Psyllium produces a modest but significant improvement in total cholesterol and LDL cholesterol levels in persons on either low-fat or high-fat diets. Psyllium, when added to a prescribed low-fat diet, may obviate the need for typical lipid-lowering medications or may prove to be a valuable adjunct to other treatments in patients with moderately elevated LDL cholesterol levels.
The mammotrope has traditionally been a favored model for studies of hormonal gene expression, biosynthesis, and release. However, the primary site(s) at which these processes are coordinated and integrated remains to be established. Because there is considerable indirect evidence to suggest that the rate of prolactin (PRL) secretion is dictated, in large part, at the level of transcription, the relative contribution of other putative regulatory foci has received less attention. The purpose of the present study was to test the primacy of transcriptional regulation at the single-cell level. To this end, we quantified within individual mammotropes the relationship between PRL gene transcription, mRNA storage, and hormone release. This was accomplished by the combined application of "real-time" measurement of gene expression, in situ hybridization cytochemistry, and reverse hemolytic plaque assay, respectively. Our results demonstrate a quantitative dissociation among these variables, suggesting that control mechanisms besides transcription play a primary role in integrating and coordinating flow through the PRL secretory pathway.
Diets containing relatively homogeneous triglycerides composed of 18-carbon chain saturated, monounsaturated or polyunsaturated fatty acids were fed to rats. Cholesterol absorption and turnover were studied. Cholesterol absorption was significantly less in rats fed tristearin than in animals fed triolein or safflower oil. Cholesterol removal from plasma was fastest in rats fed tristearin and slowest with safflower oil and triolein. Plasma cholesterol levels were lowest with tristearin and highest with safflower oil. Increased cholesterol in high density lipoproteins was observed with tristearin and triolein. Lymph and hepatic cholesterol, and lymph triglycerides were highest with safflower oil, suggesting endogenous mobilization. Cholesterol production was least with triolein. Sterol synthesis was greatest with tristearin, perhaps attributable to decreased negative feedback analogous to effects of cholestyramine. Differences in lipoprotein composition observed with the various diets are important since effects on particle size and shape may influence removal mechanisms. The mechanisms underlying the different effects of dietary triglycerides on sterol absorption and metabolism remain to be elucidated.
The effects of a diet of 10% homogeneous triglycerides of 12 to 18-carbon chain saturated fatty acids on cholesterol absorption and turnover were studied in rats. Cholesterol absorption was successively significantly less in rats fed tristearin than in groups fed tripalmitin, trimyristin and trilaurin. Lesser fatty acid absorption may explain the differences in part, since cholesterol absorption was significantly correlated with fat absorption. Cholesterol removal from plasma was fastest in rats fed tristearin. Plasma cholesterol levels were increased with the trilaurin diet although the rate of cholesterol accumulation in lymph after gavage was slower with trilaurin. Lymph triglycerides were highest with trilaurin and trimyristin diets perhaps indicating endogenous mobilization of triglyceride for lipoprotein formation. Lymph triglycerides were, however, decreased with tristearin. Sterol turnover (production, absorption plus synthesis) was increased with tristearin or trilaurin by kinetic or balance methods.
Four groups of rats were fed test diets with fats providing 75% of fatty acids as palmitate, stearate, oleate or linoleate. Absorption of radiolabeled cholesterol and the specific triglyceride into intestinal lymph lipoproteins and the lipid and protein content and composition of intestinal lymph were compared. Cholesterol and triglyceride absorptions were correlated significantly and were less with the saturated fatty acid diets. The fatty acid patterns of triglyceride-rich lymph lipoproteins mirrored the diet. Exogenous cholesterol was recovered primarily in chylomicrons, except with linoleate. In contrast, radiolabeled saturated fatty acids were recovered primarily in very low density lipoproteins and unsaturated fatty acids were recovered in chylomicrons. Lymph chylomicron size and lipid content were greater with unsaturated fat diets. Triglyceride-rich intestinal lipoproteins of rats fed saturated fats were polygonal by electron microscopy, related to the cooling of lymph samples below body temperature. A-I apolipoproteins were increased in relation to C apoproteins as lipid absorption was greater. Plasma triglycerides in all groups increased compared to rats fed the stock diet. A diet enriched in one specific fatty acid has its unique effects on lymph lipoprotein formation presumably affecting some intestinal subcellular mechanisms. Diet-induced changes in plasma lipids and lipoproteins are not directly related to these as yet unknown mechanisms.
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