Update on lipid species and paediatric nonalcoholic fatty liver disease

Multi-omics reveals goose fatty liver formation from metabolic reprogramming

To comprehensively provide insight into goose fatty liver formation, we performed an integrative analysis of the liver transcriptome, lipidome, and amino acid metabolome, as well as peripheral adipose tissue transcriptome analysis using samples collected from the overfed geese and normally fed geese. Transcriptome analysis showed that liver metabolism pathways were mainly enriched in glucolipid metabolism, amino acid metabolism, inflammation response, and cell cycle; peripheral adipose tissue and the liver cooperatively regulated liver lipid accumulation during overfeeding. Liver lipidome patterns obviously changed after overfeeding, and 157 different lipids were yielded. In the liver amino acid metabolome, the level of Lys increased after overfeeding. In summary, this is the first study describing goose fatty liver formation from an integrative analysis of transcriptome, lipidome, and amino acid metabolome, which will provide a whole new dimension to understanding the mechanism of goose fatty liver formation.

Advances in paediatric nonalcoholic fatty liver disease: Role of lipidomics

Due its close relationship with obesity, nonalcoholic fatty liver disease (NAFLD) has become a major worldwide health issue even in childhood. The most accepted pathophysiological hypothesis is represented by the “multiple hits” theory, in which both hepatic intracellular lipid accumulation and insulin resistance mainly contribute to liver injury through several factors. Among these, lipotoxicity has gained particular attention. In this view, the pathogenic role of different lipid classes in NAFLD (e.g., sphingolipids, fatty acids, ceramides, etc.) has been highlighted in recent lipidomics studies. Although there is some contrast between plasma and liver findings, lipidomic profile in the NAFLD context provides novel insights by expanding knowledge in the intricate field of NAFLD pathophysiology as well as by suggesting innovative therapeutic approaches in order to improve both NAFLD prevention and treatment strategies. Selective changes of distinct lipid species might be an attractive therapeutic target for treating NAFLD. Herein the most recent evidence in this attractive field has been summarized to provide a comprehensive overview of the lipidomic scenario in paediatric NAFLD.

Non-alcoholic fatty liver disease and lipotoxicity

Non-alcoholic fatty liver disease (NAFLD) has become the most common liver pathology worldwide due to the rising prevalence of obesity. This term includes changes from simple steatosis to steatohepatitis and fibrosis. It was previously thought to be a hepatic manifestation of metabolic syndrome, but recent literature describes this relation as much more complex and bi-directional. Development of NAFLD is associated with other metabolic syndrome components but it can also exacerbate insulin resistance and increase cardiovascular risk. Recently a lot of attention is brought to the role of lipids and lipotoxicity in pathogenesis and progression of non-alcoholic fatty disease. It seems that some lipid classes can be protective against liver injury while others are harmful in excessive amounts. This study presents an overview of the main lipids involved in the pathogenesis of non-alcoholic fatty liver disease and summarizes their association with lipotoxicity, insulin resistance, oxidative stress and other processes responsible for its progression.

Integrative proteomic and lipidomic analysis of Kaili Sour Soup-mediated attenuation of high-fat diet-induced nonalcoholic fatty liver disease in a rat model

Background

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease and is characterized by excessive fat accumulation. Kaili Sour Soup, a food typical of Guizhou Province, is believed to have significant health benefits. Thus, we aimed to identify and assess the impact of Kaili Sour Soup on NAFLD and its underlying mechanism using integrative proteomic and lipidomic analysis.

Methods

A high-fat diet and male Wistar rats were used to construct a NAFLD rat model. Haematoxylin and eosin (HE) and Oil Red O staining analyses were used to perform the histologic examination. Proteomic analysis was utilized to systematically identify the global protein profile in NAFLD with and without Kaili Sour Soup treatment. Western blot assays were used to verify the expression of proteins screened by proteomic analysis. Lipidomic analysis was performed to screen lipid metabolism in NAFLD with and without Kaili Sour Soup treatment.

Results

Kaili Sour Soup alleviated high-fat diet (HFD)-induced fatty liver and had a normalizing effect on physiological and biochemical indicators of NAFLD, including body weight, liver weight, liver index, total cholesterol (TC), triglyceride (TG), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and insulin resistance level of homeostasis model assessment (HOMA-IR). Kaili Sour Soup decreased the levels of 13 proteins (Tmem44, Rnaseh2b, Gstm6l, LOC100910877, Rufy4, Slc12a2, Pcif1, P4503A1, Sult1e1, Nop53, AABR07065656.4, AABR07065789.3) that were upregulated by HFD and increased the levels of 3 proteins (Sult1c2, Sult1c2a, Snrnp48) that were downregulated by HFD. Kaili Sour Soup attenuated the HFD-induced increase in acyl carnitine (AcCa) and enhanced the HFD-induced decreases in gangliosides (GM3) and lysophosphatidylserine (LPS) in the NAFLD rat model.

Conclusions

Altogether, this study revealed that Kaili Sour Soup attenuated HFD-induced fatty liver and systematically identified abnormal proteins and lipids involved in the role of Kaili Sour Soup in a NAFLD rat model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00553-4.

Increased serum concentration of ceramides in obese children with nonalcoholic fatty liver disease

Background

Hepatic lipid accumulation is closely related to the development of insulin resistance, which is regarded as one of the most significant risk factors of nonalcoholic fatty liver disease (NAFLD). Although the exact molecular pathway leading to impaired insulin signaling has not been definitively established, ceramides are suspected mediators of lipid induced hepatic insulin resistance. Therefore, the aim of the study was to evaluate the serum ceramides concentration in obese children with NAFLD.

Methods

The prospective study included 80 obese children (aged 7–17 years, median 12 years) admitted to our Department to diagnose initially suspected liver disease. Patients with viral hepatitis (HCV, HBV, CMV), autoimmune (AIH), toxic and metabolic (Wilson’s disease, alfa-1–antitrypsin deficiency) liver diseases and celiac disease were excluded. NAFLD was diagnosed based on pediatric diagnostic criteria in obese children with liver steatosis in ultrasound (US) as well as elevated alanine transaminase (ALT) serum activity after exclusion of other major liver diseases listed before. Ultrasonography was used as a screening method and for qualitative assessment of the steatosis degree (graded according to Saverymuttu scale). Advanced steatosis was defined as a score > 1. The total intrahepatic lipid content (TILC) was assessed by magnetic resonance proton spectroscopy (¹HMRS) which is the most accurate technique for assessment of ectopic fat accumulation. Fasting serum concentration of ceramides was measured in 62 children.

Results

NAFLD was diagnosed in 31 children. Significant, positive correlation was found between total serum concentration of ceramides and insulin (r = 0.3, p = 0.02) and HOMA-IR (r = 0.28, p = 0.03). Total ceramide concentration as well as specific fatty acid-ceramides (FA-ceramides) concentrations, namely: myristic, palmitic, palmitoleic, stearic, oleic, behenic and lignoceric were significantly higher (p = 0.004, p = 0.003, p = 0.007, p < 0.001, p = 0.035, p = 0.008, p = 0.003, p = 0.006, respectively) in children with NAFLD compared to controls (n = 14). Moreover, children with NAFLD had significantly higher activity of ALT (p < 0.001) and GGT (p < 0.001), HOMA-IR (p = 0.04), BMI (p = 0.046), waist circumference (p = 0.01) steatosis grade in ultrasound (p < 0.001) and TILC in ¹HMRS (p < 0.001) compared to children without NAFLD. We did not find significant differences in total and FA-ceramide species concentrations between children with mild (grade 1) and advanced liver steatosis in ultrasonography (grade 2–3).

Conclusion

Elevated ceramide concentrations in obese patients together with their significant correlation with insulin resistance parameters suggest their association with molecular pathways involved in insulin signaling impairment known to be strongly linked to pathogenesis of non-alcoholic fatty liver disease.