Cthrc1 is a positive regulator of osteoblastic bone formation

Background

Bone mass is maintained by continuous remodeling through repeated cycles of bone resorption by osteoclasts and bone formation by osteoblasts. This remodeling process is regulated by many systemic and local factors.

Methodology/Principal Findings

We identified collagen triple helix repeat containing-1 (Cthrc1) as a downstream target of bone morphogenetic protein-2 (BMP2) in osteochondroprogenitor-like cells by PCR-based suppression subtractive hybridization followed by differential hybridization, and found that Cthrc1 was expressed in bone tissues in vivo. To investigate the role of Cthrc1 in bone, we generated Cthrc1-null mice and transgenic mice which overexpress Cthrc1 in osteoblasts (Cthrc1 transgenic mice). Microcomputed tomography (micro-CT) and bone histomorphometry analyses showed that Cthrc1-null mice displayed low bone mass as a result of decreased osteoblastic bone formation, whereas Cthrc1 transgenic mice displayed high bone mass by increase in osteoblastic bone formation. Osteoblast number was decreased in Cthrc1-null mice, and increased in Cthrc1 transgenic mice, respectively, while osteoclast number had no change in both mutant mice. In vitro, colony-forming unit (CFU) assays in bone marrow cells harvested from Cthrc1-null mice or Cthrc1 transgenic mice revealed that Cthrc1 stimulated differentiation and mineralization of osteoprogenitor cells. Expression levels of osteoblast specific genes, ALP, Col1a1, and Osteocalcin, in primary osteoblasts were decreased in Cthrc1-null mice and increased in Cthrc1 transgenic mice, respectively. Furthermore, BrdU incorporation assays showed that Cthrc1 accelerated osteoblast proliferation in vitro and in vivo. In addition, overexpression of Cthrc1 in the transgenic mice attenuated ovariectomy-induced bone loss.

Conclusions/Significance

Our results indicate that Cthrc1 increases bone mass as a positive regulator of osteoblastic bone formation and offers an anabolic approach for the treatment of osteoporosis.     

hClp1, A Novel Kinase Revitalizes RNA Metabolism

The RNA-Induced Silencing Complex (RISC) is the effector complex in the RNA interference (RNAi) pathway. In order to become assembled into RISC, synthetic small interfering RNAs (siRNAs) are phosphorylated at the 5’ end upon transfection into cells. The enzymatic activity responsible for this phosphorylation event has so far remained elusive. Using a classical chromatographic approach, we recently identified and characterized hClp1 as the “siRNA-kinase” in HeLa cells. hClp1 is in fact a general RNA-kinase, and a component of the tRNA splicing endonuclease and the mRNA 3’ end formation machinery. We discuss the relevance of this finding, and provide further views and perspectives for the analysis of hClp1 in tRNA splicing, mRNA cleavage and polyadenylation and other RNA metabolic processes in which hClp1 might play a role.     

Hormone Specificity, Androgen Metabolism, and Social Behavior

SYNOPSIS. The ability of different sex hormones to activatesocial signals can provide important clues to the biochemicalmechanisms underlying these signals. A pattern of hormone specificityin which testosterone (T) and estradiol (E), but not dihydrotestosterone(DHT), are effective suggests that conversion (aromatization)of T to E in the brain may be involved or required; a patternin which T and DHT, but not E, are effective suggests that conversionof T to DHT may be involved. The hormone specificity of socialsignals in diverse species of vertebrates is reviewed. Aromatizationseems to be of widespread behavioral significance in mammalsandbirds. A role for conversion of T to DHT is suggested forsome signals. Aromatization of T mayalso be important for theactivation of adult female behavior in mammals and lizards,and for the early organization of behavior in mammals and birds.Patterns of hormone specificity differ both across species fora given social signal, and within a given species when differentsignals are compared. An attempt is made to integrate thesefindings by relating patterns of hormone specificity to hormonelevels, steroid receptor and enzyme concentrations and distributions,signal function and dimorphism, and phylogenetic status.     

Excess Thyroid Hormone and Carbohydrate Metabolism

ObjectiveTo review the pertinent basic and clinical research describing the complex effects of excess thyroid hormone on carbohydrate metabolism.MethodsWe performed a MEDLINE search of the English-language literature using a combination of words (ie, “thyrotoxicosis and diabetes,” “diabetic ketoacidosis and thyroid storm,” “carbohydrate metabolism and hyperthyroid,” “glucose homeostasis and thyrotoxicosis”) to identify key articles addressing various aspects of the thyroid’s influence on carbohydrate metabolism.ResultsThyroid hormone affects glucose homeostasis via its actions on a variety of organs including increased hepatic glucose output, increased futile cycling of glucose degradation products between the skeletal muscle and the liver, decreased glycogen stores in the liver and skeletal muscle, altered oxidative and nonoxidative glucose metabolism, decreased active insulin output from the pancreas, and increased renal insulin clearance. Thyroid hormone also affects adipokines and adipose tissue, further predisposing the patient to ketosis.ConclusionsThyrotoxicosis can alter carbohydrate metabolism in a type 2 diabetic patient to such an extent that diabetic ketoacidosis develops if untreated. Based on the current understanding of this relationship, all diabetic patients should be screened for thyroid dysfunction because correcting hyperthyroidism can profoundly affect glucose homeostasis. Similarly, patients presenting in diabetic ketoacidosis should undergo a thyroid function assessment. (Endocr Pract. 2009;15:254-262)     

Nontelomeric Role for Rap1 in Regulating Metabolism and Protecting against Obesity

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Leading Wnt down a PCP path: Cthrc1 acts as a coreceptor in the Wnt-PCP pathway

Wnt signaling regulates many aspects of development through canonical and PCP signaling pathways. A paper by Yamamoto et al. in this issue of Developmental Cell identifies collagen triple helix repeat containing 1 as a Wnt-binding cofactor that specifically activates the Wnt-PCP pathway.     

Starch Binding Domain-containing Protein 1/Genethonin 1 Is a Novel Participant in Glycogen Metabolism

Stbd1 is a protein of previously unknown function that is most prevalent in liver and muscle, the major sites for storage of the energy reserve glycogen. The protein is predicted to contain a hydrophobic N terminus and a C-terminal CBM20 glycan binding domain. Here, we show that Stbd1 binds to glycogen in vitro and that endogenous Stbd1 locates to perinuclear compartments in cultured mouse FL83B or Rat1 cells. When overexpressed in COSM9 cells, Stbd1 concentrated at enlarged perinuclear structures, co-localized with glycogen, the late endosomal/lysosomal marker LAMP1 and the autophagy protein GABARAPL1. Mutant Stbd1 lacking the N-terminal hydrophobic segment had a diffuse distribution throughout the cell. Point mutations in the CBM20 domain did not change the perinuclear localization of Stbd1, but glycogen was no longer concentrated in this compartment. Stable overexpression of glycogen synthase in Rat1WT4 cells resulted in accumulation of glycogen as massive perinuclear deposits, where a large fraction of the detectable Stbd1 co-localized. Starvation of Rat1WT4 cells for glucose resulted in dissipation of the massive glycogen stores into numerous and much smaller glycogen deposits that retained Stbd1. In vitro, in cells, and in animal models, Stbd1 consistently tracked with glycogen. We conclude that Stbd1 is involved in glycogen metabolism by binding to glycogen and anchoring it to membranes, thereby affecting its cellular localization and its intracellular trafficking to lysosomes.     

Anti-Diabetic Efficacy and Impact on Amino Acid Metabolism of GRA1, a Novel Small-Molecule Glucagon Receptor Antagonist

Hyperglucagonemia is implicated in the pathophysiology of hyperglycemia. Antagonism of the glucagon receptor (GCGR) thus represents a potential approach to diabetes treatment. Herein we report the characterization of GRA1, a novel small-molecule GCGR antagonist that blocks glucagon binding to the human GCGR (hGCGR) and antagonizes glucagon-induced intracellular accumulation of cAMP with nanomolar potency. GRA1 inhibited glycogenolysis dose-dependently in primary human hepatocytes and in perfused liver from hGCGR mice, a transgenic line of mouse that expresses the hGCGR instead of the murine GCGR. When administered orally to hGCGR mice and rhesus monkeys, GRA1 blocked hyperglycemic responses to exogenous glucagon. In several murine models of diabetes, acute and chronic dosing with GRA1 significantly reduced blood glucose concentrations and moderately increased plasma glucagon and glucagon-like peptide-1. Combination of GRA1 with a dipeptidyl peptidase-4 inhibitor had an additive antihyperglycemic effect in diabetic mice. Hepatic gene-expression profiling in monkeys treated with GRA1 revealed down-regulation of numerous genes involved in amino acid catabolism, an effect that was paralleled by increased amino acid levels in the circulation. In summary, GRA1 is a potent glucagon receptor antagonist with strong antihyperglycemic efficacy in preclinical models and prominent effects on hepatic gene-expression related to amino acid metabolism.     

24-Hour Changes in Circulating Prolactin,Follicle-Stimulating Hormone,Luteinizing Hormone,and Testosterone in Young Male Rats Subjected to Calorie Restriction

This work analyzes the effect of calorie restriction on the 24 h variation of pituitary-testicular function in young male Wistar rats by measuring the circulating levels of prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone. Control animals were provided an equilibrium calorie diet and the experimental animals a calorie-restriction diet equivalent to 66% of food restriction for four weeks starting on day 35 of life. Different groups of control and experimental rats were killed at 6 h intervals around the clock, beginning 1 h after light on (HALO). Compared to the control animals, the mean secretion of prolactin was augmented and that of LH and testosterone decreased in calorie-restricted rats, whereas FSH release remained unchanged. Significant changes in the 24 h secretory pattern of circulating prolactin, LH, and testosterone occurred in the calorie-restricted rats. These include the appearance of a second maximum of plasma prolactin at 21 HALO, blunting of the LH peak seen at 13 HALO, and phase-shift of the testosterone peak from 13 HALO in controls to 17 HALO in calorie-restricted rats. The significant positive correlation between individual LH and testosterone levels found in controls was no longer observed in calorie-restricted rats. Availability of nutrients presumably affects the mechanisms that modulate the circadian variation of the pituitary-gonadal axis in growing male rats.     

Circulating Thyroxine,Thyroid-Stimulating Hormone,and Hypothyroid Status and the Risk of Prostate Cancer

Background

Thyroid hormones may influence risk of cancer through their role in cell differentiation, growth, and metabolism. One study of circulating thyroid hormones supports this hypothesis with respect to prostate cancer. We undertook a prospective analysis of thyroid hormones and prostate cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.

Methods

Within the ATBC Study, a randomized controlled trial of α-tocopherol and β-carotene supplements and cancer incidence in male smokers, 402 prostate cancer cases were sampled. Controls were matched 2∶1 to cases on age and date of blood collection. Odds ratios (OR) and 95% confidence intervals (CI) of prostate cancer were estimated for quintiles of serum total and free thyroxine (T4), thyroid-stimulating hormone (TSH), thyroid-binding globulin (TBG), and by categories of thyroid status.

Results

Men with serum higher TSH had a decreased risk of prostate cancer compared to men with lower TSH (Q5 vs. Q1–4: OR = 0.70, 95% CI: 0.51–0.97, p = 0.03). When the T4 and TSH measurements were combined to define men as hypothyroid, euthyroid or hyperthyroid, hypothyroid men had a lower risk of prostate cancer compared to euthyroid men (OR = 0.48, 95% CI = 0.28–0.81, p = 0.006). We observed no association between hyperthyroid status and risk, although the number of hyperthyroid men with prostate cancer was small (n = 9).

Conclusions

In this prospective study of smokers, men with elevated TSH and those classified as being in a hypothyroid state were at decreased risk of prostate cancer. Future studies should examine the association in other populations, particularly non-smokers and other racial/ethnic groups.     

Social Modulation of Circulating Hormone Levels in the Male

SYNOPSIS. In many species, social interactions rapidly modulatecirculating hormone levels in the male. Sexual interaction ormere exposure to a conspecific female results in rapid, transientelevation of both plasma luteinizing hormone and testosteroneconcentrations in a variety of species. In contrast, aggressiveinteractions result in decreased plasma gonadotropin and testosteronelevels and increased levels of adrenal corticoids. In general,these changes are more profound and of longer duration thanthose accompanying sexual interactions, particularly among subordinatemales. These fluctuations in circulating hormone levels appearto be related to an individual's behavioral responsivity. Forexample, plasma concentrations of luteinizing hormone duringa social encounter are positively correlated with the degreeof sexual arousal shown by a male during the interaction. Similarcorrelations have been found between plasma androgen or corticoidlevels and patterns of behavior shown by males during both sexualand aggressive interactions. The causal relationship betweensuch rapid hormone fluctuations and behavior remains unclear.Are fluctuating hormone levels causing differences in behavioror aredifferent patterns of behavior causing differences inplasma hormone levels between males? Or is the correlation betweenthese two variables caused by their relationship to anotherunidentified factor? There are some data favoring the firstpossibility. Increasing the magnitude of socially induced hormonefluctuations during an aggressive encounter or preventingsuchfluctuations entirely significantly alters an animal's behavior.These data suggest that the endocrine system may play a moreimportant role in an individual's minute-to-minute responseto critical social stimuli than was previously realized.     

Genome Sequence of a Novel HIV-1 Circulating Recombinant Form 54_01B from Malaysia

We report here the first novel HIV-1 circulating recombinant form (CRF) 54_01B (CRF54_01B) isolated from three epidemiologically unlinked subjects of different risk groups in Malaysia. These recently sampled recombinants showed a complex genome organization composed of parental subtype B′ and CRF01_AE, with identical recombination breakpoints observed in the gag, pol, and vif genes. Such a discovery highlights the ongoing active generation and spread of intersubtype recombinants involving the subtype B′ and CRF01_AE lineages and indicates the potential of the new CRF in bridging HIV-1 transmission among different risk groups in Southeast Asia.     

硒缺乏与甲状腺激素代谢及功能

Ｉ型脱碘酶为含硒酶,缺硒时,该酶活性下降,使循环Ｔ４增高,外周组织Ｔ３水平下降。缺硒可加速甲状腺组织碘的耗竭,并加重某些缺碘的生物学效应,缺硒还可能与碘缺乏病的发生发展有关。以缺硒为主要病因的克山病存在甲状腺激素代谢异常,其心肌呼吸酶活性变化与缺碘引起的甲状腺功能低下相似,缺碘可缺硒引起的甲状腺激素代谢改变与克山病的发生可能有关。     

Developmental Role of Juvenile Hormone Metabolism in Lepidoptera

SYNOPSIS. Lepidopteran juvenile hormone (JH) esterase appearsto have a functional role in the regulation of embryogenesis,larval growth and development, and adult reproduction. In preovipositionaland newly laid eggs of the tobacco hornworm, Manduca sexta,JH esterase activity was elevated presumably to metabolize maternalJHs, and then declined after blastoderm formation. Also, a singlepeak in hemolymph JH esterase activity was found prior to ecdysisin the second through the fourth instar of M. sexta, the functionof which is unclear. However, in the last instar, elevated hemolymphJH esterase activity was noted prior to wandering and againprior to ecdysis to scavenge the last traces of JH necessaryfor normal development. The hemolymph JH esterase is likelyof multiple tissue origin for the prewandering peak with thefat body excluded as a source for the prepupal peak; an inhibitoryfactor from the brain and JH regulate JH esterase biosynthesis.In adult cabbage loopers, Trichoplusia ni, elevated hemolymphJH esterase activity appeared to be important in reducing theJH titer and preventing egg maturation. Structure/activity datawith trifluoromethylketones were incorporated into the designof a novel, JH esterase inhibitor, the sulfone and hydrate ofoctylthio-1,1,1- trifluoropropan-2-one, with selective and persistent,in vivo inhibitory activity. The topical application of thiscompound to last instar larvae and virgin adults of T. ni producedjuvenizing effects (delayed pupation and induced egg maturation/oviposition,respectively) providing direct evidence of a functional rolefor JH esterase in lepidopteran development.     

A Novel Role for Protein Kinase Kin2 in Regulating HAC1 mRNA Translocation,Splicing, and Translation

A signaling network called the unfolded protein response (UPR) resolves the protein-folding defects in the endoplasmic reticulum (ER) from yeasts to humans. In the yeast Saccharomyces cerevisiae, the UPR activation involves (i) aggregation of the ER-resident kinase/RNase Ire1 to form an Ire1 focus, (ii) targeting HAC1 pre-mRNA toward the Ire1 focus that cleaves out an inhibitory intron from the mRNA, and (iii) translation of Hac1 protein from the spliced mRNA. Targeting HAC1 mRNA to the Ire1 focus requires a cis-acting bipartite element (3′BE) located at the 3′ untranslated leader. Here, we report that the 3′BE plays an additional role in promoting translation from the spliced mRNA. We also report that a high dose of either of two paralogue kinases, Kin1 and Kin2, overcomes the defective UPR caused by a mutation in the 3′BE. These results define a novel role for Kin kinases in the UPR beyond their role in cell polarity and exocytosis. Consistently, targeting, splicing, and translation of HAC1 mRNA are substantially reduced in the kin1Δ kin2Δ strain. Furthermore, we show that Kin2 kinase domain itself is sufficient to activate the UPR, suggesting that Kin2 initiates a signaling cascade to ensure an optimum UPR.