Protein kinase G controls brown fat cell differentiation and mitochondrial biogenesis

Pharmacological Gq inhibition induces strong pulmonary vasorelaxation and reverses pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening disease with limited survival. Herein, we propose the pharmacological inhibition of Gq proteins as a novel concept to counteract pulmonary vasoconstriction and proliferation/migration of pulmonary artery smooth muscle cells (PASMCs) in PAH. We demonstrate that the specific pan-Gq inhibitor FR900359 (FR) induced a strong vasorelaxation in large and small pulmonary arteries in mouse, pig, and human subjects ex vivo. Vasorelaxation by FR proved at least as potent as the currently used triple therapy. We also provide in vivo evidence that local pulmonary application of FR prevented right ventricular systolic pressure increase in healthy mice as well as in mice suffering from hypoxia (Hx)-induced pulmonary hypertension (PH). In addition, we demonstrate that chronic application of FR prevented and also reversed Sugen (Su)Hx-induced PH in mice. We also demonstrate that Gq inhibition reduces proliferation and migration of PASMCs in vitro. Thus, our work illustrates a dominant role of Gq proteins for pulmonary vasoconstriction as well as remodeling and proposes direct Gq inhibition as a powerful pharmacological strategy in PH.

Sulfonylureas exert antidiabetic action on adipocytes by inhibition of PPARγ serine 273 phosphorylation

OBJECTIVE

Sulfonylureas (SUs) are still among the mostly prescribed antidiabetic drugs with an established mode of action: release of insulin from pancreatic β-cells. In addition, effects of SUs on adipocytes by activation of the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) have been described, which might explain their insulin-sensitizing potential observed in patients. However, there is a discrepancy between the impact of SUs on antidiabetic action and their rather moderate in vitro effect on PPARγ transcriptional activity. Recent studies have shown that some PPARγ ligands can improve insulin sensitivity by blocking PPARγ Ser-273 phosphorylation without having full agonist activity. It is unknown if SUs elicit their antidiabetic effects on adipocytes by inhibition of PPARγ phosphorylation. Here, we investigated if binding of SUs to PPARγ can interfere with PPARγ Ser-273 phosphorylation and determined their antidiabetic actions in vitro in primary human white adipocytes and in vivo in high-fat diet (HFD) obese mice.

METHODS

Primary human white preadipocytes were differentiated in the presence of glibenclamide, glimepiride and PPARγ ligands rosiglitazone and SR1664 to compare PPARγ Ser-273 phosphorylation, glucose uptake and adipokine expression. Transcriptional activity at PPARγ was determined by luciferase assays, quantification of PPARγ Ser-273 phosphorylation was determined by Western blotting and CDK5 kinase assays. In silico modelling was performed to gain insight into the binding characteristics of SUs to PPARγ. HFD mice were administered SUs and rosiglitazone for 6 days. PPARγ Ser-273 phosphorylation in white adipose tissue (WAT), body composition, glucose tolerance, adipocyte morphology and expression levels of genes involved in PPARγ activity in WAT and brown adipose tissue (BAT) were evaluated.

RESULTS

SUs inhibit phosphorylation of PPARγ at Ser-273 in primary human white adipocytes and exhibit a positive antidiabetic expression profile, which is characterized by up regulation of insulin-sensitizing and down regulation of insulin resistance-inducing adipokines. We demonstrate that SUs directly bind to PPARγ by in silico modelling and inhibit phosphorylation in kinase assays to a similar extend as rosiglitazone and SR1664. In HFD mice SUs reduce PPARγ phosphorylation in WAT and have comparable effects on gene expression to rosiglitazone. In BAT SUs increase UCP1 expression and reduce lipid droplets sizes.

CONCLUSIONS

Our findings indicate that a part of SUs extra-pancreatic effects on adipocytes in vitro and in vivo is probably mediated via their interference with PPARγ phosphorylation rather than via classical agonistic activity at clinical concentrations.

OCaR1 endows exocytic vesicles with autoregulatory competence by preventing uncontrolled Ca2+ release, exocytosis, and pancreatic tissue damage

Regulated exocytosis is initiated by increased Ca2+ concentrations in close spatial proximity to secretory granules, which is effectively prevented when the cell is at rest. Here we showed that exocytosis of zymogen granules in acinar cells was driven by Ca2+ directly released from acidic Ca2+ stores including secretory granules through NAADP-activated two-pore channels (TPCs). We identified OCaR1 (encoded by Tmem63a) as an organellar Ca2+ regulator protein integral to the membrane of secretory granules that controlled Ca2+ release via inhibition of TPC1 and TPC2 currents. Deletion of OCaR1 led to extensive Ca2+ release from NAADP-responsive granules under basal conditions as well as upon stimulation of GPCR receptors. Moreover, OCaR1 deletion exacerbated the disease phenotype in murine models of severe and chronic pancreatitis. Our findings showed OCaR1 as a gatekeeper of Ca2+ release that endows NAADP-sensitive secretory granules with an autoregulatory mechanism preventing uncontrolled exocytosis and pancreatic tissue damage.

NG ,NG -Dimethylarginine Dimethylaminohydrolase 1 Expression Is Dispensable for Cold- or Diet-Induced Thermogenesis

The strategy to activate thermogenic adipocytes has therapeutic potential to overcome obesity as they dissipate surplus energy as heat through various mechanisms. NG,NG-dimethylarginine dimethylaminohydrolases (DDAHs) are enzymes involved in the nitric oxide-protein kinase G signaling axis which increases thermogenic gene expression. However, the role of DDAHs in thermogenic adipocytes has not been elucidated. The adipocyte-specific Ddah1 knockout mice are generated by crossing Ddah1fl/fl mice with adiponectin Cre recombinase mice. Adipocyte-specific DDAH1 overexpressing mice are generated using adeno-associated virus-double-floxed inverse open reading frame (AAV-DIO) system. These mice are analyzed under basal, cold exposure, or high-fat diet (HFD) conditions. Primary inguinal white adipose tissue cells from adipocyte-specific Ddah1 knockout mice expressed comparable amounts of Ucp1 mRNA. Adipocyte-specific DDAH1 overexpressing mice do not exhibit enhanced activation of thermogenic adipocytes. In addition, when these mice are exposed to cold environment or fed an HFD, their body temperature/weight and thermogenesis-related gene and protein expressions are unchanged. These findings indicate that DDAH1 does not play a role in either cold- or diet-induced thermogenesis. Therefore, adipocyte targeting DDAH1 gene therapy for the treatment of obesity is unlikely to be effective.

EPAC1 enhances brown fat growth and beige adipogenesis

Brown adipose tissue (BAT) is a central thermogenic organ that enhances energy expenditure and cardiometabolic health. However, regulators that specifically increase the number of thermogenic adipocytes are still an unmet need. Here, we show that the cAMP-binding protein EPAC1 is a central regulator of adaptive BAT growth. In vivo, selective pharmacological activation of EPAC1 increases BAT mass and browning of white fat, leading to higher energy expenditure and reduced diet-induced obesity. Mechanistically, EPAC1 coordinates a network of regulators for proliferation specifically in thermogenic adipocytes, but not in white adipocytes. We pinpoint the effects of EPAC1 to PDGFRα-positive preadipocytes, and the loss of EPAC1 in these cells impedes BAT growth and worsens diet-induced obesity. Importantly, EPAC1 activation enhances the proliferation and differentiation of human brown adipocytes and human brown fat organoids. Notably, a coding variant of RAPGEF3 (encoding EPAC1) that is positively correlated with body mass index abolishes noradrenaline-induced proliferation of brown adipocytes. Thus, EPAC1 might be an attractive target to enhance thermogenic adipocyte number and energy expenditure to combat metabolic diseases.

Evidence of Flavonoids on Disease Prevention

A growing body of evidence highlights the properties of flavonoids in natural foods for disease prevention. Due to their antioxidative, anti-inflammatory, and anti-carcinogenic activities, flavonoids have been revealed to benefit skeletal muscle, liver, pancreas, adipocytes, and neural cells. In this review, we introduced the basic classification, natural sources, and biochemical properties of flavonoids, then summarize the experimental results and underlying molecular mechanisms concerning the effects of flavonoid consumption on obesity, cancers, and neurogenerative diseases that greatly threaten public health. Especially, the dosage and duration of flavonoids intervening in these diseases are discussed, which might guide healthy dietary habits for people of different physical status.

Beyond Erectile Dysfunction: cGMP-Specific Phosphodiesterase 5 Inhibitors for Other Clinical Disorders

Cyclic guanosine monophosphate (cGMP), an important intracellular second messenger, mediates cellular functional responses in all vital organs. Phosphodiesterase 5 (PDE5) is one of the 11 members of the cyclic nucleotide phosphodiesterase (PDE) family that specifically targets cGMP generated by nitric oxide-driven activation of the soluble guanylyl cyclase. PDE5 inhibitors, including sildenafil and tadalafil, are widely used for the treatment of erectile dysfunction, pulmonary arterial hypertension, and certain urological disorders. Preclinical studies have shown promising effects of PDE5 inhibitors in the treatment of myocardial infarction, cardiac hypertrophy, heart failure, cancer and anticancer-drug-associated cardiotoxicity, diabetes, Duchenne muscular dystrophy, Alzheimer's disease, and other aging-related conditions. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular, anticancer, and neurological benefits. In this review, we provide an overview of the current state of knowledge on PDE5 inhibitors and their potential therapeutic indications for various clinical disorders beyond erectile dysfunction.

RNAseq Analysis of Brown Adipose Tissue and Thyroid of Newborn Lambs Subjected to Short-Term Cold Exposure Reveals Signs of Early Whitening of Adipose Tissue

During the early postnatal period, lambs have the ability to thermoregulate body temperature via non-shivering thermogenesis through brown adipose tissue (BAT), which soon after birth begins to transform into white adipose tissue. An RNA seq approach was used to characterize the transcriptome of BAT and thyroid tissue in newborn lambs exposed to cold conditions. Fifteen newborn Romney lambs were selected and divided into three groups: group 1 (n = 3) was a control, and groups 2 and 3 (n = 6 each) were kept indoors for two days at an ambient temperature (20–22 °C) or at a cold temperature (4 °C), respectively. Sequencing was performed using a paired-end strategy through the BGISEQ-500 platform, followed by the identification of differentially expressed genes using DESeq2 and an enrichment analysis by g:Profiler. This study provides an in-depth expression network of the main characters involved in the thermogenesis and fat-whitening mechanisms that take place in the newborn lamb. Data revealed no significant differential expression of key thermogenic factors such as uncoupling protein 1, suggesting that the heat production peak under cold exposure might occur so rapidly and in such an immediate way that it may seem undetectable in BAT by day three of life. Moreover, these changes in expression might indicate the start of the whitening process of the adipose tissue, concluding the non-shivering thermogenesis period.

Apoptotic brown adipocytes enhance energy expenditure via extracellular inosine

Brown adipose tissue (BAT) dissipates energy1,2 and promotes cardiometabolic health3. Loss of BAT during obesity and ageing is a principal hurdle for BAT-centred obesity therapies, but not much is known about BAT apoptosis. Here, untargeted metabolomics demonstrated that apoptotic brown adipocytes release a specific pattern of metabolites with purine metabolites being highly enriched. This apoptotic secretome enhances expression of the thermogenic programme in healthy adipocytes. This effect is mediated by the purine inosine that stimulates energy expenditure in brown adipocytes by the cyclic adenosine monophosphate-protein kinase A signalling pathway. Treatment of mice with inosine increased BAT-dependent energy expenditure and induced 'browning' of white adipose tissue. Mechanistically, the equilibrative nucleoside transporter 1 (ENT1, SLC29A1) regulates inosine levels in BAT: ENT1-deficiency increases extracellular inosine levels and consequently enhances thermogenic adipocyte differentiation. In mice, pharmacological inhibition of ENT1 as well as global and adipose-specific ablation enhanced BAT activity and counteracted diet-induced obesity, respectively. In human brown adipocytes, knockdown or blockade of ENT1 increased extracellular inosine, which enhanced thermogenic capacity. Conversely, high ENT1 levels correlated with lower expression of the thermogenic marker UCP1 in human adipose tissues. Finally, the Ile216Thr loss of function mutation in human ENT1 was associated with significantly lower body mass index and 59% lower odds of obesity for individuals carrying the Thr variant. Our data identify inosine as a metabolite released during apoptosis with a 'replace me' signalling function that regulates thermogenic fat and counteracts obesity.

Cold exposure induces lipid dynamics and thermogenesis in brown adipose tissue of goats

Background

Adaptive thermogenesis by brown adipose tissue (BAT) is important to the maintenance of temperature in newborn mammals. Cold exposure activates gene expression and lipid metabolism to provide energy for BAT thermogenesis. However, knowledge of BAT metabolism in large animals after cold exposure is still limited.

Results

In this study, we found that cold exposure induced expression of BAT thermogenesis genes and increased the protein levels of UCP1 and PGC1α. Pathway analysis showed that cold exposure activated BAT metabolism, which involved in cGMP-PKG, TCA cycle, fatty acid elongation, and degradation pathways. These were accompanied by decreased triglyceride (TG) content and increased phosphatidylcholine (PC) and phosphatidylethanolamine (PE) content in BAT.

Conclusion

These results demonstrate that cold exposure induces metabolites involved in glycerolipids and glycerophospholipids metabolism in BAT. The present study provides evidence for lipid composition associated with adaptive thermogenesis in goat BAT and metabolism pathways regulated by cold exposure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08765-5.

Role of Endothelial Cell Lipoprotein Lipase for Brown Adipose Tissue Lipid and Glucose Handling

Cold-induced activation of brown adipose tissue (BAT) has an important impact on systemic lipoprotein metabolism by accelerating the processing of circulating triglyceride-rich lipoproteins (TRL). Lipoprotein lipase (LPL) expressed by adipocytes is translocated via endothelial to the capillary lumen, where LPL acts as the central enzyme for the vascular lipoprotein processing. Based on preliminary data showing that LPL is not only expressed in adipocytes but also in endothelial cells of cold-activated BAT, we aimed to dissect the relevance of endothelial versus adipocyte LPL for lipid and energy metabolism in the context of adaptive thermogenesis. By metabolic studies we found that cold-induced triglyceride uptake into BAT, lipoprotein disposal, glucose uptake and adaptive thermogenesis were not impaired in mice lacking Lpl exclusively in endothelial cells. This finding may be explained by a compensatory upregulation in the expression of adipocyte-derived Lpl and endothelial lipase (Lipg).

Resistin and Cardiovascular Disease: A Review of the Current Literature Regarding Clinical and Pathological Relationships

Serum resistin, mainly secreted by the bone marrow, monocytes, and macrophages, contributes to many processes, including endothelial dysfunction, Vascular Smooth Muscle Cell (VSMC) proliferation, and atherothrombosis demonstrating effects on the development of hypertension and Coronary Artery Disease (CAD). Previously published clinical studies have shown that plasma resistin levels are significantly associated with cardiovascular disease risk factors and adverse clinical outcomes associated with the condition. Resistin is associated with vascular smooth muscle cell dysfunction in vitro, most plausibly due to its relationship with oxidative stress in advanced atherosclerosis whereas in vivo studies have shown resistin to be associated with intimal hyperplasia. We aimed to summarize the role of resistin on cardiovascular disease (CVD), as we could not find any review focused on the role of resistin on CVD.

Insight Into Rho Kinase Isoforms in Obesity and Energy Homeostasis

Obesity and associated complications increasingly jeopardize global health and contribute to the rapidly rising prevalence of type 2 diabetes mellitus and obesity-related diseases. Developing novel methods for the prevention and treatment of excess body adipose tissue expansion can make a significant contribution to public health. Rho kinase is a Rho-associated coiled-coil-containing protein kinase (Rho kinase or ROCK). The ROCK family including ROCK1 and ROCK2 has recently emerged as a potential therapeutic target for the treatment of metabolic disorders. Up-regulated ROCK activity has been involved in the pathogenesis of all aspects of metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in both white and beige adipogenesis. Studies using ROCK pan-inhibitors in animal models of obesity, diabetes, and associated complications have demonstrated beneficial outcomes. Studies via genetically modified animal models further established isoform-specific roles of ROCK in the pathogenesis of metabolic disorders including obesity. However, most reported studies have been focused on ROCK1 activity during the past decade. Due to the progress in developing ROCK2-selective inhibitors in recent years, a growing body of evidence indicates more attention should be devoted towards understanding ROCK2 isoform function in metabolism. Hence, studying individual ROCK isoforms to reveal their specific roles and principal mechanisms in white and beige adipogenesis, insulin sensitivity, energy balancing regulation, and obesity development will facilitate significant breakthroughs for systemic treatment with isoform-selective inhibitors. In this review, we give an overview of ROCK functions in the pathogenesis of obesity and insulin resistance with a particular focus on the current understanding of ROCK isoform signaling in white and beige adipogenesis, obesity and thermogenesis in adipose tissue and other major metabolic organs involved in energy homeostasis regulation.

A natural anti-obesity reagent derived from sea buckthorn polysaccharides: Structure characterization and anti-obesity evaluation in vivo

Sea buckthorn polysaccharide (SBP) has received increasing attention for its various bioactive functions. In this study, a novel polysaccharide SBP-1 was initially separated from crude SBP and further purified to obtain its main fraction SBP-1-A with a Mw of 9944 Da, consisting of Rha, Ara, Gal, Glc, and GalA. The structure of SBP-1-A was characterized based on FT-IR, GC-MS, and 1D/2D NMR, and its backbone was composed of a repeated unit of → 3,4)-β-l-Rhap-(1 → 4)-α-d-GalAp-(1 → 4)-α-d-GalAp-(1 → with branches at C-4 position comprised of α-l-Araf, β-d-Galp, β-d-Glcp, α-d-Glcp. Besides, the anti-obesity effects of SBP-1 on high-fat diet mice were evaluated, indicating it could restrain the body weight gain and lipids accumulation by promoting the expression of PGC1α, UCP-1, and PRDM16 to activate the brown adipocyte and improve the thermogenesis. In summary, the results offered new supports for the structural information of SBP and its feasibility to be used as a natural anti-obesity reagent.

Priming metabolism with the type 5 phosphodiesterase: the role of cGMP-hydrolyzing enzymes

The cyclic guanosine monophosphate (cGMP) signaling system is one of the most prominent regulators of many physiopathological processes in humans and rodents. It has been strongly established as an accomplished cellular signal involved in the regulation of energy homeostasis and cell metabolism, and pharmacological enhancement of cGMP has shown beneficial effects in metabolic disorders models. cGMP intracellular levels are finely regulated by phosphodiesterases (PDEs). The main enzyme responsible for the degradation of cGMP is PDE5. Preclinical and clinical studies have shown that PDE5 inhibitors (PDE5i) have beneficial effects on improving insulin resistance and glucose metabolism representing a promising therapeutic strategy for the treatment of metabolic disorders. This review aims to describe the molecular basis underlying the use of PDE5i to prompt cell metabolism and summarize current clinical trials assessing the effects of PDE5i on glucose metabolism.

On the potential role of globins in brown adipose tissue: a novel conceptual model and studies in myoglobin knockout mice

Myoglobin (Mb) regulates O₂ bioavailability in muscle and heart as the partial pressure of O₂ (Po₂) drops with increased tissue workload. Globin proteins also modulate cellular NO pools, "scavenging" NO at higher Po₂ and converting NO₂^- to NO as Po₂ falls. Myoglobin binding of fatty acids may also signal a role in fat metabolism. Interestingly, Mb is expressed in brown adipose tissue (BAT), but its function is unknown. Herein, we present a new conceptual model that proposes links between BAT thermogenic activation, concurrently reduced Po₂, and NO pools regulated by deoxy/oxy-globin toggling and xanthine oxidoreductase (XOR). We describe the effect of Mb knockout (Mb^-/-) on BAT phenotype [lipid droplets, mitochondrial markers uncoupling protein 1 (UCP1) and cytochrome C oxidase 4 (Cox4), transcriptomics] in male and female mice fed a high-fat diet (HFD, 45% of energy, ∼13 wk), and examine Mb expression during brown adipocyte differentiation. Interscapular BAT weights did not differ by genotype, but there was a higher prevalence of mid-large sized droplets in Mb^-/-. COX4 protein expression was significantly reduced in Mb^-/- BAT, and a suite of metabolic/NO/stress/hypoxia transcripts were lower. All of these Mb^-/--associated differences were most apparent in females. The new conceptual model, and results derived from Mb^-/- mice, suggest a role for Mb in BAT metabolic regulation, in part through sexually dimorphic systems and NO signaling. This possibility requires further validation in light of significant mouse-to-mouse variability of BAT Mb mRNA and protein abundances in wild-type mice and lower expression relative to muscle and heart.NEW & NOTEWORTHY Myoglobin confers the distinct red color to muscle and heart, serving as an oxygen-binding protein in oxidative fibers. Less attention has been paid to brown fat, a thermogenic tissue that also expresses myoglobin. In a mouse knockout model lacking myoglobin, brown fat had larger fat droplets and lower markers of mitochondrial oxidative metabolism, especially in females. Gene expression patterns suggest a role for myoglobin as an oxygen/nitric oxide-sensor that regulates cellular metabolic and signaling pathways.

Gaining an understanding of behavioral genetics through studies of foraging in Drosophila and learning in C. elegans

The pursuit of understanding behavior has led to investigations of how genes, the environment, and the nervous system all work together to produce and influence behavior, giving rise to a field of research known as behavioral neurogenetics. This review focuses on the research journeys of two pioneers of aspects of behavioral neurogenetic research: Dr. Marla Sokolowski and Dr. Catharine Rankin as examples of how different approaches have been used to understand relationships between genes and behavior. Marla Sokolowski's research is centered around the discovery and analysis of foraging, a gene responsible for the natural behavioral polymorphism of Drosophila melanogaster larvae foraging behavior. Catharine Rankin's work began with demonstrating the ability to learn in Caenorhabditis elegans and then setting out to investigate the mechanisms underlying the "simplest" form of learning, habituation. Using these simple invertebrate organisms both investigators were able to perform in-depth dissections of behavior at genetic and molecular levels. By exploring their research and highlighting their findings we present ways their work has furthered our understanding of behavior and contributed to the field of behavioral neurogenetics.

Soluble guanylate cyclase chronic stimulation effects on cardiovascular reactivity in cafeteria diet-induced rat model of metabolic syndrome

Metabolic syndrome is linked to an increased risk of cardiovascular complications by a mechanism involving mainly decreased nitric oxide (NO) bioavailability and impaired NO-soluble guanylate cyclase (sGC)- cyclic guanosine monophosphate (cGMP) signalling (NO-sGC-cGMP). To further develop this scientific point, this study aimed to investigate the effects of long-term treatment with BAY 41-2272 (a sGC stimulator) on cardiovascular reactivity of spontaneously hypertensive rats (SHR) as a model of metabolic syndrome. SHR were randomly divided into 3 groups: control group, cafeteria diet (CD)-fed group and CD-fed group treated daily with BAY 41-2272 (5 mg/kg) by gastric gavage for 12 weeks. In vivo measurements of body weight, abdominal circumference, blood pressure and glucose tolerance test were performed. At the end of the feeding period, ex vivo cumulative concentration-response curves were performed on isolated perfused heart (isoproterenol (0.1 nM - 1 μM)) and thoracic aorta (phenylephrine (1 nM-10 μM), acetylcholine (1 nM-10 μM), and sodium nitroprusside (SNP) (0.1 nM-0.1 μM)). We showed that chronic CD feeding induced abdominal obesity, hypertriglyceridemia, glucose intolerance and exacerbated arterial hypertension in SHR. Compared to control group, CD-fed group showed a decrease in β-adrenoceptor-induced cardiac inotropy, in coronary perfusion pressure and in aortic contraction to phenylephrine. While relaxing effects of acetylcholine and SNP were unchanged. BAY 41-2272 long-term treatment markedly prevented arterial hypertension development and glucose intolerance, enhanced the α1-adrenoceptor-induced vasoconstriction, and restored cardiac inotropy and coronary vasodilation. These findings suggest that BAY 41-2272 may be a potential novel drug for preventing metabolic and cardiovascular complications of metabolic syndrome.

The Drosophila foraging gene plays a vital role at the start of metamorphosis for subsequent adult emergence

The foraging (for) gene has been extensively studied in many species for its functions in development, physiology, and behavior. It is common for genes that influence behavior and development to be essential genes, and for has been found to be an essential gene in both fruit flies and mammals, with for mutants dying before reaching the adult stage. However, the biological process underlying the lethality associated with this gene is not known. Here, we show that in Drosophila melanogaster, some but not all gene products of for are essential for survival. Specifically, we show that promoter 3 of for, but not promoters 1, 2, and 4 are required for survival past pupal stage. We use full and partial genetic deletions of for, and temperature-restricted knock-down of the gene to further investigate the stage of lethality. While deletion analysis shows that flies lacking for die at the end of pupal development, as pharate adults, temperature-restricted knock-down shows that for is only required at the start of pupal development, for normal adult emergence (AE) and viability. We further show that the inability of these mutants to emerge from their pupal cases is linked to deficiencies in emergence behaviors, caused by a possible energy deficiency, and finally, that the lethality of for mutants seems to be linked to protein isoform P3, transcribed from for promoter 3.

Methadone-mediated sensitization of glioblastoma cells is drug and cell line dependent

PURPOSE

D,L-methadone (MET), an analgesic drug used for pain treatment and opiate addiction, has achieved attention from oncologists and social media as possible chemoensitizing agent in cancer therapy, notably brain cancer (glioblastoma multiforme, GBM). MET has been reported to enhance doxorubicin-induced cytotoxicity in GBM cells via activation of the µ-opioid receptor (MOR). Here, we extended this work and quantified the toxic effect of MET in comparison to other opioids alone and in combination with doxorubicin and the clinically more relevant alkylating drug temozolomide (TMZ), using a set of GBM cell lines and primary GBM cells.

METHODS

MOR expression in GBM cells was investigated by immunofluorescence and immunoblotting. Resistance to drugs alone and in combination with anticancer drugs was assessed by MTT assays. Concentration effect curves were fitted by nonlinear regression analysis and IC50 values were calculated. Apoptosis and necrosis rates were determined by annexin V/propidium iodide (PI)-flow cytometry.

RESULTS

MET alone was cytotoxic in all GBM cell lines and primary GBM cells at high micromolar concentrations (IC50 ~ 60-130 µM), observed both in the metabolic MTT assay and by quantifying apoptosis and necrosis, while morphine and oxycodone were not cytotoxic in this concentration range. Naloxone was not able to block MET-induced cytotoxicity, indicating that cell death-inducing effects of MET are not MOR-dependent. We recorded doxorubicin and TMZ concentration- response curves in combination with fixed MET concentrations. MET enhanced doxorubicin-induced cytotoxicity in only one cell line, and in primary cells it was observed only in a particular MET concentration range. In all assays, MET was not effective in sensitizing cells to TMZ. In two cell lines, MET even decreased the cell's sensitivity to TMZ.

CONCLUSION

MET was found to be cytotoxic in GBM cells in vitro only at high, clinically not relevant concentrations, where it was effective in inducing apoptosis and necrosis. Sensitizing effects were only observed in combination with doxorubicin, but not with TMZ, and are dependent on cell line and the applied drug concentration. Therefore, our findings do not support the use of MET in the treatment of GBM in combination with TMZ, as no sensitizing effect of MET was observed.

Genes regulating development and behavior exhibited altered expression in Drosophila melanogaster exposed to bisphenol A: use of real-time quantitative PCR (qRT-PCR) and droplet digital PCR (ddPCR) in genotoxicity study

Toxicity of bisphenol A on morphological and life-history traits of model insect Drosophila melanogaster was reported in our previous work. In the present study, we have analyzed the adversity of bisphenol A on the reproductive behavior of adult and on the expression of selected genes in the larva and adult stage of fruit fly exposed to bisphenol A (0.007 g/2 ml. or 3.5 mg/ml), in addition to determination of LC50 value of bisphenol A in larva and pupal stage. We employed both the quantitative reverse transcriptase PCR and droplet digital PCR for analyzing the expression profile of seven genes namely, decapentaplegic, vestigial, wingless, foraging, insulin-like receptor, doublesex, and fruitless. We found bisphenol A has more adverse effects on male sexual behavior than females. Moreover, we observed significant downregulation of all the selected genes in treated larvae except, fruitless in male where it showed significant upregulation. On contrary among the treated adult flies, significant downregulation of all target genes in both sexes is evident, except, doublesex and fruitless in males which showed significant upregulation. We did not observe any deviation of male: female sex ratio from 1:1 under bisphenol A exposure. All these results suggest bisphenol A adversely affects the optimum functioning of genes which are involved in the regulation of metabolic pathways, behavioral pattern, stress response, endocrine homeostasis, neural functioning, and the development of the specific organ in Drosophila melanogaster. Our result not only provides a foundation to study further the bisphenol A toxicity on different pivotal genes in Drosophila but also suggests the use of the droplet digital PCR technology in toxicity measurement at the molecular level in eukaryotic model systems.

Quantification of Lipoprotein Uptake in Vivo Using Magnetic Particle Imaging and Spectroscopy

Lipids are a major source of energy for most tissues, and lipid uptake and storage is therefore crucial for energy homeostasis. So far, quantification of lipid uptake in vivo has primarily relied on radioactive isotope labeling, exposing human subjects or experimental animals to ionizing radiation. Here, we describe the quantification of in vivo uptake of chylomicrons, the primary carriers of dietary lipids, in metabolically active tissues using magnetic particle imaging (MPI) and magnetic particle spectroscopy (MPS). We show that loading artificial chylomicrons (ACM) with iron oxide nanoparticles (IONPs) enables rapid and highly sensitive post hoc detection of lipid uptake in situ using MPS. Importantly, by utilizing highly magnetic Zn-doped iron oxide nanoparticles (ZnMNPs), we generated ACM with MPI tracer properties superseding the current gold-standard, Resovist, enabling quantification of lipid uptake from whole-animal scans. We focused on brown adipose tissue (BAT), which dissipates heat and can consume a large part of nutrient lipids, as a model for tightly regulated and inducible lipid uptake. High BAT activity in humans correlates with leanness and improved cardiometabolic health. However, the lack of nonradioactive imaging techniques is an important hurdle for the development of BAT-centered therapies for metabolic diseases such as obesity and type 2 diabetes. Comparison of MPI measurements with iron quantification by inductively coupled plasma mass spectrometry revealed that MPI rivals the performance of this highly sensitive technique. Our results represent radioactivity-free quantification of lipid uptake in metabolically active tissues such as BAT.

CD47 differentially regulates white and brown fat function

Mechanisms that enhance energy expenditure are attractive therapeutic targets for obesity. Previously we have demonstrated that mice lacking cd47 are leaner, exhibit increased energy expenditure, and are protected against diet-induced obesity. In this study, we further defined the physiological role of cd47 deficiency in regulating mitochondrial function and energy expenditure in both white and brown adipose tissue. We observed that cd47 deficient mice (under normal chow diet) had comparable amount of white fat mass but reduced white adipocyte size as compared to wild-type mice. Subsequent ex vivo and in vitro studies suggest enhanced lipolysis, and not impaired lipogenesis or energy utilization, contributes to this phenotype. In contrast to white adipose tissue, there were no obvious morphological differences in brown adipose tissue between wild-type and knockout mice. However, mitochondria isolated from brown fat of cd47 deficient mice had significantly higher rates of free fatty acid-mediated uncoupling. This suggests that enhanced fuel availability via white adipose tissue lipolysis may perpetuate elevated brown adipose tissue energy expenditure and contributes to the lean phenotype observed in cd47 deficient mice.

A compendium of G-protein-coupled receptors and cyclic nucleotide regulation of adipose tissue metabolism and energy expenditure

With the ever-increasing burden of obesity and Type 2 diabetes, it is generally acknowledged that there remains a need for developing new therapeutics. One potential mechanism to combat obesity is to raise energy expenditure via increasing the amount of uncoupled respiration from the mitochondria-rich brown and beige adipocytes. With the recent appreciation of thermogenic adipocytes in humans, much effort is being made to elucidate the signaling pathways that regulate the browning of adipose tissue. In this review, we focus on the ligand-receptor signaling pathways that influence the cyclic nucleotides, cAMP and cGMP, in adipocytes. We chose to focus on G-protein-coupled receptor (GPCR), guanylyl cyclase and phosphodiesterase regulation of adipocytes because they are the targets of a large proportion of all currently available therapeutics. Furthermore, there is a large overlap in their signaling pathways, as signaling events that raise cAMP or cGMP generally increase adipocyte lipolysis and cause changes that are commonly referred to as browning: increasing mitochondrial biogenesis, uncoupling protein 1 (UCP1) expression and respiration.

Adenosine/A2B Receptor Signaling Ameliorates the Effects of Aging and Counteracts Obesity

The combination of aging populations with the obesity pandemic results in an alarming rise in non-communicable diseases. Here, we show that the enigmatic adenosine A2B receptor (A2B) is abundantly expressed in skeletal muscle (SKM) as well as brown adipose tissue (BAT) and might be targeted to counteract age-related muscle atrophy (sarcopenia) as well as obesity. Mice with SKM-specific deletion of A2B exhibited sarcopenia, diminished muscle strength, and reduced energy expenditure (EE), whereas pharmacological A2B activation counteracted these processes. Adipose tissue-specific ablation of A2B exacerbated age-related processes and reduced BAT EE, whereas A2B stimulation ameliorated obesity. In humans, A2B expression correlated with EE in SKM, BAT activity, and abundance of thermogenic adipocytes in white fat. Moreover, A2B agonist treatment increased EE from human adipocytes, myocytes, and muscle explants. Mechanistically, A2B forms heterodimers required for adenosine signaling. Overall, adenosine/A2B signaling links muscle and BAT and has both anti-aging and anti-obesity potential.

Protein kinase G1 regulates bone regeneration and rescues diabetic fracture healing

Bone fractures are a major cause of morbidity and mortality, particularly in patients with diabetes, who have a high incidence of fractures and exhibit poor fracture healing. Coordinated expression of osteoblast-derived vascular endothelial growth factor (VEGF) and bone morphogenic proteins (BMPs) is essential for fracture repair. The NO/cGMP/protein kinase G (PKG) signaling pathway mediates osteoblast responses to estrogens and mechanical stimulation, but the pathway's role in bone regeneration is unknown. Here, we used a mouse cortical-defect model to simulate bone fractures and studied osteoblast-specific PKG1-knockout and diabetic mice. The knockout mice had normal bone microarchitecture but after injury exhibited poor bone regeneration, with decreased osteoblasts, collagen deposition, and microvessels in the bone defect area. Primary osteoblasts and tibiae from the knockout mice expressed low amounts of Vegfa and Bmp2/4 mRNAs, and PKG1 was required for cGMP-stimulated expression of these genes. Diabetic mice also demonstrated low Vegfa and Bmp2/4 expression in bone and impaired bone regeneration after injury; notably, the cGMP-elevating agent cinaciguat restored Vegfa and BMP2/4 expression and full bone healing. We conclude that PKG1 is a key orchestrator of VEGF and BMP signaling during bone regeneration and propose pharmacological PKG activation as a novel therapeutic approach to enhance fracture healing.

cGMP manipulation in cardiometabolic disease: chances and challenges

PURPOSE OF REVIEW

Cardiovascular and metabolic diseases are closely linked and commonly occur in the same patients. This review focuses on the cyclic guanosine monophosphate (cGMP) system and its crosstalk between metabolism and the cardiovascular system.

RECENT FINDINGS

Recent studies suggest that cGMP, which serves as second messenger for nitric oxide and for natriuretic peptides, improves oxidative metabolism and insulin signaling. The clinical evidence is particularly strong for the natriuretic peptide branch of the cGMP system. Clinical trials suggested improvements in insulin sensitivity and reductions in the risk of progressing to type 2 diabetes mellitus. However, further studies are needed.

SUMMARY

Enhancing cGMP signaling through nonpharmacological or pharmacological means may improve glucose metabolism in addition to affecting the cardiovascular system. However, excessive cGMP production could have significant unwanted cardiovascular and metabolic effects.

Angiotensin-(1-7) induces beige fat thermogenesis through the Mas receptor

OBJECTIVE

Angiotensin-(1-7) [Ang-(1-7)], a component of the renin angiotensin system, is a vasodilator that exerts its effects primarily through the Mas receptor. The discovery of the Mas receptor in white adipose tissue (WAT) suggests an additional role for this peptide. The aim of the present study was to assess whether Ang-(1-7) can induce the expression of thermogenic genes in white adipose tissue and increase mitochondrial respiration in adipocytes.

MATERIALS/METHODS

Stromal Vascular fraction (SVF)-derived from mice adipose tissue was stimulated for one week with Ang-(1-7), then expression of beige markers and mitochondrial respiration were assessed. Mas^+/+ and Mas^-/- mice fed a control diet or a high fat-sucrose diet (HFSD) were exposed to a short or long term infusion of Ang-(1-7) and body weight, body fat, energy expenditure, cold resistance and expression of beige markers were assessed. Also, transgenic rats overexpressing Ang-(1-7) were fed with a control diet or a high fat-sucrose diet and the same parameters were assessed. Ang-(1-7) circulating levels from human subjects with different body mass index (BMI) or age were measured.

RESULTS

Incubation of adipocytes derived from SVF with Ang-(1-7) increased the expression of beige markers. Infusion of Ang-(1-7) into lean and obese Mas^+/+mice also induced the expression of Ucp1 and some beige markers, an effect not observed in Mas^-/- mice. Mas^-/- mice had increased body weight gain and decreased cold resistance, whereas rats overexpressing Ang-(1-7) showed the opposite effects. Overexpressing rats exposed to cold developed new thermogenic WAT in the anterior interscapular area. Finally, in human subjects the higher the BMI, low circulating concentration of Ang-(1-7) levels were detected. Similarly, the circulating levels of Ang-(1-7) peptide were reduced with age.

CONCLUSION

These data indicate that Ang-(1-7) stimulates beige markers and thermogenesis via the Mas receptor, and this evidence suggests a potential therapeutic use to induce thermogenesis of WAT, particularly in obese subjects that have reduced circulating concentration of Ang-(1-7).

Human muscle pathology is associated with altered phosphoprotein profile of mitochondrial proteins in the skeletal muscle

Analysis of human muscle diseases highlights the role of mitochondrial dysfunction in the skeletal muscle. Our previous work revealed that diverse upstream events correlated with altered mitochondrial proteome in human muscle biopsies. However, several proteins showed relatively unchanged expression suggesting that post-translational modifications, mainly protein phosphorylation could influence their activity and regulate mitochondrial processes. We conducted mitochondrial phosphoprotein profiling, by proteomics approach, of healthy human skeletal muscle (n = 10) and three muscle diseases (n = 10 each): Dysferlinopathy, Polymyositis and Distal Myopathy with Rimmed Vacuoles. Healthy human muscle mitochondrial proteins displayed 253 phosphorylation sites (phosphosites), which contributed to metabolic and redox processes and mitochondrial organization etc. Electron transport chain complexes accounted for 84 phosphosites. Muscle pathologies displayed 33 hyperphosphorylated and 14 hypophorphorylated sites with only 5 common proteins, indicating varied phosphorylation profile across muscle pathologies. Molecular modelling revealed altered local structure in the phosphorylated sites of Voltage-Dependent Anion Channel 1 and complex V subunit ATP5B1. Molecular dynamics simulations in complex I subunits NDUFV1, NDUFS1 and NDUFV2 revealed that phosphorylation induced structural alterations thereby influencing electron transfer and potentially altering enzyme activity. We propose that altered phosphorylation at specific sites could regulate mitochondrial protein function in the skeletal muscle during physiological and pathological processes.

Elucidation of cGMP-dependent induction of mitochondrial biogenesis through PKG and p38 MAPK in the kidney

Previous studies have shown that cGMP increases mitochondrial biogenesis (MB). Our laboratory has determined that formoterol and LY344864, agonists of the β₂-adrenergic receptor and 5-HT_1F receptor, respectively, signal MB in a soluble guanylyl cyclase (sGC)-dependent manner. However, the pathway between cGMP and MB produced by these pharmacological agents in renal proximal tubule cells (RPTCs) and the kidney has not been determined. In the present study, we showed that treatment of RPTCs with formoterol, LY344864, or riociguat, a sGC stimulator, induces MB through protein kinase G (PKG), a target of cGMP, and p38, an associated downstream target of PKG and a regulator of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression in RPTCs. We also examined if p38 plays a role in PGC-1α phosphorylation in vivo. Administration of l-skepinone, a potent and specific inhibitor of p38α and p38β, to naïve mice inhibited phosphorylated PGC-1α localization in the nuclear fraction of the renal cortex. Taken together, we demonstrated a pathway, sGC/cGMP/PKG/p38/PGC-1α, for pharmacological induction of MB and the importance of p38 in this pathway.

cGMP-dependent protein kinase I in vascular smooth muscle cells improves ischemic stroke outcome in mice

Recent works highlight the therapeutic potential of targeting cyclic guanosine monophosphate (cGMP)-dependent pathways in the context of brain ischemia/reperfusion injury (IRI). Although cGMP-dependent protein kinase I (cGKI) has emerged as a key mediator of the protective effects of nitric oxide (NO) and cGMP, the mechanisms by which cGKI attenuates IRI remain poorly understood. We used a novel, conditional cGKI knockout mouse model to study its role in cerebral IRI. We assessed neurological deficit, infarct volume, and cerebral perfusion in tamoxifen-inducible vascular smooth muscle cell-specific cGKI knockout mice and control animals. Stroke experiments revealed greater cerebral infarct volume in smooth muscle cell specific cGKI knockout mice (males: 96 ± 16 mm3; females: 93 ± 12 mm3, mean±SD) than in all control groups: wild type (males: 66 ± 19; females: 64 ± 14), cGKI control (males: 65 ± 18; females: 62 ± 14), cGKI control with tamoxifen (males: 70 ± 8; females: 68 ± 10). Our results identify, for the first time, a protective role of cGKI in vascular smooth muscle cells during ischemic stroke injury. Moreover, this protective effect of cGKI was found to be independent of gender and was mediated via improved reperfusion. These results suggest that cGKI in vascular smooth muscle cells should be targeted by therapies designed to protect brain tissue against ischemic stroke.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.

RGS2: A multifunctional signaling hub that balances brown adipose tissue function and differentiation

Objective

Recruitment of brown adipose tissue (BAT) is a potential new strategy for increasing energy expenditure (EE) to treat obesity. G protein–coupled receptors (GPCRs) represent promising targets to activate BAT, as they are the major regulators of BAT biological function. To identify new regulators of GPCR signaling in BAT, we studied the role of Regulator of G protein Signaling 2 (RGS2) in brown adipocytes and BAT.

Methods

We combined pharmacological and genetic tools to investigate the role of RGS2 in BAT in vitro and in vivo. Adipocyte progenitors were isolated from wild-type (WT) and RGS2 knockout (RGS2−/−) BAT and differentiated to brown adipocytes. This approach was complemented with knockdown of RGS2 using lentiviral shRNAs (shRGS2). Adipogenesis was analyzed by Oil Red O staining and by determining the expression of adipogenic and thermogenic markers. Pharmacological modulators and fluorescence staining of F-acting stress fibers were employed to identify the underlying signaling pathways. In vivo, the activity of BAT was assessed by ex vivo lipolysis and by measuring whole-body EE by indirect calorimetry in metabolic cages.

Results

RGS2 is highly expressed in BAT, and treatment with cGMP—an important enhancer of brown adipocyte differentiation—further increased RGS2 expression. Loss of RGS2 strongly suppressed adipogenesis and the expression of thermogenic genes in brown adipocytes. Mechanistically, we found increased Gq/Rho/Rho kinase (ROCK) signaling in the absence of RGS2. Surprisingly, in vivo analysis revealed elevated BAT activity in RGS2-deficient mice that was caused by enhanced Gs/cAMP signaling.

Conclusion

Overall, RGS2 regulates two major signaling pathways in BAT: Gq and Gs. On the one hand, RGS2 promotes brown adipogenesis by counteracting the inhibitory action of Gq/Rho/ROCK signaling. On the other hand, RGS2 decreases the activity of BAT through the inhibition of Gs signaling and cAMP production. Thus, RGS2 might represent a stress modulator that protects BAT from overstimulation.

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RGS2 regulates brown adipose tissue (BAT) by inhibiting two major G protein-coupled receptor (GPCR) pathways – Gq and Gs.

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Deletion of RGS2 impairs the differentiation of murine brown adipocytes due to elevated Gq/Rho/ROCK signaling.

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In vivo, RGS2 knock-out mice show an increase in BAT lipolysis and whole-body energy expenditure.

The foraging Gene and Its Behavioral Effects: Pleiotropy and Plasticity

The Drosophila melanogaster foraging (for) gene is a well-established example of a gene with major effects on behavior and natural variation. This gene is best known for underlying the behavioral strategies of rover and sitter foraging larvae, having been mapped and named for this phenotype. Nevertheless, in the last three decades an extensive array of studies describing for's role as a modifier of behavior in a wide range of phenotypes, in both Drosophila and other organisms, has emerged. Furthermore, recent work reveals new insights into the genetic and molecular underpinnings of how for affects these phenotypes. In this article, we discuss the history of the for gene and its role in natural variation in behavior, plasticity, and behavioral pleiotropy, with special attention to recent findings on the molecular structure and transcriptional regulation of this gene.

Natriuretic peptide signaling is involved in the expression of oxidative metabolism-related and muscle fiber constitutive genes in the gastrocnemius muscle

Natriuretic peptides regulate cyclic guanosine monophosphate (cGMP) levels via their receptors and have various physiological effects. Natriuretic peptide receptor C (NPR-C) increases cGMP signaling by functioning as a clearance receptor. We analyzed the role of natriuretic peptides in the skeletal muscle, which increases in mass with bone elongation, of NPR-C- mice. High-fat diet (HFD)-fed NPR-C- mice exhibited obesity resistance and higher oxygen consumption. PGC1α gene expression was upregulated in the gastrocnemius muscle of HFD-fed NPR-C- mice compared with HFD-fed NPR-C+ (wild-type) mice. Gene expression of proliferator-activated receptor delta and estrogen-related receptor α, which upregulate oxidative metabolism, was increased in the gastrocnemius muscle of NPR-C- mice, irrespective of diet. Expression of myosin heavy chain 7, a component of type I slow-twitch fiber, was enhanced. Natriuretic peptide signaling may influence oxidative metabolism-related and slow-twitch fiber constitutive gene expression in the fast-twitch gastrocnemius muscle but not in slow-twitch muscles such as the soleus.

Role of cAMP and cGMP Signaling in Brown Fat

Cold-induced activation of brown adipose tissue (BAT) is mediated by norepinephrine and adenosine that are released during sympathetic nerve activation. Both signaling molecules induce an increase in intracellular levels of 3',5'-cyclic adenosine monophosphate (cAMP) in murine and human BAT. In brown adipocytes, cAMP plays a central role, because it activates lipolysis, glucose uptake, and thermogenesis. Another well-studied intracellular second messenger is 3',5'-cyclic guanosine monophosphate (cGMP), which closely resembles cAMP. Several studies have shown that intact cGMP signaling is essential for normal adipogenic differentiation and BAT-mediated thermogenesis in mice. This chapter highlights recent observations, demonstrating the physiological significance of cyclic nucleotide signaling in BAT as well as their potential to induce browning of white adipose tissue (WAT) in mice and humans.

Vasodilator-Stimulated Phosphoprotein: Regulators of Adipokines Resistin and Phenotype Conversion of Epicardial Adipocytes

Background

Endothelial dysfunction plays a central part in the pathogenesis of coronary atherosclerosis. The adipokine resistin is one of the key players in endothelial cell dysfunction. In addition, the role of epicardial fat in coronary artery endothelial dysfunction is also emphasized.

We investigated whether vasodilator-stimulated phosphoprotein (VASP) is involved in resistin-related endothelial dysfunction and the phenotype conversion of epicardial adipocytes.

Material/Methods

Cell proliferation and migration were evaluated by MTT and Transwell chamber assay, respectively. Next, we took epicardial fat samples from patients with valvular heart disease and non-coronary artery disease. Gene expression was determined by reverse transcription-quantitative polymerase chain reaction and relative abundance of the protein by Western blotting.

Results

Resistin induced endothelial proliferation and migration in a dose-dependent manner. Both resistin-induced cell proliferation and migration were effectively blocked by ablation of VASP. The brown adipose tissue-specific genes for uncoupling protein 1 (UCP-1) and PR-domain-missing16 (PRDM16) decreased, but the white adipose tissue-specific genes for resistin and RIP140 increased in VASP-deficient adipocytes compared with the LV-sicntr group. However, disruption of the Ras homolog gene family member A (RhoA) /Rho-associated kinase (ROCK) in VASP-deficient adipocytes with specific inhibitors inverted the adipocyte phenotype existing in VASP-deficient adipocytes. Furthermore, the expressions of proinflammatory cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemoattractantprotein-1 (MCP-1) in VASP-deficient adipocytes were markedly upregulated compared with the LV-sicntr group.

Conclusions

These results suggest a physiological role for VASP in coronary atherosclerosis through regulating adipokine resistin and phenotype conversion of epicardial adipose tissue.

Inhibition of the PI3K but not the MEK/ERK pathway sensitizes human glioma cells to alkylating drugs

Background

Intrinsic chemoresistance of glioblastoma (GBM) is frequently owed to activation of the PI3K and MEK/ERK pathways. These signaling cascades are tightly interconnected however the quantitative contribution of both to intrinsic resistance is still not clear. Here, we aimed at determining the activation status of these pathways in human GBM biopsies and cells and investigating the quantitative impact of both pathways to chemoresistance.

Methods

Receptor tyrosine kinase (RTK) pathways in temozolomide (TMZ) treatment naive or TMZ resistant human GBM biopsies and GBM cells were investigated by proteome profiling and immunoblotting of a subset of proteins. Resistance to drugs and RTK pathway inhibitors was assessed by MTT assays. Apoptotic rates were determined by Annexin V staining and DNA damage with comet assays and immunoblotting.

Results

We analyzed activation of RTK pathways by proteome profiling of tumor samples of patients which were diagnosed a secondary GBM and underwent surgery and patients which underwent a second surgery after TMZ treatment due to recurrence of the tumor. We observed substantial activation of the PI3K and MEK/ERK pathways in both groups. However, AKT and CREB phosphorylation was reduced in biopsies of resistant tumors while ERK phosphorylation remained unchanged. Subsequent proteome profiling revealed that multiple RTKs and downstream targets are also activated in three GBM cell lines. We then systematically describe a mechanism of resistance of GBM cell lines and human primary GBM cells to the alkylating drugs TMZ and cisplatin. No specific inhibitor of the upstream RTKs sensitized cells to drug treatment. In contrast, we were able to restore sensitivity to TMZ and cisplatin by inhibiting PI3K in all cell lines and in human primary GBM cells. Interestingly, an opposite effect was observed when we inhibited the MEK/ERK signaling cascade with two different inhibitors.

Conclusions

Temozolomide treatment naive and TMZ resistant GBM biopsies show a distinct activation pattern of the MEK/ERK and PI3K signaling cascades indicating a role of these pathways in resistance development. Both pathways are also activated in GBM cell lines, however, only the PI3K pathway seems to play a crucial role in resistance to alkylating agents and might serve as drug target for chemosensitization.

Liraglutide suppresses obesity and induces brown fat-like phenotype via Soluble Guanylyl Cyclase mediated pathway in vivo and in vitro

Strategies for driving white adipose tissue (WAT) to acquire brown-like characteristics are a promising approach to reduce obesity. Liraglutide has been reported to active brown adipose tissue (BAT) thermogenesis and WAT browning by rapid intracerebroventricular injection in mice. In this study, we investigated the effects and possible mechanisms of liraglutide on WAT browning by chronic treatment. Here, we show that liraglutide significantly decreases body weight of mice and reduces the size of white adipocytes. By quantity polymerase chain reaction, immunoblotting analysis, cell immunofluorescence or immunocytochemical staining, we found liraglutide induced WAT browning because it up-regulated lipolytic activity, BAT, as well as mitochondrial marker genes in inguinal and peripheral renal WAT. We also confirmed liraglutide induced browning of 3T3-L1 because it enhanced expression of BAT and mitochondrial specific genes. In further, we observed that, soluble guanylyl cyclase (sGC) and protein kinase G I (PKGI) were up-regulated by liraglutide in vivo and in vitro; stimulation of sGC elevated expression of BAT markers and PKGI, which suggested that liraglutide induced WAT browning via sGC-dependent pathway. Taken together, this study expands our knowledge on the mechanism of liraglutide inducing WAT browning, and provides a theoretical support for clinical usage of liraglutide on obesity treatment.

Identification of dual mechanisms mediating 5-hydroxytryptamine receptor 1F-induced mitochondrial biogenesis

Our laboratory recently made the novel observation that 5-hydroxytryptamine 1F (5-HT1F) receptor activation induces mitochondrial biogenesis (MB), the production of new, functional mitochondria, in vitro and in vivo. We sought to determine the mechanism linking the 5-HT1F receptor to MB in renal proximal tubule cells. Using LY344864 , a selective 5-HT1F receptor agonist, we determined that the 5-HT1F receptor is coupled to Gαi/o and induces MB through Gβγ-dependent activation of Akt, endothelial nitric oxide synthase (eNOS), cyclic guanosine-monophosphate (cGMP), protein kinase G (PKG), and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). We also report that the 5-HT1F receptor signals through a second, Gβγ-dependent pathway that is linked by Akt phosphorylation of Raf. In contrast to the activated Akt pathway, Raf phosphorylation reduced extracellular signal regulated kinases (ERK1/2) and foxhead box O3a (FOXO3a) phosphorylation, suppressing an inhibitory MB pathway. These results demonstrate that the 5-HT1F receptor regulates MB through Gβγ-dependent dual mechanisms that activate a stimulatory MB pathway, Akt/eNOS/cGMP/PKG/PGC-1α, while simultaneously repressing an inhibitory MB pathway, Raf/MEK/ERK/FOXO3a. Novel mechanisms of MB provide the foundation for new chemicals that induce MB to treat acute and chronic organ injuries.

Nitric oxide signalling in cardiovascular health and disease

Nitric oxide (NO) signalling has pleiotropic roles in biology and a crucial function in cardiovascular homeostasis. Tremendous knowledge has been accumulated on the mechanisms of the nitric oxide synthase (NOS)-NO pathway, but how this highly reactive, free radical gas signals to specific targets for precise regulation of cardiovascular function remains the focus of much intense research. In this Review, we summarize the updated paradigms on NOS regulation, NO interaction with reactive oxidant species in specific subcellular compartments, and downstream effects of NO in target cardiovascular tissues, while emphasizing the latest developments of molecular tools and biomarkers to modulate and monitor NO production and bioavailability.

Interplay between Obesity-Induced Inflammation and cGMP Signaling in White Adipose Tissue

Current worldwide figures suggest that obesity is pandemic. Understanding the underlying molecular mechanisms would help develop viable anti-obesity therapies. Here, we assess the influence of obesity-induced inflammation on white adipocyte cyclic guanosine monophosphate (cGMP) signaling, which is beneficial for adipocyte differentiation and thermogenesis. We find that murine gonadal and not inguinal fat is prone to obesity-induced inflammation. Correspondingly, the cGMP cascade is dysregulated in gonadal but not in inguinal fat of obese mice. Analysis of two independent human cohorts reveals a defective cGMP pathway only in visceral fat of obese subjects. Congruently, cGMP signaling is dysregulated in tumor necrosis factor α (TNF-α)-treated primary white adipocytes. TNF-α-mediated suppression of sGCβ₁ is mediated via NF-κB, whereas PKG is repressed by JNK signaling. Additionally, TNF-α-activated JNK signaling suppresses PPARγ and aP2. Taken together, the intensity of obesity-induced inflammation dictates the amplitude of cGMP signaling dysregulation in white adipocytes through distinct pathways.

Brown and Beige Adipose Tissues in Health and Disease

Brown and beige adipocytes arise from distinct developmental origins. Brown adipose tissue (BAT) develops embryonically from precursors that also give to skeletal muscle. Beige fat develops postnatally and is highly inducible. Beige fat recruitment is mediated by multiple mechanisms, including de novo beige adipogenesis and white-to-brown adipocyte transdifferentiaiton. Beige precursors reside around vasculatures, and proliferate and differentiate into beige adipocytes. PDGFRα+Ebf2+ precursors are restricted to beige lineage cells, while another PDGFRα+ subset gives rise to beige adipocytes, white adipocytes, or fibrogenic cells. White adipocytes can be reprogramed and transdifferentiated into beige adipocytes. Brown and beige adipocytes display many similar properties, including multilocular lipid droplets, dense mitochondria, and expression of UCP1. UCP1-mediated thermogenesis is a hallmark of brown/beige adipocytes, albeit UCP1-independent thermogenesis also occurs. Development, maintenance, and activation of BAT/beige fat are guided by genetic and epigenetic programs. Numerous transcriptional factors and coactivators act coordinately to promote BAT/beige fat thermogenesis. Epigenetic reprograming influences expression of brown/beige adipocyte-selective genes. BAT/beige fat is regulated by neuronal, hormonal, and immune mechanisms. Hypothalamic thermal circuits define the temperature setpoint that guides BAT/beige fat activity. Metabolic hormones, paracrine/autocrine factors, and various immune cells also play a critical role in regulating BAT/beige fat functions. BAT and beige fat defend temperature homeostasis, and regulate body weight and glucose and lipid metabolism. Obesity is associated with brown/beige fat deficiency, and reactivation of brown/beige fat provides metabolic health benefits in some patients. Pharmacological activation of BAT/beige fat may hold promise for combating metabolic diseases. © 2017 American Physiological Society. Compr Physiol 7:1281-1306, 2017.

Enhancing natriuretic peptide signaling in adipose tissue, but not in muscle, protects against diet-induced obesity and insulin resistance

In addition to controlling blood pressure, cardiac natriuretic peptides (NPs) can stimulate lipolysis in adipocytes and promote the "browning" of white adipose tissue. NPs may also increase the oxidative capacity of skeletal muscle. To unravel the contribution of NP-stimulated metabolism in adipose tissue compared to that in muscle in vivo, we generated mice with tissue-specific deletion of the NP clearance receptor, NPRC, in adipose tissue (Nprc^AKO ) or in skeletal muscle (Nprc^MKO ). We showed that, similar to Nprc null mice, Nprc^AKO mice, but not Nprc^MKO mice, were resistant to obesity induced by a high-fat diet. Nprc^AKO mice exhibited increased energy expenditure, improved insulin sensitivity, and increased glucose uptake into brown fat. These mice were also protected from diet-induced hepatic steatosis and visceral fat inflammation. These findings support the conclusion that NPRC in adipose tissue is a critical regulator of energy metabolism and suggest that inhibiting this receptor may be an important avenue to explore for combating metabolic disease.

Induction of thermogenic adipocytes: molecular targets and thermogenic small molecules

Adipose tissue is a central metabolic organ that controls energy homeostasis of the whole body. White adipose tissue (WAT) stores excess energy in the form of triglycerides, whereas brown adipose tissue (BAT) dissipates energy in the form of heat through mitochondrial uncoupling protein 1 (Ucp1). A newly identified adipose tissue called 'beige fat' (BAT-like) is produced through a process called WAT browning. This tissue mainly resides in WAT depots and displays intermediate characteristics of both WAT and BAT. Since the recent discovery of BAT in the human body, along with the identification of molecular targets for BAT activation, stimulating energy expenditure has been considered as a great strategy to treat human obesity and metabolic diseases. Here we summarize recent findings regarding molecular targets and thermogenic small molecules that can stimulate BAT and increase energy expenditure, with an emphasis on possible therapeutic applications in humans.

Nitric Oxide Regulates Skeletal Muscle Fatigue, Fiber Type, Microtubule Organization, and Mitochondrial ATP Synthesis Efficiency Through cGMP-Dependent Mechanisms

AIM

Skeletal muscle nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathways are impaired in Duchenne and Becker muscular dystrophy partly because of reduced nNOSμ and soluble guanylate cyclase (GC) activity. However, GC function and the consequences of reduced GC activity in skeletal muscle are unknown. In this study, we explore the functions of GC and NO-cGMP signaling in skeletal muscle.

RESULTS

GC1, but not GC2, expression was higher in oxidative than glycolytic muscles. GC1 was found in a complex with nNOSμ and targeted to nNOS compartments at the Golgi complex and neuromuscular junction. Baseline GC activity and GC agonist responsiveness was reduced in the absence of nNOS. Structural analyses revealed aberrant microtubule directionality in GC1^-/- muscle. Functional analyses of GC1^-/- muscles revealed reduced fatigue resistance and postexercise force recovery that were not due to shifts in type IIA-IIX fiber balance. Force deficits in GC1^-/- muscles were also not driven by defects in resting mitochondrial adenosine triphosphate (ATP) synthesis. However, increasing muscle cGMP with sildenafil decreased ATP synthesis efficiency and capacity, without impacting mitochondrial content or ultrastructure.

INNOVATION

GC may represent a new target for alleviating muscle fatigue and that NO-cGMP signaling may play important roles in muscle structure, contractility, and bioenergetics.

CONCLUSIONS

These findings suggest that GC activity is nNOS dependent and that muscle-specific control of GC expression and differential GC targeting may facilitate NO-cGMP signaling diversity. They suggest that nNOS regulates muscle fiber type, microtubule organization, fatigability, and postexercise force recovery partly through GC1 and suggest that NO-cGMP pathways may modulate mitochondrial ATP synthesis efficiency. Antioxid. Redox Signal. 26, 966-985.

Tetrahydrobiopterin activates brown adipose tissue and regulates systemic energy metabolism

Brown adipose tissue (BAT) is a central organ that acts to increase energy expenditure; its regulatory factors could be clinically useful in the treatment of obesity. Tetrahydrobiopterin (BH4) is an essential cofactor of tyrosine hydroxylase and nitric oxide synthase (NOS). Although BH4 regulates the known regulatory factors of BAT, such as noradrenaline (NA) and NO, participation of BH4 in BAT function remains unclear. In the present study, we investigate the role of BH4 in the regulation of BAT. Hph-1 mice, a mouse model of BH4 deficiency, exhibit obesity, adiposity, glucose intolerance, insulin resistance, and impaired BAT function. Impaired BAT function was ameliorated together with systemic metabolic disturbances by BAT transplantation from BH4-sufficient mice (control mice) into BH4-deficient mice, strongly suggesting that BH4-induced BAT has a critical role in the regulation of systemic energy metabolism. Both NA derived from the sympathetic nerve and NO derived from endothelial NOS in the blood vessels participate in the regulation of BH4. In addition, a direct effect of BH4 in the stimulation of brown adipocytes via NO is implicated. Taken together, BH4 activates BAT and regulates systemic energy metabolism; this suggests an approach for metabolic disorders, such as obesity and diabetes.

Regulation of white and brown adipocyte differentiation by RhoGAP DLC1

Adipose tissues constitute an important component of metabolism, the dysfunction of which can cause obesity and type II diabetes. Here we show that differentiation of white and brown adipocytes requires Deleted in Liver Cancer 1 (DLC1), a Rho GTPase Activating Protein (RhoGAP) previously studied for its function in liver cancer. We identified Dlc1 as a super-enhancer associated gene in both white and brown adipocytes through analyzing the genome-wide binding profiles of PPARγ, the master regulator of adipogenesis. We further observed that Dlc1 expression increases during differentiation, and knockdown of Dlc1 by siRNA in white adipocytes reduces the formation of lipid droplets and the expression of fat marker genes. Moreover, knockdown of Dlc1 in brown adipocytes reduces expression of brown fat-specific genes and diminishes mitochondrial respiration. Dlc1-/- knockout mouse embryonic fibroblasts show a complete inability to differentiate into adipocytes, but this phenotype can be rescued by inhibitors of Rho-associated kinase (ROCK) and filamentous actin (F-actin), suggesting the involvement of Rho pathway in DLC1-regulated adipocyte differentiation. Furthermore, PPARγ binds to the promoter of Dlc1 gene to regulate its expression during both white and brown adipocyte differentiation. These results identify DLC1 as an activator of white and brown adipocyte differentiation, and provide a molecular link between PPARγ and Rho pathways.