Foraging dive frequency predicts body mass gain in the Adélie penguin

Quantifying food intake in wild animals is crucial to many ecological and evolutionary questions, yet it can be very challenging, especially in the marine environment. Because foraging behavior can be inferred from dive recordings in many marine creatures, we hypothesized that specific behavioral dive variables can indicate food intake. To test this hypothesis, we attached time-depth recorders to breeding Adélie penguins also implanted with RFID tags that crossed a weighbridge as they traveled to and from the ocean to feed their chicks. The weighbridge reported how much mass the penguin had gained during a foraging trip. The variables that explained a significant amount of the change in body mass while at sea were the number of foraging dives per hour (46%) and the number of undulations per hour (12%). Most importantly, every increment of 1 in the rate of foraging dives per hour equated to a penguin gaining an average 170 g of mass, over the course of a 6–60 h foraging trip. These results add to a growing understanding that different metrics of foraging success are likely appropriate for different species, and that assessing the types and frequencies of dives using time-depth recorders can yield valuable insights.

Effects of neurosecretory protein GL on food intake and fat accumulation under different dietary nutrient compositions in rats

We recently identified a novel hypothalamic small protein, named neurosecretory protein GL (NPGL), which is involved in energy homeostasis in birds and mammals. However, whether the action of NPGL is influenced by nutritional composition remains unknown. Thus, we investigated the effect of chronic intracerebroventricular infusion of NPGL for 13 days on feeding behavior and body mass gain under a normal chow diet (NC), high-fat diet, high-sucrose diet (HSD), and medium-fat/medium-sucrose diet (MFSD) in rats. NPGL stimulated food intake of NC and MFSD, especially during the light period. By contrast, NPGL decreased body mass gain under NC and increased total white adipose tissue mass in HSD- and MFSD-fed rats. These data suggest that the effects of NPGL on feeding behavior, body mass gain, and fat accumulation depend on nutrient type. Among them, sucrose in diets seems to contribute to fat accumulation elicited by NPGL.

Suitability of a 10% fat diet for use in time-restricted feeding experiments with C57BL/6 mice

Background: There is growing interest in the possible role of circadian rhythms in feeding behavior and their effect on diet-induced obesity. However, it is unclear whether widely used purified diets are suitable for use as normal control diets for rodents undergoing time-restricted feeding studies. In the present study, we compared the effects of 4% and 10% fat diets on body mass gain and food consumption during time-restricted feeding (TRF).Methods: Ad libitum-fed male C57BL/6J mice had free access to AIN-93M (4% fat) or modified 10% fat diets, whereas TRF groups were only able to consume one of these diets twice daily, at ZT23:00–01:00 and ZT11:00–13:00, for 5 weeks.Results: Total energy consumptions by the TRF-4% and TRF-10% fat groups were 26.5% and 18.6%, respectively, less than that of the ad libitum-fed groups. The body mass gains by the 4% and 10% fat diet groups fed ad libitum were similar, but the gain by the TRF-4% fat group was markedly lower than that of the TRF-10% fat group. In addition, whereas the body mass gain by the TRF-10% fat group was similar to that of its ad libitum equivalent, the gain by the TRF-4% fat group was much lower than that of the equivalent ad libitum-fed group.Conclusion: We showed for the first time that a 10% fat diet (21.9% kcal from fat) is suitable for the maintenance of body mass gain during TRF of C57BL/6 mice.Keywords: ad libitum feeding, fat content, mouse, time-restricted feeding

Maternal Thyroid Hormone Deficiency During Gestation and Lactation Alters Metabolic and Thyroid Programming of the Offspring in the Adult Stage

Environmental stimuli during critical developmental stages establish long-term physiological and structural patterns that “program” health during adult life. Little is known about how alterations in hormonal supply might have consequences in metabolic and thyroid programming. This work aims to prove that alterations in the supply of thyroid hormones during gestation and lactation have long-term consequences in the metabolic and thyroid programming of the offspring. Female Wistar rats were divided into euthyroid, hypothyroid, and hypothyroid with 20 μg/day of s.c. thyroxine (T4), replacement wet nurses. Rats were mating, and after birth, pups were grouped according to their wet nurses group. Milk quality of wet nurses was assessed on days 7, 14, and 21. Body mass gain and energy intake of the offspring were monitored for 28 weeks after weaning. At sacrifice, we extracted and weighed their thyroid gland and adipose reserves, and collected blood to measure its metabolic and thyroid profiles. Hypothyroid wet nurses presented a persistent low quality of milk, while both male and female hypothyroid offspring presented lower body mass gain, higher blood glucose, dyslipidemia, hyperinsulinemia, and hyperleptinemia, as well as lower total adipose reserves, but higher visceral reserve, diminished T3 and T4 concentrations, and lower weight of thyroid gland. Thyroxine replacement prevented all changes in both wet nurses and pups. We conclude that maternal thyroid hormone deficiency during congenital and lactation stages alters the metabolic and thyroid programming of the offspring, while the reestablishment of maternal thyroid status during critical periods of development can prevent these alterations.