Biphasic adaptative responses in VLDL metabolism and lipoprotein homeostasis during Gram-negative endotoxemia.
Level 5 - mechanism / opinion, no new human data
Non-human animal model (endotoxemic rats)
PubMed 21113081 · doi:10.1177/1753425910390722
What was done
Researchers evaluated serum metabolites, lipoprotein subclass profiles, and hepatic very low density lipoprotein (VLDL) assembly mechanisms over a 24-hour period in fasted rats challenged with Gram-negative endotoxin (lipopolysaccharide, LPS). Assayed parameters included serum non-esterified fatty acids (NEFA), glucose, triglyceride abundance across lipoprotein subclasses, VLDL particle counts, apolipoprotein B (Apob) transcription rates, apoB mRNA abundance, and transcript binding to HuR mRNA-stabilizing protein.
What was found
LPS administration induced a biphasic metabolic response over 24 hours: - First 12-hour phase: Characterized by increased NEFA, hypoglycemia, a 6.8-fold increase in hypertriglyceridemia (concentrated primarily in large VLDL), and a 5-fold increase in VLDL particle numbers. - Second 12-hour phase: Characterized by low NEFA, hyperglycemia, an increase in medium-sized VLDL, a 10-fold increase in total VLDL particle count, and increased apoB gene transcript abundance. - Mechanistic testing: Neither increased Apob transcription rate nor increased transcript binding to HuR protein accounted for the second-phase increase in apoB transcripts.
Why it matters
The study reveals a time-dependent transition in acute endotoxemia from early secretion of large, triglyceride-rich VLDL to late secretion of numerous, triglyceride-poor medium VLDL particles, refining the understanding of hepatic lipid handling during Gram-negative sepsis.
Limits
The study was conducted exclusively in a rat endotoxin model, which does not fully capture complex human clinical sepsis. Sample size per group, precise LPS dosing, and the definitive molecular driver of the late-phase apoB transcript elevation were not reported in the abstract.
Cited by
- supports LPS binds to LDL and VLDL particles via lipid interactions and binds specifically to the apoB protein.