The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity

Adiponectin is an adipocyte-derived hormone. Recent genome-wide scans have mapped a susceptibility locus for type 2 diabetes and metabolic syndrome to chromosome 3q27, where the gene encoding adiponectin is located. Here we show that decreased expression of adiponectin correlates with insulin resistance in mouse models of altered insulin sensitivity. Adiponectin decreases insulin resistance by decreasing triglyceride content in muscle and liver in obese mice. This effect results from increased expression of molecules involved in both fatty-acid combustion and energy dissipation in muscle. Moreover, insulin resistance in lipoatrophic mice was completely reversed by the combination of physiological doses of adiponectin and leptin, but only partially by either adiponectin or leptin alone. We conclude that decreased adiponectin is implicated in the development of insulin resistance in mouse models of both obesity and lipoatrophy. These data also indicate that the replenishment of adiponectin might provide a novel treatment modality for insulin resistance and type 2 diabetes.

Detection of loop-mediated isothermal amplification reaction by turbidity derived from magnesium pyrophosphate formation

The loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method that uses only one type of enzyme. One of the characteristics of the LAMP method is its ability to synthesize extremely large amount of DNA. Accordingly, a large amount of by-product, pyrophosphate ion, is produced, yielding white precipitate of magnesium pyrophosphate in the reaction mixture. Judging the presence or absence of this white precipitate allows easy distinction of whether nucleic acid was amplified by the LAMP method. Since an increase in the turbidity of the reaction mixture according to the production of precipitate correlates with the amount of DNA synthesized, real-time monitoring of the LAMP reaction was achieved by real-time measurement of turbidity.

Troglitazone increases the number of small adipocytes without the change of white adipose tissue mass in obese Zucker rats

Troglitazone (CS-045) is one of the thiazolidinediones that activate the peroxisome proliferator-activated receptor gamma (PPARgamma), which is expressed primarily in adipose tissues. To elucidate the mechanism by which troglitazone relieves insulin resistance in vivo, we studied its effects on the white adipose tissues of an obese animal model (obese Zucker rat). Administration of troglitazone for 15 d normalized mild hyperglycemia and marked hyperinsulinemia in these rats. Plasma triglyceride level was decreased by troglitazone in both obese and lean rats. Troglitazone did not change the total weight of white adipose tissues but increased the number of small adipocytes (< 2,500 micron2) approximately fourfold in both retroperitoneal and subcutaneous adipose tissues of obese rats. It also decreased the number of large adipocytes (> 5,000 micron2) by approximately 50%. In fact, the percentage of apoptotic nuclei was approximately 2.5-fold higher in the troglitazone-treated retroperitoneal white adipose tissue than control. Concomitantly, troglitazone normalized the expression levels of TNF-alpha which were elevated by 2- and 1.4-fold in the retroperitoneal and mesenteric white adipose tissues of the obese rats, respectively. Troglitazone also caused a dramatic decrease in the expression levels of leptin, which were increased by 4-10-fold in the white adipose tissues of obese rats. These results suggest that the primary action of troglitazone may be to increase the number of small adipocytes in white adipose tissues, presumably via PPARgamma. The increased number of small adipocytes and the decreased number of large adipocytes in white adipose tissues of troglitazone-treated obese rats appear to be an important mechanism by which increased expression levels of TNF-alpha and higher levels of plasma lipids are normalized, leading to alleviation of insulin resistance.

Primary structure and functional expression of the cardiac dihydropyridine-sensitive calcium channel

In cardiac muscle, where Ca2+ influx across the sarcolemma is essential for contraction, the dihydropyridine (DHP)-sensitive L-type calcium channel represents the major entry pathway of extracellular Ca2+. We have previously elucidated the primary structure of the rabbit skeletal muscle DHP receptor by cloning and sequencing the complementary DNA. An expression plasmid carrying this cDNA, microinjected into cultured skeletal muscle cells from mice with muscular dysgenesis, has been shown to restore both excitation-contraction coupling and slow calcium current missing from these cells, so that a dual role for the DHP receptor in skeletal muscle transverse tubules is suggested. We report here the complete amino-acid sequence of the rabbit cardiac DHP receptor, deduced from the cDNA sequence. We also show that messenger RNA derived from the cardiac DHP receptor cDNA is sufficient to direct the formation of a functional DHP-sensitive calcium channel in Xenopus oocytes. Furthermore, higher calcium-channel activity is observed when mRNA specific for the polypeptide of relative molecular mass approximately 140,000 (alpha 2-subunit) associated with skeletal muscle DHP receptor is co-injected.

Primary structure and functional expression from complementary DNA of a brain calcium channel

The primary structure of a voltage-dependent calcium channel from rabbit brain has been deduced by cloning and sequencing the complementary DNA. Calcium channel activity expressed from the cDNA is dramatically increased by coexpression of the alpha 2 and beta subunits, known to be associated with the dihydropyridine receptor. This channel is a high voltage-activated calcium channel that is insensitive both to nifedipine and to omega-conotoxin. We suggest that it is expressed predominantly in cerebellar Purkinje cells and granule cells.

Implantation of bone marrow mononuclear cells into ischemic myocardium enhances collateral perfusion and regional function via side supply of angioblasts, angiogenic ligands, and cytokines

BACKGROUND

Bone marrow implantation (BMI) was shown to enhance angiogenesis in a rat ischemic heart model. This preclinical study using a swine model was designed to test the safety and therapeutic effectiveness of BMI.

METHODS AND RESULTS

BM-derived mononuclear cells (BM-MNCs) were injected into a zone made ischemic by coronary artery ligation. Three weeks after BMI, regional blood flow and capillary densities were significantly higher (4.6- and 2.8-fold, respectively), and cardiac function was improved. Angiography revealed that there was a marked increase (5.7-fold) in number of visible collateral vessels. Implantation of porcine coronary microvascular endothelial cells (CMECs) did not cause any significant increase in capillary densities. Labeled BM-MNCs were incorporated into approximately 31% of neocapillaries and corresponded to approximately 8.7% of macrophages but did not actively survive as myoblasts or fibroblasts. There was no bone formation by osteoblasts or malignant ventricular arrhythmia. Time-dependent changes in plasma levels for cardiac enzymes (troponin I and creatine kinase-MB) did not differ between the BMI, CMEC, and medium-alone implantation groups. BM-MNCs contained 16% of endothelial-lineage cells and expressed basic fibroblast growth factor>>vascular endothelial growth factor>angiopoietin 1 mRNAs, and their cardiac levels were significantly upregulated by BMI. Cardiac interleukin-1beta and tumor necrosis factor-alpha mRNA expression were also induced by BMI but not by CMEC implantation. BM-MNCs were actively differentiated to endothelial cells in vitro and formed network structure with human umbilical vein endothelial cells.

CONCLUSIONS

BMI may constitute a novel safety strategy for achieving optimal therapeutic angiogenesis by the natural ability of the BM cells to secrete potent angiogenic ligands and cytokines as well as to be incorporated into foci of neovascularization.

Rings of negatively charged amino acids determine the acetylcholine receptor channel conductance

The structure-function relationship of the nicotinic acetylcholine receptor (AChR) has been effectively studied by the combination of complementary DNA manipulation and single-channel current analysis. Previous work with chimaeras between the Torpedo californica and bovine AChR delta-subunits has shown that the region comprising the hydrophobic segment M2 and its vicinity contains an important determinant of the rate of ion transport through the AChR channel. It has also been suggested that this region is responsible for the reduction in channel conductance caused by divalent cations and that segment M2 contributes to the binding site of noncompetitive antagonists. To identify those amino acid residues that interact with permeating ions, we have introduced various point mutations into the Torpedo AChR subunit cDNAs to alter the net charge of the charged or glutamine residues around the proposed transmembrane segments. The single-channel conductance properties of these AChR mutants expressed in Xenopus laevis oocytes indicate that three clusters of negatively charged and glutamine residues neighbouring segment M2 of the alpha-, beta-, gamma- and delta-subunits, probably forming three anionic rings, are major determinants of the rate of ion transport.

Calcium channel beta-subunit binds to a conserved motif in the I-II cytoplasmic linker of the alpha 1-subunit

The beta-subunit is an integral component of purified voltage-sensitive Ca2+ channels. Modulation of Ca2+ channel activity by the beta-subunit, which includes significant increases in transmembrane current and/or changes in kinetics, is observed on coexpression of six alpha 1-subunit genes with four beta-subunit genes in all alpha 1-beta combinations tested. Recent reports suggest that this regulation is not due to targeting of the alpha 1-subunit to the plasma membrane but is probably a result of a conformational change induced by the beta-subunit. Here we report that the beta-subunit binds to the cytoplasmic linker between repeats I and II of the dihydropyridine-sensitive alpha 1-subunits from skeletal (alpha 1S) and cardiac muscles (alpha 1C-a), and also with the more distantly related neuronal alpha 1A and omega-conotoxin GVIA-sensitive alpha 1B-subunits. Sequence analysis of the beta-subunit binding site identifies a conserved motif (QQ-E--L-GY--WI--E) positioned 24 amino acids from the IS6 transmembrane domain in each alpha 1-subunit. Mutations within this motif reduce the stimulation of peak currents by the beta-subunit and alter inactivation kinetics and voltage-dependence of activation. Conservation of the beta-subunit binding motif in these functionally distinct calcium channels suggests a critical role for the I-II cytoplasmic linker of the alpha 1-subunit in channel modulation by the beta-subunit.

The transient receptor potential protein homologue TRP6 is the essential component of vascular alpha(1)-adrenoceptor-activated Ca(2+)-permeable cation channel

The Drosophila transient receptor potential protein (TRP) and its mammalian homologues are thought to be Ca(2+)-permeable cation channels activated by G protein (G(q/11))-coupled receptors and are regarded as an interesting molecular model for the Ca(2+) entry mechanisms associated with stimulated phosphoinositide turnover and store depletion. However, there is little unequivocal evidence linking mammalian TRPs with particular native functions. In this study, we have found that heterologous expression of murine TRP6 in HEK293 cells reproduces almost exactly the essential biophysical and pharmacological properties of alpha(1)-adrenoceptor-activated nonselective cation channels (alpha(1)-AR-NSCC) previously identified in rabbit portal vein smooth muscle. Such properties include activation by diacylglycerol; S-shaped current-voltage relationship; high divalent cation permeability; unitary conductance of 25 to 30 pS and augmentation by flufenamate and Ca(2+); and blockade by Cd(2+), La(3+), Gd(3+), SK&F96365, and amiloride. Reverse transcriptase-polymerase chain reaction and confocal laser scanning microscopy using TRP6-specific primers and antisera revealed that the level of TRP6 mRNA expression was remarkably high in both murine and rabbit portal vein smooth muscles as compared with other TRP subtypes, and the immunoreactivity to TRP6 protein was localized near the sarcolemmal region of single rabbit portal vein myocytes. Furthermore, treatment of primary cultured portal vein myocytes with TRP6 antisense oligonucleotides resulted in marked inhibition of TRP6 protein immunoreactivity as well as selective suppression of alpha(1)-adrenoceptor-activated, store depletion-independent cation current and Ba(2+) influx. These results strongly indicate that TRP6 is the essential component of the alpha(1)-AR-NSCC, which may serve as a store depletion-independent Ca(2+) entry pathway during increased sympathetic activity.

The mouse stargazer gene encodes a neuronal Ca2+-channel gamma subunit

Stargazer mice have spike-wave seizures characteristic of absence epilepsy, with accompanying defects in the cerebellum and inner ear. We describe here a novel gene, Cacng2, whose expression is disrupted in two stargazer alleles. It encodes a 36-kD protein (stargazin) with structural similarity to the gamma subunit of skeletal muscle voltage-gated calcium (Ca2+) channels. Stargazin is brain-specific and, like other neuronal Ca2+-channel subunits, is enriched in synaptic plasma membranes. In vitro, stargazin increases steady-state inactivation of alpha1 class A Ca2+ channels. The anticipated effect in stargazer mutants, inappropriate Ca2+ entry, may contribute to their more pronounced seizure phenotype compared with other mouse absence models with Ca2+-channel defects. The discovery that the stargazer gene encodes a gamma subunit completes the identification of the major subunit types for neuronal Ca2+ channels, namely alpha1, alpha2delta, beta and gamma, providing a new opportunity to understand how these channels function in the mammalian brain and how they may be targeted in the treatment of neuroexcitability disorders.

Angiotensin II type 2 receptor overexpression activates the vascular kinin system and causes vasodilation

Angiotensin II (Ang II) is a potent vasopressor peptide that interacts with 2 major receptor isoforms - AT1 and AT2. Although blood pressure is increased in AT2 knockout mice, the underlying mechanisms remain undefined because of the low levels of expression of AT2 in the vasculature. Here we overexpressed AT2 in vascular smooth muscle (VSM) cells in transgenic (TG) mice. Aortic AT1 was not affected by overexpression of AT2. Chronic infusion of Ang II into AT2-TG mice completely abolished the AT1-mediated pressor effect, which was blocked by inhibitors of bradykinin type 2 receptor (icatibant) and nitric oxide (NO) synthase (L-NAME). Aortic explants from TG mice showed greatly increased cGMP production and diminished Ang II-induced vascular constriction. Removal of endothelium or treatment with icatibant and L-NAME abolished these AT2-mediated effects. AT2 blocked the amiloride-sensitive Na(+)/H(+) exchanger, promoting intracellular acidosis in VSM cells and activating kininogenases. The resulting enhancement of aortic kinin formation in TG mice was not affected by removal of endothelium. Our results suggest that AT2 in aortic VSM cells stimulates the production of bradykinin, which stimulates the NO/cGMP system in a paracrine manner to promote vasodilation. Selective stimulation of AT2 in the presence of AT1 antagonists is predicted to have a beneficial clinical effect in controlling blood pressure.

Presenilin-1 mutations downregulate the signalling pathway of the unfolded-protein response

Missense mutations in the human presenilin-1 (PS1) gene, which is found on chromosome 14, cause early-onset familial Alzheimer's disease (FAD). FAD-linked PS1 variants alter proteolytic processing of the amyloid precursor protein and cause an increase in vulnerability to apoptosis induced by various cell stresses. However, the mechanisms responsible for these phenomena are not clear. Here we report that mutations in PS1 affect the unfolded-protein response (UPR), which responds to the increased amount of unfolded proteins that accumulate in the endoplasmic reticulum (ER) under conditions that cause ER stress. PS1 mutations also lead to decreased expression of GRP78/Bip, a molecular chaperone, present in the ER, that can enable protein folding. Interestingly, GRP78 levels are reduced in the brains of Alzheimer's disease patients. The downregulation of UPR signalling by PS1 mutations is caused by disturbed function of IRE1, which is the proximal sensor of conditions in the ER lumen. Overexpression of GRP78 in neuroblastoma cells bearing PS1 mutants almost completely restores resistance to ER stress to the level of cells expressing wild-type PS1. These results show that mutations in PS1 may increase vulnerability to ER stress by altering the UPR signalling pathway.

A subtype of diabetes mellitus associated with a mutation of mitochondrial DNA

BACKGROUND

Several families have been described in which a mutation of mitochondrial DNA, the substitution of guanine for adenine (A-->G) at position 3243 of leucine transfer RNA, is associated with diabetes mellitus and deafness. The prevalence, clinical features, and pathophysiology of diabetes with this mutation are largely undefined.

METHODS

We studied 55 patients with insulin-dependent diabetes mellitus (IDDM) and a family history of diabetes (group 1), 85 patients with IDDM and no family history of diabetes (group 2), 100 patients with non-insulin-dependent diabetes mellitus (NIDDM) and a family history of diabetes (group 3), and 5 patients with diabetes and deafness (group 4) for the mutation. We also studied the prevalence and characteristics of diabetes in 39 patients with a syndrome consisting of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes who were known to have the mutation and 127 of their relatives (group 5).

RESULTS

We identified 16 unrelated patients with diabetes associated with the A-->G mutation: 3 patients from group 1 (6 percent), 2 patients from group 3 (2 percent), 3 patients from group 4 (60 percent), and 8 patients from group 5 (21 percent). We also identified 16 additional subjects who had diabetes and the mutation among 42 relatives of the patients with diabetes and the mutation in groups 1, 2, 3, and 4 and 20 affected subjects among the 127 relatives of the patients in group 5. Diabetes cosegregated with the mutation in a fashion consistent with maternal transmission, was frequently (in 61 percent of cases) associated with sensory hearing loss, and was generally accompanied by impaired insulin secretion.

CONCLUSIONS

Diabetes mellitus associated with the A-->G mutation at position 3243 of mitochondrial leucine transfer RNA represents a subtype of diabetes found in both patients with IDDM and patients with NIDDM in Japan.

Molecular and functional characterization of a novel mouse transient receptor potential protein homologue TRP7. Ca(2+)-permeable cation channel that is constitutively activated and enhanced by stimulation of G protein-coupled receptor

Characterization of mammalian homologues of Drosophila transient receptor potential protein (TRP) is an important clue to understand molecular mechanisms underlying Ca(2+) influx activated in response to stimulation of G(q) protein-coupled receptors in vertebrate cells. Here we have isolated cDNA encoding a novel seventh mammalian TRP homologue, TRP7, from mouse brain. TRP7 showed abundant RNA expression in the heart, lung, and eye and moderate expression in the brain, spleen, and testis. TRP7 recombinantly expressed in human embryonic kidney cells exhibited distinctive functional features, compared with other TRP homologues. Basal influx activity accompanied by reduction in Ca(2+) release from internal stores was characteristic of TRP7-expressing cells but was by far less significant in cells expressing TRP3, which is structurally the closest to TRP7 in the TRP family. TRP7 induced Ca(2+) influx in response to ATP receptor stimulation at ATP concentrations lower than those necessary for activation of TRP3 and for Ca(2+) release from the intracellular store, which suggests that the TRP7 channel is activated independently of Ca(2+) release. In fact, TRP7 expression did not affect capacitative Ca(2+) entry induced by thapsigargin, whereas TRP7 greatly potentiated Mn(2+) influx induced by diacylglycerols without involvement of protein kinase C. Nystatin-perforated and conventional whole-cell patch clamp recordings from TRP7-expressing cells demonstrated the constitutively activated and ATP-enhanced inward cation currents, both of which were initially blocked and then subsequently facilitated by extracellular Ca(2+) at a physiological concentration. Impairment of TRP7 currents by internal perfusion of the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid revealed an essential role of intracellular Ca(2+) in activation of TRP7, and their potent activation by the diacylglycerol analogue suggests that the TRP7 channel is a new member of diacylglycerol-activated cation channels. Relative permeabilities indicate that TRP7 is slightly selective to divalent cations. Thus, our findings reveal an interesting correspondence of TRP7 to the background and receptor stimulation-induced cation currents in various native systems.

Distinctive biophysical and pharmacological properties of class A (BI) calcium channel alpha 1 subunits

Transcripts for the class A Ca2+ channel alpha 1 subunit (also known as BI) are present at high levels in many parts of the mammalian CNS and are widely assumed to encode the P-type Ca2+ channel. To characterize the biophysical and pharmacological properties of alpha 1A channels, macroscopic and single-channel recordings were made in Xenopus oocytes injected with alpha 1A cRNA. alpha 1-specific properties were identified by making systematic comparisons with the more familiar class C alpha 1 subunit under the condition of a standard ancillary subunit (alpha 2/delta + beta) makeup. alpha 1A currents activate and inactivate more rapidly and display steeper voltage dependence of gating than alpha 1C currents. Unlike alpha 1C, alpha 1A channels are largely insensitive to dihydropyridines and FPL 64176, but respond to the cone snail peptide omega-CTx-MVIIC(SNX-230), a potent and fairly selective inhibitor. In comparison with P-type Ca2+ channels in rat cerebellar Purkinje cells, alpha 1A channels in oocytes are approximately 10(2)-fold less sensitive to omega-Aga-IVA and approximately 10-fold more sensitive to omega-CTx-MVIIC. alpha 1A channels are not inhibited by Bay K 8644 and inactivate much more rapidly than P-type Ca2+ channels. Thus, alpha 1A is capable of generating a Ca2+ channel phenotype quite different from P-type current.

Estrogen inhibits bone resorption by directly inducing apoptosis of the bone-resorbing osteoclasts

Estrogen deficiency causes bone loss, which can be prevented by estrogen replacement therapy. Using a recently developed technique for isolation of highly purified mammalian osteoclasts, we showed that 17 beta-estradiol (E2) was able to directly inhibit osteoclastic bone resorption. At concentrations effective for inhibiting bone resorption, E2 also directly induced osteoclast apoptosis in a dose- and time-dependent manner. ICI164,384 and tamoxifen, as pure and partial antagonists, respectively, completely or partially blocked the effect of E2 on both inhibition of osteoclastic bone resorption and induction of osteoclast apoptosis. These data suggest that the protective effects of estrogen against postmenopausal osteoporosis are mediated in part by the direct induction of apoptosis of the bone-resorbing osteoclasts by an estrogen receptor- mediated mechanism.

Stimulation of type I collagen transcription in human skin fibroblasts by TGF-beta: involvement of Smad 3

Transforming growth factor-beta (TGF-beta) stimulates the transcription of the alpha2(I) procollagen gene (COL1A2). The intracellular mediators involved in this response remain poorly understood. In this study, we demonstrate that primary human skin fibroblasts express Smads, a novel family of signaling molecules, in vitro in the absence of TGF-beta. The levels of Smad 7 mRNA was rapidly and transiently increased by TGF-beta. Transient overexpression of Smad 3 and Smad 4, but not Smad 1 or Smad 2, caused trans-activation of a CAT reporter gene driven by a 772 bp segment of the human COL1A2 promoter containing putative TGF-beta response elements. Smad stimulation of promoter activity was ligand independent, but was further enhanced by TGF-beta. Overexpression of a phosphorylation-deficient Smad 3 mutant or wild-type Smad 7, which lacks the carboxy-terminal phosphorylation motif, specifically inhibited TGF-beta-induced activation of COL1A2 promoter. A CAGACA sequence shown to be a functional Smad-binding element in the plasminogen activator inhibitor-1 gene promoter was found within the TGF-beta-response region of the proximal COL1A2 promoter. Gel mobility shift assays showed protein phosphorylation-dependent binding activity in fibroblast nuclear extracts specific for this sequence; TGF-beta treatment strongly stimulated the formation of this DNA-protein complex. Smad was identified as a component of the CAGACA-binding transcription complex in TGF-beta-treated fibroblasts by antibody supershifting. These results demonstrate that (i) Smad 3 transmits TGF-beta signals from the receptor to the COL1A2 promoter in human fibroblasts, and is likely to play an important role in stimulation of COL1A2 promoter activity elicited by TGF-beta; (ii) in fibroblasts, Smads appear to function as inducible DNA-binding transcription factors; and (iii) Smad 7 may be involved in autocrine negative feedback in the regulation of COL1A2 promoter activity by TGF-beta.

Role of collagen enzymatic and glycation induced cross-links as a determinant of bone quality in spontaneously diabetic WBN/Kob rats

INTRODUCTION

Diabetes is associated with an increased risk of fracture, although type 2 diabetes is often characterized by normal bone mineral density (BMD). Enzymatic and glycation-induced non-enzymatic cross-links play important roles in the expression of bone strength. The serum vitamin B6 concentration is lower in patients with diabetes than in healthy controls. The aim our study was to see if spontaneously diabetic WBN/Kob rats in the pre- and post-onset of diabetes would serve as a suitable model for studying the pathogenesis of the susceptibility to fracture in diabetes without the reduction of bone mineral density. Seventy male WBN/Kob rats were obtained at the ages of 1 to 18 months.

METHODS

Seventy normal male Wistar rats were used as the non-diabetic, age-matched control. The contents of enzymatic cross-links (dihydroxylysinonorleucine, hydroxylysinonorleucine, lysinonorleucine, pyridinoline and deoxypyridinoline) and non-enzymatic cross-links (pentosidine) were determined in femoral bone. We also analyzed the serum concentration of vitamin B6 (pyridoxal and pyridoxamine), femoral BMD and a three-point bending test of the femur.

RESULTS

A low level of serum vitamin B6 was associated with a decrease in enzymatic crosslinking in bone during the subclinical diabetes stage. After the onset of diabetes, there was a steady decrease in enzymatic cross-links and a steep increase in pentosidine. Furthermore, impaired bone mechanical properties in the WBN/Kob rats despite the lack of reduction in BMD coincided with impaired enzymatic cross-link formation and increases in glycation-induced pentosidine.

CONCLUSIONS

These results indicate that the alteration of enzymatic and non-enzymatic crosslinking in bone could be important for explaining the variation of fracture susceptibility in diabetes.

Indirubin and indigo are potent aryl hydrocarbon receptor ligands present in human urine

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates genes involved in xenobiotic metabolism, cellular proliferation, and differentiation. Numerous xenobiotic and biological compounds are known to interact with AhR, but it remains an orphan receptor, because its physiological ligand is unknown. We identified AhR ligands in human urine using a yeast AhR signaling assay and then characterized their properties. Two ligands, indirubin and indigo, were both present at average concentrations of approximately 0.2 nm in the urine of normal donors. Indirubin was also detected in fetal bovine serum and contributed half of the total AhR ligand activity. The activities of indirubin and indigo were comparable with or more potent than that of the archetypal ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin, in yeast AhR activation assays. We suggest that the endogenous levels and potencies of indirubin and indigo are such that they activate AhR-mediated signaling mechanisms in vivo.

Degradation of interleukin 1beta by matrix metalloproteinases

Matrix metalloproteinases (MMPs) and interleukin 1 (IL-1) are implicated in inflammation and tissue destruction, where IL-1 is a potent stimulator of connective tissue cells to produce the extracellular matrix-degrading MMPs. Here, we report that IL-1beta, but not IL-1alpha, is degraded by MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), MMP-3 (stromelysin 1), and MMP-9 (gelatinase B). This degradation was effectively blocked by tissue inhibitor of metalloproteinases (TIMP)-1. When IL-1beta was treated with MMPs it lost the ability to enhance the synthesis of prostaglandin E2 and pro-MMP-3 in human fibroblasts. The primary cleavage site of IL-1beta by MMP-2 was identified at the Glu25-Leu26 bond. These results suggest that IL-1beta stimulates connective tissue cells to produce MMPs, but activated MMPs in turn negatively regulate the activity of IL-1beta.

The I-II loop of the Ca2+ channel alpha1 subunit contains an endoplasmic reticulum retention signal antagonized by the beta subunit

The auxiliary beta subunit is essential for functional expression of high voltage-activated Ca2+ channels. This effect is partly mediated by a facilitation of the intracellular trafficking of alpha1 subunit toward the plasma membrane. Here, we demonstrate that the I-II loop of the alpha1 subunit contains an endoplasmic reticulum (ER) retention signal that severely restricts the plasma membrane incorporation of alpha1 subunit. Coimmunolabeling reveals that the I-II loop restricts expression of a chimera CD8-I-II protein to the ER. The beta subunit reverses the inhibition imposed by the retention signal. Extensive deletion of this retention signal in full-length alpha1 subunit facilitates the cell surface expression of the channel in the absence of beta subunit. Our data suggest that the beta subunit favors Ca2+ channel plasma membrane expression by inhibiting an expression brake contained in beta-binding alpha1 sequences.

Location of a delta-subunit region determining ion transport through the acetylcholine receptor channel

The combination of complementary DNA expression and single-channel current analysis provides a powerful tool for studying the structure-function relationship of the nicotinic acetylcholine receptor (AChR) (refs 1-5). We have previously shown that AChR channels consisting of subunits from different species, expressed in the surface membrane of Xenopus oocytes, can be used to relate functional properties to individual subunits. Here we report that, in extracellular solution of low divalent cation concentration, the bovine AChR channel has a smaller conductance than the Torpedo AChR channel. Replacement of the delta-subunit of the Torpedo AChR by the bovine delta-subunit makes the channel conductance similar to that of the bovine AChR channel. To locate the region in the delta-subunit responsible for this difference, we have constructed chimaeric delta-subunit cDNAs with different combinations of the Torpedo and bovine counterparts. The conductances of AChR channels containing chimaeric delta-subunits suggest that a region comprising the putative transmembrane segment M2 and the adjacent bend portion between segments M2 and M3 is involved in determining the rate of ion transport through the open channel.

Acid-inhibitory effects of vonoprazan 20 mg compared with esomeprazole 20 mg or rabeprazole 10 mg in healthy adult male subjects--a randomised open-label cross-over study

BACKGROUND

Proton pump inhibitors (PPIs) are widely used for the treatment of acid-related diseases. Vonoprazan is a member of a new class of acid suppressants; potassium-competitive acid blockers. Vonoprazan may thus be an alternative to PPIs.

AIM

To evaluate efficacy, rapidity and duration of acid-inhibitory effects of vonoprazan vs. two control PPIs, esomeprazole and rabeprazole, in 20 healthy Japanese adult male volunteers with CYP2C19 extensive metaboliser genotype.

METHODS

In this randomised, open-label, two-period cross-over study, vonoprazan 20 mg and esomeprazole 20 mg (Study V vs. E) or rabeprazole 10 mg (Study V vs. R) were orally administered daily for 7 days. Primary pharmacodynamic endpoint was gastric pH over 24 h measured as percentage of time pH ≥3, ≥4 and ≥5 (pH holding time ratios; HTRs) and mean gastric pH.

RESULTS

Acid-inhibitory effect (pH4 HTR) of vonoprazan was significantly greater than that of esomeprazole or rabeprazole on both Days 1 and 7; Day 7 difference in pH4 HTR for vonoprazan vs. esomeprazole was 24.6% [95% confidence interval (CI): 16.2-33.1] and for vonoprazan vs. rabeprazole 28.8% [95% CI: 17.2-40.4]. The Day 1 to Day 7 ratio of 24-h pH4 HTRs was >0.8 for vonoprazan, compared with 0.370 for esomeprazole and 0.393 for rabeprazole. Vonoprazan was generally well tolerated. One vonoprazan subject withdrew due to a rash which resolved after discontinuation.

CONCLUSIONS

This study demonstrated a more rapid and sustained acid-inhibitory effect of vonoprazan 20 mg vs. esomeprazole 20 mg or rabeprazole 10 mg. Therefore, vonoprazan may be a potentially new treatment for acid-related diseases.