Protocol for in vivo and ex vivo assessment of hyperglycemia and islet function in diabetic mice.

Mouse hyperglycemia model and islet function assessment are essential in diabetes research. Here, we provide a protocol to evaluate glucose homeostasis and islet functions in diabetic mice and isolated islets. We describe steps for establishing type 1 and 2 diabetes, glucose tolerance test, insulin tolerance test, glucose stimulated insulin secretion (GSIS) assay, and histological analysis for islet number and insulin expression in vivo. We then detail islet isolation, islet GSIS, ß-cell proliferation, apoptosis, and programming assays ex vivo. For complete details on the use and execution of this protocol, please refer to Zhang et al. (2022).1.

Docking study, molecular dynamic, synthesis, anti-α-glucosidase assessment, and ADMET prediction of new benzimidazole-Schiff base derivatives.

The control of postprandial hyperglycemia is an important target in the treatment of type 2 diabetes mellitus (T2DM). As a result, targeting α-glucosidase as the most important enzyme in the breakdown of carbohydrates to glucose that leads to an increase in postprandial hyperglycemia is one of the treatment processes of T2DM. In the present work, a new class of benzimidazole-Schiff base hybrids 8a-p has been developed based on the potent reported α-glucosidase inhibitors. These compounds were synthesized by sample recantations, characterized by 1H-NMR, 13C-NMR, FT-IR, and CHNS elemental analysis, and evaluated against α-glucosidase. All new compounds, with the exception of inactive compound 8g, showed excellent inhibitory activities (60.1 ± 3.6-287.1 ± 7.4 µM) in comparison to acarbose as the positive control (750.0 ± 10.5). Kinetic study of the most potent compound 8p showed a competitive type of inhibition (Ki value = 60 µM). In silico induced fit docking and molecular dynamics studies were performed to further investigate the interaction, orientation, and conformation of the title new compounds over the active site of α-glucosidase. In silico druglikeness analysis and ADMET prediction of the most potent compounds demonstrated that these compounds were druglikeness and had satisfactory ADMET profile.

In vitro assessment of the DNA damage and senility of CD117+ stem cells collected from diabetic mice.

OBJECTIVE: Angiogenesis impairment is a common feature of diabetes mellitus (DM), whereas CD117+ bone marrow cells (BMCs) injury might be responsible for such complication. In this study, we studied the effect of hyperglycemia on the DNA damage and senility of CD117+ bone marrow cells. MATERIALS AND METHODS: We isolated CD117+ BMCs from the Streptozotocin (STZ) induced diabetes and healthy control mice. Oxidative stress was detected by flow cytometric analysis. γ-H2AX, which is the DNA damage mark, was detected by using Western blotting and immunofluorescence histochemistry. We also detected the expression of γ-H2AX and p16 by using Western blotting. RESULTS: Compared with the control mice, the level of reactive oxygen species (ROS) was increased significantly in the CD117+ BMCs collected from the diabetic mice (p<0.05), and the percentage of γ-H2AX positive cells was higher significantly (p<0.01). The expression of γ-H2AX and p16 was increased significantly in the CD117+ BMCs from the diabetic mice. CONCLUSIONS: Our experiments demonstrated the oxidative stress in CD117+ BMCs under DM conditions, while accelerating the DNA damage and senility in CD117+ BMCs as well.

Assessment of the association between the polymorphism rs1256031 of the estrogen receptor ß gene and GDM susceptibility.

Estrogen has an important role in regulating glucose homeostasis, and existing evidence indicates that it might be involved in the development of hyperglycemia in pregnancy. It mediates its effect through estrogen receptors including the nuclear receptor ERß encoded by ESR2. The association between the ESR2 polymorphism rs1256031 and GDM susceptibility has not been investigated yet. This study aimed to evaluate the relationship between rs1256031 and GDM risk in Chinese population. A total of 241 GDM patients and 139 healthy pregnant women were recruited for this study. The rs1256031 genotype was examined by time-of-flight mass spectrometry and the association between rs1256031 and GDM susceptibility was assessed by binary logistic regression in three different genetic models. The polymorphism rs1256031 was not associated with GDM susceptibility in additive [OR (95% CI) = 0.871 (0.453,1.675); P = 0.680], dominant [OR (95% CI) = 0.908 (0.495,1.665); P = 0.755] or recessive [OR (95% CI) = 0.912 (0.591,1.408); P = 0.677] models after adjusting for confounding factors. We observed no association between the polymorphism rs1256031 in the ESR2 gene and GDM susceptibility in Chinese pregnant women.

Sociodemographic disparities in non-diabetic hyperglycaemia and the transition to type 2 diabetes: evidence from the English Longitudinal Study of Ageing.

AIM: To explore whether there are social inequalities in non-diabetic hyperglycaemia (NDH) and in transitions to type 2 diabetes mellitus and NDH low-risk status in England. METHODS: Some 9143 men and women aged over 50 years were analysed from waves 2, 4, 6 and 8 (2004-2016) of the English Longitudinal Study of Ageing (ELSA). Participants were categorized as: NDH 'low-risk' [HbA1c < 42 mmol/mol (< 6.0%)], NDH [HbA1c 42-47 mmol/mol (6.0-6.4%)] and type 2 diabetes [HbA1c > 47 mmol/mol (> 6.4%)]. Logistic regression models estimated the association between sociodemographic characteristics and NDH, and the transitions from NDH to diagnosed or undiagnosed type 2 diabetes and low-risk status in future waves. RESULTS: NDH was more prevalent in older participants, those reporting a disability, those living in deprived areas and in more disadvantaged social classes. Older participants with NDH were less likely to progress to undiagnosed type 2 diabetes [odds ratio (OR) 0.27, 95% confidence interval (CI) 0.08, 0.96]. NDH individuals with limiting long-standing illness (OR 1.72, 95% CI 1.16, 2.53), who were economically inactive (OR 1.60, 95% CI 1.02, 2.51) or from disadvantaged social classes (OR 1.63, 95% CI 1.02, 2.61) were more likely to progress to type 2 diabetes. Socially disadvantaged individuals were less likely (OR 0.64, 95% CI 0.41, 0.98) to progress to NDH low-risk status. CONCLUSIONS: There were socio-economic differences in NDH prevalence, transition to type 2 diabetes and transition to NDH low-risk status. Disparities in transitions included the greater likelihood of disadvantaged social groups with NDH developing type 2 diabetes and greater likelihood of advantaged social groups with NDH becoming low-risk. These socio-economic differences should be taken into account when targeting prevention initiatives.

Social and economic factors, maternal behaviours in pregnancy and neonatal adiposity in the PANDORA cohort.

BACKGROUND: Australian Indigenous women experience high rates of social disadvantage and type 2 diabetes (T2D) in pregnancy, but it is not known how social factors and maternal behaviours impact neonatal adiposity in offspring of women with hyperglycaemia in pregnancy. METHODS: Participants were Indigenous (n = 404) and Europid (n = 240) women with gestational diabetes mellitus (GDM) or T2D in pregnancy and their offspring in the Pregnancy and Neonatal Diabetes Outcomes in Remote Australia (PANDORA) study. Social, economic factors, and maternal behaviours were measured in pregnancy and six neonatal anthropometric outcomes were examined after birth. RESULTS: On univariate analysis, maternal education < 12 years (p = 0.03), unemployment (p = 0.001), welfare income vs no welfare income (p = 0.001), lower area based socio-economic score (p < 0.001), and fast food intake > 2 times/week (p = 0.002) were associated with increased sum of skinfolds (SSF) in offspring. Smoking was significantly associated with a reduction in anthropometric measures, except SSF. In multivariable models adjusted for ethnicity, BMI and hyperglycaemia, social and economic factors were no longer significant predictors of neonatal outcomes. Smoking was independently associated with a reduction in length, head circumference and fat free mass. Frequent fast food intake remained independently associated with SSF (ß-coefficient 1.08 mm, p = 0.02). CONCLUSION: In women with hyperglycaemia in pregnancy, social factors were associated with neonatal adiposity, particularly skinfold measures. Promoting smoking cessation and limited intake of energy-dense, nutrient-poor foods in pregnancy are important to improve neonatal adiposity and lean mass outcomes. Addressing inequities in social and economic factors are likely to be important, particularly for Indigenous women or women experiencing social disadvantage.

Assessment of pulsatile insulin secretion derived from peripheral plasma C-peptide concentrations by nonparametric stochastic deconvolution.

The characteristics of pulsatile insulin secretion are important determinants of type 2 diabetes pathophysiology, but they are understudied due to the difficulties in measuring pulsatile insulin secretion noninvasively. Deconvolution of either peripheral C-peptide or insulin concentrations offers an appealing alternative to hepatic vein catheterization. However, to do so, there are a series of methodological challenges to overcome. C-peptide has a relatively long half-life and accumulates in the circulation. On the other hand, peripheral insulin concentrations reflect relatively fast clearance and hepatic extraction as it leaves the portal circulation to enter the systemic circulation. We propose a method based on nonparametric stochastic deconvolution of C-peptide concentrations, using individually determined C-peptide kinetics, to overcome these limitations. The use of C-peptide (instead of insulin) concentrations allows estimation of portal (and not post-hepatic) insulin pulses, whereas nonparametric stochastic deconvolution allows evaluation of pulsatile signals without any a priori assumptions of pulse shape and occurrence. The only assumption required is the degree of smoothness of the (unknown) secretion rate. We tested this method first on simulated data and then on 29 nondiabetic subjects studied during euglycemia and hyperglycemia and compared our estimates with the profiles obtained from hepatic vein insulin concentrations. This method produced satisfactory results both in the ability to fit the data and in providing reliable estimates of pulsatile secretion, in agreement with hepatic vein measurements. In conclusion, the proposed method enables reliable and noninvasive measurement of pulsatile insulin secretion. Future studies will be needed to validate this method in people with type 2 diabetes.

Norbixin, an apocarotenoid derivative activates PPARγ in cardiometabolic syndrome: Validation by in silico and in vivo experimental assessment.

The increased prevalence of cardio-metabolic disorders worldwide prompted the exploration of new strategies for its treatment. Peroxisome Proliferator activated receptor (PPAR) play major role in regulation of lipid as well as glucose metabolism and thus, natural PPARγ activators seem to be drug of choice. AIMS: In the present work, we studied norbixin which is a natural apocarotenoid derivative for its agonistic activity for PPAR γ followed by in vivo studies for amelioration of cardio-metabolic syndrome (CMetS). MAIN METHODS: The methods include computational studies, TR-FRET binding analysis and in vivo studies on high fat diet induced rats. KEY FINDINGS: Molecular docking and molecular dynamics (MD) simulation studies showed that norbixin could be embedded into hydrophobic pocket of PPARγ and stable hydrogen bonding interactions were found with residues Glu273, Tyr327, Ser289, His323, His449 and Tyr473 of PPARγ. These results were substantiated by significant in vitro PPAR agonistic activity of norbixin in TR-FRET binding assay studies. The experimental results of norbixin in high fat diet induced CMetS in rats further confirmed that norbixin decreased insulin resistance (IR), hyperglycemia and dyslipidemia. These results were accompanied by reduced inflammatory marker hs-CRP as well as decreased oxidative stress and arterial pressure. The histopathology of heart sections also showed that norbixin could prevent the abnormal fibrotic changes in heart. Furthermore, PPARγ protein expressions were increased, whereas NF-κB expression was decreased by norbixin treatment in western blot studies. SIGNIFICANCE: These results validate norbixin as a novel PPARγ agonist and prove therapeutic potential of norbixin in treatment of CMetS.

Magnetoliposomes as Contrast Agents for Longitudinal in vivo Assessment of Transplanted Pancreatic Islets in a Diabetic Rat Model.

Magnetoliposomes (MLs) were synthesized and tested for longitudinal monitoring of transplanted pancreatic islets using magnetic resonance imaging (MRI) in rat models. The rat insulinoma cell line INS-1E and isolated pancreatic islets from outbred and inbred rats were used to optimize labeling conditions in vitro. Strong MRI contrast was generated by islets exposed to 50 µg Fe/ml for 24 hours without any increased cell death, loss of function or other signs of toxicity. In vivo experiments showed that pancreatic islets (50-1000 units) labeled with MLs were detectable for up to 6 weeks post-transplantation in the kidney subcapsular space. Islets were also monitored for two weeks following transplantation through the portal vein of the liver. Hereby, islets labeled with MLs and transplanted under the left kidney capsule were able to correct hyperglycemia and had stable MRI signals until nephrectomy. Interestingly, in vivo MRI of streptozotocin induced diabetic rats transplanted with allogeneic islets demonstrated loss of MRI contrast between 7-16 days, indicative of loss of islet structure. MLs used in this study were not only beneficial for monitoring the location of transplanted islets in vivo with high sensitivity but also reported on islet integrity and hereby indirectly on islet function and rejection.

Insulin secretory effect of sitagliptin: assessment with a hyperglycemic clamp combined with a meal challenge.

Sitagliptin, a dipeptidyl peptidase-IV inhibitor (DPP-4), sustains activity of the incretin hormones GLP-1 and GIP and improves hyperglycemia in Type 2 diabetes mellitus (T2DM). It has however proven challenging to quantify the effect of sitagliptin on rates of insulin secretion (ISR) during a prandial challenge. The tight feedback governance of ISR by plasma glucose means that in the face of treatment-related lowering of postprandial glycemia, corresponding stimulation of ISR is lessened. We postulated that sustaining a stable level of moderate hyperglycemia before and during a meal challenge (MC) would be a platform that enables greater clarity to assess the effect of sitagliptin on ISR and an approach that could be valuable to evaluate novel targets that increase insulin secretion directly and by augmenting incretins. A hyperglycemic clamp (HGC) at 160 mg/dl was conducted in 12 healthy volunteers (without diabetes) for 6 h; 3 h into the HGC, MC was administered while maintaining stable hyperglycemia of the HGC for an additional 3 h. Modeling of C-peptide response was used to calculate ISR. In crossover design of three periods (sitagliptin twice and placebo once), the effect of sitagliptin vs. placebo on ISR and the reproducibility of the response to sitagliptin were assessed. Sitagliptin increased ISR compared with placebo by 50% and 20% during the HGC alone and the HGC-MC phases, respectively ( P < 0.001 for both). There was an associated significant treatment-based increase in circulating insulin, as well as active levels of GLP-1. Robust reproducibility of the sitagliptin-mediated ISR response was observed; the intraclass correlation value was 0.94. The findings delineate the effect of sitagliptin to stimulate insulin secretion, and these benchmark data also demonstrate that an HGC-MC can be a useful platform for interrogating therapeutic targets that could potentially modulate ISR via direct action on beta-cells as well as by augmenting release or action of incretins.

p32 heterozygosity protects against age- and diet-induced obesity by increasing energy expenditure.

Obesity is increasing in prevalence and has become a global public health problem. The main cause of obesity is a perturbation in energy homeostasis, whereby energy intake exceeds energy expenditure. Although mitochondrial dysfunction has been linked to the deregulation of energy homeostasis, the precise mechanism is poorly understood. Here, we identify mitochondrial p32 (also known as C1QBP) as an important regulator of lipid homeostasis that regulates both aerobic and anaerobic energy metabolism. We show that while whole-body deletion of the p32 results in an embryonic lethal phenotype, mice heterozygous for p32 are resistant to age- and high-fat diet-induced ailments, including obesity, hyperglycemia, and hepatosteatosis. Notably, p32 +/- mice are apparently healthy, demonstrate an increased lean-to-fat ratio, and show dramatically improved insulin sensitivity despite prolonged high-fat diet feeding. The p32 +/- mice show increased oxygen consumption and heat production, indicating that they expend more energy. Our analysis revealed that haploinsufficiency for p32 impairs glucose oxidation, which results in a compensatory increase in fatty acid oxidation and glycolysis. These metabolic alterations increase both aerobic and anaerobic energy expenditure. Collectively, our data show that p32 plays a critical role in energy homeostasis and represents a potential novel target for the development of anti-obesity drugs.

Immobilized tannase treatment alters polyphenolic composition in teas and their potential anti-obesity and hypoglycemic activities in vitro.

The aim of this work was to assess the effect of immobilized-tannase treatment on black, green, white and mate tea components and on their bioactivities relevant to obesity. Tannase treatment caused predictable changes in polyphenol composition with substantial reduction in galloylated catechins in green, white and black tea. Mate tea, which is rich in chlorogenic acids, was much less affected by tannase treatment although some degradation of caffeoyl quinic acid derivatives was noted. The original tea samples were effective in inhibiting digestive enzymes in vitro. They inhibited amylase activity, some with IC50 values ∼70 µg mL(-1), but were much less effective against α-glucosidase. They also inhibited lipase activity in vitro and caused dose-dependent reductions in lipid accumulation in cultured adipocytes. The bio-transformed tea samples generally matched the effectiveness of the original samples but in some cases they were markedly improved. In particular, tannase treatment reduced the IC50 value for amylase inhibition for green tea and white tea by 15- and 6-fold respectively. In addition, the bio-transformed samples were more effective than the original samples in preventing lipid accumulation in adipocytes. These in vitro studies indicate that bio-transformed tea polyphenols could assist in the management of obesity through improvement in energy uptake and lipid metabolism and also indicate that biotechnological modification of natural food molecules can improve the benefits of a common beverage such as tea.

Assessment of In Vivo Antidiabetic Properties of Umbelliferone and Lupeol Constituents of Banana (Musa sp. var. Nanjangud Rasa Bale) Flower in Hyperglycaemic Rodent Model.

Banana is an extensively cultivated plant worldwide, mainly for its fruit, while its ancillary product, the banana flower is consumed as a vegetable and is highly recommended for diabetics in the traditional Indian medicine system. This study is based on an investigation of the in vivo antihyperglycaemic activity of Umbelliferone (C1) and Lupeol (C2) isolated from the ethanol extract of banana flower (EF) in alloxan induced diabetic rat model. Diabetic rats which were administered with C1, C2 and EF (100 and 200 mg/kg b. wt.) for 4 weeks showed deterioration in fasting hyperglycaemia and reversal of abnormalities in serum/urine protein, urea and creatinine, when compared to the diabetic control group of rats. The diabetic group of rats fed with EF, C1 and C2 (100 mg/kg b. wt.) once daily, for a period of 28 days resulted in a significant reduction of diabetic symptoms viz., polyphagia, polydipsia, polyuria and urine sugar together with an improved body weight. HbA1c extent was reduced whereas levels of insulin and Hb were increased. Both the extract and compounds wielded positive impacts in diabetic rats by reversal of altered activities of hepatic marker enzymes viz., aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP); glycolytic enzyme (hexokinase); shunt enzyme (glucose-6-phosphate dehydrogenase); gluconeogenic enzymes (glucose-6-phosphatase, fructose-1,6-bisphosphatase, lactate dehydrogenase) and pyruvate kinase. The characteristic diabetic complications such as hypercholesterolemia and hypertriacylglycerolemia also significantly reverted to normal in the serum/liver of diabetic rats. Besides these, the treatment increased the activities of enzymatic and non-enzymatic antioxidants in the serum and liver. The histological observations revealed a marked regeneration of the ß-cells in the drug treated diabetic rats. In conclusion, the present study illustrates that EF, C1 and C2 enhances the glycolytic activities, besides increasing the hepatic glucose utilization in diabetic rats by stimulating insulin secretion from the remnant ß-cells along with potential enzymatic and non-enzymatic antioxidant activities.

Social inequalities in prevalence of diagnosed and undiagnosed diabetes and impaired glucose regulation in participants in the Health Surveys for England series.

OBJECTIVES: To ascertain the extent of socioeconomic and health condition inequalities in people with diagnosed and undiagnosed diabetes and impaired glucose regulation (IGR) in random samples of the general population in England, as earlier diagnosis of diabetes and treatment of people with IGR can reduce adverse sequelae of diabetes. Various screening instruments were compared to identify IGR, in addition to undiagnosed diabetes. DESIGN: 5, annual cross-sectional health examination surveys; data adjusted for complex survey design. SETTING: Random selection of private homes across England, new sample annually 2009-2013. PARTICIPANTS: 5, nationally representative random samples of the general, free-living population: ≥ 1 adult interviewed in 24,254 of 36,889 eligible addresses selected. 18,399 adults had a valid glycated haemoglobin (HbA1c) measurement and answered the diabetes questions. MAIN OUTCOME MEASURES: Diagnosed diabetes, undiagnosed diabetes (HbA1c ≥ 48 mmol/mol), IGR (HbA1c 42-47 mmol/mol). RESULTS: Overall, 11% of the population had IGR, 2% undiagnosed and 6% diagnosed diabetes. Age-standardised prevalence was highest among Asian (19% (95% CI 16% to 23%), 3% (2% to 5%) and 12% (9% to 16%) respectively) and black participants (17% (13% to 21%), 2% (1% to 4%) and 14% (9% to 20%) respectively). These were also higher among people with lower income, less education, lower occupational class and greater deprivation. Education (OR 1.49 (95% CI 1.27 to 1.74) for no qualifications vs degree or higher) and income (1.35 (1.12 to 1.62) for lowest vs highest income quintile) remained significantly associated with IGR or undiagnosed diabetes on multivariate regression. The greatest odds of IGR or undiagnosed diabetes were with increasing age over 34 years (eg, OR 18.69 (11.53 to 30.28) aged 65-74 vs 16-24). Other significant associations were ethnic group (Asian (3.91 (3.02 to 5.05)), African-American (2.34 (1.62 to 3.38)) or 'other' (2.04 (1.07 to 3.88)) vs Caucasian); sex (OR 1.32(1.19 to 1.46) for men vs women); body mass index (3.54 (2.52 to 4.96) for morbidly obese vs not overweight); and waist circumference (2.00 (1.67 to 2.38) for very high vs low). CONCLUSIONS: Social inequalities in hyperglycaemia exist, additional to well-known demographic and anthropometric risk factors for diabetes and IGR.

Assessment of DNA damage and mRNA/miRNA transcriptional expression profiles in hyperglycemic versus non-hyperglycemic patients with type 2 diabetes mellitus.

The development of type 2 diabetes mellitus (T2D) is associated with a number of genetic and environmental factors. Hyperglycemia, a T2D hallmark, is related to several metabolic complications, comorbidities and increased DNA damage. However, the molecular alterations of a proper glucose control are still unclarified. In this study, we aimed to evaluate DNA damage (comet assay), as well as to compare the transcriptional expression (mRNA and miRNA analyzed by the microarray technique) displayed by peripheral blood mononuclear cells (PBMCs) from three distinct groups: hyperglycemic T2D patients (T2D-H, n=14), non-hyperglycemic T2D patients (T2D-N, n=15), and healthy non-diabetic individuals (n=16). The comet assay revealed significantly (p<0.05) higher levels of DNA damage in T2D-H group compared to both T2D-N and control groups, while a significant difference was not observed between the control and T2D-N groups. After bioinformatics analysis, the differentially expressed mRNAs were subjected to functional enrichment analysis (DAVID) and inflammatory response was among the enriched terms found when comparing T2D-N with controls and T2D-H with T2D-N. Concerning the gene set enrichment and gene set analyses, among the differentially expressed gene sets, three were of interest: regulation of DNA repair (T2D-H versus T2D-N), superoxide response (T2D-H versus control group), and response to endoplasmic reticulum stress (T2D-H versus control group). We also identified miRNAs related with T2D and hyperglycemia not yet associated with these conditions in the literature. Some of the differentially expressed mRNAs were among the predicted targets of the differentially expressed miRNAs. Our results showed the association of hyperglycemia with increased DNA damage and aberrant expression of miRNAs and genes related to several biological processes, such as inflammation, DNA repair, ROS production and antioxidant defense, highlighting the importance of proper glycemic control. Moreover, the transcriptional expression of miRNAs provided novel information for understanding the regulatory mechanisms involved in the T2D progression.

Fasting hyperglycemia predicts lower rates of weight gain by increased energy expenditure and fat oxidation rate.

CONTEXT: Increased adiposity and insulin resistance are associated with hyperglycemia and previous studies have reported that higher glucoses are associated with lower rates of weight gain. One possible mechanism is via increased energy expenditure (EE). OBJECTIVE: To assess the relationships between changes in EE during spontaneous weight gain and concomitant changes in glucose levels. DESIGN AND PARTICIPANTS: Body composition, metabolic, and glycemic data were available from nondiabetic Native Americans who underwent two measurements of 24-h EE during eucaloric feeding in a metabolic chamber (N = 144; time between measurements: 5.0 ± 3.3 years) or resting EE by ventilated hood system during the euglycemic-hyperinsulinemic clamp (N = 261; 4.5 ± 3.2 years). Long-term follow-up data (8.3 ± 4.3 years) for weight and body composition were available in 131 and 122 subjects, respectively. MAIN OUTCOME MEASURES: Twenty four hour EE and respiratory quotient (RQ), resting (RMR), and sleeping (SMR) metabolic rates, glucose, and insulin levels, basal glucose output (BGO). RESULTS: Weight gain-associated increase in fasting plasma glucose (FPG) levels was accompanied with decreased 24-h RQ (partial R = -0.24, P = .002) and increased 24-h EE, RMR, SMR, and fat oxidation after accounting for changes in body composition (partial R: 0.12 to 0.19, all P ≤ .05). Upon weight gain, BGO tended to increase (P = .07), while insulin infusion induced a decrease in EE (P = .04). Higher baseline FPG predicted lower rates of future weight gain (partial R = -0.18, P = .04). CONCLUSIONS: Higher FPG after weight gain was associated with greater-than-expected increase in EE. The rise in BGO and the insulin-induced EE suppression at follow-up indicate that increased hepatic gluconeogenesis may be an important mediator of EE changes associated with weight gain.

Longitudinal assessment of neuroanatomical and cognitive differences in young children with type 1 diabetes: association with hyperglycemia.

Significant regional differences in gray and white matter volume and subtle cognitive differences between young diabetic and nondiabetic children have been observed. Here, we assessed whether these differences change over time and the relation with dysglycemia. Children ages 4 to <10 years with (n = 144) and without (n = 72) type 1 diabetes (T1D) had high-resolution structural MRI and comprehensive neurocognitive tests at baseline and 18 months and continuous glucose monitoring and HbA1c performed quarterly for 18 months. There were no differences in cognitive and executive function scores between groups at 18 months. However, children with diabetes had slower total gray and white matter growth than control subjects. Gray matter regions (left precuneus, right temporal, frontal, and parietal lobes and right medial-frontal cortex) showed lesser growth in diabetes, as did white matter areas (splenium of the corpus callosum, bilateral superior-parietal lobe, bilateral anterior forceps, and inferior-frontal fasciculus). These changes were associated with higher cumulative hyperglycemia and glucose variability but not with hypoglycemia. Young children with T1D have significant differences in total and regional gray and white matter growth in brain regions involved in complex sensorimotor processing and cognition compared with age-matched control subjects over 18 months, suggesting that chronic hyperglycemia may be detrimental to the developing brain.

Effects of dipeptidyl peptidase IV inhibition on glycemic, gut hormone, triglyceride, energy expenditure, and energy intake responses to fat in healthy males.

Fat is the most potent stimulus for glucagon-like peptide-1 (GLP-1) secretion. The aims of this study were to determine whether dipeptidyl peptidase IV (DPP-IV) inhibition would enhance plasma active incretin [glucose-dependent insulinotropic polypeptide (GIP), GLP-1] concentrations and modulate the glycemic, gut hormone, triglyceride, energy expenditure, and energy intake responses to intraduodenal fat infusion. In a double-blind, randomized, placebo-controlled crossover design, 16 healthy lean males received 50 mg vildagliptin (V), or matched placebo (P), before intraduodenal fat infusion (2 kcal/min, 120 min). Blood glucose, plasma insulin, glucagon, active GLP-1, and GIP and peptide YY (PYY)-(3-36) concentrations; resting energy expenditure; and energy intake at a subsequent buffet meal (time = 120-150 min) were quantified. Data are presented as areas under the curve (0-120 min, means ± SE). Vildagliptin decreased glycemia (P: 598 ± 8 vs. V: 573 ± 9 mmol·l⁻¹·min⁻¹, P < 0.05) during intraduodenal lipid. This was associated with increased insulin (P: 15,964 ± 1,193 vs. V: 18,243 ± 1,257 pmol·l⁻¹·min⁻¹, P < 0.05), reduced glucagon (P: 1,008 ± 52 vs. V: 902 ± 46 pmol·l⁻¹·min⁻¹, P < 0.05), enhanced active GLP-1 (P: 294 ± 40 vs. V: 694 ± 78 pmol·l⁻¹·min⁻¹) and GIP (P: 2,748 ± 77 vs. V: 4,256 ± 157 pmol·l⁻¹·min⁻¹), and reduced PYY-(3-36) (P: 9,527 ± 754 vs. V: 4,469 ± 431 pM/min) concentrations compared with placebo (P < 0.05, for all). Vildagliptin increased resting energy expenditure (P: 1,821 ± 54 vs. V: 1,896 ± 65 kcal/day, P < 0.05) without effecting energy intake. Vildagliptin 1) modulates the effects of intraduodenal fat to enhance active GLP-1 and GIP, stimulate insulin, and suppress glucagon, thereby reducing glycemia and 2) increases energy expenditure. These observations suggest that the fat content of a meal, by enhancing GLP-1 and GIP secretion, may contribute to the response to DPP-IV inhibition.

Assessment of the metabolic pathways associated with glucose-stimulated biphasic insulin secretion.

Biphasic glucose-stimulated insulin secretion involves a rapid first phase followed by a prolonged second phase of insulin secretion. The biochemical pathways that control these 2 phases of insulin secretion are poorly defined. In this study, we used a gas chromatography mass spectroscopy-based metabolomics approach to perform a global analysis of cellular metabolism during biphasic insulin secretion. A time course metabolomic analysis of the clonal ß-cell line 832/13 cells showed that glycolytic, tricarboxylic acid, pentose phosphate pathway, and several amino acids were strongly correlated to biphasic insulin secretion. Interestingly, first-phase insulin secretion was negatively associated with L-valine, trans-4-hydroxy-L-proline, trans-3-hydroxy-L-proline, DL-3-aminoisobutyric acid, L-glutamine, sarcosine, L-lysine, and thymine and positively with L-glutamic acid, flavin adenine dinucleotide, caprylic acid, uridine 5'-monophosphate, phosphoglycerate, myristic acid, capric acid, oleic acid, linoleic acid, and palmitoleic acid. Tricarboxylic acid cycle intermediates pyruvate, α-ketoglutarate, and succinate were positively associated with second-phase insulin secretion. Other metabolites such as myo-inositol, cholesterol, DL-3-aminobutyric acid, and L-norleucine were negatively associated metabolites with the second-phase of insulin secretion. These studies provide a detailed analysis of key metabolites that are either negatively or positively associated with biphasic insulin secretion. The insights provided by these data set create a framework for planning future studies in the assessment of the metabolic regulation of biphasic insulin secretion.

Assessment of pancreatic ß-cell function: review of methods and clinical applications.

Type 2 diabetes mellitus (T2DM) is characterized by a progressive failure of pancreatic ß-cell function (BCF) with insulin resistance. Once insulin over-secretion can no longer compensate for the degree of insulin resistance, hyperglycemia becomes clinically significant and deterioration of residual ß-cell reserve accelerates. This pathophysiology has important therapeutic implications. Ideally, therapy should address the underlying pathology and should be started early along the spectrum of decreasing glucose tolerance in order to prevent or slow ß-cell failure and reverse insulin resistance. The development of an optimal treatment strategy for each patient requires accurate diagnostic tools for evaluating the underlying state of glucose tolerance. This review focuses on the most widely used methods for measuring BCF within the context of insulin resistance and includes examples of their use in prediabetes and T2DM, with an emphasis on the most recent therapeutic options (dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists). Methods of BCF measurement include the homeostasis model assessment (HOMA); oral glucose tolerance tests, intravenous glucose tolerance tests (IVGTT), and meal tolerance tests; and the hyperglycemic clamp procedure. To provide a meaningful evaluation of BCF, it is necessary to interpret all observations within the context of insulin resistance. Therefore, this review also discusses methods utilized to quantitate insulin-dependent glucose metabolism, such as the IVGTT and the euglycemic-hyperinsulinemic clamp procedures. In addition, an example is presented of a mathematical modeling approach that can use data from BCF measurements to develop a better understanding of BCF behavior and the overall status of glucose tolerance.