F-fluorodeoxyglucose uptake in brown adipose tissue during insulin-induced hypoglycemia and mild cold exposure in non-diabetic adults

Objective

Hypoglycemia is associated with increased heat production and, despite of this, hypothermia. Heat production is likely to be mediated by sympathetic innervation. Brown adipose tissue is activated by cold exposure and stimulated by the sympathetic nervous system. We therefore examined the effect of hypoglycemia on uptake of the labeled glucose analogue ¹⁸ F-fluorodeoxyglucose in brown adipose tissue using positron emission tomography and computer tomography.

Methods

In nine healthy adults ¹⁸ F-fluorodeoxyglucose uptake as measure of brown adipose tissue activity was assessed in a cold environment (17 °C) during euglycemia (blood glucose 4.5 mmol/L) and hypoglycemia (2.5 mmol/L) using a hyperinsulinemic glucose clamp.

Results

Brown adipose tissue activity was observed in all participants. No difference was observed in the median (range) maximal standardized uptake values of ¹⁸ F-fluorodeoxyglucose in brown adipose tissue between euglycemia and hypoglycemia: 4.2 (1.0–7.7) versus 3.1 (2.2–12.5) g/mL (p = 0.7). Similarly there were no differences in mean standardized ¹⁸ F-fluorodeoxyglucose uptake values or total brown adipose tissue volume between euglycemia and hypoglycemia. Body temperature dropped by 0.6 °C from baseline during the hypoglycemic condition and remained unchanged during the euglycemic condition. There was no correlation between the maximal standardized uptake values of ¹⁸ F-fluorodeoxyglucose in brown adipose tissue and levels of counterregulatory hormones.

Conclusions

This study shows that there is a similar amount of ¹⁸ F-fluorodeoxyglucose uptake in brown adipose tissue during hypoglycemia when compared to euglycemia, which makes a role for systemic catecholamines in brown adipose tissue activation and a role for brown adipose tissue thermogenesis in hypoglycemia associated hypothermia unlikely. Future studies in humans should determine whether hypoglycemia indeed increases energy expenditure, and if so which alternative source can explain this increase.     

A user-friendly integrated monitor-adhesive patch for long-term ambulatory electrocardiogram monitoring

BackgroundCompliance to long-term ambulatory electrocardiogram monitoring is important for diagnosis in patients with cardiac arrhythmia. This requires a system with a minimal impact on daily activities.ObjectiveThe aim of this study was to investigate if a lightweight integrated adhesive monitor for long-term use without unacceptable adverse effects is feasible.MethodsThe participants wore either a prototype lightweight monitor or a control system for a total of up to 30 days, changing patches once (investigational device) or twice (control) weekly. Comfort, skin irritation, and impact on quality of life were recorded.ResultsThe new monitor can be worn by most participants for periods of at least 6 days. Skin irritation and comfort rating were comparable, and impact on the quality of life was low compared with the control. Patients considered the device comfortable.ConclusionAn integrated adhesive monitor that can be worn on the skin up to 7 days with minimal side effects is feasible.     

Confirmation of a wear-compensation mechanism in dental roots of ruminants

Diet affects many factors of an animal's anatomy, but teeth are a specific focus of dietary research, as their durability lends them to record information on a large variety of scales. Abrasive diets like those of grazing herbivores are known to wear down teeth, but how that wear affects tooth growth and the relations between its different morphological components is rarely investigated. Seven pelleted diets varying in abrasive size and concentration were fed over a 17-month period to 49 sheep (Ovis aries), of which n = 39 qualified for morphology measurements. Using computed tomography, scans of the skulls were made over the course of the experiment, and the impact of diet-related wear was observed on tooth volume and morphology, including the position of dental burr marks, over time. Digital caliper measurements were applied to 3D renderings of the teeth, and the volume of crown and root segments were investigated separately. We aimed to detect a signal of root growth compensating for wear, and test if this mechanism would be affected by dietary abrasives. Crown-segment volume loss was correlated to root-segment volume gain. Height and burr mark measurements indicated a much higher experimental tooth wear than that previously reported for free-ranging animals. The reason for this is unclear. There was no relationship between tooth height and dentine basin depth. For all parameters, there was no effect of diet; hence, while the measurements corroborate general understanding of tooth wear and compensatory processes, these methods appear not suitable to assess subtle differences between feeding regimes.     

Prolonged fasting induces peripheral insulin resistance, which is not ameliorated by high-dose salicylate

CONTEXT: Elevated plasma free fatty acids, excess reactive oxygen species, inflammation, and gluco-counterregulatory hormones induce insulin resistance (IR) through activation of Jun NH(2)-terminal kinase and nuclear factor-kappaB inhibitor kappaB kinase, which leads to hyperphosphorylation of the insulin receptor substrate type 1. Aspirin blocks nuclear factor-kappaB inhibitor kappaB kinase and improves IR in type 2 diabetes mellitus. OBJECTIVE: We hypothesized that high-dose aspirin would also attenuate fasting-induced IR in healthy lean subjects. DESIGN: Glucose and glutathione (GHS) metabolism was studied after 12 and 60 h of fasting on two occasions: with and without aspirin (6 g/d). SETTING: The study took place at the Academic Medical Center, Metabolic Research Unit. PARTICIPANTS: Six healthy lean men participated. INTERVENTION: Intervention included 60 h of fasting with or without aspirin ( approximately 6 g/d). MAIN OUTCOME MEASURE: Main outcome measures included glucose and GSH metabolism. RESULTS: Fasting decreased insulin-mediated peripheral glucose uptake by 46% after 60 h (P = 0.03). Aspirin did not alter this effect of 60 h of fasting on insulin sensitivity (P = 0.03). GSH concentration decreased during fasting, but the fractional synthetic rate of GSH was unaffected either with or without aspirin. Fasting did not affect inflammatory parameters, although aspirin increased soluble TNF receptors I and II. CONCLUSION: Prolonged fasting induces profound peripheral IR. In contrast to type 2 diabetes mellitus, high-dose salicylate does not affect fasting-induced peripheral IR.     

Type I Gaucher disease, a glycosphingolipid storage disorder, is associated with insulin resistance

CONTEXT: Complex glycosphingolipids, in majority the ganglioside GM3, surround the insulin receptor in a special membrane compartment (raft) and modulate signaling through this receptor. Increased levels of GM3 in rafts impair insulin signaling, resulting in insulin resistance. Gaucher disease is a lysosomal storage disorder in which impaired breakdown of glucosylceramide leads to its accumulation in macrophages. Secondary to this defect, GM3 concentrations, for which glucosylceramide is the precursor, in plasma and several cell types are elevated. OBJECTIVE: We studied the influence of glycosphingolipid storage on whole body glucose and fat metabolism by measuring insulin-mediated (IMGU) and noninsulin-mediated glucose uptake (NIMGU) and suppression of free fatty acids by insulin. DESIGN AND MAIN OUTCOME MEASURES: We studied six Gaucher patients, either naive to treatment or with considerable remaining burden of disease, and six matched healthy control subjects in the basal state, during an euglycemic and a hyperglycemic clamp with somatostatin measuring NIMGU and during an euglycemic hyperinsulinemic clamp measuring IMGU, using stable isotopes. RESULTS: NIMGU (both during euglycemia and hyperglycemia) did not differ between patients and control subjects. IMGU was lower in Gaucher patients, compared with controls. Suppression of lipolysis by insulin tended to be less effective in Gaucher patients. CONCLUSION: Gaucher disease, a lysosomal glycosphingolipid storage disorder, is associated with (peripheral) insulin resistance, possibly through the influence of glycosphingolipids on insulin receptor functioning.     

European clinical guidelines for Tourette syndrome and other tic disorders—version 2.0. Part IV: deep brain stimulation

In 2011 the European Society for the Study of Tourette Syndrome (ESSTS) published its first European clinical guidelines for the treatment of Tourette Syndrome (TS) with part IV on deep brain stimulation (DBS). Here, we present a revised version of these guidelines with updated recommendations based on the current literature covering the last decade as well as a survey among ESSTS experts. Currently, data from the International Tourette DBS Registry and Database, two meta-analyses, and eight randomized controlled trials (RCTs) are available. Interpretation of outcomes is limited by small sample sizes and short follow-up periods. Compared to open uncontrolled case studies, RCTs report less favorable outcomes with conflicting results. This could be related to several different aspects including methodological issues, but also substantial placebo effects. These guidelines, therefore, not only present currently available data from open and controlled studies, but also include expert knowledge. Although the overall database has increased in size since 2011, definite conclusions regarding the efficacy and tolerability of DBS in TS are still open to debate. Therefore, we continue to consider DBS for TS as an experimental treatment that should be used only in carefully selected, severely affected and otherwise treatment-resistant patients.