Heat Stress

Oligonol Supplementation Attenuates Body Temperature and the Circulating Levels of Prostaglandin E2 and Cyclooxygenase-2 After Heat Stress in Humans

Journal of Functional Foods. 2013;16(4):318-23

Background

Oligonol is an optimized phenolic product containing catechin-type monomers and oligomers (dimers, trimers, and tetramers) of proanthocyanidin that are easily absorbed. Oligonol, a phenolic extract from lychee fruit with green tea polyphenols, has been reported to have antioxidant and anti-inflammatory effects. Supplementation with Oligonol decreases serum concentrations of cortisol, IL-1β, and IL-6, which are fever-related hormones or cytokines released after heat stress, therefore, it is thought that it has an antipyretic or fever-reducing potential.

Prostaglandin E2 is the principal mediator of fever and exerts its fever-inducing action by binding to receptors on thermoregulatory neurons in the anterior hypothalamus. PGE2 is formed in most cells from cyclooxygenase-mediated metabolism of arachidonic acid. COX-2 enzymes and production of PGE2 are involved in causing febrile and inflammatory responses. Cytokines are chemical messengers found in the circulation and help mediate fever and inflammation caused by heat stress. Interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha (TNF-α), are cytokines involved in PGE2 production in response to fever. Transcription factors, such as nuclear factor-kappa β and signal transducer and activator of transcription 3, are activated by these cytokines and lead to the induction of COX-2, which mediates fever production.


This study investigated the effect of Oligonol supplementation on circulating levels of inflammatory factors prostaglandin E2 and cyclooxygenase-2. It also checked the body temperature after heat stress in 17 healthy human male volunteers (age range 21.6–22.1 years old). The experiments were performed using a chamber with automated climate control at 26.0° C and a relative humidity of 60%–63.0%.

Study Design

Subjects ingested 100 mg of Oligonol in a beverage or a placebo before half-body immersion into hot water at 42° C for 30 minutes. Tympanic and skin temperatures were measured and mean body temperatures were calculated. Serum concentrations of PGE2 and COX-2 were analyzed before, immediately after, and 60 minutes after immersion in the hot water. All experiments were conducted in a thermoneutral climate chamber (26° C ± 0.5° C, 60% ± 3% relative humidity, and < 1 m/sec air velocity) from 2 to 5 p.m. Upon arrival at the climate chamber, the subjects wore short pants and sat in a chair in a relaxed posture for 60 minutes to become conditioned to the chamber climate before the commencement of the experiments. After 60 minutes of rest, heat load was applied to each subject via immersion of half of their body into a hot water bath of 42º C ± 0.5º C for 30 minutes. Measurements were taken at rest, immediately after immersion, and 60 minutes after. Subjects drank 0.5 L of the Oligonol beverage or the placebo beverage 1 hour before the immersion.

Results

Oligonol intake significantly prevented elevation of tympanic temperature (difference of 0.17° C after heat stress, p < .05; 0.17° C at 60 minutes, p < .05) and mean body temperatures (temperature difference: 0.18° C at post, p < .05; 0.15° C at re-60, p < .05), and lowered concentrations of serum PGE2 (increased by 13.3% vs. 29.6% at post, p < .05) and COX-2 (increased by 15.6% vs. 21.8% at post, p < .05) compared with placebo beverage.

Conclusion

The results suggest that Oligonol suppresses increases in body temperature under heat stress, and this is associated with decreases in serum levels of the inflammatory mediators PGE2 and COX-2 enzymes.