Triglycerides, Medium Chain

Absorption

Medium chain triglycerides are rapidly absorbed. They passively and directly diffuse across the gastrointestinal tract into the portal system then to liver, where they are oxidized.

Toxicity

There is limited information regarding the LD50 of medium-chain triglycerides; however, MCTs at doses up to levels of 1g/kg have been safely consumed by humans in several clinical trials.
Fat overload syndrome is a condition rarely reported with the use of intravenous lipid emulsions that is most frequently observed when the recommended lipid dose or infusion rate was exceeded. However, some cases still occurred when the lipid formulation was administered according to instructions. Fat overload syndrome results from a reduced or limited ability to metabolize lipids, accompanied by prolonged plasma clearance, leading to a sudden deterioration in the patient's condition.
If signs or symptoms of fat overload syndrome occur, stop the infusion of medium chain triglyceride-containing emulsions until triglyceride levels have normalized and symptoms have abated. The effects are usually reversible by stopping the lipid infusion. If medically appropriate, further intervention may be indicated. Lipids are not dialyzable from plasma.

Background

Medium-chain triglycerides (MCTs) are triglycerides made up of a glycerol backbone and three fatty acids with an aliphatic tail of six to 12 carbon atoms. MCTs are found in natural foods, such as coconut oil, palm kernel oil, and raw coconut meat. In the body, MCTs are broken down into glycerol and free fatty acids, which are directly absorbed into the blood stream and transported to the target organs to exert a range of biological and metabolic effects. MCTs are used in parenteral nutrition therapy: they serve as a source of calories and essential fatty acids in conditions associated with malnutrition and malabsorption.

Indications

Medium-chain triglycerides (MCTs), in combination with other compounds like fish oils, soya oil, and olive oil, is indicated in adult and pediatric patients, including term and preterm neonates, as a source of calories and essential fatty acids for parenteral nutrition when oral or enteral nutrition is not possible, insufficient, or contraindicated. MCTs are also available as over-the-counter natural products and health supplements.

Pharmacokinetics

Medium-chain triglycerides (MCTs) contained in injectable lipid emulsions serve as a source of calories and essential fatty acids, which are important substrate for energy production. MCTs exert several metabolic effects: they were shown to reduce weight, metabolic syndrome, abdominal obesity, and inflammation in animal studies. It is proposed that MCTs induces weight loss through increasing energy expenditure and fat oxidation, and altering body composition. However, it is unknown whether the effects of MCTs on energy expenditure and body weight are long-lasting and sustainable. MCTs can also play a role in food intake and satiety, as some studies showed that MCT consumption led to reduced food intake. While MCTs was shown to reduce energy intake, it was not shown to affect appetite. MCT may facilitate the absorption of calcium.

Metabolism

Medium chain triglycerides are hydrolyzed by lipoprotein lipase to glycerol and medium-chain free fatty acids such as alpha-linolenic acid and linoleic acid. Free fatty acids then undergo β-oxidation in the organs such as the liver, kidneys, and heart. Alpha-linolenic acid and linoleic acid are metabolized within a common biochemical pathway through a series of desaturation and elongation steps. Downstream products of alpha-linolenic acid are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and linoleic acid is converted to arachidonic acid.