338 Genes Nutr (2010) 5:331–341 Fig. 5 Gene ontology analysis. Forest plots showing the categoriza- tion of the signiﬁcantly regulated genes (P \ 0.05; fold change more or equal to 1.5) according to their roles in major biological processes (a), molecular functions (b) and major cellular components (c). The green bars represent the up-regulated genes, and the purple bars depict the down-regulated genes Fig. 6 Validation of the microarray data using semi-quantitative RT–PCR. A few genes that were regulated in HepG2 cells in response to treatment with extracts of the T. indica fruit pulp were selected namely PDE3A, GSTA1 and MTTP genes. The expression of the selected genes relative to that of a housekeeping gene, GADPH, was calculated and was expressed as a fold change. The PCR products for the housekeeping gene, GADPH, are shown by the red arrow. The intensity of the bands was quantitated using a densitometer scanner 123 Martinello et al. [26] showed that the extracts of the T. indica fruit pulp were able to decrease the levels of serum cholesterol and triglycerides in hypercholesterolae- mic hamsters. The molecular mechanism of the lipid- lowering activity of the fruit extracts is, however, still unknown. Our microarray analysis did not detect changes in the expression of the HMGCoA reductase gene, sug- gesting that the lipid-lowering activity is not through the inhibition of cholesterol biosynthesis. Our microarray data showed that amongst others, three genes that critically regulate lipid metabolism were differentially expressed: APOA4, APOA5, ABCG5 and MTTP. Apoliporotein A-V (ApoA-V) that is coded by APOA5 gene plays a vital role in the regulation of TG metabolism [43]. ApoA-V is thought to reduce TG levels by activating lipoprotein lipase (LPL), the enzyme that is responsible in catabolizing TG-rich lipoproteins, chylomicrons and VLDL, hence improving the clearance of these lipoproteins