CA1318593C - Nutritional fluids containing triacetin - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method of providing parenteral nutrition to a human is disclosed which comprises administering an infusion thereto containing a nutritionally effective amount of triacetin, and optionally, of glucose and amino acids.

Description

~ 3 ~

NUTRITION~L FLUIDS CONTAINING TRIACETIN

Background of the Invention Intravenous infusion is a well established and widely accepted method to provide exogenous nutrients and to reduce negative nitrogen balance during the catabolic states of sepsis, trauma or surgery. Intra-venous administration of calories, nitrogen and other nutrients in sufficient quantities to achieve tissue synthesis and anabolism is called total parenteral nutrition t"TPN").
TPN is indicated in patients who are unable to ingest food due to gasterointestinal obstruction or extensive burns; patients who refuse to eat, as in the case of depressed geriatrics or young patients suffer-ing from anorexia nervosa; and surgical patients who cannot be fed enterallyO Likewise, enteral feedings are indicated for patients who cannot be fed orally, and are administered either via an intestinal port or a catheter.
Presently available lipid preparations useful for parenteral or enteral nutrition are aqueous emul-sions of long- or medium-chain triglycerides ("lipids"). Medium-chain triglycerides are glycerol esters of (C6-Clo) fatty acids, while long-chain triglycerides are (Cl2-Clg) fatty acid esters o~ gly-cerol. Rapid administration of long-chain lipid emul-sions can lead to the "fat overload" syndrome in which lipid droplets accumulate in tissues such as the lung 3~ and liver. In addition, lipids are usually admini-stered separately from other non-lipid nutrients, such as glucose and amino acids, thus complicating the feeding methodology.
Experimental lipid preparations incorporating shorter chain length organic acids, such as tributyrin and trioctanoin, have been shown to reduce fat accumu-lation in various tissues, but these materials exhibit :1 3 ~ 3 substantial neurotoxicity and unfavorable effects on amino acid metabolism. Samson et al., J. Clin.
Invest., 35, 1291 (1956) found that the ability of medium-chain fatty acids to produce narcosis increases as the chain length of the fatty acid decreases. The administration of a medium-chain triglyceride emulsion to dogs resulted in unconsciousness and lethargy. See S. K. Young et al., Fed. Proc., 43, 865 (1984) and J.
Miles et al., Clin. Res., 31, 243A (1983). In addi-lû tion, isocaloric infusions of medium-chain triglycer-ides may lead to lactic acidosis.
Therefore, a need exists for a lipid source which is readily adaptable for TPN or total enteral nutrition, e.g., which is effective as an energy source and compatible with sugars and other nutrients, while avoiding undesirable side effects such as hepatic steatosis and neurotoxicity.

Summarv of the Invention The present invention is directed to a method of providing parenteral nutrition to a human comprising administering an infusion of an aqueous solution con-taining a nutritionally-effective amount of triacetin (1,2,3-triacetylglycerol) to said human. Despite the variety of harmful side effects observed during the administration of long~chain and medium-chain trigly-cerides to animals and human subjects, the administra-tion of greater than isocaloric amounts of triacetin to dogs could be accomplished without apparent toxicity.
The administration of triacetin may also have favorable ; effects on branched-chain amino acid and ketone body i metabolism. In dogs, it increased ketone body produc-~ tion, thus providing an alternate fuel for central ner-j vous system tissue, and at hypercaloric rates, reduced the oxidation rate of leucine by about 50%.

~3:~8~c'g Furthermore, it has been suggested that the administration of acetate, which is widely used in its ionic form in hemodialysate and parenteral nutrition solutions, results in sequestration of inorganic phos-phate, pyrophosphate and calcium in organs that meta-bolize acetate. However, it was surprisingly found that the administration of isocaloric amounts of triacetin to dogs had no significant effect upon the serum levels of calcium, phosphorus or on blood p~l.
In contrast to the long-chain fatty acids derived from the long-chain triglycerides presently employed to supplement parenteral nutrition, the short-chain fatty acid acetate derived from triacetin is not reesterified during metabolism, but rather, is oxidized in an obligatory fashion. Since accumulation of fat in tissues such as the liver (hepatic steatosis) is a major complication of parenteral nutrition, the use of a non-reesterifiable lipid source can potentially reduce this risk. The risk of hepatic steatosis would also be reduced indirectly by reducing the need for glucose in a given TPN mixture, since high rates of glucose administration have also been implicated in the pathogenesis of hepatic steatosis. When used in enteral formulae, triacetin may reduce the incidence of diarrhea observed with long-chain triglyceride-containing enteral formulae.
The water-solubility of triacetin provides a further advantage with respect to its use for paren-teral nutrition, since the problems associated with the ` 3û instability of aqueous emulsions of long- or medium-chain triglyceride are eliminated. Also, the miscibil-ity of triacetin with aqueous solutions of glucose and amino acids permits the preparation of a "three in one"
nutrient that would be more economical and that would simplify the administration of TPN~

~ 3 ~ 3 Therefore, the present invention is also directed to an aqueous solution comprising triacetin and glucose, wherein the triacetin and the glucose are present in a combined amount effective to provide the daily caloric requirement for a human patient when parenterally administered thereto for about 24 hours or less. For example, these solutions can contain about 10-30 wt-% glucose in cornbination with about 1-7%
triacetin. Lower concentrations of glucose can also be employed, so that the majority of the patient s caloric requirements are provided by triacetin.
When formulated for use as TPN fluids, these triacetin-glucose solutions can also contain a source of amino acids and effective amounts of electrolytes and/or vitamins. The normal daily calorlc requirement for an adult is usually in the range of 1500-2000K per day. Therefore, as used herein, the term "a nutrition-ally-effective amount" of triacetin, glucose, or the like is intended to mean that a significant proportion (>10-20%) of the patient's daily caloric requirement can be satisfied by the intravenous or enteric admi-nistration of these nutrients. As disclosed hereina-bove, it is believed that the parenteral administration of aqueous solutions of triacetin will be able to satisfy a significant proportion (up to about 40-50%), of the total caloric requirement of a patient on TPN, thus reducing the need to use glucose or other sugars in TPN solutions.

Brief Description of the Fiaure Figure 1 is a graphical depiction of the serum calcium, magnesium and phosphate concentrations in mongrel dogs (n=6) before and during an intravenous infusion of triacetin.

~ 3 ~ 3 Detailed Description of the Invention -Triacetin (glyceryl triacetate, Merck 9407) is commercially available in high purity. (Sigma Chemical Company9 St. Louis, M0) and can readily be dissolved to the desired concentration in water under aseptic con-ditions. Aqueous solutions of glucose (dextrose) are also commercially available, e.g., a 50% aqueous glu-cose solution is available fxom 3ristol Laboratories, Syracuse, NY ~424-87).
The source of nitrogen in TPN ~luids is either protein hydrolysates tAmigenTM_-Travenol; AminosolTM--Abbott; CPH-5TM--Cutter; HyprotigenTM--McGaw) or crystalline amino acids (AminosynTM_ Abbott; FreAmine II --McGaw; TravasolTM_-Travenol; VeinamineTM--Cutter). Protein hydrolysates are obtained from casein or fibrin and contain polypeptides which must be broken down before they can be utili~ed. Although available at lower cost than crystalline amino acids, they con-tain hiqher amounts of ammonia and free chloride. The crystalline amino acid injections contain all the essential and nonessential amino acids in the L-form.
They are more expensive than the protein hydrolysates but contain less ammonia and free chloride. For opti-mum utilization of amino acids and for promoting tissue regeneration, the nitrogen-to-calorie ratio should be about 1:150.
Electrolyte requirements will vary with the individual patient. The electrolytes present in a commercially-available protein hydrolysate injection or ~0 amino acid iniection are identified on the label and must be taken into consideration in determining the quantities to be added. Usual electrolyte concentra-tion ranges are: sodium, 100-120 mEq; potassium, 80-120 mEq; magnesium, 8-16 mEq; calcium, 5-10 mEq;
chloride, 100-120 mEq; and phosphate, 40 60 mEq. It is 131~

preferred to keep a 1:1 ratio between sodium and chloride ion. If the combination of calcium and phosphate ion exceeds 20 mEq, precipitation can occur.
In addition to the electrolytes, the daily requirement of both water-soluble and fat-soluble vita-mins may be added, usually in the form of a multivita-min infusion concentrate. Iron, folic acid and vitamin B12 should be administered separately from the TPN
fluids. Trace elements such as zinc, copper, mangan-ese, chromium and selenium are usually added, althoughthey are a concern only in long-term use of TPN.
Essential fatty acids should also be provided, but can be administered topically, via m2ss2ge, thus eliminating the need for long-chain triglyceride emul-sion administration. Alternatively, they can be givenintravenously in small quantities once or twice a week.
Procedures for the preparation, packaging and administration of intravenous and TPN fluids are well known to the art and are extensively documented. For example, see Remington's Pharmaceutical Sciences, A.
Osol, ed., Mack Publishing Co., Easton, PA (16th Ed.
1980) at pages 1488-1497.
The rate of admini-stration of the nutrient solutions of the present invention will necessarily vary, and will depend upon factors such as the concentrations of the constituents included therein, the route of administration and the nutritional requirements of the subjec's to ~hom they are administered. Such factors can readily be deter-mined and adjusted by the physician in accord withaccepted clinical practices.
The invention will be further described by reference to the following detailed examples.

1~

~ 3 ~

Example I - Phosphorus, Calcium and Magnesium Metabolism A. Materials and Methods Triacetin was purchased from Sigma Chemical Company (St. Louis, MO) and diluted in water to a 5%
v/v solution for infusion. Plasma acetate concentra-tion was determined on a 571û A Hewlett Packard gas chromatograph (Palo Alto, CA). First, 10 ~1 of 10 mM
propionate (internal standard) was added to 100 ~1 of ice cold plasma, acidified with 2û ~1 2N HCl and vor-texed for 5 seconds~ The sample was then extracted with 100 ~1 oF ice cold fat extraction-grade diethyl ether (Mallinckrodt, Paris, KY) and centrifuged. One ~1 of the supernatant was injected onto a 183 cm, GP
; 15 10% SP-1200/1% H3P04 packed column (Supelco, Bellefonte, PA). Urine and serum samples were diluted with 0.14% lanthenum chloride for quantitation of calcium and magnesium on a Perkin Elmer 2380 atomic absorption spectrophotometer (Norwalk, CT) using 422.7 nm and 285.~ nm detection wavelengths, respectively.
Serum and urinary concentrations of phosphorus were determined on a microcentrifugal analyzer, Multistat III Plus (Instrumentation Lab, Lexington,-MA). Quanti-tation of ionized calcium was performed on an Ionized Calcium Analyzer ICAl (Radiometer, Copenhagen, Denmark) using unfrozen ser~lm within 1 hour of the completion of the study. Arterial blood pH and bicarbonate concen-tration were determined on a pH/Blood Gas Analyzer ~13 (Instrumentation Lab, Lexington, MA).
B. Triacetin Infusion Surgical procedures and subsequent experiments were performed after approval from and according to criteria established by the Animal Care and Use Com-mittee of the Mayo Foundation, ~ochester, MN, following ~ 3 ~ 3 the guidelines of the National Institutes of Health onthe humane use of laboratory animals. Under N20/halo-thane anesthesia, an indwelling medical grade silastic catheter was placed in the femoral artery of 6 female mongrel dogs (13-1~ kg), filled with heparin (1000 U/ml), and placed in a subcutaneous pouch so it could be accessed the day of the study. In addition, an epi-siotomy was performed to aid in catheterization of the bladder for urine collection during the study. The animals were allowed to recover from surgery for 10 days prior to study. The evening prior to study (2100 hours), the dogs were fed a high carbohydrate meal con-sisting of 16 ml/kg CompleatTM B (Sandoz Nutrition, Minneapolis, MN) and 7 g/kg PolycoseTM (Ross Labora-tories, Columbus, ûH), providing a total of 45 kcal/kg.
The day of the study, the animals were placedin a standing sling, and the arterial catheter was exteriorized under local anesthesia and flushed with 0.45% NaCl. A 16-gauge infusion catheter (Intracath, 2û Deseret, Sandy, UT) was placed in the right heart via a lateral saphenous vein, and was kept patent with a 40 ml/hr infusion of û.45~ NaCl. A Foley catheter was placed in the bladder for urine collection. A two-hour equilibration period preceded the l-hour baseline arterial blood sampling period to assure that the ani~
mals were resting comfortably. At the end of the base-line sampling period, infusion of triacetin was initiated at 47 ~mol-kg-lomin~l and continued for 3 hours. Arterial blood was sampled at 15-30 minute 3û intervals to the end of the study~ Urine was collected during the equilibration period and again during the triacetin pPriod. The fractional excretions of calcium, magnesium and phosphorus were calculated by the following equation: (urinary mineral concentration x serum creatinine concentration) (urinary creatinine ~ 3 ~

concentration x serum mineral concentration). All statistical comparisons were performed using a two-tailed paired t-test.

C. Results During the triacetin infusion, plasma acetate increased from 0.13+0.02 to 1~32+0.15 mmol/l at 30 minutes, and gradually declined thereafter to about 1.0 mmol/l over the last hour of' study (data not shown).
Serum concentrations of calc:ium, magnesium and phos-phorus are depicted graphically in Figure 1. Total serum calcium concentrations did not change during the study. Serum phosphorus increased slightly, but not significantly, from 4.7+0.4 to 5.3+0.3 mg/dl by the end of the study. In contrast, the serum magnesium con-centration decreased from 1.7+0.1 to 1.4+û.1 mg/dl (p<
0.001) by 9C minutes and remained at this level to the end of the study. Ionized calcium was measured in two of the animals and did not change during the triacetin infusion ~data not shown). The fractional excretion of calcium, magnesium and phosphorus did not change as demonstrated by the data summarized in Table 1.

Table 1 Fract onal Ion ~xcretion Prior to and After Triacetin Infusion*
Calcium Magnesium Phosphorus Before triacetin 0.45+0.19 5.00+0.78 8.32+2.04 After triacetin 0.30+0.12 4.52+0.52 7.56+1.92 Values are the mean of six animals + SE.
--8aseline blood pH (7.41+0.01) was not signifi-cantly different from the blood pH 150 minutes after the triacetin infusion began (7.39+0.û2)o The bicar-bonate concentration, however, decreased during the ~ 3 ~

study, from 20.9+0.51 to 18~8~0.68 mEq/dl (p<0.01).
The rate of triacetin infusion approximates the resting energy expenditure in the dog (about 70 kcal-kg-l-day-l). No significant effect on serum phos-phorus or calcium was observed.
These findings are not what one would predict from the data reported by Veech et al., in Myocardialand Skeletal Muscle ~ioenerqetics, N.
Brautbar, ed., Raven Fress, NY (1986) at pages 617-646.
In their studies9 intraperitoneal administration of sodium acetate to rats resulted in net hepatic uptake of 4-12 ~mol phosphate per gram of liver within 30 minutes. Assuming no net change in intracellular phosphate pools in non-hepatic tissues, such hepatic 15~ sequestration of phosphate would result in uptake of 35-100% of extracellular phosphate, and thence in significant hypophosphatemia. The slight (about 1~%) increase in serum phosphorus that was observed was not significant, although a relatively small number of ani-mals were studied. Furthermore, this change is in theopposite direction of what would be expected if large amounts of phosphate were taken up by the liver. In the same studies, Veech et al. found accumulation of calcium in the liver after intraperitoneal acetate administration. Again, the present data failed to demonstrate the change in serum calcium that might be expected if calcium were taken up rapidly by tissues.
Finally, administration of the sodium salt of acetate would be expected to induce a significant meta-` 30 bolic alkalosis, whereas arterial blood pH did notchange in the present studies.
In summary, an isocaloric infusion of the short-chain triglyceride triacetin in dogs resulted in modest increases in plasma acetate, but did not signi-ficantly affect serum calcium or phosphorus concentra-tions. Serum mannesium decreased bv about 20~.

13~.8~j~3 probably due to cellular uptake rather than accelerated excretion. Therefore, it appears that the adrninistra-tion of high concentrations of triacetin to dogs does not adversely affect calcium and phosphorus metabolism.

Example II - Metabolic Effects of Triacetin Infusion Following the general methodology of Example I, a 5% v/v triacetin solution was infused into 5 dogs for 3 hours at a rate of 75 ~mol kg~l min-l (about 35% above resting energy expenditure). Arterial concentrations of acetate (Ac), total ketone bodies (TKB), free fatty acids (FFA), lactate (L), pyruvate (P) and glucose (Glu) were determined prior to and during the infusion. The results of this study are summarized on Table 2, below.

Table 2 Concentration Ac (mM) TKB (uM)l Glu(mM)~ P(~M)3 L(mM)4 Prior to 0.2+0.02 51+6 93+5 151+31 2-~0.3 infusion After 3 hrs 17.0+3.0 342+49 116+10 20+6 0.9+0.1 of infusion <O . 01; 2 p<O, 09; 3 P<O. 01; 4 P<O 05.- -V2 and FFA did not change, and no toxic effects, such as somnolence or coma, were observed.
Therefore, a three-hour triacetin infusion at greater than isocaloric levels induced marked increases in plasma acetate and total ketone bodies in dogs, without apparent toxicity. Only mild hyperglycemia was observed, and circulating lactate and pyruvate actually decreased. Therefore, it is believed that these data ~ 3~ 8~

further support the utility of triacetin as a paren-teral nutrient for human use, particularly in view of its water solubility.

Example III - Effects of Triacetin Infusion_on Leucine Metabolism Following the general methodology of Examples I and II, a 5% v/v triacetin solution was infused into 5 dogs at rates of 47 and 75 ~mol kg~l min~1, together with [1-14C~leucine to trace leucine release from body protein and leucine oxidation. During the isocaloric infusion of triacetin t47 ~mol kg~l min~l), the arter-ial concentration of leucine remained constant, whereas the concentration of its alpha-ketoacid, alpha-ketoiso-caproate, increased (18 + 1 to 27 + 3 ~M, p <0.001).The rate of leucine appearing from body protein and the rate of leucine oxidation were similar to those observed in saline-infused control animals. During the hypercaloric infusion of triacetin (75 ~mol.kg~l min~l), the plasma concentration of leucine decreased (110 + 6 to 9~ + 5 ~M, p <0.06) and that of alpha-ketoisocapro-ate 2gain increased (17 + 1 to 25 + 3 ~M, p < 0.05).
In contrast to the results at the lo~ler infusion rate of triacetin, the rate of leucine released from body protein and the rate of leucine oxidation decreased significantly ~5.0 ~ 0.2 to 3.9 + 0.1 ~mol kg-l-min-and 0.52 + 0.08 to 0.20 + 0.02 ~mol kg~l min~l, respectively).
These data demonstrate that the infusion of triacetin in dogs does not have the adverse effects exhibited by medium-chain triglycerides on leucine and protein metabolism at isocaloric infusion rates, and at hypercaloric infusion rates decreases the rate of pro-tein breakdown and the oxidation of at least one essen-tial amino acid.

~ 3 ~ 3 Therefore, it is believed that these datafurther support the utility of triacetin as a paren-teral nutrient for human use~ in that triacetin has been demonstrated to have no identifiable adverse effect on protein or amino acid metabolism and may, in fact~ have an inherent beneficial effect by reducing protein and amino acid breakdown and losses.
The invention has been described with refer-ence to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remain-ing within the spirit and scope of the invention.

2û

Claims (13)

WHAT IS CLAIMED IS:

1. The use of a nutritionally effective amount of triacetin, about 1-7% in aqueous solution, for providing parenteral nutrition to a human, wherein said effective amount of triacetin provides about 10-50% of the daily caloric requirement of said human.

2. The use according to claim 1 wherein said effective amount of triacetin provides about 20-40% of the daily caloric requirement of said human.

3. The use in accordance with claim 1 wherein said solution is administered intravenously.

4. The use in accordance with claim 1 wherein said solution is administered enterically.

5. The use in accordance with claim 1 where said solution further comprises glucose.

6. The use in accordance with claim 1 wherein said solution further comprises amino acids.

7. The use in accordance with claim 6 wherein said amino acids are provided by protein hydrolysates or crystalline amino acids.

8. An aqueous solution comprising triacetin and glucose, wherein said triacetin and glucose are present in a combined amount effective to provide the daily caloric requirement for a human when parenterally administered thereto for about 24 hours or less.

9. The aqueous solution of claim 8 wherein said solu-tion comprises about 10-30 wt-% glucose.

10. The aqueous solution of claim 8 wherein said solu-tion comprises about 1-7% triacetin.

11. The aqueous solution of claim 8 wherein said solu-tion further comprises amino acids.

12. The aqueous solution of claim 11 wherein the ratio of the nitrogen provided by the amino acids to the caloric content provided by the glucose and the triacetin is about 1:100-200.

13. The aqueous solution of claim 8 which further comprises an effective amount of electrolytes.