Altered dynamics of mitochondria and reactive oxygen species in the erythrocytes of migrating red-headed buntings.

Background: Blood antioxidants provide propensity to mitigate reactive oxygen species (ROS) apart from other oxidative challenges during a high-energy state of migration in night migratory songbirds. The study investigated the modulation of erythrocytes, mitochondrial abundance, hematocrit changes, and relative expression of fat transport-related genes during migration in red-headed buntings (Emberiza bruniceps). We hypothesized an increase in antioxidants along with the mitigation of mitochondria-related reactive oxygen species elevation and consequential apoptosis occurring during migration. Methods: Male red-headed buntings (n = 6) were placed under short days (8 h of light and 16 h of dark, 8L:16D)/long days (14L:10D) and photo induced to simulated non-migratory, nMig; pre-migratory, pMig; and migratory, Mig, states. Erythrocyte shape, reactive oxygen species production, mitochondrial membrane potential (MMP), reticulocyte proportion, and apoptosis were analyzed using flow cytometry and relative expression of fat metabolizing and antioxidant genes was measured by using qPCR. Results: There was a significant increase in hematocrit, erythrocyte area, and mitochondrial membrane potential. Reactive oxygen species and apoptotic erythrocyte proportion declined in the Mig state. The changes in antioxidant genes (SOD1 and NOS2), fatty acid translocase (CD36), and metabolic (FABP3, DGAT2, GOT2, and ATGL) genes showed a significant increment during the Mig state. Conclusion: These results suggested that adaptive changes occur in mitochondrial behavior and apoptosis of erythrocytes. The transition in erythrocytes, antioxidant genes, and fatty acid metabolism gene expressions suggested differences in regulatory strategies at the cellular/transcriptional level during different states of simulated migration in birds.

Night Migratory Songbirds Exhibit Metabolic Ability to Support High Aerobic Capacity during Migration.

Aerobic metabolism in night migratory songbirds exhibit seasonal plasticity, which depends not only on annual life history stages (LHSs), viz., migratory/nonmigratory or breeding/nonbreeding, but also on the time of the day. Initially, we studied daily changes in behavior/physiology alongside aerobic metabolism intermediates using gas chromatography-mass spectrometry-based chemometric analyses of serum of migratory male redheaded buntings during low-energy wintering, that is, the nonmigrating LHS. Then, the metabolic phenotype of nonmigrating birds was compared with that of photostimulated migrating buntings, the latter representing the high-energy LHS. Diurnal changes such as daytime feeding and activity were reflected by increased fatty acid (FA, viz., palmitic, oleic, and linoleic acids) levels and protein catabolites, whereas higher night-time levels of short-chain FAs indicated lipolysis in night-fasted birds. High night-time levels of taurine, a sulfur amino acid, suggested the endogenous metabolite rendering an adaptive advantage to hyperglycaemic night migratory songbirds during the LHS with low daily energy expenditure. Conversely, migrating birds, largely night-active, exhibited higher circulatory FA, its mobilization, and increased aerobic catabolism, and the adipocyte-secreted lipid, palmitoylethanolamide (PEA), capable of activating the peroxisome proliferator-activated receptor α-PGCα axis, showed elevated levels throughout the day. PEA is known for anti-inflammatory and cannabinomimetic properties, and we show, for the first time, circadian changes in PEA levels in any migrating bird. Significantly higher levels of pyridoxal phosphate also suggested the bird's protective ability to combat metabolic stress through high aerobic capacity during migration. This study elucidates putative "serum biomarkers" with a protective role in stress accrued by enhanced aerobic capacity requirements at the organismal level.

Lifestyle and Circadian Health: Where the Challenges Lie?

Modern life is facilitated by extended light hours at night and longer hours of eating. Compromised sleep, sedentary life, and modern diet adversely affect human health. Studies emphasizing importance of evidence-driven longitudinal studies on daily rhythms of human eating and sleeping behaviour provide a baseline for adequate insight into causal factors for circadian misalignment. Molecular chronobiology studies in animal models debrief endogenous regulation of organismal circadian clock; their regulation by environmental cues and how they segregate incompatible processes. But effective utilization of the knowledge needs randomized chrono-therapeutic intervention trials in humans. However, nutrition, activity, and lifestyle being society specific, baseline longitudinal studies must precede intervention trials as primary method to decipher circadian disruption. Our pilot survey studies investigating current lifestyle trends responsible for circadian rhythm disruption revealed that accelerated urban life, more than 8 hours work operations and long commutes to work inflict a sleep loss in Indian working women living in metropolitan cities. This sleep loss is sufficient to adversely impact their wellness. Besides, daily work routines and fast-food popularity have contributed to circadian disruption in daily rhythms of eating and sleep, enhancing disease consequences.

Temperature alters the hypothalamic transcription of photoperiod responsive genes in induction of seasonal response in migratory redheaded buntings.

We investigated the temperature effects on hypothalamic transcription of genes involved in the induction of photoperiodic response in redheaded buntings. Birds were exposed at 22 and 38 °C to 13-h long photoperiods (LP), with controls at 22 °C on 8-h short photoperiods (SP). At 22 °C, compared to SP, we found higher tshb, eya3 and dio2 and low dio3 and gnih mRNA expressions after a week of LP; concomitant with testis recrudescence this confirmed buntings' responsiveness to LP-induced photostimulation. tshb, dio2 and gnrh mRNA levels were further increased by 2.5 weeks of LP at 38 °C. Temperature sensitive trpm8, but not trpv4, bdnf or adcyap1 also showed LP-induced expression at 22 °C. Concomitant changes in dnmt3b and tet2 mRNA expressions further suggested epigenetic modification of temperature influence on photoperiodic responses. These results demonstrate the role of temperature in hypothalamic molecular regulation of the photoperiodic gonadal response in seasonally breeding birds.

Difference in control between spring and autumn migration in birds: insight from seasonal changes in hypothalamic gene expression in captive buntings.

We hypothesized differences in molecular strategies for similar journeys that migrants undertake to reproduce in spring and to overwinter in autumn. We tested this in redheaded buntings (Emberiza bruniceps) photoinduced into spring and autumn migratory states, with winter and summer non-migratory states as controls. Compared with controls, buntings fattened, gained weight and showed Zugunruhe (nocturnal migratory restlessness) in the migratory state. Spring migration was associated with greater fat and body mass, and higher intensity of Zugunruhe, compared with autumn migration. Circulating corticosterone levels were higher in spring, while T3 levels were higher in autumn. Hypothalamic expression of thyroid hormone-responsive (dio2, dio3), light-responsive (per2, cry1, adcyap1) and th (tyrosine hydroxylase, involved in dopamine biosynthesis) genes showed significant changes with transition from non-migratory to the migratory state. There were significantly higher mRNA expressions in autumn, except for higher th levels in the spring. Furthermore, the expression patterns of dnmt3a (not dnmt3b) and tet2 genes suggested an epigenetic difference between the non-migrant and migrant periods, and the spring and autumn migrant periods. These results demonstrate for the first time seasonal transition in hypothalamic gene expressions, and suggest differences in regulatory strategies at the transcriptional level for spring and autumn migrations in songbirds.

A camera-phone based study reveals erratic eating pattern and disrupted daily eating-fasting cycle among adults in India.

The daily rhythm of feeding-fasting and meal-timing are emerging as important determinants of health. Circadian rhythm research in animal models and retrospective analyses of human nutrition data have shown that reduced length of overnight fasting or increased late night eating increases risk for metabolic diseases including obesity and diabetes. However, the daily rhythm in eating pattern in humans is rarely measured. Traditional methods to collect nutrition information through food diary and food log pay little attention to the timing of eating which may also change from day to day. We adopted a novel cell-phone based approach to longitudinally record all events of food and beverage intake in adults. In a feasibility study daily food-eating patterns of 93 healthy individuals were recorded for 21 days using camera phones. Analysis of the daily eating patterns of these individuals indicates deviation from conventional assumption that people eat three meals-a-day within a 12 h interval. We found that eating events are widespread throughout the day, with <30% of calories consumed before noon and >30% consumed in evening and late night hours. There was little difference in eating pattern between weekdays and weekends. In this cohort more than 50% of people spread their caloric intake events over 15 h or longer. One decile of the cohort who were spouses of shift-workers or had flexible work schedule spread their caloric intake over 20 h. Although the nutrition quality and diversity of food consumed is different between South-East Asian and Western countries, such overall disruption of daily eating-fasting rhythm is similar. Therefore, in view of hypothesis that disrupted daily eating pattern may contribute to the global increase in metabolic diseases and modification of daily eating pattern is a potential modifiable behavior to contain these diseases, monitoring eating pattern is an important aspect of lifestyle.

Circadian synchronization determines critical day length for seasonal responses.

A photoperiodic species initiates fat deposition (in migrants) and gonadal recrudescence in response to a specific duration of natural daylight, called critical day length (CD), when light extends in the inductive phase of the endogenous circadian rhythm of photoinducibility (CRP). The molecular basis of species-specificCD, determined by the entrainment of the CRP, has been poorly understood. To investigate this, we measured expression levels of genes implicated in the photoperiod-induced changes in reproduction (EYA3, TSH beta, DIO2, DIO3, GNRH and GNIH) and metabolism (SIRT1, HMGCR, FASN and PPAR alpha) in photosensitive redheaded buntings subjected to light-dark cycles of varying period lengths (T-photocycles). Buntings were exposed to six T22, T24 or T26 photocycles, with 1h additional light at night falling at different phases of the entrained CRP (T2211L=6L:4D:1L:11D; T2411L=6L:4D:1L:13D,T2412L=6L:5D:1L:12D, T2413L=6L:6D:1L:11D; T2612L=6L:5D:1L:14D). Photoinduction at genetic and phenotypic levels in T2412L and T2413L, not T2411L, groups confirmed CD being close to 12h in buntings under T24. Compared to T24, exposure to T22 advanced CD by 1h, as evidenced by photoinduction in the T2211L, not T226L, group. Similarly, CD appeared to be delayed under T26, with no photoinduction in the T2612L group. Further, to show that induction of response under a T-photocycle was because of the interaction of inductive phase of the CRP with 1h during the dark period in each cycle, not with the 6h main light periods falling 2h earlier each successive 24hday in a T22 paradigm, a group of buntings was exposed to 6L:16D (T226L), to which they did not respond. The mRNA expression of genes, particularly TSH beta, DIO2, DIO3 and PPAR alpha, was significantly correlated with changes in reproductive and metabolic phenotypes. These results suggest CRP-entrainment based genetic regulation of the CD, and extend the idea that synchronization with environment is a critical measure in a seasonal species for its temporal adaptation in the wild.

Daily and seasonal activity patterns in blackheaded munia.

To test the circadian clock characteristics, activity behaviour of male blackheaded munia was recorded. Two experiments were performed. In experiment 1A, activity of munia was recorded under long days, LD (14L: 10D); and short days, SD (10L: 14D). Locomotor activity of two groups of munia exposed to equinox (12L: 12D) daylength followed by transfer of one group each to continuous dimlight (DD) and continuous bright light (LL) was recorded in experiment 1B. Experiment 2 aimed to describe seasonal trend in daily pattern of activity/rest cycle under natural illumination conditions (NDL). Hourly activity during daytime was more under SD than under LD. Munia did not exhibit bimodality in daily activity pattern; activity during morning, M (2h) was more than evening, E. A free-running activity rhythm was recorded in munia under DD; the same was arrhythmic under LL. The seasonal pattern in daily activity profiles under NDL corresponds to the seasonal changes in daylength. Daylength regulates daily and seasonal activity patterns in blackheaded munia.