Caco-2 Cell Conditions Enabling Studies of Drug Absorption from Digestible Lipid-Based Formulations

Purpose

To identify conditions allowing the use of cell-based models for studies of drug absorption during in vitro lipolysis of lipid-based formulations (LBFs).

Methods

Caco-2 was selected as the cell-based model system. Monolayer integrity was evaluated by measuring mannitol permeability after incubating Caco-2 cells in the presence of components available during lipolysis. Pure excipients and formulations representing the lipid formulation classification system (LFCS) were evaluated before and after digestion. Porcine mucin was evaluated for its capacity to protect the cell monolayer.

Results

Most undigested formulations were compatible with the cells (II-LC, IIIB-LC, and IV) although some needed mucin to protect against damaging effects (II-MC, IIIB-MC, I-LC, and IIIA-LC). The pancreatic extract commonly used in digestion studies was incompatible with the cells but the Caco-2 monolayers could withstand immobilized recombinant lipase. Upon digestion, long chain formulations caused more damage to Caco-2 cells than their undigested counterparts whereas medium chain formulations showed better tolerability after digestion.

Conclusions

Most LBFs and components thereof (undigested and digested) are compatible with Caco-2 cells. Pancreatic enzyme is not tolerated by the cells but immobilized lipase can be used in combination with the cell monolayer. Mucin is beneficial for critical formulations and digestion products.

     

Applanation resonance tonometry for intraocular pressure in humans

Glaucoma is a group of diseases associated with optic nerve damage and loss of visual field. The aetiology is not completely understood, but one of the major risk factors is elevated intraocular pressure (IOP). Reliable methods for measuring the IOP are therefore important. The aim of the study was to investigate the ability of the applanation resonance tonometry (ART) system, based on continuous force and area recording, to measure IOP in humans. Both the phase of initial indentation (IOPIndentation) and the phase when the sensor was removed (IOPRemoval) from the cornea were analysed. The Goldmann applanation tonometry (GAT) was used as reference method. The study included 24 healthy volunteers with normal IOP and 24 patients with elevated IOP. The correlation and standard deviation (SD) between IOPIndentation and IOPGAT was R = 0.92 (p < 0.001), SD = 3.6 mmHg, n = 104, and between IOPRemoval and IOPGAT R = 0.94 (p < 0.001), SD = 3.1 mmHg, n = 104. In conclusion, resonance sensor technology has made it possible to introduce a new multi-point method for measuring IOP, and the method is relevant for measuring IOP in humans. The study indicates that with further development towards elimination of position dependence, the ART has the potential to become a useful clinical instrument for IOP measurement.     

Genetic association signal near NTN4 in Tourette syndrome

Tourette syndrome (TS) is a neurodevelopmental disorder with a complex genetic etiology. Through an international collaboration, we genotyped 42 single nucleotide polymorphisms (p < 10⁻³) from the recent TS genomewide association study (GWAS) in 609 independent cases and 610 ancestry‐matched controls. Only rs2060546 on chromosome 12q22 (p = 3.3 × 10⁻⁴) remained significant after Bonferroni correction. Meta‐analysis with the original GWAS yielded the strongest association to date (p = 5.8 × 10⁻⁷). Although its functional significance is unclear, rs2060546 lies closest to NTN4, an axon guidance molecule expressed in developing striatum. Risk score analysis significantly predicted case–control status (p = 0.042), suggesting that many of these variants are true TS risk alleles. Ann Neurol 2014;76:310–315