Although the intestinal mucosa forms a crucial barrier between the host and the environment, bacterial translocation (BT) occurs frequently in neonates and may be a source of sepsis. The intestinal mucous gel layer is thought to be a vital component of the gut barrier and is composed, in part, of a family of glycoproteins known as mucins. Our aim was to study the effects of mucin on BT in an enterocyte cell-culture model using a fetal (I-407) and an adult (Caco-2) intestinal cell line. I-407 and Caco-2 cells were grown to confluence on porous filters in a two-chamber Transwell system. The integrity of the monolayers was confirmed by transepithelial electrical resistance (TEER) and permeability using the macromolecule dextran blue. Cells were treated with mucin (40 mg/ml) prior to inoculation of 1 x 10(6) Escherichia coli C25. The magnitude of BT was determined quantitatively by culturing the samples from the basal chamber of the wells and was expressed as log 10 [Colony Forming Units (CFU)/ml]. Statistical analysis was performed by the Mann-Whitney U test with statistical significance at P < 0.05. Mucin inhibited BT across both fetal and adult cultured enterocyte monolayers; however, the inhibitory effect was less on the fetal cells compared to the adult cells. Dextran-blue studies showed that monolayers were intact throughout the experiments. Despite 98% inhibition of BT, mucin had a statistically significant effect on post-bacterial inoculation TEER in Caco-2 cells and no effect in I-407 cells. The ability of mucin, a mucous-barrier glycoprotein, to inhibit BT across immature intestinal enterocytes, as in the neonate, may be diminished compared to mature adult enterocytes.

Long chain fatty acids (LCFAs) appear to be powerful stimulants for small bowel adaptation in patients with short bowel syndrome (SBS). However, the dietary lipid content may alter intestinal lipid transport. The aim of this study was to investigate the effects of a high fat diet (HFD) on in vivo lipid absorption and molecular and cellular mechanisms of LCFAs uptake by the remaining bowel. Male Sprague-Dawley rats (240-280) were randomly assigned to one of three groups: sham rats fed normal chow (sham-NC), SBS rats fed NC (SBS-NC) and SBS rats fed HFD (SBS-HFD). SBS rats underwent a 75% small bowel resection. Rats were sacrificed on day 3 or 14. Body weight, fat intake and fat clearance (total fecal fat) were measured twice a week. Fat absorbability was calculated as intake minus clearance and was expressed as percent of intake. Total RNA from the mucosa of duodenum, jejunum and ileum was extracted using TRIZOL Reagent. Northern blot analysis was performed to determine FAT/CD36 mRNA levels. Enterocyte LCFA transport was measured on day 14. LCFA uptake was determined by measuring cellular [3H]-oleate uptake over time (4-120 s). Mean (+/-SE) FAT/CD36 mRNA levels and oleate uptake kinetic parameters were analyzed using ANOVA. Fat absorbability diminished after bowel resection, suggesting fat malabsorption. Remaining bowel in SBS-NC rats responded by an increase in FAT/CD36 mRNA levels in the duodenum and ileum on day 3, and the duodenum and jejunum on day 14 compared to sham-NC animals, and was accompanied by an increase in enterocyte LCFA transport in all segments. Exposure to a HFD for 14 days resulted in significantly increased fat absorbability after 3 days compared to SBS-NC rats. However, FAT/CD36 mRNA levels (vs. SBS-NC) decreased in all segments on day 3. On day 14, FAT/CD36 mRNA levels were decreased in the duodenum and ileum and were accompanied by reduced oleate uptake by isolated enterocytes in the ileum (vs. SBS-NC). In a rat model of SBS, early high fat diet increased lipid absorptive capacity of the intestinal remnant as seen by increased fat absorbability. The main mechanisms of this effect may be an acceleration of structural intestinal adaptation resulting in an increased number of enterocytes. However, at molecular and cellular levels HFD decreased mucosal FAT/CD36 mRNA levels and oleic acid uptake by isolated enterocytes.

Low-fat diets (LFD) are used extensively in many different clinical conditions. However, the effect of this diet on lipid absorption and cellular long-chain fatty-acid (LCFA) transport is unknown. Fatty-acid translocase (FAT), the rat homologue of human CD36, is one of several LCFA plasma-membrane transport proteins that may play an important role in intestinal lipid uptake. The purpose of this study was to investigate the effects of a LFD on intestinal expression of FAT/CD36, enterocyte fatty-acid transport, and in-vivo lipid absorption in rats following bowel resection. Adult male Sprague-Dawley rats were divided into five experimental groups: normal rats fed normal chow(NR-NC) (10 kcal% fat), normal rats fed a LFD (NR-LFD) (3 kcal% fat), sham rats fed normal chow (Sham-NC), short-bowel syndrome rats fed normal chow (SBS-NC), and SBS rats fed a LFD (SBS-LFD). SBS rats underwent 75% small-bowel resection, while sham animals underwent bowel transection and reanastomosis. Food intake, fecal mass, and fecal fat were measured over the last 3 days before death on day 14. Final body weight, plasma lipids and protein, and tissue total lipids in liver, adipose tissue, and intestine were determined at death. Total RNA from the mucosa of the duodenum, jejunum, and ileum was extracted for Northern blot analysis to determine fatty-acid translocase (FAT)/CD36 mRNA levels. An established cellular LCFA transport assay was used to determine isolated enterocyte [3H]-oleate uptake. Students t-test was used to determine statistical significance (P < 0.05). NR-LFD rats demonstrated a small increase in overall food absorption and no change in fat absorption compared to NR-NC animals. A significant decrease in FAT/CD36 mRNA levels was seen in the duodenum and jejunum in NF-LFD rats (vs NR-NC) and was accompanied by reduced LCFA transport by isolated enterocytes from the jejunum and ileum. SBS-LFD rats demonstrated decreased FAT/CD36 mRNA levels in all three segments and a concomitant decrease in LCFA uptake enterocytes compared to the SBS-NC group. In addition, SBS-LFD rats showed significantly lower final body weight and plasma lipids compared to SBS-NC animals.