Periodontitis, Dental Procedures, and Young-Onset Cryptogenic Stroke

Periodontitis is associated with an increased risk of ischemic stroke, and the risk may be particularly high among young people with unexplained stroke etiology. Thus, we investigated in a case-control study whether periodontitis or recent invasive dental treatments are associated with young-onset cryptogenic ischemic stroke (CIS). We enrolled participants from a multicenter case-control SECRETO study including adults aged 18 to 49 y presenting with an imaging-positive first-ever CIS and stroke-free age- and sex-matched controls. Thorough clinical and radiographic oral examination was performed. Furthermore, we measured serum lipopolysaccharide (LPS) and lipotechoic acid (LTA) levels. Multivariate conditional regression models were adjusted for stroke risk factors, regular dentist visits, and patent foramen ovale (PFO) status. We enrolled 146 case-control pairs (median age 41.9 y; 58.2% males). Periodontitis was diagnosed in 27.5% of CIS patients and 20.1% of controls (P < 0.001). In the fully adjusted models, CIS was associated with high periodontal inflammation burden (odds ratio [OR], 95% confidence interval) with an OR of 10.48 (3.18-34.5) and severe periodontitis with an OR of 7.48 (1.24-44.9). Stroke severity increased with the severity of periodontitis, having an OR of 6.43 (1.87-23.0) in stage III to IV, grade C. Invasive dental treatments performed within 3 mo prestroke were associated with CIS, with an OR of 2.54 (1.01-6.39). Association between CIS and invasive dental treatments was especially strong among those with PFO showing an OR of 6.26 (1.72-40.2). LPS/LTA did not differ between CIS patients and controls but displayed an increasing trend with periodontitis severity. Periodontitis and recent invasive dental procedures were associated with CIS after controlling for multiple confounders. However, the role of bacteremia as a mediator of this risk was not confirmed.

Bone marrow metabolism is affected by body weight and response to exercise training varies according to anatomical location

AIM

High body weight is a protective factor against osteoporosis, but obesity also suppresses bone metabolism and whole-body insulin sensitivity. However, the impact of body weight and regular training on bone marrow (BM) glucose metabolism is unclear. We studied the effects of regular exercise training on bone and BM metabolism in monozygotic twin pairs discordant for body weight.

METHODS

We recruited 12 monozygotic twin pairs (mean ± SD age 40.4 ± 4.5 years; body mass index 32.9 ± 7.6, mean difference between co-twins 7.6 kg/m2 ; eight female pairs). Ten pairs completed the 6-month long training intervention. We measured lumbar vertebral and femoral BM insulin-stimulated glucose uptake (GU) using 18 F-FDG positron emission tomography, lumbar spine bone mineral density and bone turnover markers.

RESULTS

At baseline, heavier co-twins had higher lumbar vertebral BM GU (p < .001) and lower bone turnover markers (all p < .01) compared with leaner co-twins but there was no significant difference in femoral BM GU, or bone mineral density. Training improved whole-body insulin sensitivity, aerobic capacity (both p < .05) and femoral BM GU (p = .008). The training response in lumbar vertebral BM GU was different between the groups (time × group, p = .02), as GU tended to decrease in heavier co-twins (p = .06) while there was no change in leaner co-twins.

CONCLUSIONS

In this study, regular exercise training increases femoral BM GU regardless of weight and genetics. Interestingly, lumbar vertebral BM GU is higher in participants with higher body weight, and training counteracts this effect in heavier co-twins even without reduction in weight. These data suggest that BM metabolism is altered by physical activity.

24-hour ambulatory blood pressure and cryptogenic ischemic stroke in young adults

BACKGROUND

In young patients, up to 40% of ischemic strokes remain cryptogenic despite modern-day diagnostic work-up. There are limited data on blood pressure (BP) behavior in these patients. Thus, we aimed to compare ambulatory blood pressure (ABP) profiles between young patients with a recent cryptogenic ischemic stroke (CIS) and stroke-free controls.

PATIENTS AND METHODS

In this substudy of the international multicenter case-control study SECRETO (NCT01934725), 24-hour ambulatory blood pressure monitoring (ABPM) was performed in consecutive 18-49-year-old CIS patients and stroke-free controls. The inclusion criteria were met by 132 patients (median age, 41.9 years; 56.1% males) and 106 controls (41.9 years; 56.6% males). We assessed not only 24-hour, daytime, and nighttime ABP but also hypertension phenotypes and nocturnal dipping status.

RESULTS

24-hour and daytime ABP were higher among controls. After adjusting for relevant confounders, a non-dipping pattern of diastolic blood pressure (DBP) was associated with CIS in the entire sample (odds ratio, 3.85; 95% confidence interval, 1.20-12.42), in participants without antihypertensives (4.86; 1.07-22.02), and in participants without a patent foramen ovale (PFO) (7.37; 1.47-36.81). After excluding patients in the first tertile of the delay between the stroke and ABPM, a non-dipping pattern of DBP was not associated with CIS, but a non-dipping pattern of both systolic BP and DBP was (4.85; 1.37-17.10). In participants with a PFO and in those without hypertension by any definition, no associations between non-dipping patterns of BP and CIS emerged.

CONCLUSIONS

Non-dipping patterns of BP were associated with CIS in the absence of a PFO but not in the absence of hypertension. This may reflect differing pathophysiology underlying CIS in patients with versus without a PFO. Due to limitations of the study, results regarding absolute ABP levels should be interpreted with caution.Key MessagesNocturnal non-dipping patterns of blood pressure were associated with cryptogenic ischemic stroke except in participants with a patent foramen ovale and in those without hypertension by any definition, which may indicate differing pathophysiology underlying cryptogenic ischemic stroke in patients with and without a patent foramen ovale.It might be reasonable to include ambulatory blood pressure monitoring in the diagnostic work-up for young patients with ischemic stroke to detect not only the absolute ambulatory blood pressure levels but also their blood pressure behavior.

Systemic cross-talk between brain, gut, and peripheral tissues in glucose homeostasis: effects of exercise training (CROSSYS). Exercise training intervention in monozygotic twins discordant for body weight

BACKGROUND

Obesity and physical inactivity are major global public health concerns, both of which increase the risk of insulin resistance and type 2 diabetes. Regulation of glucose homeostasis involves cross-talk between the central nervous system, peripheral tissues, and gut microbiota, and is affected by genetics. Systemic cross-talk between brain, gut, and peripheral tissues in glucose homeostasis: effects of exercise training (CROSSYS) aims to gain new systems-level understanding of the central metabolism in human body, and how exercise training affects this cross-talk.

METHODS

CROSSYS is an exercise training intervention, in which participants are monozygotic twins from pairs discordant for body mass index (BMI) and within a pair at least the other is overweight. Twins are recruited from three population-based longitudinal Finnish twin studies, including twins born in 1983-1987, 1975-1979, and 1945-1958. The participants undergo 6-month-long exercise intervention period, exercising four times a week (including endurance, strength, and high-intensity training). Before and after the exercise intervention, comprehensive measurements are performed in Turku PET Centre, Turku, Finland. The measurements include: two positron emission tomography studies (insulin-stimulated whole-body and tissue-specific glucose uptake and neuroinflammation), magnetic resonance imaging (brain morphology and function, quantification of body fat masses and organ volumes), magnetic resonance spectroscopy (quantification of fat within heart, pancreas, liver and tibialis anterior muscle), echocardiography, skeletal muscle and adipose tissue biopsies, a neuropsychological test battery as well as biosamples from blood, urine and stool. The participants also perform a maximal exercise capacity test and tests of muscular strength.

DISCUSSION

This study addresses the major public health problems related to modern lifestyle, obesity, and physical inactivity. An eminent strength of this project is the possibility to study monozygotic twin pairs that share the genome at the sequence level but are discordant for BMI that is a risk factor for metabolic impairments such as insulin resistance. Thus, this exercise training intervention elucidates the effects of obesity on metabolism and whether regular exercise training is able to reverse obesity-related impairments in metabolism in the absence of the confounding effects of genetic factors.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT03730610 . Prospectively registered 5 November 2018.

Predicting Skeletal Muscle and Whole-Body Insulin Sensitivity Using NMR-Metabolomic Profiling

PURPOSE

Abnormal lipoprotein and amino acid profiles are associated with insulin resistance and may help to identify this condition. The aim of this study was to create models estimating skeletal muscle and whole-body insulin sensitivity using fasting metabolite profiles and common clinical and laboratory measures.

MATERIAL AND METHODS

The cross-sectional study population included 259 subjects with normal or impaired fasting glucose or type 2 diabetes in whom skeletal muscle and whole-body insulin sensitivity (M-value) were measured during euglycemic hyperinsulinemic clamp. Muscle glucose uptake (GU) was measured directly using [18F]FDG-PET. Serum metabolites were measured using nuclear magnetic resonance (NMR) spectroscopy. We used linear regression to build the models for the muscle GU (Muscle-insulin sensitivity index [ISI]) and M-value (whole-body [WB]-ISI). The models were created and tested using randomly selected training (n = 173) and test groups (n = 86). The models were compared to common fasting indices of insulin sensitivity, homeostatic model assessment-insulin resistance (HOMA-IR) and the revised quantitative insulin sensitivity check index (QUICKI).

RESULTS

WB-ISI had higher correlation with actual M-value than HOMA-IR or revised QUICKI (ρ = 0.83 vs -0.67 and 0.66; P < 0.05 for both comparisons), whereas the correlation of Muscle-ISI with the actual skeletal muscle GU was not significantly stronger than HOMA-IR's or revised QUICKI's (ρ = 0.67 vs -0.58 and 0.59; both nonsignificant) in the test dataset.

CONCLUSION

Muscle-ISI and WB-ISI based on NMR-metabolomics and common laboratory measurements from fasting serum samples and basic anthropometrics are promising rapid and inexpensive tools for determining insulin sensitivity in at-risk individuals.

Reversibility of myocardial metabolism and remodelling in morbidly obese patients 6 months after bariatric surgery

AIMS

To study myocardial substrate uptake, structure and function, before and after bariatric surgery, to clarify the interaction between myocardial metabolism and cardiac remodelling in morbid obesity.

METHODS

We studied 46 obese patients (age 44 ± 10 years, body mass index [BMI] 42 ± 4 kg/m² ), including 18 with type 2 diabetes (T2D) before and 6 months after bariatric surgery and 25 healthy age-matched control group subjects. Myocardial fasting free fatty acid uptake (MFAU) and insulin-stimulated myocardial glucose uptake (MGU) were measured using positron-emission tomography. Myocardial structure and function, and myocardial triglyceride content (MTGC) and intrathoracic fat were measured using magnetic resonance imaging and magnetic resonance spectroscopy.

RESULTS

The morbidly obese study participants, with or without T2D, had cardiac hypertrophy, impaired myocardial function and substrate metabolism compared with the control group. Surgery led to marked weight reduction and remission of T2D in most of the participants. Postoperatively, myocardial function and structure improved and myocardial substrate metabolism normalized. Intrathoracic fat, but not MTGC, was reduced. Before surgery, BMI and MFAU correlated with left ventricular hypertrophy, and BMI, age and intrathoracic fat mass were the main variables associated with cardiac function. The improvement in whole-body insulin sensitivity correlated positively with the increase in MGU and the decrease in MFAU.

CONCLUSIONS

In the present study, obesity and age, rather than myocardial substrate uptake, were the causes of cardiac remodelling in morbidly obese patients with or without T2D. Cardiac remodelling and impaired myocardial substrate metabolism are reversible after surgically induced weight loss and amelioration of T2D.

Elevated Glucose Oxidation, Reduced Insulin Secretion, and a Fatty Heart May Be Protective Adaptions in Ischemic CAD

BACKGROUND

Insulin resistance, β-cell dysfunction, and ectopic fat deposition have been implicated in the pathogenesis of coronary artery disease (CAD) and type 2 diabetes, which is common in CAD patients. We investigated whether CAD is an independent predictor of these metabolic abnormalities and whether this interaction is influenced by superimposed myocardial ischemia.

METHODS AND RESULTS

We studied CAD patients with (n = 8) and without (n = 14) myocardial ischemia and eight non-CAD controls. Insulin sensitivity and secretion and substrate oxidation were measured during fasting and oral glucose tolerance testing. We used magnetic resonance imaging/spectroscopy, positron emission and computerized tomography to characterize CAD, cardiac function, pericardial and abdominal adipose tissue, and myocardial, liver, and pancreatic triglyceride contents. Ischemic CAD was characterized by elevated oxidative glucose metabolism and a proportional decline in β-cell insulin secretion and reduction in lipid oxidation. Cardiac function was preserved in CAD groups, whereas cardiac fat depots were elevated in ischemic CAD compared to non-CAD subjects. Liver and pancreatic fat contents were similar in all groups and related with surrounding adipose masses or systemic insulin sensitivity.

CONCLUSIONS

In ischemic CAD patients, glucose oxidation is enhanced and correlates inversely with insulin secretion. This can be seen as a mechanism to prevent glucose lowering because glucose is required in oxygen-deprived tissues. On the other hand, the accumulation of cardiac triglycerides may be a physiological adaptation to the limited fatty acid oxidative capacity. Our results underscore the urgent need of clinical trials that define the optimal/safest glycemic range in situations of myocardial ischemia.

Mechanistic Insights into Sympathetic Neuronal Regeneration: Multitracer Molecular Imaging of Catecholamine Handling After Cardiac Transplantation

BACKGROUND

Post-transplant reinnervation is a unique model to study sympathetic neuronal regeneration in vivo. The differential role of subcellular mechanisms of catecholamine handling in nerve terminals has not been investigated.

METHODS AND RESULTS

Three different carbon-11-labeled catecholamines were used for positron emission tomography of transport (C-11 m-hydroxyephedrine, HED), vesicular storage (C-11 epinephrine, EPI), and metabolic degradation (C-11 phenylephrine). A 2-day protocol was used, including quantification of myocardial blood flow by N-13 ammonia. Resting myocardial blood flow and EPI, HED and phenylephrine retention were homogeneous in healthy volunteers (n=7). Washout was only observed for phenylephrine (T(1/2) 49±6 min). In nonrejecting, otherwise healthy heart transplant recipients (>1 year after surgery, n=10), resting myocardial blood flow was also homogenous. Regional catecholamine uptake of varying degrees was observed in the anterior left ventricular wall and septum. Overall, 24±19% of left ventricle showed HED uptake levels comparable with healthy volunteers, whereas it was only 8±7% for EPI (P=0.004 versus HED). Phenylephrine washout was not different from healthy volunteers in the area with restored EPI and HED retention (T(1/2) 41±7 min; P>0.05), but was significantly enhanced in the EPI/HED mismatch area (T(1/2) 36±8 min; P=0.008), consistent with inefficient vesicular storage and enhanced metabolic degradation.

CONCLUSIONS

Regeneration of subcellular components of sympathetic nerve terminal function does not occur simultaneously. In the reinnervating transplanted heart, a region with normal catecholamine transport and vesicular storage is surrounded by a borderzone, where transport is already restored but vesicular storage remains inefficient, suggesting that vesicular storage is a more delicate mechanism. This observation may have implications for other pathologies involving cardiac autonomic innervation.

Task-based evaluation of a 4D MAP-RBI-EM image reconstruction method for gated myocardial perfusion SPECT using a human observer study

We evaluated the performance of a new 4D image reconstruction method for improved 4D gated myocardial perfusion (MP) SPECT using a task-based human observer study. We used a realistic 4D NURBS-based Cardiac-Torso (NCAT) phantom that models cardiac beating motion. Half of the population was normal; the other half had a regional hypokinetic wall motion abnormality. Noise-free and noisy projection data with 16 gates/cardiac cycle were generated using an analytical projector that included the effects of attenuation, collimator-detector response, and scatter (ADS), and were reconstructed using the 3D FBP without and 3D OS-EM with ADS corrections followed by different cut-off frequencies of a 4D linear post-filter. A 4D iterative maximum a posteriori rescaled-block (MAP-RBI)-EM image reconstruction method with ADS corrections was also used to reconstruct the projection data using various values of the weighting factor for its prior. The trade-offs between bias and noise were represented by the normalized mean squared error (NMSE) and averaged normalized standard deviation (NSDav), respectively. They were used to select reasonable ranges of the reconstructed images for use in a human observer study. The observers were trained with the simulated cine images and were instructed to rate their confidence on the absence or presence of a motion defect on a continuous scale. We then applied receiver operating characteristic (ROC) analysis and used the area under the ROC curve (AUC) index. The results showed that significant differences in detection performance among the different NMSE-NSDav combinations were found and the optimal trade-off from optimized reconstruction parameters corresponded to a maximum AUC value. The 4D MAP-RBI-EM with ADS correction, which had the best trade-off among the tested reconstruction methods, also had the highest AUC value, resulting in significantly better human observer detection performance when detecting regional myocardial wall motion abnormality. We concluded that the NMSE-NSDav trade-off was shown to agree with observer performance for the detection task of the regional motion abnormality, and the optimized 4D MAP-RBI-EM method with ADS corrections provides significant improvement compared to 3D FBP and 3D OS-EM with ADS corrections in detecting regional myocardial wall motion abnormali in 4D gated MP SPECT.

Systemic metabolic markers and myocardial glucose uptake in type 2 diabetic and coronary artery disease patients treated for 16 weeks with rosiglitazone, a PPARγ agonist

INTRODUCTION

Treatment with rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist, in type 2 diabetic mellitus (T2DM) patients is under scrutiny because it affects adversely cardiovascular outcomes. In T2DM patients, with existing coronary heart disease, short-term treatment with rosiglitazone increases myocardial glucose uptake (MGU). Serum metabolic and lipoprotein subclass changes, which may be associated with this rosiglitazone-induced improvement, are unknown.

METHODS

Patients with both T2DM and coronary heart disease were separated into placebo (n = 26) and treatment (rosiglitazone 4-8 mg; n = 25) groups. After 16 weeks of treatment, serum NMR metabolomics was used to measure circulating low-molecular-weight metabolites and lipoprotein subclasses and lipids that are associated with T2DM before and after the treatment. Significant metabolic measure changes after rosiglitazone treatment were correlated to MGU values assessed with [(18)F]fluorodeoxyglucose positron emission tomography.

RESULTS

Compared to placebo, the treatment significantly increased circulating glutamine and decreased lactate concentrations. Circulating lactate concentrations showed a significant inverse association with MGU after rosiglitazone treatment.

CONCLUSION

In T2DM patients with existing coronary heart disease, short-term rosiglitazone treatment caused minor improvements in metabolism: serum lactate and glutamine concentrations changed, reflecting improvements in insulin sensitivity, and circulating lactate concentrations inversely correlated to increases in myocardial glucose uptake.

Similar patterns of myocardial metabolism and perfusion in patients with type 2 diabetes and heart disease of ischaemic and non-ischaemic origin

AIMS/HYPOTHESIS

Type 2 diabetes and insulin resistance are often associated with the co-occurrence of coronary atherosclerosis and cardiac dysfunction. The aim of this study was to define the independent relationships between left ventricular dysfunction or ischaemia and patterns of myocardial perfusion and metabolism in type 2 diabetes.

METHODS

Twenty-four type 2 diabetic patients--12 with coronary artery disease (CAD) and preserved left ventricular function and 12 with non-ischaemic heart failure (HF)--were enrolled in a cross-sectional study. Positron emission tomography (PET) was used to assess myocardial blood flow (MBF) at rest, after pharmacological stress and under euglycaemic hyperinsulinaemia. Insulin-mediated myocardial glucose disposal was determined with 2-deoxy-2-[(18)F]fluoroglucose PET.

RESULTS

There was no difference in myocardial glucose uptake (MGU) between the healthy myocardium of CAD patients and the dysfunctional myocardium of HF patients. MGU was strongly influenced by levels of systemic insulin resistance in both groups (CAD, r = 0.85, p = 0.005; HF, r = 0.77, p = 0.01). In HF patients, there was an inverse association between MGU and the coronary flow reserve (r = -0.434, p = 0.0115). A similar relationship was observed in non-ischaemic segments of CAD patients. Hyperinsulinaemia increased MBF to a similar extent in the non-ischaemic myocardial of CAD and HF patients.

CONCLUSIONS/INTERPRETATION

In type 2 diabetes, similar metabolic and perfusion patterns can be detected in the non-ischaemic regions of CAD patients with normal cardiac function and in the dysfunctional non-ischaemic myocardium of HF patients. This suggests that insulin resistance, rather than diagnosis of ischaemia or left ventricular dysfunction, affects the metabolism and perfusion features of patients with type 2 diabetes.

Impaired global myocardial flow dynamics despite normal left ventricular function and regional perfusion in chronic kidney disease: a quantitative analysis of clinical 82Rb PET/CT studies

Impaired global myocardial flow reserve (MFR) may be associated with increased risk for cardiac events and coronary artery disease progression. Chronic kidney disease (CKD) is also considered a risk factor for cardiovascular disease. We sought to investigate the effect of CKD on the myocardial microcirculation in patients referred for clinical (82)Rb PET/CT, who had normal left ventricular (LV) function and no flow-limiting coronary artery disease.

METHODS

Estimated glomerular filtration rate (eGFR) was available for 230 patients who had undergone rest and pharmacologic stress (82)Rb PET/CT for suspected coronary artery disease. CKD was defined as an eGFR less than 60 mL/min/1.73 m(2). After patients with hemodialysis, a renal transplant, abnormal regional perfusion (summed stress score > 4), or reduced LV function (LV ejection fraction < 45%) were excluded, 40 CKD patients remained. Those were compared with a control group without CKD, which was matched for age, sex, coronary risk factors, and systemic hemodynamics (n = 42). List-mode acquisition of PET enabled quantification of myocardial blood flow (MBF) and MFR using a previously validated retention model with correction for (82)Rb extraction. Rest MBF was normalized to rate-pressure product.

RESULTS

Mean eGFR in the CKD group was reduced (44 ± 14 vs. 99 ± 28 mL/min/1.73 m(2); P < 0.0001), and creatinine was significantly elevated, compared with controls (1.9 ± 1.1 vs. 0.8 ± 0.2 mg/dL; P < 0.0001). MFR was significantly reduced in CKD (2.2 ± 1.0 vs. 3.0 ± 1.2 for controls; P = 0.027). This reduction was mainly due to increased rest MBF (1.1 ± 0.4 in CKD vs. 0.8 ± 0.2 mL/min/g in controls; P = 0.007). Stress myocardial flow was comparable between both groups (2.3 ± 0.9 vs. 2.3 ± 0.8 mL/min/g; P = 0.08). Overall, MFR was significantly correlated with eGFR (r = 0.41; P = 0.0005). Stress MBF did not correlate with eGFR (r = 0.002; P = 0.45), but rest MBF showed an inverse correlation (r = -0.49; P < 0.0001). Rest MBF was also inversely correlated with hemoglobin (r = -0.28; P = 0.014), but only eGFR was an independent correlate at multivariate analysis.

CONCLUSION

MFR is impaired in patients with renal insufficiency with normal regional perfusion and LV function, mostly because of elevated rest flow. Absolute quantification of flow may be useful to identify microvascular dysfunction as a precursor of clinically overt coronary disease in this specific risk group.

Cardiac Function, Perfusion, Metabolism, and Innervation following Autologous Stem Cell Therapy for Acute ST-Elevation Myocardial Infarction. A FINCELL-INSIGHT Sub-Study with PET and MRI

Purpose: Beneficial mechanisms of bone marrow cell (BMC) therapy for acute ST-segment elevation myocardial infarct (STEMI) are largely unknown in humans. Therefore, we evaluated the feasibility of serial positron emission tomography (PET) and MRI studies to provide insight into the effects of BMCs on the healing process of ischemic myocardial damage. Methods: Nineteen patients with successful primary reteplase thrombolysis (mean 2.4 h after symptoms) for STEMI were randomized for BMC therapy (2.9 × 10⁶ CD34+ cells) or placebo after bone marrow aspiration in a double-blind, multi-center study. Three days post-MI, coronary angioplasty, and paclitaxel eluting stent implantation preceded either BMC or placebo therapy. Cardiac PET and MRI studies were performed 7–12 days after therapies and repeated after 6 months, and images were analyzed at a central core laboratory. Results: In BMC-treated patients, there was a decrease in [¹¹C]-HED defect size (−4.9 ± 4.0 vs. −1.6 ± 2.2%, p = 0.08) and an increase in [¹⁸F]-FDG uptake in the infarct area at risk (0.06 ± 0.09 vs. −0.05 ± 0.16, p = 0.07) compared to controls, as well as less left ventricular dilatation (−4.4 ± 13.3 vs. 8.0 ± 16.7 mL/m², p = 0.12) at 6 months follow-up. However, BMC treatment was inferior to placebo in terms of changes in rest perfusion in the area at risk (−0.09 ± 0.17 vs. 0.10 ± 0.17, p = 0.03) and infarct size (0.4 ± 4.2 vs. −5.1 ± 5.9 g, p = 0.047), and no effect was observed on ejection fraction (p = 0.37). Conclusion: After the acute phase of STEMI, BMC therapy showed only minor trends of long-term benefit in patients with rapid successful thrombolysis. There was a trend of more decrease in innervation defect size and enhanced glucose metabolism in the infarct-related myocardium and also a trend of less ventricular dilatation in the BMC-treated group compared to placebo. However, no consistently better outcome was observed in the BMC-treated group compared to placebo.

Myocardial substrate and route of administration determine acute cardiac retention and lung bio-distribution of cardiosphere-derived cells

BACKGROUND

Quantification of acute myocardial retention and lung bio-distribution of cardiosphere-derived cells (CDCs) following transplantation is important to improve engraftment.

METHODS AND RESULTS

We studied acute(1 hour) cardiac/lung retention in 4 groups (n = 25) of rats (normal--NL, acute ischemia-reperfusion--AI-RM, acute permanent ligation-PL, and chronic infarct by ischemia-reperfusion--CI-R) using intra-myocardial delivery, 1 group using intracoronary delivery (acute ischemia-reperfusion, AI-RC, n = 5) and 1 group using intravenous delivery (acute ischemia-reperfusion, AI-RV, n = 5) of CDCs by PET. Cardiac retention was similar in the NL, AI-RM, CI-R, and A-IRC groups (13.6% ± 2.3% vs. 12.0% ± 3.9% vs. 9.9 ± 2.8 vs. 15.4% ± 5.5%; P = NS), but higher in PL animals (22.9% ± 5.2%; P < .05). Low cardiac retention was associated with significantly higher lung activity in NL and AI-RM groups (43.3% ± 5.6% and 39.9% ± 9.3%), compared to PL (28.5% ± 5.9%), CI-R (20.2% ± 9.3%), and A-IRC (19.9% ± 5.6%) animals (P < .05 vs. AI-RM and NL). Lung activity was highest following intravenous CDC delivery (55.1% ± 9.3%, P < .001) and was associated with very low cardiac retention (0.8% ± 1.06%). Two-photon microscopy indicated that CDCs escaped to the lungs via the coronary veins following intra-myocardial injection.

CONCLUSIONS

Acute cardiac retention and lung bio-distribution vary with the myocardial substrate and injection route. Intra-myocardially injected CDCs escape into the lungs via coronary veins, an effect that is more pronounced in perfused myocardium.

Noninvasive quantification and optimization of acute cell retention by in vivo positron emission tomography after intramyocardial cardiac-derived stem cell delivery

OBJECTIVES

The aim of this study was to quantify acute myocardial retention of cardiac-derived stem cells (CDCs) and evaluate different delivery methods with positron emission tomography (PET).

BACKGROUND

Success of stem cell transplantation for cardiac regeneration is partially limited by low retention/engraftment of the delivered cells. A clinically applicable method for accurate quantification of cell retention would enable optimization of cell delivery.

METHODS

The CDCs were derived from syngeneic, male Wistar Kyoto (WK) rats labeled with [(18)F]-fluoro-deoxy-glucose ((18)FDG) and injected intramyocardially into the ischemic region of female WK rats after permanent left coronary artery ligation. The effects of fibrin glue (FG), bradycardia (adenosine), and cardiac arrest were examined. Imaging with (18)FDG PET was performed for quantification of cell retention. Quantitative polymerase chain reaction (PCR) for the male-specific SRY gene was performed to validate the PET results.

RESULTS

Myocardial retention of cells suspended in phosphate-buffered saline 1 h after delivery was 17.6 +/- 11.5% by PCR and 17.8 +/- 7.3% by PET. When CDCs were injected immediately after induction of cardiac arrest, retention was increased to 75.6 +/- 18.6%. Adenosine slowed the ventricular rate and doubled CDC retention (35.4 +/- 5.3%). A similar increase in CDC retention was observed after epicardial application of FG at the injection site (37.5 +/- 8.2%). The PCR revealed a significant increase in 3-week cell engraftment in the FG animals (22.1 +/- 18.6% and 5.3 +/- 3.1%, for FG and phosphate-buffered saline, respectively).

CONCLUSIONS

In vivo PET permits accurate measurement of CDC retention early after intramyocardial delivery. Sealing injection sites with FG or lowering ventricular rate by adenosine might be clinically translatable methods for improving stem cell engraftment in a beating heart.

Role of nuclear imaging in regenerative cardiology

Advances in noninvasive imaging techniques may aid in the understanding of cardiac stem cell therapy. Nuclear imaging enables in vivo evaluation of myocardial perfusion, metabolism, and function, in addition to the stem cell fate. This article summarizes recent clinical and experimental nuclear imaging studies in cardiac stem cell therapy.

Optimization of Rb-82 PET acquisition and reconstruction protocols for myocardial perfusion defect detection

The purpose of this study is to optimize the dynamic Rb-82 cardiac PET acquisition and reconstruction protocols for maximum myocardial perfusion defect detection using realistic simulation data and task-based evaluation. Time activity curves (TACs) of different organs under both rest and stress conditions were extracted from dynamic Rb-82 PET images of five normal patients. Combined SimSET-GATE Monte Carlo simulation was used to generate nearly noise-free cardiac PET data from a time series of 3D NCAT phantoms with organ activities modeling different pre-scan delay times (PDTs) and total acquisition times (TATs). Poisson noise was added to the nearly noise-free projections and the OS-EM algorithm was applied to generate noisy reconstructed images. The channelized Hotelling observer (CHO) with 32x32 spatial templates corresponding to four octave-wide frequency channels was used to evaluate the images. The area under the ROC curve (AUC) was calculated from the CHO rating data as an index for image quality in terms of myocardial perfusion defect detection. The 0.5 cycle cm(-1) Butterworth post-filtering on OS-EM (with 21 subsets) reconstructed images generates the highest AUC values while those from iteration numbers 1 to 4 do not show different AUC values. The optimized PDTs for both rest and stress conditions are found to be close to the cross points of the left ventricular chamber and myocardium TACs, which may promote an individualized PDT for patient data processing and image reconstruction. Shortening the TATs for <approximately 3 min from the clinically employed acquisition time does not affect the myocardial perfusion defect detection significantly for both rest and stress studies.

The Pro12Ala polymorphism of the PPARgamma2 gene is associated with hepatic glucose uptake during hyperinsulinemia in subjects with type 2 diabetes mellitus

The Ala12 allele of the peroxisome proliferator-activated receptor gamma gene (PPARG2) has been associated with reduced risk of type 2 diabetes mellitus (T2DM) and increased whole-body and skeletal muscle insulin sensitivity in nondiabetic subjects. The effect of the Pro12Ala polymorphism on tissue specific insulin sensitivity in subjects with T2DM has not been previously investigated. We studied the effect of the Pro12Ala polymorphism on the rates of whole-body, skeletal muscle, and subcutaneous adipose tissue glucose uptake (GU) in T2DM subjects, and the rates of hepatic GU in nondiabetic and T2DM subjects during hyperinsulinemia. Our study included 105 T2DM subjects whose whole-body, skeletal muscle, subcutaneous adipose tissue, and hepatic GUs were measured using (18)F-fluorodeoxyglucose and positron emission tomography during the hyperinsulinemic euglycemic clamp. Hepatic GU was also measured in 68 nondiabetic subjects. In obese (body mass index >or=27 kg/m(2)) subjects with T2DM, the rate of hepatic GU was 28% lower in subjects with the Pro12Pro genotype than in carriers of the Ala12 allele (P = .001); and a similar trend was observed in nondiabetic obese subjects (P = .137). No effect of the Pro12Ala polymorphism on the rates of whole-body, skeletal muscle, or subcutaneous adipose tissue GU was observed in T2DM subjects. We conclude that the Ala12 allele of PPARG2 is associated with higher hepatic GU in obese subjects with T2DM.

Effects of weight loss on visceral and abdominal subcutaneous adipose tissue blood-flow and insulin-mediated glucose uptake in healthy obese subjects

OBJECTIVE

Rapid weight loss with very-low-calorie diet (VLCD) is known to improve insulin sensitivity and decrease adipose tissue masses. The aim was to investigate the effects of VLCD on adipose tissue regional glucose uptake (rGU) and perfusion and their association with adipokines.

RESEARCH DESIGN AND METHODS

Sixteen healthy obese (body mass index 33+/-1.1 kg/m(2)) subjects underwent VLCD for 6 weeks. RGU and perfusion were measured using [(18)F]-fluoro-deoxy-glucose, [(15)O]H(2)O and positron emission tomography.

RESULTS

Blood-flow and rGU expressed per gram of adipose tissue were higher in visceral fat compared to abdominal subcutaneous fat (P<0.01 for both). Dieting decreased weight by 11+/-0.9 kg (P<0.0001). Visceral adipose fat decreased by 25% (P<0.001) and abdominal subcutaneous fat by 16% (P<0.001). Whole body insulin sensitivity increased by 33% (P<0.01). Perfusion of both fat depots decreased (P<0.001), while rGU remained unchanged. Among the adipokines, leptin and interleukin-6 levels seemed to be associated with abdominal subcutaneous and intra-abdominal adipose tissue insulin resistance but not with adipose tissue perfusion.

CONCLUSIONS

Abdominal adipose tissue perfusion and rGU are not related in obesity. Rapid weight loss decreases perfusion through adipose tissue depots but has no influence on rGU demonstrating the 'sink' role of adipose tissue.

Effect of weight loss on liver free fatty acid uptake and hepatic insulin resistance

OBJECTIVE

Weight loss has been shown to decrease liver fat content and whole-body insulin resistance. The current study was conducted to investigate the simultaneous effects of rapid weight reduction with a very-low-calorie diet on liver glucose and fatty acid metabolism and liver adiposity.

HYPOTHESIS

We hypothesized that liver insulin resistance and free fatty acid uptake would decrease after weight loss and that they are associated with reduction of liver fat content.

DESIGN

Thirty-four healthy obese subjects (body mass index, 33.7 +/- 8.0 kg/m(2)) were studied before and after a very-low-calorie diet for 6 wk. Hepatic glucose uptake and endogenous glucose production were measured with [(18)F]fluorodeoxyglucose during hyperinsulinemic euglycemia and fasting hepatic fatty acid uptake with [(18)F]fluoro-6-thia-heptadecanoic acid and positron emission tomography. Liver volume and fat content were measured using magnetic resonance imaging and spectroscopy.

RESULTS

Subjects lost weight (11.2 +/- 2.9 kg; P < 0.0001). Liver volume decreased by 11% (P < 0.002), which was partly explained by decreased liver fat content (P < 0.0001). Liver free fatty acid uptake was 26% lower after weight loss (P < 0.003) and correlated with the decrement in liver fat content (r = 0.54; P < 0.03). Hepatic glucose uptake during insulin stimulation was unchanged, but the endogenous glucose production decreased by 40% (P < 0.04), and hepatic insulin resistance by 40% (P < 0.05).

CONCLUSIONS

The liver responds to a 6-wk period of calorie restriction with a parallel reduction in lipid uptake and storage, accompanied by enhancement of hepatic insulin sensitivity and clearance.

Ectopic expression of the sodium-iodide symporter enables imaging of transplanted cardiac stem cells in vivo by single-photon emission computed tomography or positron emission tomography

OBJECTIVES

We examined the sodium-iodide symporter (NIS), which promotes in vivo cellular uptake of technetium 99m ((99m)Tc) or iodine 124 ((124)I), as a reporter gene for cell tracking by single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging.

BACKGROUND

Stem cells offer the promise of cardiac repair. Stem cell labeling is a prerequisite to tracking cell fate in vivo.

METHODS

The human NIS complementary deoxyribonucleic acid was transduced into rat cardiac-derived stem cells (rCDCs) using lentiviral vectors. Rats were injected intramyocardially with up to 4 million NIS(+)-rCDCs immediately after left anterior descending coronary artery ligation. Dual isotope SPECT (or PET) imaging was performed, using (99m)Tc (or (124)I) for cell detection and thallium 201 (or ammonia 13) for myocardial delineation. In a subset of animals, high resolution ex vivo SPECT scans of explanted hearts were obtained to confirm that in vivo signals were derived from the cell injection site.

RESULTS

NIS expression in rCDCs did not affect cell viability and proliferation. NIS activity was verified in isolated transduced cells by measuring (99m)Tc uptake. NIS(+) rCDCs were visualized in vivo as regions of (99m)Tc or (124)I uptake within a perfusion deficit in the SPECT and PET images, respectively. Cells could be visualized by SPECT up to 6 days post-injection. Ex vivo SPECT confirmed that in vivo (99m)Tc signals were localized to the cell injection sites.

CONCLUSIONS

Ectopic NIS expression allows noninvasive in vivo stem cell tracking in the myocardium, using either SPECT or PET. The general approach shows significant promise in tracking the fate of transplanted cells participating in cardiac regeneration, given its ability to observe living cells using clinically applicable imaging modalities.

Nonalcoholic fatty liver disease: rapid evaluation of liver fat content with in-phase and out-of-phase MR imaging

PURPOSE

To evaluate in-phase and out-of-phase magnetic resonance (MR) imaging in the estimation of liver fat content (LFC) in patients with nonalcoholic fatty liver disease (NAFLD), with hydrogen ((1)H) MR spectroscopy as the reference standard.

MATERIALS AND METHODS

Written informed consent was obtained from all subjects, and the local ethics committee approved this prospective study protocol. A total of 33 patients with type 2 diabetes mellitus who were at high risk for NAFLD (23 men, 10 women; overall mean age, 62.8 years +/- 8.3 [standard deviation]; age range, 48-77 years) underwent 1.5-T MR imaging with (1)H MR spectroscopy and in-phase and out-of-phase imaging of the liver. Three fat indexes were calculated from the signal intensity (SI) measured on the images. Two radiologists independently graded SI changes between in-phase and out-of-phase images by means of visual inspection. The Pearson correlation coefficient was used to study the relationship between the obtained parameters of SI change and LFC measured with (1)H MR spectroscopy.

RESULTS

Fat indexes calculated from in-phase and out-of-phase images correlated linearly with LFC measured with (1)H MR spectroscopy (P < .001, r = 0.94-0.96) and were superior (P = .004) to visual estimates (P < .001, r = 0.88). The simple difference in SI between in-phase and out-of-phase images was used to calculate the fat index. An intercept of the regression line with the x-axis was observed at 5.1%, discriminating between normal and elevated LFC with high sensitivity (95%) and specificity (98%).

CONCLUSION

In-phase and out-of-phase imaging can be used to rapidly estimate the LFC in patients with NAFLD. The cutoff value of 5.1% enables objective rapid and reliable discrimination of normal LFC from elevated LFC.

Analytic system matrix resolution modeling in PET: an application to Rb-82 cardiac imaging

This work explores application of a novel resolution modeling technique based on analytic physical models which individually models the various resolution degrading effects in PET (positron range, photon non-collinearity, inter-crystal scattering and inter-crystal penetration) followed by their combination and incorporation within the image reconstruction task. In addition to phantom studies, the proposed technique was particularly applied to and studied in the task of clinical Rb-82 myocardial perfusion imaging, which presently suffers from poor statistics and resolution properties in the reconstructed images. Overall, the approach is able to produce considerable enhancements in image quality. The reconstructed FWHM for a Discovery RX PET/CT scanner was seen to improve from 5.1 mm to 7.7 mm across the field-of-view (FoV) to approximately 3.5 mm nearly uniformly across the FoV. Furthermore, extended-source phantom studies indicated clearly improved images in terms of contrast versus noise performance. Using Monte Carlo simulations of clinical Rb-82 imaging, the resolution modeling technique was seen to significantly outperform standard reconstructions qualitatively, and also quantitatively in terms of contrast versus noise (contrast between the myocardium and other organs, as well as between myocardial defects and the left ventricle).

Non-invasive estimation of hepatic blood perfusion from H2 15O PET images using tissue-derived arterial and portal input functions

PURPOSE

The liver is perfused through the portal vein and the hepatic artery. When its perfusion is assessed using positron emission tomography (PET) and (15)O-labeled water (H(2) (15)O), calculations require a dual blood input function (DIF), i.e., arterial and portal blood activity curves. The former can be generally obtained invasively, but blood withdrawal from the portal vein is not feasible in humans. The aim of the present study was to develop a new technique to estimate quantitative liver perfusion from H(2) (15)O PET images with a completely non-invasive approach.

METHODS

We studied normal pigs (n=14) in which arterial and portal blood tracer concentrations and Doppler ultrasonography flow rates were determined invasively to serve as reference measurements. Our technique consisted of using model DIF to create tissue model function and the latter method to simultaneously fit multiple liver time-activity curves from images. The parameters obtained reproduced the DIF. Simulation studies were performed to examine the magnitude of potential biases in the flow values and to optimize the extraction of multiple tissue curves from the image.

RESULTS

The simulation showed that the error associated with assumed parameters was <10%, and the optimal number of tissue curves was between 10 and 20. The estimated DIFs were well reproduced against the measured ones. In addition, the calculated liver perfusion values were not different between the methods and showed a tight correlation (r=0.90).

CONCLUSION

In conclusion, our results demonstrate that DIF can be estimated directly from tissue curves obtained through H(2) (15)O PET imaging. This suggests the possibility to enable completely non-invasive technique to assess liver perfusion in patho-physiological studies.

CT-based attenuation correction in 82Rb-myocardial perfusion PET–CT: incidence of misalignment and effect on regional tracer distribution

PURPOSE

Misalignment of low-dose-CT used for attenuation correction (AC) may cause artifacts in cardiac-PET-CT. The aim was to evaluate incidence and severity of misalignment and its quantitative effects on regional myocardial (82)Rb-distribution.

METHODS

Rest/dipyridamole (82)Rb-perfusion-PET-CT studies of 92 consecutive patients were analyzed for misalignment. Two different scanning protocols were employed: the first 57 patients had separate CTs for rest and stress PET. The following 35 patients had one CT at rest, used for AC of rest and stress PET. Misalignment was visually scored on a five-point scale (0 = no, 1 = minimal, 2 = mild, 3 = moderate, and 4 = severe). In five representative patients with normal perfusion and low probability of disease, 95 polarmaps were created by shifting CT vs PET prior to reconstruction of attenuation-corrected data sets using dedicated software (three dimensions of space; magnitude of shifts, 5, 10, 14 mm).

RESULTS

PET/CT -misalignment was detected in 60% of rest and 67% of stress studies. Alignment for rest was better than that for stress (0.7 +/- 0.7 vs 1.0 +/- 0.9, P = 0.03). Comparison of the two protocols revealed no effect on the alignment of the stress study (1.0 +/- 0.9 vs 1.0 +/- 0.9, P = 0.9). Quantitatively, the largest individual effect of any artificial misalignment was a 25% reduction of relative (82)Rb uptake. With a shift of 1 cm, the largest effect in an individual was a 19% decrease. Anterior wall was most frequently influenced by misalignment, but changes of uptake also occurred in all other segments.

CONCLUSIONS

Misalignment between CT and PET in cardiac-PET-CT influences regional tracer distribution in multiple segments. Repeated CT imaging after dipyridamole does not improve alignment. These results emphasize the need for strategies to improve coregistration in clinical imaging protocols.

Cardiac sympathetic neuronal imaging using PET

INTRODUCTION

Balance of the autonomic nervous system is essential for adequate cardiac performance, and alterations seem to play a key role in the development and progression of various cardiac diseases.

PET AS AN IMAGING TOOL

PET imaging of the cardiac autonomic nervous system has advanced extensively in recent years, and multiple pre- and postsynaptic tracers have been introduced. The high spatial and temporal resolution of PET enables noninvasive quantification of neurophysiologic processes at the tissue level. Ligands for catecholamine receptors, along with radiolabeled catecholamines and catecholamine analogs, have been applied to determine involvement of sympathetic dysinnervation at different stages of heart diseases such as ischemia, heart failure, and arrhythmia.

REVIEW

This review summarizes the recent findings in neurocardiological PET imaging. Experimental studies with several radioligands and clinical findings in cardiac dysautonomias are discussed.

Low serum adiponectin is associated with high circulating oxidized low-density lipoprotein in patients with type 2 diabetes mellitus and coronary artery disease

Decrease in adiponectin level, a common feature in patients with type 2 diabetes mellitus, is considered to predict cardiovascular events. Elevated oxidized low-density lipoprotein (oxLDL), formed within the arterial wall, is commonly seen as part of the atherogenic profile. We investigated the association of adiponectin and oxLDL in 58 patients with type 2 diabetes mellitus and ischemic coronary artery disease. In addition to adiponectin, the serum lipid profile (including oxLDL), plasminogen activator inhibitor 1, high-sensitivity C-reactive protein, and whole-body glucose uptake determined by euglycemic-hyperinsulinemic clamp were evaluated. The average adiponectin level was 7.1 +/- 3.5 microg/mL and was higher in female than in male patients (P = .011). Adiponectin level correlated with whole-body glucose uptake (P = .037) and high-density lipoprotein (HDL) cholesterol concentration (P = .007) and was inversely associated with oxLDL (P = .005), triglycerides (P = .010), and plasminogen activator inhibitor 1 (P = .004). No association was found between adiponectin and high-sensitivity C-reactive protein or LDL cholesterol levels. In multiple linear regression analysis, adiponectin contributed to oxLDL concentration, whereas total cholesterol, LDL and HDL cholesterol, and triglycerides did not. In conclusion, our results suggest that low adiponectin concentration indicates increased oxidative state in the arterial wall, which further supports previous data on the role of adipose tissue in atherogenesis.

Liver steatosis coexists with myocardial insulin resistance and coronary dysfunction in patients with type 2 diabetes

Nonalcoholic fatty liver (NAFL) is a common comorbidity in patients with type 2 diabetes and links to the risk of coronary syndromes. The aim was to determine the manifestations of metabolic syndrome in different organs in patients with liver steatosis. We studied 55 type 2 diabetic patients with coronary artery disease using positron emission tomography. Myocardial perfusion was measured with [15O]H2O and myocardial and skeletal muscle glucose uptake with 2-deoxy-2-[18F]fluoro-D-glucose during hyperinsulinemic euglycemia. Liver fat content was determined by magnetic resonance proton spectroscopy. Patients were divided on the basis of their median (8%) into two groups with low (4.6 +/- 2.0%) and high (17.4 +/- 8.0%) liver fat content. The groups were well matched for age, BMI, and fasting plasma glucose. In addition to insulin resistance at the whole body level (P = 0.012) and muscle (P = 0.002), the high liver fat group had lower insulin-stimulated myocardial glucose uptake (P = 0.040) and glucose extraction rate (P = 0.0006) compared with the low liver fat group. In multiple regression analysis, liver fat content was the most significant explanatory variable for myocardial insulin resistance. In addition, the high liver fat group had increased concentrations of high sensitivity C-reactive protein, soluble forms of E-selectin, vascular adhesion protein-1, and intercellular adhesion molecule-1 (P < 0.05) and lower coronary flow reserve (P = 0.02) compared with the low liver fat group. In conclusion, in patients with type 2 diabetes and coronary artery disease, liver fat content is a novel independent indicator of myocardial insulin resistance and reduced coronary functional capacity. Further studies will reveal the effect of hepatic fat reduction on myocardial metabolism and coronary function.

The effect of PPARgamma-agonism on LDL subclass profile in patients with type 2 diabetes and coronary artery disease

Patients with type 2 diabetes (T2DM) often present a preponderance of small, dense LDL particles (small-LDL), which are associated with a high risk of myocardial infarction. Some studies suggest that PPARgamma-agonists increase LDL cholesterol but have divergent effects on various LDL subclasses in T2DM patients. We studied the effect of rosiglitazone on the LDL subclass profile in T2DM patients with verified coronary artery disease (CAD). 58 patients with T2DM (HbA1c < 8.5%) and CAD were enrolled in a 16-week, randomized, double-blind and placebo-controlled trial with rosiglitazone 8 mg/day (n = 29) or placebo (n = 29). The LDL subclass profile was measured with gel electrophoresis. Rosiglitazone improved insulin sensitivity and glycemic control. Total cholesterol did not change after rosiglitazone treatment (p = 0.062, ANCOVA adjusted for gender and baseline values), whereas LDL (including IDL) cholesterol increased from 2.33 +/- 0.48 to 2.67 +/- 0.61 mmol/l (p = 0.002 vs. baseline, p = 0.0497 vs. placebo) and large buoyant LDL (large-LDL < 250A) increased from 1.31 +/- 0.36 to 1.46 +/- 0.42 mmol/l (p = 0.010 vs. baseline, p = 0.044 vs. placebo) in the rosiglitazone group. No significant changes occurred to the concentration of small-LDL (< 250A), the average LDL particle size, or HDL or triglyceride concentrations. Whole-body insulin sensitivity was associated with the average LDL particle size after intervention in the whole population (r = 0.40, p = 0.002) and in the rosiglitazone group (r = 0.43, p = 0.020). In conclusion, in T2DM patients with CAD, rosiglitazone treatment significantly increases the concentration of large (buoyant) LDL cholesterol, but not of small dense LDL cholesterol. The long term consequences of this divergent effect of rosiglitazone on LDL subfractions require further exploration.

Effects of exhaustive stretch-shortening cycle exercise on muscle blood flow during exercise

AIM

The influence of exhaustive stretch-shortening cycle exercise (SSC) on skeletal muscle blood flow (BF) during exercise is currently unknown.

METHODS

Quadriceps femoris (QF) BF was measured in eight healthy men using positron emission tomography before and 3 days after exhaustive SSC exercise. The SSC protocol consisted of maximal and submaximal drop jumps with one leg. Needle biopsies of the vastus lateralis muscles were taken immediately and 2 days after SSC for muscle endothelial nitric oxide synthase (eNOS) and interleukin-1-beta (IL-1beta) mRNA level determinations.

RESULTS

All subjects reported subjective muscle soreness after SSC (P < 0.001), which was well in line with a decrease in maximal isometric contraction force (MVC) and increase in serum creatine kinase activity (CK) (P = 0.018). After SSC muscle BF was 25% higher in entire QF (P = 0.043) and in its deep and superficial muscle regions, whereas oxygen uptake remained unchanged (P = 0.893). Muscle biopsies revealed increased IL-1beta (30 min: 152 +/- 75%, P = 0.012 and 2 days: 108 +/- 203%, P = 0.036) but decreased or unchanged eNOS (30 min; -21 +/- 57%, P = 0.050 and 2 days: +101 +/- 204%, P = 0.779) mRNA levels after SSC.

CONCLUSION

It was concluded that fatiguing SSC exercise induces increased muscle BF during exercise, which is likely to be associated with pro-inflammatory processes in the exercised muscle.

Insulin improves myocardial blood flow in patients with type 2 diabetes and coronary artery disease

Insulin infusion improves myocardial blood flow (MBF) in healthy subjects. Until now, the effect of insulin on myocardial perfusion in type 2 diabetic subjects with coronary artery disease (CAD) has been unknown. We studied the effects of insulin on MBF in ischemic regions evaluated by single-photon emission-computed tomography and coronary angiography and in nonischemic regions in 43 subjects (ages 63 +/- 7 years) with type 2 diabetes (HbA(1c) 7.1 +/- 0.9%). MBF was measured at fasting and during a euglycemic-hyperinsulinemic clamp at rest (n = 43) and during adenosine-induced (140 mug . kg(-1) . min(-1) for 7 min) hyperemia (n = 26) using positron emission tomography and (15)O-labeled water. MBF was significantly attenuated in ischemic regions as compared with in nonischemic regions (P < 0.0001) and was increased by insulin as compared with in the fasting state (P < 0.0001). At rest, insulin infusion increased MBF by 13% in ischemic regions (P = 0.043) and 22% in nonischemic regions (P = 0.003). During adenosine infusion, insulin enhanced MBF by 20% (P = 0.018) in ischemic regions and 18% (P = 0.045) in nonischemic regions. In conclusion, insulin infusion improved MBF similarly in ischemic and nonischemic regions in type 2 diabetic subjects with CAD. Consequently, in addition to its metabolic effects, insulin infusion may improve endothelial function and thus increase the threshold for ischemia and partly contribute to the beneficial effects found in clinical trials in these subjects.

Single nucleotide polymorphisms in the peroxisome proliferator-activated receptor delta gene are associated with skeletal muscle glucose uptake

The peroxisome proliferator-activated receptors (PPARs) belong to a superfamily of nuclear receptors. It includes PPAR-delta, a key regulator of fatty acid oxidation and energy uncoupling, universally expressed in different tissues. The PPAR-delta gene (PPARD) maps to 6p21.2-p21.1 and has 11 exons and spans 35 kbp. We investigated the effects of single nucleotide polymorphisms (SNPs) of PPARD on whole-body, skeletal muscle, and subcutaneous adipose tissue glucose uptake in 129 healthy individuals using the hyperinsulinemic-euglycemic clamp technique combined with fluorine-18-labeled fluorodeoxyglucose ([18F]FDG) and positron emission tomography (PET). Three of six SNPs of PPARD and their haplogenotypes were significantly associated with whole-body insulin sensitivity. [18F]FDG-PET scanning indicated that SNPs of PPARD primarily affected insulin sensitivity by modifying glucose uptake in skeletal muscle but not in adipose tissue. Our results give evidence that SNPs of PPARD regulate insulin sensitivity particularly in skeletal muscle.

Rosiglitazone improves myocardial glucose uptake in patients with type 2 diabetes and coronary artery disease: a 16-week randomized, double-blind, placebo-controlled study

Rosiglitazone therapy improves insulin sensitivity and glucose uptake in patients with uncomplicated type 2 diabetes. In coronary artery disease (CAD), glucose is an important source of energy and preserved myocardial glucose uptake is essential for the viability of jeopardized myocardium. The aim was to test whether rosiglitazone changes myocardial metabolism in type 2 diabetic patients with CAD. We studied 54 patients (38 men and 16 women) with type 2 diabetes (HbA(1c) 7.2 + 0.9%) and CAD. Myocardial glucose uptake was measured with [(18)F]fluoro-2-deoxy-d-glucose positron emission tomography in ischemic (evaluated by single-photon emission tomography and coronary angiography) and nonischemic regions during euglycemic-hyperinsulinemic clamp before and after a 16-week intervention period with rosiglitazone (n = 27) or placebo (n = 27). Rosiglitazone significantly improved glycemic control (P < 0.0001) and whole-body insulin sensitivity (P < 0.0001). Rosiglitazone increased myocardial glucose uptake from 20.6 +/- 11.8 to 25.5 +/- 12.4 micromol . 100 g(-1) . min(-1) (P = 0.038 vs. baseline, P = 0.023 vs. placebo) in ischemic regions and from 21.7 +/- 12.1 to 28.0 +/- 12.7 micromol . 100 g(-1) . min(-1) (P = 0.014 vs. baseline, P = 0.003 vs. placebo) in nonischemic regions. The increase in myocardial glucose uptake was partly explained by the suppression of free fatty acid levels during clamp. Rosiglitazone therapy significantly increased insulin sensitivity and improved myocardial glucose uptake in type 2 diabetic patients with CAD. These results suggest that rosiglitazone therapy may facilitate myocardial glucose storage and utilization in these patients.

The effect of the Ala12 allele of the peroxisome proliferator-activated receptor-gamma2 gene on skeletal muscle glucose uptake depends on obesity: a positron emission tomography study

CONTEXT

The Pro(12)Ala polymorphism of the peroxisome proliferator-activated receptor-gamma2 gene is associated with insulin sensitivity. Obesity is a major risk factor for insulin resistance, but the association of the Pro(12)Ala polymorphism with body weight has been controversial. Furthermore, obesity may modulate the effect of this polymorphism on insulin sensitivity.

OBJECTIVE

The aim of our study was to investigate the effects of the Pro(12)Ala polymorphism on skeletal muscle and adipose tissue glucose uptake (GU) in nonobese and obese subjects.

DESIGN

The design was a cross-sectional study.

STUDY SUBJECTS

The rates of GU were investigated in 124 (72 nonobese and 52 obese; body mass index cutoff point, 27 kg/m(2)) healthy subjects with the euglycemic hyperinsulinemic clamp. Skeletal muscle and adipose tissue GU and skeletal muscle perfusion were measured using fluorine-18-labeled fluorodeoxyglucose, [(15)O]H(2)O, and positron emission tomography.

RESULTS

The rates of skeletal muscle GU were higher in nonobese subjects carrying the Ala(12) allele than in subjects carrying the Pro(12)Pro genotype (P = 0.004), whereas no differences were found in skeletal muscle perfusion between the groups. In contrast, in obese subjects the rates of skeletal muscle GU did not differ between carriers of the Ala(12) allele and carriers of the Pro(12)Pro genotype. No difference in adipose tissue GU was found in either nonobese or obese subjects according to Pro(12)Ala polymorphism.

CONCLUSIONS

We conclude that the Pro(12)Ala polymorphism modulates skeletal muscle GU differently in nonobese and obese subjects.