Dietary supplementation of levamisole modulates protein and lipid MALDI-TOF MS profiles of Nile tilapia without causing negative histological alterations

Abstract

The aim of this study was to investigate the effects of the dietary supplementation of levamisole hydrochloride on Oreochromis niloticus lipid and protein profiles through matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) and possible tissue lesions by histopathological analyzes. A total of 320 fingerlings were distributed into the following groups: fish fed supplemented diets with 100, 150 and 200 mg of levamisole kg−1 and fish fed a diet receiving no supplementation. After 8 days of feeding, stomach histopathology showed that fish fed the 100 and 150 mg kg−1 levamisole supplemented diets had a significantly lower intensity in the degeneration of columnar epithelial cells when compared to the control group (p < 0.05), possibly a result of a generalized superior health status caused by the supplementation. Liver analysis showed no significant alterations (p ≥ 0.05), while histopathology of gills showed significant alterations in the fusion of secondary lamellae, in which only fish fed the highest dose showed a significant higher value when compared to the control group (p < 0.05). In the protein analysis, a total of 106 m/z peaks were observed, where 28 peaks showed significant changes in their intensity (p < 0.05). In general, fish supplemented with 100 mg kg−1 of levamisole showed an increase in the intensity in the peaks within the m/z ranges 2814–3337, 3732–6998 and 9045–13,505, while fish fed with 150 mg kg−1 dose showed a reduction in the intensity at most of the peaks found within those intervals. Immune system related proteins occurring within those ranges suggest a positive modulation of the protein profile. There were also marked alterations in the lipid profiles. Levamisole supplemented fish showed a significant positive modulation in the glycerophosphocholines group (p < 0.05), whose function in improving fish resistance to cold water suggests an additional health benefit of this feed additive. Judging on the histopathological analyses and MALDI-TOF MS lipid and protein profiling, the 100 mg kg−1 levamisole supplementation dose provided the greatest benefits to Nile tilapia fingerlings.