Chronic infusion of islet amyloid polypeptide causes anorexia in rats

Islet amyloid polypeptide (IAPP) is a hormonal peptide that at high doses has been shown to reduce food intake. In the present study, the dose- response effects of subcutaneous infusion of IAPP (0, 2, 7, and 25 pmol·kg^{- 1}·min^-1) for 8 days on food intake and meal patterns in rats were investigated. At the end of the experiment, plasma was obtained and levels of IAPP were measured by radioimmunoassay. IAPP dose-dependently and transiently inhibited food intake. The minimal effective dose (2 pmol·kg^-1·min^-1) caused a small but significant (up to 14%, P < 0.01) inhibition of food intake that lasted 5 days. The highest dose administered (25 pmol·kg^{- 1}·min^-1) had the greatest effect (up to 44%, P < 0.001), which lasted throughout the 8-day period. Reductions in feeding during light and dark phases occurred through a decrease in number of meals consumed rather than meal size or meal duration. IAPP also decreased body weight gain and water intake dose dependently. IAPP infusion of 2, 7, and 25 pmol·kg^-1·min^-1 increased plasma IAPP concentrations from a basal level of 10.3 ± 0.7 pM to 35.1 ± 5.4, 78.1 ± 11.2, and 236.6 ± 23.6 pM, respectively, values that are likely to be close to physiological and within the pathophysiological ranges. Thus IAPP may play an important physiological or pathophysiological role in control of food intake.