Use of chuck muscles and their acceptability in restructured beef/surimi steaks.

Ten major muscles along with any unidentifiable lean, were carefully excised from 16 Choice square-cut chucks Yield Grade 2, and placed according to previously determined tenderness rankings, into one of three muscle groups. Group 1 was composed of the most tender muscles, and contained the infraspinatus, longissimus, and triceps brachii. Group 2 contained intermediate tenderness muscles and was composed of the serratus ventralis, deep pectoral, and complexus. Group 3 contained the least tender muscles and was composed of the biceps brachii, supraspinatus, rhomboideus, trapezius, deltoids, and neck muscles. Each group was restructured into beef/surimi steaks and was evaluated. Total muscle yield before trimming accounted for 66.2% of the chuck. Careful fat trimming, desinewing, and internal seam cutting on individual muscles resulted in 34.7% lean available for the restructuring of steaks. The triceps brachii, longissimus, supraspinatus, and infraspinatus required the least trimming and were easiest to excise. These muscles made up 49% of the trimmed meat and 13.7% of the total chuck. Steaks were evaluated by a consumer sensory panel for tenderness, flavor, overall preference, and intent to purchase. There were no differences detected by consumers among the muscle groups for the sensory traits studied. Tenderness and flavor were rated equal to intact steaks for all muscle groups studied. The consumer sensory panel indicated that Groups 1 and 2 would be purchased twice a month and Group 3 once a month.

Soy protein influences insulin sensitivity and cardiovascular risk in male lean SHHF rats.

Previous investigations have demonstrated a marked effect of soy protein on multiple physiological parameters associated with the metabolic syndrome (MS). This preliminary study investigated the physiological effects of soy-based diets on cardiovascular risk in a unique rodent model that reflects early stages of MS. Briefly, lean male SHHF (+/cp) rats were randomly assigned to the following treatment groups: casein (control, C); low-isoflavone (LIS) soy protein isolate; high-isoflavone (HIS) soy protein isolate; or C+ 0.01 % rosiglitazone (CR). Rats were fed for thirty-six weeks. Liver weight, heart weight, total plasma cholesterol, fasting blood glucose were lower in soy-fed animals compared to control (p < 0.01). Body weight, kidney weight, alanine aminotransferase (ALT), fasting plasma insulin, and homeostasis model assessment (HOMA) score were also lower in LIS-fed rodents (p < 0.05) compared to casein treatment. All diet groups exhibited lower urine protein (p < 0.01) and small arteriole content (p < 0.05) compared to controls. LIS feed had a slightly more profound influence on body weight, liver metabolism, and insulin sensitivity. However, both soy diets exhibited marked improvements over a casein-based diet.

Soy protein influences the development of the metabolic syndrome in male obese ZDFxSHHF rats.

Previous investigations have demonstrated a marked effect of soy protein on the metabolic syndrome (MS). The purpose of this preliminary study was to identify the effects of soy-based diets on male obese ZDFxSHHF (fa/ fa-cp/?) rats. Animals were randomly assigned to one of four diets: control, casein (C); low-isoflavone (LIS) soy protein; high-isoflavone (HIS) soy protein; or casein + rosiglitazone (CR). Physiological, biochemical, and molecular parameters were determined at sacrifice. Body weight (p < 0.01) and food intake (p < 0.05) were lower in LIS-fed rodents. Rosiglitazone-treated animals had higher body weight and adiposity (p < 0.05). LIS and CR groups exhibited better glycemic control (p < 0.05), but with a limited effect in rosiglitazone-treated animals. HIS fed rats had higher glucose and triacylglyceride levels (p < 0.01), and lower plasma insulin (p < 0.01). Renal function parameters with the exception of an increase in systolic blood pressure (p < 0.05) were all suppressed in the LIS group (p < 0.01). The CR group had twofold PPARalpha and PPARgamma mRNA abundance (p < 0.01). LIS-fed animals also exhibited greater abundance of PPARgamma mRNA (p < 0.001), and nearly threefold FAS and CPT-1 mRNA levels (p < 0.05). HIS-fed rats also had higher abundance of CPT-1 mRNA, as well as a lower abundance of ACC mRNA (p < 0.05). Soy-based diets, influenced by isoflavone content and distinct from rosiglitazone, improved several metabolic parameters in obese ZDFxSHHF rats.

Low dietary protein is associated with an increase in food intake and a decrease in the in vitro release of radiolabeled glutamate and GABA from the lateral hypothalamus.

Moderately low-protein diets lead to a rapid increase in food intake and body fat. The increase in feeding is associated with a decrease in the concentration of serum urea nitrogen, suggesting that the low-protein-induced increase in food intake may be related to the decreased metabolism of nitrogen from amino acids. We hypothesized that low dietary protein would be associated with a decrease in the synaptic release of two nitrogen-containing neurotransmitters, GABA and glutamate, whose nitrogen can be derived from amino acids. In this study, we examined the effects of a low-protein diet (10% casein) in Sprague-Dawley rats on the in vitro release of 3H-GABA and 14C-glutamate from the lateral and medial hypothalamus. The low-protein diet increased food intake by about 25% after one day. After four days, the in vitro release of radiolabeled GABA and glutamate was assessed. The calcium-dependent, potassium-stimulated release of radiolabeled GABA and glutamate from the lateral hypothalamus was decreased in rats fed the low-protein diet. The magnitude of neurotransmitter release from the lateral hypothalamus inversely correlated with food intake. No dietary differences in the release of neurotransmitters from the medial hypothalamus were observed. These results support the contention that alterations in nitrogen metabolism are associated with low-protein-induced feeding.

Food intake, energy balance and serum leptin concentrations in rats fed low-protein diets.

Studies examining the effects of low-protein diets on food intake and body weight have shown varied results. Many researchers have found low dietary protein to increase food intake, while others have found no effect or even a decrease. In 63 male Sprague-Dawley rats, we examined several low levels of dietary protein (2%, 5%, 8%, 10%, 15% vs. 20% casein) to determine the dose-response relationships between low dietary protein and food intake, body composition, energy balance and serum leptin concentrations. Food intake, over the range of low dietary protein, showed a quasi bell-shaped response curve with peak intake occurring in rats fed 8-10% casein. Peak feeding occurred at or just below the estimated protein requirement of the rats (10-12.5% casein). Compared to the 20% casein controls, food intake was severely reduced in rats fed 2% casein, while it was greater in the other low-protein groups. The amount of body fat steadily increased between the 15% casein group and the 8% casein group, and sharply declined between the 5% casein group and 2% casein group. The change in body fat reflected both the change in food intake and altered energy partitioning. Serum leptin concentrations were greater in rats fed the 5 and 8% casein diets than in control rats fed 20% casein. Serum leptin concentrations were positively associated with body fat content (r(2) = 0.763, P < 0.001). Increased serum leptin concentrations in the presence of increased food intake is suggestive of a state of leptin resistance. This animal model may provide important insights into diet-induced obesity.