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OBJECTIVE: Despite a growing armamentarium of medical therapies for ulcerative colitis (UC), colectomy remains an important therapeutic option. To better inform shared decision-making about surgery, we estimated the contemporary risk of mortality post-colectomy. METHODS: Mortality rates were estimated using the National Inpatient Sample (2016-2020). Factors associated with post-colectomy death were evaluated in multivariable regression. RESULTS: Post-colectomy mortality occurred in 1.2% [95% CI: 0.8%, 1.9%] of hospitalizations. Comorbidity burden, emergent laparotomy, and delays to surgery >5 days after admission were associated with mortality. CONCLUSIONS: Colectomy may be associated with mortality; however, this risk is heterogeneous based on patient- and procedural-related factors.
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Spiny projection neurons (SPNs) of the striatum are critical in integrating neurochemical information to coordinate motor and reward-based behavior. Mutations in the regulatory transcription factors expressed in SPNs can result in neurodevelopmental disorders (NDDs). Paralogous transcription factors Foxp1 and Foxp2, which are both expressed in the dopamine receptor 1 (D1) expressing SPNs, are known to have variants implicated in NDDs. Utilizing mice with a D1-SPN-specific loss of Foxp1, Foxp2, or both and a combination of behavior, electrophysiology, and cell-type-specific genomic analysis, loss of both genes results in impaired motor and social behavior as well as increased firing of the D1-SPNs. Differential gene expression analysis implicates genes involved in autism risk, electrophysiological properties, and neuronal development and function. Viral-mediated re-expression of Foxp1 into the double knockouts is sufficient to restore electrophysiological and behavioral deficits. These data indicate complementary roles between Foxp1 and Foxp2 in the D1-SPNs.
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Cuerpo Estriado , Factores de Transcripción Forkhead , Animales , Factores de Transcripción Forkhead/metabolismo , Factores de Transcripción Forkhead/genética , Ratones , Cuerpo Estriado/metabolismo , Proteínas Represoras/metabolismo , Proteínas Represoras/genética , Ratones Noqueados , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D1/genética , Masculino , Neuronas/metabolismo , Ratones Endogámicos C57BL , Conducta SocialRESUMEN
Long-range glutamatergic inputs originating from the cortex and thalamus are indispensable for striatal development, providing the foundation for motor and cognitive functions. Despite their significance, transcriptional regulation governing these inputs remains largely unknown. We investigated the role of a transcription factor encoded by a high-risk autism-associated gene, FOXP1, in sculpting glutamatergic inputs onto spiny projection neurons (SPNs) within the striatum. We find a neuron subtype-specific role of FOXP1 in strengthening and maturing glutamatergic inputs onto dopamine receptor 2-expressing SPNs (D2 SPNs). We also find that FOXP1 promotes synaptically driven excitability in these neurons. Using single-nuclei RNA sequencing, we identify candidate genes that mediate these cell-autonomous processes through postnatal FOXP1 function at the post-synapse. Last, we demonstrate that postnatal FOXP1 reinstatement rescues electrophysiological deficits, cell type-specific gene expression changes, and behavioral phenotypes. Together, this study enhances our understanding of striatal circuit development and provides proof of concept for a therapeutic approach for FOXP1 syndrome and other neurodevelopmental disorders.
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Cuerpo Estriado , Factores de Transcripción Forkhead , Neuronas , Receptores de Dopamina D2 , Proteínas Represoras , Animales , Factores de Transcripción Forkhead/metabolismo , Factores de Transcripción Forkhead/genética , Cuerpo Estriado/metabolismo , Cuerpo Estriado/citología , Ratones , Neuronas/metabolismo , Proteínas Represoras/metabolismo , Proteínas Represoras/genética , Fenotipo , Sinapsis/metabolismo , Sinapsis/fisiología , MasculinoRESUMEN
Long-range glutamatergic inputs from the cortex and thalamus are critical for motor and cognitive processing in the striatum. Transcription factors that orchestrate the development of these inputs are largely unknown. We investigated the role of a transcription factor and high-risk autism-associated gene, FOXP1, in the development of glutamatergic inputs onto spiny projection neurons (SPNs) in the striatum. We find that FOXP1 robustly drives the strengthening and maturation of glutamatergic input onto dopamine receptor 2-expressing SPNs (D2 SPNs) but has a comparatively milder effect on D1 SPNs. This process is cell-autonomous and is likely mediated through postnatal FOXP1 function at the postsynapse. We identified postsynaptic FOXP1-regulated transcripts as potential candidates for mediating these effects. Postnatal reinstatement of FOXP1 rescues electrophysiological deficits, reverses gene expression alterations resulting from embryonic deletion, and mitigates behavioral phenotypes. These results provide support for a possible therapeutic approach for individuals with FOXP1 syndrome.
RESUMEN
Spiny projection neurons (SPNs) of the striatum are critical in integrating neurochemical information to coordinate motor and reward-based behavior. Mutations in the regulatory transcription factors expressed in SPNs can result in neurodevelopmental disorders (NDDs). Paralogous transcription factors Foxp1 and Foxp2, which are both expressed in the dopamine receptor 1 (D1) expressing SPNs, are known to have variants implicated in NDDs. Utilizing mice with a D1-SPN specific loss of Foxp1, Foxp2, or both and a combination of behavior, electrophysiology, and cell-type specific genomic analysis, loss of both genes results in impaired motor and social behavior as well as increased firing of the D1-SPNs. Differential gene expression analysis implicates genes involved in autism risk, electrophysiological properties, and neuronal development and function. Viral mediated re-expression of Foxp1 into the double knockouts was sufficient to restore electrophysiological and behavioral deficits. These data indicate complementary roles between Foxp1 and Foxp2 in the D1-SPNs.
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BACKGROUND: Paradigm shifts in kidney cancer management have led to higher health care spending. Here, total and per capita health care spending and primary drivers of change in health expenditures for kidney cancer in the United States between 1996 and 2016 are estimated. METHODS: Public databases developed by the Institute for Health Metrics and Evaluation for the Disease Expenditure Project were used. The prevalence of kidney cancer was estimated from the Global Burden of Disease Study. Changes in health care spending on kidney cancer were assessed by joinpoint regression and expressed as annual percent changes (APCs). RESULTS: In 2016, total health care spending on kidney cancer was $3.42 billion (95% CI, $2.91 billion to $3.89 billion) compared with $1.18 billion (95% CI, $1.07 billion to $1.31 billion) in 1996. Per capita spending had two inflection points in 2005 and 2008, close to the approval years of targeted therapies, which corresponded to APCs of +2.9% (95% CI, +2.3% to +3.6%; p < .001) per year, 1996-2005; +9.2% (95% CI, +3.4% to +15.2%; p = .004) per year, 2005-2008; and +3.1% (95% CI, +2.2% to +3.9%; p < .001) per year, 2008-2016. Inpatient care was the largest contributor to health expenditures, which accounted for $1.56 billion (95% CI, $1.19 billion to $1.95 billion) in 2016. Price and intensity of care was the primary driver of increased health expenditures, whereas service utilization was the primary driver of reduced health expenditures. CONCLUSIONS: Prevalence-adjusted health care spending on kidney cancer continues to rise in the United States, which is primarily attributable to inpatient care and driven by the price and intensity of care over time.
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Gastos en Salud , Neoplasias Renales , Humanos , Estados Unidos/epidemiología , Hospitalización , Prevalencia , Neoplasias Renales/epidemiología , Neoplasias Renales/terapiaRESUMEN
BACKGROUND: Changes in clinical care for appendicitis have impacted healthcare use associated with treatment. We evaluated national trends and assessed factors associated with healthcare costs for appendicitis in the United States. DESIGN: The Disease Expenditure Project, the Global Burden of Disease study, and the National Inpatient Sample were used to estimate total national expenditures, per-capita costs for incident cases, and factors associated with inpatient costs for appendicitis management, respectively. The national estimates of appendicitis costs were obtained from 1996 to 2016. Appendicitis incidence was estimated to calculate per-capita costs. After application of survey weights for the stratified sample design, 191,180 weighted discharges for appendicitis from the 2016 National Inpatient Sample study were evaluated. The Disease Expenditure Project and the Global Burden of Disease study were used to estimate total and per-capita spending. Temporal trends were evaluated using joinpoint regression, expressed as annual percent change. Multivariable linear regression was used to evaluate patient factors associated with total hospital charges. RESULTS: In 2016, total spending on appendicitis was $9.3 billion (95% confidence interval: $8.0-$10.8], a 2-fold increase from $4.7 billion ($4.0-$5.3) in 1996. Per-capita spending decreased significantly after 2011 (annual percent change -3.7% [-4.4% to -2.9%]). Patients ≥65 years accounted for 64.1% (61.1%-67.3%) of total spending for appendicitis. The hospital charges for older patients were significantly higher among those undergoing appendectomy. CONCLUSION: Overall healthcare spending for appendicitis has doubled from 1996 to 2016, but per capita spending has decreased since 2011, driven by improved efficiency of inpatient care. Nearly two-thirds of spending is on patients ≥65 years, with significantly higher costs associated with surgical management in this population.
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Apendicitis , Humanos , Estados Unidos , Estudios Retrospectivos , Atención a la Salud , Gastos en Salud , Costos de la Atención en SaludRESUMEN
BACKGROUND & AIMS: The management of gastrointestinal (GI) cancers is associated with high health care spending. We estimated trends in United States (US) health care spending for patients with GI cancers between 1996 and 2016 and developed projections to 2030. METHODS: We used economic data, adjusted for inflation, developed by the Institute for Health Metrics and Evaluations for the Disease Expenditure Project. Corresponding US age-adjusted prevalence of GI cancers was estimated from the Global Burden of Diseases Study. Prevalence-adjusted temporal trends in the US health care spending in patients with GI cancers, stratified by cancer site, age, and setting of care, were estimated using joinpoint regression, expressed as annual percentage change (APC) with 95% confidence intervals (CIs). Autoregressive integrated moving average models were used to project spending to 2030. RESULTS: In 2016, total spending for GI cancers was primarily attributable to colorectal ($10.50 billion; 95% CI, $9.35-$11.70 billion) and pancreatic cancer ($2.55 billion; 95% CI, $2.23-$2.82 billion), and primarily for inpatient care (64.5%). Despite increased total spending, more recent per-patient spending for pancreatic (APC 2008-2016, -1.4%; 95% CI, -2.2% to -0.7%), gallbladder/biliary tract (APC 2010-2016, -4.3%; 95% CI, -4.8% to -3.8%), and gastric cancer (APC 2011-2016, -4.4%; 95% CI, -5.8% to -2.9%) decreased. Increasing price and intensity of care provision was the largest driver of higher expenditures. By 2030, it is projected more than $21 billion annually will be spent on GI cancer management. CONCLUSIONS: Total spending for GI cancers in the US is substantial and projected to increase. Expenditures are primarily driven by inpatient care for colorectal cancer, although per-capita spending trends differ by GI cancer type.
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Neoplasias Gastrointestinales , Gastos en Salud , Neoplasias Gastrointestinales/epidemiología , Neoplasias Gastrointestinales/terapia , Hospitalización , Humanos , Prevalencia , Estados Unidos/epidemiologíaAsunto(s)
Costos de la Atención en Salud/tendencias , Recursos en Salud/economía , Recursos en Salud/tendencias , Pancreatitis/economía , Pancreatitis/terapia , Aceptación de la Atención de Salud , Procedimientos Quirúrgicos del Sistema Digestivo/economía , Procedimientos Quirúrgicos del Sistema Digestivo/tendencias , Endoscopía Gastrointestinal/economía , Endoscopía Gastrointestinal/tendencias , Gastos en Salud/tendencias , Costos de Hospital/tendencias , Humanos , Incidencia , América del Norte/epidemiología , Pancreatitis/diagnóstico , Pancreatitis/epidemiología , Pancreatitis Crónica/diagnóstico , Pancreatitis Crónica/economía , Pancreatitis Crónica/epidemiología , Pancreatitis Crónica/terapia , Readmisión del Paciente/economía , Readmisión del Paciente/tendencias , Prevalencia , Factores de TiempoRESUMEN
Cannabinoid 1 receptor (CB1R) inverse agonists reduce body weight and improve several parameters of glucose homeostasis. However, these drugs have also been associated with deleterious side effects. CB1R expression is widespread in the brain and in peripheral tissues, but whether specific sites of expression can mediate the beneficial metabolic effects of CB1R drugs, while avoiding the untoward side effects, remains unclear. Evidence suggests inverse agonists may act on key sites within the central nervous system to improve metabolism. The ventromedial hypothalamus (VMH) is a critical node regulating energy balance and glucose homeostasis. To determine the contributions of CB1Rs expressed in VMH neurons in regulating metabolic homeostasis, we generated mice lacking CB1Rs in the VMH. We found that the deletion of CB1Rs in the VMH did not affect body weight in chow- and high-fat diet-fed male and female mice. We also found that deletion of CB1Rs in the VMH did not alter weight loss responses induced by the CB1R inverse agonist SR141716. However, we did find that CB1Rs of the VMH regulate parameters of glucose homeostasis independent of body weight in diet-induced obese male mice.NEW & NOTEWORTHY Cannabinoid 1 receptors (CB1Rs) regulate metabolic homeostasis, and CB1R inverse agonists reduce body weight and improve parameters of glucose metabolism. However, the cell populations expressing CB1Rs that regulate metabolic homeostasis remain unclear. CB1Rs are highly expressed in the ventromedial hypothalamic nucleus (VMH), which is a crucial node that regulates metabolism. With CRISPR/Cas9, we generated mice lacking CB1Rs specifically in VMH neurons and found that CB1Rs in VMH neurons are essential for the regulation of glucose metabolism independent of body weight regulation.
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Peso Corporal/fisiología , Glucosa/metabolismo , Homeostasis/fisiología , Neuronas/metabolismo , Receptor Cannabinoide CB1/fisiología , Núcleo Hipotalámico Ventromedial/metabolismo , Animales , Composición Corporal/fisiología , Proteína 9 Asociada a CRISPR , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Dieta Alta en Grasa , Metabolismo Energético/fisiología , Femenino , Edición Génica , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Obesidad/etiología , Obesidad/metabolismo , Receptor Cannabinoide CB1/deficiencia , Receptor Cannabinoide CB1/genéticaRESUMEN
Chronic fatigue is a debilitating disorder with widespread consequences, but effective treatment strategies are lacking. Novel genetic mouse models of fatigue may prove invaluable for studying its underlying physiological mechanisms and for testing treatments and interventions. In a screen of voluntary wheel-running behavior in N-ethyl-N-nitrosourea mutagenized C57BL/6J mice, we discovered two lines with low body weights and aberrant wheel-running patterns suggestive of a fatigue phenotype. Affected progeny from these lines had lower daily activity levels and exhibited low amplitude circadian rhythm alterations. Their aberrant behavior was characterized by frequent interruptions and periods of inactivity throughout the dark phase of the light-dark cycle and increased levels of activity during the rest or light phase. Expression of the behavioral phenotypes in offspring of strategic crosses was consistent with a recessive inheritance pattern. Mapping of phenotypic abnormalities showed linkage with a single locus on chromosome 1, and whole exome sequencing identified a single point mutation in the Slc2a4 gene encoding the GLUT4 insulin-responsive glucose transporter. The single nucleotide change (A-T, which we named "twiggy") was in the distal end of exon 10 and resulted in a premature stop (Y440*). Additional metabolic phenotyping confirmed that these mice recapitulate phenotypes found in GLUT4 knockout mice. However, to the best of our knowledge, this is the first time a mutation in this gene has been shown to result in extensive changes in general behavioral patterns. These findings suggest that GLUT4 may be involved in circadian behavioral abnormalities and could provide insights into fatigue in humans.
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Ritmo Circadiano , Codón sin Sentido , Fatiga/genética , Transportador de Glucosa de Tipo 4/genética , Animales , Conducta Animal , Modelos Animales de Enfermedad , Fatiga/fisiopatología , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , FenotipoRESUMEN
Central leptin administration can ameliorate hyperglycemia in insulin-deficient rodent models independently of insulin; however, the underlying neuronal mechanism are unclear. Here, we investigate the contribution of key elements within the central melanocortin system by examining whether central leptin injection can ameliorate hyperglycemia in total insulin-deficient mice that either lacked melanocortin 4 receptors (MC4Rs) in the whole body [knockout (KO); MC4R KO] or selectively, in single-minded homolog 1 (SIM1)-expressing neurons (SIM1ΔMC4R). We further investigated the contribution of leptin receptors (LEPRs) in agouti-related protein (AgRP)-expressing neurons (AgRP∆LEPR). Leptin injections into the cerebral ventricle attenuated mortality and elevated blood glucose in total insulin-deficient MC4R KO mice. Total insulin-deficient SIM1ΔMC4R mice exhibited the same magnitude reduction of blood glucose in response to leptin injections as MC4R KO mice, suggesting SIM1 neurons are key to MC4R-mediated, insulin-independent, glucose-lowering effects of leptin. Central leptin injection also partially rescued glucose levels in total insulin-deficient AgRP∆LEPR mice. In brain slice studies, basal discharge of AgRP neurons from mice with total insulin deficiency was increased and leptin partially reduced their firing rate without membrane potential hyperpolarization. Collectively, our findings indicate that, contrary to glucose-lowering effects of leptin in the presence of insulin or partial insulin deficiency, MC4Rs in SIM1 neurons and LEPRs in AgRP neurons are not solely responsible for glucose-lowering effects of leptin in total insulin deficiency. This indicates that the central melanocortin system operates with other neuronal systems to fully mediate glucose-lowering effects of leptin in an insulin-independent manner.
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Glucemia/metabolismo , Leptina/fisiología , Receptor de Melanocortina Tipo 4/metabolismo , Receptores de Leptina/metabolismo , Animales , Núcleo Arqueado del Hipotálamo/metabolismo , Insulina/deficiencia , Masculino , Ratones , Núcleo Hipotalámico Paraventricular/metabolismoRESUMEN
OBJECTIVE: Recent studies have suggested a critical role for toll-like receptor 4 (TLR4) in the development of alcoholic liver disease. As TLR4 is widely expressed throughout the body, it is unclear which TLR4-expressing cell types contribute to alcohol-induced liver damage. METHODS: We selectively ablated TLR4 in hepatocytes and myeloid cells. Male mice were fed a liquid diet containing either 5% alcohol or pair-fed a control diet for 4 weeks to examine chronic alcohol intake-induced liver damage and inflammation. In addition, mice were administered a single oral gavage of alcohol to investigate acute alcohol drinking-associated liver injury. RESULTS: We found that selective hepatocyte TLR4 deletion protected mice from chronic alcohol-induced liver injury and fatty liver. This result was in part due to decreased expression of endogenous lipogenic genes and enhanced expression of genes involved in fatty acid oxidation. In addition, mice lacking hepatocyte TLR4 exhibited reduced mRNA expression of inflammatory genes in white adipose tissue. Furthermore, in an acute alcohol binge model, hepatocyte TLR4 deficient mice had significantly decreased plasma alanine transaminase (ALT) levels and attenuated hepatic triglyceride content compared to their alcohol-gavaged control mice. In contrast, deleting TLR4 in myeloid cells did not affect the development of chronic-alcohol induced fatty liver, despite the finding that mice lacking myeloid cell TLR4 had significantly reduced circulating ALT concentrations. CONCLUSIONS: These findings suggest that hepatocyte TLR4 plays an important role in regulating alcohol-induced liver damage and fatty liver disease.
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Hígado Graso Alcohólico/genética , Hepatocitos/metabolismo , Receptor Toll-Like 4/genética , Adipocitos/metabolismo , Alanina Transaminasa/sangre , Animales , Hígado Graso Alcohólico/metabolismo , Eliminación de Gen , Masculino , Ratones , Células Mieloides/metabolismo , Receptor Toll-Like 4/metabolismo , Triglicéridos/metabolismoRESUMEN
Leptin is critical for energy balance, glucose homeostasis, and for metabolic and neuroendocrine adaptations to starvation. A prevalent model predicts that leptin's actions are mediated through pro-opiomelanocortin (POMC) neurons that express leptin receptors (LEPRs). However, previous studies have used prenatal genetic manipulations, which may be subject to developmental compensation. Here, we tested the direct contribution of POMC neurons expressing LEPRs in regulating energy balance, glucose homeostasis and leptin secretion during fasting using a spatiotemporally controlled Lepr expression mouse model. We report a dissociation between leptin's effects on glucose homeostasis versus energy balance in POMC neurons. We show that these neurons are dispensable for regulating food intake, but are required for coordinating hepatic glucose production and for the fasting-induced fall in leptin levels, independent of changes in fat mass. We also identify a role for sympathetic nervous system regulation of the inhibitory adrenergic receptor (ADRA2A) in regulating leptin production. Collectively, our findings highlight a previously unrecognized role of POMC neurons in regulating leptin levels.
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Leptina/genética , Neuronas/metabolismo , Proopiomelanocortina/genética , Receptores Adrenérgicos alfa 2/genética , Animales , Ingestión de Alimentos/genética , Metabolismo Energético/genética , Ayuno/metabolismo , Glucosa/genética , Glucosa/metabolismo , Homeostasis/genética , Humanos , Leptina/metabolismo , Ratones , Proopiomelanocortina/metabolismo , Receptores de Leptina/genética , Receptores de Leptina/metabolismo , Sistema Nervioso Simpático/metabolismoRESUMEN
Evolutionary ecologists aim to explain and predict evolutionary change under different selective regimes. Theory suggests that such evolutionary prediction should be more difficult for biomechanical systems in which different trait combinations generate the same functional output: "many-to-one mapping." Many-to-one mapping of phenotype to function enables multiple morphological solutions to meet the same adaptive challenges. Therefore, many-to-one mapping should undermine parallel morphological evolution, and hence evolutionary predictability, even when selection pressures are shared among populations. Studying 16 replicate pairs of lake- and stream-adapted threespine stickleback (Gasterosteus aculeatus), we quantified three parts of the teleost feeding apparatus and used biomechanical models to calculate their expected functional outputs. The three feeding structures differed in their form-to-function relationship from one-to-one (lower jaw lever ratio) to increasingly many-to-one (buccal suction index, opercular 4-bar linkage). We tested for (1) weaker linear correlations between phenotype and calculated function, and (2) less parallel evolution across lake-stream pairs, in the many-to-one systems relative to the one-to-one system. We confirm both predictions, thus supporting the theoretical expectation that increasing many-to-one mapping undermines parallel evolution. Therefore, sole consideration of morphological variation within and among populations might not serve as a proxy for functional variation when multiple adaptive trait combinations exist.
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Evolución Molecular , Carácter Cuantitativo Heredable , Smegmamorpha/genética , Adaptación Fisiológica , Animales , Ecosistema , Conducta Alimentaria , Variación Genética , Maxilares/anatomía & histología , Boca/anatomía & histología , Fenotipo , Selección Genética , Smegmamorpha/anatomía & histología , Smegmamorpha/fisiologíaRESUMEN
Atypical antipsychotics such as olanzapine often induce excessive weight gain and type 2 diabetes. However, the mechanisms underlying these drug-induced metabolic perturbations remain poorly understood. Here, we used an experimental model that reproduces olanzapine-induced hyperphagia and obesity in female C57BL/6 mice. We found that olanzapine treatment acutely increased food intake, impaired glucose tolerance, and altered physical activity and energy expenditure in mice. Furthermore, olanzapine-induced hyperphagia and weight gain were blunted in mice lacking the serotonin 2C receptor (HTR2C). Finally, we showed that treatment with the HTR2C-specific agonist lorcaserin suppressed olanzapine-induced hyperphagia and weight gain. Lorcaserin treatment also improved glucose tolerance in olanzapine-fed mice. Collectively, our studies suggest that olanzapine exerts some of its untoward metabolic effects via antagonism of HTR2C.
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Antipsicóticos/farmacología , Benzodiazepinas/farmacología , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Antagonistas de la Serotonina/farmacología , Aumento de Peso/efectos de los fármacos , Animales , Antipsicóticos/efectos adversos , Benzodiazepinas/efectos adversos , Composición Corporal , Peso Corporal , Femenino , Glucosa/química , Prueba de Tolerancia a la Glucosa , Hiperfagia/inducido químicamente , Masculino , Ratones , Ratones Endogámicos C57BL , Olanzapina , Receptor de Serotonina 5-HT2C/químicaRESUMEN
Parallel evolution of similar traits by independent populations in similar environments is considered strong evidence for adaptation by natural selection. Often, however, replicate populations in similar environments do not all evolve in the same way, thus deviating from any single, predominant outcome of evolution. This variation might arise from non-adaptive, population-specific effects of genetic drift, gene flow or limited genetic variation. Alternatively, these deviations from parallel evolution might also reflect predictable adaptation to cryptic environmental heterogeneity within discrete habitat categories. Here, we show that deviations from parallel evolution are the consequence of environmental variation within habitats combined with variation in gene flow. Threespine stickleback (Gasterosteus aculeatus) in adjoining lake and stream habitats (a lake-stream 'pair') diverge phenotypically, yet the direction and magnitude of this divergence is not always fully parallel among 16 replicate pairs. We found that the multivariate direction of lake-stream morphological divergence was less parallel between pairs whose environmental differences were less parallel. Thus, environmental heterogeneity among lake-stream pairs contributes to deviations from parallel evolution. Additionally, likely genomic targets of selection were more parallel between environmentally more similar pairs. In contrast, variation in the magnitude of lake-stream divergence (independent of direction) was better explained by differences in lake-stream gene flow; pairs with greater lake-stream gene flow were less morphologically diverged. Thus, both adaptive and non-adaptive processes work concurrently to generate a continuum of parallel evolution across lake-stream stickleback population pairs.
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The Clever Foraging Hypothesis asserts that organisms living in a more spatially complex environment will have a greater neurological capacity for cognitive processes related to spatial memory, navigation, and foraging. Because the telencephalon is often associated with spatial memory and navigation tasks, this hypothesis predicts a positive association between telencephalon size and environmental complexity. The association between habitat complexity and brain size has been supported by comparative studies across multiple species but has not been widely studied at the within-species level. We tested for covariation between environmental complexity and neuroanatomy of threespine stickleback (Gasterosteus aculeatus) collected from 15 pairs of lakes and their parapatric streams on Vancouver Island. In most pairs, neuroanatomy differed between the adjoining lake and stream populations. However, the magnitude and direction of this difference were inconsistent between watersheds and did not covary strongly with measures of within-site environmental heterogeneity. Overall, we find weak support for the Clever Foraging Hypothesis in our study.
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Exercise has numerous beneficial metabolic effects. The central nervous system (CNS) is critical for regulating energy balance and coordinating whole body metabolism. However, a role for the CNS in the regulation of metabolism in the context of the exercise remains less clear. Here, using genetically engineered mice we assessed the requirement of steroidogenic factor-1 (SF-1) expression in neurons of the ventromedial hypothalamic nucleus (VMH) in mediating the beneficial effects of exercise on metabolism. We found that VMH-specific deletion of SF-1 blunts (a) the reductions in fat mass, (b) improvements in glycemia, and (c) increases in energy expenditure that are associated with exercise training. Unexpectedly, we found that SF-1 deletion in the VMH attenuates metabolic responses of skeletal muscle to exercise, including induction of PGC-1α expression. Collectively, this evidence suggests that SF-1 expression in VMH neurons is required for the beneficial effects of exercise on metabolism.