Could Exercise Help Preserve Beta Cells in Type 1 Diabetes?

Becky McCall

October 23, 2014

Studies to explore whether exercise can help preserve pancreatic beta-cell function in patients newly diagnosed with type 1 diabetes should be conducted, say the authors of a new review.

Dr Parth Narendran (Institute of Biomedical Research, University of Birmingham, United Kingdom) and colleagues say their conclusion is motivated by an appreciation of the importance of residual insulin secretion in people with type 1 diabetes.

However, many of the trials in type 1 diabetes involving immunotherapies aimed at preserving beta-cell function have shown potential for harm, they note in their paper published online October 21 in Diabetologia.

"It made us realize that we need to think outside the box and perhaps look at what has worked in other forms of diabetes," Dr Narendran told Medscape Medical News.

In the review, they examined 706 articles looking at the effects of exercise on pancreatic beta-cell preservation in both healthy adults and those at different stages in the natural history of type 2 diabetes. These were sourced from the Cochrane Library and MEDLINE between the years 2009 and 2014 and showed evidence that exercise can preserve beta-cell function.

But "while there is beta-cell loss in both…forms of diabetes, the underlying cause is different," said Dr Narendran. This reinforces the necessity of performing research "to find out if exercise works in type 1 diabetes, rather than just extrapolating from studies of type 2."

The paper therefore serves as a "for-debate" article, which proposes that the time has come to test the beta-cell–preserving effects of exercise in patients with type 1 diabetes, he and his colleagues assert.

Preservation of Beta-Cell Function

The studies covered in their review demonstrate that exercise can preserve beta-cell function in people without diabetes, those with impaired glucose tolerance, and in people with type 2 diabetes.

"Probably the best evidence that exercise preserves beta-cell function comes from the STRRIDE study," said Dr Narendran. This study of 179 middle-aged people at risk for type 2 diabetes required participants to walk for 1 hour three times per week for 8 months. "This exercise improved their beta-cell function by 60%."

And while there is no research on exercise and beta-cell function in type 1 diabetes, the researchers did find some evidence from studies in other autoimmune conditions.

This included a study in Graves' disease, where a structured exercise program accelerated the withdrawal of antithyroid medication and halved the relapse rate over the first year. And a small clinical trial of exercise and diet was recently shown to reduce the severity of psoriasis activity by 50%, they note. Similar observations have been noted in animal models of multiple sclerosis, they add.

"The benefits seen in these autoimmune diseases cannot be explained by improvements in insulin sensitivity and suggest a direct effect on the autoimmune-disease process," they observe.

"Exercise might increase anti-inflammatory agents such as adiponectin and cortisol or decrease proinflammatory agents such as [tumor necrosis factor] TNF-alpha, [interleukin] IL-1, and/or leptin," explained Dr Narendran.

Changes such as these could "modulate the autoimmune destructive process that targets the insulin-producing beta cells in type 1 diabetes," he added.

"If exercise is shown to salvage residual beta-cell function, there would be a strong argument to implement it much earlier in the natural history of this condition and to develop strategies to encourage and support patients at this time," he and his colleagues state.

Type 1 Diabetes and Exercise: A Complex Situation

However, research has shown that people with type 1 diabetes do not undertake sufficient exercise, and exercise is not actively promoted or supported at the time of diagnosis with type 1 diabetes, the researchers explain

This could be due to the fact that the effects of physical exercise in type 1 diabetes are complex, they suggest.

For example, "some exercises such as long-distance running or walking will drop the glucose. Others such as squash, weight lifting, or short sprints will increase it, while other intermittent exercises such as football or children running around the playground will not affect the glucose levels much immediately, but they can drop later," said Dr Narendran.

"All this needs to be factored in when we ask our research patients to exercise and indeed has to be thought about when people with type 1 diabetes exercise in the day-to-day setting," he added.

For this reason, any exercise plans in clinical trials will need to clearly define the optimal intensity, type (eg, aerobic or resistance), duration, and frequency of exercise for preservation of beta cells in type 1 diabetes, and the influence of age, sex, and antibody status will also have to be factored in, say he and his colleagues.

Dr Narendran suggests initially advocating 150 minutes of moderate intensity exercise per week, combined with some strengthening exercises.

"While we don't know how intensive the exercise should be, there are some interesting data from patients with type 2 diabetes that moderate-intensity exercise may be better for beta cells than intensive exercise."

He and his colleagues are currently developing an educational package to support people with type 1 diabetes who want to exercise safely and effectively.

Exercise Meaningful at All Stages of Diabetes

It also remains uncertain at which point any residual beta-cell function is meaningful in type 1 diabetes, but some work from the Diabetes Control and Complications Trial (DCCT) suggests that a peak C peptide of 200 pmol/L is a cutoff point above which patients are protected from microvascular complications and from hypoglycemia, Dr Narendran said.

"Currently, this would be a sensible point above which to intervene" in terms of preserving beta-cell function. "That said, remember that exercise has many other benefits outside the potential to save beta cells, so there is a strong argument for advocating exercise at all stages of type 1 diabetes," he concluded.

Dr Narendran and coauthors have reported no relevant financial relationships.

Diabetologia. Published online October 21, 2014. Article

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