# The Effects of Polyphenol-Rich Black Elderly on Oxidative Stress and Hepatic Cholesterol Metabolism
## 4 Discussion  
CVD and its associated metabolic diseases are the primary health problem worldwide, and one effective strategy for the prevention of CVD is targeting hypolipidemia [3]. Herbal medicines and natural compounds with antioxidant and anti-inflammatory properties are claimed to be effective for preventing these diseases [38; 39]. Cellular cholesterol regulation is associated with plasma cholesterol levels and is essential to avoiding hypercholesterolemia and hypertriglyceridemia [40]. Black elderberry and its bioactive components, polyphenols and anthocyanins, are well known for their potent effects on oxidative stress and inflammation [23; 24; 25; 26; 27; 28; 41]. However, little is known about whether black elderberry has effects on hepatic cholesterol metabolism. In the present study, the protective effects of BEE on oxidative stress and hepatic cholesterol metabolism were investigated using an in vitro assay and HepG2 cells. Consistent with previous studies about the antioxidant effect of black elderberry, we confirmed the antioxidant effects of BEE by DPPH and ABTS radical scavenging effect and reducing power [25; 26]. SREBPs are the master regulator of lipid homeostasis [42]. SREBP2 regulates genes for cholesterol metabolism, whereas SREBP1c regulates the lipogenic genes [42]. SREBP-2,  
Figure 5: The effects of BEE on the regulation of HDACs in HepG2 cells. The cells were treated with 100 \(\mathrm{\SIUnitSymbolMicro g}\)/mL of BEE for 24 h. The expression of HDAC isoforms was measured by qRT-PCR. Data are expressed as relative expressions of control. Different letters indicate significant differences (\(p<0.05\)). Values are means \(\pm\) S.E.M. n = 6. Figure 6: The effects of BEE on the alteration of SIRTs in HepG2 cells. The cells were treated with 100 \(\mathrm{\SIUnitSymbolMicro g}\)/mL of BEE for 24 h. The expression of SIRT isoforms was measured by qRT-PCR. Data are expressed as relative expressions of control. Different letters indicate significant differences (\(p<0.05\)). Values are means \(\pm\) S.E.M. n = 6.  
the transcription factor for cholesterol metabolism, can modulate the expression of genes for cholesterol biosynthesis and uptake, i.e., HMGR and LDLR, in response to cellular cholesterol levels [43]. SREBP2 is regulated by two essential membrane proteins: SREBPP-cleavage activating protein (SCAP) and an insulin-induced gene(INSIG). The inactive SREBPP2 precursor is present in the endoplasmic reticulum, with association with SCAP and INSIG. When cellular cholesterol is deprived, SCAP undergoes conformational changes and dissociates from INSIG, and it facilitates the transport of SREBPP2 to the Golgi apparatus as the initial step in SREBPP2 activation. SREBPP2 proteins are cut by Golgi-specific S1P and S2P proteases, producing a mature transcriptionally active SREBPP fragment that is subsequently translocated to the sterol regulatory element of the nucleus [43; 44]. With the response of cellular cholesterol levels, SREBPP2 can induce HMGR and LDLR. statins are a commonly prescribed medication for CVD prevention, and they inhibit HMGR, the rate-controlling enzyme for de novo synthesis of cholesterol. Hepatic LDLR and LRP1 play a prominent role in the clearance of cholesterol-abundant apoE containing lipoproteins [45]. In the present study, there was a significant reduction in the genes involved in cholesterol biosynthesis and uptake. BEE inhibited SREBPP2 maturation, followed by decreases in HMGR and LDLR abundance. Consistent with our results, luteolin and barley sprout extract containing polyphenols significantly downregulated SREBPP2 and HMGR expression [46; 47]. In high-fat diet-induced hyperlipidemia mice, raspberry extract rich in anthocyanins modulated cholesterol metabolism by inhibiting HMGR and LDLR [48]. These results support the finding that polyphenols in BEE may be responsible for the downregulation of SREBPP2 with concomitant reductions in HMGR and LDLR in the liver.