Biliary lipids, bile acid metabolism, gallbladder motor function and small intestinal transit during ingestion of a sub-fifty oral contraceptive

Is the oral contraceptive or hormone replacement therapy a risk factor for cholelithiasis: A systematic review and meta-analysis

BACKGROUND

Association between exogenous estrogen intake and cholelithiasis risk has been reported in several epidemiological studies, including oral contraceptive (OC) and hormone replacement therapy (HRT), while the results were controversial. This study aimed to perform a comprehensive meta-analysis of this issue.

METHODS

PUBMED, EMBASE, and Cochrane library database were searched up to October 2016. Two reviewers independently extracted data from eligible studies, relative risks (RRs), and/or odds ratios (ORs) with 95% confidence intervals (95% CIs) for the highest versus lowest categories of intake were adopted. Either a fixed- or a random-effects model was adopted to estimate overall RRs or ORs. Besides, subgroup and publication bias analyses were applied to explain the heterogeneity. An original study was also conducted to verify our conclusion.

RESULTS

A total of 19 studies with approximately 556,620 participants were included in this meta-analysis. The pooled RR of cholelithiasis for the highest versus the lowest categories was 1.59 (95% CI: 1.44-1.75), indicating that exogenous estrogen was positive associated with the intake of exogenous estrogen. However, the pooled RR of OC intake and cholelithiasis risk was 1.19 (95% CI: 0.97-1.45), and the RR for HRT was 1.79 (95% CI: 1.61-2.00).

CONCLUSION

The HRT was positively associated with the cholelithiasis risk, and the OC will not increase the risk of cholelithiasis.

The deletion of the estrogen receptor α gene reduces susceptibility to estrogen-induced cholesterol cholelithiasis in female mice

Compelling evidence has demonstrated that estrogen is a critical risk factor for gallstone formation and enhances cholesterol cholelithogenesis through the hepatic estrogen receptor α (ERα), but not ERβ. To study the lithogenic mechanisms of estrogen through ERα, we investigated whether the deletion of Erα protects against gallstone formation in ovariectomized (OVX) female mice fed a lithogenic diet and treated with 17β-estradiol (E2) at 0 or 6μg/day for 56days. Our results showed that the prevalence of gallstones was reduced from 100% in OVX ERα (+/+) mice to 30% in OVX ERα (-/-) mice in response to high doses of E2 and the lithogenic diet for 56days. Hepatic cholesterol secretion was significantly diminished in OVX ERα (-/-) mice compared to OVX ERα (+/+) mice even fed the lithogenic diet and treated with E2 for 56days. These alterations decreased bile lithogenicity by reducing cholesterol saturation index of gallbladder bile. Immunohistochemical studies revealed that ERα was expressed mainly in the gallbladder smooth muscle cells. High levels of E2 impaired gallbladder emptying function mostly through the ERα and cholecystokinin-1 receptor pathway, leading to gallbladder stasis in OVX ERα (+/+) mice. By contrast, gallbladder emptying function was greatly improved in OVX ERα (-/-) mice. This markedly retarded cholesterol crystallization and the growth and agglomeration of solid cholesterol crystals into microlithiasis and stones. In conclusion, the deletion of Erα reduces susceptibility to the formation of E2-induced gallstones by diminishing hepatic cholesterol secretion, desaturating gallbladder bile, and improving gallbladder contraction function in female mice.

Cholesterol cholelithiasis in pregnant women: pathogenesis, prevention and treatment

Epidemiological and clinical studies have found that gallstone prevalence is twice as high in women as in men at all ages in every population studied. Hormonal changes occurring during pregnancy put women at higher risk. The incidence rates of biliary sludge (a precursor to gallstones) and gallstones are up to 30 and 12%, respectively, during pregnancy and postpartum, and 1-3% of pregnant women undergo cholecystectomy due to clinical symptoms or complications within the first year postpartum. Increased estrogen levels during pregnancy induce significant metabolic changes in the hepatobiliary system, including the formation of cholesterol-supersaturated bile and sluggish gallbladder motility, two factors enhancing cholelithogenesis. The therapeutic approaches are conservative during pregnancy because of the controversial frequency of biliary disorders. In the majority of pregnant women, biliary sludge and gallstones tend to dissolve spontaneously after parturition. In some situations, however, the conditions persist and require costly therapeutic interventions. When necessary, invasive procedures such as laparoscopic cholecystectomy are relatively well tolerated, preferably during the second trimester of pregnancy or postpartum. Although laparoscopic operation is recommended for its safety, the use of drugs such as ursodeoxycholic acid (UDCA) and the novel lipid-lowering compound, ezetimibe would also be considered. In this paper, we systematically review the incidence and natural history of pregnancy-related biliary sludge and gallstone formation and carefully discuss the molecular mechanisms underlying the lithogenic effect of estrogen on gallstone formation during pregnancy. We also summarize recent progress in the necessary strategies recommended for the prevention and the treatment of gallstones in pregnant women.

MS-based metabolomics facilitates the discovery of in vivo functional small molecules with a diversity of biological contexts

In vivo small molecules as necessary intermediates are involved in numerous critical metabolic pathways and biological processes associated with many essential biological functions and events. There is growing evidence that MS-based metabolomics is emerging as a powerful tool to facilitate the discovery of functional small molecules that can better our understanding of development, infection, nutrition, disease, toxicity, drug therapeutics, gene modifications and host-pathogen interaction from metabolic perspectives. However, further progress must still be made in MS-based metabolomics because of the shortcomings in the current technologies and knowledge. This technique-driven review aims to explore the discovery of in vivo functional small molecules facilitated by MS-based metabolomics and to highlight the analytic capabilities and promising applications of this discovery strategy. Moreover, the biological significance of the discovery of in vivo functional small molecules with different biological contexts is also interrogated at a metabolic perspective.

The use of stable and radioactive sterol tracers as a tool to investigate cholesterol degradation to bile acids in humans in vivo

Alterations of cholesterol homeostasis represent important risk factors for atherosclerosis and cardiovascular disease. Different clinical-experimental approaches have been devised to study the metabolism of cholesterol and particularly the synthesis of bile acids, its main catabolic products. Most evidence in humans has derived from studies utilizing the administration of labeled sterols; these have several advantages over in vitro assay of enzyme activity and expression, requiring an invasive procedure such as a liver biopsy, or the determination of fecal sterols, which is cumbersome and not commonly available. Pioneering evidence with administration of radioactive sterol derivatives has allowed to characterize the alterations of cholesterol metabolism and degradation in different situations, including spontaneous disease conditions, aging, and drug treatment. Along with the classical isotope dilution methodology, other approaches were proposed, among which isotope release following radioactive substrate administration. More recently, stable isotope studies have allowed to overcome radioactivity exposure. Isotope enrichment studies during tracer infusion has allowed to characterize changes in the degradation of cholesterol via the "classical" and the "alternative" pathways of bile acid synthesis. Evidence brought by tracer studies in vivo, summarized here, provides an exceptional tool for the investigation of sterol metabolism, and integrate the studies in vitro on human tissue.

Is there a link between oestrogen therapy and gallbladder disease?

Cholelithiasis is the most common form of benign gallbladder disease that results in major heath expenditure. Female sex hormones are causally related to cholesterol gallstone disease, which are more common in women than in men. The risk of development of cholelithiasis is further enhanced by the use of exogenous female sex hormones and by pregnancy. Oestrogens are used in oral contraceptives and in hormone replacement therapy (HRT). Oral contraceptives do not pose a greater risk for gallbladder disease. The findings from two randomised, controlled trials, the Heart and Oestrogen/Progestin Replacement Study and the Women's Health Initiative postmenopausal hormone trial, unequivocally confirm that oral oestrogen use in postmenopausal women is causally associated with gallbladder disease, and the magnitude of the effect is not influenced greatly by the presence or absence of progestins. A cautious approach should be observed when prescribing HRT. Women must be informed about the effect of oestrogen use on increased risk of benign gallbladder disease. HRT should be used in the lowest possible dose for the shortest possible time. Women harbouring asymptomatic gallstones should not receive oestrogens because of the possibility of developing cholecystitis.

P-glycoprotein attenuating effect of human intestinal fluid

PURPOSE

To evaluate the effect of human intestinal fluid (HIF) on P-glycoprotein (P-gp)-mediated efflux.

METHODS

HIF was obtained from eight healthy volunteers by duodenal aspiration. HIF was applied at different concentrations (0-75%) to the apical compartment of the Caco-2 system. Cyclosporin A (CsA) was used as a model compound for P-gp mediated efflux.

RESULTS

When the bidirectional transport of CsA across Caco-2 monolayers was assessed, a significant polarity in transport could be observed, the absorptive transport being much lower than the secretory transport. Inclusion of HIF resulted in a moderate increase of the absorptive transport, as well as a significant concentration dependent decrease of the secretory transport, without compromising the integrity of the monolayer. Interestingly, a possible gender difference could be detected as inclusion of HIF obtained from female subjects resulted in a decreased absorptive transport of CsA, whereas inclusion of HIF obtained from male subjects resulted in an increased absorptive transport. The P-gp modulating effect of HIF is not caused by a lack of glucose as an energy source for the efflux mechanism when high concentrations of HIF were present in the buffer used.

CONCLUSIONS

The results of this study indicate that the contribution of P-gp efflux carriers may be overestimated when using salt buffer solutions as transport media. Additionally, it can be concluded that (presently unidentified) components of HIF may attenuate the P-gp mediated intestinal efflux. The clinical significance of this modulating effect remains to be investigated.

Influence of oral contraceptives on fasting gallbladder volume

A total of 615 healthy fertile women (518 pill users and 97 non-users) were examined by real-time ultrasonography for fasting gallbladder volume, gallstones and biliary dysmorphism. None of the six examined combinations of oral contraceptives appeared to influence fasting gallbladder volume significantly. When fasting gallbladder volumes were reanalyzed according to the presence or absence of recognized biliary risk factors, significant modifications were detected, in both pill users and non-users. These changes related only to age and parity. Relative risks of cholelithiasis and biliary dysmorphism were not affected by contraceptive treatment.

Oral contraceptives and the risk of gallbladder disease: a meta-analysis

OBJECTIVES

This study was designed to assess the risk of gallbladder disease due to oral contraceptive use by conducting a thorough literature review.

METHODS

Controlled epidemiologic studies published through March 1992 were systematically searched and evaluated. Of 25 studies (27 publications), 9 could stand the test of critical appraisal with respect to validity. Restriction to these studies was judged to circumvent publication bias at the same time.

RESULTS

Oral contraceptive use is associated with a slightly and transiently increased rate of gallbladder disease. The results of six selected studies in which asymptomatic women were screened for gallstones were strikingly similar. Pooling of these results yielded an odds ratio, for ever vs never oral contraceptive use, of 1.36. A dose-effect relationship was indicated, suggesting that modern low-dose oral contraceptives are safer than older formulas, but an effect cannot be excluded.

CONCLUSIONS

Considering the large efforts already devoted to this exposure-disease relationship, the probably weak effect, and the rapidly changing formulas of oral contraceptives, the authors suggest that the safety of new oral contraceptives be evaluated by studying bile saturation and biliary function rather than by waiting for gallbladder disease to develop.

Lipid metabolism effects with desogestrel-containing oral contraceptives

Desogestrel is a gonane progestogen that in early studies had an improved ratio between desired progestational effects and undesired androgenic effects. A review of more than 50 clinical studies suggests that desogestrel differs from progestins currently used in oral contraception in that it does not interfere with the estrogen effects on lipoprotein metabolism. This profile is attributable to the high selectivity of desogestrel.

Different hepatobiliary effects of oral and transdermal estradiol in postmenopausal women

Estrogen-replacement therapy is important for the prevention of postmenopausal osteoporosis. However, oral synthetic and conjugated estrogens increase biliary cholesterol saturation index and risk of gallstone disease. To examine whether transdermal estrogen administration could avoid these adverse effects, 17 postmenopausal women were treated with transdermal estradiol (Estraderm TTS; Ciba-Geigy, Arnhem, The Netherlands), 100 micrograms/day for 4 weeks, and after 1 month without therapy, with oral estradiol (Progynova; Schering, Weesp, The Netherlands), 2 mg/day for 4 weeks. The increase in the serum estradiol level was much higher during transdermal than oral estradiol administration. On the contrary, the increase in the serum estrone level was much more pronounced during oral treatment. Both modes of treatment led to a similar reduction of urinary calcium excretion. A highly significant decrease in serum phosphate levels was found during transdermal therapy. Biliary cholesterol saturation index did not change during transdermal therapy (mean +/- SEM, 1.25 +/- 0.06 before and 1.22 +/- 0.07 at the end of transdermal therapy; P = NS). A slight increase in cholesterol saturation index that did not reach statistical significance was found during oral therapy (1.28 +/- 0.09 before and 1.36 +/- 0.09 during oral treatment). However, the subgroup of women with strong increases in serum estrone levels during oral estradiol therapy (greater than 0.5 pmol/mL; n = 8) generally had increased biliary cholesterol saturation index, a decrease in relative percentage chenodeoxycholic acid in bile, and increased serum sex hormone-binding globulin levels during oral treatment. Cholesterol monohydrate crystals were never found in duodenal biles during either treatment. This study indicates that transdermal estradiol does not induce lithogenic bile. On the contrary, oral estradiol leads to lithogenic bile in a subgroup of women with strong increases in serum estrone levels during oral treatment.

Mechanisms of gallstone formation in women. Effects of exogenous estrogen (Premarin) and dietary cholesterol on hepatic lipid metabolism

Our aim was to define mechanisms whereby conjugated estrogens (Premarin, exogenous estrogen; Ayerst Laboratories, New York) increase the risk of developing cholesterol gallstones and to determine the role, if any, of dietary cholesterol. We studied gallbladder motor function, biliary lipid composition and secretion, cholesterol absorption, cholesterol synthesis and esterification by peripheral blood mononuclear cells, the clearance of chylomicron remnants, and bile acid kinetics in 29 anovulatory women. 13 were studied on both a low (443 +/- 119 mumol/d) and high (2,021 +/- 262 mumol/d) cholesterol diet. Premarin increased the lithogenic index of bile (P less than 0.05), increased biliary cholesterol secretion (P less than 0.005), lowered chenodeoxycholate (CDCA) pool (P less than 0.001) and synthesis (P less than 0.05), altered biliary bile acid composition [( CA + DCA]/CDCA increases, P less than 0.005), stimulated cholesterol esterification (P less than 0.03), and enhanced the clearance of chylomicron remnants (P = 0.07). Increases in dietary cholesterol stimulated the biliary secretion of cholesterol (P = 0.07), bile acid (P less than 0.05), phospholipid (P = 0.07), and as a result, did not alter lithogenic index. The reduction in CDCA pool and synthesis by Premarin was reversed by increasing dietary cholesterol. Off Premarin, only 24% of the increase in cholesterol entering the body in the diet was recovered as biliary cholesterol or newly synthesized bile acid. On Premarin, 68% of this increase in cholesterol was recovered as these biliary lipids. We conclude that Premarin increases biliary cholesterol by enhancing hepatic lipoprotein uptake and inhibiting bile acid synthesis. These actions of Premarin divert dietary cholesterol into bile.

Prevention of gallstone recurrence by non-steroidal anti-inflammatory drugs

In laboratory animals, non-steroidal anti-inflammatory drugs (NSAIDs) are reported to inhibit diet-induced gallstone formation. To see if these drugs had a similar effect in man, 82 patients who had taken part in a comparison of ursodeoxycholic acid, placebo, and diet for prevention of gallstone recurrence were sent questionnaires about their use of NSAIDs during the period of the trial. 75 replied. After a mean follow-up of 33 (SEM 4) months none of the 12 regular users of NSAIDs had had gallstone recurrences, compared with 20 of the 63 who never or rarely used these drugs (p less than 0.02).