Effects of dietary supplementation with fish oil on prostanoid metabolism during acute coronary occlusion with or without reperfusion in diet-induced hypercholesterolemic rabbits

Liver disease secondary to intestinal failure

IFALD is a common and potentially life-threatening condition for patients with SBS requiring long-term PN. There exists the potential for decreasing its incidence by optimizing the composition and the rate of infusion of parenteral solutions, by advocating a multidisciplinary approach, and by early referral for intestinal-liver transplantation to ensure long-term survival of patients with SBS.

Parenteral fish-oil-based lipid emulsion improves fatty acid profiles and lipids in parenteral nutrition-dependent children

BACKGROUND

Total parenteral nutrition (PN), including fat administered as a soybean oil-based lipid emulsion (SOLE), is a life-saving therapy but may be complicated by PN-induced cholestasis and dyslipidemia. A fish-oil-based lipid emulsion (FOLE) as a component of PN can reverse PN-cholestasis and has been shown to improve lipid profiles.

OBJECTIVE

The objective was to describe changes in the fatty acid and lipid profiles of children with PN-cholestasis who were treated with a FOLE.

DESIGN

Lipid and fatty acid profiles of 79 pediatric patients who developed PN-cholestasis while receiving standard PN with a SOLE were examined before and after the switch to a FOLE. All patients received PN with the FOLE at a dose of 1 g · kg(-1) · d(-1) for ≥1 mo.

RESULTS

The median (interquartile range) age at the start of the FOLE treatment was 91 (56-188) d. After a median (interquartile range) of 18.3 (9.4-41.4) wk of receiving the FOLE, the subjects' median total and direct bilirubin improved from 7.9 and 5.4 mg/dL to 0.5 and 0.2 mg/dL, respectively (P < 0.0001). Serum triglyceride, total cholesterol, LDL, and VLDL concentrations significantly decreased by 51.7%, 17.4%, 23.7%, and 47.9%, respectively.

CONCLUSIONS

The switch from a SOLE to a FOLE in PN-dependent children with cholestasis and dyslipidemia was associated with a dramatic improvement in serum triglyceride and VLDL concentrations, a significant increase in serum omega-3 (n-3) fatty acids (EPA and DHA), and a decrease in serum omega-6 fatty acids (arachidonic acid). A FOLE may be the preferred lipid emulsion in patients with PN-cholestasis, dyslipidemia, or both. This trial is registered at clinicaltrials.gov as NCT00910104.

Comparison of 5 intravenous lipid emulsions and their effects on hepatic steatosis in a murine model

BACKGROUND

Plant-based intravenous lipid emulsions have been shown to contribute to parenteral nutrition-associated liver disease (PNALD). There is mounting evidence that fish oil-based emulsions may prevent this liver injury. This study compares 5 emulsions with different fat compositions and their effect on hepatic steatosis, one of the first hits in PNALD.

METHODS

C57BL/6J mice were placed on a fat-free diet and randomized into 5 equal groups. Each group received one of the commercially available intravenous lipid emulsions (Intralipid [Baxter/Fresenius Kabi, Deerfield, Ill], Liposyn II [Hospira Inc, Lake Forest, Ill], ClinOleic [Baxter/Clintec Parenteral SA, Cedex, France], SMOFlipid [Fresenius Kabi, Bad Homburg, Germany], or Omegaven [Fresenius Kabi Deutschland GmbH]) or normal saline. Liver enzymes, degree of steatosis, and fatty acid compositions were analyzed after 19 days.

RESULTS

Intralipid, Liposyn II, ClinOleic, and SMOFlipid groups all demonstrated moderate steatosis with hepatic fat contents of 17.4%, 21.9%, 22.5%, and 12.6%, respectively. Omegaven mice, however, had normal livers. Saline control mice developed biochemical evidence of essential fatty acid deficiency (EFAD). Lipid supplementation with Intralipid, Liposyn II, and Omegaven prevented the onset of biochemical EFAD, whereas administration of ClinOleic and SMOFlipid did not.

CONCLUSION

The fish oil-based lipid emulsion Omegaven prevented hepatic steatosis and EFAD in this murine model. ω-3 fatty acids may be efficacious in preventing PNALD and should be explored in the development of novel lipid emulsions.

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.

Omega-3 fatty acid supplementation prevents hepatic steatosis in a murine model of nonalcoholic fatty liver disease

Prolonged use of total parenteral nutrition can lead to nonalcoholic fatty liver disease, ranging from hepatic steatosis to cirrhosis and liver failure. It has been demonstrated that omega-3 fatty acids are negative regulators of hepatic lipogenesis and that they can also modulate the inflammatory response in mice. Furthermore, they may attenuate hepatic steatosis even in leptin-deficient ob/ob mice. We hypothesized that omega-3 fatty acid supplementation may protect the liver against hepatic steatosis in a murine model of parenteral nutrition in which all animals develop steatosis and liver enzyme disturbances. For testing this hypothesis, groups of mice received a fat-free, high-carbohydrate liquid diet ad libitum for 19 d with enteral or i.v. supplementation of an omega-3 fatty acid emulsion or a standard i.v. lipid emulsion. Control mice received food alone or the fat-free, high-carbohydrate diet without lipid supplementation. Mice that received the fat-free, high-carbohydrate diet only or supplemented with a standard i.v. lipid emulsion developed severe liver damage as determined by histology and magnetic resonance spectroscopy as well as elevation of serum liver function tests. Animals that received an i.v. omega-3 fatty acid emulsion, however, showed only mild deposits of fat in the liver, whereas enteral omega-3 fatty acids prevented hepatic pathology and led to normalization of liver function tests. In conclusion, whereas standard i.v. lipid emulsions fail to improve dietary-induced steatotic injury to the liver, i.v. supplementation of omega-3 fatty acids partially and enteral supplementation completely protects the liver against such injury.

Vitamin E supplementation attenuates myointimal proliferation of the abdominal aorta after balloon injury in diet-induced hypercholesterolemic rabbits

The effects of vitamin E supplementation in a dose of 450 mg/1000 g chow on the myointimal proliferation of the abdominal aorta after balloon injury were studied in 4 groups of rabbits (24 each). The animals were fed regular diet, regular diet plus vitamin E, 1% cholesterol-enriched diet, and 1% cholesterol-enriched diet plus vitamin E. Each animal underwent a balloon injury of the abdominal aorta and left common iliac artery after 2 weeks of feeding. The animals remained on their respective diets thereafter. In 8 balloon-injured and 8 sham-operated animals of each group, the abdominal aortas were harvested 3 days after the procedure for the analysis of prostacyclin and thromboxane A2 synthesis, thiobarbituric acid reactive substances (TBARS) levels, enzyme activities of glutathione reductase (GR) and glutathione peroxidase (GP) as well as reduced (GSH) and oxidized (GSSG) glutathione levels, 3H-thymidine uptake, cholesterol as well as vitamin E contents. In the other 8 balloon-injured rabbits of each group, the tissue was harvested 3 weeks later for the morphometric study. In dependent of high cholesterol feeding, the vitamin E-treated rabbits had lower aortic production of thromboxane B2, higher 6-keto-PGF1 alpha and higher 6-keto-PGF1 alpha/thromboxane B2 ratios in both procedures. The aortic TBARS levels of the rabbits treated high cholesterol alone were significantly higher than the other three groups in both procedures. Balloon injury had a trend to increase TBARS levels and had significantly higher 3H-thymidine uptake (each p < 0.001) than sham operation in each group. Vitamin E supplement to high cholesterol diet or regular chow reduced aortic TBARS levels (p < 0.005 and 0.01, respectively) and 3H-thymidine uptake (p < 0.05 and 0.01, respectively), as well as attenuated myointimal proliferation of the abdominal aorta and left common iliac artery after balloon injury; but only supplement to high cholesterol diet reached statistical significances (both p < 0.05 compared to rabbits fed high cholesterol alone). These results suggest that vitamin E supplement changes prostanoid metabolism to a favorable pattern and reduces lipid peroxidation of the abdominal aortic wall, thus attenuates myointimal proliferation after balloon injury; these presentations are particularly obvious in diet-induced hypercholesterolemic rabbits.

Microcirculation, vitamin E and omega 3 fatty acids: an overview

We have observed significant increases in LDF and similar trends for CBV after FO supplementation in younger subjects (both normolipidemic and hyperlipidemic). In elderly subjects, this trend appears to be reversed unless subjects are supplemented with higher doses of vit. E (100 IU/10 KG/day). Our mouse data suggest that dietary vit. E at 100 IU/Kg does not adequately protect against lipid oxidation in vivo or in vitro following an oxidative insult when mice are fed an 8% FO & 2% linoleic acid containing diet. It has been reported that FO significantly lowers triglycerides and VLDL-cholesterol (especially where subjects have higher initial triglyceride values) and tends to increase LDL-cholesterol and Apo-B100. These findings are all the more important because the oxidation of LDL from FO-supplemented subjects caused a time-dependent increase in the ability to facilitate albumin transfer which was not diminished following a 2 month washout (WO). Addition of vit. E to the FO supplement prevented this change. These data suggest that FO supplementation without sufficient vit. E may be deleterious to the vascular endothelium. The western fat blend supplement appeared to be protective with increased length of supplementation most likely due to increased MONO fatty acids which are resistant to oxidation; vit. E supplementation appeared to have little additional effect. Our combined studies, and those reported by others, suggest that in humans, increased peripheral microcirculatory flow is most likely due to changes in precapillary vascular tone i.e., vasodilation. It is also possible that subtle changes in each of the three variables i.e. blood pressure, blood viscosity and vascular tone when combined may contribute to the significant changes which we have noted as increased LDF or CBV after intervention with dietary n-3 fatty acids. We hypothesize that interactions between dietary fatty acids and vit. E alters the ratios of vasoconstrictive-platelet aggegatory/vasodilatory-antiplatelet aggregatory agents (TXA2 and endothelin/PGI2 and nitric oxide), the expression of adhesion molecules (P-selectin and E-selectin) and thereby directly influences the modulation of free radical mediated events between blood elements and the vascular endothelium. Fatty acids of the n3 series may alter these events by favoring the production of vasodilatory compounds and decreased expression of P and/or E-selectins, provided that these highly oxidizable lipids are protected by adequate antioxidants.

Fish oil supplementation attenuates myointimal proliferation of the abdominal aorta after balloon injury in diet-induced hypercholesterolemic rabbits

The effects of supplementing with fish oil on the myointimal proliferation of the abdominal aorta after balloon injury were studied in control and in rabbits fed a 1% cholesterol-enriched diet, with and without 10% fish oil supplementation. Twenty-one animals in each group underwent a balloon injury of the abdominal aorta and left common iliac artery after 2 weeks of feeding. The animals remained on their respective diets thereafter. In 7 balloon-injured and 7 sham-operated animals of each group, the abdominal aorta was harvested 3 days later for the analysis of prostanoids, malondialdehyde, superoxide dismutase activity, [3H]thymidine uptake, and cholesterol levels. In the other 7 balloon-injured rabbits of each group, the tissue was harvested 3 weeks later for morphometric study. The fish oil-treated rabbits had the lowest aortic production of thromboxane B2 levels and the highest 6-keto-PGF1 alpha/thromboxane B2 ratios among the three groups after balloon injury. The aortic malondialdehyde levels of the cholesterol-fed rabbits were significantly higher than the other two groups (each P < 0.001) independent of balloon injury. The myointimal proliferation of the abdominal aorta and left common iliac artery in the fish oil-treated rabbits was less severe than in the cholesterol-fed animals (both P < 0.001) and was comparable with the controls. These results suggest that a fish oil supplement changes prostanoid metabolism to a favorable pattern and reduces lipid peroxidation on the abdominal aortic wall, thus attenuating myointimal proliferation after balloon injury in diet-induced hypercholesterolemic rabbits.

Effects of fish oil supplementation on the changes in myocardial cyclic adenosine monophosphate, inositol 1,4,5-triphosphate and mitochondrial calcium levels during acute coronary occlusion-reperfusion in cholesterol-fed rabbits

We studied the changes in myocardial second messengers and mitochondrial calcium levels during acute coronary occlusion-reperfusion in New Zealand white male rabbits fed a high cholesterol diet with or without fish oil supplementation. Group I, control rabbits, were fed a standard laboratory rabbit chow. In addition to the standard chow, Group II rabbits received a 1% cholesterol-enriched diet for 2 weeks, while Group III rabbits were fed a 1% cholesterol and 10% fish oil supplemented diet for 2 weeks. Acute coronary occlusion for 10 min or 1 h was induced by ligating the marginal branch of the left circumflex coronary artery. The vessel was then reperfused for 1 or 4 h in short- and long-term ischemia studies respectively. In the short-term ischemia study, myocardial samples taken from the cholesterol-fed rabbits had the highest cyclic adenosine monophosphate, inositol 1,4,5-triphosphate and mitochondrial calcium levels among the normal (nonischemic) and the ischemic areas of the three groups. The cholesterol and fish oil treated rabbits significantly suppressed the elevation of cyclic adenosine monophosphate (P < 0.05 compared with the cholesterol-fed rabbits in normal and ischemic areas respectively), but did not significantly attenuate the elevation of inositol 1,4,5-triphosphate and calcium levels. In the long-term ischemia study, the cholesterol-fed rabbits had the highest levels of these three messengers among the normal areas. However, only inositol 1,4,5-triphosphate level reached statistical significance (P < 0.05 compared with control). This group of rabbits had the lowest level of cyclic adenosine monophosphate, but the highest inositol 1,4,5-triphosphate and calcium levels among the ischemic areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Fish oil supplementation attenuates free radical generation in short-term coronary occlusion-reperfusion in cholesterol-fed rabbits

We studied the changes in lipid peroxidation and prostanoid metabolism in short-term coronary occlusion-reperfusion in controls and those rabbits (11 in each group) fed a 1% high cholesterol diet with or without 10% fish oil supplementation for one week. Acute coronary occlusion for 10 minutes was induced by ligating the marginal branch of the left circumflex coronary artery. The vessels were then reperfused for 1 hour. The cholesterol and fish oil treated rabbits had the lowest malondialdehyde levels both in the ischemic and non-ischemic (normal) areas, the least increase of malondialdehyde level in the ischemic area, and the highest 6-keto-PGF1 alpha/thromboxane B2 ratio in the non-ischemic area after reperfusion among the 3 groups. These rabbits had the highest myocardial superoxide dismutase levels both in the ischemic and normal areas, and the least decrease of superoxide dismutase level in the ischemic area. These data suggest that rabbits fed a high cholesterol diet with fish oil supplementation had an attenuated lipid peroxidation, which reflected a reduced free radical generation during a short-term coronary occlusion followed by reperfusion.