Identification of Gene Signature Associated with Elevated Bone Formation Rate in Aging Mice

Osteoporosis is a disease of low bone mass resulting from bone resorption exceeding bone formation that places individuals at enhanced risk for fracture, disability, and death. There is an urgent and unmet need for novel targets in treating osteoporosis, requiring a better understanding of the endogenous mechanisms regulating bone formation. Recent work indicates that deletion of the Bmpr2 gene in skeletal progenitor cells of mice using Prx1-Cre leads to substantially elevated bone mass in young adulthood due to increased bone formation rate. Additionally, unpublished work suggests that the age-related decline in bone mass of female Bmpr2 mutant mice is reduced approximately two-fold compared to control mice and quantification of serum bone turnover markers reveals this is associated with a sustained increase in bone formation to at least 35 weeks of age (but not 55 weeks of age) with no alteration in bone resorption. Collectively, these data raise the possibility that Bmpr2 mutant mice may serve as a novel model for elucidating mechanisms that regulate osteoblast activity in aging mice. We sought to identify the gene signature associated with elevated osteoblast activity using genome-wide transcriptome profiling of marrow-free humerii from control and Bmpr2 mutant mice. Applying stringent criteria comparing individual transcripts to eight well-accepted housekeeping genes (Ppib, Gapdh, Hprt, Tbp, Ppia, GusB, Prkg1, and Ywhaz), and contrasting the results at 35 weeks of age to the transcriptome profile at 55 weeks of age, we constructed a Venn diagram sorting the genes into 15 distinct zones. Bioinformatic analyses on this refined gene set indicates that elevated bone formation rate in Bmpr2 mutant mice correlates with enrichment for genes containing binding sites for transcription factors associated with skeletal homeostasis. Further, several genes corresponding with osteoblast differentiation and activity are up-regulated in Bmpr2 mutant mice at 35 weeks of age

Elucidating the Molecular Signatures Associated with Elevated Bone Formation Rate

Osteoporosis is a disease of decreased bone density that occurs when bone resorption exceeds bone formation, thereby placing individuals at greater risk of fracture and disability. We previously reported that deletion of the Bmpr2 gene in embryonic skeletal progenitor cells causes substantially elevated bone density in young adulthood and reduced age-related decline in bone density, likely due to elevated bone formation rate. Thus, these mice may serve as a novel model in which to explore the mechanisms regulating bone formation in the aging skeleton. Here, we performed transcriptome profiling and identified a concise gene signature associated with elevated bone formation rate in Bmpr2 mutant mice, with 120 transcripts up-regulated and 131 transcripts down-regulated. Candidate-driven qRT-PCR provided secondary confirmation of this dataset. Notably, only 8 of these differentially-expressed transcripts have been previously implicated in bone physiology (Pak4, Rpl38, B2m, Fgf1, Nmu, Phospho1, Smpd3 and Inbe), thus representing potentially novel regulators of osteoblast function in the aging skeleton. Additionally, we sought to examine the cell communication events that are associated with elevated bone formation rate. Using protein samples from control and mutant mice, we took advantage of recent advancements in high-throughput phospho-profiling antibody arrays, which allow simultaneous detection of \u3e1,300 targets using very small quantities of protein. These results indicate that the phosphorylation status of at least 86 signaling effectors is differentially regulated in Bmpr2 mutant mice as compared to control littermates, including numerous proteins known to regulate osteoblast differentiation and/or activity. Collectively, our work highlights novel factors associated with elevated bone formation rate and may identify new opportunities for treating low bone density in humans

Incipient alcohol use in childhood: Early alcohol sipping and its relations with psychopathology and personality

Prior research has shown that sipping of alcohol begins to emerge during childhood and is potentially etiologically significant for later substance use problems. Using a large, community sample of 9- and 10-year-olds (N = 11,872; 53% female), we examined individual differences in precocious alcohol use in the form of alcohol sipping. We focused explicitly on features that are robust and well-demonstrated correlates of, and antecedents to, alcohol excess and related problems later in the lifespan, including youth- and parent-reported externalizing traits (i.e., impulsivity, behavioral inhibition and activation) and psychopathology. Seventeen percent of the sample reported sipping alcohol outside of a religiously sanctioned activity by age 9 or 10. Several aspects of psychopathology and personality emerged as small but reliable correlates of sipping. Nonreligious sipping was related to youth-reported impulsigenic traits, aspects of behavioral activation, prodromal psychotic-like symptoms, and mood disorder diagnoses, as well as parent-reported externalizing disorder diagnoses. Religious sipping was unexpectedly associated with certain aspects of impulsivity. Together, our findings point to the potential importance of impulsivity and other transdiagnostic indicators of psychopathology (e.g., emotion dysregulation, novelty seeking) in the earliest forms of drinking behavior

Pluralism about Knowledge

In this paper I consider the prospects for pluralism about knowledge, that is, the view that there is a plurality of knowledge relations. After a brief overview of some views that entail a sort of pluralism about knowledge, I focus on a particular kind of knowledge pluralism I call standards pluralism. Put roughly, standards pluralism is the view that one never knows anything simpliciter. Rather, one knows by this-or-that epistemic standard. Because there is a plurality of epistemic standards, there is a plurality of knowledge relations. In §1 I argue that one can construct an impressive case for standards pluralism. In §2 I clarify the relationship between standards pluralism, epistemic contextualism and epistemic relativism. In §3 I argue that standards pluralism faces a serious objection. The gist of the objection is that standards pluralism is incompatible with plausible claims about the normative role of knowledge. In §4 I finish by sketching the form that a standards pluralist response to this objection might take

Bringing Attention to Lesser-known Bone Remodeling Pathways

Osteoporosis, a disease of low bone mass, places individuals at enhanced risk for fracture, disability, and death. In the USA, hospitalizations for osteoporotic fractures exceed those for heart attack, stroke, and breast cancer and, by 2025, the number of fractures due to osteoporosis is expected to rise to nearly three million in the USA alone. Pharmacological treatments for osteoporosis are aimed at stabilizing or increasing bone mass. However, there are significant drawbacks to current pharmacological options, particularly for long-term management of this chronic condition. Moreover, the drug development pipeline is relatively bereft of new strategies. Consequently, there is an urgent and unmet need for developing new strategies and targets for treating osteoporosis. Casual observation led us to hypothesize that much of the bone remodeling research literature focused on relatively few molecular pathways. This led us to perform bibliometric analyses to determine the relative popularity of bone remodeling pathways in publications and US National Institutes of Health funding of the last 10 years. In this review article, we discuss these findings and highlight several less-examined signaling pathways that may hold promise for future therapies

Reduction in Phencyclidine Induced Sensorimotor Gating Deficits in the Rat Following Increased System Xc − Activity in the Medial Prefrontal Cortex

Rationale: Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked to glutamate dysfunction and/or oxidative stress in the prefrontal cortex. System xc −, a cystine–glutamate antiporter, is a poorly understood mechanism that contributes to both cellular antioxidant capacity and glutamate homeostasis. Objectives: Our goal was to determine whether increased system xc − activity within the prefrontal cortex would normalize a rodent measure of sensorimotor gating. Methods: In situ hybridization was used to map messenger RNA (mRNA) expression of xCT, the active subunit of system xc −, in the prefrontal cortex. Prepulse inhibition was used to measure sensorimotor gating; deficits in prepulse inhibition were produced using phencyclidine (0.3–3 mg/kg, sc). N-Acetylcysteine (10–100 μM) and the system xc − inhibitor (S)-4-carboxyphenylglycine (CPG, 0.5 μM) were used to increase and decrease system xc − activity, respectively. The uptake of 14C-cystine into tissue punches obtained from the prefrontal cortex was used to assay system xc − activity. Results: The expression of xCT mRNA in the prefrontal cortex was most prominent in a lateral band spanning primarily the prelimbic cortex. Although phencyclidine did not alter the uptake of 14C-cystine in prefrontal cortical tissue punches, intraprefrontal cortical infusion of N-acetylcysteine (10–100 μM) significantly reduced phencyclidine- (1.5 mg/kg, sc) induced deficits in prepulse inhibition. N-Acetylcysteine was without effect when coinfused with CPG (0.5 μM), indicating an involvement of system xc −. Conclusions: These results indicate that phencyclidine disrupts sensorimotor gating through system xc − independent mechanisms, but that increasing cystine–glutamate exchange in the prefrontal cortex is sufficient to reduce behavioral deficits produced by phencyclidine

Exposure to ambient particulate matter is associated with accelerated functional decline in idiopathic pulmonary fibrosis

BACKGROUND: Idiopathic pulmonary fibrosis (IPF), a progressive disease with an unknown pathogenesis, may be due in part to an abnormal response to injurious stimuli by alveolar epithelial cells. Air pollution and particulate inhalation of matter evoke a wide variety of pulmonary and systemic inflammatory diseases. We therefore hypothesized that increased average ambient particulate matter (PM) concentrations would be associated with an accelerated rate of decline in FVC in IPF. METHODS: We identified a cohort of subjects seen at a single university referral center from 2007 to 2013. Average concentrations of particulate matter < 10 and < 2.5 μg/m3 (PM10 and PM2.5, respectively) were assigned to each patient based on geocoded residential addresses. A linear multivariable mixed-effects model determined the association between the rate of decline in FVC and average PM concentration, controlling for baseline FVC at first measurement and other covariates. RESULTS: One hundred thirty-five subjects were included in the final analysis after exclusion of subjects missing repeated spirometry measurements and those for whom exposure data were not available. There was a significant association between PM10 levels and the rate of decline in FVC during the study period, with each μg/m3 increase in PM10 corresponding with an additional 46 cc/y decline in FVC (P = .008). CONCLUSIONS: Ambient air pollution, as measured by average PM10 concentration, is associated with an increase in the rate of decline of FVC in IPF, suggesting a potential mechanistic role for air pollution in the progression of disease