PKM2/STAT1 pathway governs naïve B cell fate in germinal center formation within Peyer's patches and gut mucosal immunity

This study investigates the effects of high-protein diets on intestinal B cell development and their role in Crohn's disease (CD) pathogenesis. Our results demonstrate that a high-protein diet (HPD) combined with low-dose dextran sulfate sodium (DSS) effectively models CD in juvenile mice, leading to disrupted B cell development in Peyer's patches (PPs). This is characterized by a reduction in germinal center (GC) B cells and an increase in plasma cells in PPs, accompanied by downregulation of the PKM2/STAT1 signaling pathway in B cells, as validated through single-cell RNA sequencing (scRNA-seq), BCR sequencing (scBCR-seq) and flow cytometry. Overall design: Juvenile (3 weeks old) and adult (11 weeks old) male C57BL/6J mice were were randomly assigned to either the colitis group or control group. In the colitis group, mice were fed diets with protein levels of 14% (low protein), 20% (normal protein), 30% (moderately high protein), or 40% (high protein) for one week of adaptive feeding, followed by three cycles of low-dose DSS-induced injury. Control mice were fed either a 20% or 40% protein diet without DSS exposure, receiving normal drinking water throughout. After three cycles of interventions, the three largest visible PPs closest to the ileocecal junction were collected. Samples from three mice were pooled for each group, resulting in eight PP groups for sc-RNA and sc-BCR sequencing: juvenile groups (SD, HPD, SD+DSS, HPD+DSS) and adult groups (SD, HPD, SD+DSS, HPD+DSS).