Similar increases in liver fat and NASH are associated with a metabolically harmful saturated, ceramide-enriched liver lipidome in 'Metabolic NAFLD' but not in 'PNPLA3 NAFLD'. This difference may explain why metabolic but not PNPLA3 NAFLD increases the risk of type 2 diabetes and cardiovascular disease.

Recently, vascular endothelial growth factor receptor 3 (VEGFR-3) has been shown to provide a specific marker for lymphatic endothelia in certain human tissues. In this study, we have investigated the expression of VEGFR-3 and its ligands VEGF-C and VEGF-D in fetal and adult tissues. VEGFR-3 was consistently detected in the endothelium of lymphatic vessels such as the thoracic duct, but fenestrated capillaries of several organs including the bone marrow, splenic and hepatic sinusoids, kidney glomeruli and endocrine glands also expressed this receptor. VEGF-C and VEGF-D, which bind both VEGFR-2 and VEGFR-3 were expressed in vascular smooth muscle cells. In addition, intense cytoplasmic staining for VEGF-C was observed in neuroendocrine cells such as the alpha cells of the islets of Langerhans, prolactin secreting cells of the anterior pituitary, adrenal medullary cells, and dispersed neuroendocrine cells of the gastrointestinal tract. VEGF-D was observed in the innermost zone of the adrenal cortex and in certain dispersed neuroendocrine cells. These results suggest that VEGF-C and VEGF-D have a paracrine function and perhaps a role in peptide release from secretory granules of certain neuroendocrine cells to surrounding capillaries.

Aims/hypothesis It has recently been suggested that the rs738409 G allele in PNPLA3, which encodes adiponutrin, is strongly associated with increased liver fat content in three different ethnic groups. The aims of the present study were as follows: (1) to try to replicate these findings in European individuals with quantitative measures of hepatic fat content; (2) to study whether the polymorphism influences hepatic and adipose tissue insulin sensitivity; and (3) to investigate whether PNPLA3 expression is altered in the human fatty liver. Methods We genotyped 291 Finnish individuals in whom liver fat had been measured using proton magnetic resonance spectroscopy. Hepatic PNPLA3 expression was measured in 32 participants. Hepatic and adipose tissue insulin sensitivities were measured using a euglycaemic-hyperinsulinaemic (insulin infusion 0.3 mU kg −1 min Results The rs738409 G allele in PNPLA3 was associated with increased quantitative measures of liver fat content (p=0.011) and serum aspartate aminotransferase concentrations (p=0.002) independently of age, sex and BMI. Fasting serum insulin and hepatic and adipose tissue insulin sensitivity were related to liver fat content independently of genotype status. PNPLA3 mRNA expression in the liver was positively related to obesity (r=0.62, p<0.0001) and to liver fat content (r=0.58, p=0.025) in participants who were not morbidly obese (BMI <40 kg/m 2 ). Conclusions/interpretation A common variant in PNPLA3 increases the risk of hepatic steatosis in humans.

MDM2 plays a key role in modulating p53 function. The MDM2 SNP309T > G promoter polymorphism enhances Sp1 binding and has been linked to cancer risk and young age at diagnosis although with conflicting evidence. We report a second MDM2 promoter polymorphism, SNP285G > C, residing on the SNP309G allele. SNP285C occurs in Caucasians only, where 7.7% (95% CI 7.6%-7.8%) of healthy individuals carry the SNP285C/309G haplotype. In vitro analyses reveals that SNP309G enhances but SNP285C strongly reduces Sp1 promoter binding. Comparing MDM2 promoter status among different cohorts of ovarian (n = 1993) and breast (n = 1973) cancer patients versus healthy controls (n = 3646), SNP285C reduced the risk of both ovarian (OR 0.74; CI 0.58-0.94) and breast cancer (OR 0.79; CI 0.62-1.00) among SNP309G carriers.

OBJECTIVE-To determine whether 1) hepatic ceramide and diacylglycerol concentrations, 2) SCD1 activity, and 3) hepatic lipogenic index are increased in the human nonalcoholic fatty liver.RESEARCH DESIGN AND METHODS-We studied 16 subjects with (n ϭ 8) and without (n ϭ 8) histologically determined nonalcoholic fatty liver (NAFL ϩ and NAFL Ϫ ) matched for age, sex, and BMI. Hepatic concentrations of lipids and fatty acids were quantitated using ultra-performance liquid chromatography coupled to mass spectrometry and gas chromatography. RESULTS-The absolute (nmol/mg) hepatic concentrations of diacylglycerols but not ceramides were increased in the NAFL ϩ group compared with the NAFL Ϫ group. The livers of the NAFL ϩ group contained proportionally less long-chain polyunsaturated fatty acids as compared with the NAFL Ϫ group. Liver fat percent was positively related to hepatic stearoyl-CoA desaturase 1 (SCD1) activity index (r ϭ 0.70, P ϭ 0.003) and the hepatic lipogenic index (r ϭ 0.54, P ϭ 0.030). Hepatic SCD1 activity index was positively related to the concentrations of diacylglycerols (r ϭ 0.71, P ϭ 0.002) but not ceramides (r ϭ 0.07, NS).CONCLUSIONS-We conclude that diacylglycerols but not ceramides are increased in NAFL. The human fatty liver is also characterized by depletion of long polyunsaturated fatty acids in the liver and increases in hepatic SCD1 and lipogenic activities. Diabetes 58: [203][204][205][206][207][208] 2009 N onalcoholic fatty liver disease (NAFLD) is characterized by lipid accumulation in the liver (Ն10% of liver weight), which cannot be attributed to alcohol consumption or any other liver disease (1). NAFLD covers a range from simple nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) and fibrosis (1). The fatty liver is resistant to the action of insulin to inhibit hepatic glucose (2,3) and VLDL (4) production, resulting in hyperglycemia and hypertriglyceridemia. The mechanisms underlying insulin resistance in human NAFLD are unclear. While triacylglycerols themselves are inert, lipid intermediates may act as important regulators of both oxidative stress (5) and insulin signaling (6). In vitro studies as well as studies in animals suggest that diacylglycerols, which are immediate precursors of triacylglycerols (7), can induce insulin resistance by activating specific isoforms of protein kinase C (PKC) (8,9). The concentrations of diacylglycerols have recently been shown to be increased in human NAFLD compared with subjects with normal liver histology (10). Ceramides are another class of reactive lipids that mediate saturated fat-induced insulin resistance (6). There are no data comparing ceramide and diacylglycerol concentrations in the human liver or relating them to hepatic fat content.Sources of hepatic lipids include dietary chylomicron remnants, free fatty acids released from either adipose tissue triacylglycerols or chylomicrons hydrolyzed at a rate in excess of what can be taken up by tissues (spillover), and de novo lipogenesis (11). Increased lipolysis is a...

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Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are important regulators of blood and lymphatic vessel growth and vascular permeability. The VEGF-C/VEGFR-3 signaling pathway is crucial for lymphangiogenesis, and heterozygous inactivating missense mutations of the VEGFR-3 gene are associated with hereditary lymphedema. However, VEGF-C can have potent effects on blood vessels because its receptor VEGFR-3 is expressed in certain blood vessels and because the fully processed form of VEGF-C also binds to the VEGFR-2 of blood vessels. To characterize the in vivo effects of VEGF-C on blood and lymphatic vessels, we have overexpressed VEGF-C via adenovirus- and adeno-associated virus-mediated transfection in the skin and respiratory tract of athymic nude mice. This resulted in dose-dependent enlargement and tortuosity of veins, which, along with the collecting lymphatic vessels were found to express VEGFR-2. Expression of angiopoietin 1 blocked the increased leakiness of the blood vessels induced by VEGF-C whereas vessel enlargement and lymphangiogenesis were not affected. However, angiogenic sprouting of new blood vessels was not observed in response to AdVEGF-C or AAV-VEGF-C. These results show that virally produced VEGF-C induces blood vessel changes, including vascular leak, but its angiogenic potency is much reduced compared with VEGF in normal skin.

Ceramides may mediate saturated fat–induced insulin resistance, but there are no data comparing ceramide concentrations between human tissues. We therefore performed lipidomic analysis of human subcutaneous (SCfat) and intra‐abdominal (IAfat) adipose tissue, the liver, and serum in eight subjects. The liver contained (nmol/mg tissue) significantly more ceramides (1.5–3‐fold), sphingomyelins (7–8‐fold), phosphatidylethanolamines (10–11‐fold), lysophosphatidylcholines (7–12‐fold), less ether‐linked phosphatidylcholines (2–2.5‐fold) but similar amounts of diacylglycerols as compared to SCfat and IAfat. The amounts of ceramides and their synthetic precursors, such as palmitic (16:0) free fatty acids and sphingomyelins, differed considerably between the tissues. The liver contained proportionally more palmitic, stearic (18:0), and long polyunsaturated fatty acids than adipose tissues. Stearoyl‐CoA desaturase 1 (SCD1) activity reflected by serum, estimated from the 16:1/16:0‐ratio, was closely related to that in the liver (r = 0.86, P = 0.024) but not adipose tissues. This was also true for estimated elongase (18:1/16:1, r = 0.89, P = 0.01), and Δ5 (20:4/20:3, r = 0.89, P = 0.012) and Δ6 (18:3[n‐6]/18:2, r = 1.0, P < 0.001) desaturase activities. We conclude that the human liver contains higher concentrations of ceramides and saturated free fatty acids than either SCfat or IAfat.