Food & Function Blog

Researchers from Shizuoka, Japan, have investigated the effects of dietary vitamin K on testosterpone production (steroidogenesis) in rats. Vitamin K, found in foods such as spinach and broccoli is known to be essential for blood coagulation and bone metabolism, however, it is also found in the brain, kidney and gonadal tissues, and its function there is unknown.

The aim of this study was to better understand the function Vitamin K in the gonadal tissues.  Vitamin K  supplementation has previously been shown to suppress inflammation.  Deficiency has been shown to decrease testicular testosterone levels. In this study, rats were fed either vitamin K-free or control diets for 35 days, and then administered lipopolysaccharide to induce inflammation for 6 hours. The team looked at the expression of proteins involved in steroidogenesis, including Cyp11a, a rate-limiting enzyme. The results showed that testosterone levels were significantly reduced in the vitamin K-free diet group compared with the control diet group after lipopolysaccharide was added. Levels of Cyp11a were reduced as well as other changes in the steroidogenesis pathway.  The team’s findings suggest that Testicular vitamin K might facilitate the inhibition of inflammation signal transduction and its function in the testes is to maintain steady levels of testosterone.

It is known that chronic inflammation contributes to the age-related reduction in testosterone synthesis, and lowering of testosterone levels in the blood is considered a pathogenic factor of age related diseases, such as cancer, osteoporosis and atherosclerosis. Therefore, incorporating vitamin K into the diet may contribute to maintaining sufficient levels of testosterone.

To find out more, read the article in full for free: follow the link below:

Dietary vitamin K alleviates the reduction in testosterone production induced by lipopolysaccharide administration in rat testis, Naofumi Takumi, Hitoshi Shirakawa, Yusuke Ohsaki, Asagi Ito, Takaya Watanabe, Puspo E. Giriwono, Toshiro Sato and Michio Komai, Food Funct., 2011, DOI: 10.1039/c1fo10058k

A team of researchers from Niigata, Japan, have demonstrated the beneficial effects of Inonotus obliquus (Chaga mushroom) on cognitive function in amnesic mice. Chaga has been shown in previous studies to display therapeutic effects such as anti-inflammatory and immunomodulatory activity, however, no study has been performed to evaluate whether treatment with Chaga has an anti-amnesic potential. 

In order to assess this, mice were subject to scopolamine-induced amnesia.  The methanolic extract of Chaga (MEC) was then administered orally to the mice over 7 days, and cognitive functions were assessed by various tests including passive avoidance task (PAT) and Morris water maze (MWM) methods. These tests indicated a significant improvement in learning and memory, furthermore, biochemical tests showed that MEC treatment resulted in a decrease in AChE activity and also significantly reduced oxidative-nitritive stress, demonstrated by a decrease in malondialdehyde and nitrite levels in a dose dependent manner.

This study shows that the significant cognitive enhancement observed in mice after MEC administration is closely related to higher brain anti-oxidant properties and inhibition of AChE activity.

To read the article in full for free, please follow the link below:

Amelioration of scopolamine induced cognitive dysfunction and oxidative stress by Inonotus obliquus – a medicinal mushroom, Vijayasree Vayalanellore Giridharan, Rajarajan Amirthalingam Thandavarayan and Tetsuya Konishi, Food Funct., 2011, DOI: 10.1039/c1fo10037h

Research conducted by a team in Massachusetts, including Food & Function board members Julian McClements and Eric Decker, describes the effect of “reverse micelles” formed by phospholipids on the antioxidant behaviour of two compounds on stripped soybean oil (SSO).

The ability to prevent oxidation of these oils is vital, as the oxidation reaction changes the flavour and quality of the lipids in an adverse way and can also result in toxic reaction products. The undesirable oxidation reaction can be triggered by many factors including exposure to light, high temperatures and high oxygen levels; however, the incorporation of antioxidant compounds to the bulk oil is a good way to prevent this.

In this study, phospholipids which can create “reverse micelle” structures were added to the bulk oil. The “reverse micelles” formed by the addition of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) actually promoted lipid oxidation. However, when antioxidant compounds alpha-tocopherol and Trolox were added at low concentrations, it was observed that they both displayed higher antioxidant activity in the presence of DOPC than in the absence of DOPC. Furthermore, alpha-tocopherol is a hydrophobic antioxidant and Trolox is a hydrophilic antioxidant and the latter had better anti-oxidant activity which is thought to be related to differences in their physical position in the micelle structure.

This study shows that altering the physical micro-environments in bulk oil can complement the mode of action of specific antioxidant compounds.

To read the full article for free, please follow the link below:

Bingcan Chen, Ashley Han, Michael Laguerre, David Julian McClements and Eric Andrew Decker, Role of reverse micelles on lipid oxidation in bulk oils: impact of phospholipids on antioxidant activity of a-tocopherol and Trolox, Food Funct., 2011, DOI: 10.1039/c1fo10046g

Scientists from Australia and China have reported the Angiotensin Converting Enzyme (ACE) inhibitory activity of a variety of teas (Camellia sinensis) in vitro. ACE is an important enzyme involved in the control of blood pressure, as it transforms angiotensin into angiotensin II, which is a powerful vasoconstrictor. Therapeutic ACE inhibitors are therefore an important class of pharmaceuticals which can be used to control high blood pressure. A variety of food components including polyphenolics, peptides and unsaturated fats have been shown to lower blood pressure via inhibition of ACE.

This study correlates the processing methods used to produce the tea with the observed ACE inhibitory properties. It was found that the polyphenols in green tea (non-oxidized tea) displayed the highest values for ACE inhibition, whereas the polyphenols in black and dark teas (fully-oxidized teas) had the lowest inhibitory activity of the 5 varieties tested. In addition, the ACE inhibition kinetics were explored for the range of teas in order to characterize the mechanism of inhibition. An allosteric (not Michaelis–Menten) mechanism was observed, which implies synergistic subunits within the enzyme or the occurrence of irreversible changes to the enzyme – a mechanism which is common in pharmaceutical ACE inhibitors.

To find out more, read the full article for free by following the link below:

Inhibition of angiotensin converting enzyme (ACE) activity by polyphenols from tea (Camellia sinensis) and links to processing method, Junjie Dong, Xinqing Xu, Yuerong Liang, Richard Head and Louise Bennett, Food Funct., 2011, DOI: 10.1039/C1FO10023H

New research by Food & Function Associate Editor Steven Feng Chen and co-workers describes the protective effects of certain microalgal strains against endogenous and exogenous advanced glycation endproducts (AGEs). AGEs are generated from the glycation between sugars and protein and can lead to the cross-linking of key molecules resulting in functional impairment. AGEs are believed to be important factors associated with the development of diabetic retinopathy – the leading cause of blindness in Western countries.

In this study, the extracts and active compounds of 3 microalgal strains (Chlorella zofingiensis,  Chlorella protothecoides and Nitzschia laevis) were tested for their inhibitory effects on the glycation process in a cell based model. Results showed that astaxanthin, lutein and eicosapentaenoic acid (EPA) isolated from the microalgae reduced cell proliferation and the upregulation of both vascular endothelial growth factor and MMP2 mRNA, which are vital steps in the development of diabetic retinopathy. Therefore, these microalgal species can be regarded as beneficial foods for people suffering from diabetic retinopathy.

To find out more, read the article in full for free by following the link below:

Protective actions of microalgae against endogenous and exogenous advanced glycation endproducts (AGEs) in human retinal pigment epithelial cells
Zheng Sun, Jin Liu, Xiaohui Zeng, Jieqiong Huangfu, Yue Jiang, Mingfu Wang and Feng Chen
Food Funct., 2011, DOI: c1fo10021a