Effets d'une immunomodulation de la leptine et de la cholécystokinine chez le rat en croissance
The use of antibodies to modulate the activity of existing endocrine factors is an immunomodulation. The meal-related intestinal signal cholecystokinin (CCK) and the adipose tissue-produced leptin are known as satiety hormones. Their interaction induces long- and short-terms effects. The aim of this study is to examine the zootechnical and endocrinal effects of an active immunomodulation of both CCK and leptin. Three experiments are realized. Two of them are single or double active immunization of rats against the cholecystokinin 33 (CCK-33), the unsulfated cholecystokinin octapeptide (CCK- 8ns) and the leptin. The last experiment consists in injecting leptin and CCK-8ns into immunized rats. More than 60 % of the concerned rats are really immunized against CCK-33 or CCK-8ns. Few rats develop antibodies against leptin. Very few rats respond to the double immunization against CCK and leptin. In the first experiment, the immunomodulation of CCK-8ns reduces food intake and growth. The leptin-immunized rats eat the most (P < 0.05). The second experiment shows that the immunomodulation of CCK-8ns stimulates growth by 8 % in the second part of the experiment. In both experiments, all the leptin-treated rats have a smaller feed efficiency than the control group during the second week (P < 0.05). The feed efficiency of the control group is the highest until the fourth week. We don’t observe any difference in weight lost between control rats, which get leptin and CCK-8ns injections, and control rats with saline solution injections. Rats which develop CCK-8ns antibodies and get leptin and CCK-8ns injections lose more weight than rats that develop these antibodies and get saline solution injections (P < 0.03). The endocrinal parameters of the second experiment show that leptin-immunized rats have more serum leptin than the control group (P < 0.03). We note more serum IGFBP-3 in CCK-8ns- and leptin-immunized rats than the others (P < 0.001) and less T3 and T4 in their bloodstream (respectively P < 0.004 and P < 0.002). In conclusion, the small immune response against leptin had to limit the zootechnical and endocrinal effects. New techniques must be developed in order to generate a better immune response essentially against leptin.
Life sciences, Anatomy (cytology, histology, embryology...) & physiology, Sciences du vivant, Anatomie (cytologie, histologie, embryologie...) & physiologie
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