| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
| First Page | Previous Page |
| Zinc intake and plasma zinc level are maintained in men consuming cholesterol-lowering diets Retzlaff, B. M., C. E. Walden, et al. (1995), J Am Diet Assoc 95(11): 1274-9. Abstract: OBJECTIVE: Reduced zinc intake has been reported when cholesterol-lowering diets are adopted. This study examined whether such diets compromise the zinc status of men with hypercholesterolemia. DESIGN: Zinc intake on baseline 4-day food records and baseline plasma zinc levels were compared with intake and levels 12 and 24 months after subjects adopted a low-fat, increased-fiber diet. Dietary fiber intake, supplement use, alcohol intake, and exercise were evaluated as possible confounding variables. SUBJECTS: Subjects were free-living men (n = 365) with baseline cholesterol level above the 75th percentile who were participants in a randomized trial comparing cholesterol-lowering diets with goals of 30%, 26%, 22%, and 18% of energy from fat and 300, 200, 100, and 100 mg cholesterol, respectively. STATISTICAL ANALYSES: Data were analyzed using two sample t tests, multiple linear regression, and analysis of variance. RESULTS: For all subjects combined, mean fat and cholesterol intakes approached or met the guidelines of the National Cholesterol Education Program step 2 diet, with approximately 30 g fiber per day. Density (mg/1,000 kcal) of zinc intake was unchanged from the baseline value. We found a slightly positive relationship between fiber and zinc intakes; no relationship between fiber intake and plasma zinc level; no effect of supplement use (category included all types of supplements), alcohol use, or level of exercise on plasma zinc levels; and no difference by dietary assignment in zinc intake or plasma zinc levels. APPLICATION: Zinc status does not appear to be at risk in adult men who adopt cholesterol-lowering diets. These results may not be generalized to higher-risk population groups or situations in which dietary counseling is less comprehensive. |
| Zinc uptake into MCF-10A cells is inhibited by cholesterol depletion Mouat, M. F., P. Greenspan, et al. (2003), J Nutr Biochem 14(2): 74-80. Abstract: The mechanism for cellular Zn uptake was investigated by depleting cell cholesterol levels, a treatment that disrupts lipid rafts/caveolae-dependent processes and inhibits coated-pit budding. Incubation of MCF-10A human breast epithelial cells with hydroxypropyl-beta-cyclodextrin significantly lowered cell cholesterol levels and significantly inhibited cellular zinc uptake measured at 10 min, but had no effect on 2-deoxyglucose uptake. Replacing potassium for sodium in the uptake buffer significantly stimulated Zn uptake by 20%. The effects of potassium depletion and chlorpromazine on Zn uptake were investigated to determine the contribution of coated-pit endocytosis. Potassium depletion following hypotonic shock significantly inhibited Zn uptake into MCF-10A cells approximately 15%. Chlorpromazine at 20 microg/ml inhibited uptake approximately 30%. The data support the hypothesis that Zn uptake into MCF-10A cells involves lipid rafts/caveolae. The relatively mild effects of potassium depletion and chlorpromazine suggest that a small portion of Zn uptake may require coated pit endocytosis. |
| Zonation of cholesterol and glycerolipid synthesis in regenerating rat livers Cheng, H. C., C. M. Yang, et al. (1993), Hepatology 17(2): 280-6. Abstract: Hepatic zonation of cholesterol and glycerolipid synthesis was investigated in regenerating rat livers 24 hr after partial hepatectomy. Tritiated acetate and U-14Cglycerol were injected into rats' peritoneal cavities for a short-term labeling study. Periportal and perivenous hepatocytes were isolated by digitonin collagenase perfusion. Cholesterol synthesis was significantly higher in periportal hepatocytes of the sham-operated livers (periportal/perivenous = 1.67; p < 0.05). Twenty-four hours after partial hepatectomy, cholesterol synthesis was selectively decreased by 40% (p < 0.01) in periportal hepatocytes. Consequently, hepatic zonation of cholesterol synthesis was abolished in regenerating livers. To study the cholesterol homeostasis on a long-term basis, we substituted deuterated water (25% enriched) for drinking water for 5 days to label newly synthesized cholesterol in a steady state. This procedure clearly demonstrated the net negative cholesterol balance 24 hr after partial hepatectomy. However, the newly synthesized cholesterol contributed equally to the cellular cholesterol pool in both zones. The synthesis of glycerolipids, whether measured from tritiated acetate or U-14Cglycerol, was significantly increased without apparent zonation in the regenerating livers (twofold increase in phospholipid, and threefold to sevenfold increase in triacylglycerol). We concluded that hepatic zonation of cholesterol synthesis is caused by higher de novo synthesis in periportal hepatocytes, which is abolished in regenerating livers. No zonation of glycerolipid synthesis exists in normal and regenerating livers. |