A mouse model for sleeve gastrectomy: applications for diabetes research

INTRODUCTION

Discovery of enhanced glucose tolerance following bariatric surgery has sparked renewed interest in the investigation of unchartered underlying pathways of glucose homeostasis. Delineation of this pathway may ultimately be the first step in the creation of a novel therapy for type II diabetes. Nevertheless, the technical complexity and formidable nature of these surgeries coupled with the fragile nature of small rodents has made the creation of a mouse model to study these effects incredibly challenging. We have created a simplified sleeve gastrectomy mouse model to study the effects of bariatric surgery on glucose tolerance and beta cell proliferation.

METHODS

Nineteen mice were randomized to undergo either sleeve gastrectomy (SG) (9) or sham operation (SH) (10). Weight and serum glucose were measured three times weekly and serum insulin measurements and pancreatic harvest were performed at the time of sacrifice. Five mice from each group were sacrificed after one week and the remainder sacrificed after one month.

RESULTS

Survival of mice was 100% for both groups. The SG group demonstrated an initial drop in weight and serum glucose as compared to SH, which normalized by one month following surgery. Serum insulin levels and rate of beta cell proliferation were similar in both groups after one week and one month.

CONCLUSION

The simplified sleeve gastrectomy is a technically straightforward, low-mortality technique for creating a bariatric mouse model which most faithfully replicates bariatric surgery performed in humans. This model can be a valuable tool to investigate the glucose tolerance and beta cell effects of bariatric surgery.

Specific Induction oftie1Promoter by Disturbed Flow in Atherosclerosis-Prone Vascular Niches and Flow-Obstructing Pathologies

Nonlaminar flow is a major predisposing factor to atherosclerosis. Yet little is known regarding hemodynamic gene regulation in disease-prone areas of the vascular tree in vivo. We have determined spatial patterns of expression of endothelial cell receptors in the arterial tree and of reporter gene constructs in transgenic animals. In this study we show that the endothelial cell-specific receptor Tie1 is induced by disturbed flow in atherogenic vascular niches. Specifically, tie1 expression in the adult is upregulated in vascular bifurcations and branching points along the arterial tree. It is often confined to a single ring of endothelial cells functioning as sphincters and hence experiencing the steepest gradient in shear stress. In aortic valves, tie1 is asymmetrically induced only in endothelial cells encountering changes in flow direction. Disturbance of laminar flow by a surgical interposition of a vein into an artery led to induction of tie1, specifically in the region where the differently sized vessels adjoin. In pathological settings, tie1 expression is specifically induced in areas of disturbed flow because of the emergence of aneurysms and, importantly, in endothelial cells precisely overlying atherosclerotic plaques. Hemodynamic features of atherosclerotic lesion-prone regions, recreated in vitro with the aid of a flow chamber with a built-in step, corroborated an upregulated tie1 promoter activity only in cells residing where flow separation and recirculation take place. These defined promoter elements might be harnessed for targeting gene expression to atherosclerotic lesions.

The ankle-brachial index in normal neonates and infants is significantly lower than in older children and adults

Vascular trauma from accidental or iatrogenic causes is becoming more common in children. In early infancy, the most common arterial injuries are caused by diagnostic or interventional cardiac catheterizations. Doppler arterial pressure measurements and the computed ankle-brachial pressure index (ABI) are the most helpful diagnostic modalities in the assessment and follow-up of the ischemic extremity. Because normative ABI data in small children are not available, an ABI of 0.9 or less (based on data obtained from an adult population), is used to indicate limb ischemia in young infants. The purpose of this study was to define the normal values of ABI in newborns and infants.

MATERIALS AND METHODS

Three hundred and fifty patients were divided into two groups: group 1 (n = 200; male-to-female ratio, 1:1) were full-term (gestational age 40 +/- 1.3 weeks, surface area 0.22 +/- 0.02 m2) healthy newborns following uneventful pregnancy and delivery. Group 2 (n = 150) were healthy patients aged 2 weeks to 2.5 years admitted for elective hernia repair. All the patients underwent a complete physical examination, which excluded any cardiovascular pathology. The systolic blood pressure (BP) was measured bilaterally over the brachial, tibialis posterior, and dorsalis pedis arteries. All BP data were obtained in the supine position, using an ultrasonic Doppler flow detector, an appropriately-sized pneumatic cuff and a sphygmomanometer. The chosen cuff size was long enough to completely encircle the circumference and wide enough to cover 75% of the length of the upper arm. The same cuff was applied around the ankle above the malleoli. BP values were expressed as mean +/- SD in mm Hg. If there was a difference between the BP in the two arms, the higher pressure was used for calculation of the ABI.

RESULTS

The BP measurements in newborns (group 1) were left brachial, 98 +/- 11; right brachial, 90 +/- 10 (P < .001), left and right tibialis posterior and left and right dorsalis pedis were 83, 81, 84, and 82 mm Hg, respectively. The mean computed ABI was 0.88 +/- 0.11. Fifty eight percent of the newborns had an ABI less than 0.9 (lower limit of normal in adults). The ABI values in patients belonging to group 2 increased with age and surface area. The mean ABI was 1.0, 1.1, and more than 1.1 in patients aged, 1, 1.5, and 2 years with surface areas of 0.4, 0.5 and 0.6 m2, respectively (P < .001 compared with group 1).

CONCLUSION

The normative ABI in newborns and infants is significantly lower than in older children and reaches normal (adult) values during the second year of life. These data may be used as a reference when assessing lower extremity ischemia caused by trauma in young patients.