Research Outputs
Effect of various dietary fructose concentrations on the gallstone formation process in mice
Background: little information is availaible on the effect of fructose on bile lipids. The first stage in the formation of gallstones corresponds to biliary cholesterol crystallization, derived from the vesicular transporters. The aim of this study was to investigate the influence of consuming diets with different fructose concentrations on serum lipids and their implications on gallstones formation. Methods: BALB/c mice divided into a control group as well as groups were treated with different fructose concentrations (10 %, 30 %, 50 % or 70 %) for different periods (1, 2 or 5 months). Blood, liver and bile samples were obtained. In bile samples, cholesterol and phospholipids levels were analyzed, and cholesterol transporters (vesicles and micelles) were separated by gel filtration chromatography. Results: treated animals showed: 1) increases in body weight similar to the control group; 2) a significant increase in plasma triglycerides only at very high fructose concentrations; 3) a significant increase in total serum cholesterol in the treatment for 1 month; 4) no variations in HDL-cholesterol; 5) a significant increase in serum glucose only at very high fructose concentrations in the second month of treatment; 6) no differences in the plasma alanine-aminotransferase activity; 7) a significant increase in liver triglyceride levels only at very high fructose concentrations; 8) no change in biliary lipid concentrations or in micellar and vesicular phospholipids. Conclusion: changes in plasma, liver and bile lipids were only observed at very high fructose concentrations diets. We conclude that fructose apparently does not alter the gallstone formation process in our experimental model.
GLUT1 and GLUT8 support lactose synthesis in Golgi of murine mammary epithelial cells
The mammary gland increases energy requirements during pregnancy and lactation to support epithelial proliferation and milk nutrients synthesis. Lactose, the principal carbohydrate of the milk, is synthetized in the Golgi of mammary epithelial cells by lactose synthase from glucose and UPD galactose. We studied the temporal changes in the expression of GLUT1 and GLUT8 in mammary gland and their association with lactose synthesis and proliferation in BALB/c mice. Six groups were used: virgin, pregnant at 2 and 17 days, lactating at 2 and 10 days, and weaning at 2 days. Temporal expression of GLUT1 and GLUT8 transporters by qPCR, western blot and immunohistochemistry, and its association with lactalbumin, Ki67, and cytokeratin 18 within mammary tissue was studied, along with subcellular localization. GLUT1 and GLUT8 transporters increased their expression during mammary gland progression, reaching 20-fold increasing in GLUT1 mRNA at lactation (p < 0.05) and 2-fold at protein level for GLUT1 and GLUT8 (p < 0.05 and 0.01, respectively). The temporal expression pattern was shared with cytokeratin 18 and Ki67 (p < 0.01). Endogenous GLUT8 partially co-localized with 58 K protein and α-lactalbumin in mammary tissue and with Golgi membrane–associated protein 130 in isolated epithelial cells. The spatial-temporal synchrony between expression of GLUT8/GLUT1 and alveolar cell proliferation, and its localization in cis-Golgi associated to lactose synthase complex, suggest that both transporters are involved in glucose uptake into this organelle, supporting lactose synthesis.
Efecto de una dieta alta en grasas en el proceso de formación de cálculos biliares de colesterol
Background: It is known that some nutrients play an important role in the development of cholelithiasis. Cholesterol is carried by micelles and vesicles in the bile. During the first stage of gallstone formation, cholesterol crystals derive from thermodynamically unstable vesicles. Aim: To determine the effect of a high fat diet on blood lipids and bile composition, and its implication in the formation of gallstones. Material and Methods: Two groups of 15 BALB/c mice each, coming from the same litter, were treated with a control or with a high-fat diet (64% fat and 0.14% cholesterol). After two months, the animals were sacrificed, blood and bile samples were obtained. Serum glucose and the corresponding lipid profiles were measured. In bile samples, cholesterol and phospholipid levels were analyzed, and cholesterol transporters (vesicles and micelles) were separated by gel filtration chromatography. Results: Treated animals showed an 87% increase in serum total cholesterol (p < 0.01), a 97% increase in HDL-cholesterol (p < 0.05) and a 140% increase in LDL-cholesterol (p < 0.05). No changes in serum triglycerides or glucose were observed. In bile, a 13% increase in biliary cholesterol (p < 0.05) was observed but no change in biliary phospholipids. Also, an increase in biliary vesicular transporters and an increase of cholesterol/phospholipid ratio in vesicular transporters were observed. Conclusions: A high fat diet may contribute to the formation of gallstones in our experimental model.