RESUMO
BACKGROUND: The effect of lixisenatide-a prandial once-daily glucagon-like peptide-1 receptor agonist-on glycaemic control in patients with inadequately controlled type 2 diabetes mellitus (T2DM), stratified by baseline ß-cell function, was assessed. METHODS: The 24-week GetGoal-M, -P and -S trials evaluated the efficacy and safety of lixisenatide in combination with oral antidiabetic agents. This post hoc analysis used data from patients receiving lixisenatide in these trials, divided into matched cohorts by propensity scoring, and stratified according to baseline homeostasis model assessment of ß-cell function (HOMA-ß) index levels, high HOMA-ß: > median HOMA-ß (28.49%); low HOMA-ß: ≤ median. RESULTS: The matched "low" and "high" HOMA-ß index cohorts (N = 546 patients) had comparable baseline parameters. Mean change from baseline in glycated haemoglobin (HbA1c ) was -0.85% and -0.94% for low and high HOMA-ß cohorts, respectively (P = .2607). Reductions from baseline in fasting plasma glucose (FPG; -0.77 vs -1.04 mmol/L; P = .1496) and postprandial plasma glucose (PPG; -5.82 vs -5.61 mmol/L; P = .7511) were similar in the low versus high HOMA-ß index cohorts. Reduction in body weight was significantly greater in the low versus high HOMA-ß index cohort (-2.06 vs -1.13 kg, respectively; P = .0006). CONCLUSIONS: In patients with T2DM, lixisenatide was associated with reduction in HbA1c and improvements in both FPG and PPG, regardless of ß-cell function, indicating that lixisenatide is effective in reducing hyperglycaemia, even in patients with more advanced stages of T2DM and poor residual ß-cell function.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/fisiopatologia , Hipoglicemiantes/administração & dosagem , Resistência à Insulina/fisiologia , Células Secretoras de Insulina/fisiologia , Peptídeos/administração & dosagem , Adulto , Idoso , Diabetes Mellitus Tipo 2/patologia , Método Duplo-Cego , Quimioterapia Combinada , Feminino , Humanos , Células Secretoras de Insulina/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Estudos Multicêntricos como Assunto/estatística & dados numéricos , Placebos , Ensaios Clínicos Controlados Aleatórios como Assunto/estatística & dados numéricos , Índice de Gravidade de DoençaRESUMO
AIM: Evaluate the efficacy and safety of lixisenatide, a once-daily prandial glucagon-like peptide-1 receptor agonist, in older patients with type 2 diabetes mellitus (T2DM) insufficiently controlled on oral antidiabetics (OADs). METHODS: A meta-analysis was conducted on data from older patients (≥65 years) from five of the GetGoal trials, in which patients with T2DM were treated with lixisenatide 20 µg once daily or placebo, as an add-on to OADs. The primary endpoint in all trials was change from baseline at week 24 in glycated hemoglobin (HbA1c). Other endpoints included changes in post-prandial plasma glucose (PPG), fasting plasma glucose (FPG) and weight. Composite and safety endpoints were also analyzed. RESULTS: A total of 501 patients aged ≥65 years were included in this meta-analysis: 304 received lixisenatide plus OADs and 197 received placebo as add-on to OADs. Lixisenatide as an add-on to OADs significantly reduced HbA1c, PPG, FPG and weight, with placebo-corrected treatment effects at week 24 of -0.54% (p<0.0001), -126 mg/dL (p<0.0001), -13 mg/dL (p=0.0005) and -0.90 kg (p=0.0021), respectively. Patients receiving lixisenatide plus OADs were significantly more likely to achieve composite (HbA1c levels<7%, HbA1c levels<7% and no symptomatic hypoglycemia, and HbA1c levels<7%, no weight gain and no symptomatic hypoglycemia) and safety endpoints than those receiving placebo plus OADs. Symptomatic hypoglycemia was experienced by 8.55% and 3.55% of patients in the lixisenatide plus OADs and placebo plus OADs groups, respectively (p=0.0276), although no serious hypoglycemic episodes were reported. CONCLUSIONS: Lixisenatide plus OADs improved glycemic control in older patients inadequately controlled on OADs compared with placebo plus OADs. Lixisenatide is well tailored to the pathophysiology of T2DM in older patients.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Peptídeos/uso terapêutico , Idoso , Glicemia , Peso Corporal , Método Duplo-Cego , Esquema de Medicação , Quimioterapia Combinada , Feminino , Hemoglobinas Glicadas/análise , Humanos , Hipoglicemia/induzido quimicamente , Hipoglicemiantes/administração & dosagem , Hipoglicemiantes/efeitos adversos , Masculino , Peptídeos/administração & dosagem , Peptídeos/efeitos adversos , Período Pós-Prandial , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
OBJECTIVE: Weight loss in patients with type 2 diabetes can improve glycemic control, lower blood pressure, and improve dyslipidemia. Glucagon-like peptide (GLP-1) receptor agonists are associated with weight loss and have potentially beneficial effects on cardiovascular risk biomarkers; however, there is limited information to indicate whether these effects remain outside of clinical trials. RESEARCH DESIGN AND METHODS: Medical records from the General Electric Centricity research database were analyzed retrospectively to evaluate the relationship between weight loss and glycemic control and changes in blood pressure and lipids in patients with type 2 diabetes initiating therapy with exenatide, sitagliptin, or insulin. Baseline and follow-up (90-365 days after the index date) for weight, A1C, fasting blood glucose (FBG), blood pressure, triglycerides, and LDL, HDL, and total cholesterol were assessed. RESULTS: A total of 6,280, 5,861, and 32,398 patients receiving exenatide, sitagliptin, or insulin, respectively, were included in the analysis. Exenatide-treated patients lost a mean +/- SD of 3.0 +/- 7.33 kg, sitagliptin-treated patients lost 1.1 +/- 5.39 kg, and insulin-treated patients gained 0.6 +/- 9.49 kg. There was a significant association between weight loss and a reduction in A1C and FBG with exenatide only and a reduction in blood pressure for all therapies. Weight loss was associated with some improvements in lipids, primarily in the GLP-1 receptor agonist group, with little association in the insulin group. CONCLUSIONS: Weight reduction with GLP-1 receptor agonists was associated with a shift toward a more favorable cardiovascular risk profile. Outcome trials are needed to determine whether improvement in biomarkers translates into a reduction in cardiovascular events in patients with type 2 diabetes.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Redução de Peso/fisiologia , Idoso , Glicemia/efeitos dos fármacos , Estudos de Coortes , Diabetes Mellitus Tipo 2/sangue , Exenatida , Feminino , Humanos , Insulina/uso terapêutico , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Peptídeos/uso terapêutico , Pirazinas/uso terapêutico , Fosfato de Sitagliptina , Triazóis/uso terapêutico , Peçonhas/uso terapêuticoRESUMO
CONTEXT: Fenofibrate is a peroxisome proliferator-activated receptor alpha agonist widely used in clinical practice, but its mechanism of action is incompletely understood. OBJECTIVE: The aim of the study was to assess whether improvement in subclinical inflammation or glucose metabolism contributes to its antiatherogenic effects in insulin-resistant subjects with the metabolic syndrome (MetS). DESIGN AND SETTING: We conducted a randomized, double-blind, placebo-controlled study in the research unit at an academic center. PATIENTS: We studied 25 nondiabetic insulin-resistant MetS subjects. INTERVENTION(S): We administered fenofibrate (200 mg/d) and placebo for 12 wk. MAIN OUTCOME MEASURES: Before and after treatment, we measured plasma lipids/apolipoproteins, inflammatory markers (high-sensitivity C-reactive protein, IL-6, intercellular adhesion molecule/vascular cell adhesion molecule), adipocytokines (adiponectin, TNFalpha, leptin), and insulin secretion (oral glucose tolerance test). We also assessed adipose tissue, hepatic and peripheral (muscle) insulin resistance fasting and during a euglycemic insulin clamp with (3)H glucose and (14)C palmitate infusion combined with indirect calorimetry. RESULTS: Subjects displayed severe insulin resistance and systemic inflammation. Fenofibrate significantly reduced plasma triglyceride, apolipoprotein (apo) CII, apo CIII, and apo E (all P < 0.01), with a modest increase in high-density lipoprotein-cholesterol (+12%; P = 0.06). Fenofibrate markedly decreased plasma high-sensitivity C-reactive protein by 49.5 +/- 8% (P = 0.005) and IL-6 by 29.8 +/- 7% (P = 0.03) vs. placebo. However, neither insulin secretion nor adipose tissue, hepatic or muscle insulin sensitivity or glucose/lipid oxidation improved with treatment. Adiponectin and TNF-alpha levels were also unchanged. Improvement in plasma markers of vascular/systemic inflammation was dissociated from changes in triglyceride/high-density lipoprotein-cholesterol, apo CII/CIII, or free fatty acid concentrations or insulin secretion/insulin sensitivity. CONCLUSIONS: In subjects with the MetS, fenofibrate reduces systemic inflammation independent of improvements in lipoprotein metabolism and without changing insulin sensitivity. This suggests a direct peroxisome proliferator-activated receptor alpha-mediated effect of fenofibrate on inflammatory pathways, which may be important for the prevention of CVD in high-risk patients.
Assuntos
Proteína C-Reativa/análise , Fenofibrato/farmacologia , Glucose/metabolismo , Hipolipemiantes/farmacologia , Interleucina-6/sangue , Metabolismo dos Lipídeos/efeitos dos fármacos , Síndrome Metabólica/tratamento farmacológico , Adulto , Método Duplo-Cego , Ácidos Graxos não Esterificados/sangue , Feminino , Humanos , Resistência à Insulina , Lipólise/efeitos dos fármacos , Fígado/metabolismo , Masculino , Síndrome Metabólica/metabolismo , Pessoa de Meia-Idade , Músculo Esquelético/metabolismo , PPAR alfa/fisiologiaRESUMO
OBJECTIVE: To evaluate the efficacy and safety of taspoglutide (R1583/BIM51077), a human once-weekly glucagon-like peptide-1 analog, in patients with type 2 diabetes inadequately controlled with metformin. RESEARCH DESIGN AND METHODS: Type 2 diabetic (n = 306) patients who failed to obtain glycemic control (A1C 7-9.5%) despite 1,500 mg metformin daily were randomly assigned to 8 weeks of double-blind subcutaneous treatment with placebo or taspoglutide, either 5, 10, or 20 mg once weekly or 10 or 20 mg once every 2 weeks, and followed for 4 additional weeks. All patients received their previously established dose of metformin throughout the study. Glycemic control was assessed by change in A1C (percent) from baseline. RESULTS: Significantly greater (P < 0.0001) reductions in A1C from a mean +/- SD baseline of 7.9 +/- 0.7% were observed in all taspoglutide groups compared with placebo after 8 weeks of treatment: -1.0 +/- 0.1% (5 mg once weekly), -1.2 +/- 0.1% (10 mg once weekly), -1.2 +/- 0.1% (20 mg once weekly), -0.9 +/- 0.1% (10 mg Q2W), and -1.0 +/- 0.1% (20 mg Q2W) vs. -0.2 +/- 0.1% with placebo. After 8 weeks, body weight loss was significantly greater in the 10 mg (-2.1 +/- 0.3 kg, P = 0.0035 vs. placebo) and 20 mg (-2.8 +/- 0.3 kg, P < 0.0001) once-weekly groups and the 20 mg once every 2 weeks (-1.9 +/- 0.3 kg, P = 0.0083) group than with placebo (-0.8 +/- 0.3 kg). The most common adverse event was dose-dependent, transient, mild-to-moderate nausea; the incidence of hypoglycemia was very low. CONCLUSIONS: Taspoglutide used in combination with metformin significantly improves fasting and postprandial glucose control and induces weight loss, with a favorable tolerability profile.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Metformina/uso terapêutico , Peptídeos/uso terapêutico , Método Duplo-Cego , Esquema de Medicação , Feminino , Hemoglobinas Glicadas/efeitos dos fármacos , Hemoglobinas Glicadas/metabolismo , Humanos , Hipoglicemiantes/uso terapêutico , Insulina/uso terapêutico , Lipídeos/sangue , Masculino , Peptídeos/administração & dosagem , Peptídeos/efeitos adversos , Peptídeos/sangue , Pós-Menopausa , Segurança , Esterilização ReprodutivaRESUMO
BACKGROUND: Hyperprolactinemia is associated with obesity. Furthermore, in human adipose tissue cultured in vitro, prolactin (PRL) inhibited lipoprotein lipase (LPL) activity via functional PRL receptors. OBJECTIVE: To study PRL and insulin ultradian rhythm and subcutaneous adipose tissue LPL mRNA and protein expressions in severely obese women before and after malabsorptive bariatric surgery. METHODS AND PROCEDURES: Seven severely obese, fertile women were studied twice, once before and the second time 1 year after bilio-pancreatic diversion (BPD), when the weight was stable for at least 3 months. Metabolizable energy intake and 24-h energy expenditure (EE) were measured. Fourier and PULSEFIT analyses were applied to 24-h hormonal time-series to study daily fluctuations and hormonal clearance. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp. Quantitative-competitive reverse transcriptase-PCR and western blot analysis were used to measure LPL gene expression. RESULTS: Spontaneous 24-h PRL secretion was significantly reduced after BPD (mean-daily release, 128.4 +/- 28.1 microg/l vs. 67.2 +/- 9.2 microg/l distribution volume (Vd/l.24 h), P = 0.02); insulin secretion also was significantly reduced (499.9 +/- 204.0 microg/Vd/l.24 h vs. 85.6 +/- 21.0 microg/Vd/l.24 h, P = 0.0001). Metabolizable energy/kg(FFM) did not change significantly after BPD. Twenty-four-hour EE, but not 24-h EE/FFM, was significantly decreased after BPD (P < 0.05). Insulin sensitivity significantly (P < 0.0001) increased after BPD from 21.41 +/- 1.92 to 68.62 +/- 5.03 micromol/kg(FFM)/min. LPL mRNA concentration (from 42.63 +/- 4.21% to 19.00 +/- 2.74% of cyclophilin mRNA, P = 0.001) as well as LPL protein level (from 8.94 +/- 2.73 to 3.16 +/- 1.05 as ratios of protein of interest vs. housekeeping protein, P = 0.038) significantly decreased after BPD. The major determinant of PRL secretion was insulin secretion, whereas the best predictors of LPL expression were insulin and PRL secretion rates. DISCUSSION: The restriction of lipid metabolizable energy rather than weight loss seems to be responsible for both reduction in PRL circulating levels and normalization of its secretion rhythm after bariatric surgery. Furthermore, the reduced adipose tissue LPL expression, being significantly correlated with the decrease in insulin and PRL, suggests a role of hyperinsulinemia and hyperprolactinemia in inducing and sustaining obesity.
Assuntos
Tecido Adiposo/enzimologia , Ritmo Circadiano/fisiologia , Insulina/metabolismo , Lipase Lipoproteica/metabolismo , Obesidade Mórbida/metabolismo , Obesidade Mórbida/cirurgia , Prolactina/metabolismo , Tecido Adiposo/patologia , Adulto , Cirurgia Bariátrica , Biópsia , Metabolismo Energético/fisiologia , Estradiol/sangue , Feminino , Hormônio Foliculoestimulante/sangue , Seguimentos , Análise de Fourier , Humanos , Insulina/sangue , Resistência à Insulina/fisiologia , Secreção de Insulina , Lipase Lipoproteica/genética , Prolactina/sangue , RNA Mensageiro/metabolismo , Globulina de Ligação a Hormônio Sexual/metabolismoRESUMO
BACKGROUND: No pharmacologic therapy has conclusively proved to be effective for the treatment of nonalcoholic steatohepatitis, which is characterized by insulin resistance, steatosis, and necroinflammation with or without centrilobular fibrosis. Pioglitazone is a thiazolidinedione that ameliorates insulin resistance and improves glucose and lipid metabolism in type 2 diabetes mellitus. METHODS: We randomly assigned 55 patients with impaired glucose tolerance or type 2 diabetes and liver biopsy-confirmed nonalcoholic steatohepatitis to 6 months of treatment with a hypocaloric diet (a reduction of 500 kcal per day in relation to the calculated daily intake required to maintain body weight) plus pioglitazone (45 mg daily) or a hypocaloric diet plus placebo. Before and after treatment, we assessed hepatic histologic features, hepatic fat content by means of magnetic resonance spectroscopy, and glucose turnover during an oral glucose tolerance test ([14C]glucose given with the oral glucose load and [3H]glucose given by intravenous infusion). RESULTS: Diet plus pioglitazone, as compared with diet plus placebo, improved glycemic control and glucose tolerance (P<0.001), normalized liver aminotransferase levels as it decreased plasma aspartate aminotransferase levels (by 40% vs. 21%, P=0.04), decreased alanine aminotransferase levels (by 58% vs. 34%, P<0.001), decreased hepatic fat content (by 54% vs. 0%, P<0.001), and increased hepatic insulin sensitivity (by 48% vs. 14%, P=0.008). Administration of pioglitazone, as compared with placebo, was associated with improvement in histologic findings with regard to steatosis (P=0.003), ballooning necrosis (P=0.02), and inflammation (P=0.008). Subjects in the pioglitazone group had a greater reduction in necroinflammation (85% vs. 38%, P=0.001), but the reduction in fibrosis did not differ significantly from that in the placebo group (P=0.08). Fatigue and mild lower-extremity edema developed in one subject who received pioglitazone; no other adverse events were observed. CONCLUSIONS: In this proof-of-concept study, the administration of pioglitazone led to metabolic and histologic improvement in subjects with nonalcoholic steatohepatitis. Larger controlled trials of longer duration are warranted to assess the long-term clinical benefit of pioglitazone. (ClinicalTrials.gov number, NCT00227110 [ClinicalTrials.gov] .).
Assuntos
Fígado Gorduroso/dietoterapia , Fígado Gorduroso/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Tiazolidinedionas/uso terapêutico , Glicemia/efeitos dos fármacos , Glicemia/metabolismo , Restrição Calórica , Terapia Combinada , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/dietoterapia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Método Duplo-Cego , Fígado Gorduroso/complicações , Fígado Gorduroso/patologia , Feminino , Intolerância à Glucose/dietoterapia , Intolerância à Glucose/tratamento farmacológico , Hepatite/dietoterapia , Hepatite/tratamento farmacológico , Humanos , Insulina/sangue , Resistência à Insulina , Fígado/patologia , Cirrose Hepática/patologia , Masculino , Pessoa de Meia-Idade , Necrose , PioglitazonaRESUMO
Thiazolidinediones have gained widespread use for the treatment of type 2 diabetes mellitus and other insulin resistance states, including polycystic ovary syndrome (PCOS). In thiazolidinedione-treated patients a small reduction in hemoglobin and hematocrit levels often is observed, and this generally has been attributed to fluid retention. Because testosterone is a hematopoietic hormone, we investigated whether a reduction in plasma free testosterone concentration was associated with the decrease in hemoglobin and hematocrit levels in 22 nondiabetic women (9 with normal glucose tolerance and 13 with impaired glucose tolerance; mean age, 29 +/- 5 years; mean body mass index, 35.6 +/- 5.8 kg/m2) with PCOS who were treated with pioglitazone, 45 mg/d. Before treatment and after 4 months, subjects underwent an oral glucose tolerance test and measurement of total body water content with bioimpedance. Plasma testosterone, androstenedione, dehydroepiandrosterone sulfate, hemoglobin, and hematocrit levels were evaluated at baseline and every month for 4 months. The fasting plasma glucose concentration (98 +/- 9 mg/dL) was unchanged after pioglitazone treatment, whereas the 2-hour plasma glucose concentration declined from 146 +/- 41 to 119 +/- 20 mg/dL (P = .002). Both the free androgen index and the free testosterone levels calculated according to Vermeulen et al decreased significantly (from 14.4 +/- 7.1 to 10.6 +/- 7.8 [P = .02] and from 59.4 +/- 23.4 to 46.6 +/- 23.3 [P = .03], respectively). The plasma androstenedione level declined from 259 +/- 134 to 190 +/- 109 ng/dL (P = .01), whereas the dehydroepiandrosterone sulfate level did not change significantly (from 139 +/- 90 to 127 +/- 84 mug/dL, P = .2 [not significant]). The levels of both hemoglobin (from 13.6 +/- 1.0 to 12.8 +/- 1.1 g/dL, P = .0002) and hematocrit (from 39.7% +/- 2.2% to 37.9% +/- 2.7%, P = .002) fell slightly after 4 months of pioglitazone administration. Collectively, before and after pioglitazone administration, the plasma free testosterone level according to Vermeulen et al correlated positively with the levels of hemoglobin (r = 0.49, P < .0001) and hematocrit (r = 0.40, P < .0001), as well as the free androgen index (r = 0.38 [P < .0003] with hemoglobin and r = 0.29 [P < .006] with hematocrit); the decrement in plasma free testosterone level and free androgen index also correlated with the decrements in the levels of both hemoglobin (r = 0.51 [P = .01] and r = 0.54 [P = .01], respectively) and hematocrit (r = 0.42 [P = .05] and r = 0.50 [P = .02], respectively). Body weight increased from 90.5 +/- 17.3 to 92.4 +/- 18.8 kg after pioglitazone administration (P = .05), as did body fat content (from 42.7 +/- 15.3 to 44.8 +/- 17.1 kg, P = .03), which could explain the increase in weight, because edema did not develop in any of the subjects. Total body water content did not change significantly after pioglitazone administration (from 37.7 +/- 5.0 to 37.8 +/- 4.9 L, P = .68 [not significant]). In summary, pioglitazone treatment is associated with a mild decline in hematocrit or hemoglobin level, which is correlated with the reduction in plasma testosterone level. These results suggest that increased body water content cannot explain the reduction in hematocrit or hemoglobin level in women with PCOS. Further studies are necessary to evaluate whether the same scenario is applicable to normoandrogenic women and individuals with type 2 diabetes mellitus.
Assuntos
Hematócrito , Hipoglicemiantes/efeitos adversos , Síndrome do Ovário Policístico/sangue , Testosterona/sangue , Tiazolidinedionas/efeitos adversos , Adulto , Androgênios/sangue , Composição Corporal , Índice de Massa Corporal , Peso Corporal , Feminino , Teste de Tolerância a Glucose , Hemodiluição , Hemoglobinas/metabolismo , Humanos , Hipoglicemiantes/uso terapêutico , Insulina/sangue , Resistência à Insulina , Ovulação/efeitos dos fármacos , Ovulação/fisiologia , Pioglitazona , Síndrome do Ovário Policístico/tratamento farmacológico , Tiazolidinedionas/uso terapêuticoRESUMO
Skeletal muscle insulin resistance plays a key role in the pathogenesis of type 2 diabetes. It recently has been hypothesized that excessive activity of the inhibitor of kappaB (IkappaB)/nuclear factor kappaB (NFkappaB) inflammatory pathway is a mechanism underlying skeletal muscle insulin resistance. However, it is not known whether IkappaB/NFkappaB signaling in muscle from subjects with type 2 diabetes is abnormal. We studied IkappaB/NFkappaB signaling in vastus lateralis muscle from six subjects with type 2 diabetes and eight matched control subjects. Muscle from type 2 diabetic subjects was characterized by a 60% decrease in IkappaB beta protein abundance, an indicator of increased activation of the IkappaB/NFkappaB pathway. IkappaB beta abundance directly correlated with insulin-mediated glucose disposal (Rd) during a hyperinsulinemic (40 mU x m(-2) x min(-1))-euglycemic clamp (r = 0.63, P = 0.01), indicating that increased IkappaB/NFkappaB pathway activity is associated with muscle insulin resistance. We also investigated whether reversal of this abnormality could be a mechanism by which training improves insulin sensitivity. In control subjects, 8 weeks of aerobic exercise training caused a 50% increase in both IkappaB alpha and IkappaB beta protein. In subjects with type 2 diabetes, training increased IkappaB alpha and IkappaB beta protein to levels comparable with that of control subjects, and these increments were accompanied by a 40% decrease in tumor necrosis factor alpha muscle content and a 37% increase in insulin-stimulated glucose disposal. In summary, subjects with type 2 diabetes have reduced IkappaB protein abundance in muscle, suggesting excessive activity of the IkappaB/NFkappaB pathway. Moreover, this abnormality is reversed by exercise training.
Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Exercício Físico , Proteínas I-kappa B/análise , Resistência à Insulina , Músculo Esquelético/química , Adulto , Feminino , Técnica Clamp de Glucose , Humanos , Quinase I-kappa B/metabolismo , Masculino , NF-kappa B/fisiologia , Fosforilação , Transdução de Sinais , Fator de Necrose Tumoral alfa/análiseRESUMO
Oversupply and underutilization of lipid fuels are widely recognized to be strongly associated with insulin resistance in skeletal muscle. Recent attention has focused on the mechanisms underlying this effect, and defects in mitochondrial function have emerged as a potential player in this scheme. Because evidence indicates that lipid oversupply can produce abnormalities in extracellular matrix composition and matrix changes can affect the function of mitochondria, the present study was undertaken to determine whether muscle from insulin-resistant, nondiabetic obese subjects and patients with type 2 diabetes mellitus had increased collagen content. Compared with lean control subjects, obese and type 2 diabetic subjects had reduced muscle glucose uptake (P<0.01) and decreased insulin stimulation of tyrosine phosphorylation of insulin receptor substrate-1 and its ability to associate with phosphatidylinositol 3-kinase (P<0.01 and P<.05). Because it was assayed by total hydroxyproline content, collagen abundance was increased in muscle from not only type 2 diabetic patients but also nondiabetic obese subjects (0.26+/-0.05, 0.57+/-0.18, and 0.67+/- 0.20 microg/mg muscle wet wt, lean controls, obese nondiabetics, and type 2 diabetics, respectively), indicating that hyperglycemia itself could not be responsible for this effect. Immunofluorescence staining of muscle biopsies indicated that there was increased abundance of types I and III collagen. We conclude that changes in the composition of the extracellular matrix are a general characteristic of insulin-resistant muscle.
Assuntos
Colágeno Tipo III/metabolismo , Colágeno Tipo I/metabolismo , Matriz Extracelular/metabolismo , Músculo Esquelético/metabolismo , Adulto , Biópsia , Diabetes Mellitus Tipo 2/metabolismo , Feminino , Glucose/metabolismo , Glucose/farmacologia , Humanos , Hidroxiprolina/metabolismo , Insulina/farmacologia , Proteínas Substratos do Receptor de Insulina , Resistência à Insulina/fisiologia , Masculino , Microscopia de Fluorescência , Pessoa de Meia-Idade , Obesidade/metabolismo , Fosfoproteínas/metabolismo , Fosforilação , Tirosina/metabolismoRESUMO
Type 2 diabetes is an insulin-resistant state characterized by hyperinsulinemia and accelerated atherosclerosis. In vitro and in vivo studies in rodents have suggested that nitric oxide generation plays an important role in glucose transport and insulin action. We determined nitric oxide synthase (NOS) activity in skeletal muscle of 10 type 2 diabetic (hemoglobin A(1C) = 6.8 +/- 0.1%) and 11 control subjects under basal conditions and during an 80 mU/m(2).min euglycemic insulin clamp performed with vastus lateralis muscle biopsies before and after 4 h of insulin. In diabetics, insulin-stimulated glucose disposal (Rd) was reduced by 50%, compared with controls (5.4 +/- 0.3 vs. 10.4 +/- 0.5 mg/kg.min, P < 0.01). Basal NOS activity was markedly reduced in the diabetic group (101 +/- 33 vs. 457 +/- 164 pmol/min.mg protein, P < 0.05). In response to insulin, NOS activity increased 2.5-fold in controls after 4 h (934 +/- 282 pmol/min.mg protein, P < 0.05 vs. basal), whereas insulin failed to stimulate NOS activity in diabetics (86 +/- 28 pmol/min.mg protein, P = NS from basal). Basal NOS protein content in muscle was similar in controls and diabetics and did not change following insulin. In controls, insulin-stimulated NOS activity correlated inversely with fasting plasma insulin concentration (r = -0.58, P = 0.05) and positively with Rd (r = 0.71, P = 0.03). In control and diabetic groups collectively, Rd correlated with insulin-stimulated NOS activity (r = 0.52, P = 0.02). We conclude that basal and insulin-stimulated muscle NOS activity is impaired in well-controlled type 2 diabetic subjects, and the defect in insulin-stimulated NOS activity correlates closely with the severity of insulin resistance. These results suggest that impaired NOS activity may play an important role in the insulin resistance in type 2 diabetic individuals.
Assuntos
Diabetes Mellitus Tipo 2/enzimologia , Resistência à Insulina/fisiologia , Músculo Esquelético/enzimologia , Óxido Nítrico Sintase/metabolismo , Biópsia , Glicemia/metabolismo , Índice de Massa Corporal , Ácidos Graxos não Esterificados/sangue , Feminino , Técnica Clamp de Glucose , Humanos , Insulina/sangue , Insulina/farmacologia , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/citologia , Músculo Esquelético/patologia , Valores de Referência , Sístole/fisiologiaRESUMO
Type 2 diabetes mellitus (DM) is characterized by insulin resistance and pancreatic beta cell dysfunction. In high-risk subjects, the earliest detectable abnormality is insulin resistance in skeletal muscle. Impaired insulin-mediated signaling, gene expression, glycogen synthesis, and accumulation of intramyocellular triglycerides have all been linked with insulin resistance, but no specific defect responsible for insulin resistance and DM has been identified in humans. To identify genes potentially important in the pathogenesis of DM, we analyzed gene expression in skeletal muscle from healthy metabolically characterized nondiabetic (family history negative and positive for DM) and diabetic Mexican-American subjects. We demonstrate that insulin resistance and DM associate with reduced expression of multiple nuclear respiratory factor-1 (NRF-1)-dependent genes encoding key enzymes in oxidative metabolism and mitochondrial function. Although NRF-1 expression is decreased only in diabetic subjects, expression of both PPAR gamma coactivator 1-alpha and-beta (PGC1-alpha/PPARGC1 and PGC1-beta/PERC), coactivators of NRF-1 and PPAR gamma-dependent transcription, is decreased in both diabetic subjects and family history-positive nondiabetic subjects. Decreased PGC1 expression may be responsible for decreased expression of NRF-dependent genes, leading to the metabolic disturbances characteristic of insulin resistance and DM.