Abstract P190: Long-term Intake of Muscadine Grape Extract Markedly Improves Exercise Capacity in Older Female (mRen2)27 Hypertensive Rats

Abstract

Muscadine grapes ( Vitis rotundifolia ) contain significant levels of polyphenols and their antioxidant capacity may have cardiovascular benefit. We determined the cardiovascular effects of a water soluble muscadine grape extract (MGE) from Piedmont Research & Development Corporation (PRDC, Winston-Salem, NC) that we confirmed has a high content of epicatechin, gallic acid, ellagic acid and procyanidin B2. We hypothesize that this soluble MGE with a potentially high phenolic bioavailability exhibits cardioprotective actions. The effect of long-term MGE intake on blood pressure, cardiac function and exercise tolerance was established in female and male hemizygous (mRen2)27 [mRen2] transgenic rats, an Ang II-AT 1 R-dependent model of hypertension. The mRen2 were administered MGE (8 mg of total phenolics/mL) in the drinking water for 26 weeks (7 female; 7 male); control rats (9 female; 11 male) were given water only. At 40 weeks of age, exercise tolerance was assessed by treadmill (10.2 m x min -1 , 5% inclination). The MGE-treated female mRen2 exhibited a >300% improvement in workload ( W: g X m ) as compared to the untreated group [14551 ± 1313 vs. 4498 ± 481; p<0.01]. MGE intake also extended the time to fatigue (TTF) by 300% in females (4943 ± 443 vs.1615 ± 166 sec; p<0.01). In contrast, chronic intake of MGE had no effect on either exercise workload or TTF in the male mRen2. MGE intake did not alter systolic blood pressure in females (162 ± 3 vs. 166 ± 6 mm Hg, p>0.05) and males (165 ± 5 vs. 160 ± 3 mm Hg) nor alter body weight in either group [females: 334 ± 7 g vs. 339 ± 8 g; males: 613 ± 12 g vs. 590 ± 6 g). Echocardiographic analyses revealed that although the female mRen2 exhibited a higher ejection fraction [73.4±5.1 vs. 42.3±4.5%, n=4-5, p<0.05] and a higher fractional shortening [44.2±4.2 vs. 22.1±2.7%, n=4-5, p<0.05] as compared to males, MGE treatment did not improve these indices in either group. We conclude that the marked improvement in exercise capacity in older adult hypertensive females by chronic MGE intake is not accompanied by augmented cardiac performance, perhaps reflecting the lack of an effect on blood pressure. Thus, it is possible that MGE may directly impact the skeletal muscle to improve exercise in the hypertensive mRen2 females, but not the males.