Atif B. Awad

Alteration of rat adipose tissue lipolytic response to norepinephrine by dietary fatty acid manipulation

Abstract The present study clearly shows that, by feeding rats a semi-synthetic diet of known composition enriched with saturated fatty acids, the epididymal fat pad responsiveness to norepinephrine in vitro can be abolished relative to fat pads from animals fed a similar diet but enriched with polyunsaturated fatty acids. Addition of varying concentrations of norepinephrine to the incubation medium produced a clear dose-response relationship in fat pads from animals fed diet enriched with polyunsaturated fatty acids while no effect of norepinephrine was apparent at any dose level in fat tissue from animals fed saturated fatty acids. These changes in lipolytic responsiveness were concurrent with alterations in fatty acid compositions of adipose tissue phospholipids and triglycerides as well as in total tissue contents of phospholipids and cholesterol.

Age-dependent alterations in lipids and function of rat heart sarcolemma

The objective of the present study was to examine the effect of age on heart sarcolemma structure and function. Sarcolemmal fractions were prepared from hearts of young (1-1.5 months) and adult (10-12 months) rats and assayed for marker enzyme activities. The membrane fractions were found to be devoid of other cellular organelles upon examination by electron microscopy. They were enriched with 5-nucleotidase and devoid of succinate dehydrogenase activity. The only age-related lipid compositional changes noted in these membranes were changes in the fatty acid composition of membrane phospholipids with increasing age. Most changes were detected in phosphatidylcholine and phosphatidylethanolamine with very little alteration of sphingomyelin and phosphatidylserine plus phosphatidylinositol fatty acids. Polyunsaturated fatty acids, especially 18:2 and 20:4, were decreased with saturated fatty acids increased in membrane phosphatidylcholine and phosphatidylethanolamine fractions as the animal develops. There was a decrease in the specific activities of (Na+ + K+)-ATPase and 5-nucleotidase of these membranes with age. On the other hand, membrane (K+)-rho-nitrophenylphosphatase was not affected by age.

Trans Fatty Acids in Tumor Development and the Host Survival

Because trans fatty acids exist in the American diet and their relationship to cancer incidence has been proposed, studies were designed to investigate their possible role in the development of Ehrlich tumor cells in inbred CBA mice. Feeding elaidic acid (18:1 delta 9, trans) to Ehrlich ascites tumor-bearing animals resulted in tumors that incorporated more thymidine into their cells and into their acid-insoluble fraction as compared with those grown in animals fed the natural oleic acid (18:1 delta 3, cis)-rich diet. Elaidic acid diet feeding at 5% in the diet also resulted in a reduction in the host survival rate. This reduction ranged from 23 to 45%.

The effect of alteration of nuclear lipids on messenger RNA transport from isolated nuclei

Abstract Studies were performed to examine the effect of alteration of the fatty acid composition of nuclear lipids on messenger RNA transport. Rats were maintained for four weeks on a semi-synthetic diet enriched in either saturated or polyunsaturated fatty acids. Messenger RNA transport was monitored by using a cell-free system comprised of isolated nuclei and fortified cytosol. This transport was found to be reduced by 34% from nuclei isolated from animals fed the diet enriched in saturated fatty acids as compared with the diet enriched in polyunsaturated fatty acids. The reduction was associated with a decrease in the unsaturation index of the nuclear fatty acids.

Developmental alterations in 5′-nucleotidase kinetics and lipid composition of rat heart sarcolemma

The objective of these studies was to examine the mechanism by which the specific activity of heart sarcolemma 5-nucleotidase decreases as function of age. We examined the kinetic properties and the lipid composition of the sarcolemma from animals with different ages. The age groups used were 1 month, 6-8 months and 13-15 months. It was found that the Km of this enzyme increases as the animal develops from 1 month to 6-15 months. The opposite was true with 5-nucleotidase Vmax. There was no significant difference between the middle age and the older age groups in those parameters. The results of these experiments suggest that the increase in Km in sarcolemma 5-nucleotidase could be due to the reduction of the sarcolemmal polyunsaturated fatty acid concentration, the only lipid alteration observed.

The effect of elaidic acid incorporation upon the lipid composition of ehrlich ascites tumor cells and of the host's liver.

The incorporation of elaidic acid into Ehrlich ascites tumor cells (EATC) upon feeding the host an elaidic acid-rich diet has been investigated in the present study. The EATC lipids contained only one-half the concentration of elaidic acid found in the lipids of either the host livers or of livers from normal mice. On the other hand, elaidic acid incorporation into tumor cells was close to that of ascites fluid. This incorporation was mainly into phospholipids; the highest into choline phospholipids and ethanolamine phospholipids. Some changes in the EATC fatty acid composition were noted due to this incorporation. EATC phospholipids had reduced polyunsaturated fatty acids as compared with oleic acid-grown cells. The same was true with respect to ascites fluid phospholipids, but neutral lipids were not altered. Tumor development was accompanied by an increase in elaidic acid of the host’s liver. Elaidic acid incorporation into tumor cells resulted in a reduction in the amount of all major lipids in the tumor. In contrast, elaidic acid had no effect on lipid composition of livers from normal mice and-tumor bearing mice, and also had no effect upon the lipids of the ascites fluid that bathes the tumor cells. The incorporation of elaidic acid into the lipids of EATC, normal liver and host liver did not affect the relative composition of phospholipids in these tissues. The development of the tumor did result in decreases in triacylglycerols and esterified cholesterol, and increases in phospholipids and free cholesterol in the livers of host animals.