1. Speaker: Kacy Richmond Advisor: Dr. Jun Ren (School of Pharmacy)
The Positive Effects of Tauroursodeoxycholic Acid on High-Fat Diet-Induced Cardiomyocyte Dysfunction and Endoplasmic Reticulum Stress
Speaker: Kacy Richmond
Advisor: Dr. Jun Ren (School of Pharmacy)
April 19, 2010

2. Obesity and Endoplasmic Reticulum (ER) Stress
Obesity (induced by high-fat diet) is closely associated with the activation of cellular stress signaling and inflammatory pathways.
The ER plays a crucial role in the cellular stress response.

3. Endoplasmic Reticulum (ER)
The ER is a membranous network that functions in the synthesis and processing of secretory and membrane proteins.

4. Obesity and Endoplasmic Reticulum (ER) Stress
Numerous conditions, including aging and obesity, can lead to the disruption of ER homeostasis and result in the accumulation of unfolded or misfolded proteins in the ER lumen. This often leads to cell death.

5. Endoplasmic Reticulum (ER) Stress
ER Stress induction
Obesity
Glucose intolerance
Excess lipid accumulation
Insulin resistance
Mechanical stress
Increased mechanical stress
Endoplasmic Reticulum (ER) Stress

6. ER stress signaling (TUDCA) Bip
Figure 1. ER stress signaling. The endoplasmic reticulum (ER) is an organelle which synthesizes various secretory and membrane proteins. These proteins
are correctly folded and assembled by chaperones in the ER. During stressful conditions such as upon an increase in the misfolded protein level, the
chaperones become overloaded and the ER fails to fold and export newly synthesized proteins, leading to ER stress [1–5]. Once ER stress is provoked in the
cells, various pathways are activated: phosphorylation of a subunit of translation initiation factor 2 (eIF2a), activation of c-Jun N-terminal kinase (JNK), and
splicing of X-box-binding protein-1 (XBP-1). PERK: pancreatic endoplasmic reticulum kinase, IRE1: inositol requiring 1, ATF6: activating transcription factor
6, CHOP: C/EBP homologus protein.
(TUDCA)

7. Tauroursodeoxycholic Acid (TUDCA)
Taurine-conjugated derivative of ursodeoxycholic acid (TUDCA) is a potent chemical chaperone that inhibits ER stress.
TUDCA administration to obese and diabetic mice normalized hyperglycemia; restored systemic insulin sensitivity; and enhanced insulin action in skeletal muscle.
Nevertheless, whether or not TUDCA has an effect on obesity- induced cardiac contractile dysfunction is not clear.

8. Hypothesis
ER stress chaperone — tauroursodeoxycholic acid (TUDCA) – can alleviate cardiac contractile dysfunction induced by high-fat diet (HFD).

9. Methods High-fat diet induced obesity model:
Isolated cardiomyocyte contractile functions;
Western blot analysis of ER stress proteins
C57 mice
LF (10%)
Saline
HF (45%)
TUDCA, ip, 300mg/kg/d
20 weeks
Thirty aged-matched C57 male mice will be used in this study. The mice were housed in clear plastic cages in a temperature- and humidity-controlled environment with a 12 hr-light/dark cycle (lights on at 7 AM) and maintained on an ad libitum diet of lab chow and water. Animals were handled in accordance with The Guideline of Animal Care of University of Wyoming. The animals will be fed either with normal laboratory diet (10% of total calorie) or high fat diet (45% of total calorie). Body weights and food intake will be assessed weekly. After 5 months, the animals are further divided into three group randomly based on the changes in body weights The grouping of the animals is as follows:
Group 1 is low fat control group, will receive normal saline intrapetoneally for 15 days;
Group 2 is low fat control group with TUDCA treatment (300mg/kg.bw.day-1) for 15 days.
Group 3 is high fat diet control group will be given normal saline intraperitoneally for 15 days;
Group 4 is high fat diet with TUDCA treatment group (300mg/kg.bw.day-1) for 15 days.
45% HFD mimicks the Western diet
15 days

10. Isolated cardiomyocyte contractile function
Cell length (µm)
100
105
TPS
TR90
-dL/dt (maximal velocity of shortening and relengthening)
+dL/dt
Peak shortening (PS)
(Time to peak shortening)
(Time to return)
This is a typical trace of isolated cardiomyocyte shortening upon electrical stimulus. Let me briefly introduce related parameters.
Cell shortening and relengthening were assessed using the following indices: peak shortening (PS), the amplitude myocytes shortened upon electrical stimulation, indicative of peak ventricular contractility; time-to-PS (TPS), the duration of myocyte shortening, indicative of systolic duration; time-to-90% relengthening (TR90), the duration to reach 90% relengthening,
indicative of diastolic duration (90% rather 100% relengthening was used to avoid noisy signal at baseline level); and maximal velocities of shortening/relengthening,
maximal slope (derivative) of shortening and relengthening phases, indicative of maximal velocities of ventricular pressure increase/decrease.

11. General characteristics of the miceB. C. D.
Clue: Obesity>>> ER stress. We are looking at heart function under a prediabetic condition .In our case, it is the HFD induced obesity>> mechanical stress (pressure overload)
BMI>30.
HW/BW increase >>>cardiac hypertrophy

12. 2. TUDCA partially restores cardiomyocyte functionB. C. D.
*p<0.05 vs C57-LF; #p<0.05 vs C57-HF;
*p<0.05 vs C57-LF; #p<0.05 vs C57-HF;

13. TUDCA inhibits ER stress

14. TUDCA inhibits ER stress

15. TUDCA inhibits ER stress

16. ER Stress Signaling Pathway Summary
HFD Control
p-PERK?
p-IREα
p-cJun
CHOP
p-JNK
TUDCA Treatment
Cardiac contractile dysfunction
Restored cardiac contractile function
p-eIFα
C57 HF
TUDCA-HF
Bip
C57 HF
TUDCA-HF
C57 HF
TUDCA-HF
p-eIFα

17. Results, Summary and Conclusion
HFD
Obesity
Glucose intolerance
Excess lipid accumulation
Insulin resistance
Mechanical stress
Endoplasmic Reticulum (ER) Stress
Cardiomyocyte contractile
Dysfunction, Ca 2+ abnormalities
TUDCA
Cardiomyocyte contractile function

18. Future directions
Study the impact of TUDCA on cardiac insulin signaling
Effects of TUDCA on cardiomyocyte function using tunicamycin-induced ER stress in vitro

19. Acknowledgment
Dr. Jun Ren
Subat Turdi

20. Thank you!