Negative modulation of maternal iodine deficiency and excess on milk lipid synthesis and secretion in lactating rats

Iodine is an essential micronutrient for developmental processes in the early stages; however, data on the effect of maternal iodine nutrition on milk lipids are limited. We aimed to explore the effect of inadequate and excessive iodine intake on milk lipid metabolism and its mechanisms preliminarily. Rats were treated with different concentrations of potassium iodide water to construct animal models of iodine deficiency and excess. Iodine excess reduced serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels during lactation. Iodine deficiency had no significant effect on blood lipid indicators. In early and late lactation, iodine deficiency and excess inhibited triglyceride (TG) levels in milk; in mid-lactation, the inhibitory effect of iodine deficiency was attenuated. Under iodine deficiency and excess, the level of TG and the expression of THRα1, THRβ1, ACC1, FAS, THRSP, BTN1A1, and ADFP proteins in the mammary gland were decreased during lactation; a decrease in LPL protein expression was observed in early and late lactation; and a decline of XOR protein expression was reported in mid and late lactation. Blood lipid metabolism was less sensitive to iodine deficiency during lactation. Iodine excess has a more profound effect on blood lipid metabolism, causing dyslipidemia in lactating rats. Long-term iodine deficiency and excess may have a negative role in the mechanisms regulating milk lipid synthesis and secretion by affecting thyroid hormones to inhibit the milk TG level.