High fat diet induces obesity, alters eating pattern and disrupts corticosterone circadian rhythms in female ICR mice.

Circadian, metabolic, and reproductive systems are inter-regulated. Excessive fatness and circadian disruption alter normal physiology and the endocrine milieu, including cortisol, the primary stress hormone. Our aim was to determine the effect feeding a high fat diet to female ICR mice had on diurnal feeding pattern, weight gain, body composition, hair corticosterone levels and circadian patterns of fecal corticosterone. Prepubertal (~35d of age) ICR mice were assigned to control (CON; 10% fat) or high fat (HF; 60% fat) diet and fed for 4 wk to achieve obesity under 12h light and 12h of dark. Feed intake was measured twice daily to determine diurnal intake. Mice were weighed weekly. After 4 wk on diets hair was collected to measure corticosterone, crown-rump length was measured to calculate body mass index (BMI), and body composition was measured with EchoMRI to determine percent fat. HF mice weighed more (P<0.05) after week two, BMI and percent body fat was greater (P<0.05) in HF than CON at the end of wk 4. HF mice consumed more during the day (P<0.05) than CON mice after 1 week on diets. Hair corticosterone was higher in HF mice than in CON (P<0.05). Fecal circadian sampling over 48hr demonstrated that HF mice had elevated basal corticosterone, attenuated circadian rhythms, and a shift in amplitude. High fat feeding for diet induced obesity alters circadian eating pattern and corticosterone rhythms, indicating a need to consider the impact of circadian system disruption on reproductive competence.

Relationship between body temperature and behavior of nonpregnant early-lactation dairy cows.

Animal behavior and management factors that influence behavior affect physiology and lactation performance. Circadian rhythms of core body temperature are a primary output of the master clock; however, core body temperature in early-lactation dairy cows showed poor fit to 24-h rhythms. We hypothesized that eating behavior was related to daily body temperature oscillations. The objectives of this study were to determine if oscillations in daily behaviors, specifically feeding behavior, were related to body temperature. The behavior of 11 Holstein cows (34 ± 14 d in milk; mean ± standard deviation) housed in a freestall barn was recorded every 10 min for a 48-h period. Simultaneously, data loggers (iButtons; iButtonLink Technology) recorded the body temperature of cows with the same sampling frequency. The mean temperature of all cows showed a better fit to a 2-component cosinor (R2 = 0.54) than to a single cosinor model (R2 = 0.26). Logistic regression showed that the probability (Pr) of a cow experiencing an increase in body temperature (increment, I) given that she was milking [Pr(I|milking) = 0.94] was higher than for ruminating [Pr(I|ruminating) = 0.69], lying [Pr(I|lying) = 0.66], feeding [Pr(I|feeding) = 0.16], standing [Pr(I|standing) = 0.54], and mounting [Pr(I|mounting) = 0.62]. The main limitations of this study are the length of the observation period and the sample size. Longer observation windows on core body temperature would allow to isolate the noise and the signal and identify patterns with more clarity. Oscillations in body temperature were not associated with feeding. However, findings indicate that milking, activity associated with walking to the parlor, or the temperature in the parlor may affect secondary rhythms of daily body temperature.

Impact of high-fat diet and exposure to constant light on reproductive competence of female ICR mice.

Obesity and exposure to light at night are prevalent in modern society and associated with changes in physiology and behavior that can affect a female's ability to support offspring growth during pregnancy and lactation. A 2X3 factor study of ICR mice was conducted to determine the effect of diet [control (CON; 10% fat) or high fat (HF; 60% fat)] and exposure to regular 12 h light:dark cycles (LD) or continuous low (L5) or high (L100) lux of light on gestation length, birth litter size, milk composition and litter growth to lactation day 12. HF diet reduced birth litter size, but increased postnatal d 12 litter weight (P<0.05), whereas constant light tended to increase litter weight (P=0.07). Continuous light increased gestation length, altered dam feed intake, increased serum prolactin and increased final dam and mammary gland weight (P<0.05), while decreasing mammary ATP content and milk lactose (P<0.05). Correlation analysis indicated a positive relationship between final litter weight and mammary size, metabolic stores (e.g. maternal fat pad weight), kcal of feed intake, and gestation length (P<0.05). Although CON mice spent more time eating than HF dams, the calorically dense HF diet was related to greater rates of litter growth to peak lactation. Constant light circadian disrupting effects appear to be confounded by a potential long day photoperiod response exemplified by higher circulating levels of prolactin and increased body and mammary weight of females exposed to these conditions. Other model systems may be better to study the interacting effects of obesity and circadian disruption on reproductive competence.

Low colostrum intake results in potential accumulation of peroxisome lipid substrates in vaginal tissue of 3-week-old gilts.

Low colostrum intake relates to poorer health and infertility in swine. We previously connected vaginal lipid profiles at weaning to fertility of sows. We hypothesized vaginal lipidome varied with colostrum intake. Our objective was to determine whether indicators of colostrum intake, immunocrit (IM) and weight gain 24 h postnatal (PN), related to vaginal lipids at d21 PN. Gilts (n=60) were weighed and blood sampled to measure IM. On d21 PN vaginal swabs were taken and lipids measured using multiple reaction monitoring. Abundance of multiple lipids differed (P<0.05) between gilts categorized as high versus low IM and high versus low 24 h gain. The abundance of multiple lipids correlated with IM and 24 h gain. Phosphatidylcholine PC(36:3), PC(36:2), and arachidonic acid (C20:4) positively (P<0.05) correlated with IM. The ether lipid PCo(38:6) and multiple cholesteryl esters negatively (P<0.05) correlated with IM. ROC analysis indicated arachidonic acid and docosanoic acid (C22:0) may serve as excellent biomarkers that distinguish between high and low IM. Similar to gilts found to be infertile, lipid profiles of low colostrum intake animals had greater abundance of very long chain fatty acids, lipids with high levels of unsaturation, and cholesteryl esters, which are metabolized in peroxisomes indicating their potential dysfunction.

Core circadian clock transcription factor BMAL1 regulates mammary epithelial cell growth, differentiation, and milk component synthesis.

The role the mammary epithelial circadian clock plays in gland development and lactation is unknown. We hypothesized that mammary epithelial clocks function to regulate mammogenesis and lactogenesis, and propose the core clock transcription factor BMAL1:CLOCK regulates genes that control mammary epithelial development and milk synthesis. Our objective was to identify transcriptional targets of BMAL1 in undifferentiated (UNDIFF) and lactogen differentiated (DIFF) mammary epithelial cells (HC11) using ChIP-seq. Ensembl gene IDs with the nearest transcriptional start site to ChIP-seq peaks were explored as potential targets, and represented 846 protein coding genes common to UNDIFF and DIFF cells and 2773 unique to DIFF samples. Genes with overlapping peaks between samples (1343) enriched cell-cell adhesion, membrane transporters and lipid metabolism categories. To functionally verify targets, an HC11 line with Bmal1 gene knocked out (BMAL1-KO) using CRISPR-CAS was created. BMAL1-KO cultures had lower cell densities over an eight-day growth curve, which was associated with increased (p<0.05) levels of reactive oxygen species and lower expression of superoxide dismutase 3 (Sod3). RT-qPCR analysis also found lower expression of the putative targets, prolactin receptor (Prlr), Ppara, and beta-casein (Csn2). Findings support our hypothesis and highlight potential importance of clock in mammary development and substrate transport.

Mammary Development in Gilts at One Week Postnatal Is Related to Plasma Lysine Concentration at 24 h after Birth, but Not Colostrum Dose.

Perinatal nutrition affects future milk production. The number of mammary epithelial cells affect milk production capacity. Therefore, it was hypothesized that the level of colostrum intake affects the proliferation rate and the total number of mammary epithelial cells in the gland. The ratio of newly synthesized protein to newly synthesized DNA reflects the relative amount of cellular differentiation to cell division. The study objective was to determine the relationship between the level of colostrum intake and 24 h-level of circulating amino acid, glucose and insulin with mammary parenchyma histological features, cell division and protein synthesis over the first week postnatal. One of two standardized doses of a homogenate colostrum sample, 10% (n = 8) and 20% (n = 8) of birth bodyweight, was fed to gilts over the first 24 h postnatal. Gilts were administered deuterium oxide immediately after birth and daily to label newly synthesized DNA and proteins. Gilts were euthanized on postnatal day seven, and DNA and protein were isolated from mammary parenchyma. DNA and protein fractional synthesis (f) and fractional synthetic rate (FSR) were calculated using mass isotopomer distribution analysis. The ratio of protein f and FSR to DNA f and FSR were calculated and used to indicate the relative amounts of differentiation to cell division. Mammary morphological development was also analyzed by measuring the parenchymal epithelial area and the stromal and epithelial proliferation index on postnatal day seven. Colostrum dose was not related to any of the variables used to evaluate mammary development. However, plasma lysine levels at 24 h postnatal were positively related to average daily gain (ADG; r = 0.54, p = 0.05), DNA f (r = 0.57; p = 0.03) and DNA FSR (r = 0.57; p = 0.03) in mammary parenchyma. Plasma lysine was inversely related to the ratio of protein to DNA f and FSR (r = -0.56; p = 0.04). ADG was related to the parenchymal epithelial area and DNA and protein f and FSR (p < 0.05). These relationships support the idea that the nutritional environment affects early mammary development and that higher lysine levels in the perinatal period favored a greater degree of cell division versus differentiation in mammary of neonatal pigs and thus, warrant further investigations.

A standardized model to study effects of varying 24-h colostrum dose on postnatal growth and development.

Survival, feed efficiency, growth, and fertility of swine are dependent on colostrum intake in the first 24 h after birth. This study determined the effects of three doses of a homogeneous colostrum sample on 24-h body weight, rectal temperature (RT), immunocrit, and growth and survival to postnatal day (PND) 7. Three female piglets were selected from eight litters (n = 24 piglets) at birth, removed from their litter, and bottle-fed 10% (COL10, n = 8), 15% (COL15, n = 8), or 20% (COL20, n = 8) colostrum based on birth weight over 12 bottle feedings every 2 h. At 24 h, piglets were weighed, RT recorded, and blood was collected to measure immunocrit. Piglets were returned to the litter of origin, and weight was measured daily until PND 7. Colostrum dose had an overall effect on weight gain at 24 h, RT, immunocrit, and growth to PND 7 (P < 0.05). Piglets in the 20% BrW colostrum group had greater weight gain, RT, and immunocrit at 24 h than COL10 piglets (P < 0.05), but these variables were not different between COL15 and the other treatments. Despite no difference in average daily gain after being returned to their litters, the greater weight (P < 0.05) in COL20 compared to COL10 and COL15 was sustained over 7 d. Seven piglets in each treatment survived to PND 7. This model using standardized doses of a homogeneous colostrum sample enables controlled studies aimed at understanding the role of 24-h colostrum intake on piglet development.