| Part1: Altered oral bacterial colonization is strongly associated with fat taste perception impairment,visceral fat accumulation and insulin resistance in humansObjective: To investigate the association of oral bacterial colonization with fat taste perception impairment and visceral fat accumulation and insulin resistance in humans.Methods: Participants were administered questionnaires,physical examinations,and blood specimens were collected for biochemical indexes such as blood glucose and lipid profiles.The abdominal obesity group(A-Ob group)and non-abdominal obesity group(NC group)were selected according to the waist circumference to represent humans with excessive and normal visceral fat content,respectively.The insulin resistance group(IR group)and insulin sensitivity group(IS group)were selected according to the HOMA-IR value.The fat taste threshold was detected by the 3-Alternate Forced Choice Methodology(3-AFC),and the high-fat taste sensitivity(HTS)and low-fat taste sensitivity(LTS)groups were selected according to the 4th quartile of the fat taste threshold.The differences of metabolic indicators such as visceral obesity measurement index and insulin resistance index(HOMAIR,Homeostasis Model-Insulin Resistance)were compared between HTS and LTS groups.The correlation between fat taste threshold level and waist circumference(WC),waistheight ratio(WHt R),waist-hip ratio(WHR),Chinese abdominal obesity index(CVAI),HOMA-IR,body weight,and BMI(Body mass index)was analyzed.Oral bacteria were collected for 16 S r RNA sequencing and analysis,and bacterial colonization was compared between the LTS and HTS groups and the enriched genera in the LTS group were identified using random forest analysis.The genera enriched in the A-Ob and IR groups were identified using random forest analysis.Results: Compared with the HTS group,the LTS group had higher levels of body weight,BMI,waist circumference,WHt R,WHR,CVAI,and HOMA-IR(P<0.05).Fat taste threshold was positively correlated with WC,WHt R,WHR,CVAI,HOMA-IR,body weight and BMI(P<0.05).There were significant differences in oral bacterial composition between HTS and LTS groups(β diversity,P<0.05).Random forest analysis revealed that bacteria of the genera Prevotella,Peptococcus,Haemophilus were enriched in LTS group,A-Ob group and IR group.Conclusions: Fat taste perception impairment is closely associated with visceral fat accumulation and insulin resistance in human.Increased bacterial colonization of oral Prevotella,Haemophilus and Peptococcus might be closely associated with fat taste perception impairment,visceral fat accumulation and insulin resistance in human.Part 2 Visceral fat accumulation and insulin resistance development in catch-up growth rats are accompanied by altered oral bacterial colonization,changes in fat taste sensitivity and Hh proliferation signaling pathways in taste budsObjective: To investigate the changes in visceral fat content,insulin sensitivity,oral bacterial colonization,fat taste sensitivity,and Hh(Hedgehog)proliferation signaling pathway in catch-up growth rats.Methods: Male SD rats were randomly divided into normal control(NC)and Catch-up growth(RN)groups after one week of adaptive feeding.Rats in the NC group were fed with normal chow for 8 weeks,while rats in the RN group were given a weight-matched diet with 60% of the intake of NC rats for 4 weeks,followed by refeeding normal chows for 4 weeks,and the body weight and energy intake of the rats were recorded.The fast lick test was used to detect fat taste sensitivity.Oral bacteria were collected for 16 S r RNA sequencing and analysis,and the differences in bacterial composition between the two groups were compared and the characteristic genera of the RN group were identified using random forest analysis.The IPITT(Intraperitoneal insulin tolerance test)was performed.Blood was collected for fasting blood glucose and fasting blood insulin levels.Immunofluorescence analysis was performed to detect taste bud proliferation levels.RTPCR and immunofluorescence analysis were performed to detect Hh pathway-related genes(shh and Gli1)m RNA and protein expression levels of taste bud.Results: Energy intake and body weight were significantly lower in the RN group than in the NC group during the caloric restricted period(P<0.05),and after refeeding with a normal chow,there was no significant difference in body weight between the RN and NC groups(P>0.05).The relative weight of visceral fat,HOMA-IR level,and area under the IPITT curve were significantly increased in the RN group compared with the NC group(P<0.05).There was a significant difference in oral bacterial composition between the NC and RN groups(β diversity,P<0.05).Further random forest analysis revealed that the characteristic genera of the RN group included Prevotella,Haemophilus,Bacteroides and Dorea.In addition,compared with the NC group,the fat taste perception was impaired,the number of taste buds in the circumvallate papillae of the rats in the RN group was reduced,the level of proliferation of taste buds in the circumvallate and fungiform papilla was decreased,and the expression of m RNA and protein levels of Shh and Gli1 was decreased in taste buds(P<0.05).Conclusions: Visceral fat accumulation and insulin resistance in catch-up growth rats with bacterial enrichment such as Prevotella and Haemophilus,and fat taste perception impairment,reduced number of taste buds and impaired Hh signaling proliferative pathway in taste buds.Part 3 The role of oral Prevotella in fat taste perception impairment,visceral fat accumulation and insulin resistance formationObjective: To investigate the role of oral Prevotella and taste bud Hh signaling pathways in fat taste perception impairment,visceral fat accumulation and insulin resistance formationMethods: Male SD rats were randomly divided into 3 groups,NC group(control group),Pi group(prevotella intermedia(Pi)colonization group)and PS group(prevotella intermedia colonization + SAG(Hh pathway agonist)intervention)one week of adaptation to the housing conditions.The control vehicle,prevotella intermedia,and prevotella intermedia + SAG were applied on the dorsal tongue of rats daily for 2 weeks.The rats were fed with high-fat and normal chows to test their preference for high-fat diet and their body weight and food intake were recorded.The fat taste sensitivity was measured by two-bottle preference test,and blood samples were collected to test the biochemical indicators of blood glucose,insulin and lipids profiles.Gli1 protein expression levels were determined by immunofluorescence analysis.Results: The NC group had higher intake of low concentration fat solution than control solution(P<0.05),and the NC group could perceive fat solution;the Pi group had the same intake of low concentration fat solution as control solution(P>0.05),and the Pi group had diminished perception of fat solution i.e.fat taste perception impairment.Compared with the Pi group,the PS group recovered the perception to fat solution(P<0.05)and improved fat taste sensitivity.Compared to the NC group,the Pi group had increased intake of highfat foods,increased body weight,increased relative subcutaneous and visceral fat content(P<0.05),increased HOMA-IR,and triglyceride levels(P<0.05).The relative visceral fat weight and HOMA-IR levels were reduced in the PS group compared to the Pi group(P<0.05).Compared with the NC group,the taste bud Gli1 protein expression level was reduced in the Pi group,and the taste bud Gli1 protein expression level increased in the PS group compared with the Pi group(P<0.05).Conclusions: Prevotella colonization induces fat taste perception impairement,visceral obesity,insulin resistance and inactivation of Hh pathway in rats.Activation of the Hh pathway ameliorates Prevotella colonization-induced fat taste perception impairement,visceral obesity and insulin resistance,suggesting that Prevotella may induce fat taste perception impairement,visceral fat accumulation and insulin resistance via the Hh pathway in taste buds. |
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