Uric Acid and the Risk of Alzheimer's Disease: Is There an Association?

Higher uric acid serum levels are associated with sarcopenia in west China: a cross-sectional study

Background

Sarcopenia is the decline in muscle strength and mass attributed to aging. The pathogenesis of sarcopenia may be triggered by oxidative stress and uric acid (UA) has strong antioxidant properties. The aim of this study was to investigate the relationship between UA and sarcopenia in community-dwelling adults of West China using the baseline data of West China Health and Aging Trend (WCHAT) study.

Design

A cross-sectional study.

Methods

4236 adults aged 50 years or older in communities of west China were enrolled in this study. We applied Asian Working Group for Sarcopenia (AWGS) 2019 criteria to define sarcopenia. Muscle mass was measured using skeletal muscle index (SMI) based on bioimpedance analysis (BIA). Handgrip strength (HGS) and gait speed (GS) were recorded, respectively. Different variables like anthropometry measures, life styles, chronic disease and blood test were collected. General linear model was done to investigate the relationship between UA and HGS/GS/SMI, adjusting age, ethnic groups, sleeping quality, education level, cognitive function, smoking history, drinking history, ADL score, and chronic disease.

Results

Participants were grouped according to UA quartiles by gender. After adjusting for potential confounders, a negative association between serum UA levels and sarcopenia was shown both in men and women. And a significant association between serum UA levels and HGS in women was shown as an inverted J shape. Besides, a positive association between the UA quartiles and SMI was observed, irrespective of gender.

Conclusions

Our results showed that higher uric acid levels were significantly correlated with higher muscle mass and grip strength among Chinese adults aged over 50. Higher UA serum levels might slow down the progression of sarcopenia.

Serum Uric Acid May Aggravate Alzheimer's Disease Risk by Affecting Amyloidosis in Cognitively Intact Older Adults: The CABLE Study

BACKGROUND

Serum uric acid (SUA) affects the reaction of oxidative stress and free radicals in the neurodegenerative processes. However, whether SUA impacts Alzheimer's disease (AD) pathology remains unclear.

OBJECTIVE

We aimed to explore whether high SUA levels can aggravate the neurobiological changes of AD in preclinical AD.

METHODS

We analyzed cognitively intact participants (n = 839, age 62.16 years) who received SUA and cerebrospinal fluid (CSF) biomarkers (amyloid-β [Aβ], total tau [t-Tau], and phosphorylated tau [p-Tau]) measurements from the Chinese Alzheimer's Biomarker and LifestylE (CABLE) database using multivariable-adjusted linear models.

RESULTS

Levels of SUA in the preclinical AD elevated compared with the healthy controls (p = 0.007) and subjects with amyloid pathology had higher concentration of SUA than controls (p = 0.017). Roughly, equivalent levels of SUA displayed among cognitively intact individuals with or without tau pathology and neurodegeneration. CSF Aβ1 - 42 (p = 0.019) and Aβ1 - 42/Aβ1 - 40 (p = 0.027) were decreased and CSF p-Tau/Aβ1 - 42 (p = 0.009) and t-Tau/Aβ1 - 42 (p = 0.043) were increased with the highest (> 75th percentile) SUA when compared to lowest SUA, implying a high burden of cerebral amyloidosis in individuals with high SUA. Sensitivity analyses using the usual threshold to define hyperuricemia and precluding drug effects yielded robust associations. Nevertheless, the quadratic model did not show any U-shaped relationships between them.

CONCLUSION

SUA may aggravate brain amyloid deposition in preclinical AD, which corroborated the detrimental role of SUA.

Gout and the risk of Alzheimer's disease: A Mendelian randomization study

OBJECTIVE

This study aimed to examine whether gout is causally associated with Alzheimer's disease.

METHODS

I used the publicly available summary statistics datasets of three genome-wide association studies (GWASs) on gout as the exposure dataset and meta-analysis results of four GWAS datasets consisting of 17 008 cases with Alzheimer's disease and 37 154 controls of European descent as the outcome dataset. The data were subjected to 2-sample Mendelian randomization (MR) analysis using the inverse-variance weighted (IVW), weighted median, and MR-Egger regression methods.

RESULTS

I selected seven independent single nucleotide polymorphisms (SNPs) from gout GWASs as instrumental variables (IVs) to improve inference. These SNPs were located at MAP3K11 (rs10791821), SLC2A9 (rs11722228, rs734553), GCKR (rs1260326), ABCG2 (rs2231142, rs2728125), and CNIH-2 (rs4073582). The IVW data did not support a causal association between gout and Alzheimer's disease (β = 0.013, standard error [SE] = 0.017, P = 0.445). The MR-Egger regression indicated that directional pleiotropy did not bias the result (intercept = 0.002, P = 0.654); it also revealed no causal association between gout and Alzheimer's disease (β = -0.013, SE = 0.076, P = 0.870). The weighted median approach yielded similar results (β = 0.004, SE = 0.022, P = 0.846). Cochran's Q test indicated no evidence of heterogeneity between IV estimates based on individual variants, and the results of "leave-one-out" analysis demonstrated that no single SNP drove the IVW estimate.

CONCLUSIONS

The MR analysis results did not support a causal association between gout and Alzheimer's disease.