Triglyceride administration alters leptin responsiveness in rats

Abstract

Leptin resistance is defined a reduced responsiveness to the feeding and body weight inhibiting effects of the hormone with increasing adiposity. One potential mechanism mediating this condition was identified by Banks et al. (Diabetes, 2004) who showed that acute iv infusion of saturated triglycerides (TG) blocks leptin transport across the blood brain barrier. To test this mechanism in vivo, we administered three equicaloric TG emulsions varying in saturation level to rats by oral gavage for 11 days. Cream (Cr), Intralipid (IL) or fish oil (FO) emulsions containing 20% lipid by weight (2.0 kcal/ml) were administered twice daily in a volume of 1.0 ml (5% of total daily calories) to groups of chow‐fed adult male S‐D rats. No change in body weight (BW) or leptin levels was seen in the groups during treatment, but FO decreased (p<0.05) and IL increased (p<0.01) circulating TG. On Day 11, rats were injected ip with 1.0 mg leptin/kg BW prior to lights out, and food intake was measured 4, 8 and 24 hrs later. Compared to intake following a saline injection given on Day 5, leptin significantly inhibited feeding at 8 and 24 hr post‐injection in the FO group (p<0.05), while the Cr and IL groups showed no change or increased feeding, respectively, at the same intervals (p<0.05). Our results show that saturation level determines responsiveness to injected leptin, and are consistent with the observations of Banks et al.Supported by NYONRC DK‐26687.