ER Stress in NAFLD

The investigators overall hypothesis is that exacerbation of endoplasmic reticulum (ER) stress in the liver is associated with significant alterations in phosphatidylcholines that drive the NASH phenotype in obese humans. The investigators plan to examine this hypothesis in a well-characterized cohort of obese subjects that are scheduled for bariatric surgery. Methyl-D9-choline chloride will be infused before and after a 2-week high fructose or glucose feeding to determine the biosynthesis and kinetics of secretory lipoprotein phospholipids. It is proposed that phospholipid metabolism play an important role in the pathogenesis or etiology of fatty liver in non-alcoholic conditions through mechanisms that invoke ER and oxidative stress responses.