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Atherosclerosis
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
The preferential synthesis of various lipoproteins indicates that through the formation of apoproteins, and depending upon the amount of various lipids present, there is an interconversion among these complex molecules. This represents a dynamic state, a continuous equilibrium between production and degradation, modulation of the synthesis and catabolism of lipids and proteins, and to exchange processes catalyzed by essential enzymes.296 The summation of these processes determines eventually the half-life of the individual proteins.409,410 Chylomicrons are rapidly cleared from the blood, hence their half-life is less than 1 h. During this process, nascent chylomicrons are produced in the intestine with the addition of apoA and apoB. In the circulation apoC is transferred from HDL to chylomicrons. These are then partially degraded, and triglycerides are hydrolyzed by triglyceride lipase. This lipase is activated by apoC-II, present in the capillary endothelium of extra hepatic tissues which produce diglycerides and fatty acids. Free fatty acids are released into the blood, and diglycerides are incorporated into vacuoles and endothelial microvesicles. In subsequent steps, the chylomicron triglyceride-poor particles are removed by the liver and degraded to glycerol and fatty acids, while apoC proteins are transferred back to HDL (Figure 24).
Introduction
Published in Margit Hamosh, Lingual and Gastric Lipases: Their Role in Fat Digestion, 2020
Glycerides and nonphosphorus-containing lipids which result from the esterification of glycerol and fatty acids (Figure 1). Three forms occur in nature. Triglycerides (neutral fat) are the most abundant lipids in animal tissue and serve as an important energy source. All three of the carbon molecules of glycerol are sterified with fatty acids. Monoglycerides and diglycerides are compounds resulting from ester links between glycerol and one or two fatty acids.
Nutraceuticals and Functional Foods
Published in Robert E.C. Wildman, Richard S. Bruno, Handbook of Nutraceuticals and Functional Foods, 2019
Diglycerides have been used as emulsifying agents in manufactured food products for many years. More recently, more specialized diglycerides, termed diacylglycerols (DAGs), have been produced by limited hydrolysis of triglycerides. This process results in a mixture of 1,2-diglycerides and 1,3-diglycerides. These diglycerides have absorption and metabolism characteristics like those of medium-chain triglycerides; that is, some of the fatty acids escape re-esterification within the cells of the small intestine and subsequent delivery to adipose tissue via the lymphatic system. Instead, they are delivered to the liver, where they are oxidized to produce energy and possibly to produce ketones. The result is an apparent caloric content that is somewhat less than the 9 kcal/g associated with most fats.
SLN and NLC for topical, dermal, and transdermal drug delivery
Published in Expert Opinion on Drug Delivery, 2020
Eliana B. Souto, Iara Baldim, Wanderley P. Oliveira, Rekha Rao, Nitesh Yadav, Francisco M. Gama, Sheefali Mahant
Radomska-Soukharev carried out an in-depth investigation to study the stability of lipids in SLN formulations using different lipids and varying amounts of surfactants [87]. It was found that triglycerides yield more stable products as compared to mono and diglycerides. It was postulated that a binary mixture of surfactants imparts more stability than a single surfactant. It was further stated that the nature of surfactant and its concentration have an impact in its solubilizing capacity for water in the lipid phase, and also brings about variations in the incorporation of the surfactant in the outer shell of SLN and its distribution in the molten lipid phase. SLN dispersion can cause distortion in crystallization behavior, thereby, lowering the melting enthalpy. Moreover, the effects of electrostatic and steric stabilization were found to be additive.
Development and characterization of exendin-4 loaded self-nanoemulsifying system and in vitro evaluation on Caco-2 cell line
Published in Journal of Microencapsulation, 2020
Yesim Aktas, Merve Celik Tekeli, Nevin Celebi
In recent years, in vitro lipolysis test has become an important tool for the better understanding of how lipid based drug delivery systems behave in the gastrointestinal tract. Hydrolysis of the lipids starts by gastric lipases secreted from salivary glands and the gastric mucosa and lipids consisting of medium-chain triglycerides are hydrolysed faster than long-chain triglycerides. Diglycerides, monoglycerides and fatty acids are produced as a result of lipolysis and the surface activity of these digestion products together with the dietary phospholipids and the powerful shear forces of the stomach promote the first crude emulsification of the lipids. Following the emulsification in the stomach, the lipid droplets are propelled into the duodenum for further processing. 10–25% of the total lipolysis occurs by gastric enzymes whereas the rest of the lipids are hydrolysed by pancreatic enzymes. Upon the arrival of the emulsion in the small intestine, hydrolysis of the remaining lipids occurs by pancreatic lipases. Similar to gastric lipase, the efficiency of pancreatic lipase is higher on medium-chain triglycerides than long-chain triglycerides (Thomas et al.2012).
Metabolomics markers in Neurology: current knowledge and future perspectives for therapeutic targeting
Published in Expert Review of Neurotherapeutics, 2020
Roberta Bonomo, Guido Cavaletti, Debra J. Skene
Metabolomics approach has also been used to study Multiple Sclerosis (MS). Stoessel and colleagues reported a decrease in PCs and LysoPCs during the primary progressive form of MS [143], whereas others observed a change in the ratio of LysoPC/PC lipid profile in the plasma of patients with clinically diagnosed relapsing–remitting MS [144] and in the CSF of patients with AD [145]. PCs are important for the structural support of cells, and for anti-inflammatory signaling [146]. Altered metabolism of sphingolipids has also been described in both MS [147] and AD [127]. Sphingolipids are as well involved in both the structural components of cell membranes and sustaining cellular signaling [148]. Myelin damage determines the release of its structural components in CSF and blood stream, which can be considered as potential biomarkers of the disease [149,150]. In MS, an increase in taurine concentration in the spinal cord and CSF has also been reported [151,152], possibly related to the immunomodulatory and neuroprotective reaction against the progressive nerve injury. Lipidomics assessment of CSF has demonstrated that MS patients present a different lipid profile at the time of diagnosis compared with non-MS subjects [153]. Specifically, an up-regulation of diglycerides and a down-regulation of triglycerides was observed. These findings point to the relevance of these lipids in this disorder and the significance of lipid trait characterization as a diagnostic tool. Targeted lipidomics analyses have also demonstrated that the lipid peroxidation marker 8-iso-prostaglandin F2α is increased in CSF from MS patients [154]. In addition, an increased incidence of CSF protein lipoxidation from MS patients has been reported as a result of augmented free radical production. Further investigations with larger sample sizes, prospective study design and with the presence of a healthy-control group are required to further elucidate the significance of such results.