Food & Function Blog

Researchers from Fisciano, Italy, have provided new insights into the mechanism of interaction between tau proteins and the extra-virgin olive oil component oleocanthal (OLC). Extra-virgin olive oil is the primary source of fat in the Mediterranean diet, and is widely associated with a variety of health benefits.  The olive oil phenolic compound OLC has attracted great interest due to the suggestion it could be involved in modulating diseases such as inflammation and Alzheimer’s.

Fibrillization of Tau protein is one of the leading causes of Alzheimer’s disease and OLC has been shown to halt this process. Understanding how this compound interacts with tau protein and prevents fibrillization could prove to be crucial in the fight against Alzheimer’s.

In this study, it was shown that OLC irreversibly modifies tau protein via covalent modification of the tau protein fibrillogenic fragment K18, thus preventing its fibrillization. This occurs through Schiff base formation between the 3-amino group on the lysine residues of tau protein and the carbonyl groups of OLC in a 1:1 stoichiometry.

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

New insights on the interaction mechanism between tau protein and oleocanthal, an extra-virgin olive-oil bioactive component

Maria Chiara Monti, Luigi Margarucci, Alessandra Tosco, Raffaele Riccio and Agostino Casapullo, Food Funct., 2011, DOI: 10.1039/c1fo10064e

Scientists from New Jersey, America, have reported that modified 3-polylysine (M-EPL) can improve the water solubility of poorly-soluble bioactive compounds. The discovery suggests that M-EPL could potentially be used as a biopolymer to deliver poorly soluble drugs thereby improving their bioactivities.

At concentrations above the critical aggregation concentration, M-EPL forms a polymer micelle in aqueous solutions of size 2.4-2.6 nm, which upon further aggregation results in micelles of radius 26.8-30.8 nm as determined by synchrotron small-angle X-ray scattering (SAXS). It was found that the M-EPL micelles were able to capture and solubilize compounds such as curcuminoids, which are ordinarily water-insoluble. This finding is of interest because curcuminoids (extracted from tumeric) have shown anti-inflammatory, anti-cancer, antioxidant and antimicrobial activity, but their use as drug candidates is hindered by their very poor solubility.

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

Structure of modified 3-polylysine micelles and their application in improving cellular antioxidant activity of curcuminoids
H. Yu, J. Li, K. Shi and Q. Huang, Food Funct., 2011, DOI: 10.1039/c1fo10053j

Researchers from Montreal, Canada, have investigated the link between iron deficiency and highly unsaturated fatty acids in the diet of Canadian Arctic Inuits. Impaired fatty acid synthesis has been noted in iron deficient animal models but data from humans is scarce. The typical diet of the Canadian Inuit consists primarily of red meat – an excellent source of heme iron and unsaturated n–3 fatty acids. However, recent reports have highlighted the prevalence of iron deficiency among the Inuit population – in fact these reports suggest that iron deficiency could affect up to 18% of Inuit children compared to 4.5% of American children. Although these statistics may seem counter-intuitive considering the iron and nutrient rich traditional red meat diet of the Inuit, recent trends in dietary behaviour amongst the population has seen a shift from the traditional nutrient rich diet to one containing more convenient “market foods”. This so-called “dietary transition” has resulted in concerns over inadequate iron intake – a concern which was virtually non-existent before. The high levels of iron deficiency in the Inuit population allowed investigation of the link between iron deficiency and fatty acid synthesis in humans.

The traditional Inuit diet is also rich in compounds called n-3 highly unsaturated fatty acids (or n-3 HUFA), which have previously been shown to be protective against cardiovascular disease. From the results found in this study, a correlation was observed between the activity of desaturase 5 (a crucial enzyme in the biosynthesis of n-3 HUFA) and serum ferritin (an indicator of iron status) in the Inuit population. Therefore, in a shift away from the traditional red meat Inuit diet, n-3 HUFA consumption and biosynthesis are both reduced and exacerbated by the decreased iron levels. This potentially suggests that the Inuit population may be more susceptible to obesity and cardiovascular disease, in particular ischemic heart disease.

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

Is iron status associated with highly unsaturated fatty acid status among Canadian Arctic Inuit? Yuan E. Zhou, Stan Kubow and Grace M. Egeland, Food Funct., 2011, DOI: 10.1039/c1fo10051c

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

This review from Gow-Chin Yen and co-workers in Taiwan reviews the anti-glycation properties of various foods and their mechanisms of action.  Glycation, also known as the Malliard reaction is a type of nonenzymatic browning involving the reaction of carbohydrate with protein.  It occurs ubiquitously in food, particularly during heating, processing and storage.  It has also been implicated in accelerated aging and diabetic complications in vivo although the molecular basis of this pathogenesis is not well understood.

Most studies to date have focused on the deleterious effects of toxic advanced glycation endproducts (AGEs) and it remains unclear whether phytochemicals, implicated in the reduction of toxic effects in clinical trials, actually exert protective effects against glycotoxin-induced damage.  These natural potential AGE inhibitors may provide a therapeutic approach for delaying and preventing premature aging and diabetic complications.

Interested in knowing more?  Read the full article by following the link below, all content in Food & Function is free to access until the end of 2011.

Inhibition of advanced glycation endproduct formation by foodstuffs
Chi-Hao Wu, Shang-Ming Huang, Jer-An Lin and Gow-Chin Yen
Food Funct., 2011, Advance Article
DOI: 10.1039/C1FO10026B