Serum fatty acid profiles after intravenous medium chain triglyceride administration

Medium chain triglyceride and medium-and long chain triglyceride: metabolism, production, health impacts and its applications - a review

Structured lipid is a type of modified form of lipid that is "fabricated" with the purpose to improve the nutritional and functional properties of conventional fats and oils derived from animal and plant sources. Such healthier choice of lipid received escalating attention from the public for its capability to manage the rising prevalence of metabolic syndrome. Of which, medium-chain triacylglycerol (MCT) and medium-and long-chain triacylglycerol (MLCT) are the few examples of the "new generation" custom-made healthful lipids which are mainly composed of medium chain fatty acid (MCFA). MCT is made up exclusively of MCFA whereas MLCT contains a mixture of MCFA and long chain fatty acid (LCFA), respectively. Attributed by the unique metabolism of MCFA which is rapidly metabolized by the body, MCFA and MCT showed to acquire multiple physiological and functional properties in managing and reversing certain health disorders. Several chemically or enzymatically oils and fats modification processes catalyzed by a biological or chemical catalyst such as acidolysis, interesterification and esterification are adopted to synthesis MCT and MLCT. With their purported health benefits, MCT and MLCT are widely being used as nutraceutical in food and pharmaceutical sectors. This article aims to provide a comprehensive review on MCT and MLCT, with an emphasis on the basic understanding of its structures, properties, unique metabolism; the current status of the touted health benefits; latest routes of production; its up-to-date applications in the different food systems; relevant patents filed and its drawbacks.

Medium-Chain Triglycerides Lower Blood Lipids and Body Weight in Streptozotocin-Induced Type 2 Diabetes Rats

Medium-chain triglycerides (MCTs) are distinguished from other triglycerides in that each fat molecule consists of 6 to 12 carbons in length. MCTs and long-chain triglycerides (LCTs) are absorbed and utilized in different ways. The aim of this study was to assess the effects of replacing soybean oil with MCT oil, in a low- or high-fat diet, on lipid metabolism in rats with streptozotocin-induced type 2 diabetes mellitus (T2DM). There were, thirty-two T2DM Sprague-Dawley rats divided into low-fat-soybean oil (LS), low-fat-MCT oil (LM), high-fat-soybean oil (HS), and high-fat-MCT oil (HM) groups. After 8 weeks, blood sugar, serum lipids, liver lipids, and enzyme activities related to lipid metabolism were measured. Under a high-fat diet condition, replacement of soybean oil with MCT oil lowered serum low-density lipoprotein cholesterol (LDL-C), non-esterified fatty acids, and liver total cholesterol; whilst it increased serum high-density lipoprotein cholesterol (HDL-C) and the HDL-C/LDL-C ratio. A low-fat diet with MCT oil resulted in lower body weight and reproductive white adipose tissues compared to the HS groups, and higher hepatic acyl-CoA oxidase activities (the key enzyme in the peroxisomal beta-oxidation) compared to the LS group in T2DM rats. In conclusion, MCTs showed more protective effects on cardiovascular health in T2DM rats fed a high-fat diet, by improving serum lipid profiles and reducing hepatic total cholesterol.

Triheptanoin: long-term effects in the very long-chain acyl-CoA dehydrogenase-deficient mouse

A rather new approach in the treatment of long-chain fatty acid oxidation disorders is represented by triheptanoin, a triglyceride with three medium-odd-chain heptanoic acids (C7), due to its anaplerotic potential. We here investigate the effects of a 1-year triheptanoin-based diet on the clinical phenotype of very long-chain-acyl-CoA-dehydrogenase-deficient (VLCAD^-/-) mice. The cardiac function was assessed in VLCAD^-/- mice by in vivo MRI. Metabolic adaptations were identified by the expression of genes regulating energy metabolism and anaplerotic processes using real-time PCR, and the results were correlated with the measurement of the glycolytic enzymes pyruvate dehydrogenase and pyruvate kinase. Finally, the intrahepatic lipid accumulation and oxidative stress in response to the long-term triheptanoin diet were assessed. Triheptanoin was not able to prevent the development of systolic dysfunction in VLCAD^-/- mice despite an upregulation of cardiac glucose oxidation. Strikingly, the anaplerotic effects of triheptanoin were restricted to the liver. Despite this, the hepatic lipic content was increased upon triheptanoin supplementation. Our data demonstrate that the concept of anaplerosis does not apply to all tissues equally.

Effects of medium-chain fatty acids on performance, carcass characteristics, blood biochemical parameters and immune response in Japanese quail

This study had the aim of evaluating the effects of medium-chain fatty acids (MCFA) on performance, carcass characteristics, some blood parameters and antibody titre against sheep red blood cells (SRBC) in quail. A total of 240 quail chicks were allotted to 4 treatments consisting of respectively 0, 1, 2 and 4 g/kg dietary MCFA. There were no significant differences in body weight, feed intake and feed conversion ratio among treatments at different stages of the experiment. MCFAs had no significant effect on breast, thigh, liver, spleen and bursa of Fabricius weight ratios. However, the relative weight of abdominal fat significantly decreased in quail receiving 0.2 and 0.4 MCFA as compared to other treatments. Concentrations of low-density lipoprotein-cholesterol (LDL), triglycerides and total cholesterol were decreased and high-density lipoprotein (HDL)-cholesterol was increased in quail chicks receiving MCFA compared with control quail chicks. The concentrations of SRBC antibody were not statistically different among treatments. It is concluded that MCFA significantly decreased LDL, triglycerides, cholesterol and abdominal fat and increased HDL in quail chicks.

Familial chylomicronemia syndrome and response to medium-chain triglyceride therapy in an infant with novel mutations in GPIHBP1

BACKGROUND

Severe hypertriglyceridemia predisposes to attacks of acute pancreatitis, a serious condition complicated by multiorgan failure, pancreatic necrosis, and mortality rates up to 20% in adults and 6.5% in children.

OVERVIEW

We describe an infant who suffered from an episode of acute pancreatitis from severe hypertriglyceridemia. Two major challenges complicate the case: identifying the etiology of severe hypertriglyceridemia and finding an efficacious treatment. A thorough history, physical examination, and laboratory workup failed to identify a clear etiology, prompting a genetic workup that identified compound heterozygous mutations in the glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) gene. This patient's hypertriglyceridemia responded to an infant formula rich in medium chain triglycerides (MCTs), and she remained free of pancreatitis 6 months later.

CONCLUSIONS

This case highlights the need to pursue a genetic evaluation in the absence of secondary causes of severe hypertriglyceridemia in infants. Patients with mutations in GPIHBP1 fail to respond to currently available lipid-lowering agents so dietary management-specifically, an extremely low-fat diet and supplementation with MCT-remains the cornerstone of therapy. Treatment in infants should focus on dietary measures rather than pharmacologic agents.

The effect of administered dose of lipid-based formulations on the in vitro and in vivo performance of cinnarizine as a model poorly water-soluble drug

The influence of varying the amount of lipid co-administered with the drug on drug solubilisation and absorption is poorly understood. In the current study, the effect of lipid dose on the in vitro drug distribution is compared with the in vivo absorption of cinnarizine (CZ) when formulated using long-chain triacylglyceride (LCT) and medium-chain triacylglycerides (MCT). At a fixed drug-lipid ratio, in the closed in vitro model, the drug concentrations in the aqueous phase increased and decreased for MCT and LCT, respectively, with increasing lipid dose. However, in vivo, the oral bioavailability (F%) of CZ was independent of the quantity of lipid administered for both MCT and LCT, but was higher for LCT (32.1 ± 2.3%) than for MCT (16.6 ± 2.3%). Increasing the quantity of lipid relative to the dose of CZ resulted in an increase in the oral F% when the lipid mass was increased from 125 to 250 mg, but was no greater at 500 mg lipid dose. The results confirm the limitations of the in vitro model but positively indicate that the use of the rat as a pre-clinical model for studying the bioavailability of poorly water-soluble drugs is not compromised by the mass of formulation administered.

Effects of a medium chain triglyceride oil mixture and α-lipoic acid diet on body composition, antioxidant status, and plasma lipid levels in the Golden Syrian hamster

The objective of this study was to examine the effects of the antioxidant alpha-lipoic acid (ALP) versus a medium chain triglyceride oil mixture (MCTo), which was designed to increase energy expenditure and to improve lipid profiles containing medium chain triglycerides, phytosterols, and omega-3 fatty acids in the form of flaxseed oil. A total of 48 hamsters were fed a) hypercholesterolemic (HC) control, b) HC MCTo, c) HC ALP, or d) HC MCTo/ALP diet for 4 weeks. No differences were observed on food intake, body weight, total body water, lean and fat mass, and tissue thiobarbituric acid reactive substances (TBARS). ALP alone had no effect on total cholesterol (TC); however, MCTo feeding increased TC with (P < 0.03) and without (P < 0.003) ALP when compared with control. ALP increased HDL levels compared with control (P < 0.04) and MCTo/ALP (P < 0.007) groups. MCTo, with (P < 0.0001) or without (P < 0.006) ALP, increased non-HDL cholesterol levels versus control. The non-HDL:HDL cholesterol ratio was decreased by ALP compared with MCTo (45%) and MCTo/ALP (68%) (P < 0.0001), a similar trend was seen when compared with the HC control (22%) group (P < 0.14). Triglyceride levels were not altered by any dietary treatment. Liver and heart tissue reduced glutathione (GSH) was increased (P < 0.05) by all three treatments when compared with control. Both tissues showed an increase (P < 0.05) in oxidized glutathione (GSSG) when fed ALP as compared with other treatments. Hamsters fed ALP had a lower (P < 0.05) GSH/GSSG ratio compared with other treatment groups. In conclusion, MCTo feeding does not elicit beneficial effects on circulating plasma lipids and measures of body composition. In addition, our results do not clearly support an improvement in oxidative status through supplementation of ALP. However, our results do support the existence of beneficial effects of ALP on circulating lipoprotein content in the hamster.

Octanoate oxidation measured by 13C-NMR spectroscopy in rat skeletal muscle, heart, and liver

Contribution of octanoate to the oxidative metabolism of the major sites of fatty acid oxidation (heart, liver, and resting and contracting skeletal muscle) was assessed in the intact rat with 13C-NMR spectroscopy. Under inhalation anesthesia, [2,4,6,8-13C4]octanoate was infused into the jugular vein and the sciatic nerve of one limb was stimulated for 1 h. Octanoate was a principal contributor to the acetyl-CoA pool in all tissues examined, with highest oxidation occurring in heart and soleus muscle followed by predominantly red portion of gastrocnemius muscle (RG), liver, and then white portion of gastrocnemius muscle (WG). Fractional contribution of 13C-labeled octanoate to the acetyl-CoA pool (Fc2) was 0.563 +/- 0.066 for heart and 0.367 +/- 0.054 for liver. Significant differences were observed between each of the muscle types during both rest and contraction. In muscle, Fc2 was highest in soleus (0.565 +/- 0.089 rested, 0.564 +/- 0.096 contracted), followed by RG (0.470 +/- 0.092 rested, 0.438 +/- 0.072 contracted), and lowest in WG (0.340 +/- 0.081 rested, 0.272 +/- 0.065 contracted). Our findings demonstrate that the fractional contribution of octanoate to oxidative metabolism correlates with oxidative capacity of the tissue and that octanoate metabolism increases in contracted muscle in proportion to the overall increase in oxidative rate.

Short-Time Infusion of Fish Oil-Based Lipid Emulsions, Approved for Parenteral Nutrition, Reduces Monocyte Proinflammatory Cytokine Generation and Adhesive Interaction with Endothelium in Humans

Potential impact of omega-3 fatty acids, as contained in fish oil, on immunological function has been suggested because observations of reduced inflammatory diseases in Greenland Inuit were published. A fish oil-based lipid emulsion has recently been approved for parenteral nutrition in many countries. We investigated the influence of a short infusion course of fish oil-based (omega-3) vs conventional (omega-6) lipid emulsion on monocyte function. In a randomized design, twelve healthy volunteers received omega-3 or omega-6 lipid infusion for 48 h, with cross-over repetition of the infusion course after 3 mo. Fatty acid profiles, monocyte cytokine release and adhesive monocyte-endothelium interaction were investigated. Resultant omega-6 lipid emulsion increased plasma-free fatty acids including arachidonic acid, whereas the omega-3/omega-6 fatty acid ratio in monocyte membranes remained largely unchanged. It also caused a tendency toward enhanced monocyte proinflammatory cytokine release and adhesive monocyte-endothelium interaction. In contrast, omega-3 lipid emulsion significantly increased the omega-3/omega-6 fatty acid ratio in the plasma-free fatty acid fraction and in monocyte membrane lipid pool, markedly suppressing monocyte generation of TNF-alpha, IL-1, IL-6, and IL-8 in response to endotoxin. In addition, it also significantly inhibited both monocyte-endothelium adhesion and transendothelial monocyte migration, although monocyte surface expression of relevant adhesive molecules (CD11b, CD18, CD49 days, CCR2) was unchanged. Although isocaloric, omega-3 and omega-6 lipid emulsions exert differential impact on immunological processes in humans. In addition to its nutritional value, fish oil-based omega-3 lipid emulsion significantly suppresses monocyte proinflammatory cytokine generation and features of monocyte recruitment.

n-3 fatty acids in psoriasis

Increased concentrations of free arachidonic acid (AA) and its proinflammatory metabolites have been observed in psoriatic lesions. Replacement of arachidonic acid by alternative precursor polyunsaturated fatty acids (PUFA), especially eicosapentaenoic acid (EPA), which can be metabolized via the same enzymatic pathways as AA, might be a therapeutic option in psoriasis. However the results of studies evaluating the therapeutic benefit of dietary fish oil have been conflicting and not clearly dose-dependent. To overcome the slow kinetics and limited availability of oral supplementation, we have performed three studies to assess the efficacy and safety of an intravenously administered fish oil derived lipid emulsion on different forms of psoriasis. Patients received daily infusions of either an n-3 fatty acid-based lipid emulsion (Omegaven) or a conventional n-6 lipid emulsion (Lipoven) in different time and dose regimens. In addition to an overall assessment of the clinical course of psoriasis, EPA- and AA-derived neutrophil 5-lipoxygenase (LO)--products, thromboxane (TX) B2/B3, PAF and plasma free fatty acids were investigated. Treatment with n-3 fatty acids resulted in a considerably higher response rate than infusion of n-6 lipids. A more than 10-fold increase in neutrophil EPA-derived 5-LO product formation was noted in the n-3 group, accompanied by a rapid increase in plasma-free EPA within the first days. In conclusion, intravenous n-3-fatty acid administration causes reduction of psoriasis, which may be related to changes in inflammatory eicosanoid generation. The rapidity of the response to intravenous n-3 lipids exceeds by orders of magnitude the hitherto reported kinetics of improvement of psoriatic lesions upon use of oral supplementation.

PAF-induced synthesis of tetraenoic and pentaenoic leukotrienes in the isolated rabbit lung

In an isolated rabbit lung model, we tested the hypothesis that platelet-activating factor (PAF)-induced leukotriene (LT) synthesis is critically dependent on the free precursor fatty acid supply and the possible substitution of arachidonic acid (AA) by eicosapentaenoic acid (EPA). To augment the intravascular polymorphonuclear neutrophils (PMNs) in the isolated lung, human PMNs were infused into the pulmonary artery. LTs and hydroxyeicosatetra(penta)enoic acids were quantified with HPLC techniques. Application of PAF (5 microM) or AA (10 microM) provoked the generation of limited quantities of 4-series LTs and 5-hydroxyeicosatetraenoic acid (total sum of 5-lipoxygenase products approximately 7 and approximately 27 pmol/ml in lungs both with and without infused PMNs, respectively). Combined administration amplified 5-lipoxygenase product formation, with a predominance of cysteinyl-LT synthesis in lungs both without (total sum approximately 67 pmol/ml) and, much more strikingly, with (total sum approximately 308 pmol/ml) an infusion of neutrophils. EPA (10 microM) elicited exclusive generation of 5-series LTs and 5-hydroxyeicosapentaenoic acid (total sum approximately 82 pmol/ml). Dual stimulation with PAF and EPA provoked amplification of EPA-derived 5-lipoxygenase product formation, again with predominance of cysteinyl-LTs in lungs without (total sum approximately 224 pmol/ml) and, in particular, with (total sum approximately 545 pmol/ml) preceding microvascular PMN entrapment. Combined application of PAF, AA, and EPA resulted in the synthesis of LTs derived from both fatty acids, with a predominance of 5-series products. We conclude that the PAF-evoked 5-lipoxygenase product formation in the neutrophil-harboring lung capillary bed is critically dependent on intravascular precursor fatty acid supply, with EPA representing the preferred substrate compared with AA. PMN-related transcellular eicosanoid synthesis is suggested to underlie the predominant generation of cysteinyl-LTs. The supply of n-3 versus n-6 precursor fatty acid may thus have a major impact on inflammatory mediator generation.

Medium chain fatty acid metabolism and energy expenditure: obesity treatment implications

Fatty acids undergo different metabolic fates depending on their chain length and degree of saturation. The purpose of this review is to examine the metabolic handling of medium chain fatty acids (MCFA) with specific reference to intermediary metabolism and postprandial and total energy expenditure. The metabolic discrimination between varying fatty acids begins in the GI tract, with MCFA being absorbed more efficiently than long chain fatty acids (LFCA). Subsequently, MCFA are transported in the portal blood directly to the liver, unlike LCFA which are incorporated into chylomicrons and transported through lymph. These structure based differences continue through the processes of fat utilization; MCFA enter the mitochondria independently of the carnitine transport system and undergo preferential oxidation. Variations in ketogenic and lipogenic capacity also exist. Such metabolic discrimination is supported by data in animals and humans showing increases in postprandial energy expenditure after short term feeding with MCFA. In long term MCFA feeding in animals, weight accretion has been attenuated. These differences in metabolic handling of MCFA versus LCFA are considered with the conclusion that MCFA hold potential as weight loss agents.

Omega-3 fatty acid-based lipid infusion in patients with chronic plaque psoriasis: results of a double-blind, randomized, placebo-controlled, multicenter trial

BACKGROUND

Profound changes in the metabolism of eicosanoids with increased concentrations of free arachidonic acid (AA) and its proinflammatory metabolites have been observed in psoriatic lesions. Free eicosapentaenoic acid (EPA) may compete with liberated AA and result in an antiinflammatory effect.

OBJECTIVE

Our purpose was to assess the efficacy and safety of intravenously administered fish-oil-derived lipid emulsion on chronic plaque-type psoriasis.

METHODS

A double-blind, randomized, parallel group study was performed in eight European centers. Eighty-three patients hospitalized for chronic plaque-type psoriasis with a severity score of at least 15 according to the Psoriasis Area and Severity Index (PASI) participated in a 14-day trial. They were randomly allocated to receive daily infusions with either a omega-3 fatty acid-based lipid emulsion (Omegavenous; 200 ml/day with 4.2 gm of both EPA and docosahexaenoic acid (DHA); 43 patients) or a conventional omega-6-lipid emulsion (Lipovenous; EPA+DHA < 0.1 gm/100 ml; 40 patients). The groups were well matched with respect to demographic data and psoriasis-specific medical history. Efficacy of therapy was evaluated by changes in PASI, in an overall assessment of psoriasis by the investigator, and a self-assessment by the patient. In one center neutrophil 4- versus 5-series leukotriene (LT) generation and platelet 2- versus 3- thromboxane generation were investigated and plasma-free fatty acids were determined.

RESULTS

The total PASI score decreased by 11.2 +/- 9.8 in the omega-3 group and by 7.5 +/- 8.8 in the omega-6 group (p = 0.048). In addition, the omega-3 group was superior to the omega-6 group with respect to change in severity of psoriasis per body area, change in overall erythema, overall scaling and overall infiltration, as well as change in overall assessment by the investigator and self-assessment by the patient. Response (defined as decrease in total PASI of at least 50% between admission and last value) was seen in 16 of 43 patients (37%) receiving the omega-3 emulsion and 9 of 40 patients (23%) receiving omega-6 fatty acid-based lipid emulsion. No serious side effects were observed. Within the first few days of omega-3 lipid administration, but not in the omega-6 supplemented patients, a manifold increase in plasma-free EPA concentration, neutrophil leukotriene B5 and platelet thromboxane B3 generation occurred.

CONCLUSION

Intravenous omega-3-fatty acid administration is effective in the treatment of chronic plaque-type psoriasis. This effect may be related to changes in inflammatory eicosanoid generation.

Biosynthesis of medium-chain triacylglycerols and phospholipids by HepG-2 cells

In an attempt to understand the metabolism by the liver of fatty acids (FA) of different chain length, we have studied the incorporation of [1(-14)C]-labeled C2, C8, C10, C12, and C16 into cellular lipids by HepG-2 cells. Over 90% of the radiolabeled FA were detected in phospholipids (PL) and triacylglycerols (TAG). The incorporation of C12 and C16 was three to four times higher than that of C8 and C10 (and reached 35 nmoles per mg protein after 1.5 h). The radioactivity of C2, C8, and C10 was recovered mainly in PL. C12 and C16 were incorporated at approximately equal amounts into PL and TAG. The radioactivity of both C2 and C8 was recovered exclusively in long-chain FA, suggesting oxidation of C8 into C2 units prior to FA synthesis. C10 likewise yielded mainly long-chain FA. However 10% of unchanged C10 was found in PL and up to 30% in TAG. 14C-C12 was largely incorporated unchanged. Under these conditions, the presence of C10 and C12 in PL and TAG was shown also by gas-liquid chromatography. In the presence of either C2, C8, or C10, up to 30% of 14C-monounsaturated FA were detected in PL and TAG. With C12 and C16, the fraction of 14C-monounsaturated FA was much smaller suggesting that extensive desaturation occurred during de novo synthesis.

Fish oil fatty acids and human platelets: dose-dependent decrease in dienoic and increase in trienoic thromboxane generation

Dietary enrichment of membrane phospholipids with n-3 (fish-oil-derived) fatty acids has attracted attention as a putative therapeutic regimen for suppression of inflammatory and coagulatory events. Use of n-3 fatty-acid-enriched lipid infusions for parenteral nutrition results in micromolar concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DCHA) in the plasma-free fatty acid fraction. We investigated the influence of free EPA and DCHA on platelet thromboxane (Tx) A2 and A3 formation by using a recently developed high performance liquid chromatography-ELISA technique for separate quantification of the stable hydrolysis products TxB2 and TxB3. Washed human thrombocytes were incubated with free arachidonic acid (AA; 1 microM), A23187 (0.1 microM) or thrombin (5 U/mL) for stimulation; all regimens provoked large quantities of TxA2 in the absence of TxA3. Simultaneous admixture of free EPA or free DCHA to the incubation medium (concentration range, 0.01-50 microM) largely suppressed platelet TxA2 generation in response to all stimuli used in a dose-dependent manner. The effective concentration with 50% influence of arachidonic acid was 4.2 microM, whereas the inhibitory concentration with 50% effect of EPA and DCHA were both in the same order of magnitude but differed with the nature of the agonist (0.2-7 microM). Platelet (co-)incubation with EPA, but not DCHA, provoked dose-dependent synthesis of n-3-lipid-derived thromboxane: kinetics of formation and absolute quantities of TxA3 approximated 20% of the respective TxA2 data upon stimulation with AA. Both EPA and DCHA dose-dependently suppressed U46619-provoked platelet aggregation. We conclude that EPA and DCHA are potent competitive inhibitors of TxA2 generation by intact platelets, with EPA acting as poor substrate and DCHA being no substrate for the cyclooxygenase/thromboxane synthase complex. Enrichment of the plasma-free fatty acid fraction with n-3 lipids may offer a therapeutic regimen to suppress the synthesis of the potent proaggregatory and vasoconstrictory agent TxA2.

Distinction of dicarboxylic aciduria due to medium-chain triglyceride feeding from that due to abnormal fatty acid oxidation and fasting in children

Increased amounts of dicarboxylic acids are excreted in human urine under conditions of medium-chain triglyceride (MCT) feeding, abnormal fatty acid oxidation (FAO) and fasting. Criteria to distinguish dicarboxylic aciduria originating from MCT feeding and other conditions are needed in urinary organic acid profiling for detecting inborn errors of metabolism. Patterns of dicarboxylic aciduria in children under various conditions were compared. The relative amounts of medium-chain saturated dicarboxylic acids in urine are not reliable for identifying MCT-induced dicarboxylic aciduria. On the other hand, low ratios of unsaturated to saturated dicarboxylic acids (<0.1) and 3- hydroxydecenedioic to 3-hydroxydecanedioic acids were found to be useful in identifying dicarboxylic aciduria due to MCT ingestion. Additional unique features of dicarboxylic aciduria from MCT are low ratios of 3-hydroxydodecanedioic to 3-hydroxydecanedioic acid (<0.14) and 3-hydroxyadipic to adipic acid (<0.02).

Kinetics of medium-chain triglycerides and free fatty acids in healthy volunteers and surgically stressed patients

To determine the hydrolysis rate of medium-chain triglycerides (MCTs) to medium-chain free fatty acids (MCFAs) and the disposition rate of MCFAs, five healthy volunteers (H) and eight surgically stressed patients (S) received 0.5 mL of Lipofundin 20% per kilogram body weight as an intravenous bolus. Serum MCTs (C8 and C10) and MCFAs were measured by high-performance liquid chromatography during the 120 minutes postinjection. A linear two-compartment model was found to be descriptive and robust: the apparent volumes of distribution were found to be similar in healthy and surgical subjects for both MCTs and MCFAs. The first-order transformation rate constant (hydrolysis) from MCTs to MCFAs was not significantly different between the H and S groups (overall 0.112 +/- 0.022/min, C8; 0.078 +/- 0.020/min, C10). The rate constant for tissue MCFA uptake from plasma was significantly different between S and H subjects both for C10 alone (H: 0.0337 +/- 0.0078; S: 0.1194 +/- 0.0240; p = .020) and for C8 and C10 together (H: 0.0382 +/- 0.0054; S: 0.1012 +/- 0.0168; p = .008), whereas it failed to attain significance when C8 alone was considered (H: 0.047 +/- 0.0077; S: 0.0829 +/- 0.0230; p = .210). These results show that use of MCTs is increased in surgical patients because of enhanced tissue uptake of the corresponding free fatty acids, whereas there does not seem to be an increase of MCT hydrolysis in response to acute disease. This would indicate that the stressed patient is in fact able to effectively use this alternative lipid substrate in the face of increased metabolic demand.

Influence of intravenous n-3 lipid supplementation on fatty acid profiles and lipid mediator generation in a patient with severe ulcerative colitis

N-3 fatty acids were supplied to a 36-year-old female patient suffering from ulcerative colitis and severe steroid side-effects, in a sequence of parenteral and enteral administration. During a moderately active period of disease, 200 ml d-1 fish oil-derived lipid emulsion (eicosapentaenoic acid [EPA], 4.2 g; docosahexaenoic acid [DHA], 4.2 g) was infused for 9 days, in parallel with rapid tapering of the steroid dose. Disease activity declined rapidly, and the patient was subsequently provided with 16 fish oil capsules per day (EPA, 2.9 g; DHA, 1.9 g) for 2 months. At the end of this period of therapy, severe colitis recurred with intestinal and extraintestinal manifestations. The n-3 lipid emulsion was then used for intravenous alimentation (29 days, maximum dose 300 ml per day); during this time, marked improvement of the inflammatory bowel disease was noted. During both periods of parenteral n-3 lipid administration, total plasma EPA and DHA contents increased several-fold, surpassing that of arachidonic acid; this plasma n-3 fatty acid enrichment was only maintained to a minor extent during the intermediate period of dietary fish oil supplementation. The intravenously administered EPA-containing triglycerides were rapidly hydrolyzed, as evidenced by the appearance of substantial quantities of EPA in the plasma free fatty acid fraction. Platelet and neutrophil total membrane content of EPA and DHA as well as n-3 fatty acid/AA membrane ratios similarly increased during the periods of intravenous n-3 lipid administration and declined during oral fish oil uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

A rapid GLC method for the direct analysis of plasma medium chain fatty acids

A new, rapid, gas-liquid-chromatographic (GLC) method for the direct determination of plasma medium-chain fatty acids (MCFA) (from C8 to C12) which does not require derivatization procedures is described. Analysis of underivatized MCFA by GLC showed a detection limit ranging from 0.50 to 0.217 microgram depending on chain length: the longer the chain, the higher the detection limit. Compared with the HPLC and GLC methods currently described in the literature, this GLC procedure appears to be easy, adequately sensitive, accurate and well reproducible for those MCFA, like n-octanoic and n-decanoic acids, present in plasma after p.o. or i.v. MCT administration and it requires a short time (about 30 min) for complete processing.

Parenteral nutrition using MCT/LCT or LCT: Effect on the fatty acid composition of plasma triglycerides and platelet phospholipids

Plasma triglyceride fatty acids and platelet phospholipid fatty acids were compared in 20 malnourished patients before and after 8-10 days of total parenteral nutrition which included either a conventional lipid emulsion (LCT) or a new emulsion containing medium chain triglyercides (MCT/LCT). The use of both lipid emulsions altered the fatty acid profiles. The percentage of linoleic acid in the plasma triglycerides increased with both lipid emulsions, but more markedly with LCT. The median percentage after LCT was 25.9 (range 16.9-31.5) which was significantly higher (p < 0.01) than after MCT/LCT - 14.8 (range 6.1-20.2), or in healthy volunteers. After 8-10 days on MCT/LCT the fatty acid profile retained some features of the malnourished state, despite correction of the linoleic acid content. The percentage of linolenic and arachidonic acid in the platelet phospholipids tended to be lower than after LCT use, and the percentage of linoleic acid was significantly less (p < 0.01), the median (range) being 8.2 (4.5-23.8) after MCT/LCT and 11.7 (4.8-16.0) on LCT. Short term use of MCT/LCT emulsion may correct the fatty acid changes of malnutrition rather more slowly and results in a different fatty acid profile to that seen after LCT use. Whether this has any clinical effects is unclear.

Effect of different dietary triglycerides on liver fatty acids and prostaglandin synthesis by mouse peritoneal cells

The effect of dietary triglycerides varying in fatty acid composition on the tissue fatty acids and prostaglandin synthesis was studied in mice. The dietary fats were medium-chain triglycerides (rich in C8:0 and C10:0), structured lipids (rich in 12:0), high oleic sunflower oil (rich in 18:1), corn oil (rich in n-6 polyunsaturated fatty acids), and menhaden oil (rich in n-3 polyunsaturated fatty acids) fed at 5% by weight in refined diets. The medium chain fatty acids C8 to C12 from medium-chain triglycerides and structured lipids did not accumulate in liver phospholipids. However, long-chain fatty acids from the dietary fats were incorporated into liver lipids, with n-3 polyunsaturated fatty acids replacing arachidonic acid. The synthesis of 6-keto-prostaglandin F1 alpha and prostaglandin E2 by peritoneal cells in response to intraperitoneal injection of zymosan decreased as the arachidonic acid levels were decreased. When the same dietary fats were added to the refined, fat-free diets, at 7.5 wt% levels, together with 2.5 wt% of safflower oil to provide essential fatty acids, only the long-chain fatty acids from the dietary fats were incorporated into the liver lipids. The arachidonic acid in liver lipids was enhanced after supplementation of diets with safflower oil. However, the reduction in prostaglandin synthesis by peritoneal cells in response to intraperitoneal injection of zymosan was similar to that observed when 5% fat was fed. The data suggest that dietary fats of defined composition, with or without added essential fatty acids, may be useful as alternate fat sources in parenteral nutrition in reducing inflammatory responses mediated via prostaglandins.

Insulinotropic potency of lauric acid: a metabolic rationale for medium chain fatty acids (MCF) in TPN formulation

The need for a better lipid system to satisfy the fuel requirements of patients while avoiding the adverse effects of current systems has led to suggestions that medium chain fatty acids (MCFs) be incorporated into TPN-lipid emulsions. Since clinical situations requiring TPN are associated with metabolic processes mediated by insulin, in the present study we have therefore examined the effects of a variety of medium chain fatty acids on insulin release. Using an isolated perifused mouse islet model, various doses of medium chain fatty acids and the essential fatty acid, linoleic acid, were tested and compared. The possibility of an additive effect of an insulinotropic MCF and linoleate when both are provided together was also examined. Effluent perifusate samples collected on ice during these experiments were assayed for insulin by radioimmunoassay. It was found that the ability of 5 mM of a given MCF to stimulate insulin secretion was dependent upon its chain length. Thus, while adipic acid (C6) had no effect, Caprylic acid (C8) had a minimal effect that was not statistically significant, but capric acid (C10) and lauric acid had very potent effects that were of the same magnitude to the effect of linoleate on insulin secretion. When insulin output was assessed as the mean integrated area under the curve during a 20-min perifusion, 5 mM lauric acid enhanced insulin secretion from a basal 7351 +/- 666 pg to 15,756 +/- 1680 pg (P less than 0.01, n = 5). In the same experiments, 5 mM linoleic acid stimulated insulin release to 11,260 +/- 867 pg (P less than 0.05). When C12 and linoleate were added together, each at a submaximally effective concentration of 2.5 mM, insulin output was 12,712 +/- 1011 pg (P less than 0.05, n = 5), which was not statistically different from the values obtained when the islets were perifused with 5 mM of each fatty acid alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Medium chain length fatty acids stimulate triacylglycerol synthesis in tissue culture cells

In the presence of undecanoic acid (C11) or lauric acid (C12) the synthesis of triacylglycerols was stimulated up to 10-fold both in tumor cell lines and in normal cell lines. Monocarboxylic acids of shorter or longer chain length either had no effect at all or were less effective. The increased triacylglycerol production was demonstrated, on the one hand, by the incorporation of radiolabeled glycerol into triacylglycerols and, on the other, by the incorporation of radiolabeled monocarboxylic acids, the incorporation of all (1-14C)-labeled monocarboxylic acids (C6, C12, C16, C18) regardless of their chain length, being preferentially enhanced by C11 and C12. C12 stimulated the de novo synthesis of triacylglycerols to such a degree that a 7-fold increase in the total amount of triacylglycerols per cell was observed during the first 10 hr of incubation. After removal of C12 from the tissue culture medium levels of triacylglycerols reach initial values again within 6 hr, indicating that the stimulatory effect of C12 is dependent on its continued presence. This led to the speculation that medium chain length monocarboxylic acids might be involved in the control of triacylglycerol synthesis.

The response to endotoxin in guinea pigs after intravenous black currant seed oil

The influence on the metabolic response to endotoxin of three days of total parenteral nutrition with lipids high in gammalinolenic acid (18:3 omega 6, GLA) compared to soy oil (SO) was examined in acute operatively stressed guinea pigs. GLA is the precursor of dihomogammalinolenic acid (DHLA), the substrate for synthesis of "1" series prostaglandins such as PGE1, which have previously been shown to be protective in endotoxin lung injury and traumatic shock. Guinea pigs fed an intravenous diet containing black currant seed oil (BCO) emulsion (20% GLA) or soy oil emulsion (0% GLA) for 2.5 days had their arterial pH, pCO2, pO2, and bicarbonate measured at baseline and hourly during a 7-hr infusion of endotoxin (lipopolysaccharide (LPS), 2mg/kg) or saline. Plasma lactate and fatty acid profile analyses were performed at the end of the LPS infusion. Increased levels of GLA and DHLA were present in the plasma phospholipid fraction of animals fed the black currant seed oil diet, while soy-fed animals had only trace amounts of GLA. In addition, the ratio of DHLA to arachidonate was higher in animals receiving the black currant seed oil total parenteral nutrition (TPN). After 2 hr of LPS infusion, all animals exhibited the typical shock response resulting in metabolic acidosis characterized by a significant (p less than 0.05) drop in pH from 7.34 +/- .02 (SO) and 7.39 +/- .02 (BCO) at baseline to 7.14 +/- .05 and 7.22 +/- .04 by 7 hr for SO and BCO groups, respectively. Plasma lactate values at the end of the infusion were significantly elevated compared to saline in both groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)