Scanning ion conductance microscopy (SICM) is demonstrated to be a powerful technique for quantitative nanoscale surface charge mapping of living cells. Utilizing a bias modulated (BM) scheme, in which the potential between a quasi-reference counter electrode (QRCE) in an electrolyte-filled nanopipette and a QRCE in bulk solution is modulated, it is shown that both the cell topography and the surface charge present at cellular interfaces can be measured simultaneously at high spatial resolution with dynamic potential measurements. Surface charge is elucidated by probing the properties of the diffuse double layer (DDL) at the cellular interface, and the technique is sensitive at both low-ionic strength and under typical physiological (high-ionic strength) conditions. The combination of experiments that incorporate pixel-level self-referencing (calibration) with a robust theoretical model allows for the analysis of local surface charge variations across cellular interfaces, as demonstrated on two important living systems. First, charge mapping at Zea mays root hairs shows that there is a high negative surface charge at the tip of the cell. Second, it is shown that there are distinct surface charge distributions across the surface of human adipocyte cells, whose role is the storage and regulation of lipids in mammalian systems. These are new features, not previously recognized, and their implications for the functioning of these cells are highlighted.

eral action of irisin improves glucose homeostasis and increases energy expenditure, with no data on a central role of irisin in metabolism. These studies sought to examine 1) presence of irisin in human cerebrospinal fluid (CSF) and banked human hypothalamic tissue, 2) serum irisin in maternal subjects across varying adiposities with or without gestational diabetes (GDM), and 3) their respective neonate offspring. CSF, serum, and neonatal cord serum were collected from 91 pregnant women with and without GDM attending for an elective cesarean section [body mass index (BMI): 37.7 Ϯ 7.6 kg/m 2 ; age: 32 Ϯ 8.3 yr]. Irisin was assessed by ELISA and correlated with biochemical and anthropometric data. Irisin expression was examined in human hypothalamus by immunohistochemical staining. Serum irisin in pregnant women was significantly lower in nonobese compared with obese and GDM subjects, after adjusting for BMI, lipids, and glucose. Irisin was present in neonatal cord serum (237 Ϯ 8 ng/ml) and maternal CSF (32 Ϯ 1.5 ng/ml). CSF irisin correlated positively with serum irisin levels from nonobese and obese pregnant women (P Ͻ 0.01), with CSF irisin significantly raised in GDM subjects (P Ͻ 0.05). Irisin was present in human hypothalamic sections in the paraventricular neurons, colocalized with neuropeptide Y. Irisin was detectable in CSF and in paraventricular neurons. Maternal serum irisin was lower in nonobese pregnant women after adjusting for BMI and a number of metabolic parameters. These studies indicate that irisin may have a central role in metabolism in addition to the known peripheral role. Further studies investigating the central action of irisin in human metabolic disease are required.irisin; obesity; gestational diabetes mellitus; leptin EMERGING DATA SUGGEST THAT a newly discovered polypeptide hormone, irisin, a cleaved secreted form of fibronectin type III domain containing 5 (FNDC5), has the potential to increase energy expenditure and improve glucose homeostasis in humans (4,16,31,34). This is particularly significant, since irisin can induce the transformation of white adipocytes into "beige" or "brite" adipocytes, which can ultimately lead to increased mitochondrial respiration (4, 34), with implications for weight loss. Therefore, such studies suggest the potential therapeutic applications of irisin not only in use for weight loss but also to improve glucose metabolism (4). Subsequent research has also revealed that the function of irisin appears to fall beyond its original role noted in muscle (4,9,13,21,23), and the administration of exogenous irisin could theoretically increase energy expenditure during or after weight loss. Recent studies have shown that irisin may also act as an adipokine (21, 25) as well as a potential "neurokine" (9, 12). Although the role of irisin in the brain is unclear, analysis has revealed that FNDC5 knockdown in murine embryonic stem cells reduces neurogenesis (11), whereas pharmacological doses of irisin increase proliferation of mouse hippocampal neuronal cells (20...

BackgroundThe dietary supply of methyl donors such as folate, vitamin B12, betaine, methionine, and choline is essential for normal growth, development, and physiological functions through the life course. Both human and animal studies have shown that vitamin B12 deficiency is associated with altered lipid profile and play an important role in the prediction of metabolic risk, however, as of yet, no direct mechanism has been investigated to confirm this.ResultsThree independent clinical studies of women (i) non-pregnant at child-bearing age, (ii) in early pregnancy, and (iii) at delivery showed that low vitamin B12 status was associated with higher total cholesterol, LDL cholesterol, and cholesterol-to-HDL ratio. These results guided the investigation into the cellular mechanisms of induced cholesterol biosynthesis due to vitamin B12 deficiency, using human adipocytes as a model system. Adipocytes cultured in low or no vitamin B12 conditions had increased cholesterol and homocysteine levels compared to control. The induction of cholesterol biosynthesis was associated with reduced s-adenosylmethionine (AdoMet)-to-s-adenosylhomocysteine (AdoHcy) ratio, also known as methylation potential (MP). We therefore studied whether reduced MP could lead to hypomethylation of genes involved in the regulation of cholesterol biosynthesis. Genome-wide and targeted DNA methylation analysis identified that the promoter regions of SREBF1 and LDLR, two key regulators of cholesterol biosynthesis, were hypomethylated under vitamin B12-deficient conditions, and as a result, their expressions and cholesterol biosynthesis were also significantly increased. This finding was further confirmed by the addition of the methylation inhibitor, 5-aza-2′-deoxycytidine, which resulted in increased SREBF1 and LDLR expressions and cholesterol accumulation in vitamin B12-sufficient conditions. Finally, we observed that the expression of SREBF1, LDLR, and cholesterol biosynthesis genes were increased in adipose tissue of vitamin B12 deficient mothers compared to control group.ConclusionsClinical data suggests that vitamin B12 deficiency is an important metabolic risk factor. Regulation of AdoMet-to-AdoHcy levels by vitamin B12 could be an important mechanism by which it can influence cholesterol biosynthesis pathway in human adipocytes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13148-015-0046-8) contains supplementary material, which is available to authorized users.

To assess the effects of n3 polyunsaturated fatty acids (n3PUFAs) (also known as omega-3 fatty acids) compared with comparator (e.g. placebo, anti-depressant treatment, standard care, no treatment, wait-list control) for major depressive disorder in adults.