title: Hyperphagia, lower body temperature, and reduced running wheel activity precede development of morbid obesity in New Zealand obese mice.
abstract: Among polygenic mouse models of obesity, the New Zealand obese (NZO) mouse exhibits the most severe phenotype, with fat depots exceeding 40% of total body weight at the age of 6 mo. Here we dissected the components of energy balance including feeding behavior, locomotor activity, energy expenditure, and thermogenesis compared with the related lean New Zealand black (NZB) and obese B6.V-Lep(ob)/J (ob/ob) strains (11% and 65% fat at 23 wk, respectively). NZO mice exhibited a significant hyperphagia that, when food intake was expressed per metabolic body mass, was less pronounced than that of the ob/ob strain. Compared with NZB, NZO mice exhibited increased meal frequency, meal duration, and meal size. Body temperature as determined by telemetry with implanted sensors was reduced in NZO mice, but again to a lesser extent than in the ob/ob strain. In striking contrast to ob/ob mice, NZO mice were able to maintain a constant body temperature during a 20-h cold exposure, thus exhibiting a functioning cold-induced thermogenesis. No significant differences in spontaneous home cage activity were observed among NZO, NZB, and ob/ob strains. When mice had access to voluntary running wheels, however, running activity was significantly lower in NZO than NZB mice and even lower in ob/ob mice. These data indicate that obesity in NZO mice, just as in humans, is due to a combination of hyperphagia, reduced energy expenditure, and insufficient physical activity. Because NZO mice differ strikingly from the ob/ob strain in their resistance to cold stress, we suggest that the molecular defects causing hyperphagia in NZO mice are located distal from leptin and its receptor.
authors.affiliation: Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbrücke, Nuthetal, Germany.
authors.forename: Hella S
authors.initials: HS
authors.lastname: Jürgens
authors.forename: Annette
authors.initials: A
authors.lastname: Schürmann
authors.forename: Reinhart
authors.initials: R
authors.lastname: Kluge
authors.forename: Sylvia
authors.initials: S
authors.lastname: Ortmann
authors.forename: Susanne
authors.initials: S
authors.lastname: Klaus
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Joost
authors.forename: Matthias H
authors.initials: MH
authors.lastname: Tschöp
mesh_terms: D050154:Adiposity; D000818:Animals; D001831:Body Temperature; D001835:Body Weight; D004195:Disease Models, Animal; D004435:Eating; D002149:Energy Intake; D004734:Energy Metabolism; D005247:Feeding Behavior; D006963:Hyperphagia / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology; D051379:Mice; D008814:Mice, Inbred NZB; D008820:Mice, Obese; D009043:Motor Activity; D009767:Obesity, Morbid / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D010641:Phenotype; D022722:Thermogenesis