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Glycemic and bodyweight effects of GIPR coding variation reflect differences in surface expression and intrinsic functional impairment.

The glucose-dependent insulinotropic polypeptide receptor (GIPR) is a major therapeutic target in type 2 diabetes and obesity. Missense variation in GIPR could confer phenotypic effects through alterations to constitutive activity or functional responses to GIP or pharmacological agonists. In this study, we aimed to provide a deep understanding of the molecular mechanisms that underpin the cellular and physiological impacts of GIPR coding variation by studying 30 GIPR coding variants in cellular models and pancreatic islets. Many variants showed impaired GIP-induced cyclic adenosine monophosphate responses, and population-based association analysis highlighted that these loss-of-function variants decrease body mass index but increase glycemia. In many cases, reduced function was partly driven by reduced expression at the cell surface due to impaired stability and redirection toward proteasomal degradation. Molecular dynamics simulations suggest distinct variant-induced perturbations in inter- and intrahelical interactions, which interfere with receptor stability. This study highlights the mechanisms and consequences of GIPR coding variation, which may have implications for the therapeutic targeting of this receptor.

Humans

Structural basis for small-molecule agonism at GCGR and GIPR via a conserved intracellular allosteric site.

The glucagon receptor (GCGR) and gastric inhibitory polypeptide receptor (GIPR) are class B GPCRs that regulate glucose homeostasis and energy balance, making them key targets for type 2 diabetes and obesity. Achieving preferential Gs signaling at these receptors with small molecules remains an unmet challenge. Here, we report SIM1, developed through optimization of the PCO371 scaffold, which exhibits preferential Gs signaling at GCGR and GIPR with minimal detectable β-arrestin recruitment and substantially improved efficacy at GIPR. Cryo-EM structures of SIM1-GCGR-Gs (2.53 Å) and SIM1-GIPR-Gs (2.74 Å) reveal a shared intracellular allosteric interface at the receptor-G protein coupling region, distinct from extracellular peptide recognition. Structural comparison with GLP1R suggests that intracellular conformational constraints contribute to differential SIM1 responsiveness, which is restored by targeted mutations. Guided by these insights, analogs SIM2 and SIM3 exhibited up to 20-fold enhanced potency while maintaining an apparent preferential Gs signaling profile. These findings reveal a conserved intracellular allosteric activation mechanism across multiple class B GPCRs and identify SIM1 and its analogs as valuable chemical tools for investigating receptor-specific intracellular allosteric regulation and G protein-preferential signaling.

GCGR

The effect of sex and endurance exercise training on the incretin signaling pathway in 17 rat tissues.

Incretin-based pharmacotherapies, particularly glucagon-like peptide-1 (GLP-1) receptor agonists, have transformed the treatment of type 2 diabetes, with demonstrated benefits across multiple organ systems. Their success has driven the investigation of related gut-derived hormones, most prominently dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) receptor agonists, but extend to other targets with similar metabolic functions. For this class of drugs, the extent to which organ health improvements are secondary to improved systemic glycemic control versus direct tissue signaling remains unclear, partly because receptor availability across tissues is poorly annotated. We leveraged data from the Molecular Transducers of Physical Activity Consortium to annotate incretin receptor expression across 17 tissues in Fischer 344 rats and the Genotype-Tissue Expression Portal for human-level receptor expression. Furthermore, given the role of exercise in the preservation of muscle mass during weight loss, we analyzed the effects of 1, 2, 4, or 8 wk of treadmill exercise training on incretin-related signaling at the epigenetic, transcript, and protein levels. Endurance training elicited sex- and tissue-specific changes in incretin receptor expression, including downregulation of Gcgr across brown adipose, adrenal glands, and white adipose tissue (WAT). Training-induced Gipr regulation occurred in the adrenal glands, brain cortex, and hippocampus. Collectively, these findings contribute to the map of incretin receptor biology and identify exercise-responsive regulatory axes that may underlie synergistic effects of exercise and incretin-based therapies on weight management and metabolic health.NEW & NOTEWORTHY This study provides the first multiomic, multitissue description of incretin signaling receptor expression and regulation in response to endurance exercise training. We identify time point and sex-specific changes in incretin signaling across tissues, highlighting training effects on Gcgr, Gipr, and Sctr regulation in the adrenals, WAT, and brain. These findings help establish an exercise-responsive incretin signaling axis that may identify interactions from incretin-based therapies and exercise-based lifestyle interventions.

Animals

GLP-1 Receptor Agonist and GIP/GLP-1 Receptor Dual Agonist Therapeutics at the Intersection of Alcohol Use Disorder, Obesity, and Cardiometabolic Dysfunction.

The co-occurrence of metabolic dysfunction and heavy alcohol consumption contributes substantially to global morbidity, particularly through its impact on liver disease progression. Glucagon-like peptide-1 receptor (GLP1R) agonists and glucose-dependent insulinotropic polypeptide receptor (GIPR)/GLP1R dual agonists, currently approved for the treatment of diabetes and obesity and under investigation for metabolic dysfunction-associated steatohepatitis, are considered for repurposing to reduce alcohol consumption and stabilize metabolic health in heavy-drinking populations. This review summarizes existing evidence, highlights ongoing research, and outlines key unanswered questions regarding this therapeutic potential and the paradigm shift toward metabolic circuit-based interventions in addiction treatment. The dual-target GIPR/GLP1R approach could fill a critical gap for individuals struggling with both heavy alcohol consumption and metabolic dysfunction.

Alcohol use disorder

Low-pass whole-genome sequencing reveals genomic diversity and ecotype-specific adaptation in indigenous Tigrayan chickens.

Indigenous chickens play a critical role in food security and climate resilience in smallholder systems, yet their genomic diversity and adaptive potential remain insufficiently characterised. This study employed low-pass whole-genome sequencing (LP-WGS; 0.2-1.99×) to investigate genomic diversity, population structure, inbreeding and candidate environment-associated genomic variation in 33 chickens from highland, midland, and lowland agroecologies in the Tigray region of northern Ethiopia. After imputation and stringent filtering, 23.4 million high-confidence SNPs were retained, including ~ 17% novel variants, indicating substantial uncharacterised genetic diversity in these populations. SNP density (13.8 ± 8.6 SNPs/kb) was comparable to values reported from high-coverage Ethiopian chicken datasets, demonstrating the suitability of LP-WGS for population genomics in resource-limited settings. Marked differences in genomic diversity were observed among ecotypes: midland chickens showed the highest nucleotide diversity (π = 0.00267), followed by lowland (π = 0.00233), whereas highland chickens showed the lowest diversity (π = 0.00203) and elevated genomic inbreeding (FROH and FHOM ≈ 0.18). Population structure analyses revealed clear genetic separation among ecotypes. PCA (13.91% variation explained) distinguished lowland chickens along PC1 and separated highland from midland along PC2, while ADMIXTURE and FST patterns supported three major ancestral genomic backgrounds. Functional annotation of private missense variants uncovered distinct adaptive signatures reflecting the contrasting agroecological conditions. Highland chickens showed enrichment of candidate genes potentially involved in physiological processes relevant to high-altitude environments, including cold response, angiogenesis, cardiovascular regulation and metabolic homeostasis (eg., PARP1, ACOX2, ITGB3, EDNRB, SOX8, and SOX10). Midland chickens exhibited candidate signals of selection in genes with known roles in innate antiviral immunity, bacterial defence and inflammatory regulation (eg., BAK1, CLSTN1, CYSLTR1, CYSLTR2, CXCR7, GIPR, DSCAM, GDAP1, TLR3, TLR4, TLR7, IFIH1, ADORA1, EPHB1, and TMPRSS2). Lowland chickens displayed candidate variants associated with heat-stress response, DNA damage repair, oxidative balance and cardiovascular support under extreme temperatures (e.g., MLH1, BDKRB1, GPR19, FLT1, CCL18, TGM2, and RAMP3). Overall, the results indicate substantial genomic differentiation among ecotypes and suggest candidate environment-associated genetic divergence across Tigray's diverse agroecological zones. These populations may represent important reservoirs of adaptive genetic variation for climate-resilient poultry breeding, warranting further functional validation and conservation-oriented management.

Animals