Reduction of specific enterocytes from loss of intestinal LGR4 improves lipid metabolism in mice.

Whether intestinal Leucine-rich repeat containing G-protein-coupled receptor 4 (LGR4) impacts nutrition absorption and energy homeostasis remains unknown. Here, we report that deficiency of Lgr4 (Lgr4iKO) in intestinal epithelium decreased the proportion of enterocytes selective for long-chain fatty acid absorption, leading to reduction in lipid absorption and subsequent improvement in lipid and glucose metabolism. Single-cell RNA sequencing demonstrates the heterogeneity of absorptive enterocytes, with a decrease in enterocytes selective for long-chain fatty acid-absorption and an increase in enterocytes selective for carbohydrate absorption in Lgr4iKO mice. Activation of Notch signaling and concurrent inhibition of Wnt signaling are observed in the transgenes. Associated with these alterations is the substantial reduction in lipid absorption. Decrement in lipid absorption renders Lgr4iKO mice resistant to high fat diet-induced obesity relevant to wild type littermates. Our study thus suggests that targeting intestinal LGR4 is a potential strategy for the intervention of obesity and liver steatosis.

Rspo2-LGR4 exacerbates hepatocellular carcinoma progression via activation of Wnt/b-catenin signaling pathway / Rspo2-LGR4 agrava la progresión del carcinoma hepatocelular al activar la vía de señalización Wnt/beta-catenina

Background: The leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4) plays an important role in stem cell differentiation, organ development and cancer. Whether LGR4 affects the progression of hepatocellular carcinoma (HCC) remains unknown. This study aimed to reveal the role of LGR4 in HCC. Methods: Clinical samples of HCC were collected to assess the expression of LGR4 and its correlation with patients’ clinical characteristics. The expression level of LGR4 in HCC cells was altered by pharmacological and genetic methods, and the role of LGR4 in HCC progression was analyzed by in vivo and in vitro assays. HCC was induced by diethylnitrosamine (DEN) and carbon tetrachloride (CCl4) in wild-type and LGR4 deficient mice, the effect of LGR4 on HCC was examined by histopathological evaluation and biochemical assays. Results: LGR4 expression was up-regulated in HCC samples, and its expression level was positively correlated with tumor size, microvascular invasion (MVI), TNM stage and pathological differentiation grade of HCC patients. In the mouse HCC model induced by DEN+CCl4, knockdown of LGR4 effectively inhibited the progression of HCC. Silencing of LGR4 inhibited the proliferation, migration, invasion, stem cell-like properties and Warburg effect of HCC cells. These phenotypes were promoted by R-spondin2 (Rspo2), an endogenous ligand for LGR4. Rspo2 markedly increased the nuclear translocation of β-catenin, whereas IWR-1, an inhibitor of Wnt/β-catenin signaling, reversed its effect. Deficiency of LGR4 significantly reduced the nuclear translocation of β-catenin and the expression of its downstream target genes cyclinD1 and c-Myc. Conclusions: LGR4 promotes HCC progression via Wnt/β-catenin signaling pathway. (AU)

Antecedentes: El receptor de acoplamiento de proteínas G de secuencia repetida 4 (LGR4), rico en leucina, juega un papel importante en la diferenciación de células madre, el desarrollo de órganos y el cáncer. Se desconoce si LGR4 afecta la progresión del carcinoma hepatocelular (HCC). El objetivo de este estudio es revelar el papel de LGR4 en el HCC. Métodos: Se recolectaron muestras clínicas de HCC para evaluar la expresión de LGR4 y su correlación con los resultados clínicos de HCC. Alterar los niveles de expresión de LGR4 en las células de HCC mediante métodos farmacológicos y genéticos y analizar el papel de LGR4 en la progresión del cáncer de hígado mediante mediciones in vivo e in vitro. El HCC fue inducido en ratones de tipo salvaje y con defectos de LGR4 con Nitrosamina de dietilo (DEN) y cloruro de carbono (CCl4), y los efectos de LGR4 sobre el HCC fueron detectados por evaluación histopatológica y determinación bioquímica. Resultados: La expresión de LGR4 está regulada en HCC, y su nivel de expresión está positivamente relacionado con el tamaño tumoral, la infiltración microvascular (MVI), la etapa de TNM y el grado de diferenciación patológica en pacientes con HCC. En el modelo de HCC de ratón inducido por DEN+CCl4, golpear bajo LGR4 inhibió efectivamente la progresión del HCC. El silencio de LGR4 inhibe la proliferación, migración, invasión, propiedades similares a las células madre y el efecto Warburg de las células HCC. Estos fenotipos son promovidos por el ligando endógeno roof slab-specific sponge 2 (Rspo2)de LGR4. El Rspo2 aumentó significativamente la translocación nuclear de la proteína beta-catenina, mientras que el inhibidor de la señalización Wnt/beta-cateninaIWR-1 revirtió su acción... (AU)

Hepatic LGR4 aggravates cholestasis-induced liver injury in mice.

Current therapy for hepatic injury induced by the accumulation of bile acids is limited. Leucine-rich repeat G protein-coupled receptor 4 (LGR4), also known as GPR48, is critical for cytoprotection and cell proliferation. Here, we reported a novel function for the LGR4 in cholestatic liver injury. In the bile duct ligation (BDL)-induced liver injury model, hepatic LGR4 expression was significantly downregulated. Deficiency of LGR4 in hepatocytes (Lgr4LKO) notably decreased BDL-induced liver injury measured by hepatic necrosis, fibrosis, and circulating liver enzymes and total bilirubin. Levels of total bile acids in plasma and liver were markedly reduced in these mice. However, deficiency of LGR4 in macrophages (Lyz2-Lgr4MKO) demonstrated no significant effect on liver injury induced by BDL. Deficiency of LGR4 in hepatocytes significantly attenuated S1PR2 and the phosphorylation of protein kinase B (AKT) induced by BDL. Recombinant Rspo1 and Rspo3 potentiated the taurocholic acid (TCA)-induced upregulation in S1PR2 and phosphorylation of AKT in hepatocytes. Inhibition of S1PR2-AKT signaling by specific AKT or S1PR2 inhibitors blocked the increase of bile acid secretion induced by Rspo1/3 in hepatocytes. Our studies indicate that the R-spondins (Rspos)-LGR4 signaling in hepatocytes aggravates the cholestatic liver injury by potentiating the production of bile acids in a S1PR2-AKT-dependent manner.NEW & NOTEWORTHY Deficiency of LGR4 in hepatocytes alleviates BDL-induced liver injury. LGR4 in macrophages demonstrates no effect on BDL-induced liver injury. Rspos-LGR4 increases bile acid synthesis and transport via potentiating S1PR2-AKT signaling in hepatocytes.

Rspo2-LGR4 exacerbates hepatocellular carcinoma progression via activation of Wnt/ß-catenin signaling pathway.

BACKGROUND: The leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4) plays an important role in stem cell differentiation, organ development and cancer. Whether LGR4 affects the progression of hepatocellular carcinoma (HCC) remains unknown. This study aimed to reveal the role of LGR4 in HCC. METHODS: Clinical samples of HCC were collected to assess the expression of LGR4 and its correlation with patients' clinical characteristics. The expression level of LGR4 in HCC cells was altered by pharmacological and genetic methods, and the role of LGR4 in HCC progression was analyzed by in vivo and in vitro assays. HCC was induced by diethylnitrosamine (DEN) and carbon tetrachloride (CCl4) in wild-type and LGR4 deficient mice, the effect of LGR4 on HCC was examined by histopathological evaluation and biochemical assays. RESULTS: LGR4 expression was up-regulated in HCC samples, and its expression level was positively correlated with tumor size, microvascular invasion (MVI), TNM stage and pathological differentiation grade of HCC patients. In the mouse HCC model induced by DEN+CCl4, knockdown of LGR4 effectively inhibited the progression of HCC. Silencing of LGR4 inhibited the proliferation, migration, invasion, stem cell-like properties and Warburg effect of HCC cells. These phenotypes were promoted by R-spondin2 (Rspo2), an endogenous ligand for LGR4. Rspo2 markedly increased the nuclear translocation of ß-catenin, whereas IWR-1, an inhibitor of Wnt/ß-catenin signaling, reversed its effect. Deficiency of LGR4 significantly reduced the nuclear translocation of ß-catenin and the expression of its downstream target genes cyclinD1 and c-Myc. CONCLUSIONS: LGR4 promotes HCC progression via Wnt/ß-catenin signaling pathway.

Nuclear Acly protects the liver from ischemia-reperfusion injury.

BACKGROUND AND AIMS: Hepatic ischemia-reperfusion (IR) injury is the most common complication that occurs in liver surgery and hemorrhagic shock. ATP citrate lyase (Acly) plays a pivotal role in chromatin modification via generating acetyl-CoA for histone acetylation to influence biological processes. We aim to examine the roles of Acly, which is highly expressed in hepatocytes, in liver IR injury. APPROACH AND RESULTS: The functions of Acly in hepatic IR injury were examined in the mouse model with a hepatocyte-specific knockout of Acly . The Acly target genes were analyzed by CUT&RUN assay and RNA sequencing. The relationship between the susceptibility of the steatotic liver to IR and Acly was determined by the gain of function studies in mice. Hepatic deficiency of Acly exacerbated liver IR injury. IR induced Acly nuclear translocation in hepatocytes, which spatially fueled nuclear acetyl-CoA. This alteration was associated with enhanced acetylation of H3K9 and subsequent activation of the Foxa2 signaling pathway. Nuclear localization of Acly enabled Foxa2-mediated protective effects after hypoxia-reperfusion in cultured hepatocytes, while cytosolic Acly demonstrated no effect. The presence of steatosis disrupted Acly nuclear translocation. In the steatotic liver, restoration of Acly nuclear localization through overexpression of Rspondin-1 or Rspondin-3 ameliorated the IR-induced injury. CONCLUSIONS: Our results indicate that Acly regulates histone modification by means of nuclear AcCoA production in hepatic IR. Disruption of Acly nuclear translocation increases the vulnerability of the steatotic liver to IR. Nuclear Acly thus may serve as a potential therapeutic target for future interventions in hepatic IR injury, particularly in the context of steatosis.

Eliminating Institutional Barriers to Career Advancement for Diverse Faculty in Academic Surgery.

: There is critical need to address achievement barriers in Academic Medicine. Although opportunities for professional development of women and underrepresented minority physician scientists are growing, academic promotion rates remain historically low. Moreover, underrepresented groups are not likely to advance to decanal and leadership positions. To eliminate institutional barriers to achievement for diverse faculty, strategies to strengthen environment, recruitment, professional development, and leadership were implemented. This multifaceted approach is adaptable to Academic Surgery universally and we wish to share early progress.

Building High-Performing Teams in Academic Surgery: The Opportunities and Challenges of Inclusive Recruitment Strategies.

PROBLEM: In academic surgery, women and physicians from ethnic minority groups remain inadequately represented relative to their representation in the U.S. population and among medical students and surgical trainees. Although several initiatives have been aimed at developing the academic surgery pipeline or addressing issues related to faculty retention and promotion, little is known about how recruitment practices impact diversity in academic medicine. Moreover, national standards and ideal practices specific for effective recruitment in surgery have not been established. APPROACH: A working group at the Department of Surgery at the University of Michigan implemented an inclusive search and selection process for all open faculty positions within the department in academic year 2017-2018. The strategy included mandatory training, a standing recruitment committee with diverse membership, broad promotion of positions, implementing a modified "Rooney rule," panel interviews of candidates, standardized interview protocols, a standardized evaluation tool and scoring system, and written evaluations/ranking of candidates. OUTCOMES: Implementation of this recruitment strategy resulted in several immediate measurable benefits including increased diversity of the applicant pools and of new faculty hires. In addition to these positive effects, the department noted several knowledge gaps and faced challenges to implementing all elements of the strategy. NEXT STEPS: The authors share their framework, highlighting opportunities and challenges that are broadly generalizable and relevant for building high-performing teams in academic medicine. Work to set measurable metrics and address challenges for inclusive recruitment in surgery is ongoing. Such evaluation and refinement are important for sustainability and increasing effectiveness.

Pilot Study to Evaluate the Safety, Feasibility, and Financial Implications of a Postoperative Telemedicine Program.

BACKGROUND: Telemedicine in surgery holds promise for improving access and decreasing costs, but its role remains ill-defined. This pilot study was performed to investigate the safety, feasibility, and financial implications of providing postoperative care using an electronic clinic (eClinic) at a university hospital. METHODS: An easy-to-use and secure eClinic platform was constructed in Epic (Epic Systems Corporation, Verona, WA). Patients undergoing laparoscopic cholecystectomy, appendectomy, and hernia repairs on an adult acute care surgery service were enrolled in this program over an 11-month period (March 2017 to January 2018). Patients with prolonged hospitalizations (greater than 4 nights), perioperative complications, drains, and open wounds were excluded. Demographics, clinical outcomes, encounter time, patient satisfaction survey results, and cost analysis were compared with the traditional clinic (tClinic) patient population. RESULTS: Two hundred thirty-three eligible patients (61% female; mean age 41 ±â€Š16 years) were enrolled in this program. Their demographics were no different than the tClinic. Frequencies of readmission, reoperation, and emergency department visits (2.7%, 0%, and 4.2%, respectively) in the eClinic group were also similar to the tClinic group. However, total visit time was significantly shorter in the eClinic group (14 vs 145 minutes, P < 0.01). Anonymous surveys demonstrated a high degree of satisfaction, with 85% of patients expressing desire to utilize the eClinic again. This program enhanced the capacity for new visits to tClinic, with a resultant projected increase in additional operative cases and revenue for the health care system. CONCLUSIONS: A safe and efficient postoperative telemedicine program can be constructed utilizing a widely available electronic medical record system, which can improve patient satisfaction, optimize throughput, and increase gross charges for the healthcare system.

The Surgery Innovation and Entrepreneurship Development Program (SIEDP): An Experiential Learning Program for Surgery Faculty to Ideate and Implement Innovations in Health care.

OBJECTIVE: Surgeons are continually engaged in the incorporation of new technologies in their practice. In the operating room and beyond, they combine technical skill with creative problem solving to improve tools and techniques for patient care, making them natural innovators. However, despite their innovative tendencies, education on entrepreneurship and commercialization is severely lacking. Moreover, with increasing pressure to meet productivity metrics, their availability to learn the complexities of commercialization is limited. To address these challenges, we designed the Surgery Innovation and Entrepreneurship Development Program (SIEDP) with the objective to advance faculty innovations, develop new departmental innovation initiatives, and improve faculty education in the area of innovation, entrepreneurship, and commercialization. DESIGN: The SIEDP is a first-of-its-kind experiential learning program specifically designed for busy clinical and research faculty in a major academic surgery department. Participants ideated and formed teams around health care innovations as they progressed through a 9-month curriculum of expert guest lectures and interactive workshops. A postprogram evaluation and outcome tracking method was used to evaluate attainment of educational objectives and project development milestones. SETTING: The Department of Surgery, University of Michigan Medical School, Ann Arbor, Michigan. PARTICIPANTS: Eleven surgery faculty of varying academic rank and surgical subspecialties. RESULTS: The program generated 2 faculty startup companies, 1 departmental commercial product, 3 patent disclosures, and 3 innovations that received additional funding. All participants in the program reported a significant increase in their understanding of innovation and entrepreneurship and that participation was a worthwhile faculty development activity. CONCLUSION: Despite the various challenges and time constraints of surgical practices, programs like SIEDP can educate surgeons and other academicians on innovation, entrepreneurship, and commercialization and add value to the academic mission of providing excellent education, research, and clinical care.

Diabetes-Specific Regulation of Adipocyte Metabolism by the Adipose Tissue Extracellular Matrix.

Context: The role of the extracellular matrix (ECM) in regulating adipocyte metabolism in the context of metabolic disease is poorly defined. Objective: The objective of this study was to define the metabolic phenotype of adipocytes associated with human diabetes (DM) and the role of the ECM in regulating adipocyte metabolism. Design: Adipose tissues from obese patients were studied in standard 2-dimensional (2D) cell culture and an in vitro model of decellularized adipose tissue ECM repopulated with human adipocytes, and results were correlated with DM status. Setting: This study was conducted at the Academic University Medical Center and Veteran's Administration Hospital. Patients: Seventy patients with morbid obesity undergoing bariatric surgery were included in the study. Interventions: Visceral and subcutaneous adipose tissues were collected at the time of bariatric surgery. Outcome measures: This study used metabolic assays for glucose uptake, lipolysis, and lipogenesis in adipocytes in 2D cell culture and 3-dimensional ECM culture. Results: Adipocytes from subjects with DM manifest decreased glucose uptake and decreased lipolysis in 2D culture. ECM supports differentiation of mature adipocytes and recapitulates DM-specific differences in adipocyte metabolism observed in 2D culture. ECM from subjects without DM partially rescues glucose uptake and lipolytic defects in adipocytes from subjects with DM, whereas ECM from subjects with DM impairs glucose uptake in adipocytes from subjects without DM. Conclusions: DM is associated with adipocyte metabolic dysfunction. The ECM regulates adipocyte metabolism. Nondiabetic ECM rescues metabolic dysfunction in DM adipocytes, whereas DM ECM imparts features of metabolic dysfunction to nondiabetic adipocytes. These findings suggest the ECM as a target for manipulating adipose tissue metabolism.

Performance Metrics in Professional Baseball Pitchers before and after Surgical Treatment for Neurogenic Thoracic Outlet Syndrome.

BACKGROUND: High-performance throwing athletes may be susceptible to the development of neurogenic thoracic outlet syndrome (NTOS). This condition can be career-threatening but the outcomes of treatment for NTOS in elite athletes have not been well characterized. The purpose of this study was to utilize objective performance metrics to evaluate the impact of surgical treatment for NTOS in Major League Baseball (MLB) pitchers. METHODS: Thirteen established MLB pitchers underwent operations for NTOS between July 2001 and July 2014. For those returning to MLB, traditional and advanced (PitchF/x) MLB performance metrics were acquired from public databases for various time-period scenarios before and after surgery, with comparisons made using paired t-tests, Wilcoxon matched-pair signed-rank tests, and Kruskal-Wallis analysis of variance. RESULTS: Ten of 13 pitchers (77%) achieved a sustained return to MLB, with a mean age of 30.2 ± 1.4 years at the time of surgery and 10.8 ± 1.5 months of postoperative rehabilitation before the return to MLB. Pre- and postoperative career data revealed no significant differences for 15 traditional pitching metrics, including earned run average (ERA), fielding independent pitching, walks plus hits per inning pitched (WHIP), walks per 9 innings, and strikeouts to walk ratio (SO/BB). There were also no significant differences between the 3 years before and the 3 years after surgical treatment. Using PitchF/x data for 72 advanced metrics and 25 different time-period scenarios, the highest number of significant relationships (n = 18) was observed for the 8 weeks before/12 weeks after scenario. In this analysis, 54 (75%) measures were unchanged (including ERA, WHIP, and SO/BB) and 14 (19%) were significantly improved, while only 4 (6%) were significantly decreased (including hard pitch maximal velocity 93.1 ± 1.0 vs. 92.5 ± 0.9 miles/hr, P = 0.047). Six pitchers remained active in MLB during the study period, while the other 4 had retired due to factors or injuries unrelated to NTOS. CONCLUSIONS: Objective performance metrics demonstrate that pitchers returning to MLB after surgery for NTOS have had capabilities equivalent to or better than before treatment. Thoracic outlet decompression coupled with an ample period of postoperative rehabilitation can provide effective treatment for professional baseball pitchers with career-threatening NTOS.

Nesfatin-1 promotes brown adipocyte phenotype.

Nesfatin-1, an 82 amino acid gastric peptide, is involved in regulation of food uptake and in multiple metabolic activities. Whether nesfatin-1 modulates the differentiation and lipid metabolism of brown adipocytes remains unknown. In the present study, we found that nesfatin-1 mRNA and protein were detectable in isolated brown adipocytes and gradually decreased during differentiation (95% CI 0.6057 to 1.034, p = 0.0001). The decrease in nesfatin-1 was associated with a significant reduction in p-S6. Exposure to nesfatin-1 promoted differentiation of brown adipocytes as revealed by a significant increase in UCP1 mRNA (p = 0.03) and lipolysis-related ATGL mRNA (p = 0.04). Nesfatin-1 attenuated phosphorylation of S6K and S6 during brown adipocyte differentiation. Activation of mTOR by leucine or deletion of TSC1 decreased expression of brown adipocyte-related genes UCP1, UCP3, PGC1α and PRDM16, as well as COX8B and ATP5B. Both leucine and TSC1 deletion blocked nesfatin-1-induced up-regulation of UCP1, PGC1α, COX8B and ATP5B in differentiated brown adipocytes. In conclusion, nesfatin-1 promotes the differentiation of brown adipocytes likely through the mTOR dependent mechanism.

A leadership development program for surgeons: First-year participant evaluation.

BACKGROUND: In a dynamic health care system, strong leadership has never been more important for surgeons. Little is known about how to design and conduct effectively a leadership program specifically for surgeons. We sought to evaluate critically a Leadership Development Program for practicing surgeons by exploring how the program's strengths and weaknesses affected the surgeons' development as physician-leaders. METHODS: At a large academic institution, we conducted semistructured interviews with 21 surgical faculty members who applied voluntarily, were selected, and completed a newly created Leadership Development Program in December 2012. Interview transcripts underwent qualitative descriptive analysis with thematic coding based on grounded theory. Themes were extracted regarding surgeons' evaluations of the program on their development as physician-leaders. RESULTS: After completing the program, surgeons reported personal improvements in the following 4 areas: self-empowerment to lead, self-awareness, team-building skills, and knowledge in business and leadership. Surgeons felt "more confident about stepping up as a leader" and more aware of "how others view me and my interactions." They described a stronger grasp on "giving feedback" as well as a better understanding of "business/organizational issues." Overall, surgeon-participants reported positive impacts of the program on their day-to-day work activities and general career perspective as well as on their long-term career development plans. Surgeons also recommended areas where the program could potentially be improved. CONCLUSION: These interviews detailed self-reported improvements in leadership knowledge and capabilities for practicing surgeons who completed a Leadership Development Program. A curriculum designed specifically for surgeons may enable future programs to equip surgeons better for important leadership roles in a complex health care environment.

Designing a leadership development program for surgeons.

BACKGROUND: Although numerous leadership development programs (LDPs) exist in health care, no programs have been specifically designed to meet the needs of surgeons. This study aimed to elicit practicing surgeons' motivations and desired goals for leadership training to design an evidence-based LDP in surgery. MATERIALS AND METHODS: At a large academic health center, we conducted semistructured interviews with 24 surgical faculty members who voluntarily applied and were selected for participation in a newly created LDP. Transcriptions of the interviews were analyzed using analyst triangulation and thematic coding to extract major themes regarding surgeons' motivations and perceived needs for leadership knowledge and skills. Themes from interview responses were then used to design the program curriculum specifically to meet the leadership needs of surgical faculty. RESULTS: Three major themes emerged regarding surgeons' motivations for seeking leadership training: (1) Recognizing key gaps in their formal preparation for leadership roles; (2) Exhibiting an appetite for personal self-improvement; and (3) Seeking leadership guidance for career advancement. Participants' interviews revealed four specific domains of knowledge and skills that they indicated as desired takeaways from a LDP: (1) leadership and communication; (2) team building; (3) business acumen/finance; and (4) greater understanding of the health care context. CONCLUSIONS: Interviews with surgical faculty members identified gaps in prior leadership training and demonstrated concrete motivations and specific goals for participating in a formal leadership program. A LDP that is specifically tailored to address the needs of surgical faculty may benefit surgeons at a personal and institutional level.

LGR4 and Its Role in Intestinal Protection and Energy Metabolism.

Leucine-rich repeat-containing G protein-coupled receptors were identified by the unique nature of their long leucine-rich repeat extracellular domains. Distinct from classical G protein-coupled receptors which act via G proteins, LGR4 functions mainly through Wnt/ß-catenin signaling to regulate cell proliferation, differentiation, and adult stem cell homeostasis. LGR4 is widely expressed in tissues ranging from the reproductive system, urinary system, sensory organs, digestive system, and the central nervous system, indicating LGR4 may have multiple functions in development. Here, we focus on the digestive system by reviewing its effects on crypt cells differentiation and stem cells maintenance, which are important for cell regeneration after injury. Through effects on Wnt/ß-catenin signaling and cell proliferation, LGR4 and its endogenous ligands, R-spondins, are involved in colon tumorigenesis. LGR4 also contributes to regulation of energy metabolism, including food intake, energy expenditure, and lipid metabolism, as well as pancreatic ß-cell proliferation and insulin secretion. This review summarizes the identification of LGR4, its endogenous ligand, ligand-receptor binding and intracellular signaling. Physiological functions include intestinal development and energy metabolism. The potential effects of LGR4 and its ligand in the treatment of inflammatory bowel disease, chemoradiotherapy-induced gut damage, colorectal cancer, and diabetes are also discussed.

HDAC5-mTORC1 Interaction in Differential Regulation of Ghrelin and Nucleobindin 2 (NUCB2)/Nesfatin-1.

Sodium valporate (VPA), a broad-spectrum inhibitor of histone deacetylases (HDACs), increased ghrelin whereas decreased nesfatin-1 in mice fed normal chow diet or high-fat diet. Alterations in ghrelin and nucleobindin 2/nesfatin-1 were mediated by HDAC5 but not HDAC4. Activation of mTORC1 significantly attenuated the effect of VPA on ghrelin and nesfatin-1 levels. HDAC5 coimmunoprecipitated with raptor. Inhibition of HDAC5 by VPA, trichostatin A, or siHDAC5 markedly increased acetylation of raptor Lys840 and subsequent phosphorylation of raptor Ser792, resulting in suppression of mTORC1 signaling. A raptor mutant lacking the Lys840 acetylation site showed a decrement in phosphorylation of raptor Ser792 and subsequent increase in mTORC1 signaling. These alterations were associated with reciprocal changes in ghrelin and nucleobindin 2/nesfatin-1 expression. These findings reveal HDAC5-mTORC1 signaling as a novel mechanism in the differential regulation of gastric ghrelin and nesfatin-1.