Development of enzyme-controlled colonic drug delivery using amylose and hydroxypropyl methylcellulose: optimization by factorial design.

The aim of the present study is to develop colon-targeted drug delivery systems for diclofenac sodium which release the drug specifically and instantly at target site using amylose as a carrier. Coating formulations were designed based on the full factorial design. The evaluated responses were lag time prior to drug release and T90. Compression-coated tablets of diclofenac sodium containing various proportions of amylose and HPMC were prepared. In vitro drug release studies were done by changing pH method with enzyme. In vivo studies were done to confirm the potential of formulation to release the drug at target site. The dissolution data revealed that the ratio of polymers is very important to achieve optimum formulation. Results showed that the tablet prepared according to the above formulation released drug instantly at pH 6.8 (simulating colonic pH). An in vivo study shows that optimized formulation disintegrated in the target region. The results of this study revealed that factorial design is a suitable tool for optimization of coating formulations to achieve colon delivery. It was shown that coating formulation consisting of amylose 285 mg and HPMC 150 mg coating has the potential for colonic delivery of diclofenac sodium irrespective of change in pH in a patient with IBD.

Laser method for synthesis and processing of continuous diamond films on nondiamond substrates.

A laser method based upon carbon ion implantation and pulsed laser melting of copper has been used to produce continuous diamond thin film. Carbon ions were implanted with ion energies in the range of 60 to 120 keV, and doses of 1.0 x 10(18) to 2.0 x 10(18) ions cm(-2). The ion-implanted specimens were treated with nanosecond excimer laser pulses with the following parameters: energy density, 3.0 to 5.0 J cm(-2); wavelength, 0.308 microm; pulse width, 45 nanoseconds. The specimens were characterized with scanning electron microscopy (SEM), x-ray diffraction, Rutherford backscattering/ion channeling, Auger, and Raman spectroscopy. The macroscopic Raman spectra contained a strong peak at 1332 cm(-1) with full width at half maximum of 5 cm(-1), which is very close to the quality of the spectra obtained from single-crystal diamond. The selected area electron diffraction patterns and imaging confirmed the films to be defect-free single crystal over large areas of up to several square micrometers with no grain boundaries. Low voltage SEM imaging of surface features indicated the film to be continuous with presence of growth steps.

Influence of diet on de novo lipogenesis in artificially-fed 15- and 20-day-old Zucker fatty rats.

Lean and obese Zucker rat pups were artificially fed high-fat and high-carbohydrate diets from 10-20 d of age to determine the effect of early diet composition on de novo lipogenesis and the development of obesity in the Zucker fatty rat. Amounts fed were the same as that consumed by suckling Zucker rat pups, which also were used as dam-fed controls. Lipogenic rates were measured by in vivo incorporation of tritium from 3H2O into total lipids and fatty acid and glyceride-glycerol fractions of liver, carcass and adipose tissue. Expressed on a per g tissue basis there was no difference in lipogenic rates between lean and obese pups in any tissues, even though pups accumulated a significantly higher percentage of carcass fat. High carbohydrate feeding accelerated growth and lipogenic rates in both lean and obese rats. Dam-fed pups had the lowest rates of lipogenesis and percentage of carcass fat. Thus, diet composition and method of feeding were important determinants of de novo lipogenic rates and body energy stores at this early age, but their influence was similar in lean and genetically obese animals.

Influence of diet on glucose metabolism of soleus muscle in artificially-fed 15- and 20-day-old Zucker fatty rats.

The relationship between diet and soleus muscle insulin responsiveness was examined in lean and obese Zucker rat pups that were artificially fed high-fat and high-carbohydrate liquid diets from 10 to 20 d of age and compared to pups that suckled normally. Elevated plasma glucose and insulin concentrations were found in both lean and obese artificially-fed pups at 20 d as compared to dam-fed controls. Total glucose utilization in isolated soleus muscle was estimated from the sum of the rates of 14C-glucose oxidation and 14C-glucose incorporation into glycogen and varied with genotype, age and diet. In general, soleus muscle from artificially-fed obese pups showed a lower basal and insulin-stimulated total glucose utilization than lean pups, with a greater and earlier effect due to high carbohydrate feeding. These results suggest that early dietary modification can alter peripheral target tissue insulin responsiveness and accelerate the onset of the insulin-resistant state.

Serum insulin and lipogenesis in the suckling 'fatty' fa/fa rat.

Preobese 'fatty' fa/fa rats identified by their decreased rectal temperature were either given access to high carbohydrate chow or maintained on a suckling only diet til 20 days of age. Serum insulin, hepatic and adipose tissue fatty acid synthesis and lipogenic enzyme activities were low in suckling preobese fa/fa. In animals with access to chow diet, hepatic lipogenesis was unaltered, serum insulin rose to similar levels in lean and preobese fa/fa (lean 62 +/- 5; preobese 69 +/- 4 microU/ml), but adipose tissue lipogenesis was increased to higher levels in the preobese than lean rats (lean 0.56 +/- 0.12; preobese 1.80 +/- 0.22 mumol. tissue-1. h-1). The activities of glucose-6-phosphate dehydrogenase, acetyl coenzyme A carboxylase and fatty acid synthetase were increased in adipose tissue of preobese fa/fa rats. Neither streptozotocin treatment nor pretreatment with Triton WR 1339 abolished the difference in adipose tissue lipogenesis between lean and preobese fa/fa rats. Preobese fa/fa rats showed an enhanced insulin secretory response to a glucose load.

Composition of rat milk from day 5 to 20 of lactation and milk intake of lean and preobese Zucker pups.

Milk composition and milk intake were measured in lean and preobese Zucker rat pups. Lactating dams were injected with 3H2O, which equilibrated with plasma water within 30 minutes. A constant specific activity of 3H was maintained by adding 3H2O to drinking water. Blood samples of 5 microliters were obtained from 1, 15 and 20-day-old suckling pups every 4 hours for a 24-hour period and the accumulation of tritium was used to calculate pups' milk intake. No diurnal variation in milk intake of pups was observed. Obese pups were identified at 5 weeks of age and showed no difference in milk intake compared to lean littermates at 10, 15 and 20 days of age. Milk intake of pups increased with age from 2.0 ml at day 10 to 15.8 ml by day 20. Food and water intake of dams also increased from day 10 to 20 of lactation. The protein and carbohydrate component of rat milk did not change significantly from day 5 to 20 of lactation; however, the fat component decreased significantly from 12.7% at day 5 to 4.2% at day 20.

Age-dependent development of insulin resistance of soleus muscle in genetically obese (ob/ob) mice.

The relationship between insulin binding and its biological effects was studied in soleus muscle of 3- to 15-wk-old genetically obese (ob/ob) mice. At 3 and 4 wk of age, soleus muscle from lean and obese mice bound similar amounts of insulin under equilibrium binding conditions. However, by 6 wk of age, insulin binding and total receptor concentration (Ro) were significantly decreased in soleus muscle from obese compared to lean mice. In addition lean and obese mice demonstrated an age-dependent decrease in insulin binding, Ro, and receptor affinity. At 4 wk of age, insulin-stimulated 2-deoxyglucose transport and glucose utilization were significantly lower in soleus muscle from obese mice and preceded alterations in insulin binding. The postmembrane decrease in insulin sensitivity was dissimilar for various pathways of glucose metabolism. Glucose conversion of glycogen, but not the glycolytic rate or glucose oxidation, remained sensitive to insulin stimulation. These data indicate that glucose transport and utilization rather than insulin binding may play the primary role in the development of insulin resistance of muscle in the obese diabetic syndrome.

Early development of lipogenesis in genetically obese (ob/ob) mice.

This study was designed to sequence the earliest metabolic abnormalities associated with the development of obesity in the obese hyperglycemic mouse (C57BL/6J ob/ob). In situ lipogenesis was measured with 3H2O in fetuses at day 19 of gestation and in 5-, 10-, 15-, and 35-day-old mice. Preobese 15-day-old animals were identified on the basis of rectal hypothermia. The earliest increased accumulation of fatty acids was observed in the carcass of 15-day-old preobese animals (ob/ob) compared to their lean littermates (+/?) and known lean controls (+/+). The increased carcass lipogenesis in these animals was accompanied by an increase in plasma insulin concentration. Weaned 35-day-old obese animals showed a significant increase in hepatic and subcutaneous adipose tissue lipogenesis, plasma insulin, and glucose values when compared to their littermates (+/?). The results indicate that increased carcass lipogenesis, hyperinsulinemia, and hypothermia appear between days 10 and 15 and that these abnormalities precede the hyperglycemia and increased hepatic lipogenesis observed in the mature ob/ob mice.

Lipogenesis in situ in the genetically obese Zucker fatty rat (fa/fa): role of hyperphagia and hyperinsulinaemia.

In situ fatty acid synthesis has been measured with 3H2O in anaesthetised lean and obese Zucker (fa/fa) rats. The accumulation of fatty acids was increased in both the liver and adipose tissue of young fa/fa rats as a result of both an increased rate of lipogenesis and an increase in tissue mass. Whereas total hepatic lipogenesis increased with age, total adipose tissue lipogenesis decreased in older fa/fa rats. Experiments with hepatectomized rats showed that the liver was the major site of the excess fatty acid synthesis in fa/fa rats. The enhanced rate of lipogenesis in fa/fa rats was abolished by either pair-feeding or streptozotocin treatment. The results suggest that the increased fatty acid synthesis in fa/fa rats is secondary to the hyperphagia, hyperinsulinaemia, and increased mass of hepatic and adipose tissues.