Consistency of the disposition index in the face of diet induced insulin resistance: potential role of FFA

Objective

Insulin resistance induces hyperinsulinemic compensation, which in turn maintains almost a constant disposition index. However, the signal that gives rise to the hyperinsulinemic compensation for insulin resistance remains unknown.

Methods

In a dog model of obesity we examined the possibility that potential early-week changes in plasma FFA, glucose, or both could be part of a cascade of signals that lead to compensatory hyperinsulinemia induced by insulin resistance.

Results

Hypercaloric high fat feeding in dogs resulted in modest weight gain, and an increase in adipose tissue with no change in the non-adipose tissue size. To compensate for the drop in insulin sensitivity, there was a significant rise in plasma insulin, which can be attributed in part to a decrease in the metabolic clearance rate of insulin and increased insulin secretion. In this study we observed complete compensation for high fat diet induced insulin resistance as measured by the disposition index. The compensatory hyperinsulinemia was coupled with significant changes in plasma FFAs and no change in plasma glucose.

Conclusions

We postulate that early in the development of diet induced insulin resistance, a change in plasma FFAs may directly, through signaling at the level of β-cell, or indirectly, by decreasing hepatic insulin clearance, result in the observed hyperinsulinemic compensation.     

Allosteric potentiators of the metabotropic glutamate receptor 2 (mGlu2). Part 2: 4-thiopyridyl acetophenones as non-tetrazole containing mGlu2 receptor potentiators

We have identified and synthesized a series of 4-thiopyridyl acetophenones as positive allosteric potentiators of the metabotropic glutamate receptor 2. Structure-activity relationship studies directed toward replacement of the tetrazole in the initial lead led to the discovery of 16 (EC(50)=340 nM), which showed improved brain penetration over the initial lead.     

Expression pattern of alkaline phosphatase in Dictyostelium

We used two different methods to study the expression pattern of alkaline phosphatase (alp) in Dictyostelium. In situ staining of the endogenous enzyme activity at different stages of development showed that the enzyme was active early in the aggregation stage and localized to the area where the tip of the first finger was initiated. The activity was localized to the anterior region of developing slugs, then became restricted to the region between the prestalk and prespore cells at the culmination stage. In the complete fruiting body, the activity was confined to the lower and upper cup. A second method to study alp expression utilized a beta-galactosidase reporter gene under the control of the alp promoter. A low level of beta-galactosidase activity was observed in vegetative cells, then increased during development. Reporter gene activity was restricted to PstO cells at the slug stage. At the culmination stage, the expression was restricted to prestalk cells at the interface between the prestalk and prespore cells. In the completed fruiting body, the expression was observed in the upper and lower cup.     

Obesity and Sugar‐sweetened Beverages in African‐American Preschool Children: A Longitudinal Study

A representative sample of 365 low‐income African‐American preschool children aged 3–5 years was studied to determine the association between sugar‐sweetened beverage consumption (soda, fruit drinks, and both combined) and overweight and obesity. Children were examined at a dental clinic in 2002–2003 and again after 2 years. Dietary information was collected using the Block Kids Food Frequency Questionnaire. A BMI score was computed from recorded height and weight. Overweight and obesity were defined by national reference age‐sex specific BMI: those with an age‐sex specific BMI ≥85th, but <95th percentile as overweight and those with BMI ≥95th age‐sex specific percentile as obese. The prevalence of overweight was 12.9% in baseline, and increased to 18.7% after 2 years. The prevalence of obesity increased from 10.3 to 20.4% during the same period. Baseline intake of soda and all sugar‐sweetened beverages were positively associated with baseline BMI z‐scores. After adjusting for covariates, additional intake of fruit drinks and all sugar‐sweetened beverages at baseline showed significantly higher odds of incidence of overweight over 2 years. Among a longitudinal cohort of African‐American preschool children, high consumption of sugar‐sweetened beverages was significantly associated with an increased risk for obesity.     

The power of real-time PCR

In recent years, real-time polymerase chain reaction (PCR) has emerged as a robust and widely used methodology for biological investigation because it can detect and quantify very small amounts of specific nucleic acid sequences. As a research tool, a major application of this technology is the rapid and accurate assessment of changes in gene expression as a result of physiology, pathophysiology, or development. This method can be applied to model systems to measure responses to experimental stimuli and to gain insight into potential changes in protein level and function. Thus physiology can be correlated with molecular events to gain a better understanding of biological processes. For clinical molecular diagnostics, real-time PCR can be used to measure viral or bacterial loads or evaluate cancer status. Here, we discuss the basic concepts, chemistries, and instrumentation of real-time PCR and include present applications and future perspectives for this technology in biomedical sciences and in life science education.     

Genetic population structure of endangered ring‐tailed lemurs (Lemur catta) from nine sites in southern Madagascar

Madagascar's ring‐tailed lemurs (Lemur catta) are experiencing rapid population declines due to ongoing habitat loss and fragmentation, as well as increasing exploitation for bushmeat and the illegal pet trade. Despite being the focus of extensive and ongoing behavioral studies, there is comparatively little known about the genetic population structuring of the species. Here, we present the most comprehensive population genetic analysis of ring‐tailed lemurs to date from across their likely remaining geographic range. We assessed levels of genetic diversity and population genetic structure using multilocus genotypes for 106 adult individuals from nine geographically representative localities. Population structure and F_ST analyses revealed moderate genetic differentiation with localities being geographically partitioned into northern, southern, western and also potentially central clusters. Overall genetic diversity, in terms of allelic richness and observed heterozygosity, was high in the species (AR = 4.74, H_O = 0.811). In fact, it is the highest among all published lemur estimates to date. While these results are encouraging, ring‐tailed lemurs are currently affected by ongoing habitat fragmentation and occur at lower densities in poorer quality habitats. The effects of continued isolation and fragmentation, coupled with climate‐driven environmental instability, will therefore likely impede the long‐term viability of the species.     

鼠类种群动态:食物资源影响力的实验评估

本研究在美国伊利诺斯州中东部测定了中等食物质量(莓系属的牧草)和低食物质量(高杆草牧场)栖息地内橙腹田鼠(Microtusochrogaster)和草原田鼠(M.pennsylvanicus)种群对附加食物的响应。在中等食物质量栖息地内投放附加食物,橙腹田鼠种群的波动幅度高于对照样地,但同类型食物质量栖息地内,种群平均密度和波动模式无显著的差异。仅在低等食物质量的高杆草栖息地内,投放附加食物可导致草原田鼠的种群密度高于对照样地。附加食物不直接影响两种栖息地内橙腹田鼠的成活率或成熟率,在中等食物质量栖息地中投放附加食物,繁殖活跃的成熟雌性个体比例及雄性成体的体重高于对照。附加食物不影响莓系属牧草内草原田鼠,也不能影响该动物在高杆草环境中的存活率。然而,投放附加食物,可缩短低等食物质量栖息地内草原田鼠的成熟期,提高繁殖活跃雌性的比例和迁入个体比例,增加并引起雄性个体体重增加。据此,本研究证明食物资源在橙腹田鼠和草原田鼠种群动态中只起极小的作用。     

A High Diversity of Eurasian Lineage Low Pathogenicity Avian Influenza A Viruses Circulate among Wild Birds Sampled in Egypt

Surveillance for influenza A viruses in wild birds has increased substantially as part of efforts to control the global movement of highly pathogenic avian influenza A (H5N1) virus. Studies conducted in Egypt from 2003 to 2007 to monitor birds for H5N1 identified multiple subtypes of low pathogenicity avian influenza A viruses isolated primarily from migratory waterfowl collected in the Nile Delta. Phylogenetic analysis of 28 viral genomes was performed to estimate their nearest ancestors and identify possible reassortants. Migratory flyway patterns were included in the analysis to assess gene flow between overlapping flyways. Overall, the viruses were most closely related to Eurasian, African and/or Central Asian lineage low pathogenicity viruses and belonged to 15 different subtypes. A subset of the internal genes seemed to originate from specific flyways (Black Sea-Mediterranean, East African-West Asian). The remaining genes were derived from a mixture of viruses broadly distributed across as many as 4 different flyways suggesting the importance of the Nile Delta for virus dispersal. Molecular clock date estimates suggested that the time to the nearest common ancestor of all viruses analyzed ranged from 5 to 10 years, indicating frequent genetic exchange with viruses sampled elsewhere. The intersection of multiple migratory bird flyways and the resulting diversity of influenza virus gene lineages in the Nile Delta create conditions favoring reassortment, as evident from the gene constellations identified by this study. In conclusion, we present for the first time a comprehensive phylogenetic analysis of full genome sequences from low pathogenic avian influenza viruses circulating in Egypt, underscoring the significance of the region for viral reassortment and the potential emergence of novel avian influenza A viruses, as well as representing a highly diverse influenza A virus gene pool that merits continued monitoring.     

A simplified method for growth of human microvascular endothelial cells results in decreased senescence and continued responsiveness to cytokines and growth factors

Summary Human dermal microvascular endothelial cells are used to analyze the functions of microvascular endothelium in vitro. However, the low yield and short lifespan of these cells in culture has limited the types of analysis that could be performed. Human microvascular endothelial cells are typically grown in media containing supplements such as dibutyryl cyclic AMP, hydrocortisone, bovine brain extract, and antifungal agents, each of which increase the complexity of experimental design and interpretation of results. In the present study, endothelial cells were transferred after Ulex europeus-I selection into a simplified medium consisting of Endothelial Basal Medium 131, 10% fetal bovine serum, and 2 ng/ml basic fibroblast growth factor and analyzed over 3 mo. The human microvascular endothelial cells expressed the endothelial markers von Willebrand factor, CD31, P-selectin, and E-selectin. In addition, the cells showed increased proliferation in the presence of basic fibroblast growth factor (0.5 ng/ml) or vascular endothelial cell growth factor (10 ng/ml). Tumor necrosis factor-α-induced expression of E-selectin was similar in cells at Passages 3, 6, and 12, indicating that the cells maintained responsiveness to cytokines over several weeks. Furthermore, the endothelial cells attained a typical cobblestone morphology with increased cellular density and also formed capillarylike tubes on Matrigel. In summary, the human dermal microvascular endothelial cells display the expected endothelial characteristics when grown for several passages and, therefore, provide a valuable in vitro model for human microvascular endothelium.