Cardiorenal syndrome: an evolutionary point of view.

In modern societies, lifestyle-related diseases, such as hypertension, diabetes mellitus, and obesity, are major causes of cardiovascular disease (CVD) and renal failure. In particular, chronic kidney disease (CKD), as defined by reduced glomerular filtration rate (GFR; 60 mL/min per 1.73 m) and/or the presence of renal damage for 3 months, is a significant threat to public health. Recent epidemiological studies have demonstrated that CKD is a significant risk for cardiovascular events independent of classic risk factors, such as hypertension, dyslipidemia, and diabetes mellitus. The incidence and prevalence of CKD are increasing worldwide, and CKD is a significant health problem associated with high morbidity, mortality, and healthcare costs. One of the features of lifestyle-related diseases is that an apparently minor insult to the kidney, as manifested by microalbuminuria, is associated with a heightened incidence of CVD. Why? We may be able to find an answer in the process of the evolution of life. It is plausible that the structures and functions of vital organs and molecules essential for survival in the natural environment have now become villains that jeopardize our health in a modern society. The representative examples may include the renin-angiotensin-aldosterone system (RAAS) and the circulatory systems that deliver blood supply to the sites crucial for survival, such as the brain stem. Cardiorenal syndrome is classified into 5 subtypes. This review mainly discusses the relationship among the kidney, heart, and brain in lifestyle-related diseases. However, an insight into the fundamentals of structures and functions of vital organs from an evolutionary point of view would help us understand the pathophysiological interactions in the other types of cardiorenal syndromes.