scholarly journals Duration of rise in free fatty acids determines salicylate's effect on hepatic insulin sensitivity

2013 ◽  
Vol 217 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Sandra Pereira ◽  
Wen Qin Yu ◽  
María E Frigolet ◽  
Jacqueline L Beaudry ◽  
Yaniv Shpilberg ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Muscle Protein ◽  
Hepatic Insulin Resistance ◽  
Skeletal Muscle Protein ◽  
Protein Levels ◽  
Peripheral Insulin Resistance ◽  
Plasma Ffa ◽  
A Site

We have shown in rats that sodium salicylate (SS), which inhibits IkBa kinase B (IKKB), prevents hepatic and peripheral insulin resistance caused by short-term (7 h) i.v. administration of Intralipid and heparin (IH). We wished to further determine whether this beneficial effect of SS persisted after prolonged (48 h) IH infusion, which better mimics the chronic free fatty acid (FFA) elevation of obesity. Hence, we performed hyperinsulinemic euglycemic clamps with tritiated glucose methodology to determine hepatic and peripheral insulin sensitivity in rats infused with saline, IH, IH and SS, or SS alone. SS prevented peripheral insulin resistance (P<0.05) caused by prolonged plasma FFA elevation; however, it did not prevent hepatic insulin resistance. In skeletal muscle, protein levels of phospho-IkBa were augmented by prolonged IH administration and this was prevented by SS, suggesting that IH activates while SS prevents the activation of IKKB. Markers of IKKB activation, namely protein levels of phospho-IkBa and IkBa, indicated that IKKB is not activated in the liver after prolonged FFA elevation. Phosphorylation of serine 307 at insulin receptor substrate (IRS)-1, which is a marker of proximal insulin resistance, was not altered by IH administration in the liver, suggesting that this is not a site of hepatic insulin resistance in the prolonged lipid infusion model. Our results suggest that the role of IKKB in fat-induced insulin resistance is time and tissue dependent and that hepatic insulin resistance induced by prolonged lipid elevation is not due to an IRS-1 serine 307 kinase.

scholarly journals Effect of N-acetyl-l-cysteine on insulin resistance caused by prolonged free fatty acid elevation

2015 ◽  
Vol 225 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sandra Pereira ◽  
Anu Shah ◽  
I George Fantus ◽  
Jamie W Joseph ◽  
Adria Giacca
Keyword(s):  
Oxidative Stress ◽  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Muscle Protein ◽  
Protein Carbonyl ◽  
Hepatic Insulin Resistance ◽  
Skeletal Muscle Protein ◽  
Protein Carbonyl Content ◽  
Peripheral Insulin Resistance ◽  
Plasma Ffa

Circulating free fatty acids (FFAs) are elevated in obesity and cause insulin resistance. The objective of the current study was to determine whether the antioxidantN-acetyl-l-cysteine (NAC) prevented hepatic and peripheral insulin resistance caused by prolonged elevation of plasma FFAs. Chronically cannulated Wistar rats received saline (SAL), Intralipid plus heparin (IH), IH plus NAC, or NAC i.v. infusion for 48 h. Insulin sensitivity was determined using the hyperinsulinemic–euglycemic clamp with tritiated glucose tracer. IH induced hepatic and peripheral insulin resistance (P<0.05). NAC co-infusion did not prevent insulin resistance in the liver, although it was able to prevent peripheral insulin resistance. Prolonged IH infusion did not appear to induce oxidative stress in the liver because hepatic content of protein carbonyl, malondialdehyde, and reduced to oxidized glutathione ratio did not differ across treatment groups. In alignment with our insulin sensitivity results, IH augmented skeletal muscle protein carbonyl content and this was prevented by NAC co-infusion. Taken together, our results indicate that oxidative stress mediates peripheral, but not hepatic, insulin resistance resulting from prolonged plasma FFA elevation. Thus, in states of chronic plasma FFA elevation, such as obesity, antioxidants may protect against peripheral but not hepatic insulin resistance.

scholarly journals Resistance training improves indices of muscle insulin sensitivity and β-cell function in overweight/obese, sedentary young men

2013 ◽  
Vol 115 (9) ◽  
pp. 1245-1253 ◽  
Author(s):  
Daniel M. Croymans ◽  
Ergit Paparisto ◽  
Mary M. Lee ◽  
Nina Brandt ◽  
Brian K. Le ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Cell Function ◽  
Muscle Protein ◽  
Young Men ◽  
Hepatic Insulin Resistance ◽  
Skeletal Muscle Protein ◽  
Β Cell ◽  
Β Cell Function

We examined the effects of RT on oral glucose tolerance test (OGTT)-derived indices of muscle insulin sensitivity, hepatic insulin resistance, β-cell function, and skeletal muscle proteins related to glucose transport in overweight/obese, sedentary young men. Twenty-eight participants [median body mass index (BMI) 30.9 kg/m2; age 22 yr] completed 12 wk of RT (3 sessions/wk) and were assessed for changes in OGTT-derived indices, resting metabolic rate, body composition, serum adipokines, and skeletal muscle protein content [hexokinase 2 (HK2), glucose transporter type 4 (GLUT4), RAC-β serine/threonine-protein kinase (AKT2), glycogen synthase kinase 3β, and insulin receptor substrate 1]. Individualized responses to RT were also evaluated. RT significantly improved insulin and glucose area under the curve (both P < 0.03). With the use of OGTT indices of insulin action, we noted improved muscle insulin sensitivity index (mISI; P = 0.03) and oral disposition index ( P = 0.03). BMI, lean body mass (LBM), and relative strength also increased (all P < 0.03), as did skeletal muscle protein content of HK2, GLUT4, and AKT2 (26–33%; all P < 0.02). Hepatic insulin resistance index, adiponectin, leptin, and total amylin did not change. Further analysis demonstrated the presence of highly individualized responsiveness to RT for glucose tolerance and other outcomes. RT improved oral indices of muscle insulin sensitivity and β-cell function but not hepatic insulin resistance in overweight/obese young men. In addition to the increase in LBM, the improvements in insulin action may be due, in part, to increases in key insulin signaling proteins.

Impact of PPAR-α induction on glucose homoeostasis in alcohol-fed mice

2013 ◽  
Vol 125 (11) ◽  
pp. 501-511 ◽  
Author(s):  
Valérie Lebrun ◽  
Olivier Molendi-Coste ◽  
Nicolas Lanthier ◽  
Christine Sempoux ◽  
Patrice D. Cani ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Liver Disease ◽  
Insulin Sensitivity ◽  
Alcohol Consumption ◽  
Insulin Signalling ◽  
Liver Steatosis ◽  
Hepatic Insulin Resistance ◽  
Alcoholic Fatty Liver ◽  
Glucose Homoeostasis

Alcohol consumption is a major cause of liver disease. It also associates with increased cardiovascular risk and Type 2 diabetes. ALD (alcoholic liver disease) and NAFLD (non-alcoholic fatty liver disease) share pathological features, pathogenic mechanisms and pattern of disease progression. In NAFLD, steatosis, lipotoxicity and liver inflammation participate to hepatic insulin resistance. The aim of the present study was to verify the effect of alcohol on hepatic insulin sensitivity and to evaluate the role of alcohol-induced steatosis and inflammation on glucose homoeostasis. C57BL/6J mice were fed for 20 days a modified Lieber–DeCarli diet in which the alcohol concentration was gradually increased up to 35% of daily caloric intake. OH (alcohol liquid diet)-fed mice had liver steatosis and inflammatory infiltration. In addition, these mice developed insulin resistance in the liver, but not in muscles, as demonstrated by euglycaemic–hyperinsulinaemic clamp and analysis of the insulin signalling cascade. Treatment with the PPAR-α (peroxisome-proliferator-activated receptor-α) agonist Wy14,643 protected against OH-induced steatosis and KC (Kupffer cell) activation and almost abolished OH-induced insulin resistance. As KC activation may modulate insulin sensitivity, we repeated the clamp studies in mice depleted in KC to decipher the role of macrophages. Depletion of KC using liposomes-encapsuled clodronate in OH-fed mice failed both to improve hepatic steatosis and to restore insulin sensitivity as assessed by clamp. Our study shows that chronic alcohol consumption induces steatosis, KC activation and hepatic insulin resistance in mice. PPAR-α agonist treatment that prevents steatosis and dampens hepatic inflammation also prevents alcohol-induced hepatic insulin resistance. However, KC depletion has little impact on OH-induced metabolic disturbances.

scholarly journals Role of Cannabinoid Receptor Type 1 in Insulin Resistance and Its Biological Implications

2019 ◽  
Vol 20 (9) ◽  
pp. 2109 ◽  
Author(s):  
Arulkumar Nagappan ◽  
Jooyeon Shin ◽  
Myeong Ho Jung
Keyword(s):  
Insulin Resistance ◽  
Body Weight ◽  
Insulin Sensitivity ◽  
Hepatic Steatosis ◽  
Cannabinoid Receptor ◽  
Inflammatory Responses ◽  
Hepatic Insulin Resistance ◽  
Leptin Resistance ◽  
Peripheral Tissues

Endogenous cannabinoids (ECs) are lipid-signaling molecules that specifically bind to cannabinoid receptor types 1 and 2 (CB1R and CB2R) and are highly expressed in central and many peripheral tissues under pathological conditions. Activation of hepatic CB1R is associated with obesity, insulin resistance, and impaired metabolic function, owing to increased energy intake and storage, impaired glucose and lipid metabolism, and enhanced oxidative stress and inflammatory responses. Additionally, blocking peripheral CB1R improves insulin sensitivity and glucose metabolism and also reduces hepatic steatosis and body weight in obese mice. Thus, targeting EC receptors, especially CB1R, may provide a potential therapeutic strategy against obesity and insulin resistance. There are many CB1R antagonists, including inverse agonists and natural compounds that target CB1R and can reduce body weight, adiposity, and hepatic steatosis, and those that improve insulin sensitivity and reverse leptin resistance. Recently, the use of CB1R antagonists was suspended due to adverse central effects, and this caused a major setback in the development of CB1R antagonists. Recent studies, however, have focused on development of antagonists lacking adverse effects. In this review, we detail the important role of CB1R in hepatic insulin resistance and the possible underlying mechanisms, and the therapeutic potential of CB1R targeting is also discussed.

Adrenodemedullation activates the Ca2+-dependent proteolysis in soleus muscles from rats exposed to cold

2017 ◽  
Vol 122 (2) ◽  
pp. 317-326 ◽  
Author(s):  
L. H. Manfredi ◽  
D. Lustrino ◽  
J. Machado ◽  
W. A. Silveira ◽  
N. M. Zanon ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Adrenal Medulla ◽  
Cold Exposure ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Calpain Inhibitor ◽  
Skeletal Muscle Protein ◽  
Protein Levels ◽  
Muscle Protein Metabolism

Previous studies have shown that catecholamines in vivo and in vitro inhibit the activity of Ca2+-dependent proteolysis in skeletal muscles under basal conditions. In the present study we sought to investigate the role of catecholamines in regulating the Ca2+-dependent proteolysis in soleus and extensor digitorum longus (EDL) muscles from rats acutely exposed to cold. Overall proteolysis, the activity of proteolytic systems, protein levels and gene expression of different components of the calpain system were investigated in rats submitted to adrenodemedullation (ADMX) and exposed to cold for 24 h. ADMX drastically reduced plasma epinephrine and promoted an additional increase in the overall proteolysis, which was already increased by cold exposure. The rise in the rate of protein degradation in soleus muscles from adrenodemedullated cold-exposed rats was caused by the high activity of the Ca2+-dependent proteolysis, which was associated with the generation of a 145-kDa cleaved α-fodrin fragment, a typical calpain substrate, and lower protein levels and mRNA expression of calpastatin, the endogenous calpain inhibitor. Unlike that observed for soleus muscles, the cold-induced muscle proteolysis in EDL was not affected by ADMX. In isolated soleus muscle, clenbuterol, a selective β2-adrenoceptor agonist, reduced the basal Ca2+-dependent proteolysis and completely abolished the activation of this pathway by the cholinergic agonist carbachol. These data suggest that catecholamines released from the adrenal medulla inhibit cold-induced protein breakdown in soleus, and this antiproteolytic effect on the Ca2+-dependent proteolytic system is apparently mediated through expression of calpastatin, which leads to suppression of calpain activation. NEW & NOTEWORTHY Although many effects of the sympathetic nervous system on muscle physiology are known, the role of catecholamines in skeletal muscle protein metabolism has been scarcely studied. We suggest that catecholamines released from adrenal medulla may be of particular importance for restraining the activation of the Ca2+-dependent proteolysis in soleus muscles during acute cold exposure. This finding helps us to understand the adaptive changes that occur in skeletal muscle protein metabolism during cold stress.

scholarly journals SAT-653 Exploring the Role of Brown Adipokines on Hepatic Insulin Resistance Using a Microfluidic Organ-On-Chip

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Nida Tanataweethum ◽  
Chaeeun Lee ◽  
Allyson Trang ◽  
Franklin Zhong ◽  
Kihwan Kim ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Insulin Sensitivity ◽  
Glucose Production ◽  
Conditioned Media ◽  
Hepatic Insulin Resistance ◽  
Brown Adipocyte ◽  
On Chip

Abstract The development of insulin resistance (IR) in liver is a key of pathophysiologic response in type 2 diabetes. Although insulin resistance impairs its ability to suppress hepatic glucose production, insulin regulation of lipogenesis is maintained (1). Currently available insulin sensitizers are effective at lowering glucose levels, but have significant adverse effect on weight gain due to triglyceride accumulation, which highlights a need to develop new therapeutic treatment options for type 2 diabetes. Brown adipose tissue (BAT) has been studied as a new target for anti-obesity and type 2 diabetes as BAT stimulation increases energy expenditure, reduces adiposity, and improves insulin sensitivity (2). However, the underlying mechanisms are not completely understood. To identify the role of BAT adipokines on hepatic insulin resistance, we developed an insulin resistant liver organ-on-chip model and then perfused primary mouse brown adipocyte conditioned media through the hepatocytes. Our results demonstrate that IR hepatocytes treated with brown adipocyte - conditioned media restores insulin sensitivity and improves glucose metabolism. This was verified by significantly increased expression of Phospho-Akt (Ser473) and glucose production gene markers (G6pc and PEPCK), lowered glucose production, increased glucose uptake, and increased glycogen synthesis in treated hepatocytes over IR group (p &lt; 0.05). Our results also indicate that brown adipocyte - conditioned media treatment has the potential to suppress lipogenesis in hepatic insulin resistance. This was confirmed by significantly reduced expression of a lipogenesis gene marker (SREPB1) and fatty acid uptake in treated hepatocytes over IR group (p &lt; 0.05). Current efforts are focused towards identifying the BAT adipokine via mass spectrometry. We conclude that BAT-derived endocrine factors could be a potential target for new drug discovery for obesity and type 2 diabetes treatment. Reference: (1) Langlet et al. Cell. 2017 Nov;171(4):824-835. (2) Subhadraw et al. Am J Physiol Endocrinol Metlab. 2015 Jun;308(12):E1043-E1055. Nothing to Disclose: NT, CL, AT, FZ, KK, JM, RC, AB

scholarly journals Serum sclerostin is negatively associated with insulin sensitivity in obese but not lean women

2021 ◽  
Author(s):  
Anouar Aznou ◽  
Rick I. Meijer ◽  
Dani�l H van Raalte ◽  
Martin den Heijer ◽  
Annemieke C Heijboer ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Cross Sectional Study ◽  
Obese Women ◽  
Cross Sectional ◽  
Negatively Associated ◽  
Euglycemic Clamp ◽  
Peripheral Insulin Resistance ◽  
Hyperinsulinemic Euglycemic Clamp

Objective The mechanisms underlying the development of peripheral insulin resistance are complex. Several studies have linked sclerostin, an osteocyte-derived inhibitor of the Wnt/β-catenin pathway, to obesity and insulin resistance. The aim of this study was to investigate 1) whether serum sclerostin is associated with insulin sensitivity in lean and/or obese women; and 2) whether hyperinsulinemia affects serum sclerostin concentrations. Design A cross-sectional study. Methods Insulin sensitivity was measured in lean (BMI<25 kg·m-2) and obese (BMI > 30 kg·m-2) women using a hyperinsulinemic-euglycemic clamp. Serum sclerostin was measured at baseline and during the clamp procedure. Results We studied 21 lean and 22 obese women with a median age of 40 and 43 years and a median BMI of 22.4 and 33.5 kg·m-2, respectively. Obese women had higher serum sclerostin than lean women (122±33 vs 93±33 nmol/L, p<0.01). Higher serum sclerostin was associated with lower insulin sensitivity in obese, but not in lean individuals (difference in M value between highest and lowest quartile: -7.02 mg⋅kg−1⋅min−1, p = 0.03 and 1.59 mg⋅kg−1⋅min−1, p = 0.50, respectively). Hyperinsulinemia did not affect serum sclerostin in lean nor obese women (p>0.5). Conclusion Serum sclerostin is negatively associated with insulin sensitivity as measured with the hyperinsulinemic euglycemic clamp in obese, but not lean women. This indicates a potential role of the Wnt/β-catenin pathway in regulating insulin sensitivity particularly in obese individuals. Our findings remain hypothesis-generating and should be confirmed by additional studies.

scholarly journals Role of Insulin Resistance in MAFLD

2021 ◽  
Vol 22 (8) ◽  
pp. 4156
Author(s):  
Yoshitaka Sakurai ◽  
Naoto Kubota ◽  
Toshimasa Yamauchi ◽  
Takashi Kadowaki
Keyword(s):  
Insulin Resistance ◽  
Liver Disease ◽  
Fatty Liver ◽  
Fatty Liver Disease ◽  
De Novo Lipogenesis ◽  
Hepatic Insulin Resistance ◽  
Metabolic Dysfunction ◽  
Alcoholic Fatty Liver ◽  
Fat Accumulation

Many studies have reported that metabolic dysfunction is closely involved in the complex mechanism underlying the development of non-alcoholic fatty liver disease (NAFLD), which has prompted a movement to consider renaming NAFLD as metabolic dysfunction-associated fatty liver disease (MAFLD). Metabolic dysfunction in this context encompasses obesity, type 2 diabetes mellitus, hypertension, dyslipidemia, and metabolic syndrome, with insulin resistance as the common underlying pathophysiology. Imbalance between energy intake and expenditure results in insulin resistance in various tissues and alteration of the gut microbiota, resulting in fat accumulation in the liver. The role of genetics has also been revealed in hepatic fat accumulation and fibrosis. In the process of fat accumulation in the liver, intracellular damage as well as hepatic insulin resistance further potentiates inflammation, fibrosis, and carcinogenesis. Increased lipogenic substrate supply from other tissues, hepatic zonation of Irs1, and other factors, including ER stress, play crucial roles in increased hepatic de novo lipogenesis in MAFLD with hepatic insulin resistance. Herein, we provide an overview of the factors contributing to and the role of systemic and local insulin resistance in the development and progression of MAFLD.

scholarly journals Insulin resistance and liver histopathology in metabolically unhealthy subjects do not correlate with the hepatic abundance of NLRP3 inflammasome nor circulating IL-1β levels

2021 ◽  
Vol 9 (1) ◽  
pp. e001975
Author(s):  
Nicolas Quezada ◽  
Ilse Valencia ◽  
Javiera Torres ◽  
Gregorio Maturana ◽  
Jaime Cerda ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Liver Damage ◽  
Nlrp3 Inflammasome ◽  
Low Grade ◽  
Model Assessment ◽  
Alcoholic Fatty Liver ◽  
Protein Levels ◽  
Liver Histopathology ◽  
Inflammatory Status

IntroductionSystemic chronic low-grade inflammation has been linked to insulin resistance (IR) and non-alcoholic steatohepatitis (NASH). NOD-like receptor protein 3 (NLRP3) inflammasome and its final product, interleukin (IL)-1β, exert detrimental effects on insulin sensitivity and promote liver inflammation in murine models. Evidence linking hepatic NLRP3 inflammasome, systemic IR and NASH has been scarcely explored in humans. Herein, we correlated the hepatic abundance of NLRP3 inflammasome components and IR and NASH in humans.Research design and methodsMetabolically healthy (MH) (n=11) and metabolically unhealthy (MUH) (metabolic syndrome, n=21, and type 2 diabetes, n=14) subjects were recruited. Insulin sensitivity (homeostatic model assessment of IR (HOMA-IR) and Oral Glucose Sensitivity (OGIS120)), glycemic (glycated hemoglobin), and lipid parameters were determined by standard methods. Plasma cytokines were quantified by Magpix. Hepatic NLRP3 inflammasome components were determined at the mRNA and protein levels by reverse transcription–quantitative PCR and western blot, respectively. Liver damage was assessed by histological analysis (Non-alcoholic Fatty Liver Disease Activity Score (NAS) and Steatosis, Inflammatory Activity, and Fibrosis (SAF) scores). IR and liver histopathology were correlated with NLRP3 inflammasome components as well as with liver and plasma IL-1β levels.ResultsBody Mass Index, waist circumference, and arterial hypertension frequency were significantly higher in MUH subjects. These patients also had increased high-sensitivity C reactive protein levels compared with MH subjects. No differences in the plasma levels of IL-1β nor the hepatic content of Nlrp3, apoptosis-associated speck-like (Asc), Caspase-1, and IL-1β were detected between MUH and MH individuals. MUH subjects had significantly higher NAS and SAF scores, indicating more severe liver damage. However, histological severity did not correlate with the hepatic content of NLRP3 inflammasome components nor IL-1β levels.ConclusionOur results suggest that NLRP3 inflammasome activation is linked neither to IR nor to the inflammatory status of the liver in MUH patients.

scholarly journals Caloric Restriction Reverses Hepatic Insulin Resistance and Steatosis in Rats with Low Aerobic Capacity

Endocrinology ◽  
2010 ◽  
Vol 151 (11) ◽  
pp. 5157-5164 ◽  
Author(s):  
Thomas A. Bowman ◽  
Sadeesh K. Ramakrishnan ◽  
Meenakshi Kaw ◽  
Sang Jun Lee ◽  
Payal R. Patel ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Insulin Resistance ◽  
Caloric Restriction ◽  
Visceral Obesity ◽  
Insulin Clearance ◽  
Hepatic Insulin Resistance ◽  
The Metabolic Syndrome ◽  
Cell Adhesion Molecule 1 ◽  
Muscle Triglyceride

Rats selectively bred for low aerobic running capacity exhibit the metabolic syndrome, including hyperinsulinemia, insulin resistance, visceral obesity, and dyslipidemia. They also exhibit features of nonalcoholic steatohepatitis, including chicken-wire fibrosis, inflammation, and oxidative stress. Hyperinsulinemia in these rats is associated with impaired hepatic insulin clearance. The current studies aimed to determine whether these metabolic abnormalities could be reversed by caloric restriction (CR). CR by 30% over a period of 2–3 months improved insulin clearance in parallel to inducing the protein content and activation of the carcinoembryonic antigen-related cell adhesion molecule 1, a main player in hepatic insulin extraction. It also reduced glucose and insulin intolerance and serum and tissue (liver and muscle) triglyceride levels. Additionally, CR reversed inflammation, oxidative stress, and fibrosis in liver. The data support a significant role of CR in the normalization of insulin and lipid metabolism in liver.

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