Hydrolyzed casein decreases postprandial glucose concentrations in T2DM patients irrespective of leucine content.

Lifestyle modifications, including diet, are important in the prevention and management of type 2 diabetes mellitus (T2DM). However, limited information is available on the effects of single doses of meal replacements, particularly with regard to their effect on postprandial glucose. Therefore, a study was performed comparing the effects of a single meal replacement in T2DM patients on postprandial serum glucose, insulin, and glucagon. This randomized, double-blind, partial cross-over study was performed in 36 T2DM patients who continued their oral anti-diabetic medication. Each patient received three out of four treatments separated by 7 days. The treatments were a proprietary casein hydrolysate (insuVida™) alone or with additional leucine, unhydrolyzed casein, or placebo. Blood sampling was done for 4 hr. Treatments were compared using repeated measures ANOVA. Results are given as an estimate of the difference (%) for the 4-hr epoch. Glucose concentrations were lowered by -4.7% by insuVida and insuVida plus added leucine compared to placebo (95% CI: -1.6 to -7.7%), while the effect of unhydrolyzed casein was -1.7% (-4.8 to 1.5%). Addition of leucine to insuVida induced the greatest increase in insulin (i.e., 51.8%; 41.1 to 63.4%). All three treatments increased glucagon concentrations by 14% (8 to 20%) compared to placebo. A single dose of insuVida™ with or without addition of leucine significantly lowered plasma glucose compared to placebo and intact casein in T2DM patients. This is most likely due to an insulinotropic effect of insuVida. The data suggest that this type of intervention may be a viable treatment strategy in T2DM.

Protein hydrolysates induce CCK release from enteroendocrine cells and act as partial agonists of the CCK1 receptor.

Protein has been reported to be the most satiating of all macronutrients. Upon gastrointestinal digestion, peptides are generated that stimulate the release of satiety hormones such as cholecystokinin (CCK) from enteroendocrine cells. As such, bioactive peptides could be the target of Functional Food ingredients with satiating effects. We set up an in vitro assay system to investigate if different protein hydrolysates exhibit varying CCK-releasing properties. Soy, pea, potato, casein, and whey protein hydrolysates were incubated with the enteric endocrine cell line STC-1 that endogenously expresses and secretes CCK. Release of CCK was measured by ELISA. All hydrolysates induced CCK release at low concentrations (>0.1 mg.L -1)); however, no significant differences in CCK-releasing properties between the different protein hydrolysates were found, suggesting a generic, nonspecific peptide-sensing mechanism in the STC-1 cells on hydrolyzed protein. As the ELISA exhibits sensitivity to all CCK isoforms possessing the C-terminal CCK octapeptide but varying in biological activity at the CCK 1 receptor (CCK 1R), a secondary module was added to the STC-1 cell assay. Intracellular calcium measurements were performed in CHO-CCK 1R cells. Following exposure of the STC-1 cells to the protein hydrolysates, the medium was tested on the CCK 1R assay. Released CCK was measured with higher sensitivity and lower variability than in the ELISA. Surprisingly, we found that some protein hydrolysates (soy > potato >> casein) also directly stimulated CCK 1R-expressing cells, while whey and pea protein hydrolysates were inactive. As CCK 1R is expressed in the GI tract, direct interaction of CCK 1R with dietary peptides may contribute to their satiety effects. Future experiments developing bioactive ingredients for Functional Foods for weight management could involve isolation of the active, CCK 1R-activating peptides in, for example, soy protein hydrolysates.

Comparison of 3 AT1 receptor binding assays: filtration assay, ScreenReady Target, and WGA Flashplate.

In this article, the study of 3 different angiotensin II type 1 (AT(1)) receptor binding assays in terms of reproducibility, robustness, and feasibility for high-throughput screening (HTS) is described. The following methods were used: a nonhomogeneous filtration assay in a 96-well format using CHO-AT(1) cell membranes and 2 homogeneous assays, which include the commercially available ScreenReady Target for the AT(1) receptor and the wheat germ agglutinin (WGA) Flashplate, which was coated "in-house" with the CHO-AT(1) cell membranes. Receptors were labeled with [(125)I]-Sar(1)-Ile(8)-angiotensin II, and radioligand binding was displaced using the antagonist losartan and the natural agonist angiotensin II. Reproducible K(d), B(max), and K(i) values and good total binding/nonspecific binding (TB/NSB) ratios were obtained with both the ScreenReady Targets and the filtration assay, whereas the WGA Flashplates showed unacceptably high nonspecific binding and high variation when applied as a homogeneous assay. However, when applied as a heterogeneous assay (i.e., when a wash step at the end of the assay is included), the results were significantly better. Interestingly, ligand affinities were consistently lower in Flashplate-based assays than in the filtration assay. This may be due to the immobilization of the receptors onto the solid surface of the plate, affecting their conformation. In terms of reproducibility, robustness, and feasibility for HTS, the authors conclude that the ScreenReady Target plates are most suitable for AT(1) receptor binding screening.

Human adipose cells express CD4, CXCR4, and CCR5 [corrected] receptors: a new target cell type for the immunodeficiency virus-1?

The concept that adipocytes belong to an essential endocrine system with some characteristics of immune cells has recently emerged. The aim of this paper is to present evidence of the expression of CD4, CXCR4, and CCR5 receptors by human adipocytes and to test whether adipose cells support HIV entry. Primary human preadipocytes were cultured and differentiated in vitro. Expression of the three receptors on preadipocytes and adipocytes was demonstrated by reverse transcriptase-polymerase chain reaction, immunocytochemical, and immunohistochemical analysis. Infection of adipose cells to HIV-1 was then investigated. The measurement of the viral p24 antigen in preadipocyte culture medium showed an increase of p24 levels between 24 and 72 h postexposure and then a progressive decrease to reach a low level at 10-15 days. Ten days after the infection test, supernatant of preadipocytes contained infectious particles able to infect the susceptible T-CD4 CEM cell line. The expression of viral proteins by adipocytes was confirmed using a fusion test. The presence of viral DNA was exhibited by gag-specific polymerase chain reaction, supporting the hypothesis of HIV-1 X4- and R5-virus entry in preadipocytes. Adipose cells represent the first cell type that does not belong to the immune system expressing all specific HIV receptors and may represent new HIV-1 target cells.