Dataset Information

Epac2a-null mice exhibit obesity-prone nature more susceptible to leptin resistance.

ABSTRACT:

Background

The exchange protein directly activated by cAMP (Epac), which is primarily involved in cAMP signaling, has been known to be essential for controlling body energy metabolism. Epac has two isoforms: Epac1 and Epac2. The function of Epac1 on obesity was unveiled using Epac1 knockout (KO) mice. However, the role of Epac2 in obesity remains unclear.

Methods

To evaluate the role of Epac2 in obesity, we used Epac2a KO mice, which is dominantly expressed in neurons and endocrine tissues. Physiological factors related to obesity were analyzed: body weight, fat mass, food intake, plasma leptin and adiponectin levels, energy expenditure, glucose tolerance, and insulin and leptin resistance. To determine the mechanism of Epac2a, mice received exogenous leptin and then hypothalamic leptin signaling was analyzed.

Results

Epac2a KO mice appeared to have normal glucose tolerance and insulin sensitivity until 12 weeks of age, but an early onset increase of plasma leptin levels and decrease of plasma adiponectin levels compared with wild-type mice. Acute leptin injection revealed impaired hypothalamic leptin signaling in KO mice. Consistently, KO mice fed a high-fat diet (HFD) were significantly obese, presenting greater food intake and lower energy expenditure. HFD-fed KO mice were also characterized by greater impairment of hypothalamic leptin signaling and by weaker leptin-induced decrease in food consumption compared with HFD-fed wild-type mice. In wild-type mice, acute exogenous leptin injection or chronic HFD feeding tended to induce hypothalamic Epac2a expression.

Conclusions

Considering that HFD is an inducer of hypothalamic leptin resistance and that Epac2a functions in pancreatic beta cells during demands of greater work load, hypothalamic Epac2a may have a role in facilitating leptin signaling, at least in response to higher metabolic demands. Thus, our data indicate that Epac2a is critical for preventing obesity and thus Epac2a activators may be used to manage obesity and obesity-mediated metabolic disorders.

SUBMITTER: Hwang M

PROVIDER: S-EPMC5309344 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Epac2a-null mice exhibit obesity-prone nature more susceptible to leptin resistance.

Hwang M M Go Y Y Park J-H JH Shin S-K SK Song S E SE Oh B-C BC Im S-S SS Hwang I I Jeon Y H YH Lee I-K IK Seino S S Song D-K DK

International journal of obesity (2005) 20161121 2

<h4>Background</h4>The exchange protein directly activated by cAMP (Epac), which is primarily involved in cAMP signaling, has been known to be essential for controlling body energy metabolism. Epac has two isoforms: Epac1 and Epac2. The function of Epac1 on obesity was unveiled using Epac1 knockout (KO) mice. However, the role of Epac2 in obesity remains unclear.<h4>Methods</h4>To evaluate the role of Epac2 in obesity, we used Epac2a KO mice, which is dominantly expressed in neurons and endocrin ...[more]

PMID: 27867203

Similar Datasets

Project description:ObjectiveAging and chronic glucocorticoid excess share a number of critical features, including the development of central obesity, insulin resistance and osteoporosis. Previous studies have shown that skeletal glucocorticoid signalling increases with aging and that osteoblasts mediate the detrimental skeletal and metabolic effects of chronic glucocorticoid excess. Here, we investigated whether endogenous glucocorticoid action in the skeleton contributes to metabolic dysfunction during normal aging.MethodsMice lacking glucocorticoid signalling in osteoblasts and osteocytes (HSD2OB/OCY-tg mice) and their wild-type littermates were studied until 3, 6, 12 and 18 months of age. Body composition, adipose tissue morphology, skeletal gene expression and glucose/insulin tolerance were assessed at each timepoint. Leptin sensitivity was assessed by arcuate nucleus STAT3 phosphorylation and inhibition of feeding following leptin administration. Tissue-specific glucose uptake and adipose tissue oxygen consumption rate were also measured.ResultsAs they aged, wild-type mice became obese and insulin-resistant. In contrast, HSD2OB/OCY-tg mice remained lean and insulin-sensitive during aging. Obesity in wild-type mice was due to leptin resistance, evidenced by an impaired ability of exogenous leptin to suppress food intake and phosphorylate hypothalamic STAT3, from 6 months of age onwards. In contrast, HSD2OB/OCY-tg mice remained leptin-sensitive throughout the study. Compared to HSD2OB/OCY-tg mice, leptin-resistant wild-type mice displayed attenuated sympathetic outflow, with reduced tyrosine hydroxylase expression in both the hypothalamus and thermogenic adipose tissues. Adipose tissue oxygen consumption rate declined progressively in aging wild-type mice but was maintained in HSD2OB/OCY-tg mice. At 18 months of age, adipose tissue glucose uptake was increased 3.7-fold in HSD2OB/OCY-tg mice, compared to wild-type mice.ConclusionsSkeletal glucocorticoid signalling is critical for the development of leptin resistance, obesity and insulin resistance during aging. These findings underscore the skeleton's importance in the regulation of body weight and implicate osteoblastic/osteocytic glucocorticoid signalling in the aetiology of aging-related obesity and metabolic disease.

Project description:Introduction: The ascending prevalence of obesity in recent decades is commonly associated with soaring rates of morbidity and mortality resulting in increased health care costs and decreased quality of life. A systemic state of stress characterized by low grade inflammation and pathologic formation of reactive oxygen species (ROS) usually manifest in obesity. The transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2) is the master regulator of the redox homeostasis and plays a critical role in the resolution of inflammation. Our results indicate that the natural isothiocyanate and potent NRF2 activator sulforaphane reverses the diet-induced obesity in rodents and implicate involvement of leptin receptor singling in this effect. Purpose: Here, we investigate molecular pathways underlying the effects of sulforaphane in reversing diet-induced obesity and interrogate potential pathways that link NRF2 with leptin receptor signaling by conducting whole transcriptome analysis in 6 metabolically active tissues from the diet-induced obese mice that were treated with SFN. Methods: Male 12-week-old C57/BJ wild type mice were fed with high fat diet for 16-20 weeks. Around 28 weeks of age, mice were treated with daily ip injections of either SFN (5 mg/kg) or vehicle for one week. We probed the whole transcriptome in several metabolic tissues including the hypothalamus, liver, brown adipose tissue (BAT), epididymal white adipose tissue (eWAT), inguinal white adipose tissue (iWAT), and skeletal muscle following peripheral SFN administration. Total RNA samples from each tissue were prepared with Trizol. Whole transcriptome were conducted by using Novogene sequencing platform NovaSeq 6000 PE150. The following bioinformatics analysis have been conducted. 1. Data Quality Control: filtering reads containing adapter or with low quality. 2. Statistics Analysis of Data Production and Quality. 3. Mapping Reads to Reference Genome. 4. Gene Expression Quantification. 5. Correlation analysis (For biological replicates only). 6. Differential Expression Analysis (two or more groups of samples). 7. GO Enrichment Analysis of Differentially Expressed Genes (DEGs) (two or more groups of samples). 8. KEGG Pathway Enrichment Analysis of Differentially Expressed Genes (DEGs) (two or more groups of samples). 9. GSEA Enrichment Analysis of Expressed Genes (two or more groups of samples). 10. Protein Protein Interaction Analysis. 11. Reactome Pathway Enrichment Analysis of Differentially Expressed Genes (DEGs) (two or more groups of samples and only for mouse samples). 12. Oncogene Functional Annotation analysis of Differentially Expressed Genes (DEGs) (two or more groups of samples and only for mouse sample). Results: RNAseq results indicated a significant upregulation of the NRF2 target gene HMOX1 only in the skeletal muscle. We also conducted an enrichment analysis to identify potential transcription factors for the significantly upregulated genes. NRF2 was identified as the most significant transcription factor only for the skeletal muscle gene set, providing further support for the skeletal muscle being a primary target tissue of SFN action. We thus conducted a KEGG and GO pathway analysis, and identified ribosome biogenesis, proteasome pathway, and the RNA transport as the significantly upregulated pathways in the SFN-treated muscle samples. In addition to HMOX1, the RNA seq results indicate upregulation of other genes involved in oxidative stress response capacity in SFN treated mice in the skeletal muscle. GCLM (glutamate-cysteine ligase), the first rate-limiting enzyme of glutathione synthesis, SRXN1 (Sulfiredoxin), an oxidoreductase that reduces cysteine-sulfinate, and GSR (glutathione-disulfide reductase), a central antioxidant enzyme, which reduces oxidized glutathione disulfide (GSSG) to the sulfhydryl form glutathione (GSH), and TXNRD1 (thioredoxin reductase 1) which reduces thioredoxins are all upregulated in the skeletal muscle of the SFN-treated DIO animals. Conclusions: Here, we show that the natural isothiocyanate and potent NRF2 activator sulforaphane reverses diet-induced obesity through an NRF2-dependent mechanism that requires a functional leptin receptor signaling and hyperleptinemia. Transcriptional profiling of six major metabolically relevant tissues highlights that sulforaphane suppresses fatty acid synthesis while promoting ribosome biogenesis, reducing ROS accumulation and resolving inflammation, therefore representing a unique transcriptional program that leads to protection from obesity. Our findings argue for clinical evaluation of sulforaphane for weight loss and obesity-associated metabolic disorders.

Project description:ObjectivePARKIN is an E3 ubiquitin ligase that regulates mitochondrial quality control through a process called mitophagy. Recent human and rodent studies suggest that loss of hepatic mitophagy may occur during the pathogenesis of obesity-associated fatty liver and contribute to changes in mitochondrial metabolism associated with this disease. Whole-body Prkn knockout mice are paradoxically protected against diet-induced hepatic steatosis; however, liver-specific effects of Prkn deficiency cannot be discerned in this model due to pleotropic effects of germline Prkn deletion on energy balance and subsequent protection against diet-induced obesity. We therefore generated the first liver-specific Prkn knockout mouse strain (LKO) to directly address the role of hepatic Prkn.MethodsLittermate control (WT) and LKO mice were fed regular chow (RC) or high-fat diet (HFD) and changes in body weight and composition were measured over time. Liver mitochondrial content was assessed using multiple, complementary techniques, and mitochondrial respiratory capacity was assessed using Oroboros O2K platform. Liver fat was measured biochemically and assessed histologically, while global changes in hepatic gene expression were measured by RNA-seq. Whole-body and tissue-specific insulin resistance were assessed by hyperinsulinemic-euglycemic clamp with isotopic tracers.ResultsLiver-specific deletion of Prkn had no effect on body weight or adiposity during RC or HFD feeding; however, hepatic steatosis was increased by 45% in HFD-fed LKO compared with WT mice (P < 0.05). While there were no differences in mitochondrial content between genotypes on either diet, mitochondrial respiratory capacity and efficiency in the liver were significantly reduced in LKO mice. Gene enrichment analyses from liver RNA-seq results suggested significant changes in pathways related to lipid metabolism and fibrosis in HFD-fed Prkn knockout mice. Finally, whole-body insulin sensitivity was reduced by 35% in HFD-fed LKO mice (P < 0.05), which was primarily due to increased hepatic insulin resistance (60% of whole-body effect; P = 0.11).ConclusionsThese data demonstrate that PARKIN contributes to mitochondrial homeostasis in the liver and plays a protective role against the pathogenesis of hepatic steatosis and insulin resistance.

Dataset Information

Epac2a-null mice exhibit obesity-prone nature more susceptible to leptin resistance.

Background

Methods

Results

Conclusions

Publications

Epac2a-null mice exhibit obesity-prone nature more susceptible to leptin resistance.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets