Sabrina A. Capurso

Mediterranean diet and cognitive decline

OBJECTIVE To investigate the possible role of diet in age-related cognitive decline (ARCD) and cognitive impairment of both degenerative (Alzheimers disease, AD) and vascular (vascular dementia, VaD) origin. DESIGN Literature review. RESULTS In an elderly population of southern Italy with a typical Mediterranean diet, high energy intake of monounsaturated fatty acids (MUFA) appeared to be associated with a high level of protection against ARCD. In addition, dietary fat and energy in the elderly seem to be risk factors, while fish consumption and cereals are found to reduce the prevalence of AD in European and North American countries. Finally, the relative risk of dementia (AD and VaD) was lower in the subjects of a French cohort who drank three or four glasses of red wine each day compared with total abstainers. CONCLUSION Essential components of the Mediterranean diet--MUFA, cereals and wine--seem to be protective against cognitive decline. As such, dietary antioxidants and supplements, specific macronutrients of the Mediterranean diet, oestrogens and anti-inflammatory drugs may act synergistically with other protective factors, opening up new therapeutic interventions for cognitive decline.

Lipid metabolism in cognitive decline and dementia

This review will focus on the current knowledge on circulating serum and plasma risk factors of cognitive decline of degenerative (Alzheimers disease, AD) or vascular origin (vascular dementia, VaD) linked to cholesterol homeostasis and lipoprotein disturbances, i.e. total cholesterol (TC), 24S-hydroxy-cholesterol, lipoprotein(a) (Lp(a)), or apolipoprotein E (APOE). These measures linked to lipoprotein metabolism appear to be altered in AD, VaD, or predementia syndrome relative to controls, but with contrasting results. At present, several studies have demonstrated the dependence of APOE serum levels upon the APOE genotype, nonetheless serum APOE levels seems not to be a credible risk factor or a biochemical marker for AD instead of APOE genotyping. In fact, there was no consistent association of serum or plasma apoE protein levels with the disease when controlled for APOE genotype. In addition, there are some evidence that higher Lp(a) levels could be linked with AD, although there are studies suggesting an increased presence of low molecular weight apo(a) in AD, VaD, and frontotemporal dementia, that are associated with elevated Lp(a) levels. In fact, the apo(a) gene is highly polymorphic in length due to variation in the numbers of a sequence encoding the apo(a) kringle 4 domain, and plasma levels of Lp(a) are inversely correlated with apo(a) size. Furthermore, although serum/plasma levels of TC and 24S-hydroxycholesterol are not credible diagnostic markers for AD and cognitive decline, the current evidence suggests that they may be modifiable risk/protective factors. The prevailing wisdom is that high TC is a risk factor for dementia. However, the relationship between TC and dementia may vary considerably depending on when cholesterol is measured over the life course or, alternatively, in relation to the underlying course of the disease. Several observational studies have suggested that statins, which are effective in lowering cholesterol, may reduce the risk of dementia, but the results of these reports are inconclusive. Thus, more studies with long-term follow-up and serial assessments of TC are needed to further clarify the causal relationship between cholesterol and dementia.

Dietary fatty acids intake: possible role in cognitive decline and dementia

There is a recent increase in the level of interest in the possible role of dietary fatty acids in age-related cognitive decline, and cognitive impairment of both degenerative (Alzheimers disease, AD) or vascular origin. At present, several studies suggested that an increase of saturated fatty acids (SFA) could have negative effects on cognitive functions. Furthermore, a clear reduction of risk of cognitive decline has been found in a population sample with a high intake of polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA). These findings were confirmed by studies in which high intakes of n-6 PUFA, n-3 PUFA, MUFA, and weekly fish consumption, providing large amount of n-3 PUFA, appear to be protective against the risk of AD. In our elderly population from Southern Italy, elevated unsaturated fatty acids intake (MUFA and PUFA), high levels of antioxidant compounds, and very low SFA intake could act synergistically in improving cognitive performance. Epidemiological studies on the association between diet and cognitive decline suggested a possible role of fatty acids intake in maintaining adequate cognitive functioning and possibly in preventing or delaying the onset of dementia, both of degenerative or vascular origin. Appropriate dietary measures or supplementation with specific micro- and macronutrients might open new ways for the prevention and management of cognitive decline and dementia.

Cognitive frailty: Predementia syndrome and vascular risk factors.

With increasing emphasis on early diagnosis of Alzheimer disease (AD), clinical research has focused on the identification of risk factors that may be modified at a preclinical and early clinical stage of dementing disorders. Prevalence and incidence of different predementia syndromes vary as a result of different diagnostic criteria, as well as different sampling and assessment procedures. Particular interest in mild cognitive impairment (MCI) arises from the fact that MCI is thought to be a prodromal phase and therefore highly predictive of subsequent AD. Furthermore, many of the risk factors for cerebrovascular disease (CVD) and vascular dementia (VaD), including serum total cholesterol, hypertension, atherosclerosis, and apolipoprotein E (APOE) genotype have also been shown to increase the risk of AD. Both vascular factors and APOE epsilon4 allele have been associated with higher risk of AD. Some recent studies suggested further that CVD or vascular factors increased the risk of conversion of MCI to dementia. This review will focus on the possible role of vascular risk factors in modulating the risk of age-related cognitive decline, and the progression of predementia syndrome such as MCI to dementia.

Dietary fatty acids intakes and rate of mild cognitive impairment. The Italian Longitudinal Study on Aging

The possible impact of diet, particularly the intake of fatty acids, on cognitive decline and dementia was addressed recently by several studies. We investigated the role of dietary fatty acids on the rate of mild cognitive impairment (MCI) in a population-based, prospective study carried out on 278 and 186 nondemented elderly subjects (65-84 years) at the 1st (1992-1993) and 2nd (1995-1996) survey from the cohort of Casamassima, Bari, Italy (n=704), one of the eight centers of the Italian Longitudinal Study on Aging. During the median follow-up of 2.6 years, 18 new events of MCI were diagnosed, and high polyunsaturated fatty acids (PUFA) intake appeared to be a protective factor against the development of MCI [hazard ratio (HR): 0.65, 95% confidence interval (CI): 0.43-0.98, trend-test, df=1, p<0.04]. However, when we controlled for the possible confounders (age, sex, education, Charlson comorbidity index, and total energy intake), the HR slightly changed, and the highly skewed 95% CI, while not statistically significant, may be important (HR: 0.62, 95% CI: 0.34-1.13, p=0.12). In our population, dietary fatty acids intakes were not associated with incident MCI in older age, only high PUFA intake evidenced a borderline nonsignificant trend for a protective effect against the development of MCI.

Vascular genetic factors and human longevity.

Complex inter-relationships between age-associated illnesses, such as vascular disease and Alzheimers disease (AD), suggest that biological and genetic pathways may be worthy of examination in centenarian populations to provide insights into human longevity. This is also borne out by the involvement of lipoprotein metabolism and a number of vascular genetic risk factors. Repeated findings of a higher frequency of the apolipoprotein E (APOE) epsilon4 allele in middle-aged subjects compared with centenarians were reported. Furthermore, we have also shown how in different populations there is a significant trend in reduction of serum APOE levels from APOE epsilon2- to epsilon4-carrier as well as significant differences in serum APOE levels respect to age in epsilon4-carriers but only after adjustment for HDL cholesterol. In contrast, findings of increased prevalence of the angiotensin I converting enzyme 1 (ACE1) D allele in French centenarians have not been replicated, suggesting the possibility that regional differences may occur in ACE1(*)D frequency within Europe in centenarians, as has been recently reported for APOE epsilon2 and epsilon4 alleles. A number of studies have examined the potential role in longevity of other genes involved in vascular risk, haemostasis, and blood pressure regulation [methyltetrahydrofolatereductase (MTHFR), apolipoprotein A1 (APOA-I), apolipoprotein C3 (APOC-III), apolipoprotein A4 (APOA-IV), paraoxonase 1 (PON1), plasminogen activator inhibitor type I (PAI-1)], with contrasting results. While further studies are needed to confirm the possible role of APOE concentration as putative longevity factor, this paper provides an overview of genetic vascular factors potentially involved in human longevity.

Interleukin 6-174 G/C promoter gene polymorphism in centenarians: no evidence of association with human longevity or interaction with apolipoprotein E alleles.

The C allele at position -174 in the promoter of the interleukin 6 (IL-6) gene has been associated with reduced gene expression and reduced plasma levels of IL-6. Given that IL-6 tracks with functional disability and age-related diseases, there may be attrition or reduction in the frequency of the homozygous subjects, who produce higher IL-6 serum levels, in older survivors in a population. In fact, a marked reduction of the IL-6*G/*G genotype was recently demonstrated in male though not female Italian centenarians compared with younger age groups. First aim of the present study was to investigate whether there was evidence of an association among IL-6 -174 G/C promoter polymorphism and extreme longevity in a population of 81 centenarians compared with a control group of 122 middle-aged healthy subjects (mean age: 51+/-18 SD; range: 19-73 years), from Apulia (Southern Italy). Secondly, we also tested possible interaction of apolipoprotein E (APOE) alleles with the IL-6 -174 G/C promoter polymorphism in view of our recent findings for reduced APOE epsilon4 allele in centenarians. No differences have been found in the IL-6 -174 G/C promoter allele and genotype frequencies between centenarians and controls nor was there any observed interaction with APOE alleles that are also reputed to be linked to longevity. Regional genetic differences in conjunction with differing environmental factors may explain in part previous results suggesting a role of this polymorphism in longevity.

Unsaturated fatty acids intake and all-causes mortality: a 8.5-year follow-up of the Italian Longitudinal Study on Aging

Recent evidence suggested a protective role of dietary monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) intakes against several chronic diseases and, therefore, an increased human longevity. After a median follow-up of 8.5 years, we investigated the possible role of MUFA, PUFA, and other selected food groups in protecting against all-causes mortality in a population-based, prospective study, conducted in one of the eight centers of the Italian Longitudinal Study on Aging (ILSA), Casamassima, Bari, Italy. Out of 704 elderly subjects (65-84 years), 278 nondemented persons agreed to participate at the first survey (1992-1993). During the follow-up, there were 91 deaths. A semi-quantitative food frequency questionnaire evaluating macronutrient daily intakes were performed at the first survey. Higher MUFA intake was associated with an increase of survival (hazard ratio 0.81, 95% CI 0.66-0.99), a higher unsaturated fatty acids (UFA) to SFA ratio (hazard ratio 1.20, 95% CI 0.99-1.45) increased total mortality only marginally, while no effect about other selected food groups were found. In conclusion, in this prospective study on older nondemented subjects with a typical Mediterranean diet, a higher MUFA intake increased survival, while a higher UFA/SFA ratio increased total mortality, but only marginally.

Regional European differences in allele and genotype frequencies of low density lipoprotein receptor-related protein 1 polymorphism in Alzheimer's disease.

The low density lipoprotein receptor‐related protein 1 (LRP1 gene) is a candidate gene for Alzheimers disease (AD), because it is a ligand for proteins involved in AD pathogenesis, such as apolipoprotein E (APOE), α2‐macroglobulin (A2M), amyloid precursor protein (APP), and is located on chromosome 12, within a region linked with AD. An association between a silent polymorphism (C/T) in exon 3 and late onset AD has been reported, with an increased frequency of the C allele, although with conflicting results. We examined this polymorphism in a cohort of 166 sporadic AD patients and 225 sex‐ and age‐matched nondemented controls from Southern Italy. No statistically significant differences were found in LRP1 genotype and allele frequencies between the whole AD sample and controls, nor in early‐ and late‐onset subsets of AD patients. No statistically significant differences in frequencies between LRP1 alleles and AD among APOE allele, age, or gender strata were found. Finally, comparing our results with the findings from other European populations, the LRP1 C allele frequency showed a statistically significant decreasing trend from Northern to Southern regions of Europe, with a concomitant increase in LRP1 T allele frequency, but in AD patients only. Finally, in the AD sample, a decreasing geographical trend from North to South of Europe was found for LRP1 CC genotype, and an inverse trend for LRP1 CT genotype frequency. We suggest that these regional variations in LRP1 genotype and allele frequencies in AD could be related to the different patterns of association between this polymorphism and the disease in various European studies.

Short arm of chromosome 11 and sporadic Alzheimer's disease: Catalase and cathepsin D gene polymorphisms

Catalase (CAT) -262 C/T promoter (rs1001179), cathepsin D (CTSD) exon 2 (rs17571), and apolipoprotein E (APOE) gene polymorphisms were studied in 242 patients with sporadic Alzheimers disease (AD) and 421 unrelated age-, sex-, and ethnically matched control subjects from Apulia (Southern Italy). No statistically significant differences in CAT rs1001179 and CTSD rs17571 genotype and allele distribution between AD cases and healthy controls were observed for the whole AD sample, and when AD group was categorized by age at onset in early- and late-onset AD subsets. Furthermore, we did not find any statistically significant differences in rates between CAT rs1001179 and CTSD rs17571 genotypes and AD controlling for APOE e4 allele status. Our data, at present, do not support a role of two gene polymorphisms of the short arm of the chromosome 11, the CAT rs1001179 and CTSD rs17571, as a possible susceptibility factors for sporadic AD.