Oxidative phosphorylation promoting p32 critically maintains mitochondria function essential for terminal goblet cell differentiation. Reduced colonic p32 expression in ulcerative colitis patients possibly explains a great range of diseasespecific histopathological hallmarks. BACKGROUND & AIMS:Cell differentiation in the colonic crypt is driven by a metabolic switch from glycolysis to mitochondrial oxidation. Mitochondrial and goblet cell dysfunction have been attributed to the pathology of ulcerative colitis (UC). We hypothesized that p32/gC1qR/HABP1, which critically maintains oxidative phosphorylation, is involved in goblet cell differentiation and hence in the pathogenesis of UC.METHODS: Ex vivo, goblet cell differentiation in relation to p32 expression and mitochondrial function was studied in tissue biopsies from UC patients versus controls. Functional studies were performed in goblet cell-like HT29-MTX cells in vitro. Mitochondrial respiratory chain complex V-deficient, ATP8 mutant mice were utilized as a confirmatory model. Nutritional intervention studies were performed in C57BL/6 mice. RESULTS:In UC patients in remission, colonic goblet cell differentiation was significantly decreased compared to controls in a p32-dependent manner. Plasma/serum L-lactate and colonic pAMPK level were increased, pointing at high glycolytic activity and energy deficiency. Consistently, p32 silencing in mucus-secreting HT29-MTX cells abolished butyrate-induced differentiation and induced a shift towards glycolysis. In ATP8 mutant mice, colonic p32 expression correlated with loss of differentiated goblet cells, resulting in a thinner mucus layer. Conversely, feeding mice an isocaloric glucose-free, high-protein diet increased mucosal energy supply that promoted colonic p32 level, goblet cell differentiation and mucus production. CONCLUSION:We here describe a new molecular mechanism linking mucosal energy deficiency in UC to impaired, p32-FLA 5.6.0 DTD JCMGH748 proof 7 May 2021 8:21 am ce OB dependent goblet cell differentiation that may be therapeutically prevented by nutritional intervention.

Self-sustained cell proliferation constitutes one hallmark of cancer enabled by aerobic glycolysis which is characterized by imbalanced glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) activity, named the Warburg effect. The C1q binding protein (C1QBP; gC1qR) is pivotal for mitochondrial protein translation and thus OXPHOS activity. Due to its fundamental role in balancing OXPHOS and glycolysis, c1qbp −/− mice display embryonic lethality, while gC1qR is excessively up-regulated in cancer. Although gC1qR encompasses an N-terminal mitochondrial leader it is also located in other cellular compartments. Hence, we aimed to investigate mechanisms regulating gC1qR cellular localization and its impact on tumor cell metabolism. We identified two caspase-1 cleavage sites in human gC1qR. GC1qR cleavage by active caspase-1 was unraveled as a cellular mechanism that prevents mitochondrial gC1qR import, thereby enabling aerobic glycolysis and enhanced cell proliferation. Ex vivo, tumor grading correlated with non-mitochondrial-located gC1qR as well as with caspase-1 activation in colorectal carcinoma patients. Together, active caspase-1 cleaves gC1qR and boosts aerobic glycolysis in tumor cells.

Enteroendocrine cells (EEC) produce neuropeptides, which are crucially involved in the maintenance of the intestinal barrier. Hence, EEC dysfunction is suggested to be involved in the complex pathophysiology of inflammatory bowel disease (IBD), which is characterized by decreased intestinal barrier function. However, the underlying mechanisms for EEC dysfunction are not clear and suitable models for a better understanding are lacking. Here, we demonstrate that Carboxypeptidase E (CPE) is specifically expressed in EEC of the murine colon and ileum and that its deficiency is associated with reduced intestinal levels of Neuropeptide Y (NPY) and Peptide YY (PYY), which are both produced by EEC. Moreover, cpe−/− mice exhibit an aggravated course of DSS-induced chronic colitis compared to wildtype littermates. In addition, we observed elevated mucosal IL-6 and KC transcript levels already at baseline conditions in cpe−/− mice. Moreover, supernatants obtained from isolated intestinal crypts of cpe−/− mice lead to increased IL-6 and KC expression in MODE-K cells in the presence of LPS. This effect was reversible by co-administration of recombinant NPY, suggesting a CPE mediated immunosuppressive effect in the intestines by influencing the processing of specific neuropeptides. In this context, the chemotaxis of bone marrow derived macrophages towards respective supernatants was enhanced. In conclusion, our data point to an anti-inflammatory role of CPE in the intestine by influencing local cytokine levels and thus regulating the migration of myeloid immune cells into the mucosa. These findings highlight the importance of EEC for intestinal homeostasis and propose EEC as potential therapeutic targets in IBD.

Background Induction of goblet cell differentiation during inflammation has been shown to be impaired in ulcerative colitis (UC) but not Crohn’s disease (CD), possibly explaining the intestinal goblet cell and mucus reduction observed in active UC. A metabolic switch from glycolysis to mitochondrial oxidative phosphorylation (OXPHOS) is necessary for terminal differentiation of intestinal stem cells towards goblet cells. Interestingly, intestinal energy deficiency in general and reduced level of OXPHOS in specific have been attributed to UC pathogenesis more than 30 years ago. The c1q binding protein (C1QBP; gC1qR) is indispensable for the maintenance of OXPHOS. Nevertheless, experimental evidence linking mitochondrial dysfunction with goblet cell depletion and C1QBP expression are still missing. Methods Goblet cell differentiation was studied in human biopsies from UC patients in remission, in mucus-producing HT29MTX cells and in a conplastic mouse strain with diminished mitochondrial OXPHOS activity. Furthermore, mice were fed an experimental diet to shift cellular energy production from glycolysis to OXPHOS and mucosal cell differentiation was compared with mice on an isocaloric control diet. Results In vitro, siRNA experiments in HT29MTX cells showed that butyrate-induced expression of goblet cell differentiation factor KLF4 is highly dependent on gC1qR expression. Interestingly, the latter was significantly reduced in human ileal and colonic sections of UC patients in remission compared with HN. OXPHOS-deficient conplastic B6-mt FVB mice further confirmed these findings by depicting diminished klf4 expression, lowered goblet cell numbers, a thinned intestinal mucus layer and signs of intestinal inflammation. Finally, via nutritional intervention in C57BL/6 mice we were able to increase gC1qR level and to induce goblet cell differentiation via hath1 and klf4 compared with controls. Conclusion Taken together, we here describe a new pathway linking low intestinal expression of OXPHOS-regulating gC1qR to impaired goblet cell differentiation, mucus reduction and mucosal inflammation, which could be possibly reversed by nutritional intervention.

To enable rapid proliferation, colorectal tumor cells up-regulate epidermal growth factor receptor (EGFR) signaling and aerobic glycolysis, resulting in substantial lactate release into the tumor microenvironment and impaired anti-tumor immune responses. We hypothesized that a nutritional intervention designed to reduce aerobic glycolysis may boost the EGFR-directed antibody (Ab)-based therapy of pre-existing colitis-driven colorectal carcinoma (CRC). CRC development was induced by azoxymethane (AOM) and dextran sodium sulfate (DSS) administration to C57BL/6 mice. AOM/DSS-treated mice were fed a glucose-free, high-protein diet (GFHPD) or an isoenergetic control diet (CD) in the presence or absence of an i.p. injection of an anti-EGFR mIgG2a or respective controls. AOM/DSS-treated mice on a GFHPD displayed a reduced systemic glucose metabolism associated with reduced oxidative phosphorylation (OXPHOS) complex IV expression and diminished tumor loads. Comparable but not additive to an anti-EGFR-Ab therapy, the GFHPD was accompanied by enhanced tumoral goblet cell differentiation and decreased colonic PD-L1 and splenic CD3ε, as well as PD-1 immune checkpoint expression. In vitro, glucose-free, high-amino acid culture conditions reduced proliferation but improved goblet cell differentiation of murine and human CRC cell lines MC-38 and HT29-MTX in combination with down-regulation of PD-L1 expression. We here found GFHPD to systemically dampen glycolysis activity, thereby reducing CRC progression with a similar efficacy to EGFR-directed antibody therapy.