Selective Afferent Denervation in Epididymal White Adipose Tissue Reduces Blood Pressure in Obese Male Mice Exposed to Early Life Stress

Abstract

Visceral adiposity has been largely implicated in increased sympathetic activation, and pathogenesis and target organ damage associated with the development of obesity-induced hypertension. The experimental stimulation of afferent excitatory signals from adipose tissue has been shown to contribute with the increased sympathetic activation associated with obesity-induced hypertension as part of a sympathoexcitatory mechanism called the adipose afferent reflex (AAR). Previous studies from our lab have shown that male mice exposed to maternal separation and early weaning (MSEW), a mouse model of early life stress, display increased mean arterial pressure (MAP) compared to control mice when fed a high fat diet (HF) that correlates with increased neuronal activation in non-endocrine neurons in the posterior paraventricular nucleus of the hypothalamus. Moreover, MSEW-HF males display exacerbated blood pressure responses to the acute stimulation of the AAR in epididymal white adipose tissue (eWAT) compared to controls. Therefore, the aim of this study was to determine the contribution of the afferent sensory nerves innervating the eWAT in the chronically increased blood pressure displayed by obese MSEW male mice. Male C57BL/6J mice pups were separated from the dams from postnatal day (PD) 2 to PD 16 and weaned early on PD 17. Control litters remained undisturbed with the dams and were weaned on PD 21. After weaning, Control and MSEW mice were placed on HF (60% Kcal from fat) for four months. At 14 weeks, mice (n=8) were implanted with radiotelemetry for chronic MAP measurements. After two weeks of recovery, MAP baseline was recorded during five consecutive days followed by eWAT denervation. For this procedure, eWAT was exposed and infused with vehicle (0.6% ethanol in saline; 4ul; 8 sites; bilateral) or resiniferatoxin (RTX, 10 pmol/ul, 8 sites, 4ul; bilateral). Then, MAP was continuously recorded for 4 days. RTX procedure in eWAT was validated using a GFP reporter mouse for sensory neurons, B6.129P2(Cg)-Calcatm1.1(EGFP/HBEGF)Mjz/Mmnc, and the absence of a green signal in the RTX-treated areas confirmed the afferent denervation. Sympathetic index was evaluated before and after denervations by a single injection of a ganglion blocker (mecamylamine; 5mg/kg; ip). MSEW mice fed a HF displayed significantly increased baseline MAP compared to controls (120±2 vs. 110±2 mmHg respectively, p<0.05). Ganglion blockade induced a greater MAP reduction in MSEW compared to controls (Delta MAP: -20±2 vs. -12±2 mmHg, respectively, p<0.05). Sham denervation did not change MAP from baseline in both groups. However, RTX denervation only decrease MAP in MSEW-HF mice (baseline: 120±2 vs. RTX: 112±2 mmHg, p<0.05) and abolished the baseline MAP differences between groups. MAP decrease in response to ganglion blockade after RTX denervation was similar in both groups (MSEW: -14±4 vs. Control: -15±2 mmHg). Taken together these results show that afferent sensory nerves from epididymal white adipose tissue contribute to the exacerbated obesity-induced hypertension in male mice exposed to early life stress.