Hypotension, lipodystrophy, and insulin resistance in generalized PPARγ-deficient mice rescued from embryonic lethality

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Abstract
We rescued the embryonic lethality of global PPARγ knockout by breeding Mox2-Cre (MORE) mice with floxed PPARγ mice to inactivate PPARγ in the embryo but not in trophoblasts and created a generalized PPARγ knockout mouse model, MORE-PPARγ knockout (MORE-PGKO) mice. PPARγ inactivation caused severe lipodystrophy and insulin resistance; surprisingly, it also caused hypotension. Paradoxically, PPARγ agonists had the same effect. We showed that another mouse model of lipodystrophy was hypertensive, ruling out the lipodystrophy as a cause. Further, high salt loading did not correct the hypotension in MORE-PGKO mice. In vitro studies showed that the vasculature from MORE-PGKO mice was more sensitive to endothelial-dependent relaxation caused by muscarinic stimulation, but was not associated with changes in eNOS expression or phosphorylation. In addition, vascular smooth muscle had impaired contraction in response to α-adrenergic agents. The renin-angiotensin-aldosterone system was mildly activated, consistent with increased vascular capacitance or decreased volume. These effects are likely mechanisms contributing to the hypotension. Our results demonstrated that PPARγ is required to maintain normal adiposity and insulin sensitivity in adult mice. Surprisingly, genetic loss of PPARγ function, like activation by agonists, lowered blood pressure, likely through a mechanism involving increased vascular relaxation.