Amphiregulin from regulatory T cells promotes liver fibrosis and insulin resistance in non-alcoholic steatohepatitis.

Production of amphiregulin (Areg) by regulatory T (Treg) cells promotes repair after acute tissue injury. Here, we examined the function of Treg cells in non-alcoholic steatohepatitis (NASH), a setting of chronic liver injury. Areg-producing Treg cells were enriched in the livers of mice and humans with NASH. Deletion of Areg in Treg cells, but not in myeloid cells, reduced NASH-induced liver fibrosis. Chronic liver damage induced transcriptional changes associated with Treg cell activation. Mechanistically, Treg cell-derived Areg activated pro-fibrotic transcriptional programs in hepatic stellate cells via epidermal growth factor receptor (EGFR) signaling. Deletion of Areg in Treg cells protected mice from NASH-dependent glucose intolerance, which also was dependent on EGFR signaling on hepatic stellate cells. Areg from Treg cells promoted hepatocyte gluconeogenesis through hepatocyte detection of hepatic stellate cell-derived interleukin-6. Our findings reveal a maladaptive role for Treg cell-mediated tissue repair functions in chronic liver disease and link liver damage to NASH-dependent glucose intolerance.

Effect of Low-Dose Progesterone on Glycemic Metabolism, Morphology and Function of Adipose Tissue and Pancreatic Islets in Diet-Induced Obese Female Mice.

BACKGROUND: Obesity is a worldwide concern due to its global rapid expansion and remarkable impact on individual's health by predisposing to several other diseases. About twice as many women as men suffer from severe obesity and, in fact, there are stages in a woman's life when weight gain and adiposity can result in greater damage to health. For example, obesity triples the chance of a woman developing gestational diabetes. Many hormones promote the metabolic adaptations of pregnancy, including progesterone, whose role in female obesity is still not well known despite being involved in many physiological and pathological processes. METHODS: Here we investigated whether progesterone treatment at low dose can worsen the glucose metabolism and the morpho functional aspects of adipose tissue and pancreas in obese females. Mice were assigned into four groups: normocaloric diet control (NO-CO), high-fat and -fructose diet control (HFF-CO), normocaloric diet plus progesterone (NO-PG) and high-fat and -fructose diet plus progesterone (HFF-PG) for 10 weeks. Infusion of progesterone (0.25 mg/kg/day) was done by osmotic minipump in the last 21 days of protocol. RESULTS: Animals fed a hypercaloric diet exhibited obesity with increased body weight (p < 0.0001), adipocyte hypertrophy (p < 0.0001), hyperglycemia (p = 0.03), and glucose intolerance (p = 0.001). HFF-CO and HFF-PG groups showed lower adiponectin concentration (p < 0.0001) and glucose-stimulated insulin secretion (p = 0.03), without differences in islet size. Progesterone attenuated glucose intolerance in the HFF-PG group (p = 0.03), however, did not change morphology or endocrine function of adipose tissue and pancreatic islets. CONCLUSIONS: Taken together, our results showed that low dose of progesterone does not worsen the effects of hypercaloric diet in glycemic metabolism, morphology and function of adipose tissue and pancreatic islets in female animals. These results may improve the understanding of the mechanisms underlying the pathogenesis of obesity in women and eventually open new avenues for therapeutic strategies and better comprehension of the interactions between progesterone effects and obesity.

Estradiol Protects Female ApoE KO Mice against Western-Diet-Induced Non-Alcoholic Steatohepatitis.

The prevalence of non-alcoholic fatty liver disease (NAFLD) and its severe form, non-alcoholic steatohepatitis (NASH), is higher in men than in women of reproductive age, and postmenopausal women are especially susceptible to developing the disease. AIM: we evaluated if female apolipoprotein E (ApoE) KO mice were protected against Western-diet (WD)-induced NASH. METHODS: Female ovariectomized (OVX) ApoE KO mice or sham-operated (SHAM) mice were fed either a WD or a regular chow (RC) for 7 weeks. Additionally, OVX mice fed a WD were treated with either estradiol (OVX + E2) or vehicle (OVX). RESULTS: Whole-body fat, plasma glucose, and plasma insulin were increased and associated with increased glucose intolerance in OVX mice fed a WD (OVX + WD). Plasma and hepatic triglycerides, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) hepatic enzymes were also increased in the plasma of OVX + WD group, which was associated with hepatic fibrosis and inflammation. Estradiol replacement in OVX mice reduced body weight, body fat, glycemia, and plasma insulin associated with reduced glucose intolerance. Treatment also reduced hepatic triglycerides, ALT, AST, hepatic fibrosis, and inflammation in OVX mice. CONCLUSIONS: These data support the hypothesis that estradiol protects OVX ApoE KO mice from NASH and glucose intolerance.

Fetal growth restriction followed by early catch-up growth impairs pancreatic islet morphology in male rats.

Fetal growth restriction (FGR), followed by postnatal early catch-up growth, is associated with an increased risk of metabolic dysfunction, including type 2 diabetes in humans. This study aims to determine the effects of FGR and early catch-up growth after birth on the pathogenesis of type 2 diabetes, with particular attention to glucose tolerance, pancreatic islet morphology, and fibrosis, and to elucidate its mechanism using proteomics analysis. The FGR rat model was made by inducing mild intrauterine hypoperfusion using ameroid constrictors (ACs). On day 17 of pregnancy, ACs were affixed to the uterine and ovarian arteries bilaterally, causing a 20.9% reduction in birth weight compared to sham pups. On postnatal day 4 (P4), the pups were assigned to either the good nutrition (GN) groups with 5 pups per dam to ensure postnatal catch-up growth or poor nutrition groups with 15 pups per dam to maintain lower body weight. After weaning, all pups were fed regular chow food ad libitum (P21). Rats in both FGR groups developed glucose intolerance; however, male rats in the FGR good nutrition (FGR-GN) group also developed hypertriglyceridemia and dysmorphic pancreatic islets with fibrosis. A comprehensive and functional analysis of proteins expressed in the pancreas showed that FGR, followed by early catch-up growth, severely aggravated cell adhesion-related protein expression in male offspring. Thus, FGR and early catch-up growth caused pancreatic islet morphological abnormalities and fibrosis associated with the disturbance of cell adhesion-related protein expressions. These changes likely induce glucose intolerance and dyslipidemia in male rats.

Cotadutide effect in liver and adipose tissue in obese mice.

Obesity, adipose tissue inflammation, and nonalcoholic fatty liver disease (NAFLD) are associated with insulin resistance and type 2 diabetes (T2D). Cotadutide is a dual agonist GLP-1/glucagon, currently in a preclinical study phase 2 that presents an anti-obesity effect. Diet-induced obese (DIO) C57BL/6 mice were treated for 4 weeks with cotadutide (30 nm/kg once a day at 14:00 h). The study focused on epididymal white adipose tissue (eWAT), liver (NAFLD), inflammation, lipid metabolism, AMP-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR) pathways, and the endoplasmic reticulum (ER) stress. As a result, cotadutide controlled weight gain, glucose intolerance, and insulin resistance and showed beneficial effects on plasma markers in DIO mice (triacylglycerol, total cholesterol, alanine aminotransferase, and aspartate aminotransferase, leptin, adiponectin, monocyte chemoattractant protein-1, resistin, interleukin-6, tumor necrosis factor-alpha). Also, cotadutide lessened liver fat accumulation, eWAT proinflammatory markers, and ER stress. In addition, cotadutide improved lipid metabolism genes in eWAT, fatty acid synthase, peroxisome proliferator-activated receptor gamma and mitigates adipocyte hypertrophy and apoptosis. Furthermore, the effects of cotadutide were related to liver AMPK/mTOR pathway and ER stress. In conclusion, cotadutide induces weight loss and treats glucose intolerance and insulin resistance in DIO mice. In addition, cotadutide shows beneficial effects on liver lipid metabolism, mitigating steatosis, inflammation, and ER stress. Besides, in adipocytes, cotadutide decreases hypertrophy and reduces apoptosis. These actions rescuing the AMPK and mTOR pathway, improving lipid metabolism, and lessening NAFLD, inflammation, and ER stress in both eWAT and liver of DIO mice indicate cotadutide as a potentially new pharmacological treatment for T2D and associated obesity.

Lifestyle-, environmental-, and additional health factors associated with an increased sperm DNA fragmentation: a systematic review and meta-analysis.

INTRODUCTION: Infertility affects one in every six couples in developed countries, and approximately 50% is of male origin. In 2021, sperm DNA fragmentation (SDF) testing became an evidence-based test for fertility evaluations depicting fertility more clearly than standard semen parameters. Therefore, we aimed to summarize the potential prognostic factors of a higher SDF. METHODS: We conducted a systematic search in three medical databases and included studies investigating any risk factors for SDF values. We calculated mean differences (MD) in SDF with 95% confidence interval (CI) for exposed and non-exposed individuals. RESULTS: We included 190 studies in our analysis. In the group of associated health conditions, varicocele (MD = 13.62%, CI: 9.39-17.84) and impaired glucose tolerance (MD = 13.75%, CI: 6.99-20.51) had the most significant increase in SDF. Among malignancies, testicular tumors had the highest impact, with a maximum of MD = 11.3% (CI: 7.84-14.76). Among infections, the overall effects of both Chlamydia and HPV were negligible. Of lifestyle factors, smoking had the most disruptive effect on SDF - an increase of 9.19% (CI: 4.33-14.06). Different periods of sexual abstinence did not show significant variations in SDF values. Age seemed to have a more drastic effect on SDF from age 50 onwards, with a mean difference of 12.58% (CI: 7.31-17.86). Pollution also had a detrimental effect - 9.68% (CI: 6.85-12.52). CONCLUSION: Of the above risk factors, varicocele, impaired glucose tolerance, testicular tumors, smoking, pollution, and paternal age of over 50 were associated with the highest SDF. TRIAL REGISTRATION: CRD42021282533.

Necrobiosis lipoidica of the breast associated with Crohn's disease: a case report.

BACKGROUND: Necrobiosis lipoidica located to the breast; without evidence of glucose intolerance, is extremely rare, and its association to Crohn's disease is not usual. CASE PRESENTATION: We report an interesting case of an association of necrobiosis lipoidica of the breast and Crohn's disease in a 54-year-old Moroccan woman. Skin necrobiotic changes are a characteristic feature in necrobiosis lipoidica, but they are exceptional in metastatic Crohn's disease, since there are only three published cases of necrobiotic skin lesions on the lower leg resembling erythema nodosum in metastatic Crohn's disease. CONCLUSIONS: On the basis of this rare observation, necrobiosis lipoidica without evidence of glucose intolerance should be recognized as a possible cutaneous manifestation or association of Crohn's disease.

Betaine protects against sodium arsenite-induced diabetes and hepatotoxicity in mice.

Epidemiological evidence has associated chronic exposure to inorganic arsenic with an increased occurrence of glucose intolerance and diabetes mellitus. Furthermore, inorganic arsenic induces oxidative stress in organs such as the liver. Betaine, as a methyl donor, plays a pivotal role in homocysteine metabolism. Betaine has antioxidant and anti-inflammatory properties. Therefore, the aim of this study was to evaluate the effects of betaine against sodium arsenite-induced diabetes and hepatotoxicity in mice. Forty-eight male mice were divided into 6 groups of 8. Group 1, received distilled water every day for 4 weeks by gavage. Group 2 received 500 mg/kg betaine every day for 4 weeks by gavage. Group 3 was given 10 mg/kg NaAsO2 every day for 4 weeks by gavage. Groups 4, 5, and 6 were co-treated with 125, 250, and 500 mg/kg betaine half an hour before NaAsO2 (10 mg/kg), respectively, daily for up to 4 weeks by gavage. After 28 days of the study, the mice were fasted overnight and on day 29, fasting blood glucose was measured and glucose tolerance test was performed. On day 30, the mice were anesthetized and a blood sample was taken from the heart. Serum factors (alanine aminotransferase, aspartate transaminase, and alkaline phosphatase activities), oxidative stress factors (malondialdehyde and glutathione levels, and the activity of superoxide dismutase, glutathione peroxidase, and catalase enzymes) and hepatic inflammatory factors (nitric oxide and tumor necrosis factor α) were measured. Histopathological studies were also performed on the liver and pancreas. In this study, it was shown that arsenic causes glucose intolerance, and oxidative/inflammatory hepatic damage. Co-administration of betaine prevents hepatotoxicity and glucose intolerance induced by arsenic in mice. Co-treatment of betaine with arsenic improved glucose intolerance and protected the liver against arsenic induced-oxidative damage and inflammation. Betaine at the dose of 500 mg/kg showed better results than the other doses. Accordingly, betaine can be suggested as a therapeutic agent against diabetogenic and hepatotoxic effects of arsenic.

Chaetomorpha linum polysaccharides alleviate NAFLD in mice by enhancing the PPARα/CPT-1/MCAD signaling.

BACKGROUND: Green algae contain many polysaccharides. However, there is no information on whether Chaetomorpha linum polysaccharides (CLP) can modulate lipid and glucose metabolism. MATERIAL AND METHODS: CLP were extracted from chlorella and their components were characterized. Male C57BL/6 mice were randomized and provided with control chow as the control, or high fat diet (HFD) to induce nonalcoholic fatty liver disease (NAFLD). NAFLD mice were treated orally with water as the HFD group or with 50 or 150 mg/kg CLP daily for 10 weeks. The impact of CLP treatment on lipid and glucose metabolism and the PPARα signaling was examined by histology, Western blotting and biochemistry. RESULTS: CLP mainly contained arabinogalactan sulfate. Compared with the control, HFD feeding increased body weights, lipid droplet liver deposition and induced hyperlipidemia, liver functional impairment and glucose intolerance in mice. Treatment with CLP, particularly with a higher dose of CLP, limited the HFD-increased body weights and liver lipid droplet deposition, mitigated the HFD-induced hyperlipidemia and improved liver function and glucose tolerance in mice. Mechanistically, feeding with HFD dramatically decreased the expression of liver PPARα, CPT-1, and MCAD, but treatment with CLP enhanced their expression in a trend of dose-dependent in mice. CONCLUSIONS: These findings indicated that CLP treatment alleviated the gain in body weights, NAFLD, and glucose intolerance in mice after HFD feeding by enhancing the PPARα/CPT-1/MCAD signaling.

Deficiency of M-LP/Mpv17L leads to development of ß-cell hyperplasia and improved glucose tolerance via activation of the Wnt and TGF-ß pathways.

M-LP/Mpv17L is a protein that was initially identified during screening of age-dependently expressed genes in mice. We have recently demonstrated that M-LP/Mpv17L-knockout (M-LP/Mpv17L-KO) in human hepatoma cells leads to a reduction of cellular cyclic nucleotide phosphodiesterase (PDE) activity, and that in vitro-synthesized M-LP/Mpv17L possesses PDE activity. These findings suggest that M-LP/Mpv17L functions as an atypical PDE, even though it has none of the well-conserved catalytic region or other structural motifs characteristic of the PDE family. In this study, we found that M-LP/Mpv17L-KO mice developed ß-cell hyperplasia and improved glucose tolerance. Deficiency of M-LP/Mpv17L in islets from KO mice at early postnatal stages or siRNA-mediated suppression of M-LP/Mpv17L in rat insulinoma cells led to marked upregulation of lymphoid enhancer binding factor 1 (Lef1) and transcription factor 7 (Tcf7), key nuclear effectors in the Wnt signaling pathway, and some of the factors essential for the development and maintenance of ß-cells. Moreover, at the protein level, increases in the levels of phosphorylated ß-catenin and glycogen synthase kinase-3ß (GSK-3ß) were observed, indicating activation of the Wnt and TGF-ß signaling pathways. Taken together, these findings suggest that protein kinase A (PKA)-dependent phosphorylations of ß-catenin and GSK-3ß, the key mediators of the Wnt and/or TGF-ß signaling pathways, are the most upstream events triggering ß-cell hyperplasia and improved glucose tolerance caused by M-LP/Mpv17L deficiency.

Effects of Intermittent Hypoxia on Cytokine Expression Involved in Insulin Resistance.

Sleep apnea syndrome (SAS) is a prevalent disorder characterized by recurrent apnea or hypoxia episodes leading to intermittent hypoxia (IH) and arousals during sleep. Currently, the relationship between SAS and metabolic diseases is being actively analyzed, and SAS is considered to be an independent risk factor for the development and progression of insulin resistance/type 2 diabetes (T2DM). Accumulating evidence suggests that the short cycles of decreased oxygen saturation and rapid reoxygenation, a typical feature of SAS, contribute to the development of glucose intolerance and insulin resistance. In addition to IH, several pathological conditions may also contribute to insulin resistance, including sympathetic nervous system hyperactivity, oxidative stress, vascular endothelial dysfunction, and the activation of inflammatory cytokines. However, the detailed mechanism by which IH induces insulin resistance in SAS patients has not been fully revealed. We have previously reported that IH stress may exacerbate insulin resistance/T2DM, especially in hepatocytes, adipocytes, and skeletal muscle cells, by causing abnormal cytokine expression/secretion from each cell. Adipose tissues, skeletal muscle, and the liver are the main endocrine organs producing hepatokines, adipokines, and myokines, respectively. In this review, we focus on the effect of IH on hepatokine, adipokine, and myokine expression.

Tentonin 3/TMEM150C regulates glucose-stimulated insulin secretion in pancreatic ß-cells.

Glucose homeostasis is initially regulated by the pancreatic hormone insulin. Glucose-stimulated insulin secretion in ß-cells is composed of two cellular mechanisms: a high glucose concentration not only depolarizes the membrane potential of the ß-cells by ATP-sensitive K+ channels but also induces cell inflation, which is sufficient to release insulin granules. However, the molecular identity of the stretch-activated cation channel responsible for the latter pathway remains unknown. Here, we demonstrate that Tentonin 3/TMEM150C (TTN3), a mechanosensitive channel, contributes to glucose-stimulated insulin secretion by mediating cation influx. TTN3 is expressed specifically in ß-cells and mediates cation currents to glucose and hypotonic stimulations. The glucose-induced depolarization, firing activity, and Ca2+ influx of ß-cells were significantly lower in Ttn3-/- mice. More importantly, Ttn3-/- mice show impaired glucose tolerance with decreased insulin secretion in vivo. We propose that TTN3, as a stretch-activated cation channel, contributes to glucose-stimulated insulin secretion.

Retinal Neuropathy in IGT Stage of OLETF Rats: Another Characteristic Change of Diabetic Retinopathy.

AIMS: We investigated the changes of retinal structure in normal glucose tolerance (NGT), impaired glucose tolerance (IGT), diabetes mellitus (DM), and diabetic kidney disease (DKD) stages in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. METHODS: We assigned OLETF rats to four groups based on their OGTT results and 24 h urinary microalbumin (24 h UMA) levels: NGT, IGT, DM, and DKD groups. We observed the structural and the corresponding pathological changes and quantified the expression of HIF-1α, iNOS, NF-κB, VEGF, ICAM-1, and occludin in the retina. RESULTS: Significant damage to the retinal structure, especially in retinal ganglion cells (RGCs), was observed in the IGT stage. The expression of HIF-1α, iNOS, NF-κB, VEGF, and ICAM-1 was significantly upregulated, while that of occludin was downregulated. CONCLUSION: Significant retinal neuropathy occurs in the IGT stage. Inflammation and hypoxia may damage the blood retina barrier (BRB), leading to diabetic retinopathy.

Pancreatic ß-Cell O-GlcNAc Transferase Overexpression Increases Susceptibility to Metabolic Stressors in Female Mice.

The nutrient-sensor O-GlcNAc transferase (Ogt), the sole enzyme that adds an O-GlcNAc-modification onto proteins, plays a critical role for pancreatic ß-cell survival and insulin secretion. We hypothesized that ß-cell Ogt overexpression would confer protection from ß-cell failure in response to metabolic stressors, such as high-fat diet (HFD) and streptozocin (STZ). Here, we generated a ß-cell-specific Ogt in overexpressing (ßOgtOE) mice, where a significant increase in Ogt protein level and O-GlcNAc-modification of proteins were observed in islets under a normal chow diet. We uncovered that ßOgtOE mice show normal peripheral insulin sensitivity and glucose tolerance with a regular chow diet. However, when challenged with an HFD, only female ßOgtOE (homozygous) Hz mice developed a mild glucose intolerance, despite increased insulin secretion and normal ß-cell mass. While female mice are normally resistant to low-dose STZ treatments, the ßOgtOE Hz mice developed hyperglycemia and glucose intolerance post-STZ treatment. Transcriptome analysis between islets with loss or gain of Ogt by RNA sequencing shows common altered pathways involving pro-survival Erk and Akt and inflammatory regulators IL1ß and NFkß. Together, these data show a possible gene dosage effect of Ogt and the importance O-GlcNAc cycling in ß-cell survival and function to regulate glucose homeostasis.

The Association of Trp64Arg Polymorphism in the Beta-Adrenergic Receptor With Insulin Resistance: Meta-Analysis.

Background: Insulin resistance is a metabolic disorder that occurs in type 2 diabetes mellitus and obesity. Genetic factors such as ß3-adrenoceptor polymorphism (Trp64Arg) may be involved in IR and insulin secretion. However, their association is controversial. Therefore, the current meta-analysis was conducted to clarify the relationship between the Trp64Arg and IR. Methods: The literature search was performed in PubMed, Embase, and Web of Science using the keywords "Receptors, Adrenergic, beta-3, Receptors, Adrenergic, Insulin Resistance, Protein-Coupled Receptor Kinase 3" from 2005 to February 7, 2021. We used a random-effects model to calculate the pooled effect size. We conducted subgroup analysis and regression analysis to identify sources of heterogeneity; and Egger's test and funnel plot were used to test publication bias. Finally, we conducted a sensitivity analysis. Results: We included eight papers with 1,586 subjects. There was a positive correlation between Trp64Arg mutation and insulin level (standardized mean difference = 0.20, 95% confidence intervals: 0.00 to 0.39, I2 = 57.6%, p = 0.016). However, there was no association between Trp64Arg and the homeostasis model (HOMA-IR) assessment. Egger's tests showed no publication bias; the sensitivity analysis showed that our results were stable. Regression analysis revealed no source of heterogeneity. Conclusion: Trp64Arg may be associated with IR. European ancestry, obesity, plasma insulin level, and test status may be potential factors affecting the relationship between Trp64Arg and IR.

Increased NKX6.1 expression and decreased ARX expression in alpha cells accompany reduced beta-cell volume in human subjects.

Pancreatic islet cells have plasticity, such as the abilities to dedifferentiate and transdifferentiate. Islet cell conversion to other characteristic cell is largely determined by transcription factors, but significance of expression patterns of these transcription factors in human islet cells remained unclear. Here, we present the NKX6.1-positive ratio of glucagon-positive cells (NKX6.1+/GCG+ ratio) and the ARX-negative ratio of glucagon-positive cells (ARX-/GCG+ ratio) in 34 patients who were not administered antidiabetic agents. Both of NKX6.1+/GCG+ ratio and ARX-/GCG+ ratio negatively associated with relative beta cell area. And these ratios did not have significant correlation with other parameters including age, body mass index, hemoglobin A1c, fasting plasma glucose level or relative alpha-cell area. Our data demonstrate that these expression ratios of transcription factors in glucagon-positive cells closely correlate with the reduction of beta-cell volume in human pancreas.

Intrauterine Hyperglycemia Alters the Metabolomic Profile in Fetal Mouse Pancreas in a Gender-Specific Manner.

Mounting evidence has shown that intrauterine hyperglycemia exposure during critical stages of development may be contributing to the increasing prevalence of diabetes. However, little is known about the mechanisms responsible for offspring metabolic disorder. In this present study, we explored intrauterine hyperglycemia exposure on fetal pancreatic metabolome, and its potential link to impaired glucose tolerance in adult offspring. Here, using a GDM mouse model, we found the metabolome profiling of pancreas from male and female fetus showing altered metabolites in several important pathways, including 5-methylcytosine, α-KG, branched-chain amino acids, and cystine, which are associated with epigenetic modification, insulin secretion, and intracellular redox status, respectively. This finding suggests that intrauterine exposure to hyperglycemia could cause altered metabolome in pancreas, which might be a metabolism-mediated mechanism for GDM-induced intergenerational diabetes predisposition.

Salivary Redox Biomarkers in Insulin Resistance: Preclinical Studies in an Animal Model.

Insulin resistance (IR) is a condition of impaired tissue response to insulin. Although there are many methods to diagnose IR, new biomarkers are still being sought for early and noninvasive diagnosis of the disease. Of particular interest in laboratory diagnostics is saliva collected in a stress-free, noninvasive, and straightforward manner. The purpose of the study was to evaluate the diagnostic utility of salivary redox biomarkers in preclinical studies in an animal model. The study was conducted on 20 male Wistar rats divided into two equal groups: a standard diet and a high-fat diet (HFD). In all rats fed the HFD, IR was confirmed by an elevated homeostasis model assessment (HOMA-IR) index. We have shown that IR is responsible for the depletion of the enzymatic (↓superoxide dismutase) and nonenzymatic (↓ascorbic acid, ↓reduced glutathione (GSH)) antioxidant barrier at both the central (serum/plasma) and salivary gland (saliva) levels. In IR rats, we also demonstrated significantly higher concentrations of protein/lipid oxidation (↑protein carbonyls, ↑4-hydroxynoneal (4-HNE)), glycation (↑advanced glycation end products), and nitration (↑3-nitrotyrosine) products in both saliva and blood plasma. Salivary nonenzymatic antioxidants and oxidative stress products generally correlate with their blood levels, while GSH and 4-HNE have the highest correlation coefficient. Salivary GSH and 4-HNE correlate with body weight and BMI and indices of carbohydrate metabolism (glucose, insulin, HOMA-IR) and proinflammatory adipokines (leptin, resistin, TNF-α). These biomarkers differentiate IR from healthy controls with very high sensitivity (100%) and specificity (100%). The high diagnostic utility of salivary GSH and 4-HNE is also confirmed by multivariate regression analysis. Summarizing, saliva can be used to assess the systemic antioxidant status and the intensity of systemic oxidative stress. Salivary GSH and 4-HNE may be potential biomarkers of IR progression. There is a need for human clinical trials to evaluate the diagnostic utility of salivary redox biomarkers in IR conditions.

Treatment with atrial natriuretic peptide induces adipose tissue browning and exerts thermogenic actions in vivo.

Increasing evidence suggests natriuretic peptides (NPs) coordinate inter-organ metabolic crosstalk with adipose tissues and play a critical role in energy metabolism. We recently reported A-type NP (ANP) raises intracellular temperature in cultured adipocytes in a low-temperature-sensitive manner. We herein investigated whether exogenous ANP-treatment exerts a significant impact on adipose tissues in vivo. Mice fed a high-fat-diet (HFD) or normal-fat-diet (NFD) for 13 weeks were treated with or without ANP infusion subcutaneously for another 3 weeks. ANP-treatment significantly ameliorated HFD-induced insulin resistance. HFD increased brown adipose tissue (BAT) cell size with the accumulation of lipid droplets (whitening), which was suppressed by ANP-treatment (re-browning). Furthermore, HFD induced enlarged lipid droplets in inguinal white adipose tissue (iWAT), crown-like structures in epididymal WAT, and hepatic steatosis, all of which were substantially attenuated by ANP-treatment. Likewise, ANP-treatment markedly increased UCP1 expression, a specific marker of BAT, in iWAT (browning). ANP also further increased UCP1 expression in BAT with NFD. Accordingly, cold tolerance test demonstrated ANP-treated mice were tolerant to cold exposure. In summary, exogenous ANP administration ameliorates HFD-induced insulin resistance by attenuating hepatic steatosis and by inducing adipose tissue browning (activation of the adipose tissue thermogenic program), leading to in vivo thermogenesis during cold exposure.

Chronic high-fat feeding and prolonged fasting in liver-specific ANGPTL4 knockout mice.

Obesity is associated with dyslipidemia, ectopic lipid deposition, and insulin resistance. In mice, the global or adipose-specific loss of function of the protein angiopoietin-like 4 (ANGPTL4) leads to decreased plasma triglyceride levels, enhanced adipose triglyceride uptake, and protection from high-fat diet (HFD)-induced glucose intolerance. ANGPTL4 is also expressed highly in the liver, but the role of liver-derived ANGPTL4 is unclear. The goal of this study was to determine the contribution of hepatocyte ANGPTL4 to triglyceride and glucose homeostasis in mice during a high-fat diet challenge. We generated hepatocyte-specific ANGPTL4 deficient (Angptl4LivKO) mice, fed them a 60% kcal/fat diet (HFD) for 6 mo and assessed triglyceride, liver, and glucose metabolic phenotypes. We also explored the effects of prolonged fasting on Angptl4LivKO mice. The loss of hepatocyte-derived ANGPTL4 led to no major changes in triglyceride partitioning or lipoprotein lipase activity compared with control mice. Interestingly, although there was no difference in fasting plasma triglyceride levels after a 6 h fast, after an 18-h fast, normal chow diet-fed Angptl4LivKO mice had lower triglyceride levels than control mice. On a HFD, Angptl4LivKO mice initially showed no difference in glucose tolerance and insulin sensitivity, but improved glucose tolerance emerged in these mice after 6 mo on HFD. Our data suggest that hepatocyte ANGPTL4 does not directly regulate triglyceride partitioning, but that loss of liver-derived ANGPTL4 may be protective from HFD-induced glucose intolerance and influence plasma triglyceride (TG) metabolism during prolonged fasting.NEW & NOTEWORTHY1) Angiopoietin-like 4 deficiency in hepatocytes (Angptl4LivKO) does not improve triglyceride phenotypes during high-fat feeding. 2) Angptl4LivKO mice have improved glucose tolerance after chronic high-fat diet. 3) Angptl4LivKO mice have decreased fasting plasma triglyceride levels after an 18-h fast, but not after a 6-h fast.