中链脂肪酸对高脂饲料诱导的肥胖大鼠高密度脂蛋白的调节作用

目的观察中链脂肪酸(MCFA)对高脂饲料诱导的肥胖SD大鼠高密度脂蛋白的代谢调节作用,探讨MCFA降低血胆固醇的可能机制。方法高脂饲料诱导SD大鼠肥胖,30只肥胖大鼠按空腹体重随机分为3组,每组10只,分别给予含2%(2 g/100 g)辛酸(C8∶0)、癸酸(C10∶0)和油酸(C18∶1)的高脂饲料喂养8周,于4周和8周时取眼底静脉丛血,测定血清甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-c)、低密度脂蛋白胆固醇(LDL-c)、高密度脂蛋白(HDL)、载脂蛋白A1(ApoA1)、载脂蛋白A2(ApoA2)浓度,于8周时取大鼠肝脏和小肠,ELISA法测定HDL、ApoA1、ApoA2含量,Real-time PCR法测定Apo A1及ApoA2 mRNA表达量。结果中链脂肪酸喂养肥胖大鼠4周时,3组大鼠血清血脂水平无差异,8周时,辛酸组和癸酸组血清TG、TC水平均显著低于4周时(P0.05),且显著低于油酸组(P0.05),HDL水平显著高于油酸组(P0.05)。HDL-c/LDL-c比值以辛酸组最高,且显著高于油酸组(P0.05)。8周时,大鼠小肠中HDL、ApoA1浓度及mRNA表达量也以辛酸组最高,显著高于油酸组(P0.05),但与癸酸组比较差异无统计学意义。大鼠肝脏中各项指标组间差异均无统计学意义。结论中链脂肪酸可能通过增加小肠HDL及ApoA1表达,上调HDL水平及HDL-c/LDL-c比值,降低肥胖大鼠血胆固醇水平。     

Effect of triacylglycerols containing medium- and long-chain fatty acids on body fat accumulation in rats

Effect of triacylglycerols containing medium- and long-chain fatty acids (TML) on body fat accumulation was studied in rats. Male Wistar rats were fed an experimental diet containing 25% soybean oil or TML for 6 weeks. The food intake for 6 weeks did not significantly differ between the two diet groups. However, the perirenal and mesenteric adipose tissue weight and carcass fat content were significantly lower in the TML diet group than in the soybean oil diet group. The epididymal adipose tissue weight and liver triacylglycerol content did not significantly differ between the two diet groups. The digestibility of dietary fat did not significantly differ between the two diet groups. These results suggest that an intake of TML decreases body fat accumulation compared to an intake of soybean oil in rats.     

The effect of six different C18 fatty acids on body fat and energy metabolism in mice

We studied the effects of five high-fat semi-purified diets varying at a 4% (w/w) level in either stearic, oleic, linoleic, alpha-linolenic, or gamma-linolenic acid on body fat and energy metabolism in BALB/c mice. A diet containing caprylic, capric, lauric, and myristic acid was used as a reference diet and a diet with 4% conjugated linoleic acid (CLA) was used as a positive control as it is known to effectively lower body fat in mice. The diets were fed for 35 d. Body fat was significantly lower in the CLA group than in the other groups but was not significantly different among the non-CLA groups. Among the non-CLA groups, the linoleic acid group tended to have the highest and the alpha-linolenic acid group the lowest proportion of body fat. In energy-balance studies, the percentage of energy intake that was stored in the body was significantly lower in the CLA group compared with the other dietary groups. The percentage of energy intake eliminated in excreta was highest in the stearic acid group followed by the gamma-linolenic acid group. These results were reflected in apparent fat digestibility, which was lowest in the stearic acid group. The percentage of energy intake expended as heat was highest in the CLA-fed mice. The results of the present study suggest that body fat and energy accretion in mice fed diets containing different C18 fatty acids is by far the lowest with CLA and that linoleic acid produced the highest fat intake and energy accretion.     

Short term effects of dietary medium-chain fatty acids and n-3 long-chain polyunsaturated fatty acids on the fat metabolism of healthy volunteers

Background

The amount and quality of dietary fatty acids can modulate the fat metabolism.

Objective

This dietary intervention is based on the different metabolic pathways of long-chain saturated fatty acids (LCFA), which are mostly stored in adipocytic triacylglycerols, medium-chain fatty acids (MCFA) which are preferentially available for hepatic mitochondrial β-oxidation and n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) suggested to modulate fat oxidation and storage by stimulating the peroxisomal β-oxidation. Combined dietary MCFA and n-3 LCPUFA without LCFA may synergistically stimulate fatty acid oxidation resulting in blood lipid clearance and LCFA release from adipocytes.

Design

In a short term, parallel, randomized, double-blind trial effects on the fatty acid metabolism of 10 healthy volunteers (Body Mass Index 25–30) of a formula containing 72% MCFA and 22% n-3 LCPUFA without LCFA (intake: 1.500 kcal/day; fat: 55.5% of energy) were measured in comparison to an isoenergetic formula with equal fat amount and LCFA dominated lipid profile.

Results

The plasma triacylglycerol (p < 0.1) and cholesterol (p < 0.05) content decreased in the test group. The n-3/n-6 LCPUFA (≥ C 20) ratio increased (p < 0.0001) after 4 days treatment. The LCFA content was similar in both groups despite missing LCFA in the test formula indicating LCFA release from adipocytes into the plasma. Both groups significantly reduced body weight considerably 4 kg (p < 0.01) and fat mass up to 50% of weight loss (p < 0.05).

Conclusion

Combined dietary 72% MCFA and 22% n-3 LCPUFA without LCFA stimulate the fatty acid oxidation and release from adipocytes without affecting any safety parameters measured.

     

Dietary medium-chain triacylglycerols suppress accumulation of body fat in a double-blind, controlled trial in healthy men and women.

We investigated the effect of long-term ingestion of dietary medium-chain triacylglycerols (MCT) on body weight and fat in humans. Using a double-blind, controlled protocol, we assessed the potential health benefits of MCT compared with long-chain triacylglycerols (LCT) in 78 healthy men and women [body mass index (BMI) > or = 23 kg/m(2): n = 26 (MCT), n = 30 (LCT); BMI < 23 kg/m(2): n = 15 (MCT), n = 7 (LCT)]. Changes in anthropometric variables, body weight and body fat during the 12-wk MCT treatment period were compared with those in subjects consuming the LCT diet. The subjects were asked to consume 9218 kJ/d and 60 g/d of total fat. The energy, fat, protein and carbohydrate intakes did not differ significantly between the groups. Body weight and body fat in both groups had decreased by wk 4, 8 and 12 of the study. However, in the subjects with BMI > or = 23 kg/m(2), the extent of the decrease in body weight was significantly greater in the MCT group than in the LCT group. In subjects with BMI > or = 23 kg/m(2), the loss of body fat in the MCT group (-3.86 +/- 0.3 kg) was significantly greater than that in the LCT group (-2.75 +/- 0.2 kg) at 8 wk. In addition, in subjects with BMI > or = 23 kg/m(2), the decrease in the area of subcutaneous fat in the MCT group was significantly greater than that in the LCT group at wk 4, 8 and 12. These results suggest that the MCT diet may reduce body weight and fat in individuals (BMI > or = 23 kg/m(2)) more than the LCT diet.     

Effects of different ratios of monounsaturated and polyunsaturated fatty acids to saturated fatty acids on regulating body fat deposition in hamsters

ObjectiveEffects of monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid consumption on regulating body fat accumulation and body weight gain are controversial between animal and human studies.MethodsWe designed a 2 × 2 factorial study, with two levels of MUFAs (60% and 30%) and two levels of polyunsaturated-to-saturated fatty acid (P/S) ratio (5 and 3) to prepare four kinds of experimental oils consisting of 60% MUFAs with a high or low P/S ratio (HMHR or HMLR, respectively) or 30% MUFAs with a high or low P/S ratio (LMHR or LMLR, respectively). Thirty-two male golden Syrian hamsters were randomly divided into four groups and fed the experimental diets containing 15% (w/w) fat for 12 wk.ResultsNo difference was observed in the mean daily food intake. Hamsters fed the LMLR diet had increased weight gain, epididymal and retroperitoneal white adipose tissues, plasma non-esterified fatty acids, insulin, hepatic acetyl coenzyme A carboxylase and malic enzyme activities, and mRNA expressions of peroxisome proliferator-activated receptor-α and sterol regulatory element-binding protein-1c among all groups (P < 0.05). Hamsters fed the HMHR diet had lower plasma insulin levels and hepatic acetyl coenzyme A carboxylase activities among groups (P < 0.05) and elevated hepatic acyl coenzyme A oxidase and carnitine palmitoyltransferase-I activities compared with those fed the LMLR diet (P < 0.05).ConclusionHamsters fed the LMLR diet had increased weight gain and body fat accumulation, whereas the HMHR diet appeared to be beneficial in preventing white adipose tissue accumulation by decreasing plasma insulin levels and increasing hepatic lipolytic enzyme activities involved in β-oxidation.     

鲑鱼油对人体的食用安全性及辅助降血脂作用研究

目的评价鲑鱼油的食用安全性及其辅助降血脂作用。方法选120名高血脂志愿者,按血脂水平随机分为试验组和对照组,试验组每日服用鲑鱼油胶囊,对照组服安慰剂,服食期为60天。在服食期开始前与结束后检测志愿者体内的血清总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)和高密度脂蛋白胆固醇(HDL-C)水平以及肝肾功能等各项安全性指标。结果试验组人群服用鲑鱼油后,TC、TG和LDL-C水平显著降低,与服用前比较差异有统计学意义(P0.01),与对照组比较差异亦有统计学意义(P0.01)。两组人群的HDL-C水平未见明显改变,肝肾功能及其它安全性指标均未见异常。结论鲑鱼油具有辅助降低血脂的作用,且对人体健康无损害。     

The effect of conjugated linoleic acid and medium-chain fatty acids on transepithelial calcium transport in human intestinal-like Caco-2 cells

Capric (10:0) and lauric (12:0) acid and conjugated linoleic acid (CLA) have been shown to increase paracellular permeability across human intestinal-like Caco-2 cell monolayers. While this has generated interest in terms of improved drug absorption and delivery, little has been done in terms of their potential effect on nutrient transport across the intestinal epithelium. Therefore, the objective of the present study was to investigate the effect of these fatty acids on transepithelial Ca transport in Caco-2 cells. Cells were seeded onto permeable transport membranes and allowed to differentiate, over 21 d, into intestinal-like cell monolayers. Monolayers (n 9 per treatment) were exposed to 0 (control) or 80 microm-10:0, 80 microm-12:0, 80 microm-18:2, 80 microm-CLA (mixed isomers), 80 microm-cis-9,trans-11 CLA or 80 microm-trans-10,cis-12 CLA for 22 d after seeding (chronic effect) or for 24 h before Ca transport studies (acute effect) on day 22. After exposure, transepithelial and transcellular transport of 45Ca, fluorescein transport (a marker of paracellular Ca transport) and transepithelial electrical resistance (TEER, an indicator of permeability) were measured. Overall Ca transport and TEER in Caco-2 cells were unaffected by exposure to any of the fatty acids for 24 h, or to 18:2, CLA blend or cis-9,trans-11 CLA for 22 d. Paracellular (but not total transepithelial and transcellular) Ca transport across Caco-2 cells was significantly increased (P<0.01, by about 1.5-fold relative to the control value) by exposure to 10:0, 12:0 and trans-10,cis-12 CLA for 22 d, suggesting that these non-esterified fatty acids could potentially enhance Ca absorption in vivo.     

The effect of daily walking on body fat distribution

The effect of daily walking on body fat distribution was investigated using an electronic pedometer and ultrasonography. Subjects were 77 women, aged 31 to 72 years. They were divided into four groups according to the average number of steps they walked per day (I<7,500, 7,500 ≤II<10,000, 10,000 <III<12,500, 12,500 ≤IV). Subcutaneous fat in the trunk and limbs, and the minimum thickness of subcutaneous fat (Smin) and the maximum thickness of preperitoneal fat (Pmax) below the xiphoid process were measured by ultrasonography. Abdominal wall fat index (AFI) reflecting the intra-abdominal fat accumulation was obtained by dividing Pmax by Smin. Fat distribution was analyzed by ANCOVA, controlled for age, body mass index (BMI), percent body fat, and menopausal status. Energy and macronutrient intake were obtained through a nutritional survey. There were no significant differences in anthropometric variables, energy and macronutrient intake, and subcutaneous fat thickness in trunk and limbs. Pmax of Group I was significantly higher than Group IV. Furthermore, Group I showed significantly higher AFI than the other three Groups (II, III, IV). The results of this study suggested that women who walked less than 7,500 steps per day tend to have significantly increased intra-abdominal fat accumulation.     

Less body fat accumulation in rats fed a safflower oil diet than in rats fed a beef tallow diet

The effects on body fat accumulation of long-term feeding of high fat diets of differing fatty acid composition were studied in rats. The rats were meal-fed isoenergetic diets based on safflower oil or beef tallow for 4 mo. Each diet was freshly prepared every day throughout the experimental period. Oxygen consumption and carbon dioxide production for 6 h after meals were measured between the 50th and 54th d of the experimental period. Oxygen consumption for 3 h after meals was significantly greater in the safflower oil diet group than in the beef tallow diet group, indicating greater diet-induced thermogenesis in the former group. From the assessment of respiratory quotient, the fat oxidation rate was also higher in the former. After the experimental period (4 mo), body fat accumulation was significantly less in the rats fed safflower oil. This difference was, at least in part, ascribed to increased diet-induced thermogenesis and fat oxidation. Serum triacylglycerol level was markedly lower in the rats fed safflower oil than in those fed beef tallow. The lipoprotein lipase activities in heart and soleus muscle after meals appeared to be higher in the former than in the latter. These results suggest that the consumption of the safflower oil diet increased lipoprotein lipase activity in heart and skeletal muscle, resulting in the elevation of fat oxidation rate and the depression of serum triacylglycerol level.     

The effect of storage on serum fatty acids]

To investigate the effect of storage on serum fatty acids, we examined the composition of serum fatty acids in samples from healthy men stored at different temperatures for various periods of time. The following experimental storage conditions were studied: 1) 4 degrees C for three weeks, 2) -20 degrees C for 12 months and 3) -80 degrees C for 24 months. The fatty acid composition did not change after two-week storage at 4 degrees C. At -20 degrees C, there was a decline in the content of docosapentaenoic acid (22: 5, omega 3) after one month, and docosahexaenoic acid (22: 6, omega 3) after three months. However, omega 3-polyunsaturated fatty acid as a whole did not show a significant change. At -80 degrees C, there was a decline of docosapentaenoic acid after three months, arachidonic acid (20: 4, omega 6) after 12 months, and linoleic acid (18: 2, omega 6) after 24 months. As a whole, omega 3-polyunsaturated fatty acids did not change. Omega 6-Polyunsaturated fatty acids significantly declined 5% after 24 months. Therefore, it is recommended that serum fatty acids be measured within two weeks at 4 degrees C, within a few months at -20 degrees C and within one year at -80 degrees C to estimate the composition of the major fatty acids.     

Comparative changes of fat digestibility and fat accumulation by the carbon chain length of dietary glycerol tri-homogenous fatty acids in rats

The present study was undertaken to investigate the influence of the carbon chain length of dietary glycerol tri-homogenous fatty acid on fat digestibility and body fat accumulation in rats. Thirty-six Wistar male rats were divided into six groups and fed the semipurified C8, C10, C12, C14, C16, C18 triglyceride diets, respectively. Body weight was significantly lower (p<0.05) in rats fed the C14, C16 and C18 diets than in rats fed the C8, C10 and C12 diets. Weights of adipose tissues and apparent fat digestibility were markedly low in the C16 and C18 fed rats. In these groups, fat content of whole-body carcass was significantly lower (p<0.05), but moisture, ash and protein contents were significantly greater (p<0.05) than those of the other groups. Fatty acid profile of epididymal adipose tissue revealed that dietary C8:0 was not directly incorporated into adipose tissues, and only a small amount of dietary C10:0 was directly deposited as body triglycerides. Meanwhile, dietary C12:0 was extensively incorporated into adipose tissues when compared to those of C8 and C10 rats. The present study indicated that apparent fat and energy digestibilities of dietary glycerol tripalmitin and glycerol tristearin were remarkably lower than the glycerol tricaprylin, tricaprin, trilaurin and trimyristin, which results in lower fat accumulation in the C16 and C18 fed rats.     

A high oleic sunflower oil fatty acid esters of plant sterols mixed with dietary diacylglycerol reduces plasma insulin and body fat accumulation in Psammomys obesus

Background  

Metabolic syndrome is associated with subsequent development of cardiovascular diseases and type 2 diabetes. It is characterized by reduced response to insulin, central obesity, and dyslipidemia. Intake of plant sterols (PS) has been shown to confer a healthier lipid profile and ameliorate cardiovascular disease risk factors in experimental animals and humans. In this study we used an animal model of type 2 diabetes to assess the effects of a preparation of PS esterified to high oleic sunflower oil fatty acids mixed with dietary diacylglycerol (PS-HOSO) on diabetic related metabolic parameters. Psammomys obesus (P. obesus) were fed high energy (HE) diet supplemented by either PS-HOSO or control oil. Following 4.5 weeks of intervention, animals were divided into fasting and non-fasting modes prior to outcome measurements. Glucose and insulin levels as well as blood lipid profile, body weight, and fat accumulation were evaluated in fasting and non-fasting modes.     

Effect of fat emulsions containing medium-chain triglycerides and glucose on ketone body production and excretion

The parenteral application of fat emulsions containing medium-chain triglycerides results in an increase of ketone bodies as expression of the rapid metabolism of medium-chain triglycerides. Although ketoacidosis could not be watched, it should be of advantage to reduce the ketonemia. This might be reached by application of carbohydrates. The simultaneous infusion of glucose--given to 10 healthy persons--together with a 10% fat emulsion containing 75% medium-chain triglycerides almost completely inhibited the increase of ketone bodies in serum and its urinary excretion. Other prosperous metabolic effects, eg, the rapid clearance of the triglycerides from the serum were not affected by this regimen.     

Comparative effect of casein and soybean protein isolate on body fat accumulation in adult rats.

The effect of dietary protein on the body fat accumulation was studied in rats. Adult rats weighing about 300 g were fed 21% protein (casein or soybean protein isolate) and 5% oil diets by pair-feeding for 65 days in Experiment 1. In Experiment 2, only protein and oil contents were changed, 25 and 10%, respectively. Final body weights of the two dietary groups were similar in both experiments, especially in Experiment 2. Total body fat was slightly lower in the soybean protein diet group than in the casein diet group in Experiment 2, only when it was expressed as the percentage against body weight. However, intra-abdominal fat was significantly lower in the soybean protein diet groups than in the casein diet groups in both experiments. Serum lipid levels were greatly lower in the soybean protein diet group than in the casein diet group in Experiment 2 (the data were not available in Experiment 1). The results suggest that dietary soybean protein has the effect to lower the intra-abdominal fat accumulation as compared with casein.     

The effect of fish oil supplementation on serum phospholipid fatty acids profile during pregnancy: A double blind randomized controlled trial

Omega-3 fatty acids (FAs) are essential unsaturated long-chain FAs necessary for proper health and growth. The objective of the authors in this study was to evaluate the effect of fish oil supplementation in pregnancy on maternal serum FA profiles. Participants (n = 150 pregnant women aged 18–35 years in Tabriz, Iran) were randomly assigned to receive either 1,000 mg fish oil supplements daily containing 120 mg docosahexanoic acid (DHA) and 180 mg eicosapentaenoic acid (EPA), or placebo from week 21 of pregnancy to delivery. The primary outcome measures were mean serum DHA and EPA proportion of total FAs at weeks 35–37 of pregnancy. Analyses were based on intention-to-treat. No significant differences were observed between the groups in consumption of fish and serum FAs levels at baseline. Fish oil supplementation significantly increased the mean DHA proportion of total FAs in the intervention compared to the placebo group at weeks 35–37 [adjusted Mean Difference (aMD) = 0.15; 95% CI 0.08–0.23]. The mean EPA proportion of total FAs also increased in the intervention group, but the difference between the groups was not significant (aMD = 0.04; 95% CI ?0.01 to 0.08). The dietary recommendation for consumption of 1,000 mg/day fish oil supplements during pregnancy seems beneficial for better serum FA composition.