Coagulation and proteolysis of high-protein milks in the gastric environment.

Gastric digestion of 2 commercial ultrafiltered milks and milk enriched with skim milk powder (to simulate concentration by reverse osmosis) was investigated and compared with the digestion of nonconcentrated milk. Curd formation and proteolysis of high-protein milks in simulated gastric conditions were studied using oscillatory rheology, extrusion testing, and gel electrophoresis. The presence of pepsin in the gastric fluid triggered coagulation at pH >6 and the elastic modulus of gels from high-protein milks was ~5 times larger than the gel from reference milk. Despite similar protein concentrations, the coagulum from milk enriched with skim milk powder showed higher resistance to shear deformation than the coagula from ultrafiltered milks. The gel structure was also more heterogeneous. During digestion, the degradation of coagula from high-protein milks was slowed down compared with the coagulum from reference milk, and intact milk proteins were still detected after 120 min. Differences in the digestion patterns of coagula from high-protein milks were observed and were associated with the proportion of minerals bound to caseins and the denaturation rate of whey proteins.

Autocrine actions of prolactin contribute to the regulation of lactotroph function in vivo.

Prolactin (PRL), whose principal role is regulation of lactation, is mainly synthesized and secreted by lactotroph anterior pituitary cells. Its signaling is exerted via a transmembrane PRL receptor (PRLR) expressed in a wide variety of tissues, including the anterior pituitary. Dopamine, which is secreted by tuberoinfundibular hypothalamic neurons, is the major inhibitory regulator of prolactin secretion. Although PRL is well established to stimulate hypothalamic dopamine secretion, thereby exerting a negative feedback regulation on its own release, autocrine or paracrine actions of PRL on lactotroph cells have also been suggested. Within the pituitary, PRL may inhibit both lactotroph proliferation and secretion, but in vivo evaluation of these putative functions is limited. To determine whether the autocrine actions of prolactin have a significant role in the physiologic function of lactotrophs in vivo, we examined the consequences of conditional deletion of Prlr in lactotroph cells using a novel mouse line with loxP sites flanking the Prlr gene ( Prlrlox/lox) and Cre-recombinase (Cre) expressed under the control of the pituitary-specific Prl promoter. Prlrlox/lox/Prl-Cre mice have normal PRL levels and did not develop any pituitary lactotroph adenoma, even at 20 mo of age. Nevertheless, Prlrlox/lox/Prl-Cre mice displayed an increased dopaminergic inhibitory tone compared with control Prlrlox/lox mice. These results elegantly confirm an autocrine/paracrine feedback of PRL on lactotroph cells in vivo, which can be fully compensated by an intact hypothalamic feedback system.-Bernard, V., Lamothe, S., Beau, I., Guillou, A., Martin, A., Le Tissier, P., Grattan, D., Young, J., Binart, N. Autocrine actions of prolactin contribute to the regulation of lactotroph function in vivo.

Diagnostic and referral pathways in patients with rare lipodystrophy and insulin-resistance syndromes: key milestones assessed from a national reference center.

BACKGROUND: Rare syndromes of lipodystrophy and insulin-resistance display heterogeneous clinical expressions. Their early recognition, diagnosis and management are required to avoid long-term complications. OBJECTIVE: We aimed to evaluate the patients' age at referral to our dedicated national reference center in France and their elapsed time from first symptoms to diagnosis and access to specialized care. PATIENTS AND METHODS: We analyzed data from patients with rare lipodystrophy and insulin-resistance syndromes referred to the coordinating PRISIS reference center (Adult Endocrine Department, Saint-Antoine Hospital, AP-HP, Paris), prospectively recorded between 2018 and 2023 in the French National Rare Disease Database (BNDMR, Banque Nationale de Données Maladies Rares). RESULTS: A cohort of 292 patients was analyzed, including 208 women, with the following diagnosis: Familial Partial LipoDystrophy (FPLD, n = 124, including n = 67 FPLD2/Dunnigan Syndrome); Acquired lipodystrophy syndromes (n = 98, with n = 13 Acquired Generalized Lipodystrophy, AGL); Symmetric cervical adenolipomatosis (n = 27, Launois-Bensaude syndrome, LB), Congenital generalized lipodystrophy (n = 18, CGL) and other rare severe insulin-resistance syndromes (n = 25). The median age at referral was 47.6 years [IQR: 31-60], ranging from 25.2 (CGL) to 62.2 years old (LB). The median age at first symptoms of 27.6 years old [IQR: 16.8-42.0]) and the median diagnostic delay of 6.4 years [IQR: 1.3-19.5] varied among diagnostic groups. The gender-specific expression of lipodystrophy is well-illustrated in the FPLD2 group (91% of women), presenting with first signs at 19.3 years [IQR: 14.4-27.8] with a diagnostic delay of 10.5 years [IQR: 1.8-27.0]. CONCLUSION: The national rare disease database provides an important tool for assessment of care pathways in patients with lipodystrophy and rare insulin-resistance syndromes in France. Improving knowledge to reduce diagnostic delay is an important objective of the PRISIS reference center.

Effect of emulsifiers on linseed oil emulsion structure, lipolysis and oxidation during in vitro digestion.

Health benefits have been associated with the consumption of omega-3 polyunsaturated fatty acids (PUFA). Linseed oil is rich in long chain omega-3 PUFA, but can generate toxic compounds due to its high susceptibility to oxidation. The nature of the emulsifier can affect both lipolysis and oxidation during digestion since these phenomena occur at the oil-water interface. The objective of this study was to compare the effect of low-molecular weight surfactants (cetyltrimethylammonium bromide (CTAB), Citrem), protein (sodium caseinate, fish gelatin) and polysaccharides (gum arabic, modified starch) on the structure of linseed oil emulsions, lipolysis and formation of reactive oxidation species during in vitro digestion. The emulsion stabilized with Citrem underwent extensive coalescence in the gastric phase, which strongly decreased the extent of lipid digestion and reduced the formation of oxidation markers relative to other emulsions. Emulsions stabilized by proteins and modified starch showed aggregation with partial coalescence in the gastric phase, but protein-stabilized emulsions showed better resistance to oxidation. This study shows that emulsifier properties affect the susceptibility of the emulsion to aggregation and coalescence in the gastrointestinal environment, and strongly influence the extent of lipid digestion and the formation of reactive oxidation products. These findings point out the importance of the choice of the emulsifier to control the lipid digestibility and the protection of sensible lipids thus promoting optimal nutritional properties in omega-3-enriched foods.

Gonad differentiation toward ovary.

Gonad differentiation depends on a set of cellular and hormonal signals interacting in a specific order, with very precise windows of action, to contribute to the establishment of the genital tract and a male or female phenotype. Research initially focused on the stages of gonad differentiation toward testis, in particular following the identification in 1990 of the SRY factor on chromosome Y. The mechanisms involved in gonad differentiation toward ovary took longer to identify. Thanks to patients with different sexual development (DSD) and animal knock-out models, description of the cascades involved in the activation and maintenance of ovarian development has progressed considerably in recent years.

Effect of milk proteins and food-grade surfactants on oxidation of linseed oil-in-water emulsions during in vitro digestion.

Health benefits are associated with polyunsaturated fatty acids, but their sensitivity to oxidation may generate toxic oxidation species. The objective of this study was to compare the effect of milk proteins (casein, whey protein) and surfactants (Citrem, Tween 20) on the in vitro digestion and oxidation of linseed oil emulsions. The emulsion produced with Tween 20 resisted coalescence in the gastric phase and showed the highest concentrations of free fatty acids and reactive carbonyl compounds in the intestinal digestion phase. The Citrem-stabilized emulsion showed extensive coalescence in the gastric environment, which reduced lipolysis and the formation of advanced oxidation species. The protein-stabilized emulsions showed aggregation with some coalescence in the gastric phase, and casein provided better protection than whey protein against oxidation. This study suggests that the mechanism of emulsion destabilization in the gastric environment and the type of protein can modulate lipolysis and oxidation during in vitro digestion.

Antioxidant activity of milk and polyphenol-rich beverages during simulated gastrointestinal digestion of linseed oil emulsions.

Polyunsaturated fatty acids (PUFA) are associated with health benefits. However, high PUFA intake increases the risk of lipid oxidation and formation of potentially toxic lipid oxidation species. The objective of this study was to determine the antioxidant activity of milk fractions (whole milk, skim milk, acid whey, ultrafiltration (UF) permeate) and polyphenol-rich beverages (green tea, grape juice) during simulated gastrointestinal digestion. We also determined the effect of milk and polyphenol-rich beverages on the formation of advanced oxidation species during in vitro digestion of PUFA-rich emulsion. Antioxidant activity during digestion of milk fractions emphasized the important role of proteins (more specifically caseins) and the contribution of fat to the antioxidant capacity of milk. In comparison to milk, the antioxidant activity of polyphenol-rich beverages was at least four times higher. During digestion of a PUFA-rich emulsion, the formation of 4-hydroxyhexanal (4-HHE) and 4-hydroxynonenal (4-HNE) in the intestinal phase were respectively reduced by 60% and 75%, in the presence of milk or polyphenol-rich beverages. Further reduction was observed when the emulsion was co-digested with both, milk and polyphenol-rich beverages (89% for 4-HHE and 93% for 4-HNE). These results suggest that the combination of milk and polyphenol-rich beverages increases the antioxidant activity and synergistically reduces the formation of toxic lipid oxidation species during simulated digestion of PUFA-rich foods.

[Semen quality and fertility: the role of the environment and health]. / Qualité du sperme et fertilité : rôle de l'environnement et de la santé.

Sperm quality appears to be degrading over the past 40 years. Nowadays, more than 35 % of causes of male infertility are still idiopathic. More and more studies have suggested an impact of environment on sperm quality, essentially through epigenetic and hormonal changes. Recent studies in men with impaired sperm quality, have demonstrated epigenetic variations in sperm DNA. These modifications are responsible for modifications of the expression of transmissible genes to theiroffspring. Those transgenerational effects have been particularly illustrated in drosophila and caenorhabditis elegans. In humans, consequences of the environment on fertility have been studied in obese men, who present hypogonadotropic as well as hypergonadotropic hypogonadisms. Interestingly, recent studies have suggested a correlation between sperm quality and longevity. In summary, those environmental factors are the source of new causes of infertility.

Natural and molecular history of prolactinoma: insights from a Prlr-/- mouse model.

Lactotroph adenoma, also called prolactinoma, is the most common pituitary tumor but little is known about its pathogenesis. Mouse models of prolactinoma can be useful to better understand molecular mechanisms involved in abnormal lactotroph cell proliferation and secretion. We have previously developed a prolactin receptor deficient (Prlr-/- ) mouse, which develops prolactinoma. The present study aims to explore the natural history of prolactinoma formation in Prlr-/- mice, using hormonal, radiological, histological and molecular analyses to uncover mechanisms involved in lactotroph adenoma development. Prlr-/- females develop large secreting prolactinomas from 12 months of age, with a penetrance of 100%, mimicking human aggressive densely granulated macroprolactinoma, which is a highly secreting subtype. Mean blood PRL measurements reach 14 902 ng/mL at 24 months in Prlr-/- females while PRL levels were below 15 ng/mL in control mice (p < 0.01). By comparing pituitary microarray data of Prlr-/- mice and an estrogen-induced prolactinoma model in ACI rats, we pinpointed 218 concordantly differentially expressed (DE) genes involved in cell cycle, mitosis, cell adhesion molecules, dopaminergic synapse and estrogen signaling. Pathway/gene-set enrichment analyses suggest that the transcriptomic dysregulation in both models of prolactinoma might be mediated by a limited set of transcription factors (i.e., STAT5, STAT3, AhR, ESR1, BRD4, CEBPD, YAP, FOXO1) and kinases (i.e., JAK2, AKT1, BRAF, BMPR1A, CDK8, HUNK, ALK, FGFR1, ILK). Our experimental results and their bioinformatic analysis provide insights into early genomic changes in murine models of the most frequent human pituitary tumor.

Influence of dairy matrices on nutrient release in a simulated gastrointestinal environment.

The objective of this study was to compare the kinetics of the release of nutrients (peptides and fatty acids) from different dairy matrices (milks, yogurts, and cheeses) in a simulated gastrointestinal environment. Prior to processing, different heat and homogenization treatments were applied to milks, and different drainage pH levels were used to control calcium concentration in cheeses. The dairy matrices were then subjected to simulated digestion. Matrix degradation, protein hydrolysis, and fat hydrolysis were analyzed during the gastric and intestinal digestion phases. Intense heat treatment of milk induced faster digestion of proteins in the gastric environment. Cheeses were more resistant to protein and lipid digestion than liquid or semi-solid matrices were. No direct relationship could be established between disintegration kinetics and cheese rheological properties. Fatty acid release in the intestinal phase was much faster when matrices were produced from homogenized milk. For cheeses, greater fatty acid release could not be related to faster matrix disintegration, suggesting that the lipid droplet size dispersion was more important than matrix breakdown was for the modulation of lipid digestion kinetics. Calcium soaps were produced in the intestinal environment, and their concentration was higher during the digestion of cheeses in comparison with milks and yogurts. These results suggest that processing-induced modifications to the composition, microstructure, and rheological properties of dairy matrices could be used to control nutrient delivery.

Antioxidant activity and nutrient release from polyphenol-enriched cheese in a simulated gastrointestinal environment.

Green tea polyphenols are recognized for their antioxidant properties and their effects on lipid digestion kinetics. Polyphenols are sensitive to degradation in the intestinal environment. Interactions with dairy proteins could modulate the stability and biological activity of polyphenols during digestion. The objective of this study was to evaluate the release of nutrients (polyphenols, fatty acids and peptides) and the antioxidant activity in polyphenol-enriched cheese containing different levels of calcium in a simulated gastrointestinal environment. The relationship between cheese matrix texture, matrix degradation and nutrient release during digestion was also studied. Green tea extract was added to milk at 0% or 0.1%, and cheeses were produced on a laboratory scale. The level of available calcium was adjusted to low (Ca(low)), regular (Ca(reg)) or high (Ca(high)) during the salting step of the cheese-making process. Cheeses were subjected to simulated digestion. The rate and extent of fatty acid release were 21% lower for Ca(low) cheese than for Ca(reg) and Ca(high) cheeses. The greater adhesiveness of Ca(low) cheese, which resulted in lower rates of matrix degradation and proteolysis, contributed to the reduced rate of lipolysis. The presence of green tea extract in cheese reduced the release of free fatty acids at the end of digestion by 7%. The addition of green tea extract increased cheese hardness but did not influence matrix degradation or proteolysis profiles. The formation of complexes between tea polyphenols and proteins within the cheese matrix resulted in a more than twofold increase in polyphenol recovery in the intestinal phase compared with the control (tea polyphenol extract incubated with polyphenol-free cheese). Antioxidant activity was 14% higher in the digest from polyphenol-enriched cheese than in the control. These results suggest that cheese is an effective matrix for the controlled release of nutrients and for the protection of green tea polyphenol integrity and biological activity in the gastrointestinal environment.

Interaction of green tea polyphenols with dairy matrices in a simulated gastrointestinal environment.

The consumption of polyphenols in green tea has been associated with beneficial health effects. Although polyphenols are unstable in the intestinal environment, they may be protected by interactions with dairy proteins during digestion. The objectives of this study were to evaluate the effect of a green tea extract on the digestibility of different dairy matrices and to monitor the antioxidant activity of these matrices with or without the green tea extract during digestion in a simulated gastrointestinal environment. Milk, yogurt and cheese with similar fat-to-protein ratios were subjected to simulated digestion. Matrix degradation, protein and fat hydrolysis, polyphenol concentration and radical scavenging activity were analyzed during gastric and intestinal digestion phases. Cheese was the matrix most resistant to protein and fat digestion. The addition of the green tea extract significantly decreased proteolysis in the gastric phase but had no effect in the intestinal phase. The kinetics of fatty acid release was reduced by the presence of the green tea extract. Transition from the gastric phase to the intestinal phase induced a 50% decrease in the antioxidant activity of the control (tea extract dispersed in water) due to the degradation of polyphenols. The presence of dairy matrices significantly improved polyphenol stability in the intestinal phase and increased the antioxidant activity by 29% (cheese) to 42% (milk) compared to the control. These results suggest that simultaneous consumption of green tea and dairy products helps to maintain the integrity and antioxidant activity of polyphenols during digestion.

Congenital hypogonadotropic hypogonadism and Kallmann syndrome as models for studying hormonal regulation of human testicular endocrine functions.

Men with Kallmann syndrome (KS) and those with congenital isolated hypogonadotropic hypogonadism with normal olfaction share a chronic, usually profound deficit, in FSH and LH, the two pituitary gonadotropins. Many studies indicate that this gonadotropin deficiency is already present during fetal life, thus explaining the micropenis, cryptorchidism and marked testicular hypotrophy already present at birth. In addition, neonatal activation of gonadotropin secretion is compromised in boys with severe CHH/Kallmann, preventing the first phase of postnatal testicular activation. Finally, CHH is characterized by the persistence, in the vast majority of cases, of gonadotropin deficiency at the time of puberty and during adulthood. This prevents the normal pubertal testicular reactivation required for physiological sex steroid and testicular peptide production, and for spermatogenesis. CHH/KS thus represents a pathological paradigm that can help to unravel, in vivo, the role of each gonadotropin in human testicular exocrine and endocrine functions at different stages of development. Recombinant gonadotropins with pure LH or FSH activity have been used to stimulate Leydig's cells and Sertoli's cells, respectively, and thereby to clarify their paracrine interaction in vivo. The effects of these pharmacological probes can be assessed by measuring the changes they provoke in circulating testicular hormone concentrations. This review discusses the impact of chronic gonadotropin deficiency on the endocrine functions of the interstitial compartment, which contains testosterone-, estradiol- and INSL3-secreting Leydig's cells. It also examines the regulation of inhibin B and anti-Mullerian hormone (AMH) secretion in the seminiferous tubules, and the insights provided by studies of human testicular stimulation with recombinant gonadotropins, used either individually or in combination.

Influence of cheese matrix on lipid digestion in a simulated gastro-intestinal environment.

Foods are complex nutrient assemblies which are subjected to various industrial processes that can influence their nutritional value. The food matrix acts as a nutrient-release regulator, and further understanding of its behavior during digestion is essential. The objective of this study was to compare the kinetics of matrix degradation and fatty acids release for different cheeses in a gastro-intestinal environment. The relationship between the physical characteristics of the cheeses (rheological properties, microstructure) and their digestion pattern was also studied. Rheological measurements, compositional and microstructure analyses were performed on mild Cheddar, aged Cheddar, light Cheddar and Mozzarella cheeses. Cheese samples were subjected to simulated digestion. Matrix degradation index, free oil, free fatty acids and fat droplet distribution were analyzed after 5, 30, 60, 120, 150, 180 and 240 min of digestion. Mozzarella cheese showed the highest rate of matrix degradation, free oil and fatty acids release. Aged Cheddar cheese showed rapid degradation during the gastric phase, but was more resistant to the duodenal environment. Light Cheddar showed the opposite behavior, being highly resistant to the gastric environment; however, it underwent extensive degradation at the end of the duodenal phase. The extent of matrix degradation for mild Cheddar was similar to that of Mozzarella in the gastric phase but was much lower than that of other cheeses in the duodenal phase. The cheeses under study exhibited very different digestion patterns, and these differences are discussed in relation to cheese matrix composition, microstructure and rheological properties. Results suggest that cheese degradation and kinetics of fatty acids release are mainly driven by cheese physical characteristics.

Butter making from caprine creams: effect of washing treatment on phospholipids and milk fat globule membrane proteins distribution.

A washing treatment was applied to caprine cream before churning in order to improve phospholipids and MFGM protein purification from buttermilk and butter serum. Cream obtained from a first separation was diluted with water and separated a second time using pilot plant equipment. Regular and washed creams were churned to produce buttermilk and butter, from which butter serum was extracted. The washing treatment allowed a significant decrease of the casein content. As a result, the phospholipids-to-protein ratios in washed buttermilk and butter serum were markedly increased by 2.1 and 1.7-folds respectively, which represents an advantage for the production of phospholipids concentrates. However, when compared with bovine cream, lower phospholipids-to-protein ratios were observed when the washing treatment was applied to caprine cream. A higher concentration of MFGM protein and a lower retention of phospholipids during washing treatment are responsible for the lower phospholipids-to-protein ratios in buttermilk and butter serum obtained from caprine cream. The phospholipids distribution in the butter making process was similar to the one obtained from bovine regular and washed cream. Phospholipids were preferentially concentrated in the butter serum rather than the buttermilk fraction. This simple approach permitted the production of caprine and bovine butter sera extracts containing up to 180 and 240 g phospholipids/kg sera, respectively, on a dry basis.