Mevalonate biosynthesis pathway regulates the development and survival of brown adipocytes.

The high thermogenic activity of brown adipose tissue (BAT) has received considerable attention. Here, we demonstrated the role of the mevalonate (MVA) biosynthesis pathway in the regulation of brown adipocyte development and survival. The inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in the MVA pathway and the molecular target of statins, suppressed brown adipocyte differentiation by suppressing protein geranylgeranylation-mediated mitotic clonal expansion. The development of BAT in neonatal mice exposed to statins during the fetal period was severely impaired. Moreover, statin-induced geranylgeranyl pyrophosphate (GGPP) deficiency led to the apoptosis of mature brown adipocytes. Brown adipocyte-specific Hmgcr knockout induced BAT atrophy and disrupted thermogenesis. Importantly, both genetic and pharmacological inhibition of HMGCR in adult mice induced morphological changes in BAT accompanied by an increase in apoptosis, and statin-treated diabetic mice showed worsened hyperglycemia. These findings revealed that MVA pathway-generated GGPP is indispensable for BAT development and survival.

MDMX elevation by a novel Mdmx-p53 interaction inhibitor mitigates neuronal damage after ischemic stroke.

Mdmx and Mdm2 are two major suppressor factors for the tumor suppressor gene p53. In central nervous system, Mdmx suppresses the transcriptional activity of p53 and enhances the binding of Mdm2 to p53 for degradation. But Mdmx dynamics in cerebral infarction remained obscure. Here we investigated the role of Mdmx under ischemic conditions and evaluated the effects of our developed small-molecule Protein-Protein Interaction (PPI) inhibitors, K-181, on Mdmx-p53 interactions in vivo and in vitro. We found ischemic stroke decreased Mdmx expression with increased phosphorylation of Mdmx Serine 367, while Mdmx overexpression by AAV-Mdmx showed a neuroprotective effect on neurons. The PPI inhibitor, K-181 attenuated the neurological deficits by increasing Mdmx expression in post-stroke mice brain. Additionally, K-181 selectively inhibited HDAC6 activity and enhanced tubulin acetylation. Our findings clarified the dynamics of Mdmx in cerebral ischemia and provide a clue for the future pharmaceutic development of ischemic stroke.

CRTC1 deficiency, specifically in melanocortin-4 receptor-expressing cells, induces hyperphagia, obesity, and insulin resistance.

Melanocortin-4 receptor (MC4R) is a critical regulator of appetite and energy expenditure in rodents and humans. MC4R deficiency causes hyperphagia, reduced energy expenditure, and impaired glucose metabolism. Ligand binding to MC4R activates adenylyl cyclase, resulting in increased levels of intracellular cyclic adenosine monophosphate (cAMP), a secondary messenger that regulates several cellular processes. Cyclic adenosine monophosphate responsive element-binding protein-1-regulated transcription coactivator-1 (CRTC1) is a cytoplasmic coactivator that translocates to the nucleus in response to cAMP and is reportedly involved in obesity. However, the precise mechanism through which CRTC1 regulates energy metabolism remains unknown. Additionally, there are no reports linking CRTC1 and MC4R, although both CRTC1 and MC4R are known to be involved in obesity. Here, we demonstrate that mice lacking CRTC1, specifically in MC4R cells, are sensitive to high-fat diet (HFD)-induced obesity and exhibit hyperphagia and increased body weight gain. Moreover, the loss of CRTC1 in MC4R cells impairs glucose metabolism. MC4R-expressing cell-specific CRTC1 knockout mice did not show changes in body weight gain, food intake, or glucose metabolism when fed a normal-chow diet. Thus, CRTC1 expression in MC4R cells is required for metabolic adaptation to HFD with respect to appetite regulation. Our results revealed an important protective role of CRTC1 in MC4R cells against dietary adaptation.

Stimulation of Gs signaling in MC4R cells by DREADD increases energy expenditure, suppresses food intake, and increases locomotor activity in mice.

The melanocortin 4 receptor (MC4R) plays an important role in the regulation of appetite and energy expenditure in humans and rodents. Impairment of MC4R signaling causes severe obesity. MC4R mainly couples to the G-protein Gs. Ligand binding to MC4R activates adenylyl cyclase resulting in increased intracellular cAMP levels. cAMP acts as a secondary messenger, regulating various cellular processes. MC4R can also couple with Gq and other signaling pathways. Therefore, the contribution of MC4R/Gs signaling to energy metabolism and appetite remains unclear. To study the effect of Gs signaling activation in MC4R cells on whole body energy metabolism and appetite, we generated a novel mouse strain that expresses a Gs-coupled designer receptors exclusively activated by designer drugs [Gs-DREADD (GsD)] selectively in MC4R-expressing cells (GsD-MC4R mice). Chemogenetic activation of the GsD by a designer drug [deschloroclozapine (DCZ); 0.01∼0.1 mg/kg body wt] in MC4R-expressing cells significantly increased oxygen consumption and locomotor activity. In addition, GsD activation significantly reduced the respiratory exchange ratio, promoting fatty acid oxidation, but did not affect core (rectal) temperature. A low dose of DCZ (0.01 mg/kg body wt) did not suppress food intake, but a high dose of DCZ (0.1 mg/kg body wt) suppressed food intake in MC4R-GsD mice, although either DCZ dose (0.01 or 0.1 mg/kg body wt) did not affect food intake in the control mice. In conclusion, the current study demonstrated that the stimulation of Gs signaling in MC4R-expressing cells increases energy expenditure and locomotor activity and suppresses appetite.NEW & NOTEWORTHY We report that Gs signaling in melanocortin 4 receptor (MC4R)-expressing cells regulates energy expenditure, appetite, and locomotor activity. These findings shed light on the mechanism underlying the regulation of energy metabolism and locomotor activity by MC4R/cAMP signaling.

Disruption of CRTC1 and CRTC2 in Sim1 cells strongly increases high-fat diet intake in female mice but has a modest impact on male mice.

cAMP responsive element binding protein (CREB)-regulated transcription coactivators (CRTCs) regulate gene transcription in response to an increase in intracellular cAMP or Ca2+ levels. To date, three isoforms of CRTC have been identified in mammals. All CRTCs are widely expressed in various regions of the brain. Numerous studies have shown the importance of CREB and CRTC in energy homeostasis. In the brain, the paraventricular nucleus of the hypothalamus (PVH) plays a critical role in energy metabolism, and CRTC1 and CRTC2 are highly expressed in PVH neuronal cells. The single-minded homolog 1 gene (Sim1) is densely expressed in PVH neurons and in some areas of the amygdala neurons. To determine the role of CRTCs in PVH on energy metabolism, we generated mice that lacked CRTC1 and CRTC2 in Sim1 cells using Sim-1 cre mice. We found that Sim1 cell-specific CRTC1 and CRTC2 double-knockout mice were sensitive to high-fat diet (HFD)-induced obesity. Sim1 cell-specific CRTC1 and CRTC2 double knockout mice showed hyperphagia specifically for the HFD, but not for the normal chow diet, increased fat mass, and no change in energy expenditure. Interestingly, these phenotypes were stronger in female mice than in male mice, and a weak phenotype was observed in the normal chow diet. The lack of CRTC1 and CRTC2 in Sim1 cells changed the mRNA levels of some neuropeptides that regulate energy metabolism in female mice fed an HFD. Taken together, our findings suggest that CRTCs in Sim1 cells regulate gene expression and suppress excessive fat intake, especially in female mice.

Identification of G protein-coupled receptor 55 (GPR55) as a target of curcumin.

The identification of molecular targets of bioactive food components is important to understand the mechanistic aspect of their physiological functions. Here, we have developed a screening system that enables us to determine the activation of G protein-coupled receptors (GPCRs) by food components and have identified GPR55 as a target for curcumin. Curcumin activated GPR55 and induced serum-response element- and serum-response factor-mediated transcription, which were inhibited by Rho kinase and GPR55 antagonists. Both the methoxy group and the heptadienone moiety of curcumin were required for GPR55 activation. The F1905.47 residue of GPR55 was important for the interaction with curcumin. The curcumin-induced secretion of glucagon-like peptide-1 in GLUTag cells was inhibited by a GPR55 antagonist. These results indicate that expression screening is a useful system to identify GPCRs as targets of food components and strongly suggest that curcumin activates GPR55 as an agonist, which is involved in the physiological function of curcumin.

A mouse model of weight gain after nicotine withdrawal.

Smoking cessation increases body weight. The underlying mechanisms, however, have not been fully understood. We here report an establishment of a mouse model that exhibits an augmented body weight gain after nicotine withdrawal. High fat diet-fed mice were infused with nicotine for two weeks, and then with vehicle for another two weeks using osmotic minipumps. Body weight increased immediately after nicotine cessation and was significantly higher than that of mice continued on nicotine. Mice switched to vehicle consumed more food than nicotine-continued mice during the first week of cessation, while oxygen consumption was comparable. Elevated expression of orexigenic agouti-related peptide was observed in the hypothalamic appetite center. Pair-feeding experiment revealed that the accelerated weight gain after nicotine withdrawal is explained by enhanced energy intake. As a showcase of an efficacy of pharmacologic intervention, exendin-4 was administered and showed a potent suppression of energy intake and weight gain in mice withdrawn from nicotine. Our current model provides a unique platform for the investigation of the changes of energy regulation after smoking cessation.

MiRNA-132/212 regulates tight junction stabilization in blood-brain barrier after stroke.

MicroRNA-132/212 has been supposed as a critical gene related to the blood-brain barrier (BBB) protection after stroke, but its regulation pathway including the upstream regulator and downstream targets is still unclear. Herein, we demonstrated the cAMP response element-binding protein (CREB)-regulated transcription coactivator-1 (CRTC1) to be the upstream regulator of miRNA-132/212 using CRTC1 knockout and wild-type mice. CRTC1 deletion led to the reduction of miRNA-132/212 expression in mice brain after ischemic stroke, significantly increased infarct volume, and aggravated BBB permeability with worsening neurological deficits. Furthermore, we identified that miRNA-132 repressed Claudin-1, tight junction-associated protein-1 (TJAP-1), and RNA-binding Fox-1 (RBFox-1) by directly binding to their respective 3'-untranslated regions, which alleviated the ischemic damage by enhancing neuronal survival and BBB integrity. Moreover, the co-culture of endothelial cells with CRTC1-deficient neurons aggravated the cell vulnerability to hypoxia, also supporting the idea that miRNA-132/212 cluster is regulated by CRTC1 and acts as a crucial role in the mitigation of ischemic damage. This work is a step forward for understanding the role of miRNA-132/212 in neurovascular interaction and may be helpful for potential gene therapy of ischemic stroke.

Activation of the adipocyte CREB/CRTC pathway in obesity.

Obesity is a major risk factor for the development of type II diabetes. Increases in adipose tissue mass trigger insulin resistance via the release of pro-inflammatory cytokines from adipocytes and macrophages. CREB and the CRTC coactivators have been found to promote insulin resistance in obesity, although the mechanism is unclear. Here we show that high fat diet feeding activates the CREB/CRTC pathway in adipocytes by decreasing the expression of SIK2, a Ser/Thr kinase that phosphorylates and inhibits CRTCs. SIK2 levels are regulated by the adipogenic factor C/EBPα, whose expression is reduced in obesity. Exposure to PPARγ agonist rescues C/EBPα expression and restores SIK2 levels. CRTC2/3 promote insulin resistance via induction of the chemokines CXCL1/2. Knockout of CRTC2/3 in adipocytes reduces CXCL1/2 expression and improves insulin sensitivity. As administration of CXCL1/2 reverses salutary effects of CRTC2/3 depletion, our results demonstrate the importance of the CREB/CRTC pathway in modulating adipose tissue function.

Loss of CREB Coactivator CRTC1 in SF1 Cells Leads to Hyperphagia and Obesity by High-fat Diet But Not Normal Chow Diet.

Cyclic adenosine monophosphate responsive element-binding protein-1-regulated transcription coactivator-1 (CRTC1) is a cytoplasmic coactivator that translocates to the nucleus in response to cyclic adenosine monophosphate. Whole-body knockdown of Crtc1 causes obesity, resulting in increased food intake and reduced energy expenditure. CRTC1 is highly expressed in the brain; therefore, it might play an important role in energy metabolism via the neuronal pathway. However, the precise mechanism by which CRTC1 regulates energy metabolism remains unknown. Here, we showed that mice lacking CRTC1, specifically in steroidogenic factor-1 expressing cells (SF1 cells), were sensitive to high-fat diet (HFD)-induced obesity, exhibiting hyperphagia and increased body weight gain. The loss of CRTC1 in SF1 cells impaired glucose metabolism. Unlike whole-body CRTC1 knockout mice, SF1 cell-specific CRTC1 deletion did not affect body weight gain or food intake in normal chow feeding. Thus, CRTC1 in SF1 cells is required for normal appetite regulation in HFD-fed mice. CRTC1 is primarily expressed in the brain. Within the hypothalamus, which plays an important role for appetite regulation, SF1 cells are only found in ventromedial hypothalamus. RNA sequencing analysis of microdissected ventromedial hypothalamus samples revealed that the loss of CRTC1 significantly changed the expression levels of certain genes. Our results revealed the important protective role of CRTC1 in SF1 cells against dietary metabolic imbalance.

microRNA-33 maintains adaptive thermogenesis via enhanced sympathetic nerve activity.

Adaptive thermogenesis is essential for survival, and therefore is tightly regulated by a central neural circuit. Here, we show that microRNA (miR)-33 in the brain is indispensable for adaptive thermogenesis. Cold stress increases miR-33 levels in the hypothalamus and miR-33-/- mice are unable to maintain body temperature in cold environments due to reduced sympathetic nerve activity and impaired brown adipose tissue (BAT) thermogenesis. Analysis of miR-33f/f dopamine-ß-hydroxylase (DBH)-Cre mice indicates the importance of miR-33 in Dbh-positive cells. Mechanistically, miR-33 deficiency upregulates gamma-aminobutyric acid (GABA)A receptor subunit genes such as Gabrb2 and Gabra4. Knock-down of these genes in Dbh-positive neurons rescues the impaired cold-induced thermogenesis in miR-33f/f DBH-Cre mice. Conversely, increased gene dosage of miR-33 in mice enhances thermogenesis. Thus, miR-33 in the brain contributes to maintenance of BAT thermogenesis and whole-body metabolism via enhanced sympathetic nerve tone through suppressing GABAergic inhibitory neurotransmission. This miR-33-mediated neural mechanism may serve as a physiological adaptive defense mechanism for several stresses including cold stress.

Wheat-ghretropins: novel ghrelin-releasing peptides derived from wheat protein.

Ghrelin is an endogenous orexigenic hormone mainly produced by stomach cells and is reported to influence appetite, gastrointestinal motility and growth hormone secretion. We observed that enzymatic digest of wheat gluten stimulated ghrelin secretion from mouse ghrelinoma 3-1, a ghrelin-releasing cell line. Further on, we characterized the ghrelin-releasing peptides present in the digest by comprehensive peptide analysis using liquid chromatography-mass spectrometry and structure-activity relationship. Among the candidate peptides, we found that SQQQQPVLPQQPSF, LSVTSPQQVSY and YPTSL stimulated ghrelin release. We then named them wheat-ghretropin A, B and C, respectively. In addition, we observed that wheat-ghretropin A increased plasma ghrelin concentration and food intake in mice after oral administration. Thus, we demonstrated that wheat-ghretropin stimulates ghrelin release both in vitro and in vivo. To the best of our knowledge, this is the first report of a wheat-derived exogenous bioactive peptide that stimulates ghrelin secretion.

A milk-derived pentapeptide reduces blood pressure in advanced hypertension in a CCK system-dependent manner.

We recently found that a peptide that activates the cholecystokinin (CCK) system effectively reduces blood pressure in spontaneously hypertensive rats (SHR) after the development of hypertension, after which hypotensive drugs are sometimes less effective. In this study, we investigated the vasorelaxation and antihypertensive effects of a peptide derived from a milk protein in SHR with advanced hypertension. The vasorelaxing activity was measured using the mesenteric artery isolated from SHR and the systemic blood pressure was measured by the tail-cuff method. KFWGK was released from bovine serum albumin (BSA) and the model peptide after subtilisin digestion. KFWGK relaxed the mesenteric artery and this vasorelaxation activity was inhibited by lorglumide, an antagonist of the CCK1 receptor. KFWGK more potently relaxed the artery from advanced-stage SHR than that from early-stage SHR. Orally administered KFWGK exhibited potent and long-lasting antihypertensive effects in SHR after the development of hypertension (the minimum effective dose was 5 µg kg-1). The KFWGK-induced antihypertensive effects were also blocked by a CCK antagonist, suggesting that it activates the CCK system. In conclusion, KFWGK, a CCK-dependent vasorelaxant peptide, exhibited potent antihypertensive effects in SHR after the development of hypertension.

CREB Coactivator CRTC2 Plays a Crucial Role in Endothelial Function.

The cAMP pathway is known to stabilize endothelial barrier function and maintain vascular physiology. The family of cAMP-response element binding (CREB)-regulated transcription coactivators (CRTC)1-3 activate transcription by targeting the basic leucine zipper domain of CREB. CRTC2 is a master regulator of glucose metabolism in liver and adipose tissue. However, the role of CRTC2 in endothelium remains unknown. The aim of this study was to evaluate the effect of CRTC2 on endothelial function. We focused the effect of CRTC2 in endothelial cells and its relationship with p190RhoGAP-A. We examined the effect of CRTC2 on endothelial function using a mouse aorta ring assay ex vivo and with photothrombotic stroke in endothelial cell-specific CRTC2-knock-out male mice in vivo CRTC2 was highly expressed in endothelial cells and related to angiogenesis. Among CRTC1-3, only CRTC2 was activated under ischemic conditions at endothelial cells, and CRTC2 maintained endothelial barrier function through p190RhoGAP-A expression. Ser171 was a pivotal regulatory site for CRTC2 intracellular localization, and Ser307 functioned as a crucial phosphorylation site. Endothelial cell-specific CRTC2-knock-out mice showed reduced angiogenesis ex vivo, exacerbated stroke via endothelial dysfunction, and impaired neurologic recovery via reduced vascular beds in vivo These findings suggest that CRTC2 plays a crucial protective role in vascular integrity of the endothelium via p190RhoGAP-A under ischemic conditions.SIGNIFICANCE STATEMENT Previously, the role of CRTC2 in endothelial cells was unknown. In this study, we firstly clarified that CRTC2 was expressed in endothelial cells and among CRTC1-3, only CRTC2 was related to endothelial function. Most importantly, only CRTC2 was activated under ischemic conditions at endothelial cells and maintained endothelial barrier function through p190RhoGAP-A expression. Ser307 in CRTC2 functioned as a crucial phosphorylation site. Endothelial cell-specific CRTC2-knock-out mice showed reduced angiogenesis ex vivo, exacerbated stroke via endothelial dysfunction, and impaired neurologic recovery via reduced vascular beds in vivo These results suggested that CRTC2 maybe a potential therapeutic target for reducing blood-brain barrier (BBB) damage and improving recovery.

Food texture affects glucose tolerance by altering pancreatic ß-cell function in mice consuming high-fructose corn syrup.

The incidence of metabolic diseases, such as type 2 diabetes, has increased steadily worldwide. Diet, beverages, and food texture can all markedly influence these metabolic disorders. However, the combined effects of food texture and beverages on energy metabolism remains unclear. In the present study, we examined the effect of food texture on energy metabolism in mice administered high-fructose corn syrup (HFCS). Mice were fed a soft or hard diet along with 4.2% HFCS or tap water. Body weight and total caloric intake were not affected by food texture irrespective of HFCS consumption. However, caloric intake from HFCS (i.e., drinking volume) and diet were higher and lower, respectively, in the hard food group than in the soft food group. The hard food group's preference for HFCS was absent in case of mice treated with the µ-opioid receptor antagonist naltrexone. Despite increased HFCS consumption, blood glucose levels were lower in the hard-diet group than in the soft-diet group. In HFCS-fed mice, insulin levels after glucose stimulation and insulin content in the pancreas were higher in the hard food group than the soft food group, whereas insulin tolerance did not differ between the groups. These food texture-induced differences in glucose tolerance were not observed in mice fed tap water. Thus, food texture appears to affect glucose tolerance by influencing pancreatic ß-cell function in HFCS-fed mice. These data shed light on the combined effects of eating habits and food texture on human health.

Ser-Tyr and Asn-Ala, vasorelaxing dipeptides found by comprehensive screening, reduce blood pressure via different age-dependent mechanisms.

To understand the changes in physiological responses due to aging, a number of bioactive probes based on different signal transduction pathways are necessary. In this study, we comprehensively and systematically investigated changes in blood vessel function with age using a 336-dipeptide library. In the early stage of hypertension, the most potent vasorelaxant dipeptide was Ser-Tyr (SY) in the mesenteric artery isolated from spontaneously hypertensive rats (SHR). SY-induced vasorelaxation and anti-hypertensive effects were blocked by L-NAME, an inhibitor of nitric oxide synthase (NOS), suggesting that SY activates the NO system. On the other hand, the patterns of dipeptides with vasorelaxation activity in early and advanced stages of hypertension were different. In the advanced stage, the most potent vasorelaxing dipeptide was Asn-Ala (NA). Orally administered NA (1.5 mg/kg) reduced the blood pressure in the advanced stage, at which drugs were sometimes less effective, and the anti-hypertensive effects lasted for 6 hr. The NA-induced vasorelaxation and anti-hypertensive activity was blocked by lorglumide, an antagonist of the cholecystokinin CCK1 receptor, suggesting that NA activated the CCK system. Taken together, in the early and advanced stages of hypertension, SY and NA exhibited vasorelaxing and anti-hypertensive effects via the NO and CCK systems, respectively.

Orally administered milk-derived tripeptide improved cognitive decline in mice fed a high-fat diet.

The functions of the brain, which is thought of as an organ highly independent from the periphery, are often affected by the peripheral environment. Indeed, epidemiologic studies demonstrated that diabetes was a risk factor for dementia. It was also reported that the intake of dairy products, such as milk, reduces the risk of developing dementia. We found that mice on a short-term high-fat diet (HFD) for 1 wk had reduced cognitive function. Thus, using this acute model, we investigated the effects of milk-derived peptide on cognitive decline induced by HFD. Tyr-Leu-Gly (YLG), a tripeptide derived from αS1-casein, a major bovine milk protein, is released by gastrointestinal proteases. We found that orally administered YLG improved cognitive decline induced by 1-wk HFD intake in the object recognition test. YLG also improved cognitive decline in the object location test. Thus, we found that YLG improved cognitive decline induced by HFD. Next, we examined the effects of YLG on the hippocampus, a brain area essential for cognitive function. HFD intake decreased the number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells, and this decrease was improved by YLG administration. HFD intake decreased nerve growth factor (NGF) and glial cell line-derived neurotrophic factor, whereas YLG increased NGF and ciliary neurotrophic factor, suggesting that these neurotropic factors play a role in hippocampal neurogenesis after YLG administration. In conclusion, we demonstrated that 1-wk HFD reduced cognitive function. Furthermore, we found that YLG, a milk-derived tripeptide, improved cognitive decline in mice on HFD. The HFD reduced neural stem cell proliferation, and YLG improved this reduction. YLG is the first reported milk peptide to improve cognitive decline induced by HFD intake.-Nagai, A., Mizushige, T., Matsumura, S., Inoue, K., Ohinata, K. Orally administered milk-derived tripeptide improved cognitive decline in mice fed a high-fat diet.

Comprehensive analysis of a dipeptide library to identify ghrelin release-modulating peptides.

We performed a comprehensive analysis of ghrelin release-modulating activity of a dipeptide library using MGN3-1, a ghrelin-producing cell line. We found that most dipeptides suppress ghrelin secretion, whereas the N-terminal Ser-containing dipeptides and a few others stimulate it. N-terminal amino acid residues, but not C-terminal residues, play a dominant role in the effects of dipeptides. Among dipeptides, Leu-Ile (LI) and Ser-Val (SV) most strongly suppress and stimulate ghrelin secretion, respectively. LI activates Gi signaling and SV acts via the MAPK pathway. Orally administered LI and SV reduce and increase plasma ghrelin levels and food intake in mice, respectively. In conclusion, LI and SV, found based on the comprehensive screening of a dipeptide library, modulate ghrelin secretion in vitro and in vivo.

ß-arrestin-2 in PAR-1-biased signaling has a crucial role in endothelial function via PDGF-ß in stroke.

Thrombin aggravates ischemic stroke and activated protein C (APC) has a neuroprotective effect. Both proteases interact with protease-activated receptor 1, which exhibits functional selectivity and leads to G-protein- and ß-arrestin-mediated-biased signal transduction. We focused on the effect of ß-arrestin in PAR-1-biased signaling on endothelial function after stroke or high-fat diet (HFD). Thrombin had a rapid disruptive effect on endothelial function, but APC had a slow protective effect. Paralleled by prolonged MAPK 42/44 signaling activation by APC via ß-arrestin-2, a lower cleavage rate of PAR-1 for APC than thrombin was quantitatively visualized by bioluminescence video imaging. HFD-fed mice showed lower ß-arrestin-2 levels and more severe ischemic injury. The expression of ß-arrestin-2 in capillaries and PDGF-ß secretion in HFD-fed mice were reduced in penumbra lesions. These results suggested that ß-arrestin-2-MAPK-PDGF-ß signaling enhanced protection of endothelial function and barrier integrity after stroke.

Chronic high corticosterone with voluntary corn oil ingestion induces significant body weight gain in mice.

Corticosterone (CORT) is a powerful regulator of energy metabolism, and chronically high CORT levels cause obesity and diabetes in mice. It is reported that a chronically high CORT level changes food preference, increasing the intake of comfort foods such as fatty foods. Previously, we demonstrated that unlike a high fat diet, voluntary ingestion of 100% pure corn oil increased energy expenditure and thermogenesis through the activation of the interscapular brown adipose tissue (IBAT). In the present study, we investigated whether chronically high CORT affected corn oil intake, energy expenditure, and body weight gain. We delivered CORT to mice via water bottles and placed corn oil in a separate drinking bottle in the home cage. Voluntary corn oil ingestion with CORT induced significant body weight gain, while corn oil ingestion or CORT alone had a modest effect. CORT increased corn oil intake without reducing chow intake, which further increased the total daily caloric intake. CORT suppressed mRNA related to thermogenesis in IBAT. In the hypothalamus, CORT upregulated mRNA expression of the orexigenic neuropeptide, agouti-related protein. These data suggest that chronically high CORT might increase the desire to consume dietary fat, suppressing BAT function, thereby causing obesity.