Direct effect of insulin on albumin gene expression in primary cultures of rat hepatocytes

Abstract

The purpose of this study was to identify a cell culture system in which the role of insulin in regulating albumin gene expression could be investigated. The system selected was rat hepatocytes maintained in primary culture in a chemically defined, serum-free medium. Under control conditions albumin secretion was nearly the same as the rate recorded in vivo and in perfused liver and was reasonably well maintained during 8 days of culture. Deletion of insulin from the culture medium for 3-6 days resulted in 40-60% reductions in albumin secretion. Furthermore, albumin secretion relative to the rate of total protein synthesis was reduced by approximately 50% as a result of insulin deficiency. Readdition of the hormone to insulin-deficient cultures restored secretion to the control rate. A maximal effect of insulin was observed within 3 days after readdition of the hormone, and a half-maximal response was obtained with a hormone concentration of approximately 3.0 nM. The relative abundance of albumin mRNA, as measured by solution hybridization using a complementary DNA probe, responded in a parallel fashion to the changes in albumin secretion. Thus rat hepatocytes maintained under appropriate culture conditions reflect the effects of diabetes and insulin treatment on albumin gene expression observed in vivo and provide an excellent model system in which to study the mechanism(s) of insulin action.

Medium-Chain Triacylglycerol Suppresses the Decrease of Plasma Albumin Level through the Insulin-Akt-mTOR Pathway in the Livers of Malnourished Rats

“…3). On the other hand, previous studies showed that albumin mRNA concentration and albumin synthesis are increased by insulin (35)(36)(37)(38). Therefore, the albumin improvement effect by dietary MCT may also be attributable to direct albumin mRNA expression through increased plasma insulin concentration.…”

Albumina sérica como marcador nutricional de pacientes em hemodiálise

“…Posteriormente, se o período de privação se estende, ocorre uma redução no número de mRNA responsáveis pela síntese de albumina. Este mecanismo é uma resposta adaptativa, lenta, à falta de substratos, e não é rapidamente reversível 17 . A oferta de energia parece ter uma importância maior que a de proteína na produção fisiológica de albumina, o que é justificado pelos mecanismos compensatórios expostos anteriormente.…”

Insulin Is Required to Maintain Albumin Expression by Inhibiting Forkhead Box O1 Protein

“…In diabetes, the concentration of albumin in blood is decreased, and administration of insulin is required to prevent hypoalbuminemia (6,7). Early biochemical studies have shown that insulin stimulates albumin production in the liver by activating gene transcription (5)(6)(7)(8)(9)(10)(11)(12). However, the detailed pathway by which insulin exerts this effect has not been described.…”