Mechanisms for assembly of the nucleoplasmic reticulum.

The nuclear envelope consists of an outer membrane connected to the endoplasmic reticulum, an inner membrane facing the nucleoplasm and a perinuclear space separating the two bilayers. The inner and outer nuclear membranes are physically connected at nuclear pore complexes that mediate selective communication and transfer of materials between the cytoplasm and nucleus. The spherical shape of the nuclear envelope is maintained by counterbalancing internal and external forces applied by cyto- and nucleo-skeletal networks, and the nuclear lamina and chromatin that underly the inner nuclear membrane. Despite its apparent rigidity, the nuclear envelope can invaginate to form an intranuclear membrane network termed the nucleoplasmic reticulum (NR) consisting of Type-I NR contiguous with the inner nuclear membrane and Type-II NR containing both the inner and outer nuclear membranes. The NR extends deep into the nuclear interior potentially facilitating communication and exchanges between the nuclear interior and the cytoplasm. This review details the evidence that NR intrusions that regulate cytoplasmic communication and genome maintenance are the result of a dynamic interplay between membrane biogenesis and remodelling, and physical forces exerted on the nuclear lamina derived from the cyto- and nucleo-skeletal networks.

Nuclear lipid droplets in Caco2 cells originate from nascent precursors and in situ at the nuclear envelope.

Intestinal epithelial cells convert excess fatty acids into triglyceride (TAG) for storage in cytoplasmic lipid droplets and secretion in chylomicrons. Nuclear lipid droplets (nLDs) are present in intestinal cells but their origin and relationship to cytoplasmic TAG synthesis and secretion is unknown. nLDs and related lipid-associated promyelocytic leukemia structures (LAPS) were abundant in oleate-treated Caco2 but less frequent in other human colorectal cancer cell lines and mouse intestinal organoids. nLDs and LAPS in undifferentiated oleate-treated Caco2 cells harbored the phosphatidate phosphatase Lipin1, its product diacylglycerol, and CTP:phosphocholine cytidylyltransferase (CCT)α. CCTα knockout Caco2 cells had fewer but larger nLDs, indicating a reliance on de novo PC synthesis for assembly. Differentiation of Caco2 cells caused large nLDs and LAPS to form regardless of oleate treatment or CCTα expression. nLDs and LAPS in Caco2 cells did not associate with apoCIII and apoAI and formed dependently of microsomal triglyceride transfer protein expression and activity, indicating they are not derived from endoplasmic reticulum luminal LDs precursors. Instead, undifferentiated Caco2 cells harbored a constitutive pool of nLDs and LAPS in proximity to the nuclear envelope that expanded in size and number with oleate treatment. Inhibition of TAG synthesis did affect the number of nascent nLDs and LAPS but prevented their association with promyelocytic leukemia protein, Lipin1α, and diacylglycerol, which instead accumulated on the nuclear membranes. Thus, nLD and LAPS biogenesis in Caco2 cells is not linked to lipoprotein secretion but involves biogenesis and/or expansion of nascent nLDs by de novo lipid synthesis.

Differential contributions of phosphotransferases CEPT1 and CHPT1 to phosphatidylcholine homeostasis and lipid droplet biogenesis.

The cytidine diphosphate-choline (Kennedy) pathway culminates with the synthesis of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) by choline/ethanolamine phosphotransferase 1 (CEPT1) in the endoplasmic reticulum (ER), and PC synthesis by choline phosphotransferase 1 (CHPT1) in the Golgi apparatus. Whether the PC and PE synthesized by CEPT1 and CHPT1 in the ER and Golgi apparatus has different cellular functions has not been formally addressed. Here, we used CRISPR editing to generate CEPT1-and CHPT1-KO U2OS cells to assess the differential contribution of the enzymes to feedback regulation of nuclear CTP:phosphocholine cytidylyltransferase (CCT)α, the rate-limiting enzyme in PC synthesis, and lipid droplet (LD) biogenesis. We found that CEPT1-KO cells had a 50 and 80% reduction in PC and PE synthesis, respectively, while PC synthesis in CHPT1-KO cells was also reduced by 50%. CEPT1 KO caused the posttranscriptional induction of CCTα protein expression as well as its dephosphorylation and constitutive localization on the inner nuclear membrane and nucleoplasmic reticulum. This activated CCTα phenotype was prevented by incubating CEPT1-KO cells with PC liposomes to restore end-product inhibition. Additionally, we determined that CEPT1 was in close proximity to cytoplasmic LDs and CEPT1 KO resulted in the accumulation of small cytoplasmic LDs, as well as increased nuclear LDs enriched in CCTα. In contrast, CHPT1 KO had no effect on CCTα regulation or LD biogenesis. Thus, CEPT1 and CHPT1 contribute equally to PC synthesis; however, only PC synthesized by CEPT1 in the ER regulates CCTα and the biogenesis of cytoplasmic and nuclear LDs.

The diabetes management experiences questionnaire: Psychometric validation among adults with type 1 diabetes.

AIMS: To examine the psychometric properties of the Diabetes Management Experiences Questionnaire (DME-Q). Adapted from the validated Glucose Monitoring Experiences Questionnaire, the DME-Q captures satisfaction with diabetes management irrespective of treatment modalities. METHODS: The DME-Q was completed by adults with type 1 diabetes as part of a randomized controlled trial comparing hybrid closed loop (HCL) to standard therapy. Most psychometric properties were examined with pre-randomization data (n = 149); responsiveness was examined using baseline and 26-week follow-up data (n = 120). RESULTS: Pre-randomization, participants' mean age was 44 ± 12 years, 52% were women. HbA1c was 61 ± 11 mmol/mol (7.8 ± 1.0%), diabetes duration was 24 ± 12 years and 47% used an insulin pump prior to the trial. A forced three-factor analysis revealed three expected domains, that is, 'Convenience', 'Effectiveness' and 'Intrusiveness', and a forced one-factor solution was also satisfactory. Internal consistency reliability was strong for the three subscales ( α range = 0.74-0.84) and 'Total satisfaction' ( α = 0.85). Convergent validity was demonstrated with moderate correlations between DME-Q 'Total satisfaction' and diabetes distress (PAID: rs = -0.57) and treatment satisfaction (DTSQ; rs = 0.58). Divergent validity was demonstrated with a weak correlation with prospective/retrospective memory (PRMQ: rs = -0.16 and - 0.13 respectively). Responsiveness was demonstrated, as participants randomized to HCL had higher 'Effectiveness' and 'Total satisfaction' scores than those randomized to standard therapy. CONCLUSIONS: The 22-item DME-Q is a brief, acceptable, reliable measure with satisfactory structural and construct validity, which is responsive to intervention. The DME-Q is likely to be useful for evaluation of new pharmaceutical agents and technologies in research and clinical settings.

Initiating or switching to insulin degludec/insulin aspart in a real-world population of adults with type 2 diabetes in Australia: results from a prospective, non-interventional study.

BACKGROUND: Insulin degludec/insulin aspart (IDegAsp) is a fixed-ratio co-formulation of insulin degludec and insulin aspart for the treatment of people with diabetes and suboptimal glycaemic control. Few real-world studies of IDegAsp treatment have been conducted. Here, we report results from the Australian cohort of the global ARISE study of real-world IDegAsp use. AIMS: To investigate glycaemic control and other clinical outcomes in people with type 2 diabetes (T2D) treated with IDegAsp in a real-world setting in Australia. METHODS: A total of 183 adults with T2D initiating or switching to IDegAsp in the Australian cohort of the open-label, non-interventional ARISE study were followed for 26-36 weeks from August 2019 to December 2020. RESULTS: IDegAsp was associated with significant reductions from baseline to end of study (EOS) in mean glycated haemoglobin (estimated change -0.8% (95% confidence interval (CI): -1.05 to -0.56; P < 0.0001)), fasting plasma glucose (-1.6 mmol/L (95% CI: -2.49 to -0.63; P = 0.0017)) and body weight (-2.6 kg (95% CI: -3.68 to -1.55; P < 0.0001)). In insulin-experienced patients, the mean total daily insulin dose did not change significantly (estimated change from baseline to EOS 3.8 (95% CI: -3.70 to 11.21; P = 0.3202)). The proportion of patients experiencing hypoglycaemia numerically decreased during the study (non-severe: 14.2-10.9%; nocturnal non-severe: 4.9-2.2%; and severe: 2.2-0%). CONCLUSIONS: Initiating or switching to IDegAsp in a real-world population of people with T2D in Australia was associated with significant improvements in glycaemic control and body weight, and numerically lower levels of hypoglycaemia compared with baseline.

Early Discharge to Clinic-Based Therapy of Patients Presenting With Decompensated Heart Failure (EDICT-HF): Study Protocol for a Multi-Centre Randomised Controlled Trial.

BACKGROUND: Acute decompensated heart failure involves a high rate of mortality and complications. Management typically involves a multi-day hospital admission. However, patients often lose part of their function with each successive admission, and are at a high risk for hospital-associated complications such as nosocomial infection. This study aims to determine the safety and efficacy of the management of patients presenting with acute decompensated heart failure to clinic-based therapy vs usual inpatient care using a reproducible management pathway. METHOD: An investigator-initiated, prospective, non-inferiority, 1:1 randomised-controlled trial, stratified by left ventricular ejection fraction including 460 patients with a minimum follow-up of 7 days. This is a multi-centre study to be performed in centres across Victoria, Australia. Participants will be patients with either heart failure with reduced ejection fraction (HFrEF) or heart failure with preserved ejection fraction (HFpEF), admitted for acute decompensation of heart failure. INTERVENTION: Early discharge to an outpatient-based Heart Failure Rapid Access Clinical Review (RACER) in addition to frequent medical/nursing at-home review for patients admitted with decompensated heart failure. RESULTS: The primary endpoint will be a non-inferiority assessment of re-hospitalisation at 30 days. Secondary outcomes include superiority assessment of hospitalisation at 30 days, a composite clinical endpoint of major adverse cardiac and cerebrovascular event (MACCE), hospital re-admission or mortality at 3 months, achievement of guideline-directed medical therapy, patient assessment of symptoms (visual-analogue scale quantified as area under curve and Kansas City Cardiomyopathy Questionnaire-12 [KCCQ-12]), attendance at 3-month outpatient follow-up, number of bed stays/clinics attended, proportion of patients free from congestion, change in serum creatinine level, treatment for electrolyte disturbances, time to transition from intravenous to oral diuretics, and health economics analysis (cost-benefit analysis, cost-utility analysis, incremental cost-effectiveness ratio). CONCLUSIONS: The Early Discharge to Clinic-Based Therapy of Patients Presenting with Decompensated Heart Failure (EDICT-HF) trial will help determine whether earlier discharge to out-of-hospital care is non-inferior to the usual practice of inpatient care, in patients with heart failure admitted to hospital for acute decompensation, as an alternative model of care.

Acute effects of interrupting prolonged sitting on vascular function in type 2 diabetes.

In healthy and overweight/obese adults, interrupting prolonged sitting with activity bouts mitigates impairment in vascular function. However, it is unknown whether these benefits extend to those with type 2 diabetes (T2D), nor whether an optimal frequency of activity interruptions exist. We examined the acute effects on vascular function in T2D of interrupting prolonged sitting with simple resistance activities (SRA) at different frequencies. In a randomized crossover trial, 24 adults with T2D (35-70 yr) completed three 7-h conditions: 1) uninterrupted sitting (SIT), 2) sitting with 3-min bouts of SRA every 30 min (SRA3), and 3) sitting with 6 min bouts of SRA every 60 min (SRA6). Femoral artery flow-mediated dilation (FMD), resting shear rate, blood flow, and endothelin-1 were measured at 0, 1, 3.5, 4.5, and 6.5-7 h. Mean femoral artery FMD over 7 h was significantly higher in SRA3 (4.1 ± 0.3%) compared with SIT (3.7 ± 0.3%, P = 0.04) but not in SRA6. Mean resting femoral shear rate over 7 h was increased significantly for SRA3 (45.3 ± 4.1/s, P < 0.001) and SRA6 (46.2 ± 4.1/s, P < 0.001) relative to SIT (33.1 ± 4.1/s). Endothelin-1 concentrations were not statistically different between conditions. Interrupting sitting with activity breaks every 30 min, but not 60 min, significantly increased mean femoral artery FMD over 7 h, relative to SIT. Our findings suggest that more frequent and shorter breaks may be more beneficial than longer, less frequent breaks for vascular health in those with T2D.NEW & NOTEWORTHY This is the first trial to examine both the effects of interrupting prolonged sitting on vascular function in type 2 diabetes and the effects of the frequency and duration of interruptions. Brief, simple resistance activity bouts every 30 min, but not every 60 min, increased mean femoral artery flow-mediated dilation over 7 h, relative to uninterrupted sitting. With further supporting evidence, these initial findings can have important implications for cardiovascular health in type 2 diabetes.

Different frequencies of active interruptions to sitting have distinct effects on 22 h glycemic control in type 2 diabetes.

BACKGROUND & AIMS: Whether the frequency of interruptions to sitting time involving simple resistance activities (SRAs), compared to uninterrupted sitting, differentially affected 22 h glycemic control in adults with medication-controlled type 2 diabetes (T2D). METHODS & RESULTS: Twenty-four participants (13 men; mean ± SD age 62 ± 8 years) completed three 8 h laboratory conditions: SIT: uninterrupted sitting; SRA3: sitting interrupted with 3 min of SRAs every 30 min; and, SRA6: sitting interrupted with 6 min of SRAs every 60 min. Flash glucose monitors assessed glycemic control over a 22 h period. No differences were observed between conditions for overall 22 h glycemic control as measured by AUCtotal, mean glucose and time in hyperglycemia. During the 3.5 h post-lunch period, mean glucose was significantly lower during SRA6 (10.1 mmol·L-1, 95%CI 9.2, 11.0) compared to SIT (11.1 mmol·L-1, 95%CI 10.2, 12.0; P = 0.006). Post-lunch iAUCnet was significantly lower during SRA6 (6.2 mmol·h·L-1, 95%CI 3.3, 9.1) compared to SIT (9.9 mmol·h·L-1, 95%CI 7.0, 12.9; P = 0.003). During the post-lunch period, compared to SIT (2.2 h, 95%CI 1.7, 2.6), time in hyperglycemia was significantly lower during SRA6 (1.5 h, 95%CI 1.0, 1.9, P = 0.001). Nocturnal mean glucose was significantly lower following the SRA3 condition (7.6 mmol·L-1, 95%CI 7.1, 8.1) compared to SIT (8.1 mmol·L-1, 95%CI 7.6, 8.7, P = 0.024). CONCLUSIONS: With standardized total activity time, less-frequent active interruptions to sitting may acutely improve glycemic control; while more-frequent interruptions may be beneficial for nocturnal glucose in those with medication-controlled T2D.

Mechanisms by Which Probiotic Bacteria Attenuate the Risk of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the second leading cause of cancer-related deaths worldwide. Chronic infections with hepatitis B virus (HBV) and hepatitis C virus (HCV), alcoholic liver disease (ALD), and non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) are the major extrinsic risk factors of HCC development. Genetic background is pivotal in HCC pathogenesis, and both germline mutations and single nucleotide polymorphism (SNP) are intrinsic risk factors of HCC. These HCC risk factors predispose to hepatic injury and subsequent activation of fibrogenesis that progresses into cirrhosis and HCC. Probiotic bacteria can mitigate HCC risk by modulating host gut microbiota (GM) to promote growth of beneficial microbes and inhibit HCC-associated dysbiosis, thus preventing pathogen-associated molecular patterns (PAMPs)-mediated hepatic inflammation. Probiotics have antiviral activities against HBV and HCV infections, ameliorate obesity and risk of NAFLD/NASH, and their antioxidant, anti-proliferative, anti-angiogenic, and anti-metastatic effects can prevent the HCC pathogenesis. Probiotics also upregulate the expression of tumor suppressor genes and downregulate oncogene expression. Moreover, metabolites generated by probiotics through degradation of dietary phytochemicals may mitigate the risk of HCC development. These multiple anticancer mechanisms illustrate the potential of probiotics as an adjuvant strategy for HCC risk management and treatment.

Protein kinase D1 and oxysterol-binding protein form a regulatory complex independent of phosphorylation.

Protein kinase D (PKD) controls secretion from the trans-Golgi network (TGN) by phosphorylating phosphatidylinositol 4-kinase IIIß and proteins that bind and/or transfer phosphatidylinositol 4-phosphate (PtdIns-4P), such as oxysterol-binding protein (OSBP) and ceramide transfer protein. Here, we investigated the consequences of PKD phosphorylation of OSBP at endoplasmic reticulum (ER)-Golgi membrane contact sites (MCS). Results with OSBP phospho-mutants revealed that PKD phosphorylation did not affect sterol and PtdIns-4P binding, activation of sphingomyelin (SM) synthesis at Golgi-ER MCS or other OSBP phospho-sites. Instead, an interaction was identified between the N-terminal region of OSBP and PKD1 that was independent of kinase activity and OSBP phosphorylation status. S916 autophosphorylation of PKD1 was inhibited by OSBP expression suggesting the interaction negatively regulates PKD1 activity. Stimulation of PKD1 activity by phorbol ester promoted the Golgi-localization of wild-type and phospho-mutants of OSBP but did not affect OSBP-dependent SM synthesis. Only when wild-type or kinase-dead PKD1 was overexpressed was 25-hydroxycholesterol-activated SM synthesis inhibited. We conclude that OSBP and PKD1 form a complex that inhibits both the oxysterol-dependent activity of OSBP at the ER-Golgi and activation of PKD1. Formation of the complex was independent of PKD1 activity and phosphorylation of OSBP.

Golgi localization of oxysterol binding protein-related protein 4L (ORP4L) is regulated by ligand binding.

Oxysterol binding protein (OSBP)-related protein 4L (ORP4L, also known as OSBPL2), a closely related paralogue and interacting partner of OSBP, binds sterols and phosphatidylinositol 4-phosphate [PI(4)P] and regulates cell proliferative signalling at the plasma membrane (PM). Here, we report that ORP4L also interacts with the trans-Golgi network (TGN) in an OSBP-, sterol- and PI(4)P-dependent manner. Characterization of ORP4L lipid and VAP binding mutants indicated an indirect mechanism for translocation to ER-Golgi contact sites in response to 25-hydroxycholesterol that was dependent on OSBP and PI(4)P. shRNA silencing revealed that ORP4L was required to maintain the organization and PI(4)P content of the Golgi and TGN. In contrast, the interaction of ORP4L with the PM was not dependent on its sterol, PI(4)P or VAP binding activities. At the PM, ORP4L partially localized with a genetically encoded probe for PI(4)P but not with a probe for phosphatidylinositol 4,5-bisphosphate. We conclude that ORP4L is differentially localized to the PM and ER-Golgi contacts sites. OSBP-, lipid- and VAP-regulated interactions of ORP4L with ER-Golgi contact sites are involved in the maintenance of Golgi and TGN structure.

Oxysterol-binding protein recruitment and activity at the endoplasmic reticulum-Golgi interface are independent of Sac1.

Oxysterol-binding protein (OSBP) localizes to endoplasmic reticulum (ER)-Golgi contact sites where it transports cholesterol and phosphatidylinositol 4-phosphate (PI-4P), and activates lipid transport and biosynthetic activities. The PI-4P phosphatase Sac1 cycles between the ER and Golgi apparatus where it potentially regulates OSBP activity. Here we examined whether the ER-Golgi distribution of endogenous or ectopically expressed Sac1 influences OSBP activity. OSBP and Sac1 co-localized at apparent ER-Golgi contact sites in response to 25-hydroxycholesterol (25OH), cholesterol depletion and p38 MAPK inhibitors. A Sac1 mutant that is unable to exit the ER did not localize with OSBP, suggesting that sterol perturbations cause Sac1 transport to the Golgi apparatus. Ectopic expression of Sac1 in the ER or Golgi apparatus, or Sac1 silencing, did not affect OSBP localization to ER-Golgi contact sites, OSBP-dependent activation of sphingomyelin synthesis, or cholesterol esterification in the ER. p38 MAPK inhibition and retention of Sac1 in the Golgi apparatus also caused OSBP phosphorylation and OSBP-dependent activation of sphingomyelin synthesis at ER-Golgi contacts. These results demonstrate that Sac1 expression in either the ER or Golgi apparatus has a minimal impact on the PI-4P that regulates OSBP activity or recruitment to contact sites.

How CCTα puts a leash on phospholipid synthesis.

The proportion of phosphatidylcholine (PC) in the membrane is controlled by CTP:phosphocholine cytidylyltransferase α (CCTα), which is known to be regulated by a dual auto-inhibitory and membrane-binding domain. However, the detailed mechanism by which this domain regulates CCTα activity is not clear. Ramezanpour et al. use a combined computational and biochemical approach to define new details of this mechanism, providing an elegant illustration of how the lipid-sensing domain of a phospholipid biosynthetic enzyme controls membrane homeostasis.

Bridging the molecular and biological functions of the oxysterol-binding protein family.

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute a large eukaryotic gene family that transports and regulates the metabolism of sterols and phospholipids. The original classification of the family based on oxysterol-binding activity belies the complex dual lipid-binding specificity of the conserved OSBP homology domain (OHD). Additional protein- and membrane-interacting modules mediate the targeting of select OSBP/ORPs to membrane contact sites between organelles, thus positioning the OHD between opposing membranes for lipid transfer and metabolic regulation. This unique subcellular location, coupled with diverse ligand preferences and tissue distribution, has identified OSBP/ORPs as key arbiters of membrane composition and function. Here, we will review how molecular models of OSBP/ORP-mediated intracellular lipid transport and regulation at membrane contact sites relate to their emerging roles in cellular and organismal functions.

Effects of empagliflozin treatment on cardiac function and structure in patients with type 2 diabetes: a cardiac magnetic resonance study.

BACKGROUND: The effects of empagliflozin on cardiac structure and function are not known. AIMS: To examine the changes in cardiac structure and function following the addition of empagliflozin in patients with type 2 (T2D) diabetes using cardiac magnetic resonance (CMR) imaging. METHODS: Twenty patients attending a specialist diabetes service recommended for treatment with empagliflozin, and 8 control patients with T2D on stable glucose lowering therapy were recruited for cardiac imaging. Participants underwent CMR scans at baseline and 6 months. Inclusion criteria were established T2D, age < 75 years, estimated glomerular filtration rate ≥45 mL/min/1.73 m2 . RESULTS: 17 of 20 in the empagliflozin group, and all of 8 in the control group completed the study. Empagliflozin therapy was associated with reduction in left ventricular end diastolic volume 155 mL (137 mL, 174 mL) at baseline to 145 mL (125 mL, 165 mL) at 6 months, P < 0.01, compared with the control group 153 mL (128 mL, 179 mL) at baseline and 158 mL (128 mL, 190 mL), not significant. There were no differences in measures of left ventricular mass, ejection fraction, heart rate or markers of cardiac fibrosis at baseline and 6 months in either group. CONCLUSIONS: This is the first CMR study to examine the effects of empagliflozin on cardiac function and structure, showing evidence of reduced end diastolic volume. This is likely to reflect change in plasma volume, and may explain the reduced cardiovascular death and heart failure seen in the EMPA-REG OUTCOME trial.

Cholesterol transfer at endosomal-organelle membrane contact sites.

PURPOSE OF REVIEW: Cholesterol is delivered to the limiting membrane of late endosomes by Niemann-Pick Type C1 and C2 proteins. This review summarizes recent evidence that cholesterol transfer from endosomes to the endoplasmic reticulum and other organelles is mediated by lipid-binding proteins that localize to membrane contact sites (MCS). RECENT FINDINGS: LDL-cholesterol in the late endosomal/lysosomes is exported to the plasma membrane, where most cholesterol resides, and the endoplasmic reticulum, which harbors the regulatory complexes and enzymes that control the synthesis and esterification of cholesterol. A major advance in dissecting these cholesterol transport pathways was identification of frequent and dynamic MCS between endosomes and the endoplasmic reticulum, peroxisomes and plasma membrane. Positioned at these MCS are members of the oxysterol-binding protein (OSBP) and steroidogenic acute regulatory protein-related lipid-transfer family of lipid transfer proteins that bridge the opposing membranes and directly or indirectly mediate cholesterol transfer. OSBP-related protein 1L (ORP1L), ORP5 and ORP6 mediate cholesterol transfer to the endoplasmic reticulum that regulates cholesterol homeostasis. ORP1L and STARD3 also move cholesterol from the endoplasmic reticulum-to-late endosomal/lysosomes under low-cholesterol conditions to facilitate intraluminal vesicle formation. Cholesterol transport also occurs at MCS with peroxisomes and possibly the plasma membrane. SUMMARY: Frequent contacts between organelles and the endo-lysosomal vesicles are sites for bidirectional transfer of cholesterol.

Phosphatidylcholine synthesis regulates triglyceride storage and chylomicron secretion by Caco2 cells.

Intracellular lipid droplets (LDs) supply fatty acids for energy, membrane biogenesis, and lipoprotein secretion. The surface monolayer of LDs is composed of phospholipids, primarily phosphatidylcholine (PC), that stabilize the neutral lipid core of triglyceride (TG). To determine the relationship between PC synthesis and TG storage and secretion in chylomicrons, we used a model of intestinal-derived human epithelial colorectal adenocarcinoma (Caco2) cells with knockout of PCYT1A, which encodes the rate-limiting enzyme CTP:phosphocholine cytidylyltransferase (CCT)α in the CDP-choline pathway, that were treated with the fatty acid oleate. CRISPR/Cas9 knockout of CCTα in Caco2 cells (Caco2-KO cells) reduced PC synthesis by 50%. Compared with Caco2 cells, Caco2-KO cells exposed to oleate had fewer and larger LDs and greater TG accumulation as a result. The addition of exogenous lysophosphatidylcholine to Caco2-KO cells reversed the LD morphology defect. Caco2-KO cells, differentiated into epithelial monolayers, accumulated intracellular TG and had deficient TG and chylomicron-associated apoB48 secretion; apoB100 secretion was unaffected by CCTα knockout or oleate. Metabolic-labeling and LD imaging of Caco2-KO cells indicated preferential shuttling of de novo synthesized TG into larger LDs rather than into chylomicrons. Thus, reduced de novo PC synthesis in Caco2 cells enhances TG storage in large LDs and inhibits apoB48 chylomicron secretion.

Efficacy and safety of methionine aminopeptidase 2 inhibition in type 2 diabetes: a randomised, placebo-controlled clinical trial.

AIMS/HYPOTHESIS: This multicentre randomised double-blind placebo-controlled clinical trial assessed the efficacy and safety of a methionine aminopeptidase 2 (MetAP2) inhibitor, beloranib, in individuals with obesity (BMI ≥30 kg/m2) and type 2 diabetes (HbA1c 53-97 mmol/mol [7-11%] and fasting glucose <15.6 mmol/l). METHODS: Participants were randomised (via a centralised interactive web response system) to placebo, 1.2 or 1.8 mg beloranib s.c. twice weekly for 26 weeks. Participants, investigators and the sponsor were blinded to group assignment. The primary endpoint was the change in weight from baseline to week 26. The trial was terminated early when beloranib development was stopped because of an imbalance of venous thromboembolism events in beloranib-treated individuals vs placebo that became evident during late-stage development of the drug. RESULTS: In total, 153 participants were randomised, 51 to placebo, 52 to 1.2 mg beloranib and 50 to 1.8 mg beloranib. In participants who completed week 26, the least squares mean ± SE weight change (baseline 111 kg) was -3.1 ± 1.2% with placebo (n = 22) vs -13.5 ± 1.1% and -12.7 ± 1.3% with 1.2 and 1.8 mg beloranib, respectively (n = 25; n = 19; p < 0.0001). The change in HbA1c (baseline 67 mmol/mol [8.3%]) was -6.6 ± 2.2 mmol/mol (-0.6 ± 0.2%) with placebo vs -21.9 ± 2.2 mmol/mol (-2.0 ± 0.2%) or -21.9 ± 3.3 mmol/mol (-2.0 ± 0.3%) with 1.2 or 1.8 mg beloranib (p < 0.0001), respectively. The most common beloranib adverse events were sleep related. One beloranib-treated participant experienced a non-fatal pulmonary embolism. CONCLUSIONS/INTERPRETATION: MetAP2 inhibitors represent a novel mechanism for producing meaningful weight loss and improvement in HbA1c. TRIAL REGISTRATION: ClinicalTrials.gov NCT02324491 FUNDING: The study was funded by Zafgen, Inc.

Correction to: Pioglitazone reduces cold-induced brown fat glucose uptake despite induction of browning in cultured human adipocytes: a randomised, controlled trial in humans.

The baseline insulin data given in Table 1 for the placebo group were incorrectly reported as 51 ± 10 pmol/l instead of 48 ± 10 pmol/l. This mistake also impacts on data reported in Table 4.

Pioglitazone reduces cold-induced brown fat glucose uptake despite induction of browning in cultured human adipocytes: a randomised, controlled trial in humans.

AIMS/HYPOTHESIS: Increasing brown adipose tissue (BAT) activity is a possible therapeutic strategy to increase energy expenditure and glucose and lipid clearance to ameliorate obesity and associated comorbidities. The thiazolidinedione (TZD) class of glucose-lowering drugs increase BAT browning in preclinical experimental models but whether these actions extend to humans in vivo is unknown. The aim of this study was to determine the effect of pioglitazone treatment on adipocyte browning and adaptive thermogenesis in humans. METHODS: We first examined whether pioglitazone treatment of cultured human primary subacromioclavicular-derived adipocytes induced browning. Then, in a blinded, placebo-controlled, parallel trial, conducted within the Baker Institute clinical research laboratories, 14 lean male participants who were free of cardiometabolic disease were randomised to receive either placebo (lactose; n = 7, age 22 ± 1 years) or pioglitazone (45 mg/day, n = 7, age 21 ± 1 years) for 28 days. Participants were allocated to treatments by Alfred Hospital staff independent from the study via electronic generation of a random number sequence. Researchers conducting trials and analysing data were blind to treatment allocation. The change in cold-stimulated BAT activity, assessed before and after the intervention by [18F]fluorodeoxyglucose uptake via positron emission tomography/computed tomography in upper thoracic and cervical adipose tissue, was the primary outcome measure. Energy expenditure, cardiovascular responses, core temperature, blood metabolites and hormones were measured in response to acute cold exposure along with body composition before and after the intervention. RESULTS: Pioglitazone significantly increased in vitro browning and adipogenesis of adipocytes. In the clinical trial, cold-induced BAT maximum standardised uptake value was significantly reduced after pioglitazone compared with placebo (-57 ± 6% vs -12 ± 18%, respectively; p < 0.05). BAT total glucose uptake followed a similar but non-significant trend (-50 ± 10% vs -6 ± 24%, respectively; p = 0.097). Pioglitazone increased total and lean body mass compared with placebo (p < 0.05). No other changes between groups were detected. CONCLUSIONS/INTERPRETATION: The disparity in the actions of pioglitazone on BAT between preclinical experimental models and our in vivo human trial highlight the imperative to conduct human proof-of-concept studies as early as possible in BAT research programmes aimed at therapeutic development. Our clinical trial findings suggest that reduced BAT activity may contribute to weight gain associated with pioglitazone and other TZDs. TRIAL REGISTRATION: ClinicalTrials.gov NCT02236962 FUNDING: This work was supported by the Diabetes Australia Research Program and OIS scheme from the Victorian State Government.