Regional analysis of inflammation and contractile function in reperfused acute myocardial infarction by in vivo 19F cardiovascular magnetic resonance in pigs.

Inflammatory cell infiltration is central to healing after acute myocardial infarction (AMI). The relation of regional inflammation to edema, infarct size (IS), microvascular obstruction (MVO), intramyocardial hemorrhage (IMH), and regional and global LV function is not clear. Here we noninvasively characterized regional inflammation and contractile function in reperfused AMI in pigs using fluorine (19F) cardiovascular magnetic resonance (CMR). Adult anesthetized pigs underwent left anterior descending coronary artery instrumentation with either 90 min occlusion (n = 17) or without occlusion (sham, n = 5). After 3 days, in surviving animals a perfluorooctyl bromide nanoemulsion was infused intravenously to label monocytes/macrophages. At day 6, in vivo 1H-CMR was performed with cine, T2 and T2* weighted imaging, T2 and T1 mapping, perfusion and late gadolinium enhancement followed by 19F-CMR. Pigs were sacrificed for subsequent ex vivo scans and histology. Edema extent was 35 ± 8% and IS was 22 ± 6% of LV mass. Six of ten surviving AMI animals displayed both MVO and IMH (3.3 ± 1.6% and 1.9 ± 0.8% of LV mass). The 19F signal, reflecting the presence and density of monocytes/macrophages, was consistently smaller than edema volume or IS and not apparent in remote areas. The 19F signal-to-noise ratio (SNR) > 8 in the infarct border zone was associated with impaired remote systolic wall thickening. A whole heart value of 19F integral (19F SNR × milliliter) > 200 was related to initial LV remodeling independently of edema, IS, MVO, and IMH. Thus, 19F-CMR quantitatively characterizes regional inflammation after AMI and its relation to edema, IS, MVO, IMH and regional and global LV function and remodeling.

Meal-derived glucagon responses are related to lower hepatic phosphate concentrations in obesity and type 2 diabetes.

AIM: Type 2 diabetes (T2D) alters glucagon, glucagon-like peptide (GLP)-1, glucose-dependent insulinotropic polypeptide (GIP) and hepatic energy metabolism, yet the possible relationships remain unclear. METHODS: In this observational study, lean insulin-sensitive control subjects (BMI: 23.2±1.5kg/m2), age-matched insulin-resistant obese subjects (BMI: 34.3±1.7kg/m2) and similarly obese elderly T2D patients (BMI: 32.0±2.4kg/m2) underwent mixed-meal tolerance tests (MMTTs), and assessment of hepatic γATP, inorganic phosphate (Pi) and lipids using 31P/1H magnetic resonance spectroscopy. Meal-induced secretion of glucagon and incretins was calculated from incremental areas under the concentration-time curves (iAUCs). Peripheral and adipose tissue insulin sensitivity were assessed from time courses of circulating glucose, insulin and free fatty acids. RESULTS: MMTT-derived peripheral insulin sensitivity was lowest in T2D patients (P<0.001), while glucagon concentrations were comparable across all three groups. At 260min, GLP-1 was lower in T2D patients than in controls, whereas GIP was lowest in obese individuals. Fasting glucagon concentrations correlated positively with fasting (r=0.60) and postprandial hepatocellular lipid levels (160min: r=0.51, 240min: r=0.59), and negatively with adipose tissue insulin sensitivity (r=-0.73). Higher meal-induced glucagon release (iAUC0-260min) correlated with lower fasting (r=-0.62) and postprandial Pi levels (160min: r=-0.43, 240min: r=-0.42; all P<0.05). Higher meal-induced release of GIP (iAUC0-260min) correlated positively with fasting (r=0.54) and postprandial serum triglyceride concentrations (iAUC0-260min, r=0.54; all P<0.01). CONCLUSION: Correlations between fasting glucagon and hepatic lipids and between meal-induced glucagon and hepatic Pi suggest a role for glucagon in hepatic energy metabolism.

Inverse association of insulin antibody levels with insulin sensitivity in adults with Type 1 diabetes.

AIMS: Insulin resistance may contribute to the pathogenesis of autoimmune-mediated diabetes. Antibodies against ß-cell-associated molecules, comprising islet cell antigen (ICA), glutamic acid decarboxylase (GAD) and insulin, characterize the autoimmune process. Because the link between insulin resistance and autoimmunity might be relevant for disease progression and treatment, we hypothesized that insulin resistance associates positively with ß-cell-directed antibodies in newly diagnosed Type 1 diabetes. METHODS: Within the German Diabetes Study, an observational study including adults with newly diagnosed diabetes, 142 adults [84 men, 58 women; age 33.1 (26.4, 41.9) years; diabetes duration 6.3 (4.2, 9.1) months] positive for at least one antibody against ICA, GAD or insulin underwent hyperinsulinaemic-euglycaemic clamp tests to assess insulin sensitivity (M-value) in a cross-sectional setting. RESULTS: Insulin-directed antibodies were inversely correlated with M-values (ß = -0.039). Albeit not strong, the association persisted after adjustment for age, sex and BMI, and even after further adjustment for confounders reflecting exposure to exogenous insulin and residual ß-cell secretory capacity. Correlation network-based analyses revealed a complex interaction between levels of fasting insulin and of insulin antibodies with respect to their relationship with the M-value. GAD- or ICA-directed antibodies did not correlate with insulin sensitivity. CONCLUSIONS: In adults with recent-onset Type 1 diabetes expressing at least one ß-cell-directed antibody, insulin sensitivity is inversely related to insulin antibody titres, but not to other autoantibodies. Our finding may allow for the identification of insulin resistance in adults with high levels of insulin antibodies.

Circulating adiponectin concentration is inversely associated with glucose tolerance and insulin secretion in people with newly diagnosed diabetes.

AIMS: To examine the hypothesis that changes in serum adiponectin concentration inversely relate to changes in glucose tolerance and ß-cell function already during the early stage of disease progression in recently diagnosed Type 1 and Type 2 diabetes mellitus. METHODS: Participants in the prospective observational German Diabetes Study (Type 2 diabetes, n = 94; Type 1 diabetes, n = 42) underwent i.v. glucose tolerance and glucagon stimulation testing to assess pre-hepatic ß-cell function, glucose tolerance index and C-peptide secretion within the first year of diabetes diagnosis and 2 years later. Associations of changes in serum concentrations of total adiponectin, high-molecular-weight adiponectin and their ratio with changes in the aforementioned metabolic variables were calculated using linear regression. RESULTS: Among people with Type 2 diabetes, 2-year increases in high-molecular-weight adiponectin and in high-molecular-weight/total adiponectin ratio were associated with decreases in glucose tolerance index of 0.1%/min (P = 0.020) and 0.8%/min (P = 0.013), respectively. Increases in high-molecular-weight/total adiponectin ratio were related to decreases in acute C-peptide secretion of 54.6% (P = 0.020). Among people with Type 1 diabetes, 2-year increases in total adiponectin were associated with 2-year decreases in acute C-peptide secretion of 56.2% (P = 0.035). CONCLUSIONS: Increases in adiponectin concentrations in the first 2 years after diagnosis were related to a worsening of acute insulin secretion and glucose tolerance index in Type 1 and Type 2 diabetes. (Clinical Trials Registry no.: NCT01055093).

The Impact of Dietary Factors on Glycemic Control, Insulin Sensitivity and Secretion in the First Years after Diagnosis of Diabetes.

BACKGROUND: Dietary factors play an important role in the prevention of diabetes mellitus. We tested the hypothesis that dietary factors related to diabetes onset also associate with its progression, i. e., early time courses of insulin sensitivity and secretion in both type 1 and type 2 diabetes. METHODS: In a prospective observational study, well-controlled recent-onset diabetes patients (n=127) underwent detailed metabolic characterization within the first year after diagnosis. A follow-up was conducted 2 years after the first examination. Insulin secretion and sensitivity were assessed by intravenous glucose tolerance testing. Baseline food consumption was analyzed by a food propensity questionnaire. Multivariate linear regression analysis was used to assess associations between consumption frequencies at baseline with metabolic changes during the first 2 years. RESULTS: Within the first 2 years, metabolic control did not change in patients with type 1 and type 2 diabetes on average. In type 1 diabetes, an increased consumption frequency of refined grains by one time/day at baseline associated with higher HbA1c by 0.60% (95% CI: 0.04; 1.16), P=0.04 after 2 years compared to baseline. In type 2 diabetes, an increased consumption frequency of meat/meat products by one time/day at baseline associated with lower beta-cell adaptation index (-7.25% (95% CI: -13.16; -0.93), P=0.03) after adjustment for age, sex, BMI, and changes of BMI and glucose-lowering medication. CONCLUSION: Dietary factors associate with the initial course of diabetes. Reduced consumption of refined grains in type 1 diabetes and of meat products in type 2 diabetes may contribute to preservation of insulin secretion and sensitivity.

Impaired insulin stimulation of muscular ATP production in patients with type 1 diabetes.

OBJECTIVE: in type 2 diabetic patients and their first-degree relatives, insulin resistance (IR) is associated with impairment of insulin-stimulated myocellular glucose-6-phosphate (g6p) and unidirectional flux through ATP synthase (fATP), suggesting the presence of inherited abnormal mitochondrial oxidative fitness. We hypothesized that patients with long-standing type 1 diabetes may also exhibit insulin resistance as well as lower fATP. DESIGN: this single-centre trial was registered at ClinicalTrials.gov (NCT00481598). SUBJECTS: we included eight nonobese type 1 diabetic patients (mean diabetes duration: 17 years) with near-target glycaemic control [haemoglobin A1c (HbA1c): 6.8 ± 0.4%] during treatment with continuous subcutaneous insulin infusion pumps and eight healthy volunteers (HbA1c: 5.4 ± 0.2%) of comparable age, body mass and level of physical activity. OUTCOME MEASURES: myocellular fATP, g6p and intramyocellular lipid content (IMCL) were measured with (1) H/(31) P magnetic resonance spectroscopy during fasting and hyperinsulinaemic-euglycaemic clamp tests. RESULTS: fasting fATP, g6p and IMCL did not differ between groups. During stimulation by insulin, type 1 diabetic patients exhibited approximately 50% (P < 0.001) lower whole-body glucose disposal along with approximately 42% (P = 0.003) lower intramyocellular g6p and approximately25% (P = 0.024) lower fATP. Insulin-stimulated fATP correlated positively with whole-body insulin sensitivity (R = 0.706, P = 0.002) and negatively with HbA1c (R = -0.675, P = 0.004). CONCLUSIONS: despite documented near-target glycaemic control for 1 year, nonobese patients with long-standing type 1 diabetes can exhibit insulin resistance. This associates with lower insulin-stimulated flux through muscular ATP synthase which could result from glucose toxicity.

A European evidence-based guideline for the prevention of type 2 diabetes.

BACKGROUND: The prevalence and socioeconomic burden of type 2 diabetes (T2DM) and associated co-morbidities are rising worldwide. AIMS: This guideline provides evidence-based recommendations for preventing T2DM. METHODS: A European multidisciplinary consortium systematically reviewed the evidence on the effectiveness of screening and interventions for T2DM prevention using SIGN criteria. RESULTS: Obesity and sedentary lifestyle are the main modifiable risk factors. Age and ethnicity are non-modifiable risk factors. Case-finding should follow a step-wise procedure using risk questionnaires and oral glucose tolerance testing. Persons with impaired glucose tolerance and/or fasting glucose are at high-risk and should be prioritized for intensive intervention. Interventions supporting lifestyle changes delay the onset of T2DM in high-risk adults (number-needed-to-treat: 6.4 over 1.8-4.6 years). These should be supported by inter-sectoral strategies that create health promoting environments. Sustained body weight reduction by >or= 5 % lowers risk. Currently metformin, acarbose and orlistat can be considered as second-line prevention options. The population approach should use organized measures to raise awareness and change lifestyle with specific approaches for adolescents, minorities and disadvantaged people. Interventions promoting lifestyle changes are more effective if they target both diet and physical activity, mobilize social support, involve the planned use of established behaviour change techniques, and provide frequent contacts. Cost-effectiveness analysis should take a societal perspective. CONCLUSIONS: Prevention using lifestyle modifications in high-risk individuals is cost-effective and should be embedded in evaluated models of care. Effective prevention plans are predicated upon sustained government initiatives comprising advocacy, community support, fiscal and legislative changes, private sector engagement and continuous media communication.

Mitochondrial fitness and insulin sensitivity in humans.

Human mitochondria can be studied either in biopsies or by measuring flux through ATP synthase and phosphocreatine recovery using magnetic resonance spectroscopy. Myocellular ATP production (flux through ATP synthase [fATP]) increases by up to 90% during 8 h of insulin stimulation. Fasting mitochondrial function is 14-40% lower than in controls in the presence of insulin resistance, as seen in those with type 2 diabetes, their insulin-resistant relatives or the obese. Insulin-stimulated fATP is abolished in insulin-resistant relatives and patients with type 2 diabetes, and patients frequently show decreased mitochondrial size/density. Age, fat mass, physical activity, plasma NEFA and glucose all correlate negatively with mitochondrial function, but it is for methodological reasons difficult to determine whether reduced mitochondrial content or function account for reduced ATP production in insulin resistance. Experimental plasma NEFA elevation appears to inhibit mitochondrial function by interfering with the metabolic actions of insulin, which might explain impaired mitochondrial function in obesity. Alternatively, primary mitochondrial abnormalities, as seen in those with inherited risk of type 2 diabetes, could decrease lipid oxidation, thereby raising circulating and intracellular NEFA levels. In type 2 diabetes, chronic hyperglycaemia and dyslipidaemia could first diminish the function, and subsequently reduce the size or density of mitochondria via oxidative stress and apoptosis. Many questions remain unsolved, including (1) which mechanisms regulate mitochondrial adaptation to nutrient overload; (2) what factors control the expression of genes encoding mitochondrial proteins and other signals involved in mitochondrial biogenesis; (3) which geno/phenotypes are associated with both insulin resistance and mitochondrial abnormalities; and (4) which are the most promising targets for improving mitochondrial fitness in insulin resistance?

Three-dimensional high-resolution magnetic resonance spectroscopic imaging for absolute quantification of 31P metabolites in human liver.

Liver dysfunction correlates with alterations of intracellular concentrations of (31)P metabolites. Localization and absolute quantification should help to trace regional hepatic metabolism. An improved protocol for the absolute quantification of (31)P metabolites in vivo in human liver was developed by employing three-dimensional (3D) k-space weighted spectroscopic imaging (MRSI) with B(1)-insensitive adiabatic excitation. The protocol allowed for high spatial resolution of 17.8 +/- 0.22 cm(3) in 34 min at 3 T. No pulse adjustment prior to MRSI measurement was necessary due to adiabatic excitation. The protocol geometry was identical for all measurements so that one calibration data set, acquired from phantom replacement measurement, was applied for all quantifications. The protocol was tested in 10 young, healthy volunteers, for whom 57 +/- 7 spectra were quantified. Concentrations per liter of liver volume (reproducibilities) were 2.24 +/- 0.10 mmol/L (1.8%) for phosphomonoesters (PME), 1.37 +/- 0.07 mmol/L (7.9%) for inorganic phosphate (Pi), 11.40 +/- 0.96 mmol/L (2.9%) for phosphodiesters (PDE), and 2.14 +/- 0.10 mmol/L (1.6%) for adenosine triphosphate (ATP), respectively. Taken together, this approach provides fast, simple, and reproducible high-resolution absolute quantification and detailed mapping of the spatial distribution of hepatic (31)P metabolites. This method allows for examination of regional deviations of energy metabolism in human liver diseases.

Cartilage biomarkers in hemodialysis patients and the effect of beta2-microglobulin on articular chondrocytes.

OBJECTIVE: Dialysis-related amyloidosis (DRA) is a severe complication of maintenance hemodialysis (HD). Given the predominant deposition of beta(2)-microglobulin (beta2m) fibrils on articular cartilage in early DRA, we investigated the significance of beta2m and its relationship to distinct cartilage biomarkers in early DRA diagnosis in HD patients. Furthermore, we assessed the effects of beta2m on articular chondrocytes in vitro. METHODS: Serum samples from 133 patients were collected before and after HD. Type II collagen cleavage product (C2C), procollagen II c-propeptide (CPII), aggrecan chondroitin sulfate 846 epitope (CS-486) and cartilage oligomeric matrix protein (COMP) levels were determined by enzyme-linked immunosorbent assay. Primary bovine articular chondrocytes were cultured as monolayers and incubated with beta2m at 1.5mg/l and 20mg/l. Cartilage glucosaminoglycan synthesis was measured by [(35)S]sulfate incorporation. mRNA expression of interleukin (IL)-1beta, matrix metalloproteinases (MMPs)-3 and -9 was measured by reverse-transcriptase polymerase chain reaction (RT-PCR). RESULTS: Incubation with beta2m at 20mg/l significantly decreased matrix biosynthesis. PCR analysis revealed an increase of IL-1beta, as well as MMPs-3 and -9 on the mRNA level. C2C/CPII, CS-486 and COMP levels were increased only in a subset of patients without a significant correlation with beta2m concentrations. A subgroup analysis elucidated an increase in type II collagen degradation during the first years of HD, as shown by the elevation of C2C/CPII ratio. CONCLUSION: beta2m exerted anti-anabolic effects on articular chondrocytes in vitro and might be involved in cartilage degradation in HD patients. beta2m serum levels, however, did not reflect cartilage degradation in DRA. The assessment of C2C/CPII, CS-486 or COMP concentrations apparently has minor relevance in DRA diagnosis in HD patients. However, the increased type II collagen breakdown within 5 years after HD onset possibly mirrors the early stages of DRA. Thus, the C2C/CPII ratio could be employed in longitudinal studies, since it may reflect a risk for DRA related arthropathy development in a subset of patients.

Quantitative ATP synthesis in human liver measured by localized 31P spectroscopy using the magnetization transfer experiment.

The liver plays a central role in intermediate metabolism. Accumulation of liver fat (steatosis) predisposes to various liver diseases. Steatosis and abnormal muscle energy metabolism are found in insulin-resistant and type-2 diabetic states. To examine hepatic energy metabolism, we measured hepatocellular lipid content, using proton MRS, and rates of hepatic ATP synthesis in vivo, using the 31P magnetization transfer experiment. A suitable localization scheme was developed and applied to the measurements of longitudinal relaxation times (T1) in six healthy volunteers and the ATP-synthesis experiment in nine healthy volunteers. Liver 31P spectra were modelled and quantified successfully using a time domain fit and the AMARES (advanced method for accurate, robust and efficient spectral fitting of MRS data with use of prior knowledge) algorithm describing the essential components of the dataset. The measured T1 relaxation times are comparable to values reported previously at lower field strengths. All nine subjects in whom saturation transfer was measured had low hepatocellular lipid content (1.5 +/- 0.2% MR signal; mean +/- SEM). The exchange rate constant (k) obtained was 0.30 +/- 0.02 s(-1), and the rate of ATP synthesis was 29.5 +/- 1.8 mM/min. The measured rate of ATP synthesis is about three times higher than in human skeletal muscle and human visual cortex, but only about half of that measured in perfused rat liver. In conclusion, 31P MRS at 3 T provides sufficient sensitivity to detect magnetization transfer effects and can therefore be used to assess ATP synthesis in human liver.