Aging is a major risk factor for many chronic diseases and a complex biological phenomenon. The most well studied and characterized pathways involved in metabolism and known to regulate longevity include sirtuins, AMP-activated protein kinase, insulin-like growth factor (IGF) and the mechanistic target of rapamycin (mTOR).1 These signaling pathways and related transcriptional factors are evolutionarily conserved from yeast to primates. Evidence suggests adipose tissue plays an important role in the regulation of lifespan particularly through energy homeostasis during times of scarcity and excess. Our laboratory has shown adipose triglyceride lipase (ATGL), the rate-limiting enzyme within the lipolytic pathway, is the target of dietary restriction and insulin/IGF-1 signaling pathways, both of which regulate lifespan.22 Given the convergence and necessity of ATGL-1 in the longevity response of dietary restriction and reduced insulin/IGF1 signaling pathways and the uncertainty of the downstream effects TOR has on longevity, we hypothesize that ATGL-1 plays an important role in CeTOR regulated longevity in C. elegans. This investigation was carried out by (a) determining whether levels of ATGL-1 are influenced by TOR inhibition via rapamycin and TOR specific RNA interference (RNAi) and (b) examining the role of ATGL-1 in CeTOR regulated longevity in C. elegans. We have found that rapamycin treatment does not increase expression of ATGL-1::GFP in C. elegans, however, continued research with CeTOR inhibition using rapamycin and RNAi treatment is necessary. The RNAi and longevity experiments need to be conducted. Tissue specific regulation of ATGL expression has been shown to be implicated in chronic disease and in longevity. However, there are still many insights to be discovered and understood about its role in longevity pathways, including feedback mechanisms and second messengers lipolytic products play. Elucidating the downstream effects of ATGL within model organisms will impact future chronic disease research and longevity studies. Given that these pathways are widely evolutionarily conserved, future findings will aid in understanding longevity regulatory mechanisms in humans.

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Hydrolysis of dietary lipids to free fatty acids (FFA) is a prerequisite for ruminal biohydrogenation, a bacterially mediated process that extensively saturates unsaturated FFAs thus limiting the absorption and ultimate assimilation of these healthy nutrients into ruminant produced foods. Three experiments were conducted to learn how to better enrich, isolate and study lipolytic bacteria from the rumen while providing further characterization of four prominent lipase-producing bacteria that are known to be major contributors of lipolysis in the rumen. In experiment one the effects of various physical treatments on ruminal lipase activity were investigated by comparing incubation positions, glass bead levels, transfer techniques and combinations of headspace gasses. Based on results from this experiment an incubation system was established as a standard for subsequent studies for culturing and transferring mixed and pure cultures of ruminal bacteria. In experiment two the effect of glycerol on lipolysis by Anaerovibrio lipolyticus 5S, Butyrivibrio fibrisolvens 49, Propionibacterium avidum, and Propionibacterium acnes was examined. Two levels of glycerol were examined on lipase activity and results showed that glycerol inhibited rates of FFA accumulation at both levels. In addition the mechanism behind glycerol inhibition was also examined by culturing and assaying activity of the four bacteria to determine if glycerol inhibition is a result of equilibrium displacement or lipase gene expression inhibition. Results indicated that higher and constitutively expressed lipase activity of A. lipolyticus 5S and P. avidum probably contribute more to lipolysis in ruminants than P. acnes and B. fibrisolvens 49. In the case of P. acnes and B. fibrisolvens 49 cells, results suggest that lipase gene expression is down-regulated in these bacteria. Experiment three was conducted to further characterize the lipase activity of the four different bacteria by growing them with four different energy substrates and measuring enzyme activity at early logarithmic and stationary phase. Results from this study showed that diets containing a high content of oleic acid and linolenic acid promoted higher rates of lipolysis in the rumen. In accordance with findings in experiment two these results support that P. avidum may contribute to a higher amount of lipolysis than previously considered.

Thesis (M. Med. Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 65-72).

No description available.

Thesis (M.Med.Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 65-72). Also available in print.

Thyrotropin (TSH) binds to TSH receptors on thyrocytes to regulate development and growth of the thyroid gland, and to stimulate thyroid hormone production. Thyrotropin has also been shown to act in an extra-thyroidal fashion, and to engage TSH receptors on adipocytes to induce lipolysis, similar to the response seen by stimulation with β-adrenergic receptor agonists (i.e. isoproterenol). In both cell types, cAMP-dependent kinase (PKA) is activated. Recently, PRAJA2, a novel AKAP and E3 ubiquitin ligase that targets the regulatory subunits of PKA was identified. The ubiquitin-dependent proteasomal degradation of the PKA regulatory subunits, due to PKA- phosphorylated PRAJA2, prolongs the catalytic activity of PKA, as shown in neuroblastoma cells by Lignitto et al., 2011. In adipocytes, stimulated PKA activity is required for lipolysis. Additionally, PRAJA2 has been described to have increased expression in TSH-responsive, differentiated thyroid cancer cells when compared to anaplastic thyroid tumor (Cantara et al., 2012) The aim of this study was to characterize PRAJA2 and its potential influence on adipocyte lipolysis. These data confirm that TSH and isoproterenol stimulate lipolysis in primary human differentiated adipocytes. PRAJA2 is expressed at the mRNA and protein level in differentiated adipocytes, with no change following stimulation with TSH or isoproterenol. Stimulation with isoproterenol, but not TSH, increases PKA-dependent phosphorylation of a 122kDa (potentially PRAJA2) and 69kDa protein identified in PRAJA2 immunoprecipitates. These proteins may prove important for lipolytic signaling or other PRAJA2-dependent process in adipocytes. Experimentation was unable to identify interactions between PRAJA2 and PKAR2 in differentiated adipocytes; however further investigations are required before discounting this interaction. An attempt was made to knockdown PRAJA2 in this model, and measure effects on lipolytic response; however, this was unsuccessful. Taken together, PRAJA2 appears to be phosphorylated following β-adrenergic stimulation in human adipocytes; however, further studies are needed to delineate the specific role of PRAJA2 in this human differentiated adipocyte model.

No description available.

Background: The increased incidence of obesity and associated metabolic diseases has driven research focused on genetically or pharmacologically alleviating metabolic dysfunction. These studies employ a range of fasting-refeeding models including 4-24 h fasts, "overnight" fasts, or meal feeding. Still, we lack literature that describes the physiologically relevant adaptations that accompany changes in the duration of fasting and re-feeding. Since the liver is central to whole body metabolic homeostasis, we investigated the timing of the fast-induced shift toward glycogenolysis, gluconeogenesis, and ketogenesis and the meal-induced switch toward glycogenesis and away from ketogenesis. Methods: Twelve to fourteen week old male C57BL/6J mice were fasted for 0, 4, 8, 12, or 16 h and sacrificed 4 h after lights on. In a second study, designed to understand the response to a meal, we gave fasted mice access to feed for 1 or 2 h before sacrifice. We analyzed the data using mixed model analysis of variance. Results: Fasting initiated robust metabolic shifts, evidenced by changes in serum glucose, non-esterified fatty acids (NEFAs), triacylglycerol, and beta-OH butyrate, as well as, liver triacylglycerol, non-esterified fatty acid, and glycogen content. Glycogenolysis is the primary source to maintain serum glucose during the first 8 h of fasting, while de novo gluconeogenesis is the primary source thereafter. The increase in serum a-OH butyrate results from increased enzymatic capacity for fatty acid flux through beta-oxidation and shunting of acetyl-CoA toward ketone body synthesis (increased CPT1 (Carnitine Palmitoyltransferase 1) and HMGCS2 (3-Hydroxy-3-Methylglutaryl-CoA Synthase 2) expression, respectively). In opposition to the relatively slow metabolic adaptation to fasting, feeding of a meal results in rapid metabolic changes including full depression of serum a-OH butyrate and NEFAs within an hour. Conclusions: Herein, we provide a detailed description of timing of the metabolic adaptations in response to fasting and re-feeding to inform study design in experiments of metabolic homeostasis. Since fasting and obesity are both characterized by elevated adipose tissue lipolysis, hepatic lipid accumulation, ketogenesis, and gluconeogenesis, understanding the drivers behind the metabolic shift from the fasted to the fed state may provide targets to limit aberrant gluconeogenesis and ketogenesis in obesity.

Introduction: Liposuction has undergone several improvements since its first description, including changes in the cannulas, variation in the concentration of the infiltrating solution, and the use of different devices and technologies. The use of laser technology devices for lipolysis and stimulation of skin retraction has contributed to the procedure. This article presents the authors’ experience with laser lipolysis in 400 patients, within a 5-year period, and discusses the principles of the technology and its effect on tissues. Methods: This is a study performed between July 2007 and July 2012 and included 400 patients who underwent laser lipolysis. All procedures were performed following the original protocol – infiltration of cold saline, passage of the cannula with an optic fiber for conducting the energy needed for laser lipolysis, skin retraction, and finally, conventional liposuction. Results: Hospitalization type ranged from outpatient to overnight surgery. Approximately 45% (180 of 400) of patients had minimal bruising, with involvement of 2% or more of the affected body surface. Hematoma, seroma, and dehiscence occurred in a total of 9% (36 of 400) of patients. We did not find any case of thermal burn of the skin. Conclusions: Laser lipolysis performed according to the described technique was safe and reproducible.