Nonalcoholic steatohepatitis and the cardiometabolic syndrome

Prevalence of non-alcoholic fatty liver disease in patients with diabetes mellitus, hyperlipidemia, obesity and polycystic ovary syndrome: A cross-sectional study in north of Iran

BACKGROUND AND AIM

The aim of this study was to describe the frequency of non-alcoholic fatty liver disease (NAFLD) in patients with diabetes mellitus (DM), hyperlipidemia, obesity and polycystic ovaries syndrome (PCOS).

METHODS

In a cross-sectional study, 333 patients who had one of the certain diagnosis of DM, hyperlipidemia, obesity or PCOS were enrolled. Information about demographics, anthropometric, nutritional habitude, smoking history, medical history and physical activity were recorded. Liver ultrasound examination and routine biochemistry analysis were performed.

RESULTS

Among 333 patients with one of the four above-mentioned diseases. 199 patients (59.8%) had NAFLD. Male were more likely to have NAFLD than female (72.8% vs. 50.8% respectively, P < 0.001). About, 80.7% of patients through 41-50 years age had NAFLD. The frequency of abnormal fasting blood glucose, alanine aminotransferase (ALT), triglyceride, and total cholesterol were significantly higher in patients with NAFLD (P < 0.05). Subjects with NAFLD had a higher body mass index than non-NAFLD (33.6 ± 7.9 kg/m² vs. 31.1 ± 5.0 kg/m2 respectively, P = 0.002). Patients with DM, hyperlipidemia, hypertension, and hypothyroidism were more likely to have NAFLD (P < 0.05). Patients with consumption of supper, high-fat diet, enjoy of eating and smoking were more likely to have NAFLD and patients with fruit and vegetable uptake and physical activity were less likely to have NAFLD (P < 0.05).

CONCLUSIONS

As most patients with NAFLD are asymptomatic, employed individuals with higher education levels, with a history of smoking and unhealthy diet along with DM, hyperlipidemia, PCOS and obesity seriously have to be followed and educated for lifestyle modification.

The association between dietary inflammatory index and metabolic syndrome components in Iranian adults

AIMS

Investigating the association between the dietary inflammatory index (DII^®) and metabolic syndrome (MetS) components and liver enzymes in Iranian population.

METHODS

The present cross-sectional study consist of 606 participants from East-Azarbaijan-Iran. The MetS status was determined using ATPIII NCEP criteria. Moreover, liver enzymes including alanine aminotransferase and aspartate aminotransferase were measured. The DII was calculated according to Shivappa et al. method using a validated quantitative FFQ. Logistic regression was used to determine the association between DII and MetS.

RESULTS

About 34.3% of the participants had metabolic syndrome. Higher DII score was significantly associated with MetS [OR: 2.26 (95% CI: 1.03, 4.92)] after adjusting for covariates. After adjustment, participants in the highest quartile of DII score had significantly higher FBG [OR: 2.56 (95% CI: 1.00, 7.05)] compared with the participants in the lowest quartile of DII score. No other significant association was observed between DII and liver enzymes level and other MetS components (P>0.05).

CONCLUSIONS

The results showed that the DII score was associated with overall MetS and FBG, after adjusting for all covariates. For precise conclusion there is a need for longitudinal studies with larger sample size and considering more food parameters.

Metabolic effects of Crocus sativus and protective action against non-alcoholic fatty liver disease in diabetic rats

Non-alcoholic fatty liver disease (NAFLD) is the result of the accumulation of adipose tissue deposits in the liver and it is associated with type 2 diabetes. Crocus sativus (saffron) is known for its antioxidant and its potential hypoglycemic effects. We investigated the role of saffron on NAFLD in diabetic rats. Thirty adult male rats were allocated into three groups; control (n=10), which received normal diet; streptozotocin (STZ) group (n=10), which received normal chow diet, 10% fructose in their drinking water and STZ (40 mg/kg body weight; STZ-saffron group (n=10), which followed the same dietary and pharmacological pattern as STZ group and were additionally supplemented with saffron (100 mg/kg/day). Metabolic profile was measured and histopathological examination of the liver was evaluated. STZ group exhibited the highest glucose levels at the end of the experiment (P<0.05), while there was no difference between control and STZ-saffron group (584 vs. 213 mg/dl vs. 209 mg/dl, respectively). STZ group revealed higher percentage of steatosis (5–33%) when compared to the other two groups (P<0.005). Saffron exhibits both hypoglycemic and hepatoprotective actions. Yet, further studies enlightening the exact mechanisms of saffron's mode of actions are required.

Monoacylglycerol O-acyltransferase 1 is regulated by peroxisome proliferator-activated receptor γ in human hepatocytes and increases lipid accumulation

Monoacylglycerol O-acyltransferase (MGAT) is an enzyme that is involved in triglyceride synthesis by catalyzing the formation of diacylglycerol from monoacylglycerol and fatty acyl CoAs. Recently, we reported that MGAT1 has a critical role in hepatic TG accumulation and that its suppression ameliorates hepatic steatosis in a mouse model. However, the function of MGAT enzymes in hepatic lipid accumulation has not been investigated in humans. Unlike in rodents, MGAT3 as well as MGAT1 and MGAT2 are present in humans. In this study, we evaluated the differences between MGAT subtypes and their association with peroxisome proliferator-activated receptor γ (PPARγ), a regulator of mouse MGAT1 expression. In human primary hepatocytes, basal expression of MGAT1 was lower than that of MGAT2 or MGAT3, but was strongly induced by PPARγ overexpression. A luciferase assay as well as an electromobility shift assay revealed that human MGAT1 promoter activity is driven by PPARγ by direct binding to at least two regions of the promoter in 293T and HepG2 cells. Moreover, siRNA-mediated suppression of MGAT1 expression significantly attenuated lipid accumulation by PPARγ overexpression in HepG2 cells, as evidenced by oil-red-O staining. These results suggest that human MGAT1 has an important role in fatty liver formation as a target gene of PPARγ, and blocking MGAT1 activity could be an efficient therapeutic way to reduce nonalcoholic fatty liver diseases in humans.

Abrogating monoacylglycerol acyltransferase activity in liver improves glucose tolerance and hepatic insulin signaling in obese mice

Monoacylglycerol acyltransferase (MGAT) enzymes convert monoacylglycerol to diacylglycerol (DAG), a lipid that has been linked to the development of hepatic insulin resistance through activation of protein kinase C (PKC). The expression of genes that encode MGAT enzymes is induced in the livers of insulin-resistant human subjects with nonalcoholic fatty liver disease, but whether MGAT activation is causal of hepatic steatosis or insulin resistance is unknown. We show that the expression of Mogat1, which encodes MGAT1, and MGAT activity are also increased in diet-induced obese (DIO) and ob/obmice. To probe the metabolic effects of MGAT1 in the livers of obese mice, we administered antisense oligonucleotides (ASOs) against Mogat1 to DIO and ob/ob mice for 3 weeks. Knockdown of Mogat1 in liver, which reduced hepatic MGAT activity, did not affect hepatic triacylglycerol content and unexpectedly increased total DAG content. Mogat1 inhibition also increased both membrane and cytosolic compartment DAG levels. However, Mogat1 ASO treatment significantly improved glucose tolerance and hepatic insulin signaling in obese mice. In summary, inactivation of hepatic MGAT activity, which is markedly increased in obese mice, improved glucose tolerance and hepatic insulin signaling independent of changes in body weight, intrahepatic DAG and TAG content, and PKC signaling.

Current role of fenofibrate in the prevention and management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a common health problem with a high mortality burden due to its liver- and vascular-specific complications. It is associated with obesity, high-fat diet as well as with type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS). Impaired hepatic fatty acid (FA) turnover together with insulin resistance are key players in NAFLD pathogenesis. Peroxisome proliferator-activated receptors (PPARs) are involved in lipid and glucose metabolic pathways. The novel concept is that the activation of the PPARα subunit may protect from liver steatosis. Fenofibrate, by activating PPARα, effectively improves the atherogenic lipid profile associated with T2DM and MetS. Experimental evidence suggested various protective effects of the drug against liver steatosis. Namely, fenofibrate-related PPARα activation may enhance the expression of genes promoting hepatic FA β-oxidation. Furthermore, fenofibrate reduces hepatic insulin resistance. It also inhibits the expression of inflammatory mediators involved in non-alcoholic steatohepatitis pathogenesis. These include tumor necrosis factor-α, intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1. Consequently, fenofibrate can limit hepatic macrophage infiltration. Other liver-protective effects include decreased oxidative stress and improved liver microvasculature function. Experimental studies showed that fenofibrate can limit liver steatosis associated with high-fat diet, T2DM and obesity-related insulin resistance. Few studies showed that these benefits are also relevant even in the clinical setting. However, these have certain limitations. Namely, these were uncontrolled, their sample size was small, fenofibrate was used as a part of multifactorial approach, while histological data were absent. In this context, there is a need for large prospective studies, including proper control groups and full assessment of liver histology.

Effect of dietary fatty acids on serum parameters, fatty acid compositions, and liver histology in Shaoxing laying ducks

The effects of different fatty acid (FA) contents in diet on serum parameters, FA compositions of eggs and meat, and liver morphological changes were studied in Shaoxing laying ducks. A total of 264 ducks at 17 weeks were fed a control diet or a diet containing 30 g/kg fish oil (FO), 25 g/kg sunflower oil (SO), or 30 g/kg palm oil with 20 g/kg beef tallow (PBO). Malondialdehyde (MDA) content in the liver and the serum of ducks fed the PBO diet was significantly (P<0.05) higher than that of ducks fed the other diets. Triglyceride (TG) and total cholesterol (TC) levels were significantly lower (P<0.05) in ducks fed the FO diet. Serum TC also was lower in ducks fed the SO diet. Superoxide dismutase (SOD) activity was also affected by diets. The contents of polyunsaturated FAs (PUFAs) in eggs and meat were significantly higher (P<0.001) in ducks fed the FO and SO diets than in ducks fed the control diet. The level of C22:6 (n-3) FA in ducks fed the FO diet was significantly higher than that in ducks fed the other diets. However, the conversion efficiency of the longer-chain C20:5 (n-3) FA was higher than that of C22:6 (n-3). Ducks fed the PBO diet exhibited lipid droplet accumulation in the liver. These results demonstrate that a diet enriched with different FAs has strong effects on serum lipid levels and the deposition of PUFAs into tissue lipids.

Possible Mechanisms of Local Tissue Renin-Angiotensin System Activation in the Cardiorenal Metabolic Syndrome and Type 2 Diabetes Mellitus

The role of local tissue renin-angiotensin system (tRAS) activation in the cardiorenal metabolic syndrome (CRS) and type 2 diabetes mellitus (T2DM) is not well understood. To this point, we posit that early redox stress-mediated injury to tissues and organs via accumulation of excessive reactive oxygen species (ROS) and associated wound healing responses might serve as a paradigm to better understand how tRAS is involved. There are at least five common categories responsible for generating ROS that may result in a positive feedback ROS-tRAS axis. These mechanisms include metabolic substrate excess, hormonal excess, hypoxia-ischemia/reperfusion, trauma, and inflammation. Because ROS are toxic to proteins, lipids, and nucleic acids they may be the primary instigator, serving as the injury nidus to initiate the wound healing process. Insulin resistance is central to the development of the CRS and T2DM, and there are now thought to be four major organ systems important in their development. In states of overnutrition and tRAS activation, adipose tissue, skeletal muscle (SkM), islet tissues, and liver (the quadrumvirate) are individually and synergistically related to the development of insulin resistance, CRS, and T2DM. The obesity epidemic is thought to be the driving force behind the CRS and T2DM, which results in the impairment of multiple end-organs, including the cardiovascular system, pancreas, kidney, retina, liver, adipose tissue, SkM, and nervous system. A better understanding of the complex mechanisms leading to local tRAS activation and increases in tissue ROS may lead to new therapies emphasizing global risk reduction of ROS resulting in decreased morbidity and mortality.

Association of 25(OH)D and PTH with metabolic syndrome and its traditional and nontraditional components

CONTEXT

Emerging evidence suggests that 25-hydroxy vitamin D [25(OH)D] and PTH may play a role in the etiology of the metabolic syndrome (MetS). However, evidence to date is limited and inconsistent, and few studies have examined associations with nontraditional MetS components.

OBJECTIVE

The objective of the study was to examine the association of vitamin D and PTH with MetS and its traditional and nontraditional components in a large multiethnic sample.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, we examined 654 participants from London and Toronto, Ontario, Canada, aged 30 yr and older with risk factors for type 2 diabetes.

MAIN OUTCOME MEASURES

Presence of MetS and its traditional and nontraditional components was measured.

RESULTS

Approximately 43% of the study participants were classified as having MetS. Higher 25(OH)D was significantly associated with a reduced presence of MetS after adjustment for age, sex, season, ethnicity, supplement use, physical activity, and PTH (odds ratio 0.76, 95% confidence interval 0.62-0.93). PTH was not associated with the presence of MetS after multivariate adjustment. Multivariate linear regression analyses indicated significant adjusted inverse associations of 25(OH)D with waist circumference, triglyceride level, fasting insulin, and alanine transaminase (P < 0.041). Elevated PTH was positively associated with waist circumference and high-density lipoprotein cholesterol (P < 0.04). Other associations between PTH and MetS components were attenuated after adjustment for adiposity.

CONCLUSIONS

Serum 25(OH)D, but not PTH, was significantly associated with MetS as well as a number of MetS components after multivariate adjustment. These results suggest that low 25(OH)D may play a role in the etiology of the MetS.

Caloric restriction reverses hepatic insulin resistance and steatosis in rats with low aerobic capacity

Rats selectively bred for low aerobic running capacity exhibit the metabolic syndrome, including hyperinsulinemia, insulin resistance, visceral obesity, and dyslipidemia. They also exhibit features of nonalcoholic steatohepatitis, including chicken-wire fibrosis, inflammation, and oxidative stress. Hyperinsulinemia in these rats is associated with impaired hepatic insulin clearance. The current studies aimed to determine whether these metabolic abnormalities could be reversed by caloric restriction (CR). CR by 30% over a period of 2-3 months improved insulin clearance in parallel to inducing the protein content and activation of the carcinoembryonic antigen-related cell adhesion molecule 1, a main player in hepatic insulin extraction. It also reduced glucose and insulin intolerance and serum and tissue (liver and muscle) triglyceride levels. Additionally, CR reversed inflammation, oxidative stress, and fibrosis in liver. The data support a significant role of CR in the normalization of insulin and lipid metabolism in liver.

The hypertension-diabetes continuum

Hypertension and type 2 diabetes are both common chronic conditions that affect a major proportion of the general population. They tend to occur in the same individual, suggesting common predisposing factors, which can be genetic or environmental. Although the genes causing hypertension or diabetes await elucidation, the environmental causes of these diseases are well known. Obesity and physical activity are the 2 leading factors that predispose to both diseases. Individuals with abdominal obesity are likely to develop lipid abnormalities and elevation of blood pressure and glucose. In time, hypertension and diabetes ensue. Because of the shared etiology, there is substantial overlap between hypertension and diabetes. In the Hong Kong Cardiovascular Risk Factor Prevalence Study, 40% of the subjects in the community had either raised blood pressure or raised blood glucose. Only 42% of people with diabetes had normal blood pressure and only 56% of people with hypertension had normal glucose tolerance. The presence of hypertension or diabetes should alert the clinician to the possibility of the other condition. Obesity, lipid abnormalities, raised blood pressure, and glucose are all components of the metabolic syndrome. The syndrome therefore implies a pathologic process, which is potentially reversible in the early stages. Previous efforts targeting smoking, hypertension, and hypercholesterolemia have started to bear fruit. However, obesity is on the increase in developed and developing countries. It is now time to focus on obesity and the metabolic syndrome, which require more a public health than a pharmacologic approach.

Combination drug treatment in patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) includes simple steatosis, a benign condition, and non-alcoholic steatohepatitis, a condition that beyond TG accumulation also includes necroinflammation and fibrosis. An association between NAFLD and cardiovascular disease (CVD) has been recently suggested. NAFLD patients usually have an increased CVD risk profile. NAFLD is also associated with metabolic syndrome (MetS) and is considered as the hepatic component of MetS by some authors. Currently, the only established treatment of NAFLD is gradual weight loss. However, multifactorial treatment of NAFLD risk factors may be needed to reduce the increased CVD risk of NALFD patients. Drug combinations that include antiobesity drugs (such as orlistat and sibutramine) and target CVD risk factors may be a good approach to NAFLD patients. Our group has investigated the orlistat-fenofibrate combination treatment in obese patients with MetS and the orlistat-ezetimibe and sibutramine-antihypertensive combination treatment in obese patients with hyperlipidaemia with promising results in CVD risk factor reduction and improvement of liver function tests. Small studies give promising results but double-blind, randomized trials examining the effects of such multifactorial treatment in hard CVD endpoints in NAFLD patients are missing.

PPARdelta ligand L-165041 ameliorates Western diet-induced hepatic lipid accumulation and inflammation in LDLR-/- mice

Although peroxisome proliferator-activated receptor delta (PPARdelta) has been implicated in energy metabolism and lipid oxidation process, detailed roles of PPARdelta in lipid homeostasis under pathologic conditions still remain controversial. Thus, we investigated the effect of PPARdelta ligand L-165041 on Western diet-induced fatty liver using low-density lipoprotein receptor-deficient (LDLR(-/-)) mice. LDLR(-/-) mice received either L-165041 (5mg/kg/day) or vehicle (0.1N NaOH) with Western diet for 16 weeks. According to our data, L-165041 drastically reduced lipid accumulation in the liver, decreasing total hepatic cholesterol and triglyceride content compared to the vehicle group. Gene expression analysis demonstrated that L-165041 lowered hepatic expression of PPARgamma, apolipoprotein B, interleukin 1 beta (IL-1beta), and interleukin-6. In contrast, L-165041 increased hepatic expressions of PPARdelta, lipoprotein lipase (LPL), and ATP-binding cassette transporter G1 (ABCG1). Our data suggest that L-165041 might be effective in preventing Western diet-induced hepatic steatosis by regulating genes involved in lipid metabolism and the inflammatory response.

Treating hypertension while protecting the vulnerable islet in the cardiometabolic syndrome

Hypertension, a multifactorial-polygenic disease, interacts with multiple environmental stressors and results in functional and structural changes in numerous end organs, including the cardiovascular system. This can result in coronary heart disease, stroke, peripheral vascular disease, congestive heart failure, end-stage renal disease, insulin resistance, and damage to the pancreatic islet. Hypertension is the most important modifiable risk factor for major health problems encountered in clinical practice. Whereas hypertension was once thought to be a medical condition based on discrete blood pressure readings, a new concept has emerged defining hypertension as part of a complex and progressive metabolic and cardiovascular disease, an important part of a cardiometabolic syndrome. The central role of insulin resistance, oxidative stress, endothelial dysfunction, metabolic signaling defects within tissues, and the role of enhanced tissue renin-angiotensin-aldosterone system activity as it relates to hypertension and type 2 diabetes mellitus are emphasized. Additionally, this review focuses on the effect of hypertension on functional and structural changes associated with the vulnerable pancreatic islet. Various classes of antihypertensive drugs are reviewed, especially their roles in delaying or preventing damage to the vulnerable pancreatic islet, and thus delaying the development of type 2 diabetes mellitus.

Recent advances in nonalcholic fatty liver disease

PURPOSE OF REVIEW

The purpose of this review is to summarize recent advances in defining the clinical features, pathophysiology, natural history, and treatment of nonalcoholic fatty liver disease.

RECENT FINDINGS

Nonalcoholic fatty liver disease is present in approximately 30% of the US population. A histologic grading and staging system has been developed and validated. Nonalcoholic fatty liver disease increases the risk of developing the metabolic syndrome. The presence and severity of nonalcoholic fatty liver disease correlates with the severity of obesity, fat distribution, age, and presence of other features of the metabolic syndrome. Fifteen to 20% of subjects with nonalcoholic steatohepatitis develop cirrhosis. Hepatic steatosis is associated with an increase in both free fatty acid delivery to the liver for re-esterification and increased de-novo lipogenesis. Several mechanisms of hepatocyte injury and death including free fatty acid toxicity, increased free cholesterol, cytokine-mediated injury and activation of the unfolded protein response have been defined. While many therapeutic targets have been identified and pilot studies performed, a definitive treatment for nonalcoholic steatohepatitis remains to be established.

SUMMARY

Nonalcoholic fatty liver disease is a widely prevalent disease that is critically linked to insulin resistance and the metabolic syndrome. While much new information on the pathogenesis and natural history of nonalcoholic steatohepatitis is available, an effective therapy remains to be established.

Advances in regulation mechanism of hepatocyte apoptosis in nonalcoholic fatty liver disease

The pathogenic mechanism of nonalcoholic fatty liver disease (NAFLD) still remains unclear. In recent years, many studies indicate that abnormal hepatocyte apoptosis exists in NAFLD, confirming the close relationship between NAFLD and hepatocyte apoptosis. The regulation of cell apoptosis includes two: positive or negative. In this paper, we review the research advances in the regulation of hepatocyte apoptosis during the pathogenesis of NAFLD.

Renin-angiotensin-aldosterone system and oxidative stress in cardiovascular insulin resistance

Hypertension commonly occurs in conjunction with insulin resistance and other components of the cardiometabolic syndrome. Insulin resistance plays a significant role in the relationship between hypertension, Type 2 diabetes mellitus, chronic kidney disease, and cardiovascular disease. There is accumulating evidence that insulin resistance occurs in cardiovascular and renal tissue as well as in classical metabolic tissues (i.e., skeletal muscle, liver, and adipose tissue). Activation of the renin-angiotensin-aldosterone system and subsequent elevations in angiotensin II and aldosterone, as seen in cardiometabolic syndrome, contribute to altered insulin/IGF-1 signaling pathways and reactive oxygen species formation to induce endothelial dysfunction and cardiovascular disease. This review examines currently understood mechanisms underlying the development of resistance to the metabolic actions of insulin in cardiovascular as well as skeletal muscle tissue.