336 Fig. 2 A principal components analysis (PCA) plot of HepG2 cells grown in the presence and absence of extracts of the T. indica fruit pulp showing biological replicates (n = 3) of control and treated samples. Arrays for the control group were in blue, and those for the treated group were in red. The data are clustered by treatment (a) and scan date (b). Each ball represents an array or a sample Fig. 3 Hierarchical cluster analysis of genes showing the differential expression of genes in HepG2 cells in response to the treatment with methanol extracts of T. indica fruit pulp Array Array Array Array Array Array Genes Nutr (2010) 5:331–341 Control Treated analysis, we decided to use a low concentration of 300 lg/ml where cell viability was still above 90%. We decided to use a low concentration of the extracts instead of the usual IC50 concentration, because it is known that dietary antioxidants are present in circulation in small amount because they are either poorly absorbed from the intestine or once absorbed they are quickly metabolized [18, 46]. At this low con- centration, we found that the methanol extracts of the T. indica fruit pulp were able to signiﬁcantly regulate a total of 1501 genes (P \ 0.05) with a fold change of at least 1.5. Amongst the signiﬁcantly up-regulated genes were those that code for the metallothioneins (MTs), MT1M, MT1F, MT1X and glutathione S-transferases (GSTs) namely GSTA1, GSTA2 and GSTO2. MTs and GSTs have protective roles over heavy metals such as cadmium [8] and oxidative DNA, protein and lipid damage [6, 11]. In this study, only genes encoding MT-1 but not the other two isoforms, MT-2 and MT-3, were induced by low concentration of the 123 Gene expression T. indica fruit pulp extracts. In addition, GSTs are involved in the detoxiﬁcation of xenobiotics such as toxins and carcinogens [13, 15] and regulate cellular stress response to the formation of reactive oxygen species through the JNK- associated apoptosis [39]. Omega class GSTs have dehy- droascorbate reductase and thioltransferase activities and also catalyse the reduction of monomethylarsonate, an intermediate in the pathway of arsenic biotransformation. Other diverse actions of human GSTO1-1 include modu- lation of ryanodine receptors and interaction with cytokine release inhibitory drugs. Glutathione S-transferase omega 1 and omega 2 (GSTO1 and GSTO2) catalyse monomethyl arsenate reduction during arsenic biotransformation [29]. Diseases of the cardiovascular system are the most common cause of death in developed countries. It has been established that hyperlipidaemia including high cholesterol levels in blood represents a major risk factor for the premature development of atherosclerosis and its