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Background: Casein is considered a slowly digestible protein compared with whey protein, and this may cause differences in hormone responses and the kinetics of delivering amino acids into the circulation. Objective: We investigated whether postprandial plasma hormone and metabolite responses were different when bovine casein or whey protein was co-administered with carbohydrates in healthy and prediabetic adults. Methods: White healthy male adults (n = 15) and white, well-defined male and female prediabetic adults (n = 15) received test drinks randomly on 3 different occasions at least 2 d apart which contained 50 g of maltodextrin19 (MD19) alone or in combination with 50 g of whey protein isolate (WPI) or 50 g of sodium caseinate (SC). Blood samples were collected over a 240-min time period and were analyzed for hormone profiles and defined metabolites. Results: No evidence was found that gastric emptying was different between the 2 protein drinks. Both proteins increased peak plasma insulin concentrations in prediabetic persons by 96% compared with MD19 (each, P < 0.05), which was accompanied by a reduction of peak venous blood glucose by 21% (each, P < 0.0001) without a difference between the 2 proteins. Peak plasma glucagon concentrations increased by 101% in both groups after the protein drinks (P < 0.05). The WPI drink also increased peak plasma glucose-dependent insulinotropic polypeptide concentrations in healthy volunteers by 56% (P < 0.01). Differences in plasma metabolite concentrations in volunteers could be attributed exclusively to the differences in the amino acid composition of the 2 proteins ingested. Conclusion: The WPI and the SC drinks similarly reduced postprandial glucose excursions when ingested together with carbohydrates in healthy and prediabetic volunteers. Under our experimental conditions, however, no evidence was found that gastrointestinal processing of the 2 protein varieties differed substantially. This trial was registered at clinicaltrials.gov as DRKS00005682. J Nutr doi: 10.3945/jn.114.199190.

Oral glucose tolerance tests (OGTT) are valuable tools for diagnosis of impaired glucose tolerance and insulin resistance. Protein intake modulates insulin secretion and sensitivity and thereby can alter the metabolic response. To assess these effects in the plasma metabolome, 15 healthy human volunteers underwent in random order an OGTT with and without 30 g of a protein-hydrolysate (OGTT + PL) followed by metabolite profiling via LC–MS/MS. Compared to the OGTT alone, plasma glucose response was reduced and insulin clearance retarded after OGTT + PL while suppression of catabolic markers such as free fatty acids, glycerol, lactate or acylcarnitines showed no difference between the two challenges. Clusters of plasma amino acids characterized by subgroups with similar physico-chemical characteristics revealed long-lasting declines after the OGTT and coherent increases after the OGTT + PL despite the fact that the protein-hydrolysate provided different amounts of individual amino acids. The amino acid clusters identified appear to derive from common transport processes involved in intestinal absorption and the insulin-dependent extraction by target tissues and suggest that these processes may be of high diagnostic value to assess insulin sensitivity.

This paper discusses various approaches to decompose economic time series into their trend and cyclical components. For over 30 years now, the Deutsche Bundesbank publishes trend-adjusted indicators in its Statistical Supplement 4 entitled ?Seasonally Adjusted Business Statistics? which are calculated basically as unweighted moving averages. As alternatives to the Bundesbank?s current approach, the widely used Hodrick-Prescott filter, the extended exponential smoothing filter and the Baxter-King low-pass filter are investigated. All three of the filters are able to clearly separate the trend component from the cyclical component for German economic indicators. The turning points of the growth cycles are largely consistent with the Bundesbank?s current approach. However, the trend deviation level at the end of the series is still subject to noticeable changes. This uncertainty can be quantified with the help of ARIMA forecasts. The choice of filter ultimately depends on the features of the time series to be filtered. Whereas extended exponential smoothing is well suited to I(1) processes, the Hodrick-Prescott filter is preferable for I(2) series.

The capability for electrogenic inward transport of substrates that carry different net charge is a phenomenon observed in a variety of membrane-solute transporters but is not yet understood. We employed the two-electrode voltage clamp technique combined with intracellular pH recordings and the giant patch technique to assess the selectivity for bidirectional transport and the underlying stoichiometries in proton to substrate flux coupling for electrogenic transfer of selected anionic, cationic, and neutral dipeptides by the intestinal peptide transporter PEPT1. Anionic dipeptides such as Gly-Asp and Asp-Gly are transported in their neutral and negatively charged forms with high and low affinities, respectively. The positive transport current obtained with monoanionic substrates results from the cotransport of two protons. Cationic dipeptides can be transported in neutral and positively charged form, resulting in an excess transport current as compared with neutral substrates. However, binding and transport of cationic dipeptides shows a pronounced selectivity for the position of charged side chains demonstrating that the binding domain of PEPT1 is asymmetric, both in its inward and outward facing conformation. The simultaneous presence of identically charged substrates on both membrane surfaces generates outward and, unexpectedly, enhanced inward transport currents probably by increasing the turnover rate.