Low brown adipose tissue activity linked to NAFLD

A newly identified compound activating UCP1 inhibits obesity and its related metabolic disorders

OBJECTIVE

Promoting thermogenesis in adipose tissue has been a promising strategy against obesity and related metabolic complications. We aimed to identify compounds that promote thermogenesis in adipocytes and to elucidate their functions and roles in metabolism.

METHODS

To identify compounds that directly promote thermogenesis from a structurally diverse set of 4800 compounds, we utilized a cell-based platform for high-throughput screening that induces uncoupling protein 1 (Ucp1) expression in adipocytes.

RESULTS

We identified one candidate compound that activates UCP1. Additional characterization of this compound revealed that it induced cellular thermogenesis in adipocytes with negligible cytotoxicity. In a subsequent diet-induced obesity model, mice treated with this compound exhibited a slower rate of weight gain, improved insulin sensitivity, and increased energy expenditure. Mechanistic studies have revealed that this compound increases mitochondrial biogenesis by elevating maximal respiration, which is partly mediated by the protein kinase A (PKA)-p38 mitogen-activated protein kinase (MAPK) signaling pathway. A further comprehensive genetic analysis of adipocytes treated with these compounds identified two novel UCP1-dependent thermogenic genes, potassium voltage-gated channel subfamily C member 2 (Kcnc2) and predicted gene 5627 (Gm5627).

CONCLUSIONS

The identified compound can serve as a potential therapeutic drug for the treatment of obesity and its related metabolic disorders. Furthermore, our newly clarified thermogenic genes play an important role in UCP1-dependent thermogenesis in adipocytes.

Effects of oleoylethanolamide supplementation on the expression of lipid metabolism-related genes and serum NRG4 levels in patients with non-alcoholic fatty liver disease: A randomized controlled trial

BACKGROUND

This study investigated the effects of oleoylethanolamide (OEA) supplementation on the expression levels of SIRT1, AMPK, PGC-1α, PPAR-γ, CEBP-α and CEBP-β genes and serum neuregulin 4 (NRG4) levels in patients with non-alcoholic fatty liver diseases (NAFLD).

METHODS

Sixty obese patients with NAFLD were equally allocated into either OEA or placebo group for 12 weeks. The mRNA expression levels of genes were determined using the reverse transcription polymerase chain reaction (RT-PCR) technique. Serum NRG4 level was also assessed using an enzyme-linked immunosorbent assay (ELISA) kit.

RESULTS

At the endpoint, mRNA expression levels of SIRT1(p = 0.001), PGC-1α (p = 0.011) and AMPK (p = 0.019) were significantly higher in the OEA group compared to placebo group. However, no significant differences were observed in the expression levels of PPAR-γ, CEBP-α and CEBP-β between the two groups. Serum NRG4 levels significantly increased in the OEA group compared with the placebo group after controlling for confounders (p = 0.027). In the OEA group, significant relationships were found between percent of changes in the expression levels of the SIRT1, AMPK and PGC-1α as well as serum NRG4 level with percent of changes in some anthropometric measures. Moreover, in the intervention group, percent of changes in high-density lipoprotein cholesterol was positively correlated with percent of changes in the expression levels of the SIRT1 and AMPK. While, percent of changes in triglyceride was inversely correlated with percent of changes in the expression levels of SIRT1.

CONCLUSION

OEA could beneficially affect expression levels of some lipid metabolism-related genes and serum NRG4 level. "REGISTERED UNDER IRANIAN REGISTRY OF CLINICAL TRIALS IDENTIFIER NO: IRCT20090609002017N32".

Sex, Nutrition, and NAFLD: Relevance of Environmental Pollution

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease and represents an increasing public health issue given the limited treatment options and its association with several other metabolic and inflammatory disorders. The epidemic, still growing prevalence of NAFLD worldwide cannot be merely explained by changes in diet and lifestyle that occurred in the last few decades, nor from their association with genetic and epigenetic risk factors. It is conceivable that environmental pollutants, which act as endocrine and metabolic disruptors, may contribute to the spreading of this pathology due to their ability to enter the food chain and be ingested through contaminated food and water. Given the strict interplay between nutrients and the regulation of hepatic metabolism and reproductive functions in females, pollutant-induced metabolic dysfunctions may be of particular relevance for the female liver, dampening sex differences in NAFLD prevalence. Dietary intake of environmental pollutants can be particularly detrimental during gestation, when endocrine-disrupting chemicals may interfere with the programming of liver metabolism, accounting for the developmental origin of NAFLD in offspring. This review summarizes cause-effect evidence between environmental pollutants and increased incidence of NAFLD and emphasizes the need for further studies in this field.

Imaging Brown Adipose Tissue with TSPO PET Tracers in Preclinical Animal Studies

Brown adipose tissue (BAT) is closely associated with thermogenesis and related to numerous diseases, including type 2 diabetes, nonalcoholic fatty liver disease (NAFLD), and obesity. Using molecular imaging technologies to monitor BAT could facilitate etiology elucidation, disease diagnosis, and therapeutics development. Translocator protein (TSPO), an 18 kDa protein that mainly locates on the outer mitochondrial membrane, has been proven as a promising biomarker for monitoring BAT mass. Here, we lay out the steps for imaging BAT with TSPO PET tracer [¹⁸F]-DPA in mouse studies.

GLP-1 RAs and SGLT-2 Inhibitors for Insulin Resistance in Nonalcoholic Fatty Liver Disease: Systematic Review and Network Meta-Analysis

OBJECTIVE

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and sodium-glucose cotransporter-2 (SGLT-2) inhibitors reduce glycaemia and weight and improve insulin resistance (IR) via different mechanisms. We aim to evaluate and compare the ability of GLP-1 RAs and SGLT-2 inhibitors to ameliorate the IR of nonalcoholic fatty liver disease (NAFLD) patients.

DATA SYNTHESIS

Three electronic databases (Medline, Embase, PubMed) were searched from inception until March 2021. We selected randomized controlled trials comparing GLP-1 RAs and SGLT-2 inhibitors with control in adult NAFLD patients with or without T2DM. Network meta-analyses were performed using fixed and random effect models, and the mean difference (MD) with corresponding 95% confidence intervals (CI) were determined. The within-study risk of bias was assessed with the Cochrane collaborative risk assessment tool RoB.

RESULTS

25 studies with 1595 patients were included in this network meta-analysis. Among them, there were 448 patients, in 6 studies, who were not comorbid with T2DM. Following a mean treatment duration of 28.86 weeks, compared with the control group, GLP-1 RAs decreased the HOMA-IR (MD [95%CI]; -1.573[-2.523 to -0.495]), visceral fat (-0.637[-0.992 to -0.284]), weight (-2.394[-4.625 to -0.164]), fasting blood sugar (-0.662[-1.377 to -0.021]) and triglyceride (- 0.610[-1.056 to -0.188]). On the basis of existing studies, SGLT-2 inhibitors showed no statistically significant improvement in the above indicators. Compared with SGLT-2 inhibitors, GLP-1 RAs decreased visceral fat (-0.560[-0.961 to -0.131]) and triglyceride (-0.607[-1.095 to -0.117]) significantly.

CONCLUSIONS

GLP-1 RAs effectively improve IR in NAFLD, whereas SGLT-2 inhibitors show no apparent effect.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO https://www.crd.york.ac.uk/PROSPERO/, CRD42021251704.