Insulin Receptor Substrate-1 Expression Research Articles

Sex differences in adipose insulin resistance are linked to obesity, lipolysis and insulin receptor substrate 1.

Insulin resistance is more prominent in men than women. If this involves adipose tissue is unknown and was presently examined. AdipoIR (in vivo adipose insulin resistance index) was measured in 2344 women and 787 men. In 259 of the women and 54 of the men, insulin induced inhibition of lipolysis (acylglycerol breakdown) and stimulation of lipogenesis (glucose conversion to acylglycerols) were determined in subcutaneous adipocytes; in addition, basal (spontaneous) lipolysis was also determined in the fat cells. In 234 women and 115 men, RNAseq expression of canonical insulin signal genes were measured in subcutaneous adipose tissue. Messenger RNA transcripts of the most discriminant genes were quantified in 175 women and 109 men. Men had higher AdipoIR values than women but only when obesity (body mass index 30 kg/m2 or more) was present (p < 0.0001). The latter sex dimorphism was found among physically active and sedentary people, in those with and without cardiometabolic disease and in people using nicotine or not (p = 0.0003 or less). In obesity, adipocyte insulin sensitivity (half maximum effective hormone concentration) and maximal antilipolytic effect were tenfold and 10% lower, respectively, in men than women (p = 0.005 or less). Basal rate of lipolysis was two times higher in men than women (p > 0.0001). Sensitivity and maximum effect of insulin on lipogenesis were similar in both sexes (p = 0.26 and p = 0.18, respectively). When corrected for multiple comparison only RNAseq expression of insulin receptor substrate 1 (IRS1) was lower in men than women (p < 0.0001). The mRNA transcript for IRS1 was 60% higher in women than men (p < 0.0001). In obesity, adipose tissue insulin resistance is more pronounced in men than in women. The mechanism involves less efficient insulin-mediated inhibition of adipocyte lipolysis, increased basal rate of lipolysis and decreased adipose expression of a key element of insulin signaling, IRS1.

&lt;i&gt;Artocarpus Communis&lt;/i&gt; Seed Regulates P53, IRS, HsD17β2, FTO, and CYP11a Genes in Polycystic Ovarian Syndrome Rats

Polycystic ovarian syndrome (PCOS) is a prevalent endocrine illness that affects 5-10% of reproductive women globally. It is a multifaceted hormonal disorder characterized by the involvement of numerous molecular mechanisms that contribute to its development. This study investigates the effect of &lt;em&gt;Artocarpus communis &lt;/em&gt;seed on the hormonal imbalance and P53, IRS, HsD17β2, FTO, and CYP11a genes expression in the ovaries of letrozole-induced polycystic ovarian syndrome rats. To induce PCOS in 30 female Wistar rats, letrozole was administered at a dosage of 1 mg/kg. For 12 days, &lt;em&gt;Artocarpus communis &lt;/em&gt;seed aqueous extract (100 and 250 mg/kg body weight) and Clomiphene citrate (1 mg/kg body weight), a standard medication, were given. ELISA assessed luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol levels. The levels of P53, IRS, HsD17β2, FTO, and CYP11a gene expression in the ovaries were assessed. The aqueous extract reduced LH and increased FSH levels in Letrozole-induced PCOS rats. Additionally, seed aqueous extract (250 mg/kg bw) regulated the expression of P53, type 2 17-HSD (17-HSD), fat mass and obesity-associated (FTO), 11a-hydroxylase/17,20-desmolase (CYP11a), and insulin receptor substrate (IRS) genes in the ovaries of PCOS rats. Therefore, &lt;em&gt;Artocarpus communis&lt;/em&gt; seed might have multifaceted effects on molecular pathways associated with PCOS, potentially normalizing androgen metabolism, hormonal imbalance, and ovarian function.

Microproteomic-Based Analysis of the Goat Milk Protein Synthesis Network and Casein Production Evaluation.

Goat milk has been consumed by humans since ancient times and is highly nutritious. Its quality is mainly determined by its casein content. Milk protein synthesis is controlled by a complex network with many signal pathways. Therefore, the aim of our study is to clearly depict the signal pathways involved in milk protein synthesis in goat mammary epithelial cells (GMECs) using state-of-the-art microproteomic techniques and to identify the key genes involved in the signal pathway. The microproteomic analysis identified more than 2253 proteins, with 323 pathways annotated from the identified proteins. Knockdown of IRS1 expression significantly influenced goat casein composition (α, β, and κ); therefore, this study also examined the insulin receptor substrate 1 (IRS1) gene more closely. A total of 12 differential expression proteins (DEPs) were characterized as upregulated or downregulated in the IRS1-silenced sample compared to the negative control. The enrichment and signal pathways of these DEPs in GMECs were identified using GO annotation and KEGG, as well as KOG analysis. Our findings expand our understanding of the functional genes involved in milk protein synthesis in goats, paving the way for new approaches for modifying casein content for the dairy goat industry and milk product development.

Outer Membrane Vesicles Released from Garlic Exosome-like Nanoparticles (GaELNs) Train Gut Bacteria that Reverses Type 2 Diabetes via the Gut-Brain Axis.

Gut microbiota function has numerous effects on humans and the diet humans consume has emerged as a pivotal determinant of gut microbiota function. Here, a new concept that gut microbiota can be trained by diet-derived exosome-like nanoparticles (ELNs) to release healthy outer membrane vesicles (OMVs) is introduced. Specifically, OMVs released from garlic ELN (GaELNs) trained human gut Akkermansia muciniphila (A. muciniphila) can reverse high-fat diet-induced type 2 diabetes (T2DM) in mice. Oral administration of OMVs released from GaELNs trained A. muciniphila can traffick to the brain where they are taken up by microglial cells, resulting in inhibition of high-fat diet-induced brain inflammation. GaELNs treatment increases the levels of OMV Amuc-1100, P9, and phosphatidylcholines. Increasing the levels of Amuc-1100 and P9 leads to increasing the GLP-1 plasma level. Increasing the levels of phosphatidylcholines is required for inhibition of cGas and STING-mediated inflammation and GLP-1R crosstalk with the insulin pathway that leads to increasing expression of Insulin Receptor Substrate (IRS1 and IRS2) on OMV targeted cells. These findings reveal a molecular mechanism whereby OMVs from plant nanoparticle-trained gut bacteria regulate genes expressed in the brain, and have implications for the treatment of brain dysfunction caused by a metabolic syndrome.

Polysaccharides from Dendrobium officinale improve obesity-induced insulin resistance through the gut microbiota and the SOCS3-mediated insulin receptor substrate-1 signaling pathway.

Obesity induces insulin resistance and chronic inflammation, impacting human health. The relationship between obesity, gut microbiota, and regulatory mechanisms has been studied extensively. Dendrobium officinale polysaccharide (DOP), a traditional Chinese herbal medicine, potentially reduces insulin resistance. However, the mechanism through which DOP affects gut microbiota and alleviates obesity-induced insulin resistance in rats requires further investigation. The current study aimed to assess the impact of DOP on gut microbiota and insulin resistance in rats on a high-fat diet. The results revealed that DOP effectively reduced blood lipids, glucose disorders, oxidative stress, and inflammatory infiltration in the liver of obese Sprague Dawley rats. This was achieved by downregulating SOCS3 expression and upregulating insulin receptor substrate-1 (IRS-1) by regulating the JAK/STAT/SOCS3 signaling pathway. Notably, DOP intervention enhanced the abundance of beneficial gut microbiota and reduced harmful microbiota. Correlation analysis demonstrated significant associations among intestinal microbiota, SOCS3-mediated IRS-1 expression, and inflammatory factors. Dendrobium officinale polysaccharide regulated the gut microbiota, enhanced IRS-1 expression, and mitigated liver injury and insulin resistance due to a high-fat diet. These findings depict the potential anti-insulin resistance properties of DOP and offer further evidence for addressing obesity and its complications. © 2023 Society of Chemical Industry.

The effect of oral galactose on oxidative stress in the brain of a transgenic mice model of Alzheimer’s disease

AbstractBackgroundChanges in the brain energy metabolism and oxidative stress can be found before development of Aβ plaques in Alzheimer’s disease (AD) and galactose showed potential therapeutic effect in Tg2576 mice AD model. We aimed to investigate changes in the hippocampal (HPC) energy status and oxidative stress before and after galactose treatment in this model.MethodAdult male B6; SJL‐Tg(APPSWE)2576Kha transgenic (TG) mice (Tg2576) and wild types (WT) aged 5 (5M) and 10 (10M) months were used. Oral galactose therapy was given to half of WT (WT+G) and half of TG (TG+G) group for 2 months (200mg/kg/day), while another half of each group received water ad libitum. Protein expression of insulin receptor substrate (total and phosphorylated; IRS, pIRS), AMP‐activated protein kinase (AMPK, p‐AMPK) was measured by western blot. Corticosterone levels were measured by ELISA, and spectrophotometry were used to measure the parameters of oxidative stress (MnSOD; TBARS). Data were analyzed by Kruskal‐Wallis and Mann‐Whitney U‐test (p&lt;0.05).ResultThe levels of corticosterone were decreased in 5M TG mice (p = 0.0055; n = 8) and galactose (5M TG+G) increased it to the levels of control. Galactose decreased MnSOD (p = 0.0329;n = 5) in 10M TG mice. The decrement in p/t IRS ratio (p = 0.043; n = 5) was seen only in 10M TG mice, and galactose (10M TG+G) reversed it to the levels of control. Increased AMPAK levels were found in 5M TG+G (p = 6,5e‐04; n = 5) and 5M WT+G (p = 8,6e‐05; n = 5) groups, while pAMPK was increased only in 5M TG (p = 0.013; n = 5), and decreased in 5M TG+G group after galactose treatment (p = 0.034: n = 5).ConclusionGalactose increased the corticosterone and AMPK levels in young TG mice, while in older TG mice oral galactose had the effect on the level of MnSOD and p/t IRS ratio. The potential therapeutic impact of oral galactose in Tg2576 mice seems to be connected to maintaining of oxidative stress and energy balance and depends on the animal age and AD stage at which the treatment was initiated. Supported by HRZZ IP‐2018‐01‐8938 and the Scientific Centre of Excellence for Basic, Clinical and Translational Neuroscience (project “Experimental and clinical research of hypoxic‐ischemic damage in perinatal and adult brain”, GA KK01.1.1.01.0007 funded by the European Union)

Intracerebroventricular Injection of MHY1485 Blocked the Beneficial Effect of Adiponectin on Aversive Memory in the STZ Model of Dementia.

The most prominent adipokine, adiponectin (APN), has an adverse relationship with the malfunction of adipose tissue. Obesity causes a decrease in plasma APN levels, which eventually results in insulin resistance and diabetes. In this study, we assessed how the effects of APN on memory are influenced by the insulin receptor substrate-1 (IRS-1) and the mammalian target of rapamycin (mTOR) pathways. Streptozotocin (STZ) 3 mg/kg intracerebroventricular injections on days 1 and 3 following cannulation were used to create an animal model of Alzheimer's disease. The acquisition phase was preceded by injections of MHY and adiponectin. For the passive avoidance task, the stepthrough latency and total duration in the dark compartment were recorded and evaluated, and the preference index was calculated for the novel object identification test. IRS-1 protein expression in the hippocampus was assessed by western blotting. STZ reduced the step-through latency (STL), which rose significantly (P≤0.001) in the APN+STZ group. The memory-improving effects of APN were reversed when MHY was administered first (P≤0.001). The STZ and APN+STZ+MHY groups both had a substantial decline in the preference index (P≤0.01). Compared to the control group, the STZ group's expression of the IRS- 1 protein was dramatically reduced (P≤0.0001). In contrast to the APN+STZ group, the MHYtreated group likewise showed decreased IRS-1 protein expression (P≤0.0001), but APN+STZ was able to enhance IRS-1 expression rate (P≤0.0001). In a rat model of AD, we found that adiponectin improved aversive and cognitive memory, which is at least partially mediated by the mTOR signaling cascade.

Thyme extract could overcome diabetes-induced reproductive dysfunction by inhibiting oxidative damage and increasing the expression of insulin receptor substrate and pyruvate kinase in the rat sperm.

Oxidative stress and disruption of energy metabolism in the reproductive system, especially sperm, play a significant role in diabetes-related infertility. Zataria multiflora Boissis (ZMB), a medicinal plant containing various bioactive compounds, may have efficacy in treating metabolic diseases and reproductive disorders. Therefore, the aim of this study was to investigate the effects of different doses of ZMB extract on diabetes-induced reproductive dysfunction by assessing oxidative damage and the gene expression of insulin receptor substrate (IRS) and pyruvate kinase (PK) in male rats' sperm. Sixty adult male Wistar rats were randomly divided into six groups; control (C), diabetes (D), and diabetic animals treated with glibenclamide (G, 50 mg/kg) and thyme extract (T100, T200, and T400). Diabetes was induced by intraperitoneal injection of Streptozotocin (STZ) (50 mg/kg). Insulin, glucose, oxidative and pro-inflammatory markers in the serum, and gene expressions of IRS, and PK were measured in the stored sperms in the epididymis. Changes in the process of spermatogenesis were assessed through the histological evaluation of the testis. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the quantity and quality of thyme extract. The study results indicated that body weight, food intake, and sperm parameters significantly improved in a dose-dependent manner in the T200 group compared to the other groups. Additionally, in the same group, pro-inflammatory biomarkers, DNA fragmentation, and MDA levels decreased, while the levels of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) enzymes in the stored epididymal sperm significantly improved compared to the other groups. The expression of IRS and PK, along with the mean counts of spermatogenesis cell lines (especially Sertoli cells), significantly increased in the T200 group. In conclusion, thymol appears to alleviate diabetes-induced reproductive dysfunction by inhibiting oxidative damage, improving the metabolic state, and upregulating the expression of IRS and PK genes in the sperm of male rats.

Long non‑coding RNA PEG13 regulates endothelial cell senescence through the microRNA‑195/IRS1 axis.

Atherosclerosis is a chronic inflammatory disease characterized by endothelial dysfunction and plaque formation. The present study aimed to elucidate the pathological role of the long non-coding RNA (lncRNA) paternally expressed 13 (PEG13) in the onset and progression of atherosclerosis. Specifically, its effects on human umbilical vein endothelial cell (HUVEC) proliferation, angiogenesis, senescence and senescence-associated secretory phenotype (SASP)-related factors were investigated using cell proliferation, cellular angiogenesis, β-galactosidase staining, reverse transcription-quantitative PCR and enzyme-linked immunosorbent assays. The results showed that oxidized low-density lipoprotein (ox-LDL) inhibited lncRNA PEG13 expression and HUVEC viability in a dose-dependent manner and PEG13 overexpression partially reversed these effects. Additionally, PEG13 overexpression ameliorated the ox-LDL-induced impairment of angiogenesis, cellular senescence and SASP. Furthermore, lncRNA PEG13 directly targeted microRNA (miR/miRNA)-195-5p, suppressing the ox-LDL-induced upregulation of the miRNA. The gene coding for insulin receptor substrate 1 (IRS1), an activator of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, was confirmed as a direct target of miR-195. PEG13 overexpression attenuated the ox-LDL-induced inhibition of IRS1 expression and PI3K/AKT signaling and its protective effects on HUVEC viability, angiogenesis and senescence were partially reversed by small interfering RNAs targeting IRS1. The present study demonstrated that lncRNA PEG13 attenuates ox-LDL-induced senescence in HUVECs by modulating the miR-195/IRS1/PI3K/AKT signaling pathway, suggesting a potential therapeutic target for the treatment of atherosclerosis.

Effect of Prunetin on Streptozotocin-Induced Diabetic Nephropathy in Rats - a Biochemical and Molecular Approach.

In the modern era, chronic kidney failure due to diabetes has spread across the globe. Prunetin (PRU), a component of herbal medicines, has a broad variety of pharmacological activities; these may help to slow the onset of diabetic kidney disease. The anti-nephropathic effects of PRU have not yet been reported. The present study explored the potential nephroprotective actions of PRU in diabetic rats. For 28 days, nephropathic rats were given oral doses of PRU (20, 40, and 80 mg/kg). Body weight, blood urea, creatinine, total protein, lipid profile, liver marker enzymes, carbohydrate metabolic enzymes, C-reactive protein, antioxidants, lipid peroxidative indicators, and the expression of insulin receptor substrate 1 (IRS-1) and glucose transporter 2 (GLUT-2) mRNA genes were all examined. Histological examinations of the kidneys, liver, and pancreas were also performed. The oral treatment of PRU drastically lowered the blood glucose, HbA1c, blood urea, creatinine, serum glutamic-oxaloacetic transaminase, serum glutamic pyruvic transaminase, alkaline phosphatase, lipid profile, and hexokinase. Meanwhile, the levels of fructose 1,6-bisphosphatase, glucose-6-phosphatase, and phosphoenol pyruvate carboxykinase were all elevated, but glucose-6-phosphate dehydrogenase dropped significantly. Inflammatory marker antioxidants and lipid peroxidative markers were also less persistent due to this administration. PRU upregulated the IRS-1 and GLUT-2 gene expression in the nephropathic group. The possible renoprotective properties of PRU were validated by histopathology of the liver, kidney, and pancreatic tissues. It is therefore proposed that PRU (80 mg/kg) has considerable renoprotective benefits in diabetic nephropathy in rats.

Potential molecular mechanisms underlying the ameliorative effect of Cola nitida (Vent.) Schott & Endl. on insulin resistance in rat skeletal muscles

Ethnopharmacological relevanceCola nitida (Vent.) Schott & Endl. are among the common medicinal plants employed in traditional medicine for treating diabetes and its complications. Aim of the studyThe present study investigated the effect of Cola nitida infusion on the expression of key genes involved in insulin signaling vis-à-vis Insulin receptor substrate 1 (IRS-1), tumor protein P53 gene, glucose transporter type 4 (GLUT4), phosphoinositide 3-kinases (PI3K) and B-cell lymphoma-2 (BCL2) in skeletal muscles of type 2 diabetic (T2D) rats. MethodsType 2 diabetic rats were administered C. nitida infusion at low and high doses (150 and 300 mg/kg bodyweight, respectively), while a high dose of the infusion was also administered to a normal toxicological group. Metformin served as the standard antidiabetic drug. The rats were sacrificed at the end of the experimental period. Their psoas muscles were harvested and assayed for the expressions of IRS1, p53, GLUT4, PI3K and BCL2. The studied genes were further subjected to enrichment analysis using the ShinyGO 0.76 online software. ResultsInduction of T2D upregulated the expressions of IRS-1, p53, PI3K and BCL2 in psoas muscles, while concomitantly downregulating GLUT4 expression. These expressions were significantly reversed in type 2 diabetic rats treated with C. nitida infusion, and the results were statistically significant compared to metformin. Gene enrichment analysis revealed that the genes were linked to intrinsic pathways and biological processes involved in insulin resistance. The infusion further improved muscle glucose uptake, ex vivo. Molecular docking and molecular dynamics stimulation of C. nitida infusion phytoconstituents, caffeine and theobromine with IRS-1, p53, GLUT4, PI3K and BCL2 revealed a strong binding affinity as evident by the RMSD and RMSF values. ConclusionThese results indicate the potentials of C. nitida infusion to improve glucose homeostasis in skeletal muscles of type 2 diabetic rats.

SAT072 Choline Deprivation Aggravates Hyperglycemia And Fatty Liver In Non-obese Streptozocin-induced Diabetic Rats

Abstract Disclosure: C. Liapi: None. A. Kyriakaki: None. H. Al Humadi: None. R. Al-Saigh1: None. A. Al Humadi: None. A. Lazaris: None. Background: Choline deprivation (CD) is an established model of steatohepatitis. There is a strong association between non-alcoholic fatty liver disease and diabetes mellitus that has a significant impact on the global health system. The combined state of CD and diabetes can resemble common cases in clinical practice including parenteral nutrition, pregnancy, chronic liver disease malnutrition and/ or alcoholism in diabetic individuals. The aim of this study was to investigate the effects of choline deprivation on glycemic control, insulin signaling pathway and lipid metabolism in non-obese streptozocin-induced diabetic rats. Methods: Thirty-two male adult Wistar rats were divided into four groups; control, diabetes (DM), choline-deprived diet (CDD), and combined group (DM+CDD); DM was induced by intraperitoneal streptozotocin administration. Body weight, fasting blood glucose and plasma insulin levels, lipid profile, liver biochemistry, liver histopathology and gene expression of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), glucose transporters 2 &amp; 4 (GLUT-2 &amp; -4) in hepatic tissue, were assessed. Results: The combination group (CDD+DM) showed a significant increase in blood glucose associated with a significant decrease in plasma insulin level and evidence of dyslipidemia with a significant increase in liver enzymes, histopathology showed extensive micro- and macrovesicular steatosis and a significant decrease in weight gain versus the control, CDD and DM group. A significant increase was observed in gene expression of IR, IRS-1, GLUT-2, and GLUT-4 in all the experimental groups versus the control. Conclusion: The combination of choline deficiency and diabetes has drawn some new scenarios on insulin and some hepatic metabolic pathways: (i) plasma insulin resistance with progressive hyperglycemia and hyperlipidemia.(ii) attenuation of hepatic insulin resistance or sensitization of insulin signaling pathways in the liver, due to the hepatotoxic effects of choline deficiency that could ultimately simulate features of the metabolic syndrome, and (iii) experimentally simulation of metabolic conditions seem to act synergistically, leading to poor glycemic control along with aggravation of hepatic steatosis. Presentation: Saturday, June 17, 2023

Human cytomegalovirus attenuates AKT activity by destabilizing insulin receptor substrate proteins.

Human cytomegalovirus (HCMV) requires inactivation of AKT to efficiently replicate, yet how AKT is shut off during HCMV infection has remained unclear. We show that UL38, an HCMV protein that activates mTORC1, is necessary and sufficient to destabilize insulin receptor substrate 1 (IRS1), a model insulin receptor substrate (IRS) protein. Degradation of IRS proteins in settings of excessive mTORC1 activity is an important mechanism for insulin resistance. When IRS proteins are destabilized, PI3K cannot be recruited to growth factor receptor complexes, and hence, AKT membrane recruitment, a rate limiting step in its activation, fails to occur. Despite its penchant for remodeling host cell signaling pathways, our results reveal that HCMV relies upon a cell-intrinsic negative regulatory feedback loop to inactivate AKT. Given that pharmacological inhibition of PI3K/AKT potently induces HCMV reactivation from latency, our findings also imply that the expression of UL38 activity must be tightly regulated within latently infected cells to avoid spontaneous reactivation.

The effect of heat-killed Lactobacillus brevis SBL88 on improving selective hepatic insulin resistance in non-alcoholic fatty liver disease mice without altering the gut microbiota.

There have been several reports that some probiotics improve non-alcoholic fatty liver disease (NAFLD); however, many studies have involved cocktail therapies. We evaluated whether heat-killed Lactobacillus brevis SBL88 (L.brevis SBL88) monotherapy improves the clinical features of NAFLD. The NAFLD model was induced in mice fed a high-fat diet (HFD) (HFD mice) or HFD+1% heat-killed L.brevis SBL88 (SBL mice) for 16weeks. Histopathological liver findings were analyzed. To evaluate the gut microbiota, a modified terminal restriction fragment length polymorphism analysis of the feces was performed. RNA sequencing in the liver was performed with Ion Proton™. To investigate the direct effects of heat-killed L.brevis SBL88, an in vitro study was performed. Histopathological findings revealed that fat droplets in the liver were significantly reduced in SBL mice; however, terminal restriction fragment length polymorphism did not show alterations in the gut microbiota between HFD mice and SBL mice. RNA sequencing and pathway analysis revealed that the regulation of lipid and insulin metabolism was affected. The mRNA expression of insulin receptor substrate 2 (IRS-2) was significantly higher in SBL mice, whereas the expression of IRS-1 was not significantly different. Phospho-IRS-2 expression was also significantly increased in SBL mice. In addition, an in vitro study revealed significant alterations in IRS-2 and forkhead box protein O1 expression levels. SBL mice exhibited partially improved selective hepatic insulin resistance. Our data suggest that heat-killed L.brevis SBL88 could attenuate the clinical features of NAFLD that are not mediated by alterations in the gut microbiota.

Stevia (Stevia rebaudiana) extract ameliorates insulin resistance by regulating mitochondrial function and oxidative stress in the skeletal muscle of db/db mice

BackgroundType 2 diabetes mellitus (T2DM), a growing health problem worldwide, is a metabolic disorder characterized by hyperglycemia due to insulin resistance and defective insulin secretion by pancreatic β-cells. The skeletal muscle is a central organ that consumes most of the insulin-stimulated glucose in the body, and insulin resistance can damage muscles in T2DM. Based on a strong correlation between diabetes and muscles, we investigated the effects of stevia extract (SE) and stevioside (SV) on the skeletal muscle of diabetic db/db mice.MethodsThe mice were administered saline, metformin  (200 mg/kg/day), SE (200 and 500 mg/kg/day), and SV (40 mg/kg/day) for 35 days. During administration, we checked the levels of fasting blood glucose twice a week and conducted the oral glucose tolerance test (OGTT) and insulin tolerance test (ITT). After administration, we analyzed serum biochemical parameters, triglyceride (TG), total cholesterol (TC), insulin and antioxidant enzymes, and the cross-sectional area of skeletal muscle fibers of db/db mice. Western blots were conducted using the skeletal muscle of mice to examine the effect of SE and SV on protein expression of insulin signaling, mitochondrial function, and oxidative stress.ResultsSE and SV administration lowered the levels of fasting blood glucose, OGTT, and ITT in db/db mice. The administration also decreased serum levels of TG, TC, and insulin while increasing those of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Interestingly, muscle fiber size was significantly increased in db/db mice treated with SE500 and SV. In the skeletal muscle of db/db mice, SE and SV administration activated insulin signaling by increasing the protein expression of insulin receptor substrate, Akt, and glucose transporter type 4. Furthermore, SE500 administration markedly increased the protein expression of AMP-activated protein kinase-α, sirtuin-1, and peroxisome proliferator-activated receptor-γ coactivator-1α. SV administration significantly reduced oxidative stress by down-regulating the protein expression of 4-hydroxynonenal, heme oxygenase-1, SOD, and GPx. In addition, SE500 and SV administration suppressed the expression of apoptosis-related proteins in the skeletal muscle of db/db mice.ConclusionSE and SV administration attenuated hyperglycemia in diabetic mice. Moreover, the administration ameliorated insulin resistance by regulating mitochondrial function and oxidative stress, increasing muscle fiber size. Overall, this study suggests that SE and SV administration may serve as a potential strategy for the treatment of diabetic muscles.

Trastuzumab-resistant breast cancer cells-derived tumor xenograft models exhibit distinct sensitivity to lapatinib treatment in vivo

BackgroundResistance to HER2-targeted therapies, including the monoclonal antibody trastuzumab and tyrosine kinase inhibitor lapatinib, frequently occurs and currently represents a significant clinical challenge in the management of HER2-positive breast cancer. We previously showed that the trastuzumab-resistant SKBR3-pool2 and BT474-HR20 sublines were refractory to lapatinib in vitro as compared to the parental SKBR3 and BT474 cells, respectively. The in vivo efficacy of lapatinib against trastuzumab-resistant breast cancer remained unclear.ResultsIn tumor xenograft models, both SKBR3-pool2- and BT474-HR20-derived tumors retained their resistance phenotype to trastuzumab; however, those tumors responded differently to the treatment with lapatinib. While lapatinib markedly suppressed growth of SKBR3-pool2-derived tumors, it slightly attenuated BT474-HR20 tumor growth. Immunohistochemistry analyses revealed that lapatinib neither affected the expression of HER3, nor altered the levels of phosphorylated HER3 and FOXO3a in vivo. Interestingly, lapatinib treatment significantly increased the levels of phosphorylated Akt and upregulated the expression of insulin receptor substrate-1 (IRS1) in the tumors-derived from BT474-HR20, but not SKBR3-pool2 cells. ConclusionsOur data indicated that SKBR3-pool2-derived tumors were highly sensitive to lapatinib treatment, whereas BT474-HR20 tumors exhibited resistance to lapatinib. It seemed that the inefficacy of lapatinib against BT474-HR20 tumors in vivo was attributed to lapatinib-induced upregulation of IRS1 and activation of Akt. Thus, the tumor xenograft models-derived from SKBR3-pool2 and BT474-HR20 cells serve as an excellent in vivo system to test the efficacy of other HER2-targeted therapies and novel agents to overcome trastuzumab resistance against HER2-positive breast cancer.

GHRH agonist MR-409 protects β-cells from streptozotocin-induced diabetes

Patients with type 1 diabetes (T1D) suffer from insufficient functional β-cell mass, which results from infiltration of inflammatory cells and cytokine-mediated β-cell death. Previous studies demonstrated the beneficial effects of agonists of growth hormone-releasing hormone receptor (GHRH-R), such as MR-409 on preconditioning of islets in a transplantation model. However, the therapeutic potential and protective mechanisms of GHRH-R agonists on models of T1D diabetes have not been explored. Using in vitro and invivo models of T1D, we assessed the protective propertie of the GHRH agonist, MR409 on β-cells. The treatment of insulinoma cell lines and rodent and human islets with MR-409 induces Akt signaling by induction of insulin receptor substrate 2 (IRS2), a master regulator of survival and growth in β-cells, in a PKA-dependent manner. The increase in cAMP/PKA/CREB/IRS2 axis by MR409 was associated with decrease in β-cell death and improved insulin secretory function in mouse and human islets exposed to proinflammatory cytokines. The assessment of the effects of GHRH agonist MR-409 in a model of T1D induced by low-dose streptozotocin showed that mice treated with MR-409 exhibited better glucose homeostasis, higher insulin levels, and preservation of β-cell mass. Increased IRS2 expression in β-cells in the group treated with MR-409 corroborated the invitro data and provided evidence for the underlying mechanism responsible for beneficial effects of MR-409 invivo. Collectively, our data show that MR-409 is a novel therapeutic agent for the prevention and treatment of β-cells death in T1D.

Regulation of erythroid differentiation in K562 cells by the EPAS1-IRS2 axis under hypoxic conditions.

Red blood cells (RBCs) produced in vitro have the potential to alleviate the worldwide demand for blood transfusion. Hematopoietic cell differentiation and proliferation are triggered by numerous cellular physiological processes, including low oxygen concentration (<5%). In addition, hypoxia inducible factor 2α (HIF-2α) and insulin receptor substrate 2 (IRS2) were found to be involved in the progression of erythroid differentiation. However, the function of the HIF-2α-IRS2 axis in the progression of erythropoiesis is not yet fully understood. Therefore, we used an in vitro model of erythropoiesis generated from K562 cells transduced with shEPAS1 at 5% O2 in the presence or absence of the IRS2 inhibitor NT157. We observed that erythroid differentiation was accelerated in K562 cells by hypoxia. Conversely, knockdown of EPAS1 expression reduced IRS2 expression and erythroid differentiation. Intriguingly, inhibition of IRS2 could impair the progression of hypoxia-induced erythropoiesis without affecting EPAS1 expression. These findings indicated that the EPAS1-IRS2 axis may be a crucial pathway that regulates erythropoiesis and that drugs targeting this pathway may become promising agents for promoting erythroid differentiation.

Sacha Inchi (Plukenetia volubilis L.) Oil Improves Hepatic Insulin Sensitivity and Glucose Metabolism through Insulin Signaling Pathway in a Rat Model of Type 2 Diabetes.

This study aimed to evaluate the role of sacha inchi oil (SI) in alleviating hepatic insulin resistance and improving glucose metabolism by inhibiting oxidative stress and inflammation in a rat model of type 2 diabetes. This model was established by providing a high-fat diet and streptozotocin to the rats, thereby inducing diabetes. The diabetic rats were treated orally with 0.5, 1, and 2 mL/kg body weight (b.w.) of SI or 30 mg/kg b.w. of pioglitazone daily for 5 weeks. Blood and hepatic tissues were used for insulin sensitivity, carbohydrate metabolism, oxidative stress, and inflammatory status assessment. Treatment with SI attenuated hyperglycemia and insulin resistance indices, and improved hepatic histopathological alterations in the diabetic rats in a dose-dependent manner, which is correlated with the decreased serum levels of the liver enzymes, alanine transaminase and aspartate transaminase. SI significantly diminished the hepatic oxidative status of the diabetic rats by inhibiting malondialdehyde and enhancing the antioxidant superoxide dismutase, catalase, and glutathione peroxidase activities. Moreover, pro-inflammatory cytokine levels, including tumor necrosis factor-α and interleukin-6, in the liver of the diabetic rats were significantly decreased by the SI. Furthermore, SI treatment enhanced the hepatic insulin sensitivity of the diabetic rats, as shown by the increased insulin receptor substrate-1 and p-Akt protein expression, decreased phosphoenolpyruvate carboxykinase-1 and glucose-6-phospatase protein expression, and increased hepatic glycogen content. Overall, these findings suggest that SI exerts a potential hepatic insulin-sensitizing effect and an improvement in glucose metabolism in the type 2 diabetic rats, at least in part through enhancing insulin signaling, antioxidant defense, and inhibiting inflammation.

Predictive significance of glomerular insulin receptor substrate-1 in patients with diabetic kidney disease

BackgroundIn rodents, glomerular expression of insulin receptor substrate 1 (IRS1) is decreased in diabetic kidney disease (DKD) and reduced associated functioning is involved in the development and progression of DKD. This study aimed to evaluate the significance of glomerular IRS1 expression in DKD patients, and investigated whether glomerular IRS1 expression can reflect renal pathology and predict renal outcomes. MethodsThis study included 10 patients who underwent renal biopsy and were diagnosed with DKD or minor glomerular abnormality (MGA). IRS1-positive cells were determined based on renal biopsy and immunostaining, and the associations of the number of these cells with baseline and prognostic parameters were analyzed. ResultsIRS1-positive cells were significantly decreased in DKD than in MGA. IRS1 positivity tended to be negatively correlated with global glomerulosclerosis and tubulointerstitial fibrosis. The rate of change in estimated glomerular filtration rate before and 12 months after renal biopsy was positively correlated to the number of IRS1-positive cells. Furthermore, a tendency towards negative correlation was observed between the number of glomerular IRS1-positive cells and the proteinuria. ConclusionsThis study shows the glomerular IRS1-positive cell count was significantly decreased in DKD, and that the degree IRS1 positivity was partially correlated with renal pathology and function.