Gallic acid is a dual α/ß-secretase modulator that reverses cognitive impairment and remediates pathology in Alzheimer mice.

Several plant-derived compounds have demonstrated efficacy in pre-clinical Alzheimer's disease (AD) rodent models. Each of these compounds share a gallic acid (GA) moiety, and initial assays on this isolated molecule indicated that it might be responsible for the therapeutic benefits observed. To test this hypothesis in a more physiologically relevant setting, we investigated the effect of GA in the mutant human amyloid ß-protein precursor/presenilin 1 (APP/PS1) transgenic AD mouse model. Beginning at 12 months, we orally administered GA (20 mg/kg) or vehicle once daily for 6 months to APP/PS1 mice that have accelerated Alzheimer-like pathology. At 18 months of age, GA therapy reversed impaired learning and memory as compared with vehicle, and did not alter behavior in nontransgenic littermates. GA-treated APP/PS1 mice had mitigated cerebral amyloidosis, including brain parenchymal and cerebral vascular ß-amyloid deposits, and decreased cerebral amyloid ß-proteins. Beneficial effects co-occurred with reduced amyloidogenic and elevated nonamyloidogenic APP processing. Furthermore, brain inflammation, gliosis, and oxidative stress were alleviated. We show that GA simultaneously elevates α- and reduces ß-secretase activity, inhibits neuroinflammation, and stabilizes brain oxidative stress in a pre-clinical mouse model of AD. We further demonstrate that GA increases abundance of a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10, Adam10) proprotein convertase furin and activates ADAM10, directly inhibits ß-site APP cleaving enzyme 1 (BACE1, Bace1) activity but does not alter Adam10 or Bace1 transcription. Thus, our data reveal novel post-translational mechanisms for GA. We suggest further examination of GA supplementation in humans will shed light on the exciting therapeutic potential of this molecule.

Murine osteoclasts secrete serine protease HtrA1 capable of degrading osteoprotegerin in the bone microenvironment.

Osteoclasts are multinucleated cells responsible for bone resorption. The differentiation of osteoclasts from bone marrow macrophages (BMMs) is induced by receptor activator of NF-κB ligand (RANKL). Osteoprotegerin (OPG), a decoy receptor of RANKL, inhibits osteoclastogenesis by blocking RANKL signaling. Here we investigated the degradation of OPG in vitro. Osteoclasts, but not BMMs, secreted OPG-degrading enzymes. Using mass spectrometry and RNA-sequencing analysis, we identified high-temperature requirement A serine peptidase 1 (HtrA1) as an OPG-degrading enzyme. HtrA1 did not degrade OPG pre-reduced by dithiothreitol, suggesting that HtrA1 recognizes the three-dimensional structure of OPG. HtrA1 initially cleaved the amide bond between leucine 90 and glutamine 91 of OPG, then degraded OPG into small fragments. Inhibitory activity of OPG on RANKL-induced osteoclastogenesis was suppressed by adding HtrA1 in RAW 264.7 cell cultures. These results suggest that osteoclasts potentially prepare a microenvironment suitable for osteoclastogenesis. HtrA1 may be a novel drug target for osteoporosis.

Elovl6 Deficiency Improves Glycemic Control in Diabetic db/db Mice by Expanding ß-Cell Mass and Increasing Insulin Secretory Capacity.

Dysfunctional fatty acid (FA) metabolism plays an important role in the pathogenesis of ß-cell dysfunction and loss of ß-cell mass in type 2 diabetes (T2D). Elovl6 is a microsomal enzyme that is responsible for converting C16 saturated and monounsaturated FAs into C18 species. We previously showed that Elovl6 played a critical role in the development of obesity-induced insulin resistance by modifying FA composition. To further define its role in T2D development, we assessed the effects of Elovl6 deletion in leptin receptor-deficient C57BL/KsJ db/db mice, a model of T2D. The db/db;Elovl6-/- mice had a markedly increased ß-cell mass with increased proliferation and decreased apoptosis, an adaptive increase in insulin, and improved glycemic control. db/db islets were characterized by a prominent elevation of oleate (C18:1n-9), cell stress, and inflammation, which was completely suppressed by Elovl6 deletion. As a mechanistic ex vivo experiment, isolated islets from Elovl6-/- mice exhibited reduced susceptibility to palmitate-induced inflammation, endoplasmic reticulum stress, and ß-cell apoptosis. In contrast, oleate-treated islets resulted in impaired glucose-stimulated insulin secretion with suppressed related genes irrespective of the Elovl6 gene. Taken together, Elovl6 is a fundamental factor linking dysregulated lipid metabolism to ß-cell dysfunction, islet inflammation, and ß-cell apoptosis in T2D, highlighting oleate as the potential culprit of ß-cell lipotoxicity.

Gene expression profile of the neonatal female mouse brain after administration of testosterone propionate.

INTRODUCTION: Clinical care decisions for peripubertal adolescents with gender dysphoria (GD) should be made carefully. Furthermore, the identification of biomarkers is very important for rapid and accurate diagnosis of GD in young people. AIM: The aim of this study was to investigate gene expression profiles during masculinization of the neonatal female mouse brain by testosterone and to identify biomarkers related to GD. METHODS: Microarray analysis was performed using RNAs extracted from the brains of neonatal mice treated by intraperitoneal injection of testosterone propionate during the sexual determination period. Sequence motif enrichment analysis for sex hormone receptor responsive elements was performed for the flanking regions of genes that showed significant expression changes following administration of testosterone propionate. MAIN OUTCOME MEASURES: We revealed a gene set with marked changes in expression during brain masculinization of neonatal female mice following administration of testosterone propionate. RESULTS: We identified 334 genes that showed differential expression in the masculinized neonatal female brain after testosterone propionate treatment. Interestingly, most of these genes are not reported to be expressed in a sexually dimorphic manner. Moreover, sequence motif enrichment analysis suggested that masculinization of the neonatal female brain by testosterone was controlled more by estrogen receptors than androgen receptors. CONCLUSIONS: Differences in genes that are expressed differentially following administration of testosterone injection from known sexually dimorphic genes suggest that many GD-related genes are upregulated during female brain masculinization. The gene set identified in this study provides a basis to better understand the mechanisms of GD and delineate its associated biomarkers.

Ablation of Elovl6 protects pancreatic islets from high-fat diet-induced impairment of insulin secretion.

ELOVL family member 6, elongation of very long-chain fatty acids (Elovl6) is a microsomal enzyme that regulates the elongation of C12-16 saturated and monounsaturated fatty acids and is related to the development of obesity-induced insulin resistance via the modification of the fatty acid composition. In this study, we investigated the role of systemic Elovl6 in the pancreatic islet and ß-cell function. Elovl6 is expressed in both islets and ß-cell lines. In mice fed with chow, islets of the Elovl6(-/-) mice displayed normal architecture and ß-cell mass compared with those of the wild-type mice. However, when fed a high-fat, high-sucrose (HFHS) diet, the islet hypertrophy in response to insulin resistance observed in normal mice was attenuated and glucose-stimulated insulin secretion (GSIS) increased in the islets of Elovl6(-/-) mice compared with those of the wild-type mice. Enhanced GSIS in the HFHS Elovl6(-/-) islets was associated with an increased ATP/ADP ratio and the suppression of ATF-3 expression. Our findings suggest that Elovl6 could be involved in insulin secretory capacity per ß-cell and diabetes.

SPARC is a major secretory gene expressed and involved in the development of proliferative diabetic retinopathy.

AIM: Neovascularization is an important event in proliferative diabetic retinopathy (PDR), where various secretory proteins including multiple growth factors are considered to be involved in this process. We searched for secretory proteins expressed in a surgical specimen obtained from the eyes of patients with PDR. METHODS: We developed the oligo-cap signal sequence trap (SST) strategy which enables us to screen for secretory or membrane proteins from a minimal starting material. Using this method, we were able to screen a cDNA library constructed from a surgical specimen obtained from the eyes of the patients with PDR. RESULTS: Majority of the cloned cDNAs turned out to encode secreted protein acidic and rich in cystein (SPARC), strongly suggesting that SPARC is highly expressed in PDR. Analysis of vitreous fluid from various patients has shown that the concentration of SPARC protein is increased in patients with PDR. Furthermore, subretinal injection of recombinant SPARC adenovirus induced PDR-like changes in the rat eye. CONCLUSIONS: Our results strongly suggested that SPARC is involved in the development of diabetic retinopathy (DR).

Identification of ISG12b as a putative interferon-inducible adipocytokine which is highly expressed in white adipose tissue.

AIM: A number of adipocytokines have been suggested to be involved in the disruption of glucose metabolism, and also in the development of various diabetic complications. We attempted to identify and analyze additional adipocytokines, to better understanding the roles of adipocytes and adipocytokines. METHODS: An oligo-capping signal sequence trap, developed in our laboratory for screening the cDNAs of secretory proteins, was used to sreen cDNAs expressed in mouse white adipose tissue. Profiles of the genes identified in mice and cultured cells were further investigated by northern blotting and luciferase assay. RESULTS: A cDNA fragment of interferon-stimulated gene 12b (ISG12b) was obtained in the search. A northern blot analysis revealed ISG12b to be highly expressed in white adipose tissue. Interferon alpha (IFNalpha) was shown to induce ISG12b expression in the adipose tissue of BL6 mice in vivo, and also in a 3T3-L1 preadipocyte cell line in vitro. The level of ISG12b was higher in mature adipocytes than in preadipocytes. A promoter analysis demonstrated that the 369bp upstream from the transcription initiation site of ISG12b mRNA contain strong promoter activity, and the interferon-stimulated response elements (ISREs) were not present within the 5593bp upstream region. CONCLUSION: ISG12b is an additional candidate for a adipocytokine induced to express in adipose tissue by interferon.

Granuphilin is activated by SREBP-1c and involved in impaired insulin secretion in diabetic mice.

Granuphilin is a crucial component of the docking machinery of insulin-containing vesicles to the plasma membrane. Here, we show that the granuphilin promoter is a target of SREBP-1c, a transcription factor that controls fatty acid synthesis, and MafA, a beta cell differentiation factor. Potassium-stimulated insulin secretion (KSIS) was suppressed in islets with adenoviral-mediated overexpression of granuphilin and enhanced in islets with knockdown of granuphilin (in which granuphilin had been knocked down). SREBP-1c and granuphilin were activated in islets from beta cell-specific SREBP-1c transgenic mice, as well as in several diabetic mouse models and normal islets treated with palmitate, accompanied by a corresponding reduction in insulin secretion. Knockdown- or knockout-mediated ablation of granuphilin or SREBP-1c restored KSIS in these islets. Collectively, our data provide evidence that activation of the SREBP-1c/granuphilin pathway is a potential mechanism for impaired insulin secretion in diabetes, contributing to beta cell lipotoxicity.

The effect of exercise training on adiponectin receptor expression in KKAy obese/diabetic mice.

Adiponectin is an adipocyte-derived factor that plays a pivotal role in lipid and glucose metabolism. Recently, two types of adiponectin receptors (AdipoR1 and AdipoR2) were identified. We investigated whether exercise training (ET) or dietary restriction (DR) affects the expression of adiponectin receptors in skeletal muscle and liver, thereby improving glucose and lipid metabolism in KKAy mice. KKAy mice were subjected to 8 weeks of exercise training or food restriction. Following the experimental protocol, an intravenous glucose tolerance test and an intraperitoneal insulin tolerance test were performed in addition to the measurement of blood lipid and adiponectin concentrations. The mRNA levels of adiponectin, adiponectin receptors and genes that are putatively regulated by the adiponectin receptors were also analyzed. Both the 8-week exercise training and food restriction protocol improved insulin resistance in KKAy mice but did not alter plasma adiponectin concentration nor its mRNA expression. In comparison with C57BL/6 mice, AdipoR1 expression level was significantly decreased in skeletal muscle and AdipoR2 expression level was significantly increased in the liver in KKAy mice. After the 8-week experimental protocol, the expression level of AdipoR1 mRNA was approximately 1.8-fold greater in the skeletal muscle and 1.3-fold greater in the liver, and the level of AdipoR2 mRNA was 30% less in the liver of the ET group as compared with the control group. Additionally, in the ET group, mRNA expression of acyl coenzyme A-oxidase and carnitine palmitoyl transferase 1 (CPT1) was greater in the liver but not in skeletal muscle. In contrast, no significant changes were observed in the expression of genes encoding the adiponectin receptors in addition to other genes except for CPT1 in the DR group. These findings suggest that chronic exercise training affects the expression level of adiponectin receptors thereby improving insulin resistance in KKAy mice.

Antioxidants and an inhibitor of advanced glycation ameliorate death of retinal microvascular cells in diabetic retinopathy.

BACKGROUND: Pericyte ghosts and acellular capillaries are well known as early histological changes resulting from diabetic retinopathy. These histological changes mean that the cell death of retinal microvessels has accelerated. It was reported that apoptosis of retinal microvascular cells (RMCs) was increased in diabetic patients. Therefore, we investigated apoptosis of RMCs in Goto-Kakizaki (GK) rats, a type 2 diabetic model, and involvement with antioxidants (a combination of vitamins C and E) or a novel inhibitor of advanced glycation, OPB-9195. METHODS: GK rats were treated with the antioxidants combination or OPB-9195 for 36 weeks. We obtained isolated preparations of the vascular network from their retinas by trypsin digestion. Apoptosis of retinal vascular cells was detected with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. RESULTS: We found that apoptosis of RMCs was increased in the diabetic GK rats. Furthermore, a combination of vitamins C and E and an advanced glycation end-products inhibitor mostly inhibited this increased apoptosis. CONCLUSIONS: We concluded that apoptosis of RMCs was a good marker that indicates the progression of diabetic retinopathy in GK rats. Both oxidative stress and the accumulation of advanced glycation end-products appears to promote the apoptosis of retinal microvascular cells, and antioxidants or advanced glycation end-products inhibitors might ameliorate diabetic retinopathy.

Effects of atorvastatin on glucose metabolism and insulin resistance in KK/Ay mice.

Insulin resistance plays an important role not only in the development and progression of diabetes mellitus but also in the establishment of metabolic syndrome. Improvement of insulin resistance is thus of great importance both in improving glucose metabolism and preventing atherosclerosis. Although HMG-CoA reductase inhibitors appear to favorably affect glucose metabolism, as indicated by the results of a subanalysis in the West of Scotland Coronary Prevention Study (WOSCOPS), their effects on glucose metabolism and insulin resistance have not been thoroughly investigated in animal models. In this study, the effects of atorvastatin on the glucose metabolism and insulin resistance of KK/Ay mice, an animal model of type II diabetes, were investigated. Atorvastatin significantly decreased the non-HDL-cholesterol level in the oral glucose tolerance test, inhibited increase in the 30-min glucose level, decreased plasma insulin levels before and 30 and 60 minutes after glucose loading, and decreased the insulin resistance index, compared with corresponding values in controls, indicating that atorvastatin appeared to improve glucose metabolism by improving insulin resistance. Northern blot analysis revealed decreases in levels of mRNA of sterol regulatory element binding protein-1 (SREBP-1) and glucose-6-phosphatase (G6Pase), and it may play a role in the improvement of glucose metabolism and insulin resistance.

WGEF is a novel RhoGEF expressed in intestine, liver, heart, and kidney.

Rho family GTPases regulate multiple cellular processes through their downstream effectors, where their activities are stimulated by the guanine nucleotide exchange factors. Here, we report a new member of RhoGEF, WGEF, which has the classical structure of DH-PH domain and a C-terminal SH3 domain. WGEF was shown to activate RhoA, Cdc42, and Rac1 by pulldown assay, and forced expression of WGEF resulted in marked rearrangement of the actin cytoskeleton, which is typically seen by the activation of RhoA, Cdc42, and Rac1. WGEF was highly expressed in intestine and also in liver, heart and kidney, which may suggest the involvement of WGEF in the development and functions of these organs. The expression pattern may also suggest the possible importance of WGEF in the understanding of diseases based on metabolic disorder.

Statins downregulate ATP-binding-cassette transporter A1 gene expression in macrophages.

The ATP-binding-cassette transporter A1 (ABCA1) plays an essential role in cellular cholesterol efflux and helps prevent macrophages from becoming foam cells. The statins are widely used as cholesterol-lowering agents and have other anti-atherogenic actions. We tested the effects of four different statins (fluvastatin, atorvastatin, simvastatin, and lovastatin) on ABCA1 expression in macrophages in vitro. The statins suppressed ABCA1 mRNA expression in RAW246.7 and THP-1 macrophage cell lines and in mouse peritoneal macrophages. The effect was time- and dose-dependent and was abolished by the addition of the post-reductase product, mevalonate. These findings imply that there is a possible modulation of the well-known beneficial effects of the statins on the reverse cholesterol transport pathway.

p57Kip2 regulates actin dynamics by binding and translocating LIM-kinase 1 to the nucleus.

p57Kip2 is the only cyclin-dependent kinase (Cdk) inhibitor shown to be essential for mouse embryogenesis. The fact suggests that p57 has a specific role that cannot be compensated by other Cdk inhibitors. LIM-kinase 1 (LIMK-1) is a downstream effector of the Rho family of GTPases that phosphorylates and inactivates an actin depolymerization factor, cofilin, to induce the formation of actin fiber. Here we demonstrate that p57 regulates actin dynamics by binding and translocating LIMK-1 from the cytoplasm into the nucleus, which in turn results in a reorganization of actin fiber. The central region of p57, a unique feature among the Cdk inhibitors, and the N-terminal region of LIMK-1, which contains the LIM domains were essential for the interaction. Expression of p57, but not p27Kip1 or a p57 mutant, with a deletion in the central region was shown to induce marked reorganization of actin filament and a translocation of LIMK-1. Our findings indicate p57 may act as a key regulator in embryogenesis by bearing two distinct functions, the regulation of cell cycle through binding to Cdks and the regulation of actin dynamics through binding to LIMK-1, both of which should be important in developmental procedure.

Acetyl-coenzyme A synthetase is a lipogenic enzyme controlled by SREBP-1 and energy status.

DNA microarray analysis on upregulated genes in the livers from transgenic mice overexpressing nuclear sterol regulatory element-binding protein (SREBP)-1a, identified an expressed sequence tag (EST) encoding a part of murine cytosolic acetyl-coenzyme A synthetase (ACAS). Northern blot analysis of the livers from transgenic mice demonstrated that this gene was highly induced by SREBP-1a, SREBP-1c, and SREBP-2. DNA sequencing of the 5' flanking region of the murine ACAS gene identified a sterol regulatory element with an adjacent Sp1 site. This region was shown to be responsible for SREBP binding and activation of the ACAS gene by gel shift and luciferase reporter gene assays. Hepatic and adipose tissue ACAS mRNA levels in normal mice were suppressed at fasting and markedly induced by refeeding, and this dietary regulation was nearly abolished in SREBP-1 knockout mice, suggesting that the nutritional regulation of the ACAS gene is controlled by SREBP-1. The ACAS gene was downregulated in streptozotocin-induced diabetic mice and was restored after insulin replacement, suggesting that diabetic status and insulin also regulate this gene. When acetate was administered, hepatic ACAS mRNA was negatively regulated. These data on dietary regulation and SREBP-1 control of ACAS gene expression demonstrate that ACAS is a novel hepatic lipogenic enzyme, providing further evidence that SREBP-1 and insulin control the supply of acetyl-CoA directly from cellular acetate for lipogenesis. However, its high conservation among different species and the wide range of its tissue distribution suggest that this enzyme might also play an important role in basic cellular energy metabolism.