Dietary triglyceride sources

The answer is a. (Hardman, pp 875-898.) In type I hyperlipoproteinemia, drugs that reduce levels of lipoproteins are not useful, but reduction of dietary sources of fat may help. Cholesterol levels are usually normal, but triglycerides are elevated. Maintenance of ideal body weight is recommended in all types of hyperlipidemia. Clofibrate effectively reduces the levels of VLDLs that are characteristic of types 111, IV, and V hyperlipoproteinemia administration of cholestyramine resin and lovastatin in conjunction with a low-cholesterol diet is regarded as effective therapy for type 11a, or primary, hyperbetalipoproteinemia, except in the homozygous familial form. 

The effect of dietary fats on hypertriglyceridemia is dependent on the disposition of double bonds in the fatty acids. Omega-3 fatty acids found in fish oils, but not those from plant sources, activate peroxisome proliferator-activated receptor-alpha (PPAR- ) and can induce profound reduction of triglycerides in some patients. They also have antiinflammatory and antiarrhythmic activities. In contrast, the omega-6 fatty acids present in vegetable oils may cause triglycerides to increase. 

Either native winterized or concentrated whole-body fish oils or fish liver oils have been utilized in most studies as dietary source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The physiological effects and possible health benefits of administered fish oils generally have been attributed to either EPA or DHA alone or to a synergistic effect between the two. As a result, there has been controversy over the contribution of individual fish oil constituents to particular pharmacological actions and the optimal dosages required for achieving established and/or suspected beneficial effects. The predominant marine triglyceride-derived m-3-fatty acids are all-cA-5,8,11,14,17-eicosapentaenoic acid (C20 5i3, EPA) and all-ci.v-4,7,10,13,16,19-docosa-hexaenoic acid (C22 6,3, DHA). 

Cholesterol is an essential component of cellular membranes. In addition to dietary sources, we can also synthesize cholesterol. Cholesterol is transported in the blood as a lipoprotein, which is an aggregate of water-soluble proteins, cholesterol, and other lipids, including triglycerides. Proteins are denser than lipids,... 

Chylomicrons are produced from dietary fat by the removal of resynthesised triglycerides from the mucosal cells of the small intestine into the intestinal lumen. These then enter the circulation via the thoracic dncts in the lymphatic system and enter into the subclavian veins, where triglyceride content is reduced by the action of lipoprotein lipases (LPL) on capillary endothelial surfaces in skeletal muscle and fat. The free fatty acids (FFA) from the triglycerides are used by the tissues as an energy source or stored as triglycerides. The chylomicron remnants, stripped of triglyceride and therefore denser, are then taken up by the liver by LDL receptor-mediated endocytosis, thereby delivering cholesterol to the liver. 

Dietary lipids are composed mainly of triglycerides with only small amounts of phospholipids, cholesterol, and other sterols. Chemically, triglycerides are the triacylglycerols or a glycerol molecule esterified with three FAs. Saturated FAs have no double bonds in their carbon chain examples include palmitic (16 0) and stearic acid (18 0). Unsaturated FAs have one (monoun-saturated) or more (polyunsaturated) double bonds in the carbon chain. Depending on the position of the first double bond from the methyl end, these FAs are divided into n-9, n-6, or n-3 (also called co-9, co-6, or co-3) series, with the first double bonds being between carbon 9 and 10, carbon 6 and 7, and carbon 3 and 4, respectively. Common sources of different dietary FAs are shown in Table I. Animal fats are a rich source of saturated... 

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