# Polyphenol-Rich Black Elderberry Extract Stimulates Transintestinal Cholesterol Excretion
## 1 Introduction  
Cardiovascular disease (CVD) is one of the largest causes of mortality worldwide. Hypercholesterolem and hypertriglyceridemia are significant risk factors for CVD [1]. Cholesterol synthesis and absorption are critical factors for plasma cholesterol concentration [2; 3]. Common medications used to treat or reduce hypercholesterolemia targeting target blocking hepatic cholesterol synthesis or intestinal cholesterol absorption [4]. The liver is known as a primary site for the regulation of cholesterol metabolism. It plays a central role in de novo cholesterol synthesis, assembly, and uptake of cholesterol-containing lipoprotein, with conversion of cholesterol to bile acids for the secretion of biliary cholesterols [3; 4]. Therefore, most of the studies about the regulation of cholesterol homeostasis have focused on the liver [4; 5]. The intestine contributes to cholesterol balance by absorbing dietary and biliary cholesterol, and the role of the intestine in cholesterol net balance regulation has been underestimated [6; 7; 8; 9; 10; 11]. Hepatobiliary excretion through high-density lipoprotein (HDL)-driven reverse cholesterol transport has been widely accepted as the only way to remove cholesterol from the body [3; 12]. Recent studies have revealed a non-biliary pathway for cholesterol excretion, i.e., the transintestinal cholesterol excretion (TICE) pathway [13; 14; 15]. In TICE, cholesterol is directly transported into enterocytes from circulation and subsequently excreted into the intestinal lumen [16; 17; 18]. Effective medications for stimulation of hepatobiliary excretion can lower hypercholesterolemia Puer increase gallstone formation [19]. Therefore, targeting the intestine for non-biliary cholesterol excretion to reduce hypercholesterolemia using dietary components or nutrients offers an attractive strategy for preventing CVD.  
Black elderberry (_Sambucus nigra_) contains a relatively high amount of polyphenols, especially anthocyanin [20]. It is commonly used in Europe and North America as a folk medicine to support immune function and to treat stomach ache, constipation, and diarrhea [21]. In vitro, animal, and clinical trials reported the health benefits of black elderberries for prevention of chronic disease [22; 23; 24; 25; 26; 27; 28; 29; 30]. Black elderberry is widely used in the food and nutraceutical industries as an antioxidant and anti-inflammatory agent [20; 21]. Polyphenols have been suggested as a bioactive component to reduce CVD risk by attenuating oxidative stress, inflammation, and hypercholesterolemiaaemia [31; 32; 33; 34; 35; 36]. Black elderberry rich in polyphenols exerted protective effects on hyperlipidemia [22; 23]. Black elderberry attenuated inflammation and obesity-related complications in diet-induced obese mice [22]. Furthermore, black elderberry improved HDL function and reduced aortic cholesterol in apoE knockout mice [23]. However, little is known about the effects of polyphenol-rich black elderberry (BEE) on intestinal cholesterol metabolism. Polyphenol-abundant natural products, i.e., black chokeberry and blackcurrant, altered the genes involved in intestinal cholesterol metabolism in the direction of stimulating the TICE pathway, with the flux of cholesterol from the basolateral to apical side of enterocytes [37; 38]. In the present study, we investigated whether BEE could exert hypocholesterolem effects by regulating genes involved in the intestinal cholesterol flux using Caco-2 cells.