The role of lipid‐related genes,aging‐related processes,and environment in healthspan

The inherent complexity of aging‐related traits can temper progress in unraveling the genetic origins of healthspan. We focus on two generations in the Framingham Heart Study, the original (FHS) and offspring (FHSO) cohorts, to determine whether aging‐related processes in changing environments can substantially impact the role of lipid‐related genes discovered in candidate gene (the apolipoprotein E (APOE) e2/3/4 polymorphism) and genome‐wide (the APOB rs1042034 (C/T)) studies, in regulation of total cholesterol (TC) and onset of cardiovascular disease (CVD). We demonstrate that the APOE e4 allele and APOB CC genotype can play detrimental, neutral, and protective sex‐specific roles in the etiology of CVD at different ages and in different environments. We document antagonistic roles for the e4 allele in the onset of CVD characterized by detrimental effects at younger ages (RR_{≤ 75 years} = 1.49, P = 7.5 × 10^?4) and protective effects at older ages (RR_76+years = 0.77, P = 0.044) for FHS participants. We found that disregarding the role of aging erroneously nullifies the significant effects of the e4 allele in this sample (RR = 0.92, P = 0.387). The leading biogenetic pathways mediating genetic effects on CVD may be more relevant to lipid metabolism for APOB than APOE. Aging‐related processes can modulate the strength of genetic associations with TC in the same individuals at different chronological ages. We found substantial differences in the effects of the same APOE and APOB alleles on CVD and TC across generations. The results suggest that aging‐related processes in changing environments may play key roles in the genetics of healthspan. Detailed systemic integrative analyses may substantially advance the progress.     

Growth,developmental and stress responses of larvae of the clouded sulphur butterfly Colias eriphyle to repeated exposure to high,sub‐lethal temperatures

The optimal temperature at which an organism grows and develops is commonly correlated with latitude and elevation; however, the maximum temperature for physiological performance often is not. This makes performance at temperatures between the optimum and the maximum of particular interest. Temperature can influence long‐term performance (growth and development), as well as short‐term performance (heat shock protein) responses differentially. In the present study, two populations of the clouded sulphur butterfly Colias eriphyle Edwards that differ in elevation, thermal regime and optimal and maximum temperatures are studied to quantify their responses to repeated, sub‐lethal heat treatments early in development (second instar). Heat treatments accelerate development during the second to fourth instars in both populations initially, although this effect disappears by pupation. Heat treatment decreases pupal mass in the lower elevation population, suggesting that repeated exposure to high temperatures early in development may reduce final size and fecundity in this population. Heat shock protein gene (hsp70) expression levels in the lower elevation (1633 m a.s.l.) population are highest 24 h after the start of the heat treatment and then the fall to pre‐exposure levels by 36–72 h, suggesting a rapid response to stressful temperatures. By contrast, heat treatment has no significant effect on pupal mass in the higher elevation (2347 m a.s.l.) population. This population has higher levels of hsp70 expression overall but constant expression levels, suggesting that the temperature treatments used are insufficient to elicit a heat stress response. Overall, the effects of repeated exposure to sub‐lethal high temperatures early in development on growth, final size and gene expression differ between populations that differ in thermal sensitivity.     

Polymorphism of the apolipoprotein E gene (APOE) in the populations of Russia and neighboring countries

Allele and genotype frequencies for the locus encoding apolipoprotein E, involved in the regulation of lipid metabolism (APOE), were evaluated in 16 populations representing 12 ethnic groups (a total of 1103 subjects) from Russia and neighboring countries. In the populations examined, the frequencies of allele ?4, which is the risk factor of Alzheimer’s disease and coronary heart disease, varied from less than 5 to more than 20%, while the variation of the major ?3 allele in these populations ranged from less than 75 to 95%. The frequencies of alleles ?3 and ?4 were 0.714 and 0.205 in Saami, 0.735 and 0.220 in Komi-Izhemts, 0.770 and 0.130 in Komi-Zyryans, 0.771 and 0.149 in Udmurts, 0.734 and 0.149 in Maris, 0.841 and 0.122 in Evenks, 0.788 and 0.163 in Buryats, 0.764 and 0.202 in Chukchi, 0.875 and 0.075 in Iranians, 0.956 and 0.044 in mountain-dwellers of the Pamirs, 0.771 and 0.094 in Ukrainians, and 0.795 and 0.091 in Belarussians, respectively. In Russians from different regions of the country, the frequencies of these alleles were 0.728 and 0.139 (Kostroma), 0.795 and 0.105 (Moscow), 0.857 and 0.092 (Rostov-on-Don), and 0.824 and 0.083 (Krasnodar), respectively. The latitudinal distribution of the APOE ?3 and ?4 allele frequencies in the populations examined was comparable to the frequency distribution pattern of these alleles in other populations of Eurasia.     

The Apolipoprotein E (APOE) Gene Appears Functionally Monomorphic in Chimpanzees (Pan troglodytes)

Background

The human apolipoprotein E (APOE) gene is polymorphic, with three primary alleles (E2, E3, E4) that differ at two key non-synonymous sites. These alleles are functionally different in how they bind to lipoproteins, and this genetic variation is associated with phenotypic variation for several medical traits, including cholesterol levels, cardiovascular health, Alzheimer’s disease risk, and longevity. The relative frequencies of these alleles vary across human populations, and the evolution and maintenance of this diversity is much debated. Previous studies comparing human and chimpanzee APOE sequences found that the chimpanzee sequence is most similar to the human E4 allele, although the resulting chimpanzee protein might function like the protein coded for by the human E3 allele. However, these studies have used sequence data from a single chimpanzee and do not consider whether chimpanzees, like humans, show intra-specific and subspecific variation at this locus.

Methodology and Principal Findings

To examine potential intraspecific variation, we sequenced the APOE gene of 32 chimpanzees. This sample included 20 captive individuals representing the western subspecies (P. troglodytes verus) and 12 wild individuals representing the eastern subspecies (P. t. schweinfurthii). Variation in our resulting sequences was limited to one non-coding, intronic SNP, which showed fixed differences between the two subspecies. We also compared APOE sequences for all available ape genera and fossil hominins. The bonobo APOE protein is identical to that of the chimpanzee, and the Denisovan APOE exhibits all four human-specific, non-synonymous changes and appears functionally similar to the human E4 allele.

Conclusions

We found no coding variation within and between chimpanzee populations, suggesting that the maintenance of functionally diverse APOE polymorphisms is a unique feature of human evolution.     

Gene polymorphisms of CETP and apolipoprotein E in elderly subjects with cognitive impairment

The association of cholesteryl ester transfer protein (CETP) and apolipoprotein E (APOE) gene polymorphisms with mild cognitive impairment (MCI) is under debate. Our aim was to evaluate the relationship between APOE and CETP genotypes with healthy ageing. We analysed 267 elderly subjects (55 to 80+ years), 163 with MCI and 104 healthy, and 50 healthy control subjects (35 to 55 years) from a Romanian population. Biochemical parameters and thyroid hormones were assayed in plasma. APOE and CETP TaqIB gene polymorphisms were determined. Elderly subjects had higher frequency of ɛ3/ɛ2 genotype (14.6% vs. 4%, P<0.001) than controls. Elderly subjects with MCI had lower high density lipoproteins (HDL) cholesterol (P=0.031), apoA-I (P=0.018), T3 (P=0.002), T4 (P=0.028) and TSH (P=0.001) hormone levels, higher systolic blood pressure (P=0.005), lower frequency of CETP B2 allele than the age-matched subjects. Healthy elderly subjects had CETP B2 allele associated with higher plasma apoA-I (P=0.021), lower circulating collagen (P=0.001) levels, and an increased frequency of the combined APOE ɛ2- CETP B2 genotype (18.3%) relative to MCI elderly subjects (7.6%, P=0.011). Healthy elderly subjects are characterized by higher HDL cholesterol, apoA-I levels and higher frequency of the combined APOE ɛ2 and CETP B2 alleles, indicating this pattern as representative for healthy ageing.     

Genetic interaction is associated with lower metabolic connectivity and memory impairment in clinically mild Alzheimer's disease

Metabolic connectivity as showed by [18F] fluorodeoxyglucose (FDG) positron emission tomography (FDG‐PET) reflects neuronal connectivity. The aim of this study was to investigate the genetic impact on metabolic connectivity in default mode subnetworks and its clinical‐pathological relationships in patients with Alzheimer's disease (AD). We separately investigated the modulation of 2 default mode subnetworks, as identified with independent component analysis, by comparing APOE‐ε4 carriers to noncarriers with AD. We further analyzed the interaction effects of APOE (APOE‐ε4 carriers vs noncarriers) with PICALM (rs3851179‐GG vs rs3851179‐A‐allele carriers) on episodic memory (EM) deficits, reduction in cerebral metabolic rate for glucose (CMRgl) and decreased metabolic connectivity in default mode subnetworks. The metabolic connectivity in the ventral default mode network (vDMN) was positively correlated with EM scores (β =0.441, P < .001). The APOE‐ε4 carriers had significantly lower metabolic connectivity in the vDMN than the APOE‐ε4 carriers (t(96) = ?2.233, P = .028). There was an effect of the APOE‐PICALM (rs3851179) interactions on reduced CMRgl in regions of vDMN (P < .001), and on memory deficits (F_3,93 =5.568, P = .020). This study identified that PICALM may modulates memory deficits, reduced CMRgl and decreased metabolic connectivity in the vDMN in APOE‐ε4 carriers. [18F] FDG‐PET‐based metabolic connectivity may serve a useful tool to elucidate the neural networks underlying clinical‐pathological relationships in AD.     

Association of APOE, GCPII and MMP9 polymorphisms with common diseases and lipid levels in an older adult/elderly cohort

Background and aims

The characterization of candidate gene polymorphisms in elderly populations is an important tool for the identification of risk factors for age-related diseases and conditions. We aimed to genotype the APOE polymorphisms (rs429358 and rs7412), rs61886492 (1561C>T) and rs202720 of GCPII gene and rs3918242 (− 1562C>T) of MMP9 gene in an older-adult/elderly cohort from Cuiabá city, Mato Grosso Brazil as well as to characterize risk factors for morbidities and conditions affecting this cohort.

Methods

The studied population consisted of 570 subjects from Cuiabá city, Brazil, who were subjected to clinical interviews and blood collection for laboratory examinations and DNA extraction. Restriction Fragment Length Polymorphism Polymerase Chain Reaction (RFLP-PCR), sequence-specific primer PCR (SSP-PCR) and TaqMan® allelic discrimination assay were used for genotyping.

Results

The frequencies of APOE ε2 and ε4 were 6.6% and 14.8%, respectively, and the frequencies of GCPII rs61886492 T allele, GCPII rs202720 C allele and MMP9 rs3918242 T allele were, respectively, 3.0%, 26.6% and 10.1%. Significant associations between APOE ε2 allele with lower total cholesterol and LDL-cholesterol were found. In addition, MMP9 rs3918242 T allele was associated with higher LDL-cholesterol levels, suggesting a link between lipid metabolism alteration and cardiovascular disease.

Conclusions

The present findings contributed to characterize risk factors specific for the studied population and to better understand the molecular physiopathology of common morbidities and conditions affecting older-adult/elderly people.     

Epistatic Interactions between Apolipoprotein E and Hemoglobin S Genes in Regulation of Malaria Parasitemia

Apolipoprotein E is a monomeric protein secreted by the liver and responsible for the transport of plasma cholesterol and triglycerides. The APOE gene encodes 3 isoforms Ɛ4, Ɛ3 and Ɛ2 with APOE Ɛ4 associated with higher plasma cholesterol levels and increased pathogenesis in several infectious diseases (HIV, HSV). Given that cholesterol is an important nutrient for malaria parasites, we examined whether APOE Ɛ4 was a risk factor for Plasmodium infection, in terms of prevalence or parasite density. A cross sectional survey was performed in 508 children aged 1 to 12 years in Gabon during the wet season. Children were screened for Plasmodium spp. infection, APOE and hemoglobin S (HbS) polymorphisms. Median parasite densities were significantly higher in APOE Ɛ4 children for Plasmodium spp. densities compared to non-APOE Ɛ4 children. When stratified for HbS polymorphisms, median Plasmodium spp. densities were significantly higher in HbAA children if they had an APOE Ɛ4 allele compared to those without an APOE Ɛ4 allele. When considering non-APOE Ɛ4 children, there was no quantitative reduction of Plasmodium spp. parasite densities for HbAS compared to HbAA phenotypes. No influence of APOE Ɛ4 on successful Plasmodium liver cell invasion was detected by multiplicity of infection. These results show that the APOE Ɛ4 allele is associated with higher median malaria parasite densities in children likely due to the importance of cholesterol availability to parasite growth and replication. Results suggest an epistatic interaction between APOE and HbS genes such that sickle cell trait only had an effect on parasite density in APOE Ɛ4 children. This suggests a linked pathway of regulation of parasite density involving expression of these genes. These findings have significance for understanding host determinants of regulation of malaria parasite density, the design of clinical trials as well as studies of co-infection with Plasmodium and other pathogens.     

<Emphasis Type="Italic">APOE</Emphasis> ε4 lowers age at onset and is a high risk factor for Alzheimer's disease; A case control study from central Norway

Background

The objective of this study was to analyze factors influencing the risk and timing of Alzheimer's disease (AD) in central Norway. The APOE ε4 allele is the only consistently identified risk factor for late onset Alzheimer's disease (LOAD). We have described the allele frequencies of the apolipoprotein E gene (APOE) in a large population of patients with AD compared to the frequencies in a cognitively-normal control group, and estimated the effect of the APOE ε4 allele on the risk and the age at onset of AD in this population.

Methods

376 patients diagnosed with AD and 561 cognitively-normal control individuals with no known first degree relatives with dementia were genotyped for the APOE alleles. Allele frequencies and genotypes in patients and control individuals were compared. Odds Ratio for developing AD in different genotypes was calculated.

Results

Odds Ratio (OR) for developing AD was significantly increased in carriers of the APOE ε4 allele compared to individuals with the APOE ε3/ε3 genotype. Individuals carrying APOE ε4/ε4 had OR of 12.9 for developing AD, while carriers of APOE ε2/ε4 and APOE ε3/ε4 had OR of 3.2 and 4.2 respectively. The effect of the APOE ε4 allele was weaker with increasing age. Carrying the APOE ε2 allele showed no significant protective effect against AD and did not influence age at onset of the disease. Onset in LOAD patients was significantly reduced in a dose dependent manner from 78.4 years in patients without the APOE ε4 allele, to 75.3 in carriers of one APOE ε4 allele and 72.9 in carriers of two APOE ε4 alleles. Age at onset in early onset AD (EOAD) was not influenced by APOE ε4 alleles.

Conclusion

APOE ε4 is a very strong risk factor for AD in the population of central Norway, and lowers age at onset of LOAD significantly.

     

A serum protein signature of APOE genotypes in centenarians

The discovery of treatments to prevent or delay dementia and Alzheimer's disease is a priority. The gene APOE is associated with cognitive change and late‐onset Alzheimer's disease, and epidemiological studies have provided strong evidence that the e₂ allele of APOE has a neuroprotective effect, it is associated with increased longevity and an extended healthy lifespan in centenarians. In this study, we correlated APOE genotype data of 222 participants of the New England Centenarian Study, including 75 centenarians, 82 centenarian offspring, and 65 controls, comprising 55 carriers of APOE e₂, with aptamer‐based serum proteomics (SomaLogic technology) of 4,785 human proteins corresponding to 4,137 genes. We discovered a signature of 16 proteins that associated with different APOE genotypes and replicated the signature in three independent studies. We also show that the protein signature tracks with gene expression profiles in brains of late‐onset Alzheimer's disease versus healthy controls. Finally, we show that seven of these proteins correlate with cognitive function patterns in longitudinally collected data. This analysis in particular suggests that Baculoviral IAP repeat containing two (BIRC2) is a novel biomarker of neuroprotection that associates with the neuroprotective allele of APOE. Therefore, targeting APOE e₂ molecularly may preserve cognitive function.     

Beyond MHC: signals of elevated selection pressure on Atlantic salmon (Salmo salar) immune‐relevant loci

Using Atlantic salmon (Salmo salar) as a model system, we investigated whether 18 microsatellites tightly linked to immune‐relevant genes have experienced different selection pressures than 76 loci with no obvious association with immune function. Immune‐relevant loci were identified as outliers by two outlier tests significantly more often than nonimmune linked loci (22% vs. 1.6%). In addition, the allele frequencies of immune relevant markers were more often correlated with latitude and temperature. Combined, these results support the hypothesis that immune‐relevant loci more frequently exhibit footprints of selection than other loci. They also indicate that the correlation between immune‐relevant loci and latitude may be due to temperature‐induced differences in pathogen‐driven selection or some other environmental factor correlated with latitude.     

Differential effects of short term winter thermal stress on diapausing tiger swallowtail butterflies (Papilio spp.)

Abstract It is generally thought that insects inhabiting lower latitudes are more severely impacted by changes in their thermal environment than are high latitude species. This is attributed to the wider range of temperatures to which high‐latitude species are exposed. By contrast, low‐latitude species have typically evolved in more thermally stable environments with a narrower range of temperature variation. However, deviation from this pattern can occur and here we report that under variable winter conditions a higher latitude species may be more sensitive to thermal variation than its lower latitude sister species. Using split broods, we examined the survival and adult emergence success of diapausing pupae of Papilio canadensis and P. glaucus, as well as a unique, recombinant hybrid population (“late‐flight”) to short periods of mid‐winter cold and heat stress. Our results indicate that the higher latitude, univoltine populations (P. canadensis and late‐flights) exhibit lower pupal survival than the lower latitude, facultative diapauser (P. glaucus) for all mid‐winter thermal stress treatments, both high and low. Size differences alone do not appear to account for the observed differences in survival or metabolic costs in these three phenotypes, as late‐flight individuals are similar in size to P. glaucus. We attribute the observed differences in survival and weight loss to potential metabolic differences and variation in the intensity of diapause, in addition to divergent adaptation to winter precipitation levels (e.g. snow cover) and the influences this may have on microhabitat temperature moderation.     

Impacts of thermal mismatches on chytrid fungus Batrachochytrium dendrobatidis prevalence are moderated by life stage,body size,elevation and latitude

Global climate change is increasing the frequency of unpredictable weather conditions; however, it remains unclear how species‐level and geographic factors, including body size and latitude, moderate impacts of unusually warm or cool temperatures on disease. Because larger and lower‐latitude hosts generally have slower acclimation times than smaller and higher‐latitude hosts, we hypothesised that their disease susceptibility increases under ‘thermal mismatches’ or differences between baseline climate and the temperature during surveying for disease. Here, we examined how thermal mismatches interact with body size, life stage, habitat, latitude, elevation, phylogeny and International Union for Conservation of Nature (IUCN) conservation status to predict infection prevalence of the chytrid fungus Batrachochytrium dendrobatidis (Bd) in a global analysis of 32 291 amphibian hosts. As hypothesised, we found that the susceptibility of larger hosts and hosts from lower latitudes to Bd was influenced by thermal mismatches. Furthermore, hosts of conservation concern were more susceptible than others following thermal mismatches, suggesting that thermal mismatches might have contributed to recent amphibian declines.     

Physiological adaptation along environmental gradients and replicated hybrid zone structure in swordtails (Teleostei: Xiphophorus)

Local adaptation is often invoked to explain hybrid zone structure, but empirical evidence of this is generally rare. Hybrid zones between two poeciliid fishes, Xiphophorus birchmanni and X. malinche, occur in multiple tributaries with independent replication of upstream‐to‐downstream gradients in morphology and allele frequencies. Ecological niche modelling revealed that temperature is a central predictive factor in the spatial distribution of pure parental species and their hybrids and explains spatial and temporal variation in the frequency of neutral genetic markers in hybrid populations. Among populations of parentals and hybrids, both thermal tolerance and heat‐shock protein expression vary strongly, indicating that spatial and temporal structure is likely driven by adaptation to local thermal environments. Therefore, hybrid zone structure is strongly influenced by interspecific differences in physiological mechanisms for coping with the thermal environment.     

Latitudinal differences in temperature effects on the embryonic development and hatchling phenotypes of the Asian yellow pond turtle,Mauremys mutica

The effect of incubation temperature on embryonic development and offspring traits has been widely reported for many species. However, knowledge remains limited about how such effects vary across populations. Here, we investigated whether incubation temperature (26, 28, and 30 °C) differentially affects the embryonic development of Asian yellow pond turtle (Mauremys mutica) eggs originating from low‐latitude (Guangzhou, 23°06′N) and high‐latitude (Haining, 30°19′N) populations in China. At 26 °C, the duration of incubation was shorter in the high‐latitude population than in the low‐latitude population. However, this pattern was reversed at 30 °C. As the incubation temperature increased, hatching success increased in the low‐latitude population but slightly decreased in the high‐latitude population. Hatchlings incubated at 30 °C were larger and righted themselves more rapidly than those incubated at 26 °C in the low‐latitude population. In contrast, hatchling traits were not influenced by incubation temperature in the high‐latitude population. Overall, 30 °C was a suitable developmental temperature for embryos from the low‐latitude population, whereas 26 and 28 °C were suitable for those from the high‐latitude population. This interpopulation difference in suitable developmental temperatures is consistent with the difference in the thermal environment of the two localities. Therefore, similarly to posthatching individuals, reptile embryos from different populations might have evolved diverse physiological strategies to benefit from the thermal environment in which they develop. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114 , 35–43.     

Myrmica rubra microhabitat selection and putative ecological impact

1. Myrmica rubra (European fire ant) has invaded northern latitude coastal areas in North America. This macroscale distribution suggests that M. rubra is moisture‐ and temperature‐limited, but the distribution of the invaded range may reflect the legacy of original introduction locations preserved by limited dispersal. 2. This study examined a two‐decade population change in M. rubra (1994–2015) and the microscale abiotic (moisture and temperature), biotic (plants), anthropogenic (pesticide) and physiological (thermal tolerance) limits on the invasion at the Tifft Nature Preserve in Buffalo, NY (U.S.A.). Changes in the abundance of native ants and other invertebrates were also examined. 3. Despite localised declines with pesticide treatments, overall M. rubra forager abundance increased 27% between 1994 and 2015. Abundance increased the most in the warmest areas (native ants were unaffected by temperature), but M. rubra colony locations were strongly linked to higher soil moisture and lower soil temperature. Myrmica rubra ants also exhibited relatively low thermal tolerances consistent with high‐latitude and high‐elevation ants. 4. Where local M. rubra populations increased the most, native ant species decreased, and where local M. rubra populations declined, native ant species increased. Some arthropod species had lower abundance with M. rubra presence, but the impacts were less striking. 5. Myrmica rubra population growth was promoted at the microhabitat scale where relatively higher temperatures prompted foraging, and relatively lower temperatures and high moisture supported nesting. These results suggest that macroscale M. rubra invaded‐range distributions in northern climates near coastal areas are replicated at the microscale where the ant prefers cooler, moister microsites.     

Comparative study of the metabolic responses during food shortage and subsequent recovery at different temperatures in the adult lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae)

Metabolic responses to prolonged food shortage (35 days) and subsequent re‐feeding (14 days) were investigated in adults of an introduced beetle, Alphitobius diaperinus Panzer, as a function of temperature (12, 16, 20 and 24 °C). Various qualitative and quantitative changes that greatly vary according to the temperature experienced occurred in metabolite levels during prolonged starvation. Whereas levels of protein and ATP did not change significantly, triglycerides decreased markedly and glycogen changed little. Metabolite levels were differently affected by temperature, with triglycerides being less rapidly degraded at 20 than at 24 °C and almost completely depleted at 12 and 16 °C; in contrast to higher temperatures, glycerol is accumulated at 12 °C. Physiological adaptation to starvation and low temperatures are highly linked and energy allocation for starvation vs. temperature acclimation must be strictly regulated, both being essential for insect survival. Re‐synthesis rates during recovery are probably highly temperature‐dependent for all metabolites. The proteins retained during starvation and the preferential degradation of lipids allowed a rapid recovery. Above 16 °C, adult A. diaperinus regained locomotory activity rapidly and the triglyceride, glycerol and glycogen reserves were restored. This tropical species may be able to colonize other environments such as natural and/or artificial biotopes where conditions are close to those of its natural habitat.     

Obesity Modulates the Association among APOE Genotype,Insulin, and Glucose in Men

Objective: Obesity, insulin resistance, and apolipoprotein E (APOE) genotype have all been associated with coronary heart disease. We examined the interaction between obesity and APOE genotype in determining fasting insulin and glucose levels. Research Methods and Procedures: From 1991 to 1995, 3799 subjects underwent a clinical examination and fasting insulin and glucose measurement. APOE genotypes were determined on 3500 participants. Participants taking oral hypoglycemic drugs or insulin preparations or with the rare APOE2/4 genotype were excluded. Finally, 2929 individuals were included in the present analysis. Results: In men, we observed a statistically significant interaction between obesity and APOE genotype on insulin and glucose level (p = 0.003 and 0.008, respectively). Obese men with the APOE4 genotype presented with higher levels of insulin and glucose than obese men in the other genotype groups. No association between genotype and insulin or glucose in nonobese men was observed. Obesity was associated with higher insulin levels in the three APOE genotypes groups, whereas obesity was directly associated with glucose in those with the APOE4 genotype. In women, the effect of interaction between APOE genotype and obesity on fasting insulin and glucose was not statistically significant. Obesity was associated with higher levels of fasting insulin and glucose. APOE genotype was not associated with insulin or glucose. Discussion: Obesity modulates the association between the APOE genotype and fasting insulin and glucose levels in men. Although weight control is important in all people, it may be especially important in APOE4 men to modify potentially elevated fasting insulin and glucose levels.     

Genetic variation in piñon pine, Pinus edulis, associated with summer precipitation

Three previous reports of microgeographical variation of glycerate dehydrogenase (Gly) frequencies in piñon, Pinus edulis, established the hypothesis that Gly frequencies contribute to adaptation to heterogeneous environments, specifically to variation in soil moisture. In each of these studies, the frequency of the Gly‐3 allele or of Gly‐33 homozygotes was higher on dry sites than on nearby moist sites. Here we attempt to extend these observations by testing the hypothesis that Gly frequencies respond to soil moisture variation on a range‐wide scale. Gly frequencies were surveyed in 11 natural populations, and the frequency of the Gly‐3 allele varied from 0.27 to 0.65 among the sample sites. Elevation varied from 1650 to 3100 m, and summer precipitation, defined as precipitation from April to August, varied from 13.7 to 26.4 cm. The soil types at the collection sites were schist, quaternary volcanic or a mixture of shale and sandstone. Logistic regression revealed that Gly frequencies did not respond to either elevation or soil type, but were related to summer precipitation (P < 0.01). The correlation between summer precipitation and the frequency of the Gly‐3 allele was r = ?0.92 (P < 0.001). Thus, the patterns of differentiation on microgeographical scales are consistent with greater differentiation on a range‐wide scale.     

Reproductive mode evolution in lizards revisited: updated analyses examining geographic,climatic and phylogenetic effects support the cold‐climate hypothesis

Viviparity, the bearing of live young, has evolved well over 100 times among squamate reptiles. This reproductive strategy is hypothesized to allow maternal control of the foetus' thermal environment and thereby to increase the fitness of the parents and offspring. Two hypotheses have been posited to explain this phenomenon: (i) the cold‐climate hypothesis (CCH), which advocates low temperatures as the primary selective force; and (ii) the maternal manipulation hypothesis (MMH), which advocates temperature variability as the primary selective force. Here, we investigate whether climatic and geographic variables associated with the CCH vs. the MMH best explain the current geographical distributions of viviparity in lizards while incorporating recent advances in comparative methods, squamate phylogenetics and geospatial analysis. To do this, we compared nonphylogenetic and phylogenetic models predicting viviparity based on point‐of‐capture data from 20 994 museum specimens representing 215 lizard species in conjunction with spatially explicit bioclimatic and geographic (elevation and latitude) data layers. The database we analysed emphasized Nearctic lizards from three species‐rich genera (Phrynosoma, Plestiodon and Sceloporus); however, we additionally analysed a less substantial, but worldwide sample of species to verify the universality of our Nearctic results. We found that maximum temperature of the warmest month (and, less commonly, elevation and maximum temperature of the driest quarter) was frequently the best predictor of viviparity and showed an association consistent with the CCH. Our results strongly favour the CCH over the MMH in explaining lizard reproductive mode evolution.