Different physiological traits underlying increased body fat of fatty (fa/fa) and heterozygous (+/fa) rats.
To find out whether the most characteristic physiological traits distinguishing suckling-age fa/fa pups from lean littermates also differ between +/+ and +/fa littermates, we analyzed the body composition and cold defense of 7- and 16-day-old pups and the plasma concentrations of insulin, glucose, triglycerides, and free fatty acids in 16-day-old pups. Zucker rat x Brown Norway hybrid pups were genotyped by using a molecular marker within 0.5 cM of the fa gene. At both ages the +/fa pups had significantly more body fat than their +/+ littermates. At 7 days this difference was as large as that between +/fa and fa/fa pups, but at 16 days it was only one-seventh of the fa/fa vs. +/fa difference. In contrast, there were no heterozygote differences for three parameters that show crucial abnormalities in the fa/fa pups: thermoregulatory thermogenesis and plasma concentrations of insulin and triglycerides. The physiological mechanisms underlying the increased fat content of +/fa pups thus differ from those known to fuel most of the excessive fat deposition of their fa/fa littermates.
Schwarzer
K
K
W. G. Kerckhoff-Institut, Max-Planck-Institut für Physiologische und Klinische Forschung, Bad Nauheim, Germany.
Döring
H
H
Schmidt
I
I
D000273:Adipose Tissue / Q000473:pathology*; D000818:Animals; D000833:Animals, Suckling; D001769:Blood / Q000378:metabolism; D001823:Body Composition; D001833:Body Temperature Regulation; D006579:Heterozygote; D006824:Hybridization, Genetic; D009765:Obesity / Q000235:genetics* / Q000473:pathology* / Q000503:physiopathology; D051381:Rats; D011914:Rats, Inbred BN / Q000235:genetics; D011924:Rats, Zucker / Q000235:genetics