The standard model of natural selection predicts that once the age of reproduction ends, individuals die. That’s because selection early in life strongly favors variants that benefit reproductive success, even at the cost of negative consequences late in life, one major reason humans age. This is indeed the case in almost all vertebrates. Humans are an exception to this rule, living decades beyond reproductive age; such elders contribute to the fitness of younger individuals by caring for grandchildren and also by passing down important cultural knowledge.
Age-related cognitive decline compromises these benefits, and eventually burdens the group with the need to care for dependent older members. Now, a study from researchers at the University of California, San Diego School has shown that humans have evolved gene variants that can help protect the elderly from neurodegenerative and cardiovascular diseases, thus preserving their contributions to society. The team state that these genes likely evolved to preserve valuable and wise elders, as well as to delay or prevent the emergence of dependent individuals who could divert resources and effort away from the care of the young. The study is published in the journal Proceedings of the National Academy of Sciences.
Previous studies show that a certain form of CD33 suppresses amyloid beta peptide accumulation in the brain. CD33 is a receptor that projects from the surface of immune cells, where it keeps immune reactions in check, preventing ‘self’ attack and curtailing unwanted inflammation. Amyloid beta accumulation is thought to contribute to late-onset Alzheimer’s disease, a post-reproductive condition that uniquely affects humans and is aggravated by inflammation and cerebral vascular disease. Therefore, the lab focused on the gene that encodes the CD33 protein in humans and our closest living relatives, chimpanzees. The current study shows that levels of the CD33 variant that protects against Alzheimer’s are four-fold higher in humans than chimpanzees.
The current study shows that human-specific variations in many other genes involved in the prevention of cognitive decline, such as APOE. The group state that the ancestral form of the gene, APOE4, is a notorious risk factor for Alzheimer’s and cerebral vascular disease, however, results show that variants APOE2 and APOE3 seem to have evolved to protect from dementia.
The team surmise that all of these protective gene variants are present in Africa, and thus predate the origin of the human species. For the future, the researchers state that their study does not directly prove that these factors are involved in the selection of protective variants of CD33, APOE and other genes, however, they do denote further investigation.
Michelle Petersen is the founder of Healthinnovations, having worked in the health and science industry for over 21 years, which includes tenure within the NHS and Oxford University. Healthinnovations is a publication that has reported on, influenced, and researched current and future innovations in health for the past decade.
Michelle has been picked up as an expert writer for Informa publisher’s Clinical Trials community, as well as being listed as a blog source by the world’s leading medical journals, including the acclaimed Nature-Springer journal series.
Healthinnovations is currently indexed by the trusted Altmetric and PlumX metrics systems, respectively, as a blog source for published research globally. Healthinnovations is also featured in the world-renowned BioPortfolio, BioPortfolio.com, the life science, pharmaceutical and healthcare portal.
Most recently the Texas A&M University covered The Top 10 Healthinnovations series on their site with distinguished Professor Stephen Maren calling the inclusion of himself and his team on the list a reflection of “the hard work and dedication of my students and trainees”.
Michelle Petersen’s copy was used in the highly successful marketing campaign for the mega-hit film ‘Jumanji: The Next Level, starring Jack Black, Karen Gilian, Kevin Hart and Dwayne ‘The Rock’ Johnson. Michelle Petersen’s copywriting was part of the film’s coverage by the Republic TV network. Republic TV is the most-watched English language TV channel in India since its inception in 2017.
An avid campaigner in the fight against child sex abuse and trafficking, Michelle is a passionate humanist striving for a better quality of life for all humans by helping to provide traction for new technologies and techniques within healthcare.