Deletion of intestinal epithelial AMP-activated protein kinase alters distal colon permeability but not glucose homeostasis.

Abstract Objective The intestinal epithelial barrier (IEB) restricts the passage from the lumen through the paracellular space of potentially harmful substances and microbes, and rupture of its integrity is associated with a variety of gastrointestinal disorders and extra-digestive diseases. Increased IEB permeability has been linked to disruption of metabolic homeostasis leading to obesity and type 2 diabetes. Interestingly, recent studies have uncovered compelling evidence that the AMP-activated protein kinase (AMPK) signaling pathway plays important role in the maintenance of epithelial cell barrier function. However, our understanding of the function of intestinal AMPK in the regulation of IEB and glucose homeostasis remains sparse. Methods We generated mice lacking the two α1 and α2 AMPK catalytic subunits specifically in intestinal epithelial cells (IEC AMPK KO) and determined the physiological consequences of intestinal-specific deletion of AMPK in response to high-fat diet (HFD)-induced obesity. We combined histological, functional and integrative analyses to interrogate the outcomes of gut AMPK loss on intestinal permeability in vivo and ex vivo, on the development of obesity and metabolic dysfunction. We also determined the impact of intestinal AMPK deletion in an inducible mouse model (i-IEC AMPK KO) by measuring IEB function, glucose homeostasis and composition of gut microbiota by fecal 16S rRNA sequencing. Results While there were no differences in in vivo intestinal permeability in WT and IEC AMPK KO mice, ex vivo transcellular and paracellular permeability, measured in Ussing chambers, were significantly increased in the distal colon of IEC AMPK KO mice. This was associated with a reduction in pSer425 GIV phosphorylation, a marker of leaky gut barrier. However, expression of tight junction proteins in intestinal epithelial cells and pro-inflammatory cytokines in the lamina propria were not different between genotypes. Although the HFD-fed AMPK KO mice displayed suppression of the stress polarity signaling pathway and a concomitant increase in colon permeability, loss of intestinal AMPK did not exacerbate body weight gain or adiposity. Deletion of AMPK was also not sufficient to alter glucose homeostasis or the glucose lowering action of metformin in control diet (CD)- or HFD-fed mice. Finally, CD-fed i-IEC AMPK KO mice also presented higher permeability in distal colon under homeostatic conditions but, surprisingly, this was not detected upon HFD feeding. Alteration in epithelial barrier function in i-IEC AMPK KO mice was associated with a shift in the gut microbiota composition with higher levels of Clostridiales and Desulfovibrionales. Conclusion Altogether our results have unraveled a significant role for intestinal AMPK in the maintenance of IEB integrity in distal colon but not in the regulation of glucose homeostasis. Our data also highlight the complex interaction between gut microbiota and host AMPK.