Adipose tissue expansion, as seen in obesity, is often metabolically detrimental causing insulin resistance and the metabolic syndrome. However, white adipose tissue expansion at early ages is essential to establish a functional metabolism. To understand the differences between adolescent and adult adipose tissue expansion, we studied the cellular composition of the stromal vascular fraction of subcutaneous adipose tissue of two and eight weeks old mice using single cell RNA sequencing. We identified a subset of adolescent preadipocytes expressing the mature white adipocyte marker Asc-1 that showed a low ability to differentiate into beige adipocytes compared to Asc-1 negative cells in vitro. Loss of Asc-1 in subcutaneous preadipocytes resulted in spontaneous differentiation of beige adipocytes in vitro and in vivo. Mechanistically, this was mediated by a function of the amino acid transporter ASC-1 specifically in proliferating preadipocytes involving the intracellular accumulation of the ASC-1 cargo D-serine.
Brown adipose tissue (BAT) plays an important role in the regulation of body weight and glucose homeostasis. Although increasing evidence supports white adipose tissue heterogeneity, little is known about heterogeneity within murine BAT. Recently, UCP1 high and low expressing brown adipocytes were identified, but a developmental origin of these subtypes has not been studied. To obtain more insights into brown preadipocyte heterogeneity, we use single-cell RNA sequencing of the BAT stromal vascular fraction of C57/BL6 mice and characterize brown preadipocyte and adipocyte clonal cell lines. Statistical analysis of gene expression profiles from brown preadipocyte and adipocyte clones identify markers distinguishing brown adipocyte subtypes. We confirm the presence of distinct brown adipocyte populations in vivo using the markers EIF5, TCF25, and BIN1. We also demonstrate that loss of Bin1 enhances UCP1 expression and mitochondrial respiration, suggesting that BIN1 marks dormant brown adipocytes. The existence of multiple brown adipocyte subtypes suggests distinct functional properties of BAT depending on its cellular composition, with potentially distinct functions in thermogenesis and the regulation of whole body energy homeostasis.
Background:The rates of obesity, its associated diseases, and allergies are raising at alarming rates in most countries. House dust mites (HDM) are highly allergenic and exposure often associates with an urban sedentary indoor lifestyle, also resulting in obesity. The aim of this study was to investigate the epidemiological association and physiological impact of lung inflammation on obesity and glucose homeostasis.Methods: Epidemiological data from 2207 adults of the population-based KORA FF4 cohort were used to test associations between asthma and rhinitis with metrics of body weight and insulin sensitivity. To obtain functional insights, C57BL/6J mice were Funding informationThe KORA study was initiated and financed by the Helmholtz Zentrum München-German Research Center for Environmental Health, which is funded by the German Federal Ministry of Education and Research (BMBF) and by the State of Bavaria. Mouse studies were supported by the HMGU Allergy Projects from the Helmholtz Center Munich.intranasally sensitized and challenged with HDM and simultaneously fed with either low-fat or high-fat diet for 12 weeks followed by a detailed metabolic and biochemical phenotyping of the lung, liver, and adipose tissues. Results:We found a direct association of asthma with insulin resistance but not body weight in humans. In mice, co-development of obesity and HDM-induced lung inflammation attenuated inflammation in lung and perigonadal fat, with little impact on body weight, but small shifts in the composition of gut microbiota. Exposure to HDM improved glucose tolerance, reduced hepatosteatosis, and increased energy expenditure and basal metabolic rate. These effects associate with increased activity of thermogenic adipose tissues independent of uncoupling protein 1.Conclusions: Asthma associates with insulin resistance in humans, but HDM challenge results in opposing effects on glucose homeostasis in mice due to increased energy expenditure, reduced adipose inflammation, and hepatosteatosis.
Early postnatal adipose growth is essential to establish a functional metabolism. Conversely, proportional adipose expansion in adults results in insulin resistance. Despite adipocytes, immune cells play a pivotal role in orchestrating adipose tissue function and expansion. To this end, we performed an in-depth analysis of scRNAseq data of immune cell populations of 2 weeks (pre-weaning) and 8 weeks old (adult) murine subcutaneous and perigonadal adipose depots. Our analysis revealed 15 distinct immune cell clusters. Most immune cell types were found in all depots and ages. Among the detected T-cell populations, we only observed differences in the abundance of naïve T cells, which were predominantly found in in subcutaneous white adipose tissue, irrespective of age. Similar to human, we could define several murine macrophage subtypes. Among them, perivascular macrophages (PVM) were predominantly found in subcutaneous white adipose tissue of 2 weeks old mice. RNA-velocity analysis and pseudotime trajectory construction suggested a developmental trajectory from lipid-associated macrophages (LAM) to PVM, which was further corroborated by analysis of gene expression dynamics resolved along latent time of white adipose tissue macrophages from 2 weeks old mice. Further analysis revealed that the top-ranked 100 genes of LAM were associated with the regulation of endothelial cell migration and proliferation (Nrp1, Grn, Glul, Sash1, Ccl24), blood vessel morphogenesis (Nrp1, Tgfbr2) and the regulation of epithelial cell proliferation. In summary, we provide a comprehensive overview of the immune cell composition of pre-weaning and adults murine adipose tissues. Moreover, we provide in-depth analysis of T-cell and macrophage populations and their relationship and dependency based on mRNA expression analysis. Disclosure X. Yan: None. V. Miok: None. R. Karlina: None. A. Böttcher: None. D. Lutter: None. H. Lickert: Research Support; Eli Lilly and Company. C. Garcia Caceres: None. S. Ussar: Research Support; Novo Nordisk. Funding China Scholarship Council (201908370218)
Brown adipose tissue (BAT) plays an important role in the regulation of body weight and glucose homeostasis. While increasing evidence supports white adipose tissue heterogeneity, little is known about heterogeneity within murine BAT. Using single cell RNA sequencing of the stromal vascular fraction of murine BAT and analysis of 67 brown preadipocyte and adipocyte clones we unravel heterogeneity within brown preadipocytes. Statistical analysis of gene expression profiles from these clones identifies markers distinguishing brown adipocyte lineages. We confirm the presence of distinct brown adipocyte populations in vivo using three identified markers; Eif5, Tcf25, and Bin1. Functionally, we demonstrate that loss of Bin1 enhances UCP1 expression and mitochondrial respiration, suggesting that Bin1 marks a dormant brown adipocyte type. The existence of multiple brown adipocyte lineages suggests distinct functional properties of BAT depending on its cellular composition, with potentially distinct function in thermogenesis and the regulation of whole body energy homeostasis.
Background: Dietary carbohydrates and fats are intrinsically correlated within the habitual diet. We aimed to disentangle the associations of starch and sucrose from those of fat, in relation to allergic sensitization, asthma and rhinoconjuctivitis prevalence in humans, and to investigate underlying mechanisms using murine models.Methods: Epidemiological data from participants of two German birth cohorts (age 15) were used in logistic regression analyses testing cross-sectional associations of starch and sucrose (and their main dietary sources) with aeroallergen sensitization, asthma and rhinoconjunctivitis, adjusting for correlated fats (saturated, monounsaturated, omega-6 and omega-3 polyunsaturated) and other covariates. For mechanistic insights, murine models of aeroallergen-induced allergic airway inflammation (AAI) fed with a low-fat-high-sucrose or -high-starch versus a high-fat diet were used to characterize and quantify disease development. Metabolic and physiologic parameters were used to track outcomes of dietary interventions and cellular and molecular responses to monitor the development of AAI. Oxidative stress biomarkers were measured in murine sera or lung homogenates. Results:We demonstrate a direct association of dietary sucrose with asthma prevalence in males, while starch was associated with higher asthma prevalence in females.In mice, high-carbohydrate feeding, despite scant metabolic effects, aggravated AAI compared to high-fat in both sexes, as displayed by humoral response, mucus hypersecretion, lung inflammatory cell infiltration and T H 2-T H 17 profiles. Compared to high-fat, high-carbohydrate intake was associated with increased pulmonary oxidative stress, signals of metabolic switch to glycolysis and decreased systemic anti-oxidative capacity. Conclusion:High consumption of digestible carbohydrates is associated with an increased prevalence of asthma in humans and aggravated lung allergic inflammation in mice, involving oxidative stress-related mechanisms.
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