Ghrelin secretion is more closely aligned to energy balance than with feeding behaviour in the grower pig

Abstract

Secretory characteristics of the ghrelin profile for the pig are still unknown. Our objective was to clarify the mechanisms that influence ghrelin secretion during differing feeding patterns. Pigs were initially fed a commercial pelleted diet offered ad libitum and blood samples collected for 24 h at intervals of 1 h. The pigs were then entrained for 17 days to a twice daily interval feeding regimen (0900-1000 and 1600-1700 h) and blood samples were collected for 12 h (0800-2000 h). This was followed by a similar interval feeding and blood sampling regimen with the 0900-1000 h feeding period being replaced by a sham feed where pigs were shown their usual feed but none offered. During the ad libitum feeding regimen, there was no preprandial rise or postprandial fall in circulating plasma total ghrelin concentration, which remained constant throughout the sampling period. In addition, no preprandial rise or postprandial fall in ghrelin concentrations was observed when pigs were fed either twice or once daily; however, plasma ghrelin concentration rose gradually over the 12-h sampling period during the twice daily feeding regimen and increased further when pigs were fed once per day. This increase in ghrelin levels coincided with an increase in plasma GH and non-esterified fatty acid concentrations and was not associated with either plasma glucose or insulin concentrations. These results suggest that circulating total plasma ghrelin concentrations in the pig appear to be influenced by chronic changes in energy balance rather than the feeding pattern per se.

Plasma ghrelin concentrations change with physiological state in a sciurid hibernator (Spermophilus lateralis)

“…These results indicate that ghrelin secretion may be altered by season, and therefore could play a role in the seasonal changes in food intake seen in hibernators. Scrimgeour et al (2008) provide evidence that ghrelin may reflect long term energy balance, acting as a feedback signal to the hypothalamus to defend an optimum body mass by controlling food intake. If a hibernator’s energy stores are depleted to a sufficiently low level during torpor, it will arouse and attempt to eat to make up the difference (Mrosovsky et al, 1970).…”

Cereal type and heat processing of the cereal affect nutrient digestibility and dynamics of serum insulin and ghrelin in weanling pigs1

“…The potential interaction between insulin and ghrelin concentrations in serum is a subject of debate (Soares and Leite-Moreira, 2008). In pigs, Govoni et al (2005) found a negative correlation between insulin and acylated ghrelin concentrations, whereas Scrimgeour et al (2008) were unable to detect any correlation. In the present study, the diets that triggered a greater insulin response in the early postprandial period also resulted in a greater concentration of acylated ghrelin in the late postprandial phase, which might be related to the inhibitory effects of insulin on ghrelin production (Erdmann et al, 2007).…”

“…In pigs, total ghrehn (acylated -|-des-acylated) concentration in serum may be indicative of chronic changes in energy status. Scrimgeour et al (2008) reported that total ghrelin increased with feed restriction as compared with free access to feed. Acylated ghrehn, however, was more responsive to the nutrient content of the diet and was less affected by the feeding regimen (Owusu-Asiedu et ai., 2006;Zhang et al, 2007).…”

Differential Roles for Octanoylated and Decanoylated Ghrelins in Regulating Appetite and Metabolism

“…However, some reports demonstrate that ghrelin does not play a primary role in initiating feeding nor as a regulator of feeding patterns [21]. Indeed, accumulating data suggests that ghrelin's role may be directed to maintain overall energy homeostasis as observed in humans [22, 23] and in pigs [24]. …”