PPAR-γ-induced changes in visceral fat and adiponectin levels are associated with improvement of steatohepatitis in patients with NASH.

BACKGROUND AND AIMS: Peroxisome proliferator-activated receptor (PPAR)-γ agonists decrease hepatic/visceral fat (VF) and improve necroinflammation despite subcutaneous (SC) fat weight-gain. Understanding the impact of changes in VF, VF-to-SC fat distribution (VF/SC) and adiponectin (ADPN) levels in relation to histological improvement after weight-loss or pioglitazone is relevant as novel PPAR-γ agonists are being developed for treating non-alcoholic steatohepatitis (NASH). METHODS: Fifty-five patients with NASH received a -500 kcal/d hypocaloric diet and were randomized (double-blind) to pioglitazone (45 mg/d) or placebo for 6-months. Before and after treatment patients underwent a liver biopsy and measurement of hepatic/peripheral glucose fluxes, hepatic/adipose tissue-IR and, in 35 patients, hepatic and VF/SC-fat was measured by magnetic resonance spectroscopy/imaging. Data were examined by multivariable statistical analyses combined with machine-learning techniques (partial least square discriminant analysis [PLS-DA]). RESULTS: Both pioglitazone (despite weight-gain) and placebo (if weight-loss) reduced steatosis but only pioglitazone ameliorated necroinflammation. Using machine-learning PLS-DA showed that the treatment differences induced by a PPAR-γ agonist vs placebo on metabolic variables and liver histology could be best explained by the increase in ADPN and a decrease in VF/SC, and to a lesser degree, improvement in oral glucose tolerance test-glucose concentrations and ALT. Decrease in steatosis and disease activity score (ballooning plus lobular inflammation) kept a close relationship with an increase in ADPN (r = -.71 and r = -.44, P < .007, respectively) and reduction in VF/SC fat (r = .41 and r = .37, P < .03 respectively). CONCLUSIONS: Reduction in VF and improved VF/SC-distribution, combined with an increase in ADPN, mediate the histological benefits of PPAR-γ action, highlighting the central role of fat metabolism and its distribution on steatohepatitis disease activity in patients with NASH.

Change in hepatic fat content measured by MRI does not predict treatment-induced histological improvement of steatohepatitis.

BACKGROUND & AIMS: Proof-of-concept studies frequently assess changes in intrahepatic triglyceride (IHTG) content by magnetic resonance-based techniques as a surrogate marker of histology. The aim of this study was to establish how reliable this strategy is to predict changes in liver histology in patients with non-alcoholic steatohepatitis (NASH). METHODS: Patients with NASH who had participated in our prior randomized controlled trials of pioglitazone with complete paired data for IHTG content by magnetic resonance spectroscopy and liver histology were included in the study. RESULTS: A total of 121 patients were included. Changes in IHTG were assessed in several ways: as a continuous variable (correlations), as categorical groups (IHTG change ≥0%; or IHTG reduction of 1-30%; 31-50%; 51-70%; or >70%), and in a binomial way as steatosis resolution or not (defined as achieving IHTG <5.56%). Changes in IHTG correlated with steatosis on histology (r = 0.54; p <0.01). However, the magnitude of IHTG reduction was not associated with the rate of response of the primary histological outcome (2-point improvement in the NAFLD activity score from 2 different parameters, without worsening of fibrosis) or resolution of NASH without worsening of fibrosis, neither in patients receiving pioglitazone nor placebo. Changes in lobular inflammation, hepatocyte ballooning, or liver fibrosis were also independent of changes in IHTG, irrespective of treatment arm. Steatosis resolution was not associated with better histological outcomes either. CONCLUSIONS: Changes in IHTG predict changes in steatosis but not of other liver histological parameters. This implies that IHTG response to treatment should be interpreted with caution, as it may not be as reliable as previously believed to predict a treatment's overall clinical efficacy in patients with NASH. LAY SUMMARY: Quantification of liver fat by magnetic resonance imaging (MRI) is currently used to assess treatment responses in patients with fatty liver, with the assumption that improvements in liver fat translate into less inflammation, necrosis, and fibrosis in the liver. However, in this article, we showed that changes in liver fat do not necessarily translate into changes in these parameters. This means that MRI may not be as useful to assess treatment response in patients with fatty liver as previously believed.

Modulation of Insulin Resistance in Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) has an estimated prevalence of 25% in the general population, and cirrhosis secondary to nonalcoholic steatohepatitis (NASH) is predicted to become the leading cause of liver transplantation, yet there is a lack of effective licensed treatments for these conditions. There is a close relationship between insulin resistance (IR) and NAFLD, with prevalence of NAFLD being 5-fold higher in patients with diabetes compared to those without. IR is implicated both in pathogenesis of NAFLD and in disease progression from steatosis to NASH. Thus, modulation of IR represents a potential strategy for NAFLD treatment. This review highlights key proposed mechanisms linking IR and NAFLD, such as changes in rates of adipose tissue lipolysis and de novo lipogenesis, impaired mitochondrial fatty acid ß-oxidation (FAO), changes in fat distribution, alterations in the gut microbiome, and alterations in levels of adipokines and cytokines. Furthermore, this review will discuss the main pharmacological strategies used to treat IR in patients with NAFLD and their efficacy based on recently published experimental and clinical data. These include biguanides, glucagon-like peptide 1 receptor (GLP-1) agonists, dipeptidyl peptidase 4 (DPP-4) inhibitors, peroxisome proliferator-activated receptor (PPAR-γ/α/δ) agonists, sodium glucose cotransporter 2 (SGLT2) inhibitors, and farnesoid X receptor (FXR) agonists, with further novel treatments on the horizon. Ideally, treatment would improve IR, reduce cardiovascular risk, and produce demonstrable improvements in NASH histology-this is likely to be achieved with a combinatorial approach.

Effect of canagliflozin treatment on hepatic triglyceride content and glucose metabolism in patients with type 2 diabetes.

AIM: To evaluate the impact of the sodium glucose co-transporter 2 inhibitor canagliflozin on intrahepatic triglyceride (IHTG) accumulation and its relationship to changes in body weight and glucose metabolism. MATERIALS AND METHODS: In this double-blind, parallel-group, placebo-controlled, 24-week trial subjects with inadequately controlled type 2 diabetes mellitus (T2DM; HbA1c = 7.7% ± 0.7%) from two centres were randomly assigned (1:1) to canagliflozin 300 mg or placebo. We measured IHTG by proton-magnetic resonance spectroscopy (primary outcome), hepatic/muscle/adipose tissue insulin sensitivity during a 2-step euglycaemic insulin clamp, and beta-cell function during a mixed meal tolerance test. Analyses were per protocol. RESULTS: Between 8 September 2014-13 June 2016, 56 patients were enrolled. Canagliflozin reduced HbA1c (placebo-subtracted change: -0.71% [-1.08; -0.33]) and body weight (-3.4% [-5.4; -1.4]; both P ≤ 0.001). A numerically larger absolute decrease in IHTG occurred with canagliflozin (-4.6% [-6.4; -2.7]) versus placebo (-2.4% [-4.2; -0.6]; P = 0.09). In patients with non-alcoholic fatty liver disease (n = 37), the decrease in IHTG was -6.9% (-9.5; -4.2) versus -3.8% (-6.3; -1.3; P = 0.05), and strongly correlated with the magnitude of weight loss (r = 0.69, P < 0.001). Body weight loss ≥5% with a ≥30% relative reduction in IHTG occurred more often with canagliflozin (38% vs. 7%, P = 0.009). Hepatic insulin sensitivity improved with canagliflozin (P < 0.01), but not muscle or adipose tissue insulin sensitivity. Beta-cell glucose sensitivity, insulin clearance, and disposition index improved more with canagliflozin (P < 0.05). CONCLUSIONS: Canagliflozin improves hepatic insulin sensitivity and insulin secretion and clearance in patients with T2DM. IHTG decreases in proportion to the magnitude of body weight loss, which tended to be greater and occur more often with canagliflozin.

Pioglitazone improves hepatic mitochondrial function in a mouse model of nonalcoholic steatohepatitis.

Pioglitazone is effective in improving insulin resistance and liver histology in patients with nonalcoholic steatohepatitis (NASH). Because dysfunctional mitochondrial metabolism is a central feature of NASH, we hypothesized that an important target of pioglitazone would be alleviating mitochondrial oxidative dysfunction. To this end, we studied hepatic mitochondrial metabolism in mice fed high-fructose high-transfat diet (TFD) supplemented with pioglitazone for 20 wk, using nuclear magnetic resonance-based 13C isotopomer analysis. Pioglitazone improved whole body and adipose insulin sensitivity in TFD-fed mice. Furthermore, pioglitazone reduced intrahepatic triglyceride content and fed plasma ketones and hepatic TCA cycle flux, anaplerosis, and pyruvate cycling in mice with NASH. This was associated with a marked reduction in most intrahepatic diacylglycerol classes and, to a lesser extent, some ceramide species (C22:1, C23:0). Considering the cross-talk between mitochondrial function and branched-chain amino acid (BCAA) metabolism, pioglitazone's impact on plasma BCAA profile was determined in a cohort of human subjects. Pioglitazone improved the plasma BCAA concentration profile in patients with NASH. This appeared to be related to an improvement in BCAA degradation in multiple tissues. These results provide evidence that pioglitazone-induced changes in NASH are related to improvements in hepatic mitochondrial oxidative dysfunction and changes in whole body BCAA metabolism.

Response to Pioglitazone in Patients With Nonalcoholic Steatohepatitis With vs Without Type 2 Diabetes.

BACKGROUND & AIMS: Pioglitazone is effective for long-term treatment of patients with nonalcoholic steatohepatitis (NASH) with prediabetes or type 2 diabetes. However, it is not clear how the presence of type 2 diabetes affects the drug's efficacy. We compared metabolic and histologic responses to pioglitazone in patients with NASH and prediabetes vs type 2 diabetes. METHODS: We performed a prospective study of adults with biopsy-proven NASH (52 with type 2 diabetes and 49 with prediabetes), enrolled from the general population of San Antonio, Texas, from 2008 through 2014. After a run-in period of approximately 4 weeks, when all baseline measurements were made (liver magnetic resonance proton spectroscopy, euglycemic insulin clamp with glucose turnover measurements, dual-energy absorptiometry, and liver biopsy), subjects were randomly assigned to groups given pioglitazone or placebo (45 mg/d) for 18 months; all procedures performed at baseline were then repeated. The primary outcome was a reduction in nonalcoholic fatty liver disease activity score of 2 points or more (for at least 2 components) without worsening of fibrosis (and expressed as difference vs placebo). Secondary outcomes included NASH resolution, individual histologic components, intrahepatic triglyceride content (measured by 1H magnetic resonance spectroscopy), and insulin sensitivity (measured by euglycemic insulin clamp). RESULTS: The primary outcome was met by 48% of patients with type 2 diabetes vs 46% without diabetes. Resolution of NASH was achieved in 44% of patients with type 2 diabetes vs 26% without diabetes. A significant reduction in fibrosis, from baseline, was observed only in patients with type 2 diabetes (P = .035). Intrahepatic triglyceride content was reduced by 11% ± 2% in patients with diabetes vs a reduction of 9% ± 2% in patients without diabetes (P = .62); the plasma level of alanine aminotransferase was reduced by 50 ± 10 U/L in patients with diabetes vs a reduction of 36 ± 5 U/L in patients without diabetes (P = .22). Pioglitazone was associated with a significantly greater insulin sensitivity in adipose tissue of patients with diabetes vs without diabetes (P < .001), but nonsignificant differences in responses in hepatic (P = .49) and skeletal muscle (P = .32) insulin sensitivity. CONCLUSIONS: In a prospective study, we found pioglitazone to be effective in patients with and without type 2 diabetes. However, pioglitazone reduced liver fibrosis and increased adipose tissue insulin sensitivity at significantly greater levels in patients with type 2 diabetes than in patients with prediabetes. Further studies are needed to determine the mechanisms by which pioglitazone reduces liver disease in patients with type 2 diabetes. ClinicalTrials.gov: NCT00994682.

Metabolic and histological implications of intrahepatic triglyceride content in nonalcoholic fatty liver disease.

The cut-off point of intrahepatic triglyceride (IHTG) content to define nonalcoholic fatty liver disease (NAFLD) by proton magnetic resonance spectroscopy (1 H-MRS) was established based on the 95th percentile in a group of healthy individuals (i.e., ≥5.56%). Whether this threshold correlates with metabolic and histological changes and whether a further accumulation of IHTG is associated with worsening of these parameters has not been properly assessed in a large cohort of patients. In this cross-sectional study, 352 subjects were carefully characterized with the following studies: liver 1 H-MRS; euglycemic insulin clamp with measurement of glucose turnover; oral glucose tolerance test; and a liver biopsy. Hepatic insulin sensitivity (suppression of endogenous glucose production by insulin) was affected early on after IHTG content was ∼1.5% and remained uniformly impaired (∼40%-45%), regardless of further IHTG accumulation. Skeletal muscle insulin sensitivity showed a gradual impairment at low degrees of IHTG accumulation, but remained unchanged after IHTG content reached the ∼6 ± 2% threshold. A similar pattern was observed for metabolic changes typically associated with NAFLD, such as hypertriglyceridemia and low high-density lipoprotein cholesterol (HDL-C). In contrast, adipose tissue insulin sensitivity (suppression of free fatty acids by insulin) showed a continuous worsening across the spectrum of IHTG accumulation in NAFLD (r = -0.38; P < 0.001). Histological severity of liver disease (inflammation, ballooning, and fibrosis) was not associated with the amount of IHTG content. CONCLUSION: IHTG accumulation is strongly associated with adipose tissue insulin resistance (IR), supporting the current theory of lipotoxicity as a driver of IHTG accumulation. Once IHTG accumulation reaches ∼6 ± 2%, skeletal muscle IR, hypertriglyceridemia, and low HDL-C become fully established. Histological activity appears to have an early threshold and is not significantly influenced by increasing amounts of IHTG accumulation. (Hepatology 2017;65:1132-1144).

Use of a metabolomic approach to non-invasively diagnose non-alcoholic fatty liver disease in patients with type 2 diabetes mellitus.

AIMS: To assess the utility of existing metabolomics scores to classify liver disease in patients with type 2 diabetes mellitus (T2DM). MATERIALS AND METHODS: A total of 220 patients with T2DM were recruited. Patients underwent routine laboratory tests, liver proton magnetic resonance spectroscopy (1 H-MRS), a 75-g oral glucose tolerance test, and liver biopsy if 1 H-MRS findings indicated non-alcoholic fatty liver disease. A serum sample was blindly provided to OWL Metabolomics on which to run the OWLiver Care and OWLiver tests. RESULTS: When compared with liver biopsy, the OWLiver Care and OWLiver tests had a suboptimal performance in patients with T2DM (areas under the receiver-operating characteristic [AUROC] curve both <0.70). Given the discordance of these results in this heterogeneous, multiethnic cohort compared with those of a previous report in predominantly white patients without diabetes, we examined the influence of age, ethnicity and other variables on test performance. A specific subset of patients was selected to mirror the characteristics of the population used for the development of this model (ie, white patients without T2DM). Among white patients with good glycaemic control (glycated haemoglobin <53mmol/mol [or <7%]) and without cirrhosis, the AUROC curve was significantly improved (0.79 [CI 95%: 0.68-0.90]). Among white patients with lower insulin resistance (homeostatic model assessment of insulin resistance <3) and without cirrhosis, the AUROC was even higher: 0.87 (CI 95%: 0.76-0.97). CONCLUSIONS: There is a great need to develop non-invasive approaches to diagnose non-alcoholic steatohepatitis in patients with T2DM; models originally developed for patients without diabetes cannot be directly applied to patients with T2DM.

Long-Term Pioglitazone Treatment for Patients With Nonalcoholic Steatohepatitis and Prediabetes or Type 2 Diabetes Mellitus: A Randomized Trial.

BACKGROUND: The metabolic defects of nonalcoholic steatohepatitis (NASH) and prediabetes or type 2 diabetes mellitus (T2DM) seem to be specifically targeted by pioglitazone. However, information about its long-term use in this population is limited. OBJECTIVE: To determine the efficacy and safety of long-term pioglitazone treatment in patients with NASH and prediabetes or T2DM. DESIGN: Randomized, double-blind, placebo-controlled trial. (ClinicalTrials.gov: NCT00994682). SETTING: University hospital. PARTICIPANTS: Patients (n = 101) with prediabetes or T2DM and biopsy-proven NASH were recruited from the general population and outpatient clinics. INTERVENTION: All patients were prescribed a hypocaloric diet (500-kcal/d deficit from weight-maintaining caloric intake) and then randomly assigned to pioglitazone, 45 mg/d, or placebo for 18 months, followed by an 18-month open-label phase with pioglitazone treatment. MEASUREMENTS: The primary outcome was a reduction of at least 2 points in the nonalcoholic fatty liver disease activity score in 2 histologic categories without worsening of fibrosis. Secondary outcomes included other histologic outcomes, hepatic triglyceride content measured by magnetic resonance and proton spectroscopy, and metabolic parameters. RESULTS: Among patients randomly assigned to pioglitazone, 58% achieved the primary outcome (treatment difference, 41 percentage points [95% CI, 23 to 59 percentage points]) and 51% had resolution of NASH (treatment difference, 32 percentage points [CI, 13 to 51 percentage points]) (P < 0.001 for each). Pioglitazone treatment also was associated with improvement in individual histologic scores, including the fibrosis score (treatment difference, -0.5 [CI, -0.9 to 0.0]; P = 0.039); reduced hepatic triglyceride content from 19% to 7% (treatment difference, -7 percentage points [CI, -10 to -4 percentage points]; P < 0.001); and improved adipose tissue, hepatic, and muscle insulin sensitivity (P < 0.001 vs. placebo for all). All 18-month metabolic and histologic improvements persisted over 36 months of therapy. The overall rate of adverse events did not differ between groups, although weight gain was greater with pioglitazone (2.5 kg vs. placebo). LIMITATION: Single-center study. CONCLUSION: Long-term pioglitazone treatment is safe and effective in patients with prediabetes or T2DM and NASH. PRIMARY FUNDING SOURCE: Burroughs Wellcome Fund and American Diabetes Association.

The role of liver fat and insulin resistance as determinants of plasma aminotransferase elevation in nonalcoholic fatty liver disease.

UNLABELLED: Plasma aminotransferases (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]) are usually increased in patients with nonalcoholic fatty liver disease (NAFLD). However, the factors behind their elevation remain unclear. The aim of this study was to assess the role of insulin resistance (IR) and liver triglyceride content in relation to histology in patients with NAFLD/nonalcoholic steatohepatitis (NASH) with normal or elevated ALT levels. To this end, we enrolled 440 patients, divided into three groups: no NAFLD (n = 60); NAFLD with normal ALT (n = 165); and NAFLD with elevated ALT (n = 215). We measured: (1) liver fat by proton magnetic resonance spectroscopy ((1)H-MRS); (2) severity of liver disease by biopsy (n = 293); and (3) insulin sensitivity in liver, muscle, and adipose tissue by a euglycemic hyperinsulinemic clamp with 3-(3)H-glucose. Patients with NAFLD and elevated ALT, even when well matched for body mass index to those with normal ALT, had worse adipose tissue insulin resistance (ATIR; P < 0.0001), higher liver triglyceride content (P < 0.0001), and lower plasma adiponectin (P < 0.05), but no differences in hepatic insulin resistance. Similar results were found when only patients with NASH were compared: both ATIR (P < 0.0001) and liver triglyceride content by (1)H-MRS (P < 0.0001) were worse in NASH with elevated ALT. Consistent with the (1)H-MRS data, steatosis on liver biopsy was also significantly increased in patients with NASH and elevated ALT levels (P < 0.0001). However, and most important, there were no differences in inflammation (P = 0.62), ballooning (P = 0.13), or fibrosis (P = 0.12). CONCLUSION: In patients with NAFLD or NASH, ATIR (but not HIR) and liver triglyceride content are major factors in the elevation of plasma aminotransferase levels. Patients with normal versus elevated ALT had similar severity of NASH, suggesting that plasma aminotransferase levels are misleading parameters for guiding clinical management.

Cross-talk between branched-chain amino acids and hepatic mitochondria is compromised in nonalcoholic fatty liver disease.

Elevated plasma branched-chain amino acids (BCAA) in the setting of insulin resistance have been relevant in predicting type 2 diabetes mellitus (T2DM) onset, but their role in the etiology of hepatic insulin resistance remains uncertain. We determined the link between BCAA and dysfunctional hepatic tricarboxylic acid (TCA) cycle, which is a central feature of hepatic insulin resistance and nonalcoholic fatty liver disease (NAFLD). Plasma metabolites under basal fasting and euglycemic hyperinsulinemic clamps (insulin stimulation) were measured in 94 human subjects with varying degrees of insulin sensitivity to identify their relationships with insulin resistance. Furthermore, the impact of elevated BCAA on hepatic TCA cycle was determined in a diet-induced mouse model of NAFLD, utilizing targeted metabolomics and nuclear magnetic resonance (NMR)-based metabolic flux analysis. Insulin stimulation revealed robust relationships between human plasma BCAA and indices of insulin resistance, indicating chronic metabolic overload from BCAA. Human plasma BCAA and long-chain acylcarnitines also showed a positive correlation, suggesting modulation of mitochondrial metabolism by BCAA. Concurrently, mice with NAFLD failed to optimally induce hepatic mTORC1, plasma ketones, and hepatic long-chain acylcarnitines, following acute elevation of plasma BCAA. Furthermore, elevated BCAA failed to induce multiple fluxes through hepatic TCA cycle in mice with NAFLD. Our data suggest that BCAA are essential to mediate efficient channeling of carbon substrates for oxidation through mitochondrial TCA cycle. Impairment of BCAA-mediated upregulation of the TCA cycle could be a significant contributor to mitochondrial dysfunction in NAFLD.

Relationship of vitamin D with insulin resistance and disease severity in non-alcoholic steatohepatitis.

BACKGROUND & AIMS: The role of plasma vitamin D deficiency in the development of non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) remains poorly understood. Previous studies have suggested a role for vitamin D deficiency in the pathogenesis of NAFLD/NASH, but they have been rather small, and/or NAFLD was diagnosed using only aminotransferases or liver ultrasound. This study aimed to assess the role of vitamin D deficiency in relationship to liver fat accumulation and severity of NASH. METHODS: A total of 239 patients were recruited and state-of-the-art techniques were used to measure insulin resistance (euglycemic insulin clamp with 3-(3)H-glucose), liver fat accumulation (magnetic resonance spectroscopy or (1)H-MRS), total body fat (dual energy X-ray absorptiometry), and severity of liver disease (liver biopsy). RESULTS: Patients were divided into 3 groups according to plasma 25-hydroxyvitamin D levels (normal: >30 ng/ml; insufficiency: 20-30 ng/ml; deficiency: <20 ng/ml). When well-matched for clinical parameters (BMI, total adiposity, or prevalence of prediabetes/type 2 diabetes), no significant differences were observed among groups in terms of skeletal muscle, hepatic, or adipose tissue insulin sensitivity, the amount of liver fat by (1)H-MRS, or the severity of histological inflammation, ballooning, or fibrosis. Patients were then divided according to liver histology into those with definite NASH and those without NASH. Although patients with NASH had higher insulin resistance, plasma vitamin D concentrations were similar between both groups. CONCLUSIONS: Our results suggest that plasma vitamin D levels are not associated with insulin resistance, the amount of liver fat accumulation, or the severity of NASH.

Relationship between disease severity, hyperinsulinemia, and impaired insulin clearance in patients with nonalcoholic steatohepatitis.

UNLABELLED: Hyperinsulinemia is believed to play a key role in the pathogenesis of nonalcoholic steatohepatitis (NASH) and associated cardiovascular risk. However, the relative contribution of insulin clearance to hyperinsulinemia and its relationship to liver histology have not been carefully evaluated before. To examine this, we enrolled 190 patients (32 without nonalcoholic fatty liver disease [NAFLD], 36 with simple steatosis [SS], and 122 with biopsy-proven NASH). Insulin secretion and hepatic insulin clearance were estimated by means of an oral glucose tolerance test, whereas peripheral insulin sensitivity and whole-body insulin clearance were measured during a euglycemic insulin clamp. A liver biopsy was performed to assess histology (grade/stage). Patients with NASH had similar hepatic insulin sensitivity, compared to patients with SS, but more severe adipose tissue insulin resistance and worse hyperinsulinemia. Patients with SS and NASH had a similar ∼30% reduction (P<0.01) in hepatic insulin clearance, when compared to patients without NAFLD. Reduced hepatic insulin clearance was not associated with severity of inflammation, ballooning, and fibrosis. In contrast, worse histological inflammation and ballooning (but not steatosis or fibrosis) were associated with a progressive reduction in whole-body insulin clearance (P<0.001 for trend). There was no significant difference in insulin secretion between patients with SS versus NASH. CONCLUSION: Decreased hepatic insulin clearance develops with a mild increase in liver fat (LFAT) accumulation. It appears to be largely driven by hepatic steatosis, whereas steatohepatitis is more closely associated with reduced whole-body insulin clearance. Hyperinsulinemia in NAFLD correlated strongly with impaired insulin clearance, but not with insulin secretion. Strategies that reduce LFAT and improve insulin clearance hold the potential to revert the unfavorable effects of hyperinsulinemia in these patients.

Clinical value of liver ultrasound for the diagnosis of nonalcoholic fatty liver disease in overweight and obese patients.

BACKGROUND & AIMS: Liver ultrasound (US) is usually used in the clinical setting for the diagnosis and follow-up of patients with nonalcoholic fatty liver disease (NAFLD). However, no large study has carefully assessed its performance using a semiquantitative ultrasonographic scoring system in overweight/obese patients, in comparison to magnetic resonance spectroscopy ((1) H-MRS) and histology. METHODS: We recruited 146 patients and performed: a liver US using a 5-parameter scoring system, a liver (1) H-MRS to quantify liver fat content, and a liver biopsy to assess histology. All measurements were repeated in a subgroup of patients (n = 62) after 18 months of follow-up. RESULTS: The performance of liver US (parenchymal echo alone) was rather modest, and significantly worse than (1) H-MRS (AUROC: 0.82 [0.69-0.94] vs. 0.96 [0.90-1.00]; P = 0.04). However, the AUROC improved when different echographic parameters were taken into account (AUROC: 0.89 [0.83-0.96], P = 0.15 against (1) H-MRS). Optimum sensitivity for liver US was achieved at a liver fat content ≥12.5%, suggesting that below this threshold, liver US is less sensitive. Liver (1) H-MRS showed a high accuracy for the diagnosis of NAFLD, and correlated strongly with histological steatosis (r = 0.73, P < 0.0001). None of the imaging tests was adequate enough to predict changes over time in histology. CONCLUSIONS: Despite its widespread use, liver US has several important limitations that healthcare providers should recognize, particularly because of its low sensitivity. Using a combination of echographic parameters, liver US showed a significant improvement in its diagnostic performance, but still was of limited value for monitoring treatment over time.

Limited value of plasma cytokeratin-18 as a biomarker for NASH and fibrosis in patients with non-alcoholic fatty liver disease.

BACKGROUND & AIMS: Liver biopsy is the only reliable way of diagnosing and staging NASH but its invasive nature limits its use. Plasma caspase-generated cytokeratin-18 fragments (CK-18) have been proposed as a non-invasive alternative. We studied its clinical value in a large multiethnic NAFLD population and examined its relationship to clinical/metabolic/histological parameters. METHODS: 424 middle-aged subjects in whom we measured adipose tissue, liver and muscle insulin resistance (IR), liver fat by MRS (n=275) and histology (n=318). RESULTS: Median CK-18 were elevated in patients with vs. without NAFLD by MRS (209 [IQR: 137-329] vs. 122 [IQR: 98-155]U/L) or with vs. without NASH (232 [IQR: 151-387] vs. 170 [IQR: 135-234]U/L, both p<0.001). Plasma CK-18 raised significantly with any increase in steatosis, inflammation and fibrosis, but there was a significant overlap across disease severity. The CK-18 AUROC to predict NAFLD, NASH or fibrosis were 0.77 (95% CI=0.71-0.84), 0.65 (95% CI=0.59-0.71) and 0.68 (95% CI=0.61-0.75), respectively. The overall sensitivity/specificity for NAFLD, NASH and fibrosis were 63% (57-70%)/83% (69-92%), 58% (51-65%)/68% (59-76%) and 54% (44-63%)/85% (75-92%), respectively. CK-18 correlated most strongly with ALT (r=0.57, p<0.0001) and adipose tissue IR (insulin-suppression of FFA: r=-0.43; p<0.001), less with steatosis, lobular inflammation and fibrosis (r=0.28-0.34, all p<0.001), but not with ballooning, BMI, metabolic syndrome or T2DM. CONCLUSIONS: Plasma CK-18 has a high specificity for NAFLD and fibrosis, but its limited sensitivity makes it inadequate as a screening test for staging NASH. Whether combined as a diagnostic panel with other biomarkers or clinical/laboratory tests may prove useful requires further study.