The L-Cell in Nutritional Sensing and the Regulation of Appetite.

The gastrointestinal (GI) tract senses the ingestion of food and responds by signaling to the brain to promote satiation and satiety. Representing an important part of the gut-brain axis, enteroendocrine L-cells secrete the anorectic peptide hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) in response to the ingestion of food. The release of GLP-1 has multiple effects, including the secretion of insulin from pancreatic ß-cells, decreased gastric emptying, and increased satiation. PYY also slows GI motility and reduces food intake. At least part of the gut-brain response seems to be due to direct sensing of macronutrients by L-cells, by mechanisms including specific nutrient-sensing receptors. Such receptors may represent possible pathways to target to decrease appetite and increase energy expenditure. Designing drugs or functional foods to exploit the machinery of these nutrient-sensing mechanisms may offer a potential approach for agents to treat obesity and metabolic disease.

Adaptation of ventilation to 'buffeting' in vehicles.

OBJECTIVES: Short exposures to buffeting in a vehicle driving over rough terrain induce an increase in the frequency of respiration resulting in hyperpnoea and hypocapnia. The present study investigates the adaptation to buffeting-induced hyperpnoea. METHODS: We monitored ventilation and cardiovascular function in nine healthy young adults prior to, throughout and post a 30 minute simulation of buffeting. RESULTS: All subjects had a consistent elevation of respiratory frequency throughout motion. End-tidal CO(2) decreased during the first 5 minutes of buffeting due to a transient increase in minute ventilation. Elevation of respiratory frequency was facilitated by shortening of inspiration without change in expiratory time. Tidal volume was maintained which resulted in an increase in mean inspiratory flow during buffeting. At later stages of motion there was a partial return to normal for mean inspiratory flow, minute ventilation and end-tidal CO(2)because of a slight reduction in tidal volume whilst inspiratory time remained shortened. Salivary cortisol levels were unaffected by motion, suggesting that the hyperpnoea was not secondary to non-specific stress. INTERPRETATION: The cause of elevated respiratory frequency during buffeting could be due to mechanical action on the torso, vestibular-respiratory drive or a protective reinforcement of the torso.