Does the balance between cholesterol absorption and synthesis affect LDL cholesterol?

Circulating low-density lipoprotein cholesterol (LDL-C) is dynamically regulated by a reciprocal homeostatic feedback loop between intestinal cholesterol absorption and hepatic de novo synthesis.

Clinical evidence and metabolic phenotyping

• Non-cholesterol sterols serve as validated surrogate markers to distinguish individual metabolic profiles. The phytosterols campesterol and sitosterol reflect fractional intestinal absorption, while the precursor lathosterol tracks endogenous hepatic synthesis.
• Establishing a patient's campesterol-to-lathosterol ratio (normalized to total cholesterol) differentiates absorption-dominant from synthesis-dominant hypercholesterolemia.
• These markers illustrate drug-induced metabolic shifts: statins characteristically lower lathosterol while triggering compensatory absorption, whereas ezetimibe lowers campesterol and sitosterol while inducing compensatory synthesis.

Mechanistic pathways and homeostatic feedback

• Intestinal cholesterol absorption is primarily driven by Niemann-Pick C1-Like 1 (NPC1L1) transporters, which regulate the entry of cholesterol into the body and expand the hepatic cholesterol pool.
• High intestinal absorption triggers the secretion of Cholesin, a gut-derived hormone. Cholesin binds to hepatic GPR146 receptors, inhibiting protein kinase A (PKA) signaling and suppressing sterol regulatory element-binding protein 2 (SREBP2)-mediated endogenous synthesis.
• When hepatic cholesterol levels shift, SREBP2 transcription is modulated, altering the expression of hepatic low-density lipoprotein receptors (LDLR) and directly dictating the clearance and plasma concentration of circulating LDL-C.

Bottom line

• Measuring campesterol, sitosterol, and lathosterol effectively identifies whether a patient's lipid profile is absorption- or synthesis-dominant, reflecting a tightly regulated NPC1L1-Cholesin-SREBP2 feedback loop that dictates hepatic LDLR expression and circulating LDL-C.