Effect of adipose tissue insulin resistance on metabolic parameters and liver histology in obese patients with nonalcoholic fatty liver disease

Efficacy and safety of glucagon-like peptide-1 receptor agonists in non-alcoholic fatty liver disease: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

New drugs are urgently needed for the treatment of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). The aim of this meta-analysis was to evaluate the efficacy and safety of glucagon-like peptide-1 receptor agonists (GLP-1RAs) in NAFLD/NASH.

METHODS

We searched the MEDLINE, Embase, and Cochrane Library Central to identify randomized controlled trials (RCTs) and observational studies that compared GLP-1RAs with a control treatment or baseline values with respect to efficacy and safety in patients with NAFLD/NASH. Mean differences (MDs) with 95% confidence intervals (CIs) and odds ratios (ORs) were pooled using a random-effect model.

RESULTS

Six studies were eligible and included. Among the 329 NAFLD/NASH patients included in these studies, 277 patients had type 2 diabetes (T2D). GLP-1RA treatment produced significant reductions relative to baseline in liver histology scores for steatosis (MD, 0.80; 95% CI, 0.49 to 1.11), lobular inflammation (MD, 0.22; 95% CI, 0.00 to 0.45), hepatocellular ballooning (MD, 0.41; 95% CI, 0.15 to 0.67) and fibrosis (MD, 0.35; 95% CI, 0.00 to 0.70). Compared with placebo and positive agents, GLP-1RAs significantly reduced gamma-glutamyl transpeptidase (GGT) levels (MD, 13.8 U/L; 95% CI, 7.4 to 20.3; P<0.001). The reported major adverse events associated with GLP-1RA treatment included mild to moderate gastrointestinal discomfort that resolved within a few weeks.

CONCLUSIONS

Our study suggests that in NASH patients, particularly patients with diabetes, GLP-1RAs may improve liver histology and reduce aminotransferase levels from baseline. Benefits of GLP-1RAs are considered to outweigh the risks in NAFLD/NASH patients with or without diabetes.

Dapper1 attenuates hepatic gluconeogenesis and lipogenesis by activating PI3K/Akt signaling

Studies have shown that hepatic insulin resistance, a disorder of glucose and lipid metabolism, plays a vital role in type 2 diabetes (T2D). To clarify the function of Dapper1 in glucose and lipid metabolism in the liver, we investigated the relationships between Dapper1 and adenosine triphosphate (ATP)- and Ca²⁺-mediated activation of PI3K/Akt. We observed a reduction in hepatic Dapper1 in db/db (mice that are homozygous for a spontaneous diabetes mutation) and HFD-induced diabetic mice with T2D. Hepatic overexpression of Dapper1 improved hyperglycemia, insulin resistance, and fatty liver. It also increased Akt (pAkt) signaling and repressed both gluconeogenesis and lipogenesis. Conversely, Ad-shDapper1-induced knockdown of hepatic Dapper1 promoted gluconeogenesis and lipogenesis. Furthermore, Dapper1 activated PI3K p110α/Akt in an insulin-independent manner by inducing ATP production and secretion in vitro. Blockade of P2 ATP receptors, the downstream phospholipase C (PLC), or the inositol triphosphate receptor (IP3R all reduced the Dapper1-induced increase in cytosolic free calcium and Dapper1-mediated PI3K/Akt activation, as did removal of calcium in the medium. In conclusion, Dapper1 attenuates hepatic gluconeogenesis and lipogenesis in T2D.

Methods for quantifying adipose tissue insulin resistance in overweight/obese humans

BACKGROUND/OBJECTIVES

Insulin resistance of adipose tissue is an important feature of obesity-related metabolic disease. However, assessment of lipolysis in humans requires labor-intensive and expensive methods, and there is limited validation of simplified measurement methods. We aimed to validate simplified methods for the quantification of adipose tissue insulin resistance against the assessment of insulin sensitivity of lipolysis suppression during hyperinsulinemic-euglycemic clamp studies.

SUBJECTS/METHODS

We assessed the insulin-mediated suppression of lipolysis by tracer-dilution of [1,1,2,3,3-²H₅]glycerol during hyperinsulinemic-euglycemic clamp studies in 125 overweight or obese adults (85 men, 40 women; age 50±11 years; body mass index 38±7 kg m^-2). Seven indices of adipose tissue insulin resistance were validated against the reference measurement method.

RESULTS

Low-dose insulin infusion resulted in suppression of the glycerol rate of appearance ranging from 4% (most resistant) to 85% (most sensitive), indicating a good range of adipose tissue insulin sensitivity in the study population. The reference method correlated with (1) insulin-mediated suppression of plasma glycerol concentrations (r=0.960, P<0.001), (2) suppression of plasma non-esterified fatty acid (NEFA) concentrations (r=0.899, P<0.001), (3) the Adipose tissue Insulin Resistance (Adipo-IR) index (fasting plasma insulin-NEFA product; r=-0.526, P<0.001), (4) the fasting plasma insulin-glycerol product (r=-0.467, P<0.001), (5) the Adipose Tissue Insulin Resistance Index (fasting plasma insulin-basal lipolysis product; r=0.460, P<0.001), (6) the Quantitative Insulin Sensitivity Check Index (QUICKI)-NEFA index (r=0.621, P<0.001), and (7) the QUICKI-glycerol index (r=0.671, P<0.001). Bland-Altman plots showed no systematic errors for the suppression indices but proportional errors for all fasting indices. Receiver-operator characteristic curves confirmed that all indices were able to detect adipose tissue insulin resistance (area under the curve ⩾0.801, P<0.001).

CONCLUSIONS

Adipose tissue insulin sensitivity (that is, the antilipolytic action of insulin) can be reliably quantified in overweight and obese humans by simplified index methods. The sensitivity and specificity of the Adipo-IR index and the fasting plasma insulin-glycerol product, combined with their simplicity and acceptable agreement, suggest that these may be most useful in clinical practice.

Insulin-mimetic compound hexaquis (benzylammonium) decavanadate is antilipolytic in human fat cells

AIM

To assess in rodent and human adipocytes the antilipolytic capacity of hexaquis(benzylammonium) decavanadate (B6V10), previously shown to exert antidiabetic effects in rodent models, such as lowering free fatty acids (FFA) and glucose circulating levels.

METHODS

Adipose tissue (AT) samples were obtained after informed consent from overweight women undergoing plastic surgery. Comparison of the effects of B6V10 and reference antilipolytic agents (insulin, benzylamine, vanadate) on the lipolytic activity was performed on adipocytes freshly isolated from rat, mouse and human AT. Glycerol release was measured using colorimetric assay as an index of lipolytic activity. The influence of B6V10 and reference agents on glucose transport into human fat cells was determined using the radiolabelled 2-deoxyglucose uptake assay.

RESULTS

In all the species studied, B6V10 exhibited a dose-dependent inhibition of adipocyte lipolysis when triglyceride breakdown was moderately enhanced by β-adrenergic receptor stimulation. B6V10 exerted on human adipocyte a maximal lipolysis inhibition of glycerol release that was stronger than that elicited by insulin. However, B6V10 did not inhibit basal and maximally stimulated lipolysis. When incubated at dose ≥ 10 μmol/L, B6V10 stimulated by twofold the glucose uptake in human fat cells, but - similarly to benzylamine - without reaching the maximal effect of insulin, while it reproduced one-half of the insulin-stimulation of lipogenesis in mouse fat cells.

CONCLUSION

B6V10 exerts insulin-like actions in adipocytes, including lipolysis inhibition and glucose transport activation. B6V10 may be useful in limiting lipotoxicity related to obesity and insulin resistance.

Faecalibacterium prausnitzii treatment improves hepatic health and reduces adipose tissue inflammation in high-fat fed mice

Faecalibacterium prausnitzii is considered as one of the most important bacterial indicators of a healthy gut. We studied the effects of oral F. prausnitzii treatment on high-fat fed mice. Compared to the high-fat control mice, F. prausnitzii-treated mice had lower hepatic fat content, aspartate aminotransferase and alanine aminotransferase, and increased fatty acid oxidation and adiponectin signaling in liver. Hepatic lipidomic analyses revealed decreases in several species of triacylglycerols, phospholipids and cholesteryl esters. Adiponectin expression was increased in the visceral adipose tissue, and the subcutaneous and visceral adipose tissues were more insulin sensitive and less inflamed in F. prausnitzii-treated mice. Further, F. prausnitzii treatment increased muscle mass that may be linked to enhanced mitochondrial respiration, modified gut microbiota composition and improved intestinal integrity. Our findings show that F. prausnitzii treatment improves hepatic health, and decreases adipose tissue inflammation in mice and warrant the need for further studies to discover its therapeutic potential.

Role of Adipose Tissue Insulin Resistance in the Natural History of Type 2 Diabetes: Results From the San Antonio Metabolism Study

In the transition from normal glucose tolerance (NGT) to type 2 diabetes mellitus (T2DM), the role of β-cell dysfunction and peripheral insulin resistance (IR) is well established. However, the impact of dysfunctional adipose tissue has not been fully elucidated. The aim of this study was to evaluate the role of resistance to the antilipolytic effect of insulin (adipose tissue IR [Adipo-IR]) in a large group of subjects with NGT, impaired glucose tolerance (IGT), and T2DM. Three hundred two subjects with varying glucose tolerance received an oral glucose tolerance test (OGTT) and euglycemic insulin clamp. We evaluated Adipo-IR (fasting and mean OGTT plasma free fatty acid [FFA] × insulin concentrations), peripheral IR (1/[Matsuda index] and (M/I)^-1 value), and β-cell function (calculated as the ratio of the increment in plasma insulin to glucose [OGTT/IR (ΔI/ΔG ÷ IR)]). Fasting Adipo-IR was increased twofold in obese subjects with NGT and IGT versus lean subjects with NGT (8.0 ± 1.1 and 9.2 ± 0.7 vs. 4.1 ± 0.3, respectively) and threefold in subjects with T2DM (11.9 ± 0.6; P < 0.001). Progressive decline in ΔI/ΔG ÷ IR was associated with a progressive impairment in FFA suppression during OGTT, whereas the rise in mean plasma glucose concentration only became manifest when subjects became overtly diabetic. The progressive decline in β-cell function that begins in individuals with NGT is associated with a progressive increase in FFA and fasting Adipo-IR.

Nonobese Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) refers to a group of conditions characterized by hepatic steatosis in the absence of significant alcohol consumption. NAFLD is seen commonly in patients with metabolic abnormalities associated with obesity, such as type II diabetes, dyslipidemia, and metabolic syndrome. Evidently, however, not all obese subjects develop NAFLD and, more importantly, NAFLD can be found in nonobese individuals. Although NAFLD occurring in nonobese subjects has been reported in children and adults of all ethnicities, it appears to be recognized more frequently in Asians, even when strict ethnicity-specific body mass index criteria are used to define obesity. Studies based on liver biopsies suggest that the prevalence of nonalcoholic steatohepatitis and fibrosis does not differ significantly between nonobese NAFLD and NAFLD in obese patients. Visceral obesity as opposed to general obesity, high fructose and cholesterol intake, and genetic risk factors (eg, palatin-like phospholipase domain-containing 3) may be associated with nonobese NAFLD. In general, nonalcoholic steatohepatitis is associated with increased mortality, primarily from cardiovascular causes, independent of other metabolic factors. Although data regarding the mortality impact of nonobese NAFLD are not as mature, it may be important to identify high-risk nonobese NAFLD patients and manage their metabolic profile. Currently, lifestyle modification to reduce visceral adiposity, including dietary changes and physical activity, remains the standard of care in patients with nonobese NAFLD.

Mitochondrial Adaptation in Nonalcoholic Fatty Liver Disease: Novel Mechanisms and Treatment Strategies

Nonalcoholic fatty liver disease (NAFLD) is prevalent in patients with obesity or type 2 diabetes. Nonalcoholic steatohepatitis (NASH), encompassing steatosis with inflammation, hepatocyte injury, and fibrosis, predisposes to cirrhosis, hepatocellular carcinoma, and even cardiovascular disease. In rodent models and humans with NAFLD/NASH, maladaptation of mitochondrial oxidative flux is a central feature of simple steatosis to NASH transition. Induction of hepatic tricarboxylic acid cycle closely mirrors the severity of oxidative stress and inflammation in NASH. Reactive oxygen species generation and inflammation are driven by upregulated, but inefficient oxidative flux and accumulating lipotoxic intermediates. Successful therapies for NASH (weight loss alone or with incretin therapy, or pioglitazone) likely attenuate mitochondrial oxidative flux and halt hepatocellular injury. Agents targeting mitochondrial dysfunction may provide a novel treatment strategy for NAFLD.

Deficiency of CKIP-1 aggravates high-fat diet-induced fatty liver in mice

Casein kinase 2 interacting protein-1(CKIP-1) is widely expressed in a variety of tissues and cells, and plays an important role in various critical cellular and physiological processes including cell growth, apoptosis, differentiation, cytoskeleton and bone formation. Here, we found: (1) CKIP-1 deficient mice exhibited increased body weight, liver weight, number and size of lipid droplets, and TG content comparing with WT mice after being exposed to high fat diet (HFD); (2) the levels of serum insulin, liver glycogen, phosphorylated C-Jun-N-terminal kinase-1 (pJNK1) and phosphorylated insulin receptor substrate -1(pIRS1) in CKIP-1^-/- mice were higher than those of WT mice; (3) CKIP-1 interacted with JNK1 in vitro. Our results indicate that CKIP-1 deficiency in mice aggravates HFD-induced fatty liver by upregulating JNK1 phosphorylation and further upregulating IRS-1 phosphorylation and RI.

Interorgan cross talk between fatty acid metabolism, tissue inflammation, and FADS2 genotype in humans with obesity

OBJECTIVE

Fatty acid (FA) composition affects obesity-associated low-grade inflammation. It has been shown that the fatty acid desaturase (FADS) 2 gene polymorphism associates with FA metabolism and adipose tissue (AT) inflammation. This study aimed to investigate the relationship between FA metabolism and inflammation in different tissues and the possible interorgan cross talk.

METHODS

Cross-sectional baseline data from 155 individuals with obesity (both male and female) participating in the Roux-en-Y gastric bypass operation in the ongoing Kuopio Obesity Surgery Study were used. Gas chromatograph for FA composition, liver histology, and targeted RNA expression for gene expression profile were performed.

RESULTS

It was demonstrated that the saturated fatty acid (SFA) proportion in AT correlated positively with inflammation in subcutaneous AT (SAT) and visceral AT (VAT) but not in the liver, while the monounsaturated fatty acid (MUFA) proportion in SAT and VAT correlated negatively with AT inflammation. Notably, there was a positive correlation between AT n-6 polyunsaturated fatty acids (PUFAs), but not AT SFAs or MUFAs, and liver inflammation. This correlation was modified by the FADS2 genotype.

CONCLUSIONS

The AT FA profile relates with AT inflammation. Additionally, there seems to be a complex interaction, partly regulated by the FADS2 genotype, regulating the interaction between FAs in AT and liver inflammation.

The Risk Factor Analysis for Type 2 Diabetes Mellitus Patients with Nonalcoholic Fatty Liver Disease and Positive Correlation with Serum Uric Acid

Recent years, we has witnessed a sharp increase in the complications of Type 2 diabetes mellitus (T2DM) with nonalcoholic fatty liver disease (NAFLD). Here we aimed to determine the risk factors for T2DM patients with NAFLD and the relationship of serum uric acid (SUA) in these complications. We performed retrospective analysis of 300 T2DM patients admitted into our hospital from April 2010 to January 2014. We divided the T2DM patients into two groups based on whether the patients also had NAFLD or not, Group A (without NAFLD, 155 cases) and Group B (with NAFLD, 145 cases). General information of the patients was collected and analyzed statistically. Meanwhile, we detected and compared the blood biochemistry, glucose, and fasting insulin (FINS), and further performed Logistic regression analysis and determined the risk factors in T2DM patients with NAFLD. Significantly higher BMI, waist circumference, hip circumference, WHR, systolic, and diastolic blood pressure were observed in T2DM patients with NAFLD than the patients without NAFLD, which were statistically different (P < 0.05). There were also significant higher levels of TC, TG, ALT, AST, GGT, and SUA in T2DM patients with NAFLD than those in patients without NAFLD, which were statistically different (P < 0.05). Significantly higher levels of FPG, FINS, and HOMA-IR were observed in the T2DM patients with NAFLD than those without, which were statistically significant (P < 0.05). Logistic regression analysis also showed high BMI, WHR, TG, and SUA were independent risk factors in T2DM patients with NAFLD (P < 0.05). Meanwhile, SUA levels were positively correlated with BMI, W, H, WHR, hip circumference, waist circumference, TG, ALT, AST, GGT, FPG, FINS, and HOMA-IR, which were statistically significant (P < 0.05). The risk factors for T2DM patients with NAFLD are mainly BMI, WHR, TG, and SUA. Our findings provide clinical implications for the prevention and early diagnosis of T2DM patients with NAFLD.

The CCR2 Inhibitor Propagermanium Attenuates Diet-Induced Insulin Resistance, Adipose Tissue Inflammation and Non-Alcoholic Steatohepatitis

BACKGROUND AND AIM

Obese patients with chronic inflammation in white adipose tissue (WAT) have an increased risk of developing non-alcoholic steatohepatitis (NASH). The C-C chemokine receptor-2 (CCR2) has a crucial role in the recruitment of immune cells to WAT and liver, thereby promoting the inflammatory component of the disease. Herein, we examined whether intervention with propagermanium, an inhibitor of CCR2, would attenuate tissue inflammation and NASH development.

METHODS

Male C57BL/6J mice received a high-fat diet (HFD) for 0, 6, 12 and 24 weeks to characterize the development of early disease symptoms of NASH, i.e. insulin resistance and WAT inflammation (by hyperinsulinemic-euglycemic clamp and histology, respectively) and to define the optimal time point for intervention. In a separate study, mice were pretreated with HFD followed by propagermanium treatment (0.05% w/w) after 6 weeks (early intervention) or 12 weeks (late intervention). NASH was analyzed after 24 weeks of diet feeding.

RESULTS

Insulin resistance in WAT developed after 6 weeks of HFD, which was paralleled by modest WAT inflammation. Insulin resistance and inflammation in WAT intensified after 12 weeks of HFD, and preceded NASH development. The subsequent CCR2 intervention experiment showed that early, but not late, propagermanium treatment attenuated insulin resistance. Only the early treatment significantly decreased Mcp-1 and CD11c gene expression in WAT, indicating reduced WAT inflammation. Histopathological analysis of liver demonstrated that propagermanium treatment decreased macrovesicular steatosis and tended to reduce lobular inflammation, with more pronounced effects in the early intervention group. Propagermanium improved the ratio between pro-inflammatory (M1) and anti-inflammatory (M2) macrophages, quantified by CD11c and Arginase-1 gene expression in both intervention groups.

CONCLUSIONS

Overall, early propagermanium administration was more effective to improve insulin resistance, WAT inflammation and NASH compared to late intervention. These data suggest that therapeutic interventions for NASH directed at the MCP-1/CCR2 pathway should be initiated early.

NAFLD and diabetes mellitus

The liver constitutes a key organ in systemic metabolism, contributing substantially to the development of insulin resistance and type 2 diabetes mellitus (T2DM). The mechanisms underlying these processes are not entirely understood, but involve hepatic fat accumulation, alterations of energy metabolism and inflammatory signals derived from various cell types including immune cells. Lipotoxins, mitochondrial function, cytokines and adipocytokines have been proposed to play a major part in both NAFLD and T2DM. Patients with NAFLD are commonly insulin resistant. On the other hand, a large number of patients with T2DM develop NAFLD with its inflammatory complication, NASH. The high incidence of NASH in patients with T2DM leads to further complications, such as liver cirrhosis and hepatocellular carcinoma, which are increasingly recognized. Therapeutic concepts such as thiazolidinediones (glitazones) for treating T2DM also show some efficacy in the treatment of NASH. This Review will describe the multifaceted and complex interactions between the liver and T2DM.

Insulin Resistance in Adipose Tissue but Not in Liver Is Associated with Aortic Valve Calcification

Background. Insulin resistance is involved in the pathogenesis of cardiovascular disease, but its relationship with cardiovascular calcification has yielded conflicting results. The purpose of the present study was to investigate the role of hepatic and adipose tissue insulin resistance on the presence of coronary artery (CAC > 0) and aortic valve calcification (AVC > 0). Methods. In 1201 subjects (52% women, 53.6 ± 9.3 years old) without familiar and personal history of coronary heart disease, CAC and AVC were assessed by multidetector-computed tomography. Cardiovascular risk factors were documented and lipid profile, inflammation markers, glucose, insulin, and free fatty acids were measured. Hepatic insulin resistance (HOMA-IR) and adipose tissue insulin resistance (Adipo-IR) indices were calculated. Results. There was a significant relationship between HOMA-IR and Adipo-IR indices (r = 0.758, p < 0.001). Participants in the highest quartiles of HOMA-IR and Adipo-IR indices had a more adverse cardiovascular profile and higher prevalence of CAC > 0 and AVC > 0. After full adjustment, subjects in the highest quartile of Adipo-IR index had higher odds of AVC > 0 (OR: 2.40; 95% CI: 1.30-4.43), as compared to those in the lowest quartile. Conclusions. Adipo-IR was independently associated with AVC > 0. This suggests that abnormal adipose tissue function favors insulin resistance that may promote the development and progression of AVC.

Nonalcoholic Fatty Liver Disease: The New Complication of Type 2 Diabetes Mellitus

Nonalcoholic fatty liver disease (NAFLD) is increasingly common in patients with type 2 diabetes mellitus (T2DM), with an estimated prevalence of 60% to 80%. The relationship of NAFLD and T2DM is complex, with each condition negatively affecting the other. Although NAFLD is associated with more metabolic and cardiovascular complications and worse hyperglycemia, T2DM accelerates the progression of liver disease in NAFLD. Despite the high prevalence and serious clinical implications, NAFLD is usually overlooked in clinical practice. This article focuses on understanding the relationship between NAFLD and T2DM, to provide better care for these complex patients.

Loss of UCP1 exacerbates Western diet-induced glycemic dysregulation independent of changes in body weight in female mice

We tested the hypothesis that female mice null for uncoupling protein 1 (UCP1) would have increased susceptibility to Western diet-induced "whitening" of brown adipose tissue (AT) and glucose intolerance. Six-week-old C57BL/6J wild-type (WT) and UCP1 knockout (UCP1^-/-) mice, housed at 25°C, were randomized to either a control diet (10% kcal from fat) or Western diet (45% kcal from fat and 1% cholesterol) for 28 wk. Loss of UCP1 had no effect on energy intake, energy expenditure, spontaneous physical activity, weight gain, or visceral white AT mass. Despite similar susceptibility to weight gain compared with WT, UCP1^-/- exhibited whitening of brown AT evidenced by a striking ~500% increase in mass and appearance of large unilocular adipocytes, increased expression of genes related to inflammation, immune cell infiltration, and endoplasmic reticulum/oxidative stress (P < 0.05), and decreased mitochondrial subunit protein (COX I, II, III, and IV, P < 0.05), all of which were exacerbated by Western diet (P < 0.05). UCP1^-/- mice also developed liver steatosis and glucose intolerance, which was worsened by Western diet. Collectively, these findings demonstrate that loss of UCP1 exacerbates Western diet-induced whitening of brown AT, glucose intolerance, and induces liver steatosis. Notably, the adverse metabolic manifestations of UCP1^-/- were independent of changes in body weight, visceral adiposity, and energy expenditure. These novel findings uncover a previously unrecognized metabolic protective role of UCP1 that is independent of its already established role in energy homeostasis.

Adipose tissue dysfunction increases fatty liver association with pre diabetes and newly diagnosed type 2 diabetes mellitus

BACKGROUND

To evaluate the role of adipose tissue function on the association of fatty liver (FL) with impaired fasting glucose (IFG) or newly diagnosed type 2 diabetes mellitus (nT2D).

METHODS

In 1264 subjects, computed tomography was used to evaluate FL and elevated visceral adipose tissue (VAT). Fasting plasma glucose, <5.6, 5.6-6.9 and ≥7 mmol/l, were used to defined normoglycemic (NG), IFG or nT2D, respectively. Elevated free fatty acids, low serum adiponectin levels and adipose tissue insulin resistance (Adipo-IR), were used as markers of adipose tissue dysfunction.

RESULTS

Compared to NG subjects, those with IFG or nT2D had higher prevalence of FL and elevated VAT. FL was found to be independently associated with IFG and nT2D. Adipo-IR increased the association between FL and IFG [OR: 2.46 (95% I.C.: 1.73-3.49) to 5.42 (3.11-9.41)], whereas low adiponectin levels had a higher effect on the FL and nT2D association [OR: 4.26 (2.18-8.34) to 8.53 (2.96-24.55)].

CONCLUSION

Fatty liver was independently associated with IFG and nT2D. Our results indicate for the first time, that adipose tissue dysfunction increases these associations.

Adipose Recruitment and Activation of Plasmacytoid Dendritic Cells Fuel Metaflammation

In obese individuals, visceral adipose tissue (VAT) is the seat of chronic low-grade inflammation (metaflammation), but the mechanistic link between increased adiposity and metaflammation largely remains unclear. In obese individuals, deregulation of a specific adipokine, chemerin, contributes to innate initiation of metaflammation by recruiting circulating plasmacytoid dendritic cells (pDCs) into VAT through chemokine-like receptor 1 (CMKLR1). Adipose tissue-derived high-mobility group B1 (HMGB1) protein activates Toll-like receptor 9 (TLR9) in the adipose-recruited pDCs by transporting extracellular DNA through receptor for advanced glycation end products (RAGE) and induces production of type I interferons (IFNs). Type I IFNs in turn help in proinflammatory polarization of adipose-resident macrophages. IFN signature gene expression in VAT correlates with both adipose tissue and systemic insulin resistance (IR) in obese individuals, which is represented by ADIPO-IR and HOMA2-IR, respectively, and defines two subgroups with different susceptibility to IR. Thus, this study reveals a pathway that drives adipose tissue inflammation and consequent IR in obesity.

Platycodon grandiflorus Root Extract Attenuates Body Fat Mass, Hepatic Steatosis and Insulin Resistance through the Interplay between the Liver and Adipose Tissue

The Platycodon grandiflorus root, a Korean medicinal food, is well known to have beneficial effects on obesity and diabetes. In this study, we demonstrated the metabolic effects of P. grandiflorus root ethanol extract (PGE), which is rich in platycodins, on diet-induced obesity. C57BL/6J mice (four-week-old males) were fed a normal diet (16.58% of kilocalories from fat), high-fat diet (HFD, 60% of kilocalories from fat), and HFD supplemented with 5% (w/w) PGE. In the HFD-fed mice, PGE markedly suppressed the body weight gain and white fat mass to normal control level, with simultaneous increase in the expression of thermogenic genes (such as SIRT1, PPARα, PGC1α, and UCP1), that accompanied changes in fatty acid oxidation (FAO) and energy expenditure. In addition, PGE improved insulin sensitivity through activation of the PPARγ expression, which upregulates adiponectin while decreasing leptin gene expression in adipocytes. Furthermore, PGE improved hepatic steatosis by suppressing hepatic lipogenesis while increasing expression of FAO-associated genes such as PGC1α. PGE normalized body fat and body weight, which is likely associated with the increased energy expenditure and thermogenic gene expression. PGE can protect from HFD-induced insulin resistance, and hepatic steatosis by controlling lipid and glucose metabolism.

Suppression of IGF binding protein-3 by palmitate promotes hepatic inflammatory responses

IGF-binding protein-3 (IGFBP-3) is a liver-derived, anti-inflammatory molecule that is decreased in obesity, a key risk factor for nonalcoholic fatty liver disease (NAFLD). It was not known whether IGFBP-3 levels were altered in NAFLD, whether such alterations could be the result of lipotoxicity, and whether altered IGFBP-3 could affect pathways that are involved in hepatic and systemic inflammation. Serum IGFBP-3 was decreased in patients with NAFLD, whereas liver and circulating IL-8 levels were increased. Palmitate inhibited IGFBP-3 secretion by THP-1 macrophages and enhanced IL-8 expression. Exposure of palmitate-treated THP-1 macrophages to IGFBP-3-deficient conditioned medium led to a 20-fold increase in palmitate-induced IL-8 expression by hepatocytes. Conversely, overexpression of IGFBP-3 suppressed JNK and NF-κB activation and blocked palmitate-induced IL-8 expression in hepatocytes. Silencing IGFBP-3 in Huh7 cells enhanced JNK and NF-κB activity and increased palmitate-induced IL-8 secretion. These data indicate that IGFBP-3 serves as an anti-inflammatory brake in hepatocytes against JNK and NF-κB and limits their activation and downstream production of proinflammatory cytokines. Under lipotoxic conditions, palmitate inhibits hepatic macrophage secretion of IGFBP-3, thereby releasing the brake and enhancing palmitate-induced IL-8 synthesis and secretion.-Min, H.-K., Maruyama, H., Jang, B. K., Shimada, M., Mirshahi, F., Ren, S., Oh, Y., Puri, P., Sanyal, A. J. Suppression of IGF binding protein-3 by palmitate promotes hepatic inflammatory responses.

Phenotypical heterogeneity linked to adipose tissue dysfunction in patients with Type 2 diabetes

Adipose tissue (AT) inflammation leads to increased free fatty acid (FFA) efflux and ectopic fat deposition, but whether AT dysfunction drives selective fat accumulation in specific sites remains unknown. The aim of the present study was to investigate the correlation between AT dysfunction, hepatic/pancreatic fat fraction (HFF, PFF) and the associated metabolic phenotype in patients with Type 2 diabetes (T2D). Sixty-five consecutive T2D patients were recruited at the Diabetes Centre of Sapienza University, Rome, Italy. The study population underwent clinical examination and blood sampling for routine biochemistry and calculation of insulin secretion [homoeostasis model assessment of insulin secretion (HOMA-β%)] and insulin-resistance [homoeostasis model assessment of insulin resistance (HOMA-IR) and adipose tissue insulin resistance (ADIPO-IR)] indexes. Subcutaneous (SAT) and visceral (VAT) AT area, HFF and PFF were determined by magnetic resonance. Some 55.4% of T2D patients had non-alcoholic fatty liver disease (NAFLD); they were significantly younger and more insulin-resistant than non-NAFLD subjects. ADIPO-IR was the main determinant of HFF independently of age, sex, HOMA-IR, VAT, SAT and predicted severe NAFLD with the area under the receiver operating characteristic curve (AUROC)=0.796 (95% confidence interval: 0.65-0.94, P=0.001). PFF was independently associated with increased total adiposity but did not correlate with AT dysfunction, insulin resistance and secretion or NAFLD. The ADIPO-IR index was capable of predicting NAFLD independently of all confounders, whereas it did not seem to be related to intrapancreatic fat deposition; unlike HFF, higher PFF was not associated with relevant alterations in the metabolic profile. In conclusion, the presence and severity of AT dysfunction may drive ectopic fat accumulation towards specific targets, such as VAT and liver, therefore evaluation of AT dysfunction may contribute to the identification of different risk profiles among T2D patients.

Evaluating -238 G>A Polymorphism Association in TNF-α Gene with Metabolic Parameters and Nutritional Intakes Among the Iranian NAFLD Patients

Different studies have shown that -238 G>A polymorphism in promoter region of tumor necrosis factor alpha (TNF-α) gene is associated with increased risk of non-alcoholic fatty liver disease (NAFLD). The current study investigates the association between metabolic parameters and nutritional intakes with -238 G>A of TNF-α promoter gene polymorphism among the Iranian patients with NAFLD. In this study, 75 patients with NAFLD and 76 individuals as control were enrolled. Dietary intakes were assessed using a semi-quantitative food-frequency questionnaire. Body mass index and waist to hip ratio were calculated. Biochemical assays were measured after 12 h fasting. -238 G>A Polymorphism of TNF-α gene was determined by using sequencing method. We observed no significant difference in frequency of different genotypes of this polymorphism between NAFLD and control groups (P > 0.05). Among biochemical parameters, TAC showed significant decrease in NAFLD patients with GG genotype when compared to controls (P = 0.001). The comparison of macro and micronutrient intakes between groups according to genotypes showed no statistically significant difference (P > 0.05). Although the data were not statistically significant, further studies with larger sample size are needed to determine the effect of dietary compounds in NAFLD.

Non-Alcoholic Steatohepatitis: Limited Available Treatment Options but Promising Drugs in Development and Recent Progress Towards a Regulatory Approval Pathway

The prevalence of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) is increasing world-wide in parallel to the increase of the obesity epidemic. Insulin resistance (IR) and the accumulation of triglyceride-derived toxic lipid metabolites play a key role in its pathogenesis. Multiple biomarkers are being evaluated for the non-invasive diagnosis of NASH. However, a percutaneous liver biopsy is still the gold standard method; the minimal diagnostic criteria include the presence of >5 % macrovesicular steatosis, inflammation, and liver cell ballooning. Several pharmaceutical agents have been evaluated for the treatment of NASH; however, no single therapy has been approved so far. Due to the increasing prevalence and the health burden, there is a high need to develop therapeutic strategies for patients with NASH targeting both those with early-stage disease as well as those with advanced liver fibrosis. There are unique challenges in the design of studies for these target populations. Collaborative efforts of health authorities, medical disease experts, and the pharmaceutical industry are ongoing to align options for a registrational pathway. Several companies pursuing different mechanisms of action are nearing the end of phase II with their candidates. This manuscript reviews those compounds with a variety of mode of actions that have been evaluated and/or are currently being tested with the goal of achieving a NAFLD/NASH indication.

The Pathogenesis of Nonalcoholic Fatty Liver Disease: Interplay between Diet, Gut Microbiota, and Genetic Background

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world, and it comprises a spectrum of hepatic abnormalities from simple hepatic steatosis to steatohepatitis, fibrosis, cirrhosis, and liver cancer. While the pathogenesis of NAFLD remains incompletely understood, a multihit model has been proposed that accommodates causal factors from a variety of sources, including intestinal and adipose proinflammatory stimuli acting on the liver simultaneously. Prior cellular and molecular studies of patient and animal models have characterized several common pathogenic mechanisms of NAFLD, including proinflammation cytokines, lipotoxicity, oxidative stress, and endoplasmic reticulum stress. In recent years, gut microbiota has gained much attention, and dysbiosis is recognized as a crucial factor in NAFLD. Moreover, several genetic variants have been identified through genome-wide association studies, particularly rs738409 (Ile748Met) in PNPLA3 and rs58542926 (Glu167Lys) in TM6SF2, which are critical risk alleles of the disease. Although a high-fat diet and inactive lifestyles are typical risk factors for NAFLD, the interplay between diet, gut microbiota, and genetic background is believed to be more important in the development and progression of NAFLD. This review summarizes the common pathogenic mechanisms, the gut microbiota relevant mechanisms, and the major genetic variants leading to NAFLD and its progression.

Extrahepatic Complications of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is an important cause of liver disease that is often associated with the metabolic syndrome. There is a growing awareness that extrahepatic complications occur in individuals with NAFLD, especially an increased risk of cardiovascular disease. Development of diabetes mellitus, chronic kidney disease, colorectal cancer, and endocrinopathies has been linked to NAFLD. This article reviews the extrahepatic complications affecting individuals with NAFLD and the pathogenesis underlying their development.

Diabetic and nondiabetic patients with nonalcoholic fatty liver disease have an impaired incretin effect and fasting hyperglucagonaemia

OBJECTIVE

We evaluated whether patients with histologically verified nonalcoholic fatty liver disease (NAFLD) have an impaired incretin effect and hyperglucagonaemia.

METHODS

Four groups matched for age, sex and body mass index were studied: (i) 10 patients with normal glucose tolerance and NAFLD; (ii) 10 patients with type 2 diabetes and NAFLD; (iii) eight patients with type 2 diabetes and no liver disease; and (iv) 10 controls. All participants underwent a 50-g oral glucose tolerance test (OGTT) and an isoglycaemic intravenous glucose infusion (IIGI). We determined the incretin effect by relating the beta cell secretory responses during the OGTT and IIGI. Data are presented as medians (interquartile range), and the groups were compared by using the Kruskal-Wallis test.

RESULTS

Controls exhibited a higher incretin effect [55% (43-73%)] compared with the remaining three groups (P < 0.001): 39% (44-71%) in the nondiabetic NAFLD patients, 20% (-5-50%) in NAFLD patients with type 2 diabetes, and 2% (-8-6%) in patients with type 2 diabetes and no liver disease. We found fasting hyperglucagonaemia in NAFLD patients with [7.5 pmol L(-1) (6.8-15 pmol L(-1))] and without diabetes [7.5 pmol L(-1) (5.0-8.0 pmol L(-1))]. Fasting glucagon levels were lower but similar in patients with type 2 diabetes and no liver disease [4.5 pmol L(-1) (3.0-6.0 pmol L(-1))] and controls [3.4 pmol L(-1) (1.8-6.0 pmol L(-1) )]. All groups had similar glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide responses.

CONCLUSIONS

Patients with NAFLD have a reduced incretin effect and fasting hyperglucagonaemia, with the latter occurring independently of glucose (in)tolerance.

Current Pharmacologic Therapy for Nonalcoholic Fatty Liver Disease

Weight loss, regular exercise, and diet composition modification seem to improve biochemical and histologic abnormalities. Other therapies directed at insulin resistance, oxidative stress, cytoprotection, and fibrosis may also offer benefits. Insulin sensitizers and vitamin E seem to be the most promising; however, they cause side effects. A multifaceted approach of lifestyle modifications, weight loss, and pharmacotherapy can be used in combination, but no single treatment approach has proved universally applicable to the general population with nonalcoholic steatohepatitis (NASH). Continuous clinical and preclinical studies on existing and potential drugs are needed to improve treatment of nonalcoholic fatty liver disease/NASH.

Emerging Therapies for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease is the most common cause of liver disease in the United States. There are no drug therapies approved for the treatment of nonalcoholic steatohepatitis (NASH). Multiple different pathways are involved in the pathogenesis and each can be the target of the therapy. It is possible that more than 1 target is involved in disease development and progression. Multiple clinical trials with promising agents are underway. Because NASH is a slowly progressive disease and treatment likely to be of prolonged duration, acceptance and approval of any agent will require information on long-term clinical benefits and safety.

Diagnostic value of alcoholic liver disease (ALD)/nonalcoholic fatty liver disease (NAFLD) index combined with γ-glutamyl transferase in differentiating ALD and NAFLD

BACKGROUND/AIMS

This study aimed to verify the reliability of the alcoholic liver disease (ALD)/nonalcoholic fatty liver disease (NAFLD) index (ANI) for distinguishing ALD in patients with hepatic steatosis from NAFLD, and to investigate whether ANI combined with γ-glutamyl transferase (GGT) would enhance the accuracy of diagnosis in China.

METHODS

A hundred thirty-nine cases of fatty liver disease (FLD) were divided into two groups of ALD and NAFLD. The ANI was calculated with an online calculator. All indicators and ANI values were analyzed using statistical methods.

RESULTS

ANI was significantly higher in patients with ALD than in those with NAFLD (7.11 ± 5.77 vs. -3.09 ± 3.89, p < 0.001). With a cut-off value of -0.22, the sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) of diagnosed ALD cases was 87.1%, 92.5%, and 0.934 (95% confidence interval [CI], 0.879 to 0.969), respectively. The corresponding values for aspartate aminotransferase (AST)/alanine transaminase (ALT), mean corpuscular volume (MCV), and GGT were 75.29%, 72.94%, and 0.826 (95% CI, 0.752 to 0.885); 94.34%, 83.02%, and 0.814 (95% CI, 0.739 to 0.875) and 80.23%, 79.25%, and 0.815 (95% CI, 0.740 to 0.876), respectively. ANI AUROC was significantly higher than the AST/ALT, MCV, or GGT AUROCs (all p < 0.001), moreover, ANI showed better diagnostic performance. The combination of ANI and GGT showed a better AUROC than ANI alone (0.976 vs. 0.934, p = 0.016). The difference in AUROCs between AST/ALT, MCV, and GGT was not statistically significant (all p > 0.05).

CONCLUSIONS

ANI can help distinguish ALD from NAFLD with high accuracy; when ANI was combined with GGT, its effectiveness improved further.

Hepatic ceramides dissociate steatosis and insulin resistance in patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

Recent data in mice have identified de novo ceramide synthesis as the key mediator of hepatic insulin resistance (IR) that in humans characterizes increases in liver fat due to IR ('Metabolic NAFLD' but not that due to the I148M gene variant in PNPLA3 ('PNPLA3 NAFLD'). We determined which bioactive lipids co-segregate with IR in the human liver.

METHODS

Liver lipidome was profiled in liver biopsies from 125 subjects that were divided into equally sized groups based on median HOMA-IR ('High and Low HOMA-IR', n=62 and n=63) or PNPLA3 genotype (PNPLA3(148MM/MI), n=61 vs. PNPLA3(148II), n=64). The subjects were also divided into 4 groups who had either IR, the I148M gene variant, both of the risk factors or neither.

RESULTS

Steatosis and NASH prevalence were similarly increased in 'High HOMA-IR' and PNPLA3(148MM/MI) groups compared to their respective control groups. The 'High HOMA-IR' but not the PNPLA3(148MM/MI) group had features of IR. The liver in 'High HOMA-IR' vs. 'Low HOMA-IR' was markedly enriched in saturated and monounsaturated triacylglycerols and free fatty acids, dihydroceramides (markers of de novo ceramide synthesis) and ceramides. Markers of other ceramide synthetic pathways were unchanged. In PNPLA3(148MM/MI)vs. PNPLA3(148II), the increase in liver fat was due to polyunsaturated triacylglycerols while other lipids were unchanged. Similar changes were observed when data were analyzed using the 4 subgroups.

CONCLUSIONS

Similar increases in liver fat and NASH are associated with a metabolically harmful saturated, ceramide-enriched liver lipidome in 'Metabolic NAFLD' but not in 'PNPLA3 NAFLD'. This difference may explain why metabolic but not PNPLA3 NAFLD increases the risk of type 2 diabetes and cardiovascular disease.

Effects of glucagon-like peptide-1 on glucagon secretion in patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

We evaluated the glucagon-suppressive effect of glucagon-like peptide-1 (GLP-1) and its potential effects on endogenous glucose production and whole body lipolysis in non-diabetic patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

On two separate days, 10 non-diabetic patients with liver biopsy-verified NAFLD (NAFLD activity score 2.5±1.0) and 10 matched controls underwent 2h intravenous infusions of GLP-1 (0.8 pmol×kg(-1)×min(-1)) and placebo. Since GLP-1-mediated glucagon suppression has been shown to be glucose-dependent, plasma glucose was clamped at fasting level during the first hour, and then raised and clamped at 'postprandial level' (fasting plasma glucose level plus 3 mmol/L) for the remaining hour. We evaluated relative plasma levels of glucagon, endogenous glucose production and whole body lipolysis rates with stable isotopes and respiratory quotient using indirect calorimetry.

RESULTS

Compared to controls, patients with NAFLD were insulin resistant (homeostasis model assessment (HOMA(IR)): 3.8±2.2 vs. 1.6±1.5, p=0.003) and had fasting hyperglucagonaemia (7.5±5.3 vs. 5.8±1.5 mmol/L, p=0.045). Similar relative glucagon suppression was seen in both groups during GLP-1 infusion at fasting (-97±75 vs. -93±41 pmol/L×min(-1)p=0.566) and 'postprandial' plasma glucose levels (-108±101 vs. -97±53 pmol/L×min(-1), p=0.196). Increased insulinotropic effect of GLP-1 was observed in NAFLD patients. No effect of GLP-1 on endogenous glucose production was observed in any of the groups.

CONCLUSIONS

Patients with NAFLD exhibited fasting hyperglucagonaemia, but intact GLP-1-mediated glucagon suppression independently of plasma glucose concentrations. Preserved glucagonostatic effect and increased insulinotropic effects of GLP-1 in NAFLD may be important to maintain normo-glycaemia in these patients.

Lipotoxicity in steatohepatitis occurs despite an increase in tricarboxylic acid cycle activity

The hepatic tricarboxylic acid (TCA) cycle is central to integrating macronutrient metabolism and is closely coupled to cellular respiration, free radical generation, and inflammation. Oxidative flux through the TCA cycle is induced during hepatic insulin resistance, in mice and humans with simple steatosis, reflecting early compensatory remodeling of mitochondrial energetics. We hypothesized that progressive severity of hepatic insulin resistance and the onset of nonalcoholic steatohepatitis (NASH) would impair oxidative flux through the hepatic TCA cycle. Mice (C57/BL6) were fed a high-trans-fat high-fructose diet (TFD) for 8 wk to induce simple steatosis and NASH by 24 wk. In vivo fasting hepatic mitochondrial fluxes were determined by(13)C-nuclear magnetic resonance (NMR)-based isotopomer analysis. Hepatic metabolic intermediates were quantified using mass spectrometry-based targeted metabolomics. Hepatic triglyceride accumulation and insulin resistance preceded alterations in mitochondrial metabolism, since TCA cycle fluxes remained normal during simple steatosis. However, mice with NASH had a twofold induction (P< 0.05) of mitochondrial fluxes (μmol/min) through the TCA cycle (2.6 ± 0.5 vs. 5.4 ± 0.6), anaplerosis (9.1 ± 1.2 vs. 16.9 ± 2.2), and pyruvate cycling (4.9 ± 1.0 vs. 11.1 ± 1.9) compared with their age-matched controls. Induction of the TCA cycle activity during NASH was concurrent with blunted ketogenesis and accumulation of hepatic diacylglycerols (DAGs), ceramides (Cer), and long-chain acylcarnitines, suggesting inefficient oxidation and disposal of excess free fatty acids (FFA). Sustained induction of mitochondrial TCA cycle failed to prevent accretion of "lipotoxic" metabolites in the liver and could hasten inflammation and the metabolic transition to NASH.

Metabolic Impact of Nonalcoholic Steatohepatitis in Obese Patients With Type 2 Diabetes

OBJECTIVE

Nonalcoholic steatohepatitis (NASH) is increasingly common in obese patients. However, its metabolic consequences in patients with type 2 diabetes mellitus (T2DM) are unknown.

RESEARCH DESIGN AND METHODS

We studied 154 obese patients divided in four groups: 1) control (no T2DM or NAFLD), 2) T2DM without NAFLD, 3) T2DM with isolated steatosis, and 4) T2DM with NASH. We evaluated intrahepatic triglycerides by proton MRS ((1)H-MRS) and assessed insulin secretion/resistance during an oral glucose tolerance test and a euglycemic-hyperinsulinemic clamp with glucose turnover measurements.

RESULTS

No significant differences among groups were observed in sex, BMI, or total body fat. Metabolic parameters worsened progressively with the presence of T2DM and the development of hepatic steatosis, with worse hyperinsulinemia, insulin resistance, and dyslipidemia (hypertriglyceridemia and low HDL cholesterol) in those with NASH (P < 0.001). Compared with isolated steatosis, NASH was associated with more dysfunctional and insulin-resistant adipose tissue (either as insulin suppression of plasma FFA [33 ± 3 vs. 48 ± 6%] or adipose tissue insulin resistance index [9.8 ± 1.0 vs. 5.9 ± 0.8 mmol/L ⋅ µIU/mL]; both P < 0.03). Furthermore, insulin suppression of plasma FFA correlated well with hepatic steatosis (r = -0.62; P < 0.001) and severity of steatohepatitis (rs = -0.52; P < 0.001). Hepatic insulin sensitivity was also more significantly impaired among patients with T2DM and NASH, both fasting and with increasing insulin levels within the physiological range (10 to 140 µIU/mL), compared with other groups.

CONCLUSIONS

In obese patients with T2DM, the presence of NAFLD is associated with more severe hyperinsulinemia, dyslipidemia, and adipose tissue/hepatic insulin resistance compared with patients without NAFLD. The unfavorable metabolic profile linked to NAFLD should prompt strategies to identify and treat this population early on.

Cross-Tissue Regulatory Gene Networks in Coronary Artery Disease

Inferring molecular networks can reveal how genetic perturbations interact with environmental factors to cause common complex diseases. We analyzed genetic and gene expression data from seven tissues relevant to coronary artery disease (CAD) and identified regulatory gene networks (RGNs) and their key drivers. By integrating data from genome-wide association studies, we identified 30 CAD-causal RGNs interconnected in vascular and metabolic tissues, and we validated them with corresponding data from the Hybrid Mouse Diversity Panel. As proof of concept, by targeting the key drivers AIP, DRAP1, POLR2I, and PQBP1 in a cross-species-validated, arterial-wall RGN involving RNA-processing genes, we re-identified this RGN in THP-1 foam cells and independent data from CAD macrophages and carotid lesions. This characterization of the molecular landscape in CAD will help better define the regulation of CAD candidate genes identified by genome-wide association studies and is a first step toward achieving the goals of precision medicine.

Optimal cutoff points for HOMA-IR and QUICKI in the diagnosis of metabolic syndrome and non-alcoholic fatty liver disease: A population based study

AIMS

The present study was carried out to determine the optimal cutoff points for homeostatic model assessment (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) in the diagnosis of metabolic syndrome (MetS) and non-alcoholic fatty liver disease (NAFLD).

METHODS

The baseline data of 5511 subjects aged ≥18years of a cohort study in northern Iran were utilized to analyze. Receiver operating characteristic (ROC) analysis was conducted to determine the discriminatory capability of HOMA-IR and QUICKI in the diagnosis of MetS and NAFLD. Youden index was utilized to determine the optimal cutoff points of HOMA-IR and QUICKI in the diagnosis of MetS and NAFLD.

RESULTS

The optimal cutoff points for HOMA-IR in the diagnosis of MetS and NAFLD were 2.0 [sensitivity=64.4%, specificity=66.8%] and 1.79 [sensitivity=66.2%, specificity=62.2%] in men and were 2.5 [sensitivity=57.6%, specificity=67.9%] and 1.95 [sensitivity=65.1%, specificity=54.7%] in women respectively. Furthermore, the optimal cutoff points for QUICKI in the diagnosis of MetS and NAFLD were 0.343 [sensitivity=63.7%, specificity=67.8%] and 0.347 [sensitivity=62.9%, specificity=65.0%] in men and were 0.331 [sensitivity=55.7%, specificity=70.7%] and 0.333 [sensitivity=53.2%, specificity=67.7%] in women respectively.

CONCLUSION

Not only the optimal cutoff points of HOMA-IR and QUICKI were different for MetS and NAFLD, but also different cutoff points were obtained for men and women for each of these two conditions.

Not all fats are created equal: adipose vs. ectopic fat, implication in cardiometabolic diseases

Adipose tissue is a recognized endocrine organ that acts not only as a fuel storage but also is able to secrete adipokines that can modulate inflammation. Most of the fat is composed of white adipocytes (WAT), although also brown/beige adipocytes (BAT/BeAT) have been found in humans. BAT is located close to the neck but also among WAT in the epicardial fat and perivascular fat. Adipocyte hypertrophy and infiltration of macrophages impair adipose tissue metabolism determining "adiposopathy" (i.e., sick fat) and increasing the risk to develop metabolic and cardiovascular diseases. The purpose of this review was to search and discuss the available literature on the impact of different types of fat and fat distribution on cardiometabolic risk. Visceral fat, but also ectopic fat, either in liver, muscle and heart, can increase the risk to develop insulin resistance, type 2 diabetes and cardiovascular diseases. Results recently published showed that BAT could have an impact on cardiometabolic risk, not only because it is implicated in energy metabolism but also because it can modulate glucose and lipid metabolism. Therapeutical interventions that can increase energy expenditure, successfully change fat distribution and reduce ectopic fat, also through BAT activation, were discussed.

Glucagon-like peptide 1 decreases lipotoxicity in non-alcoholic steatohepatitis

BACKGROUND & AIMS

Insulin resistance and lipotoxicity are pathognomonic in non-alcoholic steatohepatitis (NASH). Glucagon-like peptide-1 (GLP-1) analogues are licensed for type 2 diabetes, but no prospective experimental data exists in NASH. This study determined the effect of a long-acting GLP-1 analogue, liraglutide, on organ-specific insulin sensitivity, hepatic lipid handling and adipose dysfunction in biopsy-proven NASH.

METHODS

Fourteen patients were randomised to 1.8mg liraglutide or placebo for 12-weeks of the mechanistic component of a double-blind, randomised, placebo-controlled trial (ClinicalTrials.gov-NCT01237119). Patients underwent paired hyperinsulinaemic euglycaemic clamps, stable isotope tracers, adipose microdialysis and serum adipocytokine/metabolic profiling. In vitro isotope experiments on lipid flux were performed on primary human hepatocytes.

RESULTS

Liraglutide reduced BMI (-1.9 vs. +0.04kg/m(2); p<0.001), HbA1c (-0.3 vs. +0.3%; p<0.01), cholesterol-LDL (-0.7 vs. +0.05mmol/L; p<0.01), ALT (-54 vs. -4.0IU/L; p<0.01) and serum leptin, adiponectin, and CCL-2 (all p<0.05). Liraglutide increased hepatic insulin sensitivity (-9.36 vs. -2.54% suppression of hepatic endogenous glucose production with low-dose insulin; p<0.05). Liraglutide increased adipose tissue insulin sensitivity enhancing the ability of insulin to suppress lipolysis both globally (-24.9 vs. +54.8pmol/L insulin required to ½ maximally suppress serum non-esterified fatty acids; p<0.05), and specifically within subcutaneous adipose tissue (p<0.05). In addition, liraglutide decreased hepatic de novo lipogenesis in vivo (-1.26 vs. +1.30%; p<0.05); a finding endorsed by the effect of GLP-1 receptor agonist on primary human hepatocytes (24.6% decrease in lipogenesis vs. untreated controls; p<0.01).

CONCLUSIONS

Liraglutide reduces metabolic dysfunction, insulin resistance and lipotoxicity in the key metabolic organs in the pathogenesis of NASH. Liraglutide may offer the potential for a disease-modifying intervention in NASH.

Gamma glutamyl transferase is an independent determinant for the association of insulin resistance with nonalcoholic fatty liver disease in Bangladeshi adults: Association of GGT and HOMA-IR with NAFLD

AIMS

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver-related morbidity and is frequently associated with insulin resistance (HOMA-IR) syndrome. Recently serum gamma glutamyl transferase (GGT) has been considered as surrogate marker of NAFLD leading to oxidative stress and hepatocellular damage. In the present study we examined the association of serum GGT and HOMA-IR with NAFLD in Bangladeshi adult subjects.

MATERIALS AND METHODS

Under a cross-sectional analytical design a total of 110 subjects were recruited who came for their routine health check up in the BIHS Hospital, Darussalam, Dhaka, Bangladesh. After whole abdomen ultrasonography, 62 were diagnosed as non-NAFLD and 48 were NAFLD subjects. Serum glucose was measured by glucose-oxidase method, lipid profile and liver enzymes by enzymatic colorimetric method, glycosylated hemoglobin (HbA1c) was measured by high performance liquid chromatography (HPLC), serum insulin were measured by enzyme-linked immunosorbent assay. HOMA-IR was calculated by homeostasis model assessment (HOMA).

RESULTS

NAFLD subjects had significantly higher levels of GGT and HOMA-IR as compared to their non-NAFLD counterparts. Multiple linear regression analysis showed a significant positive association of HOMA-IR with GGT after adjusting the effects of waist circumference (WC) and HbA1c. In binary logistic regression analysis, HOMA-IR and GGT were found to be significant determinants of NAFLD after adjusting the effects of WC and HbA1c.

CONCLUSION

These results suggest that elevated levels of GGT and insulin resistance are more likely to develop NAFLD and thus support a role of these determinants in the pathogenesis of NAFLD in Bangladeshi adult subjects.

Peripheral insulin resistance predicts liver damage in nondiabetic subjects with nonalcoholic fatty liver disease

Surrogate indexes of insulin resistance and insulin sensitivity are widely used in nonalcoholic fatty liver disease (NAFLD), although they have never been validated in this population. We aimed to validate the available indexes in NAFLD subjects and to test their ability to predict liver damage also in comparison with the NAFLD fibrosis score. Surrogate indexes were validated by the tracer technique (6,6-D2 -glucose and U-(13) C-glucose) in the basal state and during an oral glucose tolerance test. The best-performing indexes were used in an independent cohort of 145 nondiabetic NAFLD subjects to identify liver damage (fibrosis and nonalcoholic steatohepatitis). In the validation NAFLD cohort, homeostasis model assessment of insulin resistance, insulin to glucose ratio, and insulin sensitivity index Stumvoll had the best association with hepatic insulin resistance, while peripheral insulin sensitivity was most significantly related to oral glucose insulin sensitivity index (OGIS), insulin sensitivity index Stumvoll, and metabolic clearance rate estimation without demographic parameters. In the independent cohort, only oral glucose tolerance test-derived indexes were associated with liver damage and OGIS was the best predictor of significant (≥F2) fibrosis (odds ratio = 0.76, 95% confidence interval 0.61-0.96, P = 0.0233) and of nonalcoholic steatohepatitis (odds ratio = 0.75, 95% confidence interval 0.63-0.90, P = 0.0021). Both OGIS and NAFLD fibrosis score identified advanced (F3/F4) fibrosis, but OGIS predicted it better than NAFLD fibrosis score (odds ratio = 0.57, 95% confidence interval 0.45-0.72, P < 0.001) and was also able to discriminate F2 from F3/F4 (P < 0.003).

CONCLUSION

OGIS is associated with peripheral insulin sensitivity in NAFLD and inversely associated with an increased risk of significant/advanced liver damage in nondiabetic subjects with NAFLD.

High serum uric acid and risk of nonalcoholic fatty liver disease: A systematic review and meta-analysis

OBJECTIVES

Emerging evidence connects serum uric acid (SUA) levels to nonalcoholic fatty liver disease (NAFLD). The objective of this study was to systematically evaluate the association between SUA levels and risk of NAFLD by conducting a meta-analysis of available observational studies.

DESIGN AND METHODS

We searched for relevant studies in PubMed, Embase, China National Knowledge Infrastructure, and Wanfang databases until October 2014. All observational studies that evaluated SUA levels and NAFLD risks were included. Pooled adjusted odds ratio (OR) and corresponding 95% confidence intervals (CI) were calculated comparing the highest to lowest SUA category.

RESULTS

Four cross-sectional studies, two prospective studies, and three retrospective studies involving 55,573 participants were identified. In overall risk estimates, the pooled OR of NAFLD occurrence was 1.92 (95% CI: 1.59-2.31) comparing the highest to lowest SUA levels in a random effect model. Subgroup analysis showed that high SUA levels increased the risk of NAFLD in cross-sectional studies (OR: 2.18; 95% CI: 1.58-3.03), retrospective studies (OR 1.82; 95% CI: 1.43-2.33), and prospective studies (OR 1.43; 95% CI: 1.20-1.71). The risk of NAFLD seemed more pronounced among women (OR 1.85; 95% CI: 1.43-2.38) than among men (OR 1.56; 95% CI: 1.30-1.86).

CONCLUSION

This meta-analysis suggests that increased SUA level is associated with an exacerbated risk of NAFLD. This increased risk is probably independent of conventional NAFLD risk factors.

Nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a disorder characterized by excess accumulation of fat in hepatocytes (nonalcoholic fatty liver (NAFL)); in up to 40% of individuals, there are additional findings of portal and lobular inflammation and hepatocyte injury (which characterize nonalcoholic steatohepatitis (NASH)). A subset of patients will develop progressive fibrosis, which can progress to cirrhosis. Hepatocellular carcinoma and cardiovascular complications are life-threatening co-morbidities of both NAFL and NASH. NAFLD is closely associated with insulin resistance; obesity and metabolic syndrome are common underlying factors. As a consequence, the prevalence of NAFLD is estimated to be 10-40% in adults worldwide, and it is the most common liver disease in children and adolescents in developed countries. Mechanistic insights into fat accumulation, subsequent hepatocyte injury, the role of the immune system and fibrosis as well as the role of the gut microbiota are unfolding. Furthermore, genetic and epigenetic factors might explain the considerable interindividual variation in disease phenotype, severity and progression. To date, no effective medical interventions exist that completely reverse the disease other than lifestyle changes, dietary alterations and, possibly, bariatric surgery. However, several strategies that target pathophysiological processes such as an oversupply of fatty acids to the liver, cell injury and inflammation are currently under investigation. Diagnosis of NAFLD can be established by imaging, but detection of the lesions of NASH still depend on the gold-standard but invasive liver biopsy. Several non-invasive strategies are being evaluated to replace or complement biopsies, especially for follow-up monitoring.

Gut microbiota manipulation with prebiotics in patients with non-alcoholic fatty liver disease: a randomized controlled trial protocol

Background

Evidence for the role of the gut microbiome in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) is emerging. Strategies to manipulate the gut microbiota towards a healthier community structure are actively being investigated. Based on their ability to favorably modulate the gut microbiota, prebiotics may provide an inexpensive yet effective dietary treatment for NAFLD. Additionally, prebiotics have established benefits for glucose control and potentially weight control, both advantageous in managing fatty liver disease. Our objective is to evaluate the effects of prebiotic supplementation, adjunct to those achieved with diet-induced weight loss, on heptic injury and liver fat, the gut microbiota, inflammation, glucose tolerance, and satiety in patients with NAFLD.

Methods/design

In a double blind, placebo controlled, parallel group study, adults (BMI ≥25) with confirmed NAFLD will be randomized to either a 16 g/d prebiotic supplemented group or isocaloric placebo group for 24 weeks (n = 30/group). All participants will receive individualized dietary counseling sessions with a registered dietitian to achieve 10 % weight loss. Primary outcome measures include change in hepatic injury (fibrosis and inflammation) and liver fat. Secondary outcomes include change in body composition, appetite and dietary adherence, glycemic and insulinemic responses and inflammatory cytokines. Mechanisms related to prebiotic-induced changes in gut microbiota (shot-gun sequencing) and their metabolic by-products (volatile organic compounds) and de novo lipogenesis (using deuterium incorporation) will also be investigated.

Discussion

There are currently no medications or surgical procedures approved for the treatment of NAFLD and weight loss via lifestyle modification remains the cornerstone of current care recommendations. Given that prebiotics target multiple metabolic impairments associated with NAFLD, investigating their ability to modulate the gut microbiota and hepatic health in patients with NAFLD is warranted.

Trial registration

ClinicalTrials.gov (NCT02568605) Registered 30 September 2015

The Subtle Balance between Lipolysis and Lipogenesis: A Critical Point in Metabolic Homeostasis

Excessive accumulation of lipids can lead to lipotoxicity, cell dysfunction and alteration in metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas and muscle. This is now a recognized risk factor for the development of metabolic disorders, such as obesity, diabetes, fatty liver disease (NAFLD), cardiovascular diseases (CVD) and hepatocellular carcinoma (HCC). The causes for lipotoxicity are not only a high fat diet but also excessive lipolysis, adipogenesis and adipose tissue insulin resistance. The aims of this review are to investigate the subtle balances that underlie lipolytic, lipogenic and oxidative pathways, to evaluate critical points and the complexities of these processes and to better understand which are the metabolic derangements resulting from their imbalance, such as type 2 diabetes and non alcoholic fatty liver disease.

Polyphenol-Rich Fraction of Ecklonia cava Improves Nonalcoholic Fatty Liver Disease in High Fat Diet-Fed Mice

Ecklonia cava (E. cava; CA) is an edible brown alga with beneficial effects in diabetes via regulation of various metabolic processes such as lipogenesis, lipolysis, inflammation, and the antioxidant defense system in liver and adipose tissue. We investigated the effect of the polyphenol-rich fraction of E. cava produced from Gijang (G-CA) on nonalcoholic fatty liver disease (NAFLD) in high-fat diet (HFD)-fed mice. C57BL6 mice were fed a HFD for six weeks and then the HFD group was administered 300 mg/kg of G-CA extracts by oral intubation for 10 weeks. Body weight, fat mass, and serum biochemical parameters were reduced by G-CA extract treatment. MRI/MRS analysis showed that liver fat and liver volume in HFD-induced obese mice were reduced by G-CA extract treatment. Further, we analyzed hepatic gene expression related to inflammation and lipid metabolism. The mRNA expression levels of inflammatory cytokines and hepatic lipogenesis-related genes were decreased in G-CA-treated HFD mice. The mRNA expression levels of cholesterol 7 alpha-hydroxylase 1 (CYP7A1), the key enzyme in bile acid synthesis, were dramatically increased by G-CA treatment in HFD mice. We suggest that G-CA treatment ameliorated hepatic steatosis by inhibiting inflammation and improving lipid metabolism.

Dissociation between exercise-induced reduction in liver fat and changes in hepatic and peripheral glucose homoeostasis in obese patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is associated with multi-organ (hepatic, skeletal muscle, adipose tissue) insulin resistance (IR). Exercise is an effective treatment for lowering liver fat but its effect on IR in NAFLD is unknown. We aimed to determine whether supervised exercise in NAFLD would reduce liver fat and improve hepatic and peripheral (skeletal muscle and adipose tissue) insulin sensitivity. Sixty nine NAFLD patients were randomized to 16 weeks exercise supervision (n=38) or counselling (n=31) without dietary modification. All participants underwent MRI/spectroscopy to assess changes in body fat and in liver and skeletal muscle triglyceride, before and following exercise/counselling. To quantify changes in hepatic and peripheral insulin sensitivity, a pre-determined subset (n=12 per group) underwent a two-stage hyperinsulinaemic euglycaemic clamp pre- and post-intervention. Results are shown as mean [95% confidence interval (CI)]. Fifty participants (30 exercise, 20 counselling), 51 years (IQR 40, 56), body mass index (BMI) 31 kg/m(2) (IQR 29, 35) with baseline liver fat/water % of 18.8% (IQR 10.7, 34.6) completed the study (12/12 exercise and 7/12 counselling completed the clamp studies). Supervised exercise mediated a greater reduction in liver fat/water percentage than counselling [Δ mean change 4.7% (0.01, 9.4); P<0.05], which correlated with the change in cardiorespiratory fitness (r=-0.34, P=0.0173). With exercise, peripheral insulin sensitivity significantly increased (following high-dose insulin) despite no significant change in hepatic glucose production (HGP; following low-dose insulin); no changes were observed in the control group. Although supervised exercise effectively reduced liver fat, improving peripheral IR in NAFLD, the reduction in liver fat was insufficient to improve hepatic IR.

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.