Decreased Levels of Essential Amino Acids Following Bariatric Surgery May Reflect Altered Muscle Metabolism

Dustin M Bermudez, MD, John R Pender, MD, William H Chapman, MD, Walter J Pories, MD, G. L Dohm, PhD

Department of Surgery, Brody School of Medicine, East Carolina University,

Introduction:
We hypothesize that essential amino acid metabolism is altered following bariatric surgery and that this may reflect altered muscle metabolism. Previous studies have shown that muscle catabolism increases following bariatric surgery. Essential amino acids include phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, leucine, lysine, and histidine. All are acquired only through the diet.

Methods and Procedures:
Following IRB approval, 18 patients who underwent an antecolic, antegastric roux-en-y gastric bypass were included in this study. Following two weeks of a low calorie diet (Optifast), serologic testing was performed approximately 1 week preoperatively and 1 week and 3 months postoperatively. Patients were stratified prior to surgery as either “obese, non-diabetics” or “obese diabetics” based on fasting hyperglycemia in accordance with American Diabetes Association guidelines. Quantification of metabolites was performed using mass spectrometry.

Results:
The levels of isoleucine, leucine and valine were elevated more than two times control levels prior to surgery and dropped to normal levels at 3 months postoperatively in both obese, diabetic and obese, non-diabetics (p<0.05). Tyrosine, tryptophan, lysine, phenylalanine and methionine were not elevated prior to surgery compared to controls but dropped to less than half these levels in both groups (p<0.05). Threonine and histidine levels were not affected by surgery.

Conclusions:
The mechanism for resolution of diabetes following bariatric surgery remains a mystery. Our data demonstrate that a majority of the essential amino acid levels following surgery were dramatically lowered. This may be a result of decreased intake or decreased absorption. The precise mechanism by which this occurs merits further investigation.