Effect of taurine on total parenteral nutrition-associated cholestasis

Novel Therapeutic Approaches for Mitigating Complications in Short Bowel Syndrome

Short bowel syndrome (SBS) is a particularly serious condition in which the small intestine does not absorb sufficient nutrients for biological needs, resulting in severe illness and potentially death if not treated. Given the important role of the gut in many signaling cascades throughout the body, SBS results in disruption of many pathways and imbalances in various hormones. Due to the inability to meet sufficient nutritional needs, an intravenous form of nutrition, total parental nutrition (TPN), is administered. However, TPN presents difficulties such as severe liver injury and altered signaling secondary to the continued lack of luminal contents. This manuscript aims to summarize relevant studies into the systemic effects of TPN on systems such as the gut-brain, gut-lung, and gut-liver axis, as well as present novel therapeutics currently under use or investigation as mitigation strategies for TPN induced injury.

Taurine mitigates bile duct obstruction-associated cholemic nephropathy: effect on oxidative stress and mitochondrial parameters

AIM OF THE STUDY

Cholestasis is a serious complication affecting other organs such as the liver and kidney. Oxidative stress and mitochondrial impairment are proposed as the primary mechanisms for cholestasis-induced organ injury. Taurine (TAU) is the most abundant free amino acid in the human body, which is not incorporated in the structure of proteins. Several pharmacological effects have been attributed to TAU. It has been reported that TAU effectively mitigated oxidative stress and modulated mitochondrial function. The current study aimed to evaluate the impact of TAU on oxidative stress biomarkers and mitochondrial parameters in the kidney of cholestatic animals.

MATERIAL AND METHODS

Bile duct ligated (BDL) rats were used as an antioxidant model of cholestasis. Animals were treated with TAU (500 and 1000 mg/kg, oral) for seven consecutive days. Animals were anesthetized (thiopental 80 mg/kg, i.p.), and kidney and blood specimens were collected.

RESULTS

Severe elevation in serum and urine biomarkers of renal injury was evident in the BDL group. Significant lipid peroxidation, reactive oxygen species (ROS) formation, and protein carbonylation were detected in the kidney of BDL animals. Furthermore, depleted glutathione reservoirs and a significant decrease in the antioxidant capacity of renal tissue were detected in cholestatic rats. Renal tubular atrophy and interstitial inflammation were evident in BDL animals. Cholestasis also caused significant mitochondrial dysfunction in the kidney. TAU significantly prevented cholestasis-induced renal injury by inhibiting oxidative stress and mitochondrial impairment.

CONCLUSIONS

These data indicate TAU as a potential therapeutic agent in the management of cholestasis-induced renal injury.

Effects of different carbohydrate sources on taurine status in healthy Beagle dogs

This study evaluated the effects of a grain-based (GB) and grain-free (GF) diet on protein utilization and taurine status in healthy Beagle dogs. Two practical dog diets sufficient in crude protein, sulfur amino acids, and taurine content were formulated with the same ingredients with exception of the carbohydrate sources. The GB contained sorghum, millet, and spelt while potatoes, peas, and tapioca starch were used in the GF. A total of 12 Beagle dogs were used in a completely randomized design with six replicates per treatment. The study consisted of an adaptation period of 2 wk followed by an experimental period of 28 d in which GB and GF were fed to the dogs. At the end of the adaptation period and every 2 wk after it (day 0, day 14, day 28), markers of taurine metabolism were analyzed in whole blood (taurine), plasma (taurine, methionine, and cystine), urine (taurine:creatinine), and fresh fecal samples (primary and secondary bile acids). Fecal samples were collected during the last 6 d of experimental period for digestibly assessment using titanium dioxide as an external marker. Taurine markers and digestibility data were analyzed in a repeated measures model and one-way ANOVA, respectively, using PROC GLIMMIX in SAS (version 9.4). Apparent crude protein digestibility was not affected by treatment, but dogs fed GF diet had lower apparent organic matter digestibility compared with those fed GB (P < 0.05). Greater plasma taurine concentrations were observed at days 14 and 28 compared with day 0; wherein dogs fed GF exhibited greater increase compared to those fed GB (P < 0.05). Whole blood taurine concentrations, plasma methionine concentrations, and urinary taurine:creatinine were also greater at days 14 and 28 compared with day 0 (P < 0.05), but no effect of diet was observed. Total bile acid excretion was similar between GF and GB groups, but dogs fed GF excreted a higher proportion of primary bile acids compared with those fed GB (25.49% vs. 12.09% at day 28, respectively). In summary, overall taurine status was not affected by dietary treatments, however, our results suggest that the higher content of oligosaccharides and soluble fibers in the GF diet may alter the composition of the fecal bile acid pool.

Parenteral Nutrition–Associated Cholestasis in Neonates: Multivariate Analysis of the Potential Protective Effect of Taurine

BACKGROUND

Neonates receiving parenteral nutrition (PN) are at risk for PN-associated cholestasis (PNAC); however, no preventive factors for PNAC have been clearly identified. Despite reports suggesting that taurine may prevent PNAC in neonates, such an effect of taurine has not yet been definitively demonstrated. We determined whether taurine supplementation reduces the incidence of PNAC in premature or critically ill neonates.

METHODS

This study was part of a prospective, randomized, multi-institutional trial designed to assess cholecystokinin vs placebo as a potential preventive therapy of PNAC. Taurine supplementation of PN varied between institutions. The presence or absence of taurine in PN was analyzed by multivariate analysis, with a primary outcome measure of serum conjugated bilirubin (CB) as a measure of PNAC.

RESULTS

Taurine reduced PNAC in premature infants (estimated maximum CB [95% confidence interval] 0.50 mg/dL [-0.17 to 1.18] for those receiving taurine, vs 3.45 mg/dL [1.79-5.11] for neonates not receiving taurine, approaching significance, p = .07). Taurine significantly reduced PNAC in infants with necrotizing enterocolitis (NEC; estimated maximum CB 4.04 mg/dL [2.85-5.23], NEC infants receiving taurine, vs 8.29 mg/dL [5.61-10.96], NEC infants not receiving taurine, p < .01). There were too few neonates with surgical anomalies to evaluate the effect of taurine in this group.

CONCLUSIONS

Within specific subgroups of neonatal patients, taurine supplementation does offer a very significant degree of protection against PNAC. Patients with NEC or severe prematurity are most likely to benefit substantially from taurine supplementation.

Phase IV prospective clinical study to evaluate the effect of taurine on liver function in postsurgical adult patients requiring parenteral nutrition

BACKGROUND

Taurine's role in bile acid metabolism and anti-inflammatory activity could exert a protective effect on hepatobiliary complications associated with parenteral nutrition (PN). In this study, the effects of 2 amino acid solutions, with and without taurine, on liver function administered to nonacutely ill postsurgical patients as part of a short-term PN regimen were prospectively compared.

METHODS

Adult patients randomly received (double-blind) Tauramin 10% or a standard PN solution without taurine as the control (1.5 g amino acid/kg body weight [bw]/d; infusion rate of ≤4 mg glucose/kg bw/d) for a period of 5-30 days. γ-Glutamyl transpeptidase (GGT) and other indicators of liver function, glucose metabolism, lipid profile, inflammation markers, and treatment safety data were collected.

RESULTS

Thirty-five patients receiving taurine PN and 39 receiving control PN were enrolled (intention-to-treat [ITT] population). Most patients (n = 62) discontinued after day 7 of follow-up (per-protocol [PP] population: n = 24 and n = 27, respectively). ITT patients with high GGT values after 5 days of PN comprised 68.6% and 64.1%, respectively. The mean change in GGT values with respect to the baseline values was 167 ± 192 and 157 ± 185 IU/L, respectively. Low-density lipoprotein (LDL) cholesterol levels after 7 days of PN were significantly decreased in the taurine PN group of PP patients (-2.83 ± 30.9 vs 23.9 ± 27.0 mg/dL for control PN; P < .05). None of the adverse events reported (taurine PN: n = 6; control PN: n = 7) were treatment related.

CONCLUSION

PN solutions with and without taurine had similar effects on liver function parameters, except for an LDL reduction in PN with taurine, when administered to nonacutely ill postsurgical patients in the short term (5-7 days).

Membrane transporters in a human genome-scale metabolic knowledgebase and their implications for disease

Membrane transporters enable efficient cellular metabolism, aid in nutrient sensing, and have been associated with various diseases, such as obesity and cancer. Genome-scale metabolic network reconstructions capture genomic, physiological, and biochemical knowledge of a target organism, along with a detailed representation of the cellular metabolite transport mechanisms. Since the first reconstruction of human metabolism, Recon 1, published in 2007, progress has been made in the field of metabolite transport. Recently, we published an updated reconstruction, Recon 2, which significantly improved the metabolic coverage and functionality. Human metabolic reconstructions have been used to investigate the role of metabolism in disease and to predict biomarkers and drug targets. Given the importance of cellular transport systems in understanding human metabolism in health and disease, we analyzed the coverage of transport systems for various metabolite classes in Recon 2. We will review the current knowledge on transporters (i.e., their preferred substrates, transport mechanisms, metabolic relevance, and disease association for each metabolite class). We will assess missing coverage and propose modifications and additions through a transport module that is functional when combined with Recon 2. This information will be valuable for further refinements. These data will also provide starting points for further experiments by highlighting areas of incomplete knowledge. This review represents the first comprehensive overview of the transporters involved in central metabolism and their transport mechanisms, thus serving as a compendium of metabolite transporters specific for human metabolic reconstructions.

Activation of glycine and extrasynaptic GABA(A) receptors by taurine on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis

The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been known for the processing and transmission of orofacial nociceptive information. Taurine, one of the most plentiful free amino-acids in humans, has proved to be involved in pain modulation. In this study, using whole-cell patch clamp technique, we investigated the direct membrane effects of taurine and the action mechanism behind taurine-mediated responses on the SG neurons of the Vc. Taurine showed non-desensitizing and repeatable membrane depolarizations and inward currents which remained in the presence of amino-acid receptors blocking cocktail (AARBC) with tetrodotoxin, indicating that taurine acts directly on the postsynaptic SG neurons. Further, application of taurine at different doses (10 μM to 3 mM) showed a concentration dependent depolarizations and inward currents with the EC₅₀ of 84.3 μM and 723 μM, respectively. Taurine-mediated responses were partially blocked by picrotoxin (50 μM) and almost completely blocked by strychnine (2 μM), suggesting that taurine-mediated responses are via glycine receptor (GlyR) activation. In addition, taurine (1 mM) activated extrasynaptic GABA_A receptor (GABA_AR)-mediated currents. Taken together, our results indicate that taurine can be a target molecule for orofacial pain modulation through the activation of GlyRs and/or extrasynaptic GABA_ARs on the SG neurons.

Fish oil emulsions in the management of intestinal failure-associated liver disease

The role of parenteral lipid emulsions in the treatment of intestinal failure-associated liver disease (IFALD) is both topical and controversial. There is strong evidence supporting plant-based (soy, olive) lipid emulsions as a key cause for IFALD, especially in neonates. As a result, alternate lipid formulations, most notably fish oil emulsions (FOE) have come into widespread use despite somewhat limited clinical data on their overall benefit and potential long-term consequences. This review examines putative mechanisms of action of FOE in reversing cholestasis associated with IFALD, and critically reviews published clinical studies of the use of FOE in pediatric patients with IFALD. From these works, it appears the mechanism of action of FOE is most likely related to the reduction of serum phytosterols associated with plant-based lipid emulsions rather than a specific positive benefit of the fish oils themselves. Although the use of FOE seems to correlate with a reduction in cholestasis, their actual individual benefit is not established, and data on long-term outcomes and safety are not yet available.

Innovative parenteral and enteral nutrition therapy for intestinal failure

Children with intestinal failure (IF) suffer from insufficient intestinal length or function, making them dependent on parenteral nutrition (PN) for growth and survival. PN and its components are associated with many complications ranging from simple electrolyte abnormalities to life-threatening PN-associated liver disease, which is also called intestinal failure-associated liver disease (IFALD). From a nutrition perspective, the ultimate goal is to provide adequate caloric requirements and make the transition from PN to full enteral nutrition (EN) successful. Upon review of the literature, we have summarized the most effective and innovative PN and EN therapies for this patient population. Antibiotic-coated catheters and antibiotic or ethanol locks can be implemented, as they appear effective in reducing catheter-related infection and thus further reduce the risk of IFALD. Lipid emulsions should be given judiciously. The use of an omega-3 fatty acid-based formulation should be considered in patients who develop IFALD. Trophic feeding is important for intestinal adaptation, and EN should be initiated early to help wean patients from PN. Long-term management of children with IF continues to be an emerging field. We have entered uncharted territory as more children survive complications of IF and IFALD. Careful monitoring and individualized management to ensure maintenance of growth while avoiding complications are the keys to successful patient outcomes.

ESPEN Guidelines on Parenteral Nutrition: home parenteral nutrition (HPN) in adult patients

Home parenteral nutrition (HPN) was introduced as a treatment modality in the early 1970s primarily for the treatment of chronic intestinal failure in patients with benign disease. The relatively low morbidity and mortality associated with HPN has encouraged its widespread use in western countries. Thus there is huge clinical experience, but there are still few controlled clinical studies of treatment effects and management of complications. The purpose of these guidelines is to highlight areas of good practice and promote the use of standardized treatment protocols between centers. The guidelines may serve as a framework for development of policies and procedures.

Chronic biochemical cholestasis in patients receiving home parenteral nutrition: prevalence and predisposing factors

BACKGROUND

Chronic biochemical cholestasis has been shown to be associated with a fivefold increase in histologically advanced liver disease in patients receiving home parenteral nutrition.

AIMS

To investigate prevalence of chronic biochemical cholestasis in home parenteral nutrition patients and examine factors influencing its occurrence.

METHODS

Records of all patients receiving home parenteral nutrition for >6 months treated at a single centre were reviewed and plasma biochemistry recorded. Logistic regression analysis was employed to identify factors associated with prevalence of chronic biochemical cholestasis.

RESULTS

Records of 113 patients were reviewed. The point prevalence of chronic biochemical cholestasis was 24%, increasing to 28% if patients receiving parenteral fluid and electrolytes only were excluded. In multivariate analysis, presence of colon in continuity was associated with a significantly lower prevalence of chronic biochemical cholestasis, while total parenteral calorie intake was associated with a higher prevalence of chronic biochemical cholestasis. No association was seen between small intestinal lengths or between parenteral lipid intake and chronic biochemical cholestasis in multivariate analysis.

CONCLUSIONS

Chronic biochemical cholestasis is common in patients receiving home parenteral nutrition. High parenteral calorie intake and lack of a colon in continuity with small intestine are independently associated with an increased risk of chronic biochemical cholestasis.

Cholestasis induced by total parenteral nutrition

Parenteral nutrition is a life-saving treatment for patients who have acute and chronic intestinal failure. Severe cholestasis induced by total parental nutrition (TPN-IC) is characterized by bile duct regeneration, portal inflammation, and fibrosis. Its progression could be very rapid, and in some patients liver cirrhosis may develop in few months. This article describes the definition, incidence, hepatic changes, histopathologic findings, risk factors, pathogenesis, and clinical implications of TPN-IC. The goal is to improve hospital and home management, quality of life, and prognosis of patients requiring parenteral nutrition.

Mechanisms of disease: update on the molecular etiology and fundamentals of parenteral nutrition associated cholestasis

Since its introduction into clinical practice, parenteral nutrition has revolutionized the care of premature neonates. Serum transaminase and bilirubin levels are commonly elevated in infants on parenteral nutrition, but their normalization is typical in the setting of short-term administration of parenteral nutrition uncomplicated by sepsis. Premature infants who require long-term parenteral nutrition are, however, at severe risk for developing life-threatening hepatic complications. These complications include cirrhosis, liver failure, and the concomitant risks of sepsis, coagulopathy and death. Premature infants and those with short-bowel syndrome are most susceptible to these morbid outcomes. Although it has been more than a quarter of a century since parenteral nutrition was first introduced and its association with hepatic complications described, the precise etiology of parenteral nutrition associated cholestasis (PNAC) remains a mystery; however, our understanding of the molecular components that contribute to PNAC has improved substantially. In this Review, we summarize the fundamentals of PNAC, describe animal models of the disease, review the hepatic bile acid transporters that are crucial for bile acid homeostasis, and define the roles that endotoxin, genetics, and the components of parenteral nutrition are likely to have in the molecular pathogenesis of this life-threatening condition.

Taurine status and response to intravenous taurine supplementation in adults with short-bowel syndrome undergoing long-term parenteral nutrition: a pilot study

Taurine deficiency in patients on long-term parenteral nutrition may be involved in cholestasis. We aimed to assess plasma taurine and tauro-conjugated bile acids in adults with short-bowel syndrome and their response to intravenous taurine. Thirty-two adult patients, who had been on taurine-free parenteral nutrition for a mean of 59(SE14) months for short-bowel syndrome, were studied retrospectively. In a second study, a subgroup of ten patients with chronic cholestasis received taurine-enriched (6·0(SE0·6)mg/kg per d) parenteral nutrition for 55(SE13) months. Post-absorptive plasma taurine and bile acid concentrations were measured and liver function tests routinely sampled. At baseline, plasma taurine was lower in patients with a jejunal length of less than 35cm (group A,n16) than in those with a jejunal length of 35cm or more (group B,n16): 43(SE3)v. 58(SE4)μmol/l (P=0·01). The groups were no different in terms of chronic cholestasis (1/6v.1/6 patients), total bile acids (26(SE13)v.14(SE5)μmol/l) or the ratio of tauro-conjugated:glyco-conjugated bile acids (5(SE2)v.8(SE 4)%, usual range 30–60%). After supplementation, there was an increase in plasma taurine level (63(SE8)v. 43(SE4),P=0·007) but was no change in either total bile acids or the ratio of tauro-conjugated: glyco-conjugated bile acids. There was a significant decrease in aspartate aminotransferase level. Long-term parenteral nutrition for short-bowel syndrome is associated with an impaired tauro-conjugation of bile acids (enterohepatic pool), irrespective of plasma taurine level (systemic pool) and despite long-term taurine intravenous supplementation.

Total parenteral nutrition-related gastroenterological complications

Total parenteral nutrition is a life saving therapy for patients with chronic gastrointestinal failure, being an effective method for supplying energy and nutrients when oral or enteral feeding is impossible or contraindicated. Clinical epidemiological data indicate that total parenteral nutrition may be associated with a variety of problems. Herein we reviewed data on the gastroenterological tract regarding: (i) total parenteral nutrition-related hepatobiliary complications; and (ii) total parenteral nutrition-related intestinal complications. In the first group, complications may vary from mildly elevated liver enzyme values to steatosis, steatohepatitis, cholestasis, fibrosis and cirrhosis. In particular, total parenteral nutrition is considered to be an absolute risk factor for the development of biliary sludge and gallstones and is often associated with hepatic steatosis and intrahepatic cholestasis. In general, the incidence of total parenteral nutrition-related hepatobiliary complications has been reported to be very high, ranging from 20 to 75% in adults. All these hepatobiliary complications are more likely to occur after long-term total parenteral nutrition, but they seem to be less frequent, and/or less severe in patients who are also receiving oral feeding. In addition, end-stage liver disease has been described in approximately 15-20% of patients receiving prolonged total parenteral nutrition. Total parenteral nutrition-related intestinal complications have not yet been adequately defined and described. Epidemiological studies intended to define the incidence of these complications, are still ongoing. Recent papers confirm that in both animals and humans, total parenteral nutrition-related intestinal complications are induced by the lack of enteral stimulation and are characterised by changes in the structure and function of the gut. Preventive suggestions and therapies for both these gastroenterological complications are reviewed and reported in the present review.

Liver disease due to parenteral and enteral nutrition

Liver disease due to parenteral and enteral nutrition is a well-recognized iatrogenic phenomenon, but its cause and pathogenesis have not been clearly elucidated. Various mechanisms have been postulated, but it is likely that the cause is multifactorial with significant interplay among several factors. A preventive approach to management is ideal but awaits a more complete understanding of the pathophysiology. A variety of management strategies has been proposed in small case series, but level 1 evidence-based guidelines have yet to be established. Although an abundance of both clinical and animal studies exist regarding liver disease associated with parenteral nutrition (PN), there is a paucity of data regarding enteral nutrition (EN)-associated hepatic disease. The latter probably reflects differences in the frequency and severity of PN- versus EN-associated liver disease. This article addresses the two routes of nutritional support individually, with the major focus on PN-associated liver disease.

Hepatobiliary, renal and bone complications of intestinal failure

Abnormal liver function tests in patients with intestinal failure (IF) may be due to the underlying disease, IF or the treatments given (including parenteral nutrition (PN)). PN-related liver disease in children usually relates to intrahepatic cholestasis and in adults to steatosis. Steatosis may be consequent upon an excess of carbohydrate, lipid or protein, or upon a deficiency of a specific molecule. Pigment-type gallstones are common in adults and children with IF; these develop from biliary sludge that forms during periods of gallbladder stasis. Ileal disease/resection, parenteral nutrition, surgery, rapid weight loss and drugs all increase the risk of developing gallstones. Gallstone formation may be prevented by reducing gallbladder stasis (oral/enteral feeding or prokinetic agents), altering bile composition, or by means of a prophylactic cholecystectomy. Calcium oxalate renal stones are common in patients with a short bowel and retained functioning colon and are consequent upon increased absorption of dietary oxalate; they are prevented by a low-oxalate diet. An osteopathy may occur with long-term parenteral nutrition.

Homocysteine prevents total parenteral nutrition (TPN)-induced cholestasis without changes in hepatic oxidative stress in the rat

BACKGROUND

The role of oxidative stress in total parenteral nutrition (TPN)-associated cholestasis with liver glutathione depletion was recently shown. The aims of this study were to test the appearance of cholestasis and oxidative stress during TPN, and the hypothesis that reducing oxidative stress with a precursor of glutathione (GSH), homocysteine, would restore bile flow.

METHODS

Three groups of rats (weight, 179-278 g) were studied: 1) D/aa group received dextrose and amino acids (3.4 g/d); 2) D/aa/L group received the same amount of amino acids, and lipids were added on an equicaloric basis (50 kcal/d) with a lowered amount of dextrose; and 3) a control group, which received dextrose perfusion and had free access to chow. A subgroup of D/aa/L rats (n = 6) received a TPN solution containing homocysteine. After 5 days of TPN, bile was collected during 2 hours. In liver homogenates, GSH, thiobarbituric acid reactive substances (TBARS), and carbonyl content of proteins (Prot-CO) were measured to test the level of oxidative stress and hepatic lipid and protein oxidation.

RESULTS

After TPN, bile flow was significantly lower in the D/aa group than in the control group. Addition of lipids further decreased bile flow. Addition of homocysteine to TPN with lipids significantly increased bile flow. Aspartate aminotransferase increased significantly in both TPN groups compared with the control group. gamma-Glutamyl transpeptidase was not different among TPN groups. An increased hepatic lipid oxidation was demonstrated by TBARS level in both TPN groups when compared with the control group. However, the liver GSH contents were not different. Protein oxidation was also significantly increased by TPN. The addition of homocysteine to TPN solution increased bile flow without liver injury or changes of lipid and protein oxidation.

DISCUSSION

This study shows that TPN administered to rats induces a decrease of bile flow and an oxidative stress but that the two changes are not directly correlated. Addition of lipids further impairs bile flow but does not increase the occurrence of liver injury. Consequently, it seems more likely that TPN primarily induces a cholestatic effect that in turn induces an oxidative stress rather than inducing an oxidative stress that leads to cholestasis. However, an association of both mechanisms is not totally excluded.

Plasma taurine concentrations increase after enteral glutamine supplementation in trauma patients and stressed rats

BACKGROUND

Taurine is a unique amino acid with antioxidant and osmolytic properties. Glutamine serves as the preferred fuel for the gut, liver, and immune cells and as a precursor for antioxidants. Trauma patients have low glutamine concentrations.

OBJECTIVES

We investigated the effect of glutamine-enriched enteral nutrition on plasma taurine concentrations in patients with severe trauma (injury severity score >20). Additionally, plasma taurine concentrations and organ fluxes were studied in a stressed rat model.

DESIGN

Twenty-nine patients with multiple trauma received glutamine-enriched nutrition and 31 patients received isocaloric, isonitrogenous control solution for 5 d. Plasma taurine and glutamine concentrations were measured. Male Wistar rats (250-300 g) received a glutamine-enriched diet (12%, by wt) or a control solution for 2 wk. Plasma taurine concentrations were measured. Taurine fluxes and fractional extraction rates in the liver, kidneys, and gut were assessed with a radioactive microsphere technique.

RESULTS

Both patient groups had low taurine concentrations on day 1. From day 3 onward, the glutamine-fed patients had significantly higher taurine concentrations. Rats fed a glutamine-enriched diet had significantly higher plasma taurine concentrations than did the controls. A high taurine uptake was found in the liver, kidneys, and gut of the glutamine-fed rats. Fractional extraction rates were not significantly different between the rat groups.

CONCLUSIONS

Glutamine enrichment increases plasma taurine in trauma patients and in stressed rats. Because of increased availability, organ fluxes showed a higher taurine uptake in the liver, kidneys, and gut. The reduction in morbidity with glutamine enrichment could be explained in part by increased taurine availability.

Parenteral nutrition-associated liver complications in children

Parenteral nutrition is a life-saving therapy for patients with intestinal failure. It may be associated with transient elevations of liver enzyme concentrations, which return to normal after parenteral nutrition is discontinued. Prolonged parenteral nutrition is associated with complications affecting the hepatobiliary system, such as cholelithiasis, cholestasis, and steatosis. The most common of these is parenteral nutrition-associated cholestasis (PNAC), which may occur in children and may progress to liver failure. The pathophysiology of PNAC is poorly understood, and the etiology is multifactorial. Risk factors include prematurity, long duration of parenteral nutrition, sepsis, lack of bowel motility, and short bowel syndrome. Possible etiologies include excessive caloric administration, parenteral nutrition components, and nutritional deficiencies. Several measures can be undertaken to prevent PNAC, such as avoiding overfeeding, providing a balanced source of energy, weaning parenteral nutrition, starting enteral feeding, and avoiding sepsis.

Metabolic effects of intraportal nutrition in humans

OBJECTIVE

We investigated the metabolic effects of intravenous nutrition through a portal (PN) or systemic (SN) peripheral vein.

METHODS

Twenty patients were randomized to receive PN or SN nutrition after colorectal surgery. The daily regimen included 900 kcal and 100 g of amino acid (AA). Visceral proteins and hepatic enzymes were measured on days 0, 1, 3, 5, and 7, and plasma arterovenous differences and limb flux of AA were measured on days 0, 3, and 7; urinary nitrogen and 3-CH3-histidine were analyzed daily.

RESULTS

Serum albumin on day 7 was still depressed (P = 0.01) in SN and fully restored in PN patients. Prealbumin levels increased significantly (P = 0.05) in the PN group only. Plasma levels of glutamine and asparagine were higher in PN than in SN patients, and this difference was statistically significant (P = 0.05). SN patients had significantly more negative limb-muscle balance of valine and tyrosine, whereas PN patients had a higher muscle release of citrulline and taurine.

CONCLUSIONS

In conclusion, short-term PN is safe and has some metabolic benefits: it accelerates recovery from postoperative hypoalbuminemia and hypopnealbuminemia and is associated with a higher plasma level of glutamine and an AA plasma pattern that is closer to normal. PN blunts the catabolic response of the muscle, decreasing loss of proteins and release of some AA involved in hepatic gluconeogenesis.

Parenteral nutrition-associated cholestasis

Cholestasis is a major complication that occurs frequently in patients with the short bowel syndrome and accounts for the majority of morbidity and mortality in this group of patients. The exact cause of this condition is not known and the etiology is likely multifactorial. Many new mechanistic insights into this disease are discussed and have paved the way for future investigation. For now, prompt recognition, early initiation of enteral feeding, prevention of overfeeding with parenteral nutrition, and agents that induce bile flow may be useful to prevent this catastrophic morbidity.

Prevalence of liver disease and contributing factors in patients receiving home parenteral nutrition for permanent intestinal failure

BACKGROUND

Liver cholestasis can be a life-threatening complication during home parenteral nutrition and may lead to combined liver-intestinal transplantation.

OBJECTIVE

To assess the prevalence of home parenteral nutrition-related liver disease and its contributing factors in patients with permanent intestinal failure.

DESIGN

Prospective cohort study.

SETTING

Two approved home parenteral nutrition centers.

PATIENTS

90 patients with permanent intestinal failure who were receiving home parenteral nutrition were enrolled from 1985 to 1996.

INTERVENTION

Clinical, biological, endoscopic, and ultrasonographic follow-up. Histologic examination of the liver was done in 57 patients (112 liver biopsies).

MEASUREMENTS

The Kaplan-Meier method was used to determine the actuarial occurrence of chronic cholestasis and complicated home parenteral nutrition-related liver disease (bilirubin level > or =60 micromol/L [3.5 mg/dL], factor V level < or =50%, portal hypertension, encephalopathy, ascites, gastrointestinal bleeding, or histologically proven extensive fibrosis or cirrhosis). Contributing factors were assessed by using univariate and multivariate (Cox model) analysis.

RESULTS

58 patients (65%) developed chronic cholestasis after a median of 6 months (range, 3 to 132 months), and 37 (41.5%) developed complicated home parenteral nutrition-related liver disease after a median of 17 months (range, 2 to 155 months). Of these patients, 17 showed extensive fibrosis after 26 months (range, 2 to 148 months) and 5 had cirrhosis after 37 months (range, 26 to 77 months). The prevalence of complicated home parenteral nutrition-related liver disease was 26%+/-9% at 2 years and 50%+/-13% at 6 years. Six patients died of liver disease (22% of all deaths). In multivariate analysis, chronic cholestasis was significantly associated with a parenteral nutrition-independent risk for liver disease, a bowel remnant shorter than 50 cm in length, and a parenteral lipid intake of 1 g/kg of body weight per day or more (omega-6-rich long-chain triglycerides), whereas complicated home parenteral nutrition-related liver disease was significantly associated with chronic cholestasis and lipid parenteral intake of 1 g/kg per day or more.

CONCLUSION

The prevalence of complicated home parenteral nutrition-related liver disease increased with longer duration of parenteral nutrition. This condition was one of the main causes of death in patients with permanent intestinal failure. Parenteral intake of omega-6-rich long-chain triglycerides lipid emulsion consisting of less than 1 g/kg per day is recommended in these patients.

Total parenteral nutrition and cholestasis

Hepatobiliary dysfunction is recognized as a major adverse effect of total parenteral nutrition (TPN). It is unknown if this is caused by a deficiency or toxicity of the TPN solution or the underlying pathophysiology of disease processes that require TPN therapy. This article presents algorithms for evaluating abnormal liver tests in patients on TPN and discusses treatment options and the current status of intestinal transplantation.

The effects of acetylsalicylic acid, interferon-alpha, and vitamin E on prevention of parenteral nutrition-associated cholestasis: an experimental study

BACKGROUND

Cholestasis is one of the major complications of parenteral nutrition. The purpose of this experimental study was to detect the effects of acetylsalicylic acid (ASA), vitamin E (Vit E), and interferon-alpha (IFN-alpha) on prevention of parenteral nutrition-associated cholestasis.

METHODS

Ten experimental groups, each consisting of 10 4-week-old Wistar albino rats, were formed: control 10- and 20-day groups (C10 and C20), parenteral nutrition-only 10- and 20-day groups (T10 and T20), ASA-supplemented parenteral nutrition 10- and 20-day groups (TA10 and TA20), Vit E-supplemented parenteral nutrition 10- and 20-day groups (TE10 and TE20), and IFN-alpha-supplemented 10- and 20-day groups (TF10 and TF20). Acetylsalicylic acid, Vit E, and IFN-alpha were administered in the parenteral nutrition solution through an intraperitoneal route. At the end of the study, serum total bile acids, serum aspartate and alanine aminotransferases, and alkaline phosphatase were measured biochemically. In addition, the histopathologic findings of cholestasis were evaluated by using a morphologic portal inflammation index.

RESULTS

Although the difference in the serum levels of transferases and alkaline phosphatase was not significant among all groups (p > 0.05), it was significant in total bile acid levels (p < 0.05). There was also a significant correlation between the histopathologic changes of the liver and serum total bile acid concentrations (p < 0.05). Portal inflammation in varying degrees was seen in all experimental groups, but not in the control groups. Serum total bile acid concentrations in parenteral nutrition groups receiving ASA were significantly lower than those in the parenteral nutrition-only group (p < 0.01). Although Vit E-supplemented parenteral nutrition was effective in preventing the development of cholestasis in the 10-day group (p < 0.05), it was not effective in the 20-day group when compared with incidence of cholestasis in the parenteral nutrition-only group (p > 0.05). Conversely, IFN-alpha-supplemented parenteral nutrition had no effect on cholestasis in the 10-day group (p > 0.05) but lowered cholestasis in the 20-day group when compared with incidence the parenteral nutrition-only group (p < 0.05).

CONCLUSION

Our results indicate that acetylsalicylic acid may be beneficial in preventing, and (alpha-interferon in treating, parenteral nutrition-associated cholestasis.

Immunonutrition: the role of taurine

Taurine is a sulfonated beta amino acid derived from methionine and cysteine metabolism. It is present in high concentrations in most tissues and in particular in proinflammatory cells such as polymorphonuclear phagocytes. Initial investigation into the multifaceted properties of this non-toxic physiologic amino acid revealed a link between retinal dysfunction and dietary deficiency. Since then a role for this amino acid has been found in membrane stabilization, bile salt formation, antioxidation, calcium homeostasis, growth modulation, and osmoregulation. Our own group has demonstrated a key role for taurine in modulation of apoptosis in a variety of cell types. This review summarizes our current knowledge of taurine in nutrition, host proinflammatory cell homeostasis, therapeutic applications, and its potential immunoregulatory properties. It is our belief that taurine, similar to arginine and glutamine, is now more than worthy of critical clinical analysis.

The role of taurine in infant nutrition

The importance of taurine in the diet of pre-term and term infants has not always been clearly understood and is a topic of interest to students of infant nutrition. Recent evidence indicates that it should be considered one of the "conditionally essential" amino acids in infant nutrition. Plasma values for taurine will fall if infants are fed a taurine-free formula or do not have taurine provided in the TPN solution. Urine taurine values also fall, which is indicative of an attempt by the kidney to conserve taurine. The very-low-birth-weight infant, for a variety of reasons involving the maturation of tubular transport function, cannot maximally conserve taurine by enhancing renal reabsorption and, hence, is potentially at greater risk for taurine depletion than larger pre-term or term infants, and certainly more than older children who have taurine in their diet. Taurine has an important role in fat absorption in pre-term and possibly term infants and in children with cystic fibrosis. Because taurine-conjugated bile acids are better emulsifiers of fat than glycine-conjugated bile acids, the dietary (or TPN) intake has a direct influence on absorption of lipids. Taurine supplementation of formulas or TPN solutions could potentially serve to minimize the brain phospholipid fatty acid composition differences between formula-fed and human milk-fed infants. Taurine appears to have a role in infants, children, and even adults receiving most (> 75%) of their calories from TPN solutions in the prevention of granulation of the retina and electroencephalographic changes. Taurine has also been reported to improve maturation of auditory-evoked responses in pre-term infants, although this point is not fully established. Clearly, taurine is an important osmolyte in the brain and the renal medulla. At these locations, it is a primary factor in the cell volume regulatory process, in which brain or renal cells swell or shrink in response to osmolar changes, but return to their previous volume according to the uptake or release of taurine. While there is a dearth of clinical studies in man concerning this volume regulatory response, studies in cats, rats, and dog kidney cells indicate the protective role of taurine in hyperosmolar stress. The infant depleted of taurine may not be able to respond to hyper- or hyponatremic stress without massive changes in neuronal volume, which has obvious clinical significance. The fact that the brain content of taurine is very high at birth and falls with maturation may be a protective feature, or compensation for renal immaturity Defining an amino acid as "conditionally essential" requires that deficiency result in a clinical consequence or consequences which can be reversed by supplementation. In pre-term and term infants, taurine insufficiency results in impaired fat absorption, bile acid secretion, retinal function, and hepatic function, all of which can be reversed by taurine supplementation. Therefore, this small beta-amino acid, taurine, is indeed conditionally essential.

Home parenteral nutrition. 25 years later

After 25 years, there is enough clinical outcome experience to determine appropriate use of home parenteral nutrition in different disease states and age groups. Information regarding how to avoid complications and how patients and families can find necessary psychosocial support is provided in this article. Currently, small bowel transplantation is not a safer choice, unless there is severe liver disease caused by home parenteral nutrition or lack of central intervenous access.

Taurine and human nutrition

Taurine (2-aminoethane sulphonic acid), a ubiquitous beta-amino acid not incorporated into proteins but found either free or in some simple peptides is considered as a conditionally semi-essential amino acid in man. Once thought of as no more than an innocuous end product of cysteine metabolism, taurine has in recent years generated much interest due to research findings indicating a role in numerous physiological processes. These roles are varied and include membrane stabilization, detoxification, antioxidation, osmoregulation, maintenance of calcium homeostasis, and stimulation of glycolysis and glycogenesis. Intracellular and plasma taurine levels are high and although cellular taurine is tightly regulated, plasma levels are known to decrease in response to surgical injury and numerous pathological conditions including cancer, trauma and sepsis. Decreased plasma concentrations can be restored with supplementary taurine. Although the importance of taurine as a physiological agent with pharmacological properties is now recognised, the potential advantages of dietary supplementation with taurine have not as yet been fully exploited and this is an area which could prove to be of benefit to the patient.

Prevention of liver failure in parenteral nutrition-dependent children with short bowel syndrome

Progressive liver failure in parenteral nutrition (PN)-dependent children with short bowel syndrome carries significant morbidity and mortality. The authors retrospectively reviewed 47 consecutive patients with short bowel syndrome diagnosed from October 1985 through October 1995. All patients were treated according to a protocol designed to promote intestinal motility and discourage bacterial translocation. Elements of the protocol included the use of taurine, vigilant prevention and aggressive treatment of sepsis, meticulous catheter care, early PN cycling, appropriate enteral feeding, and measures designed to inhibit gastrointestinal bacterial translocation, especially gram-negative rods. Complete blood counts and serum liver function studies were compiled from both clinic visits and hospital admissions for each patient every 3 to 6 months while they were on PN. Three patients were lost to follow-up after they had moved out of state. The length of time on PN ranged from 3 months to 9.4 years with an average of 2.2 years. Elevated aspartate aminotransferase (AST), alanine aminotransferase (ALT), and glutamyltransferase (GGT) were present in 82%, 66%, and 84% of patients, respectively. Alkaline phosphatase was elevated in 58% of patients. Eight patients (18%) are still on PN, and 31 (70%) have been weaned off PN. Five patients have died (11%). Three patients (7%) developed cholecystitis requiring cholecystectomy. No patients developed progressive liver failure. These results suggest that PN-related liver failure may be prevented in most patients with short bowel syndrome. Specific measures to prevent PN-related cholestatic jaundice need further investigation.

Liver and biliary tract changes and injury associated with total parenteral nutrition: pathogenesis and prevention

Total parenteral nutrition (TPN), now widely used, is successful in preventing and reversing malnutrition in individuals with various diseases and conditions. However, hepatic and biliary complications of TPN are encountered in both adult and pediatric patients. Certain complications, such as sepsis and TPN-associated cholestasis, occur more frequently in very young infants. Continuing problems commonly seen in adults are steatosis and steatonecrosis. Reasons for the development of these complications are multifactorial. Etiologies of hepatic complications, especially the role of deficiency/excess of nutrients in the pathogenesis of hepatobiliary disorders, are summarized. Complications caused by the duration of TPN are discussed with emphasis on prevention and management. Evidence now suggests that prompt enteral feeding, even in minimal amounts, may prevent many of the metabolic complications associated with TPN. TPN should be used only in amounts meeting needs and for a duration essential to survival.

Hepatobiliary complications of total parenteral nutrition

The relationships between various hepatobiliary disorders and the administration of total parenteral nutrition (TPN) were reviewed and, in particular, the role of TPN in their pathogenesis was critically evaluated. Several clinical and pathological entities including steatosis, steatohepatitis, cholestasis, and cholelithiasis have been commonly linked to TPN, and instances of chronic decompensated liver disease have been reported. However, it is concluded that it is often difficult to extricate the effects of TPN on hepatobiliary function from many other hepatotoxic factors that may be operative in these patients. Thus, whereas considerable evidence exists to support a role fro carbohydrate or calorie excess in TPN solutions in the pathogenesis of steatosis, a loss of enteric stimulation and not TPN per se may be the primary factor in the development of cholestasis, biliary sludge, and gallstones. The apparent predilection of infants to TPN-related cholestasis may be based on the relative immaturity of the neonatal biliary excretory system.