Diabetes Risk: Is There Something Sweet About Viral Infection?
There are many known behavioral, environmental, and genetic risk factors for T2D but until recently, viruses had only been proposed as playing a role in the development of type 1 diabetes, in which the pancreas stops producing enough insulin.
An individual may be diagnosed as having prediabetes when they exhibit impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). Previous studies have found that the incidence rate of T2D is much higher in people with prediabetes (7.6% per person-year) than among individuals with normal glucose tolerance (0.6% per person-year).
Herpes Virus Disturbs Glucose Metabolism
The new study is based on health data for 1967 subjects in the KORA (Cooperative Health Research in the Augsburg Region) population-based health research platform in the south of Germany.
Participants underwent detailed health examinations at baseline (2006-2008) and at follow-up (2013-2014), which included testing for the presence of human herpesviruses, oral glucose tolerance tests (OGTT), and measurement of glycated hemoglobin (HbA1c) (a measure of blood sugar control over the previous 3 months).
The study group had a median age of 54 years at baseline, 962 (49%) were men and 999 (51%) were women. Incidence analysis for the development of (pre)diabetes used the data for those 1257 participants with normal glucose tolerance at baseline (median age 49 years, 42% male and 58% female [528 and 729 individuals, respectively]).
Further analyses of blood samples were performed to detect the presence of antibodies to 7 of the 8 known human herpesviruses, which would indicate the presence of both primary and latent infections.
The following variables known to be associated with diabetes risk were also assessed at baseline: sex, age, BMI, years of education, never-smoking status (yes/no), leisure-time physical activity (active/inactive), parental diabetes (yes/no), and hypertension (yes/no, defined as blood pressure higher than 140/90 mmHg).
They found that age, BMI, smoking, and years of education were all associated with an individual’s risk of developing both prediabetes and T2D.
Around one-third (34%) tested positive for more viruses at the end of the follow-up period, 54% had the same number, and only 12% were positive for fewer viruses than at the start. While herpesviruses are persistent in their hosts, they may not always be detected by antibodies in the blood.
Infection usually occurs in early childhood but can take place in later life, so while the observed seroconversions may be new cases, they are more likely to be due to the immune response to a previously undetected virus.
Of the seven herpesviruses examined, HSV2 and Cytomegalovirus (CMV) were associated with the incidence of (pre)diabetes among individuals with normal glucose tolerance at baseline that was independent of other risk factors.
The study found that both HSV2 and CMV consistently and complementarily contributed to the development of (pre)diabetes, even after accounting for sex, age, BMI, education, smoking, physical activity, parental diabetes, hypertension, lipid levels, insulin resistance, and fasting glucose.
The mechanisms by which these viruses could contribute to the development of (pre)diabetes remain to be discovered. Both HSV2 and CMV cause chronic infections that could modulate the immune system by stimulating or suppressing its activity, which in turn can influence the glucose metabolism.
These results highlight the link between viruses and (pre)diabetes, and the need for more research evaluating public health viral prevention strategies, possibly including the development of effective vaccines against herpesviruses.
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