Project description:Adipose tissue beiging refers to a process through which beige adipocytes emerge in classical white adipose tissue depots. Beige adipocytes dissipate chemical energy and secrete adipokines like classical brown adipocytes to improve systemic metabolism, which offers benefits for people with obesity and metabolic diseases. Cold exposure and β3-adrenergic receptor (AR) agonist treatment are two commonly used stimuli for increasing beige adipocytes in mice, but their underlying biological processes are different. Transcriptional analysis of inguinal white adipose tissue (iWAT) has revealed that changes in extracellular matrix (ECM) pathway genes are specific to cold exposure. Hyaluronic acid (HA), a non-sulfated linear polysaccharide produced by nearly all cells, is one of the most common components of ECM. We found that cold exposure significantly increases iWAT HA levels while β3-AR agonist CL316,243 fails to do so. Increasing HA level in iWAT by Has2 overexpression significantly increases cold-induced adipose tissue beiging; in contrast, decreasing HA by Spam1 overexpression, which encodes a hyaluronidase that digests HA, significantly decreases cold-induced iWAT beiging. All of these data implicate a role of HA in promoting adipose tissue beiging that is unique to cold exposure. Given the failure of β3-AR agonists in clinical trials for obesity and metabolic diseases, increasing HA could serve as a new approach to recruiting more beige adipocytes to combat metabolic diseases.
Project description:The induction of beige adipocytes in white adipose tissue (WAT), also known as WAT beiging, improves glucose and lipid metabolism. However, the regulation of WAT beiging at the posttranscriptional level remains elusive. Here, we report that METTL3, the methyltransferase of N6-methyladenosine (m6A) mRNA modification, is induced during WAT beiging in mice. Adipose-specific depletion of Mettl3 gene undermines WAT beiging. Transcriptomic analysis of m6A modifications and mRNA expression level reveals global reduction of m6A-modified mRNAs in Mettl3-depleted beige adipose tissue. In particular, METTL3-catalyzed m6A installation on Krüppel-like factor 9 (Klf9) mRNA prevents its degradation. We further demonstrate that the m6A reader protein IGF2BP3 mediates the stabilization of m6A-modified Klf9 mRNA. Overexpressioin of KLF9 protein reverses the impaired WAT beiging elicited by Mettl3 deletion. These findings uncover a novel epitranscriptional mechanism in WAT beiging and identify METTL3-KLF9 axis as a potential therapeutic target for obesity-associated disorders.
Project description:Beige adipocytes are induced by cold temperatures or β3-adrenergic receptor (Adrb3) agonists. They create heat through glucose and fatty acid (FA) oxidation, conferring metabolic benefits. The distinct and shared mechanisms by which these treatments induce beiging are unknown. Here, we performed single-nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq) on adipose tissue from mice exposed to cold or an Adrb3 agonist to identify cellular and chromatin accessibility dynamics during beiging. Both stimuli induce chromatin remodeling that influence vascularization and inflammation in adipose. Beige adipocytes from cold-exposed mice have increased accessibility at genes regulating glycolytic processes, whereas Adrb3 activation increases cAMP responses. While both thermogenic stimuli increase accessibility at genes regulating thermogenesis, lipogenesis, and beige adipocyte development, the kinetics and magnitudes of the changes are distinct for the stimuli. Accessibility changes at lipogenic genes are linked to functional changes in lipid composition of adipose. Both stimuli tend to decrease the proportion of palmitic acids, a saturated FA in adipose. However, Adrb3 activation increases the proportion of monounsaturated FAs, whereas cold increases the proportion of polyunsaturated FAs. These findings reveal common and distinct mechanisms of cold and Adrb3 induced beige adipocyte biogenesis, and identify unique functional consequences of manipulating these pathways in vivo.
Project description:Atlas of UCP1-KO Beiging inguinal adipose tissue and tissue in which beta adrenergic signaling is blocked provides further insight into UCP1-independent mechanisms of beiging.
Project description:Comparison of gene expression pattern of subcutaneous adipose tissue from mice housed in cold (6-degree Celsius) or in thermal neutrality (30-degree celsius).Verify canonical white adipose tissue beiging pathways and genes that are regulated by cold-exposure as well as identify gap junction genes that are regulated by cold in white adipoes tissue. Total RNA obtained from mouse subcutaneous tissue from mice house at two different temperature; RNA extracted from 3-4 mice was pooled into one sample.
Project description:Comparison of gene expression pattern of subcutaneous adipose tissue from mice housed in cold (6-degree Celsius) or in thermal neutrality (30-degree celsius).Verify canonical white adipose tissue beiging pathways and genes that are regulated by cold-exposure as well as identify gap junction genes that are regulated by cold in white adipoes tissue.
Project description:Although inflammation plays critical roles in the development of atherosclerosis, its regulatory mechanisms remain incompletely understood. Perivascular adipose tissue (PVAT) has been reported to undergo inflammatory changes in response to vascular injury. Here, we showed that vascular injury induced the beiging (brown adipose tissue-like phenotype change) of PVAT, which fine-tunes inflammatory response and thus vascular remodeling as a protective mechanism. In a mouse model of endovascular injury, macrophages accumulated in PVAT, causing beiging phenotype change. Inhibition of PVAT beiging by genetically silencing PRDM16, a key regulator to beiging, exacerbated inflammation and vascular remodeling following injury. Conversely, activation of PVAT beiging attenuated inflammation and pathological vascular remodeling. Single-cell RNA sequencing revealed that beige adipocytes abundantly expressed neuregulin 4 (Nrg4) which critically regulated alternative macrophage activation. Importantly, significant beiging was observed in the diseased aortic PVAT in patients with acute aortic dissection. Taken together, vascular injury induced the beiging of adjacent PVAT with macrophage accumulation, where NRG4 secreted from the beige PVAT facilitated alternative activation of macrophages, leading to the resolution of vascular inflammation. Our study demonstrated the pivotal roles of PVAT in vascular inflammation and remodeling and will open a new avenue for treating atherosclerosis.
Project description:Although various stimuli and mediators have been identified to promote thermogenic beige fat development, less is known about the negative regulator of cold-induced beiging. We here show that lack of chemerin that is highly expressed in white adipose tissue or its receptor CMKLR1 in adipocytes enhances cold-induced beiging and thermogenesis. Our results reveal a previously unrecognized beige-inhibitory role of chemerin-CMKLR1 axis, and suggests CMKLR1 as a therapeutic target for obesity-related metabolic disorders.
Project description:Obesity, one of the most serious public health issues, is caused by energy imbalance of energy intake and expenditure. N(6)-methyladenosine (m6A) RNA modification has been recently identified as a key regulator of obesity, while the detailed mechanism is elusive. Here, we found that YTH RNA binding protein 1 (YTHDF1), an m6A reader, acts as an essential regulator of white adipose tissue metabolism. The expression of YTHDF1 decreased in adipose tissue of mice fed a high-fat diet. Adipocyte-specific Ythdf1 deficiency exacerbated obesity-induced metabolic defects and inhibited beiging of inguinal white adipose tissue (iWAT) in mice. By contrast, mice with WAT-specific Ythdf1 overexpression were resistant to obesity and showed promotion of beiging. Mechanistically, YTHDF1 regulated the translation of diverse m6A-modified mRNAs. In particular, YTHDF1 facilitated the translation of bone morphogenetic protein 8b (Bmp8b) in an m6A-dependent manner to induce the beiging process. Together, these findings suggested that YTHDF1 may be an attractive therapeutic target for the management of obesity-associated diseases.
Project description:Cold triggers VEGF dependent but hypoxia independent angiogenesis in adipose tissues and anti-VEGF agents modulate adipose metabolism The molecular mechanisms of angiogenesis in relation to adipose tissue metabolism remain poorly understood. Here we show that exposure of mice to cold led to conversion of white adipose tissue (WAT) to brown-like adipose tissue, accompanying the switch of an active angiogenic phenotype. Gene expression profile analysis showed VEGF was upregulated via most likely hypoxia-independent PGC-1 transcriptional activation. Intriguingly, VEGFR2 blockage abolished the cold-induced angiogenesis, significantly impaired nonshivering thermogenesis capacity, and markedly reduced adipose metabolism. Unexpectedly, VEGFR1 blockage resulted in opposite effects by increasing adipose vascularity and metabolism. These findings demonstrate that VEGFR2 and VEGFR1 mediate polarized activities in modulating adipose angiogenesis and metabolism. Taken together, our findings have conceptual implications in applying angiogenesis modulators for the treatment of obesity and metabolic disorders. Keywords: Time course