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1.
Am J Physiol Endocrinol Metab ; 327(1): E27-E41, 2024 Jul 01.
Article in English | MEDLINE | ID: mdl-38690938

ABSTRACT

Pancreatic endocrine cells employ a sophisticated system of paracrine and autocrine signals to synchronize their activities, including glutamate, which controls hormone release and ß-cell viability by acting on glutamate receptors expressed by endocrine cells. We here investigate whether alteration of the excitatory amino acid transporter 2 (EAAT2), the major glutamate clearance system in the islet, may occur in type 2 diabetes mellitus and contribute to ß-cell dysfunction. Increased EAAT2 intracellular localization was evident in islets of Langerhans from T2DM subjects as compared with healthy control subjects, despite similar expression levels. Chronic treatment of islets from healthy donors with high-glucose concentrations led to the transporter internalization in vesicular compartments and reduced [H3]-d-glutamate uptake (65 ± 5% inhibition), phenocopying the findings in T2DM pancreatic sections. The transporter relocalization was associated with decreased Akt phosphorylation protein levels, suggesting an involvement of the phosphoinositide 3-kinase (PI3K)/Akt pathway in the process. In line with this, PI3K inhibition by a 100-µM LY294002 treatment in human and clonal ß-cells caused the transporter relocalization in intracellular compartments and significantly reduced the glutamate uptake compared to control conditions, suggesting that hyperglycemia changes the trafficking of the transporter to the plasma membrane. Upregulation of the glutamate transporter upon treatment with the antibiotic ceftriaxone rescued hyperglycemia-induced ß-cells dysfunction and death. Our data underscore the significance of EAAT2 in regulating islet physiology and provide a rationale for potential therapeutic targeting of this transporter to preserve ß-cell survival and function in diabetes.NEW & NOTEWORTHY The glutamate transporter SLC1A2/excitatory amino acid transporter 2 (EAAT2) is expressed on the plasma membrane of pancreatic ß-cells and controls islet glutamate clearance and ß-cells survival. We found that the EAAT2 membrane expression is lost in the islets of Langerhans from type 2 diabetes mellitus (T2DM) patients due to hyperglycemia-induced downregulation of the phosphoinositide 3-kinase/Akt pathway and modification of its intracellular trafficking. Pharmacological rescue of EAAT2 expression prevents ß-cell dysfunction and death, suggesting EAAT2 as a new potential target of intervention in T2DM.


Subject(s)
Diabetes Mellitus, Type 2 , Excitatory Amino Acid Transporter 2 , Glutamic Acid , Hyperglycemia , Islets of Langerhans , Excitatory Amino Acid Transporter 2/metabolism , Humans , Diabetes Mellitus, Type 2/metabolism , Glutamic Acid/metabolism , Hyperglycemia/metabolism , Islets of Langerhans/metabolism , Islets of Langerhans/drug effects , Male , Middle Aged , Female , Protein Transport , Insulin-Secreting Cells/metabolism , Insulin-Secreting Cells/drug effects , Proto-Oncogene Proteins c-akt/metabolism , Aged , Adult , Animals , Phosphatidylinositol 3-Kinases/metabolism
2.
Am J Physiol Endocrinol Metab ; 325(5): E595-E609, 2023 11 01.
Article in English | MEDLINE | ID: mdl-37729025

ABSTRACT

Simultaneous activation of the incretin G-protein-coupled receptors (GPCRs) via unimolecular dual-receptor agonists (UDRA) has emerged as a new therapeutic approach for type 2 diabetes. Recent studies also advocate triple agonism with molecules also capable of binding the glucagon receptor. In this scoping review, we discuss the cellular mechanisms of action (MOA) underlying the actions of these novel and therapeutically important classes of peptide receptor agonists. Clinical efficacy studies of several UDRAs have demonstrated favorable results both as monotherapies and when combined with approved hypoglycemics. Although the additive insulinotropic effects of dual glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic peptide receptor (GIPR) agonism were anticipated based on the known actions of either glucagon-like peptide-1 (GLP-1) or glucose-dependent insulinotropic peptide (GIP) alone, the additional benefits from GCGR were largely unexpected. Whether additional synergistic or antagonistic interactions among these G-protein receptor signaling pathways arise from simultaneous stimulation is not known. The signaling pathways affected by dual- and tri-agonism require more trenchant investigation before a comprehensive understanding of the cellular MOA. This knowledge will be essential for understanding the chronic efficacy and safety of these treatments.


Subject(s)
Diabetes Mellitus, Type 2 , Islets of Langerhans , Humans , Incretins/pharmacology , Incretins/metabolism , Gastric Inhibitory Polypeptide/pharmacology , Gastric Inhibitory Polypeptide/metabolism , Diabetes Mellitus, Type 2/drug therapy , Diabetes Mellitus, Type 2/metabolism , Islets of Langerhans/metabolism , Glucagon-Like Peptide 1/metabolism , Receptors, Glucagon/metabolism , Glucagon-Like Peptide-1 Receptor/metabolism
3.
Medicine (Baltimore) ; 102(1): e32475, 2023 Jan 06.
Article in English | MEDLINE | ID: mdl-36607874

ABSTRACT

RATIONALE: Drug-induced aseptic meningitis (DIAM) is an uncommon meningitis and trimethoprim with or without sulfamethoxazole is the most involved antibiotic. Although DIAM is easily treated with the discontinuation of the causative drug, the diagnosis is a big challenge for physicians, as it remains a diagnosis of exclusion. Here, we present a case report of trimethoprim-sulfamethoxazole induced aseptic meningitis in a woman with acute osteomyelitis. PATIENT CONCERNS: A 52-year-old woman was admitted to the hospital for septic shock and acute osteomyelitis of the right homerus. She was started on antibiotic therapy with oxacillin and daptomycin, then oxacillin was replaced with cotrimoxazole, due to its excellent tissue penetration, including bone tissue. During cotrimoxazole therapy, the patient developed a fluent aphasia with ideomotor apraxia and muscle hypertonus. DIAGNOSIS AND INTERVENTIONS: Having excluded infectious, epileptic and vascular causes of the acute neurologic syndrome of our patient, given the improvement and full recovery after discontinuation of cotrimoxazole, we hypothesized a DIAM. OUTCOMES: After discontinuation of cotrimoxazole, in 48 hours the patient had a full recovery. LESSONS: Although DIAM can be easily managed with the withdrawal of the causative drug, it can be difficult to recognize if it is not included in the differential diagnosis. An antimicrobial stewardship program with a strict monitoring of patients by infectious disease specialists is essential, not only to optimize the appropriate use of antimicrobials, but also to improve patient outcomes and reduce the likelihood of adverse events.


Subject(s)
Anti-Infective Agents , Meningitis, Aseptic , Female , Humans , Middle Aged , Trimethoprim, Sulfamethoxazole Drug Combination/adverse effects , Meningitis, Aseptic/chemically induced , Meningitis, Aseptic/diagnosis , Anti-Bacterial Agents/adverse effects , Oxacillin/adverse effects
4.
Pharmacol Res ; 177: 106130, 2022 03.
Article in English | MEDLINE | ID: mdl-35151858

ABSTRACT

Islet cell surface autoantibodies were previously found in subjects with type 1 diabetes mellitus (T1DM), but their target antigens and pathogenic mechanisms remain elusive. The glutamate transporter solute carrier family 1, member 2 (GLT1/EAAT2) is expressed on the membrane of pancreatic ß-cells and physiologically controls extracellular glutamate concentrations thus preventing glutamate-induced ß-cell death. We hypothesized that GLT1 could be an immunological target in T1DM and that autoantibodies against GLT1 could be pathogenic. Immunoprecipitation and ELISA experiments showed that sera from T1DM subjects recognized GLT1 expressed in brain, pancreatic islets, and GLT1-transfected COS7-cell extracts. We validated these findings in two cohorts of T1DM patients by quantitative immunofluorescence assays. Analysis of the combined data sets indicated the presence of autoantibodies against GLT1 in 32 of the 87 (37%) T1DM subjects and in none of healthy controls (n = 64) (p < 0.0001). Exposure of pancreatic ßTC3 cells and human islets to purified IgGs from anti-GLT1 positive sera supplemented with complement resulted in plasma membrane ruffling, cell lysis and death. The cytotoxic effect was prevented when sera were depleted from IgGs. Furthermore, in the absence of complement, 6 out of 16 (37%) anti-GLT1 positive sera markedly reduced GLT1 transport activity in ßTC3 cells by inducing GLT1 internalization, also resulting in ß-cell death. In conclusion, we provide evidence that GLT1 is a novel T1DM autoantigen and that anti-GLT1 autoantibodies cause ß-cell death through complement-dependent and independent mechanisms. GLT1 seems an attractive novel therapeutic target for the prevention of ß-cell death in individuals with diabetes and prediabetes.


Subject(s)
Amino Acid Transport System X-AG , Diabetes Mellitus, Type 1 , Autoantibodies , Diabetes Mellitus, Type 1/therapy , Glutamic Acid/metabolism , Humans , Neuroglia/metabolism
5.
Diabetologia ; 63(12): 2548-2558, 2020 12.
Article in English | MEDLINE | ID: mdl-33029657

ABSTRACT

AIMS/HYPOTHESIS: The aim of the study was to characterise the humoral response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients with diabetes. Demonstrating the ability to mount an appropriate antibody response in the presence of hyperglycaemia is relevant for the comprehension of mechanisms related to the observed worse clinical outcome of coronavirus disease 2019 (COVID-19) pneumonia in patients with diabetes and for the development of any future vaccination campaign to prevent SARS-CoV-2 infection. METHODS: Using a highly specific and sensitive measurement of antibodies by fluid-phase luciferase immunoprecipitation assays, we characterised the IgG, IgM and IgA response against multiple antigens of SARS-CoV-2 in a cohort of 509 patients with documented diagnosis of COVID-19, prospectively followed at our institution. We analysed clinical outcomes and antibody titres according to the presence of hyperglycaemia, i.e., either diagnosed or undiagnosed diabetes, at the time of, or during, hospitalisation. RESULTS: Among patients with confirmed COVID-19, 139 (27.3%) had diabetes: 90 (17.7%) had diabetes diagnosed prior to the hospital admission (comorbid diabetes) while 49 (9.6%) had diabetes diagnosed at the time of admission (newly diagnosed). Diabetes was associated with increased levels of inflammatory biomarkers and hypercoagulopathy, as well as leucocytosis and neutrophilia. Diabetes was independently associated with risk of death (HR 2.32 [95% CI 1.44, 3.75], p = 0.001), even after adjustment for age, sex and other relevant comorbidities. Moreover, a strong association between higher glucose levels and risk of death was documented irrespective of diabetes diagnosis (HR 1.14 × 1.1 mmol/l [95% CI 1.08, 1.21], p < 0.001). The humoral response against SARS-CoV-2 in patients with diabetes was present and superimposable, as for timing and antibody titres, to that of non-diabetic patients, with marginal differences, and was not influenced by glucose levels. Of the measured antibody responses, positivity for IgG against the SARS-CoV-2 spike receptor-binding domain (RBD) was predictive of survival rate, both in the presence or absence of diabetes. CONCLUSIONS/INTERPRETATION: The observed increased severity and mortality risk of COVID-19 pneumonia in patients with hyperglycaemia was not the result of an impaired humoral response against SARS-CoV-2. RBD IgG positivity was associated with a remarkable protective effect, allowing for a cautious optimism about the efficacy of future vaccines against SARs-COV-2 in people with diabetes. Graphical abstract.


Subject(s)
Antibody Formation , Antigens, Viral/immunology , Coronavirus Infections/immunology , Diabetes Mellitus/immunology , Pneumonia, Viral/immunology , Adult , Aged , Aged, 80 and over , Antibodies, Viral/chemistry , Antibodies, Viral/immunology , Antibodies, Viral/isolation & purification , Biomarkers/analysis , Blood Coagulation Disorders/complications , Blood Coagulation Disorders/immunology , Blood Glucose/analysis , COVID-19 , Cohort Studies , Coronavirus Infections/mortality , Female , Humans , Immunity, Humoral , Immunoglobulin G/analysis , Immunoglobulin G/immunology , Male , Middle Aged , Pandemics , Pneumonia, Viral/mortality , Risk Factors , Survival Analysis
6.
JCI Insight ; 4(20)2019 10 17.
Article in English | MEDLINE | ID: mdl-31536476

ABSTRACT

The glucagon-like peptide-1 receptor agonist exenatide improves glycemic control by several and not completely understood mechanisms. Herein, we examined the effects of chronic intravenous exenatide infusion on insulin sensitivity, ß cell and α cell function and relative volumes, and islet cell apoptosis and replication in nondiabetic nonhuman primates (baboons). At baseline, baboons received a 2-step hyperglycemic clamp followed by an l-arginine bolus (HC/A). After HC/A, baboons underwent a partial pancreatectomy (tail removal) and received a continuous exenatide (n = 12) or saline (n = 12) infusion for 13 weeks. At the end of treatment, HC/A was repeated, and the remnant pancreas (head-body) was harvested. Insulin sensitivity increased dramatically after exenatide treatment and was accompanied by a decrease in insulin and C-peptide secretion, while the insulin secretion/insulin resistance (disposition) index increased by about 2-fold. ß, α, and δ cell relative volumes in exenatide-treated baboons were significantly increased compared with saline-treated controls, primarily as the result of increased islet cell replication. Features of cellular stress and secretory dysfunction were present in islets of saline-treated baboons and absent in islets of exenatide-treated baboons. In conclusion, chronic administration of exenatide exerts proliferative and cytoprotective effects on ß, α, and δ cells and produces a robust increase in insulin sensitivity in nonhuman primates.


Subject(s)
Diabetes Mellitus, Type 2/drug therapy , Exenatide/pharmacology , Hypoglycemic Agents/pharmacology , Insulin Resistance , Islets of Langerhans/drug effects , Animals , Apoptosis/drug effects , Blood Glucose/analysis , Cell Proliferation/drug effects , Cell Transdifferentiation/drug effects , Diabetes Mellitus, Type 2/blood , Diabetes Mellitus, Type 2/pathology , Disease Models, Animal , Exenatide/therapeutic use , Female , Glucose Clamp Technique , Humans , Hypoglycemic Agents/therapeutic use , Infusions, Intravenous , Insulin/metabolism , Islets of Langerhans/pathology , Male , Papio
7.
Diabetes Obes Metab ; 20 Suppl 2: 137-144, 2018 09.
Article in English | MEDLINE | ID: mdl-30230173

ABSTRACT

While a number of structural and cellular abnormalities occur in the islet of Langerhans in diabetes, and in particular in type 2 diabetes, the focus has been mostly on the insulin producing ß-cells and only more recently on glucagon producing α- and δ-cells. There is ample evidence that in type 2 diabetes mellitus (T2DM), in addition to a progressive decline in ß-cell function and associated insulin resistance in a number of insulin-sensitive tissues, alterations in glucagon secretion are also present and may play an important role in the pathogenesis of hyperglycemia both in the fasting and in the postprandial state. Recently, a number of studies have showed that there are also functional and structural alterations in glucagon-producing α-cells and somatostatin-producing δ-cells. Thus, it is becoming increasingly clear that multiple cellular alterations of multiple cell types occur, which adds even more complexity to our understanding of the pathophysiology of this common and severe disease. We believe that persistent efforts to increase the understanding of the pathophysiology of hormone secretion in the islets of Langerhans will also improve our capability to better prevent and treat diabetes mellitus.


Subject(s)
Blood Glucose/metabolism , Diabetes Mellitus, Type 2/pathology , Islets of Langerhans/cytology , Amyloid/metabolism , Animals , Glucagon-Secreting Cells/ultrastructure , Haplorhini , Humans , Islets of Langerhans/ultrastructure , Mice , Models, Animal , Pancreatic Polypeptide-Secreting Cells/ultrastructure , Papio , Rats , Somatostatin-Secreting Cells/ultrastructure
8.
J Transl Med ; 14(1): 229, 2016 07 30.
Article in English | MEDLINE | ID: mdl-27473212

ABSTRACT

AIMS/HYPOTHESIS: Potentiation of glucose-induced insulin secretion is the main mechanism of exenatide (EXE) antidiabetic action, however, increased glucose utilization by peripheral tissues has been also reported. We here studied the effect of EXE on glucose uptake by skeletal muscle cells. METHODS: 2-deoxy-glucose (2DG) uptake and intracellular signal pathways were measured in rat L6 skeletal muscle myotubes exposed to 100 nmol/l EXE for up to 48 h. Mechanisms of EXE action were explored by inhibiting AMPK activity with compound C (CC, 40 µmol/l) or siRNAs (2 µmol/l). RESULTS: Time course experiments show that EXE increases glucose uptake up to 48 h achieving its maximal effect, similar to that induced by insulin, after 20 min (2- vs 2.5-fold-increase, respectively). Differently from insulin, EXE does not stimulate: (i) IR ß-subunit- and IRS1 tyrosine phosphorylation and binding to p85 regulatory subunit of PI-3kinase; (ii) AKT activation; and (iii) ERK1/2 and JNK1/2 phosphorylation. Conversely, EXE increases phosphorylation of α-subunit of AMPK at Thr172 by 2.5-fold (p < 0.01). Co-incubation of EXE and insulin does not induce additive effects on 2DG-uptake. Inhibition of AMPK with CC, and reduction of AMPK protein expression by siRNA, completely abolish EXE-induced 2DG-uptake. Liraglutide, another GLP-1 receptor agonist, also stimulates AMPK phosphorylation and 2DG-uptake. Moreover, EXE stimulates 2DG-uptake also by L6 myotubes rendered insulin-resistant with methylglyoxal. Finally, EXE also induces glucose transporter Glut-4 translocation to the plasma membrane. CONCLUSIONS/INTERPRETATION: In L6 myotubes, EXE and liraglutide increase glucose uptake in an insulin-independent manner by activating AMPK.


Subject(s)
AMP-Activated Protein Kinases/metabolism , Glucagon-Like Peptide-1 Receptor/agonists , Glucose/metabolism , Liraglutide/pharmacology , Peptides/pharmacology , Venoms/pharmacology , Animals , Biological Transport/drug effects , Cell Line , Deoxyglucose/metabolism , Enzyme Activation/drug effects , Exenatide , Gene Expression Profiling , Gene Silencing/drug effects , Glucagon-Like Peptide-1 Receptor/metabolism , Humans , Insulin Resistance , Mice , Muscle Fibers, Skeletal/drug effects , Muscle Fibers, Skeletal/enzymology , Muscle Fibers, Skeletal/metabolism , Papio , Phosphorylation/drug effects , Proto-Oncogene Proteins c-akt/metabolism , Pyruvaldehyde/pharmacology , Rats , Signal Transduction/drug effects , Time Factors
9.
J Cell Physiol ; 231(4): 756-67, 2016 04.
Article in English | MEDLINE | ID: mdl-26332080

ABSTRACT

Islets of Langerhans control whole body glucose homeostasis, as they respond, releasing hormones, to changes in nutrient concentrations in the blood stream. The regulation of hormone secretion has been the focus of attention for a long time because it is related to many metabolic disorders, including diabetes mellitus. Endocrine cells of the islet use a sophisticate system of endocrine, paracrine and autocrine signals to synchronize their activities. These signals provide a fast and accurate control not only for hormone release but also for cell differentiation and survival, key aspects in islet physiology and pathology. Among the different categories of paracrine/autocrine signals, this review highlights the role of neurotransmitters and neuropeptides. In a manner similar to neurons, endocrine cells synthesize, accumulate, release neurotransmitters in the islet milieu, and possess receptors able to decode these signals. In this review, we provide a comprehensive description of neurotransmitter/neuropetide signaling pathways present within the islet. Then, we focus on evidence supporting the concept that neurotransmitters/neuropeptides and their receptors are interesting new targets to preserve ß-cell function and mass. A greater understanding of how this network of signals works in physiological and pathological conditions would advance our knowledge of islet biology and physiology and uncover potentially new areas of pharmacological intervention. J. Cell. Physiol. 231: 756-767, 2016. © 2015 Wiley Periodicals, Inc.


Subject(s)
Islets of Langerhans/metabolism , Neuropeptides/metabolism , Neurotransmitter Agents/metabolism , Animals , Humans , Models, Biological
10.
Diabetologia ; 58(8): 1814-26, 2015 Aug.
Article in English | MEDLINE | ID: mdl-26049399

ABSTRACT

AIMS/HYPOTHESIS: The cellular composition of the islet of Langerhans is essential to ensure its physiological function. Morphophysiological islet abnormalities are present in type 2 diabetes but the relationship between fasting plasma glucose (FPG) and islet cell composition, particularly the role of delta cells, is unknown. We explored these questions in pancreases from baboons (Papio hamadryas) with FPG ranging from normal to type 2 diabetic values. METHODS: We measured the volumes of alpha, beta and delta cells and amyloid in pancreatic islets of 40 baboons (Group 1 [G1]: FPG < 4.44 mmol/l [n = 10]; G2: FPG = 4.44-5.26 mmol/l [n = 9]; G3: FPG = 5.27-6.94 mmol/l [n = 9]; G4: FPG > 6.94 mmol/l [n = 12]) and correlated islet composition with metabolic and hormonal variables. We also performed confocal microscopy including TUNEL, caspase-3, and anti-caspase cleavage product of cytokeratin 18 (M30) immunostaining, electron microscopy, and immuno-electron microscopy with anti-somatostatin antibodies in baboon pancreases. RESULTS: Amyloidosis preceded the decrease in beta cell volume. Alpha cell volume increased ∼ 50% in G3 and G4 (p < 0.05), while delta cell volume decreased in these groups by 31% and 39%, respectively (p < 0.05). In G4, glucagon levels were higher, while insulin and HOMA index of beta cell function were lower than in the other groups. Immunostaining of G4 pancreatic sections with TUNEL, caspase-3 and M30 showed apoptosis of beta and delta cells, which was also confirmed by immuno-electron microscopy with anti-somatostatin antibodies. CONCLUSIONS/INTERPRETATION: In diabetic baboons, changes in islet composition correlate with amyloid deposition, with increased alpha cell and decreased beta and delta cell volume and number due to apoptosis. These data argue for an important role of delta cells in type 2 diabetes.


Subject(s)
Cell Death , Diabetes Mellitus, Type 2/pathology , Insulin Resistance/physiology , Islets of Langerhans/pathology , Somatostatin-Secreting Cells/pathology , Animals , Blood Glucose/metabolism , Caspase 3/metabolism , Diabetes Mellitus, Type 2/metabolism , Disease Progression , Female , Glucagon-Secreting Cells/metabolism , Glucagon-Secreting Cells/pathology , Insulin-Secreting Cells/metabolism , Insulin-Secreting Cells/pathology , Islets of Langerhans/metabolism , Male , Papio hamadryas , Somatostatin-Secreting Cells/metabolism
11.
Am J Pathol ; 185(1): 139-50, 2015 Jan.
Article in English | MEDLINE | ID: mdl-25447052

ABSTRACT

In this study, we aimed to evaluate the effects of exenatide (EXE) treatment on exocrine pancreas of nonhuman primates. To this end, 52 baboons (Papio hamadryas) underwent partial pancreatectomy, followed by continuous infusion of EXE or saline (SAL) for 14 weeks. Histological analysis, immunohistochemistry, Computer Assisted Stereology Toolbox morphometry, and immunofluorescence staining were performed at baseline and after treatment. The EXE treatment did not induce pancreatitis, parenchymal or periductal inflammatory cell accumulation, ductal hyperplasia, or dysplastic lesions/pancreatic intraepithelial neoplasia. At study end, Ki-67-positive (proliferating) acinar cell number did not change, compared with baseline, in either group. Ki-67-positive ductal cells increased after EXE treatment (P = 0.04). However, the change in Ki-67-positive ductal cell number did not differ significantly between the EXE and SAL groups (P = 0.13). M-30-positive (apoptotic) acinar and ductal cell number did not change after SAL or EXE treatment. No changes in ductal density and volume were observed after EXE or SAL. Interestingly, by triple-immunofluorescence staining, we detected c-kit (a marker of cell transdifferentiation) positive ductal cells co-expressing insulin in ducts only in the EXE group at study end, suggesting that EXE may promote the differentiation of ductal cells toward a ß-cell phenotype. In conclusion, 14 weeks of EXE treatment did not exert any negative effect on exocrine pancreas, by inducing either pancreatic inflammation or hyperplasia/dysplasia in nonhuman primates.


Subject(s)
Hypoglycemic Agents/administration & dosage , Inflammation/pathology , Pancreas, Exocrine/pathology , Pancreatic Ducts/pathology , Peptides/administration & dosage , Venoms/administration & dosage , Amylases/blood , Animals , Apoptosis , Exenatide , Female , Hyperplasia , Hypoglycemic Agents/adverse effects , Immunohistochemistry , Infusions, Intravenous , Insulin Resistance , Ki-67 Antigen/metabolism , Male , Microscopy, Fluorescence , Pancreas, Exocrine/metabolism , Pancreatic Ducts/cytology , Papio , Peptides/adverse effects , Phenotype , Venoms/adverse effects
12.
PLoS One ; 8(9): e73651, 2013.
Article in English | MEDLINE | ID: mdl-24069218

ABSTRACT

INTRODUCTION: The purpose of this study was to compare and validate the use of SenseWear Armband (SWA) placed on the arm (SWA ARM) and on the back (SWA BACK) in healthy humans during resting and a cycle-ergometer exercise and to evaluate the SWA to estimate Resting Energy Expenditure (REE) and Total Energy Expenditure (TEE) in healthy baboons. METHODS: We studied 26 (15F/11M) human subjects wearing SWA in two different anatomical sites (arm and back) during resting and a cycle-ergometer test and directly compared these results with indirect calorimetry evaluation (IC), performed at the same time. We then inserted the SWA in a metabolic jacket for baboons and evaluated the TEE and REE in free living condition for 6 days in 21 (8F/13M) non-human primates. RESULTS: In humans we found a good correlation between SWA place on the ARM and on the BACK with IC during the resting experiment (1.1±0.3 SWAs, 1±0.2 IC kcal/min) and a slight underestimation in the SWAs data compared with IC during the cycle-ergometer exercise (5±1.9 SWA ARM, 4.5±1.5 SWA BACK and 5.4±2.1 IC kcal/min). In the non-human primate (baboons) experiment SWA estimated a TEE of 0.54±0.009 kcal/min during free living and a REE of 0.82±0.06 kcal/min. CONCLUSION: SWA, an extremely simple and inexpensive apparatus, provides quite accurate measurements of energy expenditure in humans and in baboons. Energy expenditure data obtained with SWA are highly correlated with the data obtained with "gold standard", IC, in humans.


Subject(s)
Calorimetry, Indirect/methods , Energy Metabolism/physiology , Adult , Aged , Animals , Female , Humans , Male , Middle Aged
13.
Acta Diabetol ; 49(3): 167-83, 2012 Jun.
Article in English | MEDLINE | ID: mdl-22218826

ABSTRACT

In the present article, we propose the perspective that abnormal glutamate homeostasis might contribute to diabetes pathogenesis. Previous reports and our recent data indicate that chronically high extracellular glutamate levels exert direct and indirect effects that might participate in the progressive loss of ß-cells occurring in both T1D and T2D. In addition, abnormal glutamate homeostasis may impact all the three accelerators of the "accelerator hypothesis" and could partially explain the rising frequency of T1D and T2D.


Subject(s)
Diabetes Mellitus, Type 1/metabolism , Diabetes Mellitus, Type 2/metabolism , Glutamic Acid/metabolism , Insulin-Secreting Cells/metabolism , Diabetes Mellitus, Type 1/epidemiology , Diabetes Mellitus, Type 2/epidemiology , Epidemics , Homeostasis/physiology , Humans
14.
Acta Diabetol ; 49(1): 75-9, 2012 Feb.
Article in English | MEDLINE | ID: mdl-21336872

ABSTRACT

We report a case of unusually long-lasting remission of type 1 diabetes (T1D). The patient, a Caucasian man, at the age of 43 years developed a ketotic diabetes, classified as type 1 based on clinical presentation and positivity for islet autoantibodies. Shortly after diabetes onset, oral topiramate was added to preexisting valproic acid for generalized seizures and maintained thereafter. Initial intensive insulin treatment was rapidly reduced to low doses (3 Units/day) maintained for a long time and then discontinued at month 55; fasting glucose and glycosylated hemoglobin were basically normalized at 58 months. An oral glucose tolerance test performed at month 53 showed an impaired fasting glucose (6.0 mmol/l) and a value slightly above the threshold for the diagnosis of diabetes at 2 h (11.2 mmol/l). We hypothesize that this unusually prolonged preservation of ß-cell function might be ascribed to the concomitant therapy with topiramate, an antiepileptic agent with demonstrated efficacy as antidiabetic in type 2 diabetes (T2D). Topiramate should be further investigated as candidate agent for the preservation of ß-cell function also in T1D.


Subject(s)
Diabetes Mellitus, Type 1/complications , Diabetes Mellitus, Type 1/drug therapy , Fructose/analogs & derivatives , Seizures/complications , Seizures/drug therapy , Adult , Anticonvulsants/therapeutic use , Diabetes Mellitus, Type 1/rehabilitation , Fructose/therapeutic use , Humans , Male , Remission Induction , Topiramate
15.
Transplantation ; 93(2): 219-23, 2012 Jan 27.
Article in English | MEDLINE | ID: mdl-22193043

ABSTRACT

BACKGROUND: The reasons for the long-term complete or partial loss of islet graft function are unknown, but there are obviously other reasons than just pure allogeneic graft rejection. Earlier studies have shown that deposition of islet amyloid polypeptide amyloid in transplanted islets may indicate a mechanism for loss of ß cells. MATERIALS AND METHODS: Sections from liver material from four deceased islet-bearing recipients have been scrutinized for the presence of amyloid. Clinical data and certain aspects of the islet graft pathology of these patients have been published previously. RESULT: With this extended histological analysis, we demonstrate the occurrence of amyloid deposits in islets transplanted into the liver in three of four patients with type 1 diabetes. CONCLUSION: The finding adds evidence to the assumption that aggregation of islet amyloid polypeptide might be an important cause of progressing ß-cell dysfunction in clinically transplanted islets.


Subject(s)
Islet Amyloid Polypeptide/metabolism , Islets of Langerhans Transplantation/adverse effects , Adult , Diabetes Mellitus, Type 1/surgery , Fatal Outcome , Female , Humans , Immunohistochemistry , Islets of Langerhans/metabolism , Islets of Langerhans/pathology , Islets of Langerhans Transplantation/mortality , Islets of Langerhans Transplantation/pathology , Islets of Langerhans Transplantation/physiology , Liver/metabolism , Liver/pathology , Male , Middle Aged , Proprotein Convertase 2/metabolism , Tissue Donors
16.
PLoS One ; 6(11): e27617, 2011.
Article in English | MEDLINE | ID: mdl-22125617

ABSTRACT

UNLABELLED: Non-alcoholic fatty liver disease (NAFLD) is characterized by accumulation of triglycerides (TG) in hepatocytes, which may also trigger cirrhosis. The mechanisms of NAFLD are not fully understood, but insulin resistance has been proposed as a key determinant. AIMS: To determine the TG content and long chain fatty acyl CoA composition profile in liver from obese non-diabetic insulin resistant (IR) and lean insulin sensitive (IS) baboons in relation with hepatic and peripheral insulin sensitivity. METHODS: Twenty baboons with varying grades of adiposity were studied. Hepatic (liver) and peripheral (mainly muscle) insulin sensitivity was measured with a euglycemic clamp and QUICKI. Liver biopsies were performed at baseline for TG content and LCFA profile by mass spectrometry, and histological analysis. Findings were correlated with clinical and biochemical markers of adiposity and insulin resistance. RESULTS: Obese IR baboons had elevated liver TG content compared to IS. Furthermore, the concentration of unsaturated (LC-UFA) was greater than saturated (LC-SFA) fatty acyl CoA in the liver. Interestingly, LC-FA UFA and SFA correlated with waist, BMI, insulin, NEFA, TG, QUICKI, but not M/I. Histological findings of NAFLD ranging from focal to diffuse hepatic steatosis were found in obese IR baboons. CONCLUSION: Liver TG content is closely related with both hepatic and peripheral IR, whereas liver LC-UFA and LC-SFA are closely related only with hepatic IR in non-human primates. Mechanisms leading to the accumulation of TG, LC-UFA and an altered UFA: LC-SFA ratio may play an important role in the pathophysiology of fatty liver disease in humans.


Subject(s)
Fatty Acids/metabolism , Insulin Resistance , Liver/metabolism , Triglycerides/metabolism , Acyl Coenzyme A/metabolism , Adiposity , Animals , Fatty Acids, Unsaturated/metabolism , Fatty Liver/metabolism , Fatty Liver/pathology , Female , Glucose/metabolism , Glucose Clamp Technique , Humans , Linear Models , Liver/pathology , Male , Non-alcoholic Fatty Liver Disease , Papio , Spectrometry, Mass, Electrospray Ionization
17.
Curr Diabetes Rev ; 7(5): 313-24, 2011 Sep.
Article in English | MEDLINE | ID: mdl-21838680

ABSTRACT

A growing body of evidence suggests that oxidative stress plays a key role in the pathogenesis of micro- and macrovascular diabetic complications. The increased oxidative stress in subjects with type 2 diabetes is a consequence of several abnormalities, including hyperglycemia, insulin resistance, hyperinsulinemia, and dyslipidemia, each of which contributes to mitochondrial superoxide overproduction in endothelial cells of large and small vessels as well as the myocardium. The unifying pathophysiological mechanism that underlies diabetic complications could be explained by increased production of reactive oxygen species (ROS) via: (1) the polyol pathway flux, (2) increased formation of advanced glycation end products (AGEs), (3) increased expression of the receptor for AGEs, (4) activation of protein kinase C isoforms, and (5) overactivity of the hexosamine pathway. Furthermore, the effects of oxidative stress in individuals with type 2 diabetes are compounded by the inactivation of two critical anti-atherosclerotic enzymes: endothelial nitric oxide synthase and prostacyclin synthase. Of interest, the results of clinical trials in patients with type 2 diabetes in whom intensive management of all the components of the metabolic syndrome (hyperglycemia, hypercholesterolemia, and essential hypertension) was attempted (with agents that exert a beneficial effect on serum glucose, serum lipid concentrations, and blood pressure, respectively) showed a decrease in adverse cardiovascular end points. The purpose of this review is (1) to examine the mechanisms that link oxidative stress to micro- and macrovascular complications in subjects with type 2 diabetes and (2) to consider the therapeutic opportunities that are presented by currently used therapeutic agents which possess antioxidant properties as well as new potential antioxidant substances.


Subject(s)
Antioxidants/therapeutic use , Atherosclerosis/metabolism , Diabetes Mellitus, Type 2/metabolism , Diabetic Angiopathies/metabolism , Hyperglycemia/metabolism , Oxidative Stress , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/drug therapy , Diabetic Angiopathies/drug therapy , Diabetic Angiopathies/etiology , Humans , Hyperglycemia/complications , Hyperglycemia/drug therapy , Insulin Resistance
18.
J Biol Chem ; 286(16): 14007-18, 2011 Apr 22.
Article in English | MEDLINE | ID: mdl-21335552

ABSTRACT

Glutamate is the major excitatory neurotransmitter of the central nervous system (CNS) and may induce cytotoxicity through persistent activation of glutamate receptors and oxidative stress. Its extracellular concentration is maintained at physiological concentrations by high affinity glutamate transporters of the solute carrier 1 family (SLC1). Glutamate is also present in islet of Langerhans where it is secreted by the α-cells and acts as a signaling molecule to modulate hormone secretion. Whether glutamate plays a role in islet cell viability is presently unknown. We demonstrate that chronic exposure to glutamate exerts a cytotoxic effect in clonal ß-cell lines and human islet ß-cells but not in α-cells. In human islets, glutamate-induced ß-cell cytotoxicity was associated with increased oxidative stress and led to apoptosis and autophagy. We also provide evidence that the key regulator of extracellular islet glutamate concentration is the glial glutamate transporter 1 (GLT1). GLT1 localizes to the plasma membrane of ß-cells, modulates hormone secretion, and prevents glutamate-induced cytotoxicity as shown by the fact that its down-regulation induced ß-cell death, whereas GLT1 up-regulation promoted ß-cell survival. In conclusion, the present study identifies GLT1 as a new player in glutamate homeostasis and signaling in the islet of Langerhans and demonstrates that ß-cells critically depend on its activity to control extracellular glutamate levels and cellular integrity.


Subject(s)
Excitatory Amino Acid Transporter 2/biosynthesis , Gene Expression Regulation , Glutamate Plasma Membrane Transport Proteins/biosynthesis , Insulin-Secreting Cells/cytology , Animals , Apoptosis , Autophagy , Cell Survival , Excitatory Amino Acid Transporter 2/physiology , Glutamate Plasma Membrane Transport Proteins/physiology , Glutamic Acid/chemistry , Glutamic Acid/metabolism , Homeostasis , Humans , Islets of Langerhans/cytology , Mice , Models, Biological , Oxidative Stress
19.
Curr Vasc Pharmacol ; 9(5): 572-84, 2011 Sep.
Article in English | MEDLINE | ID: mdl-21143163

ABSTRACT

One of the critical points in the pathogenesis of aortic aneurysms (AAs) is the disruption of the balance between vascular extracellular matrix (ECM) deposition and degradation. AAs are common features in some genetically determined diseases of the connective tissue, such as Marfan and Ehlers-Danlos. Acquired factors determining an enhanced inflammatory state of the arterial wall also play a key role. Previous studies have determined the role of tumor growth factor ß (TGF-ß); as a principal mediator of the pathogenesis of the alterations of the arterial wall homeostasis in AAs. The medical management of any AA is mainly focused on the use of pharmacological agents that reduce hemodynamic stress of the aortic wall, since hypertension is the major risk factor for the enlargement and rupture of the AAs. However, this is far from being a comprehensive pathophysiology-based therapeutic approach. Drugs potentially able to reduce the release of TGF-ß may play a role in the pathogenesis of the AAs. They work by improving matrix repair, decreasing the proteolytic pattern and inhibition of angiotensin-converting enzyme (ACE) as well as preventing angiotensin II-induced angiotensin type-1 receptor (AT1R) activation. A new pathophysiology-based therapeutic approach, involving the mechanisms leading to the rupture of the AAs, could represent an additional tool in combination with the current established antihypertensive therapy.


Subject(s)
Aortic Aneurysm/drug therapy , Aortic Aneurysm/etiology , Animals , Aortic Aneurysm/metabolism , Aortic Aneurysm/pathology , Atherosclerosis/complications , Autoimmunity , Genetic Predisposition to Disease , Humans , Hypertension/complications , Insulin Resistance , Metalloproteases/metabolism , Oxidative Stress/drug effects , Risk Factors , Transforming Growth Factor beta/antagonists & inhibitors , Transforming Growth Factor beta/genetics
20.
Proc Natl Acad Sci U S A ; 106(33): 13992-7, 2009 Aug 18.
Article in English | MEDLINE | ID: mdl-19666551

ABSTRACT

beta-Cell dysfunction is an important factor in the development of hyperglycemia of type-2 diabetes mellitus, and pancreatic islet amyloidosis (IA) has been postulated to be one of the main contributors to impaired insulin secretion. The aim of this study was to evaluate the correlation of IA with metabolic parameters and its effect on islets of Langerhans remodeling and relative endocrine-cell volume in baboons. We sequenced the amylin peptide, determined the fibrillogenic propensities, and evaluated pancreatic histology, clinical and biochemical characteristics, and endocrine cell proliferation and apoptosis in 150 baboons with different metabolic status. Amylin sequence in the baboon was 92% similar to humans and showed superimposable fibrillogenic propensities. IA severity correlated with fasting plasma glucose (FPG) (r = 0.662, P < 0.001) and HbA1c (r = 0.726, P < 0.001), as well as with free fatty acid, glucagon values, decreased homeostasis model assessment (HOMA) insulin resistance, and HOMA-B. IA severity was associated with a decreased relative beta-cell volume, and increased relative alpha-cell volume and hyperglucagonemia. These results strongly support the concept that IA and beta-cell apoptosis in concert with alpha-cell proliferation and hypertrophy are key determinants of islets of Langerhans "dysfunctional remodeling" and hyperglycemia in the baboon, a nonhuman primate model of type-2 diabetes mellitus. The most important determinants of IA were age and FPG (R(2) = 0.519, P < 0.0001), and different FPG levels were sensitive and specific to predict IA severity. Finally, a predictive model for islet amyloid severity was generated with age and FPG as required variables.


Subject(s)
Amyloidosis/pathology , Diabetes Mellitus, Experimental/metabolism , Diabetes Mellitus, Type 2/metabolism , Glucagon-Secreting Cells/metabolism , Insulin-Secreting Cells/metabolism , Islets of Langerhans/pathology , Amyloid/metabolism , Animals , Apoptosis , Blood Glucose/metabolism , Diabetes Mellitus, Experimental/pathology , Diabetes Mellitus, Type 2/pathology , Fatty Acids/metabolism , Female , Insulin Resistance , Islet Amyloid Polypeptide , Male , Papio
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