Effect of glucagon on hepatic energy charge and arterial ketone body ratio in normal rabbits

Accumulation of 7 alpha-hydroxycholesterol in liver tissue of patients with cholesterol gallstones

Patients with cholesterol gallstones have a reduced pool of bile acids. This study was undertaken to clarify the mechanism by which bile acid biosynthesis does not increase to supranormal levels to cause a reexpansion of the pool. We investigated the first two steps of the bile acid biosynthesis pathway by assaying the activities of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in this pathway, and 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase, and by measuring the concentrations of 7 alpha-hydroxycholesterol and 7 alpha-hydroxy-4-cholesten-3-one in liver specimens from ten patients with cholesterol gallstones and ten gallstone-free controls. In the patients with gallstones, cholesterol 7 alpha-hydroxylase activity, 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase activity, and hepatic 7 alpha-hydroxy-4-cholesten-3-one concentration did not significantly different from levels in controls, but hepatic 7 alpha-hydroxycholesterol concentration was more than twofold that of controls (12.9 +/- 2.6 vs 5.3 +/- 1.2 nmol/g liver, P < 0.01). The concentration of 7 alpha-hydroxycholesterol positively correlated with the ratio of cholesterol 7 alpha-hydroxylase activity to 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase activity (r = 0.93; P < 0.005) in the gallstone-free controls. In contrast, this correlation disappeared in the patients with gallstones. These results suggest a derangement of the normal 7 alpha-hydroxycholesterol metabolism in the patients with gallstones. The reason for the accumulation of 7 alpha-hydroxycholesterol remains unclear; however, it is possible that, in patients with cholesterol gallstone, the accumulated 7 alpha-hydroxycholesterol causes inappropriate suppression of cholesterol 7 alpha-hydroxylase activity by product inhibition.

Insulin and glucagon levels in living related liver transplantation: their interaction with the recovery of graft liver function

Insulin and glucagon have opposite effects on various hepatic functions, including energy metabolism, which is essential for hepatic viability. To evaluate the effects of insulin and glucagon on the recovery of graft liver function, changes in these levels were investigated in relation to arterial ketone body ration (AKBR) during a 30-h period after graft liver reperfusion in 29 recipients of living related liver transplants. Insulin levels did not change significantly throughout this study, while glucagon levels decreased immediately after reperfusion, indicating a rapid degradation of glucagon by the graft liver. The insulin/glucagon (I/G) ratio increased after reperfusion concomitantly with AKBR. In addition, the I/G ratio was significantly correlated with AKBR after reperfusion. It is concluded that the increase in the I/G ratio was closely related to the recovery of graft liver function as reflected by the AKBR in living related liver transplantation.

Glucagon responses in rabbits with obstructive jaundice and a low energy status in the liver

Glucagon has a choleretic effect and also stimulates energy-consuming reactions, such as gluconeogenesis and ureogenesis in the liver. The effect of glucagon on energy metabolism in the liver was analyzed in rabbits with obstructive jaundice that had severe liver damage, indicated by significantly lower hepatic energy charge levels. The gluconeogenetic responses to glucagon administration, as shown by increases in the plasma glucose levels, were usually observed in normal rabbits, but these responses were completely depressed after glucagon administration in rabbits with obstructive jaundice. The energy charge levels in the latter animals decreased even further after glucagon administration. Even though the energy consumption for gluconeogenesis after glucagon administration was limited in the jaundiced rabbits, it was sufficient to cause a deterioration in the hepatic energy balance. The above findings show that the administration of glucagon increases the amount of energy expended in the liver following a reduction in the hepatic energy charge in rabbits with obstructive jaundice. Therefore, even though glucagon has a choleretic effect, it should be administered carefully to patients with obstructive jaundice, especially in those with severe liver damage, such as in patients with cholangitis.