Hypertension in obesity.

Hypertension and obesity are major components of the cardiometabolic syndrome and are both on the rise worldwide, with enormous consequences on global health and the economy. The relationship between hypertension and obesity is multifaceted; the etiology is complex and it is not well elucidated. This article, reviews the current knowledge on obesity-related hypertension. Further understanding of the underlying mechanisms of this epidemic will be important in devising future treatment avenues.

Ultrastructure of islet microcirculation, pericytes and the islet exocrine interface in the HIP rat model of diabetes.

CONTEXT: The transgenic human islet amyloid polypeptide (HIP) rat model of type 2 diabetes mellitus (T2DM) parallels the functional and structural changes in human islets with T2DM. OBJECTIVE: The transmission electron microscope (TEM) was utilized to observe the ultrastructural changes in islet microcirculation. METHODS: Pancreatic tissue from male Sprague Dawley rats (2, 4, 8, 14 months) were used as controls (SDC) and compared to the 2-, 4-, 8- and 14-month-old HIP rat models. RESULTS: The 2-month-old HIP model demonstrated no islet or microcirculation remodeling changes when compared to the SDC models. The 4-month-old HIP model demonstrated significant pericapillary amyloid deposition and diminution of pericyte foot processes as compared to the SDC models. The 8-month-old model demonstrated extensive islet amyloid deposition associated with pericyte and beta-cell apoptosis when compared with SDC. The 14-month-old HIP model demonstrated a marked reduction of beta-cells and intra-islet capillaries with near complete replacement of islets by amyloidoses. Increased cellularity in the region of the islet exocrine interface was noted in the 4- to 14-month-old HIP models as compared to SDC. In contrast to intra-islet capillary rarefaction there was noticeable angiogenesis in the islet exocrine interface. Pericytes seemed to be closely associated with collagenosis, intra-islet adipogenesis and angiogenesis in the islet exocrine interface. CONCLUSION: The above novel findings regarding the microcirculation and pericytes could assist researchers and clinicians in a better morphological understanding of T2DM and lead to new strategies for prevention and treatment of T2DM.

Insulin resistance and blood pressure.

Insulin resistance, cardiometabolic syndrome, and hypertension are common health problems with significant consequences for individuals and society. The pathogenesis of these disorders is complex and not fully understood. In this article we review the current knowledge about the effects of lifestyle modification and pharmacologic antihypertensive agents on insulin resistance and hypertension.

Mineralocorticoid receptor blockade attenuates chronic overexpression of the renin-angiotensin-aldosterone system stimulation of reduced nicotinamide adenine dinucleotide phosphate oxidase and cardiac remodeling.

The renin-angiotensin-aldosterone system contributes to cardiac remodeling, hypertrophy, and left ventricular dysfunction. Angiotensin II and aldosterone (corticosterone in rodents) together generate reactive oxygen species (ROS) via reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which likely facilitate this hypertrophy and remodeling. This investigation sought to determine whether cardiac oxidative stress and cellular remodeling could be attenuated by in vivo mineralocorticoid receptor (MR) blockade in a rodent model of the chronically elevated tissue renin-angiotensin-aldosterone system, the transgenic TG (mRen2) 27 rat (Ren2). The Ren2 overexpresses the mouse renin transgene with resultant hypertension, insulin resistance, proteinuria, and cardiovascular damage. Young (6- to 7-wk-old) male Ren2 and age-matched Sprague-Dawley rats were treated with spironolactone or placebo for 3 wk. Heart tissue ROS, immunohistochemical analysis of 3-nitrotyrosine, and NADPH oxidase (NOX) subunits (gp91(phox) recently renamed NOX2, p22(phox), Rac1, NOX1, and NOX4) were measured. Structural changes were assessed with cine-magnetic resonance imaging, transmission electron microscopy, and light microscopy. Significant increases in Ren2 septal wall thickness (cine-magnetic resonance imaging) were accompanied by perivascular fibrosis, increased mitochondria, and other ultrastructural changes visible by light microscopy and transmission electron microscopy. Although there was no significant reduction in systolic blood pressure, significant improvements were seen with MR blockade on ROS formation and NOX subunits (each P < 0.05). Collectively, these data suggest that MR blockade, independent of systolic blood pressure reduction, improves cardiac oxidative stress-induced structural and functional changes, which are driven, in part, by angiotensin type 1 receptor-mediated increases in NOX.

Ultrastructural islet study of early fibrosis in the Ren2 rat model of hypertension. Emerging role of the islet pancreatic pericyte-stellate cell.

CONTEXT: Type 2 diabetes mellitus is a multifactorial disease with polygenic and environmental stressors resulting in multiple metabolic toxicities and islet oxidative stress. We have integrated the role of the islet renin-angiotensin system (RAS) in the pathogenesis of early islet fibrosis utilizing the transgenic (mRen2)27 rodent model of hypertension and tissue RAS overexpression. OBJECTIVE: The Ren2 pancreatic islet tissue was evaluated with transmission electron microscopy to study both early cellular and extracellular matrix remodeling. ANIMALS: Four 9- to 10-week-old male Ren2 untreated models and four Sprague Dawley sex and age matched controls were used. DESIGN: Ultrastructural study to compare pancreatic islet tissue. MAIN OUTCOME MEASURES: Only qualitative and observational transmission electron microscopy findings are reported. RESULTS: Major remodeling differences in the Ren2 model were found to be located within the islet exocrine interface, including deposition of early fibrillar-banded collagen (fibrosis) and cellular remodeling of the pericyte suggesting proliferation, migration, hypertrophy and activation as compared to the Sprague Dawley controls. CONCLUSION: This study points to the possibility of the pericyte cell being one of many contributors to the fibrogenic pool of cells important for peri-islet fibrosis as a result of excess angiotensin II at the local tissue level in the Ren2 model. These findings suggest that the pericyte may be capable of differentiating into the pancreatic stellate cell. This islet ultrastructure study supports the notion that pericyte cells could be the link between islet vascular oxidative stress and peri-islet fibrosis. Pericyte-endothelial-pancreatic stellate cell associations and morphology are discussed.

Hypertension in obesity.

Obesity and HTN are on the rise in the world. HTN seems to be the most common obesity-related health problem and visceral obesity seems to be the major culprit. Unfortunately, only 31% of hypertensives are treated to goal. This translates into an increased incidence of CVD and related morbidity and mortality. Several mechanisms have been postulated as the causes of obesity-related HTN. Activation of the RAAS, SNS, insulin resistance, leptin, adiponectin, dysfunctional fat, FFA, resistin, 11 Beta dehydrogenase, renal structural and hemodynamic changes, and OSA are some of the abnormalities in obesity-related HTN. Many of these factors are interrelated. Treatment of obesity should begin with weight loss via lifestyle modifications, medications, or bariatric surgery. According to the mechanisms of obesity-related HTN, it seems that drugs that blockade the RAAS and target the SNS should be ideal for treatment. There is not much evidence in the literature that one drug is better than another in controlling obesity-related HTN. There have only been a few studies specifically targeting the obese hypertensive patient, but recent trials that emphasize the importance of BP control have enrolled both overweight and obese subjects. Until we have further studies with more in-depth information about the mechanisms of obesity-related HTN and what the targeted treatment should be, the most important factor necessary to control the obesity-related HTN pandemic and its CVD and CKD consequences is to prevent and treat obesity and to treat HTN to goal.

Renin-angiotensin-aldosterone system and oxidative stress in cardiovascular insulin resistance.

Hypertension commonly occurs in conjunction with insulin resistance and other components of the cardiometabolic syndrome. Insulin resistance plays a significant role in the relationship between hypertension, Type 2 diabetes mellitus, chronic kidney disease, and cardiovascular disease. There is accumulating evidence that insulin resistance occurs in cardiovascular and renal tissue as well as in classical metabolic tissues (i.e., skeletal muscle, liver, and adipose tissue). Activation of the renin-angiotensin-aldosterone system and subsequent elevations in angiotensin II and aldosterone, as seen in cardiometabolic syndrome, contribute to altered insulin/IGF-1 signaling pathways and reactive oxygen species formation to induce endothelial dysfunction and cardiovascular disease. This review examines currently understood mechanisms underlying the development of resistance to the metabolic actions of insulin in cardiovascular as well as skeletal muscle tissue.

Metabolic safety of antihypertensive drugs: myth versus reality.

Treatment of hypertension with the major available antihypertensive classes results in a significant improvement in cardiovascular morbidity and mortality. However, there is controversy about whether specific classes of drug therapy have deleterious or beneficial effects on glucose and lipid metabolism. Myths and misconceptions have thus arisen. Although "old" classes of antihypertensives, such as diuretics and beta-blockers, seem to have deleterious effects on glucose and lipid metabolism, the "newer" agents appear to have either neutral or beneficial profiles. The long-term significance of these metabolic changes is still debated. It is known that insulin resistance plays a major role in the pathogenesis of hypertension and type 2 diabetes mellitus. There is increasing evidence that blocking the renin-angiotensin-aldosterone system by using angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers favorably affects insulin sensitivity and, accordingly, decreases the incidence of new-onset type 2 diabetes mellitus.

Polycystic ovarian syndrome.

Polycystic ovarian syndrome (PCOS) is the most common reproductive endocrinopathy of women during their childbearing years. A significant degree of controversy exists regarding the etiology of this syndrome, but there is a growing consensus that the key features include insulin resistance, androgen excess, and abnormal gonadotropin dynamics. Familial and genetic factors cause predisposition to PCOS. Insulin resistance and adiposity put women with PCOS at a higher risk for diabetes, hypertension, dyslipidemia, and cardiovascular disease. Even though the adverse health consequences associated with PCOS are substantial, most women are not aware of these risks. Early recognition and treatment of metabolic sequelae should be the main focus of clinicians. Lifestyle modifications, mainly a balanced diet, weight loss, and regular exercise, are of utmost importance. On the pharmacologic front, various therapies including metformin, thiazolidinediones, and others appear to be very promising in the management of cardiometabolic aspects of PCOS.

The relationship between hyperinsulinemia, hypertension and progressive renal disease.

The incidence of end-stage renal disease (ESRD) has risen dramatically in the past decade, mainly due to the increasing prevalence of diabetes mellitus, and both impaired glucose tolerance and hypertension are important contributors to rising rates of ESRD. Obesity, especially the visceral type, is associated with peripheral resistance to insulin actions and hyperinsulinemia, which predisposes to development of diabetes. A common genetic predisposition to insulin resistance and hypertension and the coexistence of these two disorders predisposes to premature atherosclerosis. A constellation of metabolic and cardiovascular derangements, which also includes dyslipidemia, dysglycemia, endothelial dysfunction, fibrinolytic and inflammatory abnormalities, left ventricular hypertrophy, microalbuminuria, and increased oxidative stress, is referred to as the cardiometabolic syndrome. The components of this syndrome, individually and interdependently, substantially increase the risk of renal disease, cardiovascular disease (CVD) and mortality. Similar findings and cardiorenal risk factors can occur in subjects with android obesity without excess body weight.Recently, microalbuminuria has been gaining momentum as a component and marker for the cardiometabolic syndrome, in addition to being an early marker for progressive renal disease in patients with this syndrome or in those with diabetes. Furthermore, it is now established as an independent predictor of CVD and CVD mortality. This review examines the relationship between insulin resistance/hyperinsulinemia and hypertension in the context of cardiometabolic syndrome, progressive renal disease and accelerated CVD. The importance of microalbuminuria as an early marker for the cardiometabolic syndrome is also discussed in this review.