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

PloS one (2020-01-03)
Josefin Engelhardt, Oscar Frisell, Hanna Gustavsson, Tomas Hansson, Rajlie Sjöberg, Tracy K Collier, Lennart Balk
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Trizma® hydrochloride, reagent grade, ≥99.0% (titration), crystalline
Sigma-Aldrich
Sucrose, BioXtra, ≥99.5% (GC)
Sigma-Aldrich
Magnesium chloride hexahydrate, BioXtra, ≥99.0%
Sigma-Aldrich
β-Nicotinamide adenine dinucleotide, reduced disodium salt hydrate, ≥97% (HPLC)
Sigma-Aldrich
Thiamine pyrophosphate, ≥95%
Supelco
Thiamine Hydrochloride (B1), analytical standard
Sigma-Aldrich
Thiamine monophosphate chloride dihydrate
Sigma-Aldrich
D-Ribose 5-phosphate disodium salt hydrate, ≥98% (TLC), powder
Sigma-Aldrich
Bovine Serum Albumin, lyophilized powder, 1× crystallized, ≥97% (agarose gel electrophoresis)
Sigma-Aldrich
α-Glycerophosphate Dehydrogenase-Triosephosphate Isomerase from rabbit muscle, Type III, ammonium sulfate suspension, GDH 75-200 units/mg protein (biuret), TPI 750-2000 units/mg protein
Supelco
Thiamine pyrophosphate, Pharmaceutical Secondary Standard; Certified Reference Material