Obesity and hypertension, which often coexist, are major risk factors for heart failure and are characterized by chronic, low-grade inflammation, which promotes adverse cardiac remodeling. While ...macrophages play a key role in cardiac remodeling, dysregulation of macrophage polarization between the proinflammatory M1 and anti-inflammatory M2 phenotypes promotes excessive inflammation and cardiac injury. Metabolic shifting between glycolysis and mitochondrial oxidative phosphorylation has been implicated in macrophage polarization. M1 macrophages primarily rely on glycolysis, whereas M2 macrophages rely on the tricarboxylic acid cycle and oxidative phosphorylation; thus, factors that affect macrophage metabolism may disrupt M1/M2 homeostasis and exacerbate inflammation. The mechanisms by which obesity and hypertension may synergistically induce macrophage metabolic dysfunction, particularly during cardiac remodeling, are not fully understood. We propose that obesity and hypertension induce M1 macrophage polarization via mechanisms that directly target macrophage metabolism, including changes in circulating glucose and fatty acid substrates, lipotoxicity, and tissue hypoxia. We discuss canonical and novel proinflammatory roles of macrophages during obesity-hypertension-induced cardiac injury, including diastolic dysfunction and impaired calcium handling. Finally, we discuss the current status of potential therapies to target macrophage metabolism during heart failure, including antidiabetic therapies, anti-inflammatory therapies, and novel immunometabolic agents.
Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and ...associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.
Hypertension is a major risk factor for cardiovascular and renal diseases in the United States and worldwide. Obesity accounts for much of the risk for primary hypertension through several ...mechanisms, including neurohormonal activation, inflammation, and kidney dysfunction. As the prevalence of obesity continues to increase, hypertension and associated cardiorenal diseases will also increase unless more effective strategies to prevent and treat obesity are developed. Lifestyle modification, including diet, reduced sedentariness, and increased physical activity, is usually recommended for patients with obesity; however, the long-term success of these strategies for reducing adiposity, maintaining weight loss, and reducing blood pressure has been limited. Effective pharmacotherapeutic and procedural strategies, including metabolic surgeries, are additional options to treat obesity and prevent or attenuate obesity hypertension, target organ damage, and subsequent disease. Medications can be useful for short- and long-term obesity treatment; however, prescription of these drugs is limited. Metabolic surgery is effective for producing sustained weight loss and for treating hypertension and metabolic disorders in many patients with severe obesity. Unanswered questions remain related to the mechanisms of obesity-related diseases, long-term efficacy of different treatment and prevention strategies, and timing of these interventions to prevent obesity and hypertension-mediated target organ damage. Further investigation, including randomized controlled trials, is essential to addressing these questions, and emphasis should be placed on the prevention of obesity to reduce the burden of hypertensive cardiovascular and kidney diseases and subsequent mortality.
Excess weight gain, especially when associated with increased visceral adiposity, is a major cause of hypertension, accounting for 65% to 75% of the risk for human primary (essential) hypertension. ...Increased renal tubular sodium reabsorption impairs pressure natriuresis and plays an important role in initiating obesity hypertension. The mediators of abnormal kidney function and increased blood pressure during development of obesity hypertension include (1) physical compression of the kidneys by fat in and around the kidneys, (2) activation of the renin-angiotensin-aldosterone system, and (3) increased sympathetic nervous system activity. Activation of the renin-angiotensin-aldosterone system is likely due, in part, to renal compression, as well as sympathetic nervous system activation. However, obesity also causes mineralocorticoid receptor activation independent of aldosterone or angiotensin II. The mechanisms for sympathetic nervous system activation in obesity have not been fully elucidated but may require leptin and activation of the brain melanocortin system. With prolonged obesity and development of target organ injury, especially renal injury, obesity-associated hypertension becomes more difficult to control, often requiring multiple antihypertensive drugs and treatment of other risk factors, including dyslipidemia, insulin resistance and diabetes mellitus, and inflammation. Unless effective antiobesity drugs are developed, the effect of obesity on hypertension and related cardiovascular, renal and metabolic disorders is likely to become even more important in the future as the prevalence of obesity continues to increase.
The 7 mammalian sirtuin proteins compose a protective cavalry of enzymes that can be invoked by cells to aid in the defense against a vast array of stressors. The pathologies associated with aging, ...such as metabolic syndrome, neurodegeneration, and cancer, are either caused by or exacerbated by a lifetime of chronic stress. As such, the activation of sirtuin proteins could provide a therapeutic approach to buffer against chronic stress and ameliorate age-related decline. Here we review experimental evidence both for and against this proposal, as well as the implications that isoform-specific sirtuin activation may have for healthy aging in humans.
Abstract
Obesity contributes 65–75% of the risk for human primary (essential) hypertension (HT) which is a major driver of cardiovascular and kidney diseases. Kidney dysfunction, associated with ...increased renal sodium reabsorption and compensatory glomerular hyperfiltration, plays a key role in initiating obesity-HT and target organ injury. Mediators of kidney dysfunction and increased blood pressure include (i) elevated renal sympathetic nerve activity (RSNA); (ii) increased antinatriuretic hormones such as angiotensin II and aldosterone; (iii) relative deficiency of natriuretic hormones; (iv) renal compression by fat in and around the kidneys; and (v) activation of innate and adaptive immune cells that invade tissues throughout the body, producing inflammatory cytokines/chemokines that contribute to vascular and target organ injury, and exacerbate HT. These neurohormonal, renal, and inflammatory mechanisms of obesity-HT are interdependent. For example, excess adiposity increases the adipocyte-derived cytokine leptin which increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway. Excess visceral, perirenal and renal sinus fat compress the kidneys which, along with increased RSNA, contribute to renin–angiotensin–aldosterone system activation, although obesity may also activate mineralocorticoid receptors independent of aldosterone. Prolonged obesity, HT, metabolic abnormalities, and inflammation cause progressive renal injury, making HT more resistant to therapy and often requiring multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes, and inflammation. More effective anti-obesity drugs are needed to prevent the cascade of cardiorenal, metabolic, and immune disorders that threaten to overwhelm health care systems as obesity prevalence continues to increase.
Graphical Abstract
Over the past several decades, studies of the sympathetic nervous system in humans, sheep, rabbits, rats, and mice have substantially increased mechanistic understanding of cardiovascular function ...and dysfunction. Recently, interest in sympathetic neural mechanisms contributing to blood pressure control has grown, in part because of the development of devices or surgical procedures that treat hypertension by manipulating sympathetic outflow. Studies in animal models have provided important insights into physiological and pathophysiological mechanisms that are not accessible in human studies. Across species and among laboratories, various approaches have been developed to record, quantify, analyze, and interpret sympathetic nerve activity (SNA). In general, SNA demonstrates "bursting" behavior, where groups of action potentials are synchronized and linked to the cardiac cycle via the arterial baroreflex. In humans, it is common to quantify SNA as bursts per minute or bursts per 100 heart beats. This type of quantification can be done in other species but is only commonly reported in sheep, which have heart rates similar to humans. In rabbits, rats, and mice, SNA is often recorded relative to a maximal level elicited in the laboratory to control for differences in electrode position among animals or on different study days. SNA in humans can also be presented as total activity, where normalization to the largest burst is a common approach. The goal of the present paper is to put together a summary of "best practices" in several of the most common experimental models and to discuss opportunities and challenges relative to the optimal measurement of SNA across species.Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/guidelines-for-measuring-sympathetic-nerve-activity/.
Hyperinsulinemia and insulin resistance were proposed more than 30 years ago to be important contributors to elevated blood pressure (BP) associated with obesity and the metabolic syndrome, also ...called syndrome X. Support for this concept initially came from clinical and population studies showing correlations among hyperinsulinemia, insulin resistance, and elevated BP in individuals with metabolic syndrome. Short-term studies in experimental animals and in humans provided additional evidence that hyperinsulinemia may evoke increases in sympathetic nervous system (SNS) activity and renal sodium retention that, if sustained, could increase BP. Although insulin infusions may increase SNS activity and modestly raise BP in rodents, chronic insulin administration does not significantly increase BP in lean or obese insulin-resistant rabbits, dogs, horses, or humans. Multiple studies in humans and experimental animals have also shown that severe insulin resistance and hyperinsulinemia may occur in the absence of elevated BP. These observations question whether insulin resistance and hyperinsulinemia are major factors linking obesity/metabolic syndrome with hypertension. Other mechanisms, such as physical compression of the kidneys, activation of the renin-angiotensin-aldosterone system, hyperleptinemia, stimulation of the brain melanocortin system, and SNS activation, appear to play a more critical role in initiating hypertension in obese subjects with metabolic syndrome. However, the metabolic effects of insulin resistance, including hyperglycemia and dyslipidemia, appear to interact synergistically with increased BP to cause vascular and kidney injury that can exacerbate the hypertension and associated injury to the kidneys and cardiovascular system.
L'hyperinsulinémie et l'insulinorésistance ont été décrits il y a plus de 30 ans comme étant des facteurs importants contribuant à une pression artérielle (PA) élevée associée à l'obésité et au syndrome métabolique, également appelé syndrome X. Ce concept a été initialement soutenu par des études cliniques et démographiques montrant des corrélations entre l'hyperinsulinémie, l'insulinorésistance et une PA élevée chez les personnes atteintes du syndrome métabolique. Des études de court terme sur des animaux de laboratoire et chez l'Homme ont fourni des preuves supplémentaires que l'hyperinsulinémie peut provoquer une augmentation de l'activité du système nerveux sympathique (SNS) et de la rétention de sodium au niveau rénal qui, si elle est maintenue, pourrait augmenter la PA. Bien que les perfusions d'insuline puissent accroître l'activité du SNS et augmenter légèrement la PA chez les rongeurs, l'administration chronique d'insuline n'augmente pas significativement la PA chez les individus insulinorésistants maigres ou obèses, que ce soit chez les lapins, les chiens, les chevaux ou chez l’Homme. De multiples études chez l'Homme et les animaux de laboratoire ont également montré qu'une hyperinsulinémie et une insulinorésistance sévère peuvent survenir en absence de PA élevée. Ces observations amènent à se demander si l’insulinorésistance et l'hyperinsulinémie sont des facteurs majeurs liant l'obésité et le syndrome métabolique à l'hypertension. D'autres mécanismes, tels que la compression physique des reins, l'activation du système rénine-angiotensine-aldostérone, l'hyperleptinémie, la stimulation du système à mélanocortine du cerveau et l'activation du SNS, semblent jouer un rôle plus critique dans l'initiation de l'hypertension chez les sujets obèses atteints d'un syndrome métabolique. Cependant, les effets métaboliques de l'insulinorésistance, notamment l'hyperglycémie et la dyslipidémie, semblent interagir en synergie avec l'augmentation de la PA pour provoquer des lésions vasculaires et rénales qui peuvent exacerber l'hypertension et les dommages associés aux reins et au système cardiovasculaire.
This paper provides a personal perspective of the role of abnormal renal-pressure natriuresis in the pathogenesis of hypertension. Direct support for a major role of renal-pressure natriuresis in ...long-term control of arterial pressure and sodium balance comes from studies demonstrating that (1) pressure natriuresis is impaired in all forms of chronic hypertension and (2) prevention of pressure natriuresis from operating, by servo-control of renal perfusion pressure, also prevents the maintenance of sodium balance hypertension. Although the precise mechanisms of impaired pressure natriuresis in essential hypertension have remained elusive, recent evidence suggests that obesity and overweight may play a major role. Obesity increases renal sodium reabsorption and impairs pressure natriuresis by activation of the renin-angiotensin and sympathetic nervous systems and by altered intrarenal physical forces. Chronic obesity also causes marked structural changes in the kidneys that eventually lead to a loss of nephron function, further increases in arterial pressure, and severe renal injury in some cases. Although there are many unanswered questions about the mechanisms of obesity hypertension and renal disease, this is one of the most promising areas for future research, especially in view of the growing, worldwide "epidemic" of obesity.
PDF
