The effects of alimentary infusions of glucose, amino acids, or neutral fat on meal size in hungry pigs.

Abstract

SUMMARY1. Young growing pigs trained to press a panel in order to obtain delivery of small quantities of food were adapted to eating all their food during one readily measured meal per day.2. Twenty-nine pigs were surgically fitted with an exteriorized cannula connected to either (a) the stomach or (b) the duodenum.3. Two pigs were each fitted with two cannulae in the duodenum which were exteriorized and connected outside the body. Food was then shunted so as to pass along outside the body from the pyloric region of the duodenum to the lower part of the duodenum via the tube connecting the exteriorized cannulae.4. While feeding, the pigs were given 250 ml. infusions of solutions of (1) 0 9 % saline or (2) 15 % glucose into either the stomach or the duodenum. Similar volumes of amino acids or 15 % neutral fat were infused into the duodenum.5. The infusions lasted about 3 min and were started 2-3 min after the beginning of a meal.6. Control meals without infusions took 30-40 min. The 15 % intraduodenal glucose infusions consistently produced a suppression of eating 15-20 min after the end of the infusion.7. Infusions of 0 9 % saline, of 10 % amino acid or of 15 % neutral fat did not reduce significantly the intake of food or the duration of the meal.8. It was not clear how the glucose solution was able to suppress appetite. The possible existence of a specific glucose receptor is discussed.

Gastrointestinal satiety in animals other than man

“…0.6-0.8-fold in the baboon; Woods et al 1984) and are less effective than the equivalent gastrointestinal infusions (e.g. pig; Stephens, 1980). Using sham-fed rats, glucose infusions into the small intestine have now been shown to inhibit intake physiologically by eliminating intestinal signals from the digesta, the threshold rate of infusion for intestinal inhibition of satiety (0.46 kJ (0.11 kcal)/min) being less than the normal rate of emptying (1.34 kJ (0.32 kcal)/min; Reidelberger et al 1983).…”

Similarities and differences between intake control mechanisms in pigs, chickens and ruminants

“…Glucose, but not amino acids or fat solutions, when injected into the duodenum of fasted pigs had a depressing effect on food intake, suggesting a chemical effect of glucose in addition to the osmotic or stretch effects of this type of treatment (Stephens, 1980); again, this is blocked by vagotomy (Stephens & Heron, 1979). Glucose solution given into the duodenum of free-feeding chickens had much less effect on intake than did solutions of mannitol or potassium chloride (which are not absorbed) of the same osmolality (Shurlock & Forbes, 1981a), supporting the idea of osmotic or stretch effects.…”

The Influence of Gastrointestinal Infusions of Glucose on Regulation of Food Intake in Pigs

“…Furthermore, in contrast to the lack of effect of rapid gastric injections of glucose (Stephens, 1980 a) slow gastric infusions of glucose similarly inhibited intake according to both the energy content and osmotic concentration. Unlike in the rat (Deutsch & Gonzalez, 1980;Koopmans, 1983) these latter effects were largely inhibited by duodenal perfusion with the local anaesthetic lignocaine and thus cannot be of purely gastric origin.…”

“…Therefore even though blood glucose levels rise rapidly with feeding (Anderson, 1974;Rayner, Weekes & Bruce, 1981) it appears that glucose has no post-absorptive effects on short-term intake and that any influence of dietary carbohydrate must be pre-absorptive. Indeed a number of studies have shown that rapid injection of glucose into the duodenum during or immediately prior to feeding does suppress intake in the pig (Heron & Stephens, 1978;Houpt et al 1979; Stephens, 1980 a;Houpt, Baldwin & Houpt, 1983 a), an effect that appears to depend upon the osmotic concentration of the glucose (Houpt et al 1979(Houpt et al , 1983a. None of these studies reported the response to glucose on an energy basis.…”

“…In order to be able to infuse sufficient quantities of energy and to test for the effects of the infusions on regulation of energy intake at that meal infusions of 40 % glucose were given from 30 min before feeding until the animals finished feeding. This protocol, which also allows time for activation of hormonal mechanisms that may be involved in the control of intake, has been recently used to show that gastrointestinal infusion of fats can strongly influence food intake in pigs while conversely rapid duodenal injection of fats does not affect intake (Stephens, 1980 a). In the rabbit glucose affects food intake differently according to whether the animals are free-feeding or feed deprived Vanderweele, Novin, Rezek & Sanderson, 1974) with duodenal infusion of glucose only inhibiting intake in the free-feeding rabbit.…”