Influence of caloric intake on gastric inhibitory polypeptide, VIP and gastrin release in man

The physical state of a meal affects hormone release and postprandial thermogenesis

There is evidence that food consistency may influence postprandial physiological responses. Recently we found that homogenization of a vegetable-rich meal significantly delayed the gastric emptying rate and was more satiating than the same meal in solid-liquid form. In this present study we investigated whether homogenization also influences endocrine and metabolic responses to the meal. Eight healthy men, aged 21-28 (mean 24.5) years, were given the meal (cooked vegetables 250 g, cheese 35 g, croutons 50 g and olive oil 25 g, with water 300 ml; total energy 2.6 MJ) in both solid-liquid (SM) and homogenized (HM) form, in random order, at 1-week intervals. Variables assayed were plasma glucose, insulin and glucose-dependent insulinotropic peptide (GIP) levels for 2 h and diet-induced thermogenesis (DIT) for 5 h. Plasma glucose pattern was similar after both meals. However, HM induced significantly greater insulin, GIP and DIT responses than SM. Mean integrated areas under the curves (AUC) were 1.7 (SEM 0.38) v. 1.2 (SEM 0.33) U/l per 120 min (P = 0.005) for insulin, 19.9 (SEM 2.44) v. 16 (SEM 1.92) nmol/l per 120 min (P = 0.042) for GIP, and 237.7 (SEM 16.32) v. 126.4 (SEM 23.48) kJ/300 min (P = 0.0029) for DIT respectively. Differences between GIP-AUC after HM and SM correlated significantly with differences between insulin-AUC after HM and SM (r2 0.62, P = 0.021). These findings demonstrate that homogenization of a meal results in a coordinated series of changes of physiological gastroentero-pancreatic functions and confirm that the physical state of the meal plays an important role in modulating endocrine and metabolic responses to food.

Influence of meal composition on postprandial peripheral plasma concentrations of vasoactive peptides in man

In a randomized cross-over study healthy non-obese male human subjects received standardized isocaloric, isovolumetric meals consisting of either carbohydrate, protein or fat and a non-caloric control meal consisting of an equal volume of water. Peripheral venous plasma concentrations of calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and peptide YY (PYY) were measured pre- and postprandially. Plasma CGRP concentrations were lowered following the protein meal and following the fat meal, but remained unaltered after carbohydrate or water ingestion. Plasma VIP concentrations increased slightly following the carbohydrate meal and following water loading. The PYY concentrations increased after the protein and the carbohydrate meal and a slight rise was observed following fat ingestion. Water loading did not affect the plasma level of PYY. We conclude that the postprandial peripheral plasma concentrations of CGRP, VIP and PYY are dependent on the caloric meal composition. The VIP, but not the CGRP and PYY concentrations seem to be influenced by gastric distension. The physiological significance of the postprandial alterations in peripheral concentrations of these peptides is at present uncertain.

Plasma concentrations of vasoactive intestinal polypeptide in severely burned patients: Influence of enteral nutrition

Plasma vasoactive intestinal polypeptide (VIP) concentrations were measured at different days after burn injury. A significant decrease in VIP levels was observed on days 7 and 10. The influence of enteral nutrition was also investigated: a rise in plasma polypeptide levels was found at 60 min after nutrition restart on days 4 and 7 after injury. In burn patients, VIP may be involved in the multiple metabolic and hormonal responses which lead to an increase in the hypercatabolic state. The decrease in these polypeptide values should reflect enhanced utilisation or complex hormonal regulation. After enteral nutrition, the stimulation of VIP secretion disappeared after day 7 after burn injury. This phenomenon is probably mediated by a process of adaptation to continuous enteral nutrition.