Progress 06/15/18 to 06/14/24
Outputs
Target Audience:During the reporting period one postdoctoral associate and a graduate student have been trained in our lab through the implementation of the grant's objectives. Also, science based information gather through this project has been presented to general audiences. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Over the period of the award, one postdoctoral trainee and graduate student have been conducting and assisting with the implementation of the proposed studies. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The use of non-caloric artificial sweeteners (NCAS) has increased considerably over the past decade. Strikingly, NCAS consumption in children has tripled from 1999 to 2012. Epidemiological data suggest that consumption of NCAS is associated with adverse metabolic effects, weight gain and obesity. These associations are paradoxical, considering that consumption of NCAS is intended to substitute for sugars in the diet for the purposes of weight control or the regulation of blood glucose in susceptible individuals. Thus, although NCAS are not metabolized by host tissues, they may not be physiologically "inert" as originally thought. Nevertheless, the FDA has designated these food additives as "generally recognized as safe (GRAS)" and has approved their use based on limited understanding of their physiological effects. Although mechanistic studies linking their consumption with physiological outcomes are generally lacking in humans, NCAS activate sweet taste receptors (STRs) found not only on the tongue but also in tissues relevant to nutrient metabolism such as the gut, the pancreas and even the brain. How interactions of NCAS with STRs alter energy metabolism in mice and humans is still elusive. Understanding the role of STRs in mediating metabolic response to ingested NCAS could shed light on the association between their consumption and public health outcomes and ultimately inform health policy regarding their optimal use. During this award we published six (6) journal articles, one (1) article is currently in revision, and one (1) manuscript is pending submission. The PI is listed as the senior/corresponding author in all seven (7) journal articles. Objective.1 Elucidate the mechanisms for the regulation of glucose absorption by intestinal STRs. Over the period of the award, we elucidated the mechanism for the regulation of glucose absorption by intestinal STRs (Smith et al Mol Metab 2018) and expanded our studies in humans. Specifically, we biochemically identified that the Ile191Val variant in TAS1R2 STR is a partial loss-of-function (pLOF) polymorphism that has clinical significance. pLOF healthy adults had reduced glucose excursions following an oral glucose challenge, which recapitulated the LOF phenotype in mice (Serrano et al Mol Metab 2021). In a follow up report, we further showed that TAS1R2 pLOF is associated with reduced HbA1c independent of metabolic or diabetic status (Serrano et al, Front Nutr 2022). We also expanded our studies beyond the commitments of Objective 1. We developed two genetic mouse models of TAS1R2 and used them (T1r2-Cre/Tdtomato flox mice) to identify the expression of STRs in other enteroendocrine-type cells and the crypt. We found that STR are expressed in Paneth cells of the crypt. We intend to continue working on this unexpected aspect of STR function and use our findings for future grant applications. 1) Major activities completed / experiments conducted n/a 2) Data collected n/a 3) Summary statistics and discussion of results n/a 4) Key outcomes or other accomplishments realized n/a Objective.2 Determine the contribution of intestinal T1R2 chemosensor in the regulation of gut microbiota. Over the period of the award, we investigated contributions of intestinal STR in modulating the effects of acute and chronic saccharin feeding on gut microbiota composition and the development of glucose intolerance. Specifically, we found that chronic saccharin supplementation in mice or humans does not significantly affect gut microbiota composition or glucose homeostasis, but STR may independently regulate fecal short-chain fatty acids (SCFA) and the development glucose intolerance with aging (Serrano et al Microbiome 2021). In addition, we explored the effects of acute saccharin dosing and found it alters glucose excretion dependent on STR- mediated insulin secretion (Serrano et al, Biomedicines 2022), suggesting, along with the 3 publications from Objective .1, the presence of an intestine-pancreatic axis for the regulation of glucose homeostasis. 1) Major activities completed / experiments conducted n/a 2) Data collected n/a 3) Summary statistics and discussion of results n/a 4) Key outcomes or other accomplishments realized n/a Objective.3 Investigate the regulation of intestinal STRs in response to nutrient overconsumption and their role in the development of metabolic disease. Over the period of the award, we investigated contributions of intestinal STR in response to acute and chronic nutrient overconsumption along with saccharin supplementation. As discussed in previous annual reports, we found no interaction between STR and saccharin supplementation. 1) Major activities completed / experiments conducted A) Using the "humanized" transgenic (Tg) mouse that expresses hT1R2 receptor under the T1R2 promoter we are characterizing the effects of treatment with a positive allosteric modulator (PAM) of human T1R2 on enteroendocrine function, insulin secretion and food consumption. B) We initiated a study that explores the role of STR in the regulation of weight loss following the consumption of HFD (based on findings in humans discussed below). 2) Data collected As indicated above. 3) Summary statistics and discussion of results A) PAM potentiates the effects of hT1R2 in the Tg mouse in taste sensitivity and insulin secretion but has no effect on food intake. These results are included in a pending manuscript to be submitted in Frontiers in Nutrition. B) Final data are still pending whether STR affect weight loss following a HFD. 4) Key outcomes or other accomplishments realized We used a cohort of older obese participants who were subjected to a 6-month diet-induced weight loss program. We found that the variant predicted the amount and region of weight loss. TAS1R2 pLOF caused a reduction in waist circumference and improved body composition significantly. Notably, TAS1R2 pLOF improved glucose control and reduced HbA1c (Serrano et al, Metabolism 2024; 1st revision under review). This data suggests that T1R2 loss-of-function may regulate weight loss through mechanisms that may reduce the rate of glucose absorption. Based on these findings we expanded Objective 3 to include responses to weight loss.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2024
Citation:
Serrano J, Boyd J, Brown IS, Mason C, Smith KR, Karolyi K, Maurya SK, Meshram NN, Serna V, Link GM, Gardell SJ, Kyriazis GA. The TAS1R2 G-protein-coupled receptor is an ambient glucose sensor in skeletal muscle that regulates NAD homeostasis and mitochondrial capacity. Nat Commun. 2024 Jun 8;15(1):4915. doi: 10.1038/s41467-024-49100-8. PubMed PMID: 38851747; PubMed Central PMCID: PMC11162498.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2024
Citation:
Joan Serrano, Saki Kondo, Grace M Link, Ian S Brown, Richard E Pratley, Kedryn K Baskin, Bret H Goodpaster, Paul M Coen and George A Kyriazis. A partial loss-of-function variant (Ile191Val) of the TAS1R2 glucose receptor is associated with enhanced responses to exercise training in older adults with obesity: a retrospective analysis. Metabolism, 2024 (1st revision submitted, under review).
|
Progress 06/15/22 to 06/14/23
Outputs
Target Audience:Science based information gather through this project has been presented to general audiences. Changes/Problems:Unfortunately, an ongoing issue has been the hiring of qualified trainees and lab technicians to help complete the objectives of this proposal. Currently, we have trained personnel that is able to carry out the remaining objectives of the project and we anticipate to complete those during the NCE period. What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?We are approved for no cost extension (NCE) for one year. While the lab operations following COVID-19 restrictions have been resumed, several aspects of the project's objectives were delayed because they involve the implementation of lengthy protocols (i.e., diets). Therefore, our goal for the next year is to continue and complete objectives 1 and 3. Specifically, Objective 1: Determine the function of STRs on Paneth cells of the intestinal crypt. Objective 2: Completed Objective 3: Assess the role of STRs during weight loss following a HFD.
Impacts
What was accomplished under these goals?
The use of non-caloric artificial sweeteners (NCAS) has increased considerably over the past decade. Strikingly, NCAS consumption in children has tripled from 1999 to 2012. Epidemiological data suggest that consumption of NCAS is associated with adverse metabolic effects, weight gain and obesity. These associations are paradoxical, considering that consumption of NCAS is intended to substitute for sugars in the diet for the purposes of weight control or the regulation of blood glucose in susceptible individuals. Thus, although NCAS are not metabolized by host tissues, they may not be physiologically "inert" as originally thought. Nevertheless, the FDA has designated these food additives as "generally recognized as safe (GRAS)" and has approved their use based on limited understanding of their physiological effects. Although mechanistic studies linking their consumption with physiological outcomes are generally lacking in humans, NCAS activate sweet taste receptors (STRs) found not only on the tongue but also in tissues relevant to nutrient metabolism such as the gut, the pancreas and even the brain. How interactions of NCAS with STRs alter energy metabolism in mice and humans is still elusive. Understanding the role of STRs in mediating metabolic response to ingested NCAS could shed light on the association between their consumption and public health outcomes and ultimately inform health policy regarding their optimal use. Objective.1 Elucidate the mechanisms for the regulation of glucose absorption by intestinal STRs. 1) Major activities completed / experiments conducted As a follow up from the previous reporting period, we used T1r2-Cre/Tdtomato flox mice to identify the expression of STRs in other enteroendocrine-type cells and the crypt. We found that STR are expressed in Paneth cells of the crypt. We confirm this using mRNA pull down specifically from isolated epithelial cells. The role of STR in these cells is unknown and we are collecting preliminary data to shed light on their function. We intend to continue working on this unexpected aspect of STR function during the NCE period and use our findings for future grant applications. 2) Data collected As described above. Each activity involved several experiments and conditions including controls. 3) Summary statistics and discussion of results Final conclusions are pending. 4) Key outcomes or other accomplishments realized As a follow up to our previous studies (Serrano et al Mol Metab 2021; Serrano et al, Front Nutr 2022), we explored the role T1R2 Ile191Val loss-of-function variant in the regulation of diet-induced weight loss. We used a cohort of older obese participants who were subjected to a 6-month diet-induced weight loss program. We found that the variant predicted the amount and region of weight loss. Val carriers lost significantly more weight than their Ile/Ile counterparts, reduced their waist circumference and improved body composition. Notably, in agreement with our previous reports, they improved glucose control and reduced HbA1c. These data suggest that T1R2 loss-of-function may regulate weight loss through mechanisms that reduce the rate of glucose absorption. Based on these findings we are expanding Objective 3 (see below) to include responses to weight loss. Objective.2 Determine the contribution of intestinal T1R2 chemosensor in the regulation of gut microbiota. This objective has been completed (as indicated in the 2022 report). 1) Major activities completed / experiments conducted None to report 2) Data collected None to report 3) Summary statistics and discussion of results None to report 4) Key outcomes or other accomplishments realized None to report Objective.3 Investigate the regulation of intestinal STRs in response to nutrient overconsumption and their role in the development of metabolic disease. 1) Major activities completed / experiments conducted A) Using the "humanized" transgenic (Tg) mouse that expresses hT1R2 receptor under the T1R2 promoter we are characterizing the effects of treatment with a positive allosteric modulator (PAM) of human T1R2 on enteroendocrine function, insulin secretion and food consumption (continuation from 2022 report). B) We investigated the effects of chronic consumption of saccharin with/without high fat diet (HFD) in the regulation of metabolic responses. C) We initiated a study that explores the role of intestinal STR in the regulation of weight loss following the consumption of HFD (based on findings in humans discussed in Objective 1). 2) Data collected As indicated above. 3) Summary statistics and discussion of results A) PAM potentiates the effects of hT1R2 in the Tg mouse in taste sensitivity and insulin secretion but has no effect on food intake. We are now testing potential toxicity of chronic PAM administration. B) HFD has the anticipated effects on metabolism and increases glucose absorption. Ablation of T1R2 in the intestine reduces glucose absorption but mice gain the same amount of weight and develop the same phenotype as WT mice. Addition of Saccharin does not affect the outcomes of HFD. C) results still pending. 4) Key outcomes or other accomplishments realized Nothing to report
Publications
|
Progress 06/15/21 to 06/14/22
Outputs
Target Audience:During the reporting period onegraduate student has been trained in our lab through the implementation of the grant's objectives. Also, science based information gather through this project has been presented to general audiences. Changes/Problems:An ongoing implication of COVID-19 was that we could not hire more trainees and lab technicians to help complete the objectives of this proposal. Although we are actively seeking to hire more trainees or other scientific personnel the pool of qualified candidates is very limited. This has significant implications for the completion of the remaining components of objective 1 and objective 3 since personnel has to be trained from the beginning. What opportunities for training and professional development has the project provided?Under this reporting period one postdoctoral trainee have been conducting and assisting with the implementation of the proposed studies. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?The major goal for the next reporting period is to resume normal lab operations following COVID-19 restrictions and continue with the implementation of our Objectives. Specifically, Objective 1: A) Continue to decipher the mechanism for the regulation of glucose transport and metabolism, B) Determine the identity of intestinal cells expressing STRs Objective 2: Completed Objective 3: Assess the role of STRs during the consumption of sugars and artificial sweeteners (aspartame or sucralose)
Impacts
What was accomplished under these goals?
The use of non-caloric artificial sweeteners (NCAS) has increased considerably over the past decade. Strikingly, NCAS consumption in children has tripled from 1999 to 2012. Epidemiological data suggest that consumption of NCAS is associated with adverse metabolic effects, weight gain and obesity. These associations are paradoxical, considering that consumption of NCAS is intended to substitute for sugars in the diet for the purposes of weight control or the regulation of blood glucose in susceptible individuals. Thus, although NCAS are not metabolized by host tissues, they may not be physiologically "inert" as originally thought. Nevertheless, the FDA has designated these food additives as "generally recognized as safe (GRAS)" and has approved their use based on limited understanding of their physiological effects. Although mechanistic studies linking their consumption with physiological outcomes are generally lacking in humans, NCAS activate sweet taste receptors (STRs) found not only on the tongue but also in tissues relevant to nutrient metabolism such as the gut, the pancreas and even the brain. How interactions of NCAS with STRs alter energy metabolism in mice and humans is still elusive. Understanding the role of STRs in mediating metabolic response to ingested NCAS could shed light on the association between their consumption and public health outcomes and ultimately inform health policy regarding their optimal use. Objective.1 Elucidate the mechanisms for the regulation of glucose absorption by intestinal STRs. 1) Major activities completed / experiments conducted We continued the activities as described before. Specifically, A) We are elucidating the mechanism by which STR-mediated GLP2 secretion locally potentiates the translocation of GLUT2. We have identified the neurotransmitter vasoactive intestinal peptide (VIP) to be involved in the cascade of neuronal activation. We intend to use VIP-KO mice to establish causality. B) We used NMR spectroscopy in combination with the Ussing chamber in which can assess unbiased metabolite production by the intestinal epithelium in response to different glucose and glutamate concentrations added in the apical or basolateral site of intestinal preparations. C) We have been implementing the technique to measure postprandial glucose turnover in vivo using stable and radioactive isotopes. 2) Data collected As described above. Each activity involved several experiments and conditions including controls. 3) Summary statistics and discussion of results A) We have identified that VIP targets enterocytes to modulate glucose transport through its receptor and cAMP second messenger. B) We determined the metabolite signatures (using NMR) released by the intestinal epithelium in the blood following treatment with different substrates. The intestine releases alanine, lactate and 3-carbon intermediates. C) In response to luminal glucose, there is increased glucose oxidation, but VIP inhibits these effects. 4) Key outcomes or other accomplishments realized. A) We crossed T1r2-Cre/Tdtomato flox mice with Glucagon-eGFP-KI to specifically identify intestinal epithelial L-cells that express STRs. STRs are expressed in L-cells which are primarily reside in duodenum and jejunum. We also identified that STRs are expressed in other enteroendocrine-type cells and the crypt. Now, we are in the process of determining the identity of these cells. B) As part of understanding the role of T1R2 in human gut biology, we characterized a human variant of T1R2. Using biochemical approaches, we determined that the Ile191Val variant causes partial loss-of-function of T1R2 through reduced receptor in the plasma membrane. To test the significance and relevance of this findings in humans we used a cohort of healthy lean participants and showed that Val carriers have reduced glucose excursions during an oral glucose challenge, recapitulating the phenotype of T1R2-KO mice (based on findings from objective 1). In addition, we demonstrated that Val carriers have reduced HbA1c independent of glucose control and diabetes. These finding were published: 1. Serrano J, Seflova J, Park J, Pribadi M, Sanematsu K, Shigemura N, Serna V, Yi F, Mari A, Procko E, Pratley RE, Robia SL, Kyriazis GA. The Ile191Val is a partial loss-of-function variant of the TAS1R2 sweet-taste receptor and is associated with reduced glucose excursions in humans. Mol Metab. 2021 Dec;54:101339. doi: 10.1016/j.molmet.2021.101339. Epub 2021 Sep 9. PubMed PMID: 34509698; PubMed Central PMCID: PMC8476773. 2. Serrano J, Yi F, Smith J, Pratley RE, Kyriazis GA. The Ile191Val Variant of the TAS1R2 Subunit of Sweet Taste Receptors Is Associated With Reduced HbA1c in a Human Cohort With Variable Levels of Glucose Homeostasis. Front Nutr. 2022;9:896205. doi: 10.3389/fnut.2022.896205. eCollection 2022. PubMed PMID: 35662939; PubMed Central PMCID: PMC9160323. Objective.2 Determine the contribution of intestinal T1R2 chemosensor in the regulation of gut microbiota. This objective has been completed (as indicated in the 2021 report). 1) Major activities completed / experiments conducted None to report 2) Data collected None to report 3) Summary statistics and discussion of results None to report 4) Key outcomes or other accomplishments realized. None to report Objective.3 Investigate the regulation of intestinal STRs in response to nutrient overconsumption and their role in the development of metabolic disease. 1) Major activities completed / experiments conducted A) Using the "humanized" transgenic (Tg) mouse that expresses hT1R2 receptor under the T1R2 promoter we are characterizing the effects of treatment with a positive allosteric modulator (PAM) of human T1R2 on enteroendocrine function, insulin secretion and food consumption. B) As a follow up to our published studies exploring the effects of chronic consumption of saccharin(Serrano et al, Microbiome 2021), we investigated the effects of acute consumption of saccharin in the regulation of insulin secretion in vivo and ex vivo. 2) Data collected As indicated above 3) Summary statistics and discussion of results A) Final conclusions are pending. Preliminary data indicate that treatment with PAM potentiates the effects of hT1R2 in the Tg mouse. B) The findings pertaining to the effects of acute saccharin consumption were published: Serrano J, Meshram NN, Soundarapandian MM, Smith KR, Mason C, Brown IS, Tyrberg B, Kyriazis GA. Saccharin Stimulates Insulin Secretion Dependent on Sweet Taste Receptor-Induced Activation of PLC Signaling Axis. Biomedicines. 2022 Jan 6;10(1). doi: 10.3390/biomedicines10010120. PubMed PMID: 35052799; PubMed Central PMCID: PMC8773316. 4) Key outcomes or other accomplishments realized. Nothing to report
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2021
Citation:
Serrano J, Seflova J, Park J, Pribadi M, Sanematsu K, Shigemura N, Serna V, Yi F, Mari A, Procko E, Pratley RE, Robia SL, Kyriazis GA. The Ile191Val is a partial loss-of-function variant of the TAS1R2 sweet-taste receptor and is associated with reduced glucose excursions in humans. Mol Metab. 2021 Dec;54:101339. doi: 10.1016/j.molmet.2021.101339. Epub 2021 Sep 9. PubMed PMID: 34509698; PubMed Central PMCID: PMC8476773.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2022
Citation:
Serrano J, Meshram NN, Soundarapandian MM, Smith KR, Mason C, Brown IS, Tyrberg B, Kyriazis GA. Saccharin Stimulates Insulin Secretion Dependent on Sweet Taste Receptor-Induced Activation of PLC Signaling Axis. Biomedicines. 2022 Jan 6;10(1). doi: 10.3390/biomedicines10010120. PubMed PMID: 35052799; PubMed Central PMCID: PMC8773316.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2022
Citation:
Serrano J, Yi F, Smith J, Pratley RE, Kyriazis GA. The Ile191Val Variant of the TAS1R2 Subunit of Sweet Taste Receptors Is Associated With Reduced HbA1c in a Human Cohort With Variable Levels of Glucose Homeostasis. Front Nutr. 2022;9:896205. doi: 10.3389/fnut.2022.896205. eCollection 2022. PubMed PMID: 35662939; PubMed Central PMCID: PMC9160323.
|
Progress 06/15/20 to 06/14/21
Outputs
Target Audience:During the reporting period one postdoctoral associate have been trained in our lab through the implementation of the grant's objectives. Also, science based information gather through this project has been presented to general audiences. Changes/Problems:Due to the COVID-19 pandemic lab activities were severely tampered due to significant social distancing restrictions which has slowed down the pace for the completion of planned activities. Particularly, we encountered difficulties with Objective 3 due to the involvement of chronic dietary interventions. Another implication of COVID-19 was that we could not hire more trainees and lab technicians to help complete the objectives of this proposal. Beginning June 2021 social distancing restriction are lifted allowing for operating at full capacity, so we anticipate to proceed without any further problems. We are also actively seeking to hire more trainees or other scientific personnel. What opportunities for training and professional development has the project provided?Under this reporting period one postdoctoral trainee have been conducting and assisting with the implementation of the proposed studies. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?The major goal for the next reporting period is to resume normal lab operations following COVID-19 restrictions and continue with the implementation of our Objectives. Specifically, Objective 1: A) Continue to decipher the mechanism for the regulation of glucose transport and metabolism, B) Identify intestinal epithelial L-cells that express STRs and access their distribution and characteristics. Objective 2: Completed Objective 3: Assess the role of STRs during the consumption of sugars and artificial sweeteners (aspartame or sucralose)
Impacts
What was accomplished under these goals?
The use of non-caloric artificial sweeteners (NCAS) has increased considerably over the past decade. Strikingly, NCAS consumption in children has tripled from 1999 to 2012. Epidemiological data suggest that consumption of NCAS is associated with adverse metabolic effects, weight gain and obesity. These associations are paradoxical, considering that consumption of NCAS is intended to substitute for sugars in the diet for the purposes of weight control or the regulation of blood glucose in susceptible individuals. Thus, although NCAS are not metabolized by host tissues, they may not be physiologically "inert" as originally thought. Nevertheless, the FDA has designated these food additives as "generally recognized as safe (GRAS)" and has approved their use based on limited understanding of their physiological effects. Although mechanistic studies linking their consumption with physiological outcomes are generally lacking in humans, NCAS activate sweet taste receptors (STRs) found not only on the tongue but also in tissues relevant to nutrient metabolism such as the gut, the pancreas and even the brain. How interactions of NCAS with STRs alter energy metabolism in mice and humans is still elusive. Understanding the role of STRs in mediating metabolic response to ingested NCAS could shed light on the association between their consumption and public health outcomes and ultimately inform health policy regarding their optimal use. Objective.1 Elucidate the mechanisms for the regulation of glucose absorption by intestinal STRs. 1) Major activities completed / experiments conducted A) We have implemented studies to elucidate the mechanism by which STR-mediated GLP2 secretion locally potentiates the translocation of GLUT2. We have identified the neurotransmitter vasoactive intestinal peptide (VIP) to be involved in the cascade of neuronal activation. B) We used NMR spectroscopy in combination with the Ussing chamber in which can assess unbiased metabolite production by the intestinal epithelium in response to different glucose and glutamate concentrations added in the apical or basolateral site of intestinal preparations. C) We have been implementing the technique to measure postprandial glucose turnover in vivo using stable and radioactive isotopes. 2) Data collected As described above. Each activity involved several experiments and conditions including controls. 3) Summary statistics and discussion of results A) We have identified that VIP targets enterocytes to modulate glucose transport. B) We determined the metabolite signatures (using NMR) released by the intestinal epithelium in the blood following treatment with different substrates. These data will serve as controls for our interventions. 4) Key outcomes or other accomplishments realized. A) We crossed T1r2-Cre/Tdtomato flox mice with Glucagon-eGFP-KI to specifically identify intestinal epithelial L-cells that express STRs. Objective.2 Determine the contribution of intestinal T1R2 chemosensor in the regulation of gut microbiota. 1) Major activities completed / experiments conducted A) We have completed the proposed studies. 2) Data collected A) We have collected and analyzed data, as proposed. 3) Summary statistics and discussion of results A) Our final data analyses suggest that saccharin supplementation does not affect glucose tolerance or major swifts in gut microbiota communities. B) Saccharin feeding does not alter glucose transport or gut permeability. C) Ablation of STRs protects against age-related glucose tolerance. Taken together our preliminary findings suggest that chronic saccharin supplementation does not alter glucose metabolism and gut microbiota per se. These findings were published: Serrano J, Smith KR, Crouch AL, Sharma V, Yi F, Vargova V, LaMoia TE, Dupont LM, Serna V, Tang F, Gomes-Dias L, Blakeslee J, Hatzakis E, Peterson SN, Anderson M, Pratley RE, and Kyriazis GA. High dose saccharin supplementation does not induce gut microbiota dysbiosis or glucose intolerance in healthy humans and mice. Microbiome. 2021 Jan 12;9(1):11. doi: 10.1186/s40168-020-00976-w. PubMed PMID: 33431052; PubMed Central PMCID: PMC7802287. 4) Key outcomes or other accomplishments realized. None to report Objective.3 Investigate the regulation of intestinal STRs in response to nutrient overconsumption and their role in the development of metabolic disease. 1) Major activities completed / experiments conducted A) We have developed a "humanized" transgenic (Tg) mouse that expresses hT1R2 receptor under the T1R2 promoter. Unlike the mouse T1R2, the human T1R2 receptor can sense the artificial sweetener aspartame. We have performed basal metabolic characterization of the hT1R2Tg mouse. B) We are preparing to conduct studies using chronic consumption of sugars supplemented with aspartame or sucralose in T1R2-WT, T1R2-KO and hT1R2Tg mice. 2) Data collected A) hT1R2Tg mouse body composition, glucose tolerance tests, fed and fasted blood, tissue collection. 3) Summary statistics and discussion of results We found that the hT1R2Tg mouse respond to natural and artificial sweeteners, but can also respond to aspartame and other human-specific ligands and allosteric regulators. 4) Key outcomes or other accomplishments realized. Nothing to report
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Serrano J, Smith KR, Crouch AL, Sharma V, Yi F, Vargova V, LaMoia TE, Dupont LM, Serna V, Tang F, Gomes-Dias L, Blakeslee J, Hatzakis E, Peterson SN, Anderson M, Pratley RE, and Kyriazis GA. High dose saccharin supplementation does not induce gut microbiota dysbiosis or glucose intolerance in healthy humans and mice. Microbiome. 2021 Jan 12;9(1):11. doi: 10.1186/s40168-020-00976-w. PubMed PMID: 33431052; PubMed Central PMCID: PMC7802287.
|
Progress 06/15/19 to 06/14/20
Outputs
Target Audience:During the reporting period one postdoctoral associate and two undergraduate students have been trained in our lab through the implementation of the grant's objectives. Also, science based information gather through this project has been presented to general audiences in the form of a colloquium. Changes/Problems:Due to the COVID-19 pandemic and the temporary closure of all laboratories, grant activites completely ceased for at least 3 months (March through May 2020). Activities were resumed by June 1, 2020 but there are significant social distancing restrictions which has slowed down the pace for the completion of planned activities. However, we do not anticipate that the protocols and research goals will be affected by the pandemic. What opportunities for training and professional development has the project provided?Under this reporting period one postdoctoral trainee and two undergraduate students have been conducting and assisting with the implementation of the proposed studies. How have the results been disseminated to communities of interest?Beyond reported publications under review, key finding from our results have been presented to outreach seminars for diabetes education, particularly on the use of NCASs What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective.1 Elucidate the mechanisms for the regulation of glucose absorption by intestinal STRs. 1) Major activities completed / experiments conducted A) We have implemented studies to elucidate the mechanism by which STR-mediated GLP2 secretion locally potentiates the translocation of GLUT2. We have focused to identify the neurotransmitters' involved and the cascade of neuronal activation. B) We have optimized ex vivo studies to measure intestinal substrate oxidation through the assessment of 14CO2 in response to labeled substrates. In addition using NMR spectroscopy we have been developing a methodology using intact intestines in the Ussing chamber which can assess unbiased metabolite production by the intestinal epithelium in response to different luminal glucose and fructose concertation. C) We have been optimizing the technique to measure postprandial glucose turnover in vivo using stable and radioactive isotopes. 2) Data collected As described above. Each activity involved several experiments and conditions including controls. 3) Summary statistics and discussion of results A) We have identified VIP as a target neurotransmitter mediating the effects of GLP-2. B) We determined that the level of luminal glucose alters substrate oxidation preference in enterocytes and this mechanism involves STR activation. 4) Key outcomes or other accomplishments realized. B) We have begun to characterize the T1r2 promoter-driven Cre transgenic mice (T1r2-Cre) bred with select fluorescent reporter mice to specifically identify and evaluate intestinal epithelial cells that demonstrate capacity for glucose and NCAS sensing through STRs. Objective.2 Determine the contribution of intestinal T1R2 chemosensor in the regulation of gut microbiota. 1) Major activities completed / experiments conducted A) We have completed the proposed feeding studies (10 weeks) aiming to decipher the role of NCAS consumption in glucose tolerance and gut microbiota composition. 2) Data collected A) We have collected and analyzed: 1) fecal microbiota using 16S rRNA sequencing, 2) fecal short-chain fatty acids using Mass Spectroscopy, 3) fecal metabolites using NMR spectroscopy. B) We have completed and analyzed the glucose tolerance tests and associated measurements (body weight, food intake, water intake) 3) Summary statistics and discussion of results A) Our final data analyses suggest that saccharin supplementation does not affect glucose tolerance or major swifts in gut microbiota communities. B) Saccharin feeding does not alter glucose transport or gut permeability. C) Ablation of STRs protects against age-related glucose tolerance. Taken together our preliminary findings suggest that chronic saccharin supplementation does not alter glucose metabolism and gut microbiota per se. These findings are currently under review in the following manuscript: Serrano J, Smith KR, Crouch AL, Sharma V, Yi F, Vargova V, LaMoia TE, Dupont LM, Serna V, Tang F, Gomes-Dias L, Blakeslee J, Hatzakis E, Peterson SN, Anderson M, Pratley RE, and Kyriazis GA. High dose saccharin supplementation does not induce gut microbiota dysbiosis or glucose intolerance in healthy humans and mice. Microbiome (under revisions). 4) Key outcomes or other accomplishments realized. None to report Objective.3 Investigate the regulation of intestinal STRs in response to nutrient overconsumption and their role in the development of metabolic disease. 1) Major activities completed / experiments conducted A) We have performed basal metabolic characterization of intestine-specific deletion of T1R2 (T1R2-KOVil). B) We have conducted pilot studies to determine the dose of NCAS during chronic consumption of sugars. 2) Data collected A) Body composition, glucose tolerance tests, fed and fasted blood, tissue collection. 3) Summary statistics and discussion of results Deletion of intestinal STRs does not alter sweet taste perception, glucose tolerance or body composition. 4) Key outcomes or other accomplishments realized. Nothing to report
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2020
Citation:
Serrano J, Smith KR, Crouch AL, Sharma V, Yi F, Vargova V, LaMoia TE, Dupont LM, Serna V, Tang F, Gomes-Dias L, Blakeslee J, Hatzakis E, Peterson SN, Anderson M, Pratley RE, and Kyriazis GA. High dose saccharin supplementation does not induce gut microbiota dysbiosis or glucose intolerance in healthy humans and mice. Microbiome.
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Progress 06/15/18 to 06/14/19
Outputs
Target Audience:During the reporting period one postdoctoral associate and two undergraduate students have been trained in our lab through the implementation of the grant's objectives. Also, science based information gather through this project has been presented to general audiences in the form of a colloquium. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Under this reporting period one postdoctoral trainee and two undergraduate students have been conducting and assisting with the implementation of the proposed studies. How have the results been disseminated to communities of interest?Beyond reported publications, key finding from our results have been presented to outreach seminars for diabetes education, particularly on the use of NCASs What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The use of non-caloric artificial sweeteners (NCAS) has increased considerably over the past decade. Strikingly, NCAS consumption in children has tripled from 1999 to 2012. Epidemiological data suggest that consumption of NCASs is associated with adverse metabolic effects, weight gain and obesity. These associations are paradoxical, considering that consumption of NCASs is intended to substitute for sugars in the diet for the purposes of weight control or the regulation of blood glucose in susceptible individuals. Thus, although NCASs are not metabolized by host tissues, they may not be physiologically "inert" as originally thought. Nevertheless, the FDA has designated these food additives as "generally recognized as safe (GRAS)" and has approved their use based on limited understanding of their physiological effects. Although mechanistic studies linking their consumption with physiological outcomes are generally lacking in humans, NCASs activate sweet taste receptros (STRs) found not only on the tongue but also in tissues relevant to nutrient metabolism such as the gut, the pancreas and even the brain. How interactions of NCASs with STRs alter energy metabolism in mice and humans is still elusive. Understanding the role of STRs in mediating metabolic response to ingested NCASs could shed light on the association between their consumption and public health outcomes and ultimately inform health policy regarding their optimal use. Objective.1 Elucidate the mechanisms for the regulation of glucose absorption by intestinal STRs. 1) Major activities completed / experiments conducted A) We have quantified sugar transporters (SGLT1, GLUT2, GLUT5) and components of STR signaling (T1R2, T1R3, alpha-gustducin, TRPM5) in isolated intestinal tissue (duodenum, jejunum and proximal ileum) in fed (ad libitum) mice and purified brush border membranes (BBM) vesicles for western blot. B) We have assessed GLUT2 translocation in the jejunum using immunofluorescent staining and BBM isolation. C) We assessed SGLT1-mediated and GLUT2 glucose absorption over time using radioactive isotopes with the Ussing chamber. D) We determined the contribution of GLP-1 and GLP-2 in the regulation of glucose transport in vivo and in vitro. 2) Data collected As described above. Each activity involved several experiments and conditions including controls. 3) Summary statistics and discussion of results Major findings for this work were reported (Smith K et al. Mol Metab. 2018 Nov;17:98-111). In brief: STR signaling enhances the rate of intestinal glucose absorption specifically in response to the ingestion of a glucose-rich meal. These effects were mediated specifically by the regulation of GLUT2 transporter trafficking to the apical membrane of enterocytes. GLUT2 translocation and glucose transport was dependent and specific to glucagon-like peptide 2 (GLP-2) secretion and subsequent intestinal neuronal activation. Finally, high-sucrose feeding in wild-type mice induced rapid downregulation of STRs in the gut, leading to reduced glucose absorption. 4) Key outcomes or other accomplishments realized. A) We have initiated experiments using mice with intestine specific deletion of T1R2 gene to elucidate the details of the intestinal signaling pathway by which GLP-2 induces GLUT2 trnaslocation. B) We have generated a mouse T1r2 promoter-driven Cre transgenic mice (T1r2-Cre) bred with select fluorescent reporter mice to specifically identify and evaluate intestinal epithelial cells that demonstrate capacity for glucose and NCAS sensing through STRs. Objective.2 Determine the contribution of intestinal T1R2 chemosensor in the regulation of gut microbiota. 1) Major activities completed / experiments conducted A) We have initiated and partially concluded proposed feeding studies (10 weeks) aiming to decipher the role of NCAS consumption in glucose tolerance and gut microbiota composition. 2) Data collected A) We have collected feces and intestinal tissue from mice subjected to saccharin supplementation and controls. B) We have conducted glucose tolerance test in a similar cohort of mice in response to saccharin feeding. C) We have assessed ex vivo glucose transport, gut permeability and transporter expression in mice from the above cohorts. 3) Summary statistics and discussion of results A) Preliminary data analyses suggest that saccharin supplementation does not affect glucose tolerance or major swifts in gut microbiota communities. B) Saccharin feeding does not alter glucose transport or gut permeability. C) Ablation of STRs protects against age-related glucose tolerance. Taken together our preliminary findings suggest that chronic saccharin supplementation does not alter glucose metabolism and gut microbiota per se. 4) Key outcomes or other accomplishments realized. None to report Objective.3 Investigate the regulation of intestinal STRs in response to nutrient overconsumption and their role in the development of metabolic disease. 1) Major activities completed / experiments conducted A) We have generated and bred mice with an intestine-specific deletion of T1R2. B) We have conducted pilot studies to determine the dose of NCAS during chronic consumption of sugars. 2) Data collected A) daily water intake flavored with NCAS. 3) Summary statistics and discussion of results Nothing to report 4) Key outcomes or other accomplishments realized. Nothing to report
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2018
Citation:
Smith K, Karimian Azari E, LaMoia TE, Hussain T, Vargova V, Karolyi K, Veldhuis PP, Arnoletti JP, de la Fuente SG, Pratley RE, Osborne TF, Kyriazis GA. T1R2 receptor-mediated glucose sensing in the upper intestine potentiates glucose absorption through activation of local regulatory pathways. Mol Metab. 2018 Nov;17:98-111. doi: 10.1016/j.molmet.2018.08.009. Epub 2018 Aug 27. PubMed PMID: 30201274; PubMed Central PMCID: PMC6197762.
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