Triglyceride synthesis in normal and hyperapoB fibroblasts

The goal of this thesis was to examine the regulation of intracellular triglyceride synthesis from normals and HyperapoB patients using cultured skin fibroblasts as an experimental model. In a medium supplemented with lipoprotein-deficient serum, triglyceride synthesis and cholesterol esterification were reduced in the HyperapoB fibroblasts by 40% and 44% respectively as compared to the normal fibroblasts. These differences were due to differences in de novo synthesis, and not due to re-esterification or hydrolysis. However, unexpectedly, there was no difference in triglyceride synthesis between the cells from normals and HyperapoB when a serum-free supplemented medium was used. The stimulatory factor in lipoprotein-deficient serum was then isolated from human plasma and characterized. The factor responsible is nondialyzable and trypsin sensitive, and its effects are both concentration and time dependent. The protein responsible has been purified to homogeneity and is a small (MW 14,000), basic (pI 9.0) protein. It has been named Acylation Stimulating Protein (ASP) because it markedly stimulates triglyceride synthesis and cholesterol esterification by 80% and 42% in normal human skin fibroblasts. Further ASP is specifically bound with a KD of 9.9 $\times$ 10\sp{-7} and is internalized and degraded by normal human skin fibroblasts. In contrast, ASP has much less effect on triglyceride synthesis in HyperapoB fibroblasts with an average of only 25% triglyceride stimulation. This is consistent with its reduced maximal binding (51% of normal) and subsequent internalization into these cells. Although both cell groups demonstrate the same binding affinity for ASP (Scatchard analysis slope = $-.0725$ ug\sp{-1} normal and $-.080$R ug\sp{-1} HyperapoB) the maximal number of apparent binding sites is reduced in HyperapoB (1.217 mg\sp{-1} normal vs 0.621 mg\sp{-1} HyperapoB). The ASP effect on cells from patients with Familial Hypercholesterolemia, however, is normal with regard to ASP stimulation of triglyceride synthesis (average 55% stimulation) and ASP binding to cells. This research therefore has led to the description of a previously unrecognized protein in human plasma. This protein, ASP, appears to be the most potent stimulant of intracellular triglyceride synthesis yet describe

Leptin and adiponectin in relation to body fat percentage, waist to hip ratio and the apoB/apoA1 ratio in Asian Indian and Caucasian men and women

BACKGROUND: Asian Indian immigrants have an increased risk for developing cardiovascular disease (CVD); however, there is very little data examining how the adipokines leptin and adiponectin relate to CVD risk factors such as body fat percentage (BF%), waist to hip ratio (WHR) and the apoB/apoA1 ratio in Asian Indian men and women living in Canada. SUBJECTS AND METHODS: A cross-sectional study comparing leptin, adiponectin, lipoproteins and anthropometric parameters in Asian Indian men and women to Caucasian men and women (4 groups). Anthropometric data (BMI, BF%, WHR), circulating lipids (apoA1, apoB, total cholesterol, and HDL-cholesterol), leptin and adiponectin were measured. RESULTS: Asian Indian men and women had higher leptin and lower adiponectin concentrations then Caucasian men and women, respectively. Leptin (positively) and adiponectin (negatively) correlated with anthropometric parameters and lipoproteins in all four groups. Using stepwise forward multiple regression, a model including TC/HDL-C ratio, WHR, BF%, hip circumference and waist circumference predicted 74.2% of leptin concentration in men. In women, apoB, BF%, waist circumference and age predicted 77.5% of leptin concentration. Adiponectin concentrations in men were predicted (30.2%) by HDL-C, total cholesterol, hip circumference and BF% while in women 41.2% of adiponectin concentration was predicted by the apoB/apoA1 ratio, WHR and age. CONCLUSION: As is evident from our data, there is a strong relationship between leptin, adiponectin, and abdominal obesity with increased CVD risk, as assessed by the apoB/apoA1 ratio. Dysregulation of these parameters may account for the increased risk of CVD in Asian Indians

Rosiglitazone decreases postprandial production of acylation stimulating protein in type 2 diabetics

<p>Abstract</p> <p>Background</p> <p>We evaluated plasma ASP and its precursor C3 in type 2 diabetic men with/without rosiglitazone (ROSI) treatment compared to healthy non-obese men. We tested (1) whether plasma ASP or C3 are altered postprandially in subcutaneous adipose tissue or forearm muscle effluent assessed by arteriovenous (A-V) differences in healthy lean men and older obese diabetic men and (2) whether treatment with ROSI changes the arteriovenous gradient of ASP and/or C3.</p> <p>Methods</p> <p>In this ongoing placebo-controlled, crossover, double-blinded study, AV differences following a mixed meal were measured in diabetic men (n = 6) as compared to healthy men (n = 9).</p> <p>Results</p> <p>Postprandial arterial and adipose venous TG and venous NEFA were increased in diabetics vs. controls (p < 0.05–0.0001). ROSI treatment decreased postprandial arterial TG (p < 0.001), adipose venous NEFA (p < 0.005), reduced postprandial glucose (p < 0.0001) and insulin concentrations (p < 0.006). In healthy men, there was no change in postprandial C3, but an increase in adipose venous ASP vs. arterial ASP (p < 0.02), suggesting ASP production, with no change in forearm muscle. In older, obese diabetic subjects, arterial C3 was greater than in controls (p < 0.001). Arterial C3 was greater than venous C3 (p < 0.05), an effect that was lost with ROSI treatment. In diabetics, postprandial venous ASP was greater than arterial (p < 0.05), indicating ASP production, an effect that was lost with ROSI treatment (p < 0.01).</p> <p>Conclusion</p> <p>Increased postprandial venous production of ASP is specific for adipose tissue (absent in forearm muscle). Increased postprandial C3 and ASP in diabetic subjects is consistent with an ASP resistant state, this state is partially normalized by treatment with ROSI.</p

Adipocyte size as a determinant of metabolic disease and adipose tissue dysfunction

Obesity is a heterogeneous disease and is associated with comorbidities such as type 2 diabetes mellitus, cardiovascular disease and cancer. Several studies have examined the role of dysfunctional adipose tissue in the pathogenesis of obesity, highlighting the contrasting properties and impact of distinct fat compartments, sometimes with contradictory results. Dysfunctional adipose tissue involves enlargement, or hypertrophy, of pre-existing fat cells, which is thought to confer increases in cardiometabolic risk, independent of the level of obesity per se . In this article, we critically analyze available literature that examined the ability of adipocyte cell size to predict metabolic disease and adipose tissue dysfunction in humans. Many studies demonstrate that increased fat cell size is a significant predictor of altered blood lipid profiles and glucose–insulin homeostasis independent of adiposity indices. The contri- bution of visceral adiposity to these associations appears to be of particular importance. However, available studies are not unanimous and many fat depot-specific aspects of the relationship between increased fat cell size and cardiometabolic risk or parameters of adipose tissue dysfunction are still unresolved. Methodological factors such as the approach used to express the data may represent significant confounders in these studies. Additional studies should consider the fact that the relationship between fat cell size and common adiposity indices is non-linear, particularly when reaching the obese range. In conclusion, our analysis demonstrates that fat cell size is a significant predictor of the cardiometabolic alterations related to obesity. We propose that adipocyte hypertrophy, especially in the visceral fat compartment, may represent a strong marker of limited hyperplasic capacity in subcutaneous adipose tissues, which in turn is associated with the presence of numerous cardiometabolic alterations

The effects of acylation stimulating protein supplementation VS antibody neutralization on energy expenditure in wildtype mice

<p>Abstract</p> <p>Background</p> <p>Acylation stimulating protein (ASP) is an adipogenic hormone that stimulates triglyceride (TG) synthesis and glucose transport in adipocytes. Previous studies have shown that ASP-deficient C3 knockout mice are hyperphagic yet lean, as they display increased oxygen consumption and fatty acid oxidation compared to wildtype mice. In the present study, antibodies against ASP (Anti-ASP) and human recombinant ASP (rASP) were tested <it>in vitro</it> and<it> in vivo</it>. Continuous administration for 4 weeks via osmotic mini-pump of Anti-ASP or rASP was evaluated in wildtype mice on a high-fat diet (HFD) to examine their effects on body weight, food intake and energy expenditure.</p> <p>Results</p> <p>In mature murine adipocytes, rASP significantly stimulated fatty acid uptake (+243% vs PBS, P < 0.05) while Anti-ASP neutralized the rASP response. Mice treated with Anti-ASP showed elevated energy expenditure (P < 0.0001), increased skeletal muscle glucose oxidation (+141%, P < 0.001), reduced liver glycogen (-34%, P < 0.05) and glucose-6-phosphate content (-64%, P = 0.08) compared to control mice. There was no change in body weight, food intake, fasting insulin, adiponectin, CRP or TG levels compared to controls. Interestingly, HFD mice treated with rASP showed the opposite phenotype with reduced energy expenditure (P < 0.0001) and increased body weight (P < 0.05), cumulative food intake (P < 0.0001) and liver glycogen content (+59%, P < 0.05). Again, there was no change in circulating insulin, adiponectin, CRP or TG levels, however, plasma free fatty acids were reduced (-48%, P < 0.05).</p> <p>Conclusion</p> <p><it>In vitro</it>, Anti-ASP effectively neutralized ASP stimulated fatty acid uptake. <it>In vivo</it>, Anti-ASP treatment increased whole body energy utilization while rASP increased energy storage. Therefore, ASP is a potent anabolic hormone that may also be a mediator of energy expenditure.</p

Acylation stimulating protein is higher in Inuit from Nunavik compared to a southern Quebec population

Objectives. The Inuit of Nunavik in northern Quebec have a lower risk for ischemic heart disease (IHD) compared to Caucasian populations. Acylation stimulating protein (ASP), which is involved in the storage of dietary fat, may play a role. The objective of the study was to determine plasma concentration of ASP in an Inuit and a southern Quebec Caucasian population. Study design. This is a cross-sectional study evaluating the relationship between ASP and dietary factors, such as retinol, whose intake is higher in the Inuit. As well, concentrations of ASP were evaluated in relationship to components of the metabolic syndrome. Methods. Medical history was collected via a questionnaire and anthropometric measurements and blood samples were collected. Results. ASP was significantly higher in both the Inuit men and women compared to Caucasian men (66.1±4.1 nM vs 27.5±2.5 nM, p<0.0001) and women (71.8±3.8 nM vs 29.4±1.3 nM, p<0.0001). In addition, ASP significantly correlated with total retinol (r=0.17, p=0.02) and free retinol (r=0.15, p=0.04) in Inuit men but not with other distinctive dietary markers such as omega3 fatty acids. Conclusions. Inuit men and women have higher ASP which was unrelated to the number of risk factors for IHD that were present

Differential methylation of inflammatory and insulinotropic genes after metabolic surgery in women

Context: Biliopancreatic diversion with duodenal switch (BPD-DS), a metabolic bariatric operation, induces durable loss of excess weight and reduced cardiometabolic risk. Altered epigenetic marks are mechanistically associated with environment-driven phenotypic variations. Objective: The current study aimed to compare gene methylation levels before and after BPD-DS to identify epigenetic marks potentially linked to metabolic improvements induced by BPD-DS. Design and patients: Metabolic risk factors and gene methylation levels of 20 women studied mean 12 years (range 4-22) after BPD-DS were compared to those of 20 severely obese surgical candidates as controls, matched for pre-surgical age, body mass index and dyslipidemia and hypertension prevalences. Whole-genome blood DNA methylation analysis enabled between-group differential methylation analyses. We calculated correlations between methylation levels of the most differentially methylated CpG sites and plasma glucose and insulin levels and HOMA-IR. Results: Differential methylation analysis identified 15,343 genes demonstrating at least one differentially methylated CpG site (p<1.43x10-7). Diabetic and inflammation/immune functions were among the most overrepresented from the 200 genes exhibiting the largest group differences in methylation levels. CpG sites methylation levels of genes related to insulin action correlated significantly with fasting insulin levels and homeostatic model of insulin resistance (p≤0.002 for all). Conclusion: These findings suggest that differential methylation levels in obese controls versus treated women may partially explain the durable metabolic improvements after BPD-DS

Adiponectin and Leptin Metabolic Biomarkers in Chinese Children and Adolescents

Objective. To evaluate leptin and adiponectin as biomarkers of metabolic syndrome (MS) risk factors even in nonobese children/adolescents. Methods. Serum leptin, adiponectin, leptin:adiponectin ratio, lipids, glucose, and insulin concentrations as well as body size parameters and pubertal development were evaluated in a large population of Chinese children/adolescents (n = 3505, 6–18 years, 1722 girls and 1783 boys). Results. Leptin concentration increased while adiponectin decreased with obesity, both were influenced by pubertal development. Central obesity had an additive effect on leptin levels (above obesity alone). Leptin/adiponectin increased 8.4-fold and 3.2-fold in overweight/obesity, and 15.8- and 4.5-fold with obesity plus MS, in early and late puberty, respectively. Even in normal weight children/adolescents, higher leptin and lower adiponectin concentrations associated with increased risk profile. Conversely, overweight/obese with lower leptin or higher adiponectin concentrations had a less compromised metabolic profile. Conclusion. Leptin, adiponectin, and leptin:adiponectin ratio are informative biomarkers for obesity, central obesity, MS, and abnormal metabolic profile even in normal weight children/adolescents

The effect of atorvastatin (and subsequent metformin) on adipose tissue acylation-stimulatory-protein concentration and inflammatory biomarkers in overweight/obese women with polycystic ovary syndrome

Copyright © 2019 Sathyapalan, Hobkirk, Javed, Carroll, Coady, Pemberton, Smith, Cianflone and Atkin. Background: Atorvastatin has been shown to improve cardiovascular risk (CVR) indices in women with polycystic ovary syndrome (PCOS). Low-grade chronic inflammation of adipose tissue may link PCOS and adverse CVR. In pro-inflammatory states such as PCOS, spontaneous activation of the alternative pathway of complement results in increased generation of acylation stimulating protein (ASP) from adipocytes irrespective of body mass index. Methods: The objective of this study was to determine the effect of atorvastatin on markers of adipose tissue dysfunction and inflammation; acylation-stimulating-protein (ASP), interleukin-6 (IL-6), and monocyte-chemoattractant-protein-1 (MCP-1) in PCOS. This was a randomized, double-blind, placebo-controlled study where 40 medication-naive women with PCOS and biochemical hyperandrogenaemia were randomized to either atorvastatin 20 mg daily or placebo for 12 weeks. Following the 12 week randomization; both group of women with PCOS were subsequently started on metformin 1,500 mg daily for further 12 weeks to assess whether pre-treatment with atorvastatin potentiates the effects of metformin on markers of adipose tissue function We conducted a post-hoc review to detect plasma ASP and the pro-inflammatory cytokines IL6 and MCP-1 before and after 12 and 24 weeks of treatment. Results: There was significant reduction in ASP (156.7 ± 16.2 vs. 124.4 ± 14.8 ng/ml