C-Peptide and Its C-Terminal Fragments Improve Erythrocyte Deformability in Type 1 Diabetes Patients

Aims/hypothesis. Data now indicate that proinsulin C-peptide exerts important physiological effects and shows the characteristics of an endogenous peptide hormone. This study aimed to investigate the influence of C-peptide and fragments thereof on erythrocyte deformability and to elucidate the relevant signal transduction pathway. Methods. Blood samples from 23 patients with type 1 diabetes and 15 matched healthy controls were incubated with 6.6 nM of either human C-peptide, C-terminal hexapeptide, C-terminal pentapeptide, a middle fragment comprising residues 11–19 of C-peptide, or randomly scrambled C-peptide. Furthermore, red blood cells from 7 patients were incubated with C-peptide, penta- and hexapeptides with/without addition of ouabain, EDTA, or pertussis toxin. Erythrocyte deformability was measured using a laser diffractoscope in the shear stress range 0.3–60 Pa. Results. Erythrocyte deformability was impaired by 18–25% in type 1 diabetic patients compared to matched controls in the physiological shear stress range 0.6–12 Pa (P < .01–.001). C-peptide, penta- and hexapeptide all significantly improved the impaired erythrocyte deformability of type 1 diabetic patients, while the middle fragment and scrambled C-peptide had no detectable effect. Treatment of erythrocytes with ouabain or EDTA completely abolished the C-peptide, penta- and hexapeptide effects. Pertussis toxin in itself significantly increased erythrocyte deformability. Conclusion/interpretation. C-peptide and its C-terminal fragments are equally effective in improving erythrocyte deformability in type 1 diabetes. The C-terminal residues of C-peptide are causally involved in this effect. The signal transduction pathway is Ca2+-dependent and involves activation of red blood cell Na+, K+-ATPase

Pilot Data on Brain-to-Blood Efflux of B-Amyloid Peptides in Man

• Alzheimer’s disease (AD) is the most common cause of dementia and affects nearly 40,000 individuals in Ireland. • The b-amyloid peptide (Ab) plays a key role in the pathogenesis of the AD and the presence of Ab plaques in the brain is diagnostic. •The hypothesis posits that Ab deposition is a critical factor in the disease process and that production and clearance of Ab are key drivers of the disease1. •Flux of Ab from the brain is believed to contribute to the overall level of Ab within in brain2 and antibody mediated brain-to-blood efflux has been observed in animal models3. •Clearance of from the blood is believed to be mainly via the liver, kidney and spleen4. •Data from human studies indicate that the about 6% of the Ab pool present in the cerebrospinal fluid is cleared per hour5. •There are no data available on the magnitude of the cerebral output of Ab peptides in man or the hepatic uptake. •The aim of this work was to investigate if the concentration Ab peptides is different in jugular venous plasma and arterial plasma and so estimate direct values for both brain-to-blood Ab efflux and hepatic clearance in man

Molecular and Cellular Effects of C-peptide—New Perspectives on an Old Peptide

New results present C-peptide as a biologically active peptide hormone in its own right. Although C-peptide is formed from proinsulin and cosecreted with insulin, it is a separate entity with biochemical and physiological characteristics that differ from those of insulin. There is direct evidence of stereospecific binding of C-peptide to a cell surface receptor, which is different from those for insulin and other related hormones. The C-peptide binding site is most likely a G–protein–coupled receptor. The association constant for C-peptide binding is approximately 3 × 109M-1. Saturation of the binding occurs already at a concentration of about 1 nM, which explains why C-peptide effects are not observed in healthy subjects. Binding of C-peptide results in activation of Ca2+ and MAPK-dependent pathways and stimulation of Na+,K+-ATPase and eNOS activities. The latter 2 enzymes are both deficient in several tissues in type 1 diabetes. There is some evidence that C-peptide, and insulin may interact synergistically on the insulin signaling pathway. Clinical evidence suggests that replacement of C-peptide, together with regular insulin therapy, may be beneficial in patients with type 1 diabetes and serve to retard or prevent the development of long-term complications

C-peptide reverses nociceptive neuropathy in type 1 diabetes

Autorzy zbadali działanie terapeutyczne peptydu C w ustalonej neuropatii nocyceptywnej u szczurów BB/Wor z cukrzycą typu 1. Oceniono nocyceptywną funkcję nerwów, morfometrię niezmielinizowanych włókien nerwu łydkowego i zwoju korzenia grzbietowego (DRG), zawartość peptydu nocyceptywnego oraz ekspresję czynników neurotroficznych i ich receptorów. Peptyd C podawano w dawce substytucyjnej drogą pompy osmotycznej w ciągłym wlewie lub raz dziennie w iniekcji podskórnej. Szczury z cukrzycą leczono od 4.-7. miesiąca trwania cukrzycy i porównywano z nieleczonymi szczurami z grupy kontrolnej w tym samym okresie choroby. Peptyd C podawany przez pompę osmotyczną, lecz nie w iniekcjach podskórnych, zmniejszył hiperalgezję i cukrzycozależną redukcję liczby włókien niezmielinizowanych (p < 0,01) oraz średnią wielkość aksonów (p < 0,05) w nerwie łydkowym. Ekspresja receptora czynnika wzrostu nerwu (NGF) o dużym podobieństwie (NGFR-TrkA) w DRG zmniejszyła się znamiennie w 4. miesiącu (p < 0,01). Ekspresja receptorów insulinowego oraz IGF-1 w DGR i NFG w nerwie kulszowym zmniejszyła się znamiennie w 7. miesiącu u szczurów z cukrzycą (odpowiednio: p < 0,01, p < 0,05 i p < 0,005). Podawanie przez pompę osmotyczną zapobiegło spadkowi ekspresji NGFR-TrkA, receptora insulinowego (p < 0,05) i IGF-IR (p < 0,005) w DRG oraz zwiększyło zawartość NGF (p < 0,05) w nerwie kulszowym. Natomiast peptyd C podawany drogą podskórną wpłynął jedynie w niewielkim stopniu na morfometryczne i molekularne zmiany u szczurów z cukrzycą. Stwierdzono, że peptyd C korzystnie wpływa na cukrzycową neuropatię nocyceptywną; aby uzyskać efekt optymalny, należy utrzymywać fizjologiczne stężenie peptydu C w ciągu dnia.We examined the therapeutic effects of C-peptide on established nociceptive neuropathy in type 1 diabetic BB/Worrats. Nociceptive nerve function, unmyelinated sural nerve fiber and dorsal root ganglion (DRG) cell morphometry, nociceptive peptide content, and the expression of neurotrophic factors and their receptors were investigated. C-peptide was administered either as a continuous subcutaneous replacement dose via osmopumps or a replacement dose given once daily by subcutaneous injection. Diabetic rats were treated from 4 to 7 months of diabetes and were compared with control and untreated diabetic rats of 4- and 7-month duration. Osmopump delivery but not subcutaneous injection improved hyperalgesia and restored the diabetesinduced reduction of unmyelinated fiber number (p < 0.01) and mean axonal size (p < 0.05) in the sural nerve. High-affinity nerve growth factor (NGF) receptor (NGFR-TrkA) expression in DRGs was significantly reduced at 4 months (p < 0.01). Insulin receptor and IGF-I receptor (IGF-IR) expressions in DRGs and NGF content in sciatic nerve were significantly decreased in 7-month diabetic rats (p < 0.01, 0.05, and 0.005, respectively). Osmopump delivery prevented the decline of NGFR-TrkA, insulin receptor (p < 0.05), and IGF-IR (p < 0.005) expressions in DRGs and improved NGF content (p < 0.05) in sciatic nerve. However, subcutaneous injection had only marginal effects on morphometric and molecular changes in diabetic rats. We conclude that C-peptide exerts beneficial therapeutic effects on diabetic nociceptive neuropathy and that optimal effects require maintenance of physiological C-peptide concentrations for a major proportion of the day

Human skeletal muscle is refractory to the anabolic effects of leucine during the postprandial muscle-full period in older men

Leucine modulates muscle protein synthesis (MPS), with potential to facilitate accrual/maintenance of muscle mass. Animal models suggest that leucine boluses shortly after meals may prolong MPS and delay onset of a “muscle-full” state. However, the effects of nutrient “top-ups” in humans, and particularly older adults where deficits exist, have not been explored. We determined the effects of a leucine top-up after essential amino acid (EAA) feeding on anabolic signaling, MPS, and muscle energy metabolism in older men. During 13C6-phenylalanine infusion, 16 men (∼70 years) consumed 15 g of EAA with (n=8, FED + LEU) or without (n=8, FED) 3 g of leucine top-up 90 min later. Repeated blood and muscle sampling permitted measurement of fasting and postprandial plasma EAA, insulin, anabolic signaling including mTOR complex 1 (mTORC1) substrates, cellular ATP and phosphorylocreatine, and MPS. Oral EAA achieved rapid insulinemia (12.5 iU·ml−1 25 min post-feed), essential aminoacidemia (3000 μM, 45–65 min post-feed), and activation of mTORC1 signaling. Leucine top-up prolonged plasma EAA (2800 μM, 135 min) and leucine availability (1050 μM, 135 min post-feed). Fasting FSRs of 0.046 and 0.056%·h-1 (FED and FED + LEU respectively) increased to 0.085 and 0.085%·h-1 90–180 min post-feed and returned to basal rates after 180 min in both groups. Phosphorylation of mTORC1 substrates returned to fasting levels 240 min post-feed in both groups. Feeding had limited effect on muscle elongation factor 2 (eEF2) phosphorylation. We demonstrate the refractoriness of muscle to nutrient-led anabolic stimulation in the postprandial period; thus, leucine supplements should be taken outside of meals, or with meals containing suboptimal protein in terms of either amount or EAA composition

C-Peptide Increases Na,K-ATPase Expression via PKC- and MAP Kinase-Dependent Activation of Transcription Factor ZEB in Human Renal Tubular Cells

Replacement of proinsulin C-peptide in type 1 diabetes ameliorates nerve and kidney dysfunction, conditions which are associated with a decrease in Na,K-ATPase activity. We determined the molecular mechanism by which long term exposure to C-peptide stimulates Na,K-ATPase expression and activity in primary human renal tubular cells (HRTC) in control and hyperglycemic conditions.HRTC were cultured from the outer cortex obtained from patients undergoing elective nephrectomy. Ouabain-sensitive rubidium ((86)Rb(+)) uptake and Na,K-ATPase activity were determined. Abundance of Na,K-ATPase was determined by Western blotting in intact cells or isolated basolateral membranes (BLM). DNA binding activity was determined by electrical mobility shift assay (EMSA). Culturing of HRTCs for 5 days with 1 nM, but not 10 nM of human C-peptide leads to increase in Na,K-ATPase α(1)-subunit protein expression, accompanied with increase in (86)Rb(+) uptake, both in normal- and hyperglycemic conditions. Na,K-ATPase α(1)-subunit expression and Na,K-ATPase activity were reduced in BLM isolated from cells cultured in presence of high glucose. Exposure to1 nM, but not 10 nM of C-peptide increased PKCε phosphorylation as well as phosphorylation and abundance of nuclear ERK1/2 regardless of glucose concentration. Exposure to 1 nM of C-peptide increased DNA binding activity of transcription factor ZEB (AREB6), concomitant with Na,K-ATPase α(1)-subunit mRNA expression. Effects of 1 nM C-peptide on Na,K-ATPase α(1)-subunit expression and/or ZEB DNA binding activity in HRTC were abolished by incubation with PKC or MEK1/2 inhibitors and ZEB siRNA silencing.Despite activation of ERK1/2 and PKC by hyperglycemia, a distinct pool of PKCs and ERK1/2 is involved in regulation of Na,K-ATPase expression and activity by C-peptide. Most likely C-peptide stimulates sodium pump expression via activation of ZEB, a transcription factor that has not been previously implicated in C-peptide-mediated signaling. Importantly, only physiological concentrations of C-peptide elicit this effect

Variants at multiple loci implicated in both innate and adaptive immune responses are associated with Sjögren’s syndrome

Sjögren’s syndrome is a common autoimmune disease (~0.7% of European Americans) typically presenting as keratoconjunctivitis sicca and xerostomia. In addition to strong association within the HLA region at 6p21 (Pmeta=7.65×10−114), we establish associations with IRF5-TNPO3 (Pmeta=2.73×10−19), STAT4 (Pmeta=6.80×10−15), IL12A (Pmeta =1.17×10−10), FAM167A-BLK (Pmeta=4.97×10−10), DDX6-CXCR5 (Pmeta=1.10×10−8), and TNIP1 (Pmeta=3.30×10−8). Suggestive associations with Pmeta<5×10−5 were observed with 29 regions including TNFAIP3, PTTG1, PRDM1, DGKQ, FCGR2A, IRAK1BP1, ITSN2, and PHIP amongst others. These results highlight the importance of genes involved in both innate and adaptive immunity in Sjögren’s syndrome

Exercise and Type 2 Diabetes: The American College of Sports Medicine and the American Diabetes Association: joint position statement

Although physical activity (PA) is a key element in the prevention and management of type 2 diabetes, many with this chronic disease do not become or remain regularly active. High-quality studies establishing the importance of exercise and fitness in diabetes were lacking until recently, but it is now well established that participation in regular PA improves blood glucose control and can prevent or delay type 2 diabetes, along with positively affecting lipids, blood pressure, cardiovascular events, mortality, and quality of life. Structured interventions combining PA and modest weight loss have been shown to lower type 2 diabetes risk by up to 58% in high-risk populations. Most benefits of PA on diabetes management are realized through acute and chronic improvements in insulin action, accomplished with both aerobic and resistance training. The benefits of physical training are discussed, along with recommendations for varying activities, PA-associated blood glucose management, diabetes prevention, gestational diabetes mellitus, and safe and effective practices for PA with diabetes-related complications