Plain language summary
The small intestinal mucosa is a large organ which acts as an intestinal barrier. The jejunal mucosa is the largest part of the small intestinal mucosa, and its functions include digestion and absorption of food. Epithelium cells on the surface of the small intestine renew every few days. Therefore, this single-centre, randomised, unblinded, crossover study looked at how jejunal mucosal cells change after two weeks of an isocaloric high-fat diet (HFD) and high-carbohydrate diet (HCD) in fifteen healthy people. The study also measured ketogenesis rate-limiting enzyme 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) and mitochondria following the isocaloric HFD and HCD. Neither HFD nor HCD changes the mucosal surface enlargement factor. However, at the ultrastructural level, there was a significant surface enlargement in the bases of the villi after following HCD than HFD. In addition, HFD increased the number of mitochondrial cristae in the erythrocytes than HCD. The increased number of mitochondrial cristae in the erythrocytes was associated with the increased expression of HMGCS2. Healthcare professionals can use the results of this study to understand how short-term implementation of different diets affects jejunal mucosal morphology at the ultrastructural level. Further robust studies are required to evaluate the long-term effects of HFD and HCD in jejunal mucosa and how the morphological adaptations impact people with obesity.
Abstract
BACKGROUND AND AIMS The conditions for jejunal glucose absorption in healthy subjects have not been thoroughly studied. In this study we investigated differences in the jejunal villi enlargement factor, as well as ultrastructural aspects of the surface enterocytes and mitochondria, comparing 2 weeks of high-carbohydrate (HCD) versus high-fat diets (HFD). We also measured the ketogenesis rate-limiting enzyme 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) in relation to jejunal mitochondria. METHODS A single-centre, randomized, unblinded crossover study in 15 healthy volunteers ingesting strictly controlled equicaloric diets (either HCD or HFD), with 60% energy from the respective source. An enteroscopy was carried out after 2 weeks of each diet and jejunal mucosal biopsies were acquired. Conventional histology, immunofluorescent staining, transmission electron microscopy and confocal microscopy were used. RESULTS The villi did not demonstrate any change in the epithelial enlargement factor. Despite an increased mitosis, there were no changes in apoptotic indices. However, the ultrastructural analysis demonstrated a significant increase in the enlargement factor at the bases of the villi. The mitochondria demonstrated increased amounts of cristae after the HFD. The confocal microscopy revealed increased HMGCS2 per mitochondrial marker at the top of the villi after the HFD compared to the HCD. CONCLUSION There is a morphometric adaption in the jejunal mucosa following the 2-week diets, not only on a histological level, but rather on the ultrastructural level. This study supports the notion that mitochondrial HMGCS2 is regulated by the fat content of the diet and is involved in the expression of monosaccharide transporters.
Methodological quality
Jadad score
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2
Allocation concealment
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No
