Glucose Disappearance Research Articles

Evaluation of an Insulin Sensitivity Index from the Short Intravenous Glucose Tolerance Test

The aim of this analysis was to compare insulin sensitivity indices calculated from a short (50 min), insulin‐modified intravenous glucose tolerance test (IVGTT; Tura SI) to that from a full 180 min IVGTT using minimal model analysis (MM SI), as well as the Matsuda Index (M‐SI) from a 120 min liquid meal tolerance test (Maki et al. Diabetes Tech Ther 2011;13:661–6). The IVGTT included glucose (0.3 g/kg, t = 0 min) and regular human insulin (0.03 U/kg; t = 20 min) injection with samples collected at frequent intervals over 180 min. Tura SI was calculated as the fractional glucose disappearance rate/average increment in plasma insulin, both from 10–50 min. The MINMOD MILLENNIUM program (v6.02) was used to calculate MM SI. Subjects were overweight or obese men (n = 8) and women (n = 16) without diabetes who agreed to participate in a substudy after completing a dietary intervention trial. Mean ± SEM MM SI was 3.94 ± 3.38 × 10−4 L*min−1*mU−1, age was 48.9 ± 2.0 y and body mass index was 30.8 ± 0.6 kg/m2. Pearson correlation coefficients were: Tura SI with MM SI r = 0.963, Tura SI with M‐SI r = 0.803, and MM SI with M‐SI r = 0.776, all p < 0.001. Thus, Tura SI from the first 50 min of an insulin‐modified IVGTT correlates very strongly with 180 min MM SI (reference method), and the relationship between Tura SI with M‐SI was similar in magnitude to that between MM SI and M‐SI. These results suggest that the short IVGTT may be used as a less costly and time‐consuming alternative to the 180 min IVGTT for assessment of whole‐body insulin sensitivity.Support or Funding InformationIngredion, Westchester, IL

Chronic Angiotensin-(1-7) Improves Insulin Sensitivity in High-Fat Fed Mice Independent of Blood Pressure.

Angiotensin-(1-7) improves glycemic control in animal models of cardiometabolic syndrome. The tissue-specific sites of action and blood pressure dependence of these metabolic effects, however, remain unclear. We hypothesized that Ang-(1-7) improves insulin sensitivity by enhancing peripheral glucose delivery. Adult male C57BL/6J mice were placed on standard chow or 60% high-fat diet for 11 weeks. Ang-(1-7) (400 ng/kg per minute) or saline was infused subcutaneously during the last 3 weeks of diet, and hyperinsulinemic-euglycemic clamps were performed at the end of treatment. High-fat fed mice exhibited modest hypertension (systolic blood pressure: 137 ± 3 high fat versus 123 ± 5 mm Hg chow;P=0.001), which was not altered by Ang-(1-7) (141 ± 4 mm Hg;P=0.574). Ang-(1-7) did not alter body weight or fasting glucose and insulin in chow or high-fat fed mice. Ang-(1-7) increased the steady-state glucose infusion rate needed to maintain euglycemia in high-fat fed mice (31 ± 5 Ang-(1-7) versus 16 ± 1 mg/kg per minute vehicle;P=0.017) reflecting increased whole-body insulin sensitivity, with no effect in chow-fed mice. The improved insulin sensitivity in high-fat fed mice was because of an enhanced rate of glucose disappearance (34 ± 5 Ang-(1-7) versus 20 ± 2 mg/kg per minute vehicle;P=0.049). Ang-(1-7) enhanced glucose uptake specifically into skeletal muscle by increasing translocation of glucose transporter 4 to the sarcolemma. Our data suggest that Ang-(1-7) has direct insulin-sensitizing effects on skeletal muscle, independent of changes in blood pressure. These findings provide new insight into mechanisms by which Ang-(1-7) improves insulin action, and provide further support for targeting this peptide in cardiometabolic disease.

Effects of the BET-inhibitor, RVX-208 on the HDL lipidome and glucose metabolism in individuals with prediabetes: A randomized controlled trial

AimsHigh-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) can modulate glucose metabolism through multiple mechanisms. This study determined the effects of a novel bromodomain and extra-terminal (BET) inhibitor (RVX-208) and putative apoA-I inducer on lipid species contained within HDL (HDL lipidome) and glucose metabolism. Materials and methodsTwenty unmedicated males with prediabetes received 100mg b.i.d. RVX-208 and placebo for 29–33days separated by a wash-out period in a randomized, cross-over design trial. Plasma HDL-cholesterol and apoA-I were assessed as well as lipoprotein particle size and distribution using NMR spectroscopy. An oral glucose tolerance test (OGTT) protocol with oral and infused stable isotope tracers was employed to assess postprandial plasma glucose, indices of insulin secretion and insulin sensitivity, glucose kinetics and lipolysis. Whole plasma and HDL lipid profiles were measured using mass spectrometry. ResultsRVX-208 treatment for 4weeks increased 6 sphingolipid and 4 phospholipid classes in the HDL lipidome (p≤0.05 versus placebo), but did not change conventional clinical lipid measures. The concentration of medium-sized HDL particles increased by 11% (P=0.01) and small-sized HDL particles decreased by 10% (P=0.04) after RVX-208 treatment. In response to a glucose load, after RVX-208 treatment, plasma glucose peaked at a similar level to placebo, but 30min later with a more sustained elevation (treatment effect, P=0.003). There was a reduction and delay in total (P=0.001) and oral (P=0.003) glucose rates of appearance in plasma and suppression of endogenous glucose production (P=0.014) after RVX-208 treatment. The rate of glucose disappearance was also lower following RVX-208 (P=0.016), with no effect on glucose oxidation or total glucose disposal. ConclusionsRVX-208 increased 10 lipid classes in the plasma HDL fraction, without altering the concentrations of either apoA-I or HDL-cholesterol (HDL-C). RVX-208 delayed and reduced oral glucose absorption and endogenous glucose production, with plasma glucose maintained via reduced peripheral glucose disposal. If sustained, these effects may protect against the development of type 2 diabetes.

PAFR in adipose tissue macrophages is associated with anti-inflammatory phenotype and metabolic homoeostasis.

Metabolic dysfunction is associated with adipose tissue inflammation and macrophage infiltration. PAFR (platelet-activating factor receptor) is expressed in several cell typesand binds to PAF (platelet-activating factor) and oxidized phospholipids. Engagement of PAFR in macrophages drives them towards the anti-inflammatory phenotype. In the present study, we investigated whether genetic deficiency of PAFR affects the phenotype of ATMs (adipose tissue macrophages) and its effect on glucose and insulin metabolism. PARFKO (PAFR-knockout) and WT (wild-type) mice were fed on an SD (standard diet) or an HFD (high-fat diet). Glucose and insulin tolerance tests were performed by blood monitoring. ATMs were evaluated by FACS for phenotypic markers. Gene and protein expression was investigated by real-time reverse transcription-quantitative PCR and Western blotting respectively. Results showed that the epididymal adipose tissue of PAFRKO mice had increased gene expression of Ccr7, Nos2, Il6 and Il12, associated with pro-inflammatory mediators, and reduced expression of the anti-inflammatory Il10. Moreover, the adipose tissue of PAFRKO mice presented more pro-inflammatory macrophages, characterized by an increased frequency of F4/80(+)CD11c(+) cells. Blood monocytes of PAFRKO mice also exhibited a pro-inflammatory phenotype (increased frequency of Ly6C(+) cells) and PAFR ligands were detected in the serum of both PAFRKO and WT mice. Regarding metabolic parameters, compared with WT, PAFRKO mice had: (i) higher weight gain and serum glucose concentration levels; (ii) decreased insulin-stimulated glucose disappearance; (iii) insulin resistance in the liver; (iv) increased expression of Ldlr in the liver. In mice fed on an HFD, some of these changes were potentiated, particularly in the liver. Thus it seems that endogenous ligands of PAFR are responsible for maintaining the anti-inflammatory profile of blood monocytes and ATMs under physiological conditions. In the absence of PAFR signalling, monocytes and macrophages acquire a pro-inflammatory phenotype, resulting in adipose tissue inflammation and metabolic dysfunction.

Passiflora edulis peel intake improves insulin sensitivity, increasing incretins and hypothalamic satietogenic neuropeptide in rats on a high-fat diet

ObjectiveThis study aimed to investigate the effect of Passiflora edulis peel flour (PEPF) intake on hypothalamic neuropeptides messenger RNA expression, insulin sensitivity, and other metabolic parameters in Sprague-Dawley rats fed a high-fat (HF) diet. MethodsSprague-Dawley rats were divided in 3 groups: a control group, fed on a normal fat diet; a HF group, fed on a high-fat diet (35% fat [w/w]); and a high-fat Passiflora flour (HFPF) group, fed on a HF diet containing PEPF. The rats from the HFPF group as well as the HF group were kept on an HF diet for the first 4 wk to induce metabolic conditions related to obesity. Then the HFPF group was switched to a HF diet containing PEPF for additional 6 wk. Other groups were kept on normal-fat and HF diet without addition of PEPF during the whole period of experiment. The glucose tolerance and insulin sensitivity were evaluated through the glucose tolerance test (GTT) and the insulin tolerance test (ITT). Gut hormones and adipokines were measured through an immunoassay. The hypothalamic neuropeptides expression was assessed by real-time polymerase chain reaction. ResultsThe PEPF intake increased the hypothalamic cocaine- and amphetamine-regulated transcript expression (CART) (P < 0.05), counteracted cumulative body weight gain (P < 0.001), decreased adiposity (P < 0.05) and leptin level (P < 0.01), whereas increased adiponectin (P < 0.01), glucose-dependent insulinotropic polypeptide (P < 0.01), and glucagon-like peptide-1 (GLP-1) (P < 0.001) improved the insulin sensitivity in diet-induced obesity rats by increasing the kITT (glucose disappearance rate) (P < 0.01), which was calculated during the ITT. Other gut hormones (peptide tyrosine tyrosine, pancreatic polypeptide, and amylin) and interleukins (IL) (IL-6, tumor necrosis factor-α, IL-1β, and monocyte chemoattractant protein-1) were not changed by the PEPF intake. ConclusionOur findings provide a further understanding of how the PEPF works as a dietary component to improve glucose homeostasis and demonstrate a molecular mechanism that may increase satiety by PEPF in diet-induced obesity.

Diabetes-Associated Variation in TCF7L2 Is Not Associated With Hepatic or Extrahepatic Insulin Resistance.

A common genetic variation in TCF7L2 is associated with type 2 diabetes. However, the mechanism by which this occurs remains elusive. In addition to affecting insulin secretion, genetic variation at the TCF7L2 locus may alter insulin action or directly modify hepatic glucose metabolism. We sought to determine whether the diabetes-associated variant in this locus (the T allele of rs7903146) increases fasting endogenous glucose production (EGP), and impairs insulin-induced suppression of EGP and insulin-stimulated glucose disappearance. To address this, we studied individuals who were either homozygous for the diabetes-associated allele (TT) at rs7903146 or were homozygous for the protective allele (CC). Subjects were matched for other anthropometric characteristics and were studied using a euglycemic clamp. EGP and glucose uptake were measured using the tracer dilution technique, and the relative contribution of gluconeogenesis to EGP was quantitated using deuterated water corrected for transaldolase exchange. We report that the diabetes-associated variation in TCF7L2 did not associate with fasting EGP, insulin-induced suppression of EGP, and insulin-induced stimulation of glucose uptake. There was no association with the contribution of gluconeogenesis and glycogenolysis to EGP. These data indicate that genetic variation at TCF7L2 does not predispose an individual to type 2 diabetes by altering either hepatic or extrahepatic insulin action.

Effect of Exercise Intensity on Glucose Requirements to Maintain Euglycemia During Exercise in Type 1 Diabetes

No recommendations exist to inform the carbohydrate amount required to prevent hypoglycemia associated with exercise of different intensities in individuals with type 1 diabetes (T1D). The relationship between exercise intensity and carbohydrate requirements to maintain stable euglycemia in individuals with T1D remains to be determined. It was predicted that an "inverted-U" relationship exists between exercise intensity and the amount of glucose required to prevent hypoglycemia during exercise at basal insulinemia. Our objective was to investigate this relationship and elucidate the underlying glucoregulatory mechanisms. We subjected nine individuals (mean ± SD age, 21.5 ± 4.0 years; duration of disease, 11.4 ± 6.4 years; glycated hemoglobin, 7.9 ± 0.8% [60 mmol/mol]; body mass index, 25.4 ± 5.5 kg/m(2); VO2peak, 34.8 ± 5.1 mL·kg(-1)·min(-1); and lactate threshold, 59.9 ± 5.9% VO2peak) with T1D to a euglycemic clamp, whereby euglycemia was maintained by infusing basal insulin rates with concomitant infusion of [6,6-(2)H2]glucose for determining glucose kinetics. Glucose was infused to maintain euglycemia during and for 2 hours after exercise of different intensities (35, 50, 65, and 80% VO2peak). The glucose infusion rate (GIR), levels of glucoregulatory hormones, and rates of endogenous glucose appearance and disappearance were compared between conditions. The mean GIR to maintain euglycemia during exercise increased with intensity up to 50% (4.0 ± 1.6 g/h; P < .05) and 65% (4.1 ± 1.7 g/h), but no glucose was required at 80% VO2peak. Glucose rate of appearance and disappearance increased with intensity and, together with plasma catecholamines, reached higher levels at 80% VO2peak. Our findings support the predicted inverted-U relationship between exercise intensity and glucose requirement. However, the relationship between iv and oral glucose requirements needs to be investigated to translate these GIR data to clinical practice.

Ascorbic acid supplementation improves skeletal muscle oxidative stress and insulin sensitivity in people with type 2 diabetes: Findings of a randomized controlled study

Aim/hypothesisSkeletal muscle insulin resistance and oxidative stress are characteristic metabolic disturbances in people with type 2 diabetes. Studies in insulin resistant rodents show an improvement in skeletal muscle insulin sensitivity and oxidative stress following antioxidant supplementation. We therefore investigated the potential ameliorative effects of antioxidant ascorbic acid (AA) supplementation on skeletal muscle insulin sensitivity and oxidative stress in people with type 2 diabetes. MethodsParticipants with stable glucose control commenced a randomized cross-over study involving four months of AA (2×500mg/day) or placebo supplementation. Insulin sensitivity was assessed using a hyperinsulinaemic, euglycaemic clamp coupled with infusion of 6,6-D2 glucose. Muscle biopsies were measured for AA concentration and oxidative stress markers that included basal measures (2′,7′-dichlorofluorescin [DCFH] oxidation, ratio of reduced-to-oxidized glutathione [GSH/GSSG] and F2-Isoprostanes) and insulin-stimulated measures (DCFH oxidation). Antioxidant concentrations, citrate synthase activity and protein abundances of sodium-dependent vitamin C transporter 2 (SVCT2), total Akt and phosphorylated Akt (ser473) were also measured in muscle samples. ResultsAA supplementation significantly increased insulin-mediated glucose disposal (delta rate of glucose disappearance; ∆Rd) (p=0.009), peripheral insulin-sensitivity index (p=0.046), skeletal muscle AA concentration (p=0.017) and muscle SVCT2 protein expression (p=0.008); but significantly decreased skeletal muscle DCFH oxidation during hyperinsulinaemia (p=0.007) when compared with placebo. Total superoxide dismutase activity was also lower following AA supplementation when compared with placebo (p=0.006). Basal oxidative stress markers, citrate synthase activity, endogenous glucose production, HbA1C and muscle Akt expression were not significantly altered by AA supplementation. Conclusions/interpretationIn summary, oral AA supplementation ameliorates skeletal muscle oxidative stress during hyperinsulinaemia and improves insulin-mediated glucose disposal in people with type 2 diabetes. Findings implicate AA supplementation as a potentially inexpensive, convenient, and effective adjunct therapy in the treatment of insulin resistance in people with type 2 diabetes.

Effect of long-term high-fat diet intake on peripheral insulin sensibility, blood pressure, and renal function in female rats

BackgroundThis study determines whether 8-week high-fat diet (HFD) consumption alters insulin sensitivity, kidney function, and blood pressure (BP) in female rats when compared with standard rodent diet (ND) intake in gender- and age-matched rats.MethodsThe present study investigates, in female Wistar HanUnib rats, the effect of long-term high-fat fed group (HFD) compared with standard chow on BP by an indirect tail-cuff method using an electrosphygmomanometer, insulin and glucose function, and kidney function by creatinine and lithium clearances.ResultsThe current study shows glucose tolerance impairment, as demonstrated by increased fasting blood glucose (ND: 78±2.8 vs. HFD: 87±3.8 mg/dL) associated with reduced insulin secretion (ND: 0.58±0.07 vs. HFD: 0.40±0.03 ng/mL) in 8-week female HFD-treated rats. The incremental area under the curve (AUC, ND: 1,4558.0±536.0 vs. HFD: 1,6507.8±661.9), homeostasis model assessment of insulin resistance (HOMA-IR) index, and the first-order rate constant for the disappearance of glucose (Kitt) were significantly enhanced in 8-week HFD-treated rats compared with age-matched ND group (respectively, P=0.03, P=0.002, and P<0.0001). The current study also shows a significantly higher systolic BP measured in 5 and 8 weeks posttreatment in HFD (5-week HFD-treated: 155.25±10.54 mmHg and 8-week HFD-treated: 165±5.8 mmHg) (P=0.0001), when compared to BP values in 5-week ND, 137±4.24 mmHg and 8-week ND, 131.75±5.8 mmHg age-matched group. Otherwise, the glomerular filtration rate and renal sodium handling evaluated by FENa, FEPNa and FEPPNa, were unchanged in both groups.ConclusionWe may conclude that 8-week female HFD-fed rats compared with ND group stimulate harmful effects, such as BP rise and peripheral glucose intolerance. The increased BP occurs through insulin resistance and supposedly decreased vasodilatation response without any change on renal function.

Extracellular glucose supports lactate production but not aerobic metabolism in cardiomyocytes from both normoglycemic Atlantic cod and low glycemic short-horned sculpin.

Fish exhibit a wide range of species-specific blood glucose levels. How this relates to glucose utilization is yet to be fully realized. Here, we assessed glucose transport and metabolism in myocytes isolated from Atlantic cod (Gadus morhua) and short-horned sculpin (Myoxocephalus scorpius), species with blood glucose levels of 3.7 and 0.57 mmol l(-1), respectively. Glucose metabolism was assessed by the production of (3)H2O from [2-(3)H]glucose. Glucose metabolism was 3.5- to 6-fold higher by myocytes from Atlantic cod than by those from short-horned sculpin at the same level of extracellular glucose. In Atlantic cod myocytes, glucose metabolism displayed what appears to be a saturable component with respect to extracellular glucose, and cytochalasin B inhibited glucose metabolism. These features revealed a facilitated glucose diffusion mechanism that accounts for between 30% and 55% of glucose entry at physiological levels of extracellular glucose. Facilitated glucose diffusion appears to be minimal in myocytes for short-horned sculpin. Glucose entry by simple diffusion occurs in both cell types with the same linear relationship between glucose metabolism and extracellular glucose concentration, presumably due to similarities in membrane composition. Oxygen consumption by myocytes incubated in medium containing physiological levels of extracellular glucose (Atlantic cod 5 mmol l(-1), short-horned sculpin 0.5 mmol l(-1)) was similar in the two species and was not decreased by cytochalasin B, suggesting that these cells have the capability of oxidizing alternative on-board metabolic fuels. Cells produced lactate at low rates but glycogen levels did not change during the incubation period. In cells from both species, glucose utilization assessed by both simple chemical analysis of glucose disappearance from the medium and (3)H2O production was half the rate of lactate production and as such extracellular glucose was not available for oxidative metabolism. Overall, extracellular glucose makes only a minor contribution to ATP production but a sustained glycolysis may be necessary to support Ca(2+) transport mechanisms at either the sarcoplasmic reticulum or the sarcolemmal membrane.

Sexual Dimorphism in Hepatic, Adipose Tissue, and Peripheral Tissue Insulin Sensitivity in Obese Humans.

Glucose and lipid metabolism differ between men and women, and women tend to have better whole-body or muscle insulin sensitivity. This may be explained, in part, by differences in sex hormones and adipose tissue distribution. Few studies have investigated gender differences in hepatic, adipose tissue, and whole-body insulin sensitivity between severely obese men and women. In this study, we aimed to determine the differences in glucose metabolism between severely obese men and women using tissue-specific measurements of insulin sensitivity. Insulin sensitivity was compared between age and body mass index (BMI)-matched obese men and women by a two-step euglycemic hyperinsulinemic clamp with infusion of [6,6-2H2]glucose. Basal endogenous glucose production (EGP) and insulin sensitivity of the liver, adipose tissue, and peripheral tissues were assessed. Liver fat content was assessed by proton magnetic resonance spectroscopy in a subset of included subjects. We included 46 obese men and women (age, 48 ± 2 vs. 46 ± 2 years, p = 0.591; BMI, 41 ± 1 vs. 41 ± 1 kg/m2, p = 0.832). There was no difference in basal EGP (14.4 ± 1.0 vs. 15.3 ± 0.5 μmol · kg fat-free mass−1 · min−1, p = 0.410), adipose tissue insulin sensitivity (insulin-mediated suppression of free fatty acids, 71.6 ± 3.6 vs. 76.1 ± 2.6%, p = 0.314), or peripheral insulin sensitivity (insulin-stimulated rate of disappearance of glucose, 26.2 ± 2.1 vs. 22.7 ± 1.7 μmol · kg−1 · min−1, p = 0.211). Obese men were characterized by lower hepatic insulin sensitivity (insulin-mediated suppression of EGP, 61.7 ± 4.1 vs. 72.8 ± 2.5% in men vs. women, respectively, p = 0.028). Finally, these observations could not be explained by differences in liver fat content (men vs. women, 16.5 ± 3.1 vs. 16.0 ± 2.5%, p = 0.913, n = 27). We conclude that obese men have lower hepatic, but comparable adipose tissue and peripheral tissue, insulin sensitivity compared to similarly obese women. Hepatic insulin resistance may contribute to the higher prevalence of diabetes in obese men. Further insight into the mechanisms underlying this gender difference may reveal novel targets for diabetes prevention and/or therapy.

Divergent utilization patterns of grass fructan, inulin, and other nonfiber carbohydrates by ruminal microbes

Fructans are an important nonfiber carbohydrate in cool season grasses. Their fermentation by ruminal microbes is not well described, though such information is needed to understand their nutritional value to ruminants. Our objective was to compare kinetics and product formation of orchardgrass fructan (phlein; PHL) to other nonfiber carbohydrates when fermented in vitro with mixed or pure culture ruminal microbes. Studies were carried out as randomized complete block designs. All rates given are first-order rate constants. With mixed ruminal microbes, rate of substrate disappearance tended to be greater for glucose (GLC) than for PHL and chicory fructan (inulin; INU), which tended to differ from each other (0.74, 0.62, and 0.33h−1, respectively). Disappearance of GLC had almost no lag time (0.04h), whereas the fructans had lags of 1.4h. The maximum microbial N accumulation, a proxy for cell growth, tended to be 20% greater for PHL and INU than for GLC. The N accumulation rate for GLC (1.31h−1) was greater than for PHL (0.75h−1) and INU (0.26h−1), which also differed. More microbial glycogen (+57%) was accumulated from GLC than from PHL, though accumulation rates did not differ (1.95 and 1.44h−1, respectively); little glycogen accumulated from INU. Rates of organic acid formation were 0.80, 0.28, and 0.80h−1 for GLC, INU, and PHL, respectively, with PHL tending to be greater than INU. Lactic acid production was more than 7-fold greater for GLC than for the fructans. The ratio of microbial cell carbon to organic acid carbon tended to be greater for PHL (0.90) and INU (0.86) than for GLC (0.69), indicating a greater yield of cell mass per amount of substrate fermented with fructans. Reduced microbial yield for GLC may relate to the greater glycogen production that requires ATP, and lactate production that yields less ATP; together, these processes could have reduced ATP available for cell growth. Acetate molar proportion was less for GLC than for fructans, and less for PHL than for INU. In studies with pure cultures, all microbes evaluated showed differences in specific growth rate constants (μ) for GLC, fructose, sucrose, maltose, and PHL. Selenomonas ruminantium and Streptococcus bovis showed the highest μ for PHL (0.55 and 0.67h−1, respectively), which were 50 to 60% of the μ achieved for GLC. The 10 other species tested had μ between 0.01 and 0.11h−1 with PHL. Ruminal microbes use PHL differently than they do GLC or INU.

In vitro, ex vivo and in vivo effects of egg consumption (and egg microbiota) on the microbial community composition of gut microbiota and on immunological/metabolic/inflammatory biomarkers

Background and Objectives: Some years ago, egg consumption was considered to be bad for heart health, blood vessels or for people watching their cholesterol levels. Meanwhile, recent meta-analysis studies concluded that higher consumption of egg is not associated with increased risk of cardiovascular disease. This discrepancy raises an important question as to whether the gut microbiota plays a role in digestion, absorption and metabolism of eggs in the digestive tract. There are four primary ways in which eggs (or egg consumption) can impact on the composition of the intestinal microbiota: a) by its nutrition-related factors; through its microbiological status; b) through the potential presence of residues of drugs applied to laying hens; and d) through its allergens. Current studies suggest that high dietary fat intake may contribute to metabolic syndrome pathogenesis through altering intestinal microbiota (a decrease in gut barrier-protecting beneficial Bifidobacteria spp. population and an increase in E coli population), increasing intestinal permeability, and promoting inflammation [Brown et al., 2012; Martinez-Medina et al., 2014]. Because per capita consumption of egg has increased continuously (221 – 259 eggs) and eggs contain high levels of cholesterol and saturated-fat, we were interested in investigating whether egg consumption and egg microbiota impact on the composition of the gut microbiota and immunological/metabolic/inflammatory biomarkers in vitro, ex vivo and in vivo. Materials and Methods: Briefly, freshly defecated fecal pellets were collected aseptically from 6 – 8 donor mice, weighed, and then placed in 200 ml of MRS broth. The fecal pellets were resuspended in 200 ml MRS broth by vortexing and by gently bashing with a sterile bacteriological loop, and the resulting cell suspensions were incubated anaerobically without or with whole boiled eggs at 37 °C for 24h. After incubation, serial dilutions were made in sterile PBS and suitable dilutions were plated onto MRS agar for anaerobic culturable bacteria. Afterwards, MRS agar plates were incubated anaerobically at 37 °C for 48 hours and the numbers of colonies on the plates were counted. After the plating process, bacterial cultures were used to measure pH values. For the first time, we used Konelab 20i Clinical Chemistry Analyzer to assess the actual rate of glucose consumption by bacteria, as manifested by quantitative measurement of glucose concentrations in bacterial cell-free culture supernatants (showing the rate of glucose disappearance). However, we conducted similar experimental series with a pure culture of the human-derived Bifidobacterium DSM 20086 strain. Results: Our preliminary in vitro and ex vivo experiments show that addition of egg to MRS broth medium did not inhibit, but rather augmented the growth of culturable anaerobic bacteria from mouse faeces as well as human intestinal-derived Bifidobacterium DSM 20086 strain, as manifested by higher bacterial counts (CFU/ml). This was associated with lower pH values and glucose concentrations in bacterial cultures as reliable and quantitative indicators for prediction of the rate of glucose utilization. Conclusion: Overall, our experiments show that although egg contains high cholesterol and saturated-fat contents, it has not any demonstrably negative impacts on bacterial growth parameters in culturable anaerobic bacteria from mouse faeces as well as human-derived Bifidobacterium DSM 20086 strain. If this happens in vivo, then egg consumption may beneficially modify gut microbiota community composition, which in turn may play a favorable role in the digestion, absorption and metabolism of egg in the digestive tract. Our ongoing cell culture and in vivo studies will provide additional insights into the molecular and cellular basis, underpinning the interplay between egg metabolism and gut microbiota composition.

Abstract P645: Chronic Angiotensin-(1-7) Improves Whole-Body Insulin Sensitivity in High-Fat Fed Mice by Enhancing Skeletal Muscle Glucose Uptake

Angiotensin (Ang)-(1-7) is a vasodilatory peptide implicated in the pathophysiology of hypertension, in part by opposing deleterious Ang II cardiovascular actions. Recent studies show that Ang-(1-7) restoration lowers blood pressure and improves glycemic control in animal models of cardiometabolic syndrome. The tissue-specific sites of action and blood pressure dependence for these metabolic effects, however, remain unclear. We hypothesized that Ang-(1-7) improves insulin sensitivity by enhancing peripheral glucose delivery. To test this hypothesis, adult male C57BL/6 mice were placed on standard chow or 60% high-fat diet for 11 weeks, with Ang-(1-7) [400 ng/kg/min] or saline given during the last 3 weeks of diet by subcutaneous osmotic mini-pump. Hyperinsulinemic (4 mU/kg/min) euglycemic clamps were performed in conscious, unrestrained mice at the end of the treatment period. High-fat fed mice exhibited modest hypertension (systolic blood pressure: 137±3 high-fat vs. 123±5 mmHg chow; p=0.043), which was not altered by Ang-(1-7) infusion (141±4 mmHg; p=0.516). Body weight, body composition, and fasting plasma glucose and insulin levels were not significantly different following Ang-(1-7) treatment in chow or high-fat fed mice. Ang-(1-7) increased the glucose infusion rate (GIR) needed to maintain euglycemia in high-fat fed mice (steady-state GIR: 31±5 Ang-(1-7) vs. 16±1 mg/kg/min vehicle; p=0.017) indicating enhanced whole-body insulin sensitivity, with no significant effect in chow fed mice. The improvement in insulin sensitivity in high-fat fed mice was due to an enhanced rate of whole-body glucose disappearance (R d : 34±5 Ang-(1-7) vs. 20±2 mg/kg/min vehicle; p=0.049), with increased rates of glucose uptake in gastrocnemius, vastus, and soleus muscle. There was no effect of Ang-(1-7) on insulin-mediated suppression of hepatic glucose production. Our data shows that Ang-(1-7) has direct insulin-sensitizing effects on skeletal muscle, which are independent of changes in body weight or systemic blood pressure. These overall findings provide new insight into mechanisms by which Ang-(1-7) improves insulin action, and provide further support to targeting this peptide for treatment of cardiometabolic disease.

Type 2 diabetes alters metabolic and transcriptional signatures of glucose and amino acid metabolism during exercise and recovery.

The therapeutic benefit of physical activity to prevent and treat type 2 diabetes is commonly accepted. However, the impact of the disease on the acute metabolic response is less clear. To this end, we investigated the effect of type 2 diabetes on exercise-induced plasma metabolite changes and the muscular transcriptional response using a complementary metabolomics/transcriptomics approach. We analysed 139 plasma metabolites and hormones at nine time points, and whole genome expression in skeletal muscle at three time points, during a 60 min bicycle ergometer exercise and a 180 min recovery phase in type 2 diabetic patients and healthy controls matched for age, percentage body fat and maximal oxygen consumption (VO2). Pathway analysis of differentially regulated genes upon exercise revealed upregulation of regulators of GLUT4 (SLC2A4RG, FLOT1, EXOC7, RAB13, RABGAP1 and CBLB), glycolysis (HK2, PFKFB1, PFKFB3, PFKM, FBP2 and LDHA) and insulin signal mediators in diabetic participants compared with controls. Notably, diabetic participants had normalised rates of lactate and insulin levels, and of glucose appearance and disappearance, after exercise. They also showed an exercise-induced compensatory regulation of genes involved in biosynthesis and metabolism of amino acids (PSPH, GATM, NOS1 and GLDC), which responded to differences in the amino acid profile (consistently lower plasma levels of glycine, cysteine and arginine). Markers of fat oxidation (acylcarnitines) and lipolysis (glycerol) did not indicate impaired metabolic flexibility during exercise in diabetic participants. Type 2 diabetic individuals showed specific exercise-regulated gene expression. These data provide novel insight into potential mechanisms to ameliorate the disturbed glucose and amino acid metabolism associated with type 2 diabetes.

Enhanced mitochondrial superoxide scavenging does not improve muscle insulin action in the high fat-fed mouse.

Improving mitochondrial oxidant scavenging may be a viable strategy for the treatment of insulin resistance and diabetes. Mice overexpressing the mitochondrial matrix isoform of superoxide dismutase (sod2tg mice) and/or transgenically expressing catalase within the mitochondrial matrix (mcattg mice) have increased scavenging of O2˙ˉ and H2O2, respectively. Furthermore, muscle insulin action is partially preserved in high fat (HF)-fed mcattg mice. The goal of the current study was to test the hypothesis that increased O2˙ˉ scavenging alone or in combination with increased H2O2 scavenging (mtAO mice) enhances in vivo muscle insulin action in the HF-fed mouse. Insulin action was examined in conscious, unrestrained and unstressed wild type (WT), sod2tg, mcattg and mtAO mice using hyperinsulinemic-euglycemic clamps (insulin clamps) combined with radioactive glucose tracers following sixteen weeks of normal chow or HF (60% calories from fat) feeding. Glucose infusion rates, whole body glucose disappearance, and muscle glucose uptake during the insulin clamp were similar in chow- and HF-fed WT and sod2tg mice. Consistent with our previous work, HF-fed mcattg mice had improved muscle insulin action, however, an additive effect was not seen in mtAO mice. Insulin-stimulated Akt phosphorylation in muscle from clamped mice was consistent with glucose flux measurements. These results demonstrate that increased O2˙ˉ scavenging does not improve muscle insulin action in the HF-fed mouse alone or when coupled to increased H2O2 scavenging.

Effect of subcutaneous insulin detemir on glucose flux and lipolysis during hyperglycaemia in people with type 1 diabetes

To investigate, using a novel non-steady-state protocol, the differential effects of subcutaneous (s.c.) detemir and NPH insulin on glucose flux and lipid metabolism after insulin withdrawal. After a period of insulin withdrawal resulting in whole-blood glucose concentration of 7 mmol/l, 11 participants (five men, mean age 41.0 years, mean body mass index 25 kg/m(2)) with type 1 diabetes (mean glycated haemoglobin concentration 57 mmol/mol, mean diabetes duration 14 years) received 0.5 units per kg body weight s.c. insulin detemir or NPH insulin in random order. Stable isotopes of glucose and glycerol were infused intravenously throughout the study protocol. Glucose concentration decreased after insulin treatment as a result of suppression of endogenous glucose production, which occurred to a similar extent with both detemir and NPH insulin. The rate of glucose disappearance (Rd) was not increased significantly with either type of insulin. When the effect of detemir and NPH insulin on glucose flux at glucose concentrations between 9 and 6 mmol/l was examined, glucose rate of appearance (Ra) was similar with the two insulins; however, glucose Rd was greater with NPH insulin than with detemir at glucose concentrations of 8.0, 8.5, 7.0 and 6.0 mmol/l (p < 0.05) The percentage change in glycerol Ra, a measure of lipolysis, was greater in the NPH group than in the detemir group (p = 0.04). The results of the study are consistent with the hypothesis that detemir has a lesser effect on the periphery, as evidenced by a lesser effect on peripheral glucose uptake at specific glucose concentrations.

Optimal Waist Circumference Cutoff Value Based on Insulin Resistance and Visceral Obesity in Koreans with Type 2 Diabetes

BackgroundVisceral obesity is the most powerful contributor to the development of metabolic syndrome (MetS) and cardiovascular diseases. In light of visceral obesity, however, there is a paucity of data on the appropriate cutoff point of waist circumference (WC) in subjects with type 2 diabetes. The aim of this study was to investigate the optimal cutoff value for WC that signals insulin resistance (IR) and visceral obesity in Koreans with type 2 diabetes.MethodsWe evaluated 4,252 patients with type 2 diabetes (male 2,220, female 2,032, mean age 57.24 years) who visited our clinic between January 2003 and June 2009. WC was measured at the midpoint between the lower rib and the iliac crest, and insulin sensitivity was assessed by the rate constant of plasma glucose disappearance (Kitt %/min) using an insulin tolerance test. Visceral fat thickness was measured using ultrasonography. Statistical analysis was performed using receiver operating characteristic curve.ResultsThe optimal cutoff points for WC for identifying the presence of IR and visceral obesity, as well as two or more metabolic components, were 87 cm for men and 81 cm for women. Moreover, these cutoff points had the highest predictive powers for the presence of visceral obesity. The MetS defined by new criteria correlated with the increased carotid intima-media thickness in female subjects.ConclusionOur results suggest that the optimal cutoff values for WC in Koreans with type 2 diabetes should be reestablished based on IR and visceral obesity.

Rapid Deterioration of Insulin Secretion in Obese Adolescents Preceding the Onset of Type 2 Diabetes

To identify pathophysiologic changes that lead to the onset of type 2 diabetes (T2DM) in adolescents. Obese adolescents with normal glucose tolerance (n = 41) were studied longitudinally over the course of 4 years with serial measure of the acute insulin response to glucose (AIRg) as well as proinsulin (PI) concentrations. Insulin resistance was estimated with the homeostatic model assessment of insulin resistance (HOMA-IR), the disposition index (DI) computed as AIRg × 1/HOMA-IR, and intravenous glucose tolerance estimated as the glucose disappearance constant. Four adolescents developed diabetes mellitus (DM) during the study, and the rest of the cohort remained nondiabetic. Baseline PI exceeded the IQR of the nondiabetic group in 3 of 4 subjects with DM, and all had >85% reduction from baseline AIRg, and DI, within 6 months of diagnosis. All the subjects with DM gained weight over the course of the study, but these changes paralleled those for the nondiabetic group. HOMA-IR increased substantially in 1 of the subjects with DM at the time of diagnosis but was comparable with baseline in the other 3. The DI and glucose disappearance constant of the subjects with DM was less than the 10th percentile of the nondiabetic group before and after diagnosis. Conversion from normal glucose tolerance to T2DM in adolescents can occur rapidly, and the onset of T2DM is heralded by a substantial decrease in AIRg and DI, as well as increased release of PI. These results support loss of β-cell function as the proximate step in the development of T2DM in this age group.

The preventive effect of vitamin C on the cellular and functional integrity of kidney cells in rats following repeated exposure to paraquat

Paraquat (PQ) is a bipyridylium herbicide that is applied around trees in orchards and between crop rows to control broad-leaved and grassy weeds. Its oxidation results in the formation of superoxides which causes damage to cellular components. In this study, we determined the antioxidant effect vitamin C has on the cellular integrity of kidney function in rats following repeated exposure to PQ. Ninety-six male rats, grouped twelve rats per subgroup (A, A&lt;sub&gt;vit.c&lt;/sub&gt;, B, B&lt;sub&gt;vit.c&lt;/sub&gt;, C, C&lt;sub&gt;vit.c&lt;/sub&gt;, D and D&lt;sub&gt;vit.c&lt;/sub&gt;) were intraperitoneally injected with different sublethal increasing doses (0, 0, 2, 2, 4, 4, 6 and 6 mg/kg body weight) of PQ respectively on biweekly (14 days) intervals over a period of three months (84 days). Subsequently, the subgrouped animals (A&lt;sub&gt;vit.c&lt;/sub&gt;, B&lt;sub&gt;vit.c&lt;/sub&gt;, C&lt;sub&gt;vit.c&lt;/sub&gt; and D&lt;sub&gt;vit.c&lt;/sub&gt;) were maintained orally with 1 g/L vitamin C, while the other subgrouped animals (A, B, C and D) received drinking water with negligible vitamin content throughout the study period. At the end of each monthly (28 days) treatment, four animals per subgroup were selected. Urine samples were collected from each of the selected rats, after which each of the animals were anaesthetized with gaseous isoflurane and 5 mL of blood samples were collected using cardiac puncture procedure. The animals were later decapitated and their kidneys harvested. The samples collected were analyzed for urine [specific gravity (SG), pH, protein and glucose], blood (urea, creatinine, total protein and glucose), and the histological studies on kidney slides. The dose and exposure- time dependent PQ toxicity resulted in the reduction in urinary pH, elevation in urinary SG, and the detectable presence of protein and glucose in urine. It also caused marked elevation in serum urea and creatinine levels with reduction in serum protein and glucose levels and alterations in the cellular integrity of the renal architecture, especially the glomeruli and tubular tissues. Treatments on the PQ insulted animals with vitamin C resulted in the significant presentation of biochemical and histological values that were a complete reversal or near normalization in the parameters assayed, except the urinary pH which presented with more acidic values (vitamin C is acidic in solution). Vitamin C treatment significantly brought down the urine SG level to normal or near normal. It caused near or total disappearance of protein and glucose in urine, reduction in serum urea and creatinine concentration and elevation or normalization of serum total protein and glucose values with restoration of the renal function of treated rats. These findings clearly show that vitamin C has an important role to play in the body’s antioxidant defense system. Its use caused normalization of the biochemical and histological parameters studied and restored the health status of the affected animals.