The insulin resistance syndrome: mechanisms of clustering of cardiovascular risk.
For more than a decade, insulin resistance has been proposed as the key linking factor for the metabolic syndrome disease cluster of glucose intolerance, hypertension, dyslipidemia, obesity, and cardiovascular disease. Although most of the epidemiological, experimental, and clinical evidence still support the role of insulin resistance as an important component of this multifaceted syndrome, there is evidence amassing that a neurohormonal mechanism, including an endocrine role for adipocytes, probably plays a more fundamental role. This is supported by the strong associations between obesity, especially central adiposity, and all components of the metabolic syndrome, in contrast to the inconsistent relationships between blood pressure and markers of insulin resistance. However, much of the effect of visceral fat on cardiovascular risk factors is mediated through the metabolic actions of free fatty acids (FFA) on insulin resistance, thus resolving any obesity versus insulin resistance controversy. In addition to the roles of obesity and FFA in the development of insulin resistance syndrome, the high prevalence rates of this disease cluster among subjects from low socioeconomic groups as well as from developing countries have led to alternative hypotheses to better our understanding of the contributory roles of socioeconomic, in utero, and genetic factors in this syndrome. More recently, the pathogenetic roles of iron overload and liver dysfunction have also been re-examined. In this article, the various hypotheses which have been put forward to explain the diverse clinical manifestations of the metabolic or insulin resistance syndrome are summarized and put into perspective. While there is clinical and experimental evidence to support many of these independent pathways, alternative statistical methods such as factor analysis or structural equation modeling may be needed to unravel the complex nature of these interacting pathways. Finally, these hypotheses, if proven, will add new dimensions to our current strategies and emphasize the need to focus on behavioral and socioeconomic interventions in addition to the use of pharmacological therapy in our attempt to control this epidemic disease of modern societies.
Chan
Juliana C N
JC
Departmentof Medicine Therapeutics,Prince of Wales Hospital,TheChinese University of Hong Kong Shatin, Hong Kong. j.chan@cuhk.edu.hk
Tong
Peter C Y
PC
Critchley
Julian A J H
JA
D017667:Adipocytes / Q000502:physiology*; D000273:Adipose Tissue / Q000378:metabolism / Q000503:physiopathology; D002318:Cardiovascular Diseases / Q000209:etiology / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000503:physiopathology; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006949:Hyperlipidemias / Q000503:physiopathology; D007230:Infant, Low Birth Weight / Q000502:physiology; D007231:Infant, Newborn; D007333:Insulin Resistance / Q000502:physiology*; D019190:Iron Overload / Q000503:physiopathology; D008107:Liver Diseases / Q000503:physiopathology; D024821:Metabolic Syndrome / Q000209:etiology / Q000503:physiopathology*; D009765:Obesity / Q000150:complications / Q000378:metabolism / Q000503:physiopathology*; D012307:Risk Factors
D005230:Fatty Acids, Nonesterified; D005947:Glucose