Relationship between effects of added albumin, initial free thyroxine value and endogenous serum-binding protein concentrations on Amerlex free thyroxine estimations

We studied the effect of adding purified human albumin to sera on free thyroxine (FT4) values obtained with Amerlex radioimmunoassays. Apparent FT4 values increased with progressive addition of albumin in vitro. The effect was smallest with low and greatest with high initial FT4 concentrations, which were also linearly correlated with the incremental increase in FT4 values per g/l albumin added. Wide variations in either endogenous thyroxine binding globulin (TBG) or albumin concentrations in patient serum had little effect on the rate of increase in FT4 values when albumin was added in vitro. From Mass Action theory, calculations of the binding affinity of the endogenous albumin for the analog (2.1 X 10(5) l/mol) gave values nearly half that of the added albumin (3.94 X 10(5) l/mol). Distortions in Amerlex FT4 values caused by adding albumin in vitro may exaggerate its importance as a tracer binder and such results may be unrepresentative of patient samples.     

Serum concentrations of thyroid hormones in severe non-thyroidal illnesses (author's transl)

Pathologically low serum total triiodothyronine (T3) concentrations are a characteristic finding in patients with severe non-thyroidal illnesses. No adequate explanation has yet been offered for this phenomenon. We have, therefore, investigated the serum concentrations of total thyroxine (T4), total T3 and total 3,3',5'-triiodothyronine (reverse T3)--the metabolically-inactive metabolite of thyroxine--and of TSH in 13 patients with acute myocardial infarction, in 12 patients with compensated liver cirrhosis, in 9 patients with decompensated liver cirrhosis and in 15 patients with chronic renal failure on chronic intermittent haemodialysis by radioimmunoassay. The values obtained were compared to corresponding values of a normal control group (n - 23). According to our results the decrease in serum T3 combined with normal T4 concentrations in severe non-thyroidal illnesses seems to be a consequence of an alteration in thyroxine degradation. Two different possibilities of alteration can be considered: 1. inhibition of the overall deiodinationof T4, leading to low total T3 serum concentrations with concomitant normal to low reverse T3 serum concentrations (chronic uraemia), 2. a shift in the monodeiodination of T4 towards enhanced reverse T3 production, leading also to low total T3 concentrations, but with a concomitant increase in reverse T3 serum concentrations (myocardial infarction, liver cirrhosis). The results obtained in our patients with liver cirrhosis show, moreover, that this alteration of T4 metabolism depends on the severity of the illness.     

Concentrations of iodothyronines in serum of patients with chronic renal failure and other nonthyroidal illnesses: role of free fatty acids

The mean concentration of free thyroxin (FT4) in serum, as determined by direct equilibrium dialysis, was decreased in patients with chronic renal failure (CRF) and increased in patients with various other nonthyroidal illnesses (NTI). The mean concentration of dialyzable free triiodothyronine (FT3) in serum was equally low in both groups of patients. Patients with CRF of various etiology but a similar degree of renal failure as estimated from serum creatinine assay had very similar concentrations of FT4 and FT3 in their serum. Mean thyroxin (T4) and triiodothyronine (T3) concentrations in serum were decreased in CRF and NTI, whereas the mean reverse-T3 concentration in serum was normal in CRF and increased in NTI. T4-binding globulin and albumin were markedly decreased in CRF and NTI; T4-binding prealbumin was increased in CRF and decreased in NTI. The mean concentration of nonesterified free fatty acids (FFA) in serum was increased in NTI but not in CRF. The weak, but significant, positive correlation observed between FT4 and FFA in serum (r = 0.34, P less than 0.01) in NTI indicates that the increase in serum FT4 in this group of patients could be an effect, at least in part, of FFA competing with T4 for binding sites on serum proteins. The stronger correlation detected between the serum FT4 concentration and the FFA/albumin molar ratio in serum (r = 0.60, P less than 0.001) demonstrates the importance of a low albumin concentration for expression of the effect of FFA on FT4 in severe systemic illnesses.     

In vitro and in vivo effects of increased concentrations of free fatty acids on free thyroxin measurements as determined by five assays

To compare in vitro and in vivo effects of increased concentrations of free fatty acids (FFA) on free thyroxin (FT4) values, we measured FT4 in three pooled sera supplemented with oleate and in serum from 18 euthyroid patients before and after an infusion of fat emulsion (Intralipid). We used five FT4 RIA kits: two two-step methods [Gammacoat, Baxter (GC); Ria-gnost, Behring (RG)], two analog RIAs [Amerlex-M, Amersham (AM); Coat-Ria, BioMérieux (CR)], and one kit with labeled antibodies [Amerlex-MAB*, Amersham (AA)]. In vitro, at the maximum oleate addition of 5 mmol/L, FT4 increased when measured by the GC and RG kits, decreased by the AM kit, and showed no significant change by the CR and AA kits. In vivo, post-Intralipid, FFA concentrations rose significantly and the FT4 changes agreed with the results of the in vitro experiments, except for the RG kit, for which FT4 increased in only nine patients. We conclude that in vitro oleate addition is useful to predict the in vivo effect of increased FFA on FT4 values; moreover, in serum from euthyroid subjects with high concentrations of FFA, FT4 analyzed with the CR or AA kits should better agree with normal results for thyrotropin than FT4 values measured with the other kits.     

原发性高血压合并代谢综合征患者血清游离脂肪酸水平与颈动脉内中膜增厚关系的研究

目的 探讨原发性高血压(EH)合并代谢综合征(MS)患者游离脂肪酸(FFA)水平与颈动脉内中膜厚度(IMT)的关系.方法 选择EH合并MS患者69例(EH+MS组)、单纯EH患者57例(EH组).选取健康体检者50名作为健康对照组.比较3组患者FFA、体重指数(BMI)、颈动脉IMT及颈动脉内中膜增厚发生率情况.结果 ①EH+MS组的BMI、甘油三酯(TG)、空腹血糖(FPG)均高于单纯EH组和健康对照组[(26.0±2.1)、(24.9±2.3)、(23.6±1.6)kg/m2,(2.40±0.81)、(1.93±0.55)、(1.49±0.36)mmol/L,(5.64±0.82)、(5.10±1.08)、(4.70±0.90)mmol/L,F值分别为20.06、30.96、15.17,P＜0.05或＜0.01].②EH+MS组血清FFA高于单纯EH组及健康对照组[(562.11±55.12)、(402.65±49.53)、(356.23±45.93)μmol/L,F=277.28,P＜0.01].③3组颈动脉IMT依次为(1.10±0.13)、(0.82±0.12)、(0.70±0.11)mm,两两比较差异均有统计学意义(P均＜0.01);颈动脉IMT增厚发生率依次为28.99%(20/69)、17.54%(10/57)、2.00%(1/50),两两比较差异均有统计学意义(P均＜0.01).结论 EH合并MS患者血中FFA水平升高与颈动脉内中膜增厚相关.     

Effect of long-term storage on the concentration of albumin and free fatty acids in human sera

Stored sera from healthy persons can be used to study relationships between blood variables at the time of sampling and disease appearing several years later but storage may influence the variables. In this work we measured the concentration of albumin and free fatty acids (FFA) in samples from the JANUS serum bank of Norway. Sera from blood donors and persons participating in health screening programs have been added to the bank since 1973. The concentration of albumin and FFA was measured in 443 JANUS bank sera. The material was divided into quartiles according to the length of storage: < 3 years (n = 110), 3-6 years (n = 110), 6-12 years (n = 115) and > 12 years (n = 108). Albumin was measured colorometrically using the bromcresol green method and FFA was determined enzymatically. The serum albumin concentrations (mean &#45 SEM) in the four groups were 55.8 &#45 0.6, 56.2 &#45 0.5, 59.9 &#45 0.6 and 59.5 &#45 0.6 g/L. The values of groups 3 and 4 were significantly higher than those of groups 1 and 2 (p< 0.001). The serum FFA concentrations in the four groups were 0.56 &#45 0.03, 0.64 &#45 0.03, 0.77 &#45 0.03 and 0.85 &#45 0.04 mmol/L, i.e. a significant storage effect. The Scheffe´multiple comparison test showed that FFA values in groups 3 and 4 were significantly higher than those in groups 1 and 2 (p< 0.001 for group 4 vs. 1 and 2, and 3 vs. 1; p< 0.04 for group 3 vs. 2). Serum FFA and albumin levels were positively associated (r = 0.489, p< 0.001). Using linear regression analysis, it was estimated that serum albumin values increased by 0.28 g/L per year (i.e. 0.5%) and FFA by 0.02 mmol/L (i.e. 3.8%). Thus, measured by standard methods, serum FFA and albumin could increase in response to several years of storage at ° - 25 C. It is suggested that the storage time dependent increase in FFA is due to FFA liberation from lipoprotein triglycerides, whereas the apparent increase in albumin concentration possibly could be attributed to an unfolding of the protein, allowing more bromcresol green to be bound.     

Conflict between classifications based on free thyroxine and thyroid stimulating hormone concentrations in thyroxine-treated patients

The use of free thyroxine assay as the basis for monitoring patients on thyroxine replacement therapy was assessed. Patients with normal free thyroxine levels were divided into sub-groups on the basis of serum TSH levels. Of these, patients with normal TSH levels had higher serum free thyroxine and free 3,5,3'-triiodothyronine concentrations than patients with elevated TSH levels. No significant differences were seen in the level of duration of replacement therapy. Patients were almost equally divided between the high and normal TSH sub-groups. It was concluded that free thyroxine assay had little role to play in the monitoring of these patients.     

游离脂肪酸与子痫前期和妊娠期糖尿病发生的相关性

目的:探讨孕晚期游离脂肪酸对子痫前期和(或)妊娠期糖尿病(GDM)发病率的影响。方法:选择417例孕晚期子痫前期和(或)GDM为观察组,另选2 018例正常妊娠孕妇为对照组。检测并比较2组血清总胆固醇(TC)、三酰甘油(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)和游离脂肪酸(FFA)。采用logistic回归模型分析血脂子痫前期和(或)GDM的关系。结果:校正混杂因素[孕妇年龄、孕前体质指数(BMI)和采血时的孕周]后,孕晚期FFA浓度升高会增加子痫前期、GDM和子痫前期合并GDM的风险(P0.01)。孕晚期TG水平升高会增加子痫前期、GDM发生的风险(P0.001)。结论:孕晚期FFA水平升高可使子痫前期和(或)GDM发生风险增加。     

Effect of long-term storage on the concentration of albumin and free fatty acids in human sera.

Stored sera from healthy persons can be used to study relationships between blood variables at the time of sampling and disease appearing several years later but storage may influence the variables. In this work we measured the concentration of albumin and free fatty acids (FFA) in samples from the JANUS serum bank of Norway. Sera from blood donors and persons participating in health screening programs have been added to the bank since 1973. The concentration of albumin and FFA was measured in 443 JANUS bank sera. The material was divided into quartiles according to the length of storage: <3 years (n = 110), 3-6 years (n = 110), 6-12 years (n = 115) and >12 years (n = 108). Albumin was measured colorometrically using the bromcresol green method and FFA was determined enzymatically. The serum albumin concentrations (mean +/- SEM) in the four groups were 55.8+/-0.6, 56.2+/-0.5, 59.9+/-0.6 and 59.5+/-0.6 g/L. The values of groups 3 and 4 were significantly higher than those of groups 1 and 2 (p<0.001). The serum FFA concentrations in the four groups were 0.56+/-0.03, 0.64+/-0.03, 0.77+/-0.03 and 0.85+/-0.04 mmol/L, i.e. a significant storage effect. The Scheffé multiple comparison test showed that FFA values in groups 3 and 4 were significantly higher than those in groups 1 and 2 (p <0.001 for group 4 vs. 1 and 2, and 3 vs. 1; p<0.04 for group 3 vs. 2) Serum FFA and albumin levels were positively associated (r = 0.489, p <0.01). Using linear regression analysis, it was estimated that serum albumin values increased by 0.28 g/L per year (i.e. 0.5%) and FFA by 0.02 mmol/L (i.e. 3.8%). Thus, measured by standard methods, serum FFA and albumin could increase in response to several years of storage at -25 degrees C. It is suggested that the storage time dependent increase in FFA is due to FFA liberation from lipoprotein triglycerides, whereas the apparent increase in albumin concentration possibly could be attributed to an unfolding of the protein, allowing more bromcresol green to be bound.     

妊娠期糖尿病胰岛素抵抗与铁蛋白及游离脂肪酸的相关性研究

目的探讨高浓度铁蛋白、游离脂肪酸与妊娠期糖尿病(GDM)胰岛素抵抗(HOMA-IR)的相关性。方法 2011年6月至2012年6月该院GDM患者(患者组)采用个体匹配,按照1∶1比例选取对照,即调查每一例病例的同时,调查1例年龄相同、孕周相同的孕妇作为对照(对照组)。比较2组研究对象高浓度铁蛋白、游离脂肪酸与GDM HOMA-IR的相关性。结果 2组研究对象的HOMA-IR指数、胰岛β(HOMA-β)细胞分泌功能指数比较,差异有统计学意义(P0.05)。患者组铁蛋白浓度[(50.30±25.32)μg/L]与对照组[(23.60±12.96)μg/L]比较,差异有统计学意义(P0.05);患者组游离脂肪酸浓度[(384.73±29.60)μmol/L]与对照组[(252.62±19.41)μmol/L]比较,差异有统计学意义(P0.05)。以HOMA-IR为因变量,研究对象资料为自变量,进行Logistic回归分析,提示铁蛋白、游离脂肪酸的OR值分别为1.340、1.030,B为正值(P0.05)。结论 GDM女性体内高浓度铁蛋白、游离脂肪酸与胰岛素抵抗有关。     

Inosine causing insulin release and increased myocardial uptake of carbohydrates relative to free fatty acids in dogs

Summary. The aim of the present study was to determine the effect of i.v. inosine on myocardial substrate uptake and function in the in situ dog heart. Inosine was infused i.v. at a rate of 5 mg kg min^-1 in eight closed-chest pentobarbital anaesthetized dogs. Inosine caused a 46% decrease (P<0.01) in plasma free fatty acids (FFA), a 15% decrease (P<0.05) in plasma glycerol, an 18% decrease (P<0.05) in plasma glucose and a 46% increase (P<0.01) in blood lactate. This was associated with a 55% decrease (P<0.01) in myocardial FFA uptake and a 72% increase in lactate uptake, while glucose uptake remained unchanged. These metabolic changes were associated with a five-fold increase (P<0.05) in arterial insulin. Inosine caused an 18% increase (P<0.01) in myocardial blood flow without changing MVO₂. There was a 33% increase (P<0.01) in LV dP/dt_max, a decrease in LVEDP from 4.9 ± 0.9 (mean ± SEM) to 0.9 ± 0.3 mmHg (P<0.05) and a 24% decrease (P<0.01) in systemic vascular resistance. Inosine caused a transient 38% increase (P<0.05) in pulmonary vascular resistance. In conclusion, in addition to a positive inotropic effect and vascular effects inosine was found to cause release of insulin and to shift myocardial metabolism towards increased uptake of carbohydrates relative to FFA.     

Marine unsaturated fatty acids: structures,bioactivities, biosynthesis and benefits

Unsaturated fatty acids (UFAs) are an important category of monounsaturated and polyunsaturated fatty acids with nutritional properties. These secondary metabolites have been obtained from multitudinous natural resources, including marine organisms. Because of the increasing numerous biological importance of these marine derived molecules, this review covers 147 marine originated UFAs reported from 1978 to 2018. The review will focus on the structural characterizations, biological properties, proposed biosynthetic processes, and healthy benefits mediated by gut microbiota of these marine naturally originated UFAs.

Unsaturated fatty acids (UFAs) are an important category of monounsaturated and polyunsaturated fatty acids with nutritional properties.     

Minimal effects of free fatty acids on the competitive protein-binding assay of serum thyroxine on reusable sephadex columns

In rats, following oral administration of cream and intravenous heparin, plasma free fatty acids and triiodothyronine Sephadex uptake were elevated. Simultaneously apparent serum thyroxine, measured by the Tetrasorb-E kit, was increased, but not when measured using reusable Sephadex columns. Addition of oleate to a human serum albumin solution or to human serum produced similar effects; appreciable rises in apparent thyroxine were noted in the kit assay but only minor changes occurred when Sephadex columns were used. In the latter procedure almost all [¹⁴C]oleic acid added to serum was removed in the first barbital buffer wash, before application of the thyroxine-binding globulin solution.In the serum thyroxine assay on reusable Sephadex columns, there is minimal interference by free fatty acids because they are removed by the first barbital buffer wash.     

Serum free thyroxine concentrations in normal euthyroid subjects and ones with high serum thyroxine binding globulin concentration

Serum free thyroxine (fT4) was assayed by a commercial fT4 method in 30 normal euthyroid subjects, 19 pregnant females, 13 euthyroid subjects with high thyroxine binding globulin (TBG) and three with low or undetectable serum TBG concentration. In a number of these fT4 was also calculated on the basis of the application of the law of mass action to the binding situation. In states in which TBG was altered for congenital reasons both the experimentally determined and calculated fT4 were not significantly different from their respective means in the normal euthyroid population. Pregnant females had both lower experimental and theoretical free T4 concentrations. It is inferred from these data that TBG concentration per se is without effect on serum fT4 concentration.