induced cell apoptosis and promoted tau phosphorylation partially via targeting HSPB8 in AD. Therefore, miR-425-5p might act as a new therapeutic target for AD treatment.

Neuronal Protein Tyrosine Phosphatase 1B Hastens Amyloid β-Associated Alzheimer's Disease in Mice.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, resulting in the progressive decline of cognitive function in patients. Familial forms of AD are tied to mutations in the amyloid precursor protein, but the cellular mechanisms that cause AD remain unclear. Inflammation and amyloidosis from amyloid β (Aβ) aggregates are implicated in neuron loss and cognitive decline. Inflammation activates the protein-tyrosine phosphatase 1B (PTP1B), and this could suppress many signaling pathways that activate glycogen synthase kinase 3β (GSK3β) implicated in neurodegeneration. However, the significance of PTP1B in AD pathology remains unclear. Here, we show that pharmacological inhibition of PTP1B with trodusquemine or selective ablation of PTP1B in neurons prevents hippocampal neuron loss and spatial memory deficits in a transgenic AD mouse model with Aβ pathology (hAPP-J20 mice of both sexes). Intriguingly, while systemic inhibition of PTP1B reduced inflammation in the hippocampus, neuronal PTP1B ablation did not. These results dissociate inflammation from neuronal loss and cognitive decline and demonstrate that neuronal PTP1B hastens neurodegeneration and cognitive decline in this model of AD. The protective effect of PTP1B inhibition or ablation coincides with the restoration of GSK3β inhibition. Neuronal ablation of PTP1B did not affect cerebral amyloid levels or plaque numbers, but reduced Aβ plaque size in the hippocampus. In summary, our preclinical study suggests that targeting PTP1B may be a new strategy to intervene in the progression of AD.SIGNIFICANCE STATEMENT Familial forms of Alzheimer's disease (AD) are tied to mutations in the amyloid precursor protein, but the cellular mechanisms that cause AD remain unclear. Here, we used a mouse model expressing human amyloid precursor protein bearing two familial mutations and asked whether activation of a phosphatase PTP1B participates in the disease process. Systemic inhibition of this phosphatase using a selective inhibitor prevented cognitive decline, neuron loss in the hippocampus, and attenuated inflammation. Importantly, neuron-targeted ablation of PTP1B also prevented cognitive decline and neuron loss but did not reduce inflammation. Therefore, neuronal loss rather than inflammation was critical for AD progression in this mouse model, and that disease progression could be ameliorated by inhibition of PTP1B.

Pharmacological intervention of histone deacetylase enzymes in the neurodegenerative disorders

Reversal of aging symptoms and related disorders are the challenging task where epigenetic is a crucial player that includes DNA methylation, histone modification; chromatin remodeling and regulation that are linked to the progression of various neurodegenerative disorders (NDDs). Overexpression of various histone deacetylase (HDACs) can activate Glycogen synthase kinase 3 which promotes the hyperphosphorylation of tau and inhibits its degradation. While HDAC is important for maintaining the neuronal morphology and brain homeostasis, at the same time, these enzymes are promoting neurodegeneration, if it is deregulated. Different experimental models have also confirmed the neuroprotective effects caused by HDAC enzymes through the regulation of neuronal apoptosis, inflammatory response, DNA damage, cell cycle regulation, and metabolic dysfunction. Apart from transcriptional regulation, protein-protein interaction, histone post-translational modifications, deacetylation mechanism of non-histone protein and direct association with disease proteins have been linked to neuronal imbalance. Histone deacetylases inhibitors (HDACi) can be able to alter gene expression and shown its efficacy on experimental models, and in clinical trials for NDD's and found to be a very promising therapeutic agent with certain limitation, for instance, non-specific target effect, isoform-selectivity, specificity, and limited number of predicted biomarkers.Herein, we discussed (i) the catalytic mechanism of the deacetylation process of various HDAC's in in vivo and in vitro experimental models, (ii) how HDACs are participating in neuroprotection as well as in neurodegeneration, (iii) a comprehensive role of HDACi in maintaining neuronal homeostasis and (iv) therapeutic role of biomolecules to modulate HDACs.

Discovery and optimization of novel pyridines as highly potent and selective glycogen synthase kinase 3 inhibitors

Glycogen synthase kinase-3 plays an essential role in multiple biochemical pathways in the cell, particularly in regards to energy regulation. As such, Glycogen synthase kinase-3 is an attractive target for pharmacological intervention in a variety of disease states, particularly non-insulin dependent diabetes mellitus. However, due to homology with other crucial kinases, such as the cyclin-dependent protein kinase CDC2, developing compounds that are both potent and selective is challenging. A novel series of derivatives of 5-nitro-N2-(2-(pyridine-2ylamino)ethyl)pyridine-2,6-diamine were synthesized and have been shown to potently inhibit glycogen synthase kinase-3 (GSK3). Potency in the low nanomolar range was obtained along with remarkable selectivity. The compounds activate glycogen synthase in insulin receptor-expressing CHO-IR cells and in primary rat hepatocytes, and have acceptable pharmacokinetics and pharmacodynamics to allow for oral dosing. The X-ray co-crystal structure of human GSK3-β in complex with compound 2 is reported and provides insights into the structural determinants of the series responsible for its potency and selectivity.

Sodium acetate protects against nicotine-induced excess hepatic lipid in male rats by suppressing xanthine oxidase activity

Fatty liver is the hepatic consequence of chronic insulin resistance (IR) and related syndromes. It is mostly accompanied by inflammatory and oxidative molecules. Increased activity of xanthine oxidase (XO) exerts both inflammatory and oxidative effects and has been implicated in metabolic derangements including non-alcoholic fatty liver disease. Short chain fatty acids (SCFAs) elicit beneficial metabolic alterations in IR and related syndromes. In the present study, we evaluated the preventive effects of a SCFA, acetate, on nicotine-induced dysmetabolism and fatty liver. Twenty-four male Wistar rats (n = 6/group): vehicle-treatment (p.o.), nicotine-treated (1.0 mg/kg; p.o.), sodium acetate-treated (200 mg/kg; p.o.) and nicotine + sodium acetate-treated groups. The treatments lasted for 8 weeks. IR was estimated by oral glucose tolerance test and homeostatic model assessment of IR. Plasma and hepatic free fatty acid, triglyceride (TG), glutathione peroxidase, adenosine deaminase (ADA), XO and uric acid (UA) were measured. Nicotine exposure resulted in reduced body weight, liver weight, visceral adiposity, glycogen content and glycogen synthase activity. Conversely, exposure to nicotine increased fasting plasma glucose, lactate, IR, plasma and hepatic TG, free fatty acid, TG/HDL-cholesterol ratio, lipid peroxidation, liver function enzymes, plasma and hepatic UA, XO and ADA activities. However, plasma and hepatic glucose-6-phosphate dehydrogenase-dependent antioxidant defense was not affected by nicotine. Concomitant treatment with acetate ameliorated nicotine-induced effects. Taken together, these results indicate that nicotine exposure leads to excess deposition of lipid in the liver by enhancing XO activity. The results also imply that acetate confers hepatoprotection and is accompanied by decreased XO activity.

Inhibitory effects on melanogenesis by thymoquinone are mediated through the β‑catenin pathway in B16F10 mouse melanoma cells.

Thymoquinone (TQ) is a component found in the seeds of Nigella sativa, an annual plant growing on the Mediterranean coast, and is known for its anticancer and anti‑inflammatory effects. However, to date, at least to the best of our knowledge, limited studies are available examining the molecular mechanisms through which TQ inhibits melanogenesis. Accordingly, this study aimed to treat B16F10 mouse melanoma cells with TQ to investigate its apparent effects and its molecular regulatory mechanisms. Treatment of the B16F10 cells with 10, 15and20µM of TQ for 48h resulted in a dose‑dependent decrease in the expression of microphthalmia‑associated transcription factor (MITF), tyrosinase expression and tyrosinase activity, and these treatments simultaneously led to a decrease in the protein expression and transcription of β‑catenin, a Wnt signaling pathway protein. Pre‑treatment of the cells with the proteasome inhibitor, MG132, to confirm the inhibition of melanogenesis through the β‑catenin pathway by TQ treatment resulted in an increase in the expression of β‑catenin that was initially reduced by TQ, and the expression and activity of MITF and tyrosinase also increased. Pre‑treatment with LiCl, which is known to inactivate glycogen synthase kinase3β (GSK3β) by inducing the phosphorylation of the Ser‑9 site, resulted in an increased phospho‑GSK3β expression accompanied by β‑catenin that was initially reduced by TQ, and the recovery of the expression and activity of tyrosinase was also confirmed. The transfection of S37A cDNA into B16F10 cells that overexpress β‑catenin resulted in the recovery of β‑catenin expression that was initially reduced by TQ, and this treatment also recovered the expression and activity of tyrosinase. When zebrafish eggs were treated with 1, 2.5and5µM of TQ at 10h following fertilization, their melanin content decreased in a dose‑dependent manner. On the whole, these findings demonstrated that the inhibition of melanogenesis in B16F10 mouse melanoma cells by TQ treatment resulted from the inhibition of the β‑catenin pathway and confirmed that TQ treatment inhibited melanogenesis in zebrafish.

L-glutamine supplementation exerts cardio-renal protection in estrogen-progestin oral contraceptive-treated female rats

Glycogen and lipid disruptions represent a spectrum of metabolic disorders that are crucial risk factors for cardiovascular disease in estrogen-progestin oral contraceptive (COC) users. l-glutamine (GLN) has been shown to exert a modulatory effect in metabolic disorders-related syndromes. We therefore hypothesized that GLN supplementation would protect against myocardial and renal glycogen-lipid mishandling in COC-treated animals by modulation of Glucose-6-phosphate dehydrogenase (G6PD) and xanthine oxidase (XO) activities. Adult female Wistar rats were randomly allotted into control, GLN, COC and COC + GLN groups (six rats per group). The groups received vehicle (distilled water, p.o.), GLN (1 g/kg), COC containing 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel and COC plus GLN respectively, daily for 8 weeks. Data showed that treatment with COC led to metabolically-induced obesity with correspondent increased visceral and epicardial fat mass. It also led to increased plasma, myocardial and renal triglyceride, free fatty acid, malondialdehyde (MDA), XO activity, uric acid content and decreased glutathione content and G6PD activity. In addition, COC increased myocardial but not renal glycogen content, and increased myocardial and renal glycogen synthase activity, increased plasma and renal lactate production and plasma aspartate transaminase/alanine aminotransferase (AST/ALT) ratio. However, these alterations were attenuated when supplemented with GLN except plasma AST/ALT ratio. Collectively, the present results indicate that estrogen-progestin oral contraceptive causes metabolically-induced obesity that is accompanied by differential myocardial and renal metabolic disturbances. The findings also suggest that irrespective of varying metabolic phenotypes, GLN exerts protection against cardio-renal dysmetabolism by modulation of XO and G6PD activities.

Outer membrane vesicles enhance tau phosphorylation and contribute to cognitive impairment.

Outer membrane vesicles (OMVs) are nanosized vesicles produced by the gut microbiota (GM). The GM is well-known to be involved in the pathological process of Alzheimer's disease (AD). However, the mechanism of OMVs is not clear. In the present study, we demonstrated the involvement of OMVs in the development of cognitive (learning and memory) dysfunction induced by blood-brain barrier (BBB) disruption. More important, further study showed that OMVs induced tau phosphorylation by activating glycogen synthase kinase 3β (GSK-3β) in the hippocampus. OMVs activated astrocytes and microglia, increased secretion of inflammatory cytokines (nuclear factor κB, interleukin-1β, and tumour necrosis factor-α) in the hippocampus. Therefore, OMVs increase the permeability of the BBB and promote the activation of astrocytes and microglia, inducing an inflammatory response and tau hyperphosphorylation by activating the GSK-3β pathway and finally leading to cognitive impairment.

P.67Overexpression of a constitutively active glycogen synthase in the GSL30 mouse leads to a polyglucosan myopathy

Polyglucosan accumulation is a characteristic feature of several glycogen storage diseases of mammals, including eight in humans and one in horses — the latter associated with a gain of function, through a constitutively active mutant glycogen synthase (GYS1). GSL30 mice overexpressing constitutively active rabbit glycogen synthase in skeletal muscle, accumulate 5-6 times more glycogen in skeletal muscle than wild-type (WT) controls. We hypothesised that this excessive glycogen accumulation would also be associated with a myopathic histological phenotype characterised by polyglucosan accumulation, as seen in GYS1 mutant horses. We examined serum CK activity and skeletal muscle histology from 6 week, 3 month and 8 month old GSL30 mice compared with age-matched WT controls (n=5 to 8). Cryosections from the gastrocnemius, a predominantly fast-twitch muscle, were stained with H&E and amylase-periodic acid Schiff and scored (blinded to genotype) for the presence of internalised nuclei and amylase-resistant polyglucosan within myofibres. Whilst there was no difference in serum CK activity between groups (P>0.05), GSL30 mice had significantly greater numbers of internalised myonuclei than WT controls at 8 months (13.2±6% vs. 0.5%±0.4%; mean±SD; P<0.0001). Polyglucosan was not identified in WT control muscle, but was present increasingly in GSL30 mouse muscle fibres as they aged (reaching 70±5% of myofibres at 8 months). In 6 week old GSL30 mice, amylase-resistant polyglucosan was predominantly subsarcolemmal; by 3 months of age, punctate deposits were identified within the sarcoplasm. By 8 months of age, large pools of glycogen and amylase-resistant polyglucosan, often encompassing the entire myofiber, and focal areas of necrosis were evident. This data reveals that overexpression of glycogen leads to a polyglucosan myopathy in GSL30 mice. Future work will examine the influence of diet and exercise on the phenotype.

P.119Analysis of the structural and metabolic consequences of McArdle disease using the murine model

McArdle disease is an autosomal recessive disorder caused by the absence of the muscle glycogen phosphorylase, which leads to impairment of glycogen breakdown. The McArdle mouse, a model heavily affected by glycogen accumulation and exercise intolerance, was used to characterize disease progression at three different ages. The molecular and histopathological consequences of the disease were analyzed in five different hind-limb muscles (soleus, extensor digitorum longus, tibialis anterior, gastrocnemius and quadriceps) of young (8-week-old), adult (35-week-old) and old (70-week-old) mice. We observed progressive muscle degeneration, fibrosis and inflammation process that was not associated with an increase in muscle glycogen content during aging. Additionally, this progressive degeneration varied among muscle and fiber types. The lack of glycogen content increase was associated with the inactivation of glycogen synthase and not with compensatory expression of the Pygl and/or Pygb genes in mature muscle. Furthermore, the molecular interconnection between skeletal muscle-liver and adipose tissue was assessed in these mice in order to determine whether there was an upregulation of the oxidative metabolism during disease progression as McArdle mice presented a clear reduction in abdominal fat and liver glycogen content. In this regard, mitochondrial content and activity were assessed in both oxidative and glycolytic muscles as oxidative fibers (specially IIa fibers) presented more structural damage caused by higher glycogen accumulation than glycolytic fibers (IIx and IIx/IIb fibers). Lower levels of mitochondrial content and activity were found in the skeletal muscle of McA mice with respect to their wild-type counterparts.

The Protein Phosphatase 1 Complex Is a Direct Target of AKT that Links Insulin Signaling to Hepatic Glycogen Deposition

Insulin-stimulated hepatic glycogen synthesis is central to glucose homeostasis. Here, we show that PPP1R3G, a regulatory subunit of protein phosphatase 1 (PP1), is directly phosphorylated by AKT. PPP1R3G phosphorylation fluctuates with fasting-refeeding cycle and is required for insulin-stimulated dephosphorylation, i.e., activation of glycogen synthase (GS) in hepatocytes. In this study, we demonstrate that knockdown of PPP1R3G significantly inhibits insulin response. The introduction of wild-type PPP1R3G, and not phosphorylation-defective mutants, increases hepatic glycogen deposition, blood glucose clearance, and insulin sensitivity invivo. Mechanistically, phosphorylated PPP1R3G displays increased binding for, and promotes dephosphorylation of, phospho-GS. Furthermore, PPP1R3B, another regulatory subunit of PP1, binds to the dephosphorylated GS, thereby relaying insulin stimulation to hepatic glycogen deposition. Importantly, this PP1-mediated signaling cascade is independent of GSK3. Therefore, we reveal a regulatory axis consisting of insulin/AKT/PPP1R3G/PPP1R3B that operates in parallel to the GSK3-dependent pathway, controlling glycogen synthesis and glucose homeostasis in insulin signaling.

Further isolation and identification of anti-diabetic principles from root bark of Myrianthus arboreus P. Beauv.: The ethyl acetate fraction contains bioactive phenolic compounds that improve liver cell glucose homeostasis.

We recently reported that ethanol extract of Myrianthus arboreus P. Beauv. root bark demonstrated antidiabetic activity by modulating hepatocyte glucose homeostasis. This activity was associated significantly to the ethyl acetate (EAc) fraction. The current study sought to identify the active compounds responsible of the antidiabetic effect of M. arboreus in the EAc fraction using bioassay-directed sub-fractionation. EAc fraction was sub-fractionated using Flash chromatography. Preparative HPLC was used to isolate the pure compounds. The structures of the isolated compounds were confirmed by analysis of NMR spectroscopic and mass spectrometric data. Hepatic (H4IIE, HepG2) cells were treated with maximum non-toxic concentrations of ethanol extract, its EAc fraction and isolated compounds thereof. Glucose-6-phosphatase (G6Pase) activity was measured using the glucose oxidase method. To measure glycogen synthase (GS) activity, radioactive assays were used. Phosphorylation of AMP-activated protein kinase (AMPK) and Glycogen Synthase Kinase-3 (GSK-3) were probed by Western blot. Six sub-fractions were obtained, and the antidiabetic activity was found in two sub-fractions (SFE1 and SFE2). For the first time, two known C-glycosylflavone regio-isomers, isoorientin (1) and orientin (2) were detected and isolated from M. arboreus plant, especially from SFE2 as well as protocatechuic acid, 3,4-dihydroxybenzaldehyde (4), and chlorogenic acid isolated from SFE1. The compounds 1, 2, 4 were determined to decrease the activity of G6Pase by increasing AMPK phosphorylation and to stimulate GS through GSK-3 phosphorylation. Isoorientin which is one of the main compounds of EAc fraction, expressed the strongest effect in all bioassays, similar to that of the EAc fraction. A significant and linear correlation was found between the phosphorylation of AMPK and the activity of G6Pase modulated by all samples (R2 = 0.54; p < 0.05). Similar to G6Pase assay, a correlation was determined between the capacity of M. arboreus extracts/fractions/compounds to stimulate GS activity and to phosphorylate GSK-3 (R2 = 0.57, p < 0.01). Results demonstrate that 1, 2, 4 are responsible, at least in part, for the antidiabetic activity of M. arboreus. These compounds can be used to ensure the quality and efficacy of M. arboreus antidiabetic preparations and standardize such preparations.

Hesperidin, a citrus flavonoid ameliorates hyperglycemia by regulating key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic rats

The present study investigated the protective effect of hesperidin on carbohydrate metabolizing enzymes in streptozotocin-induced diabetic rats. Hesperidin was administered to streptozotocin-induced (40 mg/kg b.w.) diabetic rats at different dosages of (25, 50, 100 mg/kg b.w.) respectively for 30 days to evaluate its effect on fasting plasma glucose, insulin, glycosylated hemoglobin, hemoglobin, and carbohydrate metabolic enzymes. The plasma glucose levels were significantly reduced in a dose-dependent manner in hesperdin-treated group of rats when compared to the diabetic control rats. In addition, concomitant increase in hemoglobin and insulin levels and a decrease in glycosylated hemoglobin were observed in treated group of rats. The activities of the hepatic key enzymes of carbohydrate metabolism such as hexokinase and glucose-6-phosphate dehydrogenase were significantly increased, whereas glucose-6-phosphatase and fructose-1,6-bisphosphatase were significantly decreased. Furthermore, hesperidin administration prevented the loss in body weight and improved the glycogen content in the hepatic tissue of diabetic animals by reinstating the activities of glycogen synthase and glycogen phosphorylase. These results showed that hesperidin has potential antihyperglycemic activity in streptozotocin-induced diabetic rats. This was further supported by the histological studies of pancreas and liver.

Restoration of primary cilia in obese adipose-derived mesenchymal stem cells by inhibiting Aurora A or extracellular signal-regulated kinase

BackgroundObesity impairs a variety of cell types including adipose-derived mesenchymal stem cells (ASCs). ASCs are indispensable for tissue homeostasis/repair, immunomodulation, and cell renewal. It has been demonstrated that obese ASCs are defective in differentiation, motility, immunomodulation, and replication. We have recently reported that some of these defects are linked to impaired primary cilia, which are unable to properly convey and coordinate a variety of signaling pathways. We hypothesized that the rescue of the primary cilium in obese ASCs would restore their functional properties.MethodsObese ASCs derived from subcutaneous and visceral adipose tissues were treated with a specific inhibitor against Aurora A or with an inhibitor against extracellular signal-regulated kinase 1/2 (Erk1/2). Multiple molecular and cellular assays were performed to analyze the altered functionalities and their involved pathways.ResultsThe treatment with low doses of these inhibitors extended the length of the primary cilium, restored the invasion and migration potential, and improved the differentiation capacity of obese ASCs. Associated with enhanced differentiation ability, the cells displayed an increased expression of self-renewal/stemness-related genes like SOX2, OCT4, and NANOG, mediated by reduced active glycogen synthase kinase 3 β (GSK3β).ConclusionThis work describes a novel phenomenon whereby the primary cilium of obese ASCs is rescuable by the low-dose inhibition of Aurora A or Erk1/2, restoring functional ASCs with increased stemness. These cells might be able to improve tissue homeostasis in obese patients and thereby ameliorate obesity-associated diseases. Additionally, these functionally restored obese ASCs could be useful for novel autologous mesenchymal stem cell-based therapies.

Modulatory effect of isopulegol on hepatic key enzymes of glucose metabolism in high-fat diet/streptozotocin-induced diabetic rats

To investigate the antidiabetic effect of isopulegol in high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic rats. Animals were made diabetic by feeding HFD for 4 weeks followed by single intraperitoneal injection of STZ (35 mg/kg b.w.; 0.1 M citrate buffer; pH 4.0). Plasma insulin, haemoglobin and glycogen content were decreased while increased glucose and glycated haemoglobin were observed in diabetic rats. An increase in glucose-6-phosphatase, fructose-1,6-bisphosphatase, phosphoenol pyruvate carboxykinase with a decrease in hexokinase, glucose-6-phosphate dehydrogenase and glycogen synthase activities was observed in diabetic rats. The expression of cyclic response element binding protein (CREB) was increased in the hepatic tissue of diabetic rats. Isopulegol dose dependently (50, 100 and 200 mg/kg b.w.) improved insulin secretion, glucose tolerance and decreased glucose levels in diabetic-treated rats. At the effective dose of 100 mg/kg b.w., isopulegol restored the activities of metabolic enzymes and down-regulated CREB expression. Thus, isopulegol restored glucose homeostasis through its insulinotrophic property.

Sulfiredoxin-1 alleviates high glucose-induced podocyte injury though promoting Nrf2/ARE signaling via inactivation of GSK-3β

Hyperglycemia-induced podocyte injury plays a vital role in the development of diabetic nephropathy. Sulfiredoxin-1 (Srxn1) is emerging as a cytoprotective protein that protects from various insults in a wide range of cell types. However, whether Srxn1 is involved in regulating hyperglycemia-induced podocyte injury and participates in diabetic nephropathy remains unknown. In the present study, we aimed to explore the potential role of Srxn1 in regulating high glucose (HG)-induced apoptosis and oxidative stress of podocytes in vitro. Results demonstrated that Srxn1 was induced in HG-stimulated podocytes. The depletion of Srxn1 by Srxn1 siRNA-mediated gene silencing significantly exacerbated HG-induced apoptosis and the production of reactive oxygen species (ROS), while Srxn1 overexpression attenuated HG-induced apoptosis and ROS production. In-depth molecular mechanism research revealed that Srxn1 overexpression promoted the nuclear expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and reinforced antioxidant response element (ARE)-mediated transcription activity. Moreover, results confirmed that Srxn1 increased the activation of Nrf2/ARE signaling associated with inactivating glycogen synthase kinase (GSK)-3β. Notably, the inhibition of GSK-3β significantly reversed Srxn1 silencing-induced adverse effects in HG-treated cells, while the knockdown of Nrf2 abrogated the Srxn1-mediated protective effect against HG-induced podocyte injury. Taken together, our results demonstrated that Srxn1 protects podocytes from HG-induced injury by promoting the activation of Nrf2/ARE signaling associated with inactivating GSK-3β, indicating a potential role of Srxn1 in diabetic nephropathy. Our study suggests that Srxn1 may serve as a potential target for kidney protection.

Dietary milk fat globule membrane regulates JNK and PI3K/Akt pathway and ameliorates type 2 diabetes in mice induced by a high-fat diet and streptozotocin

Milk fat globule membrane (MFGM) was found to possess anti-cancer, anti-obesity and anti-inflammatory activities. The present study was carried out to evaluate the effects and possible underlying mechanisms of MFGM on type 2 diabetes (T2D) in mice. Results showed that 8-week MFGM supplementation had beneficial effects in ameliorating hyperglycemia and dyslipidemia in T2D mice induced with a high-fat diet and streptozotocin. MFGM also protected the liver and pancreas histological structures in T2D mice. Additionally, MFGM enhanced glycogen synthesis, which was associated with inhibition of glycogen synthase kinase 3 beta and activation of glycogen synthase. Furthermore, a mechanistic study illuminated that MFGM likely ameliorated glucose metabolism disorder by promoting the phosphatidylinositol 3-kinase/protein kinase B pathway while suppressing c-Jun N-terminal kinase signaling in liver and skeletal muscle. These findings suggest that MFGM may be useful as a potential functional food ingredient against diabetes.

Benefits of camellia sinensis

Tea is one of the most widely consumed beverages worldwide, and is available in various forms. Green tea is richer in antioxidants compared to other forms of tea. Tea is composed of polyphenols, caffeine, minerals, and trace amounts of vitamins, amino acids, and carbohydrates. The composition of the tea varies depending on the fermentation process employed to produce it. The phytochemicals present in green tea are known to stimulate the central nervous system and maintain overall health in humans. Skin aging is a complex process mediated by intrinsic factors such as senescence, along with extrinsic damage induced by external factors such as chronic exposure to ultraviolet (UV) irradiation—A process known as photoaging—Which can lead to erythema, edema, sunburn, hyperplasia, premature aging, and the development of non-melanoma and melanoma skin cancers. UV can cause skin damage either directly, through absorption of energy by biomolecules, or indirectly, by increased production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Green tea phytochemicals are a potent source of exogenous antioxidant candidates that could nullify excess endogenous ROS and RNS inside the body, and thereby diminish the impact of photoaging. Several in vivo and in vitro studies suggest that green tea supplementation increases the collagen and elastin fiber content, and suppresses collagen degrading enzyme MMP-3 production in the skin, conferring an anti-wrinkle effect. The precise mechanism behind the anti-photoaging effect of green tea has not been explored yet. Studies using the worm model have suggested that green tea mediated lifespan extension depends on the DAF-16 pathway. Apart from this, green tea has been reported to have stress resistance and neuroprotective properties. Its ROS scavenging activity makes it a potent stress mediator, as it can also regulate the stress induced by metal ions. It is known that tea polyphenols can induce the expression of different antioxidant enzymes and hinder the DNA oxidative damage. Growing evidence suggests that green tea can also be used as a potential agent to mediate neurodegenerative diseases, including Alzheimer’s disease. EGCG, an abundant catechin in tea, was found to suppress the neurotoxicity induced by Aβ as it activates glycogen synthase kinase-3β (GSK-3β), along with inhibiting c-Abl/FE65—the cytoplasmic non-receptor tyrosine kinase which is involved in the development of the nervous system and in nuclear translocation. Additionally, green tea polyphenols induce autophagy, thereby revitalizing the overall health of the organism consuming it. Green tea was able to activate autophagy in HL-60 xenographs by increasing the activity of PI3 kinase and BECLIN-1. This manuscript describes the reported anti-photoaging, stress resistance, and neuroprotective and autophagy properties of one of the most widely known functional foods-green tea.

2,5-Dimethylcelecoxib prevents isoprenaline-induced cardiomyocyte hypertrophy and cardiac fibroblast activation by inhibiting Akt-mediated GSK-3 phosphorylation

We previously reported that 2,5-dimethylcelecoxib (DM-celecoxib), a celecoxib derivative that is unable to inhibit cyclooxygenase-2, prevented cardiac remodeling by activating glycogen synthase kinase-3 (GSK-3) and prolonged the lifespan of heart failure mice with genetic dilated cardiomyopathy or transverse aortic constriction-induced left ventricular hypertrophy. However, it remained unclear how DM-celecoxib regulated structure and function of cardiomyocytes and cardiac fibroblasts involved in cardiac remodeling. In the present study, therefore, we investigated the effect of DM-celecoxib on isoprenaline-induced cardiomyocyte hypertrophy and cardiac fibroblast activation, because DM-celecoxib prevented isoprenaline-induced cardiac remodeling in vivo. DM-celecoxib suppressed isoprenaline-induced neonatal rat cardiomyocyte hypertrophy by the inhibition of Akt phosphorylation resulting in the activation of GSK-3 and the inhibition of β-catenin and mammalian target of rapamycin (mTOR). DM-celecoxib also suppressed the proliferation and the production of matrix metalloproteinase-2 and fibronectin of rat cardiac fibroblasts. Moreover, we found that phosphatase and tensin homolog on chromosome 10 (PTEN) could be a molecule to mediate the effect of DM-celecoxib on Akt. These results suggest that DM-celecoxib directly improves the structure and function of cardiomyocytes and cardiac fibroblasts and that this compound could be clinically useful for the treatment of β-adrenergic receptor-mediated maladaptive cardiac remodeling.

Blood feeding activates the vitellogenic stage of oogenesis in the mosquito Aedes aegypti through inhibition of glycogen synthase kinase 3 by the insulin and TOR pathways

Most mosquitoes, including Aedes aegypti, only produce eggs after blood feeding on a vertebrate host. Oogenesis in A. aegypti consists of a pre-vitellogenic stage before blood feeding and a vitellogenic stage after blood feeding. Primary egg chambers remain developmentally arrested during the pre-vitellogenic stage but complete oogenesis to form mature eggs during the vitellogenic stage. In contrast, the signaling factors that maintain primary egg chambers in pre-vitellogenic arrest or that activate vitellogenic growth are largely unclear. Prior studies showed that A. aegypti females release insulin-like peptide 3 (ILP3) and ovary ecdysteroidogenic hormone (OEH) from brain neurosecretory cells after blood feeding. Here, we report that primary egg chambers exit pre-vitellogenic arrest by 8 h post-blood meal as evidenced by proliferation of follicle cells, endoreplication of nurse cells, and formation of cytoophidia. Ex vivo assays showed that ILP3 and OEH stimulate primary egg chambers to exit pre-vitellogenic arrest in the presence of nutrients but not in their absence. Characterization of associated pathways indicated that activation of insulin/insulin growth factor signaling (IIS) by ILP3 or OEH inactivated glycogen synthase kinase 3 (GSK3) via phosphorylation by phosphorylated Akt. GSK3 inactivation correlated with accumulation of the basic helix-loop-helix transcription factor Max and primary egg chambers exiting pre-vitellogenic arrest. Direct inhibition of GSK3 by CHIR-99021 also stimulated Myc/Max accumulation and primary egg chambers exiting pre-vitellogenic arrest. Collectively, our results identify GSK3 as a key factor in regulating the pre- and vitellogenic stages of oogenesis in A. aegypti.