Hyperglycemia In Diabetic Mice Research Articles

Butyrate induced Tregs are capable of migration from the GALT to the pancreas to restore immunological tolerance during type-1 diabetes

Type-1 diabetes (T1D) is an autoimmune disease caused by progressive loss of insulin-producing beta cells in the pancreas. Butyrate is a commensal microbial-derived metabolite, implicated in intestinal homeostasis and immune regulation. Here, we investigated the mechanism of diabetes remission in non-obese diabetic (NOD) mice following butyrate administration. Sodium butyrate (150 mM) was administered to female NOD mice in drinking water after the onset of hyperglycemia (15–25 weeks age) and at 4 weeks of age (early-intervention group). Butyrate administration reduced the progression of hyperglycemia in diabetic mice and delayed onset of diabetes in the early-intervention group with a reduction in insulitis. Butyrate administration increased regulatory T cells (Tregs) in the colon, mesenteric lymph nodes, Peyer’s patches, and its protective effects diminished upon depletion of Tregs. Further, an increase in α4β7, CCR9, and GPR15 expressing Tregs in the pancreatic lymph nodes (PLN) and pancreas in butyrate-treated mice suggested migration of gut-primed Tregs towards the pancreas. Finally, the adoptive transfer experiments demonstrated that induced Tregs from gut-associated lymphoid tissue can migrate towards the pancreas and PLN and delay the onset of diabetes. Our results thus suggest that early administration of butyrate can restore immunological tolerance during T1D via induction of Tregs with migratory capabilities.

Identification of new enterosynes using prebiotics: roles of bioactive lipids and mu-opioid receptor signalling in humans and mice

ObjectiveThe enteric nervous system (ENS) plays a key role in controlling the gut-brain axis under normal and pathological conditions, such as type 2 diabetes. The discovery of intestinal actors, such...

Murine remote ischemic preconditioning suppresses diabetic ketoacidosis by enhancing glycolysis and entry into tricarboxylic acid cycle in the liver

AimsHindlimb ischemia-reperfusion (IR) was previously demonstrated by our group to decrease blood sugar levels by suppressing hepatic gluconeogenesis and enhancing glucose uptake using activation of the parasympathetic nervous system. While IR attenuated hyperglycemia in diabetic mice, it was unclear whether IR regulated energy metabolism in the liver. We investigated the mechanisms by which IR regulates energy metabolism in the liver from type1 diabetic mice. Main methodsStreptozotocin-induced diabetic male C57BL/6J mice were used to determine the effect of IR on the factors involved in energy metabolism in the liver (i.e., activation levels of AMP-activated protein kinase, aconitase and pyruvate dehydrogenase; adenosine triphosphate and fumarate concentrations; sirtuin (Sirt) 1 expression). These various signaling pathways and key enzyme activities were examined using western blot analysis and a biochemical technique including a colorimetric assay. Key findingsUnder feeding conditions (free access to normal murine chow and water), blood glucose levels and serum ketone body levels were significantly suppressed by IR, whereas phospho-AMP-activated protein kinase and its activity, pyruvate dehydrogenase, aconitase activity, and Sirt 1expression were upregulated. In contrast, peroxisome proliferator-activated receptor γ coactivator-1, which accelerated fatty acid use, was suppressed by IR. SignificanceThese results indicated that in the IR-treated diabetic liver, energy production was promoted through acceleration of the tricarboxylic acid cycle linked with increased glucose preference rather than fatty acid under feeding conditions. Therefore, IR may be beneficial against diabetic hyperglycemia, but also ketoacidosis.

Puerarin ameliorates hyperglycemia in HFD diabetic mice by promoting β-cell neogenesis via GLP-1R signaling activation

BackgroundDiabetes is characterized by β-cell loss and dysfunction. A strategy for diabetes treatment is to promote new β-cell formation. Puerarin is an isoflavone from the root of Pueraria lobata (Willd.) Ohwi. Our previous study demonstrated puerarin could ameliorate hyperglycemia in diabetic mice. However, related mechanisms and potential roles of puerarin in β-cell neogenesis have not been elucidated. PurposeThe present study aims to investigate whether anti-diabetic effect of puerarin is dependent on promoting β-cell neogenesis via GLP-1R signaling activation. MethodsA high-fat diet (HFD) induced diabetic mouse model was applied to investigate effects of puerarin in vivo, exendin-4 (GLP-1R agonist) and metformin were used as positive controls. Moreover, related mechanisms and GLP-1R downstream signal transduction were explored in isolated cultured mouse pancreatic ductal cells. ResultsPuerarin improved glucose homeostasis in HFD diabetic mice significantly. Markers of new β-cell formation (insulin, PDX1 and Ngn3) were observed in pancreatic ducts of HFD mice treated by puerarin. Of note, efficacy of puerarin in vivo was suppressed by GLP-1R antagonist exendin9-39, but enhanced by exendin-4 respectively. In cultured mouse pancreatic ductal cells, puerarin induced expressions of insulin and PDX1, upregulated GLP-1R expression and activated β-catenin and STAT3 subsequently. Expressions of insulin and PDX1 in ductal cells could be blocked by exendin9-39, or β-catenin inhibitor ICG001, or JAK2 inhibitor AG490. ConclusionThese data clarified puerarin ameliorated hyperglycemia of HFD mice via a novel mechanism involved promoting β-cell neogenesis. Our finding highlights the potential value of puerarin developing as an anti-diabetic agent.

A Novel Acetyl-CoA Carboxylase 2 Selective Inhibitor Improves Whole-Body Insulin Resistance and Hyperglycemia in Diabetic Mice through Target-Dependent Pathways.

Excess intramyocellular lipid (IMCL) deposition in skeletal muscle is closely associated with insulin resistance. Pharmacological inhibition of acetyl-CoA carboxylase (ACC) 2 offers a promising approach to treat insulin resistance through stimulation of mitochondrial fatty acid oxidation (FAO) and reduction of IMCL deposition. Previously reported experimental ACC2 inhibitors exhibited plasma glucose-lowering effects in diabetic rodents. However, their antidiabetic action may be potentially biased by off-target effects on triglyceride metabolism or by neurologic side effects. In this study, we investigated a safety profile, target dependency of its action, and antidiabetic efficacy of compound 2e, a novel olefin derivative potent ACC2 selective inhibitor. Four-day administration of suprapharmacological dose of compound 2e did not exhibit any obvious side effects in Sprague-Dawley rats. In db/db mice, single administration of compound 2e led to significantly elevated FAO and reduced IMCL deposition in skeletal muscle. In ACC2 knockout mice, treatment with pharmacological doses of compound 2e did not reduce plasma triglyceride levels, whereas A-908292, a previously reported ACC2 inhibitor, caused a significant triglyceride reduction, showing that compound 2e was devoid of off-target triglyceride-lowering activity. Chronic treatment of db/db mice with compound 2e improved hyperglycemia but did not decrease plasma triglyceride levels. Additionally, compound 2e showed significant improvements of whole-body insulin resistance in the clamp study and insulin tolerance test. Collectively, compound 2e demonstrated a good safety profile and significant antidiabetic effects through inhibition of ACC2-dependent pathways. These findings provide further evidence that selective inhibition of ACC2 is an attractive strategy against insulin resistance and type 2 diabetes. SIGNIFICANCE STATEMENT: This study shows that pharmacological inhibition of acetyl-CoA carboxylase (ACC) 2 leads to significant improvements in whole-body glucose homeostasis, independently of off-target metabolic pathways and toxicity, which were observed in previously reported ACC2 inhibitors. These findings support the concept that ACC2-selective inhibitors will be a novel remedy for treatment of type 2 diabetes.

1-Deoxynojirimycin (DNJ) Exerts Female-Prefered Anti-Hyperlipidemic Effect <i>via</i> Gender-Specifically Modulation of the Gut Microbiota and Promoted Indole-3-Propionic Acid (IPA) Production

Background: The gender disparity in lipid metabolism leaves more women with uncontrolled hyperlipidemia by current medication. Thus, discovering female-preferred anti-hyperlipidemic drugs is favorable to large numbers of women patients. Methods: We investigated the ameliorating effects of 1-deoxynojirimycin (DNJ) on hyperlipidemia and hyperglycemia in both male and female mice received high-fat diet (HFD) feeding and a single small dose of streptozocin (30 mg/kg, i.p. ). The gut microbial composition was analyzed by both 16S rDNA and 16S rRNA pyrosequencing. The metabonomic analysis on feces was performed by gas chromatography–time-of-flight mass spectrometry (GC–TOF/MS). The lipid-lowering effect of indole-3-propionic acid (IPA) was evaluated in vitro and in vivo. Findings: DNJ female-preferably alleviated hyperlipidemia but homogenously diminished hyperglycemia in diabetic mice. Oral administration of DNJ gender-specifically downregulated the expression of lipogenic genes, stimulated the growth of Akkermansia and Clostridium XIVa, and promoted the generation of indole-3-propionic acid (IPA) which tightly associated with the anti-hyperlipidemic effect of DNJ and exhibited a potent lipid-lowering effect in HepG2 cells and high-fat diet-induced obese mice. Interpretation: Our results propose DNJ as a female-preferable anti-hyperlipidemic candidate via gender-specifically modulation of gut microbial community and their metabolites, which provides insights for discovering novel gender-specific medications against hyperlipidemia. Funding Statement: This work was supported financially by the National Natural Science Foundation of China (81403155), Modern Agro-industry Technology Research System of China (CARS-18) and Key Laboratory of Creative Agriculture, Ministry of Agriculture, P.R. China Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: All the animal experiments were performed following the National Institutes of Health guide for the care and use of Laboratory Animals (NIH Publications No. 8023, revised 1978) and were approved by the Medical Ethics Committee of Zhejiang Academy of Agricultural Sciences (No. ZAAS-20170812011).

Ameliorative effects of quercetin on folliculogenesis in diabetic mice: a stereological study

A high risk of reproductive disorders can be seen in diabetic pregnancy. Reproductive disorders associated with diabetes may result from alterations in the function of the ovary. In this study, we investigated the ameliorative effects of quercetin as a phytoestrogen and antidiabetic agent on the folliculogenesis in diabetic mice. Streptozotocin-induced diabetic mice were treated with 30 mg/kg/day quercetin for four weeks. The volume of ovary, follicles, and corpus luteum were significantly decreased in the diabetic mice. The number of growing follicles (secondary, antral, and Graafian follicles) and corpus luteum was significantly decreased in the diabetic mice. Also, the volume of oocytes was significantly decreased in antral and Graafian follicles. Our results indicated that the administration of quercetin in diabetic mice increased the volume of the ovary and growing follicles, the number of growing follicles and corpus luteum. It also significantly decreased the number of atretic follicles. As a result, it may be concluded that the impaired follicular growth and development caused by hyperglycemia in diabetic mice can be alleviated by quercetin treatment.

Adipsin preserves beta cells in diabetic mice and associates with protection from type 2 diabetes in humans.

Type 2 diabetes is characterized by insulin resistance and a gradual loss of pancreatic beta cell mass and function1,2. Currently, there are no therapies proven to prevent beta cell loss and some, namely insulin secretagogues, have been linked to accelerated beta cell failure, thereby limiting their use in type 2 diabetes3,4. The adipokine adipsin/complement factor D controls the alternative complement pathway and generation of complement component C3a, which acts to augment beta cell insulin secretion5. In contrast to other insulin secretagogues, we show that chronic replenishment of adipsin in diabetic db/db mice ameliorates hyperglycemia and increases insulin levels while preserving beta cells by blocking dedifferentiation and death. Mechanistically, we find that adipsin/C3a decreases the phosphatase Dusp26; forced expression of Dusp26 in beta cells decreases expression of core beta cell identity genes and sensitizes to cell death. In contrast, pharmacological inhibition of DUSP26 improves hyperglycemia in diabetic mice and protects human islet cells from cell death. Pertaining to human health, we show that higher concentrations of circulating adipsin are associated with a significantly lower risk of developing future diabetes among middle-aged adults after adjusting for body mass index (BMI). Collectively, these data suggest that adipsin/C3a and DUSP26-directed therapies may represent a novel approach to achieve beta cell health to treat and prevent type 2 diabetes.

Regulation of hyperglycemia in diabetic mice by autolysates from β-mannanase-treated brewer's yeast.

Diabetes mellitus is a serious chronic disease, characterized by hyperglycemia. This study administered either β-mannanase-treated yeast cell autolysis supernatant (YCS) or yeast cell-wall residues after autolysis (YCR) to investigate their influence on the alleviation of diabetes in a diabetic mouse model. Application of either YCS or YCR led to body weight gain, blood glucose reduction, and an improvement in lipid composition in the diabetic mice. Administration of YCS was more effective in inhibiting oxidative stress than YCR. The expression of PPARα and CPT1α was enhanced, improving lipid biosynthesis, and Trx1 and HIF-1-α genes were downregulated due to the activation of thioredoxin following the interventions, indicating that the processes of lipid metabolism and oxidative stress were heavily involved in the reduction of diabetic characteristics following the interventions. The current study revealed that consumption of YCR also led to a reduction in hyperglycemia, this being associated with its richness in mineral elements, such as chromium and selenium. This study may highlight the potential of both YCS and YCR as functional ingredients in dietary formula for improving diabetic syndromes. © 2019 Society of Chemical Industry.

5,7-Dimethoxy-3-(2′-hydroxybenzyl)-4-chromanone inhibits α-glucosidase in vitro and alleviates postprandial hyperglycemia in diabetic mice

This study was designed to investigate the inhibitory activities of 5,7-dimethoxy-3-(2′hydro-xybenzyl)-4-chromanone (5,7-D chromanone) isolated from Portulaca oleracea L. on carbohydrate digesting enzymes and its ability to improve postprandial hyperglycemia in streptozotocin-induced diabetic mice. 5,7-D chromanone strongly inhibited α-glucosidase and α-amylase (half-maximal inhibitory concentration, IC50; 15.03 ± 2.59 μM and 12.39 ± 2.16 μM, respectively). The inhibitions were more effective than acarbose, which was the positive control. The increase in blood glucose level after ingesting starch was more significantly alleviated in the 5,7-D chromanone ingested group than in the control group of diabetic mice. In the control group, blood glucose levels were 24.64 ± 1.73, 27.22 ± 1.58, and 26.37 ± 1.41 mM, and in the 5,7-D chromanone ingested group were 23.87 ± 1.10, 23.38 ± 1.32, and 21.42 ± 1.36 mM at 30, 60, and 120 min, respectively. In addition, the area under the curve of blood glucose significantly declined with 5,7-D chromanone ingestion in diabetic mice. The results indicate that 5,7-D chromanone can help lower postprandial hyperglycemia by inhibiting carbohydrate digesting enzymes.

Micro-RNA-27a/b negatively regulates hepatic gluconeogenesis by targeting FOXO1.

In the context of hepatic insulin resistance, hepatic gluconeogenesis is abnormally increased, which results in increased hepatic glucose production and hyperglycemia, but the underlying mechanisms remain to be fully elucidated. Micro-RNAs (miRNAs) have been identified as critical regulators of diabetes and other metabolic disorders. In this study, we found that the expressions of miRNA-27 family members miRNA-27a and miRNA-27b (miR-27a/b) decreased significantly in the livers of diabetic mice. Moreover, the levels of miR-27a/b increased in the serum of patients with type 2 diabetes. Our present results showed that inhibition of miR-27a/b expression led to increased hepatic protein levels of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase and enhanced hepatic gluconeogenesis in vitro and in vivo. Overexpression of miR-27a/b suppressed hepatic glucose output and alleviated hyperglycemia in diabetic mice. Further study revealed that forkhead box O1 (FOXO1) is a downstream target of miR-27a/b. Taken together, we found novel evidence suggesting that miR-27a/b contributes to hepatic gluconeogenesis through targeting FOXO1 and provided novel mechanistic insight into the pathophysiology of insulin resistance.

A New Way for Beta Cell Neogenesis: Transdifferentiation from Alpha Cells Induced by Glucagon-Like Peptide 1.

Recent studies showed that alpha cells, especially immature cells and proalpha cells, might be the precursors of beta cells. Exposure to glucagon-like peptide 1 (GLP1) can ameliorate hyperglycemia in diabetic mice and restore the beta cell mass. In the present study, we adopted single high-dose (60 mg/kg, i.p.) streptozotocin (STZ) to model diabetes mellitus (DM) and randomly assigned short-tail (SD) rats to a normal group, a diabetic group, GLP1 groups (50 μg/kg, 100 μg/kg, and 200 μg/kg), a GLP1 (200 μg/kg) with exendin (9-39) group, and a GLP1 with LY294002 group. We found that the pancreatic insulin-glucagon-positive cell populations increased according to the increase in GLP1 exposure. By contrast, no insulin-amylase-positive cell populations or insulin/pan-cytokeratin cells were observed in the pancreatic sections. The GLP1 receptor antagonist exendin (9-39) and the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) family inhibitor LY294002 not only suppressed protein kinase B (Akt), pancreatic and duodenal homeobox 1 (Pdx1), forkhead box O 1 (FoxO1), and mast cell function-associated antigen A (MafA) mRNA expression but also increased MAFB expression. We concluded that treatment with GLP1 might result in beta cell neogenesis by promoting the transdifferentiation of alpha cells but not by pancreatic acinar cells, ductal cells, or the self-replication of beta cells. The regulation on the GLP1 receptor and its downstream transcription factor PI3K/AKT/FOXO1 pathway, which causes increased pancreatic and duodenal homeobox 1 (Pdx1) and MafA mRNA expression but causes decreased MAFB expression, may be the mechanism involved in this process.

Resveratroloside Alleviates Postprandial Hyperglycemia in Diabetic Mice by Competitively Inhibiting α-Glucosidase.

The regulation of postprandial blood glucose (PBG) levels is an effective therapeutic method to treat diabetes and prevent diabetes-related complications. Resveratroloside is a monoglucosylated form of stilbene that is present in red wine, grapes, and several traditional medicinal plants. In our study, the effect of resveratroloside on reducing PBG was studied in vitro and in vivo. In comparison to the starch treatment alone, the oral administration of resveratroloside-starch complexes significantly inhibited the PBG increase in a dose-dependent pattern in normal and diabetic mice. The PBG level treated with resveratrol (30 mg/kg) was not lower than that of resveratroloside. Further analyses demonstrated that resveratroloside strongly and effectively inhibited α-glucosidase, with an 50% inhibitory concentration value of 22.9 ± 0.17 μM, and its inhibition was significantly stronger than those of acarbose and resveratrol (264 ± 3.27 and 108 ± 2.13 μM). Moreover, a competitive inhibition mechanism of resveratroloside on α-glucosidase was determined by enzyme kinetic assays and molecular docking experiments. The molecular docking of resveratroloside with α-glucosidase demostrated the competitive inhibitory effect of resveratroloside, which occupies the catalytic site and forms strong hydrogen bonds with the residues of α-glucosidase. Resveratrol was also determined to be a competitive inhibition mechanism on α-glucosidase by enzyme kinetic assays and molecular docking experiments. This study suggested that resveratroloside had the ability to regulate PBG levels and can be considered a potential agent for the treatment of diabetes mellitus.

Pheophorbide A from Gelidium amansii improves postprandial hyperglycemia in diabetic mice through α-glucosidase inhibition.

This study was designed to determine the inhibitory effects of pheophorbide A on carbohydrate digesting enzymes and its ability to improve postprandial hyperglycemia in streptozotocin (STZ)-induced diabetic mice. Pheophorbide A caused noticeable inhibitory effects on α-glucosidase and α-amylase, with half-maximal inhibitory concentrations (IC50 ) of 80.65±5.90 and 76.48±6.31μM, respectively. The pheophorbide-mediated inhibition of α-glucosidase and α-amylase was significantly more effective than that of the positive control, acarbose. The increase in postprandial blood glucose levels was more significantly suppressed in the pheophorbide A group than in the control group of STZ-induced diabetic mice. In addition, the area under the curve was decreased by pheophorbide A intake in STZ-induced diabetic mice. Our results suggested that pheophorbide A may help to improve postprandial hyperglycemia by inhibiting the activity of carbohydrate digesting enzymes.

Definitive endoderm differentiation is promoted in suspension cultured human iPS-derived spheroids more than in adherent cells.

Human pluripotent stem cells (hPSCs), such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are very attractive cell sources for the treatment of diabetes mellitus, because numerous cells can be obtained using their infinite proliferation potential to overcome the paucity of donor islets. Advances in differentiation protocols make it possible to generate glucose responsive hPSC-beta cells, which can ameliorate hyperglycemia in diabetic mice. These protocols have mainly been based on an adherent culture system. However, in clinical applications, suspension culture methods are more suitable for large-scale culture. There are reports that suspension culture and spheroid formation promote differentiation in various cell types, including hPSCs, but, to our knowledge, there are no reports comparing gene expression patterns between suspension and adherent cultured human iPSCs (hiPSCs) during definitive endoderm (DE) differentiation. In this study, we chose several stage marker genes, not only for DE but also for posterior epiblast and primitive streak, and we examined their time course expression in suspension and adherent cultures by quantitative PT-PCR (qPCR), western blot, flow cytometry and immunocytochemistry. Our results demonstrate that expressions of these marker genes are faster and more strongly induced in suspension culture than in adherent culture during the DE differentiation process, indicating that suspension culture favors DE differentiation.

EP4 receptor-associated protein regulates gluconeogenesis in the liver and is associated with hyperglycemia in diabetic mice.

Prostaglandin E2 receptor 4-associated protein (EPRAP) is a key molecule in suppressing inflammatory responses in macrophages. EPRAP is expressed not only in macrophages but also in hepatocytes; however, the role of EPRAP in hepatocytes has not yet been defined. To examine the physiological role of hepatic EPRAP in mice, we performed the glucose tolerance test and the hyperinsulinemic-euglycemic clamp in high-fat sucrose diet (HFSD)-fed wild-type (WT) and Eprap null mice. We evaluated the contribution of EPRAP to gluconeogenesis by pyruvate tolerance test and primary hepatocyte experiments. Furthermore, lentivirus-expressing Eprap-specific small-hairpin RNA was injected in db/ db mice. HFSD-fed Eprap null mice had significantly lower blood glucose levels than HFSD-fed WT mice. Eprap null mice also had low glucose levels after fasting or pyruvic acid injection. Moreover, primary hepatocytes from Eprap-deficient mice showed decreased glucose production and lower expression of the Phosphoenol pyruvate carboxykinase and Glucose 6-phosphatase genes. Lentivirus-mediated hepatic Eprap suppression decreased glucose levels and the expression of gluconeogenic genes in db/ db mice. We conclude that EPRAP regulates gluconeogenesis in hepatocytes and is associated with hyperglycemia in diabetic mice. Our data suggest that suppression of EPRAP could be a novel strategy for the treatment of diabetes.

Preoperative Protein or Methionine Restriction Preserves Wound Healing and Reduces Hyperglycemia

BackgroundDietary restriction (DR), defined as reduced nutrient intake without malnutrition, is associated with longevity extension, improved glucose metabolism, and increased stress resistance, but also poor wound healing. Short-term preoperative DR followed by a return to normal feeding after surgery results in improved surgical outcomes in preclinical models. However, the effect of preoperative DR on wound healing and perioperative glucose homeostasis is currently unknown. Here, we tested the effects of two different preoperative DR regimens—protein restriction (PR) and methionine restriction (MR)—on wound healing and perioperative glucose homeostasis using an established murine model of wound healing in both nondiabetic and diabetic mice. Materials and methodsSurgical outcomes were tested using the McFarlane flap in nondiabetic and streptozotocin-induced diabetic mice. Short-term dietary preconditioning included 1 wk of PR or MR diet (1-2 wk) versus an isocaloric complete diet before surgery; all mice were returned to a complete diet postoperatively. Outcome measures of flap wound recovery included skin viability and laser Doppler imaging of flap perfusion and assessment of CD45+ cell infiltration. Glucose homeostasis was assessed by glucose tolerance testing and by perioperative glucose levels in the diabetic cohort. ResultsNo significant differences were observed in percentage of viable skin, perfusion, or immune cell infiltration at 7-10 d after surgery in PR or MR mice compared with controls in healthy or diabetic mice. Preoperative glucose tolerance and postoperative glucose levels were however significantly improved by both PR and MR in diabetic mice. ConclusionsShort-term dietary preconditioning with PR or MR did not impair wound healing in nondiabetic or diabetic mice. However, both regimens reduced preoperative hyperglycemia in diabetic mice. Thus, brief preoperative dietary manipulations stand as strategies to potentially improve perioperative hyperglycemia with no deleterious effects on wound healing in mice.

The liver surface as a favorable site for islet cell sheet transplantation in type 1 diabetes model mice.

IntroductionIslet transplantation is one of the most promising therapeutic approaches for patients with severe type 1 diabetes mellitus (T1DM). Transplantation of engineered islet cell sheets holds great potential for treating T1DM as it enables the creation of stable neo-islet tissues. However, a large mass of islet cell sheets is required for the subcutaneous transplantation to reverse hyperglycemia in diabetic mice. Here, we investigated whether the liver surface could serve as an alternative site for islet cell sheet transplantation.MethodsDispersed rat islet cells (0.8 × 106 cells) were cultured on laminin-332-coated thermoresponsive culture dishes. After 2 days of cultivation, we harvested the islet cell sheets by lowering the culture temperature using a support membrane with a gelatin gel. We transplanted two recovered islet cell sheets into the subcutaneous space or onto the liver surface of severe combined immunodeficiency (SCID) mice with streptozocin-induced diabetes.ResultsIn the liver surface group, the non-fasting blood glucose level decreased rapidly within several days after transplantation. In marked contrast, the hyperglycemia state was maintained in the subcutaneous space transplantation group. The levels of rat C-peptide and insulin in the liver surface group were significantly higher than those in the subcutaneous space group. An immunohistological analysis confirmed that most of the islet cells engrafted on the liver surface were insulin-positive. The CD31-positive endothelial cells formed vascular networks within the neo-islets and in the surrounding tissues. In contrast, viable islet cells were not found in the subcutaneous space group.ConclusionsCompared with the subcutaneous space, a relatively small mass of islet cell sheets was enough to achieve normoglycemia in diabetic mice when the liver surface was selected as the transplantation site. Our results demonstrate that the optimization of the transplantation site for islet cell sheets leads to significant improvements in the therapeutic efficiency for T1DM.

CRY1 dysregulation leads to hyperglycemia in diabetic mice

Hepatic glucose production (HGP) is essential for maintenance of normal glucose homeostasis. Glucagon promotes hepatic gluconeogenesis to increase the level of blood glucose upon fasting. However, during the postprandial state, insulin suppresses HGP via FOXO1 regulation. In diabetes, HGP dysregulation and insulin resistance contributes to hyperglycemia. Recently, it has been reported that CRY1 could act as a potential suppressor of hepatic gluconeogenesis by FOXO1 protein degradation. We previously reported that the level of CRY1 protein was decreased in the liver of obese and diabetic animals. However, the underlying mechanism for hepatic CRY1 dysregulation has not been thoroughly elucidated. In order to find out which factors are involved in CRY1 degradation, we screened CRY1 binding proteins in the liver of diabetic mice. We discovered that several candidate proteins appear to physically associate with CRY1 to mediate its stability. Our data support that CRY1 binding proteins could regulate CRY1 protein stability, providing a clue to understand the mechanism for hyperglycemia through CRY1 dysregulation in the liver of diabetic mice.Support or Funding InformationThis work was supported by NRF of Korea Grant MSIP 2011‐0018312 and BK21.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ultrafast glucose-responsive, high loading capacity erythrocyte to self-regulate the release of insulin

Insulin (INS) delivery system that can mimic normal insulin secretion to maintain the blood glucose level (BGL) in the normal range is an ideal treatment for diabetes. However, most of the existing closed-loop INS delivery systems respond slowly to the changes in BGL, resulting in a time lag between the abnormal BGL and the release of INS, which is not suitable for practical application. In this study, glucose oxidase (GOx)-modified erythrocytes are used as INS carriers (GOx-INS-ER) that can rapidly self-regulate the release of INS upon the changes in BGL. In this system, glucose can be broken down into gluconic acid and hydrogen peroxide by GOx-INS-ER, and the latter will rupture the erythrocyte membrane to release INS within minutes. A pulsatile release of INS can be achieved upon the changes in the glucose concentration. This GOx-INS-ER enables diabetic rats to overcome hyperglycemia within 1 h, and a single injection of this GOx-INS-ER into the STZ-induced diabetic rats can maintain the BGL in the normal range up to 9 days. Statement of SignificanceDiabetes mellitus has been a major public health threatener with global prevalence. Although, glucose-responsive carriers that can release insulin (INS) in a closed loop have been explored greatly in recent years, their sluggish glucose-responsive property and low INS-loading content greatly restrict their practical application [ACS Nano, 2013, 7, 4194].In this work, we reported INS-loaded erythrocytes featuring ultrafast glucose-responsive property and high INS loading content, which could release INS in a closed loop. These GOX-INS-ERs could respond to the changes in glucose level within several minutes and self-regulate the release of INS for a long time. Single injection of GOX-INS-ER can overcome hyperglycemia in diabetic mice within 1 h and maintain the baseline level of glucose up to 9 days. We think our method may provide a robust way to potentiate diabetes treatment.