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Maternal obesity in pregnancy is strongly associated with complications such as fetal overgrowth and infants of obese mothers have an increased risk to develop obesity, diabetes, and cardiovascular disease later in life. However, the underlying mechanisms are not well established. Circulating levels of adiponectin are low in obese pregnant women and maternal circulating adiponectin is negatively associated with birth weight. We have reported that normalizing maternal adiponectin in obese pregnant mice prevents placental dysfunction, fetal overgrowth, and programming of offspring cardio‐metabolic disease. However, the mechanistic link between maternal adiponectin, placental function, and fetal growth remains to be established. We hypothesized that trophoblast‐specific overexpression of the adiponectin receptor 2 (Adipor2) in healthy pregnant mice inhibits placental mTORC1 signaling and nutrient transport, resulting in fetal growth restriction. Using lentiviral transduction of blastocysts with a mammalian gene expression lentiviral vector for up‐regulation of Adipor2 (Adipor2‐OX), we achieved a ~ 3‐fold increase in placenta Adipor2 mRNA levels and a 2‐fold increase of the ADIPOR2 protein in the trophoblast plasma membrane. Placenta‐specific Adipor2‐OX increased placental peroxisome proliferator‐activated receptor‐α phosphorylation, ceramide synthase expression and ceramide concentrations. Furthermore, Adipor2‐OX inhibited placental mTORC1 signaling and reduced in vivo placental transport of glucose and amino acids. Lastly, Adipor2‐OX reduced fetal weight by 11%. These data provide mechanistic evidence that placental Adipor2 signaling directly affects fetal growth. We propose that low circulating adiponectin in maternal obesity causes fetal overgrowth and programs the offspring for cardio‐metabolic disease mediated by a direct effect on placental function. [ABSTRACT FROM AUTHOR]

Central insulin resistance has been linked to the development of neurodegenerative diseases and mood disorders. Various proteins belonging to the enzyme family of protein tyrosine phosphatases (PTPs) act as inhibitors of insulin signaling. Protein tyrosine phosphatase receptor type J (PTPRJ) has been identified as a negative regulator in insulin signaling in the periphery. However, the impact of PTPRJ on insulin signaling and its functional role in neuronal cells is largely unknown. Therefore, we generated a Ptprj knockout (KO) cell model in the murine neuroblast cell line Neuro2a by CRISPR‐Cas9 gene editing. Ptprj KO cells displayed enhanced insulin signaling, as shown by increased phosphorylation of the insulin receptor (INSR), IRS‐1, AKT, and ERK1/2. Further, proximity ligation assays (PLA) revealed both direct interaction of PTPRJ with the INSR and recruitment of this phosphatase to the receptor upon insulin stimulation. By RNA sequencing gene expression analysis, we identified multiple gene clusters responsible for glucose uptake and metabolism, and genes involved in the synthesis of various lipids being mainly upregulated under PTPRJ deficiency. Furthermore, multiple Ca2+ transporters were differentially expressed along with decreased protein biosynthesis. This was accompanied by an increase in endoplasmic reticulum (ER) stress markers. On a functional level, PTPRJ deficiency compromised cell differentiation and neurite outgrowth, suggesting a role in nervous system development. Taken together, PTPRJ emerges as a negative regulator of central insulin signaling, impacting neuronal metabolism and neurite outgrowth. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are well‐established signaling molecules implicated in a wide range of cellular processes, including both oxidative stress and intracellular redox signaling. In the context of insulin action within its target tissues, ROS have been reported to exert both positive and negative regulatory effects. However, the precise molecular mechanisms underlying this duality remain unclear. This Review examines the complex role of ROS in insulin action, with a particular focus on skeletal muscle. We aim to address three critical aspects: (a) the proposed intracellular pro‐oxidative redox shift elicited by insulin, (b) the evidence supporting that redox‐sensitive cysteine modifications impact insulin signaling and action, and (c) cellular mechanisms underlying how ROS can paradoxically act as both enhancers and inhibitors of insulin action. This Review underscores the urgent need for more systematic research to identify specific reactive species, redox targets, and the physiological significance of redox signaling in maintaining insulin action and metabolic health, with a particular emphasis on human skeletal muscle. [ABSTRACT FROM AUTHOR]

The cellular response to oxidants or xenobiotics comprises two key pathways, resulting in modulation of NRF2 and FOXO transcription factors, respectively. Both mount a cytoprotective response, and their activation relies on crucial protein thiol moieties. Using fumaric acid esters (FAEs), known thiol‐reactive compounds, we tested for activation of NRF2 and FOXO pathways in cultured human hepatoma cells by dimethyl/diethyl as well as monomethyl/monoethyl fumarate. Whereas only the diesters caused acute glutathione depletion and activation of the stress kinase p38MAPK, all four FAEs stimulated NRF2 stabilization and upregulation of NRF2 target genes. However, no significant FAE‐induced activation of FOXO‐dependent target gene expression was observed. Therefore, while both NRF2 and FOXO pathways are responsive to oxidants and xenobiotics, FAEs selectively activate NRF2 signaling. [ABSTRACT FROM AUTHOR]

Angiopoietin‐like protein 4 (ANGPTL4) is a secretory glycoprotein involved in regulating glucose homeostasis in non‐pregnant subjects. However, its role in glucose metabolism during pregnancy and the pathophysiology of gestational diabetes mellitus (GDM) remains elusive. Thus, this study aimed to clarify the relationship between ANGPTL4 and GDM and investigate the pathophysiology of placental ANGPTL4 in glucose metabolism. We investigated this issue using blood and placenta samples in 957 pregnant women, the human 3A‐sub‐E trophoblast cell line, and the L6 skeletal muscle cell line. We found that ANGPTL4 expression in the placenta was higher in obese pregnant women than in lean controls. Palmitic acid significantly induced ANGPTL4 expression in trophoblast cells in a dose–response manner. ANGPTL4 overexpression in trophoblast cells resulted in endoplasmic reticulum (ER) stress, which stimulated the expression and secretion of growth hormone‐variant (GH2) but not human placental lactogen. In L6 skeletal muscle cells, soluble ANGPTL4 suppressed insulin‐mediated glucose uptake through the epidermal growth factor receptor (EGFR)/extracellular signal‐regulated kinases 1/2 (ERK 1/2) pathways. In pregnant women, plasma ANGPTL4 concentrations in the first trimester predicted the incidence of GDM and were positively associated with BMI, plasma triglyceride, and plasma GH2 in the first trimester. However, they were negatively associated with insulin sensitivity index ISI0,120 in the second trimester. Overall, placental ANGPTL4 is induced by obesity and is involved in the pathophysiology of GDM via the induction of ER stress and GH2 secretion. Soluble ANGPTL4 can lead to insulin resistance in skeletal muscle cells and is an early biomarker for predicting GDM. [ABSTRACT FROM AUTHOR]

Aim: We examined the novel role of NUCB1(Nucleobindin‐1) associated with longevity in Drosophila melanogaster. Methods: We measured the lifespan, metabolic phenotypes, and mRNA levels of Drosophila insulin‐like peptides (Dilps), the protein level of phosphorylated AKT, and the localization of FOXO and its target gene expressions in the NUCB1 knockdown condition. Results: NUCB1 knockdown flies show an extended lifespan and metabolic phenotypes such as increased circulating glucose level and starvation resistance. The mRNA expression levels of Dilps and the protein level of phosphorylated AKT, a downstream component of insulin signaling, were decreased in NUCB1 knockdown flies compared with the control flies. Also, the nuclear localization of FOXO and its target gene expressions, such as d4E‐BP and InR, were elevated. Conclusions: The results show that NUCB1 knockdown flies exhibits an extended lifespan. These findings suggest that NUCB1 modulates longevity through insulin signaling in Drosophila. Geriatr Gerontol Int 2024; 24: 486–492. [ABSTRACT FROM AUTHOR]

Regulation of SIRT1 activity is vital to energy homeostasis and plays important roles in many diseases. We previously showed that insulin triggers the epigenetic regulator DBC1 to prime SIRT1 for repression by the multifunctional trafficking protein PACS‐2. Here, we show that liver DBC1/PACS‐2 regulates the diurnal inhibition of SIRT1, which is critically important for insulin‐dependent switch in fuel metabolism from fat to glucose oxidation. We present the x‐ray structure of the DBC1 S1‐like domain that binds SIRT1 and an NMR characterization of how the SIRT1 N‐terminal region engages DBC1. This interaction is inhibited by acetylation of K112 of DBC1 and stimulated by the insulin‐dependent phosphorylation of human SIRT1 at S162 and S172, catalyzed sequentially by CK2 and GSK3, resulting in the PACS‐2‐dependent inhibition of nuclear SIRT1 enzymatic activity and translocation of the deacetylase in the cytoplasm. Finally, we discuss how defects in the DBC1/PACS‐2‐controlled SIRT1 inhibitory pathway are associated with disease, including obesity and non‐alcoholic fatty liver disease. [ABSTRACT FROM AUTHOR]

In this study, we investigated the roles of ROCK1 in regulating structural and functional features of caveolae located at the cell membrane of cardiomyocytes, adipocytes, and mouse embryonic fibroblasts (MEFs) as well as related physiopathological effects. Caveolae are small bulb‐shaped cell membrane invaginations, and their roles have been associated with disease conditions. One of the unique features of caveolae is that they are physically linked to the actin cytoskeleton that is well known to be regulated by RhoA/ROCKs pathway. In cardiomyocytes, we observed that ROCK1 deficiency is coincident with an increased caveolar density, clusters, and caveolar proteins including caveolin‐1 and ‐3. In the mouse cardiomyopathy model with transgenic overexpressing Gαq in myocardium, we demonstrated the reduced caveolar density at cell membrane and reduced caveolar protein contents. Interestingly, coexisting ROCK1 deficiency in cardiomyocytes can rescue these defects and preserve caveolar compartmentalization of β‐adrenergic signaling molecules including β1‐adrenergic receptor and type V/VI adenylyl cyclase. In cardiomyocytes and adipocytes, we detected that ROCK1 deficiency increased insulin signaling with increased insulin receptor activation in caveolae. In MEFs, we identified that ROCK1 deficiency increased caveolar and total levels of caveolin‐1 and cell membrane repair ability after mechanical or chemical disruptions. Together, these results demonstrate that ROCK1 can regulate caveolae plasticity and multiple functions including compartmentalization of signaling molecules and cell membrane repair following membrane disruption by mechanical force and oxidative damage. These findings provide possible molecular insights into the beneficial effects of ROCK1 deletion/inhibition in cardiomyocytes, adipocytes, and MEFs under certain diseased conditions. [ABSTRACT FROM AUTHOR]

Obesity and metabolic disorders caused by alterations in lipid metabolism are major health issues in developed, affluent societies. Adipose tissue is the only organ that stores lipids and prevents lipotoxicity in other organs. Mature adipocytes can affect themselves and distant metabolism‐related tissues by producing various adipokines, including adiponectin and leptin. The engulfment adaptor phosphotyrosine‐binding domain‐containing 1 (GULP1) regulates intracellular trafficking of glycosphingolipids and cholesterol, suggesting its close association with lipid metabolism. However, the role of GULP1 in adipocytes remains unknown. Therefore, this study aimed to investigate the function of GULP1 in adipogenesis, glucose uptake, and the insulin signaling pathway in adipocytes. A 3T3‐L1 cell line with Gulp1 knockdown (shGulp1) and a 3T3‐L1 control group (U6) were established. Changes in shGulp1 cells due to GULP1 deficiency were examined and compared to those in U6 cells using microarray analysis. Glucose uptake was monitored via insulin stimulation in shGulp1 and U6 cells using a 2‐NBDG glucose uptake assay, and the insulin signaling pathway was investigated by western blot analysis. Adipogenesis was significantly delayed, lipid metabolism was altered, and several adipogenesis‐related genes were downregulated in shGulp1 cells compared to those in U6 cells. Microarray analysis revealed significant inhibition of peroxisome proliferator‐activated receptor signaling in shGulp1 cells compared with U6 cells. The production and secretion of adiponectin as well as the expression of adiponectin receptor were decreased in shGulp1 cells. In particular, compared with U6 cells, glucose uptake via insulin stimulation was significantly decreased in shGulp1 cells through the disturbance of ERK1/2 phosphorylation. This is the first study to identify the role of GULP1 in adipogenesis and insulin‐stimulated glucose uptake by adipocytes, thereby providing new insights into the differentiation and functions of adipocytes and the metabolism of lipids and glucose, which can help better understand metabolic diseases. [ABSTRACT FROM AUTHOR]

Poor fetal growth affects eating behavior and the mesocorticolimbic system; however, its influence on the hippocampus has been less explored. Brain insulin sensitivity has been linked to developmental plasticity in response to fetal adversity and to cognitive performance following high‐fat diet intake. We investigated whether poor fetal growth and exposure to chronic hyperpalatable food in adulthood could influence the recognition of environmental and food cues, eating behavior patterns, and hippocampal insulin signaling. At 60 days of life, we assigned male offspring from a prenatal animal model of 50% food restriction (FR) to receive either a high‐fat and ‐sugar (HFS) diet or standard chow (CON) diet. Behavioral tests were conducted at 140 days, then tissues were collected. HFS groups showed a diminished hippocampal pAkt/Akt ratio. FR‐CON and FR‐HFS groups had higher levels of suppressor of cytokine signaling 3, compared to control groups. FR groups showed increased exploration of a novel hyperpalatable food, independent of their diet, and HFS groups exhibited overall lower entropy (less random, more predictable eating behavior) when the environment changed. Poor fetal growth and chronic HFS diet in adulthood altered hippocampal insulin signaling and eating patterns, diminishing the flexibility associated with eating behavior in response to extrinsic changes in food availability in the environment. [ABSTRACT FROM AUTHOR]

Caloric restriction is a non‐pharmacological intervention known to ameliorate the metabolic defects associated with aging, including insulin resistance. The levels of miRNA expression may represent a predictive tool for aging‐related alterations. In order to investigate the role of miRNAs underlying insulin resistance in adipose tissue during the early stages of aging, 3‐ and 12‐month‐old male animals fed ad libitum, and 12‐month‐old male animals fed with a 20% caloric restricted diet were used. In this work we demonstrate that specific miRNAs may contribute to the impaired insulin‐stimulated glucose metabolism specifically in the subcutaneous white adipose tissue, through the regulation of target genes implicated in the insulin signaling cascade. Moreover, the expression of these miRNAs is modified by caloric restriction in middle‐aged animals, in accordance with the improvement of the metabolic state. Overall, our work demonstrates that alterations in posttranscriptional gene expression because of miRNAs dysregulation might represent an endogenous mechanism by which insulin response in the subcutaneous fat depot is already affected at middle age. Importantly, caloric restriction could prevent this modulation, demonstrating that certain miRNAs could constitute potential biomarkers of age‐related metabolic alterations. [ABSTRACT FROM AUTHOR]

Sugar transporters (Sts) play important roles in controlling carbohydrate transport and are responsible for mediating the movement of sugars into cells. Few studies have been conducted on expressions of Sts during insect embryonic development. In the present study, we investigated temporal expressions of St genes during the embryonic diapause process in Bombyx mori. We found that in HCl‐treated developing eggs, high gene expressions of trehalose transporter 1 (Tret1) were detected during middle and later embryonic development. St4 and St3 gene expressions gradually increased during the early stages, reached a small peak on Day 3, and large peaks were again detected on Day 7. However, in diapause eggs, expression levels of the Tret1, St4, and St3 genes all remained at low levels. Differential temporal changes in expressions of the Tret1, St4, and St3 genes found between diapause and HCl‐treated eggs were further confirmed using nondiapause eggs. Our results showed that nondiapause eggs exhibited similar changing patterns as those of HCl‐treated eggs, thus clearly indicating potential correlations between expressions of these genes and embryonic development. In addition, high gene expressions of Tret1 were also detected when dechorionated eggs were incubated in the medium. The addition of LY294002 (a specific phosphatidylinositol 3‐kinase [PI3K] inhibitor) and U0126 (a mitogen‐activated protein kinase/extracellular signal‐regulated kinase [ERK] kinase [MEK] inhibitor) partially inhibited Tret1 gene expression in dechorionated eggs, but did not affect either ecdysteroid‐phosphate phosphatase gene expression or ecdysteroid biosynthesis, clearly indicating that both PI3K and ERK are involved in increased gene expression of Tret1 that was independent of ecdysteroid levels. To our knowledge, this is the first comprehensive report to demonstrate the transcriptional regulation of St genes during embryonic development, thus providing useful information for a clearer understanding of insect egg diapause mechanisms. Highlights: Differential Sugar transporter (St) gene expressions were detected between diapause and developing eggs in Bombyx.High temporal expression levels in trehalose transporter 1 (Tret1), St3, and St4 genes were found in developing eggs.Increased Tret1 gene expression was also detected in dechorionated eggs.Phosphatidylinositol 3‐kinase and extracellular signal‐regulated kinase appear to be involved in dechorionated‐induced Tret1 gene expression.Temporal expressions of St genes appear to be regulated during embryonic development. [ABSTRACT FROM AUTHOR]

Diabetes mellitus (DM) is a chronic metabolic disease characterized by high blood glucose levels, resulting from insulin dysregulation. Parkinson's disease (PD) is the most common neurodegenerative motor disorder caused by the selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. DM and PD are both age‐associated diseases that are turning into epidemics worldwide. Previous studies have indicated that type 2 DM might be a risk factor of developing PD. However, scarce information about the link between type 1 DM (T1DM) and PD does exist. In this work, we have generated a Drosophila model of T1DM based on insulin deficiency to evaluate if T1DM could be a risk factor to trigger PD onset. As expected, model flies exhibited T1DM‐related phenotypes such as insulin deficiency, increased content of carbohydrates and glycogen, and reduced activity of insulin signaling. Interestingly, our results also demonstrated that T1DM model flies presented locomotor defects as well as reduced levels of tyrosine hydroxylase (a marker of DA neurons) in brains, which are typical PD‐related phenotypes. In addition, T1DM model flies showed elevated oxidative stress levels, which could be causative of DA neurodegeneration. Therefore, our results indicate that T1DM might be a risk factor of developing PD, and encourage further studies to shed light into the exact link between both diseases. Research Highlights: Ablation of insulin‐producing cells in Drosophila leads to an increase of carbohydrate levels and to a reduction of insulin‐like peptide levels and insulin signaling activity.Type 1 diabetes mellitus model flies exhibit increased oxidative stress levels, motor defects, and reduction of tyrosine hydroxylase content.Type 1 diabetes mellitus might be a risk factor of developing Parkinson's disease. [ABSTRACT FROM AUTHOR]

Insulin not only regulates glucose and/or lipid metabolism but also modulates brain neural activity. The nucleus tractus solitarius (NTS) is a key central integration site for sensory input from working skeletal muscle and arterial baroreceptors during exercise. Stimulation of the skeletal muscle exercise pressor reflex (EPR), the responses of which are buffered by the arterial baroreflex, leads to compensatory increases in arterial pressure to supply blood to working muscle. Evidence suggests that insulin signaling decreases neuronal excitability in the brain, thus antagonizing insulin receptors (IRs) may increase neuronal excitability. However, the impact of brain insulin signaling on the EPR remains fully undetermined. We hypothesized that antagonism of NTS IRs increases EPR function in normal healthy rodents. In decerebrate rats, stimulation of the EPR via electrically induced muscle contractions increased peak mean arterial pressure (MAP) responses 30 min following NTS microinjections of an IR antagonist (GSK1838705, 100 μM; Pre: Δ16 ± 10 mmHg vs. 30 min: Δ23 ± 13 mmHg, n = 11, p =.004), a finding absent in sino‐aortic baroreceptor denervated rats. Intrathecal injections of GSK1838705 did not influence peak MAP responses to mechano‐ or chemoreflex stimulation of the hindlimb muscle. Immunofluorescence triple overlap analysis following repetitive EPR stimulation increased c‐Fos overlap with EPR‐sensitive nuclei and IR‐positive cells relative to sham operation (p <.001). The results suggest that IR blockade in the NTS potentiates the MAP response to EPR stimulation. In addition, insulin signaling in the NTS may buffer EPR stimulated increases in blood pressure via baroreflex‐mediated mechanisms during exercise. [ABSTRACT FROM AUTHOR]

Podocytes are crucially involved in blood filtration in the glomerulus. Their proper function relies on efficient insulin responsiveness. The insulin resistance of podocytes, defined as a reduction of cell sensitivity to this hormone, is the earliest pathomechanism of microalbuminuria that is observed in metabolic syndrome and diabetic nephropathy. In many tissues, this alteration is mediated by the phosphate homeostasis‐controlling enzyme nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1). By binding to the insulin receptor (IR), NPP1 inhibits downstream cellular signaling. Our previous research found that hyperglycemic conditions affect another protein that is involved in phosphate balance, type III sodium‐dependent phosphate transporter 1 (Pit 1). In the present study, we evaluated the insulin resistance of podocytes after 24 h of incubation under hyperinsulinemic conditions. Thereafter, insulin signaling was inhibited. The formation of NPP1/IR complexes was observed at that time. A novel finding in the present study was our observation of an interaction between NPP1 and Pit 1 after the 24 h stimulation of podocytes with insulin. After downregulation of the SLC20A1 gene, which encodes Pit 1, we established insulin resistance in podocytes that were cultured under native conditions, manifested as a lack of intracellular insulin signaling and the inhibition of glucose uptake via the glucose transporter type 4. These findings suggest that Pit 1 might be a major factor that participates in the NPP1‐mediated inhibition of insulin signaling. [ABSTRACT FROM AUTHOR]

One exercise session can increase subsequent insulin‐stimulated glucose uptake (ISGU) by skeletal muscle in both sexes. We recently found that muscle expression and phosphorylation of key sites of Akt substrate of 160 kDa (AS160; also called TBC1D4) are essential for the full‐exercise effect on postexercise‐ISGU (PEX‐ISGU) in male rats. In striking contrast, AS160's role in increased PEX‐ISGU has not been rigorously tested in females. Our rationale was to address this major knowledge gap. Wild‐type (WT) and AS160‐knockout (KO) rats were either sedentary or acutely exercised. Adeno‐associated virus (AAV) vectors were engineered to express either WT‐AS160 or AS160 mutated on key serine and threonine residues (Ser588, Thr642, and Ser704) to alanine to prevent their phosphorylation. AAV vectors were delivered to the muscle of AS160‐KO rats to determine if WT‐AS160 or phosphorylation‐inactivated AS160 would influence PEX‐ISGU. AS160‐KO rats have lower skeletal muscle abundance of the GLUT4 glucose transporter protein. This GLUT4 deficit was rescued using AAV delivery of GLUT4 to determine if eliminating muscle GLUT4 deficiency would normalize PEX‐ISGU. The novel results were as follows: (1) AS160 expression was required for greater PEX‐ISGU; (2) rescuing muscle AS160 expression in AS160‐KO rats restored elevated PEX‐ISGU; (3) AS160's essential role for the postexercise increase in ISGU was not attributable to reduced muscle GLUT4 content; and (4) AS160 phosphorylation on Ser588, Thr642, and Ser704 was not essential for greater PEX‐ISGU. In conclusion, these novel findings revealed that three phosphosites widely proposed to influence PEX‐ISGU are not required for this important outcome in female rats. [ABSTRACT FROM AUTHOR]

Diaphorina citri is an important vector of Citrus Huanglongbing (HLB) disease. After feeding on young host plant shoots, the population of D. citri can increase significantly. Females also only lay eggs on young shoots. However, there are few studies on the mechanism of this phenomenon. Exogenous nutrient signals can affect the insulin signaling system of D. citri after feeding on young shoots. In this study, the expression of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system of D. citri was upregulated after feeding on young shoots. After being silenced by RNA interference technology, the results showed that the number of oviposited eggs of D. citri was significantly decreased and the ovarian development was inhibited with severe vacuolation. In addition, detection using quantitative reverse transcription–polymerase chain reaction showed that the upstream regulatory gene DcRheb of the target of rapamycin (TOR) pathway and the downstream reproduction‐related DcVg gene were also significantly downregulated. These results suggest that feeding upon young shoots may upregulate the expression levels of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system. The signal will be through upregulating the expression of DcRheb, an upstream gene of the TOR signaling pathway. This in turn influences yolk metabolism, which eventually causes the ovaries of female D. citri to mature and therefore initiate oviposition behavior. [ABSTRACT FROM AUTHOR]

Aims: The peptidyl‐prolyl cis/trans isomerase, Pin1, has a protective role in age‐related neurodegeneration by targeting different phosphorylation sites of tau and the key proteins required to produce Amyloid‐β, which are the well‐known molecular signatures of Alzheimer's disease (AD) neuropathology. The direct interaction of miR‐140‐5p with Pin1 mRNA and its inhibitory role in protein translation has been identified. The main purpose of this study was to investigate the role of miRNA‐140‐5p inhibition in promoting Pin1 expression and the therapeutic potential of the AntimiR‐140‐5p in the Aß oligomer (AßO)‐induced AD rat model. Methods: Spatial learning and memory were assessed in the Morris water maze. RT‐PCR, western blot, and histological assays were performed on hippocampal samples at various time points after treatments. miRNA‐140‐5p inhibition enhanced Pin1 and ADAM10 mRNA expressions but has little effect on Pin1 protein level. Results: The miRNA‐140‐5p inhibitor markedly ameliorated spatial learning and memory deficits induced by AßO, and concomitantly suppressed the mRNA expression of inflammatory mediators TNFα and IL‐1β, and phosphorylation of tau at three key sites (thr231, ser396, and ser404) as well as increased phosphorylated Ser473‐Akt. Conclusion: According to our results, Antimir‐140‐mediated improvement of AβO‐induced neuronal injury and memory impairment in rats may provide an appropriate rationale for evaluating miR‐140‐5p inhibitors as a promising agent for the treatment of AD. [ABSTRACT FROM AUTHOR]

Type 2 diabetes (T2DM) is characterized by insulin secretion deficiencies and systemic insulin resistance (IR) in adipose tissue, skeletal muscle, and the liver. Although the mechanism of T2DM is not yet fully known, inflammation and insulin resistance play a central role in the pathogenesis of T2DM. G protein‐coupled receptors (GPCRs) are involved in endocrine and metabolic processes as well as many other physiological processes. GPR50 (G protein‐coupled receptor 50) is an orphan GPCR that shares the highest sequence homology with melatonin receptors. The aim of this study was to investigate the effect of GPR50 on inflammation and insulin resistance in 3T3‐L1 preadipocytes. GPR50 expression was observed to be significantly increased in the adipose tissue of obese T2DM mice, while GPR50 deficiency increased inflammation in 3T3‐L1 cells and induced the phosphorylation of AKT and insulin receptor substrate (IRS) 1. Furthermore, GPR50 knockout in the 3T3‐L1 cell line suppressed PPAR‐γ expression. These data suggest that GPR50 can attenuate inflammatory levels and regulate insulin signaling in adipocytes. Furthermore, the effects are mediated through the regulation of the IRS1/AKT signaling pathway and PPAR‐γ expression. [ABSTRACT FROM AUTHOR]

The insulin signaling pathway controls cell growth and metabolism, thus its deregulation is associated with both cancer and diabetes. Phosphatidylinositol 3‐kinase (PI3K) contributes to the cascade of phosphorylation events occurring in the insulin pathway by activating the protein kinase B (PKB/AKT), which phosphorylates several substrates, including those involved in glucose uptake and storage. PI3K inactivating mutations are associated with insulin resistance while activating mutations are identified in human cancers. Here we show that RNAi‐induced depletion of the Drosophila PI3K catalytic subunit (Dp110) results in diabetic phenotypes such as hyperglycemia, body size reduction, and decreased glycogen content. Interestingly, we found that hyperglycemia produces chromosome aberrations (CABs) triggered by the accumulation of advanced glycation end‐products and reactive oxygen species. Rearing PI3KRNAi flies in a medium supplemented with pyridoxal 5′‐phosphate (PLP; the catalytically active form of vitamin B6) rescues DNA damage while, in contrast, treating PI3KRNAi larvae with the PLP inhibitor 4‐deoxypyridoxine strongly enhances CAB frequency. Interestingly, PLP supplementation rescues also diabetic phenotypes. Taken together, our results provide a strong link between impaired PI3K activity and genomic instability, a crucial relationship that needs to be monitored not only in diabetes due to impaired insulin signaling but also in cancer therapies based on PI3K inhibitors. In addition, our findings confirm the notion that vitamin B6 is a good natural remedy to counteract insulin resistance and its complications. [ABSTRACT FROM AUTHOR]

Cell cycle arrest, one of the main characteristics of cellular senescence, has been described as a crucial barrier that needs to be bypassed for cancer progression. Typically, cellular senescence can be induced by multiple stresses including telomere shortening, oncogenic activation as well as therapy treatment, and contributes to the inhibition of epithelial–mesenchymal transition (EMT), tumor suppression or progression depending on the senescence‐associated secretory phenotype (SASP) components. However, the mechanisms underlying cancer cell senescence remain partially understood. Here, according to METABRIC database, we identified that patients with senescent‐like breast tumors show better short‐term survival, lower tendency of neoplasm histological grades, lower tumor stages, and negative status of estrogen receptor (ER) and progesterone receptor (PR) compared with non‐senescent ones. Interestingly, Kyoto encyclopedia of genes and genomes (KEGG) analysis identified insulin signaling was significantly repressed in senescent breast tumors. Further verification in cultured breast cancer cells indicated that phosphoenolpyruvate carboxykinase 2 (PCK2) was significantly inhibited after therapy treatment. In addition, knockdown of PCK2 induced a senescent phenotype of breast cancer cells. Moreover, comparing with the non‐senescent group, the senescent breast cancers displayed lower EMT capacity both in patients and breast cancer cell lines after knocking down PCK2. In conclusion, we described for the first time that low expression level of PCK2 may contribute to better prognosis via triggering senescent phenotype and thereby inhibiting EMT capacity in breast cancers. [ABSTRACT FROM AUTHOR]

Introduction: Intellectual disability, accelerated aging, and early‐onset Alzheimer‐like neurodegeneration are key brain pathological features of Down syndrome (DS). Although growing research aims at the identification of molecular pathways underlying the aging trajectory of DS population, data on infants and adolescents with DS are missing. Methods: Neuronal‐derived extracellular vesicles (nEVs) were isolated form healthy donors (HDs, n = 17) and DS children (n = 18) from 2 to 17 years of age and nEV content was interrogated for markers of insulin/mTOR pathways. Results: nEVs isolated from DS children were characterized by a significant increase in pIRS1Ser636, a marker of insulin resistance, and the hyperactivation of the Akt/mTOR/p70S6K axis downstream from IRS1, likely driven by the higher inhibition of Phosphatase and tensin homolog (PTEN). High levels of pGSK3βSer9 were also found. Conclusions: The alteration of the insulin‐signaling/mTOR pathways represents an early event in DS brain and likely contributes to the cerebral dysfunction and intellectual disability observed in this unique population. [ABSTRACT FROM AUTHOR]

Limited oxygen availability impairs normal body growth, although the underlying mechanisms are not fully understood. In Drosophila, hypoxic responses in the larval fat body (FB) disturb the secretion of insulin‐like peptides from the brain, inhibiting body growth. However, the cell‐autonomous effects of hypoxia on the insulin‐signaling pathway in larval FB have been underexplored. In this study, we aimed to examine the effects of overexpression of Sima, a Drosophila hypoxia‐inducible factor‐1 (HIF‐1) α homolog and a key component of HIF‐1 transcription factor essential for hypoxic adaptation, on the insulin‐signaling pathway in larval FB. Forced expression of Sima in FB reduced the larval body growth with reduced Akt phosphorylation levels in FB cells and increased hemolymph sugar levels. Sima‐mediated growth inhibition was reversed by overexpression of TOR or suppression of FOXO. After Sima overexpression, larvae showed higher expression levels of Tribbles, a negative regulator of Akt activity, and a simultaneous knockdown of Tribbles completely abolished the effects of Sima on larval body growth. Furthermore, a reporter analysis revealed Tribbles as a direct target gene of Sima. These results suggest that Sima in FB evokes Tribbles‐mediated insulin resistance and consequently protects against aberrant insulin‐dependent larval body growth under hypoxia. [ABSTRACT FROM AUTHOR]

Hyperinsulinemia is commonly viewed as a compensatory response to insulin resistance, yet studies have demonstrated that chronically elevated insulin may also drive insulin resistance. The molecular mechanisms underpinning this potentially cyclic process remain poorly defined, especially on a transcriptome‐wide level. Transcriptomic meta‐analysis in >450 human samples demonstrated that fasting insulin reliably and negatively correlated with INSR mRNA in skeletal muscle. To establish causality and study the direct effects of prolonged exposure to excess insulin in muscle cells, we incubated C2C12 myotubes with elevated insulin for 16 h, followed by 6 h of serum starvation, and established that acute AKT and ERK signaling were attenuated in this model of in vitro hyperinsulinemia. Global RNA‐sequencing of cells both before and after nutrient withdrawal highlighted genes in the insulin receptor (INSR) signaling, FOXO signaling, and glucose metabolism pathways indicative of ‘hyperinsulinemia’ and ‘starvation’ programs. Consistently, we observed that hyperinsulinemia led to a substantial reduction in Insr gene expression, and subsequently a reduced surface INSR and total INSR protein, both in vitro and in vivo. Bioinformatic modeling combined with RNAi identified SIN3A as a negative regulator of Insr mRNA (and JUND, MAX, and MXI as positive regulators of Irs2 mRNA). Together, our analysis identifies mechanisms which may explain the cyclic processes underlying hyperinsulinemia‐induced insulin resistance in muscle, a process directly relevant to the etiology and disease progression of type 2 diabetes. [ABSTRACT FROM AUTHOR]

Androgen excess is one of the most common endocrine disorders of reproductive‐aged women, affecting up to 20% of this population. Women with elevated androgens often exhibit hyperinsulinemia and insulin resistance. The mechanisms of how elevated androgens affect metabolic function are not clear. Hyperandrogenemia in a dihydrotestosterone (DHT)‐treated female mouse model induces whole body insulin resistance possibly through activation of the hepatic androgen receptor (AR). We investigated the role of hepatocyte AR in hyperandrogenemia‐induced metabolic dysfunction by using several approaches to delete hepatic AR via animal‐, cell‐, and clinical‐based methodologies. We conditionally disrupted hepatocyte AR in female mice developmentally (LivARKO) or acutely by tail vein injection of an adeno‐associated virus with a liver‐specific promoter for Cre expression in ARfl/fl mice (adLivARKO). We observed normal metabolic function in littermate female Control (ARfl/fl) and LivARKO (ARfl/fl; Cre+/−) mice. Following chronic DHT treatment, female Control mice treated with DHT (Con‐DHT) developed impaired glucose tolerance, pyruvate tolerance, and insulin tolerance, not observed in LivARKO mice treated with DHT (LivARKO‐DHT). Furthermore, during an euglycemic hyperinsulinemic clamp, the glucose infusion rate was improved in LivARKO‐DHT mice compared to Con‐DHT mice. Liver from LivARKO, and primary hepatocytes derived from LivARKO, and adLivARKO mice were protected from DHT‐induced insulin resistance and increased gluconeogenesis. These data support a paradigm in which elevated androgens in females disrupt metabolic function via hepatic AR and insulin sensitivity was restored by deletion of hepatic AR. [ABSTRACT FROM AUTHOR]

The production of biopharmaceutical proteins in mammalian cells by transient expression or stable transformation requires robust and viable cells. Cell line engineering must therefore balance improved cell growth and viability with high productivity. We tested the ability of nonmammalian phosphatidylethanolamine‐binding proteins to enhance cell proliferation in monolayers and suspension cultures. The tobacco protein NtFT4 improved the proliferation of multiple human cell lines. Viable cell density is usually impaired by efficient transfection, but we found that the number of HEK‐293TNtFT4 cells at the peak of protein expression was twice that of standard HEK‐293T cells, and the antibody yield increased by approximately one‐third. Improved growth and viability were observed in different cell lines, in different culture media, and also after transient transfection, suggesting the beneficial trait is consistent and transferable. Additional modifications could boost the productivity of high‐density HEK‐293TNtFT4 cells even further as we showed for a fluorescent marker protein and recombinant antibody expressed in monolayer cultures. The HEK‐293TNtFT4 cell line provides a new human model platform that increases cell proliferation, also achieving a fundamental improvement in recombinant protein expression. [ABSTRACT FROM AUTHOR]

Insulin signaling is critical for the development of preovulatory follicles and progression through the antral stage. Using a conditional knockout model that escapes this blockage, we recently described the role of insulin signaling in granulosa cells during the periovulatory window in mice lacking Insr and Igf1r driven by Pgr‐Cre. These mice were infertile, exhibiting defects in ovulation, luteinization, steroidogenesis, and early embryo development. Herein, we demonstrate that while these mice exhibit normal uterine receptivity, uterine cell proliferation and decidualization are compromised resulting in complete absence of embryo implantation in uteri lacking both receptors. While the histological organization of double knockout mice appeared normal, the thickness of their endometrium was significantly reduced. This was supported by the reduced proliferation of both epithelial and stromal cells during the preimplantation stages of pregnancy. Expression and localization of the main drivers of uterine proliferation, ESR1 and PGR, was normal in knockouts, suggesting that insulin signaling acts downstream of these two receptors. While AKT/PI3K signaling was unaffected by insulin receptor ablation, activation of p44/42 MAPK was significantly reduced in both single and double knockout uteri at 3.5 dpc. Overall, we conclude that both INSR and IGF1R are necessary for optimal endometrial proliferation and implantation. [ABSTRACT FROM AUTHOR]

Glucocorticoids are among the most prescribed drugs globally due to their potent anti‐inflammatory and immunosuppressive properties. Although they have positive effects on the treatment of various disease states; long‐term administration is associated with high blood pressure, insulin resistance, and susceptibility to type 2 diabetes. The heart attempts to cope with increased blood pressure and a decrease in glucose utilization by developing pathological cardiac remodeling. However, in this process, cardiac fibrosis formation and deterioration in heart structure and functions occur. Galectin‐3, a member of the β‐galactoside binding lectins, is consistently associated with inflammation and fibrosis in the pathogenesis of various disease states including insulin resistance and heart failure. Galectin‐3 expression is markedly increased in activated macrophages and a subset of activated fibroblasts and vascular cells. Also, failing and remodeling myocardium show increased Gal‐3 expression and elevated Gal‐3 levels are related to heart failure severity and prognosis. Furthermore, Gal‐3‐related pathways are recently suggested as therapeutic targets both pharmacologically and genetically to increase insulin sensitivity in vivo. The objective of this review is to provide a summary of our current understanding of the role of glucocorticoid‐associated insulin resistance, which is important for some cardiac events, and the potential role of galectin in this pathophysiological process. [ABSTRACT FROM AUTHOR]

Exocytosis is a vesicle fusion process driven by soluble N‐ethylmaleimide‐sensitive factor attachment protein receptors (SNAREs). A classic exocytic pathway is insulin‐stimulated translocation of the glucose transporter type 4 (GLUT4) from intracellular vesicles to the plasma membrane in adipocytes and skeletal muscles. The GLUT4 exocytic pathway plays a central role in maintaining blood glucose homeostasis and is compromised in insulin resistance and type 2 diabetes. A candidate regulator of GLUT4 exocytosis is tomosyn, a soluble protein expressed in adipocytes. Tomosyn directly binds to GLUT4 exocytic SNAREs in vitro but its role in GLUT4 exocytosis was unknown. In this work, we used CRISPR‐Cas9 genome editing to delete the two tomosyn‐encoding genes in adipocytes. We observed that both basal and insulin‐stimulated GLUT4 exocytosis was markedly elevated in the double knockout (DKO) cells. By contrast, adipocyte differentiation and insulin signaling remained intact in the DKO adipocytes. In a reconstituted liposome fusion assay, tomosyn inhibited all the SNARE complexes underlying GLUT4 exocytosis. The inhibitory activity of tomosyn was relieved by NSF and α‐SNAP, which act in concert to remove tomosyn from GLUT4 exocytic SNAREs. Together, these studies revealed an inhibitory role for tomosyn in insulin‐stimulated GLUT4 exocytosis in adipocytes. We suggest that tomosyn‐arrested SNAREs represent a reservoir of fusion capacity that could be harnessed to treat patients with insulin resistance and type 2 diabetes. [ABSTRACT FROM AUTHOR]

Insulin is important for brain function and neuronal survival. Insulin signaling is initiated by the phosphorylation of insulin receptor substrate‐1 (IRS‐1) at tyrosine (pTyr) residue. However, IRS‐1 is inhibited by phosphorylation at serine (pSer). In Alzheimer's disease (AD), oxidative stress and accumulation of amyloid beta (Aβ) induce neuroinflammation, which augments pSer‐IRS‐1 and reduces pTyr‐IRS‐1 disturbing insulin signaling pathway. Coenzyme Q10 (CoQ10) and biotin possess antioxidant and anti‐inflammatory properties, and, in this study, their impact on insulin signaling is investigated in an aluminium chloride (AlCl3) model of AD. AD was induced by oral administration of AlCl3 (75 mg/kg) for 60 days. Biotin (2 mg/kg), CoQ10 (10 mg/kg), and their combination were supplemented concomitantly with AlCl3 for 60 days. Memory test and histological examination were performed. Brain levels of lipid peroxides, antioxidants (reduced glutathione and superoxide dismutase), inflammatory markers (tumor necrosis factor‐α, interleukin‐6 [IL‐6], IL‐1, and nuclear factor κB), and phosphorylated Akt (survival kinase) as well as protein levels of Aβ, IRS‐1 (pTyr and pSer), and caspase‐3 (apoptotic marker) were determined. AlCl3 resulted in impaired memory, significant increase in Aβ, lipid peroxides, inflammatory markers, caspase‐3, and pSer‐IRS‐1, with significant reduction of the antioxidants, pTyr‐IRS‐1, and p‐Akt reflecting Aβ‐induced inflammation and defective insulin signaling. Histological examination revealed focal aggregations of inflammatory cells and neuronal degeneration. The biochemical deviations and histological changes were attenuated by the concomitant treatment with biotin and, to greater extent, with CoQ10 and the combination. In conclusion, biotin and CoQ10 could protect against AD via attenuating inflammatory response and enhancing insulin signaling. [ABSTRACT FROM AUTHOR]

Numerous nutritional approaches aimed at reducing body weight have been developed as a strategy to reduce obesity. Most of these interventions rely on reducing caloric intake or limiting calories access to a few hours per day. In this work, we analyzed the effects of the extended (24 hours/day) or restricted (1 hour/day) access to a cafeteria‐style (CAF) diet, on rat body weight and hepatic lipid metabolism, with respect to control rats (CTR) fed with a standard chow diet. The body weight gain of restricted‐fed rats was not different from CTR, despite the slightly higher total caloric intake, but resulted significantly lower than extended‐fed rats, which showed a CAF diet‐induced obesity and a dramatically higher total caloric intake. However, both CAF‐fed groups of rats showed, compared to CTR, unhealthy serum and hepatic parameters such as higher serum glucose level, lower HDL values, and increased hepatic triacylglycerol and cholesterol amount. The hepatic expression and activity of key enzymes of fatty acid synthesis, acetyl‐CoA carboxylase (ACC), and fatty acid synthase (FAS), was similarly reduced in both CAF‐fed groups of rats with respect to CTR. Anyway, while in extended‐fed rats this reduction was associated to a long‐term mechanism involving sterol regulatory element‐binding protein‐1 (SREBP‐1), in restricted‐fed animals a short‐term mechanism based on PKA and AMPK activation occurred in the liver. Furthermore, hepatic fatty acid oxidation (FAO) and oxidative stress resulted significantly increased in extended, but not in restricted‐fed rats, as compared to CTR. Overall, these results demonstrate that although limiting the total caloric intake might successfully fight obesity development, the nutritional content of the diet is the major determinant for the health status. [ABSTRACT FROM AUTHOR]

The role of central juxtaposed with another zinc finger gene 1 (JAZF1) in glucose regulation remains unclear. Here, we activated mediobasal hypothalamus (MBH) JAZF1 in high‐fat diet (HFD)‐fed rats by an adenovirus expressing JAZF1 (Ad‐JAZF1). We evaluated the changes in the hypothalamic insulin receptor (InsR)‐PI3K‐Akt‐AMPK pathway and hepatic glucose production (HGP). To investigate the impact of MBH Ad‐JAZF1 on HGP, we activated MBH JAZF1 in the presence or absence of ATP‐dependent potassium (KATP) channel inhibition, hepatic branch vagotomy (HVG), or an AMPK activator (AICAR). In HFD‐fed rats, MBH Ad‐JAZF1 decreased body weight and food intake, and inhibited HGP by increasing hepatic insulin signaling. Under insulin stimulation, MBH Ad‐JAZF1 increased InsR and Akt phosphorylation, and phosphatidylinositol 3, 4, 5‐trisphosphate (PIP3) formation; however, AMPK phosphorylation was decreased in the hypothalamus. The positive effect of MBH JAZF1 on hepatic insulin signaling and HGP was prevented by treatment with a KATP channel inhibitor or HVG. The metabolic impact of hypothalamic JAZF1 was also blocked by MBH AICAR. Ad‐JAZF1 treatment in SH‐SY5Y cells resulted in an elevation of InsR and Akt phosphorylation following insulin stimulation. Our findings show that hypothalamic JAZF1 regulates HGP via the InsR‐PI3K‐Akt‐AMPK pathway and KATP channels. [ABSTRACT FROM AUTHOR]

Alzheimer's disease has recently been characterized as "diabetes of the brain" or "type 3 diabetes." Although recent clinical trials targeting amyloid β‐protein have been unsuccessful, glucose‐insulin metabolism in the brain may provide an alternative therapeutic target. In this review, we focus on three related topics: (a) how peripheral and brain insulin resistance interact with each other; (b) brain insulin resistance as a promising therapeutic target for Alzheimer's disease and anti‐diabetic drugs as potentially effective drugs; and (c) apomorphine as a novel drug that improves neuronal insulin signaling. Although apomorphine is a dopamine receptor agonist, studies in our laboratory revealed a novel effect, promoting intracellular amyloid β degradation and improving memory function in an Alzheimer's disease mouse model. Recently, we demonstrated that apomorphine treatment improved neuronal insulin resistance and activated insulin‐degrading enzyme, a major amyloid β‐degrading enzyme. In addition, we confirmed the efficacy of apomorphine for some Alzheimer's disease patients. In this context, combined treatment involving anti‐diabetic drugs and apomorphine may provide an effective therapeutic approach for Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated an essential role for insulin signaling in folliculogenesis as conditional ablation of Igf1r in primary follicles elicits defective follicle‐stimulating hormone responsiveness blocking development at the preantral stage. Thus the potential role of insulin action in the periovulatory window and in the corpus luteum is unknown. To examine this, we generated conditional Insr,Igf1r, and double receptor knockout mice driven by Pgr‐Cre. These models escape the preantral follicle block and in response to superovulatory gonadotropins exhibit normal distribution of ovarian follicles and corpora lutea. However, single ablation of Igf1r leads to subfertility and mice lacking both receptors are infertile. Double knockout mice have impaired oocyte development and ovulation. While some oocytes are released and fertilized, subsequent embryo development is retarded, and the embryos potentially fail to thrive due to lack of luteal support. In support of this, we found reduced expression of key enzymes in the steroid synthesis pathway and reduced serum progesterone. In addition to metabolic and steroidogenic pathways, RNA‐sequencing analysis revealed transcription factor‐3 as an important transcription factor downstream of insulin signaling. Collectively, these results highlight the importance of growth factors of the insulin family during two distinct windows of follicular development, ovulation, and luteinization. [ABSTRACT FROM AUTHOR]

Developmental processes transduce diverse influences during phenotype formation, thereby biasing and structuring amount and type of phenotypic variation available for evolutionary processes to act on. The causes, extent, and consequences of this bias are subject to significant debate. Here we explore the role of developmental bias in contributing to organisms' ability to innovate, to adapt to novel or stressful conditions, and to generate well integrated, resilient phenotypes in the face of perturbations. We focus our inquiry on one taxon, the horned dung beetle genus Onthophagus, and review the role developmental bias might play across several levels of biological organization: (a) gene regulatory networks that pattern specific body regions; (b) plastic developmental mechanisms that coordinate body wide responses to changing environments and; (c) developmental symbioses and niche construction that enable organisms to build teams and to actively modify their own selective environments. We posit that across all these levels developmental bias shapes the way living systems innovate, adapt, and withstand stress, in ways that can alternately limit, bias, or facilitate developmental evolution. We conclude that the structuring contribution of developmental bias in evolution deserves further study to better understand why and how developmental evolution unfolds the way it does. Research Highlights: The significance of developmental bias (DB) is much debated. We focus our inquiry on one taxon, the horned dung beetle genus Onthophagus, and review the role of DB in the evolution of novelty, adaptation, and resilience. We posit that across levels of organization DB shapes the way living systems innovate, adapt, and withstand stress. Such biases may alternately limit or facilitate developmental evolution. We conclude that the structuring contribution of developmental bias in evolution deserves further study. [ABSTRACT FROM AUTHOR]

The hypoglycemic effect of Phellinus linteus polysaccharide extract (PLPE) has been documented in several previous studies, but the functional interactions among PLPE, gut microbiota, and the hypoglycemic effect remain unclear. We examined the regulatory effect of PLPE on gut microbiota, and the molecular mechanism underlying improvement of insulin resistance, using a type 2 diabetic rat model. Here, 24 male Sprague‐Dawley rats were randomly divided into four groups that were subjected to intervention of saline (normal and model control group), metformin (120 mg/kg.bw), and PLPE (600 mg/kg.bw) by oral administration. After 8 weeks of treatment, PLPE increased levels of short‐chain fatty acids (SCFAs) by enhancing abundance of SCFA‐producing bacteria. SCFAs maintained intestinal barrier function and reduced lipopolysaccharides content in blood, thereby helping to reduce systemic inflammation and reverse insulin resistance. Our findings suggest that PLPE (in which polysaccharides are the major component) has potential application as a prebiotic for regulating gut microbiota composition in diabetic patients. [ABSTRACT FROM AUTHOR]

Growing evidence has suggested that autophagy-related protein 7 (ATG7) plays an important role in insulin signaling, but the mechanism of ATG7 in hepatic insulin sensitivity is not fully understood. The purpose of the present study is to clarify the underlying molecular mechanisms of ATG7 in obesity development. Serum and liver samples from mice fed a high fat diet (HFD) were evaluated for metabolic profile data and ATG expressions during obesity development. We found that compared with other ATGs, ATG7 expression increased earlier with lower hepatic insulin sensitivity in the 4-wk HFD-fed mice. For in vitro analyses, silencing ATG7 significantly up-regulated insulin-stimulated phosphorylation of protein kinase B (Akt) and down-regulated phosphatase and tension homolog deleted on chromosome ten (PTEN) in HepG2 cells. Replenishing PTEN to ATG7-silenced hepatocytes restored the phosphorylated Akt level. Furthermore, ATG7 silencing led to higher c-JUN expression, which transcriptionally reduced PTEN expression. These results reveal a novel mechanism by which ATG7 regulates Akt phosphorylation via the c-JUN/PTEN pathway at the early stage of HFD-induced metabolic disorder. [ABSTRACT FROM AUTHOR]

During the development of type 2 diabetes mellitus (T2DM), hyperinsulinemia is the earliest symptom. It is believed that long‐term high insulin stimulation might facilitate insulin resistance in the liver, but the underlying mechanism remains unknown. Herein, we report that hyperinsulinemia could induce persistent early growth response gene‐1 (Egr‐1) activation in hepatocytes, which provides negative feedback inhibition of insulin sensitivity by inducing the expression of protein tyrosine phosphatase‐1B (PTP1B). Deletion of Egr‐1 in the liver remarkably decreases glucose production, thus improving systemic glucose tolerance and insulin sensitivity. Mechanistic analysis indicates that Egr‐1 inhibits insulin receptor phosphorylation by directly activating PTP1B transcription in the liver. Our results reveal the molecular mechanism by which hyperinsulinemia accelerates insulin resistance in hepatocytes during the progression of T2DM. [ABSTRACT FROM AUTHOR]

Sirtuin 6 (Sirt6), a NAD+‐dependent protein deacetylase, is involved in hepatic glucose metabolism and insulin sensitivity, which impact metabolic homeostasis. In this paper, we discover that Sirt6 affects the insulin sensitivity of mice in a gender‐dependent manner; few studies have been conducted on this issue. Based on reports revealing the influences of sex hormones on insulin signaling, this investigation explores the mechanism by which Sirt6 regulates the estrogen pathway and disrupts insulin signal transduction. Hepatocyte‐specific Sirt6 knockout (Sirt6HKO) mice were generated to investigate the function of Sirt6 in hepatocytes. Mice were castrated or spayed to eliminate sex hormones. Insulin sensitivity was assessed via an insulin tolerance test (ITT) in vivo. The interaction of Sirt6 with the estrogen pathway and their impacts on insulin signal transduction were revealed by immunoblot and immunoprecipitation. Sirt6 deletion in hepatocytes significantly enhanced insulin sensitivity and signal transduction in female mice but not in male or spayed female mice as demonstrated by ITT and the phosphorylation level of Akt in the liver. We also identified upregulation of p300, ERα, and interaction of ERα with p85 in the liver of female Sirt6HKO mice. Additionally, Sirt6 was found to inhibit ERα protein stability in a p300‐dependent manner without interacting directly with ERα. Our findings show that hepatic Sirt6 downregulates the ERα protein level in a p300‐dependent manner and thus disturbs estrogen‐induced improvement in insulin sensitivity in the liver, which may partially explain the gender difference in insulin sensitivity. [ABSTRACT FROM AUTHOR]

Whilst the growing global prevalence of diabetes mellitus is a major healthcare problem, the exact pathophysiology of insulin resistance leading to diabetes mellitus remains unclear. Studies have confirmed that increased adiposity is linked to lower insulin sensitivity through the expression and release of adipocyte‐derived proteins such as adipokines. Wingless‐type (Wnt) inducible signaling pathway protein‐1 (WISP1) is a newly identified adipokine that has important roles in many molecular pathways and cellular events, with the suggestion that WISP1 adipokine is closely correlated to the progression of insulin resistance. Studies have shown that circulatory levels of WISP adipokine are higher in obese patients accompanied with increased insulin resistance. However, the exact role of WISP1 adipokine in the induction of insulin resistance is not completely understood. In this review, we detail the latest evidence showing that the WIPS1 adipokine impairs glucose homeostasis and induces diabetes mellitus. [ABSTRACT FROM AUTHOR]

Podocytes are key cells in maintaining the integrity of the glomerular filtration barrier and preventing albuminuria. Glycogen synthase kinase 3 (GSK3) is a multi‐functional serine/threonine kinase existing as two distinct but related isoforms (α and β). In the podocyte it has previously been reported that inhibition of the β isoform is beneficial in attenuating a variety of glomerular disease models but loss of both isoforms is catastrophic. However, it is not known what the role of GSK3α is in these cells. We now show that GSK3α is present and dynamically modulated in podocytes. When GSK3α is transgenically knocked down specifically in the podocytes of mice it causes mild but significant albuminuria by 6 weeks of life. Its loss also does not protect in models of diabetic or Adriamycin‐induced nephropathy. In vitro deletion of podocyte GSK3α causes cell death and impaired autophagic flux suggesting it is important for this key cellular process. Collectively this work shows that GSK3α is important for podocyte health and that augmenting its function may be beneficial in treating glomerular disease. [ABSTRACT FROM AUTHOR]

In the brain, insulin plays an important role in cognitive processes. During aging, these faculties decline, as does insulin signaling. The mechanism behind this last phenomenon is unclear. In recent studies, we reported that the mild and gradual loss of cholesterol in the synaptic fraction of hippocampal neurons during aging leads to a decrease in synaptic plasticity evoked by glutamate receptor activation and also by receptor tyrosine kinase (RTK) signaling. As insulin and insulin growth factor activity are dependent on tyrosine kinase receptors, we investigated whether the constitutive loss of brain cholesterol is also involved in the decay of insulin function with age. Using long‐term depression (LTD) induced by application of insulin to hippocampal slices as a read‐out, we found that the decline in insulin function during aging could be monitored as a progressive impairment of insulin‐LTD. The application of a cholesterol inclusion complex, which donates cholesterol to the membrane and increases membrane cholesterol levels, rescued the insulin signaling deficit and insulin‐LTD. In contrast, extraction of cholesterol from hippocampal neurons of adult mice produced the opposite effect. Furthermore, in vivo inhibition of Cyp46A1, an enzyme involved in brain cholesterol loss with age, improved insulin signaling. Fluorescence resonance energy transfer (FRET) experiments pointed to a change in receptor conformation by reduced membrane cholesterol, favoring ligand‐independent autophosphorylation. Together, these results indicate that changes in membrane fluidity of brain cells during aging play a key role in the decay of synaptic plasticity and cognition that occurs at this late stage of life. [ABSTRACT FROM AUTHOR]

Aging and apolipoprotein E4 (ApoE4) can increase the risk of cognitive impairment and neurodegenerative disorders, including Alzheimer's disease (AD), and patients with type 2 diabetes mellitus are highly susceptible to cognitive dysfunction. Recent research has indicated that metformin, a prescribed drug for type 2 diabetes, may affect cognitive function; however, findings regarding its efficacy are largely controversial. The current study reported that a 5-mo metformin administration (300 mg/kg/d) starting at 13 mo old improved the spatial memory of ApoE3-target replacement (TR) mice, not ApoE4-TR mice. It found that in aged ApoE3-TR mice, metformin treatment, at a molecular level, inhibited AMPK activity, increased insulin signaling, and activated mammalian target of rapamycin signaling, resulting in an enhanced expression of postsynaptic proteins; but the response of the neuronal AMPK activity and insulin signaling to metformin was blunt in aged ApoE4-TR mice. Meanwhile, metformin treatment also increased the phosphorylation of tau in both ApoE3-TR and ApoE4-TR mice, implying that metformin may have side effects in human. These findings suggest that metformin can improve the cognitive performance of aged mice in an APOE genotype-dependent manner, which provides empirical insights into the clinical value of metformin for ApoE4- and age-related AD prevention and treatment. [ABSTRACT FROM AUTHOR]

Most human cells utilize glucose as the primary substrate, cellular uptake requiring insulin. Insulin signaling is therefore critical for these tissues. However, decrease in insulin sensitivity due to the disruption of various molecular pathways causes insulin resistance (IR). IR underpins many metabolic disorders such as type 2 diabetes and metabolic syndrome, impairments in insulin signaling disrupting entry of glucose into the adipocytes, and skeletal muscle cells. Although the exact underlying cause of IR has not been fully elucidated, a number of major mechanisms, including oxidative stress, inflammation, insulin receptor mutations, endoplasmic reticulum stress, and mitochondrial dysfunction have been suggested. In this review, we consider the role these cellular mechanisms play in the development of IR. [ABSTRACT FROM AUTHOR]

Scallops are important marine products in Hokkaido, Japan. Not only scallop adductor muscle but also mantle is often eaten at sashimi or smoking in Japan. We showed previously that feeding the scallop mantle epithelial cell layer causes an increase in serum glucose concentration and the death of rats. To clarify the mechanism of glucose metabolism disorder by mantle epithelial cell layer, we investigated whether extracts from mantle tissue (mantle extract) induce insulin resistance using HepG2 cells. Mantle extract suppressed insulin‐stimulated phosphorylation of Akt, key protein which is involved in insulin signaling. In addition, treatment of HepG2 cells with mantle extract decreased significantly glycogen content and mRNA expression levels of glucose‐6‐phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) involved in gluconeogenesis, suggesting that mantle extract inhibits insulin signaling. These results show that mantle extract inhibits insulin signaling in HepG2 cells, suggesting that an increase in serum glucose concentration in vivo may be due to the inhibition of insulin signaling. [ABSTRACT FROM AUTHOR]

Exercise is an effective therapy for insulin resistance. However, the underlying mechanism remains to be elucidated. Previous research demonstrated that TGFβ‐activated kinase 1 (TAK1)‐dependent signaling plays a crucial character in hepatic insulin resistance. Hepatic ubiquitin specific protease 4 (USP4), USP18, and dual‐specificity phosphatases 14 (DUSP14) can suppress TAK1 phosphorylation, besides tumor necrosis factor receptor‐associated factor 3 (TRAF3) and tripartite motif 8 (TRIM8) promote its phosphorylation. In this study, we tried to verify our hypothesis that exercise improves insulin resistance in high‐fat diet (HFD)‐induced obese (DIO) rats via regulating the TAK1 dependent signaling and TAK1 regulators in liver. Forty male Sprague–Dawley rats were randomized into four groups (n = 10): standard diet and sedentary as normal control; fed on HFD and DIO‐sedentary; fed on HFD and DIO‐chronic exercise; and fed on HFD and DIO‐acute exercise. HFD feeding resulted in increased body weight, visceral fat mass, serum FFAs and hepatic lipid deposition, but decreased hepatic glycogen content and insulin sensitivity. Moreover, hepatic TRAF3 and TRIM8 protein levels increased, whereas USP4, USP18, and DUSP14 protein levels were decreased under obese status, which resulted in enhanced TAK1 phosphorylation and impaired insulin signaling. Exercise training, containing chronic and acute mode, both ameliorated insulin resistance. Meanwhile, decreased TAK1, c‐Jun N‐terminal kinase 1 (JNK1), and insulin receptor substrate 1 (IRS1) phosphorylation enhanced Akt phosphorylation in liver. Moreover, exercise enhanced USP4 and DUSP14 protein levels, whereas decreased TRIM8 protein levels in obese rats' liver. These results showed that exercise triggered a crucial modulation in TAK1‐dependent signaling and its regulators in obese rats' liver, and distinct improvement in insulin sensitivity, which provide new insights into the mechanism by which physical exercise improves insulin resistance. Exercise ameliorates insulin resistance via regulating TGFβ‐activated kinase 1 (TAK1)‐mediated insulin signaling in liver of high‐fat diet‐induced obese rats [ABSTRACT FROM AUTHOR]

Di‐(2‐ethylhexyl) phthalate (DEHP) is a commonly used plasticizer with endocrine disrupting properties. Its widespread use resulted in constant human exposure including fetal development and postnatal life. Epidemiological and experimental data have shown that DEHP has a negative influence on glucose homeostasis. However, the evidence regarding the effect of maternal DEHP exposure on hepatic glucose homeostasis is scarce. Hence, we investigated whether DEHP exposure during gestation and lactation disrupts glucose homeostasis in the rat F1 male offspring at adulthood. Pregnant rats were divided into three groups and administered with DEHP (10 and 100 mg/kg/day) or olive oil from gestational day 9 to postnatal day 21 (lactation period) through oral gavage. DEHP‐exposed offspring exhibited hyperglycemia, impaired glucose and insulin tolerances along with hyperinsulinemia at postnatal day 80. DEHP exposure significantly reduced the levels of insulin signaling molecules such as insulin receptors, IRS1, Akt and its phosphorylated forms. GSK3β and FoxO1 proteins increased in DEHP‐exposed groups whereas its phosphorylated forms decreased. Treated groups showed decreased glycogen synthase activity and glycogen concentration. Glucose‐6‐phosphatase and phosphoenolpyruvate carboxykinase mRNA level and enzyme activity increased in DEHP‐treated groups. The interaction between FoxO1‐glucose‐6‐phosphatase and FoxO1‐phosphoenolpyruvate carboxykinase was also increased. This study suggests that DEHP exposure impairs insulin signal transduction and alters glucoregulatory events leading to the development of type 2 diabetes in F1 male offspring. Di‐(2‐ethylhexyl) phthalate (DEHP) is in common use as a plasticizer with endocrine disrupting properties. Previous studies have shown that DEHP has an adverse effect on glucose metabolism. However, the effect of maternal DEHP exposure on hepatic glucoregulatory events in offspring is meagre. This study was designed to investigate the effect of maternal DEHP exposure on glucose homeostasis in the rat F1 male offspring. The findings of this study suggest that maternal DEHP exposure impairs insulin signal transduction and alters glucoregulatory events in liver leading to the development of type 2 diabetes in F1 male offspring. [ABSTRACT FROM AUTHOR]

Key points: Exercise/exercise training can enhance insulin sensitivity through adaptations in skeletal muscle, the primary site of insulin‐mediated glucose disposal; however, in humans the range of improvement can vary substantially.The purpose of this study was to determine if obesity influences the magnitude of the exercise response in relation to improving insulin sensitivity in human skeletal muscle.Electrical pulse stimulation (EPS; 24 h) of primary human skeletal muscle myotubes improved insulin action in tissue from both lean and severely obese individuals, but responses to EPS were blunted with obesity.EPS improved insulin signal transduction in myotubes from lean but not severely obese subjects and increased AMP accumulation and AMPK Thr172 phosphorylation, but to a lesser degree in myotubes from the severely obese.These data reveal that myotubes of severely obese individuals enhance insulin action and stimulate exercise‐responsive molecules with contraction, but in a manner and magnitude that differs from lean subjects. Exercise/muscle contraction can enhance whole‐body insulin sensitivity; however, in humans the range of improvements can vary substantially. In order, to determine if obesity influences the magnitude of the exercise response, this study compared the effects of electrical pulse stimulation (EPS)‐induced contractile activity upon primary myotubes derived from lean and severely obese (BMI ≥ 40 kg/m2) women. Prior to muscle contraction, insulin action was compromised in myotubes from the severely obese as was evident from reduced insulin‐stimulated glycogen synthesis, glucose oxidation, glucose uptake, insulin signal transduction (IRS1, Akt, TBC1D4), and insulin‐stimulated GLUT4 translocation. EPS (24 h) increased AMP, IMP, AMPK Thr172 phosphorylation, PGC1α content, and insulin action in myotubes of both the lean and severely obese subjects. However, despite normalizing indices of insulin action to levels seen in the lean control (non‐EPS) condition, responses to EPS were blunted with obesity. EPS improved insulin signal transduction in myotubes from lean but not severely obese subjects and EPS increased AMP accumulation and AMPK Thr172 phosphorylation, but to a lesser degree in myotubes from the severely obese. These data reveal that myotubes of severely obese individuals enhance insulin action and stimulate exercise‐responsive molecules with contraction, but in a manner and magnitude that differs from lean subjects. Key points: Exercise/exercise training can enhance insulin sensitivity through adaptations in skeletal muscle, the primary site of insulin‐mediated glucose disposal; however, in humans the range of improvement can vary substantially.The purpose of this study was to determine if obesity influences the magnitude of the exercise response in relation to improving insulin sensitivity in human skeletal muscle.Electrical pulse stimulation (EPS; 24 h) of primary human skeletal muscle myotubes improved insulin action in tissue from both lean and severely obese individuals, but responses to EPS were blunted with obesity.EPS improved insulin signal transduction in myotubes from lean but not severely obese subjects and increased AMP accumulation and AMPK Thr172 phosphorylation, but to a lesser degree in myotubes from the severely obese.These data reveal that myotubes of severely obese individuals enhance insulin action and stimulate exercise‐responsive molecules with contraction, but in a manner and magnitude that differs from lean subjects. [ABSTRACT FROM AUTHOR]

Cellular signaling regulates various cellular functions via protein phosphorylation. Phosphoproteomic data potentially include information for a global regulatory network from signaling to cellular functions, but a procedure to reconstruct this network using such data has yet to be established. In this paper, we provide a procedure to reconstruct a global regulatory network from signaling to cellular functions from phosphoproteomic data by integrating prior knowledge of cellular functions and inference of the kinase–substrate relationships (KSRs). We used phosphoproteomic data from insulin‐stimulated Fao hepatoma cells and identified protein phosphorylation regulated by insulin specifically over‐represented in cellular functions in the KEGG database. We inferred kinases for protein phosphorylation by KSRs, and connected the kinases in the insulin signaling layer to the phosphorylated proteins in the cellular functions, revealing that the insulin signal is selectively transmitted via the Pi3k‐Akt and Erk signaling pathways to cellular adhesions and RNA maturation, respectively. Thus, we provide a method to reconstruct global regulatory network from signaling to cellular functions based on phosphoproteomic data. In this study, we reconstruct global regulatory network from insulin signaling to the cellular functions via protein phosphorylation based on phosphoproteomic data. The arrows indicate phosphorylation of the quantitatively changed phosphopeptides by the protein kinases. [ABSTRACT FROM AUTHOR]

Postprandial insulin desensitization plays a critical role in maintaining whole-body glucose homeostasis by avoiding the excessive absorption of blood glucose; however, the detailed mechanisms that underlie how the major player, skeletal muscle, desensitizes insulin action remain to be elucidated. Herein, we report that early growth response gene-1 (Egr-1) is activated by insulin in skeletal muscle and provides feedback inhibition that regulates insulin sensitivity after a meal. The inhibition of the transcriptional activity of Egr-1 enhanced the phosphorylation of the insulin receptor (InsR) and Akt, thus increasing glucose uptake in L6 myotubes after insulin stimulation, whereas overexpression of Egr-1 decreased insulin sensitivity. Furthermore, deletion of Egr-1 in the skeletal muscle improved systemic insulin sensitivity and glucose tolerance, which resulted in lower blood glucose levels after refeeding. Mechanistic analysis demonstrated that EGR-1 inhibited InsR phosphorylation and glucose uptake in skeletal muscle by binding to the proximal promoter region of protein tyrosine phosphatase-1B (PTP1B) and directly activating transcription. PTP1B knockdown largely restored insulin sensitivity and enhanced glucose uptake, even under conditions of EGR-1 overexpression. Our results indicate that EGR-1/PTP1B signaling negatively regulates postprandial insulin sensitivity and suggest a potential therapeutic target for the prevention and treatment of excessive glucose absorption. [ABSTRACT FROM AUTHOR]