title: Effects of manganese deficiency on pyruvate carboxylase and phosphoenolpyruvate carboxykinase activity and carbohydrate homeostasis in adult rats.
abstract: The activities of two liver gluconeogenic enzymes, pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PEPCK), as well as liver glycogen and plasma glucose, insulin, and glucagon were measured in first- and second-generation, manganese-sufficient (control) and manganese-deficient (Mn-) adult rats. Pyruvate carboxylase activity of first generation male Mn- rats was higher than that of controls in both the fed and fasted states. In contrast, PC activity in second generation male Mn- rats was lower than control levels. In female rats, PC activity was lower than controls in both fed, first- and second-generation Mn- rats; in the fasted state, PC activity was either the same or higher than controls. Phosphoenolpyruvate carboxykinase activity was lower in male first generation Mn- rats than in controls, but there was no difference in PEPCK activity in second-generation animals. Phosphoenolpyruvate carboxylase activity was lower in both fed and fasted Mn- female rats than in controls. Plasma insulin levels were lower in the deficient rats than in controls, whereas plasma glucagon levels were similar. Manganese-deficient rats had higher concentrations of liver glycogen than their controls. These findings provide further evidence that manganese affects carbohydrate homeostasis; however, the response of the animal to manganese deficiency depends on the parameter studied and the timing of the deficiency.
authors.affiliation: Department of Nutrition, University of California, 95616, Davis, CA.
authors.forename: D L
authors.initials: DL
authors.lastname: Baly
authors.forename: C L
authors.initials: CL
authors.lastname: Keen
authors.forename: L S
authors.initials: LS
authors.lastname: Hurley