Furthermore, betulin was shown to inhibit the expression of some inflammatory factors that augment and sustain a tumorigenic environment, including IL-6 and TNF-α, in the colon tissues of experimental and control animals ^[57][85]. Other studies further demonstrated that betulin treatment inactivated the activity of protein kinase B (Akt)/mTOR signaling, which enhances other proapoptotic mediators ^{[43][55][56][58]}[72,83,84,86].

5. Protective Effects of Betulin on Liver Diseases

There are hundreds of liver diseases caused by viruses, toxins, genetic factors, alcohol, obesity, unknown causes, and other factors. Liver damage is a clinical manifestation that poses a life-threatening risk associated with a high mortality rate. Chronic diseases such as diabetes can also progressively affect the liver, thereby impairing liver function. Ample evidence has shown the beneficial effect of betulin on hepatic damage, with its spectrum of activities ranging from inhibition of SREBP-1 to upregulation of Sirt1, to reduction of NFκB signaling, etc. Since sustained excessive alcohol use can deteriorate the liver’s condition, researchers have modeled this disease pathology by inducing steatohepatitis via ethanol administration. Previous work showed that betulin (100 mg/kg b.wt.) attenuated steatosis, inflammation, and fibrosis in the liver of rats fed chronically with ethanol. The study also showed that betulin treatment could significantly improve histopathological signs of steatohepatitis, reduce liver function markers (AST and ALT) and liver and serum triglyceride levels, and restore redox imbalance by increasing GSH content and decreasing superoxide anions and TBARs concentration ^[59][60][87,88]. Similarly, another study demonstrated that betulin exerts hepatoprotective effects on alcohol-induced liver damage in mice through the Sirt1/LKB1/AMPK signaling pathway by inhibiting ethanol-induced activation of SREBP-1 and NFκB ^[61][89]. Szuster-Ciesielska et al. reported that betulin treatment inhibited the production of superoxide anions, procollagen type I, MMP-2, TIMP-1, and -2, α-SMA, and cells’ motility in acetaldehyde-induced toxicity in rat hepatic stellate cells (CFSC-2G cells) ^[62][90]. Furthermore, another study revealed that betulin decreased serum levels of ALT, AST, and triglycerides; inhibited EtOH-induced acidophilic necrosis; ameliorated liver histopathological changes; significantly decreased activity of CYP2E1 and expression of SREBP-1; markedly lessened the expression of TLR4; and improved phosphorylation of STAT3 in vitro and in vivo ^[63][91]. Elsewhere, betulin, betulinic acid, and oleanolic acid (1 μM each) were investigated for their hepatoprotective activity against ethanol-induced cytotoxicity in HepG2 cells, with betulin being the most active protectant of HepG2 cells against ethanol-induced cytotoxicity ^[64][92]. Another study proposed that betulin limited fibrosis formation and attenuated cisplatin-stimulated hepatic damage in rats by targeting apoptosis and NEK7-independent NLRP3 inflammasome pathways ^[65][66][93,94]. In addition, betulin mitigated increased levels of inflammatory factors, including IL-1α, IL-1β, IL-6, IL-18, TNF-α, TGF-β, and MMP2 in ethanol-induced liver stellate cells and chronic EtOH-treated rodents ^{[59][60][66][67]}[87,88,94,95]. The hepatoprotective effects of betulin as well as its potential molecular pathways are briefly elucidated in Table 2, showing the concentration and dose of administration of betulin.

Experimental Model		Dose/Concentration	Pharmacological Indicators	Mechanism of Action	References
-	Wistar Rats (Ethanol-induced alcoholic steatohepatitis 4 g/kg for 8 weeks)	50 and 100 mg/kg b.wt.	TG ↓ ALP ↓ AST ↓ ALT ↓ TNF-α ↓ IL-1β ↓ TGF-β ↓ TBARs ↓ GSH ↑ ROS ↓	None	[60][88]
Hepatic stellate cells (LX-2 cells) ethanol 50 mM)	Male C57BL/6 mice (Ethanol 5 g/kg b.wt. 10 days)	6.25–25 μM 20 and 50 mg/kg	SREBP1 ↓ TG ↓ ALT ↓ AST ↓ p65 ↓ collagen-I ↓ α-SMA ↓	Sirt1/LKB1/AMPK signaling pathway	[61][89]
AML-12 cells (Ethanol 50 mM)	Male C57BL/6 mice (5 g/kg b.wt. EtOH for 4 weeks)	0–25 μM 20 and 50 mg/kg	SREBP 1 ↓ Lipin1 ↓ Lipin2 ↑ ALT ↓ AST ↓ IL-1α ↓ TG ↓ PPAR-α ↑ FASN ↓ PPAR-γ ↓ IL-1β↓ IL-6 ↓ TNF-α ↓ IL-18 ↓ caspase-1 ↓	blocking of P2X7/NLRP3 signaling pathway	[66][94]
Hepatic stellate cells (HSC-T6, EtOH 50 mM)	Male C57BL/6 mice (EtOH 5 mg/kg)	12.5–25 μM 20 or 50 mg/kg	ALT ↓ AST ↓ TG ↓ CYP2E1 ↓ SREBP-1c ↓ TLR4 ↓ p-STAT3 ↑ Collagen-I ↓ α-SMA ↓	TLR4 and STAT3 pathway	[63][91]
Rat liver stellate cell CFSC-2G (EtOH 50 mM)	-	10 μM	procollagen I ↓ TNF-α ↓ MMP2 ↓ TGF-β ↓ TIMP1/2 ↓ α-SMA ↓	inhibited NFκB and MAPKs signaling pathway	[67][95]
-	LPS/D-galactosamine-induced acute liver injury BALB/c mice	2–8 mg/kg b.wt.	MPO ↓ AST ↓ ALT ↓ TNF-α ↓ IL-1β ↓ PPARγ ↑	inhibiting the NFκB signaling pathway	[59][87]
Con A-stimulated splenocytes	Concanavalin A-challenged C57BL/6J mice	0–32 μg/mL 20 mg/kg	IFN-γ ↓ IL-4 ↓ IL-6 ↓ IL-10 ↓ IL-17 ↓ IL-2 ↓ ALT ↓ AST ↓ TNF-α ↓	None	[68][26]
-	Sprague Dawley rats (Cisplatin 10 mg/kg)	8 mg/kg	caspase 3 ↓ caspase 9 ↓ tBilirubin↓ albumin ↑ caspase 8 ↓ MDA ↓ TAC ↑ IL-1 ↓ AST ↓ ALT ↓ caspase 1 ↓ p53 ↓ Bax ↓ Bcl-2 ↑	NLRP3 pathway	[65][93]