Cadmium exposure affects growth performance, energy metabolism, and neuropeptide expression in Carassius auratus gibelio.

Cadmium (Cd) is the most abundant heavy metal in aquatic environments and is easily detected on a global scale. Carassius auratus gibelio is a common aquaculture species. The aim of this study was to explore the toxic effects of 1, 2, and 4 mg/L Cd on the energy metabolism, growth performance, and neurological responses of C. gibelio. After 30 days of exposure, Cd concentrations in the liver and brain were significantly increased in Cd-exposed groups. Low-level Cd exposure (1 mg/L) increased weight and length gains, as well as food intake, in the fish. Acetylcholinesterase activity decreased significantly in the Cd-exposed groups. Energy metabolism levels (as reflected by oxygen consumption, ammonia excretion rate, and swimming activity), as well as serum T3 and T4 levels, increased significantly in the fish exposed to 1 mg/L Cd. However, energy metabolism and serum T3/T4 levels decreased significantly in the 4-mg/L Cd group. Neuropeptide gene expression levels in brain were consistent with the observed changes in food intake. In the Cd-exposed groups, the expression levels of neuropeptide Y (NPY), apelin, and metallothionein (MT) increased significantly, while those of pro-opinmelanocortin (POMC), ghrelin, and corticotrophin-releasing factor (CRF) decreased significantly. Our data suggested that in fish, low doses of Cd might increase food intake, as well as weight and length gains, but high doses of Cd might have the opposite effect. These effects might be a result of neurohumoral regulation. Long-term exposure to low doses of Cd might cause weight gain and affect food intake.