An Irf6-Esrp1/2 regulatory axis controls midface morphogenesis in vertebrates.

Irf6 and Esrp1 are important for palate development across vertebrates. In zebrafish, we found that irf6 regulates the expression of esrp1 We detailed overlapping Irf6 and Esrp1/2 expression in mouse orofacial epithelium. In zebrafish, irf6 and esrp1/2 share expression in periderm, frontonasal ectoderm and oral epithelium. Genetic disruption of irf6 and esrp1/2 in zebrafish resulted in cleft of the anterior neurocranium. The esrp1/2 mutant also developed cleft of the mouth opening. Lineage tracing of cranial neural crest cells revealed that the cleft resulted not from migration defect, but from impaired chondrogenesis. Analysis of aberrant cells within the cleft revealed expression of sox10, col1a1 and irf6, and these cells were adjacent to krt4+ and krt5+ cells. Breeding of mouse Irf6; Esrp1; Esrp2 compound mutants suggested genetic interaction, as the triple homozygote and the Irf6; Esrp1 double homozygote were not observed. Further, Irf6 heterozygosity reduced Esrp1/2 cleft severity. These studies highlight the complementary analysis of Irf6 and Esrp1/2 in mouse and zebrafish, and identify a unique aberrant cell population in zebrafish expressing sox10, col1a1 and irf6 Future work characterizing this cell population will yield additional insight into cleft pathogenesis.

Arrestin domain-containing 3 (Arrdc3) modulates insulin action and glucose metabolism in liver.

Insulin action in the liver is critical for glucose homeostasis through regulation of glycogen synthesis and glucose output. Arrestin domain-containing 3 (Arrdc3) is a member of the α-arrestin family previously linked to human obesity. Here, we show that Arrdc3 is differentially regulated by insulin in vivo in mice undergoing euglycemic-hyperinsulinemic clamps, being highly up-regulated in liver and down-regulated in muscle and fat. Mice with liver-specific knockout (KO) of the insulin receptor (IR) have a 50% reduction in Arrdc3 messenger RNA, while, conversely, mice with liver-specific KO of Arrdc3 (L-Arrdc3 KO) have increased IR protein in plasma membrane. This leads to increased hepatic insulin sensitivity with increased phosphorylation of FOXO1, reduced expression of PEPCK, and increased glucokinase expression resulting in reduced hepatic glucose production and increased hepatic glycogen accumulation. These effects are due to interaction of ARRDC3 with IR resulting in phosphorylation of ARRDC3 on a conserved tyrosine (Y382) in the carboxyl-terminal domain. Thus, Arrdc3 is an insulin target gene, and ARRDC3 protein directly interacts with IR to serve as a feedback regulator of insulin action in control of liver metabolism.

An adenosine receptor-Krüppel-like factor 4 protein axis inhibits adipogenesis.

Adipogenesis represents a key process in adipose tissue development and remodeling, including during obesity. Exploring the regulation of adipogenesis by extracellular ligands is fundamental to our understanding of this process. Adenosine, an extracellular nucleoside signaling molecule found in adipose tissue depots, acts on adenosine receptors. Here we report that, among these receptors, the A2b adenosine receptor (A2bAR) is highly expressed in adipocyte progenitors. Activation of the A2bAR potently inhibits differentiation of mouse stromal vascular cells into adipocytes, whereas A2bAR knockdown stimulates adipogenesis. The A2bAR inhibits differentiation through a novel signaling cascade involving sustained expression of Krüppel-like factor 4 (KLF4), a regulator of stem cell maintenance. Knockdown of KLF4 ablates the ability of the A2bAR to inhibit differentiation. A2bAR activation also inhibits adipogenesis in a human primary preadipocyte culture system. We analyzed the A2bARKLF4 axis in adipose tissue of obese subjects and, intriguingly, found a strong correlation between A2bAR and KLF4 expression in both subcutaneous and visceral human fat. Hence, our study implicates the A2bAR as a regulator of adipocyte differentiation and the A2bAR-KLF4 axis as a potentially significant modulator of adipose biology.

Neural crest and periderm-specific requirements of Irf6 during neural tube and craniofacial development.

IRF6 is a key genetic determinant of syndromic and non-syndromic cleft lip and palate. The ability to interrogate post-embryonic requirements of Irf6 has been hindered, as global Irf6 ablation in the mouse causes neonatal lethality. Prior work analyzing Irf6 in mouse models defined its role in the embryonic surface epithelium and periderm where it is required to regulate cell proliferation and differentiation. Several reports have also described Irf6 gene expression in other cell types, such as muscle, and neuroectoderm. However, analysis of a functional role in non-epithelial cell lineages has been incomplete due to the severity and lethality of the Irf6 knockout model and the paucity of work with a conditional Irf6 allele. Here we describe the generation and characterization of a new Irf6 floxed mouse model and analysis of Irf6 ablation in periderm and neural crest lineages. This work found that loss of Irf6 in periderm recapitulates a mild Irf6 null phenotype, suggesting that Irf6-mediated signaling in periderm plays a crucial role in regulating embryonic development. Further, conditional ablation of Irf6 in neural crest cells resulted in an anterior neural tube defect of variable penetrance. The generation of this conditional Irf6 allele allows for new insights into craniofacial development and new exploration into the post-natal role of Irf6.

A2B adenosine receptor promotes mesenchymal stem cell differentiation to osteoblasts and bone formation in vivo.

The differentiation of osteoblasts from their precursors, mesenchymal stem cells, is an important component of bone homeostasis as well as fracture healing. The A2B adenosine receptor (A2BAR) is a Gα(s)/α(q)-protein-coupled receptor that signals via cAMP. cAMP-mediated signaling has been demonstrated to regulate the differentiation of mesenchymal stem cells (MSCs) into various skeletal tissue lineages. Here, we studied the role of this receptor in the differentiation of MSCs to osteoblasts. In vitro differentiation of bone marrow-derived MSCs from A2BAR KO mice resulted in lower expression of osteoblast differentiation transcription factors and the development of fewer mineralized nodules, as compared with WT mice. The mechanism of effect involves, at least partially, cAMP as indicated by experiments involving activation of the A2BAR or addition of a cAMP analog during differentiation. Intriguingly, in vivo, microcomputed tomography analysis of adult femurs showed lower bone density in A2BAR KO mice as compared with WT. Furthermore, A2BAR KO mice display a delay in normal fracture physiology with lower expression of osteoblast differentiation genes. Thus, our study identified the A2BAR as a new regulator of osteoblast differentiation, bone formation, and fracture repair.

Differentiation of mesenchymal stem cells to osteoblasts and chondrocytes: a focus on adenosine receptors.

Skeletogenesis, either during development, post-injury or for maintenance, is a carefully coordinated process reliant on the appropriate differentiation of mesenchymal stem cells. Some well described, as well as a new regulator of this process (adenosine receptors), are alike in that they signal via cyclic-AMP (cAMP). This review highlights the known contribution of cAMP signalling to mesenchymal stem cell differentiation to osteoblasts and to chondrocytes. Focus has been given to how these regulators influence the commitment of the osteochondroprogenitor to these separate lineages.

dact1/2 modifies noncanonical Wnt signaling and calpain 8 expression to regulate convergent extension and craniofacial development.

Wnt signaling plays a crucial role in the early embryonic patterning and development, to regulate convergent extension during gastrulation and the establishment of the dorsal axis. Further, Wnt signaling is a crucial regulator of craniofacial morphogenesis. The adapter proteins Dact1 and Dact2 modulate the Wnt signaling pathway through binding to Disheveled, however, the distinct relative functions of Dact1 and Dact2 during embryogenesis remain unclear. We found that dact1 and dact2 genes have dynamic spatiotemporal expression domains that are reciprocal to one another and to wnt11f2l, that suggest distinct functions during zebrafish embryogenesis. We found that both dact1 and dact2 contribute to axis extension, with compound mutants exhibiting a similar convergent extension defect and craniofacial phenotype to the wnt11f2 mutant. Utilizing single-cell RNAseq and gpc4 mutant that disrupts noncanonical Wnt signaling, we identified dact1/2 specific roles during early development. Comparative whole transcriptome analysis between wildtype, gpc4 and dact1/2 mutants revealed a novel role for dact1/2 in regulating the mRNA expression of the classical calpain capn8. Over-expression of capn8 phenocopies dact1/2 craniofacial dysmorphology. These results identify a previously unappreciated role of capn8 and calcium-dependent proteolysis during embryogenesis. Taken together, our findings highlight the distinct and overlapping roles of dact1 and dact2 in embryonic craniofacial development, providing new insights into the multifaceted regulation of Wnt signaling.

Advanced prehospital resuscitative care: Can we identify trauma patients who might benefit?

BACKGROUND: Uncontrolled truncal hemorrhage remains the most common cause of potentially preventable death after injury. The notion of earlier hemorrhage control and blood product resuscitation is therefore attractive. Some systems have successfully implemented prehospital advanced resuscitative care (ARC) teams. Early identification of patients is key and is reliant on rapid decision making and communication. The purpose of this simulation study was to explore the feasibility of early identification of patients who might benefit from ARC in a typical US setting. METHODS: We conducted a prospective observational/simulation study at a level I trauma center and two associated emergency medical service (EMS) agencies over a 9-month period. The participating EMS agencies were asked to identify actual patients who might benefit from the activation of a hypothetical trauma center-based ARC team. This decision was then communicated in real time to the study team. RESULTS: Sixty-three patients were determined to require activation. The number of activations per month ranged from 2 to 15. The highest incidence of calls occurred between 4 pm to midnight. Of the 63 patients, 33 were transported to the trauma center. The most common presentation was with penetrating trauma. The median age was 27 years (interquartile range, 24-45 years), 75% were male, and the median Injury Severity Score was 11 (interquartile range, 7-20). Based on injury patterns, treatment received, and outcomes, it was determined that 6 (18%) of 33 patients might have benefited from ARC. Three of the patients died en-route to or soon after arrival at the trauma center. CONCLUSION: The prehospital identification of patients who might benefit from ARC is possible but faces challenges. Identifying strategies to adapt existing processes may allow better utilization of the existing infrastructure and should be a focus of future efforts. LEVEL OF EVIDENCE: Prognostic/Epidemiologic, level III.

Synergistic roles of Wnt modulators R-spondin2 and R-spondin3 in craniofacial morphogenesis and dental development.

Wnt signaling plays a critical role in craniofacial patterning, as well as tooth and bone development. Rspo2 and Rspo3 are key regulators of Wnt signaling. However, their coordinated function and relative requirement in craniofacial development and odontogensis are poorly understood. We showed that in zebrafish rspo2 and rspo3 are both expressed in osteoprogenitors in the embryonic craniofacial skeleton. This is in contrast to mouse development, where Rspo3 is expressed in osteoprogenitors while Rspo2 expression is not observed. In zebrafish, rspo2 and rspo3 are broadly expressed in the pulp, odontoblasts and epithelial crypts. However, in the developing molars of the mouse, Rspo3 is largely expressed in the dental follicle and alveolar mesenchyme while Rspo2 expression is restricted to the tooth germ. While Rspo3 ablation in the mouse is embryonic lethal, zebrafish rspo3-/- mutants are viable with modest decrease in Meckel's cartilage rostral length. However, compound disruption of rspo3 and rspo2 revealed synergistic roles of these genes in cartilage morphogenesis, fin development, and pharyngeal tooth development. Adult rspo3-/- zebrafish mutants exhibit a dysmorphic cranial skeleton and decreased average tooth number. This study highlights the differential functions of Rspo2 and Rspo3 in dentocranial morphogenesis in zebrafish and in mouse.

Automatic collision notification availability and emergency response times following vehicle collision-an analysis of the 2017 crash investigation sampling system.

OBJECTIVE: To determine whether occupants of collisions involving at least one vehicle with an available Automatic Collision Notification (ACN) system have quicker times from collision to 1) Emergency Medical Services (EMS) notification and 2) arrival to a medical center. METHODS: Using data from the 2017 Crash Investigation Sampling System, vehicles were categorized as whether ACN was available using data from the CISS's dataset of crash avoidance system availability (in which ACN is included though notably not a crash avoidance system). A Cox proportional hazards model-overall and stratified by urbanization-was used to compare the time from collision to both EMS notification and EMS arrival to a medical center. RESULTS: A total of 2,034 collisions (weight n: 2,775,512) involving 4235 occupants (weighted n: 4,987,669) were included. An estimated 259,021 (9.3%) and 546,223 occupants (11.0%) were in a collision in which one vehicle had ACN equipped. The median time to EMS notification was longer for collisions in which no involved vehicles had ACN available (median 4, IQR 2-9 minutes) than ACN-exposed collisions (median 2, IQR 1-5 minutes). There was a marginally significant higher hazard (i.e., instantaneous risk) of EMS notification for collisions with at least one vehicle having ACN available (HR 1.77, 95% CI 0.99-3.15). Likewise, there was a higher instantaneous risk of medical center arrival for occupants (HR 1.80, 95% CI 1.41-2.30) involved in collisions in which at least one vehicle had ACN available. ACN was associated with quicker EMS notification only in urban areas (HR 3.06, 95% CI 1.57-5.97) and associated with a greater reduction in time to medical facility in less urban areas (median 36 vs 45 minutes, HR 2.12, 95% CI 1.22-3.63). CONCLUSIONS: This is the first study to directly compare EMS response-related times between collisions involving vehicles with and without ACN available. The current data corroborate prior literature reporting quicker EMS notification times among collisions involving ACN-equipped vehicles. This is the first study to find that ACN is also associated to quicker times to medical center arrival, particularly for collisions occurring in less urban areas. Future research examining whether these decreased times are associated with better clinical outcomes are needed in order to fully assess ACN's ability to prevent trauma-related mortality and morbidity.

Early and prehospital trauma deaths: Who might benefit from advanced resuscitative care?

BACKGROUND: Recent civilian and military data from the United States and the United Kingdom suggest that further reductions in mortality will require prehospital or preoperating room hemorrhage control and blood product resuscitation. The aims of this study were to examine the potential preventability of prehospital and early in-hospital fatalities, and to consider the geographical location of such incidents, to contextualize how the use of advanced resuscitative techniques could be operationalized. METHODS: Retrospective analysis of prehospital and early in-hospital trauma deaths from January to December 2017. Data were obtained from the Coroner/ME's Office. Each death was reviewed by a panel of two trauma surgeons and a forensic pathologist. Anatomical and physiological survivabilities were evaluated separately, and then combined, leading to a holistic assessment of preventability. Incident locations were mapped and analyzed using ArcGIS. RESULTS: Three hundred sixteen trauma deaths were identified. Two hundred thirty-one (73%) were deemed anatomically not survivable; 29 (9%) anatomically survivable, but only with hospital care; 43 (14%) anatomically survivable with advanced prehospital care; and 13 (4%) anatomically survivable with basic prehospital care. Physiologically, 114 (36%) of the patients had been dead for some time when found; 137 (43%) had no cardiorespiratory effort on arrival of Emergency Medical Services (EMS) at the scene; 24 (8%) had cardiorespiratory effort at the scene, but not on arrival at the emergency department; and 41 (13%) had cardiorespiratory effort on arrival at the emergency department, but died shortly after. Combining the assessments, 10 (3%) deaths were deemed probably not preventable, 38 (12%) possibly preventable, and the remaining 278 (85%) not preventable. CONCLUSION: Twelve percent of trauma deaths were potentially preventable and might be amenable to advanced resuscitative interventions. Operationalizing this type of care will be challenging and will require either prehospital doctors, or very highly trained paramedics, nurses, or physician assistants. LEVEL OF EVIDENCE: Epidemiological, level III.

Stop the Bleed: gap analysis and geographical evaluation of incident locations.

BACKGROUND: Trauma is a major public health issue. In 2015, the White House launched the "Stop the Bleed" (STB) campaign, which aims to equip would-be bystanders with the ability and equipment to assist in bleeding emergencies. This study sought to estimate the number of patients who might benefit from STB intervention, in an everyday setting, and their spatial injury profile. METHODS: This is a retrospective analysis of trauma registry and medical examiners' data, collected between 2013 and 2017. The majority of patients were male. The median age was 32 years. Incidents were geocoded by ZIP code, and mapped using Quantum Geographic Information System (QGIS). RESULTS: We identified 139 patients from medical examiner records and UAB's trauma registry who might have benefitted from STB intervention. The number of incidents per year ranged from 22 to 35, averaging 2.3 incidents per month. There was no evidence of geographical clustering, although the small number of incidents precluded a formal geostatistical analysis. CONCLUSION: The number of patients who might benefit from STB interventions on a daily basis is small, and incident locations are difficult to predict. Educating the public in how to stop bleeding is appealing, but providing easy and widespread access to STB kits may be difficult. Although there are parallels to the provision of cardiopulmonary resuscitation and defibrillation for cardiac arrest, there are also differences, which should not be overlooked.

Exogenous GDF11, but not GDF8, reduces body weight and improves glucose homeostasis in mice.

Insulin resistance is associated with aging in mice and humans. We have previously shown that administration of recombinant GDF11 (rGDF11) to aged mice alters aging phenotypes in the brain, skeletal muscle, and heart. While the closely related protein GDF8 has a role in metabolism, limited data are available on the potential metabolic effects of GDF11 or GDF8 in aging. To determine the metabolic effects of these two ligands, we administered rGDF11 or rGDF8 protein to young or aged mice fed a standard chow diet, short-term high-fat diet (HFD), or long-term HFD. Under nearly all of these diet conditions, administration of exogenous rGDF11 reduced body weight by 3-17% and significantly improved glucose tolerance in aged mice fed a chow (~30% vs. saline) or HF (~50% vs. saline) diet and young mice fed a HFD (~30%). On the other hand, exogenous rGDF8 showed signifcantly lesser effect or no effect at all on glucose tolerance compared to rGDF11, consistent with data demonstrating that GFD11 is a more potent signaling ligand than GDF8. Collectively, our results show that administration of exogenous rGDF11, but not rGDF8, can reduce diet-induced weight gain and improve metabolic homeostasis.

Mechanisms of induction of adenosine receptor genes and its functional significance.

Adenosine is a metabolite generated and released from cells, particularly under injury or stress. It elicits protective or damaging responses via signaling through the adenosine receptors, including the adenylyl cyclase inhibitory A(1) and A(3), and the adenylyl cyclase stimulatory A(2A) and A(2B). Multiple adenosine receptor types, including stimulatory and inhibitory, can be found in the same cell, suggesting that a careful balance of adenosine receptor expression in a particular cell is necessary for a specific adenosine-induced response. This balance could be controlled by differential expression of the adenosine receptor genes under different stimuli. Here, we have reviewed an array of studies that have characterized basal or induced expression of the adenosine receptors and common as well as distinct mechanisms of effect, in hopes that ongoing studies on this topic will further elucidate detailed mechanisms of adenosine receptor regulation, leading to potential therapeutic applications.

What can I learn from this interaction? A qualitative analysis of medical student self-reflection and learning in a standardized patient exercise about disability.

Patients with disabilities receive fewer health services than the general population, yet they have greater health needs. Similarly, physicians report limited training in disability. The current project examines medical students' learning about disability in a project using individuals with disabilities as medical educators. Family medicine clerkship students (N = 138) across an academic year were videotaped during interviews with standardized patient educators with disabilities and during feedback sessions following the interactions. Qualitative analysis of feedback transcripts identifies three primary areas of integrating learning, reflective practice, and disability: (1) learning how disability impacts the treatment plan, (2) self-reflection and recognizing attitudes about disability, and (3) learning about the practice of medicine generally from the disability exercise. Themes are identified within each of the primary learning areas. Medical student reflection provides evidence of learning to connect disability with pain, everyday life, and treatment. Medical students learned to recognize patients' expertise in their own condition and in health care navigation. Medical students also examined how their language implies attitude. The current investigation provided evidence of the ways examining disability can serve as a cornerstone for building relationship-centered patient care and encouraging reflective practice overall.

Clearing the cervical spine in patients with distracting injuries: An AAST multi-institutional trial.

BACKGROUND: Single institution studies have shown that clinical examination of the cervical spine (c-spine) is sensitive for clearance of the c-spine in blunt trauma patients with distracting injuries. Despite an unclear definition, most trauma centers still adhere to the notion that distracting injuries adversely affect the sensitivity of c-spine clinical examination. A prospective AAST multi-institutional trial was performed to assess the sensitivity of clinical examination screening of the c-spine in awake and alert blunt trauma patients with distracting injuries. METHODS: During the 42-month study period, blunt trauma patients 18 years and older were prospectively evaluated with a standard c-spine examination protocol at 8 Level 1 trauma centers. Clinical examination was performed regardless of the presence of distracting injuries. Patients without complaints of neck pain, tenderness or pain on range of motion were considered to have a negative c-spine clinical examination. All patients with positive or negative c-spine clinical examination underwent computed tomography (CT) scan of the entire c-spine. Clinical examination findings were documented prior to the CT scan. RESULTS: During the study period, 2929 patients were entered. At least one distracting injury was diagnosed in 70% of the patients. A c-spine injury was found on CT scan in 7.6% of the patients. There was no difference in the rate of missed injury when comparing patients with a distracting injury to those without a distracting injury (10.4% vs. 12.6%, p = 0.601). Only one injury missed by clinical examination underwent surgical intervention and none had a neurological complication. CONCLUSIONS: Negative clinical examination may be sufficient to clear the cervical spine in awake and alert blunt trauma patients, even in the presence of a distracting injury. These findings suggest a potential source for improvement in resource utilization. LEVEL OF EVIDENCE: Therapeutic/care management, level IV.

TNF-alpha upregulates the A2B adenosine receptor gene: The role of NAD(P)H oxidase 4.

Proliferation of vascular smooth muscle cells (VSMC), oxidative stress, and elevated inflammatory cytokines are some of the components that contribute to plaque formation in the vasculature. The cytokine tumor necrosis factor-alpha (TNF-alpha) is released during vascular injury, and contributes to lesion formation also by affecting VSMC proliferation. Recently, an A(2B) adenosine receptor (A(2B)AR) knockout mouse illustrated that this receptor is a tissue protector, in that it inhibits VSMC proliferation and attenuates the inflammatory response following injury, including the release of TNF-alpha. Here, we show a regulatory loop by which TNF-alpha upregulates the A(2B)AR in VSMC in vitro and in vivo. The effect of this cytokine is mimicked by its known downstream target, NAD(P)H oxidase 4 (Nox4). Nox4 upregulates the A(2B)AR, and Nox inhibitors dampen the effect of TNF-alpha. Hence, our study is the first to show that signaling associated with Nox4 is also able to upregulate the tissue protecting A(2B)AR.

Reducing Patient No-Shows: An Initiative at an Integrated Care Teaching Health Center.

BACKGROUND: Patient no-shows impede the effectiveness and efficiency of health care services delivery. OBJECTIVE: To evaluate a 2-phase intervention to reduce no-show rates at an integrated care community health center that incorporates a teaching program for osteopathic family medicine residents. METHODS: The Elmont Teaching Health Center (ETHC) is 1 of 5 community-based health centers comprising the Long Island Federally Qualified Health Centers. In August 2015, the ETHC implemented a centerwide No-Show Rates Reduction Initiative divided into an assessment phase and implementation phase. The assessment phase identified reasons most frequently cited by patients for no-shows at the ETHC. The implementation phase, initiated in mid-September, addressed these reasons by focusing on reminder call verification, patient education, personal responses to patient calls, institutional awareness, and integration with multiple departments. To assess the initiative, monthly no-show rates were compared by quarter for 2015 and against rates for the previous year. RESULTS: We recorded 27,826 appointments with 6147 no-shows in 2014 and 31,696 appointments with 5690 no-shows in 2015. No-show rates in the first 3 quarters of 2015 (range, 18.2%-20.0%) were slightly lower than the rates in 2014 (20.1%-23.4%) and then changed by an increasingly wide margin in the last quarter of 2015 (15.3%), leading to a significant year (2014, 2015) by quarter (Q1, Q2, Q3, Q4) interaction (P=.004). Also, the change observed in Q4 in 2015 differed significantly from Q1 (P=.017), Q2 (P=.004), and Q3 (P=.027) in 2015, while Q1, Q2, and Q3 in 2015 did not significantly differ from one another. CONCLUSION: No-show rates were successfully reduced after a 2-phase intervention was implemented at 1 health center within a larger health care organization. Future directions include dismantling the individual components of the intervention, evaluating the role of patient volumes in no-show rates, assessing patient outcomes (eg, costs, health) in integrative care settings that treat underserved populations, and evaluating family medicine residents' training on continuity of care and no-show rates.

Correction: Adipocyte arrestin domain-containing 3 protein (Arrdc3) regulates uncoupling protein 1 (Ucp1) expression in white adipose independently of canonical changes in ß-adrenergic receptor signaling.

[This corrects the article DOI: 10.1371/journal.pone.0173823.].

Adipocyte arrestin domain-containing 3 protein (Arrdc3) regulates uncoupling protein 1 (Ucp1) expression in white adipose independently of canonical changes in ß-adrenergic receptor signaling.

Adaptive thermogenesis and cold-induced activation of uncoupling protein 1 (Ucp1) in brown adipose tissue in rodents is well-described and attributed to sympathetic activation of ß-adrenergic signaling. The arrestin domain containing protein Arrdc3 is a regulator of obesity in mice and also appears linked to obesity in humans. We generated a mouse with conditional deletion of Arrdc3, and here we present evidence that genetic ablation of Arrdc3 specifically in adipocytes results in increased Ucp1 expression in subcutaneous and parametrial adipose tissue. Although this increase in expression did not correspond with significant changes in body weight or energy expenditure, adipocyte-specific Arrdc3-null mice had improved glucose tolerance. It was previously hypothesized that Arrdc3 ablation leads to increased ß-adrenergic receptor sensitivity; however, in vitro experiments show that Arrdc3-null adipocytes responded to ß-adrenergic receptor agonist with decreased Ucp1 levels. Additionally, canonical ß-adrenergic receptor signaling was not different in Arrdc3-null adipocytes. These data reveal a role for Arrdc3 in the regulation of Ucp1 expression in adipocytes. However, this adipocyte effect is insufficient to generate the obesity-resistant phenotype of mice with ubiquitous deletion of Arrdc3, indicating a likely role for Arrdc3 in cells other than adipocytes.