Type 2 Diabetes Animal Research Articles

Disruption of insulin receptor substrate 2 (IRS2) causes non-obese type 2 diabetes with β-cell dysfunction in the golden (Syrian) hamster

Because of the advent of genome-editing technology, gene knockout (KO) hamsters have become attractive research models for diverse diseases in humans. This study established a new KO model of diabetes by disrupting the insulin receptor substrate-2 (Irs2) gene in the golden (Syrian) hamster. Homozygous KO animals were born alive but with delayed postnatal growth until adulthood. They showed hyperglycemia, high HbA1c, and impaired glucose tolerance. However, they normally responded to insulin stimulation, unlike Irs2 KO mice, an obese type 2 diabetes (T2D) model. Consistent with this, Irs2 KO hamsters did not increase serum insulin levels upon glucose administration and showed β-cell hypoplasia in their pancreas. Thus, our Irs2 KO hamster provide a unique T2D animal model that is distinct from the obese T2D models. This model may contribute to a better understanding of the pathophysiology of human non-obese T2D with β-cell dysfunction, the most common type of T2D in East Asian countries, including Japan.

Animal Models for Understanding the Mechanisms of Beta Cell Death during Type 2 Diabetes Pathogenesis.

Type 2 diabetes (T2D) has become a worldwide epidemic, primarily driven by obesity from overnutrition and sedentariness. Recent results reveal there is heterogeneity in both pathology and treatment responses in T2D patients. Therefore, a variety of T2D animal models are necessary to obtain a mechanistic understanding of distinct disease processes. T2D results from insufficient insulin, either due to beta cell loss or inborn deficiency. Although decreases in beta cell mass can occur through loss of identity or cell death, in this review, we will highlight the T2D animal models that display beta cell death, including the Zucker Diabetic Fatty Rat, sand rat, db/db mouse, and a novel diabetic zebrafish model, the Zebrafish Muscle Insulin-Resistant (zMIR) fish. Procuring a mechanistic understanding of different T2D progression trajectories under a variety of contexts is paramount for developing and testing more individualized treatments.

The Role of NF-κB and Bax/Bcl-2/Caspase-3 Signaling Pathways in the Protective Effects of Sacubitril/Valsartan (Entresto) against HFD/STZ-Induced Diabetic Kidney Disease.

LCZ696 (valsartan/sacubitril) has the potential to slow the progression of diabetic kidney disease (DKD) according to previous reports. However, the renoprotective mechanism underlying LCZ696 remains unknown. This study aimed to investigate the therapeutic potential and underlying mechanism of LCZ696 in DKD in a type 2 diabetic (T2D) rat model. This model was established in this experiment by feeding a high-fat diet (HFD) for six weeks with a single dose of streptozotocin (STZ, 30 mg/kg body weight). Valsartan or LCZ696 was orally administered to T2D animals for eight weeks. HFD/STZ rats showed hyperglycemia, impaired insulin secretion, significant increases in urea, creatinine, cytokines, nuclear factor kappa B (NF-κB), oxidative stress, caspase-3 activity, glomerular and tubular damage, glomerulsclerosis, Bax and caspese-3 expressions along with a significant decline in IL-10, antioxidant markers, and Bcl-2 expression. The administration of LCZ696 to diabetic rats reduced the serum concentrations of glucose, urea, and creatinine. In addition, ELISA results demonstrated that diabetic rats treated with LCZ696 exhibited a reduction in inflammatory (IL-1β, TNF-α, IL-6) and an increase in anti-inflammatory (IL-10) cytokine levels. In addition, a notable decrease in NF-κB and caspase-3 activity was observed. At the level of renal tissue homogenate, diabetic animals treated with LCZ696 demonstrated clear restorations in GSH content and other antioxidant enzyme levels, in addition to a significant decrease in TBARS levels. In addition, LCZ696 inhibited the expression of the Bax and cleaved caspase-3 proteins and enhanced the expression of the Bcl-2 protein. Improvements in histopathological changes in kidney tissues confirmed and significantly supported these biochemical findings. In summary, LCZ696 alleviated DKD with possible mechanisms including inhibition of inflammation and apoptosis.

Insulin modulates emotional behavior through a serotonin-dependent mechanism.

Type-2 Diabetes (T2D) is characterized by insulin resistance and accompanied by psychiatric comorbidities including major depressive disorders (MDD). Patients with T2D are twice more likely to suffer from MDD and clinical studies have shown that insulin resistance is positively correlated with the severity of depressive symptoms. However, the potential contribution of central insulin signaling in MDD in patients with T2D remains elusive. Here we hypothesized that insulin modulates the serotonergic (5-HT) system to control emotional behavior and that insulin resistance in 5-HT neurons contributes to the development of mood disorders in T2D. Our results show that insulin directly modulates the activity of dorsal raphe (DR) 5-HT neurons to dampen 5-HT neurotransmission through a 5-HT1A receptor-mediated inhibitory feedback. In addition, insulin-induced 5-HT neuromodulation is necessary to promote anxiolytic-like effect in response to intranasal insulin delivery. Interestingly, such an anxiolytic effect of intranasal insulin as well as the response of DR 5-HT neurons to insulin are both blunted in high-fat diet-fed T2D animals. Altogether, these findings point to a novel mechanism by which insulin directly modulates the activity of DR 5-HT neurons to dampen 5-HT neurotransmission and control emotional behaviors, and emphasize the idea that impaired insulin-sensitivity in these neurons is critical for the development of T2D-associated mood disorders.

1303-P: Decreased Hepatic HMGB1 in Type 2 Diabetes Increases Mitochondrial Glucose Uptake by Regulating Insulin/AKT Signaling

Introduction: High Mobility Group Box-1 (HMGB1) is strongly associated with Type 2 Diabetes (T2D) and hepatocyte function. HMGB1 can regulate mitochondrial function under high glucose conditions. Our group has shown that knockdown of HMGB1 reduces hyperglycemia with decrease insulin activity. We want to further understand the role of HMGB1 in hepatocyte mitochondrial function and the insulin/AKT signaling, a vital pathway in glucose hemostasis. We hypothesize that by decreasing HMGB1, hepatocytes increase glucose uptake by regulating mitochondrial function with more effective Insulin/AKT signaling. Methods: Primary hepatocytes and liver lysates were isolated from inducible HMGB1 KO (iHMGB1 KO) and HMGB1 Flox (wildtype) mice after Tamoxifen and Streptozotocin IP injections for HMGB1 knockout and T2D-10-weeks development. HMGB1 knockdown and insulin/AKT signaling were assessed by RT-PCR and immunoblot. Flow cytometry was performed on primary hepatocyte cell suspension for mitochondrial function/mass (TMRE, Mitotracker) and glucose uptake (NDBG) cellular markers. Results: Liver lysates showed significant decreased expression/activity of HMGB1, Insulin Receptor-B, phosphorylated AKT, PDK and SIRT3 in iHMGB1 KO T2D mice. A counter regulator of metabolic and glucose activity, phosphorylated PDH, was found increased in iHMGB1 KO mice. Flow cytometry of isolated hepatocytes showed that iHMGB1 KO T2D animals had significantly less mitochondrial mass and functioning mitochondria, however showed increased glucose uptake. Conclusion: We found a potential mechanism by which HMGB1 regulates glucose uptake by regulating mitochondrial function and mass potentially by regulating the effectiveness of the Insulin/Akt signaling in T2D. Future studies will be directed to test glucose transport/metabolism in HMGB1 KO hepatocytes guided by more effective Insulin activity in the mediation of mitochondria function at the different stages of T2D progression. Disclosure Z.Liu: None. C.Kaltenmeier: None. R.I.Mota alvidrez: None. Funding This work was funded by department of surgery support for RIMA

Fatty acids of Pleurotus florida mushroom: Potential molecules for blood glucose control

In Vitro-In Vivo antidiabetic effect of Pleurotus florida mycelia was evaluated using enzymes, yeast cell and in streptozotocin induced type 2 diabetic (T2D) animal model. P. florida mycelia was prepared by submerged fermentation process. The fungal biomass was organically extracted using mixture of ethanol and water. Highest extractives yield of 14.3% w/w was obtained in hydroalcoholic solvent with dielectric constant-δ value of 78.2 (EX78). P. florida mycelia extract (EX 78) shows higher antioxidant power with 86.87% free radical scavenging activity and with 75.29 reducing power. In-vitro α-amylase inhibition, α-glucosidase inhibition and glucose uptake activity of EX 78 shows higher effectiveness. The P. florida mycelia extract (EX 78) is also found to be effective in controlling of blood glucose and insulin level in streptozotocin-nicotinamide induced T2D animals. The blood glucose was reduced to 216 ± 6.21 mg/dl from 357 ± 0.34 mg/dl and the insulin level was increased to 0.423 ± 0.006 ng per mL from 0.164 ± 0.03 ng/mL in P. florida treated animals. The higher fatty acids, C20-eicosane; C24-tetracosane and C30-squalene present in P. florida mycelium extract was found to be effective in inhibiting human intestinal α-glucosidase and pancreatic α-amylase. The P. florida mushroom is found to be effective in controlling high blood glucose elevated liver and cardiac enzymes. Consumption of this mushroom is suitable for controlling blood glucose level in person with hyperglycaemia.

Noninvasive assessment of coronary microvascular dysfunction using SPECT myocardial perfusion imaging and myocardial perfusion entropy quantification in a rodent model of type 2 diabetes

Coronary microvascular dysfunction (CMVD) plays a major role in the occurrence of cardiovascular events (CVE). We recently suggested the clinical potential of myocardial perfusion entropy (MPE) quantification from SPECT myocardial perfusion images (MPI) for the prognosis of CVE occurrence. We hypothesized that the quantification of MPE from SPECT MPI would allow the assessment of CMVD-related MPE variations in a preclinical model of type 2 diabetes (T2D) including treatment with the anti-diabetic incretin liraglutide (LIR). Optimal conditions for the preclinical quantification of MPE using 201Tl SPECT MPI were determined in rats with a T2D-like condition induced by a high-fat diet and streptozotocin injection (feasibility study, n = 43). Using such conditions, echocardiography and post-mortem LV capillary density evaluation were then used in order to assess the effect of LIR and the ability of MPE to assess CMVD (therapeutic study, n = 39). The feasibility study identified dobutamine stress and acute NO synthase and cyclooxygenase inhibition as optimal conditions for the quantification of MPE, with significant increases in MPE being observed in T2D animals (P < 0.01 vs controls). In the therapeutic study, T2D rats were hyperglycemic (5.5 ± 0.5 vs 1.1 ± 0.3g/L for controls, P < 0.001) and had a significantly lower left ventricular ejection fraction (LVEF) (65 ± 4% vs 74 ± 9%, P < 0.01) and LV capillary density (2400 ± 300 vs 2800 ± 600mm-3, P < 0.05). LIR partially restored glycemia (3.9 ± 0.6g/L, P < 0.05 vs controls and T2D), totally prevented LVEF impairment (72 ± 7%, P = NS vs CTL), with no significant effect on capillary density. MPE was significantly increased in T2D rats (7.6 ± 0.5 vs 7.1 ± 0.5, P < 0.05), with no significant improvement in T2D-LIR rats (7.4 ± 0.4, P = NS vs controls and T2D). MPE quantification allowed the preclinical noninvasive assessment of CMVD. Both MPE and capillary density quantification suggested that LIR did not improve T2D-induced CMVD. The relevance of MPE for CMVD assessment warrants further clinical investigation.

Molecular and Electrophysiological Role of Diabetes-Associated Circulating Inflammatory Factors in Cardiac Arrhythmia Remodeling in a Metabolic-Induced Model of Type 2 Diabetic Rat.

Background: Diabetic patients have prolonged cardiac repolarization and higher risk of arrhythmia. Besides, diabetes activates the innate immune system, resulting in higher levels of plasmatic cytokines, which are described to prolong ventricular repolarization. Methods: We characterize a metabolic model of type 2 diabetes (T2D) with prolonged cardiac repolarization. Sprague-Dawley rats were fed on a high-fat diet (45% Kcal from fat) for 6 weeks, and a low dose of streptozotozin intraperitoneally injected at week 2. Body weight and fasting blood glucose were measured and electrocardiograms of conscious animals were recorded weekly. Plasmatic lipid profile, insulin, cytokines, and arrhythmia susceptibility were determined at the end of the experimental period. Outward K+ currents and action potentials were recorded in isolated ventricular myocytes by patch-clamp. Results: T2D animals showed insulin resistance, hyperglycemia, and elevated levels of plasma cholesterol, triglycerides, TNFα, and IL-1b. They also developed bradycardia and prolonged QTc-interval duration that resulted in increased susceptibility to severe ventricular tachycardia under cardiac challenge. Action potential duration (APD) was prolonged in control cardiomyocytes incubated 24 h with plasma isolated from diabetic rats. However, adding TNFα and IL-1b receptor blockers to the serum of diabetic animals prevented the increased APD. Conclusions: The elevation of the circulating levels of TNFα and IL-1b are responsible for impaired ventricular repolarization and higher susceptibility to cardiac arrhythmia in our metabolic model of T2D.

Exendin-4 Improves Cognitive Function of Diabetic Mice via Increasing Brain Insulin Synthesis

Type 2 Diabetes (T2D) patients are more prone to develop Alzheimer's Disease (AD). We have previously shown that Glucagon-like peptide-1 receptor agonist exendin-4 (Ex-4) reduces tau hyperphosphorylation in T2D animals through upregulating insulin signaling, and peripheral injected Ex-4 increases insulin levels in the T2D brain. This study aims to further clarify whether the elevated insulin in the brain is produced by nerve cells under the action of Ex-4. The neuronal cell line-HT22 was treated with Ex-4 under high glucose or normal cultivation, and the number of insulin-positive cells as well as the expression levels of insulin synthesis-related genes were examined. The db/db mice were treated with the peripheral injection of Ex-4 and/or IntraCerebroVentricular (ICV) injection of siRNA to inhibit the expression of insulin synthesis- related genes and the behavior tests were carried on. Finally, plasma glucose, Cerebrospinal Fluid (CSF) glucose, CSF insulin, phosphorylation of tau, phosphorylation of AKT and GSK-3β of db/db mice were detected. We found that Ex-4 promoted the expression of insulin synthesis-related genes and induced an obvious increase of insulin-positive HT-22 neuronal cells in a high glucose environment. Peripheral injection of Ex-4 improved the cognitive function of db/db mice and increased brain insulin levels which activated brain insulin signaling and subsequently alleviated tau hyperphosphorylation. However, when siRNA-neurod1 was injected to block insulin synthesis, the cognitive function of db/db mice was not improved under the action of Ex-4 anymore. Moreover, the brain insulin levels dropped to an extremely low level, and the phosphorylation level of tau increased significantly. This study demonstrated that Ex-4 improved cognition function by promoting brain insulin synthesis followed by the activation of brain insulin signaling and alleviation of tau hyperphosphorylation.

Type 2 diabetes progression differently affects endothelial function and vascular contractility in the aorta and the pulmonary artery

Type 2 diabetes (T2D) is associated with cardiovascular and pulmonary disease. How T2D affects pulmonary endothelial function is not well characterized. We investigated the effects of T2D progression on contractility machinery and endothelial function in the pulmonary and systemic circulation and the mechanisms promoting the dysfunction, using pulmonary artery (PA) and aorta. A high-fat (HF, 3 weeks 60% lipid-rich diet) and a high-fat/high-sucrose (HFHSu, combined 60% lipid-rich diet and 35% sucrose during 25 weeks) groups were used as prediabetes and T2D rat models. We found that T2D progression differently affects endothelial function and vascular contractility in the aorta and PA, with the contractile machinery being altered in the PA and aorta in prediabetes and T2D animals; and endothelial function being affected in both models in the aorta but only affected in the PA of T2D animals, meaning that PA is more resistant than aorta to endothelial dysfunction. Additionally, PA and systemic endothelial dysfunction in diabetic rats were associated with alterations in the nitrergic system and inflammatory pathways. PA dysfunction in T2D involves endothelial wall mineralization. The understanding of the mechanisms behind PA dysfunction in T2D can lead to significant advances in both preventative and therapeutic treatments of pulmonary disease-associated diabetes.

Alleviative effects of 20(R)-Rg3 on HFD/STZ-induced diabetic nephropathy via MAPK/NF-κB signaling pathways in C57BL/6 mice

Ethnopharmacological relevanceDiabetic nephropathy (DN) is a major complication of diabetes. The kidney disease develops in nearly 20%–40% of type 2 diabetes (T2D) patients. Ginseng is the root of Panax ginseng C. A. Meyer and has been used in prevention and treatment of diseases for more than 2000 years as a traditional oriental medicine. The 20(R)-ginsenoside Rg3, an active saponin isolated from ginseng, can prevent and treat many diseases. The object of this research was to explore the alleviative effects of 20(R)-Rg3 on DN in mice. Materials and methodsThe T2D animal model was induced by continuous access to a high fat diet (HFD) combined with a single injection of 100 mg/kg streptozotocin (STZ) in C57BL/6 mice. The mice were treated by oral gavage of the 20(R)-Rg3 (10, 20 mg/kg) for 8 weeks. Functional and histopathological analyses of the kidneys were then performed. Protein expression levels of MAPKs and NF-κB signal pathways in the kidney were evaluated by western blotting. The expressions of HO-1 and NF-κB in the kidney were measured by fluorescent labeling staining. Other assessments including fasting blood glucose (FBG) levels, blood lipids, oxidative indicators, and inflammatory factors were all performed. ResultsAbnormally elevated FBG levels were observed in HFD/STZ mice, contributing significantly to the occurrence of DN. Simultaneously, HFD/STZ mice showed the rise of serum total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels, and the decrease in high density lipoprotein cholesterol (HDL-C). DN was evidenced by the overproduction of malondialdehyde (MDA), decreased levels of superoxide dismutase (SOD) and catalase (CAT) enzymatic activities, high levels of serum blood urea nitrogen (BUN) and creatinine (Cr). Simultaneously, the results of the immunofluorescence assay showed an increased expression level in NF-κB p65 while a decrease in antioxidant enzyme HO-1 was observed. Herein, 20(R)-Rg3 treatment for 8 weeks not only attenuated FBG levels and advanced glycation end products (AGEs) levels but also improved insulin (INS) level, blood lipids, oxidative stress, and renal function by regulating MAPKs and NF-κB signal pathways in DN mice. ConclusionTaken together, the findings from the present study explicitly confirmed that 20(R)-Rg3 exerted ameliorative effects on DN mice via improving anti-oxidative activity and reducing renal inflammation.

Olfactory Dysfunction in Diabetic Rats is Associated with miR-146a Overexpression and Inflammation.

Type 2 diabetes (T2D) is associated with cognitive decline and dementia. Both neurodegenerative conditions are characterized by olfactory dysfunction (OD) which is also observed in diabetic patients. Diabetes and neurodegeneration display altered miRNAs expression; therefore, the study of miRNAs in the diabetic olfactory system is important in order to know the mechanisms involved in neurodegeneration induced by T2D. In this work we evaluated the expression of miRs206, 451, 146a and 34a in the olfactory bulb (OB) of T2D rats and its association with OD. T2D induction was performed by administering streptozotocin to neonatal rats. The olfactory function was evaluated after reaching the adulthood by employing the buried pellet and social recognition tests. After 18weeks, animals were sacrificed to determinate miRNAs and protein expression in the OB. T2D animals showed a significant increase in the latency to find the odor stimulus in the buried pellet test and a significant reduction in the interest to investigate the novel juvenile subjects in the social recognition test, indicating OD. In miRNAs analysis we observed a significant increase of miR-146a expression in the OB of T2D rats when compared to controls. This increase in miR-146a correlated with the overexpression of IL-1β in the OB of T2D rats. The present results showed that OD in T2D rats is associated with IL-1β mediated-inflammation and miR-146a overexpression, suggesting that high levels of IL-1β could trigger miR-146a upregulation as a negative feedback of the inflammatory response in the OB of T2D rats.

Diurnal Rhythmicity of Autophagy Is Impaired in the Diabetic Retina.

Retinal homeostasis is under both diurnal and circadian regulation. We sought to investigate the diurnal expression of autophagy proteins in normal rodent retina and to determine if this is impaired in diabetic retinopathy. C57BL/6J mice and Bio-Breeding Zucker (BBZ) rats were maintained under a 12h/12h light/dark cycle and eyes, enucleated over a 24 h period. Eyes were also collected from diabetic mice with two or nine-months duration of type 1 diabetes (T1D) and Bio-Breeding Zucker diabetic rat (BBZDR/wor rats with 4-months duration of type 2 diabetes (T2D). Immunohistochemistry was performed for the autophagy proteins Atg7, Atg9, LC3 and Beclin1. These autophagy proteins (Atgs) were abundantly expressed in neural retina and endothelial cells in both mice and rats. A differential staining pattern was observed across the retinas which demonstrated a distinctive diurnal rhythmicity. All Atgs showed localization to retinal blood vessels with Atg7 being the most highly expressed. Analysis of the immunostaining demonstrated distinctive diurnal rhythmicity, of which Atg9 and LC3 shared a biphasic expression cycle with the highest level at 8:15 am and 8:15 pm. In contrast, Beclin1 revealed a 24-h cycle with the highest level observed at midnight. Atg7 was also on a 24-h cycle with peak expression at 8:15 am, coinciding with the first peak expression of Atg9 and LC3. In diabetic animals, there was a dramatic reduction in all four Atgs and the distinctive diurnal rhythmicity of these autophagy proteins was significantly impaired and phase shifted in both T1D and T2D animals. Restoration of diurnal rhythmicity and facilitation of autophagy protein expression may provide new treatment strategies for diabetic retinopathy.

The renal expression of epigenetic biomarkers for diabetic nephropathy

Chronic kidney disease (CKD) is one of the most common complications in patients with diabetes. Identification of diabetic patients with high risk for CKD progression has been challenging due to various limitations of traditional diagnostic methods. Epigenetic modifications, particularly DNA methylation, have recently emerged as alternative predicting factors for diabetic nephropathy. Despite strong evidence of correlation, the mechanisms that link epigenetic changes in blood/monocytes with renal physiology are yet to be investigated. As such, it is important to examine the renal expression of these differentially methylated genes in diabetic individuals with and without CKD. Using an animal model of Type 2 diabetes (T2D) and biopsy/nephrectomy samples from patients with T2D without and with CKD, we demonstrated that CUE domain containing 1 (cuedc1), microtubule-associated protein 7 (map7), LIM Homeobox 6 (lhx6) and Thioredoxin Interacting Protein (Txnip) were downregulated in the kidneys of T2D animals and patients without CKD. Strikingly, the regulation of cuedc1, map7 and txnip were significantly reversed in the presence of kidney dysfunction and fibrosis. The expression of Protein Kinase C Epsilon (prkce) was also significantly higher in T2D patients with CKD compared to the control group. Both txnip and prkce have been shown previously to be involved in the induction of diabetic nephropathy. These data provide evidence to support the relevance of epigenetic biomarkers in blood with renal pathophysiology in T2D.

Effect of exercise on type 2 diabetes-associated cognitive impairment in rats

OBJECTIVES: Type 2 diabetes (T2D)-associated cognitive impairment is highly prevalent especially among the geriatric population. Here, we investigate the role of exercise in T2D-associated cognitive decline in rats.METHODS: T2D was induced using high-fat diet (15 days) followed by low-dose STZ (25mg/kg). The T2D animals were subjected to aerobic exercise on running wheel for 6 weeks. Effect of aerobic exercise on cognitive performance of T2D animals was measured using step-down and transfer latency tests. This was followed by the measurement of reduced glutathione levels in hippocampal homogenates. We also measured hippocampal AchE activity and levels of neuroinflammatory markers such as IL-1 β, TNF-α and MCP-1. Morphology and density of hippocampal neurons were also determined by histopathological studies.RESULTS: Exercise led to the following changes in T2D animals. It led to decrease in fasting blood glucose level (<250 mg/kg) and HbA1c (8.5 ± 0.23) compared to diabetic (11.73 ± 0.14) animals and improved insulin resistance. There was an increase in step-down latency (p < 0.001) and a decrease in transfer latency (p < 0.01) suggesting improved cognitive function. A significant increase in GSH levels (1.828 ± 0.024) compared to diabetic group (1.52 ± 0.03; p < 0.001) and decrease in AchE activity (1.4 ± 0.05) compared to diabetic group (1.65 ± 0.03; p < 0.05) were also observed. It reduced the levels of neuroinflammatory markers such as IL-1β, TNF-α and MCP-1 (p < 0.01). Hippocampal sections showed higher CA1 and CA3 neuronal density (p < 0.001) than T2D group.CONCLUSION: We may conclude that aerobic exercise could partially reverse diabetes-associated cognitive decline by reducing oxidative stress and inflammatory milieu in T2D animal brain.

Alterations in Histone Acetylation in Diabetic Painful Neuropathy

Peripheral sensory neuropathy is one of the most common complications of diabetes. Accumulating evidence suggests that chronic low-grade inflammation is involved in the pathogenesis of the disease. We hypothesize that hyperglycemia causes changes in histone acetylation and release of inflammatory mediators in the peripheral nervous system of diabetic animals with painful neuropathy; therefore blocking this increase will prevent or delay the development of neuropathy. High mobility group box 1 (HMGB1), a nuclear protein released by injured and severely stressed cells, promotes cytokine release via histone acetylation and its interaction with the Toll-like receptor (TLR). In this study we investigated the changes in inflammatory mediators and histone modifications in the dorsal root ganglia (DRG) and spinal cord dorsal horn neurons as well as compared the changes in behavior with treatment. Type 2 diabetic (T2D) animals with pain were treated with HMGB1 inhibitor Glycyrrhizin (GLC) for 2 days a week for 3 weeks at 50 mg/kg I.P. injection 6 weeks after diabetes. T2D animals demonstrated significant changes in thermal hyperalgesia manifested by a decrease in withdrawal latency to heat, mechanical hyperalgesia as measured by the Randall Sellito method of paw pressure at 6 weeks after diabetes and also exhibited marked increases in HMGB1, IL1β, TLR4 and H3K9 acetylation as determined by the Western blot analysis and immunohistochemistry. We analyzed the T2D animals with treatment or without treatment at 3 weeks after treatment. Our results show that animals treated with GLC had significant decrease in thermal hyperalgesia along with changes in histone acetylation and expression of inflammatory mediators. This preliminary study suggests that HMGB1 and histone acetylation play an important role in the inflammatory aspect of the painful neuropathy in T1D animals and may provide a novel treatment approach for this difficult-to-treat complication of diabetes. Disclosure M. Chattopadhyay: None. V. Thakur: None.

Topically Applied Curcumin-Loaded Nanoparticles Treat Erectile Dysfunction in a Rat Model of Type-2 Diabetes

BackgroundCurcumin, a naturally occurring anti-inflammatory compound, has shown promise in pre-clinical studies to treat erectile dysfunction (ED) associated with type-1 diabetes. However, poor bioavailability following oral administration limits its efficacy. The present study evaluated the potential of topical application of curcumin-loaded nanoparticles (curc-np) to treat ED in a rat model of type-2 diabetes (T2D). AimDetermine if topical application of curc-np treats ED in a T2D rat model and modulates expression of inflammatory markers. MethodsCurc-np (4 mg curcumin) or blank nanoparticles were applied every 2 days for 2 weeks to the shaved abdomen of 20-week-old Zucker diabetic fatty male rats (N = 5 per group). Lean Zucker diabetic fatty male rat controls were treated with blank nanoparticles (N = 5). Penetration of nanoparticles and curcumin release were confirmed by 2-photon fluorescence microscopy and histology. Erectile function was determined by measuring intracorporal pressure (ICP) normalized to systemic blood pressure (ICP/BP) following cavernous nerve stimulation. Corporal tissue was excised and reverse transcription and quantitative polymerase chain reaction used to determine expression of the following markers: nuclear factor (NF)-κβ, NF-κβ-activating protein (Nkap), NF erythroid 2-related factor-2, Kelch-like enoyl-CoA hydratase-associated protein-1, heme oxygenase-1 (HO-1), variable coding sequence-A1, phosphodiesterase-5, endothelial and neuronal nitric oxide synthase, Ras homolog gene family member A, and Rho-associated coiled-coil containing protein kinases-1 and -2. OutcomesErectile function by determination of ICP/BP and expression of molecular markers in corporal tissue by RT-qPCR. ResultsNanoparticles penetrated the abdominal epidermis and persisted in hair follicles for 24 hours. Curc-np-treated animals exhibited higher average ICP/BP than animals treated with blank nanoparticles at all levels of stimulation and this was statistically significant (P < .05) at 0.75 mA. In corporal tissue, Nkap expression decreased 60% and heme oxygenase-1 expression increased 60% in curc-np- compared to blank nanoparticle–treated animals. ICP/BP values inversely correlated with Nkap and directly correlated with HO-1 expression levels. Clinical TranslationThese studies demonstrate the potential for topical application of curc-np as a treatment for ED in T2D patients. ConclusionsThe T2D animal model of ED represents a more prevalent disease than the more commonly studied type-1 diabetes model. Although there is improved erectile response in curc-np-treated animals, only at the lower levels of stimulation (0.75 mA) was this significant compared to the blank nanoparticle–treated animals, suggesting more studies are needed to optimize protocols and evaluate toxicity. Topical application of curc-np to a rat model of T2D can systemically deliver curcumin, treat ED, and modulate corporal expression of inflammatory markers.Draganski A, Tar MT, Villegas G, et al. Topically Applied Curcumin-Loaded Nanoparticles Treat Erectile Dysfunction in a Rat Model of Type-2 Diabetes. J Sex Med 2018;15:645–653.

Vitamin K1 inversely correlates with glycemia and insulin resistance in patients with type 2 diabetes (T2D) and positively regulates SIRT1/AMPK pathway of glucose metabolism in liver of T2D mice and hepatocytes cultured in high glucose

There is no previous study in the literature that has examined the relationship between circulating vitamin K1 (VK1) with glycemic status in type 2 diabetes (T2D). Moreover, scientific explanation for the beneficial role of VK1 supplementation in lowering glycemia in diabetes is yet to be determined. This study for the first time demonstrated that circulating VK1 was significantly lower in T2D patients compared to age-matched control subjects, and VK1 levels in T2D were significantly and inversely associated with fasting glucose and insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR)], which suggest that boosting plasma VK1 may reduce the fasting glucose and insulin resistance in T2D patients. Using high-fat-diet-fed T2D animal model, this study further investigated the positive effect of VK1 supplementation on glucose metabolism and examined the underlying molecular mechanism. Results showed that VK1 supplementation [1, 3, 5 μg/kg body weight (BW), 8 weeks] dose dependently improved the glucose tolerance; decreased BW gain, fasting glucose and insulin, glycated hemoglobin, HOMA-IR and cytokine secretion (monocyte chemoattractant protein-1 and interleukin-6); and regulated the signaling pathway of hepatic glucose metabolism [sirtuin 1 (SIRT1)/AMP-activated protein kinase (AMPK)/phosphoinositide 3-kinase/phosphatase and tensin homolog/glucose transporter 2/glucokinase/glucose 6 phosphatase], lipid oxidation (peroxisome proliferator-activated receptor alpha/carnitine palmitoyltransferase 1A) and inflammation (nuclear factor kappa B) in T2D mice. Comparative signal silencing studies also depicted the role of SIRT1/AMPK in mediating the effect of VK1 on glucose metabolism, lipid oxidation and inflammation in high-glucose-treated cultured hepatocytes. In conclusion, this study demonstrates that circulating VK1 has a positive effect on lowering fasting glucose and insulin resistance in T2D via regulating SIRT1/AMPK signaling pathway.

Sox5 regulates beta-cell phenotype and is reduced in type 2 diabetes

Type 2 diabetes (T2D) is characterized by insulin resistance and impaired insulin secretion, but the mechanisms underlying insulin secretion failure are not completely understood. Here, we show that a set of co-expressed genes, which is enriched for genes with islet-selective open chromatin, is associated with T2D. These genes are perturbed in T2D and have a similar expression pattern to that of dedifferentiated islets. We identify Sox5 as a regulator of the module. Sox5 knockdown induces gene expression changes similar to those observed in T2D and diabetic animals and has profound effects on insulin secretion, including reduced depolarization-evoked Ca2+-influx and β-cell exocytosis. SOX5 overexpression reverses the expression perturbations observed in a mouse model of T2D, increases the expression of key β-cell genes and improves glucose-stimulated insulin secretion in human islets from donors with T2D. We suggest that human islets in T2D display changes reminiscent of dedifferentiation and highlight SOX5 as a regulator of β-cell phenotype and function.

Insulin sensitizer prevents and ameliorates experimental type 1 diabetes.

Insulin-dependent type-1 diabetes (T1D) is driven by autoimmune β-cell failure, whereas systemic resistance to insulin is considered the hallmark of insulin-independent type-2 diabetes (T2D). In contrast to this canonical dichotomy, insulin resistance appears to precede the overt diabetic stage of T1D and predict its progression, implying that insulin sensitizers may change the course of T1D. However, previous attempts to ameliorate T1D in animal models or patients by insulin sensitizers have largely failed. Sensitization to insulin by MEthyl-substituted long-chain DICArboxylic acid (MEDICA) analogs in T2D animal models surpasses that of current insulin sensitizers, thus prompting our interest in probing MEDICA in the T1D context. MEDICA efficacy in modulating the course of T1D was verified in streptozotocin (STZ) diabetic rats and autoimmune nonobese diabetic (NOD) mice. MEDICA treatment normalizes overt diabetes in STZ diabetic rats when added on to subtherapeutic insulin, and prevents/delays autoimmune T1D in NOD mice. MEDICA treatment does not improve β-cell insulin content or insulitis score, but its efficacy is accounted for by pronounced total body sensitization to insulin. In conclusion, potent insulin sensitizers may counteract genetic predisposition to autoimmune T1D and amplify subtherapeutic insulin into an effective therapeutic measure for the treatment of overt T1D.