Microbial-Driven Butyrate Regulates Jejunal Homeostasis in Piglets During the Weaning Stage

Microbe-derived butyrate plays an important role in the gut health of young mammals during the weaning stage. A greater understanding of how butyrate regulates intestinal development is necessary for overcoming post-weaning diarrheal diseases. We aimed to investigate whether jejunal microbial metabolite butyrate modulates the apoptosis/proliferation balance and immune response in piglets during the post-weaning period of the first 3 weeks of life. On the one hand, during the first week post-weaning, the relative abundances of the dominant bacterial families Erysipelotrichaceae (P < 0.01) and Lachnospiraceae (P < 0.01) were increased, which induced decreases in both butyrate production (P < 0.05) and its receptor (G-protein coupled receptor 43) expression (P < 0.01). The resulting intestinal inflammation (inferred from increased TNF-α and IFN-γ expression) contributed to the onset of cell apoptosis and the inhibition of cell-proliferation along the crypt-villus axis, which were followed by impaired jejunal morphology (i.e., increased crypt-depth) (P < 0.05) and intestinal dysfunction (i.e., decreased creatine kinase, and lactate dehydrogenase) (P < 0.05). On the other hand, during the second week post-weaning, the relative abundances of Lactobacillaceae (P < 0.01) and Ruminococcaceae (P < 0.05) were increased. The increases were accompanied by increased butyrate production (P < 0.05) and its receptor expression (P < 0.01), leading to the inhibition of cell apoptosis and the stimulation of cell proliferation via decreased pro-inflammatory cytokines and thereby the improvement of intestinal development and function. Herein, this study demonstrates that microbial-driven butyrate might be a key modulator in the maintenance of intestinal homeostasis after weaning. The findings suggest that strategies to promote butyrate production can maintain the apoptosis/proliferation balance via minimizing intestinal inflammation, and thereby improving post-weaning jejunal adaptation toward gut health

Inside-out Ca2+ signalling prompted by STIM1 conformational switch

Store-operated Ca(2+) entry mediated by STIM1 and ORAI1 constitutes one of the major Ca(2+) entry routes in mammalian cells. The molecular choreography of STIM1–ORAI1 coupling is initiated by endoplasmic reticulum (ER) Ca(2+) store depletion with subsequent oligomerization of the STIM1 ER-luminal domain, followed by its redistribution towards the plasma membrane to gate ORAI1 channels. The mechanistic underpinnings of this inside-out Ca(2+) signalling were largely undefined. By taking advantage of a unique gain-of-function mutation within the STIM1 transmembrane domain (STIM1-TM), here we show that local rearrangement, rather than alteration in the oligomeric state of STIM1-TM, prompts conformational changes in the cytosolic juxtamembrane coiled-coil region. Importantly, we further identify critical residues within the cytoplasmic domain of STIM1 (STIM1-CT) that entail autoinhibition. On the basis of these findings, we propose a model in which STIM1-TM reorganization switches STIM1-CT into an extended conformation, thereby projecting the ORAI-activating domain to gate ORAI1 channels

A new set of reference housekeeping genes for the normalization RT-qPCR data from the intestine of piglets during weaning.

The intestinal mucosal development of piglets (Sus scrofa) during the weaning stage is important to their disease susceptibility and later growth. Quantitative real-time PCR (RT-qPCR) is commonly used to screen for differentially expressed genes and, for accurate results, proper reference housekeeping genes are essential. Here we assessed the mRNA expression of 18 well-known candidate reference genes at different parts of the gastrointestinal tract (GIT) of piglets during the weaning process by RT-qPCR assay. GeNorm analysis revealed that B2M/HMBS/HPRT1 were the three most stable reference genes and GAPDH was the least stable gene in the duodenum, jejunum, ileum, colon, and whole GIT. BestKeeper analysis found that B2M/HMBS/PGK11, HMBS/B2M/HPRT1, B2M/HMBS/HSPCB, B2M/HPRT1/HMBS, and B2M/HMBS/HPRT1 were the most stable genes in the duodenum, jejunum, ileum, colon, and whole GIT, respectively, whereas GAPDH, B-actin, and 18S rRNA were the least stable genes at different parts of the GIT. To confirm the crucial role of appropriate housekeeping genes in obtaining reliable results, we analyzed the expression of ALP using each of the 18 reference genes to normalize the RT-qPCR data. We found that the expression levels of ALP normalized using the most stable reference genes (B2M/HMBS/HPRT1) differed greatly from the expression levels obtained when the data were normalized using the least stable genes (GAPDH, B-actin, and 18S). We concluded that B2M/HMBS/HPRT1 were the optimal reference genes for gene expression analysis by RT-qPCR in the intestinal mucosal development stages of piglets at weaning. Our findings provide a set of porcine housekeeping reference genes for studies of mRNA expression in different parts of the pig intestine

Acute and Chronic Effects of Protein Kinase-D Signaling on Cardiac Energy Metabolism

Protein kinase-D (PKD) is increasingly recognized as a key regulatory signaling hub in cardiac glucose uptake and also a major player in the development of hypertrophy. Glucose is one of the predominant energy substrates for the heart to support contraction. However, a cardiac substrate switch toward glucose over-usage is associated with the development of cardiac hypertrophy. Hence, regulation of PKD activity must be strictly coordinated. This review provides mechanistic insights into the acute and chronic regulatory functions of PKD signaling in the healthy and hypertrophied heart. First an overview of the activation pathways of PKD1, the most abundant isoform in the heart, is provided. Then the various regulatory roles of the PKD isoforms in the heart in relation to cardiac glucose and fatty acid metabolism, contraction, morphology, function, and the development of cardiac hypertrophy are described. Finally, these findings are integrated and the possibility of targeting this kinase as a novel strategy to combat cardiac diseases is discussed