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1.
Trafficking of nonesterified fatty acids in insulin resistance and relationship to dysglycemia.
Walker, RE, Ford, JL, Boston, RC, Savinova, OV, Harris, WS, Green, MH, Shearer, GC
American journal of physiology. Endocrinology and metabolism. 2020;(3):E392-E404
Abstract
In adipose, insulin functions to suppress intracellular lipolysis and secretion of nonesterified fatty acid (NEFA) into plasma. We applied glucose and NEFA minimal models (MM) following a frequently sampled intravenous glucose tolerance test (FSIVGTT) to assess glucose-specific and NEFA-specific insulin resistance. We used total NEFA and individual fatty acids in the NEFA MM, comparing the model parameters in metabolic syndrome (MetSyn) subjects (n = 52) with optimally healthy controls (OptHC; n = 14). Results are reported as mean difference (95% confidence interval). Using the glucose MM, MetSyn subjects had lower [-73% (-82, -57)] sensitivity to insulin (Si) and higher [138% (44, 293)] acute insulin response to glucose (AIRg). Using the NEFA MM, MetSyn subjects had lower [-24% (-35, -13)] percent suppression, higher [32% (15, 52)] threshold glucose (gs), and a higher [81% (12, 192)] affinity constant altering NEFA secretion (ϕ). Comparing fatty acids, percent suppression was lower in myristic acid (MA) than in all other fatty acids, and the stearic acid (SA) response was so unique that it did not fit the NEFA MM. MA and SA percent of total were increased at 50 min after glucose injection, whereas oleic acid (OA) and palmitic acid (PA) were decreased (P < 0.05). We conclude that the NEFA MM, as well as the response of individual NEFA fatty acids after a FSIVGTT, differ between OptHC and MetSyn subjects and that the NEFA MM parameters differ between individual fatty acids.
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2.
Common variants associated with changes in levels of circulating free fatty acids after administration of glucose-insulin-potassium (GIK) therapy in the IMMEDIATE trial.
Ellis, KL, Zhou, Y, Rodriguez-Murillo, L, Beshansky, JR, Ainehsazan, E, Selker, HP, Huggins, GS, Cupples, LA, Peter, I
The pharmacogenomics journal. 2017;(1):76-83
Abstract
Glucose-insulin-potassium (GIK) therapy may promote a shift from oxygen-wasteful free fatty acid (FFA) metabolism to glycolysis, potentially reducing myocardial damage during ischemia. Genetic variation associated with FFA response to GIK was investigated in an IMMEDIATE (Immediate Myocardial Metabolic Enhancement During Initial Assessment and Treatment in Emergency care) sub-study (n=117). In patients with confirmed acute coronary syndromes, associations between 132 634 variants and 12-h circulating FFA response were assessed. Between initial and 6-h measurements, three LINGO2 variants were associated with increased levels of total FFA (P-value for 2 degree of freedom test, P2df ⩽5.51 × 10-7). Lead LINGO2 single-nucleotide polymorphism, rs12003487, was nominally associated with reduced 30-day ejection fraction (P2df=0.03). Several LINGO2 signals were linked to alterations in epigenetic profile and gene expression levels. Between 6 and 12 h, rs7017336 nearest to IMPA1/FABP12 showed an association with decreased saturated FFAs (P2df=5.47 × 10-7). Nearest to DUSP26, rs7464104 was associated with a decrease in unsaturated FFAs (P2df=5.51 × 10-7). Genetic variation may modify FFA response to GIK, potentially conferring less beneficial outcomes.
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3.
Dihydropyridine calcium channel blockers inhibit non-esterified-fatty-acid-induced endothelial and rheological dysfunction.
Yasu, T, Kobayashi, M, Mutoh, A, Yamakawa, K, Momomura, S, Ueda, S
Clinical science (London, England : 1979). 2013;(5):247-55
Abstract
Circulating NEFAs (non-esterified fatty acids) from adipose tissue lipolysis lead to endothelial dysfunction and insulin resistance in patients with the metabolic syndrome or Type 2 diabetes mellitus. The aim of the present study was to test the hypothesis that DHP (dihydropyridine) CCBs (calcium channel blockers) prevent NEFA-induced endothelial and haemorheological dysfunction independently of their antihypertensive properties. Using a double-blind cross-over study design, nifedipine, amlodipine, diltiazem or placebo were administered to eight healthy subjects for 2 days before each study day. On the study days, the following were assessed before and after the infusion of lipid and heparin to raise serum NEFAs: endothelial function, by measuring FBF (forearm blood flow) responses to ACh (acetylcholine); leucocyte activation, by ex vivo measurement of plasma MPO (myeloperoxidase) levels, adherent leucocyte numbers and whole blood transit time through microchannels; and oxidative stress, by determining plasma levels of d-ROMs (derivatives of reactive oxygen metabolites). Effects of the CCBs on NF-κB (nuclear factor κB) p65 phospholylation stimulated by NEFAs were assessed in cultured monocytic cells in vitro. Elevated NEFAs reduced the responses to ACh and significantly increased whole blood transit time, adherent leucocyte numbers and d-ROMs. Nifedipine and amlodipine, but not diltiazem, prevented NEFA-induced endothelial dysfunction, leucocyte activation and enhancement of oxidative stress without affecting BP (blood pressure), whereas all these drugs prevented NEFA-induced p65 activation in vitro. These results suggest that DHP CCBs, independent of their antihypertensive properties in humans, prevent NEFA-induced endothelial and haemorheological dysfunction through inhibition of NEFA-induced leucocyte activation, although the sensitivity to drugs of leucocyte Ca2+ channels may differ among cells.
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4.
Does rimonabant independently affect free fatty acid and glucose metabolism?
Triay, J, Mundi, M, Klein, S, Toledo, FG, Smith, SR, Abu-Lebdeh, H, Jensen, M
The Journal of clinical endocrinology and metabolism. 2012;(3):819-27
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Abstract
CONTEXT Endocannabinoid receptor 1 blockade is proposed to improve metabolic complications of obesity via central and peripheral effects. OBJECTIVE Our objective was to test whether rimonabant improves insulin regulation of free fatty acid and glucose metabolism after controlling for fat loss. DESIGN This was a double-blind, placebo-controlled substudy of the visceral fat reduction assessed by computed tomography scan on rimonabant (VICTORIA) trial. PARTICIPANTS AND SETTING Sixty-seven abdominally obese, metabolic syndrome volunteers age 35-70 yr participated at academic medical center general clinical research centers. INTERVENTION Intervention included a 12-month lifestyle weight management program plus rimonabant 20 mg/d or placebo. MAIN OUTCOME MEASURES Body composition and two-step euglycemic, hyperinsulinemic clamp before and after intervention were performed. Insulin sensitivity was assessed as insulin concentration needed to suppress by 50% palmitate concentration [IC50(palmitate)], flux [IC50(palmitate)f], and hepatic glucose output [IC50(HGO)] and as insulin-stimulated glucose disposal (Δ glucose disappearance per Δ insulin concentration--glucose slope). RESULTS Body fat decreased by 4.5±2.9% (SD) in the rimonabant and 1.9±4.5% in the placebo group (P<0.005). The primary [improvement in IC50(palmitate) and IC50(palmitate)f] and secondary [improvement in IC50(HGO) and glucose slope] outcomes were not significantly different between the rimonabant and placebo groups. Post hoc analyses revealed that 1) changes in body mass index (BMI) and IC50(palmitate) were correlated (P=0.005) in the rimonabant group; this relationship was not significantly different from placebo when controlling for greater BMI loss (P=0.5); 2) insulin-regulated glucose disposal improved in both groups (P=0.002) and correlated with changes in BMI. CONCLUSIONS Improvements observed in insulin regulation of free fatty acid and glucose metabolism with rimonabant treatment in humans was not greater than that predicted by weight loss alone.
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Intravenous lipid and heparin infusion-induced elevation in free fatty acids and triglycerides modifies circulating androgen levels in women: a randomized, controlled trial.
Mai, K, Bobbert, T, Reinecke, F, Andres, J, Maser-Gluth, C, Wudy, SA, Möhlig, M, Weickert, MO, Hartmann, MF, Schulte, HM, et al
The Journal of clinical endocrinology and metabolism. 2008;(10):3900-6
Abstract
BACKGROUND The polycystic ovarian syndrome (PCOS) is characterized by hyperandrogenism and associated with obesity and impaired glucose metabolism. Despite the high prevalence of PCOS and the considerable clinical impact, the precise interplay between metabolism and hyperandrogenemia is not entirely clear. OBJECTIVE The objective of the study was to analyze the effects of iv lipid and heparin infusion on circulating androgen levels in healthy women. DESIGN This was a randomized, controlled, crossover trial. SETTING The study was conducted at an endocrinology center. PATIENTS Patients included 12 healthy young women during the early follicular phase of two subsequent cycles. INTERVENTION After an overnight fast, a 20% lipid/heparin or a saline/heparin infusion was administered in random order for 330 min. MAIN OUTCOME MEASURES A detailed characterization of androgen metabolism was performed. RESULTS Elevations in free fatty acids and triglycerides, induced by lipid/heparin infusion, elevates the levels of androstenedione, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), testosterone, 5alpha-dihydrotestosterone, estrone, and 17beta-estradiol. Urinary excretion of DHEA, DHEAS, 5-androstene-3beta,17beta-diol, and the sum of urinary excreted DHEA and its 16-hydroxylated downstream metabolites, 16alpha-hydroxy-DHEA and 5-androstene-3beta,16alpha,17beta-triol, were reduced. CONCLUSION The mechanism of iv lipid and heparin infusion-induced elevation of circulating androgens described here might contribute to the development of hyperandrogenism in women with PCOS and suggests that lowering of hyperlipidemia might be a potential therapeutic target in patients with PCOS to treat hyperandrogenemia.
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6.
Fenofibrate reduces lipoprotein associated phospholipase A2 mass and oxidative lipids in hypertriglyceridemic subjects with the metabolic syndrome.
Rosenson, RS
American heart journal. 2008;(3):499.e9-16
Abstract
BACKGROUND Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a macrophage-synthesized lipase that is primarily bound to small electronegative low-density lipoproteins (LDLs). Lipoprotein-associated phospholipase A2 oxidatively modifies LDL and generates the proinflammatory byproducts oxidized fatty acids (ox-FAs) and lysophosphatidylcholine. Fenofibrate reduces Lp-PLA2 mass; however, it remains unknown whether the anti-inflammatory effects of fenofibrate are related to changes in LDL subclasses. METHODS This was a randomized, double-blind, controlled clinical trial designed to investigate the effects of 3-month treatment with fenofibrate (160 mg/d) on Lp-PLA2 mass, LDL subclasses, and ox-FAs among 55 hypertriglyceridemic (> or = 1.7 and < 6.78 mmol/L) subjects with the metabolic syndrome. RESULTS Fenofibrate treatment lowered fasting Lp-PLA2 mass by 13.2% (-19.0 to -7.7) versus placebo (2.3% [-5.0 to 4.1], P = .0002) and total ox-FA by 15.5% (-34.2 to +1.4) versus an 11.5% increase with placebo (P = .0013). In age-, sex-, and treatment-adjusted models, changes in Lp-PLA2 mass were associated with reductions in chemical LDL cholesterol (r = 0.59, P < .01) and measured total LDL particles (LDL-Ps) (r = 0.64, P < .01) and small LDL-Ps (r = 0.57, P < .01). In models that included small LDL, effects of fenofibrate on Lp-PLA2 mass were attenuated (P = .125), but not in models that included LDL cholesterol (P < .0001) and LDL-Ps (P = .005). Changes in Lp-PLA2 mass were not significantly associated with changes in ox-FA or inflammatory markers. CONCLUSIONS Among hypertriglyceridemic subjects with the metabolic syndrome, fenofibrate therapy reduced Lp-PLA2 mass, and these changes were associated with fewer small LDL-Ps.
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Metabolic regulation of growth hormone by free fatty acids, somatostatin, and ghrelin in HIV-lipodystrophy.
Koutkia, P, Meininger, G, Canavan, B, Breu, J, Grinspoon, S
American journal of physiology. Endocrinology and metabolism. 2004;(2):E296-303
Abstract
Human immunodeficiency virus (HIV)-lipodystrophy is a syndrome characterized by changes in fat distribution and insulin resistance. Prior studies suggest markedly reduced growth hormone (GH) levels in association with excess visceral adiposity among patients with HIV-lipodystrophy. We investigated mechanisms of altered GH secretion in a population of 13 male HIV-infected patients with evidence of fat redistribution, compared with 10 HIV-nonlipodystrophic patients and 11 male healthy controls similar in age and body mass index (BMI). Although similar in BMI, the lipodystrophic group was characterized by increased visceral adiposity, free fatty acids (FFA), and insulin and reduced extremity fat. We investigated ghrelin and the effects of acute lowering of FFA by acipimox on GH responses to growth hormone-releasing hormone (GHRH). We also investigated somatostatin tone, comparing GH response to combined GHRH and arginine vs. GHRH alone with a subtraction algorithm. Our data demonstrate an equivalent number of GH pulses (4.1 +/- 0.6, 4.7 +/- 0.8, and 4.5 +/- 0.3 pulses/12 h in the HIV-lipodystrophic, HIV-nonlipodystrophic, and healthy control groups, respectively, P > 0.05) but markedly reduced GH secretion pulse area (1.14 +/- 0.27 vs. 4.67 +/- 1.24 ng.ml(-1).min, P < 0.05, HIV-lipodystrophic vs. HIV-nonlipodystrophic; 1.14 +/- 0.27 vs. 3.18 +/- 0.92 ng.ml(-1).min, P < 0.05 HIV-lipodystrophic vs. control), GH pulse area, and GH pulse width in the HIV-lipodystrophy patients compared with the control groups. Reduced ghrelin (418 +/- 46 vs. 514 +/- 37 pg/ml, P < 0.05, HIV-lipodystrophic vs. HIV-nonlipodystrophic; 418 +/- 46 vs. 546 +/- 45 pg/ml, P < 0.05, HIV-lipodystrophic vs. control), impaired GH response to GHRH by excess FFA, and increased somatostatin tone contribute to reduced GH secretion in patients with HIV-lipodystrophy. These data provide novel insight into the metabolic regulation of GH secretion in subjects with HIV-lipodystrophy.
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Free fatty acid metabolism during fenofibrate treatment of the metabolic syndrome.
Vega, GL, Cater, NB, Hadizadeh, DR, Meguro, S, Grundy, SM
Clinical pharmacology and therapeutics. 2003;(3):236-44
Abstract
OBJECTIVE Our objective was to determine whether fenofibrate modifies the metabolism of nonesterified (free) fatty acids as a component of its triglyceride-lowering action in male patients with the metabolic syndrome. DESIGN In a placebo-controlled trial lasting 16 weeks, patients were randomly assigned to fenofibrate (200 mg/d) or placebo for 8 weeks. They were then crossed over to placebo or treatment with fenofibrate for another 8 weeks. METHODS Thirteen adult men had clinical characteristics of the metabolic syndrome that included atherogenic dyslipidemia, hypertension, elevated fasting glucose levels, or central obesity or a combination of these. They had measurements of plasma lipid and lipoprotein levels, postheparin lipase activities, and fasting concentrations and turnover rates of nonesterified fatty acids, as well as oral glucose tolerance testing with insulin and nonesterified fatty acid measurements. Levels of apolipoprotein C-II, C-III, and B were also measured, along with levels of low-density lipoprotein cholesterol in lipoprotein species. RESULTS Fenofibrate therapy did not change plasma concentrations and turnover rates of nonesterified fatty acids. For fasting nonesterified fatty acids, the values (mean +/- SD) for placebo versus fenofibrate were 446 +/- 31 micromol/L versus 493 +/- 71 micromol/L, respectively (not significant); nonesterified fatty acid turnover rates were 336 +/- 36 micromol/min versus 334 +/- 42 micromol/min for placebo versus fenofibrate, respectively. Moreover, no changes were noted in fasting or postprandial levels of plasma glucose and insulin. Despite this lack of change, fenofibrate therapy reduced the plasma levels of triglyceride by 30% (305 +/- 143 mg/dL versus 206 +/- 90 mg/dL for placebo versus fenofibrate, respectively; P <.045), with a similar reduction in cholesterol levels of triglyceride-rich lipoproteins. Large low-density lipoprotein species were increased and small low-density lipoprotein species were decreased by fenofibrate therapy. Levels of apolipoprotein C-III were reduced significantly (P <.03), as were ratios of postheparin hepatic lipase to lipoprotein lipase (P <.05). CONCLUSION Fenofibrate therapy markedly reduced plasma triglyceride levels. However, it did not lower concentrations or turnover rates of nonesterified fatty acids, nor did it change glucose or insulin responses to an oral glucose challenge. These findings indicate that fenofibrate modifies fatty acid metabolism either in the liver or in triglyceride-rich lipoproteins but not in adipose tissue. Multiple mechanisms are likely involved as a consequence of the action of fenofibrate to activate peroxisomal-proliferator-activated receptor alpha.