The Effect Of DAAs on miRNA-122 And Insulin Resistance In Chronic HCV Patients

The hepatitis C virus (HCV) is an enveloped, single-stranded positive-sense Ribo-Nucleic Acid virus which is a major cause of chronic liver diseases, including cirrhosis and hepatocellular carcinoma (HCC), and infects approximately 3 % of the world population(150-170 million).

One of the countries most affected by HCV is Egypt. The Egyptian Demographic and Health Surveys measured antibody prevalence among the adult population aged 15-59 years at 14.7% in 2009 and at 10.0% in 2015 To attend to this challenge, Egypt developed a national strategy for Hepatitis C Virus control and established HCV prevention and treatment programs using Direct Acting-Antivirals (DAAs).

Egypt launched an ambitious national HCV treatment program aiming to treat over 250,000 chronically infected individuals per year, with the goal of achieving a national chronic infection prevalence of \<2% by 2025.

Although the consequences of chronic HCV infection are generally associated with liver manifestations such as hepatic fibrosis, cirrhosis, steatosis (known as non-alcoholic fatty liver disease, NAFLD) and HCC, the liver-related mortality of 350,000 individuals annually is still underestimated due to the lack of consideration of extrahepatic effect including a growing evidence showing that HCV infection is strongly associated with the dysregulation of glucose homoeostasis such as insulin resistance (IR) and type 2 diabetes (T2D).

HCV-related type 2 diabetes mellitus may arise from a complex interaction between IR, steatosis and inflammatory processes People infected with HCV are 4 times more likely to develop Type 2 Diabetes; and HCV-infected patients with uncontrolled glucose are at higher risk to develop advanced liver fibrosis, HCC, and exhibit decreased sustained virologic response (SVR) to traditional interferon treatment.

HCV protein NS5A and the core protein directly inhibit microsomal triglyceride transfer protein (MTP) activity, thereby reducing very low-density lipoprotein (VLDL) assembly and inducing hepatic steatosis.

Over time, accumulation of hepatic triglycerides leads to hepatic IR via decreased insulin-stimulated glycogen synthesis and enhanced hepatic gluconeogenesis; such conditions further cause peripheral IR in multiple organs through increased circulating insulin and free fatty acid levels.

Regarding the molecular mechanisms of regulation of insulin signaling by HCV infection. HCV core protein has been found to increase serine rather than tyrosine phosphorylation of IRS-1 ( insulin Receptor Substrate-1) in hepatocytes, resulting in its degradation and impaired downstream signaling Protien Kinase B signalling pathway.

HCV core protein also stimulates Insulin Receptor Substrate-1 serine phosphorylation via increasing mTOR (mammalian Target Of Rapamycin)levels, resulting in decreased Protien Kinase B signaling.

Reduced surface expression of glucose transporters GLUT1 and GLUT2 with consequential reduction in glucose uptake in HCV-infected hepatocytes has also been reported.

Despite these findings of IR development via direct effects on insulin signaling pathways, the complex relationship between intrahepatic HCV infection and extrahepatic IR remains elusive.

Several miRNAs have been determined to play a key role in regulating viral replication and pathogenesis during HCV infection.

Host miRNAs can be activated by viral integration in the host genome; viral miRNAs can target host mRNAs, , or host miRNAs can target viral mRNAs.

miR-122 expression is enriched in the liver, accounting for approximately 70 % of the total miRNA population in normal adult hepatocytes with approximately 66,000 copies per cell.

miR-122 has a role in the HCV replication cycle, where it binds to two target sites (S1 and S2) in the highly conserved 5' untranslated region of the HCV genome, thus forming a complex of HCV oligomeric miR-122 that protects the HCV genome from nucleolytic degradation as well as from the host innate immune response.

Many metabolic processes are potentially targeted by miR-122, including protein metabolism, carbohydrate metabolism, lipid metabolism and phospholipid metabolism. Signaling pathway ontology revealed several IR-related pathways [eg insulin/Insulin Growth Factor/Protien Kinase B signaling, Phosphoinositide 3-Kinase signaling, apoptosis, Epidermal Growth Factor receptor signaling,G protien-coupled receptors signaling pathway.

Antagonism of miRNA-122 not only reduces viral replication but also reduces HCV propagation by decreasing the expression of enzymes involved in lipid metabolism, which can enhance HCV replication in cell culture models.

miR-122 represents an interesting therapeutic target for the treatment of liver disease including viral hepatitis, fibrosis, steatosis and HCC. Experimental studies have elegantly demonstrated that a miR-122 inhibitor efficiently reduces viral load in chronically infected HCV patients without detectable resistance.