The effect of glutamine-supplemented total parenteral nutrition on nitrogen economy depends on severity of diseases in surgical patients.

BACKGROUND: Gln is an important substrate for enterocyte and rapid proliferation cells. Studies have shown that parenteral supplementation of Gln maintains the intracellular Gln pool, improves nitrogen balance and shortens hospital stay. However, some studies showed Gln-supplemented TPN had no effect on restoring the Gln pool in critically ill patients. OBJECTIVE: To evaluate the effect of glutamine (Gln) dipeptide supplementation of total parenteral nutrition (TPN) on postoperative nitrogen balance and immune response of patients undergoing surgery. METHODS: This study is a prospective, randomized double-blind clinical trial. APACHE II score and TISS were used to evaluate the patients after admission. Forty-eight patients with major abdominal surgery were allocated to two groups to receive isonitrogenous (0.228 g nitrogen/kg/day) and isoenergetic (30 kcal/kg/day) TPN for 6 days. Two groups (Conv and Ala-Gln) were further divided to high (APACHE>or=6) and low (APACHE <6) groups. Control group (Conv) received 1.5 g amino acids/kg/day, whereas the Ala-Gln group received 0.972 g amino acids/kg/day and 0.417 g of L-alanyl-L-glutamine (Ala-Gln)/kg/day. Blood samples were collected on day 1 and day 6 after surgery for plasma amino acid and CD4, CD8 cell and T lymphocyte analysis. Cumulative nitrogen balance were also measured on day 2, 3, 4, 5 postoperatively. RESULTS: Although there was a tendency to have better cumulative nitrogen balance on the postoperative days in the Ala-Gln group, no significant difference was observed between two groups. However, a better significant cumulative nitrogen balance was observed on the 2nd, 3rd and 5th postoperative day in the Ala-Gln group than in the Conv group in patients with APACHE II <6, whereas no significant difference was noted in patients with APACHE II >or= 6. No difference in urine 3-methylhistidine excretion were observed between the 2 groups. Patients in the Ala-Gln group had significant higher T lymphocyte and CD4 cells than did those in the Conv group. CONCLUSION: TPN supplemented with Gln dipeptide had beneficial effect on enhancing the immune response. However, the effect of Ala-Gln administration on improving nitrogen economy was only observed in patients with low APACHE II scores. These results may indicate that Gln required for reversing the catabolic condition may depend on the characteristics and severity of the diseases.

Induction of oxidative DNA damage in human foreskin fibroblast Hs68 cells by oxidized beta-Carotene and lycopene.

Two recent clinical trials suggest that beta-carotene may be harmful to smokers. In this study we examined the hypothesis that beta-carotene may become toxic when degradation occurs. beta-Carotene (BC) and lycopene (LP) with or without prior heat treatment (60 degrees C for 1 h in open air) were incubated at 20 and 40 microM with calf thymus DNA or human fibroblasts Hs68 cells. The heat treatment resulted in ca. 80% and 35% bleaching of BC and LP, respectively. When Hs68 cells were incubated with the oxidized beta-carotene (OBC) or oxidized lycopene (OLP) at 37 degrees C for 20 h, cell viability was significantly and dose-dependently decreased whereas cell viability was not affected by BC or LP. Cell death, which was already evident at 4 h after incubation with OBC or OLP, was possibly attributable to apoptosis, as shown by the increased histone-associated DNA fragmentation. However, cell lysis, measured as release of lactate dehydrogenase, also occurred at 4 h after incubation with OBC and OLP, although the extent was relatively small and was greater for OLP than for OBC. When calf thymus DNA was incubated with OBC or OLP at 37 degrees C for 20 h, the 8-hydroxy-2-deoxyguanosine (8-OH-dG) level was significantly and dose-dependently increased by OLP whereas the increase by OBC was only significant at 40 microM. When Hs68 cells were incubated with OBC and OLP for 20 h, both compounds increased the 8-OH-dG level, but the effect was only significant for 40 microM OLP. Comet (single-cell gel electrophoresis) assay of DNA damage in Hs68 cells was determined at 2 h after incubation with OBC or OLP because of its high sensitivity. Both OBC and OLP significantly and dose-dependently increased DNA breakage while BC and LP had no effect. Inclusion of BHT during incubation of cells with 40 microM OBC or OLP partially inhibited (ca. 40%, p < .05) the extent of comet formation. Intriguingly, OBC and OLP neither induce lipid peroxidation in Hs68 cells (measured as thiobarbituric acid-reactive substances released into the medium) nor increased the intracellular level of reactive oxygen species. Although it is presently unclear about what degradation products are formed, this study has demonstrated that, when oxidized, BC and LP lead to oxidative damage to both purified DNA and cellular DNA. The results suggest that such damage may contribute to the adverse effects of beta-carotene reported in recent clinical studies and caution that it is important to prevent oxidation of BC and LP for human uses such as in supplemental studies.

Effects of glutamine-supplemented total parenteral nutrition on cytokine production and T cell population in septic rats.

BACKGROUND: This study was designed to investigate the effects of total parenteral nutrition (TPN) enriched with glutamine (GLN) on in vivo cytokine production and cellular immune response in early and late septic stages of rats. METHODS: Male Wistar rats were divided into 2 experimental groups and received TPN solution at an energy level of 270 kcal/kg body weight. The TPN solutions were isonitrogenous and identical in nutrients composition except for differences in amino acid content. One group received 2% GLN, whereas the other group received glycine (Gly) instead. TPN was maintained for 5 or 6 days according to the sacrifice schedule of the rats. On day 5, sepsis was induced by cecal ligation and puncture (CLP). Respective groups of rats were sacrificed 2, 4, 6, and 24 hours after CLP. RESULTS: Sepsis resulted in a negative nitrogen balance in both groups, and nitrogen loss was significantly lower in the GLN than the Gly group. Interleukin (IL)-2 and interferon (IFN)-gamma in most of the samples collected at various time points were not detectable in plasma or peritoneal lavage fluid. No differences in plasma IL-6 and TNF-alpha concentrations were observed between the GLN and Gly groups. Also, there were no significant differences in IL-1beta, IL-6, and TNF-alpha concentrations in peritoneal lavage fluid between the 2 groups at various time points. The CD4+/CD8+ ratio was significantly higher in the GLN group than in the Gly group only at 4 hours after CLP, and no difference was observed at 24 hours after CLP. CONCLUSIONS: TPN preinfused with a GLN-supplemented solution had a beneficial effect in ameliorating the extent of negative nitrogen balance in septic rats. However, parenterally administered GLN did not reduce the production of inflammatory mediators systemically or at the site of injury, and the influence on enhancing cellular immunity was not obvious.

Soy isoflavone supplementation in postmenopausal women. Effects on plasma lipids, antioxidant enzyme activities and bone density.

OBJECTIVE: To investigate isoflavone supplementation on plasma lipids, erythrocyte antioxidant enzyme activities and bone mineral density in postmenopausal women. STUDY DESIGN: Thirty-seven postmenopausal women were given 150 mg/d of isoflavone supplements twice daily for six months. Blood was sampled before and after supplementation, at three and six months. RESULTS: There were no significant differences in plasma total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride concentrations or erythrocyte antioxidant enzyme activities after three and six months of supplementation when compared with the baseline. No significant changes were noted in calcaneus bone mineral density after supplementing isoflavones for six months. CONCLUSION: The antioxidant effect of isoflavones in normal postmenopausal women is not obvious, and supplementation with isoflavone alone may not have a hypocholesterolemic effect. Since the duration of this study was too short with respect to bone density, longer studies are needed to clarify the bone-sparing effect of isoflavone supplementation.

Effects of dietary fish oil on survival rate, plasma amino acid pattern, and inflammatory-related mediators in diabetic rats with sepsis.

This study was designed to investigate the effects of dietary fish oil on survival rates, plasma amino acid profiles, and inflammatory-related mediators in diabetic rats with sepsis. Diabetes mellitus (DM) was induced in rats by streptozotocin. The DM rats were maintained for 4 weeks on medium fat (10%, w/w) diets containing either fish oil or safflower oil. After that, sepsis was induced by cecal ligation and puncture (CLP). There were 2 groups in this study: fish oil sepsis group (FOS) and safflower oil sepsis group (SOS). The survival rate was observed after CLP. Also, changes of the amino acid pattern as well as interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, prostaglandin (PG) E(2)at 6, 12, and 24 h after CLP were investigated. The results demonstrated that survival rates were not significantly different between the 2 groups. Plasma arginine levels were significantly lower in sepsis groups than that in the DM-chow group, regardless of whether the diabetic rats were fed fish oil or safflower oil. No significant differences were observed in plasma valine, leucine, isoleucine, glutamine, or arginine concentrations between the FOS and SOS groups at different time points. Concentrations of IL-1 beta in peritoneal lavage fluid (PLF) at 6 h and TNF-alpha at 6 h as well as at 12 h after CLP in the FOS group were significantly higher than those in the SOS group. PGE(2)levels in PLF, by contrast, were lower in the FOS group at 6 and 12 h after CLP than in the SOS group. These results suggest that differences in IL-1 beta, TNF-alpha, and PGE(2)levels in PLF in the early period of sepsis did not influence the survival rates and plasma amino acid profiles of the FOS and SOS groups. Compared with safflower oil, feeding diabetic rats with fish oil had no beneficial effects on survival rates and muscle protein breakdown. The immunologic impact of dietary n-3 polyunsaturated fatty acids on diabetic rats with sepsis requires further investigation.

Effects of parenteral infusion with fish-oil or safflower-oil emulsion on hepatic lipids, plasma amino acids, and inflammatory mediators in septic rats.

This study was designed to investigate the effects of preinfusion with total parenteral nutrition (TPN) using fish-oil (FO) versus safflower-oil (SO) emulsion as fat sources on hepatic lipids, plasma amino-acid profiles, and inflammatory-related mediators in septic rats. Normal rats, with internal jugular catheters, were assigned to two different groups and received TPN. TPN provided 300 kcal. kg(-1). d(-1), with 40% of the non-protein energy as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fat emulsion, which was made of SO or FO. After receiving TPN for 6 d, each group of rats was further divided into control and sepsis subgroups. Sepsis was induced by cecal ligation and puncture; control rats received sham operation. All rats were classified into four groups as follows: FO control group (FOC; n = 7), FO sepsis group (FOS; n = 8), SO control group (SOC; n = 8), and SO sepsis group (SOS; n = 9). The results of the study demonstrated that plasma concentrations of triacylglycerol and non-esterified fatty acids did not differ between the FO and SO groups, regardless of whether the animals were septic. SOS had significantly higher total lipids and cholesterol content in the liver than did the SOC group. The FOS group, however, showed no difference from the FOC group. Plasma leucine and isoleucine levels were significantly lower in the SOS group than in the SOC group, whereas no difference in these two amino acids was observed between the FOC and FOS groups. Plasma arginine levels were significantly lower in both septic groups than in the groups without sepsis when either FO or SO was infused. Plasma glutamine levels, however, did not differ across groups. No differences in interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, or leukotriene B(4) concentrations in peritoneal lavage fluid were observed between the two septic groups. These results suggest that catabolic reaction in septic rats preinfused with FO is not as obvious as those preinfused with SO. Compared with SO emulsion, TPN with FO emulsion prevents liver fat accumulation associated with sepsis. However, parenterally administered FO had no beneficial effect in lowering cytokines and LTB(4) levels in peritoneal lavage fluid in septic rats induced by cecal ligation and puncture.

Effects of soybean oil and fish oil emulsions on glucose and lipid metabolism in streptozotocin-induced diabetic rats receiving total parenteral nutrition.

BACKGROUND: This study was designed to investigate the effects of fat emulsions with different fatty acid composition on plasma glucose and lipid metabolism in diabetic rats receiving total parenteral nutrition (TPN). METHODS: Diabetes was induced in rats with streptozotocin (STZ), and the rats were fed rat chow ad libitum for 6 weeks to achieve a chronic diabetic state. Control and diabetic rats were each divided into two TPN groups. The basal solutions of the two TPN groups were isonitrogenous and identical in nutrients composition except for the fat emulsion, which was made of soybean oil (SO) or fish oil (FO). The TPN control rats (C-SO and C-FO) and diabetic rats (DM-SO and DM-FO) received solutions with 37.5% of the non-protein energy provided as fat at an energy level of 30 kcal/100 g body wt/d. RESULTS: The results demonstrated that hyperglycemia and hypertriglyceridemia were induced by STZ in diabetic rats. There was no change in plasma glucose and insulin concentrations before and after TPN infusion in the TPN control groups, whereas plasma glucose as well as triglyceride (TG) and nonesterified fatty acid (NEFA) levels decreased significantly after TPN administration in the diabetic groups. No difference in the concentrations of plasma glucose, TGs, NEFAs, and insulin were observed between the two diabetic groups. CONCLUSIONS: These results suggest that compared with soybean oil, TPN with fish oil emulsion did not lead to lower plasma concentrations of TGs and NEFAs in STZ-induced diabetic rats. Also, no difference in plasma glucose and insulin levels between the two groups was observed.

Effects of n-3 and n-6 fatty acids on plasma eicosanoids and liver antioxidant enzymes in rats receiving total parenteral nutrition.

The effect of total parenteral nutrition (TPN) enriched with n-3 or n-6 fatty acids on the concentration of plasma eicosanoids was evaluated in rats. Rats were divided into three groups: the control group (n = 6) was fed a chow diet and infused with saline only. Two experimental groups (n = 11, 13) received TPN solutions at an energy level of 30 kcal/100g body weight with 40% energy provided as fat. The experimental groups were maintained on TPN for a period of 7 d. The basal TPN solutions were isonitrogenous and identical in nutrient composition except for differences in lipid source. One experimental group received a safflower oil emulsion, whereas the other group received a fish oil emulsion. At the end of the experimental period, plasma 6-keto prostaglandin F1 alpha, thromboxane B2, bleeding time, lipid peroxidation products, and antioxidant enzymes of liver were analyzed. The results demonstrated that the fish oil group had lower 6-keto prostaglandin F1 alpha concentration than the safflower oil group. Also, plasma thromboxane B2 was the lowest in the fish oil group among the three groups. There was no difference in bleeding time among the groups. With regard to liver lipid peroxidation products, malondialdehyde concentration was not higher in the fish oil group, whereas superoxide dismutase and glutathione peroxidase activities were lower in the fish oil group compared with the control and safflower oil groups. The results suggest that TPN prepared with fish oil fat emulsion causes less accumulation of lipid peroxidation products in the liver of rats, and may be beneficial in preventing platelet aggregation.

Effects of L-glutamine on induced hepatosteatosis in rats receiving total parenteral nutrition.

Glutamine (Gln) supplementation in total parenteral nutrition (TPN) has been shown to have a preventive effect on high glucose induced hepatic steatosis. This animal study was undertaken to evaluate whether Gln could prevent hepatic steatosis induced by high fat or high glucose infusion. After placement of internal jugular catheters, rats were divided into three groups: control (n = 8), high fat (n = 13) and high glucose (n = 14) groups. The control group was fed with a chow diet and infused with saline alone. The experimental groups were infused with either a high fat (65% of nonprotein calories) or high glucose (83% of total kilocalories) solution. Energy intake was 35 kcal/100 g body weight per day. TPN solutions were isocaloric, isonitrogenous and isovolemic. Each experimental group was divided into two subgroups, with one receiving a Gln supplement to replace 40% of total amino acid nitrogen. The results demonstrated obvious fatty infiltration in the experimental groups, mainly from triglyceride (TG) accumulation. Plasma very low density lipoprotein-triglyceride (VLDL-TG) was significantly lower in the experimental groups than in the control group, suggesting that liver secretion of TG may have been inhibited in the experimental groups. Liver fatty acid synthetase (FAS) activity and plasma free fatty acid were lower in the high fat group than in the control and high glucose groups. There was no difference in hepatic lipids content, FAS activity, VLDL-TG, hepatic uptake of fatty acids and liver histologic change in the subgroups with and without Gln supplementation. Thus, Gln supplementation in a TPN solution has no effect in preventing hepatic steatosis induced by either high glucose or high fat infusion in rats under these experimental conditions.

Effect of L-glutamine on hepatic lipids at different energy levels in rats receiving total parenteral nutrition.

The effect of glutamine on hepatic steatosis and serum amino acid pattern was studied in rats receiving total parenteral nutrition (TPN) with different levels of caloric intake. Rats were divided into four groups; a control group (n = 10) was fed a chow diet and infused with saline only. Three experimental groups (n = 8 to 10) received TPN solutions at energy levels of 25 kcal, 30 kcal, and 35 kcal/100 g body weight, respectively. The experimental groups were maintained with TPN for a period of 6 days. Each experimental group was divided into two subgroups, one of which was supplemented with glutamine, replacing 40% of the total amino acid nitrogen. All of the basal TPN solutions were isonitrogenous and identical in nutrient composition, except for the difference in energy level, which was adjusted with glucose. The results demonstrated that liver fat increased in accordance with the increase of glucose supply, and this increase was mainly due to triglyceride accumulation. Very-low-density lipoprotein-triglyceride and serum free fatty acid were significantly higher in the 30-kcal groups. There were no differences in hepatic lipid content, very-low-density lipoprotein-triglyceride secretion, or hepatic uptake of fatty acids between subgroups with and without glutamine supplementation. It was concluded that glutamine enrichment of a TPN solution did not have any effect on hepatic steatosis in normal rats.

Determination of erythrocyte glutathione peroxidase activity and its reference range in Chinese adults.

A method to assess selenium status of the body by measuring glutathione peroxidase activity in erythrocytes was studied. Reaction was measured by continuous monitoring of the decrease of NADPH at 340 nm. The erythrocyte glutathione peroxidase activity was determined at 37 degrees C, pH 7.5 by using one of the substrates, t-butyl hydroperoxide, to initiate the reaction, and using glutathione reductase as the coupling enzyme. The Km of the enzyme for glutathione and t-butyl hydroperoxide were determined to be 1.8 mM and 238 microM, respectively. The enzyme was stable at -20 degrees C or -70 degrees C for at least 5 months, and for at least 2 months when stored at 4 degrees C. The within-run and between-run coefficients of variation for this method were 3.3-4.9% and 3.0-7.1%, respectively. The test was linear up to 100 U/g hemoglobin, and had a sensitivity of 0.002 delta A/min at 3 U/L. The reference range of erythrocyte glutathione peroxidase in Chinese adults was estimated to be 28.6-87.8 U/g hemoglobin (n = 84), without a significant difference in the results between males and females.