Heart and Kidney: Fatal Twins?

The importance of renal function as both a marker of and risk factor for cardiovascular disease is increasingly recognized. This link is apparent even in the earliest stages of renal dysfunction, at levels that are conventionally considered “normal.” These findings are of considerable importance, given the prevalence of high-normal levels of albuminuria (i.e., 10 to 20 mg/L) in the general population. There is also a close link between the progression of albuminuria and the development of insulin resistance and type 2 diabetes mellitus, such that kidney disease-far from being simply a consequence of the metabolic syndrome-may be considered a component of it. It may be hypothesized that minor derangements of renal function, such as microalbuminuria or reduced glomerular filtration rate, can lead to dysfunction of the endothelium, with the consequence of sensitizing the vasculature to the injurious effects of hypertension, dyslipidemia, and other risk factors. The renin-angiotensin system (RAS) is highly activated in patients with the metabolic syndrome, and this presumably is also true for the intrarenal RAS systems. Both angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers are known to reduce the progression of renal damage. Still to be resolved, however, is the optimal dosage; several recent studies indicate that the dosage required for maximal blood pressure reduction is insufficient to provide maximal renoprotection.