Fat Clearance Research Articles

Comment on "Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women".

Yoshino et al (Reports, 11 June 2021, p. 1224) have reported that nicotinamide mononucleotide (NMN) increases muscle insulin sensitivity in prediabetic women. However, the 13 women who received NMN had hepatic lipid content of 6.3 ± 1.2%, whereas the 12 in the placebo group had 14.8 ± 2.0% (P = 0.003). Given that a target of NMN is liver fat clearance, this was not an effectively randomized trial.

Liver fat storage is controlled by HNF4\u03b1 through induction of lipophagy and is reversed by a potent HNF4\u03b1 agonist

We report the discovery of strong HNF4α agonists and their use to uncover a previously unknown pathway by which HNF4α controls the level of fat storage in the liver. This involves the induction of lipophagy by dihydroceramides, the synthesis and secretion of which is controlled by genes induced by HNF4α. The HNF4α activators are N-trans caffeoyltyramine (NCT) and N-trans feruloyltyramine (NFT), which are structurally related to the known drugs alverine and benfluorex, which we previously showed to be weak HNF4α activators. In vitro, NCT and NFT induced fat clearance from palmitate-loaded cells. In DIO mice, NCT led to recovery of hepatic HNF4α expression and reduction of steatosis. Mechanistically, increased dihydroceramide production and action downstream of HNF4α occurred through increased expression of HNF4α downstream genes, including SPNS2 and CYP26A1. NCT was completely nontoxic at the highest dose administered and so is a strong candidate for an NAFLD therapeutic.

Retraction Note to: Effect of a high fat diet on lipid absorption and fatty acid transport in a rat model of short bowel syndrome

Long chain fatty acids (LCFAs) appear to be powerful stimulants for small bowel adaptation in patients with short bowel syndrome (SBS). However, the dietary lipid content may alter intestinal lipid transport. The aim of this study was to investigate the effects of a high fat diet (HFD) on in vivo lipid absorption and molecular and cellular mechanisms of LCFAs uptake by the remaining bowel. Male Sprague-Dawley rats (240–280) were randomly assigned to one of three groups: sham rats fed normal chow (sham-NC), SBS rats fed NC (SBS-NC) and SBS rats fed HFD (SBS-HFD). SBS rats underwent a 75% small bowel resection. Rats were sacrificed on day 3 or 14. Body weight, fat intake and fat clearance (total fecal fat) were measured twice a week. Fat absorbability was calculated as intake minus clearance and was expressed as percent of intake. Total RNA from the mucosa of duodenum, jejunum and ileum was extracted using TRIZOL Reagent. Northern blot analysis was performed to determine FAT/CD36 mRNA levels. Enterocyte LCFA transport was measured on day 14. LCFA uptake was determined by measuring cellular [3H]-oleate uptake over time (4–120 s). Mean (±SE) FAT/CD36 mRNA levels and oleate uptake kinetic parameters were analyzed using ANOVA. Fat absorbability diminished after bowel resection, suggesting fat malabsorption. Remaining bowel in SBS-NC rats responded by an increase in FAT/CD36 mRNA levels in the duodenum and ileum on day 3, and the duodenum and jejunum on day 14 compared to sham-NC animals, and was accompanied by an increase in enterocyte LCFA transport in all segments. Exposure to a HFD for 14 days resulted in significantly increased fat absorbability after 3 days compared to SBS-NC rats. However, FAT/CD36 mRNA levels (vs. SBS-NC) decreased in all segments on day 3. On day 14, FAT/CD36 mRNA levels were decreased in the duodenum and ileum and were accompanied by reduced oleate uptake by isolated enterocytes in the ileum (vs. SBS-NC). In a rat model of SBS, early high fat diet increased lipid absorptive capacity of the intestinal remnant as seen by increased fat absorbability. The main mechanisms of this effect may be an acceleration of structural intestinal adaptation resulting in an increased number of enterocytes. However, at molecular and cellular levels HFD decreased mucosal FAT/CD36 mRNA levels and oleic acid uptake by isolated enterocytes.

1856-P: Hepatic Insulin Clearance Is Not Driven by Liver Fat but by Systemic Inflammation: A Mendelian Randomization Study

Introduction: Type 2 diabetes is not only associated with insulin resistance but also with decreased insulin clearance. Insulin is mostly eliminated from portal blood during the first pass through the liver. The magnitude of this effect is closely related to systemic insulin sensitivity. As insulin resistance is often accompanied by fatty liver, we here investigated whether there is a causal link between liver fat and hepatic insulin clearance (IC). Methods: We computed IC using data from oral glucose tolerance tests in 3391 non diabetic individuals and the oral C-peptide and Insulin Minimal Models. Liver fat was quantified by 1H-MR-spectroscopy in 1211 participants. We performed Mendelian randomization analyses to test for causal determination of IC by liver fat and potentially related traits using established single nucleotide polymorphisms (liver fat: 115 SNPs, alanine-aminotransferase: 155 SNPs, insulin sensitivity: 37 SNPs, C-reactive protein: 193 SNPs). Results: IC associated inversely with liver fat content (β=-0.1±0.03, p<0.003) and insulin sensitivity (β=0.6±0.03, p < 0.0001). Both liver fat content and IC were independently associated with insulin sensitivity (β=-0.2±0.03 and β=0.1±0.02 respectively, both p < 0.0001). Neither liver fat content nor alanine-aminotransferase were causally linked to IC (p=0.6 and 0.2, respectively), as indicated by the Mendelian randomization. On the other hand, both genetically determined insulin sensitivity and C-reactive protein levels influenced IC (β=0.3±0.1, p=0.04 and β=0.1±0.07, p=0.03, respectively). Conclusion: This study supports the hypothesis that systemic effects such as inflammatory activity and/or genetic factors determining insulin resistance might modulate insulin extraction in the liver. Disclosure A. Lamprinou: None. J. Machann: None. F. Schick: None. S.S. Eckstein: None. C. Dalla Man: Research Support; Self; Sanofi-Aventis Deutschland GmbH. R. Visentin: None. N. Stefan: None. A.L. Birkenfeld: None. A. Peter: None. H. Haering: None. A. Fritsche: None. M. Heni: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi. Speaker’s Bureau; Self; Novo Nordisk A/S. R. Wagner: Advisory Panel; Self; Novo Nordisk A/S. Speaker’s Bureau; Self; Novo Nordisk A/S. Other Relationship; Self; Eli Lilly and Company. Funding German Center of Diabetes Research (01GI0925)

Sphenoid Sinus Fat Packing in Transsphenoidal Surgery: Long-Term Fate Assessment Using Magnetic Resonance Imaging

Background and Objectives: Following the transsphenoidal approach (TSA), appropriate sphenoid sinus fat packing has been preferred to prevent postoperative cerebrospinal fluid leakage; however, studies on the behavior of fat tissue transplanted in the sphenoid sinus are lacking. This study aimed to determine the long-term fate of these fat grafts using magnetic resonance imaging (MRI).Subjects and Method: A total of 139 postoperative MRI scans of 41 patients who underwent sphenoid sinus fat packing using the standard TSA were evaluated. Additionally, MRI time series indicating the vital fat volumes were assessed postoperatively.Results: In 82.9% of cases, the fat volumes measured in the final MRI scans declined to <20% of the initial volumes; only 4.9% of cases exhibited declines to >60% of the initial volume. The fat tissue volume decreased significantly with time, with a median half-life of 18 months. Typically, the sphenoid sinus was eventually almost filled with air rather than transplanted fat. In the subgroup analysis, the fat clearance rate was significantly lower in patients with residual tumors than in those without such remnants (p=0.013).Conclusion: Long-term MRI surveillance of fat grafts in the sphenoid sinus revealed that the transplanted fat graft had degraded and was gradually eliminated.

Cyclocarya paliurus extract attenuates hepatic lipid deposition in HepG2 cells by the lipophagy pathway

Context Cyclocarya paliurus (CP) (Batal.) Iljinsk (Cyclocaryaceae), a plant native to China, is the sole species in the genus Cyclocarya. Its leaves have been widely used as a remedy for hyperlipidaemia in traditional folk medicine. However, the mechanism underlying CP-induced lipolysis, especially in the liver, has not been entirely elucidated. Objective This study investigates the effect of CP ethanol extract (CPE) on hepatic steatosis and the underlying molecular mechanisms involved. Materials and methods The effect of CPE at concentrations of 0, 6.25, 12.5, 25, 50, and 100 μg/mL on the viability of HepG2 cells was examined using the cell counting kit-8 (CCK-8) assay after incubation for 24 h. CPE-induced changes in intracellular lipid content were assessed by measuring the absorbance of oil red O staining at 520 nm, and the possible underlying mechanisms were further studied using quantitative reverse transcription polymerase chain reaction (RT-qPCR) analysis, western blotting, immunofluorescence studies and transmission electron microscopy. Results The half-maximal inhibitory concentration (IC50) of CPE in HepG2 cells was 97.27 μg/mL. Treatment with 50 μg/mL CPE increased lipid clearance, which was associated with increased autophagy in HepG2 cells. CPE-induced autophagy involved downregulation of phosphorylation level of mammalian target of rapamycin (0.87 ± 0.08 vs. 1.31 ± 0.10). Fluorescent double staining and electron microscopy images showed lipid deposits within autolysosomes, thereby confirming the abovementioned findings. Discussion and conclusions CPE can induce hepatic fat clearance through the autophagy-lysosome pathway known as lipophagy. CPE has potential as a functional food.

PM2.5 exposure induces age-dependent hepatic lipid metabolism disorder in female mice

Particulate matter exposure has been described to elevate the risk of lung and cardiovascular diseases. An increasing number of recent studies have indicated positive correlations between PM2.5 (the fraction of airborne particles with an aerodynamic diameter less than 2.5 μm) exposure and the risk of liver diseases. However, research on the effects of PM2.5 exposure on liver fat synthesis, secretion, and clearance mechanisms under normal diet conditions is limited, and whether these effects are age-dependent is largely unknown. Female C57BL/6 mice at different ages (4 weeks (4 w), 4 months (4 m), and 10 months (10 m)) were treated with 3 mg/kg body weight of PM2.5 every other day for 4 weeks. Subsequently, the ultrastructural changes of liver, the expression of genes involved in oxidative damage and lipid metabolism in the liver were examined. Observation of hepatic ultrastructure showed more and larger lipid droplets in the livers of 4-week-old and 10-month-old mice exposed to PM2.5. Further analysis showed that PM2.5 exposure increased the expression of genes related to lipid synthesis, but decreased the expression of genes involved in lipid transport and catabolism in the livers of 10-month-old mice. Our findings suggest that exposure to PM2.5 disrupts the normal metabolism of liver lipids and induces lipid accumulation in the liver of female mice in an age-dependent manner, with older mice being more susceptible to PM2.5.

Fat clearance and conventional fixation identified ypN0 rectal cancers following intermediate neoadjuvant radiotherapy have similar long-term outcomes.

BACKGROUNDAs a prognostic factor for colorectal cancer, lymph node (LN) status, particularly the number of LN harvested, has been demonstrated to be essential in the evaluation of quality control in terms of surgical specimen. Neoadjuvant chemoradiation, however, decreases the LN harvest. Therefore, certain approaches (such as fat clearance or methylene blue) has drawn significant attention in order to raise LN yield.AIMTo compare the long-term oncologic outcome of ypN0 rectal cancer identified using fat clearance (FC) or conventional fixation (CF) following 30 Gy in 10 fractions (30 Gy/10f) of neoadjuvant radiotherapy (nRT).METHODSThree hundred and eighty-two patients with resectable and locally advanced rectal cancer were treated by 30 Gy/10f intermediate nRT (biologically equivalent dose of 36 Gy) plus total mesorectal excision. Two specimen fixation methods (FC or CF) were non-randomly used. The ypN0 status was identified in 124 and 101 patients in the FL and CF groups, respectively. Primary endpoints were local recurrence-free survival (LRFS) and cancer-specific survival (CSS).RESULTSThe median follow-up of patients was 5.1 years. The median numbers of retrieved LNs in the FC and CF groups were 19.5 (range, 4-47) and 12 (range, 0-44), respectively, with a significant difference (P = 0.000). The percentages of patients with 12 or more retrieved nodes were 82.3% and 50.5% (101/159) in the FC and CF groups, respectively, with a significant difference (P = 0.000). The LRFS at 5 years were 95.7% and 94.6% in the FC and CF groups, respectively, without statistical difference (P = 0.819). The CSS at 5 years were 92.0% and 87.2% in the FC and CF groups, respectively, without statistical difference (P = 0.482).CONCLUSIONFor patients with ypN0 rectal cancer who underwent 30 Gy/10f preoperative radiotherapy, the increased retrieval of LNs using fat clearance is not associated with survival benefit. This time-consuming fixation method has a low efficacy as a routine practice.

Second evaluation of the mesenteric tissue after ethanol fixation improved the total and metastatic number of lymph nodes in colorectal resections

There is a correlation between prognosis of the colorectal carcinomas and the number of retrieved and metastatic lymph nodes (LNs) from mesentery/mesorectal region. At least 12 LNs must be sampled for accurate evaluation of patients. A number of factors related to surgeon, pathologist, patient and disease could affect the total LN number. For maximizing LN yield, pathologist can use ancillary methods, as fat clearance and special solutions. This study investigates the effect of second evaluation after ethanol fixation on total and metastatic LN number and assesses factors that influence the dissected LN number. 177 colorectal resections were refixed with ethanol for a night, after standard LN sampling. Mesentery/mesorectal tissue was reevaluated for missed LNs. Results were statistically analyzed, P values <0.05 were considered significant. Mean LN number increased from 26 to 30 (median: 20 to 25, P < 0.001) after ethanol fixation. Fourteen cases had additional metastatic LNs after reevaluation of the fat tissue and 5 of them upstaged. 22.5% (44/177) of the patients had <12 LNs before ethanol fixation and this decreased to 14.3% (26/177) after ethanol fixation. Resection type and length, tumor localization, size and histologic degree, pT and neoadjuvant therapy (P < 0.001) had an impact on the LN number (P = 0.034 for histologic degree, P = 0.02 for pT, P < 0.001 for others). Carrying out a second evaluation with ethanol fixation increased total and metastatic LN number and could lead upstage of pN. Ethanol fixation is cost-effective, easy accessible and applicable method; it may improve accuracy of LN assessment and staging, which are important for patients' outcome.

Fat clearance of upper gastrointestinal resection specimens increases lymph node yield and may result in nodal upstaging

IntroductionLymph node retrieval and quantification is an important element in staging upper gastrointestinal cancers. Our department introduced fat clearance for oesophagectomy and gastrectomy specimens in 2014. This study assessed the...

The Association of Estimated Delta-5-desaturase Activity with Insulin Sensitivity and Postprandial Fat Clearance in Obese Subjects is Dependent on Plasma apoB

The Association of Estimated Delta-5-desaturase Activity with Insulin Sensitivity and Postprandial Fat Clearance in Obese Subjects is Dependent on Plasma apoB

Narciclasine attenuates diet-induced obesity by promoting oxidative metabolism in skeletal muscle.

Obesity develops when caloric intake exceeds metabolic needs. Promoting energy expenditure represents an attractive approach in the prevention of this fast-spreading epidemic. Here, we report a novel pharmacological strategy in which a natural compound, narciclasine (ncls), attenuates diet-induced obesity (DIO) in mice by promoting energy expenditure. Moreover, ncls promotes fat clearance from peripheral metabolic tissues, improves blood metabolic parameters in DIO mice, and protects these mice from the loss of voluntary physical activity. Further investigation suggested that ncls achieves these beneficial effects by promoting a shift from glycolytic to oxidative muscle fibers in the DIO mice thereby enhancing mitochondrial respiration and fatty acid oxidation (FAO) in the skeletal muscle. Moreover, ncls strongly activates AMPK signaling specifically in the skeletal muscle. The beneficial effects of ncls treatment in fat clearance and AMPK activation were faithfully reproduced in vitro in cultured murine and human primary myotubes. Mechanistically, ncls increases cellular cAMP concentration and ADP/ATP ratio, which further lead to the activation of AMPK signaling. Blocking AMPK signaling through a specific inhibitor significantly reduces FAO in myotubes. Finally, ncls also enhances mitochondrial membrane potential and reduces the formation of reactive oxygen species in cultured myotubes.

Improved detection of lymph nodes in cases of rectal cancer using combined methylene blue injection and fat clearance compared with fat clearance alone

Introduction Evaluation of lymph nodes (LNs) in rectal cancer is a fundamental component of all staging systems. Fat clearance and ex-vivo injection of methylene blue into the inferior mesenteric artery are known methods that can improve LN yield in patients with rectal cancer especially after neoadjuvant chemoradiation. Both techniques were widely compared with routine manual palpation of LNs. The question is that ‘Do adding ex-vivo injection of methylene to fat clearance as a single combined technique give further superiority on fat clearance alone regarding detection of nodal harvest and status?’. Patients and methods This study was carried out through comparing clinicopathological data of 40 patients whose specimens were subjected to combined ex-vivo injection of inferior mesenteric artery and xylene fat clearance (group I) with that of 30 patients whose specimens underwent only xylene fat clearance. All patients presented with resectable rectal cancer and have received neoadjuvant chemoradiotherapy. Results There was a statistically significant difference regarding total nodal harvest in group I compared with group II (17.52±6.32 vs. 14.56±5.64; P Conclusion Using ex-vivo methylene blue injection into the inferior mesenteric artery and xylene fat clearance as a single combined technique shows a significant difference when compared with xylene fat clearance alone regarding total LN harvest and detection of the optimal number of LNs in cases of rectal cancer. However, it did not show such significance regarding detection of nodal metastases.

Total nutrient admixtures (3-in-1): pros vs cons for adults.

Total nutrient admixture (TNA) is a complete parenteral nutrition (PN) formulation composed of all macronutrients, including dextrose, amino acids, and intravenous fat emulsions (IVFE), in one bag. The TNA may be safely administered to the patient, with all components aseptically compounded and minimal administration manipulation required, lending itself to decreases in risks of catheter contamination and patient infections. The TNA is compatible and stable at recommended concentrations, and since the IVFE is in the TNA, it is infused at slower rates, allowing for better fat clearance. The TNA offers convenience of administration and a potential cost savings to the healthcare institution both directly and indirectly. Unfortunately, the TNA is not without concerns. At low macronutrient concentrations (lower than recommended), the formulation is compromised. Greater divalent and monovalent cation amounts and increased concentrations of phosphate and calcium may destabilize the TNA or result in precipitation, respectively. With the addition of IVFE in the TNA, catheter occlusion is greater and larger pore size filters are necessary, resulting in less microbial elimination. Determining if the implementation of the TNA is appropriate for an institution requires a recognition of the advantages and disadvantages of the TNA as well as an understanding of the institution's patient population and their nutrition requirements.

Size and distribution of lymph nodes in rectal cancer resection specimens.

The detection of lymph node involvement is fundamental to the staging of rectal cancer, and aids in prognostication and identification of patients who will benefit from adjuvant therapy. The anatomical variation in distribution and size of mesorectal lymph nodes has received scant attention. This study aimed to determine the size and distribution of lymph nodes in rectal cancer resection specimens. This was a prospective, observational study of rectal cancer resection specimens analyzed by a single histopathologist. This study was conducted from January 2007 to July 2013 at the authors' institution. Two hundred forty-four consecutive patients underwent resection for rectal cancer. The size and distribution of lymph nodes in the resection specimens and the anatomical position of mesorectal lymph nodes in relation to the peritoneal reflection, tumor, and anal verge were recorded. A total of 10,473 lymph nodes were retrieved in 244 patients (75 women; median age, 68 years (interquartile range, 59-75 years)). One hundred seventy-three anterior resection and 71 abdominoperineal resection specimens were analyzed. Median lymph node yield was 41 lymph nodes (interquartile range, 31-52); 344 of 10,473 (3.2%) lymph nodes were positive. Lymph nodes were distributed in the mesorectum, sigmoid mesentery, and vascular pedicle in 40%, 32%, and 28% of the patients. Sixty-eight percent of mesorectal lymph nodes were above the peritoneal reflection. Mesorectal lymph node distribution in relation to the tumor was 53% above, 36% adjacent to, and only 11% below the tumor. Ninety-five of 334 (28%) positive nodes were ≤3 mm in diameter. Resection specimens analyzed by other pathologists (<5%) have not been included, and fat clearance techniques were not used to retrieve lymph nodes. To ensure accurate nodal staging of rectal cancer, both resection and subsequent pathological evaluation should focus on the mesorectum in close proximity to the tumor and along the superior rectal artery. Small lymph nodes (<3 mm in size) should not be overlooked, and lymph node metastasis to the sigmoid mesentery is rare (see Video, Supplemental Digital Content 1, http://links.lww.com/DCR/A177).

Alcohol Fat Clearing Increases Lymph Node Yield after Surgery for Colorectal Cancer

Lymph node (LN) yield is associated with oncologic outcome in patients who undergo surgery for colorectal adenocarcinoma (CRC). Standards to maximize LN yield have been initiated to enhance treatment of patients with CRC. This study evaluates the impact of a simple alcohol-based preparation protocol on LN yield. Surgical specimens from patients with CRC were prepared using either the alcohol protocol or standard formalin fixation and LN yield was compared. In total, 80 consecutive patients (n = 40 formalin, n = 40 alcohol) were examined. Overall, median LN yield increased from 17 to 29 (P < 0.01) with the alcohol fat clearance protocol. For patients with rectal adenocarcinoma who underwent proctectomy after neoadjuvant chemoradiotherapy, LN yield increased from 15 to 23 (P = 0.02). The frequency of need for additional sampling to achieve a minimum 12 LN count was also reduced. Initiation of a standardized alcohol fat-clearing protocol increased LN yield after surgery for CRC. This simple, cost-effective measure may improve the efficiency of LN assessment and accurate staging, which may impact oncologic outcomes.

PET-CT features of the lung benign lesions misdiagnosed as lung cancer

To analyze why lung benign nodules or masses are misdiagnosed as lung cancer in positron emissin tomography-computed tomography (PET-CT). We retrospectively analyzed the imaging, clinical and pathological data of 18 patients with benign lung nodules or masses misdiagnosed as lung cancer from May 2012 to August 2013. 18F-fluorodeoxyglucose (FDG) uptake was found in all 18 patients [maximum standardized uptake value (SUVmax) of FDG ranged from 1.2-12.2, mean=4.99]. SUVmax of FDG was greater than 2.5 in 13 patients, and delayed scan was not performed in 17. The contrast enhanced CT scan and high resolution CT (HRCT) was not performed in all the patients. The diameter was greater than 3 cm in 4 patients in CT. There were 5 patients locating in contact with the pleural surface and including clear subpleural fat clearance. Other radiographic signs included regular shape and smooth margin in 7 patients, calcification in 4, satellite opacities in 3, and long spiculation in 1. Neglecting the CT features was the main cause of misdiagnosing the lung benign nodules or masses as lung cancer in PET-CT, while lacking of contrast enhanced CT scan, HRCT and PET-CT delayed scan also led to misdiagnosis. We should learn to apply the contrast enhanced CT scan, HRCT and PET-CT delayed scan and analyze the CT and PET imagings to avoid the misdiagnosis of lung benign lesions. In-depth study of other tracers is a new direction to prevent the misdiagnosis.

New enhanced and effective method for staging cancer to detect lymph nodes after fat-dissociation.

Pathologic staging is a key factor in the treatment and outcome of cancer patients, and lymph node status plays a pivotal role in this staging process. Several methods of lymph node assessment, such as the fat clearance, Schwartz solution and GEWF solution, are unpopular as they require a significant amount of time (1‑9days) to clear the fat of the resected mesentery and to visualize the lymph nodes. In the present study, we discussed a more simple and effective method, called the fat‑dissociation method, which clears the fat using enzymes and allows for easy identification of lymph nodes around vessels. This new procedure facilitates precise staging of cancer which directs the post-operative treatment plan.

Abstract 216: PCSK9 Loss-of-Function Mutation Q152H is Associated with Reduced Dietary Fat Clearance and Insulin Resistance in Humans

Introduction: PCSK9 regulates plasma LDL-C concentrations. Loss-of-function (LOF) mutations are associated with cardiovascular protection via increased clearance of LDL particles. Work from our and other labs has shown that increased cellular uptake of LDL is proapoptotic for pancreatic β-cells and impairs adipose tissue function. Moreover, obese women with high concentration of LDL (ie plasma apoB) have lower insulin sensitivity and delayed dietary fat clearance. We recently identified a novel PCSK9 LOF mutation, Q152H, causing a 79% reduction of plasma PCSK9 and 48% reduction of plasma LDL-C. The impact of this mutation on the metabolic profile remains unexplored. Hypothesis: We hypothesize that despite a cardioprotective profile, carriers of Q152H have delayed dietary TG clearance and impaired insulin sensitivity similar to subjects with high apoB. Methods/Results: The heterozygous Q152H proband woman was compared to 2 groups of obese, age, sex and BMI-matched controls with low (n=6) and high (n=7) apoB. Fasting apoB, PCSK9, total cholesterol and LDL-C concentrations were lower in the proband (0.84g/l,126ng/ml, 4.22mM and 2.11mM, respectively) compared to low apoB (0.75 ± 0.05 g/l, 267 ± 18ng/ml, 5.1 ± 0.2mM and 2.8 ± 0.3nM, respectively) and high apoB (1.25 ± 0.09 g/l, 412 ± 79ng/ml, 6.9 ± 0.4mM and 4.3 ± 0.3nM, respectively). Women with high apoB had delayed dietary TG clearance over 6 hours as compared to women with low apoB (incremental TG AUC: 6.75 ± 1.65 vs 4.06 ± 0.77 mM/6h, p=NS). Incremental AUC TG in the proband was 106% greater than that of women with high apoB and 243% greater than that of low apoB. Botnia clamp was also conducted to measure insulin secretion and sensitivity. There was no difference in insulin secretion between the proband and the control groups measured via an intravenous glucose tolerance test. However, insulin sensitivity, as measured by glucose infusion rates (GIR) during a hyperinsulinemia clamp, was 7.5mg/kg/min in the proband, 32% lower than women with high apoB (11.1 ± 1.1 mg/kg/min) and 48% lower than women with low apoB (14.3 ± 0.9 mg/kg/min). Conclusion: PCSK9 deficiency favours a cardioprotective profile; however increased clearance of LDL by peripheral tissue may induce peripheral insulin resistance in obese subjects.

Abstract 605: Association of Apolipoprotein B with Impaired Insulin Sensitivity and Secretion Is Mediated by Reduced Fat Clearance in Obese Subjects

OBJECTIVE: Human data from our lab and others have demonstrated that elevated concentrations of apoB-lipoproteins, measured as plasma apoB, are associated with insulin resistance (IR), hyperinsulinemia and the development of type 2 diabetes. However, the underlying mechanism to date remains unknown. We recently reported that LDL, the major form of apoB-lipoproteins, directly impairs the hydrolysis and storage of triglyceride-rich lipoproteins ex vivo in human white adipose tissue. Therefore, we hypothesized that the association between apoB and IR and compensatory increase in insulin secretion (IS) is mediated by delayed postprandial TG clearance in vivo in obese subjects. METHODS: We performed a Botnia clamp on normoglycemic obese men (N=14) and postmenopausal women (N=16) (BMI ≥ 27 kg/m2, age ≥ 45 years). First phase, 2 nd phase and total IS were measured during a 1-hour intravenous-glucose tolerance test (IVGTT) while insulin sensitivity was measured during a 3-hours hyperinsulinemic euglycemic clamp that followed. On a separate date, postprandial plasma clearance of TG was measured over 6 hours following the ingestion of a 13 C-triolein-labeled high-fat meal. RESULTS: Plasma apoB correlated positively with IR (r=0.15, p=0.037), 2 nd phase IS (r=0.15, p=0.039) and delayed TG clearance (AUC 6hrs of total plasma TG: r=0.64, p&lt;0.001; AUC 6hrs of 13 C-plasma TG: r=0.77, p&lt;0.001). Moreover, AUC 6hr of total plasma TG was associated with higher IR (r=0.16, p=0.042), 1 st phase IS (r=0.20, p=0.023), 2 nd phase IS (r=0.16, p=0.044) and total IS (r=0.16, p=0.046). Similarly, a positive association existed between delayed 13 C-labeled plasma TG clearance (AUC 6hrs ) and IR (r=0.41, p=0.046). A gender difference existed as TG clearance was mainly associated with IR in women (r=0.41, p=0.046) whereas it was mainly associated with 2 nd phase IS in men (r=0.41, p=0.046). As hypothesized, correcting for TG clearance eliminated the association of plasma apoB with IR and IS. CONCLUSION: The association of apoB with insulin resistance and secretion may be secondary to LDL-mediated delayed TG clearance by adipose tissue in humans.