Inhibition of atherosclerosis by dietary pectin in microswine with sustained hypercholesterolemia.

Sustained hypercholesterolemia is a known risk factor for development of atherosclerosis. In animal studies, grapefruit pectin fed concurrently with a high-lipid diet inhibits hypercholesterolemia and atherogenesis. The purpose of the present study was to determine if grapefruit pectin affects cholesterol levels and atherogenesis of animals with established hypercholesterolemia. Microswine were fed an atherogenic diet to establish hypercholesterolemia. Plasma cholesterol levels rose rapidly and for 360 days were sustained at levels 6- to 12-fold the normal level. Then, half the microswine, selected at random, were fed a diet in which 3% grapefruit pectin was substituted for cellulose, and the remaining animals received the original diet. Animals were killed 270 days later, and the extent of atherosclerosis was determined. In animals with established hypercholesterolemia, pectin did not lower their cholesterol levels. However, pectin reduced the extent of atherosclerosis in both the aorta and coronary arteries. The mean surface area covered by atherosclerosis in the aorta was 13.6% in the group that did not receive pectin compared with 5.3% in the group that did receive pectin. The mean coronary artery narrowing was 45% without pectin and 24% with pectin. We conclude that pectin may have a direct beneficial effect on atherosclerosis by a mechanism independent of cholesterol levels.

The gerbil, hamster, and guinea pig as rodent models for hyperlipidemia.

The purpose of this study was to compare the effects of a hyperlipidemic diet on three different rodent models to evaluate them on how their responses simulate human serum lipid diseases. Forty hamsters, 40 gerbils, and 20 guinea pigs were given either a chow diet or a modified high-fat, high-cholesterol diet (HF/HC) for 7 days. Food was withheld from half of the animals on each diet for 12 hours prior to collecting the blood for analysis of total cholesterol and triglyceride concentration. In all species, HF/HC feeding resulted in at least a 370% increase in total cholesterol concentration. Withholding food significantly decreased total cholesterol concentration in hamsters and gerbils fed HF/HC but had no effect on animals fed chow diet. Triglyceride concentrations were increased by the HF/HC in the hamster and the gerbil. As with total cholesterol, triglyceride concentration was decreased after food was withheld in these two animal groups. We suggest that the guinea pig is the most appropriate model for studying hypercholesterolemia because of its moderate plasma cholesterol response and normal triglyceride response to a HF/HC. We also suggest that the hamster is a good model for studying hypertriglyceridemia since increased serum triglyceride concentrations can be easily maintained on a HF/HC.

The effects of grapefruit pectin on patients at risk for coronary heart disease without altering diet or lifestyle.

Dietary intake of cholesterol has been linked to coronary heart disease. The effect of grapefruit pectin (Citrus paradisi) on plasma cholesterol, triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and the low-density lipoprotein:high-density lipoprotein cholesterol ratio was studied. The study design was a 16-week double-blind, crossover (placebo or pectin) using 27 human volunteers screened to be at medium to high risk for coronary heart disease due to hypercholesterolemia. The study did not interfere with the subjects' current diet or lifestyle. Grapefruit pectin supplementation decreased plasma cholesterol 7.6%, low-density lipoprotein cholesterol 10.8%, and the low-density lipoprotein:high-density lipoprotein cholesterol ratio 9.8%. The other plasma lipid fractions studied showed no significant differences. We conclude that a grapefruit pectin-supplemented diet, without change in lifestyle, can significantly reduce plasma cholesterol.

Grapefruit pectin inhibits hypercholesterolemia and atherosclerosis in miniature swine.

We studied the effect of dietary grapefruit pectin on plasma cholesterol and the development of atherosclerosis in 18 miniature swine. Pigs were randomized to one of three diets: no added fat (I), added fat/cellulose (II), and added fat/pectin (III). Plasma cholesterol was measured monthly. Arteries were examined for atherosclerosis at the termination of the experiment. Pectin supplementation of an added fat diet resulted in a significantly lower average plasma cholesterol than did cellulose supplementation (168 mg/dl vs. 249 mg/dl, p less than 0.05). The pectin-fed pigs also developed less atherosclerosis of their aortas (1.1% vs. 7.0%, p less than 0.05) and coronary arteries (2.9% vs. 26.2% cross-sectional narrowing, p less than 0.05). Plasma cholesterol levels correlated with the severity of aortic (r = 0.836) and coronary artery (r = 0.735) atherosclerosis. We conclude that dietary grapefruit pectin supplementation inhibits hypercholesterolemia and appears to be proportionately protective against atherosclerosis.

Methanol production from the degradation of pectin by human colonic bacteria.

When ingested, pectin can lower serum cholesterol levels in humans. Pectin is degraded by fecal bacteria in the colon. We examined the release of methanol (MeOH) by this degradation. A 0.2% glucose (2 g/L) mixture was used as the control medium. A pure culture of pectinolytic Erwinia carotovora was the control bacterium. The chief substrates were, in set 1, 0.2% pectin (2 g/L) and, in set 2, 0.1% glucose (1 g/L) and 0.1% pectin (1 g/L). Cultures of fecal bacteria and E carotovora grew for 72 h in each of the solutions. By 72 h the fecal flora culture in set 1 cleaved 30% of the possible methoxyl groups on pectin. The fecal flora in set 2 cleaved 90.7% of all possible methoxyl groups. Balance studies suggest that all of the free MeOH comes from methoxyl groups on pectin. This study demonstrates that fecal bacteria are capable of degrading pectin to release MeOH.

Unstirred water layers in rabbit intestine: effects of guar gum.

Guar gum has been shown to affect the absorption of several different nutrients in clinical studies; however, the mechanisms for decreased absorption have not been defined. A possibility not studied with regard to guar gum, but previously demonstrated to be important in absorption, is the effect of change in the unstirred water layer. As the unstirred water layer increases in thickness, the rate of absorption decreases for certain nutrients. The effect of guar gum on the unstirred water layer in the lumen of rabbit jejunum was examined by previously described techniques. It was observed that: increases in guar gum concentration resulted in an increased thickness of the unstirred water layer; for any stir rate, the addition of guar gum increased the thickness of the unstirred water layer; and stir rate is inversely related to the thickness of the unstirred water layer. It was concluded from these results that guar gum increases the thickness of the unstirred water layer in rabbit jejunum. This mechanism may explain, in part, the reduction of the rate of absorption of certain nutrients seen following guar gum ingestion.

Hypocholesterolemic agents: a comparison of the relative effectiveness of cholestyramine and pectin in rats.

Studies were carried out to evaluate the comparative effectiveness of cholestyramine and pectin as hypocholesterolemic agents. Circulating levels of serum cholesterol and lipoprotein-associated cholesterol were measured in rats fed high cholesterol diet supplemented with either cholestyramine or pectin. When compared with controls, a significant decrease in the level of total cholesterol was observed in rats fed either cholestyramine or pectin (p less than 0.001, 43% reduction in cholesterol, and p less than 0.04, 25% reduction in cholesterol, respectively) and this was due exclusively to the lowering of low density lipoprotein. Further statistical evaluation of data revealed no significant difference between the cholesterol levels of rats fed either cholestyramine or pectin (p greater than 0.07). The data acquired in this study suggest that both cholestyramine and pectin are comparable and effective hypocholesterolemic agents and the observed hypocholesterolemic effect of these agents is mediated through lowering of cholesterol associated with the low density lipoprotein.

Effect of dietary pectin on iron absorption and turnover in the rat.

The influence of dietary pectin on iron absorption and retention was studied in rats. Basal diet with low and normal iron levels were fed with and without addition of 2% citrus pectin. After 40 days rats were fasted for 24 hours and were given 59Fe in dilute HCl with or without 2% pectin by gavage. Whole-body counting techniques were employed to monitor 59Fe absorption and turnover. Rats maintained on low iron diet absorbed and retained a much higher proportion of 59Fe than rats maintained on normal level of iron. Dietary pectin at the level fed in this study had no influence on iron uptake and/or turnover in rats.

Characterization of food binding of vitamin B-6 in orange juice.

There is substantial evidence that natural vitamin B-6 exists largely in a bound form. It has been shown that the principal modes of binding represents an interaction of pyridoxal and/or pyridoxal phosphate with protein moieties. The nature and extent of binding of different forms of the vitamin in orange juice was investigated. Studies employing ultracentrifugation, ultrafiltration and, membrane dialysis of this food product suggested binding to a molecule of less than 3,500 daltons molecular weight. Binding was resistant to protease treatment although susceptible to heat-acid hydrolysis. Separation of pyridoxal, pyridoxine, and pyridoxamine species of the vitamin by ion exchange chromatography was followed by fluorometric analysis with and without preparative hydrolysis. Extensive and equal binding of both pyridoxal and pyridoxine was observed by this method. Thus, the binder(s) of vitamin B-6 in orange juice is a small dialyzable molecule which is heat stable, binds both pyridoxal and pyridoxine and is non-protein in nature.