Tirzepatide: A New Generation Therapeutic for Diabetes Type 2.

Tirzepatide (mounjaro®) is a derivative of the human glucose-dependent insulinotropic polypeptide (GIP) hormone with a position-20 being modified with 1,20- eicosanedioic acid via a chemical linker. It acts as a glucagon-like peptide-1 (GLP-1) receptor and GIP receptor agonist. It has recently been approved by FDA as an adjunct therapy to exercise and diet to improve glycemic control in patients with type II diabetes mellitus (T2DM). It represents a new transforming paradigm in the management of T2DM. This mini-review will shed light on its different pharmacokinetic and pharmacodynamic aspects.

Activation of PERK-Nrf2 oncogenic signaling promotes Mdm2-mediated Rb degradation in persistently infected HCV culture.

The mechanism of how chronic hepatitis C virus (HCV) infection leads to such a high rate of hepatocellular carcinoma (HCC) is unknown. We found that the PERK axis of endoplasmic reticulum (ER) stress elicited prominent nuclear translocation of Nrf2 in 100% of HCV infected hepatocytes. The sustained nuclear translocation of Nrf2 in chronically infected culture induces Mdm2-mediated retinoblastoma protein (Rb) degradation. Silencing PERK and Nrf2 restored Mdm2-mediated Rb degradation, suggesting that sustained activation of PERK/Nrf2 axis creates oncogenic stress in chronically infected HCV culture model. The activation of Nrf2 and its nuclear translocation were prevented by ER-stress and PERK inhibitors, suggesting that PERK axis is involved in the sustained activation of Nrf2 signaling during chronic HCV infection. Furthermore, we show that HCV clearance induced by interferon-α based antiviral normalized the ER-stress response and prevented nuclear translocation of Nrf2, whereas HCV clearance by DAAs combination does neither. In conclusion, we report here a novel mechanism for how sustained activation of PERK axis of ER-stress during chronic HCV infection activates oncogenic Nrf2 signaling that promotes hepatocyte survival and oncogenesis by inducing Mdm2-mediated Rb degradation.

Chaperone-mediated autophagy compensates for impaired macroautophagy in the cirrhotic liver to promote hepatocellular carcinoma.

Macroautophagy and chaperone-mediated autophagy (CMA) represent two major lysosomal degradation processes and often compensate for one another to facilitate cell survival. The aim of this study was to determine whether these autophagy pathways could compensate for one another to promote HCC cell survival in the cirrhotic liver. Analysis of normal liver tissue showed no expression of glypican-3 or p62 proteins, suggesting that macroautophagy is the major contributor to autophagic flux under non-pathological conditions. Of 46 cirrhotic livers with HCC examined, 39 (84%) of HCCs showed increased expression of p62, and 36 (78%) showed increased expression of glypican-3, while adjacent non-tumorous hepatocytes were negative for expression of p62 and glypican-3, similar to normal liver tissue. These results suggest that macroautophagy flux is impaired in HCC. Furthermore, more than 95% of HCCs showed altered expression of LAMP-2A compared to the surrounding non-tumorous cirrhotic liver, consistent with induction of CMA in HCC. Elevated expression of glucose-regulated protein 78 (GRP78) and heat shock cognate protein (Hsc70) were detected in 100% of HCC and adjacent non-tumorous cirrhotic livers, suggesting that unresolved ER-stress is associated with HCC risk in liver cirrhosis. Interestingly, inhibition of lysosomal degradation using hydroxychloroquine (HCQ) induced expression of the tumor suppressor p53, promoted apoptosis, and inhibited HCC growth, whereas activation of autophagy using an mTOR inhibitor (Torin1) promoted HCC growth. Results of this study suggest that induction of CMA compensates for the impairment of macroautophagy to promote HCC survival in the cirrhotic liver.

Interferon-alpha-induced hepatitis C virus clearance restores p53 tumor suppressor more than direct-acting antivirals.

The mechanism why hepatitis C virus (HCV) clearance by direct-acting antivirals (DAAs) does not eliminate the risk of hepatocellular carcinoma (HCC) among patients with advanced cirrhosis is unclear. Many viral and bacterial infections degrade p53 in favor of cell survival to adapt an endoplasmic reticulum (ER)-stress response. In this study, we examined whether HCV clearance by interferon-alpha or DAAs normalizes the ER stress and restores the expression of p53 tumor suppressor in cell culture. We found that HCV infection induces chronic ER stress and unfolded protein response in untransformed primary human hepatocytes. The unfolded protein response induces chaperone-mediated autophagy (CMA) in infected primary human hepatocytes and Huh-7.5 cells that results in degradation of p53 and induced expression of mouse double minute 2 (Mdm2). Inhibition of p53/Mdm2 interactions by small molecule (nutlin-3) or silencing Mdm2 did not rescue the p53 degradation, indicating that HCV infection induces degradation of p53 independent of the Mdm2 pathway. Interestingly, we found that HCV infection degrades p53 in a lysosome-dependent mechanism because lysosome-associated membrane protein 2A silencing restored p53 degradation. Our results show that HCV clearance induced by interferon-alpha-based antiviral therapies normalizes the ER-stress response and restores p53, whereas HCV clearance by DAAs does neither. We show that decreased expression of p53 in HCV-infected cirrhotic liver is associated with expression of chaperones associated with ER stress and the CMA response. Conclusion: HCV-induced ER stress and CMA promote p53 degradation in advanced liver cirrhosis. HCV clearance by DAAs does not restore p53, which provides a potential explanation for why a viral cure by DAAs does not eliminate the HCC risk among patients with advanced liver disease. We propose that resolving the ER-stress response is an alternative approach to reducing HCC risk among patients with cirrhosis after viral cure. (Hepatology Communications 2017;1:256-269).