An in-line digestive cartridge increases enteral fat and vitamin absorption in a porcine model of short bowel syndrome

BACKGROUND & AIMS

Short bowel syndrome (SBS) occurs after intestinal loss resulting in parenteral nutrition dependence and micronutrient deficiencies, which may lead to life-limiting complications. ALC-078 is a cartridge containing immobilized lipase that connects in-line with enteral feeding sets and digests fats in enteral nutrition (EN). In this study, we evaluate the efficacy of ALC-078 to improve fat and nutrient absorption in a porcine SBS model.

METHODS

Fifteen male Yorkshire piglets were assessed. Animals were randomized to no intestinal resection (n = 5), 75% resection (n = 5), or 75% resection + ALC-078 (n = 5). After recovery, animals were treated for 14 days. Piglets received 60% of nutrition from continuous EN and 40% from chow. The degree of fat malabsorption was determined by the coefficient of fat absorption (CFA) following a 72-h stool collection. Body weight, fat-soluble vitamins, and nutritional markers were assessed.

RESULTS

Adverse events were similar across the three groups (P = 1.00). ALC-078-treated animals had similar weight gain compared to resected piglets. Resected animals had a lower CFA compared to unresected controls (79.3% vs. 95.2%, P = 0.01) while there was no significant difference in the ALC-078 animals (87.1% vs. 95.2%, P = 0.19). Between Study Days 1 and 15, ALC-078 animals had increased concentrations of vitamin D (12.2 vs. 8.7 ng/mL, P = 0.0006), and vitamin E (4.3 vs. 2.5 mg/L, P = 0.03). These markers did not significantly change in untreated resected animals.

CONCLUSION

ALC-078 increases the absorption of fat-soluble vitamins and may improve fat malabsorption. Future studies should determine whether ALC-078 can reduce PN dependence and if these findings translate to human patients with SBS.

Analysis of gene expression during myc oncogene-induced lymphomagenesis in the bursa of Fabricius

The transcriptional effects of deregulated myc gene overexpression are implicated in tumorigenesis in a spectrum of experimental and naturally occurring neoplasms. In follicles of the chicken bursa of Fabricius, myc induction of B-cell neoplasia requires a target cell population present during early bursal development and progresses through preneoplastic transformed follicles to metastatic lymphomas. We developed a chicken immune system cDNA microarray to analyze broad changes in gene expression that occur during normal embryonic B-cell development and during myc-induced neoplastic transformation in the bursa. The number of mRNAs showing at least 3-fold change was greater during myc-induced lymphomagenesis than during normal development, and hierarchical cluster analysis of expression patterns revealed that levels of several hundred mRNAs varied in concert with levels of myc overexpression. A set of 41 mRNAs were most consistently elevated in myc-overexpressing preneoplastic and neoplastic cells, most involved in processes thought to be subject to regulation by Myc. The mRNAs for another cluster of genes were overexpressed in neoplasia independent of myc expression level, including a small subset with the expression signature of embryonic bursal lymphocytes. Overexpression of myc, and some of the genes overexpressed with myc, may be important for generation of preneoplastic transformed follicles. However, expression profiles of late metastatic tumors showed a large variation in concert with myc expression levels, and some showed minimal myc overexpression. Therefore, high-level myc overexpression may be more important in the early induction of these lymphomas than in maintenance of late-stage metastases.

Characterization of the chicken CTCF genomic locus, and initial study of the cell cycle-regulated promoter of the gene

CTCF is a multifunctional transcription factor encoded by a novel candidate tumor suppressor gene (Filippova, G. N., Lindblom, A., Meinke, L. J., Klenova, E. M., Neiman, P. E., Collins, S. J., Doggett, N. D., and Lobanenkov, V. V. (1998) Genes Chromosomes Cancer 22, 26-36). We characterized genomic organization of the chicken CTCF (chCTCF) gene, and studied the chCTCF promoter. Genomic locus of chCTCF contains a GC-rich untranslated exon separated from seven coding exons by a long intron. The 2-kilobase pair region upstream of the major transcription start site contains a CpG island marked by a "Not-knot" that includes sequence motifs characteristic of a TATA-less promoter of housekeeping genes. When fused upstream of a reporter chloramphenicol acetyltransferase gene, it acts as a strong transcriptional promoter in transient transfection experiments. The minimal 180-base pair chCTCF promoter region that is fully sufficient to confer high level transcriptional activity to the reporter contains high affinity binding element for the transcription factor YY1. This element is strictly conserved in chicken, mouse, and human CTCF genes. Mutations in the core nucleotides of the YY1 element reduce transcriptional activity of the minimal chCTCF promoter, indicating that the conserved YY1-binding sequence is critical for transcriptional regulation of vertebrate CTCF genes. We also noted in the chCTCF promoter several elements previously characterized in cell cycle-regulated genes, including the "cell cycle-dependent element" and "cell cycle gene homology region" motifs shown to be important for S/G2-specific up-regulation of cdc25C, cdc2, cyclin A, and Plk (polo-like kinase) gene promoters. Presence of the cell cycle-dependent element/cell cycle gene homology region element suggested that chCTCF expression may be cell cycle-regulated. We show that both levels of the endogenous chCTCF mRNA, and the activity of the stably transfected chCTCF promoter constructs, increase in S/G2 cells.

Loss of cell cycle controls in apoptotic lymphoblasts of the bursa of Fabricius

Lymphoblasts of the normal embryonic follicles of the chicken bursa of Fabricius undergo rapid apoptosis when exposed to gamma-radiation or when cell-cell contacts are disrupted by mechanical dispersion in short term culture. We have observed previously that overexpression of v-myc sensitizes preneoplastic bursal lymphoblasts to induction of cell death, whereas resistance to induced cell death is acquired during progression to neoplasia. In this study we observed extensive DNA degradation in the large majority of the lymphoblast population within the first hour after dispersion-induced apoptosis. Paradoxically these cells continued to progress into S-phase with the bulk of DNA cleavage and death occurring in S-phase cells (i.e., in cells with more than 2C and less than 4C DNA content). We confirmed the S phase status of apoptotic cells by determining that detection of nuclear cyclin A in individual cells also corresponded with detection of DNA breakage. Levels of cyclin E, cyclin E-dependent H1 histone kinase, and p53 proteins were maintained during dispersion-induced DNA cleavage. gamma-radiation failed either to inhibit cell cycle progression or to raise p53 levels in dispersed bursal lymphoblasts. In intact bursal follicles low doses of gamma-radiation induced p53 whereas higher, apoptosis-inducing doses failed to induce p53 or prevent G1 to S-phase progression. These results suggest that normal DNA damage-induced cell cycle checkpoint controls are lost or overridden when apoptosis is induced in bursal lymphoblasts.

Induction of apoptosis during normal and neoplastic B-cell development in the bursa of Fabricius

The lymphoid cells of embryonic bursal follicles are engaged in rapid growth and preimmune diversification of immunoglobulin genes. Disruption of follicular architecture by mechanical dispersion of these cells in short-term tissue culture was accompanied by continued cell division and extensive cell death by apoptosis. Apoptosis was suppressed in parallel cultures of intact follicles. gamma Radiation also triggered extensive apoptosis in embryonic bursal follicles within a few hours. Preneoplastic bursal stem cell populations induced by a v-myc oncogene were hypersensitive to induction of apoptosis by follicular dispersion and radiation. In contrast, tumor progression in v-myc- and v-rel-initiated bursal neoplasms was accompanied by development of resistance to induction of apoptosis. A programmed cell death pathway can be activated during normal B-cell development in the bursa, and alterations in the expression of this pathway accompany neoplastic change in this system.