Reduced Intra- and Extracellular Circulating Postprandial Lysosomal Acid Lipase Activity in Patients with MASLD.

Background/objectives: Low fasting blood lysosomal acid lipase (LAL) activity is associated with the pathogenesis of metabolic hepatic steatosis. We measured LAL activity in blood and plasma before and after an oral fat tolerance test (OFTT) in patients with metabolic-dysfunction-associated steatotic liver disease (MASLD).

Methods: Twenty-six controls and seventeen patients with MASLD but without diabetes were genotyped for the patatin-like phospholipase 3 (PNPLA3) rs738409 variant by RT-PCR and subjected to an OFTT, measuring LAL activity in blood and plasma with a fluorimetric method.

Results: LAL activity in blood both under fasting and 4 h after OFTT (0.846 ± 0.309 nmol/spot/h vs. 1.180 ± 0.503 nmol/spot/h p < 0.01) was lower in patients with MASLD compared to controls. These differences were present only in carriers of the PNPLA3 variant. In controls not carrying the PNPLA3 variant, the postprandial increase in blood LAL activity was negatively correlated with that of serum triglycerides (p < 0.05). Extracellular LAL activity in plasma was lower in patients with MASLD (n = 9) compared to controls (n = 8) in the fasting state (p < 0.01) and 4 h post-meal (p < 0.05). The area under the curve up to 6 h of plasma LAL activity was lower in patients with MASLD than in controls (p < 0.05) and correlated negatively with that of triglycerides only in controls (r = -0.841; p < 0.01).

Conclusions: Patients with MASLD have reduced LAL activity in blood and plasma both before and 4 h after a meal. In patients with MASLD, the physiological negative correlation between circulating LAL levels and postprandial hypertriglyceridemia is lost.