Insulin resistance, adiponectin, cytokines in NASH: Which is the best target to treat?

Role of growth hormone, insulin-like growth factor 1 and insulin-like growth factor-binding protein 3 in development of non-alcoholic fatty liver disease

BACKGROUND AND AIMS

Pituitary dysfunction including growth hormone (GH) deficiency may be associated with non-alcoholic fatty liver disease (NAFLD). Since the relationships among GH, IGF-1, IGFBP-3, and development of NAFLD without hypopituitarism are unclear, we examined the role of these hormones in the development of NAFLD based on clinical, laboratory and liver histology data.

PATIENTS AND METHODS

A total of 55 consecutive patients (20 males and 35 females) with NAFLD.

RESULTS

Aspartate amino transferase (AST), AST/ALT, platelet count and IGF-1, levels were significantly associated with differences in fibrosis, since these variables differed between stage 0-1 and stage 2-3 NAFLD. In multivariate analysis, platelet count (P = 0.0223, relative risk (RR), 5.899; 95% confidence interval (CI), 1.288-27.017), and IGF-1 (P = 0.0363, RR, 4.568; 95% CI, 1.101-18.945) showed significant associations with stage 2-3 NAFLD. Additionally, hyaluronic acid levels had a negative relationship with IGF-1 and the IGF-1/IGFBP-3 ratio. There was no relationship of fibrosis with GH level, but decreased GH (P = 0.0414, RR, 0.199; 95% CI, 0.042-0.989) was significantly associated with steatosis of stage 2-3. Low GH/IGF-1 and GH/IGFBP-3 ratios were found in advanced steatosis.

CONCLUSION

GH, IGF-1 and IGFBP-3 are associated with hepatic fibrosis and steatosis in NAFLD. Low levels of IGF-1 might be associated with fibrosis while low level of GH with hepatic steatosis.

What are the risk factors and settings for non-alcoholic fatty liver disease in Asia-Pacific?

The risk factors and settings for non-alcoholic fatty liver disease (NAFLD) in Asians are reviewed comprehensively. Based particularly on large community-based studies using ultrasonography, case-control series and prospective longitudinal studies, the prevalence of NAFLD in Asia is between 12% and 24%, depending on age, gender, locality and ethnicity. Further, the prevalence in China and Japan has nearly doubled in the last 10-15 years. A detailed analysis of these data shows that NAFLD risk factors for Asians resemble those in the West for age at presentation, prevalence of type 2 diabetes mellitus (T2DM) and hyperlipidemia. The apparent differences in prevalence of central obesity and overall obesity are related to criteria used to define waist circumference and body mass index (BMI), respectively. The strongest associations are with components of the metabolic syndrome, particularly the combined presence of central obesity and obesity. Non-alcoholic fatty liver disease appears to be associated with long-standing insulin resistance and likely represents the hepatic manifestation of metabolic syndrome. Not surprisingly therefore, Asians with NAFLD are at high risk of developing diabetes and cardiovascular disease. Conversely, metabolic syndrome may precede the diagnosis of NAFLD. The increasing prevalence of obesity, coupled with T2DM, dyslipidemia, hypertension and ultimately metabolic syndrome puts more than half the world's population at risk of developing NAFLD/non-alcoholic steatohepatitis/cirrhosis in the coming decades. Public health initiatives are clearly imperative to halt or reverse the global 'diabesity' pandemic, the underlying basis of NAFLD and metabolic syndrome. In addition, a perspective of NAFLD beyond its hepatic consequences is now warranted; this needs to be considered in relation to management guidelines for affected individuals.

Lower plasma adiponectin is correlated to higher alanine aminotransferase independent of metabolic factors and hepatitis B virus carrier status

BACKGROUND

Adiponectin has been linked to the metabolic syndrome and coronary artery disease in recent years. The animal and human data also suggest that adiponectin may be beneficial for liver functions. The aim of this study was to investigate the correlation between plasma adiponectin level and liver function tests in adults with or without chronic hepatitis B virus (HBV) infection.

METHODS

We analysed the blood levels of liver enzymes and adiponectin in 140 apparently healthy adults, including 21 HBV carriers.

RESULTS

We found that the plasma adiponectin levels were inversely correlated to aspartate aminotransferase (r = -0.314, P = 0.000) and alanine aminotransferase (ALT) (r = -0.430, P = 0.000). Among the HBV carriers, the ALT correlated with the plasma adiponectin levels (r = -0.521, P = 0.015). In linear regression models adjusting for age, sex and the other metabolic variables, the ALT was independently related to the plasma adiponectin levels (beta = -0.371 +/- 0.134, P = 0.007), even in HBV carriers (beta = -1.143 +/- 0.482, P = 0.034). The ALT was also independently correlated to the plasma adiponectin levels (beta = 0.552 +/- 0.132, P < 0.001) with adjustment for age, sex and insulin-resistance index by homeostasis model assessment, even in HBV carriers (beta = -1.202 +/- 0.562, P = 0.048). The subjects with normal ALT had a significantly higher least square mean of plasma adiponectin than those with abnormal ALT (4.01 +/- 0.19 vs 3.30 +/- 0.30, P = 0.014) with adjustment for age, sex, homeostasis model assessment insulin resistance and HBV status.

CONCLUSION

ALT was inversely related to adiponectin levels, independent of the metabolic factors and HBV status. Whether there is any potential prognostic and therapeutic value of adiponectin in human liver diseases remains to be investigated.

Effect of antihypertensive agents on plasma adiponectin levels in hypertensive patients with metabolic syndrome

AIM

Plasma adiponectin levels are well associated with metabolic syndrome. However, the relationship between hypertension and plasma adiponectin levels is not clear. Also, there is not enough data about the effects of different antihypertensive regimens on plasma adiponectin levels.

METHODS

Ninety-six hypertensive patients (48 male, 48 female) who fulfil the diagnostic criteria of metabolic syndrome were enrolled. Patients were treated for 3 months with metoprolol (n = 18, 100 mg/day), amlodipine (n = 20, 10 mg/day), doxazosin (n = 18, 4 mg/day), ramipril (n = 20, 5 mg/day) and valsartan (n = 20, 80 mg/day). Blood biochemistry and plasma adiponectin concentrations were measured both before and after the study. Insulin resistance was measured by homeostasis assessment index (HOMA).

RESULTS

Plasma adiponectin levels were correlated with the total cholesterol (r = -0.244, P = 0.017), triglyceride (r = -0.306, P = 0.002), high-density lipoprotein-cholesterol (r = 0.286, P = 0.005), body mass index (r = -374, P < 0.001), systolic (r = -502, P < 0.001) and diastolic blood pressures (r = -235, P = 0.021). The independent predictors of plasma adiponectin levels were HOMA (beta = -0.199, P = 0.02), body mass index (beta = -0.313, P < 0.001) and systolic blood pressures (beta = -0.483, P < 0.001). Ramipril and valsartan increased the plasma adiponectin levels significantly higher than the other regimens (P < 0.05 for both) while metoprolol did not make a significant effect.

CONCLUSION

According to the results, plasma adiponectin levels are associated with the arterial blood pressures, body fat content and the lipid parameters in hypertensive patients with metabolic syndrome. The effects of antihypertensive drugs on plasma adiponectin levels are parallel to their effects on blood pressures and insulin sensitivities. The different effects of several regimens on plasma adiponectin levels and insulin sensitivities may account for the diversity of the cardiovascular outcomes in patients with hypertension.

Steatosis as a cofactor in other liver diseases: hepatitis C virus, alcohol, hemochromatosis, and others

As obesity prevalence rises, there is evidence that fatty liver disease can act synergistically with other chronic liver diseases to aggravate parenchymal injury. This is characterized best in chronic hepatitis C, where steatosis is caused by viral and metabolic effects. There is evidence that steatosis and its metabolic abnormalities also exacerbate other diseases, such as alcoholic liver disease, hemochromatosis, and, possibly, drug-induced liver disease. The pathogenesis seems related to increased susceptibility of steatotic hepatocytes to apoptosis, enhanced oxidative injury, and altered hepatocytic regeneration. Data suggest that active management of obesity may improve liver injury and decrease the progression of fibrosis in patients who have other chronic liver diseases.

Nonalcoholic fatty liver disease and HIV infection

As persons with HIV live longer, chronic liver disease is increasingly important. Nonalcoholic fatty liver disease (NAFLD) is characterized by excess fat in hepatocytes in patients without significant alcohol use. It can progress from steatosis to nonalcoholic steatohepatitis (NASH) to cirrhosis. Visceral obesity and insulin resistance are integral to the pathogenesis of NAFLD. Patients with HIV are at greater risk of NAFLD due to antiretroviral therapy and viral hepatitis coinfection. Antiretroviral therapy can lead to patterns of injury that include steatosis and NASH. Coinfection with hepatitis C virus increases the risk of insulin resistance and hepatic steatosis, and co-existent features of NASH have also been reported. Histological-based, longitudinal studies are needed that address the interactions of NAFLD and HIV infection, the effects of antiretroviral therapy and hepatotropic virus coinfection, and inform better management strategies.

Treatment of patients with non-alcoholic fatty liver disease: current views and perspectives

Non-alcoholic fatty liver disease is considered a component of the metabolic syndrome associated with obesity. Problems still exist concerning non-alcoholic fatty liver disease patients in clinical practice, for example: (a) how to diagnose non-alcoholic fatty liver disease and its type; (b) how to select patients candidate to treatment; (c) how to treat selected patients. Non-alcoholic fatty liver disease includes steatosis and non-alcoholic steatohepatitis, but only non-alcoholic steatohepatitis evolves into cirrhosis and the absolute risk of mortality for non-alcoholic fatty liver disease is low. As yet, no tools, other than liver biopsy, are available to differentiate the various types of non-alcoholic fatty liver disease. Many drugs are, currently, under study to treat non-alcoholic fatty liver disease, even if well-performed trials are until necessary to define the best treatment. At the moment, the entity of the problem and the characteristics of patients frequently put the physician, in clinical practice, to choose the therapeutic approach arbitrarily which is considered more effective for each individual patient. Probably the future will consider the possibility of treating non-alcoholic fatty liver disease with more than one drug, by considering the various aspects and degree of this syndrome. Actually each physician should select the individual treatment on the basis of his/her knowledge and experience, by never forgetting the old saying 'primum non nocere'. However, the epidemiological entity of the problem, the characteristics of the patients, generally young, the frequent lack of clinical evidence of involvement of the liver, are all the factors that require vast well-performed clinical trials in order to define the best therapeutic approach for each individual patient.

Islet beta cell failure in type 2 diabetes

The major focus of this Review is on the mechanisms of islet beta cell failure in the pathogenesis of obesity-associated type 2 diabetes (T2D). As this demise occurs within the context of beta cell compensation for insulin resistance, consideration is also given to the mechanisms involved in the compensation process, including mechanisms for expansion of beta cell mass and for enhanced beta cell performance. The importance of genetic, intrauterine, and environmental factors in the determination of "susceptible" islets and overall risk for T2D is reviewed. The likely mechanisms of beta cell failure are discussed within the two broad categories: those with initiation and those with progression roles.

Role of adipose tissue as an inflammatory organ in human diseases

Reviews on the inflammatory role of adipose tissue outside the field of metabolism are rare. There is increasing evidence provided by numerous basic research studies from nearly all internal medicine subspecializations that adipocytes and adipocytokines are involved in primary inflammatory processes and diseases. Therefore, it is the aim of the present review to discuss and to summarize the current knowledge on the inflammatory role of adipocytokines and special types of regional adipocytes such as retroorbital, synovial, visceral, subdermal, peritoneal, and bone marrow adipocytes in internal medicine diseases. Future clinical and therapeutic implications are discussed.

Nonalcoholic fatty liver disease: from steatosis to cirrhosis

Nonalcoholic steatohepatitis (NASH), the lynchpin between steatosis and cirrhosis in the spectrum of nonalcoholic fatty liver disorders (NAFLD), was barely recognized in 1981. NAFLD is now present in 17% to 33% of Americans, has a worldwide distribution, and parallels the frequency of central adiposity, obesity, insulin resistance, metabolic syndrome and type 2 diabetes. NASH could be present in one third of NAFLD cases. Age, activity of steatohepatitis, and established fibrosis predispose to cirrhosis, which has a 7- to 10-year liver-related mortality of 12% to 25%. Many cases of cryptogenic cirrhosis are likely endstage NASH. While endstage NAFLD currently accounts for 4% to 10% of liver transplants, this may soon rise. Pathogenic concepts for NAFLD/NASH must account for the strong links with overnutrition and underactivity, insulin resistance, and genetic factors. Lipotoxicity, oxidative stress, cytokines, and other proinflammatory mediators may each play a role in transition of steatosis to NASH. The present "gold standard" management of NASH is modest weight reduction, particularly correction of central obesity achieved by combining dietary measures with increased physical activity. Whether achieved by "lifestyle adjustment" or anti-obesity surgery, this improves insulin resistance and reverses steatosis, hepatocellular injury, inflammation, and fibrosis. The same potential for "unwinding" fibrotic NASH is indicated by studies of the peroxisome proliferation activator receptor (PPAR)-gamma agonist "glitazones," but these agents may improve liver disease at the expense of worsening obesity. Future challenges are to approach NAFLD as a preventive public health initiative and to motivate affected persons to adopt a healthier lifestyle.