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Importance of muscle lipoprotein lipase in rats during suckling
Insights
Muscle lipoprotein lipase (LPL) is crucial for clearing fats in young rats, while adipose tissue LPL dominates in adults. This highlights tissue-specific roles in lipid metabolism during development.
Area of Science:
- Biochemistry
- Physiology
- Developmental Biology
Background:
- Lipoprotein lipase (LPL) hydrolyzes triacylglycerols in circulating lipoproteins.
- Understanding LPL's tissue distribution is key to lipid metabolism during development.
- Previous studies have not fully elucidated the developmental roles of LPL in different tissues.
Purpose of the Study:
- To assess the relative contribution of various tissues expressing LPL to serum triacylglycerol clearance during rat development.
- To investigate the impact of fasting on LPL activity across different tissues in developing rats.
Main Methods:
- Quantified LPL activity in cardiac muscle, skeletal muscle, brown adipose tissue (BAT), white adipose tissue (WAT), lung, and kidney of rats aged 0-60 days.
- Compared LPL activity in fed and 6-hour fasted rats.
- Correlated LPL activity changes with serum triacylglycerol concentrations.
Main Results:
- Fasting affected LPL activity differently across tissues: no change in lung/kidney, decreased in WAT and BAT (except at 14 days), and decreased in muscle at early ages (0-7 days) then increased.
- In suckling pups, muscle LPL accounted for 63-85% of total LPL activity, significantly more than WAT (<25%).
- In adult rats, WAT was the primary LPL contributor when fed, and muscle when fasted.
Conclusions:
- Serum triacylglycerol clearance in suckling rats predominantly relies on muscle LPL activity.
- Tissue-specific roles of LPL in lipid metabolism shift significantly from infancy to adulthood.
- Muscle LPL plays a critical, developmentally regulated role in managing circulating lipids during early life.
Abstract:
In order to evaluate the relative importance of groups of tissues containing lipoprotein lipase (LPL) in the removal of serum triacylglycerols during development, LPL activity was determined in cardiac and skeletal muscle, brown (BAT) and white adipose tissue (WAT), lung and kidney of rats aged 0-60 days, either fed or fasted for 6 h. On fasting, LPL activity did not change in lung and kidney, decreased in WAT except at 14 days and to a lesser extent in BAT, whereas muscle LPL decreased at 0, 3, and 7 days and increased from 14 days onward. The fasting-induced changes in serum triacylglycerol concentrations in suckling pups could be attributed to corresponding changes in muscle LPL. In the adult, the main contributor to total LPL activity was WAT in fed rats and muscle in fasted rats, as expected. In suckling pups, however, muscle LPL contributed 63-85% of the total and WAT less than 25%, whatever the nutritional state. The results strongly suggest that clearing of circulating chylomicrons during suckling largely depends on muscle LPL.