Human epicardial adipose tissue is a source of inflammatory mediators

Volumetric measurement of pericardial adipose tissue from contrast-enhanced coronary computed tomography angiography: a reproducibility study

PURPOSE

Pericardial adipose tissue may exert unique metabolic and cardiovascular risks in patients. The use of cardiac multidetector computed tomography (MDCT) imaging may enable the accurate localization and quantification of pericardial and intrathoracic adipose tissue. The reproducibility of electrocardiogram-gated high-resolution cardiac MDCT-based volumetric quantification of pericardial and intrathoracic adipose tissue has not been reported.

METHODS

We included 100 consecutive patients (age 54.5 +/- 12.0 yr, 60% men) who underwent a standard contrast-enhanced coronary CT for the evaluation of coronary artery plaque and stenosis (64-slice MDCT, temporal resolution: 210 ms, spatial resolution: 0.6 mm, 850 mAs, 120, kvp) after a presentation of acute chest pain. Two independent observers measured intrathoracic (IAT) and pericardial adipose tissue (PAT) by using a semiautomatic segmentation algorithm based on three-dimensional analysis.

RESULTS

Inter-reader reproducibility was excellent (relative difference: 7.35 +/- 7.22% for PAT and 6.23 +/- 4.91% for IAT, intraclass correlation 0.98 each). Similar results were obtained for intra-observer reproducibility (relative difference: 5.18 +/- 5.19% for PAT and 4.34 +/- 4.12% for IAT, intraclass correlation 0.99 each).

CONCLUSION

This study demonstrates that MDCT-based 3D semiautomatic segmentation for volumetric quantification of PAT and IAT is highly reproducible. Further research is warranted to assess whether volumetric measurements may substantially improve the predictive value of obesity measures for insulin resistance, type 2 diabetes mellitus, and cardiovascular diseases.

Relation of epicardial and pericoronary fat to coronary atherosclerosis and coronary artery calcium in patients undergoing coronary angiography

Fat surrounding coronary arteries might aggravate coronary artery disease (CAD). We investigated the relation between epicardial adipose tissue (EAT) and pericoronary fat and coronary atherosclerosis and coronary artery calcium (CAC) in patients with suspected CAD and whether this relation is modified by total body weight. This was a cross-sectional study of 128 patients with angina pectoris (61 +/- 6 years of age) undergoing coronary angiography. EAT volume and pericoronary fat thickness were measured with cardiac computed tomography. Severity of coronary atherosclerosis was assessed by the number of stenotic (> or =50%) coronary vessels; extent of CAC was determined by the Agatston score. Patients were stratified for median total body weight (body mass index [BMI] 27 kg/m(2)). Overall, EAT and pericoronary fat were not associated with severity of coronary atherosclerosis and extent of CAC. In patients with low BMI, those with multivessel disease had increased EAT volume (100 vs 67 cm(3), p = 0.04) and pericoronary fat thickness (9.8 vs 8.4 mm, p = 0.06) compared with those without CAD. Also, patients with severe CAC had increased EAT volume (108.0 vs 69 cm(3), p = 0.02) and pericoronary fat thickness (10.0 vs 8.2 mm, p value = 0.01) compared with those with minimal/absent CAC. In conclusion, EAT and pericoronary fat were not associated with severity of coronary atherosclerosis and CAC in patients with suspected CAD. However, in those with low BMI, increased EAT and pericoronary fat were related to more severe coronary atherosclerosis and CAC. Fat surrounding coronary arteries may be involved in the process of coronary atherosclerosis, although this is different for patients with low and high BMIs.

The association of pericardial fat with calcified coronary plaque

BACKGROUND

Pericardial fat has a higher secretion of inflammatory cytokines than subcutaneous fat. Cytokines released from pericardial fat around coronary arteries may act locally on the adjacent cells.

OBJECTIVE

We examined the relationship between pericardial fat and calcified coronary plaque.

METHODS AND PROCEDURES

Participants in the community-based Multi-Ethnic Study of Atherosclerosis (MESA) underwent a computed tomography (CT) scan for the assessment of calcified coronary plaque in 2000/2002. We measured the volume of pericardial fat using these scans in 159 whites and blacks without symptomatic coronary heart disease from Forsyth County, NC, aged 55-74 years.

RESULTS

Calcified coronary plaque was observed in 91 participants (57%). After adjusting for height, a 1 s.d. increment in pericardial fat was associated with an increased odds of calcified coronary plaque (odds ratio (95% confidence interval): 1.92 (1.27, 2.90)). With further adjustment of other cardiovascular factors, pericardial fat was still significantly associated with calcified coronary plaque. This relationship did not differ by gender and ethnicity. On the other hand, BMI and height-adjusted waist circumference were not associated with calcified coronary plaque.

DISCUSSION

Pericardial fat is independently associated with calcified coronary plaque.

Inflammation is associated with a decrease of lipogenic factors in omental fat in women

Obesity is characterized by systemic low-grade inflammation in which adipose tissue, especially the omental depot, is thought to play a key role. We have previously shown that inflammation impairs 3T3-L1 preadipocyte cell line differentiation. To explore whether this interaction also takes place in vivo, the expression of several genes related to inflammation and adipocyte differentiation was assessed in human samples. Paired adipose tissue biopsies (from omental and subcutaneous depots) were obtained from 24 women: 6 lean normoglycemic and 18 obese volunteers with different glycemic states (normoglycemic, glucose-intolerant, or type 2 diabetic). The expression levels of CD14, IL-18, leptin, adiponectin, sterol regulatory element binding transcription factor 1 (SREBP1), peroxisome proliferator-activated receptor gamma (PPARγ), pre-B-cell colony enhancing factor 1 (PBEF1) (or visfatin), glycerol-3-phosphate dehydrogenase 1 (soluble) (GPD1), lipoprotein lipase (LPL), fatty acid binding protein 4, adipocyte (FABP4), and hypoxia-inducible factor 1α were determined by quantitative real-time PCR. CD14 and IL-18 were overexpressed in omental adipose tissue compared with the subcutaneous depot, irrespective of the subject's obesity or diabetes status. A significant decrease of LPL, GPD1, and leptin expression was observed in omental tissue, and an inverse correlation between expression of CD14 and IL-18 and that of PPARγ, LPL, and FABP4 was observed. The underexpression of omental lipogenic markers was more accentuated in the presence of glucose intolerance. Furthermore, adiponectin and SREBP1 expression was also significantly decreased in omental tissue of type 2 diabetic patients. PBEF1 and HIF1α expression remained comparable in all samples. Therefore, in humans, inflammation is increased in the omental depot, as evidenced by CD14 and IL-18 expression. In this localization, the inflammatory state is associated with a decreased expression of lipogenic markers, which is more pronounced in diabetic subjects.

Obesity and vascular dysfunction

One of the most profound challenges facing public health and public health policy in Western society is the increased incidence and prevalence of both overweight and obesity. While this condition can have significant consequences for patient mortality and quality of life, it can be further exacerbated as overweight/obesity can be a powerful stimulus for the development of additional risk factors for a negative cardiovascular outcome, including increased insulin resistance, dyslipidemia and hypertension. This manuscript will present the effects of systemic obesity on broad issues of vascular function in both afflicted human populations and in the most relevant animal models. Among the topics that will be covered are alterations to vascular reactivity (both dilator and constrictor responses), adaptations in microvascular network and vessel wall structure, and alterations to the patterns of tissue/organ perfusion as a result of the progression of the obese condition. Additionally, special attention will be paid to the contribution of chronic inflammation as a contributor to alterations in vascular function, as well as the role of perivascular adipose tissue in terms of impacting vessel behavior. When taken together, it is clearly apparent that the development of the obese condition can have profound, and frequently difficult to predict, impacts on integrated vascular function. Much of this complexity appears to have its basis in the extent to which other co-morbidities associated with obesity (e.g., insulin resistance) are present and exert contributing effects.

Pathogenic potential of adipose tissue and metabolic consequences of adipocyte hypertrophy and increased visceral adiposity

When caloric intake exceeds caloric expenditure, the positive caloric balance and storage of energy in adipose tissue often causes adipocyte hypertrophy and visceral adipose tissue accumulation. These pathogenic anatomic abnormalities may incite metabolic and immune responses that promote Type 2 diabetes mellitus, hypertension and dyslipidemia. These are the most common metabolic diseases managed by clinicians and are all major cardiovascular disease risk factors. 'Disease' is traditionally characterized as anatomic and physiologic abnormalities of an organ or organ system that contributes to adverse health consequences. Using this definition, pathogenic adipose tissue is no less a disease than diseases of other body organs. This review describes the consequences of pathogenic fat cell hypertrophy and visceral adiposity, emphasizing the mechanistic contributions of genetic and environmental predispositions, adipogenesis, fat storage, free fatty acid metabolism, adipocyte factors and inflammation. Appreciating the full pathogenic potential of adipose tissue requires an integrated perspective, recognizing the importance of 'cross-talk' and interactions between adipose tissue and other body systems. Thus, the adverse metabolic consequences that accompany fat cell hypertrophy and visceral adiposity are best viewed as a pathologic partnership between the pathogenic potential adipose tissue and the inherited or acquired limitations and/or impairments of other body organs. A better understanding of the physiological and pathological interplay of pathogenic adipose tissue with other organs and organ systems may assist in developing better strategies in treating metabolic disease and reducing cardiovascular disease risk.

Thiazolidinedione insulin sensitizers and the heart: a tale of two organs?

Thiazolidinediones (TZDs) are relatively new agents for the treatment of type 2 diabetes. They act as agonists at the PPAR-gamma nuclear receptor and their therapeutic effects include decreased insulin resistance and hyperglycaemia, an improved plasma lipid, inflammation and pro-coagulant profile, and amelioration of hypertension, microalbuminuria and hepatic steatosis. The most common side effects of TZDs include weight gain and oedema, with occasional reports of congestive heart failure (CHF). This review discusses the benefit-risk profile of TZDs in treating patients with type 2 diabetes, with particular reference to the heart. To provide context, we explore briefly the epidemiology and pathophysiology of heart failure in patients with type 2 diabetes, touch on the association of heart disease and cardiovascular mortality with antihyperglycaemic treatment modalities other than TZDs, and then focus on the effects of TZDs on the heart, cardiovascular risk factors and outcomes. We describe the cluster of host factors, which seems to predispose patients with type 2 diabetes to TZD-induced or TZD-exacerbated oedema and CHF and then provide an overview of the putative mechanisms of these TZD-related side effects. We also propose that certain diuretics (amiloride and spironolactone), by targeting the distal nephron that expresses PPARgamma in collecting duct cells, might be of benefit in ameliorating the fluid retention and oedema associated with TZDs.

Threshold values of high-risk echocardiographic epicardial fat thickness

OBJECTIVE

Echocardiographic epicardial adipose tissue is a new index of cardiac and visceral adiposity with great potential as a diagnostic tool and therapeutic target. In this study, we sought to provide threshold values of echocardiographic epicardial fat thickness associated with metabolic and anthropometric risk factors.

METHODS AND PROCEDURES

Epicardial fat thickness was measured in 246 consecutive white subjects (120 women, 126 men, median age 46 years (30-65), median BMI 32 kg/m(2) (22-52), median waist circumference 100.5 cm (85-140)), who underwent routine transthoracic echocardiogram for standard clinical indications. Metabolic syndrome (MetS), Insulin resistance, BMI, and waist circumference categories were identified and epicardial fat was calculated.

RESULTS

Among 246 subjects, 58% had MetS. These subjects showed median values of epicardial fat thickness of 9.5 and 7.5 mm (in men and women, respectively), significantly higher than those found in subjects without MetS (no MetS) (P < 0.001). Receiver operating characteristics (ROC) analysis showed that epicardial fat thickness of 9.5 and 7.5 mm maximize the sensitivity and specificity to predict MetS, in men and women, respectively. In separate analyses, median epicardial fat thickness values of 9.5 and 7.5 mm were cutoff points associated with high abdominal fat in men and women, respectively. When insulin sensitivity was considered separately, epicardial fat thickness of 9.5 mm was associated with insulin resistance.

DISCUSSION

Median values of 9.5 and 7.5 mm should be considered the threshold values for high-risk echocardiographic epicardial fat thickness in white men and women, respectively. Echocardiographic epicardial fat measurement may be of help for cardiometabolic risk stratification and therapeutic interventions targeting the fat.

Relationship of epicardial fat thickness and fasting glucose

In this study we sought to evaluate whether increase in echocardiographic epicardial fat thickness, index of cardiac and visceral adiposity, is associated with impaired fasting glucose (IFG). Epicardial fat thickness and fasting plasma glucose (FPG) were measured in 115 consecutive non-diabetic Caucasian subjects [65 men, 50 women, median age of 42 years (range 30-64 years), median body mass index (BMI) of 27 kg/m(2) (range 22-33 kg/m(2)), who underwent routine transthoracic echocardiogram. Study subjects were designated as having normal fasting glucose (NFG) with FPG<100 mg/dl; and IFG with FPG (100 and <126 mg/dl). Epicardial fat thickness was significantly higher in IFG than NFG subjects (8+/-3 vs 6+/-2 mm; 7.1+/-4 vs 5.8+/-3 mm, p<0.001 for both and respectively in men and women. Epicardial fat thickness was significantly correlated with FPG (r=0.60, p<0.001). Our data indicate for the first time that higher epicardial fat thickness is associated with IFG in non-diabetic men and women. Echocardiographic epicardial fat measurement may be an additional tool for diabetes-related cardiac risk stratification.

Perivascular fat alters reactivity of coronary artery: effects of diet and exercise

Perivascular adipose tissue (PAT) has been reported to blunt agonist-induced arterial tone via a relaxing factor acting in a paracrine manner. The purpose of this study was to test the hypothesis that PAT of porcine coronary artery blunts constriction similarly and that this anticontractile effect of PAT is altered by diet and/or exercise training.

METHODS

Fourteen adult male pigs were fed a normal-fat (NF) diet, and 10 adult male pigs were fed a high-fat/cholesterol (HF) diet. Four weeks after the initiation of diet, pigs were exercised (EX) or remained sedentary (SED) for 16 wk, yielding four groups: 1) NF-SED, 2) NF-EX, 3) HF-SED, and 4) HF-EX. Left circumflex coronary artery (LCX) rings were prepared with PAT left intact or removed. LCX reactivity to acetylcholine (ACh), endothelin (ET-1), bradykinin (BK), and sodium nitroprusside (SNP) was assessed in vitro using standard techniques.

RESULTS

The results demonstrate that both ACh and ET-1 elicited dose-dependent increases in tension from LCX rings from all groups. Removal of PAT had no significant effect on ACh-induced contractions in any group. In contrast, removal of PAT increased ET-1-induced tension in LCX from NF-SED, HF-SED, and HF-EX but not NF-EX. PAT had no significant effect on relaxation responses to BK except in HF-EX animals, where removal of PAT increased BK-induced relaxation. PAT removal decreased SNP-induced relaxation in HF-LCX, but not LCX from NF pigs, suggesting basal release of a relaxing factor LCX from HF pigs.

CONCLUSION

PAT blunts contractions induced by ET-1 in LCX from NF and HF pigs. Whereas EX abolished this effect of PAT in NF pigs, exercise did not alter the anticontractile effect in HF pigs.

The emerging role of adipokines as mediators of cardiovascular function: physiologic and clinical perspectives

Interest in the biology of white adipose tissue has increased dramatically since the discovery of leptin in 1994. The identification of the product of the gene obese (ob) threw light on the role of adipose tissue in the physiopathology of obesity-related diseases and spurred the identification of numerous other adipokines, many of a proinflammatory nature. It has become increasingly evident that white adipose tissue-derived cytokines mediate between obesity-related exogenous factors (nutrition and lifestyle) and the molecular events that lead to metabolic syndrome, inflammation, and cardiovascular diseases. Here we review recent adipokine research, with particular attention to the roles of adiponectin, leptin, resistin, visfatin, apelin, omentin, and chemerin in such conditions.

Do cardiac and perivascular adipose tissue play a role in atherosclerosis?

Recent evidence suggests that epicardial and perivascular adipose tissue could mechanically and functionally affect the heart and vasculature, thereby possibly playing a role in adiposity-related atherosclerosis. Experimental and clinical observations suggest both favorable and unfavorable effects of epicardial and perivascular fat. The double role of epicardial and perivascular adipose tissue in the development of cardiovascular pathology and/or in protecting the heart and arteries warrants further studies.

Early Hypertension Is Associated With Reduced Regional Cardiac Function, Insulin Resistance, Epicardial, and Visceral Fat

Mild-to-moderate hypertension is often associated with insulin resistance and visceral adiposity. Whether these metabolic abnormalities have an independent impact on regional cardiac function is not known. The goal of this study was to investigate the effects of increased blood pressure, insulin resistance, and ectopic fat accumulation on the changes in peak systolic circumferential strain. Thirty-five male subjects (age: 47±1 years; body mass index: 28.4±0.6 kg . m −2 ; mean±SEM) included 13 with normal blood pressure (BP: 113±5/67±2 mm Hg), 13 with prehypertension (BP: 130±1/76±2 mm Hg), and 9 newly diagnosed with essential hypertension (BP: 150±2/94±2 mm Hg) who underwent cardiac magnetic resonance tissue tagging (MRI) and MRI quantitation of abdominal visceral and epicardial fat. Glucose tolerance, on oral glucose tolerance test, and insulin resistance were assessed along with the serum lipid profile. All of the subjects had normal glucose tolerance, left- and right-ventricular volumes, and ejection fraction. Across the BP groups, left ventricular mass tended to increase, and circumferential shortening was progressively reduced at basal, midheart, and apical segments (on average, from −17.0±0.5% in normal blood pressure to −15.2±0.7% in prehypertension to −13.6±0.8% in those newly diagnosed with essential hypertension; P =0.004). Reduced circumferential strain was significantly associated with raised BP independent of age ( r =0.41; P =0.01) and with epicardial and visceral fat, serum triglycerides, and insulin resistance independent of age and BP. In conclusion, regional left ventricular function is already reduced at the early stages of hypertension despite the normal global cardiac function. Insulin resistance, dyslipidemia, and ectopic fat accumulation are associated with reduced regional systolic function.

Pericardial fat, visceral abdominal fat, cardiovascular disease risk factors, and vascular calcification in a community-based sample: the Framingham Heart Study

BACKGROUND

Pericardial fat may be an important mediator of metabolic risk. Correlations with cardiovascular disease risk factors and vascular calcification in a community-based sample are lacking. We sought to examine associations between pericardial fat, metabolic risk factors, and vascular calcification.

METHODS AND RESULTS

Participants free of cardiovascular disease from the Framingham Heart Study (n=1155, mean age 63 years, 54.8% women) who were part of a multidetector computed tomography study underwent quantification of intrathoracic fat, pericardial fat, visceral abdominal fat (VAT), coronary artery calcification, and aortic artery calcification. Intrathoracic and pericardial fat volumes were examined in relation to body mass index, waist circumference, VAT, metabolic risk factors, coronary artery calcification, and abdominal aortic calcification. Intrathoracic and pericardial fat were directly correlated with body mass index (r=0.41 to 0.51, P<0.001), waist circumference (r=0.43 to 0.53, P<0.001), and VAT (r=0.62 to 0.76, P<0.001). Both intrathoracic and pericardial fat were associated with higher triglycerides (P<0.0001), lower high-density lipoprotein (P<0.0001), hypertension (P<0.0001 to 0.01), impaired fasting glucose (P<0.0001 to 0.001), diabetes mellitus (P=0.0005 to 0.009), and metabolic syndrome (P<0.0001) after multivariable adjustment. Associations generally persisted after additional adjustment for body mass index and waist circumference but not after adjustment for VAT (all P>0.05). Pericardial fat, but not intrathoracic fat, was associated with coronary artery calcification after multivariable and VAT adjustment (odds ratio 1.21, 95% confidence interval 1.005 to 1.46, P=0.04), whereas intrathoracic fat, but not pericardial fat, was associated with abdominal aortic calcification (odds ratio 1.32, 95% confidence interval 1.03 to 1.67, P=0.03).

CONCLUSIONS

Pericardial fat is correlated with multiple measures of adiposity and cardiovascular disease risk factors, but VAT is a stronger correlate of most metabolic risk factors. However, intrathoracic and pericardial fat are associated with vascular calcification, which suggests that these fat depots may exert local toxic effects on the vasculature.

Identification of omentin mRNA in human epicardial adipose tissue: comparison to omentin in subcutaneous, internal mammary artery periadventitial and visceral abdominal depots

OBJECTIVE

The purpose of this study was to determine the relative distribution of omentin and visfatin mRNA in human epicardial, peri-internal mammary, upper thoracic, upper abdominal and leg vein subcutaneous adipose tissue as well as the distribution of omentin in the nonfat cells and adipocytes of human omental adipose tissue.

BACKGROUND

Omentin is found in human omentum but not subcutaneous fat. Omentin and visfatin are considered markers of visceral abdominal fat.

RESEARCH DESIGN AND METHODS

The mRNA content of omentin and visfatin was measured by qRT-PCR analysis of fat samples removed from humans undergoing cardiac or bariatric surgery.

RESULTS

Omentin mRNA in internal mammary fat was 3.5%, that in the upper thoracic subcutaneous fat was 4.7% while that in the other subcutaneous fat depots was less than 1% of omentin in epicardial fat. The distribution of visfatin mRNA did not vary between the five depots. Omentin mRNA was preferentially expressed in the nonfat cells of omental adipose tissue since the omentin mRNA content of isolated adipocytes was 9% of that in nonfat cells, and similar results were seen for visfatin. The amount of omentin mRNA in differentiated adipocytes was 0.3% and that of visfatin 4% of that in nonfat cells. The amount of omentin mRNA in preadipocytes was virtually undetectable while that of visfatin was 3% of that in freshly isolated nonfat cells from omental adipose tissue.

CONCLUSION

Omentin mRNA is predominantly found in epicardial and omental human fat whereas visfatin mRNA is found to the same extent in epicardial, subcutaneous and omental fat.

Dietary polyunsaturated fatty acids and age-related membrane changes in the heart

Age-associated modification of cardiac membrane composition and related metabolic processes are major factors underlying the reduced capacity for invoking intrinsic cardioprotective survival mechanisms. In this brief review we examine some of these key membrane lipid modifications, which include alterations in the type and proportion of long-carbon chain polyunsaturated fatty acids (PUFAs). These changes have profound consequences on the efficacy of membrane proteins and lipids involved with numerous processes including ion homeostasis, intracellular signal transduction, free radical metabolism, and mitochondrial energy production. The resultant postoxidative modification of lipids, proteins, and DNA leads to a reduction in capacity for repair and ultimately worsening cellular dysfunction. However, some age-related detrimental adaptations may be counteracted by selectively manipulating membrane lipid and protein composition via dietary treatment with key omega-3 PUFAs. Such pervasive treatment results in manipulation of cellular function at multiple levels from cell membrane to the genome.

Expression of adrenomedullin in human epicardial adipose tissue: role of coronary status

Epicardial white adipose tissue (eWAT) is in close contact with coronary vessels and therefore could alter coronary homeostasis. Adrenomedullin (AM) is a potent vasodilatator and antioxidative peptide which has been shown to play a cytoprotective role in experimental models of acute myocardial infarction. We studied, using immunohistochemistry and qRT-PCR, the expression of AM and its receptors calcitonin receptor-like receptor (CRLR), and receptor activity-modifying protein (RAMP)2 and -3 in paired biopsies of subcutaneous WAT (sWAT) and eWAT obtained from patients with coronary artery disease (CAD) or without CAD (NCAD). In eWAT obtained from NCAD or CAD patients, immunoreactivity for AM, CRLR, and RAMP2 and -3 was detected in blood vessel walls and isolated stromal cells close to adipocytes. Some of the AM positive stromal cells colocalized CD68 immunoreactivity. eWAT from CAD patients showed increased AM immunoreactivity and AM gene expression. CRLR mRNA levels were comparable in sWAT of both groups and decreased by 40-50% in eWAT, irrespectively of the coronary status. RAMP2 mRNA concentrations did not change while RAMP3 mRNA levels increased in sWAT from CAD patients. There was a positive linear relationship between eWAT 11beta-hydroxysteroid dehydrogenase type 1 mRNA (11beta-HSD-1, the enzyme that converts inactive to active glucocorticoids) and AM mRNA. In conclusion, we demonstrate that AM and its receptors are expressed in eWAT. Our data suggest that eWAT AM, which could originate from macrophages, is related to 11beta-HSD-1 expression. AM synthesis, which is increased in eWAT during chronic CAD in humans, can play a cardioprotective role.

Endothelial dysfunction in obesity: etiological role in atherosclerosis

PURPOSE OF REVIEW

To review studies of vascular endothelial dysfunction in obesity, discuss potential mechanisms of disease, and address the therapeutic effects of weight loss interventions on arterial health.

RECENT FINDINGS

Endothelial dysfunction represents the earliest abnormality in the development of vascular disease, and is pathophysiologically linked to subsequent atherosclerosis progression and cardiovascular disease events. Obesity is closely associated with a number of established cardiovascular risk factors, including diabetes mellitus, insulin resistance, dyslipidemia, and hypertension that are cumulatively damaging to the endothelium. In addition, there is now a growing recognition of non-traditional risk factors as potential modulators of the endothelial phenotype in obesity, including fat tissue production of proatherogenic adipokines, oxidative stress, and chronic inflammation. Clinical studies have demonstrated that even modest weight loss reverses endothelial dysfunction, and the restoration of arterial homeostasis could potentially reduce cardiovascular risk.

SUMMARY

Obesity is associated with altered arterial homeostasis and endothelial dysfunction. Mechanisms of disease are related to a complex interplay of metabolic and inflammatory factors that coordinately improve along with arterial function in response to weight loss interventions.

Quantification of epicardial and peri-coronary fat using cardiac computed tomography; reproducibility and relation with obesity and metabolic syndrome in patients suspected of coronary artery disease

OBJECTIVE

Adipose tissue surrounding coronary arteries may contribute to the development of coronary atherosclerosis given its localisation and potential for local production of inflammatory cytokines. We compared various measurements for quantifying epicardial adipose tissue (EAT) and peri-coronary fat using cardiac CT. Additionally, we estimated their relationship with obesity and metabolic syndrome in patients suspected of coronary artery disease (CAD).

METHODS

EAT and peri-coronary fat measurements were performed on cardiac multi-slice CT scans in 60 patients (aged 50-70 years) referred for coronary angiography. EAT was measured as thickness on the right ventricular free wall, as area at the base of the ventricles, and as volume. Peri-coronary fat was assessed as thickness and cross-sectional area surrounding the three main coronary arteries. Linear regression analysis was used to assess the relation of EAT and peri-coronary fat with obesity and metabolic syndrome (ATPIII criteria).

RESULTS

Volumetric EAT measurements showed good reproducibility with low coefficients of variation (CVs) varying between 3.0% and 5.0%. Measurements of EAT and peri-coronary fat thickness and area were moderately reproducible (CVs 11.0-23.4%). The amount of EAT and peri-coronary fat (per standard deviation) was related with obesity (BMI > or =30 kg/m(2)) (beta 1.24; 95% CI 0.66; 1.81) and metabolic syndrome (beta 0.81; 95% CI 0.28; 1.33).

CONCLUSIONS

Volumetric quantification of EAT using cardiac CT is highly reproducible compared to more simple measurements as EAT and peri-coronary fat thickness and area. The quantity of EAT and peri-coronary fat is related with the presence of obesity and metabolic syndrome in patients suspected of CAD.

Adipocytokines and proinflammatory mediators from abdominal and epicardial adipose tissue in patients with coronary artery disease

OBJECTIVE

Epicardial and abdominal adipose tissues have recently been demonstrated to play inflammatory roles in coronary atherosclerosis. We sought to compare tissue adipocytokine levels of these two anatomically distinct adipose stores in patients with and without coronary artery diseases (CAD).

DESIGN

Samples of abdominal and epicardial fat tissues were harvested to detect the levels of adipocytokines and proinflammatory mediators.

SUBJECTS

Forty-six patients with CAD who underwent coronary artery bypass surgery and 12 non-CAD control subjects who underwent other types of open-heart surgery.

MEASUREMENTS

Tissue levels of adipocytokines (adiponectin, leptin and visfatin) and proinflammatory mediators (tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6)) were determined by enzyme-linked immunosorbent assay.

RESULTS

Tissue levels of TNF-alpha, IL-6, leptin and visfatin were significantly higher in CAD patients relative to control subjects. In addition, significantly higher tissue levels of these four cytokines from abdominal fat depots were found compared to those from epicardial fat in CAD patients. Conversely, in comparison with control subjects, tissue levels of adiponectin were significantly reduced in CAD patients with a significantly lower tissue levels of abdominal than epicardial fat depots demonstrated.

CONCLUSION

Abdominal adiposity may play more significant role than epicardial fat in the pathogenesis of coronary atherosclerosis.

Adipose Tissue of Atrial Septum as a Marker of Coronary Artery Disease

BACKGROUND

Paracrine effects of epicardial adipose tissue may promote coronary atherosclerosis. Adipose tissue is the main determinant of atrial septum thickness. The association between atrial septum thickness and coronary artery disease (CAD) has never been studied.

METHODS

We studied 75 patients who underwent coronary angiography and echocardiography within 1 week (mean [+/- SD]duration, 2.0 +/- 2.0 days). Atrial septum thickness, representing adipose tissue, was identified and measured with two-dimensional transthoracic echocardiography. Angiographic data were analyzed for the presence, extent, and severity of CAD, using a standardized 27-segment classification. Any CAD was defined as the presence of stenosis of any severity in at least one coronary vessel. The number of segments with a coronary artery with at least 20% stenosis (coronary artery greater even than 20 [CAGE >or= 20] score) was recorded.

RESULTS

The mean atrial septum thickness was 1.5 +/- 0.4 cm (median, 1.42 cm; range, 0.74 to 2.55 cm). In a simple linear regression analysis, we found no significant correlation between atrial septum thickness and clinical variables (p > 0.05). However, we found a significant correlation between atrial septum thickness and any CAD (p = 0.03), which persisted after controlling for age, gender, and body mass index (p = 0.03). Patients in the lowest quartile of atrial septum thickness had a lower proportion of subjects with any CAD (p = 0.02) and a lower median CAGE >or= 20 score compared to other quartiles (p = 0.04).

CONCLUSION

Adipose tissue of the atrial septum, represented by atrial septum thickness, is associated with the presence of CAD.

Influence of epicardial adipose tissue and adipocytokine levels on cardiac abnormalities in visceral obesity

Adipocytokine levels and visceral adipose tissue (VAT) seem to be associated with some cardiac abnormalities and a role of visceral fat in predisposing to cardiac dysfunction, possibly through a low-grade state of inflammation, has been demonstrated. In this study we firstly show that elevated levels of both monocyte chemoattractant protein 1 (MCP-1) and soluble IL-6 receptor/interleukin-6 (sIL-6R/IL-6) complex are closely correlated with epicardial fat thickness.

Leptin requires canonical migratory signaling pathways for induction of monocyte and macrophage chemotaxis

The growing worldwide obesity epidemic is frequently linked to an increased risk of developing diseases such as diabetes, cardiovascular disease, and cancer. These diseases are associated with the infiltration of macrophages in white adipose tissue (WAT), the artery wall, and tumors, respectively; and these macrophages likely contribute to disease progression and pathogenesis. Abdominal WAT, adipose tissue surrounding the heart and artery wall, as well as carcinoma cells, secrete many factors that could induce macrophage infiltration. Leptin is an adipocyte-secreted hormone, and deficiency of either leptin or its receptor has been shown to cause morbid obesity in animals and in humans. However, what is more commonly noted in human obesity is the presence of central leptin resistance leading to hyperleptinemia. As leptin receptors are present on macrophages, we hypothesized that leptin could act as a monocyte/macrophage chemoattractant. Our current study demonstrates: 1) leptin is a potent chemoattractant for monocytes and macrophages, inducing maximal chemotactic responses at 1 ng/ml; 2) leptin-mediated chemotaxis requires the presence of full-length leptin receptors on migrating cells; 3) leptin causes increased influx of intracellular calcium in macrophages; and 4) activation of janus kinase/signal transducers and activators of transduction (JAK/STAT), mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinase (PI3K) pathways are all necessary for leptin-induced macrophage migration. Taken together, these data demonstrate that leptin is a potent monocyte/macrophage chemoattractant in vitro and that canonical cell motility machinery is activated upon macrophage exposure to leptin. These data have implications for the impact of hyperleptinemia on obesity-related pathophysiological conditions such as diabetes, cardiovascular disease, and cancer.

Chemerin--a new adipokine that modulates adipogenesis via its own receptor

Chemerin, an 18 kDa protein secreted by adipose tissue, was reported to modulate immune system function through its binding to the chemerin receptor (chemerinR). We herein demonstrate that chemerin also influences adipose cell function. Our data showed that chemerin and chemerinR mRNA expressions were highly expressed in adipose tissues, and that their expression levels were up-regulated in mice fed a high-fat diet. Both chemerin and chemerinR mRNA expression dramatically increased during the differentiation of 3T3-L1 cells and human preadipocytes into adipocytes. Furthermore, recombinant chemerin induced the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK 1/2) and lipolysis in differentiated 3T3-L1 adipocytes. Thus, the adipokine chemerin likely regulates adipocyte function by autocrine/paracrine mechanisms.

Insulin resistance and the metabolic syndrome--or the pitfalls of epidemiology

The clustering of dyslipidaemia, hypertension and glucose intolerance, predominantly in overweight individuals, has been ascribed many names, including syndrome X and the metabolic syndrome. In Reaven's original description of syndrome X, a central aetiological role was attributed to insulin resistance, and this assumption has remained as the dominant paradigm for the metabolic syndrome. There are a number of conceptual problems in such a model, particularly those arising from observations that several novel markers, including measures of endothelial dysfunction and of low-grade inflammation, are as closely related to insulin resistance as are the classic components of the syndrome. Because it is difficult to envisage how these traits might develop as a consequence of insulin resistance, such observations indicate the need for a new paradigm to explain the mechanisms of association better. It has been proposed that a state of low-grade inflammation, consequent upon the production of adipocytokines, particularly from truncal fat, explains the observed relationships between insulin resistance and endothelial dysfunction better than does a model revolving around insulin resistance. Furthermore, the inflammatory cytokines generated from adipose tissue may influence vessel endothelial function without elevations in circulating concentrations. This review alludes to several problems inherent in the epidemiological method in understanding disease mechanisms. These include crude biological measures, the use of venous systemic fasting samples, imprecision of assays, naive physiological models, simplistic statistical approaches and, without clinical trials, an inability to test causation. Integrated systems biology needs more complex approaches to investigate disease mechanisms, involving cell, organ, whole organism and population studies.

Emerging role of cathepsin S in obesity and its associated diseases

Obesity is thought to be a major determinant in the development of cardiovascular diseases, but the mechanisms whereby enlarged adipose tissue affects vascular function remain poorly defined. Chronic inflammation is a common feature of obesity and atherosclerosis, and several inflammatory markers produced by adipose tissue have been considered as candidates that potentially favor the development of atherosclerotic lesions in humans. To identify other effective candidates, we combined bioclinical data for individuals of increasing weight with adipose tissue gene-expression profiling. This strategy led to the discovery of cathepsin S (CTSS), for which gene expression was strongly correlated with subjects' body mass index (BMI). CTSS is an elastolytic cysteine protease that has been implicated in the development of atherosclerotic lesions in both animal models and humans. In this review, we discuss the role of CTSS in obesity and atherosclerosis, and emphasize the potential mechanisms that could link the two diseases. We also position this protease as a potential therapeutic target to reduce associated cardiovascular risks in obese patients.

The role of periadventitial fat in atherosclerosis

CONTEXT

It has become increasingly evident that adipose tissue is a multifunctional organ that produces and secretes multiple paracrine and endocrine factors. Research into obesity, insulin resistance, and diabetes has identified a proinflammatory state associated with obesity. Substantial differences between subcutaneous and omental fat have been noted, including the fact that omental fat produces relatively more inflammatory cytokines. Periadventitial fat, as a specific adipose tissue subset, has been overlooked in the field of atherosclerosis despite its potential diagnostic and therapeutic implications.

OBJECTIVE

To review (1) evidence for the role of adventitial and periadventitial fat in vessel remodeling after injury, (2) the relationship between adventitial inflammation and atherosclerosis, (3) the association between periadventitial fat and plaque inflammation, and (4) the diagnostic and therapeutic implications of these roles and relationships for the progression of atherosclerosis.

DATA SOURCES

We present new data showing greater uptake of iron, administered in the form of superparamagnetic iron oxide, in the periadventitial fat of atherosclerotic mice than in control mice. In addition, macrophage density in the periadventitial fat of lipid-rich plaques is increased compared with fibrocalcific plaques.

CONCLUSIONS

There is a striking paucity of data on the relationship between the periadventitial fat of coronary arteries and atherosclerosis. Greater insight into this relationship might be instrumental in making strides into the pathophysiology, diagnosis, and treatment of coronary artery disease.

Echocardiographic epicardial fat thickness and coronary artery disease

BACKGROUND

The association between epicardial fat and coronary artery disease has not been evaluated. The objective of the present study was to evaluate the relationship of echocardiographic epicardial fat to the presence and severity of coronary artery disease in a clinical setting.

METHODS AND RESULTS

Two hundred and three consecutive patients who underwent echocardiography and diagnostic coronary angiography were studied. The epicardial fat thickness on the free wall of the right ventricle was measured at end-diastole from the parasternal long-axis views of 3 cardiac cycles. Coronary angiograms were analyzed for the extent and severity of coronary artery disease using Gensini's score. The patients were divided into 2 groups according to the fourth quartile of epicardial fat thickness (Group I <7.6 mm; Group II > or =7.6 mm). There were no significant differences in the baseline characteristics except for waist circumference (p=0.023). Significant correlations were demonstrated between epicardial fat thickness and age (r=0.332, p<0.001), C-reactive protein (r=0.182, p=0.009), body mass index (r=0.142, p=0.044) and waist circumference (r=0.229, p=0.001). The patients with a higher epicardial fat thickness were associated with a high Gensini's score (p=0.014). Multivariate analysis showed that age (odds ratio (OR) 5.29, p=0.003), epicardial fat thickness (OR 10.53, p=0.004), diabetes (OR 8.06, p=0.006) and smoking (OR 14.65, p=0.015) were independent factors affecting significant coronary artery stenosis.

CONCLUSIONS

Epicardial fat thickness was significantly correlated with the severity of coronary artery disease in patients with known coronary artery disease.

Epicardial adipose tissue, hepatic steatosis and obesity

OBJECTIVE

Hepatic steatosis is a common companion of obesity. Moreover, the measurement of epicardial adipose tissue (EAT) has been reported to be related with both obesity and insulin resistance. Therefore, we aimed to evaluate the relationship between hepatic steatosis, EAT and insulin resistance in obese patients.

METHODS

Sixty-three obese subjects were enrolled in the study. Patients were divided into 3 groups according to body mass index (BMI) as follows: 20 patients with 30 < or = BMI < 35 kg/m2 (Group 1, mean age 39.3+/-12.9 yr), 25 patients with 35 < or = BMI < 40 kg/m2 (Group 2, mean age 41.7+/-9.3 yr), and 18 patients with BMI > or = 40 kg/m2 (Group 3, mean age 36.8+/-13.9 yr). EAT and grade of hepatic steatosis were assessed sonographically. Anthropometrical measurements were assessed with the foot-to-foot bioelectrical impedance analysis. Insulin resistance was assessed according to basal insulin, quantitative insulin sensitivity check index (QUICKI) and homeostasis model assessment (HOMA) equations.

RESULTS

Although EAT was similarly higher in both groups 2 and 3, these groups were found to be similar in terms of the grade of hepatic steatosis. Both EAT and the grade of hepatic steatosis were correlated with whole body fat mass, abdominal adiposity, insulin resistance, and triglyceridemia but waist circumference was the only factor affecting EAT thickness. Highly sensitive C-reactive protein (hsCRP) was the only metabolic parameter that was significantly higher in Group 3 than in Group 1 (p=0.02).

CONCLUSION

Hepatic steatosis should be assessed as a valuable predictor that reflects the increments of whole body fat mass as well as abdominal adiposity. However, in an attempt to demonstrate marginal differences between patients with similar obesity levels, epicardial adipose tissue appears to be a more sensitive marker compared to hepatic steatosis.

Human epicardial adipose tissue: a review

We discuss the anatomy, physiology, and pathophysiology of epicardial adipose tissue and its relationship to coronary atherosclerosis. Epicardial fat stores triglyceride to supply free fatty acids for myocardial energy production and produces adipokines. It shares a common embryological origin with mesenteric and omental fat. Like visceral abdominal fat, epicardial fat thickness, measured by echocardiography, is increased in obesity. Epicardial fat could influence coronary atherogenesis and myocardial function because there is no fibrous fascial layer to impede diffusion of free fatty acids and adipokines between it and the underlying vessel wall as well as the myocardium. Segments of coronary arteries lacking epicardial fat or separated from it by a bridge of myocardial tissue are protected against the development of atherosclerosis in those segments. However, when epicardial fat is totally absent in congenital generalized lipodystrophy, coronary atherosclerosis can still occur. Macrophages are more numerous and densely packed in the periadventitial fat of human atherosclerotic coronary arteries with lipid cores than in that of fibrocalcific or nonatherosclerotic coronary arteries. In obese patients with multiple cardiovascular risk factors, epicardial fat around atheromatous coronaries secretes several proinflammatory cytokines and is infiltrated by macrophages, lymphocytes, and basophils. Epicardial adipokine expression in obesity without coronary atherosclerosis has not been determined. In nonobese patients, epicardial fat around atheromatous coronary arteries expresses proinflammatory cytokines but produces either less adiponectin, a vasoprotective adipokine, than fat around nonatheromatous coronaries or a similar amount compared with thoracic subcutaneous fat. Further studies should be done to test the hypothesis that adipokines produced by and released from human epicardial adipose tissue might contribute locally to the pathogenesis of coronary atherosclerosis.

Monocyte chemotactic protein-1 and its role in insulin resistance

PURPOSE OF REVIEW

In obesity, there is a strong link between increased adipose tissue mass and development of insulin resistance in tissues such as liver and muscle. Under these conditions, adipose tissue synthesizes various pro-inflammatory chemokines such as monocyte chemotactic protein-1. This review provides a summary of recent knowledge on the role of monocyte chemotactic protein-1 in adipose tissue inflammation and insulin resistance.

RECENT FINDINGS

Monocyte chemotactic protein-1 is a proinflammatory adipokine that is believed to play a role in the pathogenesis of obesity and diabetes. New in-vitro data demonstrate that monocyte chemotactic protein-1 has the ability to induce insulin resistance in adipocytes and skeletal muscle cells. By using mice that either overexpress monocyte chemotactic protein-1 or are deficient in monocyte chemotactic protein-1 or its receptor, exciting new insights have been obtained into the role of monocyte chemotactic protein-1 in adipose tissue inflammation and insulin resistance.

SUMMARY

Monocyte chemotactic protein-1 is an adipokine with insulin-resistance-inducing capacity that is related to increased adipose tissue mass in obesity and insulin resistance. It plays an important role in adipose tissue inflammation by recruiting macrophages into fat. Monocyte chemotactic protein-1 is thus a therapeutic target, and may represent an important factor linking adipose tissue inflammation, obesity and type 2 diabetes.

Relation of subepicardial adipose tissue to carotid intima-media thickness in patients with human immunodeficiency virus

Patients infected with human immunodeficiency virus (HIV) are at increased risk for subclinical atherosclerosis. Whether increased cardiac adiposity may be related to HIV subclinical atherosclerosis is still unexplored. The objective of this study was to evaluate whether echocardiographically determined subepicardial adipose tissue, an index of cardiac adiposity, is related to carotid intima-media thickness (IMT), an index of subclinical atherosclerosis, in HIV-infected patients receiving highly active antiretroviral therapy. Echocardiographic epicardial fat thickness and ultrasonographic IMT were measured in 103 consecutive HIV-infected Caucasian subjects receiving highly active antiretroviral therapy. Echocardiographic subepicardial adipose tissue showed an excellent correlation with IMT (r = 0.92, p <0.01). Multiple regression analysis showed that IMT was best predicted by epicardial fat thickness (r(2) = 0.81, p <0.01). In conclusion, this study suggests, for the first time, that epicardial adipose tissue, an index of cardiac adiposity, may be significantly related to subclinical atherosclerosis in HIV-infected patients.

Epicardial fat: properties, function and relationship to obesity

Epicardial fat is a relatively neglected component of the heart. The purpose of this review was to examine the anatomic and biochemical data on epicardial fat; to examine the relationship of epicardial fat to obesity and to explore the potential role of epicardial fat in the relationship of obesity to coronary atherothrombotic disease. Epicardial fat covers 80% of the heart's surface and constitutes 20% of total heart weight. It is present along the distribution of the coronary arteries, over the right ventricle especially along the right border, anterior surface and at the apex. There is three- to fourfold more epicardial fat associated with the right than the left ventricle. Putative physiologic functions of epicardial fat are based on observational data and include: buffering coronary arteries against the torsion induced by the arterial pulse wave and cardiac contraction, facilitating coronary artery remodelling, regulating fatty acid homeostasis in the coronary microcirculation and providing fatty acids to cardiac muscle as a local energy source in times of high demand. A considerable amount of the data on epicardial fat originates from autopsy series that have the inherent problem that conditions leading to death may have altered body composition and adiposity. With this caveat, data indicate that epicardial fat mass increases age until age 20-40 years but thereafter the amount of epicardial fat is not dependent on age. The amount of epicardial fat correlates with heart weight but the presence of myocardial ischemia and hypertrophy does not alter the ratio of epicardial fat to cardiac muscle mass. A number of properties differentiate epicardial fat from other fat depots specifically its smaller adipocytes size; different fatty acid composition, high protein content; high rates of fatty acid incorporation, fatty acid synthesis, insulin-induced lipogenesis or fatty acid breakdown; low rates of glucose utilization, low expression (mRNA) of lipoprotein lipase, stearoyl-CoA desaturase and acetyl-CoA carboxylase-alpha, and slow regression during weight loss. There is a significant direct relationship between the amount of epicardial fat and general body adiposity. Clinical imaging studies have demonstrated a strong direct correlation between epicardial fat and abdominal visceral adiposity. Several lines of evidence support a role for epicardial fat in the pathogenesis of coronary artery disease, namely the close anatomic relationship between epicardial fat and coronary arteries; the positive correlation between the amount of epicardial fat and the presence of coronary atherosclerosis and the ability of adipose tissue to secrete hormones and cytokines that modulate coronary artery atherothrombosis. Thus, epicardial fat maybe an important factor responsible for cardiovascular disease in obesity.

Proinflammatory cytokines and cardiac abnormalities in uncomplicated obesity: relationship with abdominal fat deposition

BACKGROUND AND AIM

Obesity can be considered a state of chronic, low-grade inflammation. Particularly, visceral adipose tissue (VAT) seems to be an active compartment in pro-inflammatory molecule secretion. The possible existence of a correlation between circulating cytokines, their soluble receptors, abdominal fat accumulation and echocardiographic abnormalities in uncomplicated obesity was investigated.

METHODS AND RESULTS

Echocardiographic parameters, C-reactive protein (CRP), interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6-R), tumor necrosis factor-alpha (TNF-alpha) and soluble TNF receptor I (TNFR-I) were assessed in 27 normotensive obese women (age 33.3+/-8.3 years; BMI 43.5+/-4.8 kg/m2) and 15 normal-weight controls (age 36.8+/-8.2 years; BMI 22.6+/-1.7 kg/m2). VAT was assessed by CT. The obese patients had higher serum IL-6 (p<0.01), sIL-6-R (p<0.0001), sIL-6-R/IL-6 complex (p<0.05), TNF-alpha (p<0.02), sTNF-alpha-RI (p<0.03) and CRP (p<0.0001) levels than normal women. Moreover, end-diastolic septum thickness (SW), end-diastolic posterior wall thickness (PW), absolute and indexed left ventricular mass, deceleration time (DT), myocardial performance index (MPI) and isovolumetric relaxation time (IVRT) were correlated with sIL-6-R, sIL-6-R/IL-6 complex and CRP levels. Interestingly, sIL-6-R, sIL-6-R/IL-6 complex, CRP, SW, PW, DT and MPI were higher in patients with a VAT area >130 cm2 than those with <130 cm2.

CONCLUSION

In normotensive obese women several pro-inflammatory molecules correlate with both echocardiographic abnormalities and the amount of intra-abdominal fat; these results may support a role for visceral fat in predisposing to cardiac dysfunction, possibly through a low-grade state of inflammation.

Effects of weight loss after bariatric surgery on epicardial fat measured using echocardiography

Epicardial fat assessed using echocardiography is associated with abdominal visceral adipose tissue and cardiovascular risk factors. Because of its location, epicardial fat may directly affect the coronary vasculature and myocardium through local secretion of bioactive molecules. This study examines the effects of weight loss after bariatric surgery on epicardial adipose tissue in patients with severe obesity. Clinical data and echocardiograms of 23 patients with severe obesity who had echocardiograms recorded before and 8.3 +/- 3.7 months after undergoing bariatric surgery were retrospectively reviewed. Epicardial fat thickness was measured as the hypoechoic space anterior to the right ventricle in both the parasternal long- and short-axis views, and an average was obtained. At baseline, patients had increased epicardial fat compared with normal-weight controls matched for age, gender, and ethnicity (5.3 +/- 2.4 vs 3.0 +/- 1.1 mm, p <0. 001). Epicardial fat thickness was associated with the patient's initial weight in severely obese patients (r = 0.51, p = 0.011). Patients lost an average of 40 +/- 14 kg after surgery. Epicardial fat thickness decreased from 5.3 +/- 2.4 to 4.0 +/-1.6 mm (p = 0.001). Change in epicardial fat correlated with initial epicardial fat thickness measured using echocardiography (r = 0.71, p <0.001). In conclusion, epicardial fat thickness decreases in severely obese patients who have substantial weight loss after bariatric surgery. Measuring epicardial fat thickness using echocardiography may be useful to monitor visceral fat loss with weight reduction therapies.

Volumetric assessment of epicardial adipose tissue with cardiovascular magnetic resonance imaging

OBJECTIVE

Previous studies determined the amount of epicardial fat by measuring the right ventricular epicardial fat thickness. However, it is not proven whether this one-dimensional method correlates well with the absolute amount of epicardial fat. In this prospective study, a new cardiovascular magnetic resonance imaging (CMR) method using the three-dimensional summation of slices method was introduced to assess the total amount of epicardial fat.

RESEARCH METHODS AND PROCEDURES

CMR was performed in 43 patients with congestive heart failure and in 28 healthy controls. The absolute amount of epicardial fat was assessed volumetrically in consecutive short-axis views by means of the modified Simpson's rule. Additionally, the right ventricular epicardial fat thickness was measured in two different imaging planes: long-axis view (EFT-4CV) and consecutive short-axis views (EFT-SAX).

RESULTS

Using the volumetric approach, patients with congestive heart failure had less epicardial fat mass than controls (51 g vs. 65 g, p=0.01). This finding was supported by EFT-SAX (2.9 mm vs. 4.3 mm, p<0.0001) but not by EFT-4CV (3.5 mm vs. 3.8 mm, p=not significant). Epicardial fat mass correlated moderately with EFT-SAX in both groups (r=0.466, p=0.012 in controls and r=0.590, p<0.0001 in patients) and with EFT-4CV in controls (r=0.387, p=0.042). There were no significant differences between EFT-4CV and EFT-SAX in controls (4.3 mm vs. 3.8 mm, p=0.240). However, in the heart failure group, EFT-4CV was significantly higher compared with EFT-SAX (3.5 mm vs. 2.9 mm, p=0.003). Interobserver variability and reproducibility were superior for the volumetric approach compared with thickness measurements.

DISCUSSION

Quantitative assessment of epicardial fat mass using the CMR-based volumetric approach is feasible and yields superior reproducibility compared with conventional methods.

Role of lipoprotein-associated phospholipase A2 in leukocyte activation and inflammatory responses

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an emerging cardiovascular risk marker. To explore the biologic role of Lp-PLA2 in atherosclerosis, we examined its expression and contribution to leukocyte activation under proatherogenic conditions.

METHODS AND RESULTS

Following the induction of diabetes and hypercholesterolemia in a porcine model, a rapid increase in plasma Lp-PLA2 activity was observed at 1 month. This was accompanied by upregulated Lp-PLA2 mRNA expression by peripheral blood mononuclear cells (PBMC) at 3 months, and elevated Lp-PLA2 mRNA expression in coronary arteries at 6 months. These changes were paralleled by increased inflammatory responses by circulating PBMC (ICAM-1, IL-6), in coronary tissues (ICAM-1, VCAM-1), and the subsequent accumulation of inflammatory cells. In human PBMC, proinflammatory mediators augmented the synthesis and release of functional Lp-PLA2. Furthermore, lysophosphatidylcholine (lysoPC), a product of Lp-PLA2 activity, induced an increase in several inflammatory cytokines (IL-1beta, IL-6, TNF-alpha) in a concentration-dependent manner. In contrast, Lp-PLA2 inhibition (SB677116; 1 microM) abrogated the inflammatory response elicited by oxidized LDL.

CONCLUSIONS

In an experimental model of diabetes and hypercholesterolemia, leukocyte activation was associated with augmented Lp-PLA2 expression. In vitro, Lp-PLA2 activity mediated leukocyte activation and inflammatory responses, whereas Lp-PLA2 inhibition abolished inflammatory responses induced by oxidized LDL. Collectively, these observations support a proatherogenic role for Lp-PLA2.

Perivascular Fat: Innocent Bystander or Active Player in Vascular Disease?

Although nearly all arteries are surrounded by perivascular fat, its role in vascular function and disease is clearly understudied. At least one type of perivascular fat, epicardial adipose tissue, appears to be related to both weight and age and tends to express proatherogenic/proinflammatory products in subjects with cardiovascular disease. Perivascular fat may evolve from primordial cells in the adventitia or from circulating precursors migrating through the arterial wall. Once deposited periarterially, adipose tissue may release locally a large number of products, which potentially interact with the arterial wall. Additionally, the authors propose that perivascular fat, per se, may attract circulating monocytes through the release of chemokines such as monocyte chemoattractant protein-1. Some of the macrophages traversing the arterial wall en route to the perivascular fat may be redirected and eventually populate the arterial wall itself, thereby enhancing vascular inflammatory processes and accelerating atherosclerosis.