Regulation of cytoplasmic lipid droplet mobilization in intestinal enterocytes
Date
2024-01-29
Authors
Journal Title
Journal ISSN
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ORCID
Type
Thesis
Degree Level
Masters
Abstract
Objectives: In postabsorptive state, lipids in intestinal enterocytes in the form of cytoplasmic lipid
droplets (CLDs) are mobilized towards chylomicron (CM) synthesis and secretion. The regulatory
mechanism of CLD mobilization in enterocytes remains unclear. We hypothesized that CLD
mobilization in enterocytes is regulated on a molecular level. The objective of this research is to
analyze the lipid output and tissue lipids along with proteomes of CLDs and ER isolated from
enterocytes harvested from the small intestine of rats following a cue known to mobilize CLDs.
Method: Mesenteric lymph duct and duodenum of male Sprague-Dawley rats were surgically
cannulated. Rats received a bolus intraduodenal infusion of intralipid. 5 hours later, rats received
the treatment (intraduodenal glucose or saline as control). Lymph fluid was collected for 15
minutes to measure lymph flow rates, and TG and apolipoprotein B48 (apoB48) outputs. At the
end of lymph collection, the duodenum and jejunum were harvested. Neutral lipids in the jejunum
were visualized with oil red O staining. Enterocytes were isolated, from which CLDs and ER
fractions were further isolated. Using proteomics, the total proteins found in the CLD and ER
fractions were analyzed to compare the proteins present in the CLD mobilization state (glucose
treated) and in the control.
Results: Administration of glucose into the duodenum led to an increase in lymph flow rate as
compared to the control. Glucose also led to increased TG output as compared to the control.
Lymph apoB48 output was higher in glucose than in control. Glucose administration reduced
neutral lipids in jejunal tissues compared with control. Proteomics analysis revealed differential
abundance in the proteomes in both the CLD and ER fractions between glucose and control. Top ranked proteins suggest treatment-dependent changes in various biological processes and identify
a range of candidate proteins that have vesicular transport, hydrolase activity, and lipid metabolism
functions.
Conclusion: These results show that glucose in the duodenum stimulates the release of stored
neutral lipids towards CM synthesis and secretion. CLD active mobilization is accompanied by
differential presence of proteins on CLDs and ER that are likely molecular regulators of CLD
mobilization.
Description
Keywords
cytoplasmic lipid
droplets, chylomicron, enterocytes
Citation
Degree
Master of Science (M.Sc.)
Department
Anatomy, Physiology, and Pharmacology
Program
Anatomy, Physiology, and Pharmacology