Targeting Risk Factors for Diabetes in Subjects With Normal Blood Cholesterol Using Omega-3 Fatty Acids

Type 2 (T2D) and cardiovascular disease (CVD) share many risk factors, whose accumulation over years lead to disease onset. However, while lowering plasma low-density lipoprotein cholesterol (LDLC) is cardio-protective, novel evidence over the past 10 years established a role for common LDLC-lowering variants and widely used hypocholesterolemic Statins in higher risk for T2D. This diminishes the cardio-protective role of low plasma LDLC. As these conditions decrease plasma LDLC by increasing tissue-uptake of LDL, a role for LDL receptor (LDLR) pathway was proposed. However underlying mechanisms fueling higher risk for T2D with upregulated LDLR pathway, and nutritional approaches to treat them are unclear.

The central hypothesis examined in this trial is that upregulating receptor-mediated uptake of LDL on white adipose tissue provokes the activation of an innate immunity pathway (the Nucleotide-binding domain and Leucine-rich repeat Receptor, containing a Pyrin domain 3 (NLRP3) inflammasome) leading to the accumulation of risk factors for T2D in subjects with normal plasma LDLC. This can be treated by 6-month supplementation of omega-3 fatty acids (omega-3).

To examine this hypothesis in vivo, ex vivo and in vitro, a clinical trial in conjunction with mechanistic basic research studies have been initiated at the Montreal Clinical Research Institute (IRCM). Forty eight volunteers will be recruited through advertisements in French/English newspapers and online (e.g. Google, Facebook) and placed on a 6-month supplementation of 3.6 g omega-3 per day. Participants will be stratified into 2 groups (N=24/group) with higher and lower white adipose tissue surface-expression LDL receptors (LDLR and CD36) using median plasma PCSK9 (Proprotein Convertase Subtilisin/Kexin type 9) per sex. Plasma PSCK9 will be used as investigators have shown that it is negatively associated with white adipose tissue surface-expression of LDLR and CD36.

The duration of this study is about 8 months (33 weeks) divided into 5 parts:

A. Screening and evaluation of eligibility for the study

B. Weight stabilisation (+/- 2 kg change over 4 weeks) and confirmation of eligibility after a medical examination by IRCM physician collaborators.

C. Baseline testing over 2 days (1- 4 weeks apart) to assess participants risk factors for T2D: white adipose tissue NLRP3 inflammasome activity, white adipose tissue physiology and function (ex vivo after a subcutaneous needle biopsy), systemic inflammation, dietary fat clearance (after a high fat meal), and insulin secretion and sensitivity (by gold-standard Botnia clamp technique). Participants will also be phenotyped for body composition (by dual energy x-ray absorptiometry), resting energy expenditure (by indirect calorimetry), dietary intake (by 3-day dietary journals) and physical activity level (by a questionnaire).

D. 24-week intervention with omega-3 fatty acid supplementation (3.6 g eicosapentaenoic acid (EPA) and docosahexaenoic (DHA), 2:1)

E. Post intervention testing starting over 2 days (1- 4 weeks apart) to assess risk factors for T2D that were measured at baseline.

Investigators hypothesize that subjects with low plasma PCSK9 (i.e. with higher white adipose tissue LDLR and CD36) will have higher risk factors for T2D at baseline and that the omega-3 intervention will eliminate group-differences in these risk factors.

Inclusion criteria

Men and post-menopausal women:

• Having a body mass index (BMI= 25-40 kg/m2)
• Aged between 45 and 74 years
• Having confirmed menopausal status (FSH ≥ 30 U/l)
• Non-smoker
• Sedentary (less than 2 hours of structured physical exercise (ex: sports club) per week)
• Low alcohol consumption: less than 2 alcoholic drinks/day

Exclusion criteria

• Plasma LDL cholesterol > 3.5 mmol/L (i.e. > 75th percentile in a Canadian population).
• Elevated risk of cardiovascular disease (≥ 20% of calculated Framingham Risk Score) who would require immediate medical intervention by lipid-lowering agents.
• Prior history of cardiovascular events (like stroke, transient ischemic attack, myocardial infarction, angina, heart failure…)
• Systolic blood pressure > 140 mmHg or diastolic blood pressure > 90 mmHg
• Type 1 or 2 diabetes or fasting glucose > 7.0 mmol/L
• Prior history of cancer within the last 3 years
• Thyroid disease - untreated or unstable
• Anemia - Hb < 120 g/L
• Renal dysfunction or plasma creatinine > 100 µmol/L
• Hepatic dysfunction - AST/ALT > 3 times normal limit
• Blood coagulation problems (i.e. bleeding predisposition)
• Autoimmune and chronic inflammatory disease (i.e. celiac, inflammatory bowel, Graves, multiple sclerosis, psoriasis, rheumatoid arthritis, and lupus).Known history of difficulties accessing a vein
• Claustrophobia
• Sleep apnea
• Seizures
• Concomitant medications: Hormone replacement therapy (except thyroid hormone at a stable dose), systemic corticosteroids, anti-psychotic medications and psycho-active medication, anticoagulant or anti-aggregates treatment (Aspirin, NSAIDs, warfarin, coumadin..), adrenergic agonist, anti-hypertensive drugs, weight-loss medication, lipid lowering medication
• Known substance abuse
• Already taking more than 250 mg of omega-3 supplements (EPA/DHA) per day
• Allergy to seafood or fish
• Allergy to Xylocaine
• Unable to eat the components of the high fat meal (croissant, cheese, bacon, brownies)
• None compliance to the study requirements (i.e. not being fasting) or cancellation of the same scheduled testing visit more than once.
• Lack of time to participate in the full length of the study (33 weeks)
• Have exceeded the annual total allowed radiation dose (like X-ray scans and/or tomography in the previous year or in the year to come) according to the physician's judgement.
• All other medical or psychological conditions deemed inappropriate according to the physician