Glycodeoxycholic Acid (GDCA): A Comprehensive Reference
1. Identity and Chemical Characterization
1.1 Nomenclature and Chemical Identity
Glycodeoxycholic acid is a bile acid derived from deoxycholic acid and glycine. It is a bile salt formed in the liver by conjugation of deoxycholate with glycine, usually as the sodium salt. The compound is formally known by its CAS Type 1 name as Glycine, N-((3alpha,5beta,12alpha)-3,12-dihydroxy-24-oxocholan-24-yl)-, with a CAS registry number of 360–65–6 for the anhydrous form and 1079043-81-4 for the monohydrate form. Its most commonly used abbreviation in the scientific literature is GDCA. Its formal IUPAC-adjacent name is N-[(3alpha,5beta,12alpha)-3,12-dihydroxy-24-oxocholan-24-yl]-glycine. Its molecular formula is C26H43NO5 (PubChem CID 3035026). The compound is also known by the synonym glycodeoxycholate when referring to its anionic (salt) form, and this designation is used in the Medical Subject Headings (MeSH) database with descriptor entry D006002.
1.2 Structural Features
Bile salts contain a steroid core structure, composed of a large family of molecules including four fused rings, three hydroxyl moieties, and a five- or eight-carbon external chain directly linked to the carboxylic acid group at the C terminal. The steroid core structure contains three cyclohexane rings (the A, B, and C rings) and one cyclopentane ring (the D ring), which remain unchanged for all bile salts, though the number and orientation of hydroxyl groups and the carbon side chain vary. GDCA specifically bears hydroxyl groups at the 3α and 12α positions of the steroid nucleus, distinguishing it from other glycine-conjugated bile acids. The glycine moiety is linked via an amide bond to the C-24 carboxylic acid terminus of the deoxycholate backbone.
The number and assembly behavior of functional hydroxyl groups are the most important determinants of the amphiphilic characteristics of bile salts. Among naturally occurring bile acids, lithocholic acid exhibits the highest hydrophobicity, and glycodeoxycholic acid is among the more hydrophilic members of the family.
1.3 Common Forms and Preparations
GDCA is encountered in several physicochemical forms. The free acid form (CAS 360-65-6) and the monohydrate (CAS 1079043-81-4) are the predominant research-grade materials. The compound acts as a detergent to solubilize fats for absorption and is itself absorbed; it is classified pharmacologically as a cholagogue and choleretic. In analytical and pharmaceutical contexts, a deuterium-labelled stable isotope form (GDCA-d4, CAS 1069132-37-1) is used as an internal standard for mass spectrometric quantification. GDCA is also metabolized in vivo to conjugated derivatives including glycodeoxycholate 3-O-glucuronide (GDCA-3G) and glycodeoxycholate 3-O-sulfate (GDCA-S), which have become important analytical and pharmacological tools in their own right.
In commercially available oxgall powders used for microbiological testing, glycodeoxycholic acid is one of nine individual bile acids consistently detectable, together with taurocholic acid, glycocholic acid, taurodeoxycholic acid, taurochenodeoxycholic acid, glycochenodeoxycholic acid, cholic acid, chenodeoxycholic acid, and deoxycholic acid.
2. Natural Origin and Biosynthesis
2.1 Endogenous Production in Humans
Bile acids are produced by host hepatocytes from cholesterol and are released into the gastrointestinal tract where they aid in the emulsification and absorption of dietary fat. Once host-derived primary bile acids — namely cholic acid (CA) and chenodeoxycholic acid (CDCA) in humans — enter the gastrointestinal tract, the indigenous gut microbiota transforms them into secondary bile acids; over 50 chemically distinct microbial-derived secondary bile acids have been identified.
Deoxycholate biosynthesis begins with the enzymatic oxidation, isomerization, and reduction of cholesterol in the liver to form cholic acid. In the liver, cholic acid is then chemically linked to one of two amino acids — taurine or glycine — to form conjugated cholic acids. These conjugated cholic acids are stored in the gall bladder until food consumption. After food consumption, bile is released into the intestine, where the conjugated cholic acid molecules undergo dehydroxylation mediated by enzymes produced by intestinal microflora to form conjugated deoxycholate, which is then deconjugated to form free deoxycholate. GDCA thus arises when the liver re-conjugates the secondary bile acid deoxycholic acid (itself a product of microbial 7α-dehydroxylation of cholic acid) with glycine. The majority of the human bile acid pool is in its conjugated form throughout the enterohepatic cycle, predominantly conjugated to glycine.
GDCA is a glycine-conjugated form of the secondary bile acid deoxycholic acid. Glycodeoxycholic acid is produced by the human body and can be found in the serum. The biosynthesis of glycodeoxycholic acid is dependent on microbial metabolism, which may be inhibited by nonsteroidal anti-inflammatory drugs.
2.2 Occurrence in Bile
In bile acid-depleted rabbit models used to study feedback regulation, the endogenous bile acid pool was found to comprise approximately 90% glycodeoxycholic acid and 10% glycocholic acid. In normal human bile, GDCA is a quantitatively significant component of the conjugated bile acid pool, along with glycochenodeoxycholic acid and glycocholic acid, with the specific proportions depending on diet, gut microbiota composition, and individual physiology.
3. Traditional and Historical Use
3.1 Historical Context in Eastern Medicine
Glycodeoxycholic acid, as a conjugated bile acid, has a history rooted in traditional and modern medicinal practices. Bile acids such as glycodeoxycholic acid have been valued for centuries, especially in Eastern medicine, where animal bile was often incorporated into remedies intended to promote digestive health, liver function, and detoxification. In ancient Chinese medicine, bile extracts were sometimes combined with herbal formulations to address disorders related to bile flow, jaundice, and various digestive complaints. The rationale behind these remedies was the belief that bile acids could support the body's natural detoxification processes and enhance nutrient absorption.
It is important to emphasize that GDCA was not isolated or identified as a discrete compound in pre-modern medical practice. The historical use described above refers to the use of whole bile preparations — from ox, bear, or other animals — which contained mixtures of bile acids including GDCA among many other constituents. Historically, bile acids and their derivatives have been utilized in traditional medicine and nutritional products to support digestive health, especially in populations with compromised bile production or malabsorption syndromes. No traditional medical system identified or named GDCA specifically; its characterization is an achievement of modern analytical biochemistry.
3.2 Transition to Modern Use
As clinical understanding advanced, glycodeoxycholic acid and similar bile acids began to be appreciated for their role in emulsifying dietary fats, thereby improving the absorption of fat-soluble vitamins and essential nutrients. The formal characterization of conjugated bile acid species, including GDCA, followed the development of chromatographic and mass spectrometric analytical methods in the twentieth century. The MeSH entry history for GDCA records that the compound was indexed under broader headings from 1966 and given its own MeSH descriptor in 1991, reflecting its growing independent recognition in the biomedical literature.
4. Key Constituents, Active Compounds, and Mechanisms of Action
4.1 Role as a Signaling Molecule — FXR and TGR5 Receptor Activation
Bile acids are signal molecules and metabolic integrators that activate nuclear farnesoid X receptor (FXR) and membrane Takeda G protein-coupled receptor 5 (TGR5; also known as G protein-coupled bile acid receptor 1) to regulate glucose, lipid, and energy metabolism. GDCA participates in this signaling framework as a conjugated secondary bile acid.
Bile acid supplementation exerts negative feedback on bile acid synthesis via the Farnesoid X receptor (FXR), which prevents accumulation of toxic intermediates while restoring bile flow and the gastrointestinal uptake of fat and fat-soluble vitamins. As a potent FXR ligand, GDCA exerts its action through FXR activation, leading to bile acid synthesis regulation.
In the liver, bile acids activate FXR resulting in upregulation of SHP (small heterodimer partner), an inhibitor of bile acid synthesis, gluconeogenesis, and fatty acid synthesis. In the intestine, bile acid activation of FXR upregulates FGF-15/19 and ultimately inhibits bile acid synthesis. TGR5 is also anti-inflammatory via inhibition of NF-κB-mediated proinflammatory cytokine production, induction of nitric oxide production to reduce monocyte adhesion in vascular endothelial cells, induction of endothelial nitric oxide synthase (eNOS) in liver sinusoidal endothelial cells, and inhibition of atherosclerosis by reducing macrophage inflammation and lipid loading.
4.2 Feedback Inhibition of Bile Acid Synthesis (CYP7A1 Suppression)
Glycodeoxycholic acid (GDCA) is a glycine-conjugated form of the secondary bile acid deoxycholic acid. It induces a reversible, concentration-dependent reduction in myogenic tone in rats and decreases expression of the gene encoding the cytochrome P450 (CYP) isoform 7A1 (CYP7A1) in rabbits.
Feedback regulation of derepressed hepatic bile acid biosynthesis was studied individually with glycocholic, glycodeoxycholic, and glycoursocholic acids by infusion into bile acid-depleted rabbits. In this model, the endogenous bile acid pool consisted of 90% glycodeoxycholic acid and 10% glycocholic acid. Replacement of the bile acid pool with glycocholic acid or glycodeoxycholic acid at a rate equivalent to the hepatic endogenous bile acid flux inhibited endogenous biosynthesis by 40%. In contrast, glycoursocholic acid, the 7β-hydroxy epimer of glycocholic acid, failed to suppress synthesis, demonstrating the structural specificity required for this feedback response. These findings are from animal (rabbit) studies and should not be directly extrapolated to human physiology without further investigation.
4.3 Detergent and Fat Emulsification Properties
GDCA acts as a detergent to solubilize fats for absorption and is itself absorbed. As a bile acid conjugate formed by the combination of deoxycholic acid and glycine, GDCA plays a role in the emulsification and absorption of dietary fats and fat-soluble vitamins. The amphiphilic architecture of the molecule — combining a hydrophobic steroid nucleus with a hydrophilic glycine head group — enables it to form micelles that incorporate dietary lipids, cholesterol, and fat-soluble vitamins (A, D, E, K), facilitating their uptake through intestinal epithelium.
4.4 Vascular and Cardiovascular Effects
Bile acids regulate cardiovascular function via diverse mechanisms. Although in both health and disease serum glycine-conjugated bile acids are more abundant than taurine-conjugated bile acids, their effects on myogenic tone, a key determinant of systemic vascular resistance, had not been well characterized prior to focused study. Research published in PLOS ONE (Khurana et al., 2012) established that GDCA induces a reversible, concentration-dependent reduction in myogenic tone in rat resistance arteries, indicating a physiological role for GDCA in regulating vascular tone. These findings derive entirely from animal (rat) experiments, and no human clinical data on GDCA's hemodynamic effects have been published to date.
4.5 OATP Transporter Substrate Activity
A metabolite of GDCA, glycodeoxycholate 3-O-glucuronide (GDCA-3G), has been identified as an important substrate of hepatic drug uptake transporters. In vitro, both GCDCA-3G and GDCA-3G showed at least 6 times higher uptake by OATP1B1 than by OATP1B3 or OATP2B1. These data indicate that the hepatic uptake of GCDCA-3G and GDCA-3G is predominantly mediated by OATP1B1. GCDCA-3G, in particular, is a highly sensitive and specific OATP1B1 biomarker in humans. Glycochenodeoxycholate 3-O-glucuronide and glycodeoxycholate 3-O-glucuronide are circulating OATP substrates and promising candidates as endogenous biomarkers for organic anion transporting polypeptide (OATP)-mediated drug–drug interaction (DDI) risk assessment.
GDCA sulfate (GDCA-S) has been established as a substrate of OATP1B1, OATP1B3, and sodium-dependent taurocholic acid cotransporting polypeptide (NTCP) transfected into human embryonic kidney 293 cells, with minimal uptake evident for other solute carriers.
5. Scientific Evidence by Area of Use
5.1 Bile Acid Synthesis Defects — Clinical Evidence
Summary of evidence strength: Single case report; very preliminary human data.
3β-hydroxy-Δ5-C27-steroid-oxidoreductase (3β-HSD) deficiency is a bile acid synthesis disorder that leads to the absence of normal primary bile acids and the accumulation of abnormal bile acids. This results in cholestatic jaundice, fat-soluble vitamin deficiency, acholic or fatty stools, and failure to thrive. Bile acid supplementation is used to treat this condition and its symptoms.
A 2024 case report detailed the case of a 28-year-old woman diagnosed with 3β-HSD-deficiency, who was treated with glycine-conjugated deoxycholic acid (gDCA). gDCA treatment successfully restored normal bile acid levels, improved body weight by reducing fat malabsorption, and was well-tolerated with no observed liver problems or side effects. Since the majority of the human bile acid pool is in its conjugated form throughout the enterohepatic cycle, predominantly conjugated to glycine, the authors concluded that glycine-conjugated DCA was a physiologically appropriate therapeutic choice.
This evidence is limited to a single case report published in Frontiers in Pediatrics (2024). No randomized controlled trials, cohort studies, or even case series of GDCA as a therapeutic agent exist in the peer-reviewed literature. The clinical application described was an off-label, experimental use motivated in part by the high cost of the standard treatment (cholic acid).
5.2 Acetaminophen-Induced Acute Liver Failure — Biomarker Evidence
Summary of evidence strength: Observational human study; moderate biomarker value demonstrated, but not a therapeutic agent in this context.
Acetaminophen-induced acute liver failure (ALF) remains a major clinical problem. Although a majority of patients recover after severe liver injury, a subpopulation proceeds to ALF. Bile acids are generated in the liver and accumulate in blood during liver injury and, as such, have been proposed as biomarkers for liver injury and dysfunction. The goal of one pivotal study was to determine whether individual bile acid levels could predict outcome in patients with APAP-induced ALF. Serum bile acid levels were measured using mass spectrometry.
Bile acid levels were elevated 5–80-fold above control values in injured patients on day 1 after the overdose and decreased over the course of hospital stay. Interestingly, glycodeoxycholic acid (GDCA) was significantly increased in non-surviving AALF patients compared with survivors.
GDCA values obtained at peak ALT and from Day 1 of admission indicated that GDCA could predict survival by receiver-operating characteristic analysis (AUC = 0.70 for Day 1, AUC = 0.68 for peak ALT). AALF patients also had significantly higher levels of serum bile acids than patients with active cholestatic liver injury. These data suggest measurements of GDCA in this patient cohort modestly predicted outcome and may serve as a prognostic biomarker.
Increases in serum bile acid levels in man during cholestatic liver injury (as well as other forms of liver injury) are likely an effect of liver injury and dysfunction, but not a cause, and do not directly result in cell death. Although increased serum bile acid levels may affect pathology in some models, serum bile acid concentrations alone are likely insufficient to directly cause injury in vivo.
In human studies, glycodeoxycholic acid levels are reported as a prognostic biomarker in acetaminophen-induced acute liver failure, and total serum bile acids were shown to be elevated in workers exposed to compounds in organic solvents. The evidence in this area positions GDCA as a biomarker of liver injury severity rather than as a therapeutic agent.
5.3 Drug-Induced Liver Injury (DILI) — Biomarker Evidence
Summary of evidence strength: Preliminary human observational data; further validation required.
A systematic search for relevant studies found 8 studies reporting observational data assessing bile acids as a biomarker of liver function related to DILI. In 5 animal studies and an in vitro investigation, the potential utility of bile acids as non-invasive markers of impaired hepatobiliary transport or injury due to specific drugs was described. In human studies, glycodeoxycholic acid levels are reported as a prognostic biomarker in acetaminophen-induced acute liver failure, and total serum bile acids were shown to be elevated in workers exposed to organic solvents. Previous studies have not compared bile acid profiles in DILI with those in other types of acute liver injury meeting the same diagnostic criteria.
5.4 OATP1B1 Drug Transport — Endogenous Biomarker Evidence
Summary of evidence strength: Clinical pharmacology studies in humans; biomarker utility demonstrated but not yet in routine clinical practice.
Endogenous biomarkers of drug transporters are promising tools to evaluate in vivo transporter function and potential alterations in the pharmacokinetics of their substrates. GDCA-3G, the glucuronide conjugate of GDCA, has been evaluated in human clinical pharmacology studies as an endogenous biomarker of OATP1B1-mediated hepatic drug uptake.
Among bile acids and their conjugates, glycochenodeoxycholate and glycodeoxycholate 3-O-glucuronides (GCDCA-3G and GDCA-3G) showed Cmax increases with geometric mean ratio (95% confidence interval) of 1.58 (1.13–2.22) and 1.49 (1.21–1.83), respectively, consistent with previous reports from low-dose rifampin co-administration and pharmacogenetic studies.
Two bile acid glucuronides, glycodeoxycholate 3-O-glucuronide (GDCA-3G) and glycochenodeoxycholate 3-O-glucuronide (GCDCA-3G), have been identified as OATP1B1 substrates and highly sensitive and specific endogenous biomarkers of OATP1B1 phenotype. GDCA-3G and GCDCA-3G had 6-fold higher OATP1B1-mediated hepatic uptake compared with OATP1B3 and OATP2B1. A genotype–phenotype relationship has demonstrated approximately 6-fold increases in systemic exposure of GDCA-3G in those with the SLCO1B1 c.521CC genotype relative to the c.521 TT genotype.
GCDCA-3G and GDCA-3G are two promising biomarkers that may capture weak OATP1B inhibition in addition to coproporphyrin I/III. Changes in the activity of transporters in humans can alter the pharmacokinetics of their substrates, thereby potentially altering efficacy and/or safety profiles.
5.5 Colorectal Cancer Risk — Observational and Epidemiological Evidence
Summary of evidence strength: Observational, prospective, and metabolomic data suggesting association; does not establish causation; mechanistic evidence largely from animal or cell studies.
Serum concentration of glycodeoxycholic acid, a downstream microbial metabolite of cholic acid, is strongly associated with an increased risk of proximal colorectal cancer among women.
Because fecal bile acids can be absorbed into the bloodstream through the intestine, plasma levels of seven binding bile acid metabolites — including glycocholic acid, taurocholic acid, glycochenodeoxycholic acid, taurochenodeoxycholic acid, glycohyocholic acid, glycodeoxycholic acid, and taurodeoxycholic acid — were positively associated with CRC risk before CRC diagnosis in a prospective case-control study.
The plasma levels of 7 conjugated bile acid metabolites, including glycocholic acid, taurine-conjugated cholic acid, glycodeoxycholic acid, taurochenodeoxycholic acid, and taurodeoxycholic acid, were positively correlated with risk of colon cancer. These are epidemiological associations and do not establish that GDCA directly causes colorectal cancer. The degree to which circulating GDCA levels independently predict cancer risk, as opposed to reflecting overall secondary bile acid load or gut microbial dysbiosis, has not been established.
5.6 Asthma — Metabolomic Association
Summary of evidence strength: Single metabolomic study; very preliminary and association-only.
GDCA levels are increased in the plasma of patients with asthma. This finding derives from a metabolomic endotyping study (Comhair et al., Journal of Immunology, 2015) and represents an observed association between circulating GDCA and asthma, without mechanistic elucidation or therapeutic implication. No interventional or clinical therapeutic studies have evaluated GDCA in asthma.
5.7 Liver Disease Profiling — Metabolomics and Bile Acid Panels
Summary of evidence strength: Observational/cross-sectional data from biomarker studies; GDCA is a component rather than the primary analyte of interest.
In studies of bile acid profiles in patients with non-alcoholic steatohepatitis (NASH), liver fibrosis, and cirrhosis, a panel of 23 bile acids including glycodeoxycholic acid was significantly increased in liver disease patients compared to healthy controls. GDCA's role in these studies is as one of multiple bile acid markers of hepatobiliary dysfunction, rather than as a therapeutic target or intervention.
6. Body Systems and Health Areas
6.1 Hepatobiliary System
GDCA is most directly relevant to the hepatobiliary system. Bile acids are generated in the liver and accumulate in blood during liver injury, and as such, have been proposed as biomarkers for liver injury and dysfunction. GDCA's serum levels reflect the functional state of hepatocyte bile acid export mechanisms, enterohepatic circulation integrity, and cholestatic burden. Its elevation in acute liver failure, cholestasis, NASH, and liver fibrosis marks it as a sensitive indicator of hepatocellular compromise.
6.2 Gastrointestinal System
GDCA contributes to fat digestion and vitamin absorption within the small intestine. The gut-to-liver axis plays a critical role in the transformation of primary bile acids to secondary bile acids, in the regulation of bile acid synthesis to maintain composition within the bile acid pool, and in the regulation of metabolic homeostasis to prevent hyperglycemia, dyslipidemia, obesity, and diabetes. GDCA contributes to the enterohepatic circulation's capacity to maintain lipid homeostasis and absorb fat-soluble nutrients.
6.3 Gut Microbiome
Because the formation of deoxycholate — the aglycone precursor to GDCA — depends entirely on microbial 7α-dehydroxylation of primary bile acids, the levels of GDCA in bile and serum are an indirect readout of gut microbiome composition and activity. Over 50 chemically distinct microbial-derived secondary bile acids have been identified, and both primary and secondary bile acids can act as signaling molecules, exerting their effects by activating bile acid-activated receptors, including TGR5 and FXR.
6.4 Cardiovascular System
GDCA has been shown in animal experiments to influence vascular smooth muscle tone. Bile acids regulate cardiovascular function via diverse mechanisms. The demonstration that GDCA induces a reversible, concentration-dependent reduction in myogenic tone in rat resistance arteries implicates it as a potential endogenous vasodilatory signal, though this work is preliminary and confined to animal models.
6.5 Metabolic System
Bile acids, acting through FXR and TGR5, serve as metabolic integrators regulating glucose, lipid, and energy metabolism. GDCA, as a functionally active bile acid in the circulating pool, participates in these regulatory functions. Its elevation in metabolic disease states such as NAFLD/MAFLD has been documented in metabolomic profiling studies.
6.6 Respiratory System
Elevated plasma GDCA has been observed in asthma patients in at least one metabolomic study. The mechanistic basis of this association is not established, and no therapeutic studies in respiratory disease have been conducted with GDCA.
7. Dosage Forms and Dosages Reported in Studies
GDCA has not been developed as a licensed pharmaceutical or dietary supplement in any major regulatory jurisdiction, and consequently there are no standardized dosage recommendations. The available dosage information derives exclusively from isolated case report and research contexts:
- Bile acid synthesis defect (3β-HSD deficiency): A 28-year-old woman with 3β-HSD-deficiency was treated with glycine-conjugated deoxycholic acid (gDCA). The treatment successfully restored normal bile acid levels, improved body weight by reducing fat malabsorption, and was well-tolerated. To minimize potential side effects and ensure efficient bile acid pool retention, gDCA therapy was initiated gradually. Specific milligram dosages per kilogram body weight for this case were not extracted from available sources.
- Comparative context — standard bile acid synthesis defect therapy: In a pediatric case series of 3β-HSD deficiency patients, five patients were treated with cholic acid and chenodeoxycholic acid at 7 mg/kg/day of each; seven received chenodeoxycholic acid only at 7–18 mg/kg/day; and one received cholic acid alone at 8 mg/kg/day. These dosages pertain to related bile acids used as standard treatment, not to GDCA specifically, and are provided for comparative context.
- Research/analytical use: In cell-based research, GDCA has been applied at concentrations such as 100 µM over 24-hour periods to study gene expression in hepatocellular carcinoma cell lines, as reported in one 2025 abstract from Advanced Science. These are in vitro experimental concentrations, not clinical dosages.
No dose-ranging, pharmacokinetic, or dose-escalation studies for GDCA as an administered agent have been published in the peer-reviewed literature.
8. Safety Considerations and Drug Interactions
8.1 Endogenous Tolerability
No signs of side effects have been observed in the patient treated with gDCA, nor in healthy volunteers who received gDCA in a prior project. The supposed hepatotoxic side effects of bile acid treatment have not been very well characterized. Jaundice, often self-limiting, and giant cell hepatitis have been mentioned in both children and adults receiving bile acid therapy.
The side effects of chenodeoxycholic acid (CDCA) therapy have primarily been shown in the bile acid biosynthesis defect cerebrotendinous xanthomatosis (CTX), in which cholestasis may occur as part of the disease itself. Whether GDCA carries similar risks under pathological conditions is not yet established.
8.2 Hepatotoxicity in Cholestasis
Glycodeoxycholic acid induces hepatocyte necrosis and autophagy in patients with obstructive cholestasis. This toxicity is believed to be concentration-dependent and relevant specifically under conditions of impaired bile flow, where intrahepatic bile acid concentrations rise dramatically. If intrahepatic bile acid accumulation is the major cause of injury during cholestasis, the source of accumulation must be due to either rupture of the biliary tracts where bile acids are present in millimolar quantities, or direct inhibition of bile acid export from hepatocytes. Under physiological serum concentrations, GDCA is not considered directly hepatotoxic; it is the pathological accumulation that is implicated in cell injury.
8.3 Drug–Drug Interaction Potential via OATP Transporter Inhibition
Changes in the activity of transporters in humans can alter the pharmacokinetics of their substrates, thereby potentially altering efficacy and/or safety profiles. It is therefore critical to understand the potential for new molecular entities to interact with drug transporters. One such transporter subfamily is organic anion transporting polypeptide 1B (OATP1B), particularly OATP1B1 and OATP1B3, which are accountable for the hepatic disposition and elimination of many marketed drugs such as statins.
The sensitivity (98–99%) and specificity (100%) of GDCA-3G as a phenotyping biomarker peaked at a cutoff value of 180 ng/mL for men and 90 ng/mL for women. In haplotype-based analysis, SLCO1B1*5 and *15 were associated with reduced, and SLCO1B1*1B, *14, and *35 with increased OATP1B1 function. This pharmacogenetic data implies that patients carrying reduced-function SLCO1B1 alleles will have impaired hepatic clearance of GDCA-3G, leading to elevated plasma concentrations. These findings also mean that drugs capable of inhibiting OATP1B1 (such as rifampin, ciclosporin, and some statins at high doses) may displace GDCA and its conjugates from normal hepatic uptake pathways, potentially elevating circulating GDCA levels and affecting the pharmacokinetics of other OATP1B1 substrates.
8.4 NSAIDs and Biosynthesis Inhibition
The biosynthesis of glycodeoxycholic acid is dependent on microbial metabolism, which may be inhibited by nonsteroidal anti-inflammatory drugs. Chronic NSAID use, by altering the gut microbiota or directly modulating microbial bile acid-metabolizing enzymes, may theoretically reduce endogenous GDCA production. This observation is based on limited published data, and its clinical significance has not been formally evaluated.
8.5 Evidence Limitations on Safety
The overall evidence base for the safety of exogenously administered GDCA is extremely limited: it consists of one case report describing absence of hepatotoxic side effects in a single patient and healthy volunteers. No systematic safety studies, dose-finding toxicology assessments, or long-term safety registries for GDCA as an administered agent have been published. The distinction between GDCA as an endogenous metabolite — naturally present in bile and serum — and GDCA as an exogenously administered agent is important; endogenous physiological levels do not imply therapeutic doses are safe across all populations and conditions.
9. Current Research Status and Emerging Applications
GDCA is an active subject of research across several fields. In clinical pharmacology, GDCA-3G is being validated as a sensitive and non-invasive endogenous biomarker for assessing OATP1B1 function and predicting drug–drug interaction risk in early-phase clinical trials, with the aim of eventually replacing or supplementing formal inhibitor–probe drug studies. In hepatology, GDCA profiling by mass spectrometry forms part of broader serum bile acid panels used to characterize liver disease severity and monitor therapeutic response. In oncology, the epidemiological signal linking elevated circulating GDCA to colorectal cancer risk is the subject of mechanistic investigation, though causality is not established. In rare pediatric disease, the single published case report of GDCA as an alternative treatment for 3β-HSD deficiency has opened a line of inquiry into glycine-conjugated secondary bile acids as potential bile acid replacement agents for inborn errors of bile acid synthesis, particularly in settings where standard treatments are unavailable or prohibitively expensive.
References
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