Serum cholesterol levels with pectin

Cholesterol Lowering Influence of Pectin Several Investigators (7-9) have clearly suggested that pectin when supplemented In the diet of laboratory animals and/or human volunteers causes significant reduction In serum cholesterol levels. This, Indeed, Is an Important observation, as It has been shown that the etiology of atherosclerosis and coronary artery disease Is associated with elevated serum cholesterol levels, and the observed reduction of serum cholesterol level by pectin holds promise for the treatment and/or prevention of these diseases. It Is relevant here to point out that dietary pectin has shown to retard Induced avian atherosclerosis (10). 

The laboratory must be informed when the therapeutic regimens include drugs specifically administered to change the blood level of a biochemical constituent. Cholestyramine resin, a nonabsorbable anion exchange resin administered orally to patients with hyperlipoproteinemia produced a 24% decline in serum cholesterol levels in 14 patients with essential hypercholesterolemia. In these patients the mean cholesterol fell from 414 98 mg/100 ml to 176 21 mg/100 ml (FI). Pectin added to the diet caused a 5% decrease in serum cholesterol values (K4), as did an oral hydrophobic colloid (G4). Levels fell in one case from 220 mg/ 100 ml to 160 mg/100 ml (G4). Nicotinic acid, neomycin, and p-chloro-phenoxyisobutyrate have all been used to reduce serum cholesterol (G7). 

Elevated serum cholesterol levels are invariably associated with the etiology of atherosclerosis and coronary artery disease, and it has been shown by several investigators that pectin from a variety of sources when supplemented in the diet of a number of laboratory animals, as well as human volunteers, causes lowering... 

Impairment of bile acid absorption and consequent loss of these acids via excretion presumably causes an increase in hepatic conversion of cholesterol to bile acids. This conversion lowers serum cholesterol, particularly when serum contains high levels of cholesterol derived from dietary intake. However, when fed with a cholesterol-free diet, 10% pectin supplementation stimulated a 3-fold increase in cholesterol biosynthesis (77). Biosynthesis of phospholipids and triglycerides also increased significantly hence, it was suggested that these increases occurred in response to diminished fat absorption occasioned by pectin intake. This compensatory biosynthesis of cholesterol and lipids may account for pectin s inability (in most cases) to lower serum cholesterol levels in animals fed cholesterol-free diets. 

Recently the means by which pectin lowers cholesterol levels and even the validity of this effect have been questioned. Upon finding no bile salt binding capacity for soluble pectin, Baig and Cerda (76) proposed that pectin lowered serum cholesterol levels by forming insoluble complexes with the serum low density lipoproteins (LDL) which transport circulating cholesterol. Complexing of LDL by citrus pectin was observed in vitro, but the way in which pectin or some component thereof enters the blood stream to effect such binding in vivo has not been determined. 

The effectiveness of pectin in lowering cholesterol in tissues can be influenced by many factors (1) The type of pectin - that with methoxy groups and with high viscosity (35, 36) was reported to be more effective. The results from a comparative study of several types of pectin by Mokady (36) are shown in Table IV. Neither a high degree of methylation nor high-viscosity alone was very effective (2) the level of dietary fat - with a high-fat diet (2% corn oil plus 18% beef tallow), pectin has no effect on serum cholesterol level (57). Tsai et al. also reported that with... 

In view of the fact that pectin lowers serum cholesterol levels and cholesterol Is carried by lipoproteins In the serum, we investigated the Interaction of pectin obtained from grapefruit albedo with various human serum lipoprotein fractions in vitro (22). It was observed that pectin Interacted specifically with LDL, while no Interaction was observed between pectin and high density or very low density lipoproteins. The biological significance of this observed in vitro Interaction of pectin with LDL remain unclear, primarily because of lack of evidence suggesting entry of pectin or some component of It into the blood streatm. Therefore, unless such entry and/or absorption of pectin or one of Its components is demonstrated, the biological Implication of this observed Interaction... 

Based on our knowledge of the facts that (a) lipoproteins are carriers of cholesterol in the blood stream, (b) they are involved in atherogenesis,(c) pectin when supplemented in diet causes lowering of serum and/or liver cholesterol in man as well as a number of laboratory animals and (d) polyanionic glycosaminoglycans interact with lipoproteins, it was of interest to us to investigate the interaction of polyanionic pectin with lipoproteins in order to explain the biochemical basis by which pectin may cause lowering of serum/liver cholesterol levels. 

Pectin with 62% D.E. largely counteracted the increase in liver cholesterol levels brought about by dietary cholesterol. Low ester pectin (30% D.E.), polygalacturonic acid (PGA), and 50% esterified PGA were all without effect. Conflicting reports on the efficacy of pectin as a hypocholesterolemic agent may be due to variations in these parameters. For example, citrus pectin was found to be more effective than tomato pectin in lowering serum and hepatic cholesterol levels of rats (79). 

D.E. values for the citrus and tomato pectins were 56 and 40%, respectively. Thus, differences in D.E. levels rather than pectin source could have accounted for the superior effectiveness of citrus pectin. Mokady (80) and Judd et al. (81) confirmed that serum cholesterol reduction is most pronounced with high D.E., high-molecular-weight pectin (Table I). 

During the more than two decades that pectin research has been carried out, two areas of investigation with potential benefit to human health have been in lipid metabolism (Table II) and carbohydrate metabolism (Table III). Pectin has been shown to decrease serum cholesterol in humans (6-11) as well as other animal species (10). High levels of serum cholesterol are generally considered to be a risk factor associated with ischemic heart disease (11-13). Consumption of pectin to reduce cholesterol levels in the blood might be expected to reduce the incidence of heart disease especially when serum cholesterol is elevated. 

In the present series of studies, blood serum lipids were determined by a commercial laboratory (Stat Laboratory, Wichita, Kansas). Blood cholesterol levels of subjects were lower when subjects received the experimental diets than when subjects consumed their self-selected diets- The mean cholesterol level of subjects while on the self-selected diets was 193 mg/dl and while receiving the controlled diet alone or with psyllium, cellulose, pectin, wheat bran, rice bran or corn bran were 172, 158, 168,... 

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