Dietary saturated fat reduces alcoholic hepatotoxicity in rats by altering fatty acid metabolism and membrane composition

Rats fed a saturated fat diet are protected from experimentally induced alcoholic liver disease, but the molecular mechanisms underlying this phenomenon remain in dispute. We fed male Sprague-Dawley rats intragastrically by total enteral nutrition using diets with or without ethanol. In 1 control and 1 ethanol group, the dietary fat was corn oil at a level of 45% of total energy. In other groups, saturated fat [18:82 ratio of beef tallow:medium-chain triglyceride (MCT) oil] was substituted for corn oil at levels of 10, 20, and 30% of total energy, while keeping the total energy from fat at 45%. After 70 d, liver pathology, serum alanine aminotransferase (ALT), biochemical markers of oxidative stress, liver fatty acid composition, cytochrome P450 2E1 (CYP2E1) expression and activity and cytochrome P450 4A (CYP4A) expression were assessed. In rats fed the corn oil plus ethanol diet, hepatotoxicity was accompanied by oxidative stress. As dietary saturated fat content increased, all measures of hepatic pathology and oxidative stress were progressively reduced, including steatosis (P < 0.05). Thus, saturated fat protected rats from alcoholic liver disease in a dose-responsive fashion. Changes in dietary fat composition did not alter ethanol metabolism or CYP2E1 induction, but hepatic CYP4A levels increased markedly in rats fed the saturated fat diet. Dietary saturated fat also decreased liver triglyceride, PUFA, and total FFA concentrations (P < 0.05). Increases in dietary saturated fat increased liver membrane resistance to oxidative stress. In addition, reduced alcoholic steatosis was associated with reduced fatty acid synthesis in combination with increased CYP4A-catalyzed fatty acid oxidation and effects on lipid export. These findings may be important in the nutritional management and treatment of alcoholic liver disease.     

Adaptation to chronic ethanol administration emphasized by fatty acid hydroxylations in rat liver and kidney microsomes

BACKGROUND: Long-term ethanol consumption in laboratory animals is associated with histological alterations of liver cells and modifications of fatty acid metabolism. AIM OF THE STUDY: The present study was aimed at investigating the effect of 1- and 2-month chronic treatment of rats with ethanol on the metabolism of two unsaturated (oleic and linoleic) fatty acids in liver and kidney microsomes, in relation to the CYP2E1 enzyme content in both tissues. METHODS: Rats were fed ethanol (14 g/Kg/d) or dextrose through a permanently implanted gastric cannula, as described in the intragastric feeding rat model for alcoholic liver disease (ALD). CYP2E1 level was immuno-quantified in both liver and kidney microsomes by Western blot, whereas fatty acid omega- and (omega-1)-hydroxylations were measured using HPLC and radiometric analytical methods. RESULTS: One- and two-month ethanol treatment led to a 3- to 4-fold rise of the CYP2E1 protein in both liver and kidney microsomes. Oleic and linoleic acid (omega-1)-hydroxylations were increased (approximately 3-fold) in liver microsomes after one-month of ethanol administration, but surprisingly such a rise was not observed after a two-month treatment; on the other hand, no effect was observed on the omega-hydroxylations of these fatty acids. Furthermore, as previously described for lauric acid, ethanol intake did not significantly act on the kidney microsome capability to hydroxylate unsaturated fatty acids. CONCLUSIONS: CYP2E1 is strongly inducible by ethanol and therefore accounts for the tolerance for this hepatotoxicant. Our results support the development of an adaptation process in the liver hydroxylating enzyme system, which occurs between one and two months of ethanol feeding. Although it is usually not appropriate to extrapolate animal findings to humans, rat and human CYP2E1s were observed to have comparable specificities and similar mechanisms of regulation. Thus, the present study allowed the acquirement of detailed information of CYP2E1 activity in patients with severe manifestations of ALD.     

Dietary restriction of energy and sugar results in a reduction in human cytochrome P450 2E1 activity

Dietary habits are often considered as a pathogenic factor for fatty liver. The impact of dietary intake and steatosis on drug metabolism remains poorly investigated. Our aim was to assess the effect of dietary intake on in vivo cytochrome P450 (CYP) activities in eleven patients with abnormal liver function tests potentially due to fatty liver and associated with a high-sugar diet. Liver function tests, liver volume, aminopyrine breath test (ABT) and chlorzoxazone (CZ) pharmacokinetics (area under the curve, AUC) which are known to reflect CYP2E1 activity were evaluated before and after 2 months restriction of dietary sugar intake. Features at inclusion were an increased BMI (30.3 (SD 3.2) kg/m2), high hepatic volume (1.96 (SD 0.48) litres), hyperechogenic liver parenchyma, elevated liver enzyme activities (alanine aminotransferase (EC 2.6.1.2) 58.6 (SD 17.4) IU/1 with alanine aminotransferase: aspartate aminotransferase (EC 2.6.1.1) ratio > 1), together with a normal ABT value (0.68 (SD 0.21)% specific activity of administered dose of [14C]aminopyrine in breath after 1 h) and a high CYP2E1 activity (CZ AUC 20.3 (SD 7.1) micrograms/ml per h). A dietary sugar restriction was prescribed. On the basis of repeated interviews by the same dietitian, unaware of any clinical and biochemical data, six patients remained complaint to the diet and exhibited reductions in BMI (P < 0.001), serum alanine aminotransferase (P = 0.008), liver volume (P = 0.002) and CYP2E1 activity (P = 0.007), a significant increase in ABT (P < 0.001) together with the disappearance of liver hyperechogenicity at ultrasound. In contrast, the five non-compliant patients did not show any significant change in any of these variables. In conclusion, CYP2E1 activity is induced in patients with perturbations of liver function tests potentially due to fatty liver. In these patients, effective dietary sugar restriction is associated with a reduction in liver volume, a reduction in CYP2E1 activity and an increased aminopyrine metabolism rate.     

不同脂肪酸负荷膳食对小鼠胆固醇代谢的影响

目的　为研究脂肪酸对胆固醇代谢可能的分子机制。方法　C5 7小鼠 75只 ,随机分为 5组 ,各组饲以相应配方饲料 6周。结果　与胆固醇膳食 (Chol)相比 ,胆固醇 多不饱和脂肪酸膳食 (Chol PUFA)可增加血清总胆固醇、机体总胆汁酸 (P <0 0 5 ) ,降低肝脏胆固醇 (P <0 0 5 ) ;胆固醇 单不饱和脂肪酸膳食 (Chol MUFA)动物血清总胆固醇不变 ,机体总胆汁酸明显增加 (P <0 0 5 ) ,肝脏胆固醇降低 (P <0 0 5 ) ;胆固醇 饱和脂肪酸 (Chol SFA)膳食可明显增加 (P <0 0 5 )血清总胆固醇和肝脏胆固醇 ,降低 (P <0 0 5 )机体总胆汁酸。此外 ,PUFA、MUFA和SFA均明显降低肝脏胆固醇 7α -羟化酶 (CYP7a1)mRNA和蛋白的表达。结论　膳食脂肪酸可通过CYP7a1调节机体胆固醇内稳态 ,多不饱和脂肪酸和单不饱和脂肪酸可诱导胆固醇转化为胆汁酸进而维持机体胆固醇在较低水平 ,而此过程中产生的大量胆汁酸又可反馈抑制CYP7a1的表达 ;相反 ,饱和脂肪酸可能通过直接抑制或不改变CYP7a1的表达 ,导致膳食胆固醇在体积的堆积     

Cyclic fatty acid monomers from heated oil modify the activities of lipid synthesizing and oxidizing enzymes in rat liver

Cyclic fatty acid monomers purified from a heated linseed oil were given for 2 wk to adult rats as triacylglycerol at two dose levels, i.e., 0.1 and 1 g/100 g diet, to determine their effect on some aspects of lipid metabolism. Indirect evidence of a peroxisome proliferator-like effect was observed, as determined by an elevation of some characteristic enzyme activities, such as peroxisomal acyl-CoA oxidase, and the microsomal omega- but also (omega-1)-laurate hydroxylase (CYP4A1 and CYP2E1, respectively). The dietary cyclic fatty acids induced a coordinated regulation between the activities of the lipogenic enzymes studied (Delta9-desaturase, phosphatidate phosphohydrolase) and peroxisomal oxidation, but not with mitochondrial beta-oxidation. The dose-dependent decrease of Delta9-desaturase activity (P < 0.05) with cyclic fatty acid monomer intake was accompanied by a similar decrease of the monounsaturated fatty acid level in liver. The increase in the gamma-linolenic acid level also suggested an increase in Delta6-desaturase activity with cyclic fatty acid intake (P < 0.05). In addition, our results strongly suggested that the altered liver levels of eicosapentaenoic and arachidonic acids were due to the peroxisomal retroconversion process in rats fed cyclic acids. Finally, an effect of these cyclic compounds on the carbohydrate metabolism cannot be disregarded because they decreased liver glycogen concentration. We conclude that cyclic fatty acid monomers affect different aspects of lipid metabolism, including a phenotypic peroxisome proliferator response. This provides the ground for further studies investigating the biochemical pathways that underlie the nutritional effect of such molecules.     

Influence of fat/carbohydrate ratio on progression of fatty liver disease and on development of osteopenia in male rats fed alcohol via total enteral nutrition (TEN)

Alcohol abuse is associated with the development of fatty liver disease and also with significant osteopenia in both genders. In this study, we examined ethanol-induced pathology in response to diets with differing fat/carbohydrate ratios. Male Sprague-Dawley rats were fed intragastrically with isocaloric liquid diets. Dietary fat content was either 5% (high carbohydrate, HC) or 45% (high fat, HF), with or without ethanol (12–13 g/kg/day). After 14, 28, or 65 days, livers were harvested and analyzed. In addition, bone morphology was analyzed after 65 days. HC rats gained more weight and had larger fat pads than HF rats with or without ethanol. Steatosis developed in HC + ethanol (HC + EtOH) compared to HF + ethanol (HF + EtOH) rats, accompanied by increased fatty acid (FA) synthesis and increased nuclear carbohydrate response element binding protein (ChREBP) (p < 0.05), but in the absence of effects on hepatic silent mating type information regulation 2 homolog (SIRT-1) or nuclear sterol regulatory binding element protein (SREBP-1c). Ethanol reduced serum leptin (p < 0.05) but not adiponectin. Over time, HC rats developed fatty liver independent of ethanol. FA degradation was significantly elevated by ethanol in both HC and HF groups (p < 0.05). HF + EtOH rats had increased oxidative stress from 28 days, increased necrosis compared to HF controls and higher expression of cytochromes P450, CYP2E1, and CYP4A1 compared to HC + EtOH rats (p < 0.05). In contrast, HC + EtOH rats had no significant increase in oxidative stress until day 65 with no observed increase in necrosis. Unlike liver pathology, no dietary differences were observed on ethanol-induced osteopenia in HC compared to HF groups. These data demonstrate that interactions between diet composition and alcohol are complex, dependent on the length of exposure, and are an important influence in development of fatty liver injury. Importantly, it appears that diet composition does not affect alcohol-associated skeletal toxicity.     

‘Designer oils’ low in n-6:n-3 fatty acid ratio beneficially modifies cardiovascular risks in mice

Cardiovascular benefits of dietary n-3 fatty acids have been shown. However, benefits of n-3 fatty acids as part of a high fat, low n-6:n-3 fatty acid ratio diet has not been fully characterized. Aim of this study is to investigate cardiovascular and metabolic benefits of ‘designer oils’ containing a low ratio of n-6:n-3 fatty acids in C57BL/6 mice. Three groups of C57BL/6 mice were fed an atherogenic diet supplemented with either a fish oil- or flaxseed oil-based ‘designer oil’ with an approximate n-6:n-3 fatty acid ratio of 2:1 (treated groups, n = 6 each) or with a safflower oil-based formulation with a high ratio (25:1) of n-6:n-3 fatty acids (control group, n = 6) for 6 weeks. Food intake, body weight, and blood lipid levels were monitored regularly. Fatty acid profile of the heart tissues was assessed. Histological assessment of liver samples was conducted. At the end of the study body weight and food intake was significantly higher in the flax group compared to control. The levels of 20:5n-3 and 22:6n-3 was significantly increased in the heart phospholipids in both flax and fish groups compared to control; tissue 20:4n-6 was significantly reduced in the fish group compared to control. Significant liver pathology was observed in the control group only. Lowering dietary ratio of n-6:n-3 fatty acids may significantly reduce cardiovascular and metabolic risks in mice regardless of the source of n-3 fatty acids.     

Time-course effects of protein malnutrition on hepatic fatty acids delta 6 and delta 5 desaturation in the growing rat

1. In growing rats, the time-course effects of giving a normal-protein diet (200 g casein/kg; NP) for 52 d, a low-protein diet (20 g casein/kg; LP) for 52 d and a LP diet for 26 d followed by balanced refeeding (200 g casein/kg; BR) for 26 d, on the fatty acid composition of liver total lipids and microsomal phospholipids were investigated together with delta 6- and delta 5-microsomal desaturase activities. 2. The oleic acid content (mg/g tissue) of liver total lipids increased progressively with the LP diet, while linoleic acid was increased only at days 7 and 52. 20:3 omega 6, 20:4 omega 6, 22:5 omega 6 and 22:6 omega 3 fatty acids decreased during the period on the LP diet. BR for 7 d was sufficient to restore the fatty acid composition of total lipids to control values. Changes in the fatty acid composition of liver microsomal L-alpha-phosphatidylcholines were observed only after 52 d on the LP diet; the proportions (% w/w total fatty acids) of 18:0, 20:3 omega 6 and 20:4 omega 6 fatty acids decreased while oleic acid increased. The fatty acid composition of L-alpha-phosphatidylethanolamines was less affected. 3. delta 6- and delta 5-desaturase activities decreased to 20-30% of their original values after 2 d on the LP diet; a smaller deficit prevailed after 14 d but disappeared after 25 d, to appear again after 52 d. As early as day 2 of BR, desaturase activities were greatly recovered and returned to control values at day 13. 4. The present work shows that modifications in microsomal delta 6- and delta 5-desaturase activities are not strictly paralleled by the changes in the composition of fatty acids of liver total lipids and microsomal phospholipids.     

Depletion of delta 9 desaturase (EC 1.14.99.5) enzyme activity in growing rat during dietary protein restriction.

The effects of protein restriction on delta 9 desaturase (EC 1.14.99.5) activity were studied in growing rats. A control group was fed on a balanced diet (200 g casein/kg; BD) for 28 d. The experimental group was fed on the low-protein diet (20 g casein/kg; LP) for 26 d, then refed the balanced diet (BD-R) for 2 d. Rats were born to and suckled from normally fed dams. The enzyme activity was measured after 2 and 14 d of LP, and 26 d of LP plus 2 d of BD-R, by incubations in vitro of hepatic microsomal pellets with [1-14C]steric acid. The results indicated a decreased delta 9 desaturase activity after 2 and 14 d of LP of -33 and -43% respectively. Refeeding for 2 d was sufficient to super-repair this activity (+66%). The fatty acid composition of total liver lipids and microsomal phosphatidylethanolamines (PE) and phosphatidylcholines (PC) were also investigated; 18:0 decreased in total liver lipids at 14 d of LP, when 18:1n-9 increased. Stearic acid (18:0) increased in PC at 2 d of LP and in PE at 14 d of LP; oleic acid (18:1n-9) did not change. Therefore, it is concluded that a defect occurred in the bioconversion of 18:0 into 18:1n-9 by delta 9 desaturation during protein depletion. As oleic acid is accumulated in total liver lipids during LP, we speculate that this is due to a decreased oxidation or transport of this fatty acid.     

Dietary alpha-linolenic acid and prostaglandin synthesis: a time course study

A purified diet containing 10% linseed oil as the fat source was fed to rats over a 56-day period. After the 56th day the rats were fed the same basal diet but containing 10% corn oil in place of the linseed oil. Rats were killed and blood and liver samples were taken from four to six rats on 14 days of the feeding trial. Serum and liver fatty acid profiles were determined. The platelet prostaglandin E2 (PGE2) released in serum as a result of blood coagulation for 1 h at 37 degrees C was determined. Liver homogenates were incubated and PGF2 alpha synthesizing capacity was assayed. Both serum and liver fatty acid profiles reflected the high linolenic content of the linseed oil. There was a progressive increase in fatty acids of the omega 3 series and a decrease in the omega 6 series. Notably the PG-2 series precursor, arachidonic acid (20:4 omega 6) was decreased and the precursor of the PG-3 series timnodonic acid (20:5 omega 3) was increased. These changes were reversed when corn oil was fed. PGE2 content of serum and PGF2 alpha synthesis by liver homogenates progressively decreased as the 20:4 omega 6 levels fell and the 20:5 omega 3 levels increased. PG synthesis was quickly increased in both when corn oil diets were fed. This study has implications for dietary manipulation of PG synthesis by blood components and may provide a basis for manipulation of PG synthesis in systems in which they are regulatory.     

Vitamin E supplementation does not prevent ethanol-reduced hepatic retinoic acid levels in rats

Chronic, excessive ethanol intake can increase retinoic acid (RA) catabolism by inducing cytochrome P450 2E1 (CYP2E1). Vitamin E (VE) is an antioxidant implicated in CYP2E1 inhibition. In the current study, we hypothesized that VE supplementation inhibits CYP2E1 and decreases RA catabolism, thereby preventing ethanol-induced hepatocyte hyperproliferation. For 1 month, 4 groups of Sprague-Dawley rats were fed a Lieber-DeCarli liquid ethanol (36% of the total energy) diet as follows: either ethanol alone (Alc group) or ethanol in combination with 0.1 mg/kg body weight of all-trans-RA (Alc + RA group), 2 mg/kg body weight of VE (Alc + VE group), or both together (Alc + RA + VE group). Control rats were pair-fed a liquid diet with an isocaloric amount of maltodextrin instead of ethanol. The ethanol-fed groups had 3-fold higher hepatic CYP2E1 levels, 50% lower hepatic RA levels, and significantly increased hepatocyte proliferation when compared with the controls. The ethanol-fed rats given VE had more than 4-fold higher hepatic VE concentrations than the ethanol-fed rats without VE, but this did not prevent ethanol induction of CYP2E1, lower hepatic retinoid levels, or hepatocellular hyperproliferation. Furthermore, VE supplementation could not prevent RA catabolism in liver microsomal fractions of the ethanol-fed rats in vitro. These results show that VE supplementation can neither inhibit ethanol-induced changes in RA catabolism nor prevent ethanol-induced hepatocyte hyperproliferation in the rat liver.     

Effect of dietary levels of corn oil on maternal arachidonic acid synthesis and fatty acid composition in lactating rats

OBJECTIVE: We examined the effect of different amounts of dietary corn oil rich in linoleic acid (LA) on the endogenous synthesis of arachidonic acid (AA), uptake of its precursor LA, and fatty acid composition of tissues involved in the supply of long-chain polyunsaturated fatty acids for milk synthesis. METHODS: Female Sprague Dawley rats received one of the following diets during pregnancy and lactation: a low-lipid diet (LLD; 2%), an adequate-lipid diet (ALD; 5%), or a high-lipid diet (HLD; 10%). Lipids were provided by corn oil. On day 12 of lactation we measured the endogenous synthesis of AA and quantified the conversion of (13)C-LA to (13)C-AA and the metabolic fate of (13)C-LA from all dietary groups. RESULTS: The LLD rats demonstrated larger amounts of endogenous synthesis of (13)C-AA and more dietary (13)C-LA transferred to the mammary gland (MG) than HLD rats during lactation. The proportion of medium-chain fatty acids was higher in the MG, milk clot, and liver of LLD than of HLD rats. Daily volume and 24-h yield of lipids and energy were lower in LLD rats than in HLD rats. Measurements of milk composition demonstrated that fat concentration significantly increased as lipid concentration increased in the diet. CONCLUSION: These results suggest that maternal adaptations used to compensate for diets deficient in long-chain polyunsaturated fatty acids include increased endogenous synthesis of AA and elevated uptake of LA in the MG and increased synthesis of medium-chain polyunsaturated fatty acids. It appears that the MG and liver participate together for AA synthesis for milk when this fatty acid is not provided in the diet.     

Dietary taurine content changes liver lipids in cats.

Adult female cats were fed a completely defined purified diet (taurine-free) alone or containing 0.05% taurine (the normal dietary requirement) or 1% taurine (20-fold the normal dietary requirement) for greater than 2 y. The relative composition of conjugated biliary bile acids was not different among the three groups and virtually all bile acids were conjugated with taurine. The taurine concentration in liver varied dramatically with the amount of taurine in the diet. Total liver lipid content decreased with increasing dietary taurine. Individual lipid components also varied, especially free fatty acids (which decreased with increasing dietary taurine) and triglycerides (which increased with increasing dietary taurine), indicating that taurine has a metabolic effect on lipid metabolism. Taurine deficiency also caused significant changes in the fatty acid distribution of sphingomyelin. In particular, a decrease of lignoceric acid and an increase of nervonic acid were observed. The present data suggest that hepatocellular levels of taurine can modulate the mobilization of liver lipid stores and the utilization by the liver of circulating free fatty acids. These effects are probably mediated by factors affecting membrane fluidity, such as the ratio of cholesterol to phospholipids, the degree of unsaturation of phospholipids and the changes in sphingomyelin fatty acid composition.     

Alcohol, oxidative stress and free radical damage

The involvement of free radical mechanisms in the pathogenesis of alcoholic liver disease (ALD) is demonstrated by the detection of lipid peroxidation markers in the liver and the serum of patients with alcoholism, as well as by experiments in alcohol-feed rodents that show a relationship between alcohol-induced oxidative stress and the development of liver pathology. Ethanol-induced oxidative stress is the result of the combined impairment of antioxidant defences and the production of reactive oxygen species by the mitochondrial electron transport chain, the alcohol-inducible cytochrome P450 (CYP) 2E1 and activated phagocytes. Furthermore, hydroxyethyl free radicals (HER) are also generated during ethanol metabolism by CYP2E1. The mechanisms by which oxidative stress contributes to alcohol toxicity are still not completely understood. The available evidence indicates that, by favouring mitochondrial permeability transition, oxidative stress promotes hepatocyte necrosis and/or apoptosis and is implicated in the alcohol-induced sensitization of hepatocytes to the pro-apoptotic action of TNF-alpha. Moreover, oxidative mechanisms can contribute to liver fibrosis, by triggering the release of pro-fibrotic cytokines and collagen gene expression in hepatic stellate cells. Finally, the reactions of HER and lipid peroxidation products with hepatic proteins stimulate both humoral and cellular immune reactions and favour the breaking of self-tolerance during ALD. Thus, immune responses might represent the mechanism by which alcohol-induced oxidative stress contributes to the perpetuation of chronic hepatic inflammation. Together these observations provide a rationale for the possible clinical application of antioxidants in the therapy for ALD.     

Dietary fatty acids temporarily alter liver very long-chain fatty acid composition in mice.

To determine the influence of dietary fatty acids on tissue very long-chain fatty acid (VLFA) composition, mice were fed four diets containing 15 g fat/100 g diet derived largely from either safflower oil, peanut oil, olive oil or glycerol trioleate oil. The diets varied widely in the composition of VLFA and other fatty acids. Digestibility of total dietary VLFA ranged from 84.6% in mice fed the glycerol trioleate diet to 96.7% in those fed the safflower oil diet. After 3 mo, the saturated VLFA composition of liver total lipids and sphingomyelin was lower in animals fed the glycerol trioleate oil diet than in mice fed most other diets. Although the saturated VLFA content of the peanut oil diet was more than 15-fold greater than that of the other diets, animals fed the peanut oil diet showed little or no selective increase in liver saturated VLFA. The VLFA composition of brain was comparable in all dietary groups. After 8 mo of feeding, the liver saturated VLFA composition tended to increase and differences between groups disappeared. Liver peroxisomal beta-oxidation of lignocerate (24:0) was similar among all dietary groups. These results demonstrate that dietary fatty acids shorter than VLFA temporarily influence the saturated VLFA composition of liver.     

Biotin deficiency and fatty liver and kidney syndrome in chicks given purified diets containing different fat and protein levels.

1. The occurence of biotin deficiency and fatty liver and kidney syndrome (FLKS) in chicks was studied using a 2x2x2x2 factorial-design experiment in which the variables were dietary biotin, fat and protein, and starvation. 2. The severity of biotin deficiency, using growth retardation and severity of dermal lesions as criteria, was least when the low-biotin diet also contained low levels of fat and protein. Addition of fat or protein increased the severity of the deficiency. Tissue fatty acid composition was affected by biotin deficiency only in those birds given the low-protein, low-fat diet. The main change was an increase in the ratio, 16:1 fatty acids :18:0 fatty acids. Plasma glucose and free fatty acid levels in non-fasted birds were unaffected by the dietary variables. 3. Mortality from FLKS with the diet containing low biotin, fat and protein levels was 52% at 28d, but was reduced or eliminated when the dietary level of any of these ingredients was increased. 4. Starvation considerably increased the incidnece of FLKS in the period immediately after fasting, and also affected plasma glucose and free fatty acid concentrations. Liver fatty acid composition, indicated an increase in the proportion of 18:0 at the expense of 16:1 and concentrations increased in proportion, at the expense of 18:0. 5. The relationship between biotin deficiency and FLKS, and a possible mechanism for the induction of FLKS by starvation are discussed.     

CYP1B1基因敲除对成年小鼠肝脏脂肪代谢的影响及可能机制

目的探讨CYP1B1对高脂膳食诱导的成年小鼠脂肪代谢的作用。方法 CYP1B1基因敲除(KO)和野生型(WT)雄性成年C57/BL小鼠(6 w龄)各16只,给予低脂(LFD,30%)、高脂肪(HFD,60%)饲料共6 w。小鼠处死后取血清、附睾脂肪和肝脏组织检测相应的生化和分子生物学指标。结果 6 w高脂膳食后,KO小鼠能量摄入总量稍高于WT小鼠,但其体重增量和附睾脂肪组织重量均显著低于WT小鼠;WT小鼠脂肪细胞直径明显大于KO小鼠,且血糖、血清及肝脏组织中甘油三酯(TG)水平亦明显高于KO小鼠;肝脏组织RT-PCR结果显示,CYP1B1基因敲除后,启动脂肪形成的核因子及脂肪合成相关基因如CD36、SREBP1c、SCD1等表达下降,而调控脂肪氧化分解的基因如CPT-1α,UCP-2表达显著上升;蛋白印迹结果显示,CYP1B1基因敲除增强腺苷-磷酸激酶(AMPK)的磷酸化。结论 CYP1B1基因敲除对成年小鼠营养性肥胖的保护作用可能与AMPK磷酸化增强并调控肝脏中脂肪代谢相关基因的表达有关。