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Biomedical subjects

Y T Yang

Publications and source records attributed to Y T Yang.

53 records · Page 3Linked to original sources
PubMed1978

Comparison of C18-, C20- and C22-unsaturated fatty acids in reducing fatty acid synthesis in isolated rat hepatocytes.

C18-, C20- and C22-unsaturated acids were tested for inhibition of fatty acid synthesis in hepatocytes isolated from essential fatty acid-deficient rats. Fatty acid synthesis was measured by incorporation of radioactivity from [1-14C-A1-acetate or 3H2O into fatty acids. C20-polyunsaturated fatty acids included arachidonic acid (20 : 4 (n-6)) and 4 other fatty acids formed from linoleic acid (18 : 2 (n-6)) or linolenic acid (18 : 3 (n-3)). These were (11,14)-icosadienoic acid (20 : 2 (n-6)), (8,11,14)-icosatrienoic acid (20 : 3 (n-6)), (11,14,17)-icosatrienoic acid (20 : 3 (n-3)) and (5,8,11,14,17)-icosapentaenoic acid (20 : 5 (n-3). All of these have essential fatty acid activity. The fatty acid (5,8,11)-icosatrienoic acid (20 : 3 (n-9)) was also tested. This fatty acid is formed from oleic acid (18 : 1 (n-9)) and is not an essential fatty acid or a prostaglandin precursor. C20-unsaturated fatty acids and (22 : 6 (n-3)) were as effective as stearic acid in inhibiting fatty acid synthesis and were more inhibitory than their precursor C18-unsaturated fatty acids. These results are evidence that C20-unsaturated fatty acids of the linoleic and linolenic acid series can act in short-term inhibition as well as in adaptive inhibition of fatty acid synthesis (Bloch, K. and Vance, D. (1977) Annu. Rev. Biochem. 46, 263--298). The effectiveness of (5,8,11)-icosatrienoic acid indicates that short-term inhibition by C20-unsaturated fatty acids is not limited to those fatty acids which have essential fatty acid activity.

Animals↗
PubMed1978

Effects of age, diet and lactation on lipogenesis in rat adipose, liver and mammary tissues.

Four diets varying in safflower oil content from zero to 20% were used in a study of interactions among diet and physiological state. Increasing fat in the diet did not alter food intakes but decreased digestibility coefficients. Increasing safflower oil intake did not alter milk fat content in lactating rats but increased relative amounts of unsaturated fatty acids in milk fat. In liver and perirenal adipose tissues from young male and non-lactating female rats, low fat diets increased rates of lipogenesis from glucose in vitro and specific activities of enzymes whose functions are closely associated with lipogenesis. This adaptive hyperlipogenic response was not evident or was less prominent in aged or lactating rats. In the case of lactating rats it appears that lactation produces a marked reduction in adipose lipogenesis when low fat diets are fed. Reduced glyceride glycerol synthesis in lactating as compared to non-lactating rat adipose coupled with reduced fatty acid synthesis and in increased lipolysis indicated a shift in adipose function in the direction of increased fat mobilization as would be supportive of lactation. Only minor diet effects upon mammary enzyme patterns and rates of in vitro lipogenesis were observed.

Adipose Tissue↗
PubMed1978

Dietary lipid metabolism in lactating dairy cows.

Effects of feeding an oil seed supplement treated with formalin upon lipid patterns of blood and synthesis of milk fat were evaluated. Percentages and yields of fatty acids of milk fat with chain lengths between 6 and 16 carbons were decreased while percentages and yields of stearate and linoleate were increased when the lipid supplement was fed. Calculations in cows fed control and supplement, 60% and 80%, respectively, of fatty acids of milk were derived from lipids of blood were supported by arterial-venous differences. Comparisons of the fatty acid compositions of triacylglycerol of plasma and milk fat suggested that triacylglycerol may not be the sole source of linoleate transferred from blood to milk fat. A preliminary evaluation of supplement effects upon lipoprotein patterns of serum indicated two peaks in the low density lipoprotein class and that the increase in total cholesterol of blood caused by feeding lipid supplement is due to increases in cholesterol content of the low density and high density lipoprotein classes.

Animals↗
PubMed1977

Effect of dietary vitamin E on lipid synthesis by rat lung in vitro.

The effect of dietary vitamin E on lipid synthesis from U-14 C-D-glucose and 1-14C-acetate was studied in rat lungs in vitro. One-month-old Sprague-Dawley male rats were fed either a basal vitamin E-deficient diet or one supplemented with 45 ppm vitamin E ad libitum for two months. Glucose oxidation to CO2 by lungs was significantly (p less than 0.05) decreased by the exclusion of vitamin E from the diet. Oxidation of acetate to CO2 was not affected by the presence of vitamin E in the diet. The extent of labeled carbons from both glucose and acetate incorporated into total lipids was significantly lower in the lungs of vitamin E-deficient animals than in those of the supplemented group. However, the relative amounts of phospholipids, neutral lipids are free fatty acids in total lipids, and of glyceryl moiety and fatty acids in total lipids and in phospholipid fraction were not significantly altered by the status of dietary vitamin E. The results suggest a general depression of lipid synthesis in the lungs of vitamin E-deficient rats.

Acetates↗
PubMed1976

Effect of adrenalectomy on rat mammary metabolism.

Rates and patterns of metabolism of specifically labeled glucose, pyruvate, and acetate by mammary slices indicated that rates of glucose metabolism through the Embden-Meyerhof and pentose phosphate pathways and relative pentose cycle activity were decreased by adrenalectomy. Fatty acid synthesis from acetate was not impaired. Capacity to provide reduced nicotinamide adenine dinucleotide phosphate for fatty acid synthesis was not the limiting factor responsible for decreased fatty acid synthesis from glucose in adrenalectomized, lactating rat mammary glands. Oxidation of [1-carbon-14]pyruvate and fatty acid synthesis from [2-carbon-14] pyruvate were not affected by adrenalectomy. Indirect reasoning based upon the data reported led to the suggestion that decreased fatty acid synthesis from glucose after adrenalectomy may have resulted from decreased formation of triose phosphate via the phosphofructose-kinase reaction. It is suggested further that most of the decreases in rat mammary enzyme after adrenalectomy have no direct (causative) relationship to depressed lactational performance after adrenalectomy. Restriction of food intake caused decreased fatty acid synthesis from glucose, pyruvate, and acetate, but relative fatty acid esterification activity was higher than in control and adrenalectomized animals. The effects of adrenalectomy on mammary gland metabolism can be dissociated partially from reduced food intake.

Acetates↗
PubMed1976

Theoretical model of ruminant adipose tissue metabolism in relation to the whole animal.

Based on theoretical considerations and experimental data, estimates of contributions of adipose tissue to energy expenditures in a lactating cow and a growing steer were developed. The estimates indicate that adipose energy expenditures range between 5 and 10% of total animal heat production dependent on productive function and diet. These energy expenditures can be partitioned among maintenance (3%), lipogenesis (1-5%) and lipolysis and triglyceride resynthesis (less thatn 1.0%). Specific sites at which acute and chronic effectors can act to produce changes in adipose function, and changes in adipose function produced by diet and during pregnancy, lactation and aging were discussed with emphasis being placed on the need for additional, definitive studies of specific interactions among pregnancy, diet, age, lactation and growth in producing ruminants.

Adipose Tissue↗
PubMed1975

Effects of insulin upon fatty acids synthesis from pyruvate, lactate, and glucose in rat mammary cells.

In isolated rat mammary secretory cells, insulin stimulated fatty acid synthesis from pyruvate three times, stimulated glucose conversion to fatty acids 1.2 to 1.5 times, and decreased lactate conversion to fatty acids 20 to 30%. Incubation of glucose and pyruvate together depressed fatty acid synthesis from glucose not attributable to isotope dilution. Glucose stimulated conversion of pyruvate-2-14 carbon to fatty acids without significantly affecting pyruvate-1-14 carbon conversion to 14-carbon dioxide. At differing concentrations, the electron acceptors phenazine methosulfate and N,N,N',N'-tetramethyl-p-phenylene-diamine alleviated the depression by insulin of lactate conversion to fatty acids. The data support concepts that: (1) insulin acts at important sites other than or in addition to glucose transport in regulating mammary secretory cell metabolism and, particularly, fatty acid synthesis; (2) insulin actions upon fatty acid synthesis can vary dependent upon cellular redox state (insulin increases fatty acid synthesis in cells with a low redox state and decreases fatty acid synthesis in cells in a very reduced state); and (3) pyruvate depresses glucose carbon flux through the Embden-Meyerhof pathway.

Animals↗
PubMedDate not supplied

An Sp1 binding site involves the transcription of the Fas ligand gene induced by PMA and ionomycin in Jurkat cells.

The transcriptional regulation of the Fas ligand (FasL) gene in Jurkat cells was investigated. We demonstrated that an Sp1 binding site, located between -280 and -275 bp relative to the translational start site (+1) of the FasL gene, was important for the transcription of the FasL gene by deletion and mutation analysis in Jurkat cells after phorbol 12-myristate 13-acetate (PMA) and ionomycin treatment. Nuclear extract of Jurkat cells formed complexes with the oligonucleotides bearing the Sp1 site within -280 to -275 of the FasL promoter. Apart from the constitutive complexes, a new complex was observed after PMA and ionomycin stimulation. Plasmid containing the Sp1 site sequence with site-directed mutation reduced the FasL promoter activity in driving the expression of reporter luciferase gene expression in transfected Jurkat cells after PMA and ionomycin stimulation. The binding of activated Jurkat cell nuclear extract to the mutated Sp1 binding site of the FasL promoter was ablated. In addition, the oligomer containing the Sp1 site of the FasL promoter could compete with oligomer with conserved Sp1 binding sequence in nuclear protein binding of activated Jurkat cells. The data presented in this study suggest that the transactivation of the FasL promoter via the Sp1 binding sequence (-280 to -275) involves the PMA- and ionomycin-induced expression of the FasL gene.

Binding Sites↗