Anesthesia and bariatric surgery gut preparation alter plasma acylcarnitines reflective of mitochondrial fat and branched-chain amino acid oxidation.

The period around bariatric surgery offers a unique opportunity to characterize metabolism responses to dynamic shifts in energy, gut function, and anesthesia. We analyzed plasma acylcarnitines in obese women ( n = 17) sampled in the overnight fasted/postabsorptive state approximately 1-2 wk before surgery ( condition A ), the morning of surgery (prior restriction to a 48-h clear liquid diet coupled in some cases a standard polyethylene glycol gut evacuation: condition B ), and following induction of anesthesia ( condition C ). Comparisons tested if 1 ) plasma acylcarnitine derivatives reflective of fatty acid oxidation (FAO) and xenometabolism would be significantly increased and decreased, respectively, by preoperative gut preparation/negative energy balance ( condition A vs. B ), and 2 ) anesthesia would acutely depress markers of FAO. Acylcarnitines associated with fat mobilization and FAO were significantly increased in condition B : long-chain acylcarnitines (i.e., C18:1, ~70%), metabolites from active but incomplete FAO [i.e., C14:1 (161%) and C14:2 (102%)] and medium- to short-chain acylcarnitines [i.e., C2 (91%), R -3-hydroxybutyryl-(245%), C6 (45%), and cis -3,4-methylene-heptanoyl-(17%), etc.]. Branched-chain amino acid markers displayed disparate patterns [i.e., isobutyryl-(40% decreased) vs. isovaleryl carnitine (51% increased)]. Anesthesia reduced virtually every acylcarnitine. These results are consistent with a fasting-type metabolic phenotype coincident with the presurgical "gut preparation" phase of bariatric surgery, and a major and rapid alteration of both fat and amino acid metabolism with onset of anesthesia. Whether presurgical or anesthesia-associated metabolic shifts in carnitine and fuel metabolism impact patient outcomes or surgical risks remains to be evaluated experimentally.