The Human Obesity Gene Map: The 2000 Update

This report constitutes the seventh update of the human obesity gene map incorporating published results up to the end of October 2000. Evidence from the rodent and human obesity cases caused by single‐gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci uncovered in human genome‐wide scans and in cross‐breeding experiments in various animal models, and association and linkage studies with candidate genes and other markers are reviewed. Forty‐seven human cases of obesity caused by single‐gene mutations in six different genes have been reported in the literature to date. Twenty‐four Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different quantitative trait loci reported from animal models currently reaches 115. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 130 studies reporting positive associations with 48 candidate genes. Finally, 59 loci have been linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map reveals that putative loci affecting obesity‐related phenotypes can be found on all chromosomes except chromosome Y. A total of 54 new loci have been added to the map in the past 12 months and the number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes is now above 250. Likewise, the number of negative studies, which are only partially reviewed here, is also on the rise.     

Evidence of LPL gene-exercise interaction for body fat and LPL activity: the HERITAGE Family Study.

Evidence of a gene-exercise interaction for traits related to body composition is limited. Here, the association between the lipoprotein lipase (LPL) S447X polymorphism and changes in body mass index, fat mass, percent body fat, abdominal visceral fat measured by computed tomography, and post-heparin plasma LPL activity in response to 20 wk of endurance training was investigated in 741 adult white and black subjects. Changes were compared between carriers and noncarriers of the X447 allele after adjustment for the effects of age and pretraining values. No evidence of association was observed in men. However, white women carrying the X447 allele exhibited greater reductions of body mass index (P = 0.01), fat mass (P = 0.01), and percent body fat (P = 0.03); in black women, the carriers exhibited a greater reduction of abdominal visceral fat (P = 0.05) and a greater increase in post-heparin LPL activity (P = 0.02). These results suggest that the LPL S447X polymorphism influences the training-induced changes in body fat and post-heparin LPL activity in women but not in men.     

Phylogenetic structure of specialization: A new approach that integrates partner availability and phylogenetic diversity to quantify biotic specialization in ecological networks

Biotic specialization holds information about the assembly, evolution, and stability of biological communities. Partner availabilities can play an important role in enabling species interactions, where uneven partner availabilities can bias estimates of biotic specialization when using phylogenetic diversity indices. It is therefore important to account for partner availability when characterizing biotic specialization using phylogenies. We developed an index, phylogenetic structure of specialization (PSS), that avoids bias from uneven partner availabilities by uncoupling the null models for interaction frequency and phylogenetic distance. We incorporate the deviation between observed and random interaction frequencies as weights into the calculation of partner phylogenetic α‐diversity. To calculate the PSS index, we then compare observed partner phylogenetic α‐diversity to a null distribution generated by randomizing phylogenetic distances among the same number of partners. PSS quantifies the phylogenetic structure (i.e., clustered, overdispersed, or random) of the partners of a focal species. We show with simulations that the PSS index is not correlated with network properties, which allows comparisons across multiple systems. We also implemented PSS on empirical networks of host–parasite, avian seed‐dispersal, lichenized fungi–cyanobacteria, and hummingbird pollination interactions. Across these systems, a large proportion of taxa interact with phylogenetically random partners according to PSS, sometimes to a larger extent than detected with an existing method that does not account for partner availability. We also found that many taxa interact with phylogenetically clustered partners, while taxa with overdispersed partners were rare. We argue that species with phylogenetically overdispersed partners have often been misinterpreted as generalists when they should be considered specialists. Our results highlight the important role of randomness in shaping interaction networks, even in highly intimate symbioses, and provide a much‐needed quantitative framework to assess the role that evolutionary history and symbiotic specialization play in shaping patterns of biodiversity. PSS is available as an R package at https://github.com/cjpardodelahoz/pss.     

Comparison of cytologic examination of smears and histologic examination of tissue cores obtained by fine needle aspiration biopsy of the liver

Biopsies of 30 consecutive suspected liver cancers were performed with 19-gauge fine needles having circumferentially bevelled tips that produced tiny tissue cores suitable for histologic study. The histologic results were compared with the cytologic results on aspirates obtained at the same time with 22-gauge Chiba needles. While cytologic examination of the aspiration smears produced better results than did histologic study of the tiny tissue cores, an improved overall accuracy of 86% was achieved with the combined cytologic and histologic results. The FNA core biopsy technique did not increase the complication rate.     

Suggestive Linkages Between Markers on Human 1p32-p22 and Body Fat and Insulin Levels in the Québec Family Study

A single-gene rodent mutation (diabetes) and a quantitative trait locus (dietary obese 1) mapped to the mid portion of mouse chromosome 4 have been related to obesity and/or insulin levels. Synteny relationships place their putative human homologs on 1p31 and 1p35-p31, respectively. In 137 sibships of adult brothers and sisters from the Québec Family Study, genetic linkages between seven microsatellite markers from 1p32-p22 and various obesity- and diabetes-related quantitative phenotypes were examined using single locus sibpair linkage analysis. Suggestive linkages were observed between markers D1S476 and body mass index (p>=Q.Q5), fat mass (p=0.02), the sum of six skinfolds (p=0.02), the insulin area after an oral glucose tolerance test (p=0.02), and between the neighboring marker D1S200 and body mass index (p>=0.03), and fat mass (p=0.009). Suggestive linkages were also observed between the more telomeric markers D1S193 and body mass index (p=0.03), and between the neighboring marker DIS 197 and fasting insulin level (p=0.05). No linkage was observed with the trunk to extremity skinfolds ratio. These linkages suggest that human homologs of the mouse diabetes or dietary obese 1 and/or other genes in this interval on chromosome 1 play a role in the regulation of body mass, body composition, and insulin levels, but not of subcutaneous fat distribution.     

Experimental characterisation and modelling of breast Cooper’s ligaments

Biomechanics and Modeling in Mechanobiology - The aim of this study was to characterise the mechanical behaviour of Cooper’s ligaments. Such ligaments are collagenous breast tissue that...