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Metabolic syndrome is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. It affects a large number of people, and prevalence increases with age. Some studies estimate the prevalence in the USA to be up to 25% of the population. A condition with some similarities to human metabolic syndrome is recognised in horses, see Equine Metabolic Syndrome. It is unknown if they have the same etiology.
Metabolic syndrome is also known as metabolic syndrome X, syndrome X, insulin resistance syndrome, Reaven's syndrome or CHAOS (Australia).
Additional recommended knowledge
Signs and symptoms
Symptoms and features are:
Associated diseases and signs are: elevated uric acid levels, fatty liver (especially in concurrent obesity), progressing to non-alcoholic fatty liver disease, polycystic ovarian syndrome, hemochromatosis (iron overload); and acanthosis nigricans (a skin condition featuring dark patches).
There are currently two major definitions for metabolic syndrome provided by the International Diabetes Federation and the revised National Cholesterol Education Program, respectively. The revised NCEP and IDF definitions of metabolic syndrome are very similar and it can be expected that they will identify many of the same individuals as having metabolic syndrome. The two differences are that IDF excludes any subject without increased waist circumference, while in the NCEP definition metabolic syndrome can be diagnosed based on other criteria and the IDF uses geography-specific cut points for waist circumference, while NCEP uses only one set of cut points for waist circumference regardless of geography. These two definitions are much closer to each other than the original NCEP and WHO definitions.
The World Health Organization criteria (1999) require presence of diabetes mellitus, impaired glucose tolerance, impaired fasting glucose or insulin resistance, AND two of the following:
European Group for the Study of Insulin Resistance (1999) requires insulin resistance defined as the top 25% of the fasting insulin values among non-diabetic individuals AND two or more of the following:
The US National Cholesterol Education Program Adult Treatment Panel III (2001) requires at least three of the following:
American Heart Association/Updated NCEP
There is confusion as to whether AHA/NHLBI intended to create another set of guidelines or simply update the NCEP ATP III definition. According to Scott Grundy, University of Texas Southwestern Medical School, Dallas, Texas, the intent was just to update the NCEP ATP III definition and not create a new definition.:
The cause of the metabolic syndrome is unknown. The pathophysiology is extremely complex and has been only partially elucidated. Most patients are older, obese, sedentary, and have a degree of insulin resistance. The most important factors in order are 1) aging, 2) genetics and 3) lifestyle, i.e., low physical activity and excess caloric intake. There is debate regarding whether obesity or insulin resistance is the cause of the metabolic syndrome or if they are consequences of a more far-reaching metabolic derangement. Systemic inflammation: a number of inflammatory markers (including C-reactive protein) are often increased, as are fibrinogen, interleukin 6 (IL−6), Tumor necrosis factor-alpha (TNFα) and others. Some have pointed to oxidative stress due to a variety of causes including increased uric acid levels caused by dietary fructose.
Commonly there is development of visceral fat after which the adipocytes (fat cells) of the visceral fat increase plasma levels of TNFα and alter levels of a number of other substances (e.g., adiponectin, resistin, PAI-1). TNFα has been shown not only to cause the production of inflammatory cytokines, but possibly to trigger cell signalling by interaction with a TNFα receptor that may lead to insulin resistance. An experiment with rats that were fed a diet one-third of which was sucrose has been proposed as a model for the development of the metabolic syndrome. The sucrose first elevated blood levels of triglycerides, which induced visceral fat and ultimately resulted in insulin resistance . The progression from visceral fat to increased TNFα to insulin resistance has some parallels to human development of metabolic syndrome.
Various strategies have been proposed to prevent the development of metabolic syndrome. These include increased physical activity (such as walking 30 minutes every day), and a healthy, reduced calorie diet. There are many studies that support the value of a healthy lifestyle as above. However, one study stated that these measures are effective in only a minority of people. The International Obesity Taskforce states that interventions on a sociopolitical level are required to reduce development of the metabolic syndrome in populations.
A 2007 study of 2,375 male subjects over 20 years suggested that daily intake of a pint of milk or equivalent dairy products more than halved the risk of metabolic syndrome. Other studies both support and dispute the authors' findings.
The first line treatment is change of lifestyle (i.e., caloric restriction and physical activity). However, drug treatment is frequently required. Generally, the individual disorders that comprise the metabolic syndrome are treated separately. Diuretics and ACE inhibitors may be used for hypertension). Cholesterol drugs may be used to lower LDL cholesterol and triglyceride levels, if they are elevated, and to raise HDL levels if they are low. Use of drugs that decrease insulin resistance e.g., metformin and thiazolidinediones, is controversial; this treatment is not approved by the FDA in the US.
A recent study indicated that cardiovascular exercise was therapeutic in approximately 31% of cases. The most probable benefit was to triglyceride levels, with 43% showing improvement; but fasting plasma glucose and insulin resistance of 91% of test subjects did not improve. Many other studies have supported the value of increased physical activity and restricted caloric intake (exercise and diet) to treat metabolic syndrome.
The term "metabolic syndrome" dates back to at least the late 1950s, but came into common usage in the late 1970s to describe various associations of risk factors with diabetes, that had been noted as early as the 1920s.
The terms "metabolic syndrome," "insulin resistance syndrome," and "syndrome X" are now used specifically to define a constellation of abnormalities that is associated with increased risk for the development of type 2 diabetes and atherosclerotic vascular disease (e.g. heart disease and stroke).
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Metabolic_syndrome". A list of authors is available in Wikipedia.|