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SUMMARY: Despite their fundamental role in various biological processes, the analysis of small RNA sequencing data remains a challenging task. Major obstacles arise when short RNA sequences map to multiple locations in the genome, align to regions that are not annotated or underwent post-transcriptional changes which hamper accurate mapping. In order to tackle these issues, we present a novel profiling strategy that circumvents the need for read mapping to a reference genome by utilizing the actual read sequences to determine expression intensities. After differential expression analysis of individual sequence counts, significant sequences are annotated against user defined feature databases and clustered by sequence similarity. This strategy enables a more comprehensive and concise representation of small RNA populations without any data loss or data distortion. AVAILABILITY AND IMPLEMENTATION: Code and documentation of our R package at http://ibis.helmholtz-muenchen.de/deus/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
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Software , Perfilação da Expressão Gênica , Genoma , RNA , Análise de Sequência de RNARESUMO
Mitochondria are dynamic organelles with diverse functions in tissues such as liver and skeletal muscle. To unravel the mitochondrial contribution to tissue-specific physiology, we performed a systematic comparison of the mitochondrial proteome and lipidome of mice and assessed the consequences hereof for respiration. Liver and skeletal muscle mitochondrial protein composition was studied by data-independent ultra-high-performance (UHP)LC-MS/MS-proteomics, and lipid profiles were compared by UHPLC-MS/MS lipidomics. Mitochondrial function was investigated by high-resolution respirometry in samples from mice and humans. Enzymes of pyruvate oxidation as well as several subunits of complex I, III, and ATP synthase were more abundant in muscle mitochondria. Muscle mitochondria were enriched in cardiolipins associated with higher oxidative phosphorylation capacity and flexibility, in particular CL(18:2)4 and 22:6-containing cardiolipins. In contrast, protein equipment of liver mitochondria indicated a shuttling of complex I substrates toward gluconeogenesis and ketogenesis and a higher preference for electron transfer via the flavoprotein quinone oxidoreductase pathway. Concordantly, muscle and liver mitochondria showed distinct respiratory substrate preferences. Muscle respired significantly more on the complex I substrates pyruvate and glutamate, whereas in liver maximal respiration was supported by complex II substrate succinate. This was a consistent finding in mouse liver and skeletal muscle mitochondria and human samples. Muscle mitochondria are tailored to produce ATP with a high capacity for complex I-linked substrates. Liver mitochondria are more connected to biosynthetic pathways, preferring fatty acids and succinate for oxidation. The physiologic diversity of mitochondria may help to understand tissue-specific disease pathologies and to develop therapies targeting mitochondrial function.
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Metabolismo Energético/fisiologia , Fígado/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Músculo Esquelético/metabolismo , Proteoma/metabolismo , Animais , Feminino , Humanos , Fígado/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias Hepáticas/metabolismo , Mitocôndrias Musculares/metabolismo , Proteínas Mitocondriais/análise , Músculo Esquelético/química , Especificidade de Órgãos , Mapeamento de Peptídeos/métodos , Proteoma/análiseRESUMO
AIMS/HYPOTHESIS: Prediabetes is a collective term for different subphenotypes (impaired glucose tolerance [IGT] and/or impaired fasting glucose [IFG]) with different pathophysiologies. A positive family history for type 2 diabetes (FHD) is associated with increased risk for type 2 diabetes. We assumed that it would also associate with prediabetes, but wondered whether all subphenotypes are related to a positive family history. METHODS: In a study population of 8,106 non-diabetic individuals of European origin collected from four study centres (normal glucose tolerance, NGT n = 5,482, IFG and/or IGT n = 2,624), we analysed whether having at least one first degree relative with diabetes is associated with prediabetes. The analyses were performed using the same models in each population separately. Afterwards, a meta-analysis was performed. RESULTS: FHD was significantly associated with the risk for prediabetes (IFG and/or IGT, OR 1.40; 95% CI 1.27, 1.54). This association remained significant in multivariable logistic regression models including sex, age and BMI (OR 1.26; 95% CI 1.14, 1.40). When different prediabetic outcomes were considered separately, the association was found for isolated IFG (OR 1.37; 95% CI 1.20, 1.57), isolated IGT (OR 1.25; 95% CI 1.07, 1.46) as well as for the combination IFG+IGT (OR 1.64; 95% CI 1.40, 1.93). After stratification on BMI, association between FHD and prediabetes was seen only in non-obese individuals (BMI < 30 kg/m(2)). CONCLUSIONS/INTERPRETATION: We found that FHD is an important risk factor for prediabetes, especially for combined IGT and IFG. Its relevance seems to be more evident in the non-obese.
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Anamnese , Estado Pré-Diabético/epidemiologia , Adulto , Diabetes Mellitus Tipo 2/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de RiscoRESUMO
Among obese subjects, metabolically healthy (MHO) and unhealthy obese (MUHO) subjects exist, the latter being characterized by whole-body insulin resistance, hepatic steatosis, and subclinical inflammation. Insulin resistance and obesity are known to associate with alterations in mitochondrial density, morphology, and function. Therefore, we assessed mitochondrial function in human subcutaneous preadipocytes as well as in differentiated adipocytes derived from well-matched donors. Primary subcutaneous preadipocytes from 4 insulin-resistant (MUHO) versus 4 insulin-sensitive (MHO), non-diabetic, morbidly obese Caucasians (BMI > 40 kg/m2), matched for sex, age, BMI, and percentage of body fat, were differentiated in vitro to adipocytes. Real-time cellular respiration was measured using an XF24 Extracellular Flux Analyzer (Seahorse). Lipolysis was stimulated by forskolin (FSK) treatment. Mitochondrial respiration was fourfold higher in adipocytes versus preadipocytes (p = 1.6*10-9). In adipocytes, a negative correlation of mitochondrial respiration with donors' insulin sensitivity was shown (p = 0.0008). Correspondingly, in adipocytes of MUHO subjects, an increased basal respiration (p = 0.002), higher proton leak (p = 0.04), elevated ATP production (p = 0.01), increased maximal respiration (p = 0.02), and higher spare respiratory capacity (p = 0.03) were found, compared to MHO. After stimulation with FSK, the differences in ATP production, maximal respiration and spare respiratory capacity were blunted. The differences in mitochondrial respiration between MUHO/MHO were not due to altered mitochondrial content, fuel switch, or lipid metabolism. Thus, despite the insulin resistance of MUHO, we could clearly show an elevated mitochondrial respiration of MUHO adipocytes. We suggest that the higher mitochondrial respiration reflects a compensatory mechanism to cope with insulin resistance and its consequences. Preserving this state of compensation might be an attractive goal for preventing or delaying the transition from insulin resistance to overt diabetes.
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Adipócitos/patologia , Saúde , Mitocôndrias/metabolismo , Obesidade/metabolismo , Obesidade/patologia , Adulto , Índice de Massa Corporal , Respiração Celular , Feminino , Glicólise , Humanos , Masculino , Pessoa de Meia-Idade , FenótipoRESUMO
CONTEXT: Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a heterotrimeric enzyme and central regulator of cellular energy metabolism. The impact of single nucleotide polymorphisms (SNPs) in all 7 AMPK subunit genes on adiposity, glucose metabolism, and lipid metabolism has not yet been systematically studied. OBJECTIVE: To analyze the associations of common SNPs in all AMPK genes, and of different scores thereof, with adiposity, insulin sensitivity, insulin secretion, blood glucose, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, total cholesterol, and triglycerides. STUDY DESIGN AND METHODS: A cohort of 2789 nondiabetic participants from the Tübingen Family study of type 2 diabetes, metabolically characterized by oral glucose tolerance test and genotyped by genome-wide SNP array, was analyzed. RESULTS: We identified 6 largely nonoverlapping SNP sets across 4 AMPK genes (PRKAA1, PRKAA2, PRKAG2, PRKAG3) associated with adiposity, insulin sensitivity, insulin secretion, blood glucose, total/LDL cholesterol, or HDL cholesterol, respectively. A genetic score of body-fat-increasing alleles revealed per-allele effect sizes on body mass index (BMI) of +0.22 kg/m2 (P = 2.3 × 10-7), insulin sensitivity of -0.12 × 1019 L2/mol2 (P = 9.9 × 10-6) and 2-hour blood glucose of +0.02 mmol/L (P = 0.0048). Similar effects on blood glucose were observed with scores of insulin-sensitivity-reducing, insulin-secretion-reducing and glucose-raising alleles, respectively. A genetic cholesterol score increased total and LDL cholesterol by 1.17 mg/dL per allele (P = 0.0002 and P = 3.2 × 10-5, respectively), and a genetic HDL score decreased HDL cholesterol by 0.32 mg/dL per allele (P = 9.1 × 10-6). CONCLUSIONS: We describe largely nonoverlapping genetic determinants in AMPK genes for diabetes-/atherosclerosis-related traits, which reflect the metabolic pathways controlled by the enzyme. Formation of trait-specific genetic scores revealed additivity of allele effects, with body-fat-raising alleles reaching a marked effect size. (J Clin Endocrinol Metab XX: 0-0, 2019).
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Proteínas Quinases Ativadas por AMP/genética , Adiposidade , Colesterol/metabolismo , Diabetes Mellitus Tipo 2/epidemiologia , Glucose/metabolismo , Lipídeos/análise , Polimorfismo de Nucleotídeo Único , Adulto , Biomarcadores/análise , Estudos Transversais , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Feminino , Seguimentos , Alemanha/epidemiologia , Humanos , Insulina/metabolismo , Resistência à Insulina , Masculino , Prevalência , PrognósticoRESUMO
Astrocytes provide neurons with structural support and energy in form of lactate, modulate synaptic transmission, are insulin sensitive and act as gatekeeper for water, ions, glutamate and second messengers. Furthermore, astrocytes are important for glucose sensing, possess neuroendocrine functions and also play an important role in cerebral lipid metabolism. To answer the question, if there is a connection between lipid metabolism and insulin action in human astrocytes, we investigated if storage of ectopic lipids in human astrocytes has an impact on insulin signalling in those cells. Human astrocytes were cultured in the presence of a lipid emulsion, consisting of fatty acids and triglycerides, to induce ectopic lipid storage. After several days, cells were stimulated with insulin and gene expression profiling was performed. In addition, phosphorylation of Akt as well as glycogen synthesis and cell proliferation was assessed. Ectopic lipid storage was detected in human astrocytes after lipid exposure and lipid storage was persistent even when the fat emulsion was removed from the cell culture medium. Chronic exposure to lipids induced profound changes in the gene expression profile, whereby some genes showed a reversible gene expression profile upon removal of fat, and some did not. This included FOXO-dependent expression patterns. Furthermore, insulin-induced phosphorylation of Akt was diminished and also insulin-induced glycogen synthesis and proliferation was impaired in lipid-laden astrocytes. Chronic lipid exposure induces lipid storage in human astrocytes accompanied by insulin resistance. Analyses of the gene expression pattern indicated the potential of a partially reversible gene expression profile. Targeting astrocytic insulin resistance by reducing ectopic lipid load might represent a promising treatment target for insulin resistance of the brain in obesity, diabetes and neurodegeneration.
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BACKGROUND/OBJECTIVES: Although the prevalence of obesity and its associated metabolic disorders is increasing in both sexes, the clinical phenotype differs between men and women, highlighting the need for individual treatment options. Mitochondrial dysfunction in various tissues, including white adipose tissue (WAT), has been accepted as a key factor for obesity-associated comorbidities such as diabetes. Given higher expression of mitochondria-related genes in the WAT of women, we hypothesized that gender differences in the bioenergetic profile of white (pre-) adipocytes from obese (age- and BMI-matched) donors must exist. SUBJECTS/METHODS: Using Seahorse technology, we measured oxygen consumption rates (OCR) and extracellular acidification rates (ECAR) of (pre-)adipocytes from male (n = 10) and female (n = 10) deeply-phenotyped obese donors under hypo-, normo- and hyperglycemic (0, 5 and 25 mM glucose) and insulin-stimulated conditions. Additionally, expression levels (mRNA/protein) of mitochondria-related genes (e.g. UQCRC2) and glycolytic enzymes (e.g. PKM2) were determined. RESULTS: Dissecting cellular OCR and ECAR into different functional modules revealed that preadipocytes from female donors show significantly higher mitochondrial to glycolytic activity (higher OCR/ECAR ratio, p = 0.036), which is supported by a higher ratio of UQCRC2 to PKM2 mRNA levels (p = 0.021). However, no major gender differences are detectable in in vitro differentiated adipocytes (e.g. OCR/ECAR, p = 0.248). Importantly, glucose and insulin suppress mitochondrial activity (i.e. ATP-linked respiration) significantly only in preadipocytes of female donors, reflecting their trends towards higher insulin sensitivity. CONCLUSIONS: Collectively, we show that preadipocytes, but not in vitro differentiated adipocytes, represent a model system to reveal gender differences with clinical importance for metabolic disease status. In particular preadipocytes of females maintain enhanced mitochondrial flexibility, as demonstrated by pronounced responses of ATP-linked respiration to glucose.
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Adipócitos Brancos/metabolismo , Metabolismo Energético , Glucose/metabolismo , Insulina/metabolismo , Obesidade/metabolismo , Adulto , Proteínas de Transporte/metabolismo , Células Cultivadas , Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Humanos , Masculino , Proteínas de Membrana/metabolismo , Pessoa de Meia-Idade , Consumo de Oxigênio , Fatores Sexuais , Hormônios Tireóideos/metabolismo , Proteínas de Ligação a Hormônio da TireoideRESUMO
CONTEXT: Primary dysregulation of adipose tissue lipolysis caused by genetic variation and independent of insulin resistance could explain unhealthy body fat distribution and its metabolic consequences. OBJECTIVE: To analyze common single nucleotide polymorphisms (SNPs) in 48 lipolysis-, but not insulin-signaling-related genes, to form polygenic risk scores of lipolysis-associated SNPs, and to investigate their effects on body fat distribution, glycemia, insulin sensitivity, insulin secretion, and proinsulin conversion. STUDY DESIGN, PARTICIPANTS, AND METHODS: SNP array, anthropometric, and metabolic data were available from up to 2789 participants without diabetes of the Tübingen Family study of type 2 diabetes characterized by oral glucose tolerance tests. In a subgroup (n = 942), magnetic resonance measurements of body fat stores were available. RESULTS: We identified insulin-sensitivity-independent nominal associations (P < 0.05) of SNPs in 10 genes with plasma free fatty acids (FFAs), in 7 genes with plasma glycerol and in 6 genes with both, plasma FFAs and glycerol. A score formed of the latter SNPs (in ADCY4, CIDEA, GNAS, PDE8B, PRKAA1, PRKAG2) was associated with plasma FFA and glycerol measurements (1.4*10-9 ≤ P ≤ 1.2*10-5), visceral adipose tissue mass (P = 0.0326), and proinsulin conversion (P ≤ 0.0272). The more lipolysis-increasing alleles a subject had, the lower was the visceral fat mass and the lower the proinsulin conversion. CONCLUSIONS: We found evidence for a genetic basis of adipose tissue lipolysis resulting from common SNPs in CIDEA, AMP-activated protein kinase subunits, and cAMP signaling components. A genetic score of lipolysis-increasing alleles determined lower visceral fat mass and lower proinsulin conversion.
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Gordura Intra-Abdominal/diagnóstico por imagem , Lipólise/genética , Redes e Vias Metabólicas/genética , Proinsulina/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Adulto , Alelos , Proteínas Reguladoras de Apoptose/metabolismo , AMP Cíclico/metabolismo , Ácidos Graxos não Esterificados/sangue , Ácidos Graxos não Esterificados/metabolismo , Feminino , Alemanha , Teste de Tolerância a Glucose , Glicerol/sangue , Glicerol/metabolismo , Humanos , Gordura Intra-Abdominal/metabolismo , Imageamento por Ressonância Magnética , Masculino , Metabolômica , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Medição de RiscoRESUMO
Insulin detemir (DET) represents a myristic acid (MA)-coupled insulin derivative with protracted action due to reversible albumin binding. As compared to human insulin (HI), DET provokes no or only minor body weight gain in vivo. Therefore, we compared DET's and HI's adipogenic effects. 3T3-L1 preadipocytes were differentiated with 5 nmol/l HI, 5 nmol/l DET (=DET(equimolar)), or 20 nmol/l DET (=DET(equipotent); equipotent in terms of the reported metabolic potency in vitro). Due to differentiation-suppressive effects, albumin was excluded from the studies. During the induction period, only HI allowed clonal expansion. Moreover, HI induced a 200-fold increase in specific glycerol-3-phosphate dehydrogenase activity, whereas DET(equimolar) and DET(equipotent) were markedly less adipogenic (P=0.0033). MA did not reveal adipogenic properties, and MA pretreatment did not affect HI- or DET(equipotent)-induced adipogenesis. These results were closely reflected at the level of marker gene expression (PPARgamma2, leptin) and morphology (Oil Red O-stained intracellular lipids). We conclude that DET displays reduced adipogenity, and this could contribute to DET's weight-sparing effect in vivo.
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Adipogenia/efeitos dos fármacos , Insulina/análogos & derivados , Insulina/farmacologia , Células 3T3-L1 , Adipócitos/citologia , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Animais , Diferenciação Celular/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Humanos , Insulina Detemir , Insulina de Ação Prolongada , Leptina/genética , Camundongos , PPAR gama/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Receptor tyrosine kinase regulation of phospholipase C-epsilon (PLC-epsilon), which is under the control of Ras-like and Rho GTPases, was studied with HEK-293 cells endogenously expressing PLC-coupled epidermal growth factor (EGF) receptors. PLC and Ca(2+) signaling by the EGF receptor, which activated both PLC-gamma1 and PLC-epsilon, was specifically suppressed by inactivation of Ras-related GTPases with clostridial toxins and expression of dominant-negative Rap2B. EGF induced rapid and sustained GTP loading of Rap2B, binding of Rap2B to PLC-epsilon, and Rap2B-dependent translocation of PLC-epsilon to the plasma membrane. GTP loading of Rap2B by EGF was inhibited by chelation of intracellular Ca(2+) and expression of lipase-inactive PLC-gamma1 but not of PLC-epsilon. Expression of RasGRP3, a Ca(2+)/diacylglycerol-regulated guanine nucleotide exchange factor for Ras-like GTPases, but not expression of various other exchange factors enhanced GTP loading of Rap2B and PLC/Ca(2+) signaling by the EGF receptor. EGF induced tyrosine phosphorylation of RasGRP3, but not RasGRP1, apparently caused by c-Src; inhibition of c-Src interfered with EGF-induced Rap2B activation and PLC stimulation. Collectively, these data suggest that the EGF receptor triggers activation of Rap2B via PLC-gamma1 activation and tyrosine phosphorylation of RasGRP3 by c-Src, finally resulting in stimulation of PLC-epsilon.
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Receptores ErbB/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Fosfolipases Tipo C/metabolismo , Proteínas rap de Ligação ao GTP/metabolismo , Proteína Tirosina Quinase CSK , Humanos , Fosfoinositídeo Fosfolipase C , Fosforilação , Proteínas Tirosina Quinases/metabolismo , Fatores de Tempo , Fatores ras de Troca de Nucleotídeo Guanina , Quinases da Família srcRESUMO
OBJECTIVE: Dipeptidyl-peptidase 4 (DPP-4) cleaves and inactivates the insulinotropic hormones glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide, collectively termed incretins. DPP-4 inhibitors entered clinical practice as approved therapeutics for type-2 diabetes in 2006. However, inter-individual variance in the responsiveness to DPP-4 inhibitors was reported. Thus, we asked whether genetic variation in the DPP4 gene affects incretin levels, insulin secretion, and glucose tolerance in participants of the TÜbingen Family study for type-2 diabetes (TÜF). RESEARCH DESIGN AND METHODS: Fourteen common (minor allele frequencies ≥0.05) DPP4 tagging single nucleotide polymorphisms (SNPs) were genotyped in 1,976 non-diabetic TÜF participants characterized by oral glucose tolerance tests and bioimpedance measurements. In a subgroup of 168 subjects, plasma incretin levels were determined. RESULTS: We identified a variant, i.e., SNP rs6741949, in intron 2 of the DPP4 gene that, after correction for multiple comparisons and appropriate adjustment, revealed a significant genotype-body fat interaction effect on glucose-stimulated plasma GLP-1 levels (p = 0.0021). Notably, no genotype-BMI interaction effects were detected (p = 0.8). After stratification for body fat content, the SNP negatively affected glucose-stimulated GLP-1 levels (p = 0.0229), insulin secretion (p = 0.0061), and glucose tolerance (p = 0.0208) in subjects with high body fat content only. CONCLUSIONS: A common variant, i.e., SNP rs6741949, in the DPP4 gene interacts with body adiposity and negatively affects glucose-stimulated GLP-1 levels, insulin secretion, and glucose tolerance. Whether this SNP underlies the reported inter-individual variance in responsiveness to DPP-4 inhibitors, at least in subjects with high body fat content, remains to be shown.
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Adiposidade/genética , Dipeptidil Peptidase 4/genética , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Insulina/metabolismo , Polimorfismo de Nucleotídeo Único/genética , Adulto , Glicemia/metabolismo , Cromossomos Humanos Par 2/genética , Jejum/sangue , Feminino , Estudos de Associação Genética , Loci Gênicos , Teste de Tolerância a Glucose , Humanos , Secreção de Insulina , Masculino , Pessoa de Meia-IdadeRESUMO
AIM: Inhibition of sodium/glucose cotransporter 2 (SGLT2), the key transport protein in renal glucose reabsorption, promotes glucose excretion and represents a new concept in the therapy of type-2 diabetes. In addition, SGLT2 inhibition elevates circulating glucagon concentrations and enhances hepatic glucose production. Since SGLT2 is expressed in human pancreatic α-cells and regulates glucagon release, we tested whether common variants of the SGLT2 gene SLC5A2 associate with altered plasma glucagon concentrations in the fasting state and upon glucose challenge. METHODS: A study population of 375 healthy subjects at increased risk for type-2 diabetes, phenotyped by a 5-point oral glucose tolerance test (OGTT) and genotyped for recently described SLC5A2 tagging single nucleotide polymorphisms (SNPs), was selected for plasma glucagon measurements. RESULTS: After adjustment for gender, age, body mass index, and insulin sensitivity, the four tagging SNPs (rs9924771, rs3116150, rs3813008, rs9934336), tested separately or as genetic score, were neither significantly nor nominally associated with plasma glucagon concentrations at any time during the OGTT, with the inverse AUC of glucagon or the glucagon fold-change during the OGTT (p ≥ 0.2, all). Testing for genotype-related differences in the time course of the glucagon response using MANOVA did also not reveal any significant or nominal associations (p ≥ 0.5, all). CONCLUSION: We could not obtain statistically significant evidence for a role of common SLC5A2 variants in the regulation of glucagon release in the fasting state or upon glucose challenge. Moreover, the reported nominal effects of individual SLC5A2 variants on fasting and post-challenge glucose levels may probably not be mediated by altered glucagon release.
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Jejum , Glucagon/sangue , Glucose/administração & dosagem , Transportador 2 de Glucose-Sódio/genética , Adulto , Glicemia/análise , Feminino , Teste de Tolerância a Glucose , Humanos , Insulina/sangue , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Fatores de RiscoRESUMO
OBJECTIVE: Genome-wide association studies (GWAS) have identified single-nucleotide polymorphisms (SNPs) associated with estimates of body fat distribution. Using predefined risk allele scores, the correlation of these scores with precisely quantified body fat distribution assessed by magnetic resonance (MR) imaging techniques and with metabolic traits was investigated. METHODS: Data from 4,944 MR scans from 915 subjects of European ancestry were analyzed. Body fat distribution was determined by MR imaging and liver fat content by 1 H-MR spectroscopy. All subjects underwent a five-point 75-g oral glucose tolerance test. A total of 65 SNPs with reported genome-wide significant associations regarding estimates of body fat distribution were genotyped. Four genetic risk scores were created by summation of risk alleles. RESULTS: A higher allelic load of waist-to-hip ratio SNPs was associated with lower insulin sensitivity, higher postchallenge glucose levels, and more visceral and less subcutaneous fat mass. CONCLUSIONS: GWAS-derived polymorphisms estimating body fat distribution are associated with distinct patterns of body fat distribution exactly measured by MR. Only the risk score associated with the waist-to-hip ratio in GWAS showed an unhealthy pattern of metabolism and body fat distribution. This score might be useful for predicting diseases associated with genetically determined, unhealthy obesity.
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Distribuição da Gordura Corporal , Estudo de Associação Genômica Ampla , Polimorfismo de Nucleotídeo Único , Relação Cintura-Quadril , Alelos , Índice de Massa Corporal , Estudos de Coortes , Estudos Transversais , Feminino , Seguimentos , Técnicas de Genotipagem , Teste de Tolerância a Glucose , Humanos , Insulina/sangue , Resistência à Insulina/genética , Fígado/metabolismo , Fígado/ultraestrutura , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Masculino , Obesidade/genética , População Branca/genéticaRESUMO
Exercise as a key prevention strategy for diabetes and obesity is commonly accepted and recommended throughout the world. Unfortunately, not all individuals profit to the same extent, some exhibit exercise resistance. This phenomenon of non-response to exercise is found for several endpoints, including glucose tolerance and insulin sensitivity. Since these non-responders are of notable quantity, there is the need to understand the underlying mechanisms and to identify predictors of response. This displays the basis to develop personalized training intervention regimes. In this review, we summarize the current knowledge on response variability, with focus on human studies and improvement of glucose homeostasis as outcome.
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Diabetes Mellitus/terapia , Exercício Físico , Diabetes Mellitus/fisiopatologia , Homeostase , Humanos , Resistência à Insulina , Obesidade/prevenção & controle , Medicina de PrecisãoRESUMO
OBJECTIVE: Circulating long-chain free fatty acids (FFAs) are important metabolic signals that acutely enhance fatty acid oxidation, thermogenesis, energy expenditure, and insulin secretion. However, if chronically elevated, they provoke inflammation, insulin resistance, and ß-cell failure. Moreover, FFAs act via multiple signaling pathways as very potent regulators of gene expression. In human skeletal muscle cells differentiated in vitro (myotubes), we have shown in previous studies that the expression of CSF3, the gene encoding granulocyte colony-stimulating factor (G-CSF), is markedly induced upon FFA treatment and exercise. METHODS AND RESULTS: We now report that CSF3 is induced in human myotubes by saturated, but not unsaturated, FFAs via Toll-like receptor 4-dependent and -independent pathways including activation of Rel-A, AP-1, C/EBPα, Src, and stress kinases. Furthermore, we show that human adipocytes and myotubes treated with G-CSF become insulin-resistant. In line with this, a functional polymorphism in the CSF3 gene affects adipose tissue- and whole-body insulin sensitivity and glucose tolerance in human subjects with elevated plasma FFA concentrations. CONCLUSION: G-CSF emerges as a new player in FFA-induced insulin resistance and thus may be of interest as a target for prevention and treatment of type 2 diabetes.
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Circadian rhythms govern vital functions. Their disruption provokes metabolic imbalance favouring obesity and type-2 diabetes. The aim of the study was to assess the role of clock genes in human prediabetes. To this end, genotype-phenotype associations of 121 common single nucleotide polymorphisms (SNPs) tagging ARNTL, ARNTL2, CLOCK, CRY1, CRY2, PER1, PER2, PER3, and TIMELESS were assessed in a study population of 1,715 non-diabetic individuals metabolically phenotyped by 5-point oral glucose tolerance tests. In subgroups, hyperinsulinaemic-euglycaemic clamps, intravenous glucose tolerance tests, and magnetic resonance imaging/spectroscopy were performed. None of the tested SNPs was associated with body fat content, insulin sensitivity, or insulin secretion. Four CRY2 SNPs were associated with fasting glycaemia, as reported earlier. Importantly, carriers of these SNPs' minor alleles revealed elevated fasting glycaemia and, concomitantly, reduced liver fat content. In human liver tissue samples, CRY2 mRNA expression was directly associated with hepatic triglyceride content. Our data may point to CRY2 as a novel switch in hepatic fuel metabolism promoting triglyceride storage and, concomitantly, limiting glucose production. The anti-steatotic effects of the glucose-raising CRY2 alleles may explain why these alleles do not increase type-2 diabetes risk.
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Criptocromos/genética , Glucose/metabolismo , Metabolismo dos Lipídeos , Fígado/metabolismo , Polimorfismo de Nucleotídeo Único , Adulto , Diabetes Mellitus Tipo 2/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
A substantial number of people at risk of developing type 2 diabetes could not improve insulin sensitivity by physical training intervention. We studied the mechanisms of this impaired exercise response in 20 middle-aged individuals at high risk of developing type 2 diabetes who performed 8 weeks of controlled cycling and walking training at 80% individual Vo2 peak. Participants identified as nonresponders in insulin sensitivity (based on the Matsuda index) did not differ in preintervention parameters compared with high responders. The failure to increase insulin sensitivity after training correlates with impaired upregulation of mitochondrial fuel oxidation genes in skeletal muscle, and with the suppression of the upstream regulators PGC1α and AMPKα2. The muscle transcriptomes of the nonresponders are further characterized by the activation of transforming growth factor (TGF)-ß and TGF-ß target genes, which is associated with increases in inflammatory and macrophage markers. TGF-ß1 as inhibitor of mitochondrial regulators and insulin signaling is validated in human skeletal muscle cells. Activated TGF-ß1 signaling downregulates the abundance of PGC1α, AMPKα2, the mitochondrial transcription factor TFAM, and mitochondrial enzymes. Thus, the data suggest that increased TGF-ß activity in skeletal muscle can attenuate the improvement of mitochondrial fuel oxidation after training and contribute to the failure to increase insulin sensitivity.
Assuntos
Mitocôndrias/metabolismo , Músculo Esquelético/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Adulto , Diabetes Mellitus Tipo 2/metabolismo , Exercício Físico/fisiologia , Feminino , Humanos , Resistência à Insulina/fisiologia , Masculino , Pessoa de Meia-Idade , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Fator de Crescimento Transformador beta/sangueRESUMO
OBJECTIVE: Serum concentrations of the hepatokine fibroblast growth factor (FGF) 21 are elevated in obesity, type-2 diabetes, and the metabolic syndrome. We asked whether FGF21 levels differ between subjects with metabolically healthy vs. unhealthy obesity (MHO vs. MUHO), opening the possibility that FGF21 is a cross-talker between liver and adipose tissue in MUHO. Furthermore, we studied the effects of chronic FGF21 treatment on adipocyte differentiation, lipid storage, and adipokine secretion. METHODS: In 20 morbidly obese donors of abdominal subcutaneous fat biopsies discordant for their whole-body insulin sensitivity (hereby classified as MHO or MUHO subjects), serum FGF21 was quantified. The impact of chronic FGF21 treatment on differentiation, lipid accumulation, and adipokine release was assessed in isolated preadipocytes differentiated in vitro. RESULTS: Serum FGF21 concentrations were more than two-fold higher in MUHO as compared to MHO subjects (457 ± 378 vs. 211 ± 123 pg/mL; p < 0.05). FGF21 treatment of human preadipocytes for the entire differentiation period was modestly lipogenic (+15%; p < 0.05), reduced the expression of key adipogenic transcription factors (PPARG and CEBPA, -15% and -40%, respectively; p < 0.01 both), reduced adiponectin expression (-20%; p < 0.05), markedly reduced adiponectin release (-60%; p < 0.01), and substantially increased leptin (+60%; p < 0.01) and interleukin-6 (+50%; p < 0.001) release. CONCLUSIONS: The hepatokine FGF21 exerts weak lipogenic and anti-adipogenic actions and marked adiponectin-suppressive and leptin and interleukin-6 release-promoting effects in human differentiating preadipocytes. Together with the higher serum concentrations in MUHO subjects, our findings reveal FGF21 as a circulating factor promoting the development of metabolically unhealthy adipocytes.
RESUMO
AIMS/HYPOTHESIS: Recently, cardiotrophin-1, a member of the interleukin-6 family of cytokines was described to protect beta-cells from apoptosis, to improve glucose-stimulated insulin secretion and insulin resistance, and to prevent streptozotocin-induced diabetes in mice. Here, we studied whether common single nucleotide polymorphisms (SNPs) in the CTF1 locus, encoding cardiotrophin-1, influence insulin secretion and insulin sensitivity in humans. METHODS: We genotyped 1,771 German subjects for three CTF1 tagging SNPs (rs1046276, rs1458201, and rs8046707). The subjects were metabolically characterized by an oral glucose tolerance test. Subgroups underwent magnetic resonance (MR) imaging/spectroscopy and hyperinsulinaemic-euglycaemic clamps. RESULTS: After appropriate adjustment, the minor allele of CTF1 SNP rs8046707 was significantly associated with decreased in vivo measures of insulin sensitivity. The other tested SNPs were not associated with OGTT-derived sensitivity parameters, nor did the three tested SNPs show any association with OGTT-derived parameters of insulin release. In the MR subgroup, SNP rs8046707 was nominally associated with lower visceral adipose tissue. Furthermore, the SNP rs1458201 showed a nominal association with increased VLDL levels. CONCLUSIONS: In conclusion, this study, even though preliminary and awaiting further confirmation by independent replication, provides first evidence that common genetic variation in CTF1 could contribute to insulin sensitivity in humans. Our SNP data indicate an insulin-desensitizing effect of cardiotrophin-1 and underline that cardiotrophin-1 represents an interesting target to influence insulin sensitivity.
Assuntos
Citocinas/genética , Predisposição Genética para Doença , Variação Genética , Resistência à Insulina/genética , Adiposidade/genética , Adulto , Cromossomos Humanos Par 16 , Feminino , Estudos de Associação Genética , Loci Gênicos , Genótipo , Alemanha , Humanos , Insulina/metabolismo , Secreção de Insulina , Desequilíbrio de Ligação , Metabolismo dos Lipídeos/genética , Masculino , Pessoa de Meia-Idade , Fenótipo , Polimorfismo de Nucleotídeo Único , Fatores de Risco , População BrancaRESUMO
BACKGROUND AND AIMS: Among obese subjects, metabolically healthy and unhealthy obesity (MHO/MUHO) can be differentiated: the latter is characterized by whole-body insulin resistance, hepatic steatosis, and subclinical inflammation. Aim of this study was, to identify adipocyte-specific metabolic signatures and functional biomarkers for MHO versus MUHO. METHODS: 10 insulin-resistant (IR) vs. 10 insulin-sensitive (IS) non-diabetic morbidly obese (BMI >40 kg/m2) Caucasians were matched for gender, age, BMI, and percentage of body fat. From subcutaneous fat biopsies, primary preadipocytes were isolated and differentiated to adipocytes in vitro. About 280 metabolites were investigated by a targeted metabolomic approach intracellularly, extracellularly, and in plasma. RESULTS/INTERPRETATION: Among others, aspartate was reduced intracellularly to one third (pâ=â0.0039) in IR adipocytes, pointing to a relative depletion of citric acid cycle metabolites or reduced aspartate uptake in MUHO. Other amino acids, already known to correlate with diabetes and/or obesity, were identified to differ between MUHO's and MHO's adipocytes, namely glutamine, histidine, and spermidine. Most species of phosphatidylcholines (PCs) were lower in MUHO's extracellular milieu, though simultaneously elevated intracellularly, e.g., PC aa C32â¶3, pointing to increased PC synthesis and/or reduced PC release. Furthermore, altered arachidonic acid (AA) metabolism was found: 15(S)-HETE (15-hydroxy-eicosatetraenoic acid; 0 vs. 120pM; pâ=â0.0014), AA (1.5-fold; pâ=â0.0055) and docosahexaenoic acid (DHA, C22â¶6; 2-fold; pâ=â0.0033) were higher in MUHO. This emphasizes a direct contribution of adipocytes to local adipose tissue inflammation. Elevated DHA, as an inhibitor of prostaglandin synthesis, might be a hint for counter-regulatory mechanisms in MUHO. CONCLUSION/INTERPRETATION: We identified adipocyte-inherent metabolic alterations discriminating between MHO and MUHO.