Kinetics of ethanol inhibition of galactose elimination in perfused pig liver

Partial replacement of glucose by galactose in the post-weaning diet improves parameters of hepatic health

Replacing part of glucose with galactose in the post-weaning diet beneficially affects later life metabolic health in female mice. The liver is the main site of galactose metabolism, but the direct effects of this dietary intervention on the liver in the post-weaning period are not known. The aim of this study was to elucidate this. Weanling female mice (C57BL/6JRccHsd) were fed a starch containing diet with glucose (32 en%) monosaccharide (GLU), or a diet with glucose and galactose (1:1 both 16 en%) (GLU+GAL). Body weight, body composition, and food intake were determined weekly. After 3 weeks, mice were sacrificed, and serum and liver tissues were collected. Global hepatic mRNA expression was analyzed and hepatic triglyceride (TG) and glycogen contents were determined by enzymatic assays. Body weight and body composition were similar in both groups, despite higher food intake in mice on GLU+GAL diet. Hepatic TG content was lower in GLU+GAL-fed than GLU-fed females, while glycogen levels were unaffected. Analysis of global expression patterns of hepatic mRNA showed that mainly inflammation-related pathways were affected by the diet, which were predominantly downregulated in GLU+GAL-fed females compared to GLU-fed females. This reduction in inflammation in GLU+GAL-fed females was also reflected by decreased serum concentrations of acute phase protein Serum amyloid A 3. In conclusion, replacing part of glucose with galactose in the post-weaning diet reduces hepatic TG content and hepatic inflammation.

Quantitative rat liver function test by galactose single point method

Summary

The purpose of this study was to investigate the galactose single point (GSP) method, a residual liver function test recently recommended by the US Food and Drug Administration, which can be a useful tool for rat liver function measurement. Rats were treated either with carbon tetrachloride (CCl4) alone (1 mL/kg, intraperitoneally [i.p.]) for one day or with isoniazid (INH) alone (150 mg/kg, i.p.) or (in order to ameliorate the effects of INH) with a combination of INH and bis- p-nitrophenyl phosphate (BNPP) (25 mg/kg, i.p.) for 21 days. Hepatotoxicity was assayed by plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and scores of histological activity index-necroinflammation (HAI-NI) of the respective liver specimens. The GSP method in rats was defined by the galactose blood level after 60 min. Significant differences in GSP values were observed between controls and the CCl4-treated rats. After 21 days of treatment, no significant changes in AST and ALT values were observed among the control, INH and INH-BNPP groups. There were significant differences in average GSP values for controls ( P < 0.001) and INH-BNPP ( P < 0.001) compared with INH alone. Highly significant correlations ( P < 0.001) were obtained between GSP and scores of HAI-NI for all the groups. GSP was concluded to be a more sensitive biomarker of INH-induced hepatotoxicity than AST or ALT in the rats. The GSP method has been proved to be a simple and useful tool for the quantitative determination of liver function in rats, which can possibly be extended to other animals.

Hepatic uptake and metabolism of galactose can be quantified in vivo by 2-[18F]fluoro-2-deoxygalactose positron emission tomography

Metabolism of galactose is a specialized liver function. The purpose of this PET study was to use the galactose analog 2-[(18)F]fluoro-2-deoxygalactose (FDGal) to investigate hepatic uptake and metabolism of galactose in vivo. FDGal kinetics was studied in 10 anesthetized pigs at blood concentrations of nonradioactive galactose yielding approximately first-order kinetics (tracer only; n = 4), intermediate kinetics (0.5-0.6 mmol galactose/l blood; n = 2), and near-saturation kinetics (>3 mmol galactose/l blood; n = 4). All animals underwent liver C15O PET (blood volume) and FDGal PET (galactose kinetics) with arterial and portal venous blood sampling. Flow rates in the hepatic artery and the portal vein were measured by ultrasound transit-time flowmeters. The hepatic uptake and net metabolic clearance of FDGal were quantified by nonlinear and linear regression analyses. The initial extraction fraction of FDGal from blood-to-hepatocyte was unity in all pigs. Hepatic net metabolic clearance of FDGal, K(FDGal), was 332-481 ml blood.min(-1).l(-1) tissue in experiments with approximately first-order kinetics and 15.2-21.8 ml blood.min(-1).l(-1) tissue in experiments with near-saturation kinetics. Maximal hepatic removal rates of galactose were on average 600 micromol.min(-1).l(-1) tissue (range 412-702), which was in agreement with other studies. There was no significant difference between K(FDGal) calculated with use of the dual tracer input (Kdual(FDGal)) or the single arterial input (Karterial(FDGal)). In conclusion, hepatic galactose kinetics can be quantified with the galactose analog FDGal. At near-saturated kinetics, the maximal hepatic removal rate of galactose can be calculated from the net metabolic clearance of FDGal and the blood concentration of galactose.

Effects of hyperglycemia on quantitative liver functions by the galactose load test in diabetic rats

Blood galactose clearance after an intravenous galactose load has been widely used as a quantitative liver function test. We have developed a novel quantitative rat liver function test, the galactose single point (GSP) method, to assess residual liver function with various injuries by measuring single time point galactose concentration in blood after an intravenous bolus injection of galactose. The goal of this study was to evaluate the influence of nonhepatic factors such as hyperglycemia on GSP and galactose elimination capacity (GEC) in rats. Four groups of animal studies were carried out, as follows: (1) normal control (NC), (2) streptozotocin-induced diabetes (DM), (3) carbon tetrachloride-induced hepatotoxicity (CCl(4)), and (4) streptozotocin-induced diabetes with CCl(4)-induced hepatotoxicity (DM + CCl(4)). The serum glucose levels in the diabetic groups (DM and DM + CCl(4)) were significantly increased compared with the NC and CCl(4) groups (P < .001). A significant increase in hepatic activities of aspartate aminotransferase and alanine aminotransferase was observed in the CCl(4)-treated groups (CCl(4) and DM + CCl(4)) compared with the NC and DM groups (P < .001). In comparison with the NC group, the values of GSP and GEC in the diabetic groups (DM and DM + CCl(4)) were significantly reduced (P < .001) and increased (P < .01), respectively. Galactose single point had highly significant correlations with GEC (P < .001). These results suggest that galactose metabolism tests-as quantitative parameters of liver function-should be interpreted with caution in the condition of a significant hyperglycemia.

Preoperative galactose elimination capacity predicts complications and survival after hepatic resection

OBJECTIVE

To analyze a single center's 6-year experience with 258 consecutive patients undergoing major hepatic resection for primary or secondary malignancy of the liver, and to examine the predictive value of preoperative liver function assessment.

SUMMARY BACKGROUND DATA

Despite the substantial improvements in diagnostic and surgical techniques that have made liver surgery a safer procedure, careful patient selection remains mandatory to achieve good results in patients with hepatic tumors.

METHODS

In this prospective study, 258 patients undergoing hepatic resection were enrolled: 111 for metastases, 78 for hepatocellular carcinoma (HCC), 21 for cholangiocellular carcinoma, and 48 for other primary hepatic tumors. One hundred fifty-eight patients underwent segment-oriented liver resection, including hemihepatectomies, and 100 had subsegmental resections. Thirty-two clinical and biochemical parameters were analyzed, including liver function assessment by the galactose elimination capacity (GEC) test, a measure of hepatic functional reserve, to predict postoperative (60-day) rates of death and complications and long-term survival. All variables were determined within 5 days before surgery. Data were subjected to univariate and multivariate analysis for two patient subgroups (HCC and non-HCC). The cutoffs for GEC in both groups were predefined. Long-term survival (>60 days) was subjected to Kaplan-Meier analysis and the Cox proportional hazard model.

RESULTS

In the entire group of 258 patients, a GEC less than 6 mg/min/kg was the only preoperative biochemical parameter that predicted postoperative complications and death by univariate and stepwise regression analysis. A GEC of more than 6 mg/min/kg was also significantly associated with longer survival. This predictive value could also be shown in the subgroup of 180 patients with tumors other than HCC. In the subgroup of 78 patients with HCC, a GEC less than 4 mg/min/kg predicted postoperative complications and death by univariate and stepwise regression analysis. Further, a GEC of more than 4 mg/min/kg was also associated with longer survival.

CONCLUSIONS

This prospective study establishes the preoperative determination of the hepatic reserve by GEC as a strong independent and valuable predictor for short- and long-term outcome in patients with primary and secondary hepatic tumors undergoing resection.

Potential use of pharmacological markers to quantitatively assess liver function during liver transplantation surgery

Early functioning of the transplanted liver is of crucial importance to the recipient. This function may be assessed by measuring the disposition of substances that are mainly eliminated via the liver. None of the agents currently used is ideal for this purpose. Measurement of mono-ethyleneglycinexylidide (MEGX) formation from lignocaine is useful and has been widely used in liver transplantation to assess liver graft function. MEGX formation can be affected by the use of drugs that influence liver perfusion or interfere with the CYP450 enzyme system. Indocyanine green clearance is a convenient method but both blood flow and hepatocellular function affect the test results. Tests of caffeine clearance, galactose elimination capacity and antipyrine clearance all require time-consuming, technically cumbersome and expensive serial blood sampling. The aminopyrine breath test is non-invasive, but gastric emptying and the patient's physical state affect results. The potential hazard of exposure to radioactive compounds limits the wide clinical use of both aminopyrine and erythromycin breath tests. Monitoring the rate of recovery from neuromuscular blockade induced by vecuronium and rocuronium can provide valuable information on liver function.

Nicotinamide methylation and hepatic energy reserve: a study by liver perfusion in vitro

BACKGROUND/AIMS

The synthesis of pyridine nucleotides from nicotinamide requires adenosine triphosphate. In man when exogenous nicotinamide is poorly utilized in this synthesis, the excess follows a dissipative metabolic pathway and is excreted in urine as N-methylnicotinamide. In human cirrhosis N-methylnicotinamide serum levels are higher than normal, in basal condition and after nicotinamide oral load. The aim of this study was to verify N-methylnicotinamide production in relation to hepatic content of adenosine triphosphate during in vitro perfusion of rat liver, in normal conditions and after adenosine triphosphate depletion by metabolic stress.

METHODS

"Stress" was obtained by pre-washing with saline for 15 min before the perfusion with nutritive medium.

RESULTS

The adenosine triphosphate decrease in the stressed liver was 38% after pre-washing with saline and 80% at the end of nutritive perfusion. In control liver the corresponding decreases were 1% after pre-washing with nutritive medium and 65% at the end of perfusion with the same medium. The total nicotinamide adenine dinucleotide decreases were 44% and 56% in the stressed liver, and 19% and 52% in the control liver. The output levels of N-methylnicotinamide at 90 min of rat liver nutritive perfusion were 31.50 +/- 4.72 nmol/g for normal liver and 66.40 +/- 13.17 for stressed liver (p<0.001). Liver adenosine triphosphate was inversely related to N-methylnicotinamide production (r=0.93; p<0.001).

CONCLUSIONS

These data suggest that nicotinamide methylation may be enhanced when there is hepatic adenosine triphosphate decrease and energy failure induced by hypoxia or metabolic stress, similar to that obtained in vitro by saline washing before perfusion with nutritive medium. This study shows that the evaluation of N-methylnicotinamide production in man (before and after nicotinamide load) might be useful to explore the energy state of diseased liver.

Novel galactose single point method as a measure of residual liver function: example of cefoperazone kinetics in patients with liver cirrhosis

A novel, simple, clinically useful quantitative liver function test, called the galactose single point (GSP) method, was developed to assess residual liver function by measuring galactose blood concentration 1 hour after galactose was administered (0.5 g/kg). This method was applied to the study of cefoperazone kinetics in patients with hepatic cirrhosis. To study the influence of hepatic cirrhosis on the residual liver function and the correlation between the residual liver function and the pharmacokinetics of cefoperazone, a dose of 1 g of cefoperazone was administered to 11 healthy volunteers and 12 patients with liver cirrhosis. The GSP method, the galactose elimination capacity (GEC) test, and the modified galactose elimination capacity (MGEC) test were done for each volunteer and patient to measure residual liver function. The galactose concentrations were determined enzymatically. Cefoperazone was administered intravenously, and blood and urine samples were collected at appropriate intervals after drug administration. All blood and urine samples were stored at -30 degrees C until high-performance liquid chromatography analysis. Cefoperazone plasma concentrations were much higher in cirrhosis patients than in normal subjects at all times. The elimination half-life, hepatic clearance, mean residence time, and renal clearance of cirrhosis patients differed significantly from those of healthy volunteers. The plasma protein binding was unaltered in both groups. Urinary excretion of cefoperazone was significantly increased in cirrhosis patients (23.95 +/- 5.06% for normal men and 51.09 +/- 11.50% in cirrhosis patients). Hepatic clearance, fraction excreted in urine, and total clearance significantly correlated with GSP, GEC, and MGEC (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Galactose removal kinetics during hypoxia in perfused pig liver: reduction of Vmax, but not of intrinsic clearance Vmax/Km

The galactose elimination kinetics was examined in five perfused pig livers of 1.2 kg during hypoxia induced by administration of 2, 4 or 7% oxygen in the oxygenator instead of 20% as used in nine control experiments, previously published. Galactose was given as four to five successive constant infusion rates so that successive steady-state period with galactose concentrations from 0.04 to 5 mmol l-1 were obtained in each experiment. From the relationship between the calculated elimination rate and the perfusate galactose concentration, values of the maximal elimination rate Vmax and the half saturation concentration Km were calculated. Both Vmax and Km were reduced by hypoxia: the lower the oxygen supply, the greater the reduction. Vmax was about 0.08 mmol min-1 kg-1 liver at 2% oxygen and about 0.18 mmol min-1 kg-1 liver at 4-7% oxygen; both being significantly lower than the value of 0.43 mmol min-1 kg-1 liver at 20% oxygen. Km was about 0.07 mmol l-1 at 2% oxygen and 0.13 mmol l-1 at 7% oxygen; both significantly lower than the value of 0.23 mmol l-1 at 20% oxygen. A nearly parallel reduction of liver ATP concentration and galactose Vmax indicates that the galactose Vmax may reflect the phosphorylation capacity of the liver cells. The Vmax/Km ratio (intrinsic hepatic clearance) was unchanged during hypoxia.

Treatment of liver disease with malotilate. A pharmacokinetic and pharmacodynamic phase II study in cirrhosis

Malotilate, a sulphur-containing compound with antifibrotic and hepatoprotective properties in several animal models, has been investigated in cirrhotic patients. Nine patients with cirrhosis of various aetiologies and severity, and 4 healthy volunteers, participated in a pharmacokinetic study. After a single dose of 500 mg malotilate p.o. peak malotilate plasma concentration measured by GC-MS was 35 times higher in patients (median 0.70 micrograms/ml) than in controls (median 0.019 micrograms/ml). The median apparent oral clearance was approximately 50 times lower in cirrhotics (median 2.21/min) than in healthy volunteers (1181/min). The apparent oral clearance was significantly correlated with indicators of portal-systemic shunting, such as the 2-h postprandial serum bile acids and the bioavailability of oral nitroglycerine. Urinary output of the glucuronidated metabolite-(M3), measured by HPLC, was normal in patients, whereas recovery of metabolite-M6 (resulting from ring opening and loss of sulphur) was reduced. Six patients in an open 6-month trial received malotilate 200 mg t.i.d. for 2 months and 400 mg t.i.d. for 4 months. The thrombocyte count increased and serum ferritin level fell in all patients, and serum cholinesterase rose and IgA decreased in 5 of 6. The other indicators of liver function did not show a significant change. Dry skin was the only possible adverse effect. It is concluded that first-pass elimination of malotilate is dramatically reduced in cirrhotics, and that a smaller amount of the drug reaches the liver in such patients. Malotilate was well tolerated, even in patients with advanced disease.

Quantitative liver function in the elderly assessed by galactose elimination capacity, aminopyrine demethylation and caffeine clearance

Hepatic function was assessed in 13 healthy elderly subjects, 71-88 years of age, with three quantitative tests of liver function. The galactose elimination capacity was significantly (P less than 0.05) lower in the elderly (6.08 +/- 1.30 mg X min-1 X kg-1, mean +/- SD) than in a group of 70 subjects under 40 (7.48 +/- 0.94 mg X min-1 X kg-1) and 11 subjects between the age of 40 and 70 (7.08 +/- 0.68 mg X min-1 X kg-1). The demethylation of aminopyrine as assessed by the aminopyrine breath test, and the systemic clearance of caffeine, two measures of microsomal function, demonstrated a comparable decrease but showed much more interindividual variation. Caffeine clearance decreased from 1.49 +/- 0.44 ml X min-1 X kg-1 in young adults to 0.97 +/- 0.39 ml X min-1 X kg-1 (P less than 0.01) in the elderly, and the demethylation of aminopyrine decreased from 0.79 +/- 0.15 to 0.62 +/- 0.20% dose X kg X mmol-1 (P less than 0.05). Our data indicate that aging is associated with a loss of the functioning mass of hepatocytes. The decrease in drug metabolism parallels the loss of functional mass but shows more interindividual variation probably reflecting the many genetic and environmental factors influencing these tests of microsomal function.

Kinetics of galactose uptake by perfused rat livers: applicability of a family of models

Mathematical models for general substrate uptake mechanisms in the liver have been used to describe the kinetics of galactose removal. In this study sets of galactose uptake rates to galactose concentration relations obtained by perfusion of ten livers of 200 g rats were examined. The rate of galactose uptake (v) was related to the galactose concentration in the sinusoids (calculated as the logarithmic mean of in- and outlet concentration, ĉ). In all experiments a saturation pattern emerged, but the resulting 1/v versus 1/ĉ plots were all markedly convex, discarding simple Michaelis-Menten kinetics. Data were therefore examined in the light of a family of kinetic models, including the following modifications: substrate inhibition, porto-systemic shunting, and allosterism. The kinetic constants were assessed by iterative procedures, aiming at linearization of the double reciprocal plots. The two latter models were found to fit the experimental data by entering a shunting of 61% of the hepatic blood flow, or two active sites, respectively. Since this degree of shunting is improbable the results speak in favour of allosterism. The work gives an example of whole-liver kinetic considerations when simple Michaelis-Menten is insufficient.

[Tryptophan loading test as a function parameter in liver diseases]

Because of its specific hepatic degradation tryptophan was orally administered (50 mg/kg) to patients with various chronic liver diseases (n = 30) and to healthy volunteers (n = 8) as a test for hepatic function. The plasma half life of tryptophan was determined between 4 and 8 h after the amino acid load. It was found that in patients with cirrhosis (n = 25) the half life of tryptophan was prolonged to 4.7 +/- 0.4 h (means +/- SD), compared to 2.0 +/- 0.1 h in the controls. The tryptophan half life also correlated with the plasma concentration of albumin, bilirubin, cholinesterase and prothrombin time in these patients. In addition a significant correlation was observed with the galactose elimination capacity and the 45 min retention of BSP. Thus, the oral tryptophan loading test may be suitable for a more specific determination of functional impairment of the liver in chronic liver disease. In decompensated cirrhotic patients alterations of the tryptophan metabolism seen to be related to indicators of hepatic encephalopathy. The test may therefore be used to assess the degree and risk of hepatic encephalopathy in such patients.

Histologic and ultrastructural evaluation of thyroid lesions associated with hypothyroidism in dogs

Thyroid lesions in 16 pet dogs with hypothyroidism were evaluated by light and electron microscopy. Lymphocytic thyroiditis, found in seven dogs, was characterized by diffuse infiltration of the thyroid gland by lymphocytes, plasma cells and macrophages with formation of some lymphoid nodules and destruction of follicles, progressing to replacement of most of the thyroid by fibrous connective tissue. The basement membrane around follicles was thick and had electron-dense deposits. The morphology of the thyroid lesions and the presence of circulating thyroglobulin autoantibodies suggested that lymphocytic thyroiditis was immune-mediated. Idiopathic follicular atrophy, found in nine dogs, was characterized by loss of thyroid parenchyma and replacement by adipose connective tissue. Degeneration of individual follicular cells was present in the early stage, with exfoliation into the colloid and interfollicular area. Most of the thyroid gland consisted of adipose connective tissue with either interspersed small follicles or individual follicular cells that had dilated rough endoplasmic reticulum, large Golgi apparatus, and intracytoplasmic microfollicles in the advanced stage. Follicular atrophy was a degenerative lesion of follicular cells of unknown cause, not associated with inflammatory destruction in the thyroid gland.

Attenuation of the ethanol-induced hepatic redox change after chronic alcohol consumption in baboons: metabolic consequences in vivo and in vitro

Acute ethanol administration results in increased hepatic NADH/NAD+ ratio and inhibition of galactose elimination, tricarboxylic acid cycle activity, and fatty acid oxidation. To determine how this redox change is affected by chronic alcohol consumption and to assess the resulting metabolic consequences, we studied baboons which were fed alcohol as 50% of their total calories. Redox changes were evaluated through measurement of galactose elimination in vivo and lactate/pyruvate ratios in liver slices in vitro. The metabolic consequences of these changes were assessed through measurement of CO2 production and fatty acid oxidation in liver slices and hepatic lipid accumulation. Chronic alcohol feeding resulted in attenuation of inhibition of galactose elimination, increase in the lactate/pyruvate ratio, and decrease in fatty acid oxidation which were caused by acute ethanol administration. These metabolic adaptations were associated with reduced accumulation of hepatic fat.