SERCA uncoupling may facilitate cold acclimation in dark-eyed juncos (Junco hyemalis) without regulation by sarcolipin or phospholamban.

Homeothermic endotherms defend their body temperature in cold environments using a number of behavioral and physiological mechanisms. Maintaining a stable body temperature primarily requires heat production through shivering (ST) or non-shivering thermogenesis (NST). Although the use of NST is well established in mammalian systems, the mechanisms and extent to which NST is used in birds is poorly understood. In mammals, one well-characterized mechanism of NST is through uncoupling of Ca2+ transport from ATP hydrolysis by sarco/endoplasmic reticulum ATPase (SERCA) in the skeletal muscle, which generates heat and may contribute to Ca2+ signaling for fatigue resistance and mitochondrial biogenesis. Two small proteins-sarcolipin (SLN) and phospholamban (PLN)-are known to regulate SERCA in mammals, but recent work shows inconsistent responses of SLN to cold-acclimation in birds. In this study, we measured SERCA uncoupling in the pectoralis flight muscle of control (18°C) and cold-acclimated (-8°C) dark-eyed juncos (Junco hyemalis) that exhibited suppressed SLN transcription in the cold. We measured SERCA activity and Ca2+ uptake rates for the first time in cold-acclimated birds and found greater SERCA uncoupling in the muscle of juncos in the cold. However, SERCA uncoupling was not related to SLN or PLN transcription or measures of mitochondrial biogenesis. Nonetheless, SERCA uncoupling reduced an individual's risk of hypothermia in the cold. Therefore, while SERCA uncoupling in the cold could be indicative of NST, it does not appear to be mediated by known regulatory proteins in these birds. These results prompt interesting questions about the significance of SLN and PLN in birds and the role of SERCA uncoupling in response to environmental conditions.

Sarcolipin relates to fattening, but not sarco/endoplasmic reticulum Ca2+-ATPase uncoupling, in captive migratory gray catbirds.

In order to complete their energetically demanding journeys, migratory birds undergo a suite of physiological changes to prepare for long-duration endurance flight, including hyperphagia, fat deposition, reliance on fat as a fuel source, and flight muscle hypertrophy. In mammalian muscle, SLN is a small regulatory protein which binds to sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and uncouples Ca2+ transport from ATP hydrolysis, increasing energy consumption, heat production, and cytosolic Ca2+ transients that signal for mitochondrial biogenesis, fatigue resistance and a shift to fatty acid oxidation. Using a photoperiod manipulation of captive gray catbirds (Dumetella carolinensis), we investigated whether SLN may play a role in coordinating the development of the migratory phenotype. In response to long-day photostimulation, catbirds demonstrated migratory restlessness and significant body fat stores, alongside higher SLN transcription while SERCA2 remained constant. SLN transcription was strongly correlated with h-FABP and PGC1α transcription, as well as fat mass. However, SLN was not significantly correlated with HOAD or CD36 transcripts or measurements of SERCA activity, SR membrane Ca2+ leak, Ca2+ uptake rates, pumping efficiency or mitochondrial biogenesis. Therefore, SLN may be involved in the process of storing fat and shifting to fat as a fuel, but the mechanism of its involvement remains unclear.

Evidence for a maintenance cost for birds maintaining highly flexible basal, but not summit, metabolic rates.

Reversible phenotypic flexibility allows organisms to better match phenotypes to prevailing environmental conditions and may produce fitness benefits. Costs and constraints of phenotypic flexibility may limit the capacity for flexible responses but are not well understood nor documented. Costs could include expenses associated with maintaining the flexible system or with generating the flexible response. One potential cost of maintaining a flexible system is an energetic cost reflected in the basal metabolic rate (BMR), with elevated BMR in individuals with more flexible metabolic responses. We accessed data from thermal acclimation studies of birds where BMR and/or Msum (maximum cold-induced metabolic rate) were measured before and after acclimation, as a measure of metabolic flexibility, to test the hypothesis that flexibility in BMR (ΔBMR), Msum (ΔMsum), or metabolic scope (Msum - BMR; ΔScope) is positively correlated with BMR. When temperature treatments lasted at least three weeks, three of six species showed significant positive correlations between ΔBMR and BMR, one species showed a significant negative correlation, and two species showed no significant correlation. ΔMsum and BMR were not significantly correlated for any species and ΔScope and BMR were significantly positively correlated for only one species. These data suggest that support costs exist for maintaining high BMR flexibility for some bird species, but high flexibility in Msum or metabolic scope does not generally incur elevated maintenance costs.

[Relationship between body composition and the risk of non-communicable chronic diseases in active older women from Chillán (Chile).] / Relación entre la composición corporal y el riesgo de enfermedades crónicas no transmisibles en mujeres mayores activas de Chillán (Chile).

OBJECTIVE: In Chile, the elderly represent 18% of the population. In women, the aging process impacts body composition, in addition to the coexistence of other pathologies such as chronic noncommunicable diseases (NCDs). The aim of the study was to relate body composition to the presence of chronic noncommunicable diseases in active older women in the city of Chillán. METHODS: The sample consisted of 284 women belonging to senior centers in Chillán. Body composition was determined by bioimpedanciometry. Sociodemographic information, prevalent pathologies, geriatric syndromes and physical activity were determined by means of a validated questionnaire. Data were analyzed with descriptive and inferential statistics in STATA 15.0 software with an α<0.05. RESULTS: Of the sample, 63% were under seventy-five years of age, 77.5% had less than twelve years of schooling, the predominant socioeconomic level was low, and the poor perception of health was mainly referred to as well as the use of regular medication. Arterial hypertension (AHT) and hypercholesterolemia were prevalent with 70.4% and 48.2% respectively. Body mass index (BMI) was 29.7±4.8 and 71.8% had excess malnutrition. The group older than seventy-five years presented more body fat (BMF) and extracellular water (ECW). AHT was related to higher BMI, TGM, MBC (Mean Arm Circumference), PC (Calf Circumference) and ECW (p<0.05), while Diabetes mellitus was related to BMI and MBC. CONCLUSIONS: Hypertension is the most frequent pathology and is related to higher BMI, MGT, CMB, CP and ECW, followed by DM2 which is related to BMI and CMB.

OBJETIVO: En Chile, las personas mayores representan el 18% de la población. En mujeres, el proceso de envejecimiento impacta sobre la composición corporal, además de coexistir con otras patologías como enfermedades crónicas no transmisibles (ECNT). El objetivo del estudio fue relacionar la composición corporal con la presencia de enfermedades crónicas no transmisibles en mujeres mayores activas de la ciudad de Chillán. METODOS: La muestra quedó compuesta por 284 mujeres pertenecientes a centros de adultos mayores de Chillán. La composición corporal se determinó por bioempidenciometría. La información sociodemográfica, las patologías prevalentes, los síndromes geriátricos y la actividad física se recabó mediante cuestionario validado. Los datos se analizaron con estadística descriptiva e inferencial en el software STATA 15.0 con un α<0,05. RESULTADOS: De la muestra, el 63% tenía menos de setenta y cinco años, 77,5% presentó una escolaridad por debajo de los doce años, el nivel socioeconómico predominante fue bajo, y la mala percepción de salud fue referida mayoritariamente al igual que el uso regular de medicamentos. La hipertensión arterial (HTA) y la hipercolesterolemia fueron prevalentes con un 70,4% y un 48,2%, respectivamente. El Índice de masa corporal (IMC) fue de 29,7±4,8 y el 71,8% tenía malnutrición por exceso. El grupo mayor a setenta y cinco años presentó más grasa corporal (MGT) y agua extracelular (AEC). La HTA se relacionó con mayor IMC, MGT, CMB (Circunferencia Media del Brazo), CP (Circunferencia de Pantorrilla) y AEC (p<0,05), mientras que la Diabetes mellitus con el IMC y la CMB. CONCLUSIONES: La hipertensión es la patología más frecuente y se relaciona con mayor IMC, MGT, CMB, CP y AEC, siguiéndole la DMII, que se relaciona con el IMC y la CMB.

Temperature heterogeneity correlates with intraspecific variation in physiological flexibility in a small endotherm.

Phenotypic flexibility allows individuals to reversibly modify trait values and theory predicts an individual's relative degree of flexibility positively correlates with the environmental heterogeneity it experiences. We test this prediction by integrating surveys of population genetic and physiological variation with thermal acclimation experiments and indices of environmental heterogeneity in the Dark-eyed Junco (Junco hyemalis) and its congeners. We combine field measures of thermogenic capacity for 335 individuals, 22,006 single nucleotide polymorphisms genotyped in 181 individuals, and laboratory acclimations replicated on five populations. We show that Junco populations: (1) differ in their thermogenic responses to temperature variation in the field; (2) harbor allelic variation that also correlates with temperature heterogeneity; and (3) exhibit intra-specific variation in thermogenic flexibility in the laboratory that correlates with the heterogeneity of their native thermal environment. These results provide comprehensive support that phenotypic flexibility corresponds with environmental heterogeneity and highlight its importance for coping with environmental change.

Is there a role for sarcolipin in avian facultative thermogenesis in extreme cold?

Endotherms defend their body temperature in the cold by employing shivering (ST) and/or non-shivering thermogenesis (NST). Although NST is well documented in mammals, its importance to avian heat generation is unclear. Recent work points to a prominent role for the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) in muscular NST. SERCA's involvement in both ST and NST, however, posits a tradeoff between these two heat-generating mechanisms. To explore this tradeoff, we assayed pectoralis gene expression of adult songbirds exposed to chronic temperature acclimations. Counter to mammal models, we found that cold-acclimated birds downregulated the expression of sarcolipin (SLN), a gene coding for a peptide that promotes heat generation by uncoupling SERCA Ca2+ transport from ATP hydrolysis, indicating a reduced potential for muscular NST. We also found differential expression of many genes involved in Ca2+ cycling and muscle contraction and propose that decreased SLN could promote increased pectoralis contractility for ST. Moreover, SLN transcript abundance negatively correlated with peak oxygen consumption under cold exposure (a proxy for ST) across individuals, and higher SLN transcript abundance escalated an individual's risk of hypothermia in acute cold. Our results therefore suggest that SLN-mediated NST may not be an important mechanism of-and could be a hindrance to-avian thermoregulation in extreme cold.

Body temperature maintenance acclimates in a winter-tenacious songbird.

Flexibility in heat generation and dissipation mechanisms provides endotherms the ability to match their thermoregulatory strategy with external demands. However, the degree to which these two mechanisms account for seasonal changes in body temperature regulation is little explored. Here, we present novel data on the regulation of avian body temperature to investigate how birds alter mechanisms of heat production and heat conservation to deal with variation in ambient conditions. We subjected dark-eyed juncos (Junco hyemalis) to chronic cold acclimations of varying duration and subsequently quantified their metabolic rates, thermal conductance and ability to maintain normothermia. Cold-acclimated birds adjusted traits related to both heat generation (increased summit metabolic rate) and heat conservation (decreased conductance) to improve their body temperature regulation. Increases in summit metabolic rate occurred rapidly, but plateaued after 1 week of cold exposure. In contrast, changes to conductance occurred only after 9 weeks of cold exposure. Thus, the ability to maintain body temperature continued to improve throughout the experiment, but the mechanisms underlying this improvement changed through time. Our results demonstrate the ability of birds to adjust thermoregulatory strategies in response to thermal cues and reveal that birds may combine multiple responses to meet the specific demands of their environments.

Full lifetime perspectives on the costs and benefits of lay-date variation in tree swallows.

Animals must balance various costs and benefits when deciding when to breed. The costs and benefits of breeding at different times have received much attention, but most studies have been limited to investigating short-term season-to-season fitness effects. However, breeding early, versus late, in a season may influence lifetime fitness over many years, trading off in complex ways across the breeder's lifespan. In this study, we examined the complete life histories of 867 female tree swallows (Tachycineta bicolor) breeding in Ithaca, New York, between 2002 and 2016. Earlier breeders outperformed later breeders in short-term measures of reproductive output and offspring quality. Though there were weak indications that females paid long-term future survival costs for breeding early, lifetime fledgling output was markedly higher overall in early-breeding birds. Importantly, older females breeding later in the season did not experience compensating life history advantages that suggested an alternative equal-fitness breeding strategy. Rather, most or all of the swallows appear to be breeding as early as they can, and differences in lay dates appear to be determined primarily by differences in individual quality or condition. Lay date had a significant repeatability across breeding attempts by the same female, and the first lay date of females fledged in our population was strongly influenced by the first lay date of their mothers, indicating the potential for ongoing selection on lay date. By examining performance over the entire lifespan of a large number of individuals, we were able to clarify the relationship between timing of breeding and fitness and gain new insight into the sources of variability in this important life history trait.

Association between high pre-pregnancy body mass index, excess gestational weight gain, and poor breastfeeding with overweight in 3-4-year-old Chilean children.

OBJECTIVE: The aim of this study was to determine the association between prepregnancy body mass, gestational weight gain, and inadequate breastfeeding (BF) with overweight in Chilean children ages 3 to 4 y. METHODS: This was an analytical and cross-sectional study with 560 participants. Age, residence, BF, and weight gain information were collected from child care records. The children's nutritional status (NS) was determined according to the weight-for-height z-score for sex. Bivariate relationships were evaluated by the χ2 test, and a multivariate logistic regression model was applied with the Stata version 15 software at α < 0.05. RESULTS: Prepregnancy NS values were 37% normal and 63% overweight. Excess weight gain occurred in 75% of the mothers. The children's NS was related to the duration of BF (P = 0.002), prepregnancy NS (P = 0.002), and weight gain (P = 0.004). When adjusting the logistic regression model for sex and maternal age, the overweight prepregnancy NS increased up to twice the risk for OW in children (odds ratio [OR], 2; 95% confidence interval [CI], 1.3-4.1), as well as excess weight gain (OR, 2.3; 95% CI, 1.5-5.9), and non-exclusive BF (OR, 2.4; 95% CI, 1.3-4.4). CONCLUSION: Children showing risk factors such as non-exclusive BF, prepregnancy NS with overweight, and excess gestational weight gain faced between 2 and 2.4 times more risk for overweight than children without these factors.

High-altitude shorebird migration in the absence of topographical barriers: avoiding high air temperatures and searching for profitable winds.

Nearly 20% of all bird species migrate between breeding and nonbreeding sites annually. Their migrations include storied feats of endurance and physiology, from non-stop trans-Pacific crossings to flights at the cruising altitudes of jetliners. Despite intense interest in these performances, there remains great uncertainty about which factors most directly influence bird behaviour during migratory flights. We used GPS trackers that measure an individual's altitude and wingbeat frequency to track the migration of black-tailed godwits (Limosa limosa) and identify the abiotic factors influencing their in-flight migratory behaviour. We found that godwits flew at altitudes above 5000 m during 21% of all migratory flights, and reached maximum flight altitudes of nearly 6000 m. The partial pressure of oxygen at these altitudes is less than 50% of that at sea level, yet these extremely high flights occurred in the absence of topographical barriers. Instead, they were associated with high air temperatures at lower altitudes and increasing wind support at higher altitudes. Our results therefore suggest that wind, temperature and topography all play a role in determining migratory behaviour, but that their relative importance is context dependent. Extremely high-altitude flights may thus not be especially rare, but they may only occur in very specific environmental contexts.

Divergence and Functional Degradation of a Sex Chromosome-like Supergene.

A major challenge in biology is to understand the genetic basis of adaptation. One compelling idea is that groups of tightly linked genes (i.e., "supergenes" [1, 2]) facilitate adaptation in suites of traits that determine fitness. Despite their likely importance, little is known about how alternate supergene alleles arise and become differentiated, nor their ultimate fate within species. Herein we address these questions by investigating the evolutionary history of a supergene in white-throated sparrows, Zonotrichia albicollis. This species comprises two morphs, tan and white, that differ in pigmentation and components of social behavior [3-5]. Morph is determined by alternative alleles at a balanced >100-Mb inversion-based supergene, providing a unique system for studying gene-behavior relationships. Using over two decades of field data, we document near-perfect disassortative mating among morphs, as well as the fitness consequences of rare assortative mating. We use de novo whole-genome sequencing coupled with population- and phylogenomic data to show that alternate supergene alleles are highly divergent at over 1,000 genes and that these alleles originated prior to the split of Z. albicollis from its sister species and may be polymorphic in Z. albicollis due to a past hybridization event. We provide evidence that the "white" allele may be degrading, similar to neo-Y/W sex chromosomes. We further show that the "tan" allele has surprisingly low levels of genetic diversity yet does not show several canonical signatures of recurrent positive selection. We discuss these results in the context of the origin, molecular evolution, and possible fate of this remarkable polymorphism.

Regulatory mechanisms of metabolic flexibility in the dark-eyed junco (Junco hyemalis).

Small temperate birds reversibly modify their aerobic performance to maintain thermoregulatory homeostasis under seasonally changing environmental conditions and these physiological adjustments may be attributable to changes in the expression of genes in the underlying regulatory networks. Here, we report the results of an experimental procedure designed to gain insight into the fundamental mechanisms of metabolic flexibility in the dark-eyed junco (Junco hyemalis). We combined genomic transcriptional profiles with measures of metabolic enzyme activities and whole-animal thermogenic performance from juncos exposed to four 6-week acclimation treatments that varied in temperature (cold, 3°C; warm, 24°C) and photoperiod (short day, 8 h light:16 h dark; long day, 16 h light:8 h dark). Cold-acclimated birds increased thermogenic capacity compared with warm-acclimated birds, and this enhanced performance was associated with upregulation of genes involved in muscle hypertrophy, angiogenesis, and lipid transport and oxidation, as well as with catabolic enzyme activities. These physiological changes occurred over ecologically relevant timescales, suggesting that birds make regulatory adjustments to interacting, hierarchical pathways in order to seasonally enhance thermogenic capacity.

Signatures of natural selection in the mitochondrial genomes of Tachycineta swallows and their implications for latitudinal patterns of the 'pace of life'.

Latitudinal variation in avian life histories can be summarized as a slow-fast continuum, termed the 'pace of life', that encompasses patterns in life span, reproduction, and rates of development among tropical and temperate species. Much of the variation in avian pace of life is tied to differences in rates of long-term metabolic energy expenditure. Given the vital role of the mitochondrion in metabolic processes, studies of variation in the mitochondrial genome may offer opportunities to establish mechanistic links between genetic variation and latitudinal 'pace of life' patterns. Using comparative genomic analyses, we examined complete mitochondrial genome sequences obtained from nine, broadly distributed Tachycineta swallow species to test for signatures of natural selection across the mitogenome within a phylogenetic framework. Our results show that although purifying selection is the dominant selective force acting on the mitochondrial genome in Tachycineta, three mitochondrial genes (ND2, ND5, and CYTB) contain regions that exhibit signatures of diversifying selection. Two of these genes (ND2 and ND5) encode interacting subunits of NADH dehydrogenase, and amino residues that were inferred to be targets of positive selection were disproportionately concentrated in these genes. Moreover, the positively selected sites exhibited a phylogenetic pattern that could be indicative of adaptive divergence between "fast" and "slow" lineages. These results suggest that functional variation in cytochrome b and NADH dehydrogenase could mechanistically contribute to latitudinal 'pace of life' patterns in Tachycineta.

Estado nutricional de mujeres con diabetes gestacional y características del recién nacido

El propósito fue determinar la relación entre el estado nutricional de la madre y las características de gestación del recién nacido de un grupo de embarazadas con diabetes gestacional. Se estudiaron 149 mujeres con diabetes gestacional de la Unidad de Alto Riesgo Obstétrico del Consultorio de Especialidades y Maternidad del Hospital Clínico Herminda Martin de Chillán, Chile, cuyos hijos nacieron en el año 2010. Los datos se obtuvieron de la historia clínica perinatal y la ficha del recién nacido. Las variables registradas en la madre fueron estado nutricional, vía de parto, número de gestaciones, control metabólico de la diabetes gestacional. Del niño se obtuvo el peso, circunferencia craneana y diagnóstico gestacional. Los datos fueron estudiados mediante análisis descriptivo univariado, bivariado y multivariado, ANOVA de un factor, Chi cuadrado y análisis de correspondencia múltiple. Se encontró que las mujeres con estado nutricional normal, eran multigestas, tuvieron parto vaginal, su hijo recién nacido fue adecuado para la edad gestacional, normocefálico;por otro lado, la condición de obesidad materna se relacionó con partos por cesárea, recién nacidos grandes para edad gestacional y macrocefalia; las mujeres con sobrepeso en general fueron primigestas y el recién nacido pequeño para edad gestacional con microcefalia p<0,01. Se concluyó que la obesidad en las mujeres con diabetes gestacional explica variables como la vía de parto, el número de gestaciones y el diagnóstico del recién nacido.

Nutritional status of women with gestational diabetes and characteristics of newborn. The objective was to determine the relationship between the mother’s nutritional status and the newborn’s gestational characteristics. A sample of 149 women with gestational diabetes was controlled in the High Risk Obstetric Unit of the Medical Specialties Public Health Center before delivery in the maternity ward of the Hospital Clínico Herminda Martín de Chillán, Chile in 2010. Data were obtained from the perinatal clinical history and the newborn’s chart. The variables recorded for the mother were nutritional status, type of delivery, number of pregnancies,and metabolic control. Data for the newborn were weight, length, head circumference, and gestational diagnosis.These data were analyzed by ANOVA, Chi-square test, and Multiple Correspondence. Women with a normal nutritional status were multiparous with natural childbirth; the newborn had an adequate gestational age and normal head circumference. On the other hand, maternal obesity was related to a Cesarean; the newborn was large for gestational age and had a larger head circumference. Overweight women were primiparous and the newborn was small for gestational age with a smaller head circumference (p<0,01). It was concluded that obesity in women with gestational diabetes explains variables such as type of delivery, number of gestations, and the newborn’s diagnosis.

[Nutritional status of women with gestational diabetes and characteristics of newborn]. / Estado nutricional de mujeres con diabetes gestacional y caracteristicas del recién nacido.

The objective was to determine the relationship between the mother's nutritional status and the newborn's gestational characteristics. A sample of 149 women with gestational diabetes was controlled in the High Risk Obstetric Unit of the Medical Specialties Public Health Center before delivery in the maternity ward of the Hospital Clinico Herminda Martín de Chillán, Chile in 2010. Data were obtained from the perinatal clinical history and the newborn's chart. The variables recorded for the mother were nutritional status, type of delivery, number of pregnancies, and metabolic control. Data for the newborn were weight, length, head circumference, and gestational diagnosis. These data were analyzed by ANOVA, Chi-square test, and Multiple Correspondence. Women with a normal nutritional status were multiparous with natural childbirth; the newborn had an adequate gestational age and normal head circumference. On the other hand, maternal obesity was related to a Cesarean; the newborn was large for gestational age and had a larger head circumference. Overweight women were primiparous and the newborn was small for gestational age with a smaller head circumference (p < 0.01). It was concluded that obesity in women with gestational diabetes explains variables such as type of delivery, number of gestations, and the newborn's diagnosis.