scholarly journals Metabolic Inflexibility Is an Early Marker of Bed-Rest–Induced Glucose Intolerance Even When Fat Mass Is Stable

2018 ◽  
Vol 103 (5) ◽  
pp. 1910-1920 ◽  
Author(s):  
Floriane Rudwill ◽  
Donal O’Gorman ◽  
Etienne Lefai ◽  
Isabelle Chery ◽  
Alexandre Zahariev ◽  
...  
Keyword(s):  
Insulin Sensitivity ◽  
Energy Balance ◽  
Glucose Tolerance ◽  
Glucose Intolerance ◽  
Physical Inactivity ◽  
Bed Rest ◽  
Protein Supplementation ◽  
Fat Deposition ◽  
Metabolic Flexibility ◽  
Metabolic Inflexibility

Abstract Context The effects of energy-balanced bed rest on metabolic flexibility have not been thoroughly examined. Objective We investigated the effects of 21 days of bed rest, with and without whey protein supplementation, on metabolic flexibility while maintaining energy balance. We hypothesized that protein supplementation mitigates metabolic inflexibility by preventing muscle atrophy. Design and Setting Randomized crossover longitudinal study conducted at the German Aerospace Center, Cologne, Germany. Participants and Interventions Ten healthy men were randomly assigned to dietary countermeasure or isocaloric control diet during a 21-day bed rest. Outcome Measures Before and at the end of the bed rest, metabolic flexibility was assessed during a meal test. Secondary outcomes were glucose tolerance by oral glucose tolerance test, body composition by dual energy X-ray absorptiometry, ectopic fat storage by magnetic resonance imaging, and inflammation and oxidative stress markers. Results Bed rest decreased the ability to switch from fat to carbohydrate oxidation when transitioning from fasted to fed states (i.e., metabolic inflexibility), antioxidant capacity, fat-free mass (FFM), and muscle insulin sensitivity along with greater fat deposition in muscle (P < 0.05 for all). Changes in fasting insulin and inflammation were not observed. However, glucose tolerance was reduced during acute overfeeding. Protein supplementation did not prevent FFM loss and metabolic alterations. Conclusions Physical inactivity triggers metabolic inflexibility, even when energy balance is maintained. Although reduced insulin sensitivity and increased fat deposition were observed at the muscle level, systemic glucose intolerance was detected only in response to a moderately high-fat meal. This finding supports the role of physical inactivity in metabolic inflexibility and suggests that metabolic inflexibility precedes systemic glucose intolerance.

Increased capillary density in skeletal muscle is not associated with impaired insulin sensitivity induced by bed rest in healthy young men

2018 ◽  
Vol 43 (12) ◽  
pp. 1334-1340 ◽  
Author(s):  
David Montero ◽  
Laura Oberholzer ◽  
Thomas Haider ◽  
Andreas Breenfeldt-Andersen ◽  
Sune Dandanell ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Glucose Homeostasis ◽  
Physical Inactivity ◽  
Bed Rest ◽  
Capillary Density ◽  
Human Model ◽  
Full Time ◽  
Matsuda Index

Physical inactivity alters glucose homeostasis in skeletal muscle, potentially developing into overt metabolic disease. The present study sought to investigate the role of skeletal muscle capillarization in glucose tolerance and insulin sensitivity (IS) using a classic human model of physical inactivity. Thirteen healthy males (age = 23 ± 2 years) underwent 4 days of full-time supervised and diet-controlled bed rest. Oral glucose tolerance test, indices of IS (quantitative insulin sensitivity check index (QUICKI), Matsuda index), as well as skeletal muscle biopsies with measurement of fiber type distribution, fiber cross-sectional area (FCSA), capillary-to-fiber ratio (C/F ratio), and capillary density (CD) were assessed prior to and after bed rest. Body weight and composition were unaltered by bed rest. Fasting glucose/insulin ratio (G0/I0 ratio) (−25%, P = 0.016), QUICKI (−7%, P = 0.023), and Matsuda index (−24%, P = 0.003) diminished with bed rest. Skeletal muscle FCSA decreased (−737.4 ± 763.2 μm−2 (−12%), P = 0.005) while C/F ratio was preserved, resulting in augmented CD (+93.9 ± 91.5 capillaries·mm−2 (+37%), P = 0.003) with bed rest. No association was detected between changes in skeletal muscle variables and metabolic outcomes. Independently of bed rest-induced effects, a positive linear relationship was detected between C/F ratio and G0/I0 ratio (β = 17.09, P = 0.021). In conclusion, impaired glucose homeostasis with bed rest is not prevented nor associated with enhanced skeletal muscle capillarization in healthy individuals.

Abstract 58: Angiotensin-(1-7) Mas Receptors In The Arcuate Nucleus Of The Hypothalamus Protect Against High Fat Diet-induced Insulin Resistance In Female Mice

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Darren Mehay ◽  
Sarah Bingaman ◽  
Yuval Silberman ◽  
Amy Arnold
Keyword(s):  
Body Composition ◽  
Insulin Sensitivity ◽  
Energy Balance ◽  
Glucose Tolerance ◽  
High Fat Diet ◽  
Metabolic Regulation ◽  
Arcuate Nucleus ◽  
Control Diet ◽  
High Fat ◽  
Metabolic Outcomes

Angiotensin (Ang)-(1-7) is a protective hormone of the renin-angiotensin system that improves insulin sensitivity, glucose tolerance, and energy balance in obese rodents. Our recent findings suggest that Ang-(1-7) activates mas receptors (MasR) in the arcuate nucleus of the hypothalamus (ARC), a brain region critical to control of energy balance and glucose homeostasis, to induce these positive metabolic effects. The distribution of MasR in the ARC and their role in metabolic regulation, however, is unknown. We hypothesized: (1) MasR are expressed in the ARC; and (2) deletion of ARC MasR leads to worsened metabolic outcomes following high fat diet (HFD). To test this, male and female C57Bl/6J mice were fed a 60% HFD or matched control diet ad libitum for 12 weeks. RNAscope in situ hybridization was performed on coronal ARC sections in rostral-middle-caudal regions to determine percentage of MasR positive neurons (n=5/group). In a second experiment, we assessed body composition and insulin and glucose tolerance in transgenic mice with deletion of MasR in ARC neurons (MasR-flox with AAV5-hsyn-GFP-Cre). RNAscope revealed a wide distribution on MasR-positive cells throughout the rostral to caudal extent of the ARC. The average percentage of MasR positive neurons was increased in females versus males, with HFD tending to increase MasR expression in both sexes (control diet male: 11±2; control diet female: 17±3; HFD male: 15±5; HFD female: 24±2; p sex : 0.030; p diet : 0.066; p int : 0.615; two-way ANOVA). Deletion of MasR in ARC neurons worsened insulin sensitivity in HFD but not control diet females (area under the curve for change in glucose from baseline: -1989±1359 HFD control virus vs. 2530±1762 HFD Cre virus; p=0.016), while fasting glucose, glucose tolerance, and body composition did not change. There was no effect of ARC MasR deletion on metabolic outcomes in control diet or HFD male mice. These findings suggest females have more MasR positive neurons in the ARC compared to males, which may be a sex-specific protective mechanism for glucose homeostasis. While further studies are needed to explore the role of ARC MasR in metabolic regulation, these findings support targeting Ang-(1-7) as an innovative strategy in obesity.

Insulin resistance caused by amylin in conscious rats is independent of induced hypocalcemia and fades during long-term exposure

1993 ◽  
Vol 129 (4) ◽  
pp. 360-365 ◽  
Author(s):  
Clemens Fürnsinn ◽  
Peter Nowotny ◽  
Michael Roden ◽  
Madeleine Rohac ◽  
Thomas Pieber ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Glucose Intolerance ◽  
Tolerance Test ◽  
Zucker Rats ◽  
Control Group ◽  
Short Term ◽  
Euglycemic Hyperinsulinemic Clamp

To compare the effect of short- vs long-term amylin infusion on insulin sensitivity, glucose tolerance and serum calcemia, euglycemic-hyperinsulinemic clamp (26 pmol·kg−1·min−1) and glucose tolerance tests (2.4 mmol/kg over 30 min) were performed in lean Zucker rats. Three infusion protocols were employed: control group: 24 h of iv saline; short-term amylin exposure: 22 h of iv saline followed by 2 h of iv amylin (20 μg/h); long-term amylin exposure: 24 h of iv amylin (20 μg/h). Insulin resistance was induced by short-term amylin infusion during euglycemic clamping, as shown by a 41% decrease in space-corrected glucose infusion rates (μmol·kg−1·min−1; control group, 106.0±15.0; short-term iv amylin, 62.7±15.0; p<0.00 5). After long-term amylin exposure, insulin sensitivity was identical to control values (109.9±6.7). This fading action of amylin was confirmed by data from the glucose tolerance test, demonstrating glucose intolerance after short- but not after long-term amylin exposure. Serum calcium concentration decreased during short-term (2 h) amylin infusion (from 2.52±0.15 to 2.09±0.12 mmol/l; p<0.01) and hypocalcemia of a similar extent also was present after 22 h and 24 h of amylin exposure (2.10±0.09 and 2.04±0.14 mmol/l, respectively). The data demonstrate that short-term amylin infusion induces insulin resistance and glucose intolerance, both of which vanish during long-term (>22 h) amylin exposure, being apparently independent of induced hypocalcemia.

Effect of contrasted levels of habitual physical activity on metabolic flexibility

2013 ◽  
Vol 114 (3) ◽  
pp. 371-379 ◽  
Author(s):  
Audrey Bergouignan ◽  
Edwina Antoun ◽  
Iman Momken ◽  
Dale A. Schoeller ◽  
Guillemette Gauquelin-Koch ◽  
...  
Keyword(s):  
Physical Activity ◽  
Metabolic Diseases ◽  
Bed Rest ◽  
Normal Weight ◽  
Activity Level ◽  
Habitual Physical Activity ◽  
Metabolic Flexibility ◽  
Sedentary Behaviors ◽  
Cross Sectional ◽  
Metabolic Inflexibility

The factors regulating the body's ability to switch from fat to carbohydrate oxidation in response to fuel availability changes, or metabolic flexibility (MF), are currently intensively investigated in the context of metabolic diseases. Although numerous metabolic diseases are associated with sedentary behaviors and metabolic inflexibility, the effect of habitual physical activity level (PAL) on MF regulation is surprisingly poorly known. We investigated how PAL affects MF in cross-sectional and interventional studies. MF was assessed in 44 subjects: normal-weight and overweight sedentary men submitted to 2 mo of exercise at current recommendations, normal-weight active men submitted to 1 mo of reduced PAL and normal-weight women submitted to 1 mo of bed rest, with or without exercise. MF was evaluated, before and after interventions, following two standard meals as the relationship between individual mathematical variances in insulin and nonprotein respiratory quotient (NPRQ) daily kinetics. Daily NPRQ and insulin variances differed according to habitual PAL ( P = 0.002 and P = 0.009, respectively); active subjects had higher variances in NPRQ for lower variances in insulin than sedentary subjects, indicating a better MF. Detraining increased insulin variance ( P = 0.009) and decreased NPRQ variance ( P = 0.003), while training tended to have opposite effects. Insulin and NPRQ variances were negatively related along the PAL continuum ( R2 = 0.70, P < 0.001). Variance in NPRQ was also positively related to PAL ( R2 = 0.52, P < 0.001). By assessing MF with mathematical surrogates in conditions of daily pattern in meal's intake, we showed that habitual PAL is associated with MF status, and that MF is modulated by changes in PAL.

scholarly journals Insulin sensitivity and metabolic flexibility following exercise training among different obese insulin-resistant phenotypes

2013 ◽  
Vol 305 (10) ◽  
pp. E1292-E1298 ◽  
Author(s):  
Steven K. Malin ◽  
Jacob M. Haus ◽  
Thomas P. J. Solomon ◽  
Alecia Blaszczak ◽  
Sangeeta R. Kashyap ◽  
...  
Keyword(s):  
Insulin Sensitivity ◽  
Exercise Training ◽  
Glucose Tolerance ◽  
Glucose Disposal ◽  
Oral Glucose ◽  
Metabolic Flexibility ◽  
Euglycemic Hyperinsulinemic Clamp ◽  
Hepatic Insulin Sensitivity ◽  
Peripheral Insulin Sensitivity ◽  
Chronic Hyperglycemia

Impaired fasting glucose (IFG) blunts the reversal of impaired glucose tolerance (IGT) after exercise training. Metabolic inflexibility has been implicated in the etiology of insulin resistance; however, the efficacy of exercise on peripheral and hepatic insulin sensitivity or substrate utilization in adults with IFG, IGT, or IFG + IGT is unknown. Twenty-four older (66.7 ± 0.8 yr) obese (34.2 ± 0.9 kg/m2) adults were categorized as IFG ( n = 8), IGT ( n = 8), or IFG + IGT ( n = 8) according to a 75-g oral glucose tolerance test (OGTT). Subjects underwent 12-wk of exercise (60 min/day for 5 days/wk at ∼85% HRmax) and were instructed to maintain a eucaloric diet. A euglycemic hyperinsulinemic clamp (40 mU·m2·min−1) with [6,6-2H]glucose was used to determine peripheral and hepatic insulin sensitivity. Nonoxidative glucose disposal and metabolic flexibility [insulin-stimulated respiratory quotient (RQ) minus fasting RQ] were also assessed. Glucose incremental area under the curve (iAUCOGTT) was calculated from the OGTT. Exercise increased clamp-derived peripheral and hepatic insulin sensitivity more in adults with IFG or IGT alone than with IFG + IGT ( P < 0.05). Exercise reduced glucose iAUCOGTT in IGT only ( P < 0.05), and the decrease in glucose iAUCOGTT was inversely correlated with the increase in peripheral but not hepatic insulin sensitivity ( P < 0.01). Increased clamp-derived peripheral insulin sensitivity was also correlated with enhanced metabolic flexibility, reduced fasting RQ, and higher nonoxidative glucose disposal ( P < 0.05). Adults with IFG + IGT had smaller gains in clamp-derived peripheral insulin sensitivity and metabolic flexibility, which was related to blunted improvements in postprandial glucose. Additional work is required to assess the molecular mechanism(s) by which chronic hyperglycemia modifies insulin sensitivity following exercise training.

Neuromuscular electrical stimulation and protein during bed rest increases CD11b+ skeletal muscle macrophages but does not correspond to muscle size or insulin sensitivity

2020 ◽  
Vol 45 (11) ◽  
pp. 1261-1269
Author(s):  
Paul T. Reidy ◽  
Logan T. Edvalson ◽  
Alec I. McKenzie ◽  
Jonathan J. Petrocelli ◽  
Ziad S. Mahmassani ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Older Adults ◽  
Extracellular Matrix ◽  
Electrical Stimulation ◽  
Insulin Sensitivity ◽  
Lean Mass ◽  
Neuromuscular Electrical Stimulation ◽  
Bed Rest ◽  
Protein Supplementation ◽  
Muscle Size

With this cohort, we previously demonstrated preservation of thigh lean tissue with neuromuscular electrical stimulation combined with protein supplementation (NMES+PRO) treatment during bed rest in healthy older adults. Because macrophage polarization plays a significant role in the repair and maintenance of muscle size and insulin sensitivity, we hypothesized that muscle macrophages would be induced by NMES+PRO and would correspond to an increase in lean mass and an attenuated insulin resistance response altered by bed rest. Older adults (60–80 years old; body mass index < 30 kg/m2) underwent 5 days of bed rest and were randomized to either thrice daily treatment of NMES+PRO (n = 8) or CON (n = 8). Lean mass, insulin sensitivity, and markers of muscle macrophages, inflammation, and connective tissue were determined before and after bed rest. Glucose intolerance and insulin resistance occurred after bed rest but there was not a treatment effect (p > 0.10). Proinflammatory-like macrophages (CD11b+, CD206−) increased (p < 0.05) with NMES+PRO treatment and was different than CON. Minor changes in noncontractile tissue were observed. However, changes in muscle macrophages or extracellular matrix were not related to the preservation of thigh lean mass or insulin resistance. Daily NMES+PRO treatment during bed rest induced a muscle proinflammatory-like macrophage response and was unrelated to muscle size or metabolic function. This study is listed as clinical trial NCT02566590. Novelty Neuromuscular electrical stimulation combined with protein supplementation (NMES+PRO) increased proinflammatory-like macrophages and extracellular matrix content in older adults after bed rest. NMES+PRO changes in macrophages and noncontractile tissue macrophages were not related to muscle size preservation or insulin sensitivity.

Imidazoline-like drugs improve insulin sensitivity through peripheral stimulation of adiponectin and AMPK pathways in a rat model of glucose intolerance

2015 ◽  
Vol 309 (2) ◽  
pp. E95-E104 ◽  
Author(s):  
Maud Weiss ◽  
Soumaya Bouchoucha ◽  
Farouk Aiad ◽  
Estelle Ayme-Dietrich ◽  
Nassim Dali-Youcef ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Glucose Intolerance ◽  
Rat Model ◽  
Plasma Levels ◽  
Improve Insulin Sensitivity ◽  
The Metabolic Syndrome ◽  
Ampk Phosphorylation ◽  
Stimulation Of

Altered adiponectin signaling and chronic sympathetic hyperactivity have both been proposed as key factors in the pathogenesis of metabolic syndrome. We recently reported that activation of I1 imidazoline receptors (I1R) improves several symptoms of the metabolic syndrome through sympathoinhibition and increases adiponectin plasma levels in a rat model of metabolic syndrome (Fellmann L, Regnault V, Greney H, et al. J Pharmacol Exp Ther 346: 370–380, 2013). The present study was designed to explore the peripheral component of the beneficial actions of I1R ligands (i.e., sympathoinhibitory independent effects). Aged rats displaying insulin resistance and glucose intolerance were treated with LNP509, a peripherally acting I1R agonist. Glucose tolerance, insulin sensitivity, and adiponectin signaling were assessed at the end of the treatment. Direct actions of the ligand on hepatocyte and adipocyte signaling were also studied. LNP509 reduced the area under the curve of the intravenous glucose tolerance test and enhanced insulin hypoglycemic action and intracellular signaling (Akt phosphorylation), indicating improved glucose tolerance and insulin sensitivity. LNP509 stimulated adiponectin secretion acting at I1R on adipocytes, resulting in increased plasma levels of adiponectin; it also enhanced AMPK phosphorylation in hepatic tissues. Additionally, I1R activation on hepatocytes directly enhanced AMPK phosphorylation. To conclude, I1R ligands can improve insulin sensitivity acting peripherally, independently of sympathoinhibition; stimulation of adiponectin and AMPK pathways at insulin target tissues may account for this effect. This may open a promising new way for the treatment of the metabolic syndrome.

scholarly journals Impaired glucose tolerance in rats fed low-carbohydrate, high-fat diets

2013 ◽  
Vol 305 (9) ◽  
pp. E1059-E1070 ◽  
Author(s):  
Maximilian Bielohuby ◽  
Stephanie Sisley ◽  
Darleen Sandoval ◽  
Nadja Herbach ◽  
Ayse Zengin ◽  
...  
Keyword(s):  
Weight Loss ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Impaired Glucose Tolerance ◽  
Glucose Intolerance ◽  
Fasting Glucose ◽  
Male Rats ◽  
High Fat ◽  
Insulin Metabolism ◽  
Low Carbohydrate

Moderate low-carbohydrate/high-fat (LC-HF) diets are widely used to induce weight loss in overweight subjects, whereas extreme ketogenic LC-HF diets are used to treat neurological disorders like pediatric epilepsy. Usage of LC-HF diets for improvement of glucose metabolism is highly controversial; some studies suggest that LC-HF diets ameliorate glucose tolerance, whereas other investigations could not identify positive effects of these diets or reported impaired insulin sensitivity. Here, we investigate the effects of LC-HF diets on glucose and insulin metabolism in a well-characterized animal model. Male rats were fed isoenergetic or hypocaloric amounts of standard control diet, a high-protein “Atkins-style” LC-HF diet, or a low-protein, ketogenic, LC-HF diet. Both LC-HF diets induced lower fasting glucose and insulin levels associated with lower pancreatic β-cell volumes. However, dynamic challenge tests (oral and intraperitoneal glucose tolerance tests, insulin-tolerance tests, and hyperinsulinemic euglycemic clamps) revealed that LC-HF pair-fed rats exhibited impaired glucose tolerance and impaired hepatic and peripheral tissue insulin sensitivity, the latter potentially being mediated by elevated intramyocellular lipids. Adjusting visceral fat mass in LC-HF groups to that of controls by reducing the intake of LC-HF diets to 80% of the pair-fed groups did not prevent glucose intolerance. Taken together, these data show that lack of dietary carbohydrates leads to glucose intolerance and insulin resistance in rats despite causing a reduction in fasting glucose and insulin concentrations. Our results argue against a beneficial effect of LC-HF diets on glucose and insulin metabolism, at least under physiological conditions. Therefore, use of LC-HF diets for weight loss or other therapeutic purposes should be balanced against potentially harmful metabolic side effects.

scholarly journals Liver fat, visceral adiposity, and sleep disturbances contribute to the development of insulin resistance and glucose intolerance in nondiabetic dialysis patients

2008 ◽  
Vol 295 (6) ◽  
pp. R1721-R1729 ◽  
Author(s):  
Giorgos K. Sakkas ◽  
Christina Karatzaferi ◽  
Elias Zintzaras ◽  
Christoforos D. Giannaki ◽  
Vassilios Liakopoulos ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Glucose Intolerance ◽  
Sleep Disturbances ◽  
Hemodialysis Patients ◽  
Fat Content ◽  
Curve Analysis ◽  
Visceral Adiposity ◽  
Roc Curve Analysis

Hemodialysis patients exhibit insulin resistance (IR) in target organs such as liver, muscles, and adipose tissue. The aim of this study was to identify contributors to IR and to develop a model for predicting glucose intolerance in nondiabetic hemodialysis patients. After a 2-h, 75-g oral glucose tolerance test (OGTT), 34 hemodialysis patients were divided into groups with normal (NGT) and impaired glucose tolerance (IGT). Indices of insulin sensitivity were derived from OGTT data. Measurements included liver and muscle fat infiltration and central adiposity by computed tomography scans, body composition by dual energy X-ray absorptiometer, sleep quality by full polysomnography, and functional capacity and quality of life (QoL) by a battery of exercise tests and questionnaires. Cut-off points, as well as sensitivity and specificity calculations were based on IR (insulin sensitivity index by Matsuda) using a receiver operator characteristics (ROC) curve analysis. Fifteen patients were assigned to the IGT, and 19 subjects to the NGT group. Intrahepatic fat content and visceral adiposity were significantly higher in the IGT group. IR indices strongly correlated with sleep disturbances, visceral adiposity, functional capacity, and QoL. Visceral adiposity, O2 desaturation during sleep, intrahepatic fat content, and QoL score fitted into the model for predicting glucose intolerance. A ROC curve analysis identified an intrahepatic fat content of >3.97% (sensitivity, 100; specificity, 35.7) as the best cutoff point for predicting IR. Visceral and intrahepatic fat content, as well as QoL and sleep seemed to be involved at some point in the development of glucose intolerance in hemodialysis patients. Means of reducing fat depots in the liver and splachnic area might prove promising in combating IR and cardiovascular risk in hemodialysis patients.

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