Proinsulin C-peptide potentiates the inhibitory action of insulin on glucose synthesis in primary cultured rabbit kidney-cortex tubules: metabolic studies.
Biochem Cell Biol
; 92(1): 1-8, 2014 Feb.
Article
en En
| MEDLINE
| ID: mdl-24471913
ABSTRACT
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.
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Péptido C
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Glucosa
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Insulina
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Túbulos Renales
Límite:
Animals
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Humans
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Male
Idioma:
En
Revista:
Biochem Cell Biol
Asunto de la revista:
BIOQUIMICA
Año:
2014
Tipo del documento:
Article
País de afiliación:
Polonia