[Show abstract][Hide abstract] ABSTRACT: We aimed to identify microRNAs (miRNAs) associated with type 2 diabetes and risk of developing the disease in skeletal muscle biopsies from phenotypically well-characterised twins.
We measured muscle miRNA levels in monozygotic (MZ) twins discordant for type 2 diabetes using arrays. Further investigations of selected miRNAs included target prediction, pathway analysis, silencing in cells and association analyses in a separate cohort of 164 non-diabetic MZ and dizygotic twins. The effects of elevated glucose and insulin levels on miRNA expression were examined, and the effect of low birthweight (LBW) was studied in rats.
We identified 20 miRNAs that were downregulated in MZ twins with diabetes compared with their non-diabetic co-twins. Differences for members of the miR-15 family (miR-15b and miR-16) were the most statistically significant, and these miRNAs were predicted to influence insulin signalling. Indeed, miR-15b and miR-16 levels were associated with levels of key insulin signalling proteins, miR-15b was associated with the insulin receptor in non-diabetic twins and knockdown of miR-15b/miR-16 in myocytes changed the levels of insulin signalling proteins. LBW in twins and undernutrition during pregnancy in rats were, in contrast to overt type 2 diabetes, associated with increased expression of miR-15b and/or miR-16. Elevated glucose and insulin suppressed miR-16 expression in vitro.
Type 2 diabetes is associated with non-genetic downregulation of several miRNAs in skeletal muscle including miR-15b and miR-16, potentially targeting insulin signalling. The paradoxical findings in twins with overt diabetes and twins at increased risk of the disease underscore the complexity of the regulation of muscle insulin signalling in glucose homeostasis.
[Show abstract][Hide abstract] ABSTRACT: Retraction of DiabetologiaDOI 10.1007/s00125-011-2276-4Abstract 59, presented at the 47th Annual Meeting of the EASD in 2011, has been retracted at the request of the Dean of Sahlgrenska Academy at the University of Gothenburg, Professor Larkö. The University has investigated this case and The Committee on Academic Misconduct finds that Pontus Boström is guilty of misdemeanour with reference to the points (1) conscious fabrication, corruption or suppression of basic material, and (2) conscious preparation and presentation of falsified results, and therefore finds reason to believe that scientific misconduct has occurred. The primary finding reported in the abstract—reduced protein levels of syntaxin-5 in diabetic muscle—could not be reproduced.
[Show abstract][Hide abstract] ABSTRACT: AimsTo investigate whether the presence of glutamic acid decarboxylase (GAD) autoantibodies post-partum in women with prior gestational diabetes mellitus was associated with changes in metabolic characteristics, including β–cell function and insulin sensitivity.Methods
During 1997–2010, 407 women with gestational diabetes mellitus were offered a 3–month post-partum follow-up including anthropometrics, serum lipid profile, HbA1c and GAD autoantibodies, as well as a 2–h oral glucose tolerance test (OGTT) with blood glucose, serum insulin and C–peptide at 0, 30 and 120 min. Indices of insulin sensitivity and insulin secretion were estimated to assess insulin secretion adjusted for insulin sensitivity, disposition index (DI).ResultsTwenty-two (5.4%) women were positive for GAD autoantibodies (GAD+ve) and the remainder (94.6%) were negative for GAD autoantibodies (GAD–ve). The two groups had similar age and prevalence of diabetes mellitus. Women who were GAD+ve had significantly higher 2–h OGTT glucose concentrations during their index-pregnancy (10.5 vs. 9.8 mmol/l, P = 0.001), higher fasting glucose (5.2 vs. 5.0 mmol/l, P = 0.02) and higher 2–h glucose (7.8 vs. 7.1 mmol/l, P = 0.05) post-partum. Fasting levels of C–peptide and insulin were lower in GAD+ve women compared with GAD–ve women (520 vs. 761 pmol/l, P = 0.02 and 33 vs. 53 pmol/l, P = 0.05) Indices of insulin sensitivity were similar in GAD+ve and GAD–ve women, whereas all estimates of DI were significantly reduced in GAD+ve women.ConclusionGAD+ve women had higher glucose levels and impaired insulin secretion adjusted for insulin sensitivity (DI) compared with GAD–ve women. The combination of OGTT and GAD autoantibodies post-partum identify women with impaired β–cell function. These women should be followed with special focus on development of Type 1 diabetes.This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies suggest that insulin-mediated glucose metabolism is different between muscle fiber types. We hypothesized that differences are due to fiber-type specific expression/regulation of insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese and type 2 diabetic subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared to type II fibers have higher protein levels of the insulin receptor, GLUT4, hexokinase II, glycogen synthase (GS), pyruvate dehydrogenase (PDH-E1α) and a lower protein content of Akt2, TBC1D4 and TBC1D1. In type I fibers compared to type II fibers, the phosphorylation-response to insulin was similar (TBC1D4, TBC1D1 and GS) or decreased (Akt and PDH-E1α). Phosphorylation-responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS and PDH-E1α) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared to lean and obese subjects. We conclude that human type I muscle fibers compared to type II fibers have a higher glucose handling capacity but a similar sensitivity for phosphor-regulation by insulin.
[Show abstract][Hide abstract] ABSTRACT: AimsOur object was to investigate the steady-state pharmacokinetic and pharmacodynamic interaction between the antidepressive herbal medicine St. John's wort (SJW) and the antidiabetic drug metformin.Methods
We performed an open cross-over study in 20 healthy male subjects who received 1 g of metformin twice daily for 1 week with and without 21 days of preceding and concomitant treatment with SJW. The pharmacokinetics of metformin was determined, and a 2-hour oral glucose tolerance test was performed.ResultsSJW decreased the renal clearance of metformin but did not affect any other metformin pharmacokinetic parameters. The addition of SJW decreased the area under the glucose concentration-time curve (702 mmol/L/h (95% confidence interval (643; 761)) vs. 629 mmol/L/h (95% confidence interval (568; 690)), p = 0.003), and this effect was caused by a statistically significantly higher acute insulin response.ConclusionsSJW improves glucose tolerance by enhancing insulin secretion independently of insulin sensitivity in healthy male subjects taking metformin.
British Journal of Clinical Pharmacology 09/2014; · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recent studies indicate that serum testosterone in aging men is associated with insulin sensitivity and expression of oxidative phosphorylation (OxPhos) genes, and that testosterone treatment increases lipid oxidation. Here, we investigated the effect of testosterone therapy on regulators of mitochondrial biogenesis and markers of OxPhos and lipid metabolism in skeletal muscle of aging men with subnormal bioavailable testosterone levels.
Skeletal muscle biopsies were obtained before and after treatment with either testosterone gel (n=12) or placebo (n=13) for 6 months. Insulin sensitivity and substrate oxidation were assessed by euglycemic-hyperinsulinemic clamp and indirect calorimetry. Muscle mRNA levels and protein abundance and phosphorylation of enzymes involved in mitochondrial biogenesis, OxPhos and lipid metabolism were examined by quantitative real-time PCR and western blotting.
Despite an increase in lipid oxidation (P<0.05), testosterone therapy had no effect on insulin sensitivity or mRNA levels of genes involved in mitochondrial biogenesis (PPARGC1A, PRKAA2 and PRKAG3), OxPhos (NDUFS1, ETFA, SDHA, UQCRC1, and COX5B,) or lipid metabolism (ACADVL, CD36, CPT1B, HADH, and PDK4). Consistently, protein abundance of OxPhos subunits encoded by both nuclear (SDHA, UQCRC1) and mitochondrial DNA (ND6), and protein abundance and phosphorylation of AMP-activated protein kinase and p38 MAPK were unaffected by testosterone therapy.
The beneficial effect of testosterone treatment on lipid oxidation is not explained by increased abundance or phosphorylation-dependent activity of enzymes known to regulate mitochondrial biogenesis or markers of OxPhos and lipid metabolism in skeletal muscle of aging men with subnormal bioavailable testosterone levels.
European Journal of Endocrinology 04/2014; · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There is increasing evidence that multiple proteins involved in key regulatory processes in mitochondria are phosphorylated in mammalian tissues. Insulin regulates glucose metabolism by phosphorylation-dependent signaling, and has been shown to stimulate ATP synthesis in human skeletal muscle. Here, we investigated the effect of insulin on the phosphorylation of mitochondrial proteins in human skeletal muscle in vivo. Using a combination of TiO2 phosphopeptide-enrichment, HILIC fractionation and LC-MS/MS, we compared the phosphoproteomes of isolated mitochondria from skeletal muscle samples obtained from healthy individuals before and after four hours of insulin infusion. In total, we identified 207 phosphorylation sites in 95 mitochondrial proteins. Of these phosphorylation sites, 45% were identified in both basal and insulin-stimulated samples. Insulin caused a 2-fold increase in the number of different mitochondrial phosphopeptides (87±7 vs. 40±7, p=0.015) and phosphoproteins (46±2 vs. 26±3, p=0.005) identified in each mitochondrial preparation. Almost half of the mitochondrial phosphorylation sites (n=94) were exclusively identified in the insulin-stimulated state and included the majority of novel sites. Phosphorylation sites detected more often or exclusively in insulin-stimulated samples include multiple sites in mitochondrial proteins involved in oxidative phosphorylation, tricarboxylic acid cycle, fatty acid metabolism, as well as several components of the newly defined mitochondrial inner membrane organizing system (MINOS). In conclusion, the present study demonstrates that insulin increases the phosphorylation of several mitochondrial proteins in human skeletal muscle in vivo, and provides a first step in the understanding of how insulin potentially regulates mitochondrial processes by phosphorylation-dependent mechanisms.
Journal of Proteome Research 03/2014; · 5.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVE
Accumulating evidence suggests an association between insulin sensitivity and albuminuria, which, even in the normal range, is a risk factor for cardiovascular diseases. We evaluated whether insulin sensitivity is associated with albuminuria in healthy subjects.RESEARCH DESIGN AND METHODS
We investigated 1,415 healthy, nondiabetic participants (mean age 43.9 ± 8.3 years; 54.3% women) from the RISC (Relationship between Insulin Sensitivity and Cardiovascular Disease) study, of whom 852 participated in a follow-up examination after 3 years. At baseline, insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamps, expressed as the M/I value. Oral glucose tolerance test-based insulin sensitivity (OGIS), homeostasis model assessment of insulin resistance (HOMA-IR), and urinary albumin-to-creatinine ratio (UACR) were determined at baseline and follow-up.RESULTSMicroalbuminuria (UACR ≥30 mg/g) was present in fewer than 2% at either study visit. After multivariate adjustments, there was no cross-sectional association between UACR and any measure of insulin sensitivity. Neither OGIS nor HOMA-IR were significantly associated with follow-up UACR, but in a multivariate regression analysis, baseline M/I emerged as an independent predictor of UACR at follow-up (β-coefficient -0.14; P = 0.001).CONCLUSIONS
In healthy middle-aged adults, reduced insulin sensitivity, assessed by hyperinsulinemic-euglycemic clamp, is continuously associated with a greater risk of increasing albuminuria. This finding suggests that reduced insulin sensitivity is either simply related to or might causally contribute to the initial pathogenesis of albuminuria.
[Show abstract][Hide abstract] ABSTRACT: Insulin receptor substrate-1 (IRS1) is a key mediator of insulin signal transduction. Perturbations involving IRS1 complexes may lead to the development of insulin resistance and type 2 diabetes. Surprisingly, little is known about the proteins that interact with IRS1 in humans in health and disease conditions. We used a proteomic approach to assess IRS1 interaction partners in skeletal muscle from lean healthy controls (LC), obese insulin resistant non-diabetic controls (OC), and type 2 diabetic participants (T2D) before and after insulin infusion. We identified 113 novel endogenous IRS1 interaction partners, which represents the largest IRS1 interactome in humans and provides new targets for studies of IRS1 complexes in various diseases. Furthermore, we generated the 1st global picture of IRS1 interaction partners in LC, and how they differ in OC and T2D. Interestingly, dozens of proteins in OC and/or T2D exhibited increased associations with IRS1 compared to LC under the basal and/or insulin-stimulated conditions, revealing multiple new dysfunctional IRS1 pathways in OC and T2D. This novel abnormality, increased interaction of multiple proteins with IRS1 in obesity and type 2 diabetes in humans, provides new insights into the molecular mechanism of insulin resistance, and identifies new targets for type 2 diabetes drug development.
[Show abstract][Hide abstract] ABSTRACT: Insulin resistance in obesity and type 2 diabetes is related to abnormalities in mitochondrial oxidative phosphorylation (OxPhos) in skeletal muscle. We tested the hypothesis that mitochondrial oxidative metabolism is impaired in muscle of patients with inherited insulin resistance and defective insulin signalling.
Skeletal muscle biopsies obtained from carriers (n = 6) of a mutation in the tyrosine kinase domain of the insulin receptor gene (INSR) and matched healthy controls (n = 15) were used for discovery-mode microarray-based transcriptional profiling combined with biological pathway analysis. Findings were validated by quantitative real-time PCR, immunoblotting and activity assays.
In INSR mutation carriers, insulin resistance was associated with a coordinated downregulation of OxPhos genes in skeletal muscle. This was related to a 46% decrease in mRNA levels (p = 0.036) of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and 25-50% lower protein content of OxPhos subunits encoded by mitochondrial (ND6, p = 0.042) and nuclear DNA (UQCRC1, p = 0.001; SDHA, p = 0.067; COX5A, p = 0.017 and ATP5B, p = 0.005), as well as reduced citrate synthase activity (p = 0.025). Moreover, mutation carriers showed a marked reduction in type 1 muscle fibres (35% vs 62%, p = 0.0005) and increased type 2a fibres (53% vs 32%; p = 0.002) compared with controls. There were no differences in protein content and phosphorylation of 5' AMP-activated protein kinase, p38 mitogen-activated protein kinase, Erk1 and Erk2.
These data indicate that inherited insulin resistance coincides with reduced mitochondrial oxidative capacity in a PGC-1α- and muscle fibre type-related manner. Whether this co-existence is directly or indirectly related to insulin resistance remains to be elucidated.
[Show abstract][Hide abstract] ABSTRACT: Type 2 diabetes, obesity and insulin resistance are characterized by hypertriglyceridemia and ectopic accumulation of lipids in liver and skeletal muscle. AGPAT6 encodes a novel glycerol-3 phosphate acyltransferase, GPAT4, which catalyzes the first step in the de novo triglyceride synthesis. AGPAT6-deficient mice show lower weight and resistance to diet- and genetically induced obesity. Here, we examined whether common or low-frequency variants in AGPAT6 associate with type 2 diabetes or related metabolic traits in a Danish population.
Eleven variants selected by a candidate gene approach capturing the common and low-frequency variation of AGPAT6 were genotyped in 12,068 Danes from four study populations of middle-aged individuals. The case--control study involved 4,638 type 2 diabetic and 5,934 glucose-tolerant individuals, while studies of quantitative metabolic traits were performed in 5,645 non-diabetic participants of the Inter99 Study.
None of the eleven AGPAT6 variants were robustly associated with type 2 diabetes in the Danish case--control study. Moreover, none of the AGPAT6 variants showed association with measures of obesity (waist circumference and BMI), serum lipid concentrations, fasting or 2-h post-glucose load levels of plasma glucose and serum insulin, or estimated indices of insulin secretion or insulin sensitivity.
Common and low-frequency variants in AGPAT6 do not significantly associate with type 2 diabetes susceptibility, or influence related phenotypic traits such as obesity, dyslipidemia or indices of insulin sensitivity or insulin secretion in the population studied.
BMC Medical Genetics 10/2013; 14(1):113. · 2.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVE
We evaluated whether the association of insulin sensitivity with HDL cholesterol (HDL) and triglycerides is influenced by major plasma apolipoproteins, as suggested by recent experimental evidence.RESEARCH DESIGN AND METHODS
Cross-sectional analysis of the RISC Study, a multicenter European clinical investigation in 1,017 healthy volunteers balanced in sex (women 54%) and age strata (range 30-60 years). Insulin sensitivity (M/I in µmol ⋅ min(-1) ⋅ kgFFM(-1) ⋅ nM(-1)) was measured by the clamp technique and apolipoproteins (ApoB, -C3, -A1, and -E) by Multiplex Technology.RESULTSThe center-, sex-, and age-adjusted standardized regression coefficients (STDβ) with M/I were similar for HDL and triglycerides (+19.9 ± 1.9 vs. -20.0 ± 2.0, P < 0.0001). Further adjustment for triglycerides (or HDL), BMI, and adiponectin (or nonesterified fatty acid) attenuated the strength of the association of M/I with both HDL (STDβ +6.4 ± 2.3, P < 0.01) and triglycerides (-9.5 ± 2.1, P < 0.001). Neither ApoA1 nor ApoE and ApoB showed any association with M/I independent from plasma HDL cholesterol and triglycerides. ApoC3, in contrast, in both men and women, was positively associated with M/I independently of plasma lipids. A relative enrichment of plasma lipids with ApoC3 is associated with lower body fat percentage and lower plasma alanine amino transferase.CONCLUSIONS
Our results suggest that HDL cholesterol modulates insulin sensitivity through a mechanism that is partially mediated by BMI and adiponectin but not by ApoA1. Similarly, the influence of triglycerides on insulin sensitivity is in part mediated by BMI and is unrelated to ApoE or ApoB, but it is significantly modulated by ApoC3, which appears to protect from the negative effect of plasma lipids.
[Show abstract][Hide abstract] ABSTRACT: Phosphorylation of mitochondrial proteins in a variety of biological processes is increasingly being recognized, and may contribute to the differences in function and energy demands observed in mitochondria from different tissues such as liver, heart and skeletal muscle. Here, we used a combination of TiO2 phosphopeptide-enrichment, HILIC fractionation and LC-MS/MS on isolated mitochondria to investigate the tissue-specific mitochondrial phosphoproteomes of rat liver, heart and skeletal muscle. In total, we identified 899 phosphorylation sites in 354 different mitochondrial proteins including 479 potential novel sites. Most phosphorylation sites were detected in liver mitochondria (594), followed by heart (448) and skeletal muscle (336), and more phosphorylation sites were exclusively identified in liver mitochondria than in heart and skeletal muscle. Bioinformatics analysis pointed out enrichment for phosphoproteins involved in amino acid and fatty acid metabolism in liver mitochondria, whereas heart and skeletal muscle were enriched for phosphoproteins involved in energy metabolism, in particular, tricarboxylic acid cycle and oxidative phosphorylation. Multiple tissue-specific phosphorylation sites were identified in tissue-specific enzymes such as those encoded by HMGCS2, BDH1, PCK2, CPS1 and OTC in liver mitochondria, and CKMT2 and CPT1B in heart and skeletal muscle. Kinase prediction showed an important role for PKA and PKC in all tissues, but also for proline-directed kinases in liver mitochondria. In conclusion, we provide a comprehensive map of mitochondrial phosphorylation sites, which covers approximately one third of the mitochondrial proteome, and which can be targeted for the investigation of tissue-specific regulation of mitochondrial biological processes.
Journal of Proteome Research 08/2013; · 5.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Insulin resistance may be an independent risk factor for the development of hypertension, but change in blood pressure (BP) over time has not been adequately studied in healthy individuals fully characterized for insulin sensitivity. In the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study, we measured insulin sensitivity (M/I) using the euglycemic clamp technique in 1073 healthy European adults (587 women, 486 men) aged 30 to 60 years followed up 3 years later. Systolic BP (SBP) at baseline was higher in insulin-resistant women (ie, those in the low sex-specific M/I tertile) compared with those in the intermediate (P<0.001) or high tertiles (P=0.06; mean±SD: 117±13, 111±12, 114±12 mm Hg, respectively). It did not differ across M/I tertiles in men. After adjustment for age, body mass index, baseline SBP, and other covariates, low insulin sensitivity (M/I) predicted a longitudinal rise in SBP in women but not in men; M/I was not associated with change in diastolic BP. SBP rose over time in both sexes and within all M/I tertiles (P<0.05), except in women with high insulin sensitivity. Therefore, in women (but not in men), low insulin sensitivity was associated with higher SBP at 3 years, and high insulin sensitivity was associated with a lower rise in SBP over time.
[Show abstract][Hide abstract] ABSTRACT: AIMS: The importance of reducing sedentary time is increasingly being recognized in the prevention of diabetes and cardiovascular disease. Despite this, the prospective association between sedentary time and physical activity with insulin sensitivity and cardiometabolic risk factors has been little studied. METHODS: In an analysis of data from the European RISC study, sedentary time and time spent in activity of moderate or vigorous intensity were assessed by accelerometry at baseline in 313 men and 414 women, aged 30-60years, with insulin sensitivity as measured by euglycaemic-hyperinsulinaemic clamp. Three years later, cardiometabolic risk factors (anthropometry, glucose, insulin, lipids) were available for 549 participants. RESULTS: In cross-sectional analyses using baseline data, after adjusting for age, gender, recruitment centre and time spent in activity of moderate or vigorous intensity, significant unfavourable associations were observed between higher sedentary time with body weight, HDL cholesterol, triglycerides, clamp-measured insulin sensitivity and insulin secretion (all Ptrend<0.002). Sedentary time remained significantly associated with insulin secretion after adjusting for insulin sensitivity (Ptrend=0.02). In longitudinal analyses, higher baseline sedentary time was associated with 3-year increases in fasting glucose, fasting insulin and the HOMA insulin-resistance index score for the 50% of the study population who increased their BMI by at least 0.3kg/m(2) (all Ptrend<0.01); these relationships remained significant after adjusting for time spent in activity of moderate or vigorous intensity. The 3-year increase in insulin secretion was lower in those spending more time doing activity of moderate or vigorous intensity (Ptrend=0.03). CONCLUSION: These prospective data suggest that less sedentary behaviour may partly counteract some of the negative effects of increasing body weight on glucose-insulin homoeostasis.
[Show abstract][Hide abstract] ABSTRACT: The actin-cytoskeleton-regulating GTPase Rac1 is required for insulin-stimulated GLUT4 translocation in cultured muscle cells. However, involvement of Rac1 and its downstream signaling in glucose transport in insulin sensitive and insulin resistant mature skeletal muscle has not previously been investigated. We hypothesized that Rac1 and its downstream target, p21-activated kinase (PAK), are regulators of insulin-stimulated glucose uptake in mouse and human skeletal muscle, and are dysregulated in insulin resistant states.Muscle specific inducible Rac1 knockout (KO) mice and pharmacological inhibition of Rac1 were used to determine whether Rac1 regulates insulin-stimulated glucose transport in mature skeletal muscle. Furthermore, Rac1 and PAK1 expression and signalling were investigated in muscle of insulin resistant mice and humans.Inhibition and KO of Rac1 decreased insulin-stimulated glucose transport in mouse soleus and EDL muscles ex vivo. Rac1 KO mice showed decreased insulin and glucose tolerance and trended towards higher plasma insulin concentrations following intraperitoneal glucose injection. Rac1 protein expression and PAK(Thr423) phosphorylation were decreased in muscles of high fat fed mice. In humans, insulin-stimulated PAK-activation was decreased in both acute insulin resistant (intralipid infusion) and in chronic insulin resistant states (obesity and diabetes). These findings show that Rac1 is a regulator of insulin-stimulated glucose uptake and a novel candidate involved in skeletal muscle insulin resistance.
[Show abstract][Hide abstract] ABSTRACT: Tight glycemic control in type 1 diabetes mellitus (T1DM) may be accomplished only if severe hypoglycemia can be prevented. Biosensor alarms based on the body's reactions to hypoglycemia have been suggested. In the present study, we analyzed three lead electrocardiogram (ECG) and single-channel electroencephalogram (EEG) in T1DM patients during hypoglycemia. Materials and
Electrocardiogram and EEG recordings during insulin-induced hypoglycemia in nine patients were used to assess the presence of ECG changes by heart rate, and estimates of QT interval (QTc) and time from top of T wave to end of T wave corrected for heartbeat interval and EEG changes by extraction of the power of the signal in the delta, theta, and alpha bands. These six features were assessed continuously to determine the time between changes and severe hypoglycemia.
QT interval changes and EEG theta power changes were detected in six and eight out of nine subjects, respectively. Rate of false positive calculations was one out of nine subjects for QTc and none for EEG theta power. Detection time medians (i.e., time from significant changes to termination of experiments) was 13 and 8 min for the EEG theta power and QTc feature, respectively, with no significant difference (p = .25).
Severe hypoglycemia is preceded by changes in both ECG and EEG features in most cases. Electroencephalogram theta power may be superior with respect to timing, sensitivity, and specificity of severe hypoglycemia detection. A multiparameter algorithm that combines data from different biosensors might be considered.
Journal of diabetes science and technology 01/2013; 7(1):93-9.
[Show abstract][Hide abstract] ABSTRACT: Monozygotic twins discordant for type 2 diabetes constitute an ideal model to study environmental contributions to type 2 diabetic traits. We aimed to examine whether global DNA methylation differences exist in major glucose metabolic tissues from these twins.
Skeletal muscle (n = 11 pairs) and subcutaneous adipose tissue (n = 5 pairs) biopsies were collected from 53-80 year-old monozygotic twin pairs discordant for type 2 diabetes. DNA methylation was measured by microarrays at 26,850 cytosine-guanine dinucleotide (CpG) sites in the promoters of 14,279 genes. Bisulfite sequencing was applied to validate array data and to quantify methylation of intergenic repetitive DNA sequences. The overall intra-pair variation in DNA methylation was large in repetitive (LINE1, D4Z4 and NBL2) regions compared to gene promoters (standard deviation of intra-pair differences: 10% points vs. 4% points, P<0.001). Increased variation of LINE1 sequence methylation was associated with more phenotypic dissimilarity measured as body mass index (r = 0.77, P = 0.007) and 2-hour plasma glucose (r = 0.66, P = 0.03) whereas the variation in promoter methylation did not associate with phenotypic differences. Validated methylation changes were identified in the promoters of known type 2 diabetes-related genes, including PPARGC1A in muscle (13.9±6.2% vs. 9.0±4.5%, P = 0.03) and HNF4A in adipose tissue (75.2±3.8% vs. 70.5±3.7%, P<0.001) which had increased methylation in type 2 diabetic individuals. A hypothesis-free genome-wide exploration of differential methylation without correction for multiple testing identified 789 and 1,458 CpG sites in skeletal muscle and adipose tissue, respectively. These methylation changes only reached some percentage points, and few sites passed correction for multiple testing.
Our study suggests that likely acquired DNA methylation changes in skeletal muscle or adipose tissue gene promoters are quantitatively small between type 2 diabetic and non-diabetic twins. The importance of methylation changes in candidate genes such as PPARGC1A and HNF4A should be examined further by replication in larger samples.
PLoS ONE 12/2012; 7(12):e51302. · 3.53 Impact Factor