Low-grade inflammation may play a role in the etiology of the metabolic syndrome in patients with coronary heart disease: the HIFMECH study

Hypercholesterolemia, not metabolic syndrome, related to adhesion of monocytes to cultured endothelium in nondiabetic subjects

The interaction of leukocytes and endothelium plays an important role in the development of atherosclerosis. Previous studies found that adhesion of leukocytes to endothelium is greater in subjects with hypercholesterolemia. It is not clear if metabolic syndrome, a contributing risk factor of cardiovascular disease, is related to this adhesion. Therefore, we conducted a study, in which 48 nondiabetic subjects were enrolled, to determine the relationship between leukocyte adhesion and the components of metabolic syndrome. After a 12-hour overnight fast, subjects' fasting blood was obtained for measurement of lipoprotein concentrations and glucose and insulin levels. Results of the number of monocyte adhesion to human umbilical vein endothelial cells were divided into high monocyte adhesion group and low monocyte adhesion group (n=24 in each group). Plasma concentrations of total cholesterol (245 +/- 5 vs 229+/- 4 mg/dL, P=.021) and low-density lipoprotein cholesterol (LDL-C) (162+/- 4 vs 146+/- 3 mg/dL, P=.003) were both higher in the high monocyte adhesion group than in the low monocyte adhesion group. Monocyte adhesion was significantly correlated to plasma concentrations of LDL-C (r=0.407, P=.002) but not to the total cholesterol (r=0.202, P=.085). However, there was no difference in monocyte adhesion to endothelium between subjects with or without metabolic syndrome, based on the modified criteria from the Adult Treatment Panel III of the National Cholesterol Education Program. Insulin resistance index, presented as homeostasis model assessment insulin resistance, and glucose or insulin responses to oral glucose tolerance test were similar between groups. Our study demonstrated that monocyte adhesion to endothelium has a stronger relationship with the plasma concentration LDL-C than with characteristics of metabolic syndrome.

Two major QTLs and several others relate to factors of metabolic syndrome in the family blood pressure program

Genome-wide variance components linkage analysis was performed on 4 latent factors underlying metabolic syndrome derived from 10 risk factors. The latent factors represent obesity and insulin, blood pressure, lipids and insulin, and central obesity. The metabolic syndrome factor scores were derived in 4 ethnic groups recruited in 3 Networks of the Family Blood Pressure Program: GENOA (blacks, Hispanics, and whites), HyperGEN (blacks and whites), SAPPHIRe (Asians). Heritabilities of metabolic syndrome factors ranged from 66% for obesity and insulin to 11% for blood pressure factor. We observed higher heritabilities for obesity and insulin, and lipids and insulin, whereas those for blood pressure and central obesity were smaller. Linkage analysis detected two major quantitative trait loci. One of them linked to the obesity and insulin factor with a lod score of 3.94 (P=0.00001, marker GATA11A06, D18S53, 41.24 cM) at marker positions linkage (lod 4.71, at 46.84 cM at 1-cM-apart distances linkage), located on chromosome 18p11.21 in GENOA black. The other linked to the blood pressure factor with a lod score of 3.22 (P=0.000059, marker GATA49C09, D17S1290, 82 cM) at marker positions linkage (lod 3.56, at 84.63 cM for 1 cM apart distances linkage) located on chromosome 17q23.1 in Hispanics. These quantitative trait loci, together with 4 additional ones with lod scores >2.5, and 30 additional ones with lod score >1.7, offer hope for dissecting the genetic architecture of metabolic syndrome with beneficial implications for molecular diagnosis, prognosis, and in potential medical intervention.

Calculating Insulin Resistance in the Primary Care Setting: Why Should We Worry about Insulin Levels in Euglycemic Patients?

PURPOSE

To describe measures that would determine which patients are insulin resistant and at risk for the metabolic syndrome and its sequelae cardiovascular diseases (CVD) and to analyze methods to determine the presence of insulin resistance and the advantages or disadvantages of each.

DATA SOURCES

Review of the multidisciplinary clinical and research literature.

CONCLUSIONS

Insulin resistance occurs early in the trajectory of the metabolic syndrome, making it a prime candidate for timely interventions to reduce risk for both type 2 diabetes and CVD. Therefore, prompt recognition of insulin resistance prior to the development of the full metabolic syndrome, type 2 diabetes, and/or CVD may assist in the prevention of morbidity and premature mortality. Likewise, because many insulin-resistant patients belong to minority racial groups (i.e., African American, Hispanic, Native American, or Pacific Islanders), early identification may have a positive impact on the reduction of cardiovascular health disparities.

IMPLICATIONS FOR PRACTICE

Documenting the presence of insulin resistance will assist the practitioner to determine if a low-risk patient is in jeopardy for development of type 2 diabetes and/or CVD. Early cardiovascular risk identification is important to clinical practice as it allows more time for the practitioner to counsel patients for the essential planning needed to make lifestyle changes.

[Obesity and osteoporosis]

Atherosclerosis is a chronic inflammatory disease associated with an elevation of inflammatory markers such as CRP -- a robust predictor of cardiovascular events. Inflammation also plays a pivotal role in the pathogenesis of osteoporosis. IL-6 proved to be the most important predictor of bone loss in the proximal femur. Adipocyte-produced inflammatory cytokines are the pathogenetic link between obesity and its metabolic consequences. The different components of the metabolic syndrome are at the same time well-established risk factors for osteoporosis. Physical training, weight loss, and a Mediterranean-style diet all have a proven cytokine-lowering effect. Contrary to muscle mass, adipose tissue if at all contributes only marginally to the preservation of bone. As a consequence, increasing lean body mass while reducing fat mass seems to be the most effective way to prevent both atherosclerosis and osteoporosis.

Relation Between the Metabolic Syndrome and Ischemic Stroke or Transient Ischemic Attack

Background and Purpose— The combination of risk factors known as the metabolic syndrome is receiving increased attention, but prospective data on the syndrome’s association with ischemic cerebrovascular events are scarce. We explored the relation of metabolic syndrome versus frank diabetes with first-ever ischemic stroke or transient ischemic attack (TIA) in a large cohort of patients with atherosclerotic cardiovascular disease.

Methods— Patients with coronary heart disease, screened for a clinical trial, underwent an extensive medical evaluation and follow-up for cerebrovascular disease over 4.8 to 8.1 years. National Cholesterol Education Program Adult Treatment Panel III criteria were used to define the metabolic syndrome, with body mass index substituted for waist circumference. Patients with previously diagnosed diabetes or with a fasting plasma glucose level >125 mg/dL (≥7.0 mmol/L) were considered diabetic.

Results— The study sample comprised 14 284 patients, of which 3703 (26%) fulfilled the criteria for the metabolic syndrome without diabetes and 3500 others (25%) the criteria for diabetes. Adjusting for stroke risk factors, patients with the metabolic syndrome without diabetes exhibited a 1.49-fold increased odds for ischemic stroke or TIA (95% confidence interval [CI], 1.20 to 1.84), whereas those with frank diabetes had a 2.29-fold increased odds (95% CI, 1.88 to 2.78). The relative odds for ischemic stroke or TIA, associated with presence of the metabolic syndrome per se, were 1.39 (95% CI, 1.10 to 1.77) in men but 2.10 (95% CI, 1.26 to 3.51) in women. Although all components of the metabolic syndrome were associated with increased risk for ischemic stroke or TIA, impaired fasting glucose and hypertension were the strongest predictors of risk.

Conclusions— The presence of the metabolic syndrome, even without diabetes, in patients with pre-existing atherosclerotic vascular disease identifies patients at increased risk for ischemic stroke or TIA. The suggestion of more pronounced risk associated with the metabolic syndrome in women deserves further assessment in other cohorts.

Pathophysiology of metabolic syndrome X and its links to the perinatal period

It is proposed that metabolic syndrome X is initiated in the perinatal period as a low-grade systemic inflammatory condition. Increased consumption of energy-dense diets by pregnant women and lactating mothers suppresses the activities of Delta-6 and Delta-5 desaturases not only in maternal tissues but also in fetal liver and the placenta, resulting in decreased plasma and tissue concentrations of long-chain polyunsaturated fatty acids omega-6 arachidonic acid (AA), omega-3 eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). EPA, DHA, and AA have negative feedback control on tumor necrosis factor-alpha and IL-6 synthesis. Hence, EPA, DHA, and AA deficiencies induced by an energy-dense diet increase generation of tumor necrosis factor-alpha and interleukin-6, markers of inflammation that in turn decrease production of endothelial nitric oxide and adiponectin to induce insulin resistance in maternal and fetal tissues. Increased concentrations of tumor necrosis factor-alpha and interleukin-6 enhance expression and activity of 11beta-hydroxysteroid dehydrogenase type 1 enzyme, which produces abdominal obesity, insulin resistance, hyperlipidemia, hyperphagia, and hyperleptinemia, characteristic features of metabolic syndrome X. Continued consumption of an energy-dense diet in childhood aggravates these molecular events. This implies that supplementation of long-chain polyunsaturated fatty acids (especially AA, EPA, and DHA in appropriate ratios) from the perinatal period through adulthood could prevent, arrest, or postpone development of metabolic syndrome X.

Adipose Tissue, Inflammation, and Cardiovascular Disease

Mounting evidence highlights the role of adipose tissue in the development of a systemic inflammatory state that contributes to obesity-associated vasculopathy and cardiovascular risk. Circulating mediators of inflammation participate in the mechanisms of vascular insult and atheromatous change, and many of these inflammatory proteins are secreted directly from adipocytes and adipose tissue–derived macrophages. Several factors linking obesity with an increased cardiovascular risk have been identified. The adipocyte-specific secretory protein adiponectin is a particularly promising candidate in this context. Its levels are decreased in obesity. Adiponectin may mediate some of its demonstrated cardioprotective effects through its anti-inflammatory properties. In addition to decreased expression of beneficial adipokines, secretion of a host of inflammatory factors from visceral adipose tissue may contribute to the increased cardiovascular risk associated with obesity. The cardioprotective effects of many of the most popular drug regimens corroborate these conclusions, demonstrating that along with improvements in other therapeutic end points, they mediate improvements in systemic inflammation. In some cases, these improvements are attributable to direct suppression of inflammatory signaling in adipocytes. The targeted suppression of various proinflammatory cascades in adipocytes specifically represents an exciting new therapeutic opportunity for the cardiovascular disease area.

Interaction between the C-260T polymorphism of the CD14 gene and the plasma IL-6 concentration on the risk of myocardial infarction: the HIFMECH study

Experimental and clinical observations suggest that innate immunity plays a major role in the pathogenesis and progression of atherosclerosis. A common C-260T polymorphism in the promoter of the CD14 gene, the trans-membrane receptor of lipopolysaccharides, has been inconsistently associated with coronary heart disease. Our objective was to evaluate the contribution of the CD14 polymorphism to the inflammatory response and to the risk of myocardial infarction (MI). We used an European case-control study, the HIFMECH study, comparing 533 men with MI and 575 sex- and age-matched controls. Associations between genotype and disease outcome, according to interleukin-6 (IL-6) and C-reactive protein (CRP) levels, were assessed using conditional logistic regression. The CD14/C-260T polymorphism was associated with plasma IL-6 levels, T/T subjects having higher plasma levels than C/C in cases but not in controls (mean+/-S.D.: 2.04+/-1.37 versus 1.70+/-1.15, p=0.01; 1.20+/-0.75 versus 1.35+/-0.88, p=0.31, respectively). Overall, the CD14/C-260T polymorphism was not associated with the risk of MI. However, in individuals with IL-6 plasma levels in the highest tertile, T allele carriers had a higher risk of MI than C/C (OR: 1.85; CI 95 1.05-3.25). IL-6 increased the risk of MI in carriers of the T allele (OR for first versus third IL-6 tertile: 4.02; CI 95 2.24-7.21), but not in C/C (OR: 0.75; CI 95 0.32-1.74, p=0.004 for interaction). The data indicate a role for CD14/C-260T in MI. The risk mediated by the polymorphism is highly dependent on IL-6 plasma levels.

Sleep, appetite, and obesity--what is the link?

There is a well known relationship between short sleep duration and high body mass index. A new study suggests that the missing link could be the appetite regulating hormones leptin and ghrelin.