Agricultural work and reduced circulating uric acid are both associated with initial hospital admission for Parkinson's disease

The Influence of Agricultural Work and Plasma Uric Acid on Hospital Admission for Alzheimer's Disease

BACKGROUND

Exposure to environmental neurotoxins associated with agricultural work, such as pesticides, may be a risk factor for neurodegenerative disorders such as Alzheimer's (AD) and Parkinson's (PD) diseases. There is strong evidence that such exposure is associated with the development of PD; for AD the current evidence is equivocal. Several mechanisms are proposed to mediate this environmental toxicity, one of which is oxidative stress. Uric acid (UA) is an endogenous antioxidant, low levels of which are also implicated in neurodegenerative disease.

OBJECTIVE

This study aimed to determine whether agricultural work was a risk factor for AD in a population in which its association with PD was established, and whether UA was also associated with AD in this cohort.

METHODS

Hospital records of subjects meeting criteria for AD (n = 128) or vascular dementia (VaD) (n = 178) after hospital admission for symptoms of dementia were studied. History of agricultural work and plasma UA were recorded and their relationship to diagnosis determined.

RESULTS

In contrast to previous findings in this population in which agricultural work was strongly associated with PD, a history of agricultural work was not over-represented in hospital admission for AD versus VaD. AD was associated with a reduced level of circulating UA compared with VaD.

CONCLUSION

Agricultural work as a likely proxy for exposure to pesticides appears not to be a risk factor for AD to the extent found in PD, perhaps reflecting their differences in neuronal pathology. Nevertheless, findings with UA suggests that oxidative stress may be an important factor in AD pathogenesis.

Risk Factors for Brain Health in Agricultural Work: A Systematic Review

Certain exposures related to agricultural work have been associated with neurological disorders. To date, few studies have included brain health measurements to link specific risk factors with possible neural mechanisms. Moreover, a synthesis of agricultural risk factors associated with poorer brain health outcomes is missing. In this systematic review, we identified 106 articles using keywords related to agriculture, occupational exposure, and the brain. We identified seven major risk factors: non-specific factors that are associated with agricultural work itself, toluene, pesticides, heavy metal or dust exposure, work with farm animals, and nicotine exposure from plants. Of these, pesticides are the most highly studied. The majority of qualifying studies were epidemiological studies. Nigral striatal regions were the most well studied brain area impacted. Of the three human neuroimaging studies we found, two focused on functional networks and the third focused on gray matter. We identified two major directions for future studies that will help inform preventative strategies for brain health in vulnerable agricultural workers: (1) the effects of moderators such as type of work, sex, migrant status, race, and age; and (2) more comprehensive brain imaging studies, both observational and experimental, involving several imaging techniques.

Glucose, Fructose, and Urate Transporters in the Choroid Plexus Epithelium

The choroid plexus plays a central role in the regulation of the microenvironment of the central nervous system by secreting the majority of the cerebrospinal fluid and controlling its composition, despite that it only represents approximately 1% of the total brain weight. In addition to a variety of transporter and channel proteins for solutes and water, the choroid plexus epithelial cells are equipped with glucose, fructose, and urate transporters that are used as energy sources or antioxidative neuroprotective substrates. This review focuses on the recent advances in the understanding of the transporters of the SLC2A and SLC5A families (GLUT1, SGLT2, GLUT5, GLUT8, and GLUT9), as well as on the urate-transporting URAT1 and BCRP/ABCG2, which are expressed in choroid plexus epithelial cells. The glucose, fructose, and urate transporters repertoire in the choroid plexus epithelium share similar features with the renal proximal tubular epithelium, although some of these transporters exhibit inversely polarized submembrane localization. Since choroid plexus epithelial cells have high energy demands for proper functioning, a decline in the expression and function of these transporters can contribute to the process of age-associated brain impairment and pathophysiology of neurodegenerative diseases.