Silibinin: an old drug in the high tech era of liver transplantation

The favorable impacts of silibinin polyphenols as adjunctive therapy in reducing the complications of COVID-19: A review of research evidence and underlying mechanisms

The proceeding pandemic of coronavirus disease 2019 is the latest global challenge. Like most other infectious diseases, inflammation, oxidative stress, and immune system dysfunctions play a pivotal role in the pathogenesis of COVID-19. Furthermore, the quest of finding a potential pharmaceutical therapy for preventing and treating COVID-19 is still ongoing. Silymarin, a mixture of flavonolignans extracted from the milk thistle, has exhibited numerous therapeutic benefits. We reviewed the beneficial effects of silymarin on oxidative stress, inflammation, and the immune system, as primary factors involved in the pathogenesis of COVID-19. We searched PubMed/Medline, Web of Science, Scopus, and Science Direct databases up to April 2022 using the relevant keywords. In summary, the current review indicates that silymarin might exert therapeutic effects against COVID-19 by improving the antioxidant system, attenuating inflammatory response and respiratory distress, and enhancing immune system function. Silymarin can also bind to target proteins of SARS-CoV-2, including main protease, spike glycoprotein, and RNA-dependent RNA-polymerase, leading to the inhibition of viral replication. Although multiple lines of evidence suggest the possible promising impacts of silymarin in COVID-19, further clinical trials are encouraged.

Highly bioavailable silibinin nanoparticles inhibit HCV infection

OBJECTIVE

Silibinin is a flavonolignan that is well established for its robust antiviral activity against HCV infection and has undergone several clinical trials for the management of hepatitis C. Despite its potency, silibinin suffers from poor solubility and bioavailability, restricting its clinical use. To overcome this limitation, we developed highly bioavailable silibinin nanoparticles (SB-NPs) and evaluated their efficiency against HCV infection.

DESIGN

SB-NPs were prepared using a nanoemulsification technique and were physicochemically characterised. Infectious HCV culture systems were used to evaluate the influence of SB-NP on the virus life cycle and examine their antioxidant activity against HCV-induced oxidative stress. The safety profiles of SB-NP, in vivo pharmacokinetic studies and antiviral activity against infection of primary human hepatocytes were also assessed.

RESULTS

SB-NP consisted of nanoscale spherical particles (<200 nm) encapsulating amorphous silibinin at >97% efficiency and increasing the compound's solubility by >75%. Treatment with SB-NP efficiently restricted HCV cell-to-cell transmission, suggesting that they retained silibinin's robust anti-HCV activity. In addition, SB-NP exerted an antioxidant effect via their free radical scavenging function. Oral administration of SB-NP in rodents produced no apparent in vivo toxicity, and pharmacokinetic studies revealed an enhanced serum level and superior biodistribution to the liver compared with non-modified silibinin. Finally, SB-NP efficiently reduced HCV infection of primary human hepatocytes.

CONCLUSIONS

Due to SB-NP's enhanced bioavailability, effective anti-HCV activity and an overall hepatoprotective effect, we suggest that SB-NP may be a cost-effective anti-HCV agent that merits further evaluation for the treatment of hepatitis C.

Treatment of hepatitis C virus recurrence after transplantation with sofosbuvir/ledipasvir: The role of ribavirin

BACKGROUND

Hepatitis C virus (HCV) recurrence after liver transplantation (LT) used to be a serious problem in the era of interferon-based treatment. Since the introduction of modern directly acting antivirals, treatment has become easier and shorter. According to published data, in the natural course of hepatitis C infection the duration of antiviral treatment with sofosbuvir (SOF) and ledipasvir (LDV) may be shortened to 12 instead of 24 weeks, using ribavirin (RBV) in addition. Furthermore, the question of whether or not RBV is really necessary, in a 12-week SOF/LDV treatment in the post-transplant setting, is still unanswered.

PATIENTS AND METHODS

At our institution, 100 liver transplant patients with HCV recurrence underwent interferon-free SOF-based treatment. A total of 51 patients received SOF/LDV with or without RBV. Twenty-nine HCV genotype 1 or 4 patients with histologically proven stage 0-2 fibrosis were treated with SOF/LDV for 12 weeks; another 22 patients with advanced fibrosis (stage 3-4) either received SOF/LDV plus weight-adjusted RBV or prolonged treatment for 24 weeks.

RESULTS

End of treatment response and sustained virological response (SVR) were achieved in 100% of the 51 patients, irrespective of the treatment group. Patients with prolonged treatment duration or with RBV developed significantly more adverse events (AEs) compared to the SOF/LDV group: 19 (86.4%) vs 8 (27.6%), P<.001. One of the predominant and most relevant AEs was the development of anemia in 43.1% of 10 patients receiving RBV, which was a significant result (P<.001). RBV co-medication had to be reduced in 11 (55%) patients and then stopped in 8 (40%) patients because of AEs. No significant difference was observed among the groups regarding kidney function.

CONCLUSION

The SOF/LDV combination is a reliable therapy of recurrent HCV infection after LT. It is easy to administer and to achieve SVR in immunocompromised patients without interactions with immunosuppressive medications. Considering the high rate of AEs, frequent discontinuation of RBV treatment, and the 100% SVR, the use of RBV as co-medication in a 12-week SOF/LDV regimen does not seem to be justified after LT.

Positive Effects of Different Drug Forms of Silybin in the Treatment of Metabolic Syndrome

Silymarin and silybin are widely used for their hepatoprotective properties. Our previous studies confirm positive effect of silymarin on lipoprotein profile and lipid homeostasis. Advanced drug forms may improve the bioavailability of these compounds. In this study, we investigate the effects of silybin in different drug forms (standardized silybin, micronized silybin, and silybin in form of phytosomes) on dyslipidemia and glucose metabolism in hereditary hypertriglyceridemic (HHTg) rats. Male HHTg rats were divided into four groups of seven animals and were fed by experimental diets. Silybin significantly decreased serum level of triglycerides in groups of rats fed by standardized silybin and silybin in form of phytosomes compared to control group. Results show that silybin did not affect the total cholesterol level, but significantly increased the levels of HDL cholesterol in all groups of animals. Silybin in a standardized form had the highest hypotriglyceridemic effect. On the other hand, the micronized form has caused the highest increase of protective HDL and most significantly decreased glucose and insulin levels. Our results suggest that silybin is probably responsible for some positive properties of silymarin. Subsequent dose-dependent studies of silybin action may reveal the intensity of its positive effects on lipid and glucose parameters.

Herbal products and the liver: a review of adverse effects and mechanisms

Herbal products have been used for centuries among indigenous people to treat symptoms and illnesses. Recently, their use in Western countries has grown significantly, rivaling that of prescription medications. Currently, herbal products are used mainly for weight loss and bodybuilding purposes but also to improve well-being and symptoms of chronic diseases. Many people believe that because they are natural, they must be effective and safe; however, these beliefs are erroneous. Few herbal products have been studied in well-designed controlled trials of patients with liver or other diseases, despite testimony to the contrary. Moreover, current highly effective antiviral drugs make efforts to treat hepatitis C with herbal products redundant. Herbal products are no safer than conventional drugs and have caused liver injury severe enough to require transplantation or cause death. Furthermore, their efficacy, safety, and claims are not assessed by regulatory agencies, and there is uncertainty about their reported and unreported contents. We review the history of commonly used herbal products, as well as their purported efficacies and mechanisms and their adverse effects.

The therapeutic potential of milk thistle in diabetes

Milk thistle has been known for more than 2.000 years as a herbal remedy for a variety of disorders. It has mainly been used to treat liver and gallbladder diseases. Silibum marianum, the Latin term for the plant, and its seeds contain a whole family of natural compounds, called flavonolignans. Silimarin is a dry mixture of these compounds; it is extracted after processing with ethanol, methanol, and acetone. Silimarin contains mainly silibin A, silibin B, taxifolin, isosilibin A, isosilibin B, silichristin A, silidianin, and other compounds in smaller concentrations. Apart from its use in liver and gallbladder disorders, milk thistle has recently gained attention due to its hypoglycemic and hypolipidemic properties. Recently, a substance from milk thistle has been shown to possess peroxisome proliferator-activated receptor γ (PPARγ) agonist properties. PPARγ is the molecular target of thiazolidinediones, which are used clinically as insulin sensitizers to lower blood glucose levels in diabetes type 2 patients. The thiazolidinedione type of PPARγ ligands is an agonist with a very high binding affinity. However, this ligand type demonstrates a range of undesirable side effects, thus necessitating the search for new effective PPARγ agonists. Interestingly, studies indicate that partial agonism of PPARγ induces promising activity patterns by retaining the positive effects attributed to the full agonists, with reduced side effects. In this review, the therapeutic potential of milk thistle in the management of diabetes and its complications are discussed.