Intestinal absorption and nitrogen balance following portacaval shunt

Alteration in body composition in the portacaval anastamosis rat is mediated by increased expression of myostatin

The portacaval anastamosis (PCA) rat is a model to examine nutritional consequences of portosystemic shunting in cirrhosis. Alterations in body composition and mechanisms of diminished fat mass following PCA were examined. Body composition of male Sprague-Dawley rats with end-to-side PCA and pair-fed sham-operated (SO) controls were studied 3 wk after surgery by chemical carcass analysis (n=8 each) and total body electrical conductivity (n=6 each). Follistatin, a myostatin antagonist, or vehicle was administered to PCA and SO rats (n=8 in each group) to examine whether myostatin regulated fat mass following PCA. The expression of lipogenic and lipolytic genes in white adipose tissue (WAT) was quantified by real-time PCR. Body weight, fat-free mass, fat mass, organ weights, and food efficiency were significantly lower (P < 0.001) in the PCA than SO rats. Adipocyte size and triglyceride content of epididymal fat in PCA rats were significantly lower (P < 0.01) than in SO rats. Myostatin expression was higher in the WAT of PCA compared with SO rats and was accompanied by an increase in phospho-AMP kinase Thr(172). Follistatin increased whole body fat and WAT mass, adipocyte size, and expression of lipogenic genes in WAT in PCA, but not in SO rats. Myostatin and phospho-AMP kinase protein and lipolytic gene expression were lower with follistatin. We conclude that PCA results in loss of fat mass due to an increased expression of myostatin in adipose tissue with lower lipogenic and higher fatty acid oxidation gene expression.

Altered expression of genes regulating skeletal muscle mass in the portacaval anastomosis rat

We examined the temporal relationship between portacaval anastomosis (PCA), weight gain, changes in skeletal muscle mass and molecular markers of protein synthesis, protein breakdown, and satellite cell proliferation and differentiation. Male Sprague-Dawley rats with end to side PCA (n=24) were compared with sham-operated pair-fed rats (n=24). Whole body weight, lean body mass, and forelimb grip strength were determined at weekly intervals. The skeletal muscle expression of the ubiquitin proteasome system, myostatin, its receptor (the activin 2B receptor) and its signal, cyclin-dependent kinase inhibitor (CDKI) p21, insulin-like growth factor (IGF)-I and its receptor (IGF-I receptor-alpha), and markers of satellite cell proliferation and differentiation were quantified. PCA rats did not gain body weight and had lower lean body mass, forelimb grip strength, and gastrocnemius muscle weight. The skeletal muscle expression of the mRNA of ubiquitin proteasome components was higher in PCA rats in the first 2 wk followed by a lower expression in the subsequent 2 wk (P<0.01). The mRNA and protein of myostatin, activin 2B receptor, and CDKI p21 were higher, whereas IGF-I and its receptor as well as markers of satellite cell function (proliferating nuclear cell antigen, myoD, myf5, and myogenin) were lower at weeks 3 and 4 following PCA (P < 0.05). We conclude that PCA resulted in uninhibited proteolysis in the initial 2 wk. This was followed by an adaptive response in the later 2 wk consisting of an increased expression of myostatin that may have contributed to reduced muscle protein synthesis, impaired satellite cell function, and lower skeletal muscle mass.

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.

Long-term nutritional function of orthotopic small bowel autotransplants

Nutritional function following autografting of the entire small bowel was followed in 11 dogs for 12 months. Although positive nitrogen balance was recovered within a few weeks, the animals did not achieve their preoperative body weight for up to 6 months. Fat and D-xylose absorption remained depressed and never fully recovered. Hematocrit and serum iron did not normalize until the second postoperative month or later. Abnormal serum albumin and albumin/globulin ratio persisted for 12 months. When the mesenteric vein was anastomosed to the vena cava rather than to the portal vein, this group had more severe abnormalities in body weight, hematocrit, total protein, and serum albumin, in addition to a significant rise in liver enzymes. These findings represent a discouraging portent for the functional utility of small bowel transplants.

Diet composition and surgical technique influence the postoperative recovery of portacaval shunted rats

In a series of experiments, rats were subjected to end-to-side portacaval shunts using either suture or nonsuture surgical procedures. Rats were maintained on cereal-based or purified diets in pellet form. All rats recovered preoperative body weights within the experimental periods; however, recovery of preoperative body weight was influenced by surgical technique and diet composition. Portacaval shunted rats fed a cereal-based diet required a longer period of time (14 days) to reattain preoperative body weights when compared to portacaval shunted rats fed a purified diet (7 days). Once preoperative body weight was recovered, growth rates of portacaval shunted rats were parallel to those of sham-operated controls. Rats with a suture-portacaval shunt appeared most sensitive to the feeding of a cereal-based diet. All portacaval shunted rats and sham controls fed a purified diet regained preoperative body weights within 7 days after surgery. Sham controls fed either a cereal-based or purified diet recovered preoperative body weights within an average of 4 days. Suture-portacaval shunted rats consuming a pellet form cereal-based diet showed a low feed efficiency which could be reversed by feeding a pellet form purified diet. Rats subjected to a nonsuture glue-portacaval shunt and fed a cereal-based diet showed 50% lower feed efficiencies than did glue-portacaval shunted rats fed a purified diet. Portacaval shunted rats decreased their consumption of cereal-based diets but not of purified diets postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Portacaval transposition in the rat: definition of a valuable model for hepatic research

Portacaval transposition (PCT) in rats results in a smaller loss of body mass and liver mass than end-to-side portacaval shunt (PCS). Detailed studies of liver function, mass and histology were not previously available and have been undertaken in two different strains of growing rat in order to define the value of this model. PCT rats gained weight normally, while only 50% of PCS rats regained their preoperative weight by the tenth week. Wet and dry weights of liver fell relative to control values after both operations, but the fall was significantly greater after PCS than after PCT: there were parallel changes in hepatocyte size. There was a marked rise in liver-associated enzymes in the first 2 days after PCS only, and minimal enzyme elevations persisted in this group. The extent of cellular damage seen histologically closely parallelled the rise in SGOT in individual rats. At 72 hr, PCS rats showed focal necrotic changes, and by 10 weeks there was marked fatty infiltration: PCT rats had normal histology or showed minimal changes. PCT therefore provides a model in which there is total portal diversion without the more severe effects of the conventional PCS on hepatic structure and function. This has particular value in studies of experimental hepatic encephalopathy, of hormonal and amino acid changes after portal diversion, and of factors initiating or controlling liver regeneration.