Glucose Supplementation in Hypoglycemic Mice
Following Roux-en-Y Gastric Bypass Surgery
Zoe Hsi1; Leslie Stewart, MS2; Kristin Grimsrud, DVM, Ph.D2
1University
of California, Davis; School of Veterinary Medicine, Davis CA
2University of California, Davis; Mouse Biology Program, Davis CA
Background
Materials and Methods
Materials
and
Methods
Animals: 32 C57BL/6 mice (8 males, 8 females per phase) on 60% high fat diet.
Roux-en-Y gastric bypass (RYGB) surgery is an effective treatment for obesity and
diabetes in humans.
Phase 1:
Mouse models of RYGB surgeries aid in the investigation of energy homeostasis and
the mechanisms of obesity and diabetes.
Glucose Dosing & Testing: Each animal was administered 50 mg dextrose either SQ (1
ml of 5% dextrose) or OTM (0.1 ml of 50% dextrose onto oral mucous membranes) with
a 5 day washout period. 8 mice were used as controls after washout. Blood samples
were taken at 0, 5, 15, 30, 60, 90, 120, and 180 minutes following administration.
At the Mouse Biology Program (MBP), RYBG mortality rates have reached >60%.
Mice are profoundly hypoglycemic 24 to 48 hours following surgery.
Statistics: Mixed effects linear regression with pairwise comparisons of treatments
using a Bonferroni adjustment for multiple comparisons. P<0.05 is significant.
Literature reports intensive peri-operative glycemic control has been shown to
reduce surgical site infection, morbidity, and mortality.
Phase 2:
Although glucose homeostasis is extensively studied in mice, the influence of
hypoglycemia in the post-operative period is not well documented.
Surgery: RYGB surgery was performed under isofluorane anesthesia.
Glucose and Animal Monitoring: BG was measured 3x/day for 3 days. Hypoglycemic
animals (≤60 mg/dL) were randomly allocated to one of two groups: 1) Dosed with 1
mL 5% dextrose SQ when hypoglycemic (D) or 2) Observed to be hypoglycemic and not
dosed (ND). Pain assessment via grimace scale was recorded 1x/day for 3 days. Animals
were monitored for 3 weeks total for activity levels, fecal output, and mortality.
Hypothesis
Subcutaneous (SQ) glucose administration in mice provides more
sustained systemic glucose levels than oral/transmucosal (OTM)
administration, causing decreased morbidity and mortality following
Roux-en-Y gastric bypass (RYGB) surgery.
Statistics: Log-rank test to compare survival probabilities and Mann-Whitney test to
compare grimace scale scores between treatment groups. P<0.05 is significant.
Results
Phase 1:
Phase 2:
A v e r a g e B lo o d G lu c o s e M e a s u r e m e n t s
500
B lo o d G lu c o s e (m g /d L )
SQ
O TM
400
*
*
Aspiration
Pneumonia
Aspiration
Pneumonia
*
#14
S Q S a lin e
Bedding Impaction
^
*
200
O T M S a lin e
*
Bedding Impaction
Hypoglycemia
*
Hypoglycemia
100
Surgery Site Leakage
0
50
100
150
#7
#10
#11
Surgery Site Leakage
0
Mouse # Mouse # Dose Group
#15
300
^
Cause
of Death
Cause
of Death
#2
#6
#14
#15
#7
#10
#11
#2
#6
Days
Post-Surgery
Days
Post-Surgery
No Dose
Dose
Dose
Dose
No Dose
No Dose
Dose
22
4
4
4
4
2
22
2
10
1110
11
200
M in u t e s
Table 1. Causes of deaths in post-operative mice as determined by necropsy.
Figure 1. Blood glucose measurements vs time. Results are expressed as means ± SD. Significant differences for
*SQ dextrose and ^OTM dextrose (p<0.05)
SQ administration of dextrose caused a larger and more rapid spike in blood glucose
concentration versus OTM administration. Maximum blood glucose concentration
following dosing was at 15 minutes for SQ and 30 minutes for OTM administration.
After 60 minutes, there were no significant differences in BG between dextrose groups.
BG concentrations in all animals returned approximately to baseline by 180 minutes.
Control cohorts showed a mild increase in BG at 30 minutes which was significantly lower
than dextrose treated groups.
14 out of 16 mice became hypoglycemic (≤60 mg/dL) in the 3 days post-surgery, most
frequently on day 2.
7 mice died within the 3 week post-operative period (mortality rate of 44%), 2 directly
from hypoglycemia (29% of all deaths).
Pre-death BG measurements for mice prior to hypoglycemia related deaths were
≤15 mg/dL.
Discussion
Ideas for Future Studies
Phase 1:
Raise threshold for definition of hypoglycemia from ≤60 mg/dL to ≤80 mg/dL or
administer prophylactically. Severe hypoglycemia can cause seizures, coma, and
death, so early detection should increase recoverability, animal welfare, and overall
survivability.
Sustainability of BG over time was the original criteria for determining dosing route.
OTM was anticipated to have an early spike and drop whereas SQ was expected to
increase slowly and sustain longer. The contrary results that occurred may have been
from difficult OTM dosing into the mouse’s small mouth.
Increase number of blood glucose measurements per day from 3x/day to 4x/day.
More intensive glycemic control will minimize large fluctuations.
SQ and OTM routes showed similar kinetic profiles after 60 minutes, therefore SQ was
chosen for phase 2 due to ease and reliability of administration.
Phase 2:
There was no significant difference in mortality between D and ND groups. Although
not statistically significant, grimace scale assessment anecdotally showed greater
discomfort in the ND group. Literature also shows that hypoglycemia causes
depressive-like behaviors in mice, reduced movement, and social withdrawal.
This cohort’s mortality rate of 44% is lower than the MBP’s previous 70%. Due to
procedural changes including lowered opiate dosages and smaller suture, it is not
discernible what is responsible. However, it is documented that prolonged
hypoglycemia leads to inefficient energy for wound healing. Since these mice models
are labor and financially intensive, including glucose supplementation in the RYGB
protocol is recommended.
References and Acknowledgements
References:
1.
2.
3.
4.
5.
Buchwald, H., Avidor, Y., Braunwald, E., Jensen, M. D., Pories, W., Fahrbach, K., & Schoelles, K. (2004). Bariatric Surgery: A Systematic Review and
Meta-analysis. JAMA, 292(14), 1724-1737.
Jeon, C. Y., Furuya, E. Y., Berman, M. F., & Larson, E. L. (2012). The Role of Pre-Operative and Post-Operative Glucose Control in Surgical-Site
Infections and Mortality. PLoS ONE, 7(9).
Park, M. J., Yoo, S. W., Choe, B. S., Dantzer, R., & Freund, G. G. (2012). Acute hypoglycemia causes depressive-like behaviors in
mice. Metabolism, 61(2), 229-236.
Terranova, A. (1991). The Effects of Diabetes Mellitus on Wound Healing. Plastic Surgical Nursing, 11(1), 20-25.
Maheandiran, M., Mylvaganam, S., Wu, C., El-Hayek, Y., Sugumar, S., Hazrati, L., . . . Carlen, P. L. (2013). Severe Hypoglycemia in a Juvenile
Diabetic Rat Model: Presence and Severity of Seizures Are Associated with Mortality. PLoS ONE,8(12)
Acknowledgements:
A huge thank you to Dr. Kristin Grimsrud, Dr. Kent Lloyd and Leslie Stewart at the UCD Mouse Biology Program for
their support and guidance. An additional thank you to Dr. Philip Kass for his invaluable statistical analysis. This
study was supported by the UCD Students Training in Advanced Research (STAR) program.