Patient, facility, and environmental factors associated with obesity treatment in US Veterans.

Background: Identifying patient-, facility-, and environment-level factors that influence the initiation and retention of comprehensive lifestyle management interventions (CLMI) for urban and rural Veterans could improve obesity treatment and reach at Veterans Affairs (VA) facilities. Aims: This study identified factors at these various levels that predicted treatment engagement, retention, and weight management among urban and rural Veterans. Methods: A retrospective cohort study of 631,325 Veterans was designed using VA databases to identify Veterans with class II and III obesity during 2015-2017. Primary outcomes were initiation of CLMI, bariatric surgery, or obesity pharmacotherapy within 1 year of index date. Secondary outcomes included treatment retention and successful weight loss. Generalized linear mixed models were used to evaluate the relationships between factors and obesity-related outcomes, with rurality differences assessed through interaction terms. Results: Patient characteristics associated with increased odds of initiating CLMI included female sex (p < 0.001), black race (p < 0.001), sleep apnea (p < 0.001), mood disorder (p < 0.001), and use of medications associated with weight loss (p < 0.001) or weight gain (p < 0.001). Facility use of telehealth was associated with greater odds of CLMI initiation in urban Veterans (p < 0.001) but lower retention in both populations (p = 0.003). Routine consideration of pharmacotherapy was associated with higher CLMI initiation. Environmental characteristics associated with increased odds of CLMI initiation included percent of population foreign born (OR = 1.03 per 10% increase; p < 0.001), percent black (p < 0.001), and high walkability index (p < 0.001). The relationship between total population and CLMI initiation differed by rurality, as greater population was associated with lower odds of CLMI initiation in urban areas (OR: 0.99 per 1000 population; p < 0.001), but higher odds in rural areas (OR:1.01, p = 0.01). Veterans in the south were less likely to initiate CLMI and had lower retention (p < 0.001). Conclusion: Treatment and retention of CLMI among Veterans remain low, highlighting areas for improvement to expand its reach both urban and rural Veterans.

Association between renin-angiotensin antagonism and COVID-19-related mortality in patients with essential hypertension: A single center, retrospective cohort study.

There is conflicting evidence in select mouse models and humans that suggest angiotensin-converting enzyme 2 expression is increased due to treatment with angiotensin converting enzyme inhibitors and angiotensin receptor blockers (ACEI/ARBs). Given the wide range of conditions that these medications treat, further evaluation is necessary to determine safety in the context of COVID-19. We sought to determine the association between use of ACEI/ARBs and COVID-19 severity in patients with essential hypertension. We included 714 patients with essential hypertension diagnosed with COVID-19 and admitted to University of Iowa Healthcare from March 1, 2020 to June 29, 2021. Severity of COVID-19 infection was assessed based on mortality, length of stay in hospital, intensive care unit admission, and use of supplemental oxygen, invasive ventilation, and vasopressors. Multivariable logistic and linear regression analyses were used for binary and continuous outcomes, respectively. Prior exposure to ACEI/ARBs before admission was significantly associated with lower mortality (OR: 0.454, p = .015), shorter length of stay in hospital (p < .001), and decreased adjusted odds of intensive care admission (OR: 0.719; p < .042). The present results suggest that patients with essential hypertension hospitalized with COVID-19 who had a prescription for ACEI/ARBs prior to admission exhibited less severe COVID-19 and lower in-hospital mortality.

Association between RAAS Antagonism and COVID-19-related Mortality in Patients with Overweight/Obesity-related Hypertension: A Retrospective Cohort Study. / Associação entre o Antagonismo do Sistema Renina-Angiotensina-Aldosterona e a Mortalidade Relacionada à COVID-19 em Pacientes com Hipertensão Relacionada ao Sobrepeso/Obesidade: um Estudo Retrospectivo de Coorte.

BACKGROUND: Angiotensin receptor blockers (ARB) and angiotensin-converting enzyme inhibitors (ACEI) increase the expression of ACE2, which is a receptor for entry of SARS-CoV-2 into cells. Though evidence suggests that ARB/ACEI are safe among the general population with COVID-19, their safety in patients with overweight/obesity-related hypertension deserves further evaluation. OBJECTIVE: We assessed the association between ARB/ACEI use and COVID-19 severity in patients with overweight/obesity-related hypertension. METHODS: This study included 439 adult patients with overweight/obesity (body mass index ≥ 25 kg/m2) and hypertension, diagnosed with COVID-19 and admitted to University of Iowa Hospitals and Clinic from March 1 to December 7, 2020. Mortality and severity of COVID-19 were evaluated based on length of stay in hospital, intensive care unit admission, use of supplemental oxygen, mechanical ventilation, and vasopressors. Multivariable logistic regression was used to examine the associations of ARB/ACEI use with mortality and other markers of COVID-19 severity, with a two-sided alpha set at 0.05. RESULTS: Exposure to ARB (n = 91) and ACEI (n = 149) before hospitalization was significantly associated with lower mortality (odds ratio [OR] = 0.362, 95% confidence interval [CI] 0.149 to 0.880, p = 0.025) and a shorter length of stay (95% CI -0.217 to -0.025, p = 0.015). Additionally, patients using ARB/ACEI showed a non-significant trend toward lower intensive care unit admission (OR = 0.727, 95% CI 0.485 to 1.090, p = 0.123), use of supplemental oxygen (OR = 0.929, 95% CI 0.608 to 1.421, p = 0.734), mechanical ventilation (OR = 0.728, 95% CI 0.457 to 1.161, p = 0.182), and vasopressors (OR = 0.677, 95% CI 0.430 to 1.067, p = 0.093). CONCLUSION: Results suggest that hospitalized patients with COVID-19 and overweight/obesity-related hypertension who were prescribed ARB/ACEI before admission to the hospital exhibit lower mortality and less severe COVID-19 than those who were not taking ARB/ACEI. The results also suggest that exposure to ARB/ACEI may protect patients with overweight/obesity-related hypertension from severe COVID-19 and death.

FUNDAMENTO: Os bloqueadores dos receptores da angiotensina (BRA) e os inibidores da enzima conversora da angiotensina (IECA) aumentam a expressão de ACE2, que é um receptor para entrada de SARS-CoV-2 nas células. Embora as evidências sugiram que os IECA/BRA são seguros entre a população geral com COVID-19, sua segurança em pacientes com hipertensão relacionada ao sobrepeso/obesidade merece uma avaliação mais aprofundada. OBJETIVO: Avaliamos a associação entre o uso de IECA/BRA e a gravidade da COVID-19 em pacientes com hipertensão relacionada ao sobrepeso/obesidade. MÉTODOS: O presente estudo incluiu 439 pacientes adultos com sobrepeso/obesidade (índice de massa corporal ≥ 25 kg/m2) e hipertensão, diagnosticados com COVID-19 e internados no University of Iowa Hospitals and Clinic entre 1º de março e 7 de dezembro de 2020. Foram avaliadas a mortalidade e a gravidade da COVID-19 com base no tempo de internação hospitalar, internação em unidade de terapia intensiva, uso de oxigênio suplementar, ventilação mecânica e uso de vasopressores. A regressão logística multivariável foi usada para examinar as associações do uso de IECA/BRA com a mortalidade e outros marcadores de gravidade de COVID-19, com um alfa bilateral definido em 0,05. RESULTADOS: A exposição aos BRA (n = 91) e IECA (n = 149) antes da hospitalização foi significativamente associada a menor mortalidade ( odds ratio [OR] = 0,362, intervalo de confiança [IC] de 95% 0,149 a 0,880, p = 0,025) e menor tempo de internação hospitalar (IC 95% −0,217 a −0,025, p = 0,015). Adicionalmente, os pacientes em uso de IECA/BRA apresentaram uma tendência não significativa de menor internação em unidade de terapia intensiva (OR = 0,727, IC 95% 0,485 a 1,090, p = 0,123), uso de oxigênio suplementar (OR = 0,929, IC 95% 0,608 a 1,421,p = 0,734), ventilação mecânica (OR = 0,728, IC 95% 0,457 a 1,161, p = 0,182) e vasopressores (OR = 0,677, IC 95% 0,430 a 1,067, p = 0,093). CONCLUSÃO: Os resultados sugerem que pacientes internados com COVID-19 e hipertensão relacionada ao sobrepeso/obesidade que receberam IECA/BRA antes da internação apresentam menor mortalidade e COVID-19 menos grave do que aqueles que não estavam tomando IECA/BRA. Os resultados também sugerem que a exposição aos IECA/BRA pode proteger pacientes com hipertensão relacionada ao sobrepeso/obesidade de COVID-19 grave e morte.

Associação entre o Antagonismo do Sistema Renina-Angiotensina-Aldosterona e a Mortalidade Relacionada à COVID-19 em Pacientes com Hipertensão Relacionada ao Sobrepeso/Obesidade: um Estudo Retrospectivo de Coorte / Association between RAAS Antagonism and COVID-19-related Mortality in Patients with Overweight/Obesity-related Hypertension: A Retrospective Cohort Study

Resumo Fundamento Os bloqueadores dos receptores da angiotensina (BRA) e os inibidores da enzima conversora da angiotensina (IECA) aumentam a expressão de ACE2, que é um receptor para entrada de SARS-CoV-2 nas células. Embora as evidências sugiram que os IECA/BRA são seguros entre a população geral com COVID-19, sua segurança em pacientes com hipertensão relacionada ao sobrepeso/obesidade merece uma avaliação mais aprofundada. Objetivo Avaliamos a associação entre o uso de IECA/BRA e a gravidade da COVID-19 em pacientes com hipertensão relacionada ao sobrepeso/obesidade. Métodos O presente estudo incluiu 439 pacientes adultos com sobrepeso/obesidade (índice de massa corporal ≥ 25 kg/m2) e hipertensão, diagnosticados com COVID-19 e internados no University of Iowa Hospitals and Clinic entre 1º de março e 7 de dezembro de 2020. Foram avaliadas a mortalidade e a gravidade da COVID-19 com base no tempo de internação hospitalar, internação em unidade de terapia intensiva, uso de oxigênio suplementar, ventilação mecânica e uso de vasopressores. A regressão logística multivariável foi usada para examinar as associações do uso de IECA/BRA com a mortalidade e outros marcadores de gravidade de COVID-19, com um alfa bilateral definido em 0,05. Resultados A exposição aos BRA (n = 91) e IECA (n = 149) antes da hospitalização foi significativamente associada a menor mortalidade ( odds ratio [OR] = 0,362, intervalo de confiança [IC] de 95% 0,149 a 0,880, p = 0,025) e menor tempo de internação hospitalar (IC 95% −0,217 a −0,025, p = 0,015). Adicionalmente, os pacientes em uso de IECA/BRA apresentaram uma tendência não significativa de menor internação em unidade de terapia intensiva (OR = 0,727, IC 95% 0,485 a 1,090, p = 0,123), uso de oxigênio suplementar (OR = 0,929, IC 95% 0,608 a 1,421,p = 0,734), ventilação mecânica (OR = 0,728, IC 95% 0,457 a 1,161, p = 0,182) e vasopressores (OR = 0,677, IC 95% 0,430 a 1,067, p = 0,093). Conclusão Os resultados sugerem que pacientes internados com COVID-19 e hipertensão relacionada ao sobrepeso/obesidade que receberam IECA/BRA antes da internação apresentam menor mortalidade e COVID-19 menos grave do que aqueles que não estavam tomando IECA/BRA. Os resultados também sugerem que a exposição aos IECA/BRA pode proteger pacientes com hipertensão relacionada ao sobrepeso/obesidade de COVID-19 grave e morte.

Abstract Background Angiotensin receptor blockers (ARB) and angiotensin-converting enzyme inhibitors (ACEI) increase the expression of ACE2, which is a receptor for entry of SARS-CoV-2 into cells. Though evidence suggests that ARB/ACEI are safe among the general population with COVID-19, their safety in patients with overweight/obesity-related hypertension deserves further evaluation. Objective We assessed the association between ARB/ACEI use and COVID-19 severity in patients with overweight/obesity-related hypertension. Methods This study included 439 adult patients with overweight/obesity (body mass index ≥ 25 kg/m2) and hypertension, diagnosed with COVID-19 and admitted to University of Iowa Hospitals and Clinic from March 1 to December 7, 2020. Mortality and severity of COVID-19 were evaluated based on length of stay in hospital, intensive care unit admission, use of supplemental oxygen, mechanical ventilation, and vasopressors. Multivariable logistic regression was used to examine the associations of ARB/ACEI use with mortality and other markers of COVID-19 severity, with a two-sided alpha set at 0.05. Results Exposure to ARB (n = 91) and ACEI (n = 149) before hospitalization was significantly associated with lower mortality (odds ratio [OR] = 0.362, 95% confidence interval [CI] 0.149 to 0.880, p = 0.025) and a shorter length of stay (95% CI −0.217 to −0.025, p = 0.015). Additionally, patients using ARB/ACEI showed a non-significant trend toward lower intensive care unit admission (OR = 0.727, 95% CI 0.485 to 1.090, p = 0.123), use of supplemental oxygen (OR = 0.929, 95% CI 0.608 to 1.421, p = 0.734), mechanical ventilation (OR = 0.728, 95% CI 0.457 to 1.161, p = 0.182), and vasopressors (OR = 0.677, 95% CI 0.430 to 1.067, p = 0.093). Conclusion Results suggest that hospitalized patients with COVID-19 and overweight/obesity-related hypertension who were prescribed ARB/ACEI before admission to the hospital exhibit lower mortality and less severe COVID-19 than those who were not taking ARB/ACEI. The results also suggest that exposure to ARB/ACEI may protect patients with overweight/obesity-related hypertension from severe COVID-19 and death.

The use of very low-calorie diets in subjects with obesity complicated with nonalcoholic fatty liver disease: A scoping review.

This scoping review synthesizes the existing research on the use of very low-calorie diets (VLCDs) in subjects with nonalcoholic fatty liver disease (NAFLD) and end-stage liver disease (ESLD). 19 studies were included, of which 5 were clinical trials, 11 were cohort studies, 1 was a case-control study, and 2 were case series totaling 968 subjects. About 17 studies were focused on patients with NAFLD while the two case series described in patients with ESLD on the transplant list or post-liver transplant. Six studies included subjects managed with VLCDs prior bariatric surgery. Most studies were short term and demonstrated acute improvement of diverse liver biomarkers including liver function tests, indices of hepatosteatosis and reduction in liver size. Adherence rates in these studies were between 69% and 93%. Eight studies did not report any adverse events and four subjects were reported to have discontinued VLCD due to adverse effects in two different studies. Aggregated adverse events were mild. Treatments based on VLCD in subjects with NAFLD seem to be safe and tolerable but can result in mild adverse effects. The findings of this scoping review suggest that the use of VLCD in patients with obesity complicated with NAFLD and potentially in ESLD appear to be effective to induce weight loss and to acutely reduce hepatosteatosis.

Association between preoperative serum albumin levels with risk of death and postoperative complications after bariatric surgery: a retrospective cohort study.

BACKGROUND: Hypoalbuminemia is common among individuals with obesity who qualify for bariatric surgery, but its relevance to clinical outcomes after bariatric surgery remains to be established. OBJECTIVES: To examine the association of preoperative serum albumin with 30-day postoperative outcomes. SETTING: Data from the 2015-2019 Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program Participant Use Files were used. METHODS: Preoperative serum albumin level was categorized as hypoalbuminemia (<3.5 g/dL), and normoalbuminemia (3.5-5.5 g/dL) among patients who underwent bariatric surgery. Multivariate logistic regression models were used to determine the association of preoperative hypoalbuminemia with 30-day postoperative mortality and other co-morbid outcomes. RESULTS: Among 633,011 adult patients, 85.1% were women and the mean (standard deviation) age was 44.8 (12.0) years. The prevalence of hypoalbuminemia was 6.13% (n = 38,792). After adjustment for procedure type and demographic, lifestyle, and co-morbidity covariates, the odds ratio (OR) (95% confidence interval [CI]) for mortality was 1.42 (1.10, 1.82) for hypoalbuminemia. For all other outcomes, the ORs (95% CIs) for hypoalbuminemia ranged from 1.03 (.67-1.60) for cardiac arrest requiring CPR to 2.32 (1.66-3.25) for failure to be discharged by day 30. The ORs for several associations were higher for severe hypoalbuminemia than marginal hypoalbuminemia. CONCLUSION: Preoperative hypoalbuminemia was associated with several negative 30-day postoperative bariatric surgery outcomes and tended to be worse for severe hypoalbuminemia compared with marginal hypoalbuminemia. These findings suggest that serum albumin may be a useful biomarker to screen for negative bariatric surgery outcomes.

Association of Preoperative Body Weight and Weight Loss With Risk of Death After Bariatric Surgery.

Importance: Perception of weight loss requirements before bariatric surgery varies among patients, physicians, and health insurance payers. Current clinical guidelines do not require preoperative weight loss because of a lack of scientific support regarding its benefits. Objective: To examine the association of preoperative body mass index (BMI) and weight loss with 30-day mortality after bariatric surgery. Design, Setting, and Participants: This cohort study used data from 480 075 patients who underwent bariatric surgery from 2015 to 2017 in the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program, which covers more than 90% of all bariatric surgery programs in the United States and Canada. Clinical and demographic data were collected at all participating institutions using a standardized protocol. Data analysis was performed from December 2018 to November 2019. Exposures: Preoperative BMI and weight loss. Main Outcomes and Measures: 30-day mortality after bariatric surgery. Results: Of the 480 075 patients (mean [SD] age 45.1 [12.0] years; 383 265 [79.8%] women), 511 deaths (0.1%) occurred within 30 days of bariatric surgery. Compared with patients with a preoperative BMI of 35.0 to 39.9, the multivariable-adjusted odds ratios for 30-day mortality for patients with preoperative BMI of 40.0 to 44.9, 45.0 to 49.9, 50.0 to 54.9, and 55.0 and greater were 1.37 (95% CI, 1.02-1.83), 2.19 (95% CI, 1.64-2.92), 2.61 (95% CI, 1.90-3.58), and 5.03 (95% CI, 3.78-6.68), respectively (P for trend < .001). Moreover, compared with no preoperative weight loss, the multivariable-adjusted odds ratios for 30-day mortality for patients with weight loss of more than 0% to less than 5.0%, 5.0% to 9.9%, and 10.0% and greater were 0.76 (95% CI, 0.60-0.96), 0.69 (95% CI, 0.53-0.90), and 0.58 (95% CI, 0.41-0.82), respectively (P for trend = .003). Conclusions and Relevance: In this study, even moderate weight loss (ie, >0% to <5%) before bariatric surgery was associated with a lower risk of 30-day mortality. These findings may help inform future updates of clinical guidelines regarding bariatric surgery.

Arterial compliance and endothelial function.

Decreased arterial compliance (increased stiffness) correlates with cardiovascular events, possibly due to increased cardiac afterload caused by more rapidly reflected pulse waves. Endothelium-derived mediators regulate vascular tone and structure, both of which can markedly influence arterial stiffness. Thus, increased arterial stiffness may be a mechanism by which endothelial dysfunction predisposes to complications of atherosclerosis. Conversely, therapeutic manipulation of endothelial mediators could reduce arterial stiffness and cardiovascular events. Techniques have been developed that use measures of arterial stiffness as an index of endothelial dilator function; these may provide unique prognostic information to identify high-risk subjects.

Role of leptin in the cardiovascular and endocrine complications of metabolic syndrome.

AIM: To review the potential role of leptin, hyperleptinaemia and leptin resistance in the cardiovascular and endocrine complications of metabolic syndrome. METHODS: Review of literature listed in Medline. RESULTS: Hyperleptinaemia is common in obesity and reflects increased adiposity and leptin resistance. Nevertheless, leptin resistance may not be complete as several actions of leptin, such as cardiovascular sympatho-activation, might be preserved in obese subjects known to be resistant to the metabolic effects of leptin (i.e. selective leptin resistance). Notably, the renal and sympathetic actions of leptin may play an important role in the pathogenesis of hypertension related to obesity and metabolic syndrome. Furthermore, the lipotoxic effect of leptin resistance may cause insulin resistance and beta cell dysfunction, increasing the risk of type 2 diabetes. Leptin has also been shown to possess proliferative, pro-inflammatory, pro-thrombotic, and pro-oxidative actions. CONCLUSION: Hyperleptinaemia and leptin resistance may contribute to hypertension, impaired glucose metabolism, and pro-atherogenic state in obesity and metabolic syndrome.

Role of leptin and obesity-related leptin resistance in the pathophysiology of metabolic syndrome

The prevalence of metabolic syndrome is high and will likely increase further as the obesity epidemic accelerates. Leptin is a peptide hormone mostly derived from adipose tissue that promotes negative energy balance. Hyperleptinemia is common in obesity and reflects increased fat mass and leptin resistance. Nevertheless, leptin resistance might not be complete as several actions of leptin, like cardiovascular sympathetic activation, might be preserved in obese subjects that are resistant to the metabolic actions of leptin (i.e. selective leptin resistance). Leptin may contribute to elevated blood pressure, hyperglycemia, dyslipidemia, pro-thrombotic and proinflammatory states found in metabolic syndrome. Notably, the renal and sympathetic actions of leptin appear to play a major role in the pathogenesis of hypertension related to obesity and the metabolic syndrome. Furthermore, the lipotoxic effect of leptin resistance is thought to be a major determinant of insulin resistance and may increase the risk of type 2 diabetes

Effects of aging and atherosclerosis on endothelial and vascular smooth muscle function in humans.

BACKGROUND: Nitric oxide is an endothelium dependent dilator, which may protect against atherosclerosis. Several studies have shown a decrease in nitric oxide activity with aging, however none have assessed aging and atherosclerosis separately. We tested the hypothesis that aging blunts both basal and receptor-mediated endothelial nitric oxide release in humans. METHODS: We examined whether forearm blood flow responses to intra-arterial acetylcholine, and nitroprusside, were altered with aging, with and without co-infusion of an inhibitor of nitric oxide synthase (N(G)-mono-methyl-L-arginine) in three groups of human subjects; a group with clinical atherosclerotic vascular disease (n = 31, 21 M), otherwise healthy elderly (n = 17, 13 M), and healthy young controls (n = 15, 8 M). RESULTS: There was no difference in basal flows between the three groups. There was also no difference in the dilatation to either acetylcholine or nitroprusside responses between the AVD and the healthy elderly group; however, aging significantly decreased acetylcholine or nitroprusside responses when compared to the young controls (p < 0.02). Furthermore, the ratio between acetylcholine and nitroprusside, a marker of endothelial NO synthase activity, was significantly greater in the young volunteers (0.816 +/- 0.094% vs. 0.892 +/- 0.146 % vs. 1.389 +/- 0.2%, in atherosclerotic vascular disease, healthy elderly group, and young controls respectively). CONCLUSIONS: Forearm blood flow responses to endothelium dependent and independent stimuli are blunted with aging, independent of the presence of atherosclerotic disease. Moreover, the normal aging process may induce significant global vascular dysfunction (involving the endothelium and the vascular smooth muscle); to as great a degree as clinically manifest atherosclerosis.

Emerging drugs for obesity: linking novel biological mechanisms to pharmaceutical pipelines.

Obesity is associated with hypertension, diabetes, dyslipidaemias and metabolic syndrome, and causes substantial morbidity and mortality from cardiovascular and other diseases. The cost to treat obesity and its complications in the US has increased steeply and is currently estimated to be USD 100 billion. Current therapy for obesity is mainly based on changes in lifestyle that often fail. Existing pharmacological treatment is marginally efficient and poorly tolerated. The discovery of leptin and related neural mechanisms of energy metabolism regulation has opened the doors to potential targets for new antiobesity drugs. In this review, new pharmacological targets are discussed and an update on the development of emerging antiobesity drugs is provided. Despite intense investigation, the pipelines for antiobesity drugs in late stages of development are relatively empty. Breakthrough treatments for obesity may take some years to emerge. Clinical trials will be necessary to clarify the impact of new antiobesity drugs on hard cardiovascular and metabolic end points.

Obesity-associated hypertension: new insights into mechanisms.

Obesity is strongly associated with hypertension and cardiovascular disease. Several central and peripheral abnormalities that can explain the development or maintenance of high arterial pressure in obesity have been identified. These include activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system. Obesity is also associated with endothelial dysfunction and renal functional abnormalities that may play a role in the development of hypertension. The continuing discovery of mechanisms regulating appetite and metabolism is likely to lead to new therapies for obesity-induced hypertension. Better understanding of leptin signaling in the hypothalamus and the mechanisms of leptin resistance should facilitate therapeutic approaches to reverse the phenomenon of selective leptin resistance. Other hunger and satiety signals such as ghrelin and peptide YY are potentially attractive therapeutic strategies for treatment of obesity and its complications. These recent discoveries should lead to novel strategies for treatment of obesity and hypertension.

Obesity-related hypertension: is there a role for selective leptin resistance?

Obesity is a risk factor for cardiovascular diseases, in particular for hypertension. Serum leptin levels and sympathetic nerve activity are both increased in obesity. Leptin has been demonstrated to increase sympathetic nerve activity. Thus, leptin-dependent sympathoactivation might contribute to obesity-related hypertension. However, leptin resistance occurs in obesity. One possibility is that leptin resistance is selective to the metabolic effects of leptin, sparing its sympathoexcitatory actions. In this article, we review experimental evidence supporting the novel concept of selective leptin resistance. We also discuss the sympathetic actions of leptin that are relevant to blood pressure modulation and potential mechanisms of leptin resistance. Disruption of leptin intracellular signaling pathways and resistance of specific leptin-responsive neural networks provide theoretic models of selective leptin resistance. However, most information about leptin-sympathetic actions and leptin-resistance mechanisms derive from in vitro and animal studies. Future research in humans is widely awaited.

Loss of leptin actions in obesity: two concepts with cardiovascular implications.

Obesity is associated with increased risk of hypertension and heart disease. Leptin has recently been linked to increased risk of cardiovascular disease. We review briefly here two concepts regarding loss of leptin actions that have potential implications for cardiovascular disease. These are: 1. the concept of selective leptin resistance; and 2. the concept that loss of leptin action results in lipid accumulation and lipotoxicity of skeletal muscle, pancreatic islet cells, and heart and, thereby, promotes insulin resistance, insulin deficiency and cardiac dysfunction, respectively.

Selective leptin resistance: a new concept in leptin physiology with cardiovascular implications.

Leptin, an adipocyte secreted hormone, acts in the hypothalamus to inhibit appetite and promote thermogenic metabolism, thereby reducing adiposity and body weight. Leptin has multiple autonomic and cardiovascular actions, including sympathetic activation, increases in endothelium derived nitric oxide (NO), and angiogenesis. The predominant cardiovascular effect of chronic hyperleptinemia is a pressor effect mediated by increased sympathetic activity. The sympathetic and cardiovascular actions of leptin are discussed and evidence derived from studies of obese mice for the novel concept of selective leptin resistance is reviewed. This concept holds that in some obese states, there is preservation of the sympathoexcitatory actions of leptin despite resistance to the satiety and weight-reducing actions of the hormone. Selective leptin resistance might explain how hyperleptinemia could contribute to increases in sympathetic activity and arterial pressure in obese states where there is resistance to the metabolic (satiety and weight-reducing) actions of leptin. It is speculated here, that this concept may have potential implications for human obesity, which is often associated with elevated plasma leptin and partial resistance to the satiety effects of leptin. If selective leptin resistance occurs in obese humans, then leptin could contribute to the sympathetic overactivity and hypertension despite resistance to its metabolic actions.

Impaired skeletal muscle and skin microcirculatory function in human obesity.

BACKGROUND: Obesity is associated with exaggerated blood pressure and systemic vascular resistance responses to mental stress. OBJECTIVE: To test the hypothesis that skin and muscle microvascular dilatation in response to mental stress is blunted in obesity. DESIGN AND METHODS: Blood pressure, heart rate and forearm and skin blood flow responses to mental stress were compared in 23 obese and 23 age- and sex-matched lean normotensive individuals. RESULTS: Blood pressure was almost identical in both obese (mean 94 +/- 1 mmHg) and lean (93 +/- 2 mmHg) individuals. The increase in blood pressure during mental stress was similar in obese and lean individuals (2.0 +/- 0.9% compared with 3.1 +/- 4.0%; P = 0.8). Forearm vascular resistance decreased during mental stress in both groups, but this decrease was significantly blunted in obese individuals compared with controls (decreases of 14 +/- 4% and 26 +/- 3%; P < 0.01). Skin microcirculatory dilatation was also significantly blunted in obese individuals compared with controls (decreases of 5 +/- 2 and 17 +/- 4%; P = 0.02). CONCLUSIONS: Normotensive obese individuals exhibit markedly impaired muscle and skin microcirculatory responses to mental stress. The increased propensity of obese individuals to develop hypertension under conditions of chronic psychosocial stress may underlie obesity-related hypertension and cardiovascular disease.

Hemodynamic consequences of neuropeptide Y-induced obesity.

BACKGROUND: Acute central nervous system administration of neuropeptide Y (NPY) elicits variable hemodynamic responses. Chronic intracerebroventricular (ICV) administration of NPY produces obesity in rats. Obesity has been shown to increase arterial pressure. METHODS: In this study we examined the chronic hemodynamic effects of NPY-induced obesity. Sprague-Dawley rats were implanted with radiotelemetry transmitters to continuously record heart rate and arterial pressure in the conscious state. Neuropeptide Y or vehicle was delivered into the third cerebral ventricle by osmotic minipumps over 2 weeks. Three groups were studied: vehicle, NPY-treated (free-fed), and NPY-treated (pair-fed to vehicle-treated rats). RESULTS: Neuropeptide Y increased food intake and body weight in free-fed animals, and substantially augmented visceral adiposity in both free- and pair-fed rats. Despite increased adiposity, chronic ICV administration of NPY in conscious unstressed rats did not increase arterial pressure. Neuropeptide Y decreased heart rate, suggesting a sympathoinhibitory effect. CONCLUSIONS: Obesity induced by 2-week ICV administration of NPY does not increase arterial pressure, perhaps indicating inhibition of sympathetic outflow that may oppose the pressor effect of adiposity.

The concept of selective leptin resistance: evidence from agouti yellow obese mice.

Leptin, a hormone secreted by adipose tissue, acts to inhibit appetite and promote metabolism, thereby reducing body weight. Leptin also increases sympathetic activity and arterial pressure. Several murine models of obesity, including agouti obese mice, exhibit resistance to the anorexic and weight-reducing effects of leptin. Hypertension in agouti mice has been attributed to hyperleptinemia. These observations pose a seeming paradox. If these mice are leptin-resistant, then how can leptin contribute to hypertension? We tested the novel hypothesis that these mice have selective leptin resistance, with preservation of the sympathoexcitatory action despite resistance to the weight-reducing actions. Leptin-induced decreases in food intake and body weight were less in agouti obese mice than in lean littermates. In contrast, leptin-induced increases in sympathetic nerve activity did not differ in obese and lean mice. These findings support the concept of selective leptin resistance, with resistance to the metabolic actions of leptin but preservation of the sympathoexcitatory actions. This finding may have potential implications for human obesity, which is associated with elevated plasma leptin and is thought to be a leptin-resistant state. If leptin resistance is selective in obese humans, then leptin could contribute to sympathetic overactivity and its adverse consequences in human obesity.