Regulation of lipolysis: natriuretic peptides and the development of cachexia

Adipose tissue rearrangement in cancer cachexia: The involvement of β3-adrenergic receptor associated pathways

Cancer-associated cachexia (CAC) is a complex multiple organ syndrome that significantly contributes to reduced quality of life and increased mortality among many cancer patients. Its multifactorial nature makes its early diagnosis and effective therapeutic interventions challenging. Adipose tissue is particularly impacted by cachexia, typically through increased lipolysis, browning and thermogenesis, mainly at the onset of the disease. These processes lead to depletion of fat mass and contribute to the dysfunction of other organs. The β-adrenergic signalling pathways are classical players in the regulation of adipose tissue metabolism. They are activated upon sympathetic stimulation inducing lipolysis, browning and thermogenesis, therefore contributing to energy expenditure. Despite accumulating evidence suggesting that β3-adrenergic receptor stimulation may be crucial to the adipose tissue remodelling during cachexia, the literature remains controversial. Moreover, there is limited knowledge regarding sexual dimorphism of adipose tissue in the context of cachexia. This review paper aims to present the current knowledge regarding adipose tissue wasting during CAC, with a specific focus on the role of the β3-adrenergic receptor, placing it as a potential therapeutic target against cachexia.

Increased Expression of Proinflammatory Genes in Peripheral Blood Cells Is Associated with Cardiac Cachexia in Patients with Heart Failure with Reduced Ejection Fraction

Background: Cardiac cachexia (CC) in chronic heart failure with reduced ejection fraction (HFrEF) is characterized by catabolism and inflammation predicting poor prognosis. Levels of responsible transcription factors like signal transducer and activator of transcription (STAT)1, STAT3, suppressor of cytokine signaling (SOCS)1 and SOCS3 in peripheral blood cells (PBC) are underinvestigated in CC. Expression of mediators was related to patients' functional status, body composition (BC) and metabolic gene expression in skeletal muscle (SM). Methods: Gene expression was quantified by qRT-PCR in three cohorts: non-cachectic patients (ncCHF, n = 19, LVEF 31 ± 7%, BMI 30.2 ± 5.0 kg/m2), cachectic patients (cCHF; n = 18, LVEF 27 ± 7%, BMI 24.3 ± 2.5 kg/m2) and controls (n = 17, LVEF 70 ± 7%, BMI 27.6 ± 4.6 kg/m2). BC was assessed by dual-energy X-ray absorptiometry. Blood inflammatory markers were measured. We quantified solute carrier family 2 member 4 (SLC2A4) and protein degradation by expressions of proteasome 20S subunit beta 2 and calpain-1 catalytic subunit in SM biopsies. Results: TNF and IL-10 expression was higher in cCHF than in ncCHF and controls (all p < 0.004). cCHF had a lower fat mass index (FMI) and lower fat-free mass index (FFMI) compared to ncCHF and controls (p < 0.05). STAT1 and STAT3 expression was higher in cCHF vs. ncCHF or controls (1.1 [1.6] vs. 0.8 [0.9] vs. 0.9 [1.1] RU and 4.6 [5.5] vs. 2.5 [4.8] vs. 3.0 [4.2] RU, all ANOVA-p < 0.05). The same applied for SOCS1 and SOCS3 expression (1.1 [1.5] vs. 0.4 [0.4] vs. 0.4 [0.5] and 0.9 [3.3] vs. 0.4 [1.1] vs. 0.8 [0.9] RU, all ANOVA-p < 0.04). In cCHF, higher TNF and STAT1 expression was associated with lower FMI (r = 0.5, p = 0.053 and p < 0.05) but not with lower FFMI (p > 0.4). In ncCHF, neither cytokine nor STAT/SOCS expression was associated with BC (all p > 0.3). SLC2A4 was upregulated in SM of cCHF vs. ncCHF (p < 0.03). Conclusions: Increased STAT1, STAT3, SOCS1 and SOCS3 expression suggests their involvement in CC. In cCHF, higher TNF and STAT-1 expression in PBC were associated with lower FMI. Increased SLC2A4 in cachectic SM biopsies indicates altered glucose metabolism.

Circulating ketone bodies and mortality in heart failure: a community cohort study

Background

The relationship between ketone bodies (KB) and mortality in patients with heart failure (HF) syndrome has not been well established.

Objectives

The aim of this study is to assess the distribution of KB in HF, identify clinical correlates, and examine the associations between plasma KB and all-cause mortality in a population-based HF cohort.

Methods

The plasma KB levels were measured by nuclear magnetic resonance spectroscopy. Multivariable linear regression was used to examine associations between clinical correlates and KB levels. Proportional hazard regression was employed to examine associations between KB (represented as both continuous and categorical variables) and mortality, with adjustment for several clinical covariates.

Results

Among the 1,382 HF patients with KB measurements, the median (IQR) age was 78 (68, 84) and 52% were men. The median (IQR) KB was found to be 180 (134, 308) μM. Higher KB levels were associated with advanced HF (NYHA class III-IV) and higher NT-proBNP levels (both P < 0.001). The median follow-up was 13.9 years, and the 5-year mortality rate was 51.8% [95% confidence interval (CI): 49.1%-54.4%]. The risk of death increased when KB levels were higher (HRhigh vs. low group 1.23; 95% CI: 1.05-1.44), independently of a validated clinical risk score. The association between higher KB and mortality differed by ejection fraction (EF) and was noticeably stronger among patients with preserved EF.

Conclusions

Most patients with HF exhibited KB levels that were consistent with those found in healthy adults. Elevated levels of KB were observed in patients with advanced HF. Higher KB levels were found to be associated with an increased risk of death, particularly in patients with preserved EF.

Cardiac Remodeling and Its Determinants in Anorexia Nervosa Adolescents: Impact of Weight Recovery

Cardiovascular alterations in anorexia nervosa (AN) adolescents include bradycardia and decreased systolic blood pressure and left ventricular mass. However, their determinants remain poorly understood. We assessed the associations between morphological and functional left ventricular (LV) remodeling, autonomic control by heart rate variability (HRV) analysis, thyroid hormones and brain natriuretic peptide (BNP) levels in AN female adolescents without or with weight recovery (WR). Fifty-nine female adolescents including 16 AN patients without WR (mean age 13.9 years (10−16)), 10 AN patients with WR (15.7 years (12−18)) and 33 controls (14.1 years (10−18)) underwent night heart rate (HR) recording to measure HRV (and especially SD1/SD2, the ratio between instantaneous (SD1) and long-term (SD2) standard deviation of R-R intervals, reflecting sympatho-vagal balance), speckle tracking echocardiography to assess LV global longitudinal strain (GLS) and blood test for dosage of tri-iodothyronine (T3) hormone and NT-proBNP. Compared to controls, AN patients without WR presented with lower HR (55 ± 7 vs. 68 ± 6 bpm; p < 0.001), parasympathetic hyperactivity, and higher GLS (−19.2 ± 1.8 vs. −16.9 ± 2.8%; p = 0.009). These alterations were partly abolished in AN patients with WR. In a multivariate regression analysis, T3 was the main factor explaining the variance of SD1/SD2, a sympatho-vagal balance marker. NT-proBNP levels were not correlated with cardiac alterations. AN patients had parasympathetic hyperactivity linked with their rate of T3, and a higher GLS. These alterations were partly restored in AN patients with WR.

Fat Wasting Is Damaging: Role of Adipose Tissue in Cancer-Associated Cachexia

Loss of body weight, especially loss of adipose tissue and skeletal muscle weight, characterizes cancer-associated cachexia (CAC). Clinically, therapeutic options for CAC are limited due to the complicated signaling between cancer and other organs. Recent research advances show that adipose tissues play a critical role during thermogenesis, glucose homeostasis, insulin sensitivity, and lipid metabolism. Understanding the adipocyte lipolysis, the formation of beige adipocytes, and the activation of brown adipocytes is vital for novel therapies for metabolic syndromes like CAC. The system-level crosstalk between adipose tissue and other organs involves adipocyte lipolysis, white adipose tissue browning, and secreted factors and metabolites. Novel CAC animal models and accumulating molecular signaling knowledge have provided mechanisms that may ultimately be translated into future therapeutic possibilities that benefit CAC patients. This mini review discusses the role of adipose tissue in CAC development, mechanism, and therapy.

Joint Associations of Obesity and NT-proBNP With the Incidence of Atrial Fibrillation in the ARIC Study

Background

Circulating NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) levels, a well‐known indicator of atrial wall stress and remodeling, inversely correlate with body mass index. Both are strongly predictive of atrial fibrillation (AF). Their potential interaction in relation to incident AF, however, has not been explored.

Methods and Results

In total, 9556 participants of the ARIC (Atherosclerosis Risk in Communities) study who had 2 measurements of NT‐proBNP and no baseline AF or heart failure were followed from 1996 to 1998 through 2016 for the occurrence of incident AF. Participants were categorized as obese (body mass index ≥30) and nonobese (body mass index <30) and by NT‐proBNP levels (using the median of 68.2 pg/mL as the cutoff). Over a median follow‐up of 18.3 years, we identified 1806 incident cases of AF. Analysis using multivariable Cox regression models showed that obese participants with high NT‐proBNP levels at visit 4 had a higher adjusted risk of incident AF (hazard ratio: 3.64; 95% CI, 3.15–4.22) compared with nonobese individuals with low NT‐proBNP levels. The association of obesity with AF risk was not modified by NT‐proBNP levels (P=0.46 for interaction). Increasing BNP among participants from 1990–1992 to 1996–1998 was associated with increased AF risk. After further adjustment for clinical risk factors and medications, results were similar.

Conclusions

Individuals who had both elevated body mass index and NT‐proBNP and were free of clinically recognized heart failure were at higher risk of AF development. Those who experienced an increase in NT‐proBNP levels between visits 2 and 4 were at higher risk of AF.

High brain natriuretic peptide is associated with sarcopenia in patients with type 2 diabetes: a cross-sectional study of KAMOGAWA-DM cohort study

Association between heart failure and sarcopenia has been reported, however, the association between sarcopenia and brain natriuretic peptide (BNP) is unclear. Thus, we investigated the association between sarcopenia and BNP in type 2 diabetic patients without heart failure. In this cross-sectional study, skeletal muscle mass index (SMI, kg/m²) was calculated as appendicular muscle mass, measured by bioimpedance analyzer, by the square of the height. Sarcopenia was defined as having both handgrip strength of <26 kg for men and <18 kg for women, and SMI of <7.0 kg/m² for men and <5.7 kg/m² for women. To investigate the impact of BNP levels on the presence of sarcopenia, propensity-score matching analysis was used to remove the bias of confounding variables, including age, sex, duration of diabetes, body mass index, exercise, systolic blood pressure, smoking status, hemoglobin A1c, creatinine, energy and protein intake. The area under the curve (AUC) of BNP levels for the presence of sarcopenia was calculated by the receiver operating characteristic curve (ROC). Among 433 patients (236 men and 65.4 (11.1) years), 32 patients (7.4%) were diagnosed as sarcopenia. In the propensity-matched 58 patients, BNP levels (Δ10 pg/mL incremental) were associated with the presence of sarcopenia by logistic regression analysis, (odds ratio: 1.56, 95% confidence interval: 1.14-2.13, p = 0.002). The optimal cut-off point of BNP levels for sarcopenia is 27.3 pg/mL (AUC 0.777, 95%CI, 0.691-0.863, sensitivity = 0.813, specificity = 0.736, p < 0.001). In conclusion, BNP levels were associated with sarcopenia in type 2 diabetic patients without heart failure.

Clinical Characteristics and Mid-Term Outcomes of Non-Elderly Obese Patients with Acute Decompensated Heart Failure in Japan

Obesity is a well-known risk factor for cardiovascular diseases including heart failure (HF). However, some literatures suggested better clinical outcomes in obese patients with HF. Since higher body mass index (BMI) levels of HF patients were significantly associated with younger age, the impact of obesity on clinical outcomes in non-elderly HF patients should be elucidated.Consecutive 155 non-elderly acute decompensated HF patients (< 60-year-old) who admitted to our institution between 2009 and 2013 were included. Those patients were divided into the two groups according to the BMI: the obesity group (BMI ≥ 25 kg/m², n = 81) and the non-obesity group (BMI < 25 kg/m², n = 74). The primary composite outcome of this study was defined as re-admission due to HF and all-cause death.The primary composite outcome was less frequently observed in the obesity group as compared with the non-obesity group (Hazard ratio [HR] 0.50, 95% confidence interval [CI] 0.26-0.95, P = 0.03). Re-admission due to HF was significantly less in the obesity group than in the non-obesity group (HR 0.44, 95% CI 0.23-0.86, P = 0.02), whereas all-cause death was not significantly different between the groups (P = 0.44).The mid-term outcomes in non-elderly HF patients with obesity were better as compared with non-elderly HF patients without obesity, which supports obesity paradox in this specific population.

Inverse Correlation of Venous Brain Natriuretic Peptide Levels with Body Mass Index Is due to Decreased Production

OBJECTIVE

The aim of this paper was to study the association between body mass index (BMI) and coronary sinus (CS) brain natriuretic peptide (BNP) levels in patients with heart failure and reduced systolic function (HFrEF).

BACKGROUND

There is an inverse relationship between systemic venous BNP (V-BNP) levels and BMI in patients with HFrEF. It is unclear whether this finding is due to decreased production or due to an increased metabolism of BNP. Since CS-BNP levels reflect BNP production, we hypothesized that assessing the correlation of CS-BNP levels with BMI would provide insight into the mechanism of this inverse relationship of V-BNP and BMI.

METHODS

We prospectively enrolled 54 subjects with HFrEF who were to undergo cardiac resynchronization device implantation. CS-BNP, V-BNP, and arterial BNP (A-BNP) levels were measured during the implant procedure. Subjects were divided into 2 groups based on their BMI (group 1: BMI <30 and group 2: BMI ≥30).

RESULTS

The mean age of the overall study group was 64 ± 10 years. Average BMI for group 1 was 25.8 ± 2.8 and 36.8 ± 4.6 for group 2 (p < 0.03). A history of hypertension was present in 55% (n = 26) of the subjects, while diabetes was reported in 31% (n = 15). Serum creatinine was 1.0 ± 0.2 mg/dL and TSH 2.1 ± 1.4 mIU/L. 79% of the subjects were receiving β-blockers, while 94% were receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. The mean CS-BNP, V-BNP, and A-BNP levels in group 2 were significantly lower than in group 1 (286.2 ± 170.5 vs. 417.5 ± 247.5 pg/mL, p = 0.04; 126.6 ± 32.5 vs. 228 ± 96.4 pg/mL, p = 0.01; and 151.9 ± 28.6 vs. 242 ± 88.8 pg/mL, p = 0.04, respectively). Univariate analysis and multivariate regression adjusted for age, diabetes mellitus, sex, glomerular filtration rate, and left atrial size confirmed BMI as an independent predictor of CS-BNP levels (β = -0.372, p = 0. 03) in our study.

CONCLUSIONS

In this study, we demonstrate an inverse relationship between CS-BNP levels and BMI in patients with HFrEF. These findings suggest that the previously established inverse relationship between V-BNP and BMI is due to a decreased cardiac production of BNP in obese patients rather than from increased peripheral metabolism.

Serial Echocardiographic Characteristics, Novel Biomarkers and Cachexia Development in Patients with Stable Chronic Heart Failure

Little is known regarding objective predictors of cachexia affecting patients with heart failure (HF). We studied 108 stable chronic systolic HF patients with serial echocardiography and biomarker measurements over 10 months. Cachexia was defined as weight loss ≥5 % from baseline or final BMI <20 kg/m²; 18.5 % developed cachexia. While there were no significant differences in baseline or serial echocardiographic measures in those developing cachexia, we found significant differences in baseline amino-terminal pro-B type natriuretic peptide (NT-proBNP), highly sensitive troponin I, sST2, and endothelin-1. Baseline log NT-proBNP (hazard ratio (HR) = 2.57, p = 0.004) and edema (HR = 3.36, p = 0.04) were predictive of cachexia in an adjusted analysis. When serial measurement of biomarkers was considered, only percent time with NT-proBNP ≥1000 pg/mL was predictive of cachexia. Thus, a close association exists between baseline and serial measurement of NT-proBNP and HF cachexia.

Prognostic nutritional index predicts survival and correlates with systemic inflammatory response in advanced pancreatic cancer

BACKGROUND

Recent studies have implied a prognostic value of the prognostic nutritional index (PNI) in certain types of human cancers. However, the value of PNI for predicting survival in patients with pancreatic cancer remains unknown. The goal of this study was to investigate the predictive significance of PNI in patients with advanced pancreatic cancer.

METHODS

A total of 321 consecutive patients with pathologically-confirmed locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC) were retrospectively recruited between January 2011 and August 2013. The patients were divided into a test set (n = 110) and a validation set (n = 211). We evaluated the association between PNI and overall survival (OS). The relationship between PNI and systemic inflammatory response markers, including the neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and lymphocyte/monocyte ratio (LMR) was also assessed. In addition, the associations between PNI and the TNF-α were analyzed.

RESULTS

Kaplan-Meier analyses showed that a low PNI correlated significantly with a shorter OS in patients with advanced pancreatic cancer (190 days for patients with a low PNI vs. 290 days for patients with a high PNI, log-rank = 12.566, P < 0.001). Multivariate analysis identified PNI as an independent prognostic factor for OS (hazard ratio [HR]: 0.627, 95% confidence interval [CI]: 0.453-0.868, P = 0.003). PNI also correlated positively with NLR and PLR and negatively with LMR. Additionally, patients with a low PNI exhibited high levels of TNF-α.

CONCLUSIONS

Our results confirm that PNI is associated with the systemic inflammatory response and can be used to predict survival in advanced pancreatic cancer.

Obesity and natriuretic peptides, BNP and NT-proBNP: mechanisms and diagnostic implications for heart failure

Many advances have been made in the diagnosis and management of heart failure (HF) in recent years. Cardiac biomarkers are an essential tool for clinicians: point of care B-type natriuretic peptide (BNP) and its N-terminal counterpart (NT-proBNP) levels help distinguish cardiac from non-cardiac causes of dyspnea and are also useful in the prognosis and monitoring of the efficacy of therapy. One of the major limitations of HF biomarkers is in obese patients where the relationship between BNP and NT-proBNP levels and myocardial stiffness is complex. Recent data suggest an inverse relationship between BNP and NT-proBNP levels and body mass index. Given the ever-increasing prevalence of obesity world-wide, it is important to understand the benefits and limitations of HF biomarkers in this population. This review will explore the biology, physiology, and pathophysiology of these peptides and the cardiac endocrine paradox in HF. We also examine the clinical evidence, mechanisms, and plausible biological explanations for the discord between BNP levels and HF in obese patients.

Metabolic implications when employing heavy pre- and post-exercise rapid-acting insulin reductions to prevent hypoglycaemia in type 1 diabetes patients: a randomised clinical trial

Aim

To examine the metabolic, gluco-regulatory-hormonal and inflammatory cytokine responses to large reductions in rapid-acting insulin dose administered prandially before and after intensive running exercise in male type 1 diabetes patients.

Methods

This was a single centre, randomised, controlled open label study. Following preliminary testing, 8 male patients (24±2 years, HbA1c 7.7±0.4%/61±4 mmol.l⁻¹) treated with insulin's glargine and aspart, or lispro attended the laboratory on two mornings at ∼08:00 h and consumed a standardised breakfast carbohydrate bolus (1 g carbohydrate.kg⁻¹BM; 380±10 kcal) and self-administered a 75% reduced rapid-acting insulin dose 60 minutes before 45 minutes of intensive treadmill running at 73.1±0.9% VO_2peak. At 60 minutes post-exercise, patients ingested a meal (1 g carbohydrate.kg⁻¹BM; 660±21 kcal) and administered either a Full or 50% reduced rapid-acting insulin dose. Blood glucose and lactate, serum insulin, cortisol, non-esterified-fatty-acids, β-Hydroxybutyrate, and plasma glucagon, adrenaline, noradrenaline, IL-6, and TNF-α concentrations were measured for 180 minutes post-meal.

Results

All participants were analysed. All glycaemic, metabolic, hormonal, and cytokine responses were similar between conditions up to 60 minutes following exercise. Following the post-exercise meal, serum insulin concentrations were lower under 50% (p<0.05) resulting in 75% of patients experiencing hyperglycaemia (blood glucose ≥8.0 mmol.l⁻¹; 50% n = 6, Full n = 3). β-Hydroxybutyrate concentrations decreased similarly, such that at 180 minutes post-meal concentrations were lower than rest under Full and 50%. IL-6 and TNF-α concentrations remained similar to fasting levels under 50% but declined under Full. Under 50% IL-6 concentrations were inversely related with serum insulin concentrations (r = −0.484, p = 0.017).

Conclusions

Heavily reducing rapid-acting insulin dose with a carbohydrate bolus before, and a meal after intensive running exercise may cause hyperglycaemia, but does not augment ketonaemia, raise inflammatory cytokines TNF-α and IL-6 above fasting levels, or cause other adverse metabolic or hormonal disturbances.

Trial Registration

ClinicalTrials.gov NCT01531855

The effect of age and NT-proBNP on the association of central obesity with 6-years cardiovascular mortality of middle-aged and elderly diabetic people: the population-based Casale Monferrato study

BACKGROUND

Among people with type 2 diabetes the relationship between central obesity and cardiovascular mortality has not been definitely assessed. Moreover, NT-proBNP is negatively associated with central obesity, but no study has examined their combined effect on survival. We have examined these issues in a well-characterized population-based cohort.

METHODS AND FINDINGS

Survival data of 2272 diabetic people recruited in 2000 who had no other chronic disease have been updated to 31 December 2006. NT-proBNP was measured in a subgroup of 1690 patients. Cox proportional hazards modeling was employed to estimate the independent associations between cardiovascular and all-cause mortality and waist circumference. Mean age was 67.9 years, 49.3% were men. Both age and NT-proBNP were negatively correlated with waist circumference (r = -0.11, p<0.001 and r = -0.07, p = 0.002). Out of 2272 subjects, 520 deaths (221 for CV mortality) occurred during a median follow-up of 5.4 years. Central obesity was not associated with CV mortality (hazard ratio, HR, adjusted for age, sex, diabetes duration, 1.14, 95% CI 0.86-1.52). NTproBNP was a negative confounder and age a strong modifier of this relationship (p for interaction<0.001): age<70 years, fully adjusted model HR = 3.52 (1.17-10.57) and age ≥70 years, HR = 0.80 (0.46-1.40). Respective HRs for all-cause mortality were 1.86 (1.03-3.32) and 0.73 (0.51-1.04).

CONCLUSIONS

In diabetic people aged 70 years and lower, central obesity was independently associated with increased cardiovascular mortality, independently of the negative effect of NT-proBNP. In contrast, no effect on 6-years survival was evident in diabetic people who have yet survived up to 70 years.

Cardio-adipose tissue cross-talk: relationship between adiponectin, plasma pro brain natriuretic peptide and incident heart failure

AIMS

There is increasing evidence of cross-talk between the heart, body metabolism, and adipose tissue, but the precise mechanisms are poorly understood. Natriuretic peptides (NPs) have recently emerged as the prime candidate for a mediator. In patients with heart failure (HF), infusion of NPs increases adiponectin secretion, indicating that NPs may improve adipose tissue function and in this way function as a cardio-protective agent in HF. Accordingly we investigated the interplay between plasma adiponectin, plasma proBNP, and development of HF.

METHODS AND RESULTS

We prospectively followed 5574 randomly selected men and women from the community without ischaemic heart disease or HF. Plasma adiponectin and proBNP were measured at study entry. Median follow-up time was 8.5 years (interquartile range 8.0-9.1 years). During follow-up 271 participants developed symptomatic HF. Plasma adiponectin and proBNP were strongly associated (P < 0.001). Participants with increasing adiponectin had increased risk of incident HF (P < 0.001). After adjustment for confounding risk factors (including age, gender, smoking status, body mass ratio, waist-hip ratio, glucose, glycated haemoglobin, systolic and diastolic blood pressure, lipid profile, high sensitivity C-reactive protein, estimated glomerular filtration rate, and physical activity) by Cox regression analysis, adiponectin remained an independent predictor of HF: the hazard ratio (HR) per 1 standard deviation (SD) increase in adiponectin was 1.20 [95% confidence interval (CI) 1.06-1.30; P = 0.003]. However, the association vanished when plasma proBNP was included in the analysis, HR 1.08 (95% CI 0.95-1.23; P = 0.26).

CONCLUSIONS

In conclusion, plasma adiponectin and proBNP are strongly associated. Increasing plasma adiponectin is associated with increased risk of HF. However, concomitantly elevated proBNP levels appear to explain the positive association between adiponectin and risk of HF.

Cross-talk between the heart and adipose tissue in cachectic heart failure patients with respect to alterations in body composition: a prospective study

OBJECTIVES

Cardiac cachexia (CC) is associated with changes in body composition. Lipolysis and increased energy expenditure caused by A- and B natriuretic peptides (NPs) have been suggested to play a role in CC. We tested the hypothesis that neurohormones and adipokines are associated with body composition in CC and that a progressive loss of fat free mass (FFM) and fat mass (FM) takes place.

METHODS

Body composition with regard to FFM, FM, and body fat distribution was assessed by dual energy X-ray absorptiometry (DXA) in 19 non-diabetic patients with chronic heart failure (CHF) and CC and 38 controls (non-cachectic CHF and individuals with prior myocardial infarction-both n = 19) who were followed for 12 months. Biomarkers of neurohormonal stimulation, inflammation, and endothelial dysfunction were measured.

RESULTS

N-terminal proBNP (NT-proBNP), midregional proANP (MR-proANP), and total adiponectin were elevated in CHF (p<0.001) and correlated inversely to BMI and FM. An inverse correlation was observed between pro-adrenomedullin (MR-proADM) and FFM. During follow up body weight was unaltered in all groups even though FM increased by 1.35 kg (p<0.05) and FFM decreased by 0.5 kg (p<0.05) in CC patients. The latter correlated inversely to baseline NT-proBNP, MR-proANP, and MR-proADM (p<0.05). No correlation to changes in FM was found.

CONCLUSIONS

FM was associated with plasma NPs and total adiponectin at baseline; whereas changes in FM and FFM did not correlate to changes in NPs or adiponectin during follow up. Prospectively, FFM decreased but FM increased, despite stable body weight in CC.

Impact of obesity on the expression profile of natriuretic peptide system in a rat experimental model

Natriuretic peptides (NPs) play an important role in obesity and aim of this study was to evaluate, in cardiac tissue of obese Zucker rats (O, n = 29) their transcriptomic profile compared to controls (CO, n = 24) by Real-Time PCR study; CNP protein expression was evaluated by immunostaining and immunometric tests. Myocardial histology was performed, confirming no alteration of organ structure. While ANP and BNP are cardiac peptides, CNP is mainly an endothelial hormone; thus its expression, as well as that of NPR-B and NPR-C, was also evaluated in kidney and lung of an animal subgroup (n = 20). In heart, lower BNP mRNA levels in O vs CO (p = 0.02) as well as ANP and CNP (p = ns), were detected. NPR-B/NPR-A mRNA was similar in O and CO, while NPR-C was numerically lower (p = ns) in O than in CO. In kidney, CNP/NPR-B/NPR-C mRNA was similar in O and CO, while in lung CNP/NPR-C expression decreased and NPR-B increased (p = ns) in O vs CO. Subdividing into fasting and hyperglycemic rats, the pattern of mRNA expression for each gene analyzed remained unchanged. The trend observed in heart, kidney and lung for CNP protein concentrations and immunohistochemistry reflected the mRNA expression. TNF-α and IL-6 mRNA were measured in each tissue and no significant genotype effect was detected in any tissue. The main NP variations were observed at the cardiac level, suggesting a reduced release by cardiac cells. The understanding of mechanisms involved in the modulation of the NP system in obesity could be a useful starting point for future clinical study devoted to identifying new obesity treatment strategies.

Prevalence of cachexia in chronic heart failure and characteristics of body composition and metabolic status

The prevalence of cardiac cachexia has previously been estimated to 8-42 %. However, novel treatment strategies for chronic heart failure (CHF) have improved and decreased morbidity and mortality. Therefore, we aimed to reassess the prevalence of cachexia in an outpatient CHF clinic and to characterize a CHF population with and without cachexia with respect to body composition and related biomarkers. From 2008 to 2011, we screened 238 optimally treated, non-diabetic CHF patients for cardiac cachexia, defined as unintentional non-oedematous weight loss of >5 % over ≥6 months. CHF patients (LVEF <45 %) with cachexia (n = 19) and without (n = 19) were compared to controls with prior myocardial infarction and left ventricular ejection fraction (LVEF) >45 % (n = 19). The groups were matched for age, sex, and kidney function. Body composition was assessed by dual energy X-ray absorptiometry. The prevalence of cachexia was 10.5 %. Abdominal fat ± SD (%) was reduced in cachectic CHF: 27.4 ± 10.0 versus 37.5 ± 10.6 % (CHF, no cachexia) and 40.6 ± 8.0 % (controls), (P < 0.001). NT-proBNP levels were inversely correlated to abdominal fat in a multivariate linear regression analysis adjusted for known predictors of NT-proBNP (LVEF and NYHA); (β = -0.28; P = 0.018). Myostatin levels were reduced in cachectic CHF compared to controls (P = 0.013). The prevalence of cachexia in stable CHF, treated according to recent guidelines, is lower than previously anticipated. Body alterations in cachexia consist mainly of reduced abdominal fat mass, and its inverse correlation to NT-proBNP suggests involvement of abdominal lipolysis. Our data do not support a role of circulating myostatin as a biomarker for muscle wasting.

Natriuretic peptides and cGMP signaling control of energy homeostasis

Since the discovery of natriuretic peptides (NPs) by de Bold et al. in 1981, the cardiovascular community has been well aware that they exert potent effects on vessels, heart remodeling, kidney function, and the regulation of sodium and water balance. Who would have thought that NPs are also able to exert metabolic effects and contribute to an original cross talk between heart, adipose tissues, and skeletal muscle? The attention on the metabolic role of NPs was awakened in the year 2000 with the discovery that NPs exert potent lipolytic effects mediated by the NP receptor type A/cGMP pathway in human fat cells and that they contribute to lipid mobilization in vivo. In this review, we will discuss the biological effects of NPs on the main tissues involved in the regulation of energy metabolism (i.e., white and brown adipose tissues, skeletal muscle, liver, and pancreas). These recent results on NPs are opening a new chapter into the physiological properties and therapeutic usefulness of this family of hormones.

B-type natriuretic peptide and anthropometric measures in a Brazilian elderly population with a high prevalence of Trypanosoma cruzi infection

B-type natriuretic peptide (BNP) is a diagnostic and prognostic tool in heart failure and also in Chagas disease, which is caused by the protozoan Trypanosoma cruzi and has cardiomyopathy as a main feature. BNP lipolytic actions and T. cruzi infection in the adipose tissue have been recently described. We aim to investigate the relationship between BNP and anthropometric measures and whether it is influenced by T. cruzi infection. We measured BNP, body mass index (BMI), waist circumference (WC), triceps skin-fold thickness (TSF) and performed serological, biochemical and electrocardiographic exams in 1398 subjects (37.5% infected with T. cruzi) in a community-dwelling elderly population in Bambui city, Brazil. Linear multivariate regression analysis was performed to investigate determinants of BNP levels. BNP levels were significantly (p<0.05) higher in T. cruzi-infected subjects than in the non-infected group (median=121 and 64pg/mL, respectively). BMI, WC and TSF in infected subjects were significantly lower than those in non-infected subjects (24.3 vs. 25.5kg/m2; 89.2 vs. 92.4cm; and 14.5 vs. 16.0mm, respectively). There was an inverse relationship between BNP levels and BMI (b=-0.018), WC (b=-0.005) and TSF (b=-0.193) levels. Infected and non-infected groups showed similar inverse relationships between BNP and BMI (b=-0.021 and b=-0.015, respectively). In conclusion, there was an inverse relationship between BNP levels and the anthropometric measures. Despite the actions in the adipose tissue, T. cruzi infection did not modify the associations between BNP and BMI, suggesting that body mass does not modify the accuracy of BNP in Chagas disease.

Association of amino-terminal pro-brain natriuretic peptide with metabolic syndrome

OBJECTIVE

This study evaluated the relationship between individual components in metabolic syndrome (MetS) and amino-terminal pro-brain natriuretic peptide (NT-proBNP).

METHODS

A screening program for MetS in 2008 in Taiwan excluded subjects aged <30 years and pregnant women. Fasting glucose, insulin level, high-sensitivity C-reactive protein (hsCRP), and NT-proBNP were assessed. A propensity-score matching process was used to select subjects with and without MetS comparable in age, gender, body height, and serum creatinine levels. A multiple regression model was used to determine the association between individual components of MetS and NT-proBNP. Finally 270 subjects with MetS and another 270 matched subjects without MetS aged ≥30 years were included.

RESULTS

The subjects with MetS had higher uric acid and hsCRP, but not NT-proBNP. Multiple regression model showed that log (NT-proBNP) was positively associated with systolic blood pressure (β=0.002 per mmHg, p=0.013), but negatively associated with body mass index (β=-0.017 per kg/m(2), p=0.018), triglyceride (β=-0.00048 per mg/dL, p=0.020) and insulin level (β=-0.005 per mU/L, p=0.005). Log (NT-proBNP) was neutral to waist circumference, fasting glucose, high-density lipoprotein cholesterol, and diastolic blood pressure.

CONCLUSION

MetS was not associated with serum NT-proBNP concentrations due to the contradictory effects of each component.

The Influence of Diabetes on the Relationship between N-terminal Pro-B-type Natriuretic Peptide and Body Mass Index

This study evaluated the influence of diabetes on the relationship between N-terminal pro-B-type natriuretic peptide (NT-proBNP) and body mass index (BMI). Simultaneous NT-proBNP and echocardiographic Doppler examinations were performed in 1117 patients with dyspnoea undergoing cardiac catheterization. Patients were divided into BMI ≥ 25 kg/m2 (obese), 23 − 25 kg/m2 (overweight) and < 23 kg/m2 (non-obese) groups. In the 803 non-diabetic patients, mean plasma NT-proBNP levels in non-obese, overweight and obese patients showed a significant negative correlation with BMI (862.3 ± 228.8 pg/ml, 611.5 ± 149.7 pg/ml, 278.3 ± 172.5 pg/ml, respectively). In the 314 patients with diabetes, there was no correlation between BMI and NT-proBNP. This study demonstrated that obese patients had reduced concentrations of NT-proBNP compared with non-obese patients, despite having higher left ventricular filling pressures. NT-proBNP was not reduced in obese patients with diabetes. These results suggest that factors other than cardiac status impact on NT-proBNP concentration.

Clinical features of myocardial triglyceride in different types of cardiomyopathy assessed by proton magnetic resonance spectroscopy: comparison with myocardial creatine

BACKGROUND

Myocardial lipid overstorage may produce cardiomyopathy, leading to dysfunction, but advanced heart failure may cause lipolysis via sympathetic nerve activation. In the failing heart, the creatine kinase system may also be impaired. The aims of this study were to assess myocardial triglyceride (TG) and creatine (CR) in different types of cardiomyopathy and to investigate whether they are related to the severity of cardiac dysfunction.

METHODS AND RESULTS

In patients with hypertrophic cardiomyopathy (HCM, n = 8), dilated cardiomyopathy (DCM, n = 12) or ischemic cardiomyopathy (ICM, n = 10), and normal subjects (NML, n = 22), myocardial TG and CR were evaluated using proton magnetic resonance spectroscopy. To assess cardiac sympathetic nerve activity, myocardial MIBG (a radioactive guanethidine analog) uptake was measured in DCM. Myocardial TG was significantly lower in hypertrophic cardiomyopathy (HCM) (1.92 ± 0.99 μmol/g), but higher in ICM (7.59 ± 4.36 μmol/g) than in NML hearts (4.05 ± 1.94 μmol/g). There was no significant difference in TG between DCM (4.84 ± 6.45 μmol/g) and NML. Myocardial CR in HCM (20.4 ± 8.4 μmol/g), DCM (14.8 ± 4.8 μmol/g), and ICM (19.4 ± 6.3 μmol/g) was significantly lower than that in NML hearts (27.1 ± 4.3 μmol/g). Overall, myocardial CR correlated positively with the severity of heart failure estimated by ejection fraction or myocardial BMIPP (a radioactive fatty acid analog) uptake, but TG did not. In DCM, myocardial TG correlated with body mass index, but not with MIBG uptake.

CONCLUSIONS

Myocardial TG may be related to the specific cause of disease rather than the severity of cardiac dysfunction. In contrast, myocardial CR reflects the severity of heart failure despite different pathoetiologic mechanisms of dysfunction. In DCM, myocardial TG may be affected by an overweight state rather than cardiac sympathetic nerve dysfunction. Thus, myocardial CR has a closer relationship to heart failure severity than does myocardial TG.

Role of beta1-adrenoceptor in increased lipolysis in cancer cachexia

Increased production of hormone-sensitive lipase (HSL) protein has been demonstrated to be the major cause behind enhanced lipolysis in cancer cachexia. The mechanism governing this alteration is unknown and was presently investigated. This study was conducted to detect the expression of relevant receptors in the adipocytes of cancer cachexia patients, and to elucidate their implication in the increased lipolysis. Gene expressions of beta1-adrenoceptor (ADRB1), beta2-adrenoceptor (ADRB2), beta3-adrenoceptor (ADRB3), alpha2C-adrenoceptor (ADRA2C), natriuretic peptide receptor A (NPRA), insulin receptor (INSR), and HSL were determined in adipose tissues of 34 patients by real-time PCR. Protein levels of ADRB1 and HSL were determined by western blot analysis. beta1-Adrenoceptor (ADRB1) was also detected by immunofluorescence staining. mRNA expressions of both ADRB1 and HSL were approximately 50% elevated selectively in the cachexia group, whereas mRNA levels of the other receptors were unchanged. beta1-Adrenoceptor (ADRB1) protein expression was 1.5-fold increased in cachexia as compared with the cancer controls, and 3-fold increased as compared with nonmalignant controls, and was confirmed as a membrane protein in adipocytes by immunofluorescence. Hormone-sensitive lipase (HSL) protein expression was 2-2.5-fold increased selectively in cachectic patients. There was a positive correlation between the protein expressions of ADRB1 and HSL. As much as approximately 50% of the variations in HSL protein expression could be explained by variations in ADRB1 protein expression. There was a link between ADRB1 protein level and lipolytic rate. Increased ADRB1 expression may account for some of the functional changes of HSL in patients with cancer cachexia.

N-terminal pro-B-type natriuretic Peptide in overweight and obese patients with and without diabetes: an analysis based on body mass index and left ventricular geometry

Background and Objectives

Several recent studies have shown that there is an inverse relationship between plasma B-type natriuretic peptide (BNP) and body mass index (BMI) in subjects with and without heart failure. Obesity frequently coexists with diabetes, so it is important to consider the relationship between diabetes and natriuretic peptide levels. We evaluated the influence of diabetes on the correlation of BNP and BMI.

Subjects and Methods

We examined 933 patients with chest pain and/or dyspnea undergoing cardiac catheterization between Feb. 2006 and Nov. 2007 in the Maryknoll cardiac center who had creatinine levels <2.0 mg/dL and normal systolic heart function. BMI was checked, transthoracic echocardiography was performed, and aminoterminal pro-brain natriuretic peptide (NT-proBNP) was sampled at the start of each case.

Results

In 733 non-diabetic patients, mean plasma NT-proBNP levels of non obese individuals (BMI <23 kg/m²), overweight individuals (23≤ BMI <25 kg/m²), and obese individuals (BMI ≥25 kg/m²) showed a significant negative correlation with increasing BMI (856.39±237.3 pg/mL, 601.69±159.6 pg/mL, 289.62±164.9 pg/mL, respectively, p<0.0001). However, in 200 diabetic patients, the correlation between BMI and NT-proBNP was not significant (r=-0.21, p=0.19), and NT-proBNP did not correlate with mitral E/Ea in obese diabetic patients (r=0.14, p=0.56). NT-proBNP was significantly correlated with mitral E/Ea in the non-obese (r=0.24, p=0.008) and non diabetic (r=0.32, p=0.003) groups. Left ventricular (LV) mass index was significantly correlated with NT-proBNP in all BMI groups (r=0.61, p<0.001), and patients with concentric cardiac hypertrophy showed the highest NT-proBNP levels.

Conclusion

The present study demonstrates that obese patients have reduced concentrations of NT-proBNP compared to non obese patients despite having higher LV filling pressures. However, NT-proBNP is not suppressed in obese patients with diabetes. This suggests that factors other than cardiac status affect NT-proBNP concentrations.

Control of lipolysis by natriuretic peptides and cyclic GMP

Human fat cell lipolysis was, until recently, thought to be mediated exclusively by a cAMP-dependent protein kinase (PKA)-regulated pathway under the control of catecholamines and insulin. We have shown that atrial- and B-type natriuretic peptides (ANP and BNP respectively) stimulate lipolysis in human fat cells through a cGMP-dependent protein kinase (PKG) signaling pathway independent of cAMP production and PKA activity. Pharmacological or physiological (exercise) increases in plasma ANP levels stimulate lipid mobilization in humans. This pathway becomes important during chronic treatment with beta-adrenoceptor antagonists, which inhibit catecholamine-induced lipolysis but enhance cardiac ANP release. These findings have metabolic implications and point to potential problems when natriuretic peptide secretion is altered or during therapeutic use of recombinant BNP.

Mechanism of increased lipolysis in cancer cachexia

Loss of fat mass is a key feature of cancer cachexia and has been attributed to increased adipocyte lipolysis. The mechanism behind this alteration is unknown and was presently investigated. We studied mature s.c. fat cells and differentiated preadipocytes from 26 cancer patients with and without cachexia. Hormone-induced lipolysis and expression of lipolysis-regulating genes were determined together with body composition and in vivo lipolytic activity (fasting plasma glycerol or fatty acids related to body fat). Body fat was reduced by 40% and in vivo lipolytic activity was 2-fold increased in cachexia (P = 0.001). In mature adipocytes, the lipolytic effects of catecholamines and natriuretic peptide were 2- to 3-fold increased in cachexia (P < 0.001). This was completely counteracted by inhibiting the rate-limiting lipolysis enzyme hormone-sensitive lipase (HSL). In cachexia, the expression levels of HSL mRNA and protein were increased by 50% and 100%, respectively (P = 0.005-0.03), which strongly correlated with in vitro lipolytic stimulation (r = 0.7-0.9). The antilipolytic effect of insulin in mature fat cells and the stimulated lipolytic effect in differentiated preadipocytes were unaltered in cachexia. Patients who lost weight due to other factors than cancer cachexia had no change in adipocyte lipolysis. In conclusion, adipocyte lipolysis is increased in cancer cachexia not due to nonepigenic factors or to weight loss per se, but most probably because of enhanced expression and function of adipocyte HSL. The selective inhibition of this enzyme may prevent fat loss in cancer patients.

Fat loss in cachexia—is there a role for adipocyte lipolysis?

A number of chronic diseases are associated with pronounced loss of fat and muscle mass (cachexia). The negative correlation between cachexia and survival probability, implies that prevention and treatment of this condition is essential. The mechanisms promoting cachexia are yet to be determined although several theories have been proposed. Most studies on cachexia have concentrated on muscle wasting and its possible impact on complications and survival. In this review, we present a synopsis of previous and recent studies focusing on the loss of adipose tissue. It appears that increased adipocyte lipolysis is an important factor in the cachexic process.

Cardiovascular and metabolic effects of natriuretic peptides

Natriuretic peptides (NP) are essential in mammals to regulate blood volume and pressure. The functional roles of NP are not limited to natriuresis and diuresis. Several peripheral and central actions of the peptides have been characterized. Studies on transgenic mice have revealed their key function in the regulation of cardiomyocyte growth. Plasma NP levels increase in patients with cardiovascular disorders and heart failure. They represent useful clinical markers for clinicians to diagnose heart diseases. The recent discovery of their potent lipolytic action in adipose tissue is a breakthrough in cardiovascular medicine. This new function of NP in the regulation of lipid metabolism offers interesting questions in the field of obesity, diabetes and cardiovascular diseases. This review will briefly describe the effects of NP on the cardiovascular system and lipid metabolism.

Obese patients have lower B-type and atrial natriuretic peptide levels compared with nonobese

Obesity is a risk factor for the development of heart failure, but the causal mechanism remains unclear. Impaired production or enhanced clearance of natriuretic peptides, which regulate sodium balance and sympathetic activation, may play an important role. The authors investigated the relationship of plasma B-type natriuretic peptide and atrial natriuretic peptide levels to body mass index in 100 patients referred for left heart catheterization. Hemodynamic and echocardiographic data were obtained for all study participants. Atrial natriuretic peptide and B-type natriuretic peptide levels were compared in obese (body mass index > or = 30 kg/m2) and nonobese (body mass index < 30 kg/m2) subjects. Multivariate regression analyses were performed, adjusting for clinical and hemodynamic covariates. Obese patients had significantly lower B-type natriuretic peptide (p = 0.03) and atrial natriuretic peptide (p = 0.04) levels compared with nonobese. Multivariate analysis revealed lower B-type natriuretic peptide (p = 0.095) and atrial natriuretic peptide (p = 0.007) levels in obese patients while controlling for age, sex, left ventricular end-diastolic pressure, and left ventricular ejection fraction. Low levels of circulating natriuretic peptides are thus associated with obesity and may contribute to the development of heart failure.

An Unsuspected Metabolic Role for Atrial Natriuretic Peptides

In normal and obese humans, lipid mobilization and systemic nonesterified fatty acid levels are thought to be acutely controlled by catecholamines (ie, epinephrine and norepinephrine) and insulin. Natriuretic peptides (NPs) are known to play a key role in the regulation of salt and water balance and blood pressure homeostasis. They are involved in the pathophysiology of hypertension and heart failure. NPs have recently been found to exert potent lipolytic effects (ie, activating the breakdown of stored triacylglycerols) in isolated human fat cells and to promote lipid mobilization in vivo. Atrial natriuretic peptide increases the intracellular 3', 5'-cyclic guanosine monophosphate (cGMP) concentration which activates cGMP-dependent protein kinase leading to perilipin and hormone-sensitive lipase phosphorylation and lipolysis. NPs promote lipid mobilization when administered intravenously. NPs are also responsible for the residual lipid-mobilizing action observed under oral beta-blockade in subjects performing physical exercise. NPs are therefore novel factors which may open promising research pathways to explain the control of lipid mobilization in physiological and pathological conditions. The metabolic impact of altered production and circulation of NPs remains to be established. The potential influence of NPs on the development of lipid disorders, obesity-related cardiovascular events, and cardiac cachexia will be discussed in this review.

Pharmaceutical approaches to the treatment of obesity

The recent increase in pharmaceutical companies' efforts toward the treatment of obesity reflects recognition of the related health risks, the growth of knowledge about mechanisms that control energy balance, and the potential market for new compounds. The current patent literature gives a picture of the targets that are available for pharmaceutical intervention; these include signals of satiety and signals related to fat storage that act in the hypothalamus. The regulation of energy use and storage in adipocytes and the reduction of intestinal absorption of energy are also pharmaceutical focus areas. The multiplicity of targets illustrates not only the many potential approaches to the treatment of obesity but also the complexity and redundancy of the processes that regulate energy storage in the body.

Role of Caveolae and Caveolins in Health and Disease

Although they were discovered more than 50 years ago, caveolae have remained enigmatic plasmalemmal organelles. With their characteristic “flasklike” shape and virtually ubiquitous tissue distribution, these interesting structures have been implicated in a wide range of cellular functions. Similar to clathrin-coated pits, caveolae function as macromolecular vesicular transporters, while their unique lipid composition classifies them as plasma membrane lipid rafts, structures enriched in a variety of signaling molecules. The caveolin proteins (caveolin-1, -2, and -3) serve as the structural components of caveolae, while also functioning as scaffolding proteins, capable of recruiting numerous signaling molecules to caveolae, as well as regulating their activity. That so many signaling molecules and signaling cascades are regulated by an interaction with the caveolins provides a paradigm by which numerous disease processes may be affected by ablation or mutation of these proteins. Indeed, studies in caveolin-deficient mice have implicated these structures in a host of human diseases, including diabetes, cancer, cardiovascular disease, atherosclerosis, pulmonary fibrosis, and a variety of degenerative muscular dystrophies. In this review, we provide an in depth summary regarding the mechanisms by which caveolae and caveolins participate in human disease processes.

Obesity and suppressed B-type natriuretic peptide levels in heart failure

OBJECTIVES

This investigation evaluated the relationship between obesity and B-type natriuretic peptide (BNP) in heart failure.

BACKGROUND

Obesity is a major risk factor for the development of heart failure, but the precise mechanisms remain uncertain. Physiologically, natriuretic peptides and lipolysis are closely linked.

METHODS

A total of 318 patients with heart failure were evaluated between June 2001 and June 2002. Levels of BNP were compared in obese (body mass index [BMI] > or =30 kg/m(2)) and nonobese (BMI <30 kg/m(2)) patients with respect to New York Heart Association functional class and lean body weight-adjusted peak aerobic oxygen consumption. In a subset of 36 patients, plasma levels of tumor necrosis factor-alpha, interleukin-6, and soluble intercellular adhesion molecule-1 were measured.

RESULTS

The population's BMI was 29.4 +/- 6.6 kg/m(2); 24% were lean (BMI <25 kg/m(2)), 31% overweight (BMI > or =25 to 29.9 kg/m(2)), and 45% obese (BMI > or =30 kg/m(2)). Obese patients were younger, more often African American, and more likely to have a history of antecedent hypertension, but less likely to have coronary artery disease and with only a trend toward diabetes mellitus. Levels of BNP were significantly lower in obese than in nonobese subjects (205 +/- 22 and 335 +/- 39 pg/ml, respectively; p = 0.0007), despite a similar severity of heart failure and cytokine levels. Multivariate regression analysis identified BMI as an independent negative correlate of BNP level. There were no differences in emergency department visits, heart failure hospitalization, or death between the obese and nonobese patients at 12-month follow-up.

CONCLUSIONS

Our investigation indicates that a state of reduced natriuretic peptide level exists in the obese individual with heart failure.

Role of caveolin-1 in the modulation of lipolysis and lipid droplet formation

Recently, it was shown that caveolin-1 can be redirected from the cell surface to intracellular lipid droplets in a variety of cell types. Here, we directly address the role of caveolin-1 in lipid droplet formation and breakdown, showing that caveolin-1 null mice exhibit markedly attenuated lipolytic activity. Mechanistically, although the activity of protein kinase A (PKA) was greatly increased in caveolin-1 null adipocytes, the phosphorylation of perilipin was dramatically reduced, indicating that caveolin-1 may facilitate the PKA-mediated phosphorylation of perilipin. In support of this hypothesis, coimmunoprecipitation experiments revealed that treatment with a beta(3)-adrenergic receptor agonist resulted in ligand-induced complex formation between perilipin, caveolin-1, and the catalytic subunit of PKA in wild-type but not in caveolin-1 null fat pads. We also show that caveolin-1 expression is important for efficient lipid droplet formation because caveolin-1 null embryonic fibroblasts stably transfected with perilipin accumulated approximately 4.5-fold less lipid than perilipin-transfected wild-type cells. Finally, high-pressure freeze-substitution electron microscopy of adipose tissue revealed dramatic perturbations in the architecture of the "lipid droplet cortex" (the interface between the lipid droplet surface and the cytoplasm) in caveolin-1 null perigonadal adipocytes. Taken together, our data provide the first molecular genetic evidence that caveolin-1 plays a critical functional and structural role in the modulation of both lipid droplet biogenesis and metabolism in vivo.

Functional and pharmacological characterization of the natriuretic peptide-dependent lipolytic pathway in human fat cells

A lipolytic pathway involving natriuretic peptides has recently been discovered in human fat cells. Its functional characteristics and the interactions of the atrial natriuretic peptide (ANP)-induced effects with adrenergic and insulin pathways were studied. Characterization of the action of ANP antagonists, i.e., A71915, anantin, S-28-Y (Ser-28-Tyr, a synthesized peptide), and HS-142-1 (a microbial polysaccharide), was performed. Lipolytic assays and intracellular cGMP and cAMP determinations were performed on isolated fat cells. Cell membranes were used for binding studies. At low concentrations ANP and isoproterenol [beta-adrenergic receptor (beta-AR) agonist] exerted additive lipolytic effects. The alpha(2)-AR pathway did not interfere with that of ANP. Lipolytic effects of ANP were unaltered by a 2-h pretreatment of fat cells with insulin, whereas beta-AR-induced lipolysis was reduced. Homologous desensitization occurred for ANP-dependent lipolytic pathways. Dendroapsis natriuretic peptide exhibited a similar maximal effect but a 10-fold higher lipolytic potency than ANP and mini-ANP (the shortest form of ANP). The antagonist A71915 exhibited competitive antagonistic properties with a pA(2) value of 7.51. Anantin displayed noncompetitive antagonism and exerted an inhibitory action on basal and beta-adrenergic receptor-induced lipolytic response. S-28-Y exhibited antagonist potencies toward ANP-induced lipolysis and behaved as a partial lipolytic agonist with a lower pD(2) value (7.4 +/- 0.2) than ANP (9.4 +/- 0.3). HS-142-1 exerted the weakest antagonistic effects. The results demonstrate that ANP-dependent effects do not interfere with beta- and alpha(2)-adrenergic pathways in human fat cells. They are unaffected by insulin pretreatments of fat cells but undergo desensitization. In the search of potent and specific natriuretic peptide receptor-A antagonist, in the human fat cell, A71915 was the only reliable one found.

Role of the natriuretic peptide system in lipogenesis/lipolysis

AIM

There is recent evidence that the natriuretic peptide (NP) system promotes adipose tissue lipolysis in primates. This effect is mediated by the interaction of NP with its active receptors through guanylyl cyclase activation and cGMP production. This review will briefly focus on the new aspects of NP pathophysiology in man.

DATA SYNTHESIS

NP receptors have been described in rodent adipocytes, and the expression of their mRNA is found in human adipose tissue together with high level of ANP binding sites. In isolated fat cells, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were able to stimulate lipolysis as much as isoproterenol, a non-selective beta-adrenergic receptor agonist, whereas C-type natriuretic peptide (CNP) had the lowest lipolytic effect. The potent lipolytic effect of NP has also been confirmed in samples of abdominal adipose tissue from healthy subjects. The potency order of the lipolytic effect (ANP > BNP > CNP) and ANP-induced cGMP production supported the presence of type A natriuretic peptide receptor in human fat cells. The effect of NP on lipid metabolism is confirmed by the fact that intravenous ANP infusion is followed by plasma NEFA and glycerol concentration increase (reflecting lipid mobilisation).

CONCLUSIONS

The NP system seems to play an important role in lipid metabolism, possibly affecting the pathophysiology of obesity and obesity-related disorders, such hypertension. Further studies, however, are needed to completely establish the mechanisms involved in NP-induced lipolysis and the real relevance of this new pathway specific of primates.