For example, elevated levels of α-hydroxybutyrate, β-hydroxyisobutyrate, and α-ketoglutarate have been reported 60 minutes after eating a light breakfast, compared to fasting levels, and likely reflect increased postprandial amino acid catabolism. , such as glutamate and valine, which denote insulin sensitivity.
“These findings indicate that elevated concentrations of these candidate biomarkers of insulin sensitivity should be interpreted with caution if the individual’s prandial state is not known,” he said.they write in ‘BMC Nutrition’.
Prandial status is rarely considered when analyzing biomarkers for health and disease risk, with blood typically drawn from patients fasting or after a light meal, the authors explain.
“Inconsistent observations in epidemiological studies investigating biomarkers in relation to various health and disease outcomes may be linked to differences in blood collection protocols.
“In particular, it is not clear how the time interval between the last meal and blood collection might affect blood biomarker concentrations.”
The present study, therefore, examined the effects of a bland meal on the patients’ metabolic activity (from the catabolic to the anabolic state), including serum concentrations of amino acids, kynurenine pathway metabolites, and metabolites involved in glucose regulation. The researchers also compared all biomarkers between male and female participants.
Amino acid concentrations
Sixty-three healthy adults were recruited for the study, including 36 women. Blood samples were collected fasting and intermittently up to 120 minutes after consumption of a light, low-protein breakfast. Serum samples were compared using the T test.
Amino acid concentrations increased significantly after 60 minutes for 13 of the 20 amino acids measured – and particularly alanine (up to 34%) and proline (45%) – and did not reflect the amino acid composition of the breakfast.
Serum histidine and phenylalanine (EAAs) concentrations increased significantly postprandially; leucine, isoleucine and valine remained unchanged, while threonine and methionine initially increased after 60 minutes and then returned to fasting levels.
Male participants had higher fasting serum concentrations of EAAs isoleucine, leucine, methionine, tryptophan, valine, glutamate, and tyrosine compared to females, and therefore increases after meal consumption were considerably greater in the latter case.
“For glycine, methionine, glutamine, threonine, and phenylalanine, the ratios of postprandial to fasting serum concentrations were marginally but statistically significantly higher in women compared to men at 60 or 120 minutes after breakfast, while both the proportions for the other 13 amino acids were similar between genders”, they write.
Disparity of biomarkers
The researchers observed relative changes in α-hydroxybutyrate, β-hydroxyisobutyrate, and α-ketoglutarate metabolites involved in glucose regulation 60 minutes after ingestion (25%, 20%, and 22% increase, respectively).
They observed that men had higher fasting β-hydroxyisobutyrate concentrations, suggesting poor insulin sensitivity and a higher risk of type 2 diabetes.
“So, relative to the women in our study, the male participants had an unfavorable fasting amino acid profile that was associated with insulin resistance.“, they claim.
Additional tests revealed a considerable decline in seven kynurenine metabolites (kynurenic acid, anthranilic acid, 3-hydroxykynurenine, xanthranilic acid, 3-hydroxyanthranilic acid, picolinic acid and quinolinic acid) two hours after consumption, compared to fasting levels, although postprandial kynurenine and tryptophan were unaffected.
The kynurenine pathway is crucial for the catabolism of tryptophan, which has anticancer and anti-inflammatory properties, and the observed increases in glucose concentrations may contribute to the reduction of catabolism through this pathway, say the authors.
They add: “The possible inhibitory effect of glucose on the kynurenine pathway underscores the importance of investigating whether the prandial state can affect metabolite concentrations in this pathway..”
Source: BMC nutrition
Published online January 11, 2023: http://doi.org/10.1186/s40795-022-00661-1
‘Serum concentrations of amino acids and tryptophan metabolites are affected by consumption of a light breakfast: a clinical intervention study in overweight or obese adults‘
Authors: Ingrid V. Hagen, Anita Helland, Marianne Bratlie, Oivind Midttun, Adrian McCann, Arve Ulvik, Gunnar Mellgren, Per M. Ueland, and Oddrun A. Gudbrandsen