The ATP-stimulated translocation promoter (ASTP) activity of glycerol kinase plays central role in adipogenesis

An overview of persistent chylomicronemia: much more than meets the eye

PURPOSE OF REVIEW

The aim of this review is to provide an overview of severe hypertriglyceridemia presenting in the form of chylomicronemia that persists despite treatment of secondary causes and the use of conventional lipid-lowering treatment.

RECENT FINDINGS

Persistent chylomicronemia is a rare syndromic disorder that affects carriers of bi-allelic combinations of pathogenic gene variants impairing lipoprotein lipase (LPL) activity, as well as a significant number of individuals who do not meet this genetic criterion. It is associated with a high risk of acute pancreatitis and other morbidities. Effective innovative treatments for severe hypertriglyceridemia are being developed and are becoming available. Patients with persistent chylomicronemia of any cause respond equally to next-generation therapies with LPL-independent mechanisms of action and do not generally respond to conventional LPL-dependent treatments.

SUMMARY

Not all individuals with persistent chylomicronemia carry a proven pathogenic combination of gene variants that impair LPL activity. Documenting the clinical characteristics of people with persistent chylomicronemia and their response to emerging therapies is essential to correctly establish their risk trajectory and ensure equitable access to personalized treatment.

Glycerol kinase enzyme is a prognostic predictor in esophageal carcinoma and is associated with immune cell infiltration

The influence of lipid metabolism on tumorigenesis and progression has garnered significant attention. However, the role of Glycerol Kinase (GK), a key enzyme in glycerol metabolism, in Esophageal Carcinoma (ESCA) remains unclear. To further elucidate the relationship between GK and ESCA, we investigated GK expression levels using database information. Controlled studies employing immunohistochemistry were conducted on clinical ESCA tumor samples and normal specimens, confirming GK's elevated expression in ESCA. Analysis of The Cancer Genome Atlas (TCGA) data via Kaplan-Meier (KM) survival plots revealed that increased GK expression correlates with poorer ESCA patient outcomes, particularly in overall survival (OS) and disease-specific survival (DSS). Multiple regression analysis indicated that elevated GK expression is an independent risk factor affecting ESCA prognosis. Statistical analysis of prognostic data from clinical samples further corroborated this finding. Moreover, there appears to be a significant correlation between GK expression and immune infiltration, specifically involving certain T and B lymphocytes. In conclusion, elevated GK expression in ESCA is strongly linked to poor prognosis and increased immune cell infiltration, highlighting its potential as an independent prognostic biomarker and a viable therapeutic target.

Soares B, Pimpão C, M. A. Pinto R, Costa T, Freire JPB, Corrent E, Chalvon-Demersay T, Prates JAM, Lopes PA, Soveral G. Glutamine and cystine-enriched diets modulate aquaporins gene expression in the small intestine of piglets

The regulation of glycerol permeability in the gastrointestinal tract is crucial to control fat deposition, lipolysis and gluconeogenesis. Knowing that the amino acid glutamine is a physiological regulator of gluconeogenesis, whereas cystine promotes adiposity, herein we investigated the effects of dietary supplementation with glutamine and cystine on the serum biochemical parameters of piglets fed on amino acid-enriched diets, as well as on the transcriptional profile of membrane water and glycerol channels aquaporins (AQPs) in the ileum portion of the small intestine and its impact on intestinal permeability. Twenty male piglets with an initial body weight of 8.8 ± 0.89 kg were allocated to four dietary treatments (n = 5) and received, during a four week-period, a basal diet without supplementation (control) or supplemented with 8 kg/ton of glutamine (Gln), cystine (Cys) or the combination of the two amino acids in equal proportions (Gln + Cys). Most biochemical parameters were found improved in piglets fed Gln and Cys diet. mRNA levels of AQP3 were found predominant over the others. Both amino acids, individually or combined, were responsible for a consistent downregulation of AQP1, AQP7 and AQP10, without impacting on water permeability. Conversely, Cys enriched diet upregulated AQP3 enhancing basolateral membranes glycerol permeability and downregulating glycerol kinase (GK) of intestinal cells. Altogether, our data reveal that amino acids dietary supplementation can modulate intestinal AQPs expression and unveil AQP3 as a promising target for adipogenesis regulation.

Achieving efficient nitrite accumulation in glycerol-driven partial denitrification system: Insights of influencing factors, shift of microbial community and metabolic function

Partial denitrification (PD), which could provide sufficient nitrite for subsequent anaerobic ammonium oxidation, is a novel strategy for mainstream nitrogen removal. In this study, the performance of using glycerol as electron donor for nitrite accumulation in PD process was evaluated. Results showed that a C/N of 4.5 was effective for nitrite production (average nitrite accumulation rate: 34.32 mg N h^-1 gMLVSS^-1; average nitrate-to-nitrite transformation ratio (NTR): 91.1%) with pH ranging from 6.0 to 9.0. Also, a stable nitrite accumulation was achieved in long-term operation with the average NTR of 80.1%. Mechanism investigation found that the denitrifying bacteria Saccharibacteria (77.9%) was enriched in glycerol-driven reactors. Moreover, the enzymatic activity as well as the encoding genes (i.e. narG, narH and napA) involved in nitrate reduction were much higher than that for nitrite reduction (i.e. nirK), and this disparity was responsible for the efficient nitrite accumulation in glycerol-driven PD system.

The RNA-Binding Protein A1CF Regulates Hepatic Fructose and Glycerol Metabolism via Alternative RNA Splicing

The regulation of hepatic gene expression has been extensively studied at the transcriptional level; however, the control of metabolism through posttranscriptional gene regulation by RNA-binding proteins in physiological and disease states is less understood. Here, we report a major role for the hormone-sensitive RNA-binding protein (RBP) APOBEC1 complementation factor (A1CF) in the generation of hepatocyte-specific and alternatively spliced transcripts. Among these transcripts are isoforms for the dominant and high-affinity fructose-metabolizing ketohexokinase C and glycerol kinase, two key metabolic enzymes that are linked to hepatic gluconeogenesis and found to be markedly reduced upon hepatic ablation of A1cf. Consequently, mice lacking A1CF exhibit improved glucose tolerance and are protected from fructose-induced hyperglycemia, hepatic steatosis, and development of obesity. Our results identify a previously unreported function of A1CF as a regulator of alternative splicing of a subset of genes influencing hepatic glucose production through fructose and glycerol metabolism.

Glycerol kinase enhances hepatic lipid metabolism by repressing nuclear receptor subfamily 4 group A1 in the nucleus

Glycerol kinase (GYK) plays a critical role in hepatic metabolism by converting glycerol to glycerol 3-phosphate in an ATP-dependent reaction. GYK isoform b is the only glycerol kinase present in whole cells, and has a non-enzymatic moonlighting function in the nucleus. GYK isoform b acts as a co-regulator of nuclear receptor subfamily 4 group A1 (NR4A1) and participates in the regulation of hepatic glucose metabolism by protein–protein interaction with NR4A1. Herein, GYK expression was found to upregulate the expression of NR4A1-mediated lipid metabolism-related genes (SREBP1C, FASN, ACACA, and GPAM) in HEK293T and L02 cells, and in mouse in vivo studies. GYK expression increased blood levels of cholesterol, triglyceride, and high-density lipoprotein cholesterol, but not low-density lipoprotein cholesterol levels. It enhanced the transcriptional activity of Nr4a1 target genes by negatively cooperating with NR4A1 and its enzymatic activity or by other undefined moonlighting functions. This enhancement was observed in both normal and diabetic mice. We also found a feed-forward regulation loop between GYK and NR4A1, serving as part of a GYK-NR4A1 regulatory mechanism in hepatic metabolism. Thus, GYK regulates the effect of NR4A1 on hepatic lipid metabolism in normal and diabetic mice, partially through the cooperation of GYK and NR4A1.