Novel noninvasive biomarkers of prodromal Alzheimer disease: The role of optical coherence tomography and optical coherence tomography-angiography.

BACKGROUND AND PURPOSE: A reduction of retinal thickness and an alteration of retinal perfusion have been found in Alzheimer disease (AD). Nowadays, retinal layers and retinal perfusion can be evaluated by means of noninvasive imaging techniques, namely, optical coherence tomography (OCT) and OCT-angiography (OCT-A). Here, we have compared the retinal thickness and the perfusion index, measured by means of OCT and OCT-A, in patients with mild cognitive impairment due to AD (MCI-AD) and in age- and sex-matched cognitively healthy controls. METHODS: Twenty-four MCI-AD patients and 13 control subjects were enrolled. MCI-AD patients underwent lumbar puncture; all of them showed a cerebrospinal fluid (CSF) profile compatible with AD. OCT was used for evaluating retinal volumes and thicknesses, whereas with OCT-A we measured fractal dimension (FD), vascular perfusion density (VPD), and vessel length density (VLD) of superficial capillary plexus (SCP), intermediate capillary plexus (ICP), deep capillary plexus (DCP), and choriocapillaris. The comparisons between groups were made after adjustment for age, diabetes, and hypertension. RESULTS: A significant reduction of SCP-VLD (p = 0.012), ICP-VPD (p = 0.015), ICP-VLD (p = 0.004), DCP-VPD (p = 0.012), and DCP-VLD (p = 0.009) was found in MCI-AD patients compared to controls. Conversely, FD was higher in MCI-AD than in controls (p = 0.044). CSF Aß42/total tau negatively correlated with FD (r = -0.51, p = 0.010). CONCLUSIONS: OCT-A might have a potential role in detecting new noninvasive biomarkers for early AD detection. Retinal VPD might identify amyloid angiopathy-related chronic injury, and FD could show early vessel recruitment as a compensative mechanism at disease onset. Further studies will be needed to confirm these findings.

The Italian version of cognitive function instrument (CFI): reliability and validity in a cohort of healthy elderly.

The Alzheimer's disease Cooperative Study (ADCS)-Cognitive Function Instrument (CFI) is a 14-item questionnaire administered to the subject and the referent, aimed at detecting early changes in cognitive and functional abilities in individuals without clinical impairment. It is used for monitoring annual variations in cognitive functioning in prevention trials. The aim of the present study was to validate the Italian version of the CFI. A consecutive series of 257 functionally independent subjects was recruited among relatives of patients or as volunteers. They were administered CFI and global cognition measurements: Mini-Mental Status Examination (MMSE) and Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The reliability and criterion validity were comparable to the original in both self- and partner-report. Similarly to what reported in the original version, we found a corrected item-total correlation ranging between 0.38 and 0.54 in self-report and between 0.33 and 0.64 in partner-report. Cronbach's α was 0.77 (95% CI 0.72-0.83) in self-report and 0.78 (95% CI 0.73-0.84) in partner-report. Total partner- and self-report scores were significantly correlated (rS = 0.31, p < 0.001). CFI self-report and CFI total-score (partner + self-report) were negatively correlated with MMSE (rS = - 0.15, p = 0.022; rS = - 0.17, p = 0.008) and RBANS (rS = - 0.22, p < 0.001; rS = - 0.25, p < 0.001). Analogous trends were found in the partner score, with a correlation with RBANS (rS = - 0.17, p = 0.014) and MMSE (rS = - 0.11, p = 0.071). Our results support the reliability and validity of the Italian version of CFI. In order to definitely propose the use of CFI for tracking longitudinal changes of cognitive and functional abilities in subjects without clinical impairment, data from the follow-up of this cohort are needed.

Evidence of practice effect in CANTAB spatial working memory test in a cohort of patients with mild cognitive impairment.

The Cambridge Neuropsychological Test Automated Battery (CANTAB) is a system of neuropsychological tests frequently used to track the progression of cognitive deficits in mild cognitive impairment (MCI) and Alzheimer's disease (AD). We investigated test-retest reliability in seven CANTAB tests. Twenty-five MCI patients, with either AD-like or conflicting/normal cerebrospinal fluid profiles underwent three testing sessions at 6-month intervals, including the following tests: Reaction Time and Rapid Visual Information Processing (assessing attention and reaction times); Delayed Matching-to-Sample, Paired Associates Learning, Spatial Recognition Memory and Pattern Recognition Memory (assessing memory); Spatial Working Memory (assessing executive functions). No significant difference was found when comparing the two groups. Many CANTAB measures obtained low or marginal test-retest coefficients. We observed a marked improvement in Spatial Working Memory (SWM) in both groups when comparing the baseline performance with the 6-month follow-up, but no difference in performance between 6- and 12-month follow-ups. A similar trend was documented in Paired Associates Learning (PAL), but the effect size was small. Such improvement may result from a practice effect, likely due to the learning of an effective strategy. Our evidence raised an important issue concerning the need for methodological caution when interpreting the results of longitudinal studies using SWM and PAL.

Associations of Alzheimer's disease with macular degeneration.

There is growing evidence of epidemiological, genetic, molecular and clinical links between Alzheimer's disease (AD) and age-related macular degeneration (AMD). Major interest in the relationship between AD and AMD has derived from the evidence that beta-amyloid, the main component of senile plaques, the hallmark of AD, is also an important component of drusen, the hallmark of AMD. This finding has a great potential in the present era of anti-amyloid agents for the treatment of AD. The connection between AD and AMD is also supported by the evidence that the two diseases share other pathophysiological factors, such as oxidative stress and neuroinflammation. Accordingly, a few clinical trials have evaluated the efficacy of antioxidants on visual and cognitive performance in patients presenting both disorders. In this review, we summarize the pathophysiological and clinical evidence of the relationship between these two age-related disorders. Considering the increasing prevalence of both conditions along with the aging of the population, further investigations of this important issue are highly needed.

Electrophysiological actions of zonisamide on striatal neurons: Selective neuroprotection against complex I mitochondrial dysfunction.

Since the anti-epileptic drug Zonisamide (ZNS) seems to exert beneficial effects in Parkinson's (PD) disease, we have investigated the electrophysiological effects of ZNS in a rat corticostriatal slice preparation. ZNS affected neither the resting membrane potential nor the input resistance of the putative striatal spiny neurons. In contrast, this drug depressed in a dose-dependent manner the current-evoked repetitive firing discharge with a EC(50) value of 16.38 microM. ZNS also reduced the amplitude of glutamatergic excitatory postsynaptic potentials (EPSPs) with a EC(50) value of 32.5 microM. Reduced activity of the mitochondrial respiratory chain, particularly complex I and II, is implicated in the pathophysiology of PD and Huntington's (HD) diseases, respectively. Thus, ZNS was also tested in two different in vitro neurotoxic models obtained by acutely exposing corticostriatal slices either to rotenone, a selective inhibitor of mitochondrial complex I, or to 3-nitropropionic acid (3-NP), an inhibitor of complex II. Additionally, we also investigated the effect of ZNS in an in vitro model of brain ischemia. Interestingly, low concentrations of ZNS (0.3, 1, 3 and 10 microM) significantly reduced the rotenone-induced toxicity protecting striatal slices from the irreversible loss of corticostriatal field potential (FP) amplitude via a GABA-mediated mechanism. Conversely, this drug showed no protection against 3-NP and ischemia-induced toxicity. Our data indicate that relatively high doses of ZNS are required to decrease striatal neuronal excitability while low concentrations of this drug are sufficient to protect striatum against mitochondrial impairment suggesting its possible use in the therapy of basal ganglia neurodegenerative diseases.

A2A adenosine receptor antagonists protect the striatum against rotenone-induced neurotoxicity.

Adenosine A2A receptor has emerged as an attractive non-dopaminergic target in the experimental pharmacological therapy for Parkinson's disease (PD). Moreover, it has been postulated that A2A adenosine receptor antagonists exert neuroprotective effects in experimental models of PD and progressive supranuclear palsy (PSP). Interestingly, in both these pathological conditions a deficit of mitochondrial complex I has been found. Thus, utilizing extracellular and intracellular recordings from corticostriatal brain slices, we have tested the possible neuroprotective action of two A2A receptor antagonists, ST1535 and ZM241385, on the irreversible electrophysiological effects induced by the acute application of rotenone, a pesticide acting as a selective inhibitor of mitochondrial complex I activity. Both these antagonists reduced the rotenone-induced loss of corticostriatal field potential amplitude as well as the membrane depolarization caused by this toxin on striatal spiny neurons. The use of A2A receptor antagonists might represent a promising neuroprotective strategy in basal ganglia disorders involving a deficit of mitochondrial complex I activity.