Association between serum interleukin-6 levels with the risk and clinical severity of primary open-angle glaucoma

Association between glaucoma susceptibility with combined defects in mitochondrial oxidative phosphorylation and fatty acid beta oxidation

Glaucoma is one of the leading causes of visual impairment and blindness worldwide, and is characterized by the progressive damage of retinal ganglion cells (RGCs) and the atrophy of the optic nerve head (ONH). The exact cause of RGC loss and optic nerve damage in glaucoma is not fully understood. The high energy demands of these cells imply a higher sensitivity to mitochondrial defects. Moreover, it has been postulated that the optic nerve is vulnerable towards damage from oxidative stress and mitochondrial dysfunction. To investigate this further, we conducted a pooled analysis of mitochondrial variants related to energy production, specifically focusing on oxidative phosphorylation (OXPHOS) and fatty acid β-oxidation (FAO). Our findings revealed that patients carrying non-synonymous (NS) mitochondrial DNA (mtDNA) variants within the OXPHOS complexes had an almost two-fold increased risk of developing glaucoma. Regarding FAO, our results demonstrated that longer-chain acylcarnitines (AC) tended to decrease, while shorter-chain AC tended to increase in patients with glaucoma. Furthermore, we observed that the knocking down cpt1a (a key rate-limiting enzyme involved in FAO) in zebrafish induced a degenerative process in the optic nerve and RGC, which resembled the characteristics observed in glaucoma. In conclusion, our study provides evidence that genes encoding mitochondrial proteins involved in energy metabolisms, such as OXPHOS and FAO, are associated with glaucoma. These findings contribute to a better understanding of the molecular mechanisms underlying glaucoma pathogenesis and may offer potential targets for therapeutic interventions in the future.

Evaluation of systemic IL-6 trans-signalling in patients with primary open-angle glaucoma

PURPOSE

To evaluate systemic trans-signalling of interleukin (IL)-6 in patients with primary open-angle glaucoma (POAG).

METHODS

Fifty-one POAG patients and 47 matched healthy controls were enrolled. Serum concentrations of IL-6, sIL-6R, and sgp130 were quantified.

RESULTS

Serum levels of IL-6, sIL-6R, and IL-6/sIL-6R ratios in the POAG group were significantly higher than those in control group, while only the sgp130/sIL-6R/IL-6 ratio was decreased. Among POAG subjects, advanced-stage patients exhibited significantly higher intraocular pressure (IOP), serum IL-6 and sgp130 levels, and IL-6/sIL-6R ratio than those in the early to moderate stage. The ROC curve analysis revealed that the IL-6 level and IL-6/sIL-6R ratio performed better than other parameters in diagnosing POAG and discriminating POAG severity. Serum IL-6 level was moderately correlated with IOP and C/D ratio, while a weak correlation was observed between sIL-6R levels with C/D ratio. IL-6 and sIL-6R levels were correlated with each other in POAG patients but not in healthy controls.

CONCLUSION

Overstimulation of systemic IL-6 trans-signalling has been implicated in POAG.