Effect of acute iron infusion on insulin secretion: A randomized, double-blind, placebo-controlled trial.

Chronic exposure to high iron levels increases diabetes risk partly by inducing oxidative stress, but the consequences of acute iron administration on beta cells are unknown. We tested whether the acute administration of iron for the correction of iron deficiency influenced insulin secretion and the production of reactive oxygen species. Single-center, double-blinded, randomized controlled trial conducted between June 2017 and March 2020. 32 women aged 18 to 47 years, displaying symptomatic iron deficiency without anaemia, were recruited from a community setting and randomly allocated (1:1) to a single infusion of 1000 mg intravenous ferric carboxymaltose (iron) or saline (placebo). The primary outcome was the between group mean difference from baseline to day 28 in first and second phase insulin secretion, assessed by a two-step hyperglycaemic clamp. All analyses were performed by intention to treat. This trial was registered in ClinicalTrials.gov NCT03191201. Iron infusion did not affect first and second phase insulin release. For first phase, the between group mean difference from baseline to day 28 was 0 μU × 10 min/mL [95% CI, -22 to 22, P = 0.99]. For second phase, it was -5 μUx10min/mL [95% CI, -161 to 151; P = 0.95] at the first plateau of the clamp and -249 μUx10min/mL [95% CI, -635 to 137; P = 0.20] at the second plateau. Iron infusion increased serum ascorbyl/ascorbate ratio, a marker of plasma oxidative stress, at day 14, with restoration of normal ratio at day 28 relative to placebo. Finally, high-sensitive C-reactive protein levels remained similar among groups. In iron deficient women without anaemia, intravenous administration of 1000 mg of iron in a single sitting did not impair glucose-induced insulin secretion despite a transient increase in the levels of circulating reactive oxygen species. The Swiss National Science Foundation, University of Lausanne and Leenaards, Raymond-Berger and Placide Nicod Foundations

Breath acetone as a marker of energy balance: an exploratory study in healthy humans.

An exploratory study was performed on eight healthy volunteers to assess how short-term changes in energy balance and dietary carbohydrate content impact breath acetone concentrations. Participants were studied on three occasions: on each occasion, they remained fasted and in resting conditions during the first 2 h to assess basal breath acetone and blood beta-hydroxybutyrate (BOHB). During the next 6 h, they remained fasted on one occasion (F), or were fed hourly high carbohydrate (HC) or low-carbohydrate (LC) meals to induce a positive energy balance on the other two occasions. They remained in resting conditions during 4 h, then performed a 2-hour low intensity exercise (25 W) inducing a negative energy balance. In resting conditions, breath acetone and blood BOHB concentrations increased progressively compared to basal values in F, but decreased and remained low throughout the test in HC. With LC, breath acetone increased progressively, while blood BOHB decreased. This exploratory study indicates that breath acetone reliably detects a stimulation of ketogenesis during a short-term fast. It also suggests that LC and HC differentially impact BOHB and acetone production and utilization, and reveals possible limitations to the use of breath acetone as a marker of energy balance

Odd Chain Fatty Acids; New Insights of the Relationship Between the Gut Microbiota, Dietary Intake, Biosynthesis and Glucose Intolerance

Recent findings have shown an inverse association between circulating C15:0/C17:0 fatty acids with disease risk, therefore, their origin needs to be determined to understanding their role in these pathologies. Through combinations of both animal and human intervention studies, we comprehensively investigated all possible contributions of these fatty acids from the gut-microbiota, the diet, and novel endogenous biosynthesis. Investigations included an intestinal germ-free study and a C15:0/C17:0 diet dose response study. Endogenous production was assessed through: a stearic acid infusion, phytol supplementation, and a Hacl1$^{−/−}$ mouse model. Two human dietary intervention studies were used to translate the results. Finally, a study comparing baseline C15:0/C17:0 with the prognosis of glucose intolerance. We found that circulating C15:0/C17:0 levels were not influenced by the gut-microbiota. The dose response study showed C15:0 had a linear response, however C17:0 was not directly correlated. The phytol supplementation only decreased C17:0. Stearic acid infusion only increased C17:0. Hacl1$^{−/−}$ only decreased C17:0. The glucose intolerance study showed only C17:0 correlated with prognosis. To summarise, circulating C15:0 and C17:0 are independently derived; C15:0 correlates directly with dietary intake, while C17:0 is substantially biosynthesized, therefore, they are not homologous in the aetiology of metabolic disease. Our findings emphasize the importance of the biosynthesis of C17:0 and recognizing its link with metabolic disease.The authors are grateful to the Medical Research Council for core funding (Lipid Profiling and Signalling programme grant; number UD99999906, Cambridge Lipidomics Biomarker Research Initiative; grant G0800783, MRC Human Nutrition Research PhD programme). Grant GAČR: GA15–09518S and grant Czech Science Foundation GACR: 16-06326S funded part of the gut microbiota investigation. The authors would like to acknowledge the USDA (ACNC-USDA-CRIS 6251-51000-005-03S) for funding of the dose response animal study within this manuscript. The Human study “Dairy Fat supplementation” was supported by research grants from the Hospices Civils de Lyon (Actions Incitatives); from the Programme Hospitalier de Recherche Clinique Interregional; from the Agence Nationale de la Recherche (Programme de Recherche en Nutrition Humaine and the Programme National de Recherche en Alimentation); and from the Innovation Stratégique Industrielle program of the Agence pour l’Innovation OSEO (Innovation Thérapeutique – Diabète project). K. Seyssel and M. Alligier were recipients of a doctoral fellowship from the Ministère de l’Enseignement Supérieur et de la Recherche (France). The phytol supplementation animal study was supported by grants from the Academy of Finland (138690), the Sigrid Juselius Foundation and NordForsk under the Nordic Centres of Excellence Programme in Food, Nutrition and Health, project “Mitohealth” (070010). The NIH Grant R01-DK-18243 for funding of the canine study. HACL1 knockout mouse model was supported by grants from the Flemish “Fonds Wetenschappelijk Onderzoek” (G.0721.10N) and KU Leuven (OT/14/100)

Fructose use in clinical nutrition: metabolic effects and potential consequences.

The current article presents recent findings on the metabolic effects of fructose. Fructose has always been considered as a simple 'caloric' hexose only metabolized by splanchnic tissues. Nevertheless, there is growing evidence that fructose acts as a second messenger and induces effects throughout the human body. Recent discoveries made possible with the evolution of technology have highlighted that fructose induces pleiotropic effects on different tissues. The fact that all these tissues express the specific fructose carrier GLUT5 let us reconsider that fructose is not only a caloric hexose, but could also be a potential actor of some behaviors and metabolic pathways. The physiological relevance of fructose as a metabolic driver is pertinent regarding recent scientific literature

Effect of a high fructose diet on metabolic parameters in carriers for hereditary fructose intolerance.

Hyperuricemia is an independent risk factor for the metabolic syndrome and cardiovascular disease. We hypothesized that asymptomatic carriers for hereditary fructose intolerance (OMIM 22960) would have increased uric acid and altered component of the metabolic syndrome when exposed to fructose overfeeding. Six heterozygotes for HFI (hHFI) and 6 controls (Ctrl) were studied in a randomized, controlled, crossover trial. Participants ingested two identical test meals containing 0.7 g kg <sup>-1</sup> glucose and 0.7 g kg <sup>-1</sup> fructose according to a cross-over design, once after a 7-day on a low fructose diet (LoFruD, <10 g/d) and on another occasion after 7 days on a high fructose diet (HiFruD, 1.4 g kg <sup>-1</sup> day <sup>-1</sup> fructose + 0.1 g kg <sup>-1</sup> day <sup>-1</sup> glucose). Uric acid, glucose, and insulin concentrations were monitored in fasting conditions and over 2 h postprandial, and insulin resistance indexes were calculated. HiFruD increased fasting uric acid (p < 0.05) and reduced fasting insulin sensitivity estimated by the homeostasis model assessment (HOMA) for insulin resistance (p < 0.05), in both groups. Postprandial glucose concentrations were not different between hHFI and Ctrl. However HiFruD increased postprandial plasma uric acid, insulin and hepatic insulin resistance index (HIRI) in hHFI only (all p < 0.05). Seven days of HiFruD increased fasting uric acid and slightly reduced fasting HOMA index in both groups. In contrast, HiFruD increased postprandial uric acid, insulin concentration and HIRI in hHFI only, suggesting that heterozygosity for pathogenic Aldolase B variants may confer an increased susceptibility to the effects of dietary fructose on uric acid and hepatic insulin sensitivity. This trial was registered at the U.S. Clinical Trials Registry as NCT03545581

Effects of gastric bypass surgery on postprandial gut and systemic lipid handling.

Obesity is often associated with increased postprandial triglyceride (TG) concentrations, mainly from chylomicrons- and VLDL-TG. These alterations are usually reverted to normal after gastric bypass surgery (GB), through mechanisms which remain unknown. The objective of this study was therefore to assess the contribution of exogenous labelled fatty acids ingested with a meal to postprandial blood chylomicrons and VLDL-TG concentrations after GB. 7 GB patients 3-5 years after surgery (GB: 2M/5F, mean BMI 30 ± 2 kg/m <sup>2</sup> , mean age 40 ± 3 years), 6 overweight non operated subjects (OW: 1M/5F, mean BMI 31 ± 3 kg/m <sup>2</sup> , mean age 38 ± 2 years) and 8 normal weight healthy subjects (NW: 4M/4F, mean BMI 22 ± 1 kg/m <sup>2</sup> , mean age 26 ± 4 years) were studied over 7 h following ingestion of a liquid meal containing 18 g fat labelled with 250 mg <sup>13</sup> C <sub>16</sub> palmitate, 22 g protein, 36 g fructose and 36 g glucose. TG, <sup>13</sup> C palmitate ( <sup>13</sup> C-palm) and apoB48 concentrations were measured hourly in whole plasma and/or in chylomicrons and VLDL lipoprotein sub-fractions. OW subjects had higher chylomicron-than NW (chylo-TG 96.5 (23.1) vs 28.8 (11.8) mmol/l*420min (p = 0.02)), but similar total, chylo- <sup>13</sup> C-palm and apoB48 iAUCs. In GB, chylo- <sup>13</sup> C-palm and apoB48 increased earlier after meal ingestion, but then remained lower than in NW and OW throughout the postprandial period. GB also had lower chylo-TG iAUCs than OW (8.9 (11.5) vs 96.5 (23.2) mmol/l*420min, p = 0.003). Their apoB48 iAUCs were not different from NW and OW (509.2 (90.5) vs 710.2 (80.5) and 870.1 (297.6) pg/ml*420min, all p > 0.05). An accelerated postprandial apoB48 rise, together with unchanged postprandial apoB48 iUAC, suggests that intestinal fat absorption and chylomicron secretion was quantitatively unaltered, but accelerated after gastric bypass. In contrast, the decreased postprandial chylo-TG and <sup>13</sup> C-palm iAUCs suggest that plasma chylomicron clearance was enhanced after gastric bypass

The extra-splanchnic fructose escape after ingestion of a fructose-glucose drink: An exploratory study in healthy humans using a dual fructose isotope method.

The presence of specific fructose transporters and fructose metabolizing enzymes has now been demonstrated in the skeletal muscle, brain, heart, adipose tissue and many other tissues. This suggests that fructose may be directly metabolized and play physiological or pathophysiological roles in extra-splanchnic tissues. Yet, the proportion of ingested fructose reaching the systemic circulation is generally not measured. This study aimed to assess the amount of oral fructose escaping first-pass splanchnic extraction after ingestion of a fructose-glucose drink using a dual oral-intravenous fructose isotope method. Nine healthy volunteers were studied over 2 h before and 4 h after ingestion of a drink containing 30.4 ± 1.0 g of glucose (mean ± SEM) and 30.4 ± 1.0 g of fructose labelled with 1% [U- <sup>13</sup> C <sub>6</sub> ]-fructose. A 75%-unlabeled fructose and 25%-[6,6- <sup>2</sup> H <sub>2</sub> ]-fructose solution was continuously infused (100 μg kg <sup>-1</sup> min <sup>-1</sup> ) over the 6 h period. Total systemic, oral and endogenous fructose fluxes were calculated from plasma fructose concentrations and isotopic enrichments. The fraction of fructose escaping first-pass splanchnic extraction was calculated assuming a complete intestinal absorption of the fructose drink. Fasting plasma fructose concentration before tracer infusion was 17.9 ± 0.6 μmol.L <sup>-1</sup> . Fasting endogenous fructose production detected by tracer dilution analysis was 55.3 ± 3.8 μg kg <sup>-1</sup> min <sup>-1</sup> . Over the 4 h post drink ingestion, 4.4 ± 0.2 g of ingested fructose (i.e. 14.5 ± 0.8%) escaped first-pass splanchnic extraction and reached the systemic circulation. Endogenous fructose production significantly increased to a maximum of 165.4 ± 10.7 μg kg <sup>-1</sup> ·min <sup>-1</sup> 60 min after drink ingestion (p < 0.001). These data indicate that a non-negligible fraction of fructose is able to escape splanchnic extraction and circulate in the periphery. The metabolic effects of direct fructose metabolism in extra-splanchnic tissues, and their relationship with metabolic diseases, remain to be evaluated. Our results also open new research perspectives regarding the physiological role of endogenous fructose production

Quantification des graisses abdominales sous-cutanées et viscérales par résonance magnétique nucléaire du proton à 3T : application à un protocole de surnutrition

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