Maternal GLP-1 receptor activation inhibits fetal growth.

Glucagon-like peptide 1 (GLP-1) regulates food intake, insulin production, and metabolism. Our recent study demonstrated that pancreatic α-cells-secreted (intraislet) GLP-1 effectively promotes maternal insulin secretion and metabolic adaptation during pregnancy. However, the role of circulating GLP-1 in maternal energy metabolism remains largely unknown. Our study aims to investigate systemic GLP-1 response to pregnancy and its regulatory effect on fetal growth. Using C57BL/6 mice, we observed a gradual decline in maternal blood GLP-1 concentrations. Subsequent administration of the GLP-1 receptor agonist semaglutide (Sem) to dams in late pregnancy revealed a modest decrease in maternal food intake during initial treatment. At the same time, no significant alterations were observed in maternal body weight or fat mass. Notably, Sem-treated dams exhibited a significant decrease in fetal body weight, which persisted even following the restoration of maternal blood glucose levels. Despite no observable change in placental weight, a marked reduction in the placenta labyrinth area from Sem-treated dams was evident. Our investigation further demonstrated a substantial decrease in the expression levels of various pivotal nutrient transporters within the placenta, including glucose transporter one and sodium-neutral amino acid transporter one, after Sem treatment. In addition, Sem injection led to a notable reduction in the capillary area, number, and surface densities within the labyrinth. These findings underscore the crucial role of modulating circulating GLP-1 levels in maternal adaptation, emphasizing the inhibitory effects of excessive GLP-1 receptor activation on both placental development and fetal growth.NEW & NOTEWORTHY Our study reveals a progressive decline in maternal blood glucagon-like peptide 1 (GLP-1) concentration. GLP-1 receptor agonist injection in late pregnancy significantly reduced fetal body weight, even after restoration of maternal blood glucose concentration. GLP-1 receptor activation significantly reduced the placental labyrinth area, expression of some nutrient transporters, and capillary development. Our study indicates that reducing maternal blood GLP-1 levels is a physiological adaptation process that benefits placental development and fetal growth.

The Essential Role of Pancreatic α-Cells in Maternal Metabolic Adaptation to Pregnancy.

Pancreatic α-cells are important in maintaining metabolic homeostasis, but their role in regulating maternal metabolic adaptations to pregnancy has not been studied. The objective of this study was to determine whether pancreatic α-cells respond to pregnancy and their contribution to maternal metabolic adaptation. With use of C57BL/6 mice, the findings of our study showed that pregnancy induced a significant increase of α-cell mass by promoting α-cell proliferation that was associated with a transitory increase of maternal serum glucagon concentration in early pregnancy. Maternal pancreatic GLP-1 content also was significantly increased during pregnancy. Using the inducible Cre/loxp technique, we ablated the α-cells (α-null) before and during pregnancy while maintaining enteroendocrine L-cells and serum GLP-1 in the normal range. In contrast to an improved glucose tolerance test (GTT) before pregnancy, significantly impaired GTT and remarkably higher serum glucose concentrations in the fed state were observed in α-null dams. Glucagon receptor antagonism treatment, however, did not affect measures of maternal glucose metabolism, indicating a dispensable role of glucagon receptor signaling in maternal glucose homeostasis. However, the GLP-1 receptor agonist improved insulin production and glucose metabolism of α-null dams. Furthermore, GLP-1 receptor antagonist Exendin (9-39) attenuated pregnancy-enhanced insulin secretion and GLP-1 restored glucose-induced insulin secretion of cultured islets from α-null dams. Together, these results demonstrate that α-cells play an essential role in controlling maternal metabolic adaptation to pregnancy by enhancing insulin secretion.

Bilateral visual acuity decline in males with choroideremia: a pooled, cross-sectional meta-analysis.

BACKGROUND: Choroideremia is a rare inherited retinal disease that leads to blindness. Visual acuity (VA) is a key outcome measure in choroideremia treatment studies, but VA decline rates change with age. An accurate understanding of the natural deterioration of VA in choroideremia is important to assess the treatment effect of new therapies in which VA is the primary outcome measure. We conducted a meta-analysis of data on individuals with choroideremia to determine the rate of VA deterioration between the better- and worse-seeing eye (BSE and WSE, respectively). METHODS: Data were collected from the prospective Natural History of the Progression of Choroideremia (NIGHT) study (613 eyes, baseline data only), studies included in a recent meta-analysis, and studies identified in a targeted literature search performed on March 25, 2020, including individual best-corrected VA (BCVA) and age data in male individuals with choroideremia. Best-corrected VA decline rates (measured by logMAR units) by age and trends in BCVA decline rates in the BSE and WSE were evaluated.  RESULTS: Data from 1037 males (1602 eyes; mean age, 41.8 years) were included. Before and after an age cutoff of 33.8 years, BCVA decline rates for the WSE were 0.0086 and 0.0219 logMAR per year, respectively. Before and after an age cutoff of 39.1 years, BCVA decline rates for the BSE were 0.00001 and 0.0203 logMAR per year, respectively. Differences in absolute BCVA and decline rates increased between the 2 eyes until age ~ 40; thereafter, differences in absolute BCVA and decline rates were similar between eyes. CONCLUSIONS: Using the largest choroideremia data set to date, this analysis demonstrates accelerated BCVA decline beginning between 30 and 40 years of age. Disparate interocular progression rates were observed before the transition age, with similar interocular progression rates after the transition age.

Adiponectin Promotes Maternal ß-Cell Expansion Through Placental Lactogen Expression.

Hypoadiponectinemia is a risk factor of gestational diabetes mellitus (GDM). Our previous study reported that adiponectin gene knockout mice (Adipoq -/- ) develop GDM due to insulin insufficiency. The main objective of this study was to elucidate the underlying mechanism through which adiponectin controls islet expansion during pregnancy. A significant reduction in ß-cell proliferation rates, ß-cell areas, and blood insulin concentrations was detected in Adipoq -/- mice at midpregnancy. Surprisingly, conditionally knocking down adiponectin receptor 1 (AdipoR1) or AdipoR2 genes in ß-cells during pregnancy did not reduce ß-cell proliferation rates or blood insulin concentrations. In vitro adiponectin treatment also failed to show any effect on ß-cell proliferation of isolated pancreatic islets. It was reported that placental lactogen (PL) plays a crucial role in pregnancy-induced maternal ß-cell proliferation. A significant decrease in phosphorylation of signal transducer and activator of transcription 5, a downstream molecule of PL signaling, was observed in islets from Adipoq -/- dams. The mRNA levels of mouse PL genes were robustly decreased in the placentas of Adipoq -/- dams. In contrast, adiponectin treatment increased PL expression in human placenta explants and JEG3 trophoblast cells. Most importantly, bovine PL injection restored ß-cell proliferation and blood insulin concentrations in Adipoq -/- dams. Together, these results demonstrate that adiponectin plays a vital role in pregnancy-induced ß-cell proliferation by promoting PL expression in trophoblast cells.

Radium-223 in combination with docetaxel in patients with castration-resistant prostate cancer and bone metastases: a phase 1 dose escalation/randomised phase 2a trial.

PURPOSE: Radium 223 dichloride (radium-223) is an alpha particle-emitting bone-directed therapy that prolongs overall survival in men with bone-predominant metastatic castration-resistant prostate cancer (mCRPC). Docetaxel is an antimicrotubule cytotoxic agent that improves survival in mCRPC. We investigated whether combining these potentially cross-sensitising agents to dually target tumour and bone would be safe and effective. PATIENTS AND METHODS: Phase 1 was a dose escalation study to define a recommended phase 2 dose (RP2D) of docetaxel and radium-223. In phase 2a, patients were randomised 2:1 to the recommended combination regimen or docetaxel at a dose of 75 mg/m2 every 3 weeks (q3w). Patients with bone-predominant mCRPC were eligible. End-points were safety, efficacy and treatment-related changes in serum and imaging biomarkers. RESULTS: Twenty patients were enrolled in phase 1; 53 patients were randomised in phase 2a: 36 to combination treatment and 17 to docetaxel alone. The RP2D for the combination was radium-223 55 kBq/kg every six weeks × 5 doses, plus docetaxel 60 mg/m2 q3w × 10 doses. Febrile neutropenia was dose limiting. A higher rate of febrile neutropenia was seen in the docetaxel monotherapy arm (15% vs 0%); the safety profile of the treatment groups was otherwise similar. The combination arm had more durable suppression of prostate-specific antigen (median time to progression, 6.6 vs 4.8 months, respectively), alkaline phosphatase (9 vs 7 months) and osteoblastic bone deposition markers. CONCLUSIONS: Radium-223 in combination with docetaxel at the RP2D was well tolerated. Exploratory efficacy data suggested enhanced antitumour activity for the combination relative to docetaxel alone. Comparative studies with end-points of clinical benefit are warranted. ClinicalTrials.gov number: NCT01106352.

Mutation of Npr2 leads to blurred tonotopic organization of central auditory circuits in mice.

Tonotopy is a fundamental organizational feature of the auditory system. Sounds are encoded by the spatial and temporal patterns of electrical activity in spiral ganglion neurons (SGNs) and are transmitted via tonotopically ordered processes from the cochlea through the eighth nerve to the cochlear nuclei. Upon reaching the brainstem, SGN axons bifurcate in a stereotyped pattern, innervating target neurons in the anteroventral cochlear nucleus (aVCN) with one branch and in the posteroventral and dorsal cochlear nuclei (pVCN and DCN) with the other. Each branch is tonotopically organized, thereby distributing acoustic information systematically along multiple parallel pathways for processing in the brainstem. In mice with a mutation in the receptor guanylyl cyclase Npr2, this spatial organization is disrupted. Peripheral SGN processes appear normal, but central SGN processes fail to bifurcate and are disorganized as they exit the auditory nerve. Within the cochlear nuclei, the tonotopic organization of the SGN terminal arbors is blurred and the aVCN is underinnervated with a reduced convergence of SGN inputs onto target neurons. The tonotopy of circuitry within the cochlear nuclei is also degraded, as revealed by changes in the topographic mapping of tuberculoventral cell projections from DCN to VCN. Nonetheless, Npr2 mutant SGN axons are able to transmit acoustic information with normal sensitivity and timing, as revealed by auditory brainstem responses and electrophysiological recordings from VCN neurons. Although most features of signal transmission are normal, intermittent failures were observed in responses to trains of shocks, likely due to a failure in action potential conduction at branch points in Npr2 mutant afferent fibers. Our results show that Npr2 is necessary for the precise spatial organization typical of central auditory circuits, but that signals are still transmitted with normal timing, and that mutant mice can hear even with these deficits.

Gata3 is a critical regulator of cochlear wiring.

Spiral ganglion neurons (SGNs) play a key role in hearing by rapidly and faithfully transmitting signals from the cochlea to the brain. Identification of the transcriptional networks that ensure the proper specification and wiring of SGNs during development will lay the foundation for efforts to rewire a damaged cochlea. Here, we show that the transcription factor Gata3, which is expressed in SGNs throughout their development, is essential for formation of the intricately patterned connections in the cochlea. We generated conditional knock-out mice in which Gata3 is deleted after SGNs are specified. Cochlear wiring is severely disrupted in these animals, with premature extension of neurites that follow highly abnormal trajectories toward their targets, as shown using in vitro neurite outgrowth assays together with time-lapse imaging of whole embryonic cochleae. Expression profiling of mutant neurons revealed a broad shift in gene expression toward a more differentiated state, concomitant with minor changes in SGN identity. Thus, Gata3 appears to serve as an "intermediate regulator" that guides SGNs through differentiation and preserves the auditory fate. As the first auditory-specific regulator of SGN development, Gata3 provides a useful molecular entry point for efforts to engineer SGNs for the restoration of hearing.

Developmental profiling of spiral ganglion neurons reveals insights into auditory circuit assembly.

The sense of hearing depends on the faithful transmission of sound information from the ear to the brain by spiral ganglion (SG) neurons. However, how SG neurons develop the connections and properties that underlie auditory processing is largely unknown. We catalogued gene expression in mouse SG neurons from embryonic day 12, when SG neurons first extend projections, up until postnatal day 15, after the onset of hearing. For comparison, we also analyzed the closely related vestibular ganglion (VG). Gene ontology analysis confirmed enriched expression of genes associated with gene regulation and neurite outgrowth at early stages, with the SG and VG often expressing different members of the same gene family. At later stages, the neurons transcribe more genes related to mature function, and exhibit a dramatic increase in immune gene expression. Comparisons of the two populations revealed enhanced expression of TGFß pathway components in SG neurons and established new markers that consistently distinguish auditory and vestibular neurons. Unexpectedly, we found that Gata3, a transcription factor commonly associated with auditory development, is also expressed in VG neurons at early stages. We therefore defined new cohorts of transcription factors and axon guidance molecules that are uniquely expressed in SG neurons and may drive auditory-specific aspects of their differentiation and wiring. We show that one of these molecules, the receptor guanylyl cyclase Npr2, is required for bifurcation of the SG central axon. Hence, our dataset provides a useful resource for uncovering the molecular basis of specific auditory circuit assembly events.

Changes in Sef levels influence auditory brainstem development and function.

During development of the CNS, secreted morphogens of the fibroblast growth factor (FGF) family have multiple effects on cell division, migration, and survival depending on where, when, and how much FGF signal is received. The consequences of misregulating the FGF pathway were studied in a mouse with decreased levels of the FGF antagonist Sef. To uncover effects in the nervous system, we focused on the auditory system, which is accessible to physiological analysis. We found that the mitogen-activated protein kinase pathway is active in the rhombic lip, a germinal zone that generates diverse types of neurons, including the cochlear nucleus complex of the auditory system. Sef is expressed immediately adjacent to the rhombic lip, overlapping with FGF15 and FGFR1, which is also present in the lip itself. This pattern suggests that Sef may normally function in non-rhombic lip cells and prevent them from responding to FGF ligand in the vicinity. Consistent with this idea, overexpression of Sef in chicks decreased the size of the auditory nuclei. Cochlear nucleus defects were also apparent in mice with reduced levels of Sef, with 13% exhibiting grossly dysmorphic cochlear nuclei and 26% showing decreased amounts of GFAP in the cochlear nucleus. Additional evidence for cochlear nucleus defects was obtained by electrophysiological analysis of Sef mutant mice, which have normal auditory thresholds but abnormal auditory brainstem responses. These results show both increases and decreases in Sef levels affect the assembly and function of the auditory brainstem.

The nodal precursor acting via activin receptors induces mesoderm by maintaining a source of its convertases and BMP4.

During early mouse development, the subtilisin-like proprotein convertases (SPC) Furin and PACE4 pattern the primitive ectoderm and visceral endoderm, presumably by activating the TGFss-related Nodal precursor. Here, mutation of the SPC motif provides direct evidence that Nodal processing is essential to specify anterior visceral endoderm and mesendoderm. Surprisingly, however, the Nodal precursor binds and activates activin receptors to maintain expression of Furin, PACE4, and Bmp4 in extraembryonic ectoderm at a distance from the Nodal source. In return, Bmp4 induces Wnt3, which amplifies Nodal expression in the epiblast and mediates induction of mesoderm. We conclude that uncleaved Nodal sustains the extraembryonic source of proprotein convertases and Bmp4 to amplify Nodal signaling in two nonredundant feedback loops with dual timescales and to localize primitive streak formation at the posterior pole. Based on mathematical modeling, we discuss how these sequential loops control cell fate.

Multiple roles for Nodal in the epiblast of the mouse embryo in the establishment of anterior-posterior patterning.

The TGFbeta family member Nodal has been shown to be involved in a variety of processes in development, including early axis formation. Here, we use a conditional gene inactivation strategy to show a specific requirement for Nodal in the epiblast. Complete inactivation of the Nodal locus in the epiblast using the Sox2-Cre deleter strain results in a failure to establish global anterior-posterior patterning, a phenotype that resembles the Nodal null phenotype. By contrast, mosaic inactivation of Nodal in the epiblast using the Mox2-Cre (MORE) deleter strain affects formation of the anterior mesendoderm and subsequent anterior neurectoderm patterning. Furthermore, ES cell chimera experiments indicate that Nodal-deficient ES cells preferentially populate the anterior compartment of the epiblast, suggesting that cell mixing in the epiblast is not random and that Nodal signaling mediates a novel anterior-posterior cell-sorting process within the epiblast before gastrulation.