scholarly journals Impairment of the Gβγ-SNAP25 brake on exocytosis enhances insulin action, protects against diet-induced obesity, and promotes adipocyte browning

2020 ◽  
Author(s):  
Ryan P. Ceddia ◽  
Zack Zurawski ◽  
Analisa Thompson Gray ◽  
Feyisayo Adegboye ◽  
Fubiao Shi ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Adrenergic Receptor ◽  
Snare Complex ◽  
Diet Induced Obesity ◽  
Voltage Gated Calcium Channels ◽  
Energy Stores ◽  
Vesicle Exocytosis ◽  
Glucose Stimulated Insulin Secretion

The Gβγ complex inhibits vesicle exocytosis by two mechanisms: inhibiting calcium entry by binding to voltage gated calcium channels, and binding to SNAP25 in the SNAP Receptor (SNARE) complex. To de-convolute the role of each of these mechanisms in vivo, we have made a mouse with the second mechanism disabled. The SNAP25Δ3 mutation renders the SNARE complex deficient in binding to Gβγ and was used to investigate the importance of the Gβγ-SNAP25 interaction in glucose stimulated insulin secretion (GSIS) and global metabolic homeostasis. GSIS and α2A adrenergic receptor-mediated inhibition of GSIS were not altered in SNAP25Δ3/Δ3 mice. Nevertheless, SNAP25Δ3/Δ3 mice exhibited a marked improvement in insulin sensitivity and were resistant to weight gain when challenged with a high fat diet (HFD). Reduced food consumption in the early stages of HFD feeding were partly responsible for the inability of SNAP25Δ3/Δ3 mice to gain weight on HFD. Additionally, improved insulin-mediated glucose uptake into white adipose tissue and increased ‘browning’ were observed in SNAP25Δ3/Δ3 mice, which is consistent with an impaired ability to retain energy stores. These phenotypic changes in SNAP25Δ3/Δ3 mice are all metabolically protective, indicating that pharmacological targeting of the Gβγ-SNAP25 interaction may have a metabolic benefit.

scholarly journals Brain-Specific SNAP-25 Deletion Leads to Elevated Extracellular Glutamate Level and Schizophrenia-Like Behavior in Mice

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Hua Yang ◽  
Mengjie Zhang ◽  
Jiahao Shi ◽  
Yunhe Zhou ◽  
Zhipeng Wan ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Mouse Model ◽  
Glutamate Release ◽  
Critical Role ◽  
Conditional Knockout ◽  
Snare Complex ◽  
Extracellular Glutamate ◽  
Glutamate Level

Several studies have associated reduced expression of synaptosomal-associated protein of 25 kDa (SNAP-25) with schizophrenia, yet little is known about its role in the illness. In this paper, a forebrain glutamatergic neuron-specific SNAP-25 knockout mouse model was constructed and studied to explore the possible pathogenetic role of SNAP-25 in schizophrenia. We showed that SNAP-25 conditional knockout (cKO) mice exhibited typical schizophrenia-like phenotype. A significantly elevated extracellular glutamate level was detected in the cerebral cortex of the mouse model. Compared with Ctrls, SNAP-25 was dramatically reduced by about 60% both in cytoplasm and in membrane fractions of cerebral cortex of cKOs, while the other two core members of SNARE complex: Syntaxin-1 (increased ~80%) and Vamp2 (increased ~96%) were significantly increased in cell membrane part. Riluzole, a glutamate release inhibitor, significantly attenuated the locomotor hyperactivity deficits in cKO mice. Our findings provide in vivo functional evidence showing a critical role of SNAP-25 dysfunction on synaptic transmission, which contributes to the developmental of schizophrenia. It is suggested that a SNAP-25 cKO mouse, a valuable model for schizophrenia, could address questions regarding presynaptic alterations that contribute to the etiopathophysiology of SZ and help to consummate the pre- and postsynaptic glutamatergic pathogenesis of the illness.

Abstract 450: Monocytic Glutaredoxin 1 Protects Mice Against Obesity, Hyperglycemia and Atherosclerosis

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Kevin Downs ◽  
Sina Tavakoli ◽  
John D Short ◽  
Huynh N Nguyen ◽  
Reto Asmis
Keyword(s):  
High Fat Diet ◽  
Statistical Significance ◽  
Gene Array ◽  
Metabolic Stress ◽  
Wild Type ◽  
Adipose Tissues ◽  
Atherosclerotic Lesions ◽  
Monocyte Chemotaxis

Overexpression of glutaredoxin 1 (Grx1) protects monocytes from metabolic stress-induced priming, i.e. dysregulation and hypersensitization to chemokines (Ullevig et al. ATVB 2012). To address the role of monocytic Grx1 in mice and in the development of atherogenesis and obesity, we transplanted bone marrow (BM) from either wild-type (WT) or Grx1 -/- donor mice into atherosclerosis-prone LDLR -/- mice and fed these mice a high-fat diet (HFD) for up to 20 weeks. Grx1 Leuko -/- mice showed accelerated weight gain after 9 weeks followed by early onset of hyperglycemia. After 6 weeks on HFD, atherosclerotic lesions were slightly larger in Grx1 Leuko -/- mice than in WT mice, but the differences did not reach statistical significance. However, after 20 weeks, Grx1 Leuko -/- mice showed 36% larger lesions than WT-BM recipients, and monocyte chemotaxis in vivo was increased 1.6-fold. Furthermore, compared to WT-BM recipients, adipose tissues and livers of Grx1 Leuko -/- mice also showed increased macrophage content and elevated tissue inflammation as determined by IHC and qRT-PCR-based gene array. Adipose tissue in particular, showed significant increases in the expression of proinflammatory genes in addition to an increased abundance of proinflammatory “crown-like” structures. In contrast, genes associated with inflammation resolving macrophages were significantly suppressed. Macrophages isolated from Grx1 -/- mice and stimulated with INFγ+TNFα also showed increased expression of pro-inflammatory M1-associated genes, whereas M2-associated genes were suppressed in Grx-1 -/- macrophages activated with IL-4. Furthermore, macrophages from Grx1 -/- mice exposed to metabolic stress also display increased protein S -glutathionylation, enhanced hypersensitization to chemokine, and impaired autophagy compared to macrophages from wild-type mice. Taken together, our data show that loss of monocytic Grx1 worsens monocyte priming in response to HFD-induced metabolic stress and accelerates the infiltration of dysfunctional monocyte-derived macrophages into tissues, such as aorta, liver and adipose tissues. We conclude that monocytic Grx1 is critical for maintaining metabolic homeostasis in mice and protects mice against obesity and atherogenesis.

The role of 5-HT7 receptors on isoproterenol-induced myocardial infarction in rats with high-fat diet exacerbated coronary endothelial dysfunction

2020 ◽  
Vol 39 (8) ◽  
pp. 1005-1018 ◽  
Author(s):  
I Cinar ◽  
Z Halici ◽  
B Dincer ◽  
B Sirin ◽  
E Cadirci
Keyword(s):  
Myocardial Infarction ◽  
Endothelial Dysfunction ◽  
High Fat Diet ◽  
Density Lipoprotein ◽  
Heart Tissue ◽  
High Fat ◽  
Inflammatory Status

The presence of 5-HT7r’s in both human and rat cardiovascular and immune tissues and their contribution to inflammatory conditions prompted us to hypothesize that these receptors contribute in acute myocardial infarction (MI) with underlying chronic endothelial dysfunction. We investigated the role of 5-HT7 receptors on heart tissue that damaged by isoproterenol (ISO)-induced MI in rats with high-fat diet (HFD). In vitro and in vivo effects of 5-HT7r agonist (LP44) and antagonist (SB269970) have been investigated on the H9C2 cell line and rats, respectively. For in vivo analyses, rats were fed with HFD for 8 weeks and after this period ISO-induced MI model has been applied to rat. To investigate the role of 5-HT7r’s, two different doses of LP44 and SB269970 were evaluated and compared with standard hypolipidemic agent, atorvastatin. In vitro studies showed that LP44 has protective and proliferative effects on rat cardiomyocytes. Also in in vivo studies stimulating 5-HT7r’s by LP44 improved blood lipid profile (decreased total cholesterol, low-density lipoprotein-C, and triglyceride, increased high-density lipoprotein), decreased cardiac damage markers (creatine kinase and troponin-I), and corrected inflammatory status (tumor necrosis factor-α, interleukin-6). Our results showed significant improvement in LP44 administered rats in terms of histopathologic analyses. In damaged tissues, 5-HT7 mRNA expression increased and agonist administration decreased this elevation significantly. We determined for the first time that 5-HT7r’s are overexpressed in ISO-induced MI of rats with underlying HFD-induced endothelial dysfunction. Restoration of this overexpression by LP44, a 5-HT7r agonist, ameliorated heart tissue in physiopathologic, enzymatic, and molecular level, showing the cardiac role of these receptors and suggesting them as future potential therapeutic targets.

scholarly journals RANKL Is Involved in Runx2-Triggered Hepatic Infiltration of Macrophages in Mice with NAFLD Induced by a High-Fat Diet

2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Li Zhong ◽  
Jianghan Yuan ◽  
Lu Huang ◽  
Shan Li ◽  
Liang Deng
Keyword(s):  
High Fat Diet ◽  
Macrophage Infiltration ◽  
Macrophage Migration ◽  
High Fat ◽  
Transwell Assay ◽  
Nonalcoholic Fatty Liver ◽  
Related Transcription Factor

Background. Receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) is significant in the activation of inflammation. Runt-related transcription factor 2 (Runx2) promotes the hepatic infiltration of macrophages in nonalcoholic fatty liver disease (NAFLD). We studied how RANKL affects Runx2-triggered macrophage infiltration in NAFLD. Method. 30 male C57BL/6J mice at 4 weeks of age were utilized in this study, 20 mice received a high-fat diet (HFD), and 10 mice received standard rodent chow over 8 months. The histopathologic features of the liver were identified by H&E, Oil red O, and Masson staining. Runx2, RANKL, and F4/80 were analyzed by western blot, real-time PCR, and immunohistochemistry in vivo, respectively. Lentivirus or siRNA was utilized for transwell assay to investigate the role of RANKL in Runx2-induced macrophage migration in vitro. Results. Compared to controls, during NAFLD development, HFD increased Runx2 and RANKL in vivo in NASH (P<0.01). Meanwhile, a correlation between the expression of Runx2 and RANKL (P<0.05) was evident. In addition, the hepatic infiltration of macrophages was increased upon HFD feeding, and analysis showed that the macrophage infiltration was correlated with the expression of Runx2 or RANKL (P<0.05). In vitro, we found that overexpression or deficiency of Runx2 increased or decreased the production of RANKL in mHSCs. Then, transwell assay revealed that RANKL was involved in Runx2-induced macrophage migration. Conclusions. Overall, RANKL is involved in Runx2-triggered macrophage migration during NAFLD pathogenesis, which may provide an underlying therapeutic target for NAFLD.

Ameliorative effect of selegiline in high fat diet induced obesity rat model: Possible role of dopaminergic pathway

2020 ◽  
Vol 20 ◽  
pp. 100301
Author(s):  
Amit Goyal ◽  
Ankita Sharma ◽  
Deepika Sharma ◽  
Tapan Behl ◽  
Anjoo Kamboj ◽  
...  
Keyword(s):  
Rat Model ◽  
High Fat Diet ◽  
High Fat ◽  
Diet Induced Obesity ◽  
Dopaminergic Pathway ◽  
Ameliorative Effect

scholarly journals SMRT Regulates Metabolic Homeostasis and Adipose Tissue Macrophage Phenotypes in Tandem

Endocrinology ◽  
2020 ◽  
Vol 161 (10) ◽  
Author(s):  
Jonathan H Kahn ◽  
Anna Goddi ◽  
Aishwarya Sharma ◽  
Joshua Heiman ◽  
Alanis Carmona ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
High Fat Diet ◽  
Hormone Receptors ◽  
Tissue Macrophage ◽  
Secreted Factors ◽  
Physiological Homeostasis

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.

scholarly journals CTRP9 transgenic mice are protected from diet-induced obesity and metabolic dysfunction

2013 ◽  
Vol 305 (5) ◽  
pp. R522-R533 ◽  
Author(s):  
Jonathan M. Peterson ◽  
Zhikui Wei ◽  
Marcus M. Seldin ◽  
Mardi S. Byerly ◽  
Susan Aja ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Transgenic Mice ◽  
High Fat Diet ◽  
Fat Oxidation ◽  
Acid Oxidation ◽  
Ampk Activation ◽  
High Fat ◽  
Diet Induced Obesity

CTRP9 is a secreted multimeric protein of the C1q family and the closest paralog of the insulin-sensitizing adipokine, adiponectin. The metabolic function of this adipose tissue-derived plasma protein remains largely unknown. Here, we show that the circulating levels of CTRP9 are downregulated in diet-induced obese mice and upregulated upon refeeding. Overexpressing CTRP9 resulted in lean mice that dramatically resisted weight gain induced by a high-fat diet, largely through decreased food intake and increased basal metabolism. Enhanced fat oxidation in CTRP9 transgenic mice resulted from increases in skeletal muscle mitochondrial content, expression of enzymes involved in fatty acid oxidation (LCAD and MCAD), and chronic AMPK activation. Hepatic and skeletal muscle triglyceride levels were substantially decreased in transgenic mice. Consequently, CTRP9 transgenic mice had a greatly improved metabolic profile with markedly reduced fasting insulin and glucose levels. The high-fat diet-induced obesity, insulin resistance, and hepatic steatosis observed in wild-type mice were prevented in transgenic mice. Consistent with the in vivo data, recombinant protein significantly enhanced fat oxidation in L6 myotubes via AMPK activation and reduced lipid accumulation in H4IIE hepatocytes. Collectively, these data establish CTRP9 as a novel metabolic regulator and a new component of the metabolic network that links adipose tissue to lipid metabolism in skeletal muscle and liver.

scholarly journals Hypertrophic cardiomyopathy in high-fat diet-induced obesity: role of suppression of forkhead transcription factor and atrophy gene transcription

2008 ◽  
Vol 295 (3) ◽  
pp. H1206-H1215 ◽  
Author(s):  
Cindy X. Fang ◽  
Feng Dong ◽  
D. Paul Thomas ◽  
Heng Ma ◽  
Leilei He ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Palmitic Acid ◽  
High Fat Diet ◽  
Weight Control ◽  
Dominant Negative ◽  
High Fat ◽  
Forkhead Transcription Factor ◽  
Diet Induced Obesity ◽  
Intracellular Ca

Cellular hypertrophy is regulated by coordinated pro- and antigrowth machineries. Foxo transcription factors initiate an atrophy-related gene program to counter hypertrophic growth. This study was designed to evaluate the role of Akt, the forkhead transcription factor Foxo3a, and atrophy genes muscle-specific RING finger (MuRF)-1 and atrogin-1 in cardiac hypertrophy and contractile dysfunction associated with high-fat diet-induced obesity. Mice were fed a low- or high-fat diet for 6 mo along with a food-restricted high-fat weight control group. Echocardiography revealed decreased fractional shortening and increased end-systolic diameter and cardiac hypertrophy in high-fat obese but not in weight control mice. Cardiomyocytes from high-fat obese but not from weight control mice displayed contractile and intracellular Ca2+ defects including depressed maximal velocity of shortening/relengthening, prolonged duration of shortening/relengthening, and reduced intracellular Ca2+ rise and clearance. Caspase activities were greater in high-fat obese but not in weight control mouse hearts. Western blot analysis revealed enhanced basal Akt and Foxo3a phosphorylation and reduced insulin-stimulated phosphorylation of Akt and Foxo3a without changes in total protein expression of Akt and Foxo3a in high-fat obese hearts. RT-PCR and immunoblotting results displayed reduced levels of the atrogens atrogin-1 and MuRF-1, the upregulated hypertrophic markers GATA4 and ciliary neurotrophic factor receptor-α, as well as the unchanged calcineurin and proteasome ubiquitin in high-fat obese mouse hearts. Transfection of H9C2 myoblast cells with dominant-negative Foxo3a adenovirus mimicked palmitic acid (0.8 mM for 24 h)-induced GATA4 upregulation without an additive effect. Dominant-negative Foxo3a-induced upregulation of pAkt and repression of phosphatase and tensin homologue were abrogated by palmitic acid. These results suggest a cardiac hypertrophic response in high-fat diet-associated obesity at least in part through inactivation of Foxo3a by the Akt pathway.

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