Taste-Driven Responsiveness to Fat and Sweet Stimuli in Mouse Models of Bariatric Surgery.

A preferential consumption of healthier foods, low in fat and sugar, is often reported after bariatric surgery, suggesting a switch of taste-guided food choices. To further explore this hypothesis in well-standardized conditions, analysis of licking behavior in response to oily and sweet solutions has been realized in rats that have undergone a Roux-en-Y bypass (RYGB). Unfortunately, these studies have produced conflicting data mainly due to methodological differences. Paradoxically, whereas the vertical sleeve gastrectomy (VSG) becomes the most commonly performed bariatric surgery worldwide and is easier to perform and standardize in small animals, its putative impacts on the orosensory perception of energy-dense nutrients remains unknown. Using brief-access licking tests in VSG or RYGB mice, we found that (i) VSG induces a significant reduction in the fat mass in diet-induced obese (DIO) mice, (ii) VSG partially corrects the licking responses to lipid and sucrose stimuli which are degraded in sham-operated DIO mice, (iii) VSG improves the willingness to lick oily and sucrose solutions in DIO mice and (iv) RYGB leads to close outcomes. Altogether, these data strongly suggest that VSG, as RYGB, can counteract the deleterious effect of obesity on the orosensory perception of energy-dense nutrients in mice.

Orosensory Perception of Fat/Sweet Stimuli and Appetite-Regulating Peptides before and after Sleeve Gastrectomy or Gastric Bypass in Adult Women with Obesity.

The aim of this study was to explore the impact of bariatric surgery on fat and sweet taste perceptions and to determine the possible correlations with gut appetite-regulating peptides and subjective food sensations. Women suffering from severe obesity (BMI > 35 kg/m2) were studied 2 weeks before and 6 months after a vertical sleeve gastrectomy (VSG, n = 32) or a Roux-en-Y gastric bypass (RYGB, n = 12). Linoleic acid (LA) and sucrose perception thresholds were determined using the three-alternative forced-choice procedure, gut hormones were assayed before and after a test meal and subjective changes in oral food sensations were self-reported using a standardized questionnaire. Despite a global positive effect of both surgeries on the reported gustatory sensations, a change in the taste sensitivity was only found after RYGB for LA. However, the fat and sweet taste perceptions were not homogenous between patients who underwent the same surgery procedure, suggesting the existence of two subgroups: patients with and without taste improvement. These gustatory changes were not correlated to the surgery-mediated modifications of the main gut appetite-regulating hormones. Collectively these data highlight the complexity of relationships between bariatric surgery and taste sensitivity and suggest that VSG and RYGB might impact the fatty taste perception differently.

The Tryptophan/Kynurenine Pathway: A Novel Cross-Talk between Nutritional Obesity, Bariatric Surgery and Taste of Fat.

Diet-induced obesity (DIO) reduces the orosensory perception of lipids in rodents and in some humans. Although bariatric surgery partially corrects this alteration, underlying mechanisms remain poorly understood. To explore whether metabolic changes might explain this fat taste disturbance, plasma metabolome analyses, two-bottle choice tests and fungiform papillae (Fun) counting were performed in vertical sleeve gastrectomized (VSG) mice and sham-operated controls. An exploratory clinic study was also carried out in adult patients undergone a VSG. In mice, we found that (i) the VSG reduces both the plasma neurotoxic signature due to the tryptophan/kynurenine (Trp/Kyn) pathway overactivation and the failure of fat preference found in sham-operated DIO mice, (ii) the activity of Trp/Kyn pathway is negatively correlated to the density of Fun, and (iii) the pharmacological inhibition of the Kyn synthesis mimics in non-operated DIO mice the positive effects of VSG (i.e., decrease of Kyn synthesis, increase of Fun number, improvement of the fat taste perception). In humans, a reduction of the plasma Kyn level is only found in patients displaying a post-surgery improvement of their fat taste sensitivity. Altogether these data provide a plausible metabolic explanation to the degradation of the orosensory lipid perception observed in obesity.