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There is growing evidence that type 2 diabetes or insulin resistance is linked to cognitive impairment. We recently confirmed altered lipid composition, down-regulation of insulin receptor expression and impaired basal synaptic transmission in the hippocampus of our transgenic murine model of adipocyte insulin resistance (AtENPP1-Tg). Here we evaluated whether the correction of adipose tissue dysfunction [via the subcutaneous transplantation of mesenchymal stem cells (MSC)] can improve the hippocampal synaptic transmission in AtENPP1-Tg mice versus their wildtype littermates. Animals were simply randomized to receive MSC, then weighed weekly for 12 weeks. At euthanasia, we assessed leptin in the collected serum and hippocampal synaptic high-frequency stimulation long-term potentiation (HFS-LTP) using brain slices. MSC transplantation normalized AtENPP1-Tg body and epididymal fat weights and was associated with increased leptin levels, a sign of adipocyte maturation. More importantly, transplantation restored the deficiency observed in AtENPP1-Tg HFS-LTP, the cellular readout of memory. Our results further corroborate the role of adipocyte maturation arrest in adipose tissue and highlight a role for the adipose tissue in modulating hippocampal cellular mechanisms. Further studies are warranted to explore the mechanisms for the MSC-induced improvement of hippocampal HFS-LTP.

Subcutaneous adipose tissue (scAT) and peripheral blood mononuclear cells (PBMC) play a significant role in obesity-associated systemic low-grade inflammation. High-fat diet (HFD) is known to induce inflammatory changes in both scAT and PBMC. However, the time course of the effect of HFD on these systems is still unknown. The aim of the present study was to determine the time course of the effect of HFD on PBMC and scAT. New Zealand white rabbits were fed HFD for 5 or 10 weeks (i.e. HFD-5 and HFD-10) or regular chow (i.e. control (CNT)-5 and CNT-10). Thereafter, metabolic and inflammatory parameters of PBMC and scAT were quantified. HFD induced hyperfattyacidaemia in HFD-5 and HFD-10 groups, with the development of insulin resistance in HFD-10, while no changes were observed in scAT lipid metabolism and inflammatory status. HFD activated the inflammatory pathways in PBMC of HFD-5 group and induced modified autophagy in that of HFD-10. The rate of fat oxidation in PBMC was directly associated with the expression of inflammatory markers and tended to inversely associate with autophagosome formation markers in PBMC. HFD affected systemic substrate metabolism, and the metabolic, inflammatory and autophagy pathways in PBMC in the absence of metabolic and inflammatory changes in scAT. Dietary approaches or interventions to avert HFD-induced changes in PBMC could be essential to prevent metabolic and inflammatory complications of obesity and promote healthier living.

Exercise has been proposed to increase serum testosterone concentrations. The analysis of existing literature demonstrates a large degree of variability in hormonal changes during exercise. In our manuscript, we summarized and reviewed the literature, and concluded that this variability can be explained by the effect of numerous factors, such as (a) the use of different types of exercise (e.g., endurance vs. resistance); (b) training intensity and/or duration of resting periods; (c) study populations (e.g., young vs. elderly; lean vs. obese; sedentary vs. athletes); and (d) the time point when serum testosterone was measured (e.g., during or immediately after vs. several minutes or hours after the exercise). Although exercise increases plasma testosterone concentrations, this effect depends on many factors, including the aforementioned ones. Future studies should focus on clarifying the metabolic and molecular mechanisms whereby exercise may affect serum testosterone concentrations in the short and long-terms, and furthermore, how this affects downstream mechanisms.

Intramyocellular triglyceride (imTG) in skeletal muscle plays a significant role in metabolic health, and an infusion of [(13)C(16)]palmitate can be used to quantitate the in vivo fractional synthesis rate (FSR) and absolute synthesis rate (ASR) of imTGs. However, the extramyocellular TG (emTG) pool, unless precisely excised, contaminates the imTG pool, diluting the imTG-bound tracer enrichment and leading to underestimation of FSR. Because of the difficulty of excising the emTGs precisely, it would be advantageous to be able to calculate the imTG synthesis rate without dissecting the emTGs from each sample. Here, we tested the hypothesis that the ASR of total TGs (tTGs), a combination of imTGs and emTGs, calculated as “FSR × tTG pool,” reasonably represents the imTG synthesis. Muscle lipid parameters were measured in nine healthy women at 90 and 170 min after the start of [(13)C(16)]palmitate infusion. While the measurements of tTG content, enrichment, and FSR did not correlate (P > 0.05), those of the tTG ASR were significantly correlated (r = 0.947, P < 0.05). These results demonstrate that when imTGs and emTGs are pooled, the resulting underestimation of imTG FSR is balanced by the overestimation of the imTG content. We conclude that imTG metabolism is reflected by the measurement of the tTG ASR.

Impaired adipose tissue function and lower levels of high density lipoprotein cholesterol (HDL-C) have been implicated in the development of vascular dementia, and metabolic diseases such as hypertension, atherosclerosis, type 2 diabetes (T2D) and metabolic syndrome. Interestingly, both the substrate fluxes in adipose tissue and HDL-C concentration differ between men and women. Moreover, adipose tissue cholesterol efflux has been implicated in modulation of HDL-C levels. Thus, we aimed to determine if the association between serum estradiol levels and adipose tissue cholesterol efflux is sex-dependent.We evaluated the serum estradiol levels and adipose tissue cholesterol efflux in young healthy men (n=5) and women (n=3). Adipose tissue cholesterol efflux was determined using subcutaneous microdialysis probes. Linear regression analyses were used to determine the relationship between the parameters, p0.05 was considered as statistically significant.Our data demonstrated that serum estradiol levels directly associated with adipose tissue cholesterol efflux; however, the relationships may be sex-dependent. We discussed our results in the context of currently available data regarding sex-dependent variability in adipose tissue function and HDL-C metabolism as a potential contributor to higher rates of vascular dementia in men. Further research is required to understand the sex-dependent and -independent variabilities in adipose tissue metabolism to determine novel targets for interventions to prevent the development of vascular dementia.

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide. Inflammatory processes arising from metabolic abnormalities are known to precipitate the development of CVD. Several metabolic and inflammatory markers have been proposed for predicting the progression of CVD, including high density lipoprotein cholesterol (HDL-C). For ~50 years, HDL-C has been considered as the atheroprotective ‘good’ cholesterol because of its strong inverse association with the progression of CVD. Thus, interventions to increase the concentration of HDL-C have been successfully tested in animals; however, clinical trials were unable to confirm the cardiovascular benefits of pharmaceutical interventions aimed at increasing HDL-C levels. Based on these data, the significance of HDL-C in the prevention of CVD has been called into question. Fundamental in vitro and animal studies suggest that HDL-C functionality, rather than HDL-C concentration, is important for the CVD-preventive qualities of HDL-C. Our current review of the literature positively demonstrates the negative impact of systemic and tissue (i.e. adipose tissue) inflammation in the healthy metabolism and function of HDL-C. Our survey indicates that HDL-C may be a good marker of adipose tissue health, independently of its atheroprotective associations. We summarize the current findings on the use of anti-inflammatory drugs to either prevent HDL-C clearance or improve the function and production of HDL-C particles. It is evident that the therapeutic agents currently available may not provide the optimal strategy for altering HDL-C metabolism and function, and thus, further research is required to supplement this mechanistic approach for preventing the progression of CVD. Linked Articles This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc

Backgrounds and aims: Low concentrations of plasma HDL-C are associated with the development of atherosclerotic cardiovascular diseases and type 2 diabetes. Here we aimed to explore the relationship between the in vivo fractional synthesis of triglycerides (fTG) in subcutaneous (s.q.) abdominal adipose tissue (AT), HDL-C concentrations and HDL particle size composition in non-diabetic humans. Methods: The fTG in s.q. abdominal AT was measured in 16 non-diabetic volunteers (7 women, 9 men; Age: 49 ± 20 years; BMI: 31 ± 5 kg/m; Fasting Plasma Glucose: 90 ± 10 mg/dl) after 2H2O labeling. HDL-C concentration and subclasses, large (L-HDL), intermediate (I-HDL) and small (S-HDL) were measured. Results: Linear regression analyses demonstrated significant associations of fTG with plasma concentration of HDL-C (r = 0.625,p = 0.009) and percent contribution of L-HDL (r = 0.798,p < 0.001), I-HDL (r = -0.765,p < 0.001) and S-HDL (r = -0.629, p = 0.009). When analyses were performed by gender, the associations remained significant in women (HDL-C: r = 0.822,p = 0.023; L-HDL: r = 0.892,p = 0.007; I-HDL: r = -0.927,p = 0.003) but not men. Conclusions: Our study demonstrated an in vivo association between subcutaneous abdominal adipose tissue lipid dynamics and HDL parameters in humans, but this was true for women not men. Positive association with L-HDL and negative with I-HDL suggest that subcutaneous abdominal adipose tissue lipid dynamics may play an important role in production of mature functional HDL particles. Further studies evaluating the mechanism responsible for these associations and the observed gender differences are important and warranted to identify potential novel targets of intervention to increase the production of atheroprotective subclasses of HDL-Cs and thus decreasing the risks of development of atherosclerotic conditions.

Aims To examine whether addition of amlodipine (5 mg)/atorvastatin (10 mg) “A/A” to Therapeutic Lifestyle change intervention (TLC) would beneficially modulate Metabolic Syndrome (MetS) and oxidized low-density lipoprotein cholesterol (Ox-LDL) levels. Methods Patients with MetS (n = 53) were randomized to TLC + placebo or TLC + A/A for 12 months. Anthropometric measurements, blood pressure (BP), lipid profile, plasma Ox-LDL, and area under the curve of free fatty acid (AUCFFA) during oral glucose tolerance test, a marker of adipose tissue health, were assessed before and after the intervention. Results Twenty-six patients completed the study with an overall improvement of MetS (p = 0.02). TLC + placebo was beneficial in reversing MetS comparable to TLC + A/A (54% vs. 39%; p = 0.08). Both treatments decreased systolic BP (p ≤ 0.01). TLC + A/A also decreased diastolic BP and triglyceride levels. The changes in Ox-LDL levels directly correlated with changes in weight in the TLC-placebo group (r = 0.64; p = 0.04). AUCFFA determined the loss of fat mass (r = 0.472, p = 0.03). Conclusions 1) Addition of A/A has the advantage of improving the lipid profile and BP; but TLC alone was comparable to TLC + A/A in improving MetS; 2) weight change determines the TLC-associated change in Ox-LDL levels; and 3) AT metabolic health is a significant predictor of TLC-associated loss of body fat mass.

Background: Gestational diabetes mellitus (GDM) associates with health complications in both mother and child. Obesity and impaired adipose tissue (AT) health associate with the development of GDM. However, recent studies have shown that impaired AT health may occur in the absence of obesity. In this study we studied if AT health associates with the development of GDM in non-obese women. Method: Pregnant women diagnosed with GDM were studied. Age- and body mass index (BMI)-matched non-GDM women were enrolled as Controls (n=6 per group). Fasting blood and AT samples were obtained before and during cesarian section, respectively. The serum levels of adiponectin were measured using Bioplex assay. The expression of phosphorylated p38 (p-p38) in AT was measured using Western blotting, and the average values of adipocyte sizes were estimated. The differences in variables between the groups were determined using two-tailed unequal variance Student t test; p < 0.was considered as statistically significant. Results: There were no difference in age (Control vs. GDM: 31±1 vs. 31±2, p = 0.973) and pre-pregnancy BMI (Control vs. GDM: 26±1 vs. 25±1, p = 0.852). In the GDM group, the serum concentration of adiponectin was significantly lower (Control vs. GDM: 16±3 vs. 7±1, p = 0.021); while the AT expression of p-p38 was significantly higher (Control vs. GDM: 0.55±0.14 vs. 1.42±0.23, p = 0.013). The adipocyte size was 11% lower in the GDM group, although the difference did not reach statistical significance (Control vs. GDM: 100±6 vs. 89±5, p = 0.173). Conclusion: Our data demonstrate that AT health may play a significant role in the development of GDM in non-obese women. Future studies to determine the mechanisms whereby AT health leads to the development GDM in the absence of obesity are warranted. Disclosure D.R. Tuvdendorj: None. B. Tumurbaatar: None. A. Poole: None. S. Thukuntla: None. G.O. Koutrouvelis: None. N. Abate: None.

The effects of amino acid supply and insulin infusion on skin protein kinetics (fractional synthesis rate (FSR), fractional breakdown rate (FBR), and net balance (NB)) in pigs were investigated. Four-month-old pigs were divided into four groups as follows: control, insulin (INS), amino acid (AA), and INS + AA groups based on the nutritional and hormonal conditions. l-[ring-(13)C6]Phenylalanine was infused. FBR was estimated from the enrichment ratio of arterial phenylalanine to intracellular free phenylalanine. Plasma INS was increased (p < 0.05) in the INS and INS + AA groups. Plasma glucose was maintained by infusion of glucose in the groups receiving INS. The interventions did not change the NB of skin protein. However, the interventions affected the FSR and FBR differently. An infusion of INS significantly increased both FSR and FBR, although AA infusion did not. When an AA infusion was added to the infusion of insulin (INS + AA group), FSR and FBR were both lower when compared with the INS group. Our data demonstrate that in anesthetized pigs INS infusion did not exert an anabolic effect, but rather it increased AA cycling into and out of skin protein. Because co-infusion of AAs with INS ameliorated this effect, it is likely that the increased AA cycling during INS infusion was related to AA supply. Although protein kinetics were affected by both INS and AAs, none of the interventions affected the skin protein deposition. Thus, skin protein content is closely regulated under normal circumstances and is not subject to transient changes in AAs or hormonal concentrations.

The liver plays a central role in regulating fat metabolism; however, it is not clear how the liver distributes the synthesized triglycerides (TGs) to storage and to the plasma.We have measured the relative distribution of TGs produced in the liver to storage and the plasma by means of U-(13)C(16)-palmitate infusion in anesthetized rabbits after an overnight fast.The fractional synthesis rates of TGs stored in the liver and secreted into the plasma were not significantly different (stored vs. secreted: 31.9 ± 0.8 vs. 27.7 ± 2.6%∙h(-1), p0.05). However, the absolute synthesis rates of hepatic stored and secreted TGs were 543 ± 158 and 27 ± 7 nmol∙kg(-1)∙min(-1) respectively, indicating that in fasting rabbits the TGs produced in the liver were predominately stored (92 ± 3%) rather than secreted (8 ± 3%) into the plasma. This large difference was mainly due to the larger pool size of the hepatic TGs which was 21 ± 9-fold that of plasma TGs. Plasma free fatty acids (FFAs) contributed 47 ± 1% of the FA precursor for hepatic TG synthesis, and the remaining 53 ± 1% was derived from hepatic lipid breakdown and possibly plasma TGs depending on the activity of hepatic lipase. Plasma palmitate concentration significantly correlated with hepatic palmitoyl-CoA and TG synthesis.In rabbits, after an overnight fast, the absolute synthesis rate of hepatic stored TGs was significantly higher than that of secreted due to the larger pool size of hepatic TGs. The net synthesis rate of TG was approximately half the absolute rate. Plasma FFA is a major determinant of hepatic TG synthesis, and therefore hepatic TG storage.

The aim of this study was to investigate effects and mechanisms of electroacupuncture (EA) on blood glucose and insulin sensitivity in mice fed a high-fat diet. Both wild-type (WT) and adipose ectonucleotide pyrophosphate phosphodiesterase (ENPP1) transgenic (TG) mice were fed a high-fat diet for 12 wk; for each mouse, an intraperitoneal glucose tolerance test (IPGTT) and insulin tolerance test (ITT) were performed with or without EA at abdomen or auricular areas. A high-fat diet-induced insulin resistance in both WT and TG mice. In the WT mice, EA at 3 Hz and 15 Hz, but not at 1 Hz or 100 Hz, via CV4+CV12 significantly reduced postprandial glucose levels; EA at 3 Hz was most potent. The glucose level was reduced by 61.7% at 60 min and 74.5% at 120 min with EA at 3 Hz (all P < 0.001 vs. control). Similar hypoglycemic effect was noted in the TG mice. On the contrary, EA at auricular points increased postprandial glucose level ( P < 0.03). 4). EA at 3 Hz via CV4+CV12 significantly enhanced the decrease of blood glucose after insulin injection, suggesting improvement of insulin sensitivity. Plasma free fatty acid was significantly suppressed by 42.5% at 15 min and 50.8% at 30 min with EA ( P < 0.01) in both WT and TG mice. EA improves glucose tolerance in both WT and TG mice fed a high-fat diet, and the effect is associated with stimulation parameters and acupoints and is probably attributed to the reduction of free fatty acid.

Understanding the mechanisms of CD4 memory T cell (Tmem) differentiation in malaria is critical for vaccine development. However, the metabolic regulation of CD4 Tmem differentiation is not clear, particularly in persistent infections. In this study, we investigated the role of fatty acid synthesis (FAS) in Tmem development in Plasmodium chabaudi chronic mouse malaria infection. We show that T cell-specific deletion, and early pharmaceutical inhibition of acetyl coA carboxylase 1, the rate limiting step of FAS, inhibit generation of early memory precursor effector T cells (MPEC). To compare the role of FAS during early differentiation or survival of Tmem in chronic infection, a specific inhibitor of acetyl coA carboxylase 1, 5-(Tetradecyloxy)-2-furoic acid, was administered at different times postinfection. Strikingly, the number of Tmem was only reduced when FAS was inhibited during T cell priming, but not during the Tmem survival phase. FAS inhibition during priming increased effector T cells (Teff) proliferation, and strongly decreased peak parasitemia, which is consistent with improved Teff function. Conversely, MPEC were decreased, in a T cell-intrinsic manner, upon early FAS inhibition in chronic, but not acute, infection. Early cure of infection also increased mitochondrial volume in Tmem compared to Teff, supporting previous reports in acute infection. We demonstrate that the MPEC-specific effect was due to the higher fatty acid content and synthesis in MPEC compared to terminally differentiated Teff. In conclusion, FAS in CD4 T cells regulates the early divergence of Tmem from Teff in chronic infection.

Adipose tissue (AT) helps to regulate body fat partitioning and systemic lipid/glucose metabolism. We have recently reported lipid/glucose metabolism abnormalities and increased liver triglyceride content in an AT-selective transgenic model overexpressing ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1), the AdiposeENPP1-Tg mouse.The aim of the study was to test the translational hypothesis that AT-ENPP1 overexpression associates with AT dysfunction (changes in AT gene expression, plasma fatty acid, and adipokine levels), increased liver triglyceride deposition, and systemic insulin resistance in humans.A total of 134 young normoglycemic men and women were subjected to body composition studies, hyperinsulinemic-euglycemic clamps, and AT needle biopsy. Twenty men also had liver/muscle nuclear magnetic resonance spectroscopy.Predetermined measures included AT expression of ENPP1 and other lipid metabolism/inflammation genes, plasma adipokines, and nonesterified fatty acid (NEFA) levels, liver/muscle triglyceride content, and the systemic glucose disposal rate.After statistical adjustment for body fat content, increasing AT-ENPP1 was associated with up-regulation of genes involved in NEFA metabolism and inflammation, increased postabsorptive NEFA levels, decreased plasma adiponectin, increased liver triglyceride content, and systemic insulin resistance in men. In women, there were no changes in plasma adiponectin, NEFAs, or glucose disposal rate associated with increasing AT-ENPP1, despite increased expression of lipid metabolism and inflammation genes in AT.Increased AT-ENPP1 is associated with AT dysfunction, increased liver triglyceride deposition, and systemic insulin resistance in young normoglycemic men. These findings are concordant with the AdiposeENPP1-Tg phenotype and identify a potential target of therapy for health complications of AT dysfunction, including type 2 diabetes and cardiovascular disease.

Summary Background Circulating acyl-carnitines (acyl-CNTs) are associated with insulin resistance (IR) and type 2 diabetes (T2D) in both rodents and humans. However, the mechanisms whereby circulating acyl-CNTs are increased in these conditions and their role in whole-body metabolism remains unknown. The purpose of this study was to determine if, in humans, blood cells contribute in production of circulating acyl-CNTs and associate with whole-body fat metabolism. Methods and results Eight non-diabetic healthy women (age: 47 ± 19 y; BMI: 26 ± 1 kg·m −2 ) underwent stable isotope tracer infusion and hyperinsulinemic-euglycemic clamp study to determine in vivo whole-body fatty acid flux and insulin sensitivity. Blood samples collected at baseline (0 min) and after 3 h of clamp were used to determine the synthesis rate of palmitoyl-carnitine (palmitoyl-CNT) in vitro . The fractional synthesis rate of palmitoyl-CNT was significantly higher during hyperinsulinemia (0.788 ± 0.084 vs . 0.318 ± 0.012%·hr −1 , p = 0.001); however, the absolute synthesis rate (ASR) did not differ between the periods ( p = 0.809) due to ∼30% decrease in blood palmitoyl-CNT concentration ( p = 0.189) during hyperinsulinemia. The ASR of palmitoyl-CNT significantly correlated with the concentration of acyl-CNTs in basal ( r = 0.992, p r = 0.919, p = 0.001) periods; and the basal ASR significantly correlated with plasma palmitate oxidation ( r = 0.764, p = 0.027). Conclusion In women, blood cells contribute to plasma acyl-CNT levels and the acyl-CNT production is linked to plasma palmitate oxidation, a marker of whole-body fat metabolism. Future studies are needed to confirm the role of blood cells in acyl-CNT and lipid metabolism under different physiological (i.e., in response to meal) and pathological (i.e., hyperlipidemia, IR and T2D) conditions.

In the treatment of burns, patients' own skin is the preferred material to cover burn wounds, resulting in the need to create a donor site wound. Enhancement of healing of the donor site wound would be beneficial in burn patients. Insulin, an anabolic agent, is used routinely to treat hyperglycemia after injury. We investigated whether intensive insulin treatment increases fractional synthesis rate (FSR) of the donor site wound protein and decreases the length of hospitalization normalized for total body surface area burned (LOS/TBSA).FSR of the donor site wound protein was measured in pediatric patients randomized to control (n = 13) and insulin (n = 10) treatments. Depending on the postoperative day when the tracer study was done, studies were divided into "early" (days5) and "late" (days ≥ 5) periods.FSR of the donor site wound protein was greater in the insulin group at the "early" period of wound healing (control vs insulin, 8.2 ± 3.8 vs 13.1 ± 6.9% per day; P.05); but not at the "late" (control vs insulin, 19.7 ± 4.6 vs 16.6 ± 4.0% per day; P.05). Despite these differences, LOS/TBSA was not decreased in the insulin group. Correlation analyses demonstrated that, independent of the treatment regimen, FSR positively correlated (P.05) with time after creation of the donor site and negatively correlated (P.05) with LOS/TBSA.Insulin treatment increased FSR of the donor site wound protein in the early period of wound healing; FSR correlated with LOS/TBSA independent of the treatment regimen.

Stressed pathophysiological conditions, for example, burn, result in a hypermetabolic and catabolic state leading to muscle wasting. In burns, the most common determinants for muscle catabolism are subject weight, burn size, time from injury to surgical treatment, resting energy expenditure, and sepsis.1 However, long lasting hospitalization with prolonged bed rest and major surgeries are contributors to loss of lean body mass. Furthermore, muscle catabolism is correlated with morbidity during acute burn treatment.2–4 It is well-established that pediatric burn patients are hypermetabolic and catabolic for more than 12 months postinjury.5 They also demonstrate delayed linear growth up to 2 years postinjury.6 Recent studies have shown that in a pediatric burn patient population, muscle catabolism persists up to 9 months beyond the injury.5 In this patient population, persistent muscle catabolism has multiple negative effects. First, children are in the physiological process of growing and for normal growth to occur, the catabolic condition must be reversed, that is, the rates of protein synthesis are greater than the rates of proteolysis leading to a higher net protein deposition. Second, burn victims spend days and/or months in intensive care unit during the acute phase after injury. This results in loss of mobility, loss of lean body mass, and delayed start of rehabilitation. Third, burn patients undergo numerous reconstructive surgeries in years after wound healing has occurred. Major surgeries are known stressors for the catabolic state. The combination of the acute burn injury, prolonged intensive care unit stays, and years of reconstruction surgery render the skeletal muscle persistently catabolic, making amelioration of muscle wasting an important consideration during the treatment of pediatric burn patients. Studies have shown that the tissue response to nutritional signaling (eg, amino acids) plays a critical role in protein net deposition via coordination of protein synthesis and breakdown mechanisms. In normal conditions, amino acid abundance increases muscle protein synthesis with no change or decrease in the breakdown rate, resulting in an increased net protein deposition.7–10 In critical or catabolic conditions, this depends on the severity of the condition. In less severe critical illness, there are milder changes in both protein synthesis and breakdown rates.11–13 Whereas in severe cases, namely acute phase after burn injury, amino acid availability increases protein synthesis but this increase is not sufficient to match the increase in breakdown and prevent the protein loss.14 It is not known, however, how the skeletal muscle of pediatric burn patients responds to amino acid supplementation at later periods after burn injury, for example, 6 month postinjury. Therefore, in this study we examined the effect of a steady state amino acid (AA) infusion (Travasol) on leg muscle protein turnover in pediatric burn patients at 6 month postinjury compared with that of healthy subjects. We also examined whole-body and whole-body nonmuscle basal and AA affected protein breakdown rates. Nonmuscle protein turnover represents protein turnover from tissues other than muscle, such as liver. We hypothesize that in burn victims, protein turnover is unresponsive to the anabolic signaling of AAs.

Autografting of burn wounds results in generation of donor site wounds. Here we measured donor site wound protein fractional synthesis rate (FSR) in a burn pediatric population and showed that FSR increases over time postsurgery and correlates with the length of hospital stay (LOS) normalized for total body surface area (TBSA) burn size. 3.9 +/- 1.1 days after the grafting surgery patients participated in a metabolic study consisting of continuous infusion of l-[ring-(2)H(5)]-phenylalanine and donor site wound punch biopsies. Donor site wound protein FSR was 10.4 +/- 7.5%/day. Wound FSR demonstrated linear correlation with the time postsurgery (p

Mitochondrial health is critical to physiological function, particularly in tissues with high ATP turnover, such as striated muscle. It has been postulated that derangements in skeletal muscle mitochondrial function contribute to impaired physical function in older adults. Here, we determined mitochondrial respiratory capacity and coupling control in skeletal muscle biopsies obtained from young and older adults. Twenty-four young (28 ± 7 yr) and thirty-one older (62 ± 8 yr) adults were studied. Mitochondrial respiration was determined in permeabilized myofibers from the vastus lateralis after the addition of substrates oligomycin and CCCP. Thereafter, mitochondrial coupling control was calculated. Maximal coupled respiration (respiration linked to ATP production) was lower in muscle from older vs. young subjects ( P < 0.01), as was maximal uncoupled respiration ( P = 0.06). Coupling control in response to the ATP synthase inhibitor oligomycin was lower in older adults ( P < 0.05), as was the mitochondria flux control ratio, coupled respiration normalized to maximal uncoupled respiration ( P < 0.05). Calculation of respiratory function revealed lower respiration linked to ATP production ( P < 0.001) and greater reserve respiration ( P < 0.01); i.e., respiratory capacity not used for phosphorylation in muscle from older adults. We conclude that skeletal muscle mitochondrial respiratory capacity and coupling control decline with age. Lower respiratory capacity and coupling efficiency result in a reduced capacity for ATP production in skeletal muscle of older adults.

Here we studied whether aspirin (ASA) has any influence on viability of human hepatoma-derived SKHep-1 cells and whether hydrogen peroxide (H(2)O(2)) has any relation with this effect. ASA inhibited SKHep-1 cell proliferation dose- and time-dependently. Intracellular H(2)O(2) increased as early as 15 min after ASA supplementation. Cellular apoptosis correlated with an increase in intracellular H(2)O(2) level. Moreover, in the presence of a catalase inhibitor-aminotriazol, ASA showed more apoptotic effect on SKHep-1 cells with increasing intracellular H(2)O(2) level. In conclusion, the present results shows that ASA induced SKHep-1 cell apoptosis has a relation with an early increase in intracellular H(2)O(2) level and catalase inhibitor synergizes to induce this process.

Compelling evidence indicates that type 2 diabetes mellitus, insulin resistance (IR), and metabolic syndrome are often accompanied by cognitive impairment. However, the mechanistic link between these metabolic abnormalities and CNS dysfunction requires further investigations. Here, we evaluated whether adipose tissue IR and related metabolic alterations resulted in CNS changes by studying synapse lipid composition and function in the adipocyte-specific ecto-nucleotide pyrophosphate phosphodiesterase over-expressing transgenic (AtENPP1-Tg) mouse, a model characterized by white adipocyte IR, systemic IR, and ectopic fat deposition. When fed a high-fat diet, AtENPP1-Tg mice recapitulate essential features of the human metabolic syndrome, making them an ideal model to characterize peripherally induced CNS deficits. Using a combination of gas chromatography and western blot analysis, we found evidence of altered lipid composition, including decreased phospholipids and increased triglycerides (TG) and free fatty acid in hippocampal synaptosomes isolated from high-fat diet-fed AtENPP1-Tg mice. These changes were associated with impaired basal synaptic transmission at the Schaffer collaterals to hippocampal cornu ammonis 1 (CA1) synapses, decreased phosphorylation of the GluN1 glutamate receptor subunit, down-regulation of insulin receptor expression, and up-regulation of the free fatty acid receptor 1.

To investigate the effect of acute hyperinsulinemia and the resulting decrease in plasma free fatty acid (FFA) concentrations on intramuscular TG synthesis.U-(13)C(16)-palmitate was infused for 3 h in anesthetized rabbits after overnight food deprivation. Arterial blood and leg muscle were sampled during the tracer infusion. Plasma samples were analyzed for free and TG-bound palmitate enrichments and concentrations. The enrichments and concentrations of palmitoyl-CoA and palmitoyl-carnitine as well as the enrichment of palmitate bound to TG were measured in muscle samples. Fractional synthetic rate (FSR) of intramuscular TG was calculated using the tracer incorporation method. The rabbits were divided into a control group and a hyperinsulinemic euglycemic clamp group. Insulin infusion decreased the rate of appearance of plasma free palmitate (2.00±0.15 vs 0.68±0.20 μmol⋅kg(-1)⋅min(-1); P.001), decreased plasma FFA concentration (327±61 vs 72±25 nmol/mL; P.01), decreased the total concentration of intramuscular fatty acyl-CoA plus fatty acyl-carnitine (12.1±1.6 vs 7.0±0.7 nmol/g; P.05), and decreased intramuscular TG FSR (0.48±0.05 vs 0.21±0.06%/h; P.01) in comparison with the control group. Intramuscular TG FSR was correlated (P.01) with both plasma FFA concentrations and intramuscular fatty acyl-CoA concentrations.Fatty acid availability is a determinant of intramuscular TG synthesis. Insulin infusion decreases plasma and intramuscular fatty acid availability and thereby decreases TG synthesis.

Our goal was to assess the validity of the enrichments of plasma free palmitate and intramuscular (IM) fatty acid metabolites as precursors for calculating the IM triglyceride fractional synthetic rate. We infused U-13C16-palmitate in anesthetized rabbits for 3 h and sampled adductor muscle of legs using both freeze-cut and cut-freeze approaches. We found that IM free palmitate enrichment (0.70 ± 0.07%) was lower (P < 0.0001) than IM palmitoyl-CoA enrichment (2.13 ± 0.17%) in samples taken by the freeze-cut approach. The latter was close (P = 0.33) to IM palmitoyl-carnitine enrichment (2.42 ± 0.16%). The same results were obtained from the muscle samples taken by the cut-freeze approach, except the enrichment of palmitoyl-CoA (2.21 ± 0.08%) was lower (P = 0.02) than that of palmitoyl-carnitine (2.77 ± 0.17%). Plasma free palmitate enrichment was ∼2-fold that of IM palmitoyl-CoA enrichment and palmitoyl-carnitine enrichment (P < 0.001). These findings indicate that plasma free palmitate overestimated IM precursor enrichment owing to in vivo IM lipid breakdown, whereas IM free palmitate enrichment underestimated the precursor enrichment because of lipid breakdown during muscle sampling and processing. IM palmitoyl-carnitine enrichment was an acceptable surrogate of the precursor enrichment because it was less affected by in vitro lipid breakdown after sampling.

Ectonucleotide pyrophosphate phosphodiesterase (ENPP1) has been shown to negatively modulate insulin receptor and to induce cellular insulin resistance when overexpressed in various cell types. Systemic insulin resistance has also been observed when ENPP1 is overexpressed in multiple tissues of transgenic models and attributed largely to tissue insulin resistance induced in skeletal muscle and liver. Another key tissue in regulating glucose and lipid metabolism is adipose tissue (AT). Interestingly, obese patients with insulin resistance have been reported to have increased AT ENPP1 expression. However, the specific effects of ENPP1 in AT have not been studied. To better understand the specific role of AT ENPP1 on systemic metabolism, we have created a transgenic mouse model (C57/Bl6 background) with targeted overexpression of human ENPP1 in adipocytes, using aP2 promoter in the transgene construct ( AdiposeENPP1-TG). Using either regular chow or pair-feeding protocol with 60% fat diet, we compared body fat content and distribution and insulin signaling in adipose, muscle, and liver tissues of AdiposeENPP1-TG and wild-type (WT) siblings. We also compared response to intraperitoneal glucose tolerance test (IPGTT) and insulin tolerance test (ITT). Our results show no changes in Adipose ENPP1-TG mice fed a regular chow diet. After high-fat diet with pair-feeding protocol, AdiposeENPP1-TG and WT mice had similar weights. However, AdiposeENPP1-TG mice developed fatty liver in association with changes in AT characterized by smaller adipocyte size and decreased phosphorylation of insulin receptor Tyr1361and Akt Ser473. These changes in AT function and fat distribution were associated with systemic abnormalities of lipid and glucose metabolism, including increased plasma concentrations of fatty acid, triglyceride, plasma glucose, and insulin during IPGTT and decreased glucose suppression during ITT. Thus, our results show that, in the presence of a high-fat diet, ENPP1 overexpression in adipocytes induces fatty liver, hyperlipidemia, and dysglycemia, thus recapitulating key manifestations of the metabolic syndrome.

We recently showed that mechanisms of protein turnover in skeletal muscle are unresponsive to amino acid (AA) infusion in severely burned pediatric patients at 6 months postinjury. In the current study, we evaluated whether oxandrolone treatment affects mechanisms of protein turnover in skeletal muscle and whole-body protein breakdown in pediatric burn patients 6 months postinjury.At the time of admission, patients were randomized to control or oxandrolone treatments. The treatment regimens were continued until 6 months postinjury, at which time patients (n = 26) underwent study with a stable isotope tracer infusion to measure muscle and whole-body protein turnover.Protein kinetics in leg muscle were expressed in nmol/min per 100 mL leg volume (mean ± SE). During AA infusion, rates of protein synthesis in leg muscle were increased (P.05) in both groups (basal vs AA: control, 51 ± 8 vs 86 ± 21; oxandrolone, 56 ± 7 vs 96 ± 12). In the control group, there was also a simultaneous increase in breakdown (basal vs AA: 65 ± 10 vs 89 ± 25), which resulted in no change in the net balance of leg muscle protein (basal vs AA: -15 ± 4 vs -2 ± 10). In the oxandrolone group, protein breakdown did not change (basal vs AA: 80 ± 12 vs 77 ± 9), leading to increased net balance (basal vs AA: -24 ± 7 vs 19 ± 7; P.05). Protein breakdown at the whole-body level was not different between the groups.Long-term oxandrolone treatment increased net deposition of leg muscle protein during AA infusion by attenuating protein breakdown, but did not affect whole-body protein breakdown.

This study was performed to determine if there is an age-related specificity in the response of muscle protein metabolism to severe burn injury during acute hospitalization. This is a retrospective analysis of previously published data.Nineteen adult and 58 pediatric burn-injured patients (age 43.3 ± 14.3 vs. 7.2 ± 5.3 years, adult vs. children) participated in stable isotope [ring-(2)H(5)]phenylalanine (Phe) infusion studies. Femoral arterial and venous blood samples and muscle biopsy samples were collected throughout the study. Data are presented as means ± standard deviation (SD). A p value less than 0.05 was considered statistically significant.Muscle net protein balance (NB) was higher in children (adult vs. children, -43 ± 61 vs. 8 ± 68 nmol Phe/min/100 ml leg volume, p0.05). Muscle protein fractional synthesis rate (FSR) was higher in children (adult vs. children, 0.11 ± 0.05 vs. 0.16 ± 0.10 %/h, p0.05). Leg muscle protein breakdown was not different between the groups (adult vs. children, 179 ± 115 vs. 184 ± 124 nmol Phe/min/100 ml leg volume, p0.05); synthesis rate was 134 ± 96 and 192 ± 128 nmol Phe/min/100 ml leg volume in adults and children, respectively (p = 0.07). Age significantly correlated with muscle protein NB (p = 0.01) and FSR (p = 0.02); but not with breakdown (p = 0.67) and synthesis (p = 0.07) rates measured by using a three-pool model.In burn injury, the muscle protein breakdown may be affected to the same extent in adults and children, whereas synthesis may have age-related specificities, resulting in a better but still low NB in children.

Arsenic trioxide (As(2)O(3)) has been shown to be effective for treatment of patients with refractory or relapsed acute promyelocytic leukemia and a variety of other malignant hematopoetic disorders. We studied the effect of this agent on proliferation of human hepatoma-derived cell lines (SK-Hep-1, HepG2, and HuH7). In HuH7 cells, As(2)O(3) reduced proliferation time- and dose-dependently at 1 and 2 microM, while in SK-Hep-1 and HepG2 cells, As(2)O(3) inhibited proliferation at 2 and 4 microM respectively. Cell cycle analysis by flow cytometry showed that As(2)O(3) induced apoptosis in these hepatoma-derived cells as confirmed by appearance of sub-G(1) cells. Sensitivity of hepatoma-derived cells to As(2)O(3) was inversely related to their intracellular glutathione (GSH) and intensity of GSH synthesis. Arsenic sensitivity was restored to relatively resistant cell lines when GSH was depleted by L-buthionine sulfoximine (BSO). These results indicate that As(2)O(3) may have therapeutic potential for treatment of hepatocellular carcinoma.

ObjectiveOlder patients with peripheral arterial disease (PAD) and intermittent claudication have impaired walking ability resulting from reduced lower extremity blood flow. Evidence suggests that leg muscle abnormalities may also contribute to walking intolerance in claudicants. In healthy elderly people, leg muscle protein synthesis can be augmented by nutritional supplementation with amino acids; preliminary data suggest that this increases muscle mass, walking ability, and functional status. In this study, we investigated whether amino acid supplementation would improve leg muscle protein synthesis in elderly PAD subjects, given that reduced leg blood flow might restrict the availability of amino acids to muscle.MethodsTwo groups participated in the study: a group of 11 claudicants (mean age, 62 years; mean ankle-brachial index, 0.62; 46% male) and a group of 9 age- and sex-matched healthy controls (mean ankle-brachial index, 1.1). Both groups underwent measurement of leg blood flow by using strain gauge plethysmography, as well as measurement of baseline and amino acid–stimulated protein synthesis in leg muscle. Protein synthesis was quantified from calf muscle biopsy samples by measurement of the fractional synthetic rate (FSR) of protein, by using the incorporation of the stable isotope l-[ring-2H5]-phenylalanine into muscle protein. Total protein was extracted from muscle samples, and gas chromatography/mass spectroscopy methodology was used to measure incorporation rates. After measurement of basal FSR, all subjects were given an oral drink of 15 g of essential amino acids, and the measurements of FSR were repeated. Data are expressed as mean ± SD; statistical analysis of differences between the two groups (with and without amino acid supplementation) was performed by using analysis of variance with repeated measures.ResultsCalf blood flow was reduced in the PAD subjects compared with controls (1.44 ± 0.53 mL/min per 100 mg of tissue vs 2.40 ± 0.57 mL/min per 100 mg of tissue; P = .005; t test). FSR in the basal state was equivalent between the two groups (healthy, 0.060% ± 0.025% per hour; PAD, 0.061% ± 0.029% per hour; P = .97). Equivalent increases (P < .05) occurred in both groups in response to oral amino acid supplementation (healthy, 0.087% ± 0.012% per hour; PAD, 0.104% ± 0.041% per hour; P > .05; analysis of variance).ConclusionsDespite reduced leg blood flow, elderly PAD patients synthesize calf muscle protein in the basal state in a fashion similar to that in healthy elderly people. More importantly, administration of exogenous amino acids produces a significant increase in protein synthesis in these patients that is also equivalent to that in healthy elderly people. Our goal is to use these results as the basis for an intervention study to determine whether long-term oral amino acids, by augmenting calf muscle protein synthesis, increase calf muscle mass, walking ability, and functional status in elderly claudicants.