The epidemiology of hyperuricaemia and gout in Taiwan aborigines

To determine the prevalence of hyperuricaemia, gout and gout-related factors in Central Taiwan Atayal aborigines, 342 subjects over 18 yr old were interviewed and examined. A questionnaire was designed to screen for signs and symptoms of gout and gout-related risk factors. Serum uric acid, triglyceride and creatinine were measured in all subjects. The prevalence of hyperuricaemia was 41.4% and that of gout 11.7% in aborigines. The uric acid level was 7.9+/-1.7 mg/dl in males and 5.7+/-1.5 in females, and differed significantly under age 70 yr (P < 0.001). Significantly increased triglyceride, creatinine and alcoholism was found in gouty patients compared with non-gouty patients. In 40 cases with gout, 54% had tophi and 35% of their first- degree relatives had gout. The high prevalence of hyperuricaemia and gout in Taiwan Atayal aborigines, a significant family predisposition, increased creatinine level and alcoholism suggest multiple factors affecting the hyperuricaemia.      

Acute effects of ghrelin administration on glucose and lipid metabolism

CONTEXT: Ghrelin infusion increases plasma glucose and nonesterified fatty acids, but it is uncertain whether this is secondary to the concomitant release of GH. OBJECTIVE: Our objective was to study direct effects of ghrelin on substrate metabolism. DESIGN: This was a randomized, single-blind, placebo-controlled two-period crossover study. SETTING: The study was performed in a university clinical research laboratory. PARTICIPANTS: Eight healthy men aged 27.2 +/- 0.9 yr with a body mass index of 23.4 +/- 0.5 kg/m(2) were included in the study. INTERVENTION: Subjects received infusion of ghrelin (5 pmol x kg(-1) x min(-1)) or placebo for 5 h together with a pancreatic clamp (somatostatin 330 microg x h(-1), insulin 0.1 mU x kg(-1) x min(-1), GH 2 ng x kg(-1) x min(-1), and glucagon 0.5 ng.kg(-1) x min(-1)). A hyperinsulinemic (0.6 mU x kg(-1) x min(-1)) euglycemic clamp was performed during the final 2 h of each infusion. RESULTS: Basal and insulin-stimulated glucose disposal decreased with ghrelin [basal: 1.9 +/- 0.1 (ghrelin) vs. 2.3 +/- 0.1 mg x kg(-1) x min(-1), P = 0.03; clamp: 3.9 +/- 0.6 (ghrelin) vs. 6.1 +/- 0.5 mg x kg(-1) x min(-1), P = 0.02], whereas endogenous glucose production was similar. Glucose infusion rate during the clamp was reduced by ghrelin [4.0 +/- 0.7 (ghrelin) vs. 6.9 +/- 0.9 mg.kg(-1) x min(-1); P = 0.007], whereas nonesterified fatty acid flux increased [131 +/- 26 (ghrelin) vs. 69 +/- 5 micromol/min; P = 0.048] in the basal period. Regional lipolysis (skeletal muscle, sc fat) increased insignificantly with ghrelin infusion. Energy expenditure during the clamp decreased after ghrelin infusion [1539 +/- 28 (ghrelin) vs. 1608 +/- 32 kcal/24 h; P = 0.048], but the respiratory quotient did not differ. Minor but significant elevations in serum levels of GH and cortisol were observed after ghrelin infusion. CONCLUSIONS: Administration of exogenous ghrelin causes insulin resistance in muscle and stimulates lipolysis; these effects are likely to be direct, although a small contribution of GH and cortisol cannot be excluded.     

Preserved circadian rhythm of serum insulin concentration at low plasma glucose during fasting in lean and overweight humans

Circadian rhythms in glucose metabolism are well documented. Most studies, however, evaluated such variations under conditions of continuous glucose supply, either via food intake or glucose infusion. Here we assessed in 30 subjects circadian variations in concentrations of plasma glucose, serum insulin, and C-peptide during a 72-hour fasting period to evaluate rhythms independent from glucose supply. Furthermore we assessed differences in these parameters between normal-weight (n = 20) and overweight (n = 10) subjects. Blood was sampled every 4 hours. During fasting, plasma glucose, serum insulin, and C-peptide levels gradually decreased (all P < .001). While there was no circadian variation in plasma glucose levels after the first day of fasting, serum levels of insulin were constantly higher in the morning (8.00 h) than at night (0.00 h) (P < .001), although the extent of this morning-associated rise in insulin levels decreased with the time spent fasting (P = .001). Also, morning C-peptide concentrations were higher compared to the preceding night (P < .001). The C-peptide/insulin ratio (CIR) decreased during prolonged fasting (P = .030), suggesting a decrease in hepatic insulin clearance. Moreover, CIR was significantly lower in the morning than at the night of day 1 and day 2 of fasting (P = .010 and P = .004, respectively). Compared to normal-weight subjects, overweight subjects had higher plasma glucose, as well as serum insulin and C-peptide levels (all P < .03). Data indicate preserved circadian rhythms in insulin concentrations in the presence of substantially decreased glucose levels in normal-weight and overweight subjects. This finding suggests a central nervous system contribution to the regulation of insulin secretion independent of plasma glucose levels.     

The effect of experimentally induced insulin resistance on the leptin response to hyperinsulinaemia

OBJECTIVE: Insulin is thought to be an important regulator of leptin secretion. However, increasing evidence suggests that insulin-mediated glucose uptake rather than insulin per se regulates circulating leptin concentration. Here, we hypothesised that a reduction of insulin sensitivity, ie insulin resistance, will diminish the stimulatory effect of insulin on leptin secretion as a consequence of decreased insulin-mediated glucose uptake. DESIGN: Changes in serum leptin concentration during 30 hyperinsulinaemic-hypoglycaemic clamps were studied after induction of different levels of insulin resistance in normal-weight men. In 15 subjects insulin sensitivity was reduced by exposing them to a 2.5 h antecedent hypoglycaemia (3.1 mmol/l) induced by a high rate of insulin infusion (15.0 mU/min/kg) on the day before the proper experiment ('ante-hypo' condition). In the other 15 subjects no antecedent hypoglycaemia was induced ('control' condition). The proper experiment on both conditions was a 6 h stepwise hypoglycaemic clamp induced by a constant rate of insulin infusion (1.5 mU/min/kg). SUBJECTS: Experiments were carried out in 30 lean healthy subjects (age, mean +/- s.e.m., 26 +/- 1 y; body mass index, 23.1 +/- 0.6 kg/m2). RESULTS: As expected, glucose demand during the clamp was lower in the ante-hypo condition than in the control condition (gram of glucose infused per kilogram body weight, 1.52 +/- 0.16 vs 2.01 +/- 0.17 g/kg; P < 0.05). During the clamp, leptin levels increased by 25.4 +/- 4.3% in the control condition (P < 0.05), but not in the ante-hypo condition (+4.8 +/- 4.5%; P > 0.25). Thus, serum leptin response to the clamp significantly differed between the two conditions (P < 0.01). Across both conditions, the increase of leptin levels during the clamp was correlated with the amount of glucose infused (r = 0.37; P < 0.05). CONCLUSION: Considering that insulin concentrations were identical during both clamp conditions, the data indicate that experimentally-induced insulin resistance diminishes the stimulatory effect of insulin on leptin secretion.     

Effect of calcitonin and calcitonin gene-related peptide on pancreatic functions in man.

Calcitonin gene-related peptide (CGRP) has recently been identified in central and peripheral nerve fibres, including those of blood vessels supplying the exocrine pancreas, and in pancreatic islet cells. Moreover, receptors have been characterised in the same tissue. The present study examined the effects of human CGRP and of calcitonin on exocrine pancreatic secretion and on islet cell function in nine healthy volunteers. CGRP (300 ng/kg/h) caused, respectively, a 25% and 31% inhibition of caerulein stimulated trypsin and amylase output which was similar to that seen with calcitonin (300 ng/kg/h). Arginine stimulated insulin and glucagon release was unaffected by either CGRP, or calcitonin. Calcitonin gene-related peptide caused cutaneous flushing, but did not affect the pulse rate or arterial blood pressure in the doses tested. Calcitonin gene-related peptide inhibits exocrine pancreatic secretion in vivo in man, but does not affect islet cell hormone release.     

Postmenopausal estrogen administration suppresses muscle sympathetic nerve activity

The activity of the sympathetic nervous system shows gender-specific differences with lower sympathoneural activity to the muscle vascular bed in women compared with men, with this difference vanishing after menopause. The present study tested the hypothesis that estrogen exerts regulatory influence on the autonomic nervous system in postmenopausal women. Eleven healthy postmenopausal women (age, 58.5 +/- 1.0 yr; mean +/- SEM) were studied in a randomized double-blind crossover protocol with transdermal administration of 100 microgram/day estradiol (E(2)) or placebo (P) for 2 days. Muscle sympathetic activity (MSA), blood pressure, and heart rate were recorded at rest and during sympathoexcitatory maneuvers (apnea, cold pressor test). E(2) administration significantly increased serum E(2) to physiological levels (E(2), 469.5 +/- 51.5; P, 34.8 +/- 2.2 pmol/L; P < 0.05) and significantly lowered MSA (E(2), 30.1 +/- 3.0 vs. P 37.7 +/- 3.1 bursts/min; P < 0.05). At the same time, blood pressure and heart rate were not affected. MSA was significantly enhanced during apnea and the cold pressure test, and this physiological response to the maneuvers was not changed after estrogen supplementation. In conclusion, elevation of low postmenopausal estrogen levels to physiological premenopausal levels by transdermal E(2) administration supresses MSA. This effect is most likely the consequence of a direct E(2) effect on central nervous autonomic centers, which could explain the gender-specific differences in sympathetic outflow to the muscle vascular bed. The sympathoinhibitory estrogen effects could be important for beneficial cardiovascular effects of estrogen replacement therapy in postmenopausal women.     

The neuroendocrine control of glucose allocation.

Here we propose that glucose metabolism can be understood on the basis of three concept-derived axioms: (I) A hierarchy exists among the glucose-utilizing organs with the brain served first, followed by muscle and fat. (II) Tissue-specific glucose transporters allocate glucose among organs in order to maintain brain glucose concentrations. (III) Exogenous carbohydrate supply compensates for glucose alterations that can temporarily occur in muscle and fat. Derived from the control theory, the simplest solution of allocating supply to 2 organs, e.g. brain and muscle, is a "fishbone"-structured model. We reviewed the literature, searching for neuroendocrine and metabolic mechanisms that can fulfill control functions in such a model: The tissue-specific glucose transporters are differentially regulated. GLUT 1, carrying glucose across the blood-brain-barrier, is independent of insulin. Instead, this trans-endothelial glucose transporter is rather dependent on potent regulators of blood vessel function like vascular endothelial growth factor - a pituitary counterregulatory hormone. GLUT 4, carrying glucose across the membranes of muscle and fat cells, depends on insulin. Thereby, insulin allocates glucose to muscle and fat. The hypothalamus-pituitary-adrenal (HPA) axis, the sympathetic nervous system (SNS), and vascular endothelial growth factor allocate glucose to the brain. Multiple "sensors" (some of which have only recently been identified as ATP sensitive potassium channels) measure glucose or glucose equivalents at various sites of the body: the ventromedial hypothalamus, the lateral hypothalamus, portal vein, pancreatic beta cell, renal tubule, muscle and adipose tissue. Feedback pathways both from the brain and from muscle and fat are involved in regulating glucose allocation and exogenous glucose supply. The main feedback signal from the brain is found to be glucose, that from muscle and fat appears to be leptin. In fact, the literature search revealed two or more biological mechanisms for the function of each component in the model, finding glucose regulation highly redundant. This review focuses on "brain glucose" control. The concept of glucose allocation presented here challenges the common opinion of "blood glucose" being the main parameter controlled. According to the latter opinion, hyperglycemia in the metabolic syndrome is due to a putative defect located within the closed loop including the beta cell, muscle and fat cells. That traditional view leaves some peculiarities of e.g. the metabolic syndrome unexplained. The concept of glucose allocation, however, would predict that weight gain - with abundance of glucose in muscle and fat - increases feedback to the brain (via hyperleptinemia) which in turn results in HPA-axis and SNS overdrive, impaired insulin secretion, and insulin resistance. HPA-axis overdrive would account for metabolic abnormalities such as central adiposity, hyperglycemia, dyslipidemia, and hypertension, that are well known clinical aspects the metabolic syndrome. This novel viewpoint of "brain glucose" control may shed new light on the pathogenesis of the metabolic syndrome and type 2 diabetes.