Linked content
This article is linked to Patel et al and Patel and Hunt papers. To view these article visit https://doi.org/10.1111/apt.14411 and https://doi.org/10.1111/apt.14505.
As obesity reaches epidemic proportions, nonalcoholic fatty liver disease (NAFLD) is becoming a frequent cause of patient referral to gastroenterologists. There is a close link between dysfunctional ...adipose tissue in NAFLD and common conditions such as metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. This review focuses on the pathophysiology of interactions between adipose tissue and target organs in obesity and the resulting clinical implications for the management of nonalcoholic steatohepatitis. The release of fatty acids from dysfunctional and insulin-resistant adipocytes results in lipotoxicity, caused by the accumulation of triglyceride-derived toxic metabolites in ectopic tissues (liver, muscle, pancreatic beta cells) and subsequent activation of inflammatory pathways, cellular dysfunction, and lipoapoptosis. The cross talk between dysfunctional adipocytes and the liver involves multiple cell populations, including macrophages and other immune cells, that in concert promote the development of lipotoxic liver disease, a term that more accurately describes the pathophysiology of nonalcoholic steatohepatitis. At the clinical level, adipose tissue insulin resistance contributes to type 2 diabetes mellitus and cardiovascular disease. Treatments that rescue the liver from lipotoxicity by restoring adipose tissue insulin sensitivity (eg, significant weight loss, exercise, thiazolidinediones) or preventing activation of inflammatory pathways and oxidative stress (ie, vitamin E, thiazolidinediones) hold promise in the treatment of NAFLD, although their long-term safety and efficacy remain to be established. Better understanding of pathways that link dysregulated adipose tissue, metabolic dysfunction, and liver lipotoxicity will result in improvements in the clinical management of these challenging patients.
Aims
To evaluate the effects of dulaglutide vs placebo on liver and glycaemic/metabolic measurements in a population with Type 2 diabetes and in a subgroup with non‐alcoholic fatty ...liver/non‐alcoholic steatohepatitis.
Methods
A total of 1499 participants from AWARD‐1, AWARD‐5, AWARD‐8 and AWARD‐9 clinical trials were included in this analysis (dulaglutide 1.5 mg, n=971 and placebo, n=528). Thresholds of alanine aminotransferase levels ≥30 IU/l in men and ≥19 IU/l in women were used to determine the subgroup who had non‐alcoholic fatty liver/non‐alcoholic steatohepatitis. Objectives included changes from baseline to 6 months in: (1) alanine aminotransferase, aspartate transaminase and gamma‐glutamyl transpeptidase levels in the overall population and (2) alanine aminotransferase, aspartate transaminase, gamma‐glutamyl transpeptidase and glycaemic/metabolic measurements (e.g. HbA1c, fasting serum glucose, body weight, lipids and homeostatic model assessment) in the non‐alcoholic fatty liver/non‐alcoholic steatohepatitis subgroup.
Results
In the overall population at 6 months, dulaglutide significantly reduced alanine aminotransferase, aspartate transaminase and gamma‐glutamyl transpeptidase levels vs placebo least squares mean treatment differences: –1.7 IU/l (95% CI –2.8, –0.6), P=0.003; –1.1 IU/l (95% CI –2.1, –0.1), P=0.037; –6.6 IU/l (95% CI –12.4, –0.8), P=0.025, respectively. In the subgroup with non‐alcoholic fatty liver/non‐alcoholic steatohepatitis (alanine aminotransferase levels greater than or equal to the upper limit of normal), mean baseline liver enzyme values were 38.0 IU/l, 27.8 IU/l and 43.9 IU/l for alanine aminotransferase, aspartate transaminase and gamma‐glutamyl transpeptidase, respectively. In this population, more pronounced reductions from baseline in alanine aminotransferase were observed with dulaglutide vs placebo (–8.8 IU/l vs –6.7 IU/l). In the subgroup of people with alanine aminotransferase levels less than the upper limit of normal, changes from baseline in alanine aminotransferase did not significantly differ between treatment groups (0.0 IU/l vs 0.7 IU/l).
Conclusions
Once‐weekly dulaglutide improved alanine aminotransferase, aspartate transaminase and gamma‐glutamyl transpeptidase levels compared with placebo in a pattern consistent with liver fat reductions. Our results add further weight to the notion that glucagon‐like peptide‐1 receptor agonists may provide benefit in lowering liver fat in addition to their other metabolic actions.
What's new?
Non‐alcoholic fatty liver disease is present in >75% of people with Type 2 diabetes.
Dulaglutide is a once‐weekly glucagon‐like peptide‐1 receptor agonist approved for the treatment of Type 2 diabetes.
This analysis evaluated the effects of dulaglutide on liver and glycaemic/metabolic measurements in a subgroup of people with non‐alcoholic fatty liver/non‐alcoholic steatohepatitis and Type 2 diabetes.
Treatment response of dulaglutide in the subgroup was similar to that in the overall population.
Dulaglutide improved plasma aminotransferases and gamma‐glutamyl transpeptidase in a pattern consistent with liver fat reductions.
Summary
Background Plasma adiponectin is decreased in NASH patients and the mechanism(s) for histological improvement during thiazolidinedione treatment remain(s) poorly understood.
Aim To evaluate ...the relationship between changes in plasma adiponectin following pioglitazone treatment and metabolic/histological improvement.
Methods We measured in 47 NASH patients and 20 controls: (i) fasting glucose, insulin, FFA and adiponectin concentrations; (ii) hepatic fat content by magnetic resonance spectroscopy; and (iii) peripheral/hepatic insulin sensitivity (by double‐tracer oral glucose tolerance test). Patients were then treated with pioglitazone (45 mg/day) or placebo and all measurements were repeated after 6 months.
Results Patients with NASH had decreased plasma adiponectin levels independent of the presence of obesity. Pioglitazone increased 2.3‐fold plasma adiponectin and improved insulin resistance, glucose tolerance and glucose clearance, steatosis and necroinflammation (all P < 0.01–0.001 vs. placebo). In the pioglitazone group, plasma adiponectin was significantly associated (r = 0.52, P = 0.0001) with hepatic insulin sensitivity and with the change in both variables (r = 0.44, P = 0.03). Increase in adiponectin concentration was related also to histological improvement, in particular, to hepatic steatosis (r = −0.46, P = 0006) and necroinflammation (r = −0.56, P < 0.0001) but importantly also to fibrosis (r = −0.29, P = 0.03).
Conclusions Adiponectin exerts an important metabolic role at the level of the liver, and its increase during pioglitazone treatment is critical to reverse insulin resistance and improve liver histology in NASH patients.
Summary
Background
Pioglitazone is a safe and effective option to manage patients with type 2 diabetes and nonalcoholic steatohepatitis (NASH). However, there is marked variability in treatment ...response.
Aim
To evaluate the relationship between concentrations of pioglitazone and its active metabolites and treatment outcomes in patients with NASH.
Methods
Pioglitazone concentrations were measured in patients with NASH treated with pioglitazone 45 mg/day for 18 months; liver biopsy samples were obtained at baseline and after treatment. The primary outcome was a ≥2‐point reduction in NAFLD activity score (NAS) with at least one‐point improvement in more than one liver histology category and without worsening of fibrosis. A novel marker, the pioglitazone exposure index, was calculated to consider the concentrations of pioglitazone as well as the two active metabolites.
Results
The response to pioglitazone was concentration‐dependent as evidenced by the significant relationship between both pioglitazone concentration and pioglitazone exposure index with changes in NAS (r=.48, P=.0002 and r=.51, P<.0001, respectively), steatosis (r=.41, P=.002 and r=.46, P=.0005), and inflammation (r=.44, P=.0009 and r=.40, P=.0003). The pioglitazone exposure index was also associated with a change in ballooning (P=.04). The pioglitazone exposure index was higher in patients with NASH resolution (2.85±1.38 vs 1.78±1.48, P=.018). A predictive model for the primary outcome was developed that incorporated baseline NAS and pioglitazone exposure index (AUC=0.77).
Conclusions
This study demonstrates the importance of pioglitazone exposure to variable response in patients with NASH, and indicates potential factors that may identify patients most likely to benefit from chronic pioglitazone treatment.
Linked ContentThis article is linked to Srinivas paper. To view this article visit https://doi.org/10.1111/apt.14169.
Introduction
Untargeted metabolomics workflows include numerous points where variance and systematic errors can be introduced. Due to the diversity of the lipidome, manual peak picking and ...quantitation using molecule specific internal standards is unrealistic, and therefore quality peak picking algorithms and further feature processing and normalization algorithms are important. Subsequent normalization, data filtering, statistical analysis, and biological interpretation are simplified when quality data acquisition and feature processing are employed.
Objectives
Metrics for QC are important throughout the workflow. The robust workflow presented here provides techniques to ensure that QC checks are implemented throughout sample preparation, data acquisition, pre-processing, and analysis.
Methods
The untargeted lipidomics workflow includes sample standardization prior to acquisition, blocks of QC standards and blanks run at systematic intervals between randomized blocks of experimental data, blank feature filtering (BFF) to remove features not originating from the sample, and QC analysis of data acquisition and processing.
Results
The workflow was successfully applied to mouse liver samples, which were investigated to discern lipidomic changes throughout the development of nonalcoholic fatty liver disease (NAFLD). The workflow, including a novel filtering method, BFF, allows improved confidence in results and conclusions for lipidomic applications.
Conclusion
Using a mouse model developed for the study of the transition of NAFLD from an early stage known as simple steatosis, to the later stage, nonalcoholic steatohepatitis, in combination with our novel workflow, we have identified phosphatidylcholines, phosphatidylethanolamines, and triacylglycerols that may contribute to disease onset and/or progression.
Surrogate endpoints for clinical proof of concept (POC) trials in nonalcoholic steatohepatitis (NASH) are based upon expert pathological review of liver biopsies. During early development, these ...long‐term POC studies (≥48 weeks) add cost and time to the “Go/No Go” decision process. However, it is possible to conduct short‐term noninvasive POC studies utilizing biomarkers and magnetic resonance imaging. Here, we discuss the use of shorter noninvasive POC studies relative to biopsy‐driven studies for drug development in NASH.
As morbidity and mortality related to potentially preventable liver diseases are on the rise globally, early detection of liver fibrosis offers a window of opportunity to prevent disease progression. ...Early detection of non-alcoholic fatty liver disease allows for initiation and reinforcement of guidance on bodyweight management, risk stratification for advanced liver fibrosis, and treatment optimisation of diabetes and other metabolic complications. Identification of alcohol-related liver disease provides the opportunity to support patients with detoxification and abstinence programmes. In all patient groups, identification of cirrhosis ensures that patients are enrolled in surveillance programmes for hepatocellular carcinoma and portal hypertension. When considering early detection strategies, success can be achieved from applying ad-hoc screening for liver fibrosis in established frameworks of care. Patients with type 2 diabetes are an important group to consider case findings of advanced liver fibrosis and cirrhosis, as up to 19% have advanced fibrosis (which is ten times higher than the general population) and almost 70% have non-alcoholic fatty liver disease. Additionally, patients with type 2 diabetes with alcohol use disorders have the highest proportion of liver-related morbidity of people with type 2 diabetes generally. Patients with type 2 diabetes receive an annual diabetes review as part of their routine clinical care, in which the health of many organs are considered. Yet, liver health is seldom included in this review. This Viewpoint argues that augmenting the existing risk stratification strategy with an additional liver health check provides the opportunity to detect advanced liver fibrosis, thereby opening a window for early interventions to prevent end-stage liver disease and its complications, including hepatocellular carcinoma.
We aimed to examine the mechanisms by which rosiglitazone improves glycaemic control in Type II (non-insulin-dependent) diabetic patients.
Altogether 29 diet-treated diabetic patients were assigned ...at random to rosiglitazone, 8 mg/day (n = 15), or placebo (n = 14) for 12 weeks. Patients received 75 g OGTT and two-step euglycaemic insulin (40 and 160 mU/m(2)min) clamp with 3-(3)H-glucose, (14)C-palmitate and indirect calorimetry.
After 12 weeks, rosiglitazone reduced fasting plasma glucose (195 +/- 11 to 150 +/- 7 mg/dl, p < 0.01), mean plasma glucose (PG) during OGTT (293 +/- 12 to 236 +/- 9 mg/dl, p < 0.01), and HbA1 c (8.7 +/- 0.4 to 7.4 +/- 0.3 %, p < 0.01) without changes in plasma insulin concentration. Basal endogenous glucose production (EGP) declined (3.3 +/- 0.1 to 2.9 +/- 0.1 mg/kg FFM. min, p < 0.05) and whole body glucose metabolic clearance rate increased after rosiglitazone (first clamp step: 2.8 +/- 0.2 to 3.5 +/- 0.2 ml/kg FFM. min, p < 0.01; second clamp step: 6.7 +/- 0.6 to 9.2 +/- 0.8, p < 0.05) despite increased body weight (86 +/- 4 to 90 +/- 4 kg, p < 0.01) and fat mass (33 +/- 3 to 37 +/- 3 kg, p < 0.01). Fasting plasma non-esterified fatty acid (NEFA) (735 +/- 52 to 579 +/- 49 microEq/l, p < 0.01), mean plasma NEFA during OGTT (561 +/- 33 to 424 +/- 35, p < 0.01), and basal NEFA turnover (18.3 +/- 1.5 to 15.5 +/- 1.2 microEq/kg FM. min, p < 0.05) decreased after rosiglitazone. Changes in EPG and mean plasma glucose (PG) during OGTT correlated with changes in basal EGP (r = 0.54; r = 0.58), first EGP (r = 0.36; r = 0.41), first MCR (r = -0.66; r = -0.68), second MCR (r = -0.49; r = -0.54), fasting plasma NEFA (r = 0.53; r = 0.49), and NEFA during OGTT (r = 0.66; r = 0.66).
Rosiglitazone increases hepatic and peripheral (muscle) tissue insulin sensitivity and reduces NEFA turnover despite increased total body fat mass. These results suggest that the beneficial effects of rosiglitazone on glycaemic control are mediated, in part, by the drug's effect on NEFA metabolism.
The recent discovery of two adiponectin receptors (AdipoR1 and AdipoR2) will improve our understanding of the molecular mechanisms underlying the insulin-sensitising effect of adiponectin. The aim of ...this study was to determine for the first time whether skeletal muscle AdipoR1 and/or AdipoR2 gene expression levels are associated with insulin resistance.
Using RT-PCR and northern analysis we measured AdipoR1 and AdipoR2 gene expression in skeletal muscle from healthy Mexican Americans with normal glucose tolerance who had (n=8) or did not have (n=10) a family history of Type 2 diabetes.
Gene expression profiling indicated that the AdipoR1 and AdipoR2 isoforms are highly expressed in human skeletal muscle, unlike in mice where AdipoR2 expression was highest in the liver, and AdipoR1 was highest in skeletal muscle. In the study subjects, the expression levels of AdipoR1 (p=0.004) and AdipoR2 (p=0.04), as well as plasma adiponectin concentration (p=0.03) were lower in people with a family history of Type 2 diabetes than in those with no family history of the disease. Importantly, the expression levels of both receptors correlated positively with insulin sensitivity (r=0.64, p=0.004 and r=0.47, p=0.048 respectively).
Collectively, these data indicate that both isoforms of the adiponectin receptor play a role in the insulin-sensitising effect of adiponectin.
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