Melatonin reduces β-amyloid accumulation and improves short-term memory in streptozotocin-induced sporadic Alzheimer's disease model

Melatonin is a hormone secreted by the pineal gland, it can be associated with circadian rhythms, aging and neuroprotection. Melatonin levels are decreased in sporadic Alzheimer's disease (sAD) patients, which suggests a relationship between the melatonergic system and sAD. Melatonin may reduce inflammation, oxidative stress, TAU protein hyperphosphorylation, and the formation of β-amyloid (Aβ) aggregates. Therefore, the objective of this work was to investigate the impact of treatment with 10 mg/kg of melatonin (i.p) in the animal model of sAD induced by the intracerebroventricular (ICV) infusion of 3 mg/kg of streptozotocin (STZ). ICV-STZ causes changes in the brain of rats similar to those found in patients with sAD. These changes include; progressive memory decline, the formation of neurofibrillary tangles, senile plaques, disturbances in glucose metabolism, insulin resistance and even reactive astrogliosis characterized by the upregulation of glucose levels and glial fibrillary acidic protein (GFAP). The results show that ICV-STZ caused short-term spatial memory impairment in rats after 30 days of STZ infusion without locomotor impairment which was evaluated on day 27 post-injury. Furthermore, we observed that a prolonged 30-day treatment with melatonin can improve the cognitive impairment of animals in the Y-maze test, but not in the object location test. Finally, we demonstrated that animals receiving ICV-STZ have high levels of Aβ and GFAP in the hippocampus and that treatment with melatonin reduces Aβ levels but does not reduce GFAP levels, concluding that melatonin may be useful to control the progression of amyloid pathology in the brain.

The reduction of vascular disease risk mutations contributes to longevity in the Chinese population

Aim

Genetic factors play important roles in determining human lifespan. Although some “longevity genes” have been identified to be implicated in human longevity, many disease-associated variants were also observed in the long-lived individuals. The oldest old and their offspring usually have a lower prevalence of age-related diseases, which is likely attributed to a reduction or an absence of disease risk variants.

Methods and results

To test this hypothesis, 23 disease risk single nucleotide polymorphisms (SNPs), identified by previous genome-wide association studies (GWASs), were selected and genotyped in 1074 samples consisting of 574 longevity subjects (over 90 years old) and 500 younger controls. Our results revealed that 5 SNPs (rs2144300, rs1864163, rs2200733, rs1967017, and rs7193343) displayed significantly lower allelic frequencies and odds ratios (ORs) in the longevity group than that in the control group. The frequencies of homozygous mutation genotypes and corresponding ORs of the rs1864163, rs2200733, rs127430, rs1967017, and rs12413409 were lower in the longevity subjects. Interestingly, most of the abovementioned SNPs convey susceptibility to cardiovascular disease (CVD), which is the leading cause of deaths in old adults but shows a much lower incidence in the longevity individuals and their offspring.

Conclusion

Taking into account the observation that the longevity subjects and their offspring have lower rate of cardiovascular mortality, it is then most plausible that the lack of disease risk variants, especially the CVD, is a genetic contributor to longevity in the Chinese population.

•

23 disease risk gene polymorphisms were determined in 1074 subjects.

•

5 polymorphisms displayed lower allelic frequencies in longevity subjects.

•

Lack of disease risk variants contributes to longevity.