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Biomedical subjects

M Bertolotti

Publications and source records attributed to M Bertolotti.

At least 19 recordsLinked to original sources
PubMed2001

Photonic band edge effects in finite structures and applications to chi 2 interactions.

Using the concept of an effective medium, we derive coupled mode equations for nonlinear quadratic interactions in photonic band gap structures of finite length. The resulting equations reveal the essential roles played by the density of modes and effective phase matching conditions necessary for the strong enhancement of the nonlinear response. Our predictions find confirmation in an experimental demonstration of significant enhancement of second harmonic generation near the photonic band edge. The measured conversion efficiency is in good agreement with the conversion efficiency predicted by the effective-medium model.

Journal Article↗
PubMed2001

Group velocity, energy velocity, and superluminal propagation in finite photonic band-gap structures.

We have analyzed the notions of group velocity V(g) and energy velocity V(E) for light pulses propagating inside one-dimensional photonic band gap structures of finite length. We find that the two velocities are related through the transmission coefficient t as V(E)=/t/(2)V(g). It follows that V(E)=V(g) only when the transmittance is unity (/t/(2)=1). This is due to the effective dispersive properties of finite layered structures, and it allows us to better understand a wide range of phenomena, such as superluminal pulse propagation. In fact, placing the requirement that the energy velocity should remain subluminal leads directly to the condition V(g)<or=c//t/(2). This condition places a large upper limit on the allowed group velocity of the tunneling pulse at frequencies of vanishingly small transmission.

Journal Article↗
PubMed2001

Inhibition of intestinal cholesterol absorption by surfomer (alpha-olefin maleic acid) affects hepatic cholesterol synthesis and low density lipoprotein transport in hamsters fed a fat-enriched diet.

BACKGROUND: Surfomer (alpha-olefin maleic acid) reduces intestinal cholesterol absorption. AIMS: This study was performed to investigate the effect of surfomer on cholesterol synthesis and low density lipoprotein in hamsters fed a hypercholesterolaemic, lipid-enriched diet. ANIMALS AND METHODS: Male hamsters were fed a diet enriched in cholesterol (0.07%) and saturated fatty acids (coconut oil 20%); the diet was supplemented with 3% surfomer, for 1-4 weeks. Cholesterol synthesis was assessed measuring incorporation of [3H]water into tissue sterols; low density lipoprotein clearance was determined using a primed-continuous infusion of (125I)tyramine-cellobiose lipoprotein. RESULTS: Cholesterol synthesis was suppressed after 3 weeks of hyperlipidaemic diet in liver and small bowel (by 88% and 38%, respectively) and was significantly increased by supplementing the fat-enriched diet with surfomer. Low density lipoprotein-cholesterol was increased by 44% after 4 weeks of hyperlipidaemic diet, in parallel with a decrease in hepatic low density lipoprotein clearance rates (48+/-3 vs 68+/-7 microl of plasma/h per g of tissue). Concurrent treatment with surfomer for 1, 2 or 4 weeks prevented the decrease of clearance and maintained normal low density lipoprotein-cholesterol levels at all time points. CONCLUSIONS: Surfomer represents a powerful tool to investigate the impact of cholesterol absorption on sterol homeostasis. Furthermore, since surfomer appears to normalize low density lipoprotein transport in hamsters fed a diet comparable to a lipid-rich "western-style" regimen, this drug may deserve consideration as an adjunct treatment for hypercholesterolaemia in selected patient groups.

Absorption↗
PubMed2001

Suppression of bile acid synthesis, but not of hepatic cholesterol 7alpha-hydroxylase expression, by obstructive cholestasis in humans.

Regulation of bile acid synthesis, a key determinant of cholesterol homeostasis, is still incompletely understood. To elucidate the feedback control exerted on bile acid biosynthesis in humans with obstructive cholestasis, 16 patients with bile duct obstruction were studied. In vivo 7alpha-hydroxylation, reflecting bile acid synthesis, was assayed in 13 of them by tritium release analysis. Serum 27-hydroxycholesterol was determined by gas chromatography-mass spectrometry. In a subgroup, hepatic cholesterol 7alpha-hydroxylase mRNA was assayed by real-time polymerase chain reaction (PCR), enzyme activity was determined by isotope incorporation, and microsomal cholesterol content was assayed by gas chromatography-mass spectrometry. Age-matched control subjects were studied in parallel. Hydroxylation rates were lower in cholestatic patients (108 +/- 33 mg of cholesterol per day, mean +/- SEM; controls: 297 +/- 40 mg/d; P <.01). The reduction was proportional to the severity of cholestasis, and synthetic rates were normalized in 4 subjects restudied after resolution of biliary obstruction. Consistent findings were obtained by analysis of serum 7alpha-hydroxycholesterol levels. On the other hand, hepatic cholesterol 7alpha-hydroxylase mRNA, microsomal enzyme activity, and cholesterol content tended to be increased in cholestasis. Finally, serum 27-hydroxycholesterol levels were slightly reduced in cholestatic subjects and were not related with the severity of the disease. Suppression of in vivo bile acid synthesis with no corresponding reduction in tissue 7alpha-hydroxylase expression and activity is consistent with nontranscriptional, posttranslational levels of regulation; these may play a role in the feedback control of bile acid synthesis in particular conditions. Alteration of the alternate biosynthetic pathway seems unlikely according to the present data.

Aged↗
PubMed2000

Review article: effect of bile salt pool composition on hepatic and biliary functions.

The enterohepatic recirculation of bile salts exerts important regulatory effects on many hepatic, biliary and intestinal functions: such regulation is likely to depend, to a large extent, on the physical-chemical property of hydrophobicity of the recirculating pool. The present review summarizes the main experimental evidence carried out by our research group over the past two decades, in the attempt to investigate systematically the relationships between structural properties and biological effects of bile acids in humans. Hydrophobic bile acids (chenodeoxycholic acid, deoxycholic acid), but not hydrophilic acids (ursodeoxycholic acid), significantly suppressed hepatic activity of HMG-CoA reductase, the limiting step of cholesterol synthesis, and in vivo cholesterol 7alpha-hydroxylation, the limiting step of bile acid synthesis. The output of biliary cholesterol and phospholipid was also directly related to the hydrophobicity of the bile acid pool. Finally, treatment with chenodeoxycholic acid, but not with ursodeoxycholic acid, significantly decreased gall-bladder emptying rates. When turning to the in vitro model of HepG2 cells, hydrophobic bile acids were found to induce greater cytotoxic and pro-apoptotic effects. From this series of studies, we conclude that the regulatory effects of bile acids on the liver and biliary tract are largely dependent on the hydrophobic-hydrophilic balance of the recirculating bile acid pool.

Bile Acids and Salts↗
PubMed2000

[Psychological assistance in organ transplantation].

The aim of this report is introducing with a series of psychological, psychiatric and psychosocial problems, that can arise, at every point, in the procedure of organ transplantations. Different areas of intervention are considered: the assistance to the patients and their families during the pre- and post-operative periods; the evaluation of transplant recipients' quality of life; ethical and psychological problems of living kidney donation; psychosocial support to donors' families; the training of the intensive therapy units to entertain relationships with donors' relatives; the delicate psychological aspects of transplantation during childhood. The sense of awareness about these matters is growing in Italy too, and many initiatives of psychological and psychiatric help are being developed in collaboration with several transplantation centres.

Adult↗
PubMed1998

Serum time course of naltrexone and 6 beta-naltrexol levels during long-term treatment in drug addicts.

The pharmacokinetics of naltrexone have been scarcely explored in patients during chronic treatment despite the observation that the pharmacological effect of the drug is related to its plasma concentrations. In this study we investigated the time course of serum levels of naltrexone and its active metabolite, 6 beta-naltrexol, in 13 heroin addicts (3 F, 10 M; age 22-32 years) in the 24 h after 100 mg of naltrexone orally. Six patients were studied once, at different times during chronic treatment, whereas in seven patients the study was done at the beginning and after 1 month of naltrexone treatment. Four of these patients also repeated the study after 3 months of naltrexone treatment. Serum naltrexone and 6 beta-naltrexol were assayed by GLC with a nitrogen-phosphorus detector. Our results showed large differences among patients in serum naltrexone and 6 beta-naltrexol levels. On the other hand, there were no differences in serum time course of both substances in the same patient over 3 months. Peak levels and AUCs of naltrexone were lower than those of 6 beta-naltrexol in ten addicts and higher than those of the metabolite in three patients. No significant differences in the apparent half-lives of the two drugs were detected among groups. These data are consistent with the occurrence of a decreased first-pass metabolism of naltrexone in three patients leading to a larger availability of an oral dose. The increased bioavailability of the drug is not very important for opioid receptor antagonist activity but may play a role in naltrexone treatment safety.

Administration, Oral↗
PubMed1998

Influence of age and sex on serum concentrations of total dimeric activin A.

Several studies have shown that activin A is secreted in substantial amounts into the systemic circulation. The changes that occur during menstrual cycle and pregnancy suggest a correlation with reproductive function. At present, however, no definitive evidence has confirmed this pattern throughout adult life; moreover, neither the origin nor the physiological implications of this circulating growth factor have been clearly defined. The aim of the present study was to evaluate whether circulating concentrations of activin A change in adult men and women according to age and sex, and to examine the possible correlation with serum concentrations of FSH. Total dimeric activin A was measured using a specific two-site enzyme immunoassay in serum specimens collected from a cohort of normal individuals enrolled in an epidemiological survey. A group of men (n = 106) and one of women (n=151) were subdivided into six age groups (20-30, 30-40, 40-50, 50-60, 60-70 and 70-90 years). In a small group of 8 men and 11 women, serum concentrations of activin A were evaluated twice, in specimens collected at an interval of 10 years. Serum FSH concentrations were also measured in all specimens. Serum concentrations of activin A were not significantly different in men and women and showed an age-related progressive increase between 20 and 50 years of age (P<0.01, those aged 40-50 compared with those aged 20-30 years). After the age of 50 years, activin A concentrations remained in the same range of values in women, whereas they increased significantly in men, reaching peak values between 70 and 90 years (P<0.01 compared with the group aged between 20 and 50 years). From the age of 50 years, activin A concentrations were significantly greater in men compared with those in women in the corresponding age groups (P<0.001). Activin A concentrations correlated with age in men, but not in women. No significant correlation between concentrations of activin A and FSH was found in either sex. Activin A concentrations in specimens collected 10 years apart showed an increase in seven of eight men, but not in women. Finally, no significant variations of activin A concentrations were observed when fertile and postmenopausal women were compared. The present data indicate that circulating concentrations of activin A vary according to age; furthermore, men older than 50 years have greater concentrations than women. These changes, which occur irrespectively of FSH concentrations, indicate that circulating activin A is not a hormone of the reproductive axis.

Activins↗
PubMed1997

Effect of taurohyodeoxycholic acid on biliary lipid secretion in humans.

This study aimed to determine the effect in humans of taurohyodeoxycholic acid, a 6alpha-hydroxylated bile acid with hydrophilic properties, on bile lipid secretion. Four cholecystectomized patients who had gallstones and an interrupted enterohepatic circulation were intraduodenally infused with taurohyodeoxycholic and tauroursodeoxycholic acids on separate occasions at a dose of 0.8 to 1 g/h for 3 hours. In hourly bile samples collected for 8 hours after the beginning of the infusion, biliary bile acid composition (by high-performance liquid chromatography), biliary lipid concentrations (by standard methods), and distribution of biliary carriers (by gel chromatography) were evaluated. Blood liver function tests were performed before and after the infusions. Taurohyodeoxycholic and tauroursodeoxycholic acids became the predominant biliary bile acids in all patients except for one infused with taurohyodeoxycholic acid. Taurohyodeoxycholic acid stimulated significantly greater (P < .05) cholesterol and phospholipid secretion per unit of secreted bile acid (0.098 and 0.451 micromol/micromol, respectively) compared with tauroursodeoxycholic acid (0.061 micromol/micromol for cholesterol and 0.275 micromol/micromol for phospholipids). The secretory ratio between phospholipid and cholesterol was significantly higher after infusion of taurohyodeoxycholic acid (3.88 micromol/micromol) compared with taroursodeoxycholic acid (3.09 micromol/micromol) (P < .05). Biliary enrichment with taurohyodeoxycholic acid was positively related with percent concentration of phospholipids but not with that of cholesterol. The opposite trend was observed in tauroursodeoxycholic acid-enriched biles. In both taurohyodeoxycholic acid- and tauroursodeoxycholic acid-rich bile, 80% to 90% of cholesterol was carried in a gel-chromatographic fraction corresponding to an apparent molecular weight of 80 to 200 kd. No alteration in liver function test results was observed after taurohyodeoxycholic acid infusion. In conclusion, taurohyodeoxycholic acid stimulates greater cholesterol and phospholipid secretion than tauroursodeoxycholic acid, but with a higher phospholipid/cholesterol secretory ratio. In bile enriched with both bile acids, biliary cholesterol is transported in non-micellar aggregates. Finally, in the conditions of our study, taurohyodeoxycholic acid was not hepatotoxic.

Aged↗
PubMed1997

Cholecystokinin increases bile acid synthesis with total parenteral nutrition but does not prevent stone formation.

Total parenteral nutrition (TPN) is associated with cholestasis and gallstones. Gallbladder stasis may be important in the development of gallstones, and cholecystokinin (CCK) to stimulate gallbladder contraction has been proposed as a treatment to prevent this complication. We studied in vivo bile acid synthesis and bile acid output in miniswine on TPN to test whether daily CCK improves bile acid output and normalizes bile acid profiles with TPN. Nine miniswine were nutritionally maintained with TPN for 4 weeks; four pigs received CCK (0.1 mg/kg) iv daily. In vivo bile acid synthesis was measured with injection of 7 alpha-tritiated cholesterol. An increase in tritiated water reflects the activity of 7 alpha-hydroxylation, the rate-limiting step in bile acid synthesis. At the end of 4 weeks, bile was collected and bile acid output and bile salt profiles were determined. One of five animals on TPN developed gallstones while two of four receiving daily CCK developed stones. In vivo bile acid synthesis decreased with TPN (controls, 63 +/- 9 mg/24 hr versus TPN, 13 +/- 4 mg/24 hr) and increased in TPN animals with CCK treatment (TPN-CCK, 105 +/- 35 mg/24 hr). Bile acid profiles are changed with TPN with more secondary bile acids, this was not improved with CCK. CCK improved bile acid synthesis and bile acid output but failed to prevent gallstone formation or normalize bile salt profiles. In addition to promoting gallbladder contraction, CCK may have a stimulatory effect on bile acid synthesis. CCK alone did not prevent gallstone formation.

Animals↗
PubMed1997

Effect of liver cirrhosis on the systemic availability of naltrexone in humans.

BACKGROUND/AIMS: Naltrexone is a competitive opiate antagonist with high hepatic extraction. It is used for detoxification treatment for heroin addicts and has been proposed as a possible treatment of pruritus in cholestasis. Such patients are likely to have impaired liver function, underscoring the need to understand the pharmacokinetic behavior of naltrexone in liver disease. These studies were undertaken to evaluate the effect of liver cirrhosis on the plasma time-course of naltrexone. METHODS: A total of 18 patients were investigated: seven migraine patients with normal liver function regarded as controls and 11 patients with liver cirrhosis (six with decompensated disease and five with preserved liver function). A bolus of 100 mg of naltrexone was administered orally in the morning, after an overnight fast. Blood samples were taken in basal conditions and at fixed intervals, up to 24 h after administration. Serum levels of naltrexone and of its major active metabolite, 6 beta-naltrexol, were assayed by reversed-phase HPLC analysis. RESULTS: In control subjects, circulating concentrations of naltrexone were always much lower than those of 6 beta-naltrexol (area under the curve: naltrexone, 200 +/- 97 ng/ml x 24 h; 6 beta-naltrexol, 2467 +/- 730 ng/ml x 24 h, p < 0.01). In severe cirrhosis serum levels of 6 beta-naltrexol increased more slowly, so that circulating levels of naltrexone during the first 2-4 h after drug intake were higher than those of 6 beta-naltrexol (6 beta-naltrexol/naltrexone ratio at 2 h: controls, 10.91 +/- 4.80; cirrhosis, 0.39 +/- 0.18, p < 0.01). The area under the curve for naltrexone (1610 +/- 629 ng/ml x 24 h) was significantly greater than in controls, whereas that for 6 beta-naltrexol (2021 +/- 955 ng/ml x 24 h) was not significantly different. Patients with compensated cirrhosis showed an intermediate pattern. No differences in elimination half-life of the two drugs were detected among the groups. CONCLUSIONS: Our data suggest the occurrence of important changes in the systemic availability of naltrexone and 6 beta-naltrexol in liver cirrhosis; such alterations are consistent with lesser reduction of naltrexone to 6 beta-naltrexol and appear to be related to the severity of liver disease. This must be considered when administering naltrexone in conditions of liver insufficiency.

Adult↗
PubMed1997

Analgesic drug taking: beliefs and behavior among headache patients.

OBJECTIVE: To explore beliefs and behavior with respect to analgesic drug taking in headache patients. To compare episodic headache to chronic headache sufferers. METHODS: A consecutive series of 280 headache patients, newly admitted to the Headache Center of the University of Modena, all referred by their general practitioner, were asked to fill out a brief questionnaire, specially compiled for this survey. The questionnaire invited patients to indicate how they themselves thought they should best cope with their headache, and how they actually did so in practice. RESULTS: The majority of our patients had a positive attitude towards the over-the-counter analgesics, which they believed to be more adequate than prescription drugs for acute treatment of their headache. They handled analgesics very carefully, believing it correct to take the drug only when the pain became unbearable, if it was not possible for them to stop work. Chronic headache patients tended to consume more prescription drugs than episodic headache sufferers. Furthermore, the majority of chronic sufferers, as opposed to episodic sufferers, took the analgesic even when not at work. CONCLUSIONS: The use of over-the-counter drugs is considered the best way to treat acute headache even by subjects suffering from severe idiopathic headache and seeking professional care in specialized clinics. Prescribed analgesics are underused by patients with serious episodic headache, which is precisely the group for which they are principally intended.

Adolescent↗
PubMed1997

Oral naltrexone treatment for cholestatic pruritus: a double-blind, placebo-controlled study.

BACKGROUND & AIMS: The efficacy of currently available therapeutic agents for cholestatic pruritus is often disappointing. The aim of this study was to assess the antipruritic effect of naltrexone, an oral opiate receptor antagonist. METHODS: Sixteen patients with pruritus of chronic cholestasis were randomized to receive naltrexone (4-week course of 50 mg naltrexone daily) or placebo. Pruritus, quality of sleep, fatigue (using visual analogue scales), side effects, and liver function were assessed every 2 weeks. Serum naltrexone and 6 beta-naltrexol concentrations in all patients and 5 healthy controls were measured during the first day of naltrexone treatment. RESULTS: Mean changes with respect to baseline were significantly different, in favor of the naltrexone group, for daytime itching (-54% vs. 8%; P < 0.001) and nighttime itching (-44% vs. 7%, P = 0.003). In 4 naltrexone-treated patients, side effects (transient in 3 cases) consistent with an opiate withdrawal syndrome were noted. No deterioration of the underlying disease was observed. Naltrexone and 6 beta-naltrexol levels did not differ between patients and controls, and there was no significant association with treatment response. CONCLUSIONS: For patients with cholestatic liver disease and itching, refractory to regular antipruritic therapy, oral naltrexone may be an effective and well-tolerated alternative.

Administration, Oral↗
PubMed1996

Bile acid structure and regulation of biliary protein secretion and composition in man.

To evaluate the effect of bile acid structure on total protein secretion and composition, 4 different bile acids, deoxycholic acid, chenodeoxycholic acid, cholic acid and ursodeoxycholic acid, in order of decreasing hydrophobicity, were infused intraduodenally in 5 cholecystectomized T-tube patients with interrupted enterohepatic circulation. Concentration and composition of biliary proteins were evaluated before and after acute substitution of the endogenous bile acid pool with each bile acid. Total biliary protein concentration and secretion increased progressively with increasing hydrophobicity of the infused bile acid and was highest for deoxycholic acid, followed by chenodeoxycholic acid, cholic acid and ursodeoxycholic acid. A significant increase in the 120 and 150 kDa protein bands on gel-electrophoresis was found after infusion with the more hydrophobic bile acids (deoxycholic acid and chenodeoxycholic acid). Quantitative and qualitative changes in biliary proteins, associated with the administration of bile acids that have different physico-chemical structures, may be relevant to the process of cholesterol crystal nucleation and the pathogenesis of gallstone formation.

Bile↗
PubMed1996

Effect of hypocholesterolemic doses of 17 alpha-ethinyl estradiol on cholesterol balance in liver and extrahepatic tissues.

This study was performed to investigate the effects of 17 alpha-ethinyl estradiol, a potent hypocholesterolemic agent at pharmacological doses, on cholesterol balance in the liver and extrahepatic tissues of the rat in vivo. Female Sprague-Dawley rats were treated with 17 alpha-ethinyl estradiol (5 mg/kg per day s.c. for 5 days) or with 4-aminopyrazolo(3,4-d) pyrimidine (20 mg/kg per day i.p. for 3 days). Both drug regimens suppressed plasma total and low density lipoprotein-cholesterol by more than 80%. Analysis of the kinetic parameters of low density lipoprotein transport did not show increased receptor activity in extrahepatic tissues during either treatment. 17 alpha-Ethinyl estradiol significantly increased low density lipoprotein tissue spaces and clearance rates in the liver, with a 5-fold increase in low density lipoprotein-receptor activity, whereas 4-aminopyrazolo(3,4-d)pyrimidine suppressed hepatic transport of low density lipoprotein probably due to a nospecific toxic effect. Treatment with 17 alpha-ethinyl estradiol markedly enhanced the hepatic expression of low density lipoprotein-receptor protein and mRNA despite a 7-fold increase in hepatic cholesteryl ester levels. Finally, treatment with both drugs increased cholesterol synthesis in several extrahepatic tissues, such as adrenals, ovaries, small bowel, and spleen. These findings confirm that 17 alpha-ethinyl estradiol at pharmacological doses markedly increases synthesis and expression of low density lipoprotein-receptor in the liver. Hypocholesterolemia, whether induced by activation of low density lipoprotein-receptors or by other mechanisms, fails to up-regulate low density lipoprotein transport in extrahepatic tissues, which rather respond by increasing local sterol synthesis. This suggests the occurrence of separate regulatory mechanisms for low density lipoprotein transport and cholesterol synthesis.

Adenine↗
PubMed1996

Effect of taurohyodeoxycholic acid on biliary lipid secretion in man: preliminary report.

Taurohyodeoxycholic acid and tauroursodeoxycholic acid were infused intraduodenally at a rate of 0.8 g/h for three hours in 3 cholecystectomized T-tube patients. Biliary lipid secretion and bile acid composition were evaluated before and after replacement of the endogenous bile acid pool with the two bile acids. As compared to basal values (2.78 +/- 1.67 mM/l), taurohyodeoxycholic acid induced a greater increase in the biliary concentration of phospholipids (4.12 +/- 1.23 mM/l) as compared to tauroursodeoxycholic acid (3.14 +/- 0.98 mM/l). Biliary cholesterol concentration after taurohyodeoxycholic acid (1.89 +/- 0.63 mM/l) was unchanged as compared to the pretreatment period (1.98 +/- 0.58 mM/l), while it decreased significantly after tauroursodeoxycholic acid (0.85 +/- 0.08 mM/I). Biliary cholesterol secreted per unit of bile acid was greater during taurohyodeoxycholic acid than during tauroursodeoxycholic acid, while the opposite was observed for the secretion of phospholipids.

Bile↗
PubMed1995

Regulation of hepatic cholesterol metabolism in the rat in vivo: effect of a synthetic fat-free diet on sterol synthesis and low-density lipoprotein transport.

A synthetic fat-free diet, previously shown to decrease hepatic cholesterol synthesis, was utilized to manipulate cholesterol balance in vivo in female Sprague-Dawley rats. A significant 65% decrease of hepatic cholesterol synthesis compared to controls was shown after 1 week of treatment, which remained constant during the following 3 weeks. The inhibitory effect of the diet was completely abolished by cholestyramine supplementation. At week 3 of the experimental diet, bile acid synthesis was reduced by 63%, this reduction being correlated with decreased recycling frequency of the bile acid pool. Hepatic clearance of low-density lipoprotein (LDL) was slightly decreased, with no changes in plasma cholesterol, hepatic LDL-cholesterol uptake and whole body LDL-cholesterol production. When cholesterol and saturated fatty acids were supplemented to the diets in the attempt to disclose alteration in LDL transport, LDL clearance was unaffected; plasma LDL-cholesterol and hepatic LDL-cholesterol uptake were increased, as a consequence of increased LDL-cholesterol production. On the other hand, hepatic cholesterol synthesis was further suppressed; bile acid synthesis was increased by cholesterol supplementation in the fat-free group, even if to subnormal levels. These findings suggest that: (1) bile acid synthesis is decreased by feeding a synthetic fat-free diet, probably due to slower recirculation of bile acids along the entero-hepatic axis in conditions of reduced functional need; (2) consequently, a significant reduction of hepatic cholesterol synthesis is observed with no changes in LDL-cholesterol uptake; (3) further supplementation of dietary cholesterol and saturated fats is compensated for by changes in the rates of cholesterol and bile acid synthesis, but not of LDL transport. The data confirm the existence of independent regulation for hepatic sterol synthesis and LDL transport in this species.

Animals↗