Plasma Total Homocysteine Levels are not Associated with Medial Temporal Lobe Atrophy, but with White Matter Changes in Alzheimer's Disease

Association between Homocysteine and Cerebral Small Vessel Disease: A Meta-Analysis

BACKGROUND

This study aimed to evaluate whether elevated homocysteine levels is associated with risk of different subtypes of cerebral small vessel disease (CSVD) by using meta-analysis.

MATERIALS AND METHODS

Electronic databases were systematically searched up to April 2018 for collecting the studies reporting homocysteine levels in CSVD or CSVD subtypes. After an inclusion and exclusion criteria, the data was extracted. All data was analyzed using Stata software v.12.0 (Stata Corp LP, College Station, TX). The standardized mean difference (SMD) and 95% confidence interval (CI) were used to compare continuous variables.

RESULTS

Eighteen studies met eligibility criteria with 5088 participants (1987 patients with CSVD and 3101 controls) included in the meta-analysis. Meta-analysis revealed that, compared with the controls group, the CSVD group had significantly higher homocysteine levels, with the SMD of .50 and 95% CI (.36-.64). Subgroup analyses suggested white matter lesion had significantly higher levels of homocysteine compared with controls (SMD = .56, 95% CI .39-.73), followed by silent brain infarction (SMD = .33, 95% CI .24-.42) and lacunar infarction (SMD = .17, 95% CI -.06 to .40).

CONCLUSIONS

This meta-analysis found that CSVD or CSVD subtypes have a significantly higher homocysteine levels than in controls. Further prospective population-based studies are needed to longitudinally evaluate the association between homocysteine levels and progression of different CSVD subtypes.

Microstructural white matter tissue characteristics are modulated by homocysteine: a diffusion tensor imaging study

Homocysteine level can lead to adverse effects on the brain white matter through endothelial dysfunction, microstructural inflammation, and neurotoxin effects. Despite previously observed associations between elevated homocysteine and macroscopic structural brain changes, it is still unknown whether microstructural associations of homocysteine on brain tissue properties can be observed in healthy subjects with routine MRI. To this end, we investigated potential relationships between homocysteine levels and microstructural measures computed with diffusion tensor imaging (DTI) in a cohort of 338 healthy participants. Significant positive correlations were observed between homocysteine levels and diffusivity measures in the bilateral temporal WM, the brainstem, and the bilateral cerebellar peduncle. This is the first study demonstrating that DTI is sufficiently sensitive to relate microstructural WM properties to homocysteine levels in healthy subjects.

Lowering homocysteine levels with folic acid and B-vitamins do not reduce early atherosclerosis, but could interfere with cognitive decline and Alzheimer's disease

Inheired or acquired hyperhomocysteinemia (HHcy) is associated with several impairments, as certain tumors, deep venous thrombosis, tube neural defects, osteoporosis, early atherosclerosis and vascular acute events (IMA, stroke, PVD), mild cognitive impairments till Alzheimer's disease (AD). But, vascular and neuronal derangements are the most frequent HHcy-manifestations. As far as early atherosclerosis, some clinical trials demonstrated that folates and B6-12 vitamins supplementation is unable to reduce atherosclerotic lesions and cardiovascular events, even if it lowers HHcy levels. Thus, for atherosclerosis and its acute events (IMA, stroke, PVD) HHcy acts as a powerful biomarker rather than a risk factor. For that, the supplementation with folates and B vitamins to lower atherosclerotic lesions-events in hyperhomocysteinemic patients is not recommended. On the contrary, several clinical investigations demonstrated that folates and vitamins administration is able to reduce Hcy serum levels and antagonize some mechanisms favouring neurodegenerative impairments, as mild cognitive impairment, AD and dementia. Thus, contrarily to the atherosclerotic manifestations in hyperhomocysteinemic patients, preventive treatment with folates and B6-12 vitamins reduces Hcy concentration and could prevent or delay cognitive decline and AD.

Vertebrobasilar dolichoectasia as a risk factor for cerebral microbleeds

BACKGROUND

Both vertebrobasilar dolichoectasia (VBD) and cerebral microbleeds (CMBs) are related with the risk of intracerebral hemorrhage. We aimed to examine the relationship between the VBD and CMB in ischaemic stroke patients.

METHODS

A consecutive series of 182 patients hospitalized because of ischaemic stroke or transient ischaemic attack (TIA), and who underwent gradient echo brain magnetic resonance imaging were retrospectively recruited from a prospective stroke registry. CMB locations were categorized into anterior and posterior circulation. Ectasia was defined as basilar artery (BA) diameter > 4.5 mm, and dolichosis, as either BA bifurcation above the suprasellar cistern or lateral to the margin of the clivus or dorsum sellae. Whether VBD is associated with CMB anywhere in the brain or in anterior or posterior circulation territories was analysed using binary and multinomial logistic regression models.

RESULTS

Twenty-four subjects (13.2%) had VBD and 48 (26.4%) had CMBs. CMBs were more frequently observed in patients with VBD than without (66.7% vs. 20.3%, P < 0.001). VBD was significantly associated with CMBs in any location (crude odds ratio, 7.88; 95% confidence interval, 3.10-20.02), in the posterior circulation territory only (9.63; 2.60-34.94), and in both territories (9.25; 3.40-26.29), but not in the anterior circulation only (1.14; 0.009-11.20). These associations remained unchanged after adjusting for age, gender, hypertension, leukoaraiosis and stroke subtype.

CONCLUSIONS

VBD in patients with ischaemic stroke or TIA is independently associated with CMBs, especially in the posterior circulation territory.

Is hyperhomocysteinemia an Alzheimer's disease (AD) risk factor, an AD marker, or neither?

Alzheimer's disease (AD) is the most common form of neurodegenerative disease. The vast majority cases of AD are sporadic, without clear cause, and a combination of environmental and genetic factors has been implicated. The hypothesis that homocysteine (Hcy) is a risk factor for AD was initially prompted by the observation that patients with histologically confirmed AD had higher plasma levels of Hcy, termed hyperhomocysteinemia (HHcy), than age-matched controls. Most evidence accumulated so far implicates HHcy as a risk factor for AD onset, but there are also conflicting results. In this review we summarize reports on the relationship between HHcy and AD from epidemiological investigations, including observational studies and randomized controlled clinical trials. We also examine recent in vivo and in vitro studies of potential mechanisms whereby HHcy could influence AD development. Finally, we discuss possible reasons for the existing conflicting data and provide suggestions for future studies.