Non-alcoholic fatty liver disease and the metabolic syndrome: An update

Evaluation of atherosclerotic findings in patients with nonalcoholic fatty liver disease

Background

Nonalcoholic fatty liver disease (NAFLD), a highly prevalent condition, is a feature of metabolic syndrome and is characterized by excessive accumulation of fat in the liver cells. The purpose of this study was to investigate the association between NAFLD and carotid intima-media thickness (CIMT) as an independent risk factor for atherosclerosis.

Methods

We examined 250 consecutive patients with ultrasonographically confirmed NAFLD and 85 age-matched and gender-matched controls with normal parenchymal liver echogenicity for determination of CIMT and presence of carotid atherosclerotic plaque.

Results

Compared with control subjects, patients with NAFLD showed an increased mean CIMT (0.81 ± 0.14 mm) compared with control subjects (0.58 ± 0.15 mm). This difference was statistically significant (P = 0.001). After performing multivariate analysis, the presence of NAFLD was associated with abnormal CIMT independent of other atherogenic risk factors or its association with metabolic syndrome.

Conclusion

NAFLD can be an independent risk factor for developing atherosclerosis. Therefore, NAFLD with and without metabolic syndrome can be associated with increased CIMT and increased risk of cardiovascular events in patients with NAFLD incidentally diagnosed on abdominal ultrasonography.

Centrizonal arteries and microvessels in nonalcoholic steatohepatitis

Correct classification of nonalcoholic steatohepatitis (NASH) liver biopsies is of critical importance and relies on correct orientation to microscopic liver architecture. Centrizonal arteries can cause central zones to be mistaken for portal tracts, especially in the setting of centrizonal ductular reaction, and result in either missed diagnosis or inaccurate staging of NASH. A total of 100 randomly selected biopsies from NASH Clinical Research Network participants (February 2005 to August 2006, fibrosis stage >1a) were evaluated for arteries and CD34-positive microvessels in the centrizonal region. Prevalence of both centrizonal arteries and CD34-positive microvessels was graded as 0 (none in central zones), 1 (1 to 2 central zones with vessels), 2 (<50% of central zones with vessels), or 3 (≥50% of central zones with vessels). Centrizonal arteries and CD34-positive microvessels were present in 40 and 100 cases (40% and 100%), respectively. Arteries and CD34-positive microvessels were more commonly found in central zones in biopsies with greater degrees of fibrosis (62% with arteries in stage 3 to 4 versus 21% in stage 1 to 2 and 70% with microvessels in stage 3 to 4 versus 25% in stage 1 to 2), with increased prevalence of both centrizonal arteries and CD34-positive microvessels correlating directly with fibrosis stage (P<0.001). Ductular reaction was a common finding (55%) in patients with central zone arteries. The presence of centrizonal arteries must be recognized to allow for correct orientation to liver architecture in NASH and, together with the finding of increased CD34-positive microvessel formation in higher-stage fibrosis, suggests a possible association between neoangiogenesis and NASH progression to cirrhosis.

Changes in calcium fluxes in mitochondria, microsomes, and plasma membrane vesicles of livers from monosodium L-glutamate-obese rats

The purpose of this work was to evaluate if the fat liver accumulation interferes with intracellular calcium fluxes and the liver glycogenolytic response to a calcium-mobilizing α(1)-adrenergic agonist, phenylephrine. The animal model of monosodium L-glutamate (MSG)-induced obesity was used. The adult rats develop obesity and steatosis. Calcium fluxes were evaluated through measuring the (45)Ca(2+) uptake by liver microsomes, inside-out plasma membrane, and mitochondria. In the liver, assessments were performed on the calcium-dependent glycogenolytic response to phenylephrine and the glycogen contents. The Ca(2+) uptake by microsomes and plasma membrane vesicles was reduced in livers from obese rats as a result of reduction in the Ca(2+)-ATPase activities. In addition, the plasma membrane Na(+)/K(+)-ATPase was reduced. All these matched effects could contribute to elevated resting intracellular calcium levels in the hepatocytes. Livers from obese rats, albeit smaller and with similar glycogen contents to those of control rats, released higher amounts of glucose in response to phenylephrine infusion, which corroborates these observations. Mitochondria from obese rats exhibited a higher capacity of retaining calcium, a phenomenon that could be attributed to a minor susceptibility of the mitochondrial permeability transition pore opening.

Epidemiology of the metabolic syndrome in the USA

The metabolic syndrome is a common complex entity that has emerged as a worldwide epidemic and major public health care concern with a prevalence of approximately 25% in the United States. There have been a number of different definitions of the metabolic syndrome but all center around the metabolic abnormalities of central obesity, hypertension, decreased high-density lipoproteins and elevated triglycerides with insulin resistance as the uniting physiologic factor. The importance of the metabolic syndrome is not just related to its high prevalence rate but also because it predicts the development of diabetes and cardiovascular disease. Nonalcoholic fatty liver disease is now recognized to be the hepatic component of the metabolic syndrome, which along with its individual components - particularly diabetes and elevated triglycerides, are the major risk factors for the development of nonalcoholic steatohepatitis (NASH); the most severe form of nonalcoholic fatty liver disease. NASH may progress to cirrhosis, hepatocellular carcinoma, and liver failure. It is currently the third most common cause for liver transplantation and is projected to be the leading cause for liver transplantation in 2020. Weight loss (via diet or bariatric surgery) and vitamin E have recently been demonstrated to be effective treatments of NASH. Although these and other agents may prove to be effective treatments for NASH, the most effective therapeutic strategy would be early screening and intervention to prevent the development of insulin resistance and oxidative stress at a societal level.

Exercise and Omega-3 Polyunsaturated Fatty Acid Supplementation for the Treatment of Hepatic Steatosis in Hyperphagic OLETF Rats

Background and Aims. This study examined if exercise and omega-3 fatty acid (n3PUFA) supplementation is an effective treatment for hepatic steatosis in obese, hyperphagic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Methods. Male OLETF rats were divided into 4 groups (n = 8/group): (1) remained sedentary (SED), (2) access to running wheels; (EX) (3) a diet supplemented with 3% of energy from fish oil (n3PUFA-SED); and (4) n3PUFA supplementation plus EX (n3PUFA+EX). The 8 week treatments began at 13 weeks, when hepatic steatosis is present in OLETF-SED rats. Results. EX alone lowered hepatic triglyceride (TAG) while, in contrast, n3PUFAs failed to lower hepatic TAG and blunted the ability of EX to decrease hepatic TAG levels in n3PUFAs+EX. Insulin sensitivity was improved in EX animals, to a lesser extent in n3PUFA+EX rats, and did not differ between n3PUFA-SED and SED rats. Only the EX group displayed higher complete hepatic fatty acid oxidation (FAO) to CO₂ and carnitine palmitoyl transferase-1 activity. EX also lowered hepatic fatty acid synthase protein while both EX and n3PUFA+EX decreased stearoyl CoA desaturase-1 protein. Conclusions. Exercise lowers hepatic steatosis through increased complete hepatic FAO, insulin sensitivity, and reduced expression of de novo fatty acid synthesis proteins while n3PUFAs had no effect.

Differential effect of gender on hepatic fat

BACKGROUND

There are discrepant data on whether men or women have a higher risk for hepatic steatosis.

OBJECTIVE

To examine the influence of gender on hepatic adiposity in teenagers and young adults.

MATERIALS AND METHODS

We measured subcutaneous abdominal fat (SAF), intra-abdominal fat (IAF) and hepatic tissue density (a surrogate measure of hepatic fat) using CT in 505 healthy teenagers and young adults (254 males, 251 females; ages 15-22.9 years).

RESULTS

Overall, compared to men, women had higher values of SAF (P < 0.0001) but similar measures of IAF and liver tissue density (P = 0.09 and 0.92, respectively). However, when compared to overweight/obese men, overweight/obese women had strikingly similar IAF values (P = 0.85) but lower hepatic fat (P = 0.009). Multiple regression analyses indicated that, after adjusting for age and SAF, IAF independently predicted hepatic density in males (P < 0.0001) but not in females (P = 0.36). Hepatic fat increased with body mass in males from lean to overweight and obese (P < 0.0001) but not in females (P > 0.05).

CONCLUSION

When compared to overweight and obese young women, overweight and obese young men are at greater risk for hepatic steatosis, independent of IAF.

Supplementation with probiotics modifies gut flora and attenuates liver fat accumulation in rat nonalcoholic fatty liver disease model

This study aimed to evaluate the relationship between gut probiotic flora and nonalcoholic fatty liver disease in a diet-induced rat model, and to compare the effects of two different probiotic strains on nonalcoholic fatty liver disease. Forty male Sprague-Dawley rats were randomized into 4 groups for 12 weeks: control (standard rat chow), model (fat-rich diet), Lactobacillus (fat-rich diet plus Lactobacillus acidophilus), and Bifidobacterium (fat-rich diet plus Bifidobacterium longum) groups. Probiotics were provided to rats in drinking water (10¹⁰/ml). Gut bifidobacteria and lactobacilli were obviously lower at weeks 8 and 10, respectively, in the model group compared with the control group. Supplementation with Bifidobacterium significantly attenuated hepatic fat accumulation (0.10 ± 0.03 g/g liver tissue) compared with the model group (0.16 ± 0.03 g/g liver tissue). However, there was no improvement in intestinal permeability in either the Lactobacillus or the Bifidobacterium group compared with the model group. In all 40 rats, the hepatic total lipid content was negatively correlated with gut Lactobacillus (r = −0.623, p = 0.004) and Bifidobacterium (r = −0.591, p = 0.008). Oral supplementation with probiotics attenuates hepatic fat accumulation. Further, Bifidobacterium longum is superior in terms of attenuating liver fat accumulation than is Lactobacillus acidophilus.

Potential role of leptin, adiponectin and three novel adipokines--visfatin, chemerin and vaspin--in chronic hepatitis

Chronic hepatitis C (CHC) is generally a slowly progressive disease, but some factors associated with rapid progression have been identified. Steatosis, independently of its metabolic or viral origin, leads to liver injury and fibrosis. It is suggested that hepatitis C virus may contribute to a wide spectrum of metabolic disturbances-namely, steatosis, insulin resistance, increased prevalence of impaired glucose tolerance, type 2 diabetes mellitus and lipid metabolism abnormalities. Adipokines, which are produced mainly by adipose tissue, may influence the inflammatory response and insulin sensitivity and contribute to the development of metabolic abnormalities in CHC and also regulate fibrogenesis and angiogenesis. Visfatin was described as an adipokine with immunomodulating and proinflammatory properties that promotes B-cell maturation and enhances activation of leukocytes, synthesis of adhesion molecules and production of proinflammatory cytokines. Visfatin exerts insulin-mimetic effects, decreases plasma glucose levels and regulates cell energy balance. Chemerin stimulates chemotaxis of dendritic cells, macrophages and natural killer (NK) cells toward the site of inflammation. On the other hand, it inhibits synthesis of proinflammatory mediators and enhances adiponectin production, influences adipocyte differentiation and maturation and regulates glucose uptake in adipocytes. Vaspin expression in human adipose tissue seems to be a compensatory mechanism associated with obesity and insulin resistance. Vaspin suppresses leptin, tumor necrosis factor (TNF)-α and resistin expression. Leptin protects against liver steatosis but accelerates fibrosis progression and exacerbates the inflammatory process. In contrast, adiponectin exerts a hepatoprotective effect. In this report, data indicating a possible role of these adipokines in the pathogenesis of chronic hepatitis are summarized.

Nonalcoholic Fatty liver disease: focus on lipoprotein and lipid deregulation

Obesity with associated comorbidities is currently a worldwide epidemic and among the most challenging health conditions in the 21st century. A major metabolic consequence of obesity is insulin resistance which underlies the pathogenesis of the metabolic syndrome. Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of obesity and metabolic syndrome. It comprises a disease spectrum ranging from simple steatosis (fatty liver), through nonalcoholic steatohepatitis (NASH) to fibrosis, and ultimately liver cirrhosis. Abnormality in lipid and lipoprotein metabolism accompanied by chronic inflammation is the central pathway for the development of metabolic syndrome-related diseases, such as atherosclerosis, cardiovascular disease (CVD), and NAFLD. This paper focuses on pathogenic aspect of lipid and lipoprotein metabolism in NAFLD and the relevant mouse models of this complex multifactorial disease.

Fatty Liver and Metabolic Syndrome in Nonabdominally Obese Taiwanese Adults

The aim of this study was to examine the relationship between fatty liver (FL), abdominal obesity, and metabolic syndrome (MetS). A total of 3058 adults who underwent health examinations in 2005 were enrolled. MetS was defined according to the National Cholesterol Educational Program’s Adult Treatment Panel III criteria. The relationship between FL, abdominal obesity, and MetS was analyzed using multiple logistic regression. The authors found that participants with FL alone [FL(+)/abdominal obesity(−)] had a significantly higher odds ratio for hyperglycemia (odds ratio [OR] = 2.2; 95% confidence interval [CI] = 1.5-3.3), hypertriglyceridemia (OR = 2.2; 95% CI = 1.6-3.0), low high-density lipoprotein cholesterol (OR = 2.2; 95% CI = 1.6-3.2) and a clustering of MetS components (OR = 2.5; 95% CI = 1.8-3.4) compared with participants with only abdominal obesity [FL(−)/abdominal obesity(+)]. Participants who had FL and abdominal obesity [FL(+)/abdominal obesity(+)] had the highest odds ratio for developing MetS and its components. It is concluded that FL is associated with the components of MetS independent of abdominal obesity. For nonabdominally obese patients, FL provides important information on MetS.

Does physical inactivity cause nonalcoholic fatty liver disease?

While physical activity represents a key element in the prevention and management of many chronic diseases, we and others believe that physical inactivity is a primary cause of obesity and associated metabolic disorders. Unfortunately, accumulating evidence suggests that we have engineered physical activity out of our normal daily living activity. One such consequence of our sedentary and excessive lifestyle is nonalcoholic fatty liver disease (NAFLD), which is now considered the most common cause of chronic liver disease in Westernized societies. In this review, we will present evidence that physical inactivity, low aerobic fitness, and overnutrition, either separately or in combination, are an underlying cause of NAFLD.

Higher Risk of Severe Drug-Induced Liver Injury among Hispanic HIV-Infected Patients after Initiation of Highly Active Antiretroviral Therapy

BACKGROUND

Little is known about differences across ethnicities in the development of drug-induced liver injury (DILI) after highly active antiretroviral therapy (HAART) initiation.

METHODS

This is a retrospective, longitudinal, comparative, pilot study. DILI within the first year of HAART was evaluated in 50 HIV-infected Hispanics without viral hepatitis who initiated HAART between 2000 and 2009. It was compared to white and black patients (1:1:1) matched by age and CD4 counts.

RESULTS

HAART-related DILI of any grade occurred in 30 of 150 (20%) patients and was associated with nonnucleoside reverse transcriptase inhibitor (NNRTI) use (OR 4.49 [95%CI 1.5-13.8]). Severe DILI was significantly more frequent among Hispanics compared to other groups (6% vs. 0%; P = .04). Of the 3 patients with severe DILI, 2 underwent liver imaging and had hepatic steatosis.

CONCLUSIONS

Severe DILI within the first year of HAART initiation was infrequent and restricted to Hispanics. Additional studies are needed to determine if fatty liver is involved in the excess of severe DILI observed in this group.

Effect of gender on intra-abdominal fat in teenagers and young adults

BACKGROUND

Adult men accumulate greater intra-abdominal fat (IAF) than adult women, a difference closely related to gender differences in cardiometabolic disease risk in the elderly. However, the time when this gender difference appears is a matter of controversy.

OBJECTIVE

We examine the influence of gender on IAF deposition in lean, overweight and obese teenagers and young adults.

MATERIALS AND METHODS

We measured subcutaneous abdominal fat (SAF) and IAF in 505 healthy sexually mature teenagers and young adults (254 males, 251 females; 15-22 years) using a single CT scan at the level of the umbilicus.

RESULTS

Regardless of body size, young females had greater SAF values than young males. Although lean females had higher IAF values than lean males (13.7 ± 7.8 vs. 11.2 ± 5.4; P = 0.001), overweight and obese females and males had strikingly similar IAF values (23.4 ± 11.1 vs. 23.1 ± 9.5; P = 0.88 and 36.5 ± 20.4 vs. 38.8 ± 13.2; P = 0.59, respectively). In contrast, the ratio of IAF/SAF was greater in males than females, except in the very obese. Multiple regression analysis indicated that while gender was a strong predictor of SAF in lean and overweight subjects (P's < 0.0001), it did not influence IAF after adjusting for height and weight (P = 0.35 and 0.65, respectively) in overweight and obese subjects.

CONCLUSION

Overweight and obese young women have similar absolute amounts of IAF as young men.

Activation of peroxisome proliferator-activated receptor gamma by rosiglitazone increases sirt6 expression and ameliorates hepatic steatosis in rats

BACKGROUND

Sirt6 has been implicated in the regulation of hepatic lipid metabolism and the development of hepatic steatosis. The aim of this study was to address the potential role of Sirt6 in the protective effects of rosiglitazone (RGZ) on hepatic steatosis.

METHODS

To investigate the effect of RGZ on hepatic steatosis, rats were treated with RGZ (4 mg·kg⁻¹·day⁻¹) by stomach gavage for 6 weeks. The involvement of Sirt6 in the RGZ's regulation was evaluated by Sirt6 knockdown in AML12 mouse hepatocytes.

RESULTS

RGZ treatment ameliorated hepatic lipid accumulation and increased expression of Sirt6, peroxisome proliferator-activated receptor gamma coactivtor-1-α (Ppargc1a/PGC1-α) and Forkhead box O1 (Foxo1) in rat livers. AMP-activated protein kinase (AMPK) phosphorylation was also increased by RGZ, accompanied by alterations in phosphorylation of LKB1. Interestingly, in free fatty acid-treated cells, Sirt6 knockdown increased hepatocyte lipid accumulation measured as increased triglyceride contents (p = 0.035), suggesting that Sirt6 may be beneficial in reducing hepatic fat accumulation. In addition, Sirt6 knockdown abolished the effects of RGZ on hepatocyte fat accumulation, mRNA and protein expression of Ppargc1a/PGC1-α and Foxo1, and phosphorylation levels of LKB1 and AMPK, suggesting that Sirt6 is involved in RGZ-mediated metabolic effects.

CONCLUSION

Our results demonstrate that RGZ significantly decreased hepatic lipid accumulation, and that this process appeared to be mediated by the activation of the Sirt6-AMPK pathway. We propose Sirt6 as a possible therapeutic target for hepatic steatosis.

Ceramide-mediated insulin resistance and impairment of cognitive-motor functions

Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) are associated with cognitive impairment, brain insulin resistance, and neurodegeneration. Recent studies linked these effects to increased pro-ceramide gene expression in liver and increased ceramide levels in serum. Since ceramides are neurotoxic and cause insulin resistance, we directly examined the role of ceramides as mediators of impaired signaling and central nervous system function using an in vivo model. Long Evans rat pups were administered C2Cer:N-acetylsphinganine or its inactive dihydroceramide analog (C2DCer) by i.p. injection. Rats were subjected to rotarod and Morris water maze tests of motor and cognitive function, and livers and brains were examined for histopathology and integrity of insulin/IGF signaling. C2Cer treatment caused hyperglycemia, hyperlipidemia, and mild steatohepatitis, reduced brain lipid content, and increased ceramide levels in liver, brain, and serum. Quantitative RT-PCR analysis revealed significant alterations in expression of several genes needed for insulin and IGF-I signaling, and multiplex ELISAs demonstrated inhibition of signaling through the insulin or IGF-1 receptors, IRS-1, and Akt in both liver and brain. Ultimately, the toxic ceramides generated in peripheral sources such as liver or adipose tissue caused sustained impairments in neuro-cognitive function and insulin/IGF signaling needed for neuronal survival, plasticity, and myelin maintenance in the brain. These findings support our hypothesis that a liver/peripheral tissue-brain axis of neurodegeneration, effectuated by increased toxic lipid/ceramide production and transport across the blood-brain barrier, could mediate cognitive impairment in T2DM and NASH.

Leptin induces nitric oxide-mediated inhibition of lipolysis and glyceroneogenesis in rat white adipose tissue

Leptin is secreted by white adipose tissue (WAT) and induces lipolysis and nonesterified fatty acid (NEFA) oxidation. During lipolysis, NEFA efflux is the result of triglyceride breakdown, NEFA oxidation, and re-esterification via glyceroneogenesis. Leptin's effects on glyceroneogenesis remain unexplored. We investigated the effect of a long-term treatment with leptin at a physiological concentration (10 μg/L) on lipolysis and glyceroneogenesis in WAT explants and analyzed the underlying mechanisms. Exposure of rat WAT explants to leptin for 2 h resulted in increased NEFA and glycerol efflux. However, a longer treatment with leptin (18 h) did not affect NEFA release and reduced glycerol output. RT-qPCR showed that leptin significantly downregulated the hormone-sensitive lipase (HSL), cytosolic phosphoenolpyruvate carboxykinase (Pck1), and PPARγ genes. In agreement with its effect on mRNA, leptin also decreased the levels of PEPCK-C and HSL proteins. Glyceroneogenesis, monitored by [1-(14) C] pyruvate incorporation into lipids, was reduced. Because leptin increases nitric oxide (NO) production in adipocytes, we explored the role of NO in the leptin signaling pathway. Pretreatment of explants with the NO synthase inhibitor Nω-nitro-l-arginine methyl ester eliminated the effect of leptin on lipolysis, glyceroneogenesis, and expression of the HSL, Pck1, and PPARγ genes. The NO donor S-nitroso-N-acetyl-DL penicillamine mimicked leptin effects, thus demonstrating the role of NO in these pathways. The inverse time-dependent action of leptin on WAT is consistent with a process that limits NEFA re-esterification and energy storage while reducing glycerol release, thus preventing hypertriglyceridemia.

The impact of breakfast in metabolic and digestive health

AIM

The purpose of this study is to explore whether the types and quality of breakfast could influence energy levels (blood glucose levels) and propose ideal breakfast models.

BACKGROUND

It is widely considered that a regular breakfast provides a number of health benefits; however, there is no general scientific agreement regarding what kind of food should be consumed. Evidence supports the importance of balancing blood glucose levels by low glycaemic index/load (L-GI/L) and increased protein diets, in particular in metabolic disorders, which non-alcoholic fatty liver disease (NAFLD) has a close relation to.

PATIENTS AND METHODS

This study was conducted by using a valid and standard questionnaire at the University of Worcester to evaluate the breakfast and dietary habits and energy levels. The Kruskal-Wallis test was used for statistical analysis.

RESULTS

No significant differences were found either between breakfast consumption, energy levels, types of snack and amount of caffeine intake in the morning or between types of breakfast, energy levels, types of snack, and amount of caffeine intake in the morning. However, potential differences in energy levels were found across the groups of breakfast types: glycaemia (GL) (p=.057) and protein intake (p=.056).

CONCLUSION

The types and quality of breakfast would be key as regular breakfast consumption alone did not show adequate health benefits. Lower GL foods and higher protein intake at breakfast were found to be associated with higher energy levels. It is therefore recommended that breakfast foods should be low in GL and high in protein. These changes may lead to better health status and prevention of disease, especially metabolic and liver disorders, in the long term.

Fructose and NAFLD: metabolic implications and models of induction in rats

PURPOSE: The increase in fructose consumption is paralleled by a higher incidence of obesity worldwide. This monosaccharide is linked to metabolic syndrome, being associated with hypertriglyceridemia, hypertension, insulin resistance and diabetes mellitus. It is metabolized principally in the liver, where it can be converted into fatty acids, which are stored in the form of triglycerides leading to NAFLD. Several models of NAFLD use diets high in simple carbohydrates. Thus, this study aimed to describe the major metabolic changes caused by excessive consumption of fructose in humans and animals and to present liver abnormalities resulting from high intakes of fructose in different periods of consumption and experimental designs in Wistar rats. METHODS: Two groups of rats were fasted for 48 hours and reefed for 24 or 48 hours with a diet containing 63% fructose. Another group of rats was fed an diet with 63% fructose for 90 days. RESULTS: Refeeding for 24 hours caused accumulation of large amounts of fat, compromising 100% of the hepatocytes. The amount of liver fat in animals refed for 48 hours decreased, remaining mostly in zone 2 (medium-zonal). In liver plates of Wistar rats fed 63% fructose for 45, 60 and 90 days it's possible to see that there is an increase in hepatocytes with fat accumulation according to the increased time; hepatic steatosis, however, is mild, compromising about 20% of the hepatocytes. CONCLUSIONS: Fructose is highly lipogenic, however the induction of chronic models in NAFLD requires long periods of treatment. The acute supply for 24 or 48 hours, fasted rats can cause big changes, liver steatosis with macrovesicular in all lobular zones.

Insulin resistance index (HOMA-IR) in the differentiation of patients with non-alcoholic fatty liver disease and healthy individuals

CONTEXT

Due to its good correlation to glycemic clamp, HOMA-IR has been widely utilized as insulin resistance index in clinical and epidemiological studies involving non-alcoholic fatty liver disease carriers. However, values used for this parameter have shown large variability.

OBJECTIVE

To identify the HOMA-IR cut value that best distinguishes non-diabetic non-alcoholic fatty liver disease patients from a control group.

METHODS

One hundred sixteen non-alcoholic fatty liver disease patients were studied, diagnosed by clinical, biochemical, and liver image or biopsy criteria, and 88 healthy individuals, without any liver disease and testing for oral glucose tolerance within normality. These groups did not differ in age and gender. All were submitted to oral glucose tolerance test and blood samples were collected for glucose and insulin measurements by immunofluorometric method. HOMA-IR was calculated according to the formula: fasting insulin (microU/L) x fasting glucose (nmol/L)/22.5.

RESULTS

NAFLD patients showed higher insulin, glycemia, and HOMA-IR values than control group, even when excluding glucose intolerant and diabetes mellitus patients by their glycemic curves. HOMA-IR 75th percentile for control group was 1.78 and the best area under the curve index was obtained for HOMA-IR values of 2.0 [AUC= 0.840 (0.781-0.899 CI 95%), sensitivity (Se): 85%, specificity (Sp): 83%] while value 2.5 showed best specificity without important loss in sensitivity [AUC=0,831 (0.773-0.888) Se = 72%, Sp = 94%].

CONCLUSION

HOMA-IR values above or equal to 2.0 or 2.5 show enhanced diagnostic value in distinguishing non-alcoholic fatty liver disease carriers from control group individuals.

Insulin resistance, steatohepatitis, and hepatocellular carcinoma in a new congenic strain of Fatty Liver Shionogi (FLS) mice with the Lep(ob) gene

In order to examine the influence of obesity on metabolic disorder and liver pathogenesis of the Fatty Liver Shionogi (FLS) mouse, which develops hereditary fatty liver and spontaneous liver tumors, we established a new congenic strain named FLS-Lep(ob). The Lep(ob) gene of the C57BL/6JWakShi (B6)-Lep(ob)/Lep(ob) mouse was transferred into the genome of the FLS mouse, by backcross mating. FLS-Lep(ob)/Lep(ob) mice were maintained by intercrossing between Lep(ob)-heterozygous littermates. The FLS-Lep(ob)/Lep(ob) mice of both sexes developed remarkable hyperphagia, obesity and type 2 diabetes mellitus. At 12 weeks of age, glucosuria was detected in all male and female FLS-Lep(ob)/Lep(ob) mice. Biochemical examination demonstrated that the FLS-Lep(ob)/Lep(ob) mice have severe hyperlipidemia and hyperinsulinemia. The livers of FLS-Lep(ob)/Lep(ob) mice showed microvesicular steatosis and deposition of large lipid droplets in hepatocytes throughout the lobules. The steatohepatitis-like lesions including the multifocal mononuclear cell infiltration and clusters of foamy cells were observed earlier in FLS-Lep(ob)/ Lep(ob) mice than in FLS mice. B6-Lep(ob)/Lep(ob) mice did not show hepatic inflammatory change. Furthermore, FLS-Lep(ob)/Lep(ob) mice developed multiple hepatic tumors including hepatocellular adenomas and carcinomas following steatohepatitis. In conclusion, the FLS-Lep(ob)/Lep(ob) mice developed steatohepatitis and hepatic tumors following hepatic steatosis. The FLS-Lep(ob)/Lep(ob) mouse with obesity and type 2 diabetes mellitus might be a useful animal model for human non-alcoholic steatohepatitis (NASH).

Fatty liver and global cardiometabolic risk

A nem alkoholos zsírmáj betegség (NAFLD = nonalcoholic fatty liver disease) az „iparilag fejlett” országok felnőtt lakosságának 30%-ában észlelhető. Előrehaladott, súlyosabb formája a nem alkoholos steatohepatitis (NASH = nonalcoholic steatohepatitis), amelyből az esetek 20%-ában cirrhosis alakul ki, a kialakult cirrhosis mintegy 30–40%-a májeredetű halálhoz, elsősorban hepatocellularis carcinomához vezethet. Az NAFLD-t sokan a metabolikus szindróma májbeli manifesztációjának tartják, e két jelenség kapcsolatát tekintjük át, különös tekintettel a hasi elhízás, az inzulinrezisztencia, az oxidatív stressz és a csökkent antioxidáns védelem kóroki szerepére. A májsejtek trigliceridtartalmának növekedése együtt jár az egész szervezet, illetve a máj inzulinrezisztenciájával. Klasszikus tyúk–tojás probléma: a lipidlerakódás oka az inzulinrezisztencia, vagy az inzulinrezisztencia az ectopiás lipidfelhalmozódás következménye? A patogenetikai történések egy lehetséges sorrendje: megnövekedett zsírsavfluxus, a májbeli zsírsavkínálat növekedése → VLDL-túltermelődés, atherogen dyslipidaemia → a zsírsavak fokozott oxidációja és peroxidációja, enormis szabadgyök-terhelés → az antioxidáns védekezőrendszer kimerülése → a gyulladást és az immunválaszt kiváltó mediátorok „cunamiszerű” kiáramlása → a fibrosis progresszióját elősegítő transzkripciós és transzlációs változások → carcinogenesis. Az NAFLD és a metabolikus szindróma egyaránt része a globális kardiometabolikus kockázatnak, így lényeges a korai felismerés, és – amennyiben lehetséges a kezelés – ez ma a metabolikus szindróma részelemeinek kezelési ajánlásaiban testesül meg. Orv. Hetil., 2010, 47, 1946–1950.

Nonalcoholic fatty liver disease is related to nonalcoholic fatty pancreas disease

OBJECTIVES

Obesity and insulin resistance cause fatty infiltration of many organs, including the pancreas (pancreatic steatosis [PS]) and the liver (nonalcoholic fatty liver disease [NAFLD]). In contrast to NAFLD, pathophysiological mechanisms and clinical relevance of PS remain unknown. This study aimed to identify a possible relation between PS and NAFLD.

METHODS

In this study including postmortem collected material of 80 patients, clinical and histological data were collected and revised. Patients with hepatic or pancreatic disease and alcohol abuse were excluded. Nonalcoholic fatty liver disease activity score was used for grading the histology of the liver, whereas pancreatic lipomatosis score assessed PS. Ordinal logistic regression was used to analyze correlations.

RESULTS

Interlobular and total pancreatic fat were both related to NAFLD activity score in patients without steatogenic medication (P = 0.02 and P = 0.03, respectively). When corrected for body mass index, no relation could be found. Total pancreatic fat was a significant predictor for the presence of NAFLD (P = 0.02). Presence of intralobular pancreatic fat was related to nonalcoholic steatohepatitis; however, total fat was not.

CONCLUSIONS

This study demonstrates that NAFLD and PS are related. This relationship seems to be mediated by general obesity. Intralobular pancreatic fat is associated with nonalcoholic steatohepatitis.

Clinical syndromes and consequences of antiretroviral-related hepatotoxicity

Highly active antiretroviral therapy (HAART)-related hepatotoxicity complicates the management of patients infected with human immunodeficiency virus (HIV), increases medical costs, alters the prescription patterns, and affects the guideline recommendations. Among the clinical consequences derived from HAART-related liver toxicity, hypersensitivity reactions and lactic acidosis are recognized as acute events with potential to evolve into fatal cases, whereas there seems to be other syndromes not as well characterized but of equal concern as possible long-term liver complications. Belonging to the latter category of syndrome, HAART-related nonalcoholic steatohepatitis, liver fibrosis, portal hypertension, and nodular regenerative hyperplasia are discussed in this review. Updated information on liver toxicity of current antiretroviral drugs, including the most recently licensed, is provided. Management and prevention of liver toxicity among HIV-infected patients treated with HAART are reviewed as well.

Association of cardiorespiratory fitness with elevated hepatic enzyme and liver fat in Japanese patients with impaired glucose tolerance and type 2 diabetes mellitus

No study has so far determined whether a favorable level of cardiorespiratory fitness (CF) contributes to a reduced risk of elevated hepatic enzymes and a high degree of liver fat in patients having various metabolic risks. This study investigated the association between the maximal oxygen uptake (VO2 max) and the prevalence of elevated liver enzymes and high liver fat, while considering such factors as abdominal obesity, hyperinsulinemia and the other metabolic risks. The study enrolled newly diagnosed Japanese patients (n = 84; 52 males and 32 females; aged 25-69 years) with impaired glucose tolerance (IGT) and type 2 diabetes mellitus (Type2DM) who did not receive any intervention or pharmacological therapy. The subjects were divided into 3 groups according to the distribution of the VO2max for each sex. The odds ratios (ORs) for the prevalence of elevated aspartate and alanine aminotransferase (AST and ALT) and high degree of liver fat adjusted for age, sex, disease type, daily ethanol intake, and current smoking were significantly lower in the moderate- and high CF groups in comparison to the low CF group. In addition, a significant OR for AST was maintained in the moderate and high CF group after adjusting for abdominal obesity and/or hyperinsulinemia. The significant ORs for the prevalence of elevated ALT and a high degree of liver fat were attenuated after adjusting for abdominal obesity and/or hyperinsulinemia. No significant OR for the prevalence of elevated gamma-glutamyl transferase (GGT) was recognized in all logistic models. These results indicated that CF was negatively and independently associated with the prevalence of elevated AST even in Japanese diabetic patients having various metabolic risks. It was concluded that the AST level might be useful as a simple marker reflecting physical inactivity in such subjects. Key pointsThe prevalence of elevated AST was negatively, and strongly associated with the CF level independent of abdominal obesity, hyperinsulinemia, and the other confounders in the subjects with glucose intolerance.The association between the CF level and both an elevated ALT level and a high degree of liver fat, as defined by the L/S ratio of CT images depended on abdominal fat and/or hyperinsulinemia in the subjects with glucose intolerance.No association was recognized between CF and elevated GGT in the subjects with glucose intolerance in the subjects with glucose intolerance.Having a favorable level of CF could lead to a reduced risk of hepatic-related abnormalities even in diabetic patients having the other metabolic risks.

The diagnostic accuracy of US, CT, MRI and 1H-MRS for the evaluation of hepatic steatosis compared with liver biopsy: a meta-analysis

Objective

To meta-analyse the diagnostic accuracy of US, CT, MRI and ¹H-MRS for the evaluation of hepatic steatosis.

Methods

From a comprehensive literature search in MEDLINE, EMBASE, CINAHL and Cochrane (up to November 2009), articles were selected that investigated the diagnostic performance imaging techniques for evaluating hepatic steatosis with histopathology as the reference standard. Cut-off values for the presence of steatosis on liver biopsy were subdivided into four groups: (1) >0, >2 and >5% steatosis; (2) >10, >15 and >20%; (3) >25, >30 and >33%; (4) >50, >60 and >66%. Per group, summary estimates for sensitivity and specificity were calculated. The natural-logarithm of the diagnostic odds ratio (lnDOR) was used as a single indicator of test performance.

Results

46 articles were included. Mean sensitivity estimates for subgroups were 73.3–90.5% (US), 46.1–72.0% (CT), 82.0–97.4% (MRI) and 72.7–88.5% (¹H-MRS). Mean specificity ranges were 69.6–85.2% (US), 88.1–94.6% (CT), 76.1–95.3% (MRI) and 92.0–95.7% (¹H-MRS). Overall performance (lnDOR) of MRI and ¹H-MRS was better than that for US and CT for all subgroups, with significant differences in groups 1 and 2.

Conclusion

MRI and ¹H-MRS can be considered techniques of choice for accurate evaluation of hepatic steatosis.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-010-1905-5) contains supplementary material, which is available to authorized users.

Gout and risk of non-alcoholic fatty liver disease

OBJECTIVES

To investigate the association between gout and non-alcoholic fatty liver disease (NAFLD).

METHODS

The study subjects were participants in a health-screening programme at Chang Gung Memorial Hospital from 2000 to 2006. Subjects were classified into eight groups based on serum urate (SU) level and gout status (≤ 4.9, 5.0-6.9, 7.0-8.9, and ≥ 9.0 mg/dL, without and with gout). The association between gout and NAFLD was assessed by multiple logistic regression.

RESULTS

Among a total of 54 325 subjects, 1930 (3.6%) had gout and 6169 (11.3%) had NAFLD. The prevalence of NAFLD was significantly higher in subjects with gout (23.1%, n = 445) than in those without gout (10.9%, n = 5724, p < 0.001). Among subjects with NAFLD, the severity of NAFLD was higher in gout patients. Gout was associated with an increased risk for NAFLD [odds ratio (OR) 1.42, 95% confidence interval (CI) 1.25-1.60, p < 0.001], after adjustment for age, sex, presence of metabolic syndrome, and low estimated glomerular filtration rate (eGFR). With SU ≤ 4.9 mg/dL in the absence of gout as reference, the ORs (95% CI) for NAFLD, after adjustment for age, sex, presence of metabolic syndrome, and low eGFR, were, respectively, 2.16 (1.94-2.41), 3.98 (3.55-4.46), and 5.99 (5.19-6.90) for SU levels 2-4 in those without gout and 2.61 (1.39-4.91), 2.87 (2.04-4.04), 4.53 (3.70-5.56), and 6.31 (5.12-7.77) for SU levels 1-4 in those with gout.

CONCLUSIONS

There was an independent association between gout and the risk for NAFLD. In addition, there was a dose-response relationship between SU and NAFLD in subjects with and without gout.

Intake of trans fatty acids causes nonalcoholic steatohepatitis and reduces adipose tissue fat content

We investigated the effects of dietary trans fatty acids, PUFA, and SFA on body and liver fat content, liver histology, and mRNA of enzymes involved in fatty acid metabolism. LDL receptor knockout weaning male mice were fed for 16 wk with diets containing 40% energy as either trans fatty acids (TRANS), PUFA, or SFA. Afterwards, subcutaneous and epididymal fat were weighed and histological markers of nonalcoholic fatty liver disease (NAFLD) were assessed according to the Histological Scoring System for NAFLD. PPARalpha, PPARgamma, microsomal triglyceride transfer protein (MTP), carnitine palmitoyl transferase 1 (CPT-1), and sterol regulatory element binding protein-1c (SREBP-1c) mRNA were measured by quantitative RT-PCR. Food intake was similar in the 3 groups, although mice fed the TRANS diet gained less weight than those receiving the PUFA diet. Compared with the PUFA- and SFA-fed mice, TRANS-fed mice had greater plasma total cholesterol (TC) and triglyceride (TG) concentrations, less epididymal and subcutaneous fat, larger livers with nonalcoholic steatohepatitis (NASH)-like lesions, and greater liver TC and TG concentrations. Macrosteatosis in TRANS-fed mice was associated with a higher homeostasis model assessment of insulin resistance (HOMA(IR)) index and upregulated mRNA related to hepatic fatty acid synthesis (SREBP-1c and PPARgamma) and to downregulated MTP mRNA. Diet consumption did not alter hepatic mRNA related to fatty acid oxidation (PPARalpha and CPT-1). In conclusion, compared with PUFA- and SFA-fed mice, TRANS-fed mice had less adiposity, impaired glucose tolerance characterized by greater HOMA(IR) index, and NASH-like lesions due to greater hepatic lipogenesis. These results demonstrate the role of trans fatty acid intake on the development of key features of metabolic syndrome.

Advances in understanding the role of complement in the pathogenesis of fatty liver disease

Patients with fatty liver disease (FLD) exhibit various immunologic abnormalities in the adipose tissue and the liver. Complement plays an important role in the development of FLD. Innate immune dysfunction in the adipose tissue can lead to abnormal production of adipose-derived factors, some of which can activate complement. Complement can not only amplify the inflammatory response and lead to mitochondrial damage, but also inhibit hepatic fat disposal and promote lipid accumulation in hepatocytes. An exploration of the relationship between complement ant the liver can help us have a deep understanding of the mechanisms underlying the pathogenesis of FLD. The antagonists of the C5L2 receptor provide us potential new medicines for FLD. A further study of the role of complement in stress-induced liver remodeling can help clarify the role of complement in the development and progression of FLD.

Glutathione deficiency down-regulates hepatic lipogenesis in rats

BACKGROUND

Oxidative stress is supposed to increase lipid accumulation by stimulation of hepatic lipogenesis at transcriptional level. This study was performed to investigate the role of glutathione in the regulation of this process. For that purpose, male rats were treated with buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase, for 7 days and compared with untreated control rats.

RESULTS

BSO treatment caused a significant reduction of total glutathione in liver (-70%), which was attributable to diminished levels of reduced glutathione (GSH, -71%). Glutathione-deficient rats had lower triglyceride concentrations in their livers than the control rats (-23%), whereas the circulating triglycerides and the cholesterol concentrations in plasma and liver were not different between the two groups of rats. Livers of glutathione-deficient rats had lower mRNA abundance of sterol regulatory element-binding protein (SREBP)-1c (-47%), Spot (S)14 (-29%) and diacylglycerol acyltransferase 2 (DGAT-2, -27%) and a lower enzyme activity of fatty acid synthase (FAS, -26%) than livers of the control rats. Glutathione-deficient rats had also a lower hepatic activity of the redox-sensitive protein-tyrosine phosphatase (PTP)1B, and a higher concentration of irreversible oxidized PTP1B than control rats. No differences were observed in protein expression of total PTP1B and the mature mRNA encoding active XBP1s, a key regulator of unfolded protein and ER stress response.

CONCLUSION

This study shows that glutathione deficiency lowers hepatic triglyceride concentrations via influencing lipogenesis. The reduced activity of PTP1B and the higher concentration of irreversible oxidized PTP1B could be, at least in part, responsible for this effect.

Analysis of transcriptome and metabolome profiles alterations in fatty liver induced by high-fat diet in rat

Excessive energy intake greatly contributes to the development of nonalcoholic fatty liver disease (NAFLD) in modern society. To better understand the comprehensive mechanisms of NAFLD development, we investigated the metabolic alterations of rats with NAFLD induced by high-fat diet (HFD). Male Wistar rats were fed a HFD or standard chow for control. After 16 weeks, rat serum was collected for biochemical measurement. The rats' livers were resected and subjected to histology inspection and gene expression analysis with complementary DNA microarray and metabolic analysis with gas chromatography-mass spectroscopy. In HFD rats, the serum cholesterol, triglycerides, glucose, and insulin contents were increased; and the total cholesterol and triglycerides in the livers were also significantly increased. Complementary DNA microarray analysis revealed that 130 genes were regulated by HFD. Together with real-time reverse transcriptase polymerase chain reaction, lipid metabolism regulatory members like sterol regulatory element binding factor 1 and stearoyl-coenzyme A desaturase 1 had up-regulation, whereas others like peroxisome proliferator-activated receptor, carnitine palmitoyltransferase 1, and 3-hydroxy-3-methylglutaryl-coenzyme A reductase had repressed expression, in HFD rat livers. Metabolomic analysis showed that tetradecanoic acid, hexadecanoic acid, and oleic acid had elevation and arachidonic acid and eicosapentaenoic acid had decreased content in HFD rat livers. Amino acids including glycine, alanine, aspartic acid, glutamic acid, and proline contents were decreased. The integrative results from transcriptomic and metabolomic studies revealed that, in HFD rat livers, fatty acid utilization through beta-oxidation was inhibited and lipogenesis was enhanced. These observations facilitated our understanding of the pathways involved in the development of NAFLD induced by HFD.

Regulation of hepatic gene expression by saturated fatty acids

Diets rich in saturated fatty acids have long been associated with increased plasma cholesterol concentrations and hence increased risk of cardiovascular disease. More recently, they have also been suggested to promote the development of non-alcoholic fatty liver disease. While there is now considerable evidence to suggest that polyunsaturated fatty acids exert many of their effects through regulating the activity of transcription factors, including peroxisome proliferator activated receptors, sterol regulatory binding proteins (SREBPs) and liver X receptor, our understanding of how saturated fatty acids act is still limited. Here we review the potential mechanisms whereby saturated fatty acids modulate hepatic lipid metabolism thereby impacting on the synthesis, storage and secretion of lipids. Evidence is presented that their effects are, at least partly, mediated through modulation of the activity of the SREBP family of transcription factors.

Metabolic syndrome-related composite factors over 5 years in the STANISLAS family study: genetic heritability and common environmental influences

BACKGROUND

We estimated genetic heritability and common environmental influences for various traits related to metabolic syndrome in young families from France.

METHODS

At entrance and after 5 years, nineteen traits related to metabolic syndrome were measured in a sample of families drawn from the STANISLAS study. In addition, 5 aggregates of these traits were identified using factor analysis.

RESULTS

At entrance, genetic heritability was high (20 to 44%) for plasma lipids and lipoproteins, uric acid, fasting glucose, and the related clusters "risk lipids" and "protective lipids". Intermediate or low genetic heritability (less than 20%) was shown for triglycerides, adiposity indices, blood pressure, hepatic enzyme activity, inflammatory makers and the related clusters: "liver enzymes", "adiposity/blood pressure" and "inflammation". Moreover, common environmental influences were significant for all the parameters. With regard to 5-year changes, polygenic variance was low and not statistically significant for any of the individual variables or clusters whereas shared environment influence was significant.

CONCLUSIONS

In these young families, genetic heritability of metabolic syndrome-related traits was generally lower than previously reported while the common environmental influences were greater. In addition, only shared environment contributed to short-term changes of these traits.

Sex-dependent associations of leptin with metabolic syndrome-related variables: the Stanislas study

Serum leptin has been reported to be associated in a sex-dependent manner with C-reactive protein (CRP), independently of adiposity. We tested the hypothesis that leptin is associated, independently of anthropometry indexes and in a sex-dependent way, with other inflammatory markers and variables related to metabolic syndrome (MS). In 384 healthy middle-aged adults (192 men and 192 women) total fat mass (FM), waist circumference (WC), serum leptin and 15 MS-related parameters (systolic and diastolic blood pressure, triglycerides, cholesterol, high density lipoprotein (HDL)-cholesterol, apo AI and B, fasting glucose, uric acid, CRP, orosomucoid and haptoglobin levels and aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and gamma-glutamyl transferase (GGT) activities) were measured. After adjustment for age, alcohol and cigarette consumption, WC, and total FM, leptin concentration was significantly associated with serum triglycerides, total cholesterol, apo B, uric acid and haptoglobin concentrations and liver enzyme activity only in men, and with apo AI, HDL-cholesterol (only borderline) and CRP only in women. Sex interaction terms were significant for total cholesterol, apo B, HDL cholesterol, uric acid, ALAT and GGT, and borderline significant for triglycerides, apo AI and ASAT. In this healthy population, leptin is significantly associated with various MS factors, independently of WC and total FM, depending on gender. Our study provides further evidence of sex-related differences mediated by leptin in inflammatory mechanisms and other MS-related metabolic pathways.

Nitrosamine exposure exacerbates high fat diet-mediated type 2 diabetes mellitus, non-alcoholic steatohepatitis, and neurodegeneration with cognitive impairment

Background

The current epidemics of type 2 diabetes mellitus (T2DM), non-alcoholic steatohepatitis (NASH), and Alzheimer's disease (AD) all represent insulin-resistance diseases. Previous studies linked insulin resistance diseases to high fat diets or exposure to streptozotocin, a nitrosamine-related compound that causes T2DM, NASH, and AD-type neurodegeneration. We hypothesize that low-level exposure to nitrosamines that are widely present in processed foods, amplifies the deleterious effects of high fat intake in promoting T2DM, NASH, and neurodegeneration.

Methods

Long Evans rat pups were treated with N-nitrosodiethylamine (NDEA) by i.p. Injection, and upon weaning, they were fed with high fat (60%; HFD) or low fat (5%; LFD) chow for 6 weeks. Rats were evaluated for cognitive impairment, insulin resistance, and neurodegeneration using behavioral, biochemical, molecular, and histological methods.

Results

NDEA and HFD ± NDEA caused T2DM, NASH, deficits in spatial learning, and neurodegeneration with hepatic and brain insulin and/or IGF resistance, and reductions in tau and choline acetyltransferase levels in the temporal lobe. In addition, pro-ceramide genes, which promote insulin resistance, were increased in livers and brains of rats exposed to NDEA, HFD, or both. In nearly all assays, the adverse effects of HFD+NDEA were worse than either treatment alone.

Conclusions

Environmental and food contaminant exposures to low, sub-mutagenic levels of nitrosamines, together with chronic HFD feeding, function synergistically to promote major insulin resistance diseases including T2DM, NASH, and AD-type neurodegeneration. Steps to minimize human exposure to nitrosamines and consumption of high-fat content foods are needed to quell these costly and devastating epidemics.

Epidemilogical trends strongly suggest exposures as etiologic agents in the pathogenesis of sporadic Alzheimer's disease, diabetes mellitus, and non-alcoholic steatohepatitis

Nitrosamines mediate their mutagenic effects by causing DNA damage, oxidative stress, lipid peroxidation, and pro-inflammatory cytokine activation, which lead to increased cellular degeneration and death. However, the very same pathophysiological processes comprise the "unbuilding" blocks of aging and insulin-resistance diseases including, neurodegeneration, diabetes mellitus (DM), and non-alcoholic steatohepatitis (NASH). Previous studies demonstrated that experimental exposure to streptozotocin, a nitrosamine-related compound, causes NASH, and diabetes mellitus Types 1, 2 and 3 (Alzheimer (AD)-type neurodegeneration). Herein, we review evidence that the upwardly spiraling trends in mortality rates due to DM, AD, and Parkinson's disease typify exposure rather than genetic-based disease models, and parallel the progressive increases in human exposure to nitrates, nitrites, and nitrosamines via processed/preserved foods. We propose that such chronic exposures have critical roles in the pathogenesis of our insulin resistance disease pandemic. Potential solutions include: 1) eliminating the use of nitrites in food; 2) reducing nitrate levels in fertilizer and water used to irrigate crops; and 3) employing safe and effective measures to detoxify food and water prior to human consumption. Future research efforts should focus on refining our ability to detect and monitor human exposures to nitrosamines and assess early evidence of nitrosamine-mediated tissue injury and insulin resistance.

Synergistic effect of fatty liver and smoking on metabolic syndrome

AIM: To investigate the association of fatty liver and smoking on metabolic syndrome and its components.

METHODS: This cross-sectional study enrolled participants who attended annual health screening at Shin Kong Wu Ho-Su Memorial Hospital from January to December 2005. A total of 3455 (1981 men and 1474 women) subjects were included in final analyses. Fatty liver was diagnosed using abdominal ultrasonography by trained gastroenterologists. The modified National Cholesterol Education Program Adult Treatment Panel III was used to define metabolic syndrome. The associations between smoking, fatty liver and metabolic syndrome were analyzed using multiple logistic regression.

RESULTS: Subjects with fatty liver, and who smoked tobacco, had the highest odds ratios (ORs) for high waist circumference [OR, 4.5 (95% CI: 3.3-6.1), P < 0.05], hypertriglyceridemia [OR, 8.1 (95% CI: 6.0-10.9), P < 0.05], low serum high-density lipoprotein cholesterol (HDL-C) [OR, 8.3 (95% CI: 6.1-11.3), P < 0.05], and metabolic syndrome [OR, 9.5 (95% CI: 6.7-13.4), P < 0.05] compared to subjects without fatty liver who did not smoke tobacco. We also found that the ORs for hypertriglyceridemia, low serum HDL-C, and metabolic syndrome for subjects with fatty liver who smoked tobacco had greater than the sum of the ORs for subjects with fatty liver who did not smoke plus those who did not have fatty liver and who did smoke.

CONCLUSION: Fatty liver and smoking had a synergistic effect on metabolic syndrome and its components, especially for hypertriglyceridemia and low serum HDL-C.

Serum concentrations of human angiopoietin-like protein 3 in patients with nonalcoholic fatty liver disease: association with insulin resistance

OBJECTIVE

Insulin resistance is considered a key feature of nonalcoholic fatty liver disease (NAFLD). In this setting, experimental studies have suggested a potential role of angiopoietin-like (ANGPTL) proteins in the pathogenesis of hepatic steatosis and the metabolic syndrome. In this study, we sought to investigate the plasma levels of ANGPTL protein 3 (ANGPTL3)--a liver-derived protein that modulates plasma triglyceride clearance--in patients with definite nonalcoholic steatohepatitis (NASH, n=40), borderline NASH (n=8), simple fatty liver (n=9), and healthy controls without evidence of liver disease (n=14).

METHODS

Levels of ANGPTL3 were measured by enzyme-linked immunosorbent assay and compared in the four study groups. Moreover, concentrations of ANGPTL3 were assessed in relation to the general characteristics of the study participants and the results of liver biopsy.

RESULTS

Levels of ANGPTL3 were significantly higher in patients with definite NASH (389+/-110 ng/ml, P<0.05) and borderline NASH (433+/-70 ng/ml, P<0.05) compared with controls (291+/-78 ng/ml). No significant differences were found in patients with simple fatty liver (321+/-119 ng/ml) as compared with controls. In correlation analyses of the entire study cohort, ANGPTL3 was significantly and positively associated with homeostatic model assessment for insulin resistance (r=0.28, P<0.05) but not with histological staging and pathological characteristics of NAFLD.

CONCLUSION

Although subject to future confirmation, our data suggest that ANGPTL3 levels are elevated in the more severe forms of NAFLD and could be associated with insulin resistance in this setting.

Inflammation and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the hepatic component of the metabolic syndrome. The metabolic syndrome represents a chronic inflammatory state, and individuals with the disorder demonstrate various immunologic abnormalities. Innate immune dysfunction in adipose tissue leads to abnormal production of adipose-derived factors, some of which can inhibit hepatic fat disposal and promote lipid accumulation within hepatocytes. The latter induces generation of excessive proinflammatory cytokines, particularly when the hepatic innate immune system becomes Th-1 polarized, thus promoting the development of nonalcoholic steatohepatitis (NASH). Although sustained exposure to these inflammatory mediators generally promotes the generation of various profibrogenic factors, progression from NASH to cirrhosis is actually relatively uncommon due to reduced production of other cytokines such as Th-2 cytokines.

Insulin resistance and neurodegeneration: roles of obesity, type 2 diabetes mellitus and non-alcoholic steatohepatitis

Recent studies have linked obesity, type 2 diabetes mellitus (T2DM) or non-alcoholic steatohepatitis (NASH) to insulin resistance in the brain, cognitive impairment and neurodegeneration. Insulin resistance compromises cell survival, metabolism and neuronal plasticity, and increases oxidative stress, cytokine activation and apoptosis. T2DM/NASH has been demonstrated to be associated with increased ceramide generation, suggesting a mechanistic link between peripheral insulin resistance and neurodegeneration because ceramides mediate insulin resistance and can cross the blood-brain barrier (BBB). Peripheral insulin resistance diseases may potentially cause brain insulin resistance via a liver-brain axis of neurodegeneration as a result of the trafficking of ceramides across the BBB. Therapy that includes insulin-sensitizing agents may help prevent brain insulin resistance-mediated cognitive impairment.

Increased liver oxidative stress and altered PUFA metabolism precede development of non-alcoholic steatohepatitis in SREBP-1a transgenic spontaneously hypertensive rats with genetic predisposition to hepatic steatosis

The temporal relationship of hepatic steatosis and changes in liver oxidative stress and fatty acid (FA) composition to the development of non-alcoholic steatohepatitis (NASH) remain to be clearly defined. Recently, we developed an experimental model of hepatic steatosis and NASH, the transgenic spontaneously hypertensive rat (SHR) that overexpresses a dominant positive form of the human SREBP-1a isoform in the liver. These rats are genetically predisposed to hepatic steatosis at a young age that ultimately progresses to NASH in older animals. Young transgenic SHR versus SHR controls exhibited simple hepatic steatosis which was associated with significantly increased hepatic levels of oxidative stress markers, conjugated dienes, and TBARS, with decreased levels of antioxidative enzymes and glutathione and lower concentrations of plasma alpha- and gamma-tocopherol. Transgenic rats exhibited increased plasma levels of saturated FA, decreased levels of n-3 and n-6 polyunsaturated FA (PUFA), and increased n-6/n-3 PUFA ratios. These results are consistent with the hypothesis that excess fat accumulation in the liver in association with increased oxidative stress and disturbances in the metabolism of saturated and unsaturated fatty acids may precede and contribute to the primary pathogenesis of NASH.

Contrast-enhanced computed tomography for the diagnosis of fatty liver: prospective study with same-day biopsy used as the reference standard

PURPOSE

The study purpose was to prospectively determine the accuracy of contrast-enhanced CT in diagnosing fatty liver using same-day biopsy as the reference standard.

MATERIALS AND METHODS

One hundred seventy-nine potential living liver donors underwent unenhanced and portal-phase contrast-enhanced hepatic CT and subsequent liver biopsy on the same day. Attenuation difference between the liver and the spleen on unenhanced (( pre ) L-S) and contrast-enhanced (( post ) L-S) images and blood-subtracted hepatic attenuation on contrast-enhanced images (( post ) L-B), calculated by [L - 0.3 x (0.75 x P + 0.25 x A)]/0.7 where L, P and A represent the attenuation of the liver, main portal vein and abdominal aorta, respectively, were obtained. The accuracy of these indices in diagnosing fatty liver according to various threshold levels, 5%-30% histological steatosis in increments of 5%, was compared using ROC analysis.

RESULTS

The area under the ROC curve for ( pre ) L-S, ( post ) L-S and ( post ) L-B was 0.663-0.918, 0.712-0.847 and 0.821-0.923, respectively, depending on the threshold levels of hepatic steatosis. The accuracy of ( pre ) L-S and ( post ) L-S did not differ (P >or= 0.054), despite a trend towards a lower accuracy with ( post ) L-S. ( post ) L-B yielded higher accuracy than ( pre ) L-S at threshold levels of 5% and 10% (P <or= 0.002) and similar accuracy to ( pre ) L-S at the other threshold levels (P >or= 0.144).

CONCLUSION

Portal-phase contrast-enhanced CT has a similar, or even greater, accuracy than unenhanced CT in diagnosing fatty liver.

Risk factors for and clinical characteristics of severe hyperlactataemia in patients receiving antiretroviral therapy: a case-control study

BACKGROUND

Symptomatic hyperlactataemia and lactic acidosis (SHLA) are potentially life-threatening complications associated with stavudine (d4T), an antiretroviral therapy (ART) drug widely used in developing countries.

METHODS

Cases comprised all symptomatic patients with measured lactates >or= 5 mmol/L referred to a South African hospital between August 2003 and November 2005. Matched controls were selected according to facility and duration on ART.

RESULTS

Seventy-one cases and 142 controls were included in the study. The majority of cases presented between 6 and 18 months on ART. Female sex [adjusted odds ratio (AOR) 23.4; 95% confidence interval (CI) 4.0-136.6], a baseline weight between 60 and 75 kg (AOR 4.5; 95% CI 1.4-14.1) or, in particular, >or= 75 kg (AOR 19.4; 95% CI 4.1-82.5) at ART initiation and gaining >or= 6 kg in the first 3 months on therapy (AOR 3.5; 95% CI 1.3-9.5) were independent risk factors identifying patients who may subsequently develop SHLA. Weight loss of >or= 2 kg (AOR 6.1; 95% CI 2.0-18.3), a rise in alanine aminotransferase (ALT) >or= 10 U/L (AOR 3.1; 95% CI 1.1-8.9), the presence of at least one of three major symptoms (vomiting, nausea and abdominal pains) of SHLA (AOR 12.6; 95% CI 3.3-47.2) and peripheral neuropathy (AOR 3.4; 95% CI 1.1-9.8) were the clinical parameters that were most able to identify patients with early manifestations of SHLA.

CONCLUSIONS

This is the first case-control study for SHLA in Southern Africa. Given these findings, we advise that stavudine is avoided in overweight women. Weight loss, a rise in ALT, peripheral neuropathy and/or gastrointestinal symptoms should prompt healthcare workers to assess for SHLA, especially at between 6 and 18 months on ART.

Association between omental adipose tissue macrophages and liver histopathology in morbid obesity: influence of glycemic status

BACKGROUND/AIMS

Recently we showed that macrophage accumulation in omental adipose tissue is associated with liver fibro-inflammation in morbidly obese subjects. Here, we evaluated the influence of glycemic status and extended the analysis to the spectrum of obesity-linked liver damage.

METHODS

Liver biopsies, subcutaneous and omental adipose tissue were collected in 132 obese subjects during gastric bypass surgery. HAM56+ adipose tissue macrophages were counted in subjects classified by liver histopathology and by their degree of insulin resistance.

RESULTS

In the whole population, the number of omental macrophages increased with the score of steatosis, the non-alcoholic fatty liver disease activity score, the stage of fibrosis and with fibro-inflammation index. None of these relationships were significant with subcutaneous macrophage count. In insulin-sensitive participants, omental macrophages accumulation was higher in subjects with high indexes of fibro-inflammation (p=0.012 vs. low indexes). In insulin-resistant including type 2 diabetic participants, omental macrophage count was higher both in subjects with high scores of steatosis and in subjects with high indexes of fibro-inflammation (p<0.05 vs. low scores).

CONCLUSIONS

Macrophage accumulation in omental adipose tissue is associated with aggravated steatosis and fibro-inflammation in insulin-resistant obese subjects independently of altered glycemic status.