[Heavy metals and derangement in carbohydrate metabolism in eye diseases: a systematic review]

To uncover the negative impacts of heavy metals on carbohydrate metabolism, their mechanisms and contributory factors, as well as their role on the etiopathogenesis, pathophysiology, and progression of eye diseases.

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), various databases were searched (e.g., Scopus, PubMed, etc.) to collect evidence on the link and role of heavy metals in carbohydrate metabolism and pathogenesis of eye diseases. Included studies were appraised for quality using the Critical Appraisal Skills Programme checklists and extracted data were analyzed using the narrative synthesis method.

Of the 128 papers retrieved, 24 papers met the inclusion criteria. Heavy metals are associated with the onset and progression of diabetes and eye diseases secondary to diabetes (age-related macular degeneration, cataract, and diabetic retinopathy) majorly via toxic interference (induction, inhibition and/or deactivation) of glucose metabolizing enzymes and oxidative stress. The etiology of DR is intricate and includes the simultaneous disruption of several metabolic and signaling mechanisms within the retinal neurovascular unit. The retina is more susceptible to metal-induced toxicities due to the high affinity of heavy metals to melanin content of the retinal epithelium.

This study emphasizes the harmful effects of chronic and intermittent exposure to heavy metals, suggesting no safe exposure levels. To prevent eye diseases secondary to heavy metals-induced altered carbohydrate metabolism, metal chelators, low glycemic diets, and lifestyle modifications should be exploited among vulnerable populations.