Insulin-deficient Diabetic Mice Research Articles

A Glucose-Responsive Cannula for Automated and Electronics-Free Insulin Delivery.

Automated delivery of insulin based on continuous glucose monitoring is revolutionizing the way insulin-dependent diabetes is treated. However, challenges remain for the widespread adoption of these systems, including the requirement of a separate glucose sensor, sophisticated electronics and algorithms, and the need for significant user input to operate these costly therapies. Herein, a user-centric glucose-responsive cannula is reported for electronics-free insulin delivery. The cannula-made from a tough, elastomer-hydrogel hybrid membrane formed through a one-pot solvent exchange method-changes permeability to release insulin rapidly upon physiologically relevant varying glucose levels, providing simple and automated insulin delivery with no additional hardware or software. Two prototypes of the cannula are evaluated in insulin-deficient diabetic mice. The first cannula-an ends-sealed, subcutaneously inserted prototype-normalizes blood glucose levels for 3d and controls postprandial glucose levels. The second, more translational version-a cannula with the distal end sealed and the proximal end connected to a transcutaneous injection port-likewise demonstrates tight, 3-d regulation of blood glucose levels when refilled twice daily. This proof-of-concept study may aid in the development of "smart" cannulas and next-generation insulin therapies at a reduced burden-of-care toll and cost to end-users.

Pharmacologic Inhibition of Myostatin With a Myostatin Antibody Improves the Skeletal Muscle and Bone Phenotype of Male Insulin-Deficient Diabetic Mice.

Type 1 diabetes (T1D) is associated with low bone and muscle mass, increased fracture risk, and impaired skeletal muscle function. Myostatin, a myokine that is systemically elevated in humans with T1D, negatively regulates muscle mass and bone formation. We investigated whether pharmacologic myostatin inhibition in a mouse model of insulin-deficient, streptozotocin (STZ)-induced diabetes is protective for bone and skeletal muscle. DBA/2J male mice were injected with low-dose STZ (diabetic) or vehicle (non-diabetic). Subsequently, insulin or palmitate Linbits were implanted and myostatin (REGN647-MyoAb) or control (REGN1945-ConAb) antibody was administered for 8 weeks. Body composition and contractile muscle function were assessed in vivo. Systemic myostatin, P1NP, CTX-I, and glycated hemoglobin (HbA1c) were quantified, and gastrocnemii were weighed and analyzed for muscle fiber composition and gene expression of selected genes. Cortical and trabecular parameters were analyzed (micro-computed tomography evaluations of femur) and cortical bone strength was assessed (three-point bending test of femur diaphysis). In diabetic mice, the combination of insulin/MyoAb treatment resulted in significantly higher lean mass and gastrocnemius weight compared with MyoAb or insulin treatment alone. Similarly, higher raw torque was observed in skeletal muscle of insulin/MyoAb-treated diabetic mice compared with MyoAb or insulin treatment. Additionally, muscle fiber cross-sectional area (CSA) was lower with diabetes and the combination treatment with insulin/MyoAb significantly improved CSA in type II fibers. Insulin, MyoAb, or insulin/MyoAb treatment improved several parameters of trabecular architecture (eg, bone volume fraction [BV/TV], trabecular connectivity density [Conn.D]) and cortical structure (eg, cortical bone area [Ct. Ar.], minimum moment of inertia [Imin]) in diabetic mice. Lastly, cortical bone biomechanical properties (stiffness and yield force) were also improved with insulin or MyoAb treatment. In conclusion, pharmacologic myostatin inhibition is beneficial for muscle mass, muscle function, and bone properties in this mouse model of T1D and its effects are both independent and additive to the positive effects of insulin. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Protective Effects of Hemp (Cannabis sativa) Root Extracts against Insulin-Deficient Diabetes Mellitus In Mice.

The pharmacological potential of industrial hemp (Cannabis sativa) has been widely studied. However, the majority of studies have focused on cannabidiol, isolated from the inflorescence and leaf of the plant. In the present study, we evaluated the anti-diabetic potential of hemp root water (HWE) and ethanol extracts (HEE) in streptozotocin (STZ)-induced insulin-deficient diabetic mice. The administration of HWE and HEE ameliorated hyperglycemia and improved glucose homeostasis and islet function in STZ-treated mice (p < 0.05). HWE and HEE suppressed β-cell apoptosis and cytokine-induced inflammatory signaling in the pancreas (p < 0.05). Moreover, HWE and HEE normalized insulin-signaling defects in skeletal muscles and apoptotic response in the liver and kidney induced by STZ (p < 0.05). Gas chromatography-mass spectrometry analysis of HWE and HEE showed possible active compounds which might be responsible for the observed anti-diabetic potential. These findings indicate the possible mechanisms by which hemp root extracts protect mice against insulin-deficient diabetes, and support the need for further studies geared towards the application of hemp root as a novel bioactive material.

Naringenin and Phytoestrogen 8-Prenylnaringenin Protect against Islet Dysfunction and Inhibit Apoptotic Signaling in Insulin-Deficient Diabetic Mice.

It has been shown that citrus flavanone naringenin and its prenyl derivative 8-prenylnaringenin (8-PN) possess various pharmacological activities in in vitro and in vivo models. Interestingly, it has been proposed that prenylation can enhance biological potentials, including the estrogen-like activities of flavonoids. The objective of this study was to investigate the anti-diabetic potential and molecular mechanism of 8-PN in streptozotocin (STZ)-induced insulin-deficient diabetic mice in comparison with naringenin reported to exhibit hypoglycemic effects. The oral administration of naringenin and 8-PN ameliorated impaired glucose homeostasis and islet dysfunction induced by STZ treatment. These protective effects were associated with the suppression of pancreatic β-cell apoptosis and inflammatory responses in mice. Moreover, both naringenin and 8-PN normalized STZ-induced insulin-signaling defects in skeletal muscles and apoptotic protein expression in the liver. Importantly, 8-PN increased the protein expression levels of estrogen receptor-α (ERα) in the pancreas and liver and of fibroblast growth factor 21 in the liver, suggesting that 8-PN could act as an ERα agonist in the regulation of glucose homeostasis. This study provides novel insights into the mechanisms underlying preventive effects of naringenin and 8-PN on the impairment of glucose homeostasis in insulin-deficient diabetic mice.

GABA and insulin but not nicotinamide augment α- to β-cell transdifferentiation in insulin-deficient diabetic mice

AimPoorly controlled diabetes is characterised by a partial or complete loss of pancreatic islet β-cells, which deprives the remaining islet cells of important β-cell-derived soluble signals, such as insulin or GABA. We aimed to dissect the role of the two signals in the development of islet α-cells, focusing specifically on α-/β-cell transdifferentiation and using the stem cell differentiation factor nicotinamide as a comparator. MethodsStreptozotocin (STZ)-treated diabetic mice expressing a fluorescent reporter in pancreatic islet α-cells were injected with GABA (10 mg/kg once daily), nicotinamide (150 mg/kg once daily) or insulin (1U/kg three times daily) for 10 days. The impact of the treatment on metabolic status of the animals as well as the morphology, proliferative potential and transdifferentiation of pancreatic islet cells was assessed using biochemical methods and immunofluorescence. ResultsMetabolic status of STZ-diabetic mice was not dramatically altered by the treatment interventions, although GABA therapy did reduce circulating glucagon and augment pancreatic insulin stores. The effects of the exogenous agents on islet β-cells ranged from the attenuation of apoptosis (insulin, nicotinamide) to enhancement of proliferation (GABA). Furthermore, insulin and GABA but not nicotinamide enhanced the differentiation of α-cells into β-cells and increased relative number of ‘bihormonal’ cells, expressing both insulin and glucagon. ConclusionsOur data suggest a role for endogenous insulin and GABA signalling in α-cell plasticity, which is likely to bypass the common nicotinamide-sensitive stem cell differentiation pathway.

Glucose-responsive insulin patch for the regulation of blood glucose in mice and minipigs

Glucose-responsive insulin delivery systems that mimic pancreatic endocrine function could enhance health and improve quality of life for people with type 1 and type 2 diabetes with reduced β-cell function. However, insulin delivery systems with rapid in vivo glucose-responsive behaviour typically have limited insulin-loading capacities and cannot be manufactured easily. Here, we show that a single removable transdermal patch, bearing microneedles loaded with insulin and a non-degradable glucose-responsive polymeric matrix, and fabricated via in situ photopolymerization, regulated blood glucose in insulin-deficient diabetic mice and minipigs (for minipigs >25 kg, glucose regulation lasted >20 h with patches of ~5 cm2). Under hyperglycaemic conditions, phenylboronic acid units within the polymeric matrix reversibly form glucose–boronate complexes that—owing to their increased negative charge—induce the swelling of the polymeric matrix and weaken the electrostatic interactions between the negatively charged insulin and polymers, promoting the rapid release of insulin. This proof-of-concept demonstration may aid the development of other translational stimuli-responsive microneedle patches for drug delivery. A single removable transdermal patch bearing microneedles loaded with insulin and a non-degradable glucose-responsive polymeric matrix regulates blood glucose in insulin-deficient diabetic mice and minipigs.

480-P: Reversal of Diabetic Nephropathy in T2D db/db Mouse Model by Systemic Pyruvate Kinase M2 (PKM2) Activation

Mitochondrial abnormalities induced by diabetes have been postulated to cause several complications including nephropathy. Elevated expressions of enzymes for glycolysis and mitochondrial functions in the glomeruli have been associated with protection against the development of diabetic nephropathy of chronic duration. Activation of a glycolytic enzyme, pyruvate kinase M2 (PKM2), by a small molecule selective activator (TEPP-46) or its targeted overexpression to the podocytes in mice reversed glomerular mitochondrial dysfunction and pathology in insulin deficient diabetic mice. However, the effects of PKM2 activation to stop glomerular dysfunction and pathology have not been studied in animal models of type 2 diabetes (T2D). Thus, we studied the effect of activating glycolysis and mitochondrial metabolism with PKM2 activator, TEPP-46, in db/db mice (with obesity and hyperglycemia) and BLKS mice on regular diet (RD) or high fat diet (HFD). HFD feeding induced obesity in BLKS but did not cause changes in glomerular PKM activities or functions as measured by urinary albumin to creatinine ratio (ACR). Oral feeding with TEPP-46 did not affect body weight (BW), glucose tolerance, lipids, ACR, glomerular pathology in BLKS mice on RD or HFD. In contrast, db/db mice on RD had elevated BW and hyperglycemia that were significantly increased by HFD, which also induced loss of glomerular PKM2 protein expression and activities, elevations of gene expression for fibrosis (fibronectin, TGF-b), mesangial expansion and ACR after 3 months. Intervention with oral TEPP-46 treatment for 3 months, but not 1 month, after 3 months of diabetes and HFD, (total of 6 months of diabetes), improved significantly both glomerular PK activities and ACR, without lowering hyperglycemia and hyperlipidemia of the db/db mice. These findings support the idea that systemic activation of PKM2 can improve renal functions in both T1D and T2D. Disclosure R. St-Louis: None. J. Fu: None. K. Park: None. T. Shinjo: None. J. Ludeke: None. H. Yokomizo: None. Q. Li: None. E. Wolfson: None. G.L. King: Research Support; Self; Janssen Pharmaceuticals, Inc.

Glucose-responsive insulin patch for the regulation of blood glucose in mice and minipigs.

Glucose-responsive insulin delivery systems that mimic pancreatic endocrine function could enhance health and improve quality of life for people with type 1 and type 2 diabetes with reduced β-cell function. However, insulin delivery systems with rapid in vivo glucose-responsive behaviour typically have limited insulin-loading capacities and cannot be manufactured easily. Here, we show that a single removable transdermal patch, bearing microneedles loaded with insulin and a non-degradable glucose-responsive polymeric matrix, and fabricated via in situ photopolymerization, regulated blood glucose in insulin-deficient diabetic mice and minipigs (for minipigs >25 kg, glucose regulation lasted >20 h with patches of ~5 cm2). Under hyperglycaemic conditions, phenylboronic acid units within the polymeric matrix reversibly form glucose-boronate complexes that-owing to their increased negative charge-induce the swelling of the polymeric matrix and weaken the electrostatic interactions between the negatively charged insulin and polymers, promoting the rapid release of insulin. This proof-of-concept demonstration may aid the development of other translational stimuli-responsive microneedle patches for drug delivery.

Characterization of Glycolytic Enzymes and Pyruvate Kinase M2 in Type 1 and 2 Diabetic Nephropathy.

Elevated glycolytic enzymes in renal glomeruli correlated with preservation of renal function in the Medalist Study, individuals with ≥50 years of type 1 diabetes. Specifically, pyruvate kinase M2 (PKM2) activation protected insulin-deficient diabetic mice from hyperglycemia-induced glomerular pathology. This study aims to extend these findings in a separate cohort of individuals with type 1 and type 2 diabetes and discover new circulatory biomarkers for renal protection through proteomics and metabolomics of Medalists' plasma. We hypothesize that increased glycolytic flux and improved mitochondrial biogenesis will halt the progression of diabetic nephropathy. Immunoblots analyzed selected glycolytic and mitochondrial enzymes in postmortem glomeruli of non-Medalists with type 1 diabetes (n = 15), type 2 diabetes (n = 19), and no diabetes (n = 5). Plasma proteomic (SOMAscan) (n = 180) and metabolomic screens (n = 214) of Medalists with and without stage 3b chronic kidney disease (CKD) were conducted and significant markers validated by ELISA. Glycolytic (PKM1, PKM2, and ENO1) and mitochondrial (MTCO2) enzymes were significantly elevated in glomeruli of CKD- versus CKD+ individuals with type 2 diabetes. Medalists' plasma PKM2 correlated with estimated glomerular filtration rate (r 2 = 0.077; P = 0.0002). Several glucose and mitochondrial enzymes in circulation were upregulated with corresponding downregulation of toxic metabolites in CKD-protected Medalists. Amyloid precursor protein was also significantly upregulated, tumor necrosis factor receptors downregulated, and both confirmed by ELISA. Elevation of enzymes involved in the metabolism of intracellular free glucose and its metabolites in renal glomeruli is connected to preserving kidney function in both type 1 and type 2 diabetes. The renal profile of elevated glycolytic enzymes and reduced toxic glucose metabolites is reflected in the circulation, supporting their use as biomarkers for endogenous renal protective factors in people with diabetes.

NADPH Oxidase Nox5 Aggravates Renal Injury in Akita Mouse Model of Diabetic Nephropathy

Background: Renal reactive oxygen species (ROS) play an important role in mediating kidney injury in diabetes. Increasing evidence suggests that the pro-oxidant enzyme, Nox5 plays a significant role in human diabetic nephropathy (DN). Nox5 is present in humans and rabbits but not in mice or rats. Thus, there is a paucity of information about Nox5 in conventional animal models of DN. We examined the role of Nox5 in the insulin deficient diabetic Akita mice model using human inducible transgenic mice that express Nox5 selectively in endothelial cells (VEcad+Nox5+) or in mesangial cells (SM22+Nox5+). We also examined the endogenous expression of Nox5 in a high fat fed rabbit model of kidney disease. Methods: At week 10 mice were culled and kidneys were removed for the assessment of structural damage as well as gene and protein expression of markers of inflammation, fibrosis and oxidative stress. Protein expression of Nox5 and its localization in glomerular cells (endothelial and mesangial cells) were examined in transgenic mice by immunostaining. We also examined expression of pro-fibrotic gene in high fat fed rabbits by next generation sequencing (NGS) and RT-PCR and renal injury by histochemistry. Results: Expression of Nox5 was confirmed in glomerular endothelial and mesangial cells of transgenic mice. Diabetes induced increase in glomerulosclerosis, gene and protein expression of fibronectin and MCP-1 as well as nitrotyrosine were further increase in both diabetic Nox5 transgenic mice. Moreover, increased expression of Nox5 in high fat fed rabbits vs. normal diet fed rabbits was associated with increased expression of fibronectin, CTGF, collagen IV and VCAM-1 as well as increased mesangial expansion in the kidney. Conclusions: These findings in both transgenic mice model (endothelial and mesangial cells) suggest that Nox5 plays a significant role in mediating renal injury in diabetes. Disclosure J.C. Jha: None. A. Dai: None. M.E. Cooper: Advisory Panel; Self; AbbVie Inc.. Research Support; Self; Boehringer Ingelheim GmbH. Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Speaker's Bureau; Self; Eli Lilly and Company. Advisory Panel; Self; Merck Sharp &amp; Dohme Corp., AstraZeneca. Research Support; Self; Novo Nordisk A/S. Advisory Panel; Self; Novartis AG. R.M. Touyz: None. C. Kennedy: Research Support; Self; Prometic Life Sciences Inc.. K. Jandeleit-Dahm: None.

Insulin Deficiency Is a Major Contributor to Atrial Fibrillation

Diabetes has been identified as a major independent risk factor for atrial fibrillation (AF), the most common sustained cardiac arrhythmia. However, it is unknown whether glucose and insulin disturbances observed during diabetes directly affect the function of the atria, leading to AF. Thus, we hypothesized that insulin deficiency and impaired glucose transport provide a metabolic substrate for the development and maintenance of AF during diabetes. Transesophageal atrial pacing was used to induce AF in healthy, streptozotocin-induced type 1 diabetic and insulin-treated (via a subcutaneous pump) diabetic mice (n=4-11/group). Translocation of insulin-sensitive glucose transporters (GLUTs) was measured using a photolabeled biotinylation assay in the perfused heart. Atrial fibrosis and glycogen accumulation were measured using histological analyses. As expected, insulin-deficient diabetic mice displayed hyperglycemia (434 ± 50.9 mg/dl) while insulin-treated diabetic mice remained euglycemic (118.8 ± 3.3 mg/dl, p&amp;lt;0.05). At 8 weeks, diabetic mice displayed increased duration and frequency of AF episodes vs. age-matched controls (e.g., AF duration: 18.7 ± 6.2 s vs. 1.8 ± 1.1 s, respectively, p=0.032), whereas insulin-treated diabetic animals did not. In addition, the frequency of AF episodes was significantly correlated to blood glucose level (p=0.01). GLUT-4 and -8 translocation to the atrial cell surface was significantly downregulated in diabetic mice (by 67% and 79%, respectively; p≤0.001), and rescued by insulin treatment. We did not observe any fibrosis or glycogen accumulation in the atria of (treated and untreated) diabetic mice. We conclude that, in the absence of structural remodeling and atrial fibrosis, insulin and glucose disturbances were sufficient to induce AF during diabetes. Therefore, these data suggest that insulin deficiency during diabetes leads to alterations in glucose transport and energy production in the atria, which enhances its vulnerability to atrial fibrillation. Disclosure Z. Maria: None. A. Campolo: None. B.J. Scherlag: None. J.W. Ritchey: None. V. Lacombe: None.

Taurine improves glucose tolerance in STZ-induced insulin-deficient diabetic mice.

Blood glucose levels fluctuate considerably in diabetic patients with reduced secretion of endogenous insulin. We previously reported that glucagon is secreted excessively in these patients and that taurine increases glucagon secretion in vitro. Therefore, we hypothesized that glucose tolerance would further deteriorate when taurine was administered to diabetic mice incapable of insulin secretion. We generated four groups of streptozotocin (STZ)-treated C57BL/6J mice (STZ-mice): STZ-mice without taurine treatment (STZ-Con), STZ-mice treated with 0.5% (w/v) taurine (STZ-0.5% Tau), STZ-mice treated with 1% (w/v) taurine (STZ-1% Tau), and STZ-mice treated with 2% (w/v) taurine (STZ-2% Tau). Mice were treated for 4weeks, and then, we evaluated glucose tolerance, pancreatic β-cell area and α-cell area, pancreatic insulin and glucagon content, and daily blood glucose variability. As a result, following the administration of taurine, glucose tolerance improved, both pancreatic β- and α-cell area increased, and both insulin and glucagon content increased. In the 1% taurine administration group, blood glucose variability decreased. These unexpected results suggest that taurine improves glucose tolerance, in spite of its subsequent increased glucagon production, partly by increasing pancreatic β-cells and insulin production in vivo.

Fibroblast Growth Factor 21 Protects Photoreceptor Function in Type 1 Diabetic Mice

Retinal neuronal abnormalities occur before vascular changes in diabetic retinopathy. Accumulating experimental evidence suggests that neurons control vascular pathology in diabetic and other neovascular retinal diseases. Therefore, normalizing neuronal activity in diabetes may prevent vascular pathology. We investigated whether fibroblast growth factor 21 (FGF21) prevented retinal neuronal dysfunction in insulin-deficient diabetic mice. We found that in diabetic neural retina, photoreceptor rather than inner retinal function was most affected and administration of the long-acting FGF21 analog PF-05231023 restored the retinal neuronal functional deficits detected by electroretinography. PF-05231023 administration protected against diabetes-induced disorganization of photoreceptor segments seen in retinal cross section with immunohistochemistry and attenuated the reduction in the thickness of photoreceptor segments measured by optical coherence tomography. PF-05231023, independent of its downstream metabolic modulator adiponectin, reduced inflammatory marker interleukin-1β (IL-1β) mRNA levels. PF-05231023 activated the AKT-nuclear factor erythroid 2-related factor 2 pathway and reduced IL-1β expression in stressed photoreceptors. PF-05231023 administration did not change retinal expression of vascular endothelial growth factor A, suggesting a novel therapeutic approach for the prevention of early diabetic retinopathy by protecting photoreceptor function in diabetes.

Naringin Protects Pancreatic β-Cells Against Oxidative Stress-Induced Apoptosis by Inhibiting Both Intrinsic and Extrinsic Pathways in Insulin-Deficient Diabetic Mice.

Oxidative stress has been suggested to play a central role in the pathogenesis of diabetes, as well as other metabolic disorders. Naringin, a major flavanone glycoside in citrus species, has been shown to display strong antioxidant potential in in vitro and in vivo models of oxidative stress; however, the underlying protective mechanisms in diabetes are unclear. To study the protective effects and molecular mechanisms of naringin in preventing islet dysfunction and diabetes, we examined glucose homeostasis, β-cell apoptosis, and inflammatory response in insulin-deficient diabetic mice exposed to acute oxidative stress with streptozotocin (STZ). Naringin dose-dependently ameliorated hyperglycemia and islet dysfunction in insulin-deficient diabetic mice. Naringin counteracted STZ-induced β-cell apoptosis by inhibiting both the intrinsic (mitochondria-mediated) and extrinsic (death receptor-mediated) pathways. Furthermore, these protective effects were associated with suppression of DNA damage response and nuclear factor-kappa B- and mitogen-activated protein kinase-mediated signaling pathways, as well as reduction of reactive oxygen species accumulation and pro-inflammatory cytokine production in the pancreas. Taken together, our study provides insights into the underlying mechanisms through which naringin protects the pancreatic β-cells against oxidative stress-induced apoptosis.

Mesenchymal stem cell therapy ameliorates diabetic nephropathy via the paracrine effect of renal trophic factors including exosomes.

Bone marrow-derived mesenchymal stem cells (MSCs) have contributed to the improvement of diabetic nephropathy (DN); however, the actual mediator of this effect and its role has not been characterized thoroughly. We investigated the effects of MSC therapy on DN, focusing on the paracrine effect of renal trophic factors, including exosomes secreted by MSCs. MSCs and MSC-conditioned medium (MSC-CM) as renal trophic factors were administered in parallel to high-fat diet (HFD)-induced type 2 diabetic mice and streptozotocin (STZ)-induced insulin-deficient diabetic mice. Both therapies showed approximately equivalent curative effects, as each inhibited the exacerbation of albuminuria. They also suppressed the excessive infiltration of BMDCs into the kidney by regulating the expression of the adhesion molecule ICAM-1. Proinflammatory cytokine expression (e.g., TNF-α) and fibrosis in tubular interstitium were inhibited. TGF-β1 expression was down-regulated and tight junction protein expression (e.g., ZO-1) was maintained, which sequentially suppressed the epithelial-to-mesenchymal transition of tubular epithelial cells (TECs). Exosomes purified from MSC-CM exerted an anti-apoptotic effect and protected tight junction structure in TECs. The increase of glomerular mesangium substrate was inhibited in HFD-diabetic mice. MSC therapy is a promising tool to prevent DN via the paracrine effect of renal trophic factors including exosomes due to its multifactorial action.

Overexpressing IRS1 in Endothelial Cells Enhances Angioblast Differentiation and Wound Healing in Diabetes and Insulin Resistance.

The effect of enhancing insulin’s actions in endothelial cells (ECs) to improve angiogenesis and wound healing was studied in obesity and diabetes. Insulin receptor substrate 1 (IRS1) was overexpressed in ECs using the VE-cadherin promoter to create ECIRS1 TG mice, which elevated pAkt activation and expressions of vascular endothelial growth factor (VEGF), Flk1, and VE-cadherin in ECs and granulation tissues (GTs) of full-thickness wounds. Open wound and epithelialization rates and angiogenesis significantly improved in normal mice and high fat (HF) diet–induced diabetic mice with hyperinsulinemia in ECIRS1 TG versus wild type (WT), but not in insulin-deficient diabetic mice. Increased angioblasts and EC numbers in GT of ECIRS1 mice were due to proliferation in situ rather than uptake. GT in HF-fed diabetic mice exhibited parallel decreases in insulin and VEGF-induced pAkt and EC numbers by >50% without changes in angioblasts versus WT mice, which were improved in ECIRS1 TG mice on normal chow or HF diet. Thus, HF-induced diabetes impaired angiogenesis by inhibiting insulin signaling in GT to decrease the differentiation of angioblasts to EC, which was normalized by enhancing insulin’s action targeted to EC, a potential target to improve wound healing in diabetes and obesity.

Black Ginseng Extract Counteracts Streptozotocin-Induced Diabetes in Mice.

Black ginseng, a new type of processed ginseng that has a unique ginsenoside profile, has been shown to display potent pharmacological activities in in vitro and in vivo models. Although red ginseng is considered beneficial for the prevention of diabetes, the relationship between black ginseng and diabetes is unknown. Therefore, this study was designed to evaluate the anti-diabetic potential of black ginseng extract (BGE) in streptozotocin (STZ)-induced insulin-deficient diabetic mice, in comparison with red ginseng extract (RGE). HPLC analyses showed that BGE has a different ginsenoside composition to RGE; BGE contains Rg5 and compound k as the major ginsenosides. BGE at 200 mg/kg reduced hyperglycemia, increased the insulin/glucose ratio and improved islet architecture and β-cell function in STZ-treated mice. The inhibition of β-cell apoptosis by BGE was associated with suppression of the cytokine—induced nuclear factor–κB—mediated signaling pathway in the pancreas. Moreover, these anti-diabetic effects of BGE were more potent than those of RGE. Collectively, our data indicate that BGE, in part by suppressing cytokine—induced apoptotic signaling, protects β-cells from oxidative injury and counteracts diabetes in mice.

Anti-diabetic activity of recombinant irisin in STZ-induced insulin-deficient diabetic mice

In order to investigate the hypoglycemic effects and potential mechanism of recombinant irisin on diabetes, STZ-induced diabetic mice were established and treated with irisin. The results showed that daily water and food intake, and blood glucose significantly decreased after various concentrations of recombinant irisin treatment by intraperitoneal injection, of which 1.0mg/kg was the optimal dose for lowering blood glucose. However, the body weight exhibited no significant difference during the treatment within groups, although the 0.9% NaCl treated group showed a trend of decreased body weight and the irisin treated groups showed a tendency of increasing weight. The oral glucose tolerance was improved, and serum insulin and circulating irisin content were significantly elevated in diabetic mice after 1.0mg/kg irisin-injection treatment, compared to diabetic mice treated with 0.9% NaCl. 1.0mg/kg irisin-injection also significantly increased the expression of energy and metabolism-related genes. In addition, oral administration of irisin lowered the blood glucose in diabetic mice. Our data suggested that irisin could lower blood glucose in insulin-deficient diabetic mice, to some extent, through irisin-mediated induction of energy and metabolic genes expression. These observations laid a foundation for the development of irisin-based therapy.

Fibroblast growth factor 21 analogue LY2405319 lowers blood glucose in streptozotocin-induced insulin-deficient diabetic mice by restoring brown adipose tissue function.

To investigate the effects of LY2405319, an analogue of fibroblast growth factor 21 (FGF21), on glucose homeostasis in streptozotocin (STZ)-induced insulin-deficient mice (STZ mice). Nine-week-old male C57BL/6J mice were administered a single intraperitoneal injection of STZ (150 mg/kg). One week later, after confirmation of hyperglycaemia, saline or LY2405319 (5 mg/kg) was injected subcutaneously daily for 4 weeks. Changes in glucose homeostasis, energy metabolism and brown adipose tissue (BAT) function were assessed. The STZ mice had elevated blood glucose and reduced plasma FGF21 levels, impaired glucose uptake in the BAT, and BAT mitochondria with absent or swollen cristae and fewer lipid vacuoles. LY2405319 significantly reduced blood glucose levels and this was associated with increased BAT glucose uptake and changes in gene expression and morphology, indicating improved mitochondrial lipid metabolism in the BAT. Importantly, the ability of LY2405319 to lower blood glucose in STZ mice was compromised after removing interscapular BAT. Our results show that LY2405319 reduces blood glucose levels in insulin-deficient diabetes by improving BAT metabolism. Additional studies investigating the therapeutic potential of FGF21 for the treatment of type 1 diabetes are warranted.

Lipolysis, and not hepatic lipogenesis, is the primary modulator of triglyceride levels in streptozotocin-induced diabetic mice.

Diabetic hypertriglyceridemia is thought to be primarily driven by increased hepatic de novo lipogenesis. However, experiments in animal models indicated that insulin deficiency should decrease hepatic de novo lipogenesis and reduce plasma triglyceride levels. To address the discrepancy between human data and genetically altered mouse models, we investigated whether insulin-deficient diabetic mice had triglyceride changes that resemble those in diabetic humans. Streptozotocin-induced insulin deficiency increased plasma triglyceride levels in mice. Contrary to the mouse models with impaired hepatic insulin receptor signaling, insulin deficiency did not reduce hepatic triglyceride secretion and de novo lipogenesis-related gene expression. Diabetic mice had a marked decrease in postprandial triglycerides clearance, which was associated with decreased lipoprotein lipase and peroxisome proliferator-activated receptor α mRNA levels in peripheral tissues and decreased lipoprotein lipase activity in skeletal muscle, heart, and brown adipose tissue. Diabetic heterozygous lipoprotein lipase knockout mice had markedly elevated fasting plasma triglyceride levels and prolonged postprandial triglycerides clearance. Insulin deficiency causes hypertriglyceridemia by decreasing peripheral lipolysis and not by an increase in hepatic triglycerides production and secretion.