Thioesterase superfamily member 1 undergoes stimulus-coupled conformational reorganization to regulate metabolism in mice.

In brown adipose tissue, thermogenesis is suppressed by thioesterase superfamily member 1 (Them1), a long chain fatty acyl-CoA thioesterase. Them1 is highly upregulated by cold ambient temperature, where it reduces fatty acid availability and limits thermogenesis. Here, we show that Them1 regulates metabolism by undergoing conformational changes in response to ß-adrenergic stimulation that alter Them1 intracellular distribution. Them1 forms metabolically active puncta near lipid droplets and mitochondria. Upon stimulation, Them1 is phosphorylated at the N-terminus, inhibiting puncta formation and activity and resulting in a diffuse intracellular localization. We show by correlative light and electron microscopy that Them1 puncta are biomolecular condensates that are inhibited by phosphorylation. Thus, Them1 forms intracellular biomolecular condensates that limit fatty acid oxidation and suppress thermogenesis. During a period of energy demand, the condensates are disrupted by phosphorylation to allow for maximal thermogenesis. The stimulus-coupled reorganization of Them1 provides fine-tuning of thermogenesis and energy expenditure.

Gastrointestinal Bleeding in Patients With Coronavirus Disease 2019: A Matched Case-Control Study.

INTRODUCTION: Although current literature has addressed gastrointestinal presentations including nausea, vomiting, diarrhea, abnormal liver chemistries, and hyperlipasemia as possible coronavirus disease 2019 (COVID-19) manifestations, the risk and type of gastrointestinal bleeding (GIB) in this population is not well characterized. METHODS: This is a matched case-control (1:2) study with 41 cases of GIB (31 upper and 10 lower) in patients with COVID-19 and 82 matched controls of patients with COVID-19 without GIB. The primary objective was to characterize bleeding etiologies, and our secondary aim was to discuss outcomes and therapeutic approaches. RESULTS: There was no difference in the presenting symptoms of the cases and controls, and no difference in severity of COVID-19 manifestations (P > 0.05) was observed. Ten (32%) patients with upper GIB underwent esophagogastroduodenoscopy and 5 (50%) patients with lower GIBs underwent flexible sigmoidoscopy or colonoscopy. The most common upper and lower GIB etiologies were gastric or duodenal ulcers (80%) and rectal ulcers related to rectal tubes (60%), respectively. Four of the esophagogastroduodenoscopies resulted in therapeutic interventions, and the 3 patients with rectal ulcers were referred to colorectal surgery for rectal packing. Successful hemostasis was achieved in all 7 cases that required interventions. Transfusion requirements between patients who underwent endoscopic therapy and those who were conservatively managed were not significantly different. Anticoagulation and rectal tube usage trended toward being a risk factor for GIB, although it did not reach statistical significance. DISCUSSION: In COVID-19 patients with GIB, compared with matched controls of COVID-19 patients without GIB, there seemed to be no difference in initial presenting symptoms. Of those with upper and lower GIB, the most common etiology was peptic ulcer disease and rectal ulcers from rectal tubes, respectively. Conservative management seems to be a reasonable initial approach in managing these complex cases, but larger studies are needed to guide management.

Dissociation of Adaptive Thermogenesis from Glucose Homeostasis in Microbiome-Deficient Mice.

Recent studies suggest that a key mechanism whereby the gut microbiome influences energy balance and glucose homeostasis is through the recruitment of brown and beige adipocytes, primary mediators of the adaptive thermogenic response. To test this, we assessed energy expenditure and glucose metabolism in two complementary mouse models of gut microbial deficiency, which were exposed to a broad range of thermal and dietary stresses. Neither ablation of the gut microbiome, nor the substantial microbial perturbations induced by cold ambient temperatures, influenced energy expenditure during cold exposure or high-fat feeding. Nevertheless, we demonstrated a critical role for gut microbial metabolism in maintaining euglycemia through the production of amino acid metabolites that optimized hepatic TCA (tricarboxylic acid) cycle fluxes in support of gluconeogenesis. These results distinguish the dispensability of the gut microbiome for the regulation of energy expenditure from its critical contribution to the maintenance of glucose homeostasis.

Genetic ablation of phosphatidylcholine transfer protein/StarD2 in ob/ob mice improves glucose tolerance without increasing energy expenditure.

OBJECTIVE: Phosphatidylcholine transfer protein (PC-TP; synonym StarD2) is highly expressed in liver and oxidative tissues. PC-TP promotes hepatic glucose production during fasting and aggravates glucose intolerance in high fat fed mice. However, because PC-TP also suppresses thermogenesis in brown adipose tissue (BAT), its direct contribution to obesity-associated diabetes in mice remains unclear. Here we examined the effects of genetic PC-TP ablation on glucose homeostasis in leptin-deficient ob/ob mice, which exhibit both diabetes and altered thermoregulation. ANIMALS/METHODS: Mice lacking both PC-TP and leptin (Pctp-/-;ob/ob) were prepared by crossing Pctp-/- with ob/+ mice. Glucose homeostasis was assessed by standard assays, and energy expenditure was determined by indirect calorimetry using a comprehensive laboratory animal monitoring system, which also recorded physical activity and food intake. Body composition was determined by NMR and hepatic lipids by enzymatic assays. Core body temperature was measured using a rectal thermocouple probe. RESULTS: Pctp-/-;ob/ob mice demonstrated improved glucose homeostasis, as evidenced by markedly improved glucose and pyruvate tolerance tests, without changes in insulin tolerance. However, there were no differences in EE at any ambient temperature. There were also no effects of PC-TP expression on physical activity, food intake or core body temperature. CONCLUSIONS: Improved glucose tolerance in Pctp-/-;ob/ob mice in the absence of increases in energy expenditure or core body temperature indicates a direct pathogenic role for PC-TP in diabetes in leptin deficient mice.

Thioesterase superfamily member 1 suppresses cold thermogenesis by limiting the oxidation of lipid droplet-derived fatty acids in brown adipose tissue.

OBJECTIVE: Non-shivering thermogenesis in brown adipose tissue (BAT) plays a central role in energy homeostasis. Thioesterase superfamily member 1 (Them1), a BAT-enriched long chain fatty acyl-CoA thioesterase, is upregulated by cold and downregulated by warm ambient temperatures. Them1 (-/-) mice exhibit increased energy expenditure and resistance to diet-induced obesity and diabetes, but the mechanistic contribution of Them1 to the regulation of cold thermogenesis remains unknown. METHODS: Them1 (-/-) and Them1 (+/+) mice were subjected to continuous metabolic monitoring to quantify the effects of ambient temperatures ranging from thermoneutrality (30 °C) to cold (4 °C) on energy expenditure, core body temperature, physical activity and food intake. The effects of Them1 expression on O2 consumption rates, thermogenic gene expression and lipolytic protein activation were determined ex vivo in BAT and in primary brown adipocytes. RESULTS: Them1 suppressed thermogenesis in mice even in the setting of ongoing cold exposure. Without affecting thermogenic gene transcription, Them1 reduced O2 consumption rates in both isolated BAT and primary brown adipocytes. This was attributable to decreased mitochondrial oxidation of endogenous but not exogenous fatty acids. CONCLUSIONS: These results show that Them1 may act as a break on uncontrolled heat production and limit the extent of energy expenditure. Pharmacologic inhibition of Them1 could provide a targeted strategy for the management of metabolic disorders via activation of brown fat.

Inhibition of the p38 kinase suppresses the proliferation of human ER-negative breast cancer cells.

p38 kinases are members of the mitogen-activated protein kinase family that transduce signals from various environmental stresses, growth factors, and steroid hormones. p38 is highly expressed in aggressive and invasive breast cancers. Increased levels of activated p38 are markers of poor prognosis. In this study, we tested the hypothesis that blockade of p38 signaling would inhibit breast cancer cell proliferation. We studied breast cancer cell proliferation and cell cycle regulation upon p38 blockade by using three independent approaches: dominant-negative (DN) constructs, small interfering RNA (siRNA), and small molecule inhibitors. p38alpha and p38delta are the most abundant isoforms expressed by all examined human breast tumors and breast cancer cell lines. Expression of a DN p38 inhibited both anchorage-dependent and -independent proliferation of MDA-MB-468 cells. Silencing of p38alpha, but not p38delta, using siRNA suppressed MDA-MB-468 cell proliferation. Pharmacologic inhibitors of p38 significantly inhibited the proliferation of p53 mutant and ER-negative breast cancer cells. Whereas p38 has previously been considered as a mediator of stress-induced apoptosis, we propose that p38 may have dual activities regulating survival and proliferation depending on the expression of p53. Our data suggest that p38 mediates the proliferation signal in breast cancer cells expressing mutant but not wild-type p53. Because most ER-negative breast tumors express mutant p53, our results provide the foundation for future development of p38 inhibitors to target p38 for the treatment of p53 mutant and ER-negative breast cancers.