2-Hydroxylation of Fatty Acids Represses Colorectal Tumorigenesis and Metastasis via the YAP Transcriptional Axis.

Alteration in lipid composition is an important metabolic adaptation by cancer cells to support tumorigenesis and metastasis. Fatty acid 2-hydroxylase (FA2H) introduces a chiral hydroxyl group at the second carbon of fatty acid (FA) backbones and influences lipid structures and metabolic signaling. However, the underlying mechanisms through which FA 2-hydroxylation is coupled to metabolic adaptation and tumor growth remain elusive. Here, we show that FA2H regulates specific metabolic reprogramming and oncogenic signaling in the development of colorectal cancer. FA2H is highly expressed in normal colorectal tissues. Assessments through deciphering both published high-throughput data and curated human colorectal cancer samples revealed significant suppression of FA2H in tumors, which is correlated with unfavorable prognosis. Experiments with multiple models of genetic manipulation or treatment with an enzymatic product of FA2H, (R)-2-hydroxy palmitic acid, demonstrated that FA 2-hydroxylation inhibits colorectal cancer cell proliferation, migration, epithelial-to-mesenchymal transition progression, and tumor growth. Bioinformatics analysis suggested that FA2H functions through AMP-activated protein kinase/Yes-associated protein (AMPK/YAP) pathway, which was confirmed in colorectal cancer cells, as well as in tumors. Lipidomics analysis revealed an accumulation of polyunsaturated fatty acids in cells with FA2H overexpression, which may contribute to the observed nutrient deficiency and AMPK activation. Collectively, these data demonstrate that FA 2-hydroxylation initiates a metabolic signaling cascade to suppress colorectal tumor growth and metastasis via the YAP transcriptional axis and provides a strategy to improve colorectal cancer treatment. SIGNIFICANCE: These findings identify a novel metabolic mechanism regulating the tumor suppressor function of FA 2-hydroxylation in colorectal cancer.

Excess diacylglycerol at the endoplasmic reticulum disrupts endomembrane homeostasis and autophagy.

BACKGROUND: When stressed, eukaryotic cells produce triacylglycerol (TAG) to store nutrients and mobilize autophagy to combat internal damage. We and others previously reported that in yeast, elimination of TAG synthesizing enzymes inhibits autophagy under nitrogen starvation, yet the underlying mechanism has remained elusive. RESULTS: Here, we show that disruption of TAG synthesis led to diacylglycerol (DAG) accumulation and its relocation from the vacuolar membrane to the endoplasmic reticulum (ER). We further show that, beyond autophagy, ER-accumulated DAG caused severe defects in the endomembrane system, including disturbing the balance of ER-Golgi protein trafficking, manifesting in bulging of ER and loss of the Golgi apparatus. Genetic or chemical manipulations that increase consumption or decrease supply of DAG reversed these defects. In contrast, increased amounts of precursors of glycerolipid synthesis, including phosphatidic acid and free fatty acids, did not replicate the effects of excess DAG. We also provide evidence that the observed endomembrane defects do not rely on Golgi-produced DAG, Pkc1 signaling, or the unfolded protein response. CONCLUSIONS: This work identifies DAG as the critical lipid molecule responsible for autophagy inhibition under condition of defective TAG synthesis and demonstrates the disruption of ER and Golgi function by excess DAG as the potential cause of the autophagy defect.

An improved pseudotargeted GC-MS/MS-based metabolomics method and its application in radiation-induced hepatic injury in a rat model.

The liver is the pivotal metabolic organ primarily responsible for metabolic activities, detoxification and regulation of carbohydrate, protein, amino acid, and lipid metabolism. However, very little is known about the complicated pathophysiologic mechanisms of liver injury result from ionizing radiation exposure. Therefore, a pseudotargeted metabolomics approach based on gas chromatography-tandem mass spectrometry with selected reaction monitoring (GC-MS-SRM) was developed to study metabolic alterations of liver tissues in radiation-induced hepatic injury. The pseudotargeted GC-MS-SRM method was validated with satisfactory analytical characteristics in terms of precision, linearity, sensitivity and recovery. Compared to the SIM-based approach, the SRM scanning method had mildly better precision, higher sensitivity, and wider linear ranges. A total of 37 differential metabolites associated with radiation-induced hepatic injury were identified using the GC-MS-SRM metabolomics method. Global metabolic clustering analysis showed that amino acids, carbohydrates, unsaturated fatty acids, organic acids, metabolites associated with pyrimidine metabolism, ubiquinone biosynthesis and oxidative phosphorylation appeared significantly declined after high dose irradiation exposure, whereas metabolites related to lysine catabolism, glycerolipid metabolism and glutathione metabolism presented the opposite behavior. These changes indicate energy deficiency, antioxidant defense damage, accumulation of ammonia and lipid oxidation of liver tissues in response to radiation exposure. It is shown that the developed pseudotargeted method based on GC-MS-SRM is a useful tool for metabolomics study.

Partial portacaval shunt with H-grafts to treat portal hypertension.

Partial portosystemic shunts have been popularized because of a reported low rate of mortality and morbidity (especially encephalopathy, liver failure and occlusion). The results of partial portacaval shunts [small-diameter expanded polytetrafluoroethylene (ePTFE) H-graft portacaval shunt] were retrospectively reviewed to evaluate the clinical efficacy in the treatment of portal hypertension. Forty-three patients with portal hypertension were treated by small-diameter H-graft of ePTFE portacaval shunt from May 1995 to April 2006. Thirty-three had externally ringed grafts and ten had non-ringed ones. Ten had grafts of 10 mm in diameter and 33 had grafts of 8 mm. The left gastric artery and coronary vein were ligated in all the cases. Six had pericardial devascularization and splenectomy was performed in 42. An average decrease of free portal pressure (FPP) from (33.24 ± 4.78) cmH2O before shunting and (13.65 ± 5.65) cmH2O after shunting was observed. The portal blood flow was reduced by one-third of that before shunt. Thirty-eight patients survived and no upper gastro-intestinal rebleeding occurred in the follow-up period (50.5 months in average). Two were out of contact. Color Doppler ultrasonography and/or portography revealed the shunts were patent in 38 cases and were occluded in three cases (3/41, 7.3%). Encephalopathy developed in five cases (5/41, 12.2%). Partial (small-diameter ePTFE H-graft) portacaval shunting can reduce the portal pressure effectively. Majority of the hepatic flow from the portal vein can be maintained adequately. The shunts with reinforced grafts can keep a higher rate of patency. The morbidity of encephalopathy was lower than those with total shunt. The partial portacaval shunt is effective in preventing recurrent variceal bleeding.

Small-diameter prosthetic H-graft portacaval shunts in the treatment of portal hypertension.

BACKGROUND: Portasystemic shunts, especially total shunts, are effective tools for reducing portal pressure and controlling variceal bleeding but lead to high risk of encephalopathy and accelerating liver failure. The purpose of this study is to evaluate the clinical effects of small-diameter expanded polytetrafluoroethylene (ePTFE) H-graft portacaval shunts in the treatment of portal hypertension. METHODS: Thirty-one patients with portal hypertension were treated with ePTFE small-diameter H-graft portacaval shunts from December 1995 to April 2002. Twenty-one had externally ringed grafts and 10 had non-ringed grafts; 20 had 10 mm diameter grafts and 11 had 8 mm grafts. The left gastric artery and coronary vein were ligated in 22 patients. Additionally, 6 patients underwent pericardial devascularization, and splenectomies were performed on 30 patients. RESULTS: An average decrease of free portal pressure (FPP) from (32.13 +/- 4.86) cmH2O before shunting to (12.55 +/- 5.57) cmH2O after shunting was observed. Portal blood flow was reduced by 1/3 compared with the levels measured before shunting. Twenty-eight patients survived after the operation, and no upper gastrointestinal rebleeding occurred in the follow-up period (40.2 months on average). We lost contact with one patient. Color Doppler ultrasonography and/or portography revealed the shunts to be patent in 28 cases and occluded in 2 (6.4%) cases. Encephalopathy developed in 4 patients (12.9%). CONCLUSION: Small-diameter ePTFE H-graft portacaval shunts can effectively reduce portal pressure. Moreover, the majority of the hepatopetal flow from the portal vein can be adequately maintained. The reinforced shunts may achieve a higher rate of patency. Morbidity from encephalopathy was less frequent than in patients receiving total shunts. Small-diameter H-graft portacaval shunts are also effective in preventing recurrent variceal bleeding.