Effects of Exogenous Leptin on Satiety and Satiation in Patients with Lipodystrophy and Leptin Insufficiency

To examine leptin’s role in human appetite regulation, we studied recombinant methionyl human leptin’s effects on satiation and satiety in a model of leptin insufficiency, lipodystrophy. Eight females with hypoleptinemia and lipodystrophy were given sc injections of A-100 (maximal dose, 200% of that predicted to normalize serum leptin) for 4 months. Satiation and satiety were determined before and again during leptin treatment. Satiation was measured as the time to voluntary cessation of eating from a standardized food array after a 12-h fast. Satiety was determined as the time to hunger sufficient to consume a full meal after consumption of a standardized preload. During leptin treatment, satiation time decreased (41.2 ± 18.2 to 19.5 ± 10.6 min; P = 0.01), satiety time increased (62.9 ± 64.8 to 137.8 ± 91.6 min; P = 0.04), energy consumed to produce satiation decreased (2034 ± 405 to 1135 ± 432 kcal or 8.5 ± 1.7 to 4.7 ± 1.8 MJ; P < 0.01), and the amount of food desired in the postabsorptive state decreased (P < 0.02). Ghrelin concentrations also decreased during leptin administration (284.3 ± 127.9 to 140.6 ± 104.5 pmol/liter; P < 0.002). We conclude that increased leptin in patients with lipodystrophy results in less caloric, shorter, more satiating meals and longer-lived satiety. These data support the hypothesis that leptin plays an important, permissive role in human appetite regulation.

A First Order Approximation of Satiation Time: (IRT)2/Rt

Habituation, satiation, adaptation, and boredom are a few of the words used to Label the behavioral consequences of a fundamental operation: repeated and protracted presentation of a stimulus. The cumulative measure of the response associated with that stimulus is expected to display an inflection at some time Ti after which the slope approaches zero. Ti can be estimated by dividing the square of the interresponse time (IRT)2 by the duration of the response associated with reinforcement (Rt), where Rt is expressed in the nearest whole temporal unit of interresponse time. Calculated TiS for habituation to the same sexual, aggressive, or social stimuli are compatible with general observation.

Satiation Time, Appetite, and Maximum Food Intake of Sockeye Salmon (Oncorhynchus nerka)

Three aspects of feeding relations in sockeye salmon (Oncorhynchus nerka) were studied, using Abernathy pellets. When food was presented in excess at 15 C, mean satiation time was found to be 43 ± 8 min, independent of fish size. Voluntary food intake (appetite) increased with time, approaching a plateau after 25–30 hr deprivation. The greatest increase in appetite occurred between 7 and 11 hr of fasting. The relation between the capacity of the stomach (% body weight) and fish weight (grams) was exponential (Y = 14.1 − 4.95 log10X). Five-gram fish consumed 11% dry body weight at one feeding, and 17% on a daily basis.