HIF-1: a key mediator in hypoxia.

The transcription factor HIF-1 is one of the principal mediators of homeostasis in human tissues exposed to hypoxia. It is implicated in virtually every process of rapid gene expression in response to low oxygen levels. The most common causes of tissue hypoxia are inflammation and/or insufficient circulation or a combination of both. Inflamed tissues and the areas surrounding malignant tumors are characterized by hypoxia and low concentrations of glucose. Serious and generalized inflammation can lead to sepsis and circulatory collapse resulting in acute or chronic tissue hypoxia in various vital organs which induces a rapid homeostatic process in all nucleated cells of affected organs in the human body. Under hypoxic conditions the alpha and beta subunits of HIF-1 make an active heterodimer and drive the transcription of over 60 genes important for cell survival, adaptation, anaerobic metabolism, immune reaction, cytokine production, vascularization and general tissue homeostasis. In addition, HIF-1 plays a key role in the development of physiological systems in fetal and postnatal life. It is also a critical mediator of cancer, lung and cardiovascular diseases. The better understanding of the functions of HIF-1 and the pharmacological modulation of its activity could mean a successful therapeutic approach to these diseases.

Multiple arterial thromboembolisms in a patient with the 20210 A prothrombin gene mutation.

The most recently characterized genetic defect contributing to venous thrombophilia is the 20210 A prothrombin gene mutation. We describe a patient with this defect who had arterial thrombosis resulting in considerable mesenteric ischemia. Several environmental factors, which might otherwise be considered of low thrombotic risk, may also have contributed to her condition. The recognition of the potential for novel presentations of hypercoagulable states may contribute to a reduction in the morbidity associated with acute mesenteric ischemia.

Clinical subtypes of Crohn's disease according to surgical outcome.

Patients with Crohn's disease are typically classified into perforator or nonperforator groups. The perforator group includes those who present with acute perforation, fistulas, or abscess formation. The nonperforator group presents with stricture, obstruction, or unresponsiveness to medical therapy. Our purpose was to investigate whether perianal disease constitutes a separate predictor of surgical outcome. The form of presentation was classified as perforator, nonperforator, or perianal disease in 91 patients undergoing 232 operations for Crohn's disease. Those with perforating complications presented with the highest Crohn's Disease Activity Index, followed by those with nonperforating complications, and then the perianal disease group. However, the perianal disease group appeared to have the most rapid rate of recurrence and subsequent surgery, followed next by the perforator, and then the nonperforator group. Recurrence rate and subsequent operation intervals for the perforator group appeared to lengthen when those patients were treated with steroids and/or immunosuppressants, as compared to nonsteroidal and/or antimicrobial agents. Recurrence rate and subsequent operation intervals appeared to lengthen for the nonperforator and perianal disease groups when they were treated with nonsteroidal and/or antimicrobial therapy, as compared to steroids and/or immunosuppressants. Our data indicate that perianal disease, as a form of presentation of Crohn's disease, has independent predictive value, although this is not accurately reflected by the Crohn's Disease Activity Index.

Influence of 5-fluorouracil on colonic healing and expression of transforming growth factor-beta 1.

BACKGROUND: Administration of chemotherapeutic agents in the immediate postoperative period may have beneficial effects by decreasing local cancer recurrence rates, but this must be weighed against possible impairment of wound healing. Since local expression of transforming growth factor-beta1 (TGF-beta1) is normally upreglated following creation of experimental colonic anastomoses, this study examines the effects of 5-fluorouracil (5-FU) on colonic healing and on the local expression of TGF-beta1. MATERIALS AND METHODS: Forty-eight male Sprague-Dawley rats underwent transection of the descending colon with primary anastomosis and were then randomly assigned to receive either intraperitoneal 5-FU (20 mg/kg/day) or saline (SAL). On Postoperative Days (PODs) 3, 5, and 7, bursting pressure (BP, mm Hg) and bursting energy (BE, mm Hg xs) were determined in situ. Anastomotic and nonoperated segments of colon were harvested and analyzed using the semiquantitative reverse transcriptase-polymerase chain reaction to determine the relative expression of TGF-beta1 normalized to that of a constitutive gene. RESULTS: Progressive increases in BP and BE were observed in both the 5-FU and the SAL groups, across the time course examined. Overall, these measures were decreased in the 5-FU groups compared to SAL, significantly so on PODs 5 and 7; BP, 127.8 +/- 7.6 vs 161.1 +/- 7.2 and 139.9 +/- 10.9 vs 186.0 +/- 8.6; BE, 1093.6 +/- 190.0 vs 2207.9 +/- 308.2, and 1518.5 +/- 326.5 vs 3279.3 +/- 225.7, respectively. Anastomotic TGF-beta1 expression also increased progressively in both groups over the postoperative time course. Expression in the 5-FU group, however, was significantly decreased compared to that in the SAL group on POD 3; 0.42 +/- 0.05 vs 0.84 +/- 0.04. Interestingly, this preceded the reduction in BP and BE in the 5-FU group on PODs 5 and 7. TGF-beta1 expression in nonoperated colonic segments did not change during the time points studied or in response to 5-FU administration. CONCLUSIONS: Wound healing following a colonic anastomosis is associated with local increases in TGF-beta1 expression, which in turn is diminished by the administration of 5-FU. If this deleterious effect on wound healing could be counteracted, then chemotherapy administration in the immediate postoperative period may become safer.

Localization of thrombospondin-1 and its cysteine-serine-valine-threonine-cysteine-glycine receptor in colonic anastomotic healing tissue.

Thrombospondin-1 (TSP-1) is a matrix protein implicated in mechanisms of wound healing. TSP-1 contains the sequence cysteine-serine-valine-threonine-cysteine-glycine (CSVTCG) that has been shown to function primarily as a cell adhesion domain. Our laboratory has isolated a novel receptor specific for the CSVTCG adhesive domain of TSP-1. Immunohistochemical staining techniques and computerized image analysis were used to identify and quantitate TSP-1 and its CSVTCG receptor in surgically created colon anastomotic wounds. Histopathologic and quantitative examination demonstrated increased expression of TSP-1 and its CSVTCG receptor in areas of wound healing. These findings suggest a role for TSP-1 and its CSVTCG receptor in wound healing. The control of expression and activity of these molecules may eventually be the basis for the development of wound healing agents that could significantly reduce the morbidity from surgical intervention.

Temporal expression of TGF-beta1, EGF, and PDGF-BB in a model of colonic wound healing.

BACKGROUND: Dehiscence of colonic anastomoses is a multifactorial phenomenon. One mechanism by which this can occur is a deficiency of colonic submucosal collagen. Peptide growth factors (PGFs) have been shown to play a role in the synthesis, deposition, and maturation of collagen. Specifically, in tissues other than the colon, the transforming growth factor-beta (TGF-beta1) gene has been shown to be temporally associated with expression of the procollagen gene. This study examines the temporal expression of the TGF-beta1, epidermal growth factor (EGF), and platelet-derived growth factor B (PDGF-BB) genes and their temporal relationship to the expression of the procollagen type 1 (PROC I) gene. MATERIALS AND METHODS: Forty-eight Sprague-Dawley rats underwent transection of the descending colon with primary anastomosis. Perianastomotic colonic tissue was harvested on Day 0 and postoperative days 3, 5, 6, 7, and 14. Colonic tissue was analyzed using semiquantitative reverse transcriptase-polymerase chain reaction and primers specific for the TGF-beta1, EGF, and PDGF-B growth factors. Relative expression ratios of PGFs and PROC I genes were calculated versus a constitutive gene. RESULTS: The data show that although all three of the PGFs genes were expressed in healing postoperative colonic tissue, only TGF-beta1 showed a significant increase in its level of expression versus a constitutive gene from a mean ratio of 0.4 +/- 0. 08 on Day 0 to a mean ratio of 1.9 +/- 0.27 on Day 7 (P < 0.0001 by ANOVA). The PROC I gene also showed a significant increase in expression (P < 0.001 by ANOVA) in the postoperative period which temporally correlated with the increase in the expression of the TGF-beta1 gene (r = 0.89, P < 0.05). CONCLUSIONS: The temporal correlation between an increase in the gene expression of TGF-beta1 and PROC I is initial evidence that that TGF-beta1 plays a significant role in collagen metabolism in a healing colonic anastomosis.

Effect of bowel preparation and a fiber-free liquid diet on expression of transforming growth factor and procollagen in colonic tissue preoperatively and postoperatively.

PURPOSE: Dehiscence of colonic anastomoses is prevalent and potentially fatal. In an attempt to reduce the likelihood of anastomotic dehiscence, the colon is cleansed before surgery and fiber-free diets are prescribed postoperatively. However, fiber-free diets induce colonic atrophy and impair healing. This study was designed to investigate the effect of bowel preparation and postoperative fiber-free diet on the local gene expression of transforming growth factor-beta 1 and procollagen type I. METHODS: Four Sprague-Dawley rats underwent bowel preparation with a fiber-free liquid diet and polyethylene glycol in a balanced electrolyte solution for two days (fiber-free preoperative diet group), whereas four rats received standard chow with fiber (preoperative diet with fiber group). On the third day tissue was obtained from the descending colon of each rat to assess the effect of bowel preparation. Forty additional rats had their bowels prepared and underwent transection of the descending colon and anastomosis. These rats were then randomly assigned to continue on the liquid diet (fiber-free postoperative diet group) or rat chow (postoperative diet with fiber group). On postoperative days 3, 5, 6, 7, and 14, colonic tissue was obtained from the anastomosis and analyzed with the use of semiquantitative reverse transcriptase-polymerase chain reaction to examine the relative expression of transforming growth factor-beta 1 and procollagen type I genes normalized to that of a constitutive gene. RESULTS: There was a decrease in the expression of the transforming growth factor-beta 1 and the procollagen type I genes in the fiber-free preoperative diet group compared with the preoperative diet with fiber group; however, this difference only reached statistical significance for procollagen type I. Postoperatively, significant increases in the expression of the transforming growth factor-beta 1 and procollagen type I genes over baseline levels were observed around postoperative day 7 in both groups, which temporally correlates with active phases of collagen deposition in the wounded colon. Expression of the procollagen type I gene, however, was significantly decreased at this time in the fiber-free postoperative diet group compared with the postoperative diet with fiber group. CONCLUSION: Although necessary to reduce septic complications, preoperative bowel preparation has a detrimental effect on the expression of transforming growth factor-beta 1 and procollagen type I. A postoperative fiber-free liquid diet also may be detrimental to the expression of these transcripts in the bowel. Alternative methods for delivery of colonic fuels are needed to create a better environment for colonic healing while eliminating bacteria and bulk.

Intravenous butyrate and healing of colonic anastomoses in the rat.

PURPOSE: Intracolonic infusions of short chain fatty acids promote healing of colonic anastomoses. Because the intravenous route may have wider clinical application, we studied the effect of intravenous n-butyrate on the mechanical strength of colonic anastomoses in the rat. METHODS: After placement of an indwelling intravenous catheter, the descending colon was transected and an anastomosis was performed. Rats were then randomized to receive total parenteral nutrition (TPN group; n = 15) or total parenteral nutrition plus 130 mM/l of n-butyrate (TPN+BUT group; n = 13). On the fifth postoperative day, bursting pressure and bowel wall tension of the anastomoses were measured in situ. Anastomotic tissues were analyzed for hydroxyproline. RESULTS: The TPN+BUT group had a significantly higher bursting pressure (107.5 +/- 30.3 vs. 83 +/- 41.0 mmHg; P = 0.04) and bowel wall tension (20.7 +/- 7.6 vs. 14.1 +/- 9.9 Newton; P = 0.03). Tissue hydroxyproline was not different between the two groups (TPN, 45.8 +/- 9.2, and TPN+BUT, 47.9 +/- 2.9 microg/mg tissue nitrogen). CONCLUSIONS: We conclude that intravenous butyrate improves mechanical strength of a colonic anastomosis without a detectable change in total collagen content.

Primary care office management of perianal and anal disease.

Benign anorectal processes, hemorrhoids, fissures, abscesses, fistulas, and infections, as well as some functional disorders, are common. They generate significant patient discomfort and disability. Appropriate recognition of these processes allows for outpatient, office-based intervention. With the techniques and management described in this article, many patients' symptoms can be ameliorated expeditiously.

Nutritional support in the frail elderly surgical patient.

Malnutrition is common in the elderly population, particularly residents living in nursing homes. The decrease in nutrient intake associated with aging reduces cellular function and reserve capacity. Refeeding of malnourished elderly patients prior to elective surgeries, or following emergency surgeries, can reduce surgical morbidity and mortality. A large number of elderly patients become unable to maintain their nutritional status by oral feedings. Modern techniques and materials allow the use of the gastrointestinal tract for nutritional support in most of these patients. The ultimate goal for health care in the 1990s is to provide quality life at home. Nutritional support has become an integral component of home services for the elderly.

Tube feeding-related diarrhea in acutely Ill patients.

Acutely ill patients received tube feeding for an average of 15.8 days and, on average, 35% of those days were spent in the intensive care unit (ICU). Patients were prospectively assigned either a fiber-free formula (FFF-OSMOLITE HN, Ross; n = 50) or a fiber-supplemented (soy polysaccharide 14.4 g/L) formula (FSF = JEVITY, Ross; n = 50). Diarrhea was defined as three or more loose or watery stools per day and occurred in 30% of all patients. Diarrhea developed in 29 (41%) of the 71 patients who received antibiotics during, or within 2 weeks prior to, the feeding period, whereas only 1 (3%) of the 29 patients not receiving antibiotics developed diarrhea (p less than 0.005); and this patient developed diarrhea on the day of death. Among the 30 patients with diarrhea, stool Clostridium difficile (CD) toxin was positive in 15 (50%), negative in 11 (37%), and was not measured in four. The mean serum albumin was significantly lower in patients with diarrhea (2.43) than in those without diarrhea (2.75) (p = 0.043). There were no significant differences in age, sex, diagnoses, number of feeding days, and percent ICU days between patients with and without diarrhea. While not statistically significant, patients who received FSF were observed to have a lower incidence of diarrhea, a lower percentage of diarrhea days per total feeding days, and a lower frequency of positive CD toxin assays than patients who received FFF. In this patient population, antibiotic usage was the factor most strongly associated with diarrhea during tube feedings.

Experimental studies on the healing of colonic anastomoses.

The leakage of colonic anastomoses is a potentially devastating surgical complication. Several factors, such as bowel preparation prior to surgery, surgical technique, nutritional status, and intervening pathological conditions, have been identified as significantly influencing the healing of colonic anastomoses. Due to the multifactorial nature, it is difficult to investigate the mechanisms of occurrence and prevention of colonic dehiscence in the clinical setting. For this reason, many experimental models have been used to study colonic healing and the pathogenesis of anastomotic failure. This report reviews the use of animal models for the study of colonic anastomotic healing. Special emphasis is devoted to the rationale for selecting animal models, parameters of healing, factors influencing anastomotic healing as well as the clinical potential of dietary and pharmacologic manipulations proposed to improve colonic healing.

Parenteral nutrition supplemented with short-chain fatty acids: effect on the small-bowel mucosa in normal rats.

When enteral nutrition is excluded from animals maintained solely with total parenteral nutrition (TPN), atrophy of the intestinal mucosa is observed. Short-chain fatty acids (SCFAs) are produced in the colon by the fermentation of dietary carbohydrates and fiber polysaccharides and have been shown to stimulate mucosal-cell mitotic activity in the intestine. This study compared the effects of an intravenous and an intracecal infusion of SCFAs on the small-bowel mucosa. Rats received standard TPN, TPN with SCFAs (sodium acetate, propionate, and butyrate), TPN with an intracecal infusion of SCFAs, or rat food. After 7 d jejunal and ileal mucosal weights, DNA, RNA, and protein were determined. Standard TPN produced significant atrophy of the jejunal and ileal mucosa. Both the intracecal and intravenous infusion of SCFAs significantly reduced the mucosal atrophy associated with TPN. The intravenous and intracolonic infusion of SCFAs were equally effective in inhibiting small-bowel mucosal atrophy.

Effect of liquid formula diets supplemented with citrus pectin on intestinal structure and function.

Three studies in rats and one in normal humans subjects have documented improvements in both colonic structure and function in different conditions of colonic dysfunction. It is suggested that studies be performed in patients with colonic dysfunction to confirm these observations.

Isotonic tube feeding formula induces liquid stool in normal subjects: reversal by pectin.

Diarrhea is one of the most common complications in patients who receive tube-feeding formulas. Since the colon is the final site of water and electrolyte absorption and ultimately determines fecal composition, diarrhea during tube feeding may result from altered colonic function. The lack of dietary fiber, such as pectin, in tube-feeding formulas may be one of the means by which colonic function is affected. The purpose of this study was to determine the effect of a standard, liquid, commercially available, isotonic tube-feeding formula (ITFF) and the effects of supplementing the ITFF with pectin on colonic function as measured by stool consistency and colonic fluid composition in 13 normal adults. Data were obtained when subjects consumed their regular diet, ITFF, and ITFF supplemented with pectin using the technique of in vivo dialysis of colonic fluid. Ingestion of the ITFF resulted in a significant increase in the percentage of liquid stools compared to a regular diet [median (interquartile range) = 0% (0), 60% (64); p less than 0.01]. Ingestion of the ITFF also resulted in significant decreases in the concentrations of sodium, potassium, and short-chain fatty acids, and increases in pH and osmotic gap in colonic fluid compared to the subjects' regular diet. Supplementing the ITFF with pectin significantly reduced the incidence of liquid stools [0% (0)] and promoted a normalization of colonic fluid composition. The results suggest that the addition of pectin may enhance tolerance to ITFFs.

The effect of pectin on hepatic lipogenesis in the enterally-fed rat.

The fermentation of pectin by colonic bacteria produces short-chain fatty acids (SCFA) which are then absorbed by the host. The purpose of this study was to determine whether pectin, added to a chemically defined diet, would increase hepatic lipogenesis and whether this effect is mediated by intestinal bacteria. Eighteen Sprague-Dawley rats underwent placement of a feeding gastrostomy and a swivel apparatus. Postoperatively, rats were randomly assigned to one of three groups: 1) No Pectin received a fat-free chemically defined diet, 2) Pectin received the same diet with the addition of 1% (w/v) pectin, and 3) Neomycin received the same diet with 1% w/v pectin and neomycin (80 mg/kg of body weight daily). On the 5th postoperative d, all diets included 12.5% (v/v) deuterium as D2O. After the infusion of the labeled diets for 24 hr, the content and deuterium enrichment of liver palmitate, stearate and oleate were measured and the production rates calculated. The liver content and production rates of these fatty acids were higher in Pectin animals than in either the No Pectin or Neomycin animals. Since the effect of pectin on hepatic lipogenesis was reduced by the concomitant administration of the intestinal antibiotic neomycin, it appears that this effect depends on the bacterial fermentation of pectin. It is postulated that the SCFA produced during pectin fermentation promote lipogenesis via a direct stimulatory effect, in addition to being carbon donors.

Effect of parenteral nutrition supplemented with short-chain fatty acids on adaptation to massive small bowel resection.

After massive small bowel resection, total parenteral nutrition (TPN) is prescribed to maintain nutritional status. However, TPN reduces the mass of the remaining intestinal mucosa, whereas adaptation to small bowel resection is associated with increased mucosal mass. Short-chain fatty acids (SCFAs) have been shown to stimulate mucosal cell mitotic activity. This study determined whether the addition of SCFAs to TPN following small bowel resection would prevent intestinal mucosal atrophy produced by TPN. Adult rats underwent an 80% small bowel resection and then received either standard TPN or TPN supplemented with SCFAs (sodium acetate, propionate, and butyrate). After 1 wk, jejunal and ileal mucosal weights, deoxyribonucleic acid, ribonucleic acid, and protein contents were measured and compared with the parameters obtained at the time of resection. Animals receiving TPN showed significant loss of jejunal mucosal weight, deoxyribonucleic acid, ribonucleic acid, and protein and ileal mucosal weight and deoxyribonucleic acid after small bowel resection, whereas animals receiving SCFA-supplemented TPN showed no significant change in the jejunal mucosal parameters and a significant increase in ileal mucosal protein. These data demonstrate that SCFA-supplemented TPN reduces the mucosal atrophy associated with TPN after massive bowel resection and thys may facilitate adaptation to small bowel resection.

Comparison of parenteral nutrition and enteral feeding with pectin in experimental colitis in the rat.

The effect of a pectin-supplemented enteral diet on experimental colitis was compared with parenteral nutrition and with a pectin-free enteral diet. Forty-five rats had feeding catheters placed into either the stomach (IG, n = 31) or the superior vena cava (IV, n = 14) and then received acetic acid (colitis) or saline (control) enemas. After the enema, all rats received the same diet, either IG or IV, for 6 d except for 15 rats (IGP, 9 colitis and 6 controls), which had 1% pectin added to the diet. At the end of the feeding period the IGP group had significantly less colonic inflammation and/or necrosis than either IV (p less than 0.03) or IG (p less than 0.04) groups. Nitrogen balance, serum albumin, total iron-binding capacity and body weight did not differ significantly among dietary regimens. Thus, the degree of bowel injury in experimental colitis was decreased when animals were fed a pectin-supplemented enteral diet and this effect was independent of nutritional status.

Small bowel disaccharidase activity in the rat as affected by intestinal resection and pectin feeding.

This study investigated the effects of small bowel resection (SBR) and a pectin-supplemented elemental diet (ED) on intestinal disaccharidase activity. Rats underwent placement of feeding gastrostomy and swivel apparatus. Control animals were returned to their cages while resected animals underwent an 80% SBR. Postoperatively, animals received either a pectin-free ED or the ED supplemented with 2% pectin. After 2 wk jejunal and ileal mucosal sucrase, maltase, and lactase activities and protein content were determined. Feeding the ED after SBR resulted in significant increases in all three ileal segmental disaccharidase activities but only maltase activity was significantly increased in the jejunum. The pectin-supplemented ED, however, significantly enhanced the adaptation of jejunal and ileal segmental sucrase, maltase, and lactase activity to SBR with the increase in all three jejunal disaccharidase activities being significantly greater than that of the resected animals fed the ED alone.

Enteral and parenteral nutrition in patients with enteric fistulas and short bowel syndrome.

Significant advances in the use of enteral and parenteral nutrition in patients with either enteric fistulas or short bowel syndrome include increased usage of enteral nutrition because of its trophic effects on the gut and increased usage of both enteral and parenteral nutrition in the home setting. Current investigations are directed toward identifying gut-specific fuels and dietary and pharmacologic enhancement of nutrient utilization.