Biomarkers of vascular risk, systemic inflammation, and microvascular pathology and neuropsychiatric symptoms in Alzheimer's disease

Numerous serum and plasma based biomarkers of systemic inflammation have been linked to both neuropsychiatric disorders and Alzheimer's disease (AD). The present study investigated the relationship of clinical biomarkers of cardiovascular risk (cholesterol, triglycerides, and homocysteine) and a panel of markers of systemic inflammation (CRP, TNF-α, IL1-ra, IL-7, IL-10, IL-15, IL-18) and microvascular pathology (ICAM-1, VCAM-1) to neuropsychiatric symptoms in a sample with mild AD. Biomarker data was analyzed on a sample of 194 diagnosed with mild to moderate probable AD. The sample was composed of 127 females and 67 males. The presence of neuropsychiatric symptoms was gathered from interview with caretakers/family members using the Neuropsychiatric Inventory. For the total sample, IL-15, VCAM (vascular adhesion molecule), and triglycerides were significantly and negatively related to number of neuropsychiatric symptoms, and total cholesterol and homocysteine were positively related and as a group accounted for 16.1% of the variance. When stratified by gender, different patterns of significant biomarkers were found with relationships more robust for males for both total symptoms and symptom clusters. A combination of biomarkers of systemic inflammation, microvascular pathology, and clinical biomarkers of cardiovascular risk can account for a significant portion of the variance in the occurrence of neuropsychiatric symptoms in AD supporting a vascular and inflammatory component of psychiatric disorders found in AD. Gender differences suggest distinct impact of specific risks with total cholesterol, a measure of cardiovascular risk, being the strongest marker for males and IL-15, a marker of inflammation, being the strongest for females.

X-ray imaging of differential vascular density in MMP-9-/-, PAR-1-/+, hyperhomocysteinemic (CBS-/+) and diabetic (Ins2-/+) mice

Although protease activated receptor-1 (PAR-1) and matrix metalloproteinase-9 (MMP-9) play significant role in vascular remodelling in hyperhomocysteinemia (HHcy due to cystathionine beta synthase deficiency, CBS-/+) and diabetes, mechanism remains nebulous. We hypothesized that differential vascular density and remodelling in different vascular beds in HHcy and diabetes were responsible for an adaptive metabolic homeostasis during the pathogenesis. To test this hypothesis, vascular density in mice lacking PAR-1, MMP-9, CBS and Insulin-2 gene mutant (Ins2-/+, Akita) was measured and compared with wild type (WT, C57BL/6J) mice. The vascular density was detected by x-ray angiography using KODAK 4000 MM image station, using barium sulphate as contrasting agent. The % vascular density in the hearts of WT, CBS-/+ (HHcy), MMP-9-/-, PAR-1-/+ and Ins2-/+ (type-1 diabetes) was 100 ± 2.8, 85 ± 3.3, 90 ± 3.3, 95 ± 3.8 and 73 ± 1.7, respectively. The vascular density in CBS-/+ and Akita hearts decreased while it was increased in lungs of CBS-/+ and MMP-9-/-.There was decreased vascular density in liver and kidney of Akita mice. Vascular density in brain, kidney and mesentery was decreased in CBS-/+ mice. These findings support the notation that metabolic derangement in diabetes and HHcy causes the chronic decline and/or rarefaction in vascular density.

Plasma homocysteine, apolipoprotein E status and vascular disease in elderly patients with mental illness

BACKGROUND

Total plasma homocysteine (tHcy) concentration is increased in elderly patients with mental illness. Also, patients with vascular disease have significantly higher plasma tHcy concentration compared with patients without vascular disease. Apolipoprotein E (apoE) status is associated with cardiovascular disease and a major genetic risk factor is inheritance of the e4 allele. In the present study, we investigated the association between plasma tHcy and apoE status.

METHODS

The relation between apoE status, plasma tHcy and vascular disease was investigated in a cohort of consecutively enrolled elderly patients with mental illness (n=328).

RESULTS

Plasma tHcy concentrations were increased (p<0.01) in carriers of APOE4 (13.6 micromol/L; 9.2-21.7 micromol/L) compared to non-carriers (12.4 micromol/L; 8.3-19.9 micromol/L). The proportion of patients with vascular disease was significantly (p<0.001) increased among carriers (61%) compared to non-carriers (42%). An increased percentage (p<0.001) of APOE4 carriers was observed in patients with Alzheimer's disease (AD) with (71%) or without vascular disease (42%), and in patients with vascular dementia (VaD) (54%) compared to a reference group (34%).

CONCLUSIONS

Since carriers of APOE4 showed an increased likelihood of vascular disease, these patients need more intensive control of other modifiable vascular risk factors. Furthermore, the association between plasma tHcy and the presence of APOE4 might be attributed to an increased proportion of vascular disease in APOE4 carriers.