Short- and long-term effects of corn oil on serum lipid and lipoprotein and visceral abdominal fat pad parameters of rats

Obesity, in particular, abdominal obesity, is highly correlated with metabolic disorders and cardiovascular lesions in humans and animal models and may in fact play a role in their pathogenesis. The development of obesity, while partially genetic, is largely affected by environmental and lifestyle factors such as diet. The aim of the present study was to determine the short- and long-term effects of dietary corn oil on the abdominal fat pat morphology and serum lipid and lipoprotein profile. Forty male Wistar rats were randomly separated into two groups. The experimental group was fed a corn oil-rich diet (CRD), which consisted of 32.5% of kilocalories from corn oil and provided a total number of kcal/kg/day similar to the average western diet. The control group received regular chow (6.5% kilocalories from fat source). In each group, eight rats were sacrificed after 3 weeks and the remaining 12 rats in each group were sacrificed after 10 weeks. Adipocyte size, distribution and adipocyte number per gram of abdominal fat pad were determined. The total weight of the abdominal fat pad from the CRD rats was approximately twice the weight of the pad from the control rats at both time points (5.43 ± 0.93 g versus 11.6 ± 1.98 g after 3 weeks and 6.24 ± 1.38 g versus 11.18 ± 2.17 g after 10 weeks). There was a significant increase (P < 0.001) in adipocyte number per gram of fat and in the total triacylglycerol (TAG) content of the fat pad in the CRD group compared to the control at both short-term and long-term time points. However, the adipocyte size distribution showed a similar pattern in both the CRD and control groups. Serum TAG, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and very low-density lipoprotein cholesterol (VLDL-C) were also measured. In the long-term study, higher values of TAG (P = 0.015), TC (P < 0.001), low-density lipoprotein cholesterol (P < 0.001) and VLDL-C (P = 0.005) were seen in the CRD group in comparison with the control. These results suggest that the deleterious effects of a CRD are because of serum changes rather than adipocyte morphology changes. Although further research is required, corn oil administration may be associated with the development of cardiovascular disorders.