Effects of dietary glycerol supplementation on meat quality, palatability, and lipid metabolism gene expression in the longissimus thoracis of Hanwoo steers

This study tested the hypothesis that dietary glycerol supplementation (GS) would affect growth of Hanwoo steers, beef marbling and palatability, and gene expression for lipid uptake and transport and lipogenesis in the longissimus thoracis (LT). Diets with or without 45.2 g daily glycerol supplementation/kg dry matter concentrate were tested in fourteen Hanwoo steers during a 16-week feeding trial. GS did not affect (P ≥ 0.40) the average daily gain or the gain-to-feed ratio. GS increased the LT marbling score (P = 0.01). GS enhanced (P ≤ 0.01) the sensory traits, including the flavor and overall acceptance of the LT. GS tended (0.05 < P ≤ 0.10) to upregulate mRNA levels of fatty acid translocase, lipoprotein lipase, and fatty acid binding protein 4 genes in the LT. These tendencies of upregulated expression of fatty acid uptake and cytosolic transport genes may, in part, contribute to the increased marbling by GS. The increased marbling degree caused by GS may improve palatability including the flavor and overall acceptance of the LT.

64effects of long-term exercise training and detraining on endothelial function and arterial stiffness in patients with atrial fibrillation: a randomized controlled trial with 1-year follow-up

Introduction

Exercise training (ET) improves endothelial function and arterial stiffness in patients with cardiovascular disease. However, whether ET improves endothelial function and arterial stiffness in patients with atrial fibrillation (AF) is unclear. If it does, for how long the effects are sustained remains to be determined.

Methods

In a prospective study, 58 patients with AF (age, 62 ± 7 years) were randomized into an ET group for 12 months (CT, n = 13), a group with 6-month detraining after a 6-month ET (DT, n = 15), and a medical treatment only group (MT, n = 30). For ET, cycling on a bicycle ergometer was performed in the DT and CT groups 3 times a week for 6 and 12 months, respectively. Each session started with a 10-minute warmup at 60% to 70% of the maximal heart rate (HRpeak), followed by four 4-minute intervals at 80% to 90% of the HRpeak, with 3 minutes of active recovery at 60% to 70% of the HRpeak between intervals, ending with a 5-minute cooldown period. Peak exercise oxygen consumption (Vo2), intimal-medial thickness (IMT) of the carotid artery measured on high-resolution ultrasonography, and left ventricular function were measured at baseline, after 6 months of training, and after additional 6 months of continuous training or detraining follow-up assessments. In addition, plasma von Willebrand factor (vWF), endothelin-1, nitric oxide, tumour necrosis factor alpha, interleukin-1 beta, interleukin-6, and interleukin-10 levels were measured as indices of endothelial function.

Results

The 6-month ET increased peak Vo2 (CT: 29.0 ± 6.5 ml/[kg·min] and DT: 26.0 ± 8.2 ml/[kg·min] vs. MT: 23.0 ± 5.2 ml/[kg·min], p = 0.04) and decreased plasma vWF levels (CT: 103.7 ± 30.7 IU/dL and DT: 106.0 ± 31.2 IU/dL vs. MT: 145.0 ± 47.7 IU/dL, p = 0.01). Detraining significantly reduced the ET-induced increase in Vo2 and decreased the vWF to baseline level, although continuous ET maintained changes in Vo2 (CT: 28.1 ± 5.3 ml/[kg·min] and DT: 22.4 ± 6.6 ml/[kg·min] vs. MT: 21.5 ± 4.8 ml/[kg·min], p = 0.043) and in vWF (CT: 84.3 ± 39.1 IU/dL vs. DT: 122.2 ± 27.5 IU/dL and MT: 135.9 ± 50.4 IU/dL, p = 0.014). However, carotid arterial IMT, and resting left ventricular systolic and diastolic functions showed no significant changes, with no inter-group differences after 6 months of training and 6 months of continuous training or detraining.

Conclusions

The decreased vWF level suggested that ET can be a strong non-pharmacologic option to improve endothelial function in patients with AF. However, it can rapidly lose its effects after detraining. Therefore, physicians should encourage their patients to participate in a continuous exercise program to sustain its benefits in terms of improved exercise capacity and endothelial function in patients with AF.

63Effects of exercise-based cardiac rehabilitation and detraining on exercise capacity and cardiac function in patients with atrial fibrillation: a randomized controlled trial with 1-year follow-up

Introduction

We aimed to determine whether maximal exercise capacity, left ventricular function, and quality of life (QoL) scores are sustained in patients with atrial fibrillation (AF) after termination of training following exercise-based cardiac rehabilitation (ECR).

Methods

In a prospective study, 58 patients with AF (age, 62 ± 7 years) were randomized into an exercise training group for 12 months (ECR, n = 13), a group with 6-month detraining after a 6-month exercise training (DT, n = 15), and a medical treatment only group (MT, n = 30). For exercise training, cycling on a bicycle ergometer was performed in the DT and ECR groups 3 times a week for 6 and 12 months, respectively. Each session started with a 10-minute warm-up at 60%–70% of the maximal heart rate (HRpeak), followed by four 4-minute intervals at 80%–90% of the HRpeak, with 3 minutes of active recovery at 60%–70% of the HRpeak between intervals, ending with a 5-minute cool-down period. Peak exercise oxygen consumption (Vo2), left ventricular function, plasma lipid level, N-terminal pro B-type natriuretic peptide level, and QoL score were measured at baseline, after 6 months of training, and after additional 6 months of continuous training or detraining follow-up assessments.

Results

Six months of exercise training increased the peak Vo2 (ECR: 28.2 ± 7.0 ml/[kg·min] and DT: 28.0 ± 8.3 ml/[kg·min] vs. MT: 23.0 ± 5.2 ml/[kg·min], p= 0.047) and QoL scores (36-Item Short-form Health Survey) and decreased the total cholesterol level (ECR: 146.8 ± 43.8 mg/dl and DT: 140.6 ± 22.4 vs. MT: 182 ± 44.2 mg/dl, p = 0.008). Detraining resulted in an increase in QoL score and a decrease in total cholesterol level (ECR: 142.8 ± 21.4 mg/dl and DT: 151.8 ± 39.8 vs. MT: 176.8 ± 34.2 mg/dl, p = 0.017). However, the exercise training-induced increase in peak Vo2 reverted to the baseline level after detraining (ECR: 27.1 ± 5.1 ml/kg/min vs. DT: 24.4 ± 7.2 ml/[kg·min] and MT: 21.5 ± 4.86 ml/[kg·min], p = 0.017). The resting left ventricular systolic and diastolic functions were not significantly different, with no inter-group difference after 6 months of training and 6 months of continuous training or detraining.

Conclusions

As the QoL scores are maintained despite peak Vo2 being lowered by detraining after an exercise training period in patients with AF, physicians should encourage patients’ participation in a continuous exercise program to sustain the improvement in both the QoL score and peak Vo2 with exercise training. Further studies with larger sample sizes are needed to observe the long-term effects of exercise training and detraining.

312 Effects of castration stress on behaviors and leukocyte cytokine gene expression in Korean cattle bull calves

This study investigated behavioral, physiological, and inflammatory responses, as well as leukocyte cytokine gene expression, of Korean cattle calves following surgical castration. Nineteen Korean cattle bull calves (average body weight, 254.5 kg; average age, 8.2 months) were assigned to one of two treatment groups: control (n = 9) and surgical castration (n = 10). Castration was performed surgically using Newberry knives and a Henderson castrating tool. Blood was collected immediately before castration and at 0.5 h, 6 h, 1 d, 3 d, 7 d, and 14 d after castration, and analyzed cortisol and substance P concentrations and leukocyte cytokine gene expression by quantitative real-time PCR. Behaviors were observed for 3 h, from 0.5 to 3.5 h after castration. Feed intake was recorded daily, and body weight was measured 1 d prior to the experiment and 14 d after castration. Castration decreased average daily gain (P = 0.005) and gain-to-feed ratio (P = 0.003). Castration reduced the time spent eating (P &lt; 0.001) and the frequency of eating (P = 0.003) and increased (P &lt; 0.001) the frequency of lying during the 3 h after castration. Castration temporarily increased circulating plasma cortisol (P &lt; 0.001) and salivary cortisol concentrations (P = 0.03) at 0.5 h after castration. Castration temporarily increased (P &lt; 0.05) plasma substance P concentration at 1 d after castration. Castration increased plasma haptoglobin concentration at 1 d and 3 d after castration. With regard to leukocytes, castration increased (P &lt; 0.05) mRNA levels of inflammatory cytokine interleukin-1-beta and interleukin-1 receptor antagonist (IL1RA) genes at 6 h after castration, and increased (P &lt; 0.05) IL1RA, interleukin-1-alpha, and interleukin-6 mRNA levels at 1 d after castration. In conclusion, castration of Korean cattle bull calves temporarily induced stress, retarded growth, and affected behaviors and inflammatory cytokine gene expression.

PSIX-14 Effects of substituting dietary corn with beet pulp on growth performance and microbial profiles in the rumen of Korean cattle steers

This experiment evaluated the effects of substituting corn with beet pulp (BP) on growth performance and ruminal fermentation characteristics and microbiomes in fattening steers. Twelve Korean cattle steers (body weight, 485 ± 19 kg; age, 18.0 ± 0.17 months) were divided into corn and BP groups. Both groups were fed the basal concentrate to meet 80% of the nutrient requirements. For the corn group, corn (dry matter) was supplemented for the remaining 20% of requirement by top dressing; the BP group was supplemented with 14.88% BP plus 1.92% fat to provide the iso-energy content as the corn group. Steers were fed oat grass (2 kg as-fed basis) daily. Body weight was measured, and rumen fluid was collected after 3 h of feeding using oral stomach tube methods: at the start of the experiment then at 4-week intervals. Feed intake, average daily gain, and gain-to-feed ratio were not (P &gt; 0.05) affected by BP substitution; nor were acetate, propionate, butyrate, or total volatile fatty acid concentrations in the rumen fluid (P &gt; 0.05). BP substitution increased (P &lt; 0.05) the acetate to propionate ratio at 4, 8, and 12 weeks. Genomic DNA was extracted from pellets of rumen contents, and microbial populations were measured using real-time PCR at 8 and 12 weeks. BP substitution increased relative abundances of cellulolytic bacteria including Fibrobacter succinogenes (P = 0.01) and Ruminococcus albus (P = 0.04) at 12 weeks, whereas it did not affect amylolytic bacteria, including Succinimonas amylolytica, Ruminobacter amylophilus, and Streptococcus bovis. At 8 weeks, none of the microbial populations were altered by BP substitution. In conclusion, BP could provide a good energy source substitute for corn without affecting growth performance in the fattening period of beef cattle. Increased relative abundances of several cellulolytic bacteria supported the increased ruminal acetate to propionate ratio.

PSXI-27 Association of an increased marbling score by dietary glycerol supplementation with lipid metabolism gene expression in Korean cattle steers

This study investigated effects of dietary glycerol supplementation on liver, muscle, and adipose gene expression related with gluconeogenesis and lipid metabolism and association of gene expression levels with marbling score in Korean cattle steers. Fourteen Korean cattle steers (average age 28.4 months; average body weight 733 kg) were equally assigned to two groups (0 and 5% glycerol supplementation). Glycerol was provided with glycerol (63%)-adsorbed ground wheat bran (37%, DM) by top dressing during roughage feeding. A concentrate (1.2% of body weight) and 1.0 kg of ryegrass were individually fed twice daily. After four months of study, steers were slaughtered, and marbling score was evaluated. Longissimus thoracis (LT) and subcutaneous adipose tissue at the 13th thoracic vertebra area and liver were collected and analyzed for mRNA levels by quantitative real-time PCR. Statistical significance was analyzed by analysis of variance. Correlations were analyzed using Pearson’s correlation analysis. Glycerol supplementation increased (P = 0.01) marbling score. In the LT, glycerol supplementation tended to increase (0.05 &lt; P ≤ 0.10) lipid uptake CD36 and lipoprotein lipase (LPL) mRNA levels. In subcutaneous adipose tissues, glycerol supplementation increased (P ≤ 0.05) LPL, adipogenic sterol regulatory element binding protein 1 (SREBP1), and lipogenic acetyl CoA carboxylase (ACC) mRNA levels and tended to increase (0.05 &lt; P &lt; 0.10) CD36, adipogenic peroxisome proliferator-activated gamma (PPARG), and lipogenic fatty acid synthase (FASN) expression. It did not affect (P &gt; 0.05) mRNA levels of hepatic gluconeogenesis genes. Marbling score showed significant positive correlations (0.57 &lt; r &lt; 0.68; P &lt; 0.05) with mRNA levels of several genes including LPL, PPARG, SREBP1, and ACC in adipose tissues, but not with any genes examined in the LT. Our study demonstrates that lipid uptake, adipogenesis and lipogenesis may mainly contribute to the increased marbling score by glycerol supplementation.

Rosiglitazone inhibits Kv4.3 potassium channels by open-channel block and acceleration of closed-state inactivation

BACKGROUND AND PURPOSE

Rosiglitazone is a widely used oral hypoglycaemic agent, which improves insulin resistance in type 2 diabetes. Chronic rosiglitazone treatment is associated with a number of adverse cardiac events. The present study was designed to characterize the effects of rosiglitazone on cloned K(v)4.3 potassium channels.

EXPERIMENTAL APPROACH

The interaction of rosiglitazone with cloned K(v)4.3 channels stably expressed in Chinese hamster ovary cells was investigated using whole-cell patch-clamp techniques.

KEY RESULTS

Rosiglitazone decreased the currents carried by K(v)4.3 channels and accelerated the current inactivation, concentration-dependently, with an IC(50) of 24.5 µM. The association and dissociation rate constants for rosiglitazone were 1.22 µM(-1)·s(-1) and 31.30 s(-1) respectively. Block by rosiglitazone was voltage-dependent, increasing in the voltage range for channel activation; however, no voltage dependence was found in the voltage range required for full activation. Rosiglitazone had no effect on either the deactivation kinetics or the steady-state activation of K(v)4.3 channels. Rosiglitazone shifted the steady-state inactivation curves in the hyperpolarizing direction, concentration-dependently. The K(i) for the interaction between rosiglitazone and the inactivated state of K(v)4.3 channels was 1.49 µM, from the concentration-dependent shift in the steady-state inactivation curves. Rosiglitazone also accelerated the kinetics of the closed-state inactivation of K(v)4.3 channels. Rosiglitazone did not affect either use dependence or recovery from inactivation of K(v)4.3 currents.

CONCLUSION AND IMPLICATIONS

Our results indicate that rosiglitazone potently inhibits currents carried by K(v)4.3 channels by interacting with these channels in the open state and by accelerating the closed-state inactivation of K(v)4.3 channels.

Role of ataxia telangiectasia mutated in insulin signalling of muscle-derived cell lines and mouse soleus

AIM

Ataxia telangiectasia mutated (ATM) reportedly plays a role in insulin-stimulated activation of Akt in some cell types but not in others. The role of ATM in insulin signalling has not been firmly resolved for skeletal muscle cells, for which Akt phosphorylation is a pivotal step in stimulation of glucose transport. Accordingly, our aim was to determine the role of ATM in insulin effects for cell lines derived from skeletal muscle and for skeletal muscle.

METHODS

We examined insulin effects in L6 myotubes, mouse soleus, C2C12 myotubes and differentiated rhabdomyosarcoma (RD) cells in the presence and absence of a low concentration (1 microm) of the ATM inhibitor KU55933. We also compared insulin signalling in C2C12 cells expressing shRNA against ATM and control cell lines (empty vector; cells expressing non-targeting shRNA).

RESULTS

In L6 myotubes and mouse soleus muscle, KU55933 inhibited insulin-stimulated phosphorylation of the 160 kDa substrate of Akt (AS160) despite no effect on Akt. In contrast, KU55933 prevented insulin-stimulated Akt phosphorylation in C2C12 myotubes. Furthermore, C2C12 myotubes expressing shRNA against ATM displayed reduced insulin-stimulated Akt phosphorylation compared to controls. KU55933 also decreased insulin-stimulated Akt phosphorylation in differentiated RD cells.

CONCLUSION

These model-dependent differences in the role of ATM in insulin action demonstrate a role of ATM in insulin-stimulated phosphorylation of Akt (in C2C12 and RD cells) but also allow the elucidation of a novel, Akt-independent role of ATM (in L6 myotubes and mouse soleus, at the level of AS160) in insulin signalling.