Beta blockers prevent correlation of plasma ACE2 activity with echocardiographic parameters in patients with idiopathic dilated cardiomyopathy.

Plasma angiotensin-converting enzyme (ACE) 2 activity has been demonstrated to be an independent prognostic marker in Chagas' disease, equally potent as B-type natriuretic peptide. This study aimed to investigate the prognostic potency of circulating ACE2 activity in patients with idiopathic dilated cardiomyopathy (DCM). Blood samples were withdrawn from patients with idiopathic DCM and healthy control subjects. The DCM patients were subdivided into 2 groups according to their New York Heart Association classification. The plasma ACE2 activity was measured by a fluorescence method. Plasma ACE2 activity was significantly increased in DCM patients, correlating with clinical severity. It was correlating with echocardiographic parameters in patients with DCM. Furthermore, plasma ACE2 activity had the potency to predict cardiac death and heart transplantation. However, compared with patients with Chagas' disease, the correlation and predictive value of ACE2 activity in patients with DCM was much less pronounced. Beta blocker treatment in patients with DCM was identified to prevent the association between circulating ACE2 activity and echocardiographic parameters. Although ACE2 activity in blood samples of patients with DCM without beta blockers is potent in correlating with the severity of disease and in predicting death and heart transplantation, its correlation and prediction potency are significantly diminished by beta blocker treatment.

Prognostic significance of circulating levels of hepatocyte growth factor in patients with chagas' disease and idiopathic dilated cardiomyopathy.

OBJECTIVES: Hepatocyte growth factor (HGF) plays an important role in the improvement in cardiac function and remodeling in a variety of cardiovascular diseases. It is also a strong predictor of mortality in some heart failure (HF) patients. However, its prognostic value in patients with Chagas' disease (CD) or idiopathic dilated cardiomyopathy (DCM) remains to be investigated. METHODS AND RESULTS: In this prospective cohort study, HGF concentrations were measured in patients with CD (n = 91), DCM (n = 47), and control subjects (n = 25). While no difference was detected for patients with New York Heart Association class I-II, HGF was significantly increased in advanced HF patients (New York Heart Association class III-IV) in both CD and DCM groups, compared with healthy subjects. There was a strong correlation between HGF and left ventricular ejection fraction in CD patients. However, there was no correlation in patients with DCM. Despite its strong correlation with left ventricular ejection fraction in CD patients, HGF failed to predict mortality and necessity for heart transplant in both CD and DCM patients. CONCLUSIONS: Although HGF can be significantly increased in advanced HF patients with CD and DCM, its prognostic value for endpoints is minor. Therefore, the formerly described predictive power for HGF in HF might be restricted to specific etiologies of HF.

Does the aminopeptidase A have prognostic and diagnostic value in Chagas disease and other dilated cardiomyopathies?

Chagas disease (CD), which is caused by the protozoan Trypanosoma cruzi, is a major cause of heart failure in Latin America. We investigated if plasma activity of one of the enzymes being part of the renin-angiotensin system, aminopeptidase A (APA), has diagnostic and prognostic potency in patients with CD and dilated cardiomyopathies (DCMs) due to other causes. Blood samples were taken from 94 patients with CD, 46 patients with DCM, and 34 healthy control subjects. Plasma APA activity was determined by fluorometry assays. The average follow-up time was 39 months; by the end of study, 33 patients had died and another 13 received heart transplant. There was no significant alteration in plasma APA activity in the patients with CD or DCM, as compared with that in controls. The Pearson correlation of echocardiographic data with plasma APA activity in patients with CD and DCM did not reveal any significant correlation with left-ventricular ejection fraction or other echocardiographic parameters. APA activity was unable to predict mortality or the need for heart transplant. Detection of APA activity in plasma may not prove suitable for prognosis in patients with heart failure and is unable to screen or diagnose asymptomatic patients with CD for early therapy.

Signal transduction in CHO cells stably transfected with domain-selective forms of murine ACE.

Membrane-bound human angiotensin-converting enzyme (ACE) has been reported to initiate intracellular signaling after interaction with substrates or inhibitors. Somatic ACE is known to contain two distinct, extracellular catalytic centers. We analyzed the signal transduction mechanisms in cells transfected with different forms of murine ACE (mACE) and investigated whether the two domains are similarly involved in these processes. For this purpose, CHO cells were stably transfected with mACE or with its domain-selective mutants. In addition to these modified cellular models, human umbilical vein endothelial cells were used in this study. Signal transduction molecules such as JNK and c-Jun were analyzed after activation of cells with several ACE substrates and inhibitors. ACE-targeting compounds such as substrates, inhibitors, or even the ACE product angiotensin-II induce in mACE-expressing cells a signal transduction response. These processes are also evoked by partially inactivated forms of mACE and finally result in an enhanced cyclooxygenase-2 transcription. Surprisingly, the membrane-bound ACE activity is also influenced by ACE-targeted interventions. Our data suggest that the two catalytic domains of mACE do not function independently but that the signal transduction is influenced by negative cooperativity of the two catalytic domains. This study underlines that ACE indeed has receptor-like properties which occur in a species-specific manner.

Plasma ACE2 activity is an independent prognostic marker in Chagas' disease and equally potent as BNP.

BACKGROUND: Angiotensin-converting enzyme (ACE) 2 is a novel homologue of ACE. It metabolizes angiotensin (Ang)II to Ang-(1-7). This study aims to investigate the diagnostic and prognostic potency of circulating ACE2 activity in patients with heart failure (HF) from Chagas' disease (CD). METHODS AND RESULTS: Blood samples were obtained from 111 CD patients and 40 age- and gender-matched healthy subjects. The CD patients were further subdivided according to their New York Heart Association classification. ACE2 activity was significantly increased in CD patients with HF, but not in patients without systolic dysfunction. Moreover, plasma ACE2 activity was significantly correlated with their clinical severity and echocardiographic parameters. Importantly, the potency of circulating ACE2 activity in CD patients was equally potent as that of B-type natriuretic peptide to predict cardiac death and heart transplant. Most importantly, patients with both parameters elevated were on a 5-fold higher risk to reach an endpoint than patients with increase in only 1 of the 2 parameters. CONCLUSIONS: Determination of ACE2 activity may provide a new and important diagnostic and prognostic marker for patients with CD. ACE2 activity and BNP concentration have additive predictive value and may be used in combination to offer a new dimension of prediction in HF.

Effects of ACE2 inhibition in the post-myocardial infarction heart.

BACKGROUND: There is evidence that angiotensin-converting enzyme 2 (ACE2) is cardioprotective. To assess this in the post-myocardial infarction (MI) heart, we treated adult male Sprague-Dawley rats with either placebo (PL) or C16, a selective ACE2 inhibitor, after permanent coronary artery ligation or sham operation. METHODS AND RESULTS: Coronary artery ligation resulting in MI between 25% to 50% of the left ventricular (LV) circumference caused substantial cardiac remodeling. Daily C16 administration from postoperative days 2 to 28 at a dose that inhibited myocardial ACE2 activity was associated with a significant increase in MI size and reduction in LV % fractional shortening. Treatment with C16 did not significantly affect post-MI increases in LV end-diastolic dimension but did inhibit increases in wall thickness and fibrosis in non-infarcted LV. On postoperative day 7, C16 had no significant effect on the increased level of apoptosis in the infarct and border zones nor did it significantly affect capillary density surrounding the MI. It did, however, significantly reduce the number of c-kit(+) cells in the border region. CONCLUSIONS: These findings support the notion that ACE2 exerts cardioprotective effects by preserving jeopardized cardiomyocytes in the border zone. The reduction in hypertrophy and fibrosis with C16, however, suggests that ACE2 activity has diverse effects on post-MI remodeling.

Amino-terminal fragment of C-type natriuretic peptide precursor and C-type natriuretic peptide do not correlate in patients with Chagas disease: role for neutral endopeptidase.

Atrial and B-type natriuretic peptides (ANP and BNP), but not C-type natriuretic peptide (CNP), have been identified to be diagnostic and prognostic markers in Chagas disease (CD). Although ANP and BNP excessively rise in patients with CD, increase in CNP is just minor. Our study aimed to investigate the mechanisms leading to CNP insensitivity to heart failure (HF) stimuli. Amino-terminal fragment of CNP precursor (NT-proCNP) and activity of neutral endopeptidase (NEP) were quantified to monitor CNP generation and degradation, respectively. Blood samples were collected from patients with CD and control healthy subjects. NT-proCNP concentrations were significantly lower in patients with CD without systolic dysfunction compared with healthy subjects. Despite a trend toward increase with rising heart failure clinical severity, it was significantly correlated with left ventricular ejection fraction and other echocardiographic parameters. As shown for CNP before, NT-proCNP could not predict mortality and heart transplant. Importantly, it had no statistical correlation with CNP. Additionally, NEP activity was significantly increased in New York Heart Association III and IV patients with HF but was positively correlated with CNP concentration. Our data demonstrates that generation of CNP is not enhanced under HF condition like CD. Thus, CNP rise by severe HF is caused by its less degradation that is independent of NEP activity.

The virtually mature B-type natriuretic peptide (BNP1-32) is a precursor for the more effective BNP1-30.

BACKGROUND AND PURPOSE: The B-type natriuretic peptide (BNP1-32) exerts vasorelaxing and cardioprotective activity. BNP is used as a biomarker for the diagnosis of cardiopathological conditions and recombinant BNP1-32 as a drug for the treatment of such. BNP1-32 has a short half-life and thus, similar to other vasoactive peptides like angiotensin II and bradykinin, can be enzymatically truncated forming bioactive metabolites. We aimed to investigate the metabolism of BNP1-32 in the mouse lung, to identify potential new BNP metabolites and to disclose their biological activity compared to the BNP1-32, in vitro and in vivo. EXPERIMENTAL APPROACH: Using HPLC and MS, we identified a new BNP metabolite, BNP1-30, in the lung being generated by endothelin-converting enzyme-1. KEY RESULTS: BNP1-30 is more efficient in stimulating the guanylyl cyclase (GC) receptor A and, in contrast to BNP1-32, is also able to profoundly stimulate the GC-B. In vivo, BNP1-30 reduced the mean arterial BP of normotensive mice after acute infusion significantly more than BNP1-32. In a model of severe hypertension, a 3-day infusion of BNP1-30 was able to reduce systolic BP by 30 mmHg and to improve markers of heart failure, while BNP1-32 was without significant effect. CONCLUSIONS AND IMPLICATIONS: Our results suggest that BNP1-32 is the precursor for the biologically more active BNP1-30 leading to a fundamental extension of the natriuretic peptide system. Due to expanded activity, BNP1-30 might be a promising treatment option for cardiovascular diseases. Furthermore, its potency as a new diagnostic marker of specific cardiac diseases should be evaluated.

Successive action of meprin A and neprilysin catabolizes B-type natriuretic peptide.

Natriuretic peptides such as B-type natriuretic peptide (BNP) are important cardioprotective hormones with essential functions in sodium excretion, water balance and blood pressure regulation. Consequently, the catabolism of these peptides is in the focus of clinical research. In previous studies, we demonstrated that BNP, in contrast to the structurally related atrial and C-type natriuretic peptide, was not hydrolyzed by neprilysin (NEP). Because membrane preparations of several organs of NEP-knockout mice rapidly degrade BNP, the aim of this study was to identify BNP-catabolizing peptidases responsible for this fast clearance. Using kidney membranes of wild-type and NEP-knockout mice, as well as several peptidase inhibitors, we monitored the catabolism of BNP and analyzed its degradation products. We identified meprin A, a multimeric metalloprotease expressed in the brush borders of kidney proximal tubules, to initially truncate mouse BNP in the N terminus to mBNP7-32, a BNP metabolite with conserved biological activity. Consequently, in vivo experiments with the meprin inhibitor actinonin successfully elevated plasma BNP concentration in rats. We further demonstrated that the generation of mBNP7-32 is the prerequisite to catabolize BNP and identified NEP as the peptidase degrading the truncated BNP. Thus, the cooperative, successive action of the 2 transmembranal peptidases meprin A and NEP is crucial for rapid renal BNP inactivation. Therefore, the inhibition of meprin A could be a potent tool for increasing circulating BNP levels.

Impaired spatial memory and altered dendritic spine morphology in angiotensin II type 2 receptor-deficient mice.

Mental retardation is the most frequent cause of serious handicap in children and young adults. Mutations in the human angiotensin II type 2 receptor (AT2) have been implicated in X-linked forms of mental retardation. We here demonstrate that mice lacking the AT2 receptor gene are significantly impaired in their performance in a spatial memory task and in a one-way active avoidance task. As no difference was observed between the genotypes in fear conditioning, the detected deficit in spatial memory may not relate to fear. Notably, receptor knockout mice showed increased motility in an activity meter and elevated plus maze. Importantly, these mice are characterized by abnormal dendritic spine morphology and length, both features also found to be associated with some cases of mental retardation. These findings suggest a crucial role of AT2 in normal brain function and that dysfunction of the receptor has impact on brain development and ultrastructural morphology with distinct consequences on learning and memory.

Accelerated mitochondrial adenosine diphosphate/adenosine triphosphate transport improves hypertension-induced heart disease.

BACKGROUND: Strong evidence suggests that mitochondrial malfunction, which leads to disturbed energy metabolism and stimulated apoptosis, is a linchpin in the induction and manifestation of cardiac failure. An adequate exchange of ATP and ADP over the inner mitochondrial membrane by the adenine nucleotide translocase (ANT) is thereby essential to guarantee the cellular energy supply. METHODS AND RESULTS: To explore the effect of an ameliorated mitochondrial ATP/ADP transportation on cardiac dysfunction, we generated transgenic rats overexpressing ANT1 in the heart (ANT rats) and crossed them with renin-overexpressing rats (REN rats) suffering from hypertension-induced cardiac insufficiency. Cardiac-specific ANT1 overexpression resulted in a higher ATP/ADP transportation and elevated activities of respiratory chain complexes. Increased ANT activity in double-transgenic (ANT/REN) animals did not influence excessive hypertension seen in REN rats. Hypertension-induced cardiac hypertrophy in the REN rats was prevented by parallel ANT1 overexpression, however, and left ventricular function remarkably improved. The ANT1 overexpression led to a reduction in fibrosis and an improvement in cardiac tissue architecture. Consequently, the survival rate of ANT/REN rats was enhanced. Further investigations into the cardioprotective mechanism of ANT1 overexpression revealed improved mitochondrial structure and function and significantly reduced apoptosis in ANT/REN rats, shown by lowered cytosolic/mitochondrial cytochrome c ratio, reduced caspase 3 level, and prevented DNA degradation. CONCLUSIONS: Myocardial ANT1 overexpression protects against hypertension-induced cardiac pathology. Thus, the improvement in mitochondrial function may be a basic principle for new strategies in treating heart disease.

Catabolic attacks of membrane-bound angiotensin-converting enzyme on the N-terminal part of species-specific amyloid-beta peptides.

Catabolic processes play a crucial role in the steady state of the amyloid-beta peptide (Abeta). Neprilysin (NEP) and angiotensin-converting enzyme (ACE), two transmembranal enzymes with greatest importance in peptide pharmacology, are known to play a role in Abeta catabolism. This paper focuses on the N-terminal part of Abeta. This region contains the three amino acid residues that determine the differences between human (hAbeta) and murine Abeta (mAbeta). Moreover, the N-terminal part of Abeta contains the zinc-binding site of the molecule. Consequently, all hydrolytic attacks on this part of the Alzheimer peptide should be of exceptional interest. We investigated domain-selective forms of ACE in HPLC-monitored peptide degradation studies and used mass spectrometry for product analyses. We found that ACE-evoked a hydrolysis of the N-terminal part of m- and hAbeta. The hAbeta sequence hAbeta (4-15) was found to be a better substrate for ACE compared to the corresponding murine form. Moreover, we localized the corresponding cleavage sites in the N-terminal part of Abeta as well as in the full-length molecule and identified new sites of endopeptidolytic attack by ACE. Finally, we demonstrate that both catalytic domains of mACE have similar hydrolytic activity on the N-terminal part of Abeta. Our results show that ACE besides its typical function as a dipeptidyl-carboxypeptidase has also unequivocal endopeptidolytic activities.

Neprilysin degrades murine Amyloid-ß (Aß) more efficiently than human Aß: Further implication for species-specific amyloid accumulation.

For over a century, aggregated forms of amyloid-ß protein (Aß) have been viewed as a key hallmark of brains affected by Alzheimer's disease (AD). Today, it remains unknown whether Aß aggregates (oligomers, fibrils or plaques) originate from increased production or decreased catabolism of Aß. Neprilysin (NEP, neutral endopeptidase) is a ubiquitously distributed peptidase, known to degrade Aß, amongst other peptides. In this study, we identified differences in NEP-mediated catabolism of murine and human forms of Aß, using recombinant human NEP, membrane-bound NEP from cells overexpressing the murine peptidase or from human organ preparations with high NEP activity, and purified soluble bovine NEP. NEP degraded murine Aß (mAß) faster than human Aß (hAß). These findings were observed with full-length Aß containing 40 or 42 amino acids (Aß1-40 and Aß1-42) and a truncated form (Aß4-15), which (i) contains one of the main NEP cleavage sites for Aß (between positions 9 and 10), (ii) harbours all three amino acid differences between murine and human Aß sequences, and (iii) is less prone to aggregation and thus might be a simpler model to investigate Aß biochemistry. While it has previously been shown that mAß has a far lower propensity to aggregate than hAß, evidence from this study suggests that a faster NEP-mediated turnover of mAß may provide additional protection against Aß aggregation in murine species.

Central angiotensin II controls alcohol consumption via its AT1 receptor.

Pharmacological and genetic manipulations of the renin-angiotensin system (RAS) have been found to alter the voluntary consumption of alcohol. Here we characterize the role of central angiotensin II (Ang II) in alcohol intake first by using transgenic rats that express an antisense RNA against angiotensinogen and consequently have reduced Ang II levels exclusively in the central nervous system [TGR(ASrAOGEN)680]. These rats consumed markedly less alcohol in comparison to their wild-type controls. Second, Spirapril, an inhibitor of the angiotensin-converting enzyme (ACE), which passes the blood-brain barrier, did not influence the alcohol consumption in the TGR(ASrAOGEN)680, but it significantly reduced alcohol intake in wild-type rats. Studies in knockout mice indicated that the central effect of Ang II on alcohol consumption is mediated by the angiotensin receptor AT1 whereas the AT2 receptor and the bradykinin B2 receptor are not involved. Furthermore, the dopamine concentration in the ventral tegmental area (VTA) is markedly reduced in rats with low central Ang II, strengthening our hypothesis of a role of dopaminergic transmission in Ang II-controlled alcohol preference. Our results indicate that a distinct drug-mediated control of the central RAS could be a promising therapy for alcohol disease.

Lack of angiotensin II conversion to angiotensin III increases water but not alcohol consumption in aminopeptidase A-deficient mice.

Elevated central concentrations of the vasopressor octapeptide angiotensin (Ang) II increase the water intake in mammals. Recently, we showed that central AngII is also crucial in alcohol-consuming behavior. Since the heptapeptide AngIII, an AngII metabolite, is discussed to mediate AngII-related effects, we investigated water and alcohol consumption in mice, genetically deficient in aminopeptidase A (APA), a peptidase responsible for AngII conversion to AngIII. Sixteen male APA-deficient mice and their age matched wild-type controls were monitored on their water intake under basal conditions and total fluid and alcohol intake before and after social stress in a two-bottle free-choice paradigm. Alterations were connected to the regulation in activity of Ang-related peptidases (APA, ACE; ACE2) in brain regions involved in alcohol intake and peripheral organs. In comparison to their wild-type controls, APA-deficient mice drank significantly more water but not more alcohol at all investigated time points. A reduction in water intake, as observed in wild-type animals after social stress, did not occur in knockout mice. However, the reduction in alcohol consumption after social stress was significantly reduced in both strains. Alcohol consumption upregulated all three peptidases in the kidney, but not in lung. Notable, renal ACE2 activity was significantly higher in APA-deficient mice under basal condition. While the inhibition of AngII metabolism to AngIII does not influence the alcohol intake, water consumption in mice deficient for APA was significantly elevated. These differences induced by an altered AngII/AngIII ratio oppose the hypothesis that central AngII and AngIII act in a congruent pattern.

Organ-specific distribution of ACE2 mRNA and correlating peptidase activity in rodents.

Biochemical analysis revealed that angiotensin-converting enzyme related carboxy-peptidase (ACE2) cleaves angiotensin (Ang) II to Ang-(1-7), a heptapeptide identified as an endogenous ligand for the G protein-coupled receptor Mas. No data are currently available that systematically describe ACE2 distribution and activity in rodents. Therefore, we analyzed the ACE2 expression in different tissues of mice and rats on mRNA (RNase protection assay) and protein levels (immunohistochemistry, ACE2 activity, western blot). Although ACE2 mRNA in both investigated species showed the highest expression in the ileum, the mouse organ exceeded rat ACE2, as also demonstrated in the kidney and colon. Corresponding to mRNA, ACE2 activity was highest in the ileum and mouse kidney but weak in the rat kidney, which was also confirmed by immunohistochemistry. Contrary to mRNA, we found weak activity in the lung of both species. Our data demonstrate a tissue- and species-specific pattern for ACE2 under physiological conditions.

Genetic deficiency in neprilysin or its pharmacological inhibition initiate excessive stress-induced alcohol consumption in mice.

Both acquired and inherited genetic factors contribute to excessive alcohol consumption and the corresponding development of addiction. Here we show that the genetic deficiency in neprilysin [NEP] did not change the kinetics of alcohol degradation but led to an increase in alcohol intake in mice in a 2-bottle-free-choice paradigm after one single stress stimulus (intruder). A repetition of such stress led to an irreversible elevated alcohol consumption. This phenomenon could be also observed in wild-type mice receiving an orally active NEP inhibitor. We therefore elucidated the stress behavior in NEP-deficient mice. In an Elevated Plus Maze, NEP knockouts crossed more often the area between the arms, implicating a significant stronger stress response. Furthermore, such animals showed a decreased locomotor activity under intense light in a locomotor activity test, identifying such mice to be more responsive in aversive situations than their wild-type controls. Since the reduction in NEP activity itself does not lead to significant signs of an altered alcohol preference in mice but requires an environmental stimulus, our findings build a bridge between stress components and genetic factors in the development of alcoholism. Therefore, targeting NEP activity might be a very attractive approach for the treatment of alcohol abuse in a society with increasing social and financial stress.

High-protein diet in lactation leads to a sudden infant death-like syndrome in mice.

BACKGROUND: It is well accepted that reduced foetal growth and development resulting from maternal malnutrition are associated with a number of chronic conditions in later life. On the other hand such generation-transcending effects of over-nutrition and of high-protein consumption in pregnancy and lactation, a proven fact in all developed societies, are widely unknown. Thus, we intended to describe the generation-transcending effects of a high-protein diet, covering most relevant topics of human life like embryonic mortality, infant death, and physical health in later life. METHODS: Female mice received control food (21% protein) or were fed a high protein diet (42% protein) during mating. After fertilisation, females stayed on their respective diet until weaning. At birth, pups were put to foster mothers who were fed with standard food or with HP diet. After weaning, control diet was fed to all mice. All offspring were monitored up to 360 days after birth. We determined glucose-tolerance and measured cardiovascular parameters using a tip-catheter. Finally, abdominal fat amount was measured. RESULTS AND CONCLUSIONS: We identified a worried impact of high-protein diet during pregnancy on dams' body weight gain, body weight of newborns, number of offspring, and also survival in later life. Even more important is the discovery that high-protein diet during lactation caused a more than eight-fold increase in offspring mortality. The observed higher newborn mortality during lactation is a hitherto non-described, unique link to the still incompletely understood human sudden infant death syndrome (SIDS). Thus, although offspring of lactating mothers on high-protein diet might have the advantage of lower abdominal fat within the second half of life, this benefit seems not to compensate the immense risk of an early sudden death during lactation. Our data may implicate that both pregnant women and lactating mothers should not follow classical high-protein diets.

New function for an old enzyme: NEP deficient mice develop late-onset obesity.

BACKGROUND: According to the World Health Organization (WHO) there is a pandemic of obesity with approximately 300 million people being obese. Typically, human obesity has a polygenetic causation. Neutral endopeptidase (NEP), also known as neprilysin, is considered to be one of the key enzymes in the metabolism of many active peptide hormones. METHODOLOGY/PRINCIPAL FINDINGS: An incidental observation in NEP-deficient mice was a late-onset excessive gain in body weight exclusively from a ubiquitous accumulation of fat tissue. In accord with polygenetic human obesity, mice were characterized by deregulation of lipid metabolism, higher blood glucose levels, with impaired glucose tolerance. The key role of NEP in determining body mass was confirmed by the use of the NEP inhibitor candoxatril in wild-type mice that increased body weight due to increased food intake. This is a peripheral and not a central NEP action on the switch for appetite control, since candoxatril cannot cross the blood-brain barrier. Furthermore, we demonstrated that inhibition of NEP in mice with cachexia delayed rapid body weight loss. Thus, lack in NEP activity, genetically or pharmacologically, leads to a gain in body fat. CONCLUSIONS/SIGNIFICANCE: In the present study, we have identified NEP to be a crucial player in the development of obesity. NEP-deficient mice start to become obese under a normocaloric diet in an age of 6-7 months and thus are an ideal model for the typical human late-onset obesity. Therefore, the described obesity model is an ideal tool for research on development, molecular mechanisms, diagnosis, and therapy of the pandemic obesity.

Renal ACE2 expression and activity is unaltered during established hypertension in adult SHRSP and TGR(mREN2)27.

Differential renal expression of a homolog of the angiotensin-converting enzyme (ACE), that is, ACE2, has been implicated as a genetic basis of polygenetic hypertension in the stroke-prone spontaneously hypertensive rat model. However, data on the role of ACE2 in hypertension are still inconclusive. Therefore, we analyzed kidney ACE2 mRNA, ACE2 protein and ACE2 enzyme activities in the adult polygenetic stroke-prone spontaneously hypertensive rat (SHRSP) and the monogenetic TGR(mREN2)27 rat models, in comparison with their normotensive reference strains, Wistar-Kyoto (WKY) and Spraque-Dawley (SD) rats, respectively. Kidney ACE2 mRNA was studied using quantitative real-time reverse transcriptase-PCR (RT-PCR) in cortex and medulla, whereas protein expression was scored semiquantitatively in detail in different renal structures using immunohistochemistry. Furthermore, total renal tissue ACE2 activity was measured using a fluorimetric assay that was specified by the ACE2 inhibitor DX600. In SHRSP and homozygous TGR(mREN2)27 rats with established hypertension, kidney ACE2 mRNA, protein and tissue ACE2 activities were not different from their respective WKY and SD reference strain, respectively. In addition, when we looked at renal localization, we found ACE2 protein to be predominantly present in glomeruli and endothelium with weak staining in distal and negative staining in proximal tubuli. Thus, our data challenge previous work that implicates ACE2 as a candidate gene for hypertension in SHRSP by reporting a significant reduction of ACE2 in the kidneys of SHRSP. Taken together, renal ACE2 is not altered in the SHRSP and TGR(mREN2)27 genetic rat models with established hypertension.