Part.1 Background
Type I diabetes is an autoimmune disease due to the destruction of beta cells of islets that produce insulin and the absolute insufficiency of insulin secretion.
Figure 1.
Distribution of type I diabetes patients in the global population
Table 1.
Top 10 countries or territories for estimated number of incident (new) cases o type 1 diabetes in children and adolescents (0-19 years) per annum
Table 2.
Challenges with the diagnosis of adult-onsettype 1 diabetes
In China, the incidence rate of people aged 0-14 years is 1.93/100000, significantly higher than that of people of other ages2.(The incidence rate of people aged 15-29 years is 1.28/100000, while the incidence rate of the elderly is 0.69/100000.)
Figure 2.
Age distribution of type I diabetes patients in the global population
From the above chart, we can see that in 2022, there were 530000 new confirmed cases of T1D, of which 20.1000 were patients under the age of 20. Most patients with type I diabetes get sick in children or adolescence, and some adults will also be affected.
The risk factors of type I diabetes include heredity, toxin, immune system disorder and virus infection.
Specific HLA alleles are closely associated with TD.
Figure 3.
The risk factors of type I diabetes
Type I diabetes can cause a variety of complications, including acute ketoacidosis, chronic diabetes foot and other complications involving other systems and organs. In addition, studies have shown that adults with type 1 diabetes have an increased risk of other autoimmune diseases. About 30% of adults with type 1 diabetes have thyroid autoimmunity.
Why do we do this?
At present, the treatment of T1D mainly includes drug therapy and transplantation therapy.
Insulin is the
main medication for T1D treatment, but if patients want to successfully manage T1D, they need to inject multiple
times a day to maintain blood sugar stability, or use automatic insulin delivery systems such as insulin pumps,
and continuously monitor blood sugar changes.
The above methods require lifelong use and can lead to some side effects, such as pain at the injection site,
subcutaneous fat hyperplasia, and hypoglycemia.
The transplantation of pancreas, islets, and stem cells is
an ideal treatment for T1D, but the lack of immune response and donor resources severely limits the widespread
use of this method.
We designed the Glycemic Stabilizer project to construct a Designer cell that can secrete insulin using synthetic biology methods. In this cell, high blood sugar promotes insulin synthesis and secretion, and once blood sugar drops to a certain level, it can prevent further insulin synthesis and prevent the occurrence of hypoglycemia.
Part.2 Introduction
the GI-GAL4 and LOV-VP16 genes regulated by the GIP promoter (a glucose sensitive promoter that enhances GIP promoter activity)
the insulin genes regulated by the UAS promoter (which can be activated by GAL-VP6)
When the glucose concentration increases, GI-GAL4 and LOV-VP16 proteins are expressed, but when GI-GAL4 and LOV-VP16 proteins are present alone, they cannot activate glucose expression.
When the glucose concentration reaches a pathological state, the switch opens and activates a blue light, catalyzing the covalent binding of GI-GAL4 and LOV-VP16 proteins, i.e. GI-GAL4: LOV-VP16, to assemble an active GAL4-VP16 transcription factor that binds to the UAS promoter, promoting insulin synthesis and secretion.
In this system, we utilized the promoter of GIP to control the expression of GI-GAL4 and LOV-VP16 proteins, in order to prevent blue light from mistakenly turning on and causing insulin synthesis at low blood sugar concentrations.
Additionally, considering that the GIP promoter cannot accurately sense changes in blood sugar, such as at 5mM, The GIP promoter can be activated, but at this point blood sugar is normal. Therefore, we have designed a blood sugar concentration sensing switch that can accurately sense pathological blood sugar levels to promote insulin secretion.
Figure 4.
System Overview
The above system plays a more precise regulatory role in insulin synthesis, but, the half-life of GI-GAL4 and LOV-VP16 proteins reaches the hour level, and undigested proteins continue to promote insulin synthesis, thereby posing a risk of hypoglycemia.
The system consists of miRNA and miR-BS (miRNA binding site) located in the insulin expression vector 3 '- UTR.
When miRNA is expressed, it binds to miR-BS and inhibits insulin expression. In order to achieve the regulation of blood glucose levels in the system, we further constructed a sponge controlled by the GIP promoter. Under high blood glucose conditions, the sponge binds to miRNA, releasing the binding of miRNA to insulin expression.
However, when blood glucose drops to normal levels, the expression of the sponge decreases, MiRNA is liberated and binds to miR-BS, inhibiting insulin expression.
To avoid such dangerous situations, we have designed a negative feedback system that can prevent insulin
expression when blood sugar drops.
We can use materials such as microcapsules, hollow fiber membrane tubes, and sodium alginate gel as carriers to implant engineered cells subcutaneously and achieve the goal of controlling blood sugar.
Part.3 Glycemic stabilizer
However, due to the threshold for blue light activation being when blood glucose concentration exceeds the physiological state, blue light does not activate and cannot synthesize the GAL-VP16 promoter, resulting in the inability of insulin expression.
The use of biosensors to control the blue light switch through changes in blood
glucose concentration.
We have a precise regulatory system that enables glucose concentration
response to physiological and
pathological changes, preventing insulin synthesis and release under physiological conditions.
To prevent hypoglycemia and hyperinsulinemia, the project has safety guarantees.