Non-esterified Free Fatty Acid Research Articles

Time-Dependent Progression of Metabolic Dysfunction in a Mouse Model of Polycystic Ovary Syndrome

Background: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-age women. PCOS is closely linked to metabolic disorders such as obesity, dyslipidemia, systemic insulin resistance (IR), adipose IR and white adipose tissue (WAT) dysfunction. Hyperandrogenism is a clinical hallmark of PCOS, and it plays a fundamental role in the development of metabolic perturbations associated with PCOS. Androgen excess is linked to metabolic dysfunction in multiple tissues, including WAT, in PCOS women. However, data on the disease onset and progression of WAT dysfunction and associated metabolic derangements in PCOS women are lacking. Therefore, we aim to test the hypothesis that the androgen dihydrotestosterone (DHT) induces time-dependent progression of metabolic dysfunction on both the molecular and functional levels in PCOS. This hypothesis will be tested using a well-characterized DHT-induced PCOS mouse model after 2, 4, 8 and 12 weeks of DHT administration. Methods: Three-week old female mice (C57BL/6N) were implanted with Silastic tubes filled with DHT (8 mg, s.c.) or vehicle (n=6/grp) for 2, 4, 8 and 12 weeks. Weekly body weight (BW, gravimetry), body composition (EchoMRI), retroperitoneal fat (RPF) mass (gravimetry) were assessed. Serum leptin, adiponectin and insulin were measured by ELISA, while cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and non-esterified free fatty acid (NEFA) were measured using a clinical chemistry analyzer. Adipose IR (insulin x NEFA) was calculated. RPF androgen receptor (AR), lipolytic marker adipose triglyceride lipase (ATGL), and adipogenesis marker peroxisome proliferator-activated receptor-γ (PPAR-γ) protein levels were assessed by Western blot. Results: DHT-treated mice showed significant (p<0.05) increases in BW (20.23±0.3 vs 17.63±0.1 g) and lean mass (17.77±0.5 vs 15.50±0.3 g) starting 2 weeks following DHT exposure where higher cholesterol (90.0±2.9 vs 70.0±5.8 mg/dL), insulin (0.51±0.08 vs 0.22±0.03 ng/mL) and adipo-IR (2.5-fold) as well as lower insulin-sensitizing adipokine adiponectin levels (4.9±0.2 vs 9.70±1.1 mg/mL) were also observed compared to vehicle. The increases in RPF mass (105.40±10.3 vs 32.78±1.6 mg) and total fat mass (2.43±0.5 vs 1.09±0.1 g) were only significant starting at weeks 4 and 8, respectively. DHT significantly increased NEFA (1.3- and 1.2-fold, 8- and 12-weeks post DHT, respectively) and leptin (1.5-fold, 12 weeks post DHT). Unexpectedly, DHT increased HDL-C (58.80±1.42 vs 41.40±1.2 mg/dL, 4 weeks post DHT), while decreasing triglycerides (76.17±5.4 vs 107.17±9.4 mg/mL) and LDL-C (6.5±0.8 vs 9.0±0.5 mg/mL) after 8 weeks post DHT. At the molecular level, DHT upregulated RPF AR expression (5-fold) and downregulated ATGL expression by 40% as early as 2 weeks post DHT, and downregulated PPARγ expression by 40% at 4 weeks post DHT indicating early onset of adipose tissue dysfunction. Conclusion and significance: Our findings suggest that some PCOS metabolic traits occur very early following the induction of hyperandrogenemia such as serum adiponectin, insulin and cholesterol, highlighting these markers as an early diagnosis potential biomarkers. The onset of WAT lipolysis and adipogenesis alterations as well as adipo-IR were also early events that may be drivers of disease progression. Therefore, actively screening and managing risk factors for metabolic derangements from early on in PCOS is critical for disease management. Supported by NIH-NIGMS P20GM121334 and NIH-NIMHD P50MD017338 grants and American Heart Association Predoctoral Fellowship 903804. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Alterations in nonesterified free fatty acid trafficking rather than hyperandrogenism contribute to metabolic health in obese women with polycystic ovary syndrome

To determine whether alterations in nonesterified fatty acid (NEFA) dynamics or degree of hyperandrogenism (HA) contribute to the difference in insulin sensitivity between women with metabolically healthy obese polycystic ovary syndrome (PCOS) (MHO-PCOS) and women with metabolically unhealthy obese PCOS (MUO-PCOS). Prospective cross-sectional study. Tertiary-care academic center. One hundred twenty-five obese women with PCOS. Consecutive obese (body mass index [BMI] ≥ 30 kg/m2) oligo-ovulatory women (n = 125) with PCOS underwent an oral glucose tolerance test and a subgroup of 16 participants underwent a modified frequently sampled intravenous glucose tolerance test to determine insulin-glucose and -NEFA dynamics. Degree of insulin resistance (IR) in adipose tissue (AT) basally (Adipo-IR) and dynamically (the nadir in NEFA levels observed [NEFAnadir], the time it took for NEFA levels to reach nadir [TIMEnadir], and the percent suppression in plasma NEFA levels from baseline to nadir [%NEFAsupp]); peak lipolysis rate (SNEFA) and peak rate of NEFA disposal from plasma pool (KNEFA); whole-body insulin-glucose interaction (acute response of insulin to glucose [AIRg], insulin sensitivity index [Si], glucose effectiveness [Sg], and disposition index [Di]); and HA (hirsutism score, total and free testosterone levels, and dehydroepiandrosterone sulfate levels). A total of 85 (68%) women were MUO-PCOS and 40 (32%) were MHO-PCOS using the homeostasis model of assessment of IR. Subjects with MUO-PCOS and MHO-PCOS did not differ in mean age, BMI, waist-to-hip ratio, HA, and lipoprotein levels. By a modified frequently sampled intravenous glucose tolerance test, eight women with MUO-PCOS had lesser Si, KNEFA, and the percent suppression in plasma NEFA levels from baseline to nadir (%NEFAsupp) and greater TIMEnadir, NEFAnadir, and baseline adipose tissue IR index (Adipo-IR) than eight subjects with MHO-PCOS, but similar fasting NEFA levels and SNEFA. Women with MUO-PCOS had a higher homeostasis model of assessment-β% and fasting insulin levels than women with MHO-PCOS. In bivalent analysis, Si correlated strongly and negatively with Adipo-IR and NEFAnadir, weakly and negatively with TIMEnadir, and positively with KNEFA and %NEFAsupp, in women with MUO-PCOS only. Independent of age and BMI, women with MUO-PCOS have reduced NEFA uptake and altered insulin-mediated NEFA suppression, but no difference in HA, compared with women with MHO-PCOS. Altered insulin-mediated NEFA suppression, rather than HA or lipolysis rate, contributes to variations in insulin sensitivity among obese women with PCOS.

Boswellia sacra resin as a phytogenic feed supplement to enhance ruminal fermentation, milk yield, and metabolic energy status of early lactating goats

Boswellia sacra resin (BS) is well known for its antimicrobial, antioxidant, and anti-inflammatory properties and hence could be used as an efficient dietary feed additive for ruminants during the transition period. This study was conducted to determine the effects of BS by characterizing the ruminal fermentation, nutrient digestibility, milk production, and energy status of early lactating goats fed different levels of BS. A total of 21 late pregnant Nubian goats (initial body weight 26.3 ± 3.9 kg) were stratified using a completely randomized design to the following three dietary treatments (n = 7 does/treatment): control (without supplementation of BS) and BS treatments; low BS and high BS received 2 and 4 g BS/day/animal, respectively. The treatments were started 2 weeks before parturition and continued till 7 weeks postpartum. Constituents with high biological activity (e.g., bisabolene, limonene, α-pinene, and α- and β-amyrins) were the most abundant components found in experimental BS. Linear reductions (P < 0.01) in acetate molar proportions consistent with linear increases (P < 0.01) in propionate molar proportions and linear (P = 0.01) decreases in total short-chain fatty acids (SCFAS) concentrations by BS treatments. The branched-chain volatile fatty acids were quadratically decreased (P < 0.05) by BS supplementation compared with the control. Supplementation of BS resulted in linear decreases (P < 0.01) in blood plasma glucose, nonesterified free fatty acid, and β-hydroxybutyrate concentrations compared with control. Treatment of BS resulted in linear increases (P < 0.05) in milk yield, energy-corrected milk, net energy for lactation, and feed efficiency without causing adverse effects on nutrient digestibility or dry matter intake compared with control. Goats fed BS had linear reduction (P = 0.04) in milk somatic cell count values compared with control. These results suggested that BS could be used as a novel promising natural dietary feed additive to support the transition of goats from late pregnancy to lactation.

Adipocyte‐specific Loss of Retinoic Acid Receptor Alpha (Rarα) Exacerbates Diet‐induced Obesity and Steatohepatitis in Mice

Adipocytes are the major sites of lipid storage and important for regulating lipid metabolism. Adipocytes also serve as the adipokine-releasing cells that mediates lipid and glucose homeostasis in the body. Under diet-induced conditions impaired lipid metabolism in adipocytes can lead to ectopic lipid accumulation and insulin resistance. Previous studies show that activation of retinoic acid receptors via retinoic acid signaling can inhibit adipogenesis and promote adipose tissue browning. We hypothesized that adipocyte-specific retinoic acid receptor alpha (Rarα) might play a role in protecting against diet-induced obesity. To test this hypothesis, we conducted in-vivo studies using adipocyte-specific Rarα knockout mice. Rarα floxed mice were crossed with adiponectin-Cre transgenic mice to generate adipocyte-specific knockout mice (adipo-Rarα-/-). Rarα fl/fl (control) and adipo-Rarα-/- mice were given a high fat diet for 20 weeks. During the study, the body weight of adipo-Rarα-/- significantly increased compared to control. The body composition analysis showed that loss of Rarα in adipocytes increased body fat content. Indirect calorimetry studies showed that reduced energy expenditure in adipo-Rarα-/- mice. Histological analysis showed that brown adipose tissue had increased lipid deposition. Adipo-Rarα-/- mice also had impaired glucose tolerance. In the liver, adipo-Rarα-/- mice had increased triglyceride and non-esterified free fatty acid accumulation, and fibrosis. In the plasma, adipo-Rarα-/- mice and increased free fatty acid, AST and ALT levels. Thus, our study indicates that adipocyte RARα is protective against obesity and steatohepatitis.

Mitochondrial Proton Leak Regulated by Cyclophilin D Elevates Insulin Secretion in Islets at Nonstimulatory Glucose Levels.

Fasting hyperinsulinemia precedes the development of type 2 diabetes. However, it is unclear whether fasting insulin hypersecretion is a primary driver of insulin resistance or a consequence of the progressive increase in fasting glycemia induced by insulin resistance in the prediabetic state. Herein, we have discovered a mechanism that specifically regulates non-glucose-stimulated insulin secretion (NGSIS) in pancreatic islets that is activated by nonesterified free fatty acids, the major fuel used by β-cells during fasting. We show that the mitochondrial permeability transition pore regulator cyclophilin D (CypD) promotes NGSIS, but not glucose-stimulated insulin secretion, by increasing mitochondrial proton leak. Islets from prediabetic obese mice show significantly higher CypD-dependent proton leak and NGSIS compared with lean mice. Proton leak-mediated NGSIS is conserved in human islets and is stimulated by exposure to nonesterified free fatty acids at concentrations observed in obese subjects. Mechanistically, proton leak activates islet NGSIS independently of mitochondrial ATP synthesis but ultimately requires closure of the KATP channel. In summary, we have described a novel nonesterified free fatty acid-stimulated pathway that selectively drives pancreatic islet NGSIS, which may be therapeutically exploited as an alternative way to halt fasting hyperinsulinemia and the progression of type 2 diabetes.

Hepatic Insulin Extraction in NAFLD Is Related to Insulin Resistance Rather Than Liver Fat Content.

Total insulin clearance is decreased in nonalcoholic fatty liver disease (NAFLD), but the relationship between liver fat and hepatic insulin extraction (HIE) is unknown. This cross-sectional study addresses the hypothesis that HIE is reduced in NAFLD and investigates metabolic and/or anthropometric characteristics most closely associated with insulin clearance. Nondiabetic subjects with NAFLD (n = 13) and age- and body mass index (BMI)-matched controls with normal liver enzymes (n = 15) underwent abdominal CT, dual-energy X-ray absorptiometry, oral glucose tolerance test (OGTT), and labeled two-step hyperinsulinemic-euglycemic clamps. Liver fat was estimated by the CT liver/spleen ratio. Hepatic and extrahepatic insulin clearances were modeled using clamp and OGTT data. Extrahepatic insulin clearance and HIE were not different between NAFLD and controls and did not correlate with liver fat. HIE was positively correlated with insulin sensitivity [rate of glucose disposal (Rd; low r = +0.7, P < 0.001; high r = +0.6, P = 0.001), adiponectin (r = +0.55, P = 0.004), and insulin-mediated suppression of clamp nonesterified free fatty acid (NEFA; r = +0.67, P < 0.001)] but was not associated with fasting NEFA, insulin-mediated suppression of glucose production, or measures of adiposity. Extrahepatic insulin clearance was positively associated with percent body fat (r = +0.44, P = 0.02) and subcutaneous fat (r = +0.42, P = 0.03) but not BMI, intra-abdominal fat, liver fat, Rd, adiponectin, or NEFA. HIE is not directly associated with hepatic steatosis but is associated with muscle and adipose tissue insulin resistance. The data suggest differential regulation of insulin clearance with extrahepatic insulin clearance being associated with body fat and not insulin sensitivity.

Repeated Exposure to Taekwondo Combat Modulates the Physiological and Hormonal Responses to Subsequent Bouts and Recovery Periods.

Bridge, CA, Sparks, SA, McNaughton, LR, Close, GL, Hausen, M, Gurgel, J, and Drust, B. Repeated exposure to taekwondo combat modulates the physiological and hormonal responses to subsequent bouts and recovery periods. J Strength Cond Res 32(9): 2529-2541, 2018-This study examined the physiological and hormonal responses to successive taekwondo combats using an ecologically valid competition time structure. Ten elite male international taekwondo competitors (age 19 ± 3 years) took part in a simulated championship event. The competitors performed 4 combats that were interspersed with different recovery intervals (63 ± 4, 31 ± 3 and 156 ± 5 minutes, respectively). Heart rate (HR) was measured during the combats and venous blood samples were obtained both before and after each combat to determine the plasma metabolite and hormone concentrations. The plasma noradrenaline (21.8 ± 12.8 vs. 15.0 ± 7.0 nmol·l) and lactate (13.9 ± 4.2 vs. 10.5 ± 3.2 mmol·l) responses were attenuated (p < 0.05) between combat 1 and 4. Higher (p < 0.05) HR responses were evident in the final combat when compared with the earlier combats. Higher (p < 0.05) resting HR (139 ± 10 vs. 127 ± 12 b·min), plasma lactate (3.1 ± 1.2 vs. 2.0 ± 0.7 mmol·l), glycerol (131 ± 83 vs. 56 ± 38 μmol·l) and nonesterified free fatty acid (0.95 ± 0.29 vs. 0.71 ± 0.28 mmol·l) concentrations were measured before combat 3 compared with combat 1. Repeated exposure to taekwondo combat using an ecologically valid time structure modulates the physiological and hormonal responses to subsequent bouts and recovery periods. Strategies designed to assist competitors to effectively manage the metabolic changes associated with the fight schedule and promote recovery between the bouts may be important during championship events.

Cellular and Metabolic Basis for the Ichthyotic Phenotype in NIPAL4 (Ichthyin)–Deficient Canines

Mutations in several lipid synthetic enzymes that block fatty acid and ceramide production produce autosomal recessive congenital ichthyoses (ARCIs) and associated abnormalities in permeability barrier homeostasis. However, the basis for the phenotype in patients with NIPAL4 (ichthyin) mutations (among the most prevalent ARCIs) remains unknown. Barrier function was abnormal in an index patient and in canines with homozygous NIPAL4 mutations, attributable to extensive membrane stripping, likely from detergent effects of nonesterified free fatty acid. Cytotoxicity compromised not only lamellar body secretion but also formation of the corneocyte lipid envelope (CLE) and attenuation of the cornified envelope (CE), consistent with a previously unrecognized, scaffold function of the CLE. Together, these abnormalities result in failure to form normal lamellar bilayers, accounting for the permeability barrier abnormality and clinical phenotype in NIPA-like domain-containing 4 (NIPAL4) deficiency. Thus, NIPAL4 deficiency represents another lipid synthetic ARCI that converges on the CLE (and CE), compromising their putative scaffold function. However, the clinical phenotype only partially improved after normalization of CLE and CE structure with topical ω-O-acylceramide because of ongoing accumulation of toxic metabolites, further evidence that proximal, cytotoxic metabolites contribute to disease pathogenesis.

Dietary Supplementation of Glycyrrhetinic Acid (GA) Promoting Lipid Lipolysis from Blunt Snout Bream Megalobrama amblycephala by TNF-α and LPL Expression

Glycyrrhetinic acid (GA), which is a main active principal constituent of liquorice, is extensively used as a non-nutrition sweetener or antiinflammatory in Chinese medicine. This study was carried out to evaluate the effects of different GA levels on growth, biometric parameters, plasma lipid metabolites, Tumor necrosis factor alpha (TNF-α) and Lipoprotein lipase (LPL) gene expression of Megalobrama amblycephala (average weight, 68.78 ±1.13 g). Three diets were formulated to contain various levels of GA (0, 30 and 300 mg/kg). Fish were randomly distributed into 12 cages and fed three times daily for 8 weeks. Dietary GA levels have little significant effect on weight gain and feed conversion ratio. Intraperitoneal fat ratio and viscera/body ratio decreased significantly as dietary GA levels increased, and hepatosomatic index tended to decrease as dietary GA levels increased. Plasma triglycerides, cholesterol, and non-esterified free fatty acid levels also decreased as dietary GA concentrations increased. Adipose tissue and liver TNF-α expression increased significantly with increasing dietary GA levels; whereas, LPL expression showed an opposite trend. Results of this study indicate that dietary supplementation of 300 mg/kg GA had a positive effect in promoting lipid lipolysis in Megalobrama amblycephala without having a negative effect on growth through the regulation of TNF-α and LPL expression.

Cyclosporine A attenuates cardiac dysfunction induced by sepsis via inhibiting calcineurin and activating AMPK signaling.

The aim of the present study was to investigate whether cyclosporine A (CSA) improved cardiac dysfunction at an early stage of sepsis. Male Wistar rats were randomly divided into the following three groups: the sham‑operated control group, the cecal ligation puncture (CLP) procedure‑induced sepsis group and the CSA intervention group. Cecal ligation was performed to generate a sepsis model. At different time points (2, 6, 12, 24 and 72h) following sepsis induction, blood pressure, cardiac function, and non‑esterified free fatty acid (NEFA) levels in the plasma and myocardia were measured, and the expression levels of components associated with the AMP‑activated protein kinase (AMPK)‑acetyl CoA carboxylase (ACC)‑carnitine palmitoyl transferase 1 (CPT1) signaling pathway were compared among the three groups. Sepsis induced a decrease in blood pressure and cardiac function at 24h following sepsis induction in the CLP group, and CSA treatment ameliorated these pathophysiological alterations. In addition, rats in the CLP group exhibited significant increases in calcineurin activity and NEFA accumulation in the heart when compared with those in the sham group. These effects were attenuated by CSA treatment. Mechanistically, the activity of the AMPK‑ACC‑CPT1 pathway was enhanced by CSA treatment. The present study revealed that CSA treatment increases cardiac function at an early stage of sepsis in rats. This treatment partially suppresses calcineurin activity while activating the AMPK‑TCC‑CPT1 pathway.

Maintenance of a fully functional digestive system during hibernation in the European hamster, a food-storing hibernator

Some small mammals limit energy expenditure during winter conditions through torpor bouts, which are characterized by a decrease in body temperature and metabolic rate. Individuals arise periodically from torpor to restore critical functions requiring euthermia. Although most of the species involved do not feed during hibernation and rely on body reserves to fulfil energy requirements (fat-storing species), others hoard food in a burrow (food-storing species) and can feed during interbout euthermy. Whereas fat-storing species undergo a marked atrophy of the digestive tract, food-storing species have to maintain a functional digestive system during hibernation. Our study aimed to evaluate the absorption capacities of a food-storing species, the European hamster, throughout the annual cycle. In vivo intestinal perfusions were conducted in different groups of hamsters (n=5) during the different life periods, namely before hibernation, in torpor, during interbout euthermy, and during summer rest. The triglyceride, non-esterified free fatty acid, starch, glucose and protein composition of the perfusate was evaluated before and after the 1h perfusion of a closed intestinal loop. Triglyceride, starch and protein hydrolysis rates were similar in hibernating (torpid and euthermic) and non-hibernating hamsters. Intestinal absorption of free fatty acid was also similar in all groups. However, glucose uptake rate was higher during hibernation than during the summer. In contrast with fat-storing species, the intestinal absorption capacities of food-storing species are fully maintained during hibernation to optimize nutrient assimilation during short interbout euthermy. In particular, glucose uptake rate is increased during hibernation to restore glycaemia and ensure glucose-dependent pathways.

Matured Hop Bittering Components Induce Thermogenesis in Brown Adipose Tissue via Sympathetic Nerve Activity.

Obesity is the principal symptom of metabolic syndrome, which refers to a group of risk factors that increase the likelihood of atherosclerosis. In recent decades there has been a sharp rise in the incidence of obesity throughout the developed world. Iso-α-acids, the bitter compounds derived from hops in beer, have been shown to prevent diet-induced obesity by increasing lipid oxidation in the liver and inhibition of lipid absorption from the intestine. Whereas the sharp bitterness induced by effective dose of iso-α-acids precludes their acceptance as a nutrient, matured hop bittering components (MHB) appear to be more agreeable. Therefore, we tested MHB for an effect on ameliorating diet-induced body fat accumulation in rodents. MHB ingestion had a beneficial effect but, compared to iso-α-acids and despite containing structurally similar compounds, acted via different mechanisms to reduce body fat accumulation. MHB supplementation significantly reduced body weight gain, epididymal white adipose tissue weight, and plasma non-esterified free fatty acid levels in diet-induced obese mice. We also found that uncoupling protein 1 (UCP1) expression in brown adipose tissue (BAT) was significantly increased in MHB-fed mice at both the mRNA and protein levels. In addition, MHB administration in rats induced the β-adrenergic signaling cascade, which is related to cAMP accumulation in BAT, suggesting that MHB could modulate sympathetic nerve activity innervating BAT (BAT-SNA). Indeed, single oral administration of MHB elevated BAT-SNA in rats, and this elevation was dissipated by subdiaphragmatic vagotomy. Single oral administration of MHB maintained BAT temperature at a significantly higher level than in control rats. Taken together, these findings indicate that MHB ameliorates diet-induced body fat accumulation, at least partly, by enhancing thermogenesis in BAT via BAT-SNA activation. Our data suggests that MHB is a useful tool for developing functional foods or beverages to counteract the accumulation of body fat.

Soy Protein Isolate Inhibits High Fat Diet-Induced Senescence Pathways in Osteoblasts to Maintain Bone Acquisition in Male Rats

Chronic consumption by experimental animals of a typical Western diet high in saturated fats and cholesterol during postnatal life has been demonstrated to impair skeletal development. However, underlying mechanism by which high fat, energy dense diets affect bone forming cell phenotypes is poorly understood. Here, we show that male weanling rats fed a diet containing 45% fat and 0.5% cholesterol made with casein (HF-Cas) for 6 weeks displayed lower bone mineral density and strength compared to AIN-93G-fed dietary controls. Substitution of casein with soy protein isolate (SPI) in the high fat diet (HF-SPI) prevented these effects. The bone sparing effects of SPI were associated with prevention of HF-Cas-induced osteoblast senescence pathways through suppression of p53/p21 signaling pathways. HF-Cas-fed rats had increased caveolin-1 and down-regulated Sirt1 leading to activations of PPARγ and p53/p21; whereas, rats fed HF-SPI suppressed caveolin-1and activated Sirt1 to de-acetylate PPARγ and p53 in bone. Treatment of osteoblastic cells with non-esterified free fatty acid (NEFA) increased cell senescence signaling pathways. Isoflavones significantly blocked activations of senescence-associated β-galactosidase and PPARγ/p53/p21 by NEFA. Finally, replicative senescent osteoblastic cells and bone marrow mesenchymal ST2 cells exhibited similar behavior to cells treated with NEFA and in vivo bone cells in rats fed HF-Cas diet. These results suggest that: 1) high concentrations of NEFA occurring with HF intake are mediators of osteoblast cell senescence leading to impairment of bone development and acquisition; 2) the molecular mechanisms underlying the SPI-protective effects involve isoflavone-induced inhibition of osteoblastic cell senescence to prevent HF-induced bone impairments.

Soy protein isolate inhibits high-fat diet-induced senescence pathways in osteoblasts to maintain bone acquisition in male rats.

Chronic consumption by experimental animals of a typical Western diet high in saturated fats and cholesterol during postnatal life has been demonstrated to impair skeletal development. However, the underlying mechanism by which high-fat, energy-dense diets affect bone-forming cell phenotypes is poorly understood. Here, we show that male weanling rats fed a diet containing 45% fat and 0.5% cholesterol made with casein (HF-Cas) for 6 weeks displayed lower bone mineral density and strength compared with those of AIN-93G-fed dietary controls. Substitution of casein with soy protein isolate (SPI) in the high-fat diet (HF-SPI) prevented these effects. The bone-sparing effects of SPI were associated with prevention of HF-Cas-induced osteoblast senescence pathways through suppression of the p53/p21 signaling pathways. HF-Cas-fed rats had increased caveolin-1 and down-regulated Sirt1, leading to activations of peroxisome proliferator-activated receptor γ (PPARγ) and p53/p21, whereas rats fed HF-SPI suppressed caveolin-1 and activated Sirt1 to deacetylate PPARγ and p53 in bone. Treatment of osteoblastic cells with nonesterified free fatty acid (NEFA) increased cell senescence signaling pathways. Isoflavones significantly blocked activations of senescence-associated β-galactosidase and PPARγ/p53/p21 by NEFA. Finally, replicative senescent osteoblastic cells and bone marrow mesenchymal ST2 cells exhibited behavior similar to that of cells treated with NEFA and in vivo bone cells in rats fed the HF-Cas diet. These results suggest that (1) high concentrations of NEFA occurring with HF intake are mediators of osteoblast cell senescence leading to impairment of bone development and acquisition and (2) the molecular mechanisms underlying the SPI-protective effects involve isoflavone-induced inhibition of osteoblastic cell senescence to prevent HF-induced bone impairments.

Glucosamine Enhances Body Weight Gain and Reduces Insulin Response in Mice Fed Chow Diet but Mitigates Obesity, Insulin Resistance and Impaired Glucose Tolerance in Mice High-Fat Diet

ObjectiveThis study investigated the potential of glucosamine (GlcN) to affect body weight gain and insulin sensitivity in mice normal and at risk for developing diabetes. MethodsMale C57BL/6J mice were fed either chow diet (CD) or a high fat diet (HFD) and the half of mice from CD and HFD provided with a solution of 10% (w/v) GlcN. Total cholesterol and nonesterified free fatty acid levels were determined. Glucose tolerance test and insulin tolerance test were performed. HepG2 human hepatoma cells or differentiated 3T3-L1 adipocytes were stimulated with insulin under normal (5mM) or high glucose (25mM) conditions. Effect of GlcN on 2-deoxyglucose (2-DG) uptake was determined. JNK and Akt phosphorylation and nucleocytoplasmic protein O-GlcNAcylation were assayed by Western blotting. ResultsGlcN administration stimulated body weight gain (6.58±0.82g vs. 11.1±0.42g), increased white adipose tissue fat mass (percentage of bodyweight, 3.7±0.32g vs. 5.61±0.34g), and impaired the insulin response in livers of mice fed CD. However, GlcN treatment in mice fed HFD led to reduction of body weight gain (18.02±0.66g vs. 16.22±0.96g) and liver weight (2.27±0.1 vs. 1.85±0.12g). Furthermore, obesity-induced insulin resistance and impaired Akt insulin signaling in the liver were alleviated by GlcN administration. GlcN inhibited the insulin response under low (5mM) glucose conditions, whereas it restored the insulin response for Akt phosphorylation under high (25mM) glucose conditions in HepG2 and 3T3-L1 cells. Uptake of 2-DG increased upon GlcN treatment under 5mM glucose compared to control, whereas insulin-stimulated 2-DG uptake decreased under 5mM and increased under 25mM glucose in differentiated 3T3-L1 cells. ConclusionOur results show that GlcN increased body weight gain and reduced the insulin response for glucose maintenance when fed to normal CD mice, whereas it alleviated body weight gain and insulin resistance in HFD mice. Therefore, the current data support the integrative function of the HBP reflecting the nutrient status of lipids or glucose and further implicate the importance of the pathway in insulin signaling for the regulation of metabolism.

Effects of supplementation with omega-3 on insulin sensitivity and non-esterified free fatty acid (NEFA) in type 2 diabetic patients.

The aim of this study was to determine the role of omega-3 supplementation on NEFA concentration, insulin sensitivity and resistance, and glucose and lipid metabolism in type 2 diabetic patients. Forty-four type 2 diabetic patients were randomly recruited into two groups. Group A received 4 g/day omega-3 soft gels, and group B received a placebo for 10 wks. Blood samples were collected after 12-h fast. Physical activity records, three-day food records, and anthropometric measurements were obtained from all participants at the beginning and end of the study. Omega-3 supplementation caused a significant reduction in NEFA in the intervention group compared with the placebo group (P = 0.009). Additionally, the administration of omega-3 resulted in significantly greater changes (Diff) for the intervention group in various parameters, such as insulin and Quicki indices compared with the placebo group (P < 0.05). Omega-3 fatty acid supplementation in type 2 diabetic patients improved insulin sensitivity, probably due to the decrease in NEFA concentrations.

Postprandial inflammatory responses and plasma‐free fatty acids: effects of blueberry intake (1034.6)

We studied whether a high‐fat (HF) meal‐induced postprandial (PP) lipemia affects inflammatory responses in blood monocytes, and whether blueberry intake suppresses the PP inflammatory responses in healthy human subjects. A HF breakfast increased PP plasma triglycerides and insulin, but non‐esterified free fatty acid (NEFA) levels were decreased compared to fasting levels. TNF‐α , IL‐6 and IL‐8 in PP plasma were decreased compared to fasting levels. Cytokine and NEFA levels in PP plasma were not affected by blueberry intake. To determine whether endogenous NEFAs derived from the HF diet stimulate monocyte activation, whole blood or peripheral blood mononuclear cells (PBMC) were treated with lipoprotein lipase (LPL). LPL treatment of whole blood increased NEFA levels and secretion of IL‐1β, IL‐6, and TNF‐α. IL‐1β in LPL‐treated PP whole blood was elevated compared to fasting control. Blueberry intake suppressed IL‐1β and IL‐6 production without affecting levels of NEFAs released in LPL‐treated PP blood when fasting controls were used as a covariate. LPL treatment also increased NEFA and cytokine levels in PBMC. Together, these results demonstrate that NEFA levels in plasma or whole blood are an important determinant affecting pro‐inflammatory cytokine production. Therefore, modulation of levels of plasma NEFA by dietary means could be an effective strategy to suppress HF diet‐induced inflammatory responses.Grant Funding Source: Supported by USDA‐ARS‐WHNRC Funds and US Highbush Blueberry Council grant

Breath acetone to monitor life style interventions in field conditions: An exploratory study

To assess whether breath acetone concentration can be used to monitor the effects of a prolonged physical activity on whole body lipolysis and hepatic ketogenesis in field conditions. Twenty-three non-diabetic, 11 type 1 diabetic, and 17 type 2 diabetic subjects provided breath and blood samples for this study. Samples were collected during the International Four Days Marches, in the Netherlands. For each participant, breath acetone concentration was measured using proton transfer reaction ion trap mass spectrometry, before and after a 30-50 km walk on four consecutive days. Blood non-esterified free fatty acid (NEFA), beta-hydroxybutyrate (BOHB), and glucose concentrations were measured after walking. Breath acetone concentration was significantly higher after than before walking, and was positively correlated with blood NEFA and BOHB concentrations. The effect of walking on breath acetone concentration was repeatedly observed on all four consecutive days. Breath acetone concentrations were higher in type 1 diabetic subjects and lower in type 2 diabetic subjects than in control subjects. Breath acetone can be used to monitor hepatic ketogenesis during walking under field conditions. It may, therefore, provide real-time information on fat burning, which may be of use for monitoring the lifestyle interventions.

Novel insights into pancreatic β-cell glucolipotoxicity from real-time functional analysis of mitochondrial energy metabolism in INS-1E insulinoma cells

High circulating glucose and non-esterified (free) fatty acid levels can cause pancreatic β-cell failure. The molecular mechanisms of this β-cell glucolipotoxicity are yet to be established conclusively. In the present paper we report on the involvement of mitochondrial dysfunction in fatty-acid-induced β-cell failure. We have used state-of-the-art extracellular flux technology to functionally probe mitochondrial energy metabolism in intact INS-1E insulinoma cells in real-time. We show that 24-h palmitate exposure at high glucose attenuates the glucose-sensitivity of mitochondrial respiration and lowers coupling efficiency of glucose-stimulated oxidative phosphorylation. These mitochondrial defects coincide with an increased level of ROS (reactive oxygen species), impaired GSIS (glucose-stimulated insulin secretion) and decreased cell viability. Palmitate lowers absolute glucose-stimulated respiration coupled to ATP synthesis, but does not affect mitochondrial proton leak. Palmitate is not toxic when administered at low glucose unless fatty acid β-oxidation is inhibited. Palmitoleate, on the other hand, does not affect mitochondrial respiration, ROS levels, GSIS or cell viability. Although palmitoleate protects against the palmitate-induced ROS increase and cell viability loss, it does not protect against respiratory and insulin secretory defects. We conclude that mitochondrial dysfunction contributes to fatty-acid-induced GSIS impairment, and that glucolipotoxic cell viability and GSIS phenotypes are mechanistically distinct.

Adipose tissue insulin resistance in adolescents with and without type 2 diabetes

The incidence of type 2 diabetes mellitus (T2D) is increasing in youth, yet little is known about the underlying pathophysiology. Decreased insulin suppression of lipolysis and elevated non-esterified free fatty acid (NEFA) concentrations are known to be associated with insulin resistance and T2D in adults, but less is known about the relationship in adolescents. This study aimed to assess adipose tissue insulin resistance (IR; insulin suppression of lipolysis) and its metabolic correlates in lean, obese and T2D adolescents. Forty-seven lean, obese and T2D youth underwent hyperinsulinaemic (80 mU*m(-2) *min(-1)) euglycaemic clamps. NEFAs were measured at baseline and during steady state. Insulin-mediated suppression of lipolysis (%NEFA suppression from baseline) was calculated, and metabolic risk factors were assessed by %NEFA suppression tertile. There was expected variability in %NEFA suppression within obese and T2D youth, but a subset had significantly reduced suppression of lipolysis. NEFA suppression tertile was significantly inversely associated with fasting triglycerides (P = 0.0001), log alanine aminotransferase (ALT; P = 0.02) and low-density lipoprotein cholesterol (P = 0.0002). Marked adipose tissue IR occurs in some obese and T2D adolescents, which may result in release of triglycerides into the circulation and liver deposition of fatty acids, as evidenced by higher ALT in poor NEFA suppressors.