bims-stacyt 2022-07-10 papers

Front Oncol. 2022 ;12 841758

Cytokine-Mediated STAT3 Transcription Supports ATGL/CGI-58-Dependent Adipocyte Lipolysis in Cancer Cachexia.

Aakash Y Gandhi, Jinhai Yu, Arun Gupta, Tong Guo, Puneeth Iyengar, Rodney E Infante.

Adipose tissue inflammation is observed in multiple metabolically-altered states including cancer-associated cachexia and obesity. Although cachexia is a syndrome of adipose loss and obesity is a disease of adipose excess, both pathologies demonstrate increases in circulating levels of IL-6 family cytokines, β-adrenergic signaling, and adipocyte lipolysis. While β-adrenergic-stimulated adipocyte lipolysis is well described, there is limited mechanistic insight into how cancer cachexia-associated inflammatory cytokines contribute to adipocyte lipolysis under pathologic conditions. Here, we set out to compare adipocyte lipolysis signaling by cancer cachexia-associated IL-6 family cytokines (IL-6 and LIF) to that of the β-adrenergic agonist isoproterenol. Unlike isoproterenol, the IL-6 family of cytokines required JAK/STAT3-dependent transcriptional changes to induce adipocyte lipolysis. Furthermore, cachexia-associated cytokines that used STAT3 to induce lipolysis were primarily dependent on the lipase ATGL and its cofactor CGI-58 rather than lipases HSL and MAGL. Finally, administration of JAK but not β-adrenergic inhibitors suppressed adipose STAT3 phosphorylation and associated adipose wasting in a murine model of cancer cachexia characterized by increased systemic IL-6 family cytokine levels. Combined, our results demonstrate how the IL-6 family of cytokines diverge from β-adrenergic signals by employing JAK/STAT3-driven transcriptional changes to promote adipocyte ATGL/CGI-58-dependent lipolysis contributing to adipose wasting in cancer cachexia.

Keywords: adipocyte lipolysis; adipose triglyceride lipase (ATGL); adipose wasting (malnutrition); cancer cachexia; interleukin-6 (IL-6); leukemia inhibitor factor; signal transducer and activator of transcription 3 (STAT3); β-adrenergic signaling

DOI: https://doi.org/10.3389/fonc.2022.841758

Int J Mol Sci. 2022 Jun 25. pii: 7073. [Epub ahead of print]23(13):

Glucose Stimulates Glial Cell Line-Derived Neurotrophic Factor Gene Expression in Microglia through a GLUT5-Independent Mechanism.

Muhammad S Aldhshan, Gursagar Jhanji, Nicole J Poritsanos, Tooru M Mizuno.

Feeding-regulating neurotrophic factors are expressed in both neurons and glial cells. However, nutritional regulation of anorexigenic glial cell line-derived neurotrophic factor (GDNF) and orexigenic mesencephalic astrocyte-derived neurotrophic factor (MANF) expression in specific cell types remains poorly understood. Hypothalamic glucose sensing plays a critical role in the regulation of food intake. It has been theorized that local glucose concentration modulates microglial activity partially via glucose transporter 5 (GLUT5). We hypothesized that an increased local glucose concentration stimulates GDNF expression while inhibiting MANF expression in the hypothalamus and microglia via GLUT5. The present study investigated the effect of glucose on Gdnf and Manf mRNA expression in the mouse hypothalamus and murine microglial cell line SIM-A9. Intracerebroventricular glucose treatment significantly increased Gdnf mRNA levels in the hypothalamus without altering Manf mRNA levels. Exposure to high glucose caused a significant increase in Gdnf mRNA expression and a time-dependent change in Manf mRNA expression in SIM-A9 cells. GLUT5 inhibitor treatment did not block glucose-induced Gdnf mRNA expression in these cells. These findings suggest that microglia are responsive to changes in the local glucose concentration and increased local glucose availability stimulates the expression of microglial GNDF through a GLUT5-independent mechanism, contributing to glucose-induced feeding suppression.

Keywords: feeding; glucose; hypothalamus; microglia; neurotrophic factor

DOI: https://doi.org/10.3390/ijms23137073

Cell Mol Life Sci. 2022 Jul 07. 79(8): 403

Transmissible ER stress between macrophages and tumor cells configures tumor microenvironment.

Wei Wei, Yazhuo Zhang, Qiaoling Song, Qianyue Zhang, Xiaonan Zhang, Xinning Liu, Zhihua Wu, Xiaohan Xu, Yuting Xu, Yu Yan, Chenyang Zhao, Jinbo Yang.

Endoplasmic reticulum (ER) stress initiates the unfolded protein response (UPR) and is decisive for tumor cell growth and tumor microenvironment (TME) maintenance. Tumor cells persistently undergo ER stress and could transmit it to the neighboring macrophages and surroundings. Tumor infiltrating macrophages can also adapt to the microenvironment variations to fulfill their highly energy-demanding and biological functions via ER stress. However, whether the different macrophage populations differentially sense ER stress and transmit ER stress to surrounding tumor cells has not yet been elucidated. Here, we aimed to investigate the role of transmissible ER stress, a novel regulator of intercellular communication in the TME. Murine bone marrow-derived macrophage (BMDM) can be polarized toward distinct functional endpoints termed classical (M1) and alternative (M2) activation, and their polarization status has been shown to be tightly correlated with their functional significance. We showed that tumor cells could receive the transmissible ER stress from two differentially polarized macrophage populations with different extent of ER stress activation. The proinflammatory M1-like macrophages respond to ER stress with less extent, however they could transmit more ER stress to tumor cells. Moreover, by analyzing the secreted components of two ER-stressed macrophage populations, we identified certain damage-associated molecular patterns (DAMPs), including S100A8 and S100A9, which are dominantly secreted by M1-like macrophages could lead to significant recipient tumor cells death in synergy with transferred ER stress.

Keywords: Intratumoral cell communications; MAPK; Macrophage polarization; Secreted molecules; TME editing; Tumor killing effects

DOI: https://doi.org/10.1007/s00018-022-04413-z

Nature. 2022 Jul 05.

Apoptotic brown adipocytes enhance energy expenditure via extracellular inosine.

Brown adipose tissue (BAT) dissipates energy1,2 and promotes cardio-metabolic health3. Loss of BAT during obesity and aging is a principal hurdle for BAT-centered obesity therapies, but not much is known about BAT apoptosis. Here, untargeted metabolomics demonstrated that apoptotic brown adipocytes release a specific pattern of metabolites with purine metabolites being highly enriched. Interestingly, this apoptotic secretome enhances expression of the thermogenic program in healthy adipocytes. This effect is mediated by the purine inosine which stimulates energy expenditure (EE) in brown adipocytes via the cAMP/protein kinase A signaling pathway. Treatment of mice with inosine increased BAT-dependent EE and induced "browning" of white adipose tissue. Mechanistically, the equilibrative nucleoside transporter 1 (ENT1, SLC29A1) regulates inosine levels in BAT: ENT1-deficiency increases extracellular inosine levels and consequently enhances thermogenic adipocyte differentiation. In mice, pharmacological inhibition of ENT1 as well as global and adipose-specific ablation enhanced BAT activity and counteracted diet-induced obesity, respectively. In human brown adipocytes, knockdown or blockade of ENT1 increased extracellular inosine, which enhanced thermogenic capacity. Conversely, high ENT1 levels correlated with lower expression of the thermogenic marker UCP1 in human adipose tissues. Finally, the Ile216Thr loss of function mutation in human ENT1 was associated with significantly lower BMI and 59% lower odds of obesity for individuals carrying the Thr variant. Our data identify inosine as a metabolite released during apoptosis with "replace me" signaling function that regulates thermogenic fat and counteracts obesity.

DOI: https://doi.org/10.1038/s41586-022-05041-0