Opioid Peptides, Adrenocorticotrophic Hormone and Dietary Copper Intake in Humans

Copper plays an important role in cardiac and brain function possibly through endocrine and neuroendocrine systems. The syndrome of copper deficiency is worsened by dietary fructose and other trace metals such as zinc. We investigated the effect of a low copper diet on plasma opioid peptides in 11 healthy young volunteers who were fed foods low in copper but adequate in all other nutrients. The study was divided into three dietary periods. Copper was added to the diet so that the diet contained 0.66 mg/day for 24 days (marginal Cu), 0.38 mg/day for 42 days (low Cu) and 2.49 mg/day for 24 days (adequate Cu). The indices of copper status, ceruloplasmin and plasma copper concentrations, declined and were significantly lower (p < 0.05) at the end of the low Cu period than at the beginning of the study and the end of the marginal Cu period. They increased significantly at the end of the adequate Cu diet to the levels of the marginal Cu diet. Plasma β-endorphin (BEN), Leu-enkephalin (LE), Met-enkephalin (ME) and Adrenocorticotropic hormone (ACTH) were measured by radioimmunoassay at the beginning of the study and at the end of each dietary period. No significant differences were observed in BEN, LE or ME during any of the periods. There were only small increases in LE and ME at the end of marginal and low copper diet periods and no significant changes were observed on copper repletion. Plasma ACTH was significantly lower at the end of low copper compared to baseline value but was not lower after marginal copper. Copper repletion had no significant effect on ACTH. The data show that plasma opioid peptides did not respond significantly to differential copper intake.