INTESTINAL ABSORPTIVE CAPACITY AND SITE OF ABSORPTION OF FAT UNDER STEADY STATE CONDITIONS IN THE UNANAESTHETIZED RAT

Effect of medium-chain triglycerides on growth performance, nutrient digestibility, plasma metabolites and antioxidant capacity in weanling pigs

The aim of this study was to investigate the effect of medium-chain triglycerides (MCTs) on growth performance, nutrient digestibility, plasma metabolites and antioxidant capacity in weanling pigs. A total of 160 weanling (Duroc × Landrace × Yorkshire) pigs (age: 21 ± 1 d; body weight: 7.50 ± 0.28 kg) were randomly allotted to 4 treatments, receiving the following diets for 28 d: control diet [containing 3.5% soybean oil (SO)], MCT1 diet (containing 0.7% MCTs and 2.8% SO), MCT2 diet (containing 1.4% MCTs and 2.1% SO) and MCT3 diet (containing 2.1% MCTs and 1.4% SO). Dietary inclusion of MCTs improved the average daily gain and feed efficiency (FE) of pigs compared with the control during the first 2 weeks post-weaning (P < 0.05). A similar positive effect was also observed for the overall FE in MCT2 group (P < 0.05). Compared with the control, apparent total tract digestibility (ATTD) of ether extract was improved by MCT2 and MCT3 treatment from day 12–14 post-weaning (P < 0.05). In addition, MCT2 treatment also exerted a beneficial effect on the ATTD of dry matter (P < 0.05). The increased total protein concentration and decreased urea nitrogen and malondialdehyde levels of plasma were observed in both MCT2 and MCT3 groups on day 14 post-weaning (P < 0.05). In conclusion, MCTs could improve growth performance, nutrients utilization, and antioxidant ability of weanling piglets.

Lymphatic recovery of exogenous oleic acid in rats on long chain or specific structured triacylglycerol diets

Specific structured triacylglycerols, MLM (M = medium-chain fatty acid, L = long-chain fatty acid), rapidly deliver energy and long-chain fatty acids to the body and are used for longer periods in human enteral feeding. In the present study rats were fed diets of 10 wt% MLM or LLL (L = oleic acid [18:1 n-9], M = caprylic acid [8:01) for 2 wk. Then lymph was collected 24 h following administration of a single bolus of 13C-labeled MLM or LLL. The total lymphatic recovery of exogenous 18:1 n-9 24 h after administration of a single bolus of MLM or LLL was similar in rats on the LLL diet (43% and 45%, respectively). However, the recovery of exogenous 18:1 n-9 was higher after a single bolus of MLM compared with a bolus of LLL in rats on the MLM diet (40% and 24%, respectively, P = 0.009). The recovery of lymphatic 18:1 n-9 of the LLL bolus tended to depend on the diet triacylglycerol structure and composition (P= 0.07). This study demonstrated that with a diet containing specific structured triacylglycerol, the lymphatic recovery of 18:1 n-9 after a single bolus of fat was dependent on the triacylglycerol structure of the bolus. This indicates that the lymphatic recovery of long-chain fatty acids from a single meal depends on the overall long-chain fatty acid composition of the habitual diet. This could have implications for enteral feeding for longer periods.

The recovery of 13C-labeled oleic acid in rat lymph after administration of long chain triacylglycerols or specific structured triacylglycerols

BACKGROUND

Consumption of specific structured triacylglycerols, MLM (M = medium chain fatty acid, L = long chain fatty acid), delivers fast energy and long chain fatty acids to the organism.

AIM OF THE STUDY

The purpose of the present study was to compare lymphatic absorption of (13)C-labeled MLM and (13)C-labeled LLL in rats. Stable isotope labeling enables the separation of the endogenous and exogenous fatty acids.

METHODS

Lymph was collected during 24 h following administration of MLM or LLL. Lymph fatty acid composition and (13)C-enrichment were determined and quantified by gas chromatography combustion isotope ratio mass spectrometry.

RESULTS

The recovery of 18:1n-9 was higher after administration of LLL compared with MLM (58.1% +/- 7.4% and 29.1% +/- 3.9%, respectively, P < 0.001). This may be due to a higher chylomicron formation stimulated by a higher amount of long chain fatty acids in the intestine after LLL compared with MLM administration. This was confirmed by the tendencies of higher lymphatic transport of endogenous fatty acids.

CONCLUSION

The study revealed a higher lymphatic recovery of the administered long chain fatty acids after LLL compared with MLM consumption.

The use of modular nutrients in pediatrics

BACKGROUND

Nutrient modules are commonly used by pediatricians and dietitians. There is no readily available current literature to which those using nutrient modules can refer. Therefore, we review nutrient module composition, module use in pediatrics, and complications associated with the use of nutrient modules.

METHODS

Using an online database, Meduline, we searched the literature from 1996 through 1995.

RESULTS

Nutrient modules are single or multiple nutrients that can be combined with a diet to add nutrients or to change the composition of the diet. These nutrients exist as a food or as medically compounded elements of a diet but alone are not complete foods.

DISCUSSION

The addition of modules to a diet can alter the composition of a diet so that a single nutrient may become deficient and the diet cannot support normal growth and development. With use of nutrient modules, diets can be prepared to meet the specific needs of children with common or rare nutritional problems.

CONCLUSION

Health care providers who use nutrient modules must understand the importance of diet composition and the careful monitoring of pediatric patients.

Influence of intestinal resection and type of diet on the digestive and metabolic utilization of fats in rats

The effects of the quality of dietary fat, and the influence of ursodeoxycholic acid, an exogenous bile acid, on the digestive and metabolic utilization of fat were studied in rats in which 50% of the distal small intestine was resected. The fat content of the diets was quantitatively equivalent (4%), and differed only in the type of fat: olive oil (diet A) or 1/3 medium chain triglycerides (MCT), 1/3 sunflower oil and 1/3 olive oil (diet B). The removal of 50% of the distal small intestine led to a highly significant decline in the digestive utilization of fat (ADC) in animals given diet A. Rats fed diet B showed an increase in ADC to values approaching those seen in control animals. The addition of ursodeoxycholic acid to diet B failed to cause a further rise in the ADC of fat. After intestinal resection, serum levels of triglycerides and cholesterol fell more markedly in animals given diet A than in the diet B group, while the addition of ursodeoxycholic acid to diet B led to no further change. Serum lipid levels showed no significant influence of intestinal resection, but did accurately reflect the differences in fat composition between the two types of diet tested.

Regulation of pancreatic and gallbladder functions by intraluminal fatty acids and bile acids in man

The effects of intraduodenal glycerol, fatty acid (FA) chain length and FA loads, and bile acid (BA) concentrations on pancreatic and gallbladder function were investigated in 31 healthy volunteers by a perfusion method. FA absorption rates in the duodenum and proximal jejunum were measured simultaneously. Pancreatic and gallbladder responses were augmented by increasing FA chain length and FA loads until the "maximal" secretory capacity of the pancreas and gallbladder emptying was attained. Glycerol had no effect. Raising BA concentrations above the critical micellar concentration accelerated FA absorption rates but decreased the magnitude of pancreatic and gallbladder responses to FA. Higher BA concentrations exerted an opposite effect, slowing FA absorption and increasing pancreatic and gallbladder responses. Indeed, a significant, inverse correlation was found between FA absorption and pancreatic and gallbladder responses to FA, suggesting a relationship between the length of intestine exposed to FA and the amount of cholecystokinin (and/or other neurohormonal factors) released, which stimulates pancreatic secretion and gallbladder contraction.

Inhibition of steady-state intestinal absorption of long-chain triglyceride by medium-chain triglyceride in the unanesthetized rat

Maximal steady-state intestinal absorption rates in unanesthetized rats for triolein, a long-chain triglyceride, and for trioctanoin, a medium-chain triglyceride, are known to differ. Both these lipids are hydrolyzed in the intestinal lumen but the products of hydrolysis are metabolized differently by the mucosal cell. Intraduodenal infusion of trioctanoin was found to reduce steady-state triolein absorption. Luminal lipolysis was shown not to be rate-controlling. High rates of trioctanoin infusion significantly lowered the pH of the luminal aqueous phase and altered the partition of oleic acid between aqueous and oil phases. Two possible mechanisms for the inhibition of triolein uptake are considered. In the intestinal lumen medium chain lipids might have lowered the activity of oleic acid monomers in the aqueous phase and reduced passive diffusion into mucosal cells. Alternatively, competition between long and medium chain fatty acids for some common receptor during transport into the intestinal mucosal cell may have occurred. Despite significant inhibition of triolein absorption by high levels of trioctanoin, the maximum number of calories absorbed from mixtures of triglycerides exceeded the maxima from either glyceride alone. The optimum proportion of triolein to trioctanoin in lipid infusion mixtures was about 3:4 by weight and the optimum dosages about half maximal for each triglyceride, which represented a caloric intake of 4 kcal/rat per 2 hr. The absorption coefficient for this lipid mixture was about 90%. It is suggested that in patients who have a limited intestinal absorptive capacity dietary fat intake might be doubled with a caloric supplement of medium-chain triglycerides without increase in steatorrhea of long-chain fat.