An insulin nasal spray for diabetes?

Researchers have developed a “nasal spray vaccine” that might stop children developing diabetes, the Daily Express has reported. The “remarkable breakthrough” can stop the body’s immune system from attacking insulin-producing cells, the paper reported.

The report is based on a small study in which researchers looked at whether giving insulin as a nasal spray to adults recently diagnosed with type 1 diabetes could stop their immune system from killing the cells that produce insulin, a hormone needed by the body to control blood sugar levels.

The study found that nasal insulin did not prevent the loss of insulin-producing cells, although it did seem to reduce the levels of antibodies (proteins which are part of the immune system) that target insulin. This suggests that it might suppress the immune response to insulin.

Although this finding was promising, it is too early to know whether such a spray could be used as a “vaccine” for people at risk, particularly children who have not yet developed diabetes, which was not investigated in the study. This study was carried out in adults who already had a particular type of uncommon, late-onset diabetes. Therefore, further studies will be needed in people at risk of other forms of the condition. Future studies will also need to test whether any change in antibodies really can improve clinical outcomes, including blood sugar levels, for these patients.

Where did the story come from?

The study was carried out by researchers from the Institute of Medical Research and the Royal Melbourne Hospital, both in Victoria, Australia, and the St Vincent de Paul Hospital and University Paris Descartes, both in Paris, France. It was funded by the National Health and Medical Research Council of Australia, by a Victoria State government grant and by France’s INSERM research programme. The study was published in the peer-reviewed medical journal Diabetes.

The study’s findings were described inaccurately by the Daily Express. The newspaper’s assertion that researchers had developed a nasal spray vaccine that can stop children developing diabetes was not supported by the research, which looked at adults who already had a rare form of the condition.

What kind of research was this?

This randomised controlled trial (RCT) looked at whether using an insulin nasal spray could prevent the destruction of insulin-producing cells in adults with early-onset, non-insulin-requiring type 1 diabetes. An RCT, in which some people are given a treatment and others an inactive placebo for comparison, is the best type of study to investigate the potential effectiveness of an intervention, such as a new medication.

In a healthy pancreas, the beta cells secrete the hormone insulin to help the body control blood sugar. The researchers point out that the type 1 form of diabetes is an “auto-immune disease” in which the body’s immune response mistakenly attacks the body’s own cells. This destroys the insulin-producing cells in the pancreas, leading to poor control of blood sugar and the potential need for insulin injections to correct this.

Compared with classic type 1 diabetes, which develops during childhood, people who develop type 1 diabetes later in life have greater reserves of the pancreatic cells that make insulin. In many cases, they do not initially require insulin for treatment. This is different to juvenile-onset type 1 diabetes, which requires treatment with insulin. This type of non-insulin-requiring type 1 diabetes is less common but more likely to be the result of an immune process. Type 2 diabetes is not caused by faults of the immune system. The researchers say that studies in mice have shown that giving insulin orally or nasally can prevent the immune response from happening and can protect against type 1 diabetes, but studies in humans have been poorly documented.

The researchers say that adults with recent-onset diabetes who do not yet need insulin injections (because the body can still produce some insulin) provide an opportunity to study whether nasal insulin can reduce the immune response normally seen in type 1 diabetes.

What did the research involve?

The researchers recruited 52 adults aged 30-75 years old who had been diagnosed with type 1 diabetes in the previous year. When they entered the study, all participants were controlling their glucose levels using diet and oral drugs but did not yet need insulin injections. They were randomly split into two groups. Over 10 consecutive days, and then on two consecutive days a week for 12 months, one group of participants used a self-administered dose of insulin through a metered-dose nasal spray, equivalent to 1.6mg of insulin daily. The other group was given a placebo spray.

The participants were assessed using an interview and physical examination at the start of the study and every three months for 24 months. They also had blood tests for various antibodies, including insulin autoantibodies (IAA), which destroy the insulin-producing cells. The functioning of the insulin-producing beta cells in the pancreas was assessed with a test called the glucagon-stimulated secretion of C-peptide. This is a validated measure of beta cell function and can give an estimate of the number of beta cells remaining. Blood test results were similar at the start of the study in both groups.

The participants also received advice on how to manage their diabetes with diet and non-insulin drugs, with the aim of controlling blood glucose levels. Those whose glucose levels became too high were given insulin injections.

The researchers used validated statistical methods to analyse their results.

What were the basic results?

Overall, the blood tests indicated that the insulin-producing cells declined by 35% over the 24 months, with no difference between the nasal insulin and the placebo group. Twenty-three of 52 participants (44%) progressed to having insulin injections.

However, the two groups differed in their blood levels of insulin autoantibodies (IAA) when given insulin injections. The insulin antibody response was “significantly blunted in a sustained manner” in those who had received nasal insulin. This indicates that, in the participants who took nasal insulin, fewer antibodies were created when they were given insulin injections.

Levels of other antibodies associated with diabetes, called GADA and IA2A, were similar at the start of the study in the two groups and remained unchanged throughout the study.

How did the researchers interpret the results?

The researchers say that although giving nasal insulin did not stop the loss of insulin-producing cells, there was evidence from the antibody test for IAA that it made the immune system more tolerant to insulin and could, therefore, be used to prevent diabetes in people at risk. They say that their study provides the first evidence that nasal insulin could alter the immune response to insulin. They suggest that by suppressing the immune response to insulin, this method could be used to protect people at risk of type 1 diabetes, particularly children.

Conclusion

This small study has shown that giving nasal insulin to adults with recent-onset type 1 diabetes seems to suppress the immune response to insulin normally seen in people with this disorder, although it had no effect on the loss of insulin-making cells.

Caution must be taken when interpreting the results from this study, and it is too early to know whether such a spray could be used as a “vaccine” for those at risk, in particular children. Also, this study was carried out in adults who had a relatively uncommon form of type 1 diabetes, which is caused by the immune system but which does not necessarily require insulin. Given the difference to other more common forms of the condition, the results are unlikely to be relevant to people with other forms of type 1 diabetes and, in particular, the more common type 2 diabetes.

In addition, to know whether this treatment can help prevent diabetes will require further studies in the high-risk people that the researchers refer to. Furthermore, researchers would need to test whether the change in antibodies improved clinical outcomes for these people, including blood glucose levels.