*Read for medical professionals only
p53, a famous cancer-related gene, we can often see it appear in related literature such as intestinal cancer, lung cancer, liver cancer , etc., and the cancer-suppressing and promoting cancer morphology is randomly converted, and scientists are suffering behind it. After pursuing it, he escaped after it, and he chased it and could not fly for many years.
But if, I mean if, p53 appears in a story about sun protection and weight loss as the protagonist. . . Don’t rush to scold nonsense. UV exposure leads to foraging behavior. Without P53, it really won’t work with .
Professor Carmit Levy from Tel Aviv University and his research team found that UV exposure can induce ghrelin levels to increase , making people hungry, eat more, and eventually cause weight gain. However, the weight gain is only effective in men, and female estrogen inhibits the elevated ghrelin levels induced by UV exposure [1].
research results were published in "Natural Metabolism".
human research history on ultraviolet rays is not short. In 1928, ultraviolet rays became a recognized carcinogen, and humans began to have a large-scale "sun protection culture"; but soon, people discovered that ultraviolet rays can reduce the risk of cardiovascular diseases, and " sunbathing " became a health activity. .
UV intensity is closely related to seasonal changes . When analyzing diet data, the researchers found that the food intake of men is also very significantly affected by seasonal changes. They eat more in summer and less in winter; women's food intake is very stable and not affected by the season at all. .
Men's food intake is affected by the season
Does it be eaten much? Is it related to the intensity of ultraviolet rays? There is even such a big gender difference?
With these questions in mind, Professor Carmit Levy officially began his exploration.
First of all, we need to verify whether ultraviolet rays will really affect appetite. The researchers recruited 32 patients with skin diseases who received phototherapy and received ultraviolet exposure twice or three times a week (0.1-2.5 J/cm²) for a total of 10-12 times. Through the Disease-related Appetite Questionnaire (DRAQ), researchers found that men became stronger after receiving phototherapy, felt hungry more frequently, and the total amount of food intake per meal was also greater. Women do not have these changes after receiving phototherapy.
This suggests that UV exposure does change men's appetite and food intake. So, will male mice have the same reaction?
In order to increase the exposed area in ultraviolet rays, the mice were shaved with their back hair, so that the exposed area reached about 50%-60% of the total body area. The mice were exposed to ultraviolet radiation of 50 mJ/cm² for 10 weeks. Under such conditions, the male mice of showed obvious changes in foraging behavior. The number of times ate and the amount increased, but the foraging behavior of the female mice did not change.
UV exposure had no effect on the metabolic level of mice, but male mice gained weight
Researchers also found that the metabolic level of mice did not increase or decrease due to UV exposure. Then, the food intake of male mice increased, the metabolic level remained unchanged, and they did not exercise. The final result was of course, weight gain.
By comparing the changes in hormone and polypeptide levels in mice before and after UV exposure, the researchers found that ghrelin levels in the plasma of male mice increased, and ghrelin levels in female mice remained unchanged , and Other hormones that play a key role in appetite regulation, such as insulin concentration, did not show significant changes in both male and female mice.
So, this ghrelin is the key to increasing appetite?
Ghrelin, as the name suggests, is mainly produced by the stomach and increases in the level when hungry. But if the stomach is removed, the ghrelin level in the blood will only be reduced by 65%, which means that other tissues are involved in the secretion of ghrelin.Although it sounds incredible, a series of studies have proved that skin tissues are indeed involved in the secretion of multiple hormones, and the fat cells under the skin are another source of ghrelin expression [2].
As for the increase in ghrelin levels caused by ultraviolet exposure, how do you think the "suspicion" of subcutaneous fat cells is more serious. The researchers used ex vivo human skin to simulate UV exposure and found that ghrein in male subcutaneous fat cells reached a peak at 8 hours of exposure, while ghrein expression in women was not affected.
Next, the researchers used ghretin receptor antagonist in the mice. After UV exposure, the experimental mice ate as usual, but the food intake was not as good as before taking the medicine. It was true that ghretin mediated UV rays. Increased food intake in male mice caused by exposure.
Researchers compared the promoter sequence with different expression before and after ultraviolet exposure, and obtained some possible transcription factor binding sites , and then found, oh, p53, why are you here ?
UV ray induces increased p53 levels in male ex vivo skin tissue
Researchers constructed a p53-deficient mouse model for subcutaneous fat cells and found that UV exposure at this time can no longer induce the increase in ghrelin levels in male mice , so naturally it also There is no longer any change in appetite and food intake, and there is no increase in weight.
Then why are female mice not affected by UV exposure? Through reviewing the data, the researchers found that although no clear mechanism was found, there is indeed some correlation between ghrelin and sex hormones. Ghrelin in men is positively correlated with testosterone levels, while estradiol hormone in women is related to inhibiting the synthesis of ghrelin . During ex vivo skin tissue culture, researchers also found that female estrogen and receptor levels were significantly higher than those in men.
Researchers used dihydrotestosterone and β-estradiol to stimulate UV-exposed fat cells, respectively, and found that dihydrotestosterone induced an increase in ghrelin levels, while β-estradiol inhibited the UV-induced increase in ghrelin levels. High . If the ovariectomy of female mice is removed, changes in appetite and food intake induced by ultraviolet can also be observed.
V UV Exposure Test for Volunteer
Before that, they were all laboratory-simulated UV exposure. What is the effect of UV exposure from nature (the sun)? The researchers recruited 27 volunteers, 13 men and 14 women, aged 18-55, wearing sleeveless tops and shorts in the sun for 25 minutes (UV exposure is approximately 2000mJ/cm²), before sunbathing. Blood samples were collected one day and the next day, and a professional psychological counselor asked about appetite-related questions.
Compared with normal state, men felt hunger, women did not report significant differences in hunger levels, and ghrelin levels also showed similar changes to before .
However, don't think this is a simple study on "weight loss" and "weight gain". Ghrelin has anti-inflammatory properties, can inhibit myocardial atrophy and reduce arterial pressure, which may be related to the heart benefits of "sunbathing". In addition, ghrelin also has functions that enhance learning ability, anti-anxiety and neuroprotection. Or if you look longer, will there be areas between skin fat and brain function that we have not explored?
Among many ideas, the researchers chose the seemingly simplest one as the end of the article, "The scope of application of phototherapy may be expanded as a result."
Friends who have purchased courses,
go directly to the mini program to listen to extra meals~
References:
[1] Parikh S, Parikh R, Michael K, et al. Food-seeking behavior is triggered by skin ultraviolet exposure in males[ J]. Nature metabolism, 2022, 4(7): 883-900.
[2]Knerr I, Herzog D, Rauh M, et al. Leptin and ghrelin expression in adipose tissues and serum levels in gastric banding patients[J] . European journal of clinical investigation, 2006, 36(6): 389-394.
Author of this article丨Wang Xuening
