A Comparison of Total Food Intake at a Personalised Buffet in People with Obesity, before and 24 Months after Roux-en-Y-Gastric Bypass Surgery.

Long-term reductions in the quantity of food consumed, and a shift in intake away from energy dense foods have both been implicated in the potent bariatric effects of Roux-en-Y gastric bypass (RYGB) surgery. We hypothesised that relative to pre-operative assessment, a stereotypical shift to lower intake would be observed at a personalised ad libitum buffet meal 24 months after RYGB, driven in part by decreased selection of high energy density items. At pre-operative baseline, participants (n = 14) rated their preference for 72 individual food items, each of these mapping to one of six categories encompassing high and low-fat choices in combination with sugar, complex carbohydrate or and protein. An 18-item buffet meal was created for each participant based on expressed preferences. Overall energy intake was reduced on average by 60% at the 24-month buffet meal. Reductions in intake were seen across all six food categories. Decreases in the overall intake of all individual macronutrient groups were marked and were generally proportional to reductions in total caloric intake. Patterns of preference and intake, both at baseline and at follow-up appear more idiosyncratic than has been previously suggested by verbal reporting. The data emphasise the consistency with which reductions in ad libitum food intake occur as a sequel of RYGB, this being maintained in the setting of a self-selected ad libitum buffet meal. Exploratory analysis of the data also supports prior reports of a possible relative increase in the proportional intake of protein after RYGB.

Electrochemical assay of sorbitol dehydrogenase at PEDOT modified electrodes - a new milk biomarker for confirmation of pregnancy in dairy cattle.

A robust electrochemical assay for sorbitol dehydrogenase (SORDH) activity in milk was developed using voltammetry and chronocoulometry at bare and polymer modified transducers. The motivation for the work was to evaluate the potential of SORDH as an early biomarker of bovine pregnancy using milk as sample matrix. SORDH is an enzyme involved in carbohydrate metabolism converting sorbitol, the sugar alcohol form of glucose, into fructose, with NAD+ as a cofactor being simultaneously reduced to NADH. The assay was optimised via direct NADH oxidation on glassy carbon and screen printed carbon electrodes followed by electropolymerisation of 3,4-ethylenedioxythiophene (EDOT) monomer to form an NADH responsive PEDOT surface which operated well in undiluted milk samples. Assay conditions such as incubation time and temperature were optimised resulting in a 3 min assay at 37 °C in the presence of 10 mM NAD+ and 20 mM sorbitol co-substrates, enabling NADH electro oxidation (linear range 0.25-5 mM, sensitivity 9.17 µC cm-2 mM-1 in undiluted milk). SORDH determination followed over the range 0.31-10 U mL-1 in milk samples with sensitivity 5.45 µC cm-2 U-1 mL with LOD 0.0787 U mL-1. The assay was applied to milk sample testing acquired as part of an approved animal study involving control and breeding cycles of dairy cows with focus on analysis at day 19 post artificial insemination. Significant differences between control and pregnant SORDH levels in whole milk animal samples were found (average values 2.57 and 4.07 ng mL-1 respectively), as verified using a commercial SORDH ELISA optical assay. Finally, progesterone monitoring over days 16-21 of the oestrous cycle employed an optical ELISA assay and confirmed maintenance of progesterone levels from day 19 onwards.