Laboratory assessment of the anti-feeding effect for up to 12 months of a slow release deltamethrin collar (Scalibor®) against the sand fly Phlebotomus perniciosus in dogs

Background

Leishmaniosis/leishmaniasis consists of a wide group of diseases, caused by different Leishmania species and having different hosts. Leishmaniosis caused by Leishmania infantum, a disease primarily of dogs and humans, occurs after susceptible hosts are exposed to the feeding behavior of infected sand flies. A one-year laboratory study in dogs was designed to determine the 364-day anti-feeding efficacy of a slow release deltamethrin collar against the sand fly P. perniciosus, a common host of L. infantum in the Mediterranean basin.

Methods

In this assessor-blinded study, 16 Beagle dogs were randomized into two groups using P. perniciosus engorgement rates from a Day -7 challenge. On Day 0, dogs in Group 1 received a placebo collar, while dogs in Group 2 received a deltamethrin collar (Scalibor® Protector Band). All dogs were caged, sedated and then exposed for 1 h to 85 (± 10) female and 15 (± 5) male P. perniciosus on Day 7 and every 28 days through Day 364. All flies, alive and dead, were aspirated from cages and from dogs, immediately counted and then frozen for assessment of blood engorgement. Anti-feeding efficacy was determined by comparing the arithmetic means of engorged female flies (alive, dead and moribund) in the deltamethrin group to the control group means. Insecticidal efficacy at the time flies were retrieved was assessed by comparisons between groups of mean live female fly counts.

Results

In the deltamethrin group, relative to the control group, there was a significant reduction in arithmetic mean numbers of engorged P. perniciosus of 94–98% from Day 7 through Day 364. On Day 28, in the treated group relative to the control group, there was a 74% reduction in mean live fly counts, with between-group differences significant from Days 7 through 196, although insecticidal activity remained less than 50% from Day 56.

Conclusion

Deltamethrin collar application to dogs reduced sand fly feeding by ≥ 94%, relative to unprotected control dogs, for 364 days. Thus, one collar applied to a dog can prevent or reduce the risk of sand fly transmission of Leishmania for one full year.

Efficacy of fluralaner administered either orally or topically for the treatment of naturally acquired Sarcoptes scabiei var. canis infestation in dogs

Background

The efficacy of fluralaner, formulated as a chewable tablet (Bravecto™) or topical solution (Bravecto™ Spot-on Solution), was evaluated against naturally acquired Sarcoptes scabiei var. canis infestation in dogs.

Methods

The study was performed in privately-owned dogs naturally infested with S. scabiei var. canis. All dogs living in the same household as the infested dog were enrolled into one of 3 groups (2 fluralaner treated and 1 negative control). All dogs within one household were administered the same treatment, with one dog per household included in further observations and assessments. In total, 29 dogs confirmed positive for sarcoptic mange were included. On Day 0, all dogs in group 1 (n = 9) were treated once orally with fluralaner at a minimum dose of 25 mg/kg body weight; all dogs in group 2 (n = 11) were treated once topically with fluralaner at a dose of 25 mg/kg body weight; and dogs in group 3 (n = 9) were treated once topically with saline solution. Sarcoptes scabiei var. canis mites on each dog were counted before treatment and at 4 weeks after treatment in deep skin scrapings (~4 cm²) from 5 different body areas. Clinical signs of infestation (i.e. erythematous papules; casts, scales and crusts; body areas with hair loss) and pruritus were recorded at the same time points.

Results

Single oral or topical treatment with fluralaner resulted in a 100 % reduction in mite counts post-treatment (group 1: P = 0.0009 and group 2: P = 0.0011). Resolution of clinical signs at four weeks post-treatment was variable, with improvement observed for erythematous papules, casts and crusts, and pruritus. All fluralaner treated dogs showed an improvement in overall hair re-growth compared with pre-treatment observations.

Conclusion

Fluralaner administered either orally or topically to naturally infested dogs eliminates Sarcoptes scabiei var. canis mites and improves clinical signs over a 4-week observation period.

Influence of atorvastatin on apolipoprotein E and AI kinetics in patients with type 2 diabetes

Atorvastatin reduces both plasma cholesterol and triglyceride concentrations in patients with type 2 diabetes, but mechanisms underlying triglyceride decrease and the effect of atorvastatin on high density lipoprotein (HDL) still remain unclear. Apolipoprotein (apo) E plays a crucial role in modulating production and clearance of triglyceride-rich very low density lipoprotein (VLDL). The main effect of apoAI is to modulate HDL metabolism. The aim of this work was to study the influence of atorvastatin on apoAI and apoE kinetics and to determine whether its hypocholesterolemic and hypotriglyceridemic effects could be related to changes in this apolipoprotein metabolism. Plasma VLDL-apoE, HDL-apoE, and HDL-apoAI were studied in seven patients with diabetes with mixed hyperlipidemia using a stable isotope labeling technique ([(2)H3]leucine-primed constant infusion) and monocompartmental model before and after 2 months of treatment with 40 mg/day of atorvastatin. Plasma apoE concentration was significantly reduced (44.1 +/- 19.1 versus 32 +/- 11.6 mg/l, p < 0.05) after treatment. This decrease was associated with a diminution of HDL-apoE concentration (17.46 +/- 6.71 versus 13.37 +/- 6.05 mg/l, p < 0.05) and production rate (0.202 +/- 0.085 versus 0.119 +/- 0.047 mg/kg/day, p < 0.05), whereas an increase in VLDL-apoE concentration (6.44 +/- 2.16 before versus 9.23 +/- 4.02 mg/l after, p < 0.05) and production rate (0.827 +/- 0.367 versus 1.524 +/- 0.664 mg/kg/day, p < 0.05) was observed. No significant difference was observed after treatment for apoAI parameters. We conclude that atorvastatin treatment promotes different apoE distribution between HDL and VLDL, favoring VLDL apoE content. The increased number of apoE per VLDL particle suggests that atorvastatin could enhance the direct catabolism of triglyceride-rich VLDL through apoE receptor pathways.

Apolipoprotein E kinetics: influence of insulin resistance and type 2 diabetes

BACKGROUNDS AND AIMS

Insulin resistance related to obesity and diabetes is characterized by an increase in plasma TG-rich lipoprotein concentrations. Apolipoprotein (apo) E plays a crucial role in the metabolism of these lipoproteins and particularly in the hepatic clearance of their remnants. The aim of this study was to explore apoE kinetics of obese subjects and to determine what parameters could influence its metabolism.

METHODS

Using stable-isotope labelling technique ([(2)H(3)]-leucine-primed constant infusion) and monocompartmental model (SAAM II computer software), we have studied the plasma kinetics of very-low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) apoE in 12 obese subjects (body mass index (BMI) 27.4-36.6 kg/m(2)): Seven were type 2 diabetics (age 47-65 y; HbA1c 7.1-10.2%) and five were non-diabetics (age 40-51 y, HbA1c: 4.9-5.3%). Six of the diabetic subjects were insulin resistant as assessed by insulin sensitivity index (HOMA 2.6-10.0), while non-diabetic subjects were all insulin sensitive (HOMA 1.2-2.1).

RESULTS

Plasma VLDL and HDL apoE concentrations were significantly higher in diabetic than in non-diabetic subjects (5.74+/-1.60 vs 1.46+/-1.74 mg/l, P<0.01 and 17.81+/-6.67 vs 9.97+/-3.32 mg/l, P<0.05). These increased levels were associated with significantly higher absolute production rate (APR) of VLDL and HDL apoE (0.714+/-0.343 vs 0.130+/-0.200 mg/kg/day, P<0.01, and 0.197+/-0.087 vs 0.080+/-0.060 mg/kg/day, P<0.05, respectively) while no significant difference was found for fractional catabolic rate (FCR) of VLDL and HDL apoE (3.44+/-1.64 vs 1.97+/-0.84/day and 0.30+/-0.12 vs 0.19+/-0.09/day, respectively). In the whole population, BMI was not correlated with any of apoE kinetic data. HOMA was positively correlated with FCR of VLDL apoE (r=0.64, P<0.05) and tended to be correlated with APR of VLDL apoE (r=0.58, P=0.06). HbA1c was positively correlated with APR and FCR of both VLDL apoE (r=0.91 and 0.78, P<0.01, respectively) and HDL apoE (r=0.66 and 0.69, P<0.05, respectively).

CONCLUSION

Obese diabetics are characterized by elevated VLDL and HDL apoE levels associated with enhancement of VLDL and HDL apoE production rates. Whereas obesity did not influence apoE kinetic parameters in itself, insulin resistance may lead to an increase in VLDL apoE production and fractional catabolic rates. Diabetes and the glycemic control may also specifically influence the kinetics of both VLDL and HDL apoE. All together, these disorders should explain at least part of the increase in VLDL and HDL apoE observed in diabetes.

Effect of dietary omega-3 fatty acids on high-density lipoprotein apolipoprotein AI kinetics in type II diabetes mellitus

The effect of a dietary fish oil supplementation on metabolism of HDL was studied in type II diabetes mellitus. Endogenous labeling of HDL-apo AI was performed using a 14 h primed infusion of D3-leucine in five diabetic patients before and 2 months after treatment with maxEPA(R). Isotopic enrichment curves were analyzed using a monoexponential function. After treatment, plasma cholesterol level remained unchanged (205.4+/-41.9 vs. 206.8+/-30.7 mg/dl, NS), whereas plasma triglycerides were decreased (155.4+/-67.9 vs. 202.6+/-32.2 mg/dl, P=0.06). Plasma apo AI was similar under maxEPA(R) (116.0+/-25.6 vs. 111.8+/-25.4 mg/dl, NS), and HDL-cholesterol and HDL-triglycerides were also not markedly changed (30.2+/-10.0 vs. 27.1+/-10 mg/dl, and 15.3+/-9.8 vs. 19.2+/-10.4 mg/dl, NS). HDL-apo AI fractional catabolic rate (FCR) and absolute production rate (APR) were significantly decreased after treatment with maxEPA(R) (0.27+/-0.09 vs. 0.37+/-0.08 pool day, P<0.05, and 12.1+/-2.8 vs. 16.1+/-3.3 mg/kg per day, P<0.05). These findings showed an effect of maxEPA(R) on kinetics of apolipoprotein AI in type II diabetes mellitus, probably linked to changes in plasma triglyceride level.

Effect of low-density lipoproteins on apolipoprotein AI kinetics in heterozygous familial hypercholesterolemia

In patients with heterozygous familial hypercholesterolemia (FH), both synthetic and clearance rates of high-density lipoproteins (HDL) are increased compared with control subjects. According to in vitro data on hepatocytes, the expanded pool size of low-density lipoproteins (LDL) in FH could partly explain the enhanced HDL production. Therefore, we have tested the hypothesis that a reduction of LDL pool size, achieved by LDL-apheresis, is associated with a downregulation of HDL synthesis. We studied the kinetics of HDL by infusing [5,5,5-(2)H(3)]-leucine in 7 heterozygous FH patients before and after 3 biweekly LDL-apheresis using dextran sulfate columns. Both plasma and LDL-cholesterol levels were decreased after LDL-apheresis (169 +/- 35 v 422 +/- 27 mg/dL, P <.05, and 85 +/- 19 v 327 +/- 52 mg/dL, P <.05, respectively). Plasma triglyceride level was unaffected (162 +/- 43 v 176 +/- 35 mg/dL, not significant [NS]) and HDL composition remained stable (HDL-cholesterol 29 +/- 6 v 37 +/- 7 mg/dL, NS, and HDL-triglyceride 20 +/- 6 v 19 +/- 8 mg/dL, NS). Plasma apolipoprotein AI (apo AI) was also similar (122 +/- 20 v 115 +/- 18 mg/dL, NS). Mean HDL-apo AI fractional catabolic rate (FCR) was slightly higher (0.41 +/- 0.07 v 0.36 +/- 0.14 pool/d, NS), and absolute production rate (APR) was increased (22.1 +/- 5.7 v 18.0 +/- 5.7 mg/kg/d, P <.05) after LDL-apheresis. These human kinetic data suggest that LDL do not play a major role on HDL production in heterozygous FH patients.

In vivo evidence for the role of lipoprotein lipase activity in the regulation of apolipoprotein AI metabolism: a kinetic study in control subjects and patients with type II diabetes mellitus

The aim of this study was to delineate the role of lipoprotein lipase (LPL) activity in the kinetic alterations of high density lipoprotein (HDL) metabolism in patients with type II diabetes mellitus compared with controls. The kinetics of HDL were studied by endogenous labeling of HDL apolipoprotein AI (HDL-apo AI) using a primed infusion of D(3)-leucine. The HDL-apo AI fractional catabolic rate (FCR) was significantly increased (0.32 +/- 0.07 vs. 0.23 +/- 0.05 pool/day; P < 0.01), and HDL composition was changed [HDL cholesterol, 0.77 +/- 0.16 vs. 1.19 +/- 0.37 mmol/L (P < 0.05); HDL triglycerides, 0.19 +/- 0.12 vs. 0.10 +/- 0.03 mmol/L (P < 0.05)] in diabetic patients compared with healthy subjects. HDL-apo AI FCR was correlated to plasma and HDL triglyceride concentrations (r = 0.82; P < 0.05 and r = 0.80; P < 0.05, respectively) and to homeostasis model assessment (r = 0.78; P < 0.05). Postheparin plasma LPL activity was decreased in type II diabetes (6.8 +/- 2.8 vs. 18.1 +/- 5.2 micromol/mL postheparin plasma.h; P < 0.005) compared with that in healthy subjects and was correlated to the FCR of HDL-apo AI (r = -0.63; P < 0.05). LPL activity was also correlated with HDL cholesterol (r = 0.78; P < 0.05), plasma and HDL triglycerides (r = -0.87; P < 0.005 and r = -0.83; P < 0.05, respectively), and homeostasis model assessment (r = -0.79; P < 0.05). In addition, the LPL to hepatic lipase ratio was correlated with the catabolic rate of HDL (r = -0.76; P < 0.06). These results suggest that a decrease in the LPL to hepatic lipase ratio in type II diabetes mellitus, mainly related to lowered LPL activity, could induce an increase in HDL catabolism. These alterations in HDL kinetics in type II diabetes proceed to some extent from changes in their composition, probably linked to an increase in triglyceride transfer from very low density lipoprotein particles, in close relationship with LPL activity and resistance to insulin.

Effect of low-density lipoprotein apheresis on kinetics of apolipoprotein B in heterozygous familial hypercholesterolemia

The acute reduction of low-density lipoprotein (LDL) cholesterol obtained by LDL-apheresis allows the role of the high level of circulating LDL on lipoprotein metabolism in heterozygous familial hypercholesterolemia (heterozygous FH) to be addressed. We studied apolipoprotein B (apoB) kinetics in five heterozygous FH patients before and the day after an apheresis treatment using endogenous labeling with [(2)H(3)]leucine. Compared with younger control subjects, heterozygous FH patients before apheresis showed a significant decrease in the fractional catabolic rate of LDL (0.24 +/- 0.08 vs. 0.65 +/- 0.22 day(-1); P < 0.01), and LDL production was increased in heterozygous FH patients (18.9 +/- 7.0 vs. 9.9 +/- 4.2 mg/kg.day; P < 0.05). The modeling of postapheresis apoB kinetics was performed using a nonsteady state condition, taking into account the changing pool size of very low density lipoprotein (VLDL), intermediate density lipoprotein, and LDL apoB. The postapheresis kinetic parameters did not show statistical differences compared with preapheresis parameters in heterozygous FH patients; however, a trend for increases in fractional catabolic rate of LDL (0.24 +/- 0.08 vs. 0.35 +/- 0.09 day(-1); P = 0.067) and the production of VLDL (13.7 +/- 8.3 vs. 21.9 +/- 1.6 mg/kg.day; P = 0.076) was observed. These results suggested that the marked decrease in plasma LDL obtained a short time after LDL-apheresis is able to stimulate LDL receptor activity and VLDL production in heterozygous FH.

Apolipoprotein A-I kinetics in heterozygous familial hypercholesterolemia: a stable isotope study

Heterozygous familial hypercholesterolemia (FH) is associated with a moderate decrease of plasma apoA-I and HDL-cholesterol levels. The aim of the study was to test the hypothesis that these abnormalities were related to an increase of HDL-apoA-I fractional catabolic rate (FCR). We performed a 14-h infusion of [5,5,5-(2)H(3)]leucine in seven control subjects and seven heterozygous FH patients (plasma total cholesterol 422 +/- 27 vs. 186 +/- 42 mg/dL, P < 0.001, respectively). Plasma apoA-I concentration was not changed in FH compared to controls (respectively 115 +/- 18 vs. 122 +/- 15 mg/dL, NS), and HDL-cholesterol level was decreased (37 +/- 7 vs. 46 +/- 19 mg/dL, NS). Kinetics of HDL metabolism were modeled as a single compartment as no differences were observed between HDL(2) and HDL(3) subclasses. Both mean apoA-I FCR and absolute production rate (APR) were increased in FH (respectively, 0.36 +/- 0.14 vs. 0.22 +/- 0.05 pool/d, P < 0.05, and 18.0 +/- 7.7 and 11.2 +/- 2.3 mg/kg/d, P < 0.05). Higher HDL-triglyceride and HDL-apoE levels were observed in patients with heterozygous FH. (Respectively 19 +/- 8 vs. 8 +/- 3 mg/dL, P < 0.05, and 5.3 +/- 0.8 vs. 3.7 +/- 0.9 mg/dL, P < 0.05). We conclude that the catabolism of HDL-apoA-I is increased in heterozygous FH patients. However, plasma apoA-I concentration was maintained because of an increased HDL-apoA-I production rate.

High density lipoprotein apolipoprotein AI kinetics in NIDDM: a stable isotope study

High density lipoprotein (HDL) kinetics were studied by infusing [5,5,5-2H3]-leucine in five subjects with normal glucose tolerance and eight patients with non-insulin-dependent diabetes mellitus (NIDDM) with poor metabolic control (HbA1c = 8.16 +/- 1.93%) (mean +/- SD). HDL were modelled as a single compartment since no kinetic differences were observed between HDL2 and HDL3 subclasses. Plasma apolipoprotein AI (apo AI) concentration was significantly lower in NIDDM patients (96.1 +/- 12.1 vs 124.4 +/- 13.1 mg.dl-1, p < 0.01). HDL composition was altered in NIDDM, as an increase in HDL-triglyceride and a decrease in HDL-cholesterol, negatively correlated (r = 0.780, p < 0.01). The mean fractional catabolic rate (FCR) of apo AI-HDL was significantly higher (0.39 +/- 0.16 vs 0.21 +/- 0.06 d-1, p < 0.05) while the apo AI-HDL absolute production rate was not significantly greater (13.6 +/- 5.1 vs 12.0 +/- 4.2 mg.kg-1.d-1) in diabetic patients compared to normal subjects. There were significant correlations between apo AI-HDL FCR and plasma apo AI concentration (r = -0.580, p < 0.05), plasma triglycerides (r = 0.839, p < 0.0001) or HDL-triglyceride levels (r = 0.597, p < 0.05). No correlation was observed between apo AI-HDL FCR and HbA1c or HDL-cholesterol level. These data support the view that the decrease in plasma apo AI level in patients with NIDDM is due to an increase of apo AI-HDL FCR, which may itself be related to changes in HDL composition.