Interplay between ChREBP and SREBP-1c coordinates postprandial glycolysis and lipogenesis in livers of mice

The natural dihydrochalcone phloretin reduces lipid accumulation via downregulation of IIS and sbp-1/SREBP pathways in HepG2 cells and Caenorhabditis elegans

Phloretin, a natural dihydrochalcone, exhibits significant potential in modulating lipid metabolism both in vitro and in vivo. This study investigated the effects of phloretin on lipid accumulation in HepG2 cells and Caenorhabditis elegans. In HepG2 cells, phloretin reduced lipid accumulation, ROS levels, and lipid peroxidation while ameliorating mitochondrial dysfunction. It downregulated lipid synthesis genes (SREBP, FASN) and upregulated PI3K-AKT pathway genes (AKT, FOXO, MTOR). In C. elegans, phloretin alleviated lipid accumulation-induced growth and locomotor impairments, reduced lipofuscin, ROS, glucose, and triglyceride levels, and modulated amino acid and lipid metabolism pathways. Gene expression analysis revealed downregulation of sbp-1, mdt-15, fat-5, fat-6, and fat-7, and upregulation of daf-16, age-1, and skn-1. Mutant studies confirmed that phloretin's lipid-lowering effects were mediated through the IIS and sbp-1/SREBP pathways. These findings suggest phloretin is a promising candidate for regulating lipid metabolism and preventing hyperlipidemia.

Hypoxic compound exercise improves cardiac function in Drosophila high fructose diet via KHK

Overconsumption of fructose has been linked to the development of systemic metabolic and cardiac diseases, yet few studies have focused on the link between cardiac fructose metabolism and the development of heart disease. Low-oxygen complex exercise is considered an effective means of treating and preventing metabolic diseases and improving cardiac function, however, it is unclear, the link between low-oxygen complex exercise and high-fructose-induced heart disease. Therefore, the aim of this study was to investigate the effect of hypoxic complex exercise on heart disease on a high fructose diet. The results of the study found that hypoxic compound exercise improved the upregulation of inflammatory factor Upd3 and systemic fat accumulation in the heart induced by high fructose diet by inhibiting the expression of KHK gene in the heart; and it improved the impaired cardiac rhythmic function and pumping function, improved the disorder of myofilament fiber arrangement, reduced the level of cardiac oxidative stress, and reduced cardiac collagen deposition. In addition, cardiac KHK-specific knockdown had the same effect on high fructose diet hearts. Compared with single KHK cardiac-specific knockdown or hypoxic combination exercise, hypoxic combination exercise combined with KHK cardiac-specific knockdown was superior in improving the high-fructose diet-induced increase in arrhythmia index, systolic and diastolic dysfunction, and decrease in fractional shortening. Therefore, we conclude that hypoxic complex exercise improved high-fructose diet-induced cardiac rhythmic function and pumping dysfunction by reducing KHK expression.

Integration of metabolomic and transcriptomic analyses reveals regulatory functions of the ChREBP transcription factor in energy metabolism

The transcription factor carbohydrate response element binding protein (ChREBP) activates genes of glucose, fructose, and lipid metabolism in response to carbohydrate feeding. Integrated transcriptomic and metabolomic analyses in rats with GalNac-siRNA-mediated suppression of ChREBP expression in liver reveal other ChREBP functions. GalNac-siChREBP treatment reduces expression of genes involved in coenzyme A (CoA) biosynthesis, with lowering of CoA and short-chain acyl-CoA levels. Despite suppression of pyruvate kinase, pyruvate levels are maintained, possibly via increased expression of pyruvate and amino acid transporters. In addition, expression of multiple anaplerotic enzymes is decreased by GalNac-siChREBP treatment, affecting TCA cycle intermediates. Finally, GalNAc-siChREBP treatment suppresses late steps in purine and NAD synthesis, with increases in precursors and lowering of end products in both pathways. In sum, our study reveals functions of ChREBP beyond its canonical roles in carbohydrate and lipid metabolism to include regulation of substrate transport, mitochondrial function, and energy balance.

TRIM32 regulates insulin sensitivity by controlling insulin receptor degradation in the liver

Impaired insulin receptor signaling is strongly linked to obesity-related metabolic conditions like non-alcoholic fatty liver disease (NAFLD) and Type 2 diabetes (T2DM). However, the exact mechanisms behind impaired insulin receptor (INSR) signaling in obesity induced by a high-fat diet remain elusive. In this study, we identify an E3 ubiquitin ligase, tripartite motif-containing protein 32 (TRIM32), as a key regulator of hepatic insulin signaling that targets the insulin receptor (INSR) for ubiquitination and proteasomal degradation in high-fat diet (HFD) mice. HFD induces the nuclear translocation of SREBP-1c (Sterol Regulatory Element-Binding Protein 1c), resulting in increased expression of TRIM32 in hepatocytes. TRIM32 ubiquitylates INSR and facilitates its proteasomal degradation, leading to severe insulin resistance and fat accumulation within the liver of high-fat diet induced obese (DIO) mice. Conversely, liver-specific knockdown of TRIM32 enhances INSR expression and hepatic insulin sensitivity. Reduced AMPK signaling and phosphorylation of SREBP-1c at S372 in high-fat DIO mice promotes the nuclear translocation of SREBP-1c, leading to increased TRIM32 expression. In conclusion, our results demonstrate that TRIM32 promotes diet-induced hepatic insulin resistance by targeting the INSR to degradation.

METTL3/miR-192-5p/SCD1 Axis Regulates Lipid Metabolism to Affect T Cell Differentiation in Asthma

Background: This study aimed to explore the mechanisms underlying T-cell differentiation in asthma. Methods and Results: Flow cytometry was performed to detect Th cells. LC-MS/MS was performed to assess lipid metabolism. HE staining was performed to assess the pathological changes of the lung tissues. ELISA was performed to detect cytokine levels. The results of quantitative real-time polymerase chain reaction (qRT-PCR) and western blot showed that miR-192-5p expression was decreased, while SCD1 expression was increased in CD4+T cells isolated from the peripheral blood of children with asthma. The dual luciferase reporter assay determined the direct interaction between miR-192-5p and SCD1. MiR-192-5p inhibitor reduced ASCL3 and PPARα, increased FASN and SREBP1c mRNA expression and protein levels in mouse spleen CD4+T cells, and elevated Th2 and Th17 cells, but these effects were reversed by the SCD1 inhibitor. Oleic acid (OA) reduced Th1 cells and increased Th2 and Th17 cells in mouse spleen CD4+T cells treated with an SCD1 inhibitor. Additionally, pri-miR-192-5p expression was increased in CD4+T cells isolated from the peripheral blood of asthmatic children, and the deletion of METTL3 upregulated pri-miR-192-5p expression in an m6A-dependent manner. MiR-192-5p mimic and inhibitor both reversed miR-192-5p and SCD1 expression affected by overexpression or deletion of METTL3, both in vivo and in vitro. Furthermore, METTL3 overexpression attenuated lung inflammation, elevated Th1 cells, and reduced Th2 and Th17 cells in CD4+T cells isolated from the peripheral blood of asthmatic mice. These effects were reversed by the miR-192-5p inhibitor. Conclusion: These results suggest that METTL3/miR-192-5p/SCD1 axis regulates lipid metabolism and affects T cell differentiation, thus affecting asthma progression. This study may provide novel insights into the pathogenesis of asthma and a new treatment strategy.

Glucose-Sensing Carbohydrate Response Element-Binding Protein in the Pathogenesis of Diabetic Retinopathy

Glucose-sensing ChREBP and MondoA are transcriptional factors involved in the lipogenic, inflammatory, and insulin signaling pathways implicated in metabolic disorders; however, limited ocular studies have been conducted on these proteins. We aimed to investigate the potential role of ChREBP in the pathogenesis of diabetic retinopathy (DR). We used diabetic human and mouse retinal cryosections analyzed by immunohistochemistry. qRT-PCR was performed to quantify gene expression. To explore the role of ChREBP in rods, we generated caChREBPRP mice with constitutively active (ca) ChREBP. These mice underwent retinal functional testing, which was followed by proteomic analysis using LC-MS. Furthermore, ARPE-19 cells were infected with lentiviral particles expressing human ChREBP (ARPE-19ChREBP) and subjected to global proteomics. Our results demonstrate that both proteins were expressed across the retina, although with distinct distribution patterns: MondoA was more prominently expressed in cones, while ChREBP was broadly expressed throughout the retina. Elevated expression of both proteins was observed in DR. This may have contributed to rod photoreceptor degeneration, as we observed diminished scotopic ERG amplitudes in caChREBPRP mice at P35. The retinal proteomic landscape revealed a decline in the KEGG pathways associated with phototransduction, amino acid metabolism, and cell adhesion. Furthermore, rod-specific caChREBP induced TXNIP expression. Consistent with altered retinal proteomics, ARPE-19ChREBP cells exhibit a metabolic shift toward increased glyoxylate signaling, sugar metabolism, and lysosomal activation. Our study demonstrates that ChREBP overexpression causes significant metabolic reprogramming triggering retinal functional loss in mice.

High-fat/high-sucrose diet results in a high rate of MASH with HCC in a mouse model of human-like bile acid composition

BACKGROUND

Wild-type (WT) mice fed a conventional high-fat/high-sucrose diet (HFHSD) rarely develop metabolic dysfunction-associated steatohepatitis (MASH) with HCC. Because mouse bile acid (BA) is highly hydrophilic, we hypothesized that making it hydrophobic would lead to MASH with HCC.

METHODS

Eleven-week-old WT and Cyp2a12/Cyp2c70 double knockout (DKO) mice were divided into two groups, including one which was fed a normal chow diet, and one which was fed an HFHSD. Samples were collected after 15, 30, 47, and 58 weeks for histological, biochemical, and immunological analyses.

RESULTS

In the HFHSD group, body weight gain did not differ in WT versus DKO mice, although HFHSD-fed DKO mice exhibited markedly accelerated liver inflammation, fibrosis, and carcinogenesis. HFHSD upregulated lipogenesis and downregulated fatty acid oxidation in both WT and DKO mice, which increased liver lipid accumulation and lipotoxicity. However, the increase in reactive oxygen species production and carcinogenesis observed in DKO mice could not be explained by abnormal lipid metabolism alone. Regarding BA metabolism, DKO mice had a higher hydrophobicity index. They exhibited an age-associated increase in chenodeoxycholic acid (CDCA) levels because of CYP8B1 activity inhibition due to the farnesoid X receptor activation. HFHSD further downregulated CYP8B1, presumably by activating the Liver X receptor. Liver CDCA accumulation was associated with increased inflammation, reactive oxygen species production, and hepatocyte FGF15 induction. Moreover, in noncancerous liver tissues, HFHSD appeared to activate STAT3, an oncogenic transcription factor, which was enhanced by a CDCA-rich environment.

CONCLUSIONS

Here, we developed a new model of MASH with HCC using mice with human-like BA composition and found that HFHSD and elevated hepatic CDCA synergistically increased the risk of MASH with HCC.

Temporal patterns of liver and adipose lipase abundance across the periparturient period in multiparous Holstein dairy cows

Lipases such as patatin-like phospholipase domain-containing protein 3 (PNPLA3) exist in multiple tissue types. In subcutaneous adipose tissue, PNPLA3 was not altered during the periparturient period. Conversely, strong associations between liver PNPLA3 and liver triglyceride content peripartum were identified and confirmed to be causative using knockdown approaches in a primary bovine hepatocyte model. The objective of this research was to characterize adipose and hepatic lipase abundance, as well as abundance of hepatic transcription factors (TF) involved in adipose and liver tissue lipolysis to determine potential impact on bovine fatty liver development and recovery. Adipose and liver tissue biopsy samples were collected from -28 to +56 d relative to calving (DRTC) from multiparous Holstein dairy cows randomly assigned to either a control (CTL) or ketosis induction protocol (KIP) diet. Clinical ketosis (blood BHB ≥ 3.0 mM) was used as a cowside indicator of successful induction and was achieved in CTL (n = 2) and KIP (n = 12) cows. Both adipose and liver abhydrolase domain-containing protein 5 and adipose triglyceride lipase (ATGL) differed across DRTC, as did liver perilipin 1. Hepatic mature and immature carbohydrate response element binding protein, and sterol regulatory binding protein 1c, varied or tended to vary across DRTC × treatment. Neither adipose nor liver hormone sensitive lipase (HSL) were responsive to treatment or varied across DRTC, but adipose HSL was positively associated with nonesterified fatty acids at +1 DRTC. Adipose and liver ATGL was associated with liver triglycerides across all DRTC. Patterns of adipose HSL and ATGL abundance did not explain the increase in nonesterified fatty acids observed at +1 DRTC in this study. Future investigation of lipase abundance in other adipose tissue depots is still needed to better explain regulation during this time. Bovine fatty liver development and recovery appears to be contingent upon liver PNPLA3 abundance, rather than liver ATGL.

Glucose and Insulin Differently Regulate Gluconeogenic and Ureagenic Gene Expression

Glucose and insulin positively regulate glycolysis and lipogenesis through the activation of carbohydrate response element-binding protein (ChREBP) and sterol regulatory element-binding protein 1c (SREBP1c), but their respective roles in the regulation of gluconeogenic and ureagenic genes remain unclear. We compared the effects of the insulin antagonist S961 and Chrebp deletion on hepatic glycolytic, lipogenic, gluconeogenic, and ureagenic gene expression in mice. S961 markedly increased the plasma glucose, insulin, and 3-OH-butyrate concentrations and reduced the hepatic triglyceride content, but Chrebp deletion had no additive effect. We subsequently estimated the expression of genes involved in the pathways of glycolysis, gluconeogenesis, and lipogenesis. S961 potently decreased both Chrebp and Srebf1c, but Chrebp deletion weakly decreased Srebf1c mRNA expression. Both the S961 and Chrebp deletion caused decreases in glycolytic (Gck and Pklr) and lipogenic (Fasn, Scd1, Me1, Spot14, Elovl6) gene expression. S961 increased the expression of many gluconeogenic genes (G6pc, Fbp1, Aldob, Slc37a4, Pck), whereas Chrebp deletion reduced the expression of gluconeogenic genes other than Pck1. Finally, we checked the metabolites and gene expression in the ureagenesis pathway. S961 increased ureagenic gene (Arg1, Asl, Ass1, Cps1, Otc) expression, which was consistent with the metabolite data: there were reductions in the concentrations of glutamate and aspartate and increases in those of citrulline, ornithine, urea, and proline. However, Chrebp deletion had no additive effect on ureagenesis. In conclusion, insulin rather than glucose regulate ureagenic gene expression, whereas glucose and insulin regulate gluconegenic gene expression in opposite directions.

Glycerol-3-phosphate activates ChREBP, FGF21 transcription and lipogenesis in Citrin Deficiency

Citrin Deficiency (CD) is caused by inactivation of SLC25A13, a mitochondrial membrane protein required to move electrons from cytosolic NADH to the mitochondrial matrix in hepatocytes. People with CD do not like sweets. We discovered that SLC25A13 loss causes accumulation of glycerol-3-phosphate (G3P), which activates carbohydrate response element binding protein (ChREBP) to transcribe FGF21, which acts in the brain to restrain intake of sweets and alcohol, and to transcribe key genes of de novo lipogenesis. Mouse and human data establish G3P-ChREBP as a new mechanistic component of the Randle Cycle that contributes to metabolic dysfunction-associated steatotic liver disease (MASLD) and forms part of a system that communicates metabolic states from liver to brain in a manner that alters food and alcohol choices. The data provide a framework for understanding FGF21 induction in varied conditions, suggest ways to develop FGF21-inducing drugs, and drug candidates for both lean MASLD and support of urea cycle function in CD.

Glucose-Sensing ChREBP Protein in the Pathogenesis of Dia-betic Retinopathy

Glucose-sensing ChREBP and MondoA are transcriptional factors involved in lipogenic, inflammatory, and insulin signaling pathways implicated in metabolic disorders; however, limited ocular studies have been conducted on these proteins. We aimed to investigate the potential role of ChREBP in pathogenesis of diabetic retinopathy (DR). We used diabetic human and mouse retinal cryosections analyzed by immunohistochemistry. qRT-PCR was performed to quantify gene expression. To explore the role of ChREBP in rods, we generated caChREBPRP mice with constitutively active (ca) ChREBP. These mice underwent retinal function testing, followed by proteomic analysis using LC-MS. Furthermore, ARPE-19 cells were infected with lentiviral particles expressing human ChREBP (ARPE-19ChREBP) and subjected to global proteomics. Our results demonstrate that both proteins were expressed across the retina, although with distinct distribution patterns: MondoA was more prominently expressed in cones, while ChREBP was broadly expressed throughout the retina. Elevated expression of both proteins was observed in DR. This may have contributed to rod photoreceptor degeneration as we observed diminished scotopic ERG amplitudes detected in caChREB-PRP mice at P35. The retinal proteomic landscape indicated a decline in KEGG pathways associated with phototransduction, amino acid metabolism, and cell adhesion. Furthermore, rod-specific ca-ChREBP induced TXNIP expression. Consistent with altered retinal proteomics, ARPE-19ChREBP cells displayed a metabolic shift toward increased glyoxylate signaling, sugar metabolism, and lysosomal activation. Our study demonstrates that ChREBP overexpression causes significant metabolic reprograming triggering retinal functional loss in mice.

Diabetes and the associated complications: The role of antioxidants in diabetes therapy and care

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by high blood sugar levels (hyperglycemia). Poorly managed diabetes can lead to complications affecting multiple organ systems. Antioxidants play a crucial role in reducing oxidative stress caused by reactive oxygen species (ROS), primarily triggered by uncontrolled high blood sugar levels in diabetes. Antioxidants like vitamin C, E, selenium, and alpha-lipoic acid, when used as supplements, have shown promise in reducing oxidative stress markers and improving antioxidant status in laboratory and animal studies and diabetic patients. Antioxidant supplementation may help reduce the risk of diabetic complications such as neuropathy, nephropathy, retinopathy, and cardiovascular disease. Additionally, antioxidants also have anti-inflammatory properties, which could be beneficial in reducing inflammation associated with diabetes. Antioxidant supplementation has been shown to enhance endothelial function, insulin sensitivity, and glucose metabolism, thereby aiding in glycemic control and overall diabetic management. Combining antioxidants with certain medications may have therapeutic benefits, such as effectively neutralizing free radicals and enhancing the regulation of antioxidant defense systems. This review presents an update on diabetes, the sources of free radical generation, the body's natural defense mechanisms, the clinical evidence regarding using antioxidants in managing diabetic complications, and the potential new therapeutic approaches. Overall, antioxidant supplementation may offer some benefits in managing diabetic complications. However, further studies are needed to understand the mechanisms of action, determine the optimal supplementation, explore potential interactions with other medications, and conduct long-term studies to establish the possible use of antioxidants for optimal benefits in diabetes care.

Comparison of Risk Factors Between Lean and Nonlean Metabolic Dysfunction-Associated Steatotic Liver Disease in Individuals With Type 2 Diabetes: A Multicenter Study

OBJECTIVE

A multicenter study in patients with type 2 diabetes mellitus (T2DM) was performed to assess the differences of liver steatosis and fibrosis between lean and nonlean individuals.

METHODS

Patients with T2DM from 16 centers were recruited and underwent transient elastography examination for diagnosis of liver steatosis and fibrosis. Clinical information, such as diabetes status, serum lipids profiles, and inflammatory markers, were collected. Potential risk factors of liver steatosis and fibrosis in lean (body mass index [BMI] < 23 kg/m2) and nonlean (BMI ≥ 23 kg/m2) groups were analyzed.

RESULTS

A total of 1762 patients were included. The prevalence of liver steatosis and fibrosis in the lean group was 44.7% and 23.4%, respectively. The prevalence of hypertension and cardiovascular disease was higher in lean patients when compared with nonlean group. Lean patients with liver steatosis or fibrosis were older, had longer diabetes duration, lower levels of homeostatic model assessment for insulin resistance and serum lipids. The BMI, visceral fat area, and triglyceride were among the most significant correlators of liver steatosis for both nonlean and lean patients. However, lipid profiles were different between the two groups. Besides, insulin resistance, BMI, and lipid levels were not observed to be associated with fibrosis in the lean group.

CONCLUSION

In lean patients with T2DM, liver steatosis and fibrosis were less associated with insulin resistance. Risk factors of liver steatosis were different between lean and nonlean patients, indicating the necessity of risk stratification and tailored management strategies.

Hepatocyte-specific loss of melanocortin 1 receptor disturbs fatty acid metabolism and promotes adipocyte hypertrophy

BACKGROUND/OBJECTIVES

Melanocortins mediate their biological functions via five different melanocortin receptors (MC1R - MC5R). MC1R is expressed in the skin and leukocytes, where it regulates skin pigmentation and inflammatory responses. MC1R is also present in the liver and white adipose tissue, but its functional role in these tissues is unclear. This study aimed at determining the regulatory role of MC1R in fatty acid metabolism.

METHODS

Male recessive yellow (Mc1re/e) mice, a model of global MC1R deficiency, and male hepatocyte-specific MC1R deficient mice (Mc1r LKO) were fed a chow or Western diet for 12 weeks. The mouse models were characterized for body weight and composition, liver adiposity, adipose tissue mass and morphology, glucose metabolism and lipid metabolism. Furthermore, qPCR and RNA sequencing analyses were used to investigate gene expression profiles in the liver and adipose tissue. HepG2 cells and primary mouse hepatocytes were used to study the effects of pharmacological MC1R activation.

RESULTS

Chow- and Western diet-fed Mc1re/e showed increased liver weight, white adipose tissue mass and plasma triglyceride (TG) concentration compared to wild type mice. This phenotype occurred without significant changes in food intake, body weight, physical activity or glucose metabolism. Mc1r LKO mice displayed a similar phenotype characterized by larger fat depots, increased adipocyte hypertrophy and enhanced accumulation of TG in the liver and plasma. In terms of gene expression, markers of de novo lipogenesis, inflammation and apoptosis were upregulated in the liver of Mc1r LKO mice, while enzymes regulating lipolysis were downregulated in white adipose tissue of these mice. In cultured hepatocytes, selective activation of MC1R reduced ChREBP expression, which is a central transcription factor for lipogenesis.

CONCLUSIONS

Hepatocyte-specific loss of MC1R disturbs fatty acid metabolism in the liver and leads to an obesity phenotype characterized by enhanced adipocyte hypertrophy and TG accumulation in the liver and circulation.

Integrated metabolomic and transcriptomic analysis reveals the effects and mechanisms of Jinqi Jiangtang tablets on type 2 diabetes

BACKGROUND

Type 2 diabetes (T2DM) is one of the major metabolic diseases and poses a serious challenge to human life and global economic development. Jinqi Jiangtang Tablets (JQJT) is effective in ameliorating the effects of T2DM, but the mechanism of JQJT is unclear.

PURPOSE

This study integrated metabolomics and transcriptomics to reveal the mechanism by which JQJT improves T2DM.

METHODS

The T2DM mouse model was established, and the effects of JQJT on improving T2DM were evaluated by determining the levels of blood lipids, fasting blood glucose (FBG), insulin metabolism and hepatic lipid accumulation in mice after JQJT administration for 8 weeks. Serum metabolites were detected using ultra-performance liquid chromatography/quadrupole time-of-flight-tandem mass spectrometry (UPLC-Q-TOF-MS) technology, and mouse liver differential genes were detected using transcriptomic technology. Correlation analysis was used to extract metabolites and RNA with correlations, and potential pathways were enriched and constructed using the common pathway analysis function of MetaboAnalyst 5.0. Finally, the expression of key target proteins and genes was verified by Western blot (WB) and Polymerase Chain Reaction (PCR) to further elucidate the mechanism by which JQJT improves T2DM.

RESULTS

JQJT reduced FBG and lipid levels, improved insulin resistance (IR) and hepatic lipoatrophy in mice. A total of 35 differentially abundant metabolites were identified by metabolomics, and 328 differential genes were detected by transcriptomics. The integrated metabolomics and transcriptomics results suggested that JQJT may ameliorate T2DM mainly by regulating glucose and lipid metabolic pathways. WB and PCR results showed that JQJT regulates the insulin signaling pathway, involved in fatty acid metabolism, glycogen synthesis and catabolism.

CONCLUSIONS

JQJT improved IR in T2DM mice by regulating the insulin signaling pathway, improving glycogen synthesis and glycolysis, and increasing hepatic triglyceride and fatty acid metabolism.

Supplementation of Chlorogenic Acid Alleviates the Effects of H2O2-Induced Oxidative Stress on Laying Performance, Egg Quality, Antioxidant Capacity, Hepatic Inflammation, Mitochondrial Dysfunction, and Lipid Accumulation in Laying Hens

This research examined the impact of chlorogenic acid (CGA) on laying performance, antioxidant capacity, egg quality, hepatic inflammation, mitochondrial function, and lipid metabolism in hens subjected to hydrogen peroxide (H2O2)-induced oxidative stress (OS). Three hundred sixty healthy 43-wk-old Hy-Line brown hens were randomly assigned to six treatments: a basal diet + 0 (control and H2O2), 600 (600 mg/kg CGA and 600 mg/kg CGA + H2O2), and 800 (800 mg/kg CGA and 800 mg/kg CGA + H2O2) mg/kg CGA for 84 d. On the 64th and 78th days of the trial, hens in groups H2O2, 600 mg/kg CGA + H2O2, and 800 mg/kg CGA + H2O2 were injected intraperitoneally with 10% H2O2. The results demonstrated that 600 and 800 mg/kg CGA significantly improved the egg production rate (EPR) and egg quality and reduced lipid peroxidation compared to the control group. The 800 mg/kg CGA showed greater improvements in the EPR and average egg weight (AEW) compared to the 600 mg/kg dose. Conversely, H2O2 exposure significantly decreased the EPR, AEW, and egg quality and increased feed conversion rate and average daily feed intake. H2O2 exposure significantly decreased serum T-AOC and increased serum MDA levels while reducing hepatic T-SOD, GSH-Px, and CAT activities. Meanwhile, H2O2 exposure significantly elevated liver reactive oxygen species levels, pathological damage, and NF-κB, TNFα, and IL-1β gene expression. Additionally, H2O2 treatment disrupted hepatocyte mitochondrial structure and significantly increased the expression of VDAC1 protein, and IP3R, GRP75, MCU, Fis1, and MFF genes, while downregulating the expression of MFN2 protein and PGC1α gene. Oil Red O staining demonstrated that H2O2 induced significant lipid accumulation in hepatocytes. Concurrently, H2O2 significantly increased serum triglycerides, total cholesterol, and liver triglycerides levels while decreasing serum hepatic lipase activity. This was primarily attributed to the significant upregulation of liver SREBP1, FASN, and ACC genes and the downregulation of the liver CPT1 gene induced by H2O2. Furthermore, CGA pretreatment effectively prevented the degeneration in laying performance and egg quality, as well as OS, liver inflammation, pathological damage, and mitochondrial dysfunction induced by H2O2. CGA inhibited H2O2-induced hepatic lipid accumulation by upregulating fatty acid oxidation-related gene expression and downregulating fatty acid synthesis-related gene expression. These findings indicate that the dietary addition of 800 mg/kg of CGA is the optimum supplementation dose. CGA can enhance laying performance and egg quality while alleviating OS, hepatic inflammation, mitochondrial dysfunction, and lipid accumulation in H2O2-challenged laying hens.

Knockout of the Carbohydrate Responsive Element Binding Protein Enhances Proliferation and Tumorigenesis in Renal Tubules of Mice

Glycogen-storing so-called clear cell kidney tubules (CCTs), precursor lesions of renal cell carcinoma, have been described in diabetic rats and in humans. The lesions show upregulation of the Akt/mTOR-pathway and the related transcription factor carbohydrate responsive element binding protein (ChREBP), which is supposedly pro-oncogenic. We investigated the effect of ChREBP-knockout on nephrocarcinogenesis in streptozotocin-induced diabetic and normoglycemic mice. Diabetic, but not non-diabetic mice, showed CCTs at 3, 6 and 12 months of age. Glycogenosis was confirmed by periodic acid schiff reaction and transmission electron microscopy. CCTs in ChREBP-knockout mice consisted of larger cells and occurred more frequently compared to wildtype mice. Progression towards kidney tumors was observed in both diabetic groups but occurred earlier in ChREBP-knockout mice. Proliferative activity assessed by BrdU-labeling was lower in 1-week-old but higher in 12-month-old diabetic ChREBP-knockout mice. Surprisingly, renal neoplasms occurred spontaneously in non-diabetic ChREBP-knockout, but not non-diabetic wildtype mice, indicating an unexpected tumor-suppressive function of ChREBP. Immunohistochemistry showed upregulated glycolysis and lipogenesis, along with activated Akt/mTOR-signaling in tumors of ChREBP-knockout groups. Immunohistochemistry of human clear cell renal cell carcinomas revealed reduced ChREBP expression compared to normal kidney tissue. However, the molecular mechanisms by which loss of ChREBP might facilitate tumorigenesis require further investigation.

Integration of metabolomic and transcriptomic analyses reveals novel regulatory functions of the ChREBP transcription factor in energy metabolism

Carbohydrate Response Element-Binding Protein (ChREBP) is a transcription factor that activates key genes involved in glucose, fructose, and lipid metabolism in response to carbohydrate feeding, but its other potential roles in metabolic homeostasis have not been as well studied. We used liver-selective GalNAc-siRNA technology to suppress expression of ChREBP in rats fed a high fat/high sucrose diet and characterized hepatic and systemic responses by integrating transcriptomic and metabolomic analyses. GalNAc-siChREBP-treated rats had lower levels of multiple short-chain acyl CoA metabolites compared to rats treated with GalNAc-siCtrl containing a non-targeting siRNA sequence. These changes were related to a sharp decrease in free CoA levels in GalNAc-siChREBP treated-rats, accompanied by lower expression of transcripts encoding enzymes and transporters involved in CoA biosynthesis. These activities of ChREBP likely contribute to its complex effects on hepatic lipid and energy metabolism. While core enzymes of fatty acid (FA) oxidation are induced by ChREBP knockdown, accumulation of liver acylcarnitines and circulating ketones indicate diversion of acetyl CoA to ketone production rather than complete oxidation in the TCA cycle. Despite strong suppression of pyruvate kinase and activation of pyruvate dehydrogenase, pyruvate levels were maintained, likely via increased expression of pyruvate transporters, and decreased expression of lactate dehydrogenase and alanine transaminase. GalNAc-siChREBP treatment increased hepatic citrate and isocitrate levels while decreasing levels of distal TCA cycle intermediates. The drop in free CoA levels, needed for the 2-ketoglutarate dehydrogenase reaction, as well as a decrease in transcripts encoding the anaplerotic enzymes pyruvate carboxylase, glutamate dehydrogenase, and aspartate transaminase likely contributed to these effects. GalNAc-siChREBP treatment caused striking increases in PRPP and ZMP/AICAR levels, and decreases in GMP, IMP, AMP, NaNM, NAD(P), and NAD(P)H levels, accompanied by reduced expression of enzymes that catalyze late steps in purine and NAD synthesis. ChREBP suppression also increased expression of a set of plasma membrane amino acid transporters, possibly as an attempt to replenish TCA cycle intermediates. In sum, combining transcriptomic and metabolomic analyses has revealed regulatory functions of ChREBP that go well beyond its canonical roles in control of carbohydrate and lipid metabolism to now include mitochondrial metabolism and cellular energy balance.

High-fat diet modulates bile acid composition and gut microbiota, affecting severe cholangitis and cirrhotic change in murine primary biliary cholangitis

Increasing evidence suggests that, in addition to a loss of tolerance, bile acid (BA) modulates the natural history of primary biliary cholangitis (PBC). We focused on the impacts of dietary changes on the immunopathology of PBC, along with alterations in BA composition and gut microbiota. In this study, we have taken advantage of our unique PBC model, a Cyp2c70/Cyp2a12 double knockout (DKO), which includes a human-like BA composition, and develops progressive cholangitis following immunization with the PDC-E2 mimic, 2-octynoic acid (2OA). We compared the effects of a ten-week high-fat diet (HFD) (60 % kcal from fat) and a normal diet (ND) on 2OA-treated DKO mice. Importantly, we report that 2OA-treated DKO mice fed HFD had significantly exacerbated cholangitis, leading to cirrhosis, with increased hepatic expression of Th1 cytokines/chemokines and hepatic fibrotic markers. Serum lithocholic acid (LCA) levels and the ratio of chenodeoxycholic acid (CDCA)-derived BAs to cholic acid-derived BAs were significantly increased by HFD. This was also associated with downregulated expression of key regulators of BA synthesis, including Cyp8b1, Cyp3a11, and Sult2a1. In addition, there were increases in the relative abundances of Acetatifactor and Lactococcus and decreases in Desulfovibrio and Lachnospiraceae_NK4A136_group, which corresponded to the abundances of CDCA and LCA. In conclusion, HFD and HFD-induced alterations in the gut microbiota modulate BA composition and nuclear receptor activation, leading to cirrhotic change in this murine PBC model. These findings have significant implications for understanding the progression of human PBC.

Team players in the pathogenesis of metabolic dysfunctions-associated steatotic liver disease: The basis of development of pharmacotherapy

Nutrient metabolism is regulated by several factors. Social determinants of health with or without genetics are the primary regulator of metabolism, and an unhealthy lifestyle affects all modulators and mediators, leading to the adaptation and finally to the exhaustion of cellular functions. Hepatic steatosis is defined by presence of fat in more than 5% of hepatocytes. In hepatocytes, fat is stored as triglycerides in lipid droplet. Hepatic steatosis results from a combination of multiple intracellular processes. In a healthy individual nutrient metabolism is regulated at several steps. It ranges from the selection of nutrients in a grocery store to the last step of consumption of ATP as an energy or as a building block of a cell as structural component. Several hormones, peptides, and genes have been described that participate in nutrient metabolism. Several enzymes participate in each nutrient metabolism as described above from ingestion to generation of ATP. As of now several publications have revealed very intricate regulation of nutrient metabolism, where most of the regulatory factors are tied to each other bidirectionally, making it difficult to comprehend chronological sequence of events. Insulin hormone is the primary regulator of all nutrients' metabolism both in prandial and fasting states. Insulin exerts its effects directly and indirectly on enzymes involved in the three main cellular function processes; metabolic, inflammation and repair, and cell growth and regeneration. Final regulators that control the enzymatic functions through stimulation or suppression of a cell are nuclear receptors in especially farnesoid X receptor and peroxisome proliferator-activated receptor/RXR ligands, adiponectin, leptin, and adiponutrin. Insulin hormone has direct effect on these final modulators. Whereas blood glucose level, serum lipids, incretin hormones, bile acids in conjunction with microbiota are intermediary modulators which are controlled by lifestyle. The purpose of this review is to overview the key players in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) that help us understand the disease natural course, risk stratification, role of lifestyle and pharmacotherapy in each individual patient with MASLD to achieve personalized care and target the practice of precision medicine. PubMed and Google Scholar databases were used to identify publication related to metabolism of carbohydrate and fat in states of health and disease states; MASLD, cardiovascular disease and cancer. More than 1000 publications including original research and review papers were reviewed.

Application of PPAR Ligands and Nanoparticle Technology in Metabolic Steatohepatitis Treatment

Metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH) is a major disease worldwide whose effective treatment is challenging. Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor superfamily and function as ligand-activated transcription factors. To date, three distinct subtypes of PPARs have been characterized: PPARα, PPARβ/δ, and PPARγ. PPARα and PPARγ are crucial regulators of lipid metabolism that modulate the transcription of genes involved in fatty acid (FA), bile acid, and cholesterol metabolism. Many PPAR agonists, including natural (FAs, eicosanoids, and phospholipids) and synthetic (fibrate, thiazolidinedione, glitazar, and elafibranor) agonists, have been developed. Furthermore, recent advancements in nanoparticles (NPs) have led to the development of new strategies for MASLD/MASH therapy. This review discusses the applications of specific cell-targeted NPs and highlights the potential of PPARα- and PPARγ-targeted NP drug delivery systems for MASLD/MASH treatment.

Liquorice root extract and isoliquiritigenin attenuate high-fat diet-induced hepatic steatosis and damage in rats by regulating AMPK

Objective: This study compared the ability of Liquorice roots aqueous extract (LRE) and its ingredient, isoliquiritigenin (ISL), in alleviating high-fat diet (HFD)-induced hepatic steatosis and examined if this effect involves activation of AMPK.Materials and methods: Control or HFD-fed rats were treated with the vehicle, LRE (200 mg/kg), or ISL (30 mg/kg) for 8 weeks orally.Results: ISL and LRE reduced HFD-induced hyperglycaemia, improved liver structure, lowered serum and hepatic lipids, and attenuated hepatic oxidative stress and inflammation. In the control and HFD-fed rats, ISL and LRE significantly stimulated the muscular and hepatic mRNA and protein levels of AMPK, improved oral glucose tolerance, reduced hepatic mRNA levels of SREBP1/2, and upregulated hepatic levels of PPARα and Bcl2. These effects were comparable for ISL and LRE and were prevented by co-administration of compound C, an AMPK inhibitor.Discussion and conclusion: ISL and LRE provide an effective theory to alleviate hepatic steatosis through activating AMPK.

The downregulation of SCGN induced by lipotoxicity promotes NLRP3-mediated β-cell pyroptosis

Lipotoxicity is a well-established phenomenon that could exacerbate damage to islet β-cells and play a significant role in the development of type 2 diabetes, the underlying mechanisms of which, however, remain unclear. In lipotoxic conditions, secretagogin (SCGN), an EF-hand calcium-binding protein abundantly expressed in islets, is found to undergo downregulation. In light of this, we aim to explore the role of SCGN in lipotoxicity-induced β-cell injury. Our findings show that exposure to ox-LDL in vitro or long-term high-fat diets (HFD) in vivo decreases SCGN expression and induces pyroptosis in β-cells. Moreover, restoring SCGN partially reverses the pyroptotic cell death under ox-LDL or HFD treatments. We have observed that the downregulation of SCGN facilitates the translocation of ChREBP from the cytosol to the nucleus, thereby promoting TXNIP transcription. The upregulation of TXNIP activates the NLRP3/Caspase-1 pathway, leading to pyroptotic cell death. In summary, our study demonstrates that lipotoxicity leads to the downregulation of SCGN expression in islet β-cells, resulting in ChREBP accumulation in the nucleus and subsequent activation of the NLRP3/Caspase-1 pyroptotic pathway. Thus, administering SCGN could be a potential therapeutic strategy to alleviate β-cell damage induced by lipotoxicity in type 2 diabetes.

A review on the cultivation, bioactive compounds, health-promoting factors and clinical trials of medicinal mushrooms Taiwanofungus camphoratus, Inonotus obliquus and Tropicoporus linteus

Medicinal mushrooms, such as Taiwanofungus camphoratus, Inonotus obliquus, and Tropicoporus linteus, have been used in traditional medicine for therapeutic purposes and promotion of overall health in China and many East Asian countries for centuries. Modern pharmacological studies have demonstrated the large amounts of bioactive constituents (such as polysaccharides, triterpenoids, and phenolic compounds) available in these medicinal mushrooms and their potential therapeutic properties. Due to the rising demand for the health-promoting medicinal mushrooms, various cultivation methods have been explored to combat over-harvesting of the fungi. Evidence of the robust pharmacological properties, including their anticancer, hypoglycemic, hypolipidemic, antioxidant, and antiviral activities, have been provided in various studies, where the health-benefiting properties of the medicinal fungi have been further proven through numerous clinical trials. In this review, the cultivation methods, available bioactive constituents, therapeutic properties, and potential uses of T. camphoratus, I. obliquus and T. linteus are explored.

Deciphering the molecular pathways of saroglitazar: A dual PPAR α/γ agonist for managing metabolic NAFLD

Saroglitazar (SARO), a dual peroxisome proliferator activated receptor (PPAR)-α/γ agonist, has been used to treat metabolic diseases such as insulin resistance and diabetic dyslipidemia in patients with non-alcoholic fatty liver disease (NAFLD). SARO, administered at a dose of 4 mg/day, has been consistently studied in clinical trials with different time points ranging from 4 to 24 weeks with NAFLD patients. Due to its PPAR-γ agonistic action, SARO prevents adipose tissue-mediated fatty acid delivery to the liver by increasing insulin sensitivity and regulating adiponectin and leptin levels in adipose tissue. In hepatocytes, SARO induces fatty acid β-oxidation in mitochondria and transcriptionally activates lipid metabolizing genes in peroxisomes. SARO inhibits insulin resistance, thereby preventing the activation of sterol regulatory element-binding proteins -1c and carbohydrate response element binding protein in hepatocytes through its PPAR-α agonistic action. SARO treatment reduces lipotoxicity-mediated oxidative stress by activating the nuclear factor erythroid 2-related factor 2 and transcriptionally expressing the antioxidants from the antioxidant response element in the nucleus through its PPAR-γ agonistic action. SARO provides a PPAR-α/γ-mediated anti-inflammatory effect by preventing the phosphorylation of mitogen-activated protein kinases (JNK and ERK) and nuclear factor kappa B in hepatocytes. Additionally, SARO interferes with transforming growth factor-β/Smad downstream signaling, thereby reducing liver fibrosis progression through its PPAR-α/γ agonistic actions. Thus, SARO improves insulin resistance and dyslipidemia in NAFLD, reduces lipid accumulation in the liver, and thereby prevents mitochondrial toxicity, oxidative stress, inflammation, and fibrosis progression. This review summarizes the possible molecular mechanism of SARO in the NAFLD.

A genome-first approach to variants in MLXIPL and their association with hepatic steatosis and plasma lipids

BACKGROUND

Common variants of the max-like protein X (MLX)-interacting protein-like (MLXIPL) gene, encoding the transcription factor carbohydrate-responsive element-binding protein, have been shown to be associated with plasma triglyceride levels. However, the role of these variants in steatotic liver disease (SLD) is unclear.

METHODS

We used a genome-first approach to analyze a variety of metabolic phenotypes and clinical outcomes associated with a common missense variant in MLXIPL, Gln241His, in 2 large biobanks: the UK Biobank and the Penn Medicine Biobank.

RESULTS

Carriers of MLXIPL Gln241His were associated with significantly lower serum levels of triglycerides, apolipoprotein-B, gamma-glutamyl transferase, and alkaline phosphatase. Additionally, MLXIPL Gln241His carriers were associated with significantly higher serum levels of HDL cholesterol and alanine aminotransferase. Carriers homozygous for MLXIPL Gln241His showed a higher risk of SLD in 2 unrelated cohorts. Carriers of MLXIPL Gln241His were especially more likely to be diagnosed with SLD if they were female, obese, and/or also carried the PNPLA3 I148M variant. Furthermore, the heterozygous carriage of MLXIPL Gln241His was associated with significantly higher all-cause, liver-related, and cardiovascular mortality rates. Nuclear magnetic resonance metabolomics data indicated that carriage of MLXIPL Gln241His was significantly associated with lower serum levels of VLDL and increased serum levels of HDL cholesterol.

CONCLUSIONS

Analyses of the MLXIPL Gln241His polymorphism showed a significant association with a higher risk of SLD diagnosis and elevated serum alanine aminotransferase as well as significantly lower serum triglycerides and apolipoprotein-B levels. MLXIPL might, therefore, be a potential pharmacological target for the treatment of SLD and hyperlipidemia, notably for patients at risk. More mechanistic studies are needed to better understand the role of MLXIPL Gln241His on lipid metabolism and steatosis development.

Differences in diacylglycerol acyltransferases expression patterns and regulation cause distinct hepatic triglyceride deposition in fish

Triglyceride (TAG) deposition in the liver is associated with metabolic disorders. In lower vertebrate, the propensity to accumulate hepatic TAG varies widely among fish species. Diacylglycerol acyltransferases (DGAT1 and DGAT2) are major enzymes for TAG synthesis. Here we show that large yellow croaker (Larimichthys crocea) has significantly higher hepatic TAG level than that in rainbow trout (Oncorhynchus mykiss) fed with same diet. Hepatic expression of DGATs genes in croaker is markedly higher compared with trout under physiological condition. Meanwhile, DGAT1 and DGAT2 in both croaker and trout are required for TAG synthesis and lipid droplet formation in vitro. Furthermore, oleic acid treatment increases DGAT1 expression in croaker hepatocytes rather than in trout and has no significant difference in DGAT2 expression in two fish species. Finally, effects of various transcription factors on croaker and trout DGAT1 promoter are studied. We find that DGAT1 is a target gene of the transcription factor CREBH in croaker rather than in trout. Overall, hepatic expression and transcriptional regulation of DGATs display significant species differences between croaker and trout with distinct hepatic triglyceride deposition, which bring new perspectives on the use of fish models for studying hepatic TAG deposition.

The Relationship between Pathogenesis and Possible Treatments for the MASLD-Cirrhosis Spectrum

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a term that entails a broad spectrum of conditions that vary in severity. Its development is influenced by multiple factors such as environment, microbiome, comorbidities, and genetic factors. MASLD is closely related to metabolic syndrome as it is caused by an alteration in the metabolism of fatty acids due to the accumulation of lipids because of an imbalance between its absorption and elimination in the liver. Its progression to fibrosis is due to a constant flow of fatty acids through the mitochondria and the inability of the liver to slow down this metabolic load, which generates oxidative stress and lipid peroxidation, triggering cell death. The development and progression of MASLD are closely related to unhealthy lifestyle habits, and nutritional epigenetic and genetic mechanisms have also been implicated. Currently, lifestyle modification is the first-line treatment for MASLD and nonalcoholic steatohepatitis; weight loss of ≥10% produces resolution of steatohepatitis and fibrosis regression. In many patients, body weight reduction cannot be achieved; therefore, pharmacological treatment should be offered in particular populations.

Quercetin Regulates Lipid Metabolism and Fat Accumulation by Regulating Inflammatory Responses and Glycometabolism Pathways: A Review

Fat synthesis and lipolysis are natural processes in growth and have a close association with health. Fat provides energy, maintains physiological function, and so on, and thus plays a significant role in the body. However, excessive/abnormal fat accumulation leads to obesity and lipid metabolism disorder, which can have a detrimental impact on growth and even harm one's health. Aside from genetic effects, there are a range of factors related to obesity, such as excessive nutrient intake, inflammation, glycometabolism disease, and so on. These factors could serve as potential targets for anti-obesity therapy. Quercetin is a flavonol that has received a lot of attention recently because of its role in anti-obesity. It was thought to have the ability to regulate lipid metabolism and have a positive effect on anti-obesity, but the processes are still unknown. Recent studies have shown the role of quercetin in lipid metabolism might be related to its effects on inflammatory responses and glycometabolism. The references were chosen for this review with no date restrictions applied based on the topics they addressed, and the databases PubMed and Web of Sicence was used to conduct the references research, using the following search terms: "quercetin", "obesity", "inflammation", "glycometabolism", "insulin sensitivity", etc. This review summarizes the potential mechanisms of quercetin in alleviating lipid metabolism through anti-inflammatory and hypoglycemic signaling pathways, and describes the possible signaling pathways in the interaction of inflammation and glycometabolism, with the goal of providing references for future research and application of quercetin in the regulation of lipid metabolism.

Chronic sucralose consumption inhibits farnesoid X receptor signaling and perturbs lipid and cholesterol homeostasis in the mouse livers, potentially by altering gut microbiota functions

Sucralose has raised concerns regarding its safety and recent studies have demonstrated that sucralose consumption can disrupt the normal gut microbiome and alter metabolic profiles in mice. However, the extent to which this perturbation affects the functional interaction between the microbiota and the host, as well as its potential impact on host health, remains largely unexplored. Here, we aimed to investigate whether chronic sucralose consumption, at levels within the Acceptable Daily Intake (ADI), could disturb key gut microbial functions and lead to adverse health effects in mice. Following six-month sucralose consumption, several bacterial genera associated with bile acid metabolism were decreased, including Lactobacillus and Ruminococcus. Consequently, the richness of secondary bile acid biosynthetic pathway and bacterial bile salt hydrolase gene were decreased in the sucralose-treated gut microbiome. Compared to controls, sucralose-consuming mice exhibited significantly lower ratios of free bile acids and taurine-conjugated bile acids in their livers. Additionally, several farnesoid X receptor (FXR) agonists were decreased in sucralose-treated mice. This reduction in hepatic FXR activation was associated with altered expression of down-stream genes, in the liver. Moreover, the expression of key lipogenic genes was up-regulated in the livers of sucralose-treated mice. Changes in hepatic lipid profiles were also observed, characterized by lower ceramide levels, a decreased PC/PE ratio, and a mildly increase in lipid accumulation. Additionally, sucralose-consumed mice exhibited higher hepatic cholesterol level compared to control mice, with up-regulation of cholesterol efflux genes and down-regulation of genes associated with reverse cholesterol transport. In conclusion, chronic sucralose consumption disrupts FXR signaling activation and perturbs hepatic lipid and cholesterol homeostasis, potentially by diminishing the bile acid metabolic capacity of the gut microbiome. These findings shed light on the complex interplay between sucralose, the gut microbiota, and host metabolism, raising important questions about the safety of its long-term consumption.

The Antiobesity Effects of Rosehip (Rosa canina) Flesh by Antagonizing the PPAR Gamma Activity in High-Fat Diet-Fed Mice

SCOPE

The rosehip (Rosa canina) is a perennial shrub with a reddish pseudofruit that has demonstrated antidiabetic, antiatherosclerotic, and antiobesogenic effects in rodent models but there is low information about the molecular mechanisms underlying these effects on the onset and progression of diet-induced obesity.

METHODS AND RESULTS

Four-week-old C57BL/6J male mice are subjected to a high-fat diet (HFD)-supplemented or not with R. canina flesh for 18 weeks. The results indicated that the R. canina flesh exerts a preventive effect on HFD-induced obesity with a significant reduction in body-weight gain and an improvement of hyperglycemia and insulin resistance caused by a HFD. At the tissue level, subcutaneous white adipose tissue exhibits a higher number of smaller adipocytes, with decreased lipogenesis. On its side, the liver shows a significant decrease in lipid droplet content and in the expression of genes related to lipogenesis, fatty acid oxidation, and glucose metabolism. Finally, the data suggest that most of these effects agree with the presence of a putative Perosxisome proliferator-activated receptor gamma (PPARγ) antagonist in the R. canina flesh.

CONCLUSIONS

R. canina flesh dietary supplementation slows down the steatotic effect of a HFD at least in part through the regulation of the transcriptional activity of PPARγ.

CDK6 inhibits de novo lipogenesis in white adipose tissues but not in the liver

Increased de novo lipogenesis (DNL) in white adipose tissue is associated with insulin sensitivity. Under both Normal-Chow-Diet and High-Fat-Diet, mice expressing a kinase inactive Cyclin-dependent kinase 6 (Cdk6) allele (K43M) display an increase in DNL in visceral white adipose tissues (VAT) as compared to wild type mice (WT), accompanied by markedly increased lipogenic transcriptional factor Carbohydrate-responsive element-binding proteins (CHREBP) and lipogenic enzymes in VAT but not in the liver. Treatment of WT mice under HFD with a CDK6 inhibitor recapitulates the phenotypes observed in K43M mice. Mechanistically, CDK6 phosphorylates AMP-activated protein kinase, leading to phosphorylation and inactivation of acetyl-CoA carboxylase, a key enzyme in DNL. CDK6 also phosphorylates CHREBP thus preventing its entry into the nucleus. Ablation of runt related transcription factor 1 in K43M mature adipocytes reverses most of the phenotypes observed in K43M mice. These results demonstrate a role of CDK6 in DNL and a strategy to alleviate metabolic syndromes.

Association of daily carbohydrate intake with intermuscular adipose tissue in Korean individuals with obesity: a cross-sectional study

BACKGROUND/OBJECTIVES

The prevalence of obesity, a worldwide pandemic, has been increasing steadily in Korea. Reports have shown that increased intermuscular adipose tissue (IMAT) is associated with an increased risk of cardiovascular disease, independent of body mass index. However, the relationship between dietary intake and IMAT accumulation in the Korean population remains undetermined. The objective of this study was to evaluate regional fat compartments using advanced magnetic resonance imaging (MRI) techniques. We also aimed to investigate the association between IMAT amounts and dietary intake, including carbohydrate intake, among Korean individuals with obesity.

SUBJECTS/METHODS

This cross-sectional study, performed at a medical center in South Korea, recruited 35 individuals with obesity (15 men and 20 women) and classified them into 2 groups according to sex. Anthropometry was performed, and body fat distribution was measured using MRI. Blood parameters, including glucose and lipid profiles, were analyzed using commercial kits. Linear regression analysis was used to test whether the IMAT was associated with daily carbohydrate intake.

RESULTS

Carbohydrate intake was positively associated with IMAT in all individuals, with adjustments for age, sex, height, and weight. No significant differences in blood indicators were found between the sexes.

CONCLUSIONS

Regardless of sex and age, higher carbohydrate intake was strongly correlated with greater IMAT accumulation. This suggests the need to better understand sex differences and high carbohydrate diet patterns in relation to the association between obesity and metabolic risk, which may help reduce obesity prevalence.

The Influence of Hyperglycemia on Liver Triglyceride Deposition in Partially Pancreatectomized Rats

Nonalcoholic fatty liver disease and diabetes always coexist. The relationship of fatty liver and hyperglycemia is not clear. We studied the influence of hyperglycemia on triglyceride (TG) accumulation in the liver and explored its possible mechanisms. SD rats were divided into three groups: Group A (sham operation control), Group B (partially pancreatectomized rats), and Group C (partially pancreatectomized rats treated with insulin). At 4 weeks after surgery, pancreatic weights and liver TG contents were measured. Serum biochemical parameters were determined, and oral glucose tolerance tests (OGTT) were performed. The gene expression of sterol regulatory element-binding protein1c (SREBP-1c), carbohydrate regulatory element-binding protein (ChREBP), fatty acid synthase(FAS), carnitine palmitoyltransferase 1 (CPT-1), and fibroblast growth factor 21 (FGF21) was determined by real-time PCR. Compared with Group A, postprandial glucose increased significantly; the concentrations of insulin and C-peptides, pancreatic weights and serum FGF21 levels were decreased, liver TG was increased significantly in Group B, and insulin treatment improved these changes. Compared with Group A, the gene expressions of FGF21, CPT-1 and FAS in the liver were decreased in Group B (all p<0.05). Compared with Group B, the gene expressions of FGF21, FAS, ChREBP, SREBP-1c and CPT-1 in the liver in Group C were all increased significantly (p<0.05, respectively). Hyperglycemia induced by partial pancreatectomy could lead to increased liver TG. Insulin treatment could decrease glucose levels and improve fatty liver, and genes related to lipid metabolism may play a role in this process.

The GR-KLF15 axis promotes suppression of hepatic lipogenesis during fasting

Fasting leads to many physiological changes in peripheral tissues, including the liver, where suppression of de novo lipogenesis through inhibition of sterol regulatory element-binding protein 1 (SREBP-1) expression and/or activity is a key adaptation to preserve glucose for maintenance of blood glucose levels. Yoshinori Takeuchi and colleagues provide novel mechanistic insights into the regulation of SREBP-1 expression during fasting and highlight the importance of the hypothalamic-pituitary-adrenal axis and, particularly, glucocorticoid-induced binding of the glucocorticoid receptor to enhancer regions of the KLF15 (Kruppel-like factor 15) gene as a novel mechanism underlying the suppression of SREBP-1 during fasting.

Rotundic acid improves nonalcoholic steatohepatitis in mice by regulating glycolysis and the TLR4/AP1 signaling pathway

BACKGROUND

Steatosis and inflammation are the hallmarks of nonalcoholic steatohepatitis (NASH). Rotundic acid (RA) is among the key triterpenes of Ilicis Rotundae Cortex and has exhibited multipronged effects in terms of lowering the lipid content and alleviating inflammation. The study objective is to systematically evaluate the potential mechanisms through which RA affects the development and progression of NASH.

METHODS

Transcriptomic and proteomic analyses of primary hepatocytes isolated from the control, high-fat diet-induced NASH, and RA treatment groups were performed through Gene Ontology analysis and pathway enrichment. Hub genes were identified through network analysis. Integrative analysis revealed key RA-regulated pathways, which were verified by gene and protein expression studies and cell assays.

RESULTS

Hub genes were identified and enriched in the Toll-like receptor 4 (TLR4)/activator protein-1 (AP1) signaling pathway and glycolysis pathway. RA reversed glycolysis and attenuated the TLR4/AP1 pathway, thereby reducing lipid accumulation and inflammation. Additionally, lactate release in L-02 cells increased with NaAsO2-treated and significantly decreased with RA treatment, thus revealing that RA had a major impact on glycolysis.

CONCLUSIONS

RA is effective in lowering the lipid content and reducing inflammation in mice with NASH by ameliorating glycolysis and TLR4/AP1 pathways, which contributes to the existing knowledge and potentially sheds light on the development of therapeutic interventions for patients with NASH.

Association of Aquaporin 7 and 9 with Obesity and Fatty Liver in db/db Mice

Aquaporin (AQP) 7 and AQP9 are membrane channel proteins called aquaglyceroporins and are related to glucose and lipid metabolism. AQP7 is mainly expressed in white adipose tissue (WAT) and is involved in releasing glycerol into the bloodstream. AQP9 is the glycerol channel in the liver that supplies glycerol to the hepatic cells. In this study, we investigated the relationship between the expression of aquaglyceroporins and lifestyle-related diseases, such as obesity and fatty liver, using 22-week-old db/db mice. Body weight, WAT, and liver weight showed increases in db/db mice. The levels of liver lipids, plasma lipids, insulin, and leptin were also increased in db/db mice. Gene expression related to fatty acid and triglyceride synthesis in the liver was enhanced in db/db mice. In addition, gene and protein expression of gluconeogenesis-related enzymes was increased. Conversely, lipolysis-related gene expression in WAT was reduced. In the db/db mice, AQP9 expression in the liver was raised; however, AQP7 expression in WAT was reduced. These results suggest that in db/db mice, enhanced hepatic AQP9 expression increased the supply of glycerol to the liver and induced fatty liver and hyperglycemia. Additionally, reduced AQP7 expression in WAT is associated with excessive lipid accumulation in adipocytes. Aquaglyceroporins are essential molecules for glucose and lipid metabolism, and may be potential target molecules for the treatment of obesity and lifestyle-related diseases.

F6P/G6P-mediated ChREBP activation promotes the insulin resistance-driven hepatic lipid deposition in zebrafish

Insulin-sensitive lipogenesis dominates the body lipid deposition; however, nonalcoholic fatty liver disease (NAFLD) develops in the insulin-resistant state. The regulation mechanism of insulin resistance-driven NAFLD remains elusive. Using zebrafish model of insulin resistance (ZIR, insrb-/-) and mouse hepatocytes (NCTC 1469), we explored the regulation mechanism of insulin resistance-driven hepatic lipid deposition under the stimulation of carbohydrate diet (CHD). In ZIR model, insulin resistance induced hyperlipidemia and elevated hepatic lipid deposition via elevating the gene/protein expressions of lipogenic enzymes, that was activated by carbohydrate response element binding protein (ChREBP), rather than sterol regulatory element binding proteins 1c (SREBP-1c). The metabolomic analysis in zebrafish and silencing of chrebp in mouse hepatocytes revealed that the increased hepatic frucotose-6-phosphate (F6P) and glucose-6-phosphate (G6P) promoted the ChREBP-mediated lipid deposition. We further identified that F6P alone was sufficient to activate ChREBP-mediated lipid deposition by a SREBP-1c-independent manner. Moreover, we clarified the suppressed hepatic phosphofructokinase/glucose-6-phosphatase functions and the normal glucokinase function preserved by glucose transporter 2 (GLUT2) manipulated the increased F6P/G6P content in ZIR. In conclusion, the present study revealed that insulin resistance promoted hepatic lipid deposition via the F6P/G6P-mediated ChREBP activation. Our findings deciphered the main regulation pathway for the liver lipid deposition in the insulin-resistant state and identified F6P as a new potential regulator for ChREBP.

Esculeogenin A, a Glycan from Tomato, Alleviates Nonalcoholic Fatty Liver Disease in Rats through Hypolipidemic, Antioxidant, and Anti-Inflammatory Effects

This study examined the preventative effects of esculeogenin A (ESGA), a newly discovered glycan from tomato, on liver damage and hepatic steatosis in high-fat-diet (HFD)-fed male rats. The animals were divided into six groups (each of eight rats): a control group fed a normal diet, control + ESGA (200 mg/kg), HFD, and HFD + ESAG in 3 doses (50, 100, and 200 mg/kg). Feeding and treatments were conducted for 12 weeks. Treatment with ESGA did not affect gains in the body or fat weight nor increases in fasting glucose, insulin, and HOMA-IR or serum levels of free fatty acids (FFAs), tumor-necrosis factor-α, and interleukin-6 (IL-6). On the contrary, it significantly reduced the serum levels of gamma-glutamyl transpeptidase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), total triglycerides (TGs), cholesterol (CHOL), and low-density lipoprotein cholesterol (LDL-c) in the HFD-fed rats. In addition, it improved the liver structure, attenuating the increase in fat vacuoles; reduced levels of TGs and CHOL, and the mRNA levels of SREBP1 and acetyl CoA carboxylase (ACC); and upregulated the mRNA levels of proliferator-activated receptor α (PPARα) and carnitine palmitoyltransferase I (CPT I) in HFD-fed rats. These effects were concomitant with increases in the mRNA, cytoplasmic, and nuclear levels of nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and heme oxygenase-1 (HO); a reduction in the nuclear activity of nuclear factor-kappa beta (NF-κB); and inhibition of the activity of nuclear factor kappa B kinase subunit beta (IKKβ). All of these effects were dose-dependent effects in which a normal liver structure and normal levels of all measured parameters were seen in HFD + ESGA (200 mg/kg)-treated rats. In conclusion, ESGA prevents NAFLD in HFD-fed rats by attenuating hyperlipidemia, hepatic steatosis, oxidative stress, and inflammation by acting locally on Nrf2, NF-κB, SREBP1, and PPARα transcription factors.

Human skin stem cell-derived hepatic cells as in vitro drug discovery model for insulin-driven de novo lipogenesis

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), is characterized by intrahepatic triglyceride accumulation and can progress to metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. Hepatic de novo lipogenesis (DNL), activated by glucose and insulin, is a central pathway contributing to early-stage development of MASLD. The emerging global prevalence of MASLD highlights the urgent need for pharmaceutical intervention to combat this health threat. However, the identification of novel drugs that could inhibit hepatic DNL is hampered by a lack of reliable, insulin-sensitive, human, in vitro, hepatic models. Here, we report human skin stem cell-derived hepatic cells (hSKP-HPC) as a unique in vitro model to study insulin-driven DNL (iDNL), evidenced by both gene expression and lipid accumulation readouts. Insulin-sensitive hSKP-HPC showed increased sterol regulatory element-binding protein 1c (SREBP-1c) expression, a key transcription factor for DNL. Furthermore, this physiologically relevant in vitro human steatosis model allowed both inhibition and activation of the iDNL pathway using reference inhibitors and activators, respectively. Optimisation of the lipid accumulation assay to a high-throughput, 384-well format enabled the screening of a library of annotated compounds, delivering new insights on key players in the iDNL pathway and MASLD pathophysiology. Together, these results establish the value of the hSKP-HPC model in preclinical development of antisteatotic drugs to combat MASLD.

Effects of In Utero PFOS Exposure on Epigenetics and Metabolism in Mouse Fetal Livers

Prenatal exposure to perfluorooctanesulfonate (PFOS) increases fetus' metabolic risk; however, the investigation of the underlying mechanism is limited. In this study, pregnant mice in the gestational days (GD, 4.5-17.5) were exposed to PFOS (0.3 and 3 μg/g of body weight). At GD 17.5, PFOS perturbed maternal lipid metabolism and upregulated metabolism-regulating hepatokines (Angptl4, Angptl8, and Selenop). Mass-spectrometry imaging and whole-genome bisulfite sequencing revealed, respectively, selective PFOS localization and deregulation of gene methylation in fetal livers, involved in inflammation, glucose, and fatty acid metabolism. PCR and Western blot analysis of lipid-laden fetal livers showed activation of AMPK signaling, accompanied by significant increases in the expression of glucose transporters (Glut2/4), hexose-phosphate sensors (Retsat and ChREBP), and the key glycolytic enzyme, pyruvate kinase (Pk) for glucose catabolism. Additionally, PFOS modulated the expression levels of PPARα and PPARγ downstream target genes, which simultaneously stimulated fatty acid oxidation (Cyp4a14, Acot, and Acox) and lipogenesis (Srebp1c, Acaca, and Fasn). Using human normal hepatocyte (MIHA) cells, the underlying mechanism of PFOS-elicited nuclear translocation of ChREBP, associated with a fatty acid synthesizing pathway, was revealed. Our finding implies that in utero PFOS exposure altered the epigenetic landscape associated with dysregulation of fetal liver metabolism, predisposing postnatal susceptibility to metabolic challenges.

Tibetan tea reduces obesity brought on by a high-fat diet and modulates gut flora in mice

It has been shown that Tibetan tea (TT) inhibits obesity and controls lipid metabolism. The fundamental processes by which TT prevents obesity are yet entirely unknown. Consequently, this research aimed to ascertain if TT may prevent obesity by modifying the gut flora. Our research demonstrated that TT prevented mice from gaining weight and accumulating fat due to the high-fat diet (HFD), decreased levels of blood total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C), and raised levels of high-density lipoprotein cholesterol (HDL-C). Adipogenesis-related genes such as acetyl-Coenzyme A carboxylase 1 (ACC1, LOC107476), fatty acid synthase (Fas, LOC14104), sterol regulatory element-binding protein-1c (SREBP-1c, LOC20787), CCAAT/enhancer-binding protein α (C/EBPα, LOC12606), stearoyl-CoA desaturase 1 (SCD1, LOC20249), and peroxisome proliferator-activated receptor γ (PPARγ, LOC19016) had their expression downregulated by lowering the Firmicutes/Bacteroidetes (F/B) ratio and controlling the number of certain gut bacteria. TT also alleviated HFD-induced abnormalities of the gut microbiota. The Muribaculaceae, Lachnospiraceae NK4A136_group, Alistipes, and Odoribacter families were identified as the major beneficial gut microorganisms using Spearman's correlation analysis. Fecal microbiota transplantation (FMT) demonstrated that TT's anti-obesity and gut microbiota-modulating benefits might be transmitted to mice on an HFD, demonstrating that one of TT's targets for preventing obesity is the gut microbiota. TT also increased the amount of short-chain fatty acids (SCFAs) in the feces, including acetic, propionic, and butyric acids. These results indicate the possible development of TT as a prebiotic to combat obesity and associated disorders. These results suggest that TT may act as a prebiotic against obesity and its associated diseases.

Farnesoid X receptor is an important target for the treatment of disorders of bile acid and fatty acid metabolism in mice with nonalcoholic fatty liver disease combined with cholestasis

BACKGROUND AND AIM

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been rising globally. NAFLD patients combined with cholestasis have more obvious liver fibrosis, impaired bile acid (BA), and fatty acid (FA) metabolism and severer liver injury; however, its therapeutic options are limited, and the underlying metabolic mechanisms are understood. Here, we aimed to investigate the effects of farnesoid X receptor (FXR) on BA and FA metabolism in NAFLD combined with cholestasis and related signaling pathways.

METHODS

A mouse model of NAFLD combined with cholestasis was established by joint intervention with high-fat diet (HFD) and alpha-naphthylisothiocyanate. The effects of FXR on BA and FA metabolism were evaluated by serum biochemical analysis. Liver damage was identified by histopathology. The expression of nuclear hormone receptor, membrane receptor, FA transmembrane transporter, and BA transporter protein in mice were measured by western blot.

RESULTS

NAFLD mice combined with cholestasis developed more severe cholestasis and dysregulated BA and FA metabolism. Meanwhile, the expression of FXR protein was decreased in NAFLD mice combined with cholestasis compared to the controls. Fxr-/- mice showed liver injury. HFD aggravated the liver injury with decreased BSEP expression, increased expression of NTCP, LXRα, SREBP-1c, FAS, ACC1, and CD36, and significantly increased BA and FA accumulation.

CONCLUSION

All the results suggested that FXR plays a key role in both FA and BA metabolism in NAFLD combined with cholestasis and thus may be a potential target for the treatment of disorders of BA and FA metabolism in NAFLD combined with cholestasis.

Sequential Activations of ChREBP and SREBP1 Signals Regulate the High-Carbohydrate Diet-Induced Hepatic Lipid Deposition in Gibel Carp (Carassius gibelio)

The present study investigated the sequential regulation signals of high-carbohydrate diet (HCD)-induced hepatic lipid deposition in gibel carp (Carassius gibelio). Two isonitrogenous and isolipidic diets, containing 25% (normal carbohydrate diet, NCD) and 45% (HCD) corn starch, were formulated to feed gibel carp (14.82 ± 0.04 g) for 8 weeks. The experimental fish were sampled at 2^nd, 4^th, 6^th, and 8^th week. In HCD group, the hyperlipidemia and significant hepatic lipid deposition (oil red O area and triglyceride content) was found at 4^th, 6^th, and 8^th week, while the significant hyperglycemia was found at 2^nd, 4^th, and 8^th week, compared to NCD group (P < 0.05). HCD induced hepatic lipid deposition via increased hepatic lipogenesis (acc, fasn, and acly) but not decreased hepatic lipolysis (hsl and cpt1a). When compared with NCD group, HCD significantly elevated the hepatic sterol regulatory element binding proteins 1 (SREBP1) signals (positive hepatocytes and fluorescence intensity) at 4^th, 6^th, and 8^th week (P < 0.05). The hepatic SREBP1 signals increased from 2^nd to 6^th week, but decreased at 8^th week due to substantiated insulin resistance (plasma insulin levels, plasma glucose levels, and P-AKT^Ser473 levels) in HCD group. Importantly, the hepatic carbohydrate response element binding protein (ChREBP) signals (positive hepatocytes, fluorescence intensity, and expression levels) were all significantly elevated by HCD-induced glucose-6-phosphate (G6P) accumulation at 2^nd, 4^th, 6^th, and 8^th week (P < 0.05). Compared to 2^nd and 4^th week, the hepatic ChREBP signals and G6P contents was significantly increased by HCD at 6^th and 8^th week (P < 0.05). The HCD-induced G6P accumulation was caused by the significantly increased expression of hepatic gck, pklr, and glut2 (P < 0.05) but not 6pfk at 4^th, 6^th, and 8^th week, compared to NCD group. These results suggested that the HCD-induced hepatic lipid deposition was mainly promoted by SREBP1 in earlier stage and by ChREBP in later stage for gibel carp. This study revealed the sequential regulation pathways of the conversion from feed carbohydrate to body lipid in fish.

Akkermansia muciniphila in neuropsychiatric disorders: friend or foe?

An accumulating body of evidence suggests that the bacterium Akkermansia muciniphila exhibits positive systemic effects on host health, mainly by improving immunological and metabolic functions, and it is therefore regarded as a promising potential probiotic. Recent clinical and preclinical studies have shown that A. muciniphila plays a vital role in a variety of neuropsychiatric disorders by influencing the host brain through the microbiota-gut-brain axis (MGBA). Numerous studies observed that A. muciniphila and its metabolic substances can effectively improve the symptoms of neuropsychiatric disorders by restoring the gut microbiota, reestablishing the integrity of the gut mucosal barrier, regulating host immunity, and modulating gut and neuroinflammation. However, A. muciniphila was also reported to participate in the development of neuropsychiatric disorders by aggravating inflammation and influencing mucus production. Therefore, the exact mechanism of action of A. muciniphila remains much controversial. This review summarizes the proposed roles and mechanisms of A. muciniphila in various neurological and psychiatric disorders such as depression, anxiety, Parkinson's disease, Alzheimer's disease, multiple sclerosis, strokes, and autism spectrum disorders, and provides insights into the potential therapeutic application of A. muciniphila for the treatment of these conditions.

Gallstone and Gallbladder Disease: Biliary Tract and Cholangiopathies

Cholestatic liver diseases are named primarily due to the blockage of bile flow and buildup of bile acids in the liver. Cholestasis can occur in cholangiopathies, fatty liver diseases, and during COVID-19 infection. Most literature evaluates damage occurring to the intrahepatic biliary tree during cholestasis; however, there may be associations between liver damage and gallbladder damage. Gallbladder damage can manifest as acute or chronic inflammation, perforation, polyps, cancer, and most commonly gallstones. Considering the gallbladder is an extension of the intrahepatic biliary network, and both tissues are lined by biliary epithelial cells that share common mechanisms and properties, it is worth further evaluation to understand the association between bile duct and gallbladder damage. In this comprehensive article, we discuss background information of the biliary tree and gallbladder, from function, damage, and therapeutic approaches. We then discuss published findings that identify gallbladder disorders in various liver diseases. Lastly, we provide the clinical aspect of gallbladder disorders in liver diseases and ways to enhance diagnostic and therapeutic approaches for congruent diagnosis. © 2023 American Physiological Society. Compr Physiol 13:4909-4943, 2023.

Insulin Regulation of Hepatic Lipid Homeostasis

The incidence of obesity, insulin resistance, and type II diabetes (T2DM) continues to rise worldwide. The liver is a central insulin-responsive metabolic organ that governs whole-body metabolic homeostasis. Therefore, defining the mechanisms underlying insulin action in the liver is essential to our understanding of the pathogenesis of insulin resistance. During periods of fasting, the liver catabolizes fatty acids and stored glycogen to meet the metabolic demands of the body. In postprandial conditions, insulin signals to the liver to store excess nutrients into triglycerides, cholesterol, and glycogen. In insulin-resistant states, such as T2DM, hepatic insulin signaling continues to promote lipid synthesis but fails to suppress glucose production, leading to hypertriglyceridemia and hyperglycemia. Insulin resistance is associated with the development of metabolic disorders such as cardiovascular and kidney disease, atherosclerosis, stroke, and cancer. Of note, nonalcoholic fatty liver disease (NAFLD), a spectrum of diseases encompassing fatty liver, inflammation, fibrosis, and cirrhosis, is linked to abnormalities in insulin-mediated lipid metabolism. Therefore, understanding the role of insulin signaling under normal and pathologic states may provide insights into preventative and therapeutic opportunities for the treatment of metabolic diseases. Here, we provide a review of the field of hepatic insulin signaling and lipid regulation, including providing historical context, detailed molecular mechanisms, and address gaps in our understanding of hepatic lipid regulation and the derangements under insulin-resistant conditions. © 2023 American Physiological Society. Compr Physiol 13:4785-4809, 2023.

Non-Alcoholic Fatty Liver Disease and Liver Fibrosis in Persons with Type 2 Diabetes Mellitus in Ghana: A Study of Prevalence, Severity, and Contributing Factors Using Transient Elastography

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance, and pancreatic islet cell dysfunction. T2DM is associated with non-alcoholic fatty liver disease (NAFLD) because of impaired glucose metabolism in both conditions. However, it is widely assumed that people with T2DM in sub-Saharan Africa (SSA) have a lower prevalence of NAFLD than in other parts of the world. With our recent access to transient elastography, we aimed to investigate the prevalence of, severity of, and contributing factors to NAFLD in persons with T2DM in Ghana. We performed a cross-sectional study recruiting 218 individuals with T2DM at the Kwadaso Seventh-Day Adventist and Mount Sinai Hospitals in the Ashanti region of Ghana using a simple randomized sampling technique. A structured questionnaire was used to obtain socio-demographic information, clinical history, exercise and other lifestyle factors, and anthropometric measurements. Transient elastography was performed using a FibroScan® machine to obtain the Controlled Attenuation Parameter (CAP) score and liver fibrosis score. The prevalence of NAFLD among Ghanaian T2DM participants was 51.4% (112/218), of whom 11.6% had significant liver fibrosis. An evaluation of the NAFLD group (n = 112) versus the non-NAFLD group (n = 106) revealed a higher BMI (28.7 vs. 25.2 kg/m2, p = 0.001), waist circumference (106.0 vs. 98.0 cm, p = 0.001), hip circumference (107.0 vs. 100.5 cm, p = 0.003), and waist-to-height ratio (0.66 vs. 0.62, p = 0.001) in T2DM patients with NAFLD compared to those without NAFLD. Being obese was an independent predictor of NAFLD in persons with T2DM than known history of hypertension and dyslipidaemia.

Dysregulation of Lipid and Glucose Metabolism in Nonalcoholic Fatty Liver Disease

Non-Alcoholic Fatty Liver Disease (NAFLD) is a highly prevalent condition affecting approximately a quarter of the global population. It is associated with increased morbidity, mortality, economic burden, and healthcare costs. The disease is characterized by the accumulation of lipids in the liver, known as steatosis, which can progress to more severe stages such as steatohepatitis, fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC). This review focuses on the mechanisms that contribute to the development of diet-induced steatosis in an insulin-resistant liver. Specifically, it discusses the existing literature on carbon flux through glycolysis, ketogenesis, TCA (Tricarboxylic Acid Cycle), and fatty acid synthesis pathways in NAFLD, as well as the altered canonical insulin signaling and genetic predispositions that lead to the accumulation of diet-induced hepatic fat. Finally, the review discusses the current therapeutic efforts that aim to ameliorate various pathologies associated with NAFLD.