BACKGROUND OF THE INVENTION Several disease states are characterized by an increase in gut permeability.

Examples of such disease states include colitis, Crohn's disease, irritable bowel syndrome, celiac disease, starvation, cystic fibrosis, necrotizing enterocolitis and gut damage resulting from chemotherapy and radiation treatment. Moreover, food allergies in the premature infant and/or an immature gut is associated with a higher permeability predisposing the infant to aberrant nutrient absorption and translocation of endotoxins and bacteria into the circulation.

Long chain PUFAs in enteral formulations or compositions are well known.

U. S. Patent No. 4,670, 285 discloses a specific fat blend suitable for use in infant formulations. The fat blend contains at least one C20 or C22 n-6 fatty acid and one C20 or C22 n-3 fatty acid. The C20 or C22 n-6 fatty acid is present in a total amount of about 0. 13 to 5.6% by weight of all fatty acids in the composition. The C20 or C22 n-3 fatty acid is included in a total amount of about 0. 013 to about 4.44% by weight of all fatty acids in the composition. This patent discloses the use of egg lipids to supply the fatty acids.

U. S. Patent No. 4,918, 063 discloses formulations containing mixtures of phospholipids and neutral lipids for the prevention or treatment of ulcers and inflammatory bowel disease. This patent discloses a mixture of saturated or unsaturated phospholipids, together with saturated or unsaturated triglycerides and/or sterols as providing ulcer protection in experimental animal models.

PCT International Publication No. W096/10922 discloses a fat mixture for infant formula characterized in that arachadonic acid and docosahexanoic acid are present in the form of phospholipids.

European Patent Application No. 0376628 B 1 discloses an all vegetable oil fat blend which utilizes randomized palm oil or randomized palm olein oil as the sole palmitic acid oil source. It is disclosed that the compositions are particularly useful in infant formulas particularly for preterm or low birth weight infants.

SUMMARY OF THE INVENTION The present invention is directed to methods for maintaining gut integrity and enhancing the restitution of gut integrity in an individual in need thereof, comprising administering to the individual a formulation comprising at least one n-6 poly- unsaturated fatty acid in combination with at least one n-3 polyunsaturated fatty acid, to formulations for use in the method comprising an effective amount of at least one n-6 polyunsaturated fatty acid in combination with at least one n-3 polyunsaturated fatty acid, and the to use of an effective amount of at least one n-6 polyunsaturated fatty acid in combination with at least one n-3 polyunsaturated fatty acid in the manufacture of a medicament for use in maintaining gut integrity and enhancing the restitution of gut integrity in an individual in need thereof.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 compares plasma endotoxin levels in rats supplemented with the formulation of the invention to rats that have not been supplemented.

Figure 2 shows the effect of the present formulation on intestinal PLA2 mRNA expression levels.

Figure 3 shows the effect of the present formula on intestinal PAF-receptor levels in RNA.

DETAILED DESCRIPTION OF THE INVENTION The polyunsaturated fatty acids useful in the present invention include fatty acids of twenty carbons or more having at least two carbon-carbon double bonds.

The number and position of double bonds in the fatty acids are designated by the

nomenclature conventionally used. For example, arachidonic acid has a chain length of 20 carbon atoms and 4 double bonds beginning at the sixth carbon from the end of the molecule. Accordingly, arachidonic acid is referred to as C, (, : 4 n-6. Similarly, docosahexanoic acid has a chain length of 22 carbon atoms with 6 double bonds beginning at the third carbon from the end of the molecule and is designated C,,: 6 n-3.

Preferably, the n-6 polyunsaturated fatty acid used in the present invention is arachidonic acid and the n-3 polyunsaturated fatty acid used in the present invention is docosahexanoic acid.

The method of the present invention comprises administering to an individual having one or more disorders characterized by cell damage or destruction to gut tissue an effective amount of a formulation containing at least one n-6 polyunsaturated fatty acid and at least one n-3 polyunsaturated fatty acid. Effective amounts of the n-6 polyunsaturated fatty acid is about 5 to 61 mg and preferably 10 to 51 mg/kg body weight. Similarly, effective amounts of the n-3 polyunsaturated fatty acid is about 5 to 61 and preferably 5 to 51 mg/kg body weight. The effective arachidonic acid: docosahexanoic acid ratio is about 1: 1 to 2.5: 1, and preferably 1: 1 to 2: 1. This is based on administration of 100 kcal/kg/day for a 1 kg infant.

In order to achieve the effective amounts of n-6 and n-3 polyunsaturated fatty acid indicated above, the formulations used in the present method should comprise about 4 to about 50, and preferably about 8 to about 41 mg/100 ml of polyunsaturated fatty acid. The formulations used in the present method should comprise about 4 to about 50, and preferably about 4 to about 41 mg/100 ml of the n-3 polyunsaturated fatty acid. Again, the effective arachidonic acid: docosahexanoic acid ratio is 1: 1 to 2.5: 1 and preferably 1: 1 to 2: 1.

The present invention is directed to methods for maintaining gut integrity and enhancing the restitution of gut integrity, to formulations for use in for maintaining gut integrity and enhancing the restitution of gut integrity and to the use of an effective amount at least one n-6 polyunsaturated fatty acid in combination with at least one n-3 polyunsaturated fatty acid in the manufacture of a medicament for use in for maintaining gut integrity and enhancing the restitution of gut integrity. Gut integrity is compromised in a number of disease states which increase gut

permeability, cause cell damage or destruction in the gut and cause bacterial translocation in the gut which may lead to endotoxemia. Disease states which compromise gut integrity in this manner include colitis, Crohn's disease, irritable bowel syndrome, celiac disease, starvation, cystic fibrosis, damage resulting from chemotherapy and radiation treatment and food allergies. In the premature infant, the immature gut is also associated with higher permeability which predisposes the infant to aberrant nutrition absorption and translocation of endotoxin and bacteria into the circulation. The present formulation is administered enterally to both adults and infants.

A preferred embodiment of this invention is a method or formulation for maintaining and enhancing the restitution of gut integrity in infants, particularly preterm infants. This method comprises enterally administering to the infants a nutritionally complete infant formula comprising proteins, carbohydrates, lipids and effective amounts of at least one n-6 polyunsaturated fatty acid and at least one n-3 polyunsaturated fatty acid.

The term'infant formula'will be readily recognizable to those skilled in the art. When diluted or reconstituted, if initially in concentration or powder form, to the ready to feed state, a typical infant formula will comprise about 60-110 grams of carbohydrates per liter, 10-35 grams of protein per liter, and 20-50 grams of lipid per liter, as well as vitamins, minerals, fibers, emulsifiers, etc. To such an infant formula is added the appropriate amounts of n-6 and n-3 polyunsaturated fatty acid to maintain and enhance the restitution of gut integrity in the infant in need of treatment.

Examples of suitable, commercially available infant formula to which the n-6 and n-3 polyunsaturated fatty acid may be added include S-26, S-26 LBW and SMA available from Wyeth Nutritionals International.

Specific examples of fat blends containing appropriate amounts of n-6 and n-3 polyunsaturated fatty acids according to the present invention are set forth below:

Fat Blend 1 Fatty Acid Fatty Acid % C6: 0 Caproic-- C8: 0 Caprylic 9.1 C 10: 0 Capric 6. 1 C12: 0 Lauric 10.3 C14: 0 Myristic 4.6 C14: 1 Myristoleic-- C16: 0 Palmitic 13.5 C16 : 0 at sn-2 % of Palmitic C16: 1w7 Palmitoleic C18: 0 Stearic 4. 8 C18: lw9 Oleic 32.3 C18: 2w6 Linoleic 15.9 C18: 3w3 Linolenic 1.7 C20: 0 Arachidic 0.3 C20: 2w6-- C20: 3w6-- C20: 4w6 Arachidonic 0. 6 C22: 0 Docosanoic 0.3 C22: 6w3 Docosahenxaenoic 0.4 C24: 0 Total 100

Fat Blend 2 <BR> <BR> FattyAcidFattyAcid C6: 0 Caproic 0. 35 C8: 0 Caprylic 9. 87 C10: 0 Capric 4. 63 C12: 0 Lauric 6. 4 C14: 0 Myristic 2. 46 C14: 1 Myristoleic 0. 02 C16: 0 Palmitic 13. 43 C16: at sn-2 % of Palmitic 39.0 C16: 1w7 Palmitoleic 0. 03 C18: 0 Stearic 2. 61 C18: 1w9 Oleic 39. 39 C18: 2w6 Linoleic 13. 94 C18: 3w3 Linolenic 1. 29 C20:0 Arachidic 0.01 C20: 2w6 0. 01 C20: 3w6 0. 02 C20: 4w6 Arachidonic 0. 61 C22: 0 Docosanoic 0. 3 C22: 6w3 Docosahenxaenoic 0.38 C24: 0 0. 02 Total 100

Specific examples of infant formula suitable for use in the present invention are set forth below: Infant Formula A Ingredients % Water Lactose Nonfat Dry Milk 2.83 Whey Powder 2.83 Maltodextrin 4.45 Fat Blend 4.11 Vitamins 0.02 Minerals 0.25 Taurine (). 01 Infant Formula B Ingredients % Water 57.77 Skim Milk (liquid) 29.49 Whey Protein Concentrate 2.76 Lactose 1.16 Maltodextrin 4.35 Fat Blend 4.15 Vitamins 0.03 Minerals 0.28 Taurine 0.01 100.00 The present invention will now be illustrated with reference to the following specific example.

EXAMPLES The method of the present invention was tested in a neonatal rat model of hypoxia induced gut injury. Reduced gut permeability is associated with reduced endotoxemia and a lowered intestinal phospholipase-2 (PLA) gene expression.

Lower PLA, expression levels is indicative of a down-regulation of the inflammatory cascade.

Animal Model. Rat pups were delivered via abdominal incision from time- dated pregnant Sprague-Dawley rats on the 21st day of gestation. The newborn rats were fed via the orogastric route 0. 1 ml of formula (S26-LBW formula, available from Wyeth Nutritionals International, Burlington, VT) every three hours with the volume advanced as tolerated up to 0.4 ml by 72 hours of life. In addition, animals were stressed with asphyxia twice daily by breathing 100% nitrogen gas for seconds and then cold exposure to 4°C for 10 minutes. Using this protocol, 70-80% of animals develop abdominal necrosis by the 3rd to 4th day of life as described in Caplan, M. S.; Hedlund, E.; Adler, L.; and Hsueh, W.,"Role of Asphyxia and Feeding in a Neonatal Rat Model of Necrotizing Enterocolitis,"Pedatr. Pathol., 14: 1017-1028 (1994).

Treatment Groups. There were 2 treatment groups: preterm formula (Formula A) and preterm formula with LCPUFAs (Formula B). The LCPUFAs added to Formula B were arachidonic acid and docosahexanoic acid. The LCPUFAs were added in the following amounts: 20 mg/100kcal docosahexanoic acid and 30 mg/100 kcal arachidonic acid. The first component of the study examined gut damage which was confirmed at time of necropsy by gross examination and histopathology. Gross examination and histopathology characterized changes in gut damage, maturity and integrity. The second component of the study investigated the mechanisms underlying changes in gut damage, maturity and integrity. The following outcome variables were measured: endotoxemia and PLAT.

Gut Damage. Following euthanasia, the intestines were evaluated by gross inspection and histologic evaluation for confirmation of gut damage and maturation.

Endotoxemia. Plasma endotoxin was assessed using a spectrophotometric method provided in a Limulus Amebocyte Lysate (LAL) assay commercially available from Biowhittaker, Walkersville, MD.

Phospholipase A, mRNA expression. To quantitate PLA2 mRNA expression, competitive PCR was performed using mRNA recovered from intestinal homogenate.

Serial dilutions of cRNA were added to intestinal RNA and the PCR reaction was performed using standard conditions previously described. Products were run on an agarose gel and then quantified using phosphorimaging density.

Statistics. Differences between groups of ordinate data were compared using Chi-square analysis using Yates'correction. Differences between continuous variables were compared using the Student-t test or analysis or variance where appropriate. P < 0. 05 was considered significant.

Supplementation with LCPUFAs reduced the incidence of ischemic gut damage (ischemic gut damage: 17/24 control vs. 8/24 LCPUFA, p = 0.031 using 3x2 chi-square) compared to the formula without LCPUFAs in neonatal rats (see Table 1). Animals developed symptoms of intestinal injury typically between 48 and 72 hours of life, and included abdominal distention, discoloration of the anterior abdominal wall, bloody stools, and respiratory distress.

Table 1 Effect of formula supplementation on reducing ischemic gut damage* Formula Ischemic Gut No Ischemic Gut I. D. Damage Damage A 17 7 B 8 16 *P =. 031 As seen in Figure 1, plasma endotoxin levels measured between 48-72 hours showed that LCPUFA supplemented rats had lower plasma endotoxemia (25 4 EU/ml) than the unsupplemented rats (276 39 EU/ml). Figure 2 demonstrates that Intestinal PLA2 mRNA expression was significantly lower among LCPUFA supplemented rats (0.41 + 0.09 molecules/gm tissue) as compared to unsupplemented rats (0.68 0.11 molecules/gm tissue). Moreover, intestinal PAF receptor mRNA expression was also lower among LCPUFA supplemented rats, 1.5 _ 0. 3 vs. 2.1 0.2 (Figure 3).

The results demonstrate that LCPUFA supplementation reduces gut injury in an established neonatal rat model of ischemic gut damage. Furthermore, the data demonstrate that the beneficial effect of LCPUFA supplementation includes reduced gut permeability. The reduced gut permeability was associated with a reduction in endotoxemia. Endotoxemia is a result of bacterial and/or endotoxin translocation across the gut into the systemic circulation. Concurrent lower expressions of intestinal PLA2 mRNA and PAF receptor mRNA were indicative of a reduced endotoxin induced inflammatory response.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.