Peripheral Vitamin C Levels in Alzheimer's Disease: A Cross-Sectional Study.

We previously reported lower lymphocyte vitamin C levels in individuals with type 2 diabetes mellitus and in individuals with severe Parkinson's disease. Oxidative stress has been proposed to play a key role in the progression of Alzheimer's disease. Thus, the objective of this study was to investigate the association between peripheral levels of vitamin C and the progression of cognitive dysfunction in Alzheimer's disease. Fifty individuals with Alzheimer's disease being treated at Shizuoka General Hospital were consecutively enrolled in this study from December 2009 to March 2015 (76.0±9.7 y of age [mean±SD]; 32 men and 18 women; Mini-Mental State Examination Japanese version (MMSE-J) score range, 8-27). Plasma and lymphocyte vitamin C levels in fasting blood samples were measured. The association between the MMSE-J scores and vitamin C levels was estimated using Spearman's rank correlation coefficient (ρ) and the criteria defined by Swinscow. Spearman's ρ for the relationship between peripheral vitamin C levels and the MMSE-J score was ρ=0.17 for plasma vitamin C and ρ=0.26 for lymphocyte vitamin C. Thus, the associations were relatively weak based on the criteria. In contrast with type 2 diabetes mellitus and Parkinson's disease, lymphocyte vitamin C levels in the peripheral blood may not directly reflect the progression of cognitive dysfunction in Alzheimer's disease. Additional longitudinal studies are needed to evaluate the clinical importance of changes of peripheral vitamin C status in Alzheimer's disease.

Lymphocyte vitamin C levels as potential biomarker for progression of Parkinson's disease.

OBJECTIVES: Vitamin C is a major antioxidant and also is known as a neuromodulator in dopaminergic neurons. The aim of this study was to investigate the association between lymphocyte and plasma vitamin C levels in various stages of Parkinson's disease (PD). METHODS: Sixty-two individuals with PD (age 71 ± 8.8 y [mean ± SD]) being treated at Shizuoka General Hospital from December 2007 to August 2013 were consecutively recruited. PD severity was classified using the Hoehn-Yahr scale for staging PD. Fasting blood samples were collected, and plasma and lymphocyte vitamin C levels were measured. The association between PD severity and vitamin C levels was estimated by ordinal logistic regression with confounding variables. RESULTS: The distribution of Hoehn-Yahr stages in patients was as follows: stage I, 7; II, 28; III, 16; and IV, 11. Lymphocyte vitamin C levels in patients with severe PD were significantly lower (odds ratio [OR], 0.87; 95% confidence interval [CI], 0.80-0.97; P < 0.01) compared with those at less severe stages. Plasma vitamin C levels also tended to be lower in patients with severe PD; however, this was not significant (OR, 0.98; 95% CI, 0.96-1.00; P = 0.09). CONCLUSIONS: Our findings suggest that lymphocyte vitamin C levels in the peripheral blood may be a potentially useful biomarker for the progression of PD.