Impact of Different Fat Depots on Insulin Sensitivity: Predominant Role of Liver Fat

Background

Overall obesity and, as it is increasingly appreciated, body fat distribution and ectopic fat deposition in liver and skeletal muscle, determine insulin resistance in humans. However, little is known about the independence of these relationships. Therefore, we determined the impact of different fat depots as well as fat accumulation in ectopic tissues such as liver and skeletal muscle in the prediction of insulin resistance in healthy humans.

Methods

Visceral and subcutaneous abdominal fat were determined by magnetic resonance (MR) tomography and liver fat and intramyocellular fat in the tibialis anterior muscle by ¹H-MR spectroscopy in 220 subjects. Insulin sensitivity was estimated from the oral glucose tolerance test (OGTT) and measured by a euglycemic hyperinsulinemic clamp in a subgroup (n = 157).

Results

Insulin sensitivity estimated from the OGTT correlated negatively with total body fat (r = −0.27, p < 0.0001), subcutaneous abdominal fat (r = −0.35, p < 0.0001), and visceral fat (r = −0.43, p < 0.0001). Furthermore, insulin sensitivity correlated negatively with liver fat (r = −0.53, p < 0.0001) and intramyocellular fat (r = −0.26, p < 0.0001). In multivariate regression models, high liver and visceral fat emerged as the strongest predictors of low insulin sensitivity.

Conclusion

Among various fat compartments, high liver fat and high visceral fat are the strongest determinants of insulin sensitivity in humans.     

Sustained postinfarction myocardial oedema in humans visualised by magnetic resonance imaging

OBJECTIVE—To demonstrate postinfarction myocardial oedema in humans with particular reference to the longitudinal course, using magnetic resonance imaging (MRI).
DESIGN—Prospective observational study. Subjects were studied one week, one month, three months, six months, and one year after presenting with a myocardial infarct.
SETTING—Cardiology and magnetic resonance departments in a Danish university hospital.
PATIENTS—10 patients (three women, seven men), mean (SEM) age 58.2 (3.20) years, with a first transmural myocardial infarct.
MAIN OUTCOME MEASURES—Location and duration of postinfarction myocardial oedema.
RESULTS—All patients had signs of postinfarction myocardial oedema. The magnetic resonance images were evaluated by two blinded procedures, employing two MRI and two ECG observers: (1) MRI determined oedema location was compared with the ECG determined site of infarction and almost complete agreement was found; (2) the time course of postinfarction myocardial oedema was explored semiquantitatively, using an image ranking procedure. Myocardial oedema was greatest at the initial examination one week after the infarction, with a gradual decline during the following months (Spearman's rank correlation analysis: ρ_{observer 1} = 0.94 (p < 0.0001) and ρ_{observer 2} = 0.97 (p < 0.0001)). The median duration of oedema was six months.
CONCLUSIONS—Postinfarction myocardial oedema seems surprisingly long lasting. This observation is of potential clinical interest because the oedema may have prognostic significance.


Keywords: myocardial infarction; myocardial oedema; magnetic resonance imaging     

Multislice MR perfusion imaging and regional myocardial function analysis: complimentary findings in chronic myocardial ischemia

Purpose: The purpose of this study is to assess the reliability of multislice MR perfusion imaging in comparison to regional wall function and nuclear medicine and to test different qualitative and quantitative parameters for perfusion assessment. Material and methods: 15 patients with chronic myocardial ischemia underwent CINE and first-pass perfusion MR imaging. Functional myocardial imaging was performed using a segmented CINE FLASH sequence and systolic myocardial wall thickening was assessed after semiautomated segmentation. MR first-pass perfusion studies were performed using a multislice saturation recovery TurboFLASH sequence. Different parameters were calculated for assessment of hypoperfused segments and results of MR imaging compared to ^99mTc-SestaMIBI SPECT. Results: MR perfusion imaging showed a sensitivity of 72% and a specificity of 98%. In combination with MR CINE imaging and wall thickening analysis we calculated a sensitivity of 100% and a specificity of 93%. Qualitative and quantitative perfusion parameter analysis showed significant differences between normal and hypoperfused segments for the signal intensity increase (p < 0.001), the signal intensity upslope (p < 0.001) as well as for the myocardial mean transit time (p < 0.001). Conclusion: The combination of systolic wall thickening analysis and myocardial perfusion can markedly improve the sensitivity of MRI in depiction of LV myocardial perfusion abnormalities. For assessment of hypoperfusion, different quantitative and qualitative parameters can be calculated showing significant differences between normal state and hypoperfusion.     

Associates of change in liver fat content in the morbidly obese after laparoscopic gastric banding surgery

Aim:  Hepatic steatosis affects up to 30% of the population. After weight loss, monitoring of the change in hepatic steatosis is not routinely performed. This study aimed to define the closest associates of change in liver fat content in a population of obese females following laparoscopic gastric banding surgery.
Methods:  Before and 3 months after surgery, proton magnetic resonance spectroscopy and magnetic resonance imaging were used to estimate the amount of lipid contained within the liver and abdominal subcutaneous and visceral compartments of 29 obese [mean body mass index (BMI) 39 ± 5 kg/m²], non-diabetic women aged between 20 and 62 years. Liver enzymes, fasting plasma glucose and insulin were also measured as well as body weight, BMI and waist circumference. Insulin sensitivity was estimated using homeostasis model assessment insulin resistance index.
Results:  Significant reductions occurred in body weight (p < 0.001), abdominal fat volumes (p < 0.001) and liver fat (p = 0.037) 3 months after surgery. Change in liver fat content more closely associated with change in serum gamma-glutamyl transferase (GGT; r = 0.71, p < 0.001) than with changes in weight (r = 0.10, p = 0.612) and waist circumference (r = 0.15, p = 0.468).
Conclusions:  Our findings suggest that obese non-diabetic female patients who have undergone significant weight loss over 3 months can be better assessed for the regression of excess liver fat content by monitoring changes in serum GGT levels rather than changes in simple anthropometry.     

Incidence,predictors, and prognostic value of intramyocardial hemorrhage lesions in ST elevation myocardial infarction

Background: Intra myocardial hemorrhage lesions (IMH) are underdiagnosed complication of ST elevation myocardial infarction (STEMI). We sought to determine the incidence, predictors and the prognostic value of IMH in STEMI using cardiac MR imaging (CMR) techniques. Methods: We screened for inclusion consecutive patients with STEMI treated by percutaneous coronary intervention (PCI) within the first 12 hr of evolution. IMH lesions were identified on T2‐weighted sequences on CMR between days 4 and 8 after PCI. Adverse cardiac events were defined as a composite of death + severe ventricular arrhythmias + acute coronary syndrome + acute heart failure. Results: N = 114 patients were included and n = 11 patients (10%) presented IMH lesions. Patients with IMH lesions had a larger myocardial infarction extent (25.6 ± 1.8 vs. 13.5 ± 1.0 % LV mass, P < 0.01), microvascular obstructive lesions extent (4.6 ± 1.0 vs. 1.3 ± 0.3% LV mass, P < 0.01) and lower LV ejection fraction (40.7 ± 2.3% vs. 50.7 ± 1.3%, P < 0.01). The value of glycemia at admission was an independent predictor of IMH development (Odd ratio 1.8 [1.1–2.8] per mmol l^?1, P = 0.01). The incidence of adverse cardiac events was higher in the IMH group than in the non‐IMH group during the first year following STEMI (P = 0.01, log‐rank analysis). Cox regression analysis identified the presence of IMH lesions as an independent predictor of adverse clinical outcome (Hazard Ratio = 2.8 [1.2–6.8], P = 0.02). Conclusion: Our study indicates that IMH is a rare but severe finding in STEMI, associated with a larger myocardial infarction and a worse clinical outcome. Per‐PCI glycemia might influence IMH development. © 2011 Wiley Periodicals, Inc.     

心脏磁共振特征组织追踪成像定量评价健康人群左心室心肌形变

目的:探讨3.0T心脏磁共振(CMR)特征组织追踪成像(FT)测量中国汉族健康人群左心室心肌形变参数的可行性,并分析年龄、性别对各应变参数的影响。方法:本研究共纳入健康志愿者53例。其中男27例,女26例。随后每组纳入人群按照年龄分为青年、中年及老年3个亚组。所有纳入者均行3.0TCMR检查。分析、对比不同性别和不同年龄组人群左心室整体及局部的径向、周向及纵向峰值应变(PS)、峰值收缩期应变率(PSSR)、峰值舒张期应变率(PDSR)。结果:其中,女性整体周向PS、纵向PS、心基底段周向PS大于男性;男性整体周向PSSR及心中间段周向PSSR、纵向PSSR大于女性。分析不同年龄段心肌形变结果显示,整体径向PS在男女性中老年组均明显高于中年组和青年组;女性组整体周向PS、周向PDSR老年组低于青年组。左心室整体径向、周向、纵向PS分别与部分心功能参数相关。结论:3.0TCMR-FT能客观地量化健康人群左心室心肌形变的相关参数,且不同性别、不同年龄段心肌各形变参数也存在差异,制定相应正常人群心肌形变参数范围需考虑性别及年龄的影响。     

Myocardial perfusion imaging: clinical experience and recent progress in radionuclide scintigraphy and magnetic resonance imaging

In the past 20 years, radionuclide scintigraphy has proven to be a sensitive clinical tool in the assessment of myocardial perfusion abnormalities. Magnetic resonance imaging may also be used to study myocardial perfusion, but its potential value still has to emerge in the clinical setting. This review addresses the potential and achievements of both methods in clinical cardiology.     

Association of Periaortic Fat and Abdominal Visceral Fat with Coronary Artery Atherosclerosis in Chinese Middle Aged and Elderly Patients Undergoing Computed Tomography Coronary Angiography

Background and Aims:Coronary artery disease (CAD) is usually caused by atherosclerosis, which is associated with general obesity and stronger associations with localized ectopic fat depots have been reported. We measured body ectopic fat distribution in Chinese patients to determine the association with coronary artery atherosclerosis (CA).Methods:Patients undergoing coronary computed tomography angiography (CCTA) who agreed to participate in the study (n = 750, 50.4% men, mean age 64.8 years) had cardiovascular disease and risk assessment. Body ectopic fat depots were measured from CT and their association with CA, determined from CCTA, was evaluated by univariate and multivariate logistic regression models.Results:CAD with CA (CAD-CA) was present in 57.2% of participants with CAD of moderate/severe CA (CAD-msCA) present in 23.5% and both were significantly more frequent in men than in women. Overall, men had greater body mass index (BMI) but there was no difference in waist circumference (WC) between genders. However, significantly higher visceral adipose tissue (VAT) and periaortic fat volume (PAFV) were observed in men, whereas women had significantly higher abdominal subcutaneous adipose tissue (SAT). With increasing age, there was a significant decline in BMI, WC and SAT in men, but a significant increase of WC and VAT, PAFV and epicardial fat volume (EFV) in women. A high proportion of non-calcified plaques was observed in CAD-CA, 55.3% in CAD of minimal/mild CA (CAD-mmCA) with 38.7% exclusively non-calcified plaques, and 59.7% in CAD-msCA with multiple type plaques containing non-calcified ones. Multivariate logistic regression showed a significant association of PAFV with CAD-CA and CAD-msCA that was independent of general obesity and clinical risk factors, and independent of abdominal obesity in the highest PAFV quartile patients. VATA was associated with an increased prevalence of CAD-msCA in the patients in the upper 2 VATA quartiles that was independent of clinical risk factors and both general and abdominal obesity.Conclusions:We found age and gender differences of body ectopic fat distribution in Chinese patients with higher VAT and PAFV in men and higher SAT in women. With increased age, there was a decline of WC and SAT in men but not in women and an increase in WC, VAT and PAFV in women but not in men. PAFV was significantly associated with overall CAD-CA and CAD-msCA, while VAT was associated with CAD-msCA.     

Granulocyte-colony stimulating factor administration after myocardial infarction in a porcine ischemia-reperfusion model: functional and pathological effects of dose timing.

BACKGROUND: Acute MI results in cardiomyocyte death, left ventricular (LV) dysfunction and adverse remodeling. The use of growth factors may prevent this. The aim of this study was to assess early and delayed administration of granulocyte colony-stimulating factor (G-CSF) in a porcine model of myocardial infarction (MI) and reperfusion. METHODS: MI was induced by balloon occlusion followed by reperfusion. There were 3 groups: Control (n = 11), Early (n = 17), and Delayed treatment (n = 8). The Early group received G-CSF 10 microg/kg/d every other day for 20 days beginning immediately. The Delayed group received G-CSF 10 microg/kg/d daily for 10 days beginning on day 5. Magnetic resonance imaging was performed on days 5 and 56. LV end-diastolic volumes (EDV), end-systolic volumes, ejection fraction, expansion index, sphericity index, thinning ratio, and infarct mass were calculated. Histology was analyzed at 56 days. RESULTS: At 56 days the change in EDV was 53% less in the Early (p = 0.005) and 24% greater in the Delayed (p = NS) group versus Control. The Delayed group also showed a 60% increase in normalized infarct mass (p = 0.055) and an 88% increase in expansion index (p = 0.003). Both groups had significantly less capillary density in the infarct border zone. The Delayed also had decreased arteriolar density in the mid scar. CONCLUSIONS: Early treatment with G-CSF after MI decreases ventricular dilatation, while delayed treatment has a deleterious effect on LV remodeling. This may be related to changes in myocardial vascularity. The effects of G-CSF therapy and its dose timing help to elucidate the results of recent human trials.