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A Kinetic Assay of Total Lipase Activity for Detecting Lysosomal Acid Lipase Deficiency (LAL-D) and the Molecular Characterization of 18 LAL-D Patients From Russia

Nikolay Mayanskiy, Ekaterina Brzhozovskaya, Alexander Pushkov, Tatiana Strokova, Nikolay Vlasov, Andrej Surkov, Olga Gundobina, Kirill Savostianov

JIMD Rep. 2019 Jun 3;48(1):75-82.

PMID: 31392116

Abstract:

Laboratory diagnostics of lysosomal acid lipase deficiency (LAL-D), a rare disorder associated with LIPA alterations, are based on the evaluation of LAL activity. In dry blood spots (DBS) submitted for LAL-D diagnostics (the screening cohort) over a two-year period or obtained from a cohort of retrospective LAL-D patients, we measured: (1) LAL activity using a two-reaction assay with 4-methylumbelliferone palmitate (4-MU-Palm) and Lalistat-2, a specific LAL inactivator; (2) total lipase (TL) activity by a 1-hour kinetic 4-MU-Palm cleavage reaction (no Lalistat-2). The TL activity was expressed as the area under the kinetic curve after 1 hour (TL-AUC1h) of the reaction and presented as the median (min-max). LAL activity was reduced in 30/537 individuals from the screening cohort, among which LIPA sequencing revealed six patients and one carrier. Overall, 16 (89%) individuals among six novel and 12 retrospective LAL-D patients carried at least one c.894G>A mutation (six were homozygous). The TL-AUC1h in nonLAL-D specimens with normal LAL activity (n = 90) was unambiguously higher (9471 [4015-23 585] RFU*h/punch) compared to LAL-D patients, including six new and nine retrospective patients (1810 [357-2608] RFU*h/punch). Importantly, in 13/15 examined nonLAL-D specimens with reduced LAL activity the TL-AUC1h was above a threshold of 2652 RFU*h/punch. Applying this threshold, the TL-AUC1h index discriminated all LAL-D patients (100% sensitivity) and 103/105 nonLAL-D specimens (98% specificity). Given that there is no need for Lalistat-2 and two parallel enzymatic reactions in conjunction with high sensitivity and specificity, the kinetic assay seems to be practical for LAL-D screening.
Synopsis:
Lysosomal acid lipase deficiency responsible for Wolman disease and cholesterol ester storage disease could be reliably detected using a kinetic assay of total lipase activity with a fluorogenic substrate.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP1234569095 Lalistat 2 Lalistat 2 1234569-09-5 Price
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