Effect of portacaval shunt on circulating free fatty acids and ketone bodies in rats

Reduced Liver Lipid Peroxidation in Subcellular Fractions Is Associated with a Hypometabolic State in Rats with Portacaval Anastomosis

A surgical connection between portal and inferior cava veins was performed to generate an experimental model of high circulating ammonium and hepatic hypofunctioning. After 13 weeks of portacaval anastomosis (PCA), hyperammonemia and shrinkage in the liver were observed. Low glycemic levels accompanied by elevated levels of serum alanine aminotransferase were recorded. However, the activity of serum aspartate aminotransferase was reduced, without change in circulating urea. Histological and ultrastructural observations revealed ongoing vascularization and alterations in the hepatocyte nucleus (reduced diameter with indentations), fewer mitochondria, and numerous ribosomes in the endoplasmic reticulum. High activity of hepatic caspase-3 suggested apoptosis. PCA promoted a marked reduction in lipid peroxidation determined by TBARs in liver homogenate but specially in the mitochondrial and microsomal fractions. The reduced lipoperoxidative activity was also detected in assays supplemented with Fe²⁺. Only discreet changes were observed in conjugated dienes. Fluorescent probes showed significant attenuation in mitochondrial membrane potential, reactive oxygen species (ROS), and calcium content. Rats with PCA also showed reduced food intake and decreased energy expenditure through indirect calorimetry by measuring oxygen consumption with an open-flow respirometric system. We conclude that experimental PCA promotes an angiogenic state in the liver to confront the altered blood flow by reducing the prooxidant reactions associated with lower metabolic rate, along with significant reduction of mitochondrial content, but without a clear hepatic dysfunction.

Impact of portacaval anastomosis on plasma fatty acid profile in cirrhosis: a randomized 24-month follow-up study

BACKGROUND

Portacaval anastomosis has an hypolipemic effect in familial hypercholesterolemia and in healthy animals. In cirrhosis, it raises serum cholesterol, but there is no information on its effect upon plasma fatty acids. However, indirect data suggest that portacaval shunting might contribute to the polyunsaturated fatty acid deficit of these patients. We assessed the effect of portacaval anastomosis on plasma fatty acid profile in cirrhosis.

METHODS

Forty-four Child-Pugh class A/B bleeding cirrhotics were randomized to be treated with portacaval anastomosis (n = 20) or nonsurgical therapy (n = 24). Fatty acid profile in plasma total lipids, alcohol intake, anthropometry, Child-Pugh score, serum cholesterol, triglycerides, and antioxidant micronutrients were assessed before and 3, 6, 12, 18, and 24 months after surgery or the start of nonsurgical therapy. Time course of plasma fatty acids was assessed using unbalanced repeated measures models with the above mentioned variables acting as covariates.

RESULTS

No changes in the time course of percent plasma saturated, monounsaturated, and essential fatty acids were found between groups. Percent long-chain omega-6 and omega-3 polyunsaturated fatty acids decreased during follow-up in shunted patients compared with controls (p = .007 and p < .0005). However, this was not due to a true decrease in polyunsaturated fatty acid levels but to greater increases in saturated and monounsaturated fatty acid concentrations in shunted patients compared with control patients (p = .047 and p = .006).

CONCLUSIONS

Portacaval anastomosis does not worsen plasma polyunsaturated fatty acid deficiency in cirrhosis. However, by increasing saturated and monounsaturated fatty acids, it further decreases plasma lipid unsaturation.

Changes of hepatic fatty acid metabolism produced by chronic thioacetamide administration in rats

Hepatic mitochondrial functions related to fatty acid metabolism, including the respiratory control ratio, fatty acid oxidative capacity and carnitine palmitoyltransferase I activity, were studied in vitro with mitochondria isolated from rats treated with thioacetamide for up to 12 wk. The levels of ketone bodies, carnitine, carnitine esters and malonyl-coenzyme A were also determined in liver extracts. Polarography of mitochondrial respiration from succinate or glutamate plus malate showed a lower respiratory control ratio in thioacetamide-treated rats, whereas uncoupled oxygen consumption was not altered. This suggests that the mitochondrial respiratory chain capacity remained intact in the thioacetamide-treated rats. The oxygen consumption associated with palmitoyl-coenzyme A and palmitoyl-L-carnitine oxidation by isolated liver mitochondria was increased by thioacetamide treatment on both a per-mitochondrial protein and a per-total liver basis. The carnitine palmitoyl-transferase I activity; the tissue levels of ketone bodies, carnitine and carnitine esters; and the beta-hydroxybutyrate/acetoacetate ratio were all higher in the livers of thioacetamide-treated animals than in control livers, whereas the hepatic malonyl-coenzyme A level was decreased by thioacetamide. These results indicate the increased diversion of cytosolic long-chain acyl-coenzyme As into the mitochondria for beta-oxidation rather than their esterification and use in lipogenesis. These intrahepatic metabolic changes induced by chronic thioacetamide administration may reflect the whole-body catabolic state and can be seen as adaptive for maintaining energy homeostasis under conditions of impaired glucose tolerance.

Local cerebral glucose metabolism in rats with chronic portacaval shunts

Local cerebral glucose utilization was measured with the autoradiographic [14C]deoxyglucose method in rats at 2 days and 1, 4, 8, and 12 weeks after the construction of a portacaval shunt, and in weight-matched controls. Local glucose utilization in brain was altered in shunted animals, but the magnitude and direction of the changes differed among 36 neuroanatomical structures, depending upon the length of time that the animals had been shunted. In rats shunted for 4 weeks or less, glucose utilization did not differ from control (30 of 36 structures) or was decreased (6 structures). The largest decreases of glucose utilization, noted at 1 week, occurred in the parietal (-25%) and frontal cortices (-28%) and subcortical white matter (-50%. In rats shunted for 8 weeks, however, glucose utilization was higher than control in many brain structures (13 of 36), and after 12 weeks it was higher than control in most structures (25 of 36). Only the parietal cortex did not follow this trend; it exhibited a decreased rate of glucose utilization in rats shunted for 8 weeks (-21%) that normalized in animals shunted for 12 weeks. Portal-systemic shunting of blood increased arterial blood ammonia concentrations to twice the control value of 85 +/- 3 microM in animals shunted for 1 week, and to approximately 2.5 times control in animals shunted for 4-12 weeks. Kety-Schmidt measurements of cerebral blood flow and arterial-venous (torcular) differences for ammonia across the brains of control rats and rats with portacaval shunts for 8 weeks revealed an increased cerebral uptake of ammonia in the shunted animals. The late-developing morphological changes known to occur in astrocytes and the delayed increases in local glucose consumption in rats with portacaval shunts may be related, and represent an adaptive response to sustained hyperammonemia.