An outline of reported effects of DAG on lipid/glucose metabolism is shown in Table . In animals, DAG ingestion was demonstrated to reduce plasma TG and FFA levels compared with TAG ingestion. Fujii A, et al found that DAG-rich oil reduced atherosclerosis in diabetic apoE-deficient mice, and ingestion of DAG-rich oil was associated with reduction in plasma cholesterol levels within larger TG-rich lipoproteins [13
]. Further, DAG ingestion was reported to prevent the high-sucrose-diet-induced development of impaired glucose tolerance compared with TAG oil ingestion, in male Wistar rats [14
Effects of DAG on lipid and glucose metabolism
In our previous studies with healthy volunteers, serum TG and remnant-like lipoprotein particles-cholesterol (RLP-C) concentrations after DAG ingestion were significantly lower than those after TAG ingestion [15
]. Tomonobu K, et al. also reported that postprandial TG, RLP-C, and CM-TG concentrations were significantly lower after DAG ingestion than after TAG ingestion [16
]. In our study with diabetic patients, DAG loading significantly suppressed increases in postprandial serum TG, RLP-C and RLP-TG levels as compared with TAG loading [17
Recent study found that DAG reduced postprandial increase in TG, RLP-C, and RLP-TG, especially in subjects with insulin resistance [18
]. In the subjects who consumed daily 10 g of DAG for 12 weeks, serum TG levels were decreased by 39.4%, and serum hemoglobin A1c levels were also decreased by 9.7%, compared with subjects who consumed TAG, suggesting that DAG ingestion also ameliorates glucose metabolism [19
]. Further, a long-term DAG oil consumption has been reported to increase HDL-C, and decrease fasting TG, total cholesterol, LDL-C, compared with TAG consumption [20
The apolipoprotein C-II is a cofactor of LPL, which hydrolyzes TG of CM and very-low-density lipoprotein (VLDL) [23
]. We have a therapeutic experience with DAG oil to a patient with apolipoprotein C-II deficiency, a rare autosomal recessively-inherited disease [24
]. In a patient with apolipoprotein C-II deficiency, DAG ingestion suppressed increase in serum TG, VLDL-C, and RLP-C levels compared with TAG ingestion, suggesting that DAG can decrease TG-rich lipoprotein, also independent of LPL.
In summary, DAG ameliorates fasting and postprandial TG-rich lipoproteins, and glucose metabolism, which may be favorable for metabolic disorders observed in the metabolic syndrome.