bims-mimeim 2021-05-02 papers

Issue of 2021–05–02
four papers selected by
Matthew C. Sinton, University of Glasgow

Int J Mol Sci. 2021 Apr 20. pii: 4260. [Epub ahead of print]22(8):

Viral Infection Modulates Mitochondrial Function.

Xiaowen Li, Keke Wu, Sen Zeng, Feifan Zhao, Jindai Fan, Zhaoyao Li, Lin Yi, Hongxing Ding, Mingqiu Zhao, Shuangqi Fan, Jinding Chen.

Mitochondria are important organelles involved in metabolism and programmed cell death in eukaryotic cells. In addition, mitochondria are also closely related to the innate immunity of host cells against viruses. The abnormality of mitochondrial morphology and function might lead to a variety of diseases. A large number of studies have found that a variety of viral infections could change mitochondrial dynamics, mediate mitochondria-induced cell death, and alter the mitochondrial metabolic status and cellular innate immune response to maintain intracellular survival. Meanwhile, mitochondria can also play an antiviral role during viral infection, thereby protecting the host. Therefore, mitochondria play an important role in the interaction between the host and the virus. Herein, we summarize how viral infections affect microbial pathogenesis by altering mitochondrial morphology and function and how viruses escape the host immune response.

Keywords: apoptosis; host innate immunity; mitochondrial fission and fusion; virus infection

DOI: https://doi.org/10.3390/ijms22084260

Nat Immunol. 2021 Apr 27.

Single-cell sequencing of human white adipose tissue identifies new cell states in health and obesity.

Andrew D Hildreth, Feiyang Ma, Yung Yu Wong, Ryan Sun, Matteo Pellegrini, Timothy E O'Sullivan.

White adipose tissue (WAT) is an essential regulator of energy storage and systemic metabolic homeostasis. Regulatory networks consisting of immune and structural cells are necessary to maintain WAT metabolism, which can become impaired during obesity in mammals. Using single-cell transcriptomics and flow cytometry, we unveil a large-scale comprehensive cellular census of the stromal vascular fraction of healthy lean and obese human WAT. We report new subsets and developmental trajectories of adipose-resident innate lymphoid cells, dendritic cells and monocyte-derived macrophage populations that accumulate in obese WAT. Analysis of cell-cell ligand-receptor interactions and obesity-enriched signaling pathways revealed a switch from immunoregulatory mechanisms in lean WAT to inflammatory networks in obese WAT. These results provide a detailed and unbiased cellular landscape of homeostatic and inflammatory circuits in healthy human WAT.

DOI: https://doi.org/10.1038/s41590-021-00922-4

Front Endocrinol (Lausanne). 2021 ;12 652444

Sex Differences in Brown Adipose Tissue Function: Sex Hormones, Glucocorticoids, and Their Crosstalk.

Kasiphak Kaikaew, Aldo Grefhorst, Jenny A Visser.

Excessive fat accumulation in the body causes overweight and obesity. To date, research has confirmed that there are two types of adipose tissue with opposing functions: lipid-storing white adipose tissue (WAT) and lipid-burning brown adipose tissue (BAT). After the rediscovery of the presence of metabolically active BAT in adults, BAT has received increasing attention especially since activation of BAT is considered a promising way to combat obesity and associated comorbidities. It has become clear that energy homeostasis differs between the sexes, which has a significant impact on the development of pathological conditions such as type 2 diabetes. Sex differences in BAT activity may contribute to this and, therefore, it is important to address the underlying mechanisms that contribute to sex differences in BAT activity. In this review, we discuss the role of sex hormones in the regulation of BAT activity under physiological and some pathological conditions. Given the increasing number of studies suggesting a crosstalk between sex hormones and the hypothalamic-pituitary-adrenal axis in metabolism, we also discuss this crosstalk in relation to sex differences in BAT activity.

Keywords: androgens; brown adipocytes; estrogens; glucocorticoids; progesterone; sex characteristics; sex chromosomes; steroid receptors

DOI: https://doi.org/10.3389/fendo.2021.652444

Cell Rep. 2021 Apr 27. pii: S2211-1247(21)00337-5. [Epub ahead of print]35(4): 109023

Quantification of adipocyte numbers following adipose tissue remodeling.

Caroline Moser, Leon G Straub, Yael Rachamin, Dianne H Dapito, Elisabeth Kulenkampff, Lianggong Ding, Wenfei Sun, Salvatore Modica, Miroslav Balaz, Christian Wolfrum.

To analyze the capacity of white and brown adipose tissue remodeling, we developed two mouse lines to label, quantitatively trace, and ablate white, brown, and brite/beige adipocytes at different ambient temperatures. We show here that the brown adipocytes are recruited first and reach a peak after 1 week of cold stimulation followed by a decline during prolonged cold exposure. On the contrary, brite/beige cell numbers plateau after 3 weeks of cold exposure. At thermoneutrality, brown adipose tissue, in spite of being masked by a white-like morphology, retains its brown-like physiology, as Ucp1+ cells can be recovered immediately upon beta3-adrenergic stimulation. We further demonstrate that the recruitment of Ucp1+ cells in response to cold is driven by existing adipocytes. In contrast, the regeneration of the interscapular brown adipose tissue following ablation of Ucp1+ cells is driven by de novo differentiation.

Keywords: Adipoq-CreERT2; Ucp1-CreERT2; adipocyte cell number; brite/beige adipocytes; brown adipose tissue regrowth; cold exposure; tamoxifen; thermoneutrality

DOI: https://doi.org/10.1016/j.celrep.2021.109023