Oxidative DNA damage and other risk factors, in relation to lifestyle in diabetes type II and metabolic syndrome patients

Lifestyle factors are important in prevention and treatment of lifestyle related diseases as obesity, type II diabetes and cardiovascular diseases. Patients with these diseases or in the risk zone of obtaining them are classified as having the metabolic syndrome. Diet, physical activity and stress management are considered as important factors for preventing or treating their development. In the development and progress of underlying mechanisms in these diseases, oxidative stress and inflammation are considered as important factors since these patient groups have increased levels of oxidative stress and inflammation compared to healthy subjects.

The aim of this thesis was to study the influence of dietary factors and physiological risk factors on oxidative stress and inflammation in patients with diabetes type II or metabolic syndrome. This has been investigated in two clinical studies, which have resulted in the two papers in this thesis.

In Paper I, patients with metabolic syndrome were part of a residential intervention program for 17 days, with a 5-day follow up. Six months after the start of the program the patients had significantly decreased levels of oxidative stress on DNA. During the same period the patients also had significantly decreased levels of the physiological risk factors weight, BMI, waist- and hip circumferences and body fat, and increased levels of HDL cholesterol. Initial levels and quality of cholesterol were the only factors found to have a correlation to the decrease in oxidative stress. Since the changes probably were lifestyle related, a prolonged lifestyle modification for the patients might help them to maintain the positive results from the intervention.

In Paper II patients with diabetes type II were studied and their dietary intake and relevant clinical risk variables were measured. Correlations between diet and plasma antioxidants with oxidative stress and inflammation were analysed. Plasma alpha-carotene and beta-carotene were found to be good biomarkers for fruit and vegetable intake. Further more, fruit and vegetable intake had a negative correlation with DNA oxidation and lipid peroxidation. Dietary vitamin C had a negative correlation with lipid peroxidation and plasma ascorbate with DNA oxidation. The plasma carotenoids were negatively correlated with inflammation.

In conclusion, a residential intervention program with the purpose to change diet, physical activity level and to cope with stress can result in health benefits for metabolic syndrome patients. Furthermore, antioxidants in fruit and vegetables can be an important lifestyle factor, since it seems to have a positive impact on DNA oxidation, lipid peroxidation and inflammation in diabetes type II patients. Fruit and vegetable intake and ascorbate might affect oxidative stress and carotenoids might affect inflammation, this supporting the recommendations of a high fruit and vegetable intake in this patient group.

List of scientific papers

I. Åsgård R, Hedman M, Sjöström M and Möller L (2008). Long term reduction of DNA oxidation after a life style intervention. [Submitted]

II. Åsgård R, Rytter E, Basu S, Abramsson-Zetterberg L, Möller L, Vessby B (2007). High intake of fruit and vegetables is related to low oxidative stress and inflammation in a group of patients with type 2 diabetes. Scand J Food. Nutr 4: 149-158