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1.
PLoS One ; 14(5): e0217096, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31091299

RESUMO

As in mammals, high-sucrose diets lead to obesity and insulin resistance in the model organism Drosophila melanogaster (called Drosophila hereafter). To explore the relative contributions of glucose and fructose, sucrose's component monosaccharides, we compared their effects on larval physiology. Both sugars exhibited similar effects to sucrose, leading to obesity and hyperglycemia. There were no striking differences resulting from larvae fed high glucose versus high fructose. Some small but statistically significant differences in weight and gene expression were observed that suggest Drosophila is a promising model system for understanding monosaccharide-specific effects on metabolic homeostasis.

3.
Am J Hum Genet ; 104(1): 112-138, 2019 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-30595373

RESUMO

Mitochondria (MT), the major site of cellular energy production, are under dual genetic control by 37 mitochondrial DNA (mtDNA) genes and numerous nuclear genes (MT-nDNA). In the CHARGEmtDNA+ Consortium, we studied genetic associations of mtDNA and MT-nDNA associations with body mass index (BMI), waist-hip-ratio (WHR), glucose, insulin, HOMA-B, HOMA-IR, and HbA1c. This 45-cohort collaboration comprised 70,775 (insulin) to 170,202 (BMI) pan-ancestry individuals. Validation and imputation of mtDNA variants was followed by single-variant and gene-based association testing. We report two significant common variants, one in MT-ATP6 associated (p ≤ 5E-04) with WHR and one in the D-loop with glucose. Five rare variants in MT-ATP6, MT-ND5, and MT-ND6 associated with BMI, WHR, or insulin. Gene-based meta-analysis identified MT-ND3 associated with BMI (p ≤ 1E-03). We considered 2,282 MT-nDNA candidate gene associations compiled from online summary results for our traits (20 unique studies with 31 dataset consortia's genome-wide associations [GWASs]). Of these, 109 genes associated (p ≤ 1E-06) with at least 1 of our 7 traits. We assessed regulatory features of variants in the 109 genes, cis- and trans-gene expression regulation, and performed enrichment and protein-protein interactions analyses. Of the identified mtDNA and MT-nDNA genes, 79 associated with adipose measures, 49 with glucose/insulin, 13 with risk for type 2 diabetes, and 18 with cardiovascular disease, indicating for pleiotropic effects with health implications. Additionally, 21 genes related to cholesterol, suggesting additional important roles for the genes identified. Our results suggest that mtDNA and MT-nDNA genes and variants reported make important contributions to glucose and insulin metabolism, adipocyte regulation, diabetes, and cardiovascular disease.


Assuntos
DNA Mitocondrial/genética , Genes Mitocondriais/genética , Variação Genética/genética , Metabolismo/genética , Mitocôndrias/genética , Mitocôndrias/metabolismo , Adipócitos/metabolismo , Índice de Massa Corporal , Doenças Cardiovasculares/genética , Doenças Cardiovasculares/metabolismo , Estudos de Coortes , Diabetes Mellitus/genética , Diabetes Mellitus/metabolismo , Glucose/metabolismo , Hemoglobina A Glicada/metabolismo , Humanos , Insulina/metabolismo , Locos de Características Quantitativas , Relação Cintura-Quadril
4.
Endocr Connect ; 7(12): 1226-1235, 2018 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-30352402

RESUMO

The majority of papillary thyroid carcinoma (PTC) cases comprise classic papillary (C-PTC) and follicular variant (FV-PTC) histologic sub-types. Historically, clinical equivalency was assumed, but recent data suggest C-PTC may have poorer outcomes. However, large single-institution series with long-term outcomes of C-PTC and FV-PTC, using modern pathologic criteria for FV-PTC, are needed. Our objective was to compare prevalence and impact of clinicopathologic factors, including BRAF mutation status, on long-term outcomes of C-PTC and FV-PTC. We hypothesized that patients with C-PTC would have higher risk disease features and worse survival outcomes. This retrospective study included 1293 patients treated at a single, US academic institution between 1943 and 2009 with mean follow-up of 8.6 years. All patients underwent either partial or total thyroidectomy and had invasive C-PTC or FV-PTC per modern pathology criteria. Primary study measurements included differences in recurrence-free survival (RFS), disease-specific survival (DSS) and associations with clinicopathologic factors including the BRAF mutation. Compared to FV-PTC, C-PTC was associated with multiple features of high-risk disease (P < 0.05) and significantly reduced RFS and DSS. Survival differences were consistent across univariate, multivariate and Kaplan-Meier analyses. BRAF mutations were more common in C-PTC (P = 0.002). However, on Kaplan-Meier analysis, mutational status did not significantly impact RFS or DSS for patients with either histologic sub-type. C-PTC therefore indicates higher-risk disease and predicts for significantly poorer long-term outcomes when compared to FV-PTC. The nature of this difference in outcome is not explained by traditional histopathologic findings or by the BRAF mutation.

5.
PLoS Genet ; 14(4): e1007222, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29608557

RESUMO

Human GWAS of obesity have been successful in identifying loci associated with adiposity, but for the most part, these are non-coding SNPs whose function, or even whose gene of action, is unknown. To help identify the genes on which these human BMI loci may be operating, we conducted a high throughput screen in Drosophila melanogaster. Starting with 78 BMI loci from two recently published GWAS meta-analyses, we identified fly orthologs of all nearby genes (± 250KB). We crossed RNAi knockdown lines of each gene with flies containing tissue-specific drivers to knock down (KD) the expression of the genes only in the brain and the fat body. We then raised the flies on a control diet and compared the amount of fat/triglyceride in the tissue-specific KD group compared to the driver-only control flies. 16 of the 78 BMI GWAS loci could not be screened with this approach, as no gene in the 500-kb region had a fly ortholog. Of the remaining 62 GWAS loci testable in the fly, we found a significant fat phenotype in the KD flies for at least one gene for 26 loci (42%) even after correcting for multiple comparisons. By contrast, the rate of significant fat phenotypes in RNAi KD found in a recent genome-wide Drosophila screen (Pospisilik et al. (2010) is ~5%. More interestingly, for 10 of the 26 positive regions, we found that the nearest gene was not the one that showed a significant phenotype in the fly. Specifically, our screen suggests that for the 10 human BMI SNPs rs11057405, rs205262, rs9925964, rs9914578, rs2287019, rs11688816, rs13107325, rs7164727, rs17724992, and rs299412, the functional genes may NOT be the nearest ones (CLIP1, C6orf106, KAT8, SMG6, QPCTL, EHBP1, SLC39A8, ADPGK /ADPGK-AS1, PGPEP1, KCTD15, respectively), but instead, the specific nearby cis genes are the functional target (namely: ZCCHC8, VPS33A, RSRC2; SPDEF, NUDT3; PAGR1; SETD1, VKORC1; SGSM2, SRR; VASP, SIX5; OTX1; BANK1; ARIH1; ELL; CHST8, respectively). The study also suggests further functional experiments to elucidate mechanism of action for genes evolutionarily conserved for fat storage.


Assuntos
Índice de Massa Corporal , Cruzamentos Genéticos , Drosophila melanogaster/genética , Estudo de Associação Genômica Ampla , Obesidade/genética , Interferência de RNA , Tecido Adiposo , Animais , Humanos , Camundongos , Polimorfismo de Nucleotídeo Único , Locos de Características Quantitativas
6.
Genetics ; 208(4): 1643-1656, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29487137

RESUMO

Insulin resistance is associated with obesity, cardiovascular disease, non-alcoholic fatty liver disease, and type 2 diabetes. These complications are exacerbated by a high-calorie diet, which we used to model type 2 diabetes in Drosophila melanogaster Our studies focused on the fat body, an adipose- and liver-like tissue that stores fat and maintains circulating glucose. A gene regulatory network was constructed to predict potential regulators of insulin signaling in this tissue. Genomic characterization of fat bodies suggested a central role for the transcription factor Seven-up (Svp). Here, we describe a new role for Svp as a positive regulator of insulin signaling. Tissue-specific loss-of-function showed that Svp is required in the fat body to promote glucose clearance, lipid turnover, and insulin signaling. Svp appears to promote insulin signaling, at least in part, by inhibiting ecdysone signaling. Svp also impairs the immune response possibly via inhibition of antimicrobial peptide expression in the fat body. Taken together, these studies show that gene regulatory networks can help identify positive regulators of insulin signaling and metabolic homeostasis using the Drosophila fat body.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Insulina/metabolismo , Receptores de Esteroides/metabolismo , Transdução de Sinais , Tecido Adiposo , Ração Animal , Animais , Proteínas de Ligação a DNA/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Dislipidemias/etiologia , Dislipidemias/metabolismo , Metabolismo Energético , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Redes Reguladoras de Genes , Glucose/metabolismo , Homeostase , Masculino , Metaboloma , Metabolômica/métodos , Ligação Proteica , Receptores de Esteroides/genética , Transcriptoma
7.
Mol Cell Biol ; 2017 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-29084810

RESUMO

Systemic and tissue-specific insulin resistance have been described in Drosophila, and are accompanied by many indicators of metabolic disease. The downstream mediators of insulin-resistant pathophysiology remain unclear. We analyzed insulin signaling in the fat body using loss- and gain-of-function. When expression of the sole Drosophila Insulin receptor (InR) was reduced in larval fat bodies, animals exhibited developmental delay and reduced size in a diet-dependent manner. Fat body InR knockdown also led to reduced survival on high-sugar diets. To look downstream of InR at potential mediators of insulin resistance, RNA-seq studies in insulin-resistant fat bodies revealed differential expression of genes, including those involved in innate immunity. Obesity-associated insulin resistance led to increased susceptibility of flies to infection, as in humans. Reduced innate immunity was dependent on fat body InR expression. The peptidoglycan recognition proteins (PGRPs) PGRP-SB2 and PGRP-SC2 were selected for further study based on differential expression studies. Downregulating PGRP-SB2 selectively in the fat body protected animals from the deleterious effects of overnutrition, whereas downregulating PGRP-SC2 produced InR-like phenotypes. These studies extend earlier work linking the immune and insulin signaling pathways and identify new targets of insulin signaling that could serve as potential drug targets to treat type 2 diabetes.

8.
J Lipid Res ; 57(3): 380-7, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26805007

RESUMO

We developed a Drosophila model of T2D in which high sugar (HS) feeding leads to insulin resistance. In this model, adipose TG storage is protective against fatty acid toxicity and diabetes. Initial biochemical and gene expression studies suggested that deficiency in CoA might underlie reduced TG synthesis in animals during chronic HS feeding. Focusing on the Drosophila fat body (FB), which is specialized for TG storage and lipolysis, we undertook a series of experiments to test the hypothesis that CoA could protect against the deleterious effects of caloric overload. Quantitative metabolomics revealed a reduction in substrate availability for CoA synthesis in the face of an HS diet. Further reducing CoA synthetic capacity by expressing FB-specific RNAi targeting pantothenate kinase (PK orfumble) or phosphopantothenoylcysteine synthase (PPCS) exacerbated HS-diet-induced accumulation of FFAs. Dietary supplementation with pantothenic acid (vitamin B5, a precursor of CoA) was able to ameliorate HS-diet-induced FFA accumulation and hyperglycemia while increasing TG synthesis. Taken together, our data support a model where free CoA is required to support fatty acid esterification and to protect against the toxicity of HS diets.


Assuntos
Coenzima A/metabolismo , Drosophila melanogaster/metabolismo , Ingestão de Energia , Animais , Carboidratos da Dieta/efeitos adversos , Drosophila melanogaster/efeitos dos fármacos , Drosophila melanogaster/enzimologia , Ingestão de Energia/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Fenótipo
9.
Cancer Med ; 4(6): 791-9, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25712893

RESUMO

The BRAF mutation occurs commonly in papillary thyroid carcinoma (PTC). Previous investigations of its utility to predict recurrence-free survival (RFS) and disease-specific survival (DSS) have reported conflicting results and its role remains unclear. The purpose of this retrospective study was to determine the incidence of the BRAF mutation and analyze its relationship to clinicopathologic risk factors and long-term outcomes in the largest, single-institution American cohort to date. BRAF mutational status was determined in 508 PTC patients using RFLP analysis. The relationships between BRAF mutation status, patient and tumor characteristics, RFS, and DSS were analyzed. The BRAF mutation was present in 67% of patients. On multivariate analysis, presence of the mutation predicted only for capsular invasion (HR, 1.7; 95% CI, 1.1-2.6), cervical lymph node involvement (HR, 1.7; 95% CI, 1.1-2.7), and classic papillary histology (HR, 1.8; 95% CI 1.1-2.9). There was no significant relationship between the BRAF mutation and RFS or DSS, an observation that was consistent across univariate, multivariate, and Kaplan-Meier analyses. This is the most extensive study to date in the United States to demonstrate that BRAF mutation is of no predictive value for recurrence or survival in PTC. We found correlations of BRAF status and several clinicopathologic characteristics of high-risk disease, but limited evidence that the mutation correlates with more extensive or aggressive disease. This analysis suggests that BRAF is minimally prognostic in PTC. However, prevalence of the BRAF mutation is 70% in the general population, providing the opportunity for targeted therapy.


Assuntos
Carcinoma/genética , Mutação/genética , Proteínas Proto-Oncogênicas B-raf/genética , Neoplasias da Glândula Tireoide/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma/mortalidade , Carcinoma/cirurgia , Carcinoma Papilar , Criança , Pré-Escolar , Feminino , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/genética , Recidiva Local de Neoplasia/mortalidade , Prognóstico , Estudos Retrospectivos , Fatores de Risco , Câncer Papilífero da Tireoide , Neoplasias da Glândula Tireoide/mortalidade , Neoplasias da Glândula Tireoide/cirurgia , Estados Unidos/epidemiologia , Adulto Jovem
10.
Cell ; 154(3): 664-75, 2013 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-23911328

RESUMO

The risk of specific cancers increases in patients with metabolic dysfunction, including obesity and diabetes. Here, we use Drosophila as a model to explore the effects of diet on tumor progression. Feeding Drosophila a diet high in carbohydrates was previously demonstrated to direct metabolic dysfunction, including hyperglycemia, hyperinsulinemia, and insulin resistance. We demonstrate that high dietary sugar also converts Ras/Src-transformed tissue from localized growths to aggressive tumors with emergent metastases. Whereas most tissues displayed insulin resistance, Ras/Src tumors retained insulin pathway sensitivity, increased the ability to import glucose, and resisted apoptosis. High dietary sugar increased canonical Wingless/Wnt pathway activity, which upregulated insulin receptor gene expression to promote insulin sensitivity. The result is a feed-forward circuit that amplified diet-mediated malignant phenotypes within Ras/Src-transformed tumors. By targeting multiple steps in this circuit with rationally applied drug combinations, we demonstrate the potential of combinatorial drug intervention to treat diet-enhanced malignant tumors.


Assuntos
Carboidratos da Dieta/administração & dosagem , Modelos Animais de Doenças , Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Resistência à Insulina , Neoplasias/metabolismo , Transdução de Sinais , Proteína Wnt1/metabolismo , Animais , Transformação Celular Neoplásica , Dieta Hiperlipídica , Glucose/metabolismo , Humanos , Fosfatidilinositol 3-Quinases/metabolismo
11.
Dis Model Mech ; 6(5): 1123-32, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23649823

RESUMO

Worldwide epidemiologic studies have repeatedly demonstrated an association between prenatal nutritional environment, birth weight and susceptibility to adult diseases including obesity, cardiovascular disease and type 2 diabetes. Despite advances in mammalian model systems, the molecular mechanisms underlying this phenomenon are unclear, but might involve programming mechanisms such as epigenetics. Here we describe a new system for evaluating metabolic programming mechanisms using a simple, genetically tractable Drosophila model. We examined the effect of maternal caloric excess on offspring and found that a high-sugar maternal diet alters body composition of larval offspring for at least two generations, augments an obese-like phenotype under suboptimal (high-calorie) feeding conditions in adult offspring, and modifies expression of metabolic genes. Our data indicate that nutritional programming mechanisms could be highly conserved and support the use of Drosophila as a model for evaluating the underlying genetic and epigenetic contributions to this phenomenon.


Assuntos
Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Hereditariedade/genética , Padrões de Herança/genética , Metabolismo/genética , Animais , Composição Corporal , Carboidratos/sangue , Cruzamentos Genéticos , Dieta , Epistasia Genética/genética , Comportamento Alimentar , Feminino , Perfilação da Expressão Gênica , Larva , Masculino , Obesidade/sangue , Obesidade/genética , Obesidade/patologia , Fenótipo
12.
BMC Genomics ; 14: 136, 2013 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-23445342

RESUMO

BACKGROUND: Genome-wide association studies (GWAS) identify regions of the genome that are associated with particular traits, but do not typically identify specific causative genetic elements. For example, while a large number of single nucleotide polymorphisms associated with type 2 diabetes (T2D) and related traits have been identified by human GWAS, only a few genes have functional evidence to support or to rule out a role in cellular metabolism or dietary interactions. Here, we use a recently developed Drosophila model in which high-sucrose feeding induces phenotypes similar to T2D to assess orthologs of human GWAS-identified candidate genes for risk of T2D and related traits. RESULTS: Disrupting orthologs of certain T2D candidate genes (HHEX, THADA, PPARG, KCNJ11) led to sucrose-dependent toxicity. Tissue-specific knockdown of the HHEX ortholog dHHEX (CG7056) directed metabolic defects and enhanced lethality; for example, fat-body-specific loss of dHHEX led to increased hemolymph glucose and reduced insulin sensitivity. CONCLUSION: Candidate genes identified in human genetic studies of metabolic traits can be prioritized and functionally characterized using a simple Drosophila approach. To our knowledge, this is the first large-scale effort to study the functional interaction between GWAS-identified candidate genes and an environmental risk factor such as diet in a model organism system.


Assuntos
Diabetes Mellitus Tipo 2/genética , Proteínas de Drosophila/genética , Estudo de Associação Genômica Ampla , Proteínas de Homeodomínio/genética , Proteínas Musculares/genética , Fatores de Transcrição/genética , Animais , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Corpo Adiposo/metabolismo , Corpo Adiposo/patologia , Estudos de Associação Genética , Predisposição Genética para Doença , Glucose/genética , Glucose/metabolismo , Humanos , Resistência à Insulina/genética , Especificidade de Órgãos , Fenótipo , Polimorfismo de Nucleotídeo Único
13.
Cell Signal ; 25(6): 1468-75, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23524329

RESUMO

Frizzled receptors have long been thought to couple to G proteins but biochemical evidence supporting such an interaction has been lacking. Here we expressed mammalian Wnt-Frizzled fusion proteins in Saccharomyces cerevisiae and tested the receptors' ability to activate the yeast mitogen-activated protein kinase (MAPK) pathway via heterotrimeric G proteins. Our results show that Frizzled receptors can interact with Gαi, Gαq, and Gαs proteins, thus confirming that Frizzled functions as a G protein coupled receptor (GPCR). However, the activity level of Frizzled-mediated G protein signaling was much lower than that of a typical GPCR and, surprisingly, was highest when coupled to Gαs. The Frizzled/Gαs interaction was further established in vivo as Drosophila expressing a loss-of-function Gαs allele rescued the photoreceptor differentiation phenotype of Frizzled mutant flies. Together, these data point to an important role for Frizzled as a nontraditional GPCR that preferentially couples to Gαs heterotrimeric G proteins.


Assuntos
Receptores Frizzled/metabolismo , Receptores Acoplados a Proteínas-G/metabolismo , Animais , Drosophila/metabolismo , Proteínas de Drosophila/metabolismo , Receptores Frizzled/genética , Subunidades alfa de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa Gs de Proteínas de Ligação ao GTP/metabolismo , Humanos , Proteína-6 Relacionada a Receptor de Lipoproteína de Baixa Densidade/genética , Proteína-6 Relacionada a Receptor de Lipoproteína de Baixa Densidade/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais , Proteínas Wnt/genética , Proteínas Wnt/metabolismo
14.
J Biol Chem ; 288(12): 8028-42, 2013 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-23355467

RESUMO

The Drosophila fat body is a liver- and adipose-like tissue that stores fat and serves as a detoxifying and immune responsive organ. We have previously shown that a high sugar diet leads to elevated hemolymph glucose and systemic insulin resistance in developing larvae and adults. Here, we used stable isotope tracer feeding to demonstrate that rearing larvae on high sugar diets impaired the synthesis of esterified fatty acids from dietary glucose. Fat body lipid profiling revealed changes in both carbon chain length and degree of unsaturation of fatty acid substituents, particularly in stored triglycerides. We tested the role of the fat body in larval tolerance of caloric excess. Our experiments demonstrated that lipogenesis was necessary for animals to tolerate high sugar feeding as tissue-specific loss of orthologs of carbohydrate response element-binding protein or stearoyl-CoA desaturase 1 resulted in lethality on high sugar diets. By contrast, increasing the fat content of the fat body by knockdown of king-tubby was associated with reduced hyperglycemia and improved growth and tolerance of high sugar diets. Our work supports a critical role for the fat body and the Drosophila carbohydrate response element-binding protein ortholog in metabolic homeostasis in Drosophila.


Assuntos
Drosophila melanogaster/metabolismo , Corpo Adiposo/metabolismo , Lipogênese , Animais , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Ingestão de Energia , Metabolismo Energético , Corpo Adiposo/fisiologia , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos/metabolismo , Expressão Gênica , Regulação da Expressão Gênica , Glucose/metabolismo , Glicólise , Hemolinfa/metabolismo , Hiperglicemia/metabolismo , Cetonas/metabolismo , Larva/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fosfolipídeos/metabolismo , Transcriptoma
15.
PLoS Genet ; 9(1): e1003175, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23326243

RESUMO

Diets high in carbohydrates have long been linked to progressive heart dysfunction, yet the mechanisms by which chronic high sugar leads to heart failure remain poorly understood. Here we combine diet, genetics, and physiology to establish an adult Drosophila melanogaster model of chronic high sugar-induced heart disease. We demonstrate deterioration of heart function accompanied by fibrosis-like collagen accumulation, insulin signaling defects, and fat accumulation. The result was a shorter life span that was more severe in the presence of reduced insulin and P38 signaling. We provide evidence of a role for hexosamine flux, a metabolic pathway accessed by glucose. Increased hexosamine flux led to heart function defects and structural damage; conversely, cardiac-specific reduction of pathway activity prevented sugar-induced heart dysfunction. Our data establish Drosophila as a useful system for exploring specific aspects of diet-induced heart dysfunction and emphasize enzymes within the hexosamine biosynthetic pathway as candidate therapeutic targets.


Assuntos
Cardiomiopatias , Drosophila melanogaster , Glucose , Insuficiência Cardíaca , Animais , Cardiomiopatias/genética , Cardiomiopatias/fisiopatologia , Dieta , Modelos Animais de Doenças , Drosophila melanogaster/genética , Drosophila melanogaster/fisiologia , Glucose/química , Glucose/metabolismo , Coração/fisiopatologia , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/fisiopatologia , Hexosaminas/metabolismo , Humanos , Insulina/genética , Insulina/metabolismo , Sistema de Sinalização das MAP Quinases , Transdução de Sinais
16.
Proteins ; 80(1): 71-80, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21960464

RESUMO

Previously we demonstrated by random saturation mutagenesis a set of mutations in the extracellular (EC) loops that constitutively activate the C5a receptor (C5aR) (Klco et al., Nat Struct Mol Biol 2005;12:320-326; Klco et al., J Biol Chem 2006;281:12010-12019). In this study, molecular modeling revealed possible conformations for the extracellular loops of the C5a receptors with mutations in the EC2 loop or in the EC3 loop. Comparison of low-energy conformations of the EC loops defined two distinct clusters of conformations typical either for strongly constitutively active mutants of C5aR (the CAM cluster) or for nonconstitutively active mutants (the non-CAM cluster). In the CAM cluster, the EC3 loop was turned towards the transmembrane (TM) helical bundle and more closely interacted with EC2 than in the non-CAM cluster. This suggested a structural mechanism of constitutive activity where EC3 contacts EC2 leading to EC2 interactions with helix TM3, thus triggering movement of TM7 towards TM2 and TM3. The movement initiates rearrangement of the system of hydrogen bonds between TM2, TM3 and TM7 including formation of the hydrogen bond between the side chains of D82(2.50) in TM2 and N296(7.49) in TM7, which is crucial for formation of the activated states of the C5a receptors (Nikiforovich et al., Proteins: Struct Funct Gene 2011;79:787-802). Since the relative large length of EC3 in C5aR (13 residues) is comparable with those in many other members of rhodopsin family of GPCRs (13-19 residues), our findings might reflect general mechanisms of receptor constitutive activation. The very recent X-ray structure of the agonist-induced constitutively active mutant of rhodopsin (Standfuss et al., Nature 2011;471:656-660) is discussed in view of our modeling results.


Assuntos
Simulação por Computador , Ativação Enzimática , Modelos Moleculares , Mutação de Sentido Incorreto , Receptores de Complemento/genética , Motivos de Aminoácidos , Sequência de Aminoácidos , Humanos , Ligações de Hidrogênio , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Receptor da Anafilatoxina C5a , Receptores de Complemento/química , Termodinâmica
18.
Dis Model Mech ; 4(6): 842-9, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21719444

RESUMO

Insulin-resistant, 'type 2' diabetes (T2D) results from a complex interplay between genes and environment. In particular, both caloric excess and obesity are strongly associated with T2D across many genetic backgrounds. To gain insights into how dietary excess affects insulin resistance, we studied the simple model organism Drosophila melanogaster. Larvae reared on a high-sugar diet were hyperglycemic, insulin resistant and accumulated fat--hallmarks of T2D--compared with those reared on control diets. Excess dietary sugars, but not fats or proteins, elicited insulin-resistant phenotypes. Expression of genes involved in lipogenesis, gluconeogenesis and ß-oxidation was upregulated in high-sugar-fed larvae, as were FOXO targets, consistent with known mechanisms of insulin resistance in humans. These data establish a novel Drosophila model of diet-induced insulin resistance that bears strong similarity to the pathophysiology of T2D in humans.


Assuntos
Dieta , Carboidratos da Dieta/farmacologia , Drosophila melanogaster/efeitos dos fármacos , Resistência à Insulina , Obesidade/patologia , Animais , Metabolismo dos Carboidratos/efeitos dos fármacos , Metabolismo dos Carboidratos/genética , Drosophila melanogaster/genética , Comportamento Alimentar/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Hiperglicemia/complicações , Hiperglicemia/genética , Hiperglicemia/patologia , Resistência à Insulina/genética , Metabolismo dos Lipídeos/efeitos dos fármacos , Metabolismo dos Lipídeos/genética , Obesidade/complicações , Obesidade/genética , Transcrição Genética/efeitos dos fármacos
19.
Mo Med ; 108(2): 93-8, 2011 Mar-Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21568229

RESUMO

The incidence of differentiated thyroid cancer (including papillary, follicular, and Hurthle cell carcinoma) has nearly tripled in the past 20 years. Diagnosis, treatment, and long-term management are evolving with advances in radiology, surgical techniques, nuclear medicine, genetics, and targeted therapeutics. Here we detail the current recommended course of action for differentiated thyroid cancer and options on the horizon.


Assuntos
Neoplasias da Glândula Tireoide/patologia , Biópsia por Agulha Fina , Carcinoma Papilar/patologia , Ablação por Cateter , Humanos , Radioisótopos do Iodo/uso terapêutico , Missouri/epidemiologia , Metástase Neoplásica , Estadiamento de Neoplasias , Medição de Risco , Tireoglobulina/sangue , Neoplasias da Glândula Tireoide/epidemiologia , Neoplasias da Glândula Tireoide/cirurgia , Tireoidectomia , Tireotropina/sangue
20.
Proteins ; 79(3): 787-802, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21287612

RESUMO

Molecular modeling of conformational changes occurring in the transmembrane region of the complement factor 5a receptor (C5aR) during receptor activation was performed by comparing two constitutively active mutants (CAMs) of C5aR, NQ (I124N/L127Q), and F251A, to those of the wild-type C5aR and NQ-N296A (I124N/L127Q/N296A), which have the wild-type phenotype. Modeling involved comprehensive sampling of various rotations of TM helices aligned to the crystal template of the dark-adapted rhodopsin along their long axes. By assuming that the relative energies of the spontaneously activated states of CAMs should be lower or at least comparable to energies characteristic for the ground states, we selected the plausible models for the conformational states associated with constitutive activation in C5aR. The modeling revealed that the hydrogen bonds between the side chains of D82-N119, S85-N119, and S131-C221 characteristic for the ground state were replaced by the hydrogen bonds D82-N296, N296-Y300, and S131-R134, respectively, in the activated states. Also, conformational transitions that occurred upon activation were hindered by contacts between the side chains of L127 and F251. The results rationalize the available data of mutagenesis in C5aR and offer the first specific molecular mechanism for the loss of constitutive activity in NQ-N296A. Our results also contributed to understanding the general structural mechanisms of activation in G-protein-coupled receptors lacking the "ionic lock", R(3.50) and E/D(6.30). Importantly, these results were obtained by modeling approaches that deliberately simplify many elements in order to explore potential conformations of GPCRs involving large-scale molecular movements.


Assuntos
Modelos Moleculares , Receptor da Anafilatoxina C5a/metabolismo , Mutação , Conformação Proteica , Receptor da Anafilatoxina C5a/química , Receptor da Anafilatoxina C5a/genética
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