Glucose sensing in L cells: a primary cell study

Assessment of SREBP Activation Using a Microsomal Vesicle Budding Assay

Sterol regulatory element binding proteins (SREBPs) are transcription factors that reside in the endoplasmic reticulum (ER) membrane as inactive precursors. To be active, SREBPs are translocated to the Golgi where the transcriptionally active N-terminus is cleaved and released to the nucleus to regulate gene expression. Nuclear SREBP levels can be determined by immunoblot analysis; however, this method can only determine the steady-state levels of nuclear SREBPs and does not capture the actual status of activation. The vesicle budding assay provides an alternative way to quantify the activation of SREBPs by monitoring the initiation of SREBP translocation from the ER to the Golgi through vesicles. Microsomal membranes isolated from the liver are incubated in a reaction buffer containing the necessary components to facilitate vesicle formation. Microsomal membranes and vesicles are isolated and SREBPs are quantified in each by immunoblot analysis. The amount of SREBPs found in the budded vesicles provides an assessment of the SREBP activation in the liver. Key features • This protocol describes a method to isolate budding vesicles from liver ER membranes. • The in vitro budding assay can be applied to investigate the movement of proteins from the ER to the Golgi. • This protocol was developed based on the procedures described previously with cultured cells [1-3].

Effects of novel glucose-lowering drugs on the COVID-19 patients with diabetes: A network meta-analysis of clinical outcomes

Objective

This study aimed to assess the effects of sodium-glucose co-transporter inhibitors (SGLT2i), glucagon-like peptide-1 receptor agonists (GLP-1RA), and dipeptidyl peptidase-4 inhibitors (DPP4i) on individuals subjected to diabetes and COVID-19.

Methods

PubMed, Embase, Web of Science, and Cochrane Library were systematically searched to cover studies (except for case reports and review studies) published until August 30, 2022. The primary outcome was the mortality of people with diabetes and COVID-19. The secondary outcomes comprised the requiring intensive care unit (ICU) admission and mechanical ventilation. Two reviewers independently screened studies, abstracted data, and assessed risk-of-bias. Furthermore, the network meta-analyses (NMA) were conducted.

Results

A total of 12 trials were involved in the analysis. The OR and 95% CI of mortality for SGLT2i compared with SGLT2i + GLP-1RA and DPP4i reached 0.41 (0.17,0.97) and 0.69 (0.49,0.98), respectively. The OR and 95% CI of requiring mechanical ventilation for SGLT2i compared with the DPP4i reached 0.85 (0.75,0.97).

Conclusions

As revealed by the result of this study, SGLT2i is associated with the lower mortality rate in people with diabetes and COVID-19 among novel glucose-lowering drugs. And SGLT2i is linked to lower requiring mechanical ventilation. These findings can have a large impact on clinicians' decisions amid the COVID-19 pandemic.

Non-Alcoholic Fatty Liver Disease May Be a Risk Factor for Liver Metastasis After Radical Surgery for Colorectal Cancer: A Retrospective Study

PURPOSE

Distant metastasis develops in approximately one-third of patients with colorectal cancer (CRC) who undergo radical surgery, and colorectal liver metastasis (CRLM) is the most common form of distant metastasis in CRC. Hepatectomy is the only potentially curative treatment for CRLM, but few patients with metastatic CRC meet the criteria for this radical resection, and the 5-year survival rate is poor. Identifying risk factors for CRLM is critical. Non-alcoholic fatty liver disease (NAFLD) is an independent risk factor for CRC. However, the effect of NAFLD on CRC liver metastasis after radical surgery remains unclear. Therefore, we examined the impact of NAFLD-associated hepatic fibrosis on liver metastasis after radical surgery for CRC.

METHODS

We retrospectively analyzed data from 388 patients who underwent curative surgery for CRC at our hospital between April 2008 and March 2015. The patients' clinical results, surgical procedures, postoperative course, and pathological and survival data were collected from the hospital records. The NAFLD fibrosis score was calculated and used to divide the patients into two groups (NAFLD and non-NAFLD).

RESULTS

Recurrence was observed in 83/388 (21.4%) patients after a mean follow-up of 65.6 ± 15.1 months. Twenty-five patients had liver metastasis: 8 in the NAFLD group (8/45; 17.8%) and 17 in the non-NALFD group (17/343; 5.0%) (p = 0.004). Liver metastasis-free survival was significantly worse in the NAFLD than non-NAFLD group (p < 0.001). NAFLD and cancer stage were independent risk factors for liver metastasis recurrence.

CONCLUSION

NAFLD may be a risk factor for liver metastasis in patients with CRC who undergo curative surgery.

The effect of G0S2 on insulin sensitivity: A proteomic analysis in a G0S2-overexpressed high-fat diet mouse model

BACKGROUND

Previous research has shown a tight relationship between the G0/G1 switch gene 2 (G0S2) and metabolic diseases such as non-alcoholic fatty liver disease (NAFLD) and obesity and diabetes, and insulin resistance has been shown as the major risk factor for both NAFLD and T2DM. However, the mechanisms underlying the relationship between G0S2 and insulin resistance remain incompletely understood. Our study aimed to confirm the effect of G0S2 on insulin resistance, and determine whether the insulin resistance in mice fed a high-fat diet (HFD) results from G0S2 elevation.

METHODS

In this study, we extracted livers from mice that consumed HFD and received tail vein injections of AD-G0S2/Ad-LacZ, and performed a proteomics analysis.

RESULTS

Proteomic analysis revealed that there was a total of 125 differentially expressed proteins (DEPs) (56 increased and 69 decreased proteins) among the identified 3583 proteins. Functional enrichment analysis revealed that four insulin signaling pathway-associated proteins were significantly upregulated and five insulin signaling pathway -associated proteins were significantly downregulated.

CONCLUSION

These findings show that the DEPs, which were associated with insulin resistance, are generally consistent with enhanced insulin resistance in G0S2 overexpression mice. Collectively, this study demonstrates that G0S2 may be a potential target gene for the treatment of obesity, NAFLD, and diabetes.

Metformin induces pyroptosis in leptin receptor-defective hepatocytes via overactivation of the AMPK axis

Metformin is the biguanide of hepatic insulin sensitizer for patients with non-alcohol fatty liver disease (NAFLD). Findings regarding its efficacy in restoring blood lipids and liver histology have been contradictory. In this study, we explore metformin's preventive effects on NAFLD in leptin-insensitive individuals. We used liver tissue, serum exosomes and isolated hepatocytes from high-fat diet (HFD)-induced Zucker diabetic fatty (ZDF) rats and leptin receptor (Lepr) knockout rats to investigate the correlation between hepatic Lepr defective and liver damage caused by metformin. Through immunostaining, RT-PCR and glucose uptake monitoring, we showed that metformin treatment activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its downstream cytochrome C oxidase (CCO). This leads to overactivation of glucose catabolism-related genes, excessive energy repertoire consumption, and subsequent hepatocyte pyroptosis. Single-cell RNA sequencing further confirmed the hyper-activation of glucose catabolism after metformin treatment. Altogether, we showed that functional Lepr is necessary for metformin treatment to be effective, and that long-term metformin treatment might promote NAFLD progression in leptin-insensitive individuals. This provides important insight into the clinical application of metformin.

Mutant Huntingtin Impairs Pancreatic β-cells by Recruiting IRS-2 and Disturbing the PI3K/AKT/FoxO1 Signaling Pathway in Huntington's Disease

Patients with Huntington's disease (HD) have an increased incidence of diabetes. However, the molecular mechanisms of pancreatic β-cell dysfunction have not been entirely clarified. Revealing the pathogenesis of diabetes can provide a novel understanding of the onset and progression of HD, as well as potential clues for the development of new therapeutics. Here, we demonstrated that the mouse pancreatic insulinoma cell line NIT-1 expressing N-terminal mutant huntingtin (mHTT) containing 160 polyglutamine (160Q cells) displayed lower cell proliferative ability than the cells expressing N-terminal wild-type HTT containing 20 polyglutamine (20Q cells). In addition, 160Q cells were more prone to apoptosis and exhibited deficient glucose-stimulated insulin expression and secretion. Furthermore, insulin signaling molecule insulin receptor substrate 2 (IRS-2) expression decreased and was recruited into mHTT aggregates. Consequently, glucose stimulation failed to activate the downstream molecule phosphatidylinositol-3 kinase (PI3K) in 160Q cells, leading to reduced phosphorylation levels of serine-threonine protein kinase AKT and forkhead box protein O1 (FoxO1). These data indicate that activation of the glucose-stimulated PI3K/AKT/FoxO1 signaling pathway is significantly blocked in pancreatic β-cells in HD. Importantly, insulin treatment inhibited the aggregation of mHTT and significantly improved the activation of PI3K/AKT/FoxO1 signaling in 160Q cells. These results suggest that the inhibition of the PI3K/AKT/FoxO1 pathway might be due to the recruitment of IRS-2 into mHTT aggregates in HD β-cells, ultimately contributing to the impairment of pancreatic β-cells. In conclusion, our work provides new insight into the underlying mechanisms of the high incidence of diabetes and abnormal glucose homeostasis in HD.

Fibroblast growth factor-23 (FGF-23) / soluble Klotho protein (sKlotho) / sclerostin glycoprotein ratio disturbance is a novel risk factor for cardiovascular complications in ESRD patients receiving treatment with regular hemodialysis or hemodiafiltration

AIM

Aim of the study was to explore the role of the FGF-23/sKlotho/sclerostin ratio disturbance in the determining of cardiovascular risk in end stage renal disease (ESRD) patients, receiving treatment with regular hemodialysis (НD) or hemodiafiltration (НDF) online in Russia.

MATERIALS AND METHODS

42 patients with ESRD, at the age of 18-55 years, treated with HD or HDF on line for at least 6 months, were examined. 22 (52.3%) patients received traditional HD, the remaining 20 (47.7%) - HDF online. In all the patients, in addition to a general examination, the serum levels of FGF-23, sKlotho, sclerostine (by ELISA), their associations with cardiovascular risk factors (left ventricular hypertrophy (LVH), acute coronary syndrome (ACS), serum troponin I levels) with the numbers of techniques (ECG; Eho-CGF (with calculation of left ventricular myocardium mass index (LVMMI), as well as the relative thickness of the walls of the left ventricle (RWT); sphygmography (central (aortal) blood pressure (CBP), subendocardial blood flow (SBF) - by «Sphygmocor»), and the effect of regular HD and HDF on serum levels of the studied markers, were assessed.

RESULTS

An independent effect of FGF-23 on the risk of LVH, as well as on the increase of serum troponin I in the studied ESRD patients [β=3.576 p&lt;0.01, and β=1.115, p&lt;0.05, respectively] was found. Serum Klotho was the factor most associated with the CBP [β=-0.023; p&lt;0.001]. The increased serum sclerostin was correlated with a lower incidence of both reduced SBF [r=0.492; p&lt;0.05], symptoms of coronary heart disease [r=-0.449; p&lt;0.05] and rhythm disturbances [r=-0.446; p&lt;0.05]. In addition, in HD patients higher FGF-23 and lower Klotho and sclerostine serum levels were associated with: inadequate dialysis syndrome (Kt/V &lt;1.1; r=0.463; p&lt;0.05), chronic inflammation (C-reactive protein &gt;10 mg/L; r=0.612; p&lt;0.01), and with a decrease in serum albumin level (&lt;35 g/l; r=0.459; p&lt;0.05). The FGF-23/sKlotho/sclerostin ratio disturbance was more pronounced in patients treated with traditional HD then HDF online. A direct correlation (r=0.445; p&lt;0.05) was established between FGF-23 serum levels and serum phosphorus, which was more pronounced in HD patients (r=0.545; p&lt;0.01).

CONCLUSION

In HD and HDF ESRD patients, higher serum FGF-23 and lower sKlotho and sclerostin levels were associated with a chronic inflammation, malnutrition, secondary hyperparathyroidism, and may considered as predictors of cardiovascular complications such as LVH, ACS, rhythm disturbances, persisting of subincreased serum troponin I.

Host population related variations in circadian clock gene sequences and expression patterns in Chilo suppressalis

The rice stem borer, Chilo suppressalis Walker, is one of the most important global agricultural pests. C. suppressalis has distinct rice and water-oat host populations. Asynchrony in sexual activity is thought to be the main factor maintaining reproductive segregation between these populations, particularly the obvious difference in the circadian rhythm of female calling activity between populations. However, the mechanism responsible for this difference in the timing of female calling is poorly understood. The circadian clock is an essential regulator of daily behavioral rhythms in insects, including female calling. We investigated the variation in circadian clock genes of the rice and water-oat populations of C. suppressalis. We did this by comparing deduced amino acid sequences and the expression patterns of seven circadian clock genes (clock, cycle, period, timeless, timeout, cryptochrome1, and cryptochrome2) between females from each population. We found that the two populations had different variants of the timeout and cryptochrome1 genes and differed in the expression of period, timeless and timeout. This suggests that population-related variation in the circadian clock genes period, timeless, timeout and cryptochrome1 could be responsible for the different circadian rhythms of female calling in these host population of C. suppressalis. These results provide new insights into the molecular mechanisms underlying asynchronous sexual activity in insect populations and suggest new topics for future research on the origins and maintenance of population differentiation in insects.

Identification of novel Ack1-interacting proteins and Ack1 phosphorylated sites in mouse brain by mass spectrometry

Ack1 (activated Cdc42-associated tyrosine kinase) is a non-receptor tyrosine kinase that is highly expressed in brain. This kinase contains several protein-protein interaction domains and its action is partially regulated by phosphorylation. As a first step to address the neuronal functions of Ack1, here we screened mouse brain samples to identify proteins that interact with this kinase. Using mass spectrometry analysis, we identified new putative partners for Ack1 including cytoskeletal proteins such as Drebrin or MAP4; adhesion regulators such as NCAM1 and neurabin-2; and synapse mediators such as SynGAP, GRIN1 and GRIN3. In addition, we confirmed that Ack1 and CAMKII both co-immunoprecipitate and co-localize in neurons. We also identified that adult and P5 samples contained the phosphorylated residues Thr 104 and Ser 825, and only P5 samples contained phosphorylated Ser 722, a site linked to cancer and interleukin signaling when phosphorylated. All these findings support the notion that Ack1 could be involved in neuronal plasticity.

Gene editing of the extra domain A positive fibronectin in various tumors, amplified the effects of CRISPR/Cas system on the inhibition of tumor progression

Background

The low efficiency of clustered, regularly interspaced, palindromic repeats-associated Cas (CRISPR/Cas) system editing genes in vivo limits the application. A components of the extracellular matrix (ECM), the extra domain A positive fibronectin (EDA+FN), may be a target for CRISPR/Cas system for the pro-oncogenic effects. The exclusion of EDA exon would alter the microenvironment and inhibit tumor progression, even the frequency of gene editing is still limited.

Results

The pro-oncogenic effects were confirmed by the exclusion of EDA exon from the fibronectin gene, as illustrated by the down-regulated proliferation, migration and invasion of CNE-2Z or SW480 cells (P<0.05). Furthermore, although the efficacy of EDA exon knockout through CRISPR/Cas system was shown to be low in vivo, the EDA+FN protein levels decrease obviously, inhibiting the tumor growth rate significantly (P<0.05), which was accompanied by a decrease in Ki-67 expression and microvessel numbers, and increased E-cadherin or decreased Vimentin expression (P<0.05).

Methods and materials

Human nasopharyngeal carcinoma cell line CNE-2Z, and the colorectal carcinoma cell line SW480 were transfected with CRISPR/Cas9 plasmids targeting EDA exon. The effects of the exclusion of EDA on the cell proliferation, motility and epithelial-mesenchymal transition (EMT) were investigated, and the western blot and real-time PCR were performed to analyze the underlying mechanisms. Furthermore, CRISPR/Cas9 plasmids were injected into xenograft tumors to knockout EDA exon in vivo, and tumor growth, cell proliferation, EMT rate, or vascularization were investigated using western blot, PCR and immunohistochemistry.

Conclusion

CRISPR/Cas system targeting ECM components was shown to be an effective method for the inhibition of tumor progression, as these paracrine or autocrine molecules are necessary for various tumor cells. This may represent a novel strategy for overcoming the drug evasion or resistance, in addition, circumventing the low efficiency of CRISPR/Cas system in vivo.

Evidence for a role of oestrogen receptor-related receptor in the regulation of male sexual behaviour in the moth Agrotis ipsilon

The oestrogen receptor-related receptors (ERRs) are orphan nuclear receptors that were originally identified on the basis of their close homology to the oestrogen receptors. The three mammalian ERR genes participate in the regulation of vital physiological processes including reproduction, development and metabolic homeostasis. Although unique ERRs have been found in insects, data on the function and regulation of these receptors remain sparse. In the present study, a 2095-bp full-length cDNA encoding an ERR, termed AiERR, was isolated from males of the moth Agrotis ipsilon and deposited in the GenBank database under the accession number KT944662. The predicted AiERR protein shared an overall identity of 47-82% with other known insect and mammalian ERR homologues. AiERR exhibited a broad tissue expression pattern with the detection of one transcript of approximately 2 kb in the primary olfactory centres, the antennal lobes (AL). In adult males, the amount of AiERR mRNA in the AL increased concomitantly with age and responses to the female-emitted sex pheromone. Moreover, AiERR knockdown induced an inhibition in the sex pheromone-orientated flight of male. Using A. ipsilon as a model, our study demonstrates that the insect ERR is critical for the performance of male sexual behaviour, probably by acting on central pheromone processing.

Silymarin Ameliorates Metabolic Dysfunction Associated with Diet-Induced Obesity via Activation of Farnesyl X Receptor

Background and purpose: Silymarin, a standardized extract of the milk thistle seeds, has been widely used to treat chronic hepatitis, cirrhosis, and other types of toxic liver damage. Despite increasing studies on the action of silymarin and its major active constituent, silybin in their therapeutic properties against insulin resistance, diabetes and hyperlipidaemia in vitro and in vivo, the mechanism underlying silymarin action remains unclear. Experimental approach: C57BL/6 mice were fed high-fat diet (HFD) for 3 months to induce obesity, insulin resistance, hyperlipidaemia, and fatty liver. These mice were then continuously treated with HFD alone or mixed with silymarin at 40 mg/100 g for additional 6 weeks. Biochemical analysis was used to test the serum lipid and bile acid profiles. Farnesyl X receptor (FXR) and nuclear factor kappa B (NF-κB) transactivities were analyzed in liver using a gene reporter assay based on quantitative RT-PCR. Key results: Silymarin treatment ameliorated insulin resistance, dyslipidaemia and inflammation, and reconstituted the bile acid pool in liver of diet-induced obesity. Associated with this, silybin and silymarin enhanced FXR transactivity. Consistently, in HepG2 cells, silybin inhibited NF-κB signaling, which was enhanced by FXR activation. Conclusion and implications: Our results suggest that silybin is an effective component of silymarin for treating metabolic syndrome by stimulating FXR signaling.

MicroRNA-mediated interactions between host and hepatitis C virus

MicroRNAs (miRNAs) are small noncoding RNAs. More than 2500 mature miRNAs are detected in plants, animals and several types of viruses. Hepatitis C virus (HCV), which is a positive-sense, single-stranded RNA virus, does not encode viral miRNA. However, HCV infection alters the expression of host miRNAs, either in cell culture or in patients with liver disease progression, such as liver fibrosis, cirrhosis, and hepatocellular carcinoma. In turn, host miRNAs regulate HCV life cycle through directly binding to HCV RNAs or indirectly targeting cellular mRNAs. Increasing evidence demonstrates that miRNAs are one of the centered factors in the interaction network between virus and host. The competitive viral and host RNA hypothesis proposes a latent cross-regulation pattern between host mRNAs and HCV RNAs. High loads of HCV RNA sequester and de-repress host miRNAs from their normal host targets and thus disturb host gene expression, indicating a means of adaptation for HCV to establish a persistent infection. Some special miRNAs are closely correlated with liver-specific disease progression and the changed levels of miRNAs are even higher sensitivity and specificity than those of traditional proteins. Therefore, some of them can serve as novel diagnostic/prognostic biomarkers in HCV-infected patients with liver diseases. They are also attractive therapeutic targets for development of new anti-HCV agents.

Molecular mechanisms of incretin hormone secretion

Incretin is a kind of intestinal hormone secreted by the enteroendocrine cells in the intestinal epithelium. There has been plenty of research to explore the molecular mechanisms of incretin hormone secretion, including secretion-promoting factors such as glucose, lipid, protein and other nutrients in enteroendocrine cells. This review aims to discuss the signal pathways related to incretin hormone secretion.