| 1. |
- Speakman, John R., et al.
(författare)
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Total daily energy expenditure has declined over the past three decades due to declining basal expenditure, not reduced activity expenditure
- 2023
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Ingår i: Nature Metabolism. - : NATURE PORTFOLIO. - 2522-5812. ; 5:4, s. 579-588
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Obesity is caused by a prolonged positive energy balance(1,2). Whether reduced energy expenditure stemming from reduced activity levels contributes is debated(3,4). Here we show that in both sexes, total energy expenditure (TEE) adjusted for body composition and age declined since the late 1980s, while adjusted activity energy expenditure increased over time. We use the International Atomic Energy Agency Doubly Labelled Water database on energy expenditure of adults in the United States and Europe (n = 4,799) to explore patterns in total (TEE: n = 4,799), basal (BEE: n = 1,432) and physical activity energy expenditure (n = 1,432) over time. In males, adjusted BEE decreased significantly, but in females this did not reach significance. A larger dataset of basal metabolic rate (equivalent to BEE) measurements of 9,912 adults across 163 studies spanning 100 years replicates the decline in BEE in both sexes. We conclude that increasing obesity in the United States/Europe has probably not been fuelled by reduced physical activity leading to lowered TEE. We identify here a decline in adjusted BEE as a previously unrecognized factor.
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| 2. |
- Abreu-Vieira, Gustavo, et al.
(författare)
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Cidea improves the metabolic profile through expansion of adipose tissue
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- In humans, Cidea (cell death-inducing DNA fragmentation factor alpha-like effector A) is highly but variably expressed in white fat, and expression correlates with metabolic health. Here we generate transgenic mice expressing human Cidea in adipose tissues (aP2-hCidea mice) and show that Cidea is mechanistically associated with a robust increase in adipose tissue expandability. Under humanized conditions (thermoneutrality, mature age and prolonged exposure to high-fat diet), aP2-hCidea mice develop a much more pronounced obesity than their wild-type littermates. Remarkably, the malfunctioning of visceral fat normally caused by massive obesity is fully overcome-perilipin 1 and Akt expression are preserved, tissue degradation is prevented, macrophage accumulation is decreased and adiponectin expression remains high. Importantly, the aP2-hCidea mice display enhanced insulin sensitivity. Our data establish a functional role for Cidea and suggest that, in humans, the association between Cidea levels in white fat and metabolic health is not only correlative but also causative.
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| 3. |
- Cannon, Barbara, et al.
(författare)
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Human brown adipose tissue : Classical brown rather than brite/beige?
- 2020
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Ingår i: Experimental Physiology. - 0958-0670 .- 1469-445X. ; 105:8, s. 1191-1200
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Tidskriftsartikel (refereegranskat)abstract
- New Findings What is the topic of this review? It has been suggested that human brown adipose tissue (BAT) is more similar to the brite/beige adipose tissue of mice than to classical BAT of mice. The basis of this is discussed in relationship to the physiological conditions of standard experimental mice.
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| 4. |
- de Jong, Jasper M. A., et al.
(författare)
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A stringent validation of mouse adipose tissue identity markers
- 2015
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 308:12, s. E1085-E1105
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Tidskriftsartikel (refereegranskat)abstract
- The nature of brown adipose tissue in humans is presently debated: whether it is classical brown or of brite/beige nature. The dissimilar developmental origins and proposed distinct functions of the brown and brite/beige tissues make it essential to ascertain the identity of human depots with the perspective of recruiting and activating them for the treatment of obesity and type 2 diabetes. For identification of the tissues, a number of marker genes have been proposed, but the validity of the markers has not been well documented. We used established brown (interscapular), brite (inguinal), and white (epididymal) mouse adipose tissues and corresponding primary cell cultures as validators and examined the informative value of a series of suggested markers earlier used in the discussion considering the nature of human brown adipose tissue. Most of these markers unexpectedly turned out to be noninformative concerning tissue classification (Car4, Cited1, Ebf3, Eva1, Fbxo31, Fgf21, Lhx8, Hoxc8, and Hoxc9). Only Zic1 (brown), Cd137, Epsti1, Tbx1, Tmem26 (brite), and Tcf21 (white) proved to be informative in these three tissues. However, the expression of the brite markers was not maintained in cell culture. In a more extensive set of adipose depots, these validated markers provide new information about depot identity. Principal component analysis supported our single-gene conclusions. Furthermore, Zic1, Hoxc8, Hoxc9, and Tcf21 displayed anteroposterior expression patterns, indicating a relationship between anatomic localization and adipose tissue identity (and possibly function). Together, the observed expression patterns of these validated marker genes necessitates reconsideration of adipose depot identity in mice and humans.
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| 5. |
- de Jong, Jasper M. A., et al.
(författare)
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Human brown adipose tissue is phenocopied by classical brown adipose tissue in physiologically humanized mice
- 2019
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Ingår i: Nature Metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 1:8, s. 830-843
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Tidskriftsartikel (refereegranskat)abstract
- Human and rodent brown adipose tissues (BAT) appear morphologically and molecularly different. Here we compare human BAT with both classical brown and brite/beige adipose tissues of 'physiologically humanized' mice: middle-aged mice living under conditions approaching human thermal and nutritional conditions, that is, prolonged exposure to thermoneutral temperature (approximately 30 degrees C) and to an energy-rich (high-fat, high-sugar) diet. We find that the morphological, cellular and molecular characteristics (both marker and adipose-selective gene expression) of classical brown fat, but not of brite/beige fat, of these physiologically humanized mice are notably similar to human BAT. We also demonstrate, both in silico and experimentally, that in physiologically humanized mice only classical BAT possesses a high thermogenic potential. These observations suggest that classical rodent BAT is the tissue of choice for translational studies aimed at recruiting human BAT to counteract the development of obesity and its comorbidities.
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| 6. |
- de Jong, Jasper M. A., et al.
(författare)
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Promotion of lipid storage rather than of thermogenic competence by fetal versus newborn calf serum in primary cultures of brown adipocytes
- 2018
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Ingår i: Adipocyte. - : Informa UK Limited. - 2162-3945 .- 2162-397X. ; 7:3, s. 166-179
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Tidskriftsartikel (refereegranskat)abstract
- Much current understanding of brown adipocyte development comes from in-vitro cell models. Serum type may affect the behavior of cultured cells and thus conclusions drawn. Here, we investigate effects of serum type (fetal bovine versus newborn calf) on responses to differentiation inducers (the PPAR agonist rosiglitazone or the neurotransmitter norepinephrine) in cultured primary brown adipocytes. Lipid storage was enhanced by fetal versus newborn serum. However, molecular adipose conversion (Pparg2 and Fabp4 expression) was not affected by serum type. Rosiglitazone-induced (7-days) expression of thermogenic genes (i.e. Ucp1, Pgc1a, Dio2 and Elovl3) was not systematically affected by serum type. However, importantly, acute (2h) norepinephrine-induced thermogenic gene expression was overall markedly higher (and adipose genes somewhat lower) in cells cultured in newborn serum. Thus, newborn serum promotes thermogenic competence, and the use of fetal serum in brown adipocyte cultures (as is often routine) counteracts adequate differentiation. Agents that counteract this inhibition may therefore confoundingly be ascribed genuine thermogenic competence-inducing properties.
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| 7. |
- de Jong, Jasper M. A., et al.
(författare)
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The β3-adrenergic receptor is dispensable for browning of adipose tissues
- 2017
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 312:6, s. E508-E518
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Tidskriftsartikel (refereegranskat)abstract
- Brown and brite/beige adipocytes are attractive therapeutic targets to treat metabolic diseases. To maximally utilize their functional potential, further understanding is required about their identities and their functional differences. Recent studies with β3-adrenergic receptor knockout mice reported that brite/beige adipocytes, but not classical brown adipocytes, require the β3-adrenergic receptor for cold-induced transcriptional activation of thermogenic genes. We aimed to further characterize this requirement of the β3-adrenergic receptor as a functional distinction between classical brown and brite/beige adipocytes. However, when comparing wild-type and β3-adrenergic receptor knockout mice, we observed no differences in cold-induced thermogenic gene expression (Ucp1, Pgc1a, Dio2 and Cidea) in brown or white (brite/beige) adipose tissues. Irrespective of the duration of the cold exposure or the sex of the mice, we observed no effect of the absence of the β3-adrenergic receptor. Experiments with the β3-adrenergic receptor agonist CL-316,243 verified the functional absence of β3-adrenergic signaling in these knockout mice. The β3-adrenergic receptor knockout model in the present study was maintained on a FVB/N background, whereas earlier reports used C57BL/6 and 129Sv mice. Thus, our data imply background-dependent differences in adrenergic signaling mechanisms in response to cold exposure. Nonetheless, the present data indicate that the β3-adrenergic receptor is dispensable for cold-induced transcriptional activation in both classical brown and, as opposed to earlier studies, brite/beige cells. This should be taken into account in the increasing number of studies on the induction of browning and their extrapolation to human physiology.
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| 8. |
- Fischer, Alexander W., et al.
(författare)
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Leptin Raises Defended Body Temperature without Activating Thermogenesis
- 2016
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 14:7, s. 1621-1631
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Tidskriftsartikel (refereegranskat)abstract
- Leptin has been believed to exert its weight-reducing action not only by inducing hypophagia but also by increasing energy expenditure/thermogenesis. Leptin-deficient ob/ob mice have correspondingly been thought to be thermogenically limited and to show hypothermia, mainly due to atrophied brown adipose tissue (BAT). In contrast to these established views, we found that BAT is fully functional and that leptin treatment did not increase thermogenesis in wildtype or in ob/ob mice. Rather, ob/ob mice showed a decreased but defended body temperature (i. e., were anapyrexic, not hypothermic) that was normalized to wild-type levels after leptin treatment. This was not accompanied by increased energy expenditure or BAT recruitment but, instead, was mediated by decreased tail heat loss. The weight-reducing hypophagic effects of leptin are, therefore, not augmented through a thermogenic effect of leptin; leptin is, however, pyrexic, i. e., it alters centrally regulated thresholds of thermoregulatory mechanisms, in parallel to effects of other cytokines.
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| 9. |
- Fischer, Alexander W., et al.
(författare)
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Thermoneutrality-Induced Macrophage Accumulation in Brown Adipose Tissue Does Not Impair the Tissue's Competence for Cold-Induced Thermogenic Recruitment
- 2020
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Ingår i: Frontiers in Endocrinology. - : Frontiers Media SA. - 1664-2392. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Brown adipose tissue from mice living under conditions approaching human thermal and nutritional conditions (prolonged exposure to thermoneutral temperature and to an energy-rich (high-fat, high-sugar) diet) - referred to as physiologically humanized mice, displays morphological and molecular characteristics significantly different from those observed in young, chow-fed mice maintained at room temperature - referred to as standard mice. Here, we further examined brown fat from physiologically humanized and standard mice, as well as from mice exposed to thermoneutrality for a long time but not to an energy-rich diet - referred to here as long-term thermoneutral mice. Global transcriptome analysis of brown fat revealed that genes that were the most upregulated in brown fat of thermoneutral mice (both physiologically humanized and long-term thermoneutral) were those related to inflammatory processes, including genes expressed selectively in macrophages. Cellular and molecular analyses confirmed that brown fat from thermoneutral mice was heavily infiltrated by macrophages, predominantly organized into crown-like structures. However, despite this, the brown fat of thermoneutral mice retained full competence to attain the greatest possible recruitment state and became macrophage-depleted during the process of cold acclimation. Thus, profound macrophage accumulation does not influence the thermogenic recruitment competence of brown fat.
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| 10. |
- Kalinovich, Anastasia V., et al.
(författare)
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UCP1 in adipose tissues: two steps to full browning
- 2017
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Ingår i: Biochimie. - : Elsevier BV. - 0300-9084 .- 1638-6183. ; 134, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- The possibility that brown adipose tissue thermogenesis can be recruited in order to combat the development of obesity has led to a high interest in the identification of "browning agents", i.e. agents that increase the amount and activity of UCP1 in brown and brite/beige adipose tissues. However, functional analysis of the browning process yields confusingly different results when the analysis is performed in one of two alternative steps. Thus, in one of the steps, using cold acclimation as a potent model browning agent, we find that if the browning process is followed in mice initially housed at 21 °C (the most common procedure), there is only weak molecular evidence for increases in UCP1 gene expression or UCP1 protein abundance in classical brown adipose tissue; however, in brite/beige adipose depots, there are large increases, apparently associating functional browning with events only in the brite/beige tissues. Contrastingly, in another step, if the process is followed starting with mice initially housed at 30 °C (thermoneutrality for mice, thus similar to normal human conditions), large increases in UCP1 gene expression and UCP1 protein abundance are observed in the classical brown adipose tissue depots; there is then practically no observable UCP1 gene expression in brite/beige tissues. This apparent conundrum can be resolved when it is realized that the classical brown adipose tissue at 21 °C is already essentially fully differentiated and thus expands extensively through proliferation upon further browning induction, rather than by further enhancing cellular differentiation. When the limiting factor for thermogenesis, i.e. the total amount of UCP1 protein per depot, is analyzed, classical brown adipose tissue is by far the predominant site for the browning process, irrespective of which of the two steps is analyzed. There are to date no published data demonstrating that alternative browning agents would selectively promote brite/beige tissues versus classical brown tissue to a higher degree than does cold acclimation. Thus, to restrict investigations to examine adipose tissue depots where only a limited part of the adaptation process occurs (i.e. the brite/beige tissues) and to use initial conditions different from the thermoneutrality normally experienced by adult humans may seriously hamper the identification of therapeutically valid browning agents. The data presented here have therefore important implications for the analysis of the potential of browning agents and the nature of human brown adipose tissue.
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