Triglyceride Preparations for the Prevention of Catabolism

This invention relates to triglyceride preparations for enteral administration to prevent catabolism and to increase protein synthesis in subjects undergoing severe metabolic stress.

Under normal nutritional and physiological conditions, fuel requirements of the body are largely met by glucose and fatty metabolism. The body's amino acids generally contribute little towards overall fuel economy at these times. However, during abnormal metabolic stress states induced by trauma or sepsis, fat mobilization and utilization and glucose utilization are relatively decreased due to hormonal changes precipitated by the stress. Under these conditions, an extremely high and rapid rate of muscle protein catabolism occurs.

Over the last several years, investigators have studied the metabolic consequences of trauma in man. Most of these studies concerned themselves with understanding cause and effect, as it related to biochemistry and metabolism, and subsequent physiological responses. Investigators have found for example that large (e.g. 25%) body surface area burns increase basal energy expenditure as much as two fold. The release rate of peripheral amino acids also increases approximately 3-4 times under similar traumatic conditions. These changes, if persistent, may result in protein malnutrition, alterations in essential organ functions, and, finally, multiple organ failure. For these reasons most clinicians have recommended intensive nutritional therapy for the severly injured or burned patient.

Wilmore D. W. "Panel Report on Nutritional Support of Patients with Trauma or Infection", Am. J. Clin. Nutr., 34: 1213-22, 1981, has suggested that exogenous glucose administration at intakes exceeding energy expenditure may be of little benefit in severely stressed patients. An already abundant supply of glucose is present in these patients due to their hyperglycemic state. Elevated insulin levels associated with the hyperglycemia appear to reduce the availability of free fatty acid by limiting lipodysis.

Wannenmacher, R. W., Kaminski, M. V., "Use of Lipid Calories During Pneumoccal sepsis in the Rhesus Monkey. J.P.R.N. Nut. 6: 100-105, 1982, have suggested the energy needs of stressed patients may be optimally provided when fat is incorporated into the parenteral regimen. However, controversy exists over the value of lipid emulsions because their use has been implicated in Reticulo Endothelial System (RES) system blockage, increased prostaglandin production and development of Acute Respiratory Distress Syndrome (ARDS). These complications have been thought to be a result of reduced clearance of lipid chylomicrons as well as the high percentage of polyunsaturated fatty acids and arachidonic acid precursors in the lipid source.

Moreover, controlled trials in injured laboratory animals with triglyceride emulsions containing medium chain fatty acids exclusively, have failed to show any benefit for sparing body protein although the RES blockage is minimized by MCT emulsion over current long chain triglyceride emulsions.

This invention provides medium chain and long chain fatty acids chemically synthesized into structured triglycerides (lipids) for enteral administration as the lipid calorie source, in subjects undergoing severe metabolic stress.

The structured lipids of this invention have a random distribution of medium chain fatty acids (C.sub.6-12 acid) and long chain fatty acids (C.sub.14-24 acid). They may be represented by the following formula, ##STR1##

Wherein R.sub.1, R.sub.2, and R.sub.3 may be independently a C.sub.6 to C.sub.24 acid, provided that one of R.sub.1, R.sub.2 or R.sub.3 is a C.sub.12 acid, and one of R.sub.1, R.sub.2 or R.sub.3 is omega 6 or omega 3 acid such as, C.sub.18 " or a C.sub.18 "' acid.

C.sub.18 " and C.sub.18 "' represent the number of double bonds in the fatty acid moiety being one, two and three double bonds respectively.

The structured lipids of this invention may in general be prepared by any suitable process known in the art such as direct esterification, rearrangement, transesterification, displacement and the like. For example, the structured lipids may be prepared by the rearrangement of a vegetable oil such as coconut oil with a long chain triglyceride oil such as soybean oil.

The medium chain fatty acids used in the preparation of the structured lipids of this invention may be obtained from a vegetable oil such as kernel oils having a high lauric (C.sub.12) acid content. Such oils include balassu oil, coconut oil, cohune oil, palm kernel oil, tucum oil and fractions thereof. The preferred vegetable oil is coconut oil.

The long chain fatty acids used in the preparation of the structured lipids of this invention may be polyunsaturated vegetable oils such as, corn oil, peanut oil, safflower oil, soybean oil, sunflower seed oil, and fish oils. The preferred long chain triglyceride oils are safflower oil, soybean oil, and sunflower seed oil.

Preferably, the percent composition mixtures of medium chain triglyceride oil to long chain triglyceride oils used in the preparation of the structured lipids of this invention may be 70 to 30%, 80 to 20%, 85 to 15%, or 90 to 10%. The 80 to 20% and the 85 to 15% mixtures are most preferred.

Typically, the structured lipids of this invention may be prepared from mixtures of coconut oil and soybean oil, which lipids may have the following fatty acid carbon chain length (CCL) composition.

The present invention provides enteral preparations for use in stressed patients to prevent catabolism and to increase protein synthesis. The preparations provide from about 15 to 85% of the fat calories required in the stressed patient.

Typically, the compositions of this invention provide in a 70 Kg man, from about 0.3 gms of fat/Kg of body weight/day to about 4.0 gms of fat/Kg of body weight/day.

The lipid compositions are preferably administered with additional amino acids, vitamins and minerals as required. Modified amino acid formulas specifically designed for stressed subjects are preferred. The amino acids, vitamins and minerals can be administered in the same solution as the structured lipids or separately. It is preferred that the component groups be separately packaged to facilitate tailoring the diet to the patients specific needs.

In addition to the above, the formulations may include preservatives or stabilizers, as required.

The following examples further illustrates the present invention but are not meant to be limiting.

FIG. 1 is a comparison of the oxidation rate of medium chain triglyceride (MCT), a structured lipid of this invention (710A), and a long chain triglyceride (LCT);

FIG. 2 is an Experimental Protocol for Example II.

In this example, a structured lipid preparation of this invention is compared with a medium chain lipid, and a long chain lipid for the oxidation of lipids in traumatized animals.

In this test, 18 male Sprague-Dawley rats were housed in suspension cages and allowed free access to food and water. When a proper weight of 200 grams was attained, the animals received a 25% full thickness scald burn on the dorsum for 15 seconds, under diethyl ether anesthesia. The rats were then returned to their cages and fasted overnight, but allowed to drink tap water ad libitum. On the day of the study, the animals were randomized into one of three groups to receive a 25 Kcal/Kg body weight intragastric bolus injection of lipid containing 5 u Ci (microcuries) of labeled oil.

Group I: a 20% medium chain lipid emulsion composed of 72.5% capric acid (C 8:0) and 27.5% coprylic acid (C 10:0) (obtained from Travenol Laboratories, Inc; Deerfield, Ill.).

Group II: a 20% long chain triglyceride emulsion (20% Travamulsion.RTM., Travenol Laboratories)

Group III: a 20% lipid emulsion composed of structured triglycerides obtained by rearrangement from 80% coconut oil and 20% soybean oil. Captex 710A Lot No. KH4022A (Capital City Products Co., Columbus, Ohio)

Immediately following the bolus administration of the lipid source, the rats were placed in metabolic chambers that permitted the collection and analysis of their expired breath. At 15 minute intervals for twelve hours, the specific activity of expired carbon dioxide was determined. At the end of the study, the animals were sacrificed.

The results are shown in FIG. 1. This shows the appearance of C.sup.14 O.sub.z after intragastric administration of 3.0 gm/Kg of fat in stressed rats. The results are an average of 6 rats per group.

The results show the structured lipids of this invention have an oxidation rate that falls between the medium chain triglycerides and the long chain triglycerides. Such structured lipids should be preferable and suitable for both enteral and parenteral nutrition.

In this example, a structural lipid (SL) preparation of this invention (Captex 710A) was compared with a medium chain lipid (MCT), and a long chain lipid (LCT), for the effect of total enteral nutrition on protein metabolism in thermally injured rats.

In this test, 27 male Sprague-Dawley rats were housed in suspension cages and allowed free access to food and water. When a proper weight of 200 grams was attained, the animals received a 25% full thickness scald burn on the dorsum for 15 seconds, under diethyl ether anesthesia. The rats were then returned to their cages and fasted overnight, but allowed to drink tap water ad libitum. At the start of the three day study, the animals were randomized into one of the three groups to receive a 50 ml/day entral lipid emulsion containing 50 Kcal, 2 g amino acids (AA), and 40% nonprotein calories as lipids.

The details of the test and the results are shown in tables 1 to 8.

Liver protein synthesis (PS, umol leu g day) and liver fractional synthetic rate (FSR, % day) were estimated using a 4 hr. constant intravenous infusion of [1-14c] leucine on day 3.

Mean values for cumulative nitrogen balance (CNB, mgN/day 2 and 3), serum albumin (SA, g/dl), liver fractional synthetic rates (FSR) and liver protein synthesis (PS) are summarized in the table below:

The structural lipid of this invention showed greater cumulative nitrogen balance, liver fractional synthetic rate andliver protein synthesis than the long chain triglyceride or the medium chain triglyceride.

These data show that the enteral use of the structured lipid has significant nutritional advantages over the enteral use or conventional lipids in cases of severe metabolic stress.

The experimental protocol is shown in FIG. 2.