Long-term divergent selection on fatness in mice indicates a regulation system independent of leptin production and reception.
Divergent selection in mice on fatness over 60 generations produced a fat (F) and a lean (L) line, having about 22% and 4% body fat, respectively. To elucidate the importance of the leptin regulatory feedback loop in the genetic changes produced by this selection, Lep(ob) and Lepr(db) mutations causing leptin production and leptin receptor deficiency, respectively, were introgressed individually into both lines by repeated backcrossing. The fat amount increased significantly in homozygotes for Lep(ob) or Lepr(db) in both lines, for example, in F and L males from 8.5 to 18.8 and 17.2 g (P<0.001) and from 1.25 to 18.0 and 12.7 g (P<0.001), respectively. Line differences were, however, mostly maintained after introgression. Concentrations of circulating leptin were relatively independent of the original lines but heavily dependent on the introgressed genotype. Introgression of leptin production and receptor deficiencies had separate effects from long-term selection, indicating that the genes responsible for the line divergence must act independently of the leptin regulatory system. Energy budget analysis indicated that the major line differences were in the level of energy expended on physical activity, and these differences were preserved following introgression, suggesting that multiple pathways regulate fatness, which may be independently responsive to intervention.
Bünger
Lutz
L
Institute of Cell, Animal and Population Biology, University of Edinburgh, UK. Lutz.Bunger@ed.ac.uk
Forsting
Jürgen
J
McDonald
Katharine L
KL
Horvat
Simon
S
Duncan
Jackie
J
Hochscheid
Sandra
S
Baile
Clifton A
CA
Hill
William G
WG
Speakman
John R
JR
D000273:Adipose Tissue / Q000473:pathology; D000818:Animals; D001831:Body Temperature; D004195:Disease Models, Animal; D004435:Eating; D004734:Energy Metabolism; D025461:Feedback, Physiological; D014644:Genetic Variation; D020738:Leptin / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008817:Mice, Mutant Strains; D020412:Multifactorial Inheritance; D009765:Obesity / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010805:Physical Conditioning, Animal; D011110:Polymorphism, Genetic; D011956:Receptors, Cell Surface / Q000235:genetics*; D054411:Receptors, Leptin; D013997:Time Factors
D020738:Leptin; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; C515447:leptin receptor, mouse