Inhibition of TPN-associated intestinal mucosal atrophy with monoacetoacetin

Synthesis and intravenous infusion into the rat of glyceryl bisacetoacetate, 1-acetoacetamido-2, 3-propane diol, and partially reduced glucosyl pentaacetoacetate

The efficacy of parenteral nutrition could be improved by finding a more effective energy source. Esters of short-chain fatty acids have exhibited some promise as alternatives to glucose. The present study reports on two new esters and one amide, each containing acetoacetate as the organic acid. The three compounds: glyceryl bisacetoacetate, N-2',3'-dihydroxypropyl-3-oxo-butanamide (1-acetoacetamido-2,3-propane diol), and partially reduced glucosyl pentaacetoacetate, were synthesized and then continuously infused into rats for 7 d. The infusion rate provided 50% of the rats' estimated metabolic energy requirements, and rats were fed with a reduced-energy oral diet that provided the remaining 50% of energy plus adequate protein. Rat groups for each compound were: (1) experimental-compound-infused and ad libitum-fed, (2) isoenergetic glucose-infused and pairfed, and (3) saline infused and pair-fed. Body-weight changes, N losses and N retention were measured daily. All rats died from partially reduced glucosyl pentaacetoacetate infusion at 100% and 50% of the intended rate. Rats infused with 1-acetoacetamido-2,3-propane diol failed to gain weight and to increase the plasma ketone-body concentration. Glyceryl bisacetoacetate produced hyperketonaemia, and weight gain and N variables that were similar to those for glucose-infused rats. It was concluded that only glyceryl bisacetoacetate would make a satisfactory parenteral nutrient.

Potential of the monoglyceride and triglyceride of DL-3-hydroxybutyrate for parenteral nutrition: synthesis and preliminary biological testing in the rat

Esters of short-chain organic acids have shown some promise as potential nutrients for parenteral feeding. Most glycerols are water insoluble but those of the ketone bodies have some water solubility. Of interest is that the triacylglycerol of 3-hydroxybutyrate has water solubility while the triacylglycerol of acetoacetate does not. The mono- and triacylglycerol of DL-3-hydroxybutrate were synthesized and tested for toxicity and nutritional value as parenteral nutrients. Both compounds have an estimated energy density of 19.7 kJ/g (4.7 kcal/g) and are water soluble. The compounds were infused into rats for 7 d at a rate to provide 113 kJ/d and were accompanied by a low-energy oral diet. Control, pair-fed rats were infused with isocaloric glucose or 0.9% saline. Nitrogen intake, output, and balance, body weight changes, and liver size were compared. The two glycerols of 3-hydroxybutyrate supported similar nitrogen retention, body weight changes, and liver size as found in the pair-fed control animals infused with glucose. Rats infused with saline retained less nitrogen, had decreased body weight, and had smaller livers. The data demonstrated that the glycerols of DL-3-hydroxybutyrate are not toxic, provide metabolic energy when infused intravenously, and could be used as nutrients for parenteral feeding.

Efficacy of different triglycerides in total parenteral nutrition for preventing atrophy of the gut in traumatized rats

BACKGROUND

The efficacy of different fat emulsions as components of a total parenteral nutrition (TPN) regimen on the integrity of the gut was assessed in traumatized rats. With the release of the short-chain fatty acids butyric or propionic acid during the hydrolysis of a structured triglyceride containing butyric acid (C4-L-C4-TG) or the beta-oxidation of nonanoic acid from trinonanoin (C9TG), respectively, the infusion of these two triglycerides was supposed to reveal positive effects against the TPN-induced atrophy of the intestine.

METHODS

After 3 days of fiber-free liquid diet, rats were traumatized (laparotomy) and catheterized. Afterwards they received equicaloric TPN that delivered 1008 kJ (241 kcal)/kg of body weight per day and 30% nonprotein calories as fat emulsion. The four fat emulsions tested in four groups of six animals contained either long-chain triglycerides (LCT), medium-chain triglycerides (MCT)-LCT (1:1), C9TG/LCT (1:1) or C4-L-C4-TG. Animals of a control group were infused with isovolemic 0.9% NaCl solution and were offered oral standard chow.

RESULTS

After 7 days of MCT/LCT administration, the mass-to-length ratio of the total small bowel as well as the masses of mucosa/submucosa and muscularis/serosa in 10-cm segments of the distal half of the small bowel were significantly higher than that found in the other TPN groups or not different from controls. Histometric measurement of the villus height in the ileum revealed no statistically significant differences from controls for the rats of the MCT/LCT and C4-L-C4-TG groups. In the colon, no statistically significant differences between TPN groups were found for either parameter.

CONCLUSIONS

Within the tested fatty substrates the MCT/LCT fat emulsion revealed less structural impairments in the distal half of the small bowel regarding mucosa/submucosa (mass and villus height), but also muscularis/ serosa (mass).

Colonic fermentation and nutritional recovery in rats with massive small bowel resection

BACKGROUND/AIMS

After massive small bowel resection, malabsorbed carbohydrates reach the colon and undergo fermentation. This study investigates the role of colonic fermentation in rats with 80% small bowel resection on weight gain, nitrogen balance, body composition, and intestinal adaptation.

METHODS

Resected or transected rats were fed a liquid diet enterally for 16 days with or without 30 mg/kg metronidazole to reduce fermentation. Weight gain was monitored until the rats were killed. Carcass composition, short-chain fatty acids in cecal content, total nitrogen output, and intestinal mucosal dry weight, protein, and DNA were measured.

RESULTS

Resected rats without metronidazole had a significantly better weight gain, carcass protein, nitrogen balance, and mucosal dry weight, protein, and DNA compared with that of resected rats receiving metronidazole. There were no significant differences between the two transected groups.

CONCLUSIONS

Decreasing colonic fermentation, measured by short-chain fatty acids in cecal content, reduced intestinal adaptation and nutritional recovery in rats with massive small bowel resection.

Parenteral monoacetoacetin and liver regeneration interaction after partial hepatectomy in the rat

Parenteral nutrients can be used to manipulate cell proliferation after partial hepatectomy. The relationship among macronutrients--glucose, monoacetoacetin, amino acids--and liver regeneration after partial hepatectomy was investigated. Male rats were anesthetized, received a 70% hepatectomy, and received a low-dose infusion of (1) glucose or (2) monoacetoacetin and a high-dose infusion of (3) glucose, (4) glycerol-glucose, or (5) monoacetoacetin-glucose beginning 6 hours after surgery. The five nonprotein nutrient combinations were infused with and without amino acids. Rats were killed 48 hours after partial hepatectomy, and the label and mitotic indices were determined. Each of the five treatments had a higher label index with amino acids present than with amino acids absent. Low-dose glucose and monoacetoacetin as well as high-dose glucose and glucose-glycerol had higher mitotic indices with amino acids than without amino acids. High-dose monoacetoacetin-glucose was associated with a greater mitotic index than was any other nonprotein substrate treatment, and this response was independent of amino acids being present or absent. In summary, (1) amino acids were needed for maximal cell proliferation rate; (2) the absence of amino acids and not the presence of glucose resulted in reduction of the label and mitotic indices for regenerating liver; (3) high-dose monoacetoacetin increased mitosis with or without amino acids; and (4) monoacetoacetin activity was dose dependent. The results indicate that the best nutrient for treatment of patients with liver injury is acetoacetate. The second best nutrient would be the combination of high-dose glucose and amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritional support in the patient with the systemic inflammatory response syndrome

The syndrome previously known as "sepsis" is now recognized as a generalized response to a number of stimuli that cause systemic activation of inflammatory mediators. The so-called "systemic inflammatory response syndrome" (SIRS) represents a final common endpoint to overwhelming persistent infection, massive tissue injury, prolonged tissue oxygen debt, or any other insult precipitating global inflammation. The metabolic consequences of SIRS are profound but in the past were not fully appreciated because patients died from more immediate causes (e.g., renal failure, pulmonary failure, gastrointestinal hemorrhage). As modern critical care has maintained patients in prolonged phases of recovery, the need for appreciation of the nutritional impact of the hypermetabolic response is taking center stage. The systemic activation of counterregulatory hormones, cytokines, and other mediators of inflammation has complex metabolic effects that are discussed in this review. A rational approach to assessing nutritional needs in patients with SIRS will be presented along with a discussion of how the needs are best met. Finally, the pitfalls encountered in nutritional support of patients with sepsis will be outlined along with a protocol for monitoring tolerance to and effectiveness of metabolic support in SIRS.

Glutamine enhancement of structure and function in transplanted small intestine in the rat

Total parenteral nutrition is required by all patients in need of small bowel transplantation. Untoward side effects of total parenteral nutrition include atrophy and hypofunction of the small intestine. Glutamine, the preferred fuel for the enterocyte, is presumably present in insufficient amounts in diets given to patients with intestinal dysfunction. In a rat model of total parenteral nutrition and small bowel transplantation, this study investigated the following: (1) whether glutamine improves graft structure and function, (2) the optimal route of glutamine delivery (intravenous vs direct infusion into the graft), and (3) the effect of glutamine on ultrastructure of the graft enterocyte. Lewis rats underwent small bowel transplantation as a Thiry-Vella graft and received total parenteral nutrition for 14 days while assigned to one of four infusion groups: 2% intravenous glutamine; 2% intravenous isonitrogenous mixture, nonessential amino acids (control); 2% glutamine into the graft; or 2% nonessential amino acids into the graft (control). Graft mucosal villous height, villous surface area, crypt depth, weight, protein, deoxyribonucleic acid content, glucose absorption, and enterocyte ultrastructure were then evaluated. Infusion of glutamine directly into the graft significantly increased mucosal villous height (p = .045), surface area (p = .029), and glucose absorption (p = .004) when compared with controls. Intravenous glutamine infusion significantly increased mucosal villous height (p = .002), surface area (p = .001), weight (p = .005), and glucose absorption (p = .04) when compared with controls. Most enterotrophic and functional benefits of glutamine were not significantly different between intravenous infusions and direct administration into the graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pectin and cellulose on fat absorption after massive small-bowel resection in weanling rats

The effects of pectin and cellulose on fat absorption after massive small-bowel resection were studied in rats. Weanling Wistar rats underwent 80% resection of the small intestine with gastrostomy, and fat emulsion labeled with 14C-linoleate was given via a gastrostomy tube for the fat absorption test on the 10th postoperative day. They were classified into three groups by diet as follows: E group, a fiber-free, chemically defined diet (CDD); EP group, CDD with 2% pectin; and EC group, CDD with 2% cellulose. The cumulative and hourly output of 14C in the expired air, the absorption rate of 14C in the intestine, and the metabolic utilization rate of 14C were calculated. The cumulative 14CO2 output was significantly lower in the EC group than in the E and EP groups. However, there was no significant difference in the 14CO2 output between the E and EP groups. The highest hourly 14CO2 output in the E and EP groups was observed during the first 2 hours. However, in the EC group, this fluctuated at low levels. No significant difference in the 1-14C-linoleate absorption rate was observed between the E and EP groups, whereas it was significantly lower in the EC group than in the E and EP groups. The metabolic utilization rate of 1-14C-linoleate showed no significant difference among the three groups. These data suggest that an addition of pectin to CDD does not impair small intestinal absorption of 1-14C-linoleate after massive small-bowel resection, and an addition of cellulose decreases absorption of 1-14C-linoleate.

Effect of short-chain fatty acids on the human colonic mucosa in vitro

Fermentable dietary fiber components are known to stimulate colonic crypt proliferation. As these compounds are rapidly degraded to short-chain fatty acids (SCFAs) by the anaerobic microflora, the hypothesis was tested that this trophic effect of fiber may be mediated by SCFAs. Biopsies were taken from normal cecal mucosa of 45 individuals during routine colonoscopy. They were incubated for 3 hours with sodium salts of SCFAs at physiological concentrations (three SCFAs = acetate 60 mmol/L + propionate 25 mmol/L + butyrate 10 mmol/L; acetate 60 mmol/L; propionate 25 mmol/L; butyrate 10 mmol/L) or equimolar NaCl (control). Cell proliferation was measured autoradiographically by subsequent pulse labeling with [3H]thymidine (1 hour). The labeling index (number of labeled cells divided by the total number of cells) was computed for the crypt as a whole and for five equal crypt compartments (compartment 1 = crypt base, compartment 5 = crypt surface). Cecal crypt proliferation was raised significantly in all incubation experiments with SCFAs. Butyrate (10 mmol/L, increase + 89%) and propionate (25 mmol/L, + 70%) were as effective in stimulating proliferation as the combination of three SCFAs (+103%), although the effect of acetate (+31%) was minor. Increasing the butyrate concentration to 25 mmol/L or 60 mmol/L did not result in a further increase of cell labeling. SCFAs stimulated proliferation in the basal three crypt compartments only. An expansion of the proliferative zone to compartments 4 and 5 was not observed. SCFAs, especially butyrate and propionate, are luminal trophic factors for the cecal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Feeding the rat intravenously with ketone bodies following colon anastomosis

Ketone bodies are an important metabolic fuel for the gastrointestinal system and as a consequence may promote colonic healing. Ketone bodies and glucose were compared in a dose dependent manner as nonprotein fuels for support of resected colon. Rats had their descending colons resected and received all nutrients by vein for 5 days postoperation. Colonic healing was evaluated from the air pressure required to break the wound. All rats received constant nutrients except for non-protein energy which was fed at 10.5, 21, 31.5, and 42 kcal/day using either glucose or monoacetoacetin as substrate. Colonic bursting pressure was measured on day 5 after surgery. When energy intake was 21 kcal/day or greater, the bursting pressure was two-thirds of nonwounded tissue and was independent of energy quantity and source. At 10.5 kcal/day, bursting pressure for glucose-fed animals was similar to that for animals with no added nonprotein energy while, in contrast, bursting pressure for animals fed monoacetoacetin was similar to that for animals fed 42 kcal/day. It was concluded that bursting pressure was influenced by dietary intake only if the energy intake was sufficiently low, and then ketone bodies were better than glucose for support of colonic healing.

Urogastrone reduces gut atrophy during parenteral alimentation

Urogastrone (UG) exerts trophic effects on the intestine and may play a role in maintaining normal intestinal structure and function. Since administration of nutrients parenterally results in intestinal hypoplasia and hypofunction, the aim of this study was to determine the effects of UG on intestinal structure and function in parenterally fed rats. Central venous catheters were placed into 28 Sprague-Dawley rats. Group I (n = 10) received TPN alone. Group II (n = 8) received TPN and 15 micrograms/day of UG and group III (n = 10) received rat chow ad libitum. The animals that received urogastrone had significantly greater (p less than 0.05) intestinal weight (25.6 +/- 2.5 mg/cm vs 22.6 +/- 3.0 mg/cm), mucosal weight (8.4 +/- 1.4 mg/cm vs 6.2 +/- 0.9 mg/cm), mucosal protein content (6.2 +/- 1.7 mg/cm vs 2.7 +/- 0.6 mg/cm), villous height (427 +/- 27 microns vs 293 +/- 75 microns), crypt cell production rate (14.5 +/- 1.4 metaphases/hr vs 12.3 +/- 0.7 metaphases/hr) and sucrase specific activity (6.5 +/- 2.6 vs 3.7 +/- 2.0) than animals receiving only TPN. However, these parameters remained less than in chow-fed animals. Thus, simultaneous infusion of UG prevents, in part, intestinal hypofunction and hypoplasia which occurs during TPN. This may be due to maintenance of mucosal proliferative activity and brush border enzyme activity.

Stimulation of intestinal mucosal growth with intracolonic infusion of short-chain fatty acids

Dietary fiber, which stimulates intestinal mucosal growth, is fermented by anaerobic bacteria in the rat hindgut to the short-chain fatty acids (SCFA) acetate, propionate, and butyrate. Butyrate is the preferred oxidative fuel of the colonocyte in vitro, and the provision of preferred intestinal fuels has been shown to stimulate mucosal proliferation in vivo. This study determined whether chronic colonic infusion of butyrate or a combination of SCFA would stimulate intestinal mucosal growth in an animal deprived of its normal source of SCFA, fiber fermentation in the cecum. Adult male Sprague-Dawley rats were fed a fat- and fiber-free elemental liquid diet and underwent cecectomy, ileocolic anastomosis, and insertion of a proximal colonic infusion catheter. Rats were then assigned to receive either a continuous infusion of butyrate (20 mM, 40 mM, or 150 mM), SCFA (70 mM acetate + 35 mM propionate + 20 mM butyrate), or saline, or to receive no infusion. A seventh group underwent proximal colonic transection and reanastomosis. After 7 days, jejunal, ileal, and proximal colonic segments were analyzed for mucosal weight, protein, RNA, and DNA. In the colon, the 40-mM butyrate infusion resulted in significant elevations in all mucosal parameters relative to all three control groups, saline infusion, no infusion, and transection. Both the 20-mM butyrate and the SCFA groups showed increased colonic mucosal DNA compared to controls. In the jejunum and ileum, mucosal DNA content was significantly greater in the SCFA group than in the control groups.(ABSTRACT TRUNCATED AT 250 WORDS)