Role of NLRP3 Inflammasome Activation of Adipose Tissue in the Progression of Weight Loss After Sleeve Gastrectomy in Morbidly Obese Patients.

Epidemiological studies show a very rapid increase in the epidemic of obesity in the Caribbean population. The latest prevalence data in Martinique show that 6 out of 10 adults are overweight and 1 out of 4 is obese (Body Mass Index, BMI ≥ 30 kg/m2). Obesity with a BMI ≥ 35 kg/m2 is said to be "morbid" because of its association with numerous cardiovascular comorbidities. A balanced diet and physical activity are effective behavioural modalities for weight loss, which, even at low intensity, can reduce cardiovascular complications and the risk of death. However, many patients do not adhere to these constraints over a long period of time and about 50% of them regain weight after the first year. These observations highlight the value of alternative therapies with lasting effects on weight loss and the cardio-metabolic comorbidities of obesity.

Bariatric surgery with vertical calibrated vertical gastroplasty with gastric resection (or sleeve gastrectomy) and Roux-en-Y gastric bypass are therapeutic options that are not only effective in the long term for weight loss but also beneficial in terms of insulin resistance and cardiovascular complications. Bariatric surgery is currently indicated for the treatment of morbid obesity with a BMI ≥ 40 kg/m2 or a BMI ≥ 35 kg/m2 in the presence of complications. Some patients nevertheless remain resistant to the beneficial cardio-metabolic effects of bariatric surgery. The reasons for this resistance are attributed to factors such as age > 60 years, female sex, BMI > 45 kg/m2, African-American or Hispanic origin, and history of type 2 diabetes. Regardless of these factors, several studies have pointed out that a chronic low-grade inflammatory state reduces the magnitude of weight loss and thus counters the beneficial cardio-metabolic effects of bariatric surgery.

Visceral adipose tissue is largely responsible for the inflammatory syndrome in obese patients, via the activation of nuclear transcription factors (NFkB, in particular) that stimulate the synthesis of numerous mediators and pro-inflammatory cytokines. Obesity can also induce the formation of multi-protein platforms called inflammasomes, including the active assembly of inflammatory caspases (caspase-1, in particular) that cleave the pro-interleukins IL1β and IL18 into mature pro-inflammatory cytokines IL1β and IL18. The role of the inflammasome NLRP3 ("NOD-like receptor family, pyrin domain containing 3") in the inflammatory response has been particularly studied in humans due to its association with multiple chronic inflammatory, infectious and cardio-metabolic pathologies. Among the biomolecules responsible for activation of the NLRP3 inflammasome during obesity are palmitate, sphingolipids and cholesterol crystals. The NLRP3 inflammasome is also activated by mitochondrial production of reactive oxygen species (ROS) and by mitochondrial DNA released from mitochondria damaged by lipo-toxicity phenomena associated with obesity. More generally, the mitochondrial dysfunction of the metabolic syndrome is considered to be the causal intracellular event of the deregulation of the inflammatory response mediated by the inflammasome.