The number of known proteins associated with plant lipid droplets (LDs) is small compared with other organelles. Many aspects of LD biosynthesis and degradation are unknown, and identifying and characterizing candidate LD proteins could help elucidate these processes. Here, we analyzed the proteome of LD-enriched fractions isolated from tobacco (Nicotiana tabacum) pollen tubes. Proteins that were highly enriched in comparison with the total or cytosolic fraction were further tested for LD localization via transient expression in pollen tubes. One of these proteins, PLANT UBX DOMAIN-CONTAINING PROTEIN10 (PUX10), is a member of the plant UBX domain-containing (PUX) protein family. This protein localizes to LDs via a unique hydrophobic polypeptide sequence and can recruit the AAA-type ATPase CELL DIVISION CYCLE48 (CDC48) protein via its UBX domain. PUX10 is conserved in Arabidopsis thaliana and expressed in embryos, pollen tubes, and seedlings. In pux10 knockout mutants in Arabidopsis, LD size is significantly increased. Proteomic analysis of pux10 mutants revealed a delayed degradation of known LD proteins, some of which possessed ubiquitination sites. We propose that PUX10 is involved in a protein degradation pathway at LDs, mediating an interaction between polyubiquitinated proteins targeted for degradation and downstream effectors such as CDC48.

Context Cold exposure (CE) has been shown to enhance energy expenditure by activating brown adipose tissue thermogenesis and metabolism in humans. However, it remains to be elucidated if there are gender-specific differences in cold-induced thermogenesis and metabolism. Objective To study the impact of mild CE on resting energy expenditure (REE) and metabolism in males compared with females. Setting A cross-sectional study. Participants 117 healthy young Caucasians participated in this study (58 males). Mean age was 25.1 ± 3.6 years and mean body mass index 22.3 ± 1.7 kg/m2. Intervention Participants underwent a short-term CE using water perfused mattresses to activate nonshivering thermogenesis. Main Outcome Measures REE was assessed before and 2 hours after CE followed by blood sampling. Selected metabolites and hormones were measured. Skin temperatures were monitored at various sites throughout the experiment. Results Participants showed a significant increase in REE after CE (6.5%, P < .001). This increase did not differ between genders (P = .908). However, there were differences between males and females in changes of plasma glucose (–5.1% versus –7.4%, P = .024), leptin (–14.3% versus –30.1%, P < .001) and adiponectin (5.4% versus 12.8%, P = .018) after CE. We observed a significant decrease of the supraclavicular skin temperature in men (–0.3%, P = .034), but not in women (0.3%, P = .326)(P = .019 between genders). Conclusions We did not observe a difference in the thermogenic response, measured as change of REE, to CE in women compared with men. However, we found that some metabolic and hormonal changes were more pronounced in women than in men suggesting a gender-specific response to cold.

ObjectiveObesity and type-2 diabetes (T2D) are metabolic diseases that represent a critical health problem worldwide. Metabolic disease is differentially associated with fat distribution, while visceral white adipose tissue (VAT) is particularly prone to obesity-associated inflammation. Next to their canonical function of immune suppression, regulatory T cells (Tregs) are key in controlling adipose tissue homeostasis. Towards understanding the molecular underpinnings of metabolic disease, we focus on how environmental-metabolic stimuli impinge on the functional interplay between Tregs and adipose tissue. Here, cold exposure or beta3-adrenergic signaling are a promising tool to increase energy expenditure by activating brown adipose tissue, as well as by reducing local inflammation within fat depots by supporting immunosuppressive Tregs. However, in humans, the underlying mechanisms that enable the environmental-immune crosstalk in the periphery and in the respective tissue remain currently unknown.MethodsWe used combinatorial approaches of next generation humanized mouse models and in vitro and in vivo experiments together with beta3-adrenergic stimulation to dissect the underlying mechanisms of human Treg induction exposed to environmental stimuli such as cold. To test the translational relevance of our findings, we analyzed samples from the FREECE study in which human subjects were exposed to individualized cooling protocols. Samples were analyzed ex vivo and after in vitro Treg induction using qRT-PCR, immunofluorescence, as well as with multicolor flow cytometry and cell sorting.ResultsIn vivo application of the beta3-adrenergic receptor agonist mirabegron in humanized mice induced thermogenesis and improved the Treg induction capacity of naïve T cells isolated from these animals. Using samples from the human FREECE study, we demonstrate that a short-term cold stimulus supports human Treg induction in vitro and in vivo. Mechanistically, we identify BORCS6 encoding the Ragulator-interacting protein C17orf59 to be significantly induced in human CD4+ T cells upon short-term cold exposure. Strong mTOR signaling is known to limit successful Treg induction and thus likely by interfering with mTOR activation at lysosomal surfaces, C17orf59 improves the Treg induction capacity of human naïve T cells upon cold exposure.ConclusionsThese novel insights into the molecular underpinnings of human Treg induction suggest an important role of Tregs in linking environmental stimuli with adipose tissue function and metabolic diseases. Moreover, these discoveries shed new light on potential approaches towards tailored anti-inflammatory concepts that support human adipose tissue homeostasis by enabling Tregs.

Activation of brown adipose tissue may increase energy expenditure by non-shivering thermogenesis. Cold exposure is one of the options to activate brown adipocytes. To link changes in energy metabolism with microRNA expression (miRNAs), we analyzed 158 miRNAs in serum of 169 healthy individuals before and after cold exposure. Validating the results of a miRNA array, a significant down-regulation of miR-375 after cold exposure (P < 0.0001) was detected. These changes went along with a significant negative correlation between miR-375 and visceral adipose tissue (VAT) mass (P < 0.0001), implicating a specific function of miR-375 in this depot. Significantly higher expression levels of miR-375 were found in VAT in comparison to subcutaneous fat (SAT). Using in silico prediction, we identified putative miR-375 target genes involved in the thermogenesis pathway. Cold-stimulation of subcutaneous and visceral pre-adipocytes (PACs) led to significantly higher expression levels of FABP4, FGF21, PPARGC1A and PRDM16 in VC-PACs. Analyzing miR-375 knock down and cold stimulated VC-PACs revealed a significant up-regulation of thermogenesis associated genes PPARGC1A, ELOVL3 and PRDM16. In summary, our findings identified miR-375 as a potential adipogenic and thermogenesis-associated miRNA exclusively acting in visceral adipose tissue.

Introduction. Brown adipose tissue (BAT) serves to produce heat by non-shivering thermogenesis. Activation of BAT increases energy expenditure and is seen as a putative strategy to treat obesity. There is conflicting data on the capacity for cold induced thermogenesis in individuals with higher BMI. Methods. To investigate the effect of BMI on cold-induced stimulation of energy expenditure, changes in the metabolic profile, and the expression of browning markers in subcutaneous white adipose tissue (scWAT), healthy adults (N=173, 50.9 % females) with a median age of 26.0 [Interquartile range (IQR): 23.0;28.0] years and a median BMI of 23.6 [IQR: 21.9;26.6] kg/m² were exposed to short-term mild cold exposure (CE). Resting energy expenditure (REE) was measured by indirect calorimetry and blood sampling was conducted at baseline and after CE. In a subgroup of participants with obesity, subcutaneous abdominal fat biopsies were taken before and after CE. Results. The cold-induced median increase in REE was 74 (IQR: -28; 241) kcal/day (p<0.001). This increase negatively correlated with BMI (p<0.001). Participants with BMI 18.5-24.9 kg/m² displayed a significant median increase of 103 kcal/day (p<0.001), participants with overweight or obesity were not able to increase REE (23, p=0.468 or - 30 kcal/day, p=0.917, respectively). In participants with obesity, expression of Cell death activator (CIDEA) in scWAT after CE was upregulated in females (p=0.034). Conclusions. Persons with overweight and obesity do not increase REE in response to CE, presumably reflecting lower BAT activity. Likewise, the metabolic response to cold is diminished in participants with elevated BMI.

Background: Brown adipose tissue (BAT) activity is triggered by cold exposure resulting in an increased resting energy expenditure, called cold-induced non-shivering thermogenesis (CIT). Magnetic resonance (MR)-based proton density fat fraction (PDFF) of the supraclavicular fossa has been proposed as a surrogate marker of human BAT. The present study investigates supraclavicular PDFF in relation to CIT.Methods: For this prospective cross-sectional study 39 adults were recruited, from a cross-sectional study, exploring energy expenditure after cold exposure compared to thermoneutral conditions. Participants underwent additional MR examination of neck, pelvis, and abdomen. Supraclavicular and subcutaneous gluteal adipose tissue depots were segmented semi-automatically. Mean PDFF was assessed for each compartment and the delta PDFF was calculated as the difference of both. Correlation analysis of supraclavicular PDFF to CIT was performed for the whole cohort and subgroups, sorted by body mass index (BMI) and body fat percentage.Results: Median age of participants (61.5% female) was 27 years. BMI ranged from 19.0 to 38.5 kg/m 2 , with body fat percentages from 4.6% to 45.3%. Median supraclavicular PDFF of 82.5% and median gluteal PDFF of 91.1%, were significantly different (P<0.0001). Median delta PDFF was 8.8% (3.9-21.9%). Mean CIT was 4.7%±9.0%. No statistically significant correlation of supraclavicular PDFF and CIT was found in the whole cohort and in most of the observed subgroups. Just the subgroup with normal body fat percentage revealed significant correlations between supraclavicular PDFF and CIT (rho =−0.59; P=0.003). Delta PDFF was significantly associated with CIT (rho =0.36; P=0.026).Conclusions: PDFF is influenced by adiposity. Therefore, if supraclavicular PDFF is used as approach to indirectly assess BAT presence, body composition should be considered. Delta PDFF, as the difference between gluteal and supraclavicular PDFF, may be a marker of CIT.

Cold-induced non-shivering thermogenesis (CIT) of the human body is currently discussed as an important contributor to energy metabolism, and miRNAs have recently been reported as key regulators of metabolism. Identifying the link of CIT and circulating microRNAs (miRNAs) in a large cohort of human individuals remains elusive to date. Here, we analyzed a set of 158 miRNAs in the serum of 97 female and 72 male healthy individuals before and after cold exposure (CE). Validating the results of a miRNA array, a significant down-regulation of miR-375 was measured in individuals after CIT (P<0.0001). These changes went along with a significant negative correlation between miR‑375 and the supraclavicular skin temperature (P=0.012). Additionally, the regulation of miR-375 was sex-dependent, with female individuals showing a significantly stronger decrease in expression of miR-375 under CIT compared to males. Such findings were already seen under thermoneutral conditions, where females display significant lower miR-375 expression levels (P=0.015). Besides, the lower miR‑375 expression levels were negatively correlated with the amount of visceral fat tissue in the female cohort (P=0.0002). This study identified miR-375 as a potential new sex-dependent marker for cold-induced thermogenesis.