Biomedical subjects

Hong Lan

Publications and source records attributed to Hong Lan.

14 recordsLinked to original sources

PubMed2006

Cholestasis and hypercholesterolemia in SCD1-deficient mice fed a low-fat, high-carbohydrate diet.

Stearoyl-coenzyme A desaturase 1-deficient (SCD1(-/-)) mice have impaired MUFA synthesis. When maintained on a very low-fat (VLF) diet, SCD1(-/-) mice developed severe hypercholesterolemia, characterized by an increase in apolipoprotein B (apoB)-containing lipoproteins and the appearance of lipoprotein X. The rate of LDL clearance was decreased in VLF SCD1(-/-) mice relative to VLF SCD1(+/+) mice, indicating that reduced apoB-containing lipoprotein clearance contributed to the hypercholesterolemia. Additionally, HDL-cholesterol was dramatically reduced in these mice. The presence of increased plasma bile acids, bilirubin, and aminotransferases in the VLF SCD1(-/-) mice is indicative of cholestasis. Supplementation of the VLF diet with MUFA- and PUFA-rich canola oil, but not saturated fat-rich hydrogenated coconut oil, prevented these plasma phenotypes. However, dietary oleate was not as effective as canola oil in reducing LDL-cholesterol, signifying a role for dietary PUFA deficiency in the development of this phenotype. These results indicate that the lack of SCD1 results in an increased requirement for dietary unsaturated fat to compensate for impaired MUFA synthesis and to prevent hypercholesterolemia and hepatic dysfunction. Therefore, endogenous MUFA synthesis is essential during dietary unsaturated fat insufficiency and influences the dietary requirement of PUFA.

Animals↗

PubMed2006

Positional cloning of Sorcs1, a type 2 diabetes quantitative trait locus.

We previously mapped the type 2 diabetes mellitus-2 locus (T2dm2), which affects fasting insulin levels, to distal chromosome 19 in a leptin-deficient obese F2 intercross derived from C57BL/6 (B6) and BTBR T+ tf/J (BTBR) mice. Introgression of a 7-Mb segment of the B6 chromosome 19 into the BTBR background (strain 1339A) replicated the reduced insulin linked to T2dm2. The 1339A mice have markedly impaired insulin secretion in vivo and disrupted islet morphology. We used subcongenic strains derived from 1339A to localize the T2dm2 quantitative trait locus (QTL) to a 242-kb segment comprising the promoter, first exon and most of the first intron of the Sorcs1 gene. This was the only gene in the 1339A strain for which we detected amino acid substitutions and expression level differences between mice carrying B6 and BTBR alleles of this insert, thereby identifying variation within the Sorcs1 gene as underlying the phenotype associated with the T2dm2 locus. SorCS1 binds platelet-derived growth factor, a growth factor crucial for pericyte recruitment to the microvasculature, and may thus have a role in expanding or maintaining the islet vasculature. Our identification of the Sorcs1 gene provides insight into the pathway underlying the pathophysiology of obesity-induced type 2 diabetes mellitus.

Animals↗

PubMed2006

Combined expression trait correlations and expression quantitative trait locus mapping.

Coordinated regulation of gene expression levels across a series of experimental conditions provides valuable information about the functions of correlated transcripts. The consideration of gene expression correlation over a time or tissue dimension has proved valuable in predicting gene function. Here, we consider correlations over a genetic dimension. In addition to identifying coregulated genes, the genetic dimension also supplies us with information about the genomic locations of putative regulatory loci. We calculated correlations among approximately 45,000 expression traits derived from 60 individuals in an F2 sample segregating for obesity and diabetes. By combining the correlation results with linkage mapping information, we were able to identify regulatory networks, make functional predictions for uncharacterized genes, and characterize novel members of known pathways. We found evidence of coordinate regulation of 174 G protein-coupled receptor protein signaling pathway expression traits. Of the 174 traits, 50 had their major LOD peak within 10 cM of a locus on Chromosome 2, and 81 others had a secondary peak in this region. We also characterized a Riken cDNA clone that showed strong correlation with stearoyl-CoA desaturase 1 expression. Experimental validation confirmed that this clone is involved in the regulation of lipid metabolism. We conclude that trait correlation combined with linkage mapping can reveal regulatory networks that would otherwise be missed if we studied only mRNA traits with statistically significant linkages in this small cross. The combined analysis is more sensitive compared with linkage mapping alone.

Animals↗

PubMed2004

Increased insulin translation from an insulin splice-variant overexpressed in diabetes, obesity, and insulin resistance.

Type 2 diabetes occurs when pancreatic beta-cells become unable to compensate for the underlying insulin resistance. Insulin secretion requires beta-cell insulin stores to be replenished by insulin biosynthesis, which is mainly regulated at the translational level. Such translational regulation often involves the 5'-untranslated region. Recently, we identified a human insulin splice-variant (SPV) altering only the 5'-untranslated region and conferring increased translation efficiency. We now describe a mouse SPV (mSPV) that is found in the cytoplasm and exhibits increased translation efficiency resulting in more normal (prepro)insulin protein per RNA. The RNA stability of mSPV is not increased, but the predicted secondary RNA structure is altered, which may facilitate translation. To determine the role of mSPV in insulin resistance and diabetes, mSPV expression was measured by quantitative real-time RT-PCR in islets from three diabetic and/or insulin-resistant, obese and nonobese, mouse models (BTBRob/ob, C57BL/6ob/ob, and C57BL/6azip). Interestingly, mSPV expression was significantly higher in all diabetic/insulin-resistant mice compared with wild-type littermates and was dramatically induced in primary mouse islets incubated at high glucose. This raises the possibility that the mSPV may represent a compensatory beta-cell mechanism to enhance insulin biosynthesis when insulin requirements are elevated by hyperglycemia/insulin resistance.

5' Untranslated Regions↗

PubMed2004

Selective phenotyping for increased efficiency in genetic mapping studies.

The power of a genetic mapping study depends on the heritability of the trait, the number of individuals included in the analysis, and the genetic dissimilarity among them. In experiments that involve microarrays or other complex physiological assays, phenotyping can be expensive and time-consuming and may impose limits on the sample size. A random selection of individuals may not provide sufficient power to detect linkage until a large sample size is reached. We present an algorithm for selecting a subset of individuals solely on the basis of genotype data that can achieve substantial improvements in sensitivity compared to a random sample of the same size. The selective phenotyping method involves preferentially selecting individuals to maximize their genotypic dissimilarity. Selective phenotyping is most effective when prior knowledge of genetic architecture allows us to focus on specific genetic regions. However, it can also provide modest improvements in efficiency when applied on a whole-genome basis. Importantly, selective phenotyping does not reduce the efficiency of mapping as compared to a random sample in regions that are not considered in the selection process. In contrast to selective genotyping, inferences based solely on a selectively phenotyped population of individuals are representative of the whole population. The substantial improvement introduced by selective phenotyping is particularly useful when phenotyping is difficult or costly and thus limits the sample size in a genetic mapping study.

Animals↗

PubMed2004

Distinguishing covariation from causation in diabetes: a lesson from the protein disulfide isomerase mRNA abundance trait.

Protein disulfide isomerase (Pdi) is reported to be an insulin-regulated gene whose expression level is increased in the livers of rats with streptozotocin-induced diabetes. We found that Pdi mRNA is approximately 20-fold more abundant in the diabetes-susceptible BTBR mouse strain relative to the diabetes-resistant C56BL/6 (B6) strain. A genetic analysis was carried out to determine whether there is a causal relationship between elevated Pdi expression and diabetes phenotype in BTBR-ob/ob mice. We mapped Pdi mRNA abundance as a quantitative trait in 108 (B6 x BTBR)F(2)-ob/ob mice segregating for diabetes. We detected a single linkage at the telomeric end of chromosome 11, where the Pdi gene itself resides (logarithm of odds score >30.0). No linkage was detected for the Pdi mRNA trait in the regions where we have previously identified quantitative trait loci for diabetes traits. Sequencing of the Pdi promoter and cDNA revealed several single nucleotide polymorphisms between these two mouse strains. We conclude that in our experimental model, elevated Pdi expression is cis regulated and is not linked to diabetes susceptibility. Genetic analysis is a powerful tool for distinguishing covariation from causation in expression array studies of disease traits.

Animals↗

PubMed2004

Identification of major quantitative trait loci controlling body weight variation in ob/ob mice.

The adipocyte hormone leptin constitutes an important component of the regulation of energy homeostasis; leptin-deficient animals, such as obese mice, are strikingly overweight. The seemingly uninhibited weight gain in obese mice belies the fact that control of energy homeostasis remains under precise, heritably modifiable control. Herein, we report large, heritable differences in body weight and food intake between BTBR-ob/ob and B6-ob/ob mice. We have identified two loci, called modifier of obese (Moo1 and Moo2), that explain the majority of the heritable variance in (BTBR x B6) F(2)-ob/ob mice. Using interval-specific congenic mouse lines, we mapped Moo1 to an 8-Mb segment of chromosome 2 and demonstrated that Moo1 exerts its effects primarily by regulating total fat mass. Although null alleles of leptin are rare, the majority of overweight adults are leptin resistant, suggesting that leptin-independent pathways, such as those studied here, are important regulators of energy homeostasis. Thus, the identification of these loci may provide important new insights into the pathogenesis of human obesity.

Aging↗

PubMed2004

Allitridi induces apoptosis by affecting Bcl-2 expression and caspase-3 activity in human gastric cancer cells.

AIM: To investigate the mechanism of allitridi-induced apoptosis in human gastric cancer cell line BGC823. METHODS: Growth inhibition by allitridi was analyzed using cell growth curve and MTT assay. Apoptotic cells were detected using staining with Hoechst 33342, and confirmed by flow cytometric analysis and DNA fragmentation analysis. The protein expression affected by allitridi was determined using Western blot. The activity of caspase-3 was measured using a fluorescence assay. RESULTS: Allitridi induced apoptosis, and then inhibited cells proliferation in human gastric cancer cell line BGC823. The protein level of Bcl-2 was decreased dramatically, while Bax and p53 were not significantly affected by allitridi. The expression and activity of caspase-3 started to increase after allitridi treatment for 72 h. CONCLUSION: Allitridi induced apoptosis through down-regulation of Bcl-2, and increased caspase-3 expression and its activity.

Adenocarcinoma↗

PubMed2003

Physical evidence of Mcs5, a QTL controlling mammary carcinoma susceptibility, in congenic rats.

Genetic susceptibility to breast cancer is influenced by high- and low-penetrance genes. The low-penetrance genes contributing to increased and decreased risk likely exist at appreciable frequencies in the human population. To identify high-frequency, low-penetrance modifier genes, we are using a rat genetic model. Eight quantitative trait loci, named mammary carcinoma susceptibility (Mcs) loci, have been genetically identified in two rat strains, Wistar-Kyoto (WKy) and Copenhagen. These strains are resistant to developing mammary cancer compared with susceptible Wistar-Furth (WF) female rats. Here we provide physical evidence of the existence of Mcs5 in the resistant WKy rat and further narrow the candidate region defining the QTL. Two congenic rat lines (C and D) containing large segments of the WKy Mcs5 QTL on chromosome 5 were generated on a WF background. The minimal WKy interval from markers D5Wox7 and D5Uwm37 (line C) conferred resistance to developing 7,12-dimethylbenz- [a]anthracene (DMBA)-induced mammary carcinomas. Line C females that were homozygous for the WKy allele at this interval averaged 1.1+/-0.3 carcinomas/rat compared with 6.9+/-0.4 average carcinomas/rat for WF control females (P<0.01). Line D females containing the minimal WKy interval from D5Rat26 to D5Uwm42, were as susceptible to developing mammary carcinomas as WF controls (5.7+/-0.6 versus 6.9+/-0.4, respectively). The WKy region in common to these lines from D5Rat26 to D5Uwm37 is thus not expected to contain Mcs5-associated genes. Based on results presented here, the Mcs5 locus has been physically located within a congenic interval on rat chromosome 5 between markers D5Uwm8 and D5Rat26.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2003

Dimension reduction for mapping mRNA abundance as quantitative traits.

The advent of sophisticated genomic techniques for gene mapping and microarray analysis has provided opportunities to map mRNA abundance to quantitative trait loci (QTL) throughout the genome. Unfortunately, simple mapping of each individual mRNA trait on the scale of a typical microarray experiment is computationally intensive, subject to high sample variance, and therefore underpowered. However, this problem can be addressed by capitalizing on correlation among the large number of mRNA traits. We present a method to reduce the dimensionality for mapping gene expression data as quantitative traits. We used a blind method, principal components, and a sighted method, hierarchical clustering seeded by disease relevant traits, to define new traits composed of a small collection of promising mRNAs. We validated the principle of our approach by mapping the expression levels of metabolism genes in a population of F(2)-ob/ob mice derived from the BTBR and C57BL/6J strains. We found that lipogenic and gluconeogenic mRNAs, which are known targets of insulin action, were closely associated with the insulin trait. Multiple interval mapping and Bayesian interval mapping of this new trait revealed significant linkages to chromosome regions that were contained in loci associated with type 2 diabetes in this same mouse sample. As a further statistical refinement, we show that principal component analysis also effectively reduced dimensions for mapping phenotypes composed of mRNA abundances.

Animals↗

PubMed2003

Gene expression profiles of nondiabetic and diabetic obese mice suggest a role of hepatic lipogenic capacity in diabetes susceptibility.

Obesity is a strong risk factor for the development of type 2 diabetes. We have previously reported that in adipose tissue of obese (ob/ob) mice, the expression of adipogenic genes is decreased. When made genetically obese, the BTBR mouse strain is diabetes susceptible and the C57BL/6J (B6) strain is diabetes resistant. We used DNA microarrays and RT-PCR to compare the gene expression in BTBR-ob/ob versus B6-ob/ob mice in adipose tissue, liver, skeletal muscle, and pancreatic islets. Our results show: 1) there is an increased expression of genes involved in inflammation in adipose tissue of diabetic mice; 2) lipogenic gene expression was lower in adipose tissue of diabetes-susceptible mice, and it continued to decrease with the development of diabetes, compared with diabetes-resistant obese mice; 3) hepatic expression of lipogenic enzymes was increased and the hepatic triglyceride content was greatly elevated in diabetes-resistant obese mice; 4) hepatic expression of gluconeogenic genes was suppressed at the prediabetic stage but not at the onset of diabetes; and 5) genes normally not expressed in skeletal muscle and pancreatic islets were expressed in these tissues in the diabetic mice. We propose that increased hepatic lipogenic capacity protects the B6-ob/ob mice from the development of type 2 diabetes.

Adipose Tissue↗

PubMed2003

[Effect of allitridi on cyclin D1 and p27(Kip1) protein expression in gastric carcinoma BGC823 cells].

BACKGROUND & OBJECTIVE: Previous study showed that allitridi markedly suppresses cellular proliferation, blocks cell cycle at G(1) phase, and induces cell apoptosis of human gastric cancer BGC823 cell. During the investigation of its molecular mechanisms and target genes, the authors found that protein expression of cyclin D1 and p27(Kip1) play an important role in an allitridi-induced G(1) arrest. This study was designed to explore the effect of allitridi on the expression of cyclin D1 and p27(Kip1) in BGC823 cells. METHODS: After total RNA and total protein in allitridi-treated (25 microg/ml) and allitridi-untreated BGC823 cells were abstained, Western blot analysis was performed to determine the protein levels of cyclin D1 and p27(Kip1), and RT-PCR was performed to determine the mRNA levels of cyclin D1 and p27(Kip1). RESULTS: After treated with 25 microg/ml allitridi for 24 hours, the protein levels of cyclin D1 of BGC823 cells were downregulated and the protein levels of p27(Kip1) were upregulated, and this changes were more obvious after 48 hours,while their mRNA levels remained unchanged. CONCLUSION: Allitridi may influence the protein expression of cyclin D1 and p27(Kip1) in BGC823 cells, while do not influence their mRNA transcription.

Allyl Compounds↗

PubMed2002

Loss of stearoyl-CoA desaturase-1 function protects mice against adiposity.

Stearoyl-CoA desaturase (SCD) is a central lipogenic enzyme catalyzing the synthesis of monounsaturated fatty acids, mainly oleate (C18:1) and palmitoleate (C16:1), which are components of membrane phospholipids, triglycerides, wax esters, and cholesterol esters. Several SCD isoforms (SCD1-3) exist in the mouse. Here we show that mice with a targeted disruption of the SCD1 isoform have reduced body adiposity, increased insulin sensitivity, and are resistant to diet-induced weight gain. The protection from obesity involves increased energy expenditure and increased oxygen consumption. Compared with the wild-type mice the SCD1-/- mice have increased levels of plasma ketone bodies but reduced levels of plasma insulin and leptin. In the SCD1-/- mice, the expression of several genes of lipid oxidation are up-regulated, whereas lipid synthesis genes are down-regulated. These observations suggest that a consequence of SCD1 deficiency is an activation of lipid oxidation in addition to reduced triglyceride synthesis and storage.

Adipose Tissue↗

PubMed2002

[Antidotal effects of vitamin B(6) and sodium dimercaptopropane sulfonate on acute poisoning with tetramethylene disulphotetramine in animals].

OBJECTIVE: The study was designed to examine the antidotal effects of vitamin B(6) (Vit B(6)) with sodium dimercaptopropane sulfonate (Na-DMPS) on acute poisoning with tetramethylene disulphotetramine (TETS) in animals. METHODS: Through the acute toxicity experiments, the antidotal effects of Vit B(6) with Na-DMPS on mice immediately and 10 minutes after poisoning were observed. RESULTS: Used of Vit B(6) with Na-DMPS in early stage showed excellent inhibition of tetanic convulsion in acute poisoning with TETS in mice and can reduce very significantly the death rate (P < 0.001). Vit B(6) with Na-DMPS used 10 minutes after poisoning also significantly elongate the death time (68.8 +/- 15.2) and reduce significantly the death rate (60%) then control group's death time (31.6 +/- 7.8) and the death rate (100%) on acute poisoning in mice (P < 0.01). CONCLUSION: Antidotal effects of Vit B(6) with Na-DMPS were significant on acute TETS poisoning in animals. Vit B(6) with Na-DMPS is an excellent antidote for acute TETS poisoning. It is suggested that Vit B(6) with Na-DMPS may be clinically used to rescue patients poisoned by TETS.

Acute Disease↗