Epigenetic mechanisms in Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders affecting elderly people (over 65 years old). Only a small percentage (less than 5%) of the disease is consistent with the Mendelian form of inheritance. The rest, named as Late Onset Alzheimer's Disease (more than 95%), is characterized as a complex multi-factorial disorder, missing familial traits. Although some genes have been implicated in the pathogenesis and the risk of developing sporadic AD, they only account for the minority of LOAD cases. Thus, over the past few years emerging data suggest a potential role of epigenetic mechanisms and chromatin remodeling on neurodegenerative processes leading to dementia. Alterations on the epigenomic machinery cause aberrant DNA methylation and histone acetylation. Therefore, these changes trigger alterations on the transcriptional level of genes involved in the pathogenesis of AD, such as APP. In this review we summarize recent advances on synaptic dysfunction and cognitive decline caused by common epigenetic modifications. We also discuss potential treatment strategies targeting on the epigenetic machinery.

A Multiple Indicators Multiple Causes (MIMIC) model of Behavioural and Psychological Symptoms in Dementia (BPSD)

INTRODUCTION

Although there is evidence for distinct behavioural sub-phenotypes in Alzheimer's disease (AD), their inter-relationships and the effect of clinical variables on their expression have been little investigated.

METHODS

We have analysed a sample of 1850 probable AD patients from the UK and Greece with 10 item Neuropsychiatric Inventory (NPI) data. We applied a Multiple Indicators Multiple Causes (MIMIC) approach to investigate the effect of MMSE, disease duration, gender, age and age of onset on the structure of a four-factor model consisting of "psychosis", "moods", "agitation" and "behavioural dyscontrol".

RESULTS

Specific clinical variables predicted the expression of individual factors. When the inter-relationship of factors is modelled, some previously significant associations are lost. For example, lower MMSE scores predict psychosis, agitation and behavioural dyscontrol factors, but psychosis and mood predict the agitation factor. Taking these associations into account MMSE scores did not predict agitation.

CONCLUSIONS

The complexity of the inter-relations between symptoms, factors and clinical variables is efficiently captured by this MIMIC model.

Multidrug-resistant strains of Neisseria gonorrhoeae in Greece

Eighty-seven out of 575 gonococci isolated in Greece from 1991 to 1998 belonged to serovar Bropyst and exhibited resistance to penicillin, tetracycline, erythromycin, and chloramphenicol. Conventional and molecular typing showed three clusters, A, B, and C, that were associated with networks of high- frequency transmitters (cluster A with homosexuals and clusters B and C with refugees from Eastern Europe). Study of one isolate revealed mutations in the penA, mtrR, and porB genes that may explain the multidrug-resistant phenotype.

Characterization of Neisseria gonorrhoeae strains with decreased susceptibility to fluoroquinolones isolated in Greece from 1996 to 1999

Of the 331 Neisseria gonorrhoeae strains isolated in Greece from 1996 to 1999, 39 (11.8%) exhibited decreased susceptibility to quinolones due to gyrA and parC mutations. Conventional typing and pulsed-field gel electrophoresis showed that 34 of these isolates were clonally related. Epidemiological data indicated that the epidemic clone was sustained in a group of high-frequency transmitters.

Gut hormone levels in neonates under phototherapy

Gastrin, vasoactive intestinal peptide (VIP) and neurotensin plasma levels were measured in three groups of healthy term newborn infants, on the 3rd, 4th and 5th days of life. Group A consisted of 15 babies without jaundice. Group B comprised of 15 babies with mild jaundice (bilirubin levels < 256 mumol/l) and group C included 15 babies with marked jaundice (bilirubin levels > 256 mumol/l) who received phototherapy for at least 24 h. There was no significant difference in gut hormone levels between groups A and B. Infants in group C had significantly lower gastrin levels compared to infants in groups A and B, on both days 4 and 5. VIP levels on the 4th day of life were significantly higher in group C in comparison to groups A and B. Neurotensin levels in the three groups did not differ significantly. Increased stool number was noted in infants in group C. Increased VIP levels in jaundiced infants under phototherapy may be the cause of increased stool frequency, through stimulation of intestinal water and electrolyte secretion.

Gut hormone concentrations in preterm infants with necrotizing enterocolitis

Blood levels of gastrin, neurotensin and vasoactive peptide (VIP) were estimated in 14 premature infants with necrotizing enterocolitis (NEC) and in 12 controls. In comparison to the control group, infants with NEC had (a) significantly lower gastrin levels both before [9.3 (7.8) versus 33.7 (27.1)] and after [52.4 (48.1) versus 100.8 (50.9)] the development of NEC; (b) significantly lower neurotensin levels only after the development of NEC [37.8 (10.4) versus 54.5 (20.6)1; and (c) no significant difference in VIP values [25.4 (9.7) versus 18.9 (9.9) and 24.5 (15.7) versus 26.1 (19.1)]. It is concluded that NEC can adversely affect gastrin and neurotensin concentrations in the blood.