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Over the past three decades, the global prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) has rapidly increased, leading to significant economic and clinical burdens. However, aside from resmetirom (Rezdiffra™), an oral thyroid hormone receptor-β agonist, there remains a lack of approved targeted pharmacological treatments for MASLD, emphasizing the need for more optimized therapeutic strategies. Given the limitations in the safety and efficacy of the ketogenic diet, β-hydroxybutyrate (β-OHB) has emerged as a crucial regulator in MASLD treatment, but the precise mechanisms underlying its therapeutic effects remain unclear. This study aims to investigate the therapeutic effects of β-OHB on MASLD mice and elucidate the underlying mechanisms. In this study, we demonstrate that β-OHB ameliorates lipid deposition and increases pan-β-hydroxybutyrylation (Kbhb) levels in both MASLD mice and in vitro. Additionally, β-OHB also improves excessive ROS accumulation and enhances mitochondrial respiratory capacity. Furthermore, β-OHB protects against impaired fatty acid oxidation (FAO) activity in MASLD. Proteomic analysis of β-OHB-treated mice identified a significant Kbhb modification at K239 on malate dehydrogenase 2 (MDH2), which was associated with increased MDH2 enzymatic activity. Overall, this study demonstrates β-OHB exhibits therapeutic effects on hepatic steatosis and mitochondrial dysfunction in MASLD mice. We uncover a novel mechanism where β-OHB enhances MDH2 enzymatic activity through Kbhb modification at K239, thereby maintaining mitochondrial homeostasis and alleviating lipid deposition. Graphical abstract

Non-alcoholic fatty liver disease (NAFLD) is closely associated with obesity and insulin resistance. To better understand the pathophysiology of obesity-associated NAFLD, the present study examined the involvement of liver and adipose tissues in metformin actions on reducing hepatic steatosis and inflammation during obesity. C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity-associated NAFLD and treated with metformin (150 mg/kg/d) orally for the last four weeks of HFD feeding. Compared with HFD-fed control mice, metformin-treated mice showed improvement in both glucose tolerance and insulin sensitivity. Also, metformin treatment caused a significant decrease in liver weight, but not adiposity. As indicated by histological changes, metformin treatment decreased hepatic steatosis, but not the size of adipocytes. In addition, metformin treatment caused an increase in the phosphorylation of liver AMP-activated protein kinase (AMPK), which was accompanied by an increase in the phosphorylation of liver acetyl-CoA carboxylase and decreases in the phosphorylation of liver c-Jun N-terminal kinase 1 (JNK1) and in the mRNA levels of lipogenic enzymes and proinflammatory cytokines. However, metformin treatment did not significantly alter adipose tissue AMPK phosphorylation and inflammatory responses. In cultured hepatocytes, metformin treatment increased AMPK phosphorylation and decreased fat deposition and inflammatory responses. Additionally, in bone marrow-derived macrophages, metformin treatment partially blunted the effects of lipopolysaccharide on inducing the phosphorylation of JNK1 and nuclear factor kappa B (NF-κB) p65 and on increasing the mRNA levels of proinflammatory cytokines. Taken together, these results suggest that metformin protects against obesity-associated NAFLD largely through direct effects on decreasing hepatocyte fat deposition and on inhibiting inflammatory responses in both hepatocytes and macrophages.

Background maternal health during pregnancy can affect the intestinal microbial community of offspring, but currently the impact of intrauterine environmental changes resulting from gestational diabetes mellitus (GDM) on the microbiota of offspring as well as its interaction with the immune system remains unclear. Aims to explore the impact of intrauterine microbial exposure during pregnancy of gestational diabetes mellitus on the development of neonate’s intestinal microbiota and activation of immune responses. Methods Levels of lipopolysaccharides in cord blood from GDM and expression of microbial recognition-related proteins in the placenta were measured. To evaluate embryonic intestinal colonization, pregnant mice with GDM were administered with labeled Escherichia coli or Lactobacillus . The intestinal colonization of pups was analyzed through 16S rRNA gene sequencing and labeled microbial culture. Additionally, memory T lymphocyte and dendritic cell co-culture experiments were conducted to elucidate the immune memory of intestinal microbes during the embryonic stages. Result Gestational diabetes mellitus led to elevated umbilical cord blood LPS level and increased GFP labeled Escherichia coli in the offspring’s intestine after gestational microbial exposure. The mouse model of GDM exhibited increased immune markers including TLR4, TLR5, IL-22 and IL-23 in the placenta and a recall response from memory T cells in offspring’s intestines, with similar observations found in human experiments. Furthermore, reduced intestinal microbiome diversity and an increased ratio of Firmicutes/Bacteroidetes was found in GDM progeny, with the stability of bacterial colonization been interfered. Conclusions Our investigation has revealed a noteworthy correlation between gestational diabetes and intrauterine microbial exposure, as well as alterations in the neonatal microbiota and activation of immune responses. These findings highlight the gestational diabetes’s role on offspring’s gut microbiota and immune system interactions with early-life pathogen exposure.

Background The activation of brown adipose tissue (BAT) or the browning of white adipose tissue (WAT) represents a promising therapeutic strategy for obesity. Arctiin (ARC), a lignan compound known for its anti-inflammatory, anti-tumor, and hypoglycemic properties, has not been fully elucidated regarding its effects and mechanisms on obesity. Methods In the present study, we established both high-fat diet-induced obese mouse models and mature adipocyte cultures to comprehensively investigate the therapeutic effects of ARC on obesity. Systemic energy metabolism and thermogenic capacity were assessed through metabolic cage monitoring and cold stimulation tests. Histopathological alterations in adipose tissues were examined using hematoxylin and eosin (H&E) staining, while key gene expression in adipocytes was determined by Western blotting (WB), immunohistochemistry, and immunofluorescence staining. To further elucidate the molecular mechanisms underlying ARC's anti-obesity effects, we employed an integrated approach combining network pharmacology analysis, molecular docking simulations, cellular thermal shift assay (CETSA), and WB to identify potential molecular targets and delineate the associated signaling pathways modulated by ARC treatment. Results In diet-induced obese mice, ARC administration at doses of 20 and 60 mg/kg/day ameliorated metabolic dysfunction through enhanced WAT browning and increased energy expenditure. In C3H10T1/2-induced adipocytes, ARC upregulated the protein expression of uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and other brown-specific marker genes, promoting mitochondrial function and browning of adipocytes. Mechanistically, our findings suggest that ARC may promote adipocyte browning via the A 2A R-cyclic AMP (cAMP)-protein kinase A (PKA) signaling pathway. Conclusion In summary, ARC exerts protective effects against obesity by promoting the browning of white adipocytes and holds promise as a potentially beneficial therapeutic agent for the treatment of obesity. Graphical Abstract

Elevated circulating homocysteine (Hcy) has been proposed to be associated with non-alcoholic fatty liver disease (NAFLD). It is also reported that Hcy causes protein misfolding in the endoplasmic reticulum (ER). In this study, we used a high methionine diet (HMD)-fed mouse model and cultured primary hepatocytes to investigate the effects of Hcy on hepatic lipids metabolism. C57BL/6J mice received either standard chow diet (CT, n = 10) or diet supplemented with 2% methionine (MET, n = 10) for 16 weeks. In in vitro experiments, cultured mouse primary hepatocytes were treated with Hcy, or Hcy combined with 4-phenylbutyric acid (4-PBA), or tunicamycin (TM), respectively. HMD-fed mice exhibited a mild increase in plasma Hcy level. There was no significant difference of body weight gain between the two groups. Nevertheless, HMD feeding increased epididymal fat/body weight ratio, elevated plasma triglyceride (TG) level, and decreased high-density lipoprotein cholesterol (HDL) level. Similarly, mice on HMD displayed higher liver/body weight ratio, plasma aspartate aminotransferase (AST) and its ratio to alanine aminotransferase (ALT), which was supported by the morphological observations of hepatic triglyceride accumulation in liver tissue as well as primary hepatocytes. Activation of the sterol response element-binding protein 1c (SREBP1c) in Hcy-treated hepatocytes with increased expression of genes involved in hepatic de novo lipogenesis was partially reduced by pretreatment of 4-PBA. Hcy-induced ER stress was also ameliorated by 4-PBA pretreatment, thus demonstrating an important role of Hcy-induced ER stress response in hepatic steatosis. These findings suggest that elevated Hcy was a critical factor in the pathogenesis of NAFLD. Activation of the ER stress response may be involved in Hcy-induced hepatic steatosis.

Exosome-like vesicles (ELVs), the smallest class of extracellular vesicles released from cells, function in cellular crosstalk and therefore profoundly affect physiologic responses and pathologic progression. A growing body of evidence supports a novel role for ELVs as important mediators and therapeutic targets due to their effects on regulation of both insulin signaling and β-cell mass. Pathologic conditions associated with type 2 diabetes (such as high blood glucose, inflammation, hypoxia, and fatty acids) can alter the quantity and components of ELVs secreted from the pancreas or peripheral insulin-targeting tissues. These released ELVs can either enter the blood circulation or be taken up by neighboring cells or macrophages, which can lead to insulin resistance or β-cell apoptosis. This review focuses on the roles of ELVs in insulin resistance and β-cell failure and also highlights the potential use of ELVs and exosome-based delivery systems in therapeutic interventions aimed at treating type 2 diabetes mellitus as well as the challenges associated with exosome-targeting therapeutics.

Background & Aims Ketogenic diet (KD) is recognized as an effective lifestyle intervention for managing metabolic dysfunction-associated steatotic liver disease (MASLD). This research aimed to assess the impact of KD on metabolic parameters in MASLD mice and elucidate the underlying mechanism. Methods High-fat diet (HFD)-induced MASLD mice were subjected to KD for 2 weeks. Researchers measured hepatic fat, plasma Alanine Aminotransferase (ALT), and Aspartate Aminotransferase (AST) levels to assess metabolic changes. Hepatic mitochondrial dynamics were examined using transmission electron microscopy and Western blot. Mitochondrial functions were evaluated through Quantitative Polymerase Chain Reaction (qPCR) and measurement of ATP content. In vitro, HepG2 cells were treated with palmitate (PA), β-hydroxybutyric acid (β-OHB), and/or the mitochondrial fusion inhibitor MFI8 to study mitochondrial morphology, function, and lipid deposition. Results KD feeding partially improved the MASLD phenotype and reduced Fission 1 protein (Fis1) and Dynamin-related protein 1 (Drp1) levels in the livers of MASLD mice. Additionally, KD ameliorated HFD-stimulated mitochondrial dysfunctions, as evidenced by elevated ATP levels and upregulation of key genes responsible for fatty-acid-oxidation. β-OHB mitigated PA-stimulated mitochondrial dysfunction and fission in HepG2 cells. Furthermore, β-OHB attenuated PA-stimulated lipid deposition, with this effect being counteracted by MFI8. Conclusions Our study suggests that a 2-week KD partially alleviates lipid deposition, restores mitochondrial dynamics balance, and improves mitochondrial dysfunctions in the livers of MASLD mice.

Obesity is associated with chronic inflammation in the central nervous system (CNS), and neuroinflammation has been shown to have detrimental effects on mood and cognition. The growth hormone secretagogue receptor (GHSR), the biologically relevant receptor of the orexigenic hormone ghrelin, is primarily expressed in the brain. Our previous study showed that neuronal GHSR deletion prevents high-fat diet-induced obesity (DIO). Here, we investigated the effect of neuronal GHSR deletion on emotional and cognitive functions in DIO. The neuron-specific GHSR-deficient mice exhibited reduced depression and improved spatial memory compared to littermate controls under DIO. We further examined the cortex and hippocampus, the major regions regulating cognitive and emotional behaviors, and found that the neuronal deletion of GHSR reduced DIO-induced neuroinflammation by suppressing proinflammatory chemokines/cytokines and decreasing microglial activation. Furthermore, our data showed that neuronal GHSR deletion suppresses neuroinflammation by downregulating AMPK-autophagy signaling in neurons. In conclusion, our data reveal that neuronal GHSR inhibition protects against DIO-induced depressive-like behavior and spatial cognitive dysfunction, at least in part, through AMPK-autophagy signaling-mediated neuroinflammation.

Background: The metabolic syndrome (MetS) represents a clustering of risk factors for cardiovascular diseases that includes abdominal obesity, hypertension, dyslipidemia, and insulin resistance. Objectives: The objective of this study was to reassess the parent-offspring association of MetS since the available findings are still controversial. Methods: The Cochrane Library, PubMed, Embase, and Web of Science databases were searched to identify relevant articles. All studies comparing MetS status between the offspring of parents with MetS and offspring of parents without MetS were included in the analysis. Results: A total of 9 studies met the inclusion criteria and they were analyzed. Offspring of at least 1 parent with MetS had a higher risk of MetS (OR 3.88, 95% CI 2.58–5.83, p < 0.001). Sons and daughters of fathers with MetS both had a higher risk of MetS (OR 2.31, 95% CI 1.70–3.12, p < 0.001, and OR 1.73, 95% CI 1.37–2.18, p < 0.001, respectively). Sons and daughters of mothers with MetS both had a higher risk of MetS (OR 1.95, 95% CI 1.37–2.76, p = 0.0002, and OR 1.91, 95% CI 1.54–2.35, p < 0.001, respectively). Conclusion: This meta-analysis showed that there is a higher risk of MetS in the offspring of parents with MetS. However, there was no differential association of MetS according to gender and/or age of the offspring.

The increase in fructose consumption is considered to be a risk factor for developing nonalcoholic fatty liver disease (NAFLD). We investigated the effects of docosahexaenoic acid (DHA) on hepatic lipid metabolism in fructose-treated primary mouse hepatocytes, and the changes of Endoplasmic reticulum (ER) stress pathways in response to DHA treatment. The hepatocytes were treated with fructose, DHA, fructose plus DHA, tunicamycin (TM) or fructose plus 4-phenylbutyric acid (PBA) for 24 h. Intracellular triglyceride (TG) accumulation was assessed by Oil Red O staining. The mRNA expression levels and protein levels related to lipid metabolism and ER stress response were determined by real-time PCR and Western blot. Fructose treatment led to obvious TG accumulation in primary hepatocytes through increasing expression of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC), two key enzymes in hepatic de novo lipogenesis. DHA ameliorates fructose-induced TG accumulation by upregulating the expression of carnitine palmitoyltransferase 1A (CPT-1α) and acyl-CoA oxidase 1 (ACOX1). DHA treatment or pretreatment with the ER stress inhibitor PBA significantly decreased TG accumulation and reduced the expression of glucose-regulated protein 78 (GRP78), total inositol-requiring kinase 1 (IRE1α) and p-IRE1α. The present results suggest that DHA protects against high fructose-induced hepatocellular lipid accumulation. The current findings also suggest that alleviating the ER stress response seems to play a role in the prevention of fructose-induced hepatic steatosis by DHA.