Insulin resistance in the liver: deficiency or excess of insulin?

Lignan-rich extract from Cinnamomum camphora leaf attenuates metabolic syndrome by modulating glycolipid metabolism and gut microbiota in T2DM mice

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a serious metabolic syndrome with high mortality and disability rates globally, which usually caused by unhealthy dietary patterns. Cinnamomum camphora leaf is a traditional Chinese medicinal herb used for attenuating hyperglycemia and digestive disorder, and high level of lignans has been found in C. camphora leaf.

PURPOSE

This study aimed to examine the chemical composition of lignans extracted from C. camphora leaf (LCCL), and illustrate its therapeutic effect and mechanism on T2DM and its concomitant glycolipid metabolic disorder.

METHODS

The components of LCCL were separated and purified by silica gel and macroporous adsorption resin, and were distinguished through LC/MS and NMR. The antioxidant activity of LCCL was determined by free radical scavenging assay in vitro; the hypoglycemic and hypolipidemic abilities were evaluated by α-glucosidase, α-amylase and pancreatic lipase inhibition trials, respectively. T2DM model mice were established by high-sugar and high-fat (HSHF) feed together with streptozotocin (STZ) infection, and then grouped to assess the effect of LCCL treatment. Hematoxylin-eosin (H&E), Periodic Acid-Schiff (PAS) and oil red O staining were employed to analyze the histopathology. qRT-PCR assay, 16S rRNA analysis, and western blot were conducted to illuminate the anti-diabetic mechanism of LCCL.

RESULTS

6 sesamin lignans were identifed from LCCL. The in vitro assays showed strong inhibitive abilities of LCCL with low IC50 on DPPH (33.68 ± 0.54 μg/ml),O2- (39.25 ± 0.61 μg/ml), OH• (45.72 ± 0.72 μg/ml), α-glucosidase (0.82 ± 0.14 mg/ml), α-amylase (0.86 ± 0.11 mg/ml) and pancreatic lipase (0.91 ± 0.12 mg/ml). LCCL treatment (100, 200 and 400 g kg-1mg kg-1) gradually decreased the fasting blood glucose (FBG) and fasting insulin (FINS), improved the glucose and insulin tolerance, down-regulated the homeostasis model assessment insulin resistance (HOMA-IR) indexes, alleviated the hepatic inflammatory response and oxidative stress, promoted the glycogen storage and depleted the fat accumulation in the liver. Besides, LCCL administration alleviated the glycolipid metabolism disorder in T2DM mice with a gut microbiota dependent manner, that significantly increased biodiversity, altered the composition of gut microbiota and increased the proportion of Lactobacillus.

CONCLUSION

The lignan-rich extract of C. camphor leaf (LCCL), containing at least 6 lignans compounds, displayed promising antioxidant, hypoglycemic and hypolipidemic activities. The treatment of LCCL alleviated the glycolipid metabolism disorder in T2DM mice with a gut microbiota dependent manner. These finding suggested that LCCL should be further investigated to develop its complementary therapeutic effect on T2DM.

Hepatic WDR23 proteostasis mediates insulin homeostasis by regulating insulin-degrading enzyme capacity

Maintaining insulin homeostasis is critical for cellular and organismal metabolism. In the liver, insulin is degraded by the activity of the insulin-degrading enzyme (IDE). Here, we establish a hepatic regulatory axis for IDE through WDR23-proteostasis. Wdr23KO mice have increased IDE expression, reduced circulating insulin, and defective insulin responses. Genetically engineered human cell models lacking WDR23 also increase IDE expression and display dysregulated phosphorylation of insulin signaling cascade proteins, IRS-1, AKT2, MAPK, FoxO, and mTOR, similar to cells treated with insulin, which can be mitigated by chemical inhibition of IDE. Mechanistically, the cytoprotective transcription factor NRF2, a direct target of WDR23-Cul4 proteostasis, mediates the enhanced transcriptional expression of IDE when WDR23 is ablated. Moreover, an analysis of human genetic variation in WDR23 across a large naturally aging human cohort in the US Health and Retirement Study reveals a significant association of WDR23 with altered hemoglobin A1C (HbA1c) levels in older adults, supporting the use of WDR23 as a new molecular determinant of metabolic health in humans.

Heterogeneous Pathological Changes in Liver Lobes During Liver Disease: A Perspective Review

Liver diseases have a global prevalence of 25%, accounting for 4% of all deaths worldwide, and are associated with a 36% increased risk of fatal and nonfatal cardiovascular events. Metabolic dysfunction-associated steatotic liver disease constitutes the liver expression of metabolic syndrome and represents the primary type of liver disease. Microscopical analysis of biopsies, which allows the evaluation of a small portion of tissue with inferences made to the entire organ, is considered the gold standard for determining the presence of liver diseases. However, potential sampling errors in liver biopsies are conceivable because the obtained tissue represents only a tiny fraction of the entire liver mass and may not accurately reflect the true pathological state. Studies have demonstrated the existence of sampling errors in liver biopsies, particularly concerning the severity of inflammation, degree of fibrosis, and the presence of cirrhosis. Also, clinical studies have shown that histopathological abnormalities are better detected in humans when liver samples are collected from both the right and the left lobes. However, a gap exists in clinical investigation to clarify the role of differences between these lobes in improving the diagnostic and prognostic for liver diseases. Building upon the heterogeneous nature of pathological alterations observed in liver lobes, this perspective review provided recommendations to enhance the precision of diagnosis and prognostic accuracy of liver diseases.

Role of Alkannin in the Therapeutic Targeting of Protein-Tyrosine Phosphatase 1B and Aldose Reductase in Type 2 Diabetes: An In Silico and In Vitro Evaluation

Alkannin is a plant-derived naphthoquinone that is isolated from the Boraginaceae family plants. In our previous studies, we found that shikonin, which is the R-enantiomer of alkannin, has potent antidiabetic activity by inhibiting the action of the aldose reductase (AR) enzyme and the protein-tyrosine phosphatase 1B (PTP1B). Therefore, in this study, we aim to explore the antidiabetic effect of alkannin targeting PTP1B and AR by employing in silico and in vitro techniques. For in silico, we used different parameters such as ADMET analysis, molecular docking, MD simulation, Root Mean Square Deviation (RMSD), protein-ligand mapping, and free binding energy calculation. The in vitro evaluation was done by assessing the inhibitory activity and enzyme kinetics of PTP1B and AR inhibition by alkannin. The in silico studies indicate that alkannin possesses favorable pharmacological properties and possesses strong binding affinity for diabetes target proteins. Hydrogen bonds (Val297, Ala299, Leu300, and Ser302) and hydrophobic interactions (Trp20, Val47, Tyr48, Trp79, Trp111, Phe122, Trp219, Val297, Cys298, Ala299, Leu300, and Leu301) are established by the compound, which potentially improves specificity and aids in the stabilization of the protein-ligand complex. The results from in vitro studies show a potent dose-dependent PTP1B inhibitory activity with an IC50 value of 19.47 μM, and toward AR it was estimated at 22.77 μM. Thus, from the results it is concluded that a low IC50 value of alkannin for both PTP1B and AR along with favorable pharmacological properties and optimal intra-molecular interactions indicates its utilization as a potential drug candidate for the management of diabetes and its end complications.

Exploring the Anti-Diabetic Potential of Quercetagitrin through Dual Inhibition of PTPN6 and PTPN9

Protein tyrosine phosphatases (PTPs) are pivotal contributors to the development of type 2 diabetes (T2DM). Hence, directing interventions towards PTPs emerges as a valuable therapeutic approach for managing type 2 diabetes. In particular, PTPN6 and PTPN9 are targets for anti-diabetic effects. Through high-throughput drug screening, quercetagitrin (QG) was recognized as a dual-target inhibitor of PTPN6 and PTPN9. We observed that QG suppressed the catalytic activity of PTPN6 (IC50 = 1 μM) and PTPN9 (IC50 = 1.7 μM) in vitro and enhanced glucose uptake by mature C2C12 myoblasts. Additionally, QG increased the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and insulin-dependent phosphorylation of Akt in mature C2C12 myoblasts. It further promoted the phosphorylation of Akt in the presence of palmitic acid, suggesting the attenuation of insulin resistance. In summary, our results indicate QG's role as a potent inhibitor targeting both PTPN6 and PTPN9, showcasing its potential as a promising treatment avenue for T2DM.

Insulin Resistance: An Unresolved Riddle

Insulin resistance (IR) is a rather common condition that is often diagnosed on the basis of an arbitrary "increased insulin value" or the presence of symptoms indicative of the Metabolic Syndrome [...].

Linseed oil attenuates fatty liver disease in mice fed a high-carbohydrate diet

The impact of linseed oil as a lipid source on liver disease induced by a high-carbohydrate diet (HCD) was evaluated. Adult male Swiss mice received an HCD containing carbohydrates (72.1%), proteins (14.2%), and lipids (4.0%). The Control HCD group (HCD-C) received an HCD containing lard (3.6%) and soybean oil (0.4%) as lipid sources. The L10 and L100 groups received an HCD with 10 and 100% linseed oil as lipid sources, respectively. A group of mice were euthanized before receiving the diets (day 0) and the remaining groups after 56 days of receiving the diets (HCD-C, L10, and L-100 groups). Morphological and histopathological analyses, as well as collagen deposition were evaluated. Perivenous hepatocytes (PVH) of the HCD-C group were larger (P<0.05) than periportal hepatocytes (PPH) in the median lobe (ML) and left lobe (LL). There was a greater (P<0.05) deposition of type I collagen in PPH (vs PVH) and in the ML (vs LL). The ML exhibited a higher proportion of apoptotic bodies, inflammatory infiltrate, and hepatocellular ballooning. All these alterations (hepatocyte size, deposition of type I collagen, apoptotic bodies, inflammatory infiltrate, and hepatocellular ballooning) induced by HCD were prevented or attenuated in L10 and L100 groups. Another indicator of the beneficial effects of linseed oil was the lower (P<0.05) number of binucleated hepatocytes (HCD-C vs L10 or L100 group). In general, the L100 group had greater effects than the L10 group. In conclusion, linseed oil impedes or reduces the liver injury progression induced by an HCD.

Modeling and therapeutic targeting of inflammation-induced hepatic insulin resistance using human iPSC-derived hepatocytes and macrophages

Hepatic insulin resistance is recognized as a driver of type 2 diabetes and fatty liver disease but specific therapies are lacking. Here we explore the potential of human induced pluripotent stem cells (iPSCs) for modeling hepatic insulin resistance in vitro, with a focus on resolving the controversy about the impact of inflammation in the absence of steatosis. For this, we establish the complex insulin signaling cascade and the multiple inter-dependent functions constituting hepatic glucose metabolism in iPSC-derived hepatocytes (iPSC-Heps). Co-culture of these insulin-sensitive iPSC-Heps with isogenic iPSC-derived pro-inflammatory macrophages induces glucose output by preventing insulin from inhibiting gluconeogenesis and glycogenolysis and activating glycolysis. Screening identifies TNFα and IL1β as the mediators of insulin resistance in iPSC-Heps. Neutralizing these cytokines together restores insulin sensitivity in iPSC-Heps more effectively than individual inhibition, reflecting specific effects on insulin signaling and glucose metabolism mediated by NF-κB or JNK. These results show that inflammation is sufficient to induce hepatic insulin resistance and establish a human iPSC-based in vitro model to mechanistically dissect and therapeutically target this metabolic disease driver.

Anti-Obesity Effect of Auricularia delicate Involves Intestinal-Microbiota-Mediated Oxidative Stress Regulation in High-Fat-Diet-Fed Mice

Auricularia delicate (ADe), an edible fungus belonging to the family Auriculariaceae and order Auriculariales, possesses antimicrobial, hepatoprotective, and antioxidant effects. In this study, after systematic analysis of its composition, ADe was administered to high-fat-diet (HFD)-fed mice to investigate its anti-obesity effect. ADe significantly controlled body weight; alleviated hepatic steatosis and adipocyte hypertrophy; reduced aspartate aminotransferase, total cholesterol, insulin, and resistin; and increased adiponectin levels in HFD-fed mice serum. Based on intestinal microbiota and lipidomics analysis, ADe treatment regulated the composition and abundance of 49 intestinal microorganisms and influenced the abundance of 8 lipid species compared with HFD-fed mice. Based on a correlation analysis of the intestinal microbiota and lipids, Coprococcus showed significant negative associations with ceramide (d18:0 20:0+O), phosphatidylserine (39:4), sphingomyelin (d38:4), and zymosterol (20:2). Moreover, ADe treatment decreased the levels of ROS and MDA and increased the levels of Nrf2, HO-1, and three antioxidant enzymes in HFD-fed mice livers. Collectively, the anti-obesity effect of ADe involves the regulation of oxidative stress and is mediated by the intestinal microbiota. Hence, this study provides a reference for the application of ADe as a candidate food for obesity.

Excessive gluconeogenesis causes the hepatic insulin resistance paradox and its sequelae

Background

Hepatic insulin signaling suppresses gluconeogenesis but promotes de novo lipid synthesis. Paradoxically, hepatic insulin resistance (HIR) enhances both gluconeogenesis and de novo lipid synthesis. Elucidation of the etiology of this paradox, which participates in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, the metabolic syndrome and hepatocellular carcinoma, has not been fully achieved.

Scope of review

This article briefly outlines the previously proposed hypotheses on the etiology of the HIR paradox. It then discusses literature consistent with an alternative hypothesis that excessive gluconeogenesis, the direct effect of HIR, is responsible for the aberrant lipogenesis. The mechanisms involved therein are explained, involving de novo synthesis of fructose and uric acid, promotion of glutamine anaplerosis, and induction of glucagon resistance. Thus, gluconeogenesis via lipogenesis promotes hepatic steatosis, a component of NAFLD, and dyslipidemia. Gluconeogenesis-centred mechanisms for the progression of NAFLD from simple steatosis to non-alcoholic steatohepatitis (NASH) and fibrosis are suggested. That NAFLD often precedes and predicts type 2 diabetes is explained by the ability of lipogenesis to cushion against blood glucose dysregulation in the earlier stages of NAFLD.

Major conclusions

HIR-induced excessive gluconeogenesis is a major cause of the HIR paradox and its sequelae. Such involvement of gluconeogenesis in lipid synthesis rationalizes the fact that several types of antidiabetic drugs ameliorate NAFLD. Thus, dietary, lifestyle and pharmacological targeting of HIR and hepatic gluconeogenesis may be a most viable approach for the prevention and management of the HIR-associated network of diseases.

Linseed Oil Attenuates Liver Inflammation, Fatty Acid Accumulation, and Lipid Distribution in Periportal and Perivenous Hepatocytes Induced by a High-Carbohydrate Diet in Mice

We evaluated whether linseed oil (LO) modulates the effects of a high-carbohydrate diet (HCD) on liver inflammation, fatty acid (FA) accumulation, and lipid distribution in periportal and perivenous hepatocytes. The control group (control high-carbohydrate diet [HCD-C]) received an HCD with lard and soybean oil as the lipid source. The L10 and L100 groups received the HCD with 10% and 100% of LO as the lipid source, respectively. The animals were killed by decapitation before (day 0) and after receiving the diets. Liver FA composition, inflammation, and fibrogenesis gene expression were evaluated. Also, the percentage of lipid-occupied area in periportal end perivenous hepatocytes were measured. The L100 group exhibited a higher (P < .05) liver amount of omega-3 polyunsaturated FA (n-3 PUFA) and lower (P < .05) amounts of saturated FA (SFA), monounsaturated FA (MUFA), and omega-6 polyunsaturated FA (n-6 PUFA) compared with L10 or HCD-C mice. On day 56, interleukin 10 and type IV collagen gene expression were significantly upregulated and downregulated, respectively in L100. Also, the L100 group showed lower (P < .05) FA accumulation (i.e., total FA, SFA, MUFA, and n-6 PUFA). Also, L10 and L100 presented lower (P < .05) percentage of high lipid-containing portion in periportal and perivenous hepatocytes. We concluded that LO attenuation of liver inflammation promoted by an HCD is associated with increased liver n-3 PUFA levels, so modulating FA composition, deposition, and distribution in periportal and perivenous hepatocytes.

Cardiovascular adverse events in chronic myeloid leukemia patients treated with nilotinib or imatinib: A systematic review, meta-analysis and integrative bioinformatics analysis

OBJECTIVE

The aim of this article is to assess the risk and potential mechanisms of cardiovascular adverse events in patients treated with nilotinib or imatinib by conducting a systematic review, meta-analysis and integrative bioinformatics analysis.

MATERIALS AND METHODS

Three databases were systematically searched for studies published from inception to May 29, 2022. Differential expression analysis and weighted gene coexpression network analysis (WGCNA) were performed to search for modules of genes most associated with cardiotoxicity. Protein-protein interaction (PPI) network analysis was then performed to identify hub genes for the cardiotoxicity of nilotinib. Molecular docking was used to analyze the effects of rosuvastatin and aspirin on these targets.

RESULTS

Patients treated with nilotinib as first-line treatment were associated with a higher risk of CAE (OR = 3.43 [95% CI 2.77-4.25]), CAD (OR = 5.30 [95% CI 3.85-7.29]), ACS (OR 2.7 [95% CI 1.60-4.54]), CVA (OR 5.76 [95% CI 2.84-11.28]), PAOD (OR 5.57 [95% CI 3.26-9.50]) and arrhythmia (OR 2.34 [1.17,4.67]) than those treated with imatinib, while no significant difference was found in the risk of HF (OR 1.40 [95% CI 0.42-4.69]) between the two groups. Patients who were treated with more than 600 mg daily dosage of nilotinib or followed up for more than 5 years had a higher risk of ACS and CVA. IL6, CXCL8, CCL2, SOD2, NFKBIA, and BIRC3 were identified as the top 6 hub genes in the magenta module (human cardiomyocyte samples) and were mainly enriched in the NOD-like receptor signaling pathway, IL-17 signaling pathway, TNF signaling pathway, lipid and atherosclerosis signaling pathway. TYROBP and CSF1R were identified as hub genes in the turquoise module (liver samples from Mus musculus). GSEA results showed that type II diabetes mellitus, B-cell receptor, apoptosis, insulin, natural killer cell mediated cytotoxicity,mTOR, chemokine, and T-cell receptor signaling pathways were related to the higher risk of atherosclerosis caused by nilotinib. Rosuvastatin can effectively bind to most of the hub targets and proteins enriched in the inflammatory pathways above.

CONCLUSION

CML patients who start with nilotinib have a higher risk of CAE than those with imatinib. Atherosclerosis caused by the inflammatory response and glycolipid metabolism disorder is the key mechanism of nilotinib cardiotoxicity. Rosuvastatin may be an effective treatment for the cardiotoxicity of nilotinib.

Transcriptome signature changes in the liver of a migratory passerine

The liver plays a principal role in avian migration. Here, we characterised the liver transcriptome of a long-distance migrant, the Northern Wheatear (Oenanthe oenanthe), sampled at different migratory stages, looking for molecular processes linked with adaptations to migration. The analysis of the differentially expressed genes suggested changes in the periods of the circadian rhythm, variation in the proportion of cells in G1/S cell-cycle stages and the putative polyploidization of this cell population. This may explain the dramatic increment in the liver's metabolic capacities towards migration. Additionally, genes involved in anti-oxidative stress, detoxification and innate immune responses, lipid metabolism, inflammation and angiogenesis were regulated. Lipophagy and lipid catabolism were active at all migratory stages and increased towards the fattening and fat periods, explaining the relevance of lipolysis in controlling steatosis and maintaining liver health. Our study clears the way for future functional studies regarding long-distance avian migration.

Aloe vera in diabetic dyslipidemia: Improving blood glucose and lipoprotein levels in pre-clinical and clinical studies

Dyslipidemia is a common feature of type 2 diabetes mellitus and is characterised by elevated triglyceride, decreased HDL cholesterol, and increased small dense LDL cholesterol levels. The underlying causes appears to be associated with insulin resistance, increased free fatty acid reflux, and low-grade inflammation, resulting in increased hepatic lipogenesis, and altered lipoprotein metabolism. Improved glycaemic control has been shown to have a positive effect on lipoprotein levels in diabetics. This can be achieved through medications/therapeutics and life style changes. Several classes of pharmacologic agents are currently in use to treat dyslipidemia. However, they may have dangerous long-term side effects, including an increased risk of liver dysfunction, weight gain, and cardiovascular diseases. Therefore, stronger alternatives with fewer side effects are required to reduce the diabetes associated complications. Many secondary plant metabolites have been shown to improve glucose homeostasis and lower lipid levels. Aloe vera and its constituents have long been used in a traditional medicine system for a diverse range of biological activities, including hypoglycaemic, antioxidant, anticarcinogenic, anti-inflammatory, and wound healing effects through various mechanisms and they have been covered well in literature. However, studies on the potential role of Aloe vera in the treatment of diabetic dyslipidemia are scanty. Therefore, in this systematic review, we focussed on the potential effect of Aloe vera and its active components in alleviating diabetic dyslipidemia, as well as their mechanism of action in pre-clinical and clinical studies.

The Myristic Acid:Docosahexaenoic Acid Ratio Versus the n-6 Polyunsaturated Fatty Acid:n-3 Polyunsaturated Fatty Acid Ratio as Nonalcoholic Fatty Liver Disease Biomarkers

It is well established that diets containing an increased omega-6 polyunsaturated fatty acid (n-6 PUFA) to omega-3 polyunsaturated fatty acid (n-3 PUFA) ratios are linked to inflammation and chronic diseases such as nonalcoholic fatty liver disease (NAFLD). However, the influence of an elevated n-6 PUFA:n-3 PUFA ratio in the tissues requires clarification. Herein, we identified primary experimental and clinical studies where it is possible to compare the performance of the myristic acid (Myr):docosahexaenoic acid (DHA) and n-6 PUFA:n-3 PUFA ratios in the liver and/or serum as potential NAFLD biomarkers. Articles were included if quantitative values of n-6 PUFA, n-3 PUFA, Myr, DHA, and information about liver inflammation or liver disease progression parameters were provided. Overall, most experimental (91.6%) and clinical studies (87.5%) reported higher Myr:DHA ratios associated with inflammation and/or NAFLD progression than the n-6 PUFA:n-3 PUFA ratio. We conclude that the Myr:DHA ratio represents a better biomarker of NAFLD than the n-6 PUFA:n-3 PUFA ratio. Future studies are necessary for verifying this observation.

Cardiometabolic Modification of Amyloid Beta in Alzheimer's Disease Pathology

In recent years, several studies have suggested that cardiometabolic disorders, such as diabetes, obesity, hypertension, and dyslipidemia, share strong connections with the onset of neurodegenerative disorders such as Parkinson's and Alzheimer's disease (AD). However, establishing a definitive link between medical disorders with coincident pathophysiologies is difficult due to etiological heterogeneity and underlying comorbidities. For this reason, amyloid β (Aβ), a physiological peptide derived from the sequential proteolysis of amyloid precursor protein (APP), serves as a crucial link that bridges the gap between cardiometabolic and neurodegenerative disorders. Aβ normally regulates neuronal synaptic function and repair; however, the intracellular accumulation of Aβ within the brain has been observed to play a critical role in AD pathology. A portion of Aβ is believed to originate from the brain itself and can readily cross the blood-brain barrier, while the rest resides in peripheral tissues that express APP required for Aβ generation such as the liver, pancreas, kidney, spleen, skin, and lungs. Consequently, numerous organs contribute to the body pool of total circulating Aβ, which can accumulate in the brain and facilitate neurodegeneration. Although the accumulation of Aβ corresponds with the onset of neurodegenerative disorders, the direct function of periphery born Aβ in AD pathophysiology is currently unknown. This review will highlight the contributions of individual cardiometabolic diseases including cardiovascular disease (CVD), type 2 diabetes (T2D), obesity, and non-alcoholic fatty liver disease (NAFLD) in elevating concentrations of circulating Aβ within the brain, as well as discuss the comorbid association of Aβ with AD pathology.

GLUT4 translocation in C2C12 myoblasts and primary mouse hepatocytes by an antihyperglycemic flavone from Tillandsia usneoides

BACKGROUND

Type 2 Diabetes (T2D) is characterized by deregulation in carbohydrate and lipid metabolism, with a very high mortality rate. Glucose Transporter type 4 (GLUT4) plays a crucial role in T2D and represents a therapeutic target of interest. Tillandsia usneoides (T. usneoides) is a plant used as a remedy for diabetes. T. usneoides decreased blood glucose in different experimental models. However, the involvement of GLUT4 in this effect has not yet been explored.

PURPOSE

This study aimed to investigate whether any component in T. usneoides might participate in the effect on blood glucose through a bioassay-guided fractionation, testing its potential antihyperglycemic effect in mice, as well as its influence on GLUT4 translocation in C2C12 myoblasts and primary hepatocytes.

METHODS

The aqueous extract and the Ethyl Acetate fraction (TU-AcOEt) of T. usneoides were evaluated in a hypoglycemic activity bioassay and in the glucose tolerance test in CD-1 mice. TU-AcOEt was fractionated, obtaining five fractions that were studied in an additional glucose tolerance test. C1F3 was fractioned again, and its fractions (C2F9-12, C2F22-25, and C2F38-44) were examined by HPLC. The C2F38-44 fraction was analyzed by Mass Spectrometry (MS) and subjected to additional fractionation. The fraction C3F6-9 was explored by Nuclear Magnetic Resonance (NMR), resulting in 5,7,4´-trihydroxy-3,6,3´,5´-tetramethoxyflavone (Flav1). Subsequently, a viability test was performed to evaluate the cytotoxic effect of Flav1 and fractions C2F9-12, C2F22-25. C2F38-44, and C3F30-41 in C2C12 myoblasts and primary mouse hepatocytes. Confocal microscopy was also performed to assess the effect of Flav1 and fractions on GLUT4 translocation.

RESULTS

The TU-AcOEt fraction exhibited a hypoglycemic and antihyperglycemic effect in mice, and its fractionation resulted in five fractions, among which fraction C1F3 decreased blood glucose. MS and NMR analysis revealed the presence of Flav1. Finally, Flav1 significantly promoted the translocation of GLUT4 in C2C12 myoblasts and primary hepatocytes.

CONCLUSION

To date, Flav1 has not been reported to have activity in GLUT4; this study provides evidence that T. usneoides is a plant with the potential to develop novel therapeutic agents for the control of T2D.

The Effect of a Lifestyle Intervention on Type 2 Diabetes Pathophysiology and Remission: The Stevenshof Pilot Study

Although lifestyle interventions can lead to diabetes remission, it is unclear to what extent type 2 diabetes (T2D) remission alters or improves the underlying pathophysiology of the disease. Here, we assess the effects of a lifestyle intervention on T2D reversal or remission and the effects on the underlying pathology. In a Dutch primary care setting, 15 adults with an average T2D duration of 13.4 years who were (pharmacologically) treated for T2D received a diabetes subtyping ("diabetyping") lifestyle intervention (DLI) for six months, aiming for T2D remission. T2D subtype was determined based on an OGTT. Insulin and sulphonylurea (SU) derivative treatment could be terminated for all participants. Body weight, waist/hip ratio, triglyceride levels, HbA1c, fasting, and 2h glucose were significantly improved after three and six months of intervention. Remission and reversal were achieved in two and three participants, respectively. Indices of insulin resistance and beta cell capacity improved, but never reached healthy values, resulting in unchanged T2D subtypes. Our study implies that achieving diabetes remission in individuals with a longer T2D duration is possible, but underlying pathology is only minimally affected, possibly due to an impaired beta cell function. Thus, even when T2D remission is achieved, patients need to continue adhering to lifestyle therapy.

Role of Insulin in Health and Disease: An Update

Insulin is a polypeptide hormone mainly secreted by β cells in the islets of Langerhans of the pancreas. The hormone potentially coordinates with glucagon to modulate blood glucose levels; insulin acts via an anabolic pathway, while glucagon performs catabolic functions. Insulin regulates glucose levels in the bloodstream and induces glucose storage in the liver, muscles, and adipose tissue, resulting in overall weight gain. The modulation of a wide range of physiological processes by insulin makes its synthesis and levels critical in the onset and progression of several chronic diseases. Although clinical and basic research has made significant progress in understanding the role of insulin in several pathophysiological processes, many aspects of these functions have yet to be elucidated. This review provides an update on insulin secretion and regulation, and its physiological roles and functions in different organs and cells, and implications to overall health. We cast light on recent advances in insulin-signaling targeted therapies, the protective effects of insulin signaling activators against disease, and recommendations and directions for future research.

Differential insulin sensitivity of NMR-based metabolomic measures in a two-step hyperinsulinemic euglycemic clamp study

BACKGROUND

Insulin is the key regulator of glucose metabolism, but it is difficult to dissect direct insulin from glucose-induced effects. We aimed to investigate the effects of hyperinsulemia on metabolomic measures under euglycemic conditions in nondiabetic participants.

METHODS

We assessed concentrations of 151 metabolomic measures throughout a two-step hyperinsulinemic euglycemic clamp procedure. We included 24 participants (50% women, mean age = 62 [s.d. = 4.2] years) and metabolomic measures were assessed under baseline, low-dose (10 mU/m²/min) and high-dose (40 mU/m²/min) insulin conditions. The effects of low- and high-dose insulin infusion on metabolomic measures were analyzed using linear mixed-effect models for repeated measures.

RESULTS

After low-dose insulin infusion, 90 metabolomic measures changed in concentration (p < 1.34e^-4), among which glycerol (beta [Confidence Interval] =  - 1.41 [- 1.54, - 1.27] s.d., p = 1.28e^-95) and three-hydroxybutyrate (- 1.22 [- 1.36, - 1.07] s.d., p = 1.44e^-61) showed largest effect sizes. After high-dose insulin infusion, 121 metabolomic measures changed in concentration, among which branched-chain amino acids showed the largest additional decrease compared with low-dose insulin infusion (e.g., Leucine, - 1.78 [- 1.88, - 1.69] s.d., P = 2.7e^-295). More specifically, after low- and high-dose insulin infusion, the distribution of the lipoproteins shifted towards more LDL-sized particles with decreased mean diameters.

CONCLUSION

Metabolomic measures are differentially insulin sensitive and may thus be differentially affected by the development of insulin resistance. Moreover, our data suggests insulin directly affects metabolomic measures previously associated with increased cardiovascular disease risk.

Role of Chitinase 3-Like 1 Protein in the Pathogenesis of Hepatic Insulin Resistance in Nonalcoholic Fatty Liver Disease

A recently discovered human glycoprotein, chitinase 3-like 1 (Chi3L1), may play a role in inflammation, tissue remodeling, and visceral fat accumulation. We hypothesize that Chi3L1 gene expression is important in the development of hepatic insulin resistance characterized by the generation of pAKT, pGSK, and pERK in wild type and Chi3L1 knockout (KO) murine liver following insulin stimulation. The Chi3L1 gene and protein expression was evaluated by Real Time PCR and ELISA; lipid accumulation in hepatocytes was also assessed. To alter Chi3L1 function, three different anti-Chi3L1 monoclonal antibodies (mAbs) were administered in vivo and effects on the insulin signaling cascade and hepatic lipid deposition were determined. Transmission of the hepatic insulin signal was substantially improved following KO of the CHi3L1 gene and there was reduced lipid deposition produced by a HFD. The HFD-fed mice exhibited increased Chi3L1 expression in the liver and there was impaired insulin signal transduction. All three anti-Chi3L1 mAbs partially restored hepatic insulin sensitivity which was associated with reduced lipid accumulation in hepatocytes as well. A KO of the Chi3L1 gene reduced lipid accumulation and improved insulin signaling. Therefore, Chi3L1 gene upregulation may be an important factor in the generation of NAFLD/NASH phenotype.

Glycerol Potentiates the Effects of Glucose in Promoting Glucose Recovery During Hypoglycemia: From Basic to Clinical Investigations and Their Therapeutic Application

We compared the effect of oral glucose versus oral glucose combined with glycerol (glucose + glycerol) in promoting glucose recovery during hypoglycemia. These studies were carried out in two series of experiments. In the first series of experiments, 16 overnight fasted rats received an intraperitoneal injection of lispro insulin (1 IU/kg), and 25 min later, they received oral water (control), glucose (0.25 g/kg), glycerol (2.5 g/kg), or glucose (0.25 g/kg) + glycerol (2.5 g/kg). In the second series of experiments on 164 eligible type 1 diabetic (T1D) patients, 30 individuals with a history of hypoglycemia were recruited. Five volunteers did not meet the inclusion criteria and two subjects were excluded after starting the clinical investigation; 23 patients concluded the study. All patients with symptoms of hypoglycemia ingested oral glucose (15 g) or glucose (15 g) + glycerol (9.45 g). To treat hypoglycemia in T1D patients, preparations containing glucose alone or glucose + glycerol were used alternately (2 weeks/2 weeks) in a double-blind crossover scheme. Throughout the clinical research (4 weeks), glucose concentrations were assessed with a continuous glucose monitoring device and the results after the use of glucose alone or glucose + glycerol preparations were compared. Oral glucose combined with glycerol was more effective in promoting glucose recovery in comparison with glucose alone, not only in rats but also in T1D patients. Taken together, our experimental and clinical investigations reported the best performance of oral administration of glucose + glycerol in comparison with isolated glucose.

Proteome and phosphoproteome characterization of liver in the postprandial state from diet-induced obese and lean mice

A metabolic consequence of obesity is hepatosteatosis, which can develop into more serious diseases in the non-alcoholic fatty liver disease (NAFLD) spectrum. The goal of this study was to identify the protein signature of liver in the postprandial state in obesity compared to leanness. The postprandial state is of interest due to the central role of the liver in regulating macronutrient and energy homeostasis during the fed-fast cycle and lack of previously reported controlled studies in the postprandial state. Therefore, we assessed the proteome and phosphoproteome of liver in the postprandial state from diet-induced obese (DIO) and lean mice using untargeted LC-MS/MS analysis. We identified significant alterations in the levels of proteins involved in fatty acid oxidation, activation, and transport, as well as proteins involved in energy metabolism including ketogenesis, tricarboxylic acid cycle, and electron transport chain in liver of DIO compared to lean mice. Additionally, phosphorylated proteins in liver of DIO and lean mice reflect possible regulatory mechanisms controlling fatty acid metabolism and gene expression that may contribute to hepatic metabolic alterations in obesity. Our data indicates PPARα-mediated transcriptional regulation of lipid metabolism and adaptation to hepatic lipid overload. The results of this study expand our knowledge of the molecular changes that occur in liver in the postprandial state in obesity compared to leanness. SIGNIFICANCE: Proteome and phosphoproteome studies of liver in a controlled postprandial state in obesity and leanness are lacking; however, this information is crucial to understanding how obesity-associated hepatosteatosis influences postprandial nutrient and energy metabolism. In this global shotgun proteome and phosphoproteome analysis, we identified unique protein signatures defining obesity and leanness in liver in the postprandial state and identified potential mechanisms contributing to hepatic metabolic alterations in obesity. The results of this study provide a foundation to focus future experiments on the contribution of altered protein and phosphorylation patterns to postprandial metabolism in obesity-associated hepatosteatosis.

Postprandial NMR-Based Metabolic Exchanges Reflect Impaired Phenotypic Flexibility across Splanchnic Organs in the Obese Yucatan Mini-Pig

The postprandial period represents one of the most challenging phenomena in whole-body metabolism, and it can be used as a unique window to evaluate the phenotypic flexibility of an individual in response to a given meal, which can be done by measuring the resilience of the metabolome. However, this exploration of the metabolism has never been applied to the arteriovenous (AV) exploration of organs metabolism. Here, we applied an AV metabolomics strategy to evaluate the postprandial flexibility across the liver and the intestine of mini-pigs subjected to a high fat–high sucrose (HFHS) diet for 2 months. We identified for the first time a postprandial signature associated to the insulin resistance and obesity outcomes, and we showed that the splanchnic postprandial metabolome was considerably affected by the meal and the obesity condition. Most of the changes induced by obesity were observed in the exchanges across the liver, where the metabolism was reorganized to maintain whole body glucose homeostasis by routing glucose formed de novo from a large variety of substrates into glycogen. Furthermore, metabolites related to lipid handling and energy metabolism showed a blunted postprandial response in the obese animals across organs. Finally, some of our results reflect a loss of flexibility in response to the HFHS meal challenge in unsuspected metabolic pathways that must be further explored as potential new events involved in early obesity and the onset of insulin resistance.

Reversal of obesity and liver steatosis in mice via inhibition of aryl hydrocarbon receptor and altered gene expression of CYP1B1, PPARα, SCD1, and osteopontin

BACKGROUND/OBJECTIVES

Obesity is a global epidemic and the underlying basis for numerous comorbidities. We report that the aryl hydrocarbon receptor (AHR) plays a key role in the metabolism of obesity. The AHR is a promiscuous, ligand-activated nuclear receptor primarily known for regulating genes involved in xenobiotic metabolism and T cell polarization. The aims of the work reported here were to understand the underlying mechanism of AHR-based obesity and to determine whether inhibition of AHR activity would reverse obesity.

METHODS

Mice were fed control (low fat) and Western (high fat) diets with and without the AHR antagonist alpha-naphthoflavone (aNF). Gene expression of identified AHR-regulated genes from liver and adipose tissue was characterized. To determine the role of the AHR in obesity reversal, selected mice in control and Western diet regimens were switched at midpoint to the respective control and Western diets containing aNF, and the identified AHR-regulated genes characterized.

RESULTS

AHR inhibition prevented obesity in mice on a 40-week diet regimen. The likely AHR-regulated and cross-regulated downstream effectors of AHR-based obesity were shown to be CYP1B1, PPARα-target genes, SCD1, and SPP1 (osteopontin). Western diet caused an increase of mRNA and protein expression of the Cyp1b1, Scd1, and Spp1, and PPARα-target genes in the liver, and inhibition of the AHR maintained expression of these genes near control levels. The body weight of obese mice on Western diet switched to Western diet containing aNF decreased to that of mice on control diet concurrently with a reduction in the expression of liver CYP1B1, PPARα-target genes, SCD1, and SPP1. AHR inhibition prevented hypertrophy and hyperplasia in visceral adipose tissue and limited expression levels of CYP1B1 and SPP1 to that of mice on control diet.

CONCLUSIONS

AHR inhibition prevents and reverses obesity by likely reducing liver expression of the Cyp1b1, Scd1, Spp1, and PPARα-target genes; and the AHR is a potentially potent therapeutic target for the treatment and prevention of obesity and linked diseases.

RNA-Seq analysis of the pathogenesis of STZ-induced male diabetic mouse liver

OBJECTIVE

Diabetes mellitus (DM) is a chronic disease characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. The liver is a key organ involved in glucose metabolism, and the major target proteins' changes in the pathogenesis are still unknown.

METHODS

A diabetic mouse model was induced by intraperitoneal injection of streptozotocin (STZ) solution and the RNA-Seq analysis was used to evaluate the transcription differences in the livers of diabetic mice of this study. And then, the differentially expressed genes were validated between a normal mouse group (n = 6) and a diabetic mouse group (n = 6) using quantitative real-time PCR (qRT-PCR) and Western blotting analysis. In addition, we also constructed protein-protein interacting (PPI) networks of up-regulated and down-regulated genes.

RESULTS

Transcriptome sequencing analysis revealed 370 up-regulated differentially expressed genes and 281 down-regulated differentially expressed genes in the diabetes model. The gene ontology (GO) analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis results showed that the differentially expressed genes were mainly involved in immunity, enzyme activity, metabolism, and steroid synthesis. PPI analysis results indicated that the main 15 core differential proteins (Cyp51a1, Acsl4, Ugt1a1, Stat1, Gsta2, Cbr1, Aldh1a1, Fasn, Ces1, Camk2b, Tap1, Egr1, Sqle, Lpin1, Fabp5) were involved in the pathogenesis of diabetes. The qRT-PCR results showed that expression changes of four genes (Acsl4, Stat1, Gsta2, Fabp5) were in different directions from those of RNA-Seq. Western blotting results indicated that Sqle expression change at the protein level was in opposition direction from qRT-PCR, and we speculated that Sqle may be involved in the post-transcriptional modification process.

CONCLUSIONS

Our data speculated that the pathogenesis of diabetes may be mediated mainly through steroid biosynthesis, metabolic processes, and immune responses. Further researches on these pathways may provide new targets for the prevention and treatment of diabetes.

PFKFB3, a key glucose metabolic enzyme regulated by pathogen recognition receptor TLR4 in liver cells

AIMS

Toll-like receptor 4 (TLR4) and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB3) are involved in the progress of inflammation and glucose metabolism. Here, we aimed to assess the relationship between TLR4 and PFKFB3 in liver cells.

METHODS

We detected the expression of TLR4 and PFKFB3 in both normal liver cell lines and liver cancer cell lines. Then, a small interfering RNA (siRNA) was used to knock down the expression of TLR4 and analyze the expression of PFKFB3 in the HL-7702 cell line. Further, following stimulation of the HL-7702 cell line with free fatty acids (FFA) or insulin, we observed the expression of TLR4 and PFKFB3, respectively.

RESULTS

Knocking down siRNA-mediated TLR4 significantly reduced PFKFB3 expression at the mRNA and protein level. Furthermore, activating TLR4 with FFA dramatically increased PFKFB3 expression. Insulin increased the expression of TLR4 and PFKFB3, which could be inhibited by TLR siRNA.

CONCLUSION

These findings suggest that PFKFB3 expression is regulated via the TLR4-PFKFB3 axis, which might be a bridge linking fat and glucose metabolism.

d- chiro-Inositol Ameliorates High Fat Diet-Induced Hepatic Steatosis and Insulin Resistance via PKCε-PI3K/AKT Pathway

d- chiro-Inositol (DCI) is a biologically active component found in tartary buckwheat, which can reduce hyperglycemia and ameliorate insulin resistance. However, the mechanism underlying the antidiabetic effects of DCI remains largely unclear. This study investigated the effects and underlying molecular mechanisms of DCI on hepatic gluconeogenesis in mice fed a high fat diet and saturated palmitic acid-treated hepatocytes. DCI attenuated free fatty acid uptake by the liver via lipid trafficking inhibition, reduced diacylglycerol deposition, and hepatic PKCε translocation. Thus, DCI could improve insulin sensitivity by suppressing hepatic gluconeogenesis. Subsequent analyses revealed that DCI decreased hepatic glucose output and the expression levels of PEPCK and G6 Pase in insulin resistant mice through PKCε-IRS/PI3K/AKT signaling pathway. Likewise, such effects of DCI were confirmed in HepG2 cells with palmitate-induced insulin resistance. These findings indicate a novel pathway by which DCI prevents hepatic gluconeogenesis, reduces lipid deposition, and ameliorates insulin resistance via regulation of PKCε-PI3K/AKT axis.

Biological function of dipeptidyl peptidase-4 on type 2 diabetes patients and diabetic mice

BACKGROUND

Type 2 diabetes (TD2) is a sustained metabolic disorder, characterized by high blood glucose, insulin resistance (IR). Dipeptidyl peptidase-4 (DPP4) functions as an antigenic enzyme involved in hyperglycaemia, oxidative stress, and inflammation-associated IR. Therefore, association between DPP4 and TD2 warrants to be investigated.

METHODS

In this study, blood samples of clinically diagnosed TD2 patients were harvested for biochemical tests. In addition, diabetic mice induced by high-fat diet (HFD) and single dose of streptozotocin (STZ) were used to assess the biological characteristics of DPP4 through biochemical and enzyme-linked immunosorbent assay (ELISA) tests, immunofluorescence staining, and western blot assay.

RESULTS

Compared to controls, the clinical data of patients with TD2 resulted in increased contents of fasting blood glucose (FBG), glycated hemoglobin (HbA1c), homeostatic model assessment (HOMA)-IR, blood lipids of triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL-C), and interleukin 6 (IL6) in plasma samples (p < 0.05). Notably, blood levels of DPP4 in TD2 patients were increased significantly in comparison to that in non-diabetic adults (p < 0.01). In animal study, diabetic mice showed increased levels of glucose, insulin, lipids, DPP4 activity in sera. Visibly, hepatocellular DPP4 expression was up-regulated in diabetic mice. Interestingly, DPP4 inhibitor-treated mice showed significantly reduced DPP4 expression in serum (p < 0.01), and lowered DPP4-positive cells and protein content in the liver were observed when compared to those in diabetic mice (p < 0.01).

CONCLUSIONS

Collectively, these findings reveal that DPP4 biomolecule may be positively associated with TD2 development, and the underlying mechanism may be attributed to activation of DPP4 expression in liver cells.

Asthma alleviates obesity in males through regulating metabolism and energy expenditure

Many epidemiological studies suggested a correlation between obesity and asthma. However, little is known about the molecular details explaining this correlation. Here, we show that asthma decreased body weight of asthmatic male mice fed with high fat diet via increasing energy expenditure and insulin sensitivity. The increase of energy expenditure was mainly due to upregulation of pAMPK and Sirt1. The activation of AMPK/Sirt1/PGC1α signaling promoted the expression of the thermogenic genes like ucp1, PRDM16, cidea, Elovl3, PPARα, which occurred in brown adipocyte tissue and subcutaneous white adipose tissue. Besides, by activating IL33/ILC2/AAMac pathway in subcutaneous white adipose tissue, asthma promoted subcutaneous white adipose tissue into beige fat. In addition, insulin sensitivity was improved in the asthmatic male mice by decreasing the expression of G6Pase in the liver, which was recapitulated in HepG2. In human, we found that Body Mass Index (BMI) and waist circumference were significantly lower in males suffering asthma compared with the control in the National Health and Nutrition Examination Survey (NHANES) cohort. These data together suggest asthma in males decreases obesity by improving the metabolism function of brown and subcutaneous adipose tissue, and decreasing insulin resistant in the liver.

Brain Fatty Acid Composition and Inflammation in Mice Fed with High-Carbohydrate Diet or High-Fat Diet

Both high fat diet (HFD) and high carbohydrate diet (HCD) modulate brain fatty acids (FA) composition. Notwithstanding, there is a lack of information on time sequence of brain FA deposition either for HFD or HCD. The changes in brain FA composition in mice fed with HFD or HCD for 7, 14, 28, or 56 days were compared with results of 0 (before starting given the diets). mRNA expressions of allograft inflammatory factor 1 (Aif1), cyclooxygenase-2 (Cox 2), F4/80, inducible nitric oxide synthase (iNOS), integrin subunit alpha m (Itgam), interleukin IL-1β (IL-1β), IL-6, IL-10, and tumor necrosis factor alpha (TNF-α) were measured. The HFD group had higher speed of deposition of saturated FA (SFA), monounsaturated FA (MUFA), and polyunsaturated FA (PUFA) at the beginning of the experimental period. However, on day 56, the total amount of SFA, MUFA, and PUFA were similar. mRNA expressions of F4/80 and Itgam, markers of microglia infiltration, were increased (p < 0.05) in the brain of the HCD group whereas inflammatory marker index (IMI) was higher (46%) in HFD group. In conclusion, the proportion of fat and carbohydrates in the diet modulates the speed deposition of FA and expression of inflammatory gene markers.

Sea cucumber saponin liposomes ameliorate obesity-induced inflammation and insulin resistance in high-fat-diet-fed mice

Liposomes proved to be a good form for the intake of sea cucumber saponins, which exhibited better bioactivity in preventing diseases related to metabolic syndrome.

Pharmacological evaluation of metformin and N-benzylbiguanide, a novel analogue of metformin, on the vasopressor responses to adrenergic system stimulation in pithed rats with fructose-induced insulin resistance

Metformin has been associated with cardioprotection, vasorelaxation and normalization of endothelial function during type 2 Diabetes Mellitus. However, few studies have analysed its effects on vascular adrenergic system. Our study has evaluated the vasopressor responses induced by sympathetic stimulation or by i.v. bolus injections of the agonists noradrenaline (α_1/2), methoxamine (α₁) and UK 14,304 (α₂) in rats with fructose-induced insulin resistance chronically pretreated with either metformin or EGL-6M (N-benzylbiguanide), a novel analogue of metformin. Rats were treated with fructose (15%) or tap water (control) during 16 weeks. Next, both groups were treated daily during 4 weeks with: (1) vehicle; (2) metformin (50mg/kg); or (3) EGL-6M (50mg/kg). Blood glucose and plasma insulin were determined before and after administration of glucose during oral glucose tolerance test. Animals treated with fructose showed hyperinsulinemia and insulin resistance, which were decreased by metformin and EGL-6M. In animals treated with fructose, the vasopressor responses induced by: (1) sympathetic stimulation were decreased; (2) noradrenaline were increased; and (3) methoxamine and UK 14,304 remained unaffected compared with control group. In control animals, metformin failed to modify the vasopressor responses analysed, while EGL-6M increased the vasopressor responses to sympathetic stimulation. In rats treated with fructose, metformin decreased vasopressor response to noradrenaline but did not modify the sympathetic stimulation responses. EGL-6M increased the vasopressor responses to sympathetic stimulation without modifying those to noradrenaline, methoxamine or UK 14,304. Collectively, these data suggest that EGL-6M is capable to increase insulin sensitivity and the vasopressor sympathetic outflow in rats.

l-Glutamine supplementation promotes an improved energetic balance in Walker-256 tumor-bearing rats

We evaluated the effects of supplementation with oral l-glutamine in Walker-256 tumor-bearing rats. A total of 32 male Wistar rats aged 54 days were randomly divided into four groups: rats without Walker-256 tumor, that is, control rats (C group); control rats supplemented with l-glutamine (CG group); Walker-256 tumor rats without l-glutamine supplementation (WT group); and WT rats supplemented with l-glutamine (WTG group). l-Glutamine was incorporated into standard food at a proportion of 2 g/100 g (2%). After 10 days of the experimental period, the jejunum and duodenum were removed and processed. Protein expression levels of key enzymes of gluconeogenesis, that is, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase, were analyzed by western blot and immunohistochemical techniques. In addition, plasma corticosterone, glucose, insulin, and urea levels were evaluated. The WTG group showed significantly increased plasma glucose and insulin levels ( p < 0.05); however, plasma corticosterone and urea remained unchanged. Moreover, the WTG group showed increased immunoreactive staining for jejunal phosphoenolpyruvate carboxykinase and increased expression of duodenal glucose-6-phosphatase. Furthermore, the WTG group presented with less intense cancer cachexia and slower tumor growth. These results could be attributed, at least partly, to increased intestinal gluconeogenesis and insulinemia, and better glycemia maintenance during fasting in Walker-256 tumor rats on a diet supplemented with l-glutamine.

Insulin, not glutamine dipeptide, reduces lipases expression and prevents fat wasting and weight loss in Walker 256 tumor-bearing rats

Cachexia is the main cause of mortality in advanced cancer patients. We investigated the effects of insulin (INS) and glutamine dipeptide (GDP), isolated or associated, on cachexia and metabolic changes induced by Walker 256 tumor in rats. INS (NPH, 40 UI/kg, sc) or GDP (1.5g/kg, oral gavage) was once-daily administered during 11 days after tumor cell inoculation. GDP, INS or INS+GDP treatments did not influence the tumor growth. However, INS and INS+GDP prevented retroperitoneal fat wasting and body weight loss of tumor-bearing rats. In consistency, INS and INS+GDP prevented the increased expression of triacylglycerol lipase (ATGL) and hormone sensitive lipase (HSL), without changing the expression of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) in the retroperitoneal adipose tissue of tumor-bearing rats. INS and INS+GDP also prevented anorexia and hyperlactatemia of tumor-bearing rats. However, INS and INS+GDP accentuated the loss of muscle mass (gastrocnemius, soleus and long digital extensor) without affecting the myostatin expression in the gastrocnemius muscle and blood corticosterone. GDP treatment did not promote beneficial effects. It can be concluded that treatment with INS (INS or INS+GDP), not with GDP, prevented fat wasting and weight loss in tumor-bearing rats without reducing tumor growth. These effects might be attributed to the reduction of lipases expression (ATGL and LHS) and increased food intake. The results show the physiological function of INS in the suppression of lipolysis induced by cachexia mediators in tumor-bearing rats.

Liver Fatty Acid Composition and Inflammation in Mice Fed with High-Carbohydrate Diet or High-Fat Diet

Both high-carbohydrate diet (HCD) and high-fat diet (HFD) modulate liver fat accumulation and inflammation, however, there is a lack of data on the potential contribution of carbohydrates and lipids separately. For this reason, the changes in liver fatty acid (FA) composition in male Swiss mice fed with HCD or HFD were compared, at the time points 0 (before starting the diets), and after 7, 14, 28 or 56 days. Activities of stearoyl-CoA desaturase-1 (SCD-1), ∆-6 desaturase (D6D), elongases and de novo lipogenesis (DNL) were estimated. Liver mRNA expression of acetyl-CoA carboxylase 1 (ACC1) was evaluated as an additional indicator of the de novo lipogenesis. Myeloperoxidase activity, nitric oxide (NO) production, and mRNA expressions of F4/80, type I collagen, interleukin (IL)-6, IL-1β, IL-10, and tumor necrosis factor-α (TNF-α) were measured as indication of the liver inflammatory state. The HCD group had more intense lipid deposition, particularly of saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs). This group also showed higher DNL, SCD-1, and D6D activities associated with increased NO concentration, as well as myeloperoxidase activity. Livers from the HFD group showed higher elongase activity, stored more polyunsaturated fatty acids (PUFAs) and had a lower omega-6/omega-3 fatty acid (n-6/n-3) ratio. In conclusion, liver lipid accumulation, fatty acids (FA) composition and inflammation were modulated by the dietary composition of lipids and carbohydrates. The HCD group had more potent lipogenic and inflammatory effects in comparison with HFD.

Aquaporins and Fetal Membranes From Diabetic Parturient Women: Expression Abnormalities and Regulation by Insulin

CONTEXT

During pregnancy, aquaporins (AQPs) expressed in fetal membranes are essential for controlling the homeostasis of the amniotic volume, but their regulation by insulin was never explored in diabetic women.

OBJECTIVE

The aim of our study was to investigate the involvement of AQPs 1, 3, 8, and 9 expressed in fetal membranes in diabetic parturient women and the control of their expression by insulin.

DESIGN AND PARTICIPANTS

From 129 fetal membranes in four populations (controls, type 1, type 2 [T2D], and gestational diabetes [GD]), we established an expression AQP profile. In a second step, the amnion was used to study the control of the expression and functions of AQPs 3 and 9 by insulin.

MAIN OUTCOMES AND MEASURES

The expression of transcripts and proteins of AQPs was studied by quantitative RT-PCR and ELISA. We analyzed the regulation by insulin of the expression of AQPs 3 and 9 in the amnion. A tritiated glycerol test enabled us to measure the impact of insulin on the functional characteristics. Using an inhibitor of phosphatidylinositol 3-kinase, we analyzed the insulin intracellular signaling pathway.

RESULTS

The expression of AQP3 protein was significantly weaker in groups T2D and GD. In nondiabetic fetal membranes, we showed for the amnion (but not for the chorion) a significant repression by insulin of the transcriptional expression of AQPs 3 and 9, which was blocked by a phosphatidylinositol 3-kinase inhibitor.

CONCLUSION

In fetal membranes, the repression of AQP3 protein expression and functions observed in vivo is allowed by the hyperinsulinism described in pregnant women with T2D or GD.