A Negative Feedback Loop Between TET2 and Leptin in Adipocyte Regulates Body Weight
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ABSTRACT: Ten-eleven translocation (TET) 2 is an enzyme that catalyzes DNA demethylation to regulate gene expression by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine, functioning as an essential epigenetic regulator in various biological processes. However, the regulation and function of TET2 in adipocytes during obesity are poorly understood. In this study, we demonstrate that leptin, a key adipokine in mammalian energy homeostasis regulation, suppresses adipocyte TET2 levels via JAK2-STAT3 signaling. Adipocyte Tet2 deficiency protects against high-fat diet-induced weight gain by reducing leptin levels and further improving leptin sensitivity. By interacting with C/EBPα, adipocyte TET2 increases the hydroxymethylcytosine levels of the leptin gene promoter, thereby promoting leptin gene expression. A decrease in adipose TET2 is associated with obesity-related hyperleptinemia in humans. Inhibition of TET2 suppresses the production of leptin in mature human adipocytes.Our findings support the existence of a negative feedback loop between TET2 and leptin in adipocytes and reveal a novel compensatory mechanism for the body to counteract the metabolic dysfunction caused by obesity.
Project description:Dysregulation in adipokine biosynthesis and function contributes to obesity-induced metabolic diseases. However, the identities and functions of many of the obesity-induced secretory molecules remain unknown. In this study, microarray was used to identify genes that are differentially expressed during adipocyte differentiation, further screening based on microarray result identified Leucine-rich alpha-2-glycoprotein 1 (LRG1) as an obesity-associated adipokine. Expression data of pre-adipocytes and mature adipocytes
Project description:Obesity is characterized by excess energy storage which results in dysfunctional white adipose tissue (WAT) and in turn leads to metabolic diseases. Lifestyle changes especially calorie restriction (CR) reduces the risk for age and obesity-associated complications. The impact of CR on obesity has mainly been examined with human intervention studies, which indicated alterations in circulating adipokines. However, a detailed understanding of CR-induced adipocyte secretome changes remains elusive. Therefore, we investigated the effect of CR on the secretion profile of mature human adipocytes by using proteomics technology with bioinformatic analysis. We demonstrated CR-mediated adipocyte triglyceride reduction, which resulted in a positive effect on adipokine secretion indicating an improved inflammatory phenotype and alleviation of obesity-associated metabolic dysfunction including insulin resistance and glucose intolerance. Furthermore, 6 novel adipocyte-secreted proteins were identified which were regulated by CR. Since resveratrol (RSV) mimics CR we compared results from this study with data from our previous RSV study on the adipocyte secretome. We observed that both treatment strategies lead to a less inflammatory phenotype and an altered adipokine profile indicating improvement of metabolic complications even though the CR and RSV adipocyte secretomes differed from each other.
Project description:Background/aims: Serum concentrations of the hepatokine fibroblast growth factor (FGF) 21 are elevated in obesity, type‐2 diabetes, and the metabolic syndrome. We asked whether FGF21 levels differ between subjects with metabolically healthy vs. unhealthy obesity (MHO vs. MUHO) opening the possibility that FGF21 is a cross‐talker between liver and adipose tissue in MUHO. Furthermore, we studied the effects of chronic FGF21 treatment on adipocyte differentiation, lipid storage, and adipokine secretion. Methods/study design: In 20 morbidly obese donors of abdominal subcutaneous fat biopsies discordant for their whole‐body insulin sensitivity (hereby classified as MHO or MUHO subjects), serum FGF21 was quantified. The impact of chronic FGF21 treatment on differentiation, lipid accumulation, and adipokine release was assessed in isolated preadipocytes differentiated in vitro. Results: Serum FGF21 concentrations were more than two‐fold higher in MUHO as compared to 37 MHO subjects (457 ±378 vs. 211 ±123 pg/mL; p<0.05). FGF21 treatment of human preadipocytes for the entire differentiation period was modestly lipogenic (+15%; p<0.05), reduced the expression of key adipogenic transcription factors (PPARG and CEBPA, ‐15% and ‐40%, respectively; p<0.01 both), reduced adiponectin expression (‐20%; p<0.05), markedly reduced adiponectin release (‐60%; p<0.01), and substantially increased leptin (+60%; p<0.01) and interleukin‐6 (+50%; p<0.001) release. Interpretation/conclusions: The hepatokine FGF21 exerts weak lipogenic and anti‐adipogenic actions and marked adiponectin‐suppressive and leptin and interleukin‐6 release‐promoting effects in human differentiating preadipocytes. Together with the higher serum concentrations in MUHO subjects, our findings reveal FGF21 as a circulating factor promoting the development of metabolically unhealthy adipocytes. We analysed in vitro differentiated preadipocytes from 20 human donors treated with FGF21 or control cultures.
Project description:Adipocytes are critical regulators of metabolism and energy balance. While white adipocyte dysfunction is a hallmark of obesity-associated disorders, the activation of thermogenic brown and beige adipocytes is linked to improved cardiometabolic health. As adipocytes dynamically adapt to environmental cues by functionally switching between white and thermogenic phenotypes, a molecular understanding of this adipocyte plasticity could help improving energy balance and weight loss. Here, we show that the long non-coding RNA (lncRNA) Apoptosis associated transcript in bladder cancer (AATBC) is a human-specific regulator of adipocyte plasticity. Searching for new human lncRNAs implicated in adipocyte biology we compared transcriptional profiles of human adipose tissues and cultured adipocytes and discovered that AATBC was enriched in thermogenic conditions. Using primary human adipocytes and immortalized human adipocytes we found that gain-of-function of AATBC enhanced the thermogenic phenotype whereas loss-of-function diminished this effect. The AATBC-mediated increase in mitochondrial respiration was linked to a more fragmented mitochondrial network and vice versa. While we found that AATBC is predominantly located in the nucleus, its effect on global transcription was only marginal. As AATBC is specific to humans, we expressed AATBC in adipose tissue of mice to study its systemic impact, which led to lower plasma leptin levels. Interestingly, this association was also present in human subjects, as AATBC in adipose tissue was inversely correlated with plasma leptin levels, body mass index and other measures of metabolic health. In conclusion, AATBC is a novel obesity-linked regulator of adipocyte plasticity and mitochondrial function in humans.
Project description:Adipocytes are critical regulators of metabolism and energy balance. While white adipocyte dysfunction is a hallmark of obesity-associated disorders, the activation of thermogenic brown and beige adipocytes is linked to improved cardiometabolic health. As adipocytes dynamically adapt to environmental cues by functionally switching between white and thermogenic phenotypes, a molecular understanding of this adipocyte plasticity could help improving energy balance and weight loss. Here, we show that the long non-coding RNA (lncRNA) Apoptosis associated transcript in bladder cancer (AATBC) is a human-specific regulator of adipocyte plasticity. Searching for new human lncRNAs implicated in adipocyte biology we compared transcriptional profiles of human adipose tissues and cultured adipocytes and discovered that AATBC was enriched in thermogenic conditions. Using primary human adipocytes and immortalized human adipocytes we found that gain-of-function of AATBC enhanced the thermogenic phenotype whereas loss-of-function diminished this effect. The AATBC-mediated increase in mitochondrial respiration was linked to a more fragmented mitochondrial network and vice versa. While we found that AATBC is predominantly located in the nucleus, its effect on global transcription was only marginal. As AATBC is specific to humans, we expressed AATBC in adipose tissue of mice to study its systemic impact, which led to lower plasma leptin levels. Interestingly, this association was also present in human subjects, as AATBC in adipose tissue was inversely correlated with plasma leptin levels, body mass index and other measures of metabolic health. In conclusion, AATBC is a novel obesity-linked regulator of adipocyte plasticity and mitochondrial function in humans.
Project description:While adipocytes are critical pillars of energy metabolism, their dysfunction is linked to adipose tissue (AT) inflammation, insulin resistance, and ectopic lipotoxicity in cardiometabolic diseases. However, he mechanisms causing adipocyte inflammation and insulin resistance remain unclear. Here, we show that excess cholesterol induces adipocyte dysfunction, which is suppressed by the transcription factor Nfe2l1 (nuclear factor erythroid derived-2, like-1). Nfe2l1 is required to sustain proteasome function in adipocytes and proteotoxic stress induces adipocyte inflammation via the activation of Atf3. In humans, the Nfe2l1-proteasome pathway is inversely correlated to body mass index (BMI) in an adipose-depot specific manner. In mice, loss of adipocyte Nfe2l1 caused AT inflammation with a pronounced infiltration of macrophages and T cells. Mice lacking adipocyte Nfe2l1 displayed severe adipocyte dysfunction during diet-induced obesity (DIO), characterized by lower adipokine levels, steatosis, glucose intolerance and insulin resistance. Nfe2l1ΔAT mice on an Apoe-deficient (Apoe-/-) background fed a cholesterol-rich Western Diet (WD), developed a lipoatrophy-like syndrome, dyslipidemia, and enhanced atherosclerosis. Our results reveal an important role for proteasome-mediated proteostasis in adipocytes and indicate that Nfe2l1 is linked to metabolic health in humans and preclinical mouse models. Promoting proteostasis in adipocytes may thus alleviate inflammation in obesity, potentially averting adverse cardiometabolic outcomes.
Project description:Adipose tissues serve as an energy reservoir and endocrine organ, yet the mechanisms that coordinate these functions remain elusive. Here, we show that transcriptional coregulators YAP and TAZ mediate the crosstalk between fat mass and leptin levels to maintain metabolic homeostasis. Activating YAP/TAZ in adipocytes by Lats1 and Lats2 deletion results in a profound reduction in fat mass by converting mature adipocytes into delipidated progenitor-like cells. Surprisingly, Lats1/2 knockout mice did not exhibit lipodystrophy-related metabolic dysfunction, attributed to a paradoxical increase in circulating leptin levels. Mechanistically, YAP/TAZ-TEAD signaling upregulates leptin expression by directly binding an upstream enhancer site of the leptin gene. We further show that YAP/TAZ activity is linked to, and functionally required for, leptin regulation during fasting and refeeding. These results suggest that adipocyte Hippo-YAP/TAZ plays an essential role in coordinating adipose storage capacity and systemic energy balance through dual control of adipocyte plasticity and leptin gene transcription.
Project description:While dysregulation of adipocyte endocrine function plays a central role in obesity and its complications, the vast majority of adipokines remain uncharacterized. We employed bio-orthogonal non-canonical amino acid tagging (BONCAT) and mass spectrometry to comprehensively characterize the secretome of murine visceral and subcutaneous white and interscapular brown adipocytes. Over 600 proteins were identified, the majority of which showed cell type-specific enrichment. We here describe a metabolic role for leucine-rich α-2 glycoprotein 1 (LRG1) as an obesity-regulated adipokine secreted by mature adipocytes. LRG1 overexpression significantly improved glucose homeostasis in diet-induced and genetically obese mice. This was associated with markedly reduced white adipose tissue macrophage accumulation and systemic inflammation. Mechanistically, we found LRG1 binds cytochrome c in circulation to dampen its pro-inflammatory effect. These data support a new role for LRG1 as an insulin sensitizer with therapeutic potential given its immunomodulatory function at the nexus of obesity, inflammation, and associated pathology.
Project description:Background/aims: Serum concentrations of the hepatokine fibroblast growth factor (FGF) 21 are elevated in obesity, type‐2 diabetes, and the metabolic syndrome. We asked whether FGF21 levels differ between subjects with metabolically healthy vs. unhealthy obesity (MHO vs. MUHO) opening the possibility that FGF21 is a cross‐talker between liver and adipose tissue in MUHO. Furthermore, we studied the effects of chronic FGF21 treatment on adipocyte differentiation, lipid storage, and adipokine secretion. Methods/study design: In 20 morbidly obese donors of abdominal subcutaneous fat biopsies discordant for their whole‐body insulin sensitivity (hereby classified as MHO or MUHO subjects), serum FGF21 was quantified. The impact of chronic FGF21 treatment on differentiation, lipid accumulation, and adipokine release was assessed in isolated preadipocytes differentiated in vitro. Results: Serum FGF21 concentrations were more than two‐fold higher in MUHO as compared to 37 MHO subjects (457 ±378 vs. 211 ±123 pg/mL; p<0.05). FGF21 treatment of human preadipocytes for the entire differentiation period was modestly lipogenic (+15%; p<0.05), reduced the expression of key adipogenic transcription factors (PPARG and CEBPA, ‐15% and ‐40%, respectively; p<0.01 both), reduced adiponectin expression (‐20%; p<0.05), markedly reduced adiponectin release (‐60%; p<0.01), and substantially increased leptin (+60%; p<0.01) and interleukin‐6 (+50%; p<0.001) release. Interpretation/conclusions: The hepatokine FGF21 exerts weak lipogenic and anti‐adipogenic actions and marked adiponectin‐suppressive and leptin and interleukin‐6 release‐promoting effects in human differentiating preadipocytes. Together with the higher serum concentrations in MUHO subjects, our findings reveal FGF21 as a circulating factor promoting the development of metabolically unhealthy adipocytes.
Project description:Cytokines of the IL-1 family are important modulators of obesity-induced inflammation and the development of systemic insulin resistance. Here, we report that IL-37, a newly-described antiinflammatory member of the IL-1 family, affects obesity-induced inflammation and insulin resistance. IL-37 transgenic mice (IL-37tg) did not develop an obese phenotype in response to a high-fat diet (HFD). Unlike WT mice, IL-37tg mice exhibited reduced numbers of adipose tissue macrophages and preserved glucose tolerance and insulin sensitivity after 16 weeks of HFD. A short-term HFD intervention revealed that the IL-37-mediated improvement in glucose tolerance is independent of bodyweight. IL-37tg mice manifested a beneficial metabolic profile with higher circulating levels of the anti-inflammatory adipokine adiponectin. In vitro treatment of differentiating adipocytes with recombinant IL-37 reduced adipogenesis. The beneficial effects of recombinant IL-37 involved activation of AMPK signaling. In humans, steady-state IL-37 adipose tissue mRNA levels were positively correlated with insulin sensitivity, lower adipose tissue levels of leptin and a lower inflammatory status of the adipose tissue. These findings reveal IL-37 as an important anti-inflammatory modulator during obesity-induced inflammation and insulin resistance in both mice and humans and suggest that IL-37 is a potential target for the treatment of obesity-induced insulin resistance and type 2 diabetes. Gene arrays were performed on epidydimal white adipose tissue samples from wild type and human IL37-overexpressing transgenic mice fed a high fat diet for 16 weeks.