CLINICAL RESEARCH STUDY Genetic Variation and Activity of the Renin-Angiotensin System and Severe Hypoglycemia in Type 1 Diabetes Ulrik Pedersen-Bjergaard, MD, a Sukhbir S. Dhamrait, MD, b Amar A. Sethi, PhD, c Erik Frandsen, MSc, d Børge G. Nordestgaard, DMSc, c Hugh E. Montgomery, MD, b Stig Pramming, MD, e Philip Hougaard, PhD, e Birger Thorsteinsson, DMSc a a Endocrinology Section, Division of Internal Medicine I, Hillerød Hospital, Hillerød, Denmark; b Centre for Cardiovascular Genetics, Royal Free & University College Medical School, London, UK; c Department of Clinical Biochemistry, Herlev University Hospital, University of Copenhagen, Herlev, Denmark; d Department of Clinical Physiology, Glostrup University Hospital, University of Copenhagen, Glostrup, Denmark; e Novo Nordisk A/S, Bagsværd, Denmark. ABSTRACT BACKGROUND: The deletion-allele of the angiotensin-converting enzyme (ACE) gene and elevated ACE activity are associated with increased risk of severe hypoglycemia in type 1 diabetes. We explored whether genetic and phenotypic variations in other components of the renin-angiotensin system are similarly associated. METHODS: Episodes of severe hypoglycemia were recorded in 171 consecutive type 1 diabetic outpatients during a 1-year follow-up. Participants were characterized at baseline by gene polymorphisms in angio- tensinogen, ACE, angiotensin-II receptor types 1 (AT1R) and 2 (AT2R), and by plasma angiotensinogen concentration and serum ACE activity. RESULTS: Three risk factors for severe hypoglycemia were identified: plasma angiotensinogen concentra- tion in the upper quartile (relative rate [RR] vs. lower quartile 3.1, 95% confidence interval [CI,] 1.4-6.8), serum ACE activity in the upper quartile (RR vs. lower quartile 2.9, 95% CI, 1.3-6.2), and homo- or hemizygosity for the A-allele of the X chromosome-located AT2R 1675G/A polymorphism (RR vs. noncarriers 2.5, 95% CI, 1.4-5.0). The three risk factors contributed independently to prediction of severe hypoglycemia. A backward multiple regression analysis identified a high number of renin-angiotensin system-related risk factors and reduced ability to perceive hypoglycemic warning symptoms (impaired hypoglycemia awareness) as predictors of severe hypoglycemia. CONCLUSIONS: High renin-angiotensin system activity and the A-allele of the AT2R 1675G/A polymor- phism associate with high risk of severe hypoglycemia in type 1 diabetes. A potential preventive effect of renin-angiotensin system blocking drugs in patients with recurrent severe hypoglycemia merits further investigation. © 2008 Elsevier Inc. All rights reserved. • The American Journal of Medicine (2008) 121, 246.e1-246.e8 KEYWORDS: ACE; Angiotensin-II receptor; Angiotensinogen; Counterregulation; Genetics; Hypoglycemia; Hypo- glycemia awareness; Renin-angiotensin system; Type 1 diabetes mellitus Insulin treatment of type 1 diabetes is associated with the risk of hypoglycemic episodes. Severe episodes leading to cognitive impairment and compromised self-management are a major concern for patients 1 and their relatives, 2 and represent the most significant barrier to meeting recom- mended glycemic targets. 3 The distribution of events of severe hypoglycemia among patients with type 1 diabetes is skewed, with a minority of subjects accounting for the vast majority of episodes. 4 Although important risk factors for severe hypoglycemia, such as hormonal counterregulatory failure 5 and impaired hypoglycemia awareness, 6 have been identified, these factors account for only some of the risk The study was funded by grants from The EFSD/JDRF/Novo Nordisk Programme for Research in Type 1 Diabetes, The Foundation of Harald Jensen and wife, The Foundation of Olga Bryde Nielsen, The Foundation of Region 3, The Research Foundation of Frederiksborg Amt, The Tver- gaard Foundation, and Novo Nordisk A/S. SSD was supported by grant FS/2001044 from the British Heart Foundation. HEM is funded by the Portex Endowment at Great Ormond Street Hospital. Requests for reprints should be addressed to Ulrik Pedersen-Bjergaard, MD, Endocrinology Section, Division of Internal Medicine I, Hillerød Hospital, DK-3400 Hillerød, Denmark. E-mail address: ulpebj@noh.regionh.dk 0002-9343/$ -see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjmed.2007.12.002