Copper biodistribution after acute systemic administration of copper gluconate to rats.

Neurodegenerative disorders have been linked to the decrease of copper concentrations in different regions of the brain. Therefore, intake of micronutrient supplements could be a therapeutic alternative. Since the copper distribution profile has not been elucidated yet, the aim of this study was to characterize and to analyze the concentration profile of a single administration of copper gluconate to rats by two routes of administration. Male Wistar rats were divided into three groups. The control group received vehicle (n = 5), and the experimental groups received 79.5 mg/kg of copper orally (n = 4-6) or 0.64 mg/kg of copper intravenously. (n = 3-4). Blood, striatum, midbrain and liver samples were collected at different times. Copper concentrations were assessed using atomic absorption spectrophotometry. Copper concentration in samples from the control group were considered as baseline. The highest copper concentration in plasma was observed at 1.5 h after oral administration, while copper was quickly compartmentalized within the first hour after intravenous administration. The striatum evidenced a maximum metal concentration at 0.25 h for both routes of administration, however, the midbrain did not show any change. The highest concentration of the metal was held by the liver. The use of copper salts as replacement therapy should consider its rapid and discrete accumulation into the brain and the rapid and massive distribution of the metal into the liver for both oral and intravenous routes. Development of controlled-release pharmaceutical formulations may overcome the problems that the liver accumulation may imply, particularly, for hepatic copper toxicity.

Pharmacokinetic and Toxicological Evaluation of a Zinc Gluconate-Based Chemical Sterilant Using In Vitro and In Silico Approaches.

Sclerosing agents as zinc gluconate-based chemical sterilants (Infertile®) are used for chemical castration. This solution is injected into the animal testis, but there are not enough evidences of its safety profiles for the receivers. The present work aimed to establish the pharmacokinetics and toxicological activity of Infertile, using in vitro and in silico approaches. The evaluation at the endpoint showed effects in a dose-dependent manner. Since necrosis is potentially carcinogenic, the possible cell death mechanism could be apoptosis. Our data suggested that Infertile at 60 mM presented risk for animal health. Even though Infertile is a licensed product by the Brazilian Ministry of Agriculture, Livestock and Supply, it presented a high mutagenic potential. We suggest that the optimal dose must be less than 6 mM, once, at this concentration, no mutagenicity or genotoxicity was observed.

The Effect of Zinc Supplementation on Expressed Levels of Peroxisome Proliferator-Activated Receptor Gamma and Glucose Transporter Type 1 Genes in Newborns of Women with Gestational Diabetes Mellitus.

The current study was designed to determine the beneficial effects of zinc supplementation on expressed levels of peroxisome proliferator-activated receptor gamma (PPAR-γ) and glucose transporter type 1 (GLUT1) genes in newborns of women with gestational diabetes mellitus (GDM). This randomized, double-blind, placebo-controlled clinical trial was performed among 40 women with GDM. Patients were randomly allocated to intake either 233 mg zinc gluconate (containing 30 mg zinc) (n = 20) or a placebo (n = 20) for 6 weeks. PPAR-γ and GLUT1 mRNA levels were quantified in umbilical cord blood of newborns of women with GDM. After 6 weeks of intervention, the change in serum zinc levels was greater in women consuming zinc than in the placebo group (+11.1 ± 13.4 vs. -4.8 ± 17.3 mg/dL, P = 0.002). Quantitative results of RT-PCR demonstrated that compared with the placebo, zinc supplementation resulted in a significant increase of expressed levels of PPAR-γ mRNA (P < 0.001) and GLUT1 mRNA (P < 0.001) in umbilical cord blood of newborns of women with GDM. Taken together, the current study demonstrated that zinc supplementation for 6 weeks among GDM women increased the mRNA levels of PPAR-γ and GLUT1 in their newborns compared with the placebo group.

The Effect of Zinc and Selenium Supplementation Mode on Their Bioavailability in the Rat Prostate. Should Administration Be Joint or Separate?

It is thought that zinc and selenium deficiency may play a significant role in the etiology of prostate cancer. Although joint zinc and selenium supplementation is frequently applied in the prevention of prostate diseases, the bioavailability of these elements in the prostate after co-administration is still unknown. The study examines the effect of subchronic supplementation of zinc gluconate and selenium compounds (sodium selenite or selenomethionine), administered together or separately, on their bioavailability in the prostate, as well as the induction of metallothionein-like proteins (MTs) bound to zinc in the prostate and liver. Zinc concentration in the dorso-lateral lobe of the prostate was significantly elevated already after the first month of supplementation of zinc alone. In the supplementation period, the MTs level increased together with zinc concentration. In contrast, the ventral lobe of the prostate did not demonstrate significantly higher levels of zinc until after three months of supplementation, despite the MTs induction noted after one-month supplementation. Increased selenium levels in the dorsolateral lobe were observed throughout the administration and post-administration periods, regardless of the selenium compound used or whether zinc was co-administered. The results of our studies suggested for the first time that these elements should not be administered jointly in supplementation.

Bioavailability of potassium from potatoes and potassium gluconate: a randomized dose response trial.

BACKGROUND: The bioavailability of potassium should be considered in setting requirements, but to our knowledge, the bioavailability from individual foods has not been determined. Potatoes provide 19-20% of potassium in the American diet. OBJECTIVE: We compared the bioavailability and dose response of potassium from nonfried white potatoes with skin [targeted at 20, 40, and 60 milliequivalents (mEq) K] and French fries (40 mEq K) with potassium gluconate at the same doses when added to a basal diet that contained ∼60 mEq K. DESIGN: Thirty-five healthy, normotensive men and women with a mean ± SD age of 29.7 ± 11.2 y and body mass index (in kg/m(2)) of 24.3 ± 4.4 were enrolled in a single-blind, crossover, randomized controlled trial. Participants were partially randomly assigned to the order of testing for nine 5-d interventions of additional potassium as follows: 0 (control; repeated at phases 1 and 5), 20, 40, and 60 mEq K/d consumed as a potassium gluconate supplement or as unfried potato or 40 mEq K from French fries completed at phase 9. The bioavailability of potassium was determined from the area under the curve (AUC) of serial blood draws and cumulative urinary excretion during a 24-h period and from a kinetic analysis. The effects of the potassium source and dose on the change in blood pressure and augmentation index (AIx) were determined. RESULTS: The serum potassium AUC increased with the dose (P < 0.0001) and did not differ because of the source (P = 0.53). Cumulative 24-h urinary potassium also increased with the dose (P < 0.0001) and was greater with the potato than with the supplement (P < 0.0001). The kinetic analysis showed the absorption efficiency was high across all interventions (>94% ± 12%). There were no significant differences in the change in blood pressure or AIx with the treatment source or dose. CONCLUSIONS: The bioavailability of potassium is as high from potatoes as from potassium gluconate supplements. Future studies that measure the effect of dietary potassium on blood pressure will need to evaluate the effect of various dietary sources on potassium retention and in both normal and hypertensive populations. This trial was registered at clinicaltrials.gov as NCT01881295.

Retrograde transport of radiolabelled botulinum neurotoxin type A to the CNS after intradetrusor injection in rats.

OBJECTIVE: To investigate the potential distribution of radiolabelled botulinum neurotoxin type A (BoNT/A) in the CNS after bladder injection in normal rats, by using the gamma-emitting radionuclide technetium-99 m ((99m) Tc). MATERIALS AND METHODS: BoNT/A was radiolabelled by pretreatment with 2-iminothiolane and incubation with (99m) Tc-gluconate. The labelled toxin (99m) Tc-BoNT/A was purified using size exclusion HPLC. Twenty-four female Wistar rats were evenly injected in the bladder wall with either (99m) Tc-ΒοΝΤ/Α (n = 12) or free (99m) Tc (n = 12). Four rats from each group were killed at 1, 3 and 6 h after injection, respectively. The bladder, L6-S1 spinal cord segment and L6-S1 dorsal root ganglia (DRG) were harvested and their radioactivity counted in a gamma scintillation detector. Results were calculated as % injected dose (I.D.) per gram of tissue. The paired t-test was used for comparison of means of (99m) Tc-ΒοΝΤ/Α radioactivity vs free (99m) Tc in the tissues of interest. RESULTS: Radiolabelled BoNT/A had a high radiochemical stability of 70% after 24 h. Gradual accumulation of (99m) Tc-ΒοΝΤ/Α was observed in the DRG up to 6 h after injection (P = 0.04 and P = 0.029 compared with 1 h and 3 h, respectively), while no accumulation was detected for free (99m) Tc. Consequently, (99m) Tc-ΒοΝΤ/Α radioactivity in the DRG was higher than free (99m) Tc radioactivity (3.18 ± 0.67% I.D./g vs 0.19 ± 0.10% I.D./g [P = 0.002] 6 h after injection). Values for (99m) Tc-ΒοΝΤ/Α radioactivity in the spinal cord were higher than those for free (99m) Tc, but not significantly. The bladder retained higher dosages of (99m) Tc-ΒοΝΤ/Α than free (99m) Tc at all time points. CONCLUSIONS: Significant accumulation of the radiolabelled toxin in the lumbosacral DRG, together with a less significant uptake in the respective spinal cord segment as opposed to free radioactivity provide first evidence of the retrograde transport of BoNT/A to the CNS after bladder injection in rats.

The bioavailability of different zinc compounds used as human dietary supplements in rat prostate: a comparative study.

The normal human prostate accumulates the highest levels of zinc (Zn) of any soft tissue in the body. The pool of zinc available to the body is known to significantly decrease with age. It is suggested that dietary Zn supplementation protects against oxidative damage and reduces the risk of cancer. Zinc sulfate and zinc gluconate were the most frequently mentioned in per os administration in studies on Zn supplementation. The major aim of the study was to compare the bioavailability of different Zn compounds (sulfate, gluconate and citrate) in the prostate after their daily administration to male rats at three different doses (3.0; 15.0; and 50.0 mg Zn/kg b.w.) for 30 days. The results show that bioavailability in the prostate differs significantly between individual zinc preparations. A significantly elevated Zn concentration in the dorso-lateral lobe of the prostate, compared to controls, was found in the rats supplemented with two compounds only: zinc gluconate and zinc citrate. However, after administration of zinc gluconate, this effect occurred even at the lowest dose. The lowest zinc bioavailability in the prostate was found in the rats administered zinc sulfate: no significant Zn increase was seen in particular zones of the prostate. To sum up, the use of zinc gluconate is worth considering as a possible means of zinc supplementation in men.

Drug delivery of zinc to Barrett's metaplasia by oral administration to Barrett's esophagus patients.

BACKGROUND: Delivery of a pharmacologically effective drug dosage to a target tissue is critical. Barrett's epithelia are a unique challenge for drug delivery of orally administered zinc due to rapid transit down the esophageal lumen, incomplete absorptive differentiation of these epithelia, and the use of proton-pump inhibitor drugs abrogating intestinal uptake of supplemental zinc. METHODS: Barrett's esophagus patients were administered oral zinc gluconate (26 mg zinc twice daily) for 14 days prior to biopsy procurement. Barrett's biopsies were analyzed for total zinc content by atomic absorption spectroscopy and by western immunoblot for cellular proteins known to be regulated by zinc. RESULTS: Cellular levels of both the Znt-1 transport protein and the alpha isoform of PKC were over 50% lower in the zinc treatment group. CONCLUSION: Oral zinc administration can result in effective delivery of zinc to Barrett's epithelia with resulting effects on intracellular signal transduction.

Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide.

The water-soluble zinc salts gluconate, sulfate, and acetate are commonly used as supplements in tablet or syrup form to prevent zinc deficiency and to treat diarrhea in children in combination with oral rehydration. Zinc citrate is an alternative compound with high zinc content, slightly soluble in water, which has better sensory properties in syrups but no absorption data in humans. We used the double-isotope tracer method with (67)Zn and (70)Zn to measure zinc absorption from zinc citrate given as supplements containing 10 mg of zinc to 15 healthy adults without food and compared absorption with that from zinc gluconate and zinc oxide (insoluble in water) using a randomized, double-masked, 3-way crossover design. Median (IQR) fractional absorption of zinc from zinc citrate was 61.3% (56.6-71.0) and was not different from that from zinc gluconate with 60.9% (50.6-71.7). Absorption from zinc oxide at 49.9% (40.9-57.7) was significantly lower than from both other supplements (P < 0.01). Three participants had little or no absorption from zinc oxide. We conclude that zinc citrate, given as a supplement without food, is as well absorbed by healthy adults as zinc gluconate and may thus be a useful alternative for preventing zinc deficiency and treating diarrhea. The more insoluble zinc oxide is less well absorbed when given as a supplement without food and may be minimally absorbed by some individuals. This trial was registered at clinicaltrials.gov as NCT01576627.

Mn bioavailability by polarized Caco-2 cells: comparison between Mn gluconate and Mn oxyprolinate.

BACKGROUND: Micronutrient inadequate intake is responsible of pathological deficiencies and there is a need of assessing the effectiveness of metal supplementation, frequently proposed to rebalance poor diets. Manganese (Mn) is present in many enzymatic intracellular systems crucial for the regulation of cell metabolism, and is contained in commercially available metal supplements. METHODS: We compared the effects of two different commercial Mn forms, gluconate (MnGluc) and oxyprolinate (MnOxP). For this purpose we used the polarized Caco-2 cells cultured on transwell filters, an established in vitro model of intestinal epithelium. Since micronutrient deficiency may accelerate mitochondrial efficiency, the mitochondrial response of these cells, in the presence of MnGluc and MnOxP, by microscopy methods and by ATP luminescence assay was used. RESULTS: In the presence of both MnOxP and MnGluc a sustained mitochondrial activity was shown by mitoTraker labeling (indicative of mitochondrial respiration), but ATP intracellular content remained comparable to untreated cells only in the presence of MnOxP. In addition MnOxP transiently up-regulated the antioxidant enzyme Mn superoxide dismutase more efficiently than MnGluc. Both metal treatments preserved NADH and ßNADPH diaphorase oxidative activity, avoided mitochondrial dysfunction, as assessed by the absence of a sustained phosphoERK activation, and were able to maintain cell viability. CONCLUSIONS: Collectively, our data indicate that MnOxP and MnGluc, and primarily the former, produce a moderate and safe modification of Caco-2 cell metabolism, by activating positive enzymatic mechanisms, thus could contribute to long-term maintenance of cell homeostasis.

Dietary management of hepatic copper accumulation in Labrador Retrievers.

BACKGROUND: Copper-associated chronic hepatitis (CACH) recently has been recognized in the Labrador Retriever as an inherited disorder with a late onset of clinical signs. No studies have investigated dietary management for the long-term treatment of this disease or for its potential in delaying the onset of clinical signs in subclinical cases. OBJECTIVES: To investigate the effects of a low-copper diet and zinc gluconate on hepatic copper concentrations in Labrador Retrievers with abnormal hepatic copper concentrations. ANIMALS: Twenty-four client-owned Labradors that were related to patients affected with CACH and that had been diagnosed with increased hepatic copper concentrations. METHODS: Hepatic copper concentrations were assessed before and after an average of 8 and 16 months of treatment. During this time, all dogs were fed exclusively a low-copper diet. In addition, dogs were assigned to 1 of 2 groups in a randomized double-blind manner to receive a supplement of zinc gluconate or placebo. RESULTS: Twenty-one dogs completed the study. Hepatic copper concentrations decreased in both groups at recheck 1 (n = 21; group 1, P < .001; group 2, P= .001) and at recheck 2 (n= 16; group 1, P= .03; group 2, P= .04). No difference in hepatic copper concentrations was found between the 2 groups before treatment (P= .65), at recheck 1 or at recheck 2 (P= .52-.79). CONCLUSIONS AND CLINICAL RELEVANCE: Feeding low-copper diets to Labradors is effective in decreasing hepatic copper concentrations. Adjunctive treatment with zinc does not appear to increase the copper-lowering effects of dietary management.

Toxic effects of iterative intraperitoneal administration of zinc gluconate in rats.

Although zinc is an essential trace element involved in many physiological functions, toxicological data concerning acute exposure are scarce. The aim of our study was to determine the maximal iterative dose of zinc that can be administrated in rats without any adverse effect. Saline (control group) or zinc gluconate at 1, 2 or 4 mg/kg were intraperitoneally injected in animals daily during 7 days. The tolerance of zinc treatments was evaluated by the observation of clinical symptoms, haematological parameters and biochemistry, in relation to the zinc and copper levels in blood, liver, pancreas and faeces. We found no serious adverse effect within 1 week in rats injected intraperitoneally with 1 or 2 mg/kg/day of zinc gluconate, which tends to indicate that those doses could be useful in future therapeutic research. In contrast, the therapeutic treatment of adult rats with repeated intraperitoneal injections of a 4 mg/kg/day zinc dose should be cancelled, due to the occurrence of clinical adverse effects within a few days, as intraperitoneal local intolerance or major growth underdevelopment.

Comparative toxicity and cell-tissue distribution study on nanoparticular iron complexes using avian embryos and HepG2-cells.

In this study the toxicity and intracellular availability of iron from iron dextran (FeD), iron sucrose (FeS), and iron gluconate (FeG) was compared in organs of avian (turkey) embryos and in isolated cells (HepG2) in cell culture. Iron uptake was more pronounced in embryonic liver than in renal tissue. Cellular iron uptake in liver and kidney was more or less similar for the different compounds. Only some experiments showed slightly greater iron concentrations in liver and kidney with FeG compared with FeD and FeS. Significant differences were found in the survival ratios of the eggs and the embryo weights depending on the type of iron complex administered. The rank order of toxicities was FeG>FeS>FeD. Iron accumulation in HepG2-cells was extremely high with FeS and FeG, whereas FeD did not lead to a relevant iron uptake by HepG2 cells. The excessively high iron content of the cells is an in vitro phenomenon found neither in the in ovo model with the turkey embryos nor in the clinical use of the compounds. The rank order of toxicities in HepG2 cells was FeS>FeG>FeD. Iron uptake in cell culture does not reflect the in vivo situation. The in ovo model is more suitable to assess the cellular iron uptake and iron toxicity in cells and tissues than the in vitro model. In both in ovo and in vitro experiments, FeD seemed to be superior in terms of toxicity.

Clinical evaluation of the bioavailability of zinc-enriched yeast and zinc gluconate in healthy volunteers.

Zinc (Zn)-enriched yeast and gluconate are considered two of the more biologically available supplements. However, there have been few reports comparing the bioavailability of these supplements. The objective of this study was to demonstrate whether Zn was absorbed better by healthy male volunteers when given supplements where the mineral is found organically bound in yeast or as a salt gluconate form. The trial used a randomized, two-way crossover design. Urine, blood, and fecal samples were collected and analyzed over a 48-h period after a single dose of supplement. The net Zn balance and the relative bioavailability were calculated. No differences were observed in urine excretion of the two supplements. Zinc gluconate gave higher Zn concentrations in the blood in the first 6 h but also showed greater losses in the feces. Zinc yeast also increased in blood with time but showed significantly less loss in the feces. Thus, the net Zn balance after 48 h for Zn yeast was 9.46 but for Zn gluconate it was -2.00, indicating that Zn gluconate supplementation contributed to a net loss of Zn. It was concluded that organic Zn yeast supplements are more biologically available than Zn gluconate salts.

Comparative bioavailability of mineral-enriched gluconates and yeast in rat liver after depletion-repletion feeding.

There are many forms of mineral supplements currently available. Among these mineral-enriched gluconates and yeast are considered two of the more biologically available supplements. The purpose of this study was to use zinc (Zn)- or copper (Cu)-deficient rats to determine whether the organically bound mineral in yeast or the salt gluconate form was more bioavailable, i.e., is absorbed and found in a greater concentration in liver. It was demonstrated that Zn-enriched yeast was 3.7 times more bioavailable than the Zn gluconate and that Cu-enriched yeast was 1.4 times more bioavailable than the Cu gluconate.

A bioavailability study comparing two oral formulations containing zinc (Zn bis-glycinate vs. Zn gluconate) after a single administration to twelve healthy female volunteers.

As the current nutritional zinc intake frequently falls outside the Dietary Reference Intake (DRI) and as zinc is an essential trace mineral involved in the function of many enzymes, zinc supplementation has been recommended to prevent or treat the adverse effects of zinc deficiency. The aim of the present study was to compare the oral bioavailability of zinc bis-glycinate (a new formulation) with zinc gluconate (reference formulation). A randomized, cross-over study was conducted in 12 female volunteers. The two products were administrated orally at the single dose of 15 mg (7.5 mg x 2), with a 7-day wash-out period between the two tests. Serum concentrations of zinc were assayed by a validated inductively coupled plasma optical emission spectrometry (ICP-OES) method and C(max), T(max), and areas-under-the-curve (AUCs) were determined. The comparison between the two treatments was performed by comparing the C(max), AUC(t), and AUC(inf) using an analysis of variance followed by the calculation of the 90% confidence intervals of the ratio test/reference. Bis-glycinate administration was safe and well tolerated and bis-glycinate significantly increased the oral bioavailability of zinc (+43.4%) compared with the gluconate.

The pharmacokinetics of zinc from zinc gluconate: a comparison with zinc oxide in healthy men.

OBJECTIVE: Zinc supplementation is beneficial in some clinical conditions such as age-related macula degeneration (AMD). It has been suggested that zinc absorption is influenced by the form in which zinc is ingested. Therefore, the pharmacokinetics of zinc gluconate (organic) were compared with those of zinc oxide (inorganic). METHODS: 12 healthy male subjects aged between 21 and 31 years (24 years median) orally received daily doses of 20 mg metal zinc as zinc gluconate and 17.4 mg metal zinc as zinc oxide under randomized crossover conditions for 14 days each with at least 14 days as a washout. Zinc plasma concentrations were measured by means of inductively coupled plasma-atomic emission spectroscopy. RESULTS: C(max) was found 18.3% (10.3 - 26.3%) higher following multiple-dose administration of zinc gluconate as compared to zinc oxide (mean; 0.95% confidence interval of the relative differences between both treatment conditions; p < 0.05). AUC(0-24h) was noted 8.1% (1.9 - 14.3%) higher after zinc was given as zinc gluconate when compared to zinc oxide (p < 0.05) whereas t(max) did not differ between both treatment conditions. CONCLUSIONS: Zinc absorption in humans could be improved by zinc complexation with gluconate.

Biphasic accumulation kinetics of [99mTc]-hexakis-2-methoxyisobutyl isonitrile in tumour cells and its modulation by lipophilic P-glycoprotein ligands.

AIM: To study the accumulation and washout kinetics of [99mTc]-hexakis-2-methoxyisobutyl isonitrile (99mTc-MIBI) in MDR positive and MDR negative tumour cells and how this is modified by lipophilic P-glycoprotein ligands. METHODS: The tumour cells were incubated in the presence and absence of the ligands and the uptakes of 99mTc-MIBI, rhodamine 123 and 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) were measured. RESULTS: The accumulation of 99mTc-MIBI in the tumour cells followed biphasic kinetics. Verapamil and cyclosporin A increased the membrane fluidity and significantly enhanced the 99mTc-MIBI uptake of the MDR negative cells, while the rhodamine 123 uptake was not affected. Verapamil significantly increased the uptake of rhodamine 123 and 18FDG but did not modify that of 99mTc-MIBI in the MDR positive cells. Cyclosporin A significantly increased the 18FDG uptake of the MDR positive and negative tumour cells; these effects were ouabain-sensitive. Depolarization of the cytoplasmic membrane, acidification of the extracellular medium and the administration of CCCP decreased the accumulation of 99mTc-MIBI and rhodamine 123 uptake in the tumour cells. CONCLUSIONS: Lipophilic P-glycoprotein ligands modified the biphasic accumulation kinetics of the 99mTc-MIBI uptakes of MDR negative and positive tumour cells in different and complex ways and could therefore mask the P-glycoprotein pump-dependent changes in tracer accumulation.

Influence of various phosphopeptides of caseins on iron absorption.

The influence of the origin and kind of caseinophosphopeptide (CPP) on iron absorption was assessed by comparing a commercially available CPP mixture (CPPs) and derived chromatographic fractions with the purified, chemically phosphopeptide of beta-casein [beta-CN(1-25)] using a perfused rat duodenal loop system; gluconate iron was used as control. Only iron complexed to beta-CN(1-25) displayed a better bioavailability than gluconate iron. The results obtained with various chromatographic fractions indicated that phosphopeptides of different origins (alpha(s)- versus beta-caseins) display specific effects. These findings contribute to the explanation of the discrepancy about the role of caseinophosphopeptides on mineral bioavailability in vivo.

Stimulation of butyrate production by gluconic acid in batch culture of pig cecal digesta and identification of butyrate-producing bacteria.

Gluconic acid reaches the large intestine to stimulate lactic acid bacteria. However, the fermentation pattern of gluconic acid has yet to be elucidated. Accordingly, we examined the fermentation properties induced by gluconic acid in the pig cecal digesta in vitro. We also tested sorbitol and glucose, substrates for which the fermentation rate and patterns are known. The gluconic acid-utilizing bacteria were further isolated from pig cecal digesta and identified to examine the effect of gluconic acid on hind gut fermentation. Gluconic acid was fermented more slowly than were the other two substrates. Gluconic acid stimulated butyrate production; the butyrate molar percentage reached 26%, which is considered a high butyrate production. The majority of gluconic acid fermenters were identified as lactic acid bacteria, such as Lactobacillus reuteri and L. mucosae, and acid-utilizing bacteria, such as Megasphaera elsdenii and Mitsuokella multiacida. The gluconic acid fermented by lactic acid bacteria, and the lactate and acetate that were produced were used to form butyrate by acid-utilizing bacteria, such as M. elsdenii. Gluconic acid may be useful as a prebiotic to stimulate butyrate production in the large intestine.