GLYCINE DEFICIENCY IN ADULTS WITH MORBID OBESITY: IDENTIFYING THE DYSREGULATED METABOLIC PATHWAY AND EXAMINING ITS LINK WITH INSULIN RESISTANCE

Abstract

Glycine is a nutritionally non-essential amino acid and has significantly lower plasma concentration in individuals with obesity. However, the glycine metabolic pathway that is dysregulated in obesity is unknown. It is also unclear whether altered glycine metabolism in obesity is a cause or consequence of insulin resistance. To better understand glycine metabolism in obesity, I compared the glycine kinetic parameters between individuals with morbid obesity to controls with healthy weight using stable-isotope tracers. I also measured the changes in glycine kinetics in patients with morbid obesity undergoing bariatric surgery. Another group of individuals with morbid obesity was treated dietary glycine supplementation to explore whether correcting glycine “deficiency” improves insulin resistance. I found significantly impaired de novo glycine synthesis in individuals with morbid obesity. Dietary glycine supplementation corrected glycine deficiency but did not reduce insulin resistance. Impaired glycine metabolism in obesity is most likely a metabolic consequence of insulin resistance.