Insulin Receptor Gene Expression Research Articles

Suboptimal maternal nutrition during early-to-mid gestation in the sheep enhances pericardial adiposity in the near-term fetus.

Manipulation of the maternal diet at defined stages of gestation influences long-term health by inducing changes in fetal adipose tissue development, characterised as possessing brown and white adipocytes. We determined whether suboptimal maternal nutrition in early-to-mid gestation, followed by ad libitum feeding until term, increases adiposity in the pericardial depot of the sheep fetus. Pericardial adipose tissue was sampled from near-term (140 days) fetuses delivered to mothers fed either 100% (C) or 60% (i.e. nutrient restricted (NR)) of their total metabolisable requirements from 28 to 80 days gestation and then fed ad libitum. Adipose tissue mass, uncoupling protein (UCP) 1 and gene expression of brown and white adipogenic genes was measured. Total visceral and pericardial adiposity was increased in offspring born to NR mothers. The abundance of UCP1 was increased, together with those genes involved in brown (e.g. BMP7 and C/EBPβ) and white (e.g. BMP4 and C/EBPα) adipogenesis, whereas insulin receptor gene expression was downregulated. In conclusion, suboptimal maternal nutrition between early-to-mid gestation followed by ad libitum feeding enhances pericardial adiposity near to term. A combination of raised UCP1 and adipose tissue mass could improve survival following cold exposure at birth. In the longer term, this enhanced adipogenic potential could predispose to greater pericardial adiposity.

Serum- and Growth-Factor-Free Three-Dimensional Culture System Supports Cartilage Tissue Formation by Promoting Collagen Synthesis via Sox9–Col2a1 Interaction

One of the factors preventing clinical application of regenerative medicine to degenerative cartilage diseases is a suitable source of cells. Chondrocytes, the only cell type of cartilage, grown in vitro under culture conditions to expand cell numbers lose their phenotype along with the ability to generate hyaline cartilaginous tissue. In this study we determine that a serum- and growth-factor-free three-dimensional (3D) culture system restores the ability of the passaged chondrocytes to form cartilage tissue in vitro, a process that involves sox9. Bovine articular chondrocytes were passaged twice to allow for cell number expansion (P2) and cultured at high density on 3D collagen-type-II-coated membranes in high glucose content media supplemented with insulin and dexamethasone (SF3D). The cells were characterized after monolayer expansion and following 3D culture by flow cytometry, gene expression, and histology. The early changes in signaling transduction pathways during redifferentiation were characterized. The P2 cells showed a progenitor-like antigen profile of 99% CD44(+) and 40% CD105(+) and a gene expression profile suggestive of interzone cells. P2 in SF3D expressed chondrogenic genes and accumulated extracellular matrix. Downregulating insulin receptor (IR) with HNMPA-(AM3) or the PI-3/AKT kinase pathway (activated by insulin treatment) with Wortmannin inhibited collagen synthesis. HNMPA-(AM3) reduced expression of Col2, Col11, and IR genes as well as Sox6 and -9. Co-immunoprecipitation and chromatin immunoprecipitation analyses of HNMPA-(AM3)-treated cells showed binding of the coactivators Sox6 and Med12 with Sox9 but reduced Sox9-Col2a1 binding. We describe a novel culture method that allows for increase in the number of chondrocytes and promotes hyaline-like cartilage tissue formation in part by insulin-mediated Sox9-Col2a1 binding. The suitability of the tissue generated via this approach for use in joint repair needs to be examined in vivo.

Antenatal corticosteroids alter insulin signaling pathways in fetal baboon skeletal muscle.

We hypothesize that prenatal exposure to glucocorticoids (GCs) negatively alters the insulin signal transduction pathway and has differing effects on the fetus according to gestational age (GA) at exposure. Twenty-three fetal baboons were delivered from 23 healthy, nondiabetic mothers. Twelve preterm (0.67 GA) and 11 near-term (0.95 GA) baboons were killed immediately after delivery. Half of the pregnant baboons at each gestation received two doses of i.m. betamethasone 24 h apart (170 μg/kg) before delivery, while the other half received no intervention. Vastus lateralis muscle was obtained from postnatal animals to measure the protein content and gene expression of insulin receptor β (IRβ; INSR), IRβ Tyr 1361 phosphorylation (pIRβ), IR substrate 1 (IRS1), IRS1 tyrosine phosphorylation (pIRS1), p85 subunit of PI3-kinase, AKT (protein kinase B), phospho-AKT Ser473 (pAKT), AKT1, AKT2, and glucose transporters (GLUT1 and GLUT4). Skeletal muscle from preterm baboons exposed to GCs had markedly reduced protein content of AKT and AKT1 (respectively, 73 and 72% from 0.67 GA control, P<0.001); IRβ and pIRβ were also decreased (respectively, 94 and 85%, P<0.01) in the muscle of premature GC-exposed fetuses but not in term fetuses. GLUT1 and GLUT4 tended to increase with GC exposure in preterm animals (P=0.09), while GLUT4 increased sixfold in term animals after exposure to GC (P<0.05). In conclusion, exposure to a single course of antenatal GCs during fetal life alters the insulin signaling pathway in fetal muscle in a manner dependent on the stage of gestation.

SRA regulates adipogenesis by modulating p38/JNK phosphorylation and stimulating insulin receptor gene expression and downstream signaling.

The Steroid Receptor RNA Activator (SRA) enhances adipogenesis and increases both glucose uptake and phosphorylation of Akt and FOXO1 in response to insulin. To assess the mechanism, we differentiated ST2 mesenchymal precursor cells that did or did not overexpress SRA into adipocytes using combinations of methylisobutylxanthine, dexamethasone and insulin. These studies showed that SRA overexpression promotes full adipogenesis in part by stimulation of insulin/insulin-like growth factor-1 (IGF-1) signaling. SRA overexpression inhibited phosphorylation of p38 mitogen activated protein kinase (MAPK) and c-Jun NH2-terminal kinase (JNK) in the early differentiation of ST2 cells. Conversely, knockdown of endogenous SRA in 3T3-L1 cells increased phosphorylation of JNK. Knockdown of SRA in mature 3T3-L1 adipocytes reduced insulin receptor (IR) mRNA and protein levels, which led to decreased autophosphorylation of IRβ and decreased phosphorylation of insulin receptor substrate-1 (IRS-1) and Akt. This likely reflects a stimulatory role of SRA on IR transcription, as transfection studies showed that SRA increased expression of an IR promoter-luciferase reporter construct.

Are growth factor receptors modulated by metformin in human endometrial stromal cells after stimulation with androgen and insulin?

To assess the effect of metformin on gene and protein expression of insulin receptor (IR) and IGF-1 (IGF-1R) receptor in human endometrial stromal cells after stimulation with androgen and insulin. Primary culture of endometrial stromal cells stimulated with estrogen, progesterone with or without androgen or insulin, and treated with metformin for 24 and 48 h, followed by RNA (qRT-PCR) and protein (Western blot) extraction and analysis. IR gene expression was increased after treatment with insulin (2.9-fold change, p = 0.027) and further after metformin treatment (4.7-fold change, p < 0.001), and in IGF-1R, the group treated with insulin (1.83-fold change) and metformin (1.78-fold change) showed more expression, than control group (p < 0.001). Similarly, IR protein expression was increased after addition of metformin and insulin (249,869 ± 15,878) in relation to the other groups (p < 0.001). Furthermore, cells treated with insulin (153,634 ± 29,123) and androgen plus insulin (162,854 ± 86,258) had a higher IR protein expression compared to control (104,654 ± 5,634) and androgen group (71,595 ± 3,439, (p = 0.045 and 0.021). In groups treated with insulin (127,711 ± 4,591) and androgen plus insulin (151,098 ± 5,194) the protein IGF-1R was increased compared to control (79,355 ± 3,470) and the androgen-only group (79,326 ± 3,114) (p < 0.001). Metformin in combination with insulin increased IR protein and gene expressions, while it had no influence on the protein expression of IGF-1R in endometrial stromal cells.

Human Granulosa Cells: Insulin and Insulin-Like Growth Factor-1 Receptors and Aromatase Expression Modulation by Metformin

Background/Aim: Granulosa cells are the source of the most important ovarian steroids. Even in patients without significant improvement in metabolic parameters, metformin has apparently an important effect on the ovary. The aim of this study was to evaluate gene and protein expression of an insulin receptor (IR), insulin-like growth factor-1 (IGF1) receptor (IGF1R) and aromatase in granulosa cells treated with metformin and insulin. Methods: Luteinized granulosa cells were collected from 27 patients during in vitro fertilization procedures. Cells were isolated, stored in culture for 24 h and divided into four groups: control; metformin for 30 min, and metformin for 30 min plus insulin for 30 or 60 min. Results: IR and IGF1R mRNA expression was significantly enhanced by metformin but was not affected by insulin. Aromatase mRNA expression was significantly reduced in metformin-incubated cells following stimulation with insulin for 30 min. No statistical differences were found in IGF1R and aromatase protein expression, and IR expression was not detected. Conclusion: A direct effect of metformin on the gene expression of IGF1R, IR and aromatase was observed. Further studies should investigate the role of IGF1R, IR and aromatase in ovarian physiology for a better understanding of the effect of metformin.

Molecular and Biochemical Effect of Neem Extract On Experimental Diabetes

Return to nature is now adays target of view so the aim of this study to evaluate aqueous extract effects of Neem leaf on streptozotocin (STZ) experimental diabetic rats. Sixty male rats were divided equally into 4 groups. first group used as healthy normal control, second group injected with STZ (50 mg/kg.B.W) and act as control diabetic, third group injected I/P with STZ for induction of diabetes and treated with Neem leaf extract (200 mg/kg.B.W orally / day) for 30 days and the fourth group administrated with Neem leaf extract for 15 days before induction of diabetes, then during and after injection of STZ .for 30 days Blood samples were collected at 15 & 30 days from onset of treatment. Serum was directed for estimation of glucose, lipid profile, insulin hormone, insulin receptor, HMG-coA reductase, cortisol and total IgE . Hepatic tissue subjected to PCR for stimulation insulin receptors. The recorded results revealed significant increase in glucose, cholesterol, TG, insulin and HMGcoA reductase in diabetic rats when compared to control .The treatment with Neem extract resulted in significant decrease in all these parameters whereas serum cortisol has non significant change in all groups, while HDL showed non change in diabetic. In conclusion Neem act as potent antidiabetic, antihyperlipidemic and has a good molecular activity on insulin receptor gene expression by PCR

Di(2-ethylhexyl)phthalate exposure impairs insulin receptor and glucose transporter 4 gene expression in L6 myotubes

Di(2-ethyl hexyl)-phthalate (DEHP) is an endocrine disrupter and is the most abundantly used phthalate derivative, which is suspected to be an inevitable environmental exposure contributing to the increasing incidence of type-2 diabetes in humans. Therefore, the present study was designed to address the dose-dependent effects of DEHP on insulin signaling molecules in L6 myotubes. L6 myotubes were exposed to different concentrations (25, 50, and 100 μM) of DEHP for 24 h. At the end of exposure, cells were utilized for assessing various parameters. Insulin receptor and glucose transporter4 (GLUT4) gene expression, insulin receptor protein concentration, glucose uptake and oxidation, and enzymatic and nonenzymatic antioxidants were significantly reduced, but glutamine fructose-6-phosphate amidotransferase, nitric oxide, lipid peroxidation, and reactive oxygen species levels were elevated in a dose-dependent manner in L6 myotubes exposed to DEHP. The present study in turn shows the direct adverse effect of DEHP on the expression of insulin receptor and GLUT4 gene, glucose uptake, and oxidation in L6 myotubes suggesting that DEHP exposure may have a negative influence on insulin signaling.

Transformed Drosophila Cells Evade Diet-Mediated Insulin Resistance through Wingless Signaling

The risk of specific cancers increases in patients withmetabolic dysfunction, including obesity and diabetes. Here, we use Drosophila as a model to explore the effects of diet on tumor progression. Feeding Drosophila a diet high in carbohydrates was previously demonstrated to direct metabolic dysfunction, including hyperglycemia, hyperinsulinemia, and insulin resistance. We demonstrate that high dietary sugar also converts Ras/Src-transformed tissue from localized growths to aggressive tumors with emergent metastases. Whereas most tissues displayed insulin resistance, Ras/Src tumors retained insulin pathway sensitivity, increased the ability to import glucose, and resisted apoptosis. High dietary sugar increased canonical Wingless/Wnt pathway activity, which upregulated insulin receptor gene expression to promote insulin sensitivity. The result is a feed-forward circuit that amplified diet-mediated malignant phenotypes within Ras/Src-transformed tumors. By targeting multiple steps in this circuit with rationally applied drug combinations, we demonstrate the potential of combinatorial drug intervention to treat diet-enhanced malignant tumors.

High-Energy Diet at Antepartum Decreases Insulin Receptor Gene Expression in Adipose Tissue of Postpartum Dairy Cows

Abstract The objective of the study was to determine expression of gene of insulin receptor (INSR) in adipose tissue of postpartum dairy cows fed diets containing different amounts of energy at the antepartum period. Healthy pregnant dairy cows (n=45) on 21st d of the antepartum were divided into three groups differing in diet composition, namely: control group fed a normal diet, high energy group fed a high energy diet, and low energy group fed a low energy diet. Twenty-one days after parturition, INSR gene expression in adipose tissue was determined by internally controlled reverse transcriptase PCR. The level of INSR mRNA in adipose tissues of cows fed the high energy diet was substantially lower than that in cows fed normal or low energy diets. A relatively higher level of INSR mRNA in the adipose tissue of cows fed low energy diet may be beneficial for gluconeogenesis and lipogenesis, which can relieve an energy negative balance. Reduced level of INSR mRNA in adipose tissue of cows fed high energy diet indicates that the response to insulin has significantly decreased.

Saturated fat-rich diet increases fetal lipids and modulates LPL and leptin receptor expression in rat placentas

Metabolic alterations in obese and overweight mothers impact the placenta and the fetus, leading to anomalies in fetal growth and lipid accretion. The primary aim of the study was to examine the effect of a saturated fat-rich diet (FD) on growth, lipid accretion, and lipases, leptin and leptin receptor (ObR) expression in the placenta and fetal liver. We also aimed to find a role for fetal leptin in the modulation of placental and fetal liver lipase and ObR expression. Six-week-old rats were fed with a standard rat chow (control) or a 25% FD for 7 weeks until mating and during pregnancy. Also, in a group of control rats, fetuses were injected with leptin on days 19, 20, and 21 of pregnancy. On day 21, we assessed lipidemia, insulinemia, and leptinemia in mothers and fetuses. In the placenta and fetal liver, lipid concentration was assessed by thin layer chromatography (TLC) and the gene expression of lipoprotein lipase (LPL), endothelial lipase, insulin receptor (Insr), leptin, and ObR by RT-PCR. The FD induced hypertriglyceridemia and hyperleptinemia (P<0.01) in mothers and fetuses, an increase in maternal (P<0.05) and fetal weight (P<0.01), overaccumulation of lipids in fetal liver (P<0.01), and enhanced leptin expression in the placenta and fetal liver (P<0.05). Placental expression of IR and LPL was increased (P<0.05), and ObR decreased (P<0.05) in the FD group. Fetal administration of leptin induced the placental and fetal liver downregulation of ObR (P<0.05) and upregulation of LPL expression (P<0.05). The FD led to increased fetal lipid levels, which may result from high maternal lipid availability and fetal leptin effects.

Curcumin restores diabetes induced neurochemical changes in the brain stem of Wistar rats

Diabetes mellitus, when poorly controlled, leads to debilitating central nervous system (CNS) complications including cognitive deficits, somatosensory and motor dysfunction. The present study investigated curcumin′s potential in modulating diabetes induced neurochemical changes in brainstem. Expression analysis of cholinergic, insulin receptor and GLUT-3 in the brainstem of streptozotocin (STZ) induced diabetic rats were studied. Radioreceptor binding assays, gene expression studies and immunohistochemical analysis were done in the brainstem of male Wistar rats. Our result showed that Bmax of total muscarinic and muscarinic M3 receptors were increased and muscarinic M1 receptor was decreased in diabetic rats compared to control. mRNA level of muscarinic M3, α7-nicotinic acetylcholine, insulin receptors, acetylcholine esterase, choline acetyltransferase and GLUT-3 significantly increased and M1 receptor decreased in the brainstem of diabetic rats. Curcumin and insulin treatment restored the alterations and maintained all parameters to near control. The results show that diabetes is associated with significant reduction in brainstem function coupled with altered cholinergic, insulin receptor and GLUT-3 gene expression. The present study indicates beneficial effect of curcumin in diabetic rats by regulating the cholinergic, insulin receptor and GLUT-3 in the brainstem similar to the responses obtained with insulin therapy.

Osteogenic potential of bone marrow stromal cells derived from streptozotocin-induced diabetic rats

Type1 diabetes mellitus (T1DM) is associated with a series of bone complications, which are still a great challenge in the clinic. Bone marrow stromal cells (BMSCs) are crucial to bone remodeling and are attractive candidates for tissue engineering. Hence, we aimed to investigate whether impaired functions of BMSCs play a role in the pathogenesis of bone complications associated with T1DM. BMSCs were isolated from normal and streptozotocin-induced diabetic rats, and their proliferation and osteogenic differentiation ability were analyzed. Diabetic BMSCs demonstrated reduced proliferation ability, osteoblast gene expression, alkaline phosphatase activity and mineralization. Nude mice transplanted with diabetic BMSCs in a calcium phosphate cement scaffold exhibited reduced new bone formation, as detected by hematoxylin and eosin staining and immunohistochemistry. These changes may be partially related to impaired insulin and insulin-like growth factor1 (IGF-1) signaling. Weak gene expression of insulin receptor (IR), IGF-1, insulin-like growth factor1 receptor (IGF-1R), and insulin receptor substrate-1 (IRS-1) was observed in the diabetic BMSCs compared with normal BMSCs, together with decreased protein level of IGF-1, IGF-1R, IRS-1 and phosphorylated extracellular signal-regulated kinase. Therefore, impaired proliferation and osteogenic potential of BMSCs may be responsible for bone complications related to T1DM, mediated partially by impaired insulin and IGF-1 signaling. These findings may provide a new target with which to devise strategies for therapy.

Ubiquitous Downregulation ofInRGene Expression Affects Stress Associated Hormone Metabolism inDrosophilaFemales

The effect of the ubiquitous downregulation of insulin receptor (InR) gene expression on the metabolism of juvenile hormone (JH) and dopamine (DA) in young females of D. melanogaster under normal conditions and heat stress is studied. The activity ofJH degradation and alkaline phosphatase (ALP, an enzyme regulating DA synthesis) were used as indicators of JH and DA levels, respectively. We demonstrated that, under normal conditions, the ubiquitous inhibition of the InR gene expression in D. melanogaster females induced an increase in the JH degradation and ALP activity. As we have already shown, this is indicative of the decrease in the concentration of the above hormones. It was also found that the total inactivation of InR does not affect the initiation ofJ H and DA metabolic system response to heat stress; however, it does affect its intensity. Thus, the involvement of the insulin signaling pathway in the regulation of the JH and DA metabolism in Drosophila females was demonstrated in vivo under normal and stress conditions.

β-Catenin Directly Sequesters Adipocytic and Insulin Sensitizing Activities but Not Osteoblastic Activity of PPARγ2 in Marrow Mesenchymal Stem Cells

Lineage allocation of the marrow mesenchymal stem cells (MSCs) to osteoblasts and adipocytes is dependent on both Wnt signaling and PPARγ2 activity. Activation of PPARγ2, an essential regulator of energy metabolism and insulin sensitivity, stimulates adipocyte and suppresses osteoblast differentiation and bone formation, and correlates with decreased bone mass and increased fracture rate. In contrast, activation of Wnt signaling promotes osteoblast differentiation, augments bone accrual and reduces total body fat. This study examined the cross-talk between PPARγ2 and β-catenin, a key mediator of canonical Wnt signaling, on MSC lineage determination. Rosiglitazone-activated PPARγ2 induced rapid proteolytic degradation of β-catenin, which was prevented by either inhibiting glycogen synthase kinase 3 beta (GSK3β) activity, or blocking pro-adipocytic activity of PPARγ2 using selective antagonist GW9662 or mutation within PPARγ2 protein. Stabilization of β-catenin suppressed PPARγ2 pro-adipocytic but not anti-osteoblastic activity. Moreover, β-catenin stabilization decreased PPARγ2-mediated insulin signaling as measured by insulin receptor and FoxO1 gene expression, and protein levels of phosphorylated Akt (pAkt). Cellular knockdown of β-catenin with siRNA increased expression of adipocyte but did not affect osteoblast gene markers. Interestingly, the expression of Wnt10b was suppressed by anti-osteoblastic, but not by pro-adipocytic activity of PPARγ2. Moreover, β-catenin stabilization in the presence of activated PPARγ2 did not restore Wnt10b expression indicating a dominant role of PPARγ2 in negative regulation of pro-osteoblastic activity of Wnt signaling. In conclusion, β-catenin and PPARγ2 are in cross-talk which results in sequestration of pro-adipocytic and insulin sensitizing activity. The anti-osteoblastic activity of PPARγ2 is independent of this interaction.

Striatal dopamine receptors modulate the expression of insulin receptor, IGF-1 and GLUT-3 in diabetic rats: Effect of pyridoxine treatment

The incidence of type 2 diabetes mellitus is rising at alarming proportions. Central nervous system plays an important part in orchestrating glucose metabolism, with accumulating evidence linking dysregulated central nervous system circuits to the failure of normal glucoregulatory mechanisms. Pyridoxine is a water soluble vitamin and it has important role in brain function. This study aims to evaluate the role of pyridoxine in striatal glucose regulation through dopaminergic receptor expressions in streptozotocin induced diabetic rats. Radio receptor binding assays for dopamine D1, D2 receptors were done using [3H] 7-chloro-3-methyl-1-phenyl-1,2,4,5-tetrahydro-3-benzazepin-8-ol and [3H] 5-chloro-2-methoxy-4-methylamino-N-[-2-methyl-1-(phenylmethyl)pyrrolidin-3-yl]benzamide. Gene expressions were done using fluorescently labeled Taqman probes of dopamine D1, D2 receptor, Insulin receptor, Insulin like growth factor-1(IGF-1) and Glucose transporter-3 (GLUT-3). Bmax of dopamine D1 receptor is decreased and Bmax of dopamine D2 was increased in diabetic rats compared to control. Gene expression of dopamine D1 receptor was down regulated and dopamine D2 receptor was up regulated in diabetic rats. Our results showed decreased gene expression of Insulin receptor, IGF-1 and increased gene expression of GLUT-3 in diabetic rats compared to control. Pyridoxine treatment restored diabetes induced alterations in dopamine D1, D2 receptors, Insulin receptor, IGF-1, GLUT-3 gene expressions in striatum compared to diabetic rats. Insulin treatment reversed dopamine D1, D2 receptor, GLUT-3 mRNA expression, D2 receptor binding parameters in the striatum compared to diabetic group. Our results suggest the potential role of pyridoxine supplementation in ameliorating diabetes mediated dysfunctions in striatal dopaminergic receptor expressions and insulin signaling. Thus pyridoxine has therapeutic significance in diabetes management.

Insulin and IGF1 receptors in human cardiac microvascular endothelial cells: metabolic, mitogenic and anti-inflammatory effects

Diabetes is associated with microcirculatory dysfunction and heart failure and changes in insulin and IGF1 levels. Whether human cardiac microvascular endothelial cells (HMVEC-Cs) are sensitive to insulin and/or IGF1 is not known. We studied the role of insulin receptors (IRs) and IGF1 receptors (IGF1Rs) in metabolic, mitogenic and anti-inflammatory responses to insulin and IGF1 in HMVEC-Cs and human umbilical vein endothelial cells (HUVECs). IR and IGF1R gene expression was studied using real-time RT-PCR. Receptor protein expression and phosphorylation were determined by western blot and ELISA. Metabolic and mitogenic effects were measured as glucose accumulation and thymidine incorporation. An E-selectin ELISA was used to investigate inflammatory responses. According to gene expression and protein in HMVEC-Cs and HUVECs, IGF1R is more abundant than IR. Immunoprecipitation with anti-IGF1R antibody and immunoblotting with anti-IR antibody and vice versa, showed insulin/IGF1 hybrid receptors in HMVEC-Cs. IGF1 at a concentration of 10(-8) mol/l significantly stimulated phosphorylation of both IGF1R and IR in HMVEC-Cs. In HUVECs IGF1 10(-8) mol/l phosphorylated IGF1R. IGF1 stimulated DNA synthesis at 10(-8) mol/l and glucose accumulation at 10(-7) mol/l in HMVEC-Cs. TNF-α dramatically increased E-selectin expression, but no inflammatory or anti-inflammatory effects of insulin, IGF1 or high glucose were seen. We conclude that HMVEC-Cs express more IGF1Rs than IRs, and mainly react to IGF1 due to the predominance of IGF1Rs and insulin/IGF1 hybrid receptors. TNF-α has a pronounced pro-inflammatory effect in HMVEC-Cs, which is not counteracted by insulin or IGF1.

Developmental regulation of insulin receptor gene in sciatic nerves and role of insulin on glycoprotein P0 in the Schwann cells

In view of the observations that Schwann cells contain insulin receptors, in the present study, we have investigated the developmental regulation of insulin receptor gene in the sciatic nerves of different postnatal age group rats. We have also investigated the role of insulin in the expression of the major PNS myelin glycoprotein P zero (P0) in normal as well as high glucose conditions in primary rat Schwann cells. The expression of insulin receptor gene in sciatic nerves appeared to be differentially regulated. The steady-state levels of insulin receptor mRNA increased remarkably during development and after postnatal day 10, when the peak of myelin structural gene (P0) expression occur and slowly increased further until at least postnatal day 90 in parallel with the growth of the myelin sheath. By employing immunofluorescence and RT-PCR, we observed significant increase in the P0 protein and mRNA levels in Schwann cells in response to the insulin than in insulin deprived counterparts. The presence of insulin in the high glucose medium ameliorated the altered protein and mRNA of P0 in Schwann cells compared to the insulin deprived counterparts. These studies demonstrate the importance of insulin and its receptor as possible regulatory factors in the PNS and also emphasizes their novel therapeutic applications in demyelinating diseases, especially in diabetic poly-neuropathy.

Effect of vitamin D3in reducing metabolic and oxidative stress in the liver of streptozotocin-induced diabetic rats

Diabetes mellitus is a growing health problem worldwide and is associated with severe liver complications. The aim of the present study is to analyse the status of metabolic and free-radical-scavenging enzymes and second messengers in the liver of streptozotocin (STZ)-induced diabetic rats, and to determine the hepatoprotective role of vitamin D(3). All studies were performed using the liver of adult male Wistar rats. Gene expression studies were carried out using real-time PCR with specific probes. Second messenger levels were determined using (3)H-labelled Biotrak assay kits, and glucose uptake assay with D-[(14)C]glucose. The present results show that there was a decrease in hepatic glucose uptake, malate dehydrogenase activity, glycogen content, inositol triphosphate (IP(3)) and cyclic GMP levels, and superoxide dismutase, glutathione peroxidase, phospholipase C, cyclic AMP-responsive element-binding protein, vitamin D receptor (VDR) and insulin receptor (INSR) gene expression in the diabetic rats when compared with the controls (all P < 0·05), while cyclic AMP levels and GLUT2 expression were increased (P < 0·05). Treatment of the diabetic rats with vitamin D(3) and insulin reversed the altered parameters to near control values. In conclusion, the data suggest a novel role of vitamin D(3) in restoring impaired liver metabolism in STZ-induced diabetic rats by regulating glucose uptake, storage and metabolism. We demonstrated that the restoring effect of vitamin D(3) is mediated through VDR modulation, thereby improving signal transduction and controlling free radicals in the liver of diabetic rats. These data suggest a potential role for vitamin D(3) in the treatment of diabetes-associated hepatic complications.

Insulin to treat Alzheimer’s disease: just follow your nose?

Evaluation of: Craft S, Baker LD, Montine TJ et al. Intranasal insulin therapy for Alzheimer disease and amnestic mild cognitive impairment: a pilot clinical trial. Arch. Neurol. doi:10.1001/archneurol.2011.233 (2011) (Epub ahead of print).Alzheimer’s disease (AD) is linked to CNS insulin resistance, decreased expression of insulin and insulin receptor genes, and lower cerebrospinal insulin levels. Against this background, impaired brain insulin signaling may account for some of the cognitive deficits associated with this disease. Using the intranasal method, which effectively bypasses the blood–brain barrier to deliver and target insulin directly from the nose to the brain, a series of acute clinical trials involving healthy humans and AD patients have shown that increased CNS insulin action enhances learning and memory processes. This article summarizes and evaluates data from a recently published clinical trial, in which 4 months of intranasal insulin administration (20 IU insulin/day) preserved not only general cognition but also reduced the loss of metabolic integrity of the brain in adults with mild-to-moderate AD.