Cardiovascular morbidity and mortality associated with the metabolic syndrome

NCEP-defined metabolic syndrome, diabetes, and prevalence of coronary heart disease among NHANES III participants age 50 years and older

Although the individual components of the metabolic syndrome are clearly associated with increased risk for coronary heart disease (CHD), we wanted to quantify the increased prevalence of CHD among people with metabolic syndrome. The Third National Health and Nutrition Examination Survey (NHANES III) was used to categorize adults over 50 years of age by presence of metabolic syndrome (National Cholesterol Education Program [NCEP] definition) with or without diabetes. Demographic and risk factor information was determined for each group, as well as the proportion of each group meeting specific criteria for metabolic syndrome. The prevalence of CHD for each group was then determined. Metabolic syndrome is very common, with approximately 44% of the U.S. population over 50 years of age meeting the NCEP criteria. In contrast, diabetes without metabolic syndrome is uncommon (13% of those with diabetes). Older Americans over 50 years of age without metabolic syndrome regardless of diabetes status had the lowest CHD prevalence (8.7% without diabetes, 7.5% with diabetes). Compared with those with metabolic syndrome, people with diabetes without metabolic syndrome did not have an increase in CHD prevalence. Those with metabolic syndrome without diabetes had higher CHD prevalence (13.9%), and those with both metabolic syndrome and diabetes had the highest prevalence of CHD (19.2%) compared with those with neither. Metabolic syndrome was a significant univariate predictor of prevalent CHD (OR 2.07, 95% CI 1.66-2.59). However, blood pressure, HDL cholesterol, and diabetes, but not presence of metabolic syndrome, were significant multivariate predictors of prevalent CHD. The prevalence of CHD markedly increased with the presence of metabolic syndrome. Among people with diabetes, the prevalence of metabolic syndrome was very high, and those with diabetes and metabolic syndrome had the highest prevalence of CHD. Among all individuals with diabetes, prevalence of CHD was increased compared with those with metabolic syndrome without diabetes. However, individuals with diabetes without metabolic syndrome had no greater prevalence of CHD compared with those with neither.

Renal insufficiency as a predictor of cardiovascular outcomes and mortality in elderly individuals

OBJECTIVES

This study was designed to evaluate the relationship between elevated creatinine levels and cardiovascular events.

BACKGROUND

End-stage renal disease is associated with high cardiovascular morbidity and mortality. The association of mild to moderate renal insufficiency with cardiovascular outcomes remains unclear.

METHODS

We analyzed data from the Cardiovascular Health Study, a prospective population-based study of subjects, aged >65 years, who had a serum creatinine measured at baseline (n = 5,808) and were followed for a median of 7.3 years. Proportional hazards models were used to examine the association of creatinine to all-cause mortality and incident cardiovascular mortality and morbidity. Renal insufficiency was defined as a creatinine level > or =1.5 mg/dl in men or > or =1.3 mg/dl in women.

RESULTS

An elevated creatinine level was present in 648 (11.2%) participants. Subjects with elevated creatinine had higher overall (76.7 vs. 29.5/1,000 years, p < 0.001) and cardiovascular (35.8 vs. 13.0/1,000 years, p < 0.001) mortality than those with normal creatinine levels. They were more likely to develop cardiovascular disease (54.0 vs. 31.8/1,000 years, p < 0.001), stroke (21.1 vs. 11.9/1,000 years, p < 0.001), congestive heart failure (38.7 vs. 17/1,000 years, p < 0.001), and symptomatic peripheral vascular disease (10.6 vs. 3.5/1,000 years, p < 0.001). After adjusting for cardiovascular risk factors and subclinical disease measures, elevated creatinine remained a significant predictor of all-cause and cardiovascular mortality, total cardiovascular disease (CVD), claudication, and congestive heart failure (CHF). A linear increase in risk was observed with increasing creatinine.

CONCLUSIONS

Elevated creatinine levels are common in older adults and are associated with increased risk of mortality, CVD, and CHF. The increased risk is apparent early in renal disease.

Treatment for patients with the metabolic syndrome

The metabolic syndrome, or insulin resistance syndrome, is associated with increased risk for cardiovascular disease and related mortality and has an estimated age-adjusted US prevalence of 23.7%. Dyslipidemia in the syndrome is characterized by hypertriglyceridemia, low high-density lipoprotein cholesterol, and small, dense low-density lipoprotein (LDL) particles in the context of normal/slightly elevated LDL cholesterol. Outcomes in treatment studies in or including diabetic patients suggest that a variety of therapies may be of benefit in reducing cardiovascular risk in patients with the metabolic syndrome, including physiologic therapies and pharmacologic treatments, such as aspirin, antihypertensive therapy, anti-ischemic therapy, and lipid-modifying therapies. The recently updated National Cholesterol Education Program Adult Treatment Panel III guidelines identify the metabolic syndrome as a secondary target of lipid-lowering therapy after LDL cholesterol reduction and recommend use of weight reduction and increased physical activity to address underlying risk factors as well as therapies to address specific lipid and nonlipid risk factors.

Carotid atherosclerosis and coronary heart disease in the metabolic syndrome: prospective data from the Bruneck study

OBJECTIVE

The present study aimed at prospectively evaluating carotid atherosclerosis and coronary heart disease (CHD) in subjects with the metabolic syndrome.

RESEARCH DESIGN AND METHODS

Within a prospective population-based survey examining 888 subjects aged 40-79 years, 303 subjects were identified as fulfilling World Health Organization (WHO) criteria and 158 as fulfilling the National Cholesterol Education Program (NCEP)-Adult Treatment Panel (ATP)-III criteria for diagnosing the metabolic syndrome. The 5-year change in carotid status, as assessed by echo-duplex scanning, and incident fatal and nonfatal CHD, as assessed by medical history and death certificates, were compared in subjects with the metabolic syndrome and in the rest of the sample (control subjects).

RESULTS

Compared with the control subjects, subjects with the metabolic syndrome by WHO criteria had an increased 5-year incidence and progression of carotid atherosclerosis: 51 vs. 35% developed new plaques (P = 0.021) and 34 vs. 19% developed carotid stenosis >40% (P = 0.002) after adjusting for several confounders. Subjects with the metabolic syndrome by these criteria also had an increased incidence of CHD during follow-up: 8 vs. 3% in control subjects (P = 0.012). Similar results were found when the NCEP-ATPIII criteria were used.

CONCLUSIONS

Subjects with the metabolic syndrome are at increased risk for both progressive carotid atherosclerosis and CHD.

Invited review: Identifying new mouse models of cardiovascular disease: a review of high-throughput screens of mutagenized and inbred strains

The mouse is a proven model for studying human disease. Many strains exist that exhibit either natural or engineered genetic variation and thereby enable the elucidation of pathways involved in the development of cardiovascular disease. Although those mouse models have been fundamental to advancing our knowledge base, we are still at an early stage in understanding how genes contribute to complex disorders. There remains a need for new animal models that closely represent human disease. To expedite their development, we have established the Center for New Mouse Models of Heart, Lung, Blood, and Sleep Disorders at The Jackson Laboratory. We are using a phenotype-driven approach to identify mutations leading to atherosclerosis, hypertension, obesity, blood disorders, lung dysfunction, thrombosis, and disordered sleep. Our high-throughput, comprehensive phenotyping draws from two sources for new models: 1) the natural variation among over 40 inbred mouse strains and 2) chemically induced, whole-genome mutagenized mice. Here, we review our cardiovascular screens and present some hypertensive, obese, and cardiovascular models identified with this approach.

Nonalcoholic fatty liver, steatohepatitis, and the metabolic syndrome

Nonalcoholic fatty liver disease (NAFLD) has been associated with the insulin-resistance syndrome, at present defined as the metabolic syndrome, whose limits were recently set. We assessed the prevalence of the metabolic syndrome in 304 consecutive NAFLD patients without overt diabetes, on the basis of 3 or more criteria out of 5 defined by the U.S. National Institutes of Health (waist circumference, glucose, high-density lipoprotein [HDL]-cholesterol, triglycerides, and arterial pressure). The prevalence of the metabolic syndrome increased with increasing body mass index, from 18% in normal-weight subjects to 67% in obesity. Insulin resistance (Homeostasis Model Assessment method) was significantly associated with the metabolic syndrome (odds ratio [OR], 2.5; 95% CI, 1.5-4.2; P <.001). Liver biopsy was available in 163 cases (54%). A total of 120 patients (73.6%) were classified as having nonalcoholic steatohepatitis (NASH); 88% of them had a metabolic syndrome (vs. 53% of patients with pure fatty liver; P <.0001). Logistic regression analysis confirmed that the presence of metabolic syndrome carried a high risk of NASH among NAFLD subjects (OR, 3.2; 95% CI, 1.2-8.9; P =.026) after correction for sex, age, and body mass. In particular, the syndrome was associated with a high risk of severe fibrosis (OR, 3.5; 95% CI, 1.1-11.2; P =.032). In conclusion, the presence of multiple metabolic disorders is associated with a potentially progressive, severe liver disease. The increasing prevalence of obesity, coupled with diabetes, dyslipidemia, hypertension, and ultimately the metabolic syndrome puts a very large population at risk of forthcoming liver failure in the next decades.

Arterial hypertension and ischaemic stroke

OBJECTIVES

Arterial hypertension is, besides age, the number one risk factor for ischaemic stroke. Patients with arterial hypertension frequently present with additional coexisting vascular risk factors interacting in a complex way.

MATERIAL AND METHODS

This paper reviews the benefit of antihypertensive treatment, as well as different treatment options of arterial hypertension and their side-effects.

RESULTS

Patients with definite arterial hypertension, but also patients with so-called normal or high-normal blood pressure are at increased risk to develop stroke and other cardiovascular complications. Vascular remodelling of small and large vessels provoked by arterial hypertension is the initial step in the development of atherosclerosis and lipohyalinosis. Vascular remodelling can be improved or even normalized by antihypertensive treatment with angiotensin-converting-enzyme inhibitors and angiotensin-I-receptor antagonists showing the most convincing effects. Angiotensin-converting-enzyme inhibitors and angiotensin-I-receptor antagonists have the lowest rate of side-effects, however, economic restraints hinder their general application. Statins are needed to treat dyslipidaemia. They also lower blood pressure and have a synergistic effect with the above two antihypertensive components in lowering blood pressure. In hypertensive patients, risk of stroke and other cardiovascular complications is determined by the blood pressure level and the presence or absence of target organ damage and the interaction with other risk factors, such as cigarette smoking, dyslipidaemia, and diabetes. These high-risk patients should be treated even more aggressively than usual.

CONCLUSIONS

In the vast majority of patients and healthy individuals, target blood pressure should be as high as or below 120/80 mmHg to minimize the occurrence of stroke and other cardiovascular complications.

Efficacy of rosuvastatin 10 mg in patients with the metabolic syndrome

The constellation of risk factors known as the metabolic syndrome increases the risk of coronary artery disease at any low-density lipoprotein (LDL) cholesterol level. We performed an exploratory analysis of data from 5 trials to study the effects of rosuvastatin 10 mg on lipid levels and ratios in hypercholesterolemic patients (LDL cholesterol > or =160 mg/dL and <250 mg/dL) who met a modified National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) definition of the metabolic syndrome. Of 580 patients completing 12 weeks of treatment with rosuvastatin 10 mg, 194 (33%) met the definition of the metabolic syndrome by exhibiting > or =3 of the following: body mass index >30; triglycerides > or =150 mg/dL; high-density lipoprotein (HDL) cholesterol <40 mg/dL in men and <50 mg/dL in women; blood pressure > or =130/> or =85 mm Hg or receiving current medication for hypertension; and fasting blood glucose > or =110 mg/dL. Patients with the metabolic syndrome had higher triglyceride, non-HDL cholesterol, apolipoprotein B, and lipid ratios, and lower HDL cholesterol and apolipoprotein A-I levels, at baseline compared with patients without the metabolic syndrome. In patients with the metabolic syndrome, rosuvastatin 10 mg improved LDL cholesterol (-47%), non-HDL cholesterol (-43%), non-HDL cholesterol/HDL cholesterol ratio (-47%), apolipoprotein B (-37%), apolipoprotein B/apolipoprotein A-I ratio (-40%), triglycerides (-23%), apolipoprotein A-I (+7%), and HDL cholesterol (+10%)-in a manner similar to that in hypercholesterolemic patients who did not meet these criteria. Among patients who met the metabolic syndrome criteria and who had triglycerides > or =200 mg/dL, 64% met their ATP III non-HDL goals.

Insulin secretion and insulin sensitivity pattern is different in isolated impaired glucose tolerance and impaired fasting glucose: the risk factor in Impaired Glucose Tolerance for Atherosclerosis and Diabetes study

OBJECTIVE

Isolated impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are two risk categories for type 2 diabetes. This study compared both categories with respect to the degree of insulin secretion abnormalities and insulin resistance.

RESEARCH DESIGN AND METHODS

This is a crossover comparison of a population at high risk for type 2 diabetes. The subjects were recruited from the Risk Factor in Impaired Glucose Tolerance for Atherosclerosis and Diabetes (RIAD) study. They underwent a 75-g oral glucose tolerance test, with measurement of specific insulin, C-peptide, proinsulin, and free fatty acids at baseline and every 30 min after load for 2 h. Factor analysis was performed to evaluate the importance of insulin resistance and secretion abnormalities in both categories.

RESULTS

All categories of prediabetic hyperglycemia had a higher cardiovascular risk factor level when adjusted for sex, age, and BMI compared to control subjects with normal glucose tolerance. Subjects with isolated IFG were more insulin resistant than those with IGT. By contrast, subjects with isolated IGT exhibited a more severe deficit in early- and late-phase insulin secretion versus IFG subjects. As shown with factor analysis, in IFG the insulin resistance factor explained 28.4% of the variance, whereas in IGT the insulin secretion factor was dominant, explaining 31.1% of the total variance.

CONCLUSIONS

Our cross-sectional data from the RIAD study demonstrate that isolated IFG and isolated IGT are different with respect to the degree of insulin resistance and anomalies in insulin secretion, and that subjects with IGT exhibit a deficit in the early and late phases of insulin secretion. This finding may be important for a differential approach in primary prevention of type 2 diabetes.

Insulin resistance, the metabolic syndrome, and risk of incident cardiovascular disease in nondiabetic american indians: the Strong Heart Study

OBJECTIVE

Insulin resistance (IR) and the metabolic syndrome (MS) are associated with type 2 diabetes and adverse cardiovascular disease (CVD) risk factor profiles. Whether IR and MS predict CVD independently of diabetes and other CVD risk factors is not known. This study examines whether IR and/or presence of MS are independently associated with CVD in nondiabetic American Indians (AI).

RESEARCH DESIGN AND METHODS

We examined 2283 nondiabetic AI who were free of CVD at the baseline examination of the Strong Heart Study (SHS). CVD risk factors were measured, IR was quantified using the homeostasis model assessment (HOMA), and MS as defined by the National Cholesterol Education Program Adult Treatment Panel (ATP III) was assessed for each participant. Incident CVD and diabetes were ascertained during follow-up.

RESULTS

MS was present in 798 individuals (35%), and 181 participants (7.9%) developed CVD over 7.6 +/- 1.8 years of follow-up. Age, BMI, waist circumference, and triglyceride levels increased and HDL cholesterol decreased across tertiles of HOMA-IR. Risk of diabetes increased as a function of baseline HOMA-IR (6.3, 14.6, and 30.1%; P < 0.001) and MS (12.8 vs. 24.5%). In Cox models adjusted for CVD risk factors, risk of CVD did not increase either as a function of baseline HOMA-IR or MS, but individual CVD risk factors predicted subsequent CVD.

CONCLUSIONS

Among nondiabetic AI in the SHS, HOMA-IR and MS both predict diabetes, but neither predicts CVD independently of other established CVD risk factors.

Detection of insulin resistance in Turkish adults: a hospital-based study

AIM

The aim of the present study was to investigate the usefulness of insulin sensitivity check indices in our hospital population.

METHODS

Both HOMA (insulin X glucose in mmol/l/22.5) and QUICKI (1/log insulin in microu/ml + log glucose in mg/dl) indices were calculated from fasting values in 1,774 subjects from the medical records of Baskent University Adana Hospital.

RESULTS

Subjects with diabetes, hyperlipidaemia and central obesity were characterized by significantly higher HOMA and lower QUICKI indices than those of healthy subjects. A fall in the QUICKI index (0.3469 +/- 0.028 in healthy subjects and 0.3247 +/- 0.025 in non-obese diabetics) as well as an increase in HOMA index (2.24 +/- 1.26 in healthy subjects and 3.59 +/- 2.08 in non-obese diabetics) corresponded to metabolic and clinical manifestations of insulin resistance in various groups of subjects. Age, low HDL cholesterol, male sex, type 2 DM and hypertension were independent risk factors for CAD. Age, male sex, waist circumference and CAD were found to be risk factors for hypertension. Fasting insulin and glucose levels contain sufficient information to assess insulin sensitivity over a wide range in a diverse population. The following can be accepted as mean values to assess insulin resistance in our hospital population: 0.3469 +/- 0.028 for the QUICKI index and 2.24 +/- 1.26 for the HOMA index

CONCLUSIONS

HOMA and QUICKI indices are simple and reproducible methods for determining insulin sensitivity in humans.

Cardiovascular protective role of a low-dose antihypertensive combination in obese Zucker rats

OBJECTIVE

Obesity, non-insulin-dependent diabetes mellitus (NIDDM) and hypertension are leading causes associated with increased cardiovascular morbidity and mortality. In modern times, the combined first line antihypertensive therapy with at least two drugs with a different mechanism of action to achieve a better blood pressure control, is increasing in acceptance worldwide. The aim of the present study was to determine possible beneficial effects of the low-dose combination (LDC) of an angiotensin-converting enzyme (ACE) inhibitor, perindopril (PER), and the diuretic indapamide (IND), regarding myocardial and vessels protection in an animal model of hypertension, obesity and NIDDM, such as the obese Zucker rat (OZR), and control lean Zucker rats (LZR).

DESIGN

Ten-week-old male OZR (fa/fa) and LZR (Fa/fa) were used in this study. OZR group (G1, n=8), OZR with LDC group (G2, n=8); LZR group (G3, n=8) and LZR with LDC group (G4, n=8). During 6 months, G2 and G4 received a daily dose of 1 mg/kg combination of 0.76 mg/kg PER + 0.24 mg/kg IND, (ratio of doses 0.32), by gavage, and G1 and G3 received an equal volume of vehicle throughout the experiment. In order to evaluate cardiac dimensions and left ventricular mass (LVM) transthoracic echocardiograms were performed, at baseline and at the end of the experiment. Urine and blood samples for biochemical determination were obtained. After 6 months of treatment all rats were sacrificed, hearts were harvested for light microscopy (LM), high-resolution light microscopy (HRLM), immunohistochemistry including monoclonal antibodies against transforming growth factor beta (TGFbeta1) and anti-collagen type I (COL I) and type III (COL III) and electron microscopy (EM) studies.

RESULTS

At the end of the study OZR treated with LDC presented: (1) lower blood pressure (128.9 +/- 4 versus 150.3 +/- 3.6 mmHg, P< 0.05); (2) smaller cardiac dimensions (P< 0.01); (3) lower LVM/100 g body weight (0.17 +/- 0.02 versus 0.30 +/- 0.05, P< 0.01); (4) higher fractional shortening (34.5 +/- 3.2 versus 23.3 +/- 5.9%, P< 0.01) than OZR untreated. Moreover, OZR that received LDC showed higher: (1) myocyte density (48 +/- 1.5 versus 20 +/- 2.5 myocytes/area, P< 0.01); (2) capillary density (30.5 +/- 3.1 versus 9.5 +/- 1.6 capillaries/area, P<0.01); (3) myofilament thickness (12.05 +/- 0.27 versus 9.83 +/- 0.39 nm, P<0.01); and lower amounts of: (1) TGFbeta1 in myocytes (P< 0.01), interstitium (P< 0.01) and vessel wall (P< 0.05); (2) COL I and COL III (P< 0.01), and COL I /COL III ratio (P< 0.01), compared with untreated OZR. Finally, OZR-treated with LDC showed not only unsubstantial modification in carbohydrate and lipid metabolism when compared with untreated OZR, but also an improvement in insulin/glucose ratio (P< 0.05).

CONCLUSION

These results suggest that LDC of PER + IND can control cardiovascular damage in OZR providing an additional help in the metabolic scenario likewise.

A comparison of the prevalence of the metabolic syndrome using two proposed definitions

OBJECTIVE

To compare the prevalence of the metabolic syndrome using two definitions: one proposed by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III [ATP III]) and one by the World Health Organization (WHO).

RESEARCH DESIGN AND METHODS

We used data from a nationally representative sample of the noninstitutionalized civilian population of the U.S. from the Third National Health and Nutrition Examination Survey, a cross-sectional health examination survey (1988-1994).

RESULTS

Among 8608 participants aged >or=20 years, the age-adjusted prevalence was 23.9% using the ATP III definition and 25.1% using the WHO definition. Among all participants, 86.2% were classified as either having or not having the metabolic syndrome under both definitions. Estimates differed substantially for some subgroups, however. For example, in African-American men, the WHO estimate was 24.9%, compared with the ATP III estimate of 16.5%.

CONCLUSIONS

A universally accepted definition of the metabolic syndrome is needed.

Association of albuminuria and the metabolic syndrome

Microalbuminuria clusters with the metabolic syndrome, and both conditions predict cardiovascular disease mortality. The reported relationships of microalbuminuria with the individual components of the metabolic syndrome (i.e., hyperglycemia, insulin resistance, hypertension, dyslipidemia, abdominal obesity) are variable. Each of these components, as well as intrauterine effects and diet and other lifestyle factors, may contribute to elevated risk of microalbuminuria in certain population groups. Recent evidence indicates a role for oxidation and inflammation in cardiovascular disease, and endothelial dysfunction (exacerbated by factors such as dyslipidemia) may be the mediator of this relationship. Because endothelial dysfunction can also be manifested as microalbuminuria, this provides a potential explanation of the observed association of the metabolic syndrome, chronic inflammation, and microalbuminuria.

Relation of C-reactive protein to features of the metabolic syndrome in normal glucose tolerant, impaired glucose tolerant, and newly diagnosed type 2 diabetic subjects

OBJECTIVE

To determine the relationship between CRP levels and the components of MS in normal glucose tolerant (NGT), impaired glucose tolerant (IGT), and Type 2 diabetic subjects.

MATERIAL AND METHODS

A based cross-sectional population study was performed. Eligible subjects, men and non-pregnant women, 30 to 64 year of age, were randomly recruited. Subjects with acute or chronic diseases were excluded. Only newly diagnosed type 2 diabetic or hypertensive subjects were included. Disorders related to CRP increase, also were exclusion criteria. In accordance to WHO proposal, components of MS were: High Blood Pressure, Dyslipidemia, Obesity, and Microalbuminuria, and MS was defined, for the NGT, if at least two of the criteria were fulfilled and in addition the subject had insulin resistance. The MS in IGT and DM subjects was defined if at least two of the criteria were fulfilled.

RESULTS

CRP was significantly associated with MS for the NGT (Odds ratio -OR- 3.8, CI(95%) 1.6-14.8), IGT (OR 4.9, CI(95%) 1.2-15.5), and diabetes (OR 5.6, CI(95%) 1.9-10.2). For NGT, after adjustment for obesity, CRP was not longer associated with MS. After adjust for obesity and fasting glucose (FG), the relationship between CRP and MS for IGT was lost. Finally, after adjustment for obesity, FG, and microalbuminuria, CRP was not longer associated with MS for diabetic subjects.

CONCLUSIONS

This study show a significant relationship between CRP and MS which is maintained only by obesity in the NGT, by obesity and FG in the IGT, and by obesity, FG, and microalbuminuria in the newly diagnosed diabetic subjects.

Dietary fat, fatty acid composition in plasma and the metabolic syndrome

PURPOSE OF REVIEW

The metabolic syndrome, a cluster of disorders often including abdominal obesity, is associated with a high risk of cardiovascular disease and premature death. Insulin resistance is a key feature of the metabolic syndrome. Observational studies have indicated that the type of fat in the diet may be related to the development of insulin resistance and the metabolic syndrome, also independent of possible effects on body weight. Dietary surveys are often imprecise. One way to monitor the type of fat in the diet is to record the fatty acid composition in plasma. This review summarizes recent data on the relationships between fatty acid composition in plasma and insulin resistance, diabetes and other disorders related to the metabolic syndrome.

RECENT FINDINGS

Insulin resistance and insulin resistant states are often associated with the fatty acid pattern in plasma, characterized by an increased proportion of palmitic (16 : 0) and a low proportion of linoleic (18 : 2 n-6) acids, with a distribution of other fatty acids indicating an increased activity of delta-9 and delta-6 desaturase. This shows that there may be a causal relationship between the type of fat in the diet and insulin action, an assumption supported by recent dietary intervention studies.

SUMMARY

In a public health perspective these results, from both observational and intervention studies, underline the importance of fat quality in the diet for the development of a number of prevalent diseases. Taken together with several earlier studies and recent epidemiological findings, they give strong support to present dietary guidelines.

Epidemiology of the insulin resistance syndrome

The insulin resistance syndrome consists of the co-occurrence of metabolic risk factors for type 2 diabetes and cardiovascular disease, including overall obesity, central obesity, dyslipidemia (characterized by elevated levels of triglycerides and low levels of high-density lipoprotein cholesterol), hyperglycemia, and hypertension. Using criteria proposed by the National Cholesterol Education Program Adult Treatment Panel III, national survey data suggest the insulin resistance syndrome is very common, affecting about 24% of US adults aged greater than 20 years. The syndrome is more common in older people and in Mexican Americans, and will increase in prevalence as populations age and become more obese. Identification of the syndrome warrants aggressive interventions known to prevent type 2 diabetes and cardiovascular disease, including weight reduction, increased physical activity, and control of hypertension and dyslipidemia.

Lipid abnormalities in the metabolic syndrome

The metabolic syndrome is the constellation of adverse metabolic and clinical effects of insulin resistance. Its high and increasing prevalence and its profound impact on the major diseases of the western world require that clinicians consider its diagnosis and management on a routine basis. Recently published guidelines on its definition now make convenient and reliable diagnosis possible. Also, there is new and better understanding of the complex dyslipidemias and other risk factors strongly associated with the metabolic syndrome, which greatly increase the risk of clinical atherosclerotic events. Comprehensive clinical evaluation of these dyslipidemias and associated atherosclerosis risk factors can lead to their aggressive treatment, customized according to the circumstances of each patient. These steps are now more feasible and more clearly desirable than ever before. Statins alone greatly reduce atherosclerosis risk, but combination lipid therapy is often required for optimal dyslipidemia management and atheroprevention.

Endothelial dysfunction and the metabolic syndrome

The metabolic syndrome is a highly prevalent multifaceted clinical entity produced through the interaction of genetic, hormonal, and lifestyle factors. A distinctive constellation of abnormalities precedes and predicts the accelerated development of inflammation and coagulation represent emerging risk contributors associated with obesity and insulin resistance, central components of the metabolic syndrome, which act in concert with traditional abnormalities to increase cardiovascular risk. The initiation and progression of atherosclerosis may have its origins in impaired endothelial function that can be detected at the earliest stages of development of the syndrome. The basic elements of the metabolic syndrome and accelerated phase of atherogenesis are often silent partners that present many years before the onset of type 2 diabetes mellitus. The ability to detect and monitor subclinical vascular disease, as a reflection of the multiple factors that contribute to impair arterial wall integrity, holds potential to further refine cardiovascular risk stratification. Noninvasive assessment of vascular health may also aid the clinical decision-making process by guiding therapeutic interventions to optimize vascular protection in the metabolic syndrome.

C-reactive protein, the metabolic syndrome, and risk of incident cardiovascular events: an 8-year follow-up of 14 719 initially healthy American women

BACKGROUND

The metabolic syndrome describes a high-risk population having 3 or more of the following clinical characteristics: upper-body obesity, hypertriglyceridemia, low HDL, hypertension, and abnormal glucose. All of these attributes, however, are associated with increased levels of C-reactive protein (CRP).

METHODS AND RESULTS

We evaluated interrelationships between CRP, the metabolic syndrome, and incident cardiovascular events among 14 719 apparently healthy women who were followed up for an 8-year period for myocardial infarction, stroke, coronary revascularization, or cardiovascular death; 24% of the cohort had the metabolic syndrome at study entry. At baseline, median CRP levels for those with 0, 1, 2, 3, 4, or 5 characteristics of the metabolic syndrome were 0.68, 1.09, 1.93, 3.01, 3.88, and 5.75 mg/L, respectively (P(trend) <0.0001). Over the 8-year follow-up, cardiovascular event-free survival rates based on CRP levels above or below 3.0 mg/L were similar to survival rates based on having 3 or more characteristics of the metabolic syndrome. At all levels of severity of the metabolic syndrome, however, CRP added prognostic information on subsequent risk. For example, among those with the metabolic syndrome at study entry, age-adjusted incidence rates of future cardiovascular events were 3.4 and 5.9 per 1000 person-years of exposure for those with baseline CRP levels less than or greater than 3.0 mg/L, respectively. Additive effects for CRP were also observed for those with 4 or 5 characteristics of the metabolic syndrome. The use of different definitions of the metabolic syndrome had minimal impact on these findings.

CONCLUSIONS

These prospective data suggest that measurement of CRP adds clinically important prognostic information to the metabolic syndrome.

Insulin resistance but not inflammation is associated with gestational hypertension

Hypertensive disorders of pregnancy, including gestational hypertension and preeclampsia, are leading causes of pregnancy-associated morbidity. Although insulin resistance and inflammation contribute to preeclampsia, prospective data regarding mechanisms of gestational hypertension are sparse. We conducted a prospective, nested case-control study to test the hypotheses that insulin resistance, marked by reduced sex hormone-binding globulin (SHBG) levels, and inflammation, marked by increased C-reactive protein levels, are similarly associated with gestational hypertension. We measured first-trimester C-reactive protein and SHBG levels in 51 women who subsequently developed gestational hypertension and 102 randomly selected normotensive pregnant controls. Compared with controls, first-trimester SHBG levels were significantly reduced among women who later developed gestational hypertension (176+/-73 versus 203+/-79 nmol/L; P=0.03), but there was no difference in C-reactive protein levels. There was statistically significant interaction among nulliparity, first-trimester SHBG levels, and risk of gestational hypertension, such that increasing SHBG levels were associated with significantly reduced risk of gestational hypertension among nulliparous women (odds ratio, 0.64 per 50-nmol/L increase; 95% confidence interval, 0.46, 0.90; P<0.01) but not among multiparous women. This association remained significant after adjusting for potential confounders (odds ratio, 0.55; 95% confidence interval, 0.31, 0.98; P=0.04). We conclude that insulin resistance, but not inflammation, is an independent risk factor for gestational hypertension among nulliparous women. Furthermore, important mechanistic differences exist in the pathogenesis of gestational hypertension comparing nulliparous and multiparous women.

Circulating oxidized low-density lipoprotein (LDL) is associated with risk factors of the metabolic syndrome and LDL size in clinically healthy 58-year-old men (AIR study)

OBJECTIVES

Hypothetically the atherogenic effect of the metabolic syndrome may be mediated through the increased occurrence of small LDL-particles which are easily modified to atherogenic oxidized LDL (ox-LDL). The aim of this study was to test this concept by examining the association between circulating ox-LDL, LDL-particle size, and the metabolic syndrome.

DESIGN AND RESULTS

A population-based sample of clinically healthy 58-year-old men (n = 391) was recruited. Ox-LDL was measured by ELISA (specific monoclonal antibody, mAb-4E6) and LDL-particle size by gradient gel electrophoresis. The results showed that ox-LDL significantly correlated to factors constituting the metabolic syndrome; triglycerides (r = 0.43), plasma insulin (r = 0.20), body mass index (r = 0.20), waist-to-hip ratio (r = 0.21) and HDL (r = -0.24); (P < 0.001). Ox-LDL correlated also to LDL-particle size (r = -0.42), Apo-B (r = 0.70), LDL (r = 0.65); (P < 0.001) and, furthermore, with Apo A-1 (r = -0.13) and heart rate (r = 0.13); (P < 0.01).

CONCLUSION

The metabolic syndrome was accompanied by high plasma ox-LDL concentrations compared with those without the syndrome. Ox-LDL levels were associated with most of the risk factors constituting the metabolic syndrome and was, in addition related to small LDL-particle size. To our knowledge the present study is the first one to demonstrate that circulating ox-LDL levels are associated with small LDL-particle size in a population representative sample of clinically healthy middle-aged men. The high degree of intercorrelation amongst several factors makes it difficult to clarify the independent role of any specific factor.

Impact of weight loss on the metabolic syndrome

AIM

Individuals with the metabolic syndrome (MS), a clustering of risk factors [triglycerides, glucose, high-density lipoprotein cholesterol, blood pressure (BP), abdominal obesity] defined by the National Cholesterol Education Program (NCEP), are at high risk for coronary heart disease and type 2 diabetes mellitus, and may benefit from aggressive lifestyle modification.

METHODS

We reviewed 1 year of consecutive patients' charts to determine the prevalence of the MS in obese individuals enrolled in a medically supervised rapid weight loss programme, the correlation of weight change with the components of the MS, and response to diet-induced weight loss.

RESULTS

Out of 185 individuals, 125 (68%) met the NCEP definition of the MS. A moderate decrease in weight (6.5%) induced by a very low calorie diet (VLCD) resulted in substantial reductions of systolic (11.1 mmHg) and diastolic (5.8 mmHg) blood pressure (BP), glucose (17 mg/dl), triglycerides (94 mg/dl) and total cholesterol (37 mg/dl) at 4 weeks (all p < 0.001). These improvements were sustained at the end of active weight loss (average 16.7 weeks; total weight loss 15.1%), with further significant reductions in BP and triglycerides. Weight loss was related to the changes in each criterion of the metabolic syndrome.

CONCLUSIONS

The MS is prevalent in two-thirds of obese individuals enrolling in a structured weight loss programme. Moderate weight loss with a VLCD markedly improved all aspects of the MS.

AZ 242, a novel PPARalpha/gamma agonist with beneficial effects on insulin resistance and carbohydrate and lipid metabolism in ob/ob mice and obese Zucker rats

Abnormalities in fatty acid (FA) metabolism underlie the development of insulin resistance and alterations in glucose metabolism, features characteristic of the metabolic syndrome and type 2 diabetes that can result in an increased risk of cardiovascular disease. We present pharmacodynamic effects of AZ 242, a novel peroxisome proliferator activated receptor (PPAR)alpha/gamma agonist. AZ 242 dose-dependently reduced the hypertriglyceridemia, hyperinsulinemia, and hyperglycemia of ob/ob diabetic mice. Euglycemic hyperinsulinemic clamp studies showed that treatment with AZ 242 (1 micromol/kg/d) restored insulin sensitivity of obese Zucker rats and decreased insulin secretion. In vitro, in reporter gene assays, AZ 242 activated human PPARalpha and PPARgamma with EC(50) in the micro molar range. It also induced differentiation in 3T3-L1 cells, an established PPARgamma effect, and caused up-regulation of liver fatty acid binding protein in HepG-2 cells, a PPARalpha-mediated effect. PPARalpha-mediated effects of AZ 242 in vivo were documented by induction of hepatic cytochrome P 450-4A in mice. The results indicate that the dual PPARalpha/gamma agonism of AZ 242 reduces insulin resistance and has beneficial effects on FA and glucose metabolism. This effect profile could provide a suitable therapeutic approach to the treatment of type 2 diabetes, metabolic syndrome, and associated vascular risk factors.

Atherosclerosis in type 2 diabetes mellitus and insulin resistance: mechanistic links and therapeutic targets

The ongoing heavy burden of cardiovascular disease associated with diabetes mellitus highlights the failure of current treatment strategies to address effectively the cardiovascular risk profile in such patients. Insulin resistance is not only an underlying feature in most cases of type 2 diabetes, but is also associated, through the Insulin Resistance Syndrome, with cardiovascular risk factors that promote atherothrombosis through diverse mechanisms. Growing evidence suggests that treatment with anti-diabetic agents that improve insulin sensitivity, such as the thiazolidinediones, improve multiple components of the Insulin Resistance Syndrome, have beneficial effects on various atherothrombotic mechanisms, and reduce atherosclerosis in animal models and perhaps humans as well. Given data implicating chronic inflammation as a central feature of atherosclerosis, the anti-inflammatory activity of the thiazolidinediones may contribute to their potential anti-atherosclerotic effects. An improved understanding of the mechanisms linking diabetes, atherosclerosis, and cardiovascular disease is needed in order to understand how these and other current and emerging therapies might reduce diabetes-associated cardiovascular disease.

Obesity and cardiovascular disease

Obesity is a major contributor to the prevalence of cardiovascular disease in the developed world, and yet has only recently been afforded the same level of attention as other risk factors of coronary artery disease. Obesity is a chronic metabolic disorder associated with cardiovascular disease and increased morbidity and mortality. It is apparent that a variety of adaptations/alterations in cardiac structure and function occur as excessive adipose tissue accumulates, even in the absence of comorbidities. Shifts toward a less physically demanding lifestyle are observed today throughout different populations, and this scourge associated with obesity implicates a corresponding increase in the number of individuals afflicted with the metabolic syndrome, which defines the obese patient as being "at risk." Adipose tissue is not simply a passive storehouse for fat, but an endocrine organ that is capable of synthesizing and releasing into the bloodstream a variety of molecules that may impact unfavorably the risk factor profile of a patient. Indeed, obesity may affect atherosclerosis through unrecognized variables and risk factors for coronary artery disease such as dyslipidemia, hypertension, glucose intolerance, inflammatory markers, and the prothrombotic state. By favorably modifying lipids, decreasing blood pressure, and decreasing levels of glycemia, proinflammatory cytokines, and adhesion molecules, weight loss may prevent the progression of atherosclerosis or the occurrence of acute coronary syndrome events in the obese high-risk population.

Gender differences in factors influencing insulin resistance in elderly hyperlipemic non-diabetic subjects

BACKGROUND

The increase in the prevalence of insulin resistance-related metabolic syndrome, a disorder that greatly increases the risk of diabetes, heart attack and stroke, is alarming. One of the most frequent and early symptoms of metabolic syndrome is hypertriglyceridemia. We examined the gender differences between various metabolic factors related to insulin resistance in elderly non-diabetic men and postmenopausal women of comparable age suffering from hypertriglyceridemia, and compared them with healthy subjects of equal age.

RESULTS

The indexes of insulin resistance HOMA IR and QUICKI were significantly higher in both hyperlipemic men and women than in controls; 95% confidence limits of hyperlipemic subjects did not overlap with controls. In both normolipemic and hyperlipemic men and women serum leptin correlated significantly with insulin resistance, while HDL-cholesterol correlated inversely with HOMA-IR only in women (both normo- and hyperlipemic), and serum tumor necrosis factor alpha (TNFalpha) only in hyperlipemic women. According to results of multiple regression analysis with HOMA-IR as a dependent variable, leptin played a significant role in determining insulin resistance in both genders, but--aside from leptin--triglycerides, TNFalpha and decreased HDL-cholesterol were significant determinants in women, while body mass index and decreased HDL-cholesterol were significant determinants in men. The coefficient of determination (R2) of HOMA IR by above mentioned metabolic variables was in women above 60%, in men only about 40%.

CONCLUSION

The significant role of serum leptin in determination of insulin resistance in both elderly men and postmenopausal women of equal age was confirmed. However, the study also revealed significant gender differences : in women a strong influence of triglycerides, TNFalpha and decreased HDL-cholesterol, in men only a mild role of BMI and decreased HDL-cholesterol.

Metabolic syndrome in the rat: females are protected against the pro-oxidant effect of a high sucrose diet

Metabolic syndrome is more prevalent in men than in women. In an experimental dietary model of metabolic syndrome, the high-fructose-fed rat, oxidative stress has been observed in males. Given that estradiol has been documented to exert an antioxidant effect, we investigated whether female rats were better protected than males against the adverse effects of a high-sucrose diet, and we studied the influence of hormonal status in female rats. Males and females were first fed a sucrose-based or starch-based diet for 2 weeks. In the males, the plasma triglyceride (TG)-raising effect of sucrose was accompanied by significantly lowered plasma alpha-tocopherol and a significantly lowered alpha-tocopherol/TG ratio (30%), suggesting that vitamin E depletion may predispose lipoproteins to subsequent oxidative stress. In males, after exposure of heart tissue homogenate to iron-induced lipid peroxidation, thiobarbituric reactive substances were significantly higher in the sucrose-fed than in the starch-fed rats. In contrast, in sucrose-fed females, neither a decrease in vitamin E/TG ratio nor an increased susceptibility of heart tissue to peroxidation was observed, despite both a significantly decreased heart superoxide dismutase activity (14%) and a significant 3-fold increase in plasma nitric oxide concentration compared with starch-fed females. The influence of hormonal status in female rats was then assessed using intact, ovariectomized, or estradiol-supplemented ovariectomized female rats fed the sucrose or starch diet for 2 weeks. After exposure of heart tissue to iron-induced lipid peroxidation, higher susceptibility to peroxidation was found only in ovariectomized females fed the sucrose diet compared with the starch group and not in intact females or ovariectomized females supplemented with estradiol. Thus, estrogens, by their effects on antioxidant capacity, might explain the sexual difference in the pro-oxidant effect of sucrose diet resulting in metabolic syndrome in rats.

The glucocorticoid receptor gene and its association to metabolic syndrome

In recent decades, there has been an increasing interest in the role of endogenous glucocorticoids such as cortisol in the pathogenesis of metabolic syndrome. Studies in humans have suggested a positive association between obesity, hypertension, and insulin resistance, with alleles at the glucocorticoid receptor (GR) gene. For instance, the BclI polymorphism within the intron upstream of GR exon 2 has been associated with cardiovascular risk factors such as visceral obesity, hypertension, insulin resistance, and elevated cortisol concentrations. However, the location of the BclI polymorphism is not known, and the variant has so far not been compared with the wild-type receptor for its ability to be activated by glucocorticoids. Although several other mutations in the GR gene have been postulated as being relevant to the progression to type 2 diabetes and cardiovascular diseases, conflicting results makes it difficult to determine exactly what effect these GR variations have on metabolic syndrome incidence and progression. Further studies focusing on the most compelling GR mutations might offer a better understanding of metabolic syndrome pathogenesis and progression, aiding in the development of more effective treatments for this condition.

Preventing diabetes by treating aspects of the metabolic syndrome

The metabolic syndrome often develops into and is usually present in type 2 diabetes in association with premature cardiovascular disease. Treating diabetes can prevent some of its devastating consequences, but it does not eliminate them all. With the goal to eliminate all the adverse consequences of the syndrome, the optimal approach would be through its prevention. Insulin resistance appears to be pivotal to development of the syndrome complex that includes features such as intra-abdominal or visceral obesity, hypertension, impaired glucose homeostasis, dyslipidemia with elevated triglycerides and low high-density lipoprotein without elevations of low-density lipoprotein, a procoagulant state, and impaired vascular function. Improving the insulin resistance needs to be the primary target of the therapy. Hyperglycemia, which is one feature of the metabolic syndrome, may range from impaired glucose tolerance (IGT) to overt diabetes. The risk of progression of the disease from IGT to diabetes is increased with time and the presence of various risk factors. Diabetes is a disease of serious concern because of the associated complication of the disease and the huge impact on the health care costs. Many short- and longer-term trials have shown promise in the prevention of diabetes and its metabolic and cardiovascular consequences.

Rationale for and role of thiazolidinediones in type 2 diabetes mellitus

Several classes of antihyperglycemic agents are available for the treatment of patients with type 2 diabetes. These agents, including thiazolidinediones, biguanides, insulin secretagogues, alpha-glucosidase inhibitors, and insulin, offer differing mechanisms of actions and can be used either alone or in combination. The thiazolidinediones are a newer class of oral antidiabetic agents that improve glycemic control and may preserve beta-cell function. Clinical trial data suggest that patients with type 2 diabetes experience progressive deterioration of beta-cell function. By decreasing insulin resistance, thiazolidinediones may preserve beta-cell function, and patients may experience prolonged glycemic control. The thiazolidinediones also exert beneficial effects on dyslipidemia, endothelial function, coagulation, and blood pressure. By improving these components of the metabolic syndrome, thiazolidinediones may reduce the incidence of both microvascular and macrovascular complications. This article provides an overview of the role of thiazolidinediones in the treatment of type 2 diabetes.

Clinical, physiopathological and dietetic aspects of metabolic syndrome

Hypertriglyceridaemia, diabetes, hypertension and obesity are the deadly quartet indicating a syndrome at high risk for cardiovascular disease for which, in 1998, WHO proposed the definition of Metabolic Syndrome, related to an elevated degree of insulin resistance. Treatment will often include behavioural changes that reduce body weight and increase physical activity A high-carbohydrate/low-fat diet with complex carbohydrates and mainly unsaturated fat is recommended. Replacing refined grain products and potatoes with minimally processed plant-based foods such as whole grains, fruit, and vegetables, and reducing the intake of high glycaemic load beverages may offer a simple strategy for reducing the incidence of coronary heart disease.

Low levels of leisure-time physical activity and cardiorespiratory fitness predict development of the metabolic syndrome

OBJECTIVE

Little is known about the association of leisure-time physical activity (LTPA) and cardiorespiratory fitness with development of the metabolic syndrome, which predisposes diseases such as diabetes and atherosclerosis. We studied the associations of LTPA and cardiorespiratory fitness with development of the metabolic syndrome (World Health Organization [WHO] and the National Cholesterol Education Program [NCEP] definitions).

RESEARCH DESIGN AND METHODS

LTPA over the previous 12 months, VO(2max) (ml. kg(-1). min(-1)), and cardiovascular and metabolic risk factors were assessed in a population-based cohort of 612 middle-aged men without the metabolic syndrome.

RESULTS

At the 4-year follow-up, 107 men had metabolic syndrome (WHO definition). Men engaging in >3 h/week of moderate or vigorous LTPA were half as likely as sedentary men to have the metabolic syndrome after adjustment for major confounders (age, BMI, smoking, alcohol, and socioeconomic status) or potentially mediating factors (insulin, glucose, lipids, and blood pressure), especially in high-risk men. Vigorous LTPA had an even stronger inverse association, particularly in unfit men. Men in the upper third of VO(2max) were 75% less likely than unfit men to develop the metabolic syndrome, even after adjustment for major confounders. Adjustment for possible mediating factors attenuated the association. Associations of LTPA and VO(2max) with development of the metabolic syndrome, as defined by the NCEP, were qualitatively similar.

CONCLUSIONS

In particular, high-risk men engaging in currently recommended levels of physical activity were less likely to develop the metabolic syndrome than sedentary men. Cardiorespiratory fitness was also strongly protective, although possibly not independent of mediating factors.