The relationship between diet and insulin sensitivity was examined in isolated soleus muscle from 10-wk-old lean Zucker rats. Rats were fed either a high fat or high carbohydrate diet that had 67% of calories as fat or carbohydrate, respectively, for 10 days. Plasma insulin but not plasma glucose concentrations were significantly elevated in high-fat-fed rats, indicating that a state of insulin resistance existed. The mechanisms responsible for the insulin resistance were studied by measuring insulin binding, 2-deoxyglucose uptake, and glucose metabolism in soleus muscle. The soleus muscle from the high-fat-fed rats bound significantly less insulin than high carbohydrate control rats under equilibrium binding conditions. The 35% decrease in insulin binding at maximal insulin concentrations resulted from a decrease in insulin receptor number but no change in receptor affinity. Maximal insulin-stimulated 2-deoxyglucose uptake was reduced in soleus muscle from high-fat-fed rats when compared with high carbohydrate controls. A decrease in postmembrane basal and insulin-stimulated glucose utilization was produced by high rat feeding and varied depending upon the pathway involved. An estimate of glycolysis (3H2O) formation from [5-3H]glucose) and glucose oxidation (14CO2 production from 14C-glucose) demonstrated a greater decrease in basal and insulin-stimulated utilization than in [5-3H]glucose conversion to [3H]glycogen. These results suggest that multiple sites are responsible for the observed insulin resistance in soleus muscle after high fat feeding.

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.

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.

No abstract

The influence of fiber purification and conditions of enzymatic modification on soluble fiber content of wheat fiber were examined. Crude wheat fiber was purified by a modified enzymatic extraction. Crude wheat bran contained 16% soluble dietary fiber by weight. Purification of the crude wheat bran did not alter soluble fiber content nor result in a significant loss of total dietary fiber. A technical grade hemicellulase was used to enzymatically modify the purified wheat fiber. The yield varied considerably with enzyme concentration and time. The optimized modification conditions utilized were 0.1 M acetate buffer (pH 5.0) and 60 HCU/mL per g of PIFF hemicellulase a t 30 "C for 40 min. The enzymatic modification of wheat fiber resulted in an 87% increase in soluble fiber content up to 30%.A number of studies have demonstrated that the use of soluble fibers may be an important adjunct in the treatment of diabetes. Jenkins et al. (Jenkins et al., 1977a(Jenkins et al., ,b, 1980 demonstrated that the addition of soluble types of dietary fiber such as pectin and guar into test meals reduced postprandial glycemia in normal, non-insulindependent and insulin-dependent subjects. This was attributed in part either t o an increased mouth to cecum transit time, to the decreased rate of gastric emptying, or to a slower rate of duodenal absorption, all factors associated with an increase in solubility and/or viscosity (Blackburn et ai., 1984;Jenkins e t al., 1977b Jenkins e t al., , 1979.Insoluble fibers such as cellulose or less soluble fibers such as wheat bran have been shown to be less effective as agents for lowering serum glucose values. In contrast, they have been shown to increase fecal bulk and inhibit colon tumors. Although wheat bran is a less soluble type of fiber, a number of studies have reported the use in the treatment of diabetics (Simpson e t al., 1979a,b).The objective of the present investigation was to determine the conditions under which the soluble fiber content of wheat fiber could be increased. This would increase the potential for clinical usage under circumstances requiring a more soluble type of fiber. PROCEDURESPurification of Wheat Bran. A modification of Prosky et al. (1984) and Monte and Maga (1980) was utilized for determination and purification of a commercial grade of crude wheat bran. The purification method developed is described in Figure 1.Sample Pretreatment-Extraction of Lipids. The extraction of lipid from crude wheat bran (CWB) was performed three times with use of reagent grade petroleum ether (PET) (6:l = PET:CWB) at room temperature. The defatted wheat bran (DWB) was dried overnight at 105 "C in an air oven to a constant weight. It was then passed through a Wiley mill (Model No. 4) equipped with a 0.5-mm-mesh screen.Removal of Soluble Complex Carbohydrate. DWB was incubated in a 0.08 M Na2P0, buffer (pH 6.0 DWB), containing Termamyll20 L (120 KNU (Novo-a-amylase unit)/mL per 10 g of DWB; heat-stable a-amylase; Novo Laboratories, Inc., Wilton, CT 06897) for 30 min in a hemisphe...