Increased susceptibility to metabolic syndrome in adult offspring of angiotensin type 1 receptor autoantibody-positive rats

The functional subclasses of AT1 receptor autoantibody in patients with coronary heart disease

Recently, the identification of autoantibodies (AT1-AA) targeting the second extracellular loop of angiotensin II type 1 receptor (AT1R-ECII) in patients with coronary heart disease (CHD) offers a novel perspective on the interplay between immunity and cardiovascular disease. However, much remains unknown regarding the functional diversity of AT1-AA. In this study, we measured the levels of AT1-AA in the sera of 306 CHD patients and purified AT1-AA from patient's sera (n = 127). The subclasses of AT1-AA were categorized based on their impact on intracellular calcium ([Ca2+]i) levels in mouse arterial smooth muscle cells (MASMCs). Our findings revealed 4 distinct [Ca2+]i response patterns indicating the existence of 4 functional subclasses named H1-, H2-, H3-, and H4-AT1-AA. The correlation analysis demonstrated a positive association between H1-AT1-AA and endogenous coagulation, as well as between H2-AT1-AA and exogenous coagulation; no significant correlation was observed between H3-AT1-AA and the indicators we analyzed. Conversely, H4-AT1-AA exhibited a negative correlation with both leukocyte number and bile acid levels. Logistic regression analysis showed that H2-AT1-AA possessed predictive value for severe CHD. Furthermore, in vitro experiments indicated that both H1- and H2-AT1-AA exerted cytotoxic effects on MASMCs, while H4-AT1-AA increased cell viability. Additionally, an AT1-AA-positive rat model was established by subcutaneously injecting with AT1R-ECII peptide, which produced four similar functional subclasses of rat AT1-AA upon active immunization. This study suggested that classifying different functional subclasses of AT1-AAs can facilitate more accurate evaluation of the condition and prognosis in patients with CHD, thereby providing a novel basis for clinical diagnosis and treatment.

The Molecular Basis of the Augmented Cardiovascular Risk in Offspring of Mothers with Hypertensive Disorders of Pregnancy

The review examines the impact of maternal preeclampsia (PE) on the cardiometabolic and cardiovascular health of offspring. PE, a hypertensive disorder of pregnancy, is responsible for 2 to 8% of pregnancy-related complications. It significantly contributes to adverse outcomes for their infants, affecting the time of birth, the birth weight, and cardiometabolic risk factors such as blood pressure, body mass index (BMI), abdominal obesity, lipid profiles, glucose, and insulin. Exposure to PE in utero predisposes offspring to an increased risk of cardiometabolic diseases (CMD) and cardiovascular diseases (CVD) through mechanisms that are not fully understood. The incidence of CMD and CVD is constantly increasing, whereas CVD is the main cause of morbidity and mortality globally. A complex interplay of genes, environment, and developmental programming is a plausible explanation for the development of endothelial dysfunction, which leads to atherosclerosis and CVD. The underlying molecular mechanisms are angiogenic imbalance, inflammation, alterations in the renin-angiotensin-aldosterone system (RAAS), endothelium-derived components, serotonin dysregulation, oxidative stress, and activation of both the hypothalamic-pituitary-adrenal axis and hypothalamic-pituitary-gonadal axis. Moreover, the potential role of epigenetic factors, such as DNA methylation and microRNAs as mediators of these effects is emphasized, suggesting avenues for future research and therapeutic interventions.

Advances in the allostery of angiotensin II type 1 receptor

Angiotensin II type 1 receptor (AT1R) is a promising therapeutic target for cardiovascular diseases. Compared with orthosteric ligands, allosteric modulators attract considerable attention for drug development due to their unique advantages of high selectivity and safety. However, no allosteric modulators of AT1R have been applied in clinical trials up to now. Except for the classical allosteric modulators of AT1R such as antibody, peptides and amino acids, cholesterol and biased allosteric modulators, there are non-classical allosteric modes including the ligand-independent allosteric mode, and allosteric mode of biased agonists and dimers. In addition, finding the allosteric pockets based on AT1R conformational change and interaction interface of dimers are the future of drug design. In this review, we summarize the different allosteric mode of AT1R, with a view to contribute to the development and utilization of drugs targeting AT1R allostery.

Maternal tadalafil therapy for fetal growth restriction prevents non-alcoholic fatty liver disease and adipocyte hypertrophy in the offspring

We aimed to investigate the effects of maternal tadalafil therapy on fetal programming of metabolic function in a mouse model of fetal growth restriction (FGR). Pregnant C57BL6 mice were divided into the control, L-NG-nitroarginine methyl ester (L-NAME), and tadalafil + L-NAME groups. Six weeks after birth, the male pups in each group were given a high-fat diet. A glucose tolerance test (GTT) was performed at 15 weeks and the pups were euthanized at 20 weeks. We then assessed the histological changes in the liver and adipose tissue, and the adipocytokine production. We found that the non-alcoholic fatty liver disease activity score was higher in the L-NAME group than in the control group (p < 0.05). Although the M1 macrophage numbers were significantly higher in the L-NAME/high-fat diet group (p < 0.001), maternal tadalafil administration prevented this change. Moreover, the epididymal adipocyte size was significantly larger in the L-NAME group than in the control group. This was also improved by maternal tadalafil administration (p < 0.05). Further, we found that resistin levels were significantly lower in the L-NAME group compared to the control group (p < 0.05). The combination of exposure to maternal L-NAME and a high-fat diet induced glucose impairment and non-alcoholic fatty liver disease. However, maternal tadalafil administration prevented these complications. Thus, deleterious fetal programming caused by FGR might be modified by in utero intervention with tadalafil.

AT1-receptor autoantibody exposure in utero contributes to cardiac dysfunction and increased glycolysis in fetal mice

Exposure to adverse factors in utero may lead to adaptive changes in cardiac structure and metabolism, which increases the risk of chronic cardiovascular disease later in life. Studies showed that the angiotensin II type 1 receptor autoantibodies (AT1-AAs) are able to cross the placenta into the circulation of pregnant rodents' embryo, which adversely affects embryogenesis. However, the effects of AT1-AA exposure on the fetal heart in utero are still unknown. In this study, we investigated whether intrauterine AT1-AA exposure has adverse effects on fetal heart structure, function and metabolism. AT1-AA-positive pregnant mouse models were successfully established by passive immunity, evidenced by increased AT1-AA content. Morphological and ultrasonic results showed that the fetal mice on embryonic day 18 (E18) of AT1-AA group have loose and disordered myocardial structure, and decreased left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS), compared with control groups. The myocardium of AT1-AA group fetal mice on E18 exhibited increased expression of the key molecules in the glycolytic pathway, pyruvate and lactic acid content and ATP production, suggesting that the glycolysis rate was enhanced. Furthermore, the enhanced effect of glycolysis caused by AT1-AA is mainly through the PPARβ/δ pathway. These data confirmed that fetus exposure to AT1-AA in utero developed left ventricular dysfunction, myocardial structural arrangement disorders, and enhanced glycolysis on E18. Our results support AT1-AA being a potentially harmful factor for cardiovascular disease in fetal mice.

The AT1 receptor autoantibody causes hypoglycemia in fetal rats via promoting the STT3A-GLUT1-glucose uptake axis in liver

Blood glucose is of great importance to development and metabolic homeostasis in fetuses. Stimulation of harmful factors during gestation induces pathoglycemia. Angiotensin II type 1 receptor autoantibody (AT1-AA), a newly discovered gestational harmful factor, has been shown to induce intrauterine growth restriction in fetuses and glucose disorders in adults. However, whether and how AT1-AA influences the blood glucose level of fetuses during gestation is not yet clear. The purpose of the current study was to observe the fetal blood glucose level of AT1-AA-positive pregnant rats during late pregnancy and to determine the roles that hepatic glucose transporters play in this process. We established AT1-AA-positive pregnant rats by injecting AT1-AA into the caudal veins of rats in the 2nd trimester of gestation. Although the fetal blood glucose level in the 3rd trimester of gestation decreased, hepatic glucose uptake increased detected. Through separating membrane and cytosolic proteins, we demonstrated that both the expression and membrane transport ratio of glucose transporter 1 (GLUT1), which is responsible for glucose transport in fetal hepatocytes, were upregulated, accompanied by increased expression of N-glycosyltransferase STT3A, which contributes to the N-glycosylation of GLUT1. In vitro, we identified that AT1-AA increased glucose uptake, the expression and membrane transport ratio of GLUT1 and the expression of STT3A in HepG2 cell lines via separating membrane and cytosolic proteins and immunofluorescence, resulting in the decreased glucose content in the medium. The GLUT1 inhibitor WZB117 reversed the decreases in glucose content in the medium, the increases in glucose uptake, the increases in the expression and membrane transport ratio of GLUT1 caused by AT1-AA. The N-glycosyltransferase inhibitor NGI as well as si-STT3A reversed the AT1-AA-induced upregulation of the STT3A-GLUT1-glucose uptake effect. This study demonstrates that AT1-AA lowers the blood glucose level of fetuses via the STT3A-GLUT1-glucose uptake axis in liver.

Current understanding of autoantibody against angiotensin II type 1 receptor in preeclampsia

Preeclampsia (PE) remains a leading cause of fetal and maternal mortality. Angiotensin II type 1 receptor autoantibody (AT1-AA) is implicated in the dysregulation of the renin-angiotensin-aldosterone system. A strong relationship between AT1-AA and the occurrence and severity of PE has been confirmed in previous literature. Recent evidences suggested that AT1-AA was responsible for blood pressure elevation, reactive oxygen species synthesis, and inflammatory factors release and engaged in multiple signaling cascades. The inhibition of AT1-AA might be a potential therapeutic target in future days. Here we reviewed the current understanding of AT1-AA, aiming to provide clarity surrounding the role of AT1-AA in PE.

Active immunization using hand-push emulsification method increases the operator's risk of transcutaneous immunization

Setting up an animal model by using active immunization methods is a common means of studying immune-related diseases or producing antibodies with high titer and high activities. However, the security during the process of pathogen emulsification remains unclear. In a physical examination, we unexpectedly noticed high levels of angiotensin II type 1 receptor autoantibody (AT1-AA) specific to the immunizing antigen in the sera of some researchers who had participated in setting up active immunization animal models, and we were puzzled about the cause of AT1-AA production. In this study, we intended to investigate whether the emulsified antigen was the source of infection in these researchers, and if so, how to prevent it from occurring. AT1-AA was detected by advanced ELISA method. The participants presented higher levels of AT1-AA compared with non-participants of the same laboratory. This phenomenon remained that some factors during the process of rat model establishment may contribute to AT1-AA production. Animal and glove penetration studies indicated the emulsified antigen infection was attributed to neither aerosol or fur touch nor penetrating through gloves. However, AT1-AA level was largely decreased in the participants after they used an automatic emulsification device. Because of the strong permeability of the adjuvant, we speculated that emulsified antigen might get access to the unprotected skin of the participants accidentally during the immunization process. These results demonstrated that accidental contacts of emulsified antigens may infect researchers during the process of traditional hand-push emulsification, resulting in high specific autoantibody levels, which can be prevented by using appropriate tools.

Hyperinsulinemia precedes insulin resistance in offspring rats exposed to angiotensin II type 1 autoantibody in utero

OBJECTIVE

Insulin resistance is highly associated with an adverse intrauterine environment. We previously reported that fetal rats exposed to angiotensin II type 1 receptor (AT₁R) autoantibody (AT1-AA) displayed increased susceptibility to metabolic diseases during middle age. However, the timing of the onset of insulin resistance remains unknown. In this study, we examined the offspring of AT1-AA-positive rats, tracking the development of insulin resistance.

METHODS

Pregnant rats were intravenously injected with AT1-AA. Afterwards, we collected serum samples and liver tissues of the offspring at various stages, including gestation day 18, 3 weeks (weaning period), 18 weeks (young adulthood), and 48 weeks (middle age) after birth.

RESULTS

Compared with saline control group, hepatic vacuolar degeneration was visible in AT1-AA offspring rats as early as 3 weeks; hyperinsulinemia and impaired glucose tolerance occurred at 18 weeks of age, however, insulin resistance was not observed until 48 weeks. At 18 weeks we detected suppressed protein levels of insulin receptor (IR) but increased levels of IR substrate 1 (IRS1) in the liver of AT1-AA group rats. Interestingly, both IR and IRS1/2 were significantly decreased at 48 weeks. Liver proteomic analysis indicated that the differences in protein expression between the AT1-AA and control rats became more pronounced with age, particularly in terms of mitochondrial energy metabolism.

CONCLUSION

Rats exposed to AT1-AA in utero developed hyperinsulinemia from young adulthood which subsequently progressed to insulin resistance, and was linked with abnormal hepatic structure and impaired IR signaling. Additionally, dysregulation of energy metabolism may play a fundamental role in predisposing offspring to insulin resistance.

The inhibitory effect of BKCa channels induced by autoantibodies against angiotensin II type 1 receptor is independent of AT1R

Autoantibodies against angiotensin II Type 1 receptor (AT1-AA) are routinely detected in the serum of preeclampsia patients, which results in an increase in vascular tone and an elevation in intracellular calcium concentration of rat vascular smooth muscle (VSM). The big conductance calcium-activated potassium channels (BKCa channels) account for the dominant outward currents in VSMCs, contributing to membrane hyperpolarization and vasodilation. In the present study, we investigated the effect of AT1-AA on BKCa channels. A preeclampsia model was established by passively immunizing healthy pregnant BALB/c mice with AT1-AA extracted from hybridoma culture supernatant. Blood pressure, serum AT1-AA levels, and urinary protein were measured in the immunized mice. BKCa channel expression was detected using qRT-PCR and immunohistochemical technique. The patch-clamp technique was used to record the single currents of BKCa channels in the HEK293T cells that had been transfected. AT1-AA immunized mice exhibited elevated AT1-AA and urinary protein levels compared with mice of the vehicle group. Systolic blood pressure was also increased in the immunized group. BKCa channel β1-subunit expression was reduced in the mesenteric arteries of immunized mice. AT1-AA could inhibit the BKCa currents and the inhibitory effects were not completely reversed following the application of valsartan, an inhibitor of AT1 receptor. In conclusion, AT1-AA could decrease BKCa expression and inhibit BKCa activity independent of AT1R. These inhibitory effects are likely to be contributory factors in the promotion of increased vascular tone caused by AT1-AA in preeclampsia.

The agonistic autoantibodies to the angiotensin II type 1 receptor in pregnancies complicated by hypertensive disorders

Introduction: The etiology and pathogenesis of pregnancy-related hypertensive disorders is complex and multifactorial. The aim of our study is the investigation of the differences in the autoantibodies against angiotensin II type 1 receptor (AT1-AA) titers among pregnant patients with chronic hypertension, gestational hypertension, and preeclampsia compared to the healthy pregnant women. Patients and methods: We created three study groups (preeclampsia [n = 16], chronic hypertension [n = 13], gestational hypertension [n = 17]) and the control group consisting of 17 healthy pregnant women. Every compared group was matched for mother's age, parity, prepregnancy BMI, and gestational age at time of recruitment into study. The autoantibodies titer were assessed using commercially available ELISA kit. Results: We found a statistically higher AT1-AA titer in the group of patients with gestational hypertension (GH) and preeclampsia (PE) compared to healthy normotensive pregnant women (median 9.6 versus 7.8 ng/ml, p = .01 and 10.9 ng/ml versus 7.8 ng/ml, p = .02, respectively). There was no correlation between blood pressure values and AT1-AA titer in any group. We found no correlation in group with preeclampsia between urinary protein excretion and AT1-AA titer (p = .23, R = 0.32). Conclusions: We assume that pregnancy-related hypertensive disorders might be autoimmune diseases and AT1-AA contribute to the pathophysiology of the disease. Our study may have some therapeutic implications and shows the necessity of new research into the mechanisms involved in the production of AT1-AA. Such investigations might enable to inhibit the formation of these autoantibodies or elaborate another method for AT1-AA removal.

The Prognostic Role of Angiotensin II Type 1 Receptor Autoantibody in Non-Gravid Hypertension and Pre-eclampsia: A Meta-analysis and Our Studies

Angiotensin II type 1 receptor autoantibody (AT1-AA) is found in patients with non-gravid hypertension or pre-eclampsia, but the relationship is uncertain.The aim of the present study was to assess the association between AT1-AA and high blood pressure using meta-analysis, and to evaluate the prognosis value of AT1-AA for hypertensive diseases.Literature search from PubMed, Embase, and Cochrane databases were conducted using keywords "hypertension" or "pre-eclampsia," "angiotensin II receptor type 1 autoantibody," and its aliases from April 1999 to December 2015.Studies evaluating the association between AT1-AA and non-gravid hypertension or pre-eclampsia were included in this analysis. The quality of the eligible studies was assessed based on the Newcastle-Ottawa Scale with some modifications.Two researchers then independently reviewed all included studies and extracted all relevant data. Association between AT1-AA and hypertension was tested with pooled odds ratios (ORs) and 95% confidence intervals (CIs). Finally, we evaluated whether AT1-AA predicted the prognosis of hypertension by using a summary receiver-operating characteristic (ROC) curve and sensitivity analysis.Ten studies were finally included in this meta-analysis. AT1-AA showed more significant association with pre-eclampsia than that with non-gravid hypertension (pooled OR 32.84, 95% CI 17.19-62.74; and pooled OR 4.18, 95% CI 2.20-7.98, respectively). Heterogeneity among studies was also detected probably due to different hypertensive subtypes and AT1-AA measuring methods. Area under summary ROC curve (AUC) of pre-eclampsia was 0.92 (sensitivity 0.76; specificity 0.86). Area under the ROC curve of overall hypertensive diseases or non-gravid hypertension was lower than that of pre-eclampsia (0.86 and 0.72, respectively) with lower sensitivities (0.46 and 0.26, respectively).The major limitation of this analysis was the publication bias due to lack of unpublished data and the language limitation during literature search. Prospective study with large simple size and specific measuring data collection are needed to enhance our findings in the future.Our analysis confirms that elevated AT1-AA in serum is significantly associated with hypertensive disorder, especially pre-eclampsia. AT1-AA may be a valuable indicator for poorer prognosis of patients with pre-eclampsia, and could be used in patients with hypertensive disease for risk evaluation and making individual treatment decision.

Preeclampsia As Modulator of Offspring Health

A balanced intrauterine homeostasis during pregnancy is crucial for optimal growth and development of the fetus. The intrauterine environment is extremely vulnerable to multisystem pregnancy disorders such as preeclampsia, which can be triggered by various pathophysiological factors, such as angiogenic imbalance, immune responses, and inflammation. The fetus adapts to these conditions by a mechanism known as developmental programming that can lead to increased risk of chronic noncommunicable diseases in later life. This is shown in a substantial number of epidemiological studies that associate preeclampsia with increased onset of cardiovascular and metabolic diseases in the later life of the offspring. Furthermore, animal models based predominantly on one of the pathophysiological mechanism of preeclampsia, for example, angiogenic imbalance, immune response, or inflammation, do address the susceptibility of the preeclamptic offspring to increased maternal blood pressure and disrupted metabolic homeostasis. Accordingly, we extensively reviewed the latest research on the role of preeclampsia on the offspring's metabolism and cardiovascular phenotype. We conclude that future research on the pathophysiological changes during preeclampsia and methods to intervene in the harsh intrauterine environment will be essential for effective therapies.

Preparation and Biological Activity of the Monoclonal Antibody against the Second Extracellular Loop of the Angiotensin II Type 1 Receptor

The current study was to prepare a mouse-derived antibody against the angiotensin II type 1 receptor (AT1-mAb) based on monoclonal antibody technology, to provide a foundation for research on AT1-AA-positive diseases. Balb/C mice were actively immunized with the second extracellular loop of the angiotensin II type 1 receptor (AT₁R-ECII). Then, mouse spleen lymphocytes were fused with myeloma cells and monoclonal hybridomas that secreted AT1-mAb were generated and cultured, after which those in logarithmic-phase were injected into the abdominal cavity of mice to retrieve the ascites. Highly purified AT1-mAb was isolated from mouse ascites after injection with 1 × 10⁷ hybridomas. A greater amount of AT1-mAb was purified from mouse ascites compared to the cell supernatant of hybridomas. AT1-mAb purified from mouse ascites constricted the thoracic aorta of mice and increased the beat frequency of neonatal rat myocardial cells via the AT₁R, identical to the effects of AT1-AA extracted from patients' sera. Murine blood pressure increased after intravenous injection of AT1-mAb via the tail vein. High purity and good biological activity of AT1-mAb can be obtained from mouse ascites after intraperitoneal injection of monoclonal hybridomas that secrete AT1-mAb. These data provide a simple tool for studying AT1-AA-positive diseases.

The effect of prenatal pravastatin treatment on altered fetal programming of postnatal growth and metabolic function in a preeclampsia-like murine model

OBJECTIVE

Preeclampsia alters fetal programming and results in long-term metabolic consequences in the offspring. Pravastatin has been shown to prevent preeclampsia in animal models. Our aim was to characterize the effects of preeclampsia on fetal programming of adult growth and metabolic function, and evaluate the role of preventive pravastatin therapy, using a well characterized murine model.

STUDY DESIGN

CD-1 mice were injected through the tail vein with adenovirus carrying soluble fms-like tyrosine kinase 1 (sFlt-1) and randomly allocated to pravastatin (5 mg/kg/day; sFlt-1/prav, n = 7) or water (sFlt-1, n = 6) until weaning. A control group was injected with adenovirus carrying the murine immunoglobulin G2α Fc fragment (mFc, n = 8). Male and female offspring (6-8/group) were weighed every month until 6 months of age. Intraperitoneal glucose tolerance testing was performed after 16 hours of fasting at 3 and 6 months of age; glucose and insulin responses were measured.

RESULTS

sFlt-1 offspring weight was lower than mFc control (P < .001) until 2 months of age for females and 5 months of age for males (P < .001). There were no differences in postnatal growth between mFc and sFlt-1/prav offspring. At 3 and 6 months, female sFlt-1 offspring had higher glucose response compared with mFc and sFlt-1/prav. Three-month-old male sFlt-1 had lower insulin response compared with mFc offspring.

CONCLUSION

Preeclampsia alters postnatal growth and metabolic function in the adult offspring in this animal model. Maternal therapy with prav prevents some of these alterations in the offspring.

Perindopril treatment promote left ventricle remodeling in patients with heart failure screened positive for autoantibodies against angiotensin II type 1 receptor

Background

Autoantibodies specific to the angiotensin II type I receptor (anti-AT₁-AR) have been implicated in the pathology of congestive heart failure (CHF). Anti-AT₁-AR may be associated with left ventricular function in CHF patients treated with perindopril.

Methods

Synthetic angiotensin II type 1 receptor (AT₁-R) peptides served as the target antigen. ELISA was used to screen the sera of 156 CHF patients, which were divided into positive and negative groups based on their anti-AT₁-AR reactivity. Echocardiography and a 6-minute walk test were performed at baseline and after one year of perindopril therapy. The end-point events were compared over a 5-year follow-up.

Results

Final analysis covered 138 patients, including 82 positive and 56 negative. The frequency and geometric mean titre of anti-AT₁-AR were significantly lower in the positive group after one year of treatment (all P < 0.01, from 100% to 73.2% and from 1:125.3 ± 1.0 to 1:69.2 ± 1.1). Of these, 22 patients showed no antibodies. Both groups showed improvement in left ventricular end-diastole, end-systolic dimensions, ejection fraction, and a 6-minute walk test by perindopril in combination with standard treatment regime for one year (all P < 0.01). However, the 82 patients positive for anti-AT₁-AR showed more pronounced improvement than the 56 negative patients (all P < 0.05). However, after 5 years of follow-up, the rate of all causes and cardiovascular mortality attributable to any cause and the re-hospitalisation rate showed no significant differences between the two groups (all P > 0.05).

Conclusions

Perindopril treatment significantly decreased the frequency and geometric mean titre in patients positive for anti-AT₁-AR, even to complete ablation. These patients showed greater improvement in left ventricular remodeling and heart function than negative that in patients after one year of perindopril treatment in combination with standard treatment, but no significant differences in endpoint events were observed in the following 5 years. Anti-AT₁-AR might be a useful biomarker of over-activation of the renin-angiotensin-aldosterone system for clinical medication.

Adipose tissue renin-angiotensin-aldosterone system (RAAS) and progression of insulin resistance

This review focuses on the expression of the key components of the renin-angiotensin-aldosterone axis in fat tissue. At the center of this report is the role of RAAS in normal and excessive fat mass enlargement, the leading etiology of insulin resistance. Understanding the expression and regulation of RAAS components in various fat depots allows insight not only into the processes by which these complex patterns are modified by the enlargement of adipose tissue, but also into their impact on local and systemic response to insulin.