الفهرس 
The Metabolic SyndromeOnly 14 pages are availabe for public view
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Abstract
Stroke is the second most common cause of death after ischaemic heart disease and a major cause of disability worldwide. One of its major risk factors is the metabolic syndrome. Since 1988, several definitions of the metabolic syndrome have emerged. Among them 4 are notable; the World Health Organization, the European Group for the Study of Insulin Resistance, National Cholesterol Education Program – Third Adult Treatment Panel and the International Diabetes Federation definitions. The core components of the metabolic syndrome are identical in all these definitions, namely: obesity, insulin resistance, dyslipidaemia and elevated blood pressure with the differences being mainly in the cutoff values. These differences – although seeming minor – lead to different prevalence ratios when using different definitions. Using a more recent definition increases the prevalence.
The prevalence of the metabolic syndrome in the United States ranged from 22 percent to 35 percent using different definitions. Several factors affected the prevalence including; age, race, ethnicity, postmenopausal status, smoking, low household income, high carbohydrate diet, alcohol consumption, use of atypical antipsychotics, and physical inactivity. Published data about the prevalence of the metabolic syndrome in middle-eastern/Arab population is sparse. In a Lebanese study, the ratio ranged from 5.25% to 9.19%. In Iran, it ranged from 34.7% to 37.4%. There are no published data about the prevalence of the metabolic syndrome in the general population in Egypt. However, a study found that the prevalence of abdominal obesity – an important component of the syndrome - was 24.1%.
Even though knowledge about the metabolic syndrome has multiplied recently, it is still a controversial issue that the existence of the syndrome itself is now being questioned. Whether the risk for stroke associated with the metabolic syndrome is greater than the sum of its risk factors is also a subject of debate. The components and spectrum of the syndrome are diverse affecting most of the systems including hepatic, renal, pulmonary and gastrointestinal systems. It also includes sleep disorders and psychiatric symptoms.
Understanding the pathogenesis of this disorder is a challenge and a major aim for this review. There are two recent revolutionary models namely; the inflammation model and the more recent 11β-hydroxysteroid dehydrogenase type 1 model. Both try to explain how can the diverse components of the syndrome result from a certain pathological defect. Developing a diagnostic marker for the metabolic syndrome is of extreme importance from a clinical point of view. Currently, several measures of insulin resistance are available. Additionally, CRP- adiponectin ratio, resistin, visfatin, and retinol binding protein-4 are possible future diagnostic biomarkers.
Being a worldwide epidemic, efforts have been directed towards finding effective therapeutic options to ameliorate the metabolic syndrome. Lifestyle modification through diet and exercise are still the first line of management as both proved to be effective in ameliorating abdominal obesity, type 2 diabetes, insulin resistance, dyslipidemia and elevated blood pressure. Conventional approach of management then aims at treating each component separately (e.g. using antihypertensives for elevated blood pressure, an oral hypoglycemic for type 2 diabetes etc.). Novel therapeutic options are now being introduced to the field based on the recent models of pathophysiology. These include 11β-hydroxysteroid dehydrogenase type 1 inhibitors, cannabinoid receptor antagonists and peroxisome proliferator-activated receptor- γ agonists. The three groups provide a completely new method of approaching the syndrome as they tackle the core of its pathophysiology rather than just treating its outcomes. Most of the studies on these agents are in preclinical or early clinical phases. Yet, the results so far are encouraging as each agent improved all aspects of the metabolic syndrome.
Atherosclerosis is a chronic disease that develops over a lifetime. The metabolic syndrome is increasingly being recognized as an important factor in the pathophysiology of atherosclerosis. This occurs through several mechanisms involving oxidized low density lipoprotein cholesterol, C-reactive protein, adipokines and othet cytokines. Accordingly, a recent survey reported hazard ratios of 1.40, 1.82 and 2.02 for overall mortality, coronary heart disease mortality and cardiovascular mortality, respectively, for the metabolic syndrome.
The metabolic syndrome is more associated with intracranial atherosclerosis than extracranial atherosclerosis. Therefore, a significantly increased risk of stroke was observed among individuals with the metabolic syndrome compared to those without. Studies reported about 1.6 to 3.1-fold greater odds of stroke in metabolic syndrome patients with a direct correlation between the number of the metabolic syndrome components and the risk of incident stroke. Elevated blood pressure and elevated glucose were the components associated with the highest risk. Several studies confirmed these findings. Lacunar stroke was the most prevalent subtype of stroke found in type 2 diabetes patients with metabolic syndrome. Moreover, metabolic syndrome patients was found to have at least a 60% increased risk of new-onset atrial fibrillation posing an additional risk of future strokes. There is also a positive trend between the metabolic syndrome components and silent brain infarcts which could be used as a diagnostic tool to predict and prevent future strokes.
Acute stroke management in metabolic syndrome patients faces two major challenges; resistance to aspirin and resistance to thrombolysis. Other than these challenges, a metabolic syndrome patient with acute stroke has no special guidelines and should be dealt with as usual. However, when it comes to secondary prevention of stroke in metabolic syndrome patients, all measures should be taken to prevent future vascular events as metabolic syndrome patients who developed cerebrovascular stroke represent a high risk group for recurrence. Lifestyle modifications would be the first line of treatment followed by one of three possible approaches; the conventional approach, the novel therapeutic options or the polypill approach. A polypill is pharmacologically the same as the conventional approach but is based on combining different medications in one pill (e.g. a statin, a blood pressure lowering agent and an antiplatelet in one pill). To date, there has not been a published study that compared the three approaches together to determine the ideal approach.