Nonalcoholic fatty liver disease as a component of the metabolic syndrome

Serum alanine aminotransferase, metabolic syndrome, and cardiovascular disease in an Australian population

OBJECTIVES

Elevations of serum alanine aminotransferase (ALT) are common and have been associated with metabolic syndrome (Met S) and cardiovascular risk. The aim of this study was to determine whether elevated ALT concentrations are predictive of Met S or cardiovascular events.

METHODS

In 1994/95, surviving participants of the previously conducted Busselton health population surveys completed a series of clinical and biochemical assessments. Using the Western Australian Health Department data linkage system, admissions for cardiovascular disease (CVD) were determined for 15 years before the survey (from 1980 to 1994). Incident CVD events during the 10-year follow-up period to the end of 2004 were also ascertained. Met S was defined using NCEP ATP III (2005) criteria.

RESULTS

3,719 Subjects (1,544 men and 2,175 women), aged 25-84 years who did not have serologically diagnosable chronic liver diseases or excessive consumption of alcohol, had their levels of ALT measured. The prevalence of Met S was 17% in men and 15% in women. In age-adjusted analyses, ALT was significantly associated with Met S and each of its five components and the association with Met S remained significant after adjustment for insulin resistance. There was no positive association between ALT and incident CVD events over the 10-year follow-up period in age-adjusted or multivariate-adjusted analyses.

CONCLUSIONS

The findings from this Australian population-based cohort study support a strong association between ALT concentration and Met S independent of insulin resistance. Serum ALT level does not appear to contribute significantly to cardiovascular risk assessment.

Preventive effect of pioglitazone against nonalcoholic fatty liver disease in Sprague-Dawley rats and its mechanism

AIM: To explore the prevention effect and mechanism of pioglitazone (PIO) on nonalcoholic fatty liver disease (NAFLD) in rats.

METHODS: Seventy two Sprague-Dawley rats were randomly divided into three groups: normal diet group (NG), high fat diet group (HG) and PIO group (PIOG), with 24 rats in every group. PIOG were fed with high fat diet and PIO for eight weeks. IR was tested by euglycemic-hyperinsulinemic clamp; TG, ALT, AST, FFAs, FINS and TNF-α were tested by biochemistry automatic analyzer or RIA; mRNA expression of peroxisome proliferator-activated receptor (PPARγ) was detected using RT-PCR. The expression of PPARγ and c-Jun amino-terminal kinase 1 (JNK1) were detected by Western blot.

RESULTS: The glucose infusion rate (GIR) decreased and JNK1 increased in HG rats in a time-dependent manner from 1st to 8th week (P < 0.05). Compared with NG, at the end of 8th week, the hepatic steatosis was significant in HG group. The weight, liver index, serum levels of TG, ALT, AST, FFAs, FINS and TNF-α increased, while IR was aggravated. Meanwhile, the JNK1 protein expression in liver tissue was up-regulated, while expression of PPARγ was decreased (TG: 1.23 ± 0.08 vs 0.62 ± 0.12; ALT: 92.80 ± 7.09 vs 51.34 ± 8.12; AST: 153.22 ± 20.65 vs 119.26 ± 13.61; FFAs: 511.94 ± 24.88 vs 335.31 ± 15.71; FINS: 41.23 ± 1.84 vs 22.65 ± 2.25; TNF-α: 1.02 ± 0.12 vs 0.34 ± 0.07, all P < 0.05). In PIOG, all the indexes were improved, but didn't completely return to the same as those of NG group.

CONCLUSION: PIO could prevent NAFLD induced by a high-fat diet and other IR-related diseases.

Polymorphism of human leptin receptor gene is associated with type 2 diabetic patients complicated with non-alcoholic fatty liver disease in China

BACKGROUND AND AIM

To investigate the relationship between human leptin receptor (LEPR) gene G3057A polymorphism and type 2 diabetes mellitus (T2DM) patients complicated with or without non-alcoholic fatty liver disease (NAFLD).

METHODS

Two hundred and sixteen cases of newly diagnosed T2DM patients (104 cases complicated with NAFLD) and 108 cases of normal glucose tolerances (NGT) were recruited. Hemi-nested polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and PCR-direct sequence analysis were conducted to detect the polymorphism of LEPR G3057A variation. Plasma leptin levels were measured by enzyme-linked immunosorbent assay kit. Plasma lipid and glucose metabolic parameters were measured routinely. Liver ultrasound was carried out for all subjects.

RESULTS

T2DM patients complicated with NAFLD had higher plasma insulin, leptin, triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) levels than those without NAFLD and NGT subjects. The variant frequency at nucleotide 3057 G-->A transversion was 76.0% in type 2 diabetic patients complicated with NAFLD, which was also significantly higher than those without NAFLD (62.1%) and NGT cases (53.2%). There was also significant difference in genotype distribution between the three groups (chi(2) = 14.63, P < 0.01).

CONCLUSION

The polymorphism of LEPR gene 3057 probably contributes to the onset of NAFLD by regulating lipid metabolism and affecting insulin sensitivity.

Genetic factors for resistance to diet-induced obesity and associated metabolic traits on mouse chromosome 17

Obesity is associated with increased susceptibility to dyslipidemia, insulin resistance, and hypertension, a combination of traits that comprise the traditional definition of the metabolic syndrome. Recent evidence suggests that obesity is also associated with the development of nonalcoholic fatty liver disease (NAFLD). Despite the high prevalence of obesity and its related conditions, their etiologies and pathophysiology remains unknown. Both genetic and environmental factors contribute to the development of obesity and NAFLD. Previous genetic analysis of high-fat, diet-induced obesity in C57BL/6J (B6) and A/J male mice using a panel of B6-Chr(A/J)/NaJ chromosome substitution strains (CSSs) demonstrated that 17 CSSs conferred resistance to high-fat, diet-induced obesity. One of these CSS strains, CSS-17, which is homosomic for A/J-derived chromosome 17, was analyzed further and found to be resistant to diet-induced steatosis. In the current study we generated seven congenic strains derived from CCS-17, fed them either a high-fat, simple-carbohydrate (HFSC) or low-fat, simple-carbohydrate (LFSC) diet for 16 weeks and then analyzed body weight and related traits. From this study we identified several quantitative trait loci (QTLs). On a HFSC diet, Obrq13 protects against diet-induced obesity, steatosis, and elevated fasting insulin and glucose levels. On the LFSC diet, Obrq13 confers lower hepatic triglycerides, suggesting that this QTL regulates liver triglycerides regardless of diet. Obrq15 protects against diet-induced obesity and steatosis on the HFSC diet, and Obrq14 confers increased final body weight and results in steatosis and insulin resistance on the HFSC diet. In addition, on the LFSC diet, Obrq 16 confers decreased hepatic triglycerides and Obrq17 confers lower plasma triglycerides on the LFSC diet. These congenic strains provide mouse models to identify genes and metabolic pathways that are involved in the development of NAFLD and aspects of diet-induced metabolic syndrome.