Hepatic CD36 downregulation parallels steatosis improvement in morbidly obese undergoing bariatric surgery.

BACKGROUND: The notion that hepatic expression of genes involved in lipid metabolism is altered in obese patients is relatively new and its relationship with hepatic steatosis and cardiometabolic alterations remains unclear. OBJECTIVE: We assessed the impact of Roux-en-Y gastric bypass surgery (RYGB) on the expression profile of genes related to metabolic syndrome in liver biopsies from morbidly obese individuals using a custom-made, focused cDNA microarray, and assessed the relationship between the expression profile and hepatic steatosis regression. MATERIALS AND METHODS: Plasma and liver samples were obtained from patients at baseline and 12 months after surgery. Samples were assayed for chemical and gene expression analyses, as appropriate. Gene expression profiles were assessed using custom-made, focused TaqMan low-density array cards. RESULTS: RYGB-induced weight loss produced a favorable reduction in fat deposits, insulin resistance (estimated by homeostasis model assessment of insulin resistance (HOMA-IR)), and plasma and hepatic lipid levels. Compared with the baseline values, the gene expression levels of key targets of lipid metabolism were significantly altered: CD36 was significantly downregulated (-40%; P=0.001), whereas APOB (+27%; P=0.032) and SCARB1 (+37%; P=0.040) were upregulated in response to surgery-induced weight reduction. We also observed a favorable reduction in the expression of the PAI1 gene (-80%; P=0.007) and a significant increase in the expression of the PPARA (+60%; P=0.014) and PPARGC1 genes (+36%; P=0.015). Notably, the relative fold decrease in the expression of the CD36 gene was directly associated with a concomitant reduction in the cholesterol (Spearman's r=0.92; P=0.001) and phospholipid (Spearman's r=0.76; P=0.04) contents in this tissue. CONCLUSIONS: For the first time, RYGB-induced weight loss was shown to promote a favorable downregulation of CD36 expression, which was proportional to a favorable reduction in the hepatic cholesterol and phospholipid contents in our morbidly obese subjects following surgery.

Evaluation of adipocytic changes after a simil-lipocryolysis stimulus.

Lipocryolysis is considered as an effective, well-tolerated non-invasive procedure to reduce local adiposities. However there is little information about its mechanism of action by the procedure. It is proposed that lipid phase transition or crystallization may be an unleashed apoptotic stimulus. Yet, the post-lipocryolysis apoptosis is not easily confirmed, least of all is its correlation with crystallization. In this study adipocytes from rat fat tissue were exposed to a lipocryolysis-session-like stimulus. Lipid changes were observed in all test sample.

X-ray diffraction study confirms intra-adipocitary lipid crystallization after lipocryolysis stimulus.

Lipocryolysis always claimed localized-fat-reduction to be a consequence of local apoptotic adipocyte destruction triggered by intracellular triglyceride crystallization. The idea is now under debate, for it has been suggested that the physical changes occurring in adipocytes after lipocryolysis could be better explained by a lipid gel-like transition process rather than by lipid crystallization. Since a) lipocryolysis claims apoptosis to be the key to adipocyte destruction and clinical-result achievement and b) it considers crystallization to be a necessary step for the apoptotic stimulus unleashing, any effort to untangle, prove or discard this process is very important.

Anticoagulants and other preanalytical factors interfere in plasma nitrate/nitrite quantification by the Griess method.

Nitric oxide (NO) is a signal molecule with functions such as neurotransmission, local vascular relaxation, and anti-inflammation in many physiological and pathological processes. Various factors regulate its intracellular lifetime. Due to its high reactivity in biological systems, it is transformed in the bloodstream into nitrates (NO(-)(3)) by oxyhemoglobin. The Griess reaction is a technically simple method (spectrophotometric, 540 nm) for the analysis of nitrites (NO(-)(2)) in aqueous solutions. We studied the interference of common anticoagulants in the quantification of nitrate and nitrite in plasma samples by the Griess method. We obtained rat plasma using heparin or sodium EDTA as anticoagulants, then added, or otherwise, known NO(-)(3) amounts in order to calculate their recovery. We also studied the effect of ultra-filtration performed before Griess reaction on plasma and aqueous solutions of various anticoagulants (heparin, EDTA, and also sodium citrate) to compare the recoveries of added NO(-)(3) or NO(-)(2). We used standards of NO(-)(3) or NO(-)(2) for quantification. We conclude that: (i) The bacterial nitrate reductase used to reduce NO(-)(3) to NO(-)(2) is unstable in certain storage conditions and interferes with different volumes of plasma used. (ii) The ultrafiltration (which is sometimes performed before the Griess reaction) of plasma obtained with EDTA or citrate is not recommended because it leads to overestimation of NO(minus sign)(3). In contrast, ultrafiltration is necessary when heparin is used. (iii) The absorbance at 540 nm attributed to plasma itself (basal value or background) interferes in final quantification, especially when ultrafiltration is not performed. For the quantification of plasma NO(-)(3) we recommend: sodium EDTA as anticoagulant, no ultrafiltration of plasma, and measurement of the absorbance background of each sample.