Investigation of the clinical effects of acipimox in patients with vulnerable carotid atherosclerosis.

OBJECTIVE: To investigate the clinical effects of acipimox in patients with vulnerable carotid atherosclerosis. METHODS: 80 patients with vulnerable carotid atherosclerosis who were admitted to the Department of Cardiology in Wuxi Second People's Hospital between February 2020 and October 2021 were enrolled in this study. All of these patients were randomly divided into an observation group (n = 40), who were given acipimox and conventional treatment, and a control group (n = 40), who were given conventional treatment. The levels of blood lipids and adiponectin (APN), the carotid intima-media thickness (IMT), the area, thickness and number of CAS, peak systolic velocities (PSV) and end-diastolic blood velocity (EDV) of common carotid artery (CCA), and the level of inflammatory markers were measured and compared between the two groups pretherapy and posttreatment. Then, the adverse events were collected and compared between the two groups posttreatment. RESULTS: The demographics and basic clinical characteristics were not significantly different between the two groups. At posttreatment, the levels of TC, LDL-C, ANP, IL-6, TNF-α and hs-CRP in the observation group were significantly lower than those in the control group at posttreatment. Moreover, the IMT and the area and thickness of CAS in the observation group were significantly lower than those in the control group. After treatment, PSV was lower and EDV was higher in two groups than before treatment; after treatment, compared with control group, PSV in observation group was lower, while EDV was higher. Most importantly, the rate of adverse events was similar in the two groups. CONCLUSIONS: Acipimox reduced the blood lipid levels in patients with vulnerable carotid atherosclerosis. It also stabilized vulnerable plaques and reduced CAS.

Quantification of Acipimox in Plasma and Tissues by LC-MS/MS: Application to Pharmacokinetic Comparison between Normoxia and Hypoxia.

This study aimed to evaluate the pharmacokinetics of acipimox in rats under simulated high altitude hypoxia conditions. A sensitive and reliable LC-MS/MS method has been established for the quantitation of acipimox in rat plasma and tissue homogenate and validated according to the guidelines of the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA). Western blotting and enzyme linked immunosorbent assay (ELISA) were used to investigate the expression of lipid metabolism-related proteins and free fatty acid (FFA) levels, respectively. Cell viability was detected using a Cell Counting kit-8 assay (CCK-8). The method was then successfully applied in a pharmacokinetic comparison between normoxic and hypoxic rats. The results indicated that there were significant differences in the main pharmacokinetics parameters of acipimox between normoxic and hypoxic rats. HCAR2 expression in the hypoxia group was upregulated compared to that in the normoxia group and the levels of FFA decreased more in the hypoxia group. Under the hypoxia condition, the proliferation of HK2 cells was inhibited with increasing concentrations of acipimox. The results provide important and valuable information for the safety and efficacy of acipimox, which indicated that the dosage of acipimox might be adjusted appropriately during clinical medication in hypoxia.

Acipimox in Mitochondrial Myopathy (AIMM): study protocol for a randomised, double-blinded, placebo-controlled, adaptive design trial of the efficacy of acipimox in adult patients with mitochondrial myopathy.

BACKGROUND: Mitochondrial disease is a heterogenous group of rare, complex neurometabolic disorders. Despite their individual rarity, collectively mitochondrial diseases represent the most common cause of inherited metabolic disorders in the UK; they affect 1 in every 4300 individuals, up to 15,000 adults (and a similar number of children) in the UK. Mitochondrial disease manifests multisystem and isolated organ involvement, commonly affecting those tissues with high energy demands, such as skeletal muscle. Myopathy manifesting as fatigue, muscle weakness and exercise intolerance is common and debilitating in patients with mitochondrial disease. Currently, there are no effective licensed treatments and consequently, there is an urgent clinical need to find an effective drug therapy. AIM: To investigate the efficacy of 12-week treatment with acipimox on the adenosine triphosphate (ATP) content of skeletal muscle in patients with mitochondrial disease and myopathy. METHODS: AIMM is a single-centre, double blind, placebo-controlled, adaptive designed trial, evaluating the efficacy of 12 weeks' administration of acipimox on skeletal muscle ATP content in patients with mitochondrial myopathy. Eligible patients will receive the trial investigational medicinal product (IMP), either acipimox or matched placebo. Participants will also be prescribed low dose aspirin as a non-investigational medical product (nIMP) in order to protect the blinding of the treatment assignment. Eighty to 120 participants will be recruited as required, with an interim analysis for sample size re-estimation and futility assessment being undertaken once the primary outcome for 50 participants has been obtained. Randomisation will be on a 1:1 basis, stratified by Fatigue Impact Scale (FIS) (dichotomised as < 40, ≥ 40). Participants will take part in the trial for up to 20 weeks, from screening visits through to follow-up at 16 weeks post randomisation. The primary outcome of change in ATP content in skeletal muscle and secondary outcomes relating to quality of life, perceived fatigue, disease burden, limb function, balance and walking, skeletal muscle analysis and symptom-limited cardiopulmonary fitness (optional) will be assessed between baseline and 12 weeks. DISCUSSION: The AIMM trial will investigate the effect of acipimox on modulating muscle ATP content and whether it can be repurposed as a new treatment for mitochondrial disease with myopathy. TRIAL REGISTRATION: EudraCT2018-002721-29 . Registered on 24 December 2018, ISRCTN 12895613. Registered on 03 January 2019, https://www.isrctn.com/search?q=aimm.

Acipimox inhibits human carbonic anhydrases.

Acipimox, a nicotinic acid derivative in clinical use for the treatment of hyperlipidaemia, incorporates a free carboxylic acid and an N-oxide moiety, functionalities known to interact with the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and inhibit its activity. Herein we report that acipimox acts as a low micromolar CA inhibitor (CAI) against most human (h) isoforms possessing catalytic activity, hCA I - XIV. By using computational techniques (docking and molecular dynamics simulations), we propose that acipimox coordinates through its carboxylate group to the zinc ion from the enzyme active site cavity, whereas the N-oxide group is hydrogen-bonded to the proton shuttle His residue in some isoforms (hCA I) or to active site Thr or Gln residues in other isoforms (hCA II, III, IV, VII, etc). As some CA isoforms are involved in lipogenesis, these data may be useful for the design of more effective CAIs with antiobesity activity.

Insulin resistance induced by growth hormone is linked to lipolysis and associated with suppressed pyruvate dehydrogenase activity in skeletal muscle: a 2 × 2 factorial, randomised, crossover study in human individuals.

AIMS/HYPOTHESIS: Growth hormone (GH) causes insulin resistance that is linked to lipolysis, but the underlying mechanisms are unclear. We investigated if GH-induced insulin resistance in skeletal muscle involves accumulation of diacylglycerol (DAG) and ceramide as well as impaired insulin signalling, or substrate competition between fatty acids and glucose. METHODS: Nine GH-deficient male participants were randomised and examined in a 2 × 2 factorial design with and without administration of GH and acipimox (an anti-lipolytic compound). As-treated analyses were performed, wherefore data from three visits from two patients were excluded due to incorrect GH administration. The primary outcome was insulin sensitivity, expressed as the AUC of the glucose infusion rate (GIRAUC), and furthermore, the levels of DAGs and ceramides, insulin signalling and the activity of the active form of pyruvate dehydrogenase (PDHa) were assessed in skeletal muscle biopsies obtained in the basal state and during a hyperinsulinaemic-euglycaemic clamp (HEC). RESULTS: Co-administration of acipimox completely suppressed the GH-induced elevation in serum levels of NEFA (GH versus GH+acipimox, p < 0.0001) and abrogated GH-induced insulin resistance (mean GIRAUC [95% CI] [mg min-1 kg-1] during the HEC: control, 595 [493, 718]; GH, 468 [382, 573]; GH+acipimox, 654 [539, 794]; acipimox, 754 [618, 921]; GH vs GH+acipimox: p = 0.004). GH did not significantly change either the accumulation of DAGs and ceramides or insulin signalling in skeletal muscle, but GH antagonised the insulin-stimulated increase in PDHa activity (mean ± SEM [% from the basal state to the HEC]: control, 47 ± 19; GH, -15 ± 21; GH+acipimox, 3 ± 21; acipimox, 57 ± 22; main effect: p = 0.02). CONCLUSIONS/INTERPRETATION: GH-induced insulin resistance in skeletal muscle is: (1) causally linked to lipolysis; (2) not associated with either accumulation of DAGs and ceramides or impaired insulin signalling; (3) likely to involve substrate competition between glucose and lipid intermediates. TRIAL REGISTRATION: ClinicalTrials.gov NCT02782208 FUNDING: The work was supported by the Grant for Growth Innovation (GGI), which was funded by Merck KGaA, Darmstadt, Germany. Graphical abstract.

Combination therapy of omega-3 fatty acids and acipimox for children with hypertriglyceridemia and acute lymphoblastic leukemia.

BACKGROUND: Lipemic alterations are commonly seen in pediatric patients with acute lymphoblastic leukemia (ALL) treated with corticosteroids and L-asparaginase. OBJECTIVE: In these children, hypertriglyceridemia rarely causes symptoms and mostly responds well to a low-fat diet. Only few patients demand further therapy, which is not clearly approved in the literature to date. Therefore, it may be important to compile generally accepted standard procedures for lipid-lowering therapy in the pediatric ALL population. METHODS: We performed a study on 119 newly diagnosed pediatric patients with ALL, all treated according to the ALL-BFM 2000 protocol at our institution between the years 2000 and 2009, to evaluate the incidence of hypertriglyceridemia and the efficacy of a combination therapy with omega-3 fatty acids and acipimox in hypertriglyceridemic patients who did not respond to diet. RESULTS: We observed hypertriglyceridemia in 34.5% of patients in this collective. In the majority, normalization of triglycerides was successfully managed by administration of a low-fat diet. However, 7.6% of patients (related to total study population) with hypertriglyceridemia did not show diminished lipid levels during diet and/or presented with symptoms such as abdominal pain, dyspnea, or anginal chest pain. In these cases, we performed a lipid-lowering combination therapy with omega-3 fatty acids and acipimox. We observed a prompt decline of serum triglycerides to normal values and an improvement of symptoms within days after onset of this therapy without occurrence of any side effects. CONCLUSION: In summary, the combination treatment with omega-3 fatty acids and acipimox could represent an alternative to other reported lipid-lowering therapies without severe adverse reactions.

Effects of acute NEFA manipulation on incretin-induced insulin secretion in participants with and without type 2 diabetes.

AIMS/HYPOTHESIS: Incretin effect-the potentiation of glucose-stimulated insulin release induced by the oral vs the i.v. route-is impaired in dysglycaemic states. Despite evidence from human islet studies that NEFA interfere with incretin function, little information is available about the effect in humans. We tested the impact of acute bidirectional NEFA manipulation on the incretin effect in humans. METHODS: Thirteen individuals with type 2 diabetes and ten non-diabetic volunteers had a 3 h OGTT, and, a week later, an i.v. isoglycaemic glucose infusion (ISO; OGTT matched). Both pairs of studies were repeated during an exogenous lipid infusion in the non-diabetic volunteers, and following acipimox administration (to inhibit lipolysis) in people with diabetes. Mathematical modelling of insulin secretion dynamics assessed total insulin secretion (TIS), beta cell glucose sensitivity (ß-GS), glucose-induced potentiation (PGLU) and incretin-induced potentiation (PINCR); the oral glucose sensitivity index was used to estimate insulin sensitivity. RESULTS: Lipid infusion increased TIS (from 61 [interquartile range 26] to 78 [31] nmol/m2 on OGTT and from 29 nmol/m2 [26] to 57 nmol/m2 [30] on ISO) and induced insulin resistance. PINCR decreased from 1.6 [1.1] to 1.3 [0.1] (p < 0.05). ß-GS, PGLU and glucagon, glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP) responses were unaffected. Acipimox (lowering NEFA by ~55%) reduced plasma glucose and TIS and enhanced insulin sensitivity, but did not change ß-GS, PINCR, PGLU or glucagon, GLP-1 or GIP responses. As the per cent difference, incretin effect was decreased in non-diabetic participants and unchanged in those with diabetes. CONCLUSIONS/INTERPRETATION: Raising NEFA selectively impairs incretin effect and insulin sensitivity in non-diabetic individuals, while acute NEFA reduction lowers plasma glucose and enhances insulin sensitivity in people with diabetes but does not correct the impaired incretin-induced potentiation.

Short-term acipimox treatment is associated with decreased cardiac parasympathetic modulation.

AIMS: The nicotinic acid analogue acipimox is an antilipolytic agent, which acutely inhibits lipolysis and suppresses systemic levels of free fatty acids (FFA) and improves insulin sensitivity in obese patients. These effects of acipimox are transient due to a counter-regulatory increase in growth hormone levels that reverse the antilipolytic effect of acipimox. Hypopituitary patients constitute a viable model to study the growth hormone-independent effects of acipimox and the impact of isolated changes in FFA concentrations and insulin sensitivity on parasympathetic nervous activity. The aim of the present study was to investigate if pharmacological antilipolysis with acipimox acutely affects autonomic tone. METHODS: We studied heart rate variability as a measure of autonomic tone in eight hypopituitary men with and without acipimox treatment. The standard deviation of normal-to-normal intervals, root mean square of successive differences and high frequency were measured as heart rate variability parameters. The patients were studied in the basal and insulin-stimulated state with clamped plasma glucose on two occasions in a randomized, double-blind and placebo-controlled crossover study. RESULTS: Plasma glucose (4.7 vs. 4.9 mmol l-1 , P = 0.02) and serum FFA (0.05 vs. 0.41 mmol l-1 , P < 0.001) were significantly decreased during acipimox treatment. Acipimox had an inhibitory effect on standard deviation of normal-to-normal intervals (41.3 vs. 45.3 ms, P = 0.01), root mean square of successive differences (23.2 vs. 11 ms, P = 0.03) and high frequency (3.79 vs 3.60 ln (ms2 ), P = 0.02) and these effects were reversed during clamping. CONCLUSIONS: Short-term inhibition of lipolysis by acipimox treatment lowered circulating FFA levels, improved insulin sensitivity, and was accompanied by reduced parasympathetic tone. The effect of acipimox on the parasympathetic modulation was reversed by hyperinsulinaemia.

Design,synthesis and biological evaluation of novel drugs for metabolic syndrome / 国际药学研究杂志

Objective To design and synthesize novel drugs for metabolic syndrome. Methods A kind of drugs treating met?abolic syndrome was designed by linking acipimox with the lipid lowering function group of fibrates. Primary amine intermediates were synthesized from 4-aminophenol,4-(aminomethyl)phenol and 4-(2-aminoethyl)phenol by 3 steps,then target compounds were ob?tained by coupling acipimox with these primary amine intermediates,and their hypolipidaemic activity in Triton WR-1339 induced hy?perlipi daemic mice was evaluated. Results and Conclusion 5 target compounds were synthesized and identified by 1H NMR and ESI MS methods. It showed that all the compounds could decrease blood-lipid,and 4c exhibited anti-hyperlipidemic activities close to the positive control(bezafibrate)in in vivo hypolipidemic activity tests. The results have good value for the discovery of novel drugs for metabolic myndrome.

Design, synthesis and biological evaluation of novel drugs for metabolic syndrome / 国际药学研究杂志

Objective To design and synthesize novel drugs for metabolic syndrome. Methods A kind of drugs treating metabolic syndrome was designed by linking acipimox with the lipid lowering function group of fibrates. Primary amine intermediates were synthesized from 4-aminophenol, 4- (aminomethyl)phenol and 4- (2-aminoethyl)phenol by 3 steps, then target compounds were obtained by coupling acipimox with these primary amine intermediates, and their hypolipidaemic activity in Triton WR-1339 induced hyperlipi daemic mice was evaluated. Results and Conclusion 5 target compounds were synthesized and identified by1H NMR and ESI MS methods. It showed that all the compounds could decrease blood-lipid, and 4c exhibited anti-hyperlipidemic activities close to the positive control(bezafibrate)in in vivo hypolipidemic activity tests. The results have good value for the discovery of novel drugs for metabolic myndrome.

Free fatty acid availability is closely related to myocardial lipid storage and cardiac function in hypoglycemia counterregulation.

Hypoglycemia, a major side effect of intensive glucose-lowering therapy, was recently linked to increased cardiovascular risk in patients with diabetes. Whether increased circulating free fatty acids (FFA) owing to catecholamine-induced lipolysis affect myocardial energy metabolism and thus link hypoglycemia to cardiac vulnerability is unclear. Therefore, this study investigated the impact of hypoglycemia counterregulation (± inhibition of lipolysis) on myocardial lipid content (MYCL) and left ventricular function in healthy subjects. Nine healthy men were studied in randomized order: 1) insulin/hypoglycemia test (IHT; ins+/aci-), 2) IHT during inhibition of adipose tissue lipolysis by acipimox (ins+/aci+), 3) normoglycemia with acipimox (ins-/aci+), and 4) normoglycemia with placebo (ins-/aci-). MYCL and cardiac function were assessed by employing magnetic resonance spectroscopy/imaging at baseline and at 2 and 6 h. In response to acute hypoglycemia, plasma FFA (P<0.0001) and ejection fraction (EF; from 63.2±5.5 to 69.6±6.3%, P=0.0001) increased significantly and were tightly correlated with each other (r=0.68, P=0.0002); this response was completely blunted by inhibition of adipose tissue lipolysis. In the presence of normoglycemia, inhibition of lipolysis was associated with a drop in EF (from 59.2±5.5 to 53.9±6.9%,P=0.005) and a significant decrease in plasma FFA, triglycerides, and MYCL (by 48.5%, P=0.0001). The present data indicate that an intact interorgan cross-talk between adipose tissue and the heart is a prerequisite for catecholamine-mediated myocardial contractility and preservation of myocardial lipid stores in response to acute hypoglycemia.

Therapeutic effect and safety of acipimox combined with small-dose atorvastatin on combined hyperlipidemia after renal transplantation / 器官移植

Objective To assess the therapeutic effect and safety of acipimox combined with small-dose atorvastatin on combined hyperlipidemia after renal transplantation. Methods Fifty-six patients complicated with combined hyperlipidemia after renal transplantation were randomized into the combined small-dose group [n =28,acipimox (250 mg,twice a day) +atorvastatin (1 0 mg,once a day)]and normal dose group [n =28,atorvastatin (20-40 mg,once a day)].Total cholesterol (TC),triglyceride (TG),high density lipoprotein cholesterin (HDL-C ), low density lipoprotein cholesterin (LDL-C ), aspartate aminotransaminase (AST),alanine aminotransferase (ALT),serum creatinine (Scr),blood urea nitrogen (BUN),uric acid (UA)and creatine kinase (CK)were observed before treatment and 1 ,2 and 3 months after treatment.Adverse drug reaction was recorded.Results Compared with those before treatment,TC,TG and LDL-C of the normal dose group and the combined small-dose group decreased after treatment,but HDL-C increased,and the difference had statistical significance (all in P <0.01 ).Compared with the normal dose group,TG and LDL-C of the combined small-dose group were lower and HDL-C was higher,and the difference had statistical significance (all in P <0.01 ).At each time point before and after treatment,ALT,AST,Scr, BUN,UA and CK of the normal dose group and the combined small-dose group showed no statistically significant difference (all in P >0.05).There was significant difference in the incidence of adverse reactions in the digestive system,nervous system,musculoskeletal system and skin/vascular of the normal dose group and the combined small-dose group (all in P <0.05 ).Conclusions Acipimox combined with small-dose atorvastatin can treat combined hyperlipidemia after renal transplantation safely and effectively.

What is the Key Step in Muscle Fatty Acid Oxidation after Change of Plasma Free Fatty Acids Level in Rats?

The purpose of this study was to discern the critical point in skeletal muscle fatty acid oxidation by changing plasma free fatty acids (FFA) level in rat. In the study, 3 key steps in lipid oxidation were examined after changing plasma FFA level by acipimox. The rates of both palmitate and palmitoyl- carnitine oxidation were decreased by decrease of plasma FFA level, however, carnitine palmitoyl transferase (CPT) 1 activity was not changed, suggesting CPT1 activity may not be involved in the fatty acid oxidation at the early phase of plasma FFA change. In the fasted rats, beta-hydroxy acyl-CoA dehydrogenase (beta-HAD) activity was depressed to a similar extent as palmitate oxidation by a decrease of plasma FFA level. This suggested that beta-oxidation might be an important process to regulate fatty acid oxidation at the early period of plasma FFA change. Citrate synthase activity was not altered by the change of plasma FFA level. In conclusion, the critical step in fatty acids oxidation of skeletal muscles by the change of plasma FFA level by acipimox in fasting rats might be the beta-oxidation step rather than CPT1 and TCA cycle pathways.

Determination of Acipimox in Human Serum by HPLC / 中国药房

OBJECTIVE: To establish HPLC method for the determination of acipimox in human serum. METHODS: The determination was performed on C18 column under room temperature, the mobile phase consisted of methanol -water(15:85) with a flow rate of 0.8ml/ min and detection wavelength of 260nm, the quantitation was conducted by external reference method,the serum was subjected to protein sediment by methanol,the supernate fluid obtained thereafter was undergone sample injection. RESULTS: The linear range of acipimox was 1.0-16.0?g/ml (r = 0.9 987),the minimum detection concentration was 0.5?g/ ml; the average recovery of method was 96.05% . CONCLUSION: This method is simple, fast, sensitive and accurate, and which can be applied for blood concentration monitoring and pharmacokinetic study of acipimox.

The effects on serum lipoprotein(a) of antihyperlipidemic agents

BACKGROUND: Many studies to reduce serum lipoprotein(a) are done because serum lipoprotein(a) has been known to be an independent risk factor of coronary artery disease along with age, smoking, diabetes, hypertension, and hyperlipidemia. Till now, oral estrogen/androgen therapy, niacin analogue and plasmapheresis are known therapeutic methods. This study examined the relative effects of three antihyperlipidemic agents, acipimox, lovastatin, fenofibrate. METHODS: Among 70 subjects (male-19, female-51) with their serum cholesterol level of more than 240mg/dL, 56 subjects who were completed 2 months antihyperlipidemic treatment (acipimox-20, lovastatin-18, fenofibrate-18) were examined for baseline total cholesterol, HDL cholesterol, triglyceride, and lipoprotein(a) and were followed up 2 months later. RESULTS: Mean values of each group for acipimox, lovastatin, fenofibrate were as follows: total cholesterol (268.1+/-19.03, 287.1+/-36.42, 268.9+/-25.99), HDL cholesterol (43.5+/-10.99, 42.7+/-11.88, 37.9+/-8.20), triglyceride (226.1+/-165.03, 260.4+/-175.98, 234.3+/-124.33), LDL cholesterol (179.3+/-30.40, 192.3+/-41.52, 184.1+/-38.08), lipoprotein(a) (26.2+/-15.32,34.8+/-18.56,29.9+/-12.58). Mean percentile reduction of lipoprotein(a) was acipimox-41.4%(P<0.0001), lovastatin-22.2%(P<0.0001), fenofibrate-16.1%(P<0.05), and p value was less than 0.05 in the comparison of groups. Lipoprotein(a) showed no relations with age, sex, BMI, WHR, smoking, total cholesterol, HDL cholesterol, triglyceride and LDL cholesterol. After 2 months treatment, mean reduction percentages of total cholesterol was acipimox-12.2%(P<0.0001), lovastatin-17.6%(P<0.0001), fenofibrate-8.85%(P<0.05). LDL cholesterol was acipimox-16.12%(P<0.0001), lovastatin-22.89%(P<0.0001), fenofibrate-12.06% (P<0.05). Triglyceride was acipimox-17.24%(P<0.0001), lovastatin-17.39%(P<0.0001), fenofibrate-9,78%(P<0.05). HDL cholesterol was elevated in acipimox-17.24%(P<0.05), lovastatin-16.10%(P<0.05) and fenofibrate-12.06(P<0.05). In total cholesterol(P<0.05) and LDL cholesterol(P<0.05), there were significant differences among 3 groups, but not in HDLcholesterol and triglycerides. CONCLUSION: In two months treatment of acipimox, lovastatin and fenofibrate in hyperlipidemic patients, lipoprotein(a), known for independent risk factor of coronary artery disease, was reduced significantly in the order of acipimox, lovastatin and fenofibrate.

Effect of Antiliyolytic Agents on Glueose Metabolism in Thyrotoxic Patients / 대한내분비학회지

Decreased glucose tolerance is often found in patients with thyrotoxicosis but the pathogenetic mechanisms are poorly understood. Since the concentrations of free fatty acid are usually elevated due to increased lipolysis in thyrotoxicosis, the preferential oxidation of the free fatty acids may explain the decreased glucose tolerance in hyperthyroidism. The aim of this study was to investigate whether lowering plasma free fatty acid(FFA) by acipimox, a long-acting antilipolytic agent, could affect glucose metabolism in thyrotoxicosis. We performed intravenous glucose tolerance test with acipimox or placebo in 6 untreated thyrotoxicmen and 6 age-and body mass index(BMI)-matched controls. The following results were obtained.1) The basal plasma FFA concentration in thyrotoxic patients were significantly higher than those in controls(997.0+-303.4 uEq/L vs. 290.5+-169.1 uEq/L; p<0.01). 2) Plasma FFA concentrations decreased rapidly with acipimox ingestion in both controls and thyrotoxic patients.3) Plasma glucose concentrations were significantly lower with acipimox ingestion than with placebo in thyrotoxic patients from 17min after intravenous glucose load and to the end of the study.4) Plasma insulin concentrations in thyrotoxic patients with acipimox ingestion were higher at 5, 7 min after iv glucose load.5) In thyrotoxic patients, glucose disappearance rate(K_glucose) in acipimox treatment was significantly higher than that in placebo treatment(2.44+-0.84 vs. 1.58+-0.37;p<0.05). 6) K_glucose values were inversely correlated with basal FFA concentrations(r=-0.58, p<0.05). In summary, in thyrotoxic patients with elevated plasma FFA levels, acipimox lowered plasma FFA, which in turn improved glucose tolerance.