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2.
Nat Commun ; 12(1): 2887, 2021 05 17.
Article in English | MEDLINE | ID: mdl-34001905

ABSTRACT

Obesity is a major risk factor underlying the development of metabolic disease and a growing public health concern globally. Strategies to promote skeletal muscle metabolism can be effective to limit the progression of metabolic disease. Here, we demonstrate that the levels of the Hippo pathway transcriptional co-activator YAP are decreased in muscle biopsies from obese, insulin-resistant humans and mice. Targeted disruption of Yap in adult skeletal muscle resulted in incomplete oxidation of fatty acids and lipotoxicity. Integrated 'omics analysis from isolated adult muscle nuclei revealed that Yap regulates a transcriptional profile associated with metabolic substrate utilisation. In line with these findings, increasing Yap abundance in the striated muscle of obese (db/db) mice enhanced energy expenditure and attenuated adiposity. Our results demonstrate a vital role for Yap as a mediator of skeletal muscle metabolism. Strategies to enhance Yap activity in skeletal muscle warrant consideration as part of comprehensive approaches to treat metabolic disease.


Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Adiposity/genetics , Fatty Acids/metabolism , Metabolic Diseases/genetics , Muscle, Skeletal/metabolism , Adaptor Proteins, Signal Transducing/metabolism , Animals , Gene Expression Regulation , Insulin Resistance/genetics , Male , Metabolic Diseases/metabolism , Mice, Inbred C57BL , Mice, Knockout , Obesity/genetics , Obesity/metabolism , Oxidation-Reduction , RNA Interference , Reverse Transcriptase Polymerase Chain Reaction/methods , YAP-Signaling Proteins
3.
Trials ; 22(1): 84, 2021 Jan 22.
Article in English | MEDLINE | ID: mdl-33482890

ABSTRACT

BACKGROUND: The lack of approved treatments for the majority of rare diseases is reflective of the unique challenges of orphan drug development. Novel methodologies, including new functionally relevant endpoints, are needed to render the development process more feasible and appropriate for these rare populations and thereby expedite the approval of promising treatments to address patients' high unmet medical need. Here, we describe the development of an innovative master protocol and primary outcome assessment to investigate the modified amino acid N-acetyl-L-leucine (Sponsor Code: IB1001) in three separate, multinational, phase II trials for three ultra-rare, autosomal-recessive, neurodegenerative disorders: Niemann-Pick disease type C (NPC), GM2 gangliosidoses (Tay-Sachs and Sandhoff disease; "GM2"), and ataxia telangiectasia (A-T). METHODS/DESIGN: The innovative IB1001 master protocol and novel CI-CS primary endpoints were developed through a close collaboration between the Industry Sponsor, Key Opinion Leaders, representatives of the Patient Communities, and National Regulatory Authorities. As a result, the open-label, rater-blinded study design is considerate of the practical limitations of recruitment and retention of subjects in these ultra-orphan populations. The novel primary endpoint, the Clinical Impression of Change in Severity© (CI-CS), accommodates the heterogenous clinical presentation of NPC, GM2, and A-T: at screening, the principal investigator appoints for each patient a primary anchor test (either the 8-m walk test (8MWT) or 9-hole peg test of the dominant hand (9HPT-D)) based on his/her unique clinical symptoms. The anchor tests are videoed in a standardized manner at each visit to capture all aspects related to the patient's functional performance. The CI-CS assessment is ultimately performed by independent, blinded raters who compare videos of the primary anchor test from three periods: baseline, the end of treatment, and the end of a post-treatment washout. Blinded to the time point of each video, the raters make an objective comparison scored on a 7-point Likert scale of the change in the severity of the patient's neurological signs and symptoms from video A to video B. To investigate both the symptomatic and disease-modifying effects of treatment, N-acetyl-L-leucine is assessed during two treatment sequences: a 6-week parent study and 1-year extension phase. DISCUSSION: The novel CI-CS assessment, developed through a collaboration of all stakeholders, is advantageous in that it better ensures the primary endpoint is functionally relevant for each patient, is able to capture small but meaningful clinical changes critical to the patients' quality of life (fine-motor skills; gait), and blinds the primary outcome assessment. The results of these three trials will inform whether N-acetyl-L-leucine is an effective treatment for NPC, GM2, and A-T and can also serve as a new therapeutic paradigm for the development of future treatments for other orphan diseases. TRIAL REGISTRATION: The three trials (IB1001-201 for Niemann-Pick disease type C (NPC), IB1001-202 for GM2 gangliosidoses (Tay-Sachs and Sandhoff), IB1001-203 for ataxia telangiectasia (A-T)) have been registered at www.clinicaltrials.gov (NCT03759639; NCT03759665; NCT03759678), www.clinicaltrialsregister.eu (EudraCT: 2018-004331-71; 2018-004406-25; 2018-004407-39), and https://www.germanctr.de (DR KS-ID: DRKS00016567; DRKS00017539; DRKS00020511).


Subject(s)
Ataxia Telangiectasia , Gangliosidoses, GM2 , Neurodegenerative Diseases , Female , Humans , Leucine , Male , Neurodegenerative Diseases/diagnosis , Neurodegenerative Diseases/drug therapy , Quality of Life
4.
AJNR Am J Neuroradiol ; 41(5): 938-940, 2020 05.
Article in English | MEDLINE | ID: mdl-32354709

ABSTRACT

CSF-venous fistula is an important treatable cause of spontaneous intracranial hypotension that is often difficult to detect using traditional imaging techniques. Herein, we describe the technical aspects and diagnostic performance of MR myelography when used for identifying CSF-venous fistulas. We report 3 cases in which the CSF-venous fistula was occult on CT myelography but readily detected using MR myelography.


Subject(s)
Cerebrospinal Fluid Leak/diagnostic imaging , Fistula/diagnostic imaging , Intracranial Hypotension/diagnostic imaging , Magnetic Resonance Imaging/methods , Myelography/methods , Adult , Contrast Media , Female , Fistula/complications , Gadolinium , Humans , Intracranial Hypotension/etiology , Male , Middle Aged , Tomography, X-Ray Computed/methods , Veins/diagnostic imaging
6.
Diabet Med ; 37(11): 1902-1909, 2020 11.
Article in English | MEDLINE | ID: mdl-31724226

ABSTRACT

AIM: To investigate the utility of calcaneal quantitative ultrasound compared with bone densitometry (DXA) in predicting incident low-trauma fracture in type 2 diabetes. METHODS: This retrospective cohort study included a subset of participants in the Dubbo Osteoporosis Epidemiology Study who had concurrent calcaneal quantitative ultrasound and DXA measurement, comprising 809 people without type 2 diabetes and 96 with type 2 diabetes. Fracture data had been collected prospectively. Cox proportional hazard models and receiver operating curves (ROC) were used to compare calcaneal quantitative ultrasound and DXA parameters as predictors for any low-trauma fracture. RESULTS: The median age of participants was 71 years (IQR 68-76, 50% men) for those without type 2 diabetes and 70 years (IQR 68-76, 55% men) for those with type 2 diabetes. There was no difference in low-trauma fracture incidence between groups when stratified by sex. In those without type 2 diabetes, the hazard ratio for fracture per 1 sd decrease in broadband ultrasound attenuation and femoral neck bone mineral density (BMD) was 1.47 [95% confidence interval (CI) 1.26-1.71] and 1.39 (95% CI 1.17-1.64), respectively. The corresponding figures in type 2 diabetes were 1.81 (95% CI 1.03-3.19) for broadband ultrasound attenuation and 2.55 (95% CI 1.28-5.08) for femoral neck BMD. CONCLUSION: Broadband ultrasound attenuation is comparable with femoral neck BMD as a predictor for low trauma incident fracture in type 2 diabetes. Calcaneal quantitative ultrasound offers several advantages over DXA and should be considered in further studies of bone health screening or in clinical practice where DXA is unavailable.


Subject(s)
Calcaneus/diagnostic imaging , Diabetes Mellitus, Type 2/drug therapy , Femur Neck/diagnostic imaging , Osteoporotic Fractures/epidemiology , Absorptiometry, Photon , Aged , Bone Density , Female , Fractures, Bone/epidemiology , Humans , Hypoglycemic Agents/therapeutic use , Incidence , Male , Proportional Hazards Models , Retrospective Studies , Risk Assessment , Time Factors , Ultrasonography
8.
Article in English | MEDLINE | ID: mdl-31778357

ABSTRACT

SUMMARY: Adrenal oncocytomas are rare tumours, with only approximately 160 cases reported in the literature. We report the use of urinary steroid profiling as part of their diagnostic evaluation and prognostication. A 45-year-old woman presented with clinical features of hyperandrogenism. Serum biochemistry confirmed androgen excess and computed tomography (CT) demonstrated a 3.2 cm adrenal tumour with density 39 HU pre-contrast. Urine steroid profiling showed elevated tetrahydro-11 deoxycortisol (THS), which is associated with adrenal malignancy. Laparoscopic adrenalectomy was performed, and histopathology diagnosed adrenal oncocytoma. Serum and urinary biochemistry resolved post-operatively and remained normal at 1-year follow-up. LEARNING POINTS: Differential diagnosis of adrenal masses is challenging. Current techniques for differentiating between tumour types lack sensitivity and specificity. 24-h urinary steroid profiling is a useful tool for reflecting steroid output from adrenal glands. Gas chromatography-mass spectrometry (GC-MS) of urinary steroid metabolites has sensitivity and specificity of 90% for diagnosing adrenocortical carcinoma. Adrenal oncocytoma are rare tumours. Differentiating between benign and malignant types is difficult. Data guiding prognostication and management are sparse.

9.
Eur J Clin Pharmacol ; 74(10): 1327-1332, 2018 Oct.
Article in English | MEDLINE | ID: mdl-29938343

ABSTRACT

PURPOSE: The management of type 2 diabetes mellitus (T2DM) is complex. The aim of this work is to explore factors that predict the need for add-on therapy in patients with T2DM in the community. METHODS: We accessed longitudinal, pharmacy payment claim records from the national Pharmaceutical Benefits Scheme (PBS) (Subsidises costs of medicines: government pays difference between patient co-payments, lower in concessional patients, and additional cost of drug.) for the period January 2006 to September 2014 (EREC/MI3127) from a 10% random sample of the Australian population validated to be representative of the population by the Australian Bureau of Statistics (ABS). Likely, T2DM patients were identified as those having been dispensed a single anti-hyperglycaemic drug (monotherapy). The time taken and possible factors that might lead to the addition of a second therapy were examined. An examination was made of trends in the co-prescription of either antihypertensive or anti-hyperlipidaemic agents in relation to the time (± 3 years) of initiating an anti-hyperglycaemic agent. RESULTS: Most (83%) presumed T2DM patients were initiated with metformin. The average time until the second agent was added was 4.8 years (95% CI 4.7-4.9). Satisfactory adherence, age, male gender, initiating therapy after 2012 and initiating with a sulphonylurea drug all were significant risks for add-on therapy. There was no overall trend in the initiation of antihypertensive and/or anti-hyperlipidaemic agents with respect to the time of anti-hyperglycaemic initiation. CONCLUSION: The usefulness of a longitudinal dataset of pharmacy-claim records is demonstrated. Over half of all older and socioeconmically disadvantaged T2DM patients captured in this longitudinal claims database will be prescribed a second anti-hyperglycaemic agent within 5 years of their first drug therapy. Several factors can predict the risk of prescription of add-on therapy, and these should be considered when prescribing medications to treat T2DM.


Subject(s)
Diabetes Mellitus, Type 2/drug therapy , Hypoglycemic Agents/administration & dosage , Metformin/administration & dosage , Sulfonylurea Compounds/administration & dosage , Age Factors , Aged , Australia , Databases, Factual , Drug Therapy, Combination , Female , Humans , Longitudinal Studies , Male , Medication Adherence , Middle Aged , Sex Factors , Social Class , Socioeconomic Factors , Time Factors , Vulnerable Populations
10.
Clin Obes ; 8(2): 131-139, 2018 Apr.
Article in English | MEDLINE | ID: mdl-29334695

ABSTRACT

Obesity and osteoporosis are common public health problems. Paradoxically, while obesity is associated with higher bone density, type 2 diabetic obese individuals have an increased fracture risk. Although obesity and insulin resistance co-exist, some obese individuals remain insulin-sensitive. We suggest that the apparent paradox relating obesity, bone density and fracture risk in type 2 diabetes may be at least partly influenced by differences in bone strength and quality between insulin-resistant and insulin-sensitive obese individuals. In this review, we focus on the complex interplay between, adiposity, insulin resistance and osteoporotic fracture risk and suggest that this is an important area of study that has implications for individually tailored and targeted treatment to prevent osteoporotic fracture in obese type 2 diabetic individuals.


Subject(s)
Adiposity , Diabetes Mellitus, Type 2/metabolism , Fractures, Bone/physiopathology , Insulin Resistance , Animals , Bone Density , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/physiopathology , Fractures, Bone/complications , Humans
11.
Eur J Clin Pharmacol ; 72(12): 1489-1496, 2016 Dec.
Article in English | MEDLINE | ID: mdl-27568311

ABSTRACT

PURPOSE: The study aimed to (1) determine the trends in the utilisation of metformin in Australia, (2) determine the appropriateness of metformin dosing in an Australian teaching hospital and (3) gather the opinions of prescribers on the relationship between metformin dose and renal function. METHODS: National prescription data between 1990 and 2012 were accessed. A retrospective audit (2008-2012) of metformin doses and patient renal function (20 % random sample of all in-patients prescribed metformin) was conducted at St Vincent's Hospital (SVH), Sydney. Prescribers of metformin were interviewed (semi-structured; consultants at SVH) or surveyed (Australian endocrinologists) to gather their understanding of metformin dosing in relation to renal function. RESULTS: Metformin utilisation increased fivefold nationally between 1995 and 2012. Metformin tended to be under-dosed in SVH patients with normal renal function (83.5 %) and over-dosed in patients with impaired renal function (estimated glomerular filtration rate (eGFR) <30 mL/min, 50 %). Consultants indicated that metformin doses needed to be reduced in renal impairment. Most endocrinologists (61 %) were comfortable prescribing metformin down to eGFRs around 30 mL/min. CONCLUSION: The use of metformin increased greatly over the period of the study. Metformin is prescribed frequently for patients with eGFR values below the minimal level approved in the product label (60 mL/min). While prescribers expressed their understanding of the need to reduce metformin doses in patients with renal impairment, we found that metformin doses were higher than appropriate in patients with impaired renal function. Metformin may be used safely when renal function is poor provided dosage is appropriately reduced.


Subject(s)
Drug Utilization/trends , Hypoglycemic Agents/therapeutic use , Metformin/therapeutic use , Diabetes Mellitus, Type 2/drug therapy , Diabetes Mellitus, Type 2/physiopathology , Glomerular Filtration Rate , Hospitals, Teaching/trends , Humans , Hypoglycemic Agents/administration & dosage , Metformin/administration & dosage , New South Wales , Renal Insufficiency/drug therapy , Renal Insufficiency/physiopathology
13.
J Public Health (Oxf) ; 38(2): 316-22, 2016 06.
Article in English | MEDLINE | ID: mdl-25795654

ABSTRACT

BACKGROUND: Attitudes towards physical activity are largely developed during childhood meaning that school physical education classes can have a strong influence. METHODS: National level data of school pupils (n = 21 515) in England were analysed to examine the association between school provision of physical education with sex, age, geographic and socioeconomic factors. RESULTS: Children attending independent schools had more scheduled physical education time (P < 0.001; 95% confidence interval (CI) 18 to 30 extra min per week). This association was true for males (P = 0.024); schools located in the South (P < 0.001; 95% CI 2 to 3) and rural areas (P < 0.001; 95% CI 3 to 5); or with a higher percentage of pupils eligible for free school meals (P < 0.001; 95% CI 3 to 4). Schools in more affluent areas (P < 0.001; 95% CI -1 to -2) and those with lower percentages of pupils from ethnic minorities (P < 0.001; 95% CI -1 to -2) also had higher minutes of physical education provision per week. Regarding age, 93% of schools met the guidelines in Years 1-9; only 45% did in Years 10-13. CONCLUSION: Differences in physical education were found in relation to school type, socioeconomic status and geographical factors. Age-related differences in compliance with guidelines are of concern; ways to increase provision for older children should be investigated.


Subject(s)
Physical Education and Training/statistics & numerical data , Schools/statistics & numerical data , Students/statistics & numerical data , Adolescent , Child , Cross-Sectional Studies , England , Exercise , Female , Geography , Humans , Linear Models , Male , Rural Population , Socioeconomic Factors , Surveys and Questionnaires , Urban Population
14.
J Clin Endocrinol Metab ; 100(11): 4082-91, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26378474

ABSTRACT

CONTEXT: Whereas insulin resistance and obesity coexist, some obese individuals remain insulin sensitive. OBJECTIVE: We examined phenotypic and metabolic factors associated with insulin sensitivity in both muscle and liver in obese individuals. DESIGN AND PARTICIPANTS: Sixty-four nondiabetic obese adults (29 males) underwent hyperinsulinemic (15 and 80 mU/m(2) · min)-euglycemic clamps with deuterated glucose. Top tertile subjects for glucose infusion rate during the high-dose insulin clamp were assigned Musclesen and those in the lower two tertiles were assigned Muscleres. Secondarily, top tertile subjects for endogenous glucose production suppression during the low-dose insulin clamp were deemed Liversen and the remainder Liverres. MAIN OUTCOMES MEASURES: Clinical and laboratory parameters and visceral, subcutaneous, liver, and pancreatic fat were compared. RESULTS: Musclesen and Muscleres had similar body mass index and total fat (P > .16), but Musclesen had lower glycated hemoglobin (P < .001) and systolic (P = .01) and diastolic (P = .03) blood pressure (BP). Despite similar sc fat (P = 1), Musclesen had lower visceral (P < .001) and liver (P < .001) fat. Liversen had lower visceral (P < .01) and liver (P < .01) fat and C-reactive protein (P = .02) than Liverres. When subjects were grouped by both glucose infusion rate during the high-dose insulin clamp and endogenous glucose production suppression, insulin sensitivity at either muscle or liver conferred apparent protection from the adverse metabolic features that characterized subjects insulin resistant at both sites. High-density lipoprotein-cholesterol, 1-hour glucose, systolic BP, and triglycerides explained 54% of the variance in muscle insulin sensitivity. CONCLUSIONS: Obese subjects who were insulin sensitive at muscle and/or liver exhibited favorable metabolic features, including lower BP, liver and visceral adiposity. This study identifies factors associated with, and possibly contributing to, insulin sensitivity in obesity.


Subject(s)
Insulin Resistance , Obesity/physiopathology , Adipocytes/pathology , Adipocytes/ultrastructure , Adolescent , Adult , Aged , Blood Pressure , Body Mass Index , C-Reactive Protein/metabolism , Cholesterol, HDL/blood , Female , Glucose Clamp Technique , Humans , Hyperinsulinism/metabolism , Liver/metabolism , Male , Middle Aged , Muscles/metabolism , Pancreas/metabolism , Phenotype , Subcutaneous Fat/metabolism , Triglycerides/blood , Young Adult
16.
Diabetes ; 64(1): 299-310, 2015 Jan.
Article in English | MEDLINE | ID: mdl-25114292

ABSTRACT

Perilipin 1 is a lipid droplet coat protein predominantly expressed in adipocytes, where it inhibits basal and facilitates stimulated lipolysis. Loss-of-function mutations in the PLIN1 gene were recently reported in patients with a novel subtype of familial partial lipodystrophy, designated as FPLD4. We now report the identification and characterization of a novel heterozygous frameshift mutation affecting the carboxy-terminus (439fs) of perilipin 1 in two unrelated families. The mutation cosegregated with a similar phenotype including partial lipodystrophy, severe insulin resistance and type 2 diabetes, extreme hypertriglyceridemia, and nonalcoholic fatty liver disease in both families. Poor metabolic control despite maximal medical therapy prompted two patients to undergo bariatric surgery, with remarkably beneficial consequences. Functional studies indicated that expression levels of the mutant protein were lower than wild-type protein, and in stably transfected preadipocytes the mutant protein was associated with smaller lipid droplets. Interestingly, unlike the previously reported 398 and 404 frameshift mutants, this variant binds and stabilizes ABHD5 expression but still fails to inhibit basal lipolysis as effectively as wild-type perilipin 1. Collectively, these findings highlight the physiological need for exquisite regulation of neutral lipid storage within adipocyte lipid droplets, as well as the possible metabolic benefits of bariatric surgery in this serious disease.


Subject(s)
Carrier Proteins/genetics , Diabetes Mellitus, Type 2/genetics , Frameshift Mutation , Hyperlipoproteinemia Type IV/genetics , Lipodystrophy, Familial Partial/genetics , Phosphoproteins/genetics , 1-Acylglycerol-3-Phosphate O-Acyltransferase/metabolism , 3T3-L1 Cells , Adipocytes, White/physiology , Adolescent , Adult , Amino Acid Sequence , Animals , Base Sequence , Carrier Proteins/metabolism , Family Health , Female , Humans , Insulin Resistance/genetics , Male , Mice , Middle Aged , Molecular Sequence Data , Mutagenesis, Site-Directed , Pedigree , Perilipin-1 , Phosphoproteins/metabolism
17.
Intern Med J ; 43(8): 946-8, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23919338

ABSTRACT

We describe a case of severe hyperglycaemia resulting in diabetic ketoacidosis secondary to L-asparaginase. There are few reports of this potentially life-threatening complication, particularly in the English literature. Awareness and recognition of this preventable and manageable problem will improve safe delivery of this anti-leukaemic drug.


Subject(s)
Asparaginase/adverse effects , Diabetic Ketoacidosis/chemically induced , Diabetic Ketoacidosis/diagnosis , Precursor Cell Lymphoblastic Leukemia-Lymphoma/diagnosis , Adolescent , Female , Humans , Precursor Cell Lymphoblastic Leukemia-Lymphoma/drug therapy
18.
Clin Transl Oncol ; 15(10): 759-65, 2013 Oct.
Article in English | MEDLINE | ID: mdl-23615979

ABSTRACT

A multi-modality approach that encompasses maximal surgical resection in combination with adjuvant therapy is critical for achieving optimal disease control in children with ependymoma. In view of its complex biology and variable response to therapy, ependymoma remains a challenge for clinicians involved in the care of these patients. Meanwhile, translation of molecular findings can characterize unique features of childhood ependymoma and their natural history. Furthermore, understanding the biology of pediatric ependymoma serves as a platform for development of future targeted therapies. In line with these goals, we review the molecular basis of pediatric ependymoma and its prognostic implications, as well as novel therapeutic advances in the management of ependymoma in children.


Subject(s)
Brain Neoplasms/therapy , Ependymoma/therapy , Brain Neoplasms/metabolism , Child , Ependymoma/metabolism , Humans , Prognosis
19.
Cytopathology ; 24(4): 222-7, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23379696

ABSTRACT

OBJECTIVE: To investigate the sampling performance of individual cervical cytology practitioners using the transformation zone sampling rate (TZSR) as a performance indicator and to assess the impact of dedicated on site training for those identified with a low TZSR. METHODS: The TZSR was calculated for all practitioners submitting ThinPrep(®) cervical cytology specimens to the Conquest laboratory between January 2010 and November 2011. After excluding those with less than 30 qualifying samples the 10th percentile of the TZSR was calculated. Practitioners with a TZSR below the 10th percentile were visited by a specialist cervical cytology screening facilitator after which the TZSR of these practitioners was closely monitored. RESULTS: After exclusions there were 175 practitioners who had collected 24 358 qualifying liquid-based cytology (LBC) samples. The average TZSR was 70% (range 12-96%). The 10th percentile was 44%; 18 scored below the 10th percentile. Failure to apply sufficient pressure when sampling was identified as the most common reason for a low TZSR. In some cases there was suspicion that the cervix was not always adequately visualized. Continuous monitoring after assessment identified improvement in the TZSRs of 13/18 practitioners. CONCLUSIONS: Identification of practitioners with low TZSRs compared with their peers allows these individuals to be selected for personalized observation and training by a specialist in cervical cytology which can lead to an improvement in TZSR. As previous studies show a significant correlation between the TZSR and the detection rate of cytological abnormality it is useful to investigate low TZSRs.


Subject(s)
Cytodiagnosis , Specimen Handling , Uterine Cervical Dysplasia/diagnosis , Early Detection of Cancer , Female , Humans , Mass Screening , Papanicolaou Test , Pregnancy , Surveys and Questionnaires , Vaginal Smears , Uterine Cervical Dysplasia/pathology
20.
Diabetologia ; 56(4): 875-85, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23344726

ABSTRACT

AIMS/HYPOTHESIS: Muscle insulin resistance, one of the earliest defects associated with type 2 diabetes, involves changes in the phosphoinositide 3-kinase/Akt network. The relative contribution of obesity vs insulin resistance to perturbations in this pathway is poorly understood. METHODS: We used phosphospecific antibodies against targets in the Akt signalling network to study insulin action in muscle from lean, overweight/obese and type 2 diabetic individuals before and during a hyperinsulinaemic-euglycaemic clamp. RESULTS: Insulin-stimulated Akt phosphorylation at Thr309 and Ser474 was highly correlated with whole-body insulin sensitivity. In contrast, impaired phosphorylation of Akt substrate of 160 kDa (AS160; also known as TBC1D4) was associated with adiposity, but not insulin sensitivity. Neither insulin sensitivity nor obesity was associated with defective insulin-dependent phosphorylation of forkhead box O (FOXO) transcription factor. In view of the resultant basal hyperinsulinaemia, we predicted that this selective response within the Akt pathway might lead to hyperactivation of those processes that were spared. Indeed, the expression of genes targeted by FOXO was downregulated in insulin-resistant individuals. CONCLUSIONS/INTERPRETATION: These results highlight non-linearity in Akt signalling and suggest that: (1) the pathway from Akt to glucose transport is complex; and (2) pathways, particularly FOXO, that are not insulin-resistant, are likely to be hyperactivated in response to hyperinsulinaemia. This facet of Akt signalling may contribute to multiple features of the metabolic syndrome.


Subject(s)
Insulin Resistance , Muscles/physiopathology , Proto-Oncogene Proteins c-akt/metabolism , Adult , Aged , Diabetes Mellitus, Type 2/metabolism , Female , Forkhead Box Protein O1 , Forkhead Transcription Factors/metabolism , Gene Expression Profiling , Humans , Insulin/metabolism , Insulin Secretion , Male , Metabolic Syndrome/metabolism , Middle Aged , Muscles/metabolism , Phosphorylation , Signal Transduction
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