Metabolites - substances that are created during metabolism -- can provide a wealth of information about individual health, disease, diet, and life-style. Now, they can tell us even more. Researchers have recently discovered metabolites that are specifically related to aging and shed light on how the human body ages. The team published their results in PNAS.
In order to find and analyze the metabolites, the team obtained blood samples, including red blood cells (RBCs) from 30 healthy individuals: 15 young adults (29±4 yr) and 15 older adults (81±7 yr). Previously, RBCs have been overlooked in research, but as RBCs make up approximately half of blood volume, the researchers believed it was worth exploration.
Then, they used Liquid Chromatography-Mass Spectrometry (LC-MS), a technique that separates liquids and detects substances, to identify the metabolites within the blood. From there, they could calculate the coefficients of variation, or the standard deviation of metabolite abundance divided by the average, to identify which compounds had increased or decreased in the older adults.
"We found 14 age-related compounds," senior author said. "Of these 14 compounds, half of the them had decreased in elderly people. The decrease was found in antioxidants and in compounds related to muscle strength. Therefore, elderly people had less antioxidants and less muscle strength."
They include 1,5-anhydroglucitol, dimethyl-guanosine, acetyl-carnosine, carnosine, ophthalmic acid, UDP-acetyl-glucosamine, N-acetyl-arginine, N6-acetyl-lysine, pantothenate, citrulline, leucine, isoleucine, NAD+, and NADP+. Six of them are RBC-enriched, suggesting that RBC metabolomics is highly valuable for human aging research.
The other half of the compounds that had increased were metabolites related to declining kidney and liver function.
"This makes sense," author said. "Common sense tells you that as we get older we lose abilities like muscle strength and kidney function, but no one has ever scientifically proved that this is the case before." In addition, some of the age-related metabolites that are found on the same metabolic pathways have connected changes, which suggests that age affects them simultaneously.
Age differences are partly explained by a decrease in antioxidant production or increasing inefficiency of urea metabolism among the elderly. Pearson’s coefficients demonstrated that some age-related compounds are correlated, suggesting that aging affects them concomitantly.
"Functionally related compounds show the same tendencies to increase or decrease with age, or in other words, they show similar correlations," author said.
Now that these age-related metabolites have been identified, the decline in antioxidants and muscle strength suggest that it is important for individuals to consume foods high in antioxidants and to continue exercising, especially after the age of 65. This could help increase the levels of the related metabolites in the body and improve body conditions. While many unknown components to living a long and healthy life remain, the research team will continue to uncover as much information about healthful aging.
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