Insulin resistance in non-alcoholic steatohepatitis

Lysosomal acid lipase regulates VLDL synthesis and insulin sensitivity in mice

AIMS/HYPOTHESIS

Lysosomal acid lipase (LAL) hydrolyses cholesteryl esters and triacylglycerols (TG) within lysosomes to mobilise NEFA and cholesterol. Since LAL-deficient (Lal (-/-) ) mice suffer from progressive loss of adipose tissue and severe accumulation of lipids in hepatic lysosomes, we hypothesised that LAL deficiency triggers alternative energy pathway(s).

METHODS

We studied metabolic adaptations in Lal (-/-) mice.

RESULTS

Despite loss of adipose tissue, Lal (-/-) mice show enhanced glucose clearance during insulin and glucose tolerance tests and have increased uptake of [(3)H]2-deoxy-D-glucose into skeletal muscle compared with wild-type mice. In agreement, fasted Lal (-/-) mice exhibit reduced glucose and glycogen levels in skeletal muscle. We observed 84% decreased plasma leptin levels and significantly reduced hepatic ATP, glucose, glycogen and glutamine concentrations in fed Lal (-/-) mice. Markedly reduced hepatic acyl-CoA concentrations decrease the expression of peroxisome proliferator-activated receptor α (PPARα) target genes. However, treatment of Lal (-/-) mice with the PPARα agonist fenofibrate further decreased plasma TG (and hepatic glucose and glycogen) concentrations in Lal (-/-) mice. Depletion of hepatic nuclear factor 4α and forkhead box protein a2 in fasted Lal (-/-) mice might be responsible for reduced expression of microsomal TG transfer protein, defective VLDL synthesis and drastically reduced plasma TG levels.

CONCLUSIONS/INTERPRETATION

Our findings indicate that neither activation nor inactivation of PPARα per se but rather the availability of hepatic acyl-CoA concentrations regulates VLDL synthesis and subsequent metabolic adaptations in Lal (-/-) mice. We conclude that decreased plasma VLDL production enhances glucose uptake into skeletal muscle to compensate for the lack of energy supply.

Comparison of the efficacy of liraglutide with pioglitazone on dexamethasone induced hepatic steatosis, dyslipidemia and hyperglycaemia in albino rats

Objectives:

To evaluate the efficacy of liraglutide with pioglitazone for prevention of dexamethasone induced hepatic steatosis, dyslipidemia and hyperglycemia in Albino rats.

Materials and Methods:

There were four groups of six rats each. First group received dexamethasone alone in a dose of 8 mg/kg intraperitoneally for 6 days to induce metabolic changes and considered as dexamethasone control. Second group received liraglutide 1.8 mg/kg subcutaneously 6 days before dexamethasone and 6 days during dexamethasone administration. Third group received pioglitazone 45 mg/kg orally 6 days before dexamethasone and 6 days during dexamethasone administration. Fourth group did not receive any medication and was considered as normal control. Fasting blood sugar, lipid profile, blood sugar 2 h after glucose load were measured. Liver weight, liver volume, and histopathological analysis were done.

Results:

Dexamethasone caused hepatomegaly, dyslipidemia, and hyperglycemia. Both pioglitazone and liraglutide significantly reduced hepatomegaly, dyslipidemia and hyperglycemia (P < 0.01). Reduction of blood sugar levels after glucose load was significant with pioglitazone when compared with liraglutide (P < 0.01).

Conclusion:

Liraglutide has comparable efficacy to pioglitazone in prevention of dexamethasone induced hepatomegaly, dyslipidemia and fasting hyperglycemia.

Evolving concepts in the pathogenesis of NASH: beyond steatosis and inflammation

Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis and inflammation and, in some patients, progressive fibrosis leading to cirrhosis. An understanding of the pathogenesis of NASH is still evolving but current evidence suggests multiple metabolic factors critically disrupt homeostasis and induce an inflammatory cascade and ensuing fibrosis. The mechanisms underlying these changes and the complex inter-cellular interactions that mediate fibrogenesis are yet to be fully elucidated. Lipotoxicity, in the setting of excess free fatty acids, obesity, and insulin resistance, appears to be the central driver of cellular injury via oxidative stress. Hepatocyte apoptosis and/or senescence contribute to activation of the inflammasome via a variety of intra- and inter-cellular signalling mechanisms leading to fibrosis. Current evidence suggests that periportal components, including the ductular reaction and expansion of the hepatic progenitor cell compartment, may be involved and that the Th17 response may mediate disease progression. This review aims to provide an overview of the pathogenesis of NASH and summarises the evidence pertaining to key mechanisms implicated in the transition from steatosis and inflammation to fibrosis. Currently there are limited treatments for NASH although an increasing understanding of its pathogenesis will likely improve the development and use of interventions in the future.

Current management of patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) and its progressive form, nonalcoholic steatohepatitis (NASH) are the most common causes of chronic liver disease in industrialized countries. NAFLD has also been strongly associated with type II diabetes and cardiovascular diseases. This study was a multipurposed review, which included discussion of recent studies investigating the cellular and genetic basis of these diseases, the pathogenesis of NAFLD and the current treatment and management of nonalcoholic steatohepatitis. Currently, maintaining a healthy weight through dietary changes and exercise, the use of insulin-modulating pharmacologic agents for diabetes control and the use of lipid-lowering, anti-oxidants have been the most widely recommended treatments. Inclusion of pathogenic mechanisms in treatment design will allow future therapies to target-specific pathways involved in NAFLD pathogenesis.

Non-alcoholic fatty liver disease: is iron relevant?

Non-alcoholic fatty liver disease (NAFLD) is a common and ubiquitous disorder (Bedogni et al. in Hepatology 42:44-52, 2005; Bellentani et al. in Ann Intern Med 132:112-117, 2000) which in a proportion of subjects leads to non-alcoholic steatohepatitis (NASH), advanced liver disease and hepatocellular carcinoma. Although the factors responsible for progression of disease are still uncertain, there is evidence that insulin resistance (IR) is a key operative mechanism (Angulo et al. in Hepatology 30:1356-1362, 1999) and that two stages are involved. The first is the accumulation of triglycerides in hepatocytes followed by a "second hit" which promotes cellular oxidative stress. Several factors may be responsible for the induction of oxidative stress but hepatic iron has been implicated in various studies. The topic is controversial, however, with early studies showing an association between hepatic iron (with or without hemochromatosis gene mutations) and the progression to hepatic fibrosis. Subsequent studies, however, could not confirm an association between the presence of hepatic iron and any of the histological determinants of NAFLD or NASH. Recent studies have reactivated interest in this subject firstly, with the demonstration that hepatic iron loading increases liver cholesterol synthesis with increased lipid deposition in the liver increasing the cellular lipid burden and secondly, a large clinical study has concluded that hepatocellular iron deposition is associated with an increased risk of hepatic fibrosis, thus, strongly supporting the original observation made over a decade ago. An improvement in insulin sensitivity has been demonstrated following phlebotomy therapy but a suitably powered controlled clinical trial is required before this treatment can be implemented.

Weight loss induced by 6-month lifestyle intervention improves early endothelial activation and fibrinolysis in obese adolescents

BACKGROUND

Adolescent obesity is associated with an increased risk of adult obesity and subsequent cardiovascular diseases. The present study aimed to assess the effect of weight loss after 6-month lifestyle intervention in obese adolescents on biomarkers of endothelial activation and fibrinolytic system.

METHODS

Eighty-five obese adolescents aged 10 to 16 years were assigned to a 6-month lifestyle intervention and 61 completed the programme. We examined the effect of the intervention on adhesion molecules (selectin E, soluble intercellular adhesion molecule 1 and soluble vascular adhesion molecule 1) and fibrinolytic parameters [plasminogen activator inhibitor-1 (PAI-1) and fibrinogen]. Thirty-six lean adolescents were studied only at baseline as a comparison group.

RESULTS

Compared with lean participants, obese adolescents at baseline demonstrated significantly higher levels of triglycerides, glucose, insulin, homeostasis model assessment, soluble intercellular adhesion molecule 1, PAI-1 and fibrinogen. After 6-month lifestyle intervention, those obese adolescents with decreased standard deviation score-body mass index (SDS-BMI) displayed significant decreases in insulin (19.2 ± 11.2 vs. 26.8 ± 13.2 mU/L, P≤ 0.01), homeostasis model assessment (4.24 ± 3.19 vs. 6.58 ± 4.08, P≤ 0.01), selectin E (100.2 ± 60.9 vs. 116.0 ± 69.0 ng/mL, P≤ 0.01) and PAI-1 (39.6 ± 38.0 vs. 51.8 ± 25.6 ng/mL, P≤ 0.05) with respect to the baseline levels. No changes in these parameters were observed in the obese adolescents with stable or increased SDS-BMI. The changes of triglycerides after intervention in subgroup with decreased SDS-BMI were significantly greater than those in subgroup with stable SDS-BMI.

CONCLUSIONS

The present study demonstrated increased endothelial activation and impairment of the fibrinolytic system in early life, which is in part reversible by a 6-month lifestyle intervention.

Nonalcoholic fatty liver disease is associated with insulin resistance in a young Hispanic population

OBJECTIVE

To investigate whether nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance (IR) in a young Hispanic population.

METHODS

A cross-sectional study was performed in Bogotá, Colombia, during 2006 in 263 males from the Colombian Air Force (age range 29-54 years). Anthropometric measurements and biochemical determinations (glycemia, lipid profile, insulin, and HOMA-IR) were obtained in order to determine the presence of metabolic syndrome (MS) criteria and insulin resistance in this population. In addition, ultrasound studies were performed to evaluate the presence of NAFLD.

RESULTS

NAFLD was detected in 26.6% (n=70) of the subjects. Thirty four individuals had complete MS criteria (48.5%). The presence of NAFLD was associated with higher insulin levels (11.0±5.1 vs. 6.6±3.6, p=0.001), and its prevalence increased from 11% (n=8), to 24% (n=17) to 64% (n=45) from the lowest to the highest HOMA-IR tertile. Body mass index, triglycerides and subcutaneous and visceral fat were found to be independent predictors of NAFLD.

CONCLUSIONS

These results suggest that NAFLD is associated with insulin resistance and extrahepatic adiposity in nondiabetic young Hispanic population.

Epigenomic derangement of hepatic glucose metabolism by feeding of high fructose diet and its prevention by Rosiglitazone in rats

BACKGROUND

The high consumption of fructose leads to the increasing incidence of insulin resistance by several unknown mechanisms. Hepatic glucose metabolism may also be an important target of fructose-induced-metabolic alterations.

AIM

The aim of present study was to investigate alterations in hepatic glycogenolysis, glycogenesis and gluconeogenic fluxes by feeding of 21% high fructose diet and the effects of Rosiglitazone treatment to prevent these derangements in rats.

METHODS

Rats were maintained on normal chow and high fructose diet with or without Rosiglitazone for 8 weeks and various biochemical and gene expression measures were estimated.

RESULTS

The feeding of high fructose diet impaired glucose, insulin and pyruvate tolerance tests and increased blood HbA(1c), insulin, triglyceride, free fatty acids and homeostasis model assessment after 8 weeks. In addition, high fructose diet feeding increased expression of phosphoenol-pyruvatecorboxykinase, glucose-6-phosphatase, sterol regulatory element binding proteins-1 and fatty acid synthase through enhanced expression of fork-head receptor, peroxisome proliferator activated receptor-gamma-co-activator 1 and cAMP reactive element binding protein. The treatment with Rosiglitazone inhibited all these derangements, i.e. hepato-lipogenic and gluconeogenic effects of high fructose diet feeding in rats.

CONCLUSIONS

Together these findings suggest that high fructose diet induced hepatic gluconeogenic and lipogenic rate, and increased circulating triglycerides and free fatty acids, which may be the major risk factors for glucose intolerance, hyperglycemia and insulin resistance in rats. In such situations high fructose flux also induces transcriptional cascade of gluconeogenic enzymes through the modulation of various associated transcriptional factors.

Serum retinol binding protein 4 and nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus

Retinol binding protein 4 (RBP4) is a protein secreted by adipocytes, and closely associated with insulin resistance. Whereas RBP4 is also mainly expressed in hepatocytes as the principal transport protein for retinol (vitamin A) in the circulation, and its pathophysiological role in liver remain unclear. The aim of this paper was to investigate the association between RBP4 and nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). Serum RBP4 and adiponectin concentrations were measured by radioimmunoassay in 52 diabetic patients who had NAFLD and 50 sex- and age-matched diabetic patients without any clinical features of liver diseases who had normal liver ultrasonic appearance and normal liver function. Serum RBP4 levels were elevated in diabetic patients with NAFLD (32.0+/-8.9 microg/ml vs. 41.3+/-9.8 microg/ml, p<0.001), while adiponectin decreased (17.4+/-9.3 microg/ml vs. 13.8+/-7.0 microg/ml, p=0.032). Male diabetic patients had higher serum RBP4 concentration and lower serum adiponectin concentration than female diabetic patients (38.5+/-9.9 microg/ml vs. 34.0+/-10.7 microg/ml, p=0.031 and 12.7+/-5.7 microg/ml vs. 20.23+/-9.8 microg/ml, p<0.001, respectively). Multiple logistic regression analysis revealed RBP4 and triglyceride as independent association factors for NAFLD, while the association between serum adiponectin and NAFLD was not significant. Increasing concentrations of RBP4 were independently and significantly associated with NAFLD in diabetic patients. In multiple linear regression analysis, alanine aminotransferase, fasting serum insulin and adiponectin were independent factors for serum RBP4 level. The study demonstrates that retinol binding protein 4 might contribute to the pathogenesis of nonalcoholic fatty liver disease.

Relationship between nonalcoholic fatty liver disease prevalence and visceral fat in obese adolescents

BACKGROUND

Visceral adiposity is the major risk factor for paediatric nonalcoholic fatty liver disease.

AIMS

Determine the prevalence of nonalcoholic fatty liver disease according to the visceral fat quartile.

SUBJECTS

181 obese adolescents including 113 girls (16.58+/-1.56 years) and 68 boys (16.87+/-1.62 years) were evaluated.

METHODS

The inclusion criteria were obesity and post-pubertal stage of Tanner. Visceral fat of obese adolescents was distributed in quartiles after ultrasound nonalcoholic fatty liver disease diagnosis.

RESULTS

Nonalcoholic fatty liver disease prevalence was 45.30%. It was observed that 62.07% and 76.47% of girls and boys with nonalcoholic fatty liver disease were found in the 4th quartile. In a multivariate logistic analysis it was observed that only visceral fat remained statistically significant, every 1cm increase in visceral fat was associated with a 1.97 fold (95% CI 1.06-3.66) in boys and 2.08 fold (95% CI 1.38-3.13) in girls increased risk to develop nonalcoholic fatty liver disease. Indeed it was verified a positive correlation between visceral fat, body mass index, insulin levels, homeostasis model assessment insulin resistance index and steatosis degree.

CONCLUSIONS

Our findings suggested that the expansion of visceral fat was a determinant factor to increase nonalcoholic fatty liver disease prevalence and the visceral fat measured by ultrasound might be a good predictor to identify risk for nonalcoholic fatty liver disease in obese adolescents. It was confirmed by a stronger correlation between visceral fat and body mass index.

Steatohepatitis is associated with diabetes and fibrosis in genotype 1b HCV-related chronic liver disease

Liver steatosis, diabetes mellitus and hepatitis C virus (HCV) genotype have been implicated in liver fibrosis in HCV-related chronic active hepatitis (CAH). The aim of this study was to evaluate whether steatosis and diabetes were associated with more severe liver fibrosis in patients with genotype 1b HCV-related CAH. One-hundred and eighty patients (98 men, 82 women; age range 17-68 years; median 51) infected with genotype 1b HCV underwent ultrasound examination and liver biopsy because of elevated levels of serum alanine transaminase. Based on liver histology, patients were divided into three steatosis classes: 1 (involving <33% of hepatocytes), 2 (34-66%) and 3 (>66%). Fibrosis was graded with the Ishak score (range: 0-6). Virological and epidemiologic characteristics, biochemical data, body mass index, and apparent duration of disease were recorded. Diabetes was identified according to American Diabetes Association criteria. The median fibrosis grade was 2 (23 patients had liver cirrhosis) in the three steatosis classes, with no significant differences between classes. At multivariate analysis, fibrosis was significantly related to age, alanine transaminase, diabetes, hepatitis B core antibody, steatohepatitis and grading. At binary logistic regression analysis, only diabetes and fibrosis stage were significantly associated with steatohepatitis. Steatosis was not an independent risk factor for liver disease severity in our CAH/genotype 1b HCV-infected patients. Steatohepatitis was associated as well as diabetes and affected the severity of liver fibrosis.

Cardiac abnormalities as a new manifestation of nonalcoholic fatty liver disease: echocardiographic and tissue Doppler imaging assessment

Nonalcoholic fatty liver disease (NAFLD) is linked to the metabolic syndrome. The aim of the present study is to determine the effect of the metabolic syndrome on left ventricular (LV) geometry and function using as a model patients with NAFLD. Thirty-eight patients with NAFLD, less than 55 years of age and with a normal exercise test, were compared with an age and sex-matched control group. Patients with diabetes mellitus, hypertension, and body mass index>40 were excluded. A complete echocardiographic study including tissue Doppler imaging (TDI) was performed. The following parameters were assessed by echo Doppler: peak velocities of early (E) and late (A) diastolic filling, E/A ratio, flow propagation velocity (Vp). Using TDI early diastolic velocity (E'), and systolic velocity (S') of mitral annulus were obtained. The patients with NAFLD had a significantly higher body mass index (31.4+/-5 vs. 26.4+/-4 kg/m, P=0.01), higher glucose (100.6+/-13 vs. 83.0+/-10 mg/dL, P=0.01), and triglyceride levels (126.5+/-44 vs. 206.5+/-67 mg/dL, P<0.001). Increased thickness of the intraventricular septum, posterior wall (11.03+/-2.2 vs. 8.9+/-2.9 mm, P=0.001; 8.5+/-1.7 vs. 9.7+/-2.3 mm, P=0.04), and larger LV mass and LV mass/height (160.7+/-58.7 vs.115.3+/-35.4 g, P=0.001 and 92.6+/-29.5 vs. 69.2+/-19.8 g/m, P=0.001, respectively) were found in NAFLD group. LV systolic function was similar in both groups. Patients with NAFLD had a lower E (73.6+/-11.0 vs. 86.4+/-20.0 cm/s, P<0.006) and E/A ratio (1.0+/-0.3 vs. 1.76+/-0.8 P<0.0001). Moreover, the Vp and the E' on TDI were significantly lower compared with the control group (49.0+/-9.7 vs. 74.7+/-18.4 cm/s, P<0.0001 and 10.3+/-2.0 vs. 13.8+/-1.7 cm/s, P<0.0001, respectively). On multivariate analysis the E' on TDI was the only independent parameter associated with NAFLD. In conclusion, patients with NAFLD in the absence of morbid obesity, hypertension, and diabetes have mildly altered LV geometry and early features of left ventricular diastolic dysfunction. Early diastolic velocity on TDI was found to be the only index that could identify the patients with NAFLD and metabolic syndrome.

The evolution of severe steatosis after bariatric surgery is related to insulin resistance

BACKGROUND & AIMS

In severely obese patients, factors implicated in the evolution of severe steatosis after bariatric surgery remain unresolved. Our aim was to determine whether insulin resistance (IR) influences the histologic effects induced by bariatric surgery.

METHODS

We prospectively included 185 severely obese patients (body mass index >/=35 kg/m(2)) referred for bariatric surgery. The evolution of IR (IR index = 1/quantitative insulin sensitivity check index) and liver injury with consecutive biopsy was concomitantly assessed before and 1 year after surgery.

RESULTS

At preoperative biopsy, 27% of severely obese patients disclosed severe steatosis (>/=60%). The alanine aminotransferase (P = .01) and IR indexes (P = .04) were independent predictive factors of severe steatosis at baseline. One year after surgery, surgical treatment induced a decrease in body mass index (9.5 kg/m(2); P < .0001), steatosis score (8.5%; P < .0001), and IR index (0.29; P < .0001). The preoperative IR index (P = .01) and preoperative steatosis (P = .006) were independent predictive factors in the persistence of severe steatosis after surgery. Moderate or severe steatosis was more frequently observed in patients who had conserved a higher IR index after surgery than in patients who had improved their IR index (44% vs 20.2%; P = .04).

CONCLUSIONS

IR was independently associated with severe steatosis and predicted its persistence after surgery. The amelioration of IR after surgery is associated with a decrease in the amount of fat. Taken together, the results of this prospective study in severely obese patients demonstrate that severe steatosis and its evolution after surgery are intimately connected with IR.

Insulin resistance: a metabolic pathway to chronic liver disease

Insulin resistance (IR) is the pathophysiological hallmark of nonalcoholic fatty liver disease (NAFLD), one of the most common causes of chronic liver disease in Western countries. We review the definition of IR, the methods for the quantitative assessment of insulin action, the pathophysiology of IR, and the role of IR in the pathogenesis of chronic liver disease. Increased free fatty acid flux from adipose tissue to nonadipose organs, a result of abnormal fat metabolism, leads to hepatic triglyceride accumulation and contributes to impaired glucose metabolism and insulin sensitivity in muscle and in the liver. Several factors secreted or expressed in the adipocyte contribute to the onset of a proinflammatory state, which may be limited to the liver or more extensively expressed throughout the body. IR is the common characteristic of the metabolic syndrome and its related features. It is a systemic disease affecting the nervous system, muscles, pancreas, kidney, heart, and immune system, in addition to the liver. A complex interaction between genes and the environment favors or enhances IR and the phenotypic expression of NAFLD in individual patients. Advanced fibrotic liver disease is associated with multiple features of the metabolic syndrome, and the risk of progressive liver disease should not be underestimated in individuals with metabolic disorders. Finally, the ability of insulin-sensitizing, pharmacological agents to treat NAFLD by reducing IR in the liver (metformin) and in the periphery (thiazolidinediones) are discussed.

Association between fatty liver and hyperlipidemia

AIM: To investigate the association between the formation of fatty liver and the phenotypes of hyperlipidemia.

METHODS: A total of 258 patients with hyperlipidemia were found in 413 patients with fatty liver, and 61 cases of hyperlipidemia in non-fatty liver patients were selected randomly as controls. The complications and liver function abnormalities were compared between two groups.

RESULTS: The proportion of hypertriglyceridemia and mixed hyperlipidemia was higher in the patients with fatty liver than non-fatty liver. Odds ratios (OR) of finding fatty liver in the patients with mixed hyperlipidemia and hypertrigly-ceridemia were 5.966 and 2.960 respectively, relative to hypercholesterolemia. The percentage of complications of typeⅡdiabetes mellitus, obesity, hypertension, hyperuris-emia and the evelation of serum alanine aminotransferase (ALT), -glutamyltransferase (GGT) were higher in patients with fatty liver than non-fatty liver. But, there were no differences in coincidence of diabetes mellitus, obesity, hyperten-sion, hyperurisemia, coronary heart disease, choelithiasis among various phenotypes of hyperlipidemia.

CONCLUSION: The pathogenesis of fatty liver can be related to mixed hyperlipidemia and hypertriglyceridemia. The complications of patients with fatty liver may be more common than those with non-fatty liver, but have no differences of complications among various phenotypes of hyperlipidemia.

Non-alcoholic fatty liver and insulin resistance: a cause-effect relationship?

The role of insulin resistance in non-alcoholic fatty liver disease is suggested by laboratory data (hyperinsulinemia and decreased sensitivity to endogenous and exogenous insulin). The clinical association with features of the metabolic syndrome, particularly in the most aggressive stages of the disease, further confirms a causative role. Fat accumulation in the liver may stem either from genetic defects, primarily responsible for insulin resistance, or excessive calorie intake and visceral obesity, and is mediated by adipocytokines (leptin, adiponectin, tumour necrosis factor-alpha). Progression of fatty liver to steatohepatitis may be the result of an imbalance between pro-inflammatory and anti-inflammatory cytokines, triggering the formation of reactive oxygen species and intrahepatic lipid peroxidation. This process may also be promoted or accelerated by pro-oxidant xenobiotics or environmental factors. Insulin resistance provides a target for specific treatment of non-alcoholic fatty liver, and insulin-sensitising agents (metformin or thiazolidinediones) as well as lifestyle changes to reduce visceral adiposity are the most promising therapeutic options. Future trials need to be performed in order to test the long-term effectiveness of these treatments on the basis of clinically relevant histological outcomes.

Interim results of a pilot study demonstrating the early effects of the PPAR-gamma ligand rosiglitazone on insulin sensitivity, aminotransferases, hepatic steatosis and body weight in patients with non-alcoholic steatohepatitis

BACKGROUND/AIMS

Hyperinsulinemia may cause hepatic steatosis and non-alcoholic steatohepatitis (NASH). The aims of this pilot study were to examine the safety of using the insulin-sensitizing peroxisomal proliferator activated receptor (PPAR) gamma ligand rosiglitazone in patients with NASH and determine whether improved insulin sensitivity correlates with improved fatty liver.

METHODS

Thirty subjects with NASH and elevated alanine aminotransferase (ALT) levels received rosiglitazone, 4 mg twice daily for 48 weeks; the preliminary results presented here were obtained at 24 weeks. Insulin sensitivity was measured using fasting insulin and glucose levels and liver fat content was estimated by CT imaging.

RESULTS

By 24 weeks, rosiglitazone improved insulin sensitivity and reduced liver fat content. The mean ALT decreased from 86 to 37 U/l (P<0.01). Four subjects (13%) withdrew, one because of a rise in ALT from 59 to 277 U/l that coincided with concomitant prednisone use. Subjects experienced a mean weight gain of 3.5% and hemoglobin drop of 1.1 g/dl.

CONCLUSIONS

Treatment of NASH with rosiglitazone for 24 weeks improved insulin sensitivity, reduced liver fat content and improved biochemical evidence of hepatocellular injury. These preliminary data provide evidence that hyperinsulinemia may be a cause of NASH. Strategies to improve insulin sensitivity as a treatment of NASH deserve further investigation.

Evaluation of the immune response to pneumococcal capsular polysaccharides

Antibody deficiency is the most common immunodeficiency. In 5% to 10% of the patients with recurrent infections that are evaluated for immunodeficiency, a specific deficiency in the immune response to capsular polysaccharides can be found. Patients with recurrent infections should therefore be tested for their capacity to produce antibodies against anti-capsular polysaccharides. As a clinical test, specific antibody levels are measured before and 14 days after immunization with the 23-valent pneumococcal polysaccharide vaccine. In this article we describe the indications, the method used to measure antibodies to capsular pneumococcal polysaccharide and the way the results have to be interpreted.

Increased susceptibility to nonalcoholic fatty liver disease in heterozygotes for the mutation responsible for hereditary hemochromatosis

BACKGROUND

Insulin resistance is a key feature of nonalcoholic fatty liver disease. Patients with hereditary hemochromatosis, a disease characterized by progressive iron overload due, in most cases, to homozygosity for C282Y mutation in the HFE gene, have often decreased insulin sensitivity and release.

AIMS

To determine whether increased iron parameters/heterozygosity for the mutations of the HFE gene confer susceptibility to nonalcoholic fatty liver disease.

PATIENTS

One hundred and thirty-four consecutive Italian patients with clinical and ultrasonographic diagnosis of nonalcoholic fatty liver disease (82 with hyperferritinemia), half confirmed by liver biopsy.

METHODS

Insulin was determined by radioimmunoassay. HFE gene mutations were determined by polymerase chain reaction and restriction fragment length polymorphism analysis.

RESULTS

(1) Prevalence of C282Y HFE mutation was significantly higher in patients with nonalcoholic fatty liver disease compared to controls, the difference being more striking in patients with hyperferritinemia than in those without. (2) The presence of mild iron overload was associated with a lower insulin release. (3) Carriers of C282Y mutation developed nonalcoholic fatty liver disease despite lower body mass index and triglycerides.

CONCLUSION

The mild iron overload associated with heterozygosity for C282Y HFE mutation confers susceptibility to nonalcoholic fatty liver disease, causing relative insulin deficiency.

Interaction of iron, insulin resistance, and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) has emerged as a ubiquitous liver disorder with occasional serious overtones. Although diabetes and obesity were initially held culpable, insulin resistance (IR) is now considered the fundamental operative mechanism. IR is probably the "first step" in nonalcoholic steatohepatitis (NASH). Oxidative stress may be the elusive "second" of possibly multiple steps in the progression of steatosis to fibrosing steatohepatitis. Because hepatic iron promotes oxidative stress, it was mooted as a contributory cofactor in NASH. This proposal was strengthened by an association with hepatic fibrosis. Subsequent studies have shown neither a significant increase in hepatic iron nor an association between hepatic iron and any of the histologic determinants in NASH. Likewise, the increased prevalence of hemochromatosis gene (HFE) mutations in some studies appears to be largely irrelevant to the development of hepatic fibrosis. Excess hepatic iron may occur in insulin resistance-associated iron overload (IRHIO), characterized by hyperferritinemia with normal to mild increases in transferrin saturation. Although patients with IRHIO have a high prevalence of IR-related metabolic disorders, the relationship of IRHIO to NASH is unclear. A recent study showed improvement in insulin sensitivity with the use of venesection in patients with NAFLD, but this approach cannot be implemented without extensive review.

Recurrence of insulin resistant metabolic syndrome following liver transplantation

Insulin resistant metabolic syndrome is a major clinical disorder including hyperlipidaemia, hypertension, impaired glucose tolerance and/or type 2 diabetes and central obesity, which are well established cardiovascular risk factors. We report the case of a 61-year-old woman who developed severe hypercholesterolaemia and hypertriglyceridaemia after liver transplantation. In her forties she had hypertension, mixed hyperlipidaemia, mild hyperglycaemia and moderate abdominal obesity, suggesting the presence of the metabolic syndrome. She had liver enzyme elevation and severe steatosis and hepatomegaly at ultrasonography. At age 52, cryptogenic liver cirrhosis was diagnosed and rapidly progressing liver failure developed. In 1992 she underwent liver transplantation. Seven years after transplant the patient had abdominal obesity, high blood pressure, marked hypercholesterolaemia, hypertriglyceridaemia and moderate elevation of alanine aminotransferase. She also had impaired glucose tolerance and markedly increased basal and post-glucose load plasma insulin levels. Steatohepatitis was demonstrated by serial liver biopsies. This is the first case that reports the recurrence of the metabolic syndrome following liver transplantation. We postulate that metabolic syndrome may have promoted fatty liver and subsequent progression to end stage liver disease. We also stress the need for careful management of the metabolic syndrome in order to decrease the long-term risk for cardiovascular disease.

Glucose intolerance and serum aminotransferase activities in Japanese men

BACKGROUND/AIMS

Elevated activities of serum aminotransferase are commonly observed in patients with diabetes mellitus. Few studies have addressed the relation between glucose intolerance and serum activities of aminotransferase in free-living populations.

METHODS

Using a 75 g oral glucose tolerance test, we examined the association of impaired fasting glycemia (IFG), impaired glucose tolerance (IGT), and type 2 diabetes mellitus with serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT) among 4621 men aged 49-59 years of the Japan Self-Defense Forces. Statistical adjustment was made for body mass index, waist-hip ratio, and other possible confounding factors.

RESULTS

Proportions of an elevated ALT (>50 IU/l) in men with normal glucose tolerance, IFG, IGT, and newly diagnosed diabetes mellitus were 3.5%, 9.5%, 7.7%, and 18.0%, respectively. Adjusted odds ratios of an elevated ALT for IFG, IGT, and newly diagnosed diabetes mellitus were 2.2 (95% confidence interval 1.1-4.3), 1.7 (1.2-2.4), and 4.4 (3.0-6.6), respectively. IGT and diabetes mellitus were also significantly positively associated with elevated AST (>40 IU/l) and GGT (>50 IU/l).

CONCLUSIONS

Glucose intolerance is associated with elevated serum aminotransferase independent of obesity, but even a mildly elevated ALT is relatively uncommon in free-living men with glucose intolerance.

Pathology of steatohepatitis

Pathologists have long been involved in clinical diagnosis and investigative studies of various forms of liver disease, including alcoholic liver disease. The concept that progressive fatty liver disease may result from causes other than alcohol toxicity can be noted in the literature. However, acceptance of this as a bona fide form of liver disease has been credited to an in-depth study published in 1980 of patients gathered from cases in the files of the pathology department of the Mayo Clinic in whom liver biopsies showed histological similarities to alcoholic steatohepatitis, but for whom clinical evidence of alcohol use was absent. Subsequent studies of the natural history and pathogenesis of non-alcoholic steatohepatitis have relied on detailed histopathological correlations. This chapter will elucidate the constellation of microscopic findings, the issues of concern for pathological evaluation and the knowledge to date of their significance in various forms of fatty liver disease.

Steatohepatitis in obese individuals

Nonalcoholic steatohepatitis (NASH), which is the most severe histological form of nonalcoholic fatty liver disease (NAFLD), is emerging as the most common clinically important form of liver disease in developed countries. Although its prevalence is 3% in the general population, this increases to 20-40% in obese patients. Since NASH is associated with obesity, prevalence has been predicted to increase along with the arsent epidemic of obesity and type II diabetes mellitus. The importance of this observation comes from the fact that NASH is a progressive fibrotic disease, in which cirrhosis and liver-related death occur in 25% and 10% in these patients respectively over a 10-year period. This is of particular concern given the increasing recognition of NASH in children. Treatment consists of treating obesity and its co-morbidities; diabetes and hyperlipidemia. Nascent studies suggest that a number of pharmacological therapies may be effective, but all remain unproven at present. Histological and laboratory improvement occurs with a 10% decrease in body weight. Bariatric surgery is indicated in selected patients.A greater understanding of the pathophysiological progression of NASH in obese patients must be obtained in order to develop more focused and improved therapy.

Fasting insulin and uric acid levels but not indices of iron metabolism are independent predictors of non-alcoholic fatty liver disease. A case-control study

BACKGROUND

Non-alcoholic fatty liver disease is a common reason for hepatological consultation and may herald severe hepatic and extra-hepatic disease. The aetiopathogenesis of this condition is an area of increasing interest.

AIM

To evaluate anthropometric and biochemical factors associated to non-alcoholic fatty liver disease in a case-control study. Methods. Demographic and biochemical data of 60 consecutive patients with bright liver absent-to-low alcohol consumption, no evidence of viral, genetic and autoimmune diseases, were compared to those of 60 age- and gender-matched historical controls without fatty liver by univariate and multiple logistic regression analysis.

RESULTS

Patients were more often hypertriglyceridaemic, obese and diabetic than controls (p<.01). Mean values of alanine transaminase, gammaglutamyltranspeptidase, triglycerides, uric acid, fasting and log insulin, transferrin percent saturation and ferritin were significantly higher in the patients, while transferrin and quantitative insulin sensitivity check index, a quantitative insulin sensitivity index, were lower. No iron storage was found in those who underwent liver biopsy At univariate analysis the relative risk for non-alcoholic fatty liver disease significantly increased (p<0. 05) with increasing body mass index, fasting insulin, alanine transaminase, uric acid, triglycerides and gammaglutamyltranspeptidase; it decreased with increasing transferrin and quantitative insulin sensitivity check index. Multiple logistic regression analysis disclosed only fasting insulin and uric acid to be independent predictors of non-alcoholic fatty liver disease (p<0.05).

CONCLUSIONS

Fasting insulin and serum uric acid levels indicating insulin resistance, but not indices of iron overload, are independent predictors of non-alcoholic fatty liver disease.

NASH and insulin resistance: Insulin hypersecretion and specific association with the insulin resistance syndrome

Nonalcoholic steatohepatitis (NASH) is often linked with disorders that are clearly associated with insulin resistance (IR): obesity, type 2 diabetes mellitus, and hypertriglyceridemia. We tested the hypotheses that (1) IR is an essential requirement for the development of NASH and (2) a high association between IR and liver disease is relatively specific for NASH. We measured body mass index (BMI), waist/hip ratio, and fasting serum lipid, insulin, C-peptide, and glucose levels in 66 patients with NASH (21 with advanced fibrosis and 45 with mild fibrosis). IR was determined by the homeostasis model assessment (HOMA). We also determined the strength of the association of NASH with insulin resistance syndrome (IRS) as defined by World Health Organization criteria. To assess whether the finding of IR was relatively specific to NASH rather than simply to obesity or liver disease, we compared the results of a subset of 36 patients with less-severe NASH with 36 age- and sex-matched patients with chronic hepatitis C virus (HCV) of comparable fibrotic severity. IR was confirmed in 65 patients (98%) with NASH, and 55 (87%) fulfilled minimum criteria for IRS. IR was found in lean as well as in overweight and obese patients. The IR values and the prevalence of IRS (75% vs. 8.3%) were significantly higher in those with NASH than in comparable cases of HCV. Hyperinsulinemia was attributable to increased insulin secretion rather than decreased hepatic extraction. In conclusion, most patients with NASH have IRS, and there is a near-universal association between NASH and IR irrespective of obesity. IR is present in mild as well as advanced cases of NASH but is unusual in chronic HCV of similar fibrotic severity.