In this study, the mRNA levels of FBP1 and glucose 6-phosphatase
(G6PC) remained unchanged (p>0.05) following castration (Figure 1).
Indeed, insulin inhibits the expression of rate-limiting enzymes of gluconeogenesis, that is, phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-bisphosphatase (FBPase), and glucose 6-phosphatase
(G6Pase), whereas it activates the key enzyme of glycogen synthesis, that is, glycogen synthase (GS) .
Four key enzymes regulate gluconeogenesis in humans: pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6 bisphosphatase, and glucose 6-phosphatase
. The first two are involved when carbohydrates are produced from amino acids; the latter two are involved in the final steps of gluconeogenesis.
[ACE2.sup.-/y] mice presented a reduction in the relative expression of glucokinase (GCK) and of glucose transporter type 2 (GLUT2) and increased levels of expression of glucose 6-phosphatase
(G6Pase) and phosphoenolpyruvate carboxykinase subtype 2 (PCK2).
Oral administration of Glycosin and metformin increased the hexokinase activity and decreased the activities of glucose 6-phosphatase
and fructose 1,6-bisphosphatase compared to diabetic control rats.
Dysregulation of glucose-6-phosphate by changes in the activity of glucokinase or glucose 6-phosphatase
in type 2 diabetes may be a contributing factor in the impaired suppression of glycogenolysis caused by hyperglycemia (Aiston et al.