Missense mutations in the presenilin 1 (PS1) gene cause the most common form of dominant early-onset familial Alzheimer's disease (FAD) and are associated with increased levels of amyloid beta-peptides (A beta) ending at residue 42 (A beta 42) in plasma and skin fibroblast media of gene carriers. A beta 42 aggregates readily and appears to provide a nidus for the subsequent aggregation of A beta 40 (ref. 4), resulting in the formation of innumerable neuritic plaques. To obtain in vivo information about how PS1 mutations cause AD pathology at such early ages, we characterized the neuropathological phenotype of four PS1-FAD patients from a large Colombian kindred bearing the codon 280 Glu to Ala substitution (Glu280Ala) PS1 mutation. Using antibodies specific to the alternative carboxy-termini of A beta, we detected massive deposition of A beta 42, the earliest and predominant form of plaque A beta to occur in AD (ref. 6-8), in many brain regions. Computer-assisted quantification revealed a significant increase in A beta 42, but not A beta 40, burden in the brains from 4 PS1-FAD patients compared with those from 12 sporadic AD patients. Severe cerebellar pathology included numerous A beta 42-reactive plaques, many bearing dystrophic neurites and reactive glia. Our results in brain tissue are consistent with recent biochemical evidence of increased A beta 42 levels in PS1-FAD patients and strongly suggest that mutant PS1 proteins alter the proteolytic processing of the beta-amyloid precursor protein at the C-terminus of A beta to favor deposition of A beta 42.

Objective The examination of individuals who carry fully penetrant genetic alterations that result in familial Alzheimer’s disease (FAD) provides a unique model for studying the early presymptomatic disease stages. In AD, deficits in episodic and associative memory have been linked to structural and functional changes within the hippocampal system. This study used functional MRI (fMRI) to examine hippocampal function in a group of healthy, young, cognitively-intact presymptomatic individuals (average age 33.7 years) who carry the E280A presenilin-1 (PS1) genetic mutation for FAD. These PS1 subjects will go on to develop the first symptoms of the disease around the age of 45 years. Our objective was to examine hippocampal function years before the onset of clinical symptoms. Methods Twenty carriers of the Alzheimer’s-associated E280A PS1 mutation and 19 PS1-negative control subjects participated. Both groups were matched for age, sex, education level, and neuropsychological test performance. All participants performed a face-name associative encoding task while in a Philips 1.5T fMRI scanner. Analysis focused on the hippocampal system. Results Despite identical behavioral performance, presymptomatic PS1 mutation carriers exhibited increased activation of the right anterior hippocampus during encoding of novel face-name associations compared to matched controls. Interpretation Our results demonstrate that functional changes within the hippocampal memory system occur years before cognitive decline in FAD. These presymptomatic changes in hippocampal physiology in FAD suggest that hippocampal fMRI patterns during associative encoding may also provide a preclinical biomarker in sporadic AD.

Background Sporadic late-onset Alzheimer’s disease (AD) dementia has been associated with a ‘signature’ of cortical atrophy in paralimbic and heteromodal association regions measured with MRI. Objective To investigate whether a similar pattern of cortical atrophy is present in presymptomatic presenilin 1 E280A mutation carriers an average of 6 years before clinical symptom onset. Methods 40 cognitively normal volunteers from a Colombian population with familial AD were included; 18 were positive for the AD-associated presenilin 1 mutation (carriers, mean age=38) whereas 22 were non-carriers. T1-weighted volumetric MRI images were acquired and cortical thickness was measured. A priori regions of interest from our previous work were used to obtain thickness from AD-signature regions. Results Compared to non-carriers, presymptomatic presenilin 1 mutation carriers exhibited thinner cortex within the AD-signature summary measure (p<0.008). Analyses of individual regions demonstrated thinner angular gyrus, precuneus and superior parietal lobule in carriers compared to non-carriers, with trend-level effects in the medial temporal lobe. Conclusion Results demonstrate that cognitively normal individuals genetically determined to develop AD have a thinner cerebral cortex than non-carriers in regions known to be affected by typical late-onset sporadic AD. These findings provide further support for the hypothesis that cortical atrophy is present in preclinical AD more than 5 years prior to symptom onset. Further research is needed to determine whether this method could be used to characterise the age-dependent trajectory of cortical atrophy in presymptomatic stages of AD.

Brain metabolites measured by 1H-MRS in the posterior cingulate gyrus and precuneus are optimally sensitive and specific potential noninvasive biomarkers of subclinical emergence of AD caused by the PSEN1 p.Glu280Ala (E280 A) mutation.

Lamotrigine is a phenyltriazine used in the treatment of epilepsy and bipolar disorder type I. The purpose of this study was to compare the bioavailability in healthy Colombian volunteers of two brands of lamotrigine 100 mg tablets: a new generic formulation (test product) developed by Humax Pharmaceuticals S.A (Medellín, Col) and LAMICTAL ® (reference product) from Glaxo Operations UK Ltd (Ware, UK). A single-dose, randomized, two-period, two-sequence crossover study, with six weeks washout period, was performed. Blood samples were obtained from 0 to 144 hours after dosing and plasma lamotrigine levels were determined by a validated high performance liquid chromatographic (HPLC) method. The 90% confidence intervals (CIs) for the ratios of the ln AUC 0-∞ and ln C max means between the reference and test formulations were constructed under 80/125 rule for bioequivalence limit. Fourteen subjects were enrolled in the study, but only twelve completed both treatment periods. The estimated pharmacokinetic parameters of lamotrigine for the reference and test formulations were C max 2.314 ± 0.414 µg/mL, 2.226 ± 0.355 µg/mL; AUC 0-120 70.148 ± 10.824 µg.h/mL, 69.277 ± 13.432 µg.h/mL, and for AUC 0-∞ were 78.524 ± 16.000 µg.h/mL, 77.532 ± 15.255 µg.h/mL, respectively. The 90% CIs for the ln-transformed ratio (test/reference) of AUC 0-∞ and C max were 88.97 to 110.65 and 87.77 to 106.37, respectively. Conclusions: In this single dose study it was found that the test and reference products of lamotrigine 100 mg tablets complied with the regulatory criteria for equivalence with respect to rate and extent of absorption according to the guidances of Instituto Nacional de Vigilancia de Medicamentos y Alimentos (INVIMA) and FDA.