A Longer Biliopancreatic Limb and Shorter Common Channel Enhance Weight Loss But May Have Harmful Effects in Mouse Models of Roux-en-Y Gastric Bypass

RYGB consists of the Roux limb (RL), the biliopancreatic limb (BPL), and the common channel (CC). There is no consensus on the optimal limb lengths.

Using a mouse model of RYGB, 30 diet-induced obese mice were divided into two groups with varying BPL and CC lengths: a standard BPL with a long CC (RYGB S) and a long BPL with a short CC (RYGB L). Additionally, 9 age-matched, lean control mice (LC) were also included in this study.

RYGB S had limb lengths of RL = 17%, BPL = 24%, and CC = 59%. RYGB L had limb lengths of RL = 17%, BPL = 32%, and CC = 51%. RYGB S and RYGB L had 67% and 40% survival, respectively. Mortality in RYGB L included more instances where the cause of death was not apparent. RYGB L demonstrated greater weight loss, lower energy expenditure, and lower heart mass as compared to RYGB S. Both RYGB groups had lower epidydimal fat mass, spleen mass, and bone mineral density compared to LC. RYGB L had a lower heart mass than RYGB S and LC. While the relative abundance of Eubacterium was lower in RYGB L than in RYGB S, no other gut microbiota differences were observed.

A longer BPL with a shorter CC induces greater weight loss but may lead to adverse effects, including lower heart mass, reduced bone density, and deaths with unclear causes.