Insulin Receptor Substrate-1 Gene Research Articles

Fluorescent tagging of endogenous IRS2 with an auxin-dependent degron to assess dynamic intracellular localization and function

Insulin Receptor Substrate 2 (IRS2) is a signaling adaptor protein for the insulin (IR) and Insulin-like Growth Factor-1 (IGF-1R) receptors. In breast cancer, IRS2 contributes to both initiation of primary tumor growth and establishment of secondary metastases through regulation of cancer stem cell (CSC) function and invasion. However, how IRS2 mediates its diverse functions is not well understood. We used CRISPR/Cas9-mediated gene editing to modify endogenous IRS2 to study the expression, localization, and function of this adaptor protein. A cassette containing an auxin inducible degradation (AID) sequence, 3X-FLAG tag and mNeon-green was introduced at the N-terminus of the IRS2 gene to provide rapid and reversible control of IRS2 protein degradation and analysis of endogenous IRS2 expression and localization. Live fluorescence imaging of these cells revealed that IRS2 shuttles between the cytoplasm and nucleus in response to growth regulatory signals in a PI3K-dependent manner. Inhibition of nuclear export or deletion of a putative nuclear export sequence in the C-terminal tail promotes nuclear retention of IRS2, implicating nuclear export in the mechanism by which IRS2 intracellular localization is regulated. Moreover, the acute induction of IRS2 degradation reduces tumor cell invasion, demonstrating the potential for therapeutic targeting of this adaptor protein. Our data highlight the value of our model of endogenously tagged IRS2 as a tool to study IRS2 localization and function.

Uncovering the function of insulin receptor substrate in termites' immunity through active immunization.

Insulin receptor substrate (IRS) proteins are key mediators in insulin signaling pathway. In social insect lives, IRS proteins played important roles in caste differentiation and foraging, but there function in disease defenses such as active immunization has not been reported yet. To investigate the issue, we successfully suppressed the IRS gene 3 days after dsRNA injection. Suppressing IRS gene increased the contents of glucose, trehalose, glycogen, and triglyceride and decreased the content of pyruvate in termites, and led to the metabolic disorder of glucose and lipids. IRS suppressing significantly enhanced grooming behaviors of nestmates of fungus-contaminated termites and hence increased the conidial load in the guts of the nestmates. Additionally, IRS suppressing led to significant downregulation of the immune genes Gram-negative bacteria-binding protein2 (GNBP2) and termicin and upregulation of the apoptotic gene caspase8, and hence diminished antifungal activity of nestmates of fungus-contaminated termites. The above abnormal behavioral and physiological responses significantly decreased the survival rate of dsIRS-injected nestmates of the fungus-contaminated termites. These findings suggest that IRS is involved in regulation of active immunization in termites, providing a better understanding of the link between insulin signaling and the social immunity of termites.

<i>Artocarpus Communis</i> 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 <em>Artocarpus communis </em>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, <em>Artocarpus communis </em>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, <em>Artocarpus communis</em> seed might have multifaceted effects on molecular pathways associated with PCOS, potentially normalizing androgen metabolism, hormonal imbalance, and ovarian function.

Association of IRS1 gene Pro512Ala polymorphism with nonalcoholic fatty liver disease.

This study was designed to investigate the possible effect of the insulin receptor substrate 1 (IRS1) gene rs1801276 polymorphism on the risk of nonalcoholic fatty liver disease (NAFLD). The rs1801276 polymorphism was investigated in 127 controls and 123 biopsy-proven NAFLD patients using PCR-RFLP. No deviation from Hardy-Weinberg equilibrium was discovered for the rs1801276 variant of IRS1 in either NAFLD patients or controls (P>0.05). The distribution of different rs1801276 genotypes and alleles showed significant variations between controls and NAFLD patients. In comparison to rs1801276 'CC' genotype, the "GG+GC" genotype occurred less frequently in NAFLD patients than in controls, which also persisted after adjustment for confounding factors (P = 0.041, OR = 0.60, 95% CI = 0.45-0.93). In comparison with the IRS1 rs1801276 "C" allele, the "G" allele was significantly less prevalent in NAFLD patients than in controls (P = 0.045, OR = 0.69, 95% CI = 0.58-0.91). For the first time, we reported a significant association between the IRS1 rs1801276 polymorphism and biopsy-proven NAFLD. More studies are required to further elucidate the contribution of the IRS1 gene to NAFLD susceptibility.

Influence of polymorphisms in candidate genes on carcass and meat quality traits in rabbits.

Candidate gene is a powerful approach to study gene-trait association and offers valuable information for genetic improvement using marker-assisted selection. The current work aimed to study the polymorphisms of four single nucleotide polymorphism (SNPs) at located growth hormone (GH), insulin-like growth factor-II (IGF-II), fat mass and obesity-associated (FTO), and insulin receptor substrate-1 (IRS-1) genes, and their association with the carcass, and meat quality traits in rabbits. The SNPs were genotyped using RFLP-PCR in New Zealand White and local Baladi rabbits. The results revealed that the heterozygous genotype was the most frequent in all cases, except for the FTO SNP in LB rabbits. There was a significant effect for GH genotypes on meat lightness after slaughter and hind-part weight. While, IGF-II mutation significantly affected slaughter, hot carcass, commercial carcass, and hind-part weights. The FTO SNP was associated with cooking loss and intramuscular fat weight, and the IRS-1 SNP was significantly associated with drip loss and intramuscular fat. Specific-breed effects were obtained for IGF-II SNP on cooking loss, and for the intramuscular fat. Although the results suggested that these mutations are useful candidate genes for selection, more research for detecting more variants associated with carcass and meat quality traits in rabbits are recommended.

RNA interference against the putative insulin receptor substrate gene IRS1 affects growth and development in the pest natural enemy Pardosa pseudoannulata.

Insulin signalling pathways play crucial roles in regulating growth and development in insects, but their effects on the growth and development of Arachnids, such as spiders, have rarely been studied. As a valuable pest natural enemy in agricultural fields, the molecular mechanisms of insulin signalling pathway-mediated growth and development of the wolf spider, Pardosa pseudoannulata, are of particular interest. In this study, we identified and characterized six insulin signalling pathway genes - InR, InR2, IRS1, PI3K1, PI3K2, and PDK - in Pardosa pseudoannulata. Real-time quantitative polymerase chain reaction results were used to analyse the relative expression levels of the six genes in different developmental instars and tissues, and in response to starvation treatment. In addition, the function of the insulin receptor substrate (IRS1) gene was investigated using RNA interference technology, which found that IRS1 significantly influenced nutrient content, developmental duration, body weight, and gonad development. This study revealed the roles of six key insulin signalling pathway genes in Pardosa pseudoannulata, and in particular the importance of the IRS1 gene in regulating growth and development in the spider. The results lay the foundation for further research on the internal regulation mechanisms of growth and development in Araneae species, and also provide a reference for the artificial breeding of spiders. © 2023 Society of Chemical Industry.

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.

Insulin receptor substrate 2 gene Gly1057Asp polymorphism is a risk factor for nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD), which is an emerging global chronic liver disease, has a close association with insulin resistance. We aimed to determine whether the Gly1057Asp (rs1805097) polymorphism of the insulin receptor substrate 2 (IRS2) gene is associated with NAFLD. Using the polymerase chain reaction-restriction fragment length polymorphism method, 135 patients with biopsy-proven NAFLD and 135 controls underwent IRS2 genotype analysis. Genotype and allele distributions of the IRS2 gene Gly1057Asp variant conformed to the Hardy-Weinberg equilibrium in both the case and control groups (P > .05). The Asp/Asp genotype of IRS2 gene Gly1057Asp polymorphism compared with Gly/Gly genotype was associated with a 2.1-fold increased risk for NAFLD after adjustment for confounding factors (P = .029; odds ratio = 2.10, 95% CI = 1.23-3.97). Our findings revealed for the first time that the Gly1057Asp Asp/Asp genotype of the IRS2 gene is a marker of increased NAFLD susceptibility; however, studies in other populations are required to confirm the results.

Association of insulin receptor substrate 1 (IRS-1) gene polymorphism with growth and litter-related traits in NMER rabbits

This study investigated the associations between the c.189G > T polymorphism of the insulin receptor substrate-1 (IRS-1) gene and the growth and litter size-related traits in the Native rabbit in Middle Egypt (NMER). One hundred sixty-two NMER rabbits were genotyped by RFLP-PCR using Sau3AI restriction enzyme and the associations of the reported genotypes with body weights at 5th, 6th, 8th, 10th, and 12th week old, body gain, and daily gain plus, the litter size-related traits were determined. Additionally, the genotypic and allelic frequencies, the effective (Ne ) and observed (NA ) numbers of alleles, observed (Ho ) and expected (He ) heterozygosity, Hardy-Weinberg equilibrium (HWE), and the decrease in heterozygosity because of inbreeding (FIS ) were calculated. Three genotypes; GG, GT, and TT with 0.65, 0.33, and 0.02 frequencies, respectively which fit HWE were reported. These genotypes displayed a marked low FIS value. Significant associations of the genotypes with the body weights, and gains, except at the 5th week old determined with superiority of the GT genotype compared with the other genotypes. All reported litter size-related traits significantly varied among different genotypes. In summary, the c.189G > T SNP of the IRS-1 gene is an effective genetic marker to improve growth performance and litter size traits of the NMER rabbits.

Insulin Receptor (RS2059807) And Insulin Receptor Substrate 1 (RS1801278) Genes Polymorphismsin Polycystic Ovary Syndrome

Background: Insulin resistance (IR) plays central role in the pathogenesis of polycystic ovary syndrome (PCOS). Alteration of single nucleotide polymorphisms (SNP) of gene encoding insulin receptor (INSR) and insulin receptor substrate 1 (IRS1) may be associated with insulin resistance and development of PCOS. To see the allele frequency of INSR (rs2059807) and IRS-1(rs1801278) genes polymorphisms and their associations with Bangladeshi women with PCOS. Methods: This cross-sectional study was done among 93 PCOS women (13-35 years) and 79 of age-matched healthy control in the department of Endocrinology, BSMMU. Clinical, biochemical and hormonal profile were recorded. Venous blood was taken in fasting state to measure blood glucose, insulin and genotypes Blood glucose was analyzed by glucose oxidase and insulin by chemiluminescent microparticle immunoassay. SNP genotyping were done by commercial sequencing services. Results: The risk allele (G) frequency for INSR (rs2059807) (p=1.00) and risk allele (T) for IRS-1 (rs1801278) (p=0.367) were statistically similar. Considering dominant, recessive, co-dominant, and over-dominant models, there were no significant differences between the study groups for both genes. Among the different manifestations percentage of IR was significantly raised in wild group of only IRS1 gene. Conclusion: This study failed to reveal any association between PCOS and Insulin Receptor (rs2059807), Insulin Receptor Substrate 1 (rs1801278) gene polymorphism. Only the percentage of IR was found higher in wild group than the mutant group in IRS1 gene. J Medicine 2023; Vol. 34, No. 2(1) Supplement: 210

The Effect of Sitagliptin and Exenatide on Insulin, Insulin Receptor and Insulin Receptor Substrate Gene Expression in Diabetic Rats

The Effect of Sitagliptin and Exenatide on Insulin, Insulin Receptor and Insulin Receptor Substrate Gene Expression in Diabetic Rats

High risk genetic variants of human insulin receptor substrate 1(IRS1) infer structural instability and functional interference

Insulin receptor substrate 1(IRS1) is a signaling adapter protein encoded by the IRS1 gene. This protein delivers signals from insulin and insulin-like growth factor-1(IGF-1) receptors to the phosphatidylinositol 3-kinases (P13K)/protein kinase B (Akt) and Extracellular signal-regulated kinases (Erk) - Mitogen-activated protein (MAP) kinase pathways, which regulate particular cellular processes. Mutations in this gene have been linked to type 2 diabetes mellitus, a heightened risk of insulin resistance, and an increased likelihood of developing a number of different malignancies. The structure and function of IRS1 could be severely compromised as a result of single nucleotide polymorphism (SNP) type genetic variants. In this study, we focused on identification of the most harmful non-synonymous SNPs (nsSNPs) of the IRS1 gene as well as prediction of their structural and functional consequences. Six different algorithms made the initial prediction that 59 of the 1142 IRS1 nsSNPs would have a negative impact on the protein structure. In-depth evaluations detected 26 nsSNPs located inside the functional domains of IRS1. Following that, 16 nsSNPs were identified as more harmful based on conservation profile, hydrophobic interaction, surface accessibility, homology modelling, and inter-atomic interactions. Following an in-depth analysis of protein stability, M249T (rs373826433), I223T (rs1939785175) and V204G (rs1574667052) were identified as three most deleterious SNPs and were subjected to molecular dynamics simulation for further insights. These findings will help us understand the implications for disease susceptibility, cancer progression, and the efficacy of therapeutic development against IRS1 gene mutants. Communicated by Ramaswamy H. Sarma

Enriched functional milk fat ameliorates glucose intolerance and triacylglycerol accumulation in skeletal muscle of rats fed high-fat diets.

We examined the effect of a functional milk fat (FMF) on the glucose metabolism and its association with the intramuscular triacylglycerol (TAG) content in rats fed high-fat diets. Male Wistar rats were fed for 60days with S7 (soybean oil 7%), S30 (soybean oil 30%), MF30 (soybean oil 3% + milk fat 27%), or FMF30 (soybean oil 3% + FMF 27%) diets. An oral glucose tolerance test was performed. The levels of key metabolites in gastrocnemius muscle and mRNA levels of genes involved in glucose and lipid metabolism in muscle, epididymal white adipose tissue (EWAT), and serum were assessed. The S30 diet induced glucose intolerance and led to TAG, citrate, and glucose accumulation in muscle. Moreover, we observed a downregulation of uncoupling proteins (Ucp2 and Ucp3) and insulin receptor substrate-1 (Irs1) genes, lower carnitine palmitoyl transferase-1b (CPT-1b), and phosphofructokinase-1 (PFK1) activities in muscle and lower expression of adiponectin (Adipoq) in EWAT. The FMF30 diet ameliorated the glucose intolerance and normalized the glucose and TAG levels in muscle, preventing the accumulation of citrate and enhancing glucose utilization by the PFK1. The beneficial effects might also be related to the higher expression of Adipoq in EWAT, its receptor in muscle (Adipor1), and the expression of Ucp2, Ucp3, and Irs1 in muscle, restoring the alterations observed with the S30 diet. FMF30 modulated key genes involved in glucose and lipid metabolism in skeletal muscle, improving the glucose utilization and preventing TAG, glucose, and citrate accumulation.

Suppression of Insulin Receptor Substrate 1 Inhibits Breast Cancer Growth In Vitro and in Female Athymic Mice.

Targeting the type I insulin-like growth factor receptor (IGF-IR) has not been successful in breast cancer. Data suggest the highly homologous insulin receptor (IR) may be an alternate growth stimulatory pathway used by cancer cells. Since both receptors phosphorylate the insulin receptor substrate 1 (IRS-1) protein as an immediate consequence of ligand binding, disruption of both receptors could be accomplished by suppression of IRS-1. IRS-1 gene deletion by CRISPR/Cas9 editing resulted in suppression of IGF-I, insulin, and estrogen-stimulated growth in hormone-dependent MCF-7L breast cancer cells. A doxycycline-inducible IRS-1 shRNA lentiviral construct was also used to infect MCF-7L breast cancer cells. IRS-1 shRNA downregulation resulted in decreased responses to IGF-I, insulin, and estradiol in monolayer and anchorage-independent growth assays. Decreased IRS-1 levels also suppressed estradiol-stimulated gene expression and estrogen receptor binding to DNA. Xenograft growth was also inhibited by induction of IRS-1 shRNA. These data show that IRS-1 is a critical regulator of endocrine responsive breast cancer. Efforts to target this adaptor protein could have broader growth inhibitory effects and receptor targeting.

Insulin receptor substrate-1 gene polymorphism and lipid panel data in type 2 diabetic patients with comorbid obesity and/or essential hypertension.

Objective. The hallmarks of type 2 diabetes mellitus (T2DM) are insulin resistance (IR) and insulin receptor substrate (IRS) proteins essential for the insulin signaling. IRS-1 gene has not only been shown to be associated with T2DM, but also has indicated that it may significantly correlate with diabetic complications, such as coronary heart disease and obesity. The aim of this study was to evaluate changes of the lipid panel data in T2DM patients with comorbid obesity and/or essential hypertension in connection with the IRS-1 (rs2943640) polymorphism. Methods. The study involved 33 T2DM patients and 10 healthy individuals. The IRS-1 (rs2943640) polymorphism was genotyped using a TaqMan real-time polymerase chain reaction method. Blood serum lipid panel data were determined with commercially available kits using a Cobas 6000 analyzer. Results. Analysis of the serum lipid panel data depending on the presence of the C/A alleles of IRS-1 (rs2943640) polymorphism in T2DM patients, regardless of the presence/absence of comorbidities, showed significantly lower level of high-density lipoprotein cholesterol (HDL-C) and significantly higher level of non-HDL-C in the carriers of C allele vs. carriers of A allele. In T2DM patients with comorbid obesity and essential hypertension, proatherogenic lipid changes were found in both C and A alleles carriers. Analysis of the effect of IRS-1 (rs2943640) genotypes on serum lipid panel data in T2DM patients, regardless of the presence/absence of comorbidities, showed that the CC genotype carriers had more pronounced pro-atherogenic changes vs. carriers of СА and АА genotypes. In the comorbid course of T2DM (both in combination with obesity and obesity and essential hypertension), pro-atherogenic changes were found in the carriers of the CA genotype of IRS-1 (rs2943640) polymorphism. Conclusions. The presence of the C allele of IRS-1 (rs2943640) polymorphism in both homo-zygous and heterozygous states indicates increased risk of pro-atherogenic changes in T2DM patients with comorbid obesity and/or essential hypertension.

Current Studies on Molecular Mechanisms of Insulin Resistance.

Diabetes is a metabolic disease that raises the risk of microvascular and neurological disorders. Insensitivity to insulin is a characteristic of type II diabetes, which accounts for 85-90 percent of all diabetic patients. The fundamental molecular factor of insulin resistance may be impaired cell signal transduction mediated by the insulin receptor (IR). Several cell-signaling proteins, including IR, insulin receptor substrate (IRS), and phosphatidylinositol 3-kinase (PI3K), have been recognized as being important in the impaired insulin signaling pathway since they are associated with a large number of proteins that are strictly regulated and interact with other signaling pathways. Many studies have found a correlation between IR alternative splicing, IRS gene polymorphism, the complicated regulatory function of IRS serine/threonine phosphorylation, and the negative regulatory role of p85 in insulin resistance and diabetes mellitus. This review brings up-to-date knowledge of the roles of signaling proteins in insulin resistance in order to aid in the discovery of prospective targets for insulin resistance treatment.

Insulin/IGF signaling regulates presynaptic glutamate release in aversive olfactory learning.

Insulin/insulin-like growth factor (IGF) receptor signaling (IIS) supports context-dependent learning in vertebrates and invertebrates. Here, we identify cell-specific mechanisms of IIS that integrate sensory information with food context to drive synaptic plasticity and learning. In the nematode Caenorhabditis elegans, pairing food deprivation with an odor such as butanone suppresses attraction to that odor. We find that aversive olfactory learning requires the insulin receptor substrate (IRS) protein IST-1 and atypical signaling through the insulin/IGF-1 receptor DAF-2. Cell-specific knockout and rescue demonstrate that DAF-2 acts in the AWCON sensory neuron, which detects butanone, and that learning preferentially depends upon the axonally localized DAF-2c isoform. Acute food deprivation increases DAF-2 levels in AWCON post-transcriptionally through an insulin- and insulin receptor substrate-1 (ist-1)-dependent process. Aversive learning alters the synaptic output of AWCON by suppressing odor-regulated glutamate release in wild-type animals, but not in ist-1 mutants, suggesting that axonal insulin signaling regulates synaptic transmission to support aversive memory.

Effects of Red Rice Bran Extract on High-Fat Diet-Induced Obesity and Insulin Resistance in Mice.

Insulin resistance is a salient player in the pathogenesis of obesity and its related abnormal glucose-insulin homeostasis. Red rice bran extract (RRBE) demonstrates several bioactive phytochemicals with anti-diabetic properties. However, little is known about its molecular mechanisms. Therefore, the present study was designed to investigate the anti-insulin resistant mechanisms of RRBE in a model of high-fat diet (HFD)-induced insulin resistance. In this study, mice were randomly divided into four groups: low-fat diet with distilled water (Group L), HFD with distilled water (Group H), HFD with 0.5 g/kg RRBE, and HFD with 1 g/kg RRBE. Metabolic parameters, histological changes in the pancreas, and gene expression levels were evaluated after treating HFD-fed mice with RRBE for six weeks. Mice from Group H exhib-ited significantly higher blood glucose levels prior to and after an oral glucose tolerance test, fasting serum insulin levels, islet size, pancreatic insulin expression levels, and lower skeletal muscle insulin-degrading enzyme (IDE) expression levels compared to Group L. In contrast, these were all significantly restored in the RRBE-treated groups. Also, RRBE treatment was found to upregulate the expression of insulin receptor substrate (IRS) and glucose transporter (GLUT) genes in the adipose tissues and GLUT genes in the muscles and livers of HFD-fed mice. According to our results, RRBE may ameliorate abnormal glucose-insulin metabolism by modulating the expression of insulin, IDE, IRS, and GLUT genes in the major metabolic target tissues of mice after being fed with HFD.

Reduced insulin signaling and high glucagon in early insulin resistance impaired fast-fed regulation of renal gluconeogenesis via insulin receptor substrate.

Gluconeogenesis is one of the key processes through which the kidney contributes to glucose homeostasis. Urinary exosomes (uE) have been used to study renal gene regulation noninvasively in humans and rodents. Recently, we demonstrated fast-fed regulation of phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme for gluconeogenesis, in human uE. The regulation was impaired in subjects with early insulin resistance. Here, we studied primary human proximal tubule cells (hPT) and human uE to elucidate a potential link between insulin resistance and fast-fed regulation of renal PEPCK. We demonstrate that fasted hPTs had higher PEPCK and insulin receptor substrate-2 (IRS2) mRNA and protein levels, relative to fed cells. The fast-fed regulation was, however, attenuated in insulin receptor knockdown (IRKO) hPTs. The IRKO was confirmed by the blunted insulin-induced response on PEPCK, PGC1α, p-IR, and p-AKT expression in IRKO cells. Exosomes secreted by the wild-type or IRKO hPT showed similar regulation to the respective hPT. Similarly, in human uE, the relative abundance of IRS-2 mRNA (to IRS1) was higher in the fasted state relative to the fed condition. However, the fast-fed difference was absent in subjects with early insulin resistance. These subjects had higher circulating glucagon levels relative to subjects with optimal insulin sensitivity. Furthermore, in hPT cells, glucagon significantly induced PEPCK and IRS2 gene, and gluconeogenesis. IR knockdown in hPT cells further increased the gene expression levels. Together the data suggest that reduced insulin sensitivity and high glucagon in early insulin resistance may impair renal gluconeogenesis via IRS2 regulation.

Association of Insulin Receptor Substrate-1 Gene Polymorphism (rs1801278) with Alzheimer’s Disease

Background: Alzheimer’s disease (AD) is the most common form of dementia. AD is also the leading cause of morbidity and mortality due to dementia worldwide. It has been shown that AD is associated with type 2 diabetes mellitus (T2DM) and brain insulin resistance. Rs1801278 is a polymorphism in insulin receptor substrate-1 (IRS-1) gene which changes the amino acid Arg972. This polymorphism has been found to be associated with susceptibility to AD in some populations. Objective: In the present study, our aim was to investigate the association of Arg972 IRS-1 (rs1801278) gene polymorphism and late-onset Alzheimer’s disease (LOAD) in an Iranian population. Methods: In this case-control study, 150 patients with LOAD and 150 unrelated healthy controls were recruited. Polymerase chain reaction (PCR) was performed to amplify a DNA segment of 263 base-pair (bp) length containing the single nucleotide polymorphism (SNP). The PCR product was then incubated with MvaI restriction enzyme to undergo enzymatic cleavage. Electrophoresis was thereafter carried out using agarose gel and DNA safe stain. The gel was ultimately visualized under a UV trans-illuminator. Allelic and genotypic frequencies were then compared. Results: A allele (mutant) of the gene was significantly associated with the risk of AD after adjustment for sex and age (p = 0.04, adjusted OR:1.77, 95% CI:1.00–3.11). Only AA genotype (mutant homozygote) was significantly associated with the risk of AD after adjustment for sex and age (p = 0.01, adjusted OR:2.39, 95% CI:1.22–4.66). Conclusion: SNP rs1801278 is significantly associated with the risk of developing AD in the studied Iranian population.