Aqueous Humor and Serum Concentration of Hydroxyproline in Pseudoexfoliation Syndrome

Metabolomic Profiling of Aqueous Humor in Glaucoma Points to Taurine and Spermine Deficiency: Findings from the Eye-D Study

We compared the metabolomic profile of aqueous humor from patients with primary open-angle glaucoma (POAG; n = 26) with that of a group of age- and sex-matched non-POAG controls (n = 26), all participants undergoing cataract surgery. Supervised paired partial least-squares discriminant analysis showed good predictive performance for test sets with a median area under the receiver operating characteristic of 0.89 and a p-value of 0.0087. Twenty-three metabolites allowed discrimination between the two groups. Univariate analysis after the Benjamini-Hochberg correction showed significant differences for 13 of these metabolites. The POAG metabolomic signature indicated reduced concentrations of taurine and spermine and increased concentrations of creatinine, carnitine, three short-chain acylcarnitines, 7 amino acids (glutamine, glycine, alanine, leucine, isoleucine, hydroxyl-proline, and acetyl-ornithine), 7 phosphatidylcholines, one lysophosphatidylcholine, and one sphingomyelin. This suggests an alteration of metabolites involved in osmoprotection (taurine and creatinine), neuroprotection (spermine, taurine, and carnitine), amino acid metabolism (7 amino acids and three acylcarnitines), and the remodeling of cell membranes drained by the aqueous humor (hydroxyproline and phospholipids). Five of these metabolic alterations, already reported in POAG plasma, concern spermine, C3 and C4 acylcarnitines, PC aa 34:2, and PC aa 36:4, thus highlighting their importance in the pathogenesis of glaucoma.

Serum Levels of Omentin in Pseudoexfoliation Syndrome

PURPOSE

Omentin, a member of the adipocytokines family, is derived from adipose tissue and a lower level of serum omentin is considered as a metabolic risk factor. The aim of the present study is to evaluate the serum levels of omentin in patients with pseudoexfoliation syndrome (PES).

MATERIALS AND METHODS

Patients without any systemic or ocular disease other than PES were included in the study. Age-matched and sex-matched healthy volunteers without PES were accepted as a control group. After detailed ophthalmologic examination, blood samples were obtained from a forearm vein. Serum levels of omentin were determined by the method of enzyme-linked immunosorbent assay.

RESULTS

The mean age of the PES group (12 females, 12 males, n=24) was 75.2 ± 8.4 years, and the control group (10 females, 10 males, n=20) was 75 ± 6.7 years. There was no difference between the groups in terms of age (P=0.93) and sex (P=0.9). The mean serum levels of omentin in the PES group were 801.5 ± 317.1 ng/mL and in the control group were 1150.1 ± 584.1 ng/mL. The mean serum omentin levels were significantly lower in patients with PES (P=0.016).

CONCLUSION

Lower levels of serum omentin in patients with PES compared with healthy subjects may support the theory of systemic nature of the disease.

Pharmacokinetic-pharmacodynamic and response sensitization modeling of the intraocular pressure-lowering effect of the EP4 Agonist 5-{3-[(2S)-2-{(3R)-3-hydroxy-4-[3-(trifluoromethyl)phenyl]butyl}-5-oxopyrrolidin-1-yl]propyl}thiophene-2-carboxylate (PF-04475270)

Developing a population-based pharmacokinetic-pharmacodynamic (PKPD) model is a challenge in ophthalmology due to the difficulty of obtaining adequate pharmacokinetic (PK) samples from ocular tissues to inform the pharmacodynamic (PD) model. Using limited PK data, we developed a preclinical population-based PD model suitable for capturing the time course of dog intraocular pressure (IOP) that exhibited time-dependent sensitization after topical administration of PF-04475270 [5-{3-[(2S)-2-{(3R)-3-hydroxy-4-[3-(trifluoromethyl)phenyl]butyl}-5-oxopyrrolidin-1-yl]propyl}thiophene-2-carboxylate]. A physiologically relevant PK model was chosen to simultaneously capture the concentration profiles of CP-734432, a potent EP4 agonist and the active metabolite of PF-04475270, sampled from three ocular tissues of the anterior chamber: cornea, aqueous humor, and iris-ciliary body. Two population-based PD models were developed to characterize the IOP lowering profiles: model I, a standard indirect-response model (IRM); and model II, an extension of a standard IRM that empirically incorporated a response-driven positive feedback loop to account for the observed PD sensitization. The PK model reasonably described the PK profiles in all three ocular tissues. As for the PD, model I failed to capture the overall trend in the population IOP data, and model II more adequately characterized the overall data set. This integrated PKPD model may have general utility when PD sensitization is observed and is not a result of time-dependent PK. In addition, the model is applicable in the ophthalmology drug development setting in which PK information is limited but a population-based PD model could reasonably be established.