Insulin resistance and reduced metabolic flexibility: cause or consequence of NAFLD?

From circadian clocks to non-alcoholic fatty liver disease

Introduction: The circadian rhythm is an integral regulator of various endocrine processes in the body, including sleep-wake cycles, hormonal regulation, and metabolism. In addition to metabolic, genetic, and environmental factors, a dysregulated circadian rhythm resulting from lifestyle changes has been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). An accumulating body of evidence also supports strong association between NAFLD and metabolic disorder, the pathogenesis of which is related to periodic fluctuations in hormonal homeostasis. It is clear that endocrine and circadian rhythms are tightly interconnected. Generally, the circadian rhythm regulates flux patterns of physiological functions. The present review will discuss the modulation of bodily processes by the circadian rhythm with specific attention to the regulation of NAFLD by leptin and related hormones.Areas covered: PubMed/MEDLINE was searched for articles related to concomitant occurrence of NAFLD and T2DM between January 1995 and September 2019. Areas covered included epidemiological, physiology and pathophysiology aspects.Expert opinion: NAFLD and NASH are increasingly prevalent and may be largely mitigated with effective lifestyle modification and, potentially, circadian rhythm stabilization. Improved knowledge of the specific pathogenesis of NAFLD in addition to enhanced diagnostic screening tools and prediction of future disease burden is imperative.

From "two hit theory" to "multiple hit theory": Implications of evolution of pathogenesis concepts for treatment of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is becoming a burgeoning and burdensome public health problem worldwide, along with diabetes and metabolic syndrome. In the NAFLD spectrum, non-alcoholic steatohepatitis can progress to hepatic fibrosis, especially progressive fibrosis, which can lead to cirrhosis or even hepatocellular carcinoma. However, the pathogenesis of NAFLD is extremely complex and has not yet been fully elucidated, thus there is a lack of effective treatment. In recent years, the classic "two-hit" hypothesis has been gradually surpassed and supplemented by a great deal of findings, and the "multiple hit" hypothesis has been proposed and is being accepted. The study on the interaction among cellular and molecular mechanisms, environmental and genetic factors has revealed a number of critical targets in the pathogenesis of NAFLD, providing broad directions for the development of diagnostic markers and targeted therapeutic drugs. Here we elaborate the latest advances in understanding the pathogenesis of NAFLD from multiple perspectives, in order to analyze and evaluate the prospect of developing diagnostic biomarkers and therapeutic targets based on those pathogeneses.

From NASH to diabetes and from diabetes to NASH: Mechanisms and treatment options

The worldwide prevalence of non-alcoholic fatty liver disease (NAFLD) is estimated to have reached 25% or more in adults. NAFLD is prevalent in obese individuals, but may also affect non-obese insulin-resistant individuals. NAFLD is associated with a 2- to 3-fold increased risk of developing type 2 diabetes (T2D), which may be higher in patients with more severe liver disease - fibrosis increases this risk. In NAFLD, not only the close association with obesity, but also the impairment of many metabolic pathways, including decreased hepatic insulin sensitivity and insulin secretion, increase the risk of developing T2D and related comorbidities. Conversely, patients with diabetes have a higher prevalence of steatohepatitis, liver fibrosis and end-stage liver disease. Genetics and mechanisms involving dysfunctional adipose tissue, lipotoxicity and glucotoxicity appear to play a role. In this review, we discuss the altered pathophysiological mechanisms that underlie the development of T2D in NAFLD and vice versa. Although there is no approved therapy for the treatment of NASH, we discuss pharmacological agents currently available to treat T2D that could potentially be useful for the management of NASH.

Association between nut intake and non-alcoholic fatty liver disease risk: a retrospective case-control study in a sample of Chinese Han adults

OBJECTIVES

Nut consumption has been associated with a lower risk of type 2 diabetes, metabolic syndrome and insulin resistance. However, its effect on the risk of non-alcoholic fatty liver disease (NAFLD) is unknown. Therefore, we investigated the relationship between nut consumption and NAFLD risk.

SETTING AND PARTICIPANTS

We conducted a retrospective case-control study including 534 patients diagnosed with NAFLD and 534 controls matched by sex and age (±5 years) from the Affiliated Nanping First Hospital of Fujian Medical University in China.

MAIN OUTCOME MEASURES

Information on dietary intake was collected using a semiquantitative food frequency questionnaire and nut consumption was calculated. Nut consumption was categorised using quartiles based on the distribution of daily nut intake of the controls. Binary logistic regression models were used to estimate ORs and the 95% CIs for the association between nut consumption and NAFLD risk.

RESULTS

After adjusting for potential confounding variables, nut consumption was not associated with NAFLD risk in the overall sample. When the fully adjusted model was stratified by sex, a significant inverse association was found between high nut consumption and NAFLD only among the men in the highest quartile (OR=0.43; 95% CI 0.26 to 0.71; P_{trend =} 0.01). The inverse association of nut consumption with NAFLD risk in men remained significant after controlling for other known or suspected risk factors for NAFLD.

CONCLUSIONS

Diets with a higher intake of nuts may be associated with a decreased risk of NAFLD, particularly in men.

Antioxidant Versus Pro-Apoptotic Effects of Mushroom-Enriched Diets on Mitochondria in Liver Disease

Mitochondria play a central role in non-alcoholic fatty liver disease (NAFLD) progression and in the control of cell death signalling during the progression to hepatocellular carcinoma (HCC). Associated with the metabolic syndrome, NAFLD is mostly driven by insulin-resistant white adipose tissue lipolysis that results in an increased hepatic fatty acid influx and the ectopic accumulation of fat in the liver. Upregulation of beta-oxidation as one compensatory mechanism leads to an increase in mitochondrial tricarboxylic acid cycle flux and ATP generation. The progression of NAFLD is associated with alterations in the mitochondrial molecular composition and respiratory capacity, which increases their vulnerability to different stressors, including calcium and pro-inflammatory molecules, which result in an increased generation of reactive oxygen species (ROS) that, altogether, may ultimately lead to mitochondrial dysfunction. This may activate further pro-inflammatory pathways involved in the progression from steatosis to steatohepatitis (NASH). Mushroom-enriched diets, or the administration of their isolated bioactive compounds, have been shown to display beneficial effects on insulin resistance, hepatic steatosis, oxidative stress, and inflammation by regulating nutrient uptake and lipid metabolism as well as modulating the antioxidant activity of the cell. In addition, the gut microbiota has also been described to be modulated by mushroom bioactive molecules, with implications in reducing liver inflammation during NAFLD progression. Dietary mushroom extracts have been reported to have anti-tumorigenic properties and to induce cell-death via the mitochondrial apoptosis pathway. This calls for particular attention to the potential therapeutic properties of these natural compounds which may push the development of novel pharmacological options to treat NASH and HCC. We here review the diverse effects of mushroom-enriched diets in liver disease, emphasizing those effects that are dependent on mitochondria.

FBXW7 suppresses HMGB1-mediated innate immune signaling to attenuate hepatic inflammation and insulin resistance in a mouse model of nonalcoholic fatty liver disease

Background

Innate immune dysfunction contributes to the development and progression of nonalcoholic fatty liver disease (NAFLD), however, its pathogenesis is still incompletely understood. Identifying the key innate immune component responsible for the pathogenesis of NAFLD and clarifying the underlying mechanisms may provide therapeutic targets for NAFLD. Recently, F-box- and WD repeat domain-containing 7 (FBXW7) exhibits a regulatory role in hepatic glucose and lipid metabolism. This study aims to investigate whether FBXW7 controls high-mobility group box 1 protein (HMGB1)-mediated innate immune signaling to improve NAFLD and the mechanism underlying this action.

Methods

Mice were fed a high-fat diet (HFD) for 12 or 20 weeks to establish NAFLD model. Hepatic overexpression or knockdown of FBXW7 was induced by tail-vein injection of recombinant adenovirus. Some Ad-FBXW7-injected mice fed a HFD were injected intraperitoneally with recombinant mouse HMGB1 to confirm the protective role of FBXW7 in NAFLD via inhibition of HMGB1.

Results

FBXW7 improves NAFLD and related metabolic parameters without remarkable influence of body weight and food intake. Moreover, FBXW7 markedly ameliorated hepatic inflammation and insulin resistance in the HFD-fed mice. Furthermore, FBXW7 dramatically attenuated the expression and release of HMGB1 in the livers of HFD-fed mice, which is associated with inhibition of protein kinase R (PKR) signaling. Thereby, FBXW7 restrains Toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE) signaling in HFD-fed mouse livers. In addition, exogenous HMGB1 treatment abolished FBXW7-mediated inhibition of hepatic inflammation and insulin resistance in HFD-fed mouse livers.

Conclusions

Our results demonstrate a protective role of FBXW7 in NAFLD by abating HMGB1-mediated innate immune signaling to suppress inflammation and consequent insulin resistance, suggesting that FBXW7 is a potential target for therapeutic intervention in NAFLD development.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0099-9) contains supplementary material, which is available to authorized users.

Validation of biochemical scores for liver steatosis before and 1 year after sleeve gastrectomy

BACKGROUND

Bariatric surgery is a potential treatment for liver steatosis in morbidly obese patients, showing an improvement in approximately 90% of cases of fatty liver after surgery. Liver biopsy is the gold standard method to monitor liver steatosis. Imaging tests, such as magnetic resonance (MR) spectroscopy, have shown a good accuracy in the diagnosis of liver steatosis. Several biochemical markers have been proposed as diagnostic alternatives to evaluate fatty liver.

OBJECTIVES

The aim of this study was to analyze the potential of different biochemical markers for evaluating liver steatosis in morbidly obese patients before and after undergoing sleeve gastrectomy.

SETTING

Garcilaso Clinic, Madrid, Spain.

METHODS

A prospective observational study of patients undergoing sleeve gastrectomy was performed. Diverse biochemical markers were assessed and correlated with MR spectroscopy as the diagnostic method for liver steatosis.

RESULTS

One hundred consecutive patients were included. Twelve months after surgery, mean body mass index was 28.3 ± 3.7 kg/m² and mean excess weight loss 82.5% ± 17.8%. Preoperatively, 67% of the patients had liver steatosis and 12 months after surgery the steatosis rate was reduced to 23%, as measured by MR spectroscopy. A significant direct correlation could only be observed between the percentage of lipid content, determined by MR spectroscopy and the liver fat score, at baseline and in the preoperative score. A cut-off point for liver fat score to determine the presence of liver steatosis was established at 1.22, for baseline and postoperative determinations.

CONCLUSION

The liver fat score is the most accurate biochemical score to correlate with the percentage of lipid content of the liver, determined by MR spectroscopy.

Epigenetic Markers and Microbiota/Metabolite-Induced Epigenetic Modifications in the Pathogenesis of Obesity, Metabolic Syndrome, Type 2 Diabetes, and Non-alcoholic Fatty Liver Disease

PURPOSE OF REVIEW

The metabolic syndrome is a pathological state in which one of the key components is insulin resistance. A wide spectrum of body compartments is involved in its pathophysiology. Genetic and environmental factors such as diet and physical activity are both related to its etiology. Reversible modulation of gene expression without altering the DNA sequence, known as epigenetic modifications, has been shown to drive this complex metabolic cluster of conditions. Here, we aim to examine some of the recent research of specific epigenetically mediated mechanisms and microbiota-induced epigenetic modifications on the development of adipose tissue and obesity, β-cell dysfunction and diabetes, and hepatocytes and non-alcoholic fatty disease.

RECENT FINDINGS

DNA methylation patterns and histone modifications have been identified in this context; the integrated analysis of genome, epigenome, and transcriptome is likely to expand our knowledge of epigenetics in health and disease. Epigenetic modifications induced by diet-related microbiota or metabolites possibly contribute to the insulin-resistant state. The identification of epigenetic signatures on diabetes and obesity may give us the possibility of developing new interventions, prevention measures, and follow-up strategies.

Experimental non-alcoholic steatohepatitis in Göttingen Minipigs: consequences of high fat-fructose-cholesterol diet and diabetes

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in humans, and ranges from steatosis to non-alcoholic steatohepatitis (NASH), the latter with risk of progression to cirrhosis. The Göttingen Minipig has been used in studies of obesity and diabetes, but liver changes have not been described. The aim of this study was to characterize hepatic changes in Göttingen Minipigs with or without diabetes, fed a diet high in fat, fructose, and cholesterol to see if liver alterations resemble features of human NAFLD/NASH.

METHODS

Fifty-four male castrated minipigs (age 6 to 7 months) were distributed into four groups and diet-fed for 13 months. Groups were: lean controls fed standard diet (SD, n = 8), a group fed high fat/fructose/cholesterol diet (FFC, n = 16), a group fed high fat/fructose/cholesterol diet but changed to standard diet after 7 months (diet normalization, FFC/SD, n = 16), and a streptozotocin-induced diabetic group fed high fat/fructose/cholesterol diet (FFC_DIA, n = 14). At termination, blood samples for analyses of circulating biomarkers and liver tissue for histopathological assessment and analyses of lipids and glycogen content were collected.

RESULTS

In comparison with SD and FFC/SD, FFC and FFC_DIA pigs developed hepatomegaly with increased content of cholesterol, whereas no difference in triglyceride content was found. FFC and FFC_DIA groups had increased values of circulating total cholesterol and triglycerides and the hepatic circulating markers alkaline phosphatase and glutamate dehydrogenase. In the histopathological evaluation, fibrosis (mainly located periportally) and inflammation along with cytoplasmic alterations (characterized by hepatocytes with pale, granulated cytoplasm) were found in FFC and FFC_DIA groups compared to SD and FFC/SD. Interestingly, FFC/SD also had fibrosis, a feature not seen in SD. Only two FFC and three FFC_DIA pigs had > 5% steatosis, and no hepatocellular ballooning or Mallory-Denk bodies were found in any of the pigs.

CONCLUSIONS

Fibrosis, inflammation and cytoplasmic alterations were characteristic features in the livers of FCC and FFC_DIA pigs. Overall, diabetes did not exacerbate the hepatic changes compared to FFC. The limited presence of the key human-relevant pathological hepatic findings of steatosis and hepatocellular ballooning and the variation in the model, limits its use in preclinical research without further optimisation.

Non-alcoholic fatty liver disease: causes, diagnosis, cardiometabolic consequences, and treatment strategies

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. In some patients with NAFLD, isolated steatosis can progress to advanced stages with non-alcoholic steatohepatitis (NASH) and fibrosis, increasing the risk of cirrhosis and hepatocellular carcinoma. Furthermore, NAFLD is believed to be involved in the pathogenesis of common disorders such as type 2 diabetes and cardiovascular disease. In this Review, we highlight novel concepts related to diagnosis, risk prediction, and treatment of NAFLD. First, because NAFLD is a heterogeneous disease, the advanced stages of which seem to be strongly affected by comorbidities such as insulin resistance and type 2 diabetes, early use of reliable, non-invasive diagnostic tools is needed, particularly in patients with insulin resistance or diabetes, to allow the identification of patients at different disease stages. Second, although the strongest genetic risk alleles for NAFLD (ie, the 148Met allele in PNPLA3 and the 167Lys allele in TM6SF2) are associated with increased liver fat content and progression to NASH and cirrhosis, these alleles are also unexpectedly associated with an apparent protection from cardiovascular disease. If consistent across diverse populations, this discordance in NAFLD-related risk prediction between hepatic and extrahepatic disease might need to be accounted for in the management of NAFLD. Third, drug treatments assessed in NAFLD seem to differ with respect to cardiometabolic and antifibrotic efficacy, suggesting the need to better identify and tailor the most appropriate treatment approach, or to use a combination of approaches. These emerging concepts could contribute to the development of a multidisciplinary approach for endocrinologists and hepatologists working together in the management of NAFLD.

The efficacy of saxagliptin in T2DM patients with non-alcoholic fatty liver disease: preliminary data

OBJECTIVE

To investigate the clinical efficacy and the possible mechanisms of saxagliptin in the treatment of type 2 diabetes mellitus (T2DM) combined with non-alcoholic fatty liver disease (NAFLD).

METHODS

A total of 95 T2DM and NAFLD patients were randomly divided into group A (saxagliptin group), group B (glimepiride group), and group C (glimepiride combined with polyene phosphatidylcholine group).

RESULTS

After intervention treatment for 24 w, body mass index (BMI), waist-to-hip ratio (WHR), glycated haemoglobin (HbA1c), fasting plasma glucose (FPG), fasting insulin (FINS), homeostatic model assessment of insulin resistance (HOMA-IR), interleukin-6 (IL-6), triglyceride (TG), total cholesterol (TC), alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (γ-GT), and quantitative detection of liver steatosis of study subjects were observed, the action of liver steatosis in subjects of groups A and C were significantly different from those of group B; however, there were no differences between groups A and C. The FINS, HOMA-IR, and IL-6 of subjects in group A was lower than those in groups B and C; however, there were no significant differences between the latter two groups.

CONCLUSION

For T2DM combined with NAFLD patients, the saxagliptin treatment could not only effectively control blood glucose but also attenuate insulin resistance and inflammatory injury of the liver to improve fatty liver further.

L-Ornithine L-Aspartate (LOLA) as a Novel Approach for Therapy of Non-alcoholic Fatty Liver Disease

L-ornithine L-aspartate (LOLA) has been known as an effective ammonia-lowering agent for more than 50 years with good evidence in hepatic encephalopathy. Administration of LOLA removes ammonia via two distinct mechanisms: by synthesis of urea and by the synthesis of glutamine via the enzyme glutamine synthetase. While LOLA has been used in cirrhosis and acute liver injury settings, it is less clear if LOLA could be used in non-alcoholic fatty liver disease (NAFLD). NAFLD and the progressive form non-alcoholic steatohepatitis (NASH) are currently the leading causes of chronic liver disease worldwide, with roughly 25% of the world population affected by NAFLD. Consequences of NASH are end-stage liver disease and cardiovascular morbidity and mortality. As the basis for NAFLD is excess calorie uptake and excess adipose tissue mass, the conservative therapeutic approach is weight loss by intense lifestyle change. However, no pharmacological treatment options are currently approved. LOLA is being investigated as a pharmacological tool to ameliorate liver injury in NAFLD on the basis that it lowers liver ammonia concentrations and supplies anti-oxidative glutamine and glutathione. Indirect hepatoprotective effects currently under investigation could also be beneficial.

Sex-based differences in hepatic and skeletal muscle triglyceride storage and metabolism 1

Women and men store lipid differently within the body with men storing more fat in the android region and women storing more fat in the gynoid region. Fat is predominately stored in adipose tissue as triacylglycerides (TG); however, TG are also stored in other tissues including the liver and skeletal muscle. Excess hepatic TG storage, defined as a TG concentration >5% of liver weight and known as nonalcoholic fatty liver disease (NAFLD), is related to the metabolic syndrome. Similarly, elevated skeletal muscle TG, termed intramyocellular lipids (IMCL), are related to insulin resistance in obesity and type II diabetes. Men store more hepatic TG than women and, unsurprisingly, NAFLD is more prevalent in men than women. Women store more IMCL than men, yet type II diabetes risk is not greater, which is likely due to the manner in which women store TG within muscle. Sex-based differences in TG storage between men and women are underpinned by differences in messenger RNA expression, protein content, and enzyme activities of skeletal muscle and hepatic lipid metabolic pathways. Furthermore, women have a greater reliance on lipid during exercise because of upregulation of lipid oxidative pathways. The purpose of this review is to discuss the role of sex in mediating lipid storage and metabolism within skeletal muscle and the liver at rest and during exercise and its relationship with metabolic disease.

Elevated free fatty acid level is associated with insulin-resistant state in nondiabetic Chinese people

BACKGROUND

Free fatty acids (FFAs) are associated with insulin secretion and insulin resistance. However, the associations among FFAs, obesity, and progression from a normal to a prediabetic state are unclear.

METHODS

Nondiabetic subjects (5,952) were divided in two groups according to their body mass index (BMI): obese subjects (BMI ≥24 kg/m²) and nonobese subjects (BMI <24 kg/m²). Clinical and multiple glucolipid metabolism data were collected. The homeostasis model assessment for insulin resistance (HOMA-IR) and β-cell function (HOMA-β) was used. HbA1c level between 5.7% and 6.4% was considered prediabetic. Nonparametric tests, one-way ANOVA, and linear correlation analysis were performed. R and SPSS 23.0 software programs were used to analyze the results.

RESULTS

A U-shaped relationship between FFAs and HOMA-IR was observed. After adjusting for potential confounders, the turning points of FFA levels in the curves were 0.54 mmol/L in the nonobese group and 0.61 mmol/L in the obese group. HOMA-IR levels decreased with increasing FFA concentrations before the turning points (regression coefficient [β]= - 0.9, P=0.0111, for the nonobese group; β=0.2, P=0.5094, for the obese group) and then increased (β=0.9, P=0.0069, for the nonobese group; β=1.5, P=0.0263 for the obese group) after the points. Additionally, our study also identified that FFAs were associated with the prediabetes status in obese individuals.

CONCLUSION

FFA levels were associated with insulin resistance in nondiabetic subjects, and HOMA-IR in nonobese individuals was more sensitive to FFA changes. Monitoring and controlling plasma FFA levels in obese subjects is significant in decreasing insulin resistance and preventing diabetes.

Carnitine acetyltransferase (Crat) in hunger-sensing AgRP neurons permits adaptation to calorie restriction

Hunger-sensing agouti-related peptide (AgRP) neurons ensure survival by adapting metabolism and behavior to low caloric environments. This adaption is accomplished by consolidating food intake, suppressing energy expenditure, and maximizing fat storage (nutrient partitioning) for energy preservation. The intracellular mechanisms responsible are unknown. Here we report that AgRP carnitine acetyltransferase (Crat) knockout (KO) mice exhibited increased fatty acid utilization and greater fat loss after 9 d of calorie restriction (CR). No differences were seen in mice with ad libitum food intake. Eleven days ad libitum feeding after CR resulted in greater food intake, rebound weight gain, and adiposity in AgRP Crat KO mice compared with wild-type controls, as KO mice act to restore pre-CR fat mass. Collectively, this study highlights the importance of Crat in AgRP neurons to regulate nutrient partitioning and fat mass during chronically reduced caloric intake. The increased food intake, body weight gain, and adiposity in KO mice after CR also highlights the detrimental and persistent metabolic consequence of impaired substrate utilization associated with CR. This finding may have significant implications for postdieting weight management in patients with metabolic diseases.-Reichenbach, A., Stark, R., Mequinion, M., Lockie, S. H., Lemus, M. B., Mynatt, R. L., Luquet, S., Andrews, Z. B. Carnitine acetyltransferase (Crat) in hunger-sensing AgRP neurons permits adaptation to calorie restriction.

Insulin resistance in lean and overweight non-diabetic Caucasian adults: Study of its relationship with liver triglyceride content, waist circumference and BMI

Aims

Insulin resistance is the pathophysiological precursor of type 2 diabetes mellitus (DM-2), and its relationship with non-alcoholic fatty liver disease (NAFLD) has been widely studied in patients with obesity or metabolic syndrome using not only ultrasound but also liver biopsies or proton magnetic resonance spectroscopy (H¹-MRS) to assess liver fat content. In contrast, there are no studies on insulin resistance and NAFLD in lean or overweight Caucasian individuals using H¹-MRS or liver biopsies for the quantification of hepatic triglyceride content. Our objectives were to study the presence of insulin resistance in lean and overweight Caucasian adults and investigate its possible relationship with liver triglyceride content, waist circumference (as proxy of visceral adiposity), BMI, and cardiometabolic risk factors.

Methods

A cross-sectional study was conducted in 113 non-obese, non-diabetic individuals classified as overweight (BMI 25–29.9 kg/m²) or lean (BMI 19.5–24.9 kg/m²). Hepatic triglyceride content was quantified by 3T H¹-MRS. NAFLD was defined as hepatic triglyceride content >5.56%. Insulin resistance (HOMA-IR), serum adiponectin, and tumor necrosis factor (TNF) were determined.

Results

HOMA-IR was significantly correlated with hepatic triglyceride content (r:0.76; p<0.0001). The lean-with-NAFLD group had significantly higher HOMA-IR (p<0.001) and lower serum adiponectin (p<0.05) than the overweight-without-NAFLD group. Insulin resistance was independently associated with NAFLD but not with waist circumference or BMI. Regression analysis showed hepatic triglyceride content to be the most important determinant of insulin resistance (p<0.01).

Conclusions

Our findings suggest that NAFLD, once established, seems to be involved in insulin resistance and cardio-metabolic risk factors above and beyond waist circumference and BMI in non-obese, non-diabetic Caucasian individuals.

Circular RNAs in Metabolic Diseases

Metabolic diseases include diabetes mellitus (DM), obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). Circular RNA is a new type of RNA that is different from traditional linear RNA and has a closed loop structure. However, the function of circular RNA is not yet well elucidated in metabolic diseases. Only a few studies have reported about the relationship between circular RNA and metabolic diseases such as DM and NAFLD. This chapter presents a brief review of epidemiology, pathophysiology, or treatment of DM and NAFLD and then discusses the relationship between circular RNA and DM or NAFLD. Besides, this chapter further provides an updated discussion of the most relevant discoveries regarding circular RNA and their potential applications in molecular diagnostics, nucleic acid therapy, and biomarkers.

Diabetes Mellitus and Risk of Hepatocellular Carcinoma

The occurrence of hepatocellular carcinoma (HCC) is two to three times higher in patients with diabetes mellitus (DM), the prevalence of which is increasing sharply worldwide. The purpose of this review was to describe clinical links between DM and HCC and potential biological mechanisms that may account for this association. We evaluated the role of potential pathways that could account for the development of HCC with different etiologies in the presence of DM. In addition, we also briefly discuss the potential effect of other factors such as type and dosage of antidiabetic medicines and duration of DM on HCC risk.