Actions and comparative efficacy of phosphatidylcholine formulation and isolated sodium deoxycholate for different cell types

The Role of Fat Reducing Agents on Adipocyte Death and Adipose Tissue Inflammation

Deoxycholic Acid (DCA), which is an FDA-approved compound for the reduction of submental fat, has evolved through an unanticipated and surprising sequence of events. Initially, it was used as a solvent for Phosphatidylcholine (PDC), which was thought to promote lipolysis, but it was later proven to be the bioactive component of the formula and is currently widely used as Kybella. It has also been used off-label to treat other types of fat deposits like lipomas, HIV lipodystrophy, and excess orbital fat. Despite widespread clinical use, there has been no consensus clarifying the mechanisms of DCA and PDC alone or in combination. Furthermore, despite PDC's removal from the FDA-approved formula, some studies do suggest it plays an important role in fat reduction. To provide some clarity, we conducted a PubMed search and reviewed 41 articles using a comprehensive list of terms in three main categories, using the AND operator: 1) Phosphatidylcholines 2) Deoxycholic Acid, and 3) Lipoma. We isolated articles that studied PDC, DCA, and a PDC/DCA compound using cell biology, molecular and genetic techniques. We divided relevant articles into those that studied these components using histologic techniques and those that utilized specific cell death and lipolysis measurement techniques. Most morphologic studies indicated that PDC/DCA, DCA, and PDC, all induce some type of cell death with accompanying inflammation and fibrosis. Most morphologic studies also suggest that PDC/DCA and DCA alone are non-selective for adipocytes. Biochemical studies describing PDC and DCA alone indicate that DCA acts as a detergent and rapidly induces necrosis while PDC induces TNF-α release, apoptosis, and subsequent enzymatic lipolysis after at least 24 hours. Additional papers have suggested a synergistic effect between the two compounds. Our review integrates the findings of this growing body of literature into a proposed mechanism of fat reduction and provides direction for further studies.

Lipolytic effects of nano particle sized polyenylphosphatidylcholine on adipose tissue: First promising in vitro and in vivo results

BACKGROUND

Lipolytic injectables for body contouring procedures have been reported for necrotic effects on adipose tissue causing side effects as swelling, pain and hematoma. Deoxycholic acid is widely used as a solvent in lipolytic injectables and is associated with necrosis when applied to cells. A new lipolytic preparation (NWL-10) containing only polyenylphosphatidylcholine in nano particle size, glycerrhizinate and maltose has been reported for its lipolytic action on adipose tissue. However, no data exist whether the NWL-10 mixture is responsible for apoptosis or necrosis in adipose tissue which can be associated with severer side effects as reported for deoxycholic acid preparation.

METHODS

3T3-L1 mouse cells and human adipose tissue derived stem cells were exposed to the NWL-10 mixture and to each ingredient of the mix in order to investigate cytotoxic, lipolytic, necrotic or apoptotic effects. Furthermore, a Balb/C mouse animal model was used to investigate inflammatory responses to NWL-10 by bioluminescence monitoring and histological examination.

RESULTS

A high extent of lipolysis was detected for the NWL-10 mixture when applied to both cell types with no cytotoxic effect. Interestingly, low concentration of NWL-10 resulted in necrosis whereas high concentration of NWL-10 showed a certain amount of apoptosis. Application of single ingredients of NWL-10 or various combinations of two component mixtures did not result in any apoptosis or necrosis. In addition, no inflammatory effects of NWL-10 were observed in the mouse model.

CONCLUSIONS

The NWL-10 mixture provided promising results regarding lipolysis on adipose tissue with limited apoptosis and necrosis when compared to currently available injectables. These first promising results require further fundamental and more detailed research on essentials for drug approval. NWL-10 has the potential to become a second generation product for future lipolytic injectables.

Effect of a Formulation Containing Low-Dose Sodium Deoxycholate on Local Fat Reduction

BACKGROUND

Synthetic deoxycholic acid (DCA) has been approved as an injectable drug for the nonsurgical reduction of submental fat.

OBJECTIVE

In this study, we evaluated the fat-reducing effects of a new formula containing a low dose of DCA and fat dissolution by topical application of DCA.

METHODS

Sodium deoxycholate (99.1% pure) and the new formulation containing 10% DCA were injected or topically applied to the dorsa of obese mice (induced by a high-fat diet). The rate of change in body weight was evaluated, together with comparisons of micro-computed tomography images, body composition measurements, and histology findings.

RESULTS

The results showed that the new formula containing low-dose DCA was as effective as the older high-dose formulation with respect to the rate of change in body weight and reductions in subcutaneous fat pad area, body fat weight, and the thickness of the subcutaneous fat layer. Furthermore, topical application of the high-dose, but not the low-dose, formulation yielded promising effects.

CONCLUSIONS

The development of a better protocol for the high-dose preparation, including dose optimization and application methods that minimize the adverse effects of DCA, merits further study.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine Ratings, please refer to Table of Contents or online Instructions to Authors - www.springer.com/00266 .

Phosphatidylcholine causes adipocyte-specific lipolysis and apoptosis in adipose and muscle tissues

Phosphatidylcholine (PPC) formula has been therapeutically used to reduce areas of localized fat. However, no single research has been carried out on its effect on a variety of cells in adipose and muscle tissues. Herein, the current study aimed to explore the activity of PPC on different cells in adipose and muscle tissues and to investigate the molecular mechanisms contributing to the effects of PPC on lipolysis and apoptosis. mRNA expression levels of various genes were measured by quantitative real-time PCR. Protein expression levels were observed through Western blotting and cell viability was measured by MTT assay. Lipolysis and caspase 3 activity assay were performed using commercial kits. PPC induces lipolysis and apoptosis in adipocytes (3T3-L1), but not in the other tested cells, including skeletal muscle cells (C2C12 myocytes), endothelial cells (HUVEC), and fibroblasts (BJ). The possible role of TNFα and IL-1β-mediated pathways on the effects of PPC was also revealed. We confirmed that treatment with PPC caused lipolysis and apoptosis in a dose-dependent manner (only in 3T3-L1 adipocytes). The effect of PPC observed in 3T3-L1 adipocytes was not evident in C2C12 myocytes, HUVEC, and fibroblasts. PPC also increased TNFα and IL-1β expression and release in 3T3-L1 adipocytes in a dose-dependent fashion, but not in C2C12 myocytes, HUVEC, and BJ. Suppression of TNFα or IL-1β reversed PPC-induced lipolysis and apoptosis in 3T3-L1 adipocytes, suggesting that PPC could promote adipocyte-specific lipolysis and apoptosis through TNFα and IL-1β-mediated signaling. We conclude that the specific activity of PPC on adipocyte in adipose without other tissue damages can be an effective approach for melting lipid.

Deoxycholic Acid and the Marginal Mandibular Nerve: A Cadaver Study

BACKGROUND

One of the rare but serious complications observed with deoxycholic acid administration is damage to the marginal mandibular nerve. In this study, we evaluated if deoxycholic acid directly induces histologic damage to fresh cadaveric marginal mandibular nerve.

METHODS

A segment of marginal mandibular nerve was harvested from 12 hemifaces of 6 fresh cadavers. The nerve specimen was exposed to either 0.9% sterile saline for 24 h, deoxycholic acid (10 mg/ml) for 20 min, or deoxycholic acid (10 mg/ml) for 24 h. The nerve specimens were then fixed in glutaraldehyde for a minimum of 24 h. Toluidine blue stained sections were evaluated for stain intensity using light microscopy and color deconvolution image analysis. Supraplatysmal fat was harvested as a positive control and exposed to the same treatments as the marginal mandibular nerve specimens, then evaluated using transmission electron microscopy.

RESULTS

Toluidine blue staining was less in the marginal mandibular nerve exposed to deoxycholic acid when compared to saline. The specimen exposed to deoxycholic acid for 24 h showed less toluidine blue staining than that of the nerve exposed to deoxycholic acid for 20 min. Transmission electron microscopy of submental fat exposed to deoxycholic acid revealed disruption of adipocyte cell membrane integrity and loss of cellular organelles when compared to specimens only exposed to saline.

CONCLUSIONS

Deoxycholic acid (10 mg/ml) damages the marginal mandibular nerve myelin sheath in fresh human cadaver specimens. Direct deoxycholic acid neurotoxicity may cause marginal mandibular nerve injury clinically.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Sustained release of sodium deoxycholate from PLGA-PEG-PLGA thermosensitive polymer

Delivery of the drugs to the target tissue and reducing their side effects on surrounding tissues is still a significant challenge for pharmaceutical scientists. The aim of this study was to investigate the suitability of PLGA-PEG-PLGA triblock copolymer as a matrix material for a sustained-release system of sodium deoxycholate (NaDC). The copolymer was synthesized by ring-opening polymerization reaction, using microwave irradiation and characterized by different techniques. It was shown that the introduction of NaDC to the PLGA-PEG-PLGA copolymer did not influence its inherent sol-gel transition behaviour, but increased the sol-gel transition. The results showed the appropriate NaDC/polymer interaction and the formation of NaDC/polymer-mixed micelle. The sustained release of NaDC from the copolymer lasted for 2 days. This release can be attributed to the formation of NaDC/polymer-mixed micelles and trapping NaDC in the copolymer matrix. The cytolytic efficacy of NaDC-loaded copolymer and sustained release of NaDC were investigated on human adipocytes. Overall a sustained-release formulation for NaDC can be used to study localized fat dissolution.

Comparative assessment of metal-specific adipogenic activity in zinc and vanadium-citrates through associated gene expression

Diabetes mellitus comprises a group of metabolic abnormalities due to insulin deficiency and/or resistance. Obesity contributes to diabetes, with a strong causal relationship existing between diabetes and insulin resistance, especially in patients with Diabetes mellitus II. Adipocytes emerge as key constituents of adipose tissue physiology. In their pre-mature form to mature state transformation, adipocytes fully exemplify one of the key adipogenic actions of insulin. Poised to a) gain insight into adipogenesis leading to antidiabetic factors, and b) investigate adipogenesis through careful examination of insulin contributions to interwoven mechanistic pathways, a systematic comparative study was launched involving well-defined metal-citrates (zinc and vanadium), the chemical reactivity of which was in line with their chemistry under physiological conditions. Selection of the specific compounds was based on their common aqueous coordination chemistry involving the physiological chelator citric acid. Cellular maturation of pre-adipocytes to their mature form was pursued in the presence-absence of insulin and employment of closely linked genetic targets, key to adipocyte maturation (Peroxisome proliferator-activated receptor gamma (PPAR-γ), Glucose transporter 1,3,4 (GLUT 1,3,4), Adiponectin (ADIPOQ), Glucokinase (GCK), and Insulin receptor (INS-R)). The results show a) distinct adipogenic biological profiles for the metalloforms involved in a dose-, time- and nature-dependent manner, and b) metal ion-specific adipogenic response-signals at the same or higher level than insulin toward all selected targets. Collectively, the foundations have been established for future exploitation of the distinct metal-specific adipogenic factors contributing to the functional maturation of adipose tissue and their use toward hyperglycemic control in Diabetes mellitus.

Phosphatidylcholine Causes Lipolysis and Apoptosis in Adipocytes through the Tumor Necrosis Factor Alpha-Dependent Pathway

A phosphatidylcholine (PPC) formulation has been used to treat cellulite; however, its underlying mechanism of action remains unclear. In this study, we demonstrated that PPC induces lipolysis and apoptosis in adipocytes, and evaluated a possible tumor necrosis factor alpha (TNFα)-dependent pathway, whereby PPC exerts these effects. For in vitro study, fully differentiated 3T3-L1 cells, mouse adipocytes were treated with various concentrations of PPC and cell apoptosis and lipolysis were assayed. For in vivo experiments, mice fed on a high-fat diet for 8 weeks were injected twice to abdominal subcutaneous fat tissues of either vehicle or PPC. We found that PPC induced lipolysis and apoptosis dose-dependently in fully differentiated 3T3-L1 cells. In addition, PPC augmented both expression and release of TNFα in a dose-dependent fashion. Induction of TNFα by PPC was associated with the stimulation of nuclear factor kappa B (NFκB)-mediated transcriptional activity. Small interfering RNA (siRNA)-mediated suppression of NFκB abrogated the effect of PPC on TNFα secretion. Suppression of TNFα with specific siRNA abrogated the effects of PPC on lipolysis and apoptosis. Through in vivo experiments, we demonstrated that PPC injection not only stimulated the local lipolysis and apoptosis, resulting in weight loss, but also induced TNFα mRNA expression and neutrophil infiltration. Furthermore, PPC injection prevented lipogenesis and suppressed the mRNA -expression of adipokines (such as adiponectin and leptin), due to the down-sizing of adipocytes. In conclusion, we suggest that PPC induces lipolysis and apoptosis in adipocytes through TNFα-dependent pathways.

Intralipotherapy, the State of the Art

Background:

Reconstruction intralipotherapy is a term commonly used in the field of aesthetic medicine, above all in Europe, which defines a specific injection technique developed for the treatment of localized fat with substances that provoke the lysis of adipocytes by means of an injection directly into the adipose tissue with a long needle. The aim of this study is to define the technique in detail and everything that is associated with it, on the basis of years of multicenter experience by doctors who perform it.

Materials and Methods:

From January 2010 to December 2014, 3,080 European physicians were trained in intralipotherapy technique, and approximately 152,500 patients were treated. The adipocytolytic agent used is a Conformité Européene-certified device. The technique, equipment, protocol, posology, postoperative management, and adverse events are described below.

Results:

The intralipotherapy technique combined with the appropriate adipocytolytic agent has been shown to be effective in every zone on the average of 76.7% of the cases. The variability is due to the area treated and the patient. The standardization of the technique, homogeneity of the protocol, and the posttreatment management have been essential for standardizing the results and minimizing any adverse events. The latter occurred only in a small percentage of the cases, while those more serious have been extremely rare.

Conclusion:

This study shows how the intralipotherapic technique, when performed properly with an appropriate adipocytolytic device and when proper precautions are taken, can be effective and safe for reducing undesirable subcutaneous fat deposits.

Local fat treatments: classification proposal

The poor understanding of the real, intimate action mechanisms behind any aesthetic procedures is a huge problem for many Aesthetic physicians. In addition, nomenclature of and regarding any procedure has become a true barrier when speaking about medical knowledge in the Aesthetic Medicine field since marketing and science often collide one another. Medical procedures for localized fat reduction are very different from each other and it is, at least, inaccurate to refer to all of them plainly as "fat reduction methods." A specific classification has become urgent and its categories should be able to imply what each method entails. For this classification proposal, "reversibility," "membrane disruption or inflammation," and "action selectivity," have been the selected criteria.

Reduction of unwanted submental fat with ATX-101 (deoxycholic acid), an adipocytolytic injectable treatment: results from a phase III, randomized, placebo-controlled study

Summary

What's already known about this topic?

What does this study add?

Results from a pooled analysis of two European, randomized, placebo-controlled, phase 3 studies of ATX-101 for the pharmacologic reduction of excess submental fat

BACKGROUND

The injectable adipocytolytic drug ATX-101 is the first nonsurgical treatment for the reduction of submental fat (SMF) to undergo comprehensive clinical evaluation. This study aimed to confirm the efficacy and safety of ATX-101 for SMF reduction through a post hoc pooled analysis of two large phase 3 studies.

METHODS

Patients with unwanted SMF were randomized to receive 1 or 2 mg/cm(2) of ATX-101 or a placebo injected into their SMF during a maximum of four treatment sessions spaced approximately 28 days apart, with a 12-week follow-up period. The proportions of patients with reductions in SMF of one point or more on the Clinician-Reported SMF Rating Scale (CR-SMFRS) and the proportions of patients satisfied with the appearance of their face and chin [Subject Self-Rating Scale (SSRS) score ≥4] were reported overall and in subgroups. Other efficacy measures included improvements in the Patient-Reported SMF Rating Scale (PR-SMFRS), calliper measurements of SMF thickness, and assessment of skin laxity [Skin Laxity Rating Scale (SLRS)]. Adverse events and laboratory test results were recorded.

RESULTS

Significantly greater proportions of the patients had improvements in clinician-reported measures (≥1-point improvement in CR-SMFRS: 58.8 and 63.8 % of the patients who received ATX-101 1 and 2 mg/cm(2), respectively, and 28.6 % of the placebo recipients; p < 0.001 for both ATX-101 doses vs. placebo) and patient-reported measures (≥1-point improvement in PR-SMFRS: 60.0 and 63.1 % of the patients who received ATX-101 1 and 2 mg/cm(2), respectively, vs. 34.3 % of the placebo recipients; p < 0.001 for both), analyzed alone or in combination, with ATX-101 versus placebo. These improvements correlated moderately with patient satisfaction regarding face and chin appearance (SSRS score ≥4: 60.8 and 65.4 % of the patients who received ATX-101 1 and 2 mg/cm(2), respectively, vs. 29.0 % of the placebo recipients; p < 0.001 for both). In this study, ATX-101 was effective irrespective of gender, age, or body mass index. Reduction in SMF with ATX-101 was confirmed by calliper measurements (p < 0.001 for both doses vs. placebo) and generally did not lead to worsening of skin laxity (SLRS improved or was unchanged: 91.3 and 90.5 % of the patients who received ATX-101 1 and 2 mg/cm(2), respectively, and 91.6 % of the placebo recipients). Adverse events were mostly transient, mild to moderate in intensity, and localized to the treatment area.

CONCLUSION

The findings show ATX-101 to be an effective and well-tolerated pharmacologic treatment for SMF reduction.

A histopathologic and immunohistochemical study on liquification of human adipose tissue ex vivo

BACKGROUND

This preliminary ex vivo study aimed to clarify the pathophysiologic mechanisms of fat tissue depletion by subcutaneous drug application. Therefore, the lipolytic effects of phosphatidylcholine plus deoxycholate (Lipostabil) (L) and of deoxycholate (DC) alone were compared with those of sodium chloride (NaCl) and hydrogen peroxide (H2O2) as control agents. The study enrolled 10 patients receiving abdominoplasty. The treatment periods for each sample and solution were 1, 3, 5, and 7 h. The samples were analyzed morphologically using hematoxylin-eosin (H&E) staining and also immunohistochemically using Caspase 3 and tumor necrosis factor (TNF)-alpha. Morphologic changes were seen best after 5 h of application time. Except for NaCl, all the samples in the H&E staining showed marked damage of adipocyte cell membranes, with the greatest disruption of normal cell architecture after hydrogen peroxide (H2O2) application. Immunohistochemistry using TNF-alpha showed positive results for the deoxycholate and Lipostabil samples and highly positive results for the H2O2 sample. Data from this study indicate that Lipostabil and deoxycholate induce pathways of cell necrosis involving TNF-alpha. These short-term experiments indicate that Lipostabil affects fat tissue in the way of a chemical-toxic destruction rather than via a physiologically induced, programmed cell death.

Mesotherapy for local fat reduction

Mesotherapy, which is the injection of substances locally into mesodermally derived subcutaneous tissue, developed from empirical observations of a French physician in the 1950s. Although popular in Europe for many medical purposes, it is used for local cosmetic fat reduction in the United States. This paper reviews manuscripts indexed in PubMed/MEDLINE under 'mesotherapy', which pertains to local fat reduction. The history of lipolytic mesotherapy, the physiology of body fat distribution, the mechanism of action of different lipolytic stimulators and their increased efficacy in combination are reviewed. Mesotherapy falls into two categories. Lipolytic mesotherapy using lipolytic stimulators requires more frequent treatments as the fat cells are not destroyed and can refill over time. Ablative mesotherapy destroys fat cells with a detergent, causes inflammation and scarring from the fat necrosis, but requires fewer treatments. The historic and empiric mixing of sodium channel blocking local anaesthetics in mesotherapy solutions inhibits the intended lipolysis. Major mesotherapy safety concerns include injection site infections from poor sterile technique. Cosmetic mesotherapy directs the area from which fat is lost to improve self-image. Studies were of relatively small number, many with limited sample sizes. Future research should be directed towards achieving a Food and Drug Administration indication rather than continuing expansion of off-label use.

Metabolic and structural effects of phosphatidylcholine and deoxycholate injections on subcutaneous fat: a randomized, controlled trial

BACKGROUND

Phosphatidylcholine and deoxycholate (PC-DC) injections are a popular nonsurgical method to eliminate unwanted fat. The safety and efficacy of this approach is uncertain.

OBJECTIVE

The authors evaluate the effects of PC-DC treatments on body composition, adipocyte function, and mechanisms responsible for fat loss.

METHODS

This randomized, open-label study enrolled 13 women with a body mass index (BMI) ≤30 kg/m(2) and lower abdominal subcutaneous fat suitable for small-volume liposuction. Patients were randomized by the final digit of their Social Security numbers and received between 2 and 4 PC-DC treatments, spaced 8 weeks apart. One side below the umbilicus was injected with PC-DC. The contralateral, control side received no treatment. Adipose tissue biopsies were performed on the treated side at baseline, 1 week after the first treatment, and 8 weeks after the final treatment. The primary outcome was change in adipose tissue thickness at baseline and 8 weeks after the final treatment.

RESULTS

Seven women completed the study. Treatment with PC-DC significantly reduced the thickness of the anterior subcutaneous abdominal fat (P = .004). Adipose tissue showed rapid increases in crown-like structures, macrophage infiltration, and reduced expression of leptin, hormone-sensitive lipase, adipose tissue triglyceride lipase, and CD36. Plasma C-reactive protein, lipid profile, and plasma glucose concentrations were unchanged.

CONCLUSIONS

PC-DC injections can effectively reduce abdominal fat volume and thickness by inducing adipocyte necrosis. These treatments do not appear to increase circulating markers of inflammation or affect glucose and lipid metabolism.

Phosphatidylcholine induces apoptosis of 3T3-L1 adipocytes

BACKGROUND

Phosphatidylcholine (PPC) formulation is used for lipolytic injection, even though its mechanism of action is not well understood.

METHODS

The viability of 3T3-L1 pre-adipocytes and differentiated 3T3-L1 cells was measured after treatment of PPC alone, its vehicle sodium deoxycholate (SD), and a PPC formulation. Western blot analysis was performed to examine PPC-induced signaling pathways.

RESULTS

PPC, SD, and PPC formulation significantly decreased 3T3-L1 cell viability in a concentration-dependent manner. PPC alone was not cytotoxic to CCD-25Sk human fibroblasts at concentrations <1 mg/ml, whereas SD and PPC formulation were cytotoxic. Western blot analysis demonstrated that PPC alone led to the phosphorylation of the stress signaling proteins, such as p38 mitogen-activated protein kinase and c-Jun N-terminal kinase, and activated caspase-9, -8, -3 as well as cleavage of poly(ADP-ribose) polymerase. However, SD did not activate the apoptotic pathways. Instead, SD and PPC formulation induced cell membrane lysis, which may lead to necrosis of cells.

CONCLUSIONS

PPC results in apoptosis of 3T3-L1 cells.

[A five years experience of subcutaneous chemical lipolysis with phosphatidylcholine injections]

Instead the fact that chemical lipolysis through phosphatidylcholin injections really works, this procedure eliminating limited fat deposits remains confidential in France. Inconstant results, necessity to repeat injections, unclear legacy may explain that this very basic procedure remains unsuccessful. We have proceeded to lipolysis injections for five years on a very limited number of patients: in our hands, it may be efficient on puffy cheeks, double chin, superficial cellulitis, liposuction and lipofilling sequellaes. Eyelid bags may also be considered but not recommended. On the other hand, chemical lipolysis cannot compete with liposuction. We have not noticed any drawbacks or complications which confirm the lipolysis network practitioners' opinion in more than 1000 users.

[Injection lipolysis]

A new treatment variation in the spectrum of aesthetic medicine has been investigated worldwide since 2004: so-called injection lipolysis. Advances in knowledge regarding the efficacy and mechanism of action have been achieved especially in Germany because most users are found in Germany when compared on an international level. The reason for this is that the combination of phosphatidylcholine and deoxycholic acid as active substances has been approved for i.v. treatment of fat embolisms. It is thus readily available, but the subcutaneous injection of the drug Lipostabil N® is considered as off-label use. Meanwhile injection lipolysis has become an integral component for many in the practice of aesthetic medicine. The international association of physicians performing lipolysis in the so-called NETWORK-Lipolysis (with more than 2,000 members worldwide) has in particular called for the development of internationally recognized treatment standards and protocols. When the indication for its use adheres to strict criteria and the physicians applying the method have participated in intensive training, subcutaneous injection of phosphatidylcholine/deoxycholic acid represents a meaningful addition to the scope of minimally invasive aesthetic medicine.