Underlying evidence for the health benefits of fermented foods in humans.

Fermented foods (FFs) have been a part of our diets for millennia and comprise highly diverse products obtained from plants and animals all over the world. Historically, fermentation has been used to preserve food and render certain raw materials edible. As our food systems evolve towards more sustainability, the health benefits of FFs have been increasingly touted. Fermentation generates new/transformed bioactive compounds that may occur in association with probiotic bacteria. The result can be specific, advantageous functional properties. Yet, when considering the body of human studies on the topic, whether observational or experimental, it is rare to come across findings supporting the above assertion. Certainly, results are lacking to confirm the widespread idea that FFs have general health benefits. There are some exceptions, such as in the case of lactose degradation via fermentation in individuals who are lactose intolerant; the impact of select fermented dairy products on insulin sensitivity; or the benefits of alcohol consumption. However, in other situations, the results fail to categorically indicate whether FFs have neutral, beneficial, or detrimental effects on human health. This review tackles this apparent incongruity by showing why it is complex to test the health effects of FFs and what can be done to improve knowledge in this field.

Processing & rheological properties of wheat flour dough and bread containing high levels of soluble dietary fibres blends.

Wheat flour doughs were processed with soluble dietary fibres (DF) added up to 40% (w/w flour). DF were made of a ternary mixture of maltodextrins (MT, 3/5), pectins (PE, 1/5) and inulin (IN, 1/5). The addition of DF decreased the specific mechanical energy developed by the mixer, mainly because of water addition. It increased the ratio of storage moduli and the elongational viscosity of the dough, but decreased the strain hardening index. Energy input and rheological changes at mixing largely explained the decreases of porosity characteristic time and stability time during fermentation. It was possible to add up to 30% DF with a moderate increase of bread density, and 20%, with little change of crumb cellular structure. Hence, the changes of bread crumb texture were not mainly due to bread density, but rather likely to the changes of properties of the intrinsic material. Results obtained by addition of single fibre source, especially inulin, deviated from the main trends observed for texture and rheological properties. These results provide a good basis to design breads with increased dietary fibre content.

Repeated cures with paracetamol worsen sarcopenia in old rats with suboptimal food intake.

The availability of all amino acids is of prime importance to prevent the ageing-associated decrease in skeletal muscle mass i.e. sarcopenia. Cysteine is the precursor of sulfate and glutathione that are both utilized in the liver to detoxify paracetamol (APAP). Cysteine availability could become limiting under repeated cures with APAP, especially when food intake is suboptimal. The aim of the study was to determine whether repeated cures with APAP could worsen sarcopenia. Twenty-two-month-old male Wistar rats received 3 two-week-long cures of APAP (1% of the diet) intercalated with washout periods of two weeks (APAP group). They were compared to untreated control rats euthanatized prior to the experiment (CT group) and rats pair-fed to the APAP group (PF group). Skeletal muscle mass and protein metabolism, as well as plasma amino acids and glutathione were assessed at the end of the third cure. APAP cures reduced food intake by 33, 23 and 33 % during the successive cures leading to an overall body weight loss of 8%. APAP rats lost lean mass during the experiment (-11%). This loss tended (P = 0.09) to be higher than in the PF group (-9%). The mass of hind limb muscles and the absolute synthesis rate of muscle proteins were 13 and 17% lower in the APAP group than the PF group, respectively. Plasma free cyst(e)ine (i.e. all free forms of cysteine not bound to proteins) and glutathione were 25% lower in the APAP group than the PF group. Repeated cures with APAP worsened sarcopenia in old rats with suboptimal food intake likely as a consequence of the APAP-induced shortage in cysteine/glutathione. Clinical studies are needed to clarify the effect of repeated treatments with paracetamol on skeletal muscle mass in older persons having suboptimal or insufficient dietary intakes.

Nutritional regulation of the anabolic fate of amino acids within the liver in mammals: concepts arising from in vivo studies.

At the crossroad between nutrient supply and requirements, the liver plays a central role in partitioning nitrogenous nutrients among tissues. The present review examines the utilisation of amino acids (AA) within the liver in various physiopathological states in mammals and how the fates of AA are regulated. AA uptake by the liver is generally driven by the net portal appearance of AA. This coordination is lost when demands by peripheral tissues is important (rapid growth or lactation), or when certain metabolic pathways within the liver become a priority (synthesis of acute-phase proteins). Data obtained in various species have shown that oxidation of AA and export protein synthesis usually responds to nutrient supply. Gluconeogenesis from AA is less dependent on hepatic delivery and the nature of nutrients supplied, and hormones like insulin are involved in the regulatory processes. Gluconeogenesis is regulated by nutritional factors very differently between mammals (glucose absorbed from the diet is important in single-stomached animals, while in carnivores, glucose from endogenous origin is key). The underlying mechanisms explaining how the liver adapts its AA utilisation to the body requirements are complex. The highly adaptable hepatic metabolism must be capable to deal with the various nutritional/physiological challenges that mammals have to face to maintain homeostasis. Whereas the liver responds generally to nutritional parameters in various physiological states occurring throughout life, other complex signalling pathways at systemic and tissue level (hormones, cytokines, nutrients, etc.) are involved additionally in specific physiological/nutritional states to prioritise certain metabolic pathways (pathological states or when nutritional requirements are uncovered).

Skeletal muscle wasting occurs in adult rats under chronic treatment with paracetamol when glutathione-dependent detoxification is highly activated.

The use of glutathione (GSH) and sulfate for the detoxification of paracetamol (acetaminophen, APAP) could occur at the expense of the physiological uses of cysteine (Cys). Indeed GSH and sulfate both originate from Cys. Significant APAP-induced Cys loss could generate alterations in GSH and protein metabolisms leading to muscle wasting. The study aimed to investigate the effects of chronic treatment with APAP on whole-body and tissue homeostasis (mass, GSH, proteins, and nitrogen balance) in relation to sulfur losses through APAP-detoxification pathways. Adult male Wistar rats were fed 0% APAP, 0.5% APAP or 1% APAP diets for 17 days. APAP doses were respectively around and largely above the threshold of sulfation saturation for rats. During the last days, the rats were placed in metabolic cages in order to quantify N balance and urinary APAP metabolites. Gastrocnemius muscle mass, protein and GSH contents, N balance and plasma free cyst(e)ine were 8% (P=0.02), 7% (P=0.03), 26% (P=0.01), 37% (P=0.01), and 33% (P=0.003) lower in the 1% APAP group than in the 0% APAP group, respectively. There was no significant difference in these parameters between the 0.5% APAP group and the 0% APAP group. Muscle wasting occurred when the detoxification of APAP through the GSH-dependent pathway was highly activated. Muscle protein synthesis could have been reduced due to a shortage in Cys and/or an increase in protein degradation in response to intra-muscular oxidative stress. Hence, without dietary sulphur amino acid increase, peripheral bioavailability of Cys and muscle GSH are potential players in the control of muscle mass under chronic treatment with APAP, an analgesic medication of widespread use, especially in the elderly.

Adaptations of hepatic amino acid uptake and net utilisation contributes to nitrogen economy or waste in lambs fed nitrogen- or energy-deficient diets.

We investigated the effect of relative changes in dietary nitrogen (N) and energy supply and the subsequent variations in net portal appearance (NPA) of nitrogenous and energy nutrients on the net amino acid (AA) uptake by the liver and net N supply to the peripheral tissues. Six lambs were catheterised across the splanchnic tissues and received, in a replicated Latin square, one of three dietary treatments. The diets were formulated to either match the requirements of N and energy (C), or supply only 0.8 of the N requirement (LN) or 0.8 of the energy requirement (LE). Net fluxes of AA and urea-N were measured across the portal-drained viscera, and estimation of arterial hepatic flow allowed the estimation of hepatic fluxes. Catheters were implanted into the portal and hepatic veins as well as in the abdominal aorta for the measurement of AA fluxes. Animals fed the LN diet showed more efficient N retention (0.59 of digested N) than did the C and LE diet (0.50 and 0.33, respectively; P < 0.001). The NPA of total AA-N for the LN diet was only 0.60 of the value measured for the control (C) diet (P < 0.01). Despite this, the total estimated AA-N net splanchnic fluxes were not significantly different across the three diets (3.3, 1.9 and 2.6 g total AA-N/day for C, LN and LE, respectively, P = 0.52). Thus, different metabolic regulations must have taken place across the liver between the three experimental diets. A combination of decreased net uptake of total AA-N by the liver of animals in the LN diet (0.61 of the C diet; P = 0.002) and reduced urinary urea-N production (0.52 of the C diet; P = 0.001) spared AA from catabolism in the LN diet relative to the other two diets. For the LE diet, the urinary urea-N output was 1.3 times the value of the C diet (P = 0.01). This may relate to an increased catabolism of AA by the muscle and/or, to a lesser extent, to an increased utilisation of AA for gluconeogenesis in the liver. These effects may explain the reduced whole body protein retention observed with the LE diet.

Dietary nitrogen-to-energy ratio alters amino acid partition in the whole body and among the splanchnic tissues of growing rams.

The aim of this study was to determine whether subtle changes in the energy-to-N ratio of medium-concentrate diets alters hepatic export protein synthesis and the partition of protein metabolism in the whole body of growing rams. Rams (n = 6; 41.5 +/- 2.6 kg of BW) were fitted with catheters for measurement of Leu and Phe tracer kinetics across the portal drained-viscera (PDV) and liver. Rams were assigned to receive 3 dietary treatments according to a duplicated Latin square design. Animals received forage-concentrate-based diets that were balanced for ME and available N (CON), 20% imbalanced (reduced) in available N (LN), or 20% imbalanced in ME (LE). After 15 d on each experimental diet, [ring-(2)H(5)]Phe (4.3 micromolxkg(-1)xh(-1)) and [1-(13)C]Leu (8.6 micromolxkg(-1)xh(-1)) were continuously infused into the vena cava for 10 h and, over the last 7 h of infusion, matched sets of blood samples were taken. Daily BW gain was less (P < 0.05) for the LE (0.191 kgxd(-1)) diet compared with CON (0.265 kg/d) and LN (258 kgxd(-1)) diets. Compared with CON, whole body irreversible loss rate (ILR) of Leu and Phe was less (10 to 16%, P < 0.02) for LN and LE diets, which for Leu reflected its decreased (20 to 24%, P < 0.05) net PDV absorption. The decreased whole body ILR is due to a decreased PDV ILR in both diets with a relative contribution of the PDV to the whole body ILR decreased (P < 0.05) in the LN (27%) diet compared with the CON (36%) and LE (33%) diets. This decreased PDV ILR was associated with a decreased net Leu PDV uptake in LN and LE diets (-25 and -20%, respectively; P < 0.05). Conversely, the decreased whole body Phe ILR is explained by a decreased hepatic ILR (and contribution to the whole body ILR) and was associated with a decreased net hepatic uptake of Phe in LN (-25%) and LE (-20%) diets compared with CON (P = 0.03). The fractional and absolute synthesis rates of total proteins and albumin were decreased by 10% in LE animals (P < 0.05), whereas they were not affected by the LN diet. These results suggest a specific decreased utilization of Leu at the PDV due to a specific sparing mechanism in the LN diet. Conversely, a decreased Phe utilization occurred in the liver in both diets (due to a decreased export protein synthesis and a probable decreased oxidation in LE diet, whereas only oxidation is reduced in LN diet).

Nitrogen- and energy-imbalanced diets affect hepatic protein synthesis and gluconeogenesis differently in growing lambs.

The aim of this study was to assess the metabolic fate of AA (endogenous or export protein synthesis, gluconeogenesis, or oxidation) after an imbalanced supply of energy and N in the diet of growing lambs. Eighteen INRA 401 lambs (3 mo old, 29.7 +/- 0.45 kg of BW) were fed 3 experimental diets, one providing a N and energy supply according to recommended allowances (control), one with 23% less N supply relative to energy (LN), and one with 19% less ME supply relative to N (LE). Animals were assigned to 6 blocks of 3, with each animal receiving 1 of the 3 diets, and the animals from each block were slaughtered on the same day. Liver slices from these lambs were incubated in a minimum salt medium (Krebs-Henseleit) containing physiological concentrations of propionate and AA as energy and N sources, similarly across all 3 treatments. Protein synthesis (endogenous and export) using [U-(14)C]valine and [(35)S]methionine, gluconeogenesis from [1-(14)C]propionate and [U-(14)C]alanine, and oxidation were measured. A relative sparing of AA at the liver level was observed with the LN diet because of reduced urinary N (-42%, LN vs. control, P < 0.001). The AA were also directed toward anabolic purposes in the LN diet via an increased endogenous and total export protein synthesis (+51%, LN vs. control, P = 0.01; also observed for fibrinogen synthesis, but not for albumin or transferrin) associated with a tendency for increased gluconeogenesis from alanine (+58%, LN vs. LE, P = 0.08). On the other hand, the LE diet resulted in a marked loss of N in urine (+24%, LE vs. control, P < 0.05), but no notable effect of the LE diet was demonstrated for protein synthesis or gluconeogenesis ex vivo. These data demonstrate a more efficient utilization of AA for anabolic purposes in the lambs fed LN, probably via an activation of some AA transport systems, to address the shortage of nitrogenous nutrients in the LN diet. By contrast, no such adaptation occurred in the LE lambs, probably because the regulatory mechanisms that prevailed in this case were the nutrient supply or hormones, which were not altered in our ex vivo experimental model.

Food restriction and refeeding in lambs influence muscle antioxidant status.

Compensatory growth, a frequent phenomenon observed in ruminants due to seasonal variation in food availability, affects protein metabolism including protein oxidation. These oxidation processes may have an impact on animal health as well as on meat protein degradation during post mortem aging (ie meat maturation). Sixteen male lambs were randomly divided into four groups. One group was fed ad libitum (C) and one group was food-restricted to 60% of the intake of the C group (R). The last two groups were restricted similarly to the R group and refed either ad libitum (RAL) or similarly to the C group (pair-feeding) (RPF). Muscles samples were taken immediately after slaughter. The present study showed that the restriction/refeeding pattern had no effect on protein oxidation in the muscles studied (longissimus dorsi (LD), semitendinosus (ST) and supraspinatus (SP)). However, total antioxidant capacity decreased after food restriction (-51%, -43%, P < 0.01 for ST and LD muscles, respectively) and re-increased only after ad libitum refeeding. This alteration in the total antioxidant status can partially be explained by the similar pattern of change observed in the glutathione concentration of the muscles (-25%, P < 0.05 for ST muscle and NS for the other muscles). However, none of the concentrations of other water-soluble antioxidants studied (carnosine, anserine, glutathione peroxidase and superoxide dismutase) were altered during compensatory growth. This study showed that an inappropriate feeding level following a nutritional stress induced alterations in the total antioxidant status (particularly that of glutathione), which may have consequences on animal health. Other consequences of a decrease of the animal antioxidant status in vivo could be an alteration of the protein oxidation processes during meat maturation.

Small peptides (<5kDa) found in ready-to-eat beef meat.

Dietary proteins can have biological properties, many attributed to bioactive peptides (2-50 amino acids). Since little is known about peptides in meat, we investigated the postmortem occurrence of low molecular weight peptides (<5kDa) in bovine Pectoralis profundus muscle, after 14 days storage at 4°C and vacuum cooking for 90min at 75°C. The study combined quantitative (amino acid analysis) and qualitative approaches (mass spectrometry). Eighty-nine percent of peptidic amino acids in fresh muscle corresponded to carnosine, anserine and glutathione. Levels of these compounds were lower in cooked meat compared to fresh muscle. Concomitantly, numerous larger compounds, most probably peptides, were generated in a very reproducible manner during ageing and even more during cooking of meat. Seven peptides (fragments of troponin T, nebulin, procollagen and cypher proteins) were identified in cooked meat extracts.

Ryegrass-based diet and barley supplementation: partition of nitrogenous nutrients among splanchnic tissues and hind limb in finishing lambs.

Splanchnic metabolism of nitrogenous nutrients and their uptake by the hind limb were studied in finishing lambs receiving ryegrass harvested at grazing stage with or without barley supplementation. Six multicatheterized lambs (40.2 +/- 1.5 kg) were fed with frozen ryegrass (RG) at 690 kJ of ME intake (MEI) x d(-1) x BW(-0.75) and 20.8 g of N intake (NI)/d successively without and with barley supplementation (RG + B), according to a crossover design. Barley supplementation represented 21% of DM intake and increased the MEI and the NI by 32 and 24% respectively, (P < 0.01). In the ruminal fluid, barley increased acetate and butyrate concentrations by 21.2 and 49.6%, respectively (P < 0.04), without any effect on the ammonia concentration. Consequently, the net portal appearance (NPA) of ammonia was not modified, but the NPA of total amino acids (TAA; +38%) and nonessential amino acids (NEAA; +45%) was increased (P < 0.05) by barley supplementation. Taken individually, the NPA of the essential amino acids (EAA) was increased for isoleucine (+32%; P < 0.05), threonine (+151%; P < 0.03), and lysine (+26%; P < 0.06), with no effect for the other EAA. In contrast to what was observed at the PDV level, no significant alteration in the net hepatic amino acid flux was observed for TAA, EAA, NEAA, branched-chain amino acids (BCAA), urea, and ammonia after barley supplementation, showing a relatively minor role of the liver in the regulation of the supply of amino acids to the peripheral tissues. However, taken individually, the net hepatic uptake of some NEAA involved in gluconeogenesis and/or ureagenesis was altered with barley supplementation: the alanine uptake was increased by 44% (P < 0.05), aspartate + asparagine (asx) uptake was decreased by 18% (P < 0.01), and glutamate + glutamine (glx) release tended (P < 0.10) to be increased by 208%. With barley supplementation, NI increased by 5 g of N/d, and net splanchnic release increased by 4.63 g of N/d. Consequently, the additional dietary N supply (together with energy supply) was nearly exclusively available to peripheral tissues as AA-N (N as amino acids), but no strong effect of this additional supply of AA to the hind limb could be demonstrated in terms of net AA hind limb fluxes. Consequently, barley supplementation of a ryegrass-based diet increased the net AA release by the splanchnic tissues, with little effect on the AA net uptake by the peripheral tissues.

Effect of feed intake on amino acid transfers across the ovine hindquarters.

Responses in variables of amino acid (AA) metabolism across peripheral tissues to feed intake were studied in six sheep (mean live weight 32 kg) prepared with arterio-venous catheters across the hindquarters. Four intakes (0.5, 1.0, 1.5 and 2.5 x maintenance energy) were offered over 2-week periods to each sheep in a Latin square design with two animals replicated. Animals were infused intravenously with a mixture of U-13C-labelled AA for 10 h and integrated blood samples withdrawn from the aorta and vena cava hourly between 5 and 9 h of infusion. Biopsy samples were also taken from skin and m. vastus lateralis. Data from both essential (histidine, isoleucine, leucine, lysine, phenylalanine, threonine) and nonessential (glycine, proline, serine, tyrosine) AA were modelled to give rates of inward and outward transport, protein synthesis and degradation, plus the fraction of total vascular inflow that exchanged with the hindquarter tissues. Rates of inward transport varied more than 10-fold between AA. For all essential AA (plus serine), inward transport increased with food intake (P<0.04). There were corresponding increases in AA efflux (P<0.05) from the tissues for threonine and the branched-chain AA. Protein synthesis rates estimated from the kinetics of these AA also increased with intake (P<0.02). Rates of inward transport greatly exceeded the amount of AA necessary to support protein retention, but were more similar to rates of protein synthesis. Nutritional or other strategies to enhance AA transport into peripheral tissues are unlikely to increase anabolic responses.