The rising prevalence of type 1 diabetes (T1D) over the past decades has been linked to lifestyle changes, but the underlying mechanisms are largely unknown. Recent findings point to gut-associated ...mechanisms in the control of T1D pathogenesis. In nonobese diabetic (NOD) mice, a model of T1D, diabetes development accelerates after deletion of the Toll-like receptor 4 (TLR4). We hypothesized that altered intestinal functions contribute to metabolic alterations, which favor accelerated diabetes development in TLR4-deficient (TLR4−/−) NOD mice. In 70–90-day-old normoglycemic (prediabetic) female NOD TLR4+/+ and NOD TLR4−/− mice, gut morphology and microbiome composition were analyzed. Parameters of lipid metabolism, glucose homeostasis, and mitochondrial respiratory activity were measured in vivo and ex vivo. Compared with NOD TLR4+/+ mice, NOD TLR4−/− animals showed lower muscle mass of the small intestine, higher abundance of Bacteroidetes, and lower Firmicutes in the large intestine, along with lower levels of circulating short-chain fatty acids (SCFA). These changes are associated with higher body weight, hyperlipidemia, and severe insulin and glucose intolerance, all occurring before the onset of diabetes. These mice also exhibited insulin resistance–related abnormalities of energy metabolism, such as lower total respiratory exchange rates and higher hepatic oxidative capacity. Distinct alterations of gut morphology and microbiota composition associated with reduction of circulating SCFA may contribute to metabolic disorders promoting the progression of insulin-deficient diabetes/T1D development.
Aims/hypothesis Fatty acids of marine origin, i.e. docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) act as hypolipidaemics, but they do not improve glycaemic control in obese and diabetic ...patients. Thiazolidinediones like rosiglitazone are specific activators of peroxisome proliferator-activated receptor γ, which improve whole-body insulin sensitivity. We hypothesised that a combined treatment with a DHA and EPA concentrate (DHA/EPA) and rosiglitazone would correct, by complementary additive mechanisms, impairments of lipid and glucose homeostasis in obesity. Methods Male C57BL/6 mice were fed a corn oil-based high-fat diet. The effects of DHA/EPA (replacing 15% dietary lipids), rosiglitazone (10 mg/kg diet) or a combination of both on body weight, adiposity, metabolic markers and adiponectin in plasma, as well as on liver and muscle gene expression and metabolism were analysed. Euglycaemic-hyperinsulinaemic clamps were used to characterise the changes in insulin sensitivity. The effects of the treatments were also analysed in dietary obese mice with impaired glucose tolerance (IGT). Results DHA/EPA and rosiglitazone exerted additive effects in prevention of obesity, adipocyte hypertrophy, low-grade adipose tissue inflammation, dyslipidaemia and insulin resistance, while inducing adiponectin, suppressing hepatic lipogenesis and decreasing muscle ceramide concentration. The improvement in glucose tolerance reflected a synergistic stimulatory effect of the combined treatment on muscle glycogen synthesis and its sensitivity to insulin. The combination treatment also reversed dietary obesity, dyslipidaemia and IGT. Conclusions/interpretation DHA/EPA and rosiglitazone can be used as complementary therapies to counteract dyslipidaemia and insulin resistance. The combination treatment may reduce dose requirements and hence the incidence of adverse side effects of thiazolidinedione therapy.
High intensity interval training (HIIT) is a time-efficient training approach to stimulate biogenesis in healthy populations. We hypothesized that HIIT would increase skeletal muscle insulin ...sensitivity due to improved muscle mitochondrial function in type 2 diabetes (T2D) patients and age- and BMI-matched controls (CON). We examined 18 sedentary male patients with T2D and 23 healthy male CON (age: 58±5 vs. 57±4 years, BMI: 31.4±2.4 vs. 30.4±2.3 kg.m-2) that were enrolled in a 12-week HIIT cycling protocol. CON were further grouped in insulin-sensitive (IS) and -resistant (IR) (baseline M in mg.kg-1.min-1; 7.4 ± 1.3 vs. 4.2 ± 1.1, p<0.001). Two-step hyperinsulinemic-euglycemic clamps, skeletal muscle biopsies for high resolution respirometry and magnetic resonance spectroscopy for liver fat quantification were performed. After 12 weeks of HIIT, T2D and IR CON increased their insulin sensitivity (3.9±1.9 vs. baseline: 2.7±1.6, p=0.02 and 5.5±2.1 vs. 4.2 ± 1.1, p=0.03, respectively), which returned to baseline after detraining. T2D and IR CON increased suppression of endogenous glucose production (EGP) during the high-insulin clamp (T2D: 91 ± 14% vs. baseline: 76 ± 11%, p=0.003 and IR CON: 107 ± 13% vs. 94 ± 14%, p=0.04). IR CON also increased suppression of lipolysis during the low-insulin clamp (82 ± 9 vs. 84 ± 8%, p=0.04). In T2D liver fat was decreased by 17% and remained decreased after detraining. Liver fat content remained unchanged by HIIT training in both CON groups. Muscle maximal uncoupled respiration increased in T2D and CON by 44% and 48%, respectively, at 12 weeks and remained increased after detraining in all groups (p<0.01). We conclude that at the same level of insulin resistance HIIT training improved hepatic and peripheral insulin sensitivity in patients with T2D and insulin resistant controls whereas changes in mitochondrial function occurred irrespective of insulin resistance status.
Disclosure
M. Apostolopoulou: None. D. Pesta: None. Y. Karusheva: None. S. Gancheva: None. T. Jelenik: None. A. Bierwagen: None. K. M ssig: None. J. Szendroedi: None. M. Roden: Speaker's Bureau; Self; Boehringer Ingelheim GmbH. Research Support; Self; Boehringer Ingelheim GmbH. Consultant; Self; Poxel SA. Research Support; Self; Danone Nutricia Early Life Nutrition, GlaxoSmithKline plc., Nutricia Advanced Medical Nutrition, Sanofi.
Weight loss-induced improvement in insulin sensitivity (IS) has been related to enhanced muscle energy metabolism. Thus, we hypothesized that weight loss due to bariatric surgery may induce ...epigenomic changes, which in turn modify mitochondrial function and intracellular lipids. We previously reported that IS fails to improve at 2 weeks (2 w), but then continuously increases until 52 weeks (52 w) after surgery. Now, we monitored muscle mitochondrial function and lipid intermediates in 49 obese humans (OBE; 40±10 years, BMI 51±7 kg/m2) before and for 52 w after bariatric surgery. Genome-wide gene expression and DNA methylation were analyzed in a subgroup of 16 OBE. Initial weight loss increases muscle oxidative capacity by 11% at 2 w, but transient elevation of certain muscle diacylglycerols resulting from unrestrained adipose lipolysis prevents from rapid improvement in IS. At 52 w, both mitochondrial function and intracellular lipids are comparable to lean humans. Acute alterations in expression of 1287 genes involved primarily in mitochondrial function, transcriptional regulation, protein transport, fatty acid metabolism and inflammatory processes, but not changes in DNA methylation, underlie the transient upregulation of mitochondrial function and lipolysis. At 52 w, 1091CpGs are differentially methylated, which relates to improved IS. Specifically, epigenetic alterations at 52 w in FTO gene, encoding an α-ketoglutarate dependent dioxygenase, and TOMM7 gene, encoding a translocase of the outer mitochondrial membrane, contribute to reprogramming transient changes in mRNA expression at 2 w.
In conclusion, initial metabolic changes after weight loss induce epigenetic modification of genes involved in muscle energy metabolism, which in turn leads to long-term beneficial changes in gene expression.
Disclosure
S. Gancheva: None. M. Ouni: None. C. Koliaki: None. T. Jelenik: None. D.F. Markgraf: None. J. Szendroedi: None. M. Schlensak: None. A. Schuermann: None. M. Roden: Speaker's Bureau; Self; Boehringer Ingelheim GmbH. Research Support; Self; Boehringer Ingelheim GmbH. Consultant; Self; Poxel SA. Research Support; Self; Danone Nutricia Early Life Nutrition, GlaxoSmithKline plc., Nutricia Advanced Medical Nutrition, Sanofi.
Hyperinsulinemia and impaired insulin secretion are potential contributors to the development of diabetes-related heart failure. Interference with ventricular myocardial mitochondria might play a key ...pathogenic role, but human data confirming these connections are limited. We hypothesized that ventricular myocardial mitochondrial function is impaired in hyperinsulinemia but is positively related to insulin secretion capacity. We recruited 32 heart transplant recipients without heart failure or antihyperglycemic treatment (age: 53.5±13.3years; BMI: 24.8±2.9kg/m²; HbA1c: 5.9±0.7%). We measured serum insulin levels and blood glucose every 30 minutes for three hours after an oral 75g glucose uptake. Seven patients were newly diagnosed with type 2 diabetes and six had impaired glucose tolerance. High-resolution respirometry was performed on transcatheter ventricular endomyocardial biopsies to determine mitochondrial oxidative capacity, coupling efficiency (respiratory control ratio, RCR) and intrinsic uncoupling (leak control ratio, LCR). Fasting serum insulin, a marker of insulin resistance, was inversely associated with ventricular myocardial mitochondrial RCR (r=-0.39; p=0.02) and positively with LCR (r=0.42; p=0.02), but not with oxidative capacity (p=0.34). Maximum increase of insulin in proportion to fasting levels strongly related to ventricular myocardial mitochondrial RCR (r=0.62; p=0.0001) and inversely to LCR (r=-0.46; p=0.01). This insulin secretory response related to fatty acid-dependent respiration (r=0.35; p=0.05) and tended to relate to combined oxidative capacity from fatty acid and glycolytic substrates (r=0.31; p=0.09). Maximum insulin response following glucose ingestion relates to cardiac mitochondrial efficiency and oxidative capacity, while insulin resistance might affect cardiac energy metabolism. These data suggest a pathogenic role of hyperinsulinemia as well as beta cell failure in diabetes-related heart failure.
Disclosure
E. Zweck: None. D. Scheiber: None. S. Albermann: None. J. Borger: None. T. Jelenik: None. D. Pesta: None. P. Horn: None. U. Boeken: None. P. AKhyari: Research Support; Self; Abbott, Edwards Lifesciences Corporation, Medtronic. M. Kelm: None. M. Roden: Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Poxel SA, Servier. Board Member; Self; Eli Lilly and Company. Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi. Speaker's Bureau; Self; Novo Nordisk Inc. R. Westenfeld: None. J. Szendroedi: None.
Funding
German Research Foundation (CRC1116); Heinrich-Heine University
Nuclear factor kappa-B (NFkB) has been postulated to induce cardiac fibrosis and dysfunction in heart failure and triggers inflammatory pathways. NFkB can be induced by damaged mitochondria. Its ...association with myocardial mitochondrial respiratory function in non-ischemic diabetes-related heart failure in humans is yet unclear. We hypothesized that human ventricular myocardial NFkB expression (i) is increased by type 2 diabetes mellitus (T2DM), and (ii) relates to reduced myocardial mitochondrial respiration. Heart transplant recipients with or without T2DM (as determined by oral glucose tolerance test), about to undergo post-transplant surveillance endomyocardial biopsies, were included, if they had received hearts from donors without T2DM. Thus, time since transplantation equaled diabetes-exposure of the transplanted hearts (2.9±2.4 years). We assessed normalized NFkB p105 subunit (NFkB1) mRNA expression using real-time PCR and myocardial mitochondrial respiration using high-resolution respirometry. Study participants (T2DM: n=17, Non-DM: n=32) had no histological signs of allograft rejection, heart failure (left ventricular ejection fraction 66.2±6.5%) or coronary artery disease. Age and sex distribution were similar between Non-DM and T2DM (p=0.50; p=0.40, respectively). Myocardial NFkB1 expression was 60% higher in T2DM than in Non-DM (0.28 0.21-0.44 vs. 0.45 0.29-0.71 arbitrary units, p<0.05). Fasting blood glucose, but not fasting free fatty acids (p=0.55), related to myocardial NFkB1 mRNA expression (r=0.31; p<0.05). NFkB1 expression related inversely to state 3 respiration of fatty acids and glutamate (r=-0.33; p<0.05), suggesting impaired complex I-related respiration. Our findings support the concept of a key role of NFkB in diabetes-related heart failure via altered myocardial respiratory function in humans. NFkB1 might therefore serve as a future target for treating diabetes-related heart disease.
Disclosure
E. Zweck: None. D. Scheiber: None. T. Jelenik: Employee; Self; Boehringer Ingelheim Pharmaceuticals, Inc. P. Horn: None. D. Pesta: None. D. Lassner: None. H. Schultheiss: None. U. Boeken: None. P. AKhyari: None. A. Lichtenberg: None. M. Kelm: None. M. Roden: Advisory Panel; Self; Servier. Board Member; Self; Poxel SA. Consultant; Self; Eli Lilly and Company, Gilead Sciences, Inc., ProSciento, TARGET PharmaSolutions. Research Support; Self; Boehringer Ingelheim International GmbH, Novartis Pharma K.K., Sanofi US. Speaker’s Bureau; Self; Novo Nordisk A/S. R. Westenfeld: None. J. Szendroedi: None.
Funding
German Research Council (SFB1116); Heinrich-Heine University
Impaired energy metabolism is a possible mechanism that contributes to insulin resistance and ectopic fat storage.
We examined whether meal ingestion differently affects hepatic phosphorus ...metabolites in insulin-sensitive and insulin-resistant humans.
Young, lean, insulin-sensitive humans (CONs) mean ± SD body mass index (BMI; in kg/m(2)): 23.2 ± 1.5; insulin-resistant, glucose-tolerant, obese humans (OBEs) (BMI: 34.3 ± 1.7); and type 2 diabetes patients (T2Ds) (BMI: 32.0 ± 2.4) were studied (n = 10/group). T2Ds (61 ± 7 y old) were older (P < 0.001) than were OBEs (31 ± 7 y old) and CONs (28 ± 3 y old). We quantified hepatic γATP, inorganic phosphate (Pi), and the fat content hepatocellular lipids (HCLs) with the use of (31)P/(1)H magnetic resonance spectroscopy before and at 160 and 240 min after a high-caloric mixed meal. In a subset of volunteers, we measured the skeletal muscle oxidative capacity with the use of high-resolution respirometry. Whole-body insulin sensitivity (M value) was assessed with the use of hyperinsulinemic-euglycemic clamps.
OBEs and T2Ds were similarly insulin resistant (M value: 3.5 ± 1.4 and 1.9 ± 2.5 mg · kg(-1) · min(-1), respectively; P = 0.9) and had 12-fold (P = 0.01) and 17-fold (P = 0.002) higher HCLs, respectively, than those of lean persons. Despite comparable fasting hepatic γATP concentrations, the maximum postprandial increase of γATP was 6-fold higher in OBEs (0.7 ± 0.2 mmol/L; P = 0.03) but only tended to be higher in T2Ds (0.6 ± 0.2 mmol/L; P = 0.09) than in CONs (0.1 ± 0.1 mmol/L). However, in the fasted state, muscle complex I activity was 53% lower (P = 0.01) in T2Ds but not in OBEs (P = 0.15) than in CONs.
Young, obese, nondiabetic humans exhibit augmented postprandial hepatic energy metabolism, whereas elderly T2Ds have impaired fasting muscle energy metabolism. These findings support the concept of a differential and tissue-specific regulation of energy metabolism, which can occur independently of insulin resistance. This trial was registered at clinicaltrials.gov as NCT01229059.
Abstract
Context/Objective
Impaired adipose tissue (AT) function might induce recent-onset type 2 diabetes (T2D). Understanding AT energy metabolism could yield novel targets for the treatment of ...T2D.
Design/Patients
Male patients with recently-diagnosed T2D and healthy male controls (CON) of similar abdominal subcutaneous AT (SAT)-thickness, fat mass, and age (n = 14 each), underwent hyperinsulinemic-euglycemic clamps with 6,6-2H2glucose and indirect calorimetry. We assessed mitochondrial efficiency (coupling: state 3/4o; proton leak: state 4o/u) via high-resolution respirometry in superficial (SSAT) and deep (DSAT) SAT-biopsies, hepatocellular lipids (HCL) and fat mass by proton-magnetic-resonance-spectroscopy and -imaging.
Results
T2D patients (known diabetes duration: 2.5 0.1; 5.0 years) had 43%, 44%, and 63% lower muscle insulin sensitivity (IS), metabolic flexibility (P < 0.01) and AT IS (P < 0.05), 73% and 31% higher HCL (P < 0.05), and DSAT-thickness (P < 0.001), but similar hepatic IS compared with CON. Mitochondrial efficiency was ~22% lower in SSAT and DSAT of T2D patients (P < 0.001) and ~8% lower in SSAT vs DSAT (P < 0.05). In both fat depots, mitochondrial coupling correlated positively with muscle IS and metabolic flexibility (r ≥ 0.40; P < 0.05), proton leak correlated positively (r ≥ 0.51; P < 0.01) and oxidative capacity negatively (r ≤ −0.47; P < 0.05) with fasting free fatty acids (FFA). Metabolic flexibility correlated positively with SAT-oxidative capacity (r ≥ 0.48; P < 0.05) and negatively with DSAT-thickness (r = −0.48; P < 0.05). DSAT-thickness correlated negatively with mitochondrial coupling in both depots (r ≤ −0.50; P < 0.01) and muscle IS (r = −0.59; P < 0.01), positively with FFA during clamp (r = 0.63; P < 0.001) and HCL (r = 0.49; P < 0.01).
Conclusions
Impaired mitochondrial function, insulin resistance, and DSAT expansion are AT abnormalities in recent-onset T2D that might promote whole-body insulin resistance and increased substrate flux to the liver.
Although insulin resistance is known to underlie type 2 diabetes, its role in the development of type 1 diabetes has been gaining increasing interest. In a model of type 1 diabetes, the nonobese ...diabetic (NOD) mouse, we found that insulin resistance driven by lipid- and glucose-independent mechanisms is already present in the liver of prediabetic mice. Hepatic insulin resistance is associated with a transient rise in mitochondrial respiration followed by increased production of lipid peroxides and c-Jun N-terminal kinase activity. At the onset of diabetes, increased adipose tissue lipolysis promotes myocellular diacylglycerol accumulation. This is paralleled by increased myocellular protein kinase C θ activity and serum fetuin A levels. Muscle mitochondrial oxidative capacity is unchanged at the onset but decreases at later stages of diabetes. In conclusion, hepatic and muscle insulin resistance manifest at different stages and involve distinct cellular mechanisms during the development of diabetes in the NOD mouse.
Type 2 Diabetes Mellitus (T2DM) is related to increased cardiac morbidity and mortality. Underlying mechanisms are yet unclear. Recent studies detected mitochondrial abnormalities in atrial tissue ...acquired during open-heart surgery of T2DM patients suffering from ischemic or valvular heart disease. We hypothesized that mitochondrial capacity and coupling efficiency are reduced in ventricular tissue of humans with T2DM and normal heart function. High resolution respirometry was performed in transcatheter ventricle biopsies of 29 healthy heart transplant recipients with normal left ventricular ejection fraction (64±8%) and no allograft rejection. We assessed oral glucose insulin sensitivity (OGIS) and redox potential (ORP) reflecting systemic oxidative stress. Glucose tolerant humans (CON; n=16) and T2DM (n=13) had comparable age (54±14 vs. 58±12 years; p=0.45), sex (81% vs. 85% male) and time since transplantation (26±24 vs. 25±26 months; p=0.93), while body mass index was higher in T2DM (25.0±2.9 vs. 28.1±4.9 kg/m2; p<0.05). State 3 respiration on octanoyl-carnitine was 20% lower in T2DM (101±25 vs. 81±20 pmol/(s*mg); p<0.05). Lipid-linked respiration related negatively to HbA1C (r=-0.45; p<0.05) and fasting blood glucose levels (r=-0.41; p<0.05), but positively to OGIS (r=0.56; p<0.05). Respiratory control ratios (RCR) on lipids were 21% lower in T2DM compared to CON (1.6±0.4 vs. 1.2±0.3; p<0.05) and correlated negatively with HbA1C (r=-0.44; p<0.05). Substrates of mitochondrial complex I and II induced 22% lower RCR in T2DM (2.7±0.8 vs. 2.1±0.5; p<0.05). ORP was 24% higher in T2DM (127±23 vs. 157±25 mV; p<0.01). Ventricular myocardium of T2DM and insulin resistant humans shows diminished mitochondrial oxidative capacity and coupling efficiency for lipid and glycolytic substrates which is related to hyperglycemia and oxidative stress. This might indicate targets for treatment and prevention of T2DM-related heart failure.
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