Severe thiamine deficiency in eastern Baltic cod (Gadus morhua).

Tracy K Collier,Tomas Hansson,Hanna Gustavsson,Oscar Frisell,Ilaria Corsi,Josefin Engelhardt,Lennart Balk,Rajlie Sjöberg

doi:10.1371/journal.pone.0227201

Tracy K Collier, Tomas Hansson + Show 6 more

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https://doi.org/10.1371/journal.pone.0227201

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Abstract

The eastern Baltic cod (Gadus morhua) population has been decreasing in the Baltic Sea for at least 30 years. Condition indices of the Baltic cod have decreased, and previous studies have suggested that this might be due to overfishing, predation, lower dissolved oxygen or changes in salinity. However, numerous studies from the Baltic Sea have demonstrated an ongoing thiamine deficiency in several animal classes, both invertebrates and vertebrates. The thiamine status of the eastern Baltic cod was investigated to determine if thiamine deficiency might be a factor in ongoing population declines. Thiamine concentrations were determined by chemical analyses of thiamine, thiamine monophosphate and thiamine diphosphate (combined SumT) in the liver using high performance liquid chromatography. Biochemical analyses measured the activity of the thiamine diphosphate-dependent enzyme transketolase to determine the proportion of apoenzymes in both liver and brain tissue. These biochemical analyses showed that 77% of the cod were thiamine deficient in the liver, of which 13% had a severe thiamine deficiency (i.e. 25% transketolase enzymes lacked thiamine diphosphate). The brain tissue of 77% of the cod showed thiamine deficiency, of which 64% showed severe thiamine deficiency. The thiamine deficiency biomarkers were investigated to find correlations to different biological parameters, such as length, weight, otolith weight, age (annuli counting) and different organ weights. The results suggested that thiamine deficiency increased with age. The SumT concentration ranged between 2.4–24 nmol/g in the liver, where the specimens with heavier otoliths had lower values of SumT (P = 0.0031). Of the cod sampled, only 2% of the specimens had a Fulton’s condition factor indicating a healthy specimen, and 49% had a condition factor below 0.8, indicating poor health status. These results, showing a severe thiamine deficiency in eastern Baltic cod from the only known area where spawning presently occurs for this species, are of grave concern.

Highlights

Thiamine, vitamin B1, is a water-soluble molecule consisting of a thiazole ring linked by a methylene bridge to a pyrimidine ring
Most of the biological data were acquired for all specimens (51), except for otoliths where one was missing (50), and thiamine data, where biochemical measurements were done on 30 liver samples and 22 brain samples, and chemical measurements were done on 38 liver samples
Fish are affected by thiamine deficiency during embryonic and larval development, because the thiamine deficient adult female is not able to transport the necessary amount of thiamine to the maturating eggs [100]

Summary

Introduction

Vitamin B1, is a water-soluble molecule consisting of a thiazole ring linked by a methylene bridge to a pyrimidine ring. One of them is branched-chain α-keto acid dehydrogenase, active in the metabolism of branched amino acids [3, 4] Another TDP-dependent enzyme is 2-hydroxyphytanoyl-CoA lyase, involved in the α-oxidation of certain fatty acids [5, 6]. Transketolase (TK), in the hexose monophosphate shunt [7, 8] is a TDP-dependent enzyme, and is a provider of nucleic acid bases, used as the backbone for DNA and RNA, and NADPH used as a protection against oxidation and in the synthesis of fatty acids [9] Another TDP-dependent enzyme, pyruvate dehydrogenase, acts as the bridge between glycolysis and the TCA cycle [9,10,11]. Because thiamine acts as a cofactor to enzymes in several different pathways, and a deficiency causes an imbalance of metabolites, the sub-lethal symptoms of thiamine deficiency are diverse and, depending on animal class, can include emaciation, memory loss, neurological disorders, immunosuppression, reduced vision and sense of smell, hypothermia, degradation of the blood-brain barrier, anorexia, labored breathing as well as memory-, learning-, orientation-, behaviour- and reproductive disorders [12, 23,24,25,26,27,28]

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