Pheochromocytoma (PCC) and sympathetic paraganglioma (PGL) are rare neuroendocrine tumors characterized by catecholamine production in the adrenal medulla and extra-adrenal paraganglia. PCC and PGL (PPGL) with metastasis was termed malignant PPGL. However, the distinction between “benign” and “malignant” PPGLs has been debated. Currently, all PPGLs are believed to have some metastatic potential and are assigned malignant tumors (ICD-O/3) by the WHO Classification of Endocrine Organs (2017, 4th edition). Therefore, the previous categories benign and malignant PPGL have been eliminated in favor of risk stratification approach. The Grading of Adrenal Pheochromocytoma and Paraganglioma (GAPP) is a tool for risk stratification for predicting metastasis and the prognosis of patients. At least 30% of PPGLs are hereditary, with 20 genes identified and genotype-phenotype correlations clarified. Of these genes, VHL, RET and NF1 have been well investigated and are the primary cause of bilateral PCC. In addition, mutation of succinate dehydrogenase gene subunits SDHB and SDHD are strongly correlated with extra-adrenal location, younger age, multiple tumors, metastasis and poor prognosis. Disease stratification by catecholamine phenotype and molecular profiling correlates with histological grading by GAPP. PPGLs should be understood comprehensively based on clinical, biochemical, molecular and pathological data for patient care. A flow chart for pathological diagnosis is included.

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been rapidly increasing worldwide. A choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) has been used to create a mouse model of nonalcoholic steatohepatitis (NASH). There are some reports on the effects on mice of being fed a CDAHFD for long periods of 1 to 3 months. However, the effect of this diet over a short period is unknown. Therefore, we examined the effect of 1-week CDAHFD feeding on the mouse liver. Feeding a CDAHFD diet for only 1-week induced lipid droplet deposition in the liver with increasing activity of liver-derived enzymes in the plasma. On the other hand, it did not induce fibrosis or cirrhosis. Additionally, it was demonstrated that CDAHFD significantly impaired mitochondrial respiration with severe oxidative stress to the liver, which is associated with a decreasing mitochondrial DNA copy number and complex proteins. In the gene expression analysis of the liver, inflammatory and oxidative stress markers were significantly increased by CDAHFD. These results demonstrated that 1 week of feeding CDAHFD to mice induces steatohepatitis with mitochondrial dysfunction and severe oxidative stress, without fibrosis, which can partially mimic the early stage of NASH in humans.

Sunitinib is an oral multitargeted receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity that mainly targets vascular endothelial growth factor receptors (VEGFRs). Very recently, sunitinib has been shown to be an active agent for the treatment of malignant pheochromocytomas. However, it is unclear whether sunitinib acts only through an antiangiogenic mechanism or whether it may also directly target tumor cells. Sunitinib markedly induced apoptosis of PC12 cells in a dose-dependent and time-dependent manner. Furthermore, in support of these findings, we found that sunitinib induced a reduction in the expression of the antiapoptotic molecule Bcl-2 as well as dephosphorylation of the proapoptotic molecule BAD, which results in the activation of BAD in these cells. Consistent with these apoptotic effects, our results showed that sunitinib inhibited phosphorylation of Akt and mTOR and was followed by a reduction of S6K1, which is a well-known target of mTOR. Knockdown of VEGFR-2 attenuated the sunitinib-induced effects, including apoptosis and inhibition of signaling pathways such as the phosphorylation of Akt as well as mTOR, and Bcl-2, which confirmed that these effects could be mediated by VEGFR-2. In addition, silencing of S6K1 induced apoptosis accompanied by a decrease in the phosphorylation of BAD and Bcl-2, similar to that observed with sunitinib treatment. Thus, these results together suggest that sunitinib initially exerts its apoptotic effect through the inhibition of VEGFR-2, which, when followed by reduction of its downstream effectors, including Akt/mTOR/S6K1, may lead to inhibition of the antiapoptotic molecule Bcl-2 and activation of the proapoptotic molecule BAD in PC12 cells. However, PC12 cells do not precisely reflect the pathogenesis of malignant cells. Therefore, we confirmed the key findings by replicating these experiments in human neuroblastoma SK-N-SH cells.

Sunitinib is an oral multitargeted receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity that mainly targets vascular endothelial growth factor receptors, and recently, it has been shown to be an active agent for the treatment of malignant pheochromocytomas. Previously, we demonstrated that sunitinib directly inhibited mTORC1 signaling in rat pheochromocytoma PC12 cells. Although autophagy is a highly regulated cellular process, its relevance to cancer seems to be complicated. It is of note that inhibition of mTORC1 is a prerequisite for autophagy induction. Indeed, direct mTORC1 inhibition initiates ULK1/2 autophosphorylation and subsequent Atg13 and FIP200 phosphorylation, inducing autophagy. Here, we demonstrated that sunitinib significantly increased the levels of LC3-II, concomitant with a decrease of p62 in PC12 cells. Following sunitinib treatment, immunofluorescent imaging revealed a marked increased punctate LC3-II distribution. Furthermore, Atg13 knockdown significantly reduced its protein level, which in turn abolished sunitinib-induced autophagy. Moreover, inhibition of autophagy by siRNAs targeting Atg13 or by pharmacological inhibition with ammonium chloride, enhanced both sunitinib-induced apoptosis and anti-proliferation. Thus, sunitinib-induced autophagy is dependent on the suppression of mTORC1 signaling and the formation of ULK1/2–Atg13–FIP200 complexes. Inhibition of autophagy may be a promising therapeutic option for improving the anti-tumor effect of sunitinib.

The World Health Organization has recommended 5 g/day as dietary reference intakes for salt. In Japan, the averages for men and women were 11.0 g/day and 9.3 g/day, respectively. Recently, it was reported that amounts of sodium accumulation in skeletal muscles of older people were significantly higher than those in younger people. The purpose of this study was to investigate whether the risk of sarcopenia with decreased muscle mass and strength was related to the amount of salt intake. In addition, we investigated its involvement with renalase. Four groups based on age and salt intake (“younger low-salt,” “younger high-salt,” “older low-salt,” and “older high-salt”) were compared. Stratifying by age category, body fat percentage significantly increased in high-salt groups in both younger and older people. Handgrip strength/body weight and chair rise tests of the older high-salt group showed significant reduction compared to the older low-salt group. However, there was no significant difference in renalase concentrations in plasma. The results suggest that high-salt intake may lead to fat accumulation and muscle weakness associated with sarcopenia. Therefore, efforts to reduce salt intake may prevent sarcopenia.