RESUMO
Obesity is associated with several chronic comorbidities, one of which is type 2 diabetes mellitus (T2DM). The pathogenesis of obesity and T2DM is influenced by alterations in diet macronutrient composition, which regulate energy expenditure, metabolic function, glucose homeostasis, and pancreatic islet cell biology. Recent studies suggest that increased intake of dietary carbohydrates plays a previously underappreciated role in the promotion of obesity and consequent metabolic dysfunction. Thus, in this study, we utilized mouse models to test the hypothesis that dietary carbohydrates modulate energetic, metabolic, and islet adaptions to high-fat diets. To address this, we exposed C57BL/6J mice to 12 wk of 3 eucaloric high-fat diets (>60% calories from fat) with varying total carbohydrate (1-20%) and sucrose (0-20%) content. Our results show that severe restriction of dietary carbohydrates characteristic of ketogenic diets reduces body fat accumulation, enhances energy expenditure, and reduces prevailing glycemia and insulin resistance compared with carbohydrate-rich, high-fat diets. Moreover, severe restriction of dietary carbohydrates also results in functional, morphological, and molecular changes in pancreatic islets highlighted by restricted capacity for ß-cell mass expansion and alterations in insulin secretory response. These studies support the hypothesis that low-carbohydrate/high-fat diets provide antiobesogenic benefits and suggest further evaluation of the effects of these diets on ß-cell biology in humans.
Assuntos
Dieta Hiperlipídica , Dieta Cetogênica , Carboidratos da Dieta , Metabolismo Energético , Hiperglicemia/metabolismo , Resistência à Insulina , Células Secretoras de Insulina/metabolismo , Obesidade/metabolismo , Adaptação Fisiológica , Tecido Adiposo , Animais , Diabetes Mellitus Tipo 2/metabolismo , Dieta com Restrição de Gorduras , Sacarose Alimentar , Teste de Tolerância a Glucose , Secreção de Insulina , CamundongosRESUMO
INTRODUCTION: The majority of patients with pancreatic ductal adenocarcinoma (PC) display either impaired fasting glucose/glucose intolerance or overt diabetes. However, the pathophysiologic basis of this association remains largely unexplained. METHODS: In this case-control study we aimed to study the morphological changes in the islets of patients with PC, compared to control patients with and without type 2 diabetes mellitus (T2DM). T2DM controls and PC cases had a lower ß-cell area and average islet size and density compared to non-T2DM controls (p < 0.05). RESULTS: Compared to both T2DM and non-T2DM controls, mean α-cell area was significantly lower and ß/α-ratio was higher in PC cases (p < 0.05). Furthermore, whereas islets in T2DM controls were characterized by disrupted islet architecture and presence of islet amyloid aggregates, islet composition in PC islets was not significantly different compared to non-T2DM controls (p > 0.05 vs. Control). CONCLUSIONS: Our data shows that PC is associated with a unique pattern of islet pathology characterized by preserved architecture, absence of amyloid aggregates, and relative α-cell loss indicating that distinct mechanisms are likely involved in the pathophysiology of islet failure in PC-induced DM. Insights into the mechanisms mediating ß-cell failure in PC can be important for our understanding of pathophysiology of PC.
Assuntos
Carcinoma Ductal Pancreático/complicações , Diabetes Mellitus Tipo 2 , Pancreatopatias/etiologia , Neoplasias Pancreáticas/complicações , Fatores Etários , Idoso , Amiloide/metabolismo , Autopsia , Índice de Massa Corporal , Estudos de Casos e Controles , Bases de Dados Factuais , Feminino , Células Secretoras de Glucagon/patologia , Humanos , Células Secretoras de Insulina/patologia , Ilhotas Pancreáticas/patologia , Masculino , Pessoa de Meia-Idade , Pancreatopatias/patologia , Fatores SexuaisRESUMO
Metabolic state and circadian clock function exhibit a complex bidirectional relationship. Circadian disruption increases propensity for metabolic dysfunction, whereas common metabolic disorders such as obesity and type 2 diabetes (T2DM) are associated with impaired circadian rhythms. Specifically, alterations in glucose availability and glucose metabolism have been shown to modulate clock gene expression and function in vitro; however, to date, it is unknown whether development of diabetes imparts deleterious effects on the suprachiasmatic nucleus (SCN) circadian clock and SCN-driven outputs in vivo. To address this question, we undertook studies in aged diabetic rats transgenic for human islet amyloid polypeptide, an established nonobese model of T2DM (HIP rat), which develops metabolic defects closely recapitulating those present in patients with T2DM. HIP rats were also cross-bred with a clock gene reporter rat model (Per1:luciferase transgenic rat) to permit assessment of the SCN and the peripheral molecular clock function ex vivo. Utilizing these animal models, we examined effects of diabetes on 1) behavioral circadian rhythms, 2) photic entrainment of circadian activity, 3) SCN and peripheral tissue molecular clock function, and 4) melatonin secretion. We report that circadian activity, light-induced entrainment, molecular clockwork, as well as melatonin secretion are preserved in the HIP rat model of T2DM. These results suggest that despite the well-characterized ability of glucose to modulate circadian clock gene expression acutely in vitro, SCN clock function and key behavioral and physiological outputs appear to be preserved under chronic diabetic conditions characteristic of nonobese T2DM.
Assuntos
Comportamento Animal/fisiologia , Ritmo Circadiano/genética , Diabetes Mellitus Tipo 2 , Animais , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Experimental/fisiopatologia , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Diabetes Mellitus Tipo 2/fisiopatologia , Modelos Animais de Doenças , Progressão da Doença , Polipeptídeo Amiloide das Ilhotas Pancreáticas/genética , Polipeptídeo Amiloide das Ilhotas Pancreáticas/metabolismo , Luz , Masculino , Proteínas Circadianas Period/metabolismo , Ratos , Ratos Sprague-Dawley , Ratos Transgênicos , Núcleo Supraquiasmático/metabolismo , Núcleo Supraquiasmático/patologiaRESUMO
The neurotransmitter dopamine (DA) is known to be involved in a multitude of physiological processes. We investigated sexually dimorphic effects of disruptions in DA homeostasis and its relationship to senescence using three different Drosophila melanogaster mutants namely Catsup (Catsup26 ) with elevated DA levels, and pale (ple2 ), Punch (PuZ22 ) with depleted DA levels. In all genotypes including controls, DA levels were significantly lower in old (45-50-day-old) flies compared with young (3-5-day-old) in both sexes. Interestingly, females had lower DA content than males at young age whereas this difference was not observed in old age, suggesting that males had a larger decline in DA levels with age. Females, in general, were longer lived compared with males in all genotypes except ple2 mutants with depleted DA levels. This phenotype was abolished in the ple2 rescue flies. Interestingly, females also demonstrated marked age-related decline in circadian locomotor activity compared with males. Old Catsup26 males with elevated DA levels accumulated significantly lower levels of lipid peroxidation product 4-hydroxy 2-nonenal (4-HNE) compared with age-matched wild type, ple2 and PuZ22 mutant males. In Catsup26 revertant lines this phenomenon was absent. We also observed a sexually dimorphic response in the expression levels of key stress and aging associated and/or related transcription factor genes across genotypes with elevated or depleted DA levels which was reverted to wild type levels in specific rescue lines. Taken together, our results reveal a novel sexually dimorphic involvement of DA in senescence characteristics of D. melanogaster.
Assuntos
Envelhecimento/metabolismo , Dopamina/metabolismo , Homeostase , Envelhecimento/genética , Animais , Relógios Circadianos , Dopamina/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Feminino , Genótipo , Peroxidação de Lipídeos , Locomoção , Masculino , Fatores SexuaisRESUMO
AIMS/HYPOTHESIS: Obesity and consequent insulin resistance are known risk factors for type 2 diabetes. A compensatory increase in beta cell function and mass in response to insulin resistance permits maintenance of normal glucose homeostasis, whereas failure to do so results in beta cell failure and type 2 diabetes. Recent evidence suggests that the circadian system is essential for proper metabolic control and regulation of beta cell function. We set out to address the hypothesis that the beta cell circadian clock is essential for the appropriate functional and morphological beta cell response to insulin resistance. METHODS: We employed conditional deletion of the Bmal1 (also known as Arntl) gene (encoding a key circadian clock transcription factor) in beta cells using the tamoxifen-inducible CreER(T) recombination system. Upon adulthood, Bmal1 deletion in beta cells was achieved and mice were exposed to either chow or high fat diet (HFD). Changes in diurnal glycaemia, glucose tolerance and insulin secretion were longitudinally monitored in vivo and islet morphology and turnover assessed by immunofluorescence. Isolated islet experiments in vitro were performed to delineate changes in beta cell function and transcriptional regulation of cell proliferation. RESULTS: Adult Bmal1 deletion in beta cells resulted in failed metabolic adaptation to HFD characterised by fasting and diurnal hyperglycaemia, glucose intolerance and loss of glucose-stimulated insulin secretion. Importantly, HFD-induced beta cell expansion was absent following beta cell Bmal1 deletion indicating impaired beta cell proliferative and regenerative potential, which was confirmed by assessment of transcriptional profiles in isolated islets. CONCLUSION/INTERPRETATION: Results of the study suggest that the beta cell circadian clock is a novel regulator of compensatory beta cell expansion and function in response to increased insulin demand associated with diet-induced obesity.
Assuntos
Fatores de Transcrição ARNTL/metabolismo , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Obesidade/metabolismo , Fatores de Transcrição ARNTL/genética , Animais , Proteínas CLOCK/genética , Proteínas CLOCK/metabolismo , Sobrevivência Celular/fisiologia , Ritmo Circadiano/fisiologia , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Dieta Hiperlipídica/efeitos adversos , Feminino , Hiperglicemia/genética , Hiperglicemia/metabolismo , Masculino , Camundongos , Obesidade/etiologiaRESUMO
Pancreatic islet failure is a characteristic feature of impaired glucose control in diabetes mellitus. Circadian control of islet function is essential for maintaining proper glucose homeostasis. Circadian variations in transcriptional pathways have been described in diverse cell types and shown to be critical for optimization of cellular function in vivo. In the current study, we utilized Short Time Series Expression Miner (STEM) analysis to identify diurnally expressed transcripts and biological pathways from mouse islets isolated at 4 h intervals throughout the 24 h light-dark cycle. STEM analysis identified 19 distinct chronological model profiles, and genes belonging to each profile were subsequently annotated to significantly enriched Kyoto Encyclopedia of Genes and Genomes biological pathways. Several transcriptional pathways essential for proper islet function (e.g., insulin secretion, oxidative phosphorylation), cell survival (e.g., insulin signaling, apoptosis) and cell proliferation (DNA replication, homologous recombination) demonstrated significant time-dependent variations. Notably, KEGG pathway analysis revealed "protein processing in endoplasmic reticulum - mmu04141" as one of the most enriched time-dependent pathways in islets. This study provides unique data set on time-dependent diurnal profiles of islet gene expression and biological pathways, and suggests that diurnal variation of the islet transcriptome is an important feature of islet homeostasis, which should be taken into consideration for optimal experimental design and interpretation of future islet studies.
Assuntos
Relógios Circadianos/fisiologia , Ritmo Circadiano/fisiologia , Ilhotas Pancreáticas/fisiologia , Transcriptoma/fisiologia , Animais , Glicemia/metabolismo , Proliferação de Células/fisiologia , Expressão Gênica/fisiologia , Homeostase/fisiologia , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Transdução de Sinais/fisiologiaRESUMO
Type 2 diabetes mellitus (T2DM) is a complex metabolic disease characterized by the loss of beta-cell secretory function and mass. The pathophysiology of beta-cell failure in T2DM involves a complex interaction between genetic susceptibilities and environmental risk factors. One environmental condition that is gaining greater appreciation as a risk factor for T2DM is the disruption of circadian rhythms (eg, shift-work and sleep loss). In recent years, circadian disruption has become increasingly prevalent in modern societies and consistently shown to augment T2DM susceptibility (partly mediated through its effects on pancreatic beta-cells). Since beta-cell failure is essential for development of T2DM, we will review current work from epidemiologic, clinical, and animal studies designed to gain insights into the molecular and physiological mechanisms underlying the predisposition to beta-cell failure associated with circadian disruption. Elucidating the role of circadian clocks in regulating beta-cell health will add to our understanding of T2DM pathophysiology and may contribute to the development of novel therapeutic and preventative approaches.
Assuntos
Glicemia/metabolismo , Ritmo Circadiano , Diabetes Mellitus Tipo 2/fisiopatologia , Resistência à Insulina , Células Secretoras de Insulina/metabolismo , Animais , Relógios Circadianos , Diabetes Mellitus Tipo 2/etiologia , Diabetes Mellitus Tipo 2/metabolismo , Emprego , Estresse do Retículo Endoplasmático , Exposição Ambiental , Feminino , Predisposição Genética para Doença , Humanos , Inflamação/metabolismo , Masculino , Estresse OxidativoRESUMO
Circadian clocks generate rhythms in molecular, cellular, physiological, and behavioral processes. Recent studies suggest that disruption of the clock mechanism accelerates organismal senescence and age-related pathologies in mammals. Impaired circadian rhythms are observed in many neurological diseases; however, it is not clear whether loss of rhythms is the cause or result of neurodegeneration, or both. To address this important question, we examined the effects of circadian disruption in Drosophila melanogaster mutants that display clock-unrelated neurodegenerative phenotypes. We combined a null mutation in the clock gene period (per(01)) that abolishes circadian rhythms, with a hypomorphic mutation in the carbonyl reductase gene sniffer (sni(1)), which displays oxidative stress induced neurodegeneration. We report that disruption of circadian rhythms in sni(1) mutants significantly reduces their lifespan compared to single mutants. Shortened lifespan in double mutants was coupled with accelerated neuronal degeneration evidenced by vacuolization in the adult brain. In addition, per(01)sni(1) flies showed drastically impaired vertical mobility and increased accumulation of carbonylated proteins compared to age-matched single mutant flies. Loss of per function does not affect sni mRNA expression, suggesting that these genes act via independent pathways producing additive effects. Finally, we show that per(01) mutation accelerates the onset of brain pathologies when combined with neurodegeneration-prone mutation in another gene, swiss cheese (sws(1)), which does not operate through the oxidative stress pathway. Taken together, our data suggest that the period gene may be causally involved in neuroprotective pathways in aging Drosophila.
Assuntos
Envelhecimento , Oxirredutases do Álcool/genética , Transtornos Cronobiológicos/fisiopatologia , Proteínas de Drosophila/genética , Mutação/genética , Degeneração Neural/genética , Proteínas do Tecido Nervoso/genética , Fatores Etários , Análise de Variância , Animais , Animais Geneticamente Modificados , Transtornos Cronobiológicos/genética , Ritmo Circadiano/genética , Modelos Animais de Doenças , Drosophila melanogaster , Regulação da Expressão Gênica/genética , Estresse Oxidativo/genética , Proteínas Circadianas Period/deficiênciaRESUMO
Type 2 diabetes mellitus (T2DM) is characterized by ß-cell dysfunction as a result of impaired glucose-stimulated insulin secretion (GSIS). Studies show that ß-cell circadian clocks are important regulators of GSIS and glucose homeostasis. These observations raise the question about whether enhancement of the circadian clock in ß-cells will confer protection against ß-cell dysfunction under diabetogenic conditions. To test this, we used an approach by first generating mice with ß-cell-specific inducible overexpression of Bmal1 (core circadian transcription factor; ß-Bmal1 OV ). We subsequently examined the effects of ß-Bmal1 OV on the circadian clock, GSIS, islet transcriptome, and glucose metabolism in the context of diet-induced obesity. We also tested the effects of circadian clock-enhancing small-molecule nobiletin on GSIS in mouse and human control and T2DM islets. We report that ß-Bmal1 OV mice display enhanced islet circadian clock amplitude and augmented in vivo and in vitro GSIS and are protected against obesity-induced glucose intolerance. These effects were associated with increased expression of purported BMAL1-target genes mediating insulin secretion, processing, and lipid metabolism. Furthermore, exposure of isolated islets to nobiletin enhanced ß-cell secretory function in a Bmal1-dependent manner. This work suggests therapeutic targeting of the circadian system as a potential strategy to counteract ß-cell failure under diabetogenic conditions.
Assuntos
Fatores de Transcrição ARNTL/metabolismo , Intolerância à Glucose/metabolismo , Resistência à Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Obesidade/metabolismo , Fatores de Transcrição ARNTL/genética , Animais , Glicemia/metabolismo , Relógios Circadianos/genética , Ritmo Circadiano/genética , Flavonas/farmacologia , Glucose/farmacologia , Intolerância à Glucose/etiologia , Intolerância à Glucose/genética , Humanos , Insulina/metabolismo , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Atividade Motora/genética , Obesidade/complicações , Obesidade/genéticaRESUMO
Intrinsic ß-cell circadian clocks are important regulators of insulin secretion and overall glucose homeostasis. Whether the circadian clock in ß-cells is perturbed following exposure to prodiabetogenic stressors such as proinflammatory cytokines, and whether these perturbations are featured during the development of diabetes, remains unknown. To address this, we examined the effects of cytokine-mediated inflammation common to the pathophysiology of diabetes, on the physiological and molecular regulation of the ß-cell circadian clock. Specifically, we provide evidence that the key diabetogenic cytokine IL-1ß disrupts functionality of the ß-cell circadian clock and impairs circadian regulation of glucose-stimulated insulin secretion. The deleterious effects of IL-1ß on the circadian clock were attributed to impaired expression of key circadian transcription factor Bmal1, and its regulator, the NAD-dependent deacetylase, Sirtuin 1 (SIRT1). Moreover, we also identified that Type 2 diabetes in humans is associated with reduced immunoreactivity of ß-cell BMAL1 and SIRT1, suggestive of a potential causative link between islet inflammation, circadian clock disruption, and ß-cell failure. These data suggest that the circadian clock in ß-cells is perturbed following exposure to proinflammatory stressors and highlights the potential for therapeutic targeting of the circadian system for treatment for ß-cell failure in diabetes.
Assuntos
Relógios Circadianos/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , Insulina/metabolismo , Interleucina-1beta/metabolismo , Fatores de Transcrição ARNTL/genética , Fatores de Transcrição ARNTL/metabolismo , Idoso , Animais , Relógios Circadianos/fisiologia , Diabetes Mellitus Tipo 2/metabolismo , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/fisiologia , Humanos , Células Secretoras de Insulina/metabolismo , Insulinoma , Interleucina-1beta/efeitos adversos , Interleucina-1beta/genética , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Pessoa de Meia-Idade , Membro 1 do Grupo F da Subfamília 1 de Receptores Nucleares/genética , Membro 1 do Grupo F da Subfamília 1 de Receptores Nucleares/metabolismo , Ratos , Sirtuínas/genética , Sirtuínas/metabolismoRESUMO
Coordinated communication among pancreatic islet cells is necessary for maintenance of glucose homeostasis. In diabetes, chronic exposure to pro-inflammatory cytokines has been shown to perturb ß cell communication and function. Compelling evidence has implicated extracellular vesicles (EVs) in modulating physiological and pathological responses to ß cell stress. We report that pro-inflammatory ß cell small EVs (cytokine-exposed EVs [cytoEVs]) induce ß cell dysfunction, promote a pro-inflammatory islet transcriptome, and enhance recruitment of CD8+ T cells and macrophages. Proteomic analysis of cytoEVs shows enrichment of the chemokine CXCL10, with surface topological analysis depicting CXCL10 as membrane bound on cytoEVs to facilitate direct binding to CXCR3 receptors on the surface of ß cells. CXCR3 receptor inhibition reduced CXCL10-cytoEV binding and attenuated ß cell dysfunction, inflammatory gene expression, and leukocyte recruitment to islets. This work implies a significant role of pro-inflammatory ß cell-derived small EVs in modulating ß cell function, global gene expression, and antigen presentation through activation of the CXCL10/CXCR3 axis.
Assuntos
Linfócitos T CD8-Positivos/metabolismo , Quimiocina CXCL10/metabolismo , Vesículas Extracelulares/metabolismo , Receptores CXCR3/metabolismo , Animais , Linfócitos T CD8-Positivos/imunologia , Diabetes Mellitus/patologia , Células Secretoras de Insulina/metabolismo , Macrófagos/metabolismo , Masculino , Camundongos Endogâmicos C57BLRESUMO
Circadian rhythm disruption (CD) is associated with impaired glucose homeostasis and type 2 diabetes mellitus (T2DM). While the link between CD and T2DM remains unclear, there is accumulating evidence that disruption of fasting/feeding cycles mediates metabolic dysfunction. Here, we used an approach encompassing analysis of behavioral, physiological, transcriptomic, and epigenomic effects of CD and consequences of restoring fasting/feeding cycles through time-restricted feeding (tRF) in mice. Results show that CD perturbs glucose homeostasis through disruption of pancreatic ß cell function and loss of circadian transcriptional and epigenetic identity. In contrast, restoration of fasting/feeding cycle prevented CD-mediated dysfunction by reestablishing circadian regulation of glucose tolerance, ß cell function, transcriptional profile, and reestablishment of proline and acidic amino acidrich basic leucine zipper (PAR bZIP) transcription factor DBP expression/activity. This study provides mechanistic insights into circadian regulation of ß cell function and corresponding beneficial effects of tRF in prevention of T2DM.
RESUMO
Pancreatic ß cell failure in type 2 diabetes mellitus (T2DM) is attributed to perturbations of the ß cell's transcriptional landscape resulting in impaired glucose-stimulated insulin secretion. Recent studies identified SLC4A4 (a gene encoding an electrogenic Na+-coupled HCO3- cotransporter and intracellular pH regulator, NBCe1) as one of the misexpressed genes in ß cells of patients with T2DM. Thus, in the current study, we set out to test the hypothesis that misexpression of SLC4A4/NBCe1 in T2DM ß cells contributes to ß cell dysfunction and impaired glucose homeostasis. To address this hypothesis, we first confirmed induction of SLC4A4/NBCe1 expression in ß cells of patients with T2DM and demonstrated that its expression was associated with loss of ß cell transcriptional identity, intracellular alkalinization, and ß cell dysfunction. In addition, we generated a ß cell-selective Slc4a4/NBCe1-KO mouse model and found that these mice were protected from diet-induced metabolic stress and ß cell dysfunction. Importantly, improved glucose tolerance and enhanced ß cell function in Slc4a4/NBCe1-deficient mice were due to augmented mitochondrial function and increased expression of genes regulating ß cell identity and function. These results suggest that increased ß cell expression of SLC4A4/NBCe1 in T2DM plays a contributory role in promotion of ß cell failure and should be considered as a potential therapeutic target.
Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Células Secretoras de Insulina/metabolismo , Simportadores de Sódio-Bicarbonato/metabolismo , Animais , Diabetes Mellitus Tipo 2/genética , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Expressão Gênica , Intolerância à Glucose/etiologia , Intolerância à Glucose/metabolismo , Intolerância à Glucose/prevenção & controle , Humanos , Camundongos , Camundongos Knockout , Mitocôndrias/metabolismo , Obesidade/genética , Obesidade/metabolismo , Simportadores de Sódio-Bicarbonato/deficiência , Simportadores de Sódio-Bicarbonato/genética , Estresse FisiológicoRESUMO
BACKGROUND: The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has emerged as a major pest of cotton, Gossypium hirsutum L, in the mid-southern USA. In the early 1990s L. lineolaris populations developed resistance to several classes of conventional insecticides, increasing the need for insecticides with alternative modes of action such as insect growth regulators (IGRs) for integrated pest management (IPM). The benzoylphenyl urea (BPU) class of IGRs acts by disrupting the growth and development of immature stages of insects, but little is known about its impact on adult stages. RESULTS: The effect of novaluron (Diamond™ 0.83EC), a BPU with known chitin synthesis inhibitor activity, was investigated on adult females of L. lineolaris. Treatment of 1-day-old adults with 600 ppm of novaluron in the diet prevented oviposition, while treatment of older females had no impact on oviposition. Oral novaluron exposure of adults of all ages reduced the viability of eggs laid. Novaluron treatment caused ultrastructural changes in the ovaries of 1-day-old adults (48 h post exposure), distorting the follicular epithelial cell architecture of developing oocytes. Additionally, novaluron treatment decreased the chitin content in ovarian tissue. CONCLUSION: Our results suggest that chitin or chitin-like components in the developing ovaries of adult L. lineolaris are a target of IGRs such as novaluron, but its activity is specific to a critical time during development. This enhances our understanding of the effects of BPUs on adult insects and could lead to incorporation of IGRs in IPM for controlling adult insect pest populations in the field. © 2020 Society of Chemical Industry.
Assuntos
Heterópteros , Inseticidas , Animais , Feminino , Inseticidas/farmacologia , Ninfa , Oogênese , Oviposição , Compostos de FenilureiaRESUMO
This study was focused on gaining insights into the mechanism by which the herbicide- Spectracide®, induces oxidative stress and alters behavior in Drosophila melanogaster. Exposure to Spectracide® (50%) significantly (p < 0.05) reduced the negative geotaxis response, jumping behavior and dampened locomotor activity rhythm in adult flies compared to non-exposed flies. Protein carbonyl levels indicative of oxidative damage increased significantly coupled with down-regulation of Sniffer gene expression encoding carbonyl reductase (CR) and its activity in Spectracide®-exposed flies. In silico modeling analysis revealed that the active ingredients of Spectracide® (atrazine, diquat dibromide, fluazifop-p-butyl, and dicamba) have significant binding affinity to the active site of CR enzyme, with atrazine having comparatively greater affinity. Our results suggest a mechanism by which ingredients in Spectracide® induce oxidative damage by competitive binding to the active site of a protective enzyme and impair its ability to prevent damage to proteins thereby leading to deficits in locomotor behavior in Drosophila.
Assuntos
Herbicidas/toxicidade , Modelos Moleculares , Oxirredutases do Álcool/metabolismo , Animais , Atrazina/toxicidade , Comportamento Animal/efeitos dos fármacos , Drosophila melanogaster/genética , Expressão Gênica , Locomoção/efeitos dos fármacos , Oxirredução , Estresse Oxidativo/genéticaRESUMO
The worldwide prevalence of type 2 diabetes (T2D) is increasing. Despite normal to higher bone density, patients with T2D paradoxically have elevated fracture risk resulting, in part, from poor bone quality. Advanced glycation endproducts (AGEs) and inflammation as a consequence of enhanced receptor for AGE (RAGE) signaling are hypothesized culprits, although the exact mechanisms underlying skeletal dysfunction in T2D are unclear. Lack of inducible models that permit environmental (in obesity) and temporal (after skeletal maturity) control of T2D onset has hampered progress. Here, we show in C57BL/6 mice that a onetime pharmacological intervention (streptozotocin, STZ) initiated in adulthood combined with high-fat diet-induced (HFD-induced) obesity caused hallmark features of human adult-onset T2D, including prolonged hyperglycemia, insulin resistance, and pancreatic ß cell dysfunction, but not complete destruction. In addition, HFD/STZ (i.e., T2D) resulted in several changes in bone quality that closely mirror those observed in humans, including compromised bone microarchitecture, reduced biomechanical strength, impaired bone material properties, altered bone turnover, and elevated levels of the AGE CML in bone and blood. Furthermore, T2D led to the premature accumulation of senescent osteocytes with a unique proinflammatory signature. These findings highlight the RAGE pathway and senescent cells as potential targets to treat diabetic skeletal fragility.
Assuntos
Osso e Ossos , Diabetes Mellitus Tipo 2/metabolismo , Osteócitos , Animais , Densidade Óssea , Osso e Ossos/metabolismo , Osso e Ossos/patologia , Senescência Celular , Modelos Animais de Doenças , Produtos Finais de Glicação Avançada/metabolismo , Resistência à Insulina , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Osteócitos/metabolismo , Osteócitos/patologia , Receptor para Produtos Finais de Glicação Avançada/metabolismoRESUMO
Generation of functional ß cells from pluripotent sources would accelerate diagnostic and therapeutic applications for diabetes research and therapy. However, it has been challenging to generate competent ß cells with dynamic insulin-secretory capacity to glucose and incretin stimulations. We introduced transcription factors, critical for ß-cell development and function, in differentiating human induced pluripotent stem cells (PSCs) and assessed the impact on the functionality of derived ß-cell (psBC) progeny. A perifusion system revealed stepwise transduction of the PDX1, NEUROG3, and MAFA triad (PNM) enabled in vitro generation of psBCs with glucose and GLP-1 responsiveness within 3 weeks. PNM transduction upregulated genes associated with glucose sensing, insulin secretion, and ß-cell maturation. In recipient diabetic mice, PNM-transduced psBCs showed glucose-responsive insulin secretion as early as 1 week post transplantation. Thus, enhanced pre-emptive ß-cell specification of PSCs by PNM drives generation of glucose- and incretin-responsive psBCs in vitro, offering a competent tissue-primed biotherapy.
Assuntos
Diabetes Mellitus Experimental/terapia , Peptídeo 1 Semelhante ao Glucagon/farmacologia , Glucose/farmacologia , Células-Tronco Pluripotentes Induzidas/transplante , Secreção de Insulina/efeitos dos fármacos , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Peptídeo C/metabolismo , Diferenciação Celular , Diabetes Mellitus Experimental/induzido quimicamente , Regulação da Expressão Gênica , Teste de Tolerância a Glucose , Proteína Homeobox Nkx-2.2 , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Fatores de Transcrição Maf Maior/genética , Fatores de Transcrição Maf Maior/metabolismo , Camundongos , Camundongos SCID , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Transativadores/genética , Transativadores/metabolismo , Transdução Genética , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
Development of cell replacement therapies in diabetes requires understanding of the molecular underpinnings of ß-cell maturation. The circadian clock regulates diverse cellular functions important for regulation of ß-cell function and turnover. However, postnatal ontogenesis of the islet circadian clock and its potential role in ß-cell maturation remain unknown. To address this, we studied wild-type Sprague-Dawley as well as Period1 luciferase transgenic (Per1:LUC) rats to determine circadian clock function, clock protein expression, and diurnal insulin secretion during islet development and maturation process. We additionally studied ß-cell-specific Bmal1-deficient mice to elucidate a potential role of this key circadian transcription factor in ß-cell functional and transcriptional maturation. We report that emergence of the islet circadian clock 1) occurs during the early postnatal period, 2) depends on the establishment of global behavioral circadian rhythms, and 3) leads to the induction of diurnal insulin secretion and gene expression. Islet cell maturation was also characterized by induction in the expression of circadian transcription factor BMAL1, deletion of which altered postnatal development of glucose-stimulated insulin secretion and the associated transcriptional network. Postnatal development of the islet circadian clock contributes to early-life ß-cell maturation and should be considered for optimal design of future ß-cell replacement strategies in diabetes.
Assuntos
Fatores de Transcrição ARNTL/genética , Diferenciação Celular/genética , Ritmo Circadiano/genética , Células Secretoras de Insulina/metabolismo , Animais , Animais Geneticamente Modificados , Animais Recém-Nascidos , Proteínas CLOCK/genética , Proteínas CLOCK/metabolismo , Relógios Circadianos/genética , Feminino , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Camundongos Knockout , Proteínas Circadianas Period/genética , Ratos , Ratos Sprague-Dawley , Ratos WistarRESUMO
High-fat diet (HFD)-fed mouse models have been widely used to study early type 2 diabetes. Decreased ß-cell glucokinase (GCK) expression has been observed in HFD-induced diabetes. However, owing to its crucial roles in glucose metabolism in the liver and in islet ß-cells, the contribution of decreased GCK expression to the development of HFD-induced diabetes is unclear. Here, we employed a ß-cell-targeted gene transfer vector and determined the impact of ß-cell-specific increase in GCK expression on ß-cell function and glucose handling in vitro and in vivo Overexpression of GCK enhanced glycolytic flux, ATP-sensitive potassium channel activation and membrane depolarization, and increased proliferation in Min6 cells. ß-cell-targeted GCK transduction did not change glucose handling in chow-fed C57BL/6 mice. Although adult mice fed a HFD showed reduced islet GCK expression, impaired glucose tolerance and decreased glucose-stimulated insulin secretion (GSIS), ß-cell-targeted GCK transduction improved glucose tolerance and restored GSIS. Islet perifusion experiments verified restored GSIS in isolated HFD islets by GCK transduction. Thus, our data identify impaired ß-cell GCK expression as an underlying mechanism for dysregulated ß-cell function and glycemic control in HFD-induced diabetes. Our data also imply an etiological role of GCK in diet-induced diabetes.This article has an associated First Person interview with the first author of the paper.
Assuntos
Diabetes Mellitus Experimental/enzimologia , Diabetes Mellitus Experimental/patologia , Glucoquinase/metabolismo , Células Secretoras de Insulina/enzimologia , Células Secretoras de Insulina/patologia , Animais , Cálcio/metabolismo , Proliferação de Células , Dependovirus/metabolismo , Diabetes Mellitus Experimental/genética , Dieta Hiperlipídica , Glucose/metabolismo , Teste de Tolerância a Glucose , Glicólise , Insulina/metabolismo , Espaço Intracelular/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Transdução de Sinais , Transdução Genética , Regulação para Cima/genéticaRESUMO
Circadian disruption and obesity synergize to predispose to development of type 2 diabetes mellitus (T2DM), signifying that therapeutic targeting of both circadian and metabolic dysfunctions should be considered as a potential treatment approach. To address this hypothesis, we studied rats concomitantly exposed to circadian disruption and diet-induced obesity (CDO), a rat model recently shown to recapitulate phenotypical aspects of obese T2DM (eg, circadian disruption, obesity, insulin resistance, and islet failure). CDO rats were subsequently treated daily (for 12 wk) by timed oral gavage with vehicle, melatonin (a known chronobiotic), metformin, or combination treatment of both therapeutics. Melatonin treatment alone improved circadian activity rhythms, attenuated induction of ß-cell failure, and enhanced glucose tolerance. Metformin alone did not modify circadian activity but enhanced insulin sensitivity and glucose tolerance. Importantly, the combination of melatonin and metformin had synergistic actions to modify progression of metabolic dysfunction in CDO rats through improved adiposity, circadian activity, insulin sensitivity, and islet cell failure. This study suggests that management of both circadian and metabolic dysfunctions should be considered as a potential preventative and therapeutic option for treatment of obesity and T2DM.