The Effect of rs7903146 Genotype on Islet GLP-1 Production in Humans
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: Exendin 9-39, Saline.
- Who it may be relevant to
- Registry conditions: Genetic Predisposition, Type2diabetes. Basic parameters: 25 years — 70 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- United States
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Overview
The investigators recently demonstrated that blockade of Glucagon-Like Peptide-1's (GLP-1) receptor (GLP1R) results in changes in islet function without changes in circulating GLP-1. These effects are more pronounced in people with early type 2 diabetes (T2DM) in keeping with increased expression of PC-1/3 and GLP-1 that is observed in diabetic islets. However, its regulation is at present unknown. Common genetic variation in the TCF7L2 locus (T-allele at rs7903146) arguably confers the greatest genetic risk of T2DM. It is associated with α- and β-cell dysfunction. TCF7L2 (the product of TCF7L2) was first described as the transcription factor necessary for proglucagon expression in intestinal L-cells (which secrete GLP-1). This led to speculation that TCF7L2 confers risk of diabetes via changes in circulating GLP-1. This has turned out to not be the case. This raises the possibility that these diabetogenic effects are mediated via an inability of islet GLP-1 to adapt to rising glycemia. Therefore, this experiment will determine the contribution of islet GLP-1 to the functional abnormalities of the islet associated with the TCF7L2 locus.
Detailed description
The investigators recently demonstrated that blockade of Glucagon-Like Peptide-1's (GLP-1) receptor (GLP1R) results in changes in islet function without changes in circulating GLP-1. This supports other evidence (rodents and humans) that through the (inducible) expression of a prohormone convertase (PC-1/3), the α-cell can process proglucagon to intact GLP-1. 'Islet' or 'pancreatic' GLP-1 acts in a paracrine fashion to regulate insulin (basal and 1st phase) and glucagon secretion. These effects are more pronounced in people with early type 2 diabetes (T2DM) in keeping with increased expression of PC-1/3 and GLP-1 that is observed in diabetic islets.
Although pancreatic GLP-1 adapts to support islet function in T2DM, it is unclear if this mechanism is upregulated in prediabetes and whether it contributes to the phenotype(s) observed. There is evidence that α-cell proglucagon processing is subject to paracrine regulation by the β-cell. β-cell secretion of the signaling peptide 14-3-3-Zeta is decreased by GLP1R agonism, stimulating α-cell production of GLP-1. Common genetic variation in the TCF7L2 locus (T-allele at rs7903146) arguably confers the greatest genetic risk of T2DM4. It is associated with α- and β-cell dysfunction. TCF7L2 (the product of TCF7L2) was first described as the transcription factor necessary for proglucagon expression in intestinal L-cells (which secrete GLP-1). Does a relative absence or an inability of islet GLP-1 to adapt to rising glycemia explain the increased risk of T2DM associated with the T-allele at rs7903146? This experiment will determine the contribution of islet GLP-1 to the functional abnormalities of the islet associated with the TCF7L2 locus.
Interventions
- Biological Exendin 9-39
A competitive antagonist of the GLP-1 receptor - Other Saline
Saline infusion will serve as an inactive comparator
Primary outcome measures
- Change in fasting glucose [Time frame: Change in average glucose concentration between -30 min and 0 min of each study day (saline day vs. exendin 9-39 day)]
- Change in fasting glucagon [Time frame: Change in average glucagon concentration between -30 min and 0 min of each study day (saline day vs. exendin 9-39 day)]
Secondary outcome measures (2)
- Change in fasting insulin [Time frame: Change in average insulin concentration between -30 min and 0 min of each study day (saline day vs. exendin 9-39 day)]
- Change in first phase insulin secretion [Time frame: Change in integrated insulin concentrations (area above baseline) between 0 min and 30 min of each study day (saline day vs. exendin 9-39 day)]
Eligibility criteria
Inclusion criteria
- Subjects with the TT or CC genotype at rs7903146
Exclusion criteria
- Age < 25 or > 70 years (to avoid studying subjects who could have latent type 1 diabetes, or the effects of age extremes in subjects with normal or impaired fasting glucose).
- CT genotype at rs7903146
- HbA1c > 6.5%
- Use of any glucose-lowering agents including metformin or sulfonylureas.
- For female subjects: positive pregnancy test at the time of enrollment or study.
- History of prior upper abdominal surgery such as adjustable gastric banding, pyloroplasty and vagotomy.
- Active systemic illness or malignancy.
- Symptomatic macrovascular or microvascular disease.
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: Yes
Study design
- Allocation
- Randomized
- Model
- Crossover
- Masking
- Open label
- Primary purpose
- Basic science
Study locations
United States · 1 center
- Mayo Clinic in Rochester — Rochester
Identifiers
NCT: NCT06972407 · 24-007701