Effect of vertical sleeve gastrectomy on food selection and satiation in rats

Abstract

Vertical sleeve gastrectomy (VSG) is a restrictive procedure that reduces food intake to produce weight loss. Here we assess volume and nutrient effects on the ingestive behavior of VSG and sham surgery animals. Rats given access to Ensure or pelleted chow were used to determine if liquid foods would adversely affect weight loss after surgery. Volume effects were studied by altering the caloric density of Ensure, and dietary preferences for fat and carbohydrate (sucrose) were assessed using a two-bottle test. c-Fos was used to measure neuronal activation in the nucleus of the solitary tract and area postrema in response to intragastric infusions of water, sucrose, or Intralipid. The degree of colocalization with catecholaminergic neurons was also assessed. VSG rats did not show the expected preference for a liquid diet over chow and lacked dietary preferences for fat seen in shams. Preferences for carbohydrate/sucrose solutions were unaffected by surgery. Meal size was reduced by VSG; however, VSG rats were able to alter their volume of intake to compensate for changes in caloric density, and intragastric infusions of water produced similar levels of neuronal activation among VSG, sham, and pair-fed rats. In comparison, nutrient-induced c-Fos activation was substantially increased by VSG. Colocalization between c-Fos and catecholaminergic-expressing neurons was similar among rats treated with water, sucrose, or Intralipid. VSG alters nutrient sensing in a manner that lowers the threshold for satiety and reduces fat preference to induce and maintain weight loss.

The physiology underlying Roux-en-Y gastric bypass: a status report

“…Sporadic reference will also be made to vertical sleeve gastrectomy (VSG) when appropriate. Both operations reduce eating at least temporarily (19,140,143) and lead to changes in food preferences (20,27,72). The majority of data collected with the help of preclinical studies seems to be consistent with findings in humans.…”

“…Data with a two-choice test paradigm between high-fat or low-fat diets are very consistent across laboratories. When given the choice, the postoperative intake of high-fat food decreases markedly compared with sham-operated and body weight-matched animals; relative, and in some cases, also absolute intake of low-fat food (usually standard rat chow) increased (20,27,49,72,117,158).…”

“…Data with a two-choice test paradigm between high-fat or low-fat diets are very consistent across laboratories. When given the choice, the postoperative intake of high-fat food decreases markedly compared with sham-operated and body weight-matched animals; relative, and in some cases, also absolute intake of low-fat food (usually standard rat chow) increased (20,27,49,72,117,158).Further, testing RYGB rats with liquid solutions containing increasing concentrations of fat (Intralipid) or sugar (sucrose, fructose) vs. water (two-bottle tests) also indicated that the typical strong preference for higher concentrations of fat or sugar that is observed in sham-operated and intact rats seems to be gone after RYGB (20,49,72,158). Moreover, RYGB compensated for the amount of calories ingested via the test solutions, and this was not observed in sham-operated rats; in other words, RYGB rats maintained a constant caloric intake across increasing concentrations of fat solution, while shamoperated rats increased their overall caloric intake along with the higher-fat concentrations offered (72).…”

Effects of sleeve gastrectomy and ileal transposition, alone and in combination, on food intake, body weight, gut hormones, and glucose metabolism in rats

“…SG is a restrictive surgery, and unlike gastric banding SG increases the rate of gastric emptying that may provide a physiological basis for improvement in the post prandial hormonal profile (25)(26)(27)). These findings demonstrate that the effects of SG are not only due to restriction in volume of the stomach but may also be due to activation of satiation pathways in response to nutrients (28). There is some evidence suggesting that SG surgery could be as effective as RYGB in diabetic remission of morbidly obese patients (29).…”

“…In both lean and diet-induced obese rats, intravenous or intraperitoneal infusion of PYY(3-36) leads to sustained reduction in daily caloric intake as well as lower weight gain (85,86). Increased concentration of PYY cause anorexia by interacting with PYY receptors in the arcuate nucleus (28). In obese individuals basal and meal-stimulated concentration of PYY is significantly lower as compared to the lean persons (87).…”