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Abstract

Gamma tocopherol (gT) exhibits beneficial cardiovascular effects partly due to its anti-inflammatory activity. Important sources of gT are vegetable oils. However, little is known to what extent gT can be transferred into marine animal species such as Atlantic salmon by feeding. Therefore, in this study we have investigated the transfer of dietary gT into salmon. To this end, fish were fed a diet supplemented with 170 ppm gT for 16 weeks whereby alpha tocopherol levels were adjusted to 190 ppm in this and the control diet. Feeding gT-rich diets resulted in a three-fold increase in gT concentrations in the liver and fillet compared to non-gT-supplemented controls. Tissue alpha tocopherol levels were not decreased indicating no antagonistic interaction between gamma- and alpha tocopherol in salmon. The concentration of total omega 3 fatty acids slightly increased in response to dietary gT. Furthermore, dietary gT significantly decreased malondialdehyde in the fillet, determined as a biomarker of lipid peroxidation. In the liver of gT fed salmon we observed an overall down-regulation of genes involved in lipid homeostasis. Additionally, gT improved the antioxidant capacity by up-regulating Gpx4a gene expression in the pyloric caeca. We suggest that Atlantic salmon may provide a marine functional source capable of enriching gT for human consumption.

2.2. Tissue Levels of Tocopherols, Malondialdehyde, Antioxidant Enzymes and Fatty Acid Composition

In order to evaluate the transfer of Vitamin E from the diet into the tissues of Atlantic salmon we determined the gamma and alpha tocopherol concentrations in fish fillet and liver. As summarized in , feeding the gT enriched diet resulted in a three-fold increase of gT concentrations in both fillet and liver (p < 0.0001). However, alpha tocopherol levels in fillet and liver were similar between the groups indicating no antagonistic interaction between gamma and alpha tocopherol.

2.2. Tissue Levels of Tocopherols, Malondialdehyde, Antioxidant Enzymes and Fatty Acid Composition

Most methods for analyzing lipid peroxidation in animal tissues lack specificity and sensitivity []. However, MDA is an important biomarker of lipid peroxidation and may also partly reflect the sensory quality of fish []. Using a validated HPLC method [] to measure MDA, we found that MDA concentrations were significantly decreased by 25% in the fillet of gT-fed salmon as compared to the controls (3.3 ± 0.2 mmol·MDA/kg fillet in the control vs. 2.5 ± 0.2 mmol·MDA/kg fillet in gT-fed salmon, p < 0.02).

3. Discussion

Our data indicate that feeding Atlantic salmon with gT-rich diets resulted in a significant increase in gT concentrations in fish fillet, thereby improving its nutritional value. Thus, Atlantic salmon could be considered as a potential marine functional source of gT for human nutrition. However, future human trials (e.g., bioavailability studies, intervention studies) are required to test the hypothesis whether the consumption of gT-rich Atlantic salmon results in increased plasma levels of gT that may lead to potential anti-inflammatory and anti-atherogenic effects.

3. Discussion

The enrichment of fat soluble pro-vitamins and vitamins into the food matrix is a common practice in aquaculture. However, the transfer of micronutrients including Vitamin E from the diet into the animal tissue is always accompanied by a loss in assimilation. In order to quantify the apparent Vitamin E absorption, digestibility experiments need to be conducted which was beyond the scope of our study. Furthermore, Vitamin E transfer may be experimentally determined by its whole body retention. In order to do so, Vitamin E levels need to be quantified in all tissues at the beginning and the end of a feeding trial. However, within this study Vitamin E was only determined in fillet and liver at the end of the study. Thus, it was not possible to pinpoint the exact Vitamin E retention. However, analyzed alpha and gamma tocopherol levels in liver and fillet suggest that the tissue retention of alpha tocopherol was higher as compared to gamma tocopherol which is in line with literature data []. In terms of alpha tocopherol, it has been suggested that around 40% of dietary alpha tocopherol is retained in the fillet of Atlantic salmon []. Since in the fillet of our salmon following dietary supplementation, the gamma tocopherol concentration was 2.8 fold lower as compared to alpha tocopherol a transfer efficiency of around 15% may be assumed.

Abstract

Antioxidants have a number of potential health benefits. The present investigation was designed to determine the relationship between serum alpha- and gamma-tocopherol levels (powerful antioxidants), and leukocyte telomere length (a biomarker of biological aging). A cross-sectional design was employed to study 5768 adults from the National Health and Nutrition Examination Survey (NHANES). DNA was obtained via blood samples. Telomere length was assessed using the quantitative polymerase chain reaction method. Serum concentrations of alpha- and gamma-tocopherol were measured using high performance liquid chromatography (HPLC). Results showed that for each one-year increase in age, telomeres were 15.6 base pairs shorter (F = 410.4, p < 0.0001). After adjusting for differences in the demographic covariates, for each µg/dL higher level of gamma-tocopherol, telomeres were 0.33 base pairs shorter (F = 7.1, p = 0.0126). Telomeres were approximately 1 year shorter (15.6 base pairs) for each increment of 47.3 to 55.7 µg/dL of gamma-tocopherol in the blood, depending on the variables controlled. Adults at the 75th percentile of gamma-tocopherol had 2.8–3.4 years greater cellular aging than those at the 25th percentile, depending on the covariates in the model. However, alpha-tocopherol was not related to telomere length. Evidently, gamma-tocopherol levels, but not alpha-tocopherol, account for meaningful increases in biological aging.

Abstract

The effect of hempseed in the diet of laying hens was evaluated at 0, 30, 60 and 90 g/kg concentrations. The aim of the study was to determine the effect of dietary treatment on the performance of hens, the physical characteristics of egg quality, the concentrations of α- and γ-tocopherol and the carotenoid and cholesterol contents of egg yolks, together with the breaking strength of tibial measurements. In light of the obtained results, our study aimed to address the optimal dietary level of hempseed in laying hen diets. Lohmann Brown hens (n = 240) were divided into 4 dietary treatment groups (6 cages per treatment) with 10 hens per cage. The experiment lasted for 12 weeks. The level of nutrients in all diets (wheat-corn) was well balanced. The dietary metabolisable energy was adjusted using rapeseed oil. The addition of 30 g/kg of hempseed to the diet significantly increased (P˂0.001) egg production and egg mass. Alpha-tocopherol increased significantly (P = 0.002) only in the case of the 60 g/kg hempseed level (101 mg/kg dry matter (DM) versus 83 mg/ kg DM in the control group). In contrast, the level of γ-tocopherol increased gradually from 11 mg/kg DM in the control to 29, 39 and 43 mg/kg DM at the 30, 60 and 90 g/kg levels of dietary hempseed, respectively. The concentrations of beta carotene, zeaxanthin and lutein in egg yolks were not influenced by the dietary treatment. Hempseed at 90 g/kg (P = 0.036) decreased egg shell thickness without affecting its strength. The addition of hempseed decreased (P˂0.001) the cholesterol concentration in the egg yolks in all experimental groups. The addition of 30, 60 and 90 g hempseed increased (P˂0.001) the breaking strength of the tibia to 354, 352 and 350 N, respectively, compared to 297 N in the control group. The highest level of hempseed in the diet positively influenced the Ca concentration in the tibia (P = 0.021). The concentration of P in the tibia was negatively affected in the 60 to 90 g/kg hempseed treatments (P˂0.001). Eggs are a significant source of α-tocopherol. Based on our results, there is a possibility for enrichment of egg yolks with γ-tocopherol, with all of its associated health benefits, by the addition of hempseed to the diet of laying hens. Another significant benefit of hempseed is its effect on the breaking strength of the tibia, which can help with crucial problems in the commercial breeding of laying hens.

Hens, husbandry and diets

Two hundred forty 52-week-old Lohmann Brown (Egg Production Company in Kosičky, Kosičky, Czech Republic) hens were randomly assigned to 4 treatments with 6 replicate cages and 10 hens per cage. The hens were housed in three-floor enriched cages in the same air-conditioned facility. Each cage was 7,560 cm2 in area. The cage equipment conformed to the European Council Directive 1999/74 EC (European Union 1999). The light cycle was 16 h of light and 8 h of darkness, and the light intensity was approximately 10 lux in the central storey. The control diet had no hempseed addition, and the experimental groups received diets supplemented with 30, 60 and 90 g of hempseed per kg of diet. The ingredients and nutrient composition of the diets are listed in . All diets were formulated to contain similar levels of metabolisable energy (11.6 MJ/kg) and crude protein (165 g/kg). A vitamin-mineral premix incorporated into the diet did not contain tocopherol. Feed and fresh water were supplied ad libitum. The experiment lasted 12 weeks. The Ethical Committee of the Institute of Animal Science approved the study protocol and the use of animals in the experiment.

Results

As the hempseed concentration increased, the amount of α-tocopherol, β-carotene, lutein and zeaxanthin increased accordingly (). The amount of γ-tocopherol is almost twenty times higher than that of α-tocopherol in hempseed, which was correspondingly increased in the mixed feed. In the control diet, with no hempseed added, α-tocopherol was higher, which was also observed in the diet enriched with 30 g/kg hempseed. When 60 g/kg hempseed was added, both tocopherols were almost equally present, and in the case of the 90 g/kg hempseed diet, γ-tocopherol was present at a higher concentration when compared with α-tocopherol. Regarding the tocopherol concentrations in egg yolks, eggs of hens fed with the control feed contained mostly α-tocopherol at 83 mg/kg DM; the amount of γ-tocopherol was 11.3 mg/kg DM (). The ratio between the two tocopherols was 7.35. With the increase in hempseed in the diet, the ratio decreased from 3.2 to 2.6 to 2. Between groups, there was a significant difference in both the α- and γ-tocopherol concentrations (P = 0.002 a P < 0.001, respectively). There were no significant differences in the amounts of β-carotene, lutein and zeaxanthin between treatments. In contrast, all experimental diets significantly decreased (P < 0.001) the cholesterol concentration in egg yolks. There was no effect of the hempseed concentration on cholesterol concentration.

Conclusion

In conclusion, dietary hempseed supplementation increased γ-tocopherol in egg yolks and the breaking strength of tibia and decreased cholesterol content in egg yolks. In terms of performance and bone quality, the most suitable dose for laying hens is 30 g/kg of hemp seed in the diet.