Effect of Konjac Mannan Oligosaccharides on Glucose Homeostasis via the Improvement of Insulin and Leptin Resistance In Vitro and In Vivo

Dietary neoagarotetraose extends lifespan and impedes brain aging in mice via regulation of microbiota-gut-brain axis

INTRODUCTION

Dietary oligosaccharides can impact the gut microbiota and confer tremendous health benefits.

OBJECTIVES

The aim of this study was to determine the impact of a novel functional oligosaccharide, neoagarotetraose (NAT), on aging in mice.

METHODS

8-month-old C57BL/6J mice as the natural aging mice model were orally administered with NAT for 12 months. The preventive effect of NAT in Alzheimer's disease (AD) mice was further evaluated. Aging related indicators, neuropathology, gut microbiota and short-chain fatty acids (SCFAs) in cecal contents were analyzed.

RESULTS

NAT treatment extended the lifespan of these mice by up to 33.3 %. Furthermore, these mice showed the improved aging characteristics and decreased injuries in cerebral neurons. Dietary NAT significantly delayed DNA damage in the brain, and inhibited reduction of tight junction protein in the colon. A significant increase at gut bacterial genus level (such as Lactobacillus, Butyricimonas, and Akkermansia) accompanied by increasing concentrations of SCFAs in cecal contents was observed after NAT treatment. Functional profiling of gut microbiota composition indicated that NAT treatment regulated the glucolipid and bile acid-related metabolic pathways. Interestingly, NAT treatment ameliorated cognitive impairment, attenuated amyloid-β (Aβ) and Tau pathology, and regulated the gut microbiota composition and SCFAs receptor-related pathway of Alzheimer's disease (AD) mice.

CONCLUSION

NAT mitigated age-associated cerebral injury in mice through gut-brain axis. The findings provide novel evidence for the effect of NAT on anti-aging, and highlight the potential application of NAT as an effective intervention against age-related diseases.

Effect of Arabinoxylan from Wastewater Generated during Vital Wheat Gluten Production on Liver Metabolism in Type 2 Diabetic Mice

Arabinoxylan (AX) is a dietary fiber that has been proven to have a significant antidiabetic effect. Liver metabolic disorders frequently coincide with the development of type 2 diabetes, but research on the hepatoprotective effects of AX in type 2 diabetic mice is lacking. As AX is abundant in the wastewater produced during vital wheat gluten protein production, this study used it as a raw material to evaluate its protective effect on liver function. The study employed an AX intervention in type 2 diabetic mice induced by a high-fat diet combined with streptozotocin and collected serum and liver tissue samples after 4 weeks. Serum and liver function indicators were measured using an automatic biochemistry analysis apparatus, and liver fat accumulation was observed using oil red O staining. Nontargeted metabolomics analysis of liver tissues was conducted using UHPLC-MS/MS. The results showed that AX significantly improved liver function indicators and histopathological damage, and regulated liver metabolic disorders by improving the differential metabolites of pantothenate and CoA biosynthesis, as well as purine metabolism. This study demonstrated that AX may exert a significant hepatoprotective effect by regulating metabolic disorders.

Heterologous Expression, Purification and Characterization of an Alkalic Thermophilic β-Mannanase CcMan5C from Coprinopsis cinerea

A endo-1,4-β-mannanase (CcMan5C) gene was cloned from Coprinopsis cinerea and heterologously expressed in Pichia pastoris, and the recombinant enzyme was purified by Ni-affinity chromatography and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). CcMan5C hydrolyzed only locust bean gum galactomannan (LBG) but not α-mannan from S. cerevisiae or Avicel cellulose, oat spelt xylan, or laminarin from Laminaria digitata. CcMan5C exhibited distinctive catalytic features that were different from previously reported β-mannanases. (1) CcMan5C is the first reported fungal β-mannase with an optimal alkalic pH of 8.0-9.0 for hydrolytic activity under assay conditions. (2) CcMan5C is the first reported alkalic fungal β-mannase with an optimal temperature of 70 °C for hydrolytic activity under assay conditions. (3) The organic solvents methanol, ethanol, isopropanol, and acetone at concentrations of 10% or 20% did not inhibit CcMan5C activity, while 10% or 20% isopropanol and acetone even enhanced CcMan5C activity by 9.20-34.98%. Furthermore, CcMan5C tolerated detergents such as Tween 20 and Triton X-100, and its activity was even enhanced to 26.2-45.6% by 1% or 10% Tween 20 and Triton X-100. (4) CcMan5C solution or lyophilized CcMan5C exhibited unchanged activity and even increasing activity after being stored at -20 °C or -80 °C for 12 months and retained above 50% activity after being stored at 4 °C for 12 months. These features make CcMan5C a suitable candidate for the detergent industry and paper and pulp industry.

Leptin differentially regulate cell apoptosis and cycle by histone acetylation in tibial and vertebral epiphyseal plates

Leptin showed different apoptosis regulation effects on the chondrocytes from tibial and vertebral epiphyseal plates. However, the mechanism is still unclear. In this study, we tested the protein profile of tibial and vertebral epiphyseal plate chondrocytes with and without leptin stimulation by mass spectrometry and found that the histone acetylation level of tibial chondrocytes was decreased after leptin treatment, while increased in vertebral epiphyseal plates. COIP assay showed that leptin promoted H3, H4 histone acetylation by recruiting CREB binding protein (CBP)/P300 to activate histone acetyl transferases (HATs) activity in vertebral disc chondrocytes. But in tibial plate cartilage cells, leptin did not recruit CBP and p300, thus differently affect the apoptosis of epiphyseal plate chondrocytes. Through explored the mechanism of histone acetylation modulated by leptin, and its effect on cartilage cell apoptosis and cell cycle regulation, This provides a novel target therapy possibility therapeutic approach to for the related disease.

Manno-oligosaccharides from cassia seed gum ameliorate inflammation and improve glucose metabolism in diabetic rats

Functional oligosaccharides show anti-diabetic effects through inflammation regulation with improved glucose metabolism. In this study, novel prebiotics of manno-oligosaccharides from cassia seed gum (CMOS) were incorporated into the diet of streptozotocin (STZ) plus high-fat and high-sugar diet (HFSD)-induced rats. After feeding for 8 weeks, CMOS (300-1200 mg per kg b.w. per d) significantly ameliorated the fasting blood glucose level (7.1-8.2 mmol L^-1) as compared with that of the model group (14.2 mmol L^-1), where the area under the oral glucose tolerance test curve was decreased by 20.0%-24.5%. Meanwhile, CMOS prevented STZ plus HFSD-induced damage to islet tissue with a clear and integrated morphology and reduced the glucagon/insulin area ratio (by 97.9% for 300 mg per kg b.w. per d CMOS). CMOS also reduced metabolic endotoxemia and maintained intestinal integrity with recovered mRNA expression of Zo-1 and occludin to the normal comparable level. Upon 16S rDNA sequencing, it was found that CMOS regulated the microbiota composition in the cecum with an increased relative abundance of Bifidobacteria, while that of Shigella was decreased. The molecular mechanisms involved in the anti-diabetic effects of CMOS were further studied. CMOS reduced the mRNA expression of Tlr2 and Tlr4 in the intestines of STZ plus HFSD-induced rats. Meanwhile, Nlrp3 associated inflammasome activation in the intestine and liver with glucose metabolism disorder was inhibited by CMOS, resulting in reduced interleukin-1β secretion (by 38.8-46.4% for CMOS of 300-1200 mg per kg b.w. per d) and inflammation. Furthermore, CMOS regulated the AKT/IRS/AMPK signaling pathway and improved glucose metabolism in the liver. Findings obtained here implicated that CMOS could modulate metabolic-inflammation as a functional dietary supplement.

circMAP3K4 regulates insulin resistance in trophoblast cells during gestational diabetes mellitus by modulating the miR-6795-5p/PTPN1 axis

Background

Insulin resistance (IR) during gestational diabetes mellitus (GDM) has been linked to dysregulated insulin-PI3K/Akt pathway. A defective insulin-PI3K/Akt pathway and dysregulated circular RNA (circRNA) levels have been observed in the placentas of patients with GDM; however, the mechanisms underlying this association remain unclear.

Methods

circRNAs potentially associated with GDM were selected through bioinformatics analysis and initially identified by quantitative real-time PCR (qPCR) in 9 GDM patients and 9 healthy controls, of which circMAP3K4 was further validated in additional 84 samples by qPCR. circMAP3K4 identity and localization were verified. Pearson correlation analysis was applied to evaluate the correlation between circMAP3K4 expression in the placental tissues of GDM patients and IR-related indicators. An IR model of trophoblasts was constructed using glucosamine. Interactions between miR-6795-5p and circMAP3K4 or PTPN1 were confirmed using a dual-luciferase reporter assay. The circMAP3K4/miR-6795-5p/PTPN1 axis and key markers in the insulin-PI3K/Akt pathway in placentas and trophoblasts were evaluated through qRT-PCR, immunofluorescence, and western blotting. The role of circMAP3K4 in glucose metabolism and cell growth in trophoblasts was determined using the glucose uptake and CCK8 assay, respectively.

Results

circMAP3K4 was highly expressed in the placentas of patients with GDM and the IR trophoblast model; this was associated with a dysregulated insulin-PI3K/Akt pathway. circMAP3K4 in the placentas of GDM patients was positively correlated with weight gain during pregnancy and time-glucose area under the curve of OGTT. circMAP3K4 and PTPN1 could both bind to miR-6795-5p. miR-6795-5p and PTPN1 were downregulated and upregulated, respectively, in the placentas of GDM patients and the IR trophoblast model. circMAP3K4 silencing or miR-6795-5p overexpression partially reversed the decrease in glucose uptake, inhibition in cell growth, and downregulated IRS1 and Akt phosphorylation in IR-trophoblasts; this restoration was reversed upon co-transfection with an miR-6795-5p inhibitor or PTPN1.

Conclusion

circMAP3K4 could suppress the insulin-PI3K/Akt signaling pathway via miR-6795-5p/PTPN1 axis, probably contributing to GDM-related IR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03386-8.

The Symbiotic Effect of a New Nutraceutical with Yeast β-Glucan, Prebiotics, Minerals, and Silybum marianum (Silymarin) for Recovering Metabolic Homeostasis via Pgc-1α, Il-6, and Il-10 Gene Expression in a Type-2 Diabetes Obesity Model

The use of natural products and derivatives for the prevention and control of non-communicable chronic diseases, such as type-2 diabetes (T2D), obesity, and hepatic steatosis is a way to achieve homeostasis through different metabolic pathways. Thus, male C57BL/6 mice were divided into the following groups: high-fat diet (HFD) vehicle, HFD + Supplemented, HFD + Supplemented_S, and isolated compounds. The vehicle and experimental formulations were administered orally by gavage once a day over the four weeks of the diet (28 consecutive days). We evaluated the energy homeostasis, cytokines, and mitochondrial gene expression in these groups of mice. After four weeks of supplementation, only the new nutraceutical group (HFD + Supplemented) experienced reduced fasting glycemia, insulin, HOMA index, HOMA-β, dyslipidemia, ectopic fat deposition, and hepatic fibrosis levels. Additionally, the PPARγ coactivator 1 α (Pgc-1α), interleukin-6 (Il-6), and interleukin-10 (Il-10) gene expression were augmented, while hepatic steatosis decreased and liver parenchyma was recovered. The glutathione-S-transferase activity status was found to be modulated by the supplement. We discovered that the new nutraceutical was able to improve insulin resistance and hepatic steatosis mainly by regulating IL-6, IL-10, and Pgc-1α gene expression.

Dietary Succinoglycan Riclin Improves Glycemia Control in Mice with Type 2 Diabetes

Riclin is a typical succinoglycan produced by an agrobacterium isolate. Our previous investigation has revealed that oral riclin restores the islet function in type 1 diabetic mice. However, whether dietary riclin improves glycemic control in type 2 diabetes (T2D) is unknown. Here, we found that dietary riclin (20 and 40 mg/kg) for 4 weeks significantly decreased fasting blood glucose (55 and 67%), improved insulin sensitivity, and decreased insulin resistance in high-fat-diet/streptozocin (HFD/STZ)-induced T2D. Riclin reduced the proportion of T helper 1 cell subsets in diabetic mice, alleviated pancreatic inflammation, and protected islet function. Moreover, dietary riclin enriched the diversity of gut microflora and restored the relative abundance of several bacterial genera in diabetes, including the strains of Clostridium, Parasutterella, Klebsiella, and Bacteroides. In db/db diabetic mice, riclin also improves glycemia control as observed in HFD/STZ-induced T2D mice. These data suggest that riclin has potential to be a functional food to treat T2D.

Preclinical experimental models for assessing laxative activities of substances/products under investigation: a scoping review of the literature

Constipation is a common gastrointestinal problem worldwide. Its impact on health can range from an unpleasant problem to being seriously troublesome. When lifestyle modification fails to deal with constipation, laxatives are the mainstay of therapy. There are several types of laxatives currently available; however, there still remains a need for better laxatives because certain currently available laxatives are not appropriate for or accessible to some patients. Preclinical experiments to study the laxative potential of substances/products of interest are vital to improving that situation. The selection of appropriate experimental models for assessing the laxative activities of substances/products under investigation is crucial to achieving valid and meaningful results. This article provides a scoping review of the literature, outlining, and summarizing models currently being used in preclinical experiments assessing the laxative activities of substances/products under investigation. The review includes both screening models, e.g., the isolated organ bath system, in vivo fecal assessment and intestinal transit assay, and confirmation models, e.g., in vivo constipation models. Chemical substances/drugs used to induce constipation in in vivo constipation models, e.g., loperamide, diphenoxylate, montmorillonite, and clonidine, as well as standard laxative agents used as a positive control in experimental models, e.g., bisacodyl, carbachol, lactulose, sodium picosulfate, castor oil, phenolphthalein, and yohimbine, are described in detail. The purpose of this article is to assist researchers in the design and implementation of preclinical experimental models for assessing laxative activities of substances/products under investigation to achieve valid and meaningful preclinical results prior to experimentation in humans.

Synergistic Protective Effect of Konjac Mannan Oligosaccharides and Bacillus subtilis on Intestinal Epithelial Barrier Dysfunction in Caco-2 Cell Model and Mice Model of Lipopolysaccharide Stimulation

As the first line of defense against intestinal bacteria and toxins, intestinal epithelial cells are always exposed to bacteria or lipopolysaccharide (LPS), whereas pathogenic bacteria or LPS can cause intestinal epithelial cell damage. Previous studies have shown that konjac mannan oligosaccharides (KMOS) have a positive effect on maintaining intestinal integrity, and Bacillus subtilis (BS) can promote the barrier effect of the intestine. However, it is still unknown whether KMOS and BS have a synergistic protective effect on the intestines. In this study, we used the LPS-induced Caco-2 cell injury model and mouse intestinal injury model to study the synergistic effects of KMOS and BS. Compared with KMOS or BS alone, co-treatment with KMOS and BS significantly enhanced the activity and antioxidant capacity of Caco-2 cell, protected mouse liver and ileum from LPS-induced oxidative damage, and repaired tight junction and mucus barrier damage by up-regulating the expression of Claudin-1, ZO-1 and MUC-2. Our results demonstrate that the combination of KMOS and BS has a synergistic repair effect on inflammatory and oxidative damage of Caco-2 cells and aIIeviates LPS-induced acute intestinal injury in mice.

Hemicellulose-Derived Oligosaccharides: Emerging Prebiotics in Disease Alleviation

The gut microbiota in the human body is an important component that plays a pivotal role in the ability of the host to prevent diseases and recover from these diseases. If the human microbiome changes for any reason, it affects the overall functioning of the host. Healthy and vigorous gut microbiota require dietary fiber supplementation. Recently, oligosaccharides have been found to play a significant role in the modulation of microbiota. Several such oligosaccharides, i.e., xylooligosaccharides (XOS), mannooligosaccharides (MOS), and arabino-xylooligosaccharides (AXOS), are derived from hemicellulosic macromolecules such as xylan, mannan, and arabino-xylan, respectively. These oligosaccharides serve as substrates for the probiotic production of health-promoting substances (short-chain fatty acids, branched chain amino acids etc.), which confer a variety of health benefits, including the prevention of some dreaded diseases. Among hemicellulose-derived oligosaccharides (HDOs), XOS have been largely explored, whereas, studies on MOS and AXOS are currently underway. HDOs, upon ingestion, help reduce morbidities by lowering populations of harmful or pathogenic bacteria. The ATP-binding cassette (ABC) transporters are mainly utilized for the uptake of oligosaccharides in probiotics. Butyrate generated by the selective fermentation of oligosaccharides, along with other short-chain fatty acids, reduces gut inflammation. Overall, oligosaccharides derived from hemicelluloses show a similar potential as conventional prebiotics and can be supplemented as functional foods. This review summarizes the role of HDOs in the alleviation of autoimmune diseases (inflammatory bowel disease, Crohn's disease), diabetes, urinary tract infection, cardiovascular diseases, and antimicrobial resistance (AMR) through the modulation of the gut microbiota. The mechanism of oligosaccharide utilization and disease mitigation is also explained.

Oligosaccharides from Traditional Chinese Herbal Medicines: A Review of Chemical Diversity and Biological Activities

Most of traditional Chinese herbal medicine (TCHM) substances come from medicinal plants, among which oligosaccharides have gradually attracted widespread attention at home and abroad due to their important biological activities and great medicinal potential. Numerous in vitro and in vivo experiments exhibited that oligosaccharides possess various activities, such as antitumor, anti-oxidation, modulate the gut microflora, anti-inflammatory, anti-infection, and immune-regulatory activities. Generally, biological activities are closely related to chemical structures, including molecular weight, monosaccharide composition, glycosidic bond connection, etc. The structural analysis of oligosaccharides is an important basis for studying their structure-activity relationship, but the structural diversity and complexity of carbohydrate compounds limit the study of oligosaccharides activities. Understanding the structures and biological functions of oligosaccharides is important for the development of new bioactive substances with natural oligosaccharides. This review provides a systematic introduction of the current knowledge of the chemical structures and biological activities of oligosaccharides. Most importantly, the reported chemical characteristics and biological activities of the famous TCHM oligosaccharides were briefly summarized, including Morinda officinalis, Rehmannia glutinosa, Arctium lappa, Polygala tenuifolia, Panax ginseng, Lycium barbarum and Astragalus membranaceus. TCHM oligosaccharides play an important role in nutrition, health care, disease diagnosis and prevention as well as have broad application prospects in the field of medicine.

Global transcriptomic analysis of functional oligosaccharide metabolism in Pediococcus pentosaceus

Lactic acid bacteria (LAB) are important in food fermentation and may enhance overall host health. Previous studies to explore LAB metabolism mainly focused on the genera Lacticaseibacillus and Lactococcus. Pediococcus pentosaceus, historically recognized as an important food fermentation bacterial strain, can produce bacteriocins and occasionally demonstrated probiotic functionalities. This study thoroughly surveyed the growth kinetic of three P. pentosaceus isolates in various culture formulations, especially in fructooligosaccharide (FOS), xylooligosaccharide (XOS), or konjac mannooligosaccharide (KMOS) conditions. Results showed that P. pentosaceus effectively metabolized KMOS, the culture of which led to 23.6-fold population increase. However, FOS and XOS were less metabolized by P. pentosaceus. On functional oligosaccharide cultures, P. pentosaceus could result in higher population proliferation, more acidified fermentation environment, and higher glycoside hydrolysis activities in the culture. RNA-Seq analysis classified 1572 out of 1708 putative genes as mRNA-coding genes. The dataset also revealed that the three functional oligosaccharides led to extensive global functional gene regulations. Phosphate conservation and utilization efficiency enhancement may serve as a leading transcriptional regulation direction in functional oligosaccharide metabolisms. In summary, these discovered metabolic characteristics could be employed to support future studies. KEY POINTS: • Konjac mannooligosaccharides effectively promoted P. pentosaceus proliferation. • Functional genes were highly regulated in functional oligosaccharide utilization. • Phosphate conservation was an important transcriptional regulation direction.

Effect of Leptin on Chronic Inflammatory Disorders: Insights to Therapeutic Target to Prevent Further Cardiovascular Complication

In response to obesity-associated chronic inflammatory disorders, adipose tissue releases a biologically active peptide known as leptin. Leptin activates the secretion of chemical mediators, which contribute to the pathogenesis of chronic inflammatory disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and psoriasis. Conversely, adiposity and obesity are the major aggravating risk factors in the pathogenesis of metabolic syndrome (MetS), including type II diabetes mellitus and obesity-associated hypertension. Elevated level of leptin in obesity-associated hypertension causes an increase in the production of aldosterone, which also results in elevation of arterial blood pressure. Hyperleptinemia is associated with the progress of the atherosclerosis through secretion of pro-inflammatory cytokines, like interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), IL-17, and other cytokines to promote inflammation. The release of those cytokines leads to chronic inflammatory disorders and obesity-associated MetS. Thus, the aberrant leptin level in both MetS and chronic inflammatory disorders also leads to the complication of cardiovascular diseases (CVD). Therapeutic target of leptin regarding its pro-inflammatory effect and dysregulated sympathetic nervous system activity may prevent further cardiovascular complication. This review mainly assesses the mechanism of leptin on the pathogenesis and further cardiovascular risk complication of chronic inflammatory disorders.

AT1R/GSK-3β/mTOR Signaling Pathway Involved in Angiotensin II-Induced Neuronal Apoptosis after HIE Both In Vitro and In Vivo

Objective

The focus of the present study is to evaluate the effects of Angiotensin II (Ang II) on neuronal apoptosis after HIE and the potential underlying mechanisms.

Methods

Primary neonatal rat cortical neurons were used to study the oxygen-glucose deprivation (OGD) cell model. The expressions of Ang II, AT1R, GSK-3β, p-GSK-3β, mTOR, p-mTOR, Bax, Bcl-2, and cleaved caspase-3 were detected via western blot. IF and flow cytometry were used to evaluate neuronal apoptosis. Hypoxic-ischemic encephalopathy (HIE) was established to evaluate the therapeutic effects of Ang II in vivo. Cerebral infarction areas were detected by 2,3,5-Triphenyltetrazolium chloride staining. The righting and geotaxis reflexes were also recorded. In addition, Fluoro-Jade C staining and TUNEL staining were performed to evaluate neuronal degeneration and apoptosis.

Results

Ang II significantly increased the rate of neuronal apoptosis, upregulated the expression of cleaved caspase-3, and downregulated Bcl-2/Bax ratio after OGD insult. For vivo assay, the expressions of endogenous Ang II and AT1R gradually increased and peaked at 24 h after HIE. Ang II increased NeuN-positive AT1R cell expression. In addition, Ang II increased the area of cerebral infarction, promoted neuronal degeneration and apoptosis, aggravated neurological deficits on righting and geotaxis reflexes, and was accompanied by increased expressions of phosphorylated GSK-3β and mTOR. The application of valsartan (Ang II inhibitor) or SB216763 (GSK-3β inhibitor) reversed these phenomena triggered by Ang II following HIE.

Conclusion

Ang II increased neuronal apoptosis through the AT1R/GSK-3β/mTOR signaling pathway after experimental HIE both in vitro and in vivo, and Ang II may serve as a novel therapeutic target to ameliorate brain injury after HIE.

Coniferaldehyde ameliorates the lipid and glucose metabolism in palmitic acid-induced HepG2 cells via the LKB1/AMPK signaling pathway

Impaired lipid and glucose metabolism in the liver is a crucial characteristic of nonalcoholic fatty liver disease (NAFLD). Coniferaldehyde (CA), a kind of phenolic compound found in many edible plants, has multiple biological and pharmacological functions. However, since the effect and molecular mechanism of CA on hepatic lipid and glucose metabolism disorders in NAFLD remain unknown, this study investigated its impact on the lipid and glucose metabolism of palmitic acid (PA)-induced HepG2 cells. Compared with the HepG2 cells treated only with PA, supplementation with 25, 50, and 100 µM CA reduced the levels of intracellular triglyceride (by 7.11%, 19.62%, and 31.57%) and total cholesterol (by 8.46%, 23.32%, and 27.17%), and enhanced glucose uptake (by 40.91%, 57.49%, and 61.32%) and intracellular glycogen content (by 12.75%, 41.27%, and 53.77%). Moreover, CA supplementation downregulated the expression of sterol regulatory element-binding protein-1, fatty acid synthase, and stearoyl-CoA desaturase 1 related to lipogenesis while upregulating the expression of carnitine palmitoyltransferase 1α related to fatty acid oxidation. CA supplementation also upregulated the glucose transporter 2 protein expression and phosphorylation of glycogen synthase kinase 3β while downregulating the phosphorylation of glycogen synthase. Most importantly, most of these effects of CA were reversed by pretreatment with AMP-activated protein kinase (AMPK) inhibitor and small interfering RNA-liver kinase B1 (LKB1). In conclusion, CA ameliorated the lipid and glucose metabolism in PA-induced HepG2 cells via the LKB1/AMPK signaling pathway. PRACTICAL APPLICATION: In this study, coniferaldehyde appeared to be effective in ameliorating hepatic lipid and glucose metabolism disorders in nonalcoholic fatty liver disease by reducing the levels of intracellular triglyceride and total cholesterol and enhancing glucose uptake and intracellular glycogen content via the LKB1/AMPK signaling pathway in vitro. Therefore, our findings provide new evidence in support of that supplementation with coniferaldehyde or food rich in coniferaldehyde might be considered as a viable dietary intervention strategy for preventing and treating nonalcoholic fatty liver disease.

High-efficiency expression of a superior β-mannanase engineered by cooperative substitution method in Pichia pastoris and its application in preparation of prebiotic mannooligosaccharides

β-mannanase with high specific activity is a prerequisite for the industrial preparation of prebiotic mannooligosaccharides. Three mutants, namely MEI, MER, and MEIR, were constructed by cooperative substitution based on three predominant single-point site mutations (K291E, L211I, and Q112R, respectively). Heterologous expression was facilitated in Pichia pastoris and the recombinase was characterized completely. The specific activities of MER (7481.9 U mg^-1) and MEIR (9003.1 U mg^-1) increased by 1.07- and 1.29-fold from the initial activity of ME (6970.2U mg^-1), respectively. MEIR was used for high-cell-density fermentation to further improve enzyme activity, and the expression levels achieved in the 10-L fermenter were significantly high (105,836 U mL^-1). The prebiotic mannooligosaccharides (<2000 Da) were prepared by hydrolyzing konjac gum and locust bean gum with MEIR, with 100% and 76.40% hydrolysis rates, respectively. These characteristics make MEIR highly attractive for prebiotic development in food and related industries.

DR-region of Na+/K+-ATPase is a target to ameliorate hepatic insulin resistance in obese diabetic mice

Reduced hepatic Na⁺/K⁺-ATPase (NKA) activity and NKAα1 expression are engaged in the pathologies of metabolism diseases. The present study was designed to investigate the potential roles of NKAα1 in hepatic gluconeogenesis and glycogenesis in both hepatocytes and obese diabetic mice.

Methods: Insulin resistance was mimicked by glucosamine (GlcN) in either human hepatocellular carcinoma (HepG2) cells or primary mouse primary hepatocytes. Obese diabetic mice were induced by high-fat diet (HFD) feeding for 12 weeks.

Results: We found that both NKA activity and NKAα1 protein level were downregulated in GlcN-treated hepatocytes and in the livers of obese diabetic mice. Pharmacological inhibition of NKA with ouabain worsened, while activation of NKAα1 with an antibody against an extracellular DR region of NKAα1 subunit (DR-Ab) prevented GlcN-induced increase in gluconeogenesis and decrease in glycogenesis. Likewise, the above results were also corroborated by the opposite effects of genetic knockout/overexpression of NKAα1 on both gluconeogenesis and glycogenesis. In obese diabetic mice, hepatic activation or overexpression of NKAα1 stimulated the PI3K/Akt pathway to suppress hyperglycemia and improve insulin resistance. More importantly, loss of NKA activities in NKAα1^+/- mice was associated with more susceptibility to insulin resistance following HFD feeding.

Conclusions: Our findings suggest that NKAα1 is a physiological regulator of glucose homoeostasis and its DR-region is a novel target to treat hepatic insulin resistance.

Shared genetic architecture and casual relationship between leptin levels and type 2 diabetes: large-scale cross-trait meta-analysis and Mendelian randomization analysis

OBJECTIVE

We aimed to estimate genetic correlation, identify shared loci and test causality between leptin levels and type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Our study consists of three parts. First, we calculated the genetic correlation of leptin levels and T2D or glycemic traits by using linkage disequilibrium score regression analysis. Second, we conducted a large-scale genome-wide cross-trait meta-analysis using cross-phenotype association to identify shared loci between trait pairs that showed significant genetic correlations in the first part. In the end, we carried out a bidirectional MR analysis to find out whether there is a causal relationship between leptin levels and T2D or glycemic traits.

RESULTS

We found positive genetic correlations between leptin levels and T2D (R_g=0.3165, p=0.0227), fasting insulin (FI) (R_g=0.517, p=0.0076), homeostasis model assessment-insulin resistance (HOMA-IR) (R_g=0.4785, p=0.0196), as well as surrogate estimates of β-cell function (HOMA-β) (R_g=0.4456, p=0.0214). We identified 12 shared loci between leptin levels and T2D, 1 locus between leptin levels and FI, 1 locus between leptin levels and HOMA-IR, and 1 locus between leptin levels and HOMA-β. We newly identified eight loci that did not achieve genome-wide significance in trait-specific genome-wide association studies. These shared genes were enriched in pancreas, thyroid gland, skeletal muscle, placenta, liver and cerebral cortex. In addition, we found that 1-SD increase in HOMA-IR was causally associated with a 0.329 ng/mL increase in leptin levels (β=0.329, p=0.001).

CONCLUSIONS

Our results have shown the shared genetic architecture between leptin levels and T2D and found causality of HOMA-IR on leptin levels, shedding light on the molecular mechanisms underlying the association between leptin levels and T2D.