Ghrelin is a novel gastric peptide which stimulates growth hormone and has orexigenic and adipogenic properties. Plasma ghrelin is influenced by nutritional status and is thought to play a role in regulating food intake and body weight. We examined the effect of infusing insulin (40 mU/m2/min) for 2 hours while maintaining euglycemia on plasma ghrelin in 8 subjects (5 M, 3 F) aged 46 ± 4 yrs (mean ± SEM). Plasma insulin increased from 78 ± 9 to 564± 23 pmol/L during and returned rapidly to basal values after stopping the insulin infusion. Plasma ghrelin decreased from 85 ± 28 to 61 ± 18 pmol/L (p < 0.01) by 90 minutes of and continued to be suppressed for 15 minutes after the insulin infusion was discontinued. Subsequently, plasma ghrelin rose rapidly to near-basal values (81 ± 23 pmol/L) within 60 minutes. The reciprocal relation between insulin and ghrelin was observed consistently in all subjects with the maximum insulin-induced suppression of ghrelin ranging from 19 to 64% (mean 32± 5) and occuring 90–135 minutes after starting the insulin infusion (median 120). These findings indicate that insulin is a physiological and dynamic modulator of plasma ghrelin and that insulinemia possibly mediates the effect of nutritional status on its concentration.

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