Carbohydrates and insulin resistance in clinical nutrition: Recommendations from the ESPEN expert group.

Growing evidence underscores the important role of glycemic control in health and recovery from illness. Carbohydrate ingestion in the diet or administration in nutritional support is mandatory, but carbohydrate intake can adversely affect major body organs and tissues if resulting plasma glucose becomes too high, too low, or highly variable. Plasma glucose control is especially important for patients with conditions such as diabetes or metabolic stress resulting from critical illness or surgery. These patients are particularly in need of glycemic management to help lessen glycemic variability and its negative health consequences when nutritional support is administered. Here we report on recent findings and emerging trends in the field based on an ESPEN workshop held in Venice, Italy, 8-9 November 2015. Evidence was discussed on pathophysiology, clinical impact, and nutritional recommendations for carbohydrate utilization and management in nutritional support. The main conclusions were: a) excess glucose and fructose availability may exacerbate metabolic complications in skeletal muscle, adipose tissue, and liver and can result in negative clinical impact; b) low-glycemic index and high-fiber diets, including specialty products for nutritional support, may provide metabolic and clinical benefits in individuals with obesity, insulin resistance, and diabetes; c) in acute conditions such as surgery and critical illness, insulin resistance and elevated circulating glucose levels have a negative impact on patient outcomes and should be prevented through nutritional and/or pharmacological intervention. In such acute settings, efforts should be implemented towards defining optimal plasma glucose targets, avoiding excessive plasma glucose variability, and optimizing glucose control relative to nutritional support.

Sweeteners and health: findings from recent research and their impact on obesity and related metabolic conditions.

Few topics in nutrition engender more controversy than added sugars in general, and fructose-containing sugars in particular. Some investigators have argued that added sugars are associated with increased risk of obesity, cardiovascular disease, diabetes, non-alcoholic fatty liver disease and even sugar 'addiction'. Other investigators have questioned the scientific basis for all of these assertions. This debate has extended far beyond the scientific community into various media outlets including the internet and other non-refereed venues often with heated rhetoric and little science. Against this backdrop, a group of experts and researchers in the metabolism and health effects of added sugars presented a symposium 'Sweeteners and Health: Findings from Recent Research and their Impact on Obesity and Related Metabolic Conditions' at the European Congress on Obesity on 7 May 2015. The papers in this supplement are based on the presentations made at this meeting. The current article is intended to serve as an Introduction to this supplement.

What nutritional physiology tells us about diet, sugar and obesity.

In this closing perspective, the author exposes why targeting a single nutrient like sugar is in his opinion unlikely to be efficient in preventing obesity and metabolic diseases. He defends the proposal that the concept of fructose toxicity is based on major misconceptions of nutritional physiology. He specifically proposes that (1) sugar being a non-essential nutrient does not obligatorily imply that it has no beneficial effect; (2) alterations of blood triglyceride concentration and hepatic glucose production within the normal range may merely reflect adaptations to a fructose-rich diet rather than early markers of diseases; (3) overfeeding is a normal physiological response to exposure to an energy-dense, palatable nutrient rather than the consequence of 'leptin resistance'; (4) we may presently overemphasize the role of biological regulations and of gene-related heredity when assessing the effects of fructose in particular, and the determinants of obesity in general.

Physiological handling of dietary fructose-containing sugars: implications for health.

Fructose has always been present in our diet, but its consumption has increased markedly over the past 200 years. This is mainly due to consumption of sucrose or high-fructose corn syrup in industrial foods and beverages. Unlike glucose, fructose cannot be directly used as an energy source by all cells of the human body and needs first to be converted into glucose, lactate or fatty acids in the liver, intestine and kidney. Because of this specific two-step metabolism, some energy is consumed in splanchnic organs to convert fructose into other substrates, resulting in a lower net energy efficiency of fructose compared with glucose. A high intake of fructose-containing sugars is associated with body weight gain in large cohort studies, and fructose can certainly contribute to energy imbalance leading to obesity. Whether fructose-containing foods promote obesity more than other energy-dense foods remains controversial, however. A short-term (days-weeks) high-fructose intake is not associated with an increased fasting glycemia nor to an impaired insulin-mediated glucose transport in healthy subjects. It, however, increases hepatic glucose production, basal and postprandial blood triglyceride concentrations and intrahepatic fat content. Whether these metabolic alterations are early markers of metabolic dysfunction or merely adaptations to the specific two-step fructose metabolism remain unknown.

Effects of fructose and glucose overfeeding on hepatic insulin sensitivity and intrahepatic lipids in healthy humans.

OBJECTIVE: To assess how intrahepatic fat and insulin resistance relate to daily fructose and energy intake during short-term overfeeding in healthy subjects. DESIGN AND METHODS: The analysis of the data collected in several studies in which fasting hepatic glucose production (HGP), hepatic insulin sensitivity index (HISI), and intrahepatocellular lipids (IHCL) had been measured after both 6-7 days on a weight-maintenance diet (control, C; n = 55) and 6-7 days of overfeeding with 1.5 (F1.5, n = 7), 3 (F3, n = 17), or 4 g fructose/kg/day (F4, n = 10), with 3 g glucose/kg/day (G3, n = 11), or with 30% excess energy as saturated fat (fat30%, n = 10). RESULTS: F3, F4, G3, and fat30% all significantly increased IHCL, respectively by 113 ± 86, 102 ± 115, 59 ± 92, and 90 ± 74% as compared to C (all P < 0.05). F4 and G3 increased HGP by 16 ± 10 and 8 ± 11% (both P < 0.05), and F3 and F4 significantly decreased HISI by 20 ± 22 and 19 ± 14% (both P < 0.01). In contrast, there was no significant effect of fat30% on HGP or HISI. CONCLUSIONS: Short-term overfeeding with fructose or glucose decreases hepatic insulin sensitivity and increases hepatic fat content. This indicates short-term regulation of hepatic glucose metabolism by simple carbohydrates.

Hypertriglyceridemia: a potential side effect of propofol sedation in critical illness.

PURPOSE: Hypertriglyceridemia (hyperTG) is common among intensive care unit (ICU) patients, but knowledge about hyperTG risk factors is scarce. The present study aims to identify risk factors favoring its development in patients requiring prolonged ICU treatment. METHODS: Prospective observational study in the medicosurgical ICU of a university teaching hospital. All consecutive patients staying ≥4 days were enrolled. Potential risk factors were recorded: pathology, energy intake, amount and type of nutritional lipids, intake of propofol, glucose intake, laboratory parameters, and drugs. Triglyceride (TG) levels were assessed three times weekly. Statistics was based on two-way analysis of variance (ANOVA) and linear regression with potential risk factors. RESULTS: Out of 1,301 consecutive admissions, 220 patients were eligible, of whom 99 (45 %) presented hyperTG (triglycerides >2 mmol/L). HyperTG patients were younger, heavier, with more brain injury and multiple trauma. Intake of propofol (mg/kg/h) and lipids' propofol had the highest correlation with plasma TG (r (2) = 0.28 and 0.26, respectively, both p < 0.001). Infection and inflammation were associated with development of hyperTG [C-reactive protein (CRP), r (2) = 0.19, p = 0.004]. No strong association could be found with nutritional lipids or other risk factors. Outcome was similar in normo- and hyperTG patients. CONCLUSIONS: HyperTG is frequent in the ICU but is not associated with adverse outcome. Propofol and accompanying lipid emulsion are the strongest risk factors. Our results suggest that plasma TG should be monitored at least twice weekly in patients on propofol. The clinical consequences of propofol-related hyperTG should be investigated in further studies.

The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta-analysis.

Different outcomes of the effect of catechin-caffeine mixtures and caffeine-only supplementation on energy expenditure and fat oxidation have been reported in short-term studies. Therefore, a meta-analysis was conducted to elucidate whether catechin-caffeine mixtures and caffeine-only supplementation indeed increase thermogenesis and fat oxidation. First, English-language studies measuring daily energy expenditure and fat oxidation by means of respiration chambers after catechin-caffeine mixtures and caffeine-only supplementation were identified through PubMed. Six articles encompassing a total of 18 different conditions fitted the inclusion criteria. Second, results were aggregated using random/mixed-effects models and expressed in terms of the mean difference in 24 h energy expenditure and fat oxidation between the treatment and placebo conditions. Finally, the influence of moderators such as BMI and dosage on the results was examined as well. The catechin-caffeine mixtures and caffeine-only supplementation increased energy expenditure significantly over 24 h (428.0 kJ (4.7%); P < 0.001 and 429.1 kJ (4.8%); P < 0.001, respectively). However, 24 h fat oxidation was only increased by catechin-caffeine mixtures (12.2 g (16.0%); P < 0.02 and 9.5 g (12.4%); P = 0.11, respectively). A dose-response effect on 24 h energy expenditure and fat oxidation occurred with a mean increase of 0.53 kJ mg(-1) (P < 0.01) and 0.02 g mg(-1) (P < 0.05) for catechin-caffeine mixtures and 0.44 kJ mg(-1) (P < 0.001) and 0.01 g mg(-1) (P < 0.05) for caffeine-only. In conclusion, catechin-caffeine mixtures or a caffeine-only supplementation stimulates daily energy expenditure dose-dependently by 0.4-0.5 kJ mg(-1) administered. Compared with placebo, daily fat-oxidation was only significantly increased after catechin-caffeine mixtures ingestion.

Effects of short-term overfeeding with fructose, fat and fructose plus fat on plasma and hepatic lipids in healthy men.

AIMS: The present study aimed to assess the effects of excess fat, fructose and fat-plus-fructose intakes on intrahepatocellular lipid (IHCL). METHODS: Healthy male subjects were studied after an isocaloric diet or a 7-day high-fructose (Fru: +3.5 g fructose/kg fat-free mass/day, +35% energy), high-fat (Fat: +30% energy as saturated-fat) or high-fructose, high-fat diet (FruFat: +3.5 g fructose/kg fat-free mass/day, +30% energy as fat, +65% total energy). IHCL was measured by (1)H magnetic resonance spectroscopy. RESULTS: All hypercaloric diets increased IHCL (Fru: +16%; Fat: +86%; FruFat: +133%; P<0.05). Very low-density lipoprotein (VLDL) triacylglycerols increased after Fru (+58%; P<0.05), but decreased after Fat (-22%; P<0.05), while no change was observed after FruFat. CONCLUSION: Fat and fructose both increased IHCL, but fructose increased, while fat decreased, VLDL triacylglycerols. However, excess fat and fructose combined had additive effects on IHCL and neutralizing effects on VLDL triglycerides. This suggests that fructose stimulates, while fat inhibits, hepatic VLDL triacylglycerol secretion.

Glucose flux in controlled hyperglycaemia before and after oral glucose ingestion in men with mild type 2 diabetes.

AIMS: This study aimed to determine how insufficiently suppressed endogenous glucose production vs. reduced peripheral glucose uptake contribute to postprandial hyperglycaemia in type 2 diabetes (T2D). METHODS: Eight men with T2D (age: 52+/-7 years; BMI: 26.6+/-2.3 kg/m(2); fasting glycaemia: 7.1+/-1.5 mmol/L) were compared with eight non-diabetic controls (age: 51+/-5 years; BMI: 24.6+/-2.9 kg/m(2); fasting glycaemia: 4.9+/-0.4 mmol/L). Their glucose turnover rates and hepatic glucose cycles were measured by monitoring [2H7]glucose infusion, with m+7 and m+6 enrichment, 3 h before and 4 h after the ingestion of [6,6-2H2]-labelled glucose, while maintaining glycaemia at 10 mmol/L using the pancreatic clamp technique. RESULTS: Of the 700 mg/kg oral glucose load, 71% appeared in the systemic circulation of the T2D patients vs. 63% in the controls (NS). Endogenous glucose production and hepatic glucose cycles did not differ from normal either before or after oral glucose ingestion, while peripheral glucose uptake was reduced by 40% in the T2D group both before (P<0.01) and after (P<0.05) ingestion of oral glucose. CONCLUSION: When T2D patients were compared with non-diabetic subjects with similarly controlled levels of hyperglycaemia after oral glucose ingestion, they essentially differed only in peripheral glucose uptake, whereas endogenous glucose production was apparently unaltered.

Fuel metabolism during exercise in euglycaemia and hyperglycaemia in patients with type 1 diabetes mellitus--a prospective single-blinded randomised crossover trial.

AIMS/HYPOTHESIS: We assessed systemic and local muscle fuel metabolism during aerobic exercise in patients with type 1 diabetes at euglycaemia and hyperglycaemia with identical insulin levels. METHODS: This was a single-blinded randomised crossover study at a university diabetes unit in Switzerland. We studied seven physically active men with type 1 diabetes (mean +/- SEM age 33.5 +/- 2.4 years, diabetes duration 20.1 +/- 3.6 years, HbA1c 6.7 +/- 0.2% and peak oxygen uptake [VO2peak] 50.3 +/- 4.5 ml min(-1) kg(-1)). Men were studied twice while cycling for 120 min at 55 to 60% of VO2peak, with a blood glucose level randomly set either at 5 or 11 mmol/l and identical insulinaemia. The participants were blinded to the glycaemic level; allocation concealment was by opaque, sealed envelopes. Magnetic resonance spectroscopy was used to quantify intramyocellular glycogen and lipids before and after exercise. Indirect calorimetry and measurement of stable isotopes and counter-regulatory hormones complemented the assessment of local and systemic fuel metabolism. RESULTS: The contribution of lipid oxidation to overall energy metabolism was higher in euglycaemia than in hyperglycaemia (49.4 +/- 4.8 vs 30.6 +/- 4.2%; p < 0.05). Carbohydrate oxidation accounted for 48.2 +/- 4.7 and 66.6 +/- 4.2% of total energy expenditure in euglycaemia and hyperglycaemia, respectively (p < 0.05). The level of intramyocellular glycogen before exercise was higher in hyperglycaemia than in euglycaemia (3.4 +/- 0.3 vs 2.7 +/- 0.2 arbitrary units [AU]; p < 0.05). Absolute glycogen consumption tended to be higher in hyperglycaemia than in euglycaemia (1.3 +/- 0.3 vs 0.9 +/- 0.1 AU). Cortisol and growth hormone increased more strongly in euglycaemia than in hyperglycaemia (levels at the end of exercise 634 +/- 52 vs 501 +/- 32 nmol/l and 15.5 +/- 4.5 vs 7.4 +/- 2.0 ng/ml, respectively; p < 0.05). CONCLUSIONS/INTERPRETATION: Substrate oxidation in type 1 diabetic patients performing aerobic exercise in euglycaemia is similar to that in healthy individuals revealing a shift towards lipid oxidation during exercise. In hyperglycaemia fuel metabolism in these patients is dominated by carbohydrate oxidation. Intramyocellular glycogen was not spared in hyperglycaemia.

Fish oil after abdominal aorta aneurysm surgery.

OBJECTIVE: Fish oil (FO) may attenuate the inflammatory response after major surgery such as abdominal aortic aneurysm (AAA) surgery. We aimed at evaluating the clinical impact and safety aspects of a FO containing parenteral nutrition (PN) after AAA surgery. METHODS: Intervention consisted in 4 days of either standard (STD: Lipofundin medium-chain triglyceride (MCT): long-chain triglyceride (LCT)50%-MCT50%) or FO containing PN (FO: Lipoplus: LCT40%-MCT50%-FO10%). Energy target were set at 1.3 times the preoperative resting energy expenditure by indirect calorimetry. Blood sampling on days 0, 2, 3 and 4. Glucose turnover by the (2)H(2)-glucose method. Muscle microdialysis. CLINICAL DATA: maximal daily T degrees, intensive care unit (ICU) and hospital stay. RESULTS: Both solutions were clinically well tolerated, without any differences in laboratory safety parameters, inflammatory, metabolic data, or in organ failures. Plasma tocopherol increased similarly; with FO, docosahexaenoic and eicosapentaenoic acid increased significantly by day 4 versus baseline or STD. To increased postoperatively, with a trend to lower values in FO group (P=0.09). After FO, a trend toward shorter ICU stay (1.6+/-0.4 versus 2.3+/-0.4), and hospital stay (9.9+/-2.4 versus 11.3+/-2.7 days: P=0.19) was observed. CONCLUSIONS: Both lipid emulsions were well tolerated. FO-PN enhanced the plasma n-3 polyunsaturated fatty acid content, and was associated with trends to lower body temperature and shorter length of stay.

Effects of four-week high-fructose diet on gene expression in skeletal muscle of healthy men.

AIMS: A high-fructose diet (HFrD) may play a role in the obesity and metabolic disorders epidemic. In rodents, HFrD leads to insulin resistance and ectopic lipid deposition. In healthy humans, a four-week HFrD alters lipid homoeostasis, but does not affect insulin sensitivity or intramyocellular lipids (IMCL). The aim of this study was to investigate whether fructose may induce early molecular changes in skeletal muscle prior to the development of whole-body insulin resistance. METHODS: Muscle biopsies were taken from five healthy men who had participated in a previous four-week HFrD study, during which insulin sensitivity (hyperinsulinaemic euglycaemic clamp), and intrahepatocellular lipids and IMCL were assessed before and after HFrD. The mRNA concentrations of 16 genes involved in lipid and carbohydrate metabolism were quantified before and after HFrD by real-time quantitative PCR. RESULTS: HFrD significantly (P<0.05) increased stearoyl-CoA desaturase-1 (SCD-1) (+50%). Glucose transporter-4 (GLUT-4) decreased by 27% and acetyl-CoA carboxylase-2 decreased by 48%. A trend toward decreased peroxisomal proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) was observed (-26%, P=0.06). All other genes showed no significant changes. CONCLUSION: HFrD led to alterations of SCD-1, GLUT-4 and PGC-1alpha, which may be early markers of insulin resistance.

Adiposity in children born small for gestational age.

Epidemiological studies indicate that children born small for gestational age (SGA) have an increased risk of metabolic and cardiovascular disorders as adults. This suggests that foetal undernutrition leads to permanent metabolic alterations, which predispose to metabolic abnormalities upon exposure to environmental factors such as low physical activity and/or high-energy intake in later life (thrifty phenotype hypothesis). However, this relationship is not restricted to foetal undernutrition or intrauterine growth retardation, but is also found for children born premature, or for high birth weight children. Furthermore, early post-natal nutrition, and more specifically catch-up growth, appear to modulate cardiovascular risk as well. Intrauterine growth retardation can be induced in animal models by energy/protein restriction, or ligation of uterine arteries. In such models, altered glucose homeostasis, including low beta-cell mass, low insulin secretion and insulin resistance is observed after a few weeks of age. In humans, several studies have confirmed that children born SGA have insulin resistance as adolescents and young adults. Alterations of glucose homeostasis and increased lipid oxidation can indeed be observed already in non-diabetic children born SGA at early pubertal stages. These children also have alterations of stature and changes in body composition (increased fat mass), which may contribute to the pathogenesis of insulin resistance. Permanent metabolic changes induced by foetal/early neonatal nutrition (metabolic inprinting) may involve modulation of gene expression through DNA methylation, or alterations of organ structure. It is also possible that events occurring during foetal/neonatal development lead to long-lasting alterations of the hypothalamo-pituitary-adrenal axis or the hypothalamo-pituitary-insulin-like growth factor-1 axis.

Protein synthesis in jejunum and liver of neonatal calves fed vitamin A and lactoferrin.

Rates of protein synthesis (PS) and turnover are more rapid during the neonatal period than during any other stage of postnatal life. Vitamin A and lactoferrin (Lf) can stimulate PS in neonates. However, newborn calves are vitamin A deficient and have a low Lf status, but plasma vitamin A and Lf levels increase rapidly after ingestion of colostrum. Neonatal calves (n = 6 per group) were fed colostrum or a milk-based formula without or with vitamin A, Lf, or vitamin A plus Lf to study PS in the jejunum and liver. l-[(13)C]Valine was intravenously administered to determine isotopic enrichment of free (nonprotein-bound) Val (AP(Free)) in the protein precursor pool, atom percentage excess (APE) of protein-bound Val, fractional protein synthesis rate (FSR) in the jejunum and liver, and isotopic enrichment of Val in plasma (APE(Pla)) and in the CO(2) of exhaled air (APE(Ex)). The APE, AP(Free), and FSR in the jejunum and liver did not differ significantly among groups. The APE(Ex) increased, whereas APE(Pla) decreased over time, but there were no group differences. Correlations were calculated between FSR(Jej) and histomorphometrical and histochemical data of the jejunum, and between FSR(Liv) and blood metabolites. There were negative correlations between FSR(Liv) and plasma albumin concentrations and between FSR(Jej) and the ratio of villus height:crypt depth, and there was a positive correlation between FSR(Jej) and small intestinal cell proliferation in crypts. Hence, there were no effects of vitamin A and Lf and no interactions between vitamin A and Lf on intestinal and hepatic PS. However, FSR(Jej) was correlated with histomorphometrical traits of the jejunum and FSR(Liv) was correlated with plasma albumin concentrations.

Effects of colostrum feeding and glucocorticoid administration on insulin-dependent glucose metabolism in neonatal calves.

Colostrum feeding and glucocorticoid administration affect glucose metabolism and insulin release in calves. We have tested the hypothesis that dexamethasone as well as colostrum feeding influence insulin-dependent glucose metabolism in neonatal calves using the euglycemic-hyperinsulinemic clamp technique. Newborn calves were fed either colostrum or a milk-based formula (n=14 per group) and in each feeding group, half of the calves were treated with dexamethasone (30 microg/[kg body weight per day]). Preprandial blood samples were taken on days 1, 2, and 4. On day 5, insulin was infused for 3h and plasma glucose concentrations were kept at 5 mmol/L+/-10%. Clamps were combined with [(13)C]-bicarbonate and [6,6-(2)H]-glucose infusions for 5.5h (i.e., from -150 to 180 min, relative to insulin infusion) to determine glucose turnover, glucose appearance rate (Ra), endogenous glucose production (eGP), and gluconeogenesis before and at the end of the clamp. After the clamp liver biopsies were taken to measure mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC). Dexamethasone increased plasma glucose, insulin, and glucagon concentrations in the pre-clamp period thus necessitating a reduction in the rate of glucose infusion to maintain euglycemia during the clamp. Glucose turnover and Ra increased during the clamp and were lower at the end of the clamp in dexamethasone-treated calves. Dexamethasone treatment did not affect basal gluconeogenesis or eGP. At the end of the clamp, dexamethasone reduced eGP and PC mRNA levels, whereas mitochondrial PEPCK mRNA levels increased. In conclusion, insulin increased glucose turnover and dexamethasone impaired insulin-dependent glucose metabolism, and this was independent of different feeding.

[Adipocytokines: link between obesity, type 2 diabetes and atherosclerosis]. / Les adipocytokines: lien entre obésité, diabète de type 2 et athérosclérose?

Adipose tissue, in addition to the storage of lipids function for lipids, plays active roles in normal metabolic homeostasis and in the development of several diseases, such as type 2 diabetes, dyslipaemia and atherosclerosis. These roles are mediated by adipocytokines, factors secreted by adipose tissue. These include tumor necrosis factors (TNF)-alpha, leptin, resistin, adiponectin or visfatin. Adipocytokines act in an autocrine, paracrine and endocrine manner. Adiponectin is a peculiar adipocytokine because in contrast to the markedly increased levels of leptin, resistin or TNF-alpha in obesity, its level is negatively correlated with body mass index, and is decreased in presence of insulin resistance and in type 2 diabetes. Adiponectin may play a crucial role in the development of diabetes mellitus and high adiponectin levels should protect against impairment of glucose metabolism. Moreover, adipocytokines are involved in the pathogenesis of vascular diseases and may represent a link between obesity, diabetes, inflammation and atherosclerosis. Weight loss, exercise and some antidiabetic drugs also influence plasma adipocytokines levels. For instance, thiazolidinediones treatment in patients with type 2 diabetes resulted in an increased in plasma adiponectin levels and a decrease in circulating TNF-alpha concentrations.

Stress and metabolism.

Obesity, lipid disorders, type 2 diabetes, high blood pressure and coronary heart disease are frequently encountered in wealthy populations. All these disorders frequently occur as clusters, constituting the metabolic syndrome. It is currently admitted that insulin resistance plays a central role in the pathogenesis of this syndrome. Stress responses include activation of the sympathetic nervous system and stimulation of epinephrine and cortisol release. These hormones may over the long term reduce insulin sensitivity. Cortisol may also favour the development of central obesity. In healthy individuals, mental stress increases heart rate, but simultaneously decreases vascular resistance in skeletal muscle. This results in a moderate increase in blood pressure, and an acute increase in insulin-mediated glucose disposal. In obese patients, mental stress elicits responses which differ widely from those of healthy individuals. While mental stress enhances catecholamine-mediated energy expenditure in obese patients to the same extent as in lean subjects, it fails to decrease systemic vascular resistance due to endothelial dysfunction. This leads to enhanced blood pressure responses and the absence of stimulation of glucose disposal in obese subjects during mental stress. It can be hypothesized that repeated professional or social stress may activate the sympathoadrenal system, resulting in high cortisol levels, stimulation of the sympathetic nervous system, and epinephrine secretion. All these factors may eventually lead to the development of central obesity and insulin resistance. Furthermore, the blood pressure responses to mental stress may be enhanced in insulin-resistant individuals, favouring the development of vascular complications.

Dexamethasone-induced insulin resistance shows no gender difference in healthy humans.

OBJECTIVE: Recent reports suggest that lipid-induced insulin resistance is more pronounced in men than in women. Whether such gender difference exists for other factors known to induce insulin resistance in healthy individuals remains unknown. We therefore assessed whether glucocorticoid-induced insulin resistance differs in men and women. METHODS: The insulin sensitivity and insulin secretion of 8 women and 7 men, all non obese and healthy, were evaluated with or without administration of dexamethasone (2 mg/day during 2 days) by means of a two-step hyperglycemic clamp. RESULTS: Dexamethasone decreased insulin sensitivity to the same extent in men and women. The relative increases in insulin concentration observed after dexamethasone in the basal state, during the first phase of insulin release and at the two steps of hyperglycemia were similar in men and women. The hyperinsulinemia thus attained allowed to fully compensate for insulin resistance in both genders. CONCLUSIONS: The effects of glucocorticoids on insulin sensitivity and insulin secretion show no gender difference in healthy humans.