Altered expression of insulins I and II and their mRNAs in the islets of Langerhans in dexamethasone‐induced diabetic rats

Abstract

Rats have two isomeric insulins (insulins I and II). There have been no reports on the expression of the isomeric insulins in glucocorticoid-induced diabetic rats. To clarify the relation of the expression of each insulin and its mRNAs in dexamethasone-induced diabetic rats, the amounts of the isomeric insulins and mRNAs in the islets of Langerhans were determined in vivo and in vitro. A sensitive and selective HPLC-fluorescence determination method for the isomeric insulins and a newly developed real-time quantitative RT-PCR method for their mRNAs were used. There was a greater reduction of insulin II than insulin I in the islets of Langerhans in dexamethasone-induced diabetic rats. This alteration may be caused by a disproportionate expression of the respective mRNA for the isomeric insulins that resulted from the direct effect of dexamethasone. In addition, continuous hyperglycemia may also suppress the expression of the insulin II mRNA. The overall effects of dexamethasone and hyperglycemia may cause a greater reduction of insulin II than insulin I in the dexamethasone-induced diabetic rat. Conversely, an elevated ratio of insulin I to II in the islets could suggest a diabetic condition.

Chronic Olanzapine Treatment Causes Differential Expression of Genes in Frontal Cortex of Rats as Revealed by DNA Microarray Technique

“…There are two insulin isomers in rat, namely insulin 1 and insulin 2, with the latter species being more responsive to changes in glucose levels (Toriumi and Imai, 2003). Insulin 2 is the probable analogue of human insulin in rat (Toriumi and Imai, 2003). The increase in insulin 2 gene expression was verified by QPCR, showing a significant increase (po0.01) in insulin 2 mRNA by E4-fold in olanzapine-treated rats (Table 2).…”

“…Olanzapine increased expression of insulin 2 significantly (Tables 1, 3) in exposed rat frontal cortex. There are two insulin isomers in rat, namely insulin 1 and insulin 2, with the latter species being more responsive to changes in glucose levels (Toriumi and Imai, 2003). Insulin 2 is the probable analogue of human insulin in rat (Toriumi and Imai, 2003).…”

Avaliação da função e plasticidade celuar de ilhotas pancreaticas em modelo de resistencia a insulina induzida por dexametosa em ratos

“…Resistência à insulina induzida pela dexametasona está geralmente associada ao aumento compensatório da massa de células β , aumento do conteúdo total de insulina no pâncreas (Bonner-Weir et al, 1981) e aumento da secreção de insulina estimulada por glicose (Novelli et al, 1999). Em contraste, no diabetes tipo 2 induzido por GC, marcante hiperglicemia de jejum é observada juntamente com redução dos níveis de insulina sérica (Efendic, Luft, Wajngot, 1984), redução do conteúdo total de insulina, da expressão do RNAm da insulina (Toriumi, Imai, 2003) e, especialmente, diminuição da secreção de insulina induzida por glicose in vivo (Ohneda et al, 1993), bem como in vitro (Gremlich, Roduit, Thorens, 1997).…”

Envolvimento da via colinergica na hiperinsulinemia induzida por glicocorticoide em ratos

“…No tecido adiposo, tem sido descrita diminuição da expresão e/ou fosforilação do receptor de insulina e do IRS-1 induzida pela insulina (Saad e colaboradores, 1993). Em músculo, observou-se redução da fosforilação da Akt e da proteína glicogênio sintase cinase-3 (GSK-3) induzida pela insulina por glicocorticóide, marcante hiperglicemia de jejum é observada juntamente com redução dos níveis de insulina sérica (Efendic e colaboradores, 1984), redução do conteúdo total de insulina, da expressão do RNAm (Toriumi;Imai, 2003) e, especialmente, diminuição da secreção de insulina induzida por glicose in vivo (Ohneda e colaboradores, 1993), bem como in vitro (Gremlich e colaboradores, 1997).…”