bims-obesme Biomed News
on Obesity metabolism
Issue of 2025–07–27
seven papers selected by
Xiong Weng, University of Edinburgh
  1. Deletion of EP3 prostaglandin receptor in murine macrophages aggravates diet-induced obesity by suppressing SPARC.
  2. Non-canonical functions of DNMT3A in hematopoietic stem cells regulate telomerase activity and genome integrity.
  3. Cell type-specific purifying selection of synonymous mitochondrial DNA variation.
  4. PNPLA7 mediates Parkin-mitochondrial recruitment in adipose tissue for mitophagy and inhibits browning.
  5. LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes.
  6. TMEM65 functions as the mitochondrial Na+/Ca2+ exchanger.
  7. N-acetylaspartate from fat cells regulates postprandial body temperature.
  1. EMBO J. 2025 Jul 23.
    Deletion of EP3 prostaglandin receptor in murine macrophages aggravates diet-induced obesity by suppressing SPARC.
    Wenlong Shang, Yinxiu Li, Lu Wang, Jiao Liu, Huiwen Ren, Qian Liu, Shumin Guo, Yuhong Wang, Yubo Ma, Tianyi You, Yujun Shen, Yu Zhou, Danyang Tian, Ying Yu.
      Macrophages are primary immune cells involved in obesity-triggered chronic low-grade inflammation in adipose tissues. Prostaglandin E2 (PGE2), mainly generated from macrophages, can regulate adipose tissue remodeling, yet the underlying mechanisms are not fully understood. Here, we observed that PGE2 receptor subtype 3 (EP3) was remarkably downregulated in adipose tissue macrophages from high-fat diet (HFD)-fed mice and patients with obesity. Notably, macrophage-specific deletion of EP3 exacerbated HFD-induced fat expansion, whereas EP3α isoform overexpression in macrophages alleviated obesity phenotypes. Further, EP3 deficiency suppressed secretion of anti-adipogenic matricellular protein SPARC from macrophages. SPARC deletion in macrophages abrogated the protection of EP3-overexpression against diet-induced obesity. Mechanistically, EP3 activation promoted SPARC expression by suppressing DNA methylation in macrophages through a PKA-Sp1-Dnmt1/3a signaling cascade. Finally, EP3 agonist treatment ameliorated HFD-induced obesity in mice. Thus, EP3 inhibits adipogenesis through promoting release of SPARC from macrophages, suggesting a novel therapeutic target for diet-induced obesity.
    Keywords:  E-prostanoid 3 Receptor; Macrophage; Obesity; SPARC
    DOI:  https://doi.org/10.1038/s44318-025-00508-y
  2. Cell Stem Cell. 2025 Jul 10. pii: S1934-5909(25)00256-5. [Epub ahead of print]
    Non-canonical functions of DNMT3A in hematopoietic stem cells regulate telomerase activity and genome integrity.
    Infencia Xavier Raj, Won Kyun Koh, Jessica Harrison, Christine R Zhang, Barbara Soares, Roberta Amato, Aishwarya Krishnan, David R O'Leary, Hassan Bjeije, Tyler M Parsons, Wentao Han, Andrew L Young, Ting Wang, Luis F Z Batista, Grant A Challen.
      DNMT3A is a critical regulator of hematopoietic stem cell (HSC) fate decisions and the most recurrently mutated gene in human clonal hematopoiesis (CH). DNMT3A is described as a DNA methyltransferase enzyme, but cells with DNMT3A loss of function show minor changes in DNA methylation that do not correlate with altered gene expression. To explore the possibility that Dnmt3a has DNA-methylation-independent functions in HSCs, we created an allelic series of mice with varying levels of DNA-methylation-impaired Dnmt3a. Clonal expansion of Dnmt3a-deficient HSCs was rescued by Dnmt3a proteins lacking DNA methylation capacity, suggesting that Dnmt3a has important non-canonical functions in HSCs. Dnmt3a-null HSCs can be transplanted indefinitely, implying the ability to circumvent mechanisms that limit the replicative lifespan of HSCs, such as telomere shortening. Dnmt3a-null HSCs show increased telomerase activity and sustain telomere length over serial transplantation, revealing a previously unidentified role for DNMT3A mutations in regulating HSC longevity that is unrelated to DNA methylation function.
    Keywords:  DNA methylation; DNMT3A; hematopoietic stem cell; telomerase; telomere
    DOI:  https://doi.org/10.1016/j.stem.2025.06.010
  3. Proc Natl Acad Sci U S A. 2025 Jul 29. 122(30): e2505704122
    Cell type-specific purifying selection of synonymous mitochondrial DNA variation.
    Caleb A Lareau, Patrick Maschmeyer, Yajie Yin, Jacob C Gutierrez, Ryan S Dhindsa, Anne-Sophie Gribling-Burrer, Sebastian Zielinski, Yu-Hsin Hsieh, Lena Nitsch, Veronika Dimitrova, Benan Nalbant, Frank A Buquicchio, Tsion Abay, Robert R Stickels, Jacob C Ulirsch, Patrick Yan, Fangyi Wang, Zhuang Miao, Katalin Sandor, Bence Daniel, Vincent Liu, Paul L Mendez, Petra Knaus, Manpreet Meyer, William J Greenleaf, Anshul Kundaje, Redmond P Smyth, Mathias Munschauer, Leif S Ludwig, Ansuman T Satpathy.
      While somatic variants are well-characterized drivers of tumor evolution, their influence on cellular fitness in nonmalignant contexts remains understudied. We identified a mosaic synonymous variant (m.7076A > G) in the mitochondrial DNA (mtDNA)-encoded cytochrome c-oxidase subunit 1 (MT-CO1, p.Gly391=), present at homoplasmy in 47% of immune cells from a healthy donor. Single-cell multiomics revealed strong, lineage-specific selection against the m.7076G allele in CD8+ effector memory T cells, but not other T cell subsets, mirroring patterns of purifying selection of pathogenic mtDNA alleles. The limited anticodon diversity of mitochondrial tRNAs forces m.7076G translation to rely on wobble pairing, unlike the Watson-Crick-Franklin pairing used for m.7076A. Mitochondrial ribosome profiling confirmed stalled translation of the m.7076G allele. Functional analyses demonstrated that the elevated translational and metabolic demands of short-lived effector T cells (SLECs) amplify dependence on MT-CO1, driving this selective pressure. These findings suggest that synonymous variants can alter codon syntax, impacting mitochondrial physiology in a cell type-specific manner.
    Keywords:  immunology; mitochondria; selection; single-cell
    DOI:  https://doi.org/10.1073/pnas.2505704122
  4. Nat Commun. 2025 Jul 19. 16(1): 6651
    PNPLA7 mediates Parkin-mitochondrial recruitment in adipose tissue for mitophagy and inhibits browning.
    Xuetao Ji, Xu Zhang, Tong Zhang, Yao Xue, Mengping He, Chaopu Li, Yun Huang, Haoyu Wang, Jing Ju, Li'e Cai, Yuzhu Wang, Ning Wang, Lijuan Fan, Hui Tong, Heng Fan, Qinsheng Chen, Qinwei Lu, Cong Li, Huiru Tang, Yongsheng Chang, Xingxing Kong, Hanming Shen, Aihua Gu, Hui Liang, Hongwen Zhou, Qian Wang, John Zhong Li.
      PINK1/Parkin-mediated ubiquitin-dependent mitophagy is a critical negative regulatory machinery for browning in the inguinal white adipose tissue (iWAT). However, the precise regulatory mechanism underlying PINK1/Parkin-mediated mitophagy during browning of iWAT remains largely unknown. Here we report that PNPLA7, an Endoplasmic Reticulum and mitochondria-associated membrane (MAM) protein, inhibits browning of iWAT by promoting PINK1/Parkin-mediated mitophagy upon cold challenge or β3-adrenergic receptor agonist treatment. With genetic manipulation in mice, we show that adipose tissue overexpressing PNPLA7 induces mitophagy, abolishes iWAT browning and interrupts adaptive thermogenesis. Conversely, conditional ablation of PNPLA7 in adipose tissue promotes browning of iWAT, resulting in enhanced adaptive thermogenesis. Mechanistically, PNPLA7 interacts with Parkin to promote mitochondrial recruitment of Parkin for mitophagy activation and mitochondria degradation by disrupting PKA-induced phosphorylation of Parkin under cold challenge. Taken together, our findings suggest that PNPLA7 is a critical regulator of mitophagy that resists cold-induced browning of iWAT, thus providing a direct mechanistic link between mitophagy and browning of iWAT.
    DOI:  https://doi.org/10.1038/s41467-025-61904-w
  5. Nat Metab. 2025 Jul 21.
    LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes.
    Jin Li, Yamei Deng, Marie Gasser, Jie Zhu, Emily M Walker, Vaibhav Sidarala, Emma C Reck, Dre L Hubers, Mabelle B Pasmooij, Chun-Shik Shin, Khushdeep Bandesh, Eftyhmios Motakis, Siddhi Nargund, Romy Kursawe, Venkatesha Basrur, Alexey I Nesvizhskii, Michael L Stitzel, David C Chan, Guy A Rutter, Scott A Soleimanpour.
      Protein misfolding is a contributor to the development of type 2 diabetes (T2D), but the specific role of impaired proteostasis is unclear. Here we show a robust accumulation of misfolded proteins in the mitochondria of human pancreatic islets from patients with T2D and elucidate its impact on β cell viability through the mitochondrial matrix protease LONP1. Quantitative proteomics studies of protein aggregates reveal that islets from donors with T2D have a signature resembling mitochondrial rather than endoplasmic reticulum protein misfolding. Loss of LONP1, a vital component of the mitochondrial proteostatic machinery, with reduced expression in the β cells of donors with T2D, yields mitochondrial protein misfolding and reduced respiratory function, leading to β cell apoptosis and hyperglycaemia. LONP1 gain of function ameliorates mitochondrial protein misfolding and restores human β cell survival after glucolipotoxicity via a protease-independent effect requiring LONP1-mitochondrial HSP70 chaperone activity. Thus, LONP1 promotes β cell survival and prevents hyperglycaemia by facilitating mitochondrial protein folding. These observations provide insights into the nature of proteotoxicity that promotes β cell loss during the pathogenesis of T2D, which could be considered as future therapeutic targets.
    DOI:  https://doi.org/10.1038/s42255-025-01333-7
  6. Nat Cell Biol. 2025 Jul 21.
    TMEM65 functions as the mitochondrial Na+/Ca2+ exchanger.
    Jim Lu Zhang, Yu-Chen Chang, Po-Hsuan Lai, Han-I Yeh, Chen-Wei Tsai, Yu-Lun Huang, Tsung-Yun Liu, I-Chi Lee, North Foulon, Yan Xu, Bing Rao, Hsiu-Man Shih, Yung-Chi Tu, Andres V Reyes, Shou-Ling Xu, Liang Feng, Ming-Feng Tsai.
      Mitochondria export Ca2+ via Na+/Ca2+ exchange machinery (mito-NCX) to regulate intracellular Ca2+ signalling and mitochondrial Ca2+ homeostasis. TMEM65 has recently been implicated as essential for mito-NCX, but its mechanisms and roles remain unclear. Here we show that TMEM65 depletion severely impairs mito-NCX. TMEM65 is highly expressed in the heart and brain but absent in the liver, correlating with mito-NCX activity in these tissues. Biochemical and functional analyses reveal that TMEM65 forms a homodimer, containing plausible ion-coordinating residues critical for function. Heterologous expression of TMEM65 induces Na+/Ca2+ exchange in cells lacking native mito-NCX activity. Moreover, purified, liposome-reconstituted TMEM65 exhibits key mito-NCX features. We further identify the binding site for CGP-37157, a potent, widely used mito-NCX inhibitor. Finally, TMEM65 deletion elevates mitochondrial Ca2+ and primes mitochondria to permeability transition. These findings firmly establish TMEM65 as the protein mediating mito-NCX, offering a new therapeutic target for diseases associated with mitochondrial Ca2+ dysregulation.
    DOI:  https://doi.org/10.1038/s41556-025-01721-x
  7. Nat Metab. 2025 Jul 23.
    N-acetylaspartate from fat cells regulates postprandial body temperature.
    Jessica B Felix, Pradip K Saha, Evelyn L de Groot, Lin Tan, Robert Sharp, Elizabeth S Anaya, Yafang Li, Holly Quang, Nooshin Saidi, Layla Abushamat, Christie M Ballantyne, Christopher I Amos, Philip L Lorenzi, Samuel Klein, Xia Gao, Sean M Hartig.
      N-acetylaspartate (NAA), the brain's second most abundant metabolite, provides essential substrates for myelination through its hydrolysis1. However, the physiological roles of NAA in other tissues remain unknown. Here, we show that aspartoacylase (ASPA) expression in white adipose tissue (WAT) governs blood NAA levels for postprandial body temperature regulation. Genetic ablation of Aspa in mice resulted in systemically elevated NAA levels, and the ensuing accumulation in WAT stimulated pyrimidine production. Stable isotope tracing confirmed higher incorporation of glucose-derived carbon into pyrimidine metabolites in Aspa knockout cells. Additionally, serum NAA levels positively correlated with the abundance of the pyrimidine intermediate orotidine 5'-monophosphate, and this relationship predicted lower body mass index in humans. Using whole-body and tissue-specific knockout mouse models, we observed that fat cells provided plasma NAA and suppressed postprandial body temperature elevation. Moreover, unopposed NAA from adipocytes greatly enhanced whole-body glucose disposal exclusively in WAT. Exogenous NAA also increased plasma pyrimidines and lowered body temperature. These data place WAT-derived NAA as an endocrine regulator of postprandial body temperature and define broader roles for metabolic homeostasis.
    DOI:  https://doi.org/10.1038/s42255-025-01334-6
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