Discovery and functional assessment of a novel adipocyte population driven by intracellular Wnt/β-catenin signaling in mammals

  1. Zhi Liu
  2. Tian Chen
  3. Sicheng Zhang
  4. Tianfang Yang
  5. Yun Gong
  6. Hong-Wen Deng
  7. Ding Bai
  8. Weidong Tian
  9. YiPing Chen

  • Curated by eLife

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    Evaluation Summary:

    It is becoming increasingly clear that adipocytes are not homogenous, but rather comprise several distinct subtypes with specific physiological functions. This work presents evidence for the surprising finding of a subpopulation of adipocytes displaying non-canonical Wnt signaling. The possible role of these adipocytes in thermogenesis is more ambiguous, and their physiological function remains unclear.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 and Reviewer #2 agreed to share their name with the authors.)

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Abstract

Wnt/β-catenin signaling has been well established as a potent inhibitor of adipogenesis. Here, we identified a population of adipocytes that exhibit persistent activity of Wnt/β-catenin signaling, as revealed by the Tcf/Lef-GFP reporter allele, in embryonic and adult mouse fat depots, named as Wnt + adipocytes. We showed that this β-catenin-mediated signaling activation in these cells is Wnt ligand- and receptor-independent but relies on AKT/mTOR pathway and is essential for cell survival. Such adipocytes are distinct from classical ones in transcriptomic and genomic signatures and can be induced from various sources of mesenchymal stromal cells including human cells. Genetic lineage-tracing and targeted cell ablation studies revealed that these adipocytes convert into beige adipocytes directly and are also required for beige fat recruitment under thermal challenge, demonstrating both cell autonomous and non-cell autonomous roles in adaptive thermogenesis. Furthermore, mice bearing targeted ablation of these adipocytes exhibited glucose intolerance, while mice receiving exogenously supplied such cells manifested enhanced glucose utilization. Our studies uncover a unique adipocyte population in regulating beiging in adipose tissues and systemic glucose homeostasis.

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  1. Version published to 10.7554/elife.77740 on eLife
  2. eLife

    Author Response

    Reviewer #1 (Public Review):

    Liu et al investigated the role of Wnt/β-catenin pathway in the genesis of thermogenic adipocytes. Their study shows that some adipocytes exhibited Wnt/β-catenin signaling ("Wnt+ adipocytes") in intrascapular brown adipose tissue (iBAT), inguinal white adipose tissue (iWAT), epidydimal WAT (eWAT), and bone marrow (BM). There was a different level of the possession of Wnt+ adipocytes between the different depots with iBAT expressing 17%, iWAT expressing 6.9%, and eWAT expressing the least at 1.3%. Expression of these adipocytes was noted on embryonic day 17.5 and was present in a higher percentage in female mice compared to male mice and in younger mice compared to older mice, which aligns with their observation that Wnt+ adipocytes are thermogenic.

    The authors also noted that Wnt+ adipocytes can differentiate from human stromal cells. In regards to the pathway, Wnt/β-catenin adipocytes are distinct from classical brown adipocytes at molecular and genomic levels. It was noted that Tcf7L2 was largely expressed in Wnt+ adipocytes but other Tcf proteins (Tcf 1, Tcf 3, and Lef1) were not. Wnt- cells showed a reversible delay in maturation with LF3, however, no cell death was noted. Wnt/β-catenin adipocytes seem to depend on AKT/mTOR signaling. It was further shown that insulin is a key factor in mTOR signaling and Wnt+ adipocyte differentiation.

    Upon cold exposure, UCP1+/Wnt- beige fat emerges largely surrounding Wnt+ adipocytes, implicating that Wnt+ adipocytes serve as a "beiging initiator" in a paracrine manner. Lastly, mice with implanted Wnt+ adipocytes had a significantly better glucose tolerance which suggests that Wnt+ adipocytes have a beneficial impact on whole-body metabolism. I found no major flaws in the method and data largely supports their conclusion that Wnt+ adipocytes have (at least some) a significant role in thermogenesis/metabolism, which I think is a very impressive and innovative finding.

    Thanks so much for the outstanding summary of our manuscript. We feel sorry that we somehow did not make it clear in the original manuscript that the percentage of Wnt+ adipocytes is higher in male mice than that in females.

    Reviewer #2 (Public Review):

    Liu et al present evidence for the surprising finding of Tcf/Lef-active, "Wnt+" mature adipocytes. They report that Wnt+ adipocytes arise during embryogenesis and regulate cold-induced beiging in surrounding adipocytes. Tcf/Lef transcriptional activity in these cells is Wnt-ligand independent and instead appears to be stimulated by insulin-dependent AKT/mTOR signaling. Using a diphtheria toxin inducible depletion mouse model, the authors show that Wnt+ cells play an important role in glucose homeostasis.

    As the authors have acknowledged, proper assignment of adipocyte nuclei is a notoriously difficult histological challenge. Mesenchymal cells sit directly adjacent to the adipocyte plasma membrane and their nuclei are often incorrectly assigned to the adipocyte both in vivo and in vitro. Pparg nuclear co-staining is helpful, however, Pparg is very highly expressed by endothelial cells and Col15a1+ committed preadipocytes, which are intercalated throughout the adipose. The authors have made an impressive attempt to address this concern by generating a Tcf/Lef-CreER mouse line to fluorescently label Wnt+ adipocytes, however, it is not entirely clear if the images presented support the conclusion that mature adipocytes are being labeled. Given that Wnt+ mature adipocytes are the core conclusion of this manuscript, and because this hypothesis runs counter to a large body of literature concluding that Wnt signaling inhibits adipogenesis, the authors have assumed a very high burden of proof that these are indeed Wnt+ mature adipocytes in vivo.

    Thanks for the outstanding summary of our manuscript.

    To address these concerns, the authors could utilize the specificity of in vivo single-nuclei RNA-Seq. Several data resources have been published (https://singlecell.broadinstitute.org/single_cell/study/SCP1376/a-single-cell-atlas-of-human-and-mouse-white-adipose-tissue), and the authors should re-analyze these data for subpopulations of mature adipocytes that express a transcriptional signature of active Tcf/Lef signaling. It is unfortunate that the authors were unable to successfully perform single-nuclei analysis of the Wnt+ adipocytes as this would significantly enhance this manuscript. The physiologic relevance of the single-cell analysis of immortalized, in-vitro differentiated clonal cell lines is questionable.

    We took the advice by Reviewer 2 and intersected our scRNA-seq data on Wnt+ adipocytes with the published single-nucleus sequencing (sNuc-seq) dataset of mouse iWAT (Emont et al., 2022). Because the activation of Tcf/Lef signaling in the Wnt+ adipocytes is relied on AKT/mTOR signaling but not the conventional Wnt ligands and receptors, those traditional downstream markers of Wnt signaling such Axins were not found specifically enriched in the Wnt+ adipocytes. Therefore, the AKT/mTOR-dependent Wnt signaling in Wnt+ adipocytes appears to regulate expression of genes distinct from that controlled by the conventional Wnt signaling pathway. This conclusion is supported by our recent studies that inhibition of this AKT/mTOR-dependent Wnt signaling by LF3 in Wnt+ adipocytes negatively impact pathways implicated in “PI3K/Akt signaling”, “insulin signaling”, “thermogenesis”, and “fatty acid metabolism” et al (see below for details). However, we found that one cluster (mAd3) of sNuc-seq dataset, which is relatively enriched in Tcf7l2, expresses remarked high levels of Cyp2e1 as well as Cfd that encodes Adipsin. These genes, regarded as hallmark of mAd3 cluster, are also uniquely or highly expressed in Wnt+ adipocytes. Interestingly, the percentage of mAd3 among the total iWAT adipocytes in chow-fed male group is about 5%, which is very close to that of Wnt+ adipocytes in vivo (~7%). Thus, mAd3 possibly represents Wnt+ adipocytes in iWAT. These analyses are included in the revision.

    Reviewer #3 (Public Review):

    It is becoming increasingly clear that adipocytes are not homogenous, but rather comprise several distinct subtypes with specific physiological functions. The mechanisms that underlie the development and distinct roles of each adipocyte subtype are of great interest for understanding the biology of metabolic regulation and its impairments in metabolic disease. In this manuscript, the authors describe a previously unknown population of adipocytes in mice, which are characterized by a special form of beta-catenin signaling. They perform a comprehensive series of experiments in cultured cells, in mouse models of in-vivo lineage tracing, and transplantation experiments to define the origin and function of these adipocytes. They find that the formation of these Wnt+ adipocytes is dependent on insulin signaling, and find possible roles in thermogenic adipose tissue development. Overall, the conclusions of this study are very convincing in their identification of a subpopulation of adipocytes displaying non-canonical Wnt signaling. The proposed role of these adipocytes as regulators of thermogenesis is more ambiguous, and their physiological function remains unclear.

    Thanks for the good comments. To distinguish this AKT/mTOR dependent intracellular Wnt signaling in Wnt+ adipocytes from the conventional non-canonical Wnt signaling, we feel that it would be appropriate to call this signaling as atypical Wnt signaling.

    • The new adipocyte types are identified through expression of a reporter for TCF/Lef signaling. This reporter is classically activated by Wnt/beta-catenin and using both siRNA depletion of beta-catenin as well as an allele lacking its transcriptional activation domain, the authors confirm the reporter expression is dependent on the presence of beta-catenin and TCF7L2, but independent of canonical Wnt signaling.

    • The involvement of TCF7L2 is also probed using a specific inhibitor of the beta-catenin/TCF7L2 interactions, LF3, which inhibited reporter expression. Inhibition of canonical Wnt signaling was without effect.

    • The authors isolate clonal lines of precursor cells that give rise to Wnt+ or Wnt- adipocytes from mouse brown adipose tissue. They find that Wnt+ adipocytes are dependent on the Wnt pathway, as inhibition by LF3 induces cell death.

    • To further probe the nature of Wnt+ and Wnt- adipocytes, the authors perform scRNASeq on cells after 7 days of adipose induction and find 2 distinctive cell populations. The finding of 2 distinct populations is expected, given the a priori separation of cells as a function of GFP expression. It is not clear why scRNASeq was chosen over RNASeq on the population, since the fat content of adipocytes may preclude full characterization of the most differentiated cells.

    With scRNA-seq, it would be more convincing to identify specific subpopulation of cells, as adipocytes are well known to be heterogenous.

    Overall, this experiment is less informative on the mechanisms by which Wnt+ adipocytes display Wnt signaling dependency for viability, and what their functional role might be.

    Yes, these are major questions to be addressed in our future studies.

    • The non-canonical nature of Wnt signaling in Wnt+ adipocytes prompted the authors to explore the role of the insulin/PI3K/AKT/MTOR pathway. They find enhanced basal activity of this pathway in Wnt+ adipocytes. It was not explored whether this enhanced activity persists under insulin stimulation; this is relevant as feedback mechanisms within the signaling pathway may result in lower signaling under stimulated conditions.

    • To test the relevance of insulin signaling in-vivo on non-canonical Wnt signaling in adipocytes the authors use the Akita mouse, which lacks the insulin-2 gene and find a marked decrease in reporter activity, confirming the requirement for insulin signaling for expression of this non-canonical Wnt pathway.

    • To determine the functional role of Wnt+ adipocytes, the authors explore their relationship to mitochondrial respiratory activity and thermogenesis. They perform experiments to monitor mitochondrial membrane potential and oxygen consumption rate and find higher overall O2 consumption, and lower membrane potential in adipocyte populations vicinal to Wnt+ adipocytes. Overall these results are not fully convincing: The traces are highly variable from cell to cell, and rigorous quantification of uncoupled respiration is limited by the small number of cell lines analyzed; only one cell line of Wnt- and two Wnt+ adipocytes are analyzed. In situ differences in membrane potential would be more convincing if performed on homogenous collections of Wnt- and Wnt+ adipocytes to better understand stochastic variance.

    Thanks for the suggestions. Actually, the results of mitochondrial membrane potential assay on mixed adipocyte culture gave us the initial hint of the potential paracrine effect of Wnt+ adipocytes.

    • To determine the role of Wnt+ adipocytes in-vivo thermogenesis, the authors expose mice to cold temperature and monitor the proportion of UCP1+ adipocytes in relation to Wnt signaling. They find a proportion of Wnt+ adipocytes expressing UCP1. Whether this proportion is higher or lower than that of Wnt- adipocytes is not quantified, so it is unclear whether Wnt+ adipocytes preferentially develop beige characteristics. The authors find that UCP1+, Wnt- adipocytes are topologically close to Wnt+ adipocytes, and hypothesize a paracrine signaling role. However, this correlation may be explained by known topological biases in inguinal fat pad beiging, where adipocytes closer to lymph node preferentially induce UCP1. The Wnt+ adipocyte population may coincidentally be present in this region.

    As shown in Figure 5-figure supplement 1E, while all Wnt+ adipocytes were co-stained with UCP1, the percentage of Wnt+ adipocytes did not increase after cold challenge. As shown in Figure 5-figure supplement 1C, the initial beiging response is closely associated with Wnt+ adipocytes, but not topological bias.

    • To functionally determine the role of Wnt+ adipocytes in thermogenesis, the authors ablate the Wnt+ lineage through expression of diphtheria toxin using a Fabp4-Flox-DTA mouse crossed to Tcf/Lef-CreERT2 mice. Less than 50% of these mice displayed impaired thermogenesis upon cold exposure. The authors interpret this finding to signify a partial role for Wnt+ adipocyte beiging in thermogenic regulation. This conclusion is not fully supported, as Fabp4 is expressed in many cells other than adipocytes, and therefore the phenotype of the affected mice is not unambiguously attributable to loss of Wnt+ adipocytes. An additional concern is that diphtheria toxin-induced cell death will lead to tissue inflammation, with potential functional effects on thermogenesis. The degree of cell death and inflammation should be measured and reported.

    While Fabp4 is expressed in some SVFs, the Fabp4-Flox-DTA allele is not activated by Tcf/Lef-CreERT2 allele, as T/L-GFP reporter is not seen in freshly isolated SVFs of iWAT (Figure 2-figure supplement 1A). To avoid potential side effects of DTA-induced cell death on adipose tissues, we compounded the Tcf/Lef-rtTA allele with TRE-Cre and floxed Pparg alleles (PpargF/F) to prevent the differentiation of Wnt+ adipocytes. These new results are included in the revision as supplemental results (Figure 5-figure supplement 2G).

    • The finding that Akita mice lack Wnt+ adipocytes was used to determine whether these mice are susceptible to cold-induced challenges. The authors report a decrease in cold-induced UCP1 expression in these mice. This conclusion, derived from a single immunofluorescence image, is not fully convincing in the absence of additional metrics.

    Additional analyses are included in the revision, as Figure 5-figure supplement 3.

    • To further explore the role of Wnt+ adipocytes in systemic metabolism, the authors conduct implantation studies of Wnt+ adipocytes and measure effects on glucose tolerance. They show a significant difference in glucose excursions in mice harboring fat pads developed from Wnt+ adipocytes. These results are convincing, but the conclusion may be due to enhanced volume of additional functional fat developing from Wnt+ adipocytes.

    In this experiment, unbiased mBaSVF adipocytes were used in parallel as control.

  3. eLife

    Evaluation Summary:

    It is becoming increasingly clear that adipocytes are not homogenous, but rather comprise several distinct subtypes with specific physiological functions. This work presents evidence for the surprising finding of a subpopulation of adipocytes displaying non-canonical Wnt signaling. The possible role of these adipocytes in thermogenesis is more ambiguous, and their physiological function remains unclear.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 and Reviewer #2 agreed to share their name with the authors.)

  4. eLife

    Reviewer #1 (Public Review):

    Liu et al investigated the role of Wnt/β-catenin pathway in the genesis of thermogenic adipocytes. Their study shows that some adipocytes exhibited Wnt/β-catenin signaling ("Wnt+ adipocytes") in intrascapular brown adipose tissue (iBAT), inguinal white adipose tissue (iWAT), epidydimal WAT (eWAT), and bone marrow (BM). There was a different level of the possession of Wnt+ adipocytes between the different depots with iBAT expressing 17%, iWAT expressing 6.9%, and eWAT expressing the least at 1.3%. Expression of these adipocytes was noted on embryonic day 17.5 and was present in a higher percentage in female mice compared to male mice and in younger mice compared to older mice, which aligns with their observation that Wnt+ adipocytes are thermogenic.

    The authors also noted that Wnt+ adipocytes can differentiate from human stromal cells. In regards to the pathway, Wnt/β-catenin adipocytes are distinct from classical brown adipocytes at molecular and genomic levels. It was noted that Tcf7L2 was largely expressed in Wnt+ adipocytes but other Tcf proteins (Tcf 1, Tcf 3, and Lef1) were not. Wnt- cells showed a reversible delay in maturation with LF3, however, no cell death was noted. Wnt/β-catenin adipocytes seem to depend on AKT/mTOR signaling. It was further shown that insulin is a key factor in mTOR signaling and Wnt+ adipocyte differentiation.

    Upon cold exposure, UCP1+/Wnt- beige fat emerges largely surrounding Wnt+ adipocytes, implicating that Wnt+ adipocytes serve as a "beiging initiator" in a paracrine manner. Lastly, mice with implanted Wnt+ adipocytes had a significantly better glucose tolerance which suggests that Wnt+ adipocytes have a beneficial impact on whole-body metabolism. I found no major flaws in the method and data largely supports their conclusion that Wnt+ adipocytes have (at least some) a significant role in thermogenesis/metabolism, which I think is a very impressive and innovative finding.

  5. eLife

    Reviewer #2 (Public Review):

    Liu et al present evidence for the surprising finding of Tcf/Lef-active, "Wnt+" mature adipocytes. They report that Wnt+ adipocytes arise during embryogenesis and regulate cold-induced beiging in surrounding adipocytes. Tcf/Lef transcriptional activity in these cells is Wnt-ligand independent and instead appears to be stimulated by insulin-dependent AKT/mTOR signaling. Using a diphtheria toxin inducible depletion mouse model, the authors show that Wnt+ cells play an important role in glucose homeostasis.

    As the authors have acknowledged, proper assignment of adipocyte nuclei is a notoriously difficult histological challenge. Mesenchymal cells sit directly adjacent to the adipocyte plasma membrane and their nuclei are often incorrectly assigned to the adipocyte both in vivo and in vitro. Pparg nuclear co-staining is helpful, however, Pparg is very highly expressed by endothelial cells and Col15a1+ committed preadipocytes, which are intercalated throughout the adipose. The authors have made an impressive attempt to address this concern by generating a Tcf/Lef-CreER mouse line to fluorescently label Wnt+ adipocytes, however, it is not entirely clear if the images presented support the conclusion that mature adipocytes are being labeled. Given that Wnt+ mature adipocytes are the core conclusion of this manuscript, and because this hypothesis runs counter to a large body of literature concluding that Wnt signaling inhibits adipogenesis, the authors have assumed a very high burden of proof that these are indeed Wnt+ mature adipocytes in vivo.

    To address these concerns, the authors could utilize the specificity of in vivo single-nuclei RNA-Seq. Several data resources have been published (https://singlecell.broadinstitute.org/single_cell/study/SCP1376/a-single-cell-atlas-of-human-and-mouse-white-adipose-tissue), and the authors should re-analyze these data for subpopulations of mature adipocytes that express a transcriptional signature of active Tcf/Lef signaling. It is unfortunate that the authors were unable to successfully perform single-nuclei analysis of the Wnt+ adipocytes as this would significantly enhance this manuscript. The physiologic relevance of the single-cell analysis of immortalized, in-vitro differentiated clonal cell lines is questionable.

  6. eLife

    Reviewer #3 (Public Review):

    It is becoming increasingly clear that adipocytes are not homogenous, but rather comprise several distinct subtypes with specific physiological functions. The mechanisms that underlie the development and distinct roles of each adipocyte subtype are of great interest for understanding the biology of metabolic regulation and its impairments in metabolic disease. In this manuscript, the authors describe a previously unknown population of adipocytes in mice, which are characterized by a special form of beta-catenin signaling. They perform a comprehensive series of experiments in cultured cells, in mouse models of in-vivo lineage tracing, and transplantation experiments to define the origin and function of these adipocytes. They find that the formation of these Wnt+ adipocytes is dependent on insulin signaling, and find possible roles in thermogenic adipose tissue development. Overall, the conclusions of this study are very convincing in their identification of a subpopulation of adipocytes displaying non-canonical Wnt signaling. The proposed role of these adipocytes as regulators of thermogenesis is more ambiguous, and their physiological function remains unclear.

    • The new adipocyte types are identified through expression of a reporter for TCF/Lef signaling. This reporter is classically activated by Wnt/beta-catenin and using both siRNA depletion of beta-catenin as well as an allele lacking its transcriptional activation domain, the authors confirm the reporter expression is dependent on the presence of beta-catenin and TCF7L2, but independent of canonical Wnt signaling.
    • The involvement of TCF7L2 is also probed using a specific inhibitor of the beta-catenin/TCF7L2 interactions, LF3, which inhibited reporter expression. Inhibition of canonical Wnt signaling was without effect.
    • The authors isolate clonal lines of precursor cells that give rise to Wnt+ or Wnt- adipocytes from mouse brown adipose tissue. They find that Wnt+ adipocytes are dependent on the Wnt pathway, as inhibition by LF3 induces cell death.
    • To further probe the nature of Wnt+ and Wnt- adipocytes, the authors perform scRNASeq on cells after 7 days of adipose induction and find 2 distinctive cell populations. The finding of 2 distinct populations is expected, given the a priori separation of cells as a function of GFP expression. It is not clear why scRNASeq was chosen over RNASeq on the population, since the fat content of adipocytes may preclude full characterization of the most differentiated cells. Overall, this experiment is less informative on the mechanisms by which Wnt+ adipocytes display Wnt signaling dependency for viability, and what their functional role might be.
    • The non-canonical nature of Wnt signaling in Wnt+ adipocytes prompted the authors to explore the role of the insulin/PI3K/AKT/MTOR pathway. They find enhanced basal activity of this pathway in Wnt+ adipocytes. It was not explored whether this enhanced activity persists under insulin stimulation; this is relevant as feedback mechanisms within the signaling pathway may result in lower signaling under stimulated conditions.
    • To test the relevance of insulin signaling in-vivo on non-canonical Wnt signaling in adipocytes the authors use the Akita mouse, which lacks the insulin-2 gene and find a marked decrease in reporter activity, confirming the requirement for insulin signaling for expression of this non-canonical Wnt pathway.
    • To determine the functional role of Wnt+ adipocytes, the authors explore their relationship to mitochondrial respiratory activity and thermogenesis. They perform experiments to monitor mitochondrial membrane potential and oxygen consumption rate and find higher overall O2 consumption, and lower membrane potential in adipocyte populations vicinal to Wnt+ adipocytes. Overall these results are not fully convincing: The traces are highly variable from cell to cell, and rigorous quantification of uncoupled respiration is limited by the small number of cell lines analyzed; only one cell line of Wnt- and two Wnt+ adipocytes are analyzed. In situ differences in membrane potential would be more convincing if performed on homogenous collections of Wnt- and Wnt+ adipocytes to better understand stochastic variance.
    • To determine the role of Wnt+ adipocytes in-vivo thermogenesis, the authors expose mice to cold temperature and monitor the proportion of UCP1+ adipocytes in relation to Wnt signaling. They find a proportion of Wnt+ adipocytes expressing UCP1. Whether this proportion is higher or lower than that of Wnt- adipocytes is not quantified, so it is unclear whether Wnt+ adipocytes preferentially develop beige characteristics. The authors find that UCP1+, Wnt- adipocytes are topologically close to Wnt+ adipocytes, and hypothesize a paracrine signaling role. However, this correlation may be explained by known topological biases in inguinal fat pad beiging, where adipocytes closer to lymph node preferentially induce UCP1. The Wnt+ adipocyte population may coincidentally be present in this region.
    • To functionally determine the role of Wnt+ adipocytes in thermogenesis, the authors ablate the Wnt+ lineage through expression of diphtheria toxin using a Fabp4-Flox-DTA mouse crossed to Tcf/Lef-CreERT2 mice. Less than 50% of these mice displayed impaired thermogenesis upon cold exposure. The authors interpret this finding to signify a partial role for Wnt+ adipocyte beiging in thermogenic regulation. This conclusion is not fully supported, as Fabp4 is expressed in many cells other than adipocytes, and therefore the phenotype of the affected mice is not unambiguously attributable to loss of Wnt+ adipocytes. An additional concern is that diphtheria toxin-induced cell death will lead to tissue inflammation, with potential functional effects on thermogenesis. The degree of cell death and inflammation should be measured and reported.
    • The finding that Akita mice lack Wnt+ adipocytes was used to determine whether these mice are susceptible to cold-induced challenges. The authors report a decrease in cold-induced UCP1 expression in these mice. This conclusion, derived from a single immunofluorescence image, is not fully convincing in the absence of additional metrics.
    • To further explore the role of Wnt+ adipocytes in systemic metabolism, the authors conduct implantation studies of Wnt+ adipocytes and measure effects on glucose tolerance. They show a significant difference in glucose excursions in mice harboring fat pads developed from Wnt+ adipocytes. These results are convincing, but the conclusion may be due to enhanced volume of additional functional fat developing from Wnt+ adipocytes.

  7. Version published to 10.1101/2021.01.14.426702v6 on bioRxiv
  8. Version published to 10.1101/2021.01.14.426702v5 on bioRxiv
  9. Version published to 10.1101/2021.01.14.426702v4 on bioRxiv
  10. Version published to 10.1101/2021.01.14.426702v3 on bioRxiv
  11. Version published to 10.1101/2021.01.14.426702v2 on bioRxiv
  12. Version published to 10.1101/2021.01.14.426702v1 on bioRxiv