One Carbon Metabolism in Older Adults: A comparison of the postprandial responses of plasma compounds involved in one carbon metabolism to different mixed-meals in healthy young and healthy older adults: A preliminary randomised control trial.

Abstract

Ageing is associated with altered diet and metabolism, including altered one-carbon metabolism (OCM). Disturbances of OCM, namely elevated homocysteine (Hcy), are associated with age-related diseases. Many substrates and cofactors of OCM are essential nutrients, yet, how ageing affects postprandial responses of one-carbon (OC) compounds to meals is largely unknown. This is important if acute responses affect long-term health outcomes. This study aimed to establish if plasma OC-compounds in healthy young and older adults respond differently to the intake of nutrient-dense (ND) and energy-dense (ED) meals. Healthy young and older adults (n=15 each) consumed two different breakfast meals on separate occasions in a randomised cross-over trial. One meal was ND (oats, milk, fruit, cottage cheese, toast and peanut butter); and one was ED (egg and sausage English muffins with hash browns). Plasma samples, collected at fasting and hourly for five hours postprandially, were analysed for 13 OC-compounds using high-performance liquid chromatography with tandem mass spectrometry. Postprandial concentrations of OC-compounds were not simultaneously dependent on meal type and age. Across all timepoints, older adults had similar concentrations of OC-compounds for the two meals, while young adults had higher betaine, choline, glycine and taurine for the ED meal compared to the ND meal. Fasting concentrations of some OC-compounds differed between age-groups; compared to young adults, homocysteine (Hcy) was lower at baseline and across all time points for the ED meal in older adults. Time-course responses of OC-compounds after eating were similar between the age-groups; only the ratio for dimethylglycine-to-betaine increased for older adults. Serine, methionine, S-adenosylmethionine, choline and dimethylglycine increased after consuming the ED meal for both age-groups. Serine, methionine and S-adenosylmethionine also increased for all subjects after eating the ND meal; the ED meal delayed postprandial increases of serine and methionine. Postprandial responses of plasma OC-compounds to a meal are not dependent on ageing alone, and may depend more on meal composition. Older adults may have less divergent responses to different meals, with health implications of this yet to be established. Additional postprandial research in less-healthy cohorts of older adults is justified, given the link between age-related disease and altered OCM.