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Eyeseryl: A novel synthetic tetrapeptide to fight puffy eyes
The following is a two-part article – the first part examines a novel synthetic tetrapeptide to fight puffy eyes, which leads on to the second part, entitled “A laminin-like hexapeptide to enhance skin compactness”. The skin under our eyes is the thinnest skin in our bodies, only 0.5 mm thick, and around four times thinner than the average. This is one of the reasons why the normal ageing processes of the skin are more visible around our eyes. Weakened skin folds easier in this area, causing the “puffy eyebag” effect, and the veins beneath the thin tissue show through as “dark circles”. There are two main kinds of eyebags: those caused by fluid retention and those caused by fat. As skin loses its elasticity and the connective tissue weakens through age, loose skin can accumulate around the eyes, forming folds in the eyelids. Fat, which cushions the eyes in their sockets moves forward out of the ocular cavities and accumulates in bulging bags around the eyelids. The removal of this kind of eyebag is only possible by a surgical procedure called blepharoplasty.1 The other major reason for puffy eyes is water accumulation, known as eyelid oedema. Fluid may build up for several reasons, two of the major reasons being poor lymphatic circulation and increased capillary permeability. Eyeseryl can fight puffy eyebags by working on several mechanisms, like strengthening the skin under the eyes and preventing fluid accumulation. The skin is strengthened by protecting the collagen structural network from degradation due to glycation. The local vascular system is improved by lowering high blood pressure in the vessels under the eyes in order to improve lymph drainage and avoid oedema formation. Materials and methods Determination of the ACE inhibitory activity of Eyeseryl It has been suggested that one of the mechanisms involved in the formation of bags under the eyes is poor blood circulation due to hypertension. For this reason, a valid mechanism for an antipuffiness compound would be the local improvement of blood circulation by an anti-hypertensive effect. Angiotensin I converting enzyme (ACE) is a dipeptide liberating exopeptidase, which has been classically associated with the rennin-angiotensin system regulating peripheral blood pressure. ACE removes a dipeptide from the C terminus of angiotensin I to form angiotensin II, a very hypertensitive compound. The protease renin cleaves angiotensinogen into the inactive decameric peptide angiotensin-I (Ang-I). Angiotensin-converting enzyme (ACE) then cleaves a C-terminal dipeptide from Ang-I to form an active octamer angiotensin-II (Ang-II), which can contribute to hypertension by promoting vascular smooth muscle vasoconstriction and renal tubule sodium reabsorption. ACE can also cleave many other small peptides including the vasodilating peptide bradykinin into an inactive fragment. It can also cleave the Alzheimer amyloid beta-peptide (Abeta), and retard its aggregation, deposition and fibril formation. The ACE inhibitory activity was determined according to the method of Wang.2 In this test, cleavage by ACE of a substrate yields a fluorescent dipeptide which can be measured and its intensity correlated to ACE activity. The controls used were a standard solution (where Eyeseryl was replaced by distilled water) and a blank (where ACE was replaced by distilled water). The ACE activity was calculated from the following equation and expressed as ACE%: ACE% = (b-c) / a x 100 …where a is the fluorescence intensity of the standard solution (ACE), b is the fluorescence intensity of the reaction mixture with Eyeseryl, and c is the fluorescence intensity of the blank solution (without ACE). The ACE inhibitory activity was calculated based on the following equation: ACE inhibitory activity (%) = 100 - ACE% Glycation inhibitory activity of Eyeseryl Glycation is a non-enzymatic reaction between glucose or another monosaccharide and a protein. The aldehyde group of the monosaccharide reacts with the terminal amino group of the amines to produce a Schiff’s base, forming fructosamine,??or or Amadori adduct. At a second stage, the Amadori compound may react producing a group of irreversible reactions (oxidation, crosslinking). Collagen cross-linking is related to the weakening and ageing of tissues – one of the main causes of the formation of eyebags. This test was carried out to evaluate the ability of Eyeseryl to inhibit glycation. It is known that some enzymes can suffer glycation in vivo. Among those enzymes we can find the Cu, Zn- Superoxide Dismutase (SOD). The SOD is an enzyme that converts superoxide radicals to hydrogen peroxide and oxygen. The incubation of SOD with glucose or other monosaccharides gives rise to glycation, which inactivates the enzyme.3 Some compounds can inhibit SOD glycation and, therefore, maintain its activity. In this study, the inactivation of SOD by its reaction with fructose is used as a model of glycation. The effect of Eyeseryl as an inhibitor of glycation is evaluated. The method used to assess the SOD activity is by the inhibition of the transformation of xanthine to uric acid with the enzyme xanthine oxidase (Fig. 2). With this reaction, WST-1 (2-(4- Iodophenyl)-3-(4-nitrophenyl)-5-(2,4- disulfophenyl)-2H-tetrazolium, monosodium salt) is transformed into formazan, a compound which absorbs at 470 nm. If SOD is added to this reaction, the radical O2 -- is captured and the formation of this coloured compound is avoided. In vivo determination of the anti-eyebag activity Eyeseryl has been tested in vivo on a group of 20 female volunteers. A cream containing 0.01% Eyeseryl was applied twice a day during 60 days under both eyes. Pictures were taken at 0, 15, 30, 45 and 60 days. A dermatologist scored visually
the decrease in eyebag puffiness by comparing to the picture taken
at time 0: Results and discussion There is an increase in the SOD activity measured, which means that Eyeseryl inhibits its glycation. The glycation inhibiting effect means that the tetrapeptide protects collagen from degradation, maintaining the correct supporting function of the connective network. In vivo eyebag reduction The scoring table of the dermatologist is enclosed, as well as the statistical analysis performed on the data. Since the measurements are non-parametric (which means the underlying distribution of the variable measured is not known), they are analysed using Friedman’s Test.5 Puffiness under the eyes is greatly reduced, even after only 15 days: 70% of the volunteers had improved at Day 15. Applying Friedman’s Test, the data for every timepoint is determined to be significant. At the end of the test, 95% of the volunteers had improved:
The tetrapeptide also seems
to improve dark circles based on the study of the photographs.
Conclusions Eyeseryl is capable, by working on several mechanisms related to eyebag formation, (vascular, tissue strength, etc), to improve the appearance of eye bags by reducing their size in only 15 days. The tetrapeptide also seems to improve dark circles according to visual analysis of the photographs. References 1 Triana R.J., Larrabee W.F.
Lower eyelid blepharoplasty: the aging eyelid. Facial Plast Surg
1999;15:203-212. |
