Soybean Oil High Fat Diet Reduces Hypothalamic Oxytocin Immunoreactivity

Abstract

It is well established that the intake of fatty foods induces obesity, although relatively little attention is given to the type of fat. Male mice fed a high fat diet (HFD) rich in saturated fat had significantly less weight gain, adiposity, glucose intolerance and fatty liver as compared to mice fed a high fat diet containing soybean oil (SO), rich in the polyunsaturated omega‐6 fatty acid linoleic acid (LA‐HFD) or a diet rich in a genetically modified, low LA soybean oil (PL‐HFD). Both LA‐HFD and PL‐HFD also have similarly higher levels of the phytosterol, stigmasterol, than HFD. The adverse effects of SO may be mediated, in part, by brain oxytocin, although this has not been studied. Oxytocin is anorexigenic and mouse models of obesity show reduced brain Oxt. Here we examined the effect of SO diet on oxytocin. Male C57BL/6N mice were fed for 17–27 weeks either vivarium chow (VC) or one of 4 iso‐caloric diets: HFD (coconut oil), LA‐HFD (SO), PL‐HFD (GM SO) or Stigma‐HFD (coconut oil with same amount of stigmasterol as LA‐ and PL‐HFD) or control (VC). Immunoreactivity (IR) to an antibody specific for oxytocin‐neurophysin in the paraventricular nucleus of the hypothalamus was markedly lower in LA‐, PL‐ and Stigma‐HFD groups relative to HFD and VC. Similar but less marked differences were obtained in arcuate nucleus. For the supraoptic nucleus a similar pattern was observed except that oxytocin IR in PL‐HFD was not reduced (n=5–6 experiments, 3–5 animals per group). Our findings demonstrate that the stigmasterol can decrease paraventricular oxytocin and this may help explain the obesity and diabetic propensity associated with a diet rich in SO.Support or Funding InformationSupport: APS fellowships (C.H., D.P.), UCR UGR Student Mini‐Grant (C.H), NIEHS T32 fellowship (P.D.) and Collaborative grant, UCR ORED (F.S., T.J. and M.C.C.).