Blood metabolomes and molecular markers of cellular aging in wild fish

Abstract

My work studies stress and aging physiology of wild fish using biochemical methods. The species used are two North-American temperate fish: Sander vitreus, walleye, and Salvelinus namaycush, lake trout, both species being upper-level predators of high ecological and economic importance. While using biochemical measurements is common in fish laboratory models, my thesis uses these techniques to gain insight into the biology of fishes in the wild with focus on possible environmental stress and the effect of biological aging. In my first research chapter, I determined by non-lethal sampling the whole blood metabolomic profile of S. vitreus from Winnipeg Lake to test for regional differences in metabolites across this population. Results show different blood metabolite patterns across the Southern versus the Northen basin of Lake Winnipeg. Northern S. vitreus exhibit higher concentrations of essential and branched-chain amino acids and metabolites of specific amino acid catabolism pathways, relative to Southern caught specimens. The pattern of amino acid metabolites in Northern S. vitreus may indicate heavier reliance on protein catabolism relative to the Southern fishes. Conversely, higher concentration of long-chain acylcarnitines in some Southern fish suggests higher reliance on β-oxidation for energy supply during spawning. My second research chapter investigated if patterns of changing metabolites with age in mammals may also be found in blood metabolites of Lake Winnipeg S. vitreus as they age in the wild. Results show amino acids, including essential, branched-chained and some non-essential amino acids, correlate positively with chronological age, while some medium and short-chained acyl-carnitines decrease with age. These results are similar to age-related patterns in mammals. The third research chapter investigated cellular senescence in wild-caught S. namaycush, using two common markers of aging associated with physiological decline, relative telomere length and lipofuscin accumulation. Results show no correlation of these aging markers with age in S. namaycush, in three tissues, heart, liver and red blood cells. These findings show that lipofuscin accumulation and relative telomere length data do not support increasing cellular senescence with age in this species and may represent negligible senescence in S. namaycush.