Intramyocellular Lipid Research Articles

Altered Lipid Metabolism Impairs Skeletal Muscle Force in Young Rats Submitted to a Short-Term High-Fat Diet.

Obesity and ensuing disorders are increasingly prevalent in young populations. Prolonged exposure to high-fat diets (HFD) and excessive lipid accumulation were recently suggested to impair skeletal muscle functions in rodents. We aimed to determine the effects of a short-term HFD on skeletal muscle function in young rats. Young male Wistar rats (100–125 g) were fed HFD or a regular chow diet (RCD) for 14 days. Specific force, resistance to fatigue and recovery were tested in extensor digitorum longus (EDL; glycolytic) and soleus (SOL; oxidative) muscles using an ex vivo muscle contractility system. Muscle fiber typing and insulin signaling were analyzed while intramyocellular lipid droplets (LD) were characterized. Expression of key markers of lipid metabolism was also measured. Weight gain was similar for both groups. Specific force was decreased in SOL, but not in EDL of HFD rats. Muscle resistance to fatigue and force recovery were not altered in response to the diets. Similarly, muscle fiber type distribution and insulin signaling were not influenced by HFD. On the other hand, percent area and average size of intramyocellular LDs were significantly increased in the SOL of HFD rats. These effects were consistent with the increased expression of several mediators of lipid metabolism in the SOL muscle. A short-term HFD impairs specific force and alters lipid metabolism in SOL, but not EDL muscles of young rats. This indicates the importance of clarifying the early mechanisms through which lipid metabolism affects skeletal muscle functions in response to obesogenic diets in young populations.

Intestinal microbiota lipid metabolism varies across rainbow trout (Oncorhynchus mykiss) phylogeographic divide.

This study focused on intestinal microbiome variation across the phylogeogrpahic divide of rainbow trout and its potential functional effects on ocean migration. Hindgut intestinal contents were analysed using the 16S V4 hypervariable ribosomal gene region. Core microbiome taxonomies and overall microbial diversity were identified across the species phylogeographic divide with increased diversity found in Eastern Cascade fish. To determine potential functional differences between groups PICRUSt metagenomics analysis was utilized, revealing significant enrichment of lipid and fatty acid metabolism genes in Western Cascade fish microbiomes. Decreased levels of intestinal microbial lipid metabolism in Eastern Cascade rainbow trout suggests increased lipid absorption in these fish given the consistent diets. Such absorption, and potential storage, would be an evolutionary benefit for increased migration distances experienced by Eastern Cascade fish. Core microbiome differences, and their functional associations, suggest evolutionary differences at the genetic level noticeably contribute to intestinal microbial community diversity. The possibility of genetic variation controlling intestinal microbiome diversity could have significant impacts on strain selection for rainbow trout aquaculture, especially given the consistent rearing conditions experienced in our sample populations likely result in differences in intramyocellular lipid storage.

Effect of 12 wk of resistant starch supplementation on cardiometabolic risk factors in adults with prediabetes: a randomized controlled trial

Type 2 resistant starch (RS2) has been shown to improve glycemic control and some cardiovascular endpoints in rodent and human studies. The aim of this study was to perform one of the first randomized clinical trials in adults with prediabetes and one of the longest trials to test whether RS2 can improve cardiometabolic health. 68 overweight [body mass index (BMI) ≥27 kg/m2] adults aged 35-75 y with prediabetes were randomized to consume 45 g/d of high-amylose maize (RS2) or an isocaloric amount of the rapidly digestible starch amylopectin (control) for 12 wk. At baseline and postintervention, ectopic fat depots (visceral adipose tissue, intrahepatic lipids, and intramyocellular lipids) were measured by magnetic resonance imaging/spectroscopy, energy metabolism by respiratory chamber, and carbohydrate metabolism by glycated hemoglobin (HbA1c), an intravenous glucose tolerance test, and a meal tolerance test. Cardiovascular risk factors-serum lipids, blood pressure, heart rate, and inflammatory markers (high-sensitivity C-reactive protein [hs-CRP], interleukin-6, and tumor necrosis factor [TNF]-α)-were also measured. The primary endpoints were insulin sensitivity, insulin secretion, ectopic fat, and markers of inflammation. Data were primarily analyzed as treatment effects via a linear mixed model both with and without the addition of covariates. Relative to the control group, RS2 lowered HbA1c by a clinically insignificant 0.1±0.2% (Δ=-1±2 mmol/mol; P=0.05) but did not affect insulin secretion, insulin sensitivity, the disposition index, or glucose or insulin areas under the curve relative to baseline (P≥0.23). RS2 decreased heart rate by 5±9 beats/min (P=0.02) and TNF-α concentrations by 2.1±2.7 pg/mL (P=0.004), relative to the control group. Ectopic fat, energy expenditure, substrate oxidation, and all other cardiovascular risk factors were unaffected (P≥0.06). 12 wk of supplementation with resistant starch reduced the inflammatory marker TNF-α and heart rate, but it did not significantly improve glycemic control and other cardiovascular disease risk factors, in adults with prediabetes. This trial was registered at clinicaltrials.gov as NCT01708694.

Impaired repletion of intramyocellular lipids in patients with growth hormone deficiency after a bout of aerobic exercise

BackgroundEctopic lipids such as intramyocellular lipids (IMCL) are depleted by exercise and repleted by diet, whereas intrahepatocellular lipids (IHCL) are increased immediately after exercise. So far, it is unclear how ectopic lipids behave 24 h after exercise and whether the lack of growth hormone (GH) significantly affects ectopic lipids 24 h after exercise. MethodsSeven male patients with growth hormone deficiency (GHD) and seven sedentary male control subjects (CS) were included. VO2max was assessed by spiroergometry; visceral and subcutaneous fat by whole body MRI. 1H-MR-spectroscopy was performed in M. vastus intermedius and in the liver before and after 2 h of exercise at 50% VO2max and 24 h thereafter, while diet and physical activity were standardized. ResultsSedentary male subjects (7 GHD, 7 CS) were recruited. Age, BMI, waist circumference, visceral and subcutaneous fat mass was not significantly different between GHD and CS. VO2max was significantly lower in GHD vs. CS. IMCL were diminished through aerobic exercise in both groups: (−11.5 ± 21.9% in CS; −8.9% ±19.1% in GHD) and restored after 24 h in CS (−5.5 ± 26.6% compared to baseline) but not in GHD (−17.9 ± 15.3%). IHCL increased immediately after exercise and decreased to baseline within 24 h. ConclusionThese findings suggest that GHD may affect repletion of IMCL 24 h after aerobic exercise.

Serum 25-Hydroxyvitamin D Concentrations Are Inversely Correlated with Hepatic Lipid Content in Male Collegiate Football Athletes

Lower serum 25-hydroxyvitamin D (25(OH)D) concentrations are associated with more weight and fat mass gain in adults in the general population, but it is unknown whether this is the case in collegiate football athletes with greater body weight. This study aimed to investigate associations of serum 25(OH)D concentrations with body fat and ectopic fat accumulation, and to determine which fat indicators are closely related to serum 25(OH)D in male collegiate football athletes. Thirty-four collegiate athletes aged 21 years were recruited. Serum 25(OH)D concentrations and the levels of visceral fat area (VFA), vastus lateralis intramyocellular lipid (IMCL), extramyocellular lipid (EMCL), and intrahepatic lipid (IHCL) were measured. Serum 25(OH)D concentrations were negatively associated with the IHCL values (r = −0.372, p = 0.030), and the relationship remained after adjustment for several factors (r = −0.378, p = 0.047). Additionally, multiple stepwise regression analysis of IHCL content as the dependent variable indicated that 25(OH)D concentrations were a stronger predictor of IHCL content (β = −0.363, p = 0.030) than % body fat and VO2peakFFM. Higher serum 25(OH)D concentrations are more closely related to lower IHCL content rather than any other fat indicators, suggesting that increasing serum 25(OH)D concentrations may have some effect that inhibits lipid accumulation in hepatic tissue, especially in heavy athletes.

Sex differences in body composition and association with cardiometabolic risk

BackgroundBody composition differs between men and women, with women having proportionally more fat mass and men more muscle mass. Although men and women are both susceptible to obesity, health consequences differ between the sexes. The purpose of our study was to assess sex differences in body composition using anatomic and functional imaging techniques, and its relationship to cardiometabolic risk markers in subjects with overweight/obesity.MethodsAfter written informed consent, we prospectively recruited 208 subjects with overweight/obesity who were otherwise healthy (94 men, 114 women, age 37 ± 10 years, BMI 35 ± 6 kg/m2). Subjects underwent dual-energy X-ray absorptiometry (DXA) and computed tomography (CT) for fat and muscle mass, proton MR spectroscopy (1H-MRS) for intrahepatic (IHL) and intramyocellular lipids (IMCL), an oral glucose tolerance test, serum insulin, lipids, and inflammatory markers. Men and women were compared by Wilcoxon signed rank test. Linear correlation and multivariate analyses between body composition and cardiometabolic risk markers were performed.ResultsWomen and men were of similar mean age and BMI (p ≥ 0.2). Women had higher %fat mass, extremity fat, and lower lean mass compared to men (p ≤ 0.0005). However, men had higher visceral adipose tissue (VAT) and IMCL and higher age-and BMI-adjusted IHL (p < 0.05). At similar age and BMI, men had a more detrimental cardiometabolic risk profile compared to women (p < 0.01). However, VAT in women, and IMCL in men, were more strongly associated with cardiometabolic risk markers, while more lower extremity fat was associated with a more favorable cardiometabolic profile in women compared to men (p ≤ 0.03).ConclusionsAlthough the male pattern of fat distribution is associated with a more detrimental cardiometabolic risk profile compared to women of similar age and BMI, VAT is more strongly associated with cardiometabolic risk markers in women, while IMCL are more detrimental in men. Lower extremity fat is relatively protective, in women more than in men. This suggests that detailed anatomic and functional imaging, rather than BMI, provides a more complete understanding of metabolic risk associated with sex differences in fat distribution.

Weight Loss and Exercise Decrease Saturation of Intramyocellular Lipid Species in Association with Improvements in Insulin Sensitivity

Observational cross-sectional studies have described associations between the saturation status of both phospholipids and diacylglycerol (DAG) with insulin sensitivity (IS) of skeletal muscle. The purpose of this study was to test the hypothesis that diet-induced weight loss and exercise reduce intramyocellular lipid saturation and that this is associated with improved IS. We studied forty subjects who competed a randomized controlled trial (RCT) consisting of 6 months of either Health Education Control (CON: n=13 5M/8F), Diet-induced weight-loss only (DIWL: n=13 5M/8F), or Weight-loss and Exercise (WLEX: n=14 6M/9F). DIWL and WLEX subjects had a goal of 10% weight-loss through calorie restriction. Hyperinsulinemic euglycemic clamps were employed to measure IS, and muscle biopsies were obtained to quantify intramyocellular lipids by mass spectrometry. The DIWL and WLEX groups both lost a significant amount of weight compared to CON (DIWL: -6.4%, WLEX: -11.3%, CON: -2.5%, P&amp;lt;0.05). IS measured as the glucose infusion rate required to maintain euglycemia during the clamp increased in the DIWL and WLEX groups compared to the control group (DIWL: 1.0, WLEX: 2.7, CON: 0.6 mg/FFMkg/min, P&amp;lt;0.05). Total phosphatidylethanolamine (PE), phosphatidylcholine (PC), diacylglycerols (DAG) did not significantly change following intervention (P&amp;gt;0.05). However, there were trends for unsaturated PE and PC species to increase in the WLEX only and saturated DAG and ceramide species to be reduced in both the DIWL and WLEX group. The increase in unsaturation of PE and PC were associated with improvements in IS (PE: P=0.047, r=0.35; PC: P=0.072, r=0.32) and the decrease in saturation of DAG was associated with improvements in IS (P=0.044, r=-0.36). In conclusion, weight-loss and exercise increase unsaturated PE and PC species, and reduce saturated DAG species, which are related to improved IS within skeletal muscle. Disclosure R. Standley: None. P.M. Coen: None. B.H. Goodpaster: None.

Skeletal Muscle Lipid Composition Parallels Clinical Phenotype Extremes

Intramyocellular lipid (IMCL) is generally associated with insulin resistance and lipotoxicity. However, the “athlete’s paradox” is well documented, where IMCL levels are similar between athletes and patients with type 2 diabetes despite discrepant levels of insulin sensitivity. Differences in muscle lipid metabolites between aerobically trained, lean, insulin-sensitive (LT) vs. sedentary, overweight/obese, insulin-resistant (OIR) individuals remain insufficiently characterized and may help to explain the “athlete’s paradox.” LT [n=14: 50% females, 28.5±1.6 years (Mean±SE)] and OIR [n=24: 79% females, 29.8±1.6 years] subjects each provided 2 muscle biopsies from the vastus lateralis (bilateral, 6 hours apart, ≥48 hours after last exercise, ≥8 fasting, overnight admission prior to biopsy) for mass spectrometry analysis. At a separate visit, insulin sensitivity was quantified by a hyperinsulinemic-euglycemic clamp (mg glucose/kg FFM/min). As the sequential biopsy results were not significantly different, the results were averaged for each subject. Compared with the OIR group, the LT group had lower BMI (22.3±0.5 vs. 36.2±1.2 kg/m2:p&amp;lt;0.01), higher fitness (VO2max:53.4±2.2 vs. 26.7±1.1 ml/kg/min: p&amp;lt;0.01), and higher insulin sensitivity (M-value: 17.1±0.7 vs. 8±0.5, p&amp;lt;0.01). Muscle triglycerides in the LT group were lower (nmol/mg muscle) in oleic acid (3.2±0.6 vs. 6.0±1.0, p=0.02) and palmitic acid (1.5±0.2 vs. 3.1±0.5, p&amp;lt;0.01) than the OIR group. Diacylglycerol (DAG) and palmitoylcarnitine concentrations were not significantly different. Only in the OIR group, palmitoylcarnitine correlated with the following: oleic acid (r=0.73, p&amp;lt;0.01), palmitic acid (r=0.73, p&amp;lt;0.01) and DAG (dipalmitate:r=0.53, p=0.03, palmitate+oleate: r=0.51, p=0.04). These findings suggest that either incomplete muscle lipid oxidation or increased acylcarnitine generation is present in the OIR group, thus warranting further research on training effects on muscle lipid turnover. Disclosure L.S. Chow: Research Support; Self; Eli Lilly and Company, National Institute of Diabetes and Digestive and Kidney Diseases. D.G. Mashek: None. T. Bosch: None. A. Bantle: None. M. Petterson: None. D.R. Dengel: None. M.D. Jensen: Other Relationship; Self; Novo Nordisk A/S. Consultant; Self; Novo Nordisk A/S.

Unraveling the Athlete’s Paradox—Higher Insulin Sensitivity and Lower PKC? Activation Despite Higher Bioactive Lipids in Endurance-Trained Athletes

High intramyocellular lipid (IMCL) content associates negatively with insulin sensitivity (IS) in insulin resistant, but not in endurance-trained humans. It has been hypothesized that different cellular distribution of bioactive lipids such as diacylglycerols (DAG) and ceramides (CER) could interfere with insulin action and underlie this “athlete’s paradox.” We examined endurance-trained athletes (ATH; n=9) and sedentary individuals (SED; n=12) with comparable total IMCL, as measured by 1H-magnetic resonance spectroscopy, who underwent spiroergometry and hyperinsulinemic-euglycemic clamps to assess maximal oxidative capacity and IS, respectively. In skeletal muscle biopsies, translocation of protein kinase C (PKC) θ and ε were determined by Western blotting and concentrations of DAG and CER were measured using targeted LC-tandem mass spectrometry upon separating fractions of cellular membranes, lipid droplets and cytosol by ultracentrifugation. Maximal oxidative capacity and IS were 46% and 47% higher in ATH than in SED (both p&amp;lt;0.01), respectively. The membrane:cytosol ratio of PKCθ, which reflects PKCθ activity, was 62% lower in ATH consistent with their increased IS (p&amp;lt;0.01), while there was no group difference for PKCε. Total and membrane DAG (40% and 48%, both p&amp;lt;0.01) as well as membrane CER (15%, p&amp;lt;0.05) were higher in ATH while the respective concentrations in lipid droplets and cytosol did not differ. In SED, IS correlated inversely with all stereoselective subspecies of lipid-droplet DAG. On the other hand, cytosolic sn-1,2 (C16:0-C18:2) and sn-1,3 (C18:1-C18:0) DAG correlated positively with IS in ATH. In conclusion, higher IS in endurance-trained ATH can be explained by lower muscle PKCθ activation, which may be due to differences in the stereoselectivity and/or subcompartmentation of cellular DAG between ATH and insulin resistant SED. Disclosure D. Pesta: None. E. Anadol-Schmitz: None. S. Gancheva: None. D.F. Markgraf: None. O.P. Zaharia: None. H. Katsuyama: None. Y. Kupriyanova: None. J. Hwang: None. D. Zhang: None. G.I. Shulman: Advisory Panel; Self; AstraZeneca, Janssen Research &amp; Development, Merck &amp; Co., Inc., Novo Nordisk Inc.. Research Support; Self; Gilead Sciences, Inc. M. Roden: Speaker's Bureau; Self; Boehringer Ingelheim GmbH. Research Support; Self; Boehringer Ingelheim GmbH. Consultant; Self; Poxel SA. Research Support; Self; Danone Nutricia Early Life Nutrition, GlaxoSmithKline plc., Nutricia Advanced Medical Nutrition, Sanofi.

Skeletal Muscle Dysfunction and Metabolic Abnormalities in Individuals with Familial Partial Lipodystrophy Is Associated with Diminished Mitochondrial Fatty Acid Oxidation

Background: Familial Partial Lipodystrophy, Dunnigan variety (FPLD) is characterized by post-natal fat loss leading to severe insulin resistance. Affected individuals also display striking skeletal muscle hypertrophy, but there is limited information on muscle function and energy metabolism. We therefore systematically investigated muscle and mitochondrial function in 6 individuals with FPLD and 6 matched controls. Methods: Body composition and intramyocellular lipid content (IMCL) were assessed by DEXA and magnetic resonance spectroscopy, respectively. Maximal voluntary strength and fatigue were assessed for both recumbent leg press and seated chest press. Vastus lateralis muscle biopsies were obtained prior to and following a high fat (40%) mixed-meal. Oxygen consumption in isolated mitochondria was measured using substrates supporting carbohydrate or lipid-based respiration. Insulin Sensitivity Index (SI) was calculated by minimal modelling. Results: Individuals with FPLD had significantly lower SI, lower body fat content, and higher lean mass. Peak leg press and chest press force were not different, but FPLD individuals had earlier fatigue during chest press (number of repetitions: 15 ± 0.6 vs. 20 ± 0.3, p = 0.01). They also had a 50-60% decrease in state 3 respiration measured using substrates supporting lipid-based respiration (p = 0.04). Further, mitochondrial oxidative capacity showed a strong correlation with muscle fatigue (r = 0.76, p = 0.003), and inversely correlated with fasting and post-prandial lipemia and measures of insulin resistance. Conclusion: Individuals with FPLD have higher lean body mass and lower insulin sensitivity. Despite preserved peak muscle strength, they demonstrated earlier muscle fatigue. Decreased mitochondrial fatty acid oxidative capacity, likely related to elevated IMCL, may contribute to muscular and metabolic abnormalities. Disclosure V. Simha: None. I.R. Lanza: None. N. LeBrasseur: None. K. Klaus: None. J. Port: None. M.C. Laurenti: Other Relationship; Self; GlySens Incorporated. C. Cobelli: Research Support; Self; Sanofi-Aventis. Advisory Panel; Self; Novo Nordisk Inc.. K. Nair: None.

ACC2 Deletion Enhances IMCL Reduction Along With Acetyl-CoA Metabolism and Improves Insulin Sensitivity in Male Mice.

Intramyocellular lipid (IMCL) accumulation in skeletal muscle greatly contributes to lipid-induced insulin resistance. Because acetyl-coenzyme A (CoA) carboxylase (ACC) 2 negatively modulates mitochondrial fatty acid oxidation (FAO) in skeletal muscle, ACC2 inhibition is expected to reduce IMCL via elevation of FAO and to attenuate insulin resistance. However, the concept of substrate competition suggests that enhanced FAO results in reduced glucose use because of an excessive acetyl-CoA pool in mitochondria. To identify how ACC2-regulated FAO affects IMCL accumulation and glucose metabolism, we generated ACC2 knockout (ACC2-/-) mice and investigated skeletal muscle metabolites associated with fatty acid and glucose metabolism, as well as whole-body glucose metabolism. ACC2-/- mice displayed higher capacity of glucose disposal at the whole-body levels. In skeletal muscle, ACC2-/- mice exhibited enhanced acylcarnitine formation and reduced IMCL levels without alteration in glycolytic intermediate levels. Notably, these changes were accompanied by decreased acetyl-CoA content and enhanced mitochondrial pathways related to acetyl-CoA metabolism, such as the acetylcarnitine production and tricarboxylic acid cycle. Furthermore, ACC2-/- mice exhibited lower levels of IMCL and acetyl-CoA even under HFD conditions and showed protection against HFD-induced insulin resistance. Our findings suggest that ACC2 deletion leads to IMCL reduction without suppressing glucose use via an elevation in acetyl-CoA metabolism even under HFD conditions and offer new mechanistic insight into the therapeutic potential of ACC2 inhibition on insulin resistance.

Effect of puerarin in promoting fatty acid oxidation by increasing mitochondrial oxidative capacity and biogenesis in skeletal muscle in diabetic rats

BackgroundType 2 diabetes is characterized by dyslipidemia and the accumulation of lipids in non-adipose tissue, including skeletal muscle. Puerarin, which is a natural isoflavonoid isolated from the root of the plant Pueraria lobata, has been shown to have antidiabetic activity. However, the lipid-reducing effect of puerarin, in particular in skeletal muscle, has not yet been addressed.MethodsWe examined the effect of puerarin on mitochondrial function and the oxidation of fatty acids in the skeletal muscle of high-fat diet/streptozotocin-induced diabetic rats.ResultsPuerarin effectively alleviated dyslipidemia and decreased the accumulation of intramyocellular lipids by upregulating the expression of a range of genes involved in mitochondrial biogenesis, oxidative phosphorylation, the detoxification of reactive oxygen species, and the oxidation of fatty acids in the muscle of diabetic rats. Also, the effect of puerarin on mitochondrial biogenesis might partially involve the function of the μ-opioid receptor. In addition, puerarin decreased the trafficking of fatty acid translocase/CD36 to the plasma membrane to reduce the uptake of fatty acids by myocytes. In vitro studies confirmed that puerarin acted directly on muscle cells to promote the oxidation of fatty acids in insulin-resistant myotubes treated with palmitate.ConclusionsPuerarin improved the performance of mitochondria in muscle and promoted the oxidation of fatty acids, which thus prevented the accumulation of intramyocellular lipids in diabetic rats. Our findings will be beneficial both for elucidating the mechanism of the antidiabetic activity of puerarin and for promoting the therapeutic potential of puerarin in the treatment of diabetes.

Early potential effects of resveratrol supplementation on skeletal muscle adaptation involved in exercise-induced weight loss in obese mice.

Exercise and resveratrol supplementation exhibit anti-obesity functions in the long term but have not been fully investigated yet in terms of their early potential effectiveness. Mice fed with high-fat diet were categorized into control (Cont), exercise (Ex), resveratrol supplementation (Res), and exercise combined with resveratrol supplementation (Ex + Res) groups. In the four-week period of weight loss, exercise combined with resveratrol supplementation exerted no additional effects on body weight loss but significantly improved whole-body glucose and lipid homeostasis. The combined treatment significantly decreased intrahepatic lipid content but did not affect intramyocellular lipid content. Moreover, the treatment significantly increased the contents of mtDNA and cytochrome c, the expression levels of peroxisome proliferator-activated receptor gamma coactivator-1 alpha and its downstream transcription factors, and the activities of ATPase and citrate synthase. However, exercise, resveratrol, and their combination did not promote myofiber specification toward slow-twitch type. The effects of exercise combined with resveratrol supplementation on weight loss could be partly due to enhanced mitochondrial biogenesis and not to fiber-type shift in skeletal muscle tissues.

A heterogeneous response of liver and skeletal muscle fat to the combination of a Paleolithic diet and exercise in obese individuals with type 2 diabetes: a randomised controlled trial

Aims/hypothesisThe aim of the study was to investigate ectopic fat deposition and insulin sensitivity, in a parallel single-blinded randomised controlled trial, comparing Paleolithic diet alone with the combination of Paleolithic diet and exercise in individuals with type 2 diabetes.MethodsThirty-two individuals with type 2 diabetes with BMI 25–40 kg/m2 and 30–70 years of age followed a Paleolithic diet ad libitum for 12 weeks. In addition, study participants were randomised by computer program to either supervised combined exercise training (PD-EX group) or standard care exercise recommendations (PD group). Staff performing examinations and assessing outcomes were blinded to group assignment. Thirteen participants were analysed in each group: hepatic and peripheral insulin sensitivity were measured using the hyperinsulinaemic–euglycaemic clamp technique combined with [6,6-2H2]glucose infusion, and liver fat was assessed by proton magnetic resonance spectroscopy; both analyses were secondary endpoints. Intramyocellular lipid (IMCL) content was measured by magnetic resonance spectroscopy as a secondary analysis. All examinations were performed at Umeå University Hospital, Umeå, Sweden.ResultsBoth study groups showed a median body weight loss of 7 kg. Fat mass decreased by 5.7 kg in the PD group and by 6.5 kg in the PD-EX group. Maximum oxygen uptake increased in the PD-EX group only. Liver fat showed a consistent reduction (74% decrease) in the PD group, while the response in the PD-EX group was heterogeneous (p < 0.05 for the difference between groups). IMCL content of the soleus muscle decreased by 40% in the PD group and by 22% in the PD-EX group (p < 0.05 for the difference between groups). Both groups improved their peripheral and adipose tissue insulin sensitivity, but not their hepatic insulin sensitivity. Plasma fetuin-A decreased by 11% in the PD group (p < 0.05) and remained unchanged in the PD-EX group. Liver fat changes during the intervention were correlated with changes in fetuin-A (rS = 0.63, p < 0.01). Participants did not report any important adverse events caused by the intervention.Conclusions/interpretationA Paleolithic diet reduced liver fat and IMCL content, while there was a tissue-specific heterogeneous response to added exercise training.Trial registrationClinicalTrials.gov NCT01513798FundingSwedish Diabetes Research Foundation, County Council of Västerbotten, Swedish Heart and Lung Foundation, King Gustav V and Queen Victoria’s Foundation

Moderate Weight Loss Improves Body Composition and Metabolic Function in Metabolically Unhealthy Lean Subjects.

Individuals who have "metabolically obese normal weight" (MONW) have an increased risk for cardiometabolic disease. Moderate weight loss has multiple benefits in people with obesity, but its effects in lean people are unknown. Thus, the effects of diet-induced 5% weight loss on body composition and metabolic function in MONW subjects were evaluated. Total body fat, visceral adipose tissue (VAT) and subcutaneous abdominal adipose tissue (SAT) volumes, intrahepatic and intramyocellular lipid contents, insulin sensitivity (hyperinsulinemic-euglycemic clamp), glucose tolerance, and postprandial insulin secretion and clearance rates (mixed meal with minimal modeling) were measured before and after 4.8% ± 0.5% weight loss in 11 MONW Asians (48 ± 3 years old, six men and five women, BMI 22.7 ± 0.4 kg/m2 ). Weight loss decreased total fat mass by ∼9%, VAT and SAT volumes by ∼11% and ∼17%, respectively, and intrahepatic fat by ∼50% (all P < 0.05). Fasting plasma insulin, triglyceride, and total low- and high-density lipoprotein cholesterol concentrations were also reduced (P < 0.05). Insulin sensitivity indexes (M-value and M/I ratio) increased by 21% to 26% (both P < 0.05); β-cell responsivity and postprandial insulin secretion rate did not change, but insulin clearance rate increased by 16% (P < 0.05). Diet-induced moderate weight loss improves body composition, lipid profile, and insulin sensitivity and thereby reduces cardiometabolic risk in MONW Asians.

Resveratrol improves ex vivo mitochondrial function but does not affect insulin sensitivity or brown adipose tissue in first degree relatives of patients with type 2 diabetes

ObjectiveResveratrol supplementation improves metabolic health in healthy obese men, but not in patients with type 2 diabetes (T2D) when given as add-on therapy. Therefore, we examined whether resveratrol can enhance metabolic health in men at risk of developing T2D. Additionally, we examined if resveratrol can stimulate brown adipose tissue (BAT). MethodsThirteen male first degree relatives (FDR) of patients with T2D received resveratrol (150 mg/day) and placebo for 30 days in a randomized, placebo controlled, cross-over trial. ResultsResveratrol significantly improved ex vivo muscle mitochondrial function on a fatty acid-derived substrate. However, resveratrol did not improve insulin sensitivity, expressed as the rate of glucose disposal during a two-step hyperinsulinemic-euglycemic clamp. Also, intrahepatic and intramyocellular lipid content, substrate utilization, energy metabolism, and cold-stimulated 18F-FDG glucose uptake in BAT (n = 8) remained unaffected by resveratrol. In vitro experiments in adipocytes derived from human BAT confirmed the lack of effect on BAT. ConclusionsResveratrol stimulates muscle mitochondrial function in FDR males, which is in concordance with previous results. However, no other metabolic benefits of resveratrol were found in this group. This could be attributed to subject characteristics causing alterations in metabolism of resveratrol and thereby affecting resveratrol's effectiveness. ClinicalTrials.gov IDNCT02129595.

Randomized, Placebo-Controlled Trial to Evaluate Effects of Eplerenone on Metabolic and Inflammatory Indices in HIV.

HIV-infected individuals demonstrate increased renin-angiotensin-aldosterone system activation in association with visceral adiposity, insulin resistance, and inflammation. A physiologically based treatment approach targeting mineralocorticoid receptor (MR) blockade may improve metabolic and inflammatory indices in HIV. To investigate effects of eplerenone on insulin sensitivity, inflammatory indices, and other metabolic parameters in HIV. Six-month, double-blind, randomized, placebo-controlled trial. Academic clinical research center. HIV-infected individuals with increased waist circumference and abnormal glucose homeostasis. Eplerenone 50 mg or placebo daily. The primary end point was change in insulin sensitivity measured by the euglycemic-hyperinsulinemic clamp technique. Secondary end points included change in body composition and inflammatory markers. Forty-six individuals were randomized to eplerenone (n = 25) vs placebo (n = 21). Eplerenone did not improve insulin sensitivity [0.48 (-1.28 to 1.48) vs 0.43 (-1.95 to 2.55) mg/min/μIU/mL insulin; P = 0.71, eplerenone vs placebo] when measured by the gold standard euglycemic-hyperinsulinemic clamp technique. Intramyocellular lipids (P = 0.04), monocyte chemoattractant protein-1 (P = 0.04), and high-density lipoprotein (P = 0.04) improved among those randomized to eplerenone vs placebo. Trends toward decreases in interleukin-6 (P = 0.10) and high-sensitivity C-reactive protein (P = 0.10) were also seen with eplerenone vs placebo. Plasma renin activity and aldosterone levels increased in the eplerenone vs placebo-treated group, demonstrating expected physiology. MR antagonism with eplerenone was well tolerated among the HIV population, with no considerable changes in blood pressure or potassium. MR blockade may improve selected metabolic and inflammatory indices in HIV-infected individuals. Further studies are necessary to understand the clinical potential of MR antagonism in HIV.

Differences in Muscle Metabolism Between Triathletes and Normally Active Volunteers Investigated Using Multinuclear Magnetic Resonance Spectroscopy at 7T.

Purpose: The influence of endurance training on skeletal muscle metabolism can currently be studied only by invasive sampling or through a few related parameters that are investigated by either proton (1H) or phosphorus (31P) magnetic resonance spectroscopy (MRS). The aim of this study was to compare the metabolic differences between endurance-trained triathletes and healthy volunteers using multi-parametric data acquired by both, 31P- and 1H-MRS, at ultra-high field (7T) in a single experimental protocol. This study also aimed to determine the interrelations between these MRS-derived metabolic parameters.Methods: Thirteen male triathletes and ten active male volunteers participated in the study. Proton MRS data from the vastus lateralis yielded concentrations of acetylcarnitine, carnosine, and intramyocellular lipids (IMCL). For the measurement of phosphodiesters (PDEs), inorganic phosphate (Pi), phosphocreatine (PCr), and maximal oxidative capacity (Qmax) phosphorus MRS data were acquired at rest, during 6 min of submaximal exercise and following immediate recovery.Results: The triathletes exhibited significantly higher IMCL levels, higher initial rate of PCr resynthesis (VPCr) during the recovery period, a shorter PCr recovery time constant (τPCr), and higher Qmax. Multivariate stepwise regression analysis identified PDE as the strongest independent predictor of whole-body maximal oxygen uptake (VO2max).Conclusion: In conclusion, we cannot suggest a single MRS-based parameter as an exclusive biomarker of muscular fitness and training status. There is, rather, a combination of different parameters, assessable during a single multi-nuclear MRS session that could be useful for further cross-sectional and/or focused interventional studies on skeletal muscle fitness and training effects.

FABP4 inhibitor BMS309403 decreases saturated-fatty-acid-induced endoplasmic reticulum stress-associated inflammation in skeletal muscle by reducing p38 MAPK activation

AimsFatty acid binding protein 4 (FABP4) inhibitors have been proposed as potential therapeutic approaches against insulin resistance-related inflammation and type 2 diabetes mellitus. However, the underlying molecular mechanisms by which these molecules drive these effects in skeletal muscle remain unknown. Here, we assessed whether the FABP4 inhibitor BMS309403 prevented lipid-induced endoplasmic reticulum (ER) stress-associated inflammation in skeletal muscle. Materials and methodsThe BMS309403 treatment was assessed both in the skeletal muscle of high-fat diet (HFD)-fed mice and in palmitate-stimulated C2C12 myotubes. ResultsHFD feeding promoted insulin resistance, which is characterized by increased plasma levels of glucose, insulin, non-esterified fatty acids, triglycerides, resistin, and leptin and reduced plasma levels of adiponectin compared with control mice fed a standard diet. Additionally, insulin-resistant animals showed increased FABP4 plasma levels. In line with this evidence, recombinant FABP4 attenuated the insulin-induced AKT phosphorylation in C2C12 myotubes. Treatment with BMS309403 reduced lipid-induced ER stress and inflammation in both mouse skeletal muscle and C2C12 myotubes. The effects of the FABP4 inhibitor reducing lipid-induced ER stress-associated inflammation were related to the reduction of fatty acid-induced intramyocellular lipid deposits, ROS and nuclear factor-kappaB (NF-κB) nuclear translocation. Accordingly, BMS309403 reduced lipid-induced p38 MAPK phosphorylation, which is upstream of NF-κB activation. ConclusionOverall, these findings indicate that BMS309403 reduces fatty acid-induced ER stress-associated inflammation in skeletal muscle by reducing p38 MAPK activation.

3,5-Diiodo-L-Thyronine Affects Structural and Metabolic Features of Skeletal Muscle Mitochondria in High-Fat-Diet Fed Rats Producing a Co-adaptation to the Glycolytic Fiber Phenotype.

Hyperlipidemic state-associated perturbations in the network of factors controlling mitochondrial functions, i. e., morphogenesis machinery and metabolic sensor proteins, produce metabolic inflexibility, insulin resistance and reduced oxidative capacity in skeletal muscle. Moreover, intramyocellular lipid (IMCL) accumulation leads to tissue damage and inflammation. The administration of the naturally occurring metabolite 3,5-diiodo-L-thyronine (T2) with thyromimetic actions to high fat diet (HFD)-fed rats exerts a systemic hypolipidemic effect, which produces a lack of IMCL accumulation, a shift toward glycolytic fibers and amelioration of insulin sensitivity in gastrocnemius muscle. In this study, an integrated approach combining large-scale expression profile and functional analyses was used to characterize the response of skeletal muscle mitochondria to T2 during a HFD regimen. Long-term T2 administration to HDF rats induced a glycolytic phenotype of gastrocnemius muscle as well as an adaptation of mitochondria to the fiber type, with a decreased representation of enzymes involved in mitochondrial oxidative metabolism. At the same time, T2 stimulated the activity of individual respiratory complex I, IV, and V. Moreover, T2 prevented the HFD-associated increase in the expression of peroxisome proliferative activated receptor γ coactivator-1α and dynamin-1-like protein as well as mitochondrial morphological aberrations, favoring the appearance of tubular and tethered organelles in the intermyofibrillar regions. Remarkably, T2 reverted the HDF-associated expression pattern of proinflammatory factors, such as p65 subunit of NF-kB, and increased the fiber-specific immunoreactivity of adipose differentiation–related protein in lipid droplets. All together, these results further support a role of T2 in counteracting in vivo some of the HFD-induced impairment in structural/metabolic features of skeletal muscle by impacting the mitochondrial phenotype.