A reappraisal of the blood glucose homeostat which comprehensively explains the type 2 diabetes mellitus-syndrome X complex

Blood glucose concentrations are unaffected by exercise despite very high rates of glucose flux. The plasma ionised calcium levels are even more tightly controlled after meals and during lactation. This implies 'integral control'. However, pairs of integral counterregulatory controllers (e.g. insulin and glucagon, or calcitonin and parathyroid hormone) cannot operate on the same controlled variable, unless there is some form of mutual inhibition. Flip-flop functional coupling between pancreatic alpha- and beta-cells via gap junctions may provide such a mechanism. Secretion of a common inhibitory chromogranin by the parathyroids and the thyroidal C-cells provides another. Here we describe how the insulin:glucagon flip-flop controller can be complemented by growth hormone, despite both being integral controllers. Homeostatic conflict is prevented by somatostatin-28 secretion from both the hypothalamus and the pancreatic islets. Our synthesis of the information pertaining to the glucose homeostat that has accumulated in the literature predicts that disruption of the flip-flop mechanism by the accumulation of amyloid in the pancreatic islets in type 2 diabetes mellitus will lead to hyperglucagonaemia, hyperinsulinaemia, insulin resistance, glucose intolerance and impaired insulin responsiveness to elevated blood glucose levels. It explains syndrome X (or metabolic syndrome) as incipient type 2 diabetes in which the glucose control system, while impaired, can still maintain blood glucose at the desired level. It also explains why it is characterised by high plasma insulin levels and low plasma growth hormone levels, despite normoglycaemia, and how this leads to central obesity, dyslipidaemia and cardiovascular disease in both syndrome X and type 2 diabetes.

Current concepts of cardiovascular diseases in diabetes mellitus

The incidence of diabetes has reached epidemic proportions across the world. In patients with diabetes, there is a two to four times increased risk of developing coronary artery disease (CAD). Diabetes seems to eliminate the protective benefits of hormones in women against CAD. Patients with type II diabetes also have hypertension, dyslipidemia, obesity, endothelial dysfunction and prothrombotic factors, called 'the metabolic syndrome'. Not only the incidence of CAD is higher in diabetes, the mortality of the diabetic patients after a cardiac event is significantly increased as compared to non-diabetics, including sudden death. Although in the past 35 years there has been a decline in the rate of death due to CAD in the general population, this has not been seen among patients with diabetes. Primary prevention can play an important role in decreasing the incidence of CAD in diabetic patients. Aggressive treatment of hyperlipidemia and hypertension is essential. Recent knowledge about the protective effects of aspirin, statins, angiotension converting enzyme inhibitors, and glitazones in the diabetic patients, if used appropriately will go a long way in primary and secondary prevention of CAD in patients with diabetes.

[Metabolic syndrome or insulin resistance syndrome. Recent epidemiological data]

Three definitions are currently proposed to define metabolic syndrome or insulinresistance syndrome (WHO, EGIR, NCEP-ATP III). These definitions are described and recent epidemiological data assessing the frequency of this syndrome in different populations according to these three definitions are presented. Observational studies indicates an increased cardiovascular morbidity and mortality risk in subjects with metabolic/insulin resistance syndrome. These findings imply to identify these at risk subjects and to define the optimal preventive management strategy.

The metabolic syndrome, diabetes, and subclinical atherosclerosis assessed by coronary calcium

OBJECTIVES

We compared the prevalence and extent of coronary artery calcium (CAC) among persons with the metabolic syndrome (MetS), diabetes, and neither condition.

BACKGROUND

The prevalence and extent of CAC has not been compared among those with MetS, diabetes, or neither condition.

METHODS

Of 1,823 persons (36% female) age 20 to 79 years who had screening for CAC by computed tomography, 279 had MetS, 150 had diabetes, and the remainder (n = 1,394) had neither condition. Metabolic syndrome was defined with >or=3 of the following: body mass index >or=30 kg/m(2); high-density lipoprotein cholesterol <40 mg/dl if male or <50 mg/dl if female; triglycerides >or=150 mg/dl; blood pressure >or=130/85 mm Hg or on treatment; or fasting glucose 110 to 125 mg/dl. The prevalence and odds of any and significant (>or=75th percentile) CAC among these groups and by number of MetS risk factors were determined.

RESULTS

Those with neither MetS nor diabetes, MetS, or diabetes had a prevalence of CAC of 53.5%, 58.8%, and 75.3% (p < 0.001), respectively, among men and 37.6%, 50.8%, and 52.6% (p < 0.001), respectively, among women. Coronary artery calcium increased by the number (0 to 5) of MetS risk factors (from 34.0% to 58.3%) (p < 0.001). Forty-one percent of subjects with MetS had either a >20% 10-year risk of CHD or CAC >or=75th percentile for age and gender. Risk factor-adjusted odds for the presence of CAC were 1.40 (95% confidence interval [CI] 1.05 to 1.87) among those with MetS and 1.67 (95% CI 1.12 to 2.50) among those with diabetes, versus those with neither condition.

CONCLUSIONS

Those with MetS or diabetes have an increased likelihood of CAC compared with those having neither condition.

Non-alcoholic fatty liver syndrome: a hepatic consequence of common metabolic diseases

BACKGROUND AND AIMS

The association of liver steatosis with a number of common metabolic conditions has been suggested. The aim of the present study was to evaluate the clinical features of subjects with different severities of steatosis.

METHODS

The present study was performed in 282 consecutive patients with 'bright liver' at ultrasonography and in 58 subjects without steatosis. They had no history of alcohol abuse and negative tests for the presence of hepatitis B and C virus. Patients underwent clinical examination, anthropometry, laboratory tests and routine liver ultrasonography. Steatosis was graded as absent, mild, moderate and severe.

RESULTS

A progressive increase in the prevalence of obesity (P < 0.001), type 2 diabetes (P < 0.001), alanine aminotransferase (ALT) elevation (P < 0.001) and hypertriglyceridemia (P < 0.001), and a decrease of hypercholesterolemia (P < 0.05) was observed from the control group to the groups with mild, moderate and severe steatosis. More than half the subjects with liver steatosis had insulin resistance metabolic syndrome. Obesity, diabetes and hypertriglyceridemia were more common by 5.3-fold, 4.0-fold, and 6.7-fold, respectively, in subjects with severe steatosis, as compared to controls. Prevalence of obesity, diabetes and hyperlipidemia was significantly higher in subjects with fatty liver and ALT elevation.

CONCLUSION

Fatty liver can be considered as the hepatic consequence of common metabolic diseases.

Transitioning the patient with Turner's syndrome from pediatric to adult care

The level of medical and neuropsychological complexity throughout the life span of a patient with Turner's syndrome (TS) provides the rationale for a more structured transition from pediatric to adult health care. During late adolescence, the focus of care shifts from maximizing final adult height to completing feminization with estrogen therapy, detecting early antecedents of associated adult conditions, implementing needed therapeutic lifestyle changes, and assessing psychobehavioral risk. An increased prevalence of the dysmetabolic syndrome and osteoporosis is observed in TS. The prevention of obesity and assurance of adequate calcium intake and weight-bearing activities combined with early detection and treatment of specific abnormalities can ameliorate these associated adult morbidities. During the final phase of transition, the pediatric endocrinologist should engage the patient with TS in developing a comprehensive adult care roadmap or 'transition passport', which serves as a powerful educational tool. The aim of refining the transition process is to improve adult outcomes and quality of life for patients with TS.

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.

A high risk score for coronary heart disease is associated with the metabolic syndrome in 40-year-old men and women

OBJECTIVE

Guidelines recommend follow-up of people whose 10-year risk of coronary heart disease (CHD) is > 10%. We calculated CHD risk, number of risk factors and occurrence of the metabolic syndrome among screened 40-year-old men and women.

DESIGN

A total of 1547 women and 1374 men participated in a cardiovascular risk factor screening programme in 1997-1999 in Oslo. Of 387 (13%) recalled for further examination and advice, 337 (87%) attended. We used the National Cholesterol Education Program criteria to define the metabolic syndrome and the Framingham risk score to assess absolute 10-year risk of CHD and counted nine risk factors (male, southeast-Asian origin, low education, smoking, premature familial cardiovascular disease (CVD), hypertension, high waist circumference, impaired fasting glucose or diabetes and high apolipoprotein B).

RESULTS

More than one-third of subjects recalled for hypertension (n = 88) or low high-density lipoprotein (HDL) cholesterol (n = 95) had the metabolic syndrome. Of 55 subjects with a 10-year risk score > 10%, 33 (60%) had the metabolic syndrome. Subjects with the metabolic syndrome had a higher risk score compared with their counterparts (P < 0.001); among men with the metabolic syndrome, the mean +/- SD risk score was 10.0 +/- 4.4%. Subjects with dyslipidaemia [high triglyceride and normal low-density lipoprotein (LDL) cholesterol levels] or combined hyperlipidaemia had a higher risk score and more risk factors compared with subjects with isolated high LDL cholesterol (P < 0.05). Only 12% of subjects with hypertension were taking drugs and of 237 subjects with a lipid disorder, 30% had been given dietary advice and one was taking a lipid-lowering drug.

CONCLUSION

CVD screening should focus on identifying people with features of the metabolic syndrome in this age group. The screening programme uncovered a substantial potential for CVD prevention.

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.

[Insulin resistance in obese subjects with impaired glucose tolerance. Studies with hyperinsulinemic euglycemic clamp technique]

Insulin resistance is a key factor in the pathogenesis of impaired glucose tolerance (IGT) and type 2 diabetes and is also associated with greater risk for cardiovascular disease. Insulin resistance is more common in obese individuals and is considered to be the link between obesity and IGT and diabetes. The aim of the present study was to assess insulin resistance in obese subjects with IGT. We examined 57 subjects with marked overweight or obesity (BMI > > 27.8 kg x m-2), 27 with IGT and 30 with normal glucose tolerance (NGT), assessed by an oral glucose tolerance test, according to WHO criteria. Thirty lean (BMI < 25 kg x m-2) healthy subjects served as a control group. Anthropometric and biochemical parameters were measured. Insulin sensitivity was evaluated with hyperinsulinemic euglycemic clamp technique. Subjects with IGT had higher levels of glucose, insulin, non-esterified fatty acids and glycated hemoglobin than obese with NGT, all those parameters were also higher in both obese groups in comparison to controls. We showed significant differences in insulin sensitivity between the studied groups, an index of the whole-body glucose uptake was decreased in both obese groups in comparison to controls, and it was also lower in IGT than in obese NGT group. We observed marked negative correlations between insulin sensitivity and estimated anthropometric and biochemical parameters. Our study indicates that insulin resistance is an important factor determining a deterioration of glucose tolerance in subjects with overweight and obesity.

Insulin resistance as putative cause of chronic renal transplant dysfunction

Transplantation is the preferred organ replacement therapy for most patients with end-stage renal disease. Despite impressive improvements over recent years in the treatment of acute rejection, approximately half of all grafts will loose function within 10 years after transplantation. Chronic renal transplant dysfunction, also known as transplant atherosclerosis, is a leading cause of late allograft loss. To date, no specific treatment for chronic renal transplant dysfunction is available. Although its precise pathophysiology remains unknown, it is believed that it involves a multifactorial process of alloantigen-dependent and alloantigen-independent risk factors. Obesity, posttransplant diabetes mellitus, dyslipidemia, hypertension, and proteinuria have all been identified as alloantigen-independent risk factors. Notably, these recipient-related risk factors are well-known risk factors for cardiovascular disease, which cluster within the insulin resistance syndrome in the general population. Insulin resistance is considered the central pathophysiologic feature of this syndrome. It is therefore tempting to speculate that it is insulin resistance that underlies the recipient-related risk factors for chronic renal transplant dysfunction. Recognition of insulin resistance as a central feature underlying many, if not all, recipient-related risk factors would not only improve our understanding of the pathophysiology of chronic renal transplant dysfunction, but also stimulate development of new treatment and prevention strategies.

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.

The metabolic syndrome: targeting dyslipidaemia to reduce coronary risk

The metabolic syndrome is a complex constellation of disorders, each one a significant risk factor for the development of cardiovascular disease (CVD). The increasing prevalence of this condition is a major concern for healthcare providers both in Europe and North America. The concern surrounding the prevalence of the metabolic syndrome is reflected in the recently published National Cholesterol Education Program Adult Treatment Panel III guidelines. Although complex in nature, the individual components of the metabolic syndrome appear to be linked by the presence of insulin resistance. Concurrently treating the underlying insulin resistance along with the complex array of other disorders should form the core of any management strategy. Treatment of atherogenic dyslipidaemia should be a major aim, since it is associated with a significant risk of CVD. While lifestyle modifications form the cornerstone of any dyslipidaemia management strategy, many patients require the addition of lipid-modifying drugs. Several agents are available for the treatment of lipid abnormalities, including fibrates, bile acid sequestrants, niacin and hydroxymethyl glutaryl coenzyme A reductase inhibitors (statins). Of these, statins should be used as the first treatment option in the majority of patients because they are efficacious for reducing low-density lipoprotein cholesterol, are effective across the lipid profile and are well tolerated in the majority of cases. Furthermore, the American Diabetes Association (ADA) recommends statins as first-line pharmacological treatment of dyslipidaemia in patients with diabetes mellitus. This review discusses the diagnosis and management of the metabolic syndrome and examines the potential of future treatment options.

Inflammation, the metabolic syndrome and cardiovascular risk

Over the past ten years it has become clear that cardiovascular disease (CVD) and atherosclerosis have a 'microinflammatory' component and are often associated with low levels of inflammatory markers that are in the upper part of the 'normal' range. In particular, diseases that predispose to CVD, such as the metabolic syndrome and type 2 diabetes, appear to have a very strong inflammatory component. While the inflammatory process is very complicated, single measures, such as C-reactive protein (CRP) or fibrinogen, have clear benefits as they summarise many different parts of the inflammatory process and are easy to apply. However, it is important to remember that the process of inflammation includes coagulation, fibrinolysis, complement activation, antioxidation, immune response and hormonal regulation through the hypothalamic-pituitary-adrenal axis. Furthermore, genetic variation, differences in exposure to environmental influences and the mass of inflammation-producing tissue (e.g. adipose tissue) can all influence responses. Thus, the relationship between atherosclerosis, the metabolic syndrome and inflammation is extraordinarily complex. Inflammatory markers such as CRP exhibit strong CVD-risk prediction that is consistent across sexes and a number of different populations. They reflect risk not only for 'vulnerable plaque' and myocardial infarction (MI) but also for other cardiovascular diseases. In fact, inflammation is associated with several, if not all, of the chronic diseases of old age, and it is now clear that there are important links between inflammation and general metabolism. For instance, visceral adiposity exerts a major influence on inflammation status. Medications that affect atherosclerosis appear to do so at least in part by influencing inflammation (for instance, the emerging pleiotropic effects of statins), and this has far-reaching ramifications for chronic diseases of old age and their treatment.

Risk factor clustering in the insulin resistance syndrome and its relationship to cardiovascular disease in postmenopausal white, black, hispanic, and Asian/Pacific Islander women

The aim of this study was to examine how major components of the insulin resistance (IR) syndrome relate to each other and to cardiovascular disease (CVD) in postmenopausal women in 4 ethnic groups. Baseline data from the Women's Health Initiative (WHI) on 3,083 50- to 79-year-old women (1,635 white, 802 black, 390 Hispanic, and 256 Asian/Pacific Islander) were examined. Participants underwent a personal interview and a physical examination, blood samples were drawn, and a detailed cardiovascular history was ascertained. Factor analysis was used to assess the clustering and interdependence of groups of CVD-related IR syndrome variables. Four factors were identified. An obesity factor included IR in all groups and had a significant association with CVD in white (P =.0001) and Hispanic (P =.0024) women. A dyslipidemia factor (high-density lipoprotein [HDL], triglycerides, and HDL2: total HDL ratio) also included insulin and IR and was significantly correlated with CVD in black (P=.0006) and Hispanic (P =.0217) women and had a borderline association in white women (P =.068). Total and low-density lipoprotein (LDL) cholesterol did not relate to CVD in any group. Blood pressure was related weakly to CVD in white women (P =.0434) and strongly in black women (P =.0095). Components of the IR syndrome appear to be associated with CVD in postmenopausal women, although the magnitude of these relationships differed by ethnicity.

Adequate nutrient intake can reduce cardiovascular disease risk in African Americans

Cardiovascular disease kills nearly as many Americans each year as the next seven leading causes of death combined. The prevalence of cardiovascular disease and most of its associated risk factors is markedly higher and increasing more rapidly among African Americans than in any other racial or ethnic group. Improving these statistics may be simply a matter of improving diet quality. In recent years, a substantial and growing body of evidence has revealed that dietary patterns complete in all food groups, including nutrient-rich dairy products, are essential for preventing and reducing cardiovascular disease and the conditions that contribute to it. Several cardiovascular risk factors, including hypertension, insulin resistance syndrome, and obesity, have been shown to be positively influenced by dietary patterns that include adequate intake of dairy products. The benefits of nutrient-rich dietary patterns have been specifically tested in randomized, controlled trials emphasizing African American populations. These studies demonstrated proportionally greater benefits for African Americans without evidence of adverse effects such as symptoms of lactose intolerance. As currently promoted for the prevention of certain cancers and osteoporosis, regular consumption of diets that meet recommended nutrient intake levels might also be the most effective approach for reducing cardiovascular disease risk in African Americans.

PPAR agonists in the treatment of insulin resistance and associated arterial disease

Augmented release of non-esterified fatty acids (NEFA) from insulin-resistant adipocytes appears to be the main cause of the 'atherogenic lipoprotein profile' associated with insulin resistance and type 2 diabetes. This atherogenic profile is characterised by large very-low-density lipoproteins (VLDL), small, dense low-density lipoproteins (LDL) and low levels of high-density lipoproteins (HDL), resulting in deposition of apo B lipoproteins in the vascular intima and subsequent inhibition of reverse cholesterol transport. This lipoprotein retention also results in a proinflammatory response from the vascular endothelium, which is increased in insulin resistance. Thus the ideal therapy for insulin resistance, and its complications, should both improve its associated dyslipidaemia and ameliorate the vascular atherogenic reaction. Some peroxisome proliferator-activated receptor (PPAR)-gamma and dual PPARalpha/gamma agonists improve insulin resistance and its dyslipidaemia, both in rodents and man, while in animal models they can show clear antiatherosclerotic effects. Nonetheless, it is difficult to evaluate how much of these antiatherosclerotic actions are caused by effects on the dyslipidaemia or by direct effects on vascular cells. Upregulation of PPARgamma and PPARalpha/gamma activity in macrophages can reduce secretion of proinflammatory cytokines and matrix metalloproteases, as well as increase HDL-mediated cholesterol efflux transport--all potentially antiatherosclerotic results. In addition, treatment of smooth muscle cells with PPARgamma agonists can partially revert possible atherogenic changes in the production of matrix proteoglycans induced by exposure to NEFA. Although these findings are still preliminary, and their relevance to human atherosclerosis has not been fully elaborated, these results suggest that improved PPARalpha/gamma agonism may positively modulate several of the metabolic steps connecting insulin resistance with dyslipidaemia and with the atherogenic response.

The relationship of obesity to the metabolic syndrome

Obese patients with the metabolic syndrome generally have a visceral (apple-shaped) fat distribution and are at an increased risk of macrovascular disease, while those with peripheral (pear-shaped) obesity tend not to have metabolic abnormalities and are at less risk. This difference appears to be related to the differing metabolic functions (and secretory products) of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), as well as the fact that VAT drains directly into the liver. Thus, it appears that increased VAT, but not SAT, is associated with both hepatic and peripheral biochemical abnormalities leading to insulin resistance and the associated metabolic syndrome. Insulin resistance is associated with VAT products, such as free fatty acids and their metabolites, as well as cytokines, such as tumour necrosis factor alpha (TNF-alpha). These factors may activate components of the inflammatory pathway such as nuclear factor kappa-B (NFkappaB), and inhibit insulin signalling. Insulin resistance is further associated with decreased levels of another tissue product, adiponectin. The incidence and prevalence of obesity is increasing at an unprecedented rate. The classic treatment of obesity is weight loss via lifestyle modification. However, prevention of obesity comorbidity can also be achieved by modifying the mechanisms by which obesity causes these comorbid conditions. For instance, it is now known that the peroxisome proliferator-activated receptor (PPAR) family of transcriptional regulators are crucial in regulating adipose tissue development and metabolism; this helps explain why compounds with PPARgamma agonist activity, e.g. thiazolidinediones, increase insulin action through their effects in regulating adipose tissue metabolism.

Determinants of plasminogen activator inhibitor-1 in South Asians with ischaemic stroke

To investigate the relationship of circulating plasminogen activator inhibitor-1 (PAI-1) levels with features of insulin resistance and genotype at a single nucleotide insertion/deletion (4G/5G) polymorphism in the promoter region of the PAI-1 gene in 101 South Asian ischaemic stroke patients and 102 symptom-free reference subjects. The allele frequencies were 4G-0.51, 5G-0.49 and 4G-0.61, 5G-0.39 in patients and reference subjects, respectively. There was a significant association between PAI-1 promoter genotype and PAI-1 antigen levels in patients. Regression analysis with significant correlates in the model demonstrated age, gender and triglycerides in patients and fasting insulin and HDL cholesterol in reference subjects as independent predictors of PAI-1 antigen.

Pocket tape measure for waist circumference: training medical students and residents on a simple assessment of body composition

Metabolic syndrome, the clustering of hyperglycemia, hypertension and dyslipidemia, increases the risk of coronary heart disease. Abdominal obesity is an important cue for the clinician to consider metabolic syndrome. Measurement of waist circumference is a simple means of identifying abdominal obesity. The development and distribution of pocket tape measures to medical students, residents and attending physicians were initiated to enhance identification and treatment of metabolic syndrome. Distribution of the tape measures was added to a cardiovascular nutrition component in a 4th-y medical school curriculum. The nutrition component continued to include computer-based cases and pocket reference cards. Limited data suggest that the addition of pocket tape measures to the nutrition component of an ambulatory care clerkship may increase the percentage of medical students who use waist circumference to identify patients at risk for metabolic syndrome. It is anticipated that student use will increase with role modeling by residents and attending physicians.

Researchers sound the alarm on risks associated with metabolic syndrome

As much as one-third of the population has it, and the condition has been strongly linked with CVD, diabetes, and early death. But currently very little is being done to identify or treat this dangerous cluster of conditions. If there is good news, it is that relatively simple interventions can substantially improve a person's risk profile. Get the details.

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.

Weight loss and weight maintenance, ambulatory blood pressure and cardiac autonomic tone in obese persons with the metabolic syndrome

BACKGROUND

Cardiac autonomic function may play a role in obesity-associated hypertension. Most studies on the effects of weight loss on blood pressure and autonomic function do not distinguish between acute or continuing weight loss and steady-state weight maintenance after weight loss.

OBJECTIVES

We sought to clarify the changes in ambulatory blood pressure, heart rate and heart rate variability as assessed by spectral analysis during rapid weight loss and extended weight maintenance.

PARTICIPANTS

Abdominally obese (body mass index 35.2 +/- 2.1 kg/m2, waist 114.3 +/- 9.0 cm) men and women (n = 41) with the metabolic syndrome.

METHODS AND RESULTS

The 34 men and women completing the 1-year weight maintenance period lost 14.6 +/- 3.5 kg during the 9-week very-low-calorie diet and maintained a 12.5 +/- 7.5 kg weight loss to the end of the trial. Ambulatory 24-h blood pressure decreased dramatically during the diet (-9.0 +/- 8.0/-4.6 +/- 4.9 mmHg), but had risen to near baseline levels by the end of weight maintenance (-2.2 +/- 8.2 /-1.2 +/- 6.1 mmHg). Night-time heart rate decreased (-5.5 +/- 9.6 beats/min, P = 0.012), and heart rate variability total and low-frequency power measured during 5 min of controlled breathing increased by 46-56% (P = 0.003-0.09) during rapid weight loss. These changes gradually attenuated during weight maintenance, and only the change in night-time heart rate was still of borderline significance after 1 year of weight maintenance (-3.6 +/- 8.6 beats/min, P = 0.063). Heart rate variability high-frequency power tended to increase during weight loss and weight maintenance.

CONCLUSION

Despite successful weight maintenance, the decrease in ambulatory blood pressure after rapid weight loss was largely transient. The increase in parasympathetic tone was more sustained, but also gradually attenuated during 1 year of weight maintenance.

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.

Association of hyperglycemia and insulin with diabetic cardiovascular complications

Patients with diabetes and/or insulin resistance syndrome are at increased risk for developing cardiovascular disease. The UKPDS raised a great debate about the relative importance of hyperglycemia in the development of cardiovascular disease. Recently, several epidemiologic studies have suggested that high postprandial blood glucose levels are associated with a significant risk for the development of cardiovascular disease well as a grave prognosis for these patients during acute coronary events. In addition, a number of reports reinforce the thesis that postprandial hyperglycemia is a risk factor for mortality. Our review summarizes the current knowledge on the relation between blood glucose, insulin levels, and cardiovascular morbidity and mortality, relating these data to the new World Health Organization and American Diabetes Association classification of disturbed glucose metabolism.

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.

Does Homocysteine Cause Hypertension?

Several studies, some population-based, have plasma homocysteine levels linked to blood pressure, especially systolic pressure. In one large and carefully conducted epidemiological study, each 5 micromol/l increase in plasma homocysteine was associated with an increase in systolic and diastolic blood pressure of 0.7/0.5 mmHg in men and 1.2/0.7 mmHg in women, which was independent of renal function and B vitamin status. In addition, observations that homocysteine-lowering therapies with folic acid-based treatments have been followed by decreases in blood pressure raise the possibility that the link between homocysteine and blood pressure is causal, which is important since homocysteine levels can easily be lowered by folic acid-based regimens. Mechanisms that could explain the relationship between homocysteine and blood pressure include homocysteine-induced arteriolar constriction, renal dysfunction and increased sodium reabsorption, and increased arterial stiffness. However, there is only circumstantial evidence that these mechanisms are operative in humans. In addition, confounding by subtle renal dysfunction or by unmeasured dietary and lifestyle factors cannot be excluded as an explanation for the association between homocysteine and blood pressure. At present, therefore, the hypothesis that homocysteine increases blood pressure must be considered unproven. Ongoing large intervention studies with homocysteine-lowering vitamins may show whether blood pressure is indeed lowered by these vitamins, whether the blood pressure decrease, if any, is explained by the decrease in homocysteine levels, and whether a vitamin treatment-associated decrease in cardiovascular morbidity, if any, is explained by the decrease in blood pressure.

Hypertension in obese patients: a dysmetabolic hypertension with a possible adipocyte dysfunction mechanism

Large longitudinal studies showed the epidemiological link between obesity and hypertension. During last years, multiple possible mechanisms involved in this association were identified. Adipose tissue has an important role in the genesis of hypertension in obese patients through several pathways: insulin resistance, leptin, renin-angiotensin-aldosteron system and mediators of inflammation (TNF-alpha, IL-6). Adipocyte may be the major player in the development of insulin resistance and hypertension, elements of the metabolic syndrome, responsible for the cardiovascular complications.

Microcirculation: target therapy in cardiovascular diseases - a clinical perspective

Microcirculation conduit, distribution, exchange and reception vessels usually retain a demand-dependent vascular-tissue match as well as a nutrient friendly capillary-matrix tissue match. Various stimuli can initiate a vascular-capillary matrix-tissue mismatch. Counter-regulatory mechanisms result in hyperplasia or apoptosis. Microvascular disease (MVD) as a consequence or outcome of supply-demand mismatch has clinical therapeutic and prognostic implications in the hypertensive syndrome and coronary artery disease (CAD) cases. Recognition of the role of apoptosis and MVD may initiate a paradigm shift in clinical practice. Digitalis and other anti-hypertensive agents have anti-apoptotic action and MVD blunting effects that can control LVH development to reduce congestive heart failure (CHF) progression.

Insulin therapy for reducing cardiovascular risk in patients with type 2 diabetes

Twenty-four percent of the adult American population have the metabolic syndrome. Although somewhat counterintuitive, carefully regulated treatment with insulin has been shown to reduce insulin resistance and may also retard the development of cardiovascular disease by preventing chronic hyperglycemia, a condition that synergistically contributes to many proatherogenic pathways, including glycoxidation, the polyol pathway, advanced glycation end products, interference with normal metabolic pathways, and stimulation of protein kinase C-beta and proinflammatory pathways. This article describes some of the physiologic changes that occur when hyperglycemia and insulin resistance develop in patients with type 2 diabetes and discusses therapies, including insulin, that normalize glucose and reduce insulin resistance, thereby potentially reducing cardiovascular risk.

Microvascular disease relevance in the hypertension syndrome

Hypertension is not an isolated problem. Co-morbidities of smoking, obesity, diabetes and dyslipidemia are all associated with microvascular disease (MVD) with abnormal PET scan and endothelial dysfunction. MVD may contribute to left ventricular hypertrophy (LVH) via an imbalance between hyperplasia and apoptotic signals. Digitalis and other anti-hypertensive agents have anti-apoptotic action and MVD blunting effects, respectively. Heart failure progression must then be based on the preservation of myocyte integrity. Indeed, altered contractility appears to be a consequence of rather than the cause of myocyte deterioration. LV systolic dysfunction improvement is already a late strategy. Furthermore, the efficacy of anti-hypertension therapy may be limited in restoring LV diastolic function. Recognition of the role of apoptosis and MVD may initiate a paradigm shift in clinical practice.

The metabolic syndrome and total and cardiovascular disease mortality in middle-aged men

CONTEXT

The metabolic syndrome, a concurrence of disturbed glucose and insulin metabolism, overweight and abdominal fat distribution, mild dyslipidemia, and hypertension, is associated with subsequent development of type 2 diabetes mellitus and cardiovascular disease (CVD). Despite its high prevalence, little is known of the prospective association of the metabolic syndrome with cardiovascular and overall mortality.

OBJECTIVE

To assess the association of the metabolic syndrome with cardiovascular and overall mortality using recently proposed definitions and factor analysis.

DESIGN, SETTING, AND PARTICIPANTS

The Kuopio Ischaemic Heart Disease Risk Factor Study, a population-based, prospective cohort study of 1209 Finnish men aged 42 to 60 years at baseline (1984-1989) who were initially without CVD, cancer, or diabetes. Follow-up continued through December 1998.

MAIN OUTCOME MEASURES

Death due to coronary heart disease (CHD), CVD, and any cause among men with vs without the metabolic syndrome, using 4 definitions based on the National Cholesterol Education Program (NCEP) and the World Health Organization (WHO).

RESULTS

The prevalence of the metabolic syndrome ranged from 8.8% to 14.3%, depending on the definition. There were 109 deaths during the approximately 11.4-year follow-up, of which 46 and 27 were due to CVD and CHD, respectively. Men with the metabolic syndrome as defined by the NCEP were 2.9 (95% confidence interval [CI], 1.2-7.2) to 4.2 (95% CI, 1.6-10.8) times more likely and, as defined by the WHO, 2.9 (95% CI, 1.2-6.8) to 3.3 (95% CI, 1.4-7.7) times more likely to die of CHD after adjustment for conventional cardiovascular risk factors. The metabolic syndrome as defined by the WHO was associated with 2.6 (95% CI, 1.4-5.1) to 3.0 (95% CI, 1.5-5.7) times higher CVD mortality and 1.9 (95% CI, 1.2-3.0) to 2.1 (95% CI, 1.3-3.3) times higher all-cause mortality. The NCEP definition less consistently predicted CVD and all-cause mortality. Factor analysis using 13 variables associated with metabolic or cardiovascular risk yielded a metabolic syndrome factor that explained 18% of total variance. Men with loadings on the metabolic factor in the highest quarter were 3.6 (95% CI, 1.7-7.9), 3.2 (95% CI, 1.7-5.8), and 2.3 (95% CI, 1.5-3.4) times more likely to die of CHD, CVD, and any cause, respectively.

CONCLUSIONS

Cardiovascular disease and all-cause mortality are increased in men with the metabolic syndrome, even in the absence of baseline CVD and diabetes. Early identification, treatment, and prevention of the metabolic syndrome present a major challenge for health care professionals facing an epidemic of overweight and sedentary lifestyle.

The metabolic syndrome: psychopharmacologists should weigh the evidence for weighing the patient

We are in the midst of a North American epidemic of obesity and type 2 diabetes. Since patients with psychiatric disorders who receive psychopharmacologic treatments may be at even greater risk than the general population for weight gain, dyslipidemia, and diabetes and their complications, psychopharmacologists now need standards for how to monitor and manage these risks.

Asymmetric dimethylarginine (ADMA): a potential link between endothelial dysfunction and cardiovascular diseases in insulin resistance syndrome?

Endothelium-derived nitric oxide plays a major role in the regulation of vascular tone and in the maintenance of vascular homeostasis. Endothelial dysfunction with impaired nitric oxide biosynthesis and decreased bioavailability has been implicated in insulin resistance syndrome and Type II (non-insulin-dependent) diabetes mellitus. Nitric oxide is synthesised by nitric oxide synthase. Asymmetric dimethylarginine is a major endogenous nitric oxide synthase inhibitor. Increased circulating asymmetric dimethylarginine was initially found in patients with chronic renal failure and subsequently many other disease states. Increased asymmetric dimethylarginine plasma concentrations could contribute to the development of insulin resistance and coronary heart disease. Understanding of the pathophysiological role of asymmetric dimethylarginine could lead to novel therapies in the prevention of arteriosclerosis and coronary heart disease.

Low serum magnesium levels and metabolic syndrome

Low serum magnesium levels are related to diabetes mellitus (DM) and high blood pressure (HBP), but as far as we know, there are no previous reports that analyzed the serum magnesium concentration in individuals with metabolic syndrome (MS). We performed a cross-sectional population-based study to compare 192 individuals with MS and 384 disorder-free control subjects, matched by age and gender. Magnesium supplementation treatment and conditions likely to provoke hypomagnesemia, including previous diagnosis of diabetes mellitus (DM) and/or high blood pressure (HBP), were exclusion criteria. In this regard, only incident cases of DM and HBP were included. MS was defined by the presence at least of two of the following features: hyperglycemia (> or =7.0 mmol/l); HBP (> or =160/90 mmHg); dyslipidemia (fasting triglycerides > or =1.7 mmol/l and/or HDL-cholesterol <1.0 mmol/l); and obesity (body mass index > or =30 kg/m(2) and/or waist-to-hip ratio > or =0.85 in women or > or =0.9 in men). Low serum magnesium levels were identified in 126 (65.6%) and 19 (4.9%) individuals with and without MS, p<0.00001. The mean serum magnesium level among subjects with MS was 1.8+/-0.3 mg/dl, and among control subjects 2.2+/-0.2 mg/dl, p<0.00001. There was a strong independent relationship between low serum magnesium levels and MS (odds ratio (OR)=6.8, CI(95%) 4.2-10.9). Among the components of MS, dyslipidemia (OR 2.8, CI(95%) 1.3-2.9) and HBP (OR 1.9, CI(95%) 1.4-2.8) were strongly related to low serum magnesium levels. This study reveals a strong relationship between decreased serum magnesium and MS.

Metabolic syndrome and development of diabetes mellitus: application and validation of recently suggested definitions of the metabolic syndrome in a prospective cohort study

The World Health Organization (WHO) and the National Cholesterol Education Program (NCEP) recently proposed definitions for the metabolic syndrome. Little is known of their validity, however. The authors assessed the sensitivity and specificity of the definitions of the metabolic syndrome for prevalent and incident diabetes mellitus in a Finnish population-based cohort of middle-aged men (n = 1,005) followed for 4 years since the late 1980s. Four definitions based on the WHO and NCEP recommendations were compared. All definitions identified persons at high risk for developing diabetes during the 4-year follow-up (odds ratios = 5.0-8.8). The WHO definition including waist-hip ratio > 0.90 or body mass index >or= 30 kg/m(2) was the most sensitive (0.83 and 0.67) and least specific (0.78 and 0.80) in detecting the 47 prevalent and 51 incident cases of diabetes. The NCEP definition in which adiposity was defined as waist girth > 102 cm detected only 61% of prevalent and 41% of incident diabetes, although it was the most specific (0.89 and 0.90). The WHO definition seems valid as judged by its relatively high sensitivity and specificity in predicting diabetes. The NCEP definition including waist > 102 cm also identifies persons at high risk for diabetes, but it is relatively insensitive in predicting diabetes.

[Metabolic aspects of the polycystic ovary syndrome]

The author reviews the history of the term polycystic ovaries syndrome. He emphasizes the importance of insulin resistance in this disease. According to more recent criteria for the definition of the syndrome suffices the finding of hyperandrogenism, an irregular cycle (after elimination of other classical causes of this condition) and insulin resistance. The frequency of the disease varies in different populations up to 10%. It is significantly associated in particular with type 2 diabetes and obesity. The molecular biology of the syndrome is obscure. The metabolic syndrome as well as the polycystic ovaries syndrome have partly a genetic pathogenesis as well as an environmentally induced participation caused by stress. The polycystic ovaries syndrome is nowadays unequivocally an atherogenic syndrome and is a unit very close to Reaven's metabolic syndrome X or is part of this syndrome.

The metabolic syndrome, type 2 diabetes, and cardiovascular disease: understanding the role of insulin resistance

The most common and clinically important complication in adults with diabetes is cardiovascular disease (CVD), which includes coronary heart disease, peripheral vascular disease, and stroke. Both type 2 diabetes and the insulin resistance syndrome are associated with a marked increase in the risk for CVD. The metabolic syndrome and the closely related insulin resistance syndrome have recently been recognized as important disorders, each being associated with an increase in CVD risk even in the absence of glucose intolerance. Given the significant public health burden of CVD, risk reduction has emerged as a significant clinical challenge for most practitioners. Diabetes and the insulin resistance syndrome are closely related disorders, with insulin resistance being more than a key pathogenic defect in type 2 diabetes. Even in the absence of glucose intolerance, these 2 disorders are both associated with a number of distinct pathologic findings, including hypertension, atherogenic dyslipidemia, a prothrombotic environment, and significant vascular and hemodynamic abnormalities that result from endothelial cell dysfunction. Insulin resistance is now recognized to be closely associated with the development of each of these risk factors. This article uses a case-based approach to discuss the unique features of insulin resistance and type 2 diabetes considered to be key contributors to CVD risk. A systematic approach to both evaluation and management is proposed, with priority given to therapies of demonstrated clinical benefit. Because of its critical and central role in the development of many CVD risk factors, targeted treatment of insulin resistance will also be discussed as such therapy may prove to be a critical component of care in years to come.

Update on the cardiometabolic syndrome

An array of metabolic, hemodynamic, and renal abnormalities constitutes the cardiometabolic syndrome. A hallmark of this syndrome is visceral obesity and associated insulin resistance/hyperinsulinemia. The syndrome is also associated with essential hypertension, abnormalities in the circadian rhythm of blood pressure and heart rate, the diabetic dyslipidemic syndrome, hypercoagulability, hyperuricemia, increased cardiovascular inflammation, and microalbuminuria, all of which contribute to an increased risk of cardiovascular disease morbidity and mortality. This article reviews current knowledge about the interrelationship of the various factors that make up the cardiometabolic syndrome and its implications for individuals with and without diabetes mellitus.