ROLE OF ACTIVITY‐INDUCED THERMOGENESIS IN TWENTY‐FOUR HOUR ENERGY EXPENDITURE OF LEAN AND GENETICALLY OBESE (OB/OB) MICE

Abstract

SUMMARYThe contribution made by spontaneous physical activity to 24 h energy expenditure has been assessed in lean and ob/ob mice living at 28°C. Measurements were made in young animals when the ob/ob mice were the same body weight as their lean littermates, and again when they were adult and the ob/ob mice were twice as heavy as their littermates.In the young ob/ob mice, not only was 24 h heat production lower than in their lean littermates (P<0O005) but so also was motor activity (P<001). In adults, total 24 h heat production was similar in lean and obese animals, and thus on the basis of metabolic body size it was considerably lower in the obese adults (P <0-005). The obese adults were also significantly less active than their lean littermates (P <005). Differences between genotypes were particularly marked during the night. Partition of 24 h energy expenditure into the two components of rest and activity showed that in the young ob/ob mice the lower heat production occurred because they expended 31 % less energy on rest and 47 % less on activity than did their lean littermates. In the obese adults, the lower heat production per unit metabolic body size was accounted for by 16 % less energy being expended on rest and 74 % less on activity than in the lean mice. It is concluded that differences in motor activity between lean and ob/ob mice could account, at least in part, for the development and maintenance of obesity in these animals.

Decreased Vesicular Somatodendritic Dopamine Stores in Leptin-Deficient Mice

“…As has been observed previously (Dauncey, 1986;Calcagnetti et al, 1987;Dauncey and Brown, 1987;Ahima et al, 1999;Collin et al, 2000), Lep ob/ob mice showed significantly lower locomotor activity under baseline conditions compared with wild-type mice (Fig. 7A, saline).…”

“…7). As has been observed previously (Dauncey, 1986;Calcagnetti et al, 1987;Dauncey and Brown, 1987;Ahima et al, 1999;Collin et al, 2000), Lep ob/ob mice showed significantly reduced locomotion under baseline conditions, and although activity of Lep ob/ob mice increased significantly after cocaine injection, the absolute magnitude of this effect was decreased relative to wild-type mice. However, when locomotor activity was normalized to the baseline activity, Lep ob/ob mice were not statistically different from wild-type mice.…”

Central serotonin neurons are required for arousal to CO 2

“…As in humans who do not sleep well in the cold (33), Lmx1b f/f/p mice may spend more time awake when the ambient temperature is low because they are uncomfortable. In response to cold, animals have been shown to move to warmer areas, to perform a learned task to receive a "thermal reinforcement" (34), and to increase motor activity to generate heat (35). Our data demonstrate that when Lmx1b f/f/p mice fall asleep at 23°C, their body temperature drops precipitously.…”

Central overexpression of leptin antagonist reduces wheel running and underscores importance of endogenous leptin receptor activity in energy homeostasis

“…The present study supports this finding with the observation that leptin overexpression increases voluntary WR. On the other hand, in the absence of leptin or leptin receptor function in either the ob/ob mouse (6,30) or the obese Zucker rat (26,28), physical activity levels are reduced. Moreover, the diminished WR activity in ob/ob mice is partially reversed by leptin administration (30).…”