Reduced Plasma Free Fatty Acid Research Articles

Effects of repeated weight cycling on non-alcoholic steatohepatitis in diet-induced obese mice.

Lifestyle interventions remain the treatment of choice for patients with obesity and metabolic complications, yet are difficult to maintain and often lead to cycles of weight loss and regain (weight cycling). Literature on weight cycling remains controversial and we therefore investigated the association between weight cycling and metabolic complications using preexistent obese mice. Ldlr-/-.Leiden mice received a high-fat diet (HFD) for 20 weeks to induce obesity. Subsequently, weight-cycled mice were switched between the healthy chow diet and HFD for four 2-week periods and compared to mice that received HFD for the total study period. Repeated weight cycling tended to decrease body weight and significantly reduced fat mass, whereas adipose tissue inflammation was similar relative to HFD controls. Weight cycling did not significantly affect blood glucose or plasma insulin levels yet significantly reduced plasma free fatty acid and alanine transaminase/aspartate transaminase levels. Hepatic macrovesicular steatosis was similar and microvesicular steatosis tended to be increased upon weight cycling. Weight cycling resulted in a robust decrease in hepatic inflammation compared to HFD controls while hepatic fibrosis and atherosclerosis development were not affected. These results argue against the postulate that repeated weight cycling leads to unfavorable metabolic effects, when compared to a continuous unhealthy lifestyle, and in fact revealed beneficial effects on hepatic inflammation, an important hallmark of non-alcoholic steatohepatitis.

Comparison of Metabolic Response to Colonic Fermentation in Lean Youth vs Youth With Obesity

Pediatric obesity is a growing health care burden. Understanding how the metabolic phenotype of youth with obesity may modify the effect of intestinal fermentation on human metabolism is key to designing early intervention. To assess whether adiposity and insulin resistance in youth may be associated with colonic fermentation of dietary fibers and its production of acetate, gut-derived hormone secretion, and adipose tissue lipolysis. Cross-sectional study of youths aged 15 to 22 years with body mass index in the 25th to 75th percentile or higher than the 85th percentile for age and sex throughout the New Haven County community in Connecticut. Recruitment, studies, and data collection occurred from June 2018 to September 2021. Youths were assigned to a lean, obese insulin sensitive (OIS), or obese insulin resistant (OIR) group. Data were analyzed from April 2022 to September 2022. Participants consumed 20 g of lactulose during a continuous 10-hour sodium d3-acetate intravenous infusion to measure the rate of appearance of acetate in plasma. Plasma was obtained hourly to measure acetate turnover, peptide tyrosine tyrosine (PYY), ghrelin, active glucagon-like peptide 1 (GLP-1), and free fatty acids (FFA). A total of 44 youths participated in the study (median [IQR] age, 17.5 [16.0-19.3] years; 25 [56.8%] were female; 23 [52.3%] were White). Consequent to lactulose ingestion, there was a reduction of plasma FFA, an improvement of adipose tissue insulin sensitivity index, an increase in colonic acetate synthesis, and an anorexigenic response characterized by an increased plasma concentration of PYY and active GLP-1 and a reduction of ghrelin in the subgroups. Compared with the lean and OIS groups, the OIR group showed a less marked median (IQR) rate of acetate appearance (OIR: 2.00 [-0.86 to 2.69] μmol × kg-1 × min-1; lean: 5.69 [3.04 to 9.77] μmol × kg-1 × min-1; lean vs OIR P = .004; OIS: 2.63 [1.22 to 4.52] μmol × kg-1 × min-1; OIS vs OIR P = .09), a blunted median (IQR) improvement of adipose insulin sensitivity index (OIR: 0.043 [ 0.006 to 0.155]; lean: 0.277 [0.220 to 0.446]; lean vs OIR P = .002; OIS: 0.340 [0.048 to 0.491]; OIS vs OIR P = .08), and a reduced median (IQR) PYY response (OIR: 25.4 [14.8 to 36.4] pg/mL; lean: 51.3 [31.6 to 83.3] pg/mL; lean vs OIR P = .002; OIS: 54.3 [39.3 to 77.2] pg/mL; OIS vs OIR P = .011). In this cross-sectional study, lean, OIS, and OIR youth demonstrated different associations between colonic fermentation of indigestible dietary carbohydrates and the metabolic response, with OIR youth showing minimal metabolic modifications as compared with the other 2 groups. ClinicalTrials.gov Identifier: NCT03454828.

Albumin knockout mice exhibit reduced plasma free fatty acid concentration and enhanced insulin sensitivity.

Circulating albumin is expected to play a significant role in the trafficking of plasma free fatty acids (FFA) between tissues, such as FFA transfer from adipose tissue to the liver. However, it was not yet known how disrupting FFA binding to albumin in circulation would alter lipid metabolism and any resulting impacts upon control of glycemia. To improve understanding of metabolic control, we aimed to determine whether lack of serum albumin would decrease plasma FFA, hepatic lipid storage, whole body substrate oxidation, and glucose metabolism. Male and female homozygous albumin knockout mice and C57BL/6J wild type controls, each on a standard diet containing a moderate fat content, were studied at 6–8 weeks of age. Indirect calorimetry, glucose tolerance testing, insulin tolerance testing, exercise performance, plasma proteome, and tissue analyses were performed. In both sexes of albumin knockout mice compared to the wild type mice, significant reductions (p < 0.05) were observed for plasma FFA concentration, hepatic triacylglycerol and diacylglycerol content, blood glucose during the glucose tolerance test, and blood glucose during the insulin tolerance test. Albumin deficiency did not reduce whole body fat oxidation over a 24‐h period and did not alter exercise performance in an incremental treadmill test. The system‐level phenotypic changes in lipid and glucose metabolism were accompanied by reduced hepatic perilipin‐2 expression (p < 0.05), as well as increased expression of adiponectin (p < 0.05) and glucose transporter‐4 (p < 0.05) in adipose tissue. The results indicate an important role of albumin and plasma FFA concentration in lipid metabolism and glucoregulation.

The Alzheimer’s disease drug candidate J147 decreases blood plasma fatty acid levels via modulation of AMPK/ACC1 signaling in the liver

J147 is a novel drug candidate developed to treat neurological dysfunction. Numerous studies have demonstrated the beneficial effects of J147 in cellular and animal models of disease which has led to the transitioning of the compound into human clinical trials. However, no biomarkers for its target engagement have been identified. Here, we determined if specific metabolites in the plasma could be indicative of J147′s activity in vivo. Plasma lipidomics data from three independent rodent studies were assessed along with liver lipidomics data from one of the studies. J147 consistently reduced plasma free fatty acid (FFA) levels across the independent studies. Decreased FFA levels were also found in the livers of J147-treated mice that correlated well with those in the plasma. These changes in the liver were associated with activation of the AMP-activated protein kinase/acetyl-CoA carboxylase 1 signaling pathway. A reduction in FFA levels by J147 was confirmed in HepG2 cells, where activation of the AMPK/ACC1 pathway was seen along with increases in acetyl-CoA and ATP levels which correlated with enhanced cellular bioenergetics. Our data show that J147 targets liver cells to activate the AMPK/ACC1 signaling pathway and preserve energy at the expense of inhibiting FFA synthesis.

In Vivo Metabolic Roles of G Proteins of the Gi Family Studied With Novel Mouse Models.

G protein-coupled receptors (GPCRs) are the target of ~30% to 35% of all US Food and Drug Administration-approved drugs. The individual members of the GPCR superfamily couple to 1 or more functional classes of heterotrimeric G proteins. The physiological outcome of activating a particular GPCR in vivo depends on the pattern of receptor distribution and the type of G proteins activated by the receptor. Based on the structural and functional properties of their α-subunits, heterotrimeric G proteins are subclassified into 4 major families: Gs, Gi/o, Gq/11, and G12/13. Recent studies with genetically engineered mice have yielded important novel insights into the metabolic roles of Gi/o-type G proteins. For example, recent data indicate that Gi signaling in pancreatic α-cells plays a key role in regulating glucagon release and whole body glucose homeostasis. Receptor-mediated activation of hepatic Gi signaling stimulates hepatic glucose production, suggesting that inhibition of hepatic Gi signaling could prove clinically useful to reduce pathologically elevated blood glucose levels. Activation of adipocyte Gi signaling reduces plasma free fatty acid levels, thus leading to improved insulin sensitivity in obese, glucose-intolerant mice. These new data suggest that Gi-coupled receptors that are enriched in metabolically important cell types represent potential targets for the development of novel drugs useful for the treatment of type 2 diabetes and related metabolic disorders.

Albumin Knockout Mice Exhibit Reduced Plasma Free Fatty Acids but No Impairment in Whole Body Fat Oxidation

Abstract Objectives To improve understanding of the control of lipid metabolism, we aimed to determine whether lack of serum albumin decreases plasma free fatty acids (FFA), hepatic triacylglycerol (TAG), and whole body substrate oxidation in albumin knockout mice compared to wild type mice. Methods Male and female homozygous albumin knockout mice and C57BL/6J wild type controls, each on the 5k52 diet which contains a moderate fat content, were studied at 6–8 weeks of age. Body composition was tested by magnetic resonance. Substrate oxidation was measured by indirect calorimetry over 24 hours in metabolic cages. Plasma and tissues were collected after a 5-hour fast. Plasma FFA was measured by liquid chromatography/mass spectrometry (LC/MS). Hepatic TAG was measured by a colorimetric kit. Results In albumin knockout mice compared to the wild type mice, plasma FFA (P &amp;lt; 0.0001) and hepatic TAG content (P &amp;lt; 0.0001) were each reduced, while body fat percentage was increased (P &amp;lt; 0.01). In addition, female versus male showed higher hepatic TAG levels (P &amp;lt; 0.01). These results indicate that the lack of serum albumin decreases plasma FFA and hepatic TAG accumulation. However, the average 24-hour oxygen consumption, metabolic rate, and respiratory quotient (RQ) were not altered in albumin knockout mice, indicating that total fuel oxidation and relative contribution of lipid to whole body metabolism was not significantly unaltered. Conclusions We propose that lack of albumin reduces plasma FFA which diminishes hepatic TAG content through changes in the lipid supply to the liver. The results indicate that tissue lipid accumulation can be altered by targeting albumin without substantially disrupting whole body substrate oxidation, suggesting that metabolic control of FFA trafficking toward sites of ectopic lipid deposition and toward oxidation can be regulated independently of one another. Funding Sources McKinley Educational Initiative and the Purdue University College of Health and Human Sciences

Resveratrol Improves Hepatic Redox Status and Lipid Balance of Neonates with Intrauterine Growth Retardation in a Piglet Model.

Abnormal lipid metabolism, oxidative stress (OS), and inflammation play a pivotal role in the increased susceptibility to neonatal fatty liver diseases associated with intrauterine growth retardation (IUGR). This study was firstly conducted to investigate whether resveratrol could alleviate IUGR-induced hepatic lipid accumulation, alteration of redox and immune status in a sucking piglet model and explore the possible mechanisms at transcriptional levels. A total of 36 pairs of 7 d old male normal birth weight (NBW) and IUGR piglets were orally fed with either 80 mg resveratrol/kg body weight/d or 0.5% carboxymethylcellulose sodium for a period of 14 days, respectively. Compared with the NBW piglets, the IUGR piglets displayed compromised growth performance and liver weight, reduced plasma free fatty acid (FFA) level, increased hepatic OS, abnormal hepatic lipid accumulation and weakened hepatic immune function, and hepatic aberrant transcriptional expression of some genes such as heme oxygenase 1, superoxide dismutase 1, sterol regulatory element-binding protein 1c, stearoyl-CoA desaturase 1, liver fatty acid-binding proteins 1, toll-like receptor 4, and tumor necrosis factor alpha (TNF-α). Oral administration of resveratrol to piglets decreased the levels of FFA and total triglycerides (TG) in the plasma and hepatic TNF-α concentration, and increased glutathione reductase activity and reduced glutathione level in the liver. Resveratrol restored the increased alanine aminotransferase activity in the plasma of IUGR piglets. Treatment with resveratrol ameliorated the increased hepatic malondialdehyde, protein carbonyl, TG, and FFA concentrations induced by IUGR. Resveratrol treatment alleviated the reduced lipoprotein lipase activity and its mRNA expression as well as TNF-α gene expression in the liver of IUGR piglets. Hepatic glutathione peroxidase 1 and monocyte chemotactic protein 1 genes expression of piglets was upregulated by oral resveratrol administration. In conclusion, resveratrol administration plays a beneficial role in hepatic redox status and lipid balance of the IUGR piglets.

Effects of Glutamine and Alanine Supplementation on Central Fatigue Markers in Rats Submitted to Resistance Training.

Recent evidence suggests that increased brain serotonin synthesis impairs performance in high-intensity intermittent exercise and specific amino acids may modulate this condition, delaying fatigue. This study investigated the effects of glutamine and alanine supplementation on central fatigue markers in rats submitted to resistance training (RT). Wistar rats were distributed in: sedentary (SED), trained (CON), trained and supplemented with alanine (ALA), glutamine and alanine in their free form (G + A), or as dipeptide (DIP). Trained groups underwent a ladder-climbing exercise for eight weeks, with progressive loads. In the last 21 days, supplementations were offered in water with a 4% concentration. Albeit without statistically significance difference, RT decreased liver glycogen, and enhanced the concentrations of plasma glucose, free fatty acids (FFA), hypothalamic serotonin, and ammonia in muscle and the liver. Amino acids affected fatigue parameters depending on the supplementation form. G + A prevented the muscle ammonia increase by RT, whereas ALA and DIP augmented ammonia and glycogen concentrations in muscle. DIP also increased liver ammonia. ALA and G + A reduced plasma FFA, whereas DIP increased this parameter, free tryptophan/total tryptophan ratio, hypothalamic serotonin, and the serotonin/dopamine ratio. The supplementations did not affect physical performance. In conclusion, glutamine and alanine may improve or impair central fatigue markers depending on their supplementation form.

Effect of plasma free fatty acid supply on the rate of ceramide synthesis in different muscle types in the rat.

Ceramide is a key compound in sphingolipid metabolism. Dynamics of ceramide synthesis is important in the several biological processes, such as induction of apoptosis or insulin resistance. So far, its de novo synthesis rate was evaluated indirectly, based on the content of the compound, its intermediates and the activity of respective enzymes. The aim of the present study was to directly measure ceramide synthesis rate (FSR) in different muscle types under varied plasma FFA supply in rat with the use of [U-13C] palmitate tracer and LC/MS/MS. The experiments were carried out on male Wistar rats, divided into three groups: 1-control, 2-with elevated plasma free fatty acid (FFA) concentration by means of intralipid and heparin, 3-with reduced plasma FFA concentration by means of nicotinic acid. The stable plasma FFA concentration and plasma [U-13C] palmitate enrichment was maintained for two hours by simultaneous infusion of the tracer and the respective compounds. At the end of the experiment, samples of blood from the abdominal aorta, the heart, diaphragm, soleus and white section of the gastrocnemius were taken. Muscle sphinganine, sphingosine and ceramide content and enrichment and plasma palmitate enrichment was measured with the use of LC/MS/MS. Plasma FFA concentration and composition was measured by means of gas-liquid chromatography. Under basal conditions ceramide FSR in the heart and the diaphragm was higher than in the soleus and the white gastrocnemius. Elevation in the plasma FFA concentration increased the FSR and ceramide content in each muscle, which correlated with increased HOMA-IR. The highest FSR was noted in the heart. Reduction in the plasma FFA concentration decreased ceramide FSR in each muscle type, which was accompanied by marked reduction in HOMA-IR. It is concluded that ceramide FSR depends on both the muscle type and the plasma FFA supply and is correlated with whole body insulin sensitivity under varying plasma FFA supply.

Insulin induces a shift in lipid and primary carbon metabolites in a model of fasting-induced insulin resistance.

Prolonged fasting in northern elephant seals (NES) is characterized by a reliance on lipid metabolism, conservation of protein, and reduced plasma insulin. During early fasting, glucose infusion previously reduced plasma free fatty acids (FFA); however, during late-fasting, it induced an atypical elevation in FFA despite comparable increases in insulin during both periods suggestive of a dynamic shift in tissue responsiveness to glucose-stimulated insulin secretion. To better assess the contribution of insulin to this fasting-associated shift in substrate metabolism. We compared the responses of plasma metabolites (amino acids (AA), FFA, endocannabinoids (EC), and primary carbon metabolites (PCM)) to an insulin infusion (65 mU/kg) in early- and late-fasted NES pups (n = 5/group). Plasma samples were collected prior to infusion (T0) and at 10, 30, 60, and 120 min post-infusion, and underwent untargeted and targeted metabolomics analyses utilizing a variety of GC-MS and LC-MS technologies. In early fasting, the majority (72%) of metabolite trajectories return to baseline levels within 2 h, but not in late fasting indicative of an increase in tissue sensitivity to insulin. In late-fasting, increases in FFA and ketone pools, coupled with decreases in AA and PCM, indicate a shift toward lipolysis, beta-oxidation, ketone metabolism, and decreased protein catabolism. Conversely, insulin increased PCM AUC in late fasting suggesting that gluconeogenic pathways are activated. Insulin also decreased FFA AUC between early and late fasting suggesting that insulin suppresses triglyceride hydrolysis. Naturally adapted tolerance to prolonged fasting in these mammals is likely accomplished by suppressing insulin levels and activity, providing novel insight on the evolution of insulin during a condition of temporary, reversible insulin resistance.

AnExercise-OnlyInterventioninObeseFathers RestoresGlucoseandInsulinRegulationin ConjunctionwiththeRescueofPancreaticIsletCell MorphologyandMicroRNAExpressioninMale Offspring.

Paternal obesity programs metabolic syndrome in offspring. Low-impact exercise in obese males improves the metabolic health of female offspring, however whether this occurred in male offspring remained unknown. C57BL/6NHsd (Harlan) mice were fed a control diet (CD; 6% fat, n = 7) or a high-fat diet (HFD; 21% fat, n = 16) for 18 weeks. After 9 weeks, HFD-fed mice either remained sedentary (HH, n = 8) or undertook low–moderate exercise (HE, n = 8) for another 9 weeks. Male offspring were assessed for glucose/insulin tolerance, body composition, plasma lipids, pancreatic islet cell morphology and microRNA expression. Founder HH induced glucose intolerance, insulin insensitivity, and hyperlipidaemia in male offspring (p < 0.05). Metabolic health was fully restored in male offspring by founder exercise to control levels. Founder HH reduced pancreatic β-cell area and islet cell size in male offspring, and altered the expression of 13 pancreatic microRNAs (p < 0.05). Founder HE led to partial restoration of pancreatic islet cell morphology and the expression of two pancreatic microRNAs (let7d-5p, 194-5p) in male offspring. Founder HE reduced male offspring adiposity, increased muscle mass, reduced plasma free fatty acids (FFAs), and further altered pancreatic microRNAs (35 vs. HH; 32 vs. CD) (p < 0.05). Low-impact exercise in obese fathers prior to conception, without dietary change, may be a viable intervention strategy to reduce the ill-effects of obesity-induced paternal programming in male offspring.

Exenatide improves both hepatic and adipose tissue insulin resistance: A dynamic positron emission tomography study.

Acute EX administration (1) improves Hep-IR, decreases EGP, and enhances HGU and (2) reduces Adipo-IR, improves the antilipolytic effect of insulin, and reduces plasma free fatty acid levels during OGTT. (Hepatology 2016;64:2028-2037).

Deletion of Apoptosis Inhibitor of Macrophage (AIM)/CD5L Attenuates the Inflammatory Response and Infarct Size in Acute Myocardial Infarction.

BackgroundAn excessive inflammatory response after myocardial infarction (MI) increases myocardial injury. The toll‐like receptor (TLR)‐4 is activated by the recognition of endogenous ligands and is proinflammatory when there is myocardial tissue injury. The apoptosis inhibitor of the macrophage (AIM) is known to provoke an efflux of saturated free fatty acids (FFA) due to lipolysis, which causes inflammation via the TLR‐4 pathway. Therefore, this study investigated the hypothesis that AIM causes a proinflammatory response after MI.Methods and ResultsThe left anterior descending coronary artery was ligated to induce MI in both AIM‐knockout (AIM−/−) and wild‐type (WT) mice. After 3 days, the inflammatory response from activation of the TLR‐4/NFκB pathway was assessed, and infarct size was measured by staining with triphenyltetrazolium chloride. In addition, left ventricular remodeling was examined after 28 days. Although the area at risk was similar between AIM−/− and WT mice, the infarct size was significantly smaller in AIM−/− mice (P=0.02). The heart weight–to–body weight ratio and myocardial fibrosis were also decreased in the AIM−/− mice, and the 28‐day survival rate was improved (P<0.01). With the reduction of plasma FFA in AIM−/− mice, myocardial IRAK4 and NFκB activity were decreased (all P<0.05). Moreover, there was a reduction in myeloperoxidase activity and inducible nitric oxide synthase as part of the inflammatory response (P<0.01, P=0.03, respectively). Furthermore, NFκB DNA‐binding activation via TLR‐4, neutrophil infiltration, and inflammatory mediators were decreased in AIM−/− mice.ConclusionsThe deletion of AIM reduced the inflammatory response and infarct size and improved survival after myocardial infarction.

Salacia - The new multi-targeted approach in diabetics.

Salacia species plant has been used traditionally as an Ayurvedic medicine for diabetes mellitus. Studies over the past decades have shown its multi-targeted role in diabetics. In the present review article, various mechanisms of action of Salacia on diabetics are discussed in detail. Apart from the well-known action of decreasing postprandial glucose sugar by inhibiting α-glucosidase and α-pancreatic amylase, it also inhibits aldose reductase which otherwise results in microvascular complications. Importantly, its peroxisome proliferator-activated receptor (PPAR)-γ agonist (such as thiazolidinediones, the insulin sensitizers) action increases the uptake of free fatty acid (FFA) and facilitates their storage in subcutaneous fat rather than the visceral fat. This reduces plasma FFA and insulin resistance. Furthermore, it increases the expression of and translocation to the cell surface of glucose transporter 1 and 4 receptors which result in glucose uptake by the liver and skeletal muscle and decreases plasma glucose levels. It also decreases inflammatory cytokines and increases adiponectin expression. Salacia as PPAR-α agonist (such as fibrates) has a role in the management of dyslipidemia. The activation of PPAR-α leads to the increased expression of lipoprotein lipase and apolipoprotein (Apo) A-V and decrease in hepatic Apo-C-III. These actions lower plasma triglycerides in chylomicrons and very low-density lipoprotein particles, thus liberating fatty acids, which are taken up and stored as fat in adipocytes. Salacia has been shown to suppress the overexpression of cardiac PPAR-α (similar to angiotensin-converting enzyme inhibitors/angiotensin receptor blockers) and thereby preventing diabetic cardiomyopathy. It also suppresses the cardiac angiotensin II Type 1 receptors resulting in antihypertrophic and antifibrogenic effect.

Mitochondrial substrate availability and its role in lipid-induced insulin resistance and proinflammatory signaling in skeletal muscle.

The relationship between glucose and lipid metabolism has been of significant interest in understanding the pathogenesis of obesity-induced insulin resistance. To gain insight into this metabolic paradigm, we explored the potential interplay between cellular glucose flux and lipid-induced metabolic dysfunction within skeletal muscle. Here, we show that palmitate (PA)-induced insulin resistance and proinflammation in muscle cells, which is associated with reduced mitochondrial integrity and oxidative capacity, can be attenuated under conditions of glucose withdrawal or glycolytic inhibition using 2-deoxyglucose (2DG). Importantly, these glucopenic-driven improvements coincide with the preservation of mitochondrial function and are dependent on PA oxidation, which becomes markedly enhanced in the absence of glucose. Intriguingly, despite its ability to upregulate mitochondrial PA oxidation, glucose withdrawal did not attenuate PA-induced increases in total intramyocellular diacylglycerol and ceramide. Furthermore, consistent with our findings in cultured muscle cells, we also report enhanced insulin sensitivity and reduced proinflammatory tone in soleus muscle from obese Zucker rats fed a 2DG-supplemented diet. Notably, this improved metabolic status after 2DG dietary intervention is associated with markedly reduced plasma free fatty acids. Collectively, our data highlight the key role that mitochondrial substrate availability plays in lipid-induced metabolic dysregulation both in vitro and in vivo.

Dual regulation of adipose triglyceride lipase by pigment epithelium-derived factor: A novel mechanistic insight into progressive obesity

Both elevated plasma free fatty acids (FFA) and accumulating triglyceride in adipose tissue are observed in the process of obesity and insulin resistance. This contradictory phenomenon and its underlying mechanisms have not been thoroughly elucidated. Recent studies have demonstrated that pigment epithelium-derived factor (PEDF) contributes to elevated plasma FFA and insulin resistance in obese mice via the activation of adipose triglyceride lipase (ATGL). However, we found that PEDF downregulated adipose ATGL protein expression despite of enhancing lipolysis. Plasma PEDF and FFA were increased in associated with a progressive high-fat-diet, and those outcomes were also accompanied by fat accumulation and a reduction in adipose ATGL. Exogenous PEDF injection downregulated adipose ATGL protein expression and elevated plasma FFA, while endogenous PEDF neutralization significantly rescued the adipose ATGL reduction and also reduced plasma FFA in obese mice. PEDF reduced ATGL protein expression in a time- and dose-dependent manner in differentiated 3T3-L1 cells. Small interfering RNA-mediated PEDF knockdown and antibody-mediated PEDF blockage increased endogenous ATGL expression, and PEDF overexpression downregulated ATGL. PEDF resulted in a decreased half-life of ATGL and regulated ATGL degradation via ubiquitin-dependent proteasomal degradation pathway. PEDF stimulated lipolysis via ATGL using ATGL inhibitor bromoenol lactone, and PEDF also downregulated G0/G1 switch gene 2 (G0S2) expression, which is an endogenous inhibitor of ATGL activation. Overall, PEDF attenuated ATGL protein accumulation via proteasome-mediated degradation in adipocytes, and PEDF also promoted lipolysis by activating ATGL. Elevated PEDF may contribute to progressive obesity and insulin resistance via its dual regulation of ATGL.

Effect of a sustained reduction in plasma free fatty acid concentration on insulin signalling and inflammation in skeletal muscle from human subjects

Free fatty acids (FFAs) have been implicated in the pathogenesis of insulin resistance. Reducing plasma FFA concentration in obese and type 2 diabetic (T2DM) subjects improves insulin sensitivity. However, the molecular mechanism by which FFA reduction improves insulin sensitivity in human subjects is not fully understood. In the present study, we tested the hypothesis that pharmacological FFA reduction enhances insulin action by reducing local (muscle) inflammation, leading to improved insulin signalling. Insulin-stimulated total glucose disposal (TGD), plasma FFA species, muscle insulin signalling, IBα protein, c-Jun phosphorylation, inflammatory gene (toll-like receptor 4 and monocyte chemotactic protein 1) expression, and ceramide and diacylglycerol (DAG) content were measured in muscle from a group of obese and T2DM subjects before and after administration of the antilipolytic drug acipimox for 7 days, and the results were compared to lean individuals. We found that obese and T2DM subjects had elevated saturated and unsaturated FFAs in plasma, and acipimox reduced all FFA species. Acipimox-induced reductions in plasma FFAs improved TGD and insulin signalling in obese and T2DM subjects. Acipimox increased IBα protein (an indication of decreased IB kinase-nuclear factor B signalling) in both obese and T2DM subjects, but did not affect c-Jun phosphorylation in any group. Acipimox also decreased inflammatory gene expression, although this reduction only occurred in T2DM subjects. Ceramide and DAG content did not change. To summarize, pharmacological FFA reduction improves insulin signalling in muscle from insulin-resistant subjects. This beneficial effect on insulin action could be related to a decrease in local inflammation. Notably, the improvements in insulin action were more pronounced in T2DM, indicating that these subjects are more susceptible to the toxic effect of FFAs.

Reduction of Free Fatty Acids, Safety, and Pharmacokinetics of Oral GS‐9667, an A1 Adenosine Receptor Partial Agonist

GS-9667, a new selective, partial agonist of the A(1) adenosine receptor (AR), may represent an effective therapy for Type 2 diabetes (T2DM) and dyslipidemia via lowering of free fatty acids (FFA). The objectives of the studies were to evaluate the effects of single and multiple doses of GS-9667 on plasma FFA concentrations, its pharmacokinetics (PK) and safety/tolerability. Two studies were conducted. In the single ascending dose study, healthy, non-obese, and obese subjects received a single oral dose of GS-9667 (30-1,800 mg). In the multiple, ascending dose study, healthy, obese subjects received GS-9667 (600-2,400 mg QD, 1,200 mg BID, or 600 mg QID) for 14 days. Blood and urine samples were collected for lipid profiling and PK analyses. The ECG, vital signs, and subject tolerability were monitored. Doses of GS-9667 ≥300 mg caused dose-dependent reductions in FFA levels that were reproducible over 14 days without evidence of desensitization or rebound. All doses were well tolerated. GS-9667 was rapidly absorbed and distributed; Steady-state concentrations were achieved within 3-5 days. The A(1) AR partial agonist GS-9667 reduced plasma FFA, exhibited linear kinetics, and was well-tolerated in healthy non-obese and obese subjects.

Tocotrienols Reverse Cardiovascular, Metabolic and Liver Changes in High Carbohydrate, High Fat Diet-Fed Rats

Tocotrienols have been reported to improve lipid profiles, reduce atherosclerotic lesions, decrease blood glucose and glycated haemoglobin concentrations, normalise blood pressure in vivo and inhibit adipogenesis in vitro, yet their role in the metabolic syndrome has not been investigated. In this study, we investigated the effects of palm tocotrienol-rich fraction (TRF) on high carbohydrate, high fat diet-induced metabolic, cardiovascular and liver dysfunction in rats. Rats fed a high carbohydrate, high fat diet for 16 weeks developed abdominal obesity, hypertension, impaired glucose and insulin tolerance with increased ventricular stiffness, lower systolic function and reduced liver function. TRF treatment improved ventricular function, attenuated cardiac stiffness and hypertension, and improved glucose and insulin tolerance, with reduced left ventricular collagen deposition and inflammatory cell infiltration. TRF improved liver structure and function with reduced plasma liver enzymes, inflammatory cell infiltration, fat vacuoles and balloon hepatocytes. TRF reduced plasma free fatty acid and triglyceride concentrations but only omental fat deposition was decreased in the abdomen. These results suggest that tocotrienols protect the heart and liver, and improve plasma glucose and lipid profiles with minimal changes in abdominal obesity in this model of human metabolic syndrome.

Acute hyperinsulinemia and reduced plasma free fatty acid levels decrease intramuscular triglyceride synthesis

ObjectiveTo investigate the effect of acute hyperinsulinemia and the resulting decrease in plasma free fatty acid (FFA) concentrations on intramuscular TG synthesis. Materials/MethodsU-13C16-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±0.20μmol⋅kg−1⋅min−1; P<.001), decreased plasma FFA concentration (327±61 vs 72±25nmol/mL; P<.01), decreased the total concentration of intramuscular fatty acyl-CoA plus fatty acyl-carnitine (12.1±1.6 vs 7.0±0.7nmol/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. ConclusionsFatty acid availability is a determinant of intramuscular TG synthesis. Insulin infusion decreases plasma and intramuscular fatty acid availability and thereby decreases TG synthesis.