Perivascular Adipose Tissue May Contribute To Disparate Blood Pressure Responses To Lifetime High Fat Feeding In Dahl Salt-sensitive And Salt-resistant Rats

Dahl salt-sensitive (SS) and salt-resistant (SR) rats show dramatically different blood pressure (BP) responses to being raised on a high fat, but normal salt, diet starting at weaning. Virtually no effect on BP is seen in SR rats, whereas in SS rats mean arterial pressure (MAP) reaches over 160 mmHg by adulthood. The BP difference is similar in female and male rats. The cellular and physiological mechanisms responsible have not been completely elucidated in either sex. Dysfunctional perivascular adipose tissue (PVAT) is proposed to contribute to obesity-associated hypertension through actions on other components of the vascular wall. Here we used female rats to test the hypothesis that differences in adipose tissue amount or function in SS and SR rats play a part in the distinct BP effects of high fat diet in the two strains. Rats (n=8 per strain) were fed a high fat diet (60% kcal fat) from weaning. BP was measured with telemetry. At 18 weeks of age, MAPs (mmHg) were 108±1 and 180±4 in SR and SS rats. Body weights (g) were 274±4 and 323±4. Total and visceral adipose volumes (mm3) measured by μCT were higher in SS rats versus SR rats (visceral: 22372±927 versus 14112±1495; total: 17208±732 versus 10234±984). PVAT volume around the thoracic aorta was larger in SS rats (0.228±0.017 versus 0.167±0.006). Subcutaneous adipose tissue volumes did not differ. Plasma triglycerides and cholesterol were modestly but significantly higher in SS rats. The well-known anticontractile effect of PVAT was compared in thoracic aorta from both strains. Removal of PVAT increased the AUC of the tension/PE contraction in SR rats by 1484±226 units and by a significantly smaller amount (946±162.5 units) in SS rats. Finally, aortic stiffness was estimated from pulse wave velocity measured via Doppler in a subset (n=4 each) of rats from each strain. Pulse wave velocity (M/sec) was markedly higher in SS than SR rats (11.5±1.0 versus 6.4±0.3). We conclude that differences in adipose tissue volume, location or function could account in part for the distinct BP responses of female SS and SR rats to high fat feeding.