In a recent study published within the journal Cell Reports, researchers in Cincinnati, USA, assessed the impact of dietary alteration to a high-fat eating regimen (HFD) on the intestine.

A major change in eating regimen over time can affect metabolism and physiology. In the US, a caloric imbalance could also be one factor contributing to obesity. From 1999 to 2018, the number of people that suffered from obesity rose from 30.5% to 42.4%, while metabolic diseases like dyslipidemia and diabetes rose from 25.3% to 34.2%. Long-term variations in eating regimen are known to cause obesity and metabolic diseases, but it surely shouldn’t be clear how quickly a change in eating regimen may cause changes within the body.

Study: A dietary change to a high-fat eating regimen initiates a rapid adaptation of the intestine. Image Credit: Alexei Logvinovich / Shutterstock

Concerning the study

In the current study, researchers assessed the response of intestinal epithelial cells to an HFD using physiological measurements and single-cell transcriptomics.

The team used indirect calorimetry to survey adult wild-type mice fed normal chow or switched to an HFD for seven days and assess the impact. First, the quantity of oxygen consumed (VO2) together with carbon dioxide expiration (VCO2) was estimated to calculate the respiratory exchange ratio (RER), which showed the first fuel source that the body metabolizes. Also, the team measured the full energy needed for homeostasis, called energy expenditure (EE).

The team also assessed whether an adaptive response within the proximal intestine toward acute HFD caused these metabolic changes in the entire body. Intestinal proliferation was examined together with the crypts’ depth and the villus’s height after one, three, or seven days on an HFD. Single-cell ribonucleic acid sequencing (scRNA-seq) was also performed on adult mice’s duodenum and jejunum epithelial cells in any respect time points. After checking the standard of the cells and filtering them, the team combined the datasets of cells obtained from mice that consumed normal chow and mice that were fed an HFD for one, three, or seven days. The traditional chow cells were used because the reference dataset.

The team further analyzed how each cluster of cells responded to HFD using differential gene expression evaluation. The transcriptional signature related to glutamate/glutamine metabolism was also evaluated using genes from the Molecular Signatures Database (MSigDB).

Results

Inside the first day of HFD feeding, RER levels decreased from around 0.9 to 0.8, and these differences were maintained over time. On the primary day, EE rose from roughly 0.2 to 0.5 kcal/min to almost 0.4 to 0.6 kcal/min. Over the course of seven days, there have been no significant differences in the quantity of water consumed or ambulatory movements. Mice fed an HFD gained weight while exhibiting higher energy intake from the primary day. After someday of consuming an HFD, these results showed that the mice’s metabolism modified over the entire body, and there can have also been changes of their intestines.

There was a rise in EdU (5-ethynyl-2’-deoxyuridine) incorporation after someday of HFD consumption. Nevertheless, the depth of intestinal crypts or the peak of the villus didn’t change. The team also assessed any alterations within the death of intestinal cells using cleaved caspase-3 staining together with terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) staining and located no differences at any of the assessed time points. These results showed that the HFD caused a proliferative response inside someday, but this didn’t change the scale of the intestinal surface area over the course of 1 week. Moreover,  all of the expected cell types, like EEC, enterocytes, enterocyte progenitors (EPs), goblet, Paneth cells, secretory progenitors (SPs), tuft, and stem/early-transit amplifying (TA) zone cells, were identified.

Evaluation of the transcriptional alterations induced by HFD was performed with Biological Process Gene Ontology Terms (GO-Terms), which showed that genes for fatty acid metabolic pathways had higher expression levels in several cell types after just someday of HFD. This suggested that the intestinal epithelium shifted away from the often utilized glutamine/glutamate metabolism. There was also a direct downregulation observed after someday of HFD. Gene set enrichment evaluation (GSEA) showed that almost all epithelial cells had upregulated genes that facilitated fatty acid metabolism, as evidenced by normalized enrichment scores (NESs). Specifically, NESs related to fatty acid metabolism increased at one and three days of HFD. This suggested that the body’s metabolism reacted quickly to the rise in luminal fat. By seven days, the fatty acid metabolism NESs had declined to point that enterocytes had adapted to the change to HFD.

After someday on an HFD, there was an upregulation of stress-related genes for all epithelial cell populations. Based on the scRNA-seq data, stem/early-TA, together with Paneth cells, tended to exhibit dramatic changes in gene expression in response to cellular stress. The stem/early-TA subset was found to upregulate heat-shock protein genes, and GSEA upregulated unfolded protein response (UPR) genes. This showed that stem/early-TA cells react to HFD immediately with a stress response.

This study demonstrated a multi-pronged approach to assessing how animals reply to eating regimen changes by evaluating whole-body metabolism, tissue function, morphology, and single-cell transcriptomics. Functional and transcriptional analyses showed that all sorts of intestinal epithelial cells were altered inside 24 hours. Moreover, inside every week, the intestinal epithelium had been modified to maximise fat absorption. Plasticity of the intestinal wall can have evolved during times of nutrient scarcity but could now be linked to obesity, metabolic disease, and inflammation during times of nutrient excess.

Journal reference:

• Jacob R. Enriquez, Heather A. McCauley, Kevin X. Zhang, J. Guillermo Sanchez, Gregory T. Kalin, Richard A. Lang, James M. Wells, A dietary change to a high-fat eating regimen initiates a rapid adaptation of the intestine, Cell Reports, Volume 41, Issue 7, 2022, 111641, ISSN 2211-1247, DOI: https://doi.org/10.1016/j.celrep.2022.111641, https://www.sciencedirect.com/science/article/pii/S2211124722015121