A Phase 3, Randomized, Controlled Trial of Resmetirom in NASH with Liver Fibrosis.

BACKGROUND: Nonalcoholic steatohepatitis (NASH) is a progressive liver disease with no approved treatment. Resmetirom is an oral, liver-directed, thyroid hormone receptor beta-selective agonist in development for the treatment of NASH with liver fibrosis. METHODS: We are conducting an ongoing phase 3 trial involving adults with biopsy-confirmed NASH and a fibrosis stage of F1B, F2, or F3 (stages range from F0 [no fibrosis] to F4 [cirrhosis]). Patients were randomly assigned in a 1:1:1 ratio to receive once-daily resmetirom at a dose of 80 mg or 100 mg or placebo. The two primary end points at week 52 were NASH resolution (including a reduction in the nonalcoholic fatty liver disease [NAFLD] activity score by ≥2 points; scores range from 0 to 8, with higher scores indicating more severe disease) with no worsening of fibrosis, and an improvement (reduction) in fibrosis by at least one stage with no worsening of the NAFLD activity score. RESULTS: Overall, 966 patients formed the primary analysis population (322 in the 80-mg resmetirom group, 323 in the 100-mg resmetirom group, and 321 in the placebo group). NASH resolution with no worsening of fibrosis was achieved in 25.9% of the patients in the 80-mg resmetirom group and 29.9% of those in the 100-mg resmetirom group, as compared with 9.7% of those in the placebo group (P<0.001 for both comparisons with placebo). Fibrosis improvement by at least one stage with no worsening of the NAFLD activity score was achieved in 24.2% of the patients in the 80-mg resmetirom group and 25.9% of those in the 100-mg resmetirom group, as compared with 14.2% of those in the placebo group (P<0.001 for both comparisons with placebo). The change in low-density lipoprotein cholesterol levels from baseline to week 24 was -13.6% in the 80-mg resmetirom group and -16.3% in the 100-mg resmetirom group, as compared with 0.1% in the placebo group (P<0.001 for both comparisons with placebo). Diarrhea and nausea were more frequent with resmetirom than with placebo. The incidence of serious adverse events was similar across trial groups: 10.9% in the 80-mg resmetirom group, 12.7% in the 100-mg resmetirom group, and 11.5% in the placebo group. CONCLUSIONS: Both the 80-mg dose and the 100-mg dose of resmetirom were superior to placebo with respect to NASH resolution and improvement in liver fibrosis by at least one stage. (Funded by Madrigal Pharmaceuticals; MAESTRO-NASH ClinicalTrials.gov number, NCT03900429.).

Health-Related quality of life (HRQL) assessments in a 52-Week, Double-Blind, randomized, Placebo-Controlled phase 3 study of resmetirom (MGL-3196) in patients with metabolic dysfunction associated steatohepatitis (MASH) and fibrosis.

BACKGROUND/AIMS: Resmetirom, liver directed thyroid-hormone receptor-ß agonist, received approval for MASH treatment. We assessed HRQL in MASH patients treated with resmetirom. METHODS: Non-cirrhotic MASH/NASH patients with confirmed/suspected fibrosis were enrolled in a 54-month double-blind randomized placebo-controlled Phase 3 clinical trial with serial biopsy assessments (MAESTRO-NASH, NCT03900429) at baseline and Week 52. HRQL was assessed using Chronic Liver Disease Questionnaire-NASH (CLDQ-NAFLD) and Liver Disease Quality of Life (LDQOL). Baseline HRQL score changes by treatment group (resmetirom 80 mg, resmetirom 100 mg or placebo) and histological response (improvement of fibrosis without worsening of NAS or resolution of MASH/NASH without worsening of fibrosis) were compared after 52 weeks. RESULTS: Included were 966 ITT patients: 323 received resmetirom 100 mg, 322 resmetirom 80 mg, 321 placebo. By weeks 24 and 52, patients receiving 80 or 100 mg resmetirom experienced HRQL improvement CLDQ-NAFLD worry domain (mean +0.21 to +0.24, p<0.05). At week 52, subjects who met histologic endpoints after treatment with resmetirom (100 mg and 80 mg pooled) experienced HRQL improvement in CLDQ-NAFLD Worry +0.46 (41% met MCID), LDQOL domains: Role Emotional +3.0 (28% met MCID), Health Distress +8.1 (38% MCID), Stigma +3.5 (39% MCID) and total LDQOL +2.2 (35% MCID) (all p<0.05). Similar improvements noted in histologic responders from 100 mg or 80 mg resmetirom groups when separated- no improvements in placebo or nonresponders. Baseline F3 histologic responders had similar/more pronounced HRQL improvements. CONCLUSIONS: MASH/NASH patients with fibrosis improvement or resolution of MASH with resmetirom experienced clinically meaningful and statistically significant HRQL improvements.

Hepatic Fat Reduction Due to Resmetirom in Patients With Nonalcoholic Steatohepatitis Is Associated With Improvement of Quality of Life.

BACKGROUND & AIMS: Nonalcoholic steatohepatitis (NASH) is a chronic liver disease associated with adverse clinical outcomes and impaired health-related quality of life (HRQL). METHODS: Patients with biopsy-proven non-cirrhotic NASH with hepatic fat fraction of ≥10% by magnetic resonance imaging-proton density fat fraction were enrolled in a phase 2, multicenter, double-blind, randomized, placebo-controlled study of resmetirom. HRQL was assessed using Short Form-36 throughout 36 weeks of treatment. RESULTS: One hundred twenty-five NASH patients were enrolled (50 ± 11 years old, 50% male, 94% white, body mass index 35 ± 6 kg/m2, 39% with diabetes mellitus). Of these, 84 patients received 80 mg of resmetirom daily, and 41 received placebo. At baseline, HRQL scores were not different from general population norms (Physical Component Summary [PCS] 47.9 ± 9.3 vs 50, Mental Component Summary 50.4 ± 10.0 vs 50; all P > .05). By treatment week 12, patients who received resmetirom experienced improvement of Bodily Pain and Short Form-6D utility scores (P < .05); no HRQL improvement was noted in placebo (all P > .05). Improvement in PCS continued up to week 36 of treatment with resmetirom, again with no improvement in placebo group (all P > .05). Adjusted for the baseline score and clinicodemographic confounders, meeting the endpoint of a decrease in proton density fat fraction of ≥30% by week 12 (met by 54 of 116 treatment completers; 47 of 54 on resmetirom) was independently associated with greater improvements in Physical Functioning and PCS scores at week 36 (P < .05). Patients with improvement in NASH and fibrosis on liver biopsy also showed improvement in components of HRQL. CONCLUSIONS: Patients with NASH treated who improved their hepatic fat fraction and/or Nonalcoholic Fatty Liver Disease Activity Score on serial liver biopsy experienced improvement of HRQL. Further studies are needed to confirm long-term sustainability of that improvement. CLINICALTRIALS: gov #NCT02912260.

Resmetirom (MGL-3196) for the treatment of non-alcoholic steatohepatitis: a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis, inflammation, hepatocellular injury, and progressive liver fibrosis. Resmetirom (MGL-3196) is a liver-directed, orally active, selective thyroid hormone receptor-ß agonist designed to improve NASH by increasing hepatic fat metabolism and reducing lipotoxicity. We aimed to assess the safety and efficacy of resmetirom in patients with NASH. METHODS: MGL-3196-05 was a 36-week randomised, double-blind, placebo-controlled study at 25 centres in the USA. Adults with biopsy confirmed NASH (fibrosis stages 1-3) and hepatic fat fraction of at least 10% at baseline when assessed by MRI-proton density fat fraction (MRI-PDFF) were eligible. Patients were randomly assigned 2:1 by a computer-based system to receive resmetirom 80 mg or matching placebo, orally once a day. Serial hepatic fat measurements were obtained at weeks 12 and 36, and a second liver biopsy was obtained at week 36. The primary endpoint was relative change in MRI-PDFF assessed hepatic fat compared with placebo at week 12 in patients who had both a baseline and week 12 MRI-PDFF. This trial is registered with ClinicalTrials.gov, number NCT02912260. FINDINGS: 348 patients were screened and 84 were randomly assigned to resmetirom and 41 to placebo at 18 sites in the USA. Resmetirom-treated patients (n=78) showed a relative reduction of hepatic fat compared with placebo (n=38) at week 12 (-32·9% resmetirom vs -10·4% placebo; least squares mean difference -22·5%, 95% CI -32·9 to -12·2; p<0·0001) and week 36 (-37·3% resmetirom [n=74] vs -8·5 placebo [n=34]; -28·8%, -42·0 to -15·7; p<0·0001). Adverse events were mostly mild or moderate and were balanced between groups, except for a higher incidence of transient mild diarrhoea and nausea with resmetirom. INTERPRETATION: Resmetirom treatment resulted in significant reduction in hepatic fat after 12 weeks and 36 weeks of treatment in patients with NASH. Further studies of resmetirom will allow assessment of safety and effectiveness of resmetirom in a larger number of patients with NASH with the possibility of documenting associations between histological effects and changes in non-invasive markers and imaging. FUNDING: Madrigal Pharmaceuticals.

The effect of testosterone on ovulatory function in transmasculine individuals.

BACKGROUND: An estimated 1.4 million persons in the United States identify as transgender or nonbinary, signifying that their gender identity does not correspond with their assigned sex at birth. Individuals assigned female at birth may seek gender-affirming hormone therapy with testosterone. No studies have directly examined ovulatory function in transmasculine individuals using injectable testosterone. OBJECTIVES: Our primary objective was to determine the effect of testosterone on ovulatory suppression in transmasculine individuals. Secondary objectives were to determine predictors of ovulation in transmasculine individuals on testosterone, and to assess the effect of testosterone on antimüllerian hormone. MATERIALS AND METHODS: This prospective observational study recruited participants from a community clinic that provides gender-affirming hormone therapy. Enrolled individuals were assigned female at birth and were currently using or seeking to initiate masculinizing therapy with injectable testosterone esters (transmasculine individuals). Over a 12-week study period, participants collected daily urine samples for pregnanediol-3-glucoronide testing and completed daily electronic bleeding diaries. We assessed monthly serum mid-dosing interval testosterone, estradiol and sex hormone binding globulin, and antimüllerian hormone values at baseline and study end. Ovulation was defined as pregnanediol-3-glucoronide greater than 5 µg/mL for 3 consecutive days. The primary outcome was the proportion of participants who ovulated during the study period. We examined predictors of ovulation such as age, length of time on testosterone, serum testosterone levels, body mass index, and bleeding pattern. RESULTS: From July to November 2018, we enrolled 32 individuals; 20 completed the study (14 continuing testosterone users, 6 new users). Median age was 23 years (range 18-37 years). Bleeding or spotting during the study period was noted by 41% of participants (13/32). Among continuing users, median testosterone therapy duration was 11 months (range 1-60 months). A single ovulation was observed out of a total of 61 combined months of testosterone use; however, several transient rises in pregnanediol-3-glucoronide followed by bleeding episodes were suggestive of 7 dysfunctional ovulatory cycles among 7 individuals. There was no difference in antimüllerian hormone from baseline to 12 weeks between participants initiating testosterone and continuing users of testosterone. We did not have the power to examine our intended predictors given the low numbers of ovulatory events, but found that longer time on testosterone and presence of vaginal bleeding over 12 weeks were associated with transient rises in pregnanediol-3-glucoronide. CONCLUSION: This study suggests that testosterone rapidly induces hypothalamic-pituitary-gonadal suppression, resulting in anovulation in a proportion of new users. Importantly, these data also suggest that some long-term testosterone users break through the hormonal suppression and experience an ovulatory event, thereby raising concerns pertaining to the need for contraception in transmasculine individuals engaged in sexual intercourse with sperm-producing partners. Given the small number of overall participants, this work is hypothesis generating. Larger studies are needed to confirm and to clarify these findings.

Protein tyrosine phosphatase of liver regeneration-1 is required for normal timing of cell cycle progression during liver regeneration.

Protein tyrosine phosphatase of liver regeneration-1 (Prl-1) is an immediate-early gene that is significantly induced during liver regeneration. Several in vitro studies have suggested that Prl-1 is important for the regulation of cell cycle progression. To evaluate its function in liver regeneration, we ablated the Prl-1 gene specifically in mouse hepatocytes using the Cre-loxP system. Prl-1 mutant mice (Prl-1(loxP/loxP);AlfpCre) appeared normal and fertile. Liver size and metabolic function in Prl-1 mutants were comparable to controls, indicating that Prl-1 is dispensable for liver development, postnatal growth, and hepatocyte differentiation. Mutant mice demonstrated a delay in DNA synthesis after 70% partial hepatectomy, although ultimate liver mass restoration was not affected. At 40 h posthepatectomy, reduced protein levels of the cell cycle regulators cyclin E, cyclin A2, cyclin B1, and cyclin-dependent kinase 1 were observed in Prl-1 mutant liver. Investigation of the major signaling pathways involved in liver regeneration demonstrated that phosphorylation of protein kinase B (AKT) and signal transducer and activator of transcription (STAT) 3 were significantly reduced at 40 h posthepatectomy in Prl-1 mutants. Taken together, this study provides evidence that Prl-1 is required for proper timing of liver regeneration after partial hepatectomy. Prl-1 promotes G1/S progression via modulating expression of several cell cycle regulators through activation of the AKT and STAT3 signaling pathway.

Discovery of camphor-derived pyrazolones as 11ß-hydroxysteroid dehydrogenase type 1 inhibitors.

Starting from screening hit, (4S,7R)-1,7,8,8-tetramethyl-2-phenyl-1,2,4,5,6,7-hexahydro-4,7-methano-indazol-3-one (7), we optimized the potency and pharmacokinetic properties. This led to the identification of compounds with good in vivo activity in a mouse pharmacodynamic model of inhibition of 11ßHSD1.

Design of the phase 3 MAESTRO clinical program to evaluate resmetirom for the treatment of nonalcoholic steatohepatitis.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is a progressive form of non-alcoholic fatty liver disease (NAFLD) associated with steatosis, hepatocellular injury, inflammation and fibrosis. In a Phase 2 trial in adults with NASH (NCT02912260), resmetirom, an orally administered, liver-targeted thyroid hormone receptor-ß selective agonist, significantly reduced hepatic fat (via imaging) and resolved NASH without worsening fibrosis (via liver biopsy) in a significant number of patients compared with placebo. AIMS: To present the design of the Phase 3 MAESTRO clinical programme evaluating resmetirom for treatment of NASH (MAESTRO-NAFLD-1 [NCT04197479], MAESTRO-NAFLD-OLE [NCT04951219], MAESTRO-NASH [NCT03900429], MAESTRO-NASH-OUTCOMES [NCT05500222]). METHODS: MAESTRO-NASH is a pivotal serial biopsy trial in up to 2000 adults with biopsy-confirmed at-risk NASH. Patients are randomised to a once-daily oral placebo, 80 mg resmetirom, or 100 mg resmetirom. Liver biopsies are conducted at screening, week 52 and month 54. MAESTRO-NAFLD-1 is a 52-week safety trial in ~1400 adults with NAFLD/presumed NASH (based on non-invasive testing); ~700 patients from MAESTRO-NAFLD-1 are enrolled in MAESTRO-NAFLD-OLE, a 52-week active treatment extension to further evaluate safety. MAESTRO-NASH-OUTCOMES is enrolling 700 adults with well-compensated NASH cirrhosis to evaluate the potential for resmetirom to slow progression to hepatic decompensation events. Non-invasive tests (biomarkers, imaging) are assessed longitudinally throughout, in addition to validated patient-reported outcomes. CONCLUSION: The MAESTRO clinical programme was designed in conjunction with regulatory authorities to support approval of resmetirom for treatment of NASH. The surrogate endpoints, based on week 52 liver biopsy, serum biomarkers and imaging, are confirmed by long-term clinical liver-related outcomes in MAESTRO-NASH (month 54) and MAESTRO-NASH-OUTCOMES (time to event).

Resmetirom for nonalcoholic fatty liver disease: a randomized, double-blind, placebo-controlled phase 3 trial.

Nonalcoholic steatohepatitis (NASH) is a progressive liver disease with no approved treatment. MAESTRO-NAFLD-1 was a 52-week randomized, double-blind, placebo-controlled phase 3 trial evaluating the safety of resmetirom in adults with nonalcoholic fatty liver disease and presumed NASH. Patients were randomized to three double-blind arms (100 mg resmetirom (n = 325), 80 mg resmetirom (n = 327) or placebo (n = 320)) or open-label 100 mg resmetirom (n = 171). The primary end point was incidence of treatment-emergent adverse events (TEAEs) over 52 weeks and key secondary end points were LDL-C, apoB, triglycerides (over 24 weeks), hepatic fat (over 16 and 52 weeks) and liver stiffness (over 52 weeks). Resmetirom was safe and well tolerated. TEAEs occurred in 86.5% (open-label 100 mg resmetirom), 86.1% (100 mg resmetirom), 88.4% (80 mg resmetirom) and 81.8% (placebo) of patients. TEAEs in excess of placebo included diarrhea and nausea at the initiation of treatment. Key secondary end points included least square means difference from placebo at 80 mg, 100 mg resmetirom: LDL-C (-11.1%, -12.6%), apoB (-15.6%, -18.0%), triglycerides (-15.4%, -20.4%), 16-week hepatic fat (-34.9%, -38.6%), (P < 0.0001) and liver stiffness (-1.02, -1.70) and 52-week hepatic fat (-28.8, -33.9). These findings demonstrate resmetirom was safe and well tolerated in adults with presumed NASH, supporting a role for further clinical development. (ClinicalTrials.gov identifier NCT04197479 ).

Discovery and optimization of 2-phenyloxazole derivatives as diacylglycerol acyltransferase-1 inhibitors.

In a discovery effort to find safe and effective DGAT-1 inhibitors, we have identified 2-phenyloxazole 4-carboxamide 1 as a conformationally constrained analog of a hydrazide hit, which was previously identified from high-throughput screening. Further optimization of this series has led to chemically more stable 2-phenyloxazole-based DGAT-1 inhibitor 25 with improved solubility, cell-based activity, and pharmacokinetic properties. Compound 25 also demonstrated in vivo efficacy in a diet-induced obesity (DIO) rat model.

Effects of Resmetirom on Noninvasive Endpoints in a 36-Week Phase 2 Active Treatment Extension Study in Patients With NASH.

Resmetirom (MGL-3196), a selective thyroid hormone receptor-ß agonist, was evaluated in a 36-week paired liver biopsy study (NCT02912260) in adults with biopsy-confirmed nonalcoholic steatohepatitis (NASH). The primary endpoint was relative liver fat reduction as assessed by MRI-proton density fat fraction (MRI-PDFF), and secondary endpoints included histopathology. Subsequently, a 36-week active treatment open-label extension (OLE) study was conducted in 31 consenting patients (including 14 former placebo patients) with persistently mild to markedly elevated liver enzymes at the end of the main study. In patients treated with resmetirom (80 or 100 mg orally per day), MRI-PDFF reduction at OLE week 36 was -11.1% (1.5%) mean reduction (standard error [SE]; P < 0.0001) and -52.3% (4.4%) mean relative reduction, P < 0.0001. Low-density lipoprotein (LDL) cholesterol (-26.1% [4.5%], P < 0.0001), apolipoprotein B (-23.8% [3.0%], P < 0.0001), and triglycerides (-19.6% [5.4%], P = 0.0012; -46.1 [14.5] mg/dL, P = 0.0031) were reduced from baseline. Markers of fibrosis were reduced, including liver stiffness assessed by transient elastography (-2.1 [0.8] mean kilopascals [SE], P = 0.015) and N-terminal type III collagen pro-peptide (PRO-C3) (-9.8 [2.3] ng/mL, P = 0.0004 (baseline ≥ 10 ng/mL). In the main and OLE studies, PRO-C3/C3M (matrix metalloproteinase-degraded C3), a marker of net fibrosis formation, was reduced in resmetirom-treated patients (-0.76 [-1.27, -0.24], P = 0.0044 and -0.68, P < 0.0001, respectively). Resmetirom was well tolerated, with few, nonserious adverse events. Conclusion: The results of this 36-week OLE study support the efficacy and safety of resmetirom at daily doses of 80 mg and 100 mg, used in the ongoing phase 3 NASH study, MAESTRO-NASH (NCT03900429). The OLE study demonstrates a potential for noninvasive assessments to monitor the response to resmetirom from an individual patient with NASH.

Sugar binding to recombinant wild-type and mutant glucokinase monitored by kinetic measurement and tryptophan fluorescence.

Tryptophan fluorescence was used to study GK (glucokinase), an enzyme that plays a prominent role in glucose homoeostasis which, when inactivated or activated by mutations, causes diabetes mellitus or hypoglycaemia in humans. GK has three tryptophan residues, and binding of D-glucose increases their fluorescence. To assess the contribution of individual tryptophan residues to this effect, we generated GST-GK [GK conjugated to GST (glutathione transferase)] and also pure GK with one, two or three of the tryptophan residues of GK replaced with other amino acids (i.e. W99C, W99R, W167A, W167F, W257F, W99R/W167F, W99R/W257F, W167F/W257F and W99R/W167F/W257F). Enzyme kinetics, binding constants for glucose and several other sugars and fluorescence quantum yields (varphi) were determined and compared with those of wild-type GK retaining its three tryptophan residues. Replacement of all three tryptophan residues resulted in an enzyme that retained all characteristic features of GK, thereby demonstrating the unique usefulness of tryptophan fluorescence as an indicator of GK conformation. Curves of glucose binding to wild-type and mutant GK or GST-GK were hyperbolic, whereas catalysis of wild-type and most mutants exhibited co-operativity with D-glucose. Binding studies showed the following order of affinities for the enzyme variants: N-acetyl-D-glucosamine>D-glucose>D-mannose>D-mannoheptulose>2-deoxy-D-glucose>>L-glucose. GK activators increased sugar binding of most enzymes, but not of the mutants Y214A/V452A and C252Y. Contributions to the fluorescence increase from Trp(99) and Trp(167) were large compared with that from Trp(257) and are probably based on distinct mechanisms. The average quantum efficiency of tryptophan fluorescence in the basal and glucose-bound state was modified by activating (Y214A/V452A) or inactivating (C213R and C252Y) mutations and was interpreted as a manifestation of distinct conformational states.

Potent, selective MCH-1 receptor antagonists.

This paper describes the lead optimization of a new series of potent, selective, orally bioavailable, brain-penetrant MCH-1 receptor antagonists. A major focus of the work was to achieve a selectivity profile appropriate for in vivo efficacy studies and safety.

The network of glucokinase-expressing cells in glucose homeostasis and the potential of glucokinase activators for diabetes therapy.

The glucose-phosphorylating enzyme glucokinase has structural, kinetic, and molecular genetic features that are ideal for its primary role as glucose sensor in a network of neuro/endocrine sentinel cells that maintain glucose homeostasis in many vertebrates including humans. The glucokinase-containing, insulin-producing beta-cells of the pancreas take the prominent lead in this network, functioning in the aggregate as the master gland. The beta-cells are also conceptualized as the prototype for all other glucose sensor cells, which determines our current understanding of many extrapancreatic glucose sensors. About 99% of the enzyme resides, however, in the hepato-parenchymal cells and serves its second role in a high-capacity process of blood glucose clearance. Two examples strikingly illustrate how pivotal a position glucokinase has in the regulation of glucose metabolism: 1) activating and inactivating mutations of the enzyme cause hypo- and hyperglycemia syndromes in humans described collectively as "glucokinase disease" and fully explained by the glucose sensor paradigm, and 2) glucokinase activator drugs (GKAs) have been discovered that bind to an allosteric site and increase the kcat and lower the glucose S(0.5) of the enzyme. GKAs enhance glucose-stimulated insulin release from pancreatic islets and glucose disposition by the liver. They are now intensively explored to develop a novel treatment for diabetes. Future biophysical, molecular, genetic, and pharmacological studies hold much promise to unravel the evolving complexity of the glucokinase glucose sensor system.

A glucose sensor role for glucokinase in anterior pituitary cells.

Enzymatic activity of glucokinase was demonstrated, quantitated, and characterized kinetically in rat and mouse pituitary extracts using a highly specific and sensitive spectrometric assay. A previously proposed hypothesis that the glucokinase gene might be expressed in the pituitary corticotrophic cells was therefore reexamined using mRNA in situ hybridization and immunohistochemical techniques. No evidence was found that corticotrophs are glucokinase positive, and the identity of glucokinase-expressing cells remains to be determined. The findings do, however, suggest a novel hypothesis that a critical subgroup of anterior pituitary cells might function as glucose sensor cells and that direct fuel regulation of such cells may modify the classical indirect neuroendocrine pathways that are known to control hormone secretion from anterior pituitary cells.

From clinicogenetic studies of maturity-onset diabetes of the young to unraveling complex mechanisms of glucokinase regulation.

Glucokinase functions as a glucose sensor in pancreatic beta-cells and regulates hepatic glucose metabolism. A total of 83 probands were referred for a diagnostic screening of mutations in the glucokinase (GCK) gene. We found 11 different mutations (V62A, G72R, L146R, A208T, M210K, Y215X, S263P, E339G, R377C, S453L, and IVS5 + 1G>C) in 14 probands. Functional characterization of recombinant glutathionyl S-transferase-G72R glucokinase showed slightly increased activity, whereas S263P and G264S had near-normal activity. The other point mutations were inactivating. S263P showed marked thermal instability, whereas the stability of G72R and G264S differed only slightly from that of wild type. G72R and M210K did not respond to an allosteric glucokinase activator (GKA) or the hepatic glucokinase regulatory protein (GKRP). Mutation analysis of the role of glycine at position 72 by substituting E, F, K, M, S, or Q showed that G is unique since all these mutants had very low or no activity and were refractory to GKRP and GKA. Structural analysis provided plausible explanations for the drug resistance of G72R and M210K. Our study provides further evidence that protein instability in combination with loss of control by a putative endogenous activator and GKRP could be involved in the development of hyperglycemia in maturity-onset diabetes of the young, type 2. Furthermore, based on data obtained on G264S, we propose that other and still unknown mechanisms participate in the regulation of glucokinase.

Hepatoprotection via the IL-6/Stat3 pathway.

Stat3 is a vital transcription factor that is activated downstream of the gp130 receptor, primarily via IL-6 signaling in adult liver. A new study demonstrates that Stat3 provides hepatoprotection against Fas-mediated apoptotic liver damage by two mechanisms: direct inactivation of caspases and reduction of reactive oxygen species.

Massive hepatic apoptosis associated with TGF-beta1 activation after Fas ligand treatment of IGF binding protein-1-deficient mice.

Acute liver failure caused by viral hepatitis or toxic damage involves both apoptotic and necrotic pathways. IGF binding protein-1 (IGFBP-1), a hepatocyte-derived secreted protein, is required for normal liver regeneration. To determine whether IGFBP-1 could prevent liver injury that entails direct stimulation of hepatocyte apoptosis, IGFBP-1(-/-) mice, IGFBP-1(+/+) mice, and mice pretreated with Ab's against IGFBP-1 were treated with a normally sublethal dose of Fas agonist. IGFBP-1 deficiency was associated with massive hepatocyte apoptosis and caspase activation within 3 hours of Fas agonist treatment, which could be corrected by pretreatment with IGFBP-1. IGFBP-1-deficient livers had enhanced signaling via the integrin receptor at early times (0.5 to 1 hour) after Fas agonist treatment accompanied by elevated activated matrix metalloproteinase-9 (MMP-9), a known target of fibronectin signaling and activator of TGF-beta. Within 3 hours of Fas agonist treatment, elevated expression of active TGF-beta1, a hepatocyte apoptogen, was observed in IGFBP-1-deficient livers that correlated with the appearance of the apoptotic process. Both MMP-9 and TGF-beta1 expression were suppressed by IGFBP-1 treatment, supporting their role in the apoptotic process. IGFBP-1(-/-) mice also displayed increased injury in a toxic hepatic injury model caused by CCl(4). These findings indicate that IGFBP-1 functions as a critical hepatic survival factor in the liver by reducing the level of proapoptotic signals.

Impaired hepatocyte DNA synthetic response posthepatectomy in insulin-like growth factor binding protein 1-deficient mice with defects in C/EBP beta and mitogen-activated protein kinase/extracellular signal-regulated kinase regulation.

After a two-thirds hepatectomy, normally quiescent liver cells are stimulated to reenter the cell cycle and proliferate to restore the original liver mass. One of the most rapidly and highly induced genes and proteins in regenerating liver is insulin-like growth factor binding protein 1 (IGFBP-1), a secreted protein that may modulate the activities of insulin-like growth factors (IGFs) or signal via IGF-independent mechanisms. To assess the functional role of IGFBP-1 in liver regeneration, mice with a targeted disruption of the IGFBP-1 gene were generated. Although IGFBP-1(-/-) mice demonstrated normal development, they had abnormal liver regeneration after partial hepatectomy, characterized by liver necrosis and reduced and delayed hepatocyte DNA synthesis. The abnormal regenerative response was associated with blunted activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and a reduced induction of C/EBP beta protein expression posthepatectomy. Like cell cycle abnormalities observed in hepatectomized C/EBP beta(-/-) mice, cyclin A and cyclin B1 expression was delayed and reduced in IGFBP-1(-/-) livers, whereas cyclin D1 expression was normal. Treatment of IGFBP-1(-/-) mice with a preoperative dose of IGFBP-1 induced MAPK/ERK activation and C/EBP beta expression, suggesting that IGFBP-1 may support liver regeneration at least in part via its effect on MAPK/ERK and C/EBP beta activities. These findings are the first demonstration of the involvement of IGFBP-1 in the regulation of in vivo mitogenic signaling pathways.