Animal Models Of Type 2 Diabetes Mellitus Research Articles

724-P: A First-in-Human Study of RGT-075, a Novel, Orally Bioavailable, Small-Molecule GLP-1 Receptor Agonist, in Healthy Adult Subjects

Background: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are a well-characterized and effective class of glucose-lowering agents for the treatment of patients with type 2 diabetes mellitus (T2DM) . To date, all market-authorized GLP-1 RAs are peptides, and only one is administered orally. RGT-075 is a novel, orally bioavailable, small-molecule GLP-1 RA which has shown therapeutic potential in animal models of T2DM. The results of a first-in-human study of RGT-075 are presented. Methods: A phase 1, randomized, double-blind, placebo-controlled study was conducted to investigate the safety, tolerability, and pharmacokinetics of single escalating oral doses of RGT-075 (15-280 mg) in healthy adult volunteers. Seven cohorts of 8 subjects were enrolled and randomized to treatment with RGT-075 or matching placebo (6 active/2 placebo per cohort) . Plasma and urine samples were collected over 48 hours post-dose and analyzed for RGT-075 concentrations. Results: A total of 56 healthy adults (64% male, mean age 42.5 years) participated in the study. Treatment-emergent adverse events (TEAEs) were reported by 28 of 56 (50%) subjects (24 subjects treated with RGT-075 and 4 subjects treated with placebo) . There were no serious adverse events, deaths or TEAEs that led to early withdrawal. The majority of TEAEs were considered mild, and the most common TEAEs related to study drug were nausea, vomiting, and headache. Maximum tolerated dose was not reached. Single oral doses of RGT-075 (15-280 mg) resulted in linear increases in Cmax, AUClast, and AUCinf with ascending doses through 240 mg. Mean elimination half-life ranged from 6.3-11.7 hours. Renal clearance of RGT-075 was low to negligible. Conclusion: Overall, single RGT-075 doses between 15-280 mg were safe and well-tolerated in healthy volunteers. Further clinical development of RGT-075 as a once-daily, oral therapy for T2DM is underway. Disclosure M.A.Pirner: Employee; Regor Pharmaceuticals, Inc. J.Lin: None. F.Liu: Employee; Regor Pharmaceuticals Inc. L.Yao: None. M.E.Zettler: Employee; Cardinal Health, Regor Pharmaceuticals Inc. D.J.Valacer: Employee; Regor Pharmaceuticals, Inc.

Gut Microbiota: An Important Player in Type 2 Diabetes Mellitus.

Type 2 diabetes mellitus (T2DM) is one of the common metabolic diseases in the world. Due to the rise in morbidity and mortality, it has become a global health problem. To date, T2DM still cannot be cured, and its intervention measures mainly focus on glucose control as well as the prevention and treatment of related complications. Interestingly, the gut microbiota plays an important role in the development of metabolic diseases, especially T2DM. In this review, we introduce the characteristics of the gut microbiota in T2DM population, T2DM animal models, and diabetic complications. In addition, we describe the molecular mechanisms linking host and the gut microbiota in T2DM, including the host molecules that induce gut microbiota dysbiosis, immune and inflammatory responses, and gut microbial metabolites involved in pathogenesis. These findings suggest that we can treat T2DM and its complications by remodeling the gut microbiota through interventions such as drugs, probiotics, prebiotics, fecal microbiota transplantation (FMT) and diets.

Identification of Potential Biomarkers of Type 2 Diabetes Mellitus-Related Immune Infiltration Using Weighted Gene Coexpression Network Analysis.

Background Type 2 diabetes mellitus (T2DM) is characterized by chronic low-grade inflammation, showing an increasing trend. The infiltration of immune cells into adipose tissue has been shown to be an important pathogenic cause of T2DM. The purpose of this study is to use the relevant database to identify some abnormally expressed or dysfunctional genes related to diabetes from the perspective of immune infiltration. Methods Weighted gene coexpression network analysis (WGCNA) was employed to systematically identify the coexpressed gene modules and hub genes associated with T2DM development based on a microarray dataset (GSE23561) from the Gene Expression Omnibus (GEO) database. The key genes in modules highly related to clinical features were calculated and screened by using R software, and their participation in T2DM was determined by gene enrichment analysis. The mRNA levels of CSF1R, H2AFV, LCK, and TLR9 in pre-T2DM mice and normal wild-type mice were detected by WGCNA screening and real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Results We constructed 14 coexpressed gene modules, and the brown module was shown to be significantly related to T2DM. Through verification of the protein-protein interaction (PPI) network, four upregulated hub genes, CSF1R, H2AFV, LCK, and TLR9, were screened from the brown module and successfully distinguishedT2DM patients from healthy people. These hub genes may be used as biomarkers and important indicators for patient diagnosis. Enrichment analysis showed that these hub genes were highly associated with IL-6-related inflammatory metabolism, immune regulation, and immune cell infiltration. Finally, we verified the hub genes CSF1R, LCK, and TLR9 in a T2DM animal model and found that their mRNA levels were significantly higher in animals with T2DM than in control group mice (NC). Conclusions In summary, our results suggest that these hub genes (CSF1R, LCK, and TLR9) can serve as biomarkers and immunotherapeutic targets for T2DM.

Synthesis, Characterization and Screening of Some Novel 2-Methyl-N'- [(Z)-Substituted-Phenyl ethylidene] Imidazo [1, 2-a] Pyridine-3-Carbohy drazide Derivatives as DPP-IV Inhibitors for the Treatment of Type 2 Diabetes Mellitus

Background: One of the leading global metabolic diseases marked by insulin resistance and chronic hyperglycemia is type 2 diabetes mellitus (T2DM). Since the last decade, DPP-4 enzyme inhibition has proven to be a successful, safe, and well-established therapy for the treatment of T2DM. Objective: The present work reports the synthesis, characterization, and screening of some novel 2- methyl-N'-[(Z)-substituted-phenyl ethylidene] imidazo [1, 2-a] pyridine-3-carbohydrazide derivatives as DPP-IV inhibitors for the treatment of T2DM. Methods: The molecular docking was performed to study these derivatives' binding mode in the enzyme's allosteric site. All the synthesized compounds were subjected for DPP-IV enzyme assay and in vivo antihyperglycemic activity in STZ-induced diabetic rats. Results: The synthesized derivatives exhibited potent antidiabetic activity as compared to the standard drug Sitagliptin. Out of sixteen compounds, A1, A4, B4, C2, C3, and D4 have shown promising antidiabetic activity against the DPP-IV enzyme. The most promising compound, C2, showed a percentage inhibition of 72.02±0.27 at 50 μM concentration. On the 21st-day, compound C2 showed a significant reduction in serum blood glucose level, i.e., 156.16±4.87 mg/dL, then diabetic control, which was 280.00±13.29 mg/dL whereas, standard Sitagliptin showed 133.50±11.80 mg/dL. In the in vivo antihyperglycemic activity, the compounds have exhibited good hypoglycemic potential in fasting blood glucose in the T2DM animal model. All the docked molecules have exhibited perfect binding affinity towards the active pocket of the enzyme. The synthesized derivatives were screened through Lipinski's rule of five for better optimization, and fortunately, none of them violated the rule. Conclusion: The above results indicate that compound C2 is a relatively active and selective hit molecule that can be structurally modified to enhance the DPP-IV inhibitor's potency and overall pharmacological profile. From the present work, it has been concluded that substituted pyridine-3-carbohydrazide derivatives possess excellent DPP-IV inhibitory potential and can be better optimized further by generating more in vivo, in vitro models.

Isoliquiritigenin alleviates diabetic symptoms via activating AMPK and inhibiting mTORC1 signaling in diet-induced diabetic mice

PurposeTo determine the effects of isoliquiritigenin (ISL), a chalcone compound isolated from licorice, on type 2 diabetes mellitus (T2DM). Materials and methods8-week-old C7BL/6 mice were used to establish the T2DM animal model by feeding with high-fat-high-glucose diet (HFD) combined with intraperitoneal injection of streptozotocin. The animals were treated with ISL for 3 weeks. Blood glucose levels, oral glucose tolerance, and insulin tolerance were examined, serum parameters were determined, histologic sections were prepared, activities of enzymes related to glucolipid metabolism were analyzed, and the mitochondrial function was investigated to evaluate effects of ISL on metabolism. The underlying mechanisms of ISL alleviating insulin resistance and restoring metabolic homeostasis were analyzed in HepG2 and INS-1 cells. ResultsISL exhibits a potent activity in relieving hyperglycemia of type 2 diabetic mice. It alleviates insulin resistance and restores metabolic homeostasis without obvious adversary effects in HFD-induced diabetic mice. The metabolic benefits of ISL treatment include promoting hepatic glycogenesis, inhibiting hepatic lipogenesis, reducing hepatic steatosis, and sensitizing insulin signaling. Mechanistically, ISL activates adenosine monophosphate-activated protein kinase (AMPK) and inhibits mammalian target of rapamycin complex 1 (mTORC1). It also suppresses mitochondrial function and reduces ATP production. ConclusionOur findings demonstrate that ISL is able to significantly reduce blood glucose level and alleviate insulin resistance without obvious side effects in diabetic mice, hence uncovering a great potential of ISL as a novel drug candidate in prevention and treatment of T2DM.

Ramulus Mori (Sangzhi) Alkaloids (SZ-A) Ameliorate Glucose Metabolism Accompanied by the Modulation of Gut Microbiota and Ileal Inflammatory Damage in Type 2 Diabetic KKAy Mice

The novel Traditional Chinese Medicine Ramulus Mori (Sangzhi) alkaloid tablets (SZ-A) are approved by The China National Medical Products Administration for the treatment of type 2 diabetes mellitus (T2DM). However, the extensive pharmacological characteristics and the underlying mechanism are unknown. This study investigated the mechanisms by which SZ-A ameliorates glucose metabolism in KKAy mice, an animal model of T2DM. Diabetic KKAy mice were treated intragastrically with SZ-A once daily for 8 weeks, after which glucose levels, lipid metabolism, gut microbiome, systemic inflammatory factors, luminal concentrations of short-chain fatty acids (fecal samples), and ileal proteomic changes were evaluated. The ileum tissues were collected, and the effects of SZ-A on pathological inflammatory damage were evaluated by hematoxylin and eosin staining, immunofluorescence, and immunohistochemistry. The mRNA and protein expression levels of various inflammatory markers, including monocyte chemoattractant protein-1 and phosphorylated nuclear factor kappa B p65, were detected in the ileum tissues. SZ-A improved glucose metabolism with enhanced insulin response and elevated glucagon-like peptide 1 (GLP-1) nearly 2.7-fold during the glucose tolerance test in diabetic KKAy mice. Gut microbiota analysis demonstrated that SZ-A administration elevated the abundance of Bacteroidaceae and Verrucomicrobia, reduced the levels of Rikenellaceae and Desulfovibrionaceae; and increased the concentrations of fecal acetic and propionic acids compared to the diabetic model group. Additionally, SZ-A markedly improved ileal inflammatory injury and pro-inflammatory macrophage infiltration and improved intestinal mucosal barrier function in diabetic KKAy mice. SZ-A also attenuated the levels of circulating endotoxin, pro-inflammatory cytokines, and chemokines in the mice sera. Collectively, SZ-A ameliorated the overall metabolic profile including glucose and lipid metabolism in KKAy mice, which may be associated with an improvement in GLP-1 and insulin secretion, at least in part by modulating the gut microbiome and relieving the degree of ileal and systemic inflammation.

Type 2 diabetes mellitus impaired nasal immunity and increased the risk of hyposmia in COVID-19 mild pneumonia patients

In patients with COVID-19,type 2 diabetes mellitus (T2DM) can impair the function of nasal-associated lymphoid tissue (NALT) and result in olfactory dysfunction. Exploring the causative alterations of T2DM within the nasal mucosa and NALT could provide insight into the pathogenic mechanisms and bridge the gap between innate immunity and adaptive immunity for virus clearance. Here, we designed a case-control study to compare the olfactory function (OF) among the groups of normal control (NC), COVID-19 mild pneumonia (MP), and MP patients with T2DM (MPT) after a 6–8 months’ recovery, in which MPT had a higher risk of hyposmia than MP and NC. No significant difference was found between the MP and NC. This elevated risk of hyposmia indicated that T2DM increased COVID-19 susceptibility in the nasal cavity with unknown causations. Therefore, we used the T2DM animal model (db/db mice) to evaluate how T2DM increased COVID-19 associated susceptibilities in the nasal mucosa and lymphoid tissues. Db/db mice demonstratedupregulated microvasculature ACE2 expression and significant alterations in lymphocytes component of NALT. Specifically, db/db mice NALT had increased immune-suppressive TCRγδ+ CD4−CD8− T and decreased immune-effective CD4+/CD8+ TCRβ+ T cells and decreased mucosa-protective CD19+ B cells. These results indicated that T2DM could dampen the first-line defense of nasal immunity, and further mechanic studies of metabolic damage and NALT restoration should be one of the highest importance for COVID-19 healing.

Bioactive Agent Discovery from the Natural Compounds for the Treatment of Type 2 Diabetes Rat Model.

Diabetes mellitus is a well-known chronic metabolic disease that poses a long-term threat to human health and is characterized by a relative or absolute lack of insulin, resulting in hyperglycemia. Type 2 diabetes mellitus (T2DM) typically affects many metabolic pathways, resulting in β-cell dysfunction, insulin resistance, abnormal blood glucose levels, inflammatory processes, excessive oxidative reactions, and impaired lipid metabolism. It also leads to diabetes-related complications in many organ systems. Antidiabetic drugs have been approved for the treatment of hyperglycemia in T2DM; these are beneficial for glucose metabolism and promote weight loss, but have the risk of side effects, such as nausea or an upset stomach. A wide range of active components, derived from medicinal plants, such as alkaloids, flavonoids, polyphenol, quinones, and terpenoids may act as alternative sources of antidiabetic agents. They are usually attributed to improvements in pancreatic function by increasing insulin secretions or by reducing the intestinal absorption of glucose. Ease of availability, low cost, least undesirable side effects, and powerful pharmacological actions make plant-based preparations the key player of all available treatments. Based on the study of therapeutic reagents in the pathogenesis of humans, we use the appropriate animal models of T2DM to evaluate medicinal plant treatments. Many of the rat models have characteristics similar to those in humans and have the advantages of ease of genetic manipulation, a short breeding span, and access to physiological and invasive testing. In this review, we summarize the pathophysiological status of T2DM rat models and focus on several bioactive compounds from herbal medicine with different functional groups that exhibit therapeutic potential in the T2DM rat models, in turn, may guide future approach in treating diabetes with natural drugs.

Genetic Deletion Of MicroRNA-16 In Muscle Results In Impaired Insulin Sensitivity & Exercise Capacity

Type 2 diabetes mellitus (T2DM) has become the most common metabolic disease in Western society, leading to significant health problems and financial burdens. Numerous researchers have investigated different therapeutics to target T2DM, but the underlying molecular mechanisms are still not completely understood. Our laboratory and others have demonstrated consistent downregulation of the microRNA-16 (miR-16) in skeletal muscle across human, rodent, and tissue culture models of T2DM. PURPOSE: To investigate how deletion of miR-16 gene affects insulin sensitivity and exercise capacity during insulin resistance. METHODS: 10 wildtype (WT) and 12 muscle miR-16 knockout (KO) male mice were used for this study. At 9 wks of age, bodyweight, graded exercise test (GXT), glucose tolerance test (GTT; at 0, 30, 60, and 120 min) and insulin tolerance test (ITT; at 0, 15, 30, and 60 min) were measured. At 10 wks of age, half of the mice were given high-fat diet (HFD; 45% calories from fat) to induce insulin resistance, while the remainder were fed normal chow (NC; 17% calories from fat). At 13 wks, bodyweight, GXT, GTT, and ITT were repeated to examine the effect of HFD on miR-16 KO condition. Data were analyzed by two-way ANOVA and significance was denoted at p<0.05. RESULTS: Bodyweight was increased by ~27% in WT HFD (p<0.05) and ~21% in KO HFD group (p<0.05) compared to WT NC group. Exercise capacity was decreased by ~46% in WT HFD, ~34% in KO NC, and ~153% in KO HFD group (p<0.001) compared to WT NC group. GTT area under the curve (AUC) value was ~15% greater in WT HFD (p<0.05) and ~20% greater in KO HFD group (p<0.05) compared to WT NC group. ITT curve data indicated that glucose level was ~41% greater at 15 min in KO HFD (p<0.05) compared to WT NC group. CONCLUSION: These data suggest prior observations of downregulated muscle miR-16 in human and animal models of T2DM may in part mediate impaired insulin sensitivity and exercise tolerance. Further research is warranted to elucidate molecular mechanisms of miR-16 and its potential role in insulin resistance. ACKNOWLEDGEMENTS: This study was funded by the Arkansas Bioscience Institute and American College of Sports Medicine Research Endowment Grant.

Adiponectin in onset and progression of T2DM with cardiac dysfunction in rats.

Cardiovascular disease and type 2 diabetes mellitus (T2DM) patients have low level of adiponectin, however, till now the role of adiponectin in progression of 'T2DM with cardiac dysfunction' in animal model has not been characterized. Therefore, the aim of the present study was to develop and characterize T2DM animal model with cardiac dysfunction and to study the role of cardiac adiponectin expression in cardiac dysfunction. For this, Wistar rats (M/F) were fed a high-fat diet for different time periods: 3, 4 and 5 weeks and given a single, low-dose streptozotocin (25mg/kg), intraperitoneal injection 1 week prior to the experiments. Rats in T2DM group (3 weeks) developed hyperglycaemia, hyperlipidaemia, oxidative stress with normoinsulinaemia and mild cardiac dysfunction suggesting onset of T2DM with cardiac dysfunction. Extended high-fat feeding, that is, 4 and 5 weeks induced insulin resistance accompanied with cardiac hypertrophy, cardiac dysfunction and reduced baroreflex sensitivity indicating development of T2DM with cardiac dysfunction. Cardiac adiponectin expression did not change in rats of T2DM group (3 weeks), however, it significantly decreased in rats of two T2DM groups (4 and 5 weeks) along with increased intracellular adhesion molecule-1 levels. Thus, the present study for the first time indicates that in the present T2DM animal model, as T2DM progresses cardiac adiponectin expression also decreases which might be the precipitating factor for cardiac hypertrophy and decrease in baroreflex sensitivity, which induces cardiac dysfunction.

Small intestine proteomics coupled with serum metabolomics reveal disruption of amino acid metabolism in Chinese hamsters with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, with metabolic disturbances resulting from defects in insulin secretion, insulin resistance (IR), or both. Chinese hamsters have potential value as non-obese animal models of spontaneous T2DM for studying the pathogenesis and molecular characteristics of diabetes. In this study, the molecular characteristics of the Chinese hamster diabetes animal model were investigated through small intestine proteomics and serum metabolomics. A total of 213 differentially abundant proteins and 14 differentially abundant metabolites were identified through liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-time of flight mass spectrometry (GC-TOF/MS) analysis, respectively. Annotation by bioinformatics analysis revealed that these differentially abundant proteins in the small intestine were commonly associated with abnormal glucose and lipid metabolism, IR, impaired insulin secretion, amino acid metabolism disorders, and inflammatory dysregulation. Moreover, differentially abundant metabolites in the serum were amino acids and were related to diabetic IR. Through the analysis of small intestine proteomics and serum metabolomics in the Chinese hamster diabetes model, we provide a preliminary understanding of the diabetic characteristics of this model from a molecular perspective. This study provides data incentivizing the popularization and application of Chinese hamsters in T2DM research. SignificanceSpontaneous rodent models of diabetes, such as Chinese hamsters, effectively summarizes the clinical characteristics of type 2 diabetes and has high applicative value for studying the pathophysiology of diabetes. In order to explore the potential value of the Chinese hamster diabetes animal model in the study of the T2DM molecular mechanism, we performed small intestine proteomic analysis and serum metabolomic analysis in Chinese hamsters for the first time. After an integrated analysis of proteomics and metabolomics, we have a preliminary understanding of the diabetic characteristics of this model from a molecular perspective. Further, we found that in the occurrence and development of T2DM, the metabolic abnormalities of this model are particularly prominent, especially the metabolism of amino acids. These findings not only provide basic data in support of the popularization and application of the current model in T2DM research, but also provide a new perspective for the exploration of mechanisms related to T2DM.

Lactobacillus salivarius AP-32 and Lactobacillus reuteri GL-104 decrease glycemic levels and attenuate diabetes-mediated liver and kidney injury in db/db mice

ObjectivesPatients with type 2 diabetes mellitus (T2DM) exhibit strong insulin resistance or abnormal insulin production. Probiotics, which are beneficial live micro-organisms residing naturally in the intestinal tract, play indispensable roles...

Dynamic Phenotypes and Molecular Mechanisms to Understand the Pathogenesis of Diabetic Nephropathy in Two Widely Used Animal Models of Type 2 Diabetes Mellitus.

ObjectiveWe aimed to characterize the pathogenesis of diabetic nephropathy (DN) in two commonly used type 2 diabetes mellitus (T2DM) animal models and explore the preliminary molecular mechanisms underlying DN in two models.MethodsTo verify the effect of hyperglycemia on renal tissue, we observed the cell growth inhibition rate by adding different concentration of glucose to cell supernatant. After that, a chemically-induced T2DM model was established by administering streptozotocin (STZ) to Sprague Dawley (SD) rats in combination with high fat feeding. In addition, a spontaneous T2DM model was established by feeding 8 weeks old KK-Ay mice a high-fat diet during a period of over 20 weeks. Animal body weight, fasting blood glucose (FBG), insulin tolerance, lipid metabolism, renal function, and renal pathology were periodically measured (once every 2 or 4 weeks) over a duration of 20 weeks. At the 12th week, an Affymetrix gene chip assay was performed on the renal tissues extracted from the T2DM animal models and control animals. Through screening for the differentially expressed genes, some key genes were selected for PCR validation.ResultsHigh level of glucose could inhibit the growth of kidney cells. Besides, KK-Ay mice were found to have high FBG and abnormal insulin tolerance. Renal dysfunction and pathology were observed at the 4th week following the start of model creation, which increased in severity over the length of the experiment. The T2DM SD rats also showed high FBG, abnormal glucose tolerance and abnormal lipid metabolism, but the renal function and renal pathology changed only slightly within 20 weeks. Gene profiling in animal kidneys and subsequent analyses and validation revealed differentially expressed genes and enriched pathways in DN.ConclusionKK-Ay mice with both high fasting glucose and insulin resistance were more likely to develop diabetic nephropathy than STZ-induced diabetic SD rats with low fasting glucose or only insulin resistance. The KK-Ay mice model showed earlier onset of the typical pathological characteristics associated with T2DM and obvious renal lesions suggestive of kidney damage.

Aberrant sinus node firing during β-adrenergic stimulation leads to cardiac arrhythmias in diabetic mice.

Cardiovascular complications, including cardiac arrhythmias, result in high morbidity and mortality in patients with type-2 diabetes mellitus (T2DM). Clinical and experimental data suggest electrophysiological impairment of the natural pacemaker of the diabetic heart. The present study examined sinoatrial node (SAN) arrhythmias in a mouse model of T2DM and physiologically probed their underlying cause. Electrocardiogramswere obtained from conscious diabetic db/db and lean control db/+ mice. In vivo SAN function was probed through pharmacological autonomic modulation with isoprenaline, atropine and carbachol. Blood pressure stability and heart rate variability (HRV) were evaluated. Intrinsic SAN function was evaluated through ex vivo imaging of spontaneous Ca2+ transients in isolated SAN preparations. While lean control mice showed constant RR intervals during isoprenaline challenge, the diabetic mice experienced SAN arrhythmias with large RR fluctuations in a dose-dependent manner. These arrhythmias were completely abolished by atropine pre-treatment, while carbachol pretreatment significantly increased SAN arrhythmia frequency in the diabetic mice. Blood pressure and HRV were comparable in db/db and db/+ mice, suggesting that neither augmented baroreceptor feedback nor autonomic neuropathy is a likely arrhythmia mechanism. Cycle length response to isoprenaline was comparable in isolated SAN preparations from db/db and db/+ mice; however, Ca2+ spark frequency was significantly increased in db/db mice compared to db/+ at baseline and after isoprenaline. Our results demonstrate a dysfunction of cardiac pacemaking in an animal model of T2DM upon challenge with a β-adrenergic agonist. Ex vivo, higher Ca2+ spark frequency is present in diabetic mice, which may be directly linked to in vivo arrhythmias.

The insulin resistance is reversed by exogenous 3,5,3'triiodothyronine in type 2 diabetic Goto-Kakizaki rats by an inflammatory-independent pathway.

Diabetes mellitus (DM) has a multifactorial etiology that imparts a particular challenge to effective pharmacotherapy. Thyroid hormone actions have demonstrated beneficial effects in diabetic as well as obese rats. In both conditions, inflammation status plays a crucial role in the development of insulin resistance. Taking this into consideration, the present study aimed to demonstrate another possible pathway of thyroid hormone action on insulin sensitivity in a spontaneous type 2 diabetic rat model: the Goto-Kakizaki (GK) rats. GK animals present all typical hallmarks of type 2 DM (T2DM), except the usual peripheric inflammatory condition, observed in the other T2DM animal models. GK rats were treated or not with 3,5,3'triiodothyronine (T3). Insulin sensitivity, glucose tolerance, and proteins related to glucose uptake and utilization were evaluated in the skeletal muscle, white adipose tissue, and liver. GK rats T3-treated presented enhanced insulin sensitivity, increased GLUT-4 content in the white adipose tissue and skeletal muscle, and increased hexokinase and citrate synthase content in skeletal muscle. Both non-treated and T3-treated GK rats did not present alterations in cytokine content in white adipose tissue, skeletal muscle, liver, and serum. These results indicate that T3 improves insulin sensitivity in diabetic rats by a novel inflammatory-independent mechanism.

Dual-specificity tyrosine phosphorylation-regulated kinase 1A ameliorates insulin resistance in neurons by up-regulating IRS-1 expression

Insulin resistance in the brain is a pathological mechanism that is shared between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). Although aberrant expression and phosphorylation of insulin receptor substrate 1 (IRS-1) contribute to insulin resistance, the underlying mechanism remains elusive. In this study, we used several approaches, including adeno-associated virus-based protein overexpression, immunoblotting, immunoprecipitation, immunohistochemistry, and in situ proximal ligation assays, to investigate the function of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) in IRS-1 regulation and the downstream insulin signaling in neurons. We found that DYRK1A overexpression up-regulated IRS-1 expression by slowing turnover of the IRS-1 protein. We further observed that DYRK1A directly interacted with IRS-1 and phosphorylated IRS-1's multiple serine residues. Of note, DYRK1A and IRS-1 were coordinately up-regulated in the prefrontal cortex of db/db mice brain. Furthermore, DYRK1A overexpression ameliorated chronic high insulin-induced insulin resistance in SH-SY5Y cells as well as in primary rat neurons. These findings suggest that DYRK1A protects against insulin resistance in the brain by elevating IRS-1 expression.

Dapagliflozin Attenuates Hyperglycemia Related Osteoporosis in ZDF Rats by Alleviating Hypercalciuria.

Recent studies showed that in patients with type 2 diabetes mellitus (T2DM), Sodium-dependent glucose transporters 2 inhibitor (SGLT2I) may cause potential adverse effects on skeleton such as increasing the risk of fracture. This risk is possibly mediated by effects induced by all SGLT2I class drugs but whether Dapagliflozin aggravates osteoporosis in patients with T2DM remains controversial. Therefore, we designed this study to explore how Dapagliflozin affects the metabolism and the quality of bone in. T2DM animal models The effect of Dapagliflozin on skeleton was evaluated on male ZDF (Zucker Diabetic Fatty) rats—a rat model of diet induced spontaneous T2DM. Dapagliflozin was administrated via gavage at the dosage of 1.0 mg/kg/day. Bone tissue mineral density and the microarchitecture of tibiae were measured with micro-CT and biomechanics characteristic of the femora were tested using a three-point bending test. Serum bone biomarkers and other metabolic parameters were also tested via ELISA or other assays. Our results found that diabetic rats demonstrated symptoms of osteoporosis and Dapagliflozin could help to alleviate these defections caused by diabetes. Compared to the negative controls, the serum CT (calcitonin) level in ZDF rats as well as the uric calcium and phosphate levels were elevated, and these symptoms were alleviated by Dapagliflozin. Tibiae of Dapagliflozin treated rats demonstrated decreased cortical tissue mineral density while trabecular tissue mineral density and mean bone mineral density received a rise when compared to the matched controls. ZDF rats also showed defections in femora stiffness which could be relieved by Dapagliflozin administration. The mechanism of Dapagliflozin affecting bone quality is possibly connected to the suppression of serum calcitonin and excretion of calcium via urine rose by hyperglycemia. In conclusion, Dapagliflozin can prevent osteoporosis in ZDF rats by alleviating hypercalciuria.

Effect of Exercise Intervention on Cardiac Function in Type 2 Diabetes Mellitus: A Systematic Review.

The effect of exercise on cardiac function/structure in type 2 diabetes mellitus (T2DM) with or without diabetic cardiomyopathy (DCM) is not yet completely understood. To date, results of studies have been controversial with variable outcomes due to the variety of exercise modalities. The aim of the present review was to examine the impact of exercise intervention, and different types of exercise, on cardiac function and structure in T2DM through a systematic literature review, combining both pre-clinical and clinical studies. A systematic literature search was performed on PubMed, Web of Science, and PEDro to identify studies up to 2 April 2018. Articles were included when well-defined exercise protocols were provided, and cardiac function in T2DM patients or validated animal models was examined. In diabetic animals, improvements in both diastolic and systolic function through exercise therapy were mainly attributed to reduced collagen deposition. In T2DM patients, improvements were observed in diastolic function, but not consistently in systolic function, after endurance (and combined resistance) exercise training. Different exercise intervention modalities and exercise types seemed equally effective in improving cardiac structure and function. Exercise training elicits significant improvements in diastolic function and beneficial remodeling in T2DM and DCM animal models, but not necessarily improvements in systolic function and left ventricular structure, regardless of exercise type. Therefore, exercise intervention should be a cornerstone in the treatment of T2DM patients not only to improve glycemic control but also to specifically enhance cardiac function.

ITRAQ and PRM-based quantitative proteomics in T2DM-susceptible and -tolerant models of Bama mini-pig

Type 2 diabetes mellitus (T2DM) is a complex, multifactorial metabolic disease, and the number of patients with T2DM has continued to increase in recent years. Large-scale proteomic studies on animal models of T2DM are of great importance to understand the pathophysiology of T2DM. Therefore, in our study, Isobaric tags for relative and absolute quantification (iTRAQ) and Parallel reaction monitoring (PRM) were used for proteomic analysis of skeletal muscles from T2DM-susceptible and -tolerant Bama mini-pig models induced by a high-fat, high-sugar diet. In our proteomic analysis, a total of 1646 proteins and 13 differentially expressed proteins (DEPs) were identified by iTRAQ-mass spectrometry, and 6 differentially expressed proteins were validated by PRM. Gene Ontology (GO) analysis revealed that most DEPs were extracellular matrix (ECM) proteins and participated in several biological processes, such as negative regulation of JAK-STAT cascade, negative regulation of STAT cascade, roundabout signaling pathway and peptide cross-linking via chondroitin 4-sulfate glycosaminoglycan, and the molecular functions of roundabout binding, glycosaminoglycan binding, heparin binding, sulfur compound binding, collagen binding, and kinase inhibitor activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis results showed that the differentially expressed proteins were involved in 14 pathways, including human disease pathways, metabolic pathways, signal transduction pathways, signaling molecules and interaction pathways, and the cellular process pathways associated with phagosomes and focal adhesion. In conclusion, the proteomics based on iTRAQ and PRM in T2DM-susceptible and -tolerant Bama mini-pig models showed that changes in amino acid metabolism, inflammation-associated pathways and the impaired function and environment of extracellular matrix are risk factors associated with increased pathogenesis of T2DM in Bama mini-pig.

Type 2 Diabetes Mellitus in Rats on a High-Fat Diet with Streptozotocin Induction: Evaluation of the Model

Introduction: Type 2 diabetes mellitus (T2DM) is a complex heterogeneous disease linked with genetic conditions and lifestyle, especially dietary component. Development of the accessible experimental animal model of T2DM is indispensable for elucidation of its pathogenesis and identification of novel antidiabetic agents. Methods: Modeling of experimental T2DM were performed on male Wistar rats aged 9-12 weeks with 2 weeks of dietary manipulation (58% of calories from fats) followed with 35 mg·kg-1 i.p. streptozotocin injection. To evaluate the model, we used intraperitoneal glucose and insulin tolerance test and determined fasting blood concentration of glucose, triglycerides, total cholesterol, and insulin. Additional evaluation of the model was performed by administration of pioglitazone (10 mg/kg-1 p.o.) for 7 days. Student’s t-test was used for single variable comparison between two groups. One-way ANOVA followed by Dunnett post hoc test was used for multiple comparisons versus the control group. Results: T2DM model obtained reproduced key metabolic disorders of the disease, including hyperglycemia (p&lt;0.05), hyperinsulinemia (p&lt;0.05), dyslipidemia (p&lt;0.05) and impaired glucose and insulin tolerance (p&lt;0.05). Administration of pioglitazone significantly improved these metabolic disorders. Thus, we obtained a suitable rat model of T2DM for screening of antidiabetic agents. Conclusion: In comparison of our results with other authors’ data, we have found decreased severity of plasma glucose and basal total cholesterol levels impairment, which highlights the need for careful monitoring of biochemical parameters in high-fat diet and streptozotocin-treated rats.