Triiodothyronine amplifies the adrenergic stimulation of uncoupling protein expression in rat brown adipocytes

9 pages, 9 figures.-- A page with additional content.Uncoupling protein (UCP), the mitochondrial protein specific to brown adipose tissue, is activated transcriptionally in response to cold and adrenergic agents. We studied the role of triiodothyronine (T(3)) on the adrenergic stimulation of UCP mRNA expression by use of primary cultures of rat brown adipocytes. Basal UCP mRNA levels are undetectable. Norepinephrine (NE) increases UCP mRNA during differentiation, not during proliferation. In hypothyroid conditions, UCP mRNA response to NE is almost absent. The presence of T(3) (0.2-20 nM) greatly increases the adrenergic response (30-fold). The sensitivity of UCP mRNA responses to NE is potentiated approximately 100-fold by the presence of T(3). The effect is proportional to the dose and time of preexposure to T(3). The increases obtained with NE and T(3) are prevented by actinomycin and cycloheximide. T(3) greatly stabilizes UCP mRNA transcripts. The effects of thyroxine and retinoic acid are weaker than those of T(3). In conclusion, in cultured rat brown adipocytes, T(3) is required and both synergizes with NE to increase UCP mRNA and stabilizes its mRNA transcripts.This work was supported by Grants PB 92/0061 and PB 95/0097 from Dirección General de Investigación Científica y Técnica and Fondo de Investigaciones Sanitarias de la Seguridad Social Grant 94/0274 from Fondo de Investigaciones Sanitarias of Spain.Peer reviewe

Presence and regulation of D1 and D2 deiodinases in rat white adipose tissue

Thyroid hormones regulate adipogenic differentiation, lipogenic and lipolytic metabolism, and mitochondrial activity in adipose tissue. Triiodothyronine (T3) levels in tissues are regulated by the deiodinase enzymes. The objective was to study the activity and messenger RNA (mRNA) expression of the 5′ outer-ring deiodinases (type 1 [D1] and type 2 [D2] deiodinase) and thyroid hormone concentrations in rat white adipose tissue (WAT), where only D1 activity had been described. Control, thyroidectomized, and thyroid hormone–treated rats were used. Type 1 and type 2 deiodinase mRNAs were determined in WAT by quantitative real-time polymerase chain reaction using Taqman probes; D1 and D2 activities were determined using reverse T3 and thyroxine (T4) as substrates. Thyroxine and T3 were measured by radioimmunoassay in plasma, liver, and adipose tissue. Type 1 and type 2 deiodinase mRNAs are present in epididymal rat WAT with similar abundance, which is 7% of the D2 mRNA levels in brown adipose tissue and 1% of D1 in liver. The Michaelis-Menten constants in WAT are 40 nmol/L T4 for D2 and 0.35 μmol/L reverse T3 for D1. Both D1 and D2 are regulated in rat epididymal WAT by thyroidal status. Thyroxine and T3 concentrations in plasma, liver, and WAT decreased after thyroidectomy and recovered after treatment with T4 + T3. Both D1 and D2 mRNAs increased in WAT from thyroidectomy rats; and T4 + T3 treatment inhibited them, especially D2 mRNA. Type 1 deiodinase activity did not change with thyroidal status, whereas D2 activity was inhibited by T4 + T3. The presence of both deiodinases in WAT suggests important roles in regulating T3 bioavailability for adipose tissue function and regulation of lipid metabolism and thermogenesis.Supported by SAF2006-01319 and SAF2009-2243 from MICINN and Fundacion Mutua Madrileña 2006.Peer Reviewe

Triiodothyronine is required for the stimulation of type II 5'-deiodinase mRNA in rat brown adipocytes

10 pages, 6 figures.Type II 5'-iodothyronine deiodinase (D2), produces triiodothyronine (T(3)) and is stimulated by cold exposure via norepinephrine (NE) release in brown adipose tissue. Cultured rat brown adipocytes require T(3) for the adrenergic stimulation of D2 activity. D2 mRNA expression in cultured brown adipocytes is undetectable with the use of basal conditions or NE without T(3). Full D2 expression is achieved using NE + T(3), especially after prolonged T(3) exposure. beta(3)-Adrenergic agonists mimic the NE action, whereas cAMP analogs do not. Prolonged exposure to T(3) alone increases D2 mRNA. High T(3) doses (500 nM) inhibit the adrenergic stimulation of D2 activity while increasing D2 mRNA. The effects obtained with NE + T(3) or T(3) alone are suppressed by actinomycin, but not by cycloheximide, which leads to accumulation of short D2 mRNA transcripts. Prolonged or short exposure to T(3) did not change D2 mRNA half-life, but T(3) seemed to elongate it. In conclusion, T(3) is an absolute requirement for the adrenergic stimulation of D2 mRNA in brown adipocytes. T(3) upregulates D2 mRNA, an effect that might involve stimulation of factors required for transcription or for stabilization of D2 mRNA.This work was supported by research grants PB 95–0097 from Dirección General de Investigación Científica y Técnica, FISS 94/0274 and 99/0813 from Fondo de Investigaciones Sanitarias (FIS), and CAM 08.6/0030/1998 from Comunidad de Madrid (CAM) (Spain). R. Martínez de Mena was supported by research grants FISS 94/0274 (predoctoral studies) and CAM 08.6/0030/1998 (as postdoctoral).Peer reviewe

The T3 receptor β1 isoform regulates UCP1 and D2 deiodinase in rat brown adipocytes

Brown adipose tissue (BAT) thermogenesis increases when uncoupling protein-1 (UCP1) is activated adrenergically and requires T3. In humans, UCP1 activation in BAT seems involved in body weight maintenance. BAT type 2 deiodinase (D2) increases in response to adrenergic agents, producing the T3 required for UCP1 expression. T3 actions are mediated by thyroid hormone nuclear T3 receptors (TR), TRα and TRβ. Studies in mice suggest that TRβ is required for UCP1 induction, whereas TRα regulates body temperature and adrenergic sensitivity. In the present study, we compare the effects of T3 vs. specific TRβ1 and TRα1 agonists [GC-1 and CO23] on the adrenergic induction of UCP1 and D2 in cultured rat brown adipocytes. T3 and GC-1 produced similar increases on UCP1, whereas CO23 increased UCP1 only at high doses (50 nM). GC-1 at low doses (0.2-10 nM) was less potent than T3, increasing the adrenergic stimulation of D2 activity and mRNA. At higher doses, GC-1 further stimulated whereas T3 inhibited D2 activity but not D2 mRNA, suggesting posttranscriptional effects. CO23 had no effect on D2 activity but increased D2 mRNA. T3, GC-1, or CO23 by themselves did not increase UCP1 or D2 mRNA. High T3 doses shortened D2 half-life and increased D2 turnover via proteasome, whereas GC-1 did not change D2 stability. The α1- and α2-adrenergic D2 responses increased using high T 3 doses. In summary, T3 increases the adrenergic stimulation of UCP1 and D2 expression mostly via the TRβ1 isoform, and in brown adipocytes, D2 is protected from degradation by the action of T 3 on TRβ1. Copyright © 2010 by The Endocrine Society.This work was supported by Research Grants SAF2006/01319 and SAF2009-09364 from Plan Nacional (Ministerio de Educación y Ciencia and Ministerio de Ciencia e Innovación) and FMM2006 from Fundación Médica Madrileña (Spain) (toM.-J.O.). Centro de Investigación Biomédica en Red de Fisiopatologia de la Obesidad y Nutrición (CIBERObn) is an initiative of Instituto de Salud Carlos III, Spain.Peer Reviewe

Maternal nonthyroidal illness and fetal thyroid hormone status, as studied in the streptozotocin-induced diabetes mellitus rat model

11 pages, 9 figures, 1 table.We have used the streptozotocin-induced diabetes mellitus pregnant rat as a model of maternal nonthyroidal illness. We measured the effects of different degrees of diabetes mellitus on maternal body weight, the outcome of pregnancy, circulating glucose, insulin, T4, T3, rT3, and TSH in mother and fetus, T4 and T3 in maternal and fetal tissues, and iodothyronine deiodinases in liver, lung, and brain. All of the changes in thyroid hormone status typical of nonthyroidal illnesses were observed in the mothers and were related to the degree of the metabolic imbalances. Most were controlled with a daily insulin dose of 0.5 U/100 g BW. Normalization of maternal placental T4, however, required higher insulin doses than in other maternal tissues. The number and body weight of the fetuses, their pituitary GH contents, and their thyroid hormone status were severely affected. The total extrathyroidal T4 and T3 pools decreased to one third of normal fetal values. T4 and T3 concentrations in the fetal brain were lower than normal, and the expected increase in type II 5'deiodinase activity was not observed. The low cerebral T3 only improved with adequate insulin treatment of the dams. It is concluded that maternal diabetes mellitus, and possibly other nonthyroidal illnesses that impair the availability of intracellular energy stores, may affect fetal brain T3 when thyroid hormones are essential for normal development.This work was supported by Grant 92–08 88 from the Fondo de Investigaciones Sanitarias, Spain.Peer reviewe

Consecuencias de la deprivación del iodo y hormonas tiroideas

Consecuencias de la deprivación del iodo y hormonas tiroideas

Maternal diabetes mellitus, a rat model for nonthyroidal illness: Correction of hypothyroxinemia with thyroxine treatment does not improve fetal thyroid hormone status

Maintenance of normal maternal thyroxinemia prevents severe triiodothyronine (T3) deficiency of the fetus with primary thyroid failure (1). We have studied whether thyroxine (T4) would also protect the fetal brain when maternal hypothyroxinemia is caused by nonthyroidal illnesses. We have used the streptozotocin-induced diabetes mellitus pregnant rat as a model of maternal nonthyroidal illness. We measured the effects of diabetes mellitus, and of correction of the ensuing maternal hypothyroxinemia with T4 as compared to insulin, on maternal body weight, the outcome of pregnancy, glucose, insulin, T4, T3, reverse T3, and thyrotropin levels in the maternal and fetal circulation, as well as T4 and T3 concentrations in tissues, and iodothyronine deiodinases in liver, lung, and brain. The diabetic mothers showed changes in thyroid hormone status typical of nonthyroidal illnesses. Thyroid hormone status of the fetuses was severely affected: the total T4 and T3 pools decreased to one-third of normal values. T4 and T3 concentrations in the fetal brain were lower than normal and the expected increase in 5'-deiodinase activity was not observed. Although insulin treatment avoided or mitigated these changes, the low cerebral T3 did not improve with T4 treatment of the maternal hypothyroxinemia. Several findings indicated that treatment of the severely ill dams with T4 was actually harmful for the outcome of pregnancy. These negative effects were observed without the expected increase in the maternal or fetal T3 pools.This work was supported by Grant FISS (Fondo de Investigaciones Sanitarias) 92/0888, Spain.Peer Reviewe

El número de empleados en el comportamiento tributario de los microempresarios

Esta investigación está dirigida a comparar como afecta el número de empleados que tienen los microempresarios representados como una variable de control, con el comportamiento tributario y los factores que lo afectan que son, la credibilidad, la complejidad, la capacidad económica, la implementación de las TIC, la facturación electrónica, la costumbre, la resistencia al cambio, la carga tributaria y la fiscalización, especialmente con el factor que inciden en este comportamiento de la implementación de las TIC, el cual está directamente ligado con las obligaciones derivadas del pago de la nómina y el correcto cumplimiento de sus obligaciones fiscales. Para tal efecto se realizó una investigación de corte transversal, no experimental que fue descriptiva y explicativa, donde se examinaron los factores que se obtuvieron aplicando el método logic, de carácter ordinal y fueron comparados estos en relación con la variable de control número de empleados, para determinar si esta incidía en los resultados obtenidos. De acuerdo a los resultados del presente estudio se encontró que dentro de los microempresarios que tienen empleados, la variable de implementación de las TIC es más representativa, en comparación con los resultados cuando esta variable no es tomada en cuenta

El monitoreo al control interno en empresas dedicadas al cultivo de atún aleta azul en Baja California

The aim of this research is the study of the monitoring component to the internal control, applying it in marine ranches that grow bluefin tuna in Baja California, in order to propose adjustments to the same, according to the deficiencies of the business. These companies face a range of risks that threaten their continuity and with this economic damage and decrease of jobs for the region, so they must be reduced with effective and timely measures. Direct information was collected from the two active companies and the results indicate the relevance of the monitoring to the internal control functions in carrying out it properly, showing them as entities with an effective system that helps to meet their stated objectives, through monitoring its activities and procedures, in order to satisfy the consumer with a quality product.La finalidad de esta investigación es el estudio del componente de monitoreo al control interno, al aplicarlo en ranchos marinos que cultivan atún aleta azul en Baja California, a fin de plantear ajustes al mismo, de acuerdo con las carencias del negocio. Estas empresas afrontan una gama de riegos que son una amenaza a su continuidad y con esto daños económicos y disminución de empleos para la región, por ello es que deben aminorarse al contar con medidas eficaces y oportunas. Se recabó información directa de las dos compañías activas y los resultados indican la relevancia del seguimiento a las funciones de control interno al realizarlo adecuadamente, mostrándose como entidades con un efectivo sistema que ayuda a cumplir con sus objetivos planteados, a través de supervisar sus actividades y procedimientos, a fin de satisfacer al consumidor con un producto de calidad

Implicaciones Fiscales de las Operaciones con Criptomonedas en México

Derived from the publication of the FinTech Act in 2018, the debate arose about the tax treatment of cryptocurrency operations, which are offered by financial technology institutions, because the regulation is not clear on this matter because it is not known if it is a currency, a value or an asset, therefore, tax processes are unknown. The general objective of the investigation is to analyze the fiscal implications of the operations with cryptocurrencies in Mexico. The research was developed through a qualitative approach documentary type. The study showed as a result that cryptocurrencies are not legal currencies nor are they value. Considering as a conclusion that we are dealing with an intangible asset, which must be taxed under the regime of disposal of assets.Derivado de la publicación de la Ley FinTech en 2018, surgió el debate acerca del tratamiento tributario de las operaciones con criptomonedas, que son ofrecidos por las instituciones de tecnología financiera, debido a que la regulación no es clara al respecto porque no se sabe si se trata de una moneda, un valor o un bien, por lo tanto, se desconocen los procesos fiscales. El objetivo general de la investigación es analizar las implicaciones fiscales de las operaciones con criptomonedas en México. La investigación se desarrolló mediante un enfoque cualitativo tipo documental. El estudio arrojó como resultado que las criptomonedas no son monedas de curso legal ni tampoco son valores. Considerando como conclusión que estamos ante un bien intangible, el cual deberá tributar bajo el régimen de enajenación de bienes