Steroids: Cholesterol, Bile Salts and Steroid Hormones
Steroids are compounds containing the steroid nucleus, which consist of three cyclohexane rings and one cyclopentane ring fused together. The four rings in the steroid nucleus are designated A, B, C, and D. The carbon atoms are numbered beginning with the carbons in ring A, and in steroids like cholesterol, ending with two methyl groups.
Cholesterol, which is one of the most important and abundant steroids in the body, is a
sterol because it contains an oxygen atom as a hydroxy1 group (- OH) on carbon 3. Like
many steroids, cholesterol has a double bond between carbon 5 and carbon 6, methyl groups
at carbon 10 and carbon 13, and a carbon chain at carbon 17. In other steroids, the oxygen
atom forms a carbonyl group (C=0) at carbon 3. is a component of cellular membranes, myelin sheath, and brain and nerve tissue. It is also found in the liver and bile salts; large quantities of it are found in the skin, and some of it becomes vitamin D when the skin is exposed to direct sunlight. In the adrenal gland, cholesterol is used to synthesize steroid hormones. The liver synthesizes cholesterol for the body from fats, carbohydrates, and proteins. Additional cholesterol is obtained from meat, milk, and eggs in the diet. There is no cholesterol in vegetable and plant products. The American Heart Association has recommended that we consume no more than 300 mg of cholesterol a day. Research suggest that saturated fats and cholesterol are associated with diseases such as diabetes, cancer, and atherosclerosis. Clinically, cholesterol levels are considered elevated if the total plasma cholesterol level exceeds 200 mg/dL.
Bile Salts in the body is synthesized from cholesterol in the liver and stored in the gallbladder. When bile is secreted into the small intestine, the bile salts mix with the water- insoluble fats and oils in our diets. They act much like sops due to its polar and non-polar regions, breaking down large globules of fat into smaller droplets. They help with the absorption of cholesterol into the intestinal mucosa. When large amounts of cholesterol accumulate in the gallbladder, cholesterol can become solid, which forms gallstones. Gallstones are composed of almost 100% cholesterol, with some calcium salts, fatty acids, and glycerophospholipids. Normally, small stones pass through the bile duct into the duodenum, the first part of the small intestine immediately beyond the stomach. If a large stone passes into the bile duct, it can get stuck, and the pain can be severe. If the gallstone obstructs the duct, bile cannot be excreted. Then bile pigments known as bilirubin will not be able to pass through the bile duct into the duodenum. They will back up into the liver and be excreted via the blood, causing jaundice (hyperbilirubinemia), which gives a yellow color to the skin and the whites of the eyes.
Steroid hormones are chemical messengers that serve as a communication system from one body part to another. Include sex hormones and the adrenocortical hormones and are closely related in structure to cholesterol and depend on it for their synthesis. Two of the male sex hormones, testosterone and androsterone, promote the growth of muscle and facial hair, and the maturation of the male sex organs and of sperm. The estrogens, a group of female sex hormones, direct the development of female sexual characteristics: the uterus increases in size, fat is deposited in the breasts, and the pelvis broadens. Progesterone prepares the uterus for the implantation of a fertilized egg. If an egg is not fertilized, the levels of progesterone and estrogen drop sharply, and menstruation follows. Synthetic forms of the female sex hormones are used in birth control pills. As with other kinds of steroids, side effects include weight gain and a greater risk of forming blood clots (Timberlake, 2017).
The optimal levels for the four standard tests in a lipid panel are:
* Total cholesterol: below 200 mg/dL.
* High-density lipoprotein (HDL) cholesterol: above 60 mg/dL.
* Low-density lipoprotein (LDL) cholesterol: below 100 mg/dL (less than 70 mg/dL in diabetics).
* Triglycerides: below 150 mg/dL.
Lipid levels usually tend to be on the higher side. Abnormally low levels are extremely rare. However, they can arise with severe liver disease or severe malnutrition. In adults, risk factors are obesity, lack of physical activity, diabetes and high blood pressure. In addition, certain
diseases such as hypothyroidism, chronic kidney disease and pancreatitis can also elevate lipid levels. Once the lipid levels have been found to be elevated, intervention is required. High cholesterol and triglycerides, if neglected, tend to get deposited on the walls blood vessels. Sometimes the vessel may get blocked completely. This can cause heart attacks and strokes, which can prove to be fatal. If the initial lipid profile is normal, it needs to be rechecked every four to five years. If the results are abnormal or there are other risk factors involved, such as diabetes or obesity or a family history of premature strokes and death, then lipids should be rechecked every year. Lipids may become controlled rapidly on medication, but that does not mean the patient has recovered. It is the medication that is keeping cholesterol and triglycerides low. Discontinuing the medication can lead to rising values once again and cause dangerous side effects (Mathai, 2022). New research finds that certain types of lipids in the blood play a role in how the apolipoprotein E (APOE) gene influences Alzheimer’s disease risk. A recently published study in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association takes a closer look at the connection among blood lipids, two forms of APOE, and Alzheimer’s. This study suggests that specific blood lipids could potentially be new targets for Alzheimer’s prevention ( Asia News, 2022). Lipids, especially essential fatty acids play an important role in the health and development of humans and play a critical role in the prevention of disease by altering their composition. Lipids are a source of energy and the structure of cell membranes and polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential fatty acids to regulate the inflammatory responses on the macrophage cells, which are considered anti-inflammatory agents. Moreover, they can inhibit the activation of the pro-inflammatory transcription factor and suppress the activation of mitogen-activated protein kinases (MAPKs) signaling pathway. These pathways involved inflammatory responses, which produce inflammatory cytokines and inflammatory mediators. In addition, high levels of EPA and DHA were reported from the lipid extracts including from total lipids, neutral lipids, and polar lipids of various ascidian species. The lipid extracts from ascidians have improved beneficial health effects, such as anti-diabetic and antioxidant effects (A-yeong, 2022). Cardiovascular diseases associated with high cholesterol (hypercholesterolemia) and low-density lipoproteins (LDL) levels are significant contributors to total mortality in developing and developed countries. Mathematical modeling of LDL metabolism is an important step in the development of drugs for hypercholesterolemia (Efremov et al. 2022). Bacterial bile salt hydrolysis is considered a risk factor for the development of colon cancer because of the risk of forming harmful secondary bile salts after an initial deconjugation step. In this study, the influence of enhanced bacterial bile salt transformation by the bile salt hydrolase-active Lactobacillus reuteri was studied in batch culture using the microbial suspension of the Simulator of the Human Intestinal Microbial Ecosystem. Although there have been advances in radiotherapy, chemotherapy and surgery, mortality caused by colorectal cancer remains very high and has decreased only slightly. Thirty percent of all colon cancer deaths can be linked to diet. Probably one of the most cited mechanisms is that of a high-fat diet. To resorb the increased amount of dietary fat, more conjugated primary bile salts are secreted in the small intestine. This leads to an increased of bile salts to the colon and an increased metabolism of the bile salts. Some of the bile salts generated by the micro-organisms have been incriminated in colonic carcinogenesis One of the most important bacterial bile salt trans- formations is bile salt hydrolysis, which is mediated by a wide range of colon anaerobes. The bile salt hydrolase enzyme releases the glycine and/or taurine moiety from the side chain of the bile salt steroid core and generates deconjugated primary bile salts, which are less water-soluble and are excreted more easily via the faeces. The principle of bile salt hydrolysis was used to decrease the serum cholesterol in pigs through interaction with the host’s bile salt metabolism. In the latter, the bacterial bile salt hydrolase activity in pigs was enhanced by oral administration of Lactobacillus reuteri. This caused a greater drain on the bile salt pool, resulting in a loss of feedback inhibition on bile salt synthesis and an increased conversion of cholesterol into bile salts. Because of this, the serum cholesterol levels in the pigs were lowered (De Boever, 2000) . There is considerable concern about the increasing incidence of endocrine-related cancer and deteriorating reproductive health in humans. A large number of natural and man-made chemicals have the ability to mimic the action of the endogenous steroid hormone 17b-estradiol by binding to and activating the estrogen receptor. In this matter, there is no consensus regarding the role of xenoestrogens in these effects and no conclusive studies demonstrating that xenoestrogens initiate or contribute to the development of these effects. The molecular structure of exogenous natural and synthetic estrogens may be very similar to, or strikingly different from the natural hormone (Cabaravdic, 2010).
As a conclusion, we can affirm that lipids are extremely important in our world. Fatty acids contribute to the treatment of pain, fever, and inflammation, waxes provide a waterproof coating on the skin, fur, and feathers of animals, triacyclglycerols help animals to storage energy on hibernation time, phospholipids allow the formation of pulmonary surfactant in the fetus, the cholesterol has a huge impact in human health, increasing the chance of mortal diseases, bile salts help with the absorption of cholesterol into the intestinal mucosa, and steroid hormones are chemical messengers that serve as a communication system from one body part to another. Lipids play an important role in the health and development of humans and play a critical role in the prevention of diseases by altering their composition. Lipids are a source of energy and the structure of cell membranes and polyunsaturated fatty acids that regulate the inflammatory responses on the macrophage cells, which are considered anti-inflammatory agents.
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