Fibrogenesis in fatty liver associated with obesity and diabetes mellitus type 2

Pathogenic hypothalamic extracellular matrix promotes metabolic disease

Metabolic diseases such as obesity and type 2 diabetes are marked by insulin resistance1,2. Cells within the arcuate nucleus of the hypothalamus (ARC), which are crucial for regulating metabolism, become insulin resistant during the progression of metabolic disease3-8, but these mechanisms are not fully understood. Here we investigated the role of a specialized chondroitin sulfate proteoglycan extracellular matrix, termed a perineuronal net, which surrounds ARC neurons. In metabolic disease, the perineuronal net of the ARC becomes augmented and remodelled, driving insulin resistance and metabolic dysfunction. Disruption of the perineuronal net in obese mice, either enzymatically or with small molecules, improves insulin access to the brain, reversing neuronal insulin resistance and enhancing metabolic health. Our findings identify ARC extracellular matrix remodelling as a fundamental mechanism driving metabolic diseases.

Extracellular matrix remodelling in obesity and metabolic disorders

Obesity causes extracellular matrix (ECM) remodelling which can develop into serious pathology and fibrosis, having metabolic effects in insulin-sensitive tissues. The ECM components may be increased in response to overnutrition. This review will focus on specific obesity-associated molecular and pathophysiological mechanisms of ECM remodelling and the impact of specific interactions on tissue metabolism. In obesity, complex network of signalling molecules such as cytokines and growth factors have been implicated in fibrosis. Increased ECM deposition contributes to the pathogenesis of insulin resistance at least in part through activation of cell surface integrin receptors and CD44 signalling cascades. These cell surface receptors transmit signals to the cell adhesome which orchestrates an intracellular response that adapts to the extracellular environment. Matrix proteins, glycoproteins, and polysaccharides interact through ligand-specific cell surface receptors that interact with the cytosolic adhesion proteins to elicit specific actions. Cell adhesion proteins may have catalytic activity or serve as scaffolds. The vast number of cell surface receptors and the complexity of the cell adhesome have made study of their roles challenging in health and disease. Further complicating the role of ECM-cell receptor interactions is the variation between cell types. This review will focus on recent insights gained from studies of two highly conserved, ubiquitously axes and how they contribute to insulin resistance and metabolic dysfunction in obesity. These are the collagen-integrin receptor-IPP (ILK-PINCH-Parvin) axis and the hyaluronan-CD44 interaction. We speculate that targeting ECM components or their receptor-mediated cell signalling may provide novel insights into the treatment of obesity-associated cardiometabolic complications.

Histological Manifestations of Diabetic Kidney Disease and its Relationship with Insulin Resistance

Histological manifestations of diabetic kidney disease (DKD) include mesangiolysis, mesangial matrix expansion, mesangial cell proliferation, thickening of the glomerular basement membrane, podocyte loss, foot process effacement, and hyalinosis of the glomerular arterioles, interstitial fibrosis, and tubular atrophy. Glomerulomegaly is a typical finding. Histological features of DKD may occur in the absence of clinical manifestations, having been documented in patients with normal urinary albumin excretion and normal glomerular filtration rate. Furthermore, the histological picture progresses over time, while clinical data may remain normal. Conversely, histological lesions of DKD improve with metabolic normalization following effective pancreas transplantation. Insulin resistance has been associated with the clinical manifestations of DKD (nephromegaly, glomerular hyperfiltration, albuminuria, and kidney failure). Likewise, insulin resistance may underlie the histological manifestations of DKD. Morphological changes of DKD are absent in newly diagnosed type 1 diabetes patients (with no insulin resistance) but appear afterward when insulin resistance develops. In contrast, structural lesions of DKD are typically present before the clinical diagnosis of type 2 diabetes. Several heterogeneous conditions that share the occurrence of insulin resistance, such as aging, obesity, acromegaly, lipodystrophy, cystic fibrosis, insulin receptor dysfunction, and Alström syndrome, also share both clinical and structural manifestations of kidney disease, including glomerulomegaly and other features of DKD, focal segmental glomerulosclerosis, and C3 glomerulopathy, which might be ascribed to the reduction in the synthesis of factor H binding sites (such as heparan sulfate) that leads to uncontrolled complement activation. Alström syndrome patients show systemic interstitial fibrosis markedly similar to that present in diabetes.

Identification of metabolism genes related to hepatocarcinogenesis and progression in type 2 diabetes mellitus via co-expression networks analysis

Background

Type 2 Diabetes Mellitus (T2DM) is an independent risk factor of hepatocellular carcinoma (HCC). However, the related genes and modules to hepatocarcinogenesis and progression in T2DM remain unclear.

Methods

The microarray data from Gene Expression Omnibus (GEO) were analyzed to screen differentially expressed genes (DEGs) of T2DM and HCC dataset. Then, weighted gene co-expression network analysis (WGCNA) was performed on these DEGs to detect the modules and genes, respectively. Common genes in modules with clinical interests of T2DM and HCC were obtained and annotated via GOSemSim package and Metascape. Genes related to late-stage HCC and high glycated haemoglobin (HbA1c) were also identified. These genes were validated by UALCAN analysis and univariate cox regression based on The Cancer Genome Atlas (TCGA). Finally, another two independent datasets were applied to confirm the results of our study.

Results

A total of 1288 and 1559 DEGs of T2DM and HCC were screened, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed several shared pathways in two diseases, such as pathways in cancer and metabolism. A total of 37 common genes correlated with T2DM and HCC were then identified with WGCNA. Furthermore, 12 genes from modules associated with late-stage HCC and high HbA1c were regarded as hub genes. Among these genes, 8 genes associated with tumor invasion and metastasis were validated by UALCAN analysis. Moreover, downregulations of ACAT1, SLC2A2, PCK1 and ABAT were significantly associated with poorer prognosis in HCC patients with elevated HbA1c. Additionally, the expressions of PCK1 and ABAT were raised in HepG2 cells pre-treated with metformin and phenformin.

Conclusions

The present study confirmed several metabolic genes related to hyperglycemia and malignant tumor, which may provide not only new insights into the pathogenesis of hepatocarcinogenesis and progression in T2DM, but also novel therapeutic targets for T2DM patients with HCC in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00177-x.

In Children With Nonalcoholic Fatty Liver Disease, Zone 1 Steatosis Is Associated With Advanced Fibrosis

BACKGROUND & AIMS

Focal zone 1 steatosis, although rare in adults with nonalcoholic fatty liver disease (NAFLD), does occur in children with NAFLD. We investigated whether focal zone 1 steatosis and focal zone 3 steatosis are distinct subphenotypes of pediatric NAFLD. We aimed to determine associations between the zonality of steatosis and demographic, clinical, and histologic features in children with NAFLD.

METHODS

We performed a cross-sectional study of baseline data from 813 children (age <18 years; mean age, 12.8 ± 2.7 years). The subjects had biopsy-proven NAFLD and were enrolled in the Nonalcoholic Steatohepatitis Clinical Research Network. Liver histology was reviewed using the Nonalcoholic Steatohepatitis Clinical Research Network scoring system.

RESULTS

Zone 1 steatosis was present in 18% of children with NAFLD (n = 146) and zone 3 steatosis was present in 32% (n = 244). Children with zone 1 steatosis were significantly younger (10 vs 14 years; P < .001) and a significantly higher proportion had any fibrosis (81% vs 51%; P < .001) or advanced fibrosis (13% vs 5%; P < .001) compared with children with zone 3 steatosis. In contrast, children with zone 3 steatosis were significantly more likely to have steatohepatitis (30% vs 6% in children with zone 1 steatosis; P < .001).

CONCLUSIONS

Children with zone 1 or zone 3 distribution of steatosis have an important subphenotype of pediatric NAFLD. Children with zone 1 steatosis are more likely to have advanced fibrosis and children with zone 3 steatosis are more likely to have steatohepatitis. To achieve a comprehensive understanding of pediatric NAFLD, studies of pathophysiology, natural history, and response to treatment should account for the zonality of steatosis.

Insight gained from genome-wide interaction and enrichment analysis on weight gain during citalopram treatment

Weight gain is a possible side effect of the pharmacological antidepressant treatments. Defining antidepressant prescriptions based on personal genetic makeups would decrease the risk of weight gain and increase the quality of the current antidepressant pharmacological treatments. 643 depressed, citalopram treated individuals with available clinical and genome-wide genetic information were investigated to identify the molecular pathways associated with weight gain. 111 individuals experienced weight gain during citalopram treatment. The axon guidance (p.adjust=0.005) and the developmental biology pathway (p.adjust=0.01) were enriched in variations associated with weight gain. The developmental biology pathway includes molecular cascades involved in the regulation of beta-cell development, and the transcriptional regulation of white adipocyte differentiation. A number of variations were harbored by genes whose products are involved in the synthesis of collagen (COL4A3, COL5A1 and ITGA1), activity of the thyroid-hormones (NCOR1 and NCOR2), energy metabolism (ADIPOQ, PPARGC1A) and myogenic differentiation (CDON). A molecular pathway analysis conducted in a sample of depressed patients identified new candidate genes whose future investigation may provide insights in the molecular events that drive weight gain during antidepressant treatment.

Histopathological differences utilizing the nonalcoholic fatty liver disease activity score criteria in diabetic (type 2 diabetes mellitus) and non-diabetic patients with nonalcoholic fatty liver disease

AIM: To study clinical and histopathological features of nonalcoholic fatty liver disease (NAFLD) in patients with and without type 2 diabetes mellitus (T2DM) using updated nonalcoholic steatohepatitis clinical research network (NASH-CRN) grading system.

METHODS: We retrospectively analyzed data of 235 patients with biopsy proven NAFLD with and without T2DM. This database was utilized in the previously published study comparing ethnicity outcomes in NAFLD by the same corresponding author. The pathology database from University of Chicago was utilized for enrolling consecutive patients who met the criteria for NAFLD and their detailed clinical and histopathology findings were obtained for comparison. The relevant clinical profile of patients was collected from the Electronic Medical Records around the time of liver biopsy and the histology was read by a single well-trained histopathologist. The updated criteria for type 2 diabetes have been utilized for analysis. Background data of patients with NASH and NAFLD has been included. The mean differences were compared using χ² and t-test along with regression analysis to evaluate the predictors of NASH and advanced fibrosis.

RESULTS: Patients with NAFLD and T2DM were significantly older (49.9 vs 43.0, P < 0.01), predominantly female (71.4 vs 56.3, P < 0.02), had higher rate of metabolic syndrome (88.7 vs 36.4, P < 0.01), had significantly higher aspartate transaminase (AST)/alanine transaminase (ALT) ratio (0.94 vs 0.78, P < 0.01) and Fib-4 index (1.65 vs 1.06, P < 0.01) as markers of NASH, showed higher mean NAFLD activity score (3.5 vs 3.0, P = 0.03) and higher mean fibrosis score (1.2 vs 0.52, P < 0.01) compared to patients with NAFLD without T2DM. Furthermore, advanced fibrosis (32.5 vs 12.0, P < 0.01) and ballooning (27.3 vs 13.3, P < 0.01) was significantly higher among patients with NAFLD and T2DM compared to patients with NAFLD without T2DM. On multivariate analysis, T2DM was independently associated with NASH (OR = 3.27, 95%CI: 1.43-7.50, P < 0.01) and advanced fibrosis (OR = 3.45, 95%CI: 1.53-7.77, P < 0.01) in all patients with NAFLD. There was a higher rate of T2DM (38.1 vs 19.4, P < 0.01) and cirrhosis (8.3 vs 0.0, P = 0.01) along with significantly higher mean Bilirubin (0.71 vs 0.56, P = 0.01) and AST (54.2 vs 38.3, P < 0.01) and ALT (78.7 vs 57.0, P = 0.01) level among patients with NASH when compared to patients with steatosis alone. The mean platelet count (247 vs 283, P < 0.01) and high-density lipoprotein cholesterol level (42.7 vs 48.1, P = 0.01) was lower among patients with NASH compared to patients with steatosis.

CONCLUSION: Patients with NAFLD and T2DM tend to have more advanced stages of NAFLD, particularly advanced fibrosis and higher rate of ballooning than patients with NAFLD without T2DM.

Berberine-loaded solid lipid nanoparticles are concentrated in the liver and ameliorate hepatosteatosis in db/db mice

Berberine (BBR) shows very low plasma levels after oral administration due to its poor absorption by the gastrointestinal tract. We have previously demonstrated that BBR showed increased gastrointestinal absorption and enhanced antidiabetic effects in db/db mice after being entrapped into solid lipid nanoparticles (SLNs). However, whether BBR-loaded SLNs (BBR-SLNs) also have beneficial effects on hepatosteatosis is not clear. We investigated the effects of BBR-SLNs on lipid metabolism in the liver using histological staining and reverse transcription polymerase chain reaction analysis. The results showed that oral administration of BBR-SLNs inhibited the increase of body weight and decreased liver weight in parallel with the reduction of serum alanine transaminase and liver triglyceride levels in db/db mice. The maximum drug concentration in the liver was 20-fold higher than that in the blood. BBR-SLNs reduced fat accumulation and lipid droplet sizes significantly in the liver, as indicated by hematoxylin and eosin and Oil Red O staining. The expression of lipogenic genes, including fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD1), and sterol regulatory element-binding protein 1c (SREBP1c) were downregulated, while lipolytic gene carnitine palmitoyltransferase-1 (CPT1) was upregulated in BBR-SLN-treated livers. In summary, we have uncovered an unexpected effect of BBR-SLNs on hepatosteatosis treatment through the inhibition of lipogenesis and the induction of lipolysis in the liver of db/db mice.

The extracellular matrix and insulin resistance

The extracellular matrix (ECM) is a highly-dynamic compartment that undergoes remodeling as a result of injury and repair. Over the past decade, mounting evidence in humans and rodents suggests that ECM remodeling is associated with diet-induced insulin resistance in several metabolic tissues. In addition, integrin receptors for the ECM have also been implicated in the regulation of insulin action. This review addresses what is currently known about the ECM, integrins, and insulin action in the muscle, liver, and adipose tissue. Understanding how ECM remodeling and integrin signaling regulate insulin action may aid in the development of new therapeutic targets for the treatment of insulin resistance and type 2 diabetes (T2D).

Integrin α1-null mice exhibit improved fatty liver when fed a high fat diet despite severe hepatic insulin resistance

Hepatic insulin resistance is associated with increased collagen. Integrin α1β1 is a collagen-binding receptor expressed on hepatocytes. Here, we show that expression of the α1 subunit is increased in hepatocytes isolated from high fat (HF)-fed mice. To determine whether the integrin α1 subunit protects against impairments in hepatic glucose metabolism, we analyzed glucose tolerance and insulin sensitivity in HF-fed integrin α1-null (itga1(-/-)) and wild-type (itga1(+/+)) littermates. Using the insulin clamp, we found that insulin-stimulated hepatic glucose production was suppressed by ∼50% in HF-fed itga1(+/+) mice. In contrast, it was not suppressed in HF-fed itga1(-/-) mice, indicating severe hepatic insulin resistance. This was associated with decreased hepatic insulin signaling in HF-fed itga1(-/-) mice. Interestingly, hepatic triglyceride and diglyceride contents were normalized to chow-fed levels in HF-fed itga1(-/-) mice. This indicates that hepatic steatosis is dissociated from insulin resistance in HF-fed itga1(-/-) mice. The decrease in hepatic lipid accumulation in HF-fed itga1(-/-) mice was associated with altered free fatty acid metabolism. These studies establish a role for integrin signaling in facilitating hepatic insulin action while promoting lipid accumulation in mice challenged with a HF diet.

The biochemical and histological effects of lichens in normal and diabetic rats

Oxidative stress plays an important role in causing diabetes; however, no studies have thoroughly reported on the toxic and beneficial effects of lichen extracts in patients with diabetes mellitus (DM). This study covers a previously unrecognized effect of two well-known lichen species Cetraria islandica and Pseudevernia furfuracae in streptozotocin (STZ)-induced diabetes. In experimental design, control or diabetic rats were either untreated or treated with aqueous lichen extracts (250–500 mg/kg /day) for 2 weeks starting at 72 h after STZ injection. On day 14, animals were anaesthetized, and metabolic and biochemical parameters were appreciated between control and treatment groups. The histopathology of liver was examined using three different staining methods: hematoxylin–eosin (H&E), periodic acid Schiff (PAS), and reticulin and Sudan Black B. Our experimental data showed that increasing doses of C. islandica and P. furfuracae alone did not have any detrimental effects on studied parameters and the malondialdehyde level of liver. C. islandica extract showed positive results for antioxidant capacity compared to doses of P. furfuracae extract. However, the protective effect of C. islandica extract on diabetes-induced disorders and hepatic damages is still unclear. Moreover, unfortunately, animals subjected to DM therapy did not benefit from the usage of increasing lichen doses due to their unchanged antioxidant activity in tissues. The results obtained in present study suggested that C. islandica and P. furfuracae is safe but the power of these is limited because of intensive oxidative stress in liver of type 1 diabetic rats. It is also implied that C. islandica extract is especially suitable for different administration routes in DM animals.

Zerumbone, a Natural Cyclic Sesquiterpene of Zingiber zerumbet Smith, Attenuates Nonalcoholic Fatty Liver Disease in Hamsters Fed on High-Fat Diet

We investigated the effects of zerumbone, a natural cyclic sesquiterpene, on hepatic lipid metabolism in Syrian golden hamsters fed on high-fat diet (HFD). After being fed HFD for 2 weeks, hamsters were dosed orally with zerumbone (75, 150, and 300 mg kg(-1)) once daily for 8 weeks. After treatment with zerumbone, the plasma levels of total cholesterol (TC) and triglycerides (TGs) and the contents of TC and TG in hepatic tissue as well as homeostasis model assessment of insulin resistance were lowered, especially in the zerumbone-treated group (300 mg kg(-1)). Moreover, the histological evaluation of liver specimens demonstrated that the steatosis and inflammation in liver of zerumbone-treated groups were improved. Zerumbone exhibited the ability to decrease hepatic mRNA levels of sterol regulatory element-binding protein-1c and its lipogenic target genes, such as fatty acid synthase, acetyl-CoA carboxylase 1, and stearoyl-CoA desaturase 1. The hepatic mRNA expression of peroxisome proliferator-activated receptor α , together with its target genes including carnitine palmitoyl transferase-1, acyl-CoA oxidase, and acyl-CoA oxidase 1, was also upregulated by zerumbone. In conclusion, zerumbone improves insulin sensitivity, decreases lipogenesis, and increases lipid oxidation in the liver of HFD-fed hamsters, implying a potential application in the treatment of nonalcoholic fatty liver disease.

Fructus Xanthii attenuates hepatic steatosis in rats fed on high-fat diet

Fructus Xanthii (FX) has been widely used as a traditional herbal medicine for rhinitis, headache, cold, etc. Modern pharmacological studies revealed that FX possesses anti-inflammatory, anti-oxidative, and anti-hyperglycemic properties. The present study was designed to investigate the effects of FX on glucose and insulin tolerance, and hepatic lipid metabolism in rats fed on high-fat diet (HFD). Hepatic steatosis was induced by HFD feeding. Aqueous extraction fractions of FX or vehicle were orally administered by gavage for 6 weeks. Body weight and blood glucose were monitored. Glucose and insulin tolerance test were performed. Liver morphology was visualized by hematoxylin and eosin, and oil red O staining. Expression of liver lipogenic and lipolytic genes was measured by real-time PCR. We showed here that FX improved glucose tolerance and insulin sensitivity in HFD rats. FX significantly decreased the expression of lipogenic genes and increased the expression of lipolytic genes, ameliorated lipid accumulation and decreased the total liver triglyceride (TG) content, and thus attenuated HFD-induced hepatic steatosis. In conclusion, FX improves glucose tolerance and insulin sensitivity, decreases lipogenesis and increases lipid oxidation in the liver of HFD rats, implying a potential application in the treatment of non-alcoholic fatty liver disease.

Promising role of ferulic acid, atorvastatin and their combination in ameliorating high fat diet-induced stress in mice

AIMS

The present study evaluated a comparative and combined hepatoprotective effect of atorvastatin (AS) and ferulic acid (F) against high fat diet (HFD) induced oxidative stress in terms of hyperlipidemia, anti-oxidative status, lipid peroxidation and inflammation.

MAIN METHODS

Male Swiss albino mice were given a diet containing high fat (H) (23.9% wt/wt), supplemented with AS (10mg/kg) or F (100mg/kg) and both (10 and 100mg/kg) for 8weeks. The control mice (C) were fed with normal diet.

KEY FINDINGS

The H mice exhibited increased body weight; hyperlipidemia; serum level of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6); hepatic lipid profile; lipid accumulation; reactive oxygen species (ROS) of hepatocytes, lipid peroxidation and liver antioxidant capacity was decreased. Immunofluorescent and Western blot assay revealed activation of nuclear factor kappa B (NF-κB) signaling pathway. The addition of F or AS and both in the diet significantly counteracted HFD induced body weight gain; hyperlipidemia; TNF-α, IL-6; hepatic lipid profile; fatty infiltration; NF-κB signaling pathway; ROS; lipid peroxidation and moreover elevated levels of hepatic antioxidant enzymes activity were observed.

SIGNIFICANCE

Simultaneous treatment with AS, F and their combination protected against HFD induced weight gain and oxidative stress. The protection may be attributed to the hypolipidemic and free radical scavenging activity of AS or F and their combination. This study illustrates that AS and F have relatively similar hypolipidemic, antioxidative, anti-inflammatory actions and the AS+F combination along with HFD has shown outstanding effects as compared to other treated groups.

Validation of terminal peptide of procollagen III for the detection and assessment of nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease

Liver biopsy is the reference standard for the detection of nonalcoholic steatohepatitis (NASH) within nonalcoholic fatty liver disease (NAFLD). The aim of this study was to identify a biomarker of NASH in patients without significant fibrosis. In all, 172 patients from two centers with biopsy-proven NAFLD were included in this study. Eighty-four patients from a single center were included as a derivation cohort and 88 patients from a second center were included as a validation cohort. Serum samples were tested for candidate markers of fibrosis and inflammation alongside hematological and biochemical markers. Among patients without advanced fibrosis, terminal peptide of procollagen III (PIIINP) was the only marker found to be associated with a histological diagnosis of NASH in both cohorts. PIIINP also correlated with the total NAFLD activity score (NAS) and its constituent components (P < 0.001). Area under receiver operating characteristic curve (AUROC) for PIIINP in discriminating between NASH and simple steatosis (SS) was 0.77-0.82 in patients with F0-2 fibrosis and 0.82-0.84 in patients with F0-3 fibrosis. PIIINP was elevated in patients with advanced fibrosis, the overwhelming majority of whom had NASH. When incorporating patients with all degrees of fibrosis from both cohorts, PIIINP was able to discriminate between patients with SS and those with NASH or advanced fibrosis with AUROC 0.85-0.87.

CONCLUSION

PIIINP discriminates between SS and NASH or advanced fibrosis. The use of a single biomarker in this context will be of clinical utility in detecting the minority of patients with NAFLD who have NASH or advanced fibrosis related to NASH.

Steatosis and steatohepatitis in postmortem material from Northwestern Greece

AIM: To determine the prevalence of steatosis and steatohepatitis in a series of autopsies in Northwestern Greece.

METHODS: Liver biopsy material from a total of 600 autopsies performed over a period of 2 years (2006-2008) to define the cause of death was subjected to histological examination. Patient demographic data were also collected. Tissue sections were stained with different dyes for the evaluation of liver architecture, degree of fibrosis and other pathological conditions when necessary.

RESULTS: Satisfactory tissue samples for histological evaluation were available in 498 cases (341 male, 157 female) with a mean age of 64.51 ± 17.78 years. In total, 144 (28.9%) had normal liver histology, 156 (31.3%) had evidence of steatosis, and 198 (39.8%) had typical histological findings of steatohepatitis. The most common causes of death were ischemic heart disease with or without myocardial infarction (43.4%), and traffic accidents (13.4%).

CONCLUSION: A high prevalence of steatosis and steatohepatitis was detected in postmortem biopsies from Northwestern Greece. Since both diseases can have serious clinical consequences, they should be considered as an important threat to the health of the general population in Greece.

Inflammatory mediators and insulin resistance in obesity: role of nuclear receptor signaling in macrophages

Visceral obesity is coupled to a general low-grade chronic inflammatory state characterized by macrophage activation and inflammatory cytokine production, leading to insulin resistance (IR). The balance between proinflammatory M1 and antiinflammatory M2 macrophage phenotypes within visceral adipose tissue appears to be crucially involved in the development of obesity-associated IR and consequent metabolic abnormalities. The ligand-dependent transcription factors peroxisome proliferator activated receptors (PPARs) have recently been implicated in the determination of the M1/M2 phenotype. Liver X receptors (LXRs), which form another subgroup of the nuclear receptor superfamily, are also important regulators of proinflammatory cytokine production in macrophages. Disregulation of macrophage-mediated inflammation by PPARs and LXRs therefore underlies the development of IR. This review summarizes the role of PPAR and LXR signaling in macrophages and current knowledge about the impact of these actions in the manifestation of IR and obesity comorbidities such as liver steatosis and diabetic osteopenia.

Prevalence and risk factors for significant liver fibrosis among HIV-monoinfected patients

BACKGROUND

HIV-monoinfected patients may be at risk for significant liver fibrosis, but its prevalence and determinants in these patients are unknown. Since HIV-monoinfected patients do not routinely undergo liver biopsy, we evaluated the prevalence and risk factors of significant hepatic fibrosis in this group using the aspartate aminotransferase (AST)-to-platelet ratio index (APRI).

METHODS

We conducted a cross-sectional study among HIV-infected patients negative for hepatitis B surface antigen and hepatitis C antibody in the Penn Center for AIDS Research Adult/Adolescent Database. Clinical and laboratory data were collected from the database at enrollment. Hypothesized determinants of significant fibrosis were modifiable risk factors associated with liver disease progression, hepatic fibrosis, or hepatotoxicity, including immune dysfunction (i.e., CD4 T lymphocyte count <200 cells/mm(3), HIV viremia), diseases associated with hepatic steatosis (e.g., obesity, diabetes mellitus), and use of antiretroviral therapy. The primary outcome was an APRI score >1.5, which suggests significant hepatic fibrosis. Multivariable logistic regression identified independent risk factors for significant fibrosis by APRI.

RESULTS

Among 432 HIV-monoinfected patients enrolled in the CFAR Database between November 1999 and May 2008, significant fibrosis by APRI was identified in 36 (8.3%; 95% CI, 5.9-11.4%) patients. After controlling for all other hypothesized risk factors as well as active alcohol use and site, detectable HIV viremia (adjusted OR, 2.56; 95% CI, 1.02-8.87) and diabetes mellitus (adjusted OR, 3.15; 95% CI, 1.12-10.10) remained associated with significant fibrosis by APRI.

CONCLUSIONS

Significant fibrosis by APRI score was found in 8% of HIV-monoinfected patients. Detectable HIV viremia and diabetes mellitus were associated with significant fibrosis. Future studies should explore mechanisms for fibrosis in HIV-monoinfected patients.

Kupffer cell activation is a causal factor for hepatic insulin resistance

Recruited adipose tissue macrophages contribute to chronic and low-grade inflammation causing insulin resistance in obesity. Similarly, we hypothesized here that Kupffer cells, the hepatic resident macrophages, play a pathogenic role in hepatic insulin resistance induced by a high-fat diet. Mice were fed a normal diet or high-fat diet for 3 days. Kupffer cell activation was evaluated by immunohistochemistry and quantitative RT-PCR. Insulin sensitivity was assessed in vivo by hyperinsulinemic-euglycemic clamp and insulin-activated signaling was investigated by Western blot. Liposome-encapsulated clodronate was injected intravenously to deplete macrophages prior to a short-term exposure to high-fat diet. Here, we characterized a short-term high-fat diet model in mice and demonstrated early hepatic insulin resistance and steatosis concurrent with Kupffer cell activation. We demonstrated that selective Kupffer cell depletion obtained by intravenous clodronate, without affecting adipose tissue macrophages, was sufficient to enhance insulin-dependent insulin signaling and significantly improve hepatic insulin sensitivity in vivo in this short-term high-fat diet model. Our study clearly shows that hepatic macrophage response participates to the onset of high-fat diet-induced hepatic insulin resistance and may therefore represent an attractive target for prevention and treatment of diet- and obesity-induced insulin resistance.

Change in plasma acylation stimulating protein during euglycaemic-hyperinsulinaemic clamp in overweight and obese postmenopausal women: a MONET study

OBJECTIVE

Acylation-stimulating protein (ASP) has been shown to positively stimulate fatty acid esterification and glucose uptake in adipocytes. In vitro studies demonstrate that insulin stimulates ASP secretion from adipocytes. Individuals with obesity and/or metabolic disturbances (insulin resistance and type 2 diabetes) have increased plasma ASP.

DESIGN

The present study was designed to evaluate whether ASP levels are influenced by the metabolic profiles of overweight and obese postmenopausal women during a euglycaemic/hyperinsulinaemic clamp (EHC). Patients The study population consisted of 76 overweight and obese sedentary postmenopausal women.

MEASUREMENTS

We evaluated insulin sensitivity, plasma ASP levels, body composition including visceral adipose tissue area, blood lipid profiles, liver enzymes, peak aerobic capacity, resting metabolic rate (RMR) and total energy expenditure (TEE).

RESULTS

We observed wide interindividual variations of ASP levels during the EHC. Therefore, subjects were divided into three groups based on ASP changes. Negative ASP Responders (NAR; n = 24) showed a -20% or greater decrease in ASP levels while Positive ASP Responders (PAR; n = 42) displayed ASP fluctuations superior to +20%. Ten subjects had little or no ASP change and were considered as Zero ASP responders (ZAR). PAR women displayed a worse metabolic profile than NAR women, including higher BMI, visceral adipose tissue, fasting insulin levels, lean body mass, and alanine aminotransferase (ALT), a marker of impaired liver function. After adjustment for BMI, only ALT remained significantly different, while lean body mass (P = 0.08) and visceral adipose tissue (P = 0.07) remained marginally higher. Correlation analysis of all subjects demonstrated that fasting ASP levels correlated positively with albumin and VO(2 peak) and this association remained significant after adjustments for the effect of BMI. In addition, the percentage maximal change in ASP levels during the EHC was positively associated with BMI, lean body mass, visceral adipose tissue, fasting insulin, HOMA, TEE, RMR, ALT and AST.

CONCLUSION

Overall these results suggest that an elevated ASP response during the EHC is associated with metabolic disturbances in overweight and obese postmenopausal women.

Risk factors and mechanisms of non-alcoholic steatohepatitis

The worldwide proportion of overweight and obese individuals has increased yearly for more than a decade. Along with rates of obesity, the incidence of co-morbid conditions such as type 2 diabetes, cardiovascular disease and liver disease has also increased. The form of liver disease associated with obesity is termed non-alcoholic steatohepatitis (NASH) due to the histological similarities to livers of chronic alcoholics. NASH has been observed in adult as well as pediatric populations; however, the etiology of this disease is still unknown. This review outlines some of the risk factors commonly associated with NASH and describes molecular mechanisms proposed to underlie disease pathogenesis.

High-fat diet: a trigger of non-alcoholic steatohepatitis? Preliminary findings in obese subjects

OBJECTIVE

We correlated dietary profile and markers of visceral and somatic obesities in non-alcoholic fatty liver disease.

METHODS

Patients with histologically proven fatty infiltration of the liver (n = 25, 52 +/- 11 y of age, 64% women) underwent abdominal computed tomography, bioelectrical impedance, and anthropometric measurements. Insulin resistance was evaluated (homeostasis model assessment) and dietary intake of macronutrients was estimated by 24-h recall. Main outcome measurements were correlation of carbohydrate and fat ingestion with liver histology.

RESULTS

Metabolic syndrome was present in 72% of the population, and increased waist circumference and low high-density lipoprotein cholesterol occurred in 66%. Total body fat (bioimpedance) and dietary intake of lipids were higher in patients with non-alcoholic steatohepatitis (P < 0.05), but not in diabetic subjects who exhibited more steatosis than non-alcoholic steatohepatitis. Waist circumference exhibited a good correlation with homeostasis model assessment, total energy intake, and ingestion of specific fatty acids. Body mass index correlated well with somatic and visceral adiposities.

CONCLUSION

Energy intake and visceral adiposity were predisposing factors for fatty liver disease. Lipid input correlated with non-alcoholic steatohepatitis in the entire group and after stratification for diabetes. These findings suggest that lipid intake may play a greater role in non-alcoholic steatohepatitis than hitherto suspected.