Association Between Serum Lipid Levels and Patients With Primary Angle-Closure Glaucoma in China: A Cross Sectional, Case-Control Study

Serum lipid and lipoprotein profiles and their association with intraocular pressure in primary open-angle glaucoma: an observational cross-sectional study in the Chinese population

BACKGROUND

Glaucoma is a leading cause of vision impairment and permanent blindness. Primary open-angle glaucoma (POAG) is a prominent type of primary glaucoma; however, its cause is difficult to determine. This study aimed to analyze the serum lipid profile of Chinese POAG patients and assess its correlation with intraocular pressure (IOP).

METHODS

The study included 1,139, 1,248, and 356 Chinese individuals with POAG, primary angle closure glaucoma (PACG), and controls, respectively. Peripheral whole blood samples were collected at the time of diagnosis. Enzymatic colorimetry was used to determine serum levels of different lipids: high-density lipoproteins (HDL), low-density lipoproteins (LDL), triglycerides, cholesterol, and very low-density lipoproteins (VLDL). Additionally, immunoturbidimetry was used to quantify serum levels of apolipoproteins A (APOA), B (APOB), E (APOE), and lipoprotein A [Lp(a)], while intraocular pressure (IOP) was measured in all patients with POAG.

RESULTS

After adjusting for age and sex, patients with POAG exhibited elevated serum levels of VLDL, APOA, and APOE but mitigated cholesterol levels compared with the control participants. Significantly lower serum triglyceride, VLDL, and Lp(a) levels were found in patients with PACG than in control participants. Serum cholesterol (P = 0.019; β = -0.75, 95% confidence interval [CI]: -1.38 - -0.12) and HDL levels (P < 0.001; β = -2.91, 95% CI: -4.58 - -1.25) were inversely linked to IOP in patients with POAG, after adjusting for age, sex, and ocular metrics. In addition, serum Lp(a) levels were correlated with the average IOP (P = 0.023; β = -0.0039, 95% CI: -0.0073 - -0.006) and night peak (P = 0.027; β = -0.0061, 95% CI: -0.0113 - -0.0008) in patients with POAG.

CONCLUSIONS

Significantly different serum lipid and lipoprotein profiles were observed in POAG and PACG patients. This study highlighted the differences in serum lipid and lipoprotein levels among Chinese POAG patients and their relationship with IOP and IOP fluctuation. Serum lipid and lipoprotein profiles should be considered while evaluating glaucoma risk.

Association of Retinal Nerve Fiber Layer Thinning With Elevated High Density Lipoprotein Cholesterol in UK Biobank

Purpose

The purpose of this study was to investigate the association between retinal nerve fiber layer (RNFL) thickness and high-density lipoprotein cholesterol (HDL-C) in a healthy population.

Methods

This cross-sectional study included 31,738 UK Biobank participants with high quality optical coherence tomography (OCT) images, excluding those with neurological or ocular diseases. The locally estimated scatterplot smoothing (LOESS) curve and multivariable piecewise linear regression models were applied to assess the association between HDL-C and RNFL thickness, and HDL-C subclasses were further analyzed using nuclear magnetic resonance (NMR) spectroscopy.

Results

Multivariate piecewise linear regression revealed that high HDL-C levels (>1.7 mmol/L in women or > 1.5 mmol/L in men) were associated with thinner RNFL thickness (women: β = -0.13, 95% confidence interval [CI] = -0.23 to -0.02, P = 0.017; male: β = -0.23, 95% CI = -0.37 to -0.10, P = 0.001). Conversely, a significant positive association between HDL-C and RNFL thickness was observed when HDL-C was between 1.4 and 1.7 mmol/L for female participants (β = 0.13, 95% CI = 0.02 to 0.24, P = 0.025). NMR analysis showed that these associations are potentially driven by distinct HDL-C subclasses.

Conclusions

This study revealed an association between HDL-C levels and retinal markers of neurodegenerative diseases, suggesting that elevated HDL-C may serve as a new risk factor for neurodegenerative conditions. These findings may contribute to the implementation of preventive interventions and improved patient outcomes.

Cholesterol and oxysterols in retinal neuron-glia interactions: relevance for glaucoma

Cholesterol is an essential component of cellular membranes, crucial for maintaining their structural and functional integrity. It is especially important for nervous tissues, including the retina, which rely on high amounts of plasma membranes for the transmission of the nervous signal. While cholesterol is by far the most abundant sterol, the retina also contains cholesterol precursors and metabolites, especially oxysterols, which are bioactive molecules. Cholesterol lack or excess is deleterious and some oxysterols are known for their effect on neuron survival. Cholesterol homeostasis must therefore be maintained. Retinal glial cells, especially Müller cells, the principal glial cells of the vertebrate retina, provide mechanical, nutritional, and metabolic support for the neighboring neurons. Several pieces of evidence indicate that Müller cells are major actors of cholesterol homeostasis in the retina, as it is known for other glial cells in the brain. This process is based on a close cooperation with neurons, and sterols can be signaling molecules participating in glia-neuron interactions. While some implication of cholesterol in age-related macular degeneration is now recognized, based on epidemiological and laboratory data, evidence for its role in glaucoma is still scarce. The association between cholesterolemia and glaucoma is controversial, but experimental data suggest that sterols could take part in the pathological processes. It has been demonstrated that Müller glial cells are implicated in the development of glaucoma through an ambivalent reactive retinal gliosis process. The early steps contribute to maintaining retinal homeostasis and favor the survival of ganglion cells, which are targeted during glaucoma. If gliosis persists, dysregulation of the neuroprotective functions, cytotoxic effects of gliotic Müller cells and disruption of glia-neuron interactions lead to an acceleration of ganglion cell death. Sterols could play a role in the glial cell response to glaucomatous injury. This represents an understudied but attractive topic to better understand glaucoma and conceive novel preventive or curative strategies. The present review describes the current knowledge on i) sterol metabolism in retinal glial cells, ii) the potential role of cholesterol in glaucoma, and iii) the possible relationships between cholesterol and oxysterols, glial cells and glaucoma. Focus is put on glia-neuron interactions.

The Association between Cholesterol Levels and Severity of Normal Tension Glaucoma

Purpose

To evaluate the serum lipid levels, including total cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) of patients with normal tension glaucoma (NTG) and to investigate the relationship between serum HDL levels and the severity of NTG.

Methods

In this cross-sectional, case-control study, 282 NTG subjects and 202 control subjects were enrolled from the outpatient clinic of the Department of Ophthalmology at Taichung Veterans General Hospital in central Taiwan from 2015 to 2021. Fasting cholesterol, HDL, and LDL levels were evaluated using a biochemical analyzer (ARCHITECT c16000). Glaucoma severity was classified by visual field test as mild (mean deviation [MD] ≥ -6.0dB), moderate (-12dB ≤ MD < -6 dB), and severe (MD < -12dB), based on the mean deviation.

Results

HDL levels were significantly lower in the NTG group compared with the control subjects (47 ± 18mg/dl versus 53 ± 18mg/dl; p = 0.03). There were no statistically significant differences in total cholesterol or LDL levels between the NTG and control subjects (total cholesterol levels: 194 ± 39mg/dl versus 190 ± 32mg/dl; p > 0.05; LDL levels: 113 ± 30mg/dl versus 110 ± 29mg/dl; p > 0.05). The mean serum HDL levels were lowest in the severe group (41 ± 11mg/dl) followed by the moderate (45 ± 16mg/dl) and mild (50 ± 15mg/dl) groups, with significant differences among the three groups (p = 0.02). The multivariate regression analysis revealed a statistically significant negative correlation between HDL and vertical cup-to-disc ratio (VCDR; B =-0.16, p = 0.03) among all NTG patients and a positive correlation between HDL and retinal nerve fiber layer (RNFL; r = 0.34, p = 0.03) among all NTG patients.

Conclusions

A significantly lower serum HDL concentration was found in the NTG patients, which was negatively associated with disease severity. The findings warrant further study to elucidate the role of these phenomena in the pathogenesis of glaucoma.