Glucose Turnover Research Articles

Detection of cancer-associated cachexia in lung cancer patients using whole-body [18F]FDG-PET/CT imaging: A multi-centre study.

Cancer-associated cachexia (CAC) is a metabolic syndrome contributing to therapy resistance and mortality in lung cancer patients (LCP). CAC is typically defined using clinical non-imaging criteria. Given the metabolic underpinnings of CAC and the ability of [18F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET)/computer tomography (CT) to provide quantitative information on glucose turnover, we evaluate the usefulness of whole-body (WB) PET/CT imaging, as part of the standard diagnostic workup of LCP, to provide additional information on the onset or presence of CAC. This multi-centre study included 345 LCP who underwent WB [18F]FDG-PET/CT imaging for initial clinical staging. A weight loss grading system (WLGS) adjusted to body mass index was used to classify LCP into 'No CAC' (WLGS-0/1 at baseline prior treatment and at first follow-up: N=158, 51F/107M), 'Dev CAC' (WLGS-0/1 at baseline and WLGS-3/4 at follow-up: N=90, 34F/56M), and 'CAC' (WLGS-3/4 at baseline: N=97, 31F/66M). For each CAC category, mean standardized uptake values (SUV) normalized to aorta uptake (<SUVaorta>) and CT-defined volumes were extracted for abdominal and visceral organs, muscles, and adipose-tissue using automated image segmentation of baseline [18F]FDG-PET/CT images. Imaging and non-imaging parameters from laboratory tests were compared statistically. A machine-learning (ML) model was then trained to classify LCP as 'No CAC', 'Dev CAC', and 'CAC' based on their imaging parameters. SHapley Additive exPlanations (SHAP) analysis was employed to identify the key factors contributing to CAC development for each patient. The three CAC categories displayed multi-organ differences in <SUVaorta>. In all target organs, <SUVaorta> was higher in the 'CAC' cohort compared with 'No CAC' (P<0.01), except for liver and kidneys, where <SUVaorta> in 'CAC' was reduced by 5%. The 'Dev CAC' cohort displayed a small but significant increase in <SUVaorta> of pancreas (+4%), skeletal-muscle (+7%), subcutaneous adipose-tissue (+11%), and visceral adipose-tissue (+15%). In 'CAC' patients, a strong negative Spearman correlation (ρ=-0.8) was identified between <SUVaorta> and volumes of adipose-tissue. The machine-learning model identified 'CAC' at baseline with 81% of accuracy, highlighting <SUVaorta> of spleen, pancreas, liver, and adipose-tissue as most relevant features. The model performance was suboptimal (54%) when classifying 'Dev CAC' versus 'No CAC'. WB [18F]FDG-PET/CT imaging reveals groupwise differences in the multi-organ metabolism of LCP with and without CAC, thus highlighting systemic metabolic aberrations symptomatic of cachectic patients. Based on a retrospective cohort, our ML model identified patients with CAC with good accuracy. However, its performance in patients developing CAC was suboptimal. A prospective, multi-centre study has been initiated to address the limitations of the present retrospective analysis.

Post Prandial Glucose Turnover Differs Between Adolescents & Adults with Type 1 Diabetes: Triple Tracer Mixed Meal Study.

Insulin sensitivity (SI) varies with age in Type 1 diabetes (T1D). To compare postprandial glucose turnover and insulin sensitivity between adolescents and adults with T1D. Cross-sectional comparison. Clinical Research Unit. 21 early adolescents with T1D (T1D-adol) [12F; age: 11.5 ± 0.5yrs.; BMI: 19 ± 2 kg/m2], 13 adults with T1D (T1D-adult) [5F; 37.8 ± 9.1yrs.; BMI: 27 ± 2 kg/m2] and 14 anthropometrically matched adults without diabetes (ND) [7F; 26.9 ± 7.0yrs.; BMI: 25 ± 2.5 kg/m2]. Triple-tracer mixed meal study and oral glucose models. SI between T1D-adol and T1D-adult. Post-prandial glucose excursions were not different in T1D-adol vs T1D-adult (p = 0.111) but higher than in ND (p < 0.01). Insulin excursions were also similar in T1D-adol vs. T1D-adult (p = 0.600) and they were both lower (p < 0.05) compared to ND, while glucagon excursions were lower (p < 0.01) in T1D-adol than in T1D-adult and ND. Integrated rates of endogenous glucose production and glucose disappearance were lower in T1D-adol than in T1D-adult and in ND vs. T1D-adult but did not differ between T1D-adol and ND. Meal glucose appearance did not differ between groups. Insulin sensitivity (SI) in T1D-adol vs ND was similar (p = 0.299). However, SI was higher in T1D-adol and ND vs. T1D-adult (p < 0.01). We report differences in parameters of postprandial glucose turnover and insulin sensitivity between adults and early adolescents with T1D that could, at least in part, be due to the shorter duration of diabetes among T1D-adol. These data support the concept that over time with T1D endogenous glucose production increases and SI deteriorates.

Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training.

This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90-min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O2peak) exercise using indirect calorimetry, and 6-6-[2H2]-glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE (p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased (p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST (p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole-body and skeletal muscle fat metabolism.

Pioglitazone does not affect exogenous glucose oxidation or metabolic clearance rate during steady-state aerobic exercise at high altitude

Background: Hypoxia-induced insulin insensitivity decreases exogenous glucose oxidation and metabolic clearance rate (MCR, proxy for peripheral glucose uptake) in native lowlanders exercising during the initial hours of high-altitude (HA) exposure compared sea level. These data suggest that administering an insulin sensitizing drug before HA exposure may increase exogenous glucose oxidation rate by stimulating peripheral glucose uptake. Objective: To compare the effects of pioglitazone (PIO) and placebo (PLA) on exogenous glucose oxidation and MCR during steady-state aerobic exercise at HA. We hypothesized that exogenous glucose oxidation and MCR would be higher with PIO than PLA. Methods: Using a randomized, crossover design, native lowlanders (n = 7 males, mean ± SD, age: 23 ± 6 y, body mass: 84 ± 11 kg) consumed 145 g (1.8 g/min) of glucose while performing 80-min of metabolically-matched (1.43 ± 0.16 VȮ2 L/min) treadmill exercise at HA (460 mmHg) after being administered PIO (15 mg) or PLA (microcrystalline cellulose pill) daily for five days. Substrate oxidation and glucose turnover were determined using indirect calorimetry, oral 13C-glucose and [6,6-2H2]-glucose primed, continuous infusions. Results: Exogenous glucose oxidation rate was not different between PIO (0.31 ± 0.03 g/min) and PLA (0.32 ± 0.09 g/min). Total carbohydrate oxidation with PIO (1.65 ± 0.22 g/min) was the same as PLA (1.68 ± 0.32 g/min). There were no treatment effects on glucose rate of appearance (PIO: 2.46 ± 0.27, PLA: 2.43 ± 0.27 mg/kg/min) disappearance (PIO: 2.19 ± 0.17, PLA: 2.20 ± 0.22 mg/kg/min), and MCR (PIO: 1.63 ± 0.37, PLA: 1.73 ± 0.40 mL/kg/min). Conclusion: These data do not support our hypothesis that exogenous glucose oxidation during exercise at HA can be restored through the short-term administration of PIO. Findings from this study may suggest that hypoxia-induced insulin resistance may be a symptom and not the primary etiology of dysregulated glucose metabolism during acute HA exposure. Supported by MOMRP; authors’ views not offcial US Army or DoD policy. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Pioglitazone does not enhance exogenous glucose oxidation or metabolic clearance rate during aerobic exercise in men under acute high-altitude exposure.

Insulin insensitivity decreases exogenous glucose oxidation and metabolic clearance rate (MCR) during aerobic exercise in unacclimatized lowlanders at high altitude (HA). Whether use of an oral insulin sensitizer before acute HA exposure enhances exogenous glucose oxidation is unclear. This study investigated the impact of pioglitazone (PIO) on exogenous glucose oxidation and glucose turnover compared with placebo (PLA) during aerobic exercise at HA. With the use of a randomized crossover design, native lowlanders (n = 7 males, means ± SD, age: 23 ± 6 yr, body mass: 84 ± 11 kg) consumed 145 g (1.8 g/min) of glucose while performing 80 min of steady-state (1.43 ± 0.16 V̇o2 L/min) treadmill exercise at HA (460 mmHg; [Formula: see text] 96.6 mmHg) following short-term (5 days) use of PIO (15 mg oral dose per day) or PLA (microcrystalline cellulose pill). Substrate oxidation and glucose turnover were determined using indirect calorimetry and stable isotopes ([13C]glucose and 6,6-[2H2]glucose). Exogenous glucose oxidation was not different between PIO (0.31 ± 0.03 g/min) and PLA (0.32 ± 0.09 g/min). Total carbohydrate oxidation (PIO: 1.65 ± 0.22 g/min, PLA: 1.68 ± 0.32 g/min) or fat oxidation (PIO: 0.10 ± 0.0.08 g/min, PLA: 0.09 ± 0.07 g/min) was not different between treatments. There was no treatment effect on glucose rate of appearance (PIO: 2.46 ± 0.27, PLA: 2.43 ± 0.27 mg/kg/min), disappearance (PIO: 2.19 ± 0.17, PLA: 2.20 ± 0.22 mg/kg/min), or MCR (PIO: 1.63 ± 0.37, PLA: 1.73 ± 0.40 mL/kg/min). Results from this study indicate that PIO is not an effective intervention to enhance exogenous glucose oxidation or MCR during acute HA exposure. Lack of effect with PIO suggests that the etiology of glucose metabolism dysregulation during acute HA exposure may not result from insulin resistance in peripheral tissues.NEW & NOTEWORTHY Short-term (5 days) use of the oral insulin sensitizer pioglitazone does not alter circulating glucose or insulin responses to enhance exogenous glucose oxidation during steady-state aerobic exercise in young healthy men under simulated acute (8 h) high-altitude (460 mmHg) conditions. These results indicate that dysregulations in glucose metabolism in native lowlanders sojourning at high altitude may not be due to insulin resistance at peripheral tissue.

132 Detailed Characterization of a Novel Human Ex Vivo Model for Burn Injuries

Abstract Introduction Burn injuries belong to the most common soft tissue injuries and often result in extensive trauma but are also associated with cases of major emergency such as sepsis or systemic inflammatory response syndrome. The early phase after burn injury is critical and decides about later potential complications in wound healing. Burn injuries activate numerous processes, including heat shock, inflammation and tissue regeneration responses and thereby promote the release of cytokines and other signalling molecules such as miRNAs and metabolites. Despite extensive research, skin tissue reactions in the early phases after burn injuries still need to be investigated in more detail. Therefore, reliable burn models are needed to elucidate the exact sequence of events during the healing process and to monitor potential biomarkers that could give information about treatment success. Methods We induced contact burns on fresh human abdominal skin explants that were resected during abdominoplasty. Gene and miRNA expression patterns, cytokine production profiles of key mediators such as IL8 and IL6 and skin ultrastructure were analysed for 24 hours after the burn injury. Additionally, we used open flow microperfusion (OFM), a sampling technique that allows time and location dependent collection of dermal interstitial fluid (dISF), to also monitor the release of specific miRNAs, cytokines and metabolites. Results In burn injuries, we found significant changes in gene and miRNA expression as soon as one hour after burn injury. Inflammatory genes such as IL8 were significantly up-regulated whereas miRNAs were systematically down-regulated. miRNAs were actively released and mobilized into the dISF, while miR-497-5p could be identified stably downregulated in tissue and dISF in the early phase after a burn injury. Metabolome analysis of dISF showed a striking metabolic shift in burn injuries, linking burn injury to increased amino acid and glucose turnover in wounds. Conclusions By using this ex vivo human skin model for burn injuries we were able to study the immediate early responses to burns for up to 24 h. We found that miR-497-5p could serve as potential biomarker to assess burn severity since it is not only down-regulated in skin but also mobilized into the dISF after burn injury. Furthermore, we found distinct metabolite signatures after burn injury. Applicability of Research to Practice Identification and research on potential biomarkers to assess burn severity and treatment success.

Distinct bacterial succession and functional response to alginate in the South, Equatorial, and North Pacific Ocean.

The availability of alginate, an abundant macroalgal polysaccharide, induces compositional and functional responses among marine microbes, but these dynamics have not been characterized across the Pacific Ocean. We investigated alginate-induced compositional and functional shifts (e.g., heterotrophic production, glucose turnover, hydrolytic enzyme activities) of microbial communities in the South Subtropical, Equatorial, and Polar Frontal North Pacific in mesocosms. We observed that shifts in response to alginate were site-specific. In the South Subtropical Pacific, prokaryotic cell counts, glucose turnover, and peptidase activities changed the most with alginate addition, along with the enrichment of the widest range of particle-associated taxa (161 amplicon sequence variants; ASVs) belonging to Alteromonadaceae, Rhodobacteraceae, Phormidiaceae, and Pseudoalteromonadaceae. Some of these taxa were detected at other sites but only enriched in the South Pacific. In the Equatorial Pacific, glucose turnover and heterotrophic prokaryotic production increased most rapidly; a single Alteromonas taxon dominated (60% of the community) but remained low (<2%) elsewhere. In the North Pacific, the particle-associated community response to alginate was gradual, with a more limited range of alginate-enriched taxa (82 ASVs). Thus, alginate-related ecological and biogeochemical shifts depend on a combination of factors that include the ability to utilize alginate, environmental conditions, and microbial interactions.

Glucose turnover at whole-body and skeletal muscle level in response to parenteral nutrition in male patients with alcoholic liver cirrhosis

Cirrhosis is associated with insulin resistance and impaired glucose tolerance, which may be caused by impairments at different tissue levels (liver, skeletal muscle, and/or beta cell). Here, glucose kinetics at whole-body and skeletal muscle level in patients with cirrhosis (Child-Pugh A and B) were studied during parenteral nutrition using the isotope dilution technique and arteriovenous balance approach across the leg. As opposed to the euglycemic hyperinsulinemic clamp or glucose tolerance tests applied in previous studies, this approach provides a nutrient composition more similar to a normal meal while circumventing any possible portal-systemic shunting, impaired hepatic uptake and incretin effect. We confirmed the presence of hepatic and peripheral insulin resistance in our patient population. Endogenous glucose production was less suppressed in response to parenteral nutrition. However, glucose uptake in skeletal muscle was increased. Our results suggests that in our study participants with cirrhosis, the hepatic and peripheral insulin resistance is compensated for by increased insulin secretion and thus, increased glucose uptake in muscle. Hereby, glucose homeostasis is maintained.

IL-4 activates the futile triacylglyceride cycle for glucose utilization in white adipocytes.

The development of cardiometabolic complications during obesity is strongly associated with chronic latent inflammation in hypertrophied adipose tissue (AT). IL-4 is an anti-inflammatory cytokine, playing a protective role against insulin resistance, glucose intolerance and weight gain. The positive effects of IL-4 are associated not only with the activation of anti-inflammatory immune cells in AT, but also with the modulation of adipocyte metabolism. IL-4 is known to activate lipolysis and glucose uptake in adipocytes, but the precise regulatory mechanisms and physiological significance of these processes remain unclear. In this study, we detail IL-4 effects on glucose and triacylglycerides (TAGs) metabolism and propose mechanisms of IL-4 metabolic action in adipocytes. We have shown that IL-4 activates glucose oxidation, lipid droplet (LD) fragmentation, lipolysis and thermogenesis in mature 3T3-L1 adipocytes. We found that lipolysis was not accompanied by fatty acids (FAs) release from adipocytes, suggesting FA re-esterification. Moreover, glucose oxidation and thermogenesis stimulation depended on adipocyte triglyceride lipase (ATGL) activity, but not the uncoupling protein (UCP1) expression. Based on these data, IL-4 may activate the futile TAG-FA cycle in adipocytes, which enhances the oxidative activity of cells and heat production. Thus, the positive effect of IL-4 on systemic metabolism can be the result of the activation of non-canonical thermogenic mechanism in AT, increasing TAG turnover and utilization of excessive glucose.

Unveil of the role of fungal taxa in iron(III) reduction in paddy soil.

Hitherto, research on iron(III)-reduction has mainly focused on bacteria rather than fungal communities. To acquire insight into fungi involved in iron(III) reduction, typical organic matters (containing cellulose, glucose, lactate, and acetate) and ferrihydrite were used as electron donors and acceptors, respectively, in the presence of antibiotics. After antibiotic addition, microbial iron(III) reduction was still detected at quite high rates. In comparison, rates of iron(III) reduction were significantly lower in cellulose-amended groups than those with glucose, lactate, and acetate under the antibiotic-added condition. Patterns of intermediate (e.g., acetate, pyruvate, glucose) turnover were markedly different between treatments with and without antibiotics during organic degradation. A total of 20 genera of potential respiratory and fermentative iron(III)-reducing fungi were discovered based on ITS sequencing and genome annotation. This study provided an insight into the diversity of iron(III)-reducing fungi, indicating the underestimated contribution of fungi to iron and the coupled carbon biogeochemical cycling in environments.

Glucagon-like peptide-1 receptor blockade impairs islet secretion and glucose metabolism in humans.

BACKGROUNDProglucagon can be processed to glucagon-like peptide1 (GLP-1) within the islet, but its contribution to islet function in humans remains unknown. We sought to understand whether pancreatic GLP-1 alters islet function in humans and whether this is affected by type 2 diabetes.METHODSWe therefore studied individuals with and without type 2 diabetes on two occasions in random order. On one occasion, exendin 9-39, a competitive antagonist of the GLP-1 Receptor (GLP1R), was infused, while on the other, saline was infused. The tracer dilution technique ([3-3H] glucose) was used to measure glucose turnover during fasting and during a hyperglycemic clamp.RESULTSExendin 9-39 increased fasting glucose concentrations; fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed. In people with type 2 diabetes, fasting glucagon concentrations were markedly elevated and persisted despite hyperglycemia. This impaired suppression of endogenous glucose production by hyperglycemia.CONCLUSIONThese data show that GLP1R blockade impairs islet function, implying that intra-islet GLP1R activation alters islet responses to glucose and does so to a greater degree in people with type 2 diabetes.TRIAL REGISTRATIONThis study was registered at ClinicalTrials.gov NCT04466618.FUNDINGThe study was primarily funded by NIH NIDDK DK126206. AV is supported by DK78646, DK116231 and DK126206. CDM was supported by MIUR (Italian Minister for Education) under the initiative "Departments of Excellence" (Law 232/2016).

Improved production of β-carotene in light-powered Escherichia coli by co-expression of Gloeobacter rhodopsin expression

BackgroundProviding sufficient and usable energy for the cell factory has long been a heated issue in biosynthesis as solar energy has never been rooted out from the strategy for improvement, and turning Escherichia coli (E. coli) into a phototrophic host has multiple captivating qualities for biosynthesis. In this study, β-carotene was a stable compound for production in E. coli with the expression of four enzymes (CrtE, CrtB, CrtI, CrtY) for production due to its light-harvesting feature as an antenna pigment and as an antioxidant and important precursor for human health. The expression of Gloeobacter rhodopsin (GR) in microbial organisms was proved to have potential for application.ResultsThe expression of fusion protein, GR-GFP, in E. coli showed visible GFP signal under fluorescent microscopy, and its in vivo proton pumping activity signal can be detected in induced photocurrent by electrodes on the chip under intervals of illumination. To assess the phototrophic synthesis ability of the host strain compared to wild-type and vector control strain in chemostat batch with illumination, the expression of red fluorescent protein (RFP) as a target protein showed its yield improvement in protein assay and also reflected its early dominance in RFP fluorescence signal during the incubation, whereas the synthesis of β-carotene also showed yield increase by 1.36-fold and 2.32-fold compared with its wildtype and vector control strain. To investigate the effect of GR-GFP on E. coli, the growth of the host showed early rise into the exponential phase compared to the vector control strain and glucose turnover rate was elevated in increased glucose intake rate and upregulation of ATP-related genes in glycolysis (PtsG, Pgk, Pyk).ConclusionWe reported the first-time potential application of GR in the form of fusion protein GR-GFP. Expression of GR-GFP in E. coli improved the production of β-carotene and RFP. Our work provides a strain of E. coli harboring phototrophic metabolism, thus paving path to a more sustainable and scalable production of biosynthesis.

Noninvasive assessment of metabolic turnover during inflammation by in vivo deuterium magnetic resonance spectroscopy.

Inflammation and metabolism exhibit a complex interplay, where inflammation influences metabolic pathways, and in turn, metabolism shapes the quality of immune responses. Here, glucose turnover is of special interest, as proinflammatory immune cells mainly utilize glycolysis to meet their energy needs. Noninvasive approaches to monitor both processes would help elucidate this interwoven relationship to identify new therapeutic targets and diagnostic opportunities. For induction of defined inflammatory hotspots, LPS-doped Matrigel plugs were implanted into the neck of C57BL/6J mice. Subsequently, 1H/19F magnetic resonance imaging (MRI) was used to track the recruitment of 19F-loaded immune cells to the inflammatory focus and deuterium (2H) magnetic resonance spectroscopy (MRS) was used to monitor the metabolic fate of [6,6-2H2]glucose within the affected tissue. Histology and flow cytometry were used to validate the in vivo data. After plug implantation and intravenous administration of the 19F-containing contrast agent, 1H/19F MRI confirmed the infiltration of 19F-labeled immune cells into LPS-doped plugs while no 19F signal was observed in PBS-containing control plugs. Identification of the inflammatory focus was followed by i.p. bolus injection of deuterated glucose and continuous 2H MRS. Inflammation-induced alterations in metabolic fluxes could be tracked with an excellent temporal resolution of 2 min up to approximately 60 min after injection and demonstrated a more anaerobic glucose utilization in the initial phase of immune cell recruitment. 1H/2H/19F MRI/MRS was successfully employed for noninvasive monitoring of metabolic alterations in an inflammatory environment, paving the way for simultaneous in vivo registration of immunometabolic data in basic research and patients.

130-OR: Tirzepatide Attenuates Hepatic Insulin Resistance and Glucagon Action Independent of Weight Loss and GIP Action in Diet-Induced Obese Mice

As a dual GLP-1 receptor and GIP agonist, Tirzepatide (TZP) induces weight loss and improves glycemic control in patients with type 2 diabetes. Here, we performed insulin clamp and glucagon clamp under euglycemic conditions in male C57BL/6J mice fed a high-fat diet (HFD; 12 weeks) after once-daily treatment with TZP (3 nmol/kg) or GIP (25 nmol/kg) for 5 days (n=5). TZP and GIP caused HFD-fed mice to lose 10~15% of weight, but their fat mass remained 7-fold higher than chow-fed controls (C) (Fig. 1). Insulin clamp showed that GIP caused a 37% decrease in hepatic insulin action in chow-fed mice (Fig. 2). In HFD-fed mice, TZP induced significant increases in hepatic insulin action (4-fold) and glucose turnover (25%) compared to GIP, restoring insulin sensitivity to levels comparable to controls (Fig. 2-3). TZP also increased glucose metabolism in brown fat (1,528±155 vs. 798±166 nmol/g/min in GIP). Glucagon clamp showed that TZP significantly reduced hepatic glucose production (HGP) by ~50% compared to controls and GIP (Fig. 4). CONCLUSION: These data indicate that TZP improves insulin action and reduces hepatic glucagon action in obese mice while GIP causes hepatic insulin resistance in lean mice. Our findings suggest that TZP’s glycemic control may involve amelioration of insulin resistance and glucagon resistance, independent of weight loss and GIP action in the liver. Disclosure B.Kim: None. L.A.Tauer: None. X.Hu: None. J.K.Kim: None. Funding National Institutes of Health (5U2CDK093000)

254-OR: Effects of Roux-en-Y Gastric Bypass on Postprandial Glucose Turnover Assessed through the Single-Tracer Oral Minimal Model

Rearrangements of gastrointestinal anatomy after Roux-en-Y gastric bypass (RYGB) surgery alter postprandial glucose metabolism. However, the impact on different components of glucose homeostasis remain incompletely understood. Here, we aim to evaluate the effects of RYGB on postprandial glucose turnover, production (P) and disposal (D) glucose effectiveness (GEP, GED) and production and disposal sensitivity to insulin (SIP, SID). Ten RYGB (2M, age=39.2±3.1 y, BMI=28±1 kg/m2- mean±SE) subjects and 10 healthy controls (5M, age=36.4±3.2 y, BMI=26±1 kg/m2) ingested 60g of glucose (G) labelled with [6,6-2H2]-glucose. Plasma samples were frequently drawn to measure G, insulin (I) and tracer concentrations in the following 180 min. The Single-Tracer Oral Minimal Model was used to estimate meal glucose rate of appearance (Ra), endogenous glucose production (EGP), glucose disposal (Rd), GEP, GED, SIP and SID. Incremental area under the G curve (iAUC(G)) was not different in the two groups, while iAUC(I) was significantly higher in RYGB (8346±803 vs. 5451±602 μU/mL*min, p=0.011); iAUC(Ra) normalized to the G dose was significantly higher in the first 60 min after the meal (0.72±0.04 vs. 0.28±0.03, p&amp;lt;0.001) while, throughout the experiment, EGP suppression (EGPs) normalized to basal (EGPb) was significantly lower (0.31±0.06 vs. 0.55±0.05, p=0.006) and iAUC(Rd) normalized to basal (Rdb) was higher (3.46±0.10 vs. 2.82±0.08, p&amp;lt;0.001) in RYGB than controls. Model predicted SIP was significantly lower in RYGB than controls (2.0±0.5 vs. 5.1±1.2 10-4 dL/kg/min per μU/mL, p=0.033) while no differences were observed in GEP, GED and SID. We concluded that the abnormally high I concentration in RYGB was responsible for the higher iAUC(Rd) in the operated individuals, while the reduced SIP likely works as a protective mechanism against postprandial hypoglycaemia by reducing EGPs despite the high circulating I. Disclosure A.Brunasso: None. C.Dalla man: Research Support; Sanofi-Aventis Deutschland GmbH, Becton, Dickinson and Company. D.Herzig: None. L.Bally: Research Support; Dexcom, Inc., Ypsomed AG. M.Schiavon: None. Funding Italian Minister for Education (Law 232/2016); Swiss National Science Foundation (PCEGP3_186978)

1547-P: The Differential Effect of Glucagon-Like Peptide-1 Receptor Blockade on Glucose Metabolism in People With and Without Type 2 Diabetes

Glucagon-Like Peptide-1 (GLP-1) is present within the islet but the effects of GLP-1 Receptor (GLP1R) blockade on islet function in humans remains unknown. To address this, we studied 12 nondiabetic individuals (54 ± 2 years, 33 ± 1 kg/m2) and 11 people with type 2 diabetes (DM2 - 58 ± 2 years, 34 ± 2 kg/m2) on 2 occasions in random order. On each occasion, after an overnight fast, [3-3H] glucose was used to measure glucose turnover during fasting and a hyperglycemic clamp (~9 mmol/l) using the tracer dilution technique. On one occasion exendin-9,39 (300pmol/kg/min) was infused to block GLP1R, while on the other saline was infused. Exendin-9,39 increased fasting glucose concentrations in those without (4.6 ± 0.4 vs. 5.5 ± 0.1 mmol/l, saline vs. exendin-9,39 respectively, p = 0.04) and in those with DM2 (7.3 ± 0.5 vs. 8.3 ± 0.6 mmol/l, p = 0.03). Fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed during exendin-9,39 infusion. The same pattern was seen in people with DM2 except that fasting glucagon concentrations increased (8.3 ± 0.5 vs. 10.2 ± 0.6 pmol/l, p &amp;lt; 0.01) and remained elevated throughout hyperglycemia (4.7 ± 0.4 vs. 7.7 ± 0.6 pmol/l, p &amp;lt; 0.02). Insulin secretion rate calculated by deconvolution of C-peptide concentrations was also decreased in DM2 (0.54 ± 0.08 vs. 0.51 ± 0.08 nmol/min, p = 0.02). Consequently, suppression of endogenous glucose production by hyperglycemia was impaired in people with DM2 (2.9 ± 0.4 vs. 5.7 ± 0.3 μmol/kg/min, p &amp;lt; 0.01). Intriguingly, 1st phase response to hyperglycemia was decreased in those without DM2 (3.5 ± 0.6 vs. 2.5 ± 0.5 nmol per 10 min, p = 0.04). These data show that in humans, GLP1R blockade impairs fasting α- and β-cell function resulting in fasting hyperglycemia. Subtle effects are also present in response to hyperglycemia. This implies that intra-islet GLP1R activation sustains islet responses to glucose and it does so to a greater degree in people with DM2. Disclosure A.A. Welch: None. R.A. Farahani: None. M. Zeini: None. A.M. Egan: None. M.C. Laurenti: None. C. Cobelli: None. C. Dalla Man: Research Support; Sanofi-Aventis Deutschland GmbH, Becton, Dickinson and Company. A. Vella: Other Relationship; Novo Nordisk. Advisory Panel; Rezolute, Inc. Consultant; Crinetics Pharmaceuticals, Inc., Hanmi Pharm. Co., Ltd., Zealand Pharma A/S. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK126206)

Abundance of proteins and genes associated with nutrient signaling, protein turnover, and transport of amino acids and glucose in fetuses from lactating Holstein cows

Availability of nutrients in maternal circulation and abundance of nutrient transporters, metabolic enzymes, and nutrient-responsive proteins in fetal tissues coordinate growth. To begin characterizing these mechanisms, we evaluated the abundance of nutrient signaling genes and proteins in bovine fetal tissues. Liver, entire intestine, and semitendinosus muscle were harvested from fetuses (4 female, 2 male) collected at slaughter from 6 clinically-healthy multiparous Holstein dairy cows (167 ± 7 days in milk, 37 ± 6 kg milk/d, 100 ± 3 d gestation). Data were analyzed using PROC MIXED in SAS 9.4. Among proteins measured, abundance of the amino acid (AA) utilization and insulin signaling proteins p-AKT and p-mTOR was greater (P < 0.01) in liver and intestine. The abundance of p-EEF2 (translation elongation) and SLC2A4 (glucose uptake) was greater (P < 0.05) in liver relative to intestine and muscle suggesting this organ has a greater capacity for anabolic processes. In contrast, among mTOR signaling genes, the abundance of IRS1 was greatest (P < 0.01) in muscle and lowest in the intestine, whereas, abundance of AKT1 and mTOR was greater (P < 0.01) in intestine and muscle than liver. Abundance of the protein degradation-related genes UBA1, UBE2G1, and TRIM63 was greater (P < 0.01) in muscle than intestine and liver. Among nutrient transporters, abundance of glucose transporters SLC5A1 and SLC2A2 was greatest (P < 0.01) in the intestine than liver and muscle. Several AA transporters had greater (P < 0.01) abundance in the intestine or liver compared with muscle. Overall, these molecular analyses highlighted important biological differences on various aspects of metabolism in fetal tissues.

Dual amylin and calcitonin receptor agonist treatment improves insulin sensitivity and increases muscle-specific glucose uptake independent of weight loss

Dual amylin and calcitonin receptor agonists (DACRAs) are known to induce significant weight loss as well as improve glucose tolerance, glucose control, and insulin action in rats. However, to what extent DACRAs affect insulin sensitivity beyond that induced by weight loss and if DACRAs affect glucose turnover including tissue-specific glucose uptake is still unknown. Hyperinsulinemic glucose clamp studies were carried out in pre-diabetic ZDSD and diabetic ZDF rats treated with either the DACRA KBP or the long-acting DACRA KBP-A for 12 days. The glucose rate of disappearance was assessed using 3-3H glucose and tissue-specific glucose uptake was evaluated using 14C-2-deoxy-D-glucose (14C-2DG). In diabetic ZDF rats, KBP treatment significantly reduced fasting blood glucose and improved insulin sensitivity independent of weight loss. Furthermore, KBP increased the rate of glucose clearance, likely by increasing glucose storage, but without altering the endogenous glucose production. This was confirmed in pre-diabetic ZDSD rats. Direct assessment of tissue-specific glucose uptake showed, that both KBP and KBP-A significantly increased glucose uptake in muscles. In summary, KBP treatment significantly improved insulin sensitivity in diabetic rats and markedly increased glucose uptake in muscles. Importantly, in addition to their well-established weight loss potential, the KBPs have an insulin-sensitizing effect independent of weight loss, highlighting DACRAs as promising agents for the treatment of type 2 diabetes and obesity.

Cryptosporidium parvum competes with the intestinal epithelial cells for glucose and impairs systemic glucose supply in neonatal calves

Cryptosporidiosis is one of the main causes of diarrhea in children and young livestock. The interaction of the parasite with the intestinal host cells has not been characterized thoroughly yet but may be affected by the nutritional demand of the parasite. Hence, we aimed to investigate the impact of C. parvum infection on glucose metabolism in neonatal calves. Therefore, N = 5 neonatal calves were infected with C. parvum on the first day of life, whereas a control group was not (N = 5). The calves were monitored clinically for one week, and glucose absorption, turnover and oxidation were assessed using stable isotope labelled glucose. The transepithelial transport of glucose was measured using the Ussing chamber technique. Glucose transporters were quantified on gene and protein expression level using RT-qPCR and Western blot in the jejunum epithelium and brush border membrane preparations. Plasma glucose concentration and oral glucose absorption were decreased despite an increased electrogenic phlorizin sensitive transepithelial transport of glucose in infected calves. No difference in the gene or protein abundance of glucose transporters, but an enrichment of glucose transporter 2 in the brush border was observed in the infected calves. Furthermore, the mRNA for enzymes of the glycolysis pathway was increased indicating enhanced glucose oxidation in the infected gut. In summary, C. parvum infection modulates intestinal epithelial glucose absorption and metabolism. We assume that the metabolic competition of the parasite for glucose causes the host cells to upregulate their uptake mechanisms and metabolic machinery to compensate for the energy losses.

Ketone Monoester Plus Carbohydrate Supplementation Does Not Alter Exogenous and Plasma Glucose Oxidation or Metabolic Clearance Rate During Exercise in Men Compared with Carbohydrate Alone

BackgroundIncreasing β-hydroxybutyrate (βHB) availability through ketone monoester (KE) plus carbohydrate supplementation is suggested to enhance physical performance by sparing glucose use during exercise. However, no studies have examined the effect of ketone supplementation on glucose kinetics during exercise. ObjectivesThis exploratory study primarily aimed to determine the effect of KE plus carbohydrate supplementation on glucose oxidation during steady-state exercise and physical performance compared with carbohydrate alone. MethodsUsing a randomly assigned, crossover design, 12 men consumed 573 mg KE/kg body mass plus 110 g glucose (KE+CHO) or 110 g glucose (CHO) before and during 90 min of steady-state treadmill exercise [54 ± 3% peak oxygen uptake (V˙O2peak)] wearing a weighted vest (30% body mass; 25 ± 3 kg). Glucose oxidation and turnover were determined using indirect calorimetry and stable isotopes. Participants performed an unweighted time to exhaustion (TTE; 85% V˙O2peak) after steady-state exercise and a weighted (25 ± 3 kg) 6.4 km time trial (TT) the next day after consuming a bolus of KE+CHO or CHO. Data were analyzed by paired t-tests and mixed model ANOVA. ResultsβHB concentrations were higher (P < 0.05) after exercise [2.1 mM (95% CI: 1.6, .6)] and the TT [2.6 mM (2.1, 3.1)] in KE+CHO compared with CHO. TTE was lower [−104 s (−201, −8)], and TT performance was slower [141 s (19,262)] in KE+CHO than in CHO (P < 0.05). Exogenous [−0.01 g/min (−0.07, 0.04)] and plasma [−0.02 g/min (−0.08, 0.04)] glucose oxidation and metabolic clearance rate {MCR [0.38 mg·kg−1·min−1 (−0.79, 1.54)]} were not different, and glucose rate of appearance [−0.51 mg·kg−1·min−1 (−0.97, −0.04)], and disappearance [−0.50 mg·kg−1·min−1 (−0.96, −0.04)] were lower (P < 0.05) in KE+CHO compared with CHO during steady-state exercise. ConclusionsIn the current study, rates of exogenous and plasma glucose oxidation and MCR were not different between treatments during steady-state exercise, suggesting blood glucose utilization is similar between KE+CHO and CHO. KE+CHO supplementation also results in lower physical performance compared with CHO alone.This trial was registered at www.clinicaltrials.gov as NCT04737694.