Published data suggest that inflammation and fibrosis of adipose tissue could be factors favoring the development of insulin resistance in obese individuals and that a decrease in the activity of the AMP-activity kinase protein (AMPK) could lead to these dysfunctions. However, very few data are available in humans.

There is also growing interest in persistent organic pollutants (POPs) as a cardiometabolic and type 2 diabetes (T2D) risk factor. There is some evidence to suggest that POPs directly contribute to lipid metabolism dysfunction and insulin resistance. Additionally, POPs are stocked in adipose tissue. The accumulation of POPs in adipose tissue therefore limits their bioavailability to other organs, thus reducing their systemic toxicity. It has been observed that a large amplitude weight loss leads to a significant increase in POPs in the blood.

The goal of this project is to identify adipose tissue factors/dysfunctions that contribute to insulin resistance and type 2 diabetes associated with obesity in humans and thus raise avenues for screening and treatment of these metabolic complications. More specifically, the objectives are:

• To study the relationship between AMPK, fibrosis and inflammation of adipose tissue and their role in the development of insulin resistance and T2D associated with obesity;
• To examine the relationship between POPs and the cardiometabolic profile.

Inclusion Criteria:

1. Awaiting bariatric surgery
2. BMI ≥ 35 kg/m2 without cardiometabolic complications or ≥ 30 kg/m2 if presence of type 2 diabetes or hypertension
3. ≥ 18 years old
4. Non smoker
5. Sedentary (less than 3 hours of regular physical activity per week)

Exclusion Criteria:

1. Type 1 diabetes
2. Acute event in the last 3 months (myocardial infarction, cerebrovascular hemorrhage or transient cerebral ischemia, unstable angina, peripheral vascular disease, revascularization or angioplasty, recent hospitalization for more than 4 days)
3. Infection in the last month (fever, antibiotics treatment)
4. Cancer in the last 3 years
5. Chronic inflammatory disease
6. Pharmacologic treatment (any medication affecting glucose metabolism (except those for diabetes), hypotensive medication unless stable dose for at least 1 month, lipid-lowering medication unless stable dose for at least 1 month)
7. Uncontrolled disease of pituitary or thyroid gland
8. Bleeding disorders
9. Alcohol or drug abuses
10. Claustrophobia

The study population will be composed of obese individuals with type 2 diabetes, insulin-sensitive obese individuals and insulin-resistant obese individuals, all awaiting bariatric surgery.