Search

Background: Several human and rodent studies suggest that in addition to the amount of energy consumed, timing of food intake contributes to body weight regulation. Consuming most energy in the morning has favorable effects on weight loss and weight maintenance. Whether this also affects glucose metabolism and liver fat independently from weight loss is unknown., Objective: We hypothesized that during weight loss, consuming most energy in the morning improves insulin sensitivity and reduces hepatic fat content more than consuming most energy in the evening., Methods: Twenty-three obese insulin resistant men (age 59.9±7.9 years, body mass index 34.4±3.8 kg m -2 ) followed a 4-week hypocaloric diet intervention with either 50% of daily energy consumed in the morning (BF group) or evening (D group). Insulin sensitivity, measured with a two-step hyperinsulinemic euglycemic clamp using a glucose tracer, intrahepatic triglycerides (IHTG), measured using magnetic resonance spectroscopy, and resting energy expenditure (REE) were assessed before and after the diet intervention., Results: Meal macronutrient composition and weight loss (6.5±1.5% vs 6.2±1.9%, respectively, P=0.70) did not differ between the BF and D groups. Endogenous glucose production (P⩽0.001), hepatic and peripheral insulin sensitivity (P=0.002; P=0.001, respectively) as well as IHTG content (P⩽0.001) all significantly improved with weight loss, but were not different between the BF and D groups. In addition, both groups decreased REE and respiratory quotient equally., Conclusions: During weight loss, consuming most energy in the morning instead of the evening does not have additional beneficial effects on insulin sensitivity and IHTG content. These results do not support weight independent effects of meal timing on glucose metabolism and IHTG in hypocaloric conditions in obese men.

The brain is well known to regulate blood glucose, and the hypothalamus and hindbrain, in particular, have been studied extensively to understand the underlying mechanisms. Nuclei in these regions respond to alterations in blood glucose concentrations and can alter glucose liver output or glucose tissue uptake to maintain blood glucose concentrations within strict boundaries. Interestingly, several cortico-limbic regions also respond to alterations in glucose concentrations and have been shown to project to hypothalamic nuclei and glucoregulatory organs. For instance, electrical stimulation of the shell of the nucleus accumbens (sNAc) results in increased circulating concentrations of glucose and glucagon and activation of the lateral hypothalamus (LH). Whether this is caused by the simultaneous increase in serotonin release in the sNAc remains to be determined. To study the effect of sNAc serotonin on systemic glucose metabolism, we implanted bilateral microdialysis probes in the sNAc of male Wistar rats and infused fluoxetine, a serotonin reuptake inhibitor, or vehicle after which blood glucose, endogenous glucose production (EGP) and glucoregulatory hormones were measured. Fluoxetine in the sNAc for 1h significantly increased blood glucose concentrations without an effect on glucoregulatory hormones. This increase was accompanied by a higher EGP in the fluoxetine infused rats compared to the controls. These data provide further evidence for a role of sNAc-serotonin in the regulation of glucose metabolism., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Aim: Vitamin D deficiency has been proposed to be involved in obesity-induced metabolic disease. However, data on the relationship between 25-hydroxycholecalciferol (25(OH)D) and insulin resistance have been inconsistent, and few studies have investigated the active vitamin D metabolite, 1,25-dihydroxycholecalciferol (1,25(OH) 2 D). This study aimed to determine the relationship between circulating levels of both 25(OH)D and 1,25(OH) 2 D and direct measures of glucose metabolism and insulin action in obese women., Methods: Serum levels of 25(OH)D and 1,25(OH) 2 D, and glucose metabolism and tissue-specific insulin action, as assessed in the basal state and during a two-step euglycaemic-hyperinsulinaemic clamp study with [6,6- 2 H 2 ]glucose infusion, were measured in 37 morbidly obese women (age: 43±10 years; body mass index: 44±6kg/m 2 )., Results: Sixteen subjects had circulating 25(OH)D levels<50nmol/L, consistent with vitamin D deficiency, and 21 had normal 25(OH)D levels. There were no differences in either baseline characteristics or parameters of glucose metabolism and insulin action between the groups. Serum 25(OH)D, but not 1,25(OH) 2 D, was negatively correlated with both body mass index (r=-0.42, P=0.01) and total body fat (r=-0.46, P<0.01). Neither 25(OH)D nor 1,25(OH) 2 D levels were related to any measured metabolic parameters, including fasting glucose, fasting insulin, basal endogenous glucose production, and hepatic, adipose-tissue and skeletal muscle insulin sensitivity., Conclusion: Obesity was associated with lower levels of circulating 25(OH)D, but not with the hormonally active metabolite 1,25(OH) 2 D. Neither 25(OH)D nor 1,25(OH) 2 D were related to glucose metabolism and tissue-specific insulin sensitivity in obese women, suggesting that vitamin D does not play a major role in obesity-related insulin resistance., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Background/objectives: Insulin resistance is the major contributor to cardiometabolic complications of obesity. We aimed to (1) establish cutoff points for insulin resistance from euglycemic hyperinsulinemic clamps (EHCs), (2) identify insulin-resistant obese subjects and (3) predict insulin resistance from routinely measured variables., Subjects/methods: We assembled data from non-obese (n=112) and obese (n=100) men who underwent two-step EHCs using [6,6-(2)H2]glucose as tracer (insulin infusion dose 20 and 60 mU m(-2) min(-1), respectively). Reference ranges for hepatic and peripheral insulin sensitivity were calculated from healthy non-obese men. Based on these reference values, obese men with preserved insulin sensitivity or insulin resistance were identified., Results: Cutoff points for insulin-mediated suppression of endogenous glucose production (EGP) and insulin-stimulated glucose disappearance rate (Rd) were 46.5% and 37.3 μmol kg(-)(1) min(-)(1), respectively. Most obese men (78%) had EGP suppression within the reference range, whereas only 12% of obese men had Rd within the reference range. Obese men with Rd <37.3 μmol kg(-1) min(-1) did not differ from insulin-sensitive obese men in age, body mass index (BMI), body composition, fasting glucose or cholesterol, but did have higher fasting insulin (110±49 vs 63±29 pmol l(-1), P<0.001) and homeostasis model assessment of insulin resistance (HOMA-IR) (4.5±2.2 vs 2.7±1.4, P=0.004). Insulin-resistant obese men could be identified with good sensitivity (80%) and specificity (75%) from fasting insulin >74 pmol l(-1)., Conclusions: Most obese men have hepatic insulin sensitivity within the range of non-obese controls, but below-normal peripheral insulin sensitivity, that is, insulin resistance. Fasting insulin (>74 pmol l(-1) with current insulin immunoassay) may be used for identification of insulin-resistant (or metabolically unhealthy) obese men in research and clinical settings.

Background: The best strategy to identify women with gestational diabetes mellitus (GDM) is unclear., Objectives: To perform a systematic review to calculate summary estimates of the sensitivity and specificity of the 50-g glucose challenge test for GDM., Search Strategy: Systematic search of MEDLINE, EMBASE and Web of Science., Selection Criteria: Articles that compared the 50-g glucose challenge test with the oral glucose tolerance test (OGTT, with a 75- or 100-g reference standard) before 32 weeks of gestation., Data Collection and Analysis: Summary estimates of sensitivity and specificity, with 95% confidence intervals and summary receiver operating characteristic curves, were calculated using bivariate random-effects models. Two reviewers independently selected articles that compared the 50 g glucose challenge test to the oral glucose tolerance test (OGTT, 75 or 100 gram, reference standard) before 32 weeks of gestation., Main Results: Twenty-six studies were included (13,564 women). Studies that included women with risk factors showed a pooled sensitivity of the 50-g glucose challenge test of 0.74 (95% CI 0.62-0.87), a pooled specificity of 0.77 (95% CI 0.66-0.89) (threshold value of 7.8 mmol/l), a derived positive likelihood ratio (LR) of 3.2 (95% CI 2.0-5.2) and a negative LR of 0.34 (95% CI 0.22-0.53). In studies with consecutive recruitment, the pooled sensitivity was 0.74 (95% CI 0.62-0.87) for a specificity of 0.85 (95% CI 0.80-0.91), with a derived positive LR of 4.9 (95% CI 3.5-7.0) and negative LR of 0.31 (95% CI 0.20-0.47). Increasing the threshold for disease (OGTT result) increased the sensitivity of the challenge test, and decreased the specificity., Author's Conclusions: The 50-g glucose challenge test is acceptable to screen for GDM, but cannot replace the OGTT. Further possibilities of combining the 50-g glucose challenge test with other screening strategies should be explored., (© 2012 The Authors BJOG An International Journal of Obstetrics and Gynaecology © 2012 RCOG.)

Aim/hypothesis: To assess whether low-dose glucocorticoid treatment induces adverse metabolic effects, as is evident for high glucocorticoid doses., Methods: In a randomised placebo-controlled double-blind (participants and the investigators who performed the studies and assessed the outcomes were blinded) dose-response intervention study, 32 healthy men (age 22 ± 3 years; BMI 22.4 ± 1.7 kg/m(2)) were allocated to prednisolone 7.5 mg once daily (n = 12), prednisolone 30 mg once daily (n = 12), or placebo (n = 8) for 2 weeks using block randomisation. Main outcome measures were glucose, lipid and protein metabolism, measured by stable isotopes, before and at 2 weeks of treatment, in the fasted state and during a two-step hyperinsulinaemic clamp conducted in the Clinical Research Unit of the Academic Medical Centre, Amsterdam, the Netherlands, Results: Prednisolone, compared with placebo, dose dependently and significantly increased fasting plasma glucose levels, whereas only prednisolone 30 mg increased fasting insulin levels (29 ± 15 pmol/l). Prednisolone 7.5 mg and prednisolone 30 mg decreased the ability of insulin to suppress endogenous glucose production (by 17 ± 6% and 46 ± 7%, respectively, vs placebo). Peripheral glucose uptake was not reduced by prednisolone 7.5 mg, but was decreased by prednisolone 30 mg by 34 ± 6% (p < 0.0001). Compared with placebo, prednisolone treatment tended to decrease lipolysis in the fasted state (p = 0.062), but both prednisolone 7.5 mg and prednisolone 30 mg decreased insulin-mediated suppression of lipolysis by 11 ± 5% and 34 ± 6%, respectively. Finally, prednisolone treatment increased whole-body proteolysis during hyperinsulinaemia, which tended to be driven by prednisolone 30 mg (5 ± 2%; p = 0.06). No side effects were reported by the study participants. All participants completed the study and were analysed., Conclusions/interpretation: Not only at high doses but also at low doses, glucocorticoid therapy impaired intermediary metabolism by interfering with the metabolic actions of insulin on liver and adipose tissue. These data indicate that even low-dose glucocorticoids may impair glucose tolerance when administered chronically., Trial Registration: ISRCTN83991850.