Effectiveness of resistant starch, compared to guar gum, in depressing plasma cholesterol and enhancing fecal steroid excretion

Analysing the Impact of Resistant Starch Formation in Basmati Rice Products: Exploring Associations with Blood Glucose and Lipid Profiles across Various Cooking and Storage Conditions In Vivo

Common cooking methods were used to prepare basmati rice products, including boiling 1 (boiling by absorption), boiling 2 (boiling in extra amount of water), frying, and pressure cooking. The cooked rice was held at various temperatures and times as follows: it was made fresh (T1), kept at room temperature (20-22 °C) for 24 h (T2), kept at 4 °C for 24 h (T3), and then reheated after being kept at 4 °C for 24 h (T4). The proximate composition, total dietary fibre, resistant starch (RS), and in vitro starch digestion rate of products were examined. The effect of RS on blood glucose and lipid profiles was measured in humans and rats, including a histopathological study of the liver and pancreas in rats. The basmati rice that was prepared via boiling 1 and stored with T3 was found to be low in glycaemic index and glycaemic load, and to be high in resistant starch. Similarly, in rats, the blood glucose level, cholesterol, triglycerides, and LDL were reduced by about 29.7%, 37.9%, 31.3%, and 30.5%, respectively, after the consumption of basmati rice that was prepared via boiling 1 and stored with T3. Awareness should be raised among people about the health benefits of resistant starch consumption and the right way of cooking.

Effects of Resistant Starch Ingestion on Postprandial Lipemia and Subjective Appetite in Overweight or Obese Subjects

Reports surrounding the role of resistant starch (RS) on postprandial lipemia in humans are scarce. The aim of the present study is to examine the effects of resistant starch on the postprandial lipemic response, subjective measures of appetite, and energy intake in overweight and obese subjects. In a randomized, single-blind, crossover study, 14 overweight/obese participants ate a high-fat breakfast (679 kcal, 58% from fat) and a supplement with native banana starch (NBS), high-amylose maize starch (HMS), or digestible maize starch (DMS) on three separate occasions. All supplements provided were matched by the available carbohydrate content, and the RS quantity in NBS and HMS supplements was identical. Appetite was estimated using visual analogue scale (VAS) and an ad libitum test meal. Postprandial glycemia, triglycerides, cholesterol, high-density lipoprotein (HDL) cholesterol, and insulin excursions did not differ between treatments. Subjective appetite measures of satiety were significantly increased after HMS; however, no effects on energy intake were observed during the ad libitum test meal. These findings suggest that a single acute dose of RS cannot be expected to improve postprandial lipemia in subjects with overweight or obesity on a high-fat meal. However, the potential benefits of long-term supplementation should not be ruled out based on these results.

Enzymatic Modification of Corn Starch Influences Human Fecal Fermentation Profiles

Enzymatically modified starches have been widely used in food applications to develop new products, but information regarding digestion and fecal fermentation of these products is sparse. The objective of this study was to determine the fermentation properties of corn starch modified with α-amylase, amyloglucosidase, or cyclodextrin glycosyltransferase and the possible role of hydrolysis products. Samples differed in their digestibility and availability to be fermented by the microbiota, resulting in differences in microbial metabolites produced during in vitro fermentation. The presence or absence of hydrolysis products and gelatinization affected starch composition and subsequent metabolite production by the microbiota. Amyloglucosidase-treated starch led to the greatest production of short- and branched-chain fatty acid production by the microbiota. Results from this study could be taken into consideration to confirm the possible nutritional claims and potential health benefits of these starches as raw ingredients for food development.

The influence of enzyme-resistant starch on cholesterol metabolism in rats fed on a conventional diet

Male Wistar rats were fed on a conventional diet containing normal corn starch or 6 % enzyme-resistant starch originating from either raw or retrograded high-amylose corn starch. Furthermore, the diets were either cholesterol-free or contained 1 % cholesterol and 0·1 % cholic acid. The main objective of this study was to investigate whether the addition of enzyme-resistant starch to a rat conventional diet had any effect on cholesterol metabolism. Therefore, plasma and liver cholesterol concentrations, plasma HDL:LDL cholesterol ratios and neutral steroid and bile acid excretion were determined. No significant effect of enzyme-resistant starch feeding on plasma and liver cholesterol concentrations was found. However, consumption of raw or retrograded high-amylose corn starch resulted in a decrease in esterified and total liver cholesterol concentrations of 24 and 22 %, respectively. This was accompanied by a reduction in plasma esterified and total cholesterol levels of 4 % and a tendency to higher daily faecal coprostanol and total bile acid excretion.

Adzuki resistant starch lowered serum cholesterol and hepatic 3-hydroxy-3-methylglutaryl-CoA mRNA levels and increased hepatic LDL-receptor and cholesterol 7alpha-hydroxylase mRNA levels in rats fed a cholesterol diet

We examined the effects of adzuki bean resistant starch on serum cholesterol and hepatic mRNA in rats fed a cholesterol diet. The mRNA coded for key regulatory proteins of cholesterol metabolism. The control rats were fed 15 % cornstarch (basal diet, BD). The experimental rats were fed BD plus a 0.5 % cholesterol diet (CD), or a 15 % adzuki resistant starch plus 0.5 % cholesterol diet (ACD) for 4 weeks. The serum total cholesterol and VLDL + intermediate density lipoprotein + LDL-cholesterol levels in the ACD group were significantly lower than those in the CD group throughout the feeding period. The total hepatic cholesterol concentrations in the CD and ACD groups were not significantly different. The faecal total bile acid concentration in the ACD group was significantly higher than that in the BD and CD groups. Total SCFA and acetic acid concentrations in the ACD group were significantly higher than those in the CD group but there were no significant differences in the concentrations between the ACD and BD groups. The hepatic LDL-receptor mRNA and cholesterol 7alpha-hydroxylase mRNA levels in the ACD group were significantly higher than those in the CD group and the hepatic 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase mRNA level in the ACD group was significantly lower than in the CD group. The results suggest that adzuki resistant starch has a serum cholesterol-lowering function via enhancement of the hepatic LDL-receptor mRNA and cholesterol 7alpha-hydroxylase mRNA levels and faecal bile acid excretion, and a decrease in the hepatic HMG-CoA reductase mRNA level, when it is added to a cholesterol diet.

Resistant starch fraction prepared from kintoki bean affects gene expression of genes associated with cholesterol metabolism in rats

Feeding rats beans with resistant starch reduces the serum cholesterol concentration; however, the mechanism is not fully understood. We examined the effects of resistant starch of kintoki (Phaseolus vulgaris, variety) bean on serum cholesterol and hepatic mRNAs in rats. Male F344/Du Crj rats were fed a cholesterol-free diet either with 5 g of cellulose powder (control)/100 g or 5 g of pancreatin-resistant fraction prepared from kintoki bean (kintoki)/100 g diet for 4 weeks. There were no differences in the body weight gain, food intake, liver weight, and mass of cecum contents between the groups. Serum total cholesterol, very low density lipoprotein (VLDL) + intermediate density lipoprotein (IDL) + low density lipoprotein (LDL)-cholesterol, and high density lipoprotein (HDL)-cholesterol levels in the kintoki group were significantly (at least P < 0.05) lower than in the control group throughout the feeding period. There was no difference in the serum triglyceride concentration between two groups throughout the feeding period. Total hepatic cholesterol in the control group was significantly (P < 0.01) lower than in the kintoki groups. Fecal bile acid, cecal acetate, propionate and n-butyrate concentrations in the kintoki group all were significantly (P < 0.05) higher than in the control group. Likewise, hepatic cholesterol 7alpha-hydroxylase, LDL receptor, and SR-B1 mRNA levels in the kintoki group were significantly (P < 0.05) higher than in the control group. The results suggest that resistant starch of kintoki bean reduces serum cholesterol level by increasing hepatic LDL receptor, SR-B1, and cholesterol 7alpha-hydroxylase mRNAs.

Enzyme-resistant fractions of beans lowered serum cholesterol and increased sterol excretions and hepatic mRNA levels in rats

Feeding rats beans with resistant starch reduces their serum cholesterol concentration; however, the mechanism by which this occurs is not fully understood. We examined the effects of enzyme-resistant fractions of adzuki (Vigna angularis) and tebou (Phaseolus vulgaris, var.) beans on serum cholesterol and hepatic mRNA in rats. Rats were fed a cholesterol-free diet with 50 g of cellulose powder (CP)/kg, 50 g of an enzyme-resistant fraction of adzuki starch (AS)/kg, or 50 g of an enzyme-resistant fraction of tebou starch (TS)/kg diet for 4 wk. There were no significant differences in body weight, liver weight, and cecum contents among the groups, nor was there a significant difference in food intake among the groups. The levels of serum total cholesterol, VLDL + intermediate density lipoprotein + LDL-cholesterol, and HDL cholesterol in the AS and TS groups were significantly (P < 0.05) lower than in the CP group throughout the feeding period. Total hepatic cholesterol in the CP group was significantly (P < 0.05) lower than in the AS and TS groups, fecal cholesterol excretion in the TS group was significantly (P < 0.05) greater than in the CP and AS groups, and the fecal total bile acid concentrations in the AS and TS groups were significantly (P < 0.05) higher than in the CP group. Cecal acetate, propionate, and n-butyrate concentrations in the AS and TS groups were significantly (P < 0.05) higher than in the CP group. The level of hepatic scavenger receptor class B1 (SR-B1) mRNA in the TS group was significantly (P < 0.05) higher than in the CP group, and the levels of hepatic cholesterol 7alpha-hydroxylase mRNA in the AS and TS groups were significantly (P < 0.05) higher than in the CP group. These results suggest that AS and TS have a serum cholesterol-lowering function due to the enhanced levels of hepatic SR-B1 and cholesterol 7alpha-hydroxylase mRNA.

Effect of resistant starch from corn or rice on glucose control, colonic events, and blood lipid concentrations in streptozotocin-induced diabetic rats

To examine the effect of two types of resistant starch on blood glucose and insulin levels, colonic events, hypolipidemic actions and humoral immune responses, Sprague-Dawley streptozotocin-induced diabetic rats were fed diet containing resistant starch from corn or rice. The marked body weight loss by inducing diabetes was not recovered by feeding resistant starch, even though there are no differences in food intakes compared to the non-diabetic control rats. No significant effect of resistant starch feeding on blood glucose and insulin was found. Even though the length of small intestines, and cecum, colon and rectum together with the tissue weight of cecum were not affected by feeding resistant starch, the intestinal transit time was markedly shortened by both types of resistant starch and resistant starch from corn had a more pronounced effect. The short chain fatty acids in the intestinal contents did not appear to be different among the groups. Nonetheless, both of resistant starch from corn and rice significantly lowered plasma total lipid and cholesterol concentrations compared to the diabetic control. The total liver cholesterol lowering effect was observed with resistant starch from rice. Neither immunoglobulin G nor C(3) were influenced by resistant starch.

Impact of whole wheat flour and its milling fractions on the cecal fermentations and the plasma and liver lipids in rats

The aim of the present work was to evaluate the cholesterol-lowering potency of the different milling fractions of whole wheat flour, by investigating the effects of these wheat fractions (white flour, whole flour, and bran) on digestive fermentations and lipid metabolism in Wistar rats. Compared to the control, which was fiber-free, the different cereal fractions did not affect the daily food intake or weight gain. The white flour and whole flour diets markedly enlarged the cecum and elicited acidic fermentations (pH approximately 6.2), whereas bran was less effective. It appears that white flour rather promoted propionate-rich fermentations (+62%), whereas bran favored butyrate-rich fermentations (+178%). White flour or bran did not significantly affect total steroid excretion, but whole flour was effective (+41%). Both white flour and whole flour decreased cholesterol in the d < 1.040 fraction, but only whole flour significantly lowered cholesterolemia. However, all the cereal diets significantly decreased liver lipids, whole flour being the most potent (-54%). In conclusion, the totality of the wheat grain is important for cholesterol- and triglyceride-lowering effects, and the splitting up of the grain alters its health effects.

Whole wheat and triticale flours with differing viscosities stimulate cecal fermentations and lower plasma and hepatic lipids in rats

Whole flours from oat, rye or barley effectively modify digestive fermentation and lipid metabolism, whereas the effectiveness of whole wheat flour has not been established. To address this question, cecal digestion, short-chain fatty acid (SCFA) metabolism and cholesterol metabolism were investigated in four groups of rats fed the following semipurified diets differing in their carbohydrate source: a control diet (purified wheat starch) and three whole cereal flour diets [Valoris wheat (Wv), Soissons wheat (Ws), or Carnac triticale (Tc)]. Wv is particularly viscous and rich in arabinoxylans, and Tc is richer in hemicellulose than wheat. Compared with controls, rats fed the whole-flour diets had enlarged ceca and a moderate acidification of the bulk pH ( approximately 6.4). In these rats, the cecal SCFA pool size was enhanced (P < 0.05), and the SCFA molar ratio reflected propionic/butyric acid-rich fermentations, especially in those fed TC: The portal SCFA concentrations reflected the rise of the acetic and propionic acid pools in the cecum, whereas portal butyric acid remained relatively low, probably reflecting extensive metabolism by the cecal wall. The fecal excretion of total steroids (bile acids + sterols) was markedly enhanced by all of the whole-flour diets, with Wv (+78%) > Tc (+64%) > Ws (+47%). In parallel, there was a significant plasma cholesterol-lowering effect for rats fed Wv (-27%) and Tc (-32%) and a plasma triglyceride-lowering effect (approximately -40%) in all rats fed whole-flour diets (P < 0.05). This effect was observed mainly for triglyceride-rich lipoprotein-cholesterol, whereas HDL cholesterol was unaffected. These results indicate that whole wheat flours can strikingly affect cecal SCFA, especially butyrate, and are effective plasma cholesterol-lowering agents.

Class 2 resistant starches lower plasma and liver lipids and improve mineral retention in rats

The effects of raw potato starch (RPS) and high amylose corn starch (HAS) on cecal digestion, lipid metabolism and mineral utilization (Ca and Mg) were compared in rats adapted to semipurified diets. The diets provided either 710 g wheat starch/100 g diet (control) alone or 510 g wheat starch/100 g diet plus 200 g resistant starch/100 g (RPS or HAS). Compared with rats fed the control diet, significant cecal hypertrophy (240% after 7 d of the fiber consumption) and short-chain fatty acids accumulation (especially propionic and butyric acids) occurred after both resistant starch diets. Apparent Ca, Mg, Zn, Fe and Cu absorptions were similarly enhanced by RPS and HAS (50, 50, 27, 21 and 90%, respectively). Cholesterol absorption was reduced to 14% of intake in rats fed RPS or HAS compared with 47% absorption in control rats. RPS and HAS were also effective in lowering plasma cholesterol (-31 and -27%, respectively) and triglycerides (-28 and -22%, respectively). There was no effect of the diets on cholesterol in d > 1.040 kg/L lipoproteins (HDL), whereas RPS and HAS depressed cholesterol in d < 1.040 kg/L lipoproteins (especially in triglyceride-rich lipoproteins). Moreover, there were lower concentrations of cholesterol (-50 and -40%, respectively) and triglycerides (-53 and -47%, respectively) in the livers of RPS- and HAS-fed rats. Thus, RPS and HAS have similar effects on intestinal fermentation, mineral utilization and cholesterol metabolism in rats.

Low density lipoprotein receptor mRNA in rat liver is affected by resistant starch of beans

The effects of resistant starches of beans on serum cholesterol and hepatic low density lipoprotein (LDL) receptor mRNA in rats were investigated. Rats were fed a cholesterol-free diet with 150 g/kg corn starch (CS), 150 g/kg adzuki (Vigna angularis) starch (AS), 150 g/kg kintoki (Phaseolus vulgaris, variety) starch (KS), or 150 g/kg tebou (P. vulgaris, variety) starch (TS) for 4 wk. There were no significant differences in body weight among groups through the experimental period. The liver weight in the CS group was 1.1-1.2 times higher than that in the AS, KS, and TS groups. The cecum weight in the TS was 1.4 times higher than that in the CS group, and the cecal pH in the CS group was significantly higher than in the other groups. The serum total cholesterol, very low density lipoprotein + intermediate density lipoprotein + LDL-cholesterol and high density lipoprotein (HDL)-cholesterol concentrations in the bean starch groups were significantly lower than those in the CS group through the feeding period. The total cholesterol/HDL-cholesterol ratio in the bean starch groups was also significantly lower than that in the CS group at the end of the 4-wk feeding period. The hepatic cholesterol concentration in the TS group was significantly higher than in the CS group at the end of the 4-wk feeding period. The relative quantity of hepatic apo B mRNA in the AS group was 1.2 times higher than that in the CS group, and the hepatic LDL receptor mRNA levels in the AS and TS groups were 1.8-2.0 times higher than that in the CS group. The results of this study demonstrate that AS, KS, and TS lowered the serum total cholesterol level by enhancing the hepatic LDL receptor mRNA level.

Fermentation of resistant rice starch produces propionate reducing serum and hepatic cholesterol in rats

This study was designed to investigate the effects of different proportions of rice starch and cornstarch on lipid metabolism in rats fed high dietary cholesterol. Male Wistar rats were fed a 10 g/100 g fat diet containing 1 g/100 g cholesterol with 0 (control diet), 15, 30, 45 or 63 g/100 g rice starch with an enzyme resistant starch concentration of 1.26, 1.39, 1.52, 1.65 or 1.80 g/100 g, respectively, for 4 wk. Groups fed diets with < 63 g/100 g rice starch were supplemented with cornstarch to 63 g/100 g. The two kinds of starch had different structures as seen using scanning electron microscopy (SEM). The rice starch was an aggregation (n = 20-60) of smaller granules (3-8 microm in diameter), whereas the cornstarch was composed of larger (5-15 microm in diameter), single granules. The compound rice starch (0.99 kg/L) was larger in size and denser in structure than cornstarch (0.63 kg/L). Serum total cholesterol concentrations in rats fed both the 45 and 63 g/100 g rice starch diets were significantly lower than in all other groups (P < 0.05). The serum propionate concentration in the rats fed 63 g/100 g rice starch diets was significantly higher than that of other groups. Hepatic triglyceride and total cholesterol concentrations in rats fed 63 g/100 g rice starch diets were significantly lower than in the control group. These results suggest that, because the compound rice starch was an aggregation of smaller granules, larger in size and denser in structure than cornstarch, it was digested more slowly and altered lipid metabolism. Resistant rice starch may be fermented to produce propionate, which reduces serum and hepatic cholesterol.

Dietary oligofructose lessens hepatic steatosis, but does not prevent hypertriglyceridemia in obese zucker rats

We studied the influence of oligofructose (OFS), a nondigestible fructan, on lipid metabolism in obese fa/fa Zucker rats. The addition of 10 g/100 g OFS to the diet slowed the increase in body weight without modifying serum triglycerides or glucose concentrations after 7 wk of treatment. However, an oral load of 2 g glucose and 5 g corn oil/kg body weight increased triglyceridemia more in OFS-fed rats than in control rats. After 10 wk, OFS decreased the hepatic concentration of triglycerides 57% relative to controls. The less severe steatosis was confirmed by histologic analysis. Among the key enzymes involved in fatty acid synthesis and esterification, only malic enzyme activity was significantly lower in OFS-fed rats than in controls. The epididymal fat mass was significantly lower in OFS-fed rats. In conclusion, dietary enrichment with OFS can counteract both the fat mass development and the hepatic steatosis that occur in obese Zucker rats. Future studies will be designed to clarify in obese animals the influence of dietary OFS on postprandial triglyceridemia, which is an important variable associated with the development of atherosclerosis in humans, and to analyze the biochemical mechanism underlying the "hepatoprotective" effect of OFS.

Low levels of viscous hydrocolloids lower plasma cholesterol in rats primarily by impairing cholesterol absorption

Hydrocolloids have been proposed as cholesterol-lowering agents, but their viscosity limits their use in human nutrition. A low level (1 %) of hydrocolloids (guar gum, (GG); xanthan gum, (XG); and konjac mannan) was investigated in rats fed 0.2 g/100 g cholesterol diets. Food intake and body weight gain were not altered by the diets. Bile flow and cholesterol bile flux were not modified by diet, whereas the bile acid flux was greater in rats fed hydrocolloid diets. The cecal pool of bile acids was greater than control rats only in rats fed the XG diet (+71%, P<0.001). The fecal excretion of neutral sterols was stimulated in rats fed the hydrocolloid diets; cholesterol apparent digestibility (60% in controls) was reduced to 30-36% in rats fed hydrocolloids. Bile acid fecal excretion was not altered by diet treatment. As a result, apparent steroid balance was about +40 micromol/d in controls and only +10 to +20 micromol/d in rats fed hydrocolloids. Both plasma cholesterol and triglycerides were significantly lower than controls in rats fed XG, but only cholesterol was lower in rats fed the GG diet. These effects were essentially found in the d <1.040 kg/L fraction. Liver cholesterol content was significantly lower than in controls in rats fed the GG or XG diets. Liver HMG CoA reductase was not affected by the hydrocolloid diets. In conclusion, a low percentage of viscous hydrocolloids lowers plasma cholesterol in cholesterol-fed rats. Inhibition of intestinal cholesterol absorption may be the primary mechanism.

The water-soluble extract of chicory influences serum and liver lipid concentrations, cecal short-chain fatty acid concentrations and fecal lipid excretion in rats

Sprague-Dawley rats (n = 32) were fed diets without fiber (control) or containing 1 or 5% chicory extract or 5% inulin for 4 wk; 0.2% cholesterol was added to all diets. Rats fed chicory extract and inulin diets had significantly higher serum high density lipoprotein (HDL) cholesterol and generally lower low density lipoprotein (LDL) cholesterol concentrations, thus significantly greater ratios of HDL/LDL cholesterol compared with the controls (P < 0.05). The serum apolipoprotein B/apolipoprotein A-1 ratio was significantly lower in rats fed diets containing chicory extract or inulin than that in rats fed fiber-free diets, due to significant reductions in apolipoprotein B concentration (P < 0.05). Greater liver lipid and triglyceride concentrations were observed in rats fed chicory extract or inulin diets compared with the controls (P < 0.05). However, liver phospholipid and cholesterol concentrations were not significantly different among groups (P > 0.05). Addition of 5% inulin to the diet resulted in greater cecal weight, whereas both 5% chicory extract and 5% inulin resulted in greater cecal propionic acid concentration compared with the controls (P < 0.05). Rats fed chicory extract and inulin had significantly greater fecal lipid, cholesterol and bile acid excretions than those fed fiber-free diets (P < 0.05). The results of this study suggest that the improved lipid metabolism observed in rats fed chicory extract (mainly inulin component) may be caused by an alteration in the absorption and/or synthesis of cholesterol, which might result from the changes in cecal fermentation, and by an increase in the fecal excretion of lipid, cholesterol and bile acid.

Animal models: new cholesterol raising and lowering nutrients

Most reports reviewed here have used animal models to investigate the cholesterolemic effects of phytochemicals, herbal extracts, probiotic microorganisms, and plant constituents, including fibers. These compounds represent examples of what are termed 'functional foods' in that they elicit physiologic responses with implications for chronic disease prevention. These reports are examined in light of criteria developed from animal model experiments investigating fatty acid effects in order to aid the task of appropriate extrapolation of the results to humans.

The cholesterol-lowering effect of guar gum is not the result of a simple diversion of bile acids toward fecal excretion

The effects of partially hydrolyzed, nonviscous, guar gum (PHGG) on cholesterol metabolism and digestive balance have been compared with those of native guar gum (GUAR) in rats adapted to 0.4% cholesterol diets. Both types of guar gum elicited acidic fermentations in the large intestine, but only GUAR effectively lowered plasma cholesterol (P < 0.001), chiefly in the triglyceride-rich lipoprotein fraction. The biliary bile acid excretion was significantly enhanced in rats fed GUAR (P < 0.05), as well as the intestinal and cecal bile acid pool (P < 0.001). In rats fed GUAR and to a lesser extent in those fed PHGG, the fecal excretion of bile acids and neutral sterol was higher than in controls (P < 0.01). The digestive balance (cholesterol intake-steroid excretion) was positive in control rats (+47 mumol/d), whereas it was negative in rats fed GUAR (-20 mumol/d), which could involve a higher rate of endogenous cholesterol synthesis. In rats fed PHGG, the steroid balance remained slightly positive. Liver 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity was very low (22 pmol/min/mg protein), owing to cholesterol supplementation, in control rats or in rats fed PHGG, whereas it was markedly higher (+463%) in rats fed GUAR. In conclusion, even if PHGG does alter some parameters of the enterohepatic cycle of cholesterol and bile acids, its effects are not sufficient to elicit a significant cholesterol-lowering effect. The intestinal (ileal or cecal) reabsorption of bile acids was not reduced, but rather increased, by GUAR; nevertheless the intestinal capacities of reabsorption were overwhelmed by the enlargement of the digestive pool of bile acids. In the present model, induction of HMG-CoA reductase probably takes place in the presence of elevated portal bile acid concentrations.