Characterization of thraustochytrid-specific sterol O-acyltransferase: modification of DGAT2-like enzyme to increase the sterol production in Aurantiochytrium limacinum mh0186.

IMPORTANCE: Since the global market for sterols and vitamin D are grown with a high compound annual growth rate, a sustainable source of these compounds is required to keep up with the increasing demand. Thraustochytrid is a marine oleaginous microorganism that can synthesize several sterols, which are stored as SE in lipid droplets. DGAT2C is an unconventional SE synthase specific to thraustochytrids. Although the primary structure of DGAT2C shows high similarities with that of DGAT, DGAT2C utilizes sterol as an acceptor substrate instead of diacylglycerol. In this study, we examined more detailed enzymatic properties, intracellular localization, and structure-activity relationship of DGAT2C. Furthermore, we successfully developed a method to increase sterol and provitamin D3 productivity of thraustochytrid by more than threefold in the process of elucidating the function of the DGAT2C-specific N-terminal region. Our findings could lead to sustainable sterol and vitamin D production using thraustochytrid.

Age-Related Effects of Olive Oil Polyphenol Ingestion on Oxidation of Low-Density Lipoprotein in Healthy Japanese Men: A Randomized Controlled Double-Blind Crossover Trial.

BACKGROUND: The function of olive oil polyphenols in suppressing the oxidation of low-density lipoprotein (LDL) is well-known in Europeans. However, it remains unclear whether olive oil polyphenols exert antioxidant effects in Japanese people. OBJECTIVES: The objective of this study was to determine whether the ingestion of olive oil polyphenols suppresses LDL oxidation in the Japanese population and whether this effect depends on age. METHODS: This randomized controlled double-blind crossover trial with a 2-week washout enrolled 80 healthy Japanese men aged 35-64 years. Participants ingested either 14 g of extra virgin olive oil containing 5.0 mg of olive oil polyphenols (test food) or 14 g of refined olive oil containing 0.3 mg of olive oil polyphenols (control food) for 3 weeks. The primary outcome was oxidized LDL (malondialdehyde-modified LDL; MDA-LDL). Subgroup analyses based on age (35-50 and 51-64 years) were also performed. RESULTS: In all of the participants (35-64 years), there were no significant differences in MDA-LDL between the control and test groups. However, in the 35-50 years subgroup, ingestion of olive oil polyphenols led to a significantly larger reduction in MDA-LDL as compared with the control group (p < 0.025). CONCLUSIONS: The significantly lower dietary total polyphenol intake of the 35-50 years subgroup compared to the 51-64 years subgroup suggests that the suppressive function of olive oil polyphenol intake on LDL oxidation in Japanese men is influenced by dietary habits and is more clearly demonstrated in the younger age population with a relatively low total polyphenol intake.

Ingestion of triglycerides containing medium- and long-chain fatty acids can increase metabolism of ingested long-chain triglycerides in overweight persons.

Introduction: Medium-chain fatty acids (MCFAs) have attracted considerable attention for preventing or improving obesity, which is a recognized risk factor for lifestyle-related diseases. Medium- and long-chain triglycerides (MLCTs) are expected to improve the metabolism of ingested long-chain triglycerides (LCTs). However, previous studies have reported mixed results. In this study, the effect of ingestion of MLCTs was evaluated on the metabolism of LCTs and compared to the ingestion of rapeseed oil (control oil). Methods: A randomized, double-blind, placebo-controlled crossover study was performed among sedentary participants with BMIs ranging from 25 below 30 kg/m2. Thirty participants were asked to ingest either 14 g of MLCTs or a control oil for 4 weeks. The metabolism of ingested LCTs was evaluated by measuring isotopically labeled carbon dioxide released by the degradation of carbon-13 (13C)-labeled LCTs. Results: Ingestion of MLCTs markedly enhanced the metabolism of ingested LCTs by comparison to the control oil. Conclusion: The findings of this study suggest that ingestion of MLCTs may enhance the metabolism of dietary LCTs through activation of ß-oxidation in liver mitochondria, which may increase the metabolic kinetics of ingested long-chain fatty acid (LCFAs). Clinical trial registration: https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000053101, identifier: UMIN000046604.

Effect of Continuous Ingestion of 2 g of Medium-Chain Triglycerides on Substrate Metabolism during Low-Intensity Physical Activity.

Increasing fat burning during physical activity is thought to be an effective strategy for maintaining health and preventing lifestyle-related diseases, such as obesity and diabetes. In recent years, medium-chain triglycerides (MCTs) have gained attention as a dietary component for increasing fat-burning. However, this fat-burning effect has been unclear in people with high body mass index (BMI). Therefore, we aimed to clarify the effects of 2 g of daily ingestion of MCTs over 2 weeks on substrate oxidation during low-intensity physical activity in sedentary (i.e., with no exercise habit) subjects with a BMI from 25 (kg/m2) to less than 30, which is classified as obese in Japan. A placebo-controlled, randomized, double-blind, crossover study with a 2-week washout period was conducted. The rate of fat oxidation as well as the respiratory exchange ratio (RER) during exercise (with a cycle ergometer at a 20-watt load) were measured with a human calorimeter. MCTs ingestion significantly increased fat oxidation during physical activity and decreased RER compared to long-chain triglycerides ingestion. In conclusion, we suggest that daily ingestion of 2 g of MCTs for 2 weeks increases fat burning during daily physical activities in sedentary persons with a BMI ranging from 25 to less than 30.