For Doctors in a Hurry
- Researchers investigated whether estrogen modifies the cardiac effects of fibroblast growth factor 23, which drives left ventricular hypertrophy in chronic kidney disease.
- The study compared mineral metabolism and heart phenotypes in male and female wild-type mice and Col4a3 knockout mice with progressive kidney disease.
- Male mice developed overt left ventricular hypertrophy at 20 weeks, whereas females showed no hypertrophy despite earlier increases in fibroblast growth factor 23.
- The authors concluded that estrogen antagonizes the hypertrophic effects of fibroblast growth factor 23 by targeting common molecular pathways within the heart.
- These findings suggest that estrogen provides sex-specific cardioprotection, potentially explaining why female patients with kidney disease experience lower rates of cardiac hypertrophy.
Sex Dimorphism in Uremic Cardiomyopathy
Chronic kidney disease is an independent, graded risk factor for all-cause mortality and major cardiovascular events, with the risk of death increasing significantly as the estimated glomerular filtration rate falls below 60 ml per minute per 1.73 m² [1]. Within this population, the development of left ventricular hypertrophy is a critical prognostic marker that carries an adverse prognosis and increases the risk of progression to congestive heart failure [2]. Meta-analyses indicate that patients with renal impairment face a substantially higher burden of cardiovascular mortality and sudden cardiac death compared to those with normal kidney function [3]. While clinical guidelines emphasize the importance of managing comorbidities like hypertension and diabetes to prevent heart failure, the biological basis for observed sex-specific differences in cardiac outcomes remains poorly understood [4, 5]. A recent study investigates the molecular mechanisms that may protect the female heart during the progression of renal decline, offering insights that could eventually guide sex-specific cardiovascular risk stratification in nephrology clinics.
Divergent Outcomes in Murine Chronic Kidney Disease
To investigate sex-based disparities in renal-related cardiac disease, researchers utilized age-matched wild-type mice (healthy controls) and Col4a3 knockout mice (a genetic model that simulates the progressive nature of chronic kidney disease). The study focused on assessing mineral metabolism, kidney phenotypes, and heart phenotypes to determine how renal decline influences cardiac structure. Because clinical data consistently show that males face a higher risk of cardiovascular events than females during the progression of renal impairment, the researchers separated and analyzed all experimental results by sex to identify divergent physiological responses.
In the male cohort, the progression of chronic kidney disease was marked by steady, significant increases in blood urea nitrogen (a standard marker of renal filtration failure) and fibroblast growth factor 23 (a hormone involved in phosphate regulation) compared to wild-type controls. This elevation is clinically significant because fibroblast growth factor 23 is known to contribute directly to left ventricular hypertrophy (the pathological thickening of the heart's main pumping chamber) and increased mortality in the setting of renal failure. The male mice in this study developed overt left ventricular hypertrophy at 20 weeks of age, which preceded a high rate of premature death at 22 weeks of age.
The female mice exhibited a strikingly different clinical course despite showing earlier increases in blood urea nitrogen and fibroblast growth factor 23 levels than the wild-type group. Although these biochemical markers of renal stress appeared sooner in females than in males, the female mice with chronic kidney disease did not develop left ventricular hypertrophy. This absence of structural cardiac remodeling was associated with a significant survival advantage, as the female mice with chronic kidney disease lived longer than the male mice with the same condition. For practicing physicians, these findings suggest that while both sexes experience the systemic mineral and metabolic disturbances of renal decline, female biology may offer a protective buffer against the hypertrophic signaling typically induced by fibroblast growth factor 23.
Estrogen Antagonism of Hypertrophic Signaling
The researchers utilized transcriptomics (the study of the complete set of RNA transcripts produced by the genome) to identify the proximal targets of fibroblast growth factor 23 involved in chronic kidney disease-associated left ventricular hypertrophy. Through RNA sequencing analyses, the study revealed that the proximal targets of fibroblast growth factor 23 identified in males with chronic kidney disease are established downstream targets of estrogen signaling. This discovery highlights the existence of common molecular targets of fibroblast growth factor 23 and estradiol signaling within the myocardium, suggesting a direct intersection between these two pathways at the genetic level.
To further investigate these interactions, the researchers tested the effects of fibroblast growth factor 23 and estradiol in vivo (in living mice) and on cultured neonatal mouse cardiomyocytes (isolated heart muscle cells). In vitro experiments demonstrated that fibroblast growth factor 23 induced hypertrophic growth in neonatal mouse cardiomyocytes isolated from both male and female mice, indicating that the hormone's capacity to trigger cellular enlargement is not inherently sex-dependent at the cellular level. However, co-treatment with estradiol prevented this fibroblast growth factor 23-induced hypertrophic growth in the cultured cardiomyocytes, providing evidence that estrogen can directly antagonize the pathological effects of the growth factor.
The study also examined the intracellular mechanisms driving these changes, specifically focusing on calcineurin activity (a signaling protein pathway that triggers pathological cardiac growth and remodeling). In the hearts of male mice, estradiol treatment prevented fibroblast growth factor 23-induced calcineurin activity, effectively blocking a primary pathway for cardiac hypertrophy. These findings suggest that the cardioprotective effects observed in females are mediated by estrogen's ability to interfere with the signaling cascade of fibroblast growth factor 23. Clinically, this mechanism may eventually inform the development of sex-specific therapeutic strategies to mitigate cardiovascular risk in patients with chronic kidney disease.
Loss of Protection Following Ovariectomy
To confirm that the observed cardioprotection in female mice was directly mediated by ovarian hormones rather than other genetic factors, the researchers performed an ovariectomy (the surgical removal of the ovaries) on female mice with chronic kidney disease. This intervention effectively eliminated the primary endogenous source of estrogen. Following the procedure, the previously protected female mice developed left ventricular hypertrophy, mirroring the pathological cardiac remodeling seen in their male counterparts. This finding demonstrates that the absence of estrogen renders the female myocardium vulnerable to the high levels of fibroblast growth factor 23 that characterize advancing renal failure.
The study concludes that estrogen antagonizes the hypertrophic effects of fibroblast growth factor 23, establishing a clear, female-specific cardioprotective mechanism in the context of chronic kidney disease. By identifying that estrogen interferes with the signaling pathways that drive cardiac enlargement, the researchers provide a biological basis for why premenopausal females may maintain better cardiac function despite significant mineral metabolism derangements. For clinicians, these results suggest that the loss of estrogen, such as in postmenopausal patients, may remove a critical buffer against the cardiotoxic effects of fibroblast growth factor 23. Recognizing this vulnerability could prompt physicians to monitor postmenopausal women with chronic kidney disease more aggressively for early signs of uremic cardiomyopathy.
References
1. Go AS, Chertow GM, Fan D, McCulloch CE, Hsu C. Chronic Kidney Disease and the Risks of Death, Cardiovascular Events, and Hospitalization. New England Journal of Medicine. 2004. doi:10.1056/nejmoa041031
2. Goulas I, Evripidou K, Doundoulakis I, et al. Prevalence of masked hypertension and its association with left ventricular hypertrophy in children and young adults with chronic kidney disease: a systematic review and meta-analysis.. Journal of hypertension. 2023. doi:10.1097/HJH.0000000000003402
3. Odutayo A, Wong CX, Hsiao AJ, Hopewell S, Altman DG, Emdin CA. Atrial fibrillation and risks of cardiovascular disease, renal disease, and death: systematic review and meta-analysis. BMJ. 2016. doi:10.1136/bmj.i4482
4. McDonagh TA, Metra M, Adamo M, et al. 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. European Heart Journal. 2021. doi:10.1093/eurheartj/ehab368
5. Cosentino F, Grant PJ, Aboyans V, et al. 2019 ESC Guidelines on diabetes, pre-diabetes, and cardiovascular diseases developed in collaboration with the EASD. European Heart Journal. 2019. doi:10.1093/eurheartj/ehz486
