Molecular structure-dependent cytotoxic effect of ascorbate derivatives

Mediation-adjusted multivariable Mendelian randomisation study identified novel metabolites related to mental health

BACKGROUND

From the pathway perspective, metabolites have the potential to improve knowledge about the aetiology of psychiatric diseases. Previous studies suggested a link between specific blood metabolites and mental disorders, but some Mendelian randomisation (MR) studies in particular are insufficient for various reasons.

OBJECTIVE

This study focused on bias assessment due to interdependencies between metabolites and psychiatric mediation effects.

METHODS

In a multistep framework containing network and multivariable MR, direct effects of 21 mutually adjusted metabolites on 8 psychiatric disorders were estimated based on summary statistics of genome-wide association studies from multiple resources. Robust inverse-variance weighted models were used in primary analyses. Several sensitivity analyses were performed to assess different patterns of pleiotropy and weak instrument bias. Estimates for the same phenotypes from different resources were pooled using fixed effect meta-analysis models.

FINDINGS

After adjusting for mediation effects, genetically predicted metabolite levels of six metabolites of lipid, amino acid and cofactors pathways were directly associated with overall six mental disorders (attention-deficit/hyperactivity disorder, bipolar disorder, anorexia nervosa, depression, post-traumatic stress disorder and schizophrenia). Point estimates ranged from -0.45 (95% CI -0.67; -0.24, p=1.0×104) to 1.78 (95% CI 0.85; 2.71, p=0.006). No associations were found with anxiety and suicide attempt.

CONCLUSIONS

This study provides insights into new metabolic pathways that seems to be causally related to certain mental disorders.

CLINICAL IMPLICATIONS

Further studies are needed to investigate whether the identified associations are effects of the metabolites itself or the biochemical pathway regulating the metabolites.

Association between human blood metabolome and the risk of delirium: a Mendelian Randomization study

Background

Delirium significantly contributes to both mortality and morbidity among hospitalized older adults. Furthermore, delirium leads to escalated healthcare expenditures, extended hospital stays, and enduring cognitive deterioration, all of which are acknowledged detrimental outcomes. Nonetheless, the current strategies for predicting and managing delirium remain constrained. Our aim was to employ Mendelian randomization (MR) to investigate the potential causal relationship between metabolites and delirium, as well as to identify potential therapeutic targets.

Methods

We identified 129 distinct blood metabolites from three genome-wide association studies (GWASs) conducted on the metabolome, involving a total of 147,827 participants of European descent. Genetic information pertaining to delirium was sourced from the ninth iteration of the Finngen Biobank, encompassing 359,699 individuals of Finnish ancestry. We conducted MR analyses to evaluate the connections between blood metabolites and delirium. Additionally, we extended our analysis to encompass the entire phenome using MR, aiming to uncover potential on-target consequences resulting from metabolite interventions.

Results

In our investigation, we discovered three metabolites serving as causal mediators in the context of delirium: clinical low density lipoprotein cholesterol (LDL-C) (odds ratio [OR]: 1.47, 95% confidence interval [CI]: 1.25-1.73, p = 3.92 x 10-6), sphingomyelin (OR: 1.47, 95% CI: 1.25-1.74, p = 5.97 x 10-6), and X-11593-O-methylascorbate (OR: 0.21, 95% CI: 0.10-0.43, p = 1.86 x 10-5). Furthermore, utilizing phenome-wide MR analysis, we discerned that clinical LDL-C, sphingomyelin, and O-methylascorbate not only mediate delirium susceptibility but also impact the risk of diverse ailments.

Limitations

(1) Limited representation of the complete blood metabolome, (2) reliance on the PheCode system based on hospital diagnoses may underrepresent conditions with infrequent hospital admissions, and (3) limited to European ancestry.

Conclusion

The genetic prediction of heightened O-methylascorbate levels seems to correspond to a diminished risk of delirium, in contrast to the association of elevated clinical LDL-C and sphingomyelin levels with an amplified risk. A comprehensive analysis of side-effect profiles has been undertaken to facilitate the prioritization of drug targets. Notably, O-methylascorbate emerges as a potentially auspicious target for mitigating and treating delirium, offering the advantage of lacking predicted adverse side effects.

Effect of dietary modification and antioxidant supplementation on intraocular pressure and open-angle glaucoma

Primary open-angle glaucoma (POAG) is an age-dependent, intraocular pressure (IOP)-related degeneration of the retinal ganglion cells (RGC). At present, IOP is the only modifiable factor that has been identified to prevent glaucomatous vision loss. Though the pathogenesis of glaucomatous optic neuropathy is still not well understood, increasing evidence suggests oxidative stress may contribute to the induction and progression of glaucoma. Furthermore, antioxidant use may be protective against glaucoma through various mechanisms, including reducing IOP, preserving vascular health, and preventing ganglion cell loss. This article provides a comprehensive review of the effect of oxidative stress, diet, and antioxidant therapy on IOP and open-angle glaucoma.

Ascorbic acid metabolites are involved in intraocular pressure control in the general population

Elevated intraocular pressure (IOP) is an important risk factor for glaucoma. Mechanisms involved in its homeostasis are not well understood, but associations between metabolic factors and IOP have been reported. To investigate the relationship between levels of circulating metabolites and IOP, we performed a metabolome-wide association using a machine learning algorithm, and then employing Mendelian Randomization models to further explore the strength and directionality of effect of the metabolites on IOP. We show that O-methylascorbate, a circulating Vitamin C metabolite, has a significant IOP-lowering effect, consistent with previous knowledge of the anti-hypertensive and anti-oxidative role of ascorbate compounds. These results enhance understanding of IOP control and may potentially benefit future IOP treatment and reduce vision loss from glaucoma.

•

Vitamin C and its metabolites are highly concentrated in human brain and eye tissues.

•

Multi-omics analysis finds evidence for association between ascorbic acid metabolism and intraocular pressure.

•

O-methylascorbate lowers intraocular pressure in the general population.

•

O-methylascorbate's role in intraocular pressure regulation is likely mediated by its anti-photooxidative properties.