Associations of NAFLD with circulating ceramides and impaired glycemia

Integrated lipidomic and transcriptomics to explore the effects of ethyl acetate extract of Herpetospermum pedunculosum on nonalcoholic fatty liver disease in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Herpetospermum pedunculosum (Ser.) C.B. Clarke (HP), a traditional Tibetan medicine used to treat hepatobiliary diseases, was confirmed that lignans-enriched ethyl acetate extract of HP (EAHP) could alleviate the hepatic injury by modern pharmacological evidence. However, the effects and potential mechanisms of EAHP against nonalcoholic fatty liver disease (NAFLD) are still unknown.

AIM OF THE STUDY

To reveal the effects of EAHP on NAFLD and explore the potential mechanisms from the perspective of lipidomics and transcriptomics.

MATERIALS AND METHODS

UPLC‒Q-TOF‒MS analysis was carried out to investigate the chemical components of EAHP. A Choline-deficient, L-amino acid defined, high fat diet (CDAHFD) was used to establish a NAFLD mouse model. The anti-NAFLD effects of various dosages of EAHP were evaluated by biochemical indexes and histological analysis. Hepatic lipidomic and transcriptomic analysis and multiple bioinformatics methods were used to screen biomarkers and signaling pathways. The levels of the corresponding genes were verified by qPCR.

RESULTS

36 kinds of compounds were identified by UPLC‒Q-TOF‒MS analysis. Oral treatment with EAHP significantly decrease the liver index and the levels of ALT and AST in the serum. The measurements lipid content and Oil Red O staining results suggested that EAHP ameliorated lipid metabolism disorders by reducing the content of TG and LDL-C, increasing HDL-C in the liver. H&E staining and ELISA revealed that EAHP restored hepatic inflammatory infiltration and decrease the levels of IL-1β, IL-6, TNF-α, and increase IL-10 in the serum. Lipidomic analysis showed that EAHP could regulate CDAHFD-induced lipid metabolic disorder. The different lipid metabolites included TG, phosphatidyl choline (PC), diacylglycerol (DG), phosphatidylethanolamine (PE), phosphatidylinositol (PI), ceramide (Cer). Transcriptomic analysis revealed that Bmp8b, Nbl1, Rgma, Sphk1, Thbs1, and Ugt8a were important regulators, which were associated with TGF-β signaling pathway and sphingolipid metabolism. The expressions of above genes detected by were qPCR consistent with transcriptomic data.

CONCLUSIONS

The ameliorative effects of EAHP on NAFLD are potentially attributable to the regulation of sphingolipid metabolism and TGF-β signaling pathway, etc., which results in abnormal hepatic lipid metabolism and inflammatory response.

An adipocentric perspective of pancreatic lipotoxicity in diabetes pathogenesis

Obesity and diabetes represent two increasing and invalidating public health issues that often coexist. It is acknowledged that fat mass excess predisposes to insulin resistance and type 2 diabetes mellitus (T2D), with the increasing incidence of the two diseases significantly associated. Moreover, emerging evidence suggests that obesity might also accelerate the appearance of type 1 diabetes (T1D), which is now a relatively frequent comorbidity in patients with obesity. It is a common clinical finding that not all patients with obesity will develop diabetes at the same level of adiposity, with gender, genetic, and ethnic factors playing an important role in defining the timing of diabetes appearance. The adipose tissue (AT) expandability hypothesis explains this paradigm, indicating that the individual capacity to appropriately store energy surplus in the form of fat within the AT determines and prevents the toxic deposition of lipids in other organs, such as the pancreas. Thus, we posit that when the maximal storing capacity of AT is exceeded, individuals will develop T2D. In this review, we provide insight into mechanisms by which the AT controls pancreas lipid content and homeostasis in case of obesity to offer an adipocentric perspective of pancreatic lipotoxicity in the pathogenesis of diabetes. Moreover, we suggest that improving AT function is a valid therapeutic approach to fighting obesity-associated complications including diabetes.

Cadmium exacerbates liver injury by remodeling ceramide metabolism: Multiomics and laboratory evidence

Cadmium (Cd) is a toxic heavy metal that primarily targets the liver. Cd exposure disrupts specific lipid metabolic pathways; however, the underlying mechanisms remain unclear. This study aimed to investigate the lipidomic characteristics of rat livers after Cd exposure as well as the potential mechanisms of Cd-induced liver injury. Our analysis of established Cd-exposed rat and cell models showed that Cd exposure resulted in liver lipid deposition and hepatocyte damage. Lipidomic detection, transcriptome sequencing, and experimental analyses revealed that Cd mainly affects the sphingolipid metabolic pathway and that the changes in ceramide metabolism are the most significant. In vitro experiments revealed that the inhibition of ceramide synthetase activity or activation of ceramide decomposing enzymes ameliorated the proapoptotic and pro-oxidative stress effects of Cd, thereby alleviating liver injury. In contrast, the exogenous addition of ceramide aggravated liver injury. In summary, Cd increased ceramide levels by remodeling ceramide synthesis and catabolism, thereby promoting hepatocyte apoptosis and oxidative stress and ultimately aggravating liver injury. Reducing ceramide levels can serve as a potential protective strategy to mitigate the liver toxicity of Cd. This study provides new evidence for understanding Cd-induced liver injury at the lipidomic level and insights into the health risks and toxicological mechanisms associated with Cd.

Lipidome Changes Associated with a Diet-Induced Reduction in Hepatic Fat among Adolescent Boys with Metabolic Dysfunction-Associated Steatotic Liver Disease

Little is known about lipid changes that occur in the setting of metabolic-dysfunction-associated steatotic liver disease (MASLD) regression. We previously reported improvements in hepatic steatosis, de novo lipogenesis (DNL), and metabolomic profiles associated with oxidative stress, inflammation, and selected lipid metabolism in 40 adolescent boys (11-16 y) with hepatic steatosis ≥5% (98% meeting the definition of MASLD). Participants were randomized to a low-free-sugar diet (LFSD) (n = 20) or usual diet (n = 20) for 8 weeks. Here, we employed untargeted/targeted lipidomics to examine lipid adaptations associated with the LFSD and improvement of hepatic steatosis. Our LC-MS/MS analysis revealed decreased triglycerides (TGs), diacylglycerols (DGs), cholesteryl esters (ChE), lysophosphatidylcholine (LPC), and phosphatidylcholine (PC) species with the diet intervention (p < 0.05). Network analysis demonstrated significantly lower levels of palmitate-enriched TG species post-intervention, mirroring the previously shown reduction in DNL in response to the LFSD. Targeted oxylipins analysis revealed a decrease in the abundance of 8-isoprostane and 14,15-DiHET and an increase in 8,9-DiHET (p < 0.05). Overall, we observed reductions in TGs, DGs, ChE, PC, and LPC species among participants in the LFSD group. These same lipids have been associated with MASLD progression; therefore, our findings may indicate normalization of key biological processes, including lipid metabolism, insulin resistance, and lipotoxicity. Additionally, our targeted oxylipins assay revealed novel changes in eicosanoids, suggesting improvements in oxidative stress. Future studies are needed to elucidate the mechanisms of these findings and prospects of these lipids as biomarkers of MASLD regression.

Diabetes in South Asians: Uncovering Novel Risk Factors With Longitudinal Epidemiologic Data: Kelly West Award Lecture 2023

South Asian populations have a higher prevalence and earlier age of onset of type 2 diabetes and atherosclerotic cardiovascular diseases than other race and ethnic groups. To better understand the pathophysiology and multilevel risk factors for diabetes and cardiovascular disease, we established the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study in 2010. The original MASALA study cohort (n = 1,164) included 83% Asian Indian immigrants, with an ongoing expansion of the study to include individuals of Bangladeshi and Pakistani origin. We have found that South Asian Americans in the MASALA study had higher type 2 diabetes prevalence, lower insulin secretion, more insulin resistance, and an adverse body composition with higher liver and intermuscular fat and lower lean muscle mass compared with four other U.S. race and ethnic groups. MASALA study participants with diabetes were more likely to have the severe hyperglycemia subtype, characterized by β-cell dysfunction and lower body weight, and this subtype was associated with a higher incidence of subclinical atherosclerosis. We have found several modifiable factors for cardiometabolic disease among South Asians including diet and physical activity that can be influenced using specific social network members and with cultural adaptations to the U.S. context. Longitudinal data with repeat cardiometabolic measures that are supplemented with qualitative and mixed-method approaches enable a deeper understanding of disease risk and resilience factors. Studying and contrasting Asian American subgroups can uncover the causes for cardiometabolic disease heterogeneity and reveal novel methods for prevention and treatment.

Plasma ceramides are associated with MRI-based liver fat content but not with noninvasive scores of liver fibrosis in patients with type 2 diabetes

BACKGROUND

There is growing evidence that ceramides play a significant role in the onset and progression of non-alcoholic fatty liver disease (NAFLD), a highly prevalent condition in patients with type 2 diabetes associated with hepatic and cardiovascular events. However, the relationship between plasma ceramide levels and NAFLD severity in type 2 diabetes remains unclear. The main purpose of the present study was to investigate whether circulating levels of ceramides in patients with type 2 diabetes are associated with liver steatosis assessed by the highly accurate magnetic resonance imaging proton density fat fraction (MRI-PDFF). The secondary objective was to assess the relationship between plasma ceramides and noninvasive scores of liver fibrosis.

METHODS

In this cross-sectional single-center study, plasma concentrations of 7 ceramides were measured by liquid chromatography-mass spectrometry in 255 patients with type 2 diabetes (GEPSAD cohort). Liver fat content was assessed by MRI-PDFF, and noninvasive scores of liver fibrosis (i.e. Fibrosis-4 index, NAFLD Fibrosis Score, FibroTest® and Fibrotic NASH Index) were calculated. A validation cohort of 80 patients with type 2 diabetes was also studied (LIRA-NAFLD cohort).

RESULTS

Liver steatosis, defined as a liver fat content > 5.56%, was found in 62.4 and 82.5% of individuals with type 2 diabetes in the GEPSAD and LIRA-NAFLD cohorts, respectively. In GEPSAD, MRI-PDFF-measured liver fat content was positively associated with plasma levels of total ceramides (r = 0.232, p = 0.0002), and 18:0, 20:0, 22:0 and 24:0 ceramides in univariate analysis (p ≤ 0.0003 for all). In multivariate analysis, liver fat content remained significantly associated with total ceramides (p = 0.001), 18:0 (p = 0.006), 22:0 (p = 0.0009) and 24:0 ceramides (p = 0.0001) in GEPSAD, independently of age, diabetes duration, body mass index and dyslipidemia. Overall, similar relationship between plasma ceramides and liver fat content was observed in the LIRA-NAFLD validation cohort. No significant association was found between plasma ceramides and noninvasive scores of fibrosis after adjustment for age in both cohorts.

CONCLUSIONS

Plasma ceramide levels are associated with liver steatosis in patients with type 2 diabetes, independently of traditional risk factors for NAFLD. The independent association between plasma ceramides and liver steatosis adds new insights regarding the relationship between ceramides and NAFLD in type 2 diabetes.

Changing epidemiology, global trends and implications for outcomes of NAFLD

Non-alcoholic fatty liver disease (NAFLD) has rapidly become the most common liver disease globally and is currently estimated to affect 38% of the global population. Only a minority of patients with NAFLD will progress to cirrhosis or hepatocellular carcinoma, but from this vast population the total number of patients who are at risk of such severe outcomes is increasing. Worryingly, individuals are increasingly being affected by NAFLD at an earlier age, meaning there is more time for them to develop severe complications. With considerable changes in dietary composition and urbanisation, alongside the growth in obesity and type 2 diabetes in the global population, in particular in developing countries, the global proportion of persons affected by NAFLD is projected to increase further. Yet, there are large geographical discrepancies in the prevalence rates of NAFLD and its inflammatory component non-alcoholic steatohepatitis (NASH). Such differences are partly related to differing socio-economic milieus, but also to genetic predisposition. In this narrative review, we discuss recent changes in the epidemiology of NAFLD and NASH from regional and global perspectives, as well as in special populations. We also discuss the potential consequences of these changes on hepatic and extrahepatic events.

Insights into the roles and pathomechanisms of ceramide and sphigosine-1-phosphate in nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), as one of the main causes of chronic liver disease worldwide, encompasses a spectrum of liver conditions that are not caused by other etiology, such as overt alcohol consumption, from simple steatosis to more aggressive non-alcoholic steatohepatitis (NASH) that involves liver inflammation and fibrosis, and to the lethal cirrhosis that may result in liver cancer and liver failure. The molecular mechanisms governing the transition from steatosis to NASH remain not fully understood, but the hepatic lipidome is extensively altered in the setting of steatosis and steatohepatitis, which also correlate with disease progression. With the tremendous advancement in the field of lipidomics in last two decades, a better understanding of the specific role of sphingolipids in fatty liver disease has taken shape. Among the numerous lipid subtypes that accumulate, ceramides are particularly impactful. On the one hand, excessive ceramides deposition in the liver cause hepatic steatosis. On the other hand, ceramides as lipotoxic lipid have significant effects on hepatic inflammation, apoptosis and insulin resistance that contribute to NAFLD. In this review, we summarize and evaluate current understanding of the multiple roles of ceramides in the onset of fatty liver disease and the pathogenic mechanisms underlying their effects, and we also discuss recent advances and challenges in pharmacological interventions targeting ceramide metabolism for the treatment of NAFLD.

Are isothiocyanates and polyphenols from Brassicaceae vegetables emerging as preventive/therapeutic strategies for NAFLD? The landscape of recent preclinical findings

Nonalcoholic fatty liver disease (NAFLD) is a lipid impairment-related chronic metabolic disease that affects almost 25% of the worldwide population and has become the leading cause of liver transplantation in the United States of America (USA). NAFLD may progress from simple hepatic steatosis (HS) to nonalcoholic steatohepatitis (NASH), which occurs simultaneously in an inflammatory and fibrotic microenvironment and affects approximately 5% of the global population. Recently, NASH has been suggested to be a relevant driver in progressive liver cirrhosis and a population-attributable factor in hepatocellular carcinoma patients. Moreover, predictions show that NAFLD-related annual health costs in the USA have reached ∼$100 bi., but effective therapies are still scarce. Thus, new preventative strategies for this hepatic disease urgently need to be developed. The Brassicaceae vegetable family includes almost 350 genera and 3500 species and these are one of the main types of vegetables harvested and produced worldwide. These vegetables are well-known sources of glucobrassicin-derivative molecules, such as isothiocyanates and phenolic compounds, which have shown antioxidant and antilipogenic effects in preclinical NAFLD data. In this review, we gathered prominent evidence of the in vivo and in vitro effects of these vegetable-derived nutraceutical compounds on the gut-liver-adipose axis, which is a well-known regulator of NAFLD and may represent a new strategy for disease control.