Care trajectories of surgically treated patients with a prolactinoma: why did they opt for surgery?

PURPOSE

To describe care trajectories in patients with prolactinoma, aiming to clarify the rationale for surgery.

METHODS

Retrospective observational cohort study of consecutive patients with prolactinoma undergoing surgery from 2017 to 2019 at the referral center (RC), prior to surgery being considered a viable treatment option (i.e. PRolaCT study). Demographics and clinical data (type and duration of pretreatment and surgical indications, goals, and outcomes) were collected from patient records. Care trajectories were divided into three phases: (1) diagnosis and initial treatment, (2) endocrine treatment at the RC, and (3) surgical treatment.

RESULTS

40 patients were included (31 females (77.5%), median age 26.5 (14-63) years. Indications for surgery were dopamine agonist (DA) intolerance (n = 31, 77.5%), resistance (n = 6, 15.0%), and patient/physician preference (n = 3, 7.5%). Patients were pretreated with DA (n = 39 (97.5%)), and surgery (n = 3 (7.5%)). Median disease duration at surgery was 4 (0-27) years. Primary surgical goal was total resection in 38 patients (95.0%), of which biochemical remission was achieved 6 months postoperatively in 23 patients (62.2%), and clinical remission in 6 patients (16.2%), missing data n = 1.

CONCLUSION

Care trajectories were highly individualized based on patient and tumor characteristics, as well as the multidisciplinary team's assessment (need for alternative treatment, surgical chances and risks). Most patients were pretreated pharmacologically and had broad variation in timing of referral, undergoing surgery as last-resort treatment predominantly due to DA intolerance. High quality imaging and multidisciplinary consultations with experienced neurosurgeons and endocrinologists enabling treatment tailored to patients' needs were prerequisites for adequate counseling in treatment of patients with prolactinoma.

Testosterone in men with hypogonadism and transgender males: a systematic review comparing three different preparations

Testosterone therapy is the cornerstone in the care of men with hypogonadism and transgender males. Gel and intramuscular injections are most frequently used and are registered and included in the international guidelines. The specific preparation should be selected according to the patient's preference, cost, availability, and formulation-specific properties. As the majority of men with hypogonadism and transgender males require lifelong treatment with testosterone, it is important to utilize a regimen that is effective, safe, inexpensive, and convenient to use with optimal mimicking of the physiological situation. This systematic review reviews current literature on differences between the three most used testosterone preparations in adult men with hypogonadism and transgender males. Although it appeared hardly any comparative studies have been carried out, there are indications of differences between the preparations, for example, on the stability of testosterone levels, hematocrit, bone mineral density, and patient satisfaction. However, there are no studies on the effects of testosterone replacement on endpoints such as cardiovascular disease in relation to hematocrit or osteoporotic fractures in relation to bone mineral density. The effect of testosterone therapy on health-related quality of life is strongly underexposed in the reviewed studies, while this is a highly relevant outcome measure from a patient perspective. In conclusion, current recommendations on testosterone treatment appear to be based on data primarily from non-randomized clinical studies and observational studies. The availability of reliable comparative data between the different preparations will assist in the process of individual decision-making to choose the most suitable formula.

Implementation of functional imaging using 11C-methionine PET-CT co-registered with MRI for advanced surgical planning and decision making in prolactinoma surgery

PURPOSE

To report the first experience of our multidisciplinary team with functional imaging using ¹¹C-methionine positron emission tomography-computed tomography (¹¹C-methionine PET-CT) co-registered with MRI (Met-PET/MRI^CR) in clinical decision making and surgical planning of patients with difficult to treat prolactinoma.

METHODS

In eighteen patients with prolactinoma, referred to our tertiary referral centre because of intolerance or resistance for dopamine agonists (DA), Met-PET/MRI^CR was used to aid decision-making regarding therapy.

RESULTS

Met-PET/MRI^CR was positive in 94% of the patients. MRI and Met-PET/MRI^CR findings were completely concordant in five patients, partially concordant in nine patients, and non-concordant in four patients. In five patients Met-PET/MRI^CR identified lesion(s) that were retrospectively also visible on MRI. Met-PET/MRI^CR was false negative in one patient, with a cystic adenoma on conventional MRI. Thirteen patients underwent transsphenoidal surgery, with nine achieving full biochemical remission, two clinical improvement and near normalized prolactin levels, and one patient clinical improvement with significant tumour reduction. Hence, nearly all patients (94%) were considered to have a positive outcome. Permanent complication rate was low. Three patients continued DA, two patients have a wait and scan policy.

CONCLUSION

Met-PET/MRI^CR can provide additional information to guide multidisciplinary preoperative and intraoperative decision making in selected cases of prolactinoma. This approach resulted in a high remission rate with a low rate of complications in our expert centre.

Early postoperative HPA-axis testing after pituitary tumor surgery: reliability and safety of basal cortisol and CRH test

PURPOSE

To assess the reliability and safety of a postsurgical evaluation strategy of adrenal function using CRH stimulation and basal cortisol concentrations after transsphenoidal pituitary surgery.

METHODS

Retrospective cohort study of all patients undergoing endoscopic transsphenoidal surgery from 2010 to 2017, in whom early postoperative basal cortisol and/or CRH-stimulated cortisol secretion were available, including confirmation of adrenal function during follow-up. Patients with Cushing's disease were excluded. Optimal test performances were assessed using ROC analysis.

RESULTS

A total of 156 patients were included. Sensitivity and specificity of the CRH test were 78% and 90%, respectively, and 86% and 92% for basal cortisol, respectively, using an optimal cutoff of 220 nmol/L. Eight patients had false-negative test results with the CRH test (normal test but adrenal insufficient at follow-up), and six patients with basal cortisol, the majority of which had multiple pituitary hormone deficiencies and fluid imbalances. No clinical adverse events occurred in patients with false-negative test results. The diagnostic performance of a single basal cortisol measurement was superior to the CRH test.

CONCLUSIONS

The early postoperative basal cortisol is a safe and simple measurement to guide (dis)continuation of hydrocortisone replacement. However, disturbing factors, e.g., sodium balance disorders, contraceptives, untreated hypopituitarism, and illness impact the interpretation and in those cases this measure is unreliable. We propose an algorithm in which hydrocortisone replacement at discharge is based on basal cortisol <220 nmol/L on postoperative day 2 or 3 in a stable condition.

Short-term cooling increases serum triglycerides and small high-density lipoprotein levels in humans

BACKGROUND

Cold exposure and β3-adrenergic receptor agonism, which both activate brown adipose tissue, markedly influence lipoprotein metabolism by enhancing lipoprotein lipase-mediated catabolism of triglyceride-rich lipoproteins and increasing plasma high-density lipoprotein (HDL) levels and functionality in mice. However, the effect of short-term cooling on human lipid and lipoprotein metabolism remained largely elusive.

OBJECTIVE

The objective was to assess the effect of short-term cooling on the serum lipoprotein profile and HDL functionality in men.

METHODS

Body mass index-matched young, lean men were exposed to a personalized cooling protocol for 2 hours. Before and after cooling, serum samples were collected for analysis of lipids and lipoprotein composition by ¹H-nuclear magnetic resonance. Adenosine triphosphate-binding cassette A1 (ABCA1)-mediated cholesterol efflux capacity of HDL was measured using [³H]cholesterol-loaded ABCA1-transfected Chinese hamster ovary cells.

RESULTS

Short-term cooling increased serum levels of free fatty acids, triglycerides, and cholesterol. Cooling increased the concentration of large very low-density lipoprotein (VLDL) particles accompanied by increased mean size of VLDL particles. In addition, cooling enhanced the concentration of small LDL and small HDL particles as well as the cholesterol levels within these particles. The increase in small HDL was accompanied by increased ABCA1-dependent cholesterol efflux in vitro.

CONCLUSIONS

Our data show that short-term cooling increases the concentration of large VLDL particles and increases the generation of small LDL and HDL particles. We interpret that cooling increases VLDL production and turnover, which results in formation of surface remnants that form small HDL particles that attract cellular cholesterol.

Lipid droplet dynamics and insulin sensitivity upon a 5-day high-fat diet in Caucasians and South Asians

A 5-day High-Fat High-Calorie diet (HFHC-diet) reduces insulin-stimulated glucose disposal (Rd) in South Asian, but not Caucasian healthy lean males. We aimed to investigate if differences in myocellular lipid handling are underlying this differential response. A two-step hyperinsulinemic-euglycemic clamp and muscle biopsies were performed in 12 healthy lean Caucasian and South Asian males (BMI < 25 kg/m², 19-25 years) before and after a 5-day HFHC-diet (regular diet + 375 mL cream/day; 1275 kcal/day; 94% fat). Triglyceride extractions and Western Blots for lipid droplet and mitochondrial proteins were performed. Intramyocellular lipid content and HFHC-diet response were similar between ethnicities (group effect: P = 0.094; diet effect: +~30%, P = 0.044). PLIN5 protein content increased upon the HFHC-diet (P = 0.031) and tended to be higher in South Asians (0.87 ± 0.42 AU vs. 1.35 ± 0.58 AU, P = 0.07). 4-HNE tended to increase in South Asians upon the HFHC-diet (interaction effect: P = 0.057). In Caucasians ΔPLIN5 content correlated with ΔR_d (Caucasians: r = 0.756, P = 0.011; South Asians: r = -0.085, P = 0.816), while in South Asians Δ4-HNE associated with ΔPLIN5 content (Caucasians: r = 0.312, P = 0.380; South Asians: r = 0.771, P = 0.003). These data indicate that in Caucasians, PLIN5 may be protective against HFHC-diet induced insulin resistance, which for reasons not yet understood is not observed in South Asians, who possess increased lipid peroxidation levels.

LysoPC-acyl C16:0 is associated with brown adipose tissue activity in men

INTRODUCTION

Brown adipose tissue (BAT) recently emerged as a potential therapeutic target in the treatment of obesity and associated disorders due to its fat-burning capacity. The current gold standard in assessing BAT activity is [¹⁸F]FDG PET-CT scan, which has severe limitations including radiation exposure, being expensive, and being labor-intensive. Therefore, indirect markers are needed of human BAT activity and volume.

OBJECTIVE

We aimed to identify metabolites in serum that are associated with BAT volume and activity in men.

METHODS

We assessed 163 metabolites in fasted serum of a cohort of twenty-two healthy lean men (age 24.1 (21.7-26.6) years, BMI 22.1 (20.5-23.4) kg/m²) who subsequently underwent a cold-induced [¹⁸F]FDG PET-CT scan to assess BAT volume and activity. In addition, we included three replication cohorts consisting of in total thirty-seven healthy lean men that were similar with respect to age and BMI compared to the discovery cohort.

RESULTS

After correction for multiple testing, fasting concentrations of lysophosphatidylcholine-acyl (LysoPC-acyl) C16:1, LysoPC-acyl C16:0 and phosphatidylcholine-diacyl C32:1 showed strong positive correlations with BAT volume (β= 116 (85-148) mL, R² = 0.81, p = 4.6 × 10^-7_; β = 79 (93-119) mL, R² = 0.57, p = 5.9 × 10^-4 and β= 91 (40-141) mL, R² = 0.52, p = 1.0 × 10^-3, respectively) as well as with BAT activity (β= 0.20 (0.11-0.29) g/mL, R² = 0.59, p = 1.9 × 10^-4; β = 0.15 (0.06-0.23) g/mL, R² = 0.47, p = 2.0 × 10^-3 and β= 0.13 (0.01-0.25) g/mL, R² = 0.28, p = 0.04, respectively). When tested in three independent replication cohorts (total n = 37), the association remained significant between LysoPC-acyl C16:0 and BAT activity in a pooled analysis (β= 0.15 (0.07-0.23) g/mL, R² = 0.08, p = 4.2 × 10^-4).

CONCLUSIONS

LysoPC-acyl C16:0 is associated with BAT activity in men. Since BAT is regarded as a promising tool in the battle against obesity and related disorders, the identification of such a noninvasive marker is highly relevant.

HDL functionality in South Asians as compared to white Caucasians

BACKGROUND AND AIMS

South Asians have an exceptionally high risk of developing cardiovascular disease compared to white Caucasians. A contributing factor might be dysfunction of high density lipoprotein (HDL). We aimed to compare HDL function in different age groups of both ethnicities.

METHODS AND RESULTS

HDL functionality with respect to cholesterol efflux, anti-oxidation and anti-inflammation was determined using fasting, apoB-depleted, plasma samples from South Asian and white Caucasian neonates (n = 14 each), adolescent healthy men (n = 12 each, 18-25 y), and adult overweight men (n = 12 each, 40-50 y). Adolescents were subjected to a 5-day high fat high calorie diet (HCD) and adults to an 8-day very low calorie diet (LCD). Additionally, HDL composition was measured in adolescents and adults using (1)H-NMR spectroscopy. Anti-oxidative capacity was lower in South Asian adults before LCD (19.4 ± 2.1 vs. 25.8 ± 1.2%, p = 0.045, 95%-CI = [0.1; 12.7]) and after LCD (16.4 ± 2.4 vs. 27.6 ± 2.7%, p = 0.001, 95%-CI = [4.9; 17.5]). Anti-inflammatory capacity was reduced in South Asian neonates (23.8 ± 1.2 vs. 34.9 ± 1.3%, p = 0.000001, 95%-CI = [-14.6; -7.5]), and was negatively affected by an 8-day LCD only in South Asian adults (-12.2 ± 4.3%, p = 0.005, 95%-CI = [-5.9; -1.2]). Cholesterol efflux capacity was increased in response to HCD in adolescents (South Asians: +6.3 ± 2.9%, p = 0.073, 95%-CI = [-0.02; 0.46], Caucasians: +11.8 ± 3.4%, p = 0.002, 95%-CI = [0.17;0.65]) and decreased after LCD in adults (South Asians: -10.3 ± 2.4%, p < 0.001, 95%-CI = [-0.57; -0.20], Caucasians: -13.7 ± 1.9%, p < 0.00001, 95%-CI = [-0.67; -0.33]). Although subclass analyses of HDL showed no differences between ethnicities, cholesterol efflux correlated best with cholesterol and phospholipid within small HDL compared to other HDL subclasses and constituents.

CONCLUSION

Impaired HDL functionality in South Asians may be a contributing factor to their high CVD risk.

CLINICAL TRIAL REGISTRATION

NTR 2473 (URL: http://www.trialregister.nl/).

High prevalence of cardiovascular disease in South Asians: Central role for brown adipose tissue?

Cardiovascular disease (CVD) is the leading cause of death in modern society. Interestingly, the risk of developing CVD varies between different ethnic groups. A particularly high risk is faced by South Asians, representing over one-fifth of the world's population. Here, we review potential factors contributing to the increased cardiovascular risk in the South Asian population and discuss novel therapeutic strategies based on recent insights. In South Asians, classical ('metabolic') risk factors associated with CVD are highly prevalent and include central obesity, insulin resistance, type 2 diabetes, and dyslipidemia. A contributing factor that may underlie the development of this disadvantageous metabolic phenotype is the presence of a lower amount of brown adipose tissue (BAT) in South Asian subjects, resulting in lower energy expenditure and lower lipid oxidation and glucose uptake. As it has been established that the increased prevalence of classical risk factors in South Asians cannot fully explain their increased risk for CVD, other non-classical risk factors must underlie this residual risk. In South Asians, the prevalence of "inflammatory" risk factors including visceral adipose tissue inflammation, endothelial dysfunction, and HDL dysfunction are higher compared with Caucasians. We conclude that a potential novel therapy to lower CVD risk in the South Asian population is to enhance BAT volume or its activity in order to diminish classical risk factors. Furthermore, anti-inflammatory therapy may lower non-classical risk factors in this population and the combination of both strategies may be especially effective.

Cardiovascular flexibility in middle-aged overweight South Asians vs. white Caucasians: response to short-term caloric restriction

BACKGROUND AND AIMS

South Asians have a higher risk of developing cardiovascular disease than white Caucasians. The underlying cause is unknown, but might be related to higher cardiac susceptibility to metabolic disorders. Short-term caloric restriction (CR) can be used as a metabolic stress test to study cardiac flexibility. We assessed whether metabolic and functional cardiovascular flexibility to CR differs between South Asians and white Caucasians.

METHODS AND RESULTS

Cardiovascular function and myocardial triglycerides were assessed using a 1.5T-MRI/S-scanner in 12 middle-aged overweight male South Asians and 12 matched white Caucasians before and after an 8-day very low calorie diet (VLCD). At baseline South Asians were more insulin resistant than Caucasians. Cardiac dimensions were smaller, despite correction for body surface area, and pulse wave velocity (PWV) in the distal aorta was higher in South Asians. Systolic and diastolic function, myocardial triglycerides and pericardial fat did not differ significantly between groups. After the VLCD body weight reduced on average by 4.0 ± 0.2 kg. Myocardial triglycerides increased in both ethnicities by 69 ± 18%, and diastolic function decreased although this was not significant in South Asians. However, pericardial fat and PWV in the proximal and total aorta were reduced in Caucasians only.

CONCLUSION

Myocardial triglyceride stores in middle-aged overweight and insulin resistant South Asians are as flexible and amenable to therapeutic intervention by CR as age-, sex- and BMI-matched but less insulin resistant white Caucasians. However, paracardial fat volume and PWV showed a differential effect in response to an 8-day VLCD in favor of Caucasians.

CLINICAL TRIAL REGISTRATION

NTR 2473 (URL: http://www.trialregister.nl/trialreg/admin/rctsearch.asp?Term=2473).

Middle-aged overweight South Asian men exhibit a different metabolic adaptation to short-term energy restriction compared with Europeans

AIMS/HYPOTHESIS

South Asians have a higher risk of developing type 2 diabetes than Europeans. The underlying cause of this excess risk is still poorly understood but might be related to differences in the regulation of energy/nutrient-sensing pathways in metabolic tissues and subsequent changes in whole-body substrate metabolism. In this study, we investigated the whole-body and skeletal muscle metabolic adaptations to short-term energy restriction in South Asian and European volunteers.

METHODS

Twenty-four middle-aged overweight South Asian and European men underwent a two-step hyperinsulinaemic-euglycaemic clamp, with skeletal muscle biopsies and indirect calorimetry before and after an 8 day diet very low in energy (very low calorie diet [VLCD]). Abdominal fat distribution and hepatic triacylglycerol content were assessed using MRI and MR spectroscopy.

RESULTS

South Asian men had higher hepatic triacylglycerol content than European men, and exhibited elevated clamp insulin levels that probably reflect a lower insulin clearance rate. Despite higher insulin levels, endogenous glucose production rate was similar and glucose disposal rate (Rd) and nonoxidative glucose disposal rate (NOGD) were significantly lower in South Asian than European men, indicating impaired whole-body insulin sensitivity. Energy restriction decreased abdominal fat mass and hepatic triacylglycerol content in both groups. However, the shift induced by energy restriction from glucose towards lipid oxidation observed in European men was impaired in South Asian men, indicating whole-body metabolic inflexibility. Remarkably, although energy restriction improved hepatic insulin sensitivity in both groups, Rd improved only in South Asian men owing to higher NOGD. At the molecular level, an increase in insulin-induced activation of the skeletal muscle mTOR pathway was found in South Asian men, showing that skeletal muscle energy/nutrient-sensing pathways were differentially affected by energy restriction.

CONCLUSIONS/INTERPRETATION

We conclude that South Asian men exhibit a different metabolic adaptation to short-term energy restriction than European men.

TRIAL REGISTRATION

Dutch trial registry ( www.trialregister.nl ), trial number NTR 2473.

Regulation of skeletal muscle energy/nutrient-sensing pathways during metabolic adaptation to fasting in healthy humans

During fasting, rapid metabolic adaptations are required to maintain energy homeostasis. This occurs by a coordinated regulation of energy/nutrient-sensing pathways leading to transcriptional activation and repression of specific sets of genes. The aim of the study was to investigate how short-term fasting affects whole body energy homeostasis and skeletal muscle energy/nutrient-sensing pathways and transcriptome in humans. For this purpose, 12 young healthy men were studied during a 24-h fast. Whole body glucose/lipid oxidation rates were determined by indirect calorimetry, and blood and skeletal muscle biopsies were collected and analyzed at baseline and after 10 and 24 h of fasting. As expected, fasting induced a time-dependent decrease in plasma insulin and leptin levels, whereas levels of ketone bodies and free fatty acids increased. This was associated with a metabolic shift from glucose toward lipid oxidation. At the molecular level, activation of the protein kinase B (PKB/Akt) and mammalian target of rapamycin pathways was time-dependently reduced in skeletal muscle during fasting, whereas the AMP-activated protein kinase activity remained unaffected. Furthermore, we report some changes in the phosphorylation and/or content of forkhead protein 1, sirtuin 1, and class IIa histone deacetylase 4, suggesting that these pathways might be involved in the transcriptional adaptation to fasting. Finally, transcriptome profiling identified genes that were significantly regulated by fasting in skeletal muscle at both early and late time points. Collectively, our study provides a comprehensive map of the main energy/nutrient-sensing pathways and transcriptomic changes during short-term adaptation to fasting in human skeletal muscle.

Supraclavicular skin temperature as a measure of 18F-FDG uptake by BAT in human subjects

BACKGROUND

Brown adipose tissue (BAT) has emerged as a novel player in energy homeostasis in humans and is considered a potential new target for combating obesity and related diseases. The current 'gold standard' for quantification of BAT volume and activity is cold-induced 18F-FDG uptake in BAT. However, use of this technique is limited by cost and radiation exposure. Given the fact that BAT is a thermogenic tissue, mainly located in the supraclavicular region, the aim of the current study was to investigate whether cold-induced supraclavicular skin temperature and core body temperature may be alternative markers of BAT activation in humans.

SUBJECTS/METHODS

BAT volume and activity were measured in 24 healthy lean adolescent males (mean age 24.1±0.8 years), using cold-induced 18F-FDG uptake with PET-CT. Core body temperature was measured continuously in the small intestine with use of an ingestible telemetric capsule and skin temperature was measured by eighteen wireless iButtons attached to the skin following ISO-defined locations.

RESULTS

Proximal and distal (hand/feet) skin temperatures markedly decreased upon cold exposure, while supraclavicular skin temperature significantly increased (35.2±0.1 vs. 35.5±0.1°C, p = 0.001). Furthermore, cold-induced supraclavicular skin temperature positively correlated with both total (R2 = 0.28, P = 0.010) and clavicular BAT volume (R2 = 0.20, P = 0.030) and clavicular SUVmax (R2 = 0.27, P = 0.010), while core body temperature did not.

CONCLUSIONS

Supraclavicular skin temperature as measured by iButtons may have predictive value for BAT detection in adult humans. This is highly desirable considering the increasing interest in pharmacological interventions to stimulate BAT in human subjects.

TRIAL REGISTRATION

NTR 2473.

Brown adipose tissue volume in healthy lean south Asian adults compared with white Caucasians: a prospective, case-controlled observational study

BACKGROUND

Individuals of south Asian origin have a very high risk of developing type 2 diabetes compared with white Caucasians. We aimed to assess volume and activity of brown adipose tissue (BAT), which is thought to have a role in energy metabolism by combusting fatty acids and glucose to produce heat and might contribute to the difference in incidence of type 2 diabetes between ethnic groups.

METHODS

We enrolled Dutch nationals with south Asian ancestry and matched Caucasian participants at The Rijnland Hospital (Leiderdorp, Netherlands). Eligible participants were healthy lean men aged 18-28 years, and we matched groups for BMI. We measured BAT volume and activity with cold-induced (18)F-fluorodeoxyglucose ((18)F-FDG) PET CT scans, and assessed resting energy expenditure, non-shivering thermogenesis, and serum parameters. This study is registered with the Netherlands Trial Register, number 2473.

FINDINGS

Between March 1, 2013, and June 1, 2013, we enrolled 12 participants in each group; one Caucasian participant developed hyperventilation after (18)F-FDG administration, and was excluded from all cold-induced and BAT measurements. Compared with Caucasian participants, south Asian participants did not differ in age (mean 23.6 years [SD 2.8] for south Asians vs 24.6 years [2.8] for Caucasians) or BMI (21.5 kg/m(2) [2.0] vs 22.0 kg/m(2) [1.6]), but were shorter (1.74 m [0.06] vs 1.85 m [0.04]) and lighter (65.0 kg [8.5] vs 75.1 kg [7.2]). Thermoneutral resting energy expenditure was 1297 kcal per day (SD 123) in south Asian participants compared with 1689 kcal per day (193) in white Caucasian participants (difference -32%, p=0.0008). On cold exposure, shiver temperature of south Asians was 2.0°C higher than Caucasians (p=0.0067) and non-shivering thermogenesis was increased by 20% in white Caucasians (p<0.0001) but was not increased in south Asians. Although the maximum and mean standardised uptake values of (18)F-FDG in BAT did not differ between groups, total BAT volume was lower in south Asians (188 mL [SD 81]) than it was in Caucasians (287 mL [169]; difference -34%, p=0.04). Overall, BAT volume correlated positively with basal resting energy expenditure in all assessable individuals (β=0.44, p=0.04).

INTERPRETATION

Lower resting energy expenditure, non-shivering thermogenesis, and BAT volumes in south Asian populations might underlie their high susceptibility to metabolic disturbances, such as obesity and type 2 diabetes. Development of strategies to increase BAT volume and activity might help prevent and treat such disorders, particularly in south Asian individuals.

FUNDING

Dutch Heart Foundation (2009T038) and Dutch Diabetes Research Foundation (2012.11.1500).

Higher insulin and glucagon-like peptide-1 (GLP-1) levels in healthy, young South Asians as compared to Caucasians during an oral glucose tolerance test

OBJECTIVE

Higher insulin levels during an oral glucose test (OGTT) have been shown in South Asians. We aimed to investigate if this increased insulin response causes reactive hypoglycemia later on, and if an increased glucagon-like-peptide-1 (GLP-1) response, which could contribute to the hyperinsulinemia, is present in this ethnic group.

METHODS

A prolonged, 6-h, 75-g OGTT was performed in healthy, young Caucasian (n=10) and South Asian (n=8) men. The glucose, insulin and GLP-1 response was measured and indices of insulin sensitivity and beta-cell activity were calculated.

RESULTS

Age (Caucasians (CAU) 21.5±0.7 years vs South Asians (SA) 21.4±0.7 years (mean±SEM)) and body mass index (CAU 22.7±0.7 kg/m(2) vs SA 22.1±0.8 kg/m(2)) were comparable between the two groups. South Asian men were more insulin resistant, as indicated by a comparable glucose but significantly higher insulin response, and a significantly lower Matsuda index (CAU 8.7(8.6) vs SA 3.2(19.2), median(IQR)). South Asians showed a higher GLP-1 response, as reflected by a higher area under the curve for GLP-1 (CAU 851±99.8 mmol/l vs SA 1235±155.0 mmol/L). During the whole 6-h period, no reactive hypoglycemia was observed.

CONCLUSION

Healthy, young South Asian men have higher insulin levels during an OGTT as compared to Caucasians. This does not, however, lead to reactive hypoglycemia. The hyperinsulinemia is accompanied by increased levels of GLP-1. Whether this is an adaptive response to facilitate hyperinsulinemia to overcome insulin resistance or reflects a GLP-1 resistant state has yet to be elucidated.

A 5-day high-fat, high-calorie diet impairs insulin sensitivity in healthy, young South Asian men but not in Caucasian men

South Asians (SAs) develop type 2 diabetes at a younger age and lower BMI compared with Caucasians (Cs). The underlying cause is still poorly understood but might result from an innate inability to adapt to the Westernized diet. This study aimed to compare the metabolic adaptation to a high-fat, high-calorie (HFHC) diet between both ethnicities. Twelve healthy, young lean male SAs and 12 matched Cs underwent a two-step hyperinsulinemic-euglycemic clamp with skeletal muscle biopsies and indirect calorimetry before and after a 5-day HFHC diet. Hepatic triglyceride content (HTG) and abdominal fat distribution were assessed using magnetic resonance imaging and spectroscopy. At baseline, SAs had higher insulin clamp levels than Cs, indicating reduced insulin clearance rate. Despite the higher insulin levels, endogenous glucose production was comparable between groups, suggesting lower hepatic insulin sensitivity in SAs. Furthermore, a 5-day HFHC diet decreased the insulin-stimulated (nonoxidative) glucose disposal rate only in SA. In skeletal muscle, no significant differences were found between groups in insulin/mammalian target of rapamycin signaling, metabolic gene expression, and mitochondrial respiratory chain content. Furthermore, no differences in (mobilization of) HTG and abdominal fat were detected. We conclude that HFHC feeding rapidly induces insulin resistance only in SAs. Thus, distinct adaptation to Western food may partly explain their propensity to develop type 2 diabetes.

Pathogenesis of type 2 diabetes in South Asians

The risk of developing type 2 diabetes mellitus (T2DM) is exceptionally high among both native and migrant South Asians. T2DM occurs more often and at a younger age and lower BMI, and the risk of coronary artery and cerebrovascular disease, and renal complications is higher for South Asians compared with people of White Caucasian descent. The high prevalence of T2DM and its related complications in South Asians, which comprise one-fifth of the total world's population, poses a major health and socioeconomic burden. The underlying cause of this excess risk, however, is still not completely understood. Therefore, gaining insight into the pathogenesis of T2DM in South Asians is of great importance. The predominant mechanism, in this ethnicity seems to be insulin resistance (IR) rather than an impaired β-cell function. In this systematic review, we describe several possible mechanisms that may underlie or contribute to the increased IR observed in South Asians.

Radioactive iodine in the treatment of medullary thyroid carcinoma: a controlled multicenter study

OBJECTIVE

Radioactive iodine (RAI) therapy in medullary thyroid carcinoma (MTC) is applied in some centers, based on the assumption that cross-irradiation from thyroid follicular cells may be beneficial. However, no systematic studies on the effect of RAI treatment in MTC have been performed. The aim of this study was to analyze the effect of RAI treatment on survival in MTC patients.

DESIGN

Retrospective multicenter study in eight University Medical Centers in The Netherlands.

METHODS

Two hundred and ninety three MTC patients without distant metastases who had undergone a total thyroidectomy were included between 1980 and 2007. Patients were stratified by clinical appearance, hereditary stage, screening status, and localization. All patients underwent regular surgical treatment with additional RAI treatment in 61 patients. Main outcome measures were disease-free survival (DFS) and disease-specific survival (DSS). Cure was defined as biochemical and radiological absence of disease.

RESULTS

In multivariate analysis, stratification according to clinical appearance (P=0.72), hereditary stage (P=0.96), localization (P=0.69), and screening status (P=0.31) revealed no significant effects of RAI treatment on DFS. Multivariate analysis showed no significant difference in DSS for the two groups stratified according to clinical appearance (P=0.14). Owing to limited number of events, multivariate analysis was not possible for DSS in the other groups of stratification.

CONCLUSIONS

Based on the results of the present analysis, we conclude that RAI has no place in the treatment of MTC.

[Brown adipose tissue: the body's own weapon against obesity?]

Brown adipose tissue (BAT) dissipates energy stored in triglycerides as heat via the uncoupling protein UCP1. It has recently been discovered that BAT is present and active in adults. BAT is situated predominantly around the aorta and in the supraclavicular area. BAT volume and activity are lower in individuals who are obese. This suggests that BAT significantly contributes to total energy expenditure. Several pathological conditions that are accompanied by activation of BAT, such as hyperthyroidism and phaeochromocytoma, result in the increased expenditure of energy and in weight loss. Various ways in which BAT can be manipulated to increase the expenditure of energy have been identified, e.g. exposure to cold, the use of so-called uncoupling agents or the administration of the hormone irisin. The activation of BAT could potentially be used to induce weight loss.