Causes and metabolic consequences of Fatty liver

Longitudinal evaluation of hepatic lipid deposition and composition in ob/ob and ob/+ control mice

Obesity is associated with insulin resistance (IR) and hepatosteatosis. Understanding the link between IR and hepatosteatosis could be relevant to chronic clinical outcomes. The objective of this study was to quantitatively assess lipid deposition (fractional lipid mass, fLM) and composition (fraction of polyunsaturated lipids, fPUL and mean chain length, MCL) in livers of ob/ob mice, a genetic model of obesity and mild diabetes, and ob/+ heterozygous control animals in a noninvasive manner using (1) H-MRS at 9.4T. For accurate quantification, intensity values were corrected for differences in T2 values while T1 effects were considered minimal due to the long TR values used. Values of fLM, fPUL and MCL were derived from T2 -corrected signal intensities of lipids and water resonance. Hepatic lipid signals were compared with fasted plasma insulin, glucose and lipid levels. Statistically significant correlations between fPUL and fasting plasma insulin/glucose levels were found in adolescent ob/ob mice. A similar correlation was found between fLM and fasting plasma insulin levels; however, the correlation between fLM and fasting plasma glucose levels was less obvious in adolescent ob/ob mice. These correlations were lost in adult ob/ob mice. The study showed that in adolescent ob/ob mice, there was an obvious link between lipid deposition/composition in the liver and plasma insulin/glucose levels. This correlation was lost in adult animals, probably due to the limited lipid storage capacity of the liver.

Retinoids, race and the pathogenesis of dengue hemorrhagic fever

Dengue hemorrhagic fever (DHF) is the most significant mosquito-borne viral disease worldwide in terms of illness, mortality and economic cost, but the pathogenesis of DHF is not well understood and there is no specific treatment or vaccine. Based on evidence of liver involvement, it is proposed that dengue virus and retinoids interact to cause cholestatic liver damage, resulting in the spillage of stored retinoids into the circulation and in an endogenous form of hypervitaminosisis A manifested by the signs and symptoms of the disease, including: fever, severe joint and bone pain, capillary leakage, thrombocytopenia, headache, and gastrointestinal symptoms. While retinoids in low concentration are essential for numerous biological functions, they are prooxidant, cytotoxic, mutagenic and teratogenic in higher concentration, especially when unbound to protein, and an endogenous form of vitamin A intoxication is recognized in cholestasis. The model tentatively explains the observations that 1) repeat infections are more severe than initial dengue virus infections; 2) the incidence of denue has increased dramatically worldwide in recent decades; 3) DHF is less prevalent in people of African ancestry than those of other racial backgrounds; and 4) infants are protected from dengue. The retinoid toxicity hypothesis of DHF predicts the co-existence of low serum concentrations of retinol coupled with high concentrations of retinoic acid and an increased percentage of retinyl esters to total vitamin A. Subject to such tests, it may be possible to treat DHF effectively using drugs that target the metabolism and expression of retinoids.

A systematic review: burden and severity of subclinical cardiovascular disease among those with nonalcoholic fatty liver; should we care?

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is an emerging disease and a leading cause of chronic liver disease. The prevalence in the general population is approximately 15-30% and it increases to 70-90% in obese or diabetic populations. NAFLD has been linked to increased cardiovascular disease (CVD) risk. It is therefore critical to evaluate the relationship between markers of subclinical CVD and NAFLD.

METHOD

An extensive search of databases; including the National Library of Medicine and other relevant databases for research articles meeting inclusion criteria: observational or cohort, studies in adult populations and clearly defined NAFLD and markers of subclinical CVD.

RESULTS

Twenty-seven studies were included in the review; 16 (59%) presented the association of NAFLD and carotid intima-media thickness (CIMT), 7 (26%) the association with coronary calcification and 7 (26%) the effect on endothelial dysfunction and 6 (22%) influence on arterial stiffness. CIMT studies showed significant increases among NAFLD patients compared to controls. These were independent of traditional risk factors and metabolic syndrome. The association was similar in coronary calcification studies. The presence of NAFLD is associated with the severity of the calcification. Endothelial dysfunction and arterial stiffness showed significant independent associations with NAFLD. Two studies argued the associations were not significant; however, these studies were limited to diabetic populations.

CONCLUSION

There is evidence to support the association of NAFLD with subclinical atherosclerosis independent of traditional risk factors and metabolic syndrome. However, there is need for future longitudinal studies to review this association to ascertain causality and include other ethnic populations.

Fetuin-A is linked to improved glucose tolerance after short-term exercise training in nonalcoholic fatty liver disease

Fetuin-A is synthesized in the liver and may be associated with nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. Lifestyle-induced weight loss reduces fetuin-A, but the effect of exercise alone is unknown. We determined the effect of short-term exercise training on plasma fetuin-A in 13 (50.5 ± 3.4 yr) obese adults (body mass index, 33.3 ± 0.9 kg/m(2)) with clinically diagnosed NAFLD. Subjects participated in 7 days of supervised exercise training (60 min/day at ∼85% maximum heart rate) and were instructed to maintain their normal caloric and macronutrient intake. Insulin resistance was assessed by an oral glucose tolerance test. Hepatic triglyceride content (HTGC) was determined by proton MRI. We used C2C12 skeletal muscle cells to examine the direct effect of fetuin-A on 2-deoxyglucose uptake, insulin signaling [phosphorylation of Akt and AS160 (pAkt and pAS160, respectively)], and glucose transporter-4 (GLUT-4) translocation. Insulin resistance was reduced by 29% (P < 0.05), and glucose area under the curve (AUC) was decreased by 13% (P < 0.01) after the 7 days of exercise. Furthermore, circulating fetuin-A was decreased by 11% (4.2 ± 03 vs. 3.6 ± 0.2 nM; P < 0.02), and this change correlated with reduced insulin resistance (r = 0.62; P < 0.04) and glucose AUC (r = 0.58; P < 0.04). Importantly, the exercise program did not change body weight (P = 0.12), HTGC (P = 0.73), or aerobic capacity (P = 0.14). In vitro experiments revealed that fetuin-A decreased skeletal muscle glucose uptake by downregulating pAkt and pAS160 and subsequent GLUT-4 translocation to the plasma membrane. Together, our findings highlight a role for fetuin-A in skeletal muscle insulin resistance and suggest that part of the exercise-induced improvement in glucose tolerance in patients with NAFLD may be due to lowering fetuin-A.

Phenotypic comparison of common mouse strains developing high-fat diet-induced hepatosteatosis

Genetic predisposition and environmental factors contribute to an individual's susceptibility to develop hepatosteatosis. In a systematic, comparative survey we focused on genotype-dependent and -independent adaptations early in the pathogenesis of hepatosteatosis by characterizing C3HeB/FeJ, C57BL/6NTac, C57BL/6J, and 129P2/OlaHsd mice after 7, 14, or 21 days high-fat-diet exposure. Strain-specific metabolic responses during diet challenge and liver transcript signatures in mild hepatosteatosis outline the suitability of particular strains for investigating the relationship between hepatocellular lipid content and inflammation, glucose homeostasis, insulin action, or organelle physiology. Genetic background-independent transcriptional adaptations in liver paralleling hepatosteatosis suggest an early increase in the organ's vulnerability to oxidative stress damage what could advance hepatosteatosis to steatohepatitis. "Universal" adaptations in transcript signatures and transcription factor regulation in liver link insulin resistance, type 2 diabetes mellitus, cancer, and thyroid hormone metabolism with hepatosteatosis, hence, facilitating the search for novel molecular mechanisms potentially implicated in the pathogenesis of human non-alcoholic-fatty-liver-disease.

MR fat fraction mapping: a simple biomarker for liver steatosis quantification in nonalcoholic fatty liver disease patients

RATIONALE AND OBJECTIVES

To assess the performance, postprocessing time, and intra- and interobserver agreement of a simple magnetic resonance-based mapping technique to quantify liver fat.

MATERIALS AND METHODS

This prospective, single-center study included 26 patients who were overweight with type 2 diabetes and at risk for nonalcoholic fatty liver disease. Mapping of the liver was based on a triple echo gradient-echo sequence, and (1)H magnetic resonance spectroscopy was used as the reference standard. The nonparametric Spearman correlation coefficient and the Wilcoxon test were used for comparisons between mapping and spectroscopy. The mapping was assessed for its predictive performance using the area under the curve of a receiver operating characteristic curve. Intraclass correlation coefficients were used to calculate intra- and interobserver's agreement for mapping measurements.

RESULTS

Patients had a mean fat percentage of 11.7% (range, 2-35.4%). A strong correlation was seen between mapping and spectroscopy (r = 0.89, P < .0001). A cutoff of 6.9% for fat fraction mapping was found to diagnose steatosis with 93% sensitivity and 100% specificity with an area under the curve of 0.99. Mapping of the liver had shorter acquisition and post-processing times than spectroscopy (5 min vs. 38 min; P < .0001). Mapping measurements had an intra- and interobserver agreement of 0.98 and 0.99, respectively.

CONCLUSIONS

The magnetic resonance-based liver mapping can accurately quantify liver fat with a cutoff value of 6.9% and excellent intra- and interobserver agreement. This mapping technique, with its simple methodology and short postprocessing time, has the potential to be included in routine abdominal protocols.

Circulating lysophosphatidylcholines are markers of a metabolically benign nonalcoholic fatty liver

OBJECTIVE

Nonalcoholic fatty liver (NAFL) is thought to contribute to insulin resistance and its metabolic complications. However, some individuals with NAFL remain insulin sensitive. Mechanisms involved in the susceptibility to develop insulin resistance in humans with NAFL are largely unknown. We investigated circulating markers and mechanisms of a metabolically benign and malignant NAFL by applying a metabolomic approach.

RESEARCH DESIGN AND METHODS

A total of 265 metabolites were analyzed before and after a 9-month lifestyle intervention in plasma from 20 insulin-sensitive and 20 insulin-resistant subjects with NAFL. The relevant plasma metabolites were then tested for relationships with insulin sensitivity in 17 subjects without NAFL and in plasma from 29 subjects with liver tissue samples.

RESULTS

The best separation of the insulin-sensitive from the insulin-resistant NAFL group was achieved by a metabolite pattern including the branched-chain amino acids leucine and isoleucine, ornithine, the acylcarnitines C3:0-, C16:0-, and C18:0-carnitine, and lysophosphatidylcholine (lyso-PC) C16:0 (area under the ROC curve, 0.77 [P = 0.00023] at baseline and 0.80 [P = 0.000019] at follow-up). Among the individual metabolites, predominantly higher levels of lyso-PC C16:0, both at baseline (P = 0.0039) and at follow-up (P = 0.001), were found in the insulin-sensitive compared with the insulin-resistant subjects. In the non-NAFL groups, no differences in lyso-PC C16:0 levels were found between the insulin-sensitive and insulin-resistant subjects, and these relationships were replicated in plasma from subjects with liver tissue samples.

CONCLUSIONS

From a plasma metabolomic pattern, particularly lyso-PCs are able to separate metabolically benign from malignant NAFL in humans and may highlight important pathways in the pathogenesis of fatty liver-induced insulin resistance.

Dynamic regulation of hepatic lipid droplet properties by diet

Cytoplasmic lipid droplets (CLD) are organelle-like structures that function in neutral lipid storage, transport and metabolism through the actions of specific surface-associated proteins. Although diet and metabolism influence hepatic CLD levels, how they affect CLD protein composition is largely unknown. We used non-biased, shotgun, proteomics in combination with metabolic analysis, quantitative immunoblotting, electron microscopy and confocal imaging to define the effects of low- and high-fat diets on CLD properties in fasted-refed mice. We found that the hepatic CLD proteome is distinct from that of CLD from other mammalian tissues, containing enzymes from multiple metabolic pathways. The hepatic CLD proteome is also differentially affected by dietary fat content and hepatic metabolic status. High fat feeding markedly increased the CLD surface density of perilipin-2, a critical regulator of hepatic neutral lipid storage, whereas it reduced CLD levels of betaine-homocysteine S-methyltransferase, an enzyme regulator of homocysteine levels linked to fatty liver disease and hepatocellular carcinoma. Collectively our data demonstrate that the hepatic CLD proteome is enriched in metabolic enzymes, and that it is qualitatively and quantitatively regulated by diet and metabolism. These findings implicate CLD in the regulation of hepatic metabolic processes, and suggest that their properties undergo reorganization in response to hepatic metabolic demands.

Adipokines and C-reactive protein in relation to bone mineralization in pediatric nonalcoholic fatty liver disease

AIM: To investigate bone mineral density (BMD) in obese children with and without nonalcoholic fatty liver disease (NAFLD); and the association between BMD and serum adipokines, and high-sensitivity C-reactive protein (HSCRP).

METHODS: A case-control study was performed. Cases were 44 obese children with NAFLD. The diagnosis of NAFLD was based on magnetic resonance imaging (MRI) with high hepatic fat fraction (≥ 5%). Other causes of chronic liver disease were ruled out. Controls were selected from obese children with normal levels of aminotransferases, and without MRI evidence of fatty liver as well as of other causes of chronic liver diseases. Controls were matched (1- to 1-basis) with the cases on age, gender, pubertal stage and as closely as possible on body mass index-SD score. All participants underwent clinical examination, laboratory tests, and whole body (WB) and lumbar spine (LS) BMD by dual energy X-ray absorptiometry. BMD Z-scores were calculated using race and gender specific LMS curves.

RESULTS: Obese children with NAFLD had a significantly lower LS BMD Z-score than those without NAFLD [mean, 0.55 (95%CI: 0.23-0.86) vs 1.29 (95%CI: 0.95-1.63); P < 0.01]. WB BMD Z-score was also decreased in obese children with NAFLD compared to obese children with no NAFLD, though borderline significance was observed [1.55 (95%CI: 1.23-1.87) vs 1.95 (95%CI: 1.67-2.10); P = 0.06]. Children with NAFLD had significantly higher HSCRP, lower adiponectin, but similar leptin levels. Thirty five of the 44 children with MRI-diagnosed NAFLD underwent liver biopsy. Among the children with biopsy-proven NAFLD, 20 (57%) had nonalcoholic steatohepatitis (NASH), while 15 (43%) no NASH. Compared to children without NASH, those with NASH had a significantly lower LS BMD Z-score [mean, 0.27 (95%CI: -0.17-0.71) vs 0.75 (95%CI: 0.13-1.39); P < 0.05] as well as a significantly lower WB BMD Z-score [1.38 (95%CI: 0.89-1.17) vs 1.93 (95%CI: 1.32-2.36); P < 0.05]. In multiple regression analysis, NASH (standardized β coefficient, -0.272; P < 0.01) and HSCRP (standardized β coefficient, -0.192; P < 0.05) were significantly and independently associated with LS BMD Z-score. Similar results were obtained when NAFLD (instead of NASH) was included in the model. WB BMD Z-scores were significantly and independently associated with NASH (standardized β coefficient, -0.248; P < 0.05) and fat mass (standardized β coefficient, -0.224; P < 0.05).

CONCLUSION: This study reveals that NAFLD is associated with low BMD in obese children, and that systemic, low-grade inflammation may accelerate loss of bone mass in patients with NAFLD.

A Palaeolithic-type diet causes strong tissue-specific effects on ectopic fat deposition in obese postmenopausal women

OBJECTIVES

Ectopic fat accumulation in liver and skeletal muscle may be an essential link between abdominal obesity, insulin resistance and increased risk of cardiovascular disease after menopause. We hypothesized that a diet containing a relatively high content of protein and unsaturated fat [mainly monounsaturated fatty acids (MUFAs)] but limited carbohydrates and saturated fat would reduce lipid content in liver and muscle and increase insulin sensitivity in postmenopausal women.

SUBJECTS

Ten healthy, nonsmoking postmenopausal women with a body mass index (BMI) >27 (28-35) kg m(-2) were included in the study.

INTERVENTIONS

Participants were instructed to consume an ad libitum Palaeolithic-type diet intended to provide approximately 30 energy percentage (E%) protein, 40 E% fat (mainly MUFAs) and 30 E% carbohydrate. Intramyocellular lipid (IMCL) levels in calf muscles and liver triglyceride levels were quantified using proton magnetic resonance spectroscopy ((1) H-MRS) before and 5 weeks after dietary intervention. Insulin sensitivity was estimated by homoeostasis model assessment (HOMA) indices and the euglycaemic hyperinsulinaemic clamp technique.

RESULTS

Mean energy intake decreased by 25% with a weight loss of 4.5 kg. BMI, waist and hip circumference, waist/hip ratio and abdominal sagittal diameter also decreased significantly, as did diastolic blood pressure (mean -7 mmHg), levels of fasting serum glucose, cholesterol, triglycerides, LDL/HDL cholesterol, apolipoprotein B (ApoB) and apolipoprotein A1 (ApoA1), urinary C-peptide and HOMA indices. Whole-body insulin sensitivity did not change. Liver triglyceride levels decreased by 49%, whereas IMCL levels in skeletal muscle were not significantly altered.

CONCLUSIONS

A modified Palaeolithic-type diet has strong and tissue-specific effects on ectopic lipid deposition in postmenopausal women.

Insulin resistance in type 1 diabetes: what is 'double diabetes' and what are the risks?

In this review, we explore the concept of 'double diabetes', a combination of type 1 diabetes with features of insulin resistance and type 2 diabetes. After considering whether double diabetes is a useful concept, we discuss potential mechanisms of increased insulin resistance in type 1 diabetes before examining the extent to which double diabetes might increase the risk of cardiovascular disease (CVD). We then go on to consider the proposal that weight gain from intensive insulin regimens may be associated with increased CV risk factors in some patients with type 1 diabetes, and explore the complex relationships between weight gain, insulin resistance, glycaemic control and CV outcome. Important comparisons and contrasts between type 1 diabetes and type 2 diabetes are highlighted in terms of hepatic fat, fat partitioning and lipid profile, and how these may differ between type 1 diabetic patients with and without double diabetes. In so doing, we hope this work will stimulate much-needed research in this area and an improvement in clinical practice.

Small molecule glucokinase activators disturb lipid homeostasis and induce fatty liver in rodents: a warning for therapeutic applications in humans

BACKGROUND AND PURPOSE

Small-molecule glucokinase activators (GKAs) are currently being investigated as therapeutic options for the treatment of type 2 diabetes (T2D). Because liver overexpression of glucokinase is thought to be associated with altered lipid profiles, this study aimed at assessing the potential lipogenic risks linked to oral GKA administration.

EXPERIMENTAL APPROACH

Nine GKA candidates were qualified for their ability to activate recombinant glucokinase and to stimulate glycogen synthesis in rat hepatocytes and insulin secretion in rat INS-1E cells. In vivo activity was monitored by plasma glucose and HbA1c measurements after oral administration in rodents. Risk-associated effects were assessed by measuring hepatic and plasma triglycerides and free fatty acids, as well as plasma aminotransferases, and alkaline phosphatase.

KEY RESULTS

GKAs, while efficiently decreasing glycaemia in acute conditions and HbA1c levels after chronic administration in hyperglycemic db/db mice, were potent inducers of hepatic steatosis. This adverse outcome appeared as soon as 4 days after daily oral administration at pharmacological doses and was not transient. GKA treatment similarly increased hepatic triglycerides in diabetic and normoglycaemic rats, together with a pattern of metabolic phenotypes including different combinations of increased plasma triglycerides, free fatty acids, alanine and aspartyl aminotransferases, and alkaline phosphatase. GKAs belonging to three distinct structural families induced hepatic steatosis in db/db mice, arguing in favour of a target-mediated, rather than a chemical class-mediated, effect.

CONCLUSION AND IMPLICATIONS

Given the risks associated with fatty liver disease in the general population and furthermore in patients with T2D, these findings represent a serious warning for the use of GKAs in humans.

LINKED ARTICLE

This article is commented on by Rees and Gloyn, pp. 335-338 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.02201.x.

Genetic variation in the patatin-like phospholipase domain-containing protein-3 (PNPLA-3) gene in Asian Indians with nonalcoholic fatty liver disease

BACKGROUND

The association of the rs738409 polymorphism of patatin-like phospholipase-3 (PNPLA3) with nonalcoholic fatty liver disease (NAFLD) has been suggested in other populations, but not in Asian Indians. We investigated the association of the rs738409 polymorphism of PNPLA3 with clinical, anthropometric, and biochemical profiles in Asian Indians with NAFLD.

METHODS

In this case-control study, 162 cases and 173 controls were recruited. Abdominal ultrasound, clinical, anthropometry, and biochemical profiles were determined. Fasting insulin levels and values for homeostasis model assessment of insulin resistance (HOMA-IR) were determined. Polymerase chain reaction and restriction fragment length polymorphism of the PNPLA3 gene were performed. The associations of this polymorphism with clinical, anthropometric, and biochemical profiles were investigated.

RESULTS

A higher frequency of C/G and G/G genotypes of the rs738409 polymorphism was obtained in cases as compared to controls (P=0.04), and as a consequence the frequency of the minor allele G was significantly higher in cases (P=0.003). In this study, the G allele was associated with significantly higher fasting insulin (P=0.002), HOMA-IR (P=0.05), alanine transaminase (P=0.003), and aspartate transaminase (P=0.04) values only in cases, but not in the controls. The values of serum triglycerides and total cholesterol were slightly higher in cases with G/C+G/G genotypes but statistically not significant (P>0.05). Using a multivariate logistic regression model after adjusting for age, sex, body mass index, and fasting insulin, subjects with the G/G genotype showed higher risk of NAFLD [odds ratio (OR), 1.98, 95% confidence interval (CI) 1.43-2.73, P=0.04). The relationships of the rs738409 polymorphism with the metabolic parameters were not significant after adjustment for multiple comparisons.

CONCLUSION

Asian Indians in north India carrying the allele rs738490 of PNPLA3 is predispose to develop NAFLD.

Progression of NAFLD to diabetes mellitus, cardiovascular disease or cirrhosis

NAFLD is a spectrum of progressive liver disease that encompasses simple steatosis, NASH, fibrosis and, ultimately, cirrhosis. NAFLD is recognized as the hepatic component of the metabolic syndrome, as these conditions have insulin resistance as a common pathophysiological mechanism. Therefore, NAFLD is strongly associated with type 2 diabetes mellitus and abdominal obesity. As lifestyles have become increasingly sedentary and dietary patterns have changed, the worldwide prevalence of NAFLD has increased dramatically and is projected to be the principal aetiology for liver transplantation within the next decade. Importantly, a growing body of clinical and epidemiological evidence suggests that NAFLD is associated not only with liver-related morbidity and mortality, but also with an increased risk of developing both cardiovascular disease and type 2 diabetes mellitus. This article reviews the evidence that suggests NAFLD is a multisystem disease and the factors that might determine interindividual variation in the development and progression of its major hepatic and extrahepatic manifestations (principally type 2 diabetes mellitus and cardiovascular disease).

Nuciferine prevents hepatic steatosis and injury induced by a high-fat diet in hamsters

Background

Nuciferine is a major active aporphine alkaloid from the leaves of N. nucifera Gaertn that possesses anti-hyperlipidemia, anti-hypotensive, anti-arrhythmic, and insulin secretagogue activities. However, it is currently unknown whether nuciferine can benefit hepatic lipid metabolism.

Methodology/Principal Findings

In the current study, male golden hamsters were randomly divided into four groups fed a normal diet, a high-fat diet (HFD), or a HFD supplemented with nuciferine (10 and 15 mg/kg·BW/day). After 8 weeks of intervention, HFD-induced increases in liver and visceral adipose tissue weight, dyslipidemia, liver steatosis, and mild necroinflammation in hamsters were analyzed. Nuciferine supplementation protected against HFD-induced changes, alleviated necroinflammation, and reversed serum markers of metabolic syndrome in hamsters fed a HFD. RT-PCR and western blot analyses revealed that hamsters fed a HFD had up-regulated levels of genes related to lipogenesis, increased free fatty acid infiltration, and down-regulated genes involved in lipolysis and very low density lipoprotein secretion. In addition, gene expression of cytochrome P4502E1 and tumor necrosis factor-α were also increased in the HFD group. Nuciferine supplementation clearly suppressed HFD-induced alterations in the expression of genes involved in lipid metabolism.

Conclusions/Significance

Nuciferine supplementation ameliorated HFD-induced dyslipidemia as well as liver steatosis and injury. The beneficial effects of nuciferine were associated with altered expression of hepatic genes involved in lipid metabolism.

The association between nonalcoholic fatty pancreas disease and diabetes

Background

Fatty infiltration of the pancreas has been shown to interfere with insulin secretion. Both insulin sensitivity and secretion are important in the pathogenesis of diabetes and prediabetes. However, the relationship between diabetes, prediabetes, and fatty pancreas remains unknown. We aim to investigate the relationships that fatty pancreas and nonalcoholic fatty liver disease (NAFLD) have with prediabetes and diabetes in a Chinese population.

Patients and Methods

This was a cross-sectional study. A total of 7,464 subjects were recruited. NAFLD and fatty pancreas were assessed by sonography. Clinico-metabolic parameters were compared among subjects with normoglycemia, prediabetes, and diabetes. Multinomial logistic regression was used to evaluate the relationship between fatty pancreas and NAFLD and diabetes or prediabetes with adjustment for cardiometabolic risk factors.

Results

With an increase in glycemia, a significantly greater proportion of subjects had NAFLD and fatty pancreas (test for trend p<0.05). Similar trends were also found for hypertension, general and central obesity, low-HDL cholesterol, and hypertriglyceridemia. In the logistic regression analysis, age, hypertension, male gender, hypertriglyceridemia, and central obesity were significantly associated with prediabetes and diabetes. Furthermore, the ORs of prediabetes and diabetes for NAFLD were 1.798 (95% CI 1.544–2.094) and 2.578 (95% CI 2.024–3.284), respectively. In addition, fatty pancreas was independently related to diabetes (OR, 1.379; 95% CI, 1.047–1.816) and prediabetes (OR, 1.222; 95% CI, 1.002–1.491) in male subjects.

Conclusions

Both NAFLD and fatty pancreas were associated with diabetes independent of age, gender, adiposity, and other cardiometabolic risk factors. Fatty pancreas was also related to prediabetes in males.

A weight loss diet intervention has a similar beneficial effect on both metabolically abnormal obese and metabolically healthy but obese premenopausal women

BACKGROUND/AIMS

We studied the effect of a 12-week energy-restricted diet intervention on cardiometabolic risk in two groups of nonmorbid obese premenopausal Caucasian women, i.e. a metabolically abnormal obese (MAO) and a metabolically healthy but obese (MHO) group.

METHODS

The participants were 53 MAO and 25 MHO women (age range 19-49 years; body mass index inclusion criterion: 30-39.9). We assessed changes in body weight and composition, blood lipids, insulin resistance, hepatic enzymes, inflammatory markers and adipocytokines.

RESULTS

Overall, many of the study outcomes improved with the intervention in both MAO and MHO participants, but there was no difference in the magnitude of change between the groups. Body weight, waist circumference and total fat mass decreased significantly in response to the intervention in both MAO and MHO women (all p < 0.001). Fasting insulin, insulin resistance (homeostasis model assessment), hepatic enzymes (alanine aminotransferase and γ-glutamyltransferase), fatty liver index and leptin levels also decreased in both groups after the intervention (all p < 0.001), whereas total cholesterol, triglycerides and C-reactive protein decreased significantly only in MAO women (all p < 0.001).

CONCLUSION

These findings reinforce the idea that MHO women would also benefit from a lifestyle weight reduction intervention.

Genome-wide scan revealed that polymorphisms in the PNPLA3, SAMM50, and PARVB genes are associated with development and progression of nonalcoholic fatty liver disease in Japan

We examined the genetic background of nonalcoholic fatty liver disease (NAFLD) in the Japanese population, by performing a genome-wide association study (GWAS). For GWAS, 392 Japanese NAFLD subjects and 934 control individuals were analyzed. For replication studies, 172 NAFLD and 1,012 control subjects were monitored. After quality control, 261,540 single-nucleotide polymorphisms (SNPs) in autosomal chromosomes were analyzed using a trend test. Association analysis was also performed using multiple logistic regression analysis using genotypes, age, gender and body mass index (BMI) as independent variables. Multiple linear regression analyses were performed to evaluate allelic effect of significant SNPs on biochemical traits and histological parameters adjusted by age, gender, and BMI. Rs738409 in the PNPLA3 gene was most strongly associated with NAFLD after adjustment (P = 6.8 × 10(-14), OR = 2.05). Rs2896019, and rs381062 in the PNPLA3 gene, rs738491, rs3761472, and rs2143571 in the SAMM50 gene, rs6006473, rs5764455, and rs6006611 in the PARVB gene had also significant P values (<2.0 × 10(-10)) and high odds ratios (1.84-2.02). These SNPs were found to be in the same linkage disequilibrium block and were associated with decreased serum triglycerides and increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in NAFLD patients. These SNPs were associated with steatosis grade and NAFLD activity score (NAS). Rs738409, rs2896019, rs738491, rs6006473, rs5764455, and rs6006611 were associated with fibrosis. Polymorphisms in the SAMM50 and PARVB genes in addition to those in the PNPLA3 gene were observed to be associated with the development and progression of NAFLD.

[Non-alcoholic fatty liver disease in obese children and adolescents]

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in children and adolescents in industrialized countries. Recent studies have demonstrated a prevalence rate of NAFLD in overweight and obese children and adolescents in Germany of up to 30%. The spectrum of NAFLD ranges from pure fatty infiltration (simple steatosis) to inflammation (steatohepatitis, synonymous NASH) to fibrosis and cirrhosis. Age, gender, ethnicity, insulin resistance, and sex steroids are implicated in the pathogenesis of NAFLD in childhood and adolescence. Moreover, NAFLD in the pediatric age group is associated with marked cardiovascular comorbidities. This review focuses on current data regarding epidemiology, pathophysiology, comorbidities, and treatment of NAFLD in children and adolescents.

The role of hepatokines in metabolism

The liver is known to be involved in the natural history of the ongoing epidemics of type 2 diabetes mellitus and cardiovascular disease. In particular, the liver has a role in increased glucose production and dysregulated lipoprotein metabolism, conditions that are often found in patients with nonalcoholic fatty liver disease. Additionally, several proteins that are exclusively or predominantly secreted from the liver are now known to directly affect glucose and lipid metabolism. In analogy to the functional proteins released from adipose tissue and skeletal muscle-adipokines and myokines-these liver-derived proteins are known as hepatokines. The first hepatokine that has been proven to have a major pathogenetic role in metabolic diseases is α2-HS-glycoprotein (fetuin-A). Production of this glycoprotein is increased in steatotic and inflamed liver, but not in expanded and dysregulated adipose tissue. Thus, research into this molecule and other hepatokines is expected to aid in differentiating between the contribution of liver and those of skeletal muscle and adipose tissue, to the pathogenesis of type 2 diabetes mellitus and cardiovascular disease.

Increased risk of type 2 diabetes in subjects with both elevated liver enzymes and ultrasonographically diagnosed nonalcoholic fatty liver disease: a 4-year longitudinal study

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) is reported to contribute to the development of type 2 diabetes (T2DM). We aimed to compare the risk for development of T2DM among the four groups of NAFLD status divided by the combined assessment of liver enzyme and ultrasonographic steatosis in a retrospective cohort of Korean subjects.

METHODS

This study included 7,849 individuals without diabetes who underwent annual health check-ups for 5 consecutive years. Based on the presence or absence of fatty liver on ultrasound and serum alanine aminotransferase (ALT) values at baseline, subjects were classified into controls, an increased ALT group without steatosis, a steatosis group with normal ALT, and a group with both steatosis and elevated ALT (combined abnormality).

RESULTS

During a 4-year period, the incidence of diabetes was 3.5% in the control group, 4.6% in the increased ALT group, 7.3% in the steatosis group, and 11.8% in the combined abnormality group. The hazard ratio (HR) (95% confidence interval [CI]) of incident diabetes was increased in the elevated ALT group, the steatosis group, and the combined abnormality group in a stepwise fashion. Subjects with combined abnormality group had a significantly increased HR of 1.64 (1.27-2.13) even after multivariate adjustment.

CONCLUSIONS

NAFLD subjects with both elevated ALT and ultrasonographic steatosis have significantly increased risk for future diabetes development.

Inflammation links excess fat to insulin resistance: the role of the interleukin-1 family

A growing body of evidence suggests that cytokines of the interleukin-1 (IL-1) family, particularly IL-1β but also IL-1Ra and IL-18, are involved in obesity-associated inflammation. IL-1β is produced via cleavage of pro-IL-1β by caspase-1, which in turn is activated by a multiprotein complex called the inflammasome. The components of the NLRP3 inflammasome are involved in sensing obesity-associated danger signals, both in mice and in human (obese) subjects, with caspase-1 seemingly the most crucial regulator. Autophagy is upregulated in obesity and may function as a mechanism to control IL-1β gene expression in adipose tissue to mitigate chronic inflammation. All these mechanisms are operative in human adipose tissue and appear to be more pronounced in human visceral compared to subcutaneous tissue. In animal studies, blocking caspase-1 activity results in decreased weight gain, decreased inflammation, and improved insulin sensitivity. Human intervention studies with IL-1Ra (anakinra) have reported beneficial effects in patients with diabetes, yet without significant changes in insulin sensitivity. Clearly, the IL-1 family of cytokines, especially IL-1β, plays an important role in obesity-associated inflammation and insulin resistance and may represent a therapeutic target to reverse the detrimental metabolic consequences of obesity.

Carbohydrate quality is not associated with liver enzyme activity and plasma TAG and HDL concentrations over 5 years in an older population

Non-alcoholic fatty liver disease (NAFLD) is closely associated with insulin resistance and obesity. Hence, carbohydrate quality could be of relevance to the risk of NAFLD, but prospective data are lacking. The aim of the present study was to investigate longitudinal associations between carbohydrate quality (including dietary glycaemic index (GI) and intakes of sugar, starch and fibre) and markers of liver function in an older Australian population. The analysis was based on 866 participants ( ≥ 49 years) of the Blue Mountains Eye Study with fasting blood specimens and dietary intake data at baseline and 5-year follow-up. Multi-level mixed regression analysis was used to relate dietary GI and sugar, starch and fibre intake to the liver enzymes alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT), as well as fasting TAG and HDL-cholesterol (HDL-C). After adjustment for potential confounding factors, a lower fibre intake was cross-sectionally related to higher GGT (P= 0.02) and fasting TAG (P= 0.002) levels, with fruit fibre being the most relevant fibre source (P= 0.095 for GGT; P= 0.003 for TAG). A higher dietary GI was associated with lower HDL-C (P= 0.046). Changes in carbohydrate quality during 5 years were not related to changes in ALT, GGT, TAG or HDL-C (P≥ 0.08). In conclusion, the absence of longitudinal associations between carbohydrate quality and liver enzymes and serum lipids in this older population does not support a major role of carbohydrate nutrition in liver function among the elderly.

Comparison of fatty liver index with noninvasive methods for steatosis detection and quantification

AIM: To compare noninvasive methods presently used for steatosis detection and quantification in nonalcoholic fatty liver disease (NAFLD).

METHODS: Cross-sectional study of subjects from the general population, a subgroup from the First Israeli National Health Survey, without excessive alcohol consumption or viral hepatitis. All subjects underwent anthropometric measurements and fasting blood tests. Evaluation of liver fat was performed using four noninvasive methods: the SteatoTest; the fatty liver index (FLI); regular abdominal ultrasound (AUS); and the hepatorenal ultrasound index (HRI). Two of the noninvasive methods have been validated vs liver biopsy and were considered as the reference methods: the HRI, the ratio between the median brightness level of the liver and right kidney cortex; and the SteatoTest, a biochemical surrogate marker of liver steatosis. The FLI is calculated by an algorithm based on triglycerides, body mass index, γ-glutamyl-transpeptidase and waist circumference, that has been validated only vs AUS. FLI < 30 rules out and FLI ≥ 60 rules in fatty liver.

RESULTS: Three hundred and thirty-eight volunteers met the inclusion and exclusion criteria and had valid tests. The prevalence rate of NAFLD was 31.1% according to AUS. The FLI was very strongly correlated with SteatoTest (r = 0.91, P < 0.001) and to a lesser but significant degree with HRI (r = 0.55, P < 0.001). HRI and SteatoTest were significantly correlated (r = 0.52, P < 0.001). The κ between diagnosis of fatty liver by SteatoTest (≥ S2) and by FLI (≥ 60) was 0.74, which represented good agreement. The sensitivity of FLI vs SteatoTest was 85.5%, specificity 92.6%, positive predictive value (PPV) 74.7%, and negative predictive value (NPV) 96.1%. Most subjects (84.2%) with FLI < 60 had S0 and none had S3-S4. The κ between diagnosis of fatty liver by HRI (≥ 1.5) and by FLI (≥ 60) was 0.43, which represented only moderate agreement. The sensitivity of FLI vs HRI was 56.3%, specificity 86.5%, PPV 57.0%, and NPV 86.1%. The diagnostic accuracy of FLI for steatosis > 5%, as predicted by SteatoTest, yielded an area under the receiver operating characteristic curve (AUROC) of 0.97 (95% CI: 0.95-0.98). The diagnostic accuracy of FLI for steatosis > 5%, as predicted by HRI, yielded an AUROC of 0.82 (95% CI: 0.77-0.87). The κ between diagnosis of fatty liver by AUS and by FLI (≥ 60) was 0.48 for the entire sample. However, after exclusion of all subjects with an intermediate FLI score of 30-60, the κ between diagnosis of fatty liver by AUS and by FLI either ≥ 60 or < 30 was 0.65, representing good agreement. Excluding all the subjects with an intermediate FLI score, the sensitivity of FLI was 80.3% and the specificity 87.3%. Only 8.5% of those with FLI < 30 had fatty liver on AUS, but 27.8% of those with FLI ≥ 60 had normal liver on AUS.

CONCLUSION: FLI has striking agreement with SteatoTest and moderate agreements with AUS or HRI. However, if intermediate values are excluded FLI has high diagnostic value vs AUS.

Dissociating fatty liver and diabetes

Fatty liver disease is epidemiologically associated with type 2 diabetes (T2D), leading to a speculation of a reciprocal cause-effect relationship and a vicious cycle of pathology. Here, we summarize recent literature reporting dissociation of hepatosteatosis from insulin resistance in genetic mouse models and clinical studies. We highlight rhythmic flows of metabolic intermediates between hepatic lipid synthesis and glucose production in normal circadian physiology. Blocking triglyceride (TG) secretion, subcellular lipid sequestration, lipolysis deficiency, enhanced lipogenesis, gluconeogenesis defects, or inhibition of fatty acid oxidation all result in hepatosteatosis without causing hyperglycemia or insulin resistance, suggesting that the cause-effect relationship between hepatosteatosis and diabetes does not exist in all situations.

Nordihydroguaiaretic acid improves metabolic dysregulation and aberrant hepatic lipid metabolism in mice by both PPARα-dependent and -independent pathways

Creosote bush-derived nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, possesses antioxidant properties and functions as a potent antihyperlipidemic agent in rodent models. Here, we examined the effect of chronic NDGA treatment of ob/ob mice on plasma dyslipidemia, hepatic steatosis, and changes in hepatic gene expression. Feeding ob/ob mice a chow diet supplemented with either low (0.83 g/kg diet) or high-dose (2.5 g/kg diet) NDGA for 16 wk significantly improved plasma triglyceride (TG), inflammatory chemokine levels, hyperinsulinemia, insulin sensitivity, and glucose intolerance. NDGA treatment caused a marked reduction in liver weight and TG content, while enhancing rates of fatty acid oxidation. Microarray analysis of hepatic gene expression demonstrated that NDGA treatment altered genes for lipid metabolism, with genes involved in fatty acid catabolism most significantly increased. NDGA upregulated the mRNA and nuclear protein levels of peroxisome proliferator-activated receptor α (PPARα), and the activated (phosphorylated) form of AMP-activated kinase. NDGA increased PPARα promoter activity in AML12 hepatocytes and also prevented the fatty acid suppression of PPARα expression. In contrast, PPARα siRNA abrogated the stimulatory effect of NDGA on fatty acid catabolism. Likewise, no stimulatory effect of NDGA on hepatic fatty acid oxidation was observed in the livers of PPARα-deficient mice, but the ability of NDGA to reverse fatty liver conditions was unaffected. In conclusion, the beneficial actions of NDGA on dyslipidemia and hepatic steatosis in ob/ob mice are exerted primarily through enhanced fatty acid oxidation via PPARα-dependent pathways. However, PPARα-independent pathways also contribute to NDGA's action to ameliorate hepatic steatosis.

Intrahepatic Lipid Content and Insulin Resistance Are More Strongly Associated with Impaired NEFA Suppression after Oral Glucose Loading Than with Fasting NEFA Levels in Healthy Older Individuals

Introduction. The mechanisms underlying the association between insulin resistance and intrahepatic lipid (IHL) accumulation are not completely understood. We sought to determine whether this association was explained by differences in fasting non-esterified fatty acid (NEFA) levels and/or NEFA suppression after oral glucose loading. Materials and Methods. We performed a cross-sectional analysis of 70 healthy participants in the Hertfordshire Physical Activity Trial (39 males, age 71.3 ± 2.4 years) who underwent oral glucose tolerance testing with glucose, insulin, and NEFA levels measured over two hours. IHL was quantified with magnetic resonance spectroscopy. Insulin sensitivity was measured with the oral glucose insulin sensitivity (OGIS) model, the leptin: adiponectin ratio (LAR), and the homeostasis model assessment (HOMA). Results. Measures of insulin sensitivity were not associated with fasting NEFA levels, but OGIS was strongly associated with NEFA suppression at 30 minutes and strongly inversely associated with IHL. Moreover, LAR was strongly inversely associated with NEFA suppression and strongly associated with IHL. This latter association (beta = 1.11 [1.01, 1.21], P = 0.026) was explained by reduced NEFA suppression (P = 0.24 after adjustment). Conclusions. Impaired postprandial NEFA suppression, but not fasting NEFA, contributes to the strong and well-established association between whole body insulin resistance and liver fat accumulation.

Sirtuin 1 deacetylase: a key regulator of hepatic lipid metabolism

Obesity is a serious medical problem worldwide and disruption of metabolic/energy homeostasis plays a pivotal role in this global epidemic. In obese people, fatty liver (steatosis) develops, which increases the risk for diabetes, cardiovascular disease, and even, liver cancer. Sirtuin 1 (SIRT1) is a NAD+-dependent deacetylase that functions as a key metabolic/energy sensor and mediates homeostatic responses to nutrient availability. Accumulating evidence indicates that SIRT1 is a master regulator of the transcriptional networks that control hepatic lipid metabolism. During energy-deprived conditions, SIRT1 deacetylates and alters the expression and activities of key transcriptional regulators involved in hepatic lipogenesis, fatty acid β-oxidation, and cholesterol/bile acid metabolism. This review will discuss the latest advances in this field, focusing on beneficial roles of SIRT1 in hepatic lipid metabolism including its potential as a therapeutic target for treatment of steatosis and other obesity-related metabolic diseases.

Bariatric surgery as potential treatment for nonalcoholic fatty liver disease: a future treatment by choice or by chance?

Morbid obesity is strongly associated with nonalcoholic fatty liver disease (NAFLD) which is one of the most common causes of chronic liver disease worldwide. The current best treatment of NAFLD and NASH is weight reduction through life style modifications, antiobesity medication, and bariatric surgery. Importantly, bariatric surgery is the best alternative option for weight reduction if lifestyle modifications and pharmacological therapy have not yielded long-term success. Bariatric surgery is an effective treatment option for individuals who are grossly obese and associated with marked decrease in obesity-related morbidity and mortality. The most common performed bariatric surgery is Roux-en-Y gastric bypass (RYGB). The current evidence suggests that bariatric surgery in these patients will decrease the grade of steatosis, hepatic inflammation, and fibrosis. NAFLD per se is not an indication for bariatric surgery. Further research is urgently needed to determine (i) the benefit of bariatric surgery in NAFLD patients at high risk of developing liver cirrhosis (ii) the role of bariatric surgery in modulation of complications of NAFLD like diabetes and cardiovascular disease. The outcomes of the future research will determine whether bariatric surgery will be one of the recommended choice for treatment of the most progressive type of NAFLD.

Increased fetuin-A concentrations in impaired glucose tolerance with or without nonalcoholic fatty liver disease, but not impaired fasting glucose

CONTEXT

Fetuin-A, a liver-derived glycoprotein that impairs insulin signaling, is associated with nonalcoholic fatty liver disease (NAFLD), diabetes, and the risk of cardiovascular diseases. Both prediabetes and NAFLD are associated with increased cardiovascular risk, and their concurrence significantly impairs hepatic and adipose tissue insulin sensitivity.

OBJECTIVE

Our objective was to investigate the relationship between serum fetuin-A levels and prediabetes in subjects with or without NAFLD.

DESIGN

This was a cross-sectional case-control study.

PATIENTS

A total of 510 age- and sex-matched subjects with normal glucose tolerance (NGT), impaired fasting glucose (IFG), and impaired glucose tolerance (IGT) with or without NAFLD were recruited. Each subject was assessed by abdominal ultrasound to diagnose NAFLD.

MAIN OUTCOME MEASURES

Serum fetuin-A concentrations were compared between groups. The association with clinico-metabolic parameters was examined.

RESULTS

The presence of NAFLD significantly increases fetuin-A levels in subjects with NGT and prediabetes. As compared with NGT, IGT, but not IFG, significantly increases fetuin-A levels in subjects with or without NAFLD. Serum fetuin-A concentrations were positively related to postload 2-h glucose, body mass index, triglyceride, and homeostasis model assessment of insulin resistance but negatively associated with age, high-density lipoprotein cholesterol, and adiponectin. In multiple regression analysis, age, IGT vs. NGT, and IGT with NAFLD vs. NGT were independently associated with fetuin-A levels after adjustment for cardiovascular risk factors and adiponectin.

CONCLUSIONS

IGT with or without NAFLD was independently associated with fetuin-A levels after adjustment for cardiometabolic risk factors. The elevated fetuin-A levels could have a clinical implication in the increased cardiovascular risk and insulin resistance associated with NAFLD and IGT.

Substitution of TAG oil with diacylglycerol oil in food items improves the predicted 10 years cardiovascular risk score in healthy, overweight subjects

Dietary fat is normally in TAG form, but diacylglycerol (DAG) is a natural component of edible oils. Studies have shown that consumption of DAG results in metabolic characteristics that are distinct from those of TAG, which may be beneficial in preventing and managing obesity. The objective of the present study was to investigate if food items in which part of the TAG oil is replaced with DAG oil combined with high α-linolenic acid (ALA) content would influence metabolic markers. A 12-week double-blinded randomised controlled parallel-design study was conducted. The participants (n 23) were healthy, overweight men and women, aged 37–67 years, BMI 27–35 kg/m², with waist circumference >94 cm (men) and >88 cm (women). The two groups received 20 g margarine, 11 g mayonnaise and 12 g oil per d, containing either high ALA and sn-1,3-DAG or high ALA and TAG. Substitution of TAG oil with DAG oil in food items for 12 weeks led to an improvement of the predicted 10 years cardiovascular risk score in overweight subjects by non-significantly improving markers of health such as total body fat percentage, trunk fat mass, alanine aminotransferase, systolic blood pressure, γ-glutamyl transferase, alkaline phosphatase and total fat-free mass. This may suggest that replacing TAG oil with DAG oil in healthy, overweight individuals may have beneficial metabolic effects.

Heterogeneity of the Stearoyl-CoA desaturase-1 (SCD1) gene and metabolic risk factors in the EPIC-Potsdam study

BACKGROUND

Stearoyl-CoA desaturase-1 (SCD1) is an enzyme involved in lipid metabolism. In mice and humans its activity has been associated with traits of the metabolic syndrome, but also with the prevention of saturated fatty acids accumulation and subsequent inflammation, whereas for liver fat content inconsistent results have been reported. Thus, variants of the gene encoding SCD1 (SCD1) could potentially modify metabolic risk factors, but few human studies have addressed this question.

METHODS

In a sample of 2157 middle-aged men and women randomly drawn from the Potsdam cohort of the European Prospective Investigation into Cancer and Nutrition, we investigated the impact of 7 SCD1 tagging-single nucleotide polymorphisms (rs1502593, rs522951, rs11190480, rs3071, rs3793767, rs10883463 and rs508384) and 5 inferred haplotypes with frequency >5% describing 90.9% of the genotype combinations in our population, on triglycerides, body mass index (BMI), waist circumference (WC), glycated haemoglobin (HbA1c), high-sensitivity C-reactive protein (hs-CRP), gamma-glutamyltransferase (GGT), alanine aminotransferase (ALT) and fetuin-A.

RESULTS

No significant associations between any of the SNPs or haplotypes and BMI, WC, fetuin-A and hs-CRP were observed. Associations of rs10883463 with triglycerides, GGT and HbA1c as well as of rs11190480 with ALT activity, were weak and became non-significant after multiple-testing correction. Also associations of the haplotype harbouring the minor allele of rs1502593 with HbA1c levels, the haplotype harbouring the minor alleles of rs11190480 and rs508384 with activity of ALT, and the haplotype harbouring the minor alleles of rs522951, rs10883463 and rs508384 with triglyceride and HbA1C levels and GGT activities did not withstand multiple-testing correction.

CONCLUSION

These findings suggest that there are no associations between common variants of SCD1 or its inferred haplotypes and the investigated metabolic risk factors. However, given the results from animal models, heterogeneity of human SCD1 warrants further investigation, in particular with regard to rare variants.

Association between nonalcoholic liver disease and chronic kidney disease: an ultrasound analysis from NHANES 1988-1994

BACKGROUND/AIMS

Nonalcoholic fatty liver disease (NAFLD) has been proposed to contribute to chronic kidney disease (CKD) independently of traditional cardiometabolic risk factors. We hypothesized that NAFLD is associated with CKD and that greater severity of NAFLD is associated with higher odds of CKD.

METHODS

A cross-sectional analysis of 11,469 adults who participated in the National Health and Nutrition Examination Survey (NHANES) 1988-1994. NAFLD was defined by ultrasonographic detection of steatosis in the absence of other liver diseases. CKD was defined as an estimated glomerular filtration rate of ≤60 ml/min/1.73 m(2) or the presence of albuminuria in subjects with an estimated glomerular filtration rate of >60 ml/min/1.73 m(2).

RESULTS

2,891 (25.4%) patients in the cohort had CKD. The prevalence of NAFLD was higher in individuals with CKD compared to those without CKD (42.2 vs. 34.5%, p < 0.0001). NAFLD was associated with CKD in unadjusted logistic regression analysis (OR = 1.47, 95% CI: 1.29-1.67, p < 0.0001). Adjustment for demographics and components of metabolic syndrome attenuated this relationship (OR = 1.04, 95% CI: 0.88-1.23, p = 0.64). Moderate and severe NAFLD on ultrasound were increasingly associated with prevalent CKD in unadjusted analysis, but not after adjustment for metabolic syndrome components.

CONCLUSION

After adjusting for features of metabolic syndrome, ultrasound-diagnosed NAFLD is not associated with prevalent CKD among US adults. Aggressive public health efforts are needed to prevent and treat metabolic syndrome.

Regular exercise is associated with a reduction in the risk of NAFLD and decreased liver enzymes in individuals with NAFLD independent of obesity in Korean adults

Background

We evaluated the association of regular physical exercise with the presence of non-alcoholic fatty liver disease (NAFLD) and liver enzymes in relation to obesity and insulin resistance.

Methodology/Principal Findings

A cross-sectional analysis was conducted in 72,359 healthy Korean adults without diabetes who participated in a comprehensive health check-up. Subjects who have been exercising regularly (more than 3 times per week, at least for 30 minutes each time and for consecutive 3 month) were categorized into exercise group. All subjects were categorized into deciles based on their body mass index (BMI) and we estimated the odds ratios (ORs) for having NAFLD according to exercise regularity in each decile. The diagnosis of NAFLD was based on ultrasonography findings. Individuals with NAFLD (n = 19,921) were analyzed separately to evaluate ORs for having elevated liver enzymes based on regularity of exercise. The risk for NAFLD was significantly reduced in exercise group with age- and sex-adjusted ORs of 0.53–0.72 for all BMI deciles except at BMI categories of <19.6 and 20.7–21.6 kg/m². While no difference was seen in BMI between subjects in exercise and non-exercise group across the BMI deciles, the values of body fat percentage and metabolic risk factors differed. Among NAFLD patients, subjects in exercise group had a lower risk for having elevated liver enzymes with multivariable adjusted OR of 0.85 (95% CI 0.74–0.99, for AST) and 0.74 (95% CI 0.67–0.81, for ALT) than did subjects in non-exercise group.

Conclusions/Significance

Regular exercise was associated with a reduced risk for having NAFLD and decreased liver enzymes in patients with NAFLD, and this relationship was also independent of obesity.

Associations of sex hormone-binding globulin and testosterone with diabetes among men and women (the Saku Diabetes study): a case control study

BACKGROUND

Sex hormone-binding globulin (SHBG) levels and sex hormones have been implicated in the pathogenesis of type 2 diabetes and cardiovascular diseases. As fatty liver has been suggested to be a major determinant of SHBG levels, we examined whether the associations of SHBG and testosterone with diabetes were independent of fatty liver.

METHODS

We conducted a case-control study that included 300 diabetes cases (215 men and 85 women) and 300 matched controls from the Saku cohort study. Diabetes was defined by either fasting plasma glucose levels ≥126 mg/dL, 2-h post-load glucose levels ≥200 mg/dL after a 75 g oral glucose tolerance test, or diabetes diagnosed by physicians. We fitted conditional logistic regression models to examine the associations between SHBG and total testosterone levels with diabetes by sex. To evaluate the impact of fatty liver, we used the fatty liver index (FLI), a validated measure derived from serum triglyceride levels, body mass index (BMI), waist circumference, and γ-glutamyltransferase levels.

RESULTS

After adjusting for age, family history of diabetes, smoking, physical activity, BMI, and FLI, SHBG levels were inversely associated with diabetes among women (odds ratio [OR] comparing the highest with the lowest quartiles, 0.13 [95% confidence interval {CI}, 0.02-0.96]), but not among men. Similar patterns were observed in a subgroup analysis restricted to postmenopausal women"(OR, 0.12 [95% CI, 0.01-1.17]). In contrast, testosterone levels were inversely associated with diabetes among men (OR, 0.45 [95% CI, 0.23-0.89]), but not among women.

CONCLUSIONS

Our findings suggest that SHBG in women and testosterone in men may be inversely associated with diabetes.

Role of DNA methylation in the regulation of lipogenic glycerol-3-phosphate acyltransferase 1 gene expression in the mouse neonatal liver

The liver is a major organ of lipid metabolism, which is markedly changed in response to physiological nutritional demand; however, the regulation of hepatic lipogenic gene expression in early life is largely unknown. In this study, we show that expression of glycerol-3-phosphate acyltransferase 1 (GPAT1; Gpam), a rate-limiting enzyme of triglyceride biosynthesis, is regulated in the mouse liver by DNA methylation, an epigenetic modification involved in the regulation of a diverse range of biological processes in mammals. In the neonatal liver, DNA methylation of the Gpam promoter, which is likely to be induced by Dnmt3b, inhibited recruitment of the lipogenic transcription factor sterol regulatory element-binding protein-1c (SREBP-1c), whereas in the adult, decreased DNA methylation resulted in active chromatin conformation, allowing recruitment of SREBP-1c. Maternal overnutrition causes decreased Gpam promoter methylation with increased GPAT1 expression and triglyceride content in the pup liver, suggesting that environmental factors such as nutritional conditions can affect DNA methylation in the liver. This study is the first detailed analysis of the DNA-methylation-dependent regulation of the triglyceride biosynthesis gene Gpam, thereby providing new insight into the molecular mechanism underlying the epigenetic regulation of metabolic genes and thus metabolic diseases.

High-carbohydrate diets induce hepatic insulin resistance to protect the liver from substrate overload

In population studies hepatic steatosis in subjects with Non-alcoholic fatty liver disease (NAFLD) is strongly associated with insulin resistance. This association has encouraged debate whether hepatic steatosis is the cause or the consequence of hepatic insulin resistance? Although genome-wide studies have identified several gene variants associated with either hepatic steatosis or type 2 diabetes, no variants have been identified associated with both hepatic steatosis and insulin resistance. Here, the hypothesis is proposed that high-carbohydrate diets contribute to the association between hepatic steatosis and insulin resistance through activation of the transcription factor ChREBP (Carbohydrate response element binding protein). Postprandial hyperglycaemia raises the hepatic concentrations of phosphorylated intermediates causing activation of ChREBP and induction of its target genes. These include not only enzymes of glycolysis and lipogenesis that predispose to hepatic steatosis but also glucose 6-phosphatase (G6PC) that catalyses the final reaction in glucose production and GCKR, the inhibitor of hepatic glucokinase that curtails hepatic glucose uptake. Induction of G6PC and GCKR manifests as hepatic glucose intolerance or insulin resistance. Induction of these two genes by high glucose serves to safeguard intrahepatic homeostasis of phosphorylated intermediates. The importance of GCKR in this protective mechanism is supported by "less-active" GCKR variants in association not only with hepatic steatosis and hyperuricaemia but also with lower fasting plasma glucose and decreased insulin resistance. This supports a role for GCKR in restricting hepatic glucose phosphorylation to maintain intrahepatic homeostasis. Pharmacological targeting of the glucokinase-GCKR interaction can favour either glucose clearance by the liver or intrahepatic metabolite homeostasis.

Relationship between Nonalcoholic Fatty Liver Disease and Carotid Artery Atherosclerosis Beyond Metabolic Disorders in Non-Diabetic Patients

Background

The objective of this study was to investigate the association between nonalcoholic fatty liver disease (NAFLD) and carotid artery atherosclerosis beyond metabolic disorders.

Methods

We studied 320 non-diabetic patients with ultrasonographically diagnosed NAFLD and 313 non-diabetic patients without NAFLD who have less than 40 g alcohol/week drinking history. Carotid atherosclerotic burden was assessed by carotid intima-media thickness (IMT) and plaque. All subjects were divided to the metabolic syndrome (MetS) according to International Diabetes Federation criteria.

Results

NAFLD patients had a significantly increased mean carotid IMT (0.79 ± 0.18 vs. 0.73 ± 0.13 mm; p < 0.001) than those without the condition. The prevalence of increased IMT, defined as IMT ≥ 1 mm, and carotid plaque were 52.5% and 34.1% in the patients with NAFLD vs. 35.8% and 18.8% in the patients without this condition (p < 0.001). The difference in IMT and prevalence of plaque was also significant even in patients without MetS as well as those with MetS (all p < 0.05). NAFLD-associated adjusted odds ratio for increased IMT was 1.236 [95% confidence interval (CI), 1.023-1.467, p = 0.016] without MetS and 1.178 (95% CI, 1.059-1.311, p = 0.003) with MetS. NAFLD-associated adjusted odds ratio of carotid plaque was 1.583 (95% CI, 1.309-1.857, p = 0.024) without MetS and 1.536 (95% CI, 0.512-4.604, p = 0.444) with MetS.

Conclusion

NAFLD is significantly associated with carotid atherosclerosis in non-diabetic outpatients even without MetS. Carotid screening for NAFLD might be beneficial for assessment of future atherosclerotic complications.

Association of Alanine Aminotransferase Levels (ALT) with the Hepatic Insulin Resistance Index (HIRI): a cross-sectional study

BACKGROUND

The association between serum alanine aminotransferase (ALT) levels and hepatic insulin resistance (IR) has been evaluated with the hyperinsulinemic-euglycemic clamp. However, there is no information about the association of ALT with the Hepatic Insulin Resistance Index (HIRI). The aim of this study was to evaluate the association between serum ALT levels and HIRI in subjects with differing degrees of impaired glucose metabolism.

METHODS

This cross-sectional study included subjects that had an indication for testing for type 2 diabetes mellitus (T2DM) with an oral glucose tolerance test (OGTT). Clinical and biochemical evaluations were carried out including serum ALT level quantification. HIRI was calculated for each participant. Correlation analyses and lineal regression models were used to evaluate the association between ALT levels and HIRI.

RESULTS

A total of 324 subjects (37.6% male) were included. The mean age was 40.4 ± 14.3 years and the mean body mass index (BMI) was 32.0 ± 7.3 kg/m2. Individuals were divided into 1 of 5 groups: without metabolic abnormalities (n = 113, 34.8%); with the metabolic syndrome (MetS, n = 179, 55.2%), impaired fasting glucose (IFG, n = 85, 26.2%); impaired glucose tolerance (IGT, n = 91, 28.0%), and T2DM (n = 23, 7.0%). The ALT (p < 0.001) and HOMA2-IR (p < 0.001) values progressively increased with HIRI quartiles, while ISI-Matsuda (p < 0.001) progressively decreased. After adjustment for sex, age, and BMI, we identified a significant correlation between HIRI and ALT in persons with the MetS (r = 0.22, p = 0.003), IFG (r = 0.33, p < 0.001), IGT (r = 0.37, p < 0.001), and T2DM (r = 0.72, p < 0.001). Lineal regression analysis adjusting for age, HDL-C, TG and waist circumference (WC) showed an independent association between ALT and HIRI in subjects with the MetS (beta = 0.07, p = 0.01), IFG (beta = 0.10, p = 0.02), IGT (beta = 0.09, p = 0.007), and T2DM (beta = 0.31, p = 0.003). This association was not identified in subjects without metabolic abnormalities.

CONCLUSIONS

ALT levels are independently associated with HIRI in subjects with the MetS, IFG, IGT, and T2DM. The ALT value in these subjects may be an indirect parameter to evaluate hepatic IR.

Fat deposition decreases diffusion parameters at MRI: a study in phantoms and patients with liver steatosis

PURPOSE

Assess the effect of fat deposition on the MRI diffusion coefficients in lipid emulsion-based phantoms and patients with proven isolated liver steatosis.

MATERIALS AND METHODS

Diffusion-weighted MRI with 11 b values from 0-500 s/mm(2) was performed in phantoms (fat fractions 0-18 %) with and without fat suppression and in 19 patients with normal liver (n = 14) or isolated liver steatosis (n = 5) proven by histopathology. The apparent, pure and perfusion-related diffusion coefficients and the perfusion fraction were measured. Spearman correlation coefficient and Mann-Whitney U test were used for comparisons.

RESULTS

A strong correlation between the apparent and pure diffusion coefficients and fat fractions was seen in phantoms. The pure diffusion coefficient decreased significantly in patients with liver steatosis (0.96 ± 0.16 × 10(-3) mm(2)/s versus 1.18 ± 0.09 × 10(-3) mm(2)/s in normal liver, P = 0.005), whereas the decrease in apparent diffusion coefficient did not reach statistical significance (1.26 ± 0.25 × 10(-3) mm(2)/s versus 1.41 ± 0.14 × 10(-3) mm(2)/s in normal liver, P = 0.298).

CONCLUSIONS

Fat deposition decreases the apparent and pure diffusion coefficients in lipid emulsion-based phantoms and patients with isolated liver steatosis proven by histopathology.

Polycystic ovary syndrome is a risk factor for type 2 diabetes: results from a long-term prospective study

Polycystic ovary syndrome (PCOS) recently has been identified as a risk factor associated with type 2 diabetes. However, the evidence derives from cross-sectional observational studies, retrospective studies, or short-term prospective studies. This long-term prospective study of a large cohort of women with PCOS, followed from youth to middle age, aimed at estimating, for the first time, the incidence and potential predictors of type 2 diabetes in this population. A total of 255 women with PCOS were followed for at least 10 years (mean follow-up 16.9 years). Six women were patients with diabetes at baseline, and another 42 women developed type 2 diabetes during the follow-up. The incidence rate of type 2 diabetes in the study population was 1.05 per 100 person-years. The age-standardized prevalence of diabetes at the end of follow-up was 39.3%, which is significantly higher with respect to that of the general Italian female population of a similar age (5.8%). The likelihood of developing type 2 diabetes significantly increased as BMI, fasting glucose, and glucose area under the curve at baseline increased and significantly decreased as sex hormone-binding globulin (SHBG) levels at follow-up increased. This study demonstrates that the risk of type 2 diabetes is markedly elevated in middle-aged women with PCOS and suggests including BMI, glucose, and SHBG-circulating levels in the risk stratification.

Effect of nonalcoholic Fatty liver disease on the development of type 2 diabetes in nonobese, nondiabetic korean men

Background/Aims

We have a limited understanding of the effect of nonalcoholic fatty liver disease (NAFLD) on the development of type 2 diabetes.

Methods

The study subjects included male who had received biennial medical check-ups between 2005 and 2009 and who had been diagnosed with fatty liver disease. The subjects with sustained NAFLD (FL, n=107) and sustained non-NAFLD (NFL, n=1,054) were followed to determine the development of type 2 diabetes.

Results

In the FL group, there were more subjects with impaired fasting glucose (IFG), type 2 diabetes and high HOMA-IR than there were in the NFL group during the 5-year follow-up period (32.7 vs. 17.6%, 1.9 vs. 0.3%, 17.9 vs. 5.2% respectively, p<0.05). The FL group showed a higher risk than NFL group for abnormal glucose metabolism as determined using IFG (odds ratio [OR], 2.13; confidence interval [CI], 1.36 to 3.35), type 2 diabetes (OR, 7.63; 95% CI, 1.03 to 56.79) and high HOMA-IR (OR, 3.25; 95% CI, 1.79 to 5.91) and metabolic parameters such as body mass index (OR, 3.35; 95% CI, 1.87 to 6.02), triglyceride (OR, 3.05; 95% CI, 1.92 to 4.86) and fasting blood sugar (OR, 2.18; 95% CI, 1.39 to 3.41).

Conclusions

Sustained NAFLD appears to be associated with an increased risk for the development of type 2 diabetes and deterioration of metabolic parameters in non-obese, non-diabetic Korean men.

Ursodeoxycholic acid improves insulin sensitivity and hepatic steatosis by inducing the excretion of hepatic lipids in high-fat diet-fed KK-Ay mice

Type 2 diabetes mellitus is frequently accompanied by fatty liver/nonalcoholic fatty liver disease. Hence, accumulation of lipids in the liver is considered to be one of the risk factors for insulin resistance and metabolic syndrome. Ursodeoxycholic acid (UDCA) is widely used for the treatment of liver dysfunction. We investigated the therapeutic effects of UDCA on type 2 diabetes mellitus exacerbating hepatic steatosis and the underlying mechanisms of its action using KK-A(y) mice fed a high-fat diet. KK-A(y) mice were prefed a high-fat diet; and 50, 150, and 450 mg/kg of UDCA was orally administered for 2 or 3 weeks. Administration of UDCA decreased fasting hyperglycemia and hyperinsulinemia. Hyperinsulinemic-euglycemic clamp analyses showed that UDCA improved hepatic (but not peripheral) insulin resistance. Hepatic triglyceride and cholesterol contents were significantly reduced by treatment with UDCA, although the genes involved in the synthesis of fatty acids and cholesterol, including fatty acid synthase and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, were upregulated. Fecal levels of bile acids, neutral sterols, fatty acids, and phospholipids were significantly increased by UDCA treatment. The gene expression levels and protein phosphorylation levels of endoplasmic reticulum stress markers were not changed by UDCA treatment. These results indicate that UDCA ameliorates hyperglycemia and hyperinsulinemia by improving hepatic insulin resistance and steatosis in high-fat diet-fed KK-A(y) mice. Reduction of hepatic lipids might be due to their excretion in feces, followed by enhanced utilization of glucose for the synthesis of fatty acids and cholesterol. Ursodeoxycholic acid should be effective for the treatment of type 2 diabetes mellitus accompanying hepatic steatosis.

Endoplasmic reticulum stress induces the expression of fetuin-A to develop insulin resistance

Fetuin-A is a biomarker reported to be important in many metabolic disorders, including obesity, diabetes, and hepatic steatosis. Although it is well known that fetuin-A is increased in diabetes and nonalcoholic fatty liver disease (NAFLD), the levels of fetuin-A in diabetic patients with NAFLD are unknown. Furthermore, the regulation of fetuin-A expression is still obscure. In this study, a total of 180 age- and sex-matched subjects with normal glucose tolerance, NAFLD, newly diagnosed diabetes (NDD), and NDD with NAFLD were recruited. We found that the levels of fetuin-A were significantly increased in NDD with NAFLD as compared with NDD or NAFLD subjects. We further used HepG2 cells to investigate the regulation of fetuin-A. Treatment with endoplasmic reticulum (ER) stress activator, thapsigargin, increased the expression of fetuin-A mRNA and protein in a time- and dose-dependent manner. Pretreatment with ER stress inhibitor, 4-phenylbutyrate, reversed high glucose or palmitate-induced fetuin-A expression. Moreover, treatment with 4-phenylbutyrate in both streptozotocin-induced and high-fat diet-induced diabetic mice not only decreased hepatic fetuin-A levels but also improved hyperglycemia. Taken together, we found that fetuin-A levels were increased in diabetes patients with NAFLD. Moreover, ER stress induced by high glucose and palmitate increased the expression of fetuin-A and further contributed to the development of insulin resistance.

[Non-alcoholic fatty liver disease and its association with clinical and biochemical variables in obese children and adolescents: effect of a one-year intervention on lifestyle]

OBJECTIVE

To study the frequency of non-alcoholic fatty liver disease (NAFLD), its relationship to clinical and biochemical variables, and the effect 12-month's lifestyle intervention in obese children and adolescents.

METHODS

Thirty-six obese patients aged 7 to 18 years, 42% female and 58% male, 72.2% prepubertal and 27.8% pubertal, were selected. Anthropometric measurements and glucose, insulin (baseline and after a glucose load), lipid profile, C-reactive protein, and aminotransferase tests were performed before and 12 months after dietary and physical activity intervention. Liver ultrasound was performed to determine the presence of NAFLD.

RESULTS

NAFLD was found in 66.7% (n=24), and was mild in 30.6%, moderate in 27.8%, and severe in 8.3%. Subjects with NAFLD had higher body mass index (BMI, p=0.007), waist (p=0.005), fat area (p=0.002), basal insulin (p=0.01), and HOMA-IR (p=0.008) values and lower QUICKI (p=0.02) values than those with no NAFLD. After intervention, physical activity increased (p=0.0001) and calorie intake remained unchanged. NAFLD disappeared in 9 patients (37.5%, p=0.02) and disease severity decreased in 3 patients (12.5%). In addition, BMI Z-score (p=0.005), fat area (p=0.0001), basal insulin (p<0.05), insulin resistance (p<0.005), lipid profile (p<0.03), and transaminases decreased. Weight loss was the main variable accounting for NAFLD improvement.

CONCLUSION

This group of obese children and adolescents showed a high frequency of NAFLD. The lifestyle intervention with weight reduction is effective for the treatment of NAFLD.

Role of β-adrenergic receptors in regulation of hepatic fat accumulation during aging

Excessive fat accumulation in liver (hepatic steatosis) predisposes to hepatic functional and structural impairment and overall metabolic risk. Previous studies noted an association between hepatic steatosis and age in humans and rodents. However, the mechanisms leading to age-associated hepatic fat accumulation remain unknown. Earlier work from our group showed that β-adrenergic receptor (β-AR) levels and β-AR-stimulated adenylyl cyclase activity increase in rat liver during aging. Here we investigated whether age-associated increases in β-AR signaling play a role in augmenting hepatic lipid accumulation. We demonstrate an increase in hepatic lipid content during senescence and a significant correlation between hepatic fat content and stimulation of adenylyl cyclase activity by the β-AR agonist isoproterenol in rat liver. Isoproterenol administration to young and old rodents in vivo increased hepatic lipid accumulation. Furthermore, in vitro overexpression of β1- and β2-AR subtypes in hepatocytes from young rodents increased cellular lipid content, whereas inhibition of β-ARs by receptor subtype-specific inhibitors reduced lipid levels in hepatocytes from senescent animals. Isoproterenol-induced hepatic lipid accumulation in vivo was prevented by the β-AR nonselective blocker propranolol, suggesting a novel therapeutic effect of this class of drugs in hepatic steatosis. Acipimox, which inhibits adipose tissue lipolysis, did not alter isoproterenol-mediated hepatic fat accumulation; thus β-AR responsive hepatic lipid accumulation does not appear to be related primarily to altered lipolysis. These findings suggest that augmented hepatic β-AR signaling during aging may increase lipid accumulation in liver and advocate a possible role for β-adrenergic blockers in preventing or retarding the development of hepatic steatosis.