Release Of Non-esterified Fatty Acids Research Articles

Effects of hypertriglyceridemia with or without NEFA elevation on β-cell function and insulin clearance and sensitivity.

Hypertriglyceridemia is a risk factor for developing type 2 diabetes (T2D) and might contribute to its pathogenesis either directly or through elevation of non-esterified fatty acids (NEFAs). This study aimed at comparing the glucometabolic effects of acute hypertriglyceridemia alone or combined with NEFA elevation in non-diabetic subjects. Twenty-two healthy lean volunteers underwent two 5-h intravenous infusions of either saline or Intralipid, without (n=12) or with heparin (I+H; n=10) to activate the release of NEFAs. Oral glucose tolerance tests (OGTTs) were performed during the last 3h of infusion. Insulin sensitivity, insulin secretion rate (ISR), model-derived β-cell function, and insulin clearance were measured after 2h of lipid infusion and during the OGTTs. In fasting conditions, both lipid infusions increased plasma insulin and ISR and reduced insulin clearance, without affecting plasma glucose and insulin sensitivity. These effects on insulin and ISR were more pronounced for I+H than Intralipid alone. During the OGTT, the lipid infusions markedly impaired glucose tolerance, increased plasma insulin and ISR, and decreased insulin sensitivity and clearance, without significant group differences. Intralipid alone inhibited glucose-stimulated insulin secretion (i.e. β-cell glucose sensitivity) and increased β-cell potentiation, whereas I+H had neutral effects on these β-cell functions. In healthy non-obese subjects, mild acute hypertriglyceridemia directly reduces glucose tolerance, insulin sensitivity and clearance, and has selective and opposite effects on β-cell function that are neutralized by NEFAs. These findings provide new insight into plausible biological signals that generate and sustain insulin resistance and chronic hyperinsulinemia in the development of T2D.

The lipidosis of the liver of dairy cows: Part 1 - Role of insulin and the Growth Hormone-IGF-1 axis

Lipidosis of the liver of dairy cows is a metabolic disease known since many years and is caused by an uptake of nonesterified fatty acids (NEFA) into the liver cells, limited metabolism of NEFA (oxidation and production of β-hydroxybutyrate), and resynthesis in relation to a low efflux as triglyceride (TG). The pathogenesis of lipidosis includes a) an augmented release of NEFA by mobilisation of adipose tissue, b) uptake of NEFA into the liver cells, c) metabolism of NEFA and d) re-synthesis of triglyceride and e) an efflux of TG as very low density lipoprotein (VLDL). The steps a-e are postpartum modified by hormones as an increase of growth hormone, a pronounced insulin resistance in combination with a decreased insulin and of IGF-1 concentrations. These hormonal changes are related to an uncoupling of the growth hormone-IGF-1-axis with enhanced lipolysis and consequences mentioned above. These alterations are associated with inflammation, oxidative and endoplasmatic stress. The metabolic and hormonal alterations are the result of the selection of dairy cows primarily for milk production without adequate food intake with the consequence of lipidosis, ketosis and further health risks (production diseases).

Regulation of Insulin Clearance by Non-Esterified Fatty Acids

Insulin stores lipid in adipocytes and prevents lipolysis and the release of non-esterified fatty acids (NEFA). Excessive release of NEFA during sustained energy supply and increase in abdominal adiposity trigger systemic insulin resistance, including in the liver, a major site of insulin clearance. This causes a reduction in insulin clearance as a compensatory mechanism to insulin resistance in obesity. On the other hand, reduced insulin clearance in the liver can cause chronic hyperinsulinemia, followed by downregulation of insulin receptor and insulin resistance. Delineating the cause–effect relationship between reduced insulin clearance and insulin resistance has been complicated by the fact that insulin action and clearance are mechanistically linked to insulin binding to its receptors. This review discusses how NEFA mobilization contributes to the reciprocal relationship between insulin resistance and reduced hepatic insulin clearance, and how this may be implicated in the pathogenesis of non-alcoholic fatty liver disease.

Changes of biochemical indexes of blood of high-performance cows are at subclinical ketosisand its effect on milk productivity

The article provides data on changes in biochemical indicators of blood serum of high-yielding cows under conditions of subclinical ketosis and its effect on milk's physical and chemical composition. The decrease in glucose and insulin concentrations mediates the main metabolic changes necessary to stabilize blood glucose levels, which include an increase in the rate of gluconeogenesis, a decrease in lipogenesis and an increase in the release of nonesterified fatty acids from fat, an increase in the uptake and metabolism of fatty acids in hepatocyte mitochondria, and excessive formation of ketone bodies. Fatty acids and ketone bodies are used as an alternative source of energy in the heart, kidney, skeletal muscle, and mammary glands to conserve glucose further and restore energy balance. However, cows that do not undergo the necessary metabolic adaptations are susceptible to hyperketonemia. Hypoglycemia, increased activity of enzymes, and increased activity of alanine and aspartate aminotransferases were detected in sick animals by two and three times, respectively, compared to healthy animals. The total bilirubin content in sick cows' blood serum increased three times compared to the indicators of healthy animals. An increase in milk fat (up to 5 %), 1.3 times more than in healthy animals, and a decrease in total protein (up to 3.11 %). The number of somatic cells in the average milk sample of sick animals was 349 thousand/cm3 and 90 thousand/cm3 in healthy ones, which significantly worsens milk quality. The increase in the number of somatic cells in the milk of animals suffering from subclinical ketosis is due to a decrease in both the general resistance of the body and the ability of macrophages to phagocytosis; with ketonemia, a significant amount of histamine is formed, which leads to inflammatory processes of the mammary gland; the ability of leukocytes to migrate to the foci of inflammation decreases, which determines the protracted course of the disease.

Fatty Acid Metabolism and Derived-Mediators Distinctive of PPAR-α Activation in Obese Subjects Post Bariatric Surgery

Bariatric surger (BS) is characterized by lipid metabolic changes as a response to the massive release of non-esterified fatty acids (NEFA) from adipose depots. The study aimed at evaluating changes in polyunsaturated fatty acids (PUFA) metabolism and biosynthesis of the lipid mediators N-acylethanolamines (NAE), as indices of nuclear peroxisome proliferator-activated receptor (PPAR)-α activation. The observational study was performed on 35 subjects (27 female, 8 male) with obesity, undergoing bariatric surgery. We assessed plasma FA and NAE profiles by LC-MS/MS, clinical parameters and anthropometric measures before and 1 and 6 months after bariatric surgery. One month after bariatric surgery, as body weight and clinical parameters improved significantly, we found higher plasma levels of N-oleoylethanolamine, arachidonic and a 22:6-n3/20:5-n3 ratio as evidence of PPAR-α activation. These changes corresponded to higher circulating levels of NEFA and a steep reduction of the fat mass. After 6 months 22:6-n3/20:5-n3 remained elevated and fat mass was further reduced. Our data suggest that the massive release of NEFA from adipose tissue at 1-Post, possibly by inducing PPAR-α, may enhance FA metabolism contributing to fat depot reduction and improved metabolic parameters in the early stage. However, PUFA metabolic changes favor n6 PUFA biosynthesis, requiring a nutritional strategy aimed at reducing the n6/n3 PUFA ratio.

Body composition, mineral metabolism, and endocrine function of adipose tissue: influence of a nutritional supplement of propolis

Introduction: propolis and its components influence lipid metabolism; however, its effect on body composition and mineral metabolism remains unknown. Objectives: to determine the effect of natural propolis supplementation on body composition, mineral metabolism, and the endocrine function of adipose tissue. Material and methods: twenty albino male Wistar rats (8 weeks old) were divided into two groups of 10 animals each. The rats were fed two different types of diet for 90 days: a standard diet for the control group (group C) and the same standard diet + 2 % propolis (group P). Thyroid hormones, ghrelin, leptin, adiponectin and insulin, non-esterified fatty acids (NEFA) in plasma, body composition (lean mass, fat mass and body water), and mineral deposition in target organs (spleen, brain, heart, lungs, testicles, kidneys and femur) were assessed. Results: thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) did not show any differences after supplementation with propolis, while ghrelin and adiponectin decreased (p < 0.01 and p < 0.05, respectively) and insulin (p < 0.01), leptin (p < 0.05) and NEFA (p < 0.05) increased when 2 % propolis was supplied, while weight and body fat were reduced (p < 0.05) and lean mass increased. Lastly, the propolis supplement improves calcium deposition in the spleen, lungs, testes, and femur (p < 0.05). Conclusion: propolis supplementation of the diet (2 %) causes a decrease in the secretion of ghrelin and adiponectin, increasing the release of non-esterified fatty acids and the rate of insulin secretion. In addition, propolis supplementation induces an improvement in calcium deposition in target organs without affecting the rest of minerals, which improves body composition by inducing a reduction in weight and visceral adipose tissue, and improvement in lean mass.

The Interplay Between Non-Esterified Fatty Acids and Bovine Peroxisome Proliferator-Activated Receptors: Results of an In Vivo-In Vitro Hybrid Approach

Abstract Objectives Metabolic stressors and energy deficiency related to parturition induce lipolysis in dairy cows with a subsequent increase in circulating non-esterified fatty acids (NEFA). We hypothesized that circulating NEFA directly activate the Peroxisome Proliferator-Activated Receptors (PPAR), a transcription factor with known nutrigenomics response to fatty acids, in a dose-dependent manner. Methods Whole-blood samples were collected from five cows at different times between −40 and +10 days relative to parturition to isolate serum. NEFA were extracted from said samples through solid-phase extraction. A bioluminescent reported, bound to a PPAR response element, was used to assess PPAR activation in response to the treatments. To estimate individual PPAR isotype activation, PPAR isotype-specific antagonists were used, along with the treatments. Results Isolated NEFA activate PPAR linearly up to 400 μM, with a decrease in their effect when albumin is introduced. A hybrid approach, treating cells with bovine serum from different stages of parturition, revealed that much of the PPAR activation can be explained by the amount of NEFA in the serum, and that its activation follows a quadratic tendency (calculated maximum activation at 1.47 mM NEFA of 4.8-fold vs. DMEM control, R2 = 0.91). Further analysis of the effect of serum NEFA on PPAR revealed that they mostly activate PPARδ and PPARγ, but not PPARα. However, addition of palmitic acid to the media activate PPARδ and PPARα, but not PPARγ, and only when circulating NEFA are low (0.16 mM, prepartum), while additional palmitate did not increase PPAR activation in serum with high NEFA (0.71 mM, postpartum). Finally, the addition of lipoprotein lipase to the serum, in order to mimic release of NEFA from VLDL, increased PPAR activation, recapitulating the role of dietary lipids in the regulation of PPAR. Conclusions Taken together, our results support the activation of PPAR by NEFA, helping to explain prior observations on PPAR activation in peripartum cows. Additionally, we outlined the role of dietary fatty acids in activating PPAR and their interaction with serum NEFA. Our results aid in setting the foundation for nutrigenomics approaches in ruminant nutrition. Funding Sources This study was funded by the Oregon Beef Council.

A computational model of postprandial adipose tissue lipid metabolism derived using human arteriovenous stable isotope tracer data.

Given the association of disturbances in non-esterified fatty acid (NEFA) metabolism with the development of Type 2 Diabetes and Non-Alcoholic Fatty Liver Disease, computational models of glucose-insulin dynamics have been extended to account for the interplay with NEFA. In this study, we use arteriovenous measurement across the subcutaneous adipose tissue during a mixed meal challenge test to evaluate the performance and underlying assumptions of three existing models of adipose tissue metabolism and construct a new, refined model of adipose tissue metabolism. Our model introduces new terms, explicitly accounting for the conversion of glucose to glyceraldehye-3-phosphate, the postprandial influx of glycerol into the adipose tissue, and several physiologically relevant delays in insulin signalling in order to better describe the measured adipose tissues fluxes. We then applied our refined model to human adipose tissue flux data collected before and after a diet intervention as part of the Yoyo study, to quantify the effects of caloric restriction on postprandial adipose tissue metabolism. Significant increases were observed in the model parameters describing the rate of uptake and release of both glycerol and NEFA. Additionally, decreases in the model’s delay in insulin signalling parameters indicates there is an improvement in adipose tissue insulin sensitivity following caloric restriction.

Intra-Abdominal Fat Adipocyte Hypertrophy through a Progressive Alteration of Lipolysis and Lipogenesis in Metabolic Syndrome Rats.

This study evaluates the progressive participation of enzymes involved in lipolysis and lipogenesis, leading to adipocyte hypertrophy in a metabolic syndrome (MS) rat model caused by chronic consumption of 30% sucrose in drinking water. A total of 70 male Wistar rats were divided into two groups: C and MS. Each of these groups were then subdivided into five groups which were sacrificed as paired groups every month from the beginning of the treatment until 5 months. The intra-abdominal fat was dissected, and the adipocytes were extracted. Lipoprotein lipase (LPL), hormone-sensitive lipase (HSL), protein kinases A (PKA), and perilipin A expressions were determined. The LPL and HSL activities were evaluated by spectrophotometry. Histological staining was performed in adipose tissue. Significant increases were observed in blood pressure, HOMA-IR, leptin, triglycerides, insulin, intra-abdominal fat, and number of fat cells per field (p = 0.001) and in advanced glycosylation products, adipocyte area, LPL, HSL activities and/or expression (p ≤ 0.01) in the MS groups progressively from the third month onward. Lipogenesis and lipolysis were increased by LPL activity and HSL activity and/or expression. This was associated with hyperinsulinemia and release of non-esterified fatty acids causing a positive feedback loop that contributes to the development of adipocyte hypertrophy.

Effects of the amino acid derivatives, β-hydroxy-β-methylbutyrate, taurine, and N-methyltyramine, on triacylglycerol breakdown in fat cells.

Various amino acid (AA) metabolites are used as supplements to facilitate metabolic control and enhance responsiveness of insulin-sensitive tissues. β-hydroxy-β-methylbutyrate (HMB) is a leucine metabolite proposed to prevent muscle wasting and to mitigate insulin resistance. Taurine, commonly added to energizing drinks, is a metabolite of methionine and cysteine present in bile juice, and proposed to be involved in lipid digestion and to be pro-lipolytic in adipocytes. N-methyltyramine (NMT) is a phenylalanine metabolite found in orange juices at 0.1-3ppm while its effects on lipid mobilization remain controversial. Here, the putative lipolytic effects of these AA metabolites were studied and it was tested whether they could enhance insulin antilipolytic response in adipocytes. Release of glycerol and non-esterified fatty acids (NEFAs) was measured after a 2-h incubation of adipocytes obtained from control and diet-induced obese mice or from obese patients. In mouse, none of the tested AA derivatives was lipolytic from 1μM to 1mM. These compounds did not improve insulin antilipolytic effect or isoprenaline lipolytic action, except for 1mM NMT that impaired triacylglycerol breakdown in obese mice. In human adipocytes, HMB and taurine were not lipolytic, while NMT weakly activated glycerol and NEFA release at 1mM. However, 100μM NMT impaired isoprenaline-stimulated lipolysis in a manner that was hardly added to insulin antilipolytic effect. Since none of these AA derivatives acutely helped or replaced insulin antilipolytic effect in adipocytes, the present in vitro observations do not support their proposed insulin-sensitizing properties. Moreover, NMT, HMB, and taurine were not notably lipolytic.

Two nights of recovery sleep restores the dynamic lipemic response, but not the reduction of insulin sensitivity, induced by five nights of sleep restriction.

Chronic inadequate sleep is associated with increased risk of cardiometabolic diseases. The mechanisms involved are poorly understood but involve changes in insulin sensitivity, including within adipose tissue. The aim of this study was to assess the effects of sleep restriction on nonesterified fatty acid (NEFA) suppression profiles in response to an intravenous glucose tolerance test (IVGTT) and to assess whether 2 nights of recovery sleep (a "weekend") is sufficient to restore metabolic health. We hypothesized that sleep restriction impairs both glucose and lipid metabolism, specifically adipocyte insulin sensitivity, and the dynamic lipemic response of adipocyte NEFA release during an IVGTT. Fifteen healthy men completed an inpatient study of 3 baseline nights (10 h of time in bed/night), followed by 5 nights of 5 h of time in bed/night and 2 recovery nights (10 h of time in bed/night). IVGTTs were performed on the final day of each condition. Reductions in insulin sensitivity without a compensatory change in acute insulin response to glucose were consistent with prior studies (insulin sensitivity P = 0.002; acute insulin response to glucose P = 0.23). The disposition index was suppressed by sleep restriction and did not recover after recovery sleep (P < 0.0001 and P = 0.01, respectively). Fasting NEFAs were not different from baseline in either the restriction or recovery conditions. NEFA rebound was significantly suppressed by sleep restriction (P = 0.01) but returned to baseline values after recovery sleep. Our study indicates that sleep restriction impacts NEFA metabolism and demonstrates that 2 nights of recovery sleep may not be adequate to restore glycemic health.

Buffering agent via insulin-mediated activation of PI3K/AKT signaling pathway to regulate lipid metabolism in lactating goats.

Ruminants are often fed a high-concentrate (HC) diet to meet lactating demands, yet long-term concentrate feeding induces subacute ruminal acidosis (SARA) and leads to a decrease in milk fat. Buffering agent could enhance the acid base buffer capacity and has been used to prevent ruminant rumen SARA and improve the content of milk fat. Therefore, we tested whether a buffering agent increases lipid anabolism in the livers of goats and influences of milk fat synthesis. Twelve Saanen-lactating goats were randomly assigned to two groups: one group received a HC diet (Concentrate: Forage=60:40, Control) and the other group received the same diet with a buffering agent added (10 g sodium butyrate, C(4)H(7)NaO(2); 10 g sodium bicarbonate, NaHCO(3); BG) over a 20-week experimental period. Overall, milk fat increase (4.25+/-0.08 vs. 3.24+/-0.10; P<0.05), and lipopolysaccharide levels in the jugular (1.82+/-0.14 vs. 3.76+/-0.33) and rumen fluid (23,340+/-134 vs. 42,550+/-136) decreased in the buffering agent group (P<0.05). Liver consumption and release of nonesterified fatty acid (NEFA) into the bloodstream increased (P<0.05). Phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT) and ribosomal protein S6 kinase (p70S6K) up-regulated significantly in the livers of the buffering agent group (P<0.05). It also up-regulated expression of the transcription factor sterol regulatory element binding protein-1c (SREBP-1c) and its downstream targets involved in fatty acid synthetic, including fatty acid synthetase (FAS), stearoyl-CoA desaturase (SCD-1) and acetyl-CoA carboxylase 1 (ACC1) (P<0.05). The BG diet increased insulin levels in blood (19.43+/-0.18 vs. 13.81+/-0.10, P<0.05), and insulin receptor was likewise elevated in the liver (P<0.05). Cumulatively, the BG diet increased plasma concentrations of NEFA by INS-PI3K/AKTSREBP-1c signaling pathway promoting their synthesis in the liver. The increased NEFA concentration in the blood during BG feeding may explain the up-regulated in the milk fat of lactating goats.

Overexpressing cell systems are a competitive option to primary adipocytes when predicting in vivo potency of dual GPR81/GPR109A agonists

Mathematical models predicting in vivo pharmacodynamic effects from in vitro data can accelerate drug discovery, and reduce costs and animal use. However, data integration and modeling is non-trivial when more than one drug-target receptor is involved in the biological response. We modeled the inhibition of non-esterified fatty acid release by dual G-protein-coupled receptor 81/109A (GPR81/GPR109A) agonists in vivo in the rat, to estimate the in vivo EC50 values for 12 different compounds. We subsequently predicted those potency estimates using EC50 values obtained from concentration-response data in isolated primary adipocytes and cell systems overexpressing GPR81 or GPR109A in vitro. A simple linear regression model based on data from primary adipocytes predicted the in vivo EC50 better than simple linear regression models based on in vitro data from either of the cell systems. Three models combining the data from the overexpressing cell systems were also evaluated: two piecewise linear models defining logical OR- and AND-circuits, and a multivariate linear regression model. All three models performed better than the simple linear regression model based on data from primary adipocytes. The OR-model was favored since it is likely that activation of either GPR81 or GPR109A is sufficient to deactivate the cAMP pathway, and thereby inhibit non-esterified fatty acid release. The OR-model was also able to predict the in vivo selectivity between the two receptors. Finally, the OR-model was used to predict the in vivo potency of 1651 new compounds. This work suggests that data from the overexpressing cell systems are sufficient to predict in vivo potency of GPR81/GPR109A agonists, an approach contributing to faster and leaner drug discovery.

Effect of intrapancreatic fat on diabetes outcomes after total pancreatectomy with islet autotransplantation

Pancreatic fat may adversely affect β-cell mass and function, possibly via local release of non-esterified fatty acids, and proinflammatory and vasoactive factors released by adipose tissue. However, the effects of intrapancreatic fat in patients with chronic pancreatitis undergoing total pancreatectomy with islet autotransplantation (TPIAT) have not been studied. This study investigated whether pancreatic fatty infiltration has a negative effect on metabolic outcomes following TPIAT. The association between pancreatic fatty infiltration and diabetes outcomes was studied in 79 patients with low or high pancreatic fat content (LPF [n = 53] and HPF [n = 26], respectively) undergoing TPIAT. Pancreatic fatty infiltration was stratified using gross examinations during isolation and validated with histomorphometry of archived histology samples. Fat area percentage in histology samples differed significantly between the LPF and HPF groups (2.1% ± 4.3% vs 10.6% ± 8.9%, respectively; P = 0.0009). Insulin dependence was more common in the HPF group, whereas more patients in the LPF group were insulin independent or on partial insulin supplementation at 1 year (P = 0.022). Furthermore, 1- and 2-h glucose concentrations during mixed-meal tolerance tests were significantly higher in the HPF group (P = 0.032 and 0.027, respectively) and β-scores (a composite measure of islet function and metabolic control) were significantly greater in the LPF than HPF group (6.1 ± 1.7 vs 4.6 ± 2.0; P = 0.034). Patients with HPF were more likely to be insulin dependent, with higher postprandial glucose excursion, suggesting that intrapancreatic fat may lead to β-cell dysfunction with detrimental effects on diabetes outcomes after TPIAT.

Angiopoietin-like 8 (Angptl8) controls adipocyte lipolysis and phospholipid composition

Angiopoietin-like 8 (Angptl8) inhibits lipolysis in the circulation together with Angplt3 and controls post-prandial fat storage in white adipose tissue (WAT). It is strongly induced by insulin in vivo in WAT and in vitro in adipocytes.In this study we addressed the function of Angptl8 in adipocytes by its stable lentivirus-mediated knock-down in 3T3-L1 cells, followed by analyses of triglyceride (TG) storage, lipid droplet (LD) morphology, the cellular lipidome, lipolysis, and gene expression.Depletion of Angptl8 did not drastically affect the adipocyte differentiation of 3T3-L1 cells but resulted in a moderate (18–19%) reduction of stored TGs. The lipidome analysis revealed a reduction of alkyl- phosphatidylcholines (PCs) and phosphatidylethanolamine (PE) plasmalogens, as well as saturated PCs and PEs. Importantly, the Angptl8 depleted cells displayed enhanced lipolysis as measured by release of non-esterified fatty acids (NEFAs). Consistently, mRNAs encoding Angptl4 and Leptin, which facilitate lipolysis, as well as Cpt1a, Cpt1b, and Pgc-1α involved in FA oxidation, were elevated. The Angptl8 mRNA itself was suppressed by pharmacologic treatments inducing lipolysis: stimulation with the β-adrenergic agonist isoproterenol or with the adenylate cyclase activator forskolin.To conclude, knock-down of Angptl8 in adipocytes suggests that the protein acts to inhibit intracellular lipolysis, analogous to its activity in the circulation. Depletion of Angptl8 results in an altered cellular phospholipid composition. The findings identify Angptl8 as a central insulin-regulated controller of adipocyte lipid metabolism.

Jueming prescription and its ingredients, semen cassiae and Rhizoma Curcumae Longae, stimulate lipolysis and enhance the phosphorylation of hormone‑sensitive lipase in cultured rat white adipose tissue.

The present study aimed to investigate the effect of jueming prescription (JMP) and its ingredients, semen cassiae (SC) and Rhizoma Curcumae Longae (RCL), on lipolysis, and to examine their effect on the phosphorylation of hormone‑sensitive lipase (HSL) in cultured rat white adipose tissue (WAT). Retroperitoneal WAT was aseptically excised from adult male Sprague‑Dawley rats, minced into uniform sections and subjected to exvivo culture for 24h. The tissue sections were then distributed into a 24‑well culture plate and treated with normal saline (vehicle), isoproterenol (ISO), JMP, SC and RCL. Non‑esterified fatty acid (NEFA) and glycerol release from the intact WAT explants were determined as a measurement of lipolysis, which were measured using NEFA and glycerol assay kits. The phosphorylation of HSL at Ser563 (P‑HSL S563) and 660residues (P‑HSL S660) were determined using western blot analysis. The size of the adipocytes was visualized using hematoxylin and eosin (H&E) staining. It was found that JMP‑, SC‑ and RCL‑stimulated lipolysis was responsible for increasing the release of NEFAs and glycerol from the intact WAT invitro. In addition, JMP, SC and RCL increased the levels of P‑HSL Ser563: JMP water (JW) extract, 3.52‑fold; JMP ethanol (JE) extract, 3.38‑fold; SC water (SW) extract, 4.60‑fold; SC ethanol (SE) extract, 4.20‑fold; RCL water (RW) extract, 6.98‑fold; RCL ethanol (RE) extract, 6.60‑fold. JMP, SC and RCL also increased the levels of P‑HSL Ser660: JW extract, 3.16‑fold; JE extract, 2.92‑fold; SW extract, 4.57‑fold; SE extract, 4.13‑fold; RW extract, 5.41‑fold; RE 4.96‑fold) in the WAT. The RW extract had the most marked effect. The HE staining revealed that JMP, SC and RCL reduced the size of adipocytes in the WAT. In conclusion, JMP and its ingredients, SC and RC, stimulated lipolysis and reduced the size of adipocytes, possibly via the phosphorylation of HSL in cultured rat WAT.

Hypoxia-Inducible Lipid Droplet-Associated Is Not a Direct Physiological Regulator of Lipolysis in Adipose Tissue.

Triglycerides are stored in specialized organelles called lipid droplets. Numerous proteins have been shown to be physically associated with lipid droplets and govern their function. Previously, the protein hypoxia-inducible lipid droplet-associated (HILPDA) was localized to lipid droplets and was suggested to inhibit triglyceride lipolysis in hepatocytes. We confirm the partial localization of HILPDA to lipid droplets and show that HILPDA is highly abundant in adipose tissue, where its expression is controlled by the peroxisome proliferator-activated receptor γ and by β-adrenergic stimulation. Levels of HILPDA markedly increased during 3T3-L1 adipocyte differentiation. Nevertheless, silencing of Hilpda using small interfering RNA or overexpression of Hilpda using adenovirus did not show a clear impact on 3T3-L1 adipogenesis. Following β-adrenergic stimulation, the silencing of Hilpda in adipocytes did not significantly alter the release of nonesterified fatty acids (NEFA) and glycerol. By contrast, adenoviral-mediated overexpression of Hilpda modestly attenuated the release of NEFA from adipocytes following β-adrenergic stimulation. In mice, adipocyte-specific inactivation of Hilpda had no effect on plasma levels of NEFA and glycerol after fasting, cold exposure, or pharmacological β-adrenergic stimulation. In addition, other relevant metabolic parameters were unchanged by adipocyte-specific inactivation of Hilpda. Taken together, we find that HILPDA is highly abundant in adipose tissue, where its levels are induced by peroxisome proliferator-activated receptor γ and β-adrenergic stimulation. In contrast to the reported inhibition of lipolysis by HILPDA in hepatocytes, our data do not support an important direct role of HILPDA in the regulation of lipolysis in adipocytes in vivo and in vitro.

A High-Concentrate Diet Induced Milk Fat Decline via Glucagon-Mediated Activation of AMP-Activated Protein Kinase in Dairy Cows

Dairy cows are often fed a high-concentrate (HC) diet to meet lactation demands; however, long-term concentrate feeding is unhealthy and decreases milk fat. Therefore, we investigated the effects of liver lipid metabolism on milk fat synthesis. Ten lactating Holstein cows were assigned randomly into HC and LC (low-concentrate) diet groups. After 20 weeks of feeding, milk fat declined, and lipopolysaccharide levels in the jugular, portal, and hepatic veins increased in the HC group. Liver consumption and release of nonesterified fatty acid (NEFA) into the bloodstream also decreased. AMP-activated protein kinase alpha (AMPKα) was up-regulated significantly in the livers of the HC-fed cows. The HC diet also up-regulated the expression of the transcription factor peroxisome proliferator-activated receptor α (PPARα) and its downstream targets involved in fatty acid oxidation, including carnitine palmitoyltransferase-1,2 (CPT-1, CPT-2), liver-fatty acid-binding protein (L-FABP), and acyl-CoA oxidase (ACO). The HC diet increased blood glucagon (GC) levels, and liver glucagon receptor (GCGR) expression was elevated. Cumulatively, a long-term HC diet decreased plasma concentrations of NEFA via the GC/GCGR-AMPK-PPARα signalling pathway and reduced their synthesis in the liver. The decreased NEFA concentration in the blood during HC feeding may explain the decline in the milk fat of lactating cows.

Acute Hypercortisolemia Exerts Depot-Specific Effects on Abdominal and Femoral Adipose Tissue Function.

Context:Glucocorticoids have pleiotropic metabolic functions, and acute glucocorticoid excess affects fatty acid metabolism, increasing systemic lipolysis. Whether glucocorticoids exert adipose tissue depot-specific effects remains unclear.Objective:To provide an in vivo assessment of femoral and abdominal adipose tissue responses to acute glucocorticoid administration.Design and Outcome Measures:Nine healthy male volunteers were studied on two occasions, after a hydrocortisone infusion (0.2 mg/kg/min for 14 hours) and a saline infusion, respectively, given in randomized double-blind order. The subjects were studied in the fasting state and after a 75-g glucose drink with an in vivo assessment of femoral adipose tissue blood flow (ATBF) using radioactive xenon washout and of lipolysis and glucose uptake using the arteriovenous difference technique. In a separate study (same infusion design), eight additional healthy male subjects underwent assessment of fasting abdominal ATBF and lipolysis only. Lipolysis was assessed as the net release of nonesterified fatty acids (NEFAs) from femoral and abdominal subcutaneous adipose tissue.Results:Acute hypercortisolemia significantly increased basal and postprandial ATBF in femoral adipose tissue, but the femoral net NEFA release did not change. In abdominal adipose tissue, hypercortisolemia induced substantial increases in basal ATBF and NEFA release.Conclusions:Acute hypercortisolemia induces differential lipolysis and ATBF responses in abdominal and femoral adipose tissue, suggesting depot-specific glucocorticoid effects. Abdominal, but not femoral, adipose tissue contributes to the hypercortisolemia-induced systemic NEFA increase, with likely contributions from other adipose tissue sources and intravascular triglyceride hydrolysis.

The Action of &amp;lt;i&amp;gt;p&amp;lt;/i&amp;gt;-Synephrine on Lipid Metabolism in the Perfused Rat Liver

p-synephrine and p-octopamine were found to increase lipolysis in adipocytes. The present study approaches the question if these compounds, natural products of the bitter orange (Citrus aurantium fruit), increase lipolysis and fatty acid oxidation in the liver. Experiments were done in the perfused rat liver. Non-recirculating hemoglobin-free perfusion was done using the Krebs/ Henseleit-bicarbonate buffer (pH 7.4) as perfusion fluid. Both p-synephrine and p-octopamine, at the concentrations of 100 μM, were found to stimulate the hepatic triacylglycerol lipase by 40% and 51%, respectively. These seem to be the maximal stimulations possible in the liver. In the perfused liver, p-synephrine, when present at an initial concentration of 500 μM, was able to increase the non-esterified fatty acid release after one hour of recirculating perfusion. The effects of p-synephrine on the oxidation of exogenously supplied [1-14C]octanoate and [1-14C]oleate were minimal. Only oxygen uptake, already stimulated by octanoate or oleate, was additionally increased by the infusion of p-synephrine. These results contrast with those obtained in a previous study with p-octopamine, which increased the production of 14CO2 from both [1-14C]octanoate and [1-14C]oleate. Apparently only the oxidation of endogenous fatty acids is stimulated by p-synephrine. On the other hand, both p-synephrine and p-octopamine stimulate the hepatic triacylglycerol lipase to a much lesser extent than the adipocyte lipase. It can be concluded that p-synephrine affects much more carbohydrate metabolism in the liver than lipid metabolism.