Plasma levels of n-decanoyl ghrelin, another acyl- and active-form of ghrelin, in human subjects and the effect of glucose- or meal-ingestion on its dynamics

Abstract

Besides n-octanoyl ghrelin (O-ghrelin), there is another acyl-form of ghrelin; n-decanoyl ghrelin (D-ghrelin), which has a decanoic acid modification. In this study, we examined the kinetics of D-ghrelin immunoreactivity in human plasma in comparison to O-ghrelin or total ghrelin by using a D-ghrelin-specific radioimmunoassay. The dynamics of plasma D-ghrelin was assessed following glucose- or meal-ingestion in healthy, non-obese subjects (5 males and 5 females). Correlations were also analyzed between the levels of plasma D-ghrelin and anthropometric or metabolic indicators in healthy human subjects (n=111, BMI 17.4–34.3). The plasma levels of D-ghrelin, like O- or T-ghrelin, significantly declined (p<0.05 for male and p<0.01 for female) 60min after the ingestion of glucose in non-obese subjects. However, in the same subjects, no significant decline was noted in the levels of D-ghrelin, unlike O- or T-ghrelin, upon the meal ingestion. A significant increase was observed in the proportion of plasma D-ghrelin levels to that of T-ghrelin (p<0.05) in the healthy human subjects as BMI increased, unlike the proportion of O-ghrelin to T-ghrelin, which did not change. Since D-ghrelin possesses almost the same potential as that of O-ghrelin with regard to the feeding-stimulation, these differences between the dynamics of D- and O-ghrelin in human plasma might influence appetite-control, especially in those with increased BMI.