Bile acids induce Ca2+ signaling and membrane permeabilizations in vagal nodose ganglion neurons

Vagal Sensory Gut-Brain Pathways That Control Eating-Satiety and Beyond

The vagus nerve is the body's primary sensory conduit from gut to brain, traditionally viewed as a passive relay for satiety signals. However, emerging evidence reveals a far more complex system-one that actively encodes diverse aspects of meal-related information, from mechanical stretch to nutrient content, metabolic state, and even microbial metabolites. This review challenges the view of vagal afferent neurons (VANs) as simple meal-termination sensors and highlights their specialized subpopulations, diverse sensory modalities, and downstream brain circuits, which shape feeding behavior, metabolism, and cognition. We integrate recent advances from single-cell transcriptomics, neural circuit mapping, and functional imaging to examine how VANs contribute to gut-brain communication beyond satiety, including their roles in food reward and memory formation. By synthesizing the latest research and highlighting emerging directions for the field, this review provides a comprehensive update on vagal sensory pathways and their role as integrators of meal information.

The impact of 3-sulfo-taurolithocholic acid on ATPase activity in patients' colorectal cancer and normal colon tissues, and its hepatic effects in rodents

Colorectal cancer is influenced by genetic mutations, lifestyle factors, and diet, particularly high fat intake, which raises bile acid levels in the intestinal lumen. This study hypothesized that bile acids contribute to tumorigenesis by disrupting ion transport and ATPase activity in the intestinal mucosa. The effects of 3-sulfo-taurolithocholic acid (TLC-S) on ATPase activity were investigated in colorectal cancer samples from 10 patients, using adjacent healthy tissue as controls, and in rodent liver function. ATPase activity was measured spectrophotometrically by determining inorganic phosphorus (Pi) in postmitochondrial fractions. Ca2+ dynamics were assessed in isolated mouse hepatocytes with fluorescence imaging, and rat liver mitochondria were studied using polarographic methods to evaluate respiration and oxidative phosphorylation. TLC-S increased Na+/K+ ATPase activity by 1.5 times in colorectal cancer samples compared to controls (p ≤ 0.05). In healthy mucosa, TLC-S decreased Mg2+ ATPase activity by 3.6 times (p ≤ 0.05), while Mg2+ ATPase activity in cancer tissue remained unchanged. TLC-S had no significant effect on Ca2+ ATPase activity in healthy colon mucosa but showed a trend toward decreased activity in cancer tissue. In rat liver, TLC-S decreased Ca2+ ATPase and Na+/K+ ATPase activities while increasing basal Mg2+ ATPase activity (p ≤ 0.05). Additionally, TLC-S induced cytosolic Ca2+ signals in mouse hepatocytes, partially attenuated by NED-19, an NAADP antagonist (p ≤ 0.05). TLC-S also reduced the V3 respiration rate of isolated rat liver mitochondria during α-ketoglutarate oxidation. These findings suggest that TLC-S modulates ATPase activity differently in cancerous and healthy colon tissues, playing a role in colorectal cancer development. In rat liver, TLC-S affects mitochondrial activity and ATPase function, contributing to altered cytosolic calcium levels, providing insight into the mechanistic effects of bile acids on colorectal cancer and liver function.

Functional engineering of human iPSC-derived parasympathetic neurons enhances responsiveness to gastrointestinal hormones

Food-derived biological signals are transmitted to the brain via peripheral nerves through the paracrine activity of gastrointestinal (GI) hormones. The signal transduction circuit of the brain-gut axis has been analyzed in animals; however, species-related differences and animal welfare concerns necessitate investigation using in vitro human experimental models. Here, we focused on the receptors of five GI hormones (CCK, GLP1, GLP2, PYY, and serotonin (5-HT)), and established human induced pluripotent stem cell (iPSC) lines that functionally expressed each receptor. Compared to the original iPSCs, iPSCs expressing one of the receptors did not show any differences in global mRNA expression, genomic stability, or differentiation capacities of the three germ layers. We induced parasympathetic neurons from these established iPSC lines to assess vagus nerve activity. We generated GI hormone receptor-expressing neurons (CCKAR, GLP1R, and NPY2R-neuron) and tested their responsiveness to each ligand using Ca2+ imaging and microelectrode array recording. GI hormone receptor-expressing neurons (GLP2R and HTR3A) were generated directly by gene induction into iPSC-derived peripheral nerve progenitors. These receptor-expressing neurons promise to contribute to a better understanding of how the body responds to GI hormones via the brain-gut axis, aid in drug development, and offer an alternative to animal studies.