Sirtuins in Alzheimer's Disease: SIRT2-Related GenoPhenotypes and Implications for PharmacoEpiGenetics.

Sirtuins (SIRT1-7) are NAD⁺-dependent protein deacetylases/ADP ribosyltransferases with important roles in chromatin silencing, cell cycle regulation, cellular differentiation, cellular stress response, metabolism and aging. Sirtuins are components of the epigenetic machinery, which is disturbed in Alzheimer's disease (AD), contributing to AD pathogenesis. There is an association between the SIRT2-C/T genotype (rs10410544) (50.92%) and AD susceptibility in the APOEε4-negative population (SIRT2-C/C, 34.72%; SIRT2-T/T 14.36%). The integration of SIRT2 and APOE variants in bigenic clusters yields 18 haplotypes. The 5 most frequent bigenic genotypes in AD are 33CT (27.81%), 33CC (21.36%), 34CT (15.29%), 34CC (9.76%) and 33TT (7.18%). There is an accumulation of APOE-3/4 and APOE-4/4 carriers in SIRT2-T/T > SIRT2-C/T > SIRT2-C/C carriers, and also of SIRT2-T/T and SIRT2-C/T carriers in patients who harbor the APOE-4/4 genotype. SIRT2 variants influence biochemical, hematological, metabolic and cardiovascular phenotypes, and modestly affect the pharmacoepigenetic outcome in AD. SIRT2-C/T carriers are the best responders, SIRT2-T/T carriers show an intermediate pattern, and SIRT2-C/C carriers are the worst responders to a multifactorial treatment. In APOE-SIRT2 bigenic clusters, 33CC carriers respond better than 33TT and 34CT carriers, whereas 24CC and 44CC carriers behave as the worst responders. CYP2D6 extensive metabolizers (EM) are the best responders, poor metabolizers (PM) are the worst responders, and ultra-rapid metabolizers (UM) tend to be better responders that intermediate metabolizers (IM). In association with CYP2D6 genophenotypes, SIRT2-C/T-EMs are the best responders. Some Sirtuin modulators might be potential candidates for AD treatment.

African-American TOMM40'523-APOE haplotypes are admixture of West African and Caucasian alleles.

BACKGROUND: Several studies have demonstrated a lower apolipoprotein E4 (APOE ε4) allele frequency in African-Americans, but yet an increased age-related prevalence of AD. An algorithm for prevention clinical trials incorporating TOMM40'523 (Translocase of Outer Mitochondria Membrane) and APOE depends on accurate TOMM40'523-APOE haplotypes. METHODS: We have compared the APOE and TOMM40'523 phased haplotype frequencies of a 9.5 kb TOMM40/APOE genomic region in West African, Caucasian, and African-American cohorts. RESULTS: African-American haplotype frequency scans of poly-T lengths connected in phase with either APOE ε4 or APOE ε3 differ from both West Africans and Caucasians and represent admixture of several distinct West African and Caucasian haplotypes. A new West African TOMM40'523 haplotype, with APOE ε4 connected to a short TOMM40'523 allele, is observed in African-Americans but not Caucasians. CONCLUSION: These data have therapeutic implications for the age of onset risk algorithm estimates and the design of a prevention trial for African-Americans or other mixed ethnic populations.

My story: the discovery and mapping to chromosome 21 of the Alzheimer amyloid gene.

When I decided to clone the amyloid gene I did not know that there were some twenty groups around the research world that desperately tried to do the same. If I knew that I would have never started the project. I was so ignorant about the disease that I did not know how to spell the name Alzheimer. I had to look at the papers of other researchers to make sure that I my spelling was correct. After the cloning, I was invited to numerous national and international meetings on AD. These meetings became my University where I majored in AD.

Hyperinsulinemia provokes synchronous increases in central inflammation and beta-amyloid in normal adults.

BACKGROUND: Inflammation has been implicated as a pathogenetic factor in Alzheimer disease, possibly via effects on beta-amyloid (Abeta). Hyperinsulinemia induces inflammation and is a risk factor for Alzheimer disease. Thus, insulin abnormalities may contribute to Alzheimer disease pathophysiology through effects on the inflammatory network. OBJECTIVES: To determine the effects of induced hyperinsulinemia with euglycemia on Abeta, transthyretin, and inflammatory markers and modulators in plasma and cerebrospinal fluid (CSF). DESIGN: Randomized crossover trial. SETTING: Veterans Affairs hospital clinical research unit. PARTICIPANTS: Sixteen healthy adults ranging from 55 to 81 years of age (mean age, 68.2 years). INTERVENTIONS: On separate mornings, fasting participants received randomized infusions of saline or insulin (1.0 mU.kg(-1).min(-1)) with variable dextrose levels to maintain euglycemia, achieving plasma insulin levels typical of insulin resistance. Plasma and CSF were collected after an approximately 105-minute infusion. MAIN OUTCOME MEASURES: Plasma and CSF levels of interleukin 1alpha, interleukin 1beta, interleukin 6, tumor necrosis factor alpha, F2-isoprostane (CSF only), Abeta, norepinephrine, transthyretin, and apolipoprotein E. RESULTS: Insulin increased CSF levels of F2-isoprostane and cytokines (both P<.01), as well as plasma and CSF levels of Abeta42 (both P<.05). The changes in CSF levels of Abeta42 were predicted by increased F2-isoprostane and cytokine levels (both P<.01) and reduced transthyretin levels (P = .02). Increased inflammation was modulated by insulin-induced changes in CSF levels of norepinephrine and apolipoprotein E (both P<.05). CONCLUSION: Moderate hyperinsulinemia can elevate inflammatory markers and Abeta42 in the periphery and the brain, thereby potentially increasing the risk of Alzheimer disease.

Selection of peptides binding to the amyloid b-protein reveals potential inhibitors of amyloid formation.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by extracellular amyloid plaques, cerebrovascular amyloid deposits, intracellular neurofibrillary tangles, and neuronal loss. Amyloid deposits are composed of insoluble fibers of a 39-43 amino acid peptide named the amyloid beta-protein (A beta). Neuropathological and genetic studies provide strong evidence of a key role for A beta amyloidosis in the pathogenesis of AD. Therefore, an obvious pharmacological target for treatment of AD is the inhibition of amyloid growth and/or inhibition of amyloid function. We took an unbiased approach to generate new inhibitors of amyloid formation by screening a FliTrx combinatorial peptide library for A beta binding peptides and identified four groups of peptides with different A beta binding motifs. In addition, we designed and examined peptides mimicking the A beta binding domain of transthyretin (TTR). Our results showed that A beta binding peptides selected from FliTrx peptide library and from TTR-peptide analogs are capable of inhibiting A beta aggregation and A beta deposition in vitro. These properties demonstrate that binding of selected peptides to the amyloid beta-protein may provide potent therapeutic compounds for the treatment AD.

Amyloidogenic and anti-amyloidogenic properties of recombinant transthyretin variants.

Most transthyretin (TTR) mutations lead to TTR amyloid depositions in patients with familial amyloidotic polyneuropathy and familial amyloidotic cardiomyopathy. However, though an amyloidogenic protein itself, TTR inhibits aggregation of Alzheimer's amyloid beta protein (A beta) in vitro and in vivo. The pathogenic relationship between two amyloidogenic processes remains unclear. To understand how TTR mutations influence the ability of TTR to inhibit A beta amyloidosis, forty-seven recombinant TTR variants were produced and analyzed. We showed that all recombinant proteins formed tetramers and were functional in thyroxine binding. Acid denaturation at pH 3.8 resulted in aggregation and fibril formation of all TTR variants. However, only TTR G42 and TTR P55 formed fibrils at pH 6.8. Most TTR variants bound to A beta and inhibited A beta aggregation in vitro. TTR variants S64, A71, Q89, V107, H114 and I122 revealed decreased binding to A beta and decreased inhibition of A beta aggregation. Only TTR G42 and TTR P55 completely failed to bind A beta and to inhibit A beta aggregation. We suggest that TTR variants characterized by decreased binding to A beta or by decreased inhibition of A beta aggregation in vitro may contribute to A beta amyloid formation in vivo. These TTR variants might be important targets for epidemiological studies in Alzheimer's disease.

Somatic symptoms in women 11 years after the Chornobyl accident: prevalence and risk factors.

Exposure to the Chornobyl nuclear power plant explosion resulted in widespread, persistent somatic complaints, but little is known about the nature and risk factors for these conditions. This study compares the health reports of 300 women evacuated to Kyiv from the contamination zone around the plant and 300 controls with a child in the same homeroom as the evacuees in 1997. The interview addressed somatic concerns, risk factors for poor health, and Chornobyl-related stress. Compared with controls, evacuees reported significantly more health problems and rated their health more poorly overall. These differences remained significant after controlling for demographic and clinical risk factors, including the tendency to amplify physical symptoms. Significantly more evacuees received a diagnosis of a Chornobyl-related illness by a local physician, believed that their health and their children's health had been adversely affected, and were positive for Chornobyl-induced post-traumatic stress disorder. After controlling for these Chornobyl stress variables, the differences in number of health problems commonly attributed to Chornobyl remained significant but differences in general health ratings did not. The perceptions of controls were similar to those of women in a national sample. The relationship between Chornobyl stress and illness was twice as strong in evacuees (odds ratio = 6.95) as in Kyiv controls (odds ratio = 3.34) and weakest in the national sample (odds ratio = 1.64). The results confirm the persistence and nonspecificity of the subjective medical consequences of Chornobyl and are consistent with the hypothesis that traumatic events exert their greatest negative impacts on health in vulnerable or disadvantaged groups.