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| 2. |
- Fischer, Alexander W., et al.
(författare)
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No insulating effect of obesity
- 2016
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 311:1, s. e202-e213
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Tidskriftsartikel (refereegranskat)abstract
- 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 approximate to 20 degrees 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 non-shaved 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. obesity-resistant (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.
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| 4. |
- Luijten, Ineke H. N., et al.
(författare)
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In the absence of UCP1-mediated diet-induced thermogenesis, obesity is augmented even in the obesity-resistant 129S mouse strain
- 2019
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 316:5, s. E729-E740
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Tidskriftsartikel (refereegranskat)abstract
- The attractive tenet that recruitment and activation of brown adipose tissue (BAT) and uncoupling protein 1 (UCP1) could counteract the development of obesity and its comorbidities in humans has been experimentally corroborated mainly by experiments demonstrating that UCP1-ablated mice on a C57B1/6 background (exempt from thermal stress) become more obese when fed a high-fat diet. However, concerns may be raised that this outcome of UCP1 ablation is restricted to this very special inbred and particularly obesity-prone mouse strain. Therefore, we have examined to which degree UCP1 ablation has similar metabolic effects in a mouse strain known to be obesity resistant: the 129S strain. For this, male 129S2/sv or 129SV/Pas mice and corresponding UCP1-knockout mice were fed chow or a high-fat or a cafeteria diet for 4 w.k. The absence of UCP1 augmented obesity (weight gain, body fat mass, %body fat, fat depot size) in high-fat diet- and cafeteria-fed mice, with a similar or lower food intake, indicating that, when present, UCP1 indeed decreases metabolic efficiency. The increased obesity was due to a decrease in energy expenditure. The consumption of a high-fat or cafeteria diet increased total BAT UCP1 protein levels in wild-type mice, and correspondingly. high-fat diet and cafeteria diet-fed mice demonstrated increased norepinephrine-induced oxygen consumption. There was a positive correlation between body fat and total BAT UCP1 protein content. No evidence for diet-induced adrenergic thermogenesis was found in UCP1-ablated mice. Thus, the obesity-reducing effect of UCP1 is not restricted to a particular, and perhaps not representative, mouse strain.
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| 5. |
- Luijten, Ineke, et al.
(författare)
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In the absence of UCP1-mediated diet-induced thermogenesis, obesity is augmented even in the obesity-resistant 129S mouse strain
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The attractive tenet that recruitment and activation of brown adipose tissue (BAT) and Uncoupling Protein 1 (UCP1) could counteract the development of obesity and its comorbidities in humans has been experimentally corroborated mainly by experiments demonstrating that UCP1-ablated mice on a C57Bl/6 background (housed exempt from thermal stress) become more obese when fed a high-fat diet. However, concerns may be raised that this outcome of UCP1 ablation is restricted to this very special inbred and particularly obesity-prone mouse strain. We have therefore examined to which degree UCP1 ablation has similar metabolic effects in a mouse strain known tobe obesity resistant: the 129S strain. For this, male 129S2/sv or 129SV/Pas mice and corresponding UCP1-KO mice were fed chow, or a high-fat or a cafeteria diet for 4 weeks. The absence of UCP1 augmented obesity (weight gain, body fat mass, % body fat, fat depot size) in high-fat diet- and cafeteria-fed mice, with a similar or lower food intake, indicating that, when present, UCP1 indeed decreases metabolic efficiency. The increased obesity was due to a decrease in energy expenditure. The consumption of a high-fat or cafeteria diet increased total BAT UCP1 protein levels in wild-type mice, and correspondingly, high-fat diet and cafeteria diet-fed mice demonstrated increased norepinephrine-induced oxygen consumption. There was a positive correlation between body fat and total BAT UCP1 protein content. No evidence for diet-induced adrenergic thermogenesis was found in UCP1-ablated mice. Thus, the obesity-reducing effect of UCP1 is not restricted to a particular, and perhaps not representative, mouse strain.
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| 6. |
- Nedergaard, Jan, et al.
(författare)
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Brown adipose tissue : can it keep us slim? A discussion of the evidence for and against the existence of diet-induced thermogenesis in mice and men
- 2023
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - 0962-8436 .- 1471-2970. ; 378:1888
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Forskningsöversikt (refereegranskat)abstract
- The issue under discussion here is whether a decrease in the degree of UCP1 activity (and brown adipose tissue activity in general) could be a cause of obesity in humans. This possibility principally requires the existence of the phenomenon of diet-induced thermogenesis. Obesity could be a consequence of a reduced functionality of diet-induced thermogenesis. Experiments in mice indicate that diet-induced thermogenesis exists and is dependent on the presence of UCP1 and thus of brown adipose tissue activity. Accordingly, many (but not all) experiments indicate that in the absence of UCP1, mice become obese. Whether similar mechanisms exist in humans is still unknown. A series of studies have indicated a correlation between obesity and low brown adipose tissue activity, but it may be so that the obesity itself may influence the estimates of brown adipose tissue activity (generally glucose uptake), partly explaining the relationship. Estimates of brown adipose tissue catabolizing activity would seem to indicate that it may possess a capacity sufficient to help maintain body weight, and obesity would thus be aggravated in its absence.
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| 7. |
- von Essen, Gabriella, et al.
(författare)
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Adaptive facultative diet-induced thermogenesis in wild-type but not in UCP1-ablated mice
- 2017
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 313:5, s. E515-E527
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Tidskriftsartikel (refereegranskat)abstract
- The significance of diet-induced thermogenesis (DIT) for metabolic control is still debated. Although obesogenic diets recruit UCP1 and adrenergically inducible thermogenesis, and although the absence of UCP1 may promote the development of obesity, no actual UCP1-related thermogenesis identifiable as diet-induced thermogenesis has to date been unambiguously demonstrated. Examining mice living at thermoneutrality, we have identified a process of facultative (directly elicited by acute eating), adaptive (magnitude develops over weeks on an obesogenic diet), and fully UCP1-dependent thermogenesis. We found no evidence for UCP1-independent diet-induced thermogenesis. The thermogenesis was proportional to the total amount of UCP1 protein in brown adipose tissue and was not dependent on any contribution of UCP1 in brite/beige adipose tissue, since no UCP1 protein was found there under these conditions. Total UCP1 protein amount developed proportionally to total body fat content. The physiological messenger linking obesity level and acute eating to increased thermogenesis is not known. Thus UCP1-dependent diet-induced thermogenesis limits obesity development during exposure to obesogenic diets but does not prevent obesity as such.
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| 10. |
- von Essen, Gabriella, 1962-
(författare)
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Energy flow and metabolic efficiency attributed to brown adipose tissue
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The large capacity of brown adipose tissue (BAT) to expend energy as heat makes it an interesting potential player in weight regulation and other metabolic conditions. This is of particular interest as it has been recognized that adult humans possess BAT. The protein responsible for the heat production is uncoupling protein 1 (UCP1), which, as the name implies, uncouples the respiratory chain from ATP production; instead heat is produced. Cold is the strongest recruiter and activator of BAT. However, also obesogenic food has a low but nonetheless significant effect on the recruitment and activation of UCP1, although the significance of this has been discussed.In the present thesis, I have studied the effect of diet on BAT and the possibilities for it to be obesity-protective. This can be done by comparing responses in wild-type mice and in UCP1-ablated mice. Since the effect of diet on BAT is low, it is of importance to control the temperature and maintain thermoneutrality. Other confounding factors to keep in mind are differences in actual energy and composition of food and also cohort differences. When controlling all the parameters mentioned and giving the mice the same obesogenic diet, the mice possessing UCP1 compared to UCP1-ablated mice had higher energy expenditure, and lower weight gain, despite eating more. This confirms the presence of a UCP1-dependent diet-induced thermogenesis. Thus, the conclusion must be that possessing UCP1 does result in obesity protection at thermoneutrality. However, the relevance for human energy balance is still not established.
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