Effect of intravenous lipid emulsions on hepatic cholesterol metabolism

Intestinal failure-associated liver disease: Current challenges in screening, diagnosis, and parenteral nutrition considerations

Intestinal failure-associated liver disease (IFALD) is a serious life-limiting complication that can occur throughout the clinical course of intestinal failure and its management by parenteral nutrition (PN). Despite this, there is a lack of a standardized definition for IFALD, which makes this insidious condition increasingly difficult to screen and diagnose in clinical practice. Attenuating the progression of liver disease before the onset of liver failure is key to improving morbidity and mortality in these patients. This requires timely detection and promptly addressing reversible factors. Although there are various noninvasive tools available to the clinician to detect early fibrosis or cirrhosis in various chronic liver disease states, these have not been validated in the patient population with IFALD. Such tools include biochemical composite scoring systems for fibrosis, transient elastography, and dynamic liver function tests. This review article aims to highlight the existing real need for an accurate, reproducible method to detect IFALD in its early stages. In addition, we also explore the role PN plays in the pathogenesis of this complex multifactorial condition. Various aspects of PN administration have been implicated in the etiology of IFALD, including the composition of the lipid component, nutrient excess and deficiency, and infusion timing. We aim to highlight the clinical relevance of these PN-associated factors in the development of IFALD and how these can be managed to mitigate the progression of IFALD.

Kinetics of phytosterol metabolism in neonates receiving parenteral nutrition

BACKGROUND

Phytosterols in soybean oil (SO) lipids likely contribute to parenteral nutrition-associated liver disease (PNALD) in infants. No characterization of phytosterol metabolism has been done in infants receiving SO lipids.

METHODS

In a prospective cohort study, 45 neonates (36 SO lipid vs. 9 control) underwent serial blood sample measurements of sitosterol, campesterol, and stigmasterol. Mathematical modeling was used to determine pharmacokinetic parameters of phytosterol metabolism and phytosterol exposure.

RESULTS

Compared to controls, SO lipid-exposed infants had significantly higher levels of sitosterol and campesterol (P < 0.01). During SO lipid infusion, sitosterol and campesterol reached half of steady-state plasma levels within 1.5 and 0.8 d, respectively. Steady-state level was highest for sitosterol (1.68 mg/dl), followed by campesterol (0.98 mg/dl), and lowest for stigmasterol (0.01 mg/dl). Infants born < 28 wk gestational age had higher sitosterol steady-state levels (P = 0.03) and higher area under the curve for sitosterol (P = 0.03) during the first 5 d of SO lipid (AUC5) than infants born ≥ 28 wk gestational age.

CONCLUSION

Phytosterols in SO lipid accumulate rapidly in neonates. Very preterm infants receiving SO lipid have higher sitosterol exposure, and may have poorly developed mechanisms of eliminating phytosterols that may contribute to their vulnerability to PNALD.

The effect of 5 intravenous lipid emulsions on plasma phytosterols in preterm infants receiving parenteral nutrition: a randomized clinical trial

BACKGROUND

Elevated plasma phytosterol concentrations are an untoward effect of parenteral nutrition (PN) with vegetable oil-based lipid emulsions (LEs). Phytosterols are elevated in neonatal cholestasis, but the relation remains controversial.

OBJECTIVE

The objective was to study the effect of 5 LEs on plasma phytosterols in preterm infants.

DESIGN

One hundred forty-four consecutive admitted preterm infants (birth weight: 500-1249 g) were studied. Patients were randomly assigned to receive 1 of 5 different LEs: S [100% soybean oil (SO)], MS [50% medium-chain triglycerides (MCTs) and 50% SO], MSF (50% MCTs, 40% SO, and 10% fish oil (FO)], OS (80% olive oil and 20% SO), or MOSF (30% MCTs, 25% olive oil, 30% SO, and 15% FO). Phytosterols in the LEs and in plasma (on postnatal day 7 and day 14) were measured by gas chromatography-mass spectrometry.

RESULTS

Patients in the S group had significantly higher total phytosterol intakes than did the other study groups. On PN days 7 and 14, plasma phytosterol concentrations were highest in the S group and lowest in the MOSF group. Despite similar β-sitosterol intakes between the MS and MSF groups, plasma concentrations were significantly lower in the MSF than in the MS group. Only 3 patients (2.1%) developed cholestasis: 1 in the MS, 1 in the MSF, and 1 in the MOSF group. No cases of cholestasis were observed in the S and OS groups.

CONCLUSIONS

In uncomplicated preterm infants receiving routine PN, we found a correlation between phytosterol intake and plasma phytosterol concentrations; however, cholestasis was rare and no difference in liver function at 6 wk was observed.

Steroidal compounds in commercial parenteral lipid emulsions

Parenteral nutrition lipid emulsions made from various plant oils contain steroidal compounds, called phytosterols. During parenteral administration of lipid emulsions, phytosterols can reach levels in the blood that are many fold higher than during enteral administration. The elevated phytosterol levels have been associated with the development of liver dysfunction and the rare development of liver failure. There is limited information available in the literature related to phytosterol concentrations in lipid emulsions. The objective of the current study was to validate an assay for steroidal compounds found in lipid emulsions and to compare their concentrations in the most commonly used parenteral nutrition lipid emulsions: Liposyn(®) II, Liposyn(®) III, Lipofundin(®) MCT, Lipofundin(®) N, Structolipid(®), Intralipid(®), Ivelip(®) and ClinOleic(®). Our data demonstrates that concentrations of the various steroidal compounds varied greatly between the eight lipid emulsions, with the olive oil-based lipid emulsion containing the lowest levels of phytosterols and cholesterol, and the highest concentration of squalene. The clinical impression of greater incidences of liver dysfunction with soybean versus MCT/LCT and olive/soy lipid emulsions may be reflective of the levels of phytosterols in these emulsions. This information may help guide future studies and clinical care of patients with lipid emulsion-associated liver dysfunction.

Preventing parenteral nutrition liver disease

Parenteral nutrition liver disease (PNLD) develops in 40-60% of infants who require long-term PN for intestinal failure. The clinical spectrum includes hepatic steatosis, cholestasis, cholelithiasis, and hepatic fibrosis. Progression to biliary cirrhosis and the development of portal hypertension and liver failure occurs in a minority who require combined liver and intestinal transplantation. The pathogenesis is multifactorial and is related to prematurity, low birth weight, duration of PN, short bowel syndrome requiring multiple laparotomies and recurrent sepsis. Other important mechanisms include lack of enteral feeding which leads to reduced gut hormone secretion, reduction of bile flow and biliary stasis which leads to the development of cholestasis, biliary sludge and gallstones, which exacerbate hepatic dysfunction, especially in premature neonates with immature hepatic function. The use of lipid emulsions, particularly soy bean emulsions have been associated with hepatic cholestasis in children, although there are little data now to support toxicity from other PN components. Management strategies for the prevention of parenteral nutrition liver disease include consideration of early enteral feeding, a multidisciplinary approach to the management of parenteral nutrition with a specialized nutritional care team and aseptic catheter techniques to reduce sepsis. The use of specialized lipid emulsions such as fish oil emulsions and or SMOF (Soy bean/Medium Chain Triglyceride/Olive Oil/Fish oil) improves established cholestasis and may prevent the onset. Oral administration of ursodeoxycholic acid may improve bile flow and reduce gall bladder stasis, although there is little data to suggest that prophylactic use prevents the onset of PNLD. Survival following either isolated small bowel or combined liver and small bowel transplantation is approximately 50% at 5 years making this an acceptable therapeutic option in children with irreversible liver and intestinal failure.

Reversal of severe parenteral nutrition-associated liver disease in an infant with short bowel syndrome using parenteral fish oil (Omega-3 fatty acids)

Total parenteral nutrition is an important adjunct in the care of neonates with surgical disorders. Cholestasis is at present the most worrisome complication of this technique; it is difficult to treat and may progress to eventual cirrhosis and liver failure. This article reviews the pertinent clinical and nutritional data in a surgical patient with short bowel syndrome who developed parenteral nutrition-associated liver disease successfully treated with fish-oil based lipids.

Intestinal failure-associated liver disease: what do we know today?

Intestinal failure-associated liver disease develops in 40% to 60% of infants who require long-term total parenteral nutrition (TPN) for intestinal failure and 15% to 40% of adults on home parenteral nutrition. The clinical spectrum includes hepatic steatosis, cholestasis, cholelithiasis, and hepatic fibrosis. Progression to biliary cirrhosis and the development of portal hypertension and liver failure occurs in a minority but is more common in infants and neonates than in adults. The pathogenesis is multifactorial. In infants it is related to prematurity, low birth weight, duration of PN, short bowel syndrome requiring multiple laparotomies, and recurrent sepsis. Other important mechanisms include lack of enteral feeding, which leads to reduced gut hormone secretion; reduction of bile flow and biliary stasis, which leads to the development of cholestasis; and biliary sludge and gallstones, which exacerbate hepatic dysfunction. In adults, IFALD is less common and related to age, length of time on PN, total caloric intake, and lipid or glucose overload. In preterm infants, a deficiency of taurine or cysteine may play a role, whereas in both adults and children, choline deficiency may exacerbate IFALD. Lipid emulsions, choline deficiency, and manganese toxicity are associated with both hepatic steatosis and cholestasis in adults and children. Management strategies for the prevention of intestinal failure-induced liver disease include early enteral feeding, a multidisciplinary approach to the management of parenteral nutrition, and aseptic catheter techniques to reduce sepsis. The addition of choline, taurine, and cysteine to PN solutions may also play a role. Oral administration of ursodeoxycholic acid may improve bile flow and reduce gallbladder stasis. Survival after either isolated small bowel or combined liver and small bowel transplantation is approximately 50% at 5 years, making this an acceptable therapeutic option in adults and children with irreversible liver and intestinal failure.

High serum phytosterol levels in short bowel patients on parenteral nutrition support

BACKGROUND & AIMS

Patients with short bowel syndrome (SBS) are often depending on parenteral nutrition support (PNS), sometimes complicated by liver dysfunction. Phytosterols in parenteral lipid emulsions have been suspected to be responsible for cholestasis in paediatric nutrition support. The aim of the present study was to evaluate phytosterol intake and serum phytosterol levels in adult SBS patients.

METHODS

We quantified serum levels of phytosterols, cholesterol, and markers for bile acid and cholesterol synthesis, by gas or liquid chromatography in 21 healthy controls, and in 24 adult SBS-patients, 8 with and 16 without PNS. Phytosterols and cholesterol in parenteral lipid emulsions were also quantified.

RESULTS

Serum levels in SBS-patients without PNS; with PNS; and in controls, were on average for phytosterols 11; 63; and 23 micromol/l (P<0.05 for differences), cholesterol 4,2; 3,8; and 5,1 mmol/l, lathosterol 808; 824; and 228 micromol/100 mmol cholesterol, and 7alpha-hydroxy-4-cholesten-3-one 207;191; and 18 nmol/l, respectively (P<0.05 between controls and SBS). Phytosterols in lipid emulsions ranged from 591 to 958 micromol/l.

CONCLUSIONS

SBS-patients on PNS have higher serum levels of phytosterols than other SBS-patients and controls, possibly because of phytosterols in lipid emulsions. Patients with SBS, regardless of nutrition support, have lower serum levels of cholesterol but higher cholesterol and bile acid synthesis compared to controls.

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.

Prevention of parenteral nutrition-associated liver disease in children

Liver injury is associated with parenteral nutrition therapy. Severity of injury varies from minimal and transient increases in liver-related blood tests to biliary cirrhosis and liver failure. Severe parenteral nutrition-related liver disease is usually confined to patients who have undergone massive intestinal resection. In these patients, early sepsis appears to cause initial liver injury, and recurring sepsis and inflammation, local or systemic, may result in its perpetuation and progression. Liver disease associated with parenteral nutrition is not necessarily related either to duration of parenteral nutrition or to delayed intestinal feeding. However, treatment includes enteral nutrition to promote enterohepatic circulation of bile acids and management of inflammation and sepsis, including control of intestinal bacterial overgrowth. Restriction of intravenous lipid emulsions may be important. The clinical picture of advanced liver failure related to short bowel syndrome differs from liver failure with an anatomically normal gastrointestinal tract. In the former, hyperbilirubinemia, hepatosplenomegaly, and functional hypersplenism dominate the clinical picture, and severe ascites and esophageal variceal hemorrhage are unusual. Early referral of these patients for intestinal and/or liver transplantation may provide the best chance for long-term survival.

Nutritional support at home and in the community

Technical developments in feeding, together with the growth of support structures in the community has lead to a steady increase in the number of children receiving home enteral tube feeding and home parenteral nutrition. In many cases the adverse nutritional consequences of disease can be ameliorated or prevented, and long term parenteral nutrition represents a life saving intervention. Careful follow up of children receiving home nutritional therapy is necessary to establish the ratio of risks to benefits. A considerable burden is sometimes placed on family or other carers who therefore require adequate training and ongoing support. The respective responsibilities of different agencies relating to funding and support tasks require more clear definition.