RESUMO
Studies have found that biotin favors glucose and lipid metabolism, and medications containing biotin have been developed. Despite the use of biotin as a pharmacological agent, few studies have addressed toxicity aspects including the possible interaction with cytochrome P450 enzyme family. This study analyzed the effects of pharmacological doses of biotin on the expression and activity of the cytochrome P4501A subfamily involved in the metabolism of xenobiotics. Wistar rats were treated daily with biotin (2 mg/kg, i.p.), while the control groups were treated with saline. All of the rats were sacrificed by cervical dislocation after 1, 3, 5, or 7 days of treatment. CYP1A1 and CYP1A2 mRNAs were modified by biotin while enzyme activity and protein concentration were not affected. The lack of an effect of biotin on CYP1A activity was confirmed using other experimental strategies, including (i) cotreatment of the animals with biotin and a known CYP1A inducer; (ii) the addition of biotin to the reaction mixtures for the measurement of CYP1A1 and CYP1A2 activities; and (iii) the use of an S9 mixture that was prepared from control and biotin-treated rats to analyze the activation of benzo[a]pyrene (BaP) into mutagenic metabolites using the Ames test. The results suggest that biotin does not influence the CYP1A-mediated metabolism of xenobiotics.
Assuntos
Biotina/farmacologia , Citocromo P-450 CYP1A1/metabolismo , Citocromo P-450 CYP1A2/metabolismo , Suplementos Nutricionais , Animais , Benzo(a)pireno/farmacologia , Biocatálise/efeitos dos fármacos , Citocromo P-450 CYP1A1/biossíntese , Citocromo P-450 CYP1A1/genética , Citocromo P-450 CYP1A2/biossíntese , Citocromo P-450 CYP1A2/genética , Indução Enzimática/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Fígado/efeitos dos fármacos , Fígado/enzimologia , Masculino , MicroRNAs/genética , MicroRNAs/metabolismo , Testes de Mutagenicidade , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos WistarAssuntos
Tecido Adiposo/metabolismo , Glicemia/metabolismo , Diabetes Mellitus Tipo 2/etiologia , Proteínas Musculares , Obesidade/complicações , Animais , Diabetes Mellitus/etiologia , Diabetes Mellitus/metabolismo , Transportador de Glucose Tipo 4 , Humanos , Resistência à Insulina , Camundongos , Camundongos Transgênicos , Proteínas de Transporte de Monossacarídeos/metabolismo , Obesidade/metabolismoRESUMO
Glucocorticoids inhibit insulin expression in cultured pancreatic islet cells. In this study, we provide evidence that transcriptional downregulation of insulin gene expression by glucocorticoids is the result of synergistic interaction between various elements of the insulin promoter. Similar synergistic effects on insulin gene transcription were previously reported for other key insulin regulators, cyclic adenosine monophosphate (cAMP) and glucose. Transfection of CAT constructs containing different segments of the insulin promoter into the pancreatic cell line, HIT T-15 2.2.2, demonstrated that dexamethasone decreased CAT activity in all constructs tested. However, differences were found in the relative sensitivities of the various constructs. Glucocorticoid inhibition of expression from plasmids containing A elements may result from decreased expression of the pancreatic homeodomain protein STF-1. However, a different mechanism must be invoked for insulin promoter constructs lacking A sites, which nevertheless still demonstrated negative regulation. Glucocorticoid-induced inhibition of one of these regions (-882 to -342) was seen to require pancreas-specific factors, because inhibition was observed in HIT T-15 2.2.2 cells but not in the nonpancreatic COS-1 cells. We conclude, therefore, that the human insulin gene contains multiple transcriptional elements that respond to glucocorticoids, some of which require beta cell-specific factors.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Glucocorticoides/farmacologia , Insulina/genética , Transcrição Gênica/efeitos dos fármacos , Animais , Células COS/metabolismo , Linhagem Celular , Cloranfenicol O-Acetiltransferase/genética , AMP Cíclico/farmacologia , Dexametasona/farmacologia , Sinergismo Farmacológico , Glucose/farmacologia , Humanos , Ilhotas Pancreáticas/metabolismo , Regiões Promotoras Genéticas , Receptores de Glucocorticoides/genética , TransfecçãoRESUMO
We report a 5-year-old girl with adenosine deaminase (ADA) deficiency who was asymptomatic during the first years of life. At 3 years of age, she developed chronic and recurrent sinopulmonary infections, and at 4 1/2 years of age she had one major infection with Streptococcus pneumoniae (bacteremia and septic arthritis of the hip). Immunologic evaluation at 5 years of age revealed persistent lymphopenia, decreased helper-suppressor T cell ratios, and low proliferative responses to mitogens. The IgG, IgM, and IgA levels were normal; the IgG2 level was low normal or below normal. The patient had specific antibodies against toxoids and viral antigens but failed to produce antibodies against Haemophilus influenzae type b and pneumococcal polysaccharides. Although no symptoms of allergy were present, she had persistent eosinophilia and elevated IgE levels. The patient had 0.6% of normal ADA activity in erythrocytes and approximately 1% of normal ADA activity in peripheral blood mononuclear cells. Beginning at 6 years of age, she was treated with weekly injections of polyethylene glycol-modified bovine ADA. This treatment was well tolerated and effectively reversed the biochemical consequence of ADA deficiency. Concomitantly, she improved clinically and her T lymphocyte numbers and blastogenic responses to mitogens in vitro became normal. The late onset of clinical symptoms and relatively benign clinical course in this patient emphasize the need to consider ADA deficiency in a broad spectrum of immunodeficient children.