Plasma Fatty Acid Composition Is Associated with Histological Findings of Nonalcoholic Steatohepatitis

Skylite: Skyline-Based Lipid Isomer Retention Time Evaluation for Lipidomics in Metabolic Dysfunction-Associated Steatohepatitis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent liver disorder worldwide and can progress to steatohepatitis. Elevated de novo lipogenesis (DNL) is a key contributor to hepatic steatosis. Fatty acid (FA) desaturation produces several unsaturated lipid isomers that are structurally very similar but have diverse biological functions. However, due to their structural similarity, many conventional mass spectrometry approaches cannot detect such metabolic alterations. Thus, we introduce the Skylite (Skyline-based lipid isomer retention time evaluation) workflow using conventional liquid chromatography-mass spectrometry (LC-MS) to identify important isomer features. Retention times of isomeric phosphatidylcholines are compared with the well-characterized human plasma reference standard NIST 1950. Retention time trends correlate well with fixed-charge derivatized FA in liquid chromatography and ozone-induced dissociation mass spectrometry data. The interpretation is supported by double bond diagnostic fragments in LC-MS/MS experiments of epoxidized hydrolyzed fatty acids. We investigate hepatic lipid profiles, focusing on esterified fatty acids in two mouse models of metabolic dysfunction-associated steatohepatitis (MASH). Out of 37 phosphatidylcholine sum compositions, the workflow identifies 123 lipid features. Importantly, CCl4-induced and melanocortin-4 receptor knockout mice on a western diet (WD) have significantly higher levels of mead acid, branched-chain fatty acid, and n-7 PUFA incorporated into phosphatidylcholines. While the MASH mouse liver tissues contain notable amounts of n-7 PUFA, no n-10 PUFA were detected, potentially indicating a unique desaturation pattern. The screening for altered lipid isomer profiles bridges the gap between high-throughput analyses and specialized structure-resolved techniques.

Higher levels of plasmatic saturated fatty acid were significantly associated with liver fibrosis in HIV mono-infection: A case-control study

Background

The relationship between plasmatic fatty acid (FA) composition and liver fibrosis remains scarce in people living with HIV/AIDS (PLWHA). We aimed to evaluate the association of plasmatic FAs and liver fibrosis in HIV mono-infected individuals.

Methods

This case-control study included PLWHA with liver fibrosis (cases) and randomly selected subjects without fibrosis (controls) from the PROSPEC-HIV study (NCT02542020). Participants with viral hepatitis, abusive alcohol consumption and lipid supplements use were excluded. Liver fibrosis was defined using transient elastography (TE) by liver stiffness measurement (LSM) ≥ 7.1 kPa or ≥ 6.2 kPa with M or XL probe, respectively. All HIV mono-infected participants with liver fibrosis identified at the baseline PROSPEC-HIV visit were included. Controls (1:1) were randomly selected among those HIV mono-infected participants without liver fibrosis. Plasmatic FA profile, dietary lipid intake, anthropometric measures, and blood samples were assessed. Plasmatic fatty acid was analyzed using gas chromatography and intake of fats lipids were assessed by two 24-h dietary recall (24-HDR). Multivariate logistic regression models adjusted by age, sex at birth and duration of antiretroviral therapy (ART) were performed.

Results

A total of 142 participants (71 cases and 71 controls) [62 % female, median age = 46 (IQR, 37-53) years, 14.8 % with diabetes, median CD4 count = 655 cells/mm3, 96.5 % under ART] were included. Higher percentages of plasmatic palmitc acid (16:0) and saturated fatty acids (SFA) were observed in participants with liver fibrosis (cases) compared to those without (controls). Presence of higher percentage of plasmatic palmitc acid (16:0) was associated with an increased odds for liver fibrosis [adjusted OR = 1.23 (95%CI 1.04-1.46); p = 0.02] in multivariate models.

Conclusion

This study showed the potential role of the plasmatic FA composition in the pathogenesis of liver fibrosis in PLWHA.

Mechanisms coupling lipid droplets to MASLD pathophysiology

Hepatic steatosis, the buildup of neutral lipids in lipid droplets (LDs), is commonly referred to as metabolic dysfunction-associated steatotic liver disease when alcohol or viral infections are not involved. Metabolic dysfunction-associated steatotic liver disease encompasses simple steatosis and the more severe metabolic dysfunction-associated steatohepatitis, characterized by inflammation, hepatocyte injury, and fibrosis. Previously viewed as inert markers of disease, LDs are now understood to play active roles in disease etiology and have significant nonpathological and pathological functions in cell signaling and function. These dynamic properties of LDs are tightly regulated by hundreds of proteins that coat the LD surface, controlling lipid metabolism, trafficking, and signaling. The following review highlights various facets of LD biology with the primary goal of discussing key mechanisms through which LDs promote the development of advanced liver diseases, including metabolic dysfunction-associated steatohepatitis.

Current strategies for nonalcoholic fatty liver disease treatment (Review)

Nonalcoholic fatty liver disease (NAFLD), the most common chronic hepatic disease, has become a leading health problem worldwide. The present review summarized the methods and mechanisms to treat NAFLD, including the Mediterranean diet, physical activity and exercise, bariatric surgery and specific therapeutic agents, including statins, peroxisome proliferator‑activated receptor agonists, cenicriviroc and farnesoid X receptor agonists. Biologically active substances, such as peptides, alkaloids, polyphenolic compounds, silymarin, antibiotics, fatty acids, vitamins, probiotics, synbiotics and lamiaceae have also demonstrated actions that combat NAFLD. Considering their different mechanisms of action, combining some of them may prove an efficacious treatment for NAFLD. In this light, the present review describes recent progress and future prospects in treating NAFLD.

Lipidomic Analysis Reveals Alterations in Hepatic FA Profile Associated With MASLD Stage in Patients With Obesity

CONTEXT

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by the intracellular lipid accumulation in hepatocytes. Excess caloric intake and high-fat diets are considered to significantly contribute to MASLD development.

OBJECTIVE

To evaluate the hepatic and serum fatty acid (FA) composition in patients with different stages of MASLD, and their relationship with FA dietary intake and MASLD-related risk factors.

METHODS

This was a case-control study in patients with obesity undergoing bariatric surgery at a university hospital between January 2020 and December 2021. Participants were distributed in 3 groups: no MASLD (n = 26), steatotic liver disease (n = 33), and metabolic dysfunction-associated steatohepatitis (n = 32). Hepatic and serum FA levels were determined by gas chromatography-mass spectrometry. Nutritional status was evaluated using validated food frequency questionnaires. The hepatic expression of genes involved in FA metabolism was analyzed by reverse transcription quantitative polymerase chain reaction.

RESULTS

The hepatic, but not serum, FA profiles were significantly altered in patients with MASLD compared with those without MASLD. No differences were observed in FA intake between the groups. Levels of C16:0, C18:1, and the C18:1/C18:0 ratio were higher, while C18:0 levels and C18:0/C16:0 ratio were lower in patients with MASLD, being significantly different between the 3 groups. Hepatic FA levels and ratios correlated with histopathological diagnosis and other MASLD-related parameters. The expression of genes involved in the FA metabolism was upregulated in patients with MASLD.

CONCLUSION

Alterations in hepatic FA levels in MASLD patients were due to enhancement of de novo lipogenesis in the liver.

Serum bile acid and unsaturated fatty acid profiles of non-alcoholic fatty liver disease in type 2 diabetic patients

BACKGROUND

The understanding of bile acid (BA) and unsaturated fatty acid (UFA) profiles, as well as their dysregulation, remains elusive in individuals with type 2 diabetes mellitus (T2DM) coexisting with non-alcoholic fatty liver disease (NAFLD). Investigating these metabolites could offer valuable insights into the pathophy-siology of NAFLD in T2DM.

AIM

To identify potential metabolite biomarkers capable of distinguishing between NAFLD and T2DM.

METHODS

A training model was developed involving 399 participants, comprising 113 healthy controls (HCs), 134 individuals with T2DM without NAFLD, and 152 individuals with T2DM and NAFLD. External validation encompassed 172 participants. NAFLD patients were divided based on liver fibrosis scores. The analytical approach employed univariate testing, orthogonal partial least squares-discriminant analysis, logistic regression, receiver operating characteristic curve analysis, and decision curve analysis to pinpoint and assess the diagnostic value of serum biomarkers.

RESULTS

Compared to HCs, both T2DM and NAFLD groups exhibited diminished levels of specific BAs. In UFAs, particular acids exhibited a positive correlation with NAFLD risk in T2DM, while the ω-6:ω-3 UFA ratio demonstrated a negative correlation. Levels of α-linolenic acid and γ-linolenic acid were linked to significant liver fibrosis in NAFLD. The validation cohort substantiated the predictive efficacy of these biomarkers for assessing NAFLD risk in T2DM patients.

CONCLUSION

This study underscores the connection between altered BA and UFA profiles and the presence of NAFLD in individuals with T2DM, proposing their potential as biomarkers in the pathogenesis of NAFLD.

Glycemic Control Is Associated with Histological Findings of Nonalcoholic Fatty Liver Disease

BACKGRUOUND

Poor lifestyle habits may worsen nonalcoholic fatty liver disease (NAFLD), with progression to nonalcoholic steatohepatitis (NASH) and cirrhosis. This study investigated the association between glycemic control status and hepatic histological findings to elucidate the effect of glycemic control on NAFLD.

METHODS

This observational study included 331 patients diagnosed with NAFLD by liver biopsy. Effects of the glycemic control status on histological findings of NAFLD were evaluated by comparing the following four glycemic status groups defined by the glycosylated hemoglobin (HbA1c) level at the time of NAFLD diagnosis: ≤5.4%, 5.5%-6.4%, 6.5%-7.4%, and ≥7.5%.

RESULTS

Compared with the lowest HbA1c group (≤5.4%), the higher HbA1c groups (5.5%-6.4%, 6.5%-7.4%, and ≥7.5%) were associated with advanced liver fibrosis and high NAFLD activity score (NAS). On multivariate analysis, an HbA1c level of 6.5%- 7.4% group was significantly associated with advanced fibrosis compared with the lowest HbA1c group after adjusting for age, sex, hemoglobin, alanine aminotransferase, and creatinine levels. When further controlling for body mass index and uric acid, total cholesterol, and triglyceride levels, the higher HbA1c groups were significantly associated with advanced fibrosis compared with the lowest HbA1c group. On the other hand, compared with the lowest HbA1c group, the higher HbA1c groups were also associated with a high NAS in both multivariate analyses.

CONCLUSION

Glycemic control is associated with NAFLD exacerbation, with even a mild deterioration in glycemic control, especially a HbA1c level of 6.5%-7.4%, contributing to NAFLD progression.

Liver ACSM3 deficiency mediates metabolic syndrome via a lauric acid-HNF4α-p38 MAPK axis

Metabolic syndrome combines major risk factors for cardiovascular disease, making deeper insight into its pathogenesis important. We here explore the mechanistic basis of metabolic syndrome by recruiting an essential patient cohort and performing extensive gene expression profiling. The mitochondrial fatty acid metabolism enzyme acyl-CoA synthetase medium-chain family member 3 (ACSM3) was identified to be significantly lower expressed in the peripheral blood of metabolic syndrome patients. In line, hepatic ACSM3 expression was decreased in mice with metabolic syndrome. Furthermore, Acsm3 knockout mice showed glucose and lipid metabolic abnormalities, and hepatic accumulation of the ACSM3 fatty acid substrate lauric acid. Acsm3 depletion markedly decreased mitochondrial function and stimulated signaling via the p38 MAPK pathway cascade. Consistently, Acsm3 knockout mouse exhibited abnormal mitochondrial morphology, decreased ATP contents, and enhanced ROS levels in their livers. Mechanistically, Acsm3 deficiency, and lauric acid accumulation activated nuclear receptor Hnf4α-p38 MAPK signaling. In line, the p38 inhibitor Adezmapimod effectively rescued the Acsm3 depletion phenotype. Together, these findings show that disease-associated loss of ACSM3 facilitates mitochondrial dysfunction via a lauric acid-HNF4a-p38 MAPK axis, suggesting a novel therapeutic vulnerability in systemic metabolic dysfunction.

The physiological and pathological properties of Mead acid, an endogenous multifunctional n-9 polyunsaturated fatty acid

Mead acid (MA, 5,8,11-eicosatrienoic acid) is an n-9 polyunsaturated fatty acid (PUFA) and a marker of essential fatty acid deficiency, but nonetheless generally draws little attention. MA is distributed in various normal tissues and can be converted to several specific lipid mediators by lipoxygenase and cyclooxygenase. Recent pathological and epidemiological studies on MA raise the possibility of its effects on inflammation, cancer, dermatitis and cystic fibrosis, suggesting it is an endogenous multifunctional PUFA. This review summarizes the biosynthesis, presence, metabolism and physiological roles of MA and its relation to various diseases, as well as the significance of MA in PUFA metabolism.

Time course of western diet (WD) induced nonalcoholic steatohepatitis (NASH) in female and male Ldlr-/- mice

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a global health problem. Identification of factors contributing to the onset and progression of NAFLD have the potential to direct novel strategies to combat NAFLD.

METHODS

We examined the time course of western diet (WD)-induced NAFLD and its progression to nonalcoholic steatohepatitis (NASH) in age-matched female and male Ldlr-/- mice, with time-points at 1, 4, 8, 20 and 40 weeks on the WD. Controls included Ldlr-/- mice maintained on a purified low-fat diet (LFD) for 1 and 40 weeks. The approach included quantitation of anthropometric, plasma and liver markers of disease, plus hepatic histology, lipids, oxylipins, gene expression and selected metabolites.

RESULTS

One week of feeding the WD caused a significant reduction in hepatic essential fatty acids (EFAs: 18:2, ω6, 18:3, ω3) which preceded the decline in many C20-22 ω3 and ω6 polyunsaturated fatty acids (PUFA) and PUFA-derived oxylipins after 4 weeks on the WD. In addition, expression of hepatic inflammation markers (CD40, CD44, Mcp1, Nlrp3, TLR2, TLR4, Trem2) increased significantly in both female & male mice after one week on the WD. These markers continued to increase over the 40-week WD feeding study. WD effects on hepatic EFA and inflammation preceded all significant WD-induced changes in body weight, insulin resistance (HOMA-IR), oxidative stress status (GSH/GSSG ratio) and histological and gene expression markers of macrosteatosis, extracellular matrix remodeling and fibrosis.

CONCLUSIONS

Our findings establish that feeding Ldlr-/- mice the WD rapidly lowered hepatic EFAs and induced key inflammatory markers linked to NASH. Since EFAs have an established role in inflammation and hepatic inflammation plays a major role in NASH, we suggest that early clinical assessment of EFA status and correcting EFA deficiencies may be useful in reducing NASH severity.