12 Effects of excess iron and dietary fat on lipid metabolism

Abstract

Abstract Diets rich in fat and energy are associated with metabolic syndrome. Imbalanced systemic iron status has long been epidemiologically associated with obesity-related diseases. The aim of this study is to investigate the interaction between dietary fat and injected iron in the context of glucose and lipid metabolism. C57BL6/J mice were divided into four groups and fed normal chow (NC) and high-fat diet (HFD) with adequate or excess iron for 16 weeks. Excess iron was added by intraperitoneal injection with iron dextran (120 mg/g of body weight) every other week from 4th week (NC+Fe and HFD+Fe), six times in total. The results showed that high iron levels decreased the growth rates of mice without affecting their feed intake. High iron levels increased the adipocyte numbers by 1.6-fold in subcutaneous adipose tissue (SAT) and 3.5-fold in visceral adipose tissue (VAT), while excess iron inhibited their adipocyte hypertrophy. These changes were paralleled by alterations in the levels of enzymes related to hepatic lipid storage and β-oxidation. Especially two key enzymes, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) (P < 0.01) and fat specific protein 27 (FSP27) (P < 0.01) were markedly decreased in iron-treated groups compared with their counterparts. In addition, high iron levels decreased insulin sensitivity by increasing 15% of fasting blood glucose and 23% of insulin levels and the average under curve of intraperitoneal glucose tolerance test (IPGTT) was also decreased (P < 0.05). These results were consistent with the decrease of mRNA expression of enzymes related to hepatic gluconeogenesis, phosphoenolpyruvate carboxykinase 1 (PCK1) (P < 0.05) and fructose-1,6-bisphosphatase 1 (FBP1) (P < 0.05) in iron-treated mice. Thus, high-fat diets and iron overload were associated with insulin resistance, modified lipid deposition and iron metabolism. High iron levels could protect mice from high-fat diet induced obesity by decreasing insulin sensitivity.