Effect of exercise on postprandial lipemia following a higher calorie meal in Yucatan miniature swine

Exercise has been shown to attenuate the postprandial lipemic (PPL) response to a modest kcal high-fat meal in numerous human studies, but has not been fully examined in swine. In addition, the effects of exercise on a high-fat meal of larger magnitude have not been examined in humans or in swine. Thus, the purpose of this study was to examine the PPL response to a single, high-fat/cholesterol (HFC) meal (approximately 3,000 kcal, 1,300 kcal from fat) and determine if exercise attenuates the PPL response. Sedentary, female Yucatan miniature swine (n = 10) completed 3 PPL trials: (1) pre diet (PRE); (2) post HFC diet (POST); and (3) post HFC diet plus exercise (EX, 45 minutes at 75% heart rate maximum). Blood samples were collected before (0 hour) and at 2, 4, 6, and 8 hours after the single HFC meal for PPL analysis. Postheparin lipoprotein lipase (LPL) activity was assessed at 8 hours. While fasting LPL activity was significantly increased with the HFC diet, the PPL response to the HFC meal did not differ depending on diet. Furthermore, the PPL response was not significantly altered with a single session of exercise, perhaps because of the severity of the HFC meal, the sedentary nature of the swine, or because LPL activity was not elevated after exercise. These findings suggest that administration of a HFC meal of this magnitude (approximately 3,000 kcal, 1,300 kcal from fat) will promote significant elevations in postprandial triglyceride (TG) concentrations, overwhelm the adaptive response to a HFC diet (elevated LPL activity), and attenuate the beneficial effects of a single exercise session on this system.

Lipoproteins during the estrous cycle in swine

The purpose of this study was to examine lipoprotein values at high versus low 17beta-estradiol (E2) concentrations in Yucatan miniature swine. Estrous cycles were measured by heat checking the female on a daily basis using a boar. All swine were fed a 1,050-g low-fat, standard chow diet (8% kcal from fat) once per day. Fasted (24 hours) blood samples were collected during low (early luteal, day 5) and high (late follicular, day 18) E2 concentrations to determine differences in concentrations of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL-C), high-density lipoprotein cholesterol (HDL-C), and subfractions. Concentrations of E2 differed significantly from day 5 (3.5 +/- 0.7 pg/mL) to day 18 (14.2 +/- 1.8 pg/mL) of the estrous cycle. Except for HDL(3)-C, all lipoprotein parameters examined were significantly elevated during high E2 versus low E2. TC/HDL-C and LDL-C/HDL-C ratios were significantly lower during the high E2 phase. These results suggest that lipoprotein concentrations fluctuate during the estrous cycle of swine, with high E2 concentrations associated with elevated lipoprotein concentrations.

Diminished alpha1-adrenergic-mediated contraction and translocation of PKC in senescent rat heart

Myocardial reserve function declines with aging due in part to reduced alpha- and beta-adrenergic receptor (AR)-mediated contractile augmentation. Whereas specific age-associated deficits in beta-AR signaling have been identified, it is not known which components of the alpha1-AR signaling cascade, e.g., protein kinase C (PKC) and associated anchoring proteins (receptors for activated C kinase; RACKs), underlie deficits in alpha1-AR contractile function with aging. We therefore assessed cardiac contraction (dP/dt) in Langendorff perfused hearts isolated from adult (5 mo) and senescent (24 mo) Wistar rats following maximal alpha1-AR stimulation with phenylephrine (PE), and we measured the subcellular distribution of PKCalpha and PKCepsilon, and their respective anchoring proteins RACK1 and RACK2 by Western blotting. The maximum dP/dt response to PE (10(-5) M) was significantly reduced by 41% in 24-mo-old vs. 5-mo-old (P < 0.01). Inhibitory effects of PKC blockade (chelerythrine; 10 microM) on dP/dt following alpha1-AR stimulation with PE observed in adult hearts were absent in 24-mo-old hearts (P < 0.01). In 5-mo-old hearts, PE elicited reductions in soluble PKCalpha and PKCepsilon levels, while increasing particulate PKCalpha and PKCepsilon levels to a similar extent. In contrast, soluble PKCalpha and PKCepsilon levels in 24-mo-old hearts were increased in response to PE; particulate PKCepsilon and PKCalpha were unchanged or reduced and associated with significant reductions in particulate RACK1 and RACK2. The results indicate, for the first time, that selective translocation of PKCalpha and PKCepsilon in response to alpha1-AR stimulation is disrupted in the senescent myocardium. That age-related reductions in particulate RACK1 and RACK2 levels were also observed provide evidence that alterations in PKC-anchoring proteins may contribute to impaired PKC translocation and defective alpha1-AR contraction in the aged rat heart.