In vivo tests have revealed that certain biophysical and physiological parameters of human skin change in accordance with circadian rhythms, the biological processes based on about 24-hour rhythms. Thus, skin temperature, sebum production, pH, electrical charge potential (capacitance) and transepidermal water loss (TEWL) appear to follow the circadian clock. [1] Recently, researchers from Beiersdorf also highlighted the importance of the skin cells’ internal clock.

Clock genes play a vital role in the expression of many genes - shutterstock.com / © Stokkete

Based on these findings, Ashland has developped Chronogen YST, a new extract derived from yeast protein that may help to maintain skin’s cellular rhythm and guard against UV damage.

"Over the past 10 years, research has shown that skin cells are partly regulated by the 24-hour rhythm," said Neil Astles, marketing manager for biofunctionals, Ashland Specialty Ingredients. "More than 20 percent of gene expression in a given tissue falls under circadian regulation. [2] This regulatory function within skin cells, however, may be disrupted by external factors. Chronogen YST promotes expression within clock gene proteins in vitro to resynchronize optimal skin function."

Actually Ashland explains that clock genes are now recognized as key regulators that play a vital role in the expression of many genes, including some that reside in skin cells. Modulating clock gene expression for beneficial effects on skin would therefore represent a major breakthrough in cosmetic science.

A case in point can be seen in the area of UV exposure. At night, cells undergo DNA repair and replication procedures based partly on the expression of clock genes within a closed loop system. In contrast, at the beginning of the day, DNA needs to prepare for UV exposure with antioxidant enzymes. This 24-hour cycle can be disrupted by UV exposure and, accordingly, impede cell regeneration. [3]

Skin care applications

Ashland clinically tested Chronogen YST [4] at 1 percent. For instance, a small double blind study against a placebo cream with 10 volunteers ranging in age from 23 to 38 years indicated a measurable improvement in skin turnover in vivo after 21 days (two applications per day) with topical cream containing 1 percent active Chronogen YST.

"Using a small concentration of the Chronogen YST in skin creams and serums may help to resynchronize the skin’s circadian clock," concluded Neil Astles.

The figure depicts the normal circadian cycle of DNA repair and replication at night, and antioxidant enzyme initiation during the day.

Ashland recommends using Chronogen YST in day-time formulations to help skin boost its natural defenses against UV-induced damage; night-time formulations to boost the skin’s own processes in skin regeneration; anti-aging formulations with claims on circadian rythms and formulations to help maintain the skin’s "synchronized" internal clock.

Ashland demonstrated the technical merits of Chronogen YST, which is compliant with China’s cosmetic rules, at the Personal Care and Homecare Ingredients (PCHi) exhibition held on 12-14 March in Guangzhou, China.

Other suppliers such as Silab or Lipotec have also recently proposed new ingredients based on circadian cycles.