Mechanism of Hepatic Insulin Resistance in Non-alcoholic Fatty Liver Disease

Benzyl isothiocyanate ameliorates hepatic insulin resistance in mice with high-fat diet-induced nonalcoholic fatty liver disease

The global prevalence of overweight and obesity has risen sharply over the past few decades as a result of excess calorie intake and sedentary lifestyles. Obesity increases the risk for various metabolic disorders, such as hyperlipidemia, fatty liver disease, and diabetes mellitus. Isothiocyanates, which are abundant in cruciferous vegetables, have been shown to exhibit anti-cancer, anti-inflammatory, and antioxidant properties. However, the efficacy of benzyl isothiocyanate (BITC) in preventing the adverse effects of obesity, such as hepatic steatosis and insulin resistance, remains uncertain. To address this knowledge gap, we assessed whether BITC protects against hepatic insulin resistance by using primary mouse hepatocytes and AML12 cells treated with palmitic acid (PA) and mice fed a high-fat diet supplemented with cholesterol and cholic acid (HFCCD). We found that the impairments in insulin sensitivity caused by PA, such as decreases in the phosphorylation of insulin receptor substrate (IRS) 1 (Tyr608), Akt, glycogen synthase kinase (GSK) 3β, and FOXO1 and increases in the expression of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase 1 (PEPCK) mRNA in hepatocytes, were mitigated by pretreatment with BITC. BITC also attenuated PA-induced hepatic lipid accumulation and reactive oxygen species production. In vivo, BITC significantly reduced blood glucose levels and the HOMA-IR and inhibited hepatic lipid accumulation, IRS1 phosphorylation at Ser307, and G6Pase and PEPCK expression compared with that in mice fed the HFCCD alone. These results show that BITC ameliorates the lipotoxicity associated with insulin resistance by activating the IR/IRS/Akt/FOXO1 and GSK3β pathways, which leads to decreased gluconeogenesis and increased glycogen synthesis.

Effect of pemafibrate in reducing intestinal long-chain fatty acid absorption and hepatic fibrosis in metabolic dysfunction-associated steatohepatitis rats

BACKGROUND

Pemafibrate helps regulate fatty acid dynamics in the liver, potentially preventing metabolic dysfunction-associated steatohepatitis (MASH). However, its effect on intestinal long-chain fatty acid (LCFA) metabolism in MASH remains unclear. Thus, we aimed to examine the influence of pemafibrate on intestinal LCFA metabolism and hepatic fibrosis in a MASH rat model.

METHODS

Sprague-Dawley rats were fed a high-fat and high-cholesterol diet to induce MASH and then divided into pemafibrate-treated (pemafibrate (+)) and untreated (pemafibrate (-)) groups. Triglyceride deposition in the small intestine and fibrosis, along with α-smooth muscle actin level in the liver, were evaluated. Furthermore, the mRNA expression levels of genes associated with lipid metabolism in the small intestine and markers of fibrosis and hepatic stellate cells activation in the liver were measured.

RESULTS

The pemafibrate-treated group had markedly lower triglyceride deposition and lipid absorption in the intestine, and significantly lower levels of molecules involved in intestinal lipid regulation than the pemafibrate-untreated group. Moreover, hepatic fibrosis significantly improved, and the mRNA levels of fibrosis-related molecules and hepatic stellate cell activation factors significantly decreased in the pemafibrate-treated compared with those in the pemafibrate-untreated group.

CONCLUSIONS

Pemafibrate reduced lipid droplet formation and LCFA absorption in the intestinal tract and alleviated hepatic fibrosis in MASH model rats.

Bridging the gap in obesity research: A consensus statement from the European Society for Clinical Investigation

BACKGROUND

Most forms of obesity are associated with chronic diseases that remain a global public health challenge.

AIMS

Despite significant advancements in understanding its pathophysiology, effective management of obesity is hindered by the persistence of knowledge gaps in epidemiology, phenotypic heterogeneity and policy implementation.

MATERIALS AND METHODS

This consensus statement by the European Society for Clinical Investigation identifies eight critical areas requiring urgent attention. Key gaps include insufficient long-term data on obesity trends, the inadequacy of body mass index (BMI) as a sole diagnostic measure, and insufficient recognition of phenotypic diversity in obesity-related cardiometabolic risks. Moreover, the socio-economic drivers of obesity and its transition across phenotypes remain poorly understood.

RESULTS

The syndemic nature of obesity, exacerbated by globalization and environmental changes, necessitates a holistic approach integrating global frameworks and community-level interventions. This statement advocates for leveraging emerging technologies, such as artificial intelligence, to refine predictive models and address phenotypic variability. It underscores the importance of collaborative efforts among scientists, policymakers, and stakeholders to create tailored interventions and enduring policies.

DISCUSSION

The consensus highlights the need for harmonizing anthropometric and biochemical markers, fostering inclusive public health narratives and combating stigma associated with obesity. By addressing these gaps, this initiative aims to advance research, improve prevention strategies and optimize care delivery for people living with obesity.

CONCLUSION

This collaborative effort marks a decisive step towards mitigating the obesity epidemic and its profound impact on global health systems. Ultimately, obesity should be considered as being largely the consequence of a socio-economic model not compatible with optimal human health.

The association between different insulin resistance surrogates and all-cause mortality and cardiovascular mortality in patients with metabolic dysfunction-associated steatotic liver disease

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is closely associated with insulin resistance (IR). However, the prognostic value of different alternative IR surrogates in patients with MASLD remains unclear. This study aimed to evaluate the association between various IR indices and all-cause mortality and cardiovascular mortality in MASLD patients.

METHODS

A total of 8,753 adults aged ≥ 20 years with MASLD from the National Health and Nutrition Examination Survey (NHANES, 2003-2018) were included, and their mortality data were obtained from the National Death Index (NDI). Insulin resistance surrogates [including the triglyceride-glucose (TyG) index, TyG-body mass index (TyG-BMI), TyG-waist circumference index, TyG-waist-to-height ratio index, and Homeostatic Model Assessment for IR] were stratified into quartiles. Cox proportional hazards models, receiver operating characteristic (ROC) curve analysis, restricted cubic spline (RCS), mediation analyses, and subgroup analyses were used to explore the associations between these indices and all-cause mortality as well as cardiovascular mortality in MASLD patients.

RESULTS

During a median follow-up of 98 months, 1,234 deaths were observed, including 409 cardiovascular disease (CVD)-related deaths. In the fully adjusted model, higher quartiles of TyG-related indices were significantly associated with an increased risk of all-cause mortality in MASLD patients. Furthermore, the TyG-BMI index was associated with both all-cause mortality and CVD mortality [all-cause mortality: HR (95% CI) 2.84 (1.73-4.67), P < 0.001; CVD mortality: HR (95% CI) 5.32 (2.26-12.49), P < 0.001]. The RCS analyses indicated a U-shaped relationship between TyG-BMI and mortality, with a threshold value of 270.49. Subgroup analyses demonstrated that TyG-related indices had stronger associations with mortality in elderly MASLD patients.

CONCLUSIONS

Our findings highlight the prognostic value of IR indices, particularly TyG-BMI index, in predicting all-cause mortality and CVD mortality in MASLD patients.

Curcumin mitigates obesity-driven dysbiosis and liver steatosis while promoting browning and thermogenesis in white adipose tissue of high-fat diet-fed mice

Curcumin, recognized for its antioxidant and anti-inflammatory properties, is a promising dietary supplement for liver protection. However, its role in preventing obesity-induced hepatic steatosis is not fully understood. This study aims to show that curcumin mitigates hepatic steatosis and promotes browning and thermogenesis in white adipose tissue (WAT) under obesity. Male C57BL/6 mice were assigned to four groups: standard diet (STD), STD supplemented with 100 mg/kg curcumin, high-fat diet (HFD), or HFD supplemented with 100 mg/kg curcumin, administered for 4 weeks. Compared to STD mice, HFD-fed mice exhibited significantly greater body weight, epididymal fat mass, liver weight, postprandial blood glucose (PBG), insulin, and plasma/hepatic alanine aminotransferase (ALT) and triglyceride (TG) levels, alongside an inflammatory response and macrophage infiltration. Additionally, HFD-fed mice showed reduced adiponectin, adiponectin receptor-1, and PI3K/AKT phosphorylation in liver tissue. Except for liver weight, these effects were reversed in curcumin-treated HFD mice. Curcumin inhibited adipocyte hypertrophy and elevated the expression of PGC-1α, PPARγ, and UCP-1 proteins, as well as Zic1, Prdm16, Tnfrsf9, and Tmem26 genes in epididymal fat pads (EFPs). It also significantly altered gut microbiota composition, reducing pro-inflammatory bacteria such as Helicobacter, Oscillospira, Parabacteroides, and Alistipes, thereby alleviating intestinal dysbiosis and improving obesity-related metabolic parameters. In conclusion, curcumin's protective effects against hepatic steatosis and adiposity in HFD-fed mice stem from its ability to upregulate adiponectin, enhance insulin signaling, promote WAT browning, increase thermogenesis, and modulate intestinal dysbiosis.

Disrupted metabolic flux balance between pyruvate dehydrogenase and pyruvate carboxylase in human fatty liver

Hepatic metabolism involving pyruvate carboxylase (PC) and pyruvate dehydrogenase (PDH) may be abnormal in fatty livers. In this study, [13C]bicarbonate production from [1-13C1]pyruvate in the liver and glycerol glyceroneogenesis were examined in relation to hepatic fat content using hyperpolarized [1-13C1]pyruvate and oral [U-13C3]glycerol. After an overnight fast, 15 subjects with a range of hepatic fat content received hyperpolarized [1-13C1]pyruvate intravenously to assess its conversion to [1-13C1]lactate and [13C]bicarbonate in the liver. They also received oral [U-13C3]glycerol, followed by venous blood sampling to examine glucose and the glycerol backbone of the triglycerides released primarily from the liver. From hyperpolarized [1-13C1]pyruvate, participants with high intrahepatic fat fraction produced higher [1-13C1]lactate and lower [13C]bicarbonate than those with low liver fat. The fraction of plasma triglycerides derived from oral [U-13C3]glycerol via the TCA cycle was similar between groups. The fraction of plasma [5,6-13C2]glucose, which reflects PC flux, decreased in subjects with fatty liver. In contrast, the fraction of [4,5-13C2]glucose + [6-13C1]glucose, which can be produced via either PC or PDH, was comparable between groups. The study results suggest a shift in pyruvate metabolism in fatty liver, with a decreased metabolic flux ratio of PC/PDH. The methodology in this study provides insights into fatty liver metabolism of human subjects inaccessible previously and is applicable to advanced liver diseases such as cirrhosis and hepatomas.

Sex differences in diet-induced MASLD - are female mice naturally protected?

Males suffer more often from profibrotic changes in liver than females. The underlying mechanism for this sex difference in the prevalence and manifestation of Metabolic dysfunction-associated Steatotic Liver Disease (MASLD) is not yet completely known. We studied male and female mice that were induced to develop MASLD by consuming a "fast food" diet (FFD) and assessed metabolic phenotype as well as liver histology and compared them with mice fed with a matched control diet (CD). Our aim was to check for sex-specific differences in MASLD development in a mouse model of diet-induced profibrotic changes in the liver. Our results demonstrate a clear difference in body weight, fat distribution and changes in liver tissue for male and female mice fed with FFD. We found that female mice stored lipids mainly in subcutaneous and visceral adipose tissue while males increased ectopic lipid accumulation in the liver which resulted in hepatomegaly and increased transforming growth factor β 1 (Tgfb1) and collagen I (Col1a1) expression concomitant to fibrosis development. This was absent in female mice. Analysis of estrogen receptor -α (Esr1) and -β (Esr2) expression revealed an upregulation of Esr2 in livers of male FFD-fed mice whereas in female liver tissue a higher expression in Esr1 could be observed. This study supports Esr1 and Esr2 as potential targets to reverse negative effects of diet-induced profibrotic changes in the liver.

Comorbidity patterns and implications for disease control: a network analysis of medical records from Shanghai, China

Background

The aging problem in Shanghai is rapidly increasing, leading to the development of chronic comorbidities in older adults. Studying the correlations within comorbidity patterns can assist in managing disease prevention and implicate early control.

Objectives

This study was a cross-sectional analysis based on a large sample size of 3,779,756 medical records. A network analysis and community classification were performed to illustrate disease networks and the internal relationships within comorbidity patterns among older adults in Shanghai.

Methods

The network analysis and community classification were performed using the IsingFit and Fast-greedy community functions. Datasets, including disease codes and disease prevalence, were collected from medical records.

Results

The top five prevalent diseases were hypertension (64.78%), chronic ischemic heart disease (39.06%), type 2 diabetes mellitus (24.97%), lipid metabolism disorders (21.79%), and gastritis (19.71%). The sampled population showed susceptibility to 11 comorbidities associated with hypertension, 9 with diabetes, 28 with ischemic heart disease, 26 with gastritis, and 2 with lipid metabolism disorders in male patients. Diseases such as lipid metabolism disorders, gastritis, fatty liver, polyps of the colon, osteoporosis, atherosclerosis, and heart failure exhibited strong centrality.

Conclusion

The most common comorbidity patterns were dominated by ischemic heart disease and gastritis, followed by a ternary pattern between hypertension, diabetes, and lipid metabolism disorders. Male patients were more likely to have comorbidities related to cardiovascular and sleep problems, while women were more likely to have comorbidities related to thyroid disease, inflammatory conditions, and hyperuricemia. It was suggested that healthcare professionals focus on monitoring relevant vital signs and mental health according to the specific comorbidity patterns in older adults with chronic diseases, to prevent the development of new or more severe comorbidities.

Placenta hIGF1 nanoparticle treatment in guinea pigs mitigates FGR-associated fetal sex-dependent effects on liver metabolism-related signaling pathways

Fetal development in an adverse in utero environment significantly increases the risk of developing metabolic diseases in later life, including dyslipidemia, nonalcoholic fatty liver diseases, and diabetes. The aim of this study was to determine whether improving the in utero fetal growth environment with a placental nanoparticle gene therapy would ameliorate fetal growth restriction (FGR)-associated dysregulation of fetal hepatic lipid and glucose metabolism-related signaling pathways. Using the guinea pig maternal nutrient restriction (MNR) model of placental insufficiency and FGR, placenta efficiency and fetal weight were significantly improved following three administrations of a nonviral polymer-based nanoparticle gene therapy to the placenta from mid-pregnancy (gestational day 35) until gestational day 52. The nanoparticle gene therapy transiently increased expression of human insulin-like growth factor 1 (hIGF1) in placenta trophoblast. Fetal liver tissue was collected near-term at gestational day 60. Fetal sex-specific differences in liver gene and protein expression of profibrosis and glucose metabolism-related factors were demonstrated in sham-treated FGR fetuses but not observed in FGR fetuses who received placental hIGF1 nanoparticle treatment. Increased plasma bilirubin, an indirect measure of hepatic activity, was also demonstrated with placental hIGF1 nanoparticle treatment. We speculate that the changes in liver gene and protein expression and increased liver activity that result in similar expression profiles to appropriately growing control fetuses might confer protection against increased susceptibility to aberrant liver physiology in later life. Overall, this work opens avenues for future research assessing the translational prospect of mitigating FGR-induced metabolic derangements.NEW & NOTEWORTHY A placenta-specific nonviral polymer-based nanoparticle gene therapy that improves placenta nutrient transport and near-term fetal weight ameliorates growth restriction-associated changes to fetal liver activity, and cholesterol and glucose/nutrient homeostasis genes/proteins that might confer protection against increased susceptibility to aberrant liver physiology in later life. This knowledge may have implications toward removing predispositions that increase the risk of metabolic diseases, including diabetes, dyslipidemia, and nonalcoholic fatty liver disease in later life.

Pharmacological treatment for metabolic dysfunction-associated steatotic liver disease and related disorders: Current and emerging therapeutic options

Metabolic dysfunction-associated steatotic liver disease (MASLD; formerly known as nonalcoholic fatty liver disease) is a chronic liver disease affecting over a billion individuals worldwide. MASLD can gradually develop into more severe liver pathologies, including metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and liver malignancy. Notably, although being a global health problem, there are very limited therapeutic options against MASLD and its related diseases. While a thyroid hormone receptor agonist (resmetirom) is recently approved for MASH treatment, other efforts to control these diseases remain unsatisfactory. Given the projected rise in MASLD and MASH incidence, it is urgent to develop novel and effective therapeutic strategies against these prevalent liver diseases. In this article, the pathogenic mechanisms of MASLD and MASH, including insulin resistance, dysregulated nuclear receptor signaling, and genetic risk factors (eg, patatin-like phospholipase domain-containing 3 and hydroxysteroid 17-β dehydrogenase-13), are introduced. Various therapeutic interventions against MASH are then explored, including approved medication (resmetirom), drugs that are currently in clinical trials (eg, glucagon-like peptide 1 receptor agonist, fibroblast growth factor 21 analog, and PPAR agonist), and those failed in previous trials (eg, obeticholic acid and stearoyl-CoA desaturase 1 antagonist). Moreover, given that the role of gut microbes in MASLD is increasingly acknowledged, alterations in the gut microbiota and microbial mechanisms in MASLD development are elucidated. Therapeutic approaches that target the gut microbiota (eg, dietary intervention and probiotics) against MASLD and related diseases are further explored. With better understanding of the multifaceted pathogenic mechanisms, the development of innovative therapeutics that target the root causes of MASLD and MASH is greatly facilitated. The possibility of alleviating MASH and achieving better patient outcomes is within reach. SIGNIFICANCE STATEMENT: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide, and it can progress to more severe pathologies, including steatohepatitis, cirrhosis, and liver cancer. Better understanding of the pathogenic mechanisms of these diseases has facilitated the development of innovative therapeutic strategies. Moreover, increasing evidence has illustrated the crucial role of gut microbiota in the pathogenesis of MASLD and related diseases. It may be clinically feasible to target gut microbes to alleviate MASLD in the future.

The deuterated glucose insulin tolerance test: a new tool to delineate insulin-stimulated glucose uptake from suppression of endogenous glucose production

Graphical Abstract.

Natural History of Metabolic Dysfunction-Associated Steatotic Liver Disease: From Metabolic Syndrome to Hepatocellular Carcinoma

Introduction: Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) stems from disrupted lipid metabolism in the liver, often linked to obesity, type 2 diabetes, and dyslipidemia. In Mexico, where obesity affects 36.9% of adults, MASLD prevalence has risen, especially with metabolic syndrome affecting 56.31% by 2018. MASLD can progress to Metabolic Dysfunction-Associated Steatohepatitis (MASH), affecting 5.27% globally, leading to severe complications like cirrhosis and hepatocellular carcinoma. Background: Visceral fat distribution varies by gender, impacting MASLD development due to hormonal influences. Insulin resistance plays a central role in MASLD pathogenesis, exacerbated by high-fat diets and specific fatty acids, leading to hepatic steatosis. Lipotoxicity from saturated fatty acids further damages hepatocytes, triggering inflammation and fibrosis progression in MASH. Diagnosing MASLD traditionally involves invasive liver biopsy, but non-invasive methods like ultrasound and transient elastography are preferred due to their safety and availability. These methods detect liver steatosis and fibrosis with reasonable accuracy, offering alternatives to biopsy despite varying sensitivity and specificity. Conclusions: MASLD as a metabolic disorder underscores its impact on public health, necessitating improved awareness and early management strategies to mitigate its progression to severe liver diseases.

Interplay of fatty acids, insulin and exercise in vascular health

Fatty acid metabolism, exercise, and insulin action play critical roles in maintaining vascular health, especially relevant in metabolic disorders such as obesity, type 2 diabetes, and cardiovascular disease. Insulin, a vasoactive hormone, induces arterial vasodilation throughout the arterial tree, increasing arterial compliance and enhancing tissue perfusion. These effects, however, are impaired in individuals with obesity and type 2 diabetes, and evidence suggests that vascular insulin resistance contributes to the pathogenesis of type 2 diabetes and its cardiovascular complications. Elevated plasma levels of free fatty acids in people with insulin resistance engender vascular inflammation, endothelial dysfunction, and vascular insulin resistance. Importantly, these effects are both functionally and structurally dependent, with saturated fatty acids as the primary culprits, while polyunsaturated fatty acids may support insulin sensitivity and endothelial function. Exercise enhances fatty acid oxidation, reduces circulating free fatty acids, and improves insulin sensitivity, thereby mitigating lipotoxicity and promoting endothelial function. Additionally, exercise induces beneficial vascular adaptations. This review examines the complex interplay among fatty acid metabolism, exercise training-induced vascular adaptations, and insulin-mediated vascular changes, highlighting their collective impact on vascular health and underlying mechanisms in both healthy and insulin-resistant states. It also explores the therapeutic potential of targeted exercise prescriptions and fatty acid-focused dietary strategies for enhancing vascular health, emphasizing tailored interventions to maximize metabolic benefits. Future research should investigate the pathways linking fatty acid metabolism to vascular insulin resistance, with a focus on how exercise and dietary modifications can be personalized to enhance vascular insulin sensitivity, optimize vascular health, and reduce the risks of type 2 diabetes and associated cardiovascular complications.

The Causal Role of Ectopic Fat Deposition in the Pathogenesis of Metabolic Syndrome

Consuming a "modern" Western diet and overnutrition may increase insulin secretion. Additionally, nutrition-mediated hyperinsulinemia is a major driver of ectopic fat deposition. The global prevalence of metabolic syndrome is high and growing. Within this context, people with congenital lipodystrophy often experience a severe form of metabolic syndrome. Evidence is increasingly supporting that subtle partial lipodystrophy plays an important role in the development of metabolic syndrome in the general population. In individuals in the general population with subtle partial lipodystrophy, as well as in those with congenital lipodystrophy, the subcutaneous adipose tissues are unable to accommodate surplus energy intake. In both conditions, (excess) fat is directed toward the liver, pancreas, and muscles, where it is deposited as ectopic fat, as this fat can no longer be stored in the "safe" subcutaneous fat depots. Ectopic fat depositions cause insulin resistance in the liver and muscles, as well as β-cell dysfunction in the pancreas. Support of a direct pathological role of ectopic fat deposition in this condition is further provided by the rapid normalization of hepatic insulin sensitivity and improvement in pancreatic β-cell function after marked reductions in ectopic fat depositions. Thus, ectopic fat deposition in the liver, pancreas, and muscles may play a causal role in the pathogenesis of metabolic syndrome even in the general population. As such, the prevention of ectopic fat deposition may reduce the risk of metabolic syndrome and mitigate its effects.

Biochemical basis and therapeutic potential of mitochondrial uncoupling in cardiometabolic syndrome

Mild uncoupling of oxidative phosphorylation is an intrinsic property of all mitochondria, allowing for adjustments in cellular energy metabolism to maintain metabolic homeostasis. Small molecule uncouplers have been extensively studied for their potential to increase metabolic rate, and recent research has focused on developing safe and effective mitochondrial uncoupling agents for the treatment of obesity and cardiometabolic syndrome (CMS). Here, we provide a brief overview of CMS and cover the recent mechanisms by which chemical uncouplers regulate CMS-associated risk-factors and comorbidities, including dyslipidemia, insulin resistance, steatotic liver disease, type 2 diabetes, and atherosclerosis. Additionally, we review the current landscape of uncoupling agents, focusing on repurposed FDA-approved drugs and compounds in advanced preclinical or early-stage clinical development. Lastly, we discuss recent molecular insights by which chemical uncouplers enhance cellular energy expenditure, highlighting their potential as a new addition to the current CMS drug landscape, and outline several limitations that need to be addressed before these agents can successfully be introduced into clinical practice.

A Comprehensive Review of Pathophysiological Link Between Non-alcoholic Fatty Liver Disease, Insulin Resistance, and Metabolic Syndrome

Non-alcoholic fatty liver disease (NAFLD) is a chronic condition characterized by hepatic steatosis in the absence of significant alcohol consumption and is increasingly recognized as the hepatic manifestation of metabolic syndrome (MetS). This review aims to explore the molecular mechanisms underlying the interaction between NAFLD, insulin resistance (IR), and MetS, with a focus on identifying therapeutic targets. A comprehensive review of existing literature on NAFLD, IR, and MetS was conducted. The review indicates that IR contributes to hepatic lipid accumulation through increased lipolysis, elevated free fatty acid flux, and impaired fatty acid oxidation, while MetS exacerbates the condition by promoting visceral adiposity, chronic inflammation, and impaired lipid metabolism. Additionally, dysbiosis and increased intestinal permeability in the gut-liver axis worsen IR, leading to a vicious cycle of metabolic dysfunction. In conclusion, addressing these interconnected pathways could enhance therapeutic strategies and reduce the burden of NAFLD-related complications.

High-fat-diet-induced hepatic insulin resistance per se attenuates murine de novo lipogenesis

Hepatic insulin resistance (IR) is often said to be "pathway-selective" with preserved insulin stimulation of de novo lipogenesis (DNL) despite attenuated insulin signaling toward glucose metabolism. However, DNL has not been assessed in models of liver-specific IR. We studied mice with differential tissue-specific lipid-induced IR achieved by different durations of high-fat diet (HFD) feeding. Mice with isolated hepatic IR demonstrated markedly reduced DNL, with a rebound seen in mice with whole-body IR. Insr T1150A mice (protected against diacylglycerol-PKCε-induced hepatic IR) maintained normal DNL with HFD feeding. During hyperinsulinemic clamps, hepatic IR reduced DNL, but hyperglycemia augmented DNL in both resistant and sensitive animals. Regulation through SREBP1c did not consistently correlate with changes in DNL. These results demonstrate that hepatic IR is not pathway-selective, highlighting the primacy of lipogenic substrate in stimulation of DNL. Future therapeutics to reduce lipogenesis should target substrate drivers of DNL rather than targeting plasma insulin levels.

Ceramide synthesis inhibitors prevent lipid-induced insulin resistance through the DAG-PKCε-insulin receptorT1150 phosphorylation pathway

Inhibition of the ceramide synthetic pathway with myriocin or an antisense oligonucleotide (ASO) targeting dihydroceramide desaturase (DES1) both improved hepatic insulin sensitivity in rats fed either a saturated or unsaturated fat diet and was associated with reductions in both hepatic ceramide and plasma membrane (PM)-sn-1,2-diacylglycerol (DAG) content. The insulin sensitizing effects of myriocin and Des1 ASO were abrogated by acute treatment with an ASO against DGAT2, which increased hepatic PM-sn-1,2-DAG but not hepatic C16 ceramide content. Increased PM-sn-1,2-DAG content was associated with protein kinase C (PKC)ε activation, increased insulin receptor (INSR)T1150 phosphorylation leading to reduced insulin-stimulated INSRY1152/AktS473 phosphorylation, and impaired insulin-mediated suppression of endogenous glucose production. These results demonstrate that inhibition of de novo ceramide synthesis by either myriocin treatment or DES1 knockdown protects against lipid-induced hepatic insulin resistance through a C16 ceramide-independent mechanism and that they mediate their effects to protect from lipid-induced hepatic insulin resistance via the PM-sn-1,2-DAG-PKCε-INSRT1150 phosphorylation pathway.

No Difference in Liver Damage Induced by Isocaloric Fructose or Glucose in Mice with a High-Fat Diet

Background/Objectives: The diverse effects of fructose and glucose on the progression of metabolic dysfunction-associated steatotic liver disease remain uncertain. This study investigated the effects, in animal models, of high-fat diets (HFDs) supplemented with either glucose or fructose. Methods: Six-week-old, male C57BL/6J mice were randomly allocated to four groups: normal diet (ND), HFD, HFD supplemented with fructose (30% w/v, HFD + Fru), and HFD supplemented with glucose (initially 30%, HFD + Glu). After 24 weeks, liver and plasma samples were gathered for analysis. In addition, 39 patients with obesity undergoing bariatric surgery with wedge liver biopsy were enrolled in the clinical study. Results: The HFD + Glu group consumed more water than did the HFD and HFD + Fru groups. Thus, we reduced the glucose concentration from 30% at baseline to 15% at week 2 and 10% starting from week 6. The HFD + Fru and HFD + Glu groups had a similar average caloric intake (p = 0.463). The HFD increased hepatic steatosis, plasma lipid levels, lipogenic enzymes, steatosis-related oxidative stress, hepatic inflammation, and early-stage liver fibrosis. Supplementation with fructose or glucose exacerbated liver damage, but no significant differences were identified between the two. The expression patterns of hepatic ceramides in HFD-fed mice (with or without supplemental fructose or glucose) were similar to those observed in patients with obesity and severe hepatic steatosis or metabolic dysfunction-associated steatohepatitis. Conclusions: Fructose and glucose similarly exacerbated liver damage when added to an HFD. Ceramides may be involved in the progression of hepatic lipotoxicity.

Protein kinase D2 modulates hepatic insulin sensitivity in male mice

OBJECTIVES

Protein kinase D (PKD) family is emerging as relevant regulator of metabolic homeostasis. However, the precise role of PKD2 in modulating hepatic insulin signaling has not been fully elucidated and it is the aim of this study.

METHODS

PKD inhibition was analyzed for insulin signaling in mouse and human hepatocytes. PKD2 was overexpressed in Huh7 hepatocytes and mouse liver, and insulin responses were evaluated. Mice with hepatocyte-specific PKD2 depletion (PKD2ΔHep) and PKD2fl/fl mice were fed a chow (CHD) or high fat diet (HFD) and glucose homeostasis and lipid metabolism were investigated.

RESULTS

PKD2 silencing enhanced insulin signaling in hepatocytes, an effect also found in primary hepatocytes from PKD2ΔHep mice. Conversely, a constitutively active PKD2 mutant reduced insulin-stimulated AKT phosphorylation. A more in-depth analysis revealed reduced IRS1 serine phosphorylation under basal conditions and increased IRS1 tyrosine phosphorylation in PKD2ΔHep primary hepatocytes upon insulin stimulation and, importantly PKD co-immunoprecipitates with IRS1. In vivo constitutively active PKD2 overexpression resulted in a moderate impairment of glucose homeostasis and reduced insulin signaling in the liver. On the contrary, HFD-fed PKD2ΔHep male mice displayed improved glucose and pyruvate tolerance, as well as higher peripheral insulin tolerance and enhanced hepatic insulin signaling compared to control PKD2fl/fl mice. Despite of a remodeling of hepatic lipid metabolism in HFD-fed PKD2ΔHep mice, similar steatosis grade was found in both genotypes.

CONCLUSIONS

Results herein have unveiled an unknown role of PKD2 in the control of insulin signaling in the liver at the level of IRS1 and point PKD2 as a therapeutic target for hepatic insulin resistance.

Calebin A attenuated inflammation in RAW264.7 macrophages and adipose tissue to improve hepatic glucose metabolism and hyperglycemia in high-fat diet-fed obese mice

The increased incidence of obesity, which become a global health problem, requires more functional food products with minor side and excellent effects. Calebin A (CbA) is a non-curcuminoid compound, which is reported to be an effective treatment for lipid metabolism and thermogenesis. However, its ability and mechanism of action in improving obesity-associated hyperglycemia remain unclear. This study was designed to explore the effect and mechanism of CbA in hyperglycemia via improvement of inflammation and glucose metabolism in the adipose tissue and liver in high-fat diet (HFD)-fed mice. After 10 weeks fed HFD, obese mice supplemented with CbA (25 and 100 mg/kg) for another 10 weeks showed a remarkable reducing adiposity and blood glucose. CbA modulated M1/M2 macrophage polarization, ameliorated inflammatory cytokines, and restored adiponectin as well as Glut 4 expression in the adipose tissue. In the in vitro study, CbA attenuated pro-inflammatory markers while upregulated anti-inflammatory IL-10 in LPS + IFNγ-generated M1 phenotype macrophages. In the liver, CbA attenuated steatosis, inflammatory infiltration, and protein levels of inflammatory TNF-α and IL-6. Moreover, CbA markedly upregulated Adiponectin receptor 1, AMPK, and insulin downstream Akt signaling to improve glycogen content and increase Glut2 protein. These findings indicated that CbA may be a novel therapeutic approach to treat obesity and hyperglycemia phenotype targeting on adipose inflammation and hepatic insulin signaling.

Downregulation of CerS4 Instead of CerS2 in Liver Effectively Alleviates Hepatic Insulin Resistance in HFD Male Mice

OBJECTIVE

Consumption of a high-fat diet (HFD) induces insulin resistance (IRes), significantly affecting the maintenance of normal glucose homeostasis. Nevertheless, despite decades of extensive research, the mechanisms and pathogenesis of IRes remain incomplete. Recent studies have primarily explored lipid intermediates such as diacylglycerol (DAG), given a limited knowledge about the role of ceramide (Cer), which is a potential mediator of the IRes in the liver.

METHODS

In order to investigate the role of Cer produced by CerS2 and CerS4 for the purpose of inducing the hepatic IRes, we utilized a unique in vivo model employing shRNA-mediated hydrodynamic gene delivery in the liver of HFD-fed C57BL/6J mice.

RESULTS

Downregulation of CerS4 instead of CerS2 reduced specific liver Cers, notably C18:0-Cer and C24:0-Cer, as well as acylcarnitine levels. It concurrently promoted glycogen accumulation, leading to enhanced insulin sensitivity and glucose homeostasis.

CONCLUSION

Those findings demonstrate that CerS4 downregulating lowers fasting blood glucose levels and mitigates the HFD-induced hepatic IRes. It suggests that inhibiting the CerS4-mediated C18:0-Cer synthesis holds a promise to effectively address insulin resistance in obesity.

Epoxygenase Cyp2c44 Regulates Hepatic Lipid Metabolism and Insulin Signaling by Controlling FATP2 Localization and Activation of the DAG/PKCδ Axis

Cytochrome P450 epoxygenase Cyp2c44, a murine epoxyeicosatrienoic acid (EET)-producing enzyme, promotes insulin sensitivity, and Cyp2c44-/- mice show hepatic insulin resistance. Because insulin resistance leads to hepatic lipid accumulation and hyperlipidemia, we hypothesized that Cyp2c44 regulates hepatic lipid metabolism. Standard chow diet (SCD)-fed male Cyp2c44-/- mice had significantly decreased EET levels and increased hepatic and plasma lipid levels compared with wild-type mice. We showed increased hepatic plasma membrane localization of the FA transporter 2 (FATP2) and total unsaturated fatty acids and diacylglycerol (DAG) levels. Cyp2c44-/- mice had impaired glucose tolerance and increased hepatic plasma membrane-associated PKCδ and phosphorylated IRS-1, two negative regulators of insulin signaling. Surprisingly, SCD and high-fat diet (HFD)-fed Cyp2c44-/- mice had similar glucose tolerance and hepatic plasma membrane PKCδ levels, suggesting that SCD-fed Cyp2c44-/- mice have reached their maximal glucose intolerance. Inhibition of PKCδ resulted in decreased IRS-1 serine phosphorylation and improved insulin-mediated signaling in Cyp2c44-/- hepatocytes. Finally, Cyp2c44-/- HFD-fed mice treated with the analog EET-A showed decreased hepatic plasma membrane FATP2 and PCKδ levels with improved glucose tolerance and insulin signaling. In conclusion, loss of Cyp2c44 with concomitant decreased EET levels leads to increased hepatic FATP2 plasma membrane localization, DAG accumulation, and PKCδ-mediated attenuation of insulin signaling. Thus, Cyp2c44 acts as a regulator of lipid metabolism by linking it to insulin signaling.

ARTICLE HIGHLIGHTS

Cellular Senescence and Extracellular Vesicles in the Pathogenesis and Treatment of Obesity-A Narrative Review

This narrative review explores the pathophysiology of obesity, cellular senescence, and exosome release. When exposed to excessive nutrients, adipocytes develop mitochondrial dysfunction and generate reactive oxygen species with DNA damage. This triggers adipocyte hypertrophy and hypoxia, inhibition of adiponectin secretion and adipogenesis, increased endoplasmic reticulum stress and maladaptive unfolded protein response, metaflammation, and polarization of macrophages. Such feed-forward cycles are not resolved by antioxidant systems, heat shock response pathways, or DNA repair mechanisms, resulting in transmissible cellular senescence via autocrine, paracrine, and endocrine signaling. Senescence can thus affect preadipocytes, mature adipocytes, tissue macrophages and lymphocytes, hepatocytes, vascular endothelium, pancreatic β cells, myocytes, hypothalamic nuclei, and renal podocytes. The senescence-associated secretory phenotype is closely related to visceral adipose tissue expansion and metaflammation; inhibition of SIRT-1, adiponectin, and autophagy; and increased release of exosomes, exosomal micro-RNAs, pro-inflammatory adipokines, and saturated free fatty acids. The resulting hypernefemia, insulin resistance, and diminished fatty acid β-oxidation lead to lipotoxicity and progressive obesity, metabolic syndrome, and physical and cognitive functional decline. Weight cycling is related to continuing immunosenescence and exposure to palmitate. Cellular senescence, exosome release, and the transmissible senescence-associated secretory phenotype contribute to obesity and metabolic syndrome. Targeted therapies have interrelated and synergistic effects on cellular senescence, obesity, and premature aging.

Non-Alcoholic Fatty Liver Disease Induced by Feeding Medium-Chain Fatty Acids Upregulates Cholesterol and Lipid Homeostatic Genes in Skeletal Muscle of Neonatal Pigs

Non-alcoholic fatty liver disease (NAFLD) is a range of disorders characterized by lipid accumulation in hepatocytes. Although this spectrum of disorders is associated with adult obesity, recent evidence suggests that this condition could also occur independently of obesity, even in children. Previously, we reported that pigs fed a formula containing medium-chain fatty acids (MCFAs) developed hepatic steatosis and weighed less than those fed an isocaloric formula containing long-chain fatty acids (LCFAs). Our objective was to determine the association between NAFLD and the skeletal muscle transcriptome in response to energy and lipid intake. Neonatal pigs were fed one of three formulas: a control formula (CONT, n = 6) or one of two isocaloric high-energy formulas containing either long (LCFA, n = 6) or medium (MCFA, n = 6) chain fatty acids. Pigs were fed for 22 d, and tissues were collected. Body weight at 20 and 22 d was greater for LCFA-fed pigs than their CONT or MCFA counterparts (p < 0.005). Longissimus dorsi weight was greater for LCFA compared with MCFA, while CONT was intermediate (p < 0.05). Lean gain and protein deposition were greater for LCFA than for CONT and MCFA groups (p < 0.01). Transcriptomic analysis revealed 36 differentially expressed genes (DEGs) between MCFA and LCFA, 53 DEGs between MCFA and CONT, and 52 DEGs between LCFA and CONT (FDR < 0.2). Feeding formula high in MCFAs resulted in lower body and muscle weights. Transcriptomics data suggest that the reduction in growth was associated with a disruption in cholesterol metabolism in skeletal muscles.

Diverse associations between pancreatic intra-, inter-lobular fat and the development of type 2 diabetes in overweight or obese patients

Pancreatic fat is associated with obesity and type 2 diabetes mellitus (T2DM); however, the relationship between different types of pancreatic fat and diabetes status remains unclear. Therefore, we aimed to determine the potential of different types of pancreatic fat accumulation as a risk factor for T2DM in overweight or obese patients. In total, 104 overweight or obese patients were recruited from January 2020 to December 2022. The patients were divided into three groups: normal glucose tolerance (NGT), impaired fasting glucose or glucose tolerance (IFG/IGT), and T2DM. mDixon magnetic resonance imaging (MRI) was used to detect pancreatic fat in all three groups of patients. The pancreatic head fat (PHF), body fat (PBF), and tail fat (PTF) in the IFG/IGT group were 21, 20, and 31% more than those in the NGT group, respectively. PHF, PBF, and PTF were positively associated with glucose metabolic dysfunction markers in the NGT group, and inter-lobular fat volume (IFV) was positively associated with these markers in the IFG/IGT group. The areas under the receiver operating characteristic curves for PHF, PBF, and PTF (used to evaluate their diagnostic potential for glucose metabolic dysfunction) were 0.73, 0.73, and 0.78, respectively, while those for total pancreatic volume (TPV), pancreatic parenchymal volume, IFV, and IFV/TPV were 0.67, 0.67, 0.66, and 0.66, respectively. These results indicate that intra-lobular pancreatic fat, including PHF, PTF, and PBF, may be a potential independent risk factor for the development of T2DM. Additionally, IFV exacerbates glucose metabolic dysfunction. Intra-lobular pancreatic fat indices were better than IFV for the diagnosis of glucose metabolic dysfunction.

Effect of grape-derived products on the serum levels of enzymes mainly produced by the liver: A systematic review and meta-analysis of parallel randomized controlled trials

In recent years, an increase in the incidence of liver diseases has been reported all over the world. This study aims to comprehensively summarize and quantitatively analyze the existing evidence concerning the effectiveness of grape-derived products on liver enzymes through a systematic review and meta-analytic approach. PubMed, Scopus, Cochrane Library, and ISI Web of Science were comprehensively searched until January 2024. Articles that reported the effect of grape-derived products on serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) levels were included. Weighted mean differences (WMDs) were pooled using a random-effects model. Nine studies were included in the meta-analysis. The results revealed that grape-derived products did not significantly change the concentrations of ALT (WMD: -2.70 IU/L, 95% CI: -6.14 to 0.75, p = 0.12), and AST (WMD: -1.42 IU/L, 95% CI: -3.54 to 0.70, p = 0.18). However, a significant reduction was observed in serum ALP levels (WMD: -5.49 IU/L, 95% CI: -9.57 to -1.4, p = 0.008). The present findings suggest that grape-derived products positively influence serum ALP levels among adults. However, a more comprehensive decision necessitates additional studies.

Mapping the global research landscape on nonalcoholic fatty liver disease and insulin resistance: A visualization and bibliometric study

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a liver condition that is prevalent worldwide and associated with significant health risks and economic burdens. As it has been linked to insulin resistance (IR), this study aimed to perform a bibliometric analysis and visually represent the scientific literature on IR and NAFLD.

AIM

To map the research landscape to underscore critical areas of focus, influential studies, and future directions of NAFLD and IR.

METHODS

This study conducted a bibliometric analysis of the literature on IR and NAFLD indexed in the SciVerse Scopus database from 1999 to 2022. The search strategy used terms from the literature and medical subject headings, focusing on terms related to IR and NAFLD. VOSviewer software was used to visualize research trends, collaborations, and key thematic areas. The analysis examined publication type, annual research output, contributing countries and institutions, funding agencies, journal impact factors, citation patterns, and highly cited references.

RESULTS

This analysis identified 23124 documents on NAFLD, revealing a significant increase in the number of publications between 1999 and 2022. The search retrieved 715 papers on IR and NAFLD, including 573 (80.14%) articles and 88 (12.31%) reviews. The most productive countries were China (n = 134; 18.74%), the United States (n = 122; 17.06%), Italy (n = 97; 13.57%), and Japan (n = 41; 5.73%). The leading institutions included the Università degli Studi di Torino, Italy (n = 29; 4.06%), and the Consiglio Nazionale delle Ricerche, Italy (n = 19; 2.66%). The top funding agencies were the National Institute of Diabetes and Digestive and Kidney Diseases in the United States (n = 48; 6.71%), and the National Natural Science Foundation of China (n = 37; 5.17%). The most active journals in this field were Hepatology (27 publications), the Journal of Hepatology (17 publications), and the Journal of Clinical Endocrinology and Metabolism (13 publications). The main research hotspots were "therapeutic approaches for IR and NAFLD" and "inflammatory and high-fat diet impacts on NAFLD".

CONCLUSION

This is the first bibliometric analysis to examine the relationship between IR and NAFLD. In response to the escalating global health challenge of NAFLD, this research highlights an urgent need for a better understanding of this condition and for the development of intervention strategies. Policymakers need to prioritize and address the increasing prevalence of NAFLD.

Diagnostic Performance of Insulin Resistance Indices for Identifying Metabolic Dysfunction-Associated Fatty Liver Disease

Background/objectives: Insulin resistance (IR) plays an important role in metabolic dysfunction-associated fatty liver disease (MAFLD) pathogenesis. A modified triglyceride-glucose (TyG) index, including TyG-body mass index (TyG-BMI) and TyG-waist circumference (TyG-WC), has been introduced to represent IR. This study aimed to investigate the diagnostic abilities of IR indices in MAFLD, in which fatty liver was diagnosed using computed tomography (CT). Subjects/methods: We retrospectively analyzed the clinical data and images of 852 adults aged ≥19 years who underwent abdominal CT. MAFLD was diagnosed based on the appearance of fatty liver on CT alongside at least one of the following three criteria: being overweight or obese, at least two metabolic risk abnormalities, and/or diabetes mellitus. IR indices were calculated by examining the following variables: homeostasis model assessment-IR, TyG index, TyG-BMI, TyG-WC, and visceral adiposity index. The diagnostic accuracy was evaluated using the area under the receiver operating characteristic curve. Results: For all patients, the area under the curve (AUC) of the TyG index, TyG-BMI, and TyG-WC were 0.834, 0.938, and 0.942, respectively. In men, the AUC of the TyG index, TyG-BMI, and TyG-WC were 0.812, 0.928, and 0.934, respectively. In women, the AUC of the TyG index was 0.841, and TyG-BMI and TyG-WC were 0.940 and 0.953, respectively. The AUC values tended to increase in the following order: TyG index < TyG-BMI < TyG-WC. Women showed a higher AUC than men in all items, and the TyG-WC of women showed the highest value with AUC 0.953 (95% confidence interval [CI]: 0.892-1.000, P < 0.0001). The AUC of the TyG index was 0.858 (95% CI: 0.828-0.888, P < 0.0001). Conclusions: In conclusion, TyG-WC is a powerful surrogate marker for identifying MAFLD in clinical settings.

miR-141/200c contributes to ethanol-mediated hepatic glycogen metabolism

OBJECTIVE

Hepatic glucose metabolism is profoundly perturbed by excessive alcohol intake. miR-141/200c expression is significantly induced by chronic ethanol feeding. This study aimed at identifying the role of miR-141/200c in glucose homeostasis during chronic ethanol exposure.

METHODS

WT and miR-141/200c KO mice were fed a control or an ethanol diet for 30 days, followed by a single binge of maltose dextrin or ethanol, respectively. Untargeted metabolomics analysis of hepatic primary metabolites was performed along with analyses for liver histology, gene expression, intracellular signaling pathways, and physiological relevance. Primary hepatocytes were used for mechanistic studies.

RESULTS

miR-141/200c deficiency rewires hepatic glucose metabolism during chronic ethanol feeding, increasing the abundance of glucose intermediates including G6P, an allosteric activator for GS. miR-141/200c deficiency replenished glycogen depletion during chronic ethanol feeding accompanied by reduced GS phosphorylation in parallel with increased expression of PP1 glycogen targeting subunits. Moreover, miR-141/200c deficiency prevented ethanol-mediated increases in AMPK and CaMKK2 activity. Ethanol treatment reduced glycogen content in WT-hepatocytes, which was reversed by dorsomorphin, a selective AMPK inhibitor, while KO-hepatocytes displayed higher glycogen content than WT-hepatocytes in response to ethanol treatment. Furthermore, treatment of hepatocytes with A23187, a calcium ionophore activating CaMKK2, lowered glycogen content in WT-hepatocytes. Notably, the suppressive effect of A23187 on glycogen deposition was reversed by dorsomorphin, demonstrating that the glycogen depletion by A23187 is mediated by AMPK. KO-hepatocytes exhibited higher glycogen content than WT-hepatocytes in response to A23187. Finally, miR-141/200c deficiency led to improved glucose tolerance and insulin sensitivity during chronic ethanol feeding.

CONCLUSIONS

miR-141/200c deficiency replenishes ethanol-mediated hepatic glycogen depletion through the regulation of GS activity and calcium signaling coupled with the AMPK pathway, improving glucose homeostasis and insulin sensitivity. These results underscore miR-141/200c as a potential therapeutic target for the management of alcohol intoxication.

Metabolic Dysfunction-Associated Steatotic Liver Disease: From Pathogenesis to Current Therapeutic Options

The epidemiological burden of liver steatosis associated with metabolic diseases is continuously growing worldwide and in all age classes. This condition generates possible progression of liver damage (i.e., inflammation, fibrosis, cirrhosis, hepatocellular carcinoma) but also independently increases the risk of cardio-metabolic diseases and cancer. In recent years, the terminological evolution from "nonalcoholic fatty liver disease" (NAFLD) to "metabolic dysfunction-associated fatty liver disease" (MAFLD) and, finally, "metabolic dysfunction-associated steatotic liver disease" (MASLD) has been paralleled by increased knowledge of mechanisms linking local (i.e., hepatic) and systemic pathogenic pathways. As a consequence, the need for an appropriate classification of individual phenotypes has been oriented to the investigation of innovative therapeutic tools. Besides the well-known role for lifestyle change, a number of pharmacological approaches have been explored, ranging from antidiabetic drugs to agonists acting on the gut-liver axis and at a systemic level (mainly farnesoid X receptor (FXR) agonists, PPAR agonists, thyroid hormone receptor agonists), anti-fibrotic and anti-inflammatory agents. The intrinsically complex pathophysiological history of MASLD makes the selection of a single effective treatment a major challenge, so far. In this evolving scenario, the cooperation between different stakeholders (including subjects at risk, health professionals, and pharmaceutical industries) could significantly improve the management of disease and the implementation of primary and secondary prevention measures. The high healthcare burden associated with MASLD makes the search for new, effective, and safe drugs a major pressing need, together with an accurate characterization of individual phenotypes. Recent and promising advances indicate that we may soon enter the era of precise and personalized therapy for MASLD/MASH.

Acyl ghrelin, desacyl ghrelin and their ratio affect hepatic steatosis via PPARγ signaling pathway

BACKGROUND AND STUDY AIMS

Ghrelin is an appetite hormone-containing 28-amino acid and has 4 different forms in the body. Ghrelin forms have different physiological functions in the body. This study aims to analyze the effect of acyl and desacyl ghrelin hormone on hepatic steatosis and biochemical findings in 36 male Wistar rats.

MATERIALS AND METHODS

Rats were split into 6 equal groups, consisting of control, acyl ghrelin, desacyl ghrelin, acyl/desacyl 3:1, acyl/desacyl 1:1, and acyl/desacyl 1:3 groups, and administered placebo or 200 ng/kg hormone subcutaneous twice a day for 14 days. Oral Glucose Tolerance Test (OGTT) was performed on Day 15, Insulin Tolerance Test (ITT) on Day 16, and scarification procedure on Day 17. Certain biochemical data and liver diacylglycerol (DAG), glycogen, protein kinase C and PPAR-γ levels were detected in the blood. Histological analyses were also conducted on the liver tissues.

RESULTS

The highest plasma total cholesterol and VLDL-K levels were found in the acyl/desacyl 1:3 group, and lower insulin, and HOMA-IR levels were found in groups where acyl and desacyl were administered together (p < 0.05). PPAR-γ gene expression level increased in acyl ghrelin and acyl/desacyl 1:3 groups compared to the control group. Protein kinase C gene expression was highest in the acyl/desacyl 1:3 group. The most severe degenerative findings compliant with steatosis in the liver were observed in the acyl ghrelin group (p < 0.05).

CONCLUSION

It was determined that administering rats acyl alone and acyl/desacyl by 1:3 caused the highest PPAR-γ gene expression, serum total cholesterol, HDL-K, and VLDL-K levels in the body. Besides, it is shown that desacyl ghrelin effectively regulates the blood glucose level when administered alone.

Adding a Leafy Vegetable Fraction to Diets Decreases the Risk of Red Meat Mortality in MASLD Subjects: Results from the MICOL Cohort

BACKGROUND

Dietary guidelines recommend limiting red meat intake because it has been amply associated with increased cancer mortality, particularly in patients with liver conditions, such as metabolic dysfunction-associated fatty liver disease (MASLD). MASLD is the leading cause of liver dysfunction in the world today, and no specific treatment other than lifestyle correction has yet been established. The aim of this study was to explore the protective role of leafy vegetables when associated with high red meat consumption.

METHODS

The study cohort included 1646 participants assessed during the fourth recall of the MICOL study, subdivided into two groups based on red meat intake (≤50 g/die vs. >50 g/die), in order to conduct a cancer mortality analysis. The prevalence of subjects that consumed >50 g/die was only 15.73%. Leafy vegetable intake was categorized based on median g/die consumption, and it was combined with red meat intake.

CONCLUSIONS

This is the first study to demonstrate that the consumption of about 30 g/die of leafy vegetables reduces the risk of mortality. A strong association with mortality was observed in subjects with MASLD, and the protective role of vegetables was demonstrated.

Advances in management of metabolic dysfunction-associated steatotic liver disease: from mechanisms to therapeutics

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading cause of chronic liver disease that affects over 30% of the world's population. For decades, the heterogeneity of non-alcoholic fatty liver disease (NAFLD) has impeded our understanding of the disease mechanism and the development of effective medications. However, a recent change in the nomenclature from NAFLD to MASLD emphasizes the critical role of systemic metabolic dysfunction in the pathophysiology of this disease and therefore promotes the progress in the pharmaceutical treatment of MASLD. In this review, we focus on the mechanism underlying the abnormality of hepatic lipid metabolism in patients with MASLD, and summarize the latest progress in the therapeutic medications of MASLD that target metabolic disorders.

Hepatic mitochondrial reductive stress in the pathogenesis and treatment of steatotic liver disease

Steatotic liver diseases (SLDs) affect one-third of the population, but the pathogenesis underlying these diseases is not well understood, limiting the available treatments. A common factor in SLDs is increased hepatic mitochondrial reductive stress, which occurs as a result of excessive lipid and alcohol metabolism. Recent research has also shown that genetic risk factors contribute to this stress. This review aims to explore how these risk factors increase hepatic mitochondrial reductive stress and how it disrupts hepatic metabolism, leading to SLDs. Additionally, the review will discuss the latest clinical studies on pharmaceutical treatments for SLDs, specifically peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists, thyroid hormone receptor (THR) agonists, acetyl-CoA carboxylase (ACC) inhibitors, and mitochondrial uncouplers. These treatments have a common effect of decreasing hepatic mitochondrial reductive stress, which has been largely overlooked.

Calorie Restriction Using High-Fat/Low-Carbohydrate Diet Suppresses Liver Fat Accumulation and Pancreatic Beta-Cell Dedifferentiation in Obese Diabetic Mice

In diabetes, pancreatic β-cells gradually lose their ability to secrete insulin with disease progression. β-cell dysfunction is a contributing factor to diabetes severity. Recently, islet cell heterogeneity, exemplified by β-cell dedifferentiation and identified in diabetic animals, has attracted attention as an underlying molecular mechanism of β-cell dysfunction. Previously, we reported β-cell dedifferentiation suppression by calorie restriction, not by reducing hyperglycemia using hypoglycemic agents (including sodium-glucose cotransporter inhibitors), in an obese diabetic mice model (db/db). Here, to explore further mechanisms of the effects of food intake on β-cell function, db/db mice were fed either a high-carbohydrate/low-fat diet (db-HC) or a low-carbohydrate/high-fat diet (db-HF) using similar calorie restriction regimens. After one month of intervention, body weight reduced, and glucose intolerance improved to a similar extent in the db-HC and db-HF groups. However, β-cell dedifferentiation did not improve in the db-HC group, and β-cell mass compensatory increase occurred in this group. More prominent fat accumulation occurred in the db-HC group livers. The expression levels of genes related to lipid metabolism, mainly regulated by peroxisome proliferator-activated receptor α and γ, differed significantly between groups. In conclusion, the fat/carbohydrate ratio in food during calorie restriction in obese mice affected both liver lipid metabolism and β-cell dedifferentiation.

Liver Androgen Receptor Knockout Improved High-fat Diet Induced Glucose Dysregulation in Female Mice But Not Male Mice

Previous research has indicated that liver androgen receptors may play a role in modulating disease. This study aims to investigate the pathophysiology of high-fat diet (HFD) induced dysglycemia in male and female liver androgen receptor knockout (LivARKO) mice. We performed metabolic tests on LivARKO female and male mice fed a HFD or a control diet (from Research Diets Inc.) during months 1 or 2 after starting the diet. Additionally, we performed Western blot and quantitative real-time PCR analysis on the livers of the mice to examine intermediates in the insulin signaling pathway. LivARKO-HFD female mice displayed no difference in glucose tolerance compared to female LivARKO-Control (Con) mice, whereas in wild-type female mice, HFD impaired glucose tolerance (IGT). Our data suggests that starting at 1 month, LivARKO may be protecting female mice from HFD-induced metabolic dysfunction. LivARKO-HFD female mice displayed significantly worse insulin sensitivity at 15 minutes compared to LivARKO-Con female mice, but, strangely, LivARKO-HFD female mice had significantly better insulin sensitivity at 60 and 90 minutes compared to LivARKO-Con female mice. Despite protecting against IGT, LivARKO did not protect against HFD-induced hyperinsulinemia in female mice. In contrast to females, male LivARKO-HFD mice displayed impaired glucose tolerance compared to male LivARKO-Con mice. Thus, LivARKO is not protective against HFD-induced glucose metabolic dysfunction in male mice. Lastly, LivARKO-HFD female mice maintained hepatic insulin sensitivity whereas LivARKO-HFD male mice displayed hepatic insulin resistance. These findings suggest that LivARKO delayed the onset of HFD-induced dysglycemia in female mice.

Changes in Cells Associated with Insulin Resistance

Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone. Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue. It is involved in fat metabolism, increasing the storage of triglycerides and decreasing lipolysis. Ketone body metabolism also depends on insulin action, as insulin reduces ketone body concentrations and influences protein metabolism. It increases nitrogen retention, facilitates the transport of amino acids into cells and increases the synthesis of proteins. Insulin also inhibits protein breakdown and is involved in cellular growth and proliferation. On the other hand, defects in the intracellular signaling pathways of insulin may cause several disturbances in human metabolism, resulting in several chronic diseases. Insulin resistance, also known as impaired insulin sensitivity, is due to the decreased reaction of insulin signaling for glucose levels, seen when glucose use in response to an adequate concentration of insulin is impaired. Insulin resistance may cause, for example, increased plasma insulin levels. That state, called hyperinsulinemia, impairs metabolic processes and is observed in patients with type 2 diabetes mellitus and obesity. Hyperinsulinemia may increase the risk of initiation, progression and metastasis of several cancers and may cause poor cancer outcomes. Insulin resistance is a health problem worldwide; therefore, mechanisms of insulin resistance, causes and types of insulin resistance and strategies against insulin resistance are described in this review. Attention is also paid to factors that are associated with the development of insulin resistance, the main and characteristic symptoms of particular syndromes, plus other aspects of severe insulin resistance. This review mainly focuses on the description and analysis of changes in cells due to insulin resistance.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

Amphiregulin from regulatory T cells promotes liver fibrosis and insulin resistance in non-alcoholic steatohepatitis

Production of amphiregulin (Areg) by regulatory T (Treg) cells promotes repair after acute tissue injury. Here, we examined the function of Treg cells in non-alcoholic steatohepatitis (NASH), a setting of chronic liver injury. Areg-producing Treg cells were enriched in the livers of mice and humans with NASH. Deletion of Areg in Treg cells, but not in myeloid cells, reduced NASH-induced liver fibrosis. Chronic liver damage induced transcriptional changes associated with Treg cell activation. Mechanistically, Treg cell-derived Areg activated pro-fibrotic transcriptional programs in hepatic stellate cells via epidermal growth factor receptor (EGFR) signaling. Deletion of Areg in Treg cells protected mice from NASH-dependent glucose intolerance, which also was dependent on EGFR signaling on hepatic stellate cells. Areg from Treg cells promoted hepatocyte gluconeogenesis through hepatocyte detection of hepatic stellate cell-derived interleukin-6. Our findings reveal a maladaptive role for Treg cell-mediated tissue repair functions in chronic liver disease and link liver damage to NASH-dependent glucose intolerance.

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.

Berberine prevents NAFLD and HCC by modulating metabolic disorders

Non-alcoholic fatty liver disease (NAFLD) is a global metabolic disease with high prevalence in both adults and children. Importantly, NAFLD is becoming the main cause of hepatocellular carcinoma (HCC). Berberine (BBR), a naturally occurring plant component, has been demonstrated to have advantageous effects on a number of metabolic pathways as well as the ability to kill liver tumor cells by causing cell death and other routes. This permits us to speculate and make assumptions about the value of BBR in the prevention and defense against NAFLD and HCC by a global modulation of metabolic disorders. Herein, we briefly describe the etiology of NAFLD and NAFLD-related HCC, with a particular emphasis on analyzing the potential mechanisms of BBR in the treatment of NAFLD from aspects including increasing insulin sensitivity, controlling the intestinal milieu, and controlling lipid metabolism. We also elucidate the mechanism of BBR in the treatment of HCC. More significantly, we provided a list of clinical studies for BBR in NAFLD. Taking into account our conclusions and perspectives, we can make further progress in the treatment of BBR in NAFLD and NAFLD-related HCC.

Effects of a high-fat low-carbohydrate diet under different energy conditions on glucose homeostasis and fatty liver development in rats and on gluconeogenesis in the isolated perfused liver

The beneficial effects of high-fat low-carbohydrate (HFLC) diets on glucose metabolism have been questioned and their effects on liver metabolism are not totally clear. The aim of this work was to investigate the effects of an HFLC diet under different energy conditions on glucose homeostasis, fatty liver development, and hepatic gluconeogenesis using the isolated perfused rat liver. HFLC diet (79% fat, 19% protein, and 2% carbohydrates in Kcal%) was administered to rats for 4 weeks under three conditions: ad libitum (hypercaloric), isocaloric, and hypocaloric (energy reduction of 20%). Fasting blood glucose levels and total fat in the liver were higher in all HFLC diet rats. Oral glucose tolerance was impaired in isocaloric and hypercaloric groups, although insulin sensitivity was not altered. HFLC diet also caused marked liver metabolic alterations: higher gluconeogenesis rate from lactate and a reduced capacity to metabolize alanine, the latter effect being more intense in the hypocaloric condition. Thus, even when HFLC diets are used for weight loss, our data imply that they can potentially cause harmful consequences for the liver.

Lipid Metabolism in Metabolic-Associated Steatotic Liver Disease (MASLD)

Metabolic-associated steatotic liver disease (MASLD) is a cluster of pathological conditions primarily developed due to the accumulation of ectopic fat in the hepatocytes. During the severe form of the disease, i.e., metabolic-associated steatohepatitis (MASH), accumulated lipids promote lipotoxicity, resulting in cellular inflammation, oxidative stress, and hepatocellular ballooning. If left untreated, the advanced form of the disease progresses to fibrosis of the tissue, resulting in irreversible hepatic cirrhosis or the development of hepatocellular carcinoma. Although numerous mechanisms have been identified as significant contributors to the development and advancement of MASLD, altered lipid metabolism continues to stand out as a major factor contributing to the disease. This paper briefly discusses the dysregulation in lipid metabolism during various stages of MASLD.

Exploring a novel therapeutic strategy: the interplay between gut microbiota and high-fat diet in the pathogenesis of metabolic disorders

In the past two decades, the rapid increase in the incidence of metabolic diseases, including obesity, diabetes, dyslipidemia, non-alcoholic fatty liver disease, hypertension, and hyperuricemia, has been attributed to high-fat diets (HFD) and decreased physical activity levels. Although the phenotypes and pathologies of these metabolic diseases vary, patients with these diseases exhibit disease-specific alterations in the composition and function of their gut microbiota. Studies in germ-free mice have shown that both HFD and gut microbiota can promote the development of metabolic diseases, and HFD can disrupt the balance of gut microbiota. Therefore, investigating the interaction between gut microbiota and HFD in the pathogenesis of metabolic diseases is crucial for identifying novel therapeutic strategies for these diseases. This review takes HFD as the starting point, providing a detailed analysis of the pivotal role of HFD in the development of metabolic disorders. It comprehensively elucidates the impact of HFD on the balance of intestinal microbiota, analyzes the mechanisms underlying gut microbiota dysbiosis leading to metabolic disruptions, and explores the associated genetic factors. Finally, the potential of targeting the gut microbiota as a means to address metabolic disturbances induced by HFD is discussed. In summary, this review offers theoretical support and proposes new research avenues for investigating the role of nutrition-related factors in the pathogenesis of metabolic disorders in the organism.

Ketogenic propensity is differentially related to lipid-induced hepatic and peripheral insulin resistance

AIM

Determine the ketogenic response (β-hydroxybutyrate, a surrogate of hepatic ketogenesis) to a controlled lipid overload in humans.

METHODS

In total, nineteen young, healthy adults (age: 28.4 ± 1.7 years; BMI: 22.7 ± 0.3 kg/m2 ) received either a 12 h overnight lipid infusion or saline in a randomized, crossover design. Plasma ketones and inflammatory markers were quantified by colorimetric and multiplex assays. Hepatic and peripheral insulin sensitivity was assessed by the hyperinsulinemic-euglycemic clamp. Skeletal muscle biopsies were obtained to quantify gene expression related to ketone body metabolism and inflammation.

RESULTS

By design, the lipid overload-induced hepatic (50%, p < 0.001) and peripheral insulin resistance (73%, p < 0.01) in healthy adults. Ketones increased with hyperlipidemia and were subsequently reduced with hyperinsulinemia during the clamp procedure (Saline: Basal = 0.22 mM, Insulin = 0.07 mM; Lipid: Basal = 0.78 mM, Insulin = 0.51 mM; 2-way ANOVA: Lipid p < 0.001, Insulin p < 0.001, Interaction p = 0.07). In the saline control condition, ketones did not correlate with hepatic or peripheral insulin sensitivity. Conversely, in the lipid condition, ketones were positively correlated with hepatic insulin sensitivity (r = 0.59, p < 0.01), but inversely related to peripheral insulin sensitivity (r = -0.64, p < 0.01). Hyperlipidemia increased plasma inflammatory markers, but did not impact skeletal muscle inflammatory gene expression. Gene expression related to ketone and fatty acid metabolism in skeletal muscle increased in response to hyperlipidemia.

CONCLUSION

This work provides important insight into the role of ketones in human health and suggests that ketone body metabolism is altered at the onset of lipid-induced insulin resistance.

[Non-alcoholic fatty liver disease: aspects of management of a comorbid patient. A review]

Against the background of the rapid increase in the prevalence of obesity worldwide, the frequency of the development of metabolic disorders associated with it is increasing. Non-alcoholic fatty liver disease (NAFLD) is recognized as the main hepatic manifestation of metabolic syndrome. Currently, NAFLD affects about 25-30% of the world's population and, in most cases, is associated with obesity and type 2 diabetes, as well as with increased cardiovascular risk. Diagnosis of NAFLD includes laboratory and instrumental research methods, various non-invasive tests, and the "gold standard" for confirming the diagnosis is a liver biopsy. Due to the greater availability and sufficient information content, ultrasound methods of research come to the fore in the examination of patients at risk. Lifestyle modification remains the cornerstone in the management of such patients, however, given the complex pathogenesis of the disease, treatment of NAFLD may include several therapeutic strategies. In the treatment of comorbid patients, some groups of hypoglycemic drugs are used, including ar-GLP-1, i-NGL-2, pioglitazone, lipid-lowering drugs, drugs for the treatment of obesity. The so-called hepatoprotectors, including essential phospholipids (EFL), have demonstrated their effectiveness in reducing liver damage due to antioxidant, antifibrotic, and lipid-regulating effects. According to a number of studies, EFL helps to reduce the severity of steatosis, improving both objective and subjective manifestations of hepatic dysfunction. In this connection, the guidelines of various countries include EFL group drugs in the protocol of treatment of patients with NAFLD both in monotherapy and in combination with other drugs.

In Vitro Assessment of Anti-Adipogenic and Anti-Inflammatory Properties of Black Cumin (Nigella sativa L.) Seeds Extract on 3T3-L1 Adipocytes and Raw264.7 Macrophages

Background and Objectives: This study evaluated the in vitro anti-adipogenic and anti-inflammatory properties of black cumin (Nigella sativa L.) seed extract (BCS extract) as a potential candidate for developing herbal formulations targeting metabolic disorders. Materials and Methods: We evaluated the BCS extract by assessing its 2,2-diphenyl-1-picrohydrazyl (DPPH) radical scavenging activity, levels of prostaglandin E2 (PGE2) and nitric oxide (NO), and mRNA expression levels of key pro-inflammatory mediators. We also quantified the phosphorylation of nuclear factor kappa light chain enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPK) signaling molecules. To assess anti-adipogenic effects, we used differentiated 3T3-L1 cells and BCS extract in doses from 10 to 100 μg/mL. We also determined mRNA levels of key adipogenic genes, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/BEPα), adipocyte protein 2 (aP2), lipoprotein lipase (LPL), fatty acid synthase (FAS), and sterol-regulated element-binding protein 1c (SREBP-1c) using real-time quantitative polymerase chain reaction (qPCR). Results: This study showed a concentration-dependent DPPH radical scavenging activity and no toxicity at concentrations up to 30 μg/mL in Raw264.7 cells. BCS extract showed an IC50 of 328.77 ± 20.52 μg/mL. Notably, pre-treatment with BCS extract (30 μg/mL) significantly enhanced cell viability in lipopolysaccharide (LPS)-treated Raw264.7 cells. BCS extract treatment effectively inhibited LPS-induced production of PGE2 and NO, as well as the expression of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), interleukin (IL)-1β and IL-6, possibly by limiting the phosphorylation of p38, p65, inhibitory κBα (I-κBα), and c-Jun N-terminal kinase (JNK). It also significantly attenuated lipid accumulation and key adipogenic genes in 3T3-L1 cells. Conclusions: This study highlights the in vitro anti-adipogenic and anti-inflammatory potential of BCS extract, underscoring its potential as a promising candidate for managing metabolic disorders.

The Interconnection between Hepatic Insulin Resistance and Metabolic Dysfunction-Associated Steatotic Liver Disease-The Transition from an Adipocentric to Liver-Centric Approach

The central mechanism involved in the pathogenesis of MAFLD is insulin resistance with hyperinsulinemia, which stimulates triglyceride synthesis and accumulation in the liver. On the other side, triglyceride and free fatty acid accumulation in hepatocytes promotes insulin resistance via oxidative stress, endoplasmic reticulum stress, lipotoxicity, and the increased secretion of hepatokines. Cytokines and adipokines cause insulin resistance, thus promoting lipolysis in adipose tissue and ectopic fat deposition in the muscles and liver. Free fatty acids along with cytokines and adipokines contribute to insulin resistance in the liver via the activation of numerous signaling pathways. The secretion of hepatokines, hormone-like proteins, primarily by hepatocytes is disturbed and impairs signaling pathways, causing metabolic dysregulation in the liver. ER stress and unfolded protein response play significant roles in insulin resistance aggravation through the activation of apoptosis, inflammatory response, and insulin signaling impairment mediated via IRE1/PERK/ATF6 signaling pathways and the upregulation of SREBP 1c. Circadian rhythm derangement and biological clock desynchronization are related to metabolic disorders, insulin resistance, and NAFLD, suggesting clock genes as a potential target for new therapeutic strategies. This review aims to summarize the mechanisms of hepatic insulin resistance involved in NAFLD development and progression.