Long-term High-Soybean Oil Feeding Alters Regulation of Body Temperature in Rats

Abstract

We investigated whether body temperature (BT) regulatory mechanisms are influenced by dietary fatty acids (FA). Male Wistar rats were fed a high-fat diet containing fish oil (HFD), soybean oil (HSD) or lard (HLD). At the 20-week intervention, the BT of the HSD and HLD groups were lower than that of the normal diet (ND) group in the light and dark periods. The intracerebroventricular injections of interleukin-1β and bombesin in the HSD group induced greater hyperthermia and weaker hypothermia, respectively, than in the ND group. The HSD differentially affected BT under both physiological and pharmacological conditions. In the hypothalamus, the ratio of n-6/n-3 FAs was higher in the HSD group compared with the ND group. DNA microarrays revealed increased expression of thyroid-stimulating hormone β-subunit, and decreased expression of several genes in the hypothalamus of the HSD group compared with the ND group. The HSD feeding increased several adipokine concentrations in the plasma. However, there were no adipokines or gene expressions that changed in only the HSD and HLD groups showing significant hypothermia under the physiological condition. These findings suggested that long-term HSD intake produces abnormal BT regulation. It is less likely that adipokines or proteins/peptides are involved in abnormal BT regulation under the physiological conditions after HSD feeding.Key words body temperature; hypothalamus; high-fat diet; interleukin (IL)-1β; bombesinWe now obtain more energy from fat and glucose than ever before. These changes have induced hyperlipidemia and adipocyte hypertrophy, resulting in the risk of cardiovascular diseases, diabetes mellitus and obesity. From this point of view, there are many reports on lipid and/or glucose metabolisms during high-fat diet feeding in living animals.

Comparison of the Physical Characteristics and Behavior in ABC Transporter A1, A7 or Apolipoprotein E Knockout Mice with Lipid Transport Dysfunction

“…42) The method of the FA measurement was previously described elsewhere. 43) In brief, after drying the prepared lipid solution, it was again dissolved in methanol and methylated by heat. The methylated FAs were then extracted by petroleum ether, and various FAs were measured by GLC (Shimadzu, Kyoto, Japan).…”