Ketogenic diets are trendy in the nutrition community as promoters of rapid weight loss for improved cardiometabolic health. In the absence of carbohydrates and increased consumption of fats, ketone bodies become the primary energy source via free fatty acid oxidation, and this state of ketosis mimics what occurs during starvation. β‐hydroxybutyrate (βHB) is the most abundant circulating ketone body. βHB is synthesized in the liver and transported to the peripheral tissues for conversion into energy. To study the long‐term consequences of enhanced βHB bioavailability, the secondary alcohol, 1,3‐butanediol (1,3‐BD), is commonly administered in drinking water as a precursor. After consumption, 1,3‐BD is catabolized by the liver into βHB. However, the concentration of 1,3‐BD that best represents the circulating concentration of βHB after fasting is currently unknown. The objective of the current work was to determine what concentration of 1,3‐BD best mimics the concentration of βHB after a 24 h fast in male adult rats. To test this objective, 40‐week old Wistar‐Kyoto rats were administered with or without 5%, 10%, or 20% v/v 1,3‐BD in drinking water. All rats had free access to food throughout the investigation, although some vehicle‐treated rats were fasted for the final 24 h before study termination to serve as a positive control. While 5% and 10% 1,3‐BD increased βHB in the systemic circulation 1.5‐fold (p<0.05), similar to an overnight fast, which was increased 2.0‐fold (p<0
Energy metabolism in developing brain cells. During development different energy substrates are available to cells in brain in plentiful supply. The metabolic environment, which is dictated by the milk diet rich in fat, ensures that substrates in addition to glucose are available as fuels. Some substrates serve readily as primary fuels for respiration, whereas other substrates can serve other functions in addition to serving as primary fuels. Primary fuels for respiration serve to supply acetyl CoA directly and as a result always have first priority. With this criteria in mind, a consideration of substrate priority for respiration by developing brain is presented. Many studies in the decade, 1970-1980, in human infants and in the rat pup model show that both glucose and the ketone bodies, acetoacetate and D-(-)-3-hydroxybutyrate, are taken up by brain and used for energy production and as carbon sources for lipogenesis. Products of fat metabolism, free fatty acids, ketone bodies, and glycerol dominate metabolic pools in early development as a consequence of the milk diet.
Lipid
A lipid is a type of organic molecule found in living things. It is oily or waxy. Fats are made from lipid molecules. Sources of lipid can be found in algae, seeds, meat, cheese, butter and fish. Lipids are long chains of carbon and hydrogen molecules. Lipids are classified as simple and complex. Examples of complex molecules could be steroids or phospholipids. A very important biological function of lipids is as lipid bilayers, the basis of many cell membranes. Another function of lipids is to serve as an energy reserve. Lipids can be hydrophobic (non-polar), or amphipatic (containing both polar and non-polar parts). Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), glycerides, phospholipids, and others. The main biological functions of lipids include storing energy, signalling, and acting as components of cell membranes.[3]
References
- 1 2 Stryer L. Berg J.M. Tymoczko J.L. (2007). Biochemistry (6th ed.). San Francisco: W.H. Freeman, p328/330. ISBN 978-0-7167-8724-2. - ↑ Maitland, Jr Jones (1998). Organic Chemistry. Norton, p139. ISBN 0-393-97378-6. - ↑ Fahy E.; et al. (2018).
The fat must therefore have been formed from the carbohydrates of the food. The consumption of larger amounts of sugar than can be used or stored as glycogen results in its passing straight through the body and being excreted in the urine. This condition is known as alimentary glycosuria. The power of using and storing sugar varies greatly in different individuals and in the same individual at different times. Fats.—The fats simply serve as stores of energy. After ingestion, if in small amount, they are, like carbohydrates, oxidized to the same final products CO2, and H2O. If in larger amount they are stored as fat, to serve as a reserve in case of need, in the body tissues. Like the carbohydrates they serve as the sources of part of the energy dissipated as heat, but they are not so efficient as sparers of protein material, evidently in part at least because they are less easily digested and absorbed. Factors which influence Normal Metabolism. 1. Fasting.—During fasting the body draws upon its own reserve of stored material for the requirements in the production of energy, and the rate of breakdown varies with the energy requirements.
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