RESUMO
Obesity, the major cause of the current global epidemic of type 2 diabetes (T2D), induces insulin resistance in peripheral insulin target tissues. Several mechanisms have been identified related to cross-talk between adipose tissue, skeletal muscle and liver. These mechanisms involve both increased free fatty acid release and altered secretion of adipokines from adipose tissue. A major determinant of metabolic health is the ability of subcutaneous adipose tissue (SAT) to store excess fat rather than allowing it to accumulate in ectopic depots including liver (i.e. in nonalcoholic fatty liver disease), muscle and heart, or in epicardial/pericardial and visceral fat depots which promote the metabolic complications of obesity. The ability to recruit and differentiate precursor cells into adipose cells (adipogenesis) in SAT is under genetic regulation and is reduced in high-risk individuals who have first-degree relatives with T2D. Early recruitment of new adipose cells is dependent on the cross-talk between canonical WNT and BMP4 signalling; WNT enhances their undifferentiated and proliferative state whereas BMP4 induces their commitment to the adipogenic lineage. Dysregulation of these signalling pathways is associated with impaired adipogenesis and impaired ability to respond to the need to store excess lipids in SAT. This leads to hypertrophic, dysfunctional and insulin-resistant adipose cells with a reduced content of GLUT4, the major insulin-regulated glucose transporter, which in turn reduces adipose tissue glucose uptake and de novo lipogenesis. We recently identified that reduced GLUT4 and lipogenesis in adipocytes impairs the synthesis of a novel family of lipids secreted by adipose tissue (and potentially other tissues), branched fatty acid esters of hydroxy fatty acids (FAHFAs). FAHFAs have beneficial metabolic effects, including enhancing insulin-stimulated glucose transport and glucose-stimulated GLP1 and insulin secretion, as well as powerful anti-inflammatory effects. FAHFA levels are reduced in subcutaneous adipose tissue in insulin-resistant individuals, and this novel family of lipids may become of future therapeutic use.
Assuntos
Adipogenia/fisiologia , Diabetes Mellitus Tipo 2/metabolismo , Resistência à Insulina/fisiologia , Lipogênese/fisiologia , Gordura Subcutânea/metabolismo , Adipócitos/citologia , Adipócitos/metabolismo , Índice de Massa Corporal , Diferenciação Celular , Proliferação de Células , Diabetes Mellitus Tipo 2/etnologia , Ésteres , Ácidos Graxos/metabolismo , Humanos , Metabolismo dos Lipídeos , Obesidade/metabolismoRESUMO
BACKGROUND: It has been suggested that osteoblasts are involved in the regulation of haematopoietic stem cells. Whether osteocalcin, which is derived from osteoblasts and is metabolically active, influences blood haemoglobin (Hb) levels is not known. OBJECTIVE: To determine whether plasma osteocalcin is a determinant of Hb in elderly men. METHODS: A total of 993 men (mean age 75.3 ± 3.2 years) participated in the population-based MrOS (osteoporotic fractures in men) study. Plasma osteocalcin concentration was evaluated in relation to Hb and adjustments were made for potential confounders (i.e. age, body mass index, erythropoietin, total oestradiol, fasting insulin, adiponectin, ferritin and cystatin C). RESULTS: Hb correlated (age adjusted) negatively with osteocalcin in the total study group (r = -0.12, P < 0.001) as well as in the subgroup of nondiabetic men (r = -0.16, P < 0.001). In nondiabetic men with higher osteocalcin levels, it was more likely that Hb would be in the lowest quartile (odds ratio per SD decrease in osteocalcin 1.32, 95% confidence interval 1.13-1.53). Quartiles of Hb were negatively associated (age adjusted) with osteocalcin (P < 0.001). Anaemic men (47/812) (Hb <130 g L(-1) ) had significantly higher mean osteocalcin levels than nonanaemic men (33.9 vs. 27.1 µg L(-1) , P < 0.001). In multiple stepwise linear regression analyses (adjusted for age, body mass index, total oestradiol, adiponectin, erythropoietin, fasting insulin, cystatin C, leptin, ferritin and holotranscobalamin), osteocalcin was an independent predictor of Hb concentration in nondiabetic men (P < 0.05). CONCLUSIONS: These data add further support to the evidence indicating that the bone-specific protein osteocalcin has several endocrine functions targeting the pancreas, testes, adipocytes, brain. An additional novel finding is that osteocalcin may also have a paracrine function as a regulator of haematopoiesis.
Assuntos
Hematopoese/fisiologia , Hemoglobinas/metabolismo , Osteocalcina/sangue , Fatores Etários , Idoso , Anemia/sangue , Humanos , Contagem de Leucócitos , Masculino , Síndrome Metabólica/sangue , Contagem de Plaquetas , Estudos Prospectivos , Análise de RegressãoRESUMO
OBJECTIVES: The aim of this study was to characterize diabetes risk in relation to amount and distribution of body fat (environmental factors) and genetic risk defined as having first-degree (FH1) or second-degree relatives with diabetes. DESIGN: We analysed the METSIM population of 10 197 middle-aged, randomly selected men. At baseline, information about family history of diabetes was registered and all individuals underwent extensive phenotyping. A follow-up study was conducted after 6 years. The metabolic consequences of increased visceral versus subcutaneous fat were characterized in a separate cohort of 158 healthy men (the Kuopio Cohort of the EUGENE2 study). RESULTS: At baseline, individuals with a family history of diabetes (FH+) had approximately a twofold increase in the prevalence of type 2 diabetes compared with individuals without a family history of the disease (FH-) (18.0% vs. 9.9%; P = 1.3 × 10(-31) ). FH1 individuals were more commonly overweight and obese compared with FH- (69.2% vs. 64.8%; P = 1.3 × 10(-4) ) and, for a given body mass index, showed an increased risk profile for both type 2 diabetes and cardiovascular disease as well as a greater susceptibility to the negative consequences of increased body fat also when nonobese. Subgroup analyses indicated that the metabolic consequences were due primarily to increased ectopic/visceral fat rather than subcutaneous fat. The increased risk profile in FH+ individuals was not altered by adjusting for 43 major diabetes risk genes. CONCLUSIONS: Family history of type 2 diabetes (particularly FH1) is associated with both increased risk of becoming overweight/obese and with a greater susceptibility to the negative consequences of increasing body fat, probably as a consequence of an increased propensity to accumulate ectopic (nonsubcutaneous) fat.
Assuntos
Diabetes Mellitus Tipo 2/etiologia , Transtornos do Metabolismo dos Lipídeos/etiologia , Sobrepeso/etiologia , Distribuição da Gordura Corporal , Estudos Transversais , Diabetes Mellitus Tipo 2/patologia , Humanos , Insulina/metabolismo , Resistência à Insulina/fisiologia , Secreção de Insulina , Gordura Intra-Abdominal/patologia , Transtornos do Metabolismo dos Lipídeos/patologia , Masculino , Pessoa de Meia-Idade , Obesidade/etiologia , Obesidade/patologia , Sobrepeso/patologia , Linhagem , Fatores de Risco , Gordura Subcutânea/patologia , Circunferência da CinturaRESUMO
OBJECTIVES: Blood haemoglobin (Hb) concentration declines in elderly men, whilst the level of the adipocyte-derived protein adiponectin increases with age. The association between erythropoiesis and adiponectin in elderly men is unclear. The aim of this study was to determine whether adipokines such as adiponectin and leptin are associated with anaemia and Hb concentration in elderly community-dwelling men. DESIGN AND SETTING: The Gothenburg part of the population-based Swedish Osteoporotic Fractures in Men (MrOS) cohort (n = 1010; median age 75.3 years, range 69-81). MAIN OUTCOME MEASURES: We investigated the associations between levels of adiponectin and Hb before and after adjusting for potential confounders [i.e. age, body composition, erythropoietin (EPO), total oestradiol, leptin, cystatin C and iron and B vitamin status]. RESULTS: In these elderly men, age was negatively associated with Hb (r = -0.12, P < 0.001) and positively associated with adiponectin level (r = 0.13, P < 0.001). In age-adjusted partial correlations, Hb and adiponectin levels were negatively correlated (r = -0.20, P < 0.001); this association remained significant after multivariable adjustment for age, body composition, EPO, fasting insulin, sex hormones, leptin and ferritin. Age-adjusted mean adiponectin concentrations were significantly higher in anaemic men (66/1005; Hb <130 g L(-1) ) compared to nonanaemic men (14.0 vs. 11.7 µg mL(-1) , P < 0.05). In multivariate analysis, adiponectin together with EPO, total oestradiol, insulin, albumin, transferrin saturation, HDL cholesterol, cystatin C, total body fat mass and free thyroxine, but not leptin, explained 35% of the variation in Hb level. These results remained essentially unchanged after exclusion of men with diabetes. CONCLUSIONS: Serum adiponectin, but not leptin, was negatively and independently associated with Hb. This finding suggests a possible role of adiponectin in the age-related decline in Hb level observed in apparently healthy elderly men.
Assuntos
Adiponectina/sangue , Envelhecimento/sangue , Hemoglobinas/metabolismo , Idoso , Idoso de 80 Anos ou mais , Anemia/sangue , Composição Corporal , Eritropoetina/sangue , Estradiol/sangue , Ferritinas/sangue , Hormônios Esteroides Gonadais/sangue , Humanos , Insulina/sangue , Leptina/sangue , Masculino , Análise Multivariada , Tiamina/sangueRESUMO
Today, European biomedical and health-related research is insufficiently well funded and is fragmented, with no common vision, less-than-optimal sharing of resources, and inadequate support and training in clinical research. Improvements to the competitiveness of European biomedical research will depend on the creation of new infrastructures that must be dynamic and free of bureaucracy, involve all stakeholders and facilitate faster delivery of new discoveries from bench to bedside. Taking diabetes research as the model, a new paradigm for European biomedical research is presented, which offers improved co-ordination and common resources that will benefit both academic and industrial clinical research. This includes the creation of a European Council for Health Research, first proposed by the Alliance for Biomedical Research in Europe, which will bring together and consult with all health stakeholders to develop strategic and multidisciplinary research programmes addressing the full innovation cycle. A European Platform for Clinical Research in Diabetes is proposed by the Alliance for European Diabetes Research (EURADIA) in response to the special challenges and opportunities presented by research across the European region, with the need for common standards and shared expertise and data.
Assuntos
Pesquisa Biomédica , Europa (Continente)RESUMO
AIMS/HYPOTHESIS: Pharmacological augmentation of glucagon-like peptide 1 receptor signalling by dipeptidyl peptidase 4 (DPP-4) inhibition reduced intestinal lipoprotein secretion in experimental studies, suggesting that DPP-4 inhibitors may ameliorate dyslipidaemia and thus reduce cardiovascular risk in patients with type 2 diabetes. We assessed the effects of alogliptin (Alo) and Alo co-administered with pioglitazone (Pio) vs placebo (Pbo) on triacylglycerol (TG)-rich lipoproteins in type 2 diabetes before and following a high-fat meal. METHODS: Seventy-one patients (age 18-70 years), who did not reach HbA(1c) 6.5% (48 mmol/mol) with lifestyle and/or metformin, sulfonylurea or glinide therapy, participated in this 16 week, double-centre (university hospitals) Pbo-controlled parallel-group study. All participants, people doing measurements or examinations, and people assessing the outcomes were blinded to group assignment. Fasting TG 1.7-5.0 mmol/l was among the entry criteria. Patients received a high-fat mixed meal before and 4 and 16 weeks after randomisation (allocation by central office) to Alo (n = 25), Alo/Pio (n = 22) or Pbo (n = 24). Blood was sampled at pre-specified intervals, starting at 15 min before and ending 8 h after meal ingestion. RESULTS: At week 16, Alo (n = 25) and Alo/Pio (n = 21) vs Pbo (n = 24) produced similar significant reductions in total postprandial TG response (incremental AUC [iAUC]; p < 0.001), as well as in chylomicron TG (p < 0.001) and VLDL1 TG iAUCs (p < 0.001 and p = 0.012, respectively). Postprandial chylomicron apolipoprotein B-48 iAUC showed a significant decrease after Alo treatment (p = 0.028), and a non-significant trend towards a decrease with Alo/Pio (p = 0.213). The incidence of adverse events was low and consistent with previous studies. CONCLUSIONS/INTERPRETATION: Treatment with Alo and Alo/Pio produced significant reductions in postprandial TG and TG-rich lipoproteins, contributing to an improved overall cardiometabolic risk profile in type 2 diabetes. The data support the concept that incretins not only modulate glucose metabolism but also influence chylomicron metabolism in intestinal cells. TRIAL REGISTRATION: ClinicalTrials.gov number NCT00655863.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Inibidores da Dipeptidil Peptidase IV/uso terapêutico , Hipoglicemiantes/uso terapêutico , Lipídeos/sangue , Piperidinas/uso terapêutico , Período Pós-Prandial/efeitos dos fármacos , Tiazolidinedionas/uso terapêutico , Uracila/análogos & derivados , Adulto , Idoso , Glicemia , Diabetes Mellitus Tipo 2/sangue , Inibidores da Dipeptidil Peptidase IV/farmacologia , Método Duplo-Cego , Feminino , Humanos , Hipoglicemiantes/farmacologia , Insulina/sangue , Masculino , Pessoa de Meia-Idade , Pioglitazona , Piperidinas/farmacologia , Tiazolidinedionas/farmacologia , Resultado do Tratamento , Uracila/farmacologia , Uracila/uso terapêuticoRESUMO
AIMS/HYPOTHESIS: This study investigates the role of serine/threonine protein kinase 25 (STK25), a member of the sterile 20 (STE20) superfamily of kinases, in the regulation of skeletal muscle metabolism. METHODS: The effect of depleting STK25 in muscle cells was studied by reducing the mRNA and protein content of this target in the rat myoblast cell line L6 by small interfering (si)RNA. The changes in the mRNA and protein levels of several members of the fatty acid oxidative and glucose metabolic pathways were measured by quantitative real-time (qRT)-PCR and western blot. The rate of palmitate oxidation and glucose uptake was measured after transfection with siRNA for Stk25. Expression of STK25 was also evaluated in skeletal muscle biopsies from 41 white Europid men and women with normal and impaired glucose tolerance and type 2 diabetes using qRT-PCR. RESULTS: We demonstrate that partial depletion of STK25 increases the expression of uncoupling protein 3 (Ucp3), accompanied by increased lipid oxidation, in myoblasts. In addition, a reduced level of STK25 enhances the expression of Slc2a1 (also known as Glut1), Slc2a4 (also known as Glut4) and hexokinase 2, and correspondingly, improves insulin-stimulated glucose uptake in muscle cells. Consistent with these results, significantly higher STK25 levels were observed in the skeletal muscle of type 2 diabetic patients, compared with individuals with normal glucose tolerance. CONCLUSIONS/INTERPRETATION: This is the first study indicating a possible role for STK25 in the regulation of glucose and lipid metabolism in L6 myoblasts. This kinase appears to be an interesting new mediator to be evaluated for therapeutic intervention in type 2 diabetes and related complications, as controlled increase in lipid oxidation and insulin-stimulated glucose uptake in skeletal muscle is favourable and can restore energy balance in metabolically compromised states.
Assuntos
Glucose/metabolismo , Músculo Esquelético/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Western Blotting , Linhagem Celular , Feminino , Humanos , Imuno-Histoquímica , Técnicas In Vitro , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Metabolismo dos Lipídeos/genética , Masculino , Ácido Palmítico/metabolismo , Proteínas Serina-Treonina Quinases/genética , RNA Interferente Pequeno , Ratos , Reação em Cadeia da Polimerase em Tempo RealRESUMO
AIMS/HYPOTHESIS: Type 2 diabetes and obesity are associated with increased risk of site-specific cancers. We have investigated whether metabolic alterations at the level of adipose-derived differentiating cells may affect specific phenotypes of breast cancer cells. METHODS: Growth profiles of breast cancer cell lines were evaluated in co-cultures with differentiated adipocytes or their precursor cells and upon treatment with adipocyte conditioned media. Production and release of cytokines and growth factors were assessed by real-time RT-PCR and multiplex-based ELISA assays. RESULTS: Co-cultures with either differentiated mouse 3T3-L1 or human mammary adipocytes increased viability of MCF-7 cells to a greater extent, when compared with their undifferentiated precursors. Adipocytes cultured in 25 mmol/l glucose were twofold more effective in promoting cell growth, compared with those grown in 5.5 mmol/l glucose, and activated mitogenic pathways in MCF-7 cells. Growth-promoting action was also enhanced when adipocytes were incubated in the presence of palmitate or oleate. Interestingly, 3T3-L1 and human adipocytes released higher amounts of keratinocyte-derived chemokine/IL-8, the protein 'regulated upon activation, normally T expressed, and secreted' (RANTES), and IGF-1, compared with their precursor cells. Their levels were reduced upon incubation with low glucose and enhanced by fatty acids. Moreover, both undifferentiated cells and differentiated adipocytes from obese individuals displayed about twofold higher IGF-1 release and MCF-7 cell growth induction than lean individuals. Finally, inhibition of the IGF-1 pathway almost completely prevented the growth-promoting effect of adipocytes on breast cancer cells. CONCLUSIONS/INTERPRETATION: IGF-1 release by adipocytes is regulated by glucose and fatty acids and may contribute to the control of cancer cell growth in obese individuals.
Assuntos
Adipócitos/metabolismo , Neoplasias da Mama/patologia , Proliferação de Células/efeitos dos fármacos , Glucose/farmacologia , Fator de Crescimento Insulin-Like I/metabolismo , Ácido Oleico/farmacologia , Palmitatos/farmacologia , Adenocarcinoma/patologia , Adipócitos/efeitos dos fármacos , Adipócitos/patologia , Adulto , Idoso , Comunicação Celular/fisiologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Quimiocina CCL5/metabolismo , Técnicas de Cocultura , Feminino , Humanos , Interleucina-8/metabolismo , Células MCF-7 , Pessoa de Meia-Idade , Obesidade/metabolismo , Obesidade/patologia , Transdução de Sinais/fisiologiaRESUMO
AIMS/HYPOTHESIS: The aim of this study was to investigate the association of the rs10811661 polymorphism near the CDKN2B/CDKN2A genes with glucose tolerance, insulin sensitivity and insulin release in three samples of white people with European ancestry. METHODS: Sample 1 comprised 845 non-diabetic offspring of type 2 diabetes patients recruited in five European centres participating in the EUGENE2 study. Samples 2 and 3 comprised, respectively, 864 and 524 Italian non-diabetic participants. All individuals underwent an OGTT. Screening for the rs10811661 polymorphism was performed using a TaqMan allelic discrimination assay. RESULTS: The rs10811661 polymorphism did not show a significant association with age, BMI and insulin sensitivity. Participants carrying the TT genotype showed a significant reduction in insulin release, measured by an OGTT-derived index, compared with carriers of the C allele, in the three samples. When these results were pooled with those of three published studies, and meta-analysed with a random-effects model, the T allele was significantly associated with reduced insulin secretion (-35.09 [95% CI 14.68-55.52], p = 0.0008 for CC+CT vs TT; and -29.45 [95% CI 9.51-49.38], p = 0.0038, for the additive model). In addition, in our three samples, participants carrying the TT genotype exhibited an increased risk for impaired glucose tolerance (IGT) compared with carriers of the C allele (OR 1.55 [95% CI 1.20-1.95] for the meta-analysis of the three samples). CONCLUSIONS/INTERPRETATION: Our data, together with the meta-analysis of previously published studies, show that the rs10811661 polymorphism is associated with impaired insulin release and IGT, suggesting that this variant may contribute to type 2 diabetes by affecting beta cell function.
Assuntos
Inibidor de Quinase Dependente de Ciclina p15/genética , Inibidor p16 de Quinase Dependente de Ciclina/genética , Resistência à Insulina/genética , Insulina/metabolismo , Polimorfismo Genético/genética , Adulto , Diabetes Mellitus Tipo 2/genética , Feminino , Predisposição Genética para Doença/genética , Humanos , Secreção de Insulina , Masculino , Pessoa de Meia-Idade , Análise de Sequência de DNARESUMO
Preclinical studies suggest that incretin-based therapies may be beneficial for the bone; however, clinical data are largely lacking. We assessed whether the differential effects of these therapies on body weight differed with respect to their effect on bone mineral density (BMD) and markers of calcium homeostasis in patients with type 2 diabetes (T2D). Sixty-nine metformin-treated patients with T2D were randomized to exenatide twice daily (n = 36) or insulin glargine once daily (n = 33). Total body BMD, measured by dual-energy X-ray absorptiometry, and serum markers of calcium homeostasis were assessed before and after 44-week treatment. Exenatide or insulin glargine treatment decreased body weight by 6%. Endpoint BMD was similar in both groups after 44-week therapy (LSmean ± s.e.m. between-group difference -0.002 ± 0.007 g/cm(2) ; p = 0.782). Fasting serum alkaline phosphatase, calcium and phosphate remained unaffected. Forty-four-week treatment with exenatide or insulin glargine had no adverse effects on bone density in patients with T2D, despite differential effects on body weight.
Assuntos
Peso Corporal/efeitos dos fármacos , Densidade Óssea/efeitos dos fármacos , Diabetes Mellitus Tipo 2/tratamento farmacológico , Peptídeos/farmacologia , Peçonhas/farmacologia , Absorciometria de Fóton , Densidade Óssea/fisiologia , Diabetes Mellitus Tipo 2/diagnóstico por imagem , Diabetes Mellitus Tipo 2/fisiopatologia , Exenatida , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Peptídeos/administração & dosagem , Cintilografia , Ensaios Clínicos Controlados Aleatórios como Assunto , Peçonhas/administração & dosagemRESUMO
AIMS/HYPOTHESIS: The aim of the study was to address the role of protein kinase C-delta (PKCdelta) on phosphorylation of signal transducer and activator of transcription 3 (STAT3) and activation of inflammatory genes in response to IL-6 in adipose cells. METHODS: Differentiated mouse 3T3-L1 adipocytes preincubated with the PKCdelta inhibitor rottlerin and mouse embryonic fibroblasts (MEFs) lacking PKCdelta were incubated with IL-6 and/or insulin. RNA was extracted and the gene expression was analysed by real-time PCR, while the proteins from total, nuclear and cytoplasmic lysates were analysed by immunoblotting. RESULTS: Inhibition of PKCdelta by rottlerin significantly reduced both Ser-727 and Tyr-705 phosphorylation of STAT3. Consequently, nuclear translocation of STAT3 and the IL-6-induced gene transcription and protein release of the inflammatory molecule serum amyloid A 3 (SAA3) were reduced. Similarly, the IL-6-regulated gene transcription of Il-6 (also known as Il6) to Hp and the feedback inhibitor of IL-6, Socs3, were also attenuated by rottlerin. Furthermore, PKCdelta was found to translocate to the nucleus following IL-6 treatment and this was also reduced by rottlerin. In agreement with the effect of rottlerin, Pkcdelta (also known as Prkcd) ( -/- ) MEFs also displayed a markedly reduced ability of IL-6 to activate the transcription of Saa3, Hp, Socs3 and Il6 genes compared with wild-type MEFs. These results correlated with a reduced nuclear translocation and phosphorylation of STAT3. CONCLUSIONS/INTERPRETATION: These results show that PKCdelta plays a key role in the inflammatory effect of IL-6 in adipose cells and may be a suitable target for novel anti-inflammatory agents.
Assuntos
Adipócitos/metabolismo , Inflamação/metabolismo , Interleucina-6/metabolismo , Proteína Quinase C-delta/metabolismo , Acetofenonas/farmacologia , Adipócitos/citologia , Adipócitos/efeitos dos fármacos , Animais , Benzopiranos/farmacologia , Western Blotting , Linhagem Celular , Células Cultivadas , Expressão Gênica/efeitos dos fármacos , Expressão Gênica/genética , Inflamação/genética , Interleucina-6/farmacologia , Camundongos , Fosforilação/efeitos dos fármacos , Fosforilação/genética , Proteína Quinase C-delta/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Transcrição STAT3/genética , Fator de Transcrição STAT3/metabolismo , Proteína Amiloide A Sérica/genética , Proteína Amiloide A Sérica/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Estatísticas não Paramétricas , Ativação Transcricional/efeitos dos fármacos , Ativação Transcricional/genéticaRESUMO
AIMS/HYPOTHESIS: Dickkopf-1 (DKK1) is a secreted inhibitor of canonical wingless-type MMTV integration site family (WNT) signalling; the key pathway for cell fate and development. Inhibition of WNT signalling by DKK1 in precursor cells promotes adipogenesis and inhibits osteogenesis. Previous studies have shown that treatment of type 2 diabetic patients with thiazolidinediones (TZDs) reduces bone density and increases risk of bone fractures, while body fat is increased. METHODS: We examined the effect of TZDs on secretion and DKK1 levels in pre-adipocytes and mature adipose cells and also measured circulating DKK1 levels in 11 patients with type 2 diabetes before and after treatment with the TZD rosiglitazone for 90 days. RESULTS: TZDs added in vitro rapidly increased DKK1 protein levels and secretion in both fully differentiated adipose cells and pre-adipocytes undergoing differentiation. In parallel, beta-catenin levels, a marker of canonical WNT signalling, were reduced. Serum levels of DKK1 were also increased in several of the patients with type 2 diabetes after treatment with rosiglitazone for 90 days. CONCLUSIONS/INTERPRETATION: These results provide a novel mechanism whereby peroxisome proliferator-activated receptor-gamma activation can terminate WNT signalling and promote adipogenesis. Furthermore, they provide an explanation for why TZD treatment can lead to reduced bone formation and increased risk of fractures, since inhibited WNT signalling in progenitor cells promotes adipogenesis while osteogenesis is reduced.
Assuntos
Adipócitos/metabolismo , Diabetes Mellitus Tipo 2/tratamento farmacológico , Regulação da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intercelular/biossíntese , Tiazolidinedionas/metabolismo , Células 3T3-L1 , Animais , Densidade Óssea , Diabetes Mellitus Tipo 2/metabolismo , Fraturas Ósseas , Humanos , Hipoglicemiantes/farmacologia , Camundongos , Osteogênese , PPAR gama/metabolismo , Rosiglitazona , Transdução de Sinais , Tiazolidinedionas/farmacologia , Proteínas Wnt/metabolismoRESUMO
AIM/HYPOTHESIS: The aim of the study was to examine the possible role of AMP-activated protein kinase (AMPK) in the regulation of the inflammatory response induced by cytokine action in human liver cells. METHODS: IL-6-stimulated expression of the genes for acute-phase response markers serum amyloid A (SAA1, SAA2) and haptoglobin (HP) in the human hepatocarcinoma cell line HepG2 were quantified after modulation of AMPK activity by pharmacological agonists (5-amino-4-imidazole-carboxamideriboside [AICAR], metformin) or by using small interfering (si) RNA transfection. The intracellular signalling pathway mediating the effect of AMPK on IL-6-stimulated acute-phase marker expression was characterised by assessing the phosphorylation levels of the candidate protein signal transducer and activator of transcription 3 (STAT3) in response to AMPK agonists. RESULTS: AICAR and metformin markedly blunt the IL-6-stimulated expression of SAA cluster genes as well as of haptoglobin in a dose-dependent manner. Moreover, the repression of AMPK activity by siRNA significantly reversed the inhibition of SAA expression by both AICAR and metformin, indicating that the effect of the agonists is dependent on AMPK. For the first time we show that AMPK appears to regulate IL-6 signalling by directly inhibiting the activation of the main downstream target of IL-6, STAT3. CONCLUSIONS/INTERPRETATION: We provide evidence for a key function of AMPK in suppression of the acute-phase response caused by the action of IL-6 in liver, suggesting that AMPK may act as an intracellular link between chronic low-grade inflammation and metabolic regulation in peripheral metabolic tissues.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Interleucina-6/farmacologia , Fator de Transcrição STAT3/metabolismo , Proteínas Quinases Ativadas por AMP/antagonistas & inibidores , Proteínas Quinases Ativadas por AMP/genética , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacologia , Western Blotting , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Células Cultivadas , Células Hep G2 , Humanos , Hipoglicemiantes/farmacologia , Fígado/enzimologia , Metformina/farmacologia , Fosforilação/efeitos dos fármacos , Interferência de RNA , RNA Interferente Pequeno , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Ribonucleotídeos/farmacologia , Transdução de Sinais/efeitos dos fármacosRESUMO
Pulsating mammalian myocardial cells were found to be highly susceptible in tissue culture to rapid destruction by streptolysin O. Cessation of beating occurred almost immediately, followed within minutes by multiple cell membrane bleb formation. Parallel with these changes, the cytoplasm became intensely granular and the nuclear membrane apparently thickened when viewed by phase microscopy. At the ultrastructural level, the cell membrane blebs were found to contain relatively small numbers of granular fragments. The endoplasmic reticulum of damaged heart cells was quite swollen, and its contents were considerably condensed. The myofibers were not strikingly altered, but cytoplasmic and mitochondria vacuoles were rather abundant. Cardiac endothelial, kidney epithelial, and fibroblast cells were also susceptible to lysis by this toxin, but the reactions occurred more slowly or bleb formation was less evident. An antiserotonin drug known to be protective against streptolysin-O in vivo (UML-491), did not protect against killing of cardiac cells at the tissue culture level. Serotonin could not be detected in the culture fluid after lysis of cardiac cells by streptolysin O.
Assuntos
Coração/efeitos dos fármacos , Miocárdio/citologia , Estreptolisinas/toxicidade , Animais , Técnicas de Cultura , Ergolinas/farmacologia , Rim/efeitos dos fármacos , Microscopia Eletrônica , Coelhos , Ratos , Serotonina/análise , Antagonistas da SerotoninaRESUMO
Mannose is a glucose-associated serum metabolite mainly released by the liver. Recent studies have shown several unexpected pleiotropic effects of mannose including increased regulatory T cells (Tregs), prevention of auto-immune disease and ability to reduce growth of human cancer cells. We have previously shown in large cohorts that elevated serum mannose levels are associated with future development of type 2 diabetes (T2D) and cardiovascular disease. However, potential direct effects of mannose on insulin sensitivity in vivo or in vitro are unknown. We here show that administration of mannose (0.1â¯g/kg BW twice daily) for one week in man did not elicit negative effects on meal-modified glucose tolerance, markers of inflammation or insulin levels. Tregs number and insulin signaling in human liver cells were unchanged. These data suggest that mannose is a marker, and not a mediator, of insulin resistance. To verify this, we examined serum mannose levels during long-term euglycemic hyperinsulinemic clamps in non-diabetic and T2D individuals. Mannose was reduced by insulin infusion in proportion to whole-body insulin sensitivity. Thus, mannose is a biomarker of insulin resistance which may be useful for the early identification of diabetic individuals with insulin resistance and increased risk of its complications.
Assuntos
Biomarcadores/sangue , Resistência à Insulina/fisiologia , Insulina/metabolismo , Manose/sangue , Idoso , Biomarcadores/metabolismo , Estudos de Casos e Controles , Feminino , Técnica Clamp de Glucose , Teste de Tolerância a Glucose , Humanos , Insulina/sangue , Masculino , Manose/metabolismo , Pessoa de Meia-Idade , Transdução de Sinais/fisiologiaRESUMO
Pulmonary endothelial cells are capable of metabolizing a variety of circulating hormonal substances. Indirect evidence indicates that some of the relevant enzymes are located on the plasma membrane. The associated caveolae are of special interest as globular subunits, possibly enzyme clusters, are evident in their membranes. In the present study, freeze-etch techniques were used to improve understanding of the fine structure of endothelial cells and to extend our investigations of possible sites of enzymes capable of metabolizing circulating vasoactive agents. As in other cells studied by freeze-etching, intramembranous particles are found on both inner aspects of the plasma membrane. In undifferentiated areas of plasma membrane, the particles appear to have a random distribution. These areas fracture such that approximately equal proportions of the particles adhere to the cytoplasmic aspect of the outer leaflet and the extracellular aspect of the inner leaflet. However, the particles organize into rosettes and plaques at the base of caveolae, and, after fracture, the rosettes and plaques adhere predominantly to the cytoplasmic aspect of the outer leaflet. The peculiar organization of particles in association with caveolae supports the concept that caveolae have a stomal skeletal structure and raises the possibility that the organization may be in some way related to pinocytosis.
Assuntos
Membrana Celular , Células Epiteliais , Epitélio , Pulmão/citologia , Animais , Endotélio/citologia , Técnica de Congelamento e Réplica , Técnicas Histológicas , Perfusão , RatosRESUMO
(8-L-[(14)C] phenylalanine) angiotensin I is metabolized in one passage through blood-free lungs. Approximately 20 percent of the radioactivity emerges as angiotensin 11, the remainder as lower homologs. Radioactivity is not retained by the lungs but has the same volume of distribution and mean transit time as blue dextran, a compound unlikely to leave the intravascular space. Plasma membrane fractions of lung are capable of converting angiotensin I to angiotensin II. These data, taken together, indicate the circulating angiotensin I is metabolized by enzymes of the luminal surface of pulmonary endothelial cells.
Assuntos
Angiotensina II/metabolismo , Pulmão/metabolismo , Angiotensina II/análise , Animais , Isótopos de Carbono , Membrana Celular/análise , Membrana Celular/enzimologia , Membrana Celular/metabolismo , Cromatografia , Corantes , Dextranos/metabolismo , Eletroforese , Técnicas In Vitro , Pulmão/análise , Pulmão/citologia , Pulmão/enzimologia , Microscopia Eletrônica , Nucleotidases/análise , Perfusão , Fenilalanina/metabolismo , RatosRESUMO
Replicas of fractured chromaffin cells are indicative of a range of activities thought to characterize exocytosis, including attachment of secretory vesicles to the plasma membrane, fusion, extrusion of contents, and membrane retrieval. Exocytosis sites are abundant on stimulated cells but are infrequent when calcium is omitted from the system.
Assuntos
Medula Suprarrenal/citologia , Células/metabolismo , Técnica de Congelamento e Réplica , Medula Suprarrenal/efeitos dos fármacos , Angiotensina II/farmacologia , Animais , Bradicinina/farmacologia , Cálcio , Catecolaminas/metabolismo , Membrana Celular , Cricetinae , Exocitose/efeitos dos fármacos , Espaço Extracelular , Microscopia Eletrônica , PerfusãoRESUMO
Scanning electron micrographs of the endothelium of the pulmonary artery reveal that the entire surface is covered by a meshwork of irregular projections which vastly increase the surface area. The size and density of the projections suggest that they may function to direct an eddying flow of plasma along the endothelial surface.