Sex modulates the association of fibroblast growth factor 21 with end-stage renal disease in Asian people with Type 2 diabetes: a 6.3-year prospective cohort study

Critical role of FGF21 in diabetic kidney disease: from energy metabolism to innate immunity

Diabetic kidney disease (DKD) stands as the predominant cause of chronic kidney disease (CKD) on a global scale, with its incidence witnessing a consistent annual rise, thereby imposing a substantial burden on public health. The pathogenesis of DKD is primarily rooted in metabolic disorders and inflammation. Recent years have seen a surge in studies highlighting the regulatory impact of energy metabolism on innate immunity, forging a significant area of research interest. Within this context, fibroblast growth factor 21 (FGF21), recognized as an energy metabolism regulator, assumes a pivotal role. Beyond its role in maintaining glucose and lipid metabolism homeostasis, FGF21 exerts regulatory influence on innate immunity, concurrently inhibiting inflammation and fibrosis. Serving as a nexus between energy metabolism and innate immunity, FGF21 has evolved into a therapeutic target for diabetes, nonalcoholic steatohepatitis, and cardiovascular diseases. While the relationship between FGF21 and DKD has garnered increased attention in recent studies, a comprehensive exploration of this association has yet to be systematically addressed. This paper seeks to fill this gap by summarizing the mechanisms through which FGF21 operates in DKD, encompassing facets of energy metabolism and innate immunity. Additionally, we aim to assess the diagnostic and prognostic value of FGF21 in DKD and explore its potential role as a treatment modality for the condition.

Association of serum fibroblast growth factor 21 with kidney function in a population-based Chinese cohort

Fibroblast growth factor 21 (FGF21) plays a role in kidney disease. Circulating FGF21 levels are associated with kidney function and progression in patients with type 2 diabetes (T2D). However, the association between FGF21 and kidney function in the general population is still lacking. The aim of this study was to determine the association between FGF21 and kidney function and its progression in a Chinese cohort.A total of 2425 participants from a population-based survey of diabetes and metabolic syndrome in Pinggu, Beijing, were included in the baseline analysis. After a median follow-up of 12 months, 2402 participants with baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 were analyzed in the longitudinal study. The progression of kidney function was defined as an eGFR decline exceeding 3.3% per year. Serum FGF21 levels were measured using an enzyme-linked immunosorbent assay at baseline.Male sex, body mass index (BMI), homeostasis model assessment of insulin resistance, higher levels of low-density lipoprotein cholesterol (LDL-c), uric acid, and FGF21 were associated with increased odds of a lower eGFR at baseline. The association of FGF21 with lower eGFR was independent of all the potential confounders in multivariable logistic regression (odds ratio, 1.005; 95% confidence interval 1.002-1.008). However, FGF21 was not associated with eGFR decline in the longitudinal analysis (odds ratio, 1.000; 95% confidence interval 0.998-1.001).Increased serum FGF21 levels were independently associated with lower eGFR in this nonmedicated general population. FGF21 could be a biomarker of kidney function in the general population.

Association between FGF19, FGF21 and lipocalin-2, and diabetes progression in PCOS

Women with polycystic ovary syndrome (PCOS) have an increased risk of developing type 2 diabetes. FGF19, FGF21 and lipocalin-2 have emerged as important markers of metabolic risk. This study aims to compare the levels of FGF19, FGF21 and lipocalin-2 between subjects with or without PCOS, and to investigate the relationship between proteins and diabetes progression. In this nested case-control cohort study, 128 Chinese PCOS women and 128 controls were recruited and followed-up. All subjects underwent the oral glucose tolerance test for the evaluation of glycaemic status. Baseline serum protein levels were measured using ELISA. Compared with controls, PCOS subjects had higher levels of FGF19 (P < 0.001) and FGF21 (P = 0.022), but had lower lipocalin-2 (P < 0.001). In total, 20.8% of PCOS and 9.2% of controls developed diabetes over a mean duration of 10.4 ± 1.2 and 11.3 ± 0.5 years, respectively. Logistic regression analyses suggested FGF19 was positively associated with diabetes progression in controls, after adjusting for age, follow-up duration, waist and fasting glucose (P = 0.026, odds ratio (OR) (95% CI): 7.4 (1.3-43.6)), and the positive relationship between FGF21 and diabetes progression in controls was attenuated by adjusting for age and follow-up duration (P = 0.183). Lipocalin-2 was positively correlated with diabetes progression in PCOS group (P = 0.026, OR (95% CI)): 2.5 (1.1-5.6)); however, this became attenuated after adjusting for waist and fasting glucose (P = 0.081). In conclusion, there is differential expression of FGF19, FGF21, and lipocalin-2 in PCOS. The serum level of FGF19, and FGF21 is associated with diabetes progression in women without PCOS, while lipocalin-2 was related to diabetes progression in PCOS women.

FGF21 and Chronic Kidney Disease

The global nephrology community recognizes the increasing burden of kidney disease and its poor health outcomes in the general population. Given this, strategies to establish early diagnosis, improve understanding of the natural course and develop novel therapeutic interventions to slow progression and reduce complications are encouraged. Fibroblast growth factor 21 (FGF21), a member of the endocrine FGF subfamily, has emerged as a master homeostasis regulator of local and systemic lipid, glucose and energy metabolism. In addition, FGF21 should be considered an autonomic and endocrine regulator of stress responses in general. Promising results has been shown in both dysmetabolic animal models and metabolic disease patients after pharmacological administration of FGF21 analogs. The association of FGF21 with renal function has been studied for more than ten years. However, the functional role of FGF21 in the kidney is still poorly understood. This review summarizes the biological effects of FGF21 and discusses what is currently known about this hormone and chronic kidney disease, highlighting important gaps that warrant further research.

Sex Modifies the Association of Fibroblast Growth Factor 21 With Subclinical Carotid Atherosclerosis

Background and Aims: Fibroblast growth factor 21 (FGF21), an emerging metabolic hepatokine, is associated with atherosclerosis. An interaction with sex has been described in various populations. We aimed to study whether sex modulates the relationship between FGF21 and subclinical carotid atherosclerosis in a diabetes-enriched multiethnic population of Singapore. We explore differences in intermediary mechanisms, in terms of hypertension, lipids, and inflammation, between FGF21 and atherosclerosis.

Methods: We recruited 425 individuals from a single diabetes center in Singapore, and demographics, anthropometry, metabolic profile, FGF21, and carotid ultrasonography were performed. Multivariable logistic regression models were used to study the association between subclinical atherosclerosis and FGF21 adjusting for age, ethnicity, body mass index (BMI), hemoglobin A1c (HbA1c), systolic and diastolic blood pressures, and low-density lipoprotein (LDL)-cholesterol separately for males and females as two groups after an interaction test.

Results: An interaction test assessing interaction by sex on the relationship between subclinical atherosclerosis and FGF21 showed a significant interaction with sex (P_interaction = 0.033). In the female subgroup, significant independent associations of standardized lnFGF21 with subclinical atherosclerosis were seen, with 1 SD increment in lnFGF21 being associated with 1.48-fold (95% CI: 1.03, 2.12; p = 0.036) increase in risk. In the male subgroup, the association of subclinical atherosclerosis with standardized lnFGF21 was not significant [odds ratio (OR) (95% CI): 0.90 (0.63, 1.28); p = 0.553]. We found sex interactions with pulse pressure being significantly associated in females only and triglycerides and C-reactive protein being associated with males only.

Conclusion: FGF21 is positively associated with subclinical carotid atherosclerosis in women, but not in men. The sex–racial patterns in the mechanisms by which FGF21 causes subclinical atherosclerosis needs to be explored in larger population-based studies and mechanistically studied in greater detail.

Fibroblast growth factor 21 is associated with increased serum total antioxidant capacity and oxidized lipoproteins in humans with different stages of chronic kidney disease

Background and aims

Oxidative stress (OS) induces the production of fibroblast growth factor 21 (FGF21). Previous data have revealed that FGF21 protects cells from OS injury and death, making it a potential therapeutic option for many diseases with increased OS. However, the association of this growth factor with OS markers in humans with chronic kidney disease (CKD) remains unknown. This study aims to evaluate the association of serum FGF21 with serum total antioxidant capacity (TAC) and oxidized low-density lipoproteins (OxLDL) in subjects in different stages of kidney disease.

Methods

This is a cross-sectional study that included 382 subjects with different stages of CKD, irrespective of type 2 diabetes (T2D) diagnosis. Associations of serum FGF21 with OxLDL, TAC, sex, age, body mass index (BMI), fasting plasma glucose, estimated glomerular filtration rate (eGFR), T2D, and smoking, were evaluated through bivariate and partial correlation analyses. Independent associations of these variables with serum FGF21 were evaluated using multiple linear regression analysis.

Results

Serum FGF21 was significantly and positively correlated with age (r = 0.236), TAC (lnTAC) (r = 0.217), and negatively correlated with eGFR (r = -0.429) and male sex (r = -0.102). After controlling by age, sex, BMI, T2D, smoking, and eGFR; both TAC and OxLDL were positively correlated with FGF21 (r = 0.117 and 0.158 respectively, p < 0.05). Using multiple linear regression analysis, eGFR, male sex, T2D, OxLDL, and TAC were independently associated with serum FGF21 (STDβ = -0.475, 0.162, -0.153, 0.142 and 0.136 respectively; p < 0.05 for all) adjusted for age, BMI, smoking, and fasting plasma glucose.

Conclusion

A positive association between serum FGF21 and OS has been found independently of renal function in humans. Results from the present study provide novel information for deeper understanding of the role of FGF21 in OS in humans with CKD and T2D; mechanistic studies to explain the association of serum FGF21 with oxidative stress in CKD are needed.