A quantum Monte Carlo study of the one-dimensional ionic Hubbard model

Quantum Monte Carlo methods are used to study a quantum phase transition in a 1D Hubbard model with a staggered ionic potential (D). Using recently formulated methods, the electronic polarization and localization are determined directly from the correlated ground state wavefunction and compared to results of previous work using exact diagonalization and Hartree-Fock. We find that the model undergoes a thermodynamic transition from a band insulator (BI) to a broken-symmetry bond ordered (BO) phase as the ratio of U/D is increased. Since it is known that at D = 0 the usual Hubbard model is a Mott insulator (MI) with no long-range order, we have searched for a second transition to this state by (i) increasing U at fixed ionic potential (D) and (ii) decreasing D at fixed U. We find no transition from the BO to MI state, and we propose that the MI state in 1D is unstable to bond ordering under the addition of any finite ionic potential. In real 1D systems the symmetric MI phase is never stable and the transition is from a symmetric BI phase to a dimerized BO phase, with a metallic point at the transition

Pairing fluctuations and pseudogaps in the attractive Hubbard model

The two-dimensional attractive Hubbard model is studied in the weak to intermediate coupling regime by employing a non-perturbative approach. It is first shown that this approach is in quantitative agreement with Monte Carlo calculations for both single-particle and two-particle quantities. Both the density of states and the single-particle spectral weight show a pseudogap at the Fermi energy below some characteristic temperature T*, also in good agreement with quantum Monte Carlo calculations. The pseudogap is caused by critical pairing fluctuations in the low-temperature renormalized classical regime $\omega < T$ of the two-dimensional system. With increasing temperature the spectral weight fills in the pseudogap instead of closing it and the pseudogap appears earlier in the density of states than in the spectral function. Small temperature changes around T* can modify the spectral weight over frequency scales much larger than temperature. Several qualitative results for the s-wave case should remain true for d-wave superconductors.Comment: 20 pages, 12 figure

Interventions to improve physical function and prevent adverse events in cirrhosis

Abstract Cirrhosis is associated with debilitating complications that significantly impact on a patient’s physical function and reduce quality of life. Owing to highly prevalent sarcopenia, malnutrition and hepatic encephalopathy, functional impairment or frailty is a common complication of cirrhosis. Frailty in turn increases the patient’s risk of hospitalization, accidental falls and fractures, and death. The management of frailty and its associated adverse effects is imperative in improving the overall prognosis of patients with advanced liver disease. The cornerstone of therapy revolves around optimizing physical function with appropriate nutrition and exercise. Nutritional therapy with protein supplementation has shown significant benefit, while studies on exercise have been controversial. However, newly emerging studies trend towards a beneficial effect of physical exercise with improvement in quality of life. The implementation of technology in liver disease management shows future promise. Fitbits and other wearable devices can be used to help monitor a patient’s personal progress in physical exercise and nutritional optimization. Additionally, the progressive development of new smartphone applications to help aid in the diagnosis and monitoring of complications of cirrhosis provides a sophisticated avenue for improving care of patients with cirrhosis

Type 2 diabetes complications are associated with liver fibrosis independent of hemoglobin A1c

Introduction and Objectives: The association between type 2 diabetes, non-alcoholic fatty liver disease, and liver fibrosis is well established, but it is unknown whether complications of type 2 diabetes influence fibrosis levels. We defined the complications of type 2 diabetes by the presence of diabetic nephropathy, retinopathy, or neuropathy and aimed to evaluate their association with the degree of liver fibrosis measured by the fibrosis-4 (FIB-4) index. Materials and Methods: This is a cross-sectional study evaluating the association of type 2 diabetes complications with liver fibrosis. A total of 2389 participants were evaluated from a primary care practice. FIB-4 was evaluated as a continuous and categorical measure using linear and ordinal logistic regression. Results: Patients with complications were older, had higher hemoglobin A1c, and a higher median FIB-4 score (1.34 vs. 1.12, P<0.001). On adjusted analysis, type 2 diabetes complications were associated with higher fibrosis by continuous FIB-4 score (Beta-coefficient: 0.23, 95% confidence interval [CI]: 0.004-1.65) and demonstrated increased odds of fibrosis by categorical FIB-4 score (odds ratio [OR]: 4.48, 95% CI: 1.7-11.8, P=0.003), independent of hemoglobin A1c level. Conclusions: The presence of type 2 diabetes complications is associated with the degree of liver fibrosis, independent of hemoglobin A1c level

Pharmacological Therapy of Pruritus in Primary Biliary Cholangitis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Goals: We aim to summarize the current management of pruritus in primary biliary cholangitis (PBC) by evaluating the efficacy and safety of pharmacological therapies. Background: Pruritus is a common symptom of PBC, and evidence regarding the most effective antipruritic agents available is lacking. New pharmacotherapy for PBC has shown promising antipruritic effects. Study: We performed a systematic literature review and meta-analysis including all available double-blind, randomized, placebo-controlled clinical trials that evaluated the efficacy of pharmacotherapy for the symptomatic management of pruritus in PBC. Pruritus was assessed as either a change from baseline or a postintervention score. Results: We included 33 studies and 20 medications. Using the visual analog scale, cholestyramine did not significantly improve pruritus compared with placebo [standardized mean differences (SMD): -0.94, 95% CI: -2.05 to 0.17], whereas rifampin and nalfurafine hydrochloride both significantly improved pruritus (SMD: -3.29, 95% CI: -5.78 to -0.80; n=23 and SMD: -0.58, 95% CI: -1.04 to -0.12). In addition, Bezafibrate and linerixibat significantly improved pruritus (SMD: -1.05, 95% CI: -1.41 to -0.68; n=110 and SMD: -0.31, 95% CI: -0.62 to -0.04, respectively). This effect was also present within the subgroup analysis by pruritus scale, where both bezafibrate and linerixibat significantly improved pruritus compared with placebo (SMD: -1.09, 95% CI: -1.54 to -0.65; P<0.001; visual analog scale; as postintervention score and SMD: -0.31, 95% CI: -0.62 to -0.01; P=0.04; numeric rating scale; as a change from baseline score, respectively). Conclusions: Bezafibrate and Linerixibat are potential second-line antipruritic medications for PBC, particularly those with moderate to severe pruritus

Pharmacological Therapy of Pruritus in Primary Biliary Cholangitis A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Medina-Morales E, Bernal RB, Gerger H, et al. Pharmacological Therapy of Pruritus in Primary Biliary Cholangitis A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Journal of Clinical Gastroenterology . 2023;57(2):143-152.Goals: We aim to summarize the current management of pruritus in primary biliary cholangitis (PBC) by evaluating the efficacy and safety of pharmacological therapies. Background: Pruritus is a common symptom of PBC, and evidence regarding the most effective antipruritic agents available is lacking. New pharmacotherapy for PBC has shown promising antipruritic effects. Study: We performed a systematic literature review and meta-analysis including all available double-blind, randomized, placebo-controlled clinical trials that evaluated the efficacy of pharmacotherapy for the symptomatic management of pruritus in PBC. Pruritus was assessed as either a change from baseline or a postintervention score. Results: We included 33 studies and 20 medications. Using the visual analog scale, cholestyramine did not significantly improve pruritus compared with placebo [standardized mean differences (SMD): −0.94, 95% CI: −2.05 to 0.17], whereas rifampin and nalfurafine hydrochloride both significantly improved pruritus (SMD: −3.29, 95% CI: −5.78 to −0.80; n=23 and SMD: −0.58, 95% CI: −1.04 to −0.12). In addition, Bezafibrate and linerixibat significantly improved pruritus (SMD: −1.05, 95% CI: −1.41 to −0.68; n=110 and SMD: −0.31, 95% CI: −0.62 to −0.04, respectively). This effect was also present within the subgroup analysis by pruritus scale, where both bezafibrate and linerixibat significantly improved pruritus compared with placebo (SMD: −1.09, 95% CI: −1.54 to −0.65; P<0.001; visual analog scale; as postintervention score and SMD: −0.31, 95% CI: −0.62 to −0.01; P=0.04; numeric rating scale; as a change from baseline score, respectively). Conclusions: Bezafibrate and Linerixibat are potential second-line antipruritic medications for PBC, particularly those with moderate to severe pruritus. Primary biliary cholangitis (PBC) is a chronic, immune-mediated liver disease characterized by destruction of intrahepatic bile ducts, and is associated with numerous extrahepatic complications.1 Approximately 60% to 70% of patients diagnosed with PBC experience pruritus at some point during their disease course, and nearly 35% have refractory pruritus.2 Pruritus can lead to sleep deprivation, fatigue, and emotional disturbances including depression and suicidal ideation, all of which leads to lower health-related quality of life (HRQoL).3 Successful symptomatic treatment of pruritus can improve patients’ quality of life, and is an essential component of the overall management of PBC. Treatment options for pruritus in patients with PBC are limited. Ursodeoxycholic acid (UDCA) has been shown to favorably alter the natural history of PBC, but its effect on pruritus has not been proven.4 To achieve improved control of pruritus in patients with cholestasis, the American Association for the Study of Liver Disease (AASLD) and the European Association for the Study of the Liver (EASL) recommend a step-wise pharmacological approach. Cholestyramine is considered/first-line therapy for pruritus. Rifampin, naltrexone, and sertraline are all recommended as potential second-line options.4,5 However, these medications lack adequate efficacy for the treatment of pruritus, and have unfavorable side effect profiles, which have prompted additional studies exploring novel treatment options. Novel medications have expanded the potential treatment options for the management of symptomatic pruritus in PBC. Ileal bile acid transport (IBAT) inhibitors and peroxisome proliferator-activated receptor agonists have both shown promising results in recent studies.6–9 Other novel therapeutics have also been studied. We performed a systematic review and meta-analysis of all randomized-controlled trials (RCTs) studying antipruritic medications used in PBC patients