T. Rietveld

Incorporation and washout of orally administered n-3 fatty acid ethyl esters in different plasma lipid fractions

The aim of the present study was to quantify the incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into plasma lipids after oral administration of n-3 fatty acid ethyl esters, since little is known about the rate and pattern of incorporation into plasma lipid fractions. In addition, we aimed to obtain preliminary information regarding EPA half-life, which is needed to establish an optimal dosing schedule. Five healthy volunteers ingested two 8.5 g doses of n-3 fatty acid ethyl esters daily for 7 d, supplying 6.0 g EPA/d and 5.3 g DHA/d. The fatty acid compositions of plasma phospholipids (PL), cholesteryl esters (CE) and triacylglycerols (TAG) were determined during supplementation and during a washout period of 7 d. Half-lives of EPA and DHA were calculated. The proportion of EPA in PL showed a 15-fold increase after 7 d (P < 0.001), while DHA showed a smaller increase (P < 0.01). In CE, EPA also increased (P < 0.05), while DHA did not increase at all. Remarkably, incorporation of DHA into TAG was even higher than that of EPA. Half-life of EPA in PL ranged from 1.63 to 2.31 d (mean 1.97 (SE 0.15) d), whereas mean half-life of EPA in CE was 3.27 (SE 0.56) d. In three subjects, washout of EPA and DHA from TAG seemed to follow a bi-exponential pattern, with a short half-life (< 1 d) in the initial phase and a half-life of several days in the second phase. In conclusion, EPA ethyl esters are rapidly incorporated into plasma lipids, especially into PL. The relatively long half-life of EPA in plasma would permit a dosing schedule with intervals of > or = 12 h in supplementation studies.

Minimum protein requirements in liver cirrhosis determined by nitrogen balance measurements at three levels of protein intake.

Nitrogen balance at three levels of protein intake was measured in eight patients with cirrhosis of the liver; moreover, at each level of protein intake, the effects on nitrogen balance of branched-chain amino-acid enriched protein and natural protein were compared. From these nitrogen balance data, minimum protein requirements were calculated by linear regression analysis. The patients were in a negative nitrogen balance on a 40 g protein diet (-0.75 +/- 0.15 gN.), and in positive nitrogen balance on 60 g (+1.23 +/- 0.22 gN.) or 80 g of protein per day (+2.77 +/- 0.20 g N.). Their mean minimum protein requirement (48 +/- 5 g of protein/day or 0.75 g/kg/day) is higher than expected in healthy people; the safe level of protein intake (mean + 2 sd) is 58 g per day or 1.2 g/kg/day. Nitrogen balances and protein requirements were not different on branched-chain amino-acid enriched diets. The physical condition of the patients improved when they came into positive nitrogen balance; the higher rates of protein intake were well tolerated without onset of encephalopathy. We conclude that protein requirements are elevated in cirrhosis of the liver; diets supplying less than 60 g of protein per day should not be prescribed in long term treatment of cirrhotic patients.

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.

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.

Development of hexachlorobenzene porphyria in rats: Time sequence and relationship with lipid peroxidation

The relationship between the development of porphyria and free-radical formation induced by hexachlorobenzene was studied in iron-overloaded rats. The first sign of porphyria, an increase in porphyrins in the liver, was detected at day 22. Liver malondialdehyde was also increased at day 22. During the following weeks, liver porphyrins and malondialdehyde increased simultaneously, accompanied by a decrease in uroporphyrinogen decarboxylase activity and glucose-6-phosphate activity in liver, and a high excretion of porphyrins in the urine. In the rats given hexachlorobenzene, changes were detected in the pattern of lipids in the liver microsomes. In comparison with the controls, there were decreases in C20:4 and C22:5 fatty acids, whereas the fatty acid C20:3w6 was increased. In this study of hexachlorobenzene-induced liver damage there was no difference in the time course of the development of porphyria and that of lipid peroxidation.

Influence of the 13C-enrichment of the habitual diet on a 13CO2 breath test used as an index of liver glycogen oxidation: A validation study in Western Europe and Africa

A diet containing naturally 13C-enriched carbohydrate combined with a 13CO2 breath-test analysis can be used to monitor liver glycogen oxidation in persons used to a diet low in 13C, e.g., the Western European diet. In this study, we evaluated this test principle further by changing the way we label the glycogen pool. The 13C enrichment of exhaled CO2 was studied in two groups, one in Europe and one in Africa. The European group (n = 12) was accustomed to a diet low in 13C, and they went on a 13C-enriched study diet to identify liver glycogen. The African group (n = 6) was accustomed to a diet naturally high in 13C, and they went on a diet low in 13C. The basal 13C abundance in exhaled CO2 was higher in the African group (1.0879 At%; atmospheric 1.1 atom percent) than in the European group (1.0821 At%). During the study period, the parameters for liver glycogen oxidation--the 13CO2 enrichment plateau, the plateau duration, and the return to baseline time--did not differ between groups. The abundance of 13CO2 in exhaled CO2 over time in the two groups was similar but inverse. This study confirms the use of a 13CO2 breath test to monitor liver glycogen oxidation and demonstrates how to use such a test in persons accustomed to a diet high in 13C.

Bioactive rather than total IGF-I is involved in acute responses to nutritional interventions in CAPD patients

BACKGROUND Inadequate food intake plays an important role in the development of malnutrition in continuous ambulatory peritoneal dialysis (CAPD) patients. Aim of the study. The aim of the study was to investigate in CAPD patients whether circulating insulin-like growth factor-I (IGF-I) bioactivity may offer a more sensitive index to acute nutritional interventions than total IGF-I. METHODS An open-label, randomized, crossover study of 2 days-with a 1-week interval-was performed in 12 CAPD patients in the fed state to compare a mixture of amino acids (Nutrineal 1.1%) plus glucose (AA plus G) (Physioneal 1.36% to 3.86%) dialysate versus G only as control dialysate. Fed-state conditions were created by identical liquid hourly meals. IGF-I bioactivity was measured by the kinase receptor activation assay (IGF-I KIRA); total IGF-I was measured by immunoassay. RESULTS In the fed state, both after AA plus G as well as after G dialysis IGF-I bioactivity increased compared to baseline, while no changes in circulating total IGF-I levels were observed in both treatment arms. However, the increase in IGF-I bioactivity was only significant after AA plus G dialysis (P = 0.02). CONCLUSIONS Our results provide evidence that in CAPD patients changes in circulating IGF-I bioactivity are associated with nutrient intake and that IGF-I bioactivity rather than total IGF-I is involved in acute responses to nutritional interventions in CAPD patients.

The 13CO2 breath test for liver glycogen oxidation after 3-day labeling of the liver with a naturally 13C-enriched diet

OBJECTIVE When naturally (13)C-enriched carbohydrate is used to label hepatic glycogen, (13)C-liver glycogen oxidation can be monitored subsequently by measuring the (13)C enrichment of breath CO(2) during a sedentary fast. In our previous breath test studies, we used a 1-d labeling protocol to enrich liver glycogen. Others found that after 3 d of labeling the liver glycogen (13)C enrichment is identical to the dietary carbohydrate (13)C enrichment. METHODS We compared a diet protocol in which naturally (13)C-enriched carbohydrate was given for 3 d before the breath test with our previously applied 1-d labeling design. The (13)CO(2) breath test was combined with indirect calorimetry. The results were compared with those from our previous studies. In addition, we compared liver glycogen oxidation rates with those from our present technique and different techniques as used in other published studies. RESULTS Six healthy volunteers were included in this study. The (13)C enrichment of breath CO(2) at plateau excretion level did not differ after 1 or 3 d on a labeling diet. However, the end of plateau time tended to be later after the 3-d diet, 14.3 h versus 12.5 to 13.5 h postprandially in the 1-d labeling studies. Also, the return to baseline time was later in the 3-d study, at 25.8 h versus 19.0 to 23.2 h postprandially after 1 d of labeling. The liver glycogen oxidation rate was similar in both techniques until 17 h postprandially. After this time the 3-d labeling protocol showed a higher level of liver glycogen oxidation. CONCLUSION The results indicated that the labeling of liver glycogen is slightly less complete after 1 d on a (13)C-enriched diet as compared with 3-d labeling. Our (13)C breath test results compared rather well with studies from the literature using the (13)C-NMR technique, the D(2)O technique, or the (13)CO(2) breath method to measure liver glycogen oxidation.

Beneficial Effects of Adenosine Triphosphate on Nutritional Status in Advanced Lung Cancer Patients: A Randomized Clinical Trial

Background: In a randomized clinical trial in patients with advanced non–small-cell lung cancer (NSCLC), infusion with adenosine 5′-triphosphate (ATP) inhibited loss of body weight and quality of life. In the present article, the effects of ATP on body composition, energy intake, and energy expendi- ture as secondary outcome measures in the same patients are reported. Methods: Patients with NSCLC, stage IIIB or IV, were randomized to receive either 10 IV, 30-hour ATP infusions every 2 to 4 weeks, or no ATP. Fat mass (FM), fat-free mass (FFM), and arm muscle area were assessed at 4-week intervals for 28 weeks. Food intake, body cell mass (BCM), and resting energy expendi- ture (REE) were assessed at 8-week intervals for 16 weeks. Between-group differences were tested for statistical significance by repeated-measures analysis of covariance. Results: Fifty-eight patients were randomized (28 ATP, 30 control). No change in body composition over the 28-week follow-up period was found in the ATP group, whereas p...

Transcription factor 7-like 2 gene links increased in vivo insulin synthesis to type 2 diabetes

Transcription factor 7-like 2 (TCF7L2) is the main susceptibility gene for type 2 diabetes, primarily through impairing the insulin secretion by pancreatic β cells. However, the exact in vivo mechanisms remain poorly understood. We performed a family study and determined if the T risk allele of the rs7903146 in the TCF7L2 gene increases the risk of type 2 diabetes based on real-time stable isotope measurements of insulin synthesis during an Oral Glucose Tolerance Test. In addition, we performed oral minimal model (OMM) analyses to assess insulin sensitivity and β cell function indices. Compared to unaffected relatives, individuals with type 2 diabetes had lower OMM indices and a higher level of insulin synthesis. We found a T allele-dosage effect on insulin synthesis and on glucose tolerance status, therefore insulin synthesis was higher among T-allele carriers with type 2 diabetes than in wild-type individuals. These results suggest that hyperinsulinemia is not only an adaptation to insulin resistance, but also a direct cause of type 2 diabetes.