SAT-587 Molecular Markers of Beige Adipose Following ESR1 Knockdown in the Mediobasal Hypothalamus of Adult Female Rhesus Monkeys

Abstract

Our studies in female marmoset monkeys show that the ablation of ovarian estradiol (E ₂) production fails to alter energy homeostasis or body fat accumulation. Peripheral E ₂ may therefore not play a crucial role in metabolic regulation in female primates. shRNA-mediated knockdown of ESR1 expression in the hypothalamic ventromedial nucleus (VMN) in adult female rodents, however, induces obesity and suggests ESR1 is a hypothalamic target for E ₂ regulation of energy homeostasis, and likely mediates thermogenesis in brown/beige adipose depots. In female primates, including humans, the hypothalamic estrogen receptor mediating metabolic regulation is unknown. To test the hypothesis that ESR1 mediates female primate regulation of energy homeostasis, 11 ovary intact, adult female rhesus macaques, pair housed with female peers, received five 12µl MRI-guided MBH infusions into the rostral-to-caudal extent of both right and left VMN. Each infusion comprised a gadolinium contrast agent and ~3–4 x 10 ¹⁰ adeno-associated virus 8 (AAV8) particles containing either an shRNA specific for ESR1 (n=6, ERaKD) or scrambled shRNA (n=5, control). Mid-surgery MRI scans identified targeting accuracy. ~ 1.5 yrs following AAV8 infusion, pronounced gain in BMI enabled conversion of 83% of ERaKD females to overweight/obese compared to 20% of controls (p=0.08). Percent increase in BMI remained intermittently greater (p<0.05) than controls thereafter. Adipose depots were harvested at necropsy ~2.5–3 yrs following treatment. Total RNA was isolated using the Qiagen AllPrep DNA/RNA/miRNA Universal kit. RNA was reverse transcribed with High-Capacity cDNA Reverse Transcription kit (Applied Biosystems). All quantitative real-time PCR (qRT-PCR) were performed on a StepOnePlus System using Power SYBR Green master mix (Applied Biosystems). Primer sequences were designed using NCBI Primer-Blast. Expression of TATA-box binding protein (TBP) was used as the internal control housekeeping gene. The relative expression of target genes was measured using the comparative cycle threshold (Ct) method with results expressed as target mRNA expression relative to TBP using the formula 2^-delta Ct. Upper body beige adipose represents an organ system in primates, including humans, involved in thermogenesis. Axillary beige adipose depots in ERaKD females, however, did not exhibit significantly diminished gene expression for selected markers of beige adipocytes, including PAT2, CD137 and C/EBPβ, compared to control females. More crucially, thermogenically relevant UCP1 expression also did not differ between ERaKD females and controls. Taken together, these results suggest that knockdown of VMN ESR1 in adult female monkeys, while inducing modest weight gain after 1.5 years, may not markedly alter beige adipose gene expression of initially selected thermogenically relevant genes.