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We examined the long-term effects of dietary diacylglycerol (DG) and triacylglycerol (TG) with similar fatty acid compositions on the development of obesity in C57BL/6J mice. We also analyzed the expression of genes involved in lipid metabolism at an early stage of obesity development in these mice. Compared with mice fed the high-TG diet, mice fed the high-DG diet accumulated significantly less body fat during the 8-month study period. Within the first 10 days, dietary DG stimulated β-oxidation and lipid metabolism-related gene expression, including acyl-CoA oxidase, medium-chain acyl-CoA dehydrogenase, and uncoupling protein-2 in the small intestine but not in the liver, skeletal muscle, or brown adipose tissue, suggesting the predominant contribution of intestinal lipid metabolism to the effects of DG. Furthermore, analysis of digestion products of 14CDG and those of 14CTG revealed that the radioactivity levels detected in fatty acid, 1-monoacylglycerol, and 1,3-DG in intestinal mucosa were significantly higher after intrajejunal injection of DG rather than TG.Thus, dietary DG reduces body weight gain that accompanies the stimulation of intestinal lipid metabolism, and these effects may be related to the characteristic metabolism of DG in the small intestine. We examined the long-term effects of dietary diacylglycerol (DG) and triacylglycerol (TG) with similar fatty acid compositions on the development of obesity in C57BL/6J mice. We also analyzed the expression of genes involved in lipid metabolism at an early stage of obesity development in these mice. Compared with mice fed the high-TG diet, mice fed the high-DG diet accumulated significantly less body fat during the 8-month study period. Within the first 10 days, dietary DG stimulated β-oxidation and lipid metabolism-related gene expression, including acyl-CoA oxidase, medium-chain acyl-CoA dehydrogenase, and uncoupling protein-2 in the small intestine but not in the liver, skeletal muscle, or brown adipose tissue, suggesting the predominant contribution of intestinal lipid metabolism to the effects of DG. Furthermore, analysis of digestion products of 14CDG and those of 14CTG revealed that the radioactivity levels detected in fatty acid, 1-monoacylglycerol, and 1,3-DG in intestinal mucosa were significantly higher after intrajejunal injection of DG rather than TG. Thus, dietary DG reduces body weight gain that accompanies the stimulation of intestinal lipid metabolism, and these effects may be related to the characteristic metabolism of DG in the small intestine. In Westernized countries, obesity is an important health problem. It is becoming clear that obesity is a major risk factor for various diseases, including diabetes, hypertension, and atherosclerosis. As the high fat content of the typical Western diet is considered a major cause of obesity, many studies have been conducted on dietary modification to counter obesity (1Berry E.M. Dietary fatty acids in the management of diabetes mellitus.Am. J. Clin. Nutr. 1997; 66: 991S-997SCrossref PubMed Scopus (87) Google Scholar, 2Bach A.C. Ingenbleek Y. Frey A. The usefulness of dietary medium-chain triglycerides in body weight control: fact or fancy?.J. Lipid Res. 1996; 37: 708-726Abstract Full Text PDF PubMed Google Scholar, 3Mori T.A. Bao D.Q. Burke V. Puddey I.B. Watts G.F. Beilin L.J. Dietary fish as a major component of a weight-loss diet: effect on serum lipids, glucose, and insulin metabolism in overweight hypertensive subjects.Am. J. Clin. Nutr. 1999; 70: 817-825Crossref PubMed Scopus (239) Google Scholar, 4Takahashi Y. Ide T. Dietary n-3 fatty acids affect mRNA level of brown adipose tissue uncoupling protein 1, and white adipose tissue leptin and glucose transporter 4 in the rat.Br. J. Nutr. 2000; 84: 175-184Crossref PubMed Google Scholar). We have been studying the nutritional characteristics and dietary effects of diacylglycerol (DG) (5Murata M. Hara K. Ide T. Alteration by diacylglycerols of the transport and fatty acid composition of lymph chylomicrons in rats.Biosci. Biotechnol. Biochem. 1994; 58: 1416-1419Crossref Scopus (89) Google Scholar, 6Nagao T. Watanabe H. Goto N. Onizawa K. Taguchi H. Matsuo N. Yasukawa T. Tsushima R. Shimasaki H. Itakura H. Dietary diacylglycerol suppresses accumulation of body fat compared to triacylglycerol in men in double-blind controlled trial.J. Nutr. 2000; 130: 792-797Crossref PubMed Scopus (281) Google Scholar, 7Murase T. Mizuno T. Omachi T. Onizawa K. Komine Y. Kondo H. Hase T. Tokimitsu I. Dietary diacylglycerol suppresses high fat and high sucrose diet-induced body fat accumulation in C57BL/6J mice.J. Lipid Res. 2001; 42: 372-378Abstract Full Text Full Text PDF PubMed Google Scholar, 8Taguchi H. Nagao T. Watanabe H. Onizawa K. Matsuo N. Tokimitsu I. Itakura H. Energy value and digestibility of dietary oil containing mainly 1,3-diacylglycerol are similar to those of triacylglycerol.Lipids. 2001; 36: 379-382Crossref PubMed Scopus (115) Google Scholar). DG, which consists mainly of 1,3-DG, is a minor component of various edible oils and is widely consumed in our diet. Murata et al. reported that after a single dose of DG emulsion, the extent of increase in postprandial serum triacylglycerol (TG) levels, especially for chylomicron TG, was less than the increase observed after administration of TG emulsion (5Murata M. Hara K. Ide T. Alteration by diacylglycerols of the transport and fatty acid composition of lymph chylomicrons in rats.Biosci. Biotechnol. Biochem. 1994; 58: 1416-1419Crossref Scopus (89) Google Scholar). Nagao et al. reported that dietary DG, in contrast to TG, decreased both body weight and visceral fat mass as determined by computed tomography (CT) in healthy men (6Nagao T. Watanabe H. Goto N. Onizawa K. Taguchi H. Matsuo N. Yasukawa T. Tsushima R. Shimasaki H. Itakura H. Dietary diacylglycerol suppresses accumulation of body fat compared to triacylglycerol in men in double-blind controlled trial.J. Nutr. 2000; 130: 792-797Crossref PubMed Scopus (281) Google Scholar). In addition, we have recently shown that dietary DG suppresses the accumulation of high-fat and high-sucrose diet-induced body fat in C57BL/6J mice (7Murase T. Mizuno T. Omachi T. Onizawa K. Komine Y. Kondo H. Hase T. Tokimitsu I. Dietary diacylglycerol suppresses high fat and high sucrose diet-induced body fat accumulation in C57BL/6J mice.J. Lipid Res. 2001; 42: 372-378Abstract Full Text Full Text PDF PubMed Google Scholar). These results suggested that the structure of acylglycerol, but not the fatty acid composition, markedly affects the nutritional behavior of lipids. However, the mechanisms underlying the various effects of dietary DG have yet to be fully elucidated. In this study, to gain insight into the dietary effects of DG, we examined the long-term effects of dietary DG on the development of obesity, and analyzed mRNA expression of genes involved in energy metabolism in various organs, including the liver, small intestine, brown adipose tissue, and skeletal muscle at an early stage of obesity development in C57BL/6J mice. Furthermore, we investigated the metabolic characteristics of DG in the small intestine by analyzing the digestion products in the lumen and TG synthesis-intermediates in the mucosa. We report here that dietary DG suppresses the accumulation of body fat accompanying intestinal gene expression, and that this effect may be related to the characteristic metabolism of DG in the small intestine. DG-rich oil was prepared from rapeseed oil as described previously (9Huge-Jensen B. Donna R.G. Jensen R.G. Studies on free and immobilized lipase from Muscor miehei.J. Am. Oil Chem. Soc. 1988; 65: 905-910Crossref Scopus (81) Google Scholar). As shown in Table 1, the fatty acid composition of the DG oil was similar to that of TG oil (rapeseed oil). The DG oil contained approximately 90% DG and 10% TG. The DG was comprised of 1,3-DG and 1,2-DG at a ratio of 7:3 (w/w). Carboxyl-14Ctriolein (99% pure, 102.0 mCi/mmol) was purchased from NEN Life Science Products, Inc. (Boston, MA). 1,3-Carboxyl-14Cdiolein (99% pure, 13.3 mCi/mmol) was obtained from Daiichi Pure Chemicals Co., Ltd. (Tokyo, Japan). Triolein and 1,3-diolein were purchased from Sigma (St. Louis, MO).TABLE 1.Fatty acid compositions of test oils (%)TG OilDG Oil16:04.24.218:01.92.018:160.362.018:220.220.118:39.36.420:00.60.720:11.31.322:00.30.422:10.20.2Others1.52.7 Open table in a new tab Experiment 1: Male C57BL/6J mice obtained from Japan Clea (Tokyo, Japan) at 7-weeks of age were maintained at 22 ± 1°C under a 12 h light-dark cycle (lights on from 7 AM to 7 PM). The mice were divided into three groups (n = 10 or 20, 5 mice/cage), and were allowed ad libitum access to water, and one of the three synthetic diets described in Table 2 using Roden caffe (Oriental Yeast Co., Tokyo, Japan) to minimize dispersion of diets. The energy values for each diet were calculated from the macronutrient composition using values of 4 kcal/g, 4 kcal/g, and 9 kcal/g for carbohydrate, protein, and oil, respectively. The animals were maintained on their respective diets for 8 months. During the experiments, the animals were cared for in accordance with the principles for the use of animals for research and education, following the Statement of Principles adopted by the FASEB Board.TABLE 2.Compositions of the diets (%)IngredientsLow-TGHigh-TGHigh-DGTriacylglycerol5.025.010.0Diacylglycerol——15.0Lard—5.05.0Sucrose—13.013.0Casein20.020.020.0Cellulose powder4.04.04.0Mineral mixture3.53.53.5Vitamin mixture1.01.01.0Potato starch66.528.528.5Energy (kcal/100g)391516516 Open table in a new tab Experiment 2: Mice were divided into three groups (n = 6, 3 mice/cage) and were allowed ad libitum access to the respective synthetic diets for 10 days. On the final day of the experiment, the mice in all groups were sacrificed, and each organ was rapidly dissected for β-oxidation assay and Northern blotting analysis. Food intake in Experiment 1 was measured on a per-cage basis over the course of 24 h 1 day per week. In Experiment 2, food intake was measured on a per-cage basis every day throughout the study. On the final day of the experiments, blood was collected from anesthetized mice in the non-fasting the mice under the blood were collected by the after 12 h of 10 to the of Experiment TG, fatty acids and glucose were determined using the assay test and respectively. insulin and leptin levels were measured using a insulin and leptin to the The fat were dissected from each and the of white adipose tissue and as as that of brown adipose tissue were β-oxidation was measured as reported previously H. A. study of and fatty acid in from with Lipid Res. Full Text PDF PubMed Google with minor and intestinal mucosa were and on with 5 of sucrose containing 1 and 10 and at for 5 The was for The contained 2 2 1 5 acid, and the containing protein in a final of The was by the and the at for The was by of acid, by The was three with of to The radioactivity of the was were determined using a protein assay On the final day of Experiment 2, mice were 9 AM and and the small intestine, liver, skeletal muscle and and were dissected from each and in for was using to the was on and were with a at were in at and in at and analyzed with a Tokyo, Japan). The were also with a and the mRNA levels were calculated to the mRNA values were as using the value of mice fed a diet as was prepared by and by use of from or tissue The were as acyl-CoA medium-chain acyl-CoA acid protein fatty acid transporter uncoupling protein and were with by use of TG emulsion was prepared by 10 10 10 of and 1 of DG emulsion was prepared using of 1,3-diolein and 1 of of each of which contained fatty The C57BL/6J mice that were for 12 h were on a under TG or DG emulsion containing 2 or was into the at 2 from the of after the of the small intestine from the was and on The small intestine was with 2 of The was for analysis of the lipid digestion The small intestine was with of and with containing and with of The intestine was and the mucosa was using a The and the were in and at were 5 after The were by the of et al. J. M. for the and of from Chem. Full Text PDF PubMed Google under a of and in The were by using a and as the development The were the from the using and The were to a Co., Tokyo, and the obtained were analyzed with a values are as ± groups were using and each was compared with the by test was as with our report (7Murase T. Mizuno T. Omachi T. Onizawa K. Komine Y. Kondo H. Hase T. Tokimitsu I. Dietary diacylglycerol suppresses high fat and high sucrose diet-induced body fat accumulation in C57BL/6J mice.J. Lipid Res. 2001; 42: 372-378Abstract Full Text Full Text PDF PubMed Google dietary DG significantly the body fat accumulation by a high-fat diet in C57BL/6J mice. Compared with the diet, with the high-TG diet for 8 in body weight and adipose tissue On the the high-DG diet body weight and weight by and as compared with the high-TG diet energy and fat (n = (n = (n = weight ± the high-TG ± ± intake ± the high-TG ± ± ± the high-TG ± ± ± the high-TG ± ± ± ± ± ± ± ± were after 8 of with the respective body fat weight was Food intake was measured on a per-cage basis over the course of 24 h one day per week. are the ± the high-TG Open table in a new tab Mice were after 8 of with the respective body fat weight was Food intake was measured on a per-cage basis over the course of 24 h one day per week. are the ± were in the and high-DG mice under the non-fasting after 8 of glucose, and leptin under the in the DG mice were significantly than those in the high-TG mice (n = (n = (n = ± ± ± ± ± ± ± the high-TG ± ± ± ± ± ± ± ± ± ± ± ± the high-TG ± ± ± ± ± ± the high-TG ± ± the final day of Experiment 1, blood was collected from anesthetized mice in the non-fasting the from mice in the was collected by the after 12 h of 10 to the of the are the ± the high-TG Open table in a new tab On the final day of Experiment 1, blood was collected from anesthetized mice in the non-fasting the from mice in the was collected by the after 12 h of 10 to the of the are the ± was in the energy intake the high-TG diet and the high-DG diet In addition, we previously that lipid not significantly high-TG and high-DG mice (7Murase T. Mizuno T. Omachi T. Onizawa K. Komine Y. Kondo H. Hase T. Tokimitsu I. Dietary diacylglycerol suppresses high fat and high sucrose diet-induced body fat accumulation in C57BL/6J mice.J. Lipid Res. 2001; 42: 372-378Abstract Full Text Full Text PDF PubMed Google Scholar, 8Taguchi H. Nagao T. Watanabe H. Onizawa K. Matsuo N. Tokimitsu I. Itakura H. Energy value and digestibility of dietary oil containing mainly 1,3-diacylglycerol are similar to those of triacylglycerol.Lipids. 2001; 36: 379-382Crossref PubMed Scopus (115) Google suggesting that accumulation of body fat in the DG was not related to energy the mechanisms underlying the effects of dietary DG, we examined the effects of DG on the mRNA expression of genes involved in lipid metabolism in various However, was to the in lipid metabolism were a cause or a of the body fat we investigated mRNA levels after 10 of at which were observed in body food or the high-fat groups As the small intestine is the first and of the to dietary we examined the effects of DG on intestinal gene In mice fed the high-DG diet, the acyl-CoA β-oxidation mRNA level in the small intestine was significantly higher than that in mice fed the or the high-TG diet by the level of the mRNA levels in mice were and higher than those in the and high-TG diet respectively. acyl-CoA β-oxidation mRNA levels in the high-DG mice were also higher than those of the and high-TG by and respectively. and are in the small intestine, and are to in the and metabolic of fatty acids R.G. fatty their structure and Lipid Res. PubMed Scopus Google Scholar). The mRNA level in the small intestine was higher in mice fed the high-DG diet than in mice fed the diet, and higher than in the high-TG mice. mRNA in the high-DG mice was also by and compared with the and high-TG respectively. have been to metabolic T. 2 and of energy 2000; PubMed Scopus Google Scholar, The uncoupling protein and J. 2000; PubMed Scopus Google Scholar). study that is in the small intestine and is by dietary fat T. Kondo H. Hase T. Tokimitsu I. M. expression of uncoupling protein-2 in the small by dietary fish oil and 2001; PubMed Scopus Google Scholar). In the study, the level of intestinal mRNA was by the high-DG diet, effect was observed by the high-TG diet. The high-DG diet a increase in than the or high-TG diet by and weight ± ± ± intake ± ± ± ± ± ± ± ± ± ± ± ± ± the high-TG ± ± ± ± ± ± ± ± were fed the respective diets for 10 body weight was Energy intake was measured on a per-cage basis throughout the study. was collected under non-fasting and analyzed as described in and are the ± of the high-TG Open table in a new tab Mice were fed the respective diets for 10 body weight was Energy intake was measured on a per-cage basis throughout the study. was collected under non-fasting and analyzed as described in and are the ± of On the were in the mRNA levels of or in the the high-fat groups not Furthermore, the mRNA levels of and in the skeletal muscle were not by the high-DG diet not The levels of and mRNA in were by both the high-TG and high-DG was the of were observed in mRNA levels the three groups in These results suggested that dietary DG expression of the genes involved in lipid metabolism, especially in the small intestine. the effects of DG on intestinal lipid metabolism, we examined the β-oxidation after DG As shown in the high-DG diet β-oxidation significantly by and as compared with the and high-TG diet that with the DG diet lipid in the small intestine. On the were observed in β-oxidation the three these results suggested that stimulation of intestinal lipid metabolism be one of the for the effects of dietary DG. gain insight into the by which dietary DG intestinal lipid metabolism, we investigated the metabolic characteristics of DG in the small intestine by analyzing the digestion products in the lumen and TG synthesis-intermediates in the mucosa 5 after intrajejunal injection of DG. was for on a study course of lipid metabolism of in the Lipid Res. Full Text Full Text PDF PubMed Google Scholar). of TG and DG in the intestinal lumen are shown in Table In the DG injection and higher radioactivity levels were detected in and fatty acid, compared with the TG injection In the intestinal the radioactivity levels for 1,3-DG, and fatty acid were and higher than those in the TG injection These results suggested that DG is characteristic to of the lipid and this may affect the of gene expression in the small of digestion products of or in the intestinal ± ± ± the injection ± the injection ± ± ± the injection ± ± ± ± ± the injection ± ± ± ± ± ± ± ± the injection ± ± ± the injection ± the injection after injection of DG or TG emulsion containing or the of the small intestine was Lipid of intestinal lumen was analyzed as described in and are the ± of the injection Open table in a new tab of in the intestinal ± ± ± ± the injection ± ± ± ± ± ± ± ± ± ± ± the injection ± the injection ± ± ± ± ± ± ± ± after injection of DG or TG emulsion containing or the of the small intestine was The lipid of intestinal mucosa was analyzed as described in and are the ± of the injection Open table in a new tab after injection of DG or TG emulsion containing or the of the small intestine was Lipid of intestinal lumen was analyzed as described in and are the ± of after injection of DG or TG emulsion containing or the of the small intestine was The lipid of intestinal mucosa was analyzed as described in and are the ± of of the studies on the dietary effects of fat have been conducted from the of fatty acid As a that the fatty acid composition of dietary fat mainly of TG markedly affects the development of obesity, diabetes, and (1Berry E.M. Dietary fatty acids in the management of diabetes mellitus.Am. J. Clin. Nutr. 1997; 66: 991S-997SCrossref PubMed Scopus (87) Google Scholar, Dietary on serum and Lipid Res. Full Text PDF PubMed Google Scholar, Dietary serum and J. Clin. Nutr. PubMed Scopus Google Scholar). On the been to as the of fatty or a fatty in the We have shown in both the and our studies that the structure of is a factor the nutritional behavior of lipids. results that dietary DG, compared with TG with a similar fatty acid composition, significantly suppresses body weight gain accompanying the of genes involved in lipid metabolism in the small intestine. results from a energy intake and we that the energy value per weight and digestibility of DG is similar to that of TG H. Nagao T. Watanabe H. Onizawa K. Matsuo N. Tokimitsu I. Itakura H. Energy value and digestibility of dietary oil containing mainly 1,3-diacylglycerol are similar to those of triacylglycerol.Lipids. 2001; 36: 379-382Crossref PubMed Scopus (115) Google and that energy intake was not significantly high-TG and high-DG suggesting that body fat accumulation in the was not related to energy be involved in the effects of DG. As shown in this study, in the early stage of DG were observed in β-oxidation and related gene expression in the small intestine. As the small intestine is the first organ to dietary that is the to dietary DG. The DG diet was to the mRNA level involved in fatty acid transport and β-oxidation and and in the small intestine. These results suggested that 1,3-DG structure intestinal lipid As have been to energy and the development of obesity T. 2 and of energy 2000; PubMed Scopus Google Scholar, The uncoupling protein and J. 2000; PubMed Scopus Google Scholar, M. a gene to obesity and 1997; PubMed Scopus Google Scholar, H. H. B. in the of is with decreased risk of obesity in 2001; PubMed Scopus Google of in the small intestine may to the stimulation of energy In addition, et al. reported that in one of the with β-oxidation of fatty acids in in K. in mice with of fatty acid Clin. PubMed Scopus Google stimulation of fatty acid β-oxidation is to to energy the fact that the small intestine is one of the and on β-oxidation N. K. T. T. of and levels of expression of and genes in and of Res. 1988; Google Scholar, R. The expression and of genes Chem. Full Text PDF PubMed Google is that expression of intestinal and accompanying β-oxidation in energy and to the of body fat studies on intestinal energy metabolism are to the contribution of the small intestine in diet-induced the by which dietary DG intestinal lipid metabolism and related gene expression to be an increase in fatty acid may be involved in the The is a factor by fatty acids with the M. acid of gene Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, J. fatty and are for and 1997; PubMed Scopus Google Scholar). is to by to the of genes including and K. B. J. of the in the effects of and fatty acids on gene Lipid Res. 1996; 37: Full Text PDF PubMed Google Scholar, L.J. J. R. and in of uncoupling protein gene PubMed Scopus Google Scholar). the is to be in the small intestine A. H. J. of the in the Res. 1996; PubMed Scopus Google and is to an important in the expression of the genes K. K. T. The expression of genes is development of in the small 2001; PubMed Scopus Google Scholar, K. N. of fatty acid transporter genes are by and in a and Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). is to be an for the and dietary of genes fatty acid In this is that the increase in fatty acid in the mucosa after DG in the of the of the of in the dietary of intestinal lipid metabolism using mice with gene or The increase in fatty acid in the intestinal mucosa may be by the characteristic metabolic of DG. The of TG is to and fatty into intestinal and into TG The effects of structure on and Nutr. PubMed Scopus Google Scholar, R. A. of Lipid Res. 1996; PubMed Scopus Google Scholar, The digestion and of Chem. Full Text PDF PubMed Google Scholar). On the 1,3-DG is to be to and fatty acid, which is into the mucosa or into and fatty Thus, the metabolic of 1,3-DG is from that of TG. As shown in Table 6, the of acid in the lumen of DG mice was higher than that of TG mice. of fatty acid in the lumen and into the mucosa may to the higher content of fatty acid in the mucosa. Furthermore, compared with TG DG mice of 1,3-DG in the mucosa 1,3-DG been shown to be as a for TG by diacylglycerol R. A. by from intestinal Chem. Full Text PDF PubMed Google which the of DG. The increase in 1,3-DG the of which may also to the increase in fatty acid after DG In we that the structure of the TG and affects body fat expression of genes involved in lipid metabolism and and their metabolic in the small intestine in C57BL/6J mice. the nutritional characteristics of dietary DG and especially in the small intestine, may insight for the management of obesity as as for lipid acyl-CoA diacylglycerol acid protein medium-chain acyl-CoA triacylglycerol uncoupling protein
Murase et al. (Thu,) studied this question.