Serum proprotein convertase subtilisin kexin type 9 is correlated directly with serum LDL cholesterol

BACKGROUND: Proprotein convertase subtilisin kexin type 9 (PCSK9) is gaining attention as a key regulator of serum LDL-cholesterol (LDLC). This novel serine protease causes the degradation of hepatic LDL receptors by an unknown mechanism. In humans, gain-of-function mutations in the PCSK9 gene cause a form of familial hypercholesterolemia, whereas loss-of-function mutations result in significantly decreased LDLC and decreased cardiovascular risk. Relatively little is known about PCSK9 in human serum. METHODS: We used recombinant human PCSK9 protein and 2 different anti-PCSK9 monoclonal antibodies to build a sandwich ELISA. We measured PCSK9 and lipids in 55 human serum samples and correlated the results. We used the anti-PCSK9 antibodies to assay lipoprotein particle fractions separated by sequential flotation ultracentrifugation. RESULTS: Serum concentrations of PCSK9 ranged from 11 to 115 microg/L and were directly correlated with serum concentrations of LDLC (r = 0.45, P = 0.001) and total cholesterol (r = 0.50, P = 0.0003), but not with triglycerides (r = 0.15, P = 0.28) or HDL cholesterol concentrations (r = 0.13, P = 0.36). PCSK9 was not detectable in any lipoprotein particle fraction, including LDL. CONCLUSIONS: PCSK9 is present in human serum, likely not associated with specific lipoprotein particles. The circulating concentrations of human PCSK9 are directly correlated with LDL and total cholesterol concentrations.     

Intact proinsulin and beta-cell function in lean and obese subjects with and without type 2 diabetes

OBJECTIVE: Type 2 diabetes is a heterogeneous disease in which both beta-cell dysfunction and insulin resistance are pathogenetic factors. Disproportionate hyperproinsulinemia (elevated proinsulin/insulin) is another abnormality in type 2 diabetes whose mechanism is unknown. Increased demand due to obesity and/or insulin resistance may result in secretion of immature beta-cell granules with a higher content of intact proinsulin. RESEARCH DESIGN AND METHODS: We investigated the impact of obesity on beta-cell secretion in normal subjects and in type 2 diabetic patients by measuring intact proinsulin, total proinsulin immunoreactivity (PIM), intact insulin, and C-peptide (by radioimmunoassay) by specific enzyme-linked immunosorbent assays in the fasting state and during a 120-min glucagon (1 mg i.v.) stimulation test. Lean (BMI 23.5 +/- 0.3 kg/m2) (LD) and obese (30.1 +/- 0.4 kg/m2) (OD) type 2 diabetic patients matched for fasting glucose (10.2 +/- 0.6 vs. 10.3 +/- 0.4 mmol/l) were compared with age- and BMI-matched lean (22.4 +/- 0.6 kg/m2) (LC) and obese (30.8 +/- 0.9 kg/m2) (OC) normal control subjects. RESULTS: Diabetic patients (LD vs. LC and OD vs. OC) had elevated fasting levels of intact proinsulin 6.6 +/- 1.0 vs. 1.6 +/- 0.3 pmol/l and 7.7 +/- 2.0 vs. 1.2 +/- 0.2 pmol/l; PIM: 19.9 +/- 2.5 vs. 5.4 +/- 1.0 pmol/l and 29.6 +/- 6.1 vs. 6.1 +/- 0.9 pmol/l; and total PIM/intact insulin: 39 +/- 4 vs. 15 +/- 2% and 35 +/- 5 vs. 13 +/- 2%, all P < 0.01. After glucagon stimulation, PIM levels were disproportionately elevated (PIM/intact insulin based on area under the curve analysis) in diabetic patients (LD vs. LC and OD vs. OC): 32.6 +/- 6.7 vs. 9.2 +/- 1.1% and 22.7 +/- 5.2 vs. 9.1 +/- 1.1%, both P < 0.05. Intact insulin and C-peptide net responses were significantly reduced in type 2 diabetic patients, most pronounced in the lean group. The ratio of intact proinsulin to PIM was higher in diabetic patients after stimulation in both LD versus LC: 32 +/- 3 vs. 23 +/- 2%, and OD versus OC: 28 +/- 4 vs. 16 +/- 2%, both P < 0.01. In obese normal subjects, intact proinsulin/PIM was lower both in the fasting state and after glucagon stimulation: OC versus LC: 22 +/- 3 vs. 33 +/- 3% (fasting) and 16 +/- 2 vs. 23 +/- 2% (stimulated), both P < 0.05. CONCLUSIONS: Increased secretory demand from obesity-associated insulin resistance cannot explain elevated intact proinsulin and disproportionate hyperproinsulinemia in type 2 diabetes. This abnormality may be an integrated part of pancreatic beta-cell dysfunction in this disease.     

Multiorgan insulin sensitivity in lean and obese subjects

OBJECTIVE

To provide a comprehensive assessment of multiorgan insulin sensitivity in lean and obese subjects with normal glucose tolerance.

RESEARCH DESIGN AND METHODS

The hyperinsulinemic-euglycemic clamp procedure with stable isotopically labeled tracer infusions was performed in 40 obese (BMI 36.2 ± 0.6 kg/m², mean ± SEM) and 26 lean (22.5 ± 0.3 kg/m²) subjects with normal glucose tolerance. Insulin was infused at different rates to achieve low, medium, and high physiological plasma concentrations.

RESULTS

In obese subjects, palmitate and glucose R_a in plasma decreased with increasing plasma insulin concentrations. The decrease in endogenous glucose R_a was greater during low-, medium-, and high-dose insulin infusions (69 ± 2, 74 ± 2, and 90 ± 2%) than the suppression of palmitate R_a (52 ± 4, 68 ± 1, and 79 ± 1%). Insulin-mediated increase in glucose disposal ranged from 24 ± 5% at low to 253 ± 19% at high physiological insulin concentrations. The suppression of palmitate R_a and glucose R_a were greater in lean than obese subjects during low-dose insulin infusion but were the same in both groups during high-dose insulin infusion, whereas stimulation of glucose R_d was greater in lean than obese subjects across the entire physiological range of plasma insulin.

CONCLUSIONS

Endogenous glucose production and adipose tissue lipolytic rate are both very sensitive to small increases in circulating insulin, whereas stimulation of muscle glucose uptake is minimal until high physiological plasma insulin concentrations are reached. Hyperinsulinemia within the normal physiological range can compensate for both liver and adipose tissue insulin resistance, but not skeletal muscle insulin resistance, in obese people who have normal glucose tolerance.Obesity is associated with a constellation of metabolic alterations that are risk factors for coronary heart disease, including diabetes, dyslipidemia, and nonalcoholic fatty liver disease (1). It is likely that insulin resistance in specific organ systems, namely adipose tissue, liver, and skeletal muscle, is involved in the pathogenesis of these metabolic abnormalities (2,3). The effect of insulin resistance on daily glucose and free fatty acid (FFA) metabolism in obese people who do not have diabetes is unclear, however, because it is possible that hyperinsulinemia associated with obesity can overcome the defect in insulin action and normalize metabolic function. In fact, data from large studies have demonstrated that basal plasma glucose and FFA concentrations in obese people are not different than those in lean subjects (4). Accordingly, it is possible that many obese people have multiorgan insulin resistance and are at increased risk for development of metabolic diseases even when basal glucose and FFA concentrations are normal.The assessment of insulin action is complex because insulin has multiple metabolic functions that differ across organ systems and require different doses of insulin to achieve maximal effects (5). A multistage hyperinsulinemic-euglycemic clamp procedure (HECP), conducted in conjunction with isotopically labeled tracer infusions to measure substrate kinetics, can be used to determine simultaneously insulin action in the liver (suppression of glucose R_a into plasma), muscle (stimulation of glucose R_d from plasma), and adipose tissue (suppression of adipose tissue triglyceride lipolysis; i.e., glycerol and palmitate R_a into plasma).The primary purpose of the current study was to further understand the potential insulin-related metabolic dysfunction associated with obesity by providing a comprehensive assessment of multiorgan insulin sensitivity across a physiological range of plasma insulin concentrations in lean and obese subjects through the use of a multistage HECP in conjunction with stable isotopically labeled glucose, palmitate, and glycerol tracer infusions. Only subjects who had normal fasting plasma glucose concentrations and who did not have impaired glucose tolerance or diabetes were included in this study to eliminate the potential confounding influences of basal hyperglycemia and diabetes therapy on the assessment of insulin action. Most obese people do not have impaired glucose tolerance or diabetes, so our group represents the majority of the obese population (4). We hypothesized that hepatic glucose production and adipose tissue lipolytic rate are much more sensitive to insulin than is muscle glucose uptake. Basal hyperinsulinemia and physiological increases in plasma insulin concentration in obese subjects with normal glucose tolerance should therefore be able to overcome insulin resistance in the liver and adipose tissue but not skeletal muscle, resulting in normal rates of endogenous glucose production (EGP) and lipolysis but not glucose disposal.     

Role of proprotein convertase subtilisin/kexin type 9 inhibitors in patients with coronary artery disease undergoing percutaneous coronary intervention

Introduction: Although novel therapies have improved outcomes in PCI patients, a sizeable number of patients still remain at high cardiovascular risk for recurrent event. There is therefore an unmet need for novel therapies that can improve clinical outcomes, with an associated satisfactory safety profile. Proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme is a novel lipid-lowering target with a potential to impact high-cardiovascular risk populations including patients with coronary artery disease (CAD), undergoing the percutaneous coronary intervention (PCI). A number of canonical and non-canonical pathways of PCSK9 action, including inflammation and platelet activation, as well as their inhibition, are undergoing intense investigation.

Areas covered: This review will discuss the currently available evidence on PCSK9 inhibitors, pathways of PCSK9 enzyme action and results or its inhibition, the potential role of PCSK9 inhibitors in specific populations undergoing PCI, and completed and ongoing studies in patients with CAD.

Expert commentary: PCSK9 inhibitors clinical outcomes in high risk cardiovascular disease patients and have the potential to function as powerful adjunctive therapy in patients undergoing PCI by a twofold mechanism on both lipid lowering and platelet/inflammation pathways.     

Acute insulin administration does not affect plasma leptin levels in lean or obese subjects

Abstract. Whether leptin levels are related to insulin sensitivity or subject to acute regulation by insulin is not known. In 12 obese [body mass index (BMI) = 34.0 ±1.5 kg m^-2] and 12 lean (BMI = 22.2 ±0.6 kg m^-2) non-diabetic subjects, plasma leptin concentrations were measured in the fasting state and during 2 hours of euglycaemic hyperinsulinaemia (˜600 pmol L^-2). Fasting plasma leptin was significantly higher in obese (26.6 ±3.2) than in lean subjects (6.4 ±1.2 ng mL^-1, P = 0.0001), and in women (21.1 ±3.3) than in men (7.3 = 2.3 ng mL^-1, P = 0.01). In univariate analysis, fasting plasma leptin was strongly related to all anthropometric measures (body weight, fat mass, percent fat mass, waist and hip circumferences). In multiple regression, per cent adiposity, hip circumference and duration of obesity explained 90% of the variability in fasting leptin concentrations. Fasting and stimulated (OGTT) insulin levels, insulin sensitivity (22.6 ±1.9 vs 36.7 ±2.0 μmol min^-1 kg^-1 in lean and obese subjects, respectively, P < 0.0001), glucose area, and serum triglycerides were positively related to fasting plasma leptin concentrations; none of these associations, however, was statistically significant after adjusting for BMI. During the clamp, plasma leptin concentrations remained constant in both lean and obese subjects. We conclude that neither insulin levels nor sensitivity relate to leptin levels independently of fat mass, and that leptin is not subject to acute (2 hours) regulation by insulin in lean or obese humans.     

Metabolic effects of troglitazone therapy in type 2 diabetic, obese, and lean normal subjects

OBJECTIVE: To characterize metabolic effects of troglitazone in type 2 diabetic, obese, and lean subjects, and examine the effects of troglitazone 2-3 weeks after discontinuation. RESEARCH DESIGN AND METHODS: Nine type 2 diabetic, nine obese, and nine lean subjects underwent baseline metabolic studies including an 8-h meal-tolerance test (MTT) and a 5-h glucose clamp. Subjects then received troglitazone (600 mg/day) for 12 weeks and subsequently had repeat metabolic studies. Diabetic subjects remained off hypoglycemic agents for 2-3 weeks and then underwent a 5-h glucose clamp. RESULTS: In diabetic subjects, fasting plasma glucose was reduced (P<0.05) and insulin-stimulated glucose disposal (Rd) was enhanced by treatment (P<0.02). The area under the MTT 8-h plasma glucose curve declined with therapy (P<0.001), and its change was positively correlated with the improvement in Rd (r = 0.75, P<0.05). There was also a positive correlation between the change in fasting hepatic glucose output (HGO) and the change in fasting plasma glucose with treatment (r = 0.92, P<0.001). Discontinuation of therapy for 2-3 weeks did not significantly affect fasting plasma glucose or insulin-stimulated glucose Rd. In obese subjects, insulin-stimulated glucose Rd improved with therapy (P<0.001), allowing for maintenance of euglycemia by lower plasma insulin concentrations (P<0.05). In lean subjects, an increase in fasting HGO (P<0.001) and glucose clearance (P<0.01) was observed. CONCLUSIONS: Troglitazone lowers fasting and postprandial plasma glucose in type 2 diabetes by affecting both fasting HGO and peripheral insulin sensitivity. Its effects are evident 2-3 weeks after discontinuation. In obese subjects, its insulin sensitizing effects suggest a role for its use in the primary prevention of type 2 diabetes.     

初诊2型糖尿病患者血清抵抗素与颈动脉内中膜厚度的关系

目的 探讨初诊2型糖尿病(T2DM)患者血清抵抗素水平与颈动脉内中膜厚度(CIMT)的关系.方法 选取新诊断的T2DM患者共122例,根据CIMT分为两组:CIMT正常组(CIMT<1.0 mm)70例和CIMT增厚组(CIMT≥1.0 mm,伴或不伴斑块)52例.采用酶联免疫吸附(ELISA)法检测血清抵抗素水平,并采用高频彩色多普勒超声测定CIMT.结果 与CIMT正常组相比,CIMT增厚组的血清抵抗素水平明显升高(P<0.05);Spearman相关性分析结果 显示,血清抵抗素水平与CIMT具有显著相关性(r=0.247,P=0.028),而且经校正性别、年龄、BMI后,血清抵抗素水平仍与CIMT显著相关(r=0.198,P=0.034);Logistic多因素回归分析结果 显示,血清抵抗素与CIMT增厚呈显著性关联(OR=1.39,95%CI:1.08～2.04,P=0.037).结论 血清抵抗素是T2DM患者CIMT增厚的独立相关因素.     

前蛋白转化酶枯草溶菌素9对革兰阴性菌脓毒症预后的评估价值

目的 探讨前蛋白转化酶枯草溶菌素9(PCSK9)对革兰阴性菌(G-)脓毒症患者病情严重程度和预后的评估价值.方法 选取湖南省脑科医院收治的90例G-脓毒症患者(G-脓毒症组)、40例单纯全身炎症反应综合征(SIRS)患者(单纯SIRS组)、38例革兰阳性菌(G+)脓毒症患者(G+脓毒症组)和40例体检健康人员(健康对照...     

2型糖尿病患者血清抵抗素水平的变化研究

目的探讨人血清抵抗素水平与2型糖尿病的关系.方法 2型糖尿病患者48例和正常对照组47例,采用酶联免疫分析法检测空腹血清抵抗素、胰岛素水平;同时测血糖、血压、血脂、身高、体重,计算腰围、臀围、体重指数、腰臀比值和胰岛素敏感指数、胰岛素抵抗性、胰岛B细胞功能.结果 2型糖尿病组的体重指数、甘油三酯、血清抵抗素水平显著高于正常对照组（P＜0.05）;相关分析显示血清抵抗素水平与体重指数、腰围、空腹胰岛素、血压呈正相关.在正常对照组,血清抵抗素水平与胰岛素敏感指数、胰岛素抵抗性、胰岛B细胞功能相关.而且血清抵抗素水平在糖尿病肥胖组显著高于糖尿病非肥胖组和正常对照组（P＜0.05）.结论 2型糖尿病患者血清抵抗素水平升高,与肥胖相关,血清抵抗素可能是联系肥胖和2型糖尿病的重要因素.     

Effects of cholestyramine on gallbladder and gastric emptying in obese and lean subjects

Abstract. Gallbladder stasis is frequent in obese subjects and may contribute to their increased risk for gallstone formation. The bile salt sequestrant cholestyramine acutely enhances postprandial gallbladder emptying in lean subjects, through dis-inhibition of a negative feedback between intraluminal bile salts and CCK release. In this study the effect of cholestyramine on both gallbladder and gastric antrum dynamics were studied by realtime ultrasonography in 12 obese and 15 lean subjects. For the acute study, on different days, subjects ingested a liquid meal (two egg yolks plus water 200 mL, 50 kJ) or a meal with 4g cholestyramine. Gallbladder emptying was impaired in obese patients who had significantly larger fasting gallbladder volume (39.4 ± 6.9 vs. 21.6 ± l.7mL, P <0.02), larger residual volume (12.3 ± 1.8 vs. 4.0 ± 0.5ml, P < 0.0006) and slower emptying time ( T /2: 33 ± 2 vs. 21 ± 2 min, P < 0.05) than lean subjects. Integrated antral emptying was also less in obese than lean subjects (5521 ± 578 vs. 7908 ± 491 % 120min^-1, P <0.02). Cholestyramine enhanced postprandial gallbladder emptying in both obese and lean subjects. Gastric emptying was delayed with cholestyramine in lean but not obese subjects. For the chronic study, after 1 month therapy with cholestyramine (4 g every 2 days), the motility tests were repeated in nine obese subjects. Gallbladder and gastric responses to a test meal, with or without cholestyramine, were preserved. We conclude that both gallbladder and antral emptying of a liquid test meal are impaired in obese subjects. Gallbladder emptying improves after acute administration of a low dose cholestyramine with test meal. This effect is sustained after 1 month treatment with a low dose of cholestyramine and does not interfere with gastric emptying of obese patients. Cholestyramine may improve gallbladder hypomotility in obese people.     

Enzyme-linked immunosorbent assay for circulating human resistin: resistin concentrations in normal subjects and patients with type 2 diabetes

BACKGROUND: Resistin is a recently identified adipocyte-secreted hormone in rodents, and has been proposed to serve as a link between obesity and insulin resistance. The aim of this study was to develop a sensitive enzyme-linked immunosorbent assay (ELISA) for human resistin and evaluate serum resistin concentrations in normal subjects and patients with type 2 diabetes. METHODS: Using ELISA developed by two polyclonal antibodies, resistin concentrations were measured in 90 patients with type 2 diabetes and compared to 74 healthy control subjects. RESULTS: This ELISA has high specificity and sensitivity over the concentration of range 0.5-100 ng/ml with good percentage recovery (97.1 +/- 4.7%) and reproducibility (within-day assay, CV = 4.8-8.6%; between-day assay, CV = 5.6-9.7%). The mean concentration of resistin in sera from type 2 diabetic patients was significantly higher than that in normal subjects (mean +/- S.E.: 20.8 +/- 0.7 vs. 14.9 +/- 0.5 ng/ml, p < 0.001). A moderate positive correlation was observed between serum resistin levels and body mass indices in both normal subjects (r = 0.412, p < 0.0003) and patients with type 2 diabetes (r = 0.395, p < 0.0001). CONCLUSIONS: Our ELISA will be useful to confirm the physiological and pathophysiological role of resistin in humans.     

Evaluation of plasmatic MMP-8, MMP-9, TIMP-1 and MPO levels in obese and lean women

ObjectivesTo compare the plasma concentrations of matrix metalloproteinase (MMP)-9, tissue inhibitor of MMP (TIMP)-1, MMP-8, and myeloperoxidase (MPO) for obese and lean women.Design and methodsWe recruited 30 lean and 36 obese women without comorbidities. The MMP-9, TIMP-1, and MMP-8 levels were measured using enzyme-linked immunosorbent assay (ELISA). MPO activity was assessed by a colorimetric assay.ResultsObese women had higher MMP-9 levels and MMP-9:TIMP-1 ratios than lean women. Conversely, the MMP-8 levels and MMP-8:TIMP-1 ratios in the obese women were significantly lower than those in the lean women despite neutrophil activation, which was assessed by MPO activity.ConclusionWe observed that MMP-9 and MMP-8 had distinct profiles, which suggested that these 2 enzymes play different roles in obesity.     

Lack of association of serum resistin levels with metabolic syndrome criteria in obese female patients

Background

As unclear data of resistin relation with metabolic syndrome has been published, we decide to investigate the association between metabolic syndrome and resistin levels in female obese subjects.

Subjects

A sample of 551 female obese subjects was analyzed. A complete nutritional and biochemical evaluation was performed.

Results

Levels of C reactive protein, weight, fat mass and waist circumference were higher in patients in the highest tertile group of resistin than the lowest and middle tertiles of resistin. In the multivariate analysis with metabolic syndrome presence/absence-, only fat mass remained as an independent predictor in the model. Resistin concentration increases 0.020 ng/ml (CI95%:0.006–0.038) for each kg of fat mass in female obese subjects.

Conclusion

Only fat mass was associated in an independent way. Serum resistin was not associated with the accumulation of MetS factors or the diagnosis of MetS in obese female subjects.     

肥胖人群脂联素、抵抗素和胰岛素抵抗水平的研究

目的 探讨肥胖患者血清脂联素、抵抗素和胰岛素抵抗水平的变化及意义.方法 分别测定106例肥胖者和107名健康对照者的体重指数(BMI)、腰围、臀围、空腹胰岛素、空腹血糖、血脂、脂联素和抵抗素水平,计算胰岛素抵抗指数(HOMA-IRI). 结果 肥胖者的体重指数(BMI)、体脂分布百分比(BF)、HOMA-IRI、抵抗素...     

肥胖人群脂联素、抵抗素和胰岛素抵抗水平的研究

目的探讨肥胖患者血清脂联素、抵抗素和胰岛素抵抗水平的变化及意义。方法分别测定106例肥胖者和107名健康对照者的体重指数(BMI)、腰围、臀围、空腹胰岛素、空腹血糖、血脂、脂联素和抵抗素水平,计算胰岛素抵抗指数(HOMA-IRI)。结果肥胖者的体重指数(BMI)、体脂分布百分比(BF)、HOMA-IRI、抵抗素、脂联素、总胆固醇(TC)、载脂蛋白B(apo B)与健康对照组比较,差异均有统计学意义(P<0.01、P<0.05)。脂联素和抵抗素均与BMI、BF和HOMA-IRI呈正相关([脂联素:相关系数(r)分别为0.439、0.236、0.398,P均<0.01;抵抗素:r分别为0.296(P<0.01)、0.175(P<0.05)、0.827(P<0.01)],抵抗素与腰臀比(WHR)呈正相关(r=0.169,P<0.05)。结论脂联素能较好地预测BMI和HOMA-IRI,抵抗素能较好地预测BMI。脂联素与抵抗素水平的变化可能导致肥胖和胰岛素抵抗,在向糖尿病的发生发展过程中起了一定作用。     

Plasma resistin levels are associated with homocysteine,endothelial activation,and nitrosative stress in obese youths

ObjectiveTo evaluate whether serum resistin levels are related to cardiovascular risk in obese children.Design and methodsCross-sectional study of 110 children (40 normal weight and 70 severely obese). Clinical and biochemical parameters, including lipid profile, fasting glucose and insulin, and homocysteine, were determined. The levels of adipokines (adiponectin, leptin, and resistin), markers of inflammation (high-sensitivity C-reactive protein (hs-CRP)), endothelial activation (serum concentrations of soluble intercellular and vascular cellular adhesion molecule-1 (sICAM-1, sVCAM-1)), and oxidative/nitrosative stress (malondialdehyde and urinary nitrate/nitrite) were measured.ResultsA partial correlation adjusted by gender, Tanner stage, and body mass index in obese children showed that resistin was significantly related to central obesity (p < 0.002), insulin resistance (p < 0.005), and homocysteine (p < 0.001). No association was found with other metabolic risk factors or hs-CRP levels. Malondialdehyde (p < 0.043) and sVCAM-1 (p < 0.002) were positively correlated whereas urinary nitrate/nitrite was negatively correlated (p < 0.007). In multiple regression analysis homocysteine, sVCAM-1, and urinary nitrate/nitrite remained independent determinants of resistin levels (R² adjusted = 0.347, p = 0.000).ConclusionsResistin could be considered as a promising marker for future cardiovascular disease in obese children.