Liver Insulin Receptor Research Articles

Nicotinic signaling stimulates glucagon secretion in mouse and human pancreatic α-cells.

Smoking is widely regarded as a risk factor for type 2 diabetes, as nicotine contributes to insulin resistance by desensitizing the insulin receptors in muscle, liver, or fat. Little is known, however, about the immediate regulation of islet hormonal output by nicotine, an agonist of ionotropic cholinergic receptors. We investigated this by imaging cytosolic Ca2+ dynamics in mouse and human islets using confocal microscopy and measuring glucagon secretion in response to the alkaloid from isolated mouse islets. Nicotine acutely stimulated cytosolic Ca2+ in glucagon-secreting α-cells but not in insulin-secreting β-cells. The 2.8±0.5-fold (p<0.05) increase in the Ca2+, observed in >70% of α-cells, correlated well with a 2.5±0.3-fold stimulation of glucagon secretion. Nicotine-induced elevation of cytosolic Ca2+ relied on the influx from the extracellular compartment rather than the release of the cation from intracellular depots. Metabotropic cholinergic signaling, monitored at the level of intracellular diacylglycerol, was limited to 69% of α-cells vs 94% of β-cells. We conclude that parasympathetic regulation of pancreatic islet hormone release utilizes different signaling pathways in β- (metabotropic) and α-cells (metabotropic and ionotropic), resulting in the finetuning of the ACh-induced glucagon exocytosis. Sustained nicotinic stimulation is, therefore, likely to attenuate insulin sensitivity by increasing glucagon release.

1594-P: Interorgan Insulin-Leptin Signal Cross Talk Originating in the Liver Enhances Survival under Food-Shortage Conditions

The liver can store energy and distribute it to other tissues/organs, according to the energy states involving hepatic insulin action. In addition, we and others have shown that the liver transmits metabolic information to other organs, via neuronal and humoral mechanisms. Herein, we demonstrate a novel form of inter-organ crosstalk originating in the liver, which links hepatic insulin action with hypothalamic leptin signaling and promotes survival during food shortage. We first observed that tamoxifen-inducible liver insulin receptor (IR) knockout (iLIRKO) mice ate more and consumed less oxygen with decreased hypothalamic leptin action, thereby gaining body weight. Circulating soluble leptin receptor (sLepR) levels were elevated in iLIRKO mice. We then produced tamoxifen-inducible liver leptin receptor (LepR) and IR double-knockout (iLLepRIRKO) mice. In iLLepRIRKO mice, sLepR elevations were not seen. Moreover, increased body weights, hyperphagia and decreased whole-body oxygen consumption seen in iLIRKO mice were reversed, indicating the importance of hepatic sLepR production in the liver-hypothalamus crosstalk. Human hepatic lepr and circulating sLepR levels also correlated negatively with hepatic insulin action indices. Additionally, we restricted food intake in wild type mice. Food restriction decreased hepatic insulin action and whole-body oxygen consumption with increased circulating sLepR. We furthermore performed food restriction in tamoxifen-inducible liver LepR knockout (iLLepRKO) mice. Notably, in iLLepRKO mice, the decreases in basal metabolic rates were blunted and mortality was markedly increased during food restriction. Collectively, the liver translates metabolic cues regarding energy-deficient status, which is reflected by decreased hepatic insulin action, into sLepR, thereby suppressing energy dissipation. This novel inter-organ crosstalk may assure survival of individuals facing food shortages in nature. Disclosure K.Takahashi: Speaker's Bureau; Taisho Pharmaceutical Holdings Co., Ltd. T.Yamada: Speaker's Bureau; MSD, Mitsubishi Tanabe Pharma Corporation, Eli Lilly Japan K.K., Boehringer Ingelheim Japan, Inc., Novo Nordisk, Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Holdings Co., Ltd., Abbott Japan Co., Ltd. H.Katagiri: None. Funding Japan Society for the Promotion of Science (21K08522, 22H03126, 20H05694); Japan Science and Technology Agency (JPMJPS2023)

Attenuated glucose uptake promotes catabolic metabolism through activated AMPK signaling and impaired insulin signaling in zebrafish.

Glucose metabolism in fish remains a controversial area of research as many fish species are traditionally considered glucose-intolerant. Although energy homeostasis remodeling has been observed in fish with inhibited fatty acid β-oxidation (FAO), the effects and mechanism of the remodeling caused by blocked glucose uptake remain poorly understood. In this study, we blocked glucose uptake by knocking out glut2 in zebrafish. Intriguingly, the complete lethality, found in Glut2-null mice, was not observed in glut2-/- zebrafish. Approxiamately 30% of glut2-/- fish survived to adulthood and could reproduce. The maternal zygotic mutant glut2 (MZglut2) fish exhibited growth retardation, decreased blood and tissue glucose levels, and low locomotion activity. The decreased pancreatic β-cell numbers and insulin expression, as well as liver insulin receptor a (insra), fatty acid synthesis (chrebp, srebf1, fasn, fads2, and scd), triglyceride synthesis (dgat1a), and muscle mechanistic target of rapamycin kinase (mtor) of MZglut2 zebrafish, suggest impaired insulin-dependent anabolic metabolism. Upregulated expression of lipolysis (atgl and lpl) and FAO genes (cpt1aa and cpt1ab) in the liver and proteolysis genes (bckdk, glud1b, and murf1a) in muscle were observed in the MZglut2 zebrafish, as well as elevated levels of P-AMPK proteins in both the liver and muscle, indicating enhanced catabolic metabolism associated with AMPK signaling. In addition, decreased amino acids and elevated carnitines of the MZglut2 zebrafish supported the decreased protein and lipid content of the whole fish. In summary, we found that blocked glucose uptake impaired insulin signaling-mediated anabolism via β-cell loss, while AMPK signaling-mediated catabolism was enhanced. These findings reveal the mechanism of energy homeostasis remodeling caused by blocked glucose uptake, which may be a potential strategy for adapting to low glucose levels.

Inter-organ insulin-leptin signal crosstalk from the liver enhances survival during food shortages

Crosstalk among organs/tissues is important for regulating systemic metabolism. Here, we demonstrate inter-organ crosstalk between hepatic insulin and hypothalamic leptin actions, which maintains survival during food shortages. In inducible liver insulin receptor knockout mice, body weight is increased with hyperphagia and decreased energy expenditure, accompanied by increased circulating leptin receptor (LepR) and decreased hypothalamic leptin actions. Additional hepatic LepR deficiency reverses these metabolic phenotypes. Thus, decreased hepatic insulin action suppresses hypothalamic leptin action with increased liver-derived soluble LepR. Human hepatic and circulating LepR levels also correlate negatively with hepatic insulin action indices. In mice, food restriction decreases hepatic insulin action and energy expenditure with increased circulating LepR. Hepatic LepR deficiency increases mortality with enhanced energy expenditure during food restriction. The liver translates metabolic cues regarding energy-deficient status, which is reflected by decreased hepatic insulin action, into soluble LepR, thereby suppressing energy dissipation and assuring survival during food shortages.

The Effect of Nanoparticles of &lt;i&gt;Piper crocatum&lt;/i&gt; Leaves Ethanolic Extract on Liver Insulin Receptor Expression of Diabetic Rat’s Induced by Streptozotocin

Diabetes mellitus is a disease related to hyperglycemia and insulin resistance that can lead to the outcome of chronic liver diseases such as nonalcoholic fatty liver disease (NAFLD). Red betel leaves are known as traditional plants that have anti-hyperglycemic potential. This study aimed to investigate the effect of ethanolic extract of red betel leaves nanoparticle (RbL-Nps) on the liver and hepatic insulin receptor’s (INSR) expression in diabetic rats. Thirty rats were included in this study and further divided into five groups containing six rats each. Group I (GI) comprised of the normal rats; while group II (GII), III (GIII), IV (GIV) and V (GV) comprised of diabetic rats induced by streptozotocin (STZ) at dose of 45 mg/kg bw and nicotinamide (NA) at dose of 110 mg/kg bw, intraperitoneally. Group I and II were treated with 0,5% Na-CMC orally. Group III, IV and V were given the oral administration of RbL-Nps at the doses 30, 60, and 90 mg/kg bw diluted in 0,5% Na-CMC, respectively. All groups were treated once daily and subsequently euthanized after 28 days. Liver tissues were collected for immunohistochemistry method to see the INSR expression and haematoxylin-eosin (HE) staining. Result in this study revealed that INSR expression on the GI, GIII and GIV were significantly higher compared to that on the GII (p &lt; 0.05). On the other hand, there were no significant differences on the INSR expression between GV and GII (p &gt; 0.05). Histologically, liver tissues retrieved from GII showed severe vacuolic and necrotic hepatocytes with dilatated sinusoid. Mild vacuolic and necrotic hepatocytes were observed from GV. There were no pathological changes observed in the liver tissues retrieved from GI, GII, and GIV. We concluded that RbL-Nps improved the liver condition of diabetic rats at doses of 30 and 60 mg/kg bw, but not at doses of 90 mg/kg bw.

Estrogen Promotes Microvascularization in the Fetus and Thus Vascular Function and Insulin Sensitivity in Offspring.

We have shown that normal weight offspring born to estrogen-deprived baboons exhibited insulin resistance, although liver and adipose function and insulin receptor and glucose transporter expression were unaltered. The blood microvessels have an important role in insulin action by delivering insulin and glucose to target cells. Although little is known about the regulation of microvessel development during fetal life, estrogen promotes capillary proliferation and vascular function in the adult. Therefore, we tested the hypothesis that estrogen promotes fetal microvessel development and thus vascular function and insulin sensitivity in offspring. Capillary/myofiber ratio was decreased 75% (P < 0.05) in skeletal muscle, a major insulin target tissue, of fetal baboons in which estradiol levels were depleted by administration of aromatase inhibitor letrozole. This was sustained after birth, resulting in a 50% reduction (P < 0.01) in microvessel expansion; 65% decrease (P < 0.01) in arterial flow-mediated dilation, indicative of vascular endothelial dysfunction; and 35% increase (P < 0.01) in blood pressure in offspring from estrogen-deprived baboons, changes prevented by letrozole and estradiol administration. Along with vascular dysfunction, peak insulin and glucose levels during a glucose tolerance test were greater (P < 0.05 to P < 0.01) and the homeostasis model of insulin resistance 2-fold higher (P < 0.01) in offspring of letrozole-treated than untreated animals, indicative of insulin resistance. This study makes the novel discovery that estrogen promotes microvascularization in the fetus and thus normal vascular development and function required for eliciting insulin sensitivity in offspring and that placental hormonal secretions, independent from improper fetal growth, are an important determinant of risk of developing insulin resistance.

Role of Epigallocatechin Gallate in Glucose, Lipid, and Protein Metabolism and L-Theanine in the Metabolism-Regulatory Effects of Epigallocatechin Gallate.

Epigallocatechin gallate (EGCG) and L-theanine (LTA) are important bioactive components in tea that have shown promising effects on nutrient metabolism. However, whether EGCG alone or combined with LTA can regulate the glucose, lipid, and protein metabolism of healthy rats remains unclear. Therefore, we treated healthy rats with EGCG or the combination of EGCG and LTA (EGCG+LTA) to investigate the effects of EGCG on nutrient metabolism and the role of LTA in the metabolism-regulatory effects of EGCG. The results showed that compared with the control group, EGCG activated insulin and AMP-activated protein kinase (AMPK) signals, thus regulating glucose, lipid, and protein metabolism. Compared with EGCG, EGCG+LTA enhanced hepatic and muscle glycogen levels and suppressed phosphorylation of AMPK, glycogen synthase 2, mammalian target of rapamycin, and ribosomal protein S6 kinase. In addition, EGCG+LTA inhibited the expression of liver kinase B1, insulin receptor and insulin receptor substrate, and promoted the phosphorylation level of acetyl-CoA carboxylase. Furthermore, both EGCG and EGCG+LTA were harmless for young rats. In conclusion, EGCG activated AMPK and insulin pathways, thereby promoting glycolysis, glycogen, and protein synthesis and inhibiting fatty acid (FA) and cholesterol synthesis. However, LTA cooperated with EGCG to promote glycogen metabolism and suppressed the effect EGCG on FA and protein synthesis via AMPK signals.

Differential Effects of Furin Deficiency on Insulin Receptor Processing and Glucose Control in Liver and Pancreatic β Cells of Mice.

The insulin receptor (IR) is critically involved in maintaining glucose homeostasis. It undergoes proteolytic cleavage by proprotein convertases, which is an essential step for its activation. The importance of the insulin receptor in liver is well established, but its role in pancreatic β cells is still controversial. In this study, we investigated the cleavage of the IR by the proprotein convertase FURIN in β cells and hepatocytes, and the contribution of the IR in pancreatic β cells and liver to glucose homeostasis. β-cell-specific Furin knockout (βFurKO) mice were glucose intolerant, but liver-specific Furin knockout (LFurKO) mice were normoglycemic. Processing of the IR was blocked in βFurKO cells, but unaffected in LFurKO mice. Most strikingly, glucose homeostasis in β-cell-specific IR knockout (βIRKO) mice was normal in younger mice (up to 20 weeks), and only mildly affected in older mice (24 weeks). In conclusion, FURIN cleaves the IR non-redundantly in β cells, but redundantly in liver. Furthermore, we demonstrated that the IR in β cells plays a limited role in glucose homeostasis.

Stimulatory effect of docosahexaenoic acid alone or loaded in zinc oxide or silver nanoparticles on the expression of glucose transport pathway

The role of glucose transporters (GLUTs) in diabetes mellitus has become more prominent as a possible therapeutic target. In the present study, we aimed to compare the effect of zinc oxide nanoparticles (ZnONPs), silver nanoparticles (AgNPs), and docosahexaenoic acid (DHA) alone or loaded in ZnONPs or AgNPs on insulin signaling pathway and GLUTs expression in diabetic rats. In the experimental part, rats were divided into seven groups; control, diabetic, and the other five groups were diabetic received different treatments. Fasting blood sugar (FBS), serum level of insulin, insulin resistance (IR), and serum level of phosphatidylinositol 3-kinase (PI3K) were evaluated. In addition, insulin expression in pancreatic islets was assessed by immunohistochemical analysis, and the expression of liver GLUTs 1, 2, and 4 and liver insulin receptor substrate-1 (IRS-1) was evaluated by real-time polymerase chain reactions (RT-PCR).The results of the current study showed that ZnONPs, AgNPs, and DHA alone or loaded in ZnONPs or AgNPs attenuated levels of FBS, insulin and decreased IR in diabetic rats through enhancing the expression of GLUTs as well as IRS-1 and PI3K. Furthermore, AgNPs loaded with DHA showed the most significance with high comparability to the control group.In conclusion, this study elucidated the role of GLUTs and IRS-1 in diabetes and introduced novel characteristics of ZnONPs, AgNPs, and DHA alone or loaded in ZnONPs or AgNPs as a therapeutic modality to activate GLUTs and IRS1, which may be beneficial for diabetic patients with IR.

A Case of Non-Islet Cell Tumor Hypoglycemia in Metastatic Solitary Fibrous Tumor

Abstract Introduction: Insulin like growth factor (IGF-2) mediated hypoglycemia secondary to solitary fibrous tumor (SFT), also known as Doege-Potter syndrome is a rare paraneoplastic syndrome. The tumor cells produce large amounts of high molecular weight IGF 2 precursor protein called “big IGF-2” which binds to insulin and IGF receptors in liver, muscle and other peripheral tissues. This causes reduced gluconeogenesis and increased uptake of glucose by the muscle and other tissues leading to hypoglycemia. Big IGF-2 also exerts central negative feedback of growth hormone causing reduction of IGF-I production. Most SFTs are benign and localized (approximately 78-88%). As a result, tumor excision alone would often lead to resolution of the hypoglycemia. We present a case of metastatic SFT with multiple metastasis managed with oral prednisone. Clinical Case: A 44-year-old man with metastatic SFT presented with bilateral humeral fractures. He has known metastatic disease to the brain, lung, liver, bony lytic lesions over a course of eleven years. It has progressed despite multiple chemotherapy and radiation therapies. Prior to admission, he had multiple syncopal episodes associated with fasting hypoglycemia. He reported capillary blood glucose values ranging between 30-50 mg/dl during these episodes which would improve after drinking juice or eating candy. There was no history of diabetes mellitus or use of oral hypoglycemic agents or insulin. On admission, he had a capillary blood glucose value of less than 20 mg/dl, which was confirmed by a serum glucose value of 18 mg/dl on basic metabolic panel. His renal, liver and thyroid function tests were normal. Significant labs include: serum glucose 17 mg/dl, C-peptide &amp;lt;0.10 ng/ml (n: 1-4 ng/ml), serum insulin &amp;lt;1.6 Uu/ml (n: &amp;lt;20 Uu/ml), beta-hydroxybutyrate &amp;lt;0.2 mmol/L (n: &amp;lt;0.3), cortisol 10.8 ug/dl(n: 5-15 ug/dl) glucagon 6 pg/ml(ref 8-57 pg/ml), insulin-like growth factor-1 (IGF 1) 20 ng/ml (n: 52-328), and IGF-2 level 380 ng/ml (267-616 ng/ml), improvement in blood glucose from 46 to 111 mg/dl after 1-gram glucagon administration. The IGF-2/IGF-1 ratio of 19 confirmed our clinical suspicion of non-islet cell tumor hypoglycemia (NICTH). He was started on prednisone 20 mg twice daily with marked improvement in hypoglycemia. Conclusion: NICTH is a rare cause of hypoglycemia and should be considered in the differential while evaluating hypoglycemia in malignancy. For diagnosing NICTH, assays for big IGF-II are not commercially available. However, the IGF-II:IGF-I ratio is considered to be a surrogate marker of big IGFII concentration. The normal ratio is 3 and ratio &amp;gt;10 is diagnostic of NICTH. In cases like ours where tumor resection is not possible, glucocorticoids are most effective in management of hypoglycemia by inhibiting big IGF2 production and stimulating gluconeogenesis.

Discovery of Orally Bioavailable Purine-Based Inhibitors of the Low-Molecular-Weight Protein Tyrosine Phosphatase.

Obesity-associated insulin resistance plays a central role in the pathogenesis of type 2 diabetes. A promising approach to decrease insulin resistance in obesity is to inhibit the protein tyrosine phosphatases that negatively regulate insulin receptor signaling. The low-molecular-weight protein tyrosine phosphatase (LMPTP) acts as a critical promoter of insulin resistance in obesity by inhibiting phosphorylation of the liver insulin receptor activation motif. Here, we report development of a novel purine-based chemical series of LMPTP inhibitors. These compounds inhibit LMPTP with an uncompetitive mechanism and are highly selective for LMPTP over other protein tyrosine phosphatases. We also report the generation of a highly orally bioavailable purine-based analogue that reverses obesity-induced diabetes in mice.

The IGF-1/GH-GLUTs-plasma glucose regulating axis in hybrid grouper (Epinephelus fuscoguttatus♀ × epinephelus lanceolatus♂) fed a high-carbohydrate diet

The carnivorous teleost fish is often intolerant to high levels of postprandial plasma glucose. This study aimed to evaluate the effects of insulin-like growth factor-1 (IGF-1) and growth hormone (GH) administrations on plasma glucose levels and expression of glucose transporters (GLUTs) in various tissues of hybrid grouper, and hence to further clarify the hormone-GLUTs-plasma glucose regulating axis. Twenty-four experimental fish (average body weight: 77.5 ± 5.4 g) were selected and injected with recombinant human IGF-1 (0.2 μg/g body weight) and PBS (0.01 mol/L) in enterocoelia, respectively, and in the GH injected experiment, the same quantity of fish (average body weight: 103.8 ± 5.8 g) were administrated with GH at a dose of 0.5 μg/g body weight or with PBS at a dose of 0.01 mol/L. Results showed that plasma glucose level was significantly (P < 0.05) declined by the IGF-1 administration but elevated by the GH administration. Plasma IGF-1 concentration was significantly (P < 0.01) elevated by the IGF-1 administration, while GH concentration did not significantly (P ≥ 0.05) respond to the GH administration. The relative mRNA levels of insulin-like growth factor-1 receptor a (IGF-Ra) in liver and muscle were decreased significantly with the IGF-1 administration, and a similar variation tendency was also found in insulin-like growth factor-1 receptor b (IGF-Rb) in liver, muscle and adipose tissues. Besides, the relative mRNA level of insulin receptor (IRS) in liver was significantly increased in the IGF-1 administrated group. After the GH administration, the mRNA levels of hepatic growth factor receptor 2 (GHR2) and IGF-1 were significantly elevated. As for GLUTs, the relative mRNA levels of GLUT1 and GLUT2 in liver were obviously elevated by the IGF-1 administration, while the mRNA level of GLUT4 in muscle was reduced. In liver, the protein levels of GLUT1, 2 and 4 were significantly elevated by the IGF-1 administration, and in adipose, only GLUT1 was observed to have a significantly increased protein level. The mRNA expression of GLUTs was less affected by the GH administration. The protein level of GLUT1 in liver was significantly reduced by the GH administration, while in adipose, it was significantly increased. The protein level of GLUT2 in liver or adipose showed an opposite variation as that of GLUT1. Overall, IGF-1 had a hypoglycemic effect on hybrid grouper, and this probably was through up-regulating the protein levels of hepatic GLUT1, 2 and 4 and adipose GLUT1. GH showed an opposite role in regulating plasma glucose level as IGF-1.

The low molecular weight protein tyrosine phosphatase promotes adipogenesis and subcutaneous adipocyte hypertrophy.

Obesity is a major contributing factor to the pathogenesis of Type 2 diabetes. Multiple human genetics studies suggest that high activity of the low molecular weight protein tyrosine phosphatase (LMPTP) promotes metabolic syndrome in obesity. We reported that LMPTP is a critical promoter of insulin resistance in obesity by regulating liver insulin receptor signaling and that inhibition of LMPTP reverses obesity-associated diabetes in mice. Since LMPTP is expressed in adipose tissue but little is known about its function, here we examined the role of LMPTP in adipocyte biology. Using conditional knockout mice, we found that selective deletion of LMPTP in adipocytes impaired obesity-induced subcutaneous adipocyte hypertrophy. We assessed the role of LMPTP in adipogenesis in vitro, and found that LMPTP deletion or knockdown substantially impaired differentiation of primary preadipocytes and 3T3-L1 cells into adipocytes, respectively. Inhibition of LMPTP in 3T3-L1 preadipocytes also reduced adipogenesis and expression of proadipogenic transcription factors peroxisome proliferator activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha. Inhibition of LMPTP increased basal phosphorylation of platelet-derived growth factor receptor alpha (PDGFRα) on activation motif residue Y849 in 3T3-L1, resulting in increased activation of the mitogen-associated protein kinases p38 and c-Jun N-terminal kinase and increased PPARγ phosphorylation on inhibitory residue S82. Analysis of the metabolome of differentiating 3T3-L1 cells suggested that LMPTP inhibition decreased cell glucose utilization while enhancing mitochondrial respiration and nucleotide synthesis. In summary, we report a novel role for LMPTP as a key driver of adipocyte differentiation via control of PDGFRα signaling.

Anti-Insulin Receptor Antibodies Improve Hyperglycemia in a Mouse Model of Human Insulin Receptoropathy.

Loss-of-function mutations in both alleles of the human insulin receptor gene (INSR) cause extreme insulin resistance (IR) and usually death in childhood, with few effective therapeutic options. Bivalent antireceptor antibodies can elicit insulin-like signaling by mutant INSR in cultured cells, but whether this translates into meaningful metabolic benefits in vivo, wherein the dynamics of insulin signaling and receptor recycling are more complex, is unknown. To address this, we adopted a strategy to model human insulin receptoropathy in mice, using Cre recombinase delivered by adeno-associated virus to knockout endogenous hepatic Insr acutely in floxed Insr mice (liver insulin receptor knockout [L-IRKO] + GFP), before adenovirus-mediated add back of wild-type (WT) or mutant human INSR. Two murine anti-INSR monoclonal antibodies, previously shown to be surrogate agonists for mutant INSR, were then tested by intraperitoneal injections. As expected, L-IRKO + GFP mice showed glucose intolerance and severe hyperinsulinemia. This was fully corrected by add back of WT but not with either D734A or S350L mutant INSR. Antibody injection improved glucose tolerance in D734A INSR-expressing mice and reduced hyperinsulinemia in both S350L and D734A INSR-expressing animals. It did not cause hypoglycemia in WT INSR-expressing mice. Antibody treatment also downregulated both WT and mutant INSR protein, attenuating its beneficial metabolic effects. Anti-INSR antibodies thus improve IR in an acute model of insulin receptoropathy, but these findings imply a narrow therapeutic window determined by competing effects of antibodies to stimulate receptors and induce their downregulation.

Melatonin and insulin modulates the cellular biochemistry, histoarchitecture and receptor expression during hepatic injury in diabetic rats

Aims; The present study was designed to ameliorate the integrated efficacy of exogenous melatonin and insulin on tissue biochemical, serological, histopathological architecture and receptor expression of melatonin (MT1, MT2) and insulin receptor (IR) expression against the hepatic injury in diabetic rats. Materials and Method; the rats were randomly allocated into nine different experimental groups. Diabetes was induced by streptozotocin (15 mg/kg) for 6 days. Rats having blood glucose level above 250 mg/dl were considered as diabetic. Animals euthanized after 4 weeks, blood and liver samples were collected to perform various biochemical, serological, histopathological and receptor expression of melatonin (MT1, MT2) and insulin receptor (IR). Key findings; Diabetic rats revealed significant increase in lipid peroxidation (LPO) of liver tissue, liver function tests (ALT, AST and ALP), increase in serum cholesterol, LDL, VLD, but decrease in HDL level. Further, diabetic rats exhibited significant decrement in antioxidative enzymatic system (GSH, SOD, CAT, GR, GPX, G6PDH and GST), total tissue protein and glycogen content. Histomicrograph of liver of diabetic rats resulted in vacuolization indicating cellular damages as well as upregulation in liver MT1, MT2 and IR protein expression. However, the combined therapy (Melatonin and insulin treatment) revealed significant recovery and restoration in biochemical, cellular architecture of liver cells and receptor expression pattern of MT1, MT2 and IR. Significance; It may establish a synergistic action of melatonin and insulin, which might be a novel evidence for clinicians to combat the hepatic complication along with controlling diabetes.

Berberine chloride ameliorated PI3K/Akt-p/SIRT-1/PTEN signaling pathway in insulin resistance syndrome induced in rats.

The liver is the main organ involved in lipid metabolism process and it helps in drug detoxification. Insulin resistance is considered one of risk reasons which lead to several metabolic diseases. Currently, berberine (BER) occupies a huge challenge against multiple diseases with no toxic effect. The present work was aimed to identify, does BER-chloride has a poisonous influence on the liver? and investigating the outcome of BER-chloride on PI3K/Akt-p/SIRT-1/PTEN pathway during insulin resistance syndrome. The insulin resistance model was achieved in experimental female rats via high-fat diet (HFD). Glucose, insulin, lipid profiles, and hepatic oxidative stress parameters were assessed. PI3K, AKt-p, SIRT-1, and PTEN levels in hepatic tissue were determined at genome and protein levels. Further adiponectin concentration was performed in serum, hepatic, and white adipose tissues. Molecular study of fold alteration in insulin, insulin receptor, and retinol binding protein-4 (RBP4) in liver was done. PRACTICAL APPLICATIONS: Obesity syndrome causes multiple obstacles in modern years. The current results revealed elevation the body weight of rats, plasma glucose, homeostatic model assessment, glycated hemoglobin, insulin, and lipid profiles concentrations in a group of rats, which nourished HFD for 8 weeks and this rise, was diminished after 2 weeks from BER-chloride administration. Further, BER-chloride improved transaminases enzymes, pro-oxidant, and antioxidant defense system, PI3K, AKt-p, SIRT-1, and PTEN in the liver, with downregulation of hepatic RBP4. Hence, these data provide a crucial message that BER-chloride enhanced both hepatic function and insulin signaling pathways that might be of therapeutic importance to insulin resistance with no harmful effect on the liver. BER-chloride is predicted to be a drug of choice for obesity complications cure.

Decreased Insulin Secretion but Unchanged Glucose Homeostasis in Cadmium-Exposed Male C57BL/6 Mice.

Cadmium (Cd) is a well-known toxic metal element that is largely distributed in the environment. Cd causes toxicity to most organs. Accumulating evidence suggests that Cd exposure is associated with islet dysfunction and development of diabetes, but the association remains controversial. The aim of this study is to evaluate the possible effects of chronic Cd exposure on glucose metabolism in male C57BL/6 mice. Mice were intraperitoneally injected with CdCl2 solution (1 mg.kg−1) twice a week for 24 weeks. Fasting blood glucose (FBG) levels and body weights were measured weekly. After 24 weeks, the intraperitoneal glucose tolerance test (IPGTT), intraperitoneal insulin tolerance test (IPITT), and fasting serum insulin (FSI) level test were performed. The insulin resistance index (HOMA-IR) and pancreatic β cell function index (HOMA-β) were calculated and analyzed. The expression of insulin receptor (IR) in mouse liver was detected by real-time PCR. Pancreatic tissue was collected for histological examination. The results demonstrated that FBG, IPGTT, HOMA-IR, and HOMA-β were identical between Cd exposure and control mice. In contract, mean fasting serum insulin level, area under the curve (AUC) of IPITT, and IR expression in livers of Cd-exposed mice decreased significantly compared with control mice. Cd administration induced islet atrophy and decreased islet area. The results suggested that Cd exposure decreased insulin secretion and maintained glucose homeostasis in male C57BL/6 mice and that pancreatic functions should be monitored in populations chronically exposed to Cd.

MON-611 Biux2x2

Insulin is critical for lipid synthesis and inhibition of lipolysis. The dyslipidemia of type 2 diabetes (high triglycerides (TG), low HDL) is caused by selective IR with intact insulin signaling in lipogenic pathways. By contrast, knockout of all insulin signaling pathways due to insulin receptor (INSR) mutation leads to low TG and high HDL (in humans and mice), and decreased cholesterogenic gene expression, cholesterol and bile acid synthesis, PCSK9, and hepatic FFA flux (in liver INSR -/- mice). Thyroid hormone (TH) effects on lipids generally oppose those of insulin, and include increased lipolysis, FFA, and bile formation. We used patients with homozygous (-/-) and heterozygous (+/-) INSR mutations as models to understand interactions between TH and insulin action on lipids. Materials and methods: Euthyroid patients age 12-65y with proven INSR -/- (N=5) or +/- (N=2) mutation (22.2+6.5yr; 4 males) were treated with liothyronine (T3) for 2 weeks with peak target level 25-50% above upper limit of normal. Samples were obtained before and after T3 for thyroid hormones (TSH, fT4, TT4, fT3, TT3), lipids (total cholesterol, LDL, HDL, TG, number and size of lipid particles by NMR, ApoA1, ApoB), lipid regulating enzymes (CETP activity, LCAT activity and mass, PCSK9, PTPL, Lp-PLA2), lipolysis (glycerol turnover), and palmitate turnover. Results: After initiation of T3, hyperthyroid state was achieved by day 3 based on fT3 and TT3 with TSH suppression on day 4. On the standard lipid panel, TG decreased from 64.2 at baseline to 52.6mg/dl after T3 (p=.1), total cholesterol from 143±18.2 to 119.7±9.4mg/dl (p=.0009), LDL from 76.3±15.7 to 61.1±15.5mg/dl (p=.02), and HDL from 62.2±11.9 to 55.2±10.3mg/dl (p=.026). NMR analysis of lipoprotein particles showed that triglyceride-rich lipoprotein particles (TRLP) decreased from to 20±9.8 to 13±5.7 nmol/l (p=.06), LDLP from 1115±201 to 937±195 nmol/L (p=.016), large LDLP from 139±73 to 81±48 nmol/l (p=.046), size of the LDLP from 20.5±0.4 to 20.2±0.4 nm (p=.055), ApoB from 55.7±11 to 45.4±11 mg/dl (p=0.015), HDLP from 20±3 to 18.5±2 nm (p=.08), large HDLP from 3.6±1.9 to 2.8±1.8 umol/l (p=.06), size of HDLP particles from 9.5±0.6 to 9.4±0.6 nm (p=.08), and ApoA1 from 144±4 to 129±15 mg/dl (p=.02). No significant increase in FFA was seen after T3. Lipid enzymes were unchanged after T3 except for PLAC activity, which decreased from 128±30 to 111±28 nmol/min/ml (p=0.03). There was no difference in lipolysis or palmitate turnover rate after T3. In conclusion, we found that T3 had the expected effects on lipids in INSR mutation patients. No changes in key lipid enzymes were found after T3, perhaps due to small sample size. Further long-term studies are needed to determine long-term effects of TH on lipid metabolism in the setting of normal vs. impaired insulin signaling.

SAT-243 Investigation of Intervention Effect on Thrifty Phenotype of Low Birth Weight Rat

[OBJECTIVES] Low birthweight infants caused by fetal malnutrition acquire a thrifty phenotype, according to the development of health and disease (DOHaD) theory. When these children grow in a eutrophic environment, there is a mismatch of phenotype and environment, and it becomes a risk of various metabolic diseases. We aimed to develop an interventional method by creating a rat model exhibiting hyperinsulinemia with low birth weight due to low carbohydrate & calorie restriction during pregnancy and high fat diet (HFD) exposure after growth. Since metaborome analysis of rat blood revealed various metabolic changes, we investigated whether insulin resistance caused by mismatch is improved by methyl donor supplementation. [METHODS] Pups were obtained from mother rats fed with low carbohydrate & calorie restriction diet (LC) for the entire pregnancy period. For control, we used pups from mother rats who had fed standard diet (SC) ad libitum. We made a methyl donor diet in accordance with the previous report and fed ad libitum to mothers who were 3rd trimester of gestational period or breastfeeding. The male rats were divided into an HFD group and SC group at 4 weeks of age, and the HFD group rats were exposed to HFD for 18 weeks. Then, oral glucose tolerance test was carried out to examine blood glucose level, blood insulin concentration, and the expression analysis of mRNA in the liver after an overnight fast. [Results] HFD-exposed LC rats did not cause abrupt change in body weight or in body fat mass induce by HFD exposure even if supplementation to methyl donor was given to lactating maternal rat after giving birth. The blood insulin concentration after oral glucose loading which was high in the HFD-exposed LC rats, was reduced by methyl donor supplementation. In addition, the expression of elevated in FOXO1 and decreased in insulin receptor in the HFD-exposed liver was normalized with supplementation with methyl donor to the LC rats. [Conclusion] Supplementation of pregnant or postnatal methyl donor caused metabolic changes, normalizing abnormalities in the regulation of gene expression in the liver of low birth weight rats.

Maternal High-Protein Diet during Pregnancy Modifies Rat Offspring Body Weight and Insulin Signalling but Not Macronutrient Preference in Adulthood.

Diet of mothers during gestation may impact offspring phenotype. This study evaluated the consequences of a maternal High-Protein (HP) diet during gestation on food preferences and phenotypic characteristics in adult rat offspring. Dams were fed a HP or a Normal-Protein (NP) isocaloric diet during gestation only. Weaned female pups were divided into 3 diet groups: NP control or one of two dietary self-selection (DSS) conditions. In DSS1, offspring had a free choice between proteins (100%) or a mix of carbohydrates (88%) and lipids (12%). In DSS2, the choice was between proteins (100%), carbohydrate (100%) or lipids (100%). DSS2 groups consumed more of their energy from protein and lipids, with a decreased carbohydrate intake (p < 0.0001) compared to NP groups, regardless of the maternal diet. Offspring from HP gestation dams fed the DSS2 diet (HPDSS2) had a 41.2% increase of total adiposity compared to NPDSS2 (p < 0.03). Liver Insulin receptor and Insulin substrate receptor 1 expression was decreased in offspring from HP compared to NP gestation dams. These results showed the specific effects of DSS and maternal diet and data suggested that adult, female offspring exposed to a maternal HP diet during foetal life were more prone to adiposity development, in response to postweaning food conditions.