Project description:Glucagon receptor deficient liver during postnatal development: fig S5a-S5c in Solloway et al. livers from ko and wt GCGR mice at various developmental stages
Project description:Glucagon receptor (GCGR) is a potential target for diabetes therapy. Several emerging GCGR antagonism-based therapies are under pre-clinical and clinical development. However, the GCGR antagonism as well as GCGR deficient animal accompanied with α-cell hyperplasia and hyperglucagonemia, which may limit the application of GCGR antagonism. To better understand the physiological changes in the α cells during the GCGR disruption, we performed the single cell sequencing of α cells isolated from control and gcgr-/- zebrafish. We found that α cells in gcgr-/- zebrafish dramatically increased glucagon (both gcga and gcgb) expression, we also found that several transcriptional factors that regulate glucagon expression were also increased. Based on the sequencing data, we further experimentally confirmed that gcgr-/- up-regulated glucagon mRNA level by in situ hybridization, and the gcgr-/- increased glucagon promoter activity indicated by reporter line Tg(gcga: GFP). Moreover, our results also revealed that α cells increased glucagon granule population and glucagon level in gcgr-/- zebrafish. These data suggested that hyperglucagonemia in the organism of GCGR antagonism not only contributed by the α-cell hyperplasia but also contributed by the increased glucagon expression and secretion from α cells. Our study provided more comprehensive understanding of physiological changes of α-cell during the GCGR disruption.
Project description:Glucagon, an essential regulator of glucose and lipid metabolism, also promotes weight loss, in part through potentiation of fibroblast-growth factor 21 (FGF21) secretion. However, FGF21 is only a partial mediator of metabolic actions ensuing from GcgR-activation, prompting us to search for additional pathways. Intriguingly, chronic GcgR agonism increases plasma bile acid levels. We hypothesized that GcgR agonism regulates energy metabolism, at least in part, through farnesoid X receptor (FXR). To test this hypothesis, we studied whole body and liver-specific FXR knockout (FXR∆liver) mice. Chronic GcgR agonist (IUB288) administration in diet-induced obese (DIO) Gcgr, Fgf21 and Fxr whole body or liver-specific knockout (∆liver) mice failed to reduce body weight (BW) when compared to wildtype (WT) mice. IUB288 increased energy expenditure and respiration in DIO WT mice, but not FXR∆liver mice. GcgR agonism increased [14C]-palmitate oxidation in hepatocytes isolated from WT mice in a dose-dependent manner, an effect blunted in hepatocytes from FXR∆liver mice. Our data clearly demonstrate that control of whole body energy expenditure by GcgR agonism requires intact FXR signaling in the liver. This heretofore-unappreciated aspect of glucagon biology has implications for the use of GcgR agonism in the therapy of metabolic disorders.
Project description:Glucagon and glucagon-like peptide-1 (GLP-1) are hormones involved in energy homeostasis. GLP-1 receptor (GLP-1R) agonism reduces food intake and delays gastric emptying, and glucagon receptor (GCGR) agonism increases energy expenditure by thermogenesis. BI 456906 is a subcutaneous, once-weekly injectable dual GLP-1R/GCGR agonist in development for the treatment of obesity or non-alcoholic steatohepatitis. Here we show that BI 456906 is a potent dual agonist with an extended half-life in human plasma. Key GLP-1R-mediated mechanisms of reduced food intake, delayed gastric emptying and improved glucose tolerance were confirmed in GLP-1R knockout mice. GCGR activity was confirmed by reduced plasma amino acids, increased hepatic expression of nicotinamide N-methyltransferase and increased energy expenditure. BI 456906 produced greater bodyweight reductions than maximally efficacious semaglutide doses and modulated gene expression, including genes involved in amino acid metabolism. BI 456906 is a potent dual agonist that produces bodyweight-lowering effects through both GLP-1R and GCGR agonism.
Project description:Co-agonists at the glucagon-like peptide-1/glucagon receptors (GLP1R/GCGR) show promise as treatments for metabolic dysfunction-associated steatotic liver disease (MASLD). Unlike GLP1, glucagon directly acts on the liver to reduce fat content. To date most metabolic studies have looked at heavily GLP1R-biased co-agonists and have not distinguished weight-loss versus weight loss-independent effects. We demonstrate that 24 days’ treatment with Dicretin, a GLP1/GCGR co-agonist with high potency at the GCGR, in mice with hepatic steatosis secondary to diet-induced obesity leads to superior reduction of hepatic lipid content when compared to Semaglutide or equivalent weight loss by calorie restriction. Hepatic transcriptomic and metabolomic profiling demonstrated many changes that were unique to Dicretin-treated mice: some known targets of glucagon signalling and others with as yet unclear physiological significance. Our study supports the development of GLP1/GCGR co-agonists for treatment of MASLD and related conditions.
Project description:Pancreas volume or mass varies more than 3-fold among adult humans. The heterogeneity is likely the result of genetics, diseases, and nutrition. Dietary protein intake and blood amino acid levels are known to affect pancreas mass, but the underlying mechanism is not well understood. The goal of this study is to determine how increased blood amino acid level (hyperaminoacidemia) induces pancreas expansion.Multiple complementary mouse and zebrafish models were used to study the impact of hyperaminoacidemia on pancreatic mass, acinar cell size and proliferation. Blood amino acid levels were manipulated by dietary protein content, or by pharmacologic or genetic interruption of glucagon signaling (IGS). The activation of mammalian target of rapamycin complex 1 (mTORC1) and Yes-associated protein 1 (YAP) were determined by pS6 and YAP staining. Sirolimus administration in mice and knockdown of solute carrier family 38 member 5b (slc38a5b) and yap/taz in zebrafish were used to determine the role of mTORC1, SLC38A5 and YAP/TAZ in acinar cell proliferation and pancreas expansion. We found that the IGS-induced pancreas expansion was the result of acinar cell proliferation and hypertrophy. Hyperaminoacidemia was the likely mediator as pancreas expansion was blunted by a low protein diet in mice and by knocking down the most highly expressed amino acid transporter gene, slc38a5b, in zebrafish lacking both glucagon receptor genes (gcgr-/-). In GCGR-Ab treated mice, inhibition of mTORC1 attenuated both hyperplasia and hypertrophy of acinar cells. There was a gene expression signature of YAP activation in acinar cells, consistent with increased YAP-expressing acinar cells in GCGR-Ab treated mice and increased fraction of acinar cells with nuclear YAP1 in gcgr-/- zebrafish. Knocking down yap1 or taz decreased mTORC1 activity and acinar cell hyperplasia and hypertrophy in gcgr-/- zebrafish. Hyperaminoacidemia leads to acinar cell proliferation and hypertrophy via activation of both mTORC1 and YAP pathways. The study discovered a previously unrecognized role of the YAP/Taz pathway in hyperaminoacidemia-induced acinar cell hypertrophy and hyperplasia.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:We collected whole genome testis expression data from hybrid zone mice. We integrated GWAS mapping of testis expression traits and low testis weight to gain insight into the genetic basis of hybrid male sterility.