2: Summary of Current Projects

Obesity promotes hypertension, a major risk factor for cardiovascular disease. Epidemiological studies have linked early life stress as a modifiable risk factor for increased body mass index and blood pressure. Using an advantageous mouse model of early life stress that combines postnatal maternal separation and early weaning (MSEW) with a high fat diet, we have identified two potential adipose tissue-derived targets implicated in the pathways by which these mice display exacerbated obesity-induced hypertension. Experimental studies have demonstrated that adipose afferent reflex (AAR) is enhanced in diet-induced obesity models. Specifically, the acute stimulation of adipose tissue afferent nerve fibers (e.g. capsaicin, leptin) elevates blood pressure, renal nerve activity and plasma catecholamines. Adipose tissue also expresses components of the renin-angiotensin system (RAS). Notably, it has been shown that adipose tissue-specific abrogation of the sole RAS precursor, angiotensinogen (AGT), effectively prevents high fat diet-induced increases in blood pressure. Our preliminary findings support for the novel central hypothesis postnatal MSEW aggravates obesity-induced HT in adult life by stimulating AAR reflex-mediated sympathetic activation and adipose tissue-derived AGT secretion. We will test key predictions in two multilevel specific aims: (1) To test the hypothesis that MSEW heightens obesity-induced hypertension by stimulating adipose tissue excitatory signals to increase AAR reflex. We will assess the effects of MSEW on AAR reflex in acute and chronic in vivo experiments using a novel state of the art technique, in order to determine the adipose tissue-brain axis effects on blood pressure; and (2) To test the hypothesis that MSEW exacerbates obesity-induced hypertension by increasing AGT secretion in adipose tissue. We will generate an adipose tissue-specific, tamoxifen-inducible AGT knockout mouse, expose the mice to MSEW and wean them on a high fat diet. The AGT deletion will be induced at three time points from early postnatal life to adulthood, in order to assess its effects on programming, progression and reversion of hypertension. The outcomes of these studies may provide novel early life stress-programmed adipose tissue targets with impact on blood pressure control.

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