Diet-induced Insulin Resistance In Mice Research Articles

MicroRNA-721 regulates gluconeogenesis via KDM2A-mediated epigenetic modulation in diet-induced insulin resistance in C57BL/6J mice

BackgroundAberrant gluconeogenesis is considered among primary drivers of hyperglycemia under insulin resistant conditions, with multiple studies pointing towards epigenetic dysregulation. Here we examine the role of miR-721 and effect of epigenetic modulator laccaic acid on the regulation of gluconeogenesis under high fat diet induced insulin resistance.ResultsReanalysis of miRNA profiling data of high-fat diet-induced insulin-resistant mice model, GEO dataset (GSE94799) revealed a significant upregulation of miR-721, which was further validated in invivo insulin resistance in mice and invitro insulin resistance in Hepa 1–6 cells. Interestingly, miR-721 mimic increased glucose production in Hepa 1–6 cells via activation of FOXO1 regulated gluconeogenic program. Concomitantly, inhibition of miR-721 reduced glucose production in palmitate induced insulin resistant Hepa 1–6 cells by blunting the FOXO1 induced gluconeogenesis. Intriguingly, at epigenetic level, enrichment of the transcriptional activation mark H3K36me2 got decreased around the FOXO1 promoter. Additionally, identifying targets of miR-721 using miRDB.org showed H3K36me2 demethylase KDM2A as a potential target. Notably, miR-721 inhibitor enhanced KDM2A expression which correlated with H3K36me2 enrichment around FOXO1 promoter and the downstream activation of the gluconeogenic pathway. Furthermore, inhibition of miR-721 in high-fat diet-induced insulin-resistant mice resulted in restoration of KDM2A levels, concomitantly reducing FOXO1, PCK1, and G6PC expression, attenuating gluconeogenesis, hyperglycemia, and improving glucose tolerance. Interestingly, the epigenetic modulator laccaic acid also reduced the hepatic miR-721 expression and improved KDM2A expression, supporting our earlier report that laccaic acid attenuates insulin resistance by reducing gluconeogenesis.ConclusionOur study unveils the role of miR-721 in regulating gluconeogenesis through KDM2A and FOXO1 under insulin resistance, pointing towards significant clinical and therapeutic implications for metabolic disorders. Moreover, the promising impact of laccaic acid highlights its potential as a valuable intervention in managing insulin resistance-associated metabolic diseases.Graphical

Retraction: A non-erythropoietic peptide derivative of erythropoietin decreases susceptibility to diet-induced insulin resistance in mice.

Retraction: A non-erythropoietic peptide derivative of erythropoietin decreases susceptibility to diet-induced insulin resistance in mice.

Macrophage CREBZF Orchestrates Inflammatory Response to Potentiate Insulin Resistance and Type 2 Diabetes.

Chronic adipose tissue inflammation accompanied by macrophage accumulation and activation is implicated in the pathogenesis of insulin resistance and type 2 diabetes in humans. The transcriptional coregulator CREBZF is a key factor in hepatic metabolism, yet its role in modulating adipose tissue inflammation and type 2 diabetes remains elusive. The present study demonstrates that overnutrition-induced CREBZF links adipose tissue macrophage (ATM) proinflammatory activation to insulin resistance. CREBZF deficiency in macrophages, not in neutrophils, attenuates macrophage infiltration in adipose, proinflammatory activation, and hyperglycemia in diet-induced insulin-resistant mice. The coculture assays show that macrophage CREBZF deficiency improves insulin sensitivity in primary adipocytes and adipose tissue. Mechanistically, CREBZF competitively inhibits the binding of IκBα to p65, resulting in enhanced NF-κB activity. In addition, bromocriptine is identified as a small molecule inhibitor of CREBZF in macrophages, which suppresses the proinflammatory phenotype and improves metabolic dysfunction. Furthermore, CREBZF is highly expressed in ATM of obese humans and mice, which is positively correlated with proinflammatory genes and insulin resistance in humans. This study identifies a previously unknown role of CREBZF coupling ATM activation to systemic insulin resistance and type 2 diabetes.

Influence of Brown or Germinated Brown Rice Supplementation on Fecal Short-Chain Fatty Acids and Microbiome in Diet-Induced Insulin-Resistant Mice.

Intake of whole grain foods is associated with improving metabolic profile compared to refined grain products, but the underlying mechanism remains unclear. The present study examined the effects of brown rice (BRR) or germinated brown rice (GBR) supplementation on fecal short-chain fatty acids (SCFAs), and relationship with gut microbiota, metabolism and inflammation in high fat (HF)-diet-fed mice. The results demonstrated that an HF diet supplemented with BRR or GBR comparably increased the abundance of fecal isobutyric acid compared to that in mice receiving HF+white rice (WHR) diet (p < 0.01). The abundance of valeric acid in HF+GBR-diet-fed mice was higher than those receiving HF+WHR diet (p < 0.05). The abundances of fecal isobutyric acid negatively correlated with fasting plasma glucose, insulin, cholesterol, triglycerides, tumor necrosis factor-α, plasminogen activator inhibit-1, monocyte chemotactic protein-1 and homeostatic model assessment of insulin resistance (p < 0.01). The abundance of valeric acids negatively correlated with insulin resistance (p < 0.05). The abundances of isobutyric acid positively correlated with Lactobacillus, but negatively correlated with Dubosiella genus bacteria (p < 0.05). The findings demonstrated that the increases in SCFAs in the feces of BRR and GBR-treated mice were associated with improvements in gut microbiome, metabolic and inflammatory profile, which may contribute to the antidiabetic and anti-inflammatory effects of the whole grains in HF-diet-fed mice.

SAT038 Dietary Trans-10,cis-12 Conjugated Linoleic Acid Regulates Glucose Levels In Mice With Severe Insulin Resistance: Potential Effects On The Liver Via HNF4α And FOX01

Abstract Disclosure: S.M. Lee: None. J.T. Muratalla: None. C.W. Liew: None. J. Cordoba-Chacon: None. Plasma trans-10 cis-12-conjugated linoleic acid CLA (t10c12-CLA) is inversely associated with increased risk of diabetes in humans. In mice, it is well-known that t10c12-CLA induces whole-body insulin resistance due to severe lipodystrophy (loss of whole-body adipose tissue). However, t10c12-CLA-fed mice show normal glucose levels and, t10c12-CLA improved glucose clearance in models with preexisting insulin resistance: Zucker fatty/diabetic rats, obese and insulin resistant Ldlr-/- mice, and diet-induced obese and insulin resistant male mice. In this study, we assessed whether supplementation of t10c12-CLA in a low-fat diet reduces glucose levels in adipocyte-specific insulin receptor knockout (IRFKO) mice, which is a mouse model of congenital lipodystrophy. In addition to lipodystrophy, IRFKO mice show liver steatosis and increased blood glucose levels that are consequences of whole-body insulin resistance and increased hepatic gluconeogenesis. Briefly, 5-6-week-old male and female control and IRFKO mice were fed with a low-fat diet supplemented with 0.8% t10c12-CLA for 5 weeks. In IRFKO mice, dietary t10c12-CLA did not reduce adipose tissue mass. However, dietary t10c12-CLA increased liver steatosis and plasma insulin levels. Surprisingly, dietary t10c12-CLA reduced glucose levels in both male and female IRFKO mice. Also, dietary t10c12-CLA reduced food intake and polydipsia, which were increased in IRFKO mice due to lipodystrophy and hyperglycemia, respectively. A transcriptomic analysis (RNA-seq) of livers of control and IRFKO male mice fed with a t10c12-CLA diet showed that t10c12-CLA reduced the expression of the key gluconeogenic and mitochondrial fatty oxidation genes. Previous studies have suggested that t10c12-CLA reduces the expression of Forkhead box 01 (Fox01) and Hepatocyte nuclear factor 4 alpha (HNF4α). Of note, the livers of t10c12-CLA-fed control and IRFKO male mice showed a downregulation of positive targets of FoxO1 and HNF4α. In addition, livers of t10c12-CLA-fed mice showed reduced total FOXO1 protein levels, and increased phosphorylation of FOXO1 in t10c12-CLA-fed IRFKO mice. These findings suggest that t10c12-CLA could be directly acting on the liver to alter HNF4α and FOXO1-dependent regulation of hepatic fatty acid oxidation and glucose production. These actions may explain why t10c12-CLA-fed mice do not show increased glucose levels and is potentially linked to the inverse association between t10c12-CLA levels and diabetes risk. Presentation: Saturday, June 17, 2023

NINJ2 deficiency inhibits preadipocyte differentiation and promotes insulin resistance through regulating insulin signaling.

Genetic variants in ninjurin-2 (NINJ2; nerve injury-induced protein 2) confer risk of ischemic strokes and coronary artery disease as well as endothelial activation and inflammation. However, little is known about NINJ2's in vivo functions and underlying mechanisms. The phenotypes of NINJ2 knockout mice were analyzed, and mechanisms of NINJ2 that regulate body weight, insulin resistance, and glucose homeostasis and lipogenesis were investigated in vivo and in vitro. This study found that mice lacking NINJ2 showed impaired adipogenesis, increased insulin resistance, and abnormal glucose homeostasis, all of which are risk factors for strokes and coronary artery disease. Mechanistically, NINJ2 directly interacts with insulin receptor/insulin-like growth factor 1 receptor (INSR/IGF1R), and NINJ2 knockdown can block insulin-induced mitotic clonal expansion during preadipocyte differentiation by inhibiting protein kinase B/extracellular signal-regulated kinase (AKT/ERK) signaling and by decreasing the expression of key adipocyte transcriptional regulators CCAAT/enhancer-binding protein β (C/EBP-β), C/EBP-α, and peroxisome proliferator-activated receptor γ (PPAR-γ). Furthermore, the interaction between NINJ2 and INSR/IGF1R is needed for maintaining insulin sensitivity in adipocytes and muscle via AKT and glucose transporter type 4. Notably, adenovirus-mediated NINJ2 overexpression can ameliorate diet-induced insulin resistance in mice. In conclusion, these findings reveal NINJ2 as an important new facilitator of insulin receptors, and the authors propose a unique regulatory mechanism between insulin signaling, adipogenesis, and insulin resistance.

GSK3α phosphorylates dynamin-2 to promote GLUT4 endocytosis in muscle cells.

Insulin-stimulated translocation of glucose transporter 4 (GLUT4) to plasma membrane of skeletal muscle is critical for postprandial glucose uptake; however, whether the internalization of GLUT4 is also regulated by insulin signaling remains unclear. Here, we discover that the activity of dynamin-2 (Dyn2) in catalyzing GLUT4 endocytosis is negatively regulated by insulin signaling in muscle cells. Mechanistically, the fission activity of Dyn2 is inhibited by binding with the SH3 domain of Bin1. In the absence of insulin, GSK3α phosphorylates Dyn2 to relieve the inhibition of Bin1 and promotes endocytosis. Conversely, insulin signaling inactivates GSK3α and leads to attenuated GLUT4 internalization. Furthermore, the isoform-specific pharmacological inhibition of GSK3α significantly improves insulin sensitivity and glucose tolerance in diet-induced insulin-resistant mice. Together, we identify a new role of GSK3α in insulin-stimulated glucose disposal by regulating Dyn2-mediated GLUT4 endocytosis in muscle cells. These results highlight the isoform-specific function of GSK3α on membrane trafficking and its potential as a therapeutic target for metabolic disorders.

Impact of anthocyanin component and metabolite of Saskatoon berry on gut microbiome and relationship with fecal short chain fatty acids in diet-induced insulin resistant mice

Previous studies demonstrated that oral administration of Saskatoon berry powder (SBp) reduced fasting plasma glucose (FPG), insulin resistance, lipids, and inflammatory markers in diet-induced insulin resistant rodents. Mechanism for the beneficial effects of SB remains unclear. The present study examined the effects of high fat-high sucrose (HFHS) diet supplemented with or without 5% SBp, cyanidin-3-glucoside (C3G, an anthocyanin rich in SBp) at a dosage of C3G in 5% SBp, or equimolar concentration of protocatechuic acid (PCA, a relatively stable metabolite of C3G) for 11 weeks on FPG, cholesterol, triglycerides, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), circulatory inflammatory markers, fecal microbiota, and short chain fatty acids in mice. HFHS diet significantly enhanced FPG, insulin, HOMA-IR, lipids and inflammatory markers, but reduced the abundance of fecal Bacteroidetes, Muribaculaceae and propionate compared to low fat diet. Supplementation of SBp, C3G or PCA significantly attenuated HFHS diet induced metabolic and inflammatory markers, and increased the abundances of fecal Muribaculaceae and propionate compared to HFHS diet alone. The abundances of fecal Muribaculaceae negatively correlated with FPG, lipids, HOMA-IR and inflammatory markers in the mice. The abundances of fecal propionate positively correlated with fecal Muribaculaceae and negatively correlated with the metabolic and inflammatory markers. The findings suggest that C3G in SBp and PCA contribute to the metabolic and anti-inflammatory effect of SBp in mice. The increases in fecal Muribaculaceae and propionate may play important regulatory roles in the anti-diabetic and anti-inflammatory benefits of SBp, C3G, and PCA in mice.

Impact of Germinated Brown Rice and Brown Rice on Metabolism, Inflammation, and Gut Microbiome in High Fat Diet-Induced Insulin Resistant Mice.

The constituents of germinated brown rice (GBR), brown rice (BRR), and white rice (WHR) and their impact on metabolism, inflammation, and gut microbiota in high fat (HF) diet-fed mice were examined. The contents of total fiber and γ-aminobutyric acid in BRR and GBR were higher than that in WHR (p < 0.05). Male C57 BL/6J mice received HF diet+26 g% of WHR, BRR, or GBR for 12 weeks. BRR and GBR comparably reduced HF diet-induced increases in fasting plasma glucose, lipids, insulin resistance, and inflammatory markers compared to WHR (p < 0.01). The abundance of fecal Bacteroidetes in mice fed HF+GBR or HF+BRR was higher than in HF+WHR-fed mice (p < 0.05). The abundance of fecal Lactobacillus gasseri in GBR-fed mice was greater than that in WHR- or BRR-fed mice (p < 0.05). The results indicated that GBR or BRR attenuated hyperglycemia, insulin resistance, and inflammation in mice. HF+GBR, but not HF+BRR, increased a probiotic bacteria in the gut.

SAT110 - Weight loss with semaglutide treatment or time-restricted feeding differentially improves non-alcoholic steatohepatitis in diet-induced obese insulin resistant mice

SAT110 - Weight loss with semaglutide treatment or time-restricted feeding differentially improves non-alcoholic steatohepatitis in diet-induced obese insulin resistant mice

148-OR: Partial Knockout of Skeletal Muscle Dynamin-Related Protein 1 Improves Insulin Sensitivity in Diet-Induced Insulin Resistant Mice, but Not in Normal Control Mice

Dynamin-related protein 1 (Drp1) is the key regulator of mitochondrial fission. We and others have reported excessive Drp1 activity in skeletal muscle from both animals and humans with insulin resistance, which is strongly correlated to impaired skeletal muscle insulin sensitivity. To examine whether Drp1 directly regulates skeletal muscle insulin sensitivity and whole-body glucose homeostasis, we generated tamoxifen-inducible skeletal muscle-specific heterozygous Drp1 partial knockout mice (mDrp1+/-) . Male mDrp1+/- and wildtype (WT) mice were fed with either a high-fat diet (HFD) or low-fat diet (LFD) for four weeks, received tamoxifen injections for five consecutive days, and remained on their respective diet for another four weeks. Improvements in whole-body glucose tolerance and insulin sensitivity were observed in HFD-fed mDrp1+/- mice (P&amp;lt;0.05) , but not in LFD-fed mDrp1+/- mice, when compared to their respective WT controls. Further, HFD-induced impairment in skeletal muscle insulin-stimulated Akt Ser473 phosphorylation (P&amp;lt;0.05) was mitigated in HFD-fed mDrp1+/- mice. In contrast, insulin-stimulated Akt Ser473 phosphorylation was reduced in LFD-fed mDrp1+/- mice compared to LFD-fed WT mice (P&amp;lt;0.05) . mDrp1+/- mice exhibited more fused and interconnected mitochondrial networks in skeletal muscle than WT mice. The examination of mitochondrial function revealed no change in mitochondrial respiration but reductions in mitochondrial Complex I and II and pyruvate dehydrogenase derived H2O2 production in HFD-fed mDrp1+/- mice compared to HFD-fed WT mice (P&amp;lt;0.05) . In conclusion, our data suggest that partial knockout of skeletal muscle Drp1 improves skeletal muscle insulin sensitivity and whole-body glucose homeostasis in diet-induced insulin-resistant mice but not in normal control mice. These improvements are, at least in part, due to reduced mitochondrial-derived H2O2 production. Disclosure B.A.Kugler: None. N.Lin: None. P.D.Nguyen: None. A.Ali: None. A.Sesay: None. B.Kalemba: None. H.Sesaki: None. K.Zou: None. Funding National Institutes of Health (R15DK131512) Diabetes Action Research and Education Foundation Grant (#505)

Improvement in Mung Bean Peptide on High-Fat Diet-Induced Insulin Resistance Mice Using Untargeted Serum Metabolomics.

This study aimed to elucidate the potential regulatory mechanism of mung bean peptides (MBPs) on glucolipid metabolism in insulin-resistant mice induced by high-fat diet (HFD) using untargeted serum metabolomics, enzyme linked immunosorbent assay (ELISA), intraperitoneal injection glucose tolerance test (IPGTT), insulin tolerance test (IPITT), and hematoxylin-eosin staining (H&E). The regulatory effect of MBPs for alleviating insulin resistance was studied by measuring body weight, fasting blood glucose (FBG) and serum insulin levels, C-Peptide levels, inflammatory and antioxidant factors, and histopathological observation of C57BL/6 mice. The experimental results showed that dietary intervention with MBPs (245 mg/kg/d) for 5 weeks significantly relieved insulin resistance in HFD mice. The body weight, insulin resistance index, and the levels of FBG, C-Peptide, IL-6, TNF-α, and MDA in the serum of HFD mice significantly decreased (P < 0.05). Conversely, SOD content and pancreatic β cell function index significantly increased (P < 0.05), and the damaged pancreatic tissue was repaired. One biomarker associated with insulin resistance was glycine. In addition, there were four important differential metabolites: pyroglutamate, D-glutamine, aminoadipic acid, and nicotinamide, involved in 12 metabolic pathway changes. It was found that MBPs may regulate amino acid, glycerol phospholipid, fatty acid, alkaloid, and nicotinamide metabolism to regulate the metabolic profile of HFD mice in a beneficial direction.

Bioactivity of mackerel peptides on obesity and insulin resistance, an in-vivo study

Of many metabolic irregularity risk factors, glucose intolerance, insulin resistance, and abdominal obesity are the main ones. The risk of vascular diseases and cancers is rather high in such individuals therefore its treatment and prevention are equally important for the health of population. Marine including fish biopeptides have frequently shown to prevent and or ameliorate these risk factors. In our earlier studies, Atlantic mackerel hydrolysate and its fractions showed promising effects on immunity and hypertension. We, therefore, in the current study, aimed to examine the effects of mackerel hydrolysate along its cationic peptides, isolated at pH3 using electrodialysis with ultrafiltration membrane, on metabolic disorder factors in diet-induced insulin resistant obese mice. Mice were fed the chow and or the hypercaloric diet (high fat high sucrose) for the duration of 8-weeks. Subsequently the hypercaloric fed insulin resistant obese mice were gavaged daily either the vehicle and or the test material at the dosage of 208 mg of sample protein per kg mice body weight. According to our observations, mackerel peptides could not effectively modulate food intake, weight gain, adiposity, plasma glucose and insulin concentrations, hepatic cholesterol, and triglyceride levels. Thus, obesity and metabolic impairments could not be averted by the treatments in insulin resistant obese mice. In conclusion, anti-hypertensive, and immunomodulatory attributes of mackerel peptides at the tested concentrations do not seem to be correlated with its metabolic syndrome benefiting effects. To presume a general statement about the metabolic syndrome benefiting potency of Atlantic mackerel's biopeptides further research is warranted.

Mechanism of protection from insulin resistance by toll-like receptor 2 deficiency in high-fat diet fed mice: involvement in macrophage polarization.

Toll-like receptor 2 (TLR2) deficiency can increase insulin sensitivity and improves glucose tolerance. However, it is not yet fully understood about its underlying mechanism. The regulation of M1/M2 macrophage polarization has been verified to involve in insulin resistance. Here, we evaluated whether the beneficial effect of TLR2 deficiency is mediated by TLR2-associated macrophage polarization in mice fed with high-fat diet (HFD). Wild-type and TLR2 knockout (TLR2-/-) mice received HFD for two months. Following intraperitoneal glucose tolerance and insulin resistance tests, peripheral monocytes were isolated, and in vitro induced for differentiation into M1 and M2 macrophages, respectively. Macrophages polarization was evaluated using flow cytometry. The expression of macrophage polarization marker genes and cytokine production in visceral adipose tissue were measured by qRT-PCR and ELISA. Compared to wild-type mice, TLR2-/- mice showed higher glucose tolerance and insulin sensitivity, along with significantly reduced the population of M1 and increased M2 count in vitro. Additionally, TLR2-/- mice demonstrated higher expression of M2 marker iNOS mRNA and interleukin-10 level in adipose tissues. Our results reveal that TLR2 knockout-mediated macrophages M2 polarization is a crucial factor for preventing against diet-induced insulin resistance in mice. These findings deepen our knowledge about the mechanism underlying HFD-induced insulin resistance.

Citrate enrichment in a Western diet reduces weight gain via browning of adipose tissues without resolving diet-induced insulin resistance in mice.

Citrate, a major component of processed foods, appears as either preservative or flavor enhancer. With no concentration limit, citrate is consumed in large quantities worldwide, principally in ultra-processed foods (UPF). UPF are encountered in Western diets (rich in saturated fat and sucrose), where consumption is directly associated with many conditions, such as obesity and diabetes, among others. Here, we administered a High-Fat, High-Sucrose (HFHS) diet to mice, enriched or not with citrate (67 mg g-1 diet), aimed to simulate UPF citrate consumption. Our results showed that citrate enrichment prevented the HFHS-induced lipid deposition in the liver and adipose tissues of the animals. Moreover, the treatment induced mitochondrial biogenesis in white adipose tissues, via upregulation of PCG1α. As a result, citrate enhancement upregulated UCP1, suggesting the browning of white adipose tissues. Nevertheless, the citrate-enhanced diet did not prevent HFHS-induced insulin resistance and causes further liver inflammation and injury. Altogether, our results clearly showed that, associated to UPF consumption, the excess of dietary citrate has caused harmful effects being associated to non-obesity related liver inflammatory diseases and insulin resistance.

Dose-Responses Relationship in Glucose Lowering and Gut Dysbiosis to Saskatoon Berry Powder Supplementation in High Fat-High Sucrose Diet-Induced Insulin Resistant Mice

Administration of freeze-dried powder of Saskatoon berry (SB), a popular fruit enriched with antioxidants, reduced glucose level, inflammatory markers and gut microbiota disorder in high fat-high sucrose (HFHS) diet-induced insulin resistant mice. The present study examined the dose-response relationship in metabolic, inflammatory and gut microbiotic variables to SB power (SBp) supplementation in HFHS diet-fed mice. Male C57 BL/6J mice were fed with HFHS diet supplemented with 0, 1%, 2.5% or 5% SBp for 11 weeks. HFHS diet significantly increased the levels of fast plasma glucose (FPG), cholesterol, triglycerides, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), tumor necrosis factor-α, monocyte chemotactic protein-1 and plasminogen activator inhibitor-1, but decreased fecal Bacteroidetes phylum bacteria and Muribaculaceae family bacteria compared to low fat diet. SBp dose-dependently reduced metabolic and inflammatory variables and gut dysbiosis in mice compared with mice receiving HFHS diet alone. Significant attenuation of HFHS diet-induced biochemical disorders were detected in mice receiving ≥1% SBp. The abundances of Muribaculaceae family bacteria negatively correlated with body weights, FPG, lipids, insulin, HOMA-IR and inflammatory markers in the mice. The results suggest that SBp supplementation dose-dependently attenuated HFHS diet-induced metabolic and inflammatory disorders, which was associated with the amelioration of gut dysbiosis in the mice.

279-OR: Hydroxylation Regulation of Hepatic Gluconeogenesis via Prolyl-Hydroxylase 3 in Mice

Hepatic gluconeogenesis is critical for metabolic adaption in response to fasting, and its abnormal elevation contributes to hyperglycemia and type 2 diabetes. However, whether and how hydroxylation regulates hepatic gluconeogenesis remains largely unknown. Here we identified prolyl hydroxylase 3 (PHD3) of the hydroxylase family as a key regulator for hepatic gluconeogenesis. Liver-specific knockout of PHD3 (PHD3 LKO) mice show attenuated fasting gluconeogenic genes, glycaemia and hepatic capacity to produce glucose as evidenced by a pyruvate tolerance test. The efficacies of glucagon or adenylyl cyclase activator forskolin on stimulating the expression of gluconeogenic enzymes, such as PEPCK and G6Pase, and on glucose output are abolished in PHD3-/- mouse primary hepatocytes. To determine whether the prolyl hydroxylase activity is required for PHD3’s effects on promoting gluconeogenesis, liver-specific prolyl hydroxylase-deficient knockin mice with alanine mutation in PHD3 at Pro196 (PHD3 KI) were generated. Similar to PHD3 LKO mice, PHD3 KI mice exhibit attenuated fasting gluconeogenic genes, glycaemia and hepatic capacity to produce glucose, suggesting that PHD3 regulates hepatic gluconeogenesis in a proline hydroxylase-dependent manner. Moreover, several cellular proteins that associate with PHD3 were identified by comprehensive protein analysis using LC-MS/MS followed by bioinformatic analysis including GSK3β, IRS2 and OGT, which may act as PHD3 substrates and play roles in mediating PHD3’s effects on regulating glucose metabolism. Intriguingly, expression levels of PHD3 are increased in the liver diet-induced insulin resistant mice. Together, these results demonstrate that hydroxylation plays a critical role in the regulation of hepatic gluconeogenesis under physiological and insulin resistant conditions. Hyperactivation of PHD3 may underscore the potential role of PHD3 in the development of sustained gluconeogenesis, hyperglycemia and type 2 diabetes. Disclosure Y. Xue: None. J. Gao: None. X. Dai: None. A. Cui: None. Y. Li: None. G. Cai: None. F. Ma: None. Z. Liu: None. Y. Liu: None. W. Su: None. Z. Zheng: None. D. Ding: None. Y. Jiang: None. Funding National Key Research and Development Project of China (2019YFA0802502); National Natural Science Foundation of China (81925008); Shanghai Science and Technology Commission (19140903300)

Effect of different phosphatidylcholines on high fat diet-induced insulin resistance in mice.

Phosphatidylcholine (PC) is the most abundant phospholipid in natural products and exhibits various bioactivities in vivo. However, the beneficial effects of PC on IR and the potential mechanisms are rarely reported. PCs from different biological sources vary greatly in their fatty acid compositions. The present study aimed to investigate the effect of EPA/DHA-PC derived from Sthenototeuthis oualaniensis on high fat diet (HFD)-induced IR in comparison with terrestrial soybean PC (Soy-PC) and egg yolk PC (Egg-PC) in C57BL/6J mice. The results indicated that EPA/DHA-PC, but not Soy-PC or Egg-PC, reversed HFD-induced obesity, IR and hyperglycemia. This improvement was accompanied by enhanced IRS/PI3K/AKT insulin signaling pathway in peripheral tissue, ameliorated JNK and NF-κB inflammatory pathway in white adipose tissue, and changes in the gut microbial composition. Microbiological analysis showed that EPA/DHA-PC treatment prevented the loss of Bacteroidetes, Verrucomicrobia, Akkermansia, Coriobacteriaceae_UCG-002, Lactobacillus, Clostridium_sensu_stricto_1, Bacteroides and inhibited the increase of Firmicutes, Actinobacteria, Proteobacteria, and Ileibacterium. The gut microbiota-derived metabolites LPS and TMAO were also reduced by EPA/DHA-PC. In summary, the improvement effect of PCs on IR is largely related to their fatty acid composition. EPA/DHA-PC prevented IR probably by modulating the gut microbiota composition, ameliorating the chronic inflammation in the adipose tissue and promoting transduction of insulin signaling pathways.

Mechanisms by which adiponectin reverses high fat diet-induced insulin resistance in mice

Adiponectin has emerged as a potential therapy for type 2 diabetes mellitus, but the molecular mechanism by which adiponectin reverses insulin resistance remains unclear. Two weeks of globular adiponectin (gAcrp30) treatment reduced fasting plasma glucose, triglyceride (TAG), and insulin concentrations and reversed whole-body insulin resistance, which could be attributed to both improved insulin-mediated suppression of endogenous glucose production and increased insulin-stimulated glucose uptake in muscle and adipose tissues. These improvements in liver and muscle sensitivity were associated with ∼50% reductions in liver and muscle TAG and plasma membrane (PM)-associated diacylglycerol (DAG) content and occurred independent of reductions in total ceramide content. Reductions of PM DAG content in liver and skeletal muscle were associated with reduced PKCε translocation in liver and reduced PKCθ and PKCε translocation in skeletal muscle resulting in increased insulin-stimulated insulin receptor tyrosine1162 phosphorylation, IRS-1/IRS-2-associated PI3-kinase activity, and Akt-serine phosphorylation. Both gAcrp30 and full-length adiponectin (Acrp30) treatment increased eNOS/AMPK activation in muscle and muscle fatty acid oxidation. gAcrp30 and Acrp30 infusions also increased TAG uptake in epididymal white adipose tissue (eWAT), which could be attributed to increased lipoprotein lipase (LPL) activity. These data suggest that adiponectin and adiponectin-related molecules reverse lipid-induced liver and muscle insulin resistance by reducing ectopic lipid storage in these organs, resulting in decreased plasma membrane sn-1,2-DAG-induced nPKC activity and increased insulin signaling. Adiponectin mediates these effects by both promoting the storage of TAG in eWAT likely through stimulation of LPL as well as by stimulation of AMPK in muscle resulting in increased muscle fat oxidation.

Methionine sulfoxide reductase B3 deficiency inhibits the development of diet-induced insulin resistance in mice

Oxidative and endoplasmic reticulum (ER) stress are involved in mediating high-fat diet (HFD)-induced insulin resistance. As the ER-localized methionine sulfoxide reductase B3 (MsrB3) protects cells against oxidative and ER stress, we hypothesized that MsrB3 might be associated with HFD-induced insulin resistance. To test this hypothesis, we examined the effect of MsrB3 deficiency on HFD-induced insulin resistance using MsrB3 knockout (KO) mice. Mice were fed a control diet or HFD for 12 weeks and insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. HFD consumption increased the body weight of both wild-type and MsrB3 KO mice, and no significant difference was observed between the genotypes. The HFD increased oxidative stress and induced insulin resistance in the skeletal muscle of wild-type mice, but did not affect either in MsrB3 KO mice. The unfolded protein response (UPR) was increased in MsrB3 KO mice upon consumption of HFD, but not in wild-type mice. Mitochondrial oxidative phosphorylation proteins and the levels of superoxide dismutase 2 and glutathione peroxidase 1 were increased in MsrB3 KO mice upon HFD consumption. The respiratory control ratio was reduced in wild-type mice consuming HFD but not in MsrB3 KO mice. The levels of calcium/calmodulin-dependent protein kinase kinase β, phosphorylated AMP-activated protein kinase, and peroxisome proliferator-activated receptor gamma coactivator 1α were increased in MsrB3 KO mice following HFD consumption. These results suggest that MsrB3 deficiency inhibits HFD-induced insulin resistance, and the increased mitochondrial biogenesis and antioxidant induction might be the mechanisms underlying this phenomenon.