Sex- and Regional-Specific Differences in Renal Cholesterol Biosynthesis

Hypertension is a major public health concern in the United States, contributing to nearly 500,000 deaths annually. The kidney is critical for regulating blood pressure through maintaining sodium homeostasis. Renal estrogenic signaling through G protein-coupled estrogen receptor 1 (GPER1) enhances sodium excretion and lowers blood pressure. Recent evidence suggests sex-specific differences in renal capacity to biosynthesize estrogen, including an overabundance of key steroidogenic enzymes in the renal outer medulla (OM) of female Sprague Dawley (SD) rats. This raises the question of whether cholesterol, an upstream substrate precursor for steroidogenesis is synthesized in the kidney. We hypothesis that cholesterol is biosynthesized locally in the kidney and that this process is more pronounced in females than in males. To test this, we quantified the protein abundance of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), the rate limiting enzyme in cholesterol biosynthesis and the total cholesterol levels in the cortex (CTX) and outer medulla (OM) of female and male SD rats (N = 6/group). HMGCR protein abundance was measured using western blot analysis and total cholesterol was quantified using the Amplex Red Cholesterol Assay after being extracted. We found that renal HMGCR protein abundance is region-specific, with higher levels in the OM compared to CTX in females but not males (Female OM; 0.866 ± 0.060 vs Female CTX; 0.146 ± 0.037 AU; P = 0.0001, and Male OM; 0.394 ± 0.077 vs Male CTX; 0.167 ± 0.088 AU, P = 0.091). Additionally, female rats showed higher HMGCR protein levels in the OM than males (P = 0.0028). However, total cholesterol levels did not differ significantly by sex or region (Female CTX; 5.483 ± 0.955 vs. Male CTX; 6.730 ± 0.828 µM/mg tissue, P = 0.5255 and Female OM: 5.773 ± 0.490 vs. Male OM: 7.302 ± 0.514 µM/mg tissue, P = 0.1722). Overall, these results suggest that renal cholesterol biosynthesis, is both regionally and sex-specifically regulated, despite similar total cholesterol levels. This discrepancy may highlight compensatory mechanisms in females that balance increased cholesterol biosynthesis with efficient cholesterol turnover, enhanced transport, or utilization within the kidney. Further investigations into the subcellular cholesterol localization, cholesterol fractions, and transport pathways may provide deeper insights into the regulation of renal cholesterol homeostasis and its impact on sex-specific renal outcomes. 2T32ES007028-50 to FK This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.