Changes to insulin sensitivity in glucose clearance systems and redox following dietary supplementation with a novel cysteine-rich protein: A pilot randomized controlled trial in humans with type-2 diabetes.

We recently developed a novel keratin-derived protein (KDP) rich in cysteine, glycine, and arginine, with the potential to alter tissue redox status and insulin sensitivity. The KDP was tested in 35 human adults with type-2 diabetes mellitus (T2DM) in a 14-wk randomised controlled pilot trial comprising three 2×20 g supplemental protein/day arms: KDP-whey (KDPWHE), whey (WHEY), non-protein isocaloric control (CON), with standardised exercise. Outcomes were measured morning fasted and following insulin-stimulation (80 mU/m2/min hyperinsulinaemic-isoglycaemic clamp). With KDPWHE supplementation there was good and very-good evidence for moderate-sized increases in insulin-stimulated glucose clearance rate (GCR; 26%; 90% confidence limits, CL 2%, 49%) and skeletal-muscle microvascular blood flow (46%; 16%, 83%), respectively, and good evidence for increased insulin-stimulated sarcoplasmic GLUT4 translocation (18%; 0%, 39%) vs CON. In contrast, WHEY did not effect GCR (-2%; -25%, 21%) and attenuated HbA1c lowering (14%; 5%, 24%) vs CON. KDPWHE effects on basal glutathione in erythrocytes and skeletal muscle were unclear, but in muscle there was very-good evidence for large increases in oxidised peroxiredoxin isoform 2 (oxiPRX2) (19%; 2.2%, 35%) and good evidence for lower GPx1 concentrations (-40%; -4.3%, -63%) vs CON; insulin stimulation, however, attenuated the basal oxiPRX2 response (4%; -16%, 24%), and increased GPx1 (39%; -5%, 101%) and SOD1 (26%; -3%, 60%) protein expression. Effects of KDPWHE on oxiPRX3 and NRF2 content, phosphorylation of capillary eNOS and insulin-signalling proteins upstream of GLUT4 translocation AktSer437 and AS160Thr642 were inconclusive, but there was good evidence for increased IRSSer312 (41%; 3%, 95%), insulin-stimulated NFκB-DNA binding (46%; 3.4%, 105%), and basal PAK-1Thr423/2Thr402 phosphorylation (143%; 66%, 257%) vs WHEY. Our findings provide good evidence to suggest that dietary supplementation with a novel edible keratin protein in humans with T2DM may increase glucose clearance and modify skeletal-muscle tissue redox and insulin sensitivity within systems involving peroxiredoxins, antioxidant expression, and glucose uptake.

Elevated seminal plasma myeloperoxidase is associated with a decreased sperm concentration in young men.

Myeloperoxidase is a major neutrophil protein which generates oxidants that are highly reactive, and if present in seminal fluid, could be potentially damaging to spermatozoa. We recruited young males aged 18-35 years, unscreened for fertility status, for a pilot study measuring seminal plasma myeloperoxidase. On three occasions, over a 3-month period, we measured parameters of semen quality and correlated these with seminal myeloperoxidase protein and activity. After baseline measurement, participants were supplemented daily with 250 mg of vitamin C, a potent scavenger of reactive oxygen species with antiinflammatory activities. Seminal plasma from eight of the 12 participants had measurable concentrations of myeloperoxidase protein, across a broad range (15-250 ng/mL). Median myeloperoxidase protein concentrations were ~45-fold higher in semen samples with low vs. high sperm concentrations. Seminal plasma myeloperoxidase protein concentration was inversely correlated with the percentage of rapidly motile spermatozoa assessed by computer-assisted sperm analysis, and the total number of spermatozoa per ejaculate, but positively correlated with sperm maturity, measured by DNA staining ability. We measured an inverse correlation between semen vitamin C concentration and seminal plasma myeloperoxidase protein concentration, although vitamin C supplementation had no effect on semen quality. Our pilot data suggest that high concentrations of myeloperoxidase were present in the seminal plasma of many of our young participants, and that this may be associated with decreases in semen quality. A larger study is required to confirm these findings.

The role of oxidants and vitamin C on neutrophil apoptosis and clearance.

We have investigated the role of neutrophil oxidants in the surface changes that result in recognition and uptake of neutrophils by macrophages. We have shown that H2O2 produced by stimulated neutrophils is essential for the surface expression of phosphatidylserine. This does not occur in neutrophils from mice with chronic granulomatous disease and may explain the formation of granuloma in this condition. We have also investigated the role of intracellular vitamin C on neutrophil apoptosis. Cells from vitamin C-deficient mice were found to be less likely to undergo both spontaneous and oxidant-induced apoptosis, with eventual necrosis being the most probable outcome.