A Comparative Review of the Cell Biology, Biochemistry, and Genetics of Lactose Synthesis

A metabolic profiling approach to characterize and discriminate plant-based beverages and milk

The rising demand for nondairy and nonanimal protein sources has increased plant-based beverages (PBB) consumption. However, research on their functional properties, metabolic profile, and discrimination potential is limited. This study evaluated the potential of proton nuclear magnetic resonance (1H NMR) spectroscopy as an authentication method to discriminate milk (cow and goat) and PBB macro-groups, including soy-based, fruit-based (almond and coconut), and cereal-based (rice and oat) beverages, based on their metabolic profile. A total of 22 PBB (soy-, almond-, coconut-, rice-, and oat-based beverages), 4 cow milk, and 4 goat milk cartons were analyzed with 1H NMR spectroscopy to obtain their metabolic profile. Relevant metabolites to discriminate PBB macro-groups and cow and goat milk were identified through the Mann-Whitney U test and partial least squares-discriminant analysis. Results revealed that uridine diphosphate glucose and adenosine were key metabolites for the identification of goat and cow milk. At the same time, choline and guanosine emerged as important markers for different PBB macro-group detection. In addition, lactose played a significant role in differentiating milk from PBB. In conclusion, these findings represent an initial step toward applying 1H NMR spectroscopy for authentication and nutritional analysis of PBB, opening the door for further research into their authenticity and metabolic profiling.

Glycosyltransferases: glycoengineers in human milk oligosaccharide synthesis and manufacturing

Human milk oligosaccharides (HMOs) are a diverse group of complex carbohydrates that play crucial roles in infant health, promoting a beneficial gut microbiota, modulating immune responses, and protecting against pathogens. Central to the synthesis of HMOs are glycosyltransferases, a specialized class of enzymes that catalyse the transfer of sugar moieties to form the complex glycan structures characteristic of HMOs. This review provides an in-depth analysis of glycosyltransferases, beginning with their classification based on structural and functional characteristics. The catalytic activity of these enzymes is explored, highlighting the mechanisms by which they facilitate the precise addition of monosaccharides in HMO biosynthesis. Structural insights into glycosyltransferases are also discussed, shedding light on how their conformational features enable specific glycosidic bond formations. This review maps out the key biosynthetic pathways involved in HMO production, including the synthesis of lactose, and subsequent fucosylation and sialylation processes, all of which are intricately regulated by glycosyltransferases. Industrial methods for HMO synthesis, including chemical, enzymatic, and microbial approaches, are examined, emphasizing the role of glycosyltransferases in these processes. Finally, the review discusses future directions in glycosyltransferase research, particularly in enhancing the efficiency of HMO synthesis and developing advanced analytical techniques to better understand the structural complexity and biological functions of HMOs.

Mammalian lactation as a framework for teaching development, physiology, and cell biology for social change

Mammalian lactation is a dynamic process that develops throughout the lifespan of an organism. Here we present a framework for a third semester core course in biology that centers course content on lactation allowing examination of the developmental process as a dynamic whole-body experience involving changes occurring at the molecular, cellular, and organ levels of organization. Inequitable economic, socio- and geopolitical systems structure social determinants of health, affecting rates of breastfeeding in human populations. By integrating content exploring the ways social and biological systems impact breastfeeding rates in human populations, students develop abilities to understand the relationship between science and society throughout the course, a critical core competency for engaging in social change. Importantly, they interrogate social systems while simultaneously learning about many canonical biological processes including how natural selection and constraint have shaped the anatomy, physiology, cell biology, and biochemistry of lactation, how proteins, lipids, and carbohydrates are synthesized, processed, and exported through the endomembrane system in eukaryotes, and how neuronal and hormonal feedback mechanisms regulate milk synthesis and secretion. The course is structured using a flipped-classroom design emphasizing revision and student-self assessment that supports development of biological knowledge, social responsibility, and metacognitive skills. Because mammalian lactation includes fascinating, nuanced, and complex components that cross interdisciplinary boundaries, it provides a wealth of opportunities for faculty to teach developmental biology for social change.

Sources of variation underlying the production of lactose by dairy cows

This study explored variability in the production of lactose by dairy cows, and the factors underlying it, using herd testing data from New South Wales, Australia. The dataset spanned 14 years (2008-2022) and comprised 393,772 records from 33,280 cows across 85 herds, alongside meteorological and dairy sire genetic data. Variables included milk yield, composition, and quality; reproductive data; breed information; and environmental factors. We found significant variation in lactose yield (LY), lactose percentage (LP), and milk solids yield (MSY) across breed, parity, and stage of lactation. Holsteins had the highest LY and MSY and the lowest LP, whereas Jerseys produced more MSY per unit of LY (MSY:LY ratio). We observed a negative correlation between LY and milk composition variables (fat and protein percentages) and environmental factors such as the temperature-humidity index. Heritability estimates indicated a moderate genetic influence on LY, LP, and MSY:LY (0.24-0.33). The identification of cows producing milk with a consistently lower LP or higher MSY:LY ratio highlights the potential for selective breeding against lactose output to increase the production of milk components and suppress milk volume. These findings highlight the potential to modulate lactose synthesis that could enhance the milk production efficiency of dairy cows, and potentially reduce their environmental impact.

Exposure to circadian disrupting environment and high-fat diet during pregnancy and lactation alter reproductive competence and lipid profiles of liver, mammary, plasma and milk of ICR mice

This study's objective was to determine the effects of pre-pregnancy obesity induced by a high-fat diet and exposure to circadian-disrupting light-dark phase shifts on birth littler size, pup survival to 24h and growth to lactation day 12, and their relationship to maternal feeding patterns, fecal corticosterone levels, milk composition, and lipid profiles of liver, plasma, mammary gland, and milk. A 2 by 2 factorial designed experiment of female ICR mice assigned to control (CON; 10% fat) or high-fat (HF; 60% fat) and either a 12-hour light-dark (LD) cycle or a chronic jet lag model of 6-hour phase-shifts (PS) in light-dark cycle every 3 days throughout pregnancy and lactation, resulted in 4 treatment groups: CON-LD, CON-PS, HF-LD and HF-PS. HF diet increased maternal pre-pregnancy body weight and elevated milk lactose. Whereas PS reduced milk lactose within the CON diet group, and increased maternal feed intake and fecal corticosterone levels. PS exposure also affected the time of day of birth. Neither PS nor HF affected birth litter size or pup survival. Only diet impacted final litter weight, with HF greater than CON. Among the 1204 lipids detected by multiple reaction monitoring (MRM)-profiling, diet altered 67.1% in milk, 58.1% in mammary gland, 27.2% in the liver, and 10.9% in plasma, with HF increasing the carbon length of diacylglycerols in the liver and milk, and carbon length of triacylglycerols in plasma, mammary gland and milk. Although exposure to PS had no overall impact on maternal lipid profiles, interactions (P < 0.05) were found between PS and diets in the phosphatidylcholine and phosphatidylethanolanine class of lipids. Findings support that high fat diet and exposure to circadian disrupting environments impact maternal feeding behavior and stress responses as well as lipid profiles, which may relate to their negative association with maternal health and offspring development.

Genome-wide study for signatures of selection identifies genomic regions and candidate genes associated with milk traits in sheep

Milk production traits in sheep are influenced by complex genetic factors, and understanding these traits requires the identification of candidate genes under selection. This study employed two methods, FST and XP-EHH, to identify selection signatures and candidate genes associated with milk production traits in sheep. For this purpose, 9 different breeds from the Sheep HapMap dataset generated by the International Sheep Genomics Consortium (ISGC) based on analysis of the Ovine SNP50 BeadChip were used. The dairy breeds included Brown East Friesian (n = 39), Milk Lacaune (n = 103), Chios (n = 23), Churra (n = 120), and Comisana (n = 24), while the non-dairy breeds included Afshari (n = 37), Moghani (n = 34), Galway (n = 49), and Australian Suffolk (n = 109). Genomic regions in the top 0.1 percentile of FST values revealed 71 genes, while regions with the highest positive XP-EHH values identified 69 genes. Five overlapping genes-DHRS3, TNFRSF1B, AADACL4, ARHGEF11, and LRRC71-were detected by both methods, highlighting their relevance to milk production. Several candidate genes in regions identified from FST, such as PER2, SH3PXD2A, TMEM117, DDX6, PDCD11, CALHM2, and CALHM3, have been previously associated with milk production traits. Notably, CRABP2, PEAR1, PGM1, ALG6, COX15, and OAT were identified in regions with high XP-EHH values in the dairy group. Gene ontology analysis indicated that the identified genes are enriched in pathways related to chemokine receptor activity, gap junction channel activity, and gap junction-mediated intercellular transport, as well as cellular components like the connexin complex. Further studies on these genes may improve understanding of the genetic architecture of milk production traits in sheep.

Alternative biological functions of lactose: a narrative review

Lactose, commonly known as "milk sugar," offers various health benefits beyond its role as an energy source. As a precursor for essential molecules, lactose impacts calcium absorption, has low cariogenicity, affects satiety, enhances athletic performance, and potentially functions as a prebiotic for gut health. However, not all individuals can digest lactose, with a minority of the population exhibiting gastrointestinal symptoms after its consumption. The ability to digest lactose during adulthood is a genetically conferred trait known as lactase persistence, which is also likely affected by epigenetic alterations and other endogenous factors. In the present review, we highlight the multifaceted health effects of lactose, including its impact on calcium absorption, its low cariogenicity, its role in satiety control, its ability to enhance athletic performance, and its potential benefits as a prebiotic for gut health. Since these benefits are inherently dependent on lactose intake trends and the digestion capacity of populations, we also present the latest available information on the current trends in lactose consumption around the world. Overall, the gathered evidence suggests that moderate lactose consumption is recommended, as it can foster multiple lifelong health benefits.

Systemic and mammary inflammation and mammary gland development of Holstein dairy cows around dry-off and calving

This study evaluated systemic and mammary inflammation and the immune cell population and developmental pattern of the mammary gland in Holstein dairy cows transitioning from late lactation to the dry period (LTD, n = 6) and from the dry period to early lactation (DTL, n = 7). All cows were healthy and free of mastitis at enrollment. Mammary biopsies, milk or mammary secretions, and blood samples were collected on d -7, 3, 7, and 15 relative to dry-off and on d -8, 3, 7, and 21 relative to calving. After dry-off, LTD cows had increased circulating concentrations of tumor necrosis factor (TNF)-α, haptoglobin, and fibrinogen, suggesting upregulated inflammation. Protein, SCS, and SNF contents in milk or mammary secretions increased during the early dry period but decreased after calving. In contrast, lactose concentrations in mammary secretions decreased in the early dry period and increased following calving. Skim milk concentrations of TNF-α, IL-10, and haptoglobin increased following dry-off. Consistently, mammary tissue mRNA expression of IL1B and IL10 tended to increase on d 7 and 15 following dry-off, respectively. After calving, mammary alveolar and total cells had higher apoptosis rates. Mammary alveolar, stromal, and total cell proliferation rates peaked on d 7 after dry-off in mammary tissue collected from LTD cows and were greater in the late dry period than early lactation. Mammary mRNA expression of HGF increased on d 7 and 15 after dry-off. Mammary tissue collected in the late dry period had greater gene expression of IGF1, IGF2, PRLR than that collected in early lactation. Mammary tissues collected in the early dry period had greater percentages of CD20+ B lymphocytes, CD172a+ macrophages, and neutrophils than tissues collected during late lactation. Mammary tissues collected in early lactation had greater percentages of CD20+ B lymphocytes, CD3+ T lymphocytes, and CD172a+ macrophages than tissue collected in the late dry period. In conclusion, dairy cows experienced upregulated systemic and mammary inflammation during the early dry period, which warrants further research to elucidate its effect on mammary development. Our data also suggested that the increased mammary growth during the late gestation and early dry periods was mediated by different mechanisms. The concurrent increases in immune cell infiltration and mammary cell proliferation in the mammary gland following dry-off suggest an association between mammary immune responses and growth during the early dry period.

Innovative approaches for enzyme immobilization in milk processing: advancements and industrial applications

The dairy industry is progressively integrating advanced enzyme technologies to optimize processing efficiency and elevate product quality. Among these technologies, enzyme immobilization has emerged as a pivotal innovation, offering considerable benefits in terms of enzyme reusability, stability, and overall process sustainability. This review paper explores the latest improvements in enzyme immobilization techniques and their industrial applications within milk processing. It examines various immobilization strategies, including adsorption, affinity binding, ionic and covalent binding, entrapment, encapsulation, and cross-linking, highlighting their effectiveness in improving the performance of key enzymes such as lactases, lipases, proteases and transglutaminases. The paper also delves into the economic and ecological benefits of enzyme immobilization, emphasizing its role in reducing production costs and environmental impact while maintaining or enhancing the quality of dairy products. By analyzing current trends and technological developments, this review provides a comprehensive overview of how innovative enzyme immobilization approaches are transforming milk processing. It concludes with a discussion on future research directions and potential industrial applications, underscoring the importance of continued innovation in this field to meet the increasing demands of the global dairy market.

Use of Precision Feeding during Lactation Improves the Productive Yields of Sows and Their Piglets under Commercial Farm Conditions

Adequate nutritional management in maternities is one of the most challenging aspects of swine production. This study reports the results of two studies aiming to determine, under commercial farm conditions, the effects of precision feeding (electronic sow feeders, ESFs) on the production and economic yields of lactating sows and possible nutritional and metabolic differences when compared to a control group fed with traditional feeders. The first trial showed that sows fed with ESFs weaned heavier piglets than sows fed with traditional feeders. Feed intake during the lactation period was similar in the sows of both groups; consequently, the amount of feed per kg of weaned piglet was lower in the sows fed with ESFs, which is a remarkable economic output. The second trial confirmed these findings and showed that, despite similar feed intakes, the sows fed with ESFs had lower bodyweight losses during the lactation period, but there were no major differences in milk composition or metabolic traits of sows and piglets.

Heat stress affects mammary metabolism by influencing the plasma flow to the glands

BACKGROUND

Environmental heat stress (HS) can have detrimental effects on milk production by compromising the mammary function. Mammary plasma flow (MPF) plays a crucial role in nutrient supply and uptake in the mammary gland. In this experiment, we investigated the physiological and metabolic changes in high-yielding cows exposed to different degrees of HS: no HS with thermal-humidity index (THI) below 68 (No-HS), mild HS (Mild-HS, 68 ≤ THI ≤ 79), and moderate HS (Mod-HS, 79 < THI ≤ 88) in their natural environment. Our study focused on the changes in blood oxygen supply and mammary glucose uptake and utilization.

RESULTS

Compared with No-HS, the MPF of dairy cows was greater (P < 0.01) under Mild-HS, but was lower (P < 0.01) in cows under Mod-HS. Oxygen supply and consumption exhibited similar changes to the MPF under different HS, with no difference in ratio of oxygen consumption to supply (P = 0.46). The mammary arterio-vein differences in glucose concentration were lower (P < 0.05) under Mild- and Mod-HS than under no HS. Glucose supply and flow were significantly increased (P < 0.01) under Mild-HS but significantly decreased (P < 0.01) under Mod-HS compared to No-HS. Glucose uptake (P < 0.01) and clearance rates (P < 0.01) were significantly reduced under Mod-HS compared to those under No-HS and Mild-HS. Under Mild-HS, there was a significant decrease (P < 0.01) in the ratio of lactose yield to mammary glucose supply compared to that under No-HS and Mod-HS, with no difference (P = 0.53) in the ratio of lactose yield to uptaken glucose among different HS situations.

CONCLUSIONS

Degrees of HS exert different influences on mammary metabolism, mainly by altering MPF in dairy cows. The output from this study may help us to develop strategies to mitigate the impact of different degrees of HS on milk production.

Breast size in lactating women and the content of macronutrients in human milk

INTRODUCTION

Although the primary function of a woman's breast is milk synthesis, only a few studies have evaluated the relationship between breast size and human milk composition, showing equivocal results. This study aims to test if breast size during fully established lactation is related to energy density and content of macronutrients in human milk.

MATERIALS AND METHODS

Mothers of healthy, born-on-term infants at stage III of lactogenesis (N = 137) provided breast milk samples. Milk composition was analyzed using midinfrared transmission spectroscopy. The breast size index was calculated by dividing the breast by the circumference below the breast.

RESULTS

Stepwise forward linear regression showed a negative association between breast size index and lactose concentration in breast milk (β = -.242, p = .003). The final model, which includes breast size index, feeding frequency, and maternal energy intake together explained around 13% of the variance in breast milk lactose content (R2 adj = .126, p < .001). No statistically significant relationship was found between breast size index and milk's energy density, protein, and fat content.

CONCLUSION

This is the first study that shows a negative relationship between breast size during fully established lactation and lactose concentration in milk in a large sample size. No relationship between other macronutrients and breast size indicates that large breast size is not necessary for adequate milk production; however, it may contribute to an altered lactose concentration.

Effect of sodium butyrate treatment at the basolateral membranes on the tight junction barrier function via a monocarboxylate transporter in goat mammary epithelial cells

In lactating mammary glands, tight junctions (TJs) prevent blood from mixing with milk and maintain epithelial cell polarity, which is important for milk production. This study aimed to investigate the effect of sodium acetate and sodium butyrate (SB) stimulation direction on the TJ barrier function, which is measured with regard to transepithelial electrical resistance and fluorescein flux, in goat mammary epithelial cells. The expression and localization of the TJ proteins claudin-3 and claudin-4 were examined using Western blotting and immunofluorescence. SB treatment in the lower chamber of cell culture inserts adversely affected the TJ barrier function, whereas sodium acetate barely had any effect, regardless of stimulation direction. In addition, SB treatment in the lower chamber significantly upregulated claudin-3 and claudin-4, whereas TJ proteins showed intermittent localization. Moreover, SB induced endoplasmic reticulum (ER) stress. ARC155858, a monocarboxylate transporter-1 inhibitor, alleviated the adverse impact of SB on TJs and the associated ER stress. Interestingly, sodium β-hydroxybutyrate, a butyrate metabolite, did not affect the TJ barrier function. Our findings indicate that sodium acetate and SB influence the TJ barrier function differently, and excessive cellular uptake of SB can disrupt TJs and induce ER stress.

Human Milk Oligosaccharides in Maternal Serum Respond to Oral Glucose Load and Are Associated with Insulin Sensitivity

(1) Background: Pregnancy presents a challenge to maternal glucose homeostasis; suboptimal adaptations can lead to gestational diabetes mellitus (GDM). Human milk oligosaccharides (HMOs) circulate in maternal blood in pregnancy and are altered with GDM, suggesting influence of glucose homeostasis on HMOs. We thus assessed the HMO response to glucose load during an oral glucose tolerance test (OGTT) and investigated HMO associations with glucose tolerance/insulin sensitivity in healthy pregnant women. (2) Methods: Serum of 99 women, collected at 0 h, 1 h and 2 h during a 75 g OGTT at 24-28 gestational weeks was analyzed for HMOs (2'FL, 3'SLN, LDFT, 3'SL) by HPLC; plasma glucose, insulin and C-peptide were analyzed by standard biochemistry methods. (3) Results: Serum 3'SL concentrations significantly increased from fasting to 1 h after glucose load, while concentrations of the other HMOs were unaltered. Higher 3'SL at all OGTT time points was associated with a generally more diabetogenic profile, with higher hepatic insulin resistance (HOMA-IR), lower insulin sensitivity (Matsuda index) and higher insulin secretion (C-peptide index 1). (4) Conclusions: Rapid increase in serum 3'SL post-oral glucose load (fasted-fed transition) indicates utilization of plasma glucose, potentially for sialylation of lactose. Associations of sialylated HMOs with a more diabetogenic profile suggest sustained adaptations to impaired glucose homeostasis in pregnancy. Underlying mechanisms or potential consequences of observed HMO changes remain to be elucidated.

Parental factors that impact the ecology of human mammary development, milk secretion, and milk composition-a report from "Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)" Working Group 1

The goal of Working Group 1 in the Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN) Project was to outline factors influencing biological processes governing human milk secretion and to evaluate our current knowledge of these processes. Many factors regulate mammary gland development in utero, during puberty, in pregnancy, through secretory activation, and at weaning. These factors include breast anatomy, breast vasculature, diet, and the lactating parent's hormonal milieu including estrogen, progesterone, placental lactogen, cortisol, prolactin, and growth hormone. We examine the effects of time of day and postpartum interval on milk secretion, along with the role and mechanisms of lactating parent-infant interactions on milk secretion and bonding, with particular attention to the actions of oxytocin on the mammary gland and the pleasure systems in the brain. We then consider the potential effects of clinical conditions including infection, pre-eclampsia, preterm birth, cardiovascular health, inflammatory states, mastitis, and particularly, gestational diabetes and obesity. Although we know a great deal about the transporter systems by which zinc and calcium pass from the blood stream into milk, the interactions and cellular localization of transporters that carry substrates such as glucose, amino acids, copper, and the many other trace metals present in human milk across plasma and intracellular membranes require more research. We pose the question of how cultured mammary alveolar cells and animal models can help answer lingering questions about the mechanisms and regulation of human milk secretion. We raise questions about the role of the lactating parent and the infant microbiome and the immune system during breast development, secretion of immune molecules into milk, and protection of the breast from pathogens. Finally, we consider the effect of medications, recreational and illicit drugs, pesticides, and endocrine-disrupting chemicals on milk secretion and composition, emphasizing that this area needs much more research attention.

Dynamics of Milk Parameters of Quarter Samples before and after the Dry Period on Czech Farms

This study aimed to monitor milk parameters on three different dairy farms in the Czech Republic to describe their readiness for implementing selective dry cow therapy. Fat, protein, casein, lactose, solids-not-fat content, total solids content, freezing point, titratable acidity, and somatic cell count of quarter milk samples collected from tested Holstein cows were evaluated. Associations between the tested parameters, as well as the effects of parity, farm, day of calving, and time of evaluation at dry-off and after calving, were assessed. Values of the leading milk components dynamically changed between dry-off and after calving, but only protein content was significantly affected. The most important parameter of our research, the somatic cell count of quarter milk samples, was also not affected by the time of evaluation. Even though a slight increase in the mean of somatic cell count is expected before the dry period and after calving, at dry-off, we observed 30%, 42%, and 24% of quarters with somatic cell counts above 200,000 cells per mL, while after calving, we observed 27%, 16%, and 18% of quarters with somatic cell counts above 200,000 cells per mL on Farm 1, Farm 2, and Farm 3, respectively. High somatic cell counts (>200,000 cells per mL) indicate bacterial infection, as confirmed by the significant negative correlation between this parameter and lactose content. In addition, a deficient milk fat-to-protein ratio was observed on two farms, which may indicate metabolic disorders, as well as the occurrence of intramammary infections. Despite the above, we concluded that according to the thresholds of somatic cell counts for selective dry cow therapy taken from foreign studies, a large part of the udder quarters could be dried off without the administration of antibiotics. However, it is necessary to set up more effective mechanisms for mastitis prevention.

Transcriptomic changes underlying glucocorticoid-induced suppression of milk production by dairy cows

Milk production by dairy cows is sensitive to increased levels of stress hormones such as glucocorticoids (GC) that also regulate the transcription of several genes required for milk synthesis. Whereas previous studies identified that an exogenous GC such as dexamethasone (DEX) transiently suppresses milk yield in several species without any pronounced effect on milk protein or fat percentage, the mechanism underlying this effect has not been established. In this study we sought to establish changes within the mammary glands of non-pregnant dairy cows in their second lactation (n = 3-4; 648-838 kg) following a single dose of exogenous DEX. Changes in the udder were monitored by serial biopsy of alternating quarters, concurrent with quarter-level monitoring of milk yield and composition. Dexamethasone increased serum glucose levels from 12-36 h (p <0 .05), reduced milk yield from 12-48 h (p <0 .05), increased % milk protein content at 24 h post-DEX, and transiently decreased both milk lactose and α-lactalbumin content, while not altering the level of milk fat. After 72 h, all aspects of milk production had returned to pre-treatment levels. Transcriptomic changes in the mammary glands in response to DEX were identified by RNA sequencing followed by differential gene expression analysis. Coincident with the milk yield and composition changes was the differential expression of 519 and 320 genes at 12 and 24 h after DEX (adjusted p <0 .05), respectively, with the return of all gene expression to baseline levels by 72 h. Among the transcriptomic changes in response to DEX, there was notable downregulation of elements in the lactose synthesis pathway, specifically AQP3, GALE and LALBA (α-lactalbumin) at 12 h, and sustained downregulation of LALBA at 24 h. One gene in the pathway, UGP2, was upregulated at 12-24 h post-DEX. This work supports the hypothesis that there is a direct relationship between the response to DEX and the concurrent suppression of milk yield due to the reduced synthesis of α-lactalbumin and lactose by the mammary epithelium. The ability of glucocorticoids to modulate the homeorrhetic requirements for glucose during stressful states concurrent with immune activation bears significance for dairy animals as well as a broad range of lactating mammals.

Cannabis use during lactation may alter the composition of human breast milk

BACKGROUND

Cannabis is often used by women to manage symptoms of morning sickness during pregnancy, and postpartum stress and anxiety. While exclusive breastfeeding has been recommended for the first 6 months of an infant's life, the presence of cannabinoids in the milk of cannabis users complicates this recommendation. The objective of this study was to investigate the effect of maternal cannabis use on changes in the levels of macronutrients and bioactive factors in breast milk.

METHODS

Milk was collected from women who were 6-8 weeks postpartum and were either using cannabis post-delivery, had used cannabis during pregnancy, or were non-users. Levels of cannabinoids, macronutrients, lactose, and SIgA were assessed in the milk of all subjects.

RESULTS

THC was detected in the milk of women who reported cannabis use during lactation (n = 13, median: 22 ng/mL). Carboxy-THC, 11-hydroxy-THC, CBD, and CBN were also detected in the milk of women who used cannabis postpartum. Relative to non-users (n = 17), lactose levels were higher and SIgA levels were significantly lower in the milk of subjects who used cannabis during lactation (n = 14).

CONCLUSIONS

The presence of cannabinoids, along with altered lactose and SIgA levels in the milk of cannabis users, may have implications for infant health.

IMPACT

Metabolites of cannabis are found in breast milk and can accumulate in higher concentrations with ongoing consumption, which is concerning for potential exposure among infants born to mothers who consume cannabis. This work reports that lactose levels are increased and SIgA levels are decreased in the breast milk of cannabis users, relative to the milk of non-users. Change in levels of lactose and SIgA in the milk of cannabis users may have significant implications on infant health, which must be investigated in the future to better inform mothers.

Lactose: Characteristics, Food and Drug-Related Applications, and Its Possible Substitutions in Meeting the Needs of People with Lactose Intolerance

The recent growing interest in lactose intolerance has resulted in the proliferation of lactose-free products by food manufacturing companies. Since updated papers about lactose and its uses are missing, the main purpose of this review is to investigate this sugar comprehensively. Firstly, its chemical and physical characteristics were studied, following its employment in the food and drug industries. The positive and negative health-related effects of lactose are reported, focusing on the condition of lactose intolerance, for which an adequate lactose-free diet has to be followed to avoid symptoms that impairs quality of life. Considering that EU legislation on lactose-free product labelling is still controversial, suitable options for producing and identifying lactose-free products are suggested, in order to meet lactose-intolerant people’s needs.

Multivariate and Genome-Wide Analysis of Mid-Infrared Spectra of Non-Coagulating Milk of Sarda Sheep Breed

Milk coagulation ability is crucial for the dairy sheep industry since the whole amount of milk is processed into cheese. Non-coagulating milk (NCM) is defined as milk not forming a curd within the testing time. In sheep milk, it has been reported in literature that up to 20% of milk is NCM. Although the clotting properties of individual milk have been widely studied, little attention has been given to NCM and genomic dissection of this trait. Mid-infrared (MIR) spectra can be exploited both to predict cheese-making aptitude and to discriminate between coagulating milk and NCM. The main goals of this work were (i) to assess the predictivity of MIR spectra for NCM classification and (ii) to conduct a genome-wide association study on coagulation ability. Milk samples from 949 Sarda ewes genotyped and phenotyped for milk coagulation properties (MCPs) served as the training dataset. The validation dataset included 662 ewes. Three classical MCPs were measured: rennet coagulation time (RCT), curd firmness (a30), and curd firming time (k20). Moreover, MIR spectra were acquired and stored in the region between 925.92 and 5,011.54 cm−1. The probability of a sample to be NCM was modeled by step-wise logistic regression on milk spectral information (LR-W), logistic regression on principal component (LR-PC), and canonical discriminant analysis of spectral wave number (DA-W). About 9% of the samples did not coagulate at 30 min. The use of LR-W gave a poorer classification of NCM. The use of LR-PC improved the percentage of correct assignment (45 ± 9%). The DA-W method allows us to reach 75.1 ± 10.3 and 76.5 ± 18.4% of correct assignments of the inner and external validation datasets, respectively. As far as GWA of NCM, 458 SNP associations and 45 candidate genes were detected. The genes retrieved from public databases were mostly linked to mammary gland metabolism, udder health status, and a milk compound also known to affect the ability of milk to coagulate. In particular, the potential involvement of CAPNs deserves further investigation.

Evolution of milk oligosaccharides: Origin and selectivity of the ratio of milk oligosaccharides to lactose among mammals

BACKGROUND

The carbohydrate fraction of mammalian milk is constituted of lactose and oligosaccharides, most of which contain a lactose unit at their reducing ends. Although lactose is the predominant saccharide in the milk of most eutherians, oligosaccharides significantly predominate over lactose in the milk of monotremes and marsupials.

SCOPE OF REVIEW

This review describes the most likely process by which lactose and milk oligosaccharides were acquired during the evolution of mammals and the mechanisms by which these saccharides are digested and absorbed by the suckling neonates.

MAJOR CONCLUSIONS

During the evolution of mammals, c-type lysozyme evolved to α-lactalbumin. This permitted the biosynthesis of lactose by modulating the substrate specificity of β4galactosyltransferase 1, thus enabling the concomitant biosynthesis of milk oligosaccharides through the activities of several glycosyltransferases using lactose as an acceptor. In most eutherian mammals the digestion of lactose to glucose and galactose is achieved through the action of intestinal lactase (β-galactosidase), which is located within the small intestinal brush border. This enzyme, however, is absent in neonatal monotremes and macropod marsupials. It has therefore been proposed that in these species the absorption of milk oligosaccharides is achieved by pinocytosis or endocytosis, after which digestion occurs through the actions of several lysosomal acid glycosidases. This process would enable the milk oligosaccharides of monotremes and marsupials to be utilized as a significant energy source for the suckling neonates.

GENERAL SIGNIFICANCE

The evolution and significance of milk oligosaccharides is discussed in relation to the evolution of mammals.

A Comparative Review of the Extrinsic and Intrinsic Factors Regulating Lactose Synthesis

Milk is critical for the survival of all mammalian offspring, where its production by a mammary gland is also positively associated with its lactose concentration. A clearer understanding of the factors that regulate lactose synthesis stands to direct strategies for improving neonatal health while also highlighting opportunities to manipulate and improve milk production and composition. In this review we draw a cross-species comparison of the extra- and intramammary factors that regulate lactose synthesis, with a special focus on humans, dairy animals, and rodents. We outline the various factors known to influence lactose synthesis including diet, hormones, and substrate supply, as well as the intracellular molecular and genetic mechanisms. We also discuss the strengths and limitations of various in vivo and in vitro systems for the study of lactose synthesis, which remains an important research gap.