Exercise by itself can go a long way
Exercise is an important factor in health. Many studies show this to be true. It also applies to the prevention of type 2 diabetes. The research project SMIDIG (Nordic Walking to Prevent Insulin Resistance and Diabetes in Gustavsberg) is an interesting study from several points of view and quite unique of its kind.
The study, which involves several research teams at Karolinska Institutet, is a pure exercise study, unlike most previous studies. No attempt has therefore been made to influence the dietary habits of the participants. The idea is to devise a model that works in people's everyday lives.
"We wish to be able to tell patients that they have to make this level of effort to achieve these particular effects. Just claiming that exercise is good for you is not enough," says Tomas Fritz, a GP at Gustavsbergs Healthcare Centre and one of the researchers behind the study. What is needed, he says, is to find a form of exercise that the vast majority of people are perfectly happy with, that requires a reasonable level of effort and that is easy for people to practise where they live.
Three groups are involved in the study people with type 2 diabetes, people with reduced glucose tolerance and healthy controls. Half are women, half are men, and all are in their sixties. The groups were divided so that half carried on with their usual lifestyle, while half took up Nordic walking for a total of five hours of week, split between four and ten sessions. The participants were recruited from the epidemiological study run by Professor Claes-Göran Östenson (see previous article), and the study continued for four months. During this period the participants kept an exercise diary.
All the participants are extremely well characterised. They underwent a fitness test both before and after the study period in which blood sugar levels, body weight, body fat, waist circumference, blood pressure, blood lipids etc. were recorded. Advanced ultrasound scans of the heart and blood vessels were carried out to study any changes there, and muscle biopsies were taken from a number of participants. This involves removing a small piece of tissue from the thigh muscle and is done to enable the way in which the muscle cells are affected by exercise to be studied. Analysis is under way, and some results are starting to emerge.
"All three groups have reduced their BMI (body mass index) and waist circumference. Body fat has also decreased. The blood sugar values of the type 2 diabetics have improved." Fritz reports.
Analysis of cells and genes that may be of significance in diabetes
The muscle biopsies are dealt with by another research team at the Department of Physiology and Pharmacology of Karolinska Institutet. It has been found that muscle cells from type 2 diabetics and from individuals with reduced glucose tolerance do not take up sugar as well as those from healthy controls, but it has not yet been analysed whether any change has taken place since the trial period. Another question yet to be answered is whether any improvement has taken place in the mitochondria of the cells in diabetics. The mitochondria play an important role in the energy metabolism of the cells, and their function is impaired in patients with type 2 diabetes.
"We will also analyse some 50 different genes that may be of significance in diabetes. These are genes that regulate glucose and fat metabolism and influence mitochondrial function and genes that act as transcription factors. This means that they play a key role by determining which other genes are to be activated or be inactive," says associate professor Anna Krook.
She reports that research on fat metabolism to date has been quite limited. She now wishes to see whether the genes involved become more active in exercise and whether they can be linked to clinical improvements in patients. Another gene Anna Krook and her colleagues are particularly interested is called DKGdelta and is important for insulin sensitivity in muscle cells.
"We have seen in a pilot study that in those who respond well to exercise through increased insulin sensitivity DKGdelta is up-regulated. We wish to see whether this also holds true in the larger study," she says.
First published in Medical Science, issue 1, 2009