Advances in nutrition and gastroenterology: summary of the 1997 A.S.P.E.N. Research Workshop

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Intestinal failure: Pathophysiological elements and clinical diseases

There are two main functions of gastrointestinal tract, digestion and absorption, and barrier function. The latter has an important defensive effect, which keeps the body away from the invading and damaging of bacteria and endotoxin. It maintains the systemic homeostasis. Intestinal dysfunction would happen when body suffers from diseases or harmful stimulations. The lesser dysfunction of GI tract manifests only disorder of digestion and absorption, whereas the more serious intestinal disorders would harm the intestinal protective mechanism, or intestinal barrier function, and bacterial/endotoxin translocation, of intestinal failure (IF) would ensue. This review disscussed the theory of the intestinal failure, aiming at attracting recognition and valuable comments by clinicians.

Treatment of inflammatory bowel disease in childhood: best available evidence

The physician treating children with inflammatory bowel disease is confronted with a number of specific problems, one of them being the lack of randomized, controlled drug trials in children. In this review, the role of nutritional therapy is discussed with a focus on primary treatment, especially for children with Crohn's disease. Then, the available medical therapies are highlighted, reviewing the evidence of effectiveness and side effects in children, as compared with what is known in adults. Nutritional therapy has proven to be effective in inducing and maintaining remission in Crohn's disease while promoting linear growth. Conventional treatment consists of aminosalicylates and corticosteroids, whereas the early introduction of immunosuppressives (such as azathioprine or 6-mercaptopurine) is advocated as maintenance treatment. If these drugs are not tolerated or are ineffective, methotrexate may serve as an alternative in Crohn's disease. Cyclosporine is an effective rescue therapy in severe ulcerative colitis, but only will postpone surgery. A novel strategy to treat Crohn's disease is offered by infliximab, a monoclonal antibody to the proinflammatory cytokine tumor necrosis factor (TNF)-alpha. Based on the best-available evidence, suggested usage is provided for separate drugs with respect to dosage and monitoring of side effects in children.

Effect of elective abdominal surgery on human colon protein synthesis in situ

OBJECTIVE

To determine the effect of elective abdominal surgery on the rate of human colon fractional protein synthesis in situ.

SUMMARY BACKGROUND DATA

Efficient intestinal protein synthesis plays an important role in the physiology and pathophysiology of the intestinal tract, allowing preservation of gut integrity and thereby preventing bacterial or endotoxin translocation. Because of species differences, animal studies have only limited applicability to human intestinal protein metabolism, and because of methodologic restrictions, no studies on colon protein synthesis in situ are available in humans.

METHODS

The authors used advanced mass spectrometry techniques (capillary gas chromatography and combustion isotope ratio mass spectrometry) to determine directly the incorporation rate of 1-[13C]-leucine into colon mucosal protein in control subjects and nonseptic postoperative patients. All subjects had a colostomy, which allowed easy access to the colon mucosa, and consecutive sampling from the same tissue was performed during continuous isotope infusion (0.16 micromol/kg per minute).

RESULTS

Control subjects demonstrated a colon protein fractional synthetic rate of 0.74 +/- 0.09% per hour. In postsurgical patients, colon protein synthesis was significantly higher and the tissue free leucine enrichment was significantly lower, compatible with an increased colon proteolytic rate.

CONCLUSIONS

Elective abdominal surgery followed by an uncomplicated postoperative course is associated with a stimulation of colon protein synthesis and possibly also of protein degradation. The postoperative rate of colon protein synthesis is, compared with other tissues, among the highest measured thus far in humans.

Determination of protein synthesis in human ileum in situ by continuous [1-(13)C]leucine infusion

Efficient protein synthesis plays an important role in the physiology and pathophysiology of the human gastrointestinal tract. Because of methodological restrictions, no studies on ileal protein synthesis in situ are available in humans. We used advanced mass spectrometry techniques (capillary gas chromatography/combustion isotope ratio mass spectrometry) to determine directly the incorporation rate of [1-(13)C]leucine into ileal mucosal protein in control subjects and postoperative patients. All subjects had an ileostomy, which allowed easy access to the ileal mucosa. To examine changes in ileal protein synthesis during prolonged isotope infusion (0.16 micromol. kg(-1). min(-1), 9.6 micromol/kg prime), studies were performed over a 10-h period. Mucosal biopsies were performed after 3, 6, and 10 h of infusion. Protein synthesis was calculated separately between hour 3 and hour 6 (period 1) and hour 6 and hour 10 (period 2). Control subjects demonstrated an ileal protein fractional synthetic rate of 0.62 +/- 0.06%/h in period 1 and of 0. 52 +/- 0.08%/h in period 2 (not significant). In postsurgical subjects, ileal protein synthesis was significantly higher (1.11 +/- 0.14%/h in period 1, P < 0.01 vs. controls in period 1) but declined markedly in period 2 (0.39 +/- 0.13, P < 0.01 vs. period 1 after surgery). The rate of protein synthesis in the small bowel of control subjects is, thus far, among the lowest measured in mammals and reflects the comparably slow turnover of human ileal mucosa. Postoperative disturbances of gut integrity lead to an accelerated anabolic response. During prolonged isotope infusion, stimulated protein synthesis declines because of diurnal variations or is erroneously reduced by tracer loss due to an accelerated cell turnover.

Effects of insulin-like growth factor-I and growth hormone in models of parenteral nutrition

BACKGROUND

Administration of growth factors such as growth hormone (GH) and insulin-like growth factor-I (IGF-I) is being investigated as a strategy to promote nitrogen accretion in catabolic patients who may require total parenteral nutrition (TPN). IGF-I has advantages compared with GH because IGF-I enhances insulin sensitivity, is effective in conditions of GH resistance, and selectively stimulates the gastrointestinal and immune systems.

METHODS

Experiments were conducted to evaluate the anabolic and metabolic effects associated with administration of recombinant human GH or IGF-I in rats subjected to clinically relevant stress and maintained with TPN.

RESULTS

Administration of IGF-I, but not GH, attenuates dexamethasone-induced protein catabolism and increases insulin sensitivity. Simultaneous treatment with GH and IGF-I additively increases the serum concentration of IGF-I, whole-body anabolism, and lipid oxidation. GH or IGF-I when given alone produces similar increases in the serum concentration of IGF-I. However, GH selectively increases skeletal muscle mass whereas IGF-I selectively attenuates the intestinal atrophy and abnormal intestinal ion transport induced by TPN. These tissue-selective anabolic effects of GH and IGF-I are associated with differential increases in protein synthesis in skeletal muscle and jejunum, respectively.

CONCLUSIONS

Simultaneous treatment with GH and IGF-I may offer the greatest clinical efficacy because of improved nitrogen retention in association with enhanced lipid oxidation and stimulation of protein synthesis in multiple tissue types.

Incidence, prognosis, and etiology of end-stage liver disease in patients receiving home total parenteral nutrition

BACKGROUND

Elevations in liver function tests have been reported in patients receiving total parenteral nutrition (TPN). The clinical aspects of end-stage liver disease (ESLD) associated with the prolonged use of home TPN have not been fully clarified. In previous series patients with duodenocolostomies appeared to be at higher risk than persons with some jejunum or ileum remaining in situ.

METHODS

The records of 42 patients treated with home TPN for more than 1 year were examined. This constituted 283 person-years of home TPN. Patients with duodenocolostomies were examined as a separate group on the basis of the literature experience.

RESULTS

Six of 42 patients who received chronic home TPN had ESLD with 100% subsequent mortality, at an average of 10.8 +/- 7.1 months after the initial bilirubin elevation. Thirteen of 42 patients had superior mesenteric artery or vein thrombosis (SMT) leading to duodenocolostomy. In 8 of these 13 patients with SMT and underlying inflammatory or malignant disorder, 2 had ESLD. The remaining 5 SMT patients who had only minimal liver enzyme elevation over 13.6 +/- 6.7 (range 3 to 19) years of home TPN were significantly younger (36 +/- 7 years vs 64 +/- 13 years) and did not have underlying inflammation either by clinical diagnosis or as reflected in the high normal serum albumin level (> or = 4.0 g/dL). Despite their extreme short bowel syndrome and long exposure to home TPN, ESLD did not develop.

CONCLUSIONS

Approximately 15% of patients who receive prolonged TPN have ESLD with a high rate of morbidity and mortality. The combination of chronic inflammation and the short bowel syndrome appears to be necessary for the development of ESLD with prolonged home TPN.