N humans. There are some limitations to this study. First, because it was a cross-sectional study, no causality could be defined. It is not clear whether circulating progranulin and CTRP3 levels are causative factors or markers of the pathogenesis of inflammatory diseases and atherosclerosis. Secondly, this study enrolled only Asian subjects without diabetes or CVD, so the relationship of serum progranulin and CTRP3 levels to metabolic risk factors should be further evaluated in other ethnic populations and in the context of different interventions for the treatment of diabetes and CVD. Thirdly, the subjects with renal insufficiency, defined as an eGFR ,60 (mL/min/1.73 m2), were very few in this cohort (n = 2). Therefore, to clarify the relationship of renal dysfunction with CTRP3, further studies NT 157 site including the subjects with renal impairment should be followed. Lastly, the data about smoking, alcohol, and exercise were not available in this cohort, so we could not adjust the effect of these lifestyle factors. In conclusion, this study showed that serum progranulin levels had a significant positive relationship with hsCRP and IL-6 concentrations. Furthermore, serum progranulin level was anindependent determining risk factor for carotid atherosclerosis in subjects without metabolic syndrome. On the other hand, circulating CTRP3 concentration had a significant association with cardiometabolic risk factors, such as obesity, glucose levels, lipid parameters, eGFR, and adiponectin levels. Further experimental and prospectively-designed studies should be performed to clarify the influences of these two novel adipokines, progranulin and CTRP3, on the pathogenesis and outcomes of chronic metabolic disorders and cardiovascular disease.Supporting InformationTable S1 Multiple Stepwise Regression SR3029 Analyses for Determinant Factors Associated with Serum Progranulin and CTRP3 Levels. (DOC)Author ContributionsConceived and designed the experiments: HJY BSY KMC. Performed the experiments: HCH HYC SJY. Analyzed the data: SYH. Contributed reagents/materials/analysis tools: DSC SHB. Wrote the paper: HJY KMC MB.
Sphingolipids play vital roles in stabilizing membrane structure and in cell-cell recognition [1?]. Some sphingolipid intermediates also act as signaling molecules in angiogenesis, cell growth, differentiation, and apoptosis [6?1]. One intermediate, ceramide, is a key metabolite in both anabolic and catabolic pathways, where it mediates cell differentiation, stress responses and apoptosis [6,12,13]. Although perturbed ceramide homeostasis reportedly accompanies many diseases [14,15], the crucial role of ceramide in pathological states has not been fully characterized. The initial step of sphingolipid synthesis is formation of ceramide from serine and fatty acyl-CoA in the endoplasmic reticulum (ER) [16,17]. Synthesized ceramide is then transported to 
the Golgi complex by the ceramide transfer protein CERT [18,19], where ceramide is converted to sphingomyelin by sphingomyelin synthase 1 (SMS1) [20]. Sphingomyelin is further transferred to the plasma membrane by exocytic vesicles and converted back to ceramide by sphingomyelin synthase 2 (SMS2)[17]. Thus, SMS1 has a central role in controlling sphingolipid homeostasis. Recent genetic analysis of ceramide trafficking reveals that ceramide functions in numerous essential activities. CERT mutant mice exhibit embryonic lethality due to mitochondrial degeneration [21]. CERT null flies also exhibit a higher ox.N humans. There are some limitations to this study. First, because it was a cross-sectional study, no causality could be defined. It is not clear whether circulating progranulin and CTRP3 levels are causative factors or markers of the pathogenesis of inflammatory diseases and atherosclerosis. Secondly, this study enrolled only Asian subjects without diabetes or CVD, so the relationship of serum progranulin and CTRP3 levels to metabolic risk factors should be further evaluated in other ethnic populations and in the context of different interventions for the treatment of diabetes and CVD. Thirdly, the subjects with renal insufficiency, defined as an eGFR ,60 (mL/min/1.73 m2), were very few in this cohort (n = 2). Therefore, to clarify the relationship of renal dysfunction with CTRP3, further studies including the subjects with renal impairment should be followed. Lastly, the data about smoking, alcohol, and exercise were not available in this cohort, so we could not adjust the effect of these lifestyle factors. In conclusion, this study showed that serum progranulin levels had a significant positive relationship with hsCRP and IL-6 concentrations. Furthermore, serum progranulin level was anindependent determining risk factor for carotid atherosclerosis in subjects without metabolic syndrome. On the other hand, circulating CTRP3 concentration had a significant association with cardiometabolic risk factors, such as obesity, glucose levels, lipid parameters, eGFR, and adiponectin levels. Further experimental and prospectively-designed studies should be performed to clarify the influences of these two novel adipokines, progranulin and CTRP3, on the pathogenesis and outcomes of chronic metabolic disorders and cardiovascular disease.Supporting InformationTable S1 Multiple Stepwise Regression Analyses for Determinant Factors Associated with Serum Progranulin and CTRP3 Levels. (DOC)Author ContributionsConceived and designed the experiments: HJY BSY KMC. Performed the experiments: HCH HYC SJY. Analyzed the data: SYH. Contributed reagents/materials/analysis tools: DSC SHB. Wrote the paper: HJY KMC MB.
Sphingolipids play vital roles in stabilizing membrane structure and in cell-cell recognition [1?]. Some sphingolipid intermediates also act as signaling molecules in angiogenesis, cell growth, differentiation, and apoptosis [6?1]. One intermediate, ceramide, is a key metabolite in both anabolic and catabolic pathways, where it mediates cell differentiation, stress responses and apoptosis [6,12,13]. Although perturbed ceramide homeostasis reportedly accompanies many diseases [14,15], the crucial role of ceramide in pathological states has not been fully characterized. The initial step of sphingolipid synthesis is formation of ceramide from serine 
and fatty acyl-CoA in the endoplasmic reticulum (ER) [16,17]. Synthesized ceramide is then transported to the Golgi complex by the ceramide transfer protein CERT [18,19], where ceramide is converted to sphingomyelin by sphingomyelin synthase 1 (SMS1) [20]. Sphingomyelin is further transferred to the plasma membrane by exocytic vesicles and converted back to ceramide by sphingomyelin synthase 2 (SMS2)[17]. Thus, SMS1 has a central role in controlling sphingolipid homeostasis. Recent genetic analysis of ceramide trafficking reveals that ceramide functions in numerous essential activities. CERT mutant mice exhibit embryonic lethality due to mitochondrial degeneration [21]. CERT null flies also exhibit a higher ox.