bims-mimbat Biomed News
on Mitochondrial metabolism in brown adipose tissue
Issue of 2024–12–08
four papers selected by
José Carlos de Lima-Júnior, Washington University



  1. Sci Signal. 2024 Dec 03. 17(865): eadk7971
      Activation of thermogenic brown adipose tissue (BAT) and inducible beige adipose tissue (BeAT) is triggered by environmental or metabolic stimuli, including cold ambient temperatures and nutrient stress. Thioesterase superfamily member 1 (Them1), a long-chain fatty acyl-CoA thioesterase that is enriched in BAT, suppresses acute cold-induced thermogenesis. Here, we demonstrate that Them1 expression was induced in BAT and BeAT by the carbohydrate response element binding protein (ChREBP) in response to chronic cold exposure or to the activation of the integrated stress response (ISR) by nutrient excess. Under either condition, Them1 suppressed energy expenditure. Consequently, mice lacking Them1 in BAT and BeAT exhibited resistance to obesity and glucose intolerance induced by feeding with a high-fat diet. During chronic cold exposure or ISR activation, Them1 accumulated in the nucleus, where it interacted with ChREBP and reduced the expression of its target genes, including those encoding enzymes that mediate glycolysis and de novo lipogenesis. These findings demonstrate that in response to chronic cold- or nutrient-induced stress, the induction of Them1 by ChREBP limits thermogenesis while coordinately reducing glucose utilization and lipid biosynthesis through its distinct cytoplasmic and nuclear activities. Targeted inhibition of Them1 could be a potential therapeutic approach to increase the activity of BAT and BeAT to enhance energy expenditure in the management of obesity-associated metabolic disorders.
    DOI:  https://doi.org/10.1126/scisignal.adk7971
  2. Exp Mol Med. 2024 Dec 02.
      Characterized by UCP1 expression and abundant mitochondria, brown adipose tissue (BAT) plays a crucial role in energy balance by converting chemical energy into heat through the cost of ATP production. In this study, it was demonstrated that Trib3 is a critical determinant of BAT-mediated energy expenditure and whole-body energy homeostasis. Under 60% high-fat diet conditions, Trib3 expression in BAT was elevated. Mice deficient in Trib3 are resistant to diet-induced obesity and exhibit improved glucose homeostasis due to enhanced BAT activity. Furthermore, brown adipocyte progenitor cells (APCs) lacking Trib3 exhibited increased proliferation and promoted brown adipocyte differentiation and mitochondrial biogenesis, contributing to the increase in the maximal thermogenic capacity of BAT in Trib3-deficient mice. Mechanistically, it was discovered that Trib3 expression is upregulated by free fatty acids at the transcriptional level and synergistically upregulated by DAG-PKC at the posttranslational level. This occurs through the modulation of COP1-mediated Trib3 protein turnover. Interestingly, the level of Trib3 expression in BAT increased with age. Trib3 knockout mice were protected from aging-related weight gain and impaired glucose homeostasis. These results suggest that Trib3 acts as an obesity- and aging-associated factor that negatively regulates BAT activity and that the loss of Trib3 may provide a beneficial approach to prevent obesity and aging-associated metabolic syndrome by increasing the thermogenic capacity of BAT.
    DOI:  https://doi.org/10.1038/s12276-024-01361-5
  3. Cell Metab. 2024 Dec 03. pii: S1550-4131(24)00418-2. [Epub ahead of print]36(12): 2491-2492
      Mitochondrial energy conversion supplies cellular energy but can also provide heat in brown adipose tissue (BAT). In a recent study, Shin and Latorre-Muro et al.1 show that respiratory supercomplexes in BAT are remodeled during cold to provide a tighter coupling, revealing a novel, physiologically important role for these supramolecular assemblies.
    DOI:  https://doi.org/10.1016/j.cmet.2024.10.022
  4. Biochim Biophys Acta Bioenerg. 2024 Nov 29. pii: S0005-2728(24)00498-5. [Epub ahead of print]1866(1): 149528
      The inside-out submitochondrial particles (IO-SMPs) showed a strong protective effect against mitochondrial permeability transition pore (mPTP) opening in mitochondria isolated from swine hearts 3 h after explantation. The latter condition was used to emulate situation of mitochondrial damage. We identified that the protective effect of IO-SMPs cannot be attributed to a functional modulation of the enzymatic complexes involved in mPTP formation. Indeed, oxidative phosphorylation and F1FO-ATPase activity were not affected. Conversely, mPTP desensitization might be caused by structural modification. IO-SMP incorporation into the mitochondria can modulate the membrane-bound enzyme complexes' functionality, inducing F1FO-ATPase to be unable to carry out the conformational changes useful for mPTP opening. Thus, the data are a valid starting point for IO-SMP application in the treatment of impaired cardiovascular conditions supported by mPTP opening.
    Keywords:  F(1)F(O)-ATPase; Inside-out submitochondrial particles; Mitochondrial dysfunction; Mitochondrial permeability transition pore
    DOI:  https://doi.org/10.1016/j.bbabio.2024.149528