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1.
B. D. Roebuck 《Lipids》1992,27(10):804-806
Pancreatic cancer is the fifth most common cause of death due to cancer. Except for an association with cigarette smoking, its etiology is poorly understood. Because of the dearth of epidemiological clues as to causation, studies with experiemntal animal models assume greater importance. Rodent models of pancreatic cancer indicate that while dietary fatper se does not cause pancreatic cancer, it does enhance or promote tumor development. Subsequent to treatment with a pancreatic carcinogen, high intakes of dietary unsaturated fats of the n−6 series, but not saturated fats, enhance or promote tumor development. A requisite level of linoleic acid is needed for this promotion. Fats of the n−3 series (e.g., certain fish oils) are inhibitory to tumor growth. Promotion by dietary fats appears only partly related to the high caloric content of fat. Mechanistically, certain dietary unsaturated fats appear to selectively enhance the growth rate of carcinogeninduced, pre-cancerous lesions. Irrespective of precise understanding of mechanisms of promotion, it, appears possible to intervene in the process of cancer development and reduce the burden of cancer. Experimentally, this may be accomplished by decreasing total fat intake, decreasing caloric intake, increasing exercise or increasing the intake of n−3 fatty acids. Based on a paper presented at the Symposium on Lipids in Cancer held at the AOCS Annual Meeting, Baltimore, MD, April 1990.  相似文献   

2.
Four diets which differed in fatty acid composition were provided for five months each to a group of 24 healthy nun volunteers. The diets contained 54% carbohydrates, 16% proteins and 30% lipids. One-third of the lipid part remained unchanged during the whole study, and two-thirds were modified during each period. For this latter portion, one of the following dietary fats was used: sunflower oil, peanut oil, low erucic acid rapeseed (LEAR) oil or milk fats. This procedure allowed an evaluation of the effects of various amounts of dietary linoleic acid (C18∶2ω6) and alpha-linolenic acid (C18∶3ω3) on the serum level of their metabolites. A diet providing a large amount of linoleic acid (14% of the total caloric intake) resulted in low levels of dihomo-gamma-linolenic acid (C20∶3ω6) and arachidonic acid (C20∶4ω6) in serum phospholipids and cholesteryl esters. A diet providing a small amount of linoleic acid (0.6% to 1.3% of the total caloric intake) induced high levels of ω6 fatty acid derivatives. Intermediate serum levels of C20∶3ω6 and C20∶4ω6 were found with a linoleic acid supply of about 6.5% of the total caloric intake. Serum levels of ω6 metabolites were not different after two diets providing a similar supply of C18∶2ω6 (4.5% to 6.5% of the total caloric intake), although in one of them the supply of C18∶3ω3 was higher (1.5% for LEAR oil versus 0.13% for peanut oil). Under our experimental conditions (healthy human adults fed on a normo-caloric diet with 30% lipids), we tried to determine PUFA (linoleic and linolenic acid) allowances which should be recommended for adults. The aim of the study was to obtain a hypocholesterolemic or normocholesterolemic effect while keeping normal 20∶3ω6 and 20∶4ω6 serum levels which would evidence a normal linoleic acid metabolism. The amounts recommended are: linoleic acid 5 to 6% of the total calories; alpha-linolenic acid 0.5 to 1% of the total calories.  相似文献   

3.
Dietary fat has an important influence on mammalian lipid homeostasis. However, the relationship between dietary fat types and endogenous fatty acids (FAs) in organs as well as lipid homeostasis remains unclear enough. In this study, rats are randomly divided into a control group (CN), a high-colleseed oil group (COG), and a high-sunflower oil group (SOG). FAs profile in liver and visceral fats of rats in two high-fat (HF) diet groups is compared with that in CN. Oleic, γ-linolenic, eicosadienoic, and arachidonic acid accumulate in COG liver or visceral fats, but the levels of linoleic, eicosadienoic, docosanoic, and dihomo-γ-linolenic acid decrease in COG visceral fats. However, these FAs levels increased in SOG liver or visceral fats except dihomo-γ-linolenic and arachidonic acid which changed insignificantly. The trend of initial upregulation and then downregulation of lipid metabolism-related genes expression is noted in COG liver, including stearoyl-CoA desaturase. Upregulation of adiponectin (ADPN) expression in visceral fats and downregulation of ADPN receptor 2 (Adipo-R2) expression in livers of both HF groups are observed. Correlation analysis revealed positive correlations between specific FAs content and ADPN expression level. Negative correlations are observed between Adipo-R2 expression and the content of oleic, linoleic, and γ-linolenic acid in the SOG liver. Practical applications: Dietary fat not only provides energy but is also associated with lipid homeostasis. In this work, the authors investigate the distribution of fatty acids (FAs) in vivo and their influence on genes related to lipid metabolism induced by diets enriched in oleic acid or linoleic acid. The study suggests that dietary fats modulate lipid homeostasis not only by regulating endogenous FAs levels but also by affecting the expression of genes related to lipid metabolism. This study may support the research in lipid nutrition and rational intake of dietary fat.  相似文献   

4.
In a long-term multigeneration study, conducted in our laboratories for 32-years, with occasional longevity and histopathological evaluations included, rats of our own inbred strain (originally of Wistar derivation) were fed semisynthetic diets comprising whole wheat, skim milk powder, and fat in the form of margarine products. The total source of tocopherols was the dietary fat itself. Saturated fatty acid content (S) remained relatively constant at about 20% of the fat and total tocopherol level also remained constant at about 0.12% of the fat. Polyunsaturated fatty acid (P) content, however, progressively increased almost fourfold, from 7.5% to 28.5% and alphatocopherol levels decreased to one-half level, from 0.033% to 0.016% of the fat. Hence, the ratio of polyunsaturated fatty acids to alpha-tocopherol content changed markedly from 227∶1 to 1780∶1, with other factors (relative to fat composition) held constant during the 32-year period of feedings and observations. Fat level in the diet increased over the years from 9.2% to 16.0% or from about 21% to about 33% of the caloric intake. Thus, quality and quantity of the fat in the diet progressively changed, and the impact of these changes was evaluated by comparing biological performances of the successive generations. Growth and reproduction and lactation performances were noted to be regularly satisfactory and comparable from generation to generation throughout the experimental period. Longevity studies conducted on arbitrarily selected generations also provided data showing no deleterious effects associated with a dietary change. Histopathological examinations of tissue revealed minimal myocarditis and no malignant tumors which could be attributed to a dietary factor. No vitamin E deficiencies were observed. Even the in vitro peroxide hemolysis values for the red blood cells of the animals, fed the diets containing the higher levels of polyunsaturated fatty acids, were low, indicating that the dietary fats provided sufficient absorbable tocopherol to protect the potentially oxidizable unsaturated fatty acids in the erythrocyte membrane. Biochemical data reflected responses to aging and not to any specific diet fed. It is concluded that a diet providing as much as 33% of the calories as a fat, the latter containing up to 28.5% polyunsaturated fatty acids, substantially of the essential fatty acid type, with a P/S ratio of up to 1.6∶1 and a polyunsaturated fatty acid to alphatocopherol ratio as high as 1780∶1] produces no undesirable effects in the rat. Presented in part at a symposium entitled “Long Term Nutritional Effects of Dietary Fats” at the International Society for Fat Research World Congress, September 30, 1970, Chicago, Illinois.  相似文献   

5.
Male Wistar rats were fed cholesterol-free or cholesterol-enriched diets containing partially hydrogenated soybean oil with different levels of trans-fatty acids or unhydrogenated soybean oil at the 10% level. The linoleic acid content of hydrogenated fat diets was adjusted to 3.6% of the total energy. Hydrogenated fat diets contained 29% and 41% trans-acids, mainly as t-18:1. Trans-fats exerted no untoward effects on growth parameters, but increased liver weight. Dietary hydrogenated fats influenced neither the concentration nor composition of biliary steroids, irrespective of the presence or absence of cholesterol in the diet. In rats fed a cholesterol-free diet, daily fecal output of neutral and acidic steroids was enhanced by hydrogenated fats and the magnitude of augmentation was proportional to the dietary level of trans-fatty acids. The increased fecal steroid excretion corresponded to an increase in total excreta. Hydrogenated fats also tended to enhance bile acid excretion when feeding a cholesterol-enriched diet. The results suggest that dietary trans-fatty acids, in relation to cis-polyunsaturated fatty acids, provoke demonstrable change in steroid homeodynamics.  相似文献   

6.
Several studies demonstrated that dietary oxidized oils markedly affect the vitamin E status and alter the fatty acid composition of tissue lipids in animals. It must however be emphasized that highly oxidized oils reduce the feed intake of animals, which makes it difficult to interpret the results. Therefore, the present study used a moderately thermoxidized soybean oil (peroxide value: 75 mEq O2/kg), having a similar fatty acid composition as fresh soybean oil (peroxide value: 9.5 mEq O2/kg) which was used as control. Moreover, according to a bifactorial design, two different vitamin E supplementary levels (11 vs. 511 mg α-to-copherol equivalents per kg diet) were used. The experiment was conducted with male Sprague-Dawley rats. The feeding period lasted for 40 days. In order to assess the vitamin E status, the vitamin E concentrations in plasma, liver, heart, kidney, and adipose tissue were determined. The vitamin E supply had a pronounced effect on the vitamin E concentrations of those tissues whereas the type of fat had only a slight effect. The fatty acid composition of total lipids from liver, erythrocytes, and low-density lipoproteins was also only slightly influenced by the oxidized fat. The osmotic fragility of erythrocytes was even reduced by feeding the oxidized oil. With a low vitamin E supply, the in vitro susceptibility of low-density lipoproteins to lipid peroxidation was slightly increased by feeding the oxidized oil. In contrast, with a high vitamin E supply, there was no adverse effect of the dietary oxidized oil on the susceptibility of low-density lipoproteins to lipid peroxidation. Feeding the oxidized oil, however, increased the concentrations of malondialdehyde in low-density lipoproteins suggesting an increased in vivo lipid peroxidation. Therefore, it cannot be ruled out that moderately oxidized dietary fats increase the atherogenicity of low-density lipoproteins. In contrast, a moderately oxidized oil scarcely affected the vitamin E status and the fatty acid composition of tissue lipids.  相似文献   

7.
Fats in the diet     
Fats are important constituents of the human diet since on the one hand, they contribute to the caloric density of the diet, and on the other, they serve as vehicles of essential nutrients such as linoleic and alpha-linolenic acids, as well as fat-soluble vitamins. The existence of human populations subsisting on diets with values as low as 10% or more than 50% of the calories represented by fats, has been documented, demonstrating the great adaptability of man to a wide availability of this type of food. Nevertheless, extensive epidemiological and experimental research in relation to a frequent degenerative diseases of man, arteriosclerosis, have consistently demonstrated that the proportion of saturated fats in the diet has a positive correlation with the frequency of these alterations. Mortality and fat availability in Latin America is consistent with these results. In consequence, and taking into consideration the present level of fat availability in the Region, we propose that no more than 25% of the caloric requirement should be covered by fats. Additionally, this amount of fat should have equal proportions of saturated, monounsaturated and polyunsaturated fatty acids. Cholesterol, which is contained in animal fats, is not a necessary nutrient for humans, so that no minimum consumption needs to be established. Daily ingestion of cholesterol should be restrained to no more than 100 mg/1,000 calories. Introduction of new fatty foods for human consumption should be preceded by a thorough investigation of the metabolic consequences.  相似文献   

8.
Summary So far as the industry is concerned, the evidence indicating a relationship of dietary fat to heart disease presents some interesting challenges. Undoubedly it portends a change in the fat cousumption pattern toward a lowerper capita use coupled with a shift from solid fats toward a higher proportion of edible oils. Most important of all, however, is the growing recognition that fats and oils are nutritionally valuable foods, intimately related to health and well-being, and should by no means be regarded merely as a source of calories. Although there are innumerable factors involved in the etiology of heart disease, dietary fat is an important one and fortunately is one that can be modified in whatever way proves desirable. Because the more saturated types of fats lead to higher serum cholesterol levels than do the polyunsaturated oils, and because cholesterol is somehow involved in the course of atherosclerotic heart disease, clinical tests are now in progress to determine whether prolonged use of a diet rich in these oils will lead to fewer heart attacks than does the usual American diet rich in saturated fats. So far, data are encouraging enough to merit recommendation of the modification in dietary fat to the coronary-prone individual and to justify development of new high-linoleate fat products by the industry.  相似文献   

9.
Current studies on relation of fat to health   总被引:2,自引:0,他引:2  
An increase in the linoleic to oleic acid ratio by an increase in the percentage of the polyunsaturated ω6 family of fatty acids in culinary fats and a decrease in the consumption of cholesterol-rich food were believed necessary as a prerequisite to early intervention in coronary heart disease. A decrease in total fat consumption also has been recommended. However, a decrease in the percentage of fat in the diet may not be nutritionally sound, as it may only increase the percentage of carbohydrates consumed and, thus, the synthesis of the ω9 family of fatty acids from the surfeit calories. It may be more judicious to decrease the total number of calories through less consumption of a well balanced diet. Furthermore, as thetrans-fatty acids, which are formed during hydrogenation, are not discriminated against completely by acyl-glycerol-3-phosphoryl-choline transferase or acyl coenzyme A cholesteryl transferase, it would be, from a biological viewpoint, advantageous to eliminatetrans-fatty acids from both stick and tub type margarines. One of five papers presented at the symposium, “Status of Fat in Food and Nutrition,” AOCS Fall Meeting, Chicago, September 1973.  相似文献   

10.
Medicinal research has linked dietary fats with such maladies as cancer, heart disease and stroke. The overconsumption of fats has been declared one of the major dietary health concerns in the United States by the Surgeon General. As a result, there is an increased awareness by consumers of their need to reduce the intake of calories derived from fat. The food industry has shown much interest in the development of substitutes for dietary fats and oils. To date, no substitute that can be used as a full fat replacement has entered the marketplace. Linear polyglycerols (LPGs) have been prepared by a proprietary polymerization process. Fatty acid esters prepared from LPGs were found to resist hydrolysis by digestive enzymes and were poorly absorbed in animal feeding tests. When esterified with fatty acids, LPG esters are similar to natural triglycerides in color, odor, taste and other physical characteristics. These properties make LPG oils good candidates for use in nonnutritive edible oil applications, particularly in uses that require stability at high temperatures.  相似文献   

11.
Dihydro-vitamin K1 is a dietary form of vitamin K1 (phylloquinone) produced during the hydrogenation of vegetable oils. To determine if dihydro-vitamin K1 is present in plasma following dietary intake of a hydrogenated fat, eight healthy adults consumed each of two diets containing 30% of calories from fat, of which 20% was either soybean oil or a partially hydrogenated soybean oil-based stick margarine. Of the fats and oils analyzed, dihydro-vitamin K1 was only found in the hydrogenated products. The soybean oil diet contained 180 ±12 μg (mean±SD) of vitamin K1/day and nondetectable levels of dihydro-vitamin K1, whereas the stick margarine diet contained 199±7 μg of vitamin K1/day and 23±2 μg of dihydrovitamin K1/day. After consuming each diet for five weeks, plasma dihydro-vitamin K1 concentrations were higher (P=0.002) in all eight subjects when consuming the stick margarine diet (0.56 ±0.33 nmol/L) compared to the soybean oil diet (0.12±0.11 nmol/L). There was no significant change in plasma vitamin K1 concentrations when the two diets were compared. In conclusion, dihydro-vitamin K1 is detectable in plasma following dietary intake of a hydrogenated vitamin K1-rich vegetable oil.  相似文献   

12.
The experiments reported are part of our effort to dissociate the tumor-enhancing effects of dietary fat and high caloric intake. Rats either were fed ad libitum diets containing 4% corn oil or their calories were restricted by 40% and their diets contained 13.1% corn oil. Incidence of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors was 80% in rats fed ad libitum and 20% in those fed the calorie-restricted diets. Incidence of 1,2-dimethylhydrazine (DMH)-induced colon tumors was 100% in rats fed ad libitum and 53% in those whose caloric intake was restricted by 40%. The tumor yield (tumors per tumor-bearing rat) was significantly lower in rats on caloric restriction. In another series, rats were fed diets containing 5, 15 or 20% corn oil ad libitum or were fed calorie-restricted (by 25%) diets which provided 20 or 26.6% corn oil (therefore, the same absolute amount of fat was consumed in each of the pair-fed groups). Tumor incidence and tumor yield in the two calorie-restricted groups were similar to those seen in the rats fed 5% fat ad lititum; tumor burden (total g of tumor) was 45–65% lower in the calorie-restricted rats. The data suggest that caloric intake is a more stringent determinant of tumor growth than fat intake.  相似文献   

13.
Dietary cholesterol (CHL) and triglycerides (TG) can influence plasma, hepatic, and biliary lipid composition, but effects on lipids in these three compartments during the early stages of CHL gallstone formation have not been studied in parallel. We fed prairie dogs diets containing one of four tes oils (safflower, coconut, olive, or menhaden) at either 5 or 40% of calories, in the presence of 0 or 0.34% CHL, for 3 wk. In the absence of dietary CHL, increases in dietary TG produced 50–200% increases in the concentrations of biliary CHL and hepatic cholesteryl ester (CE), while the concentrations of hepatic free CHL (FC) as well as plasma FC and CE remained relatively unchanged. Increasing dietary CHL to 0.34% resulted in increases in hepatic FC of approximately 50% for all four fats regardless of whether they were supplied at 5 or 40% of calories. CHL supplementation caused more pronounced increases in biliary CHL (200–400%), hepatic CE (50–200%), plasma FC (up to 100%), and plasma CE (up to 150%), and these increases were exacerbated by concurrent supplementation of dietary fat and CHL (biliary CHL: 300–700%; hepatic CE: 100–250%; plasma FC: up to 165%; plasma CE: 100–350%). These results indicate that enhanced secretion of biliary CHL and, to a lesser extent, increased synthesis of hepatic CE, may be primary mechanisms for maintaining the hepatic FC pool. Furthermore, dietary CHL and high levels of fat intake are independent risk factors for increasing biliary CHL concentrations, and adverse effects on lipid concentrations in plasma and bile tend to be exacerbated by ingestion of diets rich in both fat and CHL.  相似文献   

14.
Dietary fat and body weight control   总被引:3,自引:0,他引:3  
Peters JC 《Lipids》2003,38(2):123-127
The global obesity epidemic has heightened the debate about dietary factors contributing to weight gain. Media stories have promulgated the notion that obesity has increased despite reductions in dietary fat intake. Some have even speculated that lower dietary fat levels may be driving the rapid rise in weight gain within the population. A close examination of the science reveals a different picture and supports the hypothesis that dietary fat, within the context of the total dietary composition consumed by many populations, promotes obesity. Hence, dietary fat control is still an important strategy as part of an overall approach to body weight management in our modern environment. Dietary fat increases the energy density of foods. Abundant evidence from preclinical and clinical studies indicates that fat promotes excess energy intake and positive energy balance. Dietary fat does not promote its own oxidation in the body and is stored efficiently, promoting a positive fat balance. Thus, both the behavioral and metabolic responses to dietary fat increase the probability of positive energy balance and body fat gain. Restoring fat balance when consuming diets rich in fat requires increasing the size of the body fat mass, increasing physical activity, or reducing dietary fat intake. Numerous epidemiologic, preclinical, and controlled clinical studies have shown that body fat is positively associated with dietary fat intake and that dietary fat manipulation leads to appropriate changes in body fat mass. Finally, data from the National Weight Control Registry, a database of >3000 individuals who have successfully maintained a substantial weight loss, indicate that moderating dietary fat intake is a key strategy for long-term management of body weight.  相似文献   

15.
Impact of fat substitutes on fat intake   总被引:3,自引:0,他引:3  
Dietary fat is the number one nutrition concern of Americans. In response to rising consumer demand for reduced-fat foods, the food industry has developed a multitude of nonfat, lowfat, and reduced-fat versions of regular food products. To generate reduced-fat or fat-free products that have the same organoleptic characteristics of the regular fat version, food manufactures frequently employ fat substitutes in the formulation of these foods. Fat substitutes are made from either carbohydrate, protein, or fat, or a combination of these components. Researchers have questioned the impact of fat substitutes on both fat and caloric intake. The majority of research studies in which fat substitutes were either covertly or overtly substituted for dietary fat indicate that in short-term, carefully-controlled conditions, fat substitutes can decrease both dietary fat intake and percentage of calorie intake from fat. However, individuals compensate for the caloric deficit created by the fat substitutes by increasing their consumption of other macronutrients, primarily carbohydrate. The long-term effect of fat substitutes on the fat intake of free-living individuals and weight control are unknown. People tend to eat more of a food when they know that food is reduced in fat. Fat substitutes should not be considered a substitute for sound nutrition education and a healthy lifestyle which includes regular exercise.  相似文献   

16.
Malondialdehyde (MDA) production and cytosolic aldehyde dehydrogenase (ALDH) response were examined in rat liver tissues after feeding different levels of dietary vitamin E and/or selenium and polyunsaturated fat for 12–38 wk. MDA production was significantly increased by vitamin E deficiency or by high levels of polyunsaturated fat intake, but not by selenium deficiency. The activity of cytosolic ALDH increased upon increased production of MDA after 12–16 wk of feeding the lipid peroxidation-inducing diets. However, ALDH activity was suppressed after 38 wk of feeding the vitamin E-deficient diet. The results indicate that the hepatic cytosolic ALDH may be involved in the metabolism of MDA during a relatively short-term increase inin vivo lipid peroxidation, but that ALDH activity becomes suppressed after more severein vivo lipid peroxidation has been produced. Hepatic and plasma α-tocopherol levels and lipid peroxidation products were measured for the various dietary groups.  相似文献   

17.
The first law of thermodynamics dictates that body mass remains constant when caloric intake equals caloric expenditure. It should be noted, however, that different diets lead to different biochemical pathways that are not equivalent when correctly compared through the laws of thermodynamics. It is inappropriate to assume that the only thing that counts in terms of food consumption and energy balance is the intake of dietary calories and weight storage. Well-controlled studies suggest that calorie content may not be as predictive of fat loss as is reduced carbohydrate consumption. Biologically speaking, a calorie is certainly not a calorie. The ideal weight loss diet, if it even exists, remains to be determined, but a high-carbohydrate/low-protein diet may be unsatisfactory for many obese individuals.  相似文献   

18.
High levels of dietary fat have been shown to promote the development of mammary tumors induced in rats by 7,12-dimethylbenz(α)anthracene, and polyunsaturated fats were found to be more effective than saturated fats. In further studies it was found that diets containing 3% sunflowerseed oil (polyunsaturated fat) and 17% beef tallow or coconut oil (saturated fats) enhance tumorigenesis as much as a diet containing 20% sunflowerseed oil. Rats on these diets developed at least twice as many tumors as those fed diets containing either 3% sunflowerseed oil or 20% of the saturated fats alone. These results are in accord with human epidemiological data which show that breast cancer mortality in different countries is positively correlated with total fat intake but not with intake of polyunsaturated fat. Total fat intake varies greatly in different countries, but most human diets probably contain levels of polyunsaturated fat at least equivalent to 3% sunflowerseed oil.  相似文献   

19.
Endogenous Lipid Peroxidation in Broiler Chickens under Dietary Loads Growing broiler chickens were fed a Vitamin E-deficient diet containing 10% reesterified triglyceride from soy-bean-oil. Six groups with day-old broiler chicken were supplemented with 0, 20 or 100 ppm of vitamin E. On each vitamin level one group was fed with the fresh fat, the other was supplied with the fat being oxidized. Clinical data and development of body weight were registered. The animals were euthanised after 3 weeks. Pentane production of liver mitochondria and microsomes was measured and tocopherol concentrations were determined as well as the GSH-PX-activity in liver cytosol and plasma. Deficiency of vitamin E together with a high level of dietary linoleic acid leads to an imbalance in peroxidative and antioxidative metabolism and finally to disease. It is discussed if the clinical signs after consumption of linoleic acid-rich oxidized oils are caused by specific toxic secundary products.  相似文献   

20.
Fatty Acid Composition of Important Dietary Fats The recommendations issued by the German Nutrition Association (DGE) include both total fat quantities and the distribution of fatty acids in daily food intake. It is recommended that fats should account for 30% of the daily energy intake, comprising 10% each of saturated, mono-unsaturated and polyunsaturated fatty acids. An increasing number of scientific studies are quoted according to which the chain lengths of saturated fatty acids and the stereoisomers of unsaturated fatty acids play a part in raising the blood cholesterol level. Examples are given of both vegetable oils and fats and a animal and “hidden” fats. Recommendations from DGE for fat intake and fatty acid composition in fat in Germany are not reached yet. The fat intake has to be reduced.  相似文献   

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