Surveillance Outcome and Genetic Findings in Individuals at High Risk of Pancreatic Cancer.

INTRODUCTION: Pancreatic ductal adenocarcinoma (PDAC) has a poor 5-year survival rate. PDAC surveillance is recommended in high-risk individuals (HRIs) with strong PDAC family history or a pathogenic germline variant (PGV) in a PDAC susceptibility gene. We aimed to explore a potential correlation between genetic status, extent of family history, pancreatic findings, and surveillance implications in heterogeneous PDAC HRIs. METHODS: A total of 239 HRIs from 202 families were tested genetically and underwent prospective pancreatic surveillance for 6 years. RESULTS: The cohort was divided into 3 groups: familial pancreatic cancer (FPC; 70 individuals, 54 families), familial non-FPC (81 individuals, 73 families), and hereditary pancreatic cancer (PC) (88 individuals, 75 families). PGVs were detected in 37.6% of all families, including 11.1% of FPC families and 9.6% of familial non-FPC families. The hereditary PC group had earlier onset of PDAC compared with the other 2 groups. BRCA2 PGV carriers showed earlier onset of PDAC and pancreatic cysts. Of the 239 HRIs, PDAC was detected in 11 individuals (4.6%), with 73% diagnosed at an early stage; 4 (1.67%) had pancreatic neuroendocrine tumor; 6 (2.5%) had main-duct intraductal papillary neoplasm (IPMN); and 41 (17.15%) had side-branch IPMN. Seventeen individuals were referred to surgery, and 12 were alive at the end of the study. DISCUSSION: The percentage of PDAC was similar in the 3 groups studied. The hereditary PC group, and particularly BRCA2 PGV carriers, had an earlier age of PDAC onset. PGVs were detected in a significant percentage of HRIs with PC. Surveillance seems effective for detection of early-stage PDAC and precursor lesions.

Early Initiation of Adalimumab Significantly Diminishes Postoperative Crohn's Disease Endoscopic Recurrence and Is Superior to 6-Mercaptopurine Therapy: An Open-Label, Randomized Controlled Study.

Postoperative recurrence (POR) is the rule in patients with Crohn's disease (CD), mitigated with prophylactic therapy. The evidence for therapeutic choice and timing of intervention is lacking. We aimed to compare the rates of POR in patients treated early with prophylactic 6-mercaptopurine (6-MP) or adalimumab. We conducted a prospective single-center randomized open-label clinical study in which patients in surgical remission following their first ileocecectomy were randomized to receive early treatment with 6-MP or adalimumab. Patients were followed up clinically every 3 months and underwent endoscopy at weeks 32 and 58 postoperatively. The primary endpoint was endoscopic recurrence (ePOR) at 1 year (week 58), defined as a Rutgeerts score ≥ i2. We enrolled 35 patients (25 males, mean age 35 ± 1.4 years, median disease duration 5 ± 6.1 years) following ileocecectomy. Of these, seven (20%) were current smokers and nine (26%) biologics-experienced. Patients allocated to adalimumab had significantly less ePOR than patients treated with 6MP at week 32 (21% vs. 69%, p = 0.004) and 58 (47% vs. 75%), (p = 0.03, HR = 0.39, 95% CI = 0.16-0.93). POR was associated with an increased diameter of the resected small bowel surgical specimen, lower baseline body mass index (BMI), increased week 18 fecal calprotectin, increased week 18 serum alanine aminotransferase and decreased week 18 hemoglobin level. Adalimumab was more effective than 6-MP in preventing ePOR. Increased operative small bowel diameter and lower postoperative BMI were associated with ePOR. At eighteen weeks, serum hemoglobin, ALT and fecal calprotectin levels were predictive of endoscopic disease recurrence. (ClinicalTrials.gov ID NCT01629628).

Dysglycemia in non-functioning pancreatic neuroendocrine tumors (NF-PNET): Further insights into an under recognized entity.

Objective: Pancreatic neuroendocrine tumors (PNETs) are rare, but their incidence has risen significantly in recent years. Whereas diabetes mellitus (DM) is recognized in association with chronic pancreatitis and pancreatic cancer, it has not been well-characterized concerning non-functioning (NF)-PNETs.Study aim: to determine whether NF-PNETs are associated with DM/ Pre-DM and characterize the features of this putative association. Methods: Retrospective study to evaluate rate of Pre-DM /DM in subjects with NF-PNETs. Results: Study cohort of 129 patients with histologically confirmed NF-PNETs, ∼60% were men (M/F: 77/52). Abnormal glucose metabolism that preceded any treatment was seen in 70% of this cohort: overt DM in 34% and Pre-DM in 36% of the subjects. However, during follow-up, the overall prevalence rose to 80.6%, owing exclusively to newly diagnosed DM in subjects who received treatment.Patients with DM/Pre-DM were older (65 ± 11; 54 ± 14; p < 0.0001), the tumor was more commonly localized in the pancreatic body and tail (76.5% vs. 23.5% p = 0.03), while BMI (27 ± 6 vs. 28 ± 5 kg/m2), and tumor size (2.4 ± 2 vs. 2.9 ± 3.2 cm) were similar. The relative prevalence of DM in our cohort of NF-PNETs was 1.6 higher than that in the age and gender-adjusted general Israeli population (95 %CI: 1.197-2.212p = 0.03). Conclusions: We found a high rate of impaired glucose metabolism, either DM or Pre-DM, in a large cohort of NF-PNETs. The high prevalence of diabetes/pre-diabetes was unrelated to obesity or tumor size. This observation should increase awareness of the presence of DM on presentation or during treatment of "NF"-PNETs.

A Lymph Node Ratio Model for Prognosis of Patients with Pancreatic Neuroendocrine Tumors.

The objective of this study was to determine the prognostic value of lymph node (LN) involvement and the LN ratio (LNR) and their effect on recurrence rates and survival in patients with pancreatic neuroendocrine tumors (PNETs) undergoing surgery. This single-center retrospective study reviewed the medical records of 95 consecutive patients diagnosed with PNETs who underwent surgery at our medical center between 1997 and 2017. The retrieved information included patient demographics, pathology reports, treatments, and oncological outcomes. Results: 95 consecutive potentially suitable patients were identified. The 78 patients with PNETs who underwent surgery and for whom there was adequate data were included in the analysis. Their mean ± standard deviation age at diagnosis was 57.4 ± 13.4 years (range 20-82), and there were 50 males (64%) and 28 females (36%). 23 patients (30%) had LN metastases (N1). The 2.5- and 5-year disease-free survival (DFS) rates for the entire cohort were 79.5% and 71.8%, respectively, and their 2- and 5-year overall survival (OS) rates were 85.9% and 82.1%, respectively. The optimal value of the LNR was 0.1603, which correlated with the outcome (2-year OS p = 0.002 HR = 13.4 and 5-year DFS p = 0.016 HR = 7.2, respectively, and 5-year OS and 5-year DFS p = 0.004 HR = 9 and p = 0.001 HR = 10.6, respectively). However, the multivariate analysis failed to show that the LNR was an independent prognostic factor in PNETs. Patients with PNETs grade and stage are known key prognostic factors influencing OS and DFS. According to our results, LNR failed to be an independent prognostic factor.

Impact of margin ablation after EMR of large nonpedunculated colonic polyps in routine clinical practice.

BACKGROUND AND AIMS: Owing to its simplicity, effectiveness, and safety, EMR is the preferred treatment for the majority of large (≥20 mm) nonpedunculated colonic polyps (LNPCPs); however, residual and recurrent adenomas (RRAs) encountered during surveillance constitute a major limitation. Thermal ablation of the post-EMR mucosal defect margin has been shown to be highly efficacious in reducing RRA in a randomized trial setting, but data on effectiveness in clinical practice are scarce. We aimed to determine the effectiveness of this technique for reducing RRAs in routine clinical practice. METHODS: We analyzed data collected in 3 hospitals in Israel: Prospective data were available in 2 hospitals where margin thermal ablation with snare-tip soft coagulation (STSC) is routinely performed after EMR of LNPCP (TA-EMR). Only retrospective data were available from the third center, which exclusively did not perform STSC (standard EMR] [S-EMR]), during the study period. Surveillance was performed 4 to 6 months after resection. RRA was assessed endoscopically with high-definition white light and optical chromoendoscopy. The primary endpoint was RRA at first surveillance colonoscopy. RESULTS: Data from 764 patients with 824 LNPCPs were analyzed. The patient and lesion characteristics were similar between the groups. Four hundred sixty-four LNPCPs were treated by TA-EMR and 360 LNPCPs by S-EMR. RRA at first surveillance colonoscopy was detected in 14 (3.6%) of lesions in the TA-EMR group compared with 96 (31.6%) in the S-EMR group (P < .001; RR = .14; 95% CI, .07-.29). Adverse events were comparable between the 2 groups. CONCLUSION: TA-EMR leads to a significant reduction in post-EMR recurrence in routine clinical practice.

Pancreatic cyst fluid glucose: a rapid on-site diagnostic test for mucinous cysts.

Background: Pancreatic cystic fluid (PCF) analysis is frequently used for cyst diagnosis with carcinoembryonic antigen (CEA) being the most accepted biomarker. Low glucose levels in PCF were previously suggested as a marker for mucinous cysts. A bed-side glucometer is a point-of care, immediate, simple, and cheap method which requires a small volume of PCF. Objectives: The aim of our study was to identify the optimal glucose cut-off level for identifying mucinous cysts, evaluate the diagnostic accuracy of glucose compared to CEA, and validate glucometry against reference laboratory biochemical analysis. Design: A single-center prospective cohort study. Methods: Consecutive patients aged 18 and older, who underwent pancreatic cyst evaluation, at the Tel Aviv Medical Center between 2016 and 2021 were analyzed. Cyst type was defined based on clinical, laboratory, and radiologic findings. Glucose was measured using laboratory biochemical analysis and two glucometers. Receiver operating characteristic analysis derived sensitivity, specificity, and accuracy were calculated and McNemar test was used to compare between methods. Results: One hundred and one PCF samples were evaluated. The areas under the receiver operating characteristics curve for identifying mucinous cysts using glucometer, glucose laboratory, and their combination were 0.88 (p < 0.001), 0.92 (p < 0.001), and 0.93 (p < 0.001), respectively. A glucose level of 87 mg/dL was identified as the optimal laboratory glucose threshold value to detect mucinous cyst with a sensitivity of 90.9%, specificity of 83.3%, and accuracy of 89.3, higher in comparison to cyst fluid CEA. Furthermore, PCF glucose levels had the strongest association with mucinous cysts. Conclusion: Our findings suggest that PCF glucose level is more accurate than CEA for the diagnosis of mucinous cysts. Glucometry glucose level assessment demonstrated an excellent correlation with laboratory glucose measurements and may become a useful diagnostic test.

The Cytotoxic Effect of Isolated Cannabinoid Extracts on Polypoid Colorectal Tissue.

Purified cannabinoids have been shown to prevent proliferation and induce apoptosis in colorectal carcinoma cell lines. To assess the cytotoxic effect of cannabinoid extracts and purified cannabinoids on both colorectal polyps and normal colonic cells, as well as their synergistic interaction. Various blends were tested to identify the optimal synergistic effect. Methods: Biopsies from polyps and healthy colonic tissue were obtained from 22 patients undergoing colonic polypectomies. The toxicity of a variety of cannabinoid extracts and purified cannabinoids at different concentrations was evaluated. The synergistic effect of cannabinoids was calculated based on the cells' survival. Isolated cannabinoids illustrated different toxic effects on the viability of cells derived from colorectal polyps. THC-d8 and THC-d9 were the most toxic and exhibited persistent toxicity in all the polyps tested. CBD was more toxic to polypoid cells in comparison to normal colonic cells at a concentration of 15 µM. The combinations of the cannabinoids CBDV, THCV, CBDVA, CBCA, and CBGA exhibited a synergistic inhibitory effect on the viability of cells derived from colon polyps of patients. Isolated cannabinoid compounds interacted synergistically against colonic polyps, and some also possessed a differential toxic effect on polyp and adjacent colonic tissue, suggesting possible future therapeutic value.

Endoscopic ultrasound-guided radiofrequency ablation of premalignant pancreatic-cystic neoplasms and neuroendocrine tumors: prospective study.

BACKGROUND: Endoscopic ultrasound-guided radiofrequency ablation (EUS-RFA) is a developing therapeutic approach for premalignant pancreatic-cystic neoplasms (PCNs) and small pancreatic neuroendocrine tumors (PNETs). The safety and efficacy of pancreatic EUS-RFA were previously reported in small series. Herein we report our initial experience with RFA of PCNs and small PNETs. METHODS: This is a prospective single-center study including 12 patients with a median follow-up of 7 months, with either PCN or PNET &lt;2 cm. Eligible PCNs were either intraductal papillary mucinous neoplasms (IPMN) with worrisome features or mucinous cystic neoplasms (MCN) that were not eligible or refused surgery. Ablation was performed using a 19-gauge dedicated needle. RESULTS: Twelve patients were treated, five had PCNs (four IPMNs, one MCN; median size of 36 mm, range 12-60) and seven had PNETs (median size 8.9 mm, range 6-18). Among patients with PCNs, the complete radiologic response was achieved in 3/5 (60%), partial response in 1/5 (20%) and failure in 1/5 (20%). Among six patients with nonfunctioning PNETs, the complete radiologic response was achieved in 4/6 (66.7%), partial radiologic response in 0/6 (0%) and failure in 2/6 (33.3%). Following a median follow-up of 7 months. One patient with insulinoma showed complete resolution of hypoglycemia-related symptoms. Three postprocedural adverse events occurred, including one case (1/12, 8.3%) of mild acute pancreatitis and two cases (2/12, 16.7%) of abdominal pain. CONCLUSION: EUS-guided RFA for premalignant PCNs and PNETs is feasible and well-tolerated. Efficacy would be further evaluated with continued follow-up of patients.

Increased prevalence of colorectal neoplasia in patients with intraductal papillary mucinous neoplasms.

Background: The association between intraductal papillary mucinous neoplasms (IPMNs) and colorectal cancer (CRC) and polyps is controversial. Objectives: To compare the prevalence of CRC and colorectal polyps among patients with IPMN and matched average risk individuals. Methods: A match cross-sectional historical study comparing colonoscopy findings of 310 patients with IPMN cysts who underwent at least one colonoscopy examination from 2004 through 2019, with 310 age- and gender-matched average risk participants who underwent a screening colonoscopy. CRC and polyps were assessed in both groups. The prevalence and odds ratio were calculated. Results: CRC was diagnosed in 16 of 310 patients with IPMN (5.2%), and at least one polyp was detected in 96 patients (31%). The prevalence of CRC was greater among patients with IPMN than in matched individuals [5.2% versus 1.3%, p = 0.012, prevalence odds ratio (POR) 4, confidence interval (CI) 1.29-16.44]. The overall prevalence of polyps was not higher among patients with IPMN than in matched individuals (31% versus 26.8%, p = 0.291, POR 1.22, CI 0.85-1.76). However, the prevalence of colorectal adenomas with high-grade dysplasia was higher in patients with IPMN than in matched individuals (4.2% versus 1%, p = 0.02, POR 4.33, CI, 1.19-23.7). The prevalence of large polyps (i.e. more than 20 mm in size) was also greater in patients with IPMN than in matched individuals (6.1% versus 1.9%, p = 0.011, POR 3.6, CI, 1.29-12.40). Conclusion: Patients with IPMN have a significantly higher prevalence of CRC and advanced polyps than the average risk population. In view of our findings, we suggest that once the diagnosis of IPMN is made, special consideration of CRC should be undertaken.

Resection Versus Observation of Small Asymptomatic Nonfunctioning Pancreatic Neuroendocrine Tumors.

BACKGROUND: Management of asymptomatic, nonfunctioning small pancreatic neuroendocrine tumors (PNETs) is controversial because of their overall good prognosis, and the morbidity and mortality associated with pancreatic surgery. Our aim was to compare the outcomes of resection with expectant management of patients with small asymptomatic PNETs. METHODS: Retrospective review of patients with nonfunctioning asymptomatic PNETs < 2 cm that underwent resection or expectant management at the Tel-Aviv Medical Center between 2001 and 2018. RESULTS: Forty-four patients with small asymptomatic, biopsy-proven low-grade PNETs with a KI67 proliferative index < 3% were observed for a mean of 52.48 months. Gallium67DOTATOC-PET scan was completed in 32 patients and demonstrated uptake in the pancreatic tumor in 25 (78%). No patient developed systemic metastases. Two patients underwent resection due to tumor growth, and true tumor enlargement was evidenced in final pathology in one of them. Fifty-five patients underwent immediate resection. Significant complications (Clavien-Dindo grade ≥ 3) developed in 10 patients (18%), mostly due to pancreatic leak, and led to one mortality (1.8%). Pathological evaluation revealed lymphovascular invasion in 1 patient, lymph node metastases in none, and a Ki67 index ≥ 3% in 5. No case of tumor recurrence was diagnosed after mean follow-up of 52.8 months. CONCLUSIONS: No patients with asymptomatic low-grade small PNETs treated by expectant management were diagnosed with regional or systemic metastases after a 52.8-month follow-up. Local tumor progression rate was 2.1%. Surgery has excellent long-term outcomes, but it harbors significant morbidity and mortality. Observation can be considered for selected patients with asymptomatic, small, low grade PNETs.

Clinical outcomes of endoscopic balloon dilatation of intestinal strictures in patients with Crohn's disease.

Intestinal strictures are common complications of Crohn's disease (CD). Endoscopic balloon dilatation (EBD) constitutes an alternative therapy to surgery, but associated factors of procedure success are inconclusive. Therefore, we aimed to evaluate the EBD success rate and its associated factors in CD patients.This is a retrospective cohort study of consecutive EBDs that were conducted between 2006 and 2014 among patients with CD with lower gastrointestinal tract strictures. Patients' and stricture characteristics, short term procedure success and related complications at 1 week follow-up, and long-term clinical endpoints were documented.A total of 138 dilatations were performed on 64 CD patients. The overall dilatation success rate was 84.8%, with no difference between primary or anastomotic strictures, or between first or recurrent dilatation procedures. Long strictures (≥4 cm) were negatively associated with successful EBDs, but not with perforations. A multivariate analysis adjusting for age, sex, smoking, and disease duration revealed that a maximal dilatation diameter of ≥15 mm was positively associated with a successful EBD, while an inflamed stricture was negatively associated with procedure success. Strictures which were both long and inflamed were associated with the lowest EBD success rates compared with other strictures. Only 32.8% of patients required surgery during the follow-up period. Long-term prevention of surgery was negatively associated with stricture length and with a successful EBD.EBD is highly successful in treating intestinal strictures and in prevention of surgery in CD patients. Although EBD of long strictures is safe, it will not prevent surgery in the majority of cases.

A multicenter randomized trial comparing a 25-gauge EUS fine-needle aspiration device with a 20-gauge EUS fine-needle biopsy device.

BACKGROUND AND AIMS: Several studies have compared EUS-guided FNA with fine-needle biopsy (FNB), but none have proven superiority. We performed a multicenter randomized controlled trial to compare the performance of a commonly used 25-gauge FNA needle with a newly designed 20-gauge FNB needle. METHODS: Consecutive patients with a solid lesion were randomized in this international multicenter study between a 25-gauge FNA (EchoTip Ultra) or a 20-gauge FNB needle (ProCore). The primary endpoint was diagnostic accuracy for malignancy and the Bethesda classification (non-diagnostic, benign, atypical, malignant). Technical success, safety, and sample quality were also assessed. Multivariable and supplementary analyses were performed to adjust for confounders. RESULTS: A total of 608 patients were allocated to FNA (n = 306) or FNB (n = 302); 312 pancreatic lesions (51%), 147 lymph nodes (24%), and 149 other lesions (25%). Technical success rate was 100% for the 25-gauge FNA and 99% for the 20-gauge FNB needle (P = .043), with no differences in adverse events. The 20-gauge FNB needle outperformed 25-gauge FNA in terms of histologic yield (77% vs 44%, P < .001), accuracy for malignancy (87% vs 78%, P = .002) and Bethesda classification (82% vs 72%, P = .002). This was robust when corrected for indication, lesion size, number of passes, and presence of an on-site pathologist (odds ratio, 3.53; 95% confidence interval, 1.55-8.56; P = .004), and did not differ among centers (P = .836). CONCLUSION: The 20-gauge FNB needle outperformed the 25-gauge FNA needle in terms of histologic yield and diagnostic accuracy. This benefit was irrespective of the indication and was consistent among participating centers, supporting the general applicability of our findings. (Clinical trial registration number: NCT02167074.).

PANCREATIC INCIDENTALOMA: DIFFERENTIATING NONFUNCTIONING PANCREATIC NEUROENDOCRINE TUMORS FROM INTRAPANCREATIC ACCESSORY SPLEEN.

OBJECTIVE: To improve the preoperative assessment of pancreatic incidentalomas (PIs) by analysis of 1 index case and characterization of the published features of intrapancreatic accessory spleen (IPAS) compared to pancreatic neuroendocrine tumor (PNET). METHODS: A search of the literature using the online database MEDLINE. RESULTS: In all, 46 cases of IPAS have been described to date: 17 were "presumed" as IPAS based on technetium-99m (Tc-99m) scanning, fine-needle aspiration (FNA) stain for CD8, or contrast-enhanced sonography; 29 were misdiagnosed as PNET and underwent surgery. The pancreatic lesions were 1) mostly solitary; 2) solid on imaging; 3) well defined; 4) located predominantly at the pancreatic tail; 5) not exceeding 3 cm in the largest diameter; 5) all detected in adults (22-81 years); 6) not related to sex. In subjects referred for surgery, standard imaging studies/imaging protocols did not differentiate between IPAS and PNET. FNA was performed in 5/46 cases, all of which were false-positive for PNET. Immunohistochemical staining for T-cells on FNA material and specific imaging features (characteristic arciform splenic enhancement pattern on dynamic computed tomography [CT]; nuclear scintigraphies with radioisotope specifically trapped by splenic tissue [Tc-99m]) or contrast-enhanced sonography offered valuable clues. Still, distal pancreatectomy and splenectomy was carried out in 72%, and the rest had distal pancreatectomies. CONCLUSION: IPAS should be considered before surgery in patients with PIs. A new practical algorithm is presented for better preoperative evaluation of such lesions; it combines the recognition of early indicators and sequential consideration of cytologic and imaging features to decrease the hazards of unnecessary major surgery. ABBREVIATIONS: CT = computed tomography EUS = endoscopic ultrasound FNA = fine-needle aspiration HDRBC = heat-damaged red blood cells IPAS = intrapancreatic accessory spleen MRI = magnetic resonance tomography NF-PNET = nonfunctioning pancreatic neuroendocrine tumor PET = positron emission tomography PNET = pancreatic neuroendocrine tumor PI = pancreatic incidentalomas SPIO = superparamagnetic iron oxide Tc-99m = technetium-99m.

Genetic ablation or chemical inhibition of phosphatidylcholine transfer protein attenuates diet-induced hepatic glucose production.

UNLABELLED: Phosphatidylcholine transfer protein (PC-TP, synonym StARD2) is a highly specific intracellular lipid binding protein that is enriched in liver. Coding region polymorphisms in both humans and mice appear to confer protection against measures of insulin resistance. The current study was designed to test the hypotheses that Pctp-/- mice are protected against diet-induced increases in hepatic glucose production and that small molecule inhibition of PC-TP recapitulates this phenotype. Pctp-/- and wildtype mice were subjected to high-fat feeding and rates of hepatic glucose production and glucose clearance were quantified by hyperinsulinemic euglycemic clamp studies and pyruvate tolerance tests. These studies revealed that high-fat diet-induced increases in hepatic glucose production were markedly attenuated in Pctp-/- mice. Small molecule inhibitors of PC-TP were synthesized and their potencies, as well as mechanism of inhibition, were characterized in vitro. An optimized inhibitor was administered to high-fat-fed mice and used to explore effects on insulin signaling in cell culture systems. Small molecule inhibitors bound PC-TP, displaced phosphatidylcholines from the lipid binding site, and increased the thermal stability of the protein. Administration of the optimized inhibitor to wildtype mice attenuated hepatic glucose production associated with high-fat feeding, but had no activity in Pctp-/- mice. Indicative of a mechanism for reducing glucose intolerance that is distinct from commonly utilized insulin-sensitizing agents, the inhibitor promoted insulin-independent phosphorylation of key insulin signaling molecules. CONCLUSION: These findings suggest PC-TP inhibition as a novel therapeutic strategy in the management of hepatic insulin resistance.

Regulatory role for phosphatidylcholine transfer protein/StarD2 in the metabolic response to peroxisome proliferator activated receptor alpha (PPARalpha).

Phosphatidylcholine transfer protein (PC-TP, a.k.a. StarD2) is abundantly expressed in liver and is regulated by PPARalpha. When fed the synthetic PPARalpha ligand fenofibrate, Pctp(-/-) mice exhibited altered lipid and glucose metabolism. Microarray profiling of livers from fenofibrate fed wild type and Pctp(-/-) mice revealed differential expression of a broad array of metabolic genes, as well as their regulatory transcription factors. PC-TP expression in cell culture controlled the activities of both PPARalpha and HNF4alpha, suggesting that the mechanism by which it modulates hepatic metabolism is at least in part via activation of transcription factors that govern nutrient homeostasis.

Regulation of hepatic lipogenesis by the transcription factor XBP1.

Dietary carbohydrates regulate hepatic lipogenesis by controlling the expression of critical enzymes in glycolytic and lipogenic pathways. We found that the transcription factor XBP1, a key regulator of the unfolded protein response, is required for the unrelated function of normal fatty acid synthesis in the liver. XBP1 protein expression in mice was elevated after feeding carbohydrates and corresponded with the induction of critical genes involved in fatty acid synthesis. Inducible, selective deletion of XBP1 in the liver resulted in marked hypocholesterolemia and hypotriglyceridemia, secondary to a decreased production of lipids from the liver. This phenotype was not accompanied by hepatic steatosis or compromise in protein secretory function. The identification of XBP1 as a regulator of lipogenesis has important implications for human dyslipidemias.

Regulation of energy substrate utilization and hepatic insulin sensitivity by phosphatidylcholine transfer protein/StarD2.

Phosphatidylcholine transfer protein (PC-TP, also known as StarD2) is a highly specific intracellular lipid binding protein with accentuated expression in oxidative tissues. Here we show that decreased plasma concentrations of glucose and free fatty acids in fasting PC-TP-deficient (Pctp(-/-)) mice are attributable to increased hepatic insulin sensitivity. In hyperinsulinemic-euglycemic clamp studies, Pctp(-/-) mice exhibited profound reductions in hepatic glucose production, gluconeogenesis, glycogenolysis, and glucose cycling. These changes were explained in part by the lack of PC-TP expression in liver per se and in part by marked alterations in body fat composition. Reduced respiratory quotients in Pctp(-/-) mice were indicative of preferential fatty acid utilization for energy production in oxidative tissues. In the setting of decreased hepatic fatty acid synthesis, increased clearance rates of dietary triglycerides and increased hepatic triglyceride production rates reflected higher turnover in Pctp(-/-) mice. Collectively, these data support a key biological role for PC-TP in the regulation of energy substrate utilization.

Hepatic insulin resistance is sufficient to produce dyslipidemia and susceptibility to atherosclerosis.

Insulin resistance plays a central role in the development of the metabolic syndrome, but how it relates to cardiovascular disease remains controversial. Liver insulin receptor knockout (LIRKO) mice have pure hepatic insulin resistance. On a standard chow diet, LIRKO mice have a proatherogenic lipoprotein profile with reduced high-density lipoprotein (HDL) cholesterol and very low-density lipoprotein (VLDL) particles that are markedly enriched in cholesterol. This is due to increased secretion and decreased clearance of apolipoprotein B-containing lipoproteins, coupled with decreased triglyceride secretion secondary to increased expression of Pgc-1 beta (Ppargc-1b), which promotes VLDL secretion, but decreased expression of Srebp-1c (Srebf1), Srebp-2 (Srebf2), and their targets, the lipogenic enzymes and the LDL receptor. Within 12 weeks on an atherogenic diet, LIRKO mice show marked hypercholesterolemia, and 100% of LIRKO mice, but 0% of controls, develop severe atherosclerosis. Thus, insulin resistance at the level of the liver is sufficient to produce the dyslipidemia and increased risk of atherosclerosis associated with the metabolic syndrome.

Interacting proteins dictate function of the minimal START domain phosphatidylcholine transfer protein/StarD2.

The Star (steroidogenic acute regulatory protein)-related transfer (START) domain superfamily is characterized by a distinctive lipid-binding motif. START domains typically reside in multidomain proteins, suggesting their function as lipid sensors that trigger biological activities. Phosphatidylcholine transfer protein (PC-TP, also known as StarD2) is an example of a START domain minimal protein that consists only of the lipid-binding motif. PC-TP, which binds phosphatidylcholine exclusively, is expressed during embryonic development and in several tissues of the adult mouse, including liver. Although it catalyzes the intermembrane exchange of phosphatidylcholines in vitro, this activity does not appear to explain the various metabolic alterations observed in mice lacking PC-TP. Here we demonstrate that PC-TP function may be mediated via interacting proteins. Yeast two-hybrid screening using libraries prepared from mouse liver and embryo identified Them2 (thioesterase superfamily member 2) and the homeodomain transcription factor Pax3 (paired box gene 3), respectively, as PC-TP-interacting proteins. These were notable because the START domain superfamily contains multidomain proteins in which the START domain coexists with thioesterase domains in mammals and with homeodomain transcription factors in plants. Interactions were verified in pulldown assays, and colocalization with PC-TP was confirmed within tissues and intracellularly. The acyl-CoA thioesterase activity of purified recombinant Them2 was markedly enhanced by recombinant PC-TP. In tissue culture, PC-TP coactivated the transcriptional activity of Pax3. These findings suggest that PC-TP functions as a phosphatidylcholine-sensing molecule that engages in diverse regulatory activities that depend upon the cellular expression of distinct interacting proteins.

Structure and function of phosphatidylcholine transfer protein (PC-TP)/StarD2.

Phosphatidylcholine transfer protein (PC-TP) is a highly specific soluble lipid binding protein that transfers phosphatidylcholine between membranes in vitro. PC-TP is a member of the steroidogenic acute regulatory protein-related transfer (START) domain superfamily. Although its biochemical properties and structure are well characterized, the functions of PC-TP in vivo remain incompletely understood. Studies of mice with homozygous disruption of the Pctp gene have largely refuted the hypothesis that this protein participates in the hepatocellular selection and transport of biliary phospholipids, in the production of lung surfactant, in leukotriene biosynthesis and in cellular phosphatidylcholine metabolism. Nevertheless, Pctp(-/-) mice exhibit interesting defects in lipid homeostasis, the understanding of which should elucidate the biological functions of PC-TP.