Identification of an oral microbiota signature associated with an impaired orosensory perception of lipids in insulin-resistant patients

Aims Type 2 diabetes leads to multiple sensory dysfunctions affecting notably the gustatory sensitivity. Although this sensory defect, by impacting food choices, might lead to unhealthy eating behavior, underlying mechanisms remains poorly studied. We have recently reported that the composition of microbiota in contact with circumvallate gustatory papillae might affect the orosensory perception of lipids in lean and normoglycemic obese subjects. This finding has prompted us to explore whether such a phenomenon also occurs in diabetic obese patients. Methods The composition of microbiota surrounding the circumvallate papillae was analyzed in combination with the linoleic acid perception thresholds in male insulin-resistant patients and weight-matched healthy controls. Two complementary comparisons were performed: (1) controls vs diabetic and (2) diabetic low-lipid tasters versus diabetic high-lipid tasters. Results Despite subtle modifications in the oral microbiota composition, comparison of orosensory lipid perception in controls and diabetic subjects did not lead to discriminating data due to the large inter-individual variability of linoleic acid perception thresholds. In contrast, specific bacterial signatures were found by comparing diabetic low- and high-lipid tasters leading to differential molecular pathways. Surprisingly, a lower fatty taste perception was mainly found in patients treated with metformin and/or statins, suggesting a possible side effect of these antidiabetic and/or hypolipidemic drugs on taste acuity. Conclusions Collectively, these data show that the diabetic patients with defective fatty taste detection are characterized by a specific microbiota metabolism at the circumvallate papillae levels, this occurrence seeming amplified by drugs commonly used to counteract the damaging metabolic effects of T2D. Trial registration for original previous studies: ClinicalTrials.gov #NCT02028975

Elevation of the Blood Glucose Level is Involved in an Increase in Expression of Sweet Taste Receptors in Taste Buds of Rat Circumvallate Papillae

The gustation system for sweeteners is well-known to be regulated by nutritional and metabolic conditions, but there is no or little information on the underlying mechanism. Here, we examined whether elevation of the blood glucose level was involved in alteration of the expression of sweet taste receptors in circumvallate papillae (CP) and sweet taste sensitivity in male Sprague-Dawley rats. Rats under 4 h-fed conditions following 18 h-fasting exhibited elevated blood glucose levels and decreased pancreatic T1R3 expression, compared to rats after 18 h-fasting treatment, and they exhibited increased protein expression of sweet taste receptors T1R2 and T1R3 in CP. Under streptozotocin (STZ)-induced diabetes mellites (DM) conditions, the protein expression levels of T1R2 and T1R3 in CP were higher than those under control conditions, and these DM rats exhibited increased lick ratios in a low sucrose concentration range in a brief access test with a mixture of sucrose and quinine hydrochloride (QHCl). These findings indicate that the elevation of blood glucose level is a regulator for an increase in sweet taste receptor protein expression in rat CP, and such alteration in STZ-induced DM rats is involved in enhancement of their sweet taste sensitivity.

Fatty taste variability in obese subjects: the oral microbiota hypothesis

Origin of the great inter-individual variability of the fatty taste perception found in obese subjects is challenging. The fact that recent studies suggest interrelations between taste perception and oral microbiota composition, prompt us to explore the putative impact of such a connection in the context of obesity. To check this hypothesis, the oro-sensory perception thresholds of linoleic acid and the composition of oral microbiota surrounding the gustatory circumvallate papillae (CVPs) were analyzed in obese adult men (BMI ≥ 30 kg/m2, n = 42). A specific microbial signature (higher diversity, pro-inflammatory bacterial profile, lower methanogenesis activity) discriminated subjects with a degraded fatty taste sensitivity (perception threshold ≥ 0.05% LA = Low-LA tasters, n = 22) from high-LA tasters (n = 20). Collectively, these data substantiate the association between the microbial microenvironment surrounding CVPs and the fatty taste sensitivity and provide a plausible explanation about the variability of the fatty taste sensitivity in obesity.

Histomorphological investigation of tongue of Porcupine Hystrix cristate

Anatomical and histological explorations of the tongue in ten adult male Porcupine (Hystrix cristata) collected from AL-Diwanyha city by the hunter, after porcupine prepared the tongue illustrious after that the position, shape dimensions were enrolled. The square-shape of body, thicken less steadily toward caudal part of tongue. Root was tends caudally in the direction of the epiglottis. Torus linguae found on the caudal part of the dorsal surface of the tongue. In the end of lateral surface of tongue have foliate papilla osculate the premolar teeth. The length, apex, body and root of the tongue were (7.6±0.66, 1.25±0.23, 4.95±0.2, and 1.4±0.26 cm), respectively. The width, apex, body, and root of the tongue were (1.80±0.77, 0.35±0.49, 1±0.22 and 0.45±0.14, respectively. In the dorsal and lateral surface have muscle fibers from skeletal type and loose connective tissue bounded by keratinized stratified squamous epithelium while in the ventral lingual surface were non-keratinized. In the dorsal surface of body there were filiform papillae, but less at the lateral surface of the body. While the shape of circumvallate papillae was similar to furrow, and there was taste buds on the both dorsal and lateral sides of the tongue. Fungiform papillae had wide curved keratinized surface, with taste buds on the dorsal surface. Lamina propria and submucosa was loose connective tissue with more of collagen fiber.