Insulin resistance in human liver cirrhosis is not modified by porto-systemic surgical shunt

Contribution of reduced insulin sensitivity and secretion to the pathogenesis of hepatogenous diabetes: effect of liver transplantation

Diabetes mellitus frequently complicates cirrhosis but the pathogenic mechanisms are unknown. To assess the contribution of reduced insulin action and secretion, 24 cirrhotic-diabetic patients waiting for liver transplant because of an unresectable hepatocarcinoma underwent an oral glucose tolerance test (OGTT) to assess the beta-cell function and an insulin clamp combined with [3-(3)H]glucose infusion to measure whole body glucose metabolism before and 2 years after the transplant. Seven cirrhotic nondiabetic patients, 11 patients with chronic uveitis on similar immunosuppressive therapy, and 7 healthy subjects served as control groups. Cirrhotic patients showed a profound insulin resistance, and diabetics in addition also showed increased endogenous glucose production (P <.05) and insulin deficiency during the OGTT (P <.05). Liver transplantation normalized endogenous glucose production and insulin sensitivity but failed to cure diabetes in 8 of the 24 patients because a markedly low insulin response during the OGTT. Age, body mass index, family history of diabetes, immunosuppressive drugs, and pathogenesis of cirrhosis did not predict in whom liver transplant was going to cure diabetes. On the contrary, a reduced secretory response characterized the patients in whom the transplant would not be curative. In summary, insulin resistance was a primary event complicating cirrhosis but additional beta-cell secretory defects were crucial for development of diabetes. Liver transplantation, lessening insulin resistance, cured hepatogenous diabetes in 67% of cirrhotic-diabetic patients; nevertheless 33% were still diabetics because the persistence of a reduced beta-cell function, which makes these patients eventually eligible for combined islet transplantation.

Glucose intolerance and hyperinsulinemia of cirrhosis are not results of spontaneous or surgical portosystemic shunting

To assess if spontaneous portosystemic shunting from collaterals contributes to the hyperinsulinemia of cirrhosis, 12 patients with alcoholic cirrhosis underwent a 5-hour oral glucose tolerance test 1 day before and 10 days after an elective side-to-side portacaval shunt. The glucose, insulin, and C peptide responses to oral glucose post-shunt were exaggerated but comparable to preoperative values. Compared with preoperative values, the fasting molar ratio of C peptide to insulin postoperatively had increased 40% (6.0 +/- 1.2 versus 8.4 +/- 0.7), indicating improved hepatic function. These results suggest that extrahepatic portosystemic shunting secondary to spontaneous splanchnic collaterals plays little or no role in the hyperinsulinemia of cirrhosis. It appears that decreased hepatic degradation of insulin in these patients is secondary to hepatocellular dysfunction rather than a result of shunting of portal blood around the liver.

Insulin and glucagon degradation in liver are not affected by hepatic cirrhosis

Hyperinsulinemia and impaired glucose tolerance are associated with liver cirrhosis. To investigate whether insulin-degrading activity in liver tissue plays a role in hyperinsulinemia, we assayed this activity in biopsy tissue from healthy and cirrhotic subjects. There was no difference in insulin degradation between these two groups. Also glucagon-degrading activity in liver tissue, which is catalyzed by the same enzyme as insulin-degrading activity, did not differ between the two groups studied. Therefore, insulin-degrading activity does not appear to be involved in the hyperinsulinemia that occurs in liver cirrhosis. The study provides indirect evidence that hyperinsulinemia and impaired glucose metabolism in liver cirrhosis are due to different mechanisms (receptorial and post-receptorial defects, and altered feedback inhibition of insulin secretion).

Intra- and extracellular amino acid concentrations in portacaval-shunted rabbits. Role of hyperammonemia and effects of branched-chain amino acid-enriched parenteral nutrition

Intra- and extracellular amino acid concentrations were measured in rabbits in order to elucidate the possible role of hyperammonemia in lowering the postabsorptive plasma levels of branched-chain amino acids (BCAA) and to assess the effects of BCAA-enriched total parenteral nutrition (TPN) on the amino acid pattern of muscle. The pathophysiological part of this paper deals with portacaval anastomosis (PCA) and is aimed at substantiating or rejecting our hypothesis that excessive ammonia-by stimulating glutamine synthesis-reduces the intracellular glutamate pool which is then restored, at least in part, by an intensified BCAA degradation. Regarding infusion therapy, we were mainly interested in whether an amino acid solution adapted to the metabolism in liver cirrhosis causes an accumulation of BCAA in muscle or modifies the intracellular content of glutamate and glutamine. Eighteen rabbits did not undergo surgery and served as controls (group A), while 30 were given a portacaval end-to-side anastomosis (group B). Two weeks after creating the PCA, venous blood samples were taken and muscle biopsies (Bergström's technique) were performed postabsorptively. An 18-h TPN was then started, the regimen administered included dextrose, fat and, in addition, either a conventional (group B1, n = 15) or an adapted amino acid solution (group B2, n = 15). We obtained second blood specimens and muscle biopsies at the end of the infusion period. With the control animals, the same time schedule for blood sampling and muscle biopsies was followed. Fourteen days after the operation, the PCA rabbits displayed a mean plasma ammonia level 5.1 times higher than that measured in the controls (p less than or equal to 0.001). Conventional blood chemistry did not reveal any impairment of liver cell integrity or over-all hepatic function, whereas the nutritional state of the shunted animals worsened, as indicated by body weight and biochemical variables. Since in the PCA rabbits, the total amino acid pools of muscle and plasma were seen to be increased and decreased, respectively, the results concerning the individual amino acids are given in terms of both the absolute and percentage values, the latter more often revealing high levels of statistical significance. PCA induced a marked rise in the intra- and extracellular concentrations of glutamine, while the values of glutamate and alanine showed a decline in muscle and plasma. The extracellular levels of methionine, phenylalanine, and tyrosine were raised, while those of the BCAA were diminished.(ABSTRACT TRUNCATED AT 400 WORDS)