Are Vaspin and Omentin-1 Related to Insulin Resistance, Blood Pressure and Inflammation in NAFLD Patients?

Underlying Mechanisms behind the Brain-Gut-Liver Axis and Metabolic-Associated Fatty Liver Disease (MAFLD): An Update

Metabolic-associated fatty liver disease (MAFLD) includes several metabolic dysfunctions caused by dysregulation in the brain-gut-liver axis and, consequently, increases cardiovascular risks and fatty liver dysfunction. In MAFLD, type 2 diabetes mellitus, obesity, and metabolic syndrome are frequently present; these conditions are related to liver lipogenesis and systemic inflammation. This study aimed to review the connection between the brain-gut-liver axis and MAFLD. The inflammatory process, cellular alterations in hepatocytes and stellate cells, hypercaloric diet, and sedentarism aggravate the prognosis of patients with MAFLD. Thus, to understand the modulation of the physiopathology of MAFLD, it is necessary to include the organokines involved in this process (adipokines, myokines, osteokines, and hepatokines) and their clinical relevance to project future perspectives of this condition and bring to light new possibilities in therapeutic approaches. Adipokines are responsible for the activation of distinct cellular signaling in different tissues, such as insulin and pro-inflammatory cytokines, which is important for balancing substances to avoid MAFLD and its progression. Myokines improve the quantity and quality of adipose tissues, contributing to avoiding the development of MAFLD. Finally, hepatokines are decisive in improving or not improving the progression of this disease through the regulation of pro-inflammatory and anti-inflammatory organokines.

Association of Serum Vaspin Concentration with Metabolic Disorders in Obese Individuals

Vaspin, a molecule produced in visceral adipose tissue, seems to participate in the pathogenesis of metabolic disorders. The study aimed to determine the association of vaspin concentration with metabolic disorders in obese individuals. Forty obese patients and twenty normal-weight subjects underwent biochemical (fasting glucose, insulin, lipid profile, interleukin-6, hs-CRP, vaspin concentration), blood pressure, and anthropometric measurements. The HOMA-IR index was calculated. Serum vaspin concentrations in the obese group were significantly higher than in the control group (0.82 ± 0.62 vs. 0.43 ± 0.59; p < 0.001). Among the entire population, vaspin concentration was positively correlated with body weight, BMI, WHR, and the percentage and mass of adipose tissue. Positive correlations between vaspin concentration and triglyceride level, insulin concentration, and HOMA-IR value were found. Vaspin concentration was positively correlated with hs-CRP and IL-6 levels. In obese patients, positive correlations between vaspin concentration and the percentage of adipose tissue and hs-CRP level were demonstrated. Logistic regression analysis showed that increased BMI was the biggest factor stimulating vaspin concentrations (OR = 8.5; 95% CI: 1.18–61.35; p = 0.0338). An elevated vaspin level may imply its compensatory role against metabolic disorders in obese patients. Thus, vaspin appears to be a useful diagnostic parameter for new therapeutic approaches in obesity-related complications. Nevertheless, due to the small sample size, further studies are needed to confirm our results.

Adipose tissue function and insulin sensitivity in syndromic obesity of Bardet-Biedl syndrome

BACKGROUND

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive syndromic obesity of childhood onset among many other features. To date, the excess risk of metabolic complications of severe early-onset obesity in BBS remains controversial. In-depth investigation of adipose tissue structure and function with detailed metabolic phenotype has not been investigated yet.

OBJECTIVE

To investigate adipose tissue function in BBS.

DESIGN

A prospective cross-sectional study.

MAIN OUTCOME MEASURE

To determine if there are differences in insulin resistance, metabolic profile, adipose tissue function and gene expression in patients with BBS compared to BMI-matched polygenic obese controls.

METHOD

9 adults with BBS and 10 controls were recruited from the national centre for BBS, Birmingham, UK. An in-depth study of adipose tissue structure and function along with insulin sensitivity was performed using hyperinsulinemic-euglycemic clamp studies, adipose tissue microdialysis, histology and RNA sequencing, and measurement of circulating adipokines and inflammatory biomarkers.

RESULTS

Adipose tissue structure, gene expression and in vivo functional analysis between BBS and polygenic obesity cohorts were similar. Using hyperinsulinemic-euglycemic clamp and surrogate markers of insulin resistance, we found no significant differences in insulin sensitivity between BBS and obese controls. Furthermore, no significant changes were noted in an array of adipokines, cytokines, pro-inflammatory markers and adipose tissue RNA transcriptomic.

CONCLUSION

Although childhood-onset extreme obesity is a feature of BBS, detailed studies of insulin sensitivity and adipose tissue structure and function are similar to common polygenic obesity. This study adds to the literature by suggesting that it is the quality and quantity of adiposity not the duration that drives the metabolic phenotype.

Association of Serum Omentin-1 Concentration with the Content of Adipose Tissue and Glucose Tolerance in Subjects with Central Obesity

Omentin is one of the few adipokines with potentially beneficial metabolic effects. The main aim of this study was to determine the association between serum omentin-1 levels and the occurrence of central obesity and abnormal glucose tolerance, taking into account gender. The study involved 88 participants aged 30-60, including 47 women and 41 men. Two subgroups among the obese subjects were distinguished-those with normal and abnormal glucose tolerance. Anthropometric and biochemical examinations and blood pressure measurements were performed. Omentin-1 concentrations were significantly lower among patients with obesity compared to those without obesity (p = 0.027) and, similarly, comparing men with abnormal glucose tolerance with men with normal glucose tolerance (p = 0.035). In contrast, no such pattern was observed in women. The multivariable regression model showed a significant effect of gender status and important factors of tissue insulin sensitivity, such as OGGT results, WHR and amount of body fat, on the variability of serum omentin-1 concentration in the entire study population (R²adj. = 13.7%; p = 0.003). High omentin-1 levels found in men with obesity and normal glucose tolerance suggest that omentin-1 protects against metabolic disorders associated with obesity in the male population.

Adipokines in Non-Alcoholic Fatty Liver Disease: Are We on the Road toward New Biomarkers and Therapeutic Targets?

Simple Summary

Non-alcoholic fatty liver disease (NAFLD) is an unmet medical need due to its increasingly high incidence, severe clinical consequences, and the absence of feasible diagnostic tools and effective drugs. This review summarizes the preclinical and clinical data on adipokines, cytokine-like hormones secreted by adipose tissue, and NAFLD. The aim is to establish the potential of adipokines as diagnostic and prognostic biomarkers, as well as their potential as therapeutic targets for NAFLD. The limitations of current research are also discussed, and future perspectives are outlined.

Abstract

Non-alcoholic fatty liver disease (NAFLD) has become the major cause of chronic hepatic illness and the leading indication for liver transplantation in the future decades. NAFLD is also commonly associated with other high-incident non-communicable diseases, such as cardiovascular complications, type 2 diabetes, and chronic kidney disease. Aggravating the socio-economic impact of this complex pathology, routinely feasible diagnostic methodologies and effective drugs for NAFLD management are unavailable. The pathophysiology of NAFLD, recently defined as metabolic associated fatty liver disease (MAFLD), is correlated with abnormal adipose tissue–liver axis communication because obesity-associated white adipose tissue (WAT) inflammation and metabolic dysfunction prompt hepatic insulin resistance (IR), lipid accumulation (steatosis), non-alcoholic steatohepatitis (NASH), and fibrosis. Accumulating evidence links adipokines, cytokine-like hormones secreted by adipose tissue that have immunometabolic activity, with NAFLD pathogenesis and progression; however, much uncertainty still exists. Here, the current knowledge on the roles of leptin, adiponectin, ghrelin, resistin, retinol-binding protein 4 (RBP4), visfatin, chemerin, and adipocyte fatty-acid-binding protein (AFABP) in NAFLD, taken from preclinical to clinical studies, is overviewed. The effect of therapeutic interventions on adipokines’ circulating levels are also covered. Finally, future directions to address the potential of adipokines as therapeutic targets and disease biomarkers for NAFLD are discussed.

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

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

Chronic Inflammation—A Link between Nonalcoholic Fatty Liver Disease (NAFLD) and Dysfunctional Adipose Tissue

Nonalcoholic fatty liver disease (NAFLD) is a new challenge in modern medicine, due to its high prevalence in the world. The pathogenesis of NAFLD is a complex dysmetabolic process, following the “multiple-hit” hypothesis that involves hepatocytes excessive accumulation of triglycerides, insulin resistance (IR), increased oxidative stress, chronic low-grade inflammatory response and lipotoxicity. In this review, we provide an overview of the interrelation of these processes, the link between systemic and local inflammation and the role of dysfunctional adipose tissue (AT) in the NAFLD development. Multiple extrahepatic triggers of the pathophysiological mechanisms of NAFLD are described: nutritional deficiency or malnutrition, unhealthy food intake, the dysfunction of the liver–gut axis, the involvement of the mesenteric adipose tissue, the role of adipokines such as adiponectin, of food intake hormone, the leptin and leptin resistance (LR) and adipose tissue’s hormone, the resistin. In addition, a wide range of intrahepatic players are involved: oxidative stress, fatty acid oxidation, endoplasmic reticulum stress, mitochondrial dysfunction, resident macrophages (Kupffer cells), neutrophils, dendritic cells (DCs), B and T lymphocytes contributing to the potential evolution of NAFLD to nonalcoholic steatohepatitis (NASH). This interdependent approach to complex dysmetabolic imbalance in NAFLD, integrating relevant studies, could contribute to a better clarification of pathogenesis and consequently the development of new personalized treatments, targeting de novo lipogenesis, chronic inflammation and fibrosis. Further studies are needed to focus not only on treatment, but also on prevention strategy in NAFLD.

Vaspin attenuates steatosis-induced fibrosis via GRP78 receptor by targeting AMPK signaling pathway

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease that is rapidly becoming a public health problem. An imbalance in lipid distribution to the hepatocytes and metabolism causes hepatocyte steatosis. Vaspin is a newly discovered adipokine that has been linked to a variety of metabolic disorders. The effects of vaspin on steatosis and fibrosis pathogenesis and related mechanisms are unclear. Thus, this study investigated the molecular mechanism of vaspin on hepatocyte steatosis and fibrosis. HepG2 cells were treated with 1.2 mM free fatty acid and the intracellular lipid values were measured by flow cytometry and Nile red assay. RT-qPCR was used to assess the effect of vaspin and blocking of the GRP78 receptor on the expression of lipogenesis, oxidation, uptake, and secretion of fatty acid (FA), as well as AMPK activity. In co-cultured HepG2 and LX-2 cell lines, the expression of main proteins of hepatocyte fibrosis was analyzed using Western blot analysis. In the HepG2 cell line, we discovered that vaspin increased oxidation, FA secretion and gene expression, and AMPK activity and decreased lipogenesis and FA uptake and gene expression. Western blot analysis in co-cultured HepG2 and LX-2 cell lines showed that α-SMA and TGF-β1 protein expression decreased. The data demonstrated that vaspin acts as a novel regulator of hepatocyte steatosis through the GRP78 receptor, effectively reducing hepatocyte fibrosis through AMPK activation and decreasing NF-κB gene expression.

The relation of omentin gene expression and glucose homeostasis of visceral and subcutaneous adipose tissues in non-diabetic adults

BACKGROUND

Adipose tissue (AT) is a passive reservoir for energy storage and an active endocrine organ responsible for synthesizing bioactive molecules called adipokines. Omentin is known as an anti-inflammatory adipokine that can modulate insulin sensitivity. The present study aimed to investigate the relationship between omentin mRNA expression and glucose homeostasis of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in non-diabetic adults.

METHODS

VAT and SAT adipose tissues were collected from 137 adults aged ≥ 18 years hospitalized for abdominal surgery. Before surgery, preoperative blood samples were taken from the participants to measure fasting plasma glucose, insulin, and triglyceride. BMI, HOMA-IR, HOMA-B, and QUICKI were calculated. Insulin levels were measured with Mercodia kits using enzyme-linked immunosorbent assay (ELISA). In order to obtain omentin mRNA expression, real-time PCR was performed.

RESULTS

Overall, 91 (66.4%) subjects were healthy [without insulin resistance (IR)], and 46 (33.6%) participants were with IR. In healthy and IR subjects, omentin gene expression was 1.04 and 2.32, respectively in VAT, and 3.06 and 1.30, respectively, in SAT (P > 0.05). After controlling for age and BMI, linear regression analysis indicated a significant positive association of SAT omentin expression with insulin concentration (β = 0.048; 95% CI 0.009, 0.088, P = 0.017) and HOMA-IR (β = 0.173; 95% CI 0.023, 0.323, P = 0.014). Moreover, a negative association of SAT omentin expression with HOMA-B (β = - 0.001; 95% CI 0.002, - 0.001, P < 0.001) was observed.

CONCLUSION

This study's finding confirms a direct association between IR with omentin mRNA levels in SAT. Besides, the indicator of insulin sensitivity had an inverse association with omentin gene expression in SAT. This aspect of research suggests that omentin secretion from SAT has a strong link with insulin regulation.

High-Intensity Interval Training Does Not Change Vaspin and Omentin and Does Not Reduce Visceral Adipose Tissue in Obese Rats

This study aimed to determine the expression of omentin and vaspin, inflammatory markers, body composition, and lipid profile in diet-induced obese rats and high-intensity interval training (HIIT). Forty Wistar rats were divided into four groups: untrained normal diet, trained normal diet (T-ND), untrained high-fat diet (Unt-HFD), and trained high-fat diet (T-HFD). For the animals of the Unt-HFD and T-HFD groups, a high-fat diet was offered for 4 weeks. After that, all the animals in the T-ND and T-HFD groups were submitted to HITT, three times per week, for 10 weeks (2 weeks of adaptation and 8 weeks of HIIT). Muscle (gastrocnemius), liver, epididymal adipose tissue, retroperitoneal adipose tissue, visceral adipose tissue (VAT), and serum were collected to analyze TNF-α, IL-6, PCR, IL-8, IL-10, IL-4, vaspin, and omentin. A body composition analysis was performed before adaptation to HIIT protocol and after the last exercise session using dual-energy X-ray absorptiometry. Omentin and vaspin in the VAT were quantified using Western blotting. The results showed that, when fed a high-fat diet, the animals obtained significant gains in body fat and elevated serum concentrations of vaspin and blood triglycerides. The HIIT was able to minimize body fat gain but did not reduce visceral fat despite the increase in maximum exercise capacity. Moreover, there was a reduction in the serum levels of adiponectin, IL-6, and IL-10. Finally, we concluded that, although the training protocol was able to slow down the weight gain of the animals, there was no reduction in visceral fat or an improvement in the inflammatory profile, including no changes in omentin and vaspin.

Association of vaspin rs2236242 gene polymorphism with serum vaspin level, insulin resistance and diabetes in an Iranian diabetic/pre-diabetic population

BACKGROUND

In recent years, the role of vaspin as an insulin-sensitizer has been studied widely. This is the investigation that examined the association of vaspin polymorphism rs2236242 on the vaspin level and the risk of type 2 diabetes and insulin-resistant Iranian pre-diabetic/diabetic population.

METHODS

A case-control study was conducted on 160 participants includes 80 participants holding (FBG) fasting blood glucose 3.88-5.55 (mmol/L) in the normal group, and 80 participants holding FBG≥5.55 (mmol/L) in a diabetic/pre-diabetic group. The serum vaspin and insulin were determined with ELISA (enzyme-linked assay) and biochemical variables by standard method. Tetra arms amplification system for the vaspin gene was performed. Statistical analysis was done using SPSS software version 20.

RESULTS

The means of age, body mass index (BMI), waist circumference (WC), hip circumference (HC), FBG, and vaspin were significantly different between normal and type 2 diabetic/impaired fasting blood group (P-value<0.05). rs2236242 showed association with Hip circumference (P-value<0.05). A significant association between allele A of rs2236242 with type 2 diabetes was seen (P-value<0.001). The vaspin levels showed a negative correlation with FBG (r =-0.296, P=0.001).

CONCLUSIONS

Allele A of rs2236242 is a protective risk for type 2 diabetes, but no association of rs2236242 with insulin resistance was seen. The lower level of vaspin is a predictor for the progression of type 2 diabetes.

[Changes in serum levels of adipokine after treatment in children with Kawasaki disease]

OBJECTIVE

To study the changes in the serum levels of Chemerin and Omentin-1 in children with Kawasaki disease (KD) in the acute stage after intravenous immunoglobulin (IVIG) treatment and related clinical significance.

METHODS

A total of 60 children who were diagnosed with KD from January 2015 to April 2019 were enrolled as subjects. Forty healthy children and 40 children with acute infectious diseases were enrolled as the healthy control group and the infection control group respectively. According to the sensitivity to IVIG treatment, the children with KD were divided into an IVIG sensitive group with 51 children and a non-IVIG sensitive group with 9 children. According to the presence or absence of coronary artery lesion, the children with KD were divided into a CAL group with 13 children and a non-CAL group with 47 children. ELISA was used to measure the serum levels of Omentin-1 and Chemerin before and after the treatment.

RESULTS

The children with KD had significantly higher serum levels of Chemerin and Omentin-1 than the healthy control and infection control groups before treatment (P<0.05). After 48 hours of treatment, the IVIG sensitive group had a significant reduction in the serum level of Chemerin (P<0.05), while there was no significant change in the serum level of Omentin-1 after treatment (P>0.05). Before treatment, the non-IVIG sensitive group had a significantly higher serum level of Chemerin than the IVIG sensitive group (P<0.05), and the CAL group had a significantly higher serum level of Chemerin than the non-CAL group, while there was no significant difference in the serum level of Omentin-1 between the IVIG sensitive and non-IVIG sensitive groups, as well as between the CAL and non-CAL groups (P>0.05).

CONCLUSIONS

High serum levels of Chemerin and Omentin-1 may play an important role in the development and progression of KD. Chemerin may be involved in the development of CAL in children with KD. The serum level of Chemerin may be used as a new index for predicting the sensitivity to IVIG treatment.

Pentoxifylline with metformin treatment improves biochemical parameters in patients with nonalcoholic steatohepatitis

Background

The progression of the nonalcoholic fatty liver disease to nonalcoholic steatohepatitis (NASH) is multifactorial, and there is still a lack of approved medications for its treatment. The study aimed to evaluate the impact of combined treatment with Pentoxifylline and Metformin on biochemical parameters in patients with Nash. Setting: Outpatient hepatology clinic.

Methods

A prospective trial was conducted. The first cohort included patients with biopsy-proven Nash, while the second cohort consisted of patients with biopsy-confirmed NAFLD. Blood tests were checked at baseline and every three months. Pentoxifylline at a dosage of 400 mg t.i.d. and Metformin at the dosage of 500 mg t.i.d. were introduced for six months in Nash group. The impact of the treatment was assessed based on biochemical results after combined treatment with low-cost medications.

Results

All 33 Nash patients completed 24 weeks of treatment. We observed significant improvement (p<0.05) of median values after treatment for the following parameters: serum uric acid levels decreased by 51.0 mmol/L, calcium decreased for 0.27 mmoL/L, magnesium showed an increase of 0.11 mmoL/L. Insulin resistance improved as a reduction of HOMA - IR by 1.3 was detected. A significant decrease of median in liver enzymes, alanine aminotransferase, aspartate aminotransferase and gamma-glutamyltransferase by 24.0 U/L, 9.1 U/L, 10.8 U/L respectively, was noted.

Conclusions

Pentoxifylline and Metformin may provide possible treatment option in Nash. Some new potential benefit of the therapy in improving liver function whilst decreasing cardiovascular risk was perceived.

Predictive Values of Serum Uric Acid and Alanine-aminotransferase for Fatty Liver Index in Montenegrin Population

Background

Alanine-aminotransferase (ALT) and uric acid cut-off levels used in non-alcoholic fatty liver disease (NAFLD) diagnosis are advised to be lowered. Due to contradictory results on the utility of both these biomarkers for NAFLD screening, we aimed to determine their cut-off levels that can be applied to Montenegrin population with the fatty liver disease.

Methods

A total of 771 volunteers were enrolled. A fatty liver index (FLI) score ≥60 was used as proxy of NAFLD. The receiver operating characteristic curve analysis with the area under the curve (AUC) was used to determine the cut-off values of ALT and uric acid associated with FLI ≥60.

Results

ALT was independent predictor of FLI in both men and women, whereas serum uric acid was its independent predictor only in women. Lower cut-off levels of ALT are associated with the increased prevalence of NAFLD [i.e., ALT was 19 IU/L (AUC=0.746, sensitivity 63%, specificity 72%, P<0.001) in women and 22 IU/L (AUC=0.804, sensitivity 61%, specificity 95%, P<0.001) in men]. The cut-off value for uric acid was 274 μmol/L (AUC=0.821, sensitivity 68%, specificity 82%, P<0.001) in women.

Conclusions

Lower cut-off levels of ALT in both genders, and serum uric acid in females, can be reliable predictors of the FLI.

Inflammatory Potential of Diet: Association With Chemerin, Omentin, Lipopolysaccharide-Binding Protein, and Insulin Resistance in the Apparently Healthy Obese

OBJECTIVE

Low-grade inflammation is a characteristic of various conditions, including obesity. Diet is regarded as a strong modifier of inflammation. The potential links between inflammatory properties of diet and adipokines as well as insulin resistance (IR) warrant further investigation. Therefore, this study aimed to examine the associations of the dietary inflammatory index (DII) with serum chemerin, omentin, and lipopolysaccharide-binding protein (LBP) as well as IR among apparently healthy obese adults.

DESIGN

In this cross-sectional study, 171 abdominally obese subjects were recruited in the northwest of Iran. Demographic data, dietary intake, anthropometric indices, and physical activity (PA) were assessed. DII scores were calculated based on dietary intake, using a validated 168-item food frequency questionnaire (FFQ). Basal blood samples were collected to determine the biochemical parameters. A linear regression test with adjusted beta estimates was applied for data analysis.

RESULT

Compared to those with higher DII score, the group with lower DII score (anti-inflammatory diet) had higher protein (83.62 ± 36.42 g vs. 71.61 ± 25.94 g) and lower carbohydrate (325.00 ± 125.76 g vs. 378.19 ± 137.69 g) intake. Participants with higher DII score had lower consumption of polyunsaturated and monounsaturated fats as well as fiber and higher saturated fats (p < .001). Those with elevated DII score had higher levels of chemerin (p = .034) and LBP (p = .040), compared to those with lower DII. Omentin showed no significant differences between groups with different DII scores. Additionally, people with a more proinflammatory diet had higher FBS (p = .005); however, other markers of IR did not differ by DII scores.

CONCLUSIONS

The results suggest that increased inflammatory potential of diet, as indicated by higher DII score, is associated with elevated levels of chemerin and LBP. While DII was positively associated with FBS, no significant correlation was found for insulin and other indices of IR.