SMRT Regulates Metabolic Homeostasis and Adipose Tissue Macrophage Phenotypes in Tandem.

TitleSMRT Regulates Metabolic Homeostasis and Adipose Tissue Macrophage Phenotypes in Tandem.
Publication TypeJournal Article
Year of Publication2020
AuthorsKahn JH, Goddi A, Sharma A, Heiman J, Carmona A, Li Y, Hoffman A, Schoenfelt K, Ye H, Bobe AM, Becker L, Hollenberg AN, Cohen RN
JournalEndocrinology
Volume161
Issue10
Date Published2020 10 01
ISSN1945-7170
KeywordsAdipocytes, Adipose Tissue, Animals, Cell Differentiation, Energy Metabolism, Homeostasis, Macrophages, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Nuclear Receptor Co-Repressor 2, Obesity, Organ Specificity, Phenotype
Abstract

The Silencing Mediator of Retinoid and Thyroid Hormone Receptors (SMRT) is a nuclear corepressor, regulating the transcriptional activity of many transcription factors critical for metabolic processes. While the importance of the role of SMRT in the adipocyte has been well-established, our comprehensive understanding of its in vivo function in the context of homeostatic maintenance is limited due to contradictory phenotypes yielded by prior generalized knockout mouse models. Multiple such models agree that SMRT deficiency leads to increased adiposity, although the effects of SMRT loss on glucose tolerance and insulin sensitivity have been variable. We therefore generated an adipocyte-specific SMRT knockout (adSMRT-/-) mouse to more clearly define the metabolic contributions of SMRT. In doing so, we found that SMRT deletion in the adipocyte does not cause obesity-even when mice are challenged with a high-fat diet. This suggests that adiposity phenotypes of previously described models were due to effects of SMRT loss beyond the adipocyte. However, an adipocyte-specific SMRT deficiency still led to dramatic effects on systemic glucose tolerance and adipocyte insulin sensitivity, impairing both. This metabolically deleterious outcome was coupled with a surprising immune phenotype, wherein most genes differentially expressed in the adipose tissue of adSMRT-/- mice were upregulated in pro-inflammatory pathways. Flow cytometry and conditioned media experiments demonstrated that secreted factors from knockout adipose tissue strongly informed resident macrophages to develop a pro-inflammatory, MMe (metabolically activated) phenotype. Together, these studies suggest a novel role for SMRT as an integrator of metabolic and inflammatory signals to maintain physiological homeostasis.

DOI10.1210/endocr/bqaa132
Alternate JournalEndocrinology
PubMed ID32770234
PubMed Central IDPMC7478322
Grant ListP30 DK042086 / DK / NIDDK NIH HHS / United States
R01 DK056123 / DK / NIDDK NIH HHS / United States
R01 DK078125 / DK / NIDDK NIH HHS / United States
T32 DK087703 / DK / NIDDK NIH HHS / United States
P30 DK020595 / DK / NIDDK NIH HHS / United States