Enzyme 10 Chapter Summary

In one of the chapters Matt Ridley concludes that chromosome 10 is related to stress. He relates chromosome 10 to stress by a small organic molecule called cholesterol that correlates to stress levels. The cholesterol gets manufactured in the body from sugars in the diet. This small organic molecule called cholesterol can form many steroids that have important functions in the body like, testosterone, cortisol, progesterone, aldosterone and oestradiol. Matt Ridley focuses on cortisol which causes stress according to Matt Ridley. Matt Ridley says that a gene called CYP17 found on chromosome 10 codes for an enzyme that catalyzes cholesterol to form the hormone called cortisol. The higher levels of cortisol in the blood stream indicates that the
stress levels are high and low level of cortisol in the blood stream indicates that the stress levels are low. The function of cortisol is to integrate the mind with the body by altering the configuration of the brain. Matt Ridley also explains that the cortisol also interferes with the immunes system, the cortisol suppresses the immune system when there is a lot of cortisol flowing through the veins. If the immune system is suppressed then a person is more likely to catch colds or infections as Matt Ridley says in the book.
Our understanding in the CYP17 has changed very slightly from the information that has been given by Matt Ridley.
In the article of “CYP17 gene polymorphisms” it reinforces the information that Matt Ridley had previously talked about, this article talks about how this gene codes for an enzyme “cytochrome P-450c17α (CYP17) gene, located on chromosome 10, which functions at key branch points in steroid hormone biosynthesis in the adrenal gland, ovary and gonads”(Sharp 729). Matt Ridley mostly talks about how this Gene CYP17 is important for making steroids from cholesterol but according the review article“CYP17 gene polymorphisms” the gene CYP17 also plays important role in cancer depending on which variant someone has of that particular gene. For example, Sharp explains that “the CYP17 gene is polymorphic prompted investigation of the role of a gene variants in the etiology of disease and conditions in which estrogens and androgens play important role in breast cancer, polycystic ovary syndrome, endometrial cancer, and prostate cancer”(Sharp 729). This statement says that there is different variants of the gene CYP17 that can encode different variants of the enzyme that will produce different variants of steroids that can contribute to different cancers depending on the type of steroid produced. Matt Ridley does not talk about how CYP17 can cause cancer if there is a different variant of that gene. He only explains that this CYP17 gene that codes for enzyme that can convert
cholesterol to steroids that play important functions in the body.
According to scientist there is new information on the gene CYP17.
Such as, if a person has a different variant of this gene it can cause cancer it is critical to understanding this gene. Matt Ridley failed to mention that this gene can have different variants which would give different variants enzymes that could cause cancer. The variants are caused by polymorphisms in the gene CYP17 which in turn affect the hormone levels which can cause cancer like, prostate cancer in males. In the article of “CYP17 Polymorphisms and Prostate Cancer Outcomes” it is a strong interest of area to look for polymorphisms or SNPs in the gene CYP17, they explain that polymorphisms in “men with genetic variants in CYP17 have altered enzymatic activity not only affecting their baseline hormone levels, but that such SNPs may also alter responsiveness to targeted therapies such as abiraterone acetate, a CYP17 protein inhibitor” (Vasaitis 1095). This helps us understand that polymorphisms and SNPs also play a big role in the Gene CYP17, and depending on the polymorphism of that gene it can be deleterious to the person or help them survive depending on the polymorphism. This gene has a certain polymorphism of the gene CYP17 that actually helps a person survive who has castration-resistant cancer, this means the treatments to lower testosterone levels are not working for the patient and have become resistant to treatment. The results of the article “CYP17 Polymorphisms and Prostate Cancer Outcomes”
says that “These findings support the notion that there is local, intracrine production which allows testosterone to act inside the cell, and CYP17 is a crucial enzyme in the testosterone biosynthesis pathway. If variant CYP17 alleles impair this process, there may be a decrease in local testosterone production, which in turn may reduce cellular proliferation and thereby prolong patient survival” (Vasaitis 1098). This is critical information that CYP17 gene can have different version that can cause cancer but also prolong a patient’s life by having a certain polymorphism in the gene. Matt Ridley failed to mention that the gene CYP17 can cause cancer by polymorphisms or SNPs. On the other hand, Ridley is correct that this gene can decrease the function of the immune system.
In the chapter of stress Matt Ridley focuses on cortisol and how it can cause stress depending on the level of stress hormone called cortisol. The levels of cortisol in the blood stream determines how stressed a person is. Matt explains that stress is caused by outside environment that can increase cortisol which reduces the activity and numbers of lymphocytes which are white blood cells. More recent research confirms that Ridley’s conclusions and statements where correct that cortisol affects the immune system. For example, the article “The Fight-or-flight Stress Response and the Augmentation of Immune Function” says that “acute stress, chronic stress has been shown to dysregulate immune responses and to suppresses immunity by decreasing numbers trafficking and function of protective immune cells while increasing regulatory/suppressor T cells”( Dhabhar 216). This supports the conclusion stated by Matt Ridley that there two types of stressors, short term stressors and long term stressors. Matt says that Short term stressors cause increase of epinephrine and norepinephrine immediately in the body, these hormone causes the body to go into ‘fight or flight’ mode. Matt also concludes that stressors that last longer activates a different pathway that is much slower but also releases cortisol in more persistent way that decreases the working of the immune system. More recent research form scientist say that “short-duration stress that activate the survival promoting aspects of the fight-or-flight response, and result in immuno-preparatory, or immune enhancing physiological conditions”( Dhabhar 230). They also say that “repeated or prolonged stress that may result in dysregulation or suppression of immune function” just as Matt Ridley concludes in his book (Dhabhar 230). As a matter of fact, Matt Ridley was correct as he concluded that stress affects the immune system, it affects it in a way where it is suppressed by stress making it more likely for a person to catch an infection.
This shows that some information has changed from when Matt Ridley wrote his book about 15 years ago. Some of the new information that has been discovered since Matt Radley’s time, is that the CYP17 gene can have polymorphisms and SNPs which in turn can affect enzymatic levels and can affect the hormone levels that could lead to certain type of cancer like prostate cancer in men. On the other hand, some information and conclusions that Matt Ridley’s explains in his book had stayed consistent. For example, both authors Dhabhar and Ridley conclude that cortisol does affects the immune system and it suppresses the immune system depending on the level of cortisol in the blood stream. Furthermore, the author Sharp reinforces the mechanism of CYP17 gene that converts cholesterol to many different steroids and hormones in the body as Ridley concluded in his book. In the end most of the information has been consistent, besides some of the new information that has been discovered through polymorphisms and SNPs on CYP17 that can cause abnormalities.