Metabolism
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
There are major differences in the fuels metabolized by different tissues. The liver is the only organ capable of taking up most compounds and performing most conversions between fuels. Skeletal muscle oxidizes free fatty acids and ketone bodies for energy production. Glucose becomes an important fuel for skeletal muscle only during hyperglycaemia or local anaerobic conditions. Skeletal muscle releases amino acids (mainly alanine and glutamine) from protein during starvation. In contrast, the main fuels for cardiac muscle are free fatty acids, lactate and ketone bodies. Brain and nervous tissue use glucose as a chief source of energy normally, but during fasting, acetoacetate and β-hydroxybutyrate may become important sources of energy. Adipose tissues store energy as fat and can convert glucose to triacylglycerols. Adipose tissues also accept triacylglycerols for storage. The breakdown of fat by adipose tissues to free fatty acids and free glycerol releases energy.
The digestive system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Intact triglycerides are too large to be absorbed. Therefore, pancreatic lipase acts on the lipid droplets to hydrolyze the triglyceride molecules into monoglycerides and free fatty acids. These constituent molecules are water-insoluble and would tend to float on the surface of the aqueous chyme. Therefore, they must be transported to the absorptive surface. This process is carried out by micelles, which are sphere-like structures formed by the amphipathic bile salts. The bile salts associate with each other such that the polar region of the molecules orient outward, making them water-soluble. The nonpolar region faces inward, away from the surrounding water. The monoglycerides and free fatty acids are carried in this interior region of the micelle. Upon reaching the brush border of the absorptive cells, the monoglycerides and free fatty acids leave the micelles and enter the cells by simple diffusion. Because they are nonpolar, these molecules move passively through the lipid bilayer of the cell membrane. This process takes place primarily in the jejunum and proximal ileum. The bile salts are absorbed in the distal ileum by way of either passive diffusion or secondary active transport.
Phosphatidate Phosphohydrolase in Plants and Microorganisms
David N. Brindley, John R. Sabine in Phosphatidate Phosphohydrolase, 2017
Triacylglycerols accumulated in the stationary phase of growth of S. cerevisiae and incorporation of [14C]acetate into triacylglycerols increased, while incorporation into phospholipids remained constant.97 The accumulation of triacylglycerols could not be correlated with a change in fatty acid synthesis. Measurement of soluble and membrane-bound phosphatidate phosphohydrolase activities showed that the activity of the soluble enzyme was higher in the stationary than the exponential phase of growth. The activity of the membrane-bound enzyme also increased, as did the glycerophosphate acyltransferase activity, but to a lesser extent than a soluble phosphatidate phosphohydrolase which was about threefold higher in stationary than early exponential phases of growth. The activities of cholinephosphotransferase and diacylglycerol acyltransferase (which require diacylglycerol as a substrate) remained relatively constant. Therefore, an increase in triacylglycerol accumulation was closely correlated with an increase in phosphatidate phosphohydrolase activity, which gave a change in the partitioning of phosphatidate between diacylglycerol (required for triacylglycerol biosynthesis) and CDP-diacylglycerol (required for phospholipid biosynthesis)97 (Figure 20).
Lipogenic stromal cells as members of the foam-cell population in human atherosclerosis: Immunocytochemical and ultrastructural assessment of 6 cases
Published in Ultrastructural Pathology, 2022
Yong-Xin Ru, Zhang Xue-Bin, Xiao-Ling Yan, Dong Shu-Xu, Zhang Yongqiang, Li Ying, Liu Jing, Brian Eyden
Much still needs to be clarified in atherosclerosis, and a number of points for future research may be mentioned here. In our study, the most abundant lipid was triglyceride lipid whereas conventionally it is the cholesterol type of lipid that is emphasized in atherosclerosis.48 The matrix is relatively poorly explored in atherosclerosis. The dense intercellular material seen between some of the cells in our study defied categorization as either lamina or fibronectin; this would be important in confirming the identification of lipoleiomyocytes and lipomyofibroblasts which would be associated with lamina and fibronectin respectively. There is a role for immuno-electronmicroscopy here. Finally, we briefly indicated mitochondria in our cases of atherosclerosis and the relationship between lipid and mitochondria has received attention recently. Further studies will bring additional understanding to this significant disease.
Development of self-microemulsifying lipid-based formulations of trans-resveratrol by systematically constructing lipid-surfactant-water phase diagrams using long-chain lipids
Published in Drug Development and Industrial Pharmacy, 2021
Carolina Aloisio, Ankita V. Shah, Marcela Longhi, Abu T. M. Serajuddin
In the present investigation, it was observed that using only cod liver oil, a LC triglyceride, with a surfactant would not lead to the formation of microemulsion. It is essential that a monoglyceride should also be present in the system along with the triglyceride. This is in agreement with the development of cyclosporine A formulations mentioned earlier, where Sandimmune® containing the triglyceride of long chain fatty acids formed crude emulsion while Neoral® containing mixtures of mono- and di-glycerides resulted in microemulsion. The possible mechanism of the effect of monoglyceride may be analogous to what was observed with medium chain lipids, where Prajapati et al. [28] postulated that the monoglyceride participates with the surfactant in forming a curvature surrounding oil globules in microemulsions. The results of the present investigation also demonstrate that all surfactants do not behave similarly (e.g. Kolliphor RH 40 vs. Tween 80) in providing phase diagrams and microemulsions with long chain lipids and, therefore, careful studies would be necessary in selecting surfactants for the systems.
Proteomic profiling of fatty acid binding proteins in muscular dystrophy
Published in Expert Review of Proteomics, 2020
Paul Dowling, Stephen Gargan, Margit Zweyer, Dieter Swandulla, Kay Ohlendieck
Triacylglycerol is stored in intracellular structures, such as lipid droplets in adipocytes, and can be swiftly mobilized by hydrolysis to produce non-esterified fatty acids as high-energy substrates for oxidative pathways. During phases of extensive physical activity, fatty acids are released from adipose tissue, but the liver also provides fatty acids in the form of very-low-density lipoprotein [16]. In the circulatory system, fatty acids are closely associated with the highly abundant serum protein albumin [32] and specific fatty acid translocases are involved in the regulated uptake to intracellular domains [33]. Within specific cell types, a variety of lipid chaperones are of intrinsic importance for the efficient uptake, transport and release of free fatty acids, as well as their bioenergetic utilization or storage as high-energy fat molecules [34].
Related Knowledge Centers
- Ester
- Fatty Acid
- Glyceride
- Glycerol
- Unsaturated Fat
- Vegetable Oil
- Adipose Tissue
- Sebaceous Gland
- Saturated & Unsaturated Compounds
- Saturated Fat