Placental Transcriptome Profiling in Subtypes of Diabetic Pregnancies Is Strongly Confounded by Fetal Sex.

The placenta is a temporary organ with a unique structure and function to ensure healthy fetal development. Placental dysfunction is involved in pre-eclampsia (PE), fetal growth restriction, preterm birth, and gestational diabetes mellitus (GDM). A diabetic state affects maternal and fetal health and may lead to functional alterations of placental metabolism, inflammation, hypoxia, and weight, amplifying the fetal stress. The placental molecular adaptations to the diabetic environment and the adaptive spatio-temporal consequences to elevated glucose or insulin are largely unknown (2). We aimed to identify gene expression signatures related to the diabetic placental pathology of placentas from women with diabetes mellitus. Human placenta samples (n = 77) consisting of healthy controls, women with either gestational diabetes mellitus (GDM), type 1 or type 2 diabetes, and women with GDM, type 1 or type 2 diabetes and superimposed PE were collected. Interestingly, gene expression differences quantified by total RNA sequencing were mainly driven by fetal sex rather than clinical diagnosis. Association of the principal components with a full set of clinical patient data identified fetal sex as the single main explanatory variable. Accordingly, placentas complicated by type 1 and type 2 diabetes showed only few differentially expressed genes, while possible effects of GDM and diabetic pregnancy complicated by PE were not identifiable in this cohort. We conclude that fetal sex has a prominent effect on the placental transcriptome, dominating and confounding gene expression signatures resulting from diabetes mellitus in settings of well-controlled diabetic disease. Our results support the notion of placenta as a sexual dimorphic organ.

Diabetic pregnancy as a novel risk factor for cardiac dysfunction in the offspring-the heart as a target for fetal programming in rats.

AIMS/HYPOTHESIS: The impact of diabetic pregnancy has been investigated extensively regarding offspring metabolism; however, little is known about the influence on the heart. We aimed to characterise the effects of a diabetic pregnancy on male adult offspring cardiac health after feeding a high-fat diet in an established transgenic rat model. METHODS: We applied our rat model for maternal type 2 diabetes characterised by maternal insulin resistance with hyperglycaemia and hyperinsulinaemia. Diabetes was induced preconceptionally via doxycycline-induced knock down of the insulin receptor in transgenic rats. Male wild-type offspring of diabetic and normoglycaemic pregnancies were raised by foster mothers, followed up into adulthood and subgroups were challenged by a high-fat diet. Cardiac phenotype was assessed by innovative speckle tracking echocardiography, circulating factors, immunohistochemistry and gene expression in the heart. RESULTS: When feeding normal chow, we did not observe differences in cardiac function, gene expression and plasma brain natriuretic peptide between adult diabetic or normoglycaemic offspring. Interestingly, when being fed a high-fat diet, adult offspring of diabetic pregnancy demonstrated decreased global longitudinal (-14.82 ± 0.59 vs -16.60 ± 0.48%) and circumferential strain (-23.40 ± 0.57 vs -26.74 ± 0.34%), increased relative wall thickness (0.53 ± 0.06 vs 0.37 ± 0.02), altered cardiac gene expression, enlarged cardiomyocytes (106.60 ± 4.14 vs 87.94 ± 1.67 µm), an accumulation of immune cells in the heart (10.27 ± 0.30 vs 6.48 ± 0.48 per fov) and higher plasma brain natriuretic peptide levels (0.50 ± 0.12 vs 0.12 ± 0.03 ng/ml) compared with normoglycaemic offspring on a high-fat diet. Blood pressure, urinary albumin, blood glucose and body weight were unaltered between groups on a high-fat diet. CONCLUSIONS/INTERPRETATION: Diabetic pregnancy in rats induces cardiac dysfunction, left ventricular hypertrophy and altered proinflammatory status in adult offspring only after a high-fat diet. A diabetic pregnancy itself was not sufficient to impair myocardial function and gene expression in male offspring later in life. This suggests that a postnatal high-fat diet is important for the development of cardiac dysfunction in rat offspring after diabetic pregnancy. Our data provide evidence that a diabetic pregnancy is a novel cardiac risk factor that becomes relevant when other challenges, such as a high-fat diet, are present.

Kidney Injury Caused by Preeclamptic Pregnancy Recovers Postpartum in a Transgenic Rat Model.

Preeclampsia (PE) is characterized by the onset of hypertension (≥140/90 mmHg) and presence of proteinuria (>300 mg/L/24 h urine) or other maternal organ dysfunctions. During human PE, renal injuries have been observed. Some studies suggest that women with PE diagnosis have an increased risk to develop renal diseases later in life. However, in human studies PE as a single cause of this development cannot be investigated. Here, we aimed to investigate the effect of PE on postpartum renal damage in an established transgenic PE rat model. Female rats harboring the human-angiotensinogen gene develop a preeclamptic phenotype after mating with male rats harboring the human-renin gene, but are normotensive before and after pregnancy. During pregnancy PE rats developed mild tubular and glomerular changes assessed by histologic analysis, increased gene expression of renal damage markers such as kidney injury marker 1 and connective-tissue growth factor, and albuminuria compared to female wild-type rats (WT). However, four weeks postpartum, most PE-related renal pathologies were absent, including albuminuria and elevated biomarker expression. Only mild enlargement of the glomerular tuft could be detected. Overall, the glomerular and tubular function were affected during pregnancy in the transgenic PE rat. However, almost all these pathologies observed during PE recovered postpartum.

Short-Chain Fatty Acid Propionate Protects From Hypertensive Cardiovascular Damage.

BACKGROUND: Arterial hypertension and its organ sequelae show characteristics of T cell-mediated inflammatory diseases. Experimental anti-inflammatory therapies have been shown to ameliorate hypertensive end-organ damage. Recently, the CANTOS study (Canakinumab Antiinflammatory Thrombosis Outcome Study) targeting interleukin-1ß demonstrated that anti-inflammatory therapy reduces cardiovascular risk. The gut microbiome plays a pivotal role in immune homeostasis and cardiovascular health. Short-chain fatty acids (SCFAs) are produced from dietary fiber by gut bacteria and affect host immune homeostasis. Here, we investigated effects of the SCFA propionate in 2 different mouse models of hypertensive cardiovascular damage. METHODS: To investigate the effect of SCFAs on hypertensive cardiac damage and atherosclerosis, wild-type NMRI or apolipoprotein E knockout-deficient mice received propionate (200 mmol/L) or control in the drinking water. To induce hypertension, wild-type NMRI mice were infused with angiotensin II (1.44 mg·kg-1·d-1 subcutaneous) for 14 days. To accelerate the development of atherosclerosis, apolipoprotein E knockout mice were infused with angiotensin II (0.72 mg·kg-1·d-1 subcutaneous) for 28 days. Cardiac damage and atherosclerosis were assessed using histology, echocardiography, in vivo electrophysiology, immunofluorescence, and flow cytometry. Blood pressure was measured by radiotelemetry. Regulatory T cell depletion using PC61 antibody was used to examine the mode of action of propionate. RESULTS: Propionate significantly attenuated cardiac hypertrophy, fibrosis, vascular dysfunction, and hypertension in both models. Susceptibility to cardiac ventricular arrhythmias was significantly reduced in propionate-treated angiotensin II-infused wild-type NMRI mice. Aortic atherosclerotic lesion area was significantly decreased in propionate-treated apolipoprotein E knockout-deficient mice. Systemic inflammation was mitigated by propionate treatment, quantified as a reduction in splenic effector memory T cell frequencies and splenic T helper 17 cells in both models, and a decrease in local cardiac immune cell infiltration in wild-type NMRI mice. Cardioprotective effects of propionate were abrogated in regulatory T cell-depleted angiotensin II-infused mice, suggesting the effect is regulatory T cell-dependent. CONCLUSIONS: Our data emphasize an immune-modulatory role of SCFAs and their importance for cardiovascular health. The data suggest that lifestyle modifications leading to augmented SCFA production could be a beneficial nonpharmacological preventive strategy for patients with hypertensive cardiovascular disease.

Speckle Tracking Echocardiography: New Ways of Translational Approaches in Preeclampsia to Detect Cardiovascular Dysfunction.

Several studies have shown that women with a preeclamptic pregnancy exhibit an increased risk of cardiovascular disease. However, the underlying molecular mechanisms are unknown. Animal models are essential to investigate the causes of this increased risk and have the ability to assess possible preventive and therapeutic interventions. Using the latest technologies such as speckle tracking echocardiography (STE), it is feasible to map subclinical changes in cardiac diastolic and systolic function as well as structural changes of the maternal heart. The aim of this work is to compare cardiovascular changes in an established transgenic rat model with preeclampsia-like pregnancies with findings from human preeclamptic pregnancies by STE. The same algorithms were used to evaluate and compare the changes in echoes of human and rodents. Parameters of functionality such as global longitudinal strain (animal -23.54 ± 1.82% vs. -13.79 ± 0.57%, human -20.60 ± 0.47% vs. -15.45 ± 1.55%) as well as indications of morphological changes such as relative wall thickness (animal 0.20 ± 0.01 vs. 0.25 ± 0.01, human 0.34 ± 0.01 vs. 0.40 ± 0.02) are significantly altered in both species after preeclamptic pregnancies. Thus, the described rat model simulates the human situation quite well and is a valuable tool for future investigations regarding cardiovascular changes. STE is a unique technique that can be applied in animal models and humans with a high potential to uncover cardiovascular maladaptation and subtle pathologies.

Accurate assessment of LV function using the first automated 2D-border detection algorithm for small animals - evaluation and application to models of LV dysfunction.

Echocardiography is the most commonly applied technique for non-invasive assessment of cardiac function in small animals. Manual tracing of endocardial borders is time consuming and varies with operator experience. Therefore, we aimed to evaluate a novel automated two-dimensional software algorithm (Auto2DE) for small animals and compare it to the standard use of manual 2D-echocardiographic assessment (2DE). We hypothesized that novel Auto2DE will provide rapid and robust data sets, which are in agreement with manually assessed data of animals.2DE and Auto2DE were carried out using a high-resolution imaging-system for small animals. First, validation cohorts of mouse and rat cine loops were used to compare Auto2DE against 2DE. These data were stratified for image quality by a blinded expert in small animal imaging. Second, we evaluated 2DE and Auto2DE in four mouse models and four rat models with different cardiac pathologies.Automated assessment of LV function by 2DE was faster than conventional 2DE analysis and independent of operator experience levels. The accuracy of Auto2DE-assessed data in healthy mice was dependent on cine loop quality, with excellent agreement between Auto2DE and 2DE in cine loops with adequate quality. Auto2DE allowed for valid detection of impaired cardiac function in animal models with pronounced cardiac phenotypes, but yielded poor performance in diabetic animal models independent of image quality.Auto2DE represents a novel automated analysis tool for rapid assessment of LV function, which is suitable for data acquisition in studies with good and very good echocardiographic image quality, but presents systematic problems in specific pathologies.

Disturbed Placental Imprinting in Preeclampsia Leads to Altered Expression of DLX5, a Human-Specific Early Trophoblast Marker.

BACKGROUND: Preeclampsia is a complex and common human-specific pregnancy syndrome associated with placental pathology. The human specificity provides both intellectual and methodological challenges, lacking a robust model system. Given the role of imprinted genes in human placentation and the vulnerability of imprinted genes to loss of imprinting changes, there has been extensive speculation, but no robust evidence, that imprinted genes are involved in preeclampsia. Our study aims to investigate whether disturbed imprinting contributes to preeclampsia. METHODS: We first aimed to confirm that preeclampsia is a disease of the placenta by generating and analyzing genome-wide molecular data on well-characterized patient material. We performed high-throughput transcriptome analyses of multiple placenta samples from healthy controls and patients with preeclampsia. Next, we identified differentially expressed genes in preeclamptic placentas and intersected them with the list of human imprinted genes. We used bioinformatics/statistical analyses to confirm association between imprinting and preeclampsia and to predict biological processes affected in preeclampsia. Validation included epigenetic and cellular assays. In terms of human specificity, we established an in vitro invasion-differentiation trophoblast model. Our comparative phylogenetic analysis involved single-cell transcriptome data of human, macaque, and mouse preimplantation embryogenesis. RESULTS: We found disturbed placental imprinting in preeclampsia and revealed potential candidates, including GATA3 and DLX5, with poorly explored imprinted status and no prior association with preeclampsia. As a result of loss of imprinting, DLX5 was upregulated in 69% of preeclamptic placentas. Levels of DLX5 correlated with classic preeclampsia markers. DLX5 is expressed in human but not in murine trophoblast. The DLX5high phenotype resulted in reduced proliferation, increased metabolism, and endoplasmic reticulum stress-response activation in trophoblasts in vitro. The transcriptional profile of such cells mimics the transcriptome of preeclamptic placentas. Pan-mammalian comparative analysis identified DLX5 as part of the human-specific regulatory network of trophoblast differentiation. CONCLUSIONS: Our analysis provides evidence of a true association among disturbed imprinting, gene expression, and preeclampsia. As a result of disturbed imprinting, the upregulated DLX5 affects trophoblast proliferation. Our in vitro model might fill a vital niche in preeclampsia research. Human-specific regulatory circuitry of DLX5 might help explain certain aspects of preeclampsia.

A Grhl2-dependent gene network controls trophoblast branching morphogenesis.

Healthy placental development is essential for reproductive success; failure of the feto-maternal interface results in pre-eclampsia and intrauterine growth retardation. We found that grainyhead-like 2 (GRHL2), a CP2-type transcription factor, is highly expressed in chorionic trophoblast cells, including basal chorionic trophoblast (BCT) cells located at the chorioallantoic interface in murine placentas. Placentas from Grhl2-deficient mouse embryos displayed defects in BCT cell polarity and basement membrane integrity at the chorioallantoic interface, as well as a severe disruption of labyrinth branching morphogenesis. Selective Grhl2 inactivation only in epiblast-derived cells rescued all placental defects but phenocopied intraembryonic defects observed in global Grhl2 deficiency, implying the importance of Grhl2 activity in trophectoderm-derived cells. ChIP-seq identified 5282 GRHL2 binding sites in placental tissue. By integrating these data with placental gene expression profiles, we identified direct and indirect Grhl2 targets and found a marked enrichment of GRHL2 binding adjacent to genes downregulated in Grhl2(-/-) placentas, which encoded known regulators of placental development and epithelial morphogenesis. These genes included that encoding the serine protease inhibitor Kunitz type 1 (Spint1), which regulates BCT cell integrity and labyrinth formation. In human placenta, we found that human orthologs of murine GRHL2 and its targets displayed co-regulation and were expressed in trophoblast cells in a similar domain as in mouse placenta. Our data indicate that a conserved Grhl2-coordinated gene network controls trophoblast branching morphogenesis, thereby facilitating development of the site of feto-maternal exchange. This might have implications for syndromes related to placental dysfunction.

CD74-Downregulation of Placental Macrophage-Trophoblastic Interactions in Preeclampsia.

RATIONALE: We hypothesized that cluster of differentiation 74 (CD74) downregulation on placental macrophages, leading to altered macrophage-trophoblast interaction, is involved in preeclampsia. OBJECTIVE: Preeclamptic pregnancies feature hypertension, proteinuria, and placental anomalies. Feto-placental macrophages regulate villous trophoblast differentiation during placental development. Disturbance of this well-balanced regulation can lead to pathological pregnancies. METHODS AND RESULTS: We performed whole-genome expression analysis of placental tissue. CD74 was one of the most downregulated genes in placentas from preeclamptic women. By reverse transcriptase-polymerase chain reaction, we confirmed this finding in early-onset (<34 gestational week, n=26) and late-onset (≥34 gestational week, n=24) samples from preeclamptic women, compared with healthy pregnant controls (n=28). CD74 protein levels were analyzed by Western blot and flow cytometry. We identified placental macrophages to express CD74 by immunofluorescence, flow cytometry, and RT-PCR. CD74-positive macrophages were significantly reduced in preeclamptic placentas compared with controls. CD74-silenced macrophages showed that the adhesion molecules ALCAM, ICAM4, and Syndecan-2, as well as macrophage adhesion to trophoblasts were diminished. Naive and activated macrophages lacking CD74 showed a shift toward a proinflammatory signature with an increased secretion of tumor necrosis factor-α, chemokine (C-C motif) ligand 5, and monocyte chemotactic protein-1, when cocultured with trophoblasts compared with control macrophages. Trophoblasts stimulated by these factors express more CYP2J2, sFlt1, TNFα, and IL-8. CD74-knockout mice showed disturbed placental morphology, reduced junctional zone, smaller placentas, and impaired spiral artery remodeling with fetal growth restriction. CONCLUSIONS: CD74 downregulation in placental macrophages is present in preeclampsia. CD74 downregulation leads to altered macrophage activation toward a proinflammatory signature and a disturbed crosstalk with trophoblasts.

The TetO rat as a new translational model for type 2 diabetic retinopathy by inducible insulin receptor knockdown.

AIMS/HYPOTHESIS: Although the renin-angiotensin system plays an important role in the progression of diabetic retinopathy, its influence therein has not been systematically evaluated. Here we test the suitability of a new translational model of diabetic retinopathy, the TetO rat, for addressing the role of angiotensin-II receptor 1 (AT1) blockade in experimental diabetic retinopathy. METHODS: Diabetes was induced by tetracycline-inducible small hairpin RNA (shRNA) knockdown of the insulin receptor in rats, generating TetO rats. Systemic treatment consisted of an AT1 blocker (ARB) at the onset of diabetes, following which, 4-5 weeks later the retina was analysed in vivo and ex vivo. Retinal function was assessed by Ganzfeld electroretinography (ERG). RESULTS: Retinal vessels in TetO rats showed differences in vessel calibre, together with gliosis. The total number and the proportion of activated mononuclear phagocytes was increased. TetO rats presented with loss of retinal ganglion cells (RGC) and ERG indicated photoreceptor malfunction. Both the inner and outer blood-retina barriers were affected. The ARB treated group showed reduced gliosis and an overall amelioration of retinal function, alongside RGC recovery, whilst no statistically significant differences in vascular and inflammatory features were detected. CONCLUSIONS/INTERPRETATION: The TetO rat represents a promising translational model for the early neurovascular changes associated with type 2 diabetic retinopathy. ARB treatment had an effect on the neuronal component of the retina but not on the vasculature.

Protective Function of Ahnak1 in Vascular Healing after Wire Injury.

AIM: Vascular remodeling following injury substantially accounts for restenosis and adverse clinical outcomes. In this study, we investigated the role of the giant scaffold protein Ahnak1 in vascular healing after endothelial denudation of the murine femoral artery. METHODS: The spatiotemporal expression pattern of Ahnak1 and Ahnak2 was examined using specific antibodies and real-time quantitative PCR. Following wire-mediated endothelial injury of Ahnak1-deficient mice and wild-type (WT) littermates, the processes of vascular healing were analyzed. RESULTS: Ahnak1 and Ahnak2 showed a mutually exclusive vascular expression pattern, with Ahnak1 being expressed in the endothelium and Ahnak2 in the medial cells in naïve WT arteries. After injury, a marked increase of Ahnak1- and Ahnak2-positive cells at the lesion site became evident. Both proteins showed a strong upregulation in neointimal cells 14 days after injury. Ahnak1-deficient mice showed delayed vascular healing and dramatically impaired re-endothelialization that resulted in prolonged adverse vascular remodeling, when compared to the WT littermates. CONCLUSION: The large scaffold and adaptor proteins Ahnak1 and Ahnak2 exhibit differential expression patterns and functions in naïve and injured arteries. Ahnak1 plays a nonredundant protective role in vascular healing.

Hypertensive retinopathy in a transgenic angiotensin-based model.

Severe hypertension destroys eyesight. The RAS (renin-angiotensin system) may contribute to this. This study relied on an established angiotensin, AngII (angiotensin II)-elevated dTGR (double-transgenic rat) model and same-background SD (Sprague-Dawley) rat controls. In dTGRs, plasma levels of AngII were increased. We determined the general retinal phenotype and observed degeneration of ganglion cells that we defined as vascular degeneration. We also inspected relevant gene expression and lastly observed alterations in the outer blood-retinal barrier. We found that both scotopic a-wave and b-wave as well as oscillatory potential amplitude were significantly decreased in dTGRs, compared with SD rat controls. However, the b/a-wave ratio remained unchanged. Fluorescence angiography of the peripheral retina indicated that exudates, or fluorescein leakage, from peripheral vessels were increased in dTGRs compared with controls. Immunohistological analysis of blood vessels in retina whole-mount preparations showed structural alterations in the retina of dTGRs. We then determined the general retinal phenotype. We observed the degeneration of ganglion cells, defined vascular degenerations and finally found differential expression of RAS-related genes and angiogenic genes. We found the expression of both human angiotensinogen and human renin in the hypertensive retina. Although the renin gene expression was not altered, the AngII levels in the retina were increased 4-fold in the dTGR retina compared with that in SD rats, a finding with mechanistic implications. We suggest that alterations in the outer blood-retinal barrier could foster an area of visual-related research based on our findings. Finally, we introduce the dTGR model of retinal disease.

An increased population of regulatory T cells improves the pathophysiology of placental ischemia in a rat model of preeclampsia.

The reduced uterine perfusion pressure (RUPP) rat model of preeclampsia exhibits much of the pathology characterizing this disease, such as hypertension, inflammation, suppressed regulatory T cells (TRegs), reactive oxygen species (ROS), and autoantibodies to the ANG II type I receptor (AT1-AA) during pregnancy. The objective of this study was to determine whether supplementation of normal pregnant (NP) TRegs into RUPP rats would attenuate the pathophysiology associated with preeclampsia during pregnancy. CD4(+)/CD25(+) T cells were isolated from spleens of NP and RUPP rats, cultured, and injected into gestation day (GD) 12 normal pregnant rats that underwent the RUPP procedure on GD 14. On GD 1, mean arterial pressure (MAP) was recorded, and blood and tissues were collected for analysis. One-way ANOVA was used for statistical analysis. MAP increased from 99 ± 2 mmHg in NP (n = 12) to 127 ± 2 mmHg in RUPP (n = 21) but decreased to 118 ± 2 mmHg in RUPP+NP TRegs (n = 17). Circulating IL-6 and IL-10 were not significantly changed, while circulating TNF-α and IL-17 were significantly decreased after supplementation of TRegs. Placental and renal ROS were 339 ± 58.7 and 603 ± 88.1 RLU·min(-1)·mg(-1) in RUPP and significantly decreased to 178 ± 27.8 and 171 ± 55.6 RLU·min(-1)·mg(-1), respectively, in RUPP+NP TRegs; AT1-AA was 17.81 ± 1.1 beats per minute (bpm) in RUPP but was attenuated to 0.50 ± 0.3 bpm with NP TRegs. This study demonstrates that NP TRegs can significantly improve inflammatory mediators, such as IL-17, TNF-α, and AT1-AA, which have been shown to increase blood pressure during pregnancy.

Maternal haemodynamics in Hypertensive Disorders of Pregnancy under antihypertensive therapy (HyperDiP): study protocol for a prospective observational case-control study.

INTRODUCTION: Hypertensive disorders of pregnancy (HDP) are associated with a high incidence of maternal and perinatal morbidity and mortality. HDP, in particular pre-eclampsia, have been determined as risk factors for future cardiovascular disease. Recently, the common hypothesis of pre-eclampsia being a placental disorder was challenged as numerous studies show evidence for short-term and long-term cardiovascular changes in pregnancies affected by HDP, suggesting a cardiovascular origin of the disease. Despite new insights into the pathophysiology of HDP, concepts of therapy remain unchanged and evidence for improved maternal and neonatal outcome by using antihypertensive agents is lacking. METHODS AND ANALYSIS: A prospective observational case-control study, including 100 women with HDP and 100 healthy controls, which will assess maternal haemodynamics using the USCOM 1A Monitor and Arteriograph along with cardiovascular markers (soluble fms-like kinase 1/placental-like growth factor, N-terminal pro-B type natriuretic peptide) in women with HDP under antihypertensive therapy, including a follow-up at 3 months and 1 year post partum, will be conducted over a 50-month period in Vienna. A prospective, longitudinal study of cardiovascular surrogate markers conducted in Oslo will serve as a comparative cohort for the Vienna cohort of haemodynamic parameters in pregnancy including a longer follow-up period of up to 3 years post partum. Each site will provide a dataset of a patient group and a control group and will be assessed for the outcome categories USCOM 1A measurements, Arteriograph measurements and Angiogenic marker measurements. To estimate the effect of antihypertensive therapy on outcome parameters, ORs with 95% CIs will be computed. Longitudinal changes of outcome parameters will be compared between normotensive and hypertensive pregnancies using mixed-effects models. ETHICS AND DISSEMINATION: Ethical approval has been granted to all participating centres. Results will be published in international peer-reviewed journals and will be presented at national and international conferences.

Functional changes of the gastric bypass microbiota reactivate thermogenic adipose tissue and systemic glucose control via intestinal FXR-TGR5 crosstalk in diet-induced obesity.

BACKGROUND: Bariatric surgery remains the most effective therapy for adiposity reduction and remission of type 2 diabetes. Although different bariatric procedures associate with pronounced shifts in the gut microbiota, their functional role in the regulation of energetic and metabolic benefits achieved with the surgery are not clear. METHODS: To evaluate the causal as well as the inherent therapeutic character of the surgery-altered gut microbiome in improved energy and metabolic control in diet-induced obesity, an antibiotic cocktail was used to eliminate the gut microbiota in diet-induced obese rats after gastric bypass surgery, and gastric bypass-shaped gut microbiota was transplanted into obese littermates. Thorough metabolic profiling was combined with omics technologies on samples collected from cecum and plasma to identify adaptions in gut microbiota-host signaling, which control improved energy balance and metabolic profile after surgery. RESULTS: In this study, we first demonstrate that depletion of the gut microbiota largely reversed the beneficial effects of gastric bypass surgery on negative energy balance and improved glucolipid metabolism. Further, we show that the gastric bypass-shaped gut microbiota reduces adiposity in diet-induced obese recipients by re-activating energy expenditure from metabolic active brown adipose tissue. These beneficial effects were linked to improved glucose homeostasis, lipid control, and improved fatty liver disease. Mechanistically, these effects were triggered by modulation of taurine metabolism by the gastric bypass gut microbiota, fostering an increased abundance of intestinal and circulating taurine-conjugated bile acid species. In turn, these bile acids activated gut-restricted FXR and systemic TGR5 signaling to stimulate adaptive thermogenesis. CONCLUSION: Our results establish the role of the gut microbiome in the weight loss and metabolic success of gastric bypass surgery. We here identify a signaling cascade that entails altered bile acid receptor signaling resulting from a collective, hitherto undescribed change in the metabolic activity of a cluster of bacteria, thereby readjusting energy imbalance and metabolic disease in the obese host. These findings strengthen the rationale for microbiota-targeted strategies to improve and refine current therapies of obesity and metabolic syndrome. Video Abstract Bariatric Surgery (i.e. RYGB) or the repeated fecal microbiota transfer (FMT) from RYGB donors into DIO (diet-induced obesity) animals induces shifts in the intestinal microbiome, an effect that can be impaired by oral application of antibiotics (ABx). Our current study shows that RYGB-dependent alterations in the intestinal microbiome result in an increase in the luminal and systemic pool of Taurine-conjugated Bile acids (TCBAs) by various cellular mechanisms acting in the intestine and the liver. TCBAs induce signaling via two different receptors, farnesoid X receptor (FXR, specifically in the intestines) and the G-protein-coupled bile acid receptor TGR5 (systemically), finally resulting in metabolic improvement and advanced weight management. BSH, bile salt hydrolase; BAT brown adipose tissue.

Roux-en-Y gastric bypass contributes to weight loss-independent improvement in hypothalamic inflammation and leptin sensitivity through gut-microglia-neuron-crosstalk.

OBJECTIVE: Hypothalamic inflammation and endoplasmic reticulum (ER) stress are extensively linked to leptin resistance and overnutrition-related diseases. Surgical intervention remains the most efficient long-term weight-loss strategy for morbid obesity, but mechanisms underlying sustained feeding suppression remain largely elusive. This study investigated whether Roux-en-Y gastric bypass (RYGB) interacts with obesity-associated hypothalamic inflammation to restore central leptin signaling as a mechanistic account for post-operative appetite suppression. METHODS: RYGB or sham surgery was performed in high-fat diet-induced obese Wistar rats. Sham-operated rats were fed ad libitum or by weight matching to RYGB via calorie restriction (CR) before hypothalamic leptin signaling, microglia reactivity, and the inflammatory pathways were examined to be under the control of gut microbiota-derived circulating signaling. RESULTS: RYGB, other than CR-induced adiposity reduction, ameliorates hypothalamic gliosis, inflammatory signaling, and ER stress, which are linked to enhanced hypothalamic leptin signaling and responsiveness. Mechanistically, we demonstrate that RYGB interferes with hypothalamic ER stress and toll-like receptor 4 (TLR4) signaling to restore the anorexigenic action of leptin, which most likely results from modulation of a circulating factor derived from the altered gut microbial environment upon RYGB surgery. CONCLUSIONS: Our data demonstrate that RYGB interferes with hypothalamic TLR4 signaling to restore the anorexigenic action of leptin, which most likely results from modulation of a circulating factor derived from the post-surgical altered gut microbial environment.

Intrauterine Exposure to Diabetic Milieu Does Not Induce Diabetes and Obesity in Male Adulthood in a Novel Rat Model.

Several studies show an association of maternal diabetes during pregnancy with adverse offspring metabolic health. Other studies, however, suggest that this effect might be biased by obesity, which is independently associated with offspring metabolic disease and often coexistent to maternal diabetes. We performed a prospective study in a rat model to test the hypothesis that the burden of a diabetic pregnancy without obesity deteriorates metabolic health in male offspring. We generated maternal type 2 diabetes before conception that persisted during pregnancy by knockdown of the insulin receptor in small hairpin RNA-expressing transgenic rats. Male WT (wild type) offspring were followed up until adulthood and metabolically challenged by high-fat diet. Blood glucose was measured continuously via a telemetry device. Glucose and insulin tolerance tests were performed, and body composition was analyzed. Weight gain and glucose levels during adolescence and adulthood were similar in male offspring of diabetic and control pregnancies. Body weight and fat mass after high-fat diet, as well as glucose and insulin tolerance tests, were unaltered between male adult offspring of both groups. Glycemic control consisting of up to 49 000 individual glucose measures was comparable between both groups. Intrauterine exposure to maternal hyperglycemia and hyperinsulinemia without obesity had no impact on male offspring metabolic health in our model. We conclude that the intrauterine exposure itself does not represent a mechanism for fetal programming of diabetes and obesity in our model. Other maternal metabolic parameters during pregnancy, such as obesity, might impact long-term offspring metabolic health.

Nitric oxide sensitive guanylyl cyclase activity decreases during cerebral postnatal development because of a reduction in heterodimerization.

Soluble guanylyl cyclase (sGC) is the major physiological receptor for nitric oxide (NO) throughout the central nervous system. Three different subunits form the alpha(1)/beta(1) and alpha(2)/beta(1) heterodimeric enzymes that catalyze the reaction of GTP to the second messenger cGMP. Both forms contain a prosthetic heme group which binds NO and mediates activation by NO. A number of studies have shown that NO/cGMP signaling plays a major role in neuronal cell differentiation during development of the central nervous system. In the present work, we studied regulation and expression of sGC in brain of rats during postnatal development using biochemical methods. We consistently observed a surprising decrease in cerebral NO sensitive enzyme activity in adult animals in spite of stable expression of sGC subunits. Total hemoprotein heme content was decreased in cerebrum of adult animals, likely because of an increase in heme oxygenase activity. But the loss of sGC activity was not simply because of heme loss in intact heterodimeric enzymes. This was shown by enzyme activity determinations with cinaciguat which can be used to test heme occupancy in intact heterodimers. A reduction in heterodimerization in cerebrum of adult animals was demonstrated by co-precipitation analysis of sGC subunits. This explained the observed decrease in NO sensitive guanylyl cyclase activity in cerebrum of adult animals. We conclude that differing efficiencies in heterodimer formation may be an important reason for the lack of correlation between sGC protein expression and sGC activity that has been described previously. We suggest that heterodimerization of sGC is a regulated process that changes during cerebral postnatal development because of still unknown signaling mechanisms.

Statins Reverse Postpartum Cardiovascular Dysfunction in a Rat Model of Preeclampsia.

Preeclampsia is associated with increased cardiovascular long-term risk; however, the underlying functional and structural mechanisms are unknown. We investigated maternal cardiac alterations after preeclampsia. Female rats harboring the human angiotensinogen gene [TGR(hAogen)L1623] develop a preeclamptic phenotype with hypertension and albuminuria during pregnancy when mated with male rats bearing the human renin gene [TGR(hRen)L10J] but behave physiologically normal before and after pregnancy. Furthermore, rats were treated with pravastatin. We tested the hypothesis that statins are a potential therapeutic intervention to reduce cardiovascular alterations due to simulated preeclamptic pregnancy. Although hypertension persists for only 8 days in pregnancy, former preeclampsia rats exhibit significant cardiac hypertrophy 28 days after pregnancy observed in both speckle tracking echocardiography and histological staining. In addition, fibrosis and capillary rarefaction was evident. Pravastatin treatment ameliorated the remodeling and improved cardiac output postpartum. Preeclamptic pregnancy induces irreversible structural changes of cardiac hypertrophy and fibrosis, which can be moderated by pravastatin treatment. This pathological cardiac remodeling might be involved in increased cardiovascular risk in later life.

High-sensitivity cardiac troponin I in women with a history of early-onset preeclampsia.

OBJECTIVE: Preeclampsia is associated with an elevated risk of cardiovascular disease later in life. Women with a history of preeclampsia are at risk of developing hypertension as well as ischemic heart disease. Identification of women at the highest risk is important to initiate preventive strategies. We investigated whether high-sensitivity cardiac troponin I (hs-cTnI) levels are associated with a history of early-onset preeclampsia, and with hypertension in these high-risk women. METHODS: Approximately 9-10 years after pregnancy, hs-cTnI levels were measured for 339 women of the Preeclampsia Risk Evaluation in FEMales cohort, consisting of 177 women with a history of early-onset preeclampsia and 162 women with a previous uncomplicated index pregnancy. Associations were analyzed using several statistical tests and linear regression analysis. RESULTS: The median hs-cTnI levels (IQR) were 2.50 ng/l (2.30) in women with a history of early-onset preeclampsia and 2.35 ng/l (2.50) in women without a history of preeclampsia, P = 0.53. Among women with a history of early-onset preeclampsia, the hs-cTnI levels were higher in women who were hypertensive compared with their normotensive counterparts (medians 2.60 versus 2.30; P = 0.03). In addition, blood pressure levels increased with increasing hs-cTnI levels. CONCLUSION: We did not find a difference in hs-cTnI levels between women with and without a history of early-onset preeclampsia. Nonetheless, hs-cTnI levels were statistically significantly higher in current hypertensive women with a history of preeclampsia compared with their normotensive counterparts. Therefore, hs-cTnI levels might improve risk prediction for women at the highest risk of cardiovascular disease.