What Are the Clinical Uses of Medium Chain Triglycerides?

Medium-cha에서 중성지방 수치s (MCT) refer to saturated fatty 산s with carb에 cha에서 lengths 의 8–12, primarily found naturally 에서 coconut 기름, with very low levels 에서 other natural foods. They have a caloric value 의 34.73 kJ (8.3 kcal) per gram.

1 Metabolic characteristics 의 MCT

나는ngested MCT is broken down by lipases 에서 the stomach 그리고 duodenum 에서to glycerol 그리고 medium-cha에서 fatty 산 (M-CFA), which have good water solubility. In the small intestine, they can be absorbed without bile emulsification, 그리고 their hydrolysis rate is six times that 의 long-chain 중성지방 수치s (LCT) [1]. They are then absorbed in the small intestinal mucosal epithelial cells in the form of glycerol 그리고 MCTs, directly entering the portal vein via small intestinal capillaries, and rapidly transported to the liver.

MCTs have different effects on the gastrointestinal tract compared to LCTs. They have a weaker inhibitory effect on gastric emptying (duodenum-gastric feedback inhibition) [2], but a stronger stimulatory effect on cholecystokinin release [3], and the same stimulatory effect on pancreatic secretion as LCTs [4].

M CFA undergoes oxidation, metabolism, and conversion in the liver at the same rate as 포도당 [5], with oxidation occurring within mitochondria. Unlike LCT, M CFA does not rely on carnitine as a carrier when crossing the mitochondrial membrane, resulting in faster oxidation rates than LCT. MCT is more likely to produce ketone bodies (ketone bodies) 동안 metabolism in the body than LCT.

MCTs ingested in the diet have three metabolic pathways in the body: ① Oxidative decomposition: Approximately 50% of dietary MCTs are oxidized [6], with the primary forms of M CFA oxidative decomposition being β-oxidation, Ω-oxidation, Ω-2 oxidation, and Ω-1 hydroxylation, ultimately excreted in urine in various forms such as 3-, 6-, and 7-hydroxyoctanoic acid [7]. Previous studies have used the detection of dicarboxylic 산 in urine to evaluate MCT oxidation, but it is currently believed that dicarboxylic acids in urine are not exclusively derived 에서 MCT oxidation [8]; ② Storage in the body in the form of fat; ③ Conversion into long-chain fatty acids: Using the 13C labeling method to trace the metabolic pathways of M CFA, it was found that myristic acid (14:0) and palmitic acid (16:0) were formed [6], and Carnielli et al. also suggested that the conversion of MCT to LCT is an important pathway [9].

2 Effects of MCT on energy and major nutrient metabolism

MCT does not easily induce appetite, has a lower energy density than LCT, and is less likely to be deposited in adipose tissue [10]. Experimental studies have shown that replacing part of LCT with MCT (30%–60%) in the diet does not easily cause weight gain in healthy males [11]; 24-hour energy metabolism measurements demonstrated that MCT (15–30 g/day) can increase energy expenditure by up to 5%; simultaneously, urinary levels of adrenaline and dopamine increased, suggesting that this effect is related to MCT stimulation of sympathetic nervous system excitation [12]. On the other hand, since it can stimulate insulin secretion, promote anabolic metabolism, increase fatty acid 합성, and lead to hyper중성지방 수치mia (TG), it does not support the role of MCT in weight 제어 [10].

이effects of MCT on 단백질 metabolism remain inconclusive. Some experiments suggest that under identical feeding conditions, MCT is more effective than LCT in increasing protein retention and protein utilization in chickens, while also exhibiting a strong weight-gain effect [13]; however, another study in chicks indicated that feed containing MCT reduced energy utilization and protein retention in chickens, though protein utilization remained unchanged [14].

에 관 한 연구 MCT diets for non-insulin-dependent diabetes mellitus (NIDDM) have not yet determined their effects on glucose metabolism. Some studies suggest that MCT increases insulin-mediated glucose metabolism [15]; however, another study on NIDDM patients indicated that a diabetic diet supplemented with MCT had minimal effects on blood glucose control and did not increase insulin-mediated glucose metabolism [16].

The effects of MCT on lipid metabolism are complex. MCT increases plasma total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) to a degree comparable to palmitic acid (16:0) and significantly 높은er than oleic acid (16:1) [17]. A study in rats showed that MCT increases 간 triglyceride synthesis more strongly than n-3 polyunsaturated fatty acids, which is an important factor influencing plasma TG concentrations [18]. In another 6-day oral MCT intake experiment, TG increased by 42%, and high-density lipoprotein (HDL) decreased by 15% [19]. However, many studies suggest that MCT may have beneficial effects on lipid metabolism.

MCT can alleviate type I hyperlipidemia caused by lipoprotein lipase deficiency. In a case report, a low-fat, low-energy diet (585.76 kJ/day, 10 g fat/day) was ineffective, but adding 30 g of MCT daily reduced the patient's TG from 10 g/L to 2.5 g/L. The possible mechanism is that MCTs regulate lipoproteins rich in triglycerides, increasing TG clearance [20]. Rats fed MCTs showed greater increases in body protein content compared to those fed LCTs, while MCTs rarely entered the liver or adipose tissue [21].

3 Clinical application studies of MCT

The ketogenic effect of MCT has been widely recognized and applied. Ketogenic diets formulated with MCT are helpful in improving drug resistance in epilepsy treatment; inducing a ketogenic state in tumor patients with MCT can inhibit tumor glucose metabolism and growth while maintaining the patient's nutritional status [22].

Since MCTs ingested via the intestine do not form chylomicrons and are transported via the lymphatic system, they have been attempted as a lipid source for patients with lymphatic fistulas to reduce fat loss and prevent malnutrition. The incidence of chylous fistula after neck surgery is approximately 1–2.5%. In cases where this complication occurs, MCT can be used to formulate enteral 영양formulations to reduce the leakage of chylous fluid. In approximately 50% of cases, this approach has shown good efficacy, thereby avoiding the need for parenteral nutrition (PN)[23]. Chylous ascites and chylous pleural effusion are common complications following complex abdominal surgery. Conservative treatment with MCT-based diets should be the first choice, with PN considered if ineffective. Surgical repair may be performed if conservative treatment fails [24,25]. Additionally, reports indicate that a low-fat MCT-containing diet was successfully used in two patients with primary lymphangiectasia [26]; in a premature infant with congenital hypothyroidism and chylothorax, MCT formula milk replaced breast milk and achieved good therapeutic effects [27].

MCT can also be used to treat patients with fat malabsorption. A controlled trial in AIDS patients with fat malabsorption and diarrhea demonstrated that MCT significantly reduced fecal fat content, bowel movement frequency, and weight. Additionally, it was proven that the therapeutic effect of MCT on diarrhea is independent of the underlying cause, being effective for both aseptic and infectious diarrhea [28]. In patients with pancreatic insufficiency and steatorrhea, replacing part of LCT with MCT without adding pancreatic enzymes can improve symptoms of malabsorption [29].

MCT is also used in sports nutrition. As an energy source, MCT synergistically supplies energy with carbohydrates, prolonging energy release and effectively maintaining energy requirements 동안 prolonged exercise in athletes [30]. In an 8-week pre-competition preparation for a world-class bodybuilder, replacing 25% of the normal fat content with MCT resulted in a reduction in body fat from 9% to 7%, similar to the effect of a traditional low-fat diet containing only 5% LCT [31]. When MCT and LCT are consumed together (in a 30:70 ratio), there is no difference in carbohydrate utilization or glycogen breakdown, but free fatty acids and plasma ketone bodies increase [32]. A 7-week feeding study in rats with MCT, LCT, and carbohydrate control diets showed that MCT increased intestinal sucrase activity by reducing the degradation of the sucrose-isomaltase complex [33].

Studies on MCT inevitably involve dosage issues. Depending on the experimental objectives, the dosage of MCT varies widely. For example, when used for ketogenic purposes, the dosage is relatively high, accounting for 50% to 70% of total calories. In studies exploring other applications of MCT, different methods are used to quantify dosage, including the percentage of MCT in total calories, the percentage of MCT in fat calories, and the weight ratio of MCT to carbohydrates. The percentage of MCT in total calories can reach up to 40% [11]; the percentage of MCT in fat calories should not exceed 90%, with common ratios ranging from 50% to 70%, as using MCT as the sole fat source can lead to essential fatty acid deficiencies. The ratio of MCT to carbohydrates (by weight) can vary widely. In animal experiments, MCT doses are typically designed based on the percentage of MCT in the total feed weight, generally ranging from 10% to 30%.

MCT administration methods are diverse, including oral administration, enteral feeding, and use in parenteral nutrition (PN). Currently, in PN applications, fat emulsions containing MCT are transitioning from physical mixing of MCT and long-chain triglycerides (LCT) to chemical mixing, with chemically mixed fat emulsions referred to as structured fat emulsions.

참조

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