Proinsulin C-peptide potentiates the inhibitory action of insulin on glucose synthesis in primary cultured rabbit kidney-cortex tubules: Metabolic studies
| Autor: | Rafal Derlacz, Anna Kiersztan, Michal Usarek, Adam K. Jagielski, Paulina Krempa, Jakub Drozak, Jadwiga Bryła, Agnieszka Girstun, Anna Dylewska |
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| Rok vydání: | 2014 |
| Předmět: |
Male
medicine.medical_specialty medicine.medical_treatment Biology Inhibitory postsynaptic potential Biochemistry Internal medicine medicine Rabbit kidney Animals Humans Insulin Molecular Biology Cells Cultured Proinsulin Alanine C-Peptide Cell Biology Cortex (botany) Proinsulin C-Peptide Glucose Kidney Tubules Endocrinology Gluconeogenesis Rabbits |
| Zdroj: | Biochemistry and Cell Biology. 92:1-8 |
| ISSN: | 1208-6002 0829-8211 |
| Popis: | Effects of equimolar concentrations of proinsulin C-peptide and insulin on glucose synthesis were studied in primary cultures of rabbit kidney-cortex tubules grown in the presence of alanine, glycerol, and octanoate. The rhodamine-labeled C-peptide entered renal tubular cells and localized in nuclei, both in the presence and absence of insulin; preincubations with the unlabeled compound inhibited internalization. C-peptide did not affect glucose formation when added alone but potentiated the inhibitory action of insulin by about 20% due to a decrease in flux through glucose-6-phosphate isomerase (GPI) and (or) glucose-6-phosphatase (G6Pase). GPI inhibition was caused by: (i) increased intracellular contents of fructose-1,6-bisphosphate and fructose-1-phosphate, inhibitors of the enzyme and (ii) reduced level of the phosphorylated GPI, which exhibits higher enzymatic activity in the presence of casein kinase 2. A decrease in flux through G6Pase, due to diminished import of G6P by G6P-transporter from the cytoplasm into endoplasmic reticulum lumen, is also suggested. The data show for the first time that in the presence of insulin and C-peptide, both GPI and G6P-ase may act as regulatory enzymes of renal gluconeogenic pathway. |
| Databáze: | OpenAIRE |
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