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Q24 - C-STAR Blood Glucose Control

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Endocrine System Physiology Cell Signaling & Communication

C-STAR (caffeine-stimulated advanced regulators) is a system constructed in cells that contain a gene encoding a synthetic human glucagon-like peptide (shGLP-1). These cells were encased in microscopic capsules.

The shGLP-1 peptide is used to treat type 2 diabetes because it stimulates pancreatic B cells to secrete insulin in a blood glucose-dependent response.

In the cells that contain C-STAR, there are proteins which form dimers in the presence of caffeine molecules. The active dimer causes phosphorylation of the STAT3 transcription factor, which turns on the transcription of the shGLP-1 gene.

C-STAR system diagram showing caffeine-induced protein dimerization, STAT3 phosphorylation, and shGLP-1 gene activation

The performance of the C-STAR system was tested on three groups of laboratory mice:

  1. Wild type (WT)
  2. Diet-induced obesity (DIO)
  3. DIO with administration of C-STAR microcapsules

All mice received caffeine orally daily. An oral glucose tolerance test was performed. 2 g of glucose per 1 kg of body weight was administered and blood glucose concentration was measured for 120 minutes. Error bars in the figure show the standard error.

Oral glucose tolerance test results showing blood glucose concentration over time for WT, DIO, and DIO + C-STAR mice

True or False?

Q24.1. In WT mice, glucose levels returned to basal level after 90 minutes.
Q24.2. STAT3 is indispensable for the synthesis of shGLP-1 in the C-STAR system.
Q24.3. C-STAR caused blood glucose levels of DIO mice to be similar to WT mice 60 minutes after glucose administration.
Q24.4. Both WT mice and DIO mice are needed as controls to assess the effectiveness of C-STAR in this experiment.
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Question reproduced from IBO 2023, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF