Diabetes is a progression factor for hepatic fibrosis in a high fat fed mouse obesity model of non-alcoholic steatohepatitis

Progress in the Study of Animal Models of Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) has recently been proposed as an alternative term to NAFLD. MASLD is a globally recognized chronic liver disease that poses significant health concerns and is frequently associated with obesity, insulin resistance, and hyperlipidemia. To better understand its pathogenesis and to develop effective treatments, it is essential to establish suitable animal models. Therefore, attempts have been made to establish modelling approaches that are highly similar to human diet, physiology, and pathology to better replicate disease progression. Here, we reviewed the pathogenesis of MASLD disease and summarised the used animal models of MASLD in the last 7 years through the PubMed database. In addition, we have summarised the commonly used animal models of MASLD and describe the advantages and disadvantages of various models of MASLD induction, including genetic models, diet, and chemically induced models, to provide directions for research on the pathogenesis and treatment of MASLD.

An antifibrotic compound that ameliorates hyperglycaemia and fat accumulation in cell and HFD mouse models

AIMS/HYPOTHESIS

Appropriate management of blood glucose levels and the prevention of complications are important in the treatment of diabetes. We have previously reported on a compound named HPH-15 that is not only antifibrotic but also AMP-activated protein kinase (AMPK)-activating. In this study, we evaluated whether HPH-15 is useful as a therapeutic medication for diabetes.

METHODS

We examined the effects of HPH-15 on AMPK activation, glucose uptake, fat accumulation and lactic acid production in L6-GLUT4, HepG2 and 3T3-L1 cells, as a model of muscle, liver and fat tissue, respectively. Additionally, we investigated the glucose-lowering, fat-accumulation-suppressing, antifibrotic and AMPK-activating effect of HPH-15 in mice fed a high-fat diet (HFD).

RESULTS

HPH-15 at a concentration of 10 µmol/l increased AMPK activation, glucose uptake and membrane translocation of GLUT4 in each cell model to the same extent as metformin at 2 mmol/l. The production of lactic acid (which causes lactic acidosis) in HPH-15-treated cells was equal to or less than that observed in metformin-treated cells. In HFD-fed mice, HPH-15 lowered blood glucose from 11.1±0.3 mmol/l to 8.2±0.4 mmol/l (10 mg/kg) and 7.9±0.4 mmol/l (100 mg/kg) and improved insulin resistance. The HPH-15 (10 mg/kg) group showed the same level of AMPK activation as the metformin (300 mg/kg) group in all organs. The HPH-15-treated HFD-fed mice also showed suppression of fat accumulation and fibrosis in the liver and fat tissue; these effects were more significant than those obtained with metformin. Mice treated with high doses of HPH-15 also exhibited a 44% reduction in subcutaneous fat.

CONCLUSIONS/INTERPRETATION

HPH-15 activated AMPK at lower concentrations than metformin in vitro and in vivo and improved blood glucose levels and insulin resistance in vivo. In addition, HPH-15 was more effective than metformin at ameliorating fatty liver and adipocyte hypertrophy in HFD-fed mice. HPH-15 could be effective in preventing fatty liver, a common complication in diabetic individuals. Additionally, in contrast to metformin, high doses of HPH-15 reduced subcutaneous fat in HFD-fed mice. Presumably, HPH-15 has a stronger inhibitory effect on fat accumulation and fibrosis than metformin, accounting for the reduction of subcutaneous fat. Therefore, HPH-15 is potentially a glucose-lowering medication that can lower blood glucose, inhibit fat accumulation and ameliorate liver fibrosis.

A novel experimental mouse model of diabetic nonalcoholic steatohepatitis: A critical role for acid-sensitive Ion Channel 1a

BACKGROUND

A two-way relationship exists between type 2 diabetes (T2DM) and human nonalcoholic steatohepatitis (NASH). Several diabetic NASH models have the disadvantages of long cycles or inconsistent with the actual incidence of human disease, which would be costly and time-consuming to investigate disease pathogenesis and develop drugs. Therefore, there is an urgent need to establish a diabetic NASH mouse model.

METHODS

The combination between Fructose-palmitate-cholesterol diet (FPC) and Streptozotocin (STZ) (FPC+STZ) was used to construct diabetic NASH mouse model. The in vivo effects of silencing acid-sensitive Ion Channel 1a (ASIC1a) were examined with an adeno-associated virus 9 (AAV9) carrying ASIC1a short hairpin RNA (shRNA) in FPC+STZ model.

RESULTS

The mice fed with FPC for 12 weeks had insulin resistance, hyperinsulinemia, lipid accumulation, and increased hepatic levels of inflammatory factors. However, it still did not develop remarkable liver fibrosis. Most interestingly, noticeable fibrotic scars were observed in the liver of mice from FPC+STZ group. Furthermore, insulin therapy significantly ameliorated FPC+STZ-induced NASH-related liver fibrosis, indicating that hyperglycemia is of great significance in NASH development and progression. Importantly, ASIC1a was found to be involved in the pathogenesis of diabetic NASH as demonstrated that silencing ASIC1a in HSCs significantly ameliorated FPC+STZ-induced NASH fibrosis. Mechanistically, ASIC1a interacted with Poly Adp-adenosine ribose polymerase (PARP1) to promote HSC activation by inducing autophagy.

CONCLUSION

A FPC diet combined with an injection of STZ induces a diabetic NASH mouse model in a shorter period. Targeting ASIC1a may provide a novel therapeutic target for the treatment of diabetic NASH.

A male mouse model for metabolic dysfunction-associated steatotic liver disease and hepatocellular carcinoma

The lack of an appropriate preclinical model of metabolic dysfunction-associated steatotic liver disease (MASLD) that recapitulates the whole disease spectrum impedes exploration of disease pathophysiology and the development of effective treatment strategies. Here, we develop a mouse model (Streptozotocin with high-fat diet, STZ + HFD) that gradually develops fatty liver, metabolic dysfunction-associated steatohepatitis (MASH), hepatic fibrosis, and hepatocellular carcinoma (HCC) in the context of metabolic dysfunction. The hepatic transcriptomic features of STZ + HFD mice closely reflect those of patients with obesity accompanying type 2 diabetes mellitus, MASH, and MASLD-related HCC. Dietary changes and tirzepatide administration alleviate MASH, hepatic fibrosis, and hepatic tumorigenesis in STZ + HFD mice. In conclusion, a murine model recapitulating the main histopathologic, transcriptomic, and metabolic alterations observed in MASLD patients is successfully established.

Postpartum development of metabolic dysfunction-associated steatotic liver disease in a lean mouse model of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is associated with increased postpartum risk for metabolic dysfunction-associated steatotic liver disease (MASLD). GDM-related MASLD predisposes to advanced liver disease, necessitating a better understanding of its development in GDM. This preclinical study evaluated the MASLD development in a lean GDM mouse model with impaired insulin secretion capacity. Lean GDM was induced by short-term 60% high-fat diet and low-dose streptozotocin injections (60 mg/kg for 3 days) before mating in C57BL/6N mice. The control dams received only high-fat diet or low-fat diet. Glucose homeostasis was assessed during pregnancy and postpartum, whereas MASLD was assessed on postpartum day 30 (PP30). GDM dams exhibited a transient hyperglycemic phenotype during pregnancy, with hyperglycaemia reappearing after lactation. Lower insulin levels and impaired glucose-induced insulin response were observed in GDM mice during pregnancy and postpartum. At PP30, GDM dams displayed higher hepatic triglyceride content compared controls, along with increased MAS (MASLD) activity scores, indicating lipid accumulation, inflammation, and cell turnover indices. Additionally, at PP30, GDM dams showed elevated plasma liver injury markers. Given the absence of obesity in this double-hit GDM model, the results clearly indicate that impaired insulin secretion driven pregnancy hyperglycaemia has a distinct contribution to the development of postpartum MASLD.

Moderate-Intensity Constant and High-Intensity Interval Training Confer Differential Metabolic Benefits in Skeletal Muscle, White Adipose Tissue, and Liver of Candidates to Undergo Bariatric Surgery

Background/Objectives: Bariatric surgery candidates require presurgical physical training, therefore, we compared the metabolic effects of a constant moderate-intensity training program (MICT) vs. a high-intensity interval training (HIIT) in this population. Methods: Seventeen participants performed MICT (n = 9, intensity of 50% of heart rate reserve (HRR) and/or 4-5/10 subjective sensation of effort (SSE)) or HIIT (n = 8, 6 cycles of 2.5 min at 80% of the HRR and/or 7-8/10 of SSE, interspersed by 6 cycles of active rest at 20% of the FCR) for 10 sessions for 4 weeks. After training, tissue samples (skeletal muscle, adipose tissue, and liver) were extracted, and protein levels of adiponectin, GLUT4, PGC1α, phospho-AMPK/AMPK, collagen 1 and TGFβ1 were measured. Results: Participants who performed MICT showed higher protein levels of PGC-1α in skeletal muscle samples (1.1 ± 0.27 vs. 0.7 ± 0.4-fold change, p < 0.05). In the liver samples of the people who performed HIIT, lower protein levels of phospho-AMPK/AMPK (1.0 ± 0.37 vs. 0.52 ± 0.22-fold change), PGC-1α (1.0 ± 0.18 vs. 0.69 ± 0.15-fold change), and collagen 1 (1.0 ± 0.26 vs. 0.59 ± 0.28-fold change) were observed (all p < 0.05). In subcutaneous adipose tissue, higher adiponectin levels were found only after HIIT training (1.1 ± 0.48 vs. 1.9 ± 0.69-fold change, p < 0.05). Conclusions: Our results show that both MICT and HIIT confer metabolic benefits in candidates undergoing bariatric surgery; however, most of these benefits have a program-specific fashion. Future studies should aim to elucidate the mechanisms behind these differences.

Intestinal Inflammation and Regeneration-Interdigitating Processes Controlled by Dietary Lipids in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a disease of chronic inflammatory conditions of the intestinal tract due to disturbance of the inflammation and immune system. Symptoms of IBD include abdominal pain, diarrhea, bleeding, reduced weight, and fatigue. In IBD, the immune system attacks the intestinal tract's inner wall, causing chronic inflammation and tissue damage. In particular, interlukin-6 and interlukin-17 act on immune cells, including T cells and macrophages, to amplify the immune responses so that tissue damage and morphological changes occur. Of note, excessive calorie intake and obesity also affect the immune system due to inflammation caused by lipotoxicity and changes in lipids supply. Similarly, individuals with IBD have alterations in liver function after sustained high-fat diet feeding. In addition, excess dietary fat intake, along with alterations in primary and secondary bile acids in the colon, can affect the onset and progression of IBD because inflammatory cytokines contribute to insulin resistance; the factors include the release of inflammatory cytokines, oxidative stress, and changes in intestinal microflora, which may also contribute to disease progression. However, interfering with de novo fatty acid synthase by deleting the enzyme acetyl-CoA-carboxylase 1 in intestinal epithelial cells (IEC) leads to the deficiency of epithelial crypt structures and tissue regeneration, which seems to be due to Lgr5+ intestinal stem cell function. Thus, conflicting reports exist regarding high-fat diet effects on IBD animal models. This review will focus on the pathological basis of the link between dietary lipids intake and IBD and will cover the currently available pharmacological approaches.

Maternal betaine supplementation ameliorates fatty liver disease in offspring mice by inhibiting hepatic NLRP3 inflammasome activation

BACKGROUND/OBJECTIVES

Previous research has shown maternal betaine supplementation alleviates fetal-derived hepatic steatosis. Therefore, this study examined the anti-inflammatory effect of maternal betaine intake in offspring mice and its mechanism.

MATERIALS/METHODS

Female C57BL/6J mice and their offspring were randomly divided into 3 groups according to the treatment received during gestation and lactation: control diet (CD), fatty liver disease (FLD), and fatty liver disease + 1% betaine (FLD-BET). The FLD group was given a high-fat diet and streptozotocin (HFD + STZ), and the FLD-BET group was treated with HFD + STZ + 1% betaine. After weaning, the offspring mice were given a normal diet for 5 weeks and then dissected to measure the relevant indexes.

RESULTS

Compared to the CD group, the offspring mice in the FLD group revealed obvious hepatic steatosis and increased serum levels of alanine aminotransferase, interleukin (IL)-6, and tumor necrosis factor (TNF)-α; maternal betaine supplementation reversed these changes. The hepatic mRNA expression levels of IL-6, IL-18, and Caspase-1 were significantly higher in the FLD group than in the CD group. Maternal betaine supplementation reduced the expression of IL-1β, IL-6, IL-18, and apoptosis-associated speck-like protein containing C-terminal caspase recruitment domain (ASC). Maternal betaine supplementation also reversed the increasing protein expressions of nitric oxide dioxygenase-like receptor family pyrin domain containing 3 (NLRP3), ASC, Caspase-1, IL-1β, and IL-18 in offspring mice exposed to HFD + STZ. Maternal betaine supplementation decreased the homocysteine (Hcy) and s-adenosine homocysteine (SAH) levels significantly in the livers. Furthermore, the hepatic Hcy concentrations showed significant inverse relationships with the mRNA expression of TNF-α, NLRP3, ASC, and IL-18. The hepatic SAH concentration was inversely associated with the IL-1β mRNA expression.

CONCLUSIONS

The lipotropic and anti-inflammatory effect of maternal betaine supplementation may be associated with the inhibition of NLRP3 inflammasome in the livers of the offspring mice.

Comparison of digital and traditional skin wound closure assessment methods in mice

BACKGROUND

Chronic skin wounds are a common complication of many diseases such as diabetes. Various traditional methods for assessing skin wound closure are used in animal studies, including wound tracing, calliper measurements and histological analysis. However, these methods have poorly defined wound closure or practical limitations. Digital image analysis of wounds is an increasingly popular, accessible alternative, but it is unclear whether digital assessment is consistent with traditional methods. This study aimed to optimise and compare digital wound closure assessment with traditional methods, using a diabetic mouse model. Diabetes was induced in male C57BL/6J mice by high-fat diet feeding combined with low dose (65 mg/kg of body weight) streptozotocin injections. Mice fed normal chow were included as controls. After 18 weeks, four circular full-thickness dorsal skin wounds of 4 mm diameter were created per mouse. The wounds were photographed and measured by callipers. Wound closure rate (WCR) was digitally assessed by two reporters using two methods: wound outline (WCR-O) and re-epithelialisation (WCR-E). Wounded skin tissues were collected at 10-days post-wounding and wound width was measured from haematoxylin and eosin-stained skin tissue.

RESULTS

Between reporters, WCR-O was more consistent than WCR-E, and WCR-O correlated with calliper measurements. Histological analysis supported digital assessments, especially WCR-E, when wounds were histologically closed.

CONCLUSIONS

WCR-O could replace calliper measurements to measure skin wound closure, but WCR-E assessment requires further refinement. Small animal studies of skin wound healing can greatly benefit from standardised definitions of wound closure and more consistent digital assessment protocols.

Production, Exacerbating Effect, and EV-Mediated Transcription of Hepatic CCN2 in NASH: Implications for Diagnosis and Therapy of NASH Fibrosis

Non-alcoholic steatohepatitis (NASH) is characterized by steatosis, hepatocyte ballooning, and inflammation and may progress to include increasingly severe fibrosis, which portends more serious disease and is predictive of patient mortality. Diagnostic and therapeutic options for NASH fibrosis are limited, and the underlying fibrogenic pathways are under-explored. Cell communication network factor 2 (CCN2) is a well-characterized pro-fibrotic molecule, but its production in and contribution to NASH fibrosis requires further study. Hepatic CCN2 expression was significantly induced in NASH patients with F3-F4 fibrosis and was positively correlated with hepatic Col1A1, Col1A2, Col3A1, or αSMA expression. When wild-type (WT) or transgenic (TG) Swiss mice expressing enhanced green fluorescent protein (EGFP) under the control of the CCN2 promoter were fed up to 7 weeks with control or choline-deficient, amino-acid-defined diet with high (60%) fat (CDAA-HF), the resulting NASH-like hepatic pathology included a profound increase in CCN2 or EGFP immunoreactivity in activated hepatic stellate cells (HSC) and in fibroblasts and smooth muscle cells of the vasculature, with little or no induction of CCN2 in other liver cell types. In the context of CDAA-HF diet-induced NASH, Balb/c TG mice expressing human CCN2 under the control of the albumin promoter exhibited exacerbated deposition of interstitial hepatic collagen and activated HSC compared to WT mice. In vitro, palmitic acid-treated hepatocytes produced extracellular vesicles (EVs) that induced CCN2, Col1A1, and αSMA in HSC. Hepatic CCN2 may aid the assessment of NASH fibrosis severity and, together with pro-fibrogenic EVs, is a therapeutic target for reducing NASH fibrosis.

AGER1 deficiency-triggered ferroptosis drives fibrosis progression in nonalcoholic steatohepatitis with type 2 diabetes mellitus

Hyperglycemia is an independent risk factor for the rapid progression of nonalcoholic steatohepatitis (NASH) to liver fibrosis with an incompletely defined mechanism. Ferroptosis is a novel form of programmed cell death that has been identified as a pathogenic mechanism in various diseases. However, the role of ferroptosis in the development of liver fibrosis in NASH with type 2 diabetes mellitus (T2DM) is unclear. Here, we observed the histopathological features of the progression of NASH to liver fibrosis as well as hepatocyte epithelial-mesenchymal transition (EMT) in a mouse model of NASH with T2DM and high-glucose-cultured steatotic human normal liver (LO2) cells. The distinctive features of ferroptosis, including iron overload, decreased antioxidant capacity, the accumulation of reactive oxygen species, and elevated lipid peroxidation products, were confirmed in vivo and in vitro. Liver fibrosis and hepatocyte EMT were markedly alleviated after treatment with the ferroptosis inhibitor ferrostatin-1. Furthermore, a decrease in the gene and protein levels of AGE receptor 1 (AGER1) was detected in the transition from NASH to liver fibrosis. Overexpression of AGER1 dramatically reversed hepatocyte EMT in high-glucose-cultured steatotic LO2 cells, whereas the knockdown of AGER1 had the opposite effect. The mechanisms underlying the phenotype appear to be associated with the inhibitory effects of AGER1 on ferroptosis, which is dependent on the regulation of sirtuin 4. Finally, in vivo adeno-associated virus-mediated AGER1 overexpression effectively relieved liver fibrosis in a murine model. Collectively, these findings suggest that ferroptosis participates in the pathogenesis of liver fibrosis in NASH with T2DM by promoting hepatocyte EMT. AGER1 could reverse hepatocyte EMT to ameliorate liver fibrosis by inhibiting ferroptosis. The results also suggest that AGER1 may be a potential therapeutic target for the treatment of liver fibrosis in patients with NASH with T2DM. Chronic hyperglycemia is associated with increased advanced glycation end products, resulting in the downregulation of AGER1. AGER1 deficiency downregulates Sirt4, which disturbs key regulators of ferroptosis (TFR-1, FTH, GPX4, and SLC7A11). These lead to increased iron uptake, decreasing the antioxidative capacity and enhanced lipid ROS production, ultimately leading to ferroptosis, which further promotes hepatocyte epithelial-mesenchymal transition and fibrosis progression in NASH with T2DM.

Constant-moderate versus high-intensity interval training on heart adiponectin levels in high-fat fed mice: a preventive and treatment approach

CONTEXT

Research has described that adiponectin plays a key role in cardiomyocytes metabolism, however, the effects of exercise during obesity on cardiac adiponectin levels is unclear.

OBJECTIVE

To investigate the effects of constant-moderate endurance (END) and high-intensity interval training (HIIT), on heart adiponectin levels in mice.

MATERIAL AND METHODS

Two experiments were conducted: (1) preventive (EX1): 10 week-old male mice were fed standard (CHOW) or high-fat diet (HFD;45% fat) and simultaneously trained with END and HIIT for 10 weeks; (2) Treatment (EX2): after 10 weeks of dietary intervention, another cohort of 10 week-old mice were trained by both programmes for 10 weeks.

RESULTS

In EX1, END and HIIT decreased low-molecular weight adiponectin (∼0.5-fold; p < 0.05) and increased GLUT4 levels (∼2-fold; p < .05). In EX2, HFD significantly decreased high-molecular weight adiponectin (∼0.7-fold; p < .05), and END reversed this change.Discussion and conclusion: HFD and exercise influence heart adiponectin isoforms and therefore might impact cardiomyocyte metabolism.

Hypoglycemic Effect of the N-Butanol Fraction of Torreya grandis Leaves on Type 2 Diabetes Mellitus in Rats through the Amelioration of Oxidative Stress and Enhancement of β-Cell Function

Materials and Methods

Sprague-Dawley rats were randomly divided into six groups: control, T2DM, metformin, high-dose BFTL (800 mg/kg), middle-dose BFTL (400 mg/kg), and low-dose BFTL (200 mg/kg). After 4 weeks of BFTL treatment, the correlations of serum indicators with protein expression in tissue were determined, and pathological changes in the liver, kidneys, and pancreas were analyzed.

Results

Compared with the results in the T2DM group, serum fasting blood glucose, triglyceride, total cholesterol, malondialdehyde, alanine aminotransferase, and aspartate aminotransferase levels were significantly decreased (p < 0.05), whereas superoxide dismutase and glutathione peroxidase levels were significantly increased (p < 0.05) in the high-, middle-, and low-dose BFTL groups. The treatment also improved oral glucose tolerance. In addition, the pathological changes of the liver, kidney, and pancreas were improved by BFTL treatment. Cytochrome and caspase-3 expression in pancreatic was significantly decreased (p < 0.05) by BFTL treatment, whereas the Bcl-2/Bax ratio was significantly increased (p < 0.05). Discussion and Conclusion. BFTL exerted significant hypoglycemic effect on T2DM model rats, and its mechanism involved the suppression of blood glucose levels and oxidative stress by improving the metabolism of blood lipids and antioxidant capacity, boosting β-cell function, and inhibiting β-cell apoptosis.

Angiotensin Converting Enzyme-2 Therapy Improves Liver Fibrosis and Glycemic Control in Diabetic Mice With Fatty Liver

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and is frequently associated with type 2 diabetes. However, there is no specific medical therapy to treat this condition. Angiotensin-converting enzyme 2 (ACE2) of the protective renin angiotensin system generates the antifibrotic peptide angiotensin-(1-7) from profibrotic angiotensin II peptide. In this study, we investigated the therapeutic potential of ACE2 in diabetic NAFLD mice fed a high-fat (20%), high-cholesterol (2%) diet for 40 weeks. Mice were given a single intraperitoneal injection of ACE2 using an adeno-associated viral vector at 30 weeks of high-fat, high-cholesterol diet (15 weeks after induction of diabetes) and sacrificed 10 weeks later. ACE2 significantly reduced liver injury and fibrosis in diabetic NAFLD mice compared with the control vector injected mice. This was accompanied by reductions in proinflammatory cytokine expressions, hepatic stellate cell activation, and collagen 1 expression. Moreover, ACE2 therapy significantly increased islet numbers, leading to an increased insulin protein content in β-cells and plasma insulin levels with subsequent reduction in plasma glucose levels compared with controls. Conclusion: We conclude that ACE2 gene therapy reduces liver fibrosis and hyperglycemia in diabetic NAFLD mice and has potential as a therapy for patients with NAFLD with diabetes.

Polyphenol-Rich Extracts of Xylopia and Aframomum Species Show Metabolic Benefits by Lowering Hepatic Lipid Accumulation in Diet-Induced Obese Mice

Metabolic syndrome is a complex condition associated with a series of pathologies featuring glucose intolerance, diabetes, high blood pressure, dyslipidemia, microalbuminuria, overweight, and obesity. It is also related to nonalcoholic fatty liver disease (NAFLD), recognized as the most familiar cause of chronic liver disease worldwide. The overall prevalence of metabolic syndrome and, consequently, the one of NAFLD is constantly increasing worldwide. The initial management of these diseases involves lifestyle modifications, including changes in diet and physical exercise. In addition to conventional drugs like orlistat, botanicals are traditionally used to counteract these disorders, and some of them are currently under evaluation. The present work evaluated the in vivo beneficial effects of hydroalcoholic extracts of two Cameroonian spices, focusing on obesity-related hepatic lipid injury in high-fat-fed C57BL/6 mice. Hydroethanolic extracts were prepared and characterized by reverse phase-high-performance liquid chromatography (HPLC)-photodiode array detection and ultra performance liquid chromatography-triple time-of-flight electrospray ionization tandem mass spectroscopy (TOF-ESI-MS/MS) analysis. Plant extracts were orally administered for 30 days at different dose levels (100 and 200 mg kg^-1 body weight (BW)) to obese C57BL/6 mice. Food intake (FI) and BW were recorded daily. Plasma biochemical parameters and lipid content were estimated at the beginning and at the end of the experiment. Liver tissues were subjected to histological examinations, lipid content, as well as oxidative stress markers, and FAME (fatty acid methyl esters) were estimated. Oral administration of extracts at 200 mg kg^-1 BW significantly reduced FI and prevented BW gain. A decrease in the weight of the liver and a decrease in the hepatic and plasma lipid content were observed. Plasma enzyme (serum glutamic-oxaloacetic transaminase, SGOT; serum glutamic pyruvic transaminase, SGPT; alkaline phosphatase, ALP) activities were not indicative of any organ damage. Chemical analysis suggested that phenolic acids (4-caffeoylquinic acid, p-coumaric acid 4-O-glucoside, 5-caffeoylshikimic acid, caffeic acid hexose, and 4-O-methyl gallic acid) and flavonoids (morusin derivatives, naringenin-7-O-glucoside, and homoisoflavanone) identified in the extracts could potentially justify the biological properties observed. The main findings of this study showed that Xylopia parviflora (A. Rich.) Benth and Aframomum citratum (Pereira ex Oliv. et Hanb.) K. Shum decreased hepatic lipid accumulation in high-fat-diet (HFD)-induced obese C57BL/6 mice and confirmed, at least in part, our previous in vitro and ex vivo studies. The molecular mechanisms underlying these effects are still unclear and will be explored in the future.

Sitagliptin Is More Effective Than Gliclazide in Preventing &nbsp;Pro-Fibrotic and Pro-Inflammatory Changes in a Rodent Model of Diet-Induced Non-Alcoholic Fatty Liver Disease

A diet-induced non-alcoholic fatty liver disease (NAFLD) model causing obesity in rodents was used to examine whether sitagliptin and gliclazide therapies have similar protective effects on pathological liver change. Methods: Male mice were fed a high-fat diet (HFD) or standard chow (Chow) ad libitum for 25 weeks and randomly allocated to oral sitagliptin or gliclazide treatment for the final 10 weeks. Fasting blood glucose and circulating insulin were measured. Inflammatory and fibrotic liver markers were assessed by qPCR. The second messenger ERK and autophagy markers were examined by Western immunoblot. F4/80, collagens and CCN2 were assessed by immunohistochemistry (IHC). Results: At termination, HFD mice were obese, hyperinsulinemic and insulin-resistant but non-diabetic. The DPP4 inhibitor sitagliptin prevented intrahepatic induction of pro-fibrotic markers collagen-IV, collagen-VI, CCN2 and TGF-β1 and pro-inflammatory markers TNF-α and IL-1β more effectively than sulfonylurea gliclazide. By IHC, liver collagen-VI and CCN2 induction by HFD were inhibited only by sitagliptin. Sitagliptin had a greater ability than gliclazide to normalise ERK-protein liver dysregulation. Conclusion: These data indicate that sitagliptin, compared with gliclazide, exhibits greater inhibition of pro-fibrotic and pro-inflammatory changes in an HFD-induced NAFLD model. Sitagliptin therapy, even in the absence of diabetes, may have specific benefits in diet-induced NAFLD.

Targeting CCN2 protects against progressive non-alcoholic steatohepatitis in a preclinical model induced by high-fat feeding and type 2 diabetes

Type 2 diabetes is an independent risk factor for non-alcoholic steatohepatitis (NASH) progression and its mediators have not been resolved. In this study, a pathogenic role of cellular communication network factor 2 (CCN2) protein in NASH pathology, was investigated in an established preclinical NASH model. Male wild type C57BL/6 mice received either Chow or high fat diet (HFD) for 26 weeks, with some mice in each group randomly selected to receive low dose streptozotocin (STZ: 3 i.p. injections, 65 mg/kg) at 15 weeks to induce type 2 diabetes. In the final 10 of the 26 weeks mice from each group were administered i.p. either rabbit anti-CCN2 neutralizing antibody (CCN2Ab) or as control normal rabbit IgG, at a dose of 150 µg per mouse twice/week. NASH developed in the HFD plus diabetes (HFD+DM) group. Administration of CCN2Ab significantly downregulated collagen I and collagen III mRNA induction and prevented pro-inflammatory MCP-1 mRNA induction in HFD+DM mice. At the protein level, CCN2Ab significantly attenuated collagen accumulation by PSR stain and collagen I protein induction in HFD+DM. Phosphorylation of the pro-fibrotic ERK signalling pathway in liver in HFD+DM was attenuated by CCN2Ab treatment. Intrahepatic CCN1 mRNA was induced, whereas CCN3 was downregulated at both the mRNA and protein levels in HFD+DM. CCN3 down-regulation was prevented by CCN2Ab treatment. This in vivo study indicates that CCN2 is a molecular target in NASH with high fat diet and diabetes, and that regulation of ERK signalling is implicated in this process.

Prediction of new onset of diabetes mellitus during a 10-year period by using a combination of levels of alanine aminotransferase and γ-glutamyl transferase

Levels of alanine aminotransferase (ALT) and γ-glutamyl transferase (GGT) have been reported to be associated with increased risk of diabetes mellitus (DM). However, whether a combination of levels of ALT and GGT predicts new onset of DM better than does ALT or GGT alone in both males and females has not fully been addressed. We investigated the relationship between the combination of ALT and GGT and DM development during a 10-year follow-up period in 13,919 subjects (male/female: 8,983/4,936; age 48 ± 10 years) who received health examinations. During the 10-year period, 617 males (6.9%) and 153 females (3.1%) had new onset of DM. Multivariable Cox proportional hazard models with a restricted cubic spline showed that hazard ratios (HRs) of DM development increased with higher levels of ALT and GGT at baseline in both sexes after adjustment of confounding factors. When divided into 4 subgroups of high (H-) and low (L-) levels of ALT (male/female: 27/21 U/L) and GGT (male/female: 43/23 U/L) using cutoff values shown by receiver operating characteristic curve analyses, the adjusted HR in the H-ALT/H-GGT group was significantly higher than HR in the L-ALT/L-GGT group as the reference in males (HR [95% confidence interval]: 1.73[1.36-2.20], p < 0.001) but was not significantly higher in females (1.50 [0.97-2.33], p = 0.065). The addition of the combination of H-ALT/H-GGT to traditional risk factors with and without H-ALT or H-GGT alone significantly improved the discriminatory capability for predicting development of DM. In conclusion, the combination of H-ALT/H-GGT efficiently predicts development of DM in male individuals but not significantly in female individuals.

The Effect of a Sustained High-Fat Diet on the Metabolism of White and Brown Adipose Tissue and Its Impact on Insulin Resistance: A Selected Time Point Cross-Sectional Study

(1) Background: studies on the long-term dynamic changes in fat depot metabolism in response to a high-fat diet (HFD) on hepatic lipid deposition and insulin resistance are sparse. This study investigated the dynamic changes produced by HFD and the production of dysfunctional fat depots on insulin resistance and liver lipid metabolism. (2) Methods: mice fed a chow or HFD (45% kcal fat) diet had three fat depots, liver, and blood collected at 6, 10, 20, and 30 weeks. Anthropometric changes and gene markers for adipogenesis, thermogenesis, ECM remodeling, inflammation, and tissue insulin resistance were measured. (3) Results: early responses to the HFD were increased body weight, minor deposition of lipid in liver, increased adipocyte size, and adipogenesis. Later changes were dysfunctional adipose depots, increased liver fat, insulin resistance (shown by changes in ITT) accompanied by increased inflammatory markers, increased fibrosis (fibrosis > 2-fold, p < 0.05 from week 6), and the presence of crown cells in white fat depots. Later, changes did not increase thermogenic markers in response to the increased calories and decreased UCP1 and PRDM16 proteins in WAT. (4) Conclusions: HFD feeding initially increased adipocyte diameter and number, but later changes caused adipose depots to become dysfunctional, restricting adipose tissue expansion, changing the brown/beige ratios in adipose depots, and causing ectopic lipid deposition and insulin resistance.

Beta vulgaris L. (Beetroot) Methanolic Extract Prevents Hepatic Steatosis and Liver Damage in T2DM Rats by Hypoglycemic, Insulin-Sensitizing, Antioxidant Effects, and Upregulation of PPARα

Simple Summary

Beetroot is one of the most consumable plants across the world. Previous studies have shown many health benefits of beetroot, with evidence of having potent hypoglycemic, antioxidant, and anti-inflammatory effects. The data obtained from this study further confirmed this effect in streptozotocin-diabetic animals. They showed the ability of methanolic beetroot extract to prevent the associated hepatic oxidative stress, inflammation, steatosis, and dyslipidaemia. However, the protection mechanisms involve, at least, upregulation of endogenous antioxidants, anti-apoptotic Bcl2, and PPARα.

Abstract

The present study examined if methanolic beetroot extract (BE) could prevent dyslipidemia and hepatic steatosis and damage in a type-2 diabetes mellitus (T2DM) rat model and studied some mechanisms of action. T2DM was induced in adult male Wistar rats by a low single dose of streptozotocin (STZ) (35 mg/kg, i.p) and a high-fat diet (HFD) feeding for 5 weeks. Control or T2DM rats then continued on standard or HFDs for another 12 weeks and were treated with the vehicle or BE (250 or 500 mg/kg). BE, at both doses, significantly improved liver structure and reduced hepatic lipid accumulation in the livers of T2DM rats. They also reduced body weight gain, serum glucose, insulin levels, serum and hepatic levels of cholesterol, triglycerides, free fatty acids, and serum levels of low-density lipoproteins in T2DM rats. In concomitant, they significantly reduced serum levels of aspartate and alanine aminotransferases, hepatic levels of malondialdehyde, tumor-necrosis factor-α, interleukin-6, and mRNA of Bax, cleaved caspase-3, and SREBP1/2. However, both doses of BE significantly increased hepatic levels of total glutathione, superoxide dismutase, and mRNA levels of Bcl2 and PPARα in the livers of both the control and T2DM rats. All of these effects were dose-dependent and more profound with doses of 500 mg/kg. In conclusion, chronic feeding of BE to STZ/HFD-induced T2DM in rats prevents hepatic steatosis and liver damage by its hypoglycemic and insulin-sensitizing effects and its ability to upregulate antioxidants and PPARα.

Multi-omics of a pre-clinical model of diabetic cardiomyopathy reveals increased fatty acid supply impacts mitochondrial metabolic selectivity

The incidence of type 2 diabetes (T2D) is increasing globally, with long-term implications for human health and longevity. Heart disease is the leading cause of death in T2D patients, who display an elevated risk of an acute cardiovascular event and worse outcomes following such an insult. The underlying mechanisms that predispose the diabetic heart to this poor prognosis remain to be defined. This study developed a pre-clinical model (Rattus norvegicus) that complemented caloric excess from a high-fat diet (HFD) and pancreatic β-cell dysfunction from streptozotocin (STZ) to produce hyperglycaemia, peripheral insulin resistance, hyperlipidaemia and elevated fat mass to mimic the clinical features of T2D. Ex vivo cardiac function was assessed using Langendorff perfusion with systolic and diastolic contractile depression observed in T2D hearts. Cohorts representing untreated, individual HFD- or STZ-treatments and the combined HFD + STZ approach were used to generate ventricular samples (n = 9 per cohort) for sequential and integrated analysis of the proteome, lipidome and metabolome by liquid chromatography-tandem mass spectrometry. This study found that in T2D hearts, HFD treatment primed the metabolome, while STZ treatment was the major driver for changes in the proteome. Both treatments equally impacted the lipidome. Our data suggest that increases in β-oxidation and early TCA cycle intermediates promoted rerouting via 2-oxaloacetate to glutamate, γ-aminobutyric acid and glutathione. Furthermore, we suggest that the T2D heart activates networks to redistribute excess acetyl-CoA towards ketogenesis and incomplete β-oxidation through the formation of short-chain acylcarnitine species. Multi-omics provided a global and comprehensive molecular view of the diabetic heart, which distributes substrates and products from excess β-oxidation, reduces metabolic flexibility and impairs capacity to restore high energy reservoirs needed to respond to and prevent subsequent acute cardiovascular events.

Differential Effects of 'Vaping' on Lipid and Glucose Profiles and Liver Metabolic Markers in Obese Versus Non-obese Mice

Tobacco smoking increases the risk of metabolic disorders due to the combination of harmful chemicals, whereas pure nicotine can improve glucose tolerance. E-cigarette vapour contains nicotine and some of the harmful chemicals found in cigarette smoke at lower levels. To investigate how e-vapour affects metabolic profiles, male Balb/c mice were exposed to a high-fat diet (HFD, 43% fat, 20kJ/g) for 16weeks, and e-vapour in the last 6weeks. HFD alone doubled fat mass and caused dyslipidaemia and glucose intolerance. E-vapour reduced fat mass in HFD-fed mice; only nicotine-containing e-vapour improved glucose tolerance. In chow-fed mice, e-vapour increased lipid content in both blood and liver. Changes in liver metabolic markers may be adaptive responses rather than causal. Future studies can investigate how e-vapour differentially affects metabolic profiles with different diets.

Exercise induces favorable metabolic changes in white adipose tissue preventing high-fat diet obesity

Diet and/or exercise are cost effective interventions to treat obesity. However, it is unclear if the type of exercise undertaken can prevent the onset of obesity and if it can act through different effects on fat depots. In this study we did not allow obesity to develop so we commenced the high-fat diet (HFD) and exercise programs concurrently and investigated the effect of endurance exercise (END) and high-intensity interval training (HIIT) on changes in cellular adipogenesis, thermogenesis, fibrosis, and inflammatory markers in three different fat depots, on a HFD and a chow diet. This was to assess the effectiveness of exercise to prevent the onset of obesity-induced changes. Mice fed with chow or HFD (45% kcal fat) were trained and performed either END or HIIT for 10 weeks (3 x 40 min sessions/week). In HFD mice, both exercise programs significantly prevented the increase in body weight (END: 17%, HIIT: 20%), total body fat mass (END: 46%, HIIT: 50%), increased lean mass as a proportion of body weight (Lean mass/BW) by 14%, and improved insulin sensitivity by 22%. Further evidence of the preventative effect of exercise was seen significantly decreased markers for adipogenesis, inflammation, and extracellular matrix accumulation in both subcutaneous adipose tissue (SAT) and epididymal adipose tissue (EPI). In chow, no such marked effects were seen with both the exercise programs on all the three fat depots. This study establishes the beneficial effect of both HIIT and END exercise in preventing metabolic deterioration, collagen deposition, and inflammatory responses in fat depots, resulting in an improved whole body insulin resistance in HFD mice.

Insulin treatment improves liver histopathology and decreases expression of inflammatory and fibrogenic genes in a hyperglycemic, dyslipidemic hamster model of NAFLD

Background

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are highly prevalent comorbidities in patients with Type 2 diabetes. While many of these patients eventually will need treatment with insulin, little is known about the effects of insulin treatment on histopathological parameters and hepatic gene expression in diabetic patients with co-existing NAFLD and NASH. To investigate this further, we evaluated the effects of insulin treatment in NASH diet-fed hamsters with streptozotocin (STZ) -induced hyperglycemia.

Methods

Forty male Syrian hamsters were randomized into four groups (n = 10/group) receiving either a NASH-inducing (high fat, fructose and cholesterol) or control diet (CTRL) for four weeks, after which they were treated with STZ or sham-injected and from week five treated with either vehicle (CTRL, NASH, NASH-STZ) or human insulin (NASH-STZ-HI) for four weeks by continuous s.c. infusion via osmotic minipumps.

Results

NASH-STZ hamsters displayed pronounced hyperglycemia, dyslipidemia and more severe liver pathology compared to both CTRL and NASH groups. Insulin treatment attenuated dyslipidemia in NASH-STZ-HI hamsters and liver pathology was considerably improved compared to the NASH-STZ group, with prevention/reversal of hepatic steatosis, hepatic inflammation and stellate cell activation. In addition, expression of inflammatory and fibrotic genes was decreased compared to the NASH-STZ group.

Conclusions

These results suggest that hyperglycemia is important for development of inflammation and profibrotic processes in the liver, and that insulin administration has beneficial effects on liver pathology and expression of genes related to inflammation and fibrosis in a hyperglycemic, dyslipidemic hamster model of NAFLD.

Gallic Acid Ameliorated Impaired Lipid Homeostasis in a Mouse Model of High-Fat Diet-and Streptozotocin-Induced NAFLD and Diabetes through Improvement of β-oxidation and Ketogenesis

Gallic acid (GA) is a simple polyphenol found in food and traditional Chinese medicine. Here, we determined the effects of GA administration in a combined mouse model of high-fat diet (HFD)-induced obesity and low-dose streptozotocin (STZ)-induced hyperglycemia, which mimics the concurrent non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes pathological condition. By combining the results of physiological assessments, pathological examinations, metabolomic studies of blood, urine, liver, and muscle, and measurements of gene expression, we attempted to elucidate the efficacy of GA and the underlying mechanism of action of GA in hyperglycemic and dyslipidemic mice. HFD and STZ induced severe diabetes, NAFLD, and other metabolic disorders in mice. However, the results of liver histopathology and serum biochemical examinations indicated that daily GA treatment alleviated the high blood glucose levels in the mice and decelerated the progression of NAFLD. In addition, our results show that the hepatoprotective effect of GA in diabetic mice occurs in part through a partially preventing disordered metabolic pathway related to glucose, lipids, amino acids, purines, and pyrimidines. Specifically, the mechanism responsible for alleviation of lipid accumulation is related to the upregulation of β-oxidation and ketogenesis. These findings indicate that GA alleviates metabolic diseases through novel mechanisms.

MUTYH is associated with hepatocarcinogenesis in a non-alcoholic steatohepatitis mouse model

Non-alcoholic steatohepatitis (NASH)-related HCC is associated with oxidative stress. However, the mechanisms underlying the development of NASH-related HCC is unclear. MUTYH is one of the enzymes that is involved in repair of oxidative DNA damage. The aim of this study was to investigate the association between MUTYH and NASH-related hepatocarcinogenesis. MUTYH wild-type (Mutyh^+/+), heterozygous (Mutyh^+/-), and MUTYH-null (Mutyh^-/-) mice were fed a high-fat high-cholesterol (HFHC) diet or HFHC + high iron diet (20 mice per group) for 9 months. Five of 20 Mutyh^-/- mice fed an HFHC + high iron diet developed liver tumors, and they developed more liver tumors than other groups (especially vs. Mutyh^+/+ fed an HFHC diet, P = 0.0168). Immunohistochemical analysis revealed significantly higher accumulation of oxidative stress markers in mice fed an HFHC + high iron diet. The gene expression profiles in the non-tumorous hepatic tissues were compared between wild-type mice that developed no liver tumors and MUTYH-null mice that developed liver tumors. Gene Set Enrichment Analysis identified the involvement of the Wnt/β-catenin signaling pathway and increased expression of c-Myc in MUTYH-null liver. These findings suggest that MUTYH deficiency is associated with hepatocarcinogenesis in patients with NASH with hepatic iron accumulation.

Second hits exacerbate alcohol-related organ damage: an update

Chronic and excessive alcohol abuse cause direct and indirect detrimental effects on a wide range of body organs and systems and accounts for ~4% of deaths worldwide. Many factors influence the harmful effects of alcohol. This concise review presents newer insights into the role of select second hits in influencing the progression of alcohol-induced organ damage by synergistically acting to generate a more dramatic downstream biological defect. This review specifically addresses on how a lifestyle factor of high fat intake exacerbates alcoholic liver injury and its progression. This review also provides the mechanistic insights into how increasing matrix stiffness during liver injury promotes alcohol-induced fibrogenesis. It also discusses how hepatotropic viral (HCV, HBV) infections as well as HIV (which is traditionally not known to be hepatotropic), are potentiated by alcohol exposure to promote hepatotoxicity and fibrosis progression. Finally, this review highlights the impact of reactive aldehydes generated during alcohol and cigarette smoke coexposure impair innate antimicrobial defense and increased susceptibility to infections. This review was inspired by the symposium held at the 17th Congress of the European Society for Biomedical research on Alcoholism in Lille, France entitled 'Second hits in alcohol-related organ damage'.

Pathophysiology of NAFLD and NASH in Experimental Models: The Role of Food Intake Regulating Peptides

Obesity, diabetes, insulin resistance, sedentary lifestyle, and Western diet are the key factors underlying non-alcoholic fatty liver disease (NAFLD), one of the most common liver diseases in developed countries. In many cases, NAFLD further progresses to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and to hepatocellular carcinoma. The hepatic lipotoxicity and non-liver factors, such as adipose tissue inflammation and gastrointestinal imbalances were linked to evolution of NAFLD. Nowadays, the degree of adipose tissue inflammation was shown to directly correlate with the severity of NAFLD. Consumption of higher caloric intake is increasingly emerging as a fuel of metabolic inflammation not only in obesity-related disorders but also NAFLD. However, multiple causes of NAFLD are the reason why the mechanisms of NAFLD progression to NASH are still not well understood. In this review, we explore the role of food intake regulating peptides in NAFLD and NASH mouse models. Leptin, an anorexigenic peptide, is involved in hepatic metabolism, and has an effect on NAFLD experimental models. Glucagon-like peptide-1 (GLP-1), another anorexigenic peptide, and GLP-1 receptor agonists (GLP-1R), represent potential therapeutic agents to prevent NAFLD progression to NASH. On the other hand, the deletion of ghrelin, an orexigenic peptide, prevents age-associated hepatic steatosis in mice. Because of the increasing incidence of NAFLD and NASH worldwide, the selection of appropriate animal models is important to clarify aspects of pathogenesis and progression in this field.

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.

The American lifestyle-induced obesity syndrome diet in male and female rodents recapitulates the clinical and transcriptomic features of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

The pathogenesis of nonalcoholic fatty liver disease (NAFLD) and the progression to nonalcoholic steatohepatitis (NASH) and increased risk of hepatocellular carcinoma remain poorly understood. Additionally, there is increasing recognition of the extrahepatic manifestations associated with NAFLD and NASH. We demonstrate that intervention with the American lifestyle-induced obesity syndrome (ALIOS) diet in male and female mice recapitulates many of the clinical and transcriptomic features of human NAFLD and NASH. Male and female C57BL/6N mice were fed either normal chow (NC) or ALIOS from 11 to 52 wk and underwent comprehensive metabolic analysis throughout the duration of the study. From 26 wk, ALIOS-fed mice developed features of hepatic steatosis, inflammation, and fibrosis. ALIOS-fed mice also had an increased incidence of hepatic tumors at 52 wk compared with those fed NC. Hepatic transcriptomic analysis revealed alterations in multiple genes associated with inflammation and tissue repair in ALIOS-fed mice. Ingenuity Pathway Analysis confirmed dysregulation of metabolic pathways as well as those associated with liver disease and cancer. In parallel the development of a robust hepatic phenotype, ALIOS-fed mice displayed many of the extrahepatic manifestations of NAFLD, including hyperlipidemia, increased fat mass, sarcopenia, and insulin resistance. The ALIOS diet in mice recapitulates many of the clinical features of NAFLD and, therefore, represents a robust and reproducible model for investigating the pathogenesis of NAFLD and its progression.NEW & NOTEWORTHY Nonalcoholic fatty liver disease (NAFLD) affects 30% of the general population and can progress to nonalcoholic steatohepatitis (NASH) and potentially hepatocellular carcinoma. Preclinical models rely on mouse models that often display hepatic characteristics of NAFLD but rarely progress to NASH and seldom depict the multisystem effects of the disease. We have conducted comprehensive metabolic analysis of both male and female mice consuming a Western diet of trans fats and sugar, focusing on both their hepatic phenotype and extrahepatic manifestations.

Fatty acid transport protein-2 regulates glycemic control and diabetic kidney disease progression

Kidney disease is one of the most devastating complications of diabetes, and tubular atrophy predicts diabetic kidney disease (DKD) progression to end-stage renal disease. We have proposed that fatty acids bound to albumin contribute to tubular atrophy by inducing lipotoxicity, after filtration across damaged glomeruli, and subsequent proximal tubule reabsorption by a fatty acid transport protein-2-dependent (FATP2-dependent) mechanism. To address this possibility, genetic (Leprdb/db eNOS-/-) and induced (high-fat diet plus low-dose streptozotocin) mouse models of obesity and DKD were bred with global FATP2 gene-deleted mice (Slc27a2) and then phenotyped. DKD-prone mice with the Slc27a2-/- genotype demonstrated normalization of glomerular filtration rate, reduced albuminuria, improved kidney histopathology, and longer life span compared with diabetic Slc27a2+/+ mice. Genetic and induced DKD-prone Slc27a2-/- mice also exhibited markedly reduced fasting plasma glucose, with mean values approaching euglycemia, despite increased obesity and decreased physical activity. Glucose lowering in DKD-prone Slc27a2-/- mice was accompanied by β cell hyperplasia and sustained insulin secretion. Together, our data indicate that FATP2 regulates DKD pathogenesis by a combined lipotoxicity and glucotoxicity (glucolipotoxicity) mechanism.

Animal Models of Fibrosis in Nonalcoholic Steatohepatitis: Do They Reflect Human Disease?

Nonalcoholic steatohepatitis (NASH) is one of the most common chronic liver diseases in the world, yet no pharmacotherapies are available. The lack of translational animal models is a major barrier impeding elucidation of disease mechanisms and drug development. Multiple preclinical models of NASH have been proposed and can broadly be characterized as diet-induced, deficiency-induced, toxin-induced, genetically induced, or a combination of these. However, very few models develop advanced fibrosis while still reflecting human disease etiology or pathology, which is problematic since fibrosis stage is considered the best prognostic marker in patients and an important endpoint in clinical trials of NASH. While mice and rats predominate the NASH research, several other species have emerged as promising models. This review critically evaluates animal models of NASH, focusing on their ability to develop advanced fibrosis while maintaining their relevance to the human condition.

Hepatocellular carcinoma in the context of non-alcoholic steatohepatitis (NASH): recent advances in the pathogenic mechanisms

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. HCC is particularly aggressive and is one of the leading causes of cancer mortality. In recent decades, the epidemiological landscape of HCC has undergone significant changes. While chronic viral hepatitis and excessive alcohol consumption have long been identified as the main risk factors for HCC, non-alcoholic steatohepatitis (NASH), paralleling the worldwide epidemic of obesity and type 2 diabetes, has become a growing cause of HCC in the US and Europe. Here, we review the recent advances in epidemiological, genetic, epigenetic and pathogenic mechanisms as well as experimental mouse models that have improved the understanding of NASH progression toward HCC. We also discuss the clinical management of patients with NASH-related HCC and possible therapeutic approaches.

Apolipoprotein-AI mimetic peptides D-4F and L-5F decrease hepatic inflammation and increase insulin sensitivity in C57BL/6 mice

BACKGROUND

Apolipoprotein-AI (apo-AI) is the major apolipoprotein found in high density lipoprotein particles (HDLs). We previously demonstrated that apo-AI injected directly into high-fat diet fed mice improved insulin sensitivity associated with decreased hepatic inflammation. While our data provides compelling proof of concept, apoA-I mimetic peptides are more clinically feasible. The aim of this study was to test whether apo-AI mimetic peptide (D-4F and L-5F) treatment will emulate the effects of full-length apo-AI to improve insulin sensitivity.

METHODS

Male C57BL/6 mice were fed a high-fat diet for 16 weeks before receiving D4F mimetic peptide administered via drinking water or L5F mimetic peptide administered by intraperitoneal injection bi-weekly for a total of five weeks. Glucose tolerance and insulin tolerance tests were conducted to assess the effects of the peptides on insulin resistance. Effects of the peptides on inflammation, gluconeogenic enzymes and lipid synthesis were assessed by real-time PCR of key markers involved in the respective pathways.

RESULTS

Treatment with apo-AI mimetic peptides D-4F and L-5F showed: (i) improved blood glucose clearance (D-4F 1.40-fold AUC decrease compared to HFD, P<0.05; L-4F 1.17-fold AUC decrease compared to HFD, ns) in the glucose tolerance test; (ii) improved insulin tolerance (D-4F 1.63-fold AUC decrease compared to HFD, P<0.05; L-5F 1.39-fold AUC compared to HFD, P<0.05) in the insulin tolerance test. The metabolic test results were associated with (i) decreased hepatic inflammation of SAA1, IL-1β IFN-γ and TNFα (2.61-5.97-fold decrease compared to HFD, P<0.05) for both mimetics; (ii) suppression of hepatic mRNA expression of gluconeogenesis-associated genes (PEPCK and G6Pase; 1.66-3.01-fold decrease compared to HFD, P<0.001) for both mimetics; (iii) lipogenic-associated genes, (SREBP1c and ChREBP; 2.15-3.31-fold decrease compared to HFD, P<0.001) for both mimetics and; (iv) reduced hepatic macrophage infiltration (F4/80 and CD68; 1.77-2.15-fold compared to HFD, P<0.001) for both mimetics.

CONCLUSION

Apo-AI mimetic peptides treatment led to improved glucose homeostasis. This effect is associated with reduced expression of inflammatory markers in the liver and reduced infiltration of macrophages, suggesting an overall suppression of hepatic inflammation. We also showed altered expression of genes associated with gluconeogenesis and lipid synthesis, suggesting that glucose and lipid synthesis is suppressed. These findings suggest that apoA-I mimetic peptides could be a new therapeutic option to reduce hepatic inflammation that contributes to the development of overnutrition-induced insulin resistance.

Thrombospondin-1: A Key Protein That Induces Fibrosis in Diabetic Complications

Fibrosis accompanies most common pathophysiological features of diabetes complications in different organs. It is characterized by an excessive accumulation of extracellular matrix (ECM) components, the response to which contributes to inevitable organ injury. The extracellular protein thrombospondin-1 (TSP-1), a kind of extracellular glycoprotein, is upregulated by the increased activity of some transcription factors and results in fibrosis by activating multiple pathways in diabetes. The results of studies from our team and other colleagues indicate that TSP-1 is associated with the pathological process leading to diabetic complications and is considered to be the most important factor in fibrosis. This review summarizes the molecular mechanism of increased TSP-1 induced by hyperglycemia and the role of TSP-1 in fibrosis during the development of diabetes complications.

New drugs for NAFLD: lessons from basic models to the clinic

The term nonalcoholic fatty liver disease (NAFLD) comprises a spectrum of increasingly harmful conditions ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) to liver fibrosis and end-stage cirrhosis. NAFLD is the currently most common form of chronic liver disease in both adults and children worldwide. As NAFLD evolves as a global pandemic alongside the still growing prevalence of metabolic syndrome, obesity, and diabetes, it is inevitable to develop effective counterstrategies. Over the last decades, great effort has been dedicated to the understanding of the pathogenesis of NAFLD. This includes the development of an array of models for NAFLD, ranging from advanced in vitro (primary cells, 3D cultures, biochip, spheroids, organoids) to in vivo rodent models (particularly in mice). Based on these approaches novel therapies have been proposed and subsequently evaluated for patients with advanced forms of NAFLD, in particular those with NASH and liver fibrosis or cirrhosis. In this review, we delineate the current understanding of disease pathophysiology and depict how novel therapeutic strategies aim to exploit these different mechanisms to ameliorate, treat, or stop progression of NASH. We also discuss obstacles and chances along the way from basic models to promising clinical treatment options.

Effects of (-)-epicatechin on the time course of the expression of perilipins in a diet-induced model of nonalcoholic steatohepatitis

The existing treatments for nonalcoholic steatohepatitis (NASH) are not completely effective. The need for new alternatives without adverse effects and low cost, such as the flavonoid (-)-epicatechin (EC), which has beneficial effects on lipid metabolism and cardiovascular diseases, arises. The objective of this work was to analyze EC effects in the NASH induced by a Paigen-type diet (PD). Mice were administered with (1) normal chow and water, (2) PD + fructose 30% and (3) PD + fructose 30% + EC (1 mg/kg) per gavage during 9 weeks. At the end of each treatment, serum was collected for analysis of the biochemical profile and liver enzymes. The liver was collected for microscopic analysis and for the evaluation of the relative expression of Plin2, Plin3, CD36, adiponectin and UCP2. Results showed that EC reduced weight gain and decreased triglyceride (TG), low-density lipoprotein cholesterol, TG/high-density lipoprotein and the activity of liver enzymes (alanine aminotransferase and alkaline phosphatase), suggesting lower liver damage. The microscopic analysis showed less "balloonization" of the hepatocyte, small drops of lipids, less accumulation of collagen and infiltration of inflammatory cells as compared to nontreated group. Finally, a decrease in the expression of Plin 2 was observed. While CD36 decreased, adiponectin and UCP2 increased. In conclusion, EC improves the biochemical profile, the microscopic characteristics and protein expression. Therefore, it may be a possible therapeutic approach for NASH since it prevents the progression of the hepatic and metabolic damage induced by high-fat diets.

Germacrone cooperates with dexmedetomidine to alleviate high-fat diet-induced type 2 diabetes mellitus via upregulating AMPKα1 expression

The aim of the present study was to investigate the effects of germacrone (GM) and dexmedetomidine (DEX) in treating type 2 diabetes mellitus (T2DM). A high-fat diet (HFD)-induced T2DM rat model was established. The experimental rats were divided into the control group, HFD group, GM treatment group, DEX treatment group and GM + DEX treatment group. In addition, adenosine monophosphate-activated protein kinase (AMPK) inhibitor compound C (CC) was used to inhibit AMPKα1 expression. All rats received their respective treatment daily for 21 days. Blood glucose and lipid levels, apoptosis of hepatic cells, and levels of inflammatory factors and oxidative stress indicators in serum samples were evaluated. Protein expression of AMPKα1 and its downstream targets were also investigated. Results demonstrated that blood glucose concentration, blood lipid indicators (endothelin, total cholesterol, triglyceride and low density lipoprotein cholesterol), cell apoptosis in liver tissues, total oxidant status, malondialdehyde, interleukin (IL)-6, tumor necrosis factor-α (TNF-α) and IL-1β levels in serum were increased in the high-fat group compared to the control but decreased following GM and/or DEX treatment. By contrast, high-density lipoprotein cholesterol and antioxidative stress indicator superoxide dismutase (SOD) were decreased in the high-fat group but increased following GM and/or DEX treatment. Protein expression of AMPKα1 and the catabolic genes carnitine palmitoyltransferase-1, peroxisome proliferator-activated receptor-α and acyl coenzyme A were decreased whilst anabolic genes, including sterol regulatory element binding protein-1c, fatty acid synthase and diacylglycerol acyltransferase-2, were increased in the HFD group. These effects were attenuated by GM and/or DEX treatment. AMPKα1 inhibition resulted in decreased SOD and increased cell apoptosis in liver tissues as well as increased IL-6, TNF-α and IL-1β levels compared with the HFD group. However, these effects were abolished following treatment with CC, GM and DEX together. Taken together these results indicated that GM worked synergistically with DEX to attenuate symptoms of high-fat-induced T2DM, with the effect potentially involving an increase in AMPKα1 expression.

Effects of probiotics on nonalcoholic fatty liver disease: a systematic review and meta-analysis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become prevalent in recent decades, especially in developed countries, and approaches for the prevention and treatment of NAFLD are not clear. The aim of this research was to analyze and summarize randomized controlled trials that investigated the effects of probiotics on NAFLD.

METHODS

Seven databases (PubMed, Embase, the Web of Science, the Cochrane Library, China National Knowledge Infrastructure, Wan Fang Data, and VIP Database) were searched. Then, eligible studies were identified. Finally, proper data extraction, synthesis and analysis were performed by trained researchers.

RESULTS

Anthropometric parameters: with use of probiotics weight was reduced by 2.31 kg, and body mass index (BMI) was reduced by 1.08 kg/m². Liver function: probiotic treatment reduced the alanine aminotransferase level by 7.22 U/l, the aspartate aminotransferase level by 7.22 U/l, the alkaline phosphatase level by 25.87 U/l, and the glutamyl transpeptidase level by -5.76 U/l. Lipid profiles: total cholesterol, low-density lipoprotein cholesterol, and triglycerides were significantly decreased after probiotic treatment. Their overall effects (shown as standard mean difference) were -0.73, -0.54, and -0.36, respectively. Plasma glucose: probiotics reduced the plasma glucose level by 4.45 mg/dl and the insulin level by 0.63. Cytokines: probiotic treatment decreased tumor necrosis factor alpha by 0.62 and leptin by 1.14. Degree of liver fat infiltration (DFI): the related risk of probiotics for restoring DFI was 2.47 (95% confidence interval, 1.61-3.81, p < 0.001).

CONCLUSION

Probiotic treatment or supplementation is a promising therapeutic method for NAFLD.

The Effects of Diabetes and High-Fat Diet on Polymodal Nociceptor and Cold Thermoreceptor Nerve Terminal Endings in the Corneal Epithelium

Purpose

There is a substantial body of evidence indicating that corneal sensory innervation is affected by pathology in a range of diseases. However, there are no published studies that have directly assessed whether the nerve fiber density of the different subpopulations of corneal sensory neurons are differentially affected. The present study explored the possibility that the intraepithelial nerve fiber density of corneal polymodal nociceptors and cold thermoreceptors are differentially affected in mice fed with a high-fat high cholesterol (HFHC; 21% fat, 2% cholesterol) diet and in those that also have diabetes.

Methods

The mice were fed the HFHC diet for the duration of the experiment (up to 40 weeks). Mice in the diabetes group had hyperglycaemia induced with streptozotocin after 15 weeks on the HFHC diet. Age-matched control animals were fed a standard diet. All corneal nerve fibers were labeled with a pan neuronal antibody (antiprotein gene product 9.5), and polymodal nociceptors and cold thermoreceptors were labeled with antibodies directed against transient receptor potential cation channel, subfamily V, member 1 and transient receptor potential cation channel subfamily M member 8, respectively.

Results

The mice fed a HFHC diet and those that in addition have hyperglycemia have similar reductions in corneal nerve fiber density consistent with small fiber neuropathy. Importantly, both treatments more markedly affected the intraepithelial axons of cold thermoreceptors than those of polymodal nociceptors.

Conclusions

The results provide evidence that distinct subpopulations of corneal sensory neurons can be differentially affected by pathology.

Constant-Moderate and High-Intensity Interval Training Have Differential Benefits on Insulin Sensitive Tissues in High-Fat Fed Mice

In a mouse model of diet-induced obesity, this study determined if two exercise prescriptions with equivalent time and distance covered, [constant-moderate endurance (END) and high intensity interval training (HIIT)], exert differential metabolic benefits on insulin sensitive tissues. Male 10 week old C57BL/6 mice were fed a high fat diet (HFD; 45% kcal fat) ad libitum for 10 weeks and for a further 10 weeks they underwent END or HIIT training (3 × 40 min sessions/wk). Untrained HFD and chow-fed mice acted as controls. At 30 weeks of age, mice were sacrificed and quadriceps muscle, subcutaneous adipose tissue (SAT) and liver were excised. Neither END nor HIIT altered body weight or composition in HFD mice. In quadriceps, HFD decreased high-molecular weight adiponectin protein, which was normalized by END and HIIT. In contrast, HIIT but not END reversed the HFD-driven decrease in the adiponectin receptor 1 (AdipoR1). In SAT, both programs tended to decrease collagen VI protein (p = 0.07–0.08) in HFD, whereas only HIIT induced an increase in the mRNA (3-fold vs. HFD untrained) and protein (2-fold vs. HFD untrained) of UCP1. In liver, only END reversed collagen I accumulation seen in HFD untrained mice. Our results suggest that HIIT may promote better systemic metabolic changes, compared to END, which may be the result of the normalization of muscle AdipoR1 and increased UCP1 seen in SAT. However, END was more effective in normalizing liver changes, suggesting differential metabolic effects of END and HIIT in different tissues during obesity.

Skeletal muscle adiponectin induction depends on diet, muscle type/activity, and exercise modality in C57BL/6 mice

Changes in skeletal muscle adiponectin induction have been described in obesity and exercise. However, whether changes are consistent across muscle types and with different exercise modalities, remain unclear. This study compared the effects of diet and two isocaloric training programs on adiponectin induction and its regulators in three muscles: quadriceps (exercising/glycolytic-oxidative), gastrocnemius (exercising/glycolytic), and masseter (nonexercising/glycolytic). Ten-week-old male C57BL/6 mice were fed a high-fat diet (HFD) (45% fat) or standard CHOW diet (12% fat) ad libitum and underwent one of two training regimes: (1) constant-moderate training (END), or (2) high intensity interval training (HIIT) for 10 weeks (3 × 40 min sessions/week). Chow and HFD-fed untrained mice were used as control. Compared with Chow, HFD induced an increase in protein levels of low-molecular weight (LMW) adiponectin in gastrocnemius and masseter (~2-fold; P < 0.05), and a decrease of high-molecular weight adiponectin (HMW-most bioactive form) in quadriceps (~0.5-fold; P < 0.05). Only END prevented these changes (P < 0.05). HFD induced a decrease of adiponectin receptor 1 (AdipoR1) protein in exercising muscles of untrained mice (~0.5-0.8-fold; P < 0.05); notably, END also decreased AdipoR1 protein levels in lean and HFD mice. This type of training also normalized HFD-driven mRNA changes found in some adiponectin downstream factors (sirtuin 1, Pgc-1a, and Ucp2) in the three muscles tested. Our results indicate that diet, muscle type/activity, and exercise modality influences muscle adiponectin profile, and some of its mediators. These parameters should be taken into consideration when investigating this endocrine response of the skeletal muscle, particularly in the context of obesity and metabolic disorders.

Inhibition of Plasminogen Activator Inhibitor 1 Attenuates Hepatic Steatosis but Does Not Prevent Progressive Nonalcoholic Steatohepatitis in Mice

Plasminogen activator inhibitor 1 (PAI‐1), an essential regulator of fibrinolysis, is increasingly implicated in the pathogenesis of metabolic disorders, such as obesity and nonalcoholic fatty liver disease (NAFLD). Pharmacologic inhibition of PAI‐1 is emerging as a highly promising therapeutic strategy for obesity and its sequelae. Given the well‐established profibrotic function of PAI‐1, we considered whether PAI‐1 may serve as a target for antifibrotic therapy in nonalcoholic steatohepatitis (NASH). We therefore determined the effect of genetic Pai‐1 deletion and pharmacologic PAI‐1 inhibition on the development of NASH‐related fibrosis in mice. Pai‐1 knockout (Pai‐1^–/–) and wild‐type control (Pai‐1^+/+) mice were fed a high‐fat/high‐cholesterol high‐sugar (HFHS) diet or a methionine‐ and choline‐deficient (MCD) diet to induce steatohepatitis with fibrosis. PAI‐1 was pharmacologically inhibited using the small molecule inhibitor TM5441 in wild‐type C57BL/6 mice fed an HFHS or MCD diet. Either genetic deletion of Pai‐1 or pharmacologic inhibition of PAI‐1 attenuated MCD diet‐induced hepatic steatosis but did not prevent hepatic inflammation or fibrosis. Targeted inhibition of PAI‐1 conferred transient protection from HFHS diet‐induced obesity and hepatic steatosis, an effect that was lost with prolonged exposure to the obesigenic diet. Neither genetic deletion of Pai‐1 nor pharmacologic inhibition of PAI‐1 prevented HFHS diet‐induced hepatic inflammation or fibrosis. Conclusion:Pai‐1 regulates hepatic lipid accumulation but does not promote NASH progression. The PAI‐1 inhibitor TM5441 effectively attenuates diet‐induced obesity and hepatic steatosis but does not prevent NASH‐related fibrosis in mice.

Multiple liver insults synergize to accelerate experimental hepatocellular carcinoma

The urgent unmet need for hepatocellular carcinoma (HCC) therapies is addressed here by characterising a novel mouse model of HCC in the context of ongoing liver damage and overnutrition. Male C57Bl/6J mice were treated with diethylnitrosamine (DEN) and thioacetamide (TAA), and some were provided with an atherogenic high fat diet (HFD). Inflammation, steatosis, fibrosis, 87 genes, liver lesions and intratumoural leukocyte subsets were quantified up to 24 weeks of age. Adding HFD to DEN/TAA increased fibrosis, steatosis and inflammation, and the incidence of both HCC and non-HCC dysplastic lesions. All lesions contained α-SMA positive fibroblasts. Macrophage marker F4/80 was not significantly different between treatment groups, but the macrophage-associated genes Arg-1 and Cd47 were differentially expressed. Fibrosis, cancer and cell death associated genes were upregulated in DEN/TAA/HFD livers. Fewer Kupffer cells and plasmacytoid dendritic cells were in tumours compared to control liver. In conclusion, combining a hepatotoxin with an atherogenic diet produced more intrahepatic tumours, dysplastic lesions and fibrosis compared to hepatotoxin alone. This new HCC model provides a relatively rapid means of examining primary HCC and potential therapies in the context of multiple hepatotoxins including those derived from overnutrition.

Regulation and bioactivity of the CCN family of genes and proteins in obesity and diabetes

Across the years the CCNs have been increasingly implicated in the development of obesity, diabetes and its complications. Evidence for this is currently derived from their dysregulation in key metabolic pathological states in humans, animal and in vitro models, and also pre-clinical effects of their bioactivities. CCN2 is the best studied in this disease process and the other CCNs are yet to be better defined. Key steps where CCNs may play a pathogenic metabolic role include: (i) obesity and insulin resistance, where CCN2 inhibits fat cell differentiation in vitro and CCN3 may induce obesity and insulin resistance; (ii) elevated blood glucose levels to diabetes mellitus onset, where CCN2 may contribute to pancreatic beta cell and islet function; and (iii) in diabetes complications, such as nephropathy, retinopathy, liver disease (NAFLD/NASH), CVD and diabetes with heart failure. In contrast, CCN1, CCN2 and possibly CCN3, may have a reparative role in wound healing in diabetes, and CCN2 in islet cell development. In terms of CCN2 regulation by a diabetes metabolic environment and related mechanisms, the author's laboratory and others have progressively shown that advanced glycation-end products, protein kinase C isoforms, saturated fatty acids, reactive oxygen species and haemodynamic factors upregulate CCN2 in relevant cell and animal systems. Recent data has suggested that CCN2, CCN3 and CCN6 may affect energy homeostasis including in regulating glycolysis and mitochondrial function. This paper will address the current data implicating CCNs in diabetes and its complications, focusing on recent aspects with translational clinical relevance and future directions.

Differential metabolic effects of constant moderate versus high intensity interval training in high-fat fed mice: possible role of muscle adiponectin

Exercise regimens may have differing effects in the presence of obesity. In addition to being fat derived, adiponectin has recently been described as a myokine that regulates insulin sensitivity, which may link to exercise-related metabolic benefits in obesity. Whether skeletal muscle adiponectin varies in different exercise modalities is unclear. This study investigated the comparative effects of 10 weeks of endurance constant-moderate intensity exercise (END) with high intensity interval training (HIIT), on metabolic outcomes, including muscle adiponectin in a mouse model of diet-induced obesity. Ten-week-old male C57BL/6 mice were fed a high-fat diet (HFD) (45% FAT) or standard CHOW diet ab libitum and underwent one of three training regimes: (1) no exercise, (2) END, or (3) HIIT (8 bouts of 2.5 min with eight periods of rest of 2.5 min) for 10 weeks (3 × 40 min sessions/week). Chow-fed mice acted as controls. Compared with HFD alone, both training programs similarly protected against body weight gain (HFD = 45 ± 2; END = 37 ± 2; HIIT = 36 ± 2 g), preserved lean/fat tissue mass ratio (HFD = 0.64 ± 0.09; END = 0.34 ± 0.13; HIIT = 0.33 ± 0.13), and improved blood glucose excursion during an insulin tolerance test (HFD = 411 ± 54; END = 350 ± 57; HIIT = 320 ± 66 arbitrary units [AU]). Alterations in fasting glycemia, insulinemia, and AST/ALT ratios were prevented only by END. END, but not HIIT increased skeletal muscle adiponectin mRNA (14-fold; P < 0.05) and increased protein content of high molecular weight (HMW) adiponectin (3.3-fold), whereas HIIT induced a milder increase (2.4-fold). Compared with HFD, neither END nor HIIT altered circulating low (LMW) or high (HMW) molecular weight adiponectin forms. Furthermore, only END prevented the HFD downregulation of PGC1α (P < 0.05) mRNA levels downstream of muscle adiponectin. These data show that different training programs affect muscle adiponectin to differing degrees. Together these results suggest that END is a more effective regimen to prevent HFD-induced metabolic disturbances in mice.

Increasing Dietary Medium-Chain Fatty Acid Ratio Mitigates High-fat Diet-Induced Non-Alcoholic Steatohepatitis by Regulating Autophagy

Previous studies have demonstrated that saturated fatty acids (SFAs) are more lipotoxic than unsaturated fatty acids (UFAs) in inhibiting hepatic autophagy and promoting non-alcoholic steatohepatitis (NASH). However, there have been few studies have investigated the effects of carbon chain length on SFA-induced autophagy impairment and lipotoxicity. To investigate whether SFAs with shorter carbon chain lengths have differential effects on hepatic autophagy and NASH development, we partially replaced lard with coconut oil to elevate the ratio of medium-chain fatty acids (MCFAs) to long-chain fatty acids (LCFAs) in a mouse high-fat diet (HFD) and fed mice for 16 weeks. In addition, we treated HepG2 cells with different combinations of fatty acids to study the mechanisms of MCFAs-mediated hepatic protections. Our results showed that increasing dietary MCFA/LCFA ratio mitigated HFD-induced Type 2 diabetes and NASH in mice. Importantly, we demonstrated that increased MCFA ratio exerted its protective effects by restoring Rubicon-suppressed autophagy. Our study suggests that the relative amount of LCFAs and MCFAs in the diet, in addition to the amount of SFAs, can significantly contribute to autophagy impairment and hepatic lipotoxicity. Collectively, we propose that increasing dietary MCFAs could be an alternative therapeutic and prevention strategy for Type 2 diabetes and NASH.

Animal Models of Nonalcoholic Fatty Liver Disease-A Starter's Guide

Nonalcoholic fatty liver disease (NAFLD) constitutes a major health concern with the increasing incidence of obesity and diabetes in many Western countries, reaching a prevalence of up to 30% in the general population. Animal models have played a vital role in elucidating the pathophysiological mechanisms of NAFLD and continue to do so. A myriad of different models exists, each with its advantages and disadvantages. This review presents a brief overview of these models with a particular focus on the basic mechanisms and physical, biochemical and histological phenotype. Both nutritional and chemically induced, as well as genetic models are examined, including models combining different approaches.

Utility and reliability of non-invasive muscle function tests in high-fat-fed mice

NEW FINDINGS

What is the central question of this study? Non-invasive muscle function tests have not been validated for use in the study of muscle performance in high-fat-fed mice. What is the main finding and its importance? This study shows that grip strength, hang wire and four-limb hanging tests are able to discriminate the muscle performance between chow-fed and high-fat-fed mice at different time points, with grip strength being reliable after 5, 10 and 20 weeks of dietary intervention. Non-invasive tests are commonly used for assessing muscle function in animal models. The value of these tests in obesity, a condition where muscle strength is reduced, is unclear. We investigated the utility of three non-invasive muscle function tests, namely grip strength (GS), hang wire (HW) and four-limb hanging (FLH), in C57BL/6 mice fed chow (chow group, n = 48) or a high-fat diet (HFD group, n = 48) for 20 weeks. Muscle function tests were performed at 5, 10 and 20 weeks. After 10 and 20 weeks, HFD mice had significantly reduced GS (in newtons; mean ± SD: 10 weeks chow, 1.89 ± 0.1 and HFD, 1.79 ± 0.1; 20 weeks chow, 1.99 ± 0.1 and HFD, 1.75 ± 0.1), FLH [in seconds per gram body weight; median (interquartile range): 10 weeks chow, 2552 (1337-4964) and HFD, 1230 (749-1994); 20 weeks chow, 2048 (765-3864) and HFD, 1036 (717-1855)] and HW reaches [n; median (interquartile range): 10 weeks chow, 4 (2-5) and HFD, 2 (1-3); 20 weeks chow, 3 (1-5) and HFD, 1 (0-2)] and higher falls [n; median (interquartile range): 10 weeks chow, 0 (0-2) and HFD, 3 (1-7); 20 weeks chow, 1 (0-4) and HFD, 8 (5-10)]. Grip strength was reliable in both dietary groups [intraclass correlation coefficient (ICC) = 0.5-0.8; P < 0.05], whereas FLH showed good reliability in chow (ICC = 0.7; P < 0.05) but not in HFD mice after 10 weeks (ICC < 0.5). Our data demonstrate that non-invasive muscle function tests are valuable and reliable tools for assessment of muscle strength and function in high-fat-fed mice.

The pro-fibrotic role of dipeptidyl peptidase 4 in carbon tetrachloride-induced experimental liver injury

Liver fibrosis is a progressive pathological process involving inflammation and extracellular matrix deposition. Dipeptidyl peptidase 4 (DPP4), also known as CD26, is a cell surface glycoprotein and serine protease. DPP4 binds to fibronectin, can inactivate specific chemokines, incretin hormone and neuropeptides, and influences cell adhesion and migration. Such properties suggest a pro-fibrotic role for this peptidase but this hypothesis needs in vivo examination. Experimental liver injury was induced with carbon tetrachloride (CCl₄) in DPP4 gene knockout (gko) mice. DPP4 gko had less liver fibrosis and inflammation and fewer B cell clusters than wild type mice in the fibrosis model. DPP4 inhibitor-treated mice also developed less liver fibrosis. DNA microarray and PCR showed that many immunoglobulin (Ig) genes and some metabolism-associated transcripts were differentially expressed in the gko strain compared with wild type. CCl₄-treated DPP4 gko livers had more IgM⁺ and IgG⁺ intrahepatic lymphocytes, and fewer CD4⁺, IgD⁺ and CD21⁺ intrahepatic lymphocytes. These data suggest that DPP4 is pro-fibrotic in CCl₄-induced liver fibrosis and that the mechanisms of DPP4 pro-fibrotic action include energy metabolism, B cells, NK cells and CD4⁺ cells.