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The proton-coupled folate transporter (PCFT-SLC46A1) is required for intestinal folate absorption and is mutated in the autosomal recessive disorder, hereditary folate malabsorption (HFM). This report characterizes properties and requirements of the R376 residue in PCFT function, including a R376Q mutant associated with HFM. Gln, Cys, and Ala substitutions resulted in markedly impaired transport of 5-formyltetrahydrofolate (5-FTHF) and 5-methyltetrahydrofolate (5-MTHF) due to an increase in [K.sub.m] and decrease in [V.sub.max] in HeLa R1-11 transfectants lacking endogenous folate transport function. In contrast, although the influx [K.sub.m] for pemetrexed was increased, transport was fully preserved at saturating concentrations and enhanced for the like-charged R376K- and R376H-PCFT. Pemetrexed and 5-FTHF influx mediated by R376Q-PCFT was markedly decreased at pH 5.5 compared with wild-type PCFT. However, while pemetrexed transport was substantially preserved at low pH (4.5-5.0), 5-FTHF transport remained very low. Electrophysiological studies in Xenopus oocytes demonstrated that 1) the R376Q mutant, like wild-type PCFT, transports protons in the absence of folate substrate, and in this respect has channel-like properties; and 2) the influx [K.sub.m] mediated by R376Q-PCFT is increased for 5-MTHF, 5-FTHF, and pemetrexed. The data suggest that mutation of the R376 residue to Gin impairs proton binding which, in turn, modulates the folate-binding pocket and depresses the rate of conformational alteration of the carrier, a change that appears to be, in part, substrate dependent. reduced folate carrier; folate receptors; heme carrier protein-1; folate deficiency; folate transport; intestinal folate absorption; choroid plexus doi: 10.1152/ajpcell.00113.2010.

Angiotensin converting enzyme (ACE) has been shown to be involved in regulation of apoptosis in nonintestinal tissues. This study examined the role of ACE in the modulation of intestinal adaptation utilizing ACE knockout mice ([ACE.sup.-/-]). A 60% small bowel resection (SBR) was used, since this model results in a significant increase in intestinal epithelial cell (EC) apoptosis as well as proliferation. Baseline villus height, crypt depth, and intestinal EC proliferation were higher, and EC apoptosis rates were lower in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice. After SBR, EC apoptosis rates remained significantly lower in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice. Furthermore, villus height and crypt depth after SBR continued to be higher in [ACE.sup.-/-] mice. The finding of a lower bax-to-bcl-2 protein ratio in [ACE.sup.-/-] mice may account for reduced EC apoptotic rates after SBR in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice. The baseline higher rate of EC proliferation in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice may be due to an increase in the expression of several EC growth factor receptors. In conclusion, ACE appears to have an important role in the modulation of intestinal EC apoptosis and proliferation and suggests that the presence of ACE in the intestinal epithelium has a critical role in guiding epithelial cell adaptive response. short bowel syndrome; bax; bcl-2; intestine; adaptation

Following the loss of functional small bowel surface area, the intestine undergoes a compensatory adaptive response. The observation that adaptation is inhibited in vitamin A-deficient rats following submassive intestinal resection suggested that vitamin A is required for this response and raised the possibility that exogenous vitamin A could augment adaptation. Therefore, to directly assess whether chronically administered retinoic acid could stimulate gut adaptation in a model of short bowel syndrome and to address the mechanisms of any such effects, Sprague-Dawley rats were implanted with controlled release retinoic acid or control pellets and then subjected to mid-small bowel or sham resections. At 2 wk postoperation, changes in gut morphology, crypt cell proliferation and apoptosis, enterocyte migration, the extracellular matrix, and gene expression were assessed. Retinoic acid had significant trophic effects in resected and sham-resected rats. Retinoic acid markedly inhibited apoptosis and stimulated crypt cell proliferation and enterocyte migration postresection. Data presented indicate that these proadaptive effects of retinoic acid may be mediated via changes in the extracellular matrix (e.g., by increasing collagen IV synthesis, decreasing E-cadherin expression, and reducing integrin [[beta].sub.3] levels), via affects on Hedgehog signaling (e.g., by reducing expression of the Hedgehog receptors Ptch and Ptch2 and the Gli1 transcription factor), by increasing expression of Reg1 and Pap1, and by modulation of retinoid and peroxisome proliferator-activated receptor signaling pathways. These studies are the first to demonstrate that retinoic acid can significantly enhance intestinal adaptation and suggest it may be beneficial in patients with short bowel syndrome. vitamin A; apoptosis; enterocyte migration; Hedgehog signaling; extracellular matrix doi: 10.1152/ajpgi.00567.2006

Byline: Cuneyt Turan (1,2), Musa Ozdemir (2) Keywords: Short bowel syndrome; Intestinal plication; Intestinal transit time Abstract: Short bowel syndrome (SBS) can occur after extensive intestinal resections. In SBS, the aim of surgical techniques is to prolong intestinal transit time (ITT) and to increase the absorptive surface. This experimental study was conducted to research the effect of extramucosal intestinal plication on ITT in rats. Thirty Sprague-Dawley rats were divided into three groups. In the control group, barium solution was administrated by gavage. Forty-five minutes later, the rats were sacrificed, and the total length of their small bowels (SBs) and the distance of the barium in the SBs were measured. The ratio of the distance of the barium to the length of the SB was calculated, and the ITT was found for normal rats. Intestinal plication (made with three seromuscular sutures at the same level: one on the antimesenteric side, and two on the lateral sides of the bowel) and laparotomy and bowel manipulation were carried out in the study and sham groups, respectively, and ITT was measured by the same method after 1 week. A one-way ANOVA test was used to compare the groups in terms of body weight, total length of the SB, distance of the barium in the SB, and the ratio of this distance to the length of the SB. The rats were statistically homogeneous in terms of body weight and total length of the SB ( p &gt 0.05). The distances of the barium in the small bowel in the control, sham, and study groups were 73.4+-8.5 cm, 77.5+-6.8 cm, and 56.3+-3.6 cm, respectively. The distances of barium in the SB in the study group were statistically shorter than in the other groups ( p &lt 0.05). The ratios of the distance of the barium to the length of the SB in the control, sham, and study groups were 65.8+-7.3, 66.4+-4.5, and 49.9+-3.8, respectively. In the study group, this ratio was also statistically lower than in the other groups ( p &lt 0.05). Extramucosal intestinal plication retarded ITT significantly in the study group compared with the other groups. This technique does not entail any risk of morbidity and mortality therefore, it can be used in the treatment of SBS. Author Affiliation: (1) Cocuk Cerrahisi Anabilim DalA+-, Erciyes Universitesi TA+-p Fakultesi, 38039, Kayseri, Turkiye (2) Department of Pediatric Surgery, Erciyes University, 38039 , Kayseri, Turkey Article History: Registration Date: 03/02/2004 Accepted Date: 17/10/2003 Online Date: 13/05/2004 Article note: Presented at XX Annual Meeting of Turkish Association of Pediatric Surgeons, 15--19 October 2002, Mersin, Turkey.

Byline: Barbara E. Wildhaber (1), Hua Yang (1), Arnold G. Coran (1), Daniel H. Teitelbaum (1) Keywords: Short bowel syndrome; Intraepithelial lymphocytes; Apoptosis; Proliferation; Microarray Abstract: Background The intestinal adaptive response [increased epithelial cell (EC) proliferation and apoptosis] after massive small bowel resection (SBR) is partially controlled by intraepithelial lymphocytes (IEL). To identify IEL factors contributing to EC adaptation post-SBR we utilized microarray assays. Methods Mice underwent a 70% SBR (SBR1w/SBR4w) or sham operation (Sham1w/Sham4w). After 1 or 4 weeks (1w, 4w) small bowel was harvested, and IEL isolated. Determination of the EC-proliferation rate used BrdU incorporation, and of the EC-apoptotic rate used Annexin V staining. Affymetrix system microarrays (12,491 genes) were performed to examine IEL-mRNA expression. Results were considered significant if fold-change (FC) between groups was &gt 2 and P &lt 0.05 (F-test), or FC&gt 3 and 0.05&gt P &gt 0.01, or FC&gt 4 and P &gt 0.05. Significant genes were confirmed by conventional RT-PCR. Results The SBR EC-proliferation rate increased significantly in both 1w and 4w groups compared to Sham: SBR1w 0.24+-0.07 vs. Sham1w 0.12+-0.02 ( P =0.03) SBR4w 0.35+-0.04 vs. Sham4w 0.19+-0.02 ( P &lt 0.01). The EC-apoptotic rate was unchanged in the 1w group, but significantly differed from controls after 4 weeks: SBR4w 39.92+-6.78 vs. Sham4w 12.56+-6.44 ( P &lt 0.01). Microarray results were analyzed to identify potential growth-modifying IEL genes. The following were identified (function in parenthesis A, apoptosis P, proliferation): lipocalin 2 (promotes A), angiotensin converting enzyme (increases A), Rap2 interacting protein (reduces A, promotes P), amphiregulin (promotes P) and leucine-rich-[alpha]2-glycoprotein (promotes A, reduces P). Based on RT-PCR results these genes showed significant changes between groups. The increase in ACE at 1w preceded the observed apoptotic changes. The alterations in lipocalin 2, Rap2 and amphiregulin at 4w coincided with the marked changes in growth and apoptosis in the SBR mice. Conclusions IEL undergo temporal changes after SBR. These findings provide profound insight into potential IEL-dependent regulation of EC homeostasis post-SBR. Author Affiliation: (1) Department of Surgery, Section of Pediatric Surgery, C.S. Mott Children's Hospital, University of Michigan, Mott F3970, Box 0245, Ann Arbor, Michigan, 48109, USA Article History: Accepted Date: 10/12/2002 Online Date: 01/05/2003