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Background: Sex differences exist in type 2 diabetes (T2D), and androgens have been implicated in the etiology of T2D in a sex-specific manner. We therefore aimed to investigate whether androgens play a role in explaining sex differences in glucose homeostasis and incidence of T2D., Methods: We used observational data from the German population-based KORA F4 study (n = 1975, mean age: 54 years, 41% women) and its follow-up examination KORA FF4 (median follow-up 6.5 years, n = 1412). T2D was determined through self-reporting and confirmed by contacting the physicians and/or reviewing the medical charts. Multivariable linear and logistic regression models were employed to explore associations. Mediation analyses were performed to assess direct effects (DE) and indirect effects (IE), and the mediating role of androgens (total testosterone (TT), dehydroepiandrosterone (DHEA), dehydroepiandrosterone-sulfate (DHEAs)) in the association between sex (women vs. men) and glucose- and insulin-related traits (cross-sectional analysis) and incidence of T2D (longitudinal analysis)., Results: After adjustment for confounders, (model 1: adjusted for age; model 2: model 1 + smoking + alcohol consumption + physical activity), women had lower levels of TT, DHEAs, fasting glucose levels, fasting insulin levels, 2 h-glucose levels and HOMA-IR, compared to men. An inverse association was observed for TT and glucose- and insulin-related traits in men, while a positive association was observed for TT and fasting glucose levels in women. We found a mediatory role of TT on the association of sex with fasting glucose levels (IE: β = 3.08, 95% CI: 2.04, 4.30), fasting insulin levels (IE: β = 0.39, 95% CI:0.30, 0.47), 2 h-glucose levels (IE: β = 12.77, 95% CI: 9.01, 16.03) and HOMA-IR (IE: β = 0.41, 95% CI: 0.33, 0.50). Also, the inconsistent mediatory role of TT was seen on the association of sex with incidence of T2D (DE: 0.12, 95% CI: 0.06, 0.20 and IE: OR = 7.60, 95% CI: 3.43, 24.54). The opposing DE and IE estimates suggest that the association between sex and either glucose homeostasis or the incidence of T2D may differ when TT is considered as a potential mediator, with higher TT levels being beneficial for glucose metabolism or incidence of T2D in men, while in women, detrimental. No mediatory role was observed for either DHEA or DHEAs on glucose homeostasis or the incidence of T2D., Conclusions: The dimorphic mediatory role of TT highlights its complex role in metabolic health, contributing differently to the glucose dysregulation and risk of T2D in men and women., Competing Interests: Declarations Competing interests The authors declare no competing interests. Ethics approval All study participants have provided written informed consent. The study was approved by the Ethics Committees of the Bavarian Chamber of Physicians (Ethical Approval Number 06068) adhering to the declaration of Helsinki. Informed consent Informed consent was obtained from all individual participants included in the study., (© 2024. The Author(s).)

Understanding normal aging of kidney function is pivotal to help distinguish individuals at particular risk for chronic kidney disease. Glomerular filtration rate (GFR) is typically estimated via serum creatinine (eGFRcrea) or cystatin C (eGFRcys). Since population-based age-group-specific reference values for eGFR and eGFR-decline are scarce, we aimed to provide such reference values from population-based data of a wide age range. In four German population-based cohorts (KORA-3, KORA-4, AugUR, DIACORE), participants underwent medical exams, interview, and blood draw up to five times within up to 25 years. We analyzed eGFRcrea and eGFRcys cross-sectionally and longitudinally (12,000 individuals, age 25-95 years). Cross-sectionally, we found age-group-specific eGFRcrea to decrease approximately linearly across the full age range, for eGFRcys up to the age of 60 years. Within age-groups, there was little difference by sex or diabetes status. Longitudinally, linear mixed models estimated an annual eGFRcrea decline of -0.80 [95% confidence interval -0.82, -0.77], -0.79 [-0.83, -0.76], and -1.20 mL/min/1.73m 2 [-1.33, -1.08] for the general population, "healthy" individuals, or individuals with diabetes, respectively. Reference values for eGFR using cross-sectional data were shown as percentile curves for "healthy" individuals and for individuals with diabetes. Reference values for eGFR-decline using longitudinal data were presented as 95% prediction intervals for "healthy" individuals and for individuals with diabetes, obesity, and/or albuminuria. Thus, our results can help clinicians to judge eGFR values in individuals seen in clinical practice according to their age and to understand the expected range of annual eGFR-decline based on their risk profile., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Research has indicated that sex hormone-binding globulin (SHBG) is associated with glucose homeostasis and may play a role in the etiology of type 2 diabetes (T2D). While it is unclear whether SHBG may mediate sex differences in glucose control and subsequently, incidence of T2D. We used observational data from the German population-based KORA F4 study (n = 1937, mean age: 54 years, 41% women) and its follow-up examination KORA FF4 (median follow-up 6.5 years, n = 1387). T2D was initially assessed by self-report and validated by contacting the physicians and/ or reviewing the medical charts. Mediation analyses were performed to assess the role of SHBG in mediating the association between sex (women vs. men) and glucose- and insulin-related traits (cross-sectional analysis) and incidence of T2D (longitudinal analysis). After adjustment for confounders, (model 1: adjusted for age; model 2: model 1 + smoking + alcohol consumption + physical activity), women had lower fasting glucose levels compared to men (β = -4.94 (mg/dl), 95% CI: -5.77, -4.11). SHBG levels were significantly higher in women than in men (β = 0.47 (nmol/l), 95% CI:0.42, 0.51). Serum SHBG may mediate the association between sex and fasting glucose levels with a proportion mediated (PM) of 30% (CI: 22-41%). Also, a potential mediatory role of SHBG was observed for sex differences in incidence of T2D (PM = 95% and 63% in models 1 and 2, respectively). Our novel findings suggest that SHBG may partially explain sex-differences in glucose control and T2D incidence., (© 2024. The Author(s).)

Background: We aimed to evaluate the relationship of fatty liver, estimated by the fatty liver index (FLI), with kidney function and chronic kidney disease (CKD) in a German cohort study, given the lack of prospective evidence in Europeans., Methods: We included 2920 participants (51.6% women, mean age 56.1 years) from the KORA study, of which 1991 were followed up for an average of 6.5 years (± 0.3). Kidney function was assessed using the glomerular filtration rate estimated by creatinine (eGFR-Cr) or cystatin C (eGFR-cC). We used multiple logistic or linear regressions to evaluate the associations between the FLI, kidney function and CKD (eGFR < 60 ml/min/1.73 m2) and mediation analysis to explore the mediation effects of metabolic factors., Results: The prevalence of FLI ≥60 and CKD was 40.4% and 5.6% at baseline, respectively, and 182 participants developed CKD during the follow-up. Cross-sectionally, FLI was significantly inversely associated with eGFR-cC {β = -1.14 [95% confidence interval (CI) -1.81 to -0.47]} and prevalent CKD based on eGFR-cC [OR 1.28 (95% CI 1.01-1.61)], but not with other markers. After adjusting for lifestyle factors, we found a positive association between FLI and incident CKD defined by eGFR-cC or/eGFR-Cr, which was attenuated after controlling for metabolic risk factors. Mediation analysis showed that the association was completely mediated by inflammation, diabetes and hypertension jointly., Conclusion: The positive association between FLI and CKD incidence was fully mediated by the joint effect of metabolic risk factors. Future longitudinal studies need to explore the chronological interplay between fatty liver, cardiometabolic risk factors and kidney function with repeated measurements., (© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)