Kathleen Brennan, MD Assistant Clinical Professor Department of OBGYN

1. Leptin and soluble leptin receptor and risk of clinical diabetes in African-American, Hispanic, and Asian postmenopausal women. Kathleen Brennan, MD Assistant Clinical Professor Department of OBGYN Division of Reproductive Endocrinology and Infertility UCLA October 17, 2013 WHI Diabetes/Obesity SIG

2. Menopause and Adiposity • Increased waist circumference • Increase in fat mass • Preferential central/abdominal fat deposition • Increased levels of adipocytokines • Increased risk of insulin resistance and cardiovascular disease • Prevalence of metabolic syndrome in PMP women as high as 40-50% Sowers, et al. J ClinEndocrinolMetab 2007. Lobo. Maturitas 2008. Ford, et al. JAMA 2002. Park, et al. Arch Intern Med 2003. Carr MC. J ClinEndocrinolMetab 2003.

3. Leptin • Leptin • Protein secreted by adipocytes • Acts on hypothalamus to regulate body weight homeostasis • Increased body fat  increased leptin • Leptin resistance • Fasting and very low calorie diet  decreased leptin • Has been implicated in various pathways leading to development of cardiovascular disease and DM Considine, et al. NEJM 1996. Di Carlo, et al. Gynecol Endocrinol 2002. Harris, et al. Endocrinology 1998. Barash, et al Endocrinolgy 1996. Chehab, et al. Nature Genet 1996.

4. Soluble Leptin Receptor • Major leptin binding protein in the circulation • Soluble leptin receptor (sOB-R) levels are low in obese individuals • Levels increase with weight loss and low-calorie diet • Majority of leptin bound in lean subjects and unbound in obese subjects • Soluble leptin receptor levels are inversely proportional to leptin levels Lee et al. Nature 1996. Sinha et al. J Clin Invest 1996. Lammert et al. Biochem Biophys Res Commun 2001. Ogawa et al. Metabolism 2004.

5. Leptin and Diabetes • Conflicting evidence regarding relationship between leptin and both insulin sensitivity and DM in humans • Leptin may suppress insulin synthesis and secretion, and increase insulin sensitivity • Increased leptin levels may be associated with insulin resistance • May be a result of leptin resistance • Some population studies have reported that leptin or sOB-R levels predict the development of DM • Others have not after adjusting for potential confounders (like BMI) Huerta. Rev Endocr Metab Dis 2006. Huang et al. J Biol Chem 2001. Soderberg, et al. In J Obesity 2007. Welsh et al. Diabetes Care 2009. Sun et al. Diabetes 2010. Sandhofer et al. Obes Res 2001 Ogawa et al. Metabolism 2004. Bandaru et al. Meab Syndr Relat D 2011.

6. Leptin and Diabetes • Unclear if or how the relationship between leptin and DM is affected by adiposity, insulin resistance, or sOB-R levels. • Understanding the relationships between levels of leptin or sOB-R and DM risk may have clinical implications for DM risk prediction. Sun et al. Diabetes 2010. Bandaru et al. MetabSyndrRelat D 2011. Ley et al. Diabetes Care 2008. Wannamethee et al. Diabetes Care 2007. Schmidt et al. Diabetalogia 2006.

7. Study Objective • To investigate the prospective relationships of leptin and sOB-R on the development of DM using a nested case-control study of postmenopausal ethnic minority women in the WHI-OS. • Additionally, we further explored possible differences in the relationships between both leptin and sOB-R and DM risk on obese and non-obese women within our study population

8. Hypothesis Higher leptin and lower leptin receptor levels are associated with increased DM risk.

9. Materials and Methods • 93,676 postmenopausal women • Ages 50-79 • 82,069 women free of diabetes (DM) at enrollment • Questionnaires mailed annually • Incident diabetes identified by new DM treatment or hospitalization for DM

10. Materials and Methods • 642 Black, Hispanic, or Asian/Pacific Islander women developed diabetes • Matched to 1289 study participants who were free of disease • Age • Ethnicity • Clinical center • Time of blood draw • Length of follow-up

11. Baseline Characteristics

12. * Adjusted for BMI. ** Adjusted for BMI and matching factors (age, race/ethnicity, clinical center, duration of follow-up, and time of blood draw). † Bolded values represent p<0.05. Spearman correlation coefficients among controls

13. Relative risk estimates for DM by quartiles of serum leptin or sOB-R levels

14. A. Relative risk for clinical diabetes per unit increase in leptin concentration by obesity status p-heterogeneity=0.002

15. B. Relative risk for clinical diabetes per unit increase in sOB-R concentration by obesity status p-heterogeneity=0.03

16. Results summary • Higher leptin and lower sOB-R levels were associated with increased DM risk. • These relationships were stronger in non-obese women. • Controlling for HOMA-IR in the multivariable models led to an inverse association between leptin levels and DM risk and a direct association between sOB-R levels and DM risk.

17. Concluding thoughts • Leptin levels are strongly correlated to insulin resistance and may primarily serve as a marker for adiposity and related conditions. • Holding insulin resistance constant may reveal weaker, potentially protective associations between leptin levels and DM risk which are typically overshadowed by the stronger effects of adiposity or insulin resistance • Holding insulin resistance constant also reversed the association between sOB-R and DM risk

18. Concluding thoughts • The associations between leptin and sOB-R differed in obese and non-obese women • Leptin may protect against the development of DM in obese women • Higher levels of sOB-R seem to be protective in non-obese women, but not in obese women.