Hongwen Zhou

Serum PCSK9 is associated with multiple metabolic factors in a large Han Chinese population

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that regulates cholesterol metabolism through low-density lipoprotein receptor (LDLR) degradation. Gain-of-function and loss-of-function mutations within PCSK9 gene lead to hypercholesterolemia or hypocholesterolemia respectively. Studies in the U.S. and Canada reported a correlation between multiple metabolic factors and circulating PCSK9 concentrations. However, there is no data available on circulating PCSK9 levels in Chinese. A sandwich ELISA assay was applied to measure serum PCSK9 levels in a Chinese population of 2719 adults from Nanjing district, China, which represents a large and uniform ethnic population of Han Chinese. Serum PCSK9 levels ranged from 12.85 to 222.50 ng/ml with a mean concentration of 69.35 ng/ml in this population. Serum PCSK9 levels were slightly higher in women than in men. Compared to premenopausal women, postmenopausal women had significantly higher PCSK9 levels. Serum PCSK9 levels were correlated with multiple metabolic variables including age, BMI, total cholesterol, LDL cholesterol, triglycerides, fasting blood glucose, systolic blood pressure (SP) and diastolic blood pressure (DP) in this population. After stepwise regression analysis, there was a significant positive association between serum PCSK9 levels and total cholesterol, triglycerides and SP in men. In women, there was a positive correlation between PCSK9 levels and total cholesterol, age and DP. Our study indicates that the serum PCSK9 level may be a biomarker of metabolic status and cardiovascular disease.

The effect of cholesteryl ester transfer protein on pancreatic beta cell dysfunction in mice

BackgroundCholesterol accumulation causes pancreatic beta cell lipotoxicity and dysfunction. Cholesteryl ester transfer protein (CETP) plays an important role in blood lipid homeostasis. However, its role in tissue lipid metabolism remains unclear. We hypothesized that plasma CETP impact cholesterol homeostasis in the beta cells, thus damaging their functions.MethodsThe adipose tissue-specific CETP expression transgenic (aP2-CETPTg) mice, characterized by high CETP levels in the circulation, were used in this study. Pancreatic islet cholesterol and beta cell function were assessed in mice. We further measured mRNA levels of the genes involved in beta cell proliferation and differentiation, inflammation and cholesterol metabolism. TUNEL assay was applied to investigate beta cell apoptosis in islets.ResultsThe aP2-CETPTg mice exhibited glucose intolerance, lower plasma insulin concentrations but increased insulin sensitivity compared with wild type mice. In addition, glucose-stimulated insulin secretion from isolated pancreatic islets significantly decreased, and free cholesterol significantly increased. Moreover, the number and size of islets from aP2-CETPTg mice were significantly decreased. Genes involved in beta cell proliferation, such as Pdx1 and BETA2, were down-regulated; genes involved in inflammation and ER stress, such as IL-1β, CHOP, and Xbp1 were up-regulated, in line with an increase of beta cell apoptosis.ConclusionsPlasma CETP causes free cholesterol accumulation in islets which could contribute to beta cell dysfunction. Thus, CETP inhibition could be a novel protective strategy for dyslipidemia related to diabetes and obese.

The Effects of Estrogen on Serum Level and Hepatocyte Expression of PCSK9

OBJECTIVE We previously reported that serum PCSK9 levels are higher in postmenopausal women than in premenopausal women in a Han Chinese population. Whether this difference is related to estrogen has not been well-characterized. This study aims to examine if the alteration in estrogen level is responsible for the changes of serum PCSK9 concentration. MATERIALS/METHODS A sandwich ELISA assay was used to measure serum PCSK9 levels in 727 healthy women aged from 26 to 85 years old. Anthropometric and biochemical examination of parameters such as estrogen and serum lipids was also performed for these individuals. Next, we measured serum PCSK9 and estrogen levels of 30 healthy fertile women (24-26 years old) in their menstrual cycles and analyzed the correlation between serum PCSK9 level and estrogen concentration. Moreover, cell culture studies were carried out to examine if estrogen at physiological and non-physiological concentrations regulates hepatocyte PCSK9 expression. RESULTS Serum PCSK9 concentrations were significantly increased with aging. Aged group had higher serum PCSK9 levels than the middle aged group and the young group (60.29±28.47 vs 71.38±34.22 vs 83.81±33.50 ng/ml). Serum PCSK9 levels were positively correlated with age, BMI, serum total cholesterol and LDL-cholesterol (P<0.01), but not correlated with estrogen levels. There was no significantly difference of PCSK9 levels between the lower and the upper estradiol (E2) tertiles in the 727 women. There was either no significant difference in PCSK9 levels during the menstrual, ovulatory, luteal phases in the 30 healthy fertile women. Cell culture studies showed that 17β-estradiol at physiological concentrations did not significantly alter PCSK9 expression in human hepatocytes. CONCLUSION The serum PCSK9 levels were higher in postmenopausal women than those in pre-menopausal women. However, the difference in serum PCSK9 levels between postmenopausal and premenopausal woman appeared to be independent of estrogen status, and estrogen at physiological concentrations does not affect human hepatocyte PCSK9 expression.

Association of Serum Uric Acid with 2-Hour Postload Glucose in Chinese with Impaired Fasting Plasma Glucose and/or HbA1c

Objective To examine whether serum uric acid (SUA) is associated with 2-hour postload glucose (2-h PG) in Chinese with impaired fasting plasma glucose (IFG) and/or HbA1c (IA1C). Research Design and Methods Anthropometric and biochemical examinations, such as SUA concentration, were performed in 3763 individuals from all the villages in Baqiao County, China. A 75-g oral glucose tolerance test (OGTT) was conducted in 1197 Chinese with prediabetes as having IFG (110≤ fasting plasma glucose [FPG] <126 mg/dl and HbA1c <6.5%), IA1C (5.7% ≤ HbA1c <6.5% and FPG <126 mg/dl), or both. Results The present study included 1197 participants with IFG and/or IA1C (mean age 56.5±10.3 years; 50.6% men). In multivariate linear regression, after adjustment for gender, age, smoking and drinking, body mass index (BMI), systolic and diastolic blood pressure (SBP, DBP), lipid profiles, logarithmic transformed C-reactive protein (log-CRP), estimated glomerular filtration rate (e-GFR), FPG and HbA1c, with a 1-mg/dl increment of SUA, 2-h PG increased by 5.04±0.72 (P<0.001), 3.06±1.08 (P = 0.001), 5.40±1.26 (P<0.001), and 2.34±2.16 mg/dl (P = 0.056) in all participants, in participants with normal glucose tolerance (NGT), with impaired glucose tolerance (IGT), and with 2-h newly diagnosed diabetes (2-h NDM, with 2-h PG ≥200 mg/dl), respectively. In both men and women, 2-h PG increased progressively and significantly from the lower to the upper SUA tertiles (P<0.001). Moreover, in multivariate logistic regression, 1-standard deviation (SD; 1.53 mg/dl) increment of SUA was significantly associated with a 36% higher risk for 2-h NDM (Odds ratio [CI 95%]: 1.36 [1.09–1.99]; P = 0.03). Conclusions SUA is significantly associated with 2-h PG in Chinese with IFG and/or IA1C.

Human cholesteryl ester transfer protein enhances insulin-mediated glucose uptake in adipocytes

AIMS Adipose tissue plays an important role in the pathogenesis of insulin resistance, obesity, and Type-2 diabetes. Human adipocytes express abundant cholesteryl ester transfer protein (CETP). However, the function and role of CETP in regulating lipoprotein metabolism are mostly unknown. In this study, we examined whether CETP affected the insulin-mediated responses in adipocytes. MAIN METHODS Because mouse 3T3-L1 preadipocytes do not express CETP, we established a stable cell line expressing human CETP by transfecting the cells with pcDNA3.1/human CETP. We used a standard approach to differentiate the cells into mature adipocytes, and we examined the cholesterol balance and insulin responses. KEY FINDINGS The human CETP stable cell line expressed stable levels of CETP without affecting the expression of either peroxisome proliferator-activated receptor-gamma (PPARγ) or glucose transporter-4 (GLUT4) throughout cell differentiation. CETP expression significantly increased the level of both total and free cholesterol in the mature adipocytes. Upon insulin stimulation, CETP expressing cells had significantly higher protein kinase B (Akt) phosphorylation and 2-(3)H-deoxyglucose uptake, as compared with 3T3-L1 cells and cells transfected with control vector. SIGNIFICANCE Human CETP expression increased cellular cholesterol levels and enhanced insulin-stimulated Akt phosphorylation and glucose uptake in adipocytes. Thus, CETP may modulate glucose metabolism and insulin action in addition to its effects on lipoprotein metabolism.

Relationship of Serum Betatrophin with Nonalcoholic Fatty Liver in a Chinese Population

Objective This study aimed to investigate the association of serum betatrophin with the status and progression of nonalcoholic fatty liver disease (NAFLD). Methods A total of 249 subjects who received ultrasonic examination of liver fat content (LFC) were recruited. Anthropometric and biochemical examinations were performed. Serum betatrophin was measured by ELISA. Results Compared with control group, serum betatrophin significantly increased in NAFLD group (P < 0.05). There was significant difference in serum betatrophin among control, low liver fat content (LLFC), and high liver fat content (HLFC) groups (P < 0.01). After adjustment for gender, age, BMI, FPG and HbA1c, the betatrophin positively correlated with LFC (r = 0.185, P < 0.01) and TG (r = 0.195, P < 0.01). Stepwise multiple regression analysis indicated serum betatrophin was independently related to LFC (P < 0.05). Multivariate logistic regression analysis revealed subjects in the highest tertile of serum betatrophin had higher odds of having NAFLD after adjustment for traditional NAFLD risk factors (OR = 2.88, 95%CI: 1.15–7.19) (P<0.05). Conclusion Serum betatrophin is an independent risk factor for NAFLD and potential non-invasive marker for its progression. Serum betatrophin may be helpful for the early diagnosis of NAFLD and improvement of its prognosis.

Islet neogenesis-associated protein-related pentadecapeptide improves the function of allograft after islets transplantation

Abstract Objective: To investigate the protective effects of a pentadecapeptide of islet neogenesis-associated protein (INGAP-PP) on transplanted islets function. Methods: Islets were cultured in RPMI 1640 with or without INGAP-PP (10 μg/mL). After 24 h, the viability of the islets and glucose-stimulated insulin secretion (GSIS) were measured. The expression of genes B cell lymphoma/lewkmia2 (Bcl2) and protein kinase B (Akt) were detected by RT-PCR assay. Healthy rats transplanted with islets under the renal capsule were injected with INGAP-PP or saline in in the abdominal cavity. One week later, the expression of insulin nestin pancreatic (nestin) and duodenal homeobox 1 (Pdx1) and proliferating cell nuclear antigen (PCNA) in the transplanted islets were observed by immunohistochemistry. After that they were transplanted to the renal capsule of diabetic rats. Results: 1. The amount of insulin released was increased in co-cultured group in concentration of 16.7 mmol/L glucose, which was (185.00±20.01 μU/mL) vs. (58.67±17.03 μU/mL). Gene expression of Bcl2 (0.61±0.22 vs. 0.50±0.21) and Akt (1.12±0.19 vs. 0.94±0.16) in the co-cultured group were increased compared with that of the control group. Islets viability in the co-cultured group (683.9±7.08) was higher than that of control group (547.9±8.02). The stimulating index (SI) of the co-cultured group was also higher than that of the control group. 2. The group of islets under the renal capsule which were co-cultured and injected with INGAP-PP had the more nestin expression in the islets. Conclusions: The function of islet can be protected by the INGAP-PP, which will promote the viability, differentiation and regeneration of islet before transplantation. And it will be beneficial for the function of allograft after islets transplantation.

Integrated DNA-based/biochemical screening for early diagnosis of multiple endocrine neoplasia type 2A (MEN2A).

Multiple endocrine neoplasia type 2A (MEN2A), a subtype of MEN2, is characterized by medullary thyroid cancer, pheochromocytoma, and primary hyperparathyroidism. A Han Chinese pedigree with MEN2A was investigated following confirmation of the probands diagnosis by pathological findings and DNA/biochemical screening. DNA samples from 4 other family members were collected and exon 5, 8, 10, 11, 13, 16 and 18 of the RET proto-oncogene were sequenced and then analyzed. A missense mutation of TGG (Trp) to TGC (Cys) at codon 634 (the classic MEN2A mutation) in exon 11 of the RET gene was detected in 3 family members, including the proband. Sequencing data were compared with the human gene mutation database. Elevated serum calcitonin level was detected initially; medullary thyroid carcinoma was revealed in the 3 cases and adrenal pheochromocytoma was also found in the proband. Elective operations were successfully performed on the adrenal and thyroid glands because of pheochromocytoma and medullary thyroid carcinoma. Our case study confirms that integrated DNA-based/biochemical screening is crucial for early diagnosis of MEN2A and is helpful in the screening of their relatives. In addition, DNA-based screening may occasionally uncover a previously unknown RET sequence.