The effect of preoperative carbohydrate loading on hormonal changes, hepatic glycogen, and glucoregulatory enzymes...

The effect of preoperative glucose infusion on preoperative alterations in hepatic glycogen content, the activity of key hepatic glucoregulatory enzymes (fructose 1,6-diphosphatase [FDPase]), pyruvate kinase (PK), hormonal developments, and plasma levels of free fatty acids (FFA) were investigated in 16 patients undergoing open cholecystectomy. Patients were randomized to receive (group G) or not receive (group C) overnight glucose infusion (5 mg.kg-1.d-1) preoperatively. Infusion of glucose overnight resulted in preoperative elevations of insulin and c-peptide (P < 0.05) and lower plasma levels of FFA, while the same glucose levels were found in both groups, 4.6 mmol/L. During and after surgery, only minor changes in the plasma levels of insulin, c-peptide, catecholamines, glucagon, cortisol, growth hormone, and FFA were found, with minimal differences between groups. The hepatic glycogen content was 65% higher in group G and a significant reduction was confirmed only in this group of patients during surgery. The higher glycogen content was associated with a higher FDPase activity ratio (P < 0.05), which remained unchanged during surgery. In contrast, a significant (P < 0.05) increase in the activity of this enzyme was found in group C. The PK activity ratio did not differ between groups and remained unchanged during surgery. The finding of enhanced FDPase activity suggests that the indirect route (via gluconeogenesis) represents an important contributor to the increased glycogen formation during glucose infusion. Additionally, surgery in the overnight fasted patient induces enzymatic changes favoring gluconeogenesis. Lastly, preoperative high-dose glucose infusion has only minor effects on the endocrine response, plasma levels of FFA, and glycogen depletion during elective open cholecystectomy.