Inducible nitric oxide distribution in the fatty liver of a mouse with high fat diet-induced obesity

SERT-Deficient Mice Fed Western Diet Reveal Altered Metabolic and Pro-Inflammatory Responses of the Liver: A Link to Abnormal Behaviors

BACKGROUND

The inheritance of the short SLC6A4 allele, encoding the serotonin transporter (SERT) in humans, increases susceptibility to neuropsychiatric and metabolic disorders, with aging and female sex further exacerbating these conditions. Both central and peripheral mechanisms of the compromised serotonin (5-HT) system play crucial roles in this context. Previous studies on SERT-deficient (Sert-/-) mice, which model human SERT deficiency, have demonstrated emotional and metabolic disturbances, exacerbated by exposure to a high-fat Western diet (WD). Growing evidence suggests the significance of hepatic regulatory mechanisms in the neurobiology of central nervous system disorders, supporting the 'liver-brain' concept. However, the relationship between aberrant behavior and hepatic alterations under conditions of SERT deficiency remains poorly investigated.

METHODS

One-year-old female Sert-/- mice and their wild-type (WT) littermates were subjected to a control diet (CD) or the WD for a duration of three weeks. The WD had a higher caloric content and was characterized by an elevated saturated fat content (21%) compared to the CD (4.5%) and contained 0.2% cholesterol. Mice were evaluated for anxiety-like behavior, exploration and locomotor activity in the open field test, as well as glucose tolerance and histological indicators of hepatic steatosis. Hepatic pro-inflammatory and metabolism-related gene expression and markers of nitrosative stress, were analyzed utilizing real-time polymerase chain reaction (RT-PCR) and correlated with behavioral and histological outcomes.

RESULTS

In comparison to unchallenged mice, Sert-/-/WD mutants, but not the WT/WD group, had increased locomotion and anxiety-like behavior, increased hepatic steatosis, and elevated expression of insulin receptor B and pro-inflammatory cytokines interleukin-1β (Il-1β) and Tnf, as well as decreased expression of leptin receptor B. The two genotypes displayed distinct gene expression patterns of nitric oxide (NO)-related molecules inducible NO synthase (iNos) and arginase (Arg2), insulin receptor-related signaling factors: cluster of differentiation 36 (Cd36), ecto-nucleotide pyrophosphatase/phosphodiesterase (Enpp), protein tyrosine phosphatase N1 (Ptpn1), cytochrome P450 omega-hydroxylase 4A14 (Cyp4a14), acyl-CoA synthetase 1 (Acsl1) and phosphatase and tensin homolog (Pten). Furthermore, there were profound differences in correlations between molecular, histological, and behavioral measurements across the two genotypes.

CONCLUSIONS

Our findings suggest that the genetic deficiency of SERT results in abnormal hepatic pro-inflammatory and metabolic adaptations in response to WD. The significant correlations observed between behavioral measures and pro-inflammatory and metabolic alterations in WD-fed mice suggest the importance of liver-brain interactions and their role in the aberrant behaviors exhibited by Sert-/- mutants. This study presents the first evidence that altered liver functions are associated with pathological behaviors arising from genetic SERT deficiency.

The protective effects of Aster yomena (Kitam.) Honda on high-fat diet-induced obese C57BL/6J mice

BACKGROUND/OBJECTIVES

Aster yomena (Kitam.) Honda (AY) has remarkable bioactivities, such as antioxidant, anti-inflammation, and anti-cancer activities. On the other hand, the effects of AY against obesity-induced insulin resistance have not been reported. Therefore, this study examined the potential of AY against obesity-associated insulin resistance in high-fat diet (HFD)-fed mice.

MATERIALS/METHODS

An obesity model was established by feeding C57BL/6J mice a 60% HFD for 16 weeks. The C57BL6/When ethyl acetate fraction from AY (EFAY) at doses of 100 and 200 mg/kg/day was administered orally to mice fed a HFD for the last 4 weeks. Normal and control groups were administered water orally. The body weight and fasting blood glucose were measured every week. Dietary intake was measured every other day. After dissection, blood and tissues were collected from the mice.

RESULTS

The administration of EFAY reduced body and organ weights significantly compared to HFD-fed control mice. The EFAY-administered groups also improved the serum lipid profile by decreasing the triglyceride, total cholesterol, and low-density lipoprotein compared to the control group. In addition, EFAY ameliorated the insulin resistance-related metabolic dysfunctions, including the fasting blood glucose and serum insulin level, compared to the HFD-fed control mice. The EFAY inhibited lipid synthesis and insulin resistance by down-regulation of hepatic fatty acid synthase and up-regulation of the AMP-activated protein kinase pathway. EFAY also reduced lipid peroxidation in the liver, indicating that EFAY protected hepatic injury induced by obesity.

CONCLUSIONS

These results suggest that EFAY improved obesity-associated insulin resistance by regulating the lipid and glucose metabolism, suggesting that AY could be used as a functional food to prevent obesity and insulin resistance.

White Button Mushroom Extracts Modulate Hepatic Fibrosis Progression, Inflammation, and Oxidative Stress In Vitro and in LDLR-/- Mice

Liver fibrosis can be caused by non-alcoholic steatohepatitis (NASH), among other conditions. We performed a study to analyze the effects of a nontoxic, water-soluble extract of the edible mushroom Agaricus bisporus (AB) as a potential inhibitor of fibrosis progression in vitro using human hepatic stellate cell (LX2) cultures and in vivo in LDLR-/- mice. Treatment of LX2 cells with the AB extract reduced the levels of fibrotic and oxidative-related markers and increased the levels of GATA4 expression. In LDLR-/- mice with high-fat diet (HFD)-induced liver fibrosis and inflammation, the progression of fibrosis, oxidative stress, inflammation, and apoptosis were prevented by AB extract treatment. Moreover, in the mouse model, AB extract could exert an antiatherogenic effect. These data suggest that AB mushroom extract seems to exert protective effects by alleviating inflammation and oxidative stress during the progression of liver fibrosis, possibly due to a decrease in Toll-like receptor 4 (TLR4) expression and a reduction in Nod-like receptor protein 3 (NLRP3) inflammasome activation. In addition, we observed a potential atheroprotective effect in our mouse model.

The Effect of CB1 Antagonism on Hepatic Oxidative/Nitrosative Stress and Inflammation in Nonalcoholic Fatty Liver Disease

Dysfunction of the endocannabinoid system (ES) has been identified in nonalcoholic fatty liver disease (NAFLD) and associated metabolic disorders. Cannabinoid receptor type 1 (CB1) expression is largely dependent on nutritional status. Thus, individuals suffering from NAFLD and metabolic syndrome (MS) have a significant increase in ES activity. Furthermore, oxidative/ nitrosative stress and inflammatory process modulation in the liver are highly influenced by the ES. Numerous experimental studies indicate that oxidative and nitrosative stress in the liver is associated with steatosis and portal inflammation during NAFLD. On the other hand, inflammation itself may also contribute to reactive oxygen species (ROS) production due to Kupffer cell activation and increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. The pathways by which endocannabinoids and their lipid-related mediators modulate oxidative stress and lipid peroxidation represent a significant area of research that could yield novel pharmaceutical strategies for the treatment of NAFLD. Cumulative evidence suggested that the ES, particularly CB1 receptors, may also play a role in inflammation and disease progression toward steatohepatitis. Pharmacological inactivation of CB1 receptors in NAFLD exerts multiple beneficial effects, particularly due to the attenuation of hepatic oxidative/nitrosative stress parameters and significant reduction of proinflammatory cytokine production. However, further investigations regarding precise mechanisms by which CB1 blockade influences the reduction of hepatic oxidative/nitrosative stress and inflammation are required before moving toward the clinical phase of the investigation.

Effects of Cabbage-Apple Juice Fermented by Lactobacillus plantarum EM on Lipid Profile Improvement and Obesity Amelioration in Rats

This study aimed to investigate the potential of cabbage-apple juice, fermented by Lactobacillus plantarum EM isolated from kimchi, to protect against obesity and dyslipidemia that are induced by a high-fat diet in a rat model. Male rats were fed a modified AIN-93M high-fat diet (HFD), the same diet supplemented with non-fermented cabbage-apple juice, or the same diet supplemented with fermented cabbage-apple juice for eight weeks. In the HFD-fermented cabbage- apple juice administered groups the following parameters decreased: body weight, liver and white fat pad weights, serum triglyceride (TG), total cholesterol (TC), LDL-cholesterol, insulin, glucose and leptin levels, TG levels, while HDL-C and adiponectin levels in serum increased as compared with the HFD group. The HFD-fed rats that were supplemented with fermented cabbage-apple juice exhibited significantly lower fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and malic enzyme gene expression levels when compared to the exclusively HFD-fed rats. The anti-obesity and hypolipidemic effects were marginally greater in the fermented juice administered group than in the non-fermented juice administered group. These results suggest that cabbage-apple juice-especially fermented cabbage-apple juice-might have beneficial effects on lipid metabolism dysfunction and obesity-related abnormalities. However, further studies are necessary for analyzing the biochemical regulatory mechanisms of fermented juice for obesity amelioration and lipid metabolic homeostasis.

Hepatocellular iNOS protects liver from NASH through Nrf2-dependent activation of HO-1

Multiple molecular events are involved in non-alcoholic steatohepatitis (NASH). There is no consensus on the role of inducible nitric oxide synthase (iNOS) in the progression of NASH. The present study therefore investigated the role of iNOS in NASH pathogenesis using bone marrow-transplanted iNOS chimeric mice under high-fat diet (HFD) conditions. The chimeric mice were fed a HFD for 16 wk, and primary hepatocytes were stimulated with oleic acid (OA). The molecular mechanisms underlying the role of iNOS in NASH were investigated. Marked hepatic steatosis and injury observed in the HFD mice and OA-stimulated hepatocytes were reduced by hepatocyte-derived iNOS. Mechanistically, iNOS upregulated heme oxygenase 1 (HO-1) by augmenting nuclear factor erythroid 2-related factor 2 (Nrf-2) binding to the HO-1 gene promoter. In conclusion, hepatocyte-derived iNOS may play a protective role against the progression of NASH by upregulating HO-1 through Nrf-2. Upregulation of hepatocellular iNOS may represent a potentially new therapeutic paradigm to combat NASH.

Role of CYP2E1 in Mitochondrial Dysfunction and Hepatic Injury by Alcohol and Non-Alcoholic Substances

Alcoholic fatty liver disease (AFLD) and non-alcoholic fatty liver disease (NAFLD) are two pathological conditions that are spreading worldwide. Both conditions are remarkably similar with regard to the pathophysiological mechanism and progression despite different causes. Oxidative stressinduced mitochondrial dysfunction through post-translational protein modifications and/or mitochondrial DNA damage has been a major risk factor in both AFLD and NAFLD development and progression. Cytochrome P450-2E1 (CYP2E1), a known important inducer of oxidative radicals in the cells, has been reported to remarkably increase in both AFLD and NAFLD. Interestingly, CYP2E1 isoforms expressed in both endoplasmic reticulum (ER) and mitochondria, likely lead to the deleterious consequences in response to alcohol or in conditions of NAFLD after exposure to high fat diet (HFD) and in obesity and diabetes. Whether CYP2E1 in both ER and mitochondria work simultaneously or sequentially in various conditions and whether mitochondrial CYP2E1 may exert more pronounced effects on mitochondrial dysfunction in AFLD and NAFLD are unclear. The aims of this review are to briefly describe the role of CYP2E1 and resultant oxidative stress in promoting mitochondrial dysfunction and the development or progression of AFLD and NAFLD, to shed a light on the function of the mitochondrial CYP2E1 as compared with the ER-associated CYP2E1. We finally discuss translational research opportunities related to this field.

Resilient hepatic mitochondrial function and lack of iNOS dependence in diet-induced insulin resistance

Obesity-derived inflammation and metabolic dysfunction has been related to the activity of the inducible nitric oxide synthase (iNOS). To understand the interrelation between metabolism, obesity and NO^., we evaluated the effects of obesity-induced NO^. signaling on liver mitochondrial function. We used mouse strains containing mitochondrial nicotinamide transhydrogenase activity, while prior studies involved a spontaneous mutant of this enzyme, and are, therefore, more prone to oxidative imbalance. Wild-type and iNOS knockout mice were fed a high fat diet for 2, 4 or 8 weeks. iNOS knockout did not protect against diet-induced metabolic changes. However, the diet decreased fatty-acid oxidation capacity in liver mitochondria at 4 weeks in both wild-type and knockout groups; this was recovered at 8 weeks. Interestingly, other mitochondrial functional parameters were unchanged, despite significant modifications in insulin resistance in wild type and iNOS knockout animals. Overall, we found two surprising features of obesity-induced metabolic dysfunction: (i) iNOS does not have an essential role in obesity-induced insulin resistance under all experimental conditions and (ii) liver mitochondria are resilient to functional changes in obesity-induced metabolic dysfunction.

7-Hydroxymatairesinol improves body weight, fat and sugar metabolism in C57BJ/6 mice on a high-fat diet

7-Hydroxymatairesinol (7-HMR) is a plant lignan abundant in various concentrations in plant foods. The objective of this study was to test HMRLignan™, a purified form of 7-HMR, and the correspondingPicea abiesextract (total extractP. abies; TEP) as dietary supplements on a background of a high-fat diet (HFD)-induced metabolic syndrome in mice and in the 3T3-L1 adipogenesis model. Mice, 3 weeks old, were fed a HFD for 60 d. Subgroups were treated with 3 mg/kg body weight 7-HMR (HMRLignan™) or 10 mg/kg body weight TEP by oral administration. 7-HMR and TEP limited the increase in body weight (−11 and −13 %) and fat mass (−11 and −18 %) in the HFD-fed mice. Epididymal adipocytes were 19 and −12 % smaller and the liver was less steatotic (−62 and −65 %). Serum lipids decreased in TEP-treated mice (−11 % cholesterol, −23 % LDL and −15 % TAG) and sugar metabolism was ameliorated by both lignan preparations, as shown by a more than 70 % decrease in insulin secretion and insulin resistance. The expression of several metabolic genes was modulated by the HFD with an effect that was reversed by lignan. In 3T3-L1 cells, the 7-HMR metabolites enterolactone (ENL) and enterodiol (END) showed a 40 % inhibition of cell differentiation accompanied by the inhibited expression of the adipogenic genesPPARγ,C/EBPαandaP2. Furthermore, END and ENL caused a 10 % reduction in TAG uptake in HEPA 1–6 hepatoma cells. In conclusion, 7-HMR and TEP reduce metabolic imbalances typical of the metabolic syndrome and obesity in male mice, whereas their metabolites inhibit adipogenesis and lipid uptakein vitro.

Curcumin suppresses Notch‑1 signaling: Improvements in fatty liver and insulin resistance in rats

Curcumin is a well‑known phenolic substance and has many pharmacological effects associated with metabolism. However, the exact molecular mechanisms underlying this process have yet to be determined. The Notch pathway is a signal transduction pathway involved in energy metabolism. The present study aimed to investigate the effects of curcumin administration on glucose‑lipid metabolism in rats subjected to a high fat diet, and investigate changes in Notch‑1 signaling. Sprague‑Dawley rats (n=40) were randomly divided into four groups (10 rats/group): Control diet group, high fat diet group, high fat diet plus curcumin low dose group and high fat diet plus curcumin high dose group. Following 8 weeks of treatment with curcumin (100 mg/kg in the low dose group and 200 mg/kg in the high dose group), serum metabolic markers and hepatic gene expression patterns were investigated. No differences in body weight following 8 weeks of curcumin administration (P>0.05) were observed; however, curcumin treatment did reduce visceral fat levels (peri‑epididymal and peri‑renal), and decreased cholesterol, triglyceride and low‑density lipoprotein levels in serum compared with the high fat diet rats that did not receive curcumin (P<0.05, P<0.01). An oral glucose tolerance test and an intraperitoneal insulin tolerance test revealed that insulin resistance was reduced (P<0.05 or P<0.01) and tissue section analysis revealed that hepatosteatosis was attenuated following treatment with curcumin. Furthermore, the protein expression of Notch‑1 and its downstream target Hes‑1 were suppressed. These effects were also in parallel with an upregulation of fatty acid oxidation‑associated gene expression, including peroxisome proliferator‑activated receptor (PPAR)‑α, carnitine palmitoyltransferase 1 and PPAR‑γ (P<0.05). In addition, curcumin administration led to a downregulation in the expression of lipogenic genes, including sterol regulatory element‑binding protein, fatty acid synthase and acetyl‑CoA carboxylase (P<0.05). The expression of inflammation‑associated genes, including nuclear factor‑κB, tumor necrosis factor‑α and prostaglandin‑endoperoxide synthase 2 were also suppressed. The results of the present study suggest that the hepatic Notch‑1 pathway can be suppressed via curcumin treatment, which may ameliorate fatty liver and insulin resistance in rats subjected to a high fat diet.

Evaluation of inducible nitric oxide synthase inhibition on kidney function and structure in high-fat diet-induced kidney disease

NEW FINDINGS

What is the central question of this study? The metabolic pathways regulating the effects of obesity on the kidney remain unknown. We sought to determine whether inducible nitric oxide synthase (iNOS) is involved in the underlying mechanisms of high-fat diet-induced kidney disease using a specific iNOS inhibitor, N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL). What is the main finding and its importance? We did not demonstrate an upregulation of iNOS renal expression after high caloric intake, suggesting that iNOS might not be a crucial player in the development of obesity-induced kidney disease. Although L-NIL treatment clearly ameliorated systemic metabolic parameters, the effect on loss of renal function, impairment of tubular integrity, oxidative stress and inflammation appeared to be more moderate. Central obesity is related to caloric excess, promoting deleterious cellular responses in targeted organs. Nitric oxide (NO) has been determined as a key player in the pathogenesis of metabolic diseases. Here, we investigated the implication of inducible NO synthase (iNOS) in the development of obesity-induced kidney disease. C57Bl/6 male mice were randomized to a low-fat diet (LFD) or a high-fat diet (HFD) and treated with N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL), a specific iNOS inhibitor, for 16 weeks. Mice fed an HFD exhibited a significant increase in body weight, fasting blood glucose and plasma concentrations of non-esterified fatty acids, triglyceride and insulin. Inhibition of iNOS prevented these changes in mice fed an HFD. Interestingly, the significant increase in albuminuria and mesangial matrix expansion were not ameliorated with L-NIL, whereas a significant decrease in proteinuria, N-acetyl-β-d-glucosaminidase excretion and renal triglyceride content were found, suggesting that iNOS inhibition is more suitable for tubular function than glomerular function. The urinary concentration of hydrogen peroxide, a stable product of reactive oxygen species production, that was found to be increased in mice fed an HFD, was significantly reduced with L-NIL. Finally, despite a moderate effect of L-NIL on inflammatory processes in the kidney, we demonstrated a positive impact of this treatment on adipocyte hypertrophy and on adipose tissue inflammation. These results suggest that inhibition of iNOS leads to a moderate beneficial effect on kidney function in mice fed an HFD. Further studies are needed for better understanding of the role of iNOS in obesity-induced kidney disease.

Withania somnifera as a potential candidate to ameliorate high fat diet-induced anxiety and neuroinflammation

Background

The epidemic of obesity has reached alarming levels in both developing and developed nations. Excessive calorie intake and sedentary lifestyle due to technological advancements are the main causal factors for overweight and obesity among the human population. Obesity has been associated with a number of co-morbidities such as hypertension, type 2 diabetes mellitus, cardiovascular diseases, and neurodegeneration and dementia. The progression of neurological disorders in obese subjects has been mainly attributed to neuroinflammation. Withania somnifera has been used in numerous Ayurvedic formulations owing to its wide array of health-promoting properties. The current study was designed to test the hypothesis whether dry leaf powder of W. somnifera has anxiolytic and anti-neuroinflammatory potential in diet-induced obesity.

Methods

Young adult female rats were divided into four groups: low fat diet group (LFD) fed with regular chow feed, high fat diet group (HFD) fed with diet containing 30% fat by weight, low fat diet plus extract group (LFDE) fed with regular chow feed supplemented with dry leaf powder of W. somnifera 1 mg/g of body weight (ASH), and high fat diet plus extract group (HFDE) fed with diet containing 30% fat by weight and supplemented with ASH. All the animals were kept on respective feeding regimen for 12 weeks; following which, the animals were tested for their anxiety-like behavior using elevated plus maze test. The animals were sacrificed and used to study various inflammatory markers such as GFAP, Iba1, PPARγ, iNOS, MCP-1, TNFα, IL-1β, IL-6, and various markers of NF-κB pathway by Western blotting and quantitative real-time PCR. Serum levels of leptin, insulin and pro-inflammatory cytokines were also assayed.

Results

ASH treated rats showed less anxiety levels as compared to HFD animals. At molecular level, ASH ameliorated the HFD-induced reactive gliosis and microgliosis and suppressed the expression of inflammatory markers such as PPARγ, iNOS, MCP-1, TNFα, IL-1β, and IL-6. Further, ASH ameliorated leptin and insulin resistance and prevented HFD-induced apoptosis.

Conclusions

Dry leaf powder of W. somnifera may prove to be a potential therapeutic agent to attenuate neuroinflammation associated with obesity and may prevent its co-morbidities.

Non-alcoholic fatty liver disease: A sign of systemic disease

Non-alcoholic fatty liver disease (NAFLD) is the most common form of liver disease and leading cause of cirrhosis in the United States and developed countries. NAFLD is closely associated with obesity, insulin resistance and metabolic syndrome, significantly contributing to the exacerbation of the latter. Although NAFLD represents the hepatic component of metabolic syndrome, it can also be found in patients prior to their presentation with other manifestations of the syndrome. The pathogenesis of NAFLD is complex and closely intertwined with insulin resistance and obesity. Several mechanisms are undoubtedly involved in its pathogenesis and progression. In this review, we bring together the current understanding of the pathogenesis that makes NAFLD a systemic disease.

Altered glucose and lipid homeostasis in liver and adipose tissue pre-dispose inducible NOS knockout mice to insulin resistance

On the basis of diet induced obesity and KO mice models, nitric oxide is implied to play an important role in the initiation of dyslipidemia induced insulin resistance. However, outcomes using iNOS KO mice have so far remained inconclusive. The present study aimed to assess IR in iNOS KO mice after 5 weeks of LFD feeding by monitoring body composition, energy homeostasis, insulin sensitivity/signaling, nitrite content and gene expressions changes in the tissues. We found that body weight and fat content in KO mice were significantly higher while the respiratory exchange ratio (RER), volume of carbon dioxide (VCO₂), and heat production were lower as compared to WT mice. Furthermore, altered systemic glucose tolerance, tissue insulin signaling, hepatic gluconeogenesis, augmented hepatic lipids, adiposity, as well as gene expression regulating lipid synthesis, catabolism and efflux were evident in iNOS KO mice. Significant reduction in eNOS and nNOS gene expression, hepatic and adipose tissue nitrite content, circulatory nitrite was also observed. Oxygen consumption rate of mitochondrial respiration has remained unaltered in KO mice as measured using extracellular flux analyzer. Our findings establish a link between the NO status with systemic and tissue specific IR in iNOS KO mice at 5 weeks.

CD36 genetic variation, fat intake and liver fibrosis in chronic hepatitis C virus infection

AIM

To analyze the association of the CD36 polymorphism (rs1761667) with dietary intake and liver fibrosis (LF) in chronic hepatitis C (CHC) patients.

METHODS

In this study, 73 patients with CHC were recruited. The CD36 genotype (G > A) was determined by a TaqMan real-time PCR system. Dietary assessment was carried out using a three-day food record to register the daily intake of macronutrients. Serum lipids and liver enzymes were measured by a dry chemistry assay. LF evaluated by transient elastography (Fibroscan^®) and APRI score was classified as mild LF (F1-F2) and advanced LF (F3-F4).

RESULTS

Overall, the CD36 genotypic frequencies were AA (30.1%), AG (54.8%), and GG (15.1%), whereas the allelic A and G frequencies were 57.5% and 42.5%, respectively. CHC patients who were carriers of the CD36 AA genotype had a higher intake of calories attributable to total fat and saturated fatty acids than those with the non-AA genotypes. Additionally, aspartate aminotransferase (AST) serum values were higher in AA genotype carriers compared to non-AA carriers (91.7 IU/L vs 69.8 IU/L, P = 0.02). Moreover, the AA genotype was associated with an increase of 30.23 IU/L of AST (β = 30.23, 95%CI: 9.0-51.46, P = 0.006). Likewise, the AA genotype was associated with advanced LF compared to the AG (OR = 3.60, 95%CI: 1.16-11.15, P = 0.02) or AG + GG genotypes (OR = 3.52, 95%CI: 1.18-10.45, P = 0.02).

CONCLUSION

This study suggests that the CD36 (rs1761667) AA genotype is associated with higher fat intake and more instances of advanced LF in CHC patients.

Treatment with geraniol ameliorates methionine-choline-deficient diet-induced non-alcoholic steatohepatitis in rats

BACKGROUND AND AIM

Non-alcoholic steatohepatitis (NASH) is one of the most common causes of chronic liver disease and is considered to be a causative factor of cryptogenic cirrhosis and hepatocellular carcinoma. The aim of this work was to investigate whether treatment with geraniol (a monoterpene) attenuated NASH induced by methionine-choline-deficient (MCD) diet in rats.

METHODS

Rats were fed with MCD diet to induce NASH and treated with geraniol (200 mg/kg/day) for 10 weeks.

RESULTS

Treatment with geraniol reduced histological scores, fibrosis, and apoptosis in livers, lowered activities of alanine aminotransferase and aspartate aminotransferase in serum, and attenuated hepatic fat accumulation in rats fed with MCD diet. Treatment with geraniol preserved hepatic mitochondrial function, evidenced by reduced mitochondrial reactive oxygen species formation, enhanced adenosine triphosphate formation and membrane integrity, restored mitochondrial electron transport chain enzyme activity, and increased mitochondrial DNA content in rats fed with MCD diet. Treatment with geraniol reduced uncoupling protein 2 protein expression, and enhanced protein expression of prohibitin, mRNA expression of peroxisome proliferator-activated receptor α, and activity of mitochondrial carnitine palmitoyl transferase-I in livers of rats fed with MCD diet. Treatment with geraniol abated oxidative stress, evidenced by reduced malondialdehyde and 3-nitrotyrosine formation, enhanced activity of glutathione S-epoxide transferase, and down-regulated expression of inducible nitric oxide synthase and cytochrome P450 2E1 in livers of rats fed with MCD diet. Treatment with geraniol reduced myeloperoxidase activity and protein expression of tumor necrosis factor alpha and IL-6 in livers of rats fed with MCD diet.

CONCLUSION

Treatment with geraniol attenuated MCD-induced NASH in rats.

Diet-induced dyslipidemia leads to nonalcoholic fatty liver disease and oxidative stress in guinea pigs

Chronic dyslipidemia imposed by a high-fat and high-caloric dietary regime leads to debilitating disorders such as obesity, nonalcoholic fatty liver disease (NAFLD), and insulin resistance. As disease rates surge, so does the need for high validity animal models to effectively study the causal relationship between diet and disease progression. The dyslipidemic guinea pig displays a high similarity with the human lipoprotein profile and may in this aspect be superior to other rodent models. This study investigated the effects of 2 long-term Westernized diets (0.35% cholesterol, 18.5% vegetable oil and either 15% or 20% sucrose) compared with isocaloric standard chow in adult guinea pigs. Biochemical markers confirmed dyslipidemia in agreement with dietary regimens; however, both high-fat groups displayed a decreased tissue fat percentage compared with controls. Macroscopic appearance, histopathologic evaluation, and plasma markers of liver function confirmed NAFLD in high-fat groups, supported by liver redox imbalance and markers suggesting hepatic endothelial dysfunction. Plasma markers indicated endothelial dysfunction in response to a high-fat diet, although atherosclerotic lesions were not evident. Evaluation of glucose tolerance showed no indication of insulin resistance. The 5% increase in sucrose between the 2 high-fat diets did not lead to significant differences between groups. In conclusion, we find the dyslipidemic guinea pig to be a valid model of diet imposed dyslipidemia, particularly with regards to hepatic steatosis and endothelial dysfunction. Furthermore, the absence of obesity supports the present study setup as targeting NAFLD in nonobese individuals.

Dysregulated Hepatic Methionine Metabolism Drives Homocysteine Elevation in Diet-Induced Nonalcoholic Fatty Liver Disease

Methionine metabolism plays a central role in methylation reactions, production of glutathione and methylarginines, and modulating homocysteine levels. The mechanisms by which these are affected in NAFLD are not fully understood. The aim is to perform a metabolomic, molecular and epigenetic analyses of hepatic methionine metabolism in diet-induced NAFLD. Female 129S1/SvlmJ;C57Bl/6J mice were fed a chow (n = 6) or high-fat high-cholesterol (HFHC) diet (n = 8) for 52 weeks. Metabolomic study, enzymatic expression and DNA methylation analyses were performed. HFHC diet led to weight gain, marked steatosis and extensive fibrosis. In the methionine cycle, hepatic methionine was depleted (30%, p< 0.01) while s-adenosylmethionine (SAM)/methionine ratio (p< 0.05), s-adenosylhomocysteine (SAH) (35%, p< 0.01) and homocysteine (25%, p< 0.01) were increased significantly. SAH hydrolase protein levels decreased significantly (p <0.01). Serine, a substrate for both homocysteine remethylation and transsulfuration, was depleted (45%, p< 0.01). In the transsulfuration pathway, cystathionine and cysteine trended upward while glutathione decreased significantly (p< 0.05). In the transmethylation pathway, levels of glycine N-methyltransferase (GNMT), the most abundant methyltransferase in the liver, decreased. The phosphatidylcholine (PC)/ phosphatidylethanolamine (PE) ratio increased significantly (p< 0.01), indicative of increased phosphatidylethanolamine methyltransferase (PEMT) activity. The protein levels of protein arginine methytransferase 1 (PRMT1) increased significantly, but its products, monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), decreased significantly. Circulating ADMA increased and approached significance (p< 0.06). Protein expression of methionine adenosyltransferase 1A, cystathionine β-synthase, γ-glutamylcysteine synthetase, betaine-homocysteine methyltransferase, and methionine synthase remained unchanged. Although gene expression of the DNA methyltransferase Dnmt3a decreased, the global DNA methylation was unaltered. Among individual genes, only HMG-CoA reductase (Hmgcr) was hypermethylated, and no methylation changes were observed in fatty acid synthase (Fasn), nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfκb1), c-Jun, B-cell lymphoma 2 (Bcl-2) and Caspase 3. NAFLD was associated with hepatic methionine deficiency and homocysteine elevation, resulting mainly from impaired homocysteine remethylation, and aberrancy in methyltransferase reactions. Despite increased PRMT1 expression, hepatic ADMA was depleted while circulating ADMA was increased, suggesting increased export to circulation.

Effects of 5-aminolevulinic acid on a murine model of diet-induced obesity

The effects of 5-aminolevulinic acid (5-ALA) on obesity were investigated using a murine model (diet-induced obese mice). Diet-induced obese mice were divided into 4 groups: a control group (C group), which was fed a high-fat diet; a low-5-ALA dose (10 mg/kg/day) group (10A group); a moderate-5-ALA dose (30 mg/kg/day) group (30A group); and a high-5-ALA dose (100 mg/kg/day) group (100A group). 5-ALA was administered by mixing the high fat diet for 8 weeks. Body weight increases in the 30A and 100A groups were significantly smaller compared with those of the C group. Body fat measurements by X-ray computed tomography indicated that the 100A group showed a tendency toward low visceral fat quantities during the final week of the study. Visceral fat weights in the 30A and 100A groups were slightly low. The levels of serum alanine aminotransferase (ALT) and total cholesterol (TC) in the 10A group was slightly low, whereas the 30A and 100A groups showed significantly lower ALT and TC values. Liver lipid concentration showed a dose-dependent decrease with ALA. Thus, in this diet-induced obese murine model, administration of 5-ALA had a significantly beneficial impact on the visceral fat, serum ALT and TC, and liver lipid concentration.

High-fat diet induces hepatic insulin resistance and impairment of synaptic plasticity

High-fat diet (HFD)-induced obesity is associated with insulin resistance, which may affect brain synaptic plasticity through impairment of insulin-sensitive processes underlying neuronal survival, learning, and memory. The experimental model consisted of 3 month-old C57BL/6J mice fed either a normal chow diet (control group) or a HFD (60% of calorie from fat; HFD group) for 12 weeks. This model was characterized as a function of time in terms of body weight, fasting blood glucose and insulin levels, HOMA-IR values, and plasma triglycerides. IRS-1/Akt pathway was assessed in primary hepatocytes and brain homogenates. The effect of HFD in brain was assessed by electrophysiology, input/output responses and long-term potentiation. HFD-fed mice exhibited a significant increase in body weight, higher fasting glucose- and insulin levels in plasma, lower glucose tolerance, and higher HOMA-IR values. In liver, HFD elicited (a) a significant decrease of insulin receptor substrate (IRS-1) phosphorylation on Tyr608 and increase of Ser307 phosphorylation, indicative of IRS-1 inactivation; (b) these changes were accompanied by inflammatory responses in terms of increases in the expression of NFκB and iNOS and activation of the MAP kinases p38 and JNK; (c) primary hepatocytes from mice fed a HFD showed decreased cellular oxygen consumption rates (indicative of mitochondrial functional impairment); this can be ascribed partly to a decreased expression of PGC1α and mitochondrial biogenesis. In brain, HFD feeding elicited (a) an inactivation of the IRS-1 and, consequentially, (b) a decreased expression and plasma membrane localization of the insulin-sensitive neuronal glucose transporters GLUT3/GLUT4; (c) a suppression of the ERK/CREB pathway, and (d) a substantial decrease in long-term potentiation in the CA1 region of hippocampus (indicative of impaired synaptic plasticity). It may be surmised that 12 weeks fed with HFD induce a systemic insulin resistance that impacts profoundly on brain activity, i.e., synaptic plasticity.

Rimonabant Improves Oxidative/Nitrosative Stress in Mice with Nonalcoholic Fatty Liver Disease

The present study deals with the effects of rimonabant on oxidative/nitrosative stress in high diet- (HFD-) induced experimental nonalcoholic fatty liver disease (NAFLD). Male mice C57BL/6 were divided into the following groups: control group fed with control diet for 20 weeks (C; n = 6); group fed with HFD for 20 weeks (HF; n = 6); group fed with standard diet and treated with rimonabant after 18 weeks (R; n = 9); group fed with HFD and treated with rimonabant after 18 weeks (HFR; n = 10). Daily dose of rimonabant (10 mg/kg) was administered to HFR and R group by oral gavage for two weeks. Treatment induced a decrease in hepatic malondialdehyde concentration in HFR group compared to HF group (P < 0.01). The concentration of nitrites + nitrates in liver was decreased in HFR group compared to HF group (P < 0.01). Liver content of reduced glutathione was higher in HFR group compared to HF group (P < 0.01). Total liver superoxide dismutase activity in HFR group was decreased in comparison with HF group (P < 0.01). It was found that rimonabant may influence hepatic iron, zinc, copper, and manganese status. Our study indicates potential usefulness of cannabinoid receptor type 1 blockade in the treatment of HFD-induced NAFLD.

Protective effect of boswellic acids versus pioglitazone in a rat model of diet-induced non-alcoholic fatty liver disease: influence on insulin resistance and energy expenditure

Non-alcoholic fatty liver disease (NAFLD) is closely linked to insulin resistance, oxidative stress, and cytokine imbalance. Boswellic acids, a series of pentacyclic triterpene molecules that are produced by plants in the genus Boswellia, has been traditionally used for the treatment of a variety of diseases. This study aimed at evaluating the protective effect of boswellic acids in a model of diet-induced NAFLD in rats in comparison to the standard insulin sensitizer, pioglitazone. Rats were fed with a high-fat diet (HFD) for 12 weeks to induce NAFLD. Starting from week 5, rats received boswellic acids (125 or 250 mg/kg) or pioglitazone parallel to the HFD. Feeding with HFD induced hepatic steatosis and inflammation in rats. In addition, liver index, insulin resistance index, activities of liver enzymes, and serum lipids deviated from normal. Further, serum tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and cyclooxygenase 2 were elevated; this was associated with an increase in hepatic expression of inducible nitric oxide synthase (iNOS) and formation of 4-hydroxy-2-nonenal (HNE). Rats treated with boswellic acids (125 or 250 mg/kg) or pioglitazone showed improved insulin sensitivity and a reduction in liver index, activities of liver enzymes, serum TNF-α and IL-6 as well as hepatic iNOS expression and HNE formation compared to HFD group. Furthermore, at the cellular level, boswellic acids (250 mg/kg) ameliorated the expression of thermogenesis-related mitochondrial uncoupling protein-1 and carnitine palmitoyl transferase-1 in white adipose tissues. Data from this study indicated that boswellic acids might be a promising therapy in the clinical management of NAFLD if appropriate safety and efficacy data are available.

Lingonberry (Vaccinium vitis-idaea L.) Exhibits Antidiabetic Activities in a Mouse Model of Diet-Induced Obesity

Vaccinium vitis-idaea, commonly known as lingonberry, has been identified among species used by the Cree of Eeyou Istchee of northern Quebec to treat symptoms of diabetes. In a previous study, the ethanol extract of berries of V. vitis-idaea enhanced glucose uptake in C2C12 muscle cells via stimulation of AMP-activated protein kinase (AMPK) pathway. The purpose of this study was to examine the effect of plant extract in a dietary mouse model of mild type 2 diabetes. C57BL/6 mice fed a high-fat diet (HFD, ∼35% lipids) for 8 weeks that become obese and insulin-resistant (diet-induced obesity, DIO) were used. Treatment began by adding V. vitis-idaea extract to HFD at 3 different concentrations (125, 250, and 500 mg/Kg) for a subsequent period of 8 weeks (total HFD, 16 weeks). The plant extract significantly decreased glycemia and strongly tended to decrease insulin levels in this model. This was correlated with a significant increase in GLUT4 content and activation of the AMPK and Akt pathways in skeletal muscle. V. vitis-idaea treatment also improved hepatic steatosis by decreasing hepatic triglyceride levels and significantly activated liver AMPK and Akt pathways. The results of the present study confirm that V. vitis-idaea represents a culturally relevant treatment option for Cree diabetics and pave the way to clinical studies.

Functional roles of protein nitration in acute and chronic liver diseases

Nitric oxide, when combined with superoxide, produces peroxynitrite, which is known to be an important mediator for a number of diseases including various liver diseases. Peroxynitrite can modify tyrosine residue(s) of many proteins resulting in protein nitration, which may alter structure and function of each target protein. Various proteomics and immunological methods including mass spectrometry combined with both high pressure liquid chromatography and 2D PAGE have been employed to identify and characterize nitrated proteins from pathological tissue samples to determine their roles. However, these methods contain a few technical problems such as low efficiencies with the detection of a limited number of nitrated proteins and labor intensiveness. Therefore, a systematic approach to efficiently identify nitrated proteins and characterize their functional roles is likely to shed new insights into understanding of the mechanisms of hepatic disease pathophysiology and subsequent development of new therapeutics. The aims of this review are to briefly describe the mechanisms of hepatic diseases. In addition, we specifically describe a systematic approach to efficiently identify nitrated proteins to study their causal roles or functional consequences in promoting acute and chronic liver diseases including alcoholic and nonalcoholic fatty liver diseases. We finally discuss translational research applications by analyzing nitrated proteins in evaluating the efficacies of potentially beneficial agents to prevent or treat various diseases in the liver and other tissues.

Dietary habits and behaviors associated with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent causes of health problems in Western (industrialized) countries. Moreover, the incidence of infantile NAFLD is increasing, with some of these patients progressing to nonalcoholic steatohepatitis. These trends depend on dietary habits and life-style. In particular, overeating and its associated obesity affect the development of NAFLD. Nutritional problems in patients with NAFLD include excess intake of energy, carbohydrates, and lipids, and shortages of polyunsaturated fatty acids, vitamins, and minerals. Although nutritional therapeutic approaches are required for prophylaxis and treatment of NAFLD, continuous nutrition therapy is difficult for many patients because of their dietary habits and lifestyle, and because the motivation for treatment differs among patients. Thus, it is necessary to assess the nutritional background and to identify nutritional problems in each patient with NAFLD. When assessing dietary habits, it is important to individually evaluate those that are consumed excessively or insufficiently, as well as inappropriate eating behaviors. Successful nutrition therapy requires patient education, based on assessments of individual nutrients, and continuing the treatment. In this article, we update knowledge about NAFLD, review the important aspects of nutritional assessment targeting treatment success, and present some concrete nutritional care plans which can be applied generally.

Decoding cell death signals in liver inflammation

Inflammation can be either beneficial or detrimental to the liver, depending on multiple factors. Mild (i.e., limited in intensity and destined to resolve) inflammatory responses have indeed been shown to exert consistent hepatoprotective effects, contributing to tissue repair and promoting the re-establishment of homeostasis. Conversely, excessive (i.e., disproportionate in intensity and permanent) inflammation may induce a massive loss of hepatocytes and hence exacerbate the severity of various hepatic conditions, including ischemia-reperfusion injury, systemic metabolic alterations (e.g., obesity, diabetes, non-alcoholic fatty liver disorders), alcoholic hepatitis, intoxication by xenobiotics and infection, de facto being associated with irreversible liver damage, fibrosis, and carcinogenesis. Both liver-resident cells (e.g., Kupffer cells, hepatic stellate cells, sinusoidal endothelial cells) and cells that are recruited in response to injury (e.g., monocytes, macrophages, dendritic cells, natural killer cells) emit pro-inflammatory signals including - but not limited to - cytokines, chemokines, lipid messengers, and reactive oxygen species that contribute to the apoptotic or necrotic demise of hepatocytes. In turn, dying hepatocytes release damage-associated molecular patterns that-upon binding to evolutionary conserved pattern recognition receptors-activate cells of the innate immune system to further stimulate inflammatory responses, hence establishing a highly hepatotoxic feedforward cycle of inflammation and cell death. In this review, we discuss the cellular and molecular mechanisms that account for the most deleterious effect of hepatic inflammation at the cellular level, that is, the initiation of a massive cell death response among hepatocytes.

Fatty liver accompanies an increase in lactobacillus species in the hind gut of C57BL/6 mice fed a high-fat diet

High-fat (HF) diets can produce obesity and have been linked to the development of nonalcoholic fatty liver disease and changes in the gut microbiome. To test the hypothesis that HF feeding increases certain predominant hind gut bacteria and development of steatohepatitis, C57BL/6 mice were fed an HF (45% energy) or low-fat (LF) (10% energy) diet for 10 wk. At the end of the feeding period, body weights in the HF group were 34% greater than those in the LF group (P < 0.05). These changes were associated with dramatic increases in lipid droplet number and size, inflammatory cell infiltration, and inducible nitric oxide (NO) synthase protein concentration in the livers of mice fed the HF diet. Consistent with the fatty liver phenotype, plasma leptin and tumor necrosis factor-α concentrations were also elevated in mice fed the HF diet, indicative of chronic inflammation. Eight of 12 pairs of polymerase chain reaction (PCR) primers for bacterial species that typically predominate hind gut microbial ecology generated specific PCR products from the fecal DNA samples. The amount of DNA from Lactobacillus gasseri and/or Lactobacillus taiwanensis in the HF group was 6900-fold greater than that in the LF group. Many of these bacteria are bile acid resistant and are capable of bile acid deconjugation. Because bile acids are regulators of hepatic lipid metabolism, the marked increase of gut L. gasseri and/or L. taiwanensis species bacteria with HF feeding may play a role in development of steatohepatitis in this model.

Nutrition therapy for liver diseases based on the status of nutritional intake

The dietary intake of patients with nonalcoholic fatty liver disease (NAFLD) is generally characterized by high levels of carbohydrate, fat, and/or cholesterol, and these dietary patterns influence hepatic lipid metabolism in the patients. Therefore, careful investigation of dietary habits could lead to better nutrition therapy in NAFLD patients. The main treatment for chronic hepatitis C (CHC) is interferon-based antiviral therapy, which often causes a decrease in appetite and energy intake; hence, nutritional support is also required during therapy to prevent undernourishment, treatment interruption, and a reduction in quality of life. Moreover, addition of some nutrients that act to suppress viral proliferation is recommended. As a substitutive treatment, low-iron diet therapy, which is relatively safe and effective for preventing hepatocellular carcinoma, is also recommended for CHC patients. Some patients with liver cirrhosis (LC) have decreased dietary energy and protein intake, while the number of LC patients with overeating and obesity is increasing, indicating that the nutritional state of LC patients has a broad spectrum. Therefore, nutrition therapy for LC patients should be planned on an assessment of their complications, nutritional state, and dietary intake. Late evening snacks, branched-chain amino acids, zinc, and probiotics are considered for effective nutritional utilization.

Increased phosphodiesterase type 5 levels in a mouse model of type 2 diabetes mellitus

INTRODUCTION

Diabetes mellitus (DM) is a major risk factor for developing erectile dysfunction (ED) and men with DM are often less responsive to phosphodiesterase type 5 (PDE5) inhibitors than ED due to other causes.

AIMS

The aim of this study was to explore potential mechanisms whereby PDE5 inhibitors may have reduced efficacy in type 2 DM.

METHODS

At 4 weeks of age, mice were either fed a high-fat diet (HFD) for 22-36 weeks or fed regular chow (control). An additional group of mice in the same genetic background had a genetic form of type 1 DM.

MAIN OUTCOME MEASURES

Glucose tolerance testing, intracorporal pressures (ICPs), oxidative stress (OS), apoptotic cell death (active caspase-3 and apostain), PDE5, p53, and cyclic guanosine monophosphate (cGMP) levels, and histological examination of inflow arteries were performed in mice fed a HFD and control mice. A group of mice with type 1 DM were studied for PDE5 expression levels.

RESULTS

All mice fed a HFD had impaired glucose tolerance compared with the age-matched mice fed on standard chow diet (control). HFD fed mice had reduced maximum ICPs following in vivo cavernous nerve electrical stimulation and increased apoptotic cell death, OS, and p53 levels in the corporal tissue. Interestingly, PDE5 levels were increased and cGMP levels were decreased. In contrast, mice with type 1 DM did not have increases in PDE5.

CONCLUSIONS

Taken together, our results suggest that type 2 DM-induced ED is associated with findings that could lead to reduced cGMP and may account for reduced efficacy of PDE5 inhibitors.

Ferric citrate CYP2E1-independently promotes alcohol-induced apoptosis in HepG2 cells via oxidative/nitrative stress which is attenuated by pretreatment with baicalin

In the case of alcoholic liver injury, an iron overload is always present. Both alcohol and iron can individually induce oxidative stress in liver. However, the combined effect of physiological concentrations of alcohol and iron on oxidative stress in hepatocytes remains unknown. Baicalin has been demonstrated to be an antioxidant or iron chelator in animal experiments. In this study, we investigated the injury to hepatocytes CYP2E1-independently induced by the combination of alcohol and iron and the protective effect of baicalin. Compared with cells treated with ethanol alone, ferric citrate enhanced the accumulation of reactive oxygen and nitrogen species, increased the occurrence of protein carbonylation/nitration and the levels of 4-hydroxy-2-nonenal, changed the distribution of iNOS, and eventually resulted in apoptosis. However, pretreatment with baicalin inhibited the oxidative stress induced by the combination of alcohol and iron, mainly by chelating iron. Our findings therefore suggest that iron could CPY2E1-independently enhance the oxidative stress induced by alcohol, which probably contributes to the pathogenesis of alcoholic liver disease. Baicalin is a promising phytomedicine for preventing alcoholic liver disease.

Enhancement of hematopoiesis and lymphopoiesis in diet-induced obese mice

A rodent model of diet-induced obesity revealed that obesity significantly altered hematopoietic and lymphopoietic functions in the bone marrow and thymus. C57BL/6 mice were fed a mixed high-fat diet (HFD) of 45% fat or 10% fat diet (lean controls) for 180 d. A sustained increase in the numbers of cells found in bone marrow and thymus of HFD mice occurred from day 90 to day 180. However, with the exception of a 10-18% increase in the proportion of lymphocytes, the composition of monocytes, granulocytes, erythrocytes, and mixed progenitor lineages remained normal in the marrow. Likewise, thymuses of HFD mice increased 30-50% in size compared with controls, with analogous increases in thymocyte numbers. The overall thymus cellular composition remained normal. Although increased blood and lymphatic volume in obese mice would play a role in increased hematopoiesis, there were large and disproportionate increases in blood leukocytes of HFD mice, indicating that homeostasis was not maintained. Leptin, which promotes lymphopoiesis and myelopoiesis, reached 100 ng/mL in sera from HFD mice. Moreover, a three- to sixfold increase in adipocytes in marrow resulted in spiked leptin mRNA expression in bones of HFD mice compared with lean controls. Other cytokines and growth factors did not show any increases in obese marrow. The substantial increase in lymphopoietic and hematopoietic processes in HFD mice indicates that the primary tissues are another facet of the immune system dysregulated by obesity, which was perhaps fostered by higher amounts of leptin in marrow and serum.

Ping-tang Recipe () improves insulin resistance and attenuates hepatic steatosis in high-fat diet-induced obese rats

OBJECTIVE

To investigate the therapeutic effects of Ping-tang Recipe (, PTR) on high-fat diet (HFD)-induced insulin resistance and non-alcoholic fatty liver disease (NAFLD), and to elucidate the underlying mechanisms.

METHODS

Forty male SD rats were included in the study. Ten rats were fed on normal diet as normal control, and thirty rats were fed on HFD for 8 weeks to induce obesity, followed with low dose (0.42 g/kg) or high dose (0.84 g/kg) of PTR or vehicle for 8 weeks with 10 animals for each group. Glucose metabolism and insulin sensitivity were evaluated by oral glucose tolerance test and insulin tolerance test. Hepatic steatosis was measured by immunohistochemistry. Liver lipid metabolic genes were analyzed by quantitative real-time polymerase chain reaction, while AMP-activated protein kinase (AMPK) expression was examined by Western blot.

RESULTS

Rats fed on HFD developed abdominal obesity, insulin resistance and NAFLD. PTR treatment reduced visceral fat (peri-epididymal and peri-renal) accumulation, improved glucose metabolism, and attenuated hepatic steatosis. The expressions of the key lipolytic regulating genes, including peroxisome proliferators-activated receptor γ co-activator 1α (PGC-1α), peroxisome proliferator-activated receptor γ (PRAR-γ) and α (PRAR-α), were up-regulated (P<0.05 or P<0.01), while the expressions of lipogenic genes such as sterol regulatory element-binding protein 1c (SREBP-1c), fatty acid synthase (FAS) and liver fatty acid-binding protein (L-FABP) were down-regulated (P<0.05 or P<0.01). In addition, PTR activated AMPK and promoted acetyl-CoA carboxylase phosphorylation in the liver.

CONCLUSIONS

PTR improves insulin resistance and reverse hepatic steatosis in the rat model of HFD-induced obesity through promotion of lipolysis and reduction of lipogenesis, which involves the AMPK signaling pathway, thus representing a new therapeutic intervention for obesity related insulin resistance and NAFLD.

Chronic intermittent hypoxia is a major trigger for non-alcoholic fatty liver disease in morbid obese

BACKGROUND & AIMS

Morbid obesity is frequently associated with low grade systemic inflammation, increased macrophage accumulation in adipose tissue (AT), obstructive sleep apnea (OSA), and nonalcoholic fatty liver disease (NAFLD). It has been suggested that chronic intermittent hypoxia (CIH) resulting from OSA could be an independent factor for early stage of NAFLD in addition to other well-recognized factors (dyslipidemia or insulin resistance). Moreover, macrophage accumulation in AT is associated with local hypoxia in fat tissue. We hypothesized that the association between CIH and morbid obesity could exert additional specific deleterious effects both in the liver and adipose tissues.

METHODS

One hundred and one morbidly obese subjects were prospectively recruited and underwent bariatric surgery during which a liver needle biopsy as well as surgical subcutaneous and omental AT biopsies were obtained. Oxygen desaturation index (ODI) quantified the severity of nocturnal CIH.

RESULTS

Histopathologic analysis of liver biopsies demonstrated that NAFLD lesions (ballooning of hepatocytes, lobular inflammation), NAFLD activity score (NAS), and fibrosis were significantly more severe in patients with the highest ODI tertile (p values ≤0.001 for all hepatic lesions). In multivariate analysis, after adjustment for age, obesity, and insulin resistance status, CIH remained independently associated with hepatic fibrosis, fibroinflammation, and NAS. By contrast, no association was found between CIH, macrophage accumulation, and adipocytes size in both subcutaneous and omental adipose tissue.

CONCLUSIONS

In morbidly obese patients, CIH was strongly associated with more severe liver injuries but did not worsen obesity induced macrophage accumulation in adipose tissue depots.