Clinical benefits of switching to insulin degludec irrespective of previous basal insulin therapy in people with Type 1 or Type 2 diabetes: evidence from a European, multicentre, retrospective, non-interventional study (EU-TREAT).

AIMS: To investigate whether the benefits of switching to insulin degludec observed in the European retrospective chart review study EU-TREAT were dependent on the previous basal insulin used. METHODS: People with Type 1 or Type 2 diabetes were switched to insulin degludec from other basal insulins ≥6 months before data collection. Participants were stratified into three groups based on their previous basal insulin: insulin glargine 100 units/ml (Type 1: n=888; Type 2: n=259); insulin detemir (Type 1: n=726; Type 2: n=415); and neutral protamine Hagedorn (Type 1: n=53; Type 2: n=95). Their glycaemic control and hypoglycaemia incidence at 6 and 12 months post-switch vs pre-switch was then evaluated. RESULTS: Significant HbA1c reductions were achieved in all previous basal insulin groups for participants with Type 1 diabetes [insulin glargine 100 units/ml: -2.08 mmol/mol (-0.19%); insulin detemir: -2.40 mmol/mol (-0.22%)] and those with Type 2 diabetes [insulin glargine 100 units/ml: -5.90 mmol/mol (-0.54%); insulin detemir: -6.01 mmol/mol (-0.55%); neutral protamine Hagedorn: -2.73 mmol/mol (-0.25%)] at 6 months, except for the relatively small neutral protamine Hagedorn group in those with Type 1 diabetes [-1.75 mmol/mol (-0.16%)], where statistical significance was not reached. At 6 months in the Type 1 diabetes group, switching to insulin degludec from insulin glargine 100 units/ml resulted in significantly lower hypoglycaemia rates across all hypoglycaemia categories; for the insulin detemir group, this significance was also observed for severe and nocturnal non-severe hypoglycaemia, while the low number of people in the neutral protamine Hagedorn group resulted in nonsignificant reductions in hypoglycaemia rates. At 6 months in the people with Type 2 diabetes, switching to insulin degludec resulted in significantly lower rates of hypoglycaemia across all categories for all groups. Similar outcomes were observed at 12 months. CONCLUSIONS: Switching to insulin degludec from other basal insulins can improve glycaemic control and/or reduce hypoglycaemia risk in people with diabetes (although there was a nonsignificant reduction in HbA1c and hypoglycaemia rates for the neutral protamine Hagedorn group in Type 1 diabetes) under routine care.

Correction factors for the calculation of metabolic equivalents (MET) in overweight to extremely obese subjects.

BACKGROUND/OBJECTIVES: The metabolic equivalent (MET) is a construct that is commonly used to quantify physical activity as well as exercise performance. 'One MET' is equal to a resting oxygen uptake of 3.5 ml O2 kg(-1) min(-)(1). However, this assumption is unlikely valid in obese subjects. The aim of our study was to quantify the difference between calculated and measured METs in overweight to severely obese subjects and to provide body mass index (BMI)-specific MET correction factors. SUBJECTS/METHODS: Resting oxygen uptake (VO2-REE) was measured in 1331 patients with a BMI >25 kg m(-2) (72.0% women; age: 42.5 ± 13.0 years; BMI: 42.5 ± 7.0 kg m(-)(2)) by indirect calorimetry and MET-REE, that is, VO2-REE related to body weight was calculated. Six hundred and fifty-two subjects (70.9% women) additionally underwent a bicycle cardiopulmonary exercise test for measurement of maximal MET (MET peak). RESULTS: Mean MET-REE was 2.47 ± 0.33 ml O2 kg(-1) min(-1) in women and 2.62 ± 0.34 ml O2 kg(-1) min(-1) in men, that is, markedly lower than the expected 3.5 ml O2 kg(-1) min(-1). MET-REE decreased with increasing BMI (P<0.001 for both sexes). On this dataset, gender-specific MET correction factors were developed for distinct BMI groups. During the exercise test, women performed 4.4 ± 1.3 MET peak and men 4.7 ± 1.3. After applying our correction factors, MET peak increased to 6.2 ± 1.7 and 6.1 ± 1.6, respectively. CONCLUSIONS: Data indicate that the commonly used 1-MET value of 3.5 ml O2 kg(-)(1) min(-)(1) largely overestimates values in overweight to severely obese subjects. Our correction factors can help to reduce this systematic error and thus appear to be valuable for clinical practice as well as research studies.

Altered brain activity in severely obese women may recover after Roux-en Y gastric bypass surgery.

OBJECTIVE: Neuroimaging studies have demonstrated alterations in brain activity in obese (OB) subjects that might be causally linked to their disorder. Roux-en Y gastric bypass (RYGB) surgery induces a marked and sustained weight loss and may affect brain activity. The aim of this study was to compare brain activity pattern between severely OB women (n=11), normal-weight women (NW, n=11) and previously severely OB women who had undergone RYGB surgery (RYGB, n=9) on average 3.4±0.8 years (all >1 year) before the experiment. DESIGN: Brain activity was assessed by functional magnetic resonance imaging during a one-back task containing food- and non-food-related pictures and during resting state. Hunger and satiety were repeatedly rated on a visual analog scale during the experiment. RESULTS: As compared with NW and also with RYGB women, OB women showed (1) a higher cerebellar and a lower fusiform gyrus activity during the visual stimulation independently of the picture category, (2) a higher hypothalamic activation during the presentation of low- vs high-caloric food pictures, (3) a higher hippocampal and cerebellar activity during the working memory task and (4) a stronger functional connectivity in frontal regions of the default mode network during resting state. There were no differences in brain activity between the NW and RYGB women, both during picture presentation and during resting state. RYGB women generally rated lower on hunger and higher on satiety, whereas there were no differences in these ratings between the OB and NW women. CONCLUSION: Data provide evidence for an altered brain activity pattern in severely OB women and suggest that RYGB surgery and/or the surgically induced weight loss reverses the obesity-associated alterations.

Intranasal administration of insulin to the brain impacts cognitive function and peripheral metabolism.

In recent years, the central nervous system (CNS) has emerged as a principal site of insulin action. This notion is supported by studies in animals relying on intracerebroventricular insulin infusion and by experiments in humans that make use of the intranasal pathway of insulin administration to the brain. Employing neurobehavioural and metabolic measurements as well as functional imaging techniques, these studies have provided insight into a broad range of central and peripheral effects of brain insulin. The present review focuses on CNS effects of insulin administered via the intranasal route on cognition, in particular memory function, and whole-body energy homeostasis including glucose metabolism. Furthermore, evidence is reviewed that suggests a pathophysiological role of impaired brain insulin signaling in obesity and type 2 diabetes, which are hallmarked by peripheral and possibly central nervous insulin resistance, as well as in conditions such as Alzheimer's disease where CNS insulin resistance might contribute to cognitive dysfunction.

Whole body vibration added to endurance training in obese women - a pilot study.

Whole body vibration (WBV) training is an increasingly popular training method that is strongly promoted for weight loss, but scientific data on its effectiveness, particularly in obese subjects, are sparse. 14 obese women (BMI: 37.4 ± 1.3 kg/m2) randomized to 2 different groups (each n=7) participated in a 6-week endurance training program that was either combined or not combined with additional WBV training. Anthropometric measures, phase angle and body composition (assessed by bioelectrical impedance analysis; BIA), and resting energy expenditure (REE) were obtained before and after the training program. Body weight did not change during the training period (P=0.87), but waist circumference decreased in both groups (P=0.007; WBV: -3.4 ± 1.4 cm; no-WBV: -1.7 ± 0.7 cm) independent of WBV training (P=0.29 for group×time interaction). BIA revealed an enhancing effect of WBV training in comparison to no-WBV training on the phase angle (+0.20 ± 0.12° vs. -0.19 ± 0.12°; P=0.04) and calculated body cell mass (+0.8 ± 0.2 vs. -0.3 ± 0.4 kg; P=0.02), while calculated percentage fat mass decreased in both conditions (P=0.05) to similar extent (P=0.59; WBV: -0.8 ± 0.2%; no-WBV: -0.4 ± 0.5%). REE increased across the training (P=0.01; WBV: +77 ± 33 kcal/24 h; no-WBV: +68 ± 34 kcal/24 h), with this increase again not depending on WBV condition (P=0.85). Results of our pilot study in obese women provide preliminary evidence for a beneficial effect of WBV, when added to endurance training, on the bioelectrical phase angle, an increasingly recognized marker of individual's health status.

[Disturbed sleep as risk factor for metabolic syndrome]. / Schlechter Schlaf als Risikofaktor für das metabolische Syndrom.

Sleep disorders, sleep fragmentation, and chronically reduced sleep duration are increasingly common in western societies. In parallel, incidence of the metabolic syndrome and its key components, i.e. type 2 diabetes and obesity, is rapidly increasing. A huge number of epidemiological studies has shown a robust association between disturbed sleep quality, reduced sleep duration and the development of components of the metabolic syndrome. Moreover, there is growing evidence from experimental studies proving a causal link between sleep loss and disturbed human energy homeostasis. Short term sleep loss has been shown to reduce insulin sensitivity and glucose tolerance, increase feelings of hunger by modulating orexigenic/anorexigenic hormonal signaling, and disturb physical activity behavior. This review attempts to present an overview of the presently available literature on the link between sleep loss and disturbed human energy homeostasis, as well as on potential pathophysiological mechanisms.

Central nervous insulin resistance: a promising target in the treatment of metabolic and cognitive disorders?

Research on functions and signalling pathways of insulin has traditionally focused on peripheral tissues such as muscle, fat and liver, while the brain was commonly believed to be insensitive to the effects of this hormone secreted by pancreatic beta cells. However, since the discovery some 30 years ago that insulin receptors are ubiquitously found in the central nervous system, an ever-growing research effort has conclusively shown that circulating insulin accesses the brain, which itself does not synthesise insulin, and exerts pivotal functions in central nervous networks. As an adiposity signal reflecting the amount of body fat, insulin provides direct negative feedback to hypothalamic nuclei that control whole-body energy and glucose homeostasis. Moreover, insulin affects distinct cognitive processes, e.g. by triggering the formation of psychological memory contents. Accordingly, metabolic and cognitive disorders such as obesity, type 2 diabetes mellitus and Alzheimer's disease are associated with resistance of central nervous structures to the effects of insulin, which may derive from genetic polymorphisms as well as from long-term exposure to excess amounts of circulating insulin due to peripheral insulin resistance. Thus, overcoming central nervous insulin resistance, e.g. by pharmacological interventions, appears to be an attractive strategy in the treatment and prevention of these disorders. Enhancement of central nervous insulin signalling by administration of intranasal insulin, insulin analogues and insulin sensitisers in basic research approaches has yielded encouraging results that bode well for the successful translation of these effects into future clinical practice.

Blocking AMPA receptor signalling by caroverine infusion does not affect counter-regulation of hypoglycaemia in healthy men.

AIMS/HYPOTHESIS: Glutamatergic pathways are assumed to play a critical role in the hormonal stress response to hypoglycaemia. In rats, glutamate signalling at the amino-3-hydroxy-5-methyl-4-isoxazol propionate (AMPA) receptor contributes to hormone release induced by behavioural stressors. We hypothesised that blocking the AMPA receptor by caroverine in healthy men would impair their perception of neuroglycopenia and thereby diminish hormonal counter-regulation as well as symptoms of hypoglycaemia, as a model of stress. METHODS: In a balanced double-blind study, two hypoglycaemic clamp sessions (mean blood glucose 2.4 mmol/l for 50 min) were performed in ten healthy men during intravenous administration of 80 mg caroverine or placebo. We assessed concentrations of counter-regulatory hormones as well as subjective symptoms related to hypoglycaemia. RESULTS: AMPA receptor antagonisation by caroverine did not influence the perception of neuroglycopenic and autonomic hypoglycaemia-associated symptoms (p > 0.39 for all). Notwithstanding, caroverine did increase basal and counter-regulatory glucagon secretion (p < 0.002) and slightly enhanced counter-regulatory growth hormone concentrations (p = 0.07). Counter-regulatory release of ACTH, cortisol, adrenaline (epinephrine) and noradrenaline (norepinephrine) did not differ between conditions (p > 0.11 for all). CONCLUSIONS/INTERPRETATION: Antagonising AMPA receptor signalling by caroverine infusion failed to diminish and even slightly amplified counter-regulatory hormone release during hypoglycaemia in healthy men. The discrepancy with previous findings in rats may be due to different dosages or administration routes and calls for further investigations on the role of AMPA receptor signalling in hypoglycaemia counter-regulation in humans.

Obese men respond to cognitive but not to catabolic brain insulin signaling.

CONTEXT AND OBJECTIVE: Insulin acts in the brain to reduce food intake and body weight and is considered a major adiposity signal in energy homeostasis. In normal-weight men, intranasal insulin administration reduces body fat and improves declarative memory. The present experiments aimed to generalize these findings to obese patients, with a view to evaluate the therapeutic potential of the compound. DESIGN, SUBJECTS AND MEASUREMENTS: Insulin and placebo, respectively, were intranasally administered four times a day (amounting to 160 IU day(-1)) over 8 weeks to two groups of 15 obese men each. RESULTS: Contrasting with the catabolic effects in normal-weight men, insulin treatment did not induce any significant reduction of body weight (P>0.50) and body fat (P>0.44) in the obese subjects. However, in accordance with the effects in normal-weight men, declarative memory and mood were improved (P<0.05) and hypothalamic-pituitary-adrenal axis activity as assessed by circulating ACTH (P<0.01) and cortisol levels (P<0.04) was reduced. CONCLUSIONS: Our results indicate that in obese men, intranasal insulin is functionally active in the central nervous system but fails to affect the neuronal networks critically involved in body weight regulation. We conclude that obesity in men is associated with central nervous resistance to the adiposity signal insulin. This defect likely contributes to the persistence of obesity in spite of elevated levels of circulating insulin in obese patients.

Short-term nocturnal hypoglycaemia increases morning food intake in healthy humans.

AIMS: Hypoglycaemia during wakefulness increases hunger and food intake. Patients with Type 1 diabetes mellitus are at high risk of recurrent hypoglycaemia and weight gain. Given the background of frequent hypoglycaemic episodes during night-time sleep in diabetic patients, we investigated morning food intake after nocturnal hypoglycaemia. METHODS: We tested 16 healthy normal-weight subjects (eight women) on three nights. A linear fall in plasma glucose to a nadir of 2.2 mmol/l within 60 min was induced by insulin infusion immediately after sleep onset ('early hypo') or after about 3.5 h of sleep ('late hypo'). On a control night, no hypoglycaemia was induced. Spontaneous food intake at a breakfast buffet was registered on the subsequent morning. RESULTS: Compared with the control condition (700 +/- 93 kcal), subjects ate more after 'late hypo' (867 +/- 108 kcal; P = 0.041), but not after 'early hypo' (852 +/- 111 kcal; P = 0.130). Analyses of macronutrient fractions revealed that in comparison with the control condition, subjects ate significantly more carbohydrates after both 'late hypo' (277 +/- 25 kcal vs. 206 +/- 23 kcal, P < 0.001) and 'early hypo' (245 +/- 23 kcal, P = 0.048), with this effect being more pronounced after late than early nocturnal hypoglycaemia (P = 0.026). CONCLUSIONS: In healthy subjects, nocturnal hypoglycaemia during sleep stimulates spontaneous food intake the following morning, with carbohydrate intake being especially affected. Effects were more pronounced after 'late hypo', suggesting the influence of temporal dynamics. Although healthy non-diabetic subjects were studied, similar mechanisms may contribute to the frequently observed body weight gain in insulin-treated diabetic patients.

Mood and cognitive functions during acute euglycaemia and mild hyperglycaemia in type 2 diabetic patients.

INTRODUCTION: Hyperglycaemia at levels above 15 mmol/l has been shown to impair cognitive functions in type 2 diabetic patients, while effects of mild hyperglycaemia and acute euglycaemia on mood and cognition have rarely been compared. We examined mood and cognitive functions in patients with T2DM during acute euglycaemia in comparison with moderate hyperglycaemia. METHODS: One euglycaemic (5 mmol/l) and one hyperglycaemic clamp (10.5 mmol/l) of 90 min each were performed in 15 T2DM patients in a balanced, single-blind, within-subject comparison. Mood, cognitive functions (assessed via short-term memory and attention tests) and symptoms related to glycaemic changes were assessed during a baseline period and during both glycaemic plateaus. In addition, patients estimated their blood glucose level and counterregulatory hormones were measured. RESULTS: None of the assessed aspects of cognitive functions differed between conditions (all p > or = 0.2). Patients rated higher on the well-being scale (p=0.04) and tended to feel less anger (p=0.08) during hyperglycaemia. Self-estimated blood glucose levels were higher during the hyper- than euglycaemic condition (8.6 +/- 2.5 vs 7.2 +/- 1.2 mmol/l; p<0.05) although most individual estimations did not match the actual glucose levels. Counterregulatory hormone levels did not differ (all p>0.25). CONCLUSIONS: Data indicate that T2DM patients are not cognitively impaired by moderate hyperglycaemia (10.5 mmol/l), pointing to the possibility of a glycaemic threshold for cognitive impairments at higher glycaemic levels.

Differential adaptation of neurocognitive brain functions to recurrent hypoglycemia in healthy men.

Antecedent hypoglycemia is known to attenuate hormonal and symptomatic responses to subsequent hypoglycemia. Whether this pertains also to hypoglycemia-induced cognitive dysfunction is controversially discussed. Neurocognitive adaptation might essentially depend on the type of function. Here, we compared the influence of recurrent hypoglycemia in 15 healthy men on counterregulatory hormones, subjective symptoms of hypoglycemia, short-term memory performance (word recall), and performance on an auditory attention task (oddball). The attention task was also used to record event-related brain potential (ERP) indicators of stimulus processing. In each subject, three consecutive hypoglycemic clamps were performed, two on day 1 and the third on day 2. Neurocognitive testing was performed during baseline and at two different hypoglycemic plateaus (2.8 and 2.5 mmol/l) during the first and last clamp. As expected, hormonal responses were significantly reduced to the last as compared to the first hypoglycemia indicating adaptation. Subjective symptoms also decreased in response to recurrent hypoglycemia. Short-term memory performance deteriorated distinctly on the first hypoglycemic clamp, but maintained the normal level on the last clamp (P=0.006). Likewise, the impairment in reaction time (P=0.022) and response accuracy (P=0.005) was distinctly smaller on the last than first hypoglycemia. In parallel, the hypoglycemia-induced decrease in P3 amplitude (P=0.019) and the increase in P3 latency (P=0.049) were diminished with recurrent hypoglycemia, indicating that late stages of controlled stimulus processing likewise adapted. In contrast, the distinct decrease in amplitudes of the N1 and P2 components of the ERP (preceding the P3) was closely comparable in response to the first and last hypoglycemia (P>0.3). Together results indicate an adaptation to recurrent hypoglycemia for signs of controlled stimulus processing presumably involving hippocampo-prefrontocortical circuitry, while earlier automatic stages of processing appear to be spared.

Sleep loss and the development of diabetes: a review of current evidence.

Emerging evidence suggests that short duration of sleep and sleep disturbances increase the risk of developing diabetes. The mechanism of this presumed adverse influence of sleep loss on glucose metabolism is not well understood yet. However, in diabetes research and diabetes care, the multitude of influences of sleep and sleep loss on glucose regulation has been largely neglected so far. Here, we provide a short overview of the current epidemiological and experimental evidence for a potential contribution of sleep loss to the development of diabetes.

Excess triiodothyronine as a risk factor of coronary events.

BACKGROUND: Abnormalities in cardiac function, eg, arrhythmias and congestive heart failure, often accompany thyrotoxicosis. A relationship between thyroid hormone excess and the cardiac complications of angina pectoris and myocardial infarction (MI) remains largely speculative. METHODS: The results of thyroid function studies on blood samples drawn from a total of 1049 patients (aged 40 years or older) immediately on emergency medical admission were related to frequencies of angina pectoris and myocardial infarction as determined according to current diagnostic algorithms. After 3 years, those patients who had initially presented with angina pectoris or acute MI were observed for subsequent coronary events; of these (n=185), 98% of the subjects (n=181) could be reevaluated. RESULTS: On hospital admission, the relative rate of angina pectoris and MI was markedly high (odds ratio, 2.6; 95% confidence interval, 1.3-5.2; P=.007) in patients with elevated serum free and total triiodothyronine (T(3)) levels. An initially elevated free T(3) level was a risk factor for subsequent coronary events during the 3-year follow-up (adjusted odds ratio, 4.8; 95% confidence interval, 1.3-17.4; P=.02). CONCLUSIONS: An elevation of serum free T(3) levels at hospital admission is associated with a 2.6-fold greater likelihood of the presence of a coronary event. Moreover, an initially elevated T(3) level is associated with a 3-fold higher risk of developing a subsequent coronary event during the next 3 years. Excess T(3) seemed to be a factor associated with the development and progression of acute myocardial ischemia.

Adaptation of cognitive function to hypoglycemia in healthy men.

OBJECTIVE: Antecedent hypoglycemia reduces hypoglycemic counterregulation and symptoms, thereby provoking the hypoglycemia unawareness syndrome. The effects of antecedent hypoglycemia on hypoglycemia-induced cognitive dysfunction are less well established. RESEARCH DESIGN AND METHODS: To determine whether antecedent hypoglycemia also reduces hypoglycemic cognitive dysfunction, we performed stepwise hypoglycemic clamp experiments (4.1, 3.6, 3.1, and 2.6 mmol/l) during a 6-h period in 30 young healthy men. A total of 15 subjects additionally received a 2.5-h antecedent hypoglycemic clamp (3.1 mmol/l) on the preceding day (prior-hypo group), whereas the other 15 subjects did not (control group). Cognitive function was assessed by auditory-evoked brain potentials (AEBPs) and reaction time during a vigilance task and short-term memory recall. Tests were performed during the stepwise hypoglycemic clamp at baseline and at each hypoglycemic plateau. RESULTS: In both groups, performance on all measures of cognitive function deteriorated during stepwise hypoglycemia (all P < 0.01). However, after antecedent hypoglycemia, the hypoglycemia-induced decrease in the amplitude of the P3 of the AEBP was distinctly reduced compared with the control condition (P < 0.05). Also, short-term memory performance was less impaired in the prior-hypo group than in the control group (P < 0.005), and a minor hypoglycemic impairment of reaction time (P < 0.05) was evident in the prior-hypo group. CONCLUSIONS: Data provide evidence that a single episode of mild antecedent hypoglycemia (3.1 mmol/l) attenuates several aspects of cognitive dysfunction during subsequent hypoglycemia 18-24 h later.

Plasma omentin-1 levels are related to exercise performance in obese women and increase upon aerobic endurance training.

INTRODUCTION: Omentin-1 is an adipokine that is primarily released from visceral adipose tissue stromal cells. The effects of exercise on omentin-1 regulation are not clear so far. Therefore, the effect of endurance training on circulating omentin-1 levels and its relation to exercise performance was assessed in obese women. METHODS: 13 obese women (age: 44.8±3.3 years; BMI: 37.8±1.3 kg·m(-2)) participated in a 6-week endurance training program. Omentin-1, metabolic traits (glucose, insulin, HOMA-IR, lipids profile), and exercise performance (cardiopulmonary exercise test (V̇O2,peak, Wpeak), 6 min walking test, 6MWT) were assessed before and after the training. RESULTS: After the training program circulating omentin-1 were 10.4% higher than before the program (690±50 ng·ml(-1) vs. 618±42; p=0.04), while body weight remained unchanged (p=0.9). Before training, omentin-1 levels were significantly correlated with Wpeak (given in absolute and relative values) as well as with 6MWT (all r≥0.603; all p≤0.029) and the correlations with absolute as well as relativeV̇O2,peak approached significance (both r≥0.534; both p≤0.060). After training, respective correlations were generally weaker and did not reach significance any longer (all r≤0.465; all p≥0.109). Neither before nor after the training program were significant correlations found between omentin-1 levels and the other measured metabolic blood markers (all p≥0.157). DISCUSSION: Data show a rather strong relationship between exercise performance and circulating omentin-1 levels as well as an increase of the adipokine in response to 6-week of endurance training in obese women. Our findings may hint to a skeletal muscle-adipose tissue crosstalk in regard of omentin-1 regulation.

The selfish brain: competition for energy resources.

The brain occupies a special hierarchical position in the organism. It is separated from the general circulation by the blood-brain barrier, has high energy consumption and a low energy storage capacity, uses only specific substrates, and it can record information from the peripheral organs and control them. Here we present a new paradigm for the regulation of energy supply within the organism. The brain gives priority to regulating its own adenosine triphosphate (ATP) concentration. In that postulate, the peripheral energy supply is only of secondary importance. The brain has two possibilities to ensure its energy supply: allocation or intake of nutrients. The term 'allocation' refers to the allocation of energy resources between the brain and the periphery. Neocortex and the limbic-hypothalamus-pituitary-adrenal (LHPA) system control the allocation and intake. In order to keep the energy concentrations constant, the following mechanisms are available to the brain: (1) high and low-affinity ATP-sensitive potassium channels measure the ATP concentration in neurons of the neocortex and generate a 'glutamate command' signal. This signal affects the brain ATP concentration by locally (via astrocytes) stimulating glucose uptake across the blood-brain barrier and by systemically (via the LHPA system) inhibiting glucose uptake into the muscular and adipose tissue. (2) High-affinity mineralocorticoid and low-affinity glucocorticoid receptors determine the state of balance, i.e. the setpoint, of the LHPA system. This setpoint can permanently and pathologically be displaced by extreme stress situations (chronic metabolic and psychological stress, traumatization, etc.), by starvation, exercise, infectious diseases, hormones, drugs, substances of abuse, or chemicals disrupting the endocrine system. Disorders in the 'energy on demand' process or the LHPA-system can influence the allocation of energy and in so doing alter the body mass of the organism. In summary, the presented model includes a newly discovered 'principle of balance' of how pairs of high and low-affinity receptors can originate setpoints in biological systems. In this 'Selfish Brain Theory', the neocortex and limbic system play a central role in the pathogenesis of diseases such as anorexia nervosa and obesity.

Hypoglycemia, but not insulin, acutely decreases LH and T secretion in men.

Hypoandrogenemia is frequently associated with hyperinsulinemia in men with the metabolic syndrome. We questioned whether insulin or changes in blood glucose levels influence pituitary gonadotropin secretion or testicular steroidogenesis in healthy men. Also, the relationship between hypoglycemia-induced activation of the hypothalamus-pituitary-adrenal axis and altered steroidogenesis was examined. Euglycemic and hypoglycemic clamp experiments were performed in 30 healthy men over a period of 6 h. Half of the men were infused with insulin at a rate of 1.5 mU/min.kg; the other half were infused at a rate of 15.0 mU/min.kg. Plasma glucose was held constant during a euglycemic clamp session and was decreased stepwise in a hypoglycemic clamp session. LH and total/free T concentrations decreased under hypoglycemic conditions regardless of the rate of insulin infusion. With euglycemic conditions, LH and T levels remained unchanged. Dehydroepiandrosterone concentrations increased during hypoglycemia, but not during the euglycemic conditions. The FSH concentration was not affected by insulin or glycemic clamps. Hypoglycemia acutely suppresses T secretion, and this effect is apparently mediated by pituitary LH. Insulin is ineffective. As counterregulation to hypoglycemia begins at normoglycemic ranges in poorly controlled type 2 diabetes and probably also in patients with long-term perturbed glucose regulation in the metabolic syndrome, control of glucose-responsive neurons in the brain may contribute to hypoandrogenemia. Apart from down-regulation of hypothalamic release of GnRH, concurrent activation of the pituitary-adrenal axis (i.e. increased release of dehydroepiandrosterone) may add to the suppressive effect of hypoglycemia on gonadal steroidogenesis.

Glucose metabolism rather than insulin is a main determinant of leptin secretion in humans.

Circulating plasma insulin and glucose levels are thought to be major regulators of leptin secretion. There is evidence from in vitro and animal experiments that glucose metabolism rather than insulin alone is a main determinant of leptin expression. Here, we tested the hypothesis that in humans also leptin secretion is primarily regulated by glucose uptake and only secondarily by plasma insulin and glucose. In 30 lean and healthy men we induced 4 experimental conditions by using the blood glucose clamp technique. A total of 60 hypoglycemic and euglycemic clamps, lasting 6 h each, were performed. During these clamps insulin was infused at either high (15.0 mU/min x kg) or low (1.5 mU/min x kg) rates, resulting in low-insulin-hypo, high-insulin-hypo, low-insulin-eu, and high-insulin-eu conditions. Serum leptin increased from 0-360 min by 20.5 +/- 4.1% in the low-insulin-hypo, 33.6 +/- 7.6% in the high-insulin-hypo, 39.6 +/- 6.0% in the low-insulin-eu, and 60.4 +/- 7.6% in the high-insulin-eu condition. Multiple regression analysis revealed a significant effect of circulating insulin (low vs. high insulin; P = 0.001) and blood glucose (hypoglycemia vs. euglycemia; P = 0.001) on the rise of serum leptin. However, when the total amount of dextrose infused during the clamp (grams of dextrose per kg BW) was included into the regression model, this variable was significantly related to the changes in serum leptin (P = 0.001), whereas circulating insulin and glucose had no additional effect. These findings in humans support previous in vitro data that leptin secretion is mainly related to glucose metabolism.

Supraphysiological hyperinsulinemia acutely increases hypothalamic-pituitary-adrenal secretory activity in humans.

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis in association with hyperinsulinemia is frequently found in patients with type 1 and type 2 diabetes mellitus and in subjects with abdominal adiposity. We questioned whether insulin could cause HPA axis activation and, if so, whether this insulin action may arise at the adrenal level or at a central (i.e. hypothalamic-pituitary) level. Experiments lasting for 6 h each were done in 30 lean healthy men. In 15 men, insulin was infused at a rate of 1.5 mU min(-1) kg(-1). Plasma glucose concentration was held constant during an euglycemic clamp session and was decreased stepwise in a hypoglycemic clamp session. The sequence of the 2 clamp sessions was random, and a 4-weeks recovery period was allowed between the two sessions. The protocol was essentially the same in another 15 men, with the exception that insulin was infused at a rate of 15.0 mU min(-1) kg(-1). During the euglycemic clamp sessions, we found plasma ACTH levels to increase only in the high-, but not in the low-insulin group (group by time interaction, P < 0.01); serum cortisol levels were greater in the high than in the low-insulin group (P < 0.02). In the hypoglycemic clamp sessions, plasma ACTH levels increased in the same pattern in the 2 groups; serum cortisol was greater in the high than in the low-insulin group at the beginning of the clamp (plasma glucose approximately 4.1 mmol/L; P < 0.05). Our results demonstrate that insulin acutely stimulates the HPA secretory activity in humans. The pattern suggests an effect of insulin at both peripheral and central levels of the HPA axis.