Ileectomy-induced Bile Overaccumulation in Mouse Intestine

Summary

Small intestine-dependent bile acid reabsorption and feedback inhibition of hepatic bile acid synthesis is important for systemic homeostasis and health. In this study, we describe a mouse model for ileal resection to evaluate ileectomy-induced bile malabsorption, overaccumulation, and toxicity in mouse intestine.

Abstract

Intestinal resection is a common therapeutic approach for human diseases such as obesity, inflammatory bowel disease, Crohn's disease, and colon cancer that often results in severe short bowel syndrome-like adverse effects including bile acid diarrhea, dehydration, electrolyte disturbances, and nutrient malabsorption. Here we introduce a murine ileal resection model, termed ileectomy, to evaluate tissue communication and the maintenance of systemic homeostasis. After ileal resection, circulating blood is permanently devoid of the ileum-specific endocrine hormone fibroblast growth factor 15 (FGF15), which releases its endocrinal inhibition of bile acid synthesis in the liver. In combination with the increased production and abolished reabsorption of bile acids after removing the ileum, mice that underwent surgery suffer from bile salt overaccumulation in the intestine and associated diarrhea, morbidity, and mortality. Novel usage of the surgery model introduced in this study may provide mechanistic and functional insights into ileal control of systemic metabolic regulation in physiology and disease.

Introduction

In modern biomedical research, genetically manipulated animal models are widely utilized to glean insights into human diseases. In particular, tissue or cell-specific gain-and-loss functions of genes have been used to study molecular regulation as well as induced biological effects. Despite the advancements in manipulating target genes in vivo, there are lingering limitations. First, many cell or tissue specific deletions will affect multiple organs. For example, epithelial gene deletion will eliminate expression in epithelia of multiple tissues. Further, even if deletion is restricted to a specific tissue, spatial control is rarely feasible. For example, in ....

Protocol

Animal protocol was reviewed and approved by the Institutional Animal Care and Use Committee at Case Western Reserve University School of Medicine and was conducted in accordance with the National Institutes of Health (NIH) Guide for the Care and Use of Laboratory Animals (8th Edition, 2011). Mice were euthanized by methods compliant with the American Veterinary Medical Association (AVMA) Guidelines for Euthanasia of Animals (2013 Edition). C57BL/6J, male, 8 - 16 week old mice were used in this protocol. Mice were housed in a 12 h dark/light cycle environment.

1. Pre-operative Preparation

1. Transfer mice to a clean cage 24 h befor....

Results

The procedures for ileectomy are shown in Figure 1. The first step includes preparing mouse abdominal skin, making an abdominal incision, and using retractors to fully expose the intestine (Figure 1A-C). Next, the mouse cecum was located (Figure 1D); given that its size and shape make it an easily identifiable landmark. The cecum, ileum, and part of the distal jejunu.......

Discussion

In order to perform a successful ileectomy, the superior mesenteric artery must be ligated in advance to block the blood supply to the resecting segment. The ischemic ileal segment will turn dark purple after ligation. The ileal segment must then be completely resected. A normal blood supply must be ensured for the retained ends. This is essential to avoid bleeding and improper removal, which can easily cause surgical failure due to ischemic necrosis after suturing. During the anastomosis, it is important to join the ile.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Dissection microscope	Olympus	SZ61	For surgery
Animal temperature controller	Physitemp Instruments, Inc.	TCAT-2LV	For body temperature control
Isoflurane anesthetic vaporizer	VetEquip	911104	For anesthesia
Dissection forceps	Fine Science Tools, Inc.	11274-20	For surgery
Scissors	Fine Science Tools, Inc.	14084-08	For surgery
Needle holder	Roboz Surgical Instrument Co.	RS-7882	For surgery
Micro knives-needle blade	Fisher Scientific	10318-14	For surgery
6-0 monofilament suture	Ethicon	1698G	For abdominal skin closure
7-0 silk suture	Ethicon	766G	For ligation
8-0 monofilament suture	Ethicon	1714G	For anastomosis
Surgical sponges	Dynarex Corp.	3333	For surgery
Small cotton-tipped applicators	Fisher Scientific	23-400-118	For surgery
Isoflurane	Piramal Healthcare Limited	66794-013-25	For anasthesia
Buprenorphine hydrochloride	Reckitt-Benckiser Pharmaceuticals	12496-0757-1	For analgesia
0.9% sodium chloride Injection	B. Braun Medical Inc.	0264-7800-10	For washing/injection
Povidone iodine prep solution	Dynarex Corp.	1413	For skin preparation
Puralube vet ointment	Dechra Veterinary Products	17033-211-38	For eye pretection
Hair remover lotion	Church & Dwight Co., Inc.		For skin preparation
Intensive care unit	ThermoCare	FW-1	For post-surgery recovery
DietGel recovery	ClearH2O	72-06-5022	For post-surgery recovery
Aurum total RNA fatty and fibrous tissue kit	Bio-Rad	7326830	For RNA isolation
iScript reverse transcription supermix for RT-qPCR	Bio-Rad	1708841	For reverse transcription assay
TaqMan fast advanced master mix	Applied Biosystems/Life Technologies	4444965	For QPCR analysis
Total bile acid assay kit	Genzyme Diagnostic	DZ042A-K01	For bile acid assay
C57BL/6J	The Jackson Laboratory