Chronic central infusion of cocaine- and amphetamine-regulated transcript (CART 55-102): effects on body weight homeostasis in lean and high-fat-fed obese rats.
BACKGROUND
Cocaine- and amphetamine-regulated transcript (CART) is expressed within hypothalamic nuclei implicated in the regulation of feeding behaviour. It is up-regulated by leptin, and CART-derived peptides acutely inhibit food intake.


OBJECTIVE
The present study was designed to assess the long-term effects of central CART administration on food intake, body weight, plasma levels of glucose, insulin, leptin, free fatty acids and triglycerides, and on fuel utilisation in normal and high-fat-fed obese rats.


METHODS
Normal and high-fat-fed obese rats were cannulated intracerebroventricularly (i.c.v.) and infused for 6 days with CART (55-102) or its vehicle. At day 4, animals were placed in an indirect calorimeter for a 24 h period during which the respiratory quotient and the energy expenditure were determined hourly.


RESULTS
In both normal and obese animals, the chronic i.c.v. infusion of CART (55-102) had marked, sustained inhibitory effects on food intake and body weight gain that were accompanied by decreases in plasma insulin and leptin levels. Using indirect calorimetry, it was observed that CART infusion promoted an increase in lipid oxidation in normal and in obese animals, although this increase reached statistical significance only in the obese group. The hypothalamic CART mRNA expression was found to be higher in obese rats (displaying hyperleptinaemia) than in normal animals.


CONCLUSIONS
The data together show that chronic i.c.v. CART infusion is effective in inhibiting food intake, favouring lipid oxidation and limiting fat storage, both in normal and high-fat-diet-induced obese rats. The CART pathway thus seems to be an important determinant of body weight homeostasis in normal animals as well as in a model of nutritionally induced obesity.
Rohner-Jeanrenaud
F
F
Endocrine Research and Clinical Investigation, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, Indiana, USA. F.Rohner-Jeanrenaud@hcuge.ch
Craft
L S
LS
Bridwell
J
J
Suter
T M
TM
Tinsley
F C
FC
Smiley
D L
DL
Burkhart
D R
DR
Statnick
M A
MA
Heiman
M L
ML
Ravussin
E
E
Caro
J F
JF
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015152:Blotting, Northern; D001835:Body Weight / Q000187:drug effects; D002153:Calorimetry, Indirect; D002940:Circadian Rhythm; D017931:DNA Primers; D004041:Dietary Fats / Q000008:administration & dosage; D004195:Disease Models, Animal; D002149:Energy Intake / Q000187:drug effects*; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005786:Gene Expression Regulation; D015918:Infusion Pumps, Implantable; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D009419:Nerve Tissue Proteins; D009765:Obesity / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D012119:Respiration; D014280:Triglycerides / Q000097:blood; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D001786:Blood Glucose; D017931:DNA Primers; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D020738:Leptin; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; D014280:Triglycerides; C428723:cocaine- and amphetamine-regulated transcript protein (55-102); D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein