A single site in human β-hexosaminidase A binds both 6-sulfate-groups on hexosamines and the sialic acid moiety of GM2 ganglioside

AbstractHuman β-hexosaminidase A (Hex A) (αβ) is composed of two subunits whose primary structures are ∼60% identical. Deficiency of either subunit results in severe neurological disease due to the storage of GM2 ganglioside; Tay–Sachs disease, α deficiency, and Sandhoff disease, β deficiency. Whereas both subunits contain active sites only the α-site can efficiently bind negatively charged 6-sulfated hexosamine substrates and GM2 ganglioside. We have recently identified the αArg424 as playing a critical role in the binding of 6-sulfate-containing substrates, and βAsp452 as actively inhibiting their binding. To determine if these same residues affect the binding of the sialic acid moiety of GM2 ganglioside, an αArg424Gln form of Hex A was expressed and its kinetics analyzed using the GM2 activator protein:[3H]-GM2 ganglioside complex as a substrate. The mutant showed a ∼3-fold increase in its Km for the complex. Next a form of Hex B (ββ) containing a double mutation, βAspLeu453AsnArg (duplicating the α-aligning sequences), was expressed. As compared to the wild type (WT), the mutant exhibited a >30-fold increase in its ability to hydrolyze a 6-sulfated substrate and was now able to hydrolyze GM2 ganglioside when the GM2 activator protein was replaced by sodium taurocholate. Thus, this α-site is critical for binding both types of negatively charge substrates

High prevalence of impaired awareness of hypoglycemia and severe hypoglycemia among people with insulin-treated type 2 diabetes: The Dutch Diabetes Pearl Cohort

Objective People with type 2 diabetes on insulin are at risk for hypoglycemia. Recurrent hypoglycemia can cause impaired awareness of hypoglycemia (IAH), and increase the risk for severe hypoglycemia. The aim of this study was to assess the prevalence and determinants of self-reported IAH and severe hypoglycemia in a Dutch nationwide cohort of people with insulin-treated type 2 diabetes. Research design and methods Observational study of The Dutch Diabetes Pearl, a cohort of people with type 2 diabetes treated in primary, secondary and tertiary diabetes care centers. The presence of IAH and the occurrence of severe hypoglycemia in the past year, defined as an event requiring external help to re

Sex differences in cardiometabolic risk factors, pharmacological treatment and risk factor control in type 2 diabetes: findings from the Dutch Diabetes Pearl cohort

Introduction Sex differences in cardiometabolic risk factors and their management in type 2 diabetes (T2D) have not been fully identified. Therefore, we aimed to examine differences in cardiometabolic risk factor levels, pharmacological treatment and achievement of risk factor control between women and men with T2D. Research design and methods Cross-sectional data from the Dutch Diabetes Pearl cohort were used (n=6637, 40% women). Linear and Poisson regression analyses were used to examine sex differences in cardiometabolic risk factor levels, treatment, and control. Results Compared with men, women had a significantly higher body mass index (BMI) (mean difference 1.79kg/ m2 (95% CI 1.49 to 2.08)), while no differences were found in hemoglobin A1c (HbA1c) and systolic blood pressure (SBP). Women had lower diastolic blood pressure (−1.94mm Hg (95% CI −2.44 to −1.43)), higher total cholesterol (TC

Vascular effects of Katp channel blockade by glibenclamide in humans

Contains fulltext : 146852.pdf (Publisher’s version ) (Open Access)169 p

Reproducibility of skin microcirculatory measurements in humans, with special emphasis on capillaroscopy.

The reproducibility of capillaroscopic measurements of capillary blood cell velocity (CBV) in human nailfolds was investigated by use of the computerized system CapiFlow. Therefore, CBV measurements of two capillaries of each of three fingers together with laser Doppler fluxmetry (LDF) and skin temperature measurements were performed three times in five healthy volunteers. Short-term (1.5 h) intra-individual coefficient of variation (CV) of CBV was 18.4%. Long-term (7 days) CV amounted to 55.8%. Inter-individual CV was 55.9%. Short- and long-term intra-individual CVs of LDF were 25.4% and 37.3%. Inter-individual variation was 36.0%. Skin temperature showed short- and long-term CVs of 3.7% and 5.5% and inter-individual CV of 5.8%. In conclusion, measurement of CBV using CapiFlow is a suitable method to assess acute effects, but has limited value in investigating long-term effects. Because of the wide interindividual variability in both CBV and LDF, power calculations will reveal large numbers to investigate. Skin temperature has a relatively small intra- and inter-individual variation and is more suitable for long-term studies

Body mass index and the efficacy of needle-free jet injection for the administration of rapid-acting insulin analogs, a post hoc analysis

Item does not contain fulltextWe recently showed in a euglycaemic glucose clamp study among 18 healthy volunteers that using jet injectors rather than conventional pens significantly improved the time-action profiles of rapid-acting insulin analogs. Here, we investigated whether such profiles were modified by body mass index (BMI) and related weight parameters by comparing insulin administration by jet injection to that by conventional pen in subgroups defined by BMI, waist-to-hip ratio, waist circumference and insulin dose. After conventional administration, times to peak insulin levels (T-INS(max)) occurred 31.1 [95% confidence interval (CI) 13.7-48.5] min later and time to maximum glucose requirement (T-GIR(max)) 56.9 (95%CI 26.6-87.3) min later in more obese (BMI > 23.6 kg/m(2)) than in lean subjects (BMI < 23.6 kg/m(2)). In contrast, T-INS(max) and T-GIR(max) were similar in subjects with high and low BMI, when insulin was administered by jet injection. We conclude that using jet injection for insulin administration may especially benefit subjects with higher body weight

Concomitant Intake of Coca-Cola to Manage the Drug-Drug Interaction Between Velpatasvir and Omeprazole Studied in Healthy Volunteers

Contains fulltext : 208787.pdf (publisher's version ) (Closed access)We aimed to evaluate the effect of the acid beverage Coca-Cola on the pharmacokinetics of velpatasvir (VEL) when given with omeprazole. This was an open-label, randomized, crossover trial in 11 healthy adults. A single dose of sofosbuvir/velpatasvir (SOF/VEL) 400/100 mg was administered alone (reference) or with omeprazole 40 mg once daily with water (intervention I); in the intervention II arm, omeprazole 40 mg was combined with 250 mL of Coca-Cola. Geometric mean ratios (GMRs) were calculated for VEL area under the concentration-time curve from zero to infinity (AUC0-inf ) and maximum plasma concentration (Cmax ). VEL exposure was reduced by 26.7% when SOF/VEL was coadministered with omeprazole vs. reference: GMRs (90% confidence interval (CI)) were 73.3% (55.6-96.8) and 69.1% (52.3-91.2) for AUC0-inf and Cmax , respectively. Intake of SOF/VEL with Coca-Cola compensated for the interaction with omeprazole and resulted in a higher VEL exposure. GMRs (90% CI) were 161.6% (122.4-213.3) for AUC0-inf and 143.9% (109.0-190.0) for Cmax . Therefore, Coca-Cola can be used to overcome the drug-drug interaction between VEL and omeprazole

No role of calcium- and ATP-dependent potassium channels in insulin-induced vasodilation in humans in vivo.

Item does not contain fulltextThe mechanism of insulin-induced vasodilation has not been completely clarified, but could be important in future treatment strategies of insulin resistance. Recently, a role for calcium-dependent and ATP-dependent potassium (K(Ca) and K(ATP)) channels in insulin-induced vasodilation has been demonstrated in in vitro studies. A role for these channels has never been confirmed in humans in vivo. Therefore, we investigated the role of these channels in insulin-induced vasodilation in humans in vivo. A hyperinsulinemic euglycemic clamp was combined with intra-arterial infusion of placebo, tetraethylammonium (blocker of K(Ca) channels) or glibenclamide (blocker of K(ATP) channels) in three groups of 12 healthy volunteers. Bilateral forearm blood flow was measured with venous occlusion plethysmography. Systemic hyperinsulinemia induced a 20+/-9% vasodilation (p=0.001). Neither tetraethylammonium nor glibenclamide reduced this vasodilation as compared to placebo. According to the results of the present study, insulin-induced vasodilation seems not to be mediated by the opening of K(Ca) and K(ATP) channels in humans in vivo

Microcirculatory effects of KATP channel blockade by sulphonylurea derivatives in humans.

Item does not contain fulltextBACKGROUND: Recent investigations have shown that glibenclamide inhibits the opening of vascular ATP-sensitive potassium channels during ischemia. This observation may implicate cardiovascular effects of sulphonylurea derivatives when used under conditions of ischemia in patients with Type 2 diabetes mellitus. In addition to resistance arteries, the (pre) capillary vessels also contain ATP-dependent potassium channels. Closure of these channels by sulphonylurea derivatives might affect the development of microvascular disease in Type 2 diabetes mellitus. Therefore, we investigated the microcirculatory effects of sulphonylurea derivatives in Type 2 diabetic patients as compared with healthy volunteers. MATERIALS AND METHODS: Arteriovenous blood flow (skin temperature and laser Doppler flux) and capillary blood cell velocity were measured before and during infusion of four doses of glibenclamide (0.1, 0.3, 1.0 and 3.0 microg min-1 dL-1) into the brachial artery of 14 Type 2 diabetic patients and 13 healthy controls. The experiments included appropriate time control studies. RESULTS: Both skin temperature and laser Doppler flux decreased in response to glibenclamide in healthy volunteers (-7 +/- 2%, P &lt; 0.0005 and -31 +/- 11%, P = 0.001, respectively), but did not change in Type 2 diabetic patients (1 +/- 3%, P = 0.29 and 4 +/- 14%, P = 0.97). However, capillary blood cell velocity decreased in Type 2 diabetic patients (-38 +/- 18%, P = 0.04), but did not change in healthy volunteers (-1 +/- 11%, P = 0.28). CONCLUSIONS: The results of the present study indicate that glibenclamide indeed affects microvascular blood flow. Glibenclamide may induce redistribution of the microvascular skin flow from nutritive flow to arteriovenous shunt flow in Type 2 diabetic patients. Therefore, closure of ATP-dependent potassium channels by glibenclamide possibly plays a role in the development of microangiopathy in Type 2 diabetic patients

Pharmacokinetic similarity demonstrated after crushing of the elbasvir/grazoprevir fixed-dose combination tablet for HCV infection

Contains fulltext : 225279.pdf (Publisher’s version ) (Open Access)BACKGROUND: Finding a suitable treatment for HCV patients with swallowing disorders is still a major challenge. In practice, direct-acting antivirals are crushed without knowledge of adequate absorption. Crushing can alter drug exposure, possibly leading to treatment failure, development of resistance or toxicity. Currently, there is no information about crushing of the fixed-dose combination tablet of elbasvir/grazoprevir; therefore, crushing of this tablet is not recommended. OBJECTIVES: To investigate the influence of crushing on the pharmacokinetics of the elbasvir/grazoprevir fixed-dose combination tablet. METHODS: We conducted an open-label, two-period, randomized, cross-over, Phase I, single-dose trial in 11 healthy adult volunteers. Subjects randomly received whole-tablet elbasvir/grazoprevir or crushed and suspended elbasvir/grazoprevir in a fasted state. Pharmacokinetic similarity criteria (90% CIs lie within 70%-143% acceptance range) were used for AUC0-∞ and AUC0-72. RESULTS: Mean plasma concentration-time curves of elbasvir and grazoprevir showed similar pharmacokinetic profiles. The primary pharmacokinetic parameters AUC0-∞ and AUC0-72 of elbasvir and grazoprevir after intake of a crushed tablet were on average 12%-16% higher compared with the whole tablet, but 90% CIs were all within the predefined boundaries of pharmacokinetic similarity. Crushing leads to a higher Cmax of grazoprevir (42%); no significant difference was found between treatments with regard to the Cmax of elbasvir. No serious adverse events were reported during the trial. CONCLUSIONS: Pharmacokinetic similarity could be demonstrated for a crushed and suspended tablet compared with a whole tablet, without impacting drug safety or efficacy. Crushed and suspended administration of elbasvir/grazoprevir can be used in patients with swallowing disorders