Non-Cholesterol Sterol Levels Predict Hyperglycemia and Conversion to Type 2 Diabetes in Finnish Men Henna Cederberg 1 , Helena Gylling 2,3 , Tatu A. Miettinen 3{ , Jussi Paananen 4 , Jagadish Vangipurapu 4 , Jussi Pihlajama ¨ki 2 , Teemu Kuulasmaa 4 , Alena Stanc ˇa ´ kova ´ 4 , Ulf Smith 5 , Johanna Kuusisto 1 , Markku Laakso 1 * 1 Department of Medicine, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland, 2 Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland, 3 Department of Medicine, Division of Internal Medicine, University of Helsinki, Helsinki, Finland, 4 Department of Medicine, University of Eastern Finland, Kuopio, Finland, 5 Department of Molecular and Clinical Medicine, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden Abstract We investigated the levels of non-cholesterol sterols as predictors for the development of hyperglycemia (an increase in the glucose area under the curve in an oral glucose tolerance test) and incident type 2 diabetes in a 5-year follow-up study of a population-based cohort of Finnish men (METSIM Study, N = 1,050) having non-cholesterol sterols measured at baseline. Additionally we determined the association of 538,265 single nucleotide polymorphisms (SNP) with non-cholesterol sterol levels in a cross-sectional cohort of non-diabetic offspring of type 2 diabetes (the Kuopio cohort of the EUGENE2 Study, N = 273). We found that in a cross-sectional METSIM Study the levels of sterols indicating cholesterol absorption were reduced as a function of increasing fasting glucose levels, whereas the levels of sterols indicating cholesterol synthesis were increased as a function of increasing 2-hour glucose levels. A cholesterol synthesis marker desmosterol significantly predicted an increase, and two absorption markers (campesterol and avenasterol) a decrease in the risk of hyperglycemia and incident type 2 diabetes in a 5-year follow-up of the METSIM cohort, mainly attributable to insulin sensitivity. A SNP of ABCG8 was associated with fasting plasma glucose levels in a cross-sectional study but did not predict hyperglycemia or incident type 2 diabetes. In conclusion, the levels of some, but not all non-cholesterol sterols are markers of the worsening of hyperglycemia and type 2 diabetes. Citation: Cederberg H, Gylling H, Miettinen TA, Paananen J, Vangipurapu J, et al. (2013) Non-Cholesterol Sterol Levels Predict Hyperglycemia and Conversion to Type 2 Diabetes in Finnish Men. PLoS ONE 8(6): e67406. doi:10.1371/journal.pone.0067406 Editor: Alexander J. Travis, Cornell University College of Veterinary Medicine, United States of America Received December 10, 2012; Accepted May 16, 2013; Published June 28, 2013 Copyright: ß 2013 Cederberg et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work has been supported by the Academy of Finland (M.L.), the Finnish Diabetes Research Foundation (M.L.), the Finnish Cardiovascular Research Foundation (M.L.), the Strategic Research Funding from the University of Eastern Finland, Kuopio, Finland (M.L.), and EVO grant 5263 from the Kuopio University Hospital (M.L.). The funding bodies named above had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: markku.laakso@kuh.fi { Deceased. Introduction Type 2 diabetes is associated with atherogenic dyslipidemia [1] increasing the risk of cardiovascular mortality and morbidity [2]. Abnormalities in cholesterol metabolism in type 2 diabetes include enhanced cholesterol synthesis and reduced cholesterol absorption [3–6]. Also insulin resistance and obesity have been previously associated with elevated cholesterol synthesis and low cholesterol absorption in cross-sectional studies [7–10]. However, the mechanisms underlying the association of non-cholesterol sterol levels with hyperglycemia have remained unclear. Atherogenic dyslipidemia predicts the development of type 2 diabetes [1], and therefore sterols associated with cholesterol synthesis and absorp- tion could also contribute to the risk of the development of hyperglycemia and type 2 diabetes. Single nucleotide polymorphisms (SNPs) in the sitosterolemia genes ABCG5 and ABCG8, encoding the ATP-binding cassette sub- family G member proteins, have been shown to regulate cholesterol absorption [11–13]. These transporters actively efflux plant sterols and, to a lesser extent cholesterol, back into the intestinal lumen. In a previous genome-wide association study SNPs rs4245791 and rs41360247 in/near ABCG8 were associated with serum phytosterol levels [14]. The impact of SNPs in ABCG5/8, and possible other, yet undiscovered SNPs on the association between non-cholesterol sterol levels and glucose metabolism is largely unknown. To investigate in more detail the association of non-cholesterol sterols with the risk of the worsening of hyperglycemia and incident type 2 diabetes we addressed 1) the relationship of cholesterol synthesis markers (squalene, cholestenol, lathosterol, and desmosterol) and absorption markers (campesterol, sitosterol, avenasterol, and cholestanol) with fasting and 2-hour glucose levels in a cross-sectional setting, 2) the association of non-cholesterol sterol levels as predictors for the worsening of hyperglycemia and the development of incident type 2 diabetes in a 5-year follow-up of the METSIM (METabolic Syndrome In Men) Study, and 3) the role of insulin sensitivity, insulin secretion and genetic factors in this relationship. PLOS ONE | www.plosone.org 1 June 2013 | Volume 8 | Issue 6 | e67406