RESUMEN
OBJECTIVE: To determine the gene sequence and tissue distribution of uncoupling protein 3 (Ucp3) in the collared lemming, we quantified mRNA expression of Ucp3 under known states of altered energy expenditure (photoperiod-induced weight gain and loss, cold exposure, and fasting) and measured mitochondrial oxygen consumption to assess possible functional changes in energy expenditure. RESEARCH METHODS AND PROCEDURES: The Ucp3 gene sequence information was obtained using the reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends methods. Northern blots were used to determine mRNA expression levels. Respirometry was used to measure oxygen consumption rates in isolated mitochondria. RESULTS: The lemming Ucp3 gene has a 97% sequence similarity with other published Ucp3 sequences at the amino acid level. Ucp3 mRNA is expressed in muscle, heart, and brown adipose tissue of collared lemmings. Long-photoperiod lemmings have a higher expression of Ucp3 mRNA than short-photoperiod lemmings (p < 0.001) in both muscle and brown adipose tissue. Transferring lemmings from long to short photoperiods (inducing weight gain) significantly decreased Ucp3 mRNA expression (p < 0.01), whereas transferring lemmings from short to long photoperiods (inducing weight loss) significantly increased Ucp3 expression (p < 0.001). Muscle Ucp3 mRNA expression was significantly decreased by 10 days of mild (10 degrees C) cold exposure (p < 0.001). Muscle Ucp3 mRNA expression was significantly increased by fasting (p < 0.01) and was correlated to plasma free fatty acid levels (r = 0.7). Photoperiod transfer did not alter mitochondrial coupling. DISCUSSION: These data suggest that UCP3 may not be involved in energy expenditure in the collared lemming.
Asunto(s)
Peso Corporal/fisiología , Proteínas Portadoras/genética , Proteínas Portadoras/fisiología , Metabolismo Energético/fisiología , Regulación de la Expresión Génica , Secuencia de Aminoácidos , Animales , Arvicolinae , Secuencia de Bases , Proteínas Portadoras/metabolismo , Frío , ADN Complementario/química , ADN Complementario/genética , Metabolismo Energético/genética , Ayuno/fisiología , Amplificación de Genes , Canales Iónicos , Masculino , Proteínas Mitocondriales , Datos de Secuencia Molecular , Consumo de Oxígeno , Fotoperiodo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Aminoácido , Proteína Desacopladora 3 , Aumento de Peso/fisiología , Pérdida de Peso/fisiologíaAsunto(s)
Proteínas Portadoras/fisiología , Proteínas de Transporte de Membrana/fisiología , Proteínas Mitocondriales/fisiología , Fenómenos Fisiológicos de la Nutrición/fisiología , Obesidad/genética , Termogénesis/fisiología , Animales , Proteínas Portadoras/genética , Humanos , Canales Iónicos , Metabolismo de los Lípidos , Proteínas de Transporte de Membrana/genética , Mitocondrias/química , Proteínas Mitocondriales/genética , Fosforilación Oxidativa , Especies Reactivas de Oxígeno/metabolismo , Termogénesis/genética , Proteína Desacopladora 2 , Proteína Desacopladora 3RESUMEN
OBJECTIVE: To determine the role of total energy expenditure (TEE) and its components in the ability of collared lemmings to increase weight in response to a decrease in photoperiod. RESEARCH METHODS AND PROCEDURES: Energy expenditure was measured by 24-hour indirect calorimetry concurrent with food-intake studies. TEE and resting and nonresting energy expenditure (REE and NREE, respectively) were adjusted for body weight by analysis of covariance (ANCOVA). Uncoupling protein 1 (Ucp1) mRNA levels from interscapular brown adipose tissue were determined by Northern blot. RESULTS: TEE and REE of lemmings exposed to a short photoperiod for 10 days were significantly lower than that of lemmings exposed to a long photoperiod (p < 0.05), whereas NREE was not significantly different (p = 0.44). Ucp1 mRNA levels in interscapular brown adipose tissue were 50% lower in short- vs. long-photoperiod lemmings (p < 0.01). Ucp1 mRNA levels were positively related to REE (r2 = 0.79, p < 0.01). After adjustment of REE for differences in Ucp1 mRNA levels, there was no longer a significant difference attributable to photoperiod treatment (p = 0.54). DISCUSSION: The results of this study indicate that the increase in body mass that occurs when collared lemmings are exposed to a short photoperiod may be primarily fueled by a decrease in REE and is correlated with a decrease in Ucp1 mRNA levels.
Asunto(s)
Arvicolinae/fisiología , Proteínas Portadoras/fisiología , Metabolismo Energético , Proteínas de la Membrana/fisiología , Fotoperiodo , Aumento de Peso , Tejido Adiposo Pardo/química , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Northern Blotting , Composición Corporal , Temperatura Corporal , Peso Corporal , Calorimetría Indirecta , Proteínas Portadoras/genética , Clonación Molecular , ADN Complementario/química , ADN Complementario/genética , Ingestión de Alimentos , Canales Iónicos , Masculino , Proteínas de la Membrana/genética , Proteínas Mitocondriales , Datos de Secuencia Molecular , ARN Mensajero/análisis , Proteína Desacopladora 1RESUMEN
OBJECTIVE: Evidence indicates that estrogen depresses hepatic lipid oxidation. We tested the hypothesis that estradiol (E(2)) treatment depresses transcription of carnitine palmitoyltransferase-1 (Cpt 1) mRNA and increases adiposity. RESEARCH METHODS AND PROCEDURES: Six ovariectomized female rats were given a subcutaneous pellet of E(2) (5 mg/d), and six were given placebo. Rats were pair-fed by group for 18 days. Body composition was assessed chemically: mRNA for liver Cpt 1, adipose tissue uncoupling protein-2 (Ucp 2), and quadriceps Ucp 3 by Northern analysis; serum glucose, triglycerides (TGs), and free fatty acids by standard techniques; and serum insulin and glucagon by radioimmunoassay. RESULTS: E(2)-treated rats lost more weight than placebo-treated rats (37.3 +/- 6.0 vs. 16.2 +/- 2.6 g, p < 0.01), but did not differ in final carcass composition (adjusted for eviscerated body mass). E(2)-treated rats had lower liver Cpt 1 (p < 0.001) and skeletal muscle Ucp 3 (p < 0.05) mRNA and lower concentrations of glucose, glucagon, and free fatty acids (p < 0.05). E(2)-treated rats tended to have higher insulin (p = -0.067) and TG (p = 0.097). TG tended to be correlated with Cpt 1 mRNA (r = -0.56 and p = 0.07). DISCUSSION: These results suggest that, although E(2) is likely to suppress lipid oxidation and promote TG synthesis, these effects are not manifested in a relative increase in carcass adiposity after 18 days of treatment, at least under conditions of negative energy balance. The possible role of E(2)-mediated changes in insulin and glucagon secretion on hepatic substrate metabolism warrants further study.