Olivier Ballevre

The rate of protein digestion affects protein gain differently during aging in humans

In young men ingesting protein meals, slowly digested proteins (caseins: CAS) induce a higher protein gain than those that are rapidly digested (whey proteins: WP). Our aim was to assess whether or not this is true in elderly men receiving mixed meals. The effects of meals containing either CAS or two different amounts of WP (WP‐iN: isonitrogenous with CAS, or WP‐iL: providing the same amount of leucine as CAS) on protein metabolism (assessed by combining oral and intravenous leucine tracers) were compared in nine healthy, elderly (mean ±s.e.m. age 72 ± 1 years) and six young men (24 ± 1 years). In both age groups, WP‐iL and WP‐iN were digested faster than CAS (P < 0.001, ANOVA). Proteolysis was inhibited similarly whatever the meal and age groups (P= NS). Protein synthesis was higher with WP‐iN than with CAS or WP‐iL (P < 0.01), irrespective of age (P= NS). An age‐related effect (P < 0.05) was found with postprandial leucine balance. Leucine balance was higher with CAS than with WP‐iL (P < 0.01) in young men, but not in elderly subjects (P= NS). In isonitrogenous conditions, leucine balance was higher with WP‐iN than with CAS (P < 0.001) in both age groups, but the magnitude of the differences was higher in the elderly men (P= 0.05). In conclusion, during aging, protein gain was greater with WP (rapidly digested protein), and lower with CAS (slowly digested protein). This suggests that a ‘fast’ protein might be more beneficial than a ‘slow’ one to limit protein losses during aging.

Antihypertensive effects and mechanisms of chlorogenic acids

Chlorogenic acids (CGAs) are potent antioxidants found in certain foods and drinks, most notably in coffee. In recent years, basic and clinical investigations have implied that the consumption of chlorogenic acid can have an anti-hypertension effect. Mechanistically, the metabolites of CGAs attenuate oxidative stress (reactive oxygen species), which leads to the benefit of blood-pressure reduction through improved endothelial function and nitric oxide bioavailability in the arterial vasculature. This review article highlights the physiological and biochemical findings on this subject and highlights some remaining issues that merit further scientific and clinical exploration. In the framework of lifestyle modification for the management of cardiovascular risk factors, the dietary consumption of CGAs may hold promise for providing a non-pharmacological approach for the prevention and treatment of high blood pressure.

Production rates and metabolism of short-chain fatty acids in the colon and whole body using stable isotopes

Short-chain fatty acids (SCFA; mainly acetate, propionate and butyrate) are largely produced in non-ruminants during the colonic bacterial fermentation of non-digestible carbohydrates. These intestinal exogenous SCFA pass in part through the splanchnic bed and reach the peripheral bloodstream, mixing with the endogenous circulating SCFA. The whole-body turnover of SCFA is thus composed of an endogenous peripheral turnover and an exogenous production that depends on dietary intake of non-digestible carbohydrates. In the present work methods were developed for determining the SCFA turnover in animals and in human subjects using stable isotopes. The original studies performed to determine endogenous and exogenous metabolism of SCFA in animals and in human subjects are summarised. Using intravenous infusion of 13C-labelled SCFA the whole-body turnover of acetate, propionate and butyrate was assessed in rats in a fasted state. The endogenous turnover of acetate and its oxidation were determined in healthy human subjects in the post-absorptive state, using intravenous infusion of [1-13C]acetate. Intragastric tracer infusions were performed to evaluate the splanchnic first-pass retention of acetate in adults. Finally, an original model was developed in healthy human subjects using intravenous infusion of [1-13C]acetate to determine in vivo the true colonic acetate production after ingestion of a non-digestible disaccharide. These present studies using stable isotopes provide the basis for a novel strategy to evaluate in vivo, in human subjects, the production of SCFA in the large intestine.

Development of a rapid and convenient method to purify mucins and determine their in vivo synthesis rate in rats.

The intestinal mucoprotein synthesis rate was measured in vivo for the first time. For this, a rapid, reproducible, and convenient method to purify mucoproteins from large numbers of intestinal samples at the same time was developed. The method takes advantage of both the high mucin resistance to protease activities due to their extensive glycosylations and the high mucin molecular size. Intestinal homogenates were partially digested with Flavourzyme. Nonprotected proteins partially degraded were easily separated from mucoproteins by small gel filtration chromatography using Sepharose CL-4B. Electrophoretically pure mucins were obtained. Their amino acid composition was typical of purified intestinal epithelial mucins. The mucoprotein synthesis rate was determined in vivo in rats using the flooding dose method with the stable isotope L-[1-13C]valine. Free L-[1-13C]valine enrichments in the intracellular pool were determined by GC-MS. L-[1-13C]valine enrichments into purified mucoproteins or intestinal mucosal proteins were measured by gas chromatography-combustion-isotope ratio mass spectrometry. In rats, we found that the gut mucosa protein synthesis rate (%/day) decreased regularly from duodenum (122%/day) to colon (43%/day). In contrast, mucoprotein fractional synthesis rates were in the same range along the digestive tract, between 112%/day (colon) and 138%/day (ileum).

Maternal Docosahexaenoic Acid Feeding Protects Against Impairment of Learning and Memory and Oxidative Stress in Prenatally Stressed Rats: Possible Role of Neuronal Mitochondria Metabolism

AIMS Docosahexaenoic acid (22:6n-3; DHA) is known to play a critical role in postnatal brain development. However, no study has been performed to investigate its preventive effect on prenatal stress-induced behavioral and molecular alterations in offspring. In the present study, rats were exposed to restraint stress on days 14-20 of pregnancy, three times a day, 2 hours each time; DHA was given at the doses of 100 and 300 mg/kg/day for two weeks. RESULTS We showed that prenatal restraint stress caused (1) learning and memory impairment, (2) BDNF mRNA level decrease, (3) oxidative damage to proteins, (4) enhanced expression of nitric oxide synthase and apoptosis, and (5) abnormalities in mitochondrial metabolism that included changes in mitochondrial complexes I-V, and enhancement of expression of proteins involved in mitochondrial fusion/fission (Mfn-1, Mfn-2, Drp-1) and autophagy (Atg3, Atg7, Beclin-1, p-Akt, and p-mTOR) in the hippocampus of offspring. INNOVATION Besides the well-known role in child brain development, we reported the novel finding of DHA in protecting prenatal stress-induced cognitive dysfunction involving the modulation of mitochondrial function and dynamics. CONCLUSION Maternal feeding of DHA significantly prevented prenatal stress-induced impairment of learning and memory and normalized the biomarkers of oxidative damage, apoptosis, and mitochondrial metabolism in the hippocampus of both male and female offspring. These results suggest that maternal feeding of DHA exerts preventive effects on prenatal stress-induced brain dysfunction and that modulation of mitochondrial metabolism may play critical role in DHA protection.

Plasma glutamine response to enteral administration of glutamine in human volunteers (free glutamine versus protein-bound glutamine)

The goal of the present work was to compare the plasma glutamine response to exogenous glutamine administration in human volunteers; glutamine was provided as a free amino acid, bound to proteins, or in the form of peptides. Plasma glutamine concentrations were measured in eight human volunteers at 30, 60, 90, 120, and 240 min after receiving a drink containing 30 g of protein from one of the five different proteins tested (sodium caseinate, sodium caseinate + free glutamine, carob germ flour, carob protein concentrate, and carob protein hydrolysate). Peak plasma glutamine concentrations were 42% higher than postabsorptive basal values when exogenous glutamine was administered in the form of free glutamine added to caseinate (925.9 +/- 67.7 versus 651.3 +/- 44.0 micromol/L, respectively). In contrast, when glutamine was offered 100% bound to proteins (carob proteins), peak plasma glutamine concentration increased only between 18% and 23% from basal values, possibly because of the lower digestibility of carob proteins versus that of caseinate + free glutamine, to a different glutamine utilization at the gut level, or to a different response in endogenous glutamine kinetics to enteral administration of glutamine, depending on the molecular form of the glutamine source (free or protein bound).

A Milk-Based Wolfberry Preparation Prevents Prenatal Stress-Induced Cognitive Impairment of Offspring Rats, and Inhibits Oxidative Damage and Mitochondrial Dysfunction In Vitro

Lycium barbarum (Fructus Lycii, Wolfberry, or Gouqi) belongs to the Solanaceae. The red-colored fruits of L. barbarum have been used for a long time as an ingredient in Chinese cuisine and brewing, and also in traditional Chinese herbal medicine for improving health. However, its effects on cognitive function have not been well studied. In the present study, prevention of a milk-based wolfberry preparation (WP) on cognitive dysfunction was tested in a prenatal stress model with rats and the antioxidant mechanism was tested by in vitro experiments. We found that prenatal stress caused a significant decrease in cognitive function (Morris water maze test) in female offspring. Pretreatment of the mother rats with WP significantly prevented the prenatal stress-induced cognitive dysfunction. In vitro studies showed that WP dose-dependently scavenged hydroxyl and superoxide radicals (determined by an electron spin resonance spectrometric assay), and inhibited FeCl2/ascorbic acid-induced dysfunction in brain tissue and tissue mitochondria, including increases in reactive oxygen species and lipid peroxidation and decreases in the activities of complex I, complex II, and glutamate cysteine ligase. These results suggest that dietary supplementation with WP may be an effective strategy for preventing the brain oxidative mitochondrial damage and cognitive dysfunction associated with prenatal stress.

Determination of taurine metabolism by measurement of 15N-enriched taurine in cat urine by gas chromatography—mass spectrometry

To understand the biological function of taurine, a study of taurine kinetics in the cat was undertaken. This paper describes a method developed for the accurate determination of 15N-taurine enrichment in cat urine by gas chromatography-mass spectrometry. 15N-Taurine was given to six animals as an oral bolus dose of 20 mg/kg body weight, and the urine was pooled on a daily basis. The hydrolysed or non-hydrolysed urine samples (for total and free taurine, respectively) were directly derivatized without further purification. The N-pentafluorobenzoyl di-n-butyl amide derivative obtained was analysed, and the fragment [M-(di-n-butyl amide)]+, carrier of the labelled nitrogen atom, was selectively recorded at m/z 302 (14N-taurine) and m/z 303 (15N-taurine). Calibration curves prepared in hydrolysed and non-hydrolysed urine samples spiked with 15N-taurine gave similar slopes to the calibration curve prepared in water. The average coefficient of variation observed for the mole percent excess in the non-hydrolysed samples was 1.22% (n = 92) and for the hydrolysed urine 1.00% (n = 98). There was no significant difference between free and total taurine enrichment. The half-life of taurine in cat body was found to be 29.3 +/- 2.9 h and 35.0 +/- 1.4 h for free and total taurine, respectively (non-significant). The taurine body pool, calculated by extrapolation of the curve to zero time, had a value of 137 +/- 22 ng/kg and 157 +/- 11 mg/kg for free and total taurine, respectively.

Acetogenic fibers reduce fasting glucose turnover but not peripheral insulin resistance in metabolic syndrome patients

BACKGROUND & AIMS The acute ingestion of an acetogenic indigestible carbohydrate (lactulose) increased acetate turnover associated with decreased lipolysis (glycerol turnover) in insulin-resistant patients. It is not known whether a decreased lipolysis by chronic ingestion of acetogenic indigestible carbohydrates or fibers improves glucose turnover and insulin sensitivity. METHODS Twenty-one men with metabolic syndrome ingested daily standardized drinks, with or without 28 g acetogenic fibers (acacia gum and pectin), for 5 weeks in a randomized double-blind crossover controlled study design. Euglycaemic-hyperinsulinaemic (EH) clamps coupled with kinetic studies were performed in the fasting state after treatments. RESULTS Flatulence was more frequent with fiber treatment. Body weight, lipids as well as acetate and glycerol turnovers were unchanged. Fasting endogenous glucose turnover was improved after fiber treatment (7.9 ± 1.3 μmol kg(-1) min(-1)) compared with control (8.6 ± 1.6 μmol kg(-1) min(-1), P < 0.05). But insulin sensitivity (glucose infusion rate) during the EH clamp was not different at the end of fiber and control treatments, 3.7 ± 1.8 and 3.8 ± 1.5 mg kg(-1) min(-1), respectively, nor fasting plasma glucose and insulin. CONCLUSIONS The chronic ingestion of acacia gum and pectin fibers did not decrease lipolysis but improved fasting endogenous glucose turnover with no effect on peripheral insulin resistance in metabolic syndrome patients.

Chicory increases acetate turnover, but not propionate and butyrate peripheral turnovers in rats.

Chicory roots are rich in inulin that is degraded into SCFA in the caecum and colon. Whole-body SCFA metabolism was investigated in rats during food deprivation and postprandial states. After 22 h of food deprivation, sixteen rats received an IV injection of radioactive 14C-labelled SCFA. The volume of distribution and the fractional clearance rate of SCFA were 0.25-0.27 litres/kg and 5.4-5.9 %/min, respectively. The half-life in the first extracellular rapidly decaying compartment was between 0.9 and 1.4 min. After 22 h of food deprivation, another seventeen rats received a primed continuous IV infusion of 13C-labelled SCFA for 2 h. Isotope enrichment (13C) of SCFA was determined in peripheral arterial blood by MS. Peripheral acetate, propionate and butyrate turnover rates were 29, 4 and 0.3 micromol/kg per min respectively. Following 4 weeks of treatment with chicory root or control diets, eighteen fed rats received a primed continuous IV infusion of 13C-labelled SCFA for 2 h. Intestinal degradation of dietary chicory lowered caecal pH, enhanced caecal and colonic weights, caecal SCFA concentrations and breath H2. The diet with chicory supplementation enhanced peripheral acetate turnover by 25 % (P = 0.017) concomitant with an increase in plasma acetate concentration. There were no changes in propionate or butyrate turnovers. In conclusion, by setting up a multi-tracer approach to simultaneously assess the turnovers of acetate, propionate and butyrate it was demonstrated that a chronic chicory-rich diet significantly increases peripheral acetate turnover but not that of propionate or butyrate in rats.