Laicheng Wang

A novel role for thyroid-stimulating hormone: Up-regulation of hepatic 3-hydroxy-3-methyl-glutaryl-coenzyme a reductase expression through the cyclic adenosine monophosphate/protein kinase A/cyclic adenosine monophosphate–responsive element binding protein pathway†

Elevated thyroid‐stimulating hormone (TSH) and hypercholesterolemia commonly coexist, as typically seen in hypothyroidism, but there is no known mechanism directly linking the two. Here, we demonstrated that in liver cells, TSH promoted the expression of 3‐hydroxy‐3‐methyl‐glutaryl coenzyme A reductase (HMGCR), a rate‐limiting enzyme in cholesterol synthesis, by acting on the TSH receptor in hepatocyte membranes and stimulating the cyclic adenosine monophosphate / protein kinase A / cyclic adenosine monophosphate–responsive element binding protein (cAMP/PKA/CREB) signaling system. In thyroidectomized rats, the production of endogenous thyroid hormone was eliminated and endogenous TSH was suppressed through pituitary suppression with constant administration of exogenous thyroid hormone, and hepatic HMGCR expression was increased by administration of exogenous TSH. These results suggested that TSH could up‐regulate hepatic HMGCR expression, which indicated a potential mechanism for hypercholesterolemia involving direct action of TSH on the liver. (HEPATOLOGY 2010)

Polymorphisms of KIRs Gene and HLA-C Alleles in Patients with Ankylosing Spondylitis: Possible Association with Susceptibility to the Disease

IntroductionAn emerging body of evidence is accumulating to suggest that killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) class I ligands contribute to the pathogenesis of diverse kinds of autoimmune diseases. However, the functional effects of their polymorphism remain largely unknown to date. Thus, the present study was undertaken to determine the association of the polymorphisms KIRs gene and HLA-C alleles with the susceptibility to ankylosing spondylitis (AS) by means of polymerase chain reaction/sequence-specific primers for genotyping KIRs from genomic DNA of 119 patients with AS together with 128 healthy donors as a control group.Results and DiscussionWe found that the frequencies of KIR3DS1 and KIR2DL5 were statistically significantly higher in the patient group than those in the control group (P = 0.016 and P = 0.003, respectively). Meanwhile, the percentage of patients, who were carrying two or more of the activating KIRs, was higher than that of control group. With respect to HLA-C alleles, individuals with AS showed an increased frequency of HLA-Cw02. If HLA-C was divided into group 1 or group 2 based on whether there was an asparagine or lysine present at position 80 of the alpha-chain, HLA-C group 2 was more common in subjects with AS compared to control subjects. The genotype 2DS1+/HLA-C lys80+ was more common in subjects with AS. Moreover, the CD69 expression, a NK activation marker, remarkably increased in patient with AS.ConclusionIn conclusions, this study suggests that KIR3DS1 may severe as AS susceptive genes to trigger continuous injury of arthrosis. The imbalance of activating and inhibitory KIR as well as HLA-C group 1 and group 2 may be the key factor, which influences the pathogenesis of AS. Moreover, KIR2DS1 might associate with the susceptibility of AS by influencing NK cell activity once group 2 HLA-C ligands are present.

Presence of thyrotropin receptor in hepatocytes: not a case of illegitimate transcription

The function of thyrotropin (TSH) in the thyroid gland is mediated by thyrotropin receptor (TSHR). In addition to the thyroid, TSHR expression has been described in some non‐thyroidal tissues, although it is uncertain whether TSHR is present in hepatocytes. One study has reported hepatic expression of TSHR mRNA, but this was considered to be because of illegitimate transcription, and there has not been a study investigating its protein expression and function in hepatocytes. Here, we examined the expression of TSHR in human and rat liver tissues, as well as human normal hepatocyte cell line L‐02. Our results demonstrated that hepatic TSHR mRNA could be detected and had the same sequence as that of thyroid‐derived mRNA. TSHR protein was also expressed and mainly located in the hepatocyte cell membrane. Moreover, bovine TSH and immunoglobulin from sera of patients with Graves’ disease stimulated cAMP production in these cells. Taken together, these data show that TSHR is present and functional in hepatocytes, and this expression is not a case of illegitimate transcription. Given the pivotal role of the liver in body metabolism and many human diseases, our findings provide important implications for a potentially novel physiopathological role of TSH via acting on the TSHR in hepatocytes besides its classical role in regulating the thyroid function.

Association of +45G15G(T/G) and +276(G/T) polymorphisms in the ADIPOQ gene with polycystic ovary syndrome among Han Chinese women.

OBJECTIVE Polycystic ovary syndrome (PCOS) is frequently associated with insulin resistance (IR) and consequently with increased risk of metabolic disorders. Adiponectin is the most abundant adipocytokine and may play a role in the regulation of insulin sensitivity and IR in PCOS. The aim of the present study was to evaluate the genetic influence of the adiponectin (ADIPOQ) gene polymorphisms in the development of PCOS among Han Chinese women. METHODS Two single nucleotide polymorphisms (SNPs),+45G15G(T/G) and +276(G/T), in the ADIPOQ gene were genotyped in 120 patients with PCOS and 120 healthy control subjects. All of them were Han Chinese women. RESULTS Both SNPs were found to be significantly associated with PCOS (P=0.021, odds ratios=1.629, 95% confidence intervals: 1.074-2.469 and P=0.015, 1.576, 1.091-2.279 respectively). In SNP +276(G/T), the allele G was found to be significantly associated with increased fasting insulin levels, homeostasis model assessment to assess IR index, and area under the curve glucose levels, but decreased glucose and insulin ratio in the PCOS patients. Furthermore, the patients carrying genotypes G/G and G/T had significantly decreased levels of serum adiponectin (6.16+/-3.18 plus 5.93+/-3.23 vs 8.96+/-3.21 microg/ml, P=0.030) compared with the patients with genotype T/T. CONCLUSIONS The present study provides evidence that SNPs +45G15G(T/G) and +276(G/T) in the ADIPOQ gene are associated with PCOS in Han Chinese women. SNP +276(G/T) may contribute to an impact of insulin levels and IR, which are implicated in the susceptibility for PCOS.

Molecular characterization and expression of the antimicrobial peptide defensin from the housefly (Musca domestica)

Abstract.A 430-bp cDNA encoding the insect antimicrobial peptide defensin was cloned from the housefly, and designated Musca domestica defensin (Mdde). The open reading frame of the cDNA encoded a 92-amino acid peptide with an N-terminal signal sequence followed by a propeptide that is processed by cleavage to a 40-amino acid mature peptide. Northern analysis and in situ hybridization identified the corresponding mRNA in the fat body of bacterially challenged houseflies and in the epidermis of the body wall of naive and challenged houseflies. The Gram-negative bacterium (Escherichia coli) is a strong inducer of the gene. By RT-PCR, Mdde mRNA was also detected in naive and challenged insects. These findings suggest that the defensin gene is constitutively expressed in the epidermis of the housefly body wall. The predicted mature form of Mdde was expressed as a recombinant peptide in E. coli and Pichia pastoris. The recombinant Mdde expressed in Pichia was active against Gram-positive and some Gram-negative bacteria.

Polymorphisms of KIR Gene and HLA-C Alleles: Possible Association with Susceptibility to HLA-B27-Positive Patients with Ankylosing Spondylitis

AbstractAccumulating evidences indicate that killer cell immunoglobulin-like receptors (KIRs) and their corresponding specific HLA-C ligands contribute to the pathogenesis of multiple autoimmune diseases via the modulation of natural killer (NK) cell and T cell functions. The present study was performed to investigate whether the polymorphism of KIR genes and HLA ligands associates with the susceptibility of ankylosing spondylitis (AS). Previous studies have demonstrated a strong association between HLA-B27 gene and the pathogenesis of AS. In this study, 115 unrelated HLA-B27-positive AS patients and 119 HLA-B27-positive healthy controls were recruited. Polymerase chain reaction using sequence-specific primers was used to determine the genotypes of KIR genes and HLA-C alleles. The results showed that the frequencies of KIR2DL1 and KIR2DL5 were significantly higher in the AS patient group than those in the control group (p = 0.012 and p = 0.009, respectively). Meanwhile, individuals with AS showed an increased frequency of HLA-Cw*08 (p = 0.001, pc  = 0.008) compared with that in controls. Our findings indicate that with the genetic background of HLA-B27, variation at the KIRs and their corresponding specific HLA-C ligands may influence the ability of NK cells and T cells to recognize and lyse targets in immune responses, which thereby contributes to pathogenesis of AS.

Inhibitory KIR and specific HLA-C gene combinations confer susceptibility to or protection against chronic hepatitis B.

Antiviral activity of natural killer (NK) cells is regulated partially through inhibitory and activating killer cell immunoglobulin-like receptors (KIR) interacting with human leukocyte antigen C (HLA-C) ligands. The highly polymorphic nature of HLA-C and KIR genes endows individuals with diverse HLA-C/KIR combinations, which may confer susceptibility to or protection against a certain challenge. We analyzed the genes encoding KIR receptors and HLA-C ligands and HLA-C/KIR combinations in patients with chronic hepatitis B and healthy subjects. We found that inhibitory receptor KIR2DL1 in combination with HLA-C2 ligand confers susceptibility to chronic hepatitis B (CHB), whereas inhibitory receptor KIR2DL3 or KIR2DL3 homozygote in the presence of HLA-C1C1 genotype shows protection against CHB. Our data reveal that inhibitory NK cell interactions are important in determining antiviral immunity and that distinct affinity inhibitory responses will exert different impact on the development of CHB.

Melatonin Receptor 1A Gene Polymorphism Associated with Polycystic Ovary Syndrome

Background/Aims: Melatonin receptor 1A (MTNR1A) gene is a regulator of circadian rhythms and reproductive processes. The MTNR1A gene is also a potential candidate gene of polycystic ovary syndrome (PCOS). The aim of the present study was to determine whether or not the MTNR1A gene polymorphism is associated with a predisposition to PCOS. Methods: The single nucleotide polymorphism (SNP) rs2119882 in the MTNR1A gene was detected in 482 patients with PCOS and 522 healthy Chinese Han women. Subsequently, the association of MTNR1A gene variants with plasma glucose, insulin levels during oral glucose tolerance tests (OGTTs) and hormone levels was investigated. Results: The frequencies of genotypes and allelotypes of SNP rs2119882 differed significantly between PCOS cases and healthy controls (p < 0.001 and p = 0.002, respectively). SNP rs2119882 was associated with higher fasting plasma glucose concentrations (p = 0.021) and OGTT-induced insulin release at 0, 30, 60, and 120 min (all p < 0.05) in PCOS cases, as well as an increased homeostasis model assessment for insulin resistance (p = 0.005). Conclusion: SNP rs2119882 is associated with PCOS.

Thyroid-stimulating hormone regulates hepatic bile acid homeostasis via SREBP-2/HNF-4α/CYP7A1 axis

BACKGROUND & AIMS Bile acids (BAs) play a crucial role in dietary fat digestion and in the regulation of lipid, glucose, and energy metabolism. Thyroid-stimulating hormone (TSH) is a hormone produced by the anterior pituitary gland that directly regulates several metabolic pathways. However, the impact of TSH on BA homeostasis remains largely unknown. METHODS We analyzed serum BA and TSH levels in healthy volunteers under strict control of caloric intake. Thyroidectomized rats were administered thyroxine and injected with different doses of TSH. Tshr(-/-) mice were supplemented with thyroxine, and C57BL/6 mice were injected with Tshr-siRNA via the tail vein. The serum BA levels, BA pool size, and fecal BA excretion rate were measured. The regulation of SREBP-2, HNF-4α, and CYP7A1 by TSH were analyzed using luciferase reporter, RNAi, EMSA, and CHIP assays. RESULTS A negative correlation was observed between the serum levels of TSH and the serum BA levels in healthy volunteers. TSH administration led to a decrease in BA content and CYP7A1 activity in thyroidectomized rats supplemented with thyroxine. When Tshr was silenced in mice, the BA pool size, fecal BA excretion rate, and serum BA levels all increased. Additionally, we found that HNF-4α acts as a critical molecule through which TSH represses CYP7A1 activity. We further confirmed that the accumulation of mature SREBP-2 protein could impair the capacity of nuclear HNF-4α to bind to the CYP7A1 promoter, a mechanism that appears to mediate the effects of TSH. CONCLUSIONS TSH represses hepatic BA synthesis via a SREBP-2/HNF-4α/CYP7A1 signaling pathway. This finding strongly supports the notion that TSH is an important pathophysiological regulator of liver BA homeostasis independently of thyroid hormones.

Thyrotropin increases hepatic triglyceride content through upregulation of SREBP-1c activity

BACKGROUND & AIMS Hallmarks of non-alcoholic fatty liver disease (NAFLD) are increased triglyceride accumulation within hepatocytes. The prevalence of NAFLD increases steadily with increasing thyrotropin (TSH) levels. However, the underlying mechanisms are largely unknown. Here, we focused on exploring the effect and mechanism of TSH on the hepatic triglyceride content. METHODS As the function of TSH is mediated through the TSH receptor (TSHR), Tshr(-/-) mice (supplemented with thyroxine) were used. Liver steatosis and triglyceride content were analysed in Tshr(-/-) and Tshr(+/+) mice fed a high-fat or normal chow diet, as well as in Srebp-1c(-/-) and Tshr(-/-)Srebp-1c(-/-) mice. The expression levels of proteins and genes involved in liver triglyceride metabolism was measured. RESULTS Compared with control littermates, the high-fat diet induced a relatively low degree of liver steatosis in Tshr(-/-) mice. Even under chow diet, hepatic triglyceride content was decreased in Tshr(-/-) mice. TSH caused concentration- and time-dependent effects on intracellular triglyceride contents in hepatocytes in vitro. The activity of SREBP-1c, a key regulator involved in triglyceride metabolism and in the pathogenesis of NAFLD, was significantly lower in Tshr(-/-) mice. In Tshr(-/-)Srebp-1c(-/-) mice, the liver triglyceride content showed no significant difference compared with Tshr(+/+)Srebp-1c(-/-) mice. When mice were injected with forskolin (cAMP activator), H89 (inhibitor of PKA) or AICAR (AMPK activator), or HeG2 cells received MK886 (PPARα inhibitor), triglyceride contents presented in a manner dependent on SREBP-1c activity. The mechanism, underlying TSH-induced liver triglyceride accumulation, involved that TSH, through its receptor TSHR, triggered hepatic SREBP-1c activity via the cAMP/PKA/PPARα pathway associated with decreased AMPK, which further increased the expression of genes associated with lipogenesis. CONCLUSIONS TSH increased the hepatic triglyceride content, indicating an essential role for TSH in the pathogenesis of NAFLD.