CLAUDIA C. RAMIREZ SANCHEZALI KURAISHY, PH.D.

UNIVERSITY OF CALIFORNIA SAN DIEGO

Interplay between Epigenetics and Hyperlipidemia may cause

Insulin Resistance

A little bit of background

Epigenetics: Changes in phenotype from causes above the level of DNA, from structural changes (histones and methylation)

Hyperlipidemia: High concentration of lipids in body.

Diabetes: Condition of high glucose levels in the blood. Type 1: Cells are Insulin dependant. Hormone Insulin

is not sufficiently secreted. Type 2: Cells are Insulin insensitive (do not respond

correctly)

Why is this important?

Obesity is one of the factors leading to diabetes

By 2007 diabetes affected 7.8% of the American population (American Diabetes Association).

Minorities are at a higher risk of Type 2 diabetes.

It is still unclear why Type 2 diabetes occurs.

What happens is…

Bacterial polysaccharide LPS + cell receptor TLR4 = inflammatory pathway

Phosphorylating epigenetic regulator BMI1.

What do we address?

High concentration of free fatty acids may be signaling through a receptor called TLR4, resulting in a failure to respond to insulin.

Understanding how this signaling results in insulin insensitivity is critical to understanding Type 2 diabetes and identifying novel targets for therapy.

Hypothesis

Free fatty acids may signal through TLR4 and phosphorylate the epigenetic regulator BMI1, thus modulating its activity and changing the expression levels of a wide variety of genes. Chronic phosphorylation of BMI1 may result in semi-permanent epigenetic changes which may then result in insulin insensitivity.

Methods

Western Blots: To determine BMI1 phosphorylation by free fatty acids. (LPS, BSA, Palmitic Acid in macrophages and fibroblasts)

Co-immunoprecipitation: To determine what proteins are phosphoryalting BMI1.

Methods

Cloning BMI1: To determine where BMI1 is being phosphroyated

BMI1 insert is ligated into pGEX vector in order to clone the insert.

Results

L1 L2 L3 H1 H2 H3

Mice fed with high fat diet (H1, H2, H3 show more phosphorylation than mice fed a low fat diet (L1,L2,L3)

•From this Western blot, we think that there may be a difference in BMI1 phosphorylation between hepatocytes from mice fed a low fat versus a high fat diet.

- LPS - LPS

WT JNK1-/-

p-BMI1BMI1

•BMI1 is phosphorylated after LPS treatment in a JNK1-dependent manner

p-BMI1BMI1

In conclusion…In conclusion… What’s next?What’s next?

Data is still inconclusive in many regards.

There is a difference in BMI1 phosphorylation between hepatocytes from mice fed a low fat and a high fat diet. (High fat diet = More BMI1 phosphorylation)

Find clear demonstration that free fatty acids phosphorylate BMI1.

Isolate the BMI1 protein and incubate it with lysates from LPS treated cells together with radioactive p32.

Conclusion and Future Directions

Acknowledgements

Dr. Ali Kuraishy for giving me the opportunity to work under his supervision.

Anne Chang (Manager), Dr. Michael Karin’s Lab, and Dr. Emil Bogennman and Mercedes Gonzalez from the STEP-UP Program.

MESA Program at Southwestern College, NSF and LIPP Family Foundation