Viewpoints on the way to a consensus session: where does insulin resistance start? The liver

Mercaptonicotinic acid activated thiolated chitosan (MNA-TG-chitosan) to enable peptide oral delivery by opening cell tight junctions and enhancing transepithelial transport

Recent advances in peptide delivery and nanotechnology has resulted in emergence of several non-parenteral administration routes that replace subcutaneous injections associated with patient discomfort. Thiolated biopolymers are relatively new materials being explored to enhance mucoadhesivity and permeability in these efforts, yet their pH dependent reactivity remains an obstacle. This work focussed on improving the mucoadhesivity of thiolated chitosans by activating them with mercaptonicotinic acid, in a bid to create a novel thiomerized chitosan that can open cell tight junctions for application in oral delivery. The synthesized mercaptonicotinic acid activated thiolated chistoan (MNA-TG-chitosan), along with thiolated chitosan (TG-chitosan) and unmodified chitosan were then used to create insulin nanoparticles (insNPs) using spray drying encapsulation process. Use of MNA-TG-chitosan in place of chitosan resulted in reduction of particle size of insNPs from 318 to 277 nm with no significant changes in polydispersity index (~ 0.2), encapsulation efficiency (~ 99%), insulin loading content (~ 25%) and morphology. Results from in-vitro cytotoxicity on TR146, CaCo2 and HepG2 cell lines revealed no significant effects on cell viability at 50-1000 μg/mL concentration. insNPs encapsulated with the new material, MNA-TG-chitosan, resulted in a 1.5-fold and 4.4-fold higher cellular uptake by HepG2 liver cells where insulin is metabolized, approximately 40% and 600% greater insulin transport through TR146 buccal cell monolayers, and 40% and 150% greater apparent permeability than insNPs encapsulated with unmodified chitosan and TG-chitosan respectively. The higher permeation achieved on using MNA-TG chitosan was attributed to the greater opening of the cell tight junction evidenced by reduction of transepithelial electrical resistance of TR146 buccal cell monolayers. This study demonstrates MNA-TG-chitosan as a promising material for improved peptide oral delivery.

Qidan Tiaozhi capsule attenuates metabolic syndrome via activating AMPK/PINK1-Parkin-mediated mitophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Qidan Tiaozhi capsule (QD), a traditional Chinese medicine, has been used to treat metabolic syndrome for over a decade. However, the mechanism of QD in the treatment of metabolic syndrome is still unknown.

AIM OF THE STUDY

Growing studies demonstrate that impaired mitophagy is one of the important causes of metabolic syndrome. Thus, this research aims to investigate the mechanism of mitophagy in the QD treatment of metabolic syndrome.

MATERIALS AND METHODS

Network pharmacology and molecular docking were used to probe the mechanism of QD treatment of metabolic syndrome. In an oleic acid-induced cell model, glucose consumption and uptake capacity, triglyceride (TG), total cholesterol (TC), malonaldehyde (MDA), superoxide dismutase (SOD) and ROS levels, and mitochondrial membrane potential (MMP) were examined. mRFP-GFP-LC3 adenovirus and GFP-LC3 lentivirus were used to examine the effect of QD on mitophagy. The IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were also determined. What's more, the PINK1 gene was silenced to verify the above findings. In a high-fat diet-fed mouse model, body weight, organ indexes, OGTT, ITT, HOMA-IR, insulin sensitivity, serum MDA, SOD, TC, TG, LDL-C and HDL-C, hepatic TC, TG, LDL-C and HDL-C levels, hepatic steatosis, and IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were investigated.

RESULTS

Results from network pharmacology and molecular docking suggested that QD might suppress oxidative stress to improve metabolic syndrome. In an oleic acid-induced cell model, compared with the model group, enhanced glucose consumption and uptake ability, inhibited intracellular lipid accumulation, TC, TG, MDA and ROS levels, and increased SOD level and MMP were found in QD groups. And mitophagy levels, IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were promoted. Interestingly, PINK1 silencing reversed the therapeutic action of QD on oleic acid-induced cells. In high-fat diet-fed mice, inhibited body weight, abdominal fat indexes, liver indexes, HOMA-IR, serum and hepatic TC, TG and LDL-C, serum MDA and hepatic steatosis, and increased insulin sensitivity, serum and hepatic HDL-C, serum SOD, and activated IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were found in QD groups.

CONCLUSION

QD activates AMPK/PINK1-Parkin-mediated mitophagy to suppress oxidative stress to treat metabolic syndrome.

Gut-flora metabolites is not associated with synchronous carotid artery plaque and non-alcoholic fatty liver disease in asymptomatic adults: A STROBE-compliant article

Synchronous non-alcoholic fatty liver disease (NAFLD) and carotid artery plaque formation increase the risk of mortality in patients with cardiovascular disease (CVD). Metabolic status and host gut flora are associated with NAFLD and CVD, but the risk factors require further evaluation.To evaluate the risk factors associated with NAFLD and CVD, including gut-flora-related examinations.This cross-sectional study included 235 subjects aged over 40 years who underwent abdominal ultrasound examination and carotid artery ultrasound examination on the same day or within 12 months of abdominal ultrasound between January 2018 and December 2019. All subjects underwent blood tests, including endotoxin and trimethylamine-N-oxide.The synchronous NAFLD and carotid artery plaque subjects had a higher proportion of men and increased age compared with those without NAFLD and no carotid artery plaque. The synchronous NAFLD and carotid artery plaque group had increased body mass index (BMI), blood pressure, hemoglobin A1C (5.71% vs 5.42%), triglyceride (TG) (164.61 mg/dL vs 102.61 mg/dL), and low-density lipoprotein (135.27 mg/dL vs 121.42 mg/dL). In multiple logistic regression analysis, increased BMI, mean systolic blood pressure, and TG > 110 mg/dL were independent risk factors for synchronous NAFLD and carotid artery plaque formation. Endotoxin and trimethylamine-N-oxide levels were not significantly different between the 2 groups.Host metabolic status, such as elevated BMI, TG, and systolic blood pressure, are associated with synchronous NAFLD and carotid artery plaque in asymptomatic adults. Aggressive TG control, blood pressure control, and weight reduction are indicated in patients with NAFLD.

m6A Regulates Liver Metabolic Disorders and Hepatogenous Diabetes

N⁶-methyladenosine (m⁶A) is one of the most abundant modifications on mRNAs and plays important roles in various biological processes. The formation of m⁶A is catalyzed by a methyltransferase complex (MTC) containing a key factor methyltransferase-like 3 (Mettl3). However, the functions of Mettl3 and m⁶A modification in hepatic lipid and glucose metabolism remain unclear. Here, we showed that both Mettl3 expression and m⁶A level increased in the livers of mice with high fat diet (HFD)-induced metabolic disorders. Overexpression of Mettl3 aggravated HFD-induced liver metabolic disorders and insulin resistance. In contrast, hepatocyte-specific knockout of Mettl3 significantly alleviated HFD-induced metabolic disorders by slowing weight gain, reducing lipid accumulation, and improving insulin sensitivity. Mechanistically, Mettl3 depletion-mediated m⁶A loss caused extended RNA half-lives of metabolism-related genes, which consequently protected mice against HFD-induced metabolic syndrome. Our findings reveal a critical role of Mettl3-mediated m⁶A in HFD-induced metabolic disorders and hepatogenous diabetes.

The mother relationship between insulin resistance and non-alcoholic steatohepatitis: Glucosinolates hydrolysis products as a promising insulin resistance-modulator and fatty liver-preventer

Non-alcoholic fatty liver disease (NFLD) is one of the present public health problems which have no specific and effective treatment. The speed of the disease progression depends on the patient's lifestyle. Due to life stresses and lack of time, a high number of people depend on fast food containing a high amount of fats which one of the main causes of insulin resistance (IR). IR is one of the metabolic disorders which strongly intersected with molecular NAFLD and leading to its progression into non-alcoholic steatohepatitis (NASH). In this review, we introduced the updated statistics of NAFLD and NASH progression all over the world shows its importance, etiologies, and pathogenesis. Also, IR and its role in NASH initiation and progression explored, and current treatments with its limitations have been explained. Glucosinolates (GLS) is a group of phytochemicals which known by its potent hydrolysis products with promising anti-cancer effect. In this review, we have collected the recent experimental studies of different GLS hydrolysis products against IR and chronic liver diseases supported by our lab finding. Finally, we recommend this group of phytochemicals as promising molecules to be studied experimentally and clinically against a wide range of chronic liver diseases with an acceptable safety margin.

Mitophagy in Hepatic Insulin Resistance: Therapeutic Potential and Concerns

Metabolic syndrome, characterized by central obesity, hypertension, and hyperlipidemia, increases the morbidity and mortality of cardiovascular disease, type 2 diabetes, nonalcoholic fatty liver disease, and other metabolic diseases. It is well known that insulin resistance, especially hepatic insulin resistance, is a risk factor for metabolic syndrome. Current research has shown that hepatic fatty acid accumulation can cause hepatic insulin resistance through increased gluconeogenesis, lipogenesis, chronic inflammation, oxidative stress and endoplasmic reticulum stress, and impaired insulin signal pathway. Mitochondria are the major sites of fatty acid β-oxidation, which is the major degradation mechanism of fatty acids. Mitochondrial dysfunction has been shown to be involved in the development of hepatic fatty acid–induced hepatic insulin resistance. Mitochondrial autophagy (mitophagy), a catabolic process, selectively degrades damaged mitochondria to reverse mitochondrial dysfunction and preserve mitochondrial dynamics and function. Therefore, mitophagy can promote mitochondrial fatty acid oxidation to inhibit hepatic fatty acid accumulation and improve hepatic insulin resistance. Here, we review advances in our understanding of the relationship between mitophagy and hepatic insulin resistance. Additionally, we also highlight the potential value of mitophagy in the treatment of hepatic insulin resistance and metabolic syndrome.

Comprehensive analysis of differences of N6-methyladenosine RNA methylomes between high-fat-fed and normal mouse livers

Aim: To assess the m⁶A methylome in mouse fatty liver induced by a high-fat diet (HFD). Materials & methods: MeRIP-seq was performed to identify differences in the m⁶A methylomes between the normal liver and fatty liver induced by an HFD. Results: As compared with the control group, the upmethylated coding genes upon feeding an HFD were primarily enriched in processes associated with lipid metabolism, while genes with downmethylation were enriched in processes associated with metabolism and translation. Furthermore, many RNA-binding proteins that potentially bind to differentially methylated m⁶A sites were mainly annotated in processes of RNA splicing. Conclusion: These findings suggest that differential m⁶A methylation may act on functional genes through RNA-binding proteins to regulate the metabolism of lipids in fatty liver disease.

Non-alcoholic fatty liver disease with obesity as an independent predictor for incident gastric and colorectal cancer: a population-based longitudinal study

Background

Colorectal cancer is known to be an extrahepatic complication of non-alcoholic fatty liver disease (NAFLD). However, the interaction of NAFLD with obesity for incident colorectal cancer has not been clarified yet. Moreover, the effect of NAFLD and obesity for incident gastric cancer has not been clarified yet. Thus, we investigated whether NAFLD with or without obesity would be a risk factor for incident gastric cancer as well as colorectal cancer.

Methods

The study period was set from 2003 to 2016. NAFLD was diagnosed by abdominal ultrasonography using standardised criteria. We applied the Cox proportional hazards model to investigate the effect of NAFLD with or without obesity at baseline on incident gastric cancer as well as colorectal cancer. Age, sex, lifestyle factors including smoking states, alcohol consumption and exercise, and diabetes were used as covariates.

Results

During the study period, 27 944 individuals (16 454 men and 11 490 women) were registered in the NAfld in Gifu Area, Longitudinal Analysis study. During the mean (SD) observational period of 2357 (1458) days, incident gastric cancers were diagnosed in 48 individuals (incident rate 0.48 per 1000 person-years) and incident colorectal cancers were diagnosed in 52 individuals (incident rate 0.51 per 1000 person-years). The adjusted HR of NAFLD with obesity for incident gastric cancer was 3.58 (95% CI 1.73 to 7.38, p=0.001) and that for incident colorectal cancer was 2.96 (95% CI 1.73 to 7.38, p=0.003).

Conclusion

NAFLD with obesity was a risk factor for both incident gastric cancer and colorectal cancer in apparently healthy Japanese individuals.

Do flavanols-rich natural products relieve obesity-related insulin resistance?

Growing evidence support that insulin resistance may occur as a severe problem due to chronic energetic overfeeding and subsequent obesity. When an abundance of glucose and saturated fat enter the cell, impaired blood flow, hypoxia, inflammation and macrophage infiltration in obese adipose tissue may induce oxidative stress and insulin resistance. Excessive circulating saturated fatty acids ectopically accumulate in insulin-sensitive tissues and impair insulin action. In this context, excessive hepatic lipid accumulation may play a central, pathogenic role in insulin resistance. It is thought that dietary polyphenols may ameliorate obesity-related insulin resistance by attenuating inflammatory responses and oxidative stress. The most often occurring natural polyphenolic compounds are flavonoids. In this review, the possible mechanistic effect of flavonoid-rich natural products on insulin resistance-related metabolic pathways is discussed. Polyphenol intake can prevent high-fat-diet-induced insulin resistance via cell surface G protein-coupled estrogen receptors by upregulating the expression of related genes, and their pathways, which are responsible for the insulin sensitivity.

The Prevalence of Non-alcoholic Fatty Liver Disease and Diabetes Mellitus in an Iranian Population

BACKGROUND Type II diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD) are important causes of morbidity and mortality worldwide. We aimed to estimate the prevalence of DM in the context of NAFLD. METHODS In this cross-sectional study, we studied 5052 participants, aged 18 years and older, of a baseline population-based cohort in northern Iran (N=6143). The prevalence of DM was estimated in individuals with and without NAFLD. The association between NAFLD and T2DM was evaluated using logistic regression with the adjustment of confounding effects of age, sex, body mass index, lipid profiles, and fasting insulin. RESULTS In men, the prevalence (95% confidence interval) of T2DM was 5.34% (4.35%-6.34%) and 15.06% (13.12%-17.00%) in individuals without and with NAFLD, respectively (p <0.001). In women without NAFLD, the prevalence was 8.27% (6.83%-9.71%) while in the presence of NAFLD, the prevalence was 27.21% (24.59%-29.83%), (p <0.001). In univariate analysis, the chance of having T2DM was 3.700 (3.130-4.380) times more in patients with NAFLD compared with subjects without NAFLD (p<0.001). This chance was reduced (Odds Ratio=1.976, 95% CI: 1.593-2.451, p <0.001) after removing the effects of other variables. CONCLUSION The prevalence of T2DM is increased in the context of NAFLD. This condition may be considered as an independent predictor of T2DM.

Oral Administration of Apple Procyanidins Ameliorates Insulin Resistance via Suppression of Pro-Inflammatory Cytokine Expression in Liver of Diabetic ob/ob Mice

Procyanidins, the main ingredient of apple polyphenols, are known to possess antioxidative and anti-inflammatory effects associated closely with the pathophysiology of insulin resistance and type 2 diabetes. We investigated the effects of orally administered apple procyanidins (APCs) on glucose metabolism using diabetic ob/ob mice. We found no difference in body weight or body composition between mice treated with APCs and untreated mice. A 4 week oral administration of APCs containing water [0.5% (w/v)] ameliorated glucose tolerance, insulin resistance, and hepatic gluconeogenesis in ob/ob mice. APCs also suppressed the increase in the level of the pancreatic β-cell. Insulin-stimulated Akt phosphorylation was significantly enhanced; pro-inflammatory cytokine expression levels were significantly decreased, and c-Jun N-terminal kinase phosphorylation was downregulated in the liver of those mice treated with APCs. In conclusion, APCs ameliorate insulin resistance by improving hepatic insulin signaling through suppression of hepatic inflammation in ob/ob mice, which may be a mechanism with possible beneficial health effects of APCs in disturbed glucose metabolism.

Aerobic capacity and hepatic mitochondrial lipid oxidation alters susceptibility for chronic high-fat diet-induced hepatic steatosis

Rats selectively bred for high capacity running (HCR) or low capacity running (LCR) display divergence for intrinsic aerobic capacity and hepatic mitochondrial oxidative capacity, both factors associated with susceptibility for nonalcoholic fatty liver disease. Here, we tested if HCR and LCR rats display differences in susceptibility for hepatic steatosis after 16 wk of high-fat diets (HFD) with either 45% or 60% of kcals from fat. HCR rats were protected against HFD-induced hepatic steatosis, whereas only the 60% HFD induced steatosis in LCR rats, as marked by a doubling of liver triglycerides. Hepatic complete fatty acid oxidation (FAO) and mitochondrial respiratory capacity were all lower in LCR compared with HCR rats. LCR rats also displayed lower hepatic complete and incomplete FAO in the presence of etomoxir, suggesting a reduced role for noncarnitine palmitoyltransferase-1-mediated lipid catabolism in LCR versus HCR rats. Hepatic complete FAO and mitochondrial respiration were largely unaffected by either chronic HFD; however, 60% HFD feeding markedly reduced 2-pyruvate oxidation, a marker of tricarboxylic acid (TCA) cycle flux, and mitochondrial complete FAO only in LCR rats. LCR rats displayed lower levels of hepatic long-chain acylcarnitines than HCR rats but maintained similar levels of hepatic acetyl-carnitine levels, further supporting lower rates of β-oxidation, and TCA cycle flux in LCR than HCR rats. Finally, only LCR rats displayed early reductions in TCA cycle genes after the acute initiation of a HFD. In conclusion, intrinsically high aerobic capacity confers protection against HFD-induced hepatic steatosis through elevated hepatic mitochondrial oxidative capacity.

Non-Alcoholic Fatty Liver Disease and Extra-Hepatic Cancers

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease but the second cause of death among NAFLD patients are attributed to malignancies at both gastrointestinal (liver, colon, esophagus, stomach, and pancreas) and extra-intestinal sites (kidney in men, and breast in women). Obesity and related metabolic abnormalities are associated with increased incidence or mortality for a number of cancers. NAFLD has an intertwined relationship with metabolic syndrome and significantly contributes to the risk of hepatocellular carcinoma (HCC), but recent evidence have fuelled concerns that NAFLD may be a new, and added, risk factor for extra-hepatic cancers, particularly in the gastrointestinal tract. In this review we critically appraise key studies on NAFLD-associated extra-hepatic cancers and speculate on how NAFLD may influence carcinogenesis at these sites.

Saturation of subcutaneous adipose tissue expansion and accumulation of ectopic fat associated with metabolic dysfunction during late and post-pubertal growth

BACKGROUND/OBJECTIVE

Puberty is a period defined by large changes in adipose tissue accumulation and distribution; however, longitudinal patterns of ectopic fat development have not been shown. We have previously shown significant declines in beta-cell function (BCF) across puberty and hypothesize that accumulation of ectopic fat deposition, particularly hepatic fat, will predict this fall.

SUBJECT/METHODS

We conducted a longitudinal study and examined 2-year change in abdominal fat distribution and type 2 diabetes risk markers in 76 Hispanic children and young adults (16.1±0.5 years, 66% obese, 52% male, 51% post-pubertal). Subcutaneous abdominal adipose tissue (SAAT), visceral adipose tissue (VAT), hepatic fat fraction (HFF) and pancreatic fat fraction (PFF) were measured by 3-Tesla magnetic resonance imaging, and markers of type 2 diabetes risk were collected at fasting and during an oral glucose tolerance test (OGTT).

RESULTS

Baseline pubertal status significantly moderated the 2-year change in ectopic fat deposition, such that VAT, HFF and PFF increased in individuals during late and post-pubertal growth, whereas children earlier in their pubertal development decreased ectopic accumulation and had less VAT accumulation (VAT: pTanner*time=0.044, 0.31±0.08 l vs 0.03±0.10 l; HFF: pTanner*time=0.007, 1.34±0.87% vs -2.61±1.11%; PFF: pTanner*time<0.001, 1.61±0.39% vs -0.96±0.50%). Independent of pubertal status, the 2-year increase in HFF and VAT significantly associated with a decline in BCF (ß=-1.04, P=0.038; ß=-1.81, P=0.020) and metabolic function, while accumulation of SAAT significantly associated with BCF (ß=1.36, P=0.012) and metabolic improvement. HFF accumulation was the only depot to significantly predict clinical markers of type 2 diabetes risk, fasting glucose and HbA1c, and circulating free fatty acid levels (ß=1.00, P=0.034; ß=1.00, P=0.015; ß=01.01, P=0.024).

CONCLUSIONS

The accumulation of SAAT defends against type 2 diabetes risk and potentially ectopic fat accumulation. Intra-abdominal VAT and HFF accumulation both associate with metabolic decline and BCF, while HFF predicts an even greater number of metabolic risk features.

Insight into the impact of dietary saturated fat on tissue-specific cellular processes underlying obesity-related diseases

This study investigated the influence of three high-fat diets (HFDs), differing in the percentage of total calories from saturated fat (SF) (6%, 12%, 24%) but identical in total fat (40%), for a 16-week period in mice on a variety of tissue-specific cellular processes believed to be at the root of obesity-related diseases. Specifically, we examined ectopic lipid accumulation, oxidative capacity [peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) mRNA and protein; mtDNA; Cox IV and cytochrome C protein; citrate synthase activity; and gene expression of fission 1, mitofusin (Mfn) 1 and Mfn2], oxidative stress (4-hydroxy-2-nonenal), endoplasmic reticulum (ER) stress (binding immunoglobulin protein, activating transcription factor 6-p50, p-eukaryotic initiation factor 2 alpha and x-box binding protein 1 spliced protein), inflammatory [p-c-Jun N-terminal kinase (JNK), p-nuclear factor kappa-B, p-p38 mitogen-activated protein kinase) and insulin signaling (p-Akt), and inflammation [tumor necrosis factor-alpha, monocyte chemotactic protein-1, interleukin-6, F4/80, toll-like receptor (TLR)2 and TLR4 gene expression] in various tissues, including the adipose tissue, liver, skeletal muscle and heart. In general, adipose and hepatic tissues were the only tissues which displayed evidence of dysfunction. All HFDs down-regulated adipose, cardiac and hepatic PGC-1α mRNA and hepatic citrate synthase activity, and induced adipose tissue oxidative stress, whereas only the 6%-SF and 12%-SF diet produced hepatic steatosis. However, compared to the 6%-SF and 24%-SF diets, consumption of the 12%-SF diet resulted in the greatest degree of dysregulation (hepatic ER and oxidative stress, JNK activation, increased F4/80 gene expression and down-regulation of adipose tissue Akt signaling). These findings suggest that the saturated fatty acid composition of an HFD can greatly influence the processes responsible for obesity-related diseases - nonalcoholic fatty liver disease, in particular - as well as provide further evidence that the mechanisms at the root of these diseases are diet and tissue sensitive.

Circulating lysophosphatidylcholines are markers of a metabolically benign nonalcoholic fatty liver

OBJECTIVE

Nonalcoholic fatty liver (NAFL) is thought to contribute to insulin resistance and its metabolic complications. However, some individuals with NAFL remain insulin sensitive. Mechanisms involved in the susceptibility to develop insulin resistance in humans with NAFL are largely unknown. We investigated circulating markers and mechanisms of a metabolically benign and malignant NAFL by applying a metabolomic approach.

RESEARCH DESIGN AND METHODS

A total of 265 metabolites were analyzed before and after a 9-month lifestyle intervention in plasma from 20 insulin-sensitive and 20 insulin-resistant subjects with NAFL. The relevant plasma metabolites were then tested for relationships with insulin sensitivity in 17 subjects without NAFL and in plasma from 29 subjects with liver tissue samples.

RESULTS

The best separation of the insulin-sensitive from the insulin-resistant NAFL group was achieved by a metabolite pattern including the branched-chain amino acids leucine and isoleucine, ornithine, the acylcarnitines C3:0-, C16:0-, and C18:0-carnitine, and lysophosphatidylcholine (lyso-PC) C16:0 (area under the ROC curve, 0.77 [P = 0.00023] at baseline and 0.80 [P = 0.000019] at follow-up). Among the individual metabolites, predominantly higher levels of lyso-PC C16:0, both at baseline (P = 0.0039) and at follow-up (P = 0.001), were found in the insulin-sensitive compared with the insulin-resistant subjects. In the non-NAFL groups, no differences in lyso-PC C16:0 levels were found between the insulin-sensitive and insulin-resistant subjects, and these relationships were replicated in plasma from subjects with liver tissue samples.

CONCLUSIONS

From a plasma metabolomic pattern, particularly lyso-PCs are able to separate metabolically benign from malignant NAFL in humans and may highlight important pathways in the pathogenesis of fatty liver-induced insulin resistance.

Selective hepatic insulin resistance in a murine model heterozygous for a mitochondrial trifunctional protein defect

Earlier reports suggest a link between mitochondrial dysfunction and development of hepatic insulin resistance. Here we used a murine model heterozygous (HET) for a mitochondrial trifunctional protein (MTP) gene defect to determine if a primary defect in mitochondrial long-chain fatty acid oxidation disrupts hepatic insulin action. Hyperinsulinemic-euglycemic clamps and signaling studies were performed for assessment of whole-body and hepatic insulin resistance/signaling. In addition, hepatic fatty acid oxidation and hepatic insulin action were assessed in vitro using primary hepatocytes isolated from HET and wildtype (WT) mice. In both hepatic mitochondria and isolated primary hepatocytes, heterozygosity of MTP caused an ∼50% reduction in mitochondrial fatty acid oxidation, a significantly impaired glucose disposal during the insulin clamp, and a markedly lower insulin-stimulated suppression of hepatic glucose production. HET mice also exhibited impaired insulin signaling, with increased hepatic phosphorylation of IRS2 (ser731) and reduced Akt phosphorylation (ser473) in both hepatic tissue and isolated primary hepatocytes. Assessment of insulin-stimulated FOXO1/phospho-FOXO1 protein content and PEPCK/G6Pase messenger RNA (mRNA) expression did not reveal differences between HET and WT mice. However, insulin-induced phosphorylation of GSK3β was significantly blunted in HET mice. Hepatic insulin resistance was associated with an increased methylation status of the catalytic subunit of protein phosphatase 2A (PP2A-C), but was not associated with differences in hepatic diacylglycerol content, activated protein kinase C-ϵ (PKC-ϵ), inhibitor κB kinase β (IKK-β), c-Jun N-terminal kinase (JNK), or phospho-JNK protein contents. Surprisingly, hepatic ceramides were significantly lower in the HET mice compared with WT.

CONCLUSION

A primary defect in mitochondrial fatty acid β-oxidation causes hepatic insulin resistance selective to hepatic glycogen metabolism that is associated with elevated methylated PP2A-C, but independent of other mechanisms commonly considered responsible for insulin resistance. (HEPATOLOGY 2013;).

The role of hepatokines in metabolism

The liver is known to be involved in the natural history of the ongoing epidemics of type 2 diabetes mellitus and cardiovascular disease. In particular, the liver has a role in increased glucose production and dysregulated lipoprotein metabolism, conditions that are often found in patients with nonalcoholic fatty liver disease. Additionally, several proteins that are exclusively or predominantly secreted from the liver are now known to directly affect glucose and lipid metabolism. In analogy to the functional proteins released from adipose tissue and skeletal muscle-adipokines and myokines-these liver-derived proteins are known as hepatokines. The first hepatokine that has been proven to have a major pathogenetic role in metabolic diseases is α2-HS-glycoprotein (fetuin-A). Production of this glycoprotein is increased in steatotic and inflamed liver, but not in expanded and dysregulated adipose tissue. Thus, research into this molecule and other hepatokines is expected to aid in differentiating between the contribution of liver and those of skeletal muscle and adipose tissue, to the pathogenesis of type 2 diabetes mellitus and cardiovascular disease.

Rate of weight gain and cardiometabolic abnormalities in children and adolescents

OBJECTIVE

To investigate whether the rate of weight gain is associated with cardiometabolic risk, independent of weight measured concurrently.

STUDY DESIGN

Healthy 7- to 17-year-old risperidone-treated patients (N = 105, 88% were boys) had blood pressure, anthropometry, and laboratory tests performed. Growth history was extracted from medical records. The rate of change in age- and sex-adjusted weight and body mass index (BMI) z score after the initiation of risperidone was individually modeled. Multivariable linear regression analyses explored the association of the rate of weight or BMI z score change with cardiometabolic outcomes, independent of last measured weight or BMI z score, respectively.

RESULTS

Following a mean of 1.9 years (SD = 1.0) of risperidone treatment, the absolute increase in weight and BMI z scores was 0.61 (SD = 0.61) and 0.62 (SD = 0.73), respectively. After controlling for the final weight z score, the rate of change in weight z score was significantly associated with final glucose (P < .04), C-peptide (P < .004), the homeostasis model assessment insulin resistance index (P < .02), high-density lipoprotein (HDL) cholesterol (P < .0001), a metabolic syndrome score (P < .005), adiponectin (P < .04), and high-sensitivity C-reactive protein (P < .04). After controlling for the final BMI z score, the rate of change in BMI z score was associated with final HDL cholesterol (P < .04), leptin (P < .03), and adiponectin (P < .04), with a suggestion of an association with the final homeostasis model assessment insulin resistance index (P < .08).

CONCLUSIONS

Compared with weight measured concurrently, the rate of weight gain in risperidone-treated children accounts for an equal or larger share of the variance in certain cardiometabolic outcomes (eg, HDL cholesterol [ΔR(2) = 8% vs ΔR(2) = 11%] and high-sensitivity C-reactive protein [ΔR(2) = 5% vs ΔR(2) = 9%]) and may serve as a treatment target.

The potential role of fatty liver in paediatric metabolic syndrome: a distinct phenotype with high metabolic risk?

BACKGROUND

The prevalence of obesity and its metabolic consequences has dramatically increased in the last two decades urging physicians to find a reliable definition for early detection, treatment and possibly prevention of metabolic syndrome (MS). MS could be diagnosed in adult patients in the presence of a large waist circumference and ≥2 of the following features: high serum triglycerides, low serum high-density lipoprotein cholesterol, high blood pressure and high fasting glucose. The definition of MS in children is more problematic, and the potential role of its single components on metabolic risk remains largely undefined. Recent evidence strongly suggests not only a relationship between non-alcoholic fatty liver disease (NAFLD) and MS in obese children, adolescents and adults, but also the key role exerted by liver fat deposition in the pathogenesis of MS.

CONCLUSION

We propose that NAFLD should be routinely checked in obese subjects because early lifestyle changes may be effective in reducing the overall risk of MS.

Are hepatic steatosis and carotid intima media thickness associated in obese patients with normal or slightly elevated gamma-glutamyl-transferase?

BACKGROUND

Hepatic steatosis (HS) has been associated with obesity and metabolic syndrome (MS), conditions carrying a high risk of coronary artery disease. We aimed to determine whether HS was an independent factor of atherogenic risk beyond its association with MS and its components.

METHODS

We assessed the circulating levels of the heat shock protein-70 (HSP-70), a chaperone involved in inflammation, endoplasmic reticulum stress and apoptosis at liver and endothelial level and the gamma-glutamyl transferase activity (γ-GT) correlating them to carotid intima-media thickness (IMT), along with lipid profile, HOMA, C-reactive protein, fibrinogen, ferritin, adiposity type as well as spleen volume in 52 obese pts with grade 1, 128 with grade 2, and 20 with grade 3 of HS evaluated by sonography.

RESULTS

Patients with different grade of HS demonstrated overlapping HSP-70 levels; similarly performed obese subjects regarding IMT. Using multiple regression analysis, IMT was predicted by age, visceral adiposity and by HOMA (β = 0.50, p < 0.0001, β = 0.30, p = 0.01 and β = 0.18, p = 0.048 respectively, while the severity of HS was predicted by visceral and subcutaneous adiposity and HOMA (β = 0.50, p < 0.0001 and β = 0.27, p = 0.001 and β = 0.18, p = 0.024, respectively).

CONCLUSION

In our series of patients with normal or mild elevation of γ-GT, the severity of HS does not entail higher IMT, which may be linked to MS stigmata.

Fatty liver as a consequence and cause of insulin resistance: lessons from type 2 diabetic liver

Obesity is less common in the Asian population, but Asian people may be susceptible to obesity-associated metabolic dysregulation. Accumulating evidence suggests that insulin resistance is closely associated with ectopic fat accumulation in the liver. Whether this correlation is due to a causal relationship between the conditions has long been the subject of debate. Insulin resistance and type 2 diabetes affects liver pathology, typically leading to nonalcoholic fatty liver disease (NAFLD) by dynamically altering the hepatic genes involved in glucose and lipid metabolism. Conversely, how overnutrition induces hepatic insulin resistance has been studied intensively, and has been shown to involve excessive energy flux into mitochondria, toxic lipids, reactive oxygen species, and hepatokines. In this review, we focus on NAFLD both as a consequence and as a cause of insulin resistance through lessons learned from the liver of patients with type 2 diabetes.

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.

Prevalence, metabolic features, and prognosis of metabolically healthy obese Italian individuals: the Cremona Study

OBJECTIVE

Some obese individuals have normal insulin sensitivity. It is controversial whether this phenotype is associated with increased all-cause mortality risk.

RESEARCH DESIGN AND METHODS

Fifteen-year all-cause mortality data were obtained through the Regional Health Registry for 2,011 of 2,074 Caucasian middle-aged individuals of the Cremona Study, a population study on the prevalence of diabetes in Italy. Individuals were divided in four categories according to BMI (nonobese: <30 kg/m²; obese: ≥30 kg/m²) and estimated insulin resistance (insulin sensitive: homeostasis model assessment of insulin resistance <2.5; insulin resistant ≥2.5).

RESULTS

Obese insulin-sensitive subjects represented 11% (95% CI 8.1-14.5) of the obese population. This phenotype had similar BMI but lower waist circumference, blood pressure, fasting glucose, triglycerides, and fibrinogen and higher HDL cholesterol than obese insulin-resistant subjects. In the 15-year follow-up, 495 deaths (cardiovascular disease [CVD]: n = 221; cancer: n = 180) occurred. All-cause mortality adjusted for age and sex was higher in the obese insulin-resistant subjects (hazard ratio 1.40 [95% CI 1.08-1.81], P = 0.01) but not in the obese insulin-sensitive subjects (0.99 [0.46-2.11], P = 0.97) when compared with nonobese insulin-sensitive subjects. Also, mortality for CVD and cancer was higher in the obese insulin-resistant subjects but not in the obese insulin-sensitive subjects when compared with nonobese insulin-sensitive subjects.

CONCLUSIONS

In contrast to obese insulin-resistant subjects, metabolically healthy obese individuals are less common than previously thought and do not show increased all-cause, cancer, and CVD mortality risks in a 15-year follow-up study.

A simple index of lipid overaccumulation is a good marker of liver steatosis

BACKGROUND

Liver steatosis is often found in association with common cardiometabolic disorders, conditions that may all occur in a shared context of abdominal obesity and dyslipidemia. An algorithm for identifying liver steatosis is the fatty liver index (FLI). The lipid accumulation product (LAP) is an index formulated in a representative sample of the US population to identify cardiometabolic disorders. Because FLI and LAP share two components, namely waist circumference and fasting triglycerides, we evaluated the ability of LAP to identify liver steatosis in the same study population from the Northern Italian town where FLI was initially developed.

METHODS

We studied 588 individuals (59% males) aged 21 to 79 years. Liver steatosis was detected by ultrasonography and coded ordinally as none, intermediate and severe. 44% of the individuals had liver steatosis. Using proportional-odds ordinal logistic regression, we evaluated the ability of log-transformed LAP (lnLAP) to identify liver steatosis. We considered the benefits to our model of including terms for sex, age, suspected liver disease and ethanol intake. We calculated the 3-level probability of liver steatosis according to lnLAP and sex, providing tables and nomograms for risk assessment.

RESULTS

An ordinal proportional-odds model consisting of lnLAP and sex offered a reasonably accurate identification of liver steatosis. The odds of more severe vs. less severe steatosis increased for increasing values of lnLAP (odds ratio [OR] = 4.28, 95%CI 3.28 to 5.58 for each log-unit increment) and was more likely among males (OR = 1.88, 95%CI 1.31 to 2.69).

CONCLUSION

In a study sample of adults from Northern Italy, the simple calculation of LAP was a reasonably accurate approach to recognizing individuals with ultrasonographic liver steatosis. LAP may help primary care physicians to select subjects for liver ultrasonography and intensified lifestyle counseling, and researchers to select patients for epidemiologic studies. A more thorough assessment of LAP's potential for identifying liver steatosis will require its cross-evaluation in external populations.

Central role of fatty liver in the pathogenesis of insulin resistance in obese adolescents

OBJECTIVE

We evaluated the role of fatty liver in the alteration of insulin sensitivity and beta-cell function in two groups of obese adolescents, differing in hepatic fat content (hepatic fat fraction [HFF]) but with similar intrabdominal intramyocellular lipid content (IMCL) and overall degree of obesity.

RESEARCH DESIGN AND METHODS

We studied 23 obese adolescents with high HFF (HFF >5.5%) and 20 obese adolescents with low HFF (HFF <5.5%), matched for age, Tanner stage, BMI z score, and percentages of body fat, visceral fat, and IMCL. All subjects underwent an oral glucose tolerance test and a two-step hyperinsulinemic-euglycemic clamp, magnetic resonance imaging and (1)H nuclear magnetic resonance to assess abdominal fat distribution, HFF, and IMCL, respectively.

RESULTS

The high HFF group showed significantly lower whole-body insulin sensitivity index (P = 0.001) and estimates of insulin secretion (P = 0.03). The baseline hepatic glucose production (EGP) rate was not different between the two groups. Suppression of EGP was significantly lower (P = 0.04) in the high HFF group during low-dose insulin; no differences were observed during the second step. Baseline fatty acids, glycerol concentrations, and clamp suppression of glycerol turnover did not differ between the groups. During the second step, the glucose disposal rate was significantly lower (P = 0.01) in the high HFF group.

CONCLUSIONS

Fatty liver, independent of visceral fat and IMCL, plays a central role in the insulin-resistant state in obese adolescents.