The relationship between energy expenditure and environmental temperature in congenitally obese and non‐obese Zucker rats.

Armitage, George; Harris, Ruth B. S.; Hervey, G. R.; Tobin, Graham A.

doi:10.1113/jphysiol.1984.sp015196

Cited by 35 publications

(37 citation statements)

References 24 publications

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“…Nevertheless, even when behavioural options for thermoregulation are widened, there still appears to be an increase in energy expenditure on exposure to mild cold. Rats kept in groups of three and fed ad libitum increase their 24 h heat production by approximately 20-25 % when measured at 20 compared with 29°C (Armitage, Harris, Hervey & Tobin, 1984), while a 7 % increase in 24 h heat production has been found in women at 20 compared with 28°C when provided with 'normal' clothing and bedding (Warwick & Busby, 1990).…”

Section: <0*01mentioning

confidence: 99%

Influence of mild cold on the components of 24 hour thermogenesis in rats.

Brown

Livesey

Dauncey

1991

The Journal of Physiology

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SUMMARY1. The influence of two weeks' acclimation to either 28°C (thermal neutrality) or 21°C (mild cold) on 24 h heat production and motor activity has been investigated in male Wistar rats. Food intake was controlled and provided as a single meal of approximately 170 kJ per day. Mathematical modelling was used to relate metabolic rate to measured movement and time of day.2. For animals at thermal neutrality it was clear that metabolic rate increased during periods of substantial measured movement and returned to baseline during periods of minimal activity. Total heat production could therefore be divided into two components: underlying and movement-induced thermogenesis.3. At 21°C, a more complex model was needed. During periods of substantial activity, the relation between metabolic rate and movement was similar to that at 28°C and total heat production could be divided into the same two components of underlying and movement-induced thermogenesis. However, during periods of prolonged inactivity, a different model was required, which included a component of extra metabolic activity, termed supplementary thermogenesis. By fitting this model to data at 28 and 21°C, it was possible to partition 24 h heat production into the three possible sources of underlying, movement-induced and supplementary thermogenesis.4. Total 24 h heat production was approximately 25% higher for rats at 21 compared with 28°C (P < 0-01) and underlying thermogenesis was approximately 20 % higher for those in the mild cold (P < 00 1). Measured movement was significantly reduced in the mild cold (P < 0 05) although it was energetically less efficient since there was no difference in movement-induced thermogenesis, which accounted for 18 and 15% of total heat production at 28 and 21°C respectively.

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Section: <0*01mentioning

confidence: 99%

Influence of mild cold on the components of 24 hour thermogenesis in rats.

Brown

Livesey

Dauncey

1991

The Journal of Physiology

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“…Thus, under the current experimental conditions for mice, an insulating effect of increasing obesity would successively diminish the heat loss and thus enhance, in a self-amplifying way, the further development of obesity. Additionally, the adaptation to living at a relatively cold temperature may in itself promote additional insulation (via fur), affecting metabolic rate.Despite these possible profound influences of alterations in thermal insulation, data on the effects of obesity on insulation are scarce and only found for a few specific rodent models in studies concerned mainly with other issues (1,5,17,21,28). We have failed to find studies either in mice or in human that systematically empirically quantitate the effect of a series of different obesities on insulation.…”

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confidence: 93%

No insulating effect of obesity

Fischer

Csikasz

Essen

et al. 2016

American Journal of Physiology-Endocrinology and Metabolism

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The development of obesity may be aggravated if obesity itself insulates against heat loss and thus diminishes the amount of food burnt for body temperature control. This would be particularly important under normal laboratory conditions where mice experience a chronic cold stress (at Ϸ20°C). We used Scholander plots (energy expenditure plotted against ambient temperature) to examine the insulation (thermal conductance) of mice, defined as the inverse of the slope of the Scholander curve at subthermoneutral temperatures. We verified the method by demonstrating that shaved mice possessed only half the insulation of nonshaved mice. We examined a series of obesity models [mice fed high-fat diets and kept at different temperatures, classical diet-induced obese mice, ob/ob mice, and obesity-prone (C57BL/6) vs. obesityresistant (129S) mice]. We found that neither acclimation temperature nor any kind or degree of obesity affected the thermal insulation of the mice when analyzed at the whole mouse level or as energy expenditure per lean weight. Calculation per body weight erroneously implied increased insulation in obese mice. We conclude that, in contrast to what would be expected, obesity of any kind does not increase thermal insulation in mice, and therefore, it does not in itself aggravate the development of obesity. It may be discussed as to what degree of effect excess adipose tissue has on insulation in humans and especially whether significant metabolic effects are associated with insulation in humans. obesity; insulation; ob/ob DESPITE THE PRESENT INTEREST IN METABOLISM in connection with the global obesity epidemic, there is little knowledge concerning the extent to which obesity as such affects metabolism. There is widespread interest in issues such as the release of adipokines from adipose tissue depots, but many basic issues, such as the ability of adipose tissue to affect metabolism physically, have been little examined. One of these issues is the question of the ability of adipose tissue to function as a thermal insulation barrier, decreasing the heat loss from the organism and in this way decreasing the amount of energy needed to keep the organism warm, thereby increasing the amount of excess energy prone to storage in the form of (additional) fat.Whether an insulating effect of obesity exists is of significance both for humans and for animal models of obesity. However, with regard to experimental animals, the issue of insulation is of further interest. This is because most metabolic experiments are conducted with mice kept under conditions (standard laboratory conditions of Ϸ21°C) that are principally cold for the mouse (10,19,27,37,38,42,44) and thus where a high proportion of total metabolism (nearly half) is devoted to counteracting the resulting heat loss. This is a condition very different from that which is relevant for the metabolic physiology of most humans (living in a thermoneutral environment). Thus, under the current experimental conditions for mice, an insulating effect of increasing obesit...

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“…At normal temperatures the IBAT pads comprise mainly 'white' adipose cells, so the greater weight in obese rats is to be expected; the obese rats showed no defect in their ability to increase the pad weight in the cold, which presumably reflects ability to increase the numbers of 'brown' cells. The loss of body weight in the cold may reflect the rats' inability to increase food intake sufficiently to match metabolism in the cold (Armitage et al 1984).…”

Section: Discussionmentioning

confidence: 99%

Thyroid Function in Male Zucker Rats Exposed to Cold

Whitaker¹,

Robinson²,

Rayfield³

et al. 1988

Exp Physiol

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SUMMARYNon-obese and obese Zucker rats were exposed to 6 OC for 20 days. At the end of the experiment thyroid stimulating hormone (TSH), circulating thyroid hormones, and the weights of the thyroid gland and a brown adipose tissue pad were measured. TSH and 3,5,3'-triiodothyronine concentrations and brown adipose tissue weights increased in response to cold in both phenotypes but by larger amounts in obese rats. Free thyroxine was lower in obese rats. There appears to be no defect in thyroid function in congenitally obese rats exposed to cold, or in their ability to develop brown adipose tissue.

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The relationship between energy expenditure and environmental temperature in congenitally obese and non‐obese Zucker rats.

Cited by 35 publications

References 24 publications

Influence of mild cold on the components of 24 hour thermogenesis in rats.

Influence of mild cold on the components of 24 hour thermogenesis in rats.

No insulating effect of obesity

Thyroid Function in Male Zucker Rats Exposed to Cold

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