oa Editorial [Hot topic:Current Hypertension Reviews, Hot Topics “Obesity, Hypertension, and the Metabolic Syndrome” (Guest Editor: Kazuko Masuo)]

Obesity, hypertension, obesity-related hypertension, metabolic syndrome and type 2 diabetes have increased dramatically in prevalence and now pose a significant burden on health and health budgets. Indeed, several large cohort longitudinal studies such as the National Health and Nutrition Examination Survey (NHANES), the Behavioural Risk Factor Surveillance System (BRFSS) have found that obesity, diabetes and hypertension have increased in the United States in the past decade, and have demonstrated very close associations between the prevalence of obesity and the incidence of hypertension and diabetes. In addition, obesity, hypertension and diabetes mellitus are stated as risk factors for cardiovascular events. For example, the Framingham Heart study demonstrated higher cardiovascular and all-cause mortality in diabetic subjects compared to nondiabetic patients. Furthermore, the National Heart Foundation Risk Factor Prevalence Survey in Australia showed that central obesity plus smoking could predict future coronary heart disease and cardiovascular disease death. It is widely recognized that heightened sympathetic nerve activity, insulin resistance (or hyperinsulinemia), stimulated renin-angiotensin- aldosterone system (RAAS), adiponectin and leptin in some way relate to obesity, hypertension, and metabolic syndrome. Indeed, many investigators have indicated that insulin resistance may play a major role in obesity, hypertension, and obesity-related hypertension. On the other hand, some investigators have reported that heightened sympathetic nerve activity may be a prime mover for obesity, hypertension, obesity-related hypertension, and insulin resistance (metabolic syndrome). Furthermore, there are a number of studies that have examined the relationships between RAAS and insulin resistance in obesity, hypertension and diabetes. Most investigations, however, emphasize the close linkage between insulin resistance, heightened sympathetic nerve activity and stimulated RAAS. Further, recent investigations demonstrated that adiponectin and leptin play important roles in the pathogenesis and development of obesity, hypertension, and metabolic syndrome. However, the precise relationships between heightened sympathetic nerve activity, stimulated RAAS, insulin resistance and other hormonal mechanisms in obesity, hypertension and metabolic syndrome remain uncertain. With the development of tools to examine genetic polymorphisms, studies have demonstrated that genetic polymorphisms of the β2- and β3-adrenoceptor gene have also been associated with insulin resistance, obesity, hypertension, and diabetes in many epidemiological studies. Thus, the genetic polymorphism might be another factor responsible for the close relationships between insulin resistance and heightened sympathetic nerve activity. Similarly, angiotensin-converting enzyme (ACE) polymorphisms, angiotensin II type 1 and type 2 receptors polymorphisms, and leptin receptor polymorphisms are closely related to obesity, hypertension and diabetes. These genetic investigations also support the close interactions between these conditions and sympathetic nervous system, the RAAS, and leptin. The purpose of this special issue is to provide a synthesis of the current findings on obesity, hypertension and the metabolic syndrome with a special focus on the mechanisms of onset. A better understanding of the relationships of genetic background with sympathetic nervous system activity, insulin resistance and RAAS to the cause of obesity-rerlated illness may assist in the management of obesity-related illness. Further, clarification of the pathogenesis and mechanisms of obesity-related illness may lead to the prevention of obesity and result in the reduction of cardiovascular risks. Each chapter in this issue was written by one of the experts in the area. The editor hopes that this issue will help obese patients suffering from hypertension and diabetes to prevent their more serious cardiovascular risk and help medical practitioners who are treating those patients, and finally prevent the global health issue.