Background: Type 2 diabetes mellitus (T2DM) is usually associated with overweight or obesity. T2DM is under strong genetic influence and a family history of T2DM (FH+) may be the most potent risk factor for the disease. Recently we have shown that FH+ individuals show increased susceptibility to weight gain and increased adiposity. The autonomic nervous system (ANS) is linked to systems regulating energy balance and to endocrine and cardiovascular disturbances associated with T2DM, and may therefore be involved in the genetic predisposition to T2DM. Previous studies of ANS in FH+, estimated by heart rate variability (HRV), have been equivocal, possibly due to confounding by concurrent obesity and/or gender effects. We tested the effects of FH+ on HRV in non-obese females to assess the involvement of the ANS in the genetic susceptibilities to T2DM and obesity.

Method: Non-diabetic, non-obese female subjects were categorised as FH+ (≥1 1st degree relative with T2DM, n=17, age 57±2 years, BMI 24.8±0.7 kg/m2) or FH- (no family history of T2DM, n=18, 56±2 years, 25.0±0.8 kg/m2). Electrocardiograph traces were analysed for frequency domain heart rate variability (HRV) as total power (TP), low frequency (LF 0.04 – 0.15 Hz) and high frequency (HF 0.15 – 0.40 Hz) domains. Effects of FH+ were assessed by one-way ANOVA of log-transformed variables.

Results: FH+ was associated with reduced HRV in all parameters tested, (LF p=0.0018; HF p=0.0002; TP p=0.0008). The LF/HF ratio, reflecting sympathovagal balance, was comparable between groups (p=0.68). These results were not influenced by menopausal status.

Conclusion: We conclude that decreased HRV, implying altered autonomic modulation, is present in non-obese females with a family history of T2DM. This suggests that the ANS may be involved in the genetic susceptibility to T2DM and/or obesity, but further studies are required to ascertain if this is limited to non-obese females.