Aim: The haptoglobin (Hp) 2-2 genotype has been shown to increase the risk of coronary artery disease, kidney dysfunction and mortality from cardiovascular and renal causes in type 1 diabetes (T1D). Similar associations, however, have not been observed in those without diabetes. As cardiac autonomic neuropathy (CAN) is a cardiovascular disease risk factor, we assessed the presence of an association between the Hp 2-2 genotype and CAN.
Methods: The study included 216 individuals with childhood-onset T1D and 200 individuals with normal glucose tolerance (NGT) of similar age and gender distribution to their counterparts with T1D. CAN was assessed using an electrocardiogram as an abnormal, age-specific, heart rate response to deep breathing. Multivariable logistic regression models were used to assess the association between the Hp 2-2 genotype and CAN.
Results: Compared with NGT, participants with T1D had a similar proportion of Hp 2-2 carriers (41.5% vs. 32.0%, p = 0.05) but a greater CAN prevalence (28.2% vs. 5.0%, p < 0.0001). In multivariable logistic regression models, those carrying the Hp 2-2 genotype had significantly higher odds of CAN compared with Hp 1-1 or Hp 2-1 carriers (OR = 2.27, p = 0.01). The presence of T1D (OR = 4.20, p = 0.0003), hypertension (OR = 2.08, p = 0.03), eGFR (OR = 0.98, p = 0.01) and WBC count (OR = 1.21, p = 0.02) were also associated with CAN. There was no T1D by Hp interaction (p = 0.92), although in stratified analyses, the Hp-CAN association was significant only in T1D.
Conclusions: The Hp 2-2 genotype was independently associated with greater odds of CAN in T1D though no definitive conclusions could be made in NGT.
Keywords: Cardiac autonomic neuropathy; Haptoglobin genotype; Normal glucose tolerance; Type 1 diabetes.