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

Reductions in liver enzymes are associated with anti-hyperglycaemic and anti-obesity effects of tofogliflozin in people with type 2 diabetes: Post-hoc analyses

AIMS

How the pathology of type 2 diabetes (T2D), including hyperglycaemia and obesity, affects liver enzymes has not been clinically demonstrated. Thus, we compared time courses of gamma-glutamyltransferase (GGT) and alanine aminotransferase (ALT) with those of fasting plasma glucose (FPG) and body weight (BW) during treatment with the SGLT2 inhibitor tofogliflozin for T2D.

MATERIALS AND METHODS

We post-hoc analysed preexisting data on 1046 people with T2D administered tofogliflozin or placebo for 24 weeks in four tofogliflozin studies. First, time courses of percent changes in variables during the intervention were analysed using a mixed effect model to explore the similarity of the time courses and to evaluate time-treatment interactions. Second, clinical factors related to the percent changes in GGT and ALT were clarified using multivariate analyses.

RESULTS

GGT levels and FPG values rapidly and significantly decreased via tofogliflozin as early as week 4, with decreases maintained until week 24. Conversely, BW and ALT decreased progressively until week 24. Time courses of FPG (p = .365, time-treatment interaction) and GGT (p = .510) reductions were parallel between tofogliflozin and placebo from weeks 4 to 24, while BW and ALT reductions (p < .001, respectively) were not. Reductions in GGT at week 24 were associated with reductions in FPG and BW at week 24, whereas ALT reductions were only associated with reductions in BW.

CONCLUSIONS

Reductions in GGT and ALT were associated with the anti-hyperglycaemic and anti-obesity effects of tofogliflozin, respectively, in people with T2D. Therefore, GGT and ALT may be surrogate markers for hyperglycaemia and obesity in T2D.

What Does Sarcopenia Have to Do with Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease. As the second stage of developing steatosis, nonalcoholic hepatitis (NASH) carries the risk of fibrosis, cirrhosis, and hepatocellular carcinoma. Sarcopenia is defined as a condition characterized by a decrease in muscle mass and functional decline. Both NAFLD and sarcopenia are global problems. The pathophysiological mechanisms that link the two entities of the disease are insulin resistance, inflammation, nutritional deficiencies, impairment of myostatin and adiponectin, or physical inactivity. Furthermore, disorders of the gut-liver axis appear to induce the process of developing NAFLD and sarcopenia. The correlations between NAFLD and sarcopenia appear to be bidirectional, so the main objective of the review was to determine the cause-and-effect relationship between the two diseases.

Novel Curcumin Analogue L6H4 in Treating Liver Fibrosis and Type 2 Diabetes

Purpose

The objective of this study was to evaluate the therapeutic efficacy of the curcumin analogue L6H4 in attenuating liver fibrosis and alleviating insulin resistance in streptozotocin-induced diabetic rats.

Methods

Male Sprague-Dawley rats were fed a high-fat diet to induce insulin resistance, followed by streptozotocin injection to induce diabetes. The rats were then treated with L6H4 for eight weeks. Body weight, metabolic parameters, liver function, and liver histopathology were evaluated. Immunohistochemistry was performed to assess the expression of TGF-β1, TIMP-2, and MMP-2 in liver tissues. Statistical analysis was conducted using one-way ANOVA and Spearman rank correlation test.

Results

L6H4 treatment effectively reversed the weight gain associated with a high-fat diet and improved metabolic parameters in diabetic rats. Liver function markers, such as ALT and AST, were reduced after L6H4 treatment. Histological analysis showed improved liver morphology and reduced fibrosis in L6H4-treated rats. Electron microscopy revealed improved ultrastructural features of hepatocytes. Immunohistochemistry demonstrated downregulation of TGF-β1 and TIMP-2 expression and restoration of MMP-2 expression in the liver tissue of L6H4-treated rats. Correlation analysis showed a significant positive correlation between TGF-β1 and TIMP-2 expression.

Conclusion

The findings suggest that L6H4 has therapeutic potential in attenuating liver fibrosis and alleviating insulin resistance in streptozotocin-induced diabetic rats. The hepatoprotective effect of L6H4 may be attributed to its anti-inflammatory properties and its ability to target molecules involved in fibrosis. Further research is warranted to explore the potential of L6H4 as a treatment option for nonalcoholic fatty liver disease and type 2 diabetes.

Non-Alcoholic Fatty Liver Disease (NAFLD) Pathogenesis and Natural Products for Prevention and Treatment

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease, affecting approximately one-quarter of the global population, and has become a world public health issue. NAFLD is a clinicopathological syndrome characterized by hepatic steatosis, excluding ethanol and other definite liver damage factors. Recent studies have shown that the development of NAFLD is associated with lipid accumulation, oxidative stress, endoplasmic reticulum stress, and lipotoxicity. A range of natural products have been reported as regulators of NAFLD in vivo and in vitro. This paper reviews the pathogenesis of NAFLD and some natural products that have been shown to have therapeutic effects on NAFLD. Our work shows that natural products can be a potential therapeutic option for NAFLD.

Association between grip strength and non-alcoholic fatty liver disease: A systematic review and meta-analysis

Background

The association between grip strength (GS) and non-alcoholic fatty liver disease (NAFLD) has been reported by recent epidemiological studies, however, the results of these studies are inconsistent. This meta-analysis was conducted to collect all available data and estimate the risk of NAFLD among people with low GS, as well as the risk of low GS among patients with NAFLD.

Methods

We systematically searched several literature databases including PubMed, Web of Science, Cochrane Library, and Embase from inception to March 2022. These observational studies reported the risk of NAFLD among people with low GS and/or the risk of low GS among patients with NAFLD. Qualitative and quantitative information was extracted, statistical heterogeneity was assessed using the I² test, and potential for publication bias was assessed qualitatively by a visual estimate of a funnel plot and quantitatively by calculation of the Begg’s test and the Egger’s test.

Results

Of the citations, 10 eligible studies involving 76,676 participants met inclusion criteria. The meta-analysis of seven cross-section studies (69,757 participants) showed that people with low GS had increased risk of NAFLD than those with normal GS (summary OR = 3.32, 95% CI: 1.91–5.75). In addition, the meta-analysis of four studies (14,920 participants) reported that the risk of low GS patients with NAFLD was higher than those in normal people (summary OR = 3.31, 95% CI: 2.45–4.47).

Conclusion

In this meta-analysis, we demonstrated a strong relationship between low GS and NAFLD. We found an increased risk of NAFLD among people with low GS, and an increased risk of lower GS among NAFLD patients.

Systematic review registration

[www.crd.york.ac.uk/prospero], identifier [CRD42022334687].

Contribution of organokines in the development of NAFLD/NASH associated hepatocellular carcinoma

Globally the incidence of hepatocellular carcinoma (HCC) is on an upsurge. Evidence is accumulating that liver disorders like nonalcoholic fatty liver disease (NAFLD) and its more progressive form nonalcoholic steatohepatitis (NASH) are associated with increased risk of developing HCC. NAFLD has a prevalence of about 25% and 50%-90% in obese population. With the growing burden of obesity epidemic worldwide, HCC presents a major healthcare burden. While cirrhosis is one of the major risk factors of HCC, available literature suggests that NAFLD/NASH associated HCC also develops in minimum or noncirrhotic livers. Therefore, there is an urgent need to understand the pathogenesis and risk factors associated with NAFLD and NASH related HCC that would help in early diagnosis and favorable prognosis of HCC secondary to NAFLD. Adipokines, hepatokines and myokines are factors secreted by adipocytes, hepatocytes and myocytes, respectively, playing essential roles in cellular homeostasis, energy balance and metabolism with autocrine, paracrine and endocrine effects. In this review, we endeavor to focus on the role of these organokines in the pathogenesis of NAFLD/NASH and its progression to HCC to augment the understanding of the factors stimulating hepatocytes to acquire a malignant phenotype. This shall aid in the development of novel therapeutic strategies and tools for early diagnosis of NAFLD/NASH and HCC.

Whole-Body MRI-Derived Adipose Tissue Characterization and Relationship to Pulmonary Function Impairment

Background: Specification of adipose tissues by whole-body magnetic resonance imaging (MRI) was performed and related to pulmonary function parameters in a population-based cohort. Methods: 203 study participants underwent whole-body MRI and pulmonary function tests as part of the KORA (Cooperative Health Research in the Augsburg Region) MRI study. Both visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were derived from the T1-Dixon sequence, and hepatic adipose tissue from the proton density fat fraction (PDFFhepatic). Associations between adipose tissue parameters and spirometric indices such as forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and Tiffeneau-index (FEV1/FVC) were examined using multivariate linear regression analysis excluding cofounding effects of other clinical parameters. Results: VAT (β = −0.13, p = 0.03) and SAT (β = −0.26, p < 0.001), but not PDFFhepatic were inversely associated with FEV1, while VAT (β = −0.27, p < 0.001), SAT (β = −0.41, p < 0.001), and PDFFhepatic (β = −0.17, p = 0.002) were inversely associated with FVC. PDFFhepatic was directly associated with the Tiffeneau index (β = 2.46, p < 0.001). Conclusions: In the adjusted linear regression model, VAT was inversely associated with all measured spirometric parameters, while PDFFhepatic revealed the strongest association with the Tiffeneau index. Non-invasive adipose tissue quantification measurements might serve as novel biomarkers for respiratory impairment.

Alalwan T, Zahid MN, Spadaccini D, Gasparri C, Peroni G, Faragli A, Alogna A, La Porta E, Ali Redha A, Negro M, Cerullo G, D’Antona G, Rondanelli M. The Ketogenic Diet: Is It an Answer for Sarcopenic Obesity?

This review aims to define the effectiveness of the ketogenic diet (KD) for the management of sarcopenic obesity. As the combination of sarcopenia and obesity appears to have multiple negative metabolic effects, this narrative review discusses the effects of the ketogenic diet as a possible synergic intervention to decrease visceral adipose tissue (VAT) and fatty infiltration of the liver as well as modulate and improve the gut microbiota, inflammation and body composition. The results of this review support the evidence that the KD improves metabolic health and expands adipose tissue γδ T cells that are important for glycaemia control during obesity. The KD is also a therapeutic option for individuals with sarcopenic obesity due to its positive effect on VAT, adipose tissue, cytokines such as blood biochemistry, gut microbiota, and body composition. However, the long-term effect of a KD on these outcomes requires further investigations before general recommendations can be made.

An Overview of Alkylresorcinols Biological Properties and Effects

The investigation of alkylresorcinols has drawn an increasing interest recently. Alkylresorcinols (ARs) are natural chemical compounds synthesized by bacteria, fungi, sponges, and higher plants, possessing a lipophilic polyphenol structures and a myriad of biological properties. Human takes ARs as a component of a whole grain diet (from whole grain rye, wheat, and barley products), and thus, alkylresorcinols are frequently used as whole grain intake markers. Besides, ARs are considered as promising bioregulators of metabolic and immune processes, as well as adjuvant therapeutic agents for antimicrobial and anticancer treatment. In this review, we attempted to systematize the accumulated information concerning ARs origin, metabolism, biological properties, and their effect on human health.

A Novel Identified Peptide Hormone "Metabolitin" Attenuates Lipid Absorption in the Small Intestine of Diabetic Mice with Nonalcoholic Fatty Liver Disease by Regulating Neurotensin and AMPK Signaling Pathway

AIM

The purpose of this study was to explore the effect of a novel identified peptide hormone "metabolitin" on lipid absorption in the small intestine of mice with type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD) and potential mechanisms.

METHODS

T2DM was induced in mice by 4-6 weeks of high-fat diets followed by intraperitoneal injection of 35 mg/kg STZ. NAFLD was induced in diabetic mice by a month of high-fat diets. Oral administration of 4 pmol/g or 12 pmol/g metabolitin every two days was performed during one-month high-fat diets. Triglyceride (TG) and total cholesterol (TC) detection and Oil Red O staining were performed to evaluate lipid absorption. The neurotensin (NT) levels in the intestinal tissues and serum were determined by ELISA. Lipogenesis- and lipolysis-related proteins, AMP-activated protein kinase (AMPK), and p-AMPK were examined by Western blot analysis.

RESULTS

It was found that glucose tolerance test (GTT), insulin tolerance test (ITT), TG, and TC indicated lower levels in the serum of NAFLD/T2DM mice receiving 4 pmol/g and 12 pmol/g metabolitin compared to the mice receiving normal saline (P < 0.05). No significant difference was noted in the TC level of the feces among mice with different diets (P > 0.05), but compared to NAFLD/T2DM mice with normal saline, the mice administrated with 4 pmol/g and 12 pmol/g metabolitin revealed much higher TG levels in the feces (P < 0.05). The results of Oil Red O staining revealed that the intestinal epithelial cells of NAFLD/T2DM mice receiving 12 pmol/g metabolitin indicated resistance to lipid absorption and the area of staining was smaller than that of NAFLD/T2DM mice with normal saline (P < 0.05). The NAFLD/T2DM mice receiving 4 pmol/g and 12 pmol/g metabolitin showed a higher extent of p-AMPK concomitant with lower levels of NT in the serum and small intestine than the mice with normal saline (P < 0.05). Western blot analysis also suggested that NAFLD/T2DM mice receiving 4 pmol/g and 12 pmol/g metabolitin revealed lower expressions in fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase-1 (SCD-1), and sterol regulatory element-binding transcription factor-1 (SREBP1) proteins and higher expressions in carnitine palmitoyltransferase 1 (CPT1), peroxisome proliferator-activated receptor alpha (PPARα), and fatty acid translocase (CD36) proteins than NAFLD/T2DM mice with normal saline (P < 0.05).

CONCLUSION

According to the data we observed, oral administration of metabolitin could attenuate lipid absorption in the small intestine of NAFLD/T2DM mice, which may be a novel therapeutic approach for NAFLD/T2DM.

Sarcopenia modifies the associations of nonalcoholic fatty liver disease with all-cause and cardiovascular mortality among older adults

The contribution of nonalcoholic fatty liver disease (NAFLD) to all-cause and cardiovascular mortality remains controversial. Sarcopenia, a measure of muscle mass, strength and function, may identify which persons are most at risk for adverse effects of NAFLD. We aimed to test the hypothesis that sarcopenia modifies the associations between NAFLD and all-cause and cardiovascular mortality. A total of 2446 older adults (≥ 60 years) from the third National Health and Nutrition Examination Survey were enrolled. Their mortality data were linked to death certificates in the National Death Index. Sarcopenia was defined as having low skeletal muscle mass together with slow gait speed, which captures both muscle mass and muscle function. Ultrasound tests were used for the assessment of hepatic steatosis. During follow-up (median 16.8 years), 1530 older subjects died from any cause, of which 379 were cardiovascular-related. All-cause and cardiovascular mortality rates were 4.31 and 1.07 per 100 person-years, respectively. In a multivariate model, using participants without NAFLD and sarcopenia as the reference group, individuals with both NAFLD and sarcopenia had 1.69 times [95% confidence interval (CI) 1.23-2.31] and 2.17 times (95% CI 1.33-3.54) higher risks of all-cause and cardiovascular mortality, respectively. However, NAFLD persons without sarcopenia had hazard ratios for all-cause and cardiovascular mortality similar to those of the reference group. Sarcopenia modified the associations of NAFLD with all-cause and cardiovascular mortality. Sarcopenia may identify older adults who are at the highest risk for adverse outcomes associated with NAFLD.

Differences among Three Skeletal Muscle Mass Indices in Predicting Non-Alcoholic Fatty Liver Disease: Korean Nationwide Population-Based Study

Recent studies have investigated the relationship between sarcopenia and non-alcoholic fatty liver disease (NAFLD); however, there is no unified definition of sarcopenia. Thus, we aimed to investigate the differences among three skeletal muscle mass indices (SMI) in predicting NAFLD. This study included 8133 adults from the 2008–2010 Korea National Health and Nutrition Survey. SMI was calculated as appendicular skeletal muscle mass divided by height-square (hSMI), weight (wSMI), or body mass index (bSMI). The presence of NAFLD was defined by using the NAFLD-liver fat score. On the receiver operating characteristic curve analysis, the predictive power of wSMI for NAFLD was significantly higher than those of hSMI and bSMI in men (wSMI vs. hSMI, p = 0.003; wSMI vs. bSMI, p < 0.001). In women, the predictive power of hSMI was only significantly higher than that of bSMI (p = 0.023), and other predictive powers were not significantly different. In addition, hSMI was correlated with insulin resistance and NAFLD-liver fat score in the opposite direction to wSMI and bSMI in both men and women. Among the three definitions of SMI, wSMI showed the highest diagnostic performance for predicting NAFLD in men, suggesting the importance of defining sarcopenia for its association with specific diseases.

Buchholzia coriacea seed (wonderful kolanut) alleviates insulin resistance, steatosis, inflammation and oxidative stress in high fat diet model of fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a hepatic condition with multiple pathological features and it currently has no specific treatment or approved drug. Wonderful kolanut widely consumed fresh or cooked has been applied in the treatment of numerous diseases in folk medicine. In this study, we evaluate the therapeutic potentials of hydroethanolic extract of defatted Buccholzia coriacea seeds (HEBCS) in NAFLD model. HEBCS was subjected to liquid chromatography - mass spectrometry, and 30 male BALB/c mice (28 ± 2 g) were allocated to three (3) experimental groups (n = 10/group). Mice in group I were fed chow diet (CD); those in group II, high fat diet (HFD) and group III, HFD and 250 mg/kg HEBCS p.o. daily for six weeks. HEBCS alleviates HFD-induced insulin resistance and high plasma insulin and glucose levels. It further alleviates hepatic steatosis, and alters plasma lipid profile. HEBCS also protected against HFD-induced inflammation, oxidative stress and hepatocellular damage. In conclusion, HEBCS alleviated NAFLD in mice via suppression of insulin resistance, hyperlipidemia, inflammation and oxidative stress. PRACTICAL APPLICATIONS: Bioactive polyphenols and alkaloids were identified in hydroethanolic extract of defatted Buccholzia coriacea seeds (HEBCS). This study projects HEBCS as a potential therapeutic agent in the treatment of NAFLD. NAFLD is a multi-factorial condition and therefore, HEBCS is promising considering its multiple-target actions in the current model of NAFLD. HEBCS alleviates insulin resistance, metabolic dysfunction, steatosis, and inflammation in this model. There is a need to further investigate HEBCS in other models of NAFLD as a lead to future use in clinical studies.

Pulmonary function test abnormalities in children and adolescents with non-alcoholic fatty liver disease

Association between pulmonary function tests (PFTs) and non-alcoholic fatty liver disease (NAFLD) has been reported in adult studies; however, there is lack of pediatric studies. Our study aimed to evaluate PFTs in children with NAFLD. A total of 137 children with NAFLD and 100 healthy children of matched age and sex were included in the study. Different PFTs including forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, residual volume (RV), and total lung capacity (TLC) were performed for all included children. Lipid profile, insulin resistance, fasting and postprandial glucose level, and high sensitive C reactive protein (hs-CRP) were measured. FEV1 %, FVC %, FEV1/FVC ratio, RV, and TLC were significantly lower in the patient group compared with the control group (P < 0.05), while RV and hs-CRP were significantly higher in children with NAFLD. Restrictive lung dysfunction was the commonest pulmonary dysfunction detected in children with NAFLD (21.9%). PFT indices were significantly correlated with grade and duration of NAFLD, insulin resistance, waist circumference, and hs-CRP. Regression analysis revealed that insulin resistance and hs-CRP were independently associated with decreased PFT indices.Conclusion: PFT indices were impaired in children with NAFLD and this impairment was independently associated with insulin resistance and hs-CRP. What is Known: • Pulmonary function tests (PFTs) abnormalities are common in adults with nonalcoholic fatty liver disease (NAFLD). • Studies involving PFTs abnormalities in pediatric NAFLD are lacking. What is New: • It is the first study that assessed PFT in pediatric patients with NAFLD. • PFTs abnormalities are present in children with NAFLD. • Insulin resistance and high sensitive C reactive protein are independently associated with the decline of PFTs in children with NAFLD.

The association of impaired lung function and nonalcoholic fatty liver disease: a systematic review

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) and impaired lung function share similar risk factors and phenotypes, such as obesity and type 2 diabetes. The study is an updated meta-analysis to evaluate the association between NAFLD and impaired lung function.

METHODS

A total of 696 articles were identified with mention of NAFLD and lung function (or pulmonary function testing) in MEDLINE, EMBASE, and Scopus. After de-duplication, 455 articles were screened, 18 underwent full-text review. Five studies met our review and inclusion criteria with an interrater reliability kappa score of 1.

RESULTS

Five studies with a total of 118 118 subjects (28.4% with NAFLD) were included. The cross-sectional studies supported a statistically significant relationship between decreased pulmonary function tests and NAFLD. There was no association observed with obstructive lung pattern. One of the longitudinal studies revealed an association with increased rate of decline in forced vital capacity in patients with NAFLD and FIB4 score ≥1.30 (-21.7 vs. -27.4 mL/year, P = 0.001 in males, -22.4 vs. -27.9 mL/year, P = 0.016 in females). The second longitudinal study revealed that patients with impaired pulmonary function had an increased hazard ratio of developing NAFLD dependent on the severity of pulmonary impairment.

CONCLUSIONS

This is the first systematic review that supports an association of NAFLD with decreased (restrictive) lung function. The estimated severity of liver fibrosis correlates with the rate of progression of restrictive lung function. There are also data showing that patients with impaired lung function have a higher risk of developing NAFLD.

Hepatokine Selenoprotein P-Mediated Reductive Stress Causes Resistance to Intracellular Signal Transduction

Significance: Selenoprotein P functions as a redox protein through its intrinsic thioredoxin domain and by distributing selenium to intracellular glutathione peroxidases, that is, glutathione peroxidase 1 and 4. Recent Advances: Selenoprotein P was rediscovered as a hepatokine that causes the pathology of type 2 diabetes and aging-related diseases, including exercise resistance in the skeletal muscle, insulin secretory failure in pancreatic β cells, angiogenesis resistance in vascular endothelial cells, and myocardial ischemic-reperfusion injury. It was unexpected for the antioxidant selenoprotein P to cause insulin resistance, because oxidative stress associated with obesity and fatty liver is a causal factor for hepatic insulin resistance. Critical Issues: Oxidative stress induced by the accumulation of reactive oxygen species (ROS) has a causal role in the development of insulin resistance, whereas ROS themselves function as intracellular second messengers that promote insulin signal transduction. ROS act both positively and negatively in insulin signaling depending on their concentrations. It might be possible that selenoprotein P causes "reductive stress" by eliminating a physiological ROS burst that is required for insulin signal transduction, thereby causing insulin resistance. In a large-scale intervention study, selenium supplementation that upregulates selenoprotein P was paradoxically associated with an increased risk for diabetes in humans. This review discusses the molecular mechanisms underlying the selenoprotein P-mediated resistance to angiogenesis and to exercise. Future Directions: Selenoprotein P may be the first identified intrinsic factor that induces reductive stress, causing resistance to intracellular signal transduction, which may be the therapeutic target against sedentary-lifestyle-associated diseases, such as diabetes and obesity.

Newly identified peptide hormone inhibits intestinal fat absorption and improves NAFLD through its receptor GPRC6A

BACKGROUND & AIMS

Circulating peptides and G protein-coupled receptors (GPCRs) have gained much attention because of their biofunctions in metabolic disorders including obesity and non-alcoholic fatty liver disease (NAFLD). Herein, we aimed to characterize the role and therapeutic potential of a newly identified peptide hormone in NAFLD.

METHODS

Using bioinformatics, we identified a murine circulating pentadecapeptide flanked by potential convertase cleavage sites of osteocalcin (OCN), which we named 'metabolitin (MTL)'. We used ligand-receptor binding, receptor internalization, bioluminescence resonance energy transfer and Nano isothermal titration calorimetry assays to study the binding relationship between MTL and GPRC6A. For in vivo biological studies, wild-type mice kept on a high-fat diet (HFD) were injected or gavaged with MTL to study its function in NAFLD.

RESULTS

We confirmed that MTL binds to GPRC6A and OCN interacts with GPRC6A using in vitro biological studies. Both intraperitoneal and oral administration of MTL greatly improved NAFLD and insulin resistance in a mouse model. Interacting with GPRC6A expressed in intestines, MTL can significantly inhibit intestinal neurotensin secretion, which in turn inhibits triglyceride but not cholesterol gut absorption, mediated by the 5'AMP-activated protein kinase pathway. In addition, glucagon like peptide-1 secretion was induced by MTL treatment.

CONCLUSIONS

Oral or intraperitoneal MTL significantly improves the symptoms of NAFLD by inhibiting lipid absorption and insulin resistance. MTL could be a potential therapeutic candidate for the treatment of NAFLD.

LAY SUMMARY

A novel murine peptide hormone, herein named 'metabolitin', inhibits fatty acid absorption and improves systemic insulin resistance in a murine model of obesity and non-alcoholic fatty liver disease. Thus, metabolitin has therapeutic potential for the treatment of patients with non-alcoholic fatty liver disease.

Asthma and Obesity in Children

Asthma and obesity are two major chronic diseases in children and adolescents. Recent scientific evidence points out a causative role of obesity in asthma predisposition. However, studies assessing the real impact of excessive weight gain on lung function in children have shown heterogeneous results. In this review, the pathological mechanisms linking obesity and development of asthma in children are summarized and factors influencing this relationship are evaluated. Common disease modifying factors including age, sex, ethnicity, development of atopic conditions, and metabolic alterations significantly affect the onset and phenotypic characteristics of asthma. Given this, the impact of these several factors on the obesity–asthma link were considered, and from revision of the literature we suggest the possibility to define three main clinical subtypes on the basis of epidemiological data and physiological–molecular pathways: obese-asthmatic and atopy, obese-asthmatic and insulin-resistance, and obese-asthmatic and dyslipidemia. The hypothesis of the different clinical subtypes characterizing a unique phenotype might have an important impact for both future clinical management and research priorities. This might imply the necessity to study the obese asthmatic child with a “multidisciplinary approach”, evaluating the endocrinological and pneumological aspects simultaneously. This different approach might also make it possible to intervene earlier in a specific manner, possibly with a personalized and tailored treatment. Surely this hypothesis needs longitudinal and well-conducted future studies to be validated.

Uncarboxylated osteocalcin ameliorates hepatic glucose and lipid metabolism in KKAy mice via activating insulin signaling pathway

Osteocalcin, expressed in osteoblasts of the bone marrow, undergoes post-translational carboxylation and deposits in mineralized bone matrix. A portion of osteocalcin remains uncarboxylated (uncarboxylated osteocalcin, GluOC) that is released into blood where it functions as a hormone to regulate insulin secretion and insulin sensitivity. As insulin resistance is closely associated with metabolic syndrome, this study is aimed to elucidate how GluOC regulates glucose and lipid metabolism in KKAy mice, an animal model displaying obese, hyperglycemia, hyperinsulinemia, insulin resistance, and hepatic steatosis. GluOC (3, 30 ng/g per day, ig) was orally administered to female KKAy mice for 4 weeks. Whole-body insulin sensitivity, glucose metabolism, hepatic steatosis, dyslipidemia were examined using routine laboratory assays. We found that GluOC administration significantly enhanced insulin sensitivity in KKAy mice by activating hepatic IRβ/PI3K/Akt pathway and elevated the whole-body insulin sensitivity with decreased FPI and HOMA-IR index. Furthermore, GluOC administration alleviated hyperglycemia through suppressing gluconeogenesis and promoting glycogen synthesis in KKAy mice and in cultured hepatocytes in vitro. Moreover, GluOC administration dose-dependently ameliorated dyslipidemia and attenuated hepatic steatosis in KKAy mice by inhibiting hepatic de novo lipogenesis and promoting fatty-acid β-oxidation. These results demonstrate that GluOC effectively enhances hepatic insulin sensitivity, improves hyperglycemia and ameliorates hepatic steatosis in KKAy mice, suggesting that GluOC could be a promising drug candidate for treating metabolic syndrome.

Relationship between Muscle Mass/Strength and Hepatic Fat Content in Post-Menopausal Women

Background and Objectives: Recent studies have shown that low skeletal muscle mass can contribute to non-alcoholic fatty liver disease through insulin resistance. However, the association between muscle mass/strength and hepatic fat content remains unclear in postmenopausal women. Methods: In this study, we assessed the associations between muscle mass/strength and various severities of non-alcoholic fatty liver disease. Using single-voxel proton magnetic resonance spectroscopy, 96 postmenopausal women between the ages of 50 and 65 were divided into four groups (G0–G3) by hepatic fat content: G0 (hepatic fat content <5%, n = 20), G1 (5% ≤ hepatic fat content < 10%, n = 27), G2 (10% ≤ hepatic fat content < 25%, n = 31), and G3 (hepatic fat content ≥25%, n = 18). Muscle mass indexes were estimated as skeletal muscle index (SMI)% (total lean mass/weight × 100) and appendicular skeletal muscular mass index (ASM)% (appendicular lean mass/weight × 100) by dual energy X-ray absorptiometry. Maximal isometric voluntary contraction of the handgrip, elbow flexors, and knee extensors was measured using an adjustable dynamometer chair. Fasting plasma glucose, insulin, and follicle-stimulating hormones were assessed in venous blood samples. Results: The results showed negative correlations between hepatic fat content and SMI% (r = −0.42, p < 0.001), ASM% (r = −0.29, p = 0.005), maximal voluntary force of grip (r = −0.22, p = 0.037), and knee extensors (r = −0.22, p = 0.032). Conclusions: These significant correlations almost remained unchanged even after controlling for insulin resistance. In conclusion, negative correlations exist between muscle mass/strength and the progressed severity of non-alcoholic fatty liver disease among post-menopausal women, and the correlations are independent of insulin resistance.

Hydroxychloroquine Improves Obesity-Associated Insulin Resistance and Hepatic Steatosis by Regulating Lipid Metabolism

The burden of obesity and associated cardiometabolic diseases has been considered as an important risk factor for lupus patients. Therefore, whether obesity is involved in the over-activation of autoimmune response has attracted more and more attention. Hydroxychloroquine is a synthetic antimalarial drug and has been the clinical treatment of rheumatic diseases irreplaceable first-line drugs. Hydroxychloroquine has been suggested to have beneficial effects on lipids and insulin sensitivity, which may contribute in lowering high cardiovascular risk in SLE patients. However, its mechanism on insulin sensitivity and lipid disorders is far from being completely understood. In the present study, the therapeutic effects of hydroxychloroquine were evaluated under pathological conditions in vivo. Obesity was induced in C57BL/6 mice fed with high-fed diet, or in mice fed with high-fat diet and hydroxychloroquine. In addition, healthy mice that received normal chow diet were also monitored. The present results revealed that hydroxychloroquine reduced weight, hepatic steatosis, glucose, and insulin resistance. Furthermore, hydroxychloroquine downregulated the expression of peroxisome proliferator-activated receptor gamma in the liver. According to these present results, genes about lipid metabolism went down in high-fat mice liver. Hydroxychloroquine shows potential in ameliorating obesity-induced pathology, which acts though PPARγ to facilitate the healthy function of hepatic tissues. This evidence shows that hydroxychloroquine plays a role in improving obesity-induced lipotoxicity and insulin resistance though the peroxisome proliferator-activated receptor gamma pathway.

Mitochondrial Dysfunction and Diabetes: Is Mitochondrial Transfer a Friend or Foe?

Obesity, insulin resistance and type 2 diabetes are accompanied by a variety of systemic and tissue-specific metabolic defects, including inflammation, oxidative and endoplasmic reticulum stress, lipotoxicity, and mitochondrial dysfunction. Over the past 30 years, association studies and genetic manipulations, as well as lifestyle and pharmacological invention studies, have reported contrasting findings on the presence or physiological importance of mitochondrial dysfunction in the context of obesity and insulin resistance. It is still unclear if targeting mitochondrial function is a feasible therapeutic approach for the treatment of insulin resistance and glucose homeostasis. Interestingly, recent studies suggest that intact mitochondria, mitochondrial DNA, or other mitochondrial factors (proteins, lipids, miRNA) are found in the circulation, and that metabolic tissues secrete exosomes containing mitochondrial cargo. While this phenomenon has been investigated primarily in the context of cancer and a variety of inflammatory states, little is known about the importance of exosomal mitochondrial transfer in obesity and diabetes. We will discuss recent evidence suggesting that (1) tissues with mitochondrial dysfunction shed their mitochondria within exosomes, and that these exosomes impair the recipient's cell metabolic status, and that on the other hand, (2) physiologically healthy tissues can shed mitochondria to improve the metabolic status of recipient cells. In this context the determination of whether mitochondrial transfer in obesity and diabetes is a friend or foe requires further studies.

Exosomes and diabetes

Diabetes is a group of metabolic diseases characterized by elevated blood glucose levels that drive the development of life-threatening complications. Diabetes results from a situation of insufficient insulin action, either by deficient production of the hormone by the pancreas, or by the development of insulin resistance in peripheral tissues such as liver, muscle, or the adipose depots. Communication between organs is thus central to the maintenance of glucose homoeostasis. Recently, several studies are evidencing that small vesicles called exosomes released by, amongst other, the adipose tissue can regulate gene expression in other tissues, hence modulating interorgan crosstalk. Therefore, exosomes participate in the development of diabetes and its associated complications. Their study holds the potential of providing us with novel biomarkers for the early diagnosis and stratification of patients at risk of developing diabetes, hence allowing the timely implementation of more personalized therapies. On the other hand, the molecular dissection of the pathways initiated by exosomes under situations of metabolic stress could help to gain a deeper knowledge of the pathophysiology of diabetes and its associated metabolic diseases.

Decreased lung function is associated with risk of developing non-alcoholic fatty liver disease: A longitudinal cohort study

BACKGROUND

Decreased lung function is associated with non-alcoholic fatty liver disease (NAFLD), based on linking mechanisms such as insulin resistance and systemic inflammation However, its association with the risk of developing NAFLD is unclear. Our aim was to investigate whether baseline lung function is associated with incident NAFLD in middle-aged healthy Koreans.

METHODS

A cohort study of 96,104 subjects (mean age: 35.7 years) without NAFLD were followed up from 2002 to 2015. NAFLD was diagnosed by ultrasound after the exclusion of other possible causes of liver diseases. Baseline percent predicted forced expiratory volume in one second (FEV1%) and forced vital capacity (FVC%) were categorized in quartiles. Adjusted hazard ratios (aHR) and 95% confidence intervals (CIs) (using the highest quartile as reference) were calculated for incident NAFLD at follow-up, controlling for covariates and potential confounders.

RESULTS

During 579,714.5 person-years of follow-up, 24,450 participants developed NAFLD (incidence rate, 42.2 per 1,000 person-years). The mean follow-up period was 5.9±3.4 years. Regardless of smoking history, the risk for incident NAFLD increased with decreasing quartiles of FEV1 (%) and FVC (%) in a dose-response manner (p for trend<0.001). In never smokers, the aHRs (95% CIs) for incident NAFLD were 1.15 (1.08-1.21), 1.11 (1.05-1.18), and 1.08 (1.02-1.14) in quartiles 1-3 for FEV1 (%) and 1.12 (1.06-1.18), 1.11 (1.05-1.18), and 1.09 (1.03-1.15) in quartiles 1-3 for FVC (%), compared with the highest quartile reference. Similar inverse association was present in smoke-exposed subjects (aHR for incident NAFLD were 1.14, 1.21, 1.13 and 1.17, 1.11, 1.09 across FEV1(%) and FVC(%) quartile in increasing order, respectively).

CONCLUSIONS

Reduced lung function was a risk factor for incident NAFLD in a large middle-aged Korean cohort with over half a million person-years of follow-up.

Pathophysiological significance of hepatokine overproduction in type 2 diabetes

Currently, many studies draw attention to novel secretory factors, such as adipokines or myokines, derived from the tissues that were not originally recognized as endocrine organs. The liver may contribute to the onset of various kinds of pathologies of type 2 diabetes by way of the production of secretory proteins "hepatokines." Using the comprehensive gene expression analyses in human livers, we have rediscovered selenoprotein P and LECT2 as hepatokines involved in the onset of dysregulated glucose metabolism. Overproduction of selenoprotein P, previously reported as a transport protein of selenium, induces insulin resistance and hyperglycemia in type 2 diabetic condition. Selenoprotein P also contributes to vascular complications of type 2 diabetes directly by inducing VEGF resistance in vascular endothelial cells. Notably, selenoprotein P impairs health-promoting effects of exercise by inhibiting ROS/AMPK/PGC-1α pathway in the skeletal muscle through its receptor LRP1. Overproduction of LECT2, previously reported as a neutrophil chemotactic protein, links obesity to insulin resistance in the skeletal muscle. Further studies would develop novel diagnostic or therapeutic procedures targeting hepatokines to combat over-nutrition-related diseases such as type 2 diabetes.

Steatosis in South African women: How much and why?

Background

Globally, steatosis is the commonest type of liver pathology and is closely associated with obesity and the metabolic syndrome. Obesity is common in urban African females but no data is available on hepatic fat content in this population group when compared to other ethnic groups. The aim of this study was therefore to compare hepatic fat content in woman from different ethnic groups in South Africa and to characterise the principle determinants of liver fat.

Materials and methods

A convenience sample of 106 (48 Indian, 29 African and 29 Caucasian) female volunteers aged 20–60 years and having no history of cardiometabolic disorders were recruited. Hepatic fat was determined from CT scans using the liver-spleen attenuation ratio (LAR), which decreases with increasing levels of hepatic fat. Anthropometric and cardiometabolic parameters were measured with insulin resistance determined using the HOMA index and dysglycaemia defined as fasting glucose ≥5.60 mmol/L.

Results

The African subjects had significantly lower hepatic fat content (LAR as median [interquartile range]: 1.35 [1.28, 1.41]) than the Indian (1.22 [1.10, 1.35]; p<0.005) and Caucasian (1.27 [1.16, 1.33]; p<0.05) females even though they had significantly higher BMIs than both groups (p<0.0005 and p<0.05, respectively). Linear regression showed that: subcutaneous abdominal fat was a significant (unstandardised β = 0.007; p = 0.03) negative, whilst insulin resistance (β = -0.97; p = 0.01) and dysglycaemia (β = -3.58; p = 0.01) were significant positive determinants of liver fat; higher hepatic fat levels in subjects with the metabolic syndrome were explained by insulin resistance and dysglycaemia.

Discussion

African ethnicity is associated with low liver fat content. Subcutaneous abdominal fat protects against steatosis, possibly by acting as a triglyceride reservoir. Insulin resistance and dysglycaemia lead to greater hepatic fat deposition and explain higher liver fat levels in subjects with the metabolic syndrome. These observations must be further investigated in longitudinal surveys.

Microbial Regulation of Glucose Metabolism and Insulin Resistance

Type 2 diabetes is a combined disease, resulting from a hyperglycemia and peripheral and hepatic insulin resistance. Recent data suggest that the gut microbiota is involved in diabetes development, altering metabolic processes including glucose and fatty acid metabolism. Thus, type 2 diabetes patients show a microbial dysbiosis, with reduced butyrate-producing bacteria and elevated potential pathogens compared to metabolically healthy individuals. Furthermore, probiotics are a known tool to modulate the microbiota, having a therapeutic potential. Current literature will be discussed to elucidate the complex interaction of gut microbiota, intestinal permeability and inflammation leading to peripheral and hepatic insulin resistance. Therefore, this review aims to generate a deeper understanding of the underlying mechanism of potential microbial strains, which can be used as probiotics.

The Common Mechanisms of Sarcopenia and NAFLD

Current studies have shown that sarcopenia and nonalcoholic fatty liver disease (NAFLD) have similar pathophysiological profiles. The cooccurrence of sarcopenia and NAFLD has been observed in elderly patients. The actions of these conditions are linked, and their treatments are similar. Therefore, studies should be conducted on NAFLD-sarcopenia rather than on NAFLD or sarcopenia.

Weight-adjusted lean body mass and calf circumference are protective against obesity-associated insulin resistance and metabolic abnormalities

Background

To test the hypothesis that preserved muscle mass is protective against obesity-associated insulin resistance and metabolic abnormalities, we analyzed the relationship of lean body mass and computed tomography-assessed sectional areas of specific skeletal muscles with insulin resistance and metabolic abnormalities in a healthy cohort.

Methods

A total of 195 subjects without diabetes who had completed a medical examination were included in this study. Various anthropometric indices such as circumferences of the arm, waist, hip, thigh, and calf were measured. Body composition (fat and lean body mass) was determined by bioelectrical impedance analysis. Sectional areas of specific skeletal muscles (iliopsoas, erector spinae, gluteus, femoris, and rectus abdominis muscles) were measured using computed tomography.

Findings

Fat and lean body mass were significantly correlated with metabolic abnormalities and insulin resistance indices. When adjusted by weight, relationships of fat and lean body mass with metabolic parameters were mirror images of each other. The weight-adjusted lean body mass negatively correlated with systolic and diastolic blood pressures; fasting plasma glucose, HbA1c, alanine aminotransferase, and triglyceride, and insulin levels; and hepatic insulin resistance indices, and positively correlated with HDL-cholesterol levels and muscle insulin sensitivity indices. Compared with weight-adjusted lean body mass, weight-adjusted sectional areas of specific skeletal muscles showed similar, but not as strong, correlations with metabolic parameters. Among anthropometric measures, the calf circumference best reflected lean body mass, and weight-adjusted calf circumference negatively correlated with metabolic abnormalities and insulin resistance indices.

Interpretation

Weight-adjusted lean body mass and skeletal muscle area are protective against weight-associated insulin resistance and metabolic abnormalities. The calf circumference reflects lean body mass and may be useful as a protective marker against obesity-associated metabolic abnormalities.

Downregulation of miR-192 causes hepatic steatosis and lipid accumulation by inducing SREBF1: Novel mechanism for bisphenol A-triggered non-alcoholic fatty liver disease

Exposure to Bisphenol A (BPA) has been associated with the development of nonalcoholic fatty liver disease (NAFLD) but the underlying mechanism remains unclear. Given that microRNA (miRNA) is recognized as a key regulator of lipid metabolism and a potential mediator of environmental cues, this study was designed to explore whether exposure to BPA-triggered abnormal steatosis and lipid accumulation in the liver could be modulated by miR-192. We showed that male post-weaning C57BL/6 mice exposed to 50μg/kg/day of BPA by oral gavage for 90days displayed a NAFLD-like phenotype. In addition, we found in mouse liver and human HepG2 cells that BPA-induced hepatic steatosis and lipid accumulation were associated with decreased expression of miR-192, upregulation of SREBF1 and a series of genes involved in de novo lipogenesis. Downregulation of miR-192 in BPA-exposed hepatocytes could be due to defective pre-miR-192 processing by DROSHA. Using HepG2 cells, we further confirmed that miR-192 directly acted on the 3'UTR of SREBF1, contributing to dysregulation of lipid homeostasis in hepatocytes. MiR-192 mimic and lentivirus-mediated overexpression of miR-192 improved BPA-induced hepatic steatosis by suppressing SREBF1. Lastly, we noted that lipid accumulation was not a strict requirement for developing insulin resistance in mice after BPA treatment. In conclusion, this study demonstrated a novel mechanism in which NAFLD associated with BPA exposure arose from alterations in the miR-192-SREBF1 axis.

Impaired lung function is associated with non-alcoholic fatty liver disease independently of metabolic syndrome features in middle-aged and elderly Chinese

BACKGROUND

Associations between lung function and non-alcoholic fatty liver disease (NAFLD) have been reported. However, evidence from large-scale populations about the relationship is scarce. The objective of the study was to evaluate the relationship between lung function and NAFLD in middle-aged and elderly Chinese.

METHODS

A total of 1842 participants aged 40 years or older were recruited from Chongming District, Shanghai, China. Lung function, evaluated by forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) was measured with standard spirometry. The NAFLD was evaluated by ultrasonography.

RESULTS

The subjects with NAFLD had lower FVC (% predicted) (0.85 ± 0.26 vs. 0.90 ± 0.28, p < 0.001) and FEV1 (% predicted) (0.93 ± 0.29 vs. 0.98 ± 0.34, p < 0.001) than non-NAFLD. After adjusting for potential risk factors, the lowest quartile of FVC (% predicted) and FEV1 (% predicted) was associated with increased prevalence of NAFLD, with the fully adjusted odds ratio of 1.37 and 1.24 (95% confidence interval [CI] 1.18-1.97, p < 0.001, 95% CI 1.11-1.87, p = 0.009), respectively.

CONCLUSIONS

Impaired lung function is associated with non-alcoholic fatty liver disease, independent of conventional metabolic risk factors.

Steroidogenic acute regulatory protein (StAR) overexpression attenuates HFD-induced hepatic steatosis and insulin resistance

Non-alcoholic fatty liver disease (NAFLD) covers a wide spectrum of liver pathology. Intracellular lipid accumulation is the first step in the development and progression of NAFLD. Steroidogenic acute regulatory protein (StAR) plays an important role in the synthesis of bile acid and intracellular lipid homeostasis and cholesterol metabolism. We hypothesize that StAR is involved in non-alcoholic fatty liver disease (NAFLD) pathogenesis. The hypothesis was identified using free fatty acid (FFA)-overloaded NAFLD in vitro model and high-fat diet (HFD)-induced NAFLD mouse model transfected by recombinant adenovirus encoding StAR (StAR). StAR expression was also examined in pathology samples of patients with fatty liver by immunohistochemical staining. We found that the expression level of StAR was reduced in the livers obtained from fatty liver patients and NAFLD mice. Additionally, StAR overexpression decreased the levels of hepatic lipids and maintained the hepatic glucose homeostasis due to the activation of farnesoid x receptor (FXR). StAR overexpression attenuated the impairment of insulin signaling in fatty liver. This protective role of StAR was owing to a reduction of intracellular diacylglycerol levels and the phosphorylation of PKCε. Furthermore, FXR inactivation reversed the observed beneficial effects of StAR. The present study revealed that StAR overexpression can reduce hepatic lipid accumulation, regulate glucose metabolism and attenuate insulin resistance through a mechanism involving the activation of FXR. Our study suggests that StAR may be a potential therapeutic target for NAFLD.

A possible link between hepatic mitochondrial dysfunction and diet-induced insulin resistance

BACKGROUND

Mitochondria are the main cellular sites devoted to ATP production and lipid oxidation. Therefore, the mitochondrial dysfunction could be an important determinant of cellular fate of circulating lipids, that accumulate in the cytoplasm, if they are not oxidized. The ectopic fat accumulation is associated with the development of insulin resistance, and a link between mitochondrial dysfunction and insulin resistance has been proposed.

METHODS

Recent data on the possible link existing between mitochondrial dysfunction in the liver and diet induced obesity will be summarized, focusing on the three factors that affect the mitochondrial oxidation of metabolic fuels, i.e. organelle number, organelle activity, and energetic efficiency of the mitochondrial machinery in synthesizing ATP. Search in PubMed relevant articles from 2003 to 2014 was conducted, by using query “liver mitochondria and obesity” “hepatic mitochondria and obesity” “liver mitochondria and high fat diet” and “hepatic mitochondria and high fat diet” and including related articles by the same groups.

RESULTS

Several works, by using different physiological approaches, have dealt with alteration in mitochondrial function in obesity and diabetes. Most results show that hepatic mitochondrial function is impaired in models of obesity and insulin resistance induced by high-fat or highfructose feeding.

CONCLUSIONS

Since mitochondria are the main producers of both cellular energy and free radicals, dysfunctional mitochondria could play an important role in the development of insulin resistance and ectopic fat storage in the liver, thus supporting the emerging idea that mitochondrial dysfunction is closely related to the development of obesity, type 2 diabetes mellitus and non-alcoholic steatohepatitis.

Where does liver fat go? A possible molecular link between fatty liver and diabetes

An elevation of fatty acid delivery amplifies the TCA cycle flux with a rise in anaplerosis/cataplerosis, leading to a proportional rise in oxidative stress and inflammation in liver.

Plekhs1 and Prdx3 are candidate genes responsible for mild hyperglycemia associated with obesity in a new animal model of F344-fa-nidd6 rat

Type 2 diabetes is a polygenic disease and characterized by hyperglycemia and insulin resistance, and it is strongly associated with obesity. However, the mechanism by which obesity contributes to onset of type 2 diabetes is not well understood. We generated rat strains with a hyperglycemic quantitative trait locus (QTL) derived from the Otsuka Long-Evans Tokushima Fatty rat and a fa/fa (Lepr^–/–) locus derived from the Zucker Fatty rat. Phenotypes for plasma glucose, and insulin levels were measured, and RNA and protein levels were determined using reverse transcription quantitative PCR and Western blot analyses, respectively. Compared with the obese control strain F344-fa (Lepr^–/–), plasma glucose levels of the obese F344-fa-nidd6 (Lepr^–/– and Nidd6/of) significantly increased, and plasma insulin levels significantly decreased. These phenotypes were not observed in the lean strains, suggesting that the Nidd6/of locus harbors a diabetogenic gene associated with obesity. We measured the expression of 41 genes in the Nidd6/of QTL region of each strain and found that the mRNA expression levels of the two genes significantly differed between the obese strains. The two genes, pleckstrin homology domain-containing, family S member 1 (Plechs1) and peroxiredoxin III (Prdx3), were differentially expressed only in the obese rats, suggesting that these two genes are involved in the mild elevation of blood glucose levels and insulin resistance in obesity.

Ultrastructure of the liver microcirculation influences hepatic and systemic insulin activity and provides a mechanism for age-related insulin resistance

While age‐related insulin resistance and hyperinsulinemia are usually considered to be secondary to changes in muscle, the liver also plays a key role in whole‐body insulin handling and its role in age‐related changes in insulin homeostasis is largely unknown. Here, we show that patent pores called ‘fenestrations’ are essential for insulin transfer across the liver sinusoidal endothelium and that age‐related loss of fenestrations causes an impaired insulin clearance and hyperinsulinemia, induces hepatic insulin resistance, impairs hepatic insulin signaling, and deranges glucose homeostasis. To further define the role of fenestrations in hepatic insulin signaling without any of the long‐term adaptive responses that occur with aging, we induced acute defenestration using poloxamer 407 (P407), and this replicated many of the age‐related changes in hepatic glucose and insulin handling. Loss of fenestrations in the liver sinusoidal endothelium is a hallmark of aging that has previously been shown to cause deficits in hepatic drug and lipoprotein metabolism and now insulin. Liver defenestration thus provides a new mechanism that potentially contributes to age‐related insulin resistance.

Pathogenesis of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease and a risk factor for cirrhosis and hepatocellular carcinoma. The pathological features of NASH include steatosis, hepatocyte injury, inflammation, and various degrees of fibrosis. Steatosis reflects disordered lipid metabolism. Insulin resistance and excessive fatty acid influx to the liver are two important contributing factors. Steatosis is also likely associated with lipotoxicity and cellular stresses such as oxidative stress and endoplasmic reticulum stress, which result in hepatocyte injury. Inflammation and fibrosis are frequently triggered by various signals such as proinflammatory cytokines and chemokines, released by injuried hepatocytes and activated Kupffer cells. Although much progress has been made, the pathogenesis of NASH is not fully elucidated. The purpose of this review is to discuss the current understanding of NASH pathogenesis, mainly focusing on factors contributing to steatosis, hepatocyte injury, inflammation, and fibrosis.

Association Between Pulmonary Function and Nonalcoholic Fatty Liver Disease in the NHANES III Study

Emerging evidence indicates that nonalcoholic fatty liver disease (NAFLD) is associated with a wide variety of extrahepatic complications. However, the potential association between impaired pulmonary function and NAFLD has been less investigated. This study examined the relationship between pulmonary function and hepatic steatosis in 9976 adults participating in a cross-sectional analysis of the Third National Health and Nutrition Examination Survey (NHANES III). NAFLD was defined as hepatic steatosis presented on ultrasound examinations in the absence of other known liver diseases. The associations between predicted forced expiratory volume in 1 second (FEV1)% or predicted forced vital capacity (FVC)% and NAFLD were examined using multivariable linear regression while controlling for confounders. The association between obstructive or restrictive spirometry patterns and NAFLD was also evaluated using multivariable logistic regression analysis. After adjustment for multiple covariates, predicted FEV1% and FVC% were significantly and inversely associated with the degree of hepatic steatosis (P for trend <0.001 for both). The restrictive lung pattern was significantly related to participants with moderate and severe hepatic steatosis as compared with those without steatosis (OR 1.65, 95% CI 1.14-2.39 and OR 1.85, 95% CI 1.13-2.82), whereas the obstructive lung pattern was not associated with the presence of hepatic steatosis. Individuals with a greater degree of hepatic steatosis were at greater risk for poor pulmonary function, especially in restrictive pattern. These novel findings demonstrate that impaired pulmonary function is also an extrahepatic complication of NAFLD.

Ghrelin-ghrelin O-acyltransferase system in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is currently considered as the most common liver disease in Western countries, and is rapidly becoming a serious threat to public health worldwide. However, the underlying mechanisms leading to the development of NAFLD are still not fully understood. The ghrelin-ghrelin O-acyltransferase (GOAT) system has recently been found to play a crucial role in both the development of steatosis and its progression to nonalcoholic steatohepatitis. Ghrelin, the natural ligand of the growth hormone secretagogue receptor, is a 28-amino acid peptide possessing a unique acylation on the serine in position 3 catalyzed by GOAT. The ghrelin-GOAT system is involved in insulin resistance, lipid metabolism dysfunction, and inflammation, all of which play important roles in the pathogenesis of NAFLD. A better understanding of ghrelin-GOAT system biology led to the identification of its potential roles in NAFLD. Molecular targets modulating ghrelin-GOAT levels and the biologic effects are being studied, which provide a new insight into the pathogenesis of NAFLD. This review probes into the possible relationship between the ghrelin-GOAT system and NAFLD, and considers the potential mechanisms by which the ghrelin-GOAT system brings about insulin resistance and other aspects concerning NAFLD.

Soy β-conglycinin improves obesity-induced metabolic abnormalities in a rat model of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has a variety of causes including calorie over-intake, an unbalanced diet, and/or genetic dysfunction of lipid metabolism. We hypothesized that NAFLD symptoms could be mitigated by specific nutritional factors. Here, we show that the potential for soy β-conglycinin (βCG) to improve obesity-induced metabolic abnormalities in the Otsuka Long Evans Tokushima fatty (OLETF) rat model of NAFLD. Long Evans Tokushima Otsuka (i.e., wild-type) and OLETF rats were provided a normal diet containing 20% casein for 4 weeks as a control. In a third (βCG) group, OLETF rats were fed a diet in which half of the casein was replaced by βCG. There was no difference in food intake between groups. Rats in the βCG group had decreased liver weight and lipid content (triglycerides, cholesterol, and phospholipids) compared to controls. In addition, βCG consumption decreased fatty acid synthase gene expression and enzymatic activity. These findings indicate that dietary intake of βCG can improve obesity-induced metabolic dysfunction, possibly via suppression of de novo fatty acid synthesis.

Mitochondrial dysfunction in steatotic rat livers occurs because a defect in complex i makes the liver susceptible to prolonged cold ischemia

Steatotic livers are susceptible to cold ischemia, which is thought to be secondary to mitochondrial dysfunction. Ischemic preconditioning (IPC) has been reported to improve liver function in the setting of warm ischemia/reperfusion injury, but the effect of IPC on steatotic liver mitochondrial function (MF) with cold ischemia has not been previously evaluated. We aimed to evaluate MF with various severities of hepatic steatosis after various durations of cold ischemia storage with or without IPC. Male Sprague-Dawley rats were fed a normal diet or a high-fat/high-sucrose diet for 1, 2, or 4 weeks to induce mild (<30%), moderate (30%-60%), or severe (>60%) macrovesicular steatosis, respectively. Liver MF was tested with high-resolution respirometry after 1.5, 4, 8, 12, 18, and 24 hours of cold ischemia. Rats in each group (n = 10) underwent 10 minutes of IPC or no IPC before cold ischemia. The baseline (time 0) respiration was similar for lean and severely steatotic livers despite decreased mitochondrial complex I (C-I) activity in severely steatotic livers. Hepatic steatosis was associated with increased C-I-mediated leaks and decreased respiratory control ratios (RCRs) after cold ischemia. Mildly, moderately, and severely steatotic livers showed significantly lower RCRs after 8, 1.5, and 1.5 hours of cold ischemia, respectively, in comparison with lean livers. IPC restored RCRs in mildly steatotic livers to levels comparable to those in lean livers for up to 24 hours of cold ischemia via the attenuation of C-I-mediated leaks, but it had no beneficial effect on moderately and severely steatotic livers. In conclusion, steatotic livers exhibited apparent mitochondrial dysfunction through an alteration in C-I activity, and this made them more susceptible to prolonged cold ischemia. The clinically based IPC protocol used here restored MF in cases of mild hepatic steatosis by attenuating C-I-mediated leaks after prolonged cold ischemia, but it did work not in livers with moderate or severe steatosis.

Wheat alkylresorcinols suppress high-fat, high-sucrose diet-induced obesity and glucose intolerance by increasing insulin sensitivity and cholesterol excretion in male mice

BACKGROUND

Epidemiologic studies have shown that the consumption of whole grains can reduce the risk of type 2 diabetes mellitus, cardiovascular disease, and all-cause mortality. However, the underlying mechanisms remain a matter of debate.

OBJECTIVE

We aimed to determine the effects of wheat bran-derived alkylresorcinols on diet-induced metabolic disorders in mice.

METHODS

We fed C57BL/6J mice a normal refined diet or a high-fat, high-sucrose diet [29.1% fat, 20.7% protein, 34.0% carbohydrates containing 20.0% sucrose (w/w)] alone (FS) or containing 0.4% (wt:wt) alkylresorcinols (FS-AR) for 10 wk.

RESULTS

The alkylresorcinols suppressed FS-induced increases in body weight by 31.0% as well as FS-induced hepatic triglyceride accumulation (means ± SEMs: 29.6 ± 3.18 and 19.8 ± 2.42 mg/g tissue in the FS and FS-AR groups, respectively), without affecting energy intake. We measured circadian changes in blood metabolic hormones and found that FS-induced hyperinsulinemia (5.1 and 2.1 μg/L at night in the FS and FS-AR groups, respectively) and hyperleptinemia (21.6 and 10.8 μg/L at night in the FS and FS-AR groups, respectively) were suppressed by alkylresorcinols. Glucose and insulin tolerance tests showed that alkylresorcinols significantly reduced fasting blood glucose concentrations (190 ± 3.62 and 160 ± 8.98 mg/dL in the FS and FS-AR groups, respectively) and suppressed glucose intolerance as well as insulin resistance induced by the FS diet. Furthermore, alkylresorcinols significantly increased insulin-stimulated hepatic serine/threonine protein kinase B phosphorylation compared to the FS diet (+81.3% and +57.4% for Ser473 and Thr308, respectively). On the other hand, pyruvate and starch tolerance tests suggested that alkylresorcinols did not affect gluconeogenesis and carbohydrate digestion, respectively. Alkylresorcinols significantly increased fecal cholesterol excretion by 39.6% and reduced blood cholesterol concentrations by 30.4%, while upregulating the expression of hepatic cholesterol synthetic genes such as sterol regulatory element binding protein 2 (Srebf2) and 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 1 (Hmgcs1).

CONCLUSIONS

These findings suggest that wheat alkylresorcinols increase glucose tolerance and insulin sensitivity by suppressing hepatic lipid accumulation and intestinal cholesterol absorption, which subsequently suppresses diet-induced obesity in mice.

Normal controlled attenuation parameter values: a prospective study of healthy subjects undergoing health checkups and liver donors in Korea

BACKGROUND/AIMS

The controlled attenuation parameter (CAP) is a noninvasive method of assessing hepatic steatosis. We defined the normal range of CAP values in healthy subjects and evaluated the associated factors.

METHODS

CAP values were measured in a cohort of healthy subjects who were screened as living liver transplantation donors and those who underwent health checkups. Subjects with current or a history of chronic liver disease, abnormalities on liver-related laboratory tests, or fatty liver on ultrasonography or biopsy were excluded.

RESULTS

The mean age of the 264 recruited subjects (131 males and 133 females; 76 potential liver donors and 188 subjects who had undergone health checkups) was 49.2 years. The mean CAP value was 224.8 ± 38.7 dB/m (range 100.0-308.0 dB/m), and the range of normal CAP values (5th-95th percentiles) was 156.0-287.8 dB/m. The mean CAP value was significantly higher in the health checkup than in the potential liver donor group (227.5 ± 42.0 vs. 218.2 ± 28.3 dB/m, P = 0.040). CAP values did not differ significantly according to gender or age in either group (all P > 0.05). In a multivariate linear regression analysis, body mass index (β = 0.271, P = 0.024) and triglyceride levels (β = 0.348, P = 0.008) were found to be independently associated with CAP values.

CONCLUSION

We determined the normal range of CAP values and found that body mass index and triglyceride levels were associated with the CAP values of healthy subjects.

A network biology workflow to study transcriptomics data of the diabetic liver

BACKGROUND

Nowadays a broad collection of transcriptomics data is publicly available in online repositories. Methods for analyzing these data often aim at deciphering the influence of gene expression at the process level. Biological pathway diagrams depict known processes and capture the interactions of gene products and metabolites, information that is essential for the computational analysis and interpretation of transcriptomics data.The present study describes a comprehensive network biology workflow that integrates differential gene expression in the human diabetic liver with pathway information by building a network of interconnected pathways. Worldwide, the incidence of type 2 diabetes mellitus is increasing dramatically, and to better understand this multifactorial disease, more insight into the concerted action of the disease-related processes is needed. The liver is a key player in metabolic diseases and diabetic patients often develop non-alcoholic fatty liver disease.

RESULTS

A publicly available dataset comparing the liver transcriptome from lean and healthy vs. obese and insulin-resistant subjects was selected after a thorough analysis. Pathway analysis revealed seven significantly altered pathways in the WikiPathways human pathway collection. These pathways were then merged into one combined network with 408 gene products, 38 metabolites and 5 pathway nodes. Further analysis highlighted 17 nodes present in multiple pathways, and revealed the connections between different pathways in the network. The integration of transcription factor-gene interactions from the ENCODE project identified new links between the pathways on a regulatory level. The extension of the network with known drug-target interactions from DrugBank allows for a more complete study of drug actions and helps with the identification of other drugs that target proteins up- or downstream which might interfere with the action or efficiency of a drug.

CONCLUSIONS

The described network biology workflow uses state-of-the-art pathway and network analysis methods to study the rewiring of the diabetic liver. The integration of experimental data and knowledge on disease-affected biological pathways, including regulatory elements like transcription factors or drugs, leads to improved insights and a clearer illustration of the overall process. It also provides a resource for building new hypotheses for further follow-up studies. The approach is highly generic and can be applied in different research fields.

Ageing, adipose tissue, fatty acids and inflammation

A common feature of ageing is the alteration in tissue distribution and composition, with a shift in fat away from lower body and subcutaneous depots to visceral and ectopic sites. Redistribution of adipose tissue towards an ectopic site can have dramatic effects on metabolic function. In skeletal muscle, increased ectopic adiposity is linked to insulin resistance through lipid mediators such as ceramide or DAG, inhibiting the insulin receptor signalling pathway. Additionally, the risk of developing cardiovascular disease is increased with elevated visceral adipose distribution. In ageing, adipose tissue becomes dysfunctional, with the pathway of differentiation of preadipocytes to mature adipocytes becoming impaired; this results in dysfunctional adipocytes less able to store fat and subsequent fat redistribution to ectopic sites. Low grade systemic inflammation is commonly observed in ageing, and may drive the adipose tissue dysfunction, as proinflammatory cytokines are capable of inhibiting adipocyte differentiation. Beyond increased ectopic adiposity, the effect of impaired adipose tissue function is an elevation in systemic free fatty acids (FFA), a common feature of many metabolic disorders. Saturated fatty acids can be regarded as the most detrimental of FFA, being capable of inducing insulin resistance and inflammation through lipid mediators such as ceramide, which can increase risk of developing atherosclerosis. Elevated FFA, in particular saturated fatty acids, maybe a driving factor for both the increased insulin resistance, cardiovascular disease risk and inflammation in older adults.