Rice consumption and predisposition to metabolic diseases: The role of PPARγ and GLUT4 dysregulation

Abstract

Metabolic diseases of significant dietary cause have been multiplying since the climax of the Industrial Revolution and are approaching pandemic proportions. Diet has been promulgated as a cornerstone in tackling these diseases. Understanding the long-term molecular modulatory functions of a diet on key metabolic pathways associated with the pathophysiology of these diseases cannot be overemphasised. Since rice is a staple food for more than half of the world's population and has been linked to some metabolic diseases, we assert that understanding the long-term molecular modulatory effect of rice cultivars on PPARγ and GLUT4 gene products could reduce the burden of these diseases. This would be done by harnessing which property of a rice cultivar alters important metabolic pathways necessary for normal body function. Forty-eight nulliparous rats fed for 90 days with differing rice cultivars were mated with male rats raised on standard pellet. The resulting pups and dams were sacrificed (n = 6). Their adipose tissue, hepatic tissue and muscle tissue were investigated for PPARγ and GLUT4 gene expression regulations. Protein was also extracted from the aforementioned tissues, separated on SDS-PAGE and blotted and probed with PPARγ and GLUT4 primary antibodies, followed by a secondary antibody. Global hepatic DNA methylation due to the interventions were quantified using a DNA methylation kit. Our findings showed that germination status and high amylose composition properties in rice cultivars prevented the downregulation of GLUT4 gene products in standard-chow- and high-fat-diet-fed rats. It also prevented the upregulation of PPAR gene products in the same rats. Alterations in mRNA and protein regulations were inherited by the offspring. Furthermore, germinated rice cultivars with high amylose content demonstrated lower hepatic DNA methylation levels compared with low-amylose white rice. Also, a 50% correlation was observed between mRNA and protein levels of the various interventions employed. In overall, the findings point towards an expected lesser burden of diet-related metabolic diseases if the beneficial properties of a high-amylose content and germination status in a rice cultivar are harnessed. Keywords: Amylose content, Germination status, GLUT4, Metabolic diseases, PPARγ, Rice