The Kidney-Heart Connection in Obesity

There is a strong relationship between the kidney and the heart, where if one of these organs fails, so does the other, in the so-called cardiorenal syndrome (CRS). Besides, there are also interactions with the rest of the body leading to a metabolic state that establishes a feedback loop that is perpetuated. The CRS is characterized by hemodynamic changes, activation of neuro-humoral systems, natriuretic peptides, and changes in mineral metabolism. In this scenario, the kidney and heart, connected by a dysfunctional endothelium, inevitably fail. In obesity, this syndrome is exacerbated due to the complications of adipose tissue dysfunction, in the so-called cardiorenal metabolic syndrome (CRMetS). Obesity promotes adipose tissue dysfunction because it exceeds lipid storage capacity and leads to a lipotoxic state, characterized by inflammation, hypertension, insulin resistance and dyslipidemia, oxidative stress, and hyperuricemia, among others, that affect different organs other than the adipose tissue. In addition, the pro-inflammatory gut microbiota present in obese patients releases uremic toxins, contributing to oxidative stress and inflammation, perpetuating and accelerating the progression of this pathology. In this article, we describe the contribution of obesity, the factors and mechanisms implicated in the development of the CRMetS. Despite the great knowledge about the CRS, more research is needed to characterize the CRMetS given the global obesity epidemic.

Autophagy as an emerging target in cardiorenal metabolic disease: From pathophysiology to management

Although advances in medical technology and health care have improved the early diagnosis and management for cardiorenal metabolic disorders, the prevalence of obesity, insulin resistance, diabetes, hypertension, dyslipidemia, and kidney disease remains high. Findings from numerous population-based studies, clinical trials, and experimental evidence have consolidated a number of theories for the pathogenesis of cardiorenal metabolic anomalies including resistance to the metabolic action of insulin, abnormal glucose and lipid metabolism, oxidative and nitrosative stress, endoplasmic reticulum (ER) stress, apoptosis, mitochondrial damage, and inflammation. Accumulating evidence has recently suggested a pivotal role for proteotoxicity, the unfavorable effects of poor protein quality control, in the pathophysiology of metabolic dysregulation and related cardiovascular complications. The ubiquitin-proteasome system (UPS) and autophagy-lysosomal pathways, two major although distinct cellular clearance machineries, govern protein quality control by degradation and clearance of long-lived or damaged proteins and organelles. Ample evidence has depicted an important role for protein quality control, particularly autophagy, in the maintenance of metabolic homeostasis. To this end, autophagy offers promising targets for novel strategies to prevent and treat cardiorenal metabolic diseases. Targeting autophagy using pharmacological or natural agents exhibits exciting new strategies for the growing problem of cardiorenal metabolic disorders.

Autophagy: a housekeeper in cardiorenal metabolic health and disease

Autophagy, literally translated means self-eating, is a primary degradative pathway and plays an important role in the regulation of cellular homeostasis through elimination of aggregated proteins, damaged organelles, and intracellular pathogens. Autophagy has been classified into microautophagy, macroautophagy, and chaperone-mediated autophagy, depending on the choice of the pathway by which the cellular material is delivered to lysosomes. Dysregulation of autophagy may contribute to the development of cardiorenal metabolic syndrome (CRS), including insulin resistance, obesity, hypertension, maladaptive immune modulation, and associated cardiac and renal disease. Clarifying the pathways and mechanisms of autophagy under normal conditions is essential to understanding its dysregulation in the development of CRS. Here, we highlight a recent surge in autophagy research, such as the cellular quality control through the disposal and recycling of cellular components, and summarize our contemporary understanding of molecular mechanisms of autophagy in diverse organ or tissues involved in the pathogenesis of CRS. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Uric Acid - key ingredient in the recipe for cardiorenal metabolic syndrome

Elevated serum uric acid levels are a frequent finding in persons with obesity, hypertension, cardiovascular and kidney disease as well as in those with the cardiorenal metabolic syndrome (CRS). The increased consumption of a fructose-rich Western diet has contributed to the increasing incidence of the CRS, obesity and diabetes especially in industrialized populations. There is also increasing evidence that supports a causal role of high dietary fructose driving elevations in uric acid in association with the CRS. Animal and epidemiological studies support the notion that elevated serum uric acid levels play an important role in promoting insulin resistance and hypertension and suggest potential pathophysiological mechanisms that contribute to the development of the CRS and associated cardiovascular disease and chronic kidney disease. To this point, elevated serum levels of uric acid appear to contribute to impaired nitric oxide production/endothelial dysfunction, increased vascular stiffness, inappropriate activation of the renin-angiotensin-aldosterone system, enhanced oxidative stress, and maladaptive immune and inflammatory responses. These abnormalities, in turn, promote vascular, cardiac and renal fibrosis as well as associated functional abnormalities. Small clinical trials have suggested that uric acid-lowering therapies may be beneficial in such patients; however, a consensus on the treatment of asymptomatic hyperuricemia is lacking. Larger randomized controlled trials need to be performed in order to critically evaluate the beneficial effect of lowering serum uric acid in patients with the CRS and those with diabetes and/or hypertension.

Arterial Stiffness: A Nexus between Cardiac and Renal Disease

Vascular disease is the leading cause of morbidity and mortality in the Western world, and vascular function is determined by structural and functional properties of the arterial vascular wall. Cardiorenal metabolic syndrome such as obesity, diabetes, hypertension, kidney disease, and aging are conditions that predispose to arterial stiffening, which is a pathological alteration of the vascular wall and ultimately results in target organ damage in heart and kidney. In this review, we provide new insights on the interactions between arterial stiffness, vascular resistance and pulse wave velocity as well as final end-organ damage in heart and kidney. Better understanding of the mechanisms of arterial functional and hemodynamic alteration may help in developing more refined therapeutic strategies aimed to reduce cardiovascular and chronic kidney diseases.

Estrogen and mitochondria function in cardiorenal metabolic syndrome

The cardiorenal metabolic syndrome (CRS) consists of a constellation of cardiac, renal, and metabolic disorders including insulin resistance (IR), obesity, metabolic dyslipidemia, high-blood pressure, and evidence of early cardiac and renal disease. Mitochondria dysfunction often occurs in the CRS, and this dysfunction is promoted by excess reactive oxygen species, genetic factors, IR, aging, and altered mitochondrial biogenesis. Recently, it has been shown that there are important sex-related differences in mitochondria function and metabolic, cardiovascular, and renal components. Sex differences in the CRS have mainly been attributed to the estrogen's effects that are mainly mediated by estrogen receptor (ER) α, ERβ, and G-protein coupled receptor 30. In this review, we discuss the effects of estrogen on the mitochondrial function, insulin metabolic signaling, glucose transport, lipid metabolism, and inflammatory responses from liver, pancreatic β cells, adipocytes, skeletal muscle, and cardiovascular tissue.

Cardiorenal metabolic syndrome and cardiometabolic risks in minority populations

Cardiovascular disease (CVD), including heart disease and stroke, is the leading cause of death in the USA, regardless of self-determined race/ethnicity, and largely driven by cardiometabolic risk (CMR) and cardiorenal metabolic syndrome (CRS). The primary drivers of increased CMR include obesity, hypertension, insulin resistance, hyperglycemia, dyslipidemia, chronic kidney disease as well as associated adverse behaviors of physical inactivity, smoking, and unhealthy eating habits. Given the importance of CRS for public health, multiple stakeholders, including the National Minority Quality Forum (the Forum), the American Association of Clinical Endocrinologists (AACE), the American College of Cardiology (ACC), and the Association of Black Cardiologists (ABC), have developed this review to inform clinicians and other health professionals of the unique aspects of CMR in racial/ethnic minorities and of potential means to improve CMR factor control, to reduce CRS and CVD in diverse populations, and to provide more effective, coordinated care. This paper highlights CRS and CMR as sources of significant morbidity and mortality (particularly in racial/ethnic minorities), associated health-care costs, and an evolving index tool for cardiometabolic disease to determine geographical and environmental factors. Finally, this work provides a few examples of interventions potentially successful at reducing disparities in cardiometabolic health.

Resistance to insulin and kidney disease in the cardiorenal metabolic syndrome; role for angiotensin II

The presence of insulin resistance is increasingly recognized as an important contributor to early stage kidney disease independent of the contribution of diabetes. Important in this relationship is the strong correlation between hyperinsulinemia and low levels of albuminuria (e.g. microalbuminuria). Recent work highlight mechanisms for glomerular/tubulointerstitial injury with excess insulin and emerging evidence identifies a unique role for insulin metabolic signaling and altered handling of salt reabsorption at the level of the proximal tubule. Evidence is also emerging for the role of insulin signaling in the glomerulus both epithelial and endothelial. Central to the mechanism of injury is inappropriate activation of the RAAS.

The Role of Overweight and Obesity in the Cardiorenal Syndrome

The presence of a group of interactive maladaptive factors including hypertension, insulin resistance, metabolic dyslipidemia, obesity, microalbuminuria, and/or reduced renal function constitute the cardiorenal metabolic syndrome (CRS). Overweight, obesity, and chronic kidney disease (CKD) have grown to pandemic proportions in industrialized countries during the past decade. The fact that these interactive factors promote heart and renal disease has been documented in large population-based studies. Obesity seems to be the driving force behind the development of heart disease and CKD and therefore the CRS. The relationship between overweight/obesity and kidney disease begins in early childhood and appears to be related to overconsumption of high-fructose corn syrup and insufficient physical activity. Today, 13 million children are obese, and over 70% of these children are likely to become obese adults. Indeed, approximately 30% of male and 34% of female adults in the United States are obese. This lifestyle-related epidemic will be a major societal medical and economic problem that will accentuate the current epidemic of CKD in the United States and other industrialized and emerging industrialized countries. In this article, we will review the potential mechanisms by which obesity and other metabolic abnormalities interact to promote heart and progressive kidney disease.