Galectin-3 promotes the adipogenic differentiation of PDGFRα+ cells and ectopic fat formation in regenerating muscle.

Worldwide prevalence of obesity is associated with the increase of lifestyle-related diseases. The accumulation of intermuscular adipose tissue (IMAT) is considered a major problem whereby obesity leads to sarcopenia and metabolic disorders and thus is a promising target for treating these pathological conditions. However, whereas obesity-associated IMAT is suggested to originate from PDGFRα+ mesenchymal progenitors, the processes underlying this adipogenesis remain largely unexplored. Here, we comprehensively investigated intra- and extracellular changes associated with these processes using single-cell RNA sequencing and mass spectrometry. Our single-cell RNA sequencing analysis identified a small PDGFRα+ cell population in obese mice directed strongly toward adipogenesis. Proteomic analysis showed that the appearance of this cell population is accompanied by an increase in galectin-3 in interstitial environments, which was found to activate adipogenic PPARγ signals in PDGFRα+ cells. Moreover, IMAT formation during muscle regeneration was significantly suppressed in galectin-3 knockout mice. Our findings, together with these multi-omics datasets, could unravel microenvironmental networks during muscle regeneration highlighting possible therapeutic targets against IMAT formation in obesity.

Gene expressions associated with longer lifespan and aging exhibit similarity in mammals.

Although molecular features underlying aging and species maximum lifespan (MLS) have been comprehensively studied by transcriptome analyses, the actual impact of transcriptome on aging and MLS remains elusive. Here, we found that transcriptional signatures that are associated with mammalian MLS exhibited significant similarity to those of aging. Moreover, transcriptional signatures of longer MLS and aging both exhibited significant similarity to that of longer-lived mouse strains, suggesting that gene expression patterns associated with species MLS contribute to extended lifespan even within a species and that aging-related gene expression changes overall represent adaptations that extend lifespan rather than deterioration. Finally, we found evidence of co-evolution of MLS and promoter sequences of MLS-associated genes, highlighting the evolutionary contribution of specific transcription factor binding motifs such as that of E2F1 in shaping MLS-associated gene expression signature. Our results highlight the importance of focusing on adaptive aspects of aging transcriptome and demonstrate that cross-species genomics can be a powerful approach for understanding adaptive aging transcriptome.

Gasdermin D-mediated release of IL-33 from senescent hepatic stellate cells promotes obesity-associated hepatocellular carcinoma.

Long-term senescent cells exhibit a secretome termed the senescence-associated secretory phenotype (SASP). Although the mechanisms of SASP factor induction have been intensively studied, the release mechanism and how SASP factors influence tumorigenesis in the biological context remain unclear. In this study, using a mouse model of obesity-induced hepatocellular carcinoma (HCC), we identified the release mechanism of SASP factors, which include interleukin-1ß (IL-1ß)- and IL-1ß-dependent IL-33, from senescent hepatic stellate cells (HSCs) via gasdermin D (GSDMD) amino-terminal-mediated pore. We found that IL-33 was highly induced in senescent HSCs in an IL-1ß-dependent manner in the tumor microenvironment. The release of both IL-33 and IL-1ß was triggered by lipoteichoic acid (LTA), a cell wall component of gut microbiota that was transferred and accumulated in the liver tissue of high-fat diet-fed mice, and the release of these factors was mediated through cell membrane pores formed by the GSDMD amino terminus, which was cleaved by LTA-induced caspase-11. We demonstrated that IL-33 release from HSCs promoted HCC development via the activation of ST2-positive Treg cells in the liver tumor microenvironment. The accumulation of GSDMD amino terminus was also detected in HSCs from human NASH-associated HCC patients, suggesting that similar mechanism could be involved in a certain type of human HCC. These results uncover a release mechanism for SASP factors from sensitized senescent HSCs in the tumor microenvironment, thereby facilitating obesity-associated HCC progression. Furthermore, our findings highlight the therapeutic potential of inhibitors of GSDMD-mediated pore formation for HCC treatment.