No abstract

Vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) are the most common surgical options for the treatment of obesity and metabolic disorder. Whereas RYGB may result in greater and more durable weight loss, recent clinical and pre-clinical studies in rats have raised concerns that RYGB surgery may increase risk for alcohol use disorder (AUD). In contrast, recent clinical reports suggest a lesser risk for AUD following VSG, although no preclinical studies have been done to confirm that. Therefore, the present study sought to determine the effects of VSG on ethanol intake and preferences in rodent models using protocols similar to those previously used in animal studies for RYGB. Male Sprague Dawley rats and male C57B6 mice were made obese on a high fat diet (60%kcal from fat) and received VSG or no surgery (controls). All animals then were given access to increasing concentrations of ethanol (2%, 4%, 6%, and 8%), presented for few days each. Compared to controls, VSG rats consumed significantly less of 2, 6 and 8% ethanol and showed significantly reduced preferences to 6 and 8% ethanol over water. VSG mice also displayed reduced intake and preference for 6 and 8% ethanol solutions. After a two-week period of forced abstinence, 8% ethanol was reintroduced and the VSG rats and mice continued to exhibit reduced consumption and less preference for ethanol. Regarding the underlying mechanism, we hypothesized that the removal of the ghrelin producing part of the stomach in the VSG surgery is a possible contributor to the observed reduced ethanol preference. To test for functional changes at the ghrelin receptors, the VSG and control rats were given IP injections of acyl-ghrelin (2.5nmol and 5nmol) prior to ethanol access. Neither concentration of ghrelin resulted in a significant increase in 8% ethanol consumption of VSG or control subjects. Next, the rats were given IP injections of the ghrelin receptor antagonist, JMV (2.5mg/kg body weight). This dose induced a significant reduction in 8% ethanol consumption in the VSG group, but no effect on ethanol intake in the controls. While ghrelin injection was uninformative, increased sensitivity to subthreshold doses of the ghrelin receptor antagonist may indicate reduced ghrelin signaling following VSG. Overall, these findings suggest that bariatric patients with increased susceptibility to AUD may benefit from receiving VSG instead of RYGB surgery, and that changes in ghrelin signaling, at least in part, may play a role in the differential AUD risks between the two most commonly performed bariatric surgical procedures.

Roux-en-Y gastric bypass (RYGB) surgery is a commonly performed and very effective method to achieve significant, long-term weight loss. Opioid analgesics are primarily used to manage postoperative pain as fewer alternative medication options are available for bariatric surgery patients than for the general population. Recent clinical studies support a greater risk for substance use following bariatric surgery, including an increased use of opioid medications. The present study is the first to study morphine self-administration in a rat model of RYGB. High fat diet-induced obese (HFD-DIO) rats underwent RYGB (n=14) or sham-surgery with ad libitum HFD (SHAM, n=14) or a restricted amount that resulted in weight matched to the RYGB cohort (SHAM-WM, n=8). An additional normal-diet (ND, n=7), intact (no surgery) group of rats was included. Two months after the surgeries, rats were fitted with jugular catheters and trained on a fixed ratio-2 lick task to obtain morphine intravenously. Both morphine-seeking (number of licks on an empty spout to obtain morphine infusion) and consumption (number of infusion) were significantly greater in RYGB than any control group beginning on Day 3 and reached a two-fold increase over a period of two weeks. These findings demonstrate that RYGB increases motivation for taking morphine and that this effect is independent of weight loss. Further research is warranted to reveal the underlying mechanisms and to determine whether increased morphine use represents a risk for opioid addiction following RYGB. Identifying risk factors preoperatively could help with personalized postoperative care to prevent opioid abuse and addiction.