排序方式: 共有48条查询结果,搜索用时 15 毫秒
1.
De Spiegeleer B Van Dorpe S Vergote V Wynendaele E Pauwels E Van De Wiele C Garcia-Solis P Solis-Sainz JC 《Peptides》2012,33(2):272-278
Different iodinated mouse obestatin peptides have been characterized toward their in vitro stability in the main metabolic compartments plasma, liver and kidney. Using HPLC-UV for quantification, significant differences in the degradation kinetics of the iodinated peptides, arising from both enzymatic proteolysis and dehalogenation, were found when compared to the native, unmodified peptide. HPLC-MS/MS analysis demonstrated that the cleavage sites were dependent upon the biological matrix and the location of the amino acid residue incorporating the iodine atom(s). The degrading proteases were found to target peptide bonds further away from the iodine incorporation, while proteolytic cleavages of nearby peptide bonds were more limited. Diiodinated amino acid residue containing peptides were found to be more susceptible to deiodination than the mono-iodinated derivative. In plasma, the percentage of peptide degradation solely attributed to deiodinase activity after 20 min incubation reached up to 25% for 2,5-diiodo-H(19)-obestatin compared to 20% and only 3% for (3,5-diiodo-Y(16))- and (3-iodo-Y(16)) obestatin, respectively. Hence, our results demonstrate that the different iodinated peptides pose significantly different metabolization properties and thus, also different biological activities are expected for peptides upon iodination. 相似文献
2.
Nicholas V.C. Ralston Laura J. Raymond 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(11):2405-2416
Background
Methylmercury (CH3Hg+) toxicity is characterized by challenging conundrums: 1) “selenium (Se)-protective” effects, 2) undefined biochemical mechanism/s of toxicity, 3) brain-specific oxidative damage, 4) fetal vulnerability, and 5) its latency effect. The “protective effects of Se” against CH3Hg+ toxicity were first recognized >50?years ago, but awareness of Se's vital functions in the brain has transformed understanding of CH3Hg+ biochemical mechanisms. Mercury's affinity for Se is ~1 million times greater than its affinity for sulfur, revealing it as the primary target of CH3Hg+ toxicity.Scope of review
This focused review examined research literature regarding distinctive characteristics of CH3Hg+ toxicity to identify Se-dependent aspects of its biochemical mechanisms and effects.Conclusions
Research indicates that CH3Hg+ irreversibly inhibits the selenoenzymes that normally prevent/reverse oxidative damage in the brain. Unless supplemental Se is provided, consequences increase as CH3Hg+ approaches/exceeds equimolar stoichiometries with Se, thus forming HgSe and inducing a conditioned Se deficiency. As the biochemical target of CH3Hg+ toxicity, Se-physiology provides perspectives on the brain specificity of its oxidative damage, accentuated fetal vulnerability, and latency. This review reconsiders the concept that Se is a “tonic” that protects against CH3Hg+ toxicity and recognizes Se's role as Hg's molecular “target”. As the most potent intracellular nucleophile, the selenoenzyme inhibition paradigm has broad implications in toxicology, including resolution of conundrums of CH3Hg+ toxicity.General significance
Mercury-dependent sequestration of selenium and the irreversible inhibition of selenoenzymes, especially those required to prevent and reverse oxidative damage in the brain, are primarily responsible for the characteristic effects of mercury toxicity. 相似文献3.
da-Silva WS Ribich S Arrojo e Drigo R Castillo M Patti ME Bianco AC 《FEBS letters》2011,585(3):2065-544
Exposure of cell lines endogenously expressing the thyroid hormone activating enzyme type 2 deiodinase (D2) to the chemical chaperones tauroursodeoxycholic acid (TUDCA) or 4-phenylbutiric acid (4-PBA) increases D2 expression, activity and T3 production. In brown adipocytes, TUDCA or 4-PBA induced T3-dependent genes and oxygen consumption (∼2-fold), an effect partially lost in D2 knockout cells. In wild type, but not in D2 knockout mice, administration of TUDCA lowered the respiratory quotient, doubled brown adipose tissue D2 activity and normalized the glucose intolerance associated with high fat feeding. Thus, D2 plays a critical role in the metabolic effects of chemical chaperones. 相似文献
4.
K. Wang Y. N. Sun J. Y. Liu L. Zhang Y. Ye L. X. Lin Y. Q. Yan Z. P. Chen 《Biological trace element research》2009,130(1):72-85
Thyroid function ultimately depends on appropriate iodine supply to the gland. There is a complex series of checks and balances
that the thyroid uses to control the orderly utilization of iodine for hormone synthesis. The aim of our study is to evaluate
the mechanism underlying the effect of iodine excess on thyroid hormone metabolism. Based on the successful establishment
of animal models of normal-iodine (NI) and different degrees of high-iodine (HI) intake in Wistar rats, the content of monoiodotyrosine
(MIT), diiodotyrosine (DIT), T4, and T3 in thyroid tissues, the activity of thyroidal type 1 deiodinase (D1) and its (Dio1) mRNA expression level were measured. Results showed that, in the case of iodine excess, the biosynthesis of both MIT and
DIT, especially DIT, was increased. There was an obvious tendency of decreasing in MIT/DIT ratio with increased doses of iodine
intake. In addition, iodine excess greatly inhibited thyroidal D1 activity and mRNA expression. T3 was greatly lower in the HI group, while there was no significant difference of T4 compared with NI group. The T3/T4 ratio was decreased in HI groups, antiparalleled with increased doses of iodine intakes. In conclusion, the increased biosyntheses
of DIT relative to MIT and the inhibition of thyroidal Dio1 mRNA expression and D1 activity may be taken as an effective way to protect an organism from impairment caused by too much
T3. These observations provide new insights into the cellular regulation mechanism of thyroid hormones under physiological and
pathological conditions. 相似文献
5.
6.
Yan Xiong Feng Yue Zhihao Jia Yun Gao Wen Jin Keping Hu Yong Zhang Dahai Zhu Gongshe Yang Shihuan Kuang 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2018,1863(4):409-419
The thermogenic activities of brown and beige adipocytes can be exploited to reduce energy surplus and counteract obesity. Recent RNA sequencing studies have uncovered a number of long noncoding RNAs (lncRNAs) uniquely expressed in white and brown adipose tissues (WAT and BAT), but whether and how these lncRNAs function in adipogenesis remain largely unknown. Here, we report the identification of a novel brown adipocyte-enriched LncRNA (AK079912), and its nuclear localization, function and regulation. The expression of AK079912 increases during brown preadipocyte differentiation and in response to cold-stimulated browning of white adipocytes. Knockdown of AK079912 inhibits brown preadipocyte differentiation, manifested by reductions in lipid accumulation and down-regulation of adipogenic and BAT-specific genes. Conversely, ectopic expression of AK079912 in white preadipocytes up-regulates the expression of genes involved in thermogenesis. Mechanistically, inhibition of AK079912 reduces mitochondrial copy number and protein levels of mitochondria electron transport chain (ETC) complexes, whereas AK079912 overexpression increases the levels of ETC proteins. Lastly, reporter and pharmacological assays identify Pparγ as an upstream regulator of AK079912. These results provide new insights into the function of non-coding RNAs in brown adipogenesis and regulating browning of white adipocytes. 相似文献
7.
A. Rubio C. Osuna M. A. Lopez-Gonzalez R. J. Reiter J. M. Guerrero 《Bioscience reports》1991,11(2):111-117
Type II thyroxine 5-deiodinase (5-D) activity in both pineal and Harderian glands of the Swiss mouse was studied. Pineal 5-D activity exhibited a nyctohemeral profile with a maximal peak value at 05.00 h, which coincides with that for pineal melatonin production. However, no rhythm of 5-D activity in the Harderian gland could be found. In pineal gland, light at night inhibited the nocturnal increase in 5-D activity, while isoproterenol, a -adrenergic agonist, could not stimulate the enzyme. In the Harderian gland, neither darkness, nor light at night, or isoproterenol were capable of modifying basal values of 5-D activity. 相似文献
8.
Mario Calomme Jean Vanderpas Baudouin François Micheline Van Caillie-Bertrand Nicole Vanovervelt Christian Van Hoorebeke Dirk Vanden Berghe 《Biological trace element research》1995,47(1-3):349-353
Type I 5′-deiodinase was recently characterized as a selenocysteine-containing enzyme in humans and other mammals. Up to now,
the effect of selenium (Se) supplementation on thyroid hormone metabolism in humans has only been reported in the very peculiar
nutritional environment of Central Africa, where combined severe iodine and Se deficiency occurs. In this study, a group of
phenylketonuria subjects with a low selenium status, but a normal iodine intake were supplemented with selenium to investigate
changes in their thyroid hormone metabolism. After 3 wk of selenium supplementation (1 μg/kg/d), both the concentrations of
the prohormone thyroxine (T4) and the metabolic inactive reverse triiodothyronine (rT3) decreased significantly. Clinically,
the phenylketonuria subjects remained euthyroid before and after selenium supplementation. The individual changes of plasma
Se and glutathione peroxidase activity were closely associated with individual changes of plasma T4 and rT3. 相似文献
9.
J P Chanoine G S Stein L E Braverman V Shalhoub J B Lian C A Huber W J DeVito 《Journal of cellular biochemistry》1992,50(4):392-399
We have recently demonstrated that the iv administration of acidic fibroblast growth factor (a-FGF) to rats for 6 days results in a marked increase in thyroid weight with colloid accumulation and flat, quiescent follicular cells. Whereas a-FGF administration consistently increases thyroid weight, there are only minor alterations in serum TSH and thyroid hormones, and no change in intrathyroidal metabolism of 125I metabolism. In the present work, we studied the effects of 1 or 6 daily injections of a-FGF (60 micrograms/kg BW) or vehicle on the mRNA levels for histone, c-fos, actin, type I 5' deiodinase (5'D-I), thyroid peroxidase, and thyroglobulin and cathepsin D in the thyroid, liver and bone. Rats were sacrificed 0.5, 2, 4, 8 and 24 h after the 1st or the 6th a-FGF injection and thyroid, liver, and calvarium were removed. The relative amounts of mRNAs were determined by slot blot analysis. There was a 43% increase in thyroid weight in rats treated with a-FGF for 6 days compared to vehicle-treated rats. We observed an increase in c-fos mRNA content in the thyroid gland 0.5 to 4 h after 1 or 6 injections of a-FGF. In contrast, treatment with a-FGF for 1 or 6 days did not affect histone mRNA content, a marker of proliferative activity or actin mRNA levels. Treatment with a-FGF caused a marked decrease in thyroid 5' D-I mRNA content in the thyroid. The decrease was present 2 h after the first injection and reached a nadir 8 h later.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
Tibial dyschondroplasia (TD) is a genetic leg defect in broilers with a lesion of avascular, non-calcified cartilage below the growth plate of the proximal tibiatarsus. This disease is considered to result from the inability of chondrocytes to undergo terminal differentiation. Thyroid hormones are required for chondrocyte differentiation. The thyroid gland produces and secrets mostly L-thyroxine or T4 and T4 plays most of its biological activities through conversion to triiodothyronine or T3 in local tissues by iodothyronine deiodinases type 1 or type 2, which are tissue specific. In this study, no differences were found in the plasma concentrations of total T3 and T4 between two chicken lines divergently selected for the incidence of TD. Plasma T4 was higher than T3, especially in older chickens. Younger birds had much higher T3 than older birds, but there were no significant age differences in T4. The expression level of deiodinase type 2 in the growth plates of broilers with TD was one-eighth of those birds without the disease. The expression levels of deiodinase type 2 (DIO2) in commercial broilers without the disease were much higher than those with TD and lower than those without the disease in the susceptible and resistant lines, respectively. These results indicate that the inadequate expression of DIO2 in the growth plates contributes to the pathogenesis of TD in broilers and that TD is a tissue-specific hypothyroidism. 相似文献