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Objective: Liver-specific inactivation of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) by a dominant-negative transgene (l-SACC1 mice) impaired insulin clearance, caused insulin resistance, and increased hepatic lipogenesis. To discern whether this phenotype reflects a physiological function of CEACAM1 rather than the effect of the dominant-negative transgene, we characterized the metabolic phenotype of mice with null mutation of the Ceacam1 gene (Cc1(-/-)).Research Design and Methods: Mice were originally generated on a mixed C57BL/6x129sv genetic background and then backcrossed 12 times onto the C57BL/6 background. More than 70 male mice of each of the Cc1(-/-) and wild-type Cc1(+/+) groups were subjected to metabolic analyses, including insulin tolerance, hyperinsulinemic-euglycemic clamp studies, insulin secretion in response to glucose, and determination of fasting serum insulin, C-peptide, triglyceride, and free fatty acid levels.Results: Like l-SACC1, Cc1(-/-) mice exhibited impairment of insulin clearance and hyperinsulinemia, which caused insulin resistance beginning at 2 months of age, when the mutation was maintained on a mixed C57BL/6x129sv background, but not until 5-6 months of age on a homogeneous inbred C57BL/6 genetic background. Hyperinsulinemic-euglycemic clamp studies revealed that the inbred Cc1(-/-) mice developed insulin resistance primarily in liver. Despite substantial expression of CEACAM1 in pancreatic beta-cells, insulin secretion in response to glucose in vivo and in isolated islets was normal in Cc1(-/-) mice (inbred and outbred strains).Conclusions: Intact insulin secretion in response to glucose and impairment of insulin clearance in l-SACC1 and Cc1(-/-) mice suggest that the principal role of CEACAM1 in insulin action is to mediate insulin clearance in liver. [ABSTRACT FROM AUTHOR]

The Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, also CD66a), a transmembrane glycoprotein of the immunoglobulin superfamily, is a pivotal mediator of various physiological and pathological processes, including oncologic disorders. However, its precise role in tumorigenicity is contradictory discussed by several clinical studies. This review aims to elucidate the clinical significance of CEACAM1 in different cancer entities focusing on tumour formation, progression and metastasis as well as on CEACAM1-mediated treatment resistance. Furthermore, we discuss the contribution of CEACAM1 to cancer immunity and modulation of the inflammatory microenvironment and finally provide a comprehensive review of treatment regimens targeting this molecule., (© 2024 The Author(s). European Journal of Clinical Investigation published by John Wiley & Sons Ltd on behalf of Stichting European Society for Clinical Investigation Journal Foundation.)

Objectives: Hepatic CEACAM1 expression declines with advanced hepatic fibrosis stage in patients with metabolic dysfunction-associated steatohepatitis (MASH). Global and hepatocyte-specific deletions of Ceacam1 impair insulin clearance to cause hepatic insulin resistance and steatosis. They also cause hepatic inflammation and fibrosis, a condition characterized by excessive collagen production from activated hepatic stellate cells (HSCs). Given the positive effect of PPARγ on CEACAM1 transcription and on HSCs quiescence, the current studies investigated whether CEACAM1 loss from HSCs causes their activation., Methods: We examined whether lentiviral shRNA-mediated CEACAM1 donwregulation (KD-LX2) activates cultured human LX2 stellate cells. We also generated LratCre + Cc1 fl/fl mutants with conditional Ceacam1 deletion in HSCs and characterized their MASH phenotype. Media transfer experiments were employed to examine whether media from mutant human and murine HSCs activate their wild-type counterparts., Results: LratCre + Cc1 fl/fl mutants displayed hepatic inflammation and fibrosis but without insulin resistance or hepatic steatosis. Their HSCs, like KD-LX2 cells, underwent myofibroblastic transformation and their media activated wild-type HSCs. This was inhibited by nicotinic acid treatment which blunted the release of IL-6 and fatty acids, both of which activate the epidermal growth factor receptor (EGFR) tyrosine kinase. Gefitinib inhibition of EGFR and its downstream NF-κB/IL-6/STAT3 inflammatory and MAPK-proliferation pathways also blunted HSCs activation in the absence of CEACAM1., Conclusions: Loss of CEACAM1 in HSCs provoked their myofibroblastic transformation in the absence of insulin resistance and hepatic steatosis. This response is mediated by autocrine HSCs activation of the EGFR pathway that amplifies inflammation and proliferation., Competing Interests: Declaration of competing interest None declared., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Background: The role of insulin resistance in hepatic fibrosis in Metabolic dysfunction-Associated SteatoHepatitis (MASH) remains unclear. Carcinoembryonic Antigen-related Cell Adhesion Molecule1 protein (CEACAM1) promotes insulin clearance to maintain insulin sensitivity and repress de novo lipogenesis, as bolstered by the development of insulin resistance and steatohepatitis in AlbuminCre + Cc1 fl/fl mice with liver-specific mouse gene encoding CEACAM1 protein (Ceacam1) deletion. We herein investigated whether these mice also developed hepatic fibrosis and whether hepatic CEACAM1 is reduced in patients with MASH at different fibrosis stages., Methods: AlbuminCre + Cc1 fl/fl mice were fed a regular or a high-fat diet before their insulin metabolism and action were assessed during IPGTT, and their livers excised for histochemical, immunohistochemical and Western blot analysis. Sirius red staining was used to assess fibrosis, and media transfer was employed to examine whether mutant hepatocytes activated hepatic stellate cells (HSCs). Hepatic CEACAM1 protein levels in patients with varying disease stages were assessed by ELISA., Results: Hepatocytic deletion of Ceacam1 caused hyperinsulinemia-driven insulin resistance emanating from reduced hepatic insulin clearance. AlbuminCre + Cc1 fl/fl livers showed inflammation, fibrosis and hepatic injury, with more advanced bridging and chicken-wire hepatic fibrosis under high-fat conditions. Media transferred from hepatocytes isolated from mutant mice activated control HSCs, likely owing to their elevated endothelin1 content. Interestingly, hepatic CEACAM1 levels were lower in the livers of patients with MASH and declined gradually with advanced fibrosis stage., Conclusions: Hepatic CEACAM1 levels declined with progression of MASH in humans. The phenotype of AlbuminCre + Cc1 fl/fl mice assigned a key role to CEACAM1 loss from hepatocytes in hepatic fibrosis independently of other liver cells., (© 2024 The Authors. European Journal of Clinical Investigation published by John Wiley & Sons Ltd on behalf of Stichting European Society for Clinical Investigation Journal Foundation.)

Alcohol-associated liver disease (ALD) is a leading factor of liver-related death worldwide. ALD has various manifestations that include steatosis, hepatitis, and cirrhosis and is currently without approved pharmacotherapies. The Src homology phosphatase 2 (Shp2) is a drug target in some cancers due to its positive regulation of Ras-mitogen-activated protein kinase signaling and cell proliferation. Shp2 pharmacological inhibition yields beneficial outcomes in animal disease models, but its impact on ALD remains unexplored. This study aims to investigate the effects of Shp2 inhibition and its validity using a preclinical mouse model of ALD. We report that the administration of SHP099, a potent and selective allosteric inhibitor of Shp2, partially ameliorated ethanol-induced hepatic injury, inflammation, and steatosis in mice. Additionally, Shp2 inhibition was associated with reduced ethanol-evoked activation of extracellular signal-regulated kinase (ERK), oxidative, and endoplasmic reticulum (ER) stress in the liver. Besides the liver, excessive alcohol consumption induces multi-organ injury and dysfunction, including the intestine. Notably, Shp2 inhibition diminished ethanol-induced intestinal inflammation and permeability, abrogated the reduction in tight junction protein expression, and the activation of ERK and stress signaling in the ileum. Collectively, Shp2 pharmacological inhibition mitigates the deleterious effects of ethanol in the liver and intestine in a mouse model of ALD. Given the multifactorial aspects underlying ALD pathogenesis, additional studies are needed to decipher the utility of Shp2 inhibition alone or as a component in a multitherapeutic regimen to combat this deadly malady., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Over 65 % of people with obesity display the metabolic-associated fatty liver disease (MAFLD), which can manifest as steatohepatitis, fibrosis, cirrhosis, or liver cancer. The development and progression of MAFLD involve hepatic insulin resistance and reduced insulin clearance. This review discusses the relationships between altered insulin signaling, hepatic insulin resistance, and reduced insulin clearance in the development of MAFLD and how this provides the impetus for exploring the use of insulin sensitizers to curb this disease. The review also explores the role of the insulin receptor in hepatocytes and hepatic stellate cells and how it signals in metabolic and end-stage liver diseases. Finally, we discuss new research findings that indicate that advanced hepatic diseases may be an insulin-sensitive state in the liver and deliberate whether insulin sensitizers should be used to manage late-stage liver diseases., Competing Interests: Declaration of competing interest T.D.H.J. has submitted patents on bilirubin- and obesity-related disorders. The remaining authors have no conflict of interest to declare., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Lipid microdomains, ordered membrane phases containing cholesterol and glycosphingolipids, play an essential role in cancer cell adhesion and ultimately metastasis. Notably, elevated levels of cholesterol-rich lipid microdomains are found in cancer cells relative to their normal counterparts. Therefore, alterations of lipid microdomains through cholesterol modulation could be used as a strategy to prevent cancer metastasis. In this study, methyl-beta-cyclodextrin (MβCD), sphingomyelinase (SMase), and simvastatin (Simva) were used to investigate the effects of cholesterol on the adhesive behaviors of four non-small cell lung cancer (NSCLC) cell lines (H1299, H23, H460, and A549) and a small cell lung cancer (SCLC) cell line (SHP-77) on E-selectin, a vascular endothelial molecule that initiates circulating tumor cell recruitment at metastatic sites. Under hemodynamic flow conditions, the number of adherent NSCLC cells on E-selectin significantly decreased by MβCD and Simva treatments, whereas SMase treatment did not show a significant effect. Significant increases in rolling velocities were detected only for H1299 and H23 cells after MβCD treatment. In contrast, cholesterol depletion did not affect SCLC cell attachment and rolling velocities. Moreover, cholesterol depletion by MβCD and Simva induced CD44 shedding and resulted in an enhanced membrane fluidity in the NSCLC cells, whereas it did not affect the membrane fluidity of the SCLC cells which lacked detectable expression of CD44. Our finding suggests that cholesterol regulates the E-selectin-mediated adhesion of NSCLC cells by redistributing the CD44 glycoprotein and thus modulating the membrane fluidity. NEW & NOTEWORTHY This study investigates the effects of cholesterol on the adhesive behaviors of lung cancer cells in recruitment at metastatic sites. Using cholesterol-modulating compounds, we found that reducing cholesterol decreases the adhesion of non-small cell lung cancer (NSCLC) cells while having no significant effect on small cell lung cancer (SCLC) cells. The study suggests that cholesterol regulates NSCLC cell metastasis by redistributing the adhesion proteins on the cells and modulating cells' membrane fluidity.

Defects in insulin processing and granule maturation are linked to pancreatic beta-cell failure during type 2 diabetes (T2D). Phosphatidylinositol transfer protein alpha (PITPNA) stimulates activity of phosphatidylinositol (PtdIns) 4-OH kinase to produce sufficient PtdIns-4-phosphate (PtdIns-4-P) in the trans-Golgi network to promote insulin granule maturation. PITPNA in beta-cells of T2D human subjects is markedly reduced suggesting its depletion accompanies beta-cell dysfunction. Conditional deletion of Pitpna in the beta-cells of Ins-Cre, Pitpna flox/flox mice leads to hyperglycemia resulting from decreasing glucose-stimulated insulin secretion (GSIS) and reducing pancreatic beta-cell mass. Furthermore, PITPNA silencing in human islets confirms its role in PtdIns-4-P synthesis and leads to impaired insulin granule maturation and docking, GSIS, and proinsulin processing with evidence of ER stress. Restoration of PITPNA in islets of T2D human subjects reverses these beta-cell defects and identify PITPNA as a critical target linked to beta-cell failure in T2D., (© 2023. The Author(s).)

Objectives: Hepatocytic CEACAM1 plays a critical role in NASH pathogenesis, as bolstered by the development of insulin resistance, visceral obesity, steatohepatitis and fibrosis in mice with global Ceacam1 (Cc1) deletion. In contrast, VECadCre+Cc1 fl/fl mice with endothelial loss of Cc1 manifested insulin sensitivity with no visceral obesity despite elevated NF-κB signaling and increased systemic inflammation. We herein investigated whether VECadCre+Cc1 fl/fl male mice develop hepatic fibrosis and whether this is mediated by increased production of endothelin1 (ET1), a transcriptional NF-κB target., Methods: VECadCre+Et1.Cc1 fl/fl mice with combined endothelial loss of Cc1/Et1 genes were generated. Histological and immunohistochemical analyses were conducted on their livers and on liver tissue biopsies from adult patients undergoing bariatric surgery or from patients with NASH diagnosis receiving liver transplant., Results: Hepatic fibrosis and inflammatory infiltration developed in VECadCre+Cc1 fl/fl liver parenchyma. This was preceded by increased ET1 production and reversed with combined endothelial loss of Et1. Conditioned media from VECadCre+Cc1 fl/fl , but not VECadCre+Et1.Cc1 fl/fl primary liver endothelial cells activated wild-type hepatic stellate cells; a process inhibited by bosentan, an ET A R/ET B R dual antagonist. Consistently, immunohistochemical analysis of liver biopsies from patients with NASH showed a decline in endothelial CEACAM1 in parallel with increased plasma endothelin1 levels and progression of hepatic fibrosis stage., Conclusions: The data demonstrated that endothelial CEACAM1 plays a key role in preventing hepatic fibrogenesis by reducing autocrine endothelin1 production., Competing Interests: Declaration of competing interest None declared., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Long-term exposure to solar radiation can lead to skin damage such as photoageing, and photocarcinogenesis. This can be prevented by topically applying α-tocopherol phosphate (α-TP). The major challenge is that a significant amount of α-TP needs to reach viable skin layers for effective photoprotection. This study aims to develop candidate formulations of α-TP (gel-like, solution, lotion, and gel), and investigate formulation characteristics' effect on membrane diffusion and human skin permeation. All the formulations developed in the study had an appealing appearance and no signs of separation. All formulations had low viscosity and high spreadability except the gel. The flux of α-TP through the polyethersulfone membrane was the highest for lotion (6.63 ± 0.86 mg/cm 2 /h), followed by control gel-like (6.14 ± 1.76 mg/cm 2 /h), solution (4.65 ± 0.86 mg/cm 2 /h), and gel (1.02 ± 0.22 mg/cm 2 /h). The flux of α-TP through the human skin membrane was numerically higher for lotion compared to the gel-like (328.6 vs.175.2 µg/cm 2 /h). The lotion delivered 3-fold and 5-fold higher α-TP in viable skin layers at 3 h and 24 h, respectively, compared to that of the gel-like. The low skin membrane penetration rate and deposition of α-TP in viable skin layers were observed for the solution and gel. Our study demonstrated that dermal penetration of α-TP was influenced by characteristics of formulation such as formulation type, pH, and viscosity. The α-TP in the lotion scavenged higher DPPH free radicals compared to that of gel-like (almost 73% vs. 46%). The IC 50 of α-TP in lotion was significantly lower than that of gel-like (397.2 vs. 626.0 µg/mL). The preservative challenge test specifications were fulfilled by Geogard 221 and suggested that the combination of benzyl alcohol and Dehydroacetic Acid effectively preserved 2% α-TP lotion. This result confirms the suitability of the α-TP cosmeceutical lotion formulation employed in the present work for effective photoprotection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Aim: Non-alcoholic fatty liver disease (NAFLD) exhibits a racial disparity. We examined the prevalence and the association between race, gender, and NAFLD among prediabetes and diabetes populations among adults in the United States. Methods: We analyzed data for 3,190 individuals ≥18 years old from the National Health and Nutrition Examination Survey (NHANES) 2017-2018. NAFLD was diagnosed by FibroScan ® using controlled attenuation parameter (CAP) values: S0 (none) < 238, S1 (mild) = 238-259, S2 (moderate) = 260-290, S3 (severe) > 290. Data were analyzed using Chi-square test and multinomial logistic regression, adjusting for confounding variables and considering the design and sample weights. Results: Of the 3,190 subjects, the prevalence of NAFLD was 82.6%, 56.4%, and 30.5% ( p < 0.0001) among diabetes, prediabetes and normoglycemia populations respectively. Mexican American males with prediabetes or diabetes had the highest prevalence of severe NAFLD relative to other racial/ethnic groups ( p < 0.05). In the adjusted model, among the total, prediabetes, and diabetes populations, a one unit increase in HbA1c was associated with higher odds of severe NAFLD [adjusted odds ratio (AOR) = 1.8, 95% confidence level (CI) = 1.4-2.3, p < 0.0001; AOR = 2.2, 95% CI = 1.1-4.4, p = 0.033; and AOR = 1.5, 95% CI = 1.1-1.9, p = 0.003 respectively]. Conclusion: We found that prediabetes and diabetes populations had a high prevalence and higher odds of NAFLD relative to the normoglycemic population and HbA1c is an independent predictor of NAFLD severity in prediabetes and diabetes populations. Healthcare providers should screen prediabetes and diabetes populations for early detection of NAFLD and initiate treatments including lifestyle modification to prevent the progression to non-alcoholic steatohepatitis or liver cancer., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Shaheen, Schrode, Tedlos, Pan, Najjar and Friedman.)

Insulin action is impaired in type 2 diabetes. The functions of the hormone are an integrated product of insulin secretion from pancreatic β-cells and insulin clearance by receptor-mediated endocytosis and degradation, mostly in liver (hepatocytes) and, to a lower extent, in extrahepatic peripheral tissues. Substantial evidence indicates that genetic or acquired abnormalities of insulin secretion or action predispose to type 2 diabetes. In recent years, along with the discovery of the molecular foundation of receptor-mediated insulin clearance, such as through the membrane glycoprotein CEACAM1, a consensus has begun to emerge that reduction of insulin clearance contributes to the disease process. In this review, we consider the evidence suggesting a pathogenic role for reduced insulin clearance in insulin resistance, obesity, hepatic steatosis, and type 2 diabetes.

The genetic and molecular basis of developing high blood pressure and renal disease are not well known. Resp18 mutant Dahl salt-sensitive (SS- Resp18 mutant ) rats fed a 2% NaCl diet for six weeks have high blood pressure, increased renal fibrosis, and decreased mean survival time. Impairment of the dopaminergic system also leads to hypertension that involves renal and non-renal mechanisms. Deletion of any of the five dopamine receptors may lead to salt-sensitive hypertension. Therefore, we investigated the interaction between Resp18 and renal dopamine in SS- Resp18 mutant and Dahl salt-sensitive (SS) rats. We found that SS- Resp18 mutant rats had vascular dysfunction, as evidenced by a decrease in vasorelaxation in response to sodium nitroprusside. The pressure-natriuresis curve in SS- Resp18 mutant rats was shifted down and to the right of SS rats. SS- Resp18 mutant rats had decreased glomerular filtration rate and dopamine receptor subtypes, D1R and D5R. Renal dopamine levels were decreased, but urinary dopamine levels were increased, which may be the consequence of increased renal dopamine production, followed by secretion into the tubular lumen. The increased renal dopamine production in SS- Resp18 mutant rats in vivo was substantiated by the increased dopamine production in renal proximal tubule cells treated with L-DOPA. Overall, our study provides evidence that targeted disruption of the Resp18 locus in the SS rat dysregulates the renal dopaminergic system.

Cell death-inducing DNA fragmentation factor-α-like effector C (CIDEC), originally identified to be a lipid droplet-associated protein in adipocytes, positively associates with insulin sensitivity. Recently, we discovered that it is expressed abundantly in human endothelial cells and regulates vascular function. The current study was designed to characterize the physiological effects and molecular actions of endothelial CIDEC in the control of vascular phenotype and whole-body glucose homeostasis. To achieve this, we generated a humanized mouse model expressing endothelial-specific human CIDEC (E-CIDECtg). E-CIDECtg mice exhibited protection against high-fat diet-induced glucose intolerance, insulin resistance, and dyslipidemia. Moreover, these mice displayed improved insulin signaling and endothelial nitric oxide synthase activation, enhanced endothelium-dependent vascular relaxation, and improved vascularization of adipose tissue, skeletal muscle, and heart. Mechanistically, we identified a novel interplay of CIDEC-vascular endothelial growth factor A (VEGFA)-vascular endothelial growth factor receptor 2 (VEGFR2) that reduced VEGFA and VEGFR2 degradation, thereby increasing VEGFR2 activation. Overall, our results demonstrate a protective role of endothelial CIDEC against obesity-induced metabolic and vascular dysfunction, in part, by modulation of VEGF signaling. These data suggest that CIDEC may be investigated as a potential future therapeutic target for mitigating obesity-related cardiometabolic disease., (© 2022 by the American Diabetes Association.)

Insulin stores lipid in adipocytes and prevents lipolysis and the release of non-esterified fatty acids (NEFA). Excessive release of NEFA during sustained energy supply and increase in abdominal adiposity trigger systemic insulin resistance, including in the liver, a major site of insulin clearance. This causes a reduction in insulin clearance as a compensatory mechanism to insulin resistance in obesity. On the other hand, reduced insulin clearance in the liver can cause chronic hyperinsulinemia, followed by downregulation of insulin receptor and insulin resistance. Delineating the cause-effect relationship between reduced insulin clearance and insulin resistance has been complicated by the fact that insulin action and clearance are mechanistically linked to insulin binding to its receptors. This review discusses how NEFA mobilization contributes to the reciprocal relationship between insulin resistance and reduced hepatic insulin clearance, and how this may be implicated in the pathogenesis of non-alcoholic fatty liver disease.

(1) Background: Mice with global Ceacam1 deletion developed plaque-like aortic lesions even on C57BL/6J background in the presence of increased endothelial cell permeability and insulin resistance. Loss of endothelial Ceacam1 gene caused endothelial dysfunction and reduced vascular integrity without affecting systemic insulin sensitivity. Because endothelial cell injury precedes atherosclerosis, we herein investigated whether the loss of endothelial Ceacam1 initiates atheroma formation in the absence of insulin resistance. (2) Methods: Endothelial cell-specific Ceacam1 null mice on C57BL/6J.Ldlr -/- background ( Ldlr -/- VECadCre+Cc1 fl/fl ) were fed an atherogenic diet for 3-5 months before metabolic, histopathological, and en-face analysis of aortae were compared to their control littermates. Sirius Red stain was also performed on liver sections to analyze hepatic fibrosis. (3) Results: These mice displayed insulin sensitivity without significant fat deposition on aortic walls despite hypercholesterolemia. They also displayed increased inflammation and fibrosis. Deleting Ceacam1 in endothelial cells caused hyperactivation of VEGFR2/Shc/NF-κB pathway with resultant transcriptional induction of NF-κB targets. These include IL-6 that activates STAT3 inflammatory pathways, in addition to endothelin-1 and PDGF-B profibrogenic effectors. It also induced the association between SHP2 phosphatase and VEGFR2, downregulating the Akt/eNOS pathway and reducing nitric oxide production, a characteristic feature of endothelial dysfunction. Similarly, hepatic inflammation and fibrosis developed in Ldlr -/- VECadCre+Cc1 fl/fl mice without an increase in hepatic steatosis. (4) Conclusions: Deleting endothelial cell Ceacam1 caused hepatic and aortic inflammation and fibrosis with increased endothelial dysfunction and oxidative stress in the presence of hypercholesterolemia. However, this did not progress into frank atheroma formation. Because these mice remained insulin sensitive, the study provides an in vivo demonstration that insulin resistance plays a critical role in the pathogenesis of frank atherosclerosis.

The NAD-dependent deacetylase SIRT1 improves β cell function. Accordingly, nicotinamide mononucleotide (NMN), the product of the rate-limiting step in NAD synthesis, prevents β cell dysfunction and glucose intolerance in mice fed a high-fat diet. The current study was performed to assess the effects of NMN on β cell dysfunction and glucose intolerance that are caused specifically by increased circulating free fatty acids (FFAs). NMN was intravenously infused, with or without oleate, in C57BL/6J mice over a 48-h-period to elevate intracellular NAD levels and consequently increase SIRT1 activity. Administration of NMN in the context of elevated plasma FFA levels considerably improved glucose tolerance. This was due not only to partial protection from FFA-induced β cell dysfunction but also, unexpectedly, to a significant decrease in insulin clearance. However, in conditions of normal FFA levels, NMN impaired glucose tolerance due to decreased β cell function. The presence of this dual action of NMN suggests caution in its proposed therapeutic use in humans.

Non-alcoholic fatty liver disease (NAFLD) is spreading worldwide, with a racial/ethnic disparity. We examined the gender role in the racial/ethnic difference in NAFLD in the US population. We analyzed data for 3,292 individuals ≥18 years old from NHANES 2017-2018, a representative sample of the non-institutionalized adult population in the US. Exclusions were subjects with elevated transferrin level, chronic hepatitis B or C, excessive alcohol use, or prescription medications that might cause hepatic steatosis. NAFLD was diagnosed by FibroScan ® using controlled attenuation parameter (CAP) values: S0 <238, S1 = 238-259, S2 = 260-290, S3 >290. Data were analyzed using Chi square and multinomial regression. The overall prevalence of NAFLD was 47.9% [S2 = 16.1%, and S3 = 31.8%]. The prevalence of S3 was highest among Mexican Americans (46%), lowest among Blacks (22.7%), 29.9% in other Hispanics and 32.1% in Whites ( p < 0.05). It was higher among Mexican American males (54.1%) compared to Mexican American females (37.7%) ( p < 0.05). In the adjusted model, Mexican Americans were two times more likely than Whites to have S2 and S3 ( p < 0.05). Only male Mexican Americans had higher odds of S2 and S3 relative to male White ( p < 0.05). Males had higher odds of S3 relative to non-menopausal females ( p < 0.05). There was no difference in the odds of S2 or S3 NAFLD among the menopausal females with or without hormone therapy relative to non-menopausal females ( p > 0.05). While Mexican Americans had the highest prevalence of severe NAFLD relative to the other racial/ethnic groups, only male Mexican Americans, but not females, had higher likelihood of both moderate and severe NAFLD relative to Whites. Interventions that specifically target Mexican American males are needed to increase awareness about NAFLD and its prevention., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Shaheen, Schrode, Pan, Kermah, Puri, Zarrinpar, Elisha, Najjar and Friedman.)

Hepatic steatosis (HS) is a growing problem in adults worldwide, with racial/ethnic disparity in the prevalence of the disease. The purpose of this study was to characterize the racial/ethnic prevalence of the stages (normal/mild [S0/S1], moderate [S2], and severe [S3]) of HS in Mexican Americans and other Hispanics compared to other racial/ethnic groups. We analyzed data for 5,492 individuals 12 years and older from the newly released National Health and Nutrition Examination Survey 2017-2018, which is a representative sample of the US adult population. HS was diagnosed by FibroScan using controlled attenuation parameter values: S0, <238; S1, 238-259; S2, 260-290; S3, >290. We analyzed the data using the bivariate chi-squared test and multinomial regression. The prevalence of HS overall was 46.9% (S2,16.6%; S3, 30.3%). The prevalence of S3 was highest among Mexican Americans (42.8%), lowest among Blacks (21.6%), 27.6% in other Hispanics, and 30.6% in Whites (P < 0.05). Mexican Americans were about 2 times more likely than Whites to have S2 and S3, while other Hispanics showed no difference from Whites. In an adjusted model, the common risk factors of S2 and S3 were male sex, older ages, high waist-to-hip ratio, body mass index ≥25, and high triglycerides (P < 0.05). Other risk factors for S3 were hemoglobin A1c ≥5.7 and highly sensitive C-reactive protein ≥10 mg/dL (P < 0.05). Conclusion: Our study challenges the paradigm that HS is higher in Hispanics overall; rather, our data show that HS is higher in Mexican Americans and not non-Mexican American Hispanics., (© 2021 The Authors. Hepatology Communications published by Wiley Periodicals LLC on behalf of American Association for the Study of Liver Diseases.)

CEACAM1 regulates endothelial barrier integrity. Because insulin signaling in extrahepatic target tissues is regulated by insulin transport through the endothelium, we aimed at investigating the metabolic role of endothelial CEACAM1. To this end, we generated endothelial cell-specific Ceacam1 null mice ( VECadCre+Cc1 fl/fl ) and carried out their metabolic phenotyping and mechanistic analysis by comparison to littermate controls. Hyperinsulinemic-euglycemic clamp analysis showed intact insulin sensitivity in VECadCre+Cc1 fl/fl mice. This was associated with the absence of visceral obesity and lipolysis and normal levels of circulating non-esterified fatty acids, leptin, and adiponectin. Whereas the loss of endothelial Ceacam1 did not affect insulin-stimulated receptor phosphorylation, it reduced IRS-1/Akt/eNOS activation to lower nitric oxide production resulting from limited SHP2 sequestration. It also reduced Shc sequestration to activate NF-κB and increase the transcription of matrix metalloproteases, ultimately inducing plasma IL-6 and TNFα levels. Loss of endothelial Ceacam1 also induced the expression of the anti-inflammatory CEACAM1-4L variant in M2 macrophages in white adipose tissue. Together, this could cause endothelial barrier dysfunction and facilitate insulin transport, sustaining normal glucose homeostasis and retaining fat accumulation in adipocytes. The data assign a significant role for endothelial cell CEACAM1 in maintaining insulin sensitivity in peripheral extrahepatic target tissues.

Objective: NAFLD is a complex disease marked by cellular abnormalities leading to NASH. NAFLD patients manifest low hepatic levels of CEACAM1, a promoter of insulin clearance. Consistently, Cc1 -/- null mice displayed spontaneous hyperinsulinemia/insulin resistance and steatohepatitis. Liver-specific reconstitution of Ceacam1 reversed these metabolic anomalies in 8-month-old Cc1 -/-xliver+ mice fed a regular chow diet. The current study examined whether it would also reverse progressive hepatic fibrosis in mice fed a high-fat (HF) diet., Methods: 3-Month-old mice were fed a high-fat diet for 3-5 months, and metabolic and histopathological analysis were conducted to evaluate their NASH phenotype., Results: Reconstituting CEACAM1 to Cc1 -/- livers curbed diet-induced liver dysfunction and NASH, including macrovesicular steatosis, lobular inflammation, apoptosis, oxidative stress, and chicken-wire bridging fibrosis. Persistence of hepatic fibrosis in HF-fed Cc1 -/- treated with nicotinic acid demonstrated a limited role for lipolysis and adipokine release in hepatic fibrosis caused by Ceacam1 deletion., Conclusions: Restored metabolic and histopathological phenotype of HF-fed Cc1 -/-xliver+xliver+ assigned a critical role for hepatic CEACAM1 in preventing NAFLD/NASH including progressive hepatic fibrosis., Competing Interests: Declaration of competing interest None declared., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Patients with nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) commonly develop atherosclerosis through a mechanism that is not well delineated. These diseases are associated with steatosis, inflammation, oxidative stress, and fibrosis. The role of insulin resistance in their pathogenesis remains controversial. Albumin ( Alb ) Cre + Cc1 flox ( fl ) /fl mice with the liver-specific null deletion of the carcinoembryonic antigen-related cell adhesion molecule 1 ( Ceacam1 ; alias Cc1 ) gene display hyperinsulinemia resulting from impaired insulin clearance followed by hepatic insulin resistance, elevated de novo lipogenesis, and ultimately visceral obesity and systemic insulin resistance. We therefore tested whether this mutation causes NAFLD/NASH and atherosclerosis. To this end, mice were propagated on a low-density lipoprotein receptor ( Ldlr ) -/- background and at 4 months of age were fed a high-cholesterol diet for 2 months. We then assessed the biochemical and histopathologic changes in liver and aortae. Ldlr -/- AlbCre + Cc1 fl/fl mice developed chronic hyperinsulinemia with proatherogenic hypercholesterolemia, a robust proinflammatory state associated with visceral obesity, elevated oxidative stress (reduced NO production), and an increase in plasma and tissue endothelin-1 levels. In parallel, they developed NASH (steatohepatitis, apoptosis, and fibrosis) and atherosclerotic plaque lesions. Mechanistically, hyperinsulinemia caused down-regulation of the insulin receptor followed by inactivation of the insulin receptor substrate 1-protein kinase B-endothelial NO synthase pathway in aortae, lowering the NO level. This also limited CEACAM1 phosphorylation and its sequestration of Shc-transforming protein (Shc), activating the Shc-mitogen-activated protein kinase-nuclear factor kappa B pathway and stimulating endothelin-1 production. Thus, in the presence of proatherogenic dyslipidemia, hyperinsulinemia and hepatic insulin resistance driven by liver-specific deletion of Ceacam1 caused metabolic and vascular alterations reminiscent of NASH and atherosclerosis. Conclusion: Altered CEACAM1-dependent hepatic insulin clearance pathways constitute a molecular link between NASH and atherosclerosis., (© 2020 The Authors. Hepatology Communications published by Wiley Periodicals LLC on behalf of the American Association for the Study of Liver Diseases.)

Biomarkers are indicators of pathogenic processes, typical biological processes, or pharmacological reactions to a therapy. It has several potential usages in cancer; differential diagnosis, prognosis, risk assessment, therapeutic response, and monitoring of disease progression. Recently, advances in oncomarkers raised significant opportunities for enhancing management of cancer. Chromosomal aberration, molecular impairment and epigenetic alteration might be applied to diagnose and prognose cancer and its epidemiology. Some oncomarkers are specific and highly sensitive for detection. An oncomarker might be used to see how the body reacts to an intervention or a situation. The present study represents a short review about various genetic oncomarkers with diagnostic and prognostic values.

Objective: PTEN haploinsufficiency plays an important role in prostate cancer development in men. However, monoallelic deletion of Pten gene failed to induce high prostate intraepithelial neoplasia (PIN) until Pten +/- mice aged or fed a high-calorie diet. Because CEACAM1, a cell adhesion molecule with a potential tumor suppression activity, is induced in Pten +/- prostates, the study aimed at examining whether the rise of CEACAM1 limited neoplastic progression in Pten +/- prostates., Methods: Pten +/- were crossbred with Cc1 -/- mice harboring a null deletion of Ceacam1 gene to produce Pten +/- /Cc1 -/- double mutants. Prostates from 7-month old male mice were analyzed histologically and biochemically for PIN progression., Results: Deleting Ceacam1 in Pten +/- mice caused an early development of high-grade PIN in parallel to hyperactivation of PI3 kinase/Akt and Ras/MAP kinase pathways, with an increase in cell proliferation, epithelial-to-mesenchymal transition, angiogenesis and inflammation relative to Pten +/- and Cc1 -/- individual mutants. It also caused a remarkable increase in lipogenesis in prostate despite maintaining insulin sensitivity. Concomitant Ceacam1 deletion with Pten +/- activated the IL-6/STAT3 signaling pathways to suppress Irf-8 transcription that in turn, led to a decrease in the expression level of promyelocytic leukemia gene, a well characterized tumor suppressor in prostate., Conclusions: Ceacam1 deletion accelerated high-grade prostate intraepithelial neoplasia in Pten haploinsufficient mice while preserving insulin sensitivity. This demonstrated that the combined loss of Ceacam1 and Pten advanced prostate cancer by increasing lipogenesis and modifying the STAT3-dependent inflammatory microenvironment of prostate., Competing Interests: Declaration of competing interest None declared., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: Patients with nonalcoholic steatohepatitis (NASH) are at risk for developing cirrhosis and hepatic cancer. Currently, the definitive gold-standard method of diagnosing NASH is a liver biopsy, an invasive and costly method. Our objective was to compare three non-invasive methods of identifying NASH by using data on 10,007 subjects from NHANES III (1988-1994) to determine the prevalence and variables associated with NASH, as defined by each non-invasive method., Methods: We used ultrasound data to identify subjects with moderate-to-severe hepatic steatosis, of whom we identified the NASH population using either the HAIR score, the NASH liver fat score, or the Gholam score, each of which had been validated with liver biopsy. We performed multinomial logistic regression to compare each NASH population to the normal population (those with no-to-mild hepatic steatosis)., Results: We identified 1136 (9.5%) subjects as having NASH by at least one method and 219 (1.8%) were identified by all 3 methods. Independent of the non-invasive method used, Mexican-Americans (MA) had the highest prevalence of NASH. All three methods identified significant risk factors for NASH (p<0.05), including: elevated waist-to-hip ratio, elevated levels of C-peptide, total cholesterol, or C-reactive protein (CRP)., Conclusion: We conclude that the combined non-invasive methods can help identify candidates with a high likelihood of being diagnosed with NASH. Health care providers can screen people with the combined non-invasive methods for the risk factors and identify candidates for interventions, including exercise and/or referral to biopsy.

The Carcinoembryonic Antigen-Related Cell Adhesion Molecule (CEACAM) family of proteins plays a significant role in regulating peripheral insulin action by participating in the regulation of insulin metabolism and energy balance. In light of their differential expression, CEACAM1 regulates chiefly insulin extraction, whereas CEACAM2 appears to play a more important role in regulating insulin secretion and overall energy balance, including food intake, energy expenditure and spontaneous physical activity. We will focus this review on the role of CEACAM2 in regulating insulin metabolism and energy balance with an overarching goal to emphasize the importance of the coordinated regulatory effect of these related plasma membrane glycoproteins on insulin metabolism and action.

Upon its secretion from pancreatic β-cells, insulin reaches the liver through the portal circulation to exert its action and eventually undergo clearance in the hepatocytes. In addition to insulin secretion, hepatic insulin clearance regulates the homeostatic level of insulin that is required to reach peripheral insulin target tissues to elicit proper insulin action. Receptor-mediated insulin uptake followed by its degradation constitutes the basic mechanism of insulin clearance. Upon its phosphorylation by the insulin receptor tyrosine kinase, carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) takes part in the insulin-insulin receptor complex to increase the rate of its endocytosis and targeting to the degradation pathways. This review summarizes how this process is regulated and how it is associated with insulin-degrading enzyme in the liver. It also discusses the physiological implications of impaired hepatic insulin clearance: Whereas reduced insulin clearance cooperates with increased insulin secretion to compensate for insulin resistance, it can also cause hepatic insulin resistance. Because chronic hyperinsulinemia stimulates hepatic de novo lipogenesis, impaired insulin clearance also causes hepatic steatosis. Thus impaired insulin clearance can underlie the link between hepatic insulin resistance and hepatic steatosis. Delineating these regulatory pathways should lead to building more effective therapeutic strategies against metabolic syndrome.

Background: CEACAM1 regulates insulin sensitivity by promoting insulin clearance. Accordingly, global C57BL/6J.Cc1 -/- null mice display hyperinsulinemia due to impaired insulin clearance at 2 months of age, followed by insulin resistance, steatohepatitis, visceral obesity and leptin resistance at 6 months. The study aimed at investigating the primary role of hepatic CEACAM1 in insulin and lipid homeostasis independently of its metabolic effect in extra-hepatic tissues., Methods: Liver-specific C57BL/6J.AlbCre+Cc1 fl/fl mice were generated and their metabolic phenotype was characterized by comparison to that of their littermate controls at 2-9 months of age, using hyperinsulinemic-euglycemic clamp analysis and indirect calorimetry. The effect of hyperphagia on insulin resistance was assessed by pair-feeding experiments., Results: Liver-specific AlbCre+Cc1 fl/fl mutants exhibited impaired insulin clearance and hyperinsulinemia at 2 months, followed by hepatic insulin resistance (assessed by hyperinsulinemic-euglycemic clamp analysis) and steatohepatitis at ~ 7 months of age, at which point visceral obesity and hyperphagia developed, in parallel to hyperleptinemia and blunted hypothalamic STAT3 phosphorylation in response to an intraperitoneal injection of leptin. Hyperinsulinemia caused hypothalamic insulin resistance, followed by increased fatty acid synthase activity, which together with defective hypothalamic leptin signaling contributed to hyperphagia and reduced physical activity. Pair-feeding experiment showed that hyperphagia caused systemic insulin resistance, including blunted insulin signaling in white adipose tissue and lipolysis, at 8-9 months of age., Conclusion: AlbCre+Cc1 fl/fl mutants provide an in vivo demonstration of the key role of impaired hepatic insulin clearance and hyperinsulinemia in the pathogenesis of secondary hepatic insulin resistance independently of lipolysis. They also reveal an important role for the liver-hypothalamic axis in the regulation of energy balance and subsequently, systemic insulin sensitivity., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The role of insulin-degrading enzyme (IDE), a metalloprotease with high affinity for insulin, in insulin clearance remains poorly understood., Objective: This study aimed to clarify whether IDE is a major mediator of insulin clearance, and to define its role in the etiology of hepatic insulin resistance., Methods: We generated mice with liver-specific deletion of Ide (L-IDE-KO) and assessed insulin clearance and action., Results: L-IDE-KO mice exhibited higher (~20%) fasting and non-fasting plasma glucose levels, glucose intolerance and insulin resistance. This phenotype was associated with ~30% lower plasma membrane insulin receptor levels in liver, as well as ~55% reduction in insulin-stimulated phosphorylation of the insulin receptor, and its downstream signaling molecules, AKT1 and AKT2 (reduced by ~40%). In addition, FoxO1 was aberrantly distributed in cellular nuclei, in parallel with up-regulation of the gluconeogenic genes Pck1 and G6pc. Surprisingly, L-IDE-KO mice showed similar plasma insulin levels and hepatic insulin clearance as control mice, despite reduced phosphorylation of the carcinoembryonic antigen-related cell adhesion molecule 1, which upon its insulin-stimulated phosphorylation, promotes receptor-mediated insulin uptake to be degraded., Conclusion: IDE is not a rate-limiting regulator of plasma insulin levels in vivo., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a transmembrane glycoprotein that is expressed on epithelial, endothelial and immune cells. CEACAM1 is a differentiation antigen involved in the maintenance of epithelial polarity that is induced during hepatocyte differentiation and liver regeneration. CEACAM1 regulates insulin sensitivity by promoting hepatic insulin clearance, and controls liver tolerance and mucosal immunity. Obese insulin-resistant humans with non-alcoholic fatty liver disease manifest loss of hepatic CEACAM1. In mice, deletion or functional inactivation of CEACAM1 impairs insulin clearance and compromises metabolic homeostasis which initiates the development of obesity and hepatic steatosis and fibrosis with other features of non-alcoholic steatohepatitis, and adipogenesis in white adipose depot. This is followed by inflammation and endothelial and cardiovascular dysfunctions. In obstructive and inflammatory liver diseases, soluble CEACAM1 is shed into human bile where it can serve as an indicator of liver disease. On immune cells, CEACAM1 acts as an immune checkpoint regulator, and deletion of Ceacam1 gene in mice causes exacerbation of inflammation and hyperactivation of myeloid cells and lymphocytes. Hence, hepatic CEACAM1 resides at the central hub of immune and metabolic homeostasis in both humans and mice. This review focuses on the regulatory role of CEACAM1 in liver and biliary tract architecture in health and disease, and on its metabolic role and function as an immune checkpoint regulator of hepatic inflammation.

Protein arginine methyltransferase 5 (PRMT5) regulates gene expression either transcriptionally by symmetric dimethylation of arginine residues on histones H4R3, H3R8, and H2AR3 or at the posttranslational level by methylation of nonhistone target proteins. Although emerging evidence suggests that PRMT5 functions as an oncogene, its role in metabolic diseases is not well-defined. We investigated the role of PRMT5 in promoting high-fat-induced hepatic steatosis. A high-fat diet up-regulated PRMT5 levels in the liver but not in other metabolically relevant tissues such as skeletal muscle or white and brown adipose tissue. This was associated with repression of master transcription regulators involved in mitochondrial biogenesis. In contrast, lentiviral short hairpin RNA-mediated reduction of PRMT5 significantly decreased phosphatidylinositol 3-kinase/AKT signaling in mouse AML12 liver cells. PRMT5 knockdown or knockout decreased basal AKT phosphorylation but boosted the expression of peroxisome proliferator-activated receptor α (PPARα) and PGC-1α with a concomitant increase in mitochondrial biogenesis. Moreover, by overexpressing an exogenous WT or enzyme-dead mutant PRMT5 or by inhibiting PRMT5 enzymatic activity with a small-molecule inhibitor, we demonstrated that the enzymatic activity of PRMT5 is required for regulation of PPARα and PGC-1α expression and mitochondrial biogenesis. Our results suggest that targeting PRMT5 may have therapeutic potential for the treatment of fatty liver., (© 2018 Huang et al.)

Objective: Mice with global null mutation of Ceacam1 (Cc1 -/- ), display impairment of insulin clearance that causes hyperinsulinemia followed by insulin resistance, elevated hepatic de novo lipogenesis, and visceral obesity. In addition, they manifest abnormal vascular permeability and elevated blood pressure. Liver-specific rescuing of Ceacam1 reversed all of the metabolic abnormalities in Cc1 -/-liver+ mice. The current study examined whether Cc1 -/- male mice develop endothelial and cardiac dysfunction and whether this relates to the metabolic abnormalities caused by defective insulin extraction., Methods and Results: Myography studies showed reduction of agonist-stimulated nitric oxide production in resistance arterioles in Cc1 -/- , but not Cc1 -/-liver+ mice. Liver-based rescuing of CEACAM1 also attenuated the abnormal endothelial adhesiveness to circulating leukocytes in parallel to reducing plasma endothelin-1 and recovering plasma nitric oxide levels. Echocardiography studies revealed increased septal wall thickness, cardiac hypertrophy and reduced cardiac performance in Cc1 -/- , but not Cc1 -/-xliver+ mice. Insulin signaling experiments indicated compromised IRS1/Akt/eNOS pathway leading to lower nitric oxide level, and activated Shc/MAPK pathway leading to more endothelin-1 production in the aortae and hearts of Cc1 -/- , but not Cc1 -/-xliver+ mice. The increase in the ratio of endothelin-1 receptor A/B indicated an imbalance in the vasomotor activity of Cc1 -/- mice, which was normalized in Cc1 -/-xliver+ mice., Conclusions: The data underscore a critical role for impaired CEACAM1-dependent hepatic insulin clearance pathways and resulting hyperinsulinemia and lipid accumulation in aortae and heart in regulating the cardiovascular function., (Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Aims/hypothesis: The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes insulin clearance. Mice with global null mutation (Cc1 -/- ) or with liver-specific inactivation (L-SACC1) of Cc1 (also known as Ceacam1) gene display hyperinsulinaemia resulting from impaired insulin clearance, insulin resistance, steatohepatitis and obesity. Because increased lipolysis contributes to the metabolic phenotype caused by transgenic inactivation of CEACAM1 in the liver, we aimed to further investigate the primary role of hepatic CEACAM1-dependent insulin clearance in insulin and lipid homeostasis. To this end, we examined whether transgenic reconstitution of CEACAM1 in the liver of global Cc1 -/- mutant mice reverses their abnormal metabolic phenotype., Methods: Insulin response was assessed by hyperinsulinaemic-euglycaemic clamp analysis and energy balance was analysed by indirect calorimetry. Mice were overnight-fasted and refed for 7 h to assess fatty acid synthase activity in the liver and the hypothalamus in response to insulin release during refeeding., Results: Liver-based rescuing of CEACAM1 restored insulin clearance, plasma insulin level, insulin sensitivity and steatohepatitis caused by global deletion of Cc1. It also reversed the gain in body weight and total fat mass observed with Cc1 deletion, in parallel to normalising energy balance. Mechanistically, reversal of hyperphagia appeared to result from reducing fatty acid synthase activity and restoring insulin signalling in the hypothalamus., Conclusions/interpretation: Despite the potential confounding effects of deleting Cc1 from extrahepatic tissues, liver-based rescuing of CEACAM1 resulted in full normalisation of the metabolic phenotype, underscoring the key role that CEACAM1-dependent hepatic insulin clearance pathways play in regulating systemic insulin sensitivity, lipid homeostasis and energy balance.

Exenatide, a glucagon-like peptide-1 receptor agonist, induces insulin secretion. Its role in insulin clearance has not been adequately examined. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance to maintain insulin sensitivity. Feeding C57BL/6J mice a high-fat diet down-regulates hepatic Ceacam1 transcription to cause hyperinsulinemia, insulin resistance, and hepatic steatosis, as in Ceacam1 null mice ( Cc1 -/- ). Thus, we tested whether exenatide regulates Ceacam1 expression in high-fat diet-fed mice and whether this contributes to its insulin sensitizing effect. Exenatide (100 nM) induced the transcriptional activity of wild-type Ceacam1 promoter but not the constructs harboring block mutations of peroxisome proliferator-activated receptor response element and retinoid X receptor alpha, individually or collectively, in HepG2 human hepatoma cells. Chromatin immunoprecipitation analysis demonstrated binding of peroxisome proliferator-activated receptor gamma to Ceacam1 promoter in response to rosiglitazone and exenatide. Consistently, exenatide induced Ceacam1 messenger RNA expression within 12 hours in the absence but not in the presence of the glucagon-like peptide-1 receptor antagonist exendin 9-39. Exenatide (20 ng/g body weight once daily intraperitoneal injection in the last 30 days of feeding) restored hepatic Ceacam1 expression and insulin clearance to curb diet-induced metabolic abnormalities and steatohepatitis in wild-type but not Cc1 -/- mice fed a high-fat diet for 2 months. Conclusion : Exenatide promotes insulin clearance in parallel with insulin secretion to prevent chronic hyperinsulinemia and the resulting hepatic steatosis, and this contributes to its insulin sensitizing effect. Our data further highlight the relevance of physiologic insulin metabolism in maintaining insulin sensitivity and normal lipid metabolism. ( Hepatology Communications 2018;2:35-47).

Aims/hypothesis: Cc2 -/- mice lacking the gene encoding the carcinoembryonic-antigen-related cell adhesion molecule 2 (Cc2 [also known as Ceacam2]) exhibit hyperphagia that leads to obesity and insulin resistance. This starts at 2 months of age in female mice. Male mutants maintain normal body weight and insulin sensitivity until the last age previously examined (7-8 months), owing to increased sympathetic tone to white adipose tissue and energy expenditure. The current study investigates whether insulin resistance develops in mutant male mice at a later age and whether this is accompanied by changes in insulin homeostasis., Methods: Insulin response was assessed by insulin and glucose tolerance tests. Energy balance was analysed by indirect calorimetry., Results: Male Cc2 -/- mice developed overt metabolic abnormalities at about 9 months of age. These include elevated global fat mass, hyperinsulinaemia and insulin resistance (as determined by glucose and insulin intolerance, fed hyperglycaemia and decreased insulin signalling pathways). Pair-feeding experiments showed that insulin resistance resulted from hyperphagia. Indirect calorimetry demonstrated that older mutant male mice had compromised energy expenditure. Despite increased insulin secretion caused by Cc2 deletion, chronic hyperinsulinaemia did not develop in mutant male mice until about 9 months of age, at which point insulin clearance began to decline substantially. This was probably mediated by a marked decrease in hepatic CEACAM1 expression., Conclusions/interpretation: The data demonstrate that at about 9 months of age, Cc2 -/- male mice develop a reduction in energy expenditure and energy imbalance which, combined with a progressive decrease in CEACAM1-dependent hepatic insulin clearance, causes chronic hyperinsulinaemia and sustained age-dependent insulin resistance. This represents a novel mechanistic underpinning of age-related impairment of hepatic insulin clearance.

Impairment of insulin clearance is being increasingly recognized as a critical step in the development of insulin resistance and metabolic disease. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes insulin clearance. Null deletion or liver-specific inactivation of Ceacam1 in mice causes a defect in insulin clearance, insulin resistance, steatohepatitis, and visceral obesity. Immunohistological analysis revealed reduction of hepatic CEACAM1 in obese subjects with fatty liver disease. Thus, we aimed to determine whether this occurs at the hepatocyte level in response to systemic extrahepatic factors and whether this holds across species. Northern and Western blot analyses demonstrate that CEACAM1 mRNA and protein levels are reduced in liver tissues of obese individuals compared to their lean age-matched counterparts. Furthermore, Western analysis reveals a comparable reduction of CEACAM1 protein in primary hepatocytes derived from the same obese subjects. Similar to humans, Ceacam1 mRNA level, assessed by quantitative RT-PCR analysis, is significantly reduced in the livers of obese Zucker ( fa/fa , ZDF) and Koletsky ( f/f ) rats relative to their age-matched lean counterparts. These studies demonstrate that the reduction of hepatic CEACAM1 in obesity occurs at the level of hepatocytes and identify the reduction of hepatic CEACAM1 as a common denominator of obesity across multiple species.

The pathogenesis of human non-alcoholic fatty liver disease (NAFLD) remains unclear, in particular in the context of its relationship to insulin resistance and visceral obesity. Work on the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in mice has resolved some of the related questions. CEACAM1 promotes insulin clearance by enhancing the rate of uptake of the insulin-receptor complex. It also mediates a negative acute effect of insulin on fatty acid synthase activity. This positions CEACAM1 to coordinate the regulation of insulin and lipid metabolism. Fed a regular chow diet, global null mutation of Ceacam1 manifest hyperinsulinemia, insulin resistance, obesity, and steatohepatitis. They also develop spontaneous chicken-wire fibrosis, characteristic of non-alcoholic steatohepatitis. Reduction of hepatic CEACAM1 expression plays a significant role in the pathogenesis of diet-induced metabolic abnormalities, as bolstered by the protective effect of hepatic CEACAM1 gain-of-function against the metabolic response to dietary fat. Together, this emphasizes that loss of hepatic CEACAM1 links NAFLD to insulin resistance and obesity.

The Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 (CEACAM1) promotes insulin sensitivity by inducing insulin clearance and reducing de novo lipogenesis in the liver. Consistently, Cc1 -/- mice with null deletion of Ceacam1 gene exhibit hyperinsulinemia and insulin resistance, in addition to steatohepatitis. They also exhibit early pericellular fibrosis. Redelivering Ceacam1 to the liver reverses the altered metabolism and histopathology of Cc1 -/- mice. Exenatide, a long-acting glucagon-like peptide-1 receptor agonist, induces Ceacam1 transcription and consequently, reverses impaired insulin clearance and insulin resistance caused by high-fat intake. Additionally, it reverses fat accumulation in the liver. The current studies show that exenatide also restored the activities of alanine transaminase and aspartate aminotransferase, and reversed the inflammatory and oxidative stress response to high-fat diet in wild-type, but not in Cc1 -/- mice. Exenatide also prevented diet-induced activation of the TGFβ/Smad2/Smad3 pro-fibrogenic pathways, and normalized the mRNA levels of pro-fibrogenic genes in wild-type, but not in Cc1 -/- mice. Together, the data demonstrate that exenatide prevented diet-induced pro-fibrogenesis and hepatocellular injury in a CEACAM1-dependent mechanism.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is an Ig-ITIM superfamily member that regulates integrin αIIbβ3 function. We hypothesized that its twin protein, CEACAM2, exerts a similar physiologic role in murine platelets. CEACAM2-deficient mice (Cc2 -/- ) displayed prolonged tail bleeding times and increased volume of blood loss. Cc2 -/- platelets have moderate integrin αIIbβ3-mediated functional defects with impaired kinetics of platelet spreading on fibrinogen and type I collagen and delayed kinetics in the retraction of fibrin clots in vitro. This functional integrin αIIbβ3 defect could not be attributed to altered integrin αIIbβ3 expression. Cc2 -/- platelets displayed normal 'inside-out' signaling properties as demonstrated by normal agonist-induced binding of soluble fluorescein isothiocyanate (FITC)-fibrinogen and JON/A antibody binding. This data provides direct evidence that disruption of CEACAM2 induces a moderate integrin αIIbβ3-mediated platelet function defect, and that CEACAM2 is essential to maintain a normal integrin αIIbβ3-mediated platelet function.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) regulates insulin sensitivity by promoting hepatic insulin clearance and mediating suppression of fatty acid synthase activity. Feeding C57BL/6J male mice with a high-fat (HF) diet for 3-4 weeks triggered a >60% decrease in hepatic CEACAM1 levels to subsequently impair insulin clearance and cause systemic insulin resistance and hepatic steatosis. This study aimed at investigating whether lipolysis drives reduction in hepatic CEACAM1 and whether this constitutes a key mechanism leading to diet-induced metabolic abnormalities. Blocking lipolysis with a daily intraperitoneal injection of nicotinic acid in the last two days of a 30-day HF feeding regimen demonstrated that white adipose tissue (WAT)-derived fatty acids repressed hepatic CEACAM1-dependent regulation of insulin and lipid metabolism in 3-month-old male C57BL/6J mice. Adenoviral-mediated CEACAM1 redelivery countered the adverse metabolic effect of the HF diet on insulin resistance, hepatic steatosis, visceral obesity, and energy expenditure. It also reversed the effect of HF diet on inflammation and fibrosis in WAT and liver. This assigns a causative role for lipolysis-driven decrease in hepatic CEACAM1 level and its regulation of insulin and lipid metabolism in sustaining systemic insulin resistance, hepatic steatosis, and other abnormalities associated with excessive energy supply., (Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.)

High fat diet reduces the expression of CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1), a transmembrane glycoprotein that promotes insulin clearance and down-regulates fatty acid synthase activity in the liver upon its phosphorylation by the insulin receptor. Because peroxisome proliferator-activated receptor α (PPARα) transcriptionally suppresses CEACAM1 expression, we herein examined whether high fat down-regulates CEACAM1 expression in a PPARα-dependent mechanism. By activating PPARα, the lipid-lowering drug fenofibrate reverses dyslipidemia and improves insulin sensitivity in type 2 diabetes in part by promoting fatty acid oxidation. Despite reducing glucose-stimulated insulin secretion, fenofibrate treatment does not result in insulin insufficiency. To examine whether this is mediated by a parallel decrease in CEACAM1-dependent hepatic insulin clearance pathways, we fed wild-type and Pparα -/- null mice a high fat diet supplemented with either fenofibrate or Wy14643, a selective PPARα agonist, and examined their effect on insulin metabolism and action. We demonstrated that the decrease in insulin secretion by fenofibrate and Wy14643 is accompanied by reduction in insulin clearance in wild-type but not Pparα -/- mice, thereby maintaining normoinsulinemia and insulin sensitivity despite continuous high fat intake. Intact insulin secretion in L-CC1 mice with protected hepatic insulin clearance and CEACAM1 levels provides in vivo evidence that insulin secretion responds to changes in insulin clearance to maintain physiologic insulin and glucose homeostasis. These results also emphasize the relevant role of hepatic insulin extraction in regulating insulin sensitivity., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

FK506-binding protein-51 (FKBP51) is a molecular cochaperone recently shown to be a positive regulator of peroxisome proliferator-activated receptor (PPAR)γ, the master regulator of adipocyte differentiation and function. In cellular models of adipogenesis, loss of FKBP51 not only reduced PPARγ activity but also reduced lipid accumulation, suggesting that FKBP51 knock-out (KO) mice might have insufficient development of adipose tissue and lipid storage ability. This model was tested by examining wild-type (WT) and FKBP51-KO mice under regular and high-fat diet conditions. Under both diets, FKBP51-KO mice were resistant to weight gain, hepatic steatosis, and had greatly reduced white adipose tissue (WAT) but higher amounts of brown adipose tissue. Under high-fat diet, KO mice were highly resistant to adiposity and exhibited reduced plasma lipids and elevated glucose and insulin tolerance. Profiling of perigonadal and sc WAT revealed elevated expression of brown adipose tissue lineage genes in KO mice that correlated increased energy expenditure and a shift of substrate oxidation to carbohydrates, as measured by indirect calorimetry. To directly test PPARγ involvement, WT and KO mice were fed rosiglitazone agonist. In WT mice, rosiglitazone induced whole-body weight gain, increased WAT mass, a shift of substrate oxidation to lipids, and elevated expression of PPARγ-regulated lipogenic genes in WAT. In contrast, KO mice had reduced rosiglitazone responses for these parameters. Our results identify FKBP51 as an important regulator of PPARγ in WAT and as a potential new target in the treatment of obesity and diabetes.