Human liver glycogen metabolism assessed with a 13C-enriched diet and a 13CO2 breath test

BACKGROUND

Adequate liver glycogen stores to maintain hepatic glucose output by glycogenolysis in the post-absorptive state are essential to prevent protein loss through gluconeogenesis. There are no simple techniques to monitor liver glycogen use.

METHODS

In this study, we labelled liver glycogen with naturally 13C-enriched carbohydrate and measured the pattern of 13CO2 excretion and the post-prandial time during which oxidation of 13C-labelled liver glycogen was demonstrable by 13CO2 enrichment in breath. Two experiments were performed in 24 healthy volunteers.

RESULTS

In the first experiment we observed that breath 13CO2 enrichment returned to baseline values at 20.3 (SD 2.3, n = 12) hours post-prandially, indicating exhaustion of the 13C-labelled liver glycogen at that time. In a second experiment, breath 13CO2 enrichment in the early hours of the post-prandial phase was studied. After a steep decline, which started 2-4 h after the last meal, the 13CO2 enrichment reached a plateau phase 6 h post-prandially. This plateau phase lasted for about 6-8 h, suggesting steady-state glycogenolysis during this period. The plateau phase was followed by a further decline in 13CO2 excretion, suggesting a gradually diminishing contribution of 13C-labelled liver glycogen to substrate oxidation.

CONCLUSION

It is possible to label liver glycogen with a diet of naturally 13C-enriched carbohydrate. The oxidation of the labelled liver glycogen can be monitored by measuring 13C-enrichment in breath CO2.

13C breath test in gastroenterological practice

Breath tests (BTs) are used in gastroenterological practice to study (patho)physiological and metabolic processes in an indirect way. In these tests the appearance in breath of a metabolite of a specific test substance is studied. The assumption underlying each BT is that one step-the process of interest-in the absorption and metabolism of the tracer is rate-limiting. Both hydrogen gas excretion and carbon dioxide appearance in breath can be studied. When a carbon-labelled test substance is used. the stable isotope 13C is preferred to the radioactive isotope 14C. Measurements of 13C in expired air are performed by mass spectrometry. Because of the indirect nature of BTs, involving a sequence of reactions and metabolic pools, they usually supply semiquantitative data. The tests are nevertheless useful because they often replace invasive techniques with a simple procedure that is safe because there is no radioactivity involved. BTs have been used to measure gastric emptying, the presence of Helicobacter pylori in the stomach, small-bowel bacterial overgrowth, exocrine pancreatic function as well as liver metabolic capacity; other potential applications of BTs are being studied.

Evaluation studies of the 13C-mixed triglyceride breath test in healthy controls and adult cystic fibrosis patients with exocrine pancreatic insufficiency

The 13C-mixed triglyceride (13C-MTG) breath test (BT) is a safe and noninvasive method to measure exocrine pancreatic function. We examined the reproducibility of the 13C-MTG BT in a group of 17 healthy controls and 8 adult patients with cystic fibrosis (CF). In controls no statistically significant difference in percentage dose recovered (PDR) was found between the first and the second result of repeated tests: the mean values were 35.5 +/- 5.5 vs. 32.3 +/- 7.4 PDR (n = 17). Also in the group of CF patients (n = 8) no significant difference between duplicate tests was found: mean values 17.5 +/- 7.5 and 17.5 +/- 7.8 PDR, respectively. The coefficient of repeatability is 8 PDR for the controls and CF patients together. Two factors might influence the outcome of the test. First, individually measured CO2 excretion instead of the usually assumed 9 mmol/h/kg CO2 production might alter the result of the 13CO2-MTG BT. Therefore CO2 production was measured by indirect calorimetry in 12 healthy controls and 13 CF patients. Measured CO2 excretion was not significantly different between healthy controls and CF patients. Secondly, exercise might influence BT results due to its separate effects on both CO2 production and excretion. The influence of physical exercise at a level of 25 or 50 W was studied on a bicycle ergometer in 4 healthy controls during the last 5 min of each 30-min sampling period. Exercise gave lower test results, on average 85% of the PDR value at rest. Incidently, it was observed in 1 patient that use of 13C-enriched food during the day preceding the test caused inappropriately low test results in the 13C-MTG BT. The 13C-MTG BT is a test with a fair but less than desirable reproducibility. Test conditions should be standardized to eliminate confounding influences. Exercise should be limited or strictly defined. Diet on the day preceding the test should not contain naturally 13C-enriched food. There is no need to measure individual CO2 production.

Dietary level and source of neutral detergent fiber and ileal endogenous nitrogen flow in pigs

Two experiments were conducted to study the effect of dietary level and source of neutral detergent fiber (NDF) on ileal dry matter flow and on total and endogenous N flow at the terminal ileum. Twenty-two crossbred 6-wk-old castrated male pigs with an average BW of 9 kg were used. The pigs were fitted with a post-valvular T-cecal cannula and two indwelling blood catheters. During the experimental period of 10 d, the pigs were 11 wk of age with an average BW of 14 kg. They were fed 2.6 times their maintenance requirement for energy of a corn starch-based, semisynthetic diet. The diets contained 178 g of soy isolate/kg as the only source of nitrogen (N). In diets of Exp. 1, purified NDF was included at 0 and 200 g/kg of feed at the expense of glucose. The diets of Exp. 2 contained one of the three different NDF sources (purified NDF, wheat bran, or sunflower hulls) at a level of 144 g of NDF/kg of DM. The purified NDF (pNDF) was isolated from the same batch as the wheat bran (WB) used in Exp. 2. The endogenous N flow at the terminal ileum of these pigs was determined with the 15N-isotope dilution method. The inclusion of NDF in the experimental diets increased (P < .05) the daily DM flow at the terminal ileum. Dry matter flow was increased .697 g for every g/kg increase in NDF in the diet. The different sources of dietary NDF gave similar (P > .05) ileal DM flows.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hulls of faba beans (Vicia faba L.) with a low or high content of condensed tannins on the apparent ileal and fecal digestibility of nutrients and the excretion of endogenous protein in ileal digesta and feces of pigs

In three experiments (Exp. 1, 2, and 3) with young pigs (BW 10 to 26 kg), the effects of dietary inclusion of hulls of faba beans (Vicia faba L.) (200 g/kg) with a low (< .1% catechin equivalents; LT) or high tannin content (3.3% catechin equivalents; HT) on the apparent ileal (Exp. 1 and 2) and fecal (Exp. 3) digestibility of nutrients were determined. In addition, the true digestibility of protein of the diets and the excretion of endogenous protein (N x 6.25) in ileal digesta and feces of pigs were measured, using the 15N isotope dilution technique (Exp. 3). Diets contained either casein and faba bean cotyledons as highly soluble (HS) protein sources (Exp. 1 to 3) or potato protein, soy concentrate, sunflower meal, meat meal, and fish meal as protein sources with a low solubility (LS) (Exp. 1). Control diets contained cellulose as a fiber source (64 to 73 g/kg). Inclusion of either type of hulls decreased the apparent ileal digestibility for DM, organic matter (OM), and nonprotein organic matter (NPOM) (P < .05). Inclusion of LT hulls instead of cellulose only reduced the apparent ileal digestibility of crude protein (N x 6.25; CP) in Exp. 3 (P < .05). Inclusion of HT instead of LT hulls reduced the apparent ileal digestibility of CP (by 7 to 10 units) and amino acids (by 4 to 29 units) (P < .05). The LT hulls decreased apparent and true ileal digestibility of CP from 88 to 83 and from 97 to 94, respectively (P < .05). Inclusion of HT instead of LT hulls decreased apparent and true ileal CP digestibility from 83 to 74 and 94 to 90 (P < .05) and increased the excretion of endogenous CP from 22 to 32 and from 13 to 23 g/kg of DM intake at the ileal and fecal level, respectively (P < .05). It is concluded that condensed tannins in faba beans interact with both dietary and endogenous proteins in the digestive tract of pigs. This reduces the true digestibility of dietary protein and increases the excretion of endogenously secreted proteins. Tannins from faba beans show some preference to interact with proteins with a high content of proline and histidine.

Effect of dietary fish oil on blood levels of free fatty acids, ketone bodies and triacylglycerol in humans

Although the reduction of serum triacylglycerol concentrations by dietary fish oil is a well-known effect, the exact mechanism of this effect has not been previously studied in human subjects. Therefore, the aim of this study was (i) to examine the effect of short-term fish oil supplementation on blood concentrations of ketone bodies, free fatty acids and triacylglycerol in healthy humans and (ii) to verify whether the observed relationships between these variables would be consistent with reduced lipolysis and/or enhanced hepatic fatty acid oxidation after fish oil supplementation. Twenty subjects (21-23 years, normal liver function tests) were randomly divided into two groups to supplement their usual diet with either 30 g/d of fish oil (n = 11) or olive oil (n = 9). Venous blood samples were drawn after an overnight fast, before and after 1, 3 and 7 d of fish oil/olive oil supplementation. Blood concentrations of triacylglycerol and free fatty acids decreased consistently after fish oil supplementation; the reduction was already significant after one day of fish oil (P < 0.001 for triacylglycerol and P = 0.01 for free fatty acids). In contrast, neither of these blood values changed after olive oil supplementation (P > 0.10). No significant changes in glucose, insulin or ketone body levels were observed in either group after supplementation. After fish oil, but not after olive oil supplementation, the ratio of blood ketone body levels to free fatty acid levels increased significantly (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Body composition in patients with acquired immunodeficiency syndrome: a validation study of bioelectric impedance analysis

The objective of this validation study was to explore bioelectric impedance analysis (BIA) as a way to assess nutritional status and body composition. The study was done in the outpatient department of the AIDS unit at University Hospital Dijkzigt, Rotterdam, The Netherlands. Eleven clinically stable patients with AIDS were studied. Total body water, body fat, lean body mass, and body cell mass were measured and calculated with multiple dilution techniques and BIA. With linear regression analysis, a strong correlation was found between total body water and lean body mass derived from BIA and multiple dilution techniques (r2 = .96 and .98, respectively), and slightly weaker correlation was found for body cell mass and body fat (r2 = .88 and .76, respectively). These results suggest that BIA is a suitable method for the assessment of body cell mass in HIV-infected patients without opportunistic infections. The technique is safe, noninvasive, fast, and inexpensive.

Nocturnal oral glucose supplementation. The effects on protein metabolism in cirrhotic patients and in healthy controls

Nocturnal glucose administration might prevent gluconeogenesis and concomitant protein loss due to hepatic glycogen depletion. In this study the effects of nocturnal oral glucose supplements on nitrogen metabolism were investigated in 8 cirrhotic patients and in 8 healthy controls. During the night, either polymeric glucose was given or water as placebo. In the patients with cirrhosis on placebo, nitrogen balance was not different from controls: -63 +/- 8 vs. -55 +/- 4 mg N/kg b.wt./9 h (mean +/- SEM). Cirrhotic patients had increased nocturnal protein turnover rates (measured with 15N-glycine) and increased early morning levels of free fatty acids (FFA), lactate, insulin, glucagon and growth hormone. After glucose, nitrogen balance improved by 36% in the cirrhotic group, with a decrease in protein turnover rates and a decrease in plasma levels of beta-hydroxybutyrate, urea and glucagon. In the controls, glucose had no effects on nitrogen balance, on protein turnover or on the hormone levels, except for reduced FFA and ketone body levels. These data show that nocturnal calorie supplements improve nitrogen balance during the night in cirrhotic patients but not in healthy controls. Long interprandial intervals should be avoided in cirrhotic patients.

The validity of bioelectrical impedance analysis in estimating total body water in patients with cirrhosis

This study assessed the validity of bioelectrical impedance analysis (BIA) to predict total body water (TBW) in patients with cirrhosis. TBW was estimated by deuterium oxide dilution (D2O) and compared with TBW predicted by BIA in 27 patients with cirrhosis with and without ascites or edema (Group A), in a subgroup of 18 'dry' cirrhotics without clinical signs of fluid overload (Group B) and in 27 healthy controls. Three different BIA regression equations were used. In all three groups of subjects high correlation coefficients were obtained between D2O-TBW and BIA-TBW (r > 0.88). In the cirrhotic Group A, BIA significantly underpredicted D2O-TBW by all 3 equations (2.9-3.8 l) and the regression lines were different from the lines of identity by two equations. Standard errors of estimate were high in Group A (3.04-3.97 l) in comparison with Group B (1.79-2.46 l) and the controls (1.03-1.41 l). In the 'dry' cirrhotics (Group B) and in the controls, TBW was correctly predicted by two of three BIA equations, and regression lines were not significantly different from lines of identity. Correlation coefficients in Group B were higher than in Group A (r = 0.96-0.97 vs. 0.89-0.92) and were comparable with controls (r = 0.98-0.99). We conclude that BIA is not a valid method of estimating TBW in cirrhotic patients with ascites and edema. In cirrhotic patients without clinical signs of fluid overload BIA can be used to predict TBW, although accuracy is slightly lower than in healthy controls.

Oral pharmacokinetics of cyclosporin in patients with primary biliary cirrhosis and patients with skin diseases

The pharmacokinetics of cyclosporin after oral administration were studied in seven patients with non-end stage primary biliary cirrhosis (PBC) without previous cyclosporin treatment (Group I), a control group of nine patients with skin diseases (mainly psoriasis; Group II) and six patients with PBC after prolonged cyclosporin treatment (Group III). Whole blood concentrations of cyclosporin were measured using a non-specific (N) radioimmunoassay (RIA) and--in a majority of the cases--also by a RIA specific (S) for the parent drug. No difference in cyclosporin absorption was observed between patients with PBC and those with a skin disease. The mean values for the area under the blood concentration-time curve for the first 6 h after the test dose (AUC0-6) and the maximal blood concentrations (Cmax) were significantly higher for Group I compared with Group II patients (P = 0.007 and 0.03, respectively), but the time to maximal blood concentrations (tc,max) did not differ. There was a trend toward higher mean AUC0-6 (P = 0.08) and Cmax (P = 0.08) values for Group III compared with Group I patients. Tc,max values were not influenced by prolonged cyclosporin treatment. The ratio of cyclosporin whole blood concentrations measured by the non-specific and specific RIA's (N/S ratio) increased with time without obvious differences between the three groups. These data suggest that cyclosporin absorption and its biotransformation in the liver are not impaired in patients with non-end stage PBC and that neither is affected by prolonged treatment.

Whole-body and segmental bioelectrical-impedance analysis in patients with cirrhosis of the liver: changes after treatment of ascites

Bioelectrical impedance analysis (BIA) is a simple technique for determining body water and calculating body composition. It has been validated in healthy control subjects but not in patients with liver disease. We examined the ability of BIA to detect changes in total body water (TBW) due to removal of ascites. In 12 cirrhotic patients, BIA of the whole body and of body segments was performed before and after treatment of ascites with paracentesis (n = 12) and diuretics (n = 2). TBW changes predicted by BIA, by using two prediction equations, were significantly less than body weight changes (51% and 45% of the weight loss). BIA of body segments showed highly significant changes in both the trunk and the leg and small changes in the arm. These data indicate that BIA of the whole body is not a suitable technique for monitoring fluid changes in cirrhotic patients with ascites. Changes in BIA of body segments may be due to mobilization of edema after the removal of ascites.

Primary bile acid malabsorption: a pathophysiologic and clinical entity?

Primary bile acid malabsorption is defined as chronic diarrhoea with bile acid malabsorption of unknown cause and a symptomatic response to cholestyramine. Convincing evidence of the proposed pathophysiology--a defect of the active bile acid absorption in the distal ileum--has never been substantiated. We found no evidence of a bile acid transport defect across the ileal brush border membrane in 10 patients with primary bile acid malabsorption; moreover, transport was significantly higher than in a control group. In the patients with primary bile acid malabsorption the estimated bile acid pool was significantly larger than in a control group and in a group of patients with ileal disease. In addition, the oro-anal transit time of radiopaque markers was shorter in the primary bile acid malabsorption group than in both other groups. This suggests that the bile acid pool size as well as intestinal motility could play a role in the pathophysiology of primary bile acid malabsorption.

Effects of ultraviolet B light on cutaneous immune responses of humans with deeply pigmented skin

The incidence of skin cancers of the basal and squamous cell types is extremely low among genetically black-skinned human beings, whereas these types of skin cancers are common among Caucasians, especially those who live in geographic areas of high sun exposure. Ultraviolet B light (UVB) is thought to be the primary oncogenic agent in sunlight. We have recently demonstrated that acute, low-dose exposure of Caucasian skin to UVB impairs the induction of contact hypersensitivity to dinitrochlorobenzene (DNCB) in approximately 40% of normal individuals. Importantly, this trait--termed UVB susceptibility--was found to be a characteristic of virtually 100% of patients with a history of biopsy-proved skin cancer, implying that UVB susceptibility may be a risk factor for this disease. Because melanin pigment is thought to be protective of some of the deleterious effects of UVB radiation, we have examined the capacity of a low-dose regimen of UVB to alter induction of contact hypersensitivity in individuals with genetically melanized or heavily tanned skin. Our results indicate that UVB radiation depletes heavily pigmented skin of Langerhans cells, just as it does in Caucasian skin. Moreover, UVB-susceptibility exists as a polymorphic trait in individuals with genetically determined black skin, as well as in individuals with heavily tanned skin, and the incidence of this trait is similar to that found among normal Caucasian subjects. Thus, melanin does not appear to protect against the deleterious effects of an acute, low-dose regimen of UVB on induction of cutaneous immunity, and the UVB susceptibility trait is equally well-represented in both black- and Caucasian-skinned individuals. We conclude that although UVB susceptibility may function as a risk factor for skin cancer in Caucasians, it does not function similarly in black-skinned human beings, probably because melanin effectively protects against the mutagenic properties of UVB radiation.

Cyclosporin A blood levels during use of cyclosporin as oral solution or in capsules: comparison of pharmacokinetic parameters

Recently cyclosporin A (CsA) capsules have been introduced to meet a number of disadvantages associated with the use of the oral solution. We compared the pharmacokinetics of the oral solution and the capsules in a group of nine renal transplant patients during the first 3 weeks after transplantation. After a morning dose of CsA, whole blood concentrations were measured at regular intervals for 12 h. Subsequently, a cross-over was made to the alternative form of administration, and 3 or 4 days later a second pharmacokinetic profile was obtained. Comparison of the trough level, the maximum concentration, the time to reach the maximal concentration and the area under the blood concentration curve, showed no significant differences. Our findings thus suggest a similar bioavailability of CsA administered as oral solution or in capsules in the early post-transplant period.

The selenium-75-homocholic acid taurine test reevaluated: combined measurement of fecal selenium-75 activity and 3 alpha-hydroxy bile acids in 211 patients

The recommended reference values for the selenium-75-homocholic acid taurine (75SeHCAT) test, used in the analysis of chronic diarrhea, were evaluated in 211 patients by comparing simultaneous measurements of 3 alpha-hydroxy bile acids and 75Se activity in daily collected stools. An initial evaluation in 11 patients showed that the fecal collection method, which allows inspection and additional analysis of stools, was equivalent to the abdominal retention method. Selenium-75-HCAT whole-body retention half-life (WBR50) was greater than 2.8 days in less than 10% of the patients with bile acid malabsorption and less than 1.7 days in less than 10% of the normals. We recommend that a 75SeHCAT WBR50 less than 1.7 days is abnormal, a WBR50 greater than 2.8 days is normal, and a WBR50 in the range 1.7-2.8 days is equivocal, which was the case in 48% (94/195) of the patients in this study.

Primary bile acid diarrhoea without an ileal carrier defect: quantification of active bile acid transport across the ileal brush border membrane

Unexplained bile acid malabsorption associated with diarrhoea that responds to cholestyramine was first described in 1973 but convincing evidence of the proposed mechanism--a defective active ileal bile acid transport--has never been substantiated. Active bile acid transport was quantified in vitro using brush border membrane vesicles prepared from terminal ileal biopsy specimens from 10 patients who fulfilled the criteria of idiopathic bile acid diarrhoea. They were recruited from 181 patients with bile acid malabsorption of various causes. Transport was quantified as in vitro Na+ dependent bile acid transport (INBAT), expressed as pmol taurocholate/mg brush border membrane protein/15 seconds, and in vitro Na+ dependent bile acid local transport capacity (INBALTC), expressed as pmol taurocholate/g ileal biopsy tissue/15 seconds. The lowest INBAT and INBALTC values in the 10 patients with idiopathic bile acid diarrhoea were well above the 10th centile values of a control group of 132 patients. Both INBAT (mean (range) 88 (30-136)) and INBALTC (158 (85-268)) values were significantly higher in the 10 patients than in the control group (INBAT: mean (range) 63 (1-244), INBALTC: mean (range) 98 (1-408)). Quantification of active ileal bile acid transport in these 10 patients with idiopathic bile acid malabsorption suggests that a genetic (carrier) defect is rare in adults.

Porphyrin synthesis by human hepatocytes and HepG2 cells--effects of enzyme inducers and delta-aminolevulinic acid

Experiments were carried out to investigate the possibility of inducing porphyria in human hepatocytes and HepG2 cells in culture. After treatment with hexachlorobenzene, 3-methylcholanthrene, phenobarbital or dimethyl sulfoxide, protoporphyrin was the predominating porphyrin accumulating in presence of delta-aminolevulinic acid. The typical uroporphyrin accumulation, as is seen in hexachlorobenzene-induced porphyria in vivo, was absent. In HepG2 cells, the activities of uroporphyrinogen decarboxylase and porphobilinogen deaminase were not influenced by cytochrome P-450 inducers, hexachlorobenzene or dimethyl sulfoxide during 48 h of culture. Therefore, the use of these cells in the study of porphyria cutanea tarda does not seem promising.

Photodynamic therapy for gastrointestinal tumors

Photodynamic therapy is based on the administration of a compound that is preferentially accumulated by a tumor and which causes tumor destruction after exposure to light of a specific wavelength. The photosensitizers most commonly used in treating tumors of the gastrointestinal tract are porphyrins--hematoporphyrin derivative and dihematoporphyrin ether. These compounds have been used with success to produce reduction in tumor size of esophageal, gastric, and colorectal cancers. In some instances long-lasting complete remission have been observed after photodynamic therapy. New developments include photosensitizers that react to light of a longer wavelength, which is able to penetrate tissue to a greater depth, the use of 5-aminolevulinic acid, which is preferentially converted to porphyrin in malignant cells, and combination of photodynamic therapy with thermic laser, radiotherapy, or chemotherapy.

Na+-dependent bile acid transport in the ileum: the balance between diarrhea and constipation

Ileal Na+-dependent bile acid transport was quantified in vitro as the uptake of 3H-taurocholate into brush-border membrane vesicles. Vesicles were prepared from ileal biopsies of 158 patients placed in 10 diagnostic categories. Active bile acid transport (expressed as picomoles taurocholate uptake per milligram brush-border membrane protein per 15 s, median and interquartile ranges indicated) did not differ significantly in 6 categories: irritable bowel syndrome (71, 35-97; n = 21), colon polyps (42, 30-89; n = 29), colitis (62, 33-91; n = 31), postvagotomy or postcholecystectomy (69, 37-97; n = 11), diarrhea without increased bile acid loss (58, 48-85; n = 12), and lack of gastrointestinal pathology (74, 45-103; n = 22). A decreased active bile acid transport was found in 3 categories: ileal disease (4, 1-36; n = 11), partial ileal resection (5, 1-35; n = 5), and constipation (41, 22-50; n = 8). Bile acid transport was increased in patients with bile acid-losing diarrhea with endoscopically and histologically normal ilea (111, 94-135; n = 8). These findings indicate that a low fecal bile acid loss, presumed to be present in constipated patients, is associated with a low Na+-dependent ileal bile acid transport and a high bile acid loss is associated with a high active bile acid transport. Ileal bile acid transport might be regulated by the availability of bile acids to the ileal enterocytes.

[75Se]-selenohomotaurocholic acid degradation by bacterial enzymes in vitro and in vivo. Is it still a specific indicator for active ileal bile acid uptake?

The stability of the bile acid analogue [75Se]-selenohomotaurocholic acid (75SeH-CAT) was studied in man. When 75SeHCAT was administered to patients for diagnostic purposes the majority of labeled material present in the feces was found deconjugated. In vitro incubation of 75SeHCAT, by addition of fecal homogenate or with addition of purified enzyme, showed identical deconjugation. The relative differences in polarities of 75SeHCAT, [75Se]-selenohomocholic acid (75SeHCA), [14C]-taurocholic acid (14C-TCA) and [14C]-cholic acid (14C-CA) were estimated by isoelectric focusing and selective chloroform extractions at various pH values. The pI values representing the pH where these molecules become uncharged were for 75SeHCA and 75SeHCAT 3.1, for 14C-TCA 3.0 and for 14C-CA 3.9. These results suggest that from these bile acids only 14C-CA is a candidate for passive absorption in the colon, while 75SeHCA would be far too polar for passive diffusion. Indeed, we could demonstrate the inability of 75SeHCA for passive absorption in healthy persons. In conclusion, 75SeHCAT, specifically selected to monitor active ileal bile acid transport, functions as a good indicator of this process in its conjugated form. In contrast to published data it is susceptible to bacterial degradation, and therefore gives rise to a diminished whole-body retention.

Effect of a late evening meal on nitrogen balance in patients with cirrhosis of the liver

OBJECTIVE

To assess whether a late evening meal would improve nitrogen balance in patients with cirrhosis of the liver.

DESIGN

Randomised crossover study of meal schedules comparing three meals a day with four or six meals a day, the four and six meal schedules both including a late evening meal (2300).

SETTING

Metabolic ward.

PATIENTS

Seven men and two women aged 34-66 with cirrhosis of the liver (Child's grade B).

INTERVENTIONS

Patients spent two seven day periods in the ward. For five days of each period they received, in random order, isonitrogenous isocaloric diets supplied in three meals a day and in four or six meals a day.

MAIN OUTCOME MEASURE

Nitrogen balance, calculated as the difference between dietary intake and the total of urinary, faecal, and integumental nitrogen loss.

RESULTS

Faecal nitrogen loss was no different between three meals a day and four or six meals a day. On both four and six meals a day, however, patients had nitrogen balances that were more positive (or less negative) than on three meals a day (1.26 (SD 2.1) g/24 h v 0.26 (2.2) g/24 h, p less than 0.01). Six meals a day did not produce significantly better improvements in nitrogen balance than four meals a day.

CONCLUSIONS

A late evening meal seemed to improve the efficiency of nitrogen metabolism, but longer term studies are needed to assess whether this leads to a better nutritional state.

Effects of the glucosidase inhibitor acarbose in patients with liver cirrhosis

In this preliminary study, we examined the effects of acarbose and placebo together with a standardized breakfast on blood glucose levels, on breath hydrogen excretion and on plasma insulin and glucagon levels; in addition, the effects on fasting blood levels of metabolites were studied following an evening meal with acarbose or placebo. Acarbose significantly reduced blood glucose levels in 10 patients with alcoholic cirrhosis following a meal containing 100 g of carbohydrate. There were no significant changes in plasma insulin after breakfast but glucagon levels were increased at 1 h after the meal. Breath hydrogen excretion did not change significantly. Acarbose given with a late evening snack reduced fasting beta-hydroxybutyrate levels the next morning in these cirrhotic patients.