scholarly journals Lipotoxic Stress Induces Pancreaticβ-Cell Apoptosis through Modulation of Bcl-2 Proteins by the Ubiquitin-Proteasome System

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Sara A. Litwak ◽  
Jibran A. Wali ◽  
Evan G. Pappas ◽  
Hamdi Saadi ◽  
William J. Stanley ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Cell Death ◽  
Er Stress ◽  
Ubiquitin Proteasome System ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Ubiquitin Proteasome

Pancreaticβ-cell loss induced by saturated free fatty acids (FFAs) is believed to contribute to type 2 diabetes. Previous studies have shown induction of endoplasmic reticulum (ER) stress, increased ubiquitinated proteins, and deregulation of the Bcl-2 family in the pancreas of type 2 diabetic patients. However, the precise mechanism ofβ-cell death remains unknown. In the present study we demonstrate that the FFA palmitate blocks the ubiquitin-proteasome system (UPS) and causes apoptosis through induction of ER stress and deregulation of Bcl-2 proteins. We found that palmitate and the proteasome inhibitor MG132 induced ER stress inβ-cells, resulting in decreased expression of the prosurvival proteins Bcl-2, Mcl-1, and Bcl-XL, and upregulation of the prodeath BH3-only protein PUMA. On the other hand, pharmacological activation of the UPS by sulforaphane ameliorated ER stress, upregulated prosurvival Bcl-2 proteins, and protectedβ-cells from FFA-induced cell death. Furthermore, transgenic overexpression of Bcl-2 protected islets from FFA-induced cell deathin vitroand improved glucose-induced insulin secretionin vivo. Together our results suggest that targeting the UPS and Bcl-2 protein expression may be a valuable strategy to preventβ-cell demise in type 2 diabetes.

Degradation of mutant huntingtin via the ubiquitin/proteasome system is modulated by FE65

2012 ◽  
Vol 443 (3) ◽  
pp. 681-689 ◽  
Author(s):  
Wan Ning Vanessa Chow ◽  
Hon Wing Luk ◽  
Ho Yin Edwin Chan ◽  
Kwok-Fai Lau
Keyword(s):  
Cell Death ◽  
Degradation Mechanism ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Adaptor Protein ◽  
Ubiquitin Proteasome System ◽  
Exon 1 ◽  
Ubiquitin Proteasome

An unstable expansion of the polyglutamine repeat within exon 1 of the protein Htt (huntingtin) causes HD (Huntington's disease). Mounting evidence shows that accumulation of N-terminal mutant Htt fragments is the source of disruption of normal cellular processes which ultimately leads to neuronal cell death. Understanding the degradation mechanism of mutant Htt and improving its clearance has emerged as a new direction in developing therapeutic approaches to treat HD. In the present study we show that the brain-enriched adaptor protein FE65 is a novel interacting partner of Htt. The binding is mediated through WW–polyproline interaction and is dependent on the length of the polyglutamine tract. Interestingly, a reduction in mutant Htt protein level was observed in FE65-knockdown cells, and the process requires the UPS (ubiquitin/proteasome system). Moreover, the ubiquitination level of mutant Htt was found to be enhanced when FE65 is knocked down. Immunofluroescence staining revealed that FE65 associates with mutant Htt aggregates. Additionally, we demonstrated that overexpression of FE65 increases mutant Htt-induced cell death both in vitro and in vivo. These results suggest that FE65 facilitates the accumulation of mutant Htt in cells by preventing its degradation via the UPS, and thereby enhances the toxicity of mutant Htt.

scholarly journals Distinct Gut Microbiota Induced by Different Fat-to-Sugar-Ratio High-Energy Diets Share Similar Pro-obesity Genetic and Metabolite Profiles in Prediabetic Mice

mSystems ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Kai Shan ◽  
Hongyan Qu ◽  
Keru Zhou ◽  
Liangfang Wang ◽  
Congmin Zhu ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Gut Microbiota ◽  
Early Stage ◽  
Amplicon Sequencing ◽  
High Energy ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients

ABSTRACT Gut microbiota play important roles in host metabolism, especially in diabetes. However, why different diets lead to similar diabetic states despite being associated with different microbiota is not clear. Mice were fed two high-energy diets (HED) with the same energy density but different fat-to-sugar ratios to determine the associations between the microbiota and early-stage metabolic syndrome. The two diets resulted in different microbiota but similar diabetic states. Interestingly, the microbial gene profiles were not significantly different, and many common metabolites were identified, including l-aspartic acid, cholestan-3-ol (5β, 3α), and campesterol, which have been associated with lipogenesis and inflammation. Our study suggests that different metabolic-syndrome-inducing diets may result in different microbiota but similar microbiomes and metabolomes. This suggests that the metagenome and metabolome are crucial for the prognosis and pathogenesis of obesity and metabolic syndrome. IMPORTANCE Various types of diet can lead to type 2 diabetes. The gut microbiota in type 2 diabetic patients are also different. So, two questions arise: whether there are any commonalities between gut microbiota induced by different pro-obese diets and whether these commonalities lead to disease. Here we found that high-energy diets with two different fat-to-sugar ratios can both cause obesity and prediabetes but enrich different gut microbiota. Still, these different gut microbiota have similar genetic and metabolite compositions. The microbial metabolites in common between the diets modulate lipid accumulation and macrophage inflammation in vivo and in vitro. This work suggests that studies that only use 16S rRNA amplicon sequencing to determine how the microbes respond to diet and associate with diabetic state are missing vital information.

scholarly journals Transthyretin and Amyloid in the Islets of Langerhans in Type-2 Diabetes

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Gunilla T. Westermark ◽  
Per Westermark
Keyword(s):  
Type 2 Diabetes ◽  
Islets Of Langerhans ◽  
Islet Cells ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Amyloid Fibril Protein ◽  
Type 2 Diabetic

Transthyretin (TTR) is a major amyloid fibril protein in certain systemic forms of amyloidosis. It is a plasma protein, mainly synthesized by the liver but expression occurs also at certain minor locations, including the endocrine cells in the islets of Langerhans. With the use of immunohistochemistry and in situ hybridization, we have studied the distribution of transthyretin-containing cells in islets of Langerhans in type-2 diabetic and nondiabetic individuals. TTR expression was particularly seen in alpha (glucagon) cells. Islets from type-2 diabetic patients had proportionally more transthyretin-reactive islet cells, including beta cells. A weak transthyretin immunoreaction in IAPP-derived amyloid occurred in some specimens. In seeding experiments in vitro, we found that TTR fibrils did not seed IAPP while IAPP fibrils seeded TTR. It is suggested that islet expression of transthyretin may be altered in type-2 diabetes.

scholarly journals Islet Amyloid Polypeptide: Structure, Function, and Pathophysiology

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Rehana Akter ◽  
Ping Cao ◽  
Harris Noor ◽  
Zachary Ridgway ◽  
Ling-Hsien Tu ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Cell Death ◽  
Type 1 Diabetes ◽  
Islet Amyloid Polypeptide ◽  
Amyloid Formation ◽  
Islet Amyloid

The hormone islet amyloid polypeptide (IAPP, or amylin) plays a role in glucose homeostasis but aggregates to form islet amyloid in type-2 diabetes. Islet amyloid formation contributes toβ-cell dysfunction and death in the disease and to the failure of islet transplants. Recent work suggests a role for IAPP aggregation in cardiovascular complications of type-2 diabetes and hints at a possible role in type-1 diabetes. The mechanisms of IAPP amyloid formationin vivoorin vitroare not understood and the mechanisms of IAPP inducedβ-cell death are not fully defined. Activation of the inflammasome, defects in autophagy, ER stress, generation of reactive oxygen species, membrane disruption, and receptor mediated mechanisms have all been proposed to play a role. Open questions in the field include the relative importance of the various mechanisms ofβ-cell death, the relevance of reductionist biophysical studies to the situationin vivo, the molecular mechanism of amyloid formationin vitroandin vivo, the factors which trigger amyloid formation in type-2 diabetes, the potential role of IAPP in type-1 diabetes, the development of clinically relevant inhibitors of islet amyloidosis toxicity, and the design of soluble, bioactive variants of IAPP for use as adjuncts to insulin therapy.

scholarly journals Autocrine Exosomal Fibulin-1 as a Target of MiR-1269b Induces Epithelial–Mesenchymal Transition in Proximal Tubule in Diabetic Nephropathy

2021 ◽  
Vol 9 ◽  
Author(s):  
Yi-Chun Tsai ◽  
Wei-Wen Hung ◽  
Wei-An Chang ◽  
Ping-Hsun Wu ◽  
Ling-Yu Wu ◽  
...  
Keyword(s):  
Diabetic Nephropathy ◽  
Epithelial Mesenchymal Transition ◽  
Cell Communication ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Mesenchymal Transition ◽  
Type 2 Diabetic

Background: Diabetic nephropathy (DN) is an increasing threat to human health and is regarded to be the leading cause of end-stage renal disease worldwide. Exosomes deliver biomolecule massages and may play a key role in cell communication and the progression of DN.Methods: A cross-disciplinary study, including in vivo, in vitro, and human studies, was conducted to explore the cross-talk within proximal tubular epithelial cells (PTECs) in DN. Exosomal protein from PTECs treated with high glucose (HG) was purified and examined using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Next-generation sequencing (NGS) was utilized to analyze RNAs extracted from PTECs from a type 2 diabetic patient and a normal individual. HK-2 cells were used to assess exosomal protein and its modulation and biofunction in DN. Normal individuals and type 2 diabetic patients were enrolled, and nondiabetic db/m mice and diabetic db/db mice were used to validate the molecular mechanism of exosomes in DN.Results: HG stimulated PTECs to increase Fibulin-1 (FBLN1) expression, and PTECs secreted FBLN1 through exosome delivery, thereby inducing epithelial–mesenchymal transition (EMT) in PTECs. Transcriptome analysis found that FBLN1 expression was modulated by miR-1269b, which was downregulated by HG in HK-2 cells. While transfection of miR-1269b reversed FBLN1-mediated EMT in PTECs, miR-1269b inhibitor modulated the phenotype of PTECs toward mesenchymal type under normal glucose (NG) condition. Most importantly, urinary FBLN1 and exosomal miR-1269b levels were correlated with the severity of kidney injury in type 2 diabetic patients.Conclusion: This study demonstrated the communication within PTECs through exosome transmission in an autocrine pattern. MiR-1269b–FBLN1 epigenetic regulatory network could be a potential therapeutic strategy to prevent the progression of DN.

scholarly journals Natural Hydrogen Sulfide Donors from Allium sp. as a Nutraceutical Approach in Type 2 Diabetes Prevention and Therapy

Nutrients ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1581 ◽  
Author(s):  
Melino ◽  
Leo ◽  
Papajani
Keyword(s):  
Type 2 Diabetes ◽  
Medicinal Plants ◽  
Dietary Therapy ◽  
Diabetic Patients ◽  
Organosulfur Compounds ◽  
Type 2 Dm ◽  
Peripheral Arterial Diseases

Type 2 diabetes mellitus (DM) is a socially relevant chronic disease with high prevalence worldwide. DM may lead to several vascular, macrovascular, and microvascular complications (cerebrovascular, coronary artery, and peripheral arterial diseases, retinopathy, neuropathy, and nephropathy), often accelerating the progression of atherosclerosis. Dietary therapy is generally considered to be the first step in the treatment of diabetic patients. Among the current therapeutic options, such as insulin therapy and hypoglycemic drugs, in recent years, attention has been shifting to the effects and properties—that are still not completely known—of medicinal plants as valid and inexpensive therapeutic supports with limited side effects. In this review, we report the relevant effects of medicinal plants and nutraceuticals in diabetes. In particular, we paid attention to the organosulfur compounds (OSCs) present in plant extracts that due to their antioxidant, hypoglycemic, anti-inflammatory, and immunomodulatory effects, can contribute as cardioprotective agents in type 2 DM. OSCs derived from garlic (Allium sp.), due to their properties, can represent a valuable support to the diet in type 2 DM, as outlined in this manuscript based on both in vitro and in vivo studies. Moreover, a relevant characteristic of garlic OSCs is their ability to produce the gasotransmitter H2S, and many of their effects can be explained by this property. Indeed, in recent years, several studies have demonstrated the relevant effects of endogenous and exogenous H2S in human DM, including by in vitro and in vivo experiments and clinical trials; therefore, here, we summarize the effects and the underlying molecular mechanisms of H2S and natural H2S donors.

scholarly journals Interleukin-6 autoantibodies are involved in the pathogenesis of a subset of type 2 diabetes

2009 ◽  
Vol 204 (3) ◽  
pp. 265-273 ◽  
Author(s):  
K Fosgerau ◽  
P Galle ◽  
T Hansen ◽  
A Albrechtsen ◽  
C de Lemos Rieper ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Glucose Tolerance ◽  
Impaired Glucose Tolerance ◽  
Interleukin 6 ◽  
Plasma Levels ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Type 2 Diabetic

AbstractInterleukin-6 (IL6) is critically involved in inflammation and metabolism. About 1% of people produce IL6 autoantibodies (aAb-IL6) that impair IL6 signaling in vivo. We tested the hypothesis that the prevalence of such aAb-IL6 is increased in type 2 diabetic patients and that aAb-IL6 plays a direct role in causing hyperglycemia. In humans, the prevalence of circulating high-affinity neutralizing aAb-IL6 was 2.5% in the type 2 diabetic patients and 1% in the controls (odds ratio 2.5, 95% confidence interval 1.2–4.9, P=0.01). To test for the role of aAb-IL6 in causing hyperglycemia, such aAb-IL6 were induced in mice by a validated vaccination procedure. Mice with plasma levels of aAb-IL6 similar to the 2.5% type 2 diabetic patients developed obesity and impaired glucose tolerance (area under the curve (AUC) glucose, 2056±62 vs 1793±62, P=0.05) as compared with sham-vaccinated mice, when challenged with a high-fat diet. Mice with very high plasma levels of aAb-IL6 developed elevated fasting plasma glucose (mM, 4.8±0.4 vs 3.3±0.1, P<0.001) and impaired glucose tolerance (AUC glucose, 1340±38 vs 916±25, P<0.001) as compared with sham-control mice on normal chow. In conclusion, the prevalence of plasma aAb-IL6 at levels known to impair IL6 signaling in vivo is increased 2.5-fold in people with type 2 diabetes. In mice, matching levels of aAb-IL6 cause obesity and hyperglycemia. These data suggest that a small subset of type 2 diabetes may in part evolve from an autoimmune attack against IL6.

scholarly journals A breakthrough-like effect of metformin reduces peripheral resistance to triiodothyronine in euthyroid, non-insulin-resistant, type 2 diabetic patients

2021 ◽  
Author(s):  
Melinda Kertész ◽  
Szilárd Kun ◽  
Eszter Sélley ◽  
Zsuzsanna Nagy ◽  
Tamás Kőszegi ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Blood Pressure ◽  
Type 2 Diabetes ◽  
In Vitro Study ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Akt Phosphorylation ◽  
Type 2 Diabetic

Background: Type 2 diabetes is characterized, beyond the insulin resistance, by polyhormonal resistance. Thyroid hormonal resistance has not yet been described in this population of patients. Metformin is used to decrease insulin resistance, and at present it is assumed to influence the effect of triiodothyronine, as well. Methods: In this open label, pilot, hypothesis generating, follow-up study 21 patients were included, all of them euthyroid with drug naïve, newly diagnosed type 2 diabetes. Before and after four weeks of metformin therapy fructosamine, homeostasis model assessment for insulin resistance (HOMA-IR), thyroid hormones, T3/T4 ratio, and TSH, as well as blood pressure and heart rate using ambulatory blood pressure monitor were measured. We also conducted an in vitro study to investigate the possible mechanisms of T3 resistance, assessing T3 induced Akt phosphorylation among normal (5 mM) and high (25 mM) glucose levels with or without metformin treatment in a human embryonal kidney cell line. Results: Metformin decreased the level of T3 (p<0.001), the ratio of T3/T4 (p=0.038), fructosamine (p=0.008) and HOMA-IR (p=0.022). All these changes were accompanied by an unchanged TSH, T4, triglyceride, plasma glucose, bodyweight, blood pressure and heart rate. In our in vitro study, T3 induced Akt phosphorylation decreased in cells grown in 25 mM glucose medium compared to those in 5 mM. Metformin could not reverse this effect. Conclusion: Metformin seems to improve T3 sensitivity in the cardiovascular system in euthyroid, type 2 diabetic patients, the mechanism of which may be supracellular.

Metabolic and endothelial effects of trimetazidine on forearm skeletal muscle in patients with type 2 diabetes and ischemic cardiomyopathy

2006 ◽  
Vol 290 (1) ◽  
pp. E54-E59 ◽  
Author(s):  
Lucilla D. Monti ◽  
Emanuela Setola ◽  
Gabriele Fragasso ◽  
Riccardo P. Camisasca ◽  
Pietro Lucotti ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Lipid Oxidation ◽  
Ischemic Cardiomyopathy ◽  
Glucose Oxidation ◽  
Diabetic Patients ◽  
Vascular Effects ◽  
Type 2 Diabetic Patients ◽  
Double Blind ◽  
Endothelin 1

The aim of the present study was to evaluate the effect of prolonged inhibition of β-oxidation on glucose and lipid muscle forearm metabolism and cGMP and endothelin-1 forearm release in patients with type 2 diabetes mellitus and ischemic cardiomyopathy. Fifteen patients were randomly allocated in a double-blind cross-over parallel study with trimetazidine (20 mg tid) or placebo lasting 15 days. At the end of each period, all patients underwent euglycemic hyperinsulinemic clamps with forearm indirect calorimetry and endothelial balance of vasodilator and vasoconstricor factors. Compared with placebo, trimetazidine induced 1) an increase in insulin-induced forearm glucose uptake and glucose oxidation accompained by a reduction in forearm lipid oxidation and citrate release and 2) a decrease of endothelin-1 release paralleled by a significant increase in forearm cGMP release. Forearm glucose oxidation significantly correlated with cGMP release ( r = 0.37, P < 0.04), whereas forearm lipid oxidation positively correlated with endothelin-1 release ( r = 0.40, P < 0.03). In conclusion, for the first time, we demonstrated that insulin-induced forearm glucose oxidation and forearm cGMP release were increased whereas forearm endothelin-1 release was decreased during trimetazidine treatment. Muscle's metabolic and vascular effects of trimetazidine add new interest in the use of trimetazidine in type 2 diabetic patients with cardiovascular disease.

scholarly journals Breakdown of Filamentous Myofibrils by the UPS–Step by Step

Biomolecules ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 110
Author(s):  
Dina Aweida ◽  
Shenhav Cohen
Keyword(s):  
Protein Quality ◽  
Protein Structures ◽  
Ubiquitin Proteasome System ◽  
Surface Proteins ◽  
Catalytic Core ◽  
Complex Protein ◽  
Ubiquitin Proteasome ◽  
Aaa Atpases

Protein degradation maintains cellular integrity by regulating virtually all biological processes, whereas impaired proteolysis perturbs protein quality control, and often leads to human disease. Two major proteolytic systems are responsible for protein breakdown in all cells: autophagy, which facilitates the loss of organelles, protein aggregates, and cell surface proteins; and the ubiquitin-proteasome system (UPS), which promotes degradation of mainly soluble proteins. Recent findings indicate that more complex protein structures, such as filamentous assemblies, which are not accessible to the catalytic core of the proteasome in vitro, can be efficiently degraded by this proteolytic machinery in systemic catabolic states in vivo. Mechanisms that loosen the filamentous structure seem to be activated first, hence increasing the accessibility of protein constituents to the UPS. In this review, we will discuss the mechanisms underlying the disassembly and loss of the intricate insoluble filamentous myofibrils, which are responsible for muscle contraction, and whose degradation by the UPS causes weakness and disability in aging and disease. Several lines of evidence indicate that myofibril breakdown occurs in a strictly ordered and controlled manner, and the function of AAA-ATPases is crucial for their disassembly and loss.

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